Fixed dose injection device

Abstract

To provide a drug delivery device for sequentially delivering a predefined plurality of fixed doses.SOLUTION: The drug delivery device comprises a housing assembly, a drive mechanism comprising a drive tube and adapted to sequentially deliver the predefined plurality of doses, and an activation mechanism for activating the drive mechanism. The drive mechanism further comprises a pre-strained torsional drive spring conserving an initial amount of energy, and adapted for rotating the drive tube, where each activation of the drive mechanism, and completion of a drive tube dose sequence reduces the amount of conserved energy in the drive spring, and where the initial amount of conserved energy, which is the conserved energy before the first activation, is sufficient to deliver the predefined plurality of fixed doses.SELECTED DRAWING: Figure 15A

Description

[Technical Field]

[0001] The present invention relates to a medication delivery device for delivering a predetermined plurality of fixed doses, and in particular to such a medication delivery device in which the ejection of the fixed doses is driven by a pre-tensioned torsion spring. [Background technology]

[0002] Drug delivery devices for self-administration of different liquid formulations currently exist in a variety of shapes and sizes. Some are adapted to connect to an infusion set, while others connect to or are integrated with a needle. The latter type is called an injection device. Some are durable devices with a cartridge containing a drug reservoir, which can be replaced. Others are disposable devices that are discarded when the cartridge is empty. Disposable devices can be either multi-dose devices, which allow the user to set the desired dose size before each injection, or single-dose devices, which can only deliver a single dose of a given size. The latter exist with so-called "shield activation," in which the cannula is covered by a shield on the front of the device that releases the dose when pressed. The cannula is then only exposed to enter the skin when the user presses the device against the skin, thereby depressing the shield and releasing the dose. These injection devices are discarded after a single injection.

[0003] Fixed-dose devices are preferred by some users because they may be resistant to or unable to operate the device to deliver the correct dose every time. For example, when the device is used by children or the elderly, simplicity and ease of use are important to avoid user error leading to over- or under-dosing. In other cases, treatment regimens prescribe fixed doses of, for example, GLP-1-type drugs.

[0004] However, the device itself accounts for a significant portion of the cost of the unit, not to mention the amount of material used and therefore the need to dispose of it. It would therefore be desirable to create a fixed dose device that can deliver multiple doses of a fixed volume.

[0005] In existing multi-dose devices, the motor consists of a spring that winds up when adjusting the dose. One solution is to make a regular multi-dose device where the maximum dose size is limited and it is therefore only possible to dial up to a fixed dose size. However, this poses the risk that the user will not dial up enough and therefore get a smaller dose than expected; this problem is solved in US Pat. No. 5,649,499 filed by Novo Nordisk, in which a ratchet tube is locked in the housing until the full dose is set and the drive mechanism is released.

[0006] Another fixed-dose device is disclosed in U.S. Patent Application Publication No. 2007 / 0122999 filed by Sanofi-Aventis. The disclosure relates to an injection device having a longitudinally displaceable dose tracker that provides automatic dose setting according to a preselected dose size. The disclosed injection device comprises an elongated housing 10 extending along a longitudinal axis (z) and a piston rod 20, 120 for operably engaging with a piston 7 of a cartridge 6 filled with a medicament. The injection device further comprises a dose tracker 60, 150, 250, 350, 450, 550 selectively operably engageable with the piston rod 20, 120, wherein the dose tracker is proximally displaceable relative to the housing 10 from an initial position (i) (see FIG. 25) toward at least a first activation position (a) (see FIG. 26) for setting a dose, and the dose tracker is distally displaceable relative to the housing (10) from the activation position (a) toward the initial position (i) for dispensing a dose. The injection device includes a spring 80, 144 to bias the dose tracker proximally. The injection device further includes an interlock 84, 184, 284, 584 to lock the dose tracker in the initial position (i), and a release member 100, 101, 190, 290, 590 to release the interlock 84, 184, 284. For example, when the release member 190 is activated to release or unlock the dose tracker 150, the dose tracker 150 begins to rotate relative to the housing under the action of the relaxation spring 144. An alternative fixed-dose device from which the size of the fixed dose can be selected is disclosed in U.S. Patent No. 5,999,223 filed by Merch Sharp & Dohme Corp. However, allowing the possibility to select between fixed doses of different sizes increases the complexity of the device, and the selection function is not always desirable. The ability to provide different fixed dose sizes can alternatively be obtained using a set of two or more different fixed-dose devices.

[0007] An alternative fixed-dose device is disclosed in U.S. Patent No. 6,277,999 filed by Copernicus. The disclosure relates to an injection device for delivering a defined number of equal doses of a fluid substance. The disclosed injection device includes a housing 1 having a safety release mechanism and a dose delivery mechanism disposed along the longitudinal axis of the housing. The housing is coupled to an enclosure 3 for receiving a reservoir containing the fluid substance. The safety release mechanism includes a setting sleeve 5 that is axially non-displaceable. The safety release mechanism is rotatable about the axis of the housing through a defined setting angle (a) in two opposite directions. The setting sleeve 5 is coupled to a torsion spring 10 that is tensioned by rotation of the setting sleeve 5 during device disarming. The dose delivery mechanism includes a threaded ring 6 and a piston rod 4 that is non-rotatable and axially displaceable within the setting sleeve 5. When the piston rod 4 cooperates with the threaded ring 6, the threaded ring 6 and the piston rod 4 are fixed during device disarming. During delivery of each dose, the piston rod 4 is displaced along the housing 1 a defined distance due to the unwinding of the spring 10 and the rotation of the screw ring 6. The displacement of the piston rod 4 causes the fluid substance to be expelled from the reservoir. As shown, the torsion spring must be tensioned to allow the dose to be expelled. An alternative design utilizing spring compression is also described in U.S. Patent No. 5,629,999 filed by Copernicus. Another alternative device utilizing spring compression before each fixed dose is also disclosed in U.S. Patent No. 5,629,999 filed by Owen Mumford. However, disarming the device between doses is not always desirable because the user must provide sufficient force to disarm the device.

[0008] An alternative fixed-dose device is disclosed in U.S. Patent No. 6,299,949 filed by Menarini. This disclosure relates to a device for automatically injecting two doses of a medication in two successive doses. This disclosure describes an automatic injection device with a sliding sheath 30 that, when depressed at its front end 3 against an injection site, interacts with cam means 26, 27, 28 to activate the trigger of a plunger 8 and control the delivery of a medication dose. A plunger guide means 44 is provided on the inner surface of the outer housing 1 to control the trigger sequence, and a dose knob 4 is used to arm or set the device in a dose delivery condition. The device is adapted for automatic needle re-coating and resetting of the unlocked condition after each dose is delivered. The number of device components is reduced, resulting in a simpler structure and reduced costs. Devices with similar functionality by the same applicant are disclosed in U.S. Patent Nos. 6,299,949 and 6,299,949. As shown, all alternatives utilize a compression spring as the power means to drive the plunger.

[0009] US Patent Nos. 5,629,999, 5,729,963, 5,729,973, and 5,729,973 all describe drug delivery devices actuated by a torsion spring, which is tensioned during dose setting. US Patent No. 5,629,999 relates to a fixed dose drug delivery device, whereas US Patent Nos. 5,729,999 and 5,729,973 relate to variable dose drug delivery devices.

[0010] Therefore, there is an unmet need for an alternative injection device for delivering a predetermined fixed dose that addresses the need for a simple, safe, user-friendly, and robust medication delivery device.

[0011] In view of the above, it is an object of the present invention to provide a user-friendly, safe and robust medication delivery device for delivering predetermined multiple fixed doses. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] International Publication No. 2020 / 089167 [Patent Document 2] International Publication No. 2019 / 09179 [Patent Document 3] International Publication No. 2017 / 106221 [Patent Document 4] International Publication No. 2018 / 007259 [Patent Document 5] International Publication No. 2017 / 098460 [Patent Document 6] International Publication No. 94 / 26331 [Patent Document 7] International Publication No. 2013 / 034651 [Patent Document 8] International Publication No. 2013 / 034647 [Patent Document 9] International Publication No. 2011 / 111006 [Patent Document 10] U.S. Patent Publication No. 2013 / 0096513 [Patent Document 11] International Publication No. 2014 / 060369 [Patent Document 12] International Publication No. 2014 / 198858 Summary of the Invention

[0013] In the present disclosure, embodiments and aspects are described that address one or more of the above objects or that address objects apparent from the following disclosure as well as the description of the exemplary embodiments.

[0014] In a first aspect, there is provided a drug delivery device for sequentially delivering a plurality of predetermined fixed doses, the drug delivery device comprising: a housing assembly; a drive mechanism comprising a drive tube, the drive mechanism being adapted to sequentially deliver a plurality of predetermined doses; an actuation mechanism for actuating the drive mechanism; A medication delivery device is provided in which the drive mechanism comprises a pre-tensioned torsion drive spring (108, 208) adapted to store an initial amount of energy and to rotate the drive tube, and each actuation of the drive mechanism and completion of a drive tube dose sequence reduces the amount of stored energy in the drive spring, such that the initial amount of stored energy, which is the energy stored before the first actuation, is sufficient to deliver a predetermined multiple of the fixed doses.

[0015] This provides a medication delivery device for delivering a predetermined plurality of fixed doses without disarming or retracting the drive mechanism between doses, since the stored energy before the first actuation is sufficient to deliver the predetermined plurality of fixed doses. The fixed dose medication delivery device according to the present invention is adapted to deliver a plurality of doses of a desired amount. The total content of the medication divided by the desired amount of fixed dose determines the predetermined plurality of amounts. Each actuation of the drive mechanism reduces the stored energy because the spring is not retracted before each dose.

[0016] In a further aspect, the housing assembly comprises a guide structure comprising a stop and start guide portion and a drive guide portion; - the drive-tube is adapted to be guided along the stop and actuation guide portions for actuation of the drive mechanism, and along the drive guide portions for delivery of a fixed dose, and dosing is stopped, whereby the drive-tube is adapted to be guided in response to performance of a drive-tube dose sequence including actuation, dosing, and stopping dosing; the drive mechanism further comprising a piston rod operatively connected to the housing assembly and the drive tube; an actuation mechanism adapted to move the drive-tube along the stop and actuation guide portion in the first axial direction from the first axial position to the second axial position, thereby actuating the drive mechanism;

[0017] In a further aspect, the drive mechanism is further adapted to bias the drive-tube in a second axial direction opposite the first axial direction, and the drive mechanism is adapted to rotate the drive-tube along the drive guide portion and toward the stop and actuation guide portion in response to actuation of the drive-tube, thereby delivering a fixed dose of a predetermined plurality of fixed doses, and the drive-tube is operably positioned to be guided along the stop and actuation guide portion to deliver a subsequent fixed dose of the plurality of fixed doses.

[0018] In a further or alternative aspect, the housing further comprises internal threads, the piston rod further comprises external threads for threadably engaging the internal threads of the housing assembly, and the drive-tube is axially splined to the piston rod such that the drive-tube is axially movable and rotationally locked relative to the drive-tube, thereby operably connecting the piston rod to the housing assembly and the drive-tube.

[0019] In further or alternative aspects, the torsional drive spring is compressed such that the drive mechanism is adapted to bias the drive tube in the second axial direction such that the drive spring is adapted to bias the drive tube toward the first position during administration, thereby ensuring that the guide surface is intact during administration.

[0020] In a further or alternative aspect, the medication delivery device includes an axially movable spring base and the drive mechanism includes a compression return spring positioned between the axially movable spring base and the housing, whereby the torsional drive spring and the return spring are coupled in series, whereby the drive mechanism is adapted to bias the drive tube in the second axial direction.

[0021] In a further or alternative aspect, the drug delivery device is adapted for drug delivery at a distal end, the drug delivery device having a central axial axis defined between the distal end and the proximal end, the drug delivery device having a slidably disposed spring base, a torsion spring disposed between the spring base and the drive tube, the drive tube being positioned by a component of the central axial axis in a direction opposite to gravity, which is a second axial direction, during activation and administration, thereby urging the drive tube in a distal direction, and the drive mechanism being adapted to urge the drive tube in the second axial direction.

[0022] In a further or alternative aspect, a torsion drive spring is disposed between the drive tube and the housing assembly.

[0023] In a further or alternative aspect, the housing assembly includes a fixed spring base, and one end of the torsion drive spring is attached to the fixed spring base, thereby making the spring base a fixed part of the housing assembly.

[0024] In a further or alternative aspect, the stop and actuation guide portions of the guide structure are axial portions and the drive guide portion of the guide structure of the housing assembly comprises a helical portion.

[0025] In a further or alternative aspect, the stop and actuation guide portions of the guide structure are axial portions and the drive guide portions of the guide structure of the housing assembly comprise lateral portions.

[0026] In a further or alternative aspect, the stop and actuation guide portions of the guide structure are axial portions, and the drive guide portion of the guide structure of the housing assembly comprises a stepped portion comprising an interval between a portion from a first group comprising a lateral and helical portion and a portion from a second group comprising a radial, helical, and axial portion.

[0027] In a further or alternative aspect, the drive-tube includes corresponding guide structure adapted to cooperate with the guide structure of the housing assembly.

[0028] In a further or alternative aspect, the guide structure of the drive-tube comprises an axial portion and a helical portion.

[0029] In a further or alternative aspect, when the drive-tube is in a first position, the axial portions of the housing assembly and the drive-tube guide structure abut and the helical portions of the housing assembly and the drive-tube guide structure abut, and when the drive-tube is in a second position, an axial clearance is provided between the housing assembly and the axial portions of the drive-tube, thereby allowing the helical portion of the drive-tube to slide over the helical portion of the housing assembly.

[0030] In further or alternative embodiments, each of the delivered doses is an equal amount.

[0031] In a further or alternative aspect, the medication delivery device comprises a resetting mechanism whereby each of the delivered doses is of equal volume.

[0032] In further or alternative embodiments, the drive spring is pre-tensioned to deliver a predetermined number of doses using a constant force, which can be measured as an axial force transmitted from the piston rod, where the constant force is defined as a force that varies by less than 20 percent between the first and last doses.

[0033] In further or alternative embodiments, the predetermined plurality of fixed doses is 2, 3, 4, 5 or 6, preferably 4.

[0034] In a further or alternative aspect, the drug delivery device comprises a drug-filled cartridge having a proximally disposed piston, the piston rod being operatively arranged to advance the piston.

[0035] In a further or alternative aspect, the medication delivery device includes an integrated needle and the actuation mechanism includes a needle shield axially movable to cover and uncover the needle, the shield adapted to actuate the actuation mechanism in response to proximal movement to uncover the needle.

[0036] In a further or alternative aspect, the medication delivery device comprises a needle mount for the injection needle, and the activation mechanism comprises an axially movable release button adapted to activate the drive mechanism in response to axial movement.

[0037] In a further or alternative aspect, the actuation mechanism includes a connector operably connected to the drive mechanism, the connector adapted to actuate the drive-tube in response to axial movement.

[0038] In a further or alternative aspect, the actuation mechanism comprises a shield for covering the integrated needle and a connector operably connected to the drive mechanism, the shield operably disposed to engage the connector in response to rotating the shield, the shield being axially movable and adapted to move the connector, thereby actuating the drive-tube in response to the axial movement.

[0039] In further or alternative embodiments, the first position of the drive-tube is a distal position and the second position is a proximal position.

[0040] In a further or alternative aspect, the drug delivery device is an injection device.

[0041] In further or alternative aspects, the medication delivery device further comprises a medication reservoir having a piston arranged to expel medication from the reservoir, a piston rod adapted to advance the piston axially, the piston rod axially splined to the housing assembly whereby the piston rod is axially movable and rotationally locked relative to the housing assembly, a drive tube further comprising internal threads, the piston rod further comprising external threads for threadably engaging the internal threads of the drive tube whereby the piston rod is operably connected to the housing assembly and the drive tube, and a drive mechanism further comprising a compression drive spring for axially moving the drive tube and piston, whereby the drive mechanism and drive and return guides are adapted to return the drive tube to the first position.

[0042] In a further or alternative aspect, the medication delivery device further comprises an axially movable spring base, and the compression drive spring is positioned between the spring base and the housing, whereby the torsion drive spring and the compression drive spring are coupled in series.

[0043] In a further or alternative aspect, the compression drive spring is integral with the torsion drive spring.

[0044] In a further aspect, the drive spring is pre-tensioned to deliver predetermined multiple doses at a constant force.

[0045] In a further aspect, the housing assembly includes a guide structure including a stop and actuation guide portion and a drive guide portion.

[0046] In a further aspect, the drive-tube is adapted to be guided along the stop and actuation guide portions for actuation of the drive mechanism and along the drive guide portions for delivery of a fixed dose, and dosing is stopped, whereby the drive-tube is adapted to be guided in response to execution of a drive-tube dose sequence including actuation, dosing, and stopping dosing.

[0047] In a further aspect, the medication delivery device comprises a reservoir having a piston, and the drive mechanism further comprises a piston rod for engaging and advancing the piston rod to expel the dose.

[0048] In a second aspect of the present disclosure, there is provided a drug delivery device for sequentially delivering a plurality of predetermined fixed doses, the drug delivery device comprising: a housing assembly comprising a guide structure comprising a stop and start guide portion and a drive guide portion; a drive mechanism adapted to sequentially deliver a plurality of predetermined doses, the drive mechanism comprising: a drive-tube adapted to be guided along the stop and actuation guide portions for actuation of the drive mechanism, and along the drive guide portions for delivery of a fixed dose, and dosing is stopped, whereby the drive-tube is adapted to be guided in response to performance of a drive-tube dose sequence including actuation, dosing, and stopping dosing; a torsion drive spring adapted to store an initial amount of energy and to rotate the drive tube; a drive mechanism comprising a housing assembly and a piston rod operatively connected to a drive tube; an actuation mechanism adapted to move the drive-tube along the stop and actuation guide portion in a first axial direction from a first axial position to a second axial position, thereby actuating the drive mechanism; the drive mechanism is further adapted to bias the drive-tube in a second axial direction opposite the first axial direction, the drive mechanism being adapted to rotate the drive-tube along the drive guide portion and toward the stop and actuation guide portion in response to actuation of the drive-tube to thereby deliver a fixed dose of a predetermined plurality of fixed doses, the drive-tube being operably positioned to be guided along the stop and actuation guide portion to deliver a subsequent fixed dose of the plurality of fixed doses; A medication delivery device is provided in which each activation of the drive mechanism and completion of a drive tube dose sequence reduces the amount of stored energy in the drive spring, and the initial amount of stored energy, which is the energy stored before the first activation, is sufficient to deliver a predetermined multiple of the fixed doses.

[0049] This provides a medication delivery device for delivering a predetermined multiple fixed doses without disarming or retracting the drive mechanism between doses, since the stored energy before the first activation is sufficient to deliver the predetermined multiple fixed doses. As shown, the amount of the fixed dose is determined by the housing and the guide of the drive mechanism. Therefore, the fixed dose medication delivery device according to the present invention is adapted to deliver multiple doses of a desired amount. The total content of the medication divided by the desired amount of the fixed dose determines the predetermined multiple amount. As also shown in the fixed dose medication delivery device according to the present invention, the fixed dose can be adjusted only by modifying the drive mechanism and guide of the device.

[0050] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Brief explanation of the drawings]

[0051] [Figure 1A] FIG. 1A shows an exploded view of an injection device according to a first embodiment of the present disclosure. [Figure 1B] FIG. 1B illustrates details of the cartridge holder of the embodiment shown in FIG. 1A. [Figure 1C] Figure 1C illustrates details of the shield-following and moving parts of the cleaning assembly of the embodiment shown in Figure 1A. Figure 1C illustrates the structure in both black and white and grayscale of window W1, where the piston is separated from the chamber. [Figure 1D-1F]Figures 1D-1F illustrate details of the shield-following portion, cannula, needle hub, and cartridge-engagement structure of the cleaning assembly of the embodiment shown in Figure 1A. In Figure 1F, window W2 illustrates the assembly in grayscale, and window W3 illustrates a cross-section of the hub in grayscale to reveal the guides on the inner surface. [Figures 2A-2D] Figures 2A-2D illustrate further details of the cleaning assembly of the embodiment shown in Figure 1A. Figures 2B, 2C, and 2D illustrate the structure in both black and white and grayscale with windows W4, W5, and W6, respectively, to enhance assessability of the voids, angled surfaces, and separate components. Window W6 is angled to show the slit in the hub. [Figures 3A-3F] 3A-3F illustrate details of the guide structure of the elongated housing structure of the embodiment shown in FIG. 1A. [Figure 4A-4B] 4A and 4B illustrate details of the zero adjustment nut of the embodiment shown in FIG. 1A. [Figure 5] FIG. 5 illustrates further details of the zero adjustment mechanism provided on the elongated housing structure of the embodiment shown in FIG. 1A. [Figure 6] Figure 6 illustrates a cross-sectional view of a proximal portion of the injection device of the embodiment of Figure 1 A. The illustrated injection device includes a piston washer. [Figure 7] FIG. 7 shows details of the piston rod of the embodiment shown in FIG. 1A. [Figure 8A-8B] 8A and 8B show details of the drive-tube of the embodiment shown in FIG. 1A. [Figure 9A-9B] 9A and 9B show details of the housing insert portion of the embodiment shown in FIG. 1A. [Figures 10A-10C] 10A-10C show details of the elongated shield structure of the embodiment shown in FIG. 1A. [Figures 11A-11B] 11A and 11B show details of the connector of the embodiment shown in FIG. 1A. [Figures 12A-12B]12A and 12B show cross-sectional views of the proximal end of the injection device from two different angles. The illustrated device is the same as the embodiment shown in FIG. 1A. [Figures 13A-13D] 13A-13D show details of the drive mechanism of the embodiment shown in FIG. 1A. [Figures 14A-14B] Figures 14A and 14B show cross-sectional views of the entire injection device from two different angles. The illustrated device is the same as the embodiment shown in Figure 1A. [Figures 15A-15B] Figures 15A and 15B illustrate user actions and states during operation of the injection device of Figure 1 A. Figure 15A illustrates the action to obtain a first fixed dose, and Figure 15B illustrates the subsequent doses. [Figures 16A-16T] 16A-16T show the injection device of FIG. 1A in different states and intermediate positions, thereby providing detailed illustrations of the operation of the device. [Figure 17] FIG. 17 shows an exploded view of an injection device according to a second embodiment of the present disclosure. [Figure 18] FIG. 18 illustrates a cross-sectional detail of the embodiment shown in FIG. [Figure 19] FIG. 19 illustrates details of the housing of the embodiment shown in FIG. [Figure 20] FIG. 20 illustrates details of the inner tubular portion of the housing of the embodiment shown in FIG. [Figure 21] FIG. 21 illustrates details of the relocking tube of the embodiment shown in FIG. [Figure 22] FIG. 22 illustrates details of the connector of the embodiment shown in FIG. [Figures 23A-23B] 23A and 23B illustrate details of the drive-tube of the embodiment shown in FIG. [Figure 24] FIG. 24 illustrates details of the elongated shield structure of the embodiment shown in FIG. [Figures 15A-15B]Figures 15A and 15B illustrate user actions and states during operation of the injection device of Figure 1 A. Figure 15A illustrates the action to obtain a first fixed dose, and Figure 15B illustrates the subsequent doses. [Figures 25A-25G] 25A-25G show the injection device of FIG. 17 in different states and intermediate positions, thereby providing detailed illustrations of the operation of the device during the first dose. [Figures 26A-26B] 26A and 26B show the injection device of FIG. 17 in different states and intermediate positions during subsequent doses. DETAILED DESCRIPTION OF THE INVENTION

[0052] In the figures, similar structures are primarily identified by similar reference numbers. The letter "a" following a reference number is used to indicate the distal end of the structure, and "b" following the number is used to indicate the proximal end. Reference numbers, including a first number followed by a "." and a second number, are used to indicate functional or structural details of the structure. In this manner, the first number indicates a primary (relatively large) structure, and the second number indicates a secondary (relatively small) structure or specific function. The letters c, d, and e following a reference number indicate features with rotational symmetry.

[0053] When terms such as "top" and "bottom," "right" and "left," "horizontal" and "vertical," or similar relative expressions are used below, they only refer to the accompanying drawings and not necessarily to actual usage situations. The drawings shown are schematic, and therefore their relative dimensions as well as the configuration of different structures are intended to serve for illustrative purposes only. When the term "member" is used for a given component, it can be used to define a single component or a portion of a component having one or more functions.

[0054] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the embodiments.

[0055] It should also be understood that, although terms such as "first," "second," and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first subject may be referred to as a second subject, and similarly, a second subject may be referred to as a first subject, without departing from the scope of the present disclosure. A first subject and a second subject are both subjects, but are not the same subject. Furthermore, the terms "subject," "user," and "patient" are used interchangeably herein.

[0056] As used herein, the term "when" can be interpreted to mean "when" or "upon" or "upon determining" or "upon detecting," depending on the context. Similarly, the phrase "when determined" or "when [described condition or event] is detected" can be interpreted to mean "upon determining," or "upon determining," or "upon detecting [described condition or event]," depending on the context.

[0057] As used herein, the terms distal and proximal end are analogous to terms from anatomy used to describe ends located away from or closest to the point of attachment to the body. Thus, the distal end of an injection device is defined in the context of a user holding the device in an injection-ready position, whereby the end having the injection needle is the distal end and the opposite end is the proximal end. Additionally, the distal and proximal ends of individual components of the device are also defined in that context.

[0058] As used herein, trailing edge and leading edge are used to describe the edges of a structure that moves relative to another structure. The leading edge is the edge in the direction of movement, and the trailing edge is the opposite. Thus, the leading edge and trailing edge are defined according to the direction of relative movement between the structures.

[0059] As used herein, rotational symmetry is a property of a structure when it looks the same or retains the same function after several rotations by partial turns. The degree of rotational symmetry of a structure is the number of distinct orientations that look the same for each rotation. Degree n rotational symmetry, where n is 2 or greater, is also called n-fold rotational symmetry or n-th discrete rotational symmetry, where n is greater than or equal to 2 and about a specific point (2D) or axis (3D), meaning that a rotation through an angle of 360° / n does not change the object. The properties of a structure can relate to both the visible appearance and the functional capabilities of structural features.

[0060] As used herein, the term clockwise direction is used to describe the direction in which the hands of a clock rotate when viewed from the front. Thus, clockwise rotation of an injection device is the clockwise rotation observed when viewing the device from the front of the distal end. Counterclockwise or anticlockwise rotation is defined as the opposite direction.

[0061] As used herein, the proximal face is the face of the device when viewed distally from the proximal end, and the distal face is the face of the device when viewed proximally from the distal end.

[0062] As used herein, the positive axial or longitudinal direction is defined from the proximal end to the distal end. The positive axial and distal directions are used interchangeably with the same meaning. Similarly, the definitions of negative axial and proximal directions are used interchangeably with the same meaning. The central axis of the device is defined through the center of the injection device in the positive axial direction, also referred to as the longitudinal axis.

[0063] As used herein, the positive radial direction is defined along the radial axis originating at the central axis and perpendicular to the central axis.

[0064] A positive circumferential or positive angular direction is defined relative to a point located a radial distance from the central axis, with the circumferential direction being counterclockwise and perpendicular to the axial and radial directions. Directions as used in this disclosure can be both positive and negative. For example, the term axial direction encompasses a positive axial direction from the proximal end to the distal end and a negative axial direction in the opposite direction.

[0065] Both the radial and circumferential directions are referred to herein as transverse because they are orthogonal to the axial direction. A transverse plane is defined herein as the plane that spans two vectors, the radial and the circumferential, for a given coordinate along the axis and with the central axis as the normal vector.

[0066] As used herein, axial movement of a structure is used to describe movement, where the displacement vector of the structure has a component in the axial direction. Translational movement is used to describe uniform movement in the axial direction only. Pure, exact, or uniform axial movement is the same as translational motion, and these terms are used interchangeably.

[0067] Radial movement of a structure is used to describe movement, where the displacement vector of the structure has a component in the radial direction. Pure, strictly radial movement is used to describe uniform movement in the radial direction only. Thus, pure, strictly, and uniform radial movement are the same, and these terms are used interchangeably.

[0068] Circumferential, angular, or rotational movement of a structure is used to describe movement, where the displacement vector of the structure has a component in the circumferential direction. Pure, strictly circumferential movement is used to describe uniform movement in the circumferential direction only. Thus, pure, strictly, and uniform circumferential movement are the same as pure, strictly, and uniform angular or rotational movement, and these terms are used interchangeably. The definition of rotational movement for a structure also encompasses the special case where the structure includes a central axis that defines the axis of rotation. In this special case, all positions of the structure off the central axis undergo circumferential movement, while the displacement vector of positions on the central axis is zero. Therefore, a structure that rotates about its own central axis and moves axially is said to perform rotational movement.

[0069] Helical movement of a structure is used to describe combined axial and angular or rotational movement, where the displacement vector of the structure includes circumferential and axial components. The definition of helical movement for a structure also encompasses the special case where the structure includes a central axis that defines the axis of rotation. In this special case, all positions of the structure off the central axis undergo helical movement, but the displacement vectors of positions on the central axis include only an axial component. Therefore, a structure that rotates about its own central axis and moves axially is said to perform helical movement.

[0070] In this context, pure, precise, and uniform movement are abstract mathematical definitions, and these terms are used to describe ideal or abstract movement of a device. Therefore, structures within a real device should not be expected to exhibit this ideal behavior; rather, such structures should be expected to move in a pattern that approximates such ideal movement.

[0071] As used herein, a right-handed thread or helical portion is a thread or helical portion whose helix moves in a positive axial direction when the thread is turned clockwise. A right-handed thread is typically a default thread and is threaded in a positive axial direction by counterclockwise rotation, which is typically performed with the right hand. Similarly, a screw with a left-handed thread is threaded in a positive axial direction by clockwise rotation, and thus may be performed with the left hand, mirroring the movement of the right hand to operate a right-handed screw.

[0072] Embodiments of the present disclosure in which the injection device is adapted to provide multiple predetermined fixed doses will be described in detail in relation to an injection device comprising a reusable integrated needle cannula with a rinsing chamber. However, in alternative embodiments, a needle magazine as described in EP 2015 / 7959.6, entitled "An injection device with integrated needles" and filed by Novo Nordisk, may be integrated in place of a single reusable needle.

[0073] First embodiment FIGS. 1-16 illustrate a first embodiment of an injection device for delivering multiple fixed doses according to the present disclosure. FIG. 1A shows an exploded view of the injection device. FIGS. 1B-14 show further details of individual structures and mechanisms. FIGS. 15A and 15B show a series of perspective views of the injection device 100 during use, thereby illustrating user actions from receiving the device, priming the device, and delivering multiple fixed doses. FIG. 16 illustrates in detail the interrelationship of the mechanical structures during operation. As used herein, a state defines a particular arrangement or configuration of the device, and states and actions provide a framework for describing the operating principles of the device.

[0074] FIG. 1A shows the cap 105, the shield tip 119, the shield following portion 120.1 of the cleaning module 120 (see FIG. 2B), the needle hub 125 with the needle cannula 124, the housing insert portion 160, the tubular elongated needle shield structure 110, the cartridge holder 130, the cartridge 135, the tubular elongated housing structure 140, the connector 170, the shield return spring 107, the drive tube 180, the dose drive spring 108, the piston rod 109, and the spring base 165.

[0075] Housing Assembly The injection device includes a housing assembly, which provides a rigid frame with guides and connectors for guiding and connecting other device components. The housing assembly includes a housing insert 160, a tubular elongated housing structure 140, a cartridge holder 130, and a spring base 165. After final assembly, these structures are fixedly connected, and the housing assembly can provide a frame of reference for describing the relative movement and position of other structures. The elongated housing structure 140 includes internal threads for engaging with the external threads of the piston rod. The internal threads can be provided in the form of an integral nut member that is rotationally and axially fixed to the housing structure 140. In one example, the nut member is an integral part of the housing structure 140. Alternatively, the nut member can be a separate part that is secured to the housing during assembly of the injection device, for example, by gluing or welding. The nut member has an internal surface with internal threads that engage with the external threads of the piston rod 109 to cause the piston rod to move helically when rotated relative to the housing structure. Alternatively, the internal threads can be provided directly within the housing. The housing insert 160 includes a cap snap at the end of the track for bayonet attachment to the cap. The housing insert 160 further includes a proximal edge for guiding the shield. For further explanation, the housing assembly may be referred to as the housing for short, and the needle shield assembly may be referred to as the needle shield.

[0076] The injection device 100 comprises a drive mechanism and a trigger or activation mechanism. The drive mechanism comprises a piston rod 109, a drive spring 108, and a drive tube 180, the structures being operably disposed within the housing for ejecting a dose. The trigger mechanism comprises an elongated shield structure 110 and a connector 170, the structures being operably disposed within the housing for triggering the dose ejection mechanism.

[0077] Needle Shield Assembly The injection device further comprises a needle shield assembly comprising a shield tip 119 and an elongated shield structure 110. The elongated shield structure 110 comprises a window 111 for inspection of the medicament, and the elongated shield can be positioned in a first position where it overlaps the cartridge holder window 131 and in a second position where it does not overlap, with a solid portion of the elongated shield structure covering the window 131 in the second position.

[0078] Cartridge Holder Cartridge holder 130 is adapted to receive cartridge 135. The cartridge holder includes a window 131 for inspecting the medication in cartridge 135. Figure 1B shows cartridge holder 130 in profile, including an axial rib 132 for axially guiding the needle hub, a flexible arm for engaging the cartridge neck 137 (Figure 1A), and a proximally extending tab 130.1 for aligning and positioning the cartridge when inserted into the housing during assembly. A circumferentially extending flange 134 is provided on the inner surface of the distal end of the cartridge holder to provide a small axial clearance for the distal end surface of the cartridge after assembly and in the initial unpackaged state.

[0079] cartridge As further shown in FIG. 1A, elongated cartridge 135 has a distal end 135a sealed by a puncturable septum and an open proximal end 135b closed by a piston. The piston is not shown in FIG. 1. The cartridge includes a reservoir containing multiple fixed doses of medication. At distal end 135a, a septum is provided that is capped by a cap. The cap and the main portion of the reservoir are separated by a neck portion 137.

[0080] Needle Assembly The injection device further comprises a needle assembly comprising a needle hub 125 and a reusable needle cannula 124. The cannula comprises a proximal end for piercing the pierceable septum and establishing fluid communication with the reservoir, and a distal end for insertion into the skin of a subject or user of the device.

[0081] Piston washer Although not shown in FIG. 1 , a piston washer may be connected to the piston rod to provide a hold-down for contacting the piston. Alternatively, a dose measuring module for measuring relative rotation between the piston rod and the piston may be provided between the piston rod and the piston. Such a measuring module also provides a suitable hold-down. Such a dose measuring module is described in WO 2014 / 1128155, entitled "Dose capturing cartridge module for drug delivery device." Alternatively, the piston rod directly contacts the piston.

[0082] cap The cap 105 is adapted for removably mounting to the housing insert portion 160. The cap includes an inner surface having protrusions 105.2 (FIG. 16F) adapted to be guided by axial and circumferential cap mounting tracks 161, which will be described in detail later in this application. The protrusions are further adapted to cooperate with snap locks 161.1, thereby removably locking the cap 105 to the inner housing portion 160. The cap is adapted to be mounted and dismounted by continuous axial and rotational movement, thereby providing a bayonet coupling with the injection device. The inner surface of the cap 105 further includes axially extending ribs 105.1 (FIG. 16A) protruding from the inner surface and adapted to transmit torque to the shield structure 110 through axially extending ribs 116 on the outer surface of the shield, as described below with reference to FIG. 16A.

[0083] Spring base Spring base 165 is fixedly mounted at its proximal end to housing structure 140 and is adapted to receive and support compressible torsion drive spring 108 .

[0084] Drive spring The drive spring 108 is pre-tensioned or wound and positioned between the spring base and the drive tube 180. The drive spring is further adapted to induce a torque on the drive tube, thereby ejecting the medication. The drive spring includes torsion sections 108.3, 108.4, with relatively small spacing between the coils, and compressible section 108.4 adapted to transmit an axial force to the drive tube after compression and during ejection of the medication. The ability to drive the drive tube axially allows for termination of the dose mechanism and allows for resetting of the drive tube.

[0085] Return spring Connector return spring 107 is positioned between spring base 165 and connector 170 and is adapted to bias the connector in a distal direction.

[0086] Cleaning Assembly Cleaning the needle between injections allows the same integrated needle to be used multiple times in a clean condition. Therefore, in an alternative embodiment of the present disclosure, the injection device includes a cleaning assembly 120, as illustrated in FIG. 2B. The movable shield structure 110 is fixedly connected to the cleaning assembly 120 through a shield-following portion 120.1; the principles of the cleaning module are disclosed in further detail in WO 2019 / 101670. The cleaning assembly 120 includes a cleaning agent that keeps the distal end of the needle cannula 124 clean between injections. The shield-following portion 120.1 of the cleaning module is fixedly connected to a shield tip 119, which is again fixedly connected to the movably disposed elongated needle shield structure 110. The shield tip 119 can snap onto the needle shield structure 110 via resilient arms 119.1 that engage with the elongated shield structure 110, thereby allowing the washing chamber assembly 120 to follow the axial and rotational movements of the movably disposed shield structure 110. The shield structure 110, which is connected to the washing assembly 120, is movably disposed relative to a needle cannula 124 that is fixed to the housing.

[0087] Cleaning assembly 120 preferably contains a chamber with a liquid cleaning agent, which in one example may be the same preservative contained in the liquid agent in cartridge 135. In a preferred example, the cleaning agent is a pharmaceutical solution containing the same preservative as that contained in cartridge 135, which is loaded into the chamber of the cleaning module during start-up of the injection device. In an alternative embodiment, the cleaning agent is embedded within a porous plug. In a further alternative, the cleaning agent is embedded within the matrix of a solid plug.

[0088] The shield can be positioned in different positions. The initial position is defined by an initial angular position and a corresponding initial axial position. The locked position is defined by a locked angular position and a corresponding locked axial position. The unlocked distal position is defined by an unlocked angular position and a corresponding distal unlocked axial position. The movable shield can be changed by a combination of rotation and proximal movement from the initial position to a locked position in which the shield is axially locked. In both positions, the needle tip is covered by the shield and housed within the irrigation chamber assembly. During use, the shield can be further rotated and moved proximally to the unlocked distal position, thereby exposing the tip. By further moving the shield proximally, the shield exposes more of the needle and an injection can be performed. After injection, the shield is returned to the locked position, thereby irrigating the needle tip.

[0089] If for some reason it is desirable to reuse the needle without cleaning it, the cleaning module may be omitted.

[0090] Returning to the illustrated embodiment 100, FIG. 1B illustrates a perspective view of a cartridge holder 130 having proximally extending tabs 130.1 for aligning and positioning the cartridge holder 130 relative to the housing 140 when inserted into the housing during assembly. FIG. 1C illustrates an exploded view of a cleaning module 120 comprising a shield-following portion 120.1 and a movable portion 120.2 comprising a piston 122 and a piston rod 123 having a radially extending arm 123.1 for cooperating with a needle hub 125 and the shield-following portion 120.1. The radially extending arm 123.1 comprises a chamber housing engagement surface 123.2 for engaging the cleaning chamber 120 and a hub engagement portion 123.3 for engaging the hub 125. The needle-following portion 120.1 comprises a cleaning chamber housing 121 comprising a distal tubular portion, a central tubular portion, and a proximal tubular portion. The sections are integrally connected. A cap is provided on the distal end of the distal tubular section, capping the distal bulkhead onto the wash chamber housing. A shield tab 121.1 for fitting onto the shield tip 119 and a hub push tab 121.2 are provided on the outer surface of the central tubular section. Window W1 in FIG. 1C illustrates the same components in grayscale to better illustrate the sloped surface and void portion. As shown in FIG. 2B, the proximal end of the wash chamber housing 121 is provided with a sloped proximal surface guide 121.3 for guiding the piston rod 123 and piston 122 proximally in response to rotation. Window W3 in the figure confirms understanding of the mechanism that guides or pushes the piston rod proximally. The rotating piston rod 123 will provide a first well-defined axial movement by releasing static friction, further rotating it, and forcing it into the sloped surface 121.3 of the wash chamber. Shown on FIG. 2D is a detergent reservoir 121.4 for surrounding the distal end of the needle cannula in a sterile condition prior to use and in a clean condition during use.

[0091] FIG. 1D shows in perspective view the relative positioning of needle cannula 124, the movable portion of wash chamber 120.2, including piston 122 and piston rod 122, and the cartridge-engaging structure, including hard portion 126 and a soft inner plug (not shown). The soft inner plug may be made of rubber and adapted to surround the proximal end of the needle cannula in a sterile initial condition prior to use. Hard portion 126 provides support for the soft inner plug and is adapted to move the cartridge proximally when the needle establishes a fluid connection with the agent in the reservoir and in response to moving hub 125 proximally. The soft plug can be penetrated by the proximal sharp end of the needle cannula. Hard portion 126 includes a radially extending hub-engaging tab 126.1 and a radially extending cartridge-engaging tab 126.2. The rigid portion further includes a distally extending blocking portion 126.3 for blocking further axial movement of the hub when the hub is in the proximal position. As seen in FIG. 2D , the blocking portion 126.3 is adapted to engage a small recess or circumferential slit 125.7 in the hub after a small relative rotation. The rigid portion 126 includes a proximal surface at its proximal end 126b that abuts a distal surface of the assembled cartridge. Thus, proximal movement of the rigid portion 126 of the cartridge-engaging structure provides proximal movement of the cartridge.

[0092] 1E illustrates a perspective view of the needle hub 125. The hub 125 comprises a central circular disk portion 125.9 and a proximally extending skirt portion 125.11 extending from the disk portion. The skirt portion 125.11 is adapted to surround the distal end of the cartridge 135 and the cartridge-engaging structure comprising the rigid portion 126. The needle hub 125 further comprises axially extending fingers 125.1 extending proximally from the skirt portion 125.11 and adapted to cooperate with axially extending ribs 132 of the cartridge holder to permit relative axial movement and prevent relative rotational movement between the hub and the cartridge holder. Extending from the distal surface of the central disc portion 125.9 are two axial tube sections (angular segments, curved like a tube but not extending 360 degrees circumferentially) or flanges 125.12 that connect tubular portion 125.13 with the central portion 125.9. The tubular portions are adapted to surround the cleaning assembly 120. As best seen in FIG. 2D , an adhesive tower 125.10 for securing a needle cannula is centrally provided on the central disc portion 125.9. The hub 125 further includes a track provided on the skirt portion 125.11 and adapted to guide the rotational movement of the cartridge-engaging structure. The track includes a proximal axial portion 125.2 that provides an initial position for the hub-engaging tab 126.1 of the cartridge-engaging structure, and a helical portion 125.3 for rotating the tab 126.1, and thereby the rigid portion 126 of the cartridge-engaging structure, in response to guided proximal movement of the needle hub 125. The track further includes a distal axial portion 125.4 that is adapted to allow or guide relative axial movement of the tab 126.1, and thereby the rigid portion 126 of the cartridge-engaging structure, upon completion of rotation. A rib 128 is provided on the inner surface of the axially extending flange 125.12 that projects in a negative radial direction, i.e., toward the center of the hub 125. The rib 128 includes an axially extending surface 128.1 that is flush with the edge of the flange 125.12. The axially extending surface 128.1 provides a rotational stop for engagement with the piston rod 123.At the distal end of the rib 128, a circumferentially extending surface 128.2 is further provided (see also window W3 in FIG. 1F and FIG. 2D), which provides an axial stop for engagement with the pressure tab 121.2 on the chamber housing.

[0093] FIG. 1F illustrates the assembly of the modules shown in FIG. 1D with the hub 125 shown in FIG. 1E in an initial, unpackaged state before a fluid connection is established between the needle cannula and the reservoir of the cartridge 135. Note that an axial clearance is provided between the blocking portion 126.3 and the proximal surface of the central portion 125.9, allowing relative axial movement between the hub 125 and the rigid portion 126 of the cartridge-engaging structure that abuts the cartridge 135. The clearance therefore allows the needle cannula to be inserted into the cartridge in response to relative axial movement. Window W2 illustrates the entire assembly, shown in black and white on a grayscale. Window W3 illustrates the inner surfaces of the needle hub 125 and guide 128, having surfaces 128.1 and 128.2.

[0094] FIG. 2A illustrates a perspective view of the wash chamber housing 121 positioned within the needle hub 125 in an unpackaged state. A tubular portion 125.13 surrounds the proximal portion of the wash chamber housing, and a radially extending hub push tab 121.2 rests on the hub's distal support surface 127 in a first angular position. As described in detail later in this application, the needle shield is adapted to be guided in a proximal helical movement upon initialization. When the wash chamber housing is secured to the needle shield, the push tab 121.2 performs a proximal helical movement relative to the rotationally fixed needle hub in response to initialization. The needle hub is axially movable between distal and proximal positions. When the needle hub is axially movably positioned on the cartridge holder 130, the chamber housing push tab 121.2 urges the needle hub from the distal to the proximal position in response to the needle shield moving from the initial to the locked position. Furthermore, during the axial movement of the shield, the push tab 121.2 is also rotated with the shield from the initial to the locked angular position. In the locked angular position, the push tab 121.2 is angularly aligned with the notch 125.5 in the tubular portion 125.13 of the needle hub and aligned with the axial stop surface 128.2. Axial clearance is provided between the push tab 125.2 and the axial stop surface 128.2. Between the initial and locked angular positions of the shield, the hub moves a proximal distance to connect the proximal end of the needle cannula 124 with the reservoir of the cartridge 135. The proximal movement of the hub also provides rotation of the cartridge engagement structure, thereby rotating the tab 126.2 having a cam surface and forcing it into the axial clearance between the distal surface of the distal end of the cartridge and the proximal surface of the circumferentially extending flange 134 (see FIG. 1A). This increases the axial clearance between the cartridge and circumferential flange 134, urging the cartridge proximally relative to the cartridge, and deflecting the neck engagement arm 133. In the locked position of the shield, which corresponds to the proximal position of the hub 125, contact is established between the blocking portion 126.3 of the cartridge engagement structure and the central hub portion 125.9. In this position, the wash chamber housing can move proximally until it abuts against stop surface 128.2.When the shield 120.1 and shield following portion 120.1 are in the locked position, the shield following portion is adapted to move in a further proximal spiral movement with the shield to a distal unlocked position. When the shield and shield following portion 120.1 are in the distal unlocked position, the shield and shield following portion may move further in a strictly proximal direction to deliver the dose through the needle.

[0095] FIG. 2B illustrates a perspective view of the wash chamber piston rod 123 disposed within the wash chamber housing 121. As illustrated, the angled surface 121.3 on the proximal surface of the chamber housing 121 is axially aligned with the axially extending surface 123.2 of the piston rod. In this initial position, the piston rod surface 123.3 is positioned abutting the rotation stop 128.1 of the hub 125 and is therefore unable to move counterclockwise relative to the hub. Circumferential clearance is initially provided between the angled surface 121.3 and the chamber housing engagement surface 123.2, and in response to proximal helical movement of the chamber housing, the angled surface 121.3 and the engagement surface 123.2 will approach and engage each other to contact. This overcomes any static or adhesive friction between the plunger 122 and the chamber housing 123 through relative rotation. In response to further rotation of the shield to the locked position, the ramped surface induces a proximally directed force on the piston rod 123, causing the piston rod 123 and plunger to be withdrawn from the wash chamber housing.

[0096] When the plunger 136 in the cartridge 130 is positioned against the piston rod 109, proximal movement of the cartridge relative to the cartridge holder (which is part of the housing assembly) will induce an overpressure within the cartridge. If the reservoir is in fluid contact with the needle cannula, liquid will flow into the wash chamber. The additional feature of withdrawing the plunger 122 from the wash chamber housing 121 is provided to overcome adhesion friction between the plunger and the chamber housing 121, but withdrawal also adds flow between the reservoir and the chamber housing 121 when a fluid connection is established.

[0097] Housing Structure 3A and 3B illustrate perspective views of features disposed on the inner surface of tubular housing structure 140 in an axial cut of the housing. In FIG. 3B, the axial cut is provided in a plane including the central axis of window 141, while in FIG. 3A, the cut is rotated 90 degrees around the central axis, so that one of windows 141c is visible behind the cut plane. As seen in FIGS. 3C-3F, tubular housing structure 140 comprises outer tubular portion 143 and inner tubular portion 154. In the illustrated example, inner tubular portion 154 is integrally connected to the outer tubular portion. The outer tubular portion comprises an outer surface having an outer diameter and an inner surface having an inner diameter. Similarly, the inner tubular portion comprises an outer surface having an outer diameter and an inner surface having an inner diameter.

[0098] In Figures 3A and 3B, inner tubular portion 154 has been removed to provide a clearer view of the structure between outer tubular portion 143 and inner tubular portion 154. The figures illustrate a distal guide structure of housing 142 protruding from the inner surface. Distal guide structure 142 is adapted to guide shield structure 110. The figures further illustrate a central guide structure of housing 144c and a proximal guide structure of housing 146c. Central guide structure 144d, positioned 180 degrees from 144c in a rotational symmetry, is also shown in Figure 3D. Central guide structure 144 also protrudes from the inner surface and provides an integral connection between outer tubular portion 143 and inner tubular portion 154. The central guide structure is further adapted to guide connector 170 and shield structure 110. Proximal guide structure 146c forms a recess in its surface and is adapted to guide connector 170. Distal, central, and proximal guides 142c, 144c, and 146c all have corresponding rotationally positioned guides, not all of which are shown or indicated. However, for example, reference to distal guide 142 may refer to any of the rotationally positioned distal guides, and in the illustrated example 142, may refer to either or both of distal guides 142c and 142d.

[0099] The distal guide 142 includes a first axial portion 142.1, a first transverse portion 142.2, a second axial portion 142.3, a second transverse portion 142.4, and a third axial portion 142.5 that provides a rotation stop. The central guide includes a proximal transverse portion 144.1, a first axial portion 144.2, a distal transverse portion 144.3, and a second axial portion 144.4. The proximal guide includes a first axial portion 146.1, a first transverse portion 146.2, a second axial portion 146.3, a third axial portion 146.4, a ramp portion 146.5, and a flush portion 146.6. Collectively, the guide surfaces provide a closed track that allows for annular guiding of the connector. The surfaces of the lateral portions extend radially and circumferentially, the surfaces of the axial portions extend axially and radially, and the surfaces of the ramp portions 146.4 extend from the bottom of the recess to the surfaces of the coplanar portions 446.5, which extend axially and circumferentially and are coplanar with the inner surface.

[0100] FIG. 3C corresponds to the cut shown in FIG. 3A, with the inner tubular portion 154 remaining. Note that the central guide 144 is positioned within the annular space between the outer tubular portion 143 and the inner tubular portion 154. FIG. 3D illustrates a perspective view of the housing structure 140 with a tubular cut made. The tubular cut is made in a plane that includes the inner surface of the housing structure, and the cut removes structure outside that plane, thereby leaving only the structure on the inner surface visible. FIG. 3D shows an internal connecting structure 140.3 for connecting with the housing insert 160. The connecting structure 140.3 is adapted to angularly position the insert relative to the housing structure 140. FIG. 3D also shows a rib 140.1, which, together with the radial surface of the guide 142, supports the radial center position of the shield structure 110. A proximally positioned rib 140.2 supports the radial position of the return spring 107. At the proximal end, a portion of the elongated housing structure 140 is shown proximal to rib 140.2. FIG. 3E corresponds to the cutaway shown in FIG. 3B, with the inner tubular portion 154 remaining, as in FIG. 3C. FIG. 3F shows a perspective view of FIG. 3D, but the structure is viewed from a different angle revealing details of proximal guide 146c. Proximal guide 146c is seen as the peripheral edge of a recess, but the edge is positioned in a plane with the inner surface. As can be seen, guides 142, 144, 146 are provided with two-fold rotational symmetry. The guides shifted in the other direction relative to proximal guide 146c are not visible due to the angle of the perspective view.

[0101] 3A-3F collectively illustrate the technical details of the housing structure 140 according to the first embodiment. The housing's distal guide 142 is adapted to rotationally and axially guide the shield along connected guide surfaces, comprising a first axial portion 142.1, a first transverse portion 142.2, a second axial portion 142.3, and a second transverse portion 142.4. The central guide is adapted to rotationally and axially guide the connector and comprises a proximal transverse portion 144.1, a first axial portion 144.2, a distal transverse portion 144.3, and a second axial portion 144.4. As described below, the first axial portion 144.2 of the central guide 144 further provides a rotational stop for the shield 110 during injection. The proximal guide is adapted to guide the connector through an axial and rotational actuation cycle and comprises a first axial portion 143.1 adapted to provide a rotational stop and guide proximal axial movement, a first transverse portion 146.2 for guiding rotational counterclockwise movement, and a second axial portion 146.2 adapted to provide a rotational stop and, together with a third axial portion 146.3, guide distal axial movement. The proximal guide further comprises a ramp portion 146.5 and a flush portion for guiding the connector back to the beginning of an actuation or administration cycle.

[0102] Zero point adjustment mechanism 4A and 4B show perspective views of a zero-point adjustment nut 106 according to an alternative embodiment of the present disclosure. As shown, the distal face is visible at the distal end 106a in FIG. 3A and the proximal face is visible at the proximal end 106b in FIG. 3B. The adjustment nut 106 includes an internal thread 106.1 for engaging with the external threads 109.1 of the piston rod 109 and an externally threaded portion 106.2 for engaging with the internal threads 154.2 of the housing. The external threads 106.2 are provided proximally on the nut 106 in the illustrated embodiment and are shown as two externally threaded portions protruding from the outer surface. The external threads 106.2 may be made of any number of externally threaded portions. Alternatively, the threaded connections 106.2, 154.2 between the nut 106 and the housing may be replaced by purely rotational guides.

[0103] Additionally, ratchet arms 106.3 are provided on the outer surface of the adjustment nut 106. In an embodiment of the present disclosure, two ratchet arms 106.3c and 106.3d are positioned with two-fold rotational symmetry at the distal end 106a of the adjustment nut 106. Any suitable number of ratchet arms 106.3 may be provided. However, at least two rotationally symmetric ratchet arms are preferred to increase the rotational stability of the adjustment nut 106. The two-fold rotational symmetry means that a 180-degree rotation around the central axis of the nut 106 does not change the appearance of the nut 106.

[0104] FIG. 5 shows a perspective view of the elongated housing structure 140 cut in half, allowing the interior surface of the structure to be viewed. The elongated housing structure defines a distal end 140a and a proximal end 140b. As can be seen, an inner tubular portion 154 adapted to support the adjustment nut 106 is provided on the interior surface of the elongated housing structure 140. The inner tubular portion 154 is also illustrated as a half-tube due to the cut. The illustrated embodiment includes axial teeth 154.3 adapted to engage with the ratchet arms 106.3 of the adjustment nut 106, allowing the nut 106 to rotate in only one direction. The allowed rotation direction is clockwise, meaning that the interface between the ratchet arms 106.3 and the teeth 154.3 prevents counterclockwise rotation of the nut relative to the housing. The prevented or blocked direction of the adjustment nut 106 is the same direction as the direction of rotation of the piston rod as the piston rod advances distally during administration. In this way, the adjustment nut cannot be unintentionally displaced during administration.

[0105] In some embodiments, the inner tubular portion 154 further comprises an internal thread 154.2 oriented such that the adjustment nut 106 spirals proximally when rotated in the permitted clockwise direction. The threaded connection 106.2, 154.2 between the nut and the housing thereby provides additional gearing between the rotation of the adjustment nut 106 and the axial displacement of the rotationally fixed piston rod 109, which can be useful, for example, to compensate for the relatively large pitch of the threaded connection between the adjustment nut 106 and the piston rod 109.

[0106] During assembly of the injection device, it is desirable to ensure that the distance or gap between the piston rod 109 and the piston 136 within the cartridge 135 is minimized. Minimizing the gap ensures that medication is expelled from the reservoir in response to moving the piston rod 109 distally. When a washer 104 is attached to the piston rod 109, as disclosed in the preferred embodiment shown in FIG. 6 , the objective is to minimize the gap between the distal surface of the washer 104 and the proximal surface of the piston 136 so that the washer 104 and piston 136 abut one another when the injection device is positioned in a storage-enabling state and when the device is ready to be delivered to an end user. In the following, elimination of the gap will be described with reference to the piston rod abutting the piston, but the same considerations apply when the gap between the piston and washer is eliminated.

[0107] When the adjusting nut is rotated relative to the housing structure during final assembly, the piston rod 109 is advanced spirally distally until the piston rod 109 or washer 104 abuts the piston 136 inside the cartridge 135. In embodiments with a threaded connection 106.2, 154.2 between the nut and the housing, the advancement of the piston rod relative to the housing is compensated or opposed by proximal movement of the adjusting nut relative to the housing.

[0108] Rotation of the adjusting nut is preferably accomplished by using a special tool in the production line that is adapted to engage and impart rotation to the adjusting nut. In one preferred example, the piston rod 109 is positioned to engage with the adjusting nut to provide a subassembly, which is then placed within the inner tubular portion 154 of the housing. Electronic computerized equipment is then used to detect the relative position of the piston 136 within the cartridge 135 used for that particular injection device. Once the positions of the piston 136 and the piston rod 109 are obtained, the computer can determine the required angular displacement of the positioned adjusting nut 106 to position the piston rod in abutment with the piston 136 when the injection device is assembled.

[0109] During assembly, the position of the proximal end of the piston rod 104 is therefore adjusted by rotating the adjustment nut in a unidirectional interface with the inner tubular portion 154. What is important here is that the adjustment nut can be rotated in a direction that advances the piston rod 109 into contact with the piston 136.

[0110] After assembly, the piston rod 109 or washer 104 abuts the piston 136, preventing further clockwise rotation of the adjusting nut. Furthermore, in either assembled state, there is no external interface between the nut 106 and the external surroundings. Therefore, there is no possibility of contacting the external surface with an external tool and applying an external torque to the nut.

[0111] A result of the above is that the adjustment nut 106 is self-locking with respect to the housing structure and does not need to be physically secured to the housing. Therefore, it is not necessary to weld or glue the nut member 11 to the housing.

[0112] Drive mechanism FIG. 6 shows a cross-sectional view of the proximal portion of the injection device after zero-point adjustment between the piston 136 and the washer 104. The piston rod 109 is positioned in a proximal position, indicating that the first dose has not been ejected. FIG. 7 shows a perspective view of the piston rod 109, illustrating in detail the external threads 109.1 and the axial track 109.2. FIGS. 8A and 8B illustrate the drive-tube 180 in perspective views from different angles. The figures show a tab 183c protruding from the outer surface and providing structure for cooperation with the connector 170 during actuation of the drive-tube 180 and for re-locking the shield structure 110 after the dose has been ejected. The tab 183 comprises a distally oriented surface 183.1 (distal surface or distally oriented surface means that at least a component of the normal vector is oriented in the distal direction) and an axial portion 183.2 that provides an angularly oriented surface for cooperation with the connector 170. The figure also shows a helical structure 184c that protrudes from the outer surface and is adapted to axially block the connector during administration in response to an unsuccessful attempt to stop administration. Tab 183 is positioned proximal to a lateral opening provided in helical structure 184. The figure further illustrates axial surface 182c that cooperates with the housing during activation and is adapted to provide a rotational stop that defines the end of the dose. Features 182, 183, and 184 will be described in detail later in this application.

[0113] The drive tube 180 includes an inward protrusion 180.2 projecting from its inner surface and adapted to engage an axial track 109.2 of the piston rod 109. The piston rod 109 is adapted to be slidably disposed within the drive tube, thereby permitting relative axial displacement but preventing relative rotation. The drive tube 180 includes a ratchet arm 181c for engaging with teeth 165.1 on the inside of the tubular spring base 165, thereby forming a one-way ratchet interface, such that the drive tube 180 is rotatable in only one direction, which in the disclosed example is a counterclockwise direction for dispensing a dose. The ratchet arm 181c therefore prevents clockwise rotation of the piston rod 109. In the illustrated example, the drive tube includes two ratchet arms 181c, 181d arranged with two-fold rotational symmetry. The ratchet arm 181 provides a dose click during ejection in response to the drive tube 180 and piston rod 135 rotating in a counterclockwise direction.

[0114] The engagement between the piston rod 109 and the drive tube 180 prevents relative rotation. Therefore, when the adjustment nut 106 rotates clockwise during zero adjustment, the nut induces distal translation of the piston rod 109 because the drive tube is locked against clockwise rotation.

[0115] 1, in an embodiment according to the present disclosure, is disposed inside the drive tube 180 and is fixedly attached at each end to the drive tube and spring base 165. The distal end includes distal attachment means 108.1 fixedly attached to the drive tube 180 and proximal attachment means 108.2 fixedly attached to the spring base 165. The drive spring is wound or tensioned during assembly, thereby storing energy to rotate the drive tube with sufficient torque to thereby deliver multiple doses without further tension.

[0116] Incorporating a torsion spring into the drive mechanism offers several advantages. The inventors recognized that, for one embodiment configured with a compression spring, the compression spring advances into the cartridge as it releases energy. If the injection device were designed without allowing the compression spring to advance into the cartridge, the overall length of the device would increase. Therefore, in a limited-length configuration, the spring diameter is limited by the diameter of the cartridge. The inventors discovered that the torsion spring does not need to extend into the cartridge to limit the overall length of the device. Therefore, a torsion drive spring is not limited by the diameter of the cartridge or piston rod, which is advantageous in limited-length configurations.

[0117] The torsion drive spring according to an embodiment of the present disclosure is positioned proximal to the cartridge and on the outside of the piston rod 109. This allows the spring to encompass a larger volume, thereby increasing the mass, i.e., the amount of spring material (e.g., steel). In other words, the material or mass used can be increased, thereby improving performance related to long-term storage and administration. Increasing the mass can reduce the internal stress of the spring and / or flatten the spring outer diameter, thus minimizing the variability in administration time between the first and last administration of the device. The present inventors also found that when the maximum internal stress of the spring is reduced, the stress induced in the plastic components supporting the spring is also reduced, which is necessary to enable long-term storage.

[0118] The present inventors have further discovered that in one embodiment in which the torsion drive spring is disposed inside the drive tube, the drive tube can be adapted to provide dose clicks, allowing for an increase in the number of dose clicks by increasing the diameter, and therefore the number of dose clicks can be increased without extending the axial length of the device.

[0119] According to one embodiment of the present disclosure, the outer surface of the drive tube includes a dose click providing structure adapted to provide a dose click, e.g., a ratchet arm that rides on teeth provided on a surrounding structure. Alternatively, the ratchet arm is provided on a surrounding structure and teeth on the drive tube. As the circumference of the outer surface of the drive tube 180 increases with the diameter of the drive tube, the number of dose clicks also increases. In the case of a rotary drive tube, the number of dose clicks is determined as the relationship between the circumference of the drive tube and the distance between the dose click providing structure, e.g., the distance between the teeth (number of dose clicks = 2 * pi * radius / distance between teeth). Therefore, the number of dose clicks can be increased by increasing the radius, but without increasing the length of the spring and, thereby, the length of the device. In contrast, to increase the number of dose clicks of a piston driven by a compression spring disposed within the piston, the length of the compression spring must be increased. In the case of a compression spring, the number of dose clicks is determined by dividing the axial extension of the spring by the distance between the teeth (number of dose clicks = axial extension / distance between teeth).

[0120] Furthermore, the inventors of the present invention have discovered that the energy required to release the trigger mechanism, i.e., the actuation energy, is a function of the internal stress of the drive spring. Therefore, actuation of a torsion drive spring enabled dose engine requires less force than a similar design based on a compression spring.

[0121] Additionally, the inventors have found that embodiments with drive mechanisms based on torsion drive springs are easier to assemble than equivalent embodiments based on compression drive springs. Compared to compression springs, torsion springs are relatively short and therefore easier to handle.

[0122] The rotating drive tube is readily adapted to work with an electronic dose capture device, which registers the rotating structure during administration, as described in WO2019 / 110494, entitled "Drug delivery system with multipolar magnet and sensor system."

[0123] Housing insertion part 9A and 9B illustrate two different perspective views of the housing insert 160, which is fixedly attached to the distal end of the elongated housing structure 110 via alignment and snap structures 160c.3. The housing insert includes a cap attachment track 161. As can be seen, the cap attachment track 161c includes an axially extending track portion 161c.2 having proximal and distal ends and a circumferentially extending track portion 161c.3 having first and second ends. At the first end of the circumferential track, a snap lock 161c.1 is positioned, and the second end is connected to the proximal end of the axially extending track 161c.2, thereby forming a track for bayonet coupling to cooperate with an internal protrusion of the cap 105. A rotation stop 161c.4 is also provided at the second end of the track 161c. The housing insert portion 160 further includes an axially extending slit 163c on its inner surface for cooperating with an axially extending rib 116c on the outer surface of the shield, as will be described below (see FIG. 10A). The inner housing portion 160 further includes a proximal guide 162 for guiding the shield 110. The illustrated proximal guide 162d extends circumferentially and, in a counterclockwise direction, includes a helical portion 162d.1, a lateral portion 162d.2 having zero pitch, and an axial portion 162d.3. Alternatively, a threaded connection may be used for the bayonet connection.

[0124] Long and narrow shield structure 10A and 10B show perspective views of a cylindrical elongated shield structure 110 disposed inside a tubular housing 140. In FIG. 10A, the distal face of the shield structure 110 is visible, and in FIG. 10B, the proximal face is visible. FIG. 10C shows a portion of the shield structure in a side perspective view. The elongated shield structure 110 comprises a tubular portion with an outer surface having an outer diameter and an inner surface having an inner diameter. Axially extending ribs 116c are disposed on the distal end protruding from the outer surface. The ribs are adapted to cooperate with internal ribs of the cap 105 and with slits 163 on the inner surface of the housing insert portion 165.

[0125] The shield structure 110 further includes a stepped spiral guide 112 disposed on its outer surface and adapted to cooperate with the housing insert portion proximal guide 162 and the housing distal guide 142. The stepped spiral guide 112 is provided in the annular space between the outer surface of the tubular portion of the shield structure 110 and the inner surface of the housing outer tubular portion 143. The stepped spiral guide includes a continuous protruding structure extending axially and circumferentially, including a proximal lateral protruding portion, a proximal left-hand spiral protruding portion, a central lateral protruding portion, a distal left-hand spiral protruding portion, and a distal lateral protruding portion. The continuous protruding structure includes a plurality of axially and circumferentially oriented surface portions that provide guide surfaces (a circumferential surface or a circumferentially oriented surface means that at least a component of the normal vector is oriented in the circumferential direction). The surface portions can be seen in FIG. 10 and are referred to by the following terms and reference numbers: a proximal axial guide portion 112.1, a first proximal lateral guide portion 112.2, a second proximal lateral guide portion 112.3, a first proximal helical guide portion 112.4, a second proximal helical guide portion 112.5, a first central lateral guide portion 112.6, a second central lateral guide portion 112.7, a first distal helical guide portion 112.8, a second distal helical guide portion 112.9, a first distal lateral guide portion 112.10, a second distal lateral guide portion 112.11, and a distal axial guide portion 112.12. In this manner, guide portions 112.2, 112.4, 112.6, 112.8, and 112.10 provide the distal surface of stepped spiral guide 112, and guide portions 112.3, 112.5, 112.7, 112.9, and 112.11 provide the proximal surface.

[0126] The elongated shield structure 110 further includes a proximal guide 114 positioned at a proximal end of the shield structure 110. The distal face is visible in FIG. 10A, and the proximal face is visible in FIG. 10B. The proximal guide 114 is adapted to cooperate with the housing connector 170 and the central guide 144. The proximal guide 114 extends axially and circumferentially and includes a first left-handed helical portion 114.1, a first right-handed helical portion 114.2, a second right-handed helical portion 114.3, a second left-handed helical portion 114.4, a first axial portion 114.5, a first lateral portion 114.6, a second axial portion 114.7, a third axial portion 114.8, and a second lateral portion 114.9.

[0127] Guide portions 114.1-114.9 are all surface portions, with guide portions 114.1, 114.2, 114.3, 114.4, and 114.9 providing the proximal face of proximal guide 114, and surface portion 114.6 providing the distal face, i.e., visible from proximal and distal positions, respectively. Proximal face guide portions 114.1, 114.2, 114.3, and 114.4 are adapted to cooperate with the connector during actuation.

[0128] The guide portion 114.6 on the distal surface of the proximal guide is adapted to cooperate with the connector during administration in response to premature release of pressure on the shield, which will be described in detail later in this application.

[0129] The third axial portion 114.8 is adapted to cooperate with the central guide 144 of the housing to provide a rotational stop and prevent further counterclockwise rotation of the shield relative to the housing and during administration. Similarly, the second transverse portion 114.9 provides an axial stop that cooperates with the central guide 144 to prevent further proximal movement of the shield during administration.

[0130] Proximal guide 114 includes a locking structure 115 comprising guide portions 114.4 and 114.5, which in the illustrated embodiment is part of a hook-like structure that is adapted to releasably lock onto a corresponding hook-like structure of connector 170 during administration, as will be described in detail below.

[0131] The shield further comprises a click arm 113, with an axial surface portion 113.1 providing a rotation stop. In an initial state, the click arm is radially compressed by the inner surface of the housing insert 160.

[0132] connector 11A and 11B show perspective views of connector 170 disposed inside tubular housing 140 and between elongated shield structure 110 and drive-tube 180. Connector 170 is adapted to establish a connection between the shield and drive-tube and to actuate drive-tube 180. Connector 170 is further operably connected with an automatic relocking mechanism adapted to automatically relock the shield at the end of a dose. Connector 170 includes a distal guide 172 adapted to cooperate with shield proximal guide 114. Distal guide 172 extends circumferentially and axially and includes a left-handed helical portion 172.1, a right-handed helical portion 172.2, a first axial portion 172.3, a lateral portion 172.4, and a second axial portion 172.5.

[0133] Guide portions 172.1-114.5 are all surface portions, with guide portions 114.1 and 114.2 providing the distal face of distal guide 172 and surface portion 172.4 providing the proximal face. Distal face guide portions 172.1 and 172.2 are adapted to cooperate with the shield's proximal guide during actuation. Proximal face guide portion 172.4 is adapted to cooperate with the shield's proximal guide guide portion 114.6 during administration in response to premature release of pressure on the shield, as will be described in detail later in this application.

[0134] The return spring 107 biases the connector distally, and therefore the left-handed helical portion biases the connector clockwise and the shield counterclockwise in response to establishing engagement between the left-handed helical portion 172.1 and the first left-handed helical portion 114.1 of the shield's proximal guide or establishing engagement between the left-handed helical portion 172.1 and the second left-handed helical portion 114.1 of the shield's proximal guide.

[0135] Distal guide 172 includes a locking structure 171 including a left-handed helical portion 172.1 and a first axial portion 172.3. Locking structure 171 is part of a hook-like structure adapted to releasably lock with a corresponding hook-like structure on proximal guide 114 of the shield. A releasable lock between the hook-like structures is established in response to second left-handed helical portion 114.4 of locking structure 115 of the shield abutting left-handed helical portion 172.1 of locking structure 171 of the connector under axial compression from return spring 107. This biases the shield in a counterclockwise direction, biases the connector toward a counterclockwise direction, and establishes abutment between first axial portion 172.3 of the connector and first axial portion 114.5 of the shield. To unlock, the friction established in the abutment between the two left-handed helical portions 114.4 and 172.1 must be overcome in response to counterclockwise rotation of the connector.

[0136] Connector 170 comprises a tubular portion 170.1 having a full 360-degree circumference and two axially extending tubular portions 170.2 formed by two notches in the tubing, thereby providing only a fraction of the circumference. Connector 170 has an outer surface having an outer diameter and an inner surface having an inner diameter. As illustrated in FIGS. 12A and 12B, which are cross-sectional views of the proximal end of the injection device, the outer surface of the connector is positioned in close proximity to the inner surface of the housing's outer tubular portion 143. The connector surrounds the housing's inner tubular portion 154 and the drive tube 180. The inner diameter of the connector is larger than the outer diameter of the tubular portion of the shield structure 110; therefore, guide portions 172.1-172.4 are provided with shoulders projecting in a negative radial direction to allow contact between the shield's proximal guide 114 and the connector's distal guide 172.

[0137] The connector further includes a central guide 174 adapted to cooperate with the housing's central guide 144, thereby controlling the position of the connector relative to the housing. The connector's central guide extends axially and circumferentially and includes a first axial portion 174.1 providing a rotational stop, a first lateral portion 174.2, a second axial portion 174.3, a left-handed helical portion 174.4, a third axial portion 174.5, a fourth axial portion 174.6, and a second lateral portion 174.7.

[0138] Connector central guide 174 defines a blocking structure comprising a second lateral portion 174.7 adapted to prevent unintentional axial movement of the connector and thereby unintentional actuation of drive-tube 180.

[0139] The central guide 174 further defines a seat or locking structure 173 including a first lateral portion 174.2 and a second axial portion 174.3, the locking structure adapted to provide a rotational lock to prevent rotation and distal movement of the connector in an initial position in which the connector 170 is in its distal-most position.

[0140] Connector 170 further includes an actuation tab 178 disposed on the inner surface and extending radially from the inner surface in a negative radial direction. Actuation tab 178 includes a first lateral portion 178.1 providing a proximal contact surface adapted to actuate drive tube 180. Actuation tab further includes an axial portion 178.2 adapted to release the automatic relocking mechanism in response to a clockwise impact from drive tube 180, and a second lateral portion 178.3 providing a retention portion to prevent split doses in response to premature release of pressure against the shield.

[0141] The connector further includes a proximal guide in the form of a click arm 176 adapted to cooperate with the housing's proximal guide 146. A circle surrounding the two-fold symmetrically arranged click arms 176c and 176d in their relaxed state defines a diameter greater than the connector's outer diameter and greater than the housing's inner diameter. Thus, in response to placing the connector 170 inside the housing's outer tubular portion 143 with the click arm 176 in contact with the inner surface, the click arm is deflected in a negative radial direction. In this position, the click arm 176 exerts a radial force radially on the housing's inner surface. The click arm includes a first axial portion 176.1 for cooperating with the housing's proximal guide's axial guide portions 146.1 and 146.3, and an axially and circumferentially extending outer surface portion 176.2 adapted to cooperate with the axial portion 146.4, the ramp portion 146.5, and the flush portion 146.6.

[0142] Proximal portion of the injection device Returning to Figures 12A and 12B, Figures 12A and 12B illustrate cross sections of the proximal end of the device. Figure 12A illustrates a central cross section with windows 141 (although they are located on the distal portion of the device, not visible in Figure 12). Figure 12B illustrates a central cross section rotated 90 degrees relative to Figure 12A. Drive-tube 180, as shown in Figure 12B, comprises four tubular sections: first tubular section 185, second tubular section 186, third tubular section 187, and fourth tubular section 188.

[0143] The first tubular portion 185 is also a distal tubular portion and is disposed inside the inner tubular portion 154 of the housing. The distal tubular portion comprises an outer tubular portion 185.1 in contact with the inner tubular portion 154. The outer tubular portion 185.1 is connected to the second tubular portion 186 and further comprises an axial surface portion 182c adapted to define the end of the dose and to cooperate with the housing during activation. The outer tubular portion 185.1 further comprises a distal helical surface portion 189c adapted to cooperate with the proximal helical surface portion of the inner tubular portion 154 of the housing during administration (see also FIG. 8A). The distal tubular portion 185 further comprises an intermediate tubular portion 185.2 extending proximally. A proximal portion of the intermediate tubular portion 185.2 is surrounded by a second tubular portion 186, thereby defining an annular spring receiving space that provides a distal base for the drive spring 108. An outer surface of the proximal portion of the intermediate tubular portion 185.2 defines a spring snap 180.2 for axially fitting onto the drive spring 108 in response to axial insertion of the drive spring into the annular spring receiving space. The distal tubular portion 185 further includes an inner tubular portion 185.3 extending distally from the intermediate tubular portion and including an inward protrusion 180.2 adapted to engage an axial track 109.2 of the piston rod 109.

[0144] Second tubular portion 186 includes protruding helical structures 184c and 184d on its outer surface. Second tubular portion 186 further includes axial surface portion 182d, which is arranged in two-fold rotational symmetry with axial surface portion 182c and adapted to cooperate with the housing during activation and to define the end of the dose. Second tubular portion 186 further includes distal helical surface portion 189d, which is arranged in two-fold rotational symmetry with distal helical surface portion 189c and adapted to cooperate with proximal helical surface portion 157d of inner tubular portion 154 of the housing during administration (see also FIGS. 8A and 13A). Protruding helical structure 184 protrudes from the outer surface of second tubular portion 186 and extends to the inner surface of connector 170. The helical structure 184 is adapted to axially block the connector during administration in response to premature release of pressure on the connector, whereby the helical structure 184 blocks axial movement of the activation tab 178 that protrudes inward from the inner surface of the connector 170.

[0145] The second tubular portion 186 and the third tubular portion 187 are surrounded by the return spring 107. Together with the inner tubular portion 165.2 of the spring base 165, the second and third tubular portions 186, 187 define an annular space that houses a portion of the drive spring 108. The fourth tubular portion 188 of the drive tube 180 is also the proximal tubular portion and includes a ratchet arm 181c for engaging the teeth 165.1 inside the outer tubular portion 165.3 of the spring base.

[0146] Starting mechanism FIG. 13A illustrates a perspective view of housing inner tubular portion 154 and drive-tube 180, with distal tubular portion 185 inserted within inner tubular portion 154 and therefore not visible in the figure, where drive-tube 180 is in a home position. Before the first dose, the home position is also referred to as the start position. After the first dose, the home position is also referred to as the end position of the dose. FIG. 13B illustrates a cross-section taken along line CC as shown, viewed from the proximal end. FIG. 13C illustrates cross-section CC as viewed from the distal end.

[0147] FIG. 13A further illustrates actuation tab 178 on the inner surface of connector 170 (only the tab; the rest of the connector is not shown in FIG. 13A ). The connector with actuation tab 178 is positioned so that it contacts protruding tab 183, ready to impart proximal movement to the drive tube, thereby actuating the drive tube. Drive tube 180 is biased distally and counterclockwise by a drive spring. In FIG. 13A , the drive tube is illustrated in a rest position, with axial surface portion 182 abutting axial surface portion 156 of housing inner tubular portion 154, thereby preventing counterclockwise rotation of drive tube 180. In the rest position, distal helical surface portion 182 also abuts proximal helical surface portion 157 of housing inner tubular portion 154, thereby preventing distal movement of drive tube 180.

[0148] 13D illustrates in detail the proximal end of helical surface portion 157d.1, which defines the beginning of the helical dispensing actuation, and the distal end of helical surface portion 157d.2, which defines the end of the helical dispensing actuation. Similarly, distal helical surface portion 189d defines a leading point or edge 189d.1 and a trailing point or edge 189d.2. In response to moving the connector proximally, actuation tab 178 induces proximal movement of drive tube 180 when it is positioned in abutting contact with protruding tab 183. This causes leading edge 189d.1 to move proximally along axial surface portion 182d until it passes the proximal end of the axial surface portion and reaches start point 157d.1 of the helical dispensing trajectory. Counterclockwise biasing of drive-tube 189 causes drive-tube 189 to rotate in a counterclockwise direction, and distal biasing causes leading edge 189d.1 to contact the helical dose trajectory of inner tubular portion 154. The drive-tube with leading edge 189d.1 then travels in a distal spiral motion along the helical dose trajectory until it reaches end point 157d.2. A small depression can be seen at end point 157d.2 of the helical dose trajectory. However, because the depression is smaller than the extension of helical surface portion 189d, it does not affect the helical movement of leading edge 189d.1. The same effect can be achieved with angularly shifted surface portion 182c and distal helical surface portion 189c.

[0149] Cross section of the injection device in the activated state Figures 14A and 14B illustrate cross sections of injection device 100. Figure 14A corresponds to Figure 12A and illustrates a central cross section with window 141. Figure 14B illustrates a central cross section of the device after a 90 degree rotation relative to the view of Figure 14A. Drive-tube 180 comprises four tubular sections, as shown in Figure 12B.

[0150] 14 illustrates device 100 in an actuated state, with the shield rotated to actuate the device. The shield moved proximally in a spiral motion along with needle assembly 120. The proximal movement of the shield induced proximal movement of needle hub 125, thereby causing needle 124 to establish a fluid connection with the reservoir within cartridge 135. Cartridge 135 and plunger 136 were also moved proximally, and the plunger was stopped from moving proximally due to abutment with washer 104, thereby filling the chamber of cleaning assembly 120 (washer 104 is shown in FIG. 6 but not in FIG. 14).

[0151] Device operation Figure 15 is used to explain the operating principle of an embodiment of the present disclosure from a user's perspective, and a more detailed explanation of the operating principle will be given below with reference to Figure 16. Figure 15A shows a user operation of the injection device 100 to obtain a first dose, and Figure 15B shows operation to obtain a subsequent dose, which can be any of the fixed doses in a sequence between the first and last dose of the plurality of fixed doses. The injection device may be stored and delivered in secondary packaging, and in the unpackaged state (A1), the injection device has been unpacked from the secondary packaging.

[0152] As illustrated in FIG. 15A , when a user desires to obtain a first fixed dose, the injection device is unpackaged, thereby providing it in an unpackaged state (A1). The injection device is then activated by the user. Activation can be accomplished by grasping the device's main portion 102 with the right hand and the cap 105 with the left hand. The user then rotates the cap counterclockwise (for the illustrated example). This causes the cap to disengage the cap snap 161.1 of the housing assembly and engage the needle shield, causing the needle shield to follow the rotation of the cap 105 until the cap 105 is rotated to the rotation stop 161.4. Due to the shield's stepped spiral guide 112 and the housing assembly's proximal guide 162, the needle shield undergoes combined proximal and rotational movement in response to the user rotating the cap. Furthermore, this initial rotation of the cap and the combined rotation and proximal movement of the needle shield cause the needle cannula 124 to puncture the septum of the cartridge 135, thereby establishing fluid communication with the medication reservoir within the cartridge 135. This action also displaces the cartridge 135 proximally, forcing it against the piston rod 109 or piston washer 104. With the cannula establishing the fluid connection and the piston positioned against the piston rod, the integrated needle is primed, as will be described in detail below. When the cap reaches the rotation stop, the injection device is positioned in the unlocked cap and in the actuation state (B1), with the cap unlocked and positioned for removal. The actuation state is also shown in cross section in FIG. 15.

[0153] In the following step, the user pulls the cap 105 of the injection device, which places the injection device in the uncapped state (C1) and the shield is locked against axial translation.

[0154] The user then manually rotates the shield counterclockwise, thereby placing the device in the shield unlocked state (D1), where the shield can be placed in the unlocked position and pushed proximally into the housing. Due to the guide between the shield and the housing 112, 162, the shield undergoes combined proximal and rotational movement when operated between the capped state and the shield unlocked state. During the needle shield's rotational unlocking movement, the needle shield does not cover the cartridge inspection window 141 in the housing, thereby allowing the medication in the cartridge to be inspected. In addition, the piston 136 is also visible through the inspection window 141, and the position of the piston 136 relative to the fixed dose markings on the housing indicates the piston's progression during use, thereby indicating the number of fixed doses remaining in the reservoir. In FIG. 15A, in the shield unlocked state (D1), the piston 136 is placed in its initial position, with four doses remaining in the reservoir. During proximal movement of the needle shield, the distal end of the needle tip protrudes through a septum at the distal end of the cleaning assembly 120, thereby relieving any excess pressure on the needle.

[0155] The user then presses the needle shield against the injection site, displacing the shield and connector 170 proximally against the force of the shield return spring 107. This inserts the needle into the patient's skin or subcutaneous layers. This action causes axial movement of the shield to trigger the drive mechanism, and a fixed dose is delivered through the needle cannula in the dosed state (E1). At the end of the dose, the piston 136 has moved to the next position indicated by the fixed dose remaining scale on the housing, and the injection device can be removed from the injection site. A notched window in the remaining scale indicates the piston in its next position. As the piston 136 progresses through the dosed state, it may be useful to define metastable states for each dosed state, i.e., an initial dosed state (E2.1) and a final dosed state (E2.2), where the piston is in a pressurized proximal position and a relaxed distal position, respectively.

[0156] After the dose is completed, the user removes the device from the skin, thereby releasing pressure from the shield. Consequently, the shield moves distally due to the action of return spring 107. Due to guides 112, 162 between the shield and the housing and guides 114, 142 between the shield and the connector 170, the shield undergoes distal translation and then a combined distal and rotational movement, which causes the shield to automatically return to the relocked state (F1).

[0157] The user then applies the cap 105 by axial movement to place the device in the capped state (G1), which is the last state shown in the sequence shown in Figure 15 A. The cap-unlocked and capped states technically differ within the same sequence in that the cartridge contains fewer doses in the capped state.

[0158] Finally, the cap is turned, thereby snap-locking onto the housing assembly, into the cap-locked state (A2) illustrated in FIG. 15B.

[0159] The cap-locked state (A2) differs from the out-of-box state (A1) in that the device has been triggered. This is illustrated in FIGS. 15A and 15B, where the shield in state (A2) is shifted proximally and rotationally compared to the shield's position in state (A1). Furthermore, in state (A2), the cartridge contains fewer doses than in state (A1). When the user turns the cap to obtain a subsequent dose, the cap is rotated to the cap-unlocked position without rotating the shield, because the shield has already been rotated to the triggered but axially locked position. The cap-unlocked state (B2) differs from the cap-unlocked state (B1) in that in state (B2), the cartridge contains fewer doses than in state (B1); corresponding differences can be observed between C1-C2, D1-D2...G1-G2, A2-A3, B2-B3..., etc. This pattern of movement can continue until the final dose is delivered and it becomes impossible to trigger the drive mechanism again.

[0160] Detailed description of the device's operation 16A-16T collectively illustrate the relative and functional arrangement of different structures during a series of states of injection device 100, thereby illustrating in detail the operation of the device.

[0161] In one embodiment of the present disclosure, an injection device 100 for sequentially delivering multiple fixed doses comprises a housing including an elongated housing structure 140, a cartridge holder 130, and a housing insert 160, an internal thread, a shield including an elongated shield structure 110 and a needle tip 119, a needle hub 125 including a fixedly attached needle cannula 104, a cap 105 adapted to be removably mounted on the housing and cover the distal end of the shield, a cartridge 135 having a movably disposed cartridge plunger 136, and a drive mechanism including a torsion drive spring 108, a drive tube 180, and a piston rod 109 having an external thread for cooperating with the internal thread of the housing, the piston rod being disposed in connection with the plunger 136, and the torsion spring being adapted to provide torque for rotating the drive tube 180 relative to the housing. The drive tube includes a ratchet mechanism that ensures rotation in the administration direction and blocks rotation in the non-administration direction. The drive tube is axially splined to the piston rod, thereby permitting relative axial movement and preventing relative rotation. The drive tube is adapted to advance the piston rod in response to rotating the drive tube in a dispensing direction, and due to the threaded connection with the housing, the piston rod is adapted to advance the plunger 136 within the cartridge 135 to eject a fixed dose. The drive mechanism is adapted to be activated by changing the drive tube from a distal position, in which the drive mechanism is in a stationary mode, to a proximal position, in which the drive mechanism is in a dispensing mode. In the distal position, the drive tube is rotationally locked to the housing. In the proximal position, the drive tube is rotationally unlocked from the housing, and applied torque can rotate the drive tube through a predetermined angle to eject a fixed dose. In the stationary mode of the drive mechanism, the piston rod is rotationally and axially locked, the piston rod being rotationally locked to the housing through the splined connection with the drive tube 180 and axially locked through the threaded connection with the housing.

[0162] The torsion spring is pre-tensioned to deliver multiple doses without binding during use. The drive mechanism is adapted to change modes upon activation, and as described below, the drive mechanism is adapted to be repeatedly activated until the last dose is expelled.

[0163] The cap can be placed in an axially locked position and an axially unlocked position. The cap can be repositioned by rotating the cap relative to the housing. When the cap is in the axially unlocked position, the cap can be removed from the housing.

[0164] The needle hub 125 is movably disposed on the housing and can be moved between a distal position and a proximal position relative to the housing. The needle hub 125 is disposed in connection with the cartridge and is rotationally locked relative to the housing. When the needle hub is in the distal position, the proximal end of the needle cannula is disposed distal to the puncturable septum of the cartridge. With the needle hub 125 in the proximal position, the needle cannula extends through the septum and is positioned in fluid communication with the cartridge reservoir. In response to moving the needle hub from the distal to the proximal position, the needle cannula punctures the septum of the cartridge, moving the cartridge a proximal distance relative to the housing and the axially locked piston rod.

[0165] The shield can be positioned in different positions. The initial position is defined by an initial angular position and a corresponding initial axial position. The locked position is defined by a locked angular position and a corresponding locked axial position. The unlocked distal position is defined by the unlocked angular position and a corresponding distal unlocked axial position. The unlocked proximal position is defined by the unlocked angular position and a corresponding proximal unlocked axial position. In the initial position, the shield is adapted to prevent axial and clockwise movement and to allow counterclockwise movement. In the locked position, the shield is adapted to prevent clockwise and axial movement. In this position, the shield is further adapted to allow counterclockwise rotation. In the unlocked distal position, the shield is adapted to prevent counterclockwise and distal movement of the shield and further adapted to allow proximal movement. In the unlocked distal position, the shield is further adapted to allow clockwise rotation if the applied torque exceeds a predetermined threshold. When the shield is in the initial and locked positions, the needle tip is covered by the shield. In the unlocked position, the shield is adapted to be moved proximally from the unlocked distal position, where the needle tip is not covered by the shield and pressure in the reservoir can be released, to the unlocked proximal position, where the needle tip extends further from the shield and can be inserted into the subject's subcutaneous layer. The shield can be manually operated between different positions by a user. As viewed with respect to the shield in the initial, locked, distal unlocked, and proximal unlocked positions, a set of four different angular and axial positions is defined, i.e., three different angular positions and four different axial positions.

[0166] The connector can be placed in an initial position defined by an initial angular and axial position, which is rotationally locked and positioned in the housing's central guide 144, which also prevents distal movement of the connector. The connector is biased distally by a return spring 107.

[0167] 16A-16T collectively illustrate the injection device 100 positioned in different states and intermediate positions, with the outer portions of the housing and cap cut away to illustrate portions of the internal structure.

[0168] Figure 16A illustrates the injection device in an unpackaged state, showing the cap 105, shield structure 110, housing insert 160, cartridge holder 130, connector 170, drive tube 180, and return spring 107, as well as the spring base 165. In Figure 16A, reference numerals are also provided for the proximal guide 162 of the housing insert, the stepped spiral guide 112 of the shield, and the distal guide 142 of the housing. A user receives the device from a pharmacy and unpacks the device from the secondary packaging. By unpacking, the user has provided the injection device in an unpackaged state.

[0169] Figures 16B-16E collectively illustrate intermediate positions between the unwrapped state illustrated in Figure 16A and the cap unlocked state illustrated in Figure 16F. In Figure 16B, reference numerals are provided for details of the proximal guide 162 and the distal guide 142, specifically, helical portion 162.1, lateral portion 162.2, axial portion 162.3, first axial portion 142.1, first lateral portion 142.2, second axial portion 142.3, and second lateral portion 142.4. Reference numerals are provided for details of the stepped helical guide 112 in Figures 16C and 16E. Specifically, the proximal axial guide portion 112.1, the first proximal lateral guide portion 112.2, the second proximal lateral guide portion 112.3, the first proximal helical guide portion 112.4, the second proximal helical guide portion 112.5, the first central lateral guide portion 112.6, the second central lateral guide portion 112.7, the first distal helical guide portion 112.8, the second distal helical guide portion 112.9, the first distal lateral guide portion 112.10, the second distal lateral guide portion 112.11, and the distal axial guide portion 112.12. Reference numerals for details of the shield's proximal guide 114 are shown in FIG. 16DC. Specifically, the shield has a first left-handed helical portion 114.1, a first right-handed helical portion 114.2, and a second right-handed helical portion 114.3. The reference numerals for the details of the distal guide 172 of the connector are shown in Figure 16C, in particular the left helical portion 172.1, the right helical portion 172.2 and the first axial portion 172.3.

[0170] Unpacked state The first user action is to rotate the cap counterclockwise until it reaches the cap axial unlocked position, which causes the shield to change from the initial position to the locked position, which causes the device to change from the unwrapped state, through several intermediate positions, to the cap unlocked state, also called the shield actuation state.

[0171] More specifically, Figure 16A illustrates the configuration of the injection device as provided in the unpackaged state. The cap 105 is disposed in an axially locked position and the shield is disposed in an initial position. A small circumferential clearance is provided between the axially extending rib 116 protruding from the inner surface of the cap and the axially extending rib 105.1 protruding from the outer surface of the shield. The protrusion on the inner surface of the cap 105.2 is removably retained in the cap mounting track 161 by a snap lock 161.1.

[0172] FIG. 16B illustrates a first intermediate configuration of the injection device. Circumferential clearance is eliminated by rotation, and abutment is provided between the axially extending rib 116 of the cap and the axially extending rib 105.1 of the shield. Further rotation transmits torque from the cap to the shield. In the first intermediate configuration, circumferential clearance is provided between the first proximal helical guide 112.4 of the shield and the helical portion 162.1 of the housing insert, allowing relative counterclockwise rotation between the shield and the housing. Furthermore, only a small axial clearance is provided between the first proximal lateral guide portion 112.2 of the shield and the lateral portion 162.2 of the housing, preventing distal movement of the shield beyond the axial clearance. Similarly, only a small axial clearance is provided between the second proximal lateral guide portion 112.3 of the shield and the first lateral portion 142.2 of the housing, preventing proximal movement beyond the axial clearance.

[0173] 16C, the circumferential clearance between the stepped spiral guide 112 and the proximal guide 162 of the housing is eliminated, providing abutment between the first proximal spiral guide 112.4 of the shield and the spiral portion 162.1 of the housing. In this position, a circumferential clearance is further provided between the second proximal lateral guide portion 112.3 of the shield and the first lateral portion 142.2 of the housing, thereby preventing the lateral portion 142.2 from blocking axial movement.

[0174] In the third intermediate position of the injection device illustrated in FIG. 16D, the shield is further rotated. In response to the rotation, the abutment between the shield's spiral guide portion and the housing provides a combined rotational and proximal movement relative to the housing. Thus, the stepped spiral guide 112 is moved proximally along the spiral guide portion 162.1. The stepped spiral guide portion has leading and trailing edges defined according to the direction of relative movement between the shield and the housing. Due to the relative movement, the area of ​​abutment progressively decreases until the trailing edge of the first proximal spiral guide portion 112.4 reaches the proximal edge of the spiral portion 162.1. In this position of minimum abutment, the abutment between the stepped spiral guide and the housing shifts from an abutment between the spiral portions to an abutment between the lateral portions, thereby guiding the shield in pure rotation in response to further counterclockwise rotation. In FIG. 16D , an abutment between the shield's first proximal helical guide portion 112.4 and the housing's helical portion 162.1 is provided between the distal portion (near the trailing edge) and the trailing edge of the first proximal helical guide portion 112.4. Furthermore, as illustrated in FIG. 16D , the connector is positioned in an initial angular and axial position, rotationally locked to the housing and prevented from distal movement, and the connector is biased distally by the return spring 107. Due to the proximal helical movement of the shield, a rest position abutment is established between the shield's proximal guide's first left-handed helical portion 114.1 and the connector's left-handed helical portion 172.1. In this position of the shield, a small axial clearance is provided between the second proximal helical guide portion 112.5 and the first lateral portion 142.2, thereby preventing pure axial movement in the proximal direction beyond the clearance.

[0175] In the fourth intermediate position of the injection device illustrated in FIG. 16E, the shield is further rotated. The contact between the lateral portion of the stepped spiral guide 112 and the housing provides a pure rotation. Therefore, the stepped spiral guide 112 is moved counterclockwise along the lateral portion 162.2. The lateral guide portion 162.1 defines first and second edges, with the second edge being in a counterclockwise position relative to the first edge. The first central lateral portion 112.6 has leading and trailing edges defined in accordance with the direction of relative movement between the shield and the housing. Due to the relative movement, the area of ​​contact progressively decreases until the trailing edge of the first central lateral guide portion 112.6 reaches the second edge of the spiral portion 162.2. In this position of minimum abutment, the abutment between the stepped helical guide and the housing is shifted from abutment between the lateral portions to abutment between the helical portions, thereby guiding the shield in helical motion in response to further counterclockwise rotation. In FIG. 16E, abutment is provided between the first central lateral guide portion 112.6 of the shield and the lateral portion 162.2 of the housing between the center and rear edges of the guide portions. In the illustrated arrangement, a small axial clearance is provided between the second central lateral guide portion 112.7 and the first lateral portion 142.2 of the housing, thereby limiting proximal motion.

[0176] Cap unlocked, shield activated and locked As illustrated in FIG. 16F, in the cap unlocked and shield locked state, the cap 105 is positioned in the axial unlocked position and the shield is positioned in the locked position. The cap is positioned with the protrusion 105.2 on the inner surface of the cap at the second end of the circumferential track portion 161.3, such that the protrusion 105.1 is angularly aligned with the axial track portion 161.2 and can be moved distally. The shield is positioned in the locked position, and abutment is established between the stepped helical guide 112 and both the lateral portion 162.2 and the helical portion 162.1. In addition to the abutment between the first left-handed helical portion 114.1 of the shield's proximal guide and the first left-handed helical portion 172.1 of the connector, an additional abutment is provided between the first right-handed helical portion 114.2 and the right-handed helical portion 172.2. Due to the proximal movement of the shield, the connector has been moved proximally relative to its initial axial position and against the biasing force of spring 107. The connector is still rotationally locked. To prevent clockwise rotation toward the unwrapped state, the axial surface portion 113.1 of the click arm abuts the axial portion 162.3 of the housing. The click 113 is radially biased from its compressed state behind the housing insert portion 162.

[0177] The cap is removed A second user action is to pull the cap distally, which causes the device to change from the cap unlocked state to the cap removed state.

[0178] In the state illustrated in Figure 16G, the cap has been removed from the main part 102 of the injection device shown in Figure 16F. The position of the shield has not changed relative to the arrangement in Figure 16F and is still in the locked position. The shield is locked axially but is allowed to perform a proximal helical movement guided by the abutment between the stepped helical guide 112 and the helical part 162.1 of the housing.

[0179] Shield unlocked A third user action is to rotate the shield in a locked position counterclockwise until it reaches the unlocked position, thereby changing the device from an uncapped state to a shield unlocked state through several intermediate positions.

[0180] FIG. 16H illustrates a first intermediate position in which the shield is rotated. In response to rotation, the abutment between the shield's spiral guide portion and the housing provides combined rotational and proximal movement relative to the housing. Thus, the stepped spiral guide 112 is moved proximally along the spiral guide portion 162.1. The stepped spiral guide portion has leading and trailing edges defined according to the direction of relative movement between the shield and the housing. Due to the relative movement, the area of ​​abutment progressively decreases until the trailing edge of the first distal spiral guide portion 112.8 reaches the proximal edge of the spiral portion 162.1. At this position of minimum abutment, the abutment between the stepped spiral guide and the housing shifts from an abutment between the spiral portions to an abutment between the lateral portions, thereby guiding the shield in pure rotation in response to further counterclockwise rotation. In FIG. 16H, abutment between the shield's first distal helical guide portion 112.8 and the housing's helical portion 162.1 is provided between the proximal portion (near the leading edge) and the trailing edge of the first distal helical guide portion 112.8. Additionally, in the shield's position illustrated in FIG. 16H, abutment is established between the shield's proximal guide's first left-handed helical portion 114.1 and the connector's first left-handed helical portion 172.1. In this shield position, a small axial clearance is provided between the second proximal helical guide portion 112.5 and the first lateral portion 142.2, thereby preventing pure axial movement in the proximal direction beyond the clearance. Due to the shield's proximal helical movement, the connector abutting the shield has been moved further in the proximal direction. Due to the rotational movement of the shield and the connector being rotationally locked by the central guide 144 of the housing, the shield 110 rotates relative to the connector 170, causing the right-handed spiral portion 172.2 to slide along the first right-handed spiral portion 114.2, thereby moving the first left-handed spiral portion 172.1 out of contact with the first left-handed spiral portion 114.1 of the proximal guide of the shield.

[0181] From the first intermediate position shown in FIG. 16H to the shield unlocked position shown in FIG. 16K1, the shield rotates in a proximal spiral motion guided by the first distal helical portion 112.8, followed by a pure rotational motion guided by the first lateral portion 112.10. An arrangement for guiding the pure rotational motion is illustrated in FIG. 16J. Proximal rotational movement of the shield 110 relative to the housing 140 moves the shield 110 relative to the connector 170, and the shield moves the connector relative to the housing. The right-hand helical portion 172.2 slides from the first right-hand helical portion 114.2 (FIG. 16H) along the second right-hand helical portion until the trailing edge of the helical portion 172.2 reaches the proximal edge of the second right-hand helical portion (FIG. 16J). As the trailing edge passes, the connector's distal guide locking structure 171 moves into engagement with the shield's proximal guide locking structure 115, establishing a new abutment between the second left-handed helical portion 114.4 and the connector's left-handed helical portion 172.1 ( FIG. 16K1 ). Because the left-handed helical portions 114.4, 172.1 of the locking structures 115, 171 are abutting under the biasing force of the return spring 107, the shield is biased counterclockwise, causing the distal axial guide portion 112.12 to contact and rotationally stop the housing's third axial portion 142.5. Due to the biasing force and helical engagement, a releasable locking mechanism is provided. A torque exceeding the release threshold torque is required to release the lock. As described above, the connector 170 is moving simultaneously relative to the housing. The connector 170 is pushed out of its rotational engagement with the housing's central guide 144 (FIG. 16H). This has the rear edge of the second axial guide portion 174.3 past the distal end of the intermediate guide's first axial portion 144.2, thereby shifting the first axial portion 144.2 from abutting against the second axial guide portion 174.3 to abutting against the left-handed helical portion 174.4. The connector 170 is guided along the left-handed helical guide portion 174.4 until the connector's click arm 176 abuts against the housing's proximal guide's first axial portion 146.1, as shown in FIG. 16K1. FIG. 16K2 illustrates the relative orientation of the connector 170 to the drive tube 180 with the connector's angle portion removed.The remaining portion includes the actuation tab. The position of actuation tab 178 is indicated by lateral portion 178.1 and axial portion 178.2. As shown, lateral portion 178.1 abuts lateral portion 183.1 of protruding tab 183 on the drive tube. This positions connector 170 to transmit force and proximal movement to the drive tube. FIGS. 16K3 and 16K4 show the configuration of FIG. 16K2 from the opposite side (180-degree rotation about the central axial axis). As also shown in FIG. 16K3, upon placing the shield in the shield-locked state, the connector translates the drive tube a small distance proximally relative to its initial position, thereby revealing proximal helical surface portion 157 (see FIG. 16K3). The initial position of drive tube 180 is shown in FIG. 13A. FIG. 16K4 illustrates the injection device in grayscale, providing a better impression of the surface orientation and elongation of different structures.

[0182] Administration status A fourth user action is to rotate the shield in the unlocked distal position proximally until it reaches the unlocked proximal position, thereby changing the device from the shield unlocked state to the administration state, through several intermediate positions.

[0183] From the unlocked shield position shown in FIG. 16K1 to the first injection device configuration shown in FIG. 16L1, the shield is pushed axially from the unlocked distal position to the unlocked proximal position, thereby forcing the activation tab 178 through a lateral opening in the outer helical structure 184. The proximal movement of the shield causes the shield to move the interlocked connector 170. The connector abutting the drive-tube 180 moves the drive-tube 180 from a distal rest position, where the drive-tube is rotationally locked by the housing, to a proximal rotated position, where the drive-tube rotates relative to the housing. The proximal movement compresses the torsionally tensioned drive spring 109 into a compressed state. From the device's first configuration in the dispense state (FIG. 16L1) to its final illustrated configuration in the dispense state (FIG. 16N1), the drive-tube has rotated 360 degrees, i.e., a full rotation, during distal helical movement back to its initial position in the housing (FIGS. 13A and 13N3), where it is rotationally locked to the housing, thereby expelling a fixed dose. The drive-tube's rotational movement causes the drive-tube with the leading edge of distal helical surface portion 189 to move counterclockwise along proximal helical surface portion 157 of inner tubular portion 154 of the housing from the initial dispense position illustrated in FIG. 16L3 to the intermediate shield unlocked position illustrated in FIGS. 16M3 and 16M4, where axial portion 183.2 abuts against axial portion 178.2 of tab 178, as shown in FIG. 16M2. The drive tube, with the leading edge of distal helical surface portion 189, continues its distal helical movement along surface portion 157 until it reaches axial surface portion 156 of housing inner tubular portion 154. The drive tube is rotated by torsionally pretensioned drive spring 108, and the drive tube's helical surface portion remains in contact with housing helical surface portion 157 as compressed drive spring 108 expands during unwinding. This returns the drive tube to its initial position, which corresponds to the drive tube reaching the stop-dose position, and further counterclockwise rotation is prevented, as illustrated in Figures 13A and 13N3.In this position, actuation tab 178 can be moved proximally through a lateral opening in outer helical structure 184 in response to release of axially and proximally directed force on the shield, i.e., release of pressure on shield tip 119 as the device is lifted from the skin. As viewed with the drive tube in the start dispense position, intermediate shield unlocked position, and stop dispense position, three different sets of angular and axial positions are defined, i.e., three different angular coordinates and three different axial coordinates.

[0184] Initializing the automatic relocking mechanism During rotation of the drive-tube 189 from the intermediate shield unlocked position to the stop dispense position, the drive-tube applies a torque to the connector that exceeds the release threshold torque, thereby disengaging the connector's locking structure 171 from the shield's locking structure 115 and rotating the connector until it abuts a rotation stop provided within the housing. By disengaging the locking structures from one another, the automatic shield relocking mechanism is initiated.

[0185] During counterclockwise rotation, the trailing edge of the left-handed helical portion 172.1 moves slightly proximally along the second left-handed helical portion 114.1 until it clears the proximal edge of the second left-handed helical portion 114.1. This shifts the connector from abutting the left-handed helical portion 114.4 of the shield to abutting the right-handed helical portion 114.3 of the shield, i.e., re-establishing abutment between the right-handed helical portion 172.2 of the connector and the second right-handed helical portion 114.3 of the shield. Due to the right-handed helical abutment, the connector is biased counterclockwise under the distally directed biasing force of the return spring 107. However, during connector rotation, the connector arm 176 rotates along the first lateral portion 146.2 of the housing proximal guide and to an angular position of abutment between the axial surface 176.1 of the connector arm and the second axial portion 143.3 of the housing proximal guide. An optional and additional abutment is provided between the connector's central guide third axial portion 174.5 and the housing's central guide first axial portion 144.2, which prevents further counterclockwise rotation of the connector 170. As the shield 110, in this unlocked proximal position, is prevented from clockwise rotation due to the abutment between the shield's stepped helical guide distal axial guide portion 112.12 and the housing's distal guide second axial portion 142.3, and possibly due to the optional abutment between the shield's proximal guide third axial portion 114.8 and the housing's central guide second axial portion 144.4, the connector may only move the shield axially in pure axial movement.

[0186] Split dose prevention During actuation of the drive-tube 180, the connector is moved in a purely proximal axial direction until the actuation tab 178 ratches at the position indicated by the patterned rectangle in FIG. 16L3. As described above, this movement of the connector results in the drive-tube 180 moving between a distal rest position where the drive-tube is rotationally locked by the housing, and a proximal rotated position where the drive-tube rotates relative to the housing due to the torsion provided by the drive spring 108. This axial movement moves the actuation tab through a lateral opening in the helical structure 184, and as the drive-tube reaches the proximal rotated position, the drive-tube begins to rotate and the outer helical structure 184, which protrudes from the outer surface of the drive-tube, rotates into lateral overlap with the actuation tab 178, thereby holding the actuation tab and connector in a position proximal to the helical structure 184. During rotational movement of the connector from the start-dose position, seen in FIG. 16L3, to the stop-dose position, seen in FIG. 16N3, activation tab 178 is retained on the proximal side of drive-tube helix 184, thereby preventing a split dose. If pressure is released prematurely, i.e., before the stop-dose position is reached, the connector and shield will be moved distally until axial abutment between distally oriented retention portion 178.3 of activation tab 178 and helix 184. Thereafter, if the axial proximal force on the shield is not re-established, the activation tab will slide along helix 184 as the drive-tube rotates to the stop-dose position, thereby causing the activation tab to be moved in a purely distal axial direction through a lateral opening in helix 184.

[0187] Figures 16M1-16M3 illustrate the same configuration of injection device 100. Figure 16M2 illustrates the device from the same angle as Figure 16M1, but with the angled portion of the connector cut away. Figures 16M2 and 16M3 are views from opposite locations (rotated 180 degrees about the central axial axis). Figure 16M4 illustrates Figure 16M3 in grayscale.

[0188] Figures 16N1-16N3 illustrate the same configuration of injection device 100. Figure 16N2 illustrates the device from the same angle as Figure 16N1, but with the angled portion of the connector cut away. Figures 16N2 and 16N3 are views from opposite locations (rotated 180 degrees about the central axial axis).

[0189] Relocked state A fifth user action is to release the axially directed force on the shield by lifting the needle tip 119 from the skin, which causes the shield, which is in the unlocked proximal position, to move distally until it reaches the locked position, thereby changing the device from the administration state, through several intermediate positions, to the re-locked state.

[0190] From the final dispensed position shown in FIG. 16N1 to the intermediate position shown in FIG. 16P, shield 110 is moved axially by connector 170 from an unlocked proximal position to an unlocked distal position, thereby moving activation tab 178 through a lateral opening in outer helix 184. From the intermediate position shown in FIG. 16P to the intermediate position shown in FIG. 16Q, the connector rotates the shield in a clockwise direction. From the intermediate position shown in FIG. 16Q to the relocked state shown in FIG. 16S, the shield is moved distally by connector 170 during clockwise rotation.

[0191] During distal movement, the right-handed helical portion 172.2 of the connector abuts the second right-handed helical portion 114.2 of the shield. Due to the helical abutment between the connector and the shield, the shield is urged in a clockwise direction, thereby urging the distal axial portion 112.12 toward the second axial portion 142.3 of the housing. The shield is therefore guided axially along the distal guide of the housing until the trailing edge of the helical portion 172.2 reaches the distal edge of the second axial portion 142.2, thereby allowing the shield to rotate in a clockwise direction in response to further distal movement, as illustrated in the intermediate position shown in FIG. 16P. During clockwise rotation, exemplified by the intermediate configurations shown in Figures 16P-16Q, stepped helical guide 112 slides between first lateral portion 142.2 and lateral portion 162.2, while the connector biases shield 110 to slide along shield's proximal guide 114. When the trailing edge of first distal lateral guide portion 112.10 reaches the edge between lateral portion 162.2 and helical portion 162.1 (Figure 16Q), the shield can move in a combined distal and rotational movement guided by the connector moving along second right-hand helical portion 114.3 to a rest position abutting proximal guide's first left-hand helical portion 114.1 (Figure 16S).

[0192] During distal movement of the shield, connector 170 moves distally, guided by first axial portion 144.2 of the housing's central guide, which prevents counterclockwise rotation, as illustrated in the final configuration of the administered state (FIG. 16N1) and the intermediate configurations of FIGS. 16P and 16Q. Clockwise rotation of the connector is initiated when the leading edge of left-handed helical portion 174.4 reaches the proximal edge of first axial portion 144.2. During distal movement, connector arm or click arm 176 moves along axial guide portions 146.3 and 146.4 and along ramp portion 146.4 to flush surface portion 146.5, thereby radially compressing click arm 176, as shown in FIG. 16Q. As connector 170 is moved further distally, left helical portion 174.4 slides along housing central guide 144, inducing clockwise rotation until the trailing edge of helical portion 174.4 reaches the proximal edge of first axial portion 144.2. At this position, the connector has nearly reached a rest position with the shield's proximal guide, with left helical portion 172.1 abutting first left helical portion 114.1 and the connector arm returning to abutment with first axial portion 146.1 of the proximal guide, as illustrated in FIG. 16R. The connector arm has thereby been reset to its initial position, ready to guide the connector during a new activation and administration cycle. From the intermediate position of FIG. 16R to the relocked position of FIG. 16S, the connector is moved distally into the seat where the first lateral portion 144.1 abuts the first axial portion 174.2 and the axial portions 144.1, 144.2, 174.1, and 174.3 prevent rotation.

[0193] With the cap on, with the cap locked The fifth user action is to put on the cap as illustrated in FIG. 16T, whereby the protrusion 105.2 is inserted into the axial track portion 161.2, so that the cap can be rotated to place the device in the cap-locked state shown in FIG. 15B (the cap-locked state is not shown in connection with the detailed description of the actions). As seen in FIG. 16T, the axially extending rib is in a position that moves away from the protrusion 116 when the cap is rotated to the locked position. Therefore, there is no interaction between the cap 105 and the shield 110 when the cap is locked.

[0194] Second embodiment Figures 17-26 illustrate a second embodiment 200 of an injection device for delivering multiple fixed doses according to the present disclosure. Figure 17 shows an exploded view of the injection device, and Figure 18 shows a cross-sectional view. Figures 18-23 show further details of the individual structures and mechanisms. Figures 25 and 26 illustrate in detail the interrelationship of the mechanical structures during operation.

[0195] 17 shows the cap 205, the shield tip 219, and the shield follower portion 220.1 of the cleaning module, which also includes a movable portion, corresponding to the movable portion 120.2 of the first embodiment 1. FIG. 17 further shows the needle hub 225 with the needle cannula 224, the tubular elongated housing structure 240, and the housing cap portion 260 connected at the distal end of the housing structure 240. The figure also shows the tubular elongated needle shield structure 210, the cartridge holder 230, the cartridge 235, the connector 270, the shield return spring 207, the drive tube 280, the dose drive spring 208, the piston rod 209, and the spring base 265. The figure also shows the piston washer 204 with a ratchet arm and an external thread for engaging a toothed ring and an internal thread, respectively, on the inner surface of the piston rod 209, whereby a zero-point adjustment for the piston in the cartridge 235 can be performed. 18 illustrates a cross-sectional view of the injection device 200 with the injection device in an unpackaged state. The cross-sectional plane cuts through the window 211 in the shield.

[0196] Housing Assembly The injection device includes a housing assembly, which provides a rigid frame with guides and connectors for guiding and connecting other components of the device. The housing assembly includes a housing cap portion 260, a tubular elongated housing structure 240, a cartridge holder 230 with a window 231, and a spring base 265. After final assembly, these structures are fixedly connected, and the housing assembly can provide a frame of reference for describing the relative movement and position of other structures. The elongated housing structure 140 includes internal threads 254.3 for engaging the external threads of the piston rod.

[0197] The injection device 200 comprises a drive mechanism and a trigger or activation mechanism. The drive mechanism comprises a piston rod 209, a drive spring 208, and a drive tube 280, the structures operably disposed within the housing for ejecting a dose. The trigger mechanism comprises an elongated shield structure 210 and a connector 280, the structures operably disposed within the housing for triggering the dose ejection mechanism.

[0198] The tubular portion 254 comprises a central guide 244 comprising an outer axial portion 244.1 arranged symmetrically about the longitudinal axis at a first radial position and thereby defining a first diameter, and an inner axial portion 244.2 arranged symmetrically about the longitudinal axis at a second radial position and thereby defining a second diameter.

[0199] Needle Shield Assembly The injection device further comprises a needle shield assembly comprising a shield tip 219 and an elongated shield structure 210. The elongated shield structure 110 comprises a window 211 for inspection of the medication, and the elongated shield can be positioned in a first position where it overlaps the cartridge holder window 231 and in a second position where it does not overlap, with a solid portion of the elongated shield structure covering the window 231 in the second position.

[0200] Cartridges and Cartridge Holders The cartridge holder 230 is adapted to receive the cartridge 235. The cartridge holder includes a window 231 for inspecting the medication in the cartridge 235. The cartridge 135 and the cartridge holder 230 are structurally and functionally similar to the cartridge 135 and the cartridge holder 130 of the first embodiment, respectively.

[0201] Needle Assembly The needle assembly, including needle hub 225 and needle 224, is structurally and functionally similar to the needle assembly of the first embodiment.

[0202] cap Cap 205 is adapted for removable attachment to housing cap portion 260. The cap includes an inner surface having protrusions adapted to mate with bayonet coupling tracks. The inner surface of cap 105 further includes axially extending ribs (not shown) protruding from the inner surface and adapted to transmit torque to shield structure 110 through axially extending ribs 216 on the outer surface of the shield. Cap 205 is structurally and functionally similar to cap 105 of the first embodiment, except that cap 205 also encloses the shield and a main portion of the cartridge.

[0203] Spring base Spring base 265 is fixedly mounted at a proximal end to housing structure 240 and is adapted to receive and support compressible torsion drive spring 108 .

[0204] Drive spring The drive spring 208 is pre-tensioned or wound and positioned between the spring base and the drive tube 280. The drive spring is further adapted to induce a torque on the drive tube, which may expel the medication. The drive spring comprises a torsion and compressible section. The ability to drive the drive tube axially allows for termination of the dose mechanism and allows for resetting of the drive tube.

[0205] Return spring Connector return spring 207 is positioned between spring base 265 and relock tube 279 and is adapted to bias the relock tube in a distal direction. In the return configuration, relock tube 279 abuts shield 210, and the shield engages the connector, thereby allowing shield 210 and connector 270 to be returned together with relock tube 279.

[0206] Cleaning Assembly The cleaning assembly is structurally and functionally similar to the cleaning assembly of the first embodiment.

[0207] Housing Structure 19 illustrates a perspective view of features located on the inner surface of tubular housing structure 240 in an axial cut of the housing. As seen in FIG. 19, tubular housing structure 240 comprises an outer tubular portion 243 and an inner tubular portion 254. In the illustrated example, inner tubular portion 254 is integrally connected to the outer tubular portion. The outer tubular portion comprises an outer surface having an outer diameter and an inner surface having an inner diameter, the outer tubular portion adapted to house a drive mechanism assembly and a relocking tube 279.

[0208] Housing structure 240 comprises a guide structure comprising an axial surface portion 256 that provides a sliding surface and rotational stop, and a helical surface portion 257 that provides a sliding surface adapted to guide drive tube 280 during administration.

[0209] 20 details the inner tubular portion 254 in a perspective view with the outer tubular portion 243 cut away. The inner tubular portion includes a tubular drive-tube engaging portion 254.1 for receiving a distal portion of the drive-tube, and a tubular drive piston rod engaging portion 254.2 with threads 254.3 for threadably engaging the piston rod 209. The piston rod engaging portion further includes a connector 254.4 for providing a snap connection with the cartridge holder 230.

[0210] Zero point adjustment mechanism As can be seen in FIG. 17, the piston washer is provided with external threads and ratchet arms for cooperating with threads and a toothed ring on the inner surface of the piston, thereby allowing zero point adjustment in a manner similar to that described for the first embodiment.

[0211] Drive mechanism The structure and function of the drive mechanism of the second embodiment are similar to those of the first embodiment. In particular, a drive-tube 280 is axially splined to the piston rod. FIGS. 23A and 23B illustrate the drive-tube 280 in perspective views from different angles. As seen in FIG. 23, as a departure from the first embodiment, the drive-tube 280 of the second embodiment includes a closed guide track 284 including a first lateral portion 284.1, a right-handed helical portion 284.2, and a left-handed helical portion 284.3. The lateral guide portion 284.1 includes a proximally oriented surface that provides a connector seat, and the connector seats before and after actuation of the drive-tube. The lateral portion further includes an abutment structure 283 including a distally oriented surface portion 283.1 that provides an abutment surface for abutting the connector during actuation. The right-handed helical portion 284.2 comprises a distal surface that provides an abutment surface for the connector in response to premature release of shield pressure, i.e., a split-dose prevention feature. The left-handed helical portion 284.3 provides a ramp surface for rotating the connector at the end of the dose, thereby initiating a reset of the shield. As with the first embodiment 100, the drive tube of the injection device 200 comprises a guide structure comprising an axial surface portion 282 adapted to slidably engage an axial surface portion 256 of the housing in a rotationally locked arrangement, and a helical surface portion 289 for slidably engaging a helical surface portion 257 of the housing during administration.

[0212] The same considerations for incorporating a torsion spring into the drive mechanism of the second embodiment provide the same advantages as those mentioned in the first embodiment.

[0213] Long and narrow shield structure 24 shows a perspective view of a cylindrical elongated shield structure 210. The proximal portion of the shield is disposed inside a connector 270, which is again disposed inside the housing portions 240, 260. The elongated shield structure 210 comprises a tubular portion with an outer surface having an outer diameter and an inner surface having an inner diameter. An axially extending rib 216 is positioned at the distal end protruding from the outer surface. The rib is adapted to cooperate with an internal rib of the cap 205.

[0214] The shield structure 210 further includes a radial guide 212 disposed at the proximal end and extending radially therefrom, whereby the shield is adapted to cooperate with a connector 270 .

[0215] The elongated shield structure 210 further includes a proximal guide 214 positioned at the proximal end of the shield structure 210. The proximal surface of the proximal guide is visible in FIG. 24 . The proximal guide 214 is adapted to cooperate with the connector 270 and the relock tube 279. The proximal guide 214 extends axially and circumferentially and includes a first lateral portion 214.1, an axial portion 214.2, a right-hand helical portion 214.3, and a second lateral portion 214.4. The proximal guide 214 further includes a notch 214.5 that provides a rotational lock for locking the shield in the shield actuation state, allowing it to be returned to the unwrapped state. The notch provides a right-hand helical guide portion 214.6. Guide portions 214.1-214.4 are all surface portions and provide the proximal surface of the proximal guide 214.

[0216] connector 22 shows a perspective view of a connector 270 disposed inside tubular housing portions 240, 260 and between elongated shield structure 110 and drive-tube 280. Connector 270 is adapted to establish a connection between shield 210 and drive-tube 280 and to actuate drive-tube 280. Connector 270 includes a distal guide 272 adapted to cooperate with shield proximal guide 114. Distal guide 272 includes a circumferentially extending, distally oriented surface, lateral surface portion 272.1.

[0217] The connector further includes a stepped helical track 274 for cooperation with the shield's radial guide 212. The stepped helical track includes a distal lateral portion 274.1, a distal helical portion 274.2, a central lateral portion 274.3, a proximal helical portion 274.4, and a proximal lateral portion 274.5. Due to the helical portion of the stepped helical track, rotational movement of the shield 210 can be translated into proximal movement of the shield, and due to the lateral portion of the stepped helical track 274, a distally directed force on the shield can be translated into the connector 270, thereby moving the shield distally. When the shield exerts a distal force on the helical portion of the stepped helical track 244, the connector can move distally, or both distally and rotationally.

[0218] The connector 270 includes a first tubular portion 270.1 having a full 360-degree circumference and a second tubular portion 270.2 having two notches, whereby the remainder of the second tubular portion forms two axially extending tube portions 276. The first tubular portion includes a stepped helical track 274, and the two axially extending tube portions 276 include a distal lateral surface 272.1 forming a distal guide 272, a first axial surface providing a first axial guide 276.1, and a second axial surface positioned clockwise relative to the first surface providing a second axial guide 276.2. A shield may be disposed within the first tubular portion 270.1 with a radial guide 212 extending through the stepped helical track 274. The axially extending tube portion 276 extends proximally from the inner surface of the first tubular portion 270.1 and therefore has a smaller diameter. A lateral surface portion 272.1 is provided on the distally oriented surface of the axially extending tube portion 276, and the diameter of the tube portion 276 corresponds to the diameter of the shield 210, so that the proximal guide 214, having a proximally oriented surface, is adapted to cooperate with the lateral guide portion 272.1. The diameter of the axially extending tube portion 276 further corresponds to the diameter of the inner axial portion 244.2 of the central guide, thereby allowing the axially extending tube portion 276 to cooperate with the inner axial portion 244.2. The connector 270 has an outer surface having an outer diameter and an inner surface having an inner diameter. 18, a cross-sectional view of the injection device 200, the outer surface of the connector first tubular portion 270.1 is disposed in close proximity to the inner surface of the tubular housing cap portion 260. An axially extending tubular portion 276 surrounds the housing inner tubular portion 254 and the drive tube 280. The axially extending arm 276 is further adapted to cooperate with the housing's central guide 244.1, thereby guiding movement of the connector relative to the housing.

[0219] Connector 270 further includes an actuation tab 278 disposed at the proximal end of axially extending tubular portion 270.2 and extending radially from the inner surface, i.e., toward the center of the tubular portion. Actuation tab 278 extends within drive-tube closed guide track 284. Actuation tab 278 includes a first lateral portion 278.1 providing a proximally oriented contact surface adapted to engage a distally oriented surface 283.1 of an abutment structure in lateral portion 284.1 of the closed guide track, thereby enabling proximal movement and actuation of drive-tube 280. Actuation tab 278 further includes a proximally oriented surface portion 278.2 adapted to engage the distally oriented surface of closed guide track 284, thereby allowing the connector to be guided during a dose cycle and thereby preventing a split dose in response to premature release of proximal pressure on the shield. In response to guiding the proximal portion 278.2 of the actuation tab along the left-handed helical guide portion 284.3, the shield relocking mechanism is actuated.

[0220] relocking tube The relocking tube 279 includes a first tubular portion 279.1 and a second tubular portion having two notches, such that the remainder of the second tubular portion forms two axially extending tube portions 279.2. The relocking tube includes an axially extending guide track 279.4 that extends a relatively small distance from the proximal end (e.g., 1 / 10 of the length of the relocking tube) to the distal end. The two axially extending tube portions 279.2 include an axial guide portion 279.5, a first lateral guide portion 279.6, a right-hand helical portion 279.7, and a second lateral portion 279.8. The axially extending tube portion 279.2 further includes an axial portion 279.9 that provides a rotational stop and an axial guide for the connector. Axially extending tube portion 279.2 extends proximally from the inner surface of first tubular portion 279.1 and therefore has a smaller diameter. Helical and lateral guide portions 279.6-279.8 are provided on the distally oriented surface of axially extending tube portion 279.2, and the diameter of tube portion 279.2 corresponds to the diameter of shield 210, so that proximal guide 214, having a proximally oriented surface, is adapted to cooperate with helical and lateral guide portions 279.6-279.8. The diameter of axially extending tube portion 279.2 further corresponds to the diameter of central guide inner axial portion 244.2. The diameter of the first tubular portion corresponds to the diameter of central guide outer axial portion 244.1. An axially extending guide track 279.4 is adapted to cooperate with the central guide outer portion 244.1, whereby the relock tube 279 is rotationally locked and axially guided between a distal position defined by the proximal end of the guide track 279.4 and a proximal position (FIG. 18 shows that there may be axial play between the outer portion 244.1 and the proximal end of the track). The relock tube 279 has an outer surface having an outer diameter and an inner surface having an inner diameter. As illustrated in FIG. 18, the outer surface of the relock tube first tubular portion 279.1 is positioned in close proximity to the inner surface of the housing outer tubular portion 243, and the return spring is located between the spring base 265 and the proximal edge of the relock tube 279, whereby the relock tube may be biased distally in response to proximal movement.An axially extending tube portion 279.2 surrounds the housing inner tubular portion 254 and may cooperate with the connector's axially extending tube portion 270.2.

[0221] Detailed description of the device's operation 25A-26B collectively illustrate the relative and functional arrangement of different structures during a series of states of injection device 200, thereby illustrating in detail the operation of the device.

[0222] In one embodiment of the present disclosure, an injection device 200 for sequentially delivering multiple fixed doses comprises a housing including an elongated housing structure 240, a cartridge holder 230, and a housing insert 260, an internal thread, a shield including an elongated shield structure 210 and a needle tip 219, a needle hub 225 including a fixedly attached needle cannula 204, a cap 205 adapted to be removably mounted on the housing and cover a major portion of the shield, a cartridge 235 having a movably disposed cartridge plunger or piston 236, and a drive mechanism including a torsion drive spring 208, a drive tube 280, and a piston rod 209 having an external thread for cooperating with the internal thread of the housing, the piston rod being disposed in connection with the piston 236, and the torsion spring being adapted to provide torque for rotating the drive tube 280 relative to the housing. The drive tube comprises a ratchet mechanism 281, 265.1 that ensures rotation in the administration direction and blocks in the non-administration direction. The drive tube is axially splined to the piston rod, thereby permitting relative axial movement and preventing relative rotation. The drive tube is adapted to advance the piston rod in response to rotating the drive tube in a dispensing direction, and due to the threaded connection with the housing, the piston rod is adapted to advance piston 236 within cartridge 235 to eject a fixed dose. The drive mechanism is adapted to be activated by changing the drive tube from a distal position, in which the drive mechanism is in a stationary mode, to a proximal position, in which the drive mechanism is in a dispensing mode. In the distal position, the drive tube is rotationally locked to the housing. In the proximal position, the drive tube is rotationally unlocked from the housing, and applied torque can rotate the drive tube through a predetermined angle to eject a fixed dose. In the stationary mode of the drive mechanism, the piston rod is rotationally and axially locked, the piston rod being rotationally locked to the housing through the splined connection with drive tube 280 and axially locked through the threaded connection with the housing.

[0223] The torsion spring 208 is pre-tensioned to deliver multiple doses without binding during use. The drive mechanism is adapted to change modes upon activation, and as explained below, the drive mechanism is adapted to be repeatedly activated until the last dose is expelled.

[0224] The cap can be placed in an axially locked position and an axially unlocked position. The cap can be repositioned by rotating the cap relative to the housing. When the cap is in the axially unlocked position, the cap can be removed from the housing.

[0225] The shield can be positioned in different positions. The initial position is defined by an initial angular position and a corresponding initial axial position. The disengaged position is defined by a disengaged angular position and a corresponding disengaged axial position. The disengaged distal position is defined by a disengaged angular position and a corresponding distally engaged axial position. The disengaged proximal position is defined by a disengaged angular position and a corresponding proximally engaged axial position. In the initial position, the shield is adapted to allow counterclockwise movement. In the disengaged position, the shield is adapted to prevent clockwise movement and allow clockwise movement. The shield does not engage with the connector in the sense that proximal movement of the shield does not translate into proximal movement of the connector, thereby preventing the shield from actuating the drive-tube in this position. In the disengaged distal position, the shield is adapted to prevent counterclockwise and distal movement of the shield and is further adapted to allow proximal movement. In the engaged distal position, the shield is further adapted to allow clockwise rotation if the applied torque exceeds a predetermined threshold. When the shield is in the initial and disengaged positions, the needle tip is covered by the shield. In the engaged position, the shield is adapted to be moved proximally from the engaged distal position, where the needle tip is not covered by the shield and pressure in the reservoir can be released, to the engaged proximal position, where the needle tip extends further from the shield and can be inserted into the subject's subcutaneous layer. In this position, further proximal movement can be prevented by blocking the shield tip 119 relative to the needle hub 125. The shield can be manually operated between different positions by a user. As viewed with respect to the shield in the initial, disengaged, distally engaged, and proximally engaged positions, a set of four different angular and axial positions is defined: three different angular positions and four different axial positions.

[0226] The connector may be positioned at an initial or first position defined by a first angle and a corresponding distal position, and the connector is allowed to move along the rotationally locked relocking tube 279 to a guided proximal position until the connector 270 meets an axial stop on the housing or until the shield tip 219 abuts the hub 225. Thus, the connector may be further positioned at a second position defined by the first angular position and a proximal position. Additionally, the connector may be positioned at a third position defined by a second angular position and a corresponding distal position, the first and third positions being defined by the same axial position.

[0227] 25A-26B collectively illustrate a portion of injection device 200 in different states and intermediate positions, with the outer portion of the housing and entire cap cut away to reveal a portion of the internal structure. Each illustrated state is illustrated in a view in which some of the internal components are hidden by the connector and relock tube, e.g., FIG. 25B1, and each illustrated state is illustrated in a view in which the outer portion of the relock tube and a portion of the outer portion of the connector are removed, e.g., FIG. 25B3. Some illustrated states are also provided in grayscale, e.g., FIG. 25B2 corresponding to FIG. 25B1 and FIG. 25B4 corresponding to FIG. 25B3.

[0228] Unpacked state Figure 25A illustrates a portion of injection device 200 in an unpackaged state, showing shield structure 210, cartridge holder 230, connector 270, drive tube 280 and return spring 207, relock tube 279, and spring base 265. Figure 25A1 illustrates a portion of the injection device in black and white, while Figure 25A2 illustrates the same in greyscale to better illustrate the different components of the structure.

[0229] Cap unlocked The first user action is to rotate the cap counterclockwise until it reaches the axially unlocked position, which changes the shield from its initial position to a disengaged position, thereby changing from the unwrapped state to the cap unlocked state, as shown in FIGS. 25B1 and 25B2. In the cap unlocked state, the cap can be moved axially. The cap unlocked state is also referred to as the shield activated state, as the shield activates the device without engaging the connector, or the shield disengaged state, as the shield cannot activate the drive mechanism. In contrast to embodiment 100, the shield 210 of embodiment 200 is not necessarily axially locked to the housing in this state, but because the shield does not engage the connector, axial movement cannot be transmitted from the shield to the connector, and the connector cannot move to activate the drive-tube 280. When the shield's radial guide 212 engages the stepped helical track 274 of the connector 270, the radial guide 212 abuts the proximal surface of the stepped helical track's distal helical guide portion 274.2 during the shield's proximal spiral movement from the initial to the disengaged position. In the disengaged position, the radial guide rests on the central lateral portion 273.4 and is not proximally present on the track 274. During the shield's proximal spiral movement, the shield moves the relock tube 279 proximally against the biasing force of the return spring 208, and in the disengaged position, the relock tube's axially extending portion 279.2 moves into the notch 214.5, thereby providing rotational locking. When the shield is in the disengaged position, the right-hand helical portion 279.7 of the relock tube abuts the right-hand helical guide portion 214.6 of the notch and the right-hand helical portion 214.3 of the proximal guide, thereby biasing the shield distally. A distal force is transferred from the shield to the connector through the abutment between the radial guide 212 and the track 274, thereby also biasing the connector distally. Therefore, in the following conditions, the relock tube 279, shield 210, and connector are biased distally. In FIG. 25B, the shield does not extend to the spring base and therefore appears uncompressed.However, even if the illustrated embodiment is slightly inaccurate, the shield is at least slightly compressed in this state, otherwise components would rattle inside the device when going from up to down or vice versa.

[0230] The cap is removed A second user action is to pull the cap distally, which causes the device to change from the cap unlocked state to the cap removed state.

[0231] Since the cap is not shown in FIGS. 25A-26B, FIGS. 25B1 and 25B2 also illustrate the state in which the cap is removed.

[0232] Shield engaged or activated A third user action is to rotate the shield, which is in the disengaged or non-activated position (because the drive mechanism cannot be activated), in a counterclockwise direction until it reaches the engaged distal or activated position, thereby changing the device from the cap-off state to the shield-unlocked state.

[0233] 25C1 and 25C2, the shield rotates in a proximal helical movement guided by distal helical portion 274.4, followed by a purely rotational movement guided by proximal lateral portion 274.5. During the shield's proximal helical movement along distal helical portion 274.4, notch right-hand helical guide portion 214.6 and shield right-hand helical portion 214.3 abut and slide against relock tube right-hand helical portion 279.7, thereby forcing rotationally locked relock tube 279 proximally. During pure rotational movement of the shield, the abutment between the relock tube helical portion 279.7 and the shield helical portions 214.7, 214.3 shifts to an abutment between only the right-hand helical portions 214.3, 279.7, and then to an abutment between the proximal guide second lateral portion 214.4 and the relock tube first lateral guide portion 279.6. Because the abutment surface between the shield second lateral portion 214.4 and the relock tube first lateral portion 279.6 extends in a direction perpendicular to the biasing force of the return spring, the abutment provides a resting position for the relock tube 279 and the shield 210. Due to the biasing force and the abutment between the lateral portions 214.4, 279.6, a releasable locking mechanism is provided between the shield 210 and the relock tube 279. A torque greater than a release threshold torque is required to release the lock. During helical movement of the shield, the first lateral surface portion 214.1 of the shield's proximal guide and the lateral surface portion 272.1 are abutted, and during pure rotational movement, the shield slides relative to the connector until abutment occurs between the axial portion 276.1 of the axially extending portion 276 and the axial portion 214.2 of the axial guide. Therefore, releasing the lock and thereby establishing abutment between the shield's helical portions 214.3, 279.7 and the relocking tube also disengages the shield and the connector's transverse portions 214.1, 272.1. Another axial portion 276.2 of the connector's axially extending tube portion 276 is rotationally locked counterclockwise relative to the rotationally locked axial portion 279.9 of the relocking tube, which is slidably disposed in the central guide 244 engaged in the axial track 279.4. The connector's actuation tab 278 seats within a lateral portion 284.1 of the closed guide track within the drive tube.In the engaged distal position, the shield is adapted to move the connector proximally to actuate the drive tube.

[0234] Administration status A fourth user action is to push the shield from the engaged distal position proximally until it reaches the engaged proximal position, thereby changing the device from the shield unlocked state to the dispensed state, which is exemplified by the configuration shown in Figures 25D-25E.

[0235] 25D1 and 25D2, the shield moves in a proximal, purely axial movement guided by the relock tube moving along central guide 144. During the proximal movement of the shield, the shield causes engaged relock tube 179 to translate proximally to compress return spring 208, and further causes the shield to translate engaged connector proximally, which causes actuation tab 278 to engage the proximal surface of lateral portion 284.1 of the closed guide track, also translating the drive-tube proximally. The drive-tube is thereby moved from a distal position where it is rotationally locked to the housing to a proximal position where it is rotationally unlocked from the housing. As illustrated in Figure 25D2, the torque provided by drive spring 207 rotates the drive-tube, causing the actuation tab to slide out of lateral portion 284.1 and into right-hand helical portion 284.2 of the closed guide track. Figure 25D also reveals axial portion 282 for abutting axial portion 257 of housing inner tubular portion 254 (see Figure 19) and helical portion 256 of the housing for abutting helical portion 289 of the drive-tube (see Figure 23).

[0236] 25E illustrates another configuration for administration following the configuration of FIG. 25D in which drive tube 180 has rotated further during administration, whereby activation tab 278 is positioned at the proximal end of right-handed helical portion 284.2 and abutment has just changed from right-handed helical portion 284.2 to left-handed helical portion 284.3. As in the above configuration, the connector abuts against shield proximal guide axial portion 114.2, and relock tube first lateral guide portion 279.6 abuts shield proximal guide second lateral portion 214.4, transmitting axial distal force from relock tube 279 through shield 210 to connector 270.

[0237] Initializing the automatic relocking mechanism When the drive-tube stops rotating by reaching the end of the dose, the proximal portion 278.2 of the activation tab 278 moves out of engagement in a right-handed helical trajectory, thereby preventing the connector from further distal movement. Because axial movement of the connector is no longer prevented by the drive-tube, the connector will move axially distally and rotate in response to releasing pressure from the shield, thereby moving the connector into engagement with the left-handed helical portion 184.3 of the drive-tube. This has initiated the automatic relocking mechanism.

[0238] Split dose prevention During the administration cycle, the activation tab 278 is engaged in the closed guide track 284. Therefore, in response to lifting the shield from the skin before the dose is completed, the activation tab will be blocked by the first lateral portion 284.1 or the right-hand helical portion 284.2 of the guide track 284, and the drive tube will continue to rotate until the dose is completed. Upon completion of rotation, the connector, along with the activation tab and shield, will push the connector distally, preventing a split or interrupted dose and ensuring the next dose is correctly delivered. If the shield were to extend to the distal position, the needle tip would be positioned within the irrigation chamber, which could create overpressure within the irrigation chamber. Overpressure could unintentionally stop administration.

[0239] Relocked state A fifth user action is to release the axially directed force on the shield by lifting the needle tip 219 from the skin, which causes the shield, which is in the engaged proximal position, to move distally until it reaches the disengaged position, thereby changing the device from the administered state, through the intermediate position shown in FIG. 25F, to the disengaged or deactivated state shown in FIG. 25G.

[0240] Automatic relocking mechanism FIG. 25F illustrates an intermediate position between the dispensed state and the disengaged state shown in FIG. 25G, in which the drive tube has rotated into abutment with axial portion 257, thereby completing the dose. During rotation of the drive tube and in response to releasing pressure from the shield, activation tab 278 is shifted into abutment with left-handed helical portion 284.3, and due to compression from return spring 207, activation tab 278 is moved along a left-handed helical trajectory, thereby rotating connector 270 to a second angle and distal position. Force from the compression spring is transferred from the relock tube through the shield to the connector. During connector rotation, it is rotated due to abutment between the connector and axial portion 214.2 of the shield's proximal guide. Due to rotation of the shield, and once the relock tube is rotationally locked, the abutment between the shield and relock tube shifts to abutment between right-handed helical portion 214.3 of the shield and right-handed helical guide 274.7 of the relock tube. The helical abutment surface allows axial movement of the relock tube 279 to be translated into rotational movement of the shield, and when the relock tube is biased distally, it is moved distally and the shield is rotated to a disengaged position, thereby disengaging the first lateral portion 214.1 of the shield's locking structure 215 from abutment with the lateral portion 272.1 of the connector's distally-oriented lateral guide portion 272. Because the two lateral portions 214.1, 272.1 are lateral, they can be slid in response to the application of relative rotation.

[0241] With the cap on, with the cap locked A fifth user action, not illustrated, is placing a cap on injection device 200, whereby protrusions on the inner surface of the cap are inserted into axial tracks on the housing, which allows the cap to be rotated to place the device in a cap-locked state. The cap-locked state of injection device 200 is not illustrated. When cap 205 is rotated back to the locked state, it does not engage the shield, and therefore the shield is not pushed toward the initial position.

[0242] 26A and 26B illustrate two configurations for obtaining a second or subsequent dose if the connector is not rotated back to its first position. Once the relock tube is moved to its distal position, the connector 270 can be left in a third position having a second angular position, as shown in FIG. 25G2, or can be forced by the shield 210 to rotate to a first position having a first angular position as the radial guide slides distally along the proximal helical guide 274.4. In the latter case, the new dose would start from the configuration shown in FIG. 25B. In the first case, the new dose would start from the configuration shown in FIG. 25G2 and continue to the configuration shown in FIG. 26A, with the shield urging the relock tube proximally until the axial portion 214.2 of the shield abuts the axially extending portion 270.2 of the connector. In response to further rotation, the connector is forced back to the first position having a first angular position as shown in Figure 26. From here, the next dose continues as described beginning with Figure 25C.

[0243] Additional Embodiments The additional alternative embodiments described are not individually illustrated or provided with reference numbers, but the features of the alternative embodiments correspond to the features of the illustrated embodiment, whereby the features of the alternative embodiments provide one or more functions similar to or equivalent to the features of the illustrated embodiment.

[0244] In an alternative embodiment, there is provided a drug delivery device for sequentially delivering a plurality of predetermined fixed doses, the drug delivery device comprising: a housing assembly; a drive mechanism comprising a drive tube, the drive mechanism being adapted to sequentially deliver a plurality of predetermined doses; an actuation mechanism for actuating the drive mechanism; A medication delivery device is provided in which the drive mechanism comprises a pre-tensioned torsion drive spring (108, 208) adapted to store an initial amount of energy and to rotate the drive tube, and each actuation of the drive mechanism and completion of a drive tube dose sequence reduces the amount of stored energy in the drive spring, and the initial amount of stored energy, which is the energy stored before the first actuation, is sufficient to deliver a predetermined multiple of the fixed doses.

[0245] This provides a medication delivery device for delivering a predetermined multiple fixed doses without arming or pulling the drive mechanism between doses, since the stored energy before the first activation is sufficient to deliver the predetermined multiple fixed doses. The fixed dose medication delivery device according to the present invention is adapted to deliver multiple doses of a desired amount. The total content of medication divided by the desired amount of fixed dose determines the predetermined multiple amount.

[0246] In an alternative embodiment, the housing assembly comprises a guide structure comprising a stop and start guide portion and a drive guide portion; - the drive-tube is adapted to be guided along the stop and actuation guide portions for actuation of the drive mechanism, and along the drive guide portions for delivery of a fixed dose, and dosing is stopped, whereby the drive-tube is adapted to be guided in response to performance of a drive-tube dose sequence including actuation, dosing, and stopping dosing; the drive mechanism further comprising a piston rod operatively connected to the housing assembly and the drive tube; an actuation mechanism adapted to move the drive-tube along the stop and actuation guide portion in a first axial direction from a first axial position to a second axial position, thereby actuating the drive mechanism;

[0247] The drive guide portion corresponds to the helical portion 157, 257 of the first and second embodiments, and the stop and start guide portion corresponds to the axial portion 156, 256 of the first and second embodiments. The drive tube, torsion drive spring, and piston rod correspond to the drive tube 180, 280, torsion drive spring 108, 208, and piston rod 109, 209.

[0248] As shown, the amount of the fixed dose is determined by the housing and guides of the drive mechanism. Therefore, the fixed dose drug delivery device according to the present invention is adapted to deliver multiple doses of a desired amount. As also shown in the fixed dose drug delivery device according to the present invention, the fixed dose can be adjusted only by modifying the drive mechanism and guides of the device.

[0249] The drive mechanism is further adapted to urge the drive tube in a second axial direction opposite to the first axial direction, and the drive mechanism is adapted to rotate the drive tube 180, 280 along the drive guide portion 157, 257 to the stop and actuation guide portion 156, 157 in response to actuation of the drive tube, thereby delivering a fixed dose of a predetermined plurality of fixed doses, and the drive tube is operably positioned to be guided along the stop and actuation guide portion to deliver a subsequent fixed dose of the plurality of fixed doses.

[0250] In an alternative embodiment, the housing further includes internal threads, the piston rod further includes external threads for threadably engaging the internal threads of the housing assembly, and the drive-tube is axially splined to the piston rod such that the drive-tube is axially movable and rotationally locked relative to the drive-tube, thereby operably connecting the piston rod to the housing assembly and the drive-tube.

[0251] In an alternative embodiment, the torsion drive spring is compressed, whereby the drive mechanism is adapted to bias the drive tube in the second axial direction.

[0252] In an alternative embodiment, the medication delivery device includes an axially movable spring base, and the drive mechanism includes a compression return spring positioned between the axially movable spring base and the housing, whereby the torsional drive spring and the return spring are coupled in series, whereby the drive mechanism is adapted to bias the drive tube in the second axial direction. The spring base corresponds to spring base 165, 265 of the first and second embodiments.

[0253] In an alternative embodiment, the drug delivery device is adapted for drug delivery at the distal end, the drug delivery device having a central axial axis defined between the distal end and the proximal end. The drug delivery device further includes a slidably disposed spring base, the torsion drive spring being disposed between the spring base and the drive tube. The drive tube is positioned with the component of the central axial axis in a direction opposite to the force of gravity, which is the second axial direction, during actuation and administration, thereby biasing the drive tube distally, and the drive mechanism is adapted to bias the drive tube in the second axial direction, i.e., gravity is utilized as the biasing force. The spring base corresponds to spring base 165, 265 of the first and second embodiments.

[0254] In an alternative embodiment, the torsion drive spring is disposed between the drive tube and the housing assembly.

[0255] In an alternative embodiment, the housing assembly includes a fixed spring base to which one end of the torsion drive spring is attached, the spring base corresponding to spring bases 165, 265 of the first and second embodiments.

[0256] In an alternative embodiment, the stop and actuation guide portions of the guide structure are axial portions and the drive guide portion of the guide structure of the housing assembly comprises a helical portion, the axial portion corresponding to axial portion 156, 256 and the helical portion corresponding to helical portion 157, 257 of the first and second embodiments.

[0257] In an alternative embodiment, the stop and actuation guide portions of the guide structure are axial portions and the drive guide portion of the guide structure of the housing assembly comprises a lateral portion, the axial portion corresponding to axial portion 156, 256 and the lateral portion corresponding to helical portion 157, 257 of the first and second embodiments.

[0258] In an alternative embodiment, the stop and actuation guide portions of the guide structure are axial portions, and the drive guide portion of the guide structure of the housing assembly comprises a stepped portion comprising a spacing between a portion from a first group comprising lateral and helical portions and a portion from a second group comprising radial, helical, and axial portions. The axial portion corresponds to axial portion 156, 256, and the stepped portion corresponds to helical portion 157, 257 of the first and second embodiments.

[0259] In an alternative aspect, the drive-tube includes corresponding guide structures 182, 189, 282, 287 adapted to cooperate with guide structures 156, 157, 256, 257 of the housing assembly. The corresponding guide structures of the drive-tube correspond to the corresponding guide structures 182, 189, 282, 287 of the drive-tubes of the first and second embodiments. The guide structures of the housing assembly correspond to the guide structures of the housing assemblies 156, 157, 256, 257 of the first and second embodiments.

[0260] In an alternative aspect, the drive-tube guide structure comprises an axial portion and a helical portion, the axial portion corresponding to axial portion 182, 282 and the helical portion corresponding to helical portion 189, 289 of the first and second embodiments.

[0261] In an alternative embodiment, when the drive-tube is in a first position, the axial portions of the housing assembly and drive-tube guide structure abut and the helical portions of the housing assembly and drive-tube guide structure abut, and when the drive-tube is in a second position, axial clearance is provided between the housing assembly and drive-tube axial portions, allowing the helical portion of the drive-tube to slide over the helical portion of the housing assembly. The axial portions of the housing assembly and drive-tube guide structure correspond to axial portions 156, 256, 182, 282 of the housing assembly and drive-tube guide structure. The helical portions of the housing assembly and drive-tube guide structure correspond to helical portions 157, 257, 189, 289 of the housing assembly and drive-tube guide structure of the first and second embodiments.

[0262] In an alternative embodiment, each of the delivered doses is an equal amount.

[0263] In an alternative aspect, the drug delivery device includes a reset mechanism whereby each of the delivered doses is of equal size.

[0264] In an alternative embodiment, the drive spring is pre-tensioned to deliver a predetermined number of doses with a constant force, which can be measured as an axial force transmitted from the piston rod, where the constant force is defined as a force that varies by less than 20 percent between the first and last doses. The force can be measured by placing a force-measuring sensor between the piston rod and the cartridge piston during administration of the predetermined number of fixed doses.

[0265] In alternative embodiments, the predetermined plurality of fixed doses is 2, 3, 4, 5 or 6, preferably 4.

[0266] In an alternative embodiment, the drug delivery device comprises a drug-filled cartridge having a proximally disposed piston, with a piston rod (109, 209) operatively arranged to advance the piston, the cartridge corresponding to cartridge 135, 235 and the piston corresponding to piston 136, 236 of the first and second embodiments.

[0267] In an alternative embodiment, the medication delivery device includes an integrated needle cannula and an actuation mechanism includes a needle shield axially movable into and out of the needle. The shield is adapted to actuate the actuation mechanism in response to proximal movement, thereby uncovering the needle. The needle cannula corresponds to the needle cannula 124, 224, and the shield corresponds to the elongated shield structure 110, 210 of the first and second embodiments.

[0268] In an alternative embodiment, the medication delivery device includes a needle mount for removably mounting an injection needle, and the activation mechanism includes an axially movable release button adapted to activate the drive mechanism in response to axial movement of the release button, the release button corresponding to the shield of the first and second embodiments.

[0269] In an alternative embodiment, the actuation mechanism includes a connector operably connected to the drive mechanism, the connector adapted to actuate the drive-tube in response to axial movement, the connector corresponding to connectors 170, 270 of the first and second embodiments.

[0270] In an alternative embodiment, the actuation mechanism includes a shield for covering the integrated needle and a connector operably connected to the drive mechanism, the shield operably disposed to engage the connector in response to rotating the shield, the shield axially movable and adapted to move the connector, thereby actuating the drive-tube in response to the axial movement. The needle cannula corresponds to needle cannula 124, 224, and the shield corresponds to elongated shield structure 110, 210 of the first and second embodiments. The connector corresponds to connector 170, 270 of the first and second embodiments.

[0271] In an alternative embodiment, the first position of the drive-tube is a distal position and the second position is a proximal position.

[0272] In an alternative embodiment, the drug delivery device is an injection device.

[0273] In an alternative embodiment, the medication delivery device further includes a medication reservoir having a piston arranged to expel medication from the reservoir, and a piston rod adapted to advance the piston axially, the piston rod axially splined to the housing assembly, whereby the piston rod is axially movable relative to the housing assembly and rotationally locked. The drive tube further includes an internal thread, and the piston rod further includes an external thread for threadably engaging with the internal thread of the drive tube, whereby the piston rod is operably connected to the housing assembly and the drive tube and can be advanced upon rotation of the drive tube. The drive mechanism further includes a compression drive spring for axially moving the drive tube and the piston, whereby the drive mechanism and drive guide portion are adapted to drive the drive tube to a first position. During actuation, the drive tube moves together with the piston rod, whereby the piston rod is separated from the piston. During administration, the drive tube performs combined axial and rotational movement, whereby the axial and rotational contributions of the drive tube move the piston rod axially.

[0274] In an alternative embodiment, the medication delivery device further comprises an axially movable spring base, and a compression drive spring is positioned between the spring base and the housing, whereby the torsion drive spring and the compression drive spring are coupled in series. The spring base corresponds to the spring bases 165, 265 of the first and second embodiments.

[0275] In an alternative embodiment, the compression drive spring is integral with a torsion drive spring corresponding to the drive springs 108, 208 of the first and second embodiments, the drive spring being a torsion drive spring having a compression section.

[0276] In an alternative embodiment, there is provided a medication delivery device for sequentially delivering a plurality of predetermined fixed doses, the medication delivery device comprising a housing assembly, a drive mechanism, and an actuation mechanism.

[0277] The housing assembly includes a guide structure including a stop and actuation guide portion and a drive guide portion, the drive guide portion corresponding to the helical portion 157, 257 of the first and second embodiments, and the stop and actuation guide portion corresponding to the axial portion 156, 256 of the first and second embodiments.

[0278] The drive mechanism is adapted to sequentially deliver a predetermined number of doses and includes a drive tube, a torsion drive spring, and a piston rod. The drive tube is adapted to be guided along the stop and actuation guide portion for actuation of the drive mechanism. The drive tube is further adapted to be guided along the stop and actuation guide portion for delivery of a fixed dose, with dosing being stopped by stopping rotation of the drive tube. The drive tube is thereby adapted to be guided in response to execution of a drive-tube dose sequence, including actuation, dosing, and dosing stop. The torsion drive spring is adapted to store an initial amount of energy and is adapted to rotate the drive tube; i.e., in the unpackaged state, the torsion spring is pretensioned by winding it up, thereby storing an initial amount of energy. The piston rod is operably connected to the housing assembly and the drive tube. The drive tube, torsion drive spring, and piston rod correspond to drive tubes 180, 280, torsion drive springs 108, 208, and piston rods 109, 209.

[0279] An activation mechanism is adapted to move the drive tube along the stop and activation guide portion in the first axial direction from the first axial position to the second axial position, thereby activating the drive mechanism. In some embodiments, the medication delivery device may include a shield or push button adapted to operate the activation mechanism to activate the drive mechanism.

[0280] The drive mechanism is further adapted to bias the drive tube in a second axial direction opposite the first axial direction. The drive mechanism is adapted to rotate the drive tube along the drive guide portion and toward the stop and actuation guide portion in response to actuation of the drive mechanism, thereby delivering a fixed dose of a predetermined plurality of fixed doses, and the drive tube is operably positioned to be guided along the stop and actuation guide portion to deliver a subsequent fixed dose of the plurality of fixed doses. In some embodiments, the biasing means may be a compressible torsion drive spring or a compressible return spring coupled in series with the torsion drive spring.

[0281] Each activation of the drive mechanism and completion of the drive tube dose sequence reduces the amount of energy stored in the torsion drive spring. The initial amount of stored energy, which is the stored energy before the first activation, is sufficient or greater than the energy required to deliver a predetermined number of fixed doses.

[0282] In the above description of exemplary embodiments, different structures and means for providing the described functionality for the different components have been described to the extent that the concept of the present invention is clear to those skilled in the art. The detailed construction and specification for the different components are considered to be the subject of normal design procedures carried out by those skilled in the art along the lines described herein.

Claims

1. 1. A drug delivery device for sequentially delivering a plurality of predetermined fixed doses, said drug delivery device comprising: a housing assembly; a drive mechanism comprising a drive-tube (180, 280), said drive mechanism being adapted to deliver said predetermined doses sequentially; - an actuation mechanism for actuating said drive mechanism, 1. A medication delivery device comprising: a drive mechanism comprising a pre-tensioned torsion drive spring (108, 208) adapted to store an initial amount of energy and to rotate the drive tube (180, 280); wherein each actuation of the drive mechanism and completion of a drive-tube dose sequence reduces the amount of stored energy of the drive spring (108, 208); and wherein the initial amount of stored energy, being the stored energy prior to the first actuation, is sufficient to deliver the predetermined multiple of the fixed doses.

2. - said housing assembly comprises a guide structure comprising a stop and start guide portion (156, 256) and a drive guide portion (157, 257); - said drive-tube (180, 280) is adapted to be guided along said stop and actuation guide portions (156, 256) for actuation of said drive mechanism, and along said drive guide portions (157, 257) for delivery of a fixed dose, and dosing is stopped, whereby said drive-tube is adapted to be guided in response to execution of a drive-tube dose sequence comprising actuation, dosing, and stopping dosing; the drive mechanism further comprises a piston rod operatively connected to the housing assembly and the drive tube; 2. The medication delivery device of claim 1, wherein the actuation mechanism is adapted to move the drive tube along the stop and actuation guide portion (156, 256) in a first axial direction from a first axial position to a second axial position, thereby actuating the drive mechanism.

3. 3. The medication delivery device of claim 2, wherein the drive mechanism is further adapted to urge the drive-tube in a second axial direction opposite to the first axial direction, and the drive mechanism is adapted to rotate the drive-tube along the drive guide portion and to the stop and actuation guide portion in response to actuation of the drive-tube, thereby delivering a fixed dose of the predetermined plurality of fixed doses, and the drive-tube is operably positioned to be guided along the stop and actuation guide portion to deliver a subsequent fixed dose of the plurality of fixed doses.

4. 4. The medication delivery device of claim 2, wherein the housing further comprises an internal thread, the piston rod further comprises an external thread for threadably engaging the internal thread of the housing assembly, and the drive tube is axially splined to the piston rod, whereby the drive tube is axially movable and rotationally locked relative to the drive tube, whereby the piston rod is operably connected to the housing assembly and the drive tube.

5. 5. The medication delivery device of claim 1, wherein the torsion drive spring (108, 208) is compressed, whereby the drive mechanism is adapted to bias the drive tube (180, 280) in the second axial direction.

6. A medication delivery device according to any one of claims 1 to 5, wherein the torsion drive spring (108, 208) is disposed between the drive tube (180, 280) and the housing assembly.

7. A medication delivery device according to any preceding claim, wherein the housing assembly comprises a fixed spring base (165, 265), one end of the torsion drive spring (108, 208) being attached to the fixed spring base.

8. 8. The drug delivery device of claim 2, wherein the stop and actuation guide portion (156, 256) of the guide structure is an axial portion, and the drive guide portion (157, 257) of the guide structure of the housing assembly comprises a helical portion.

9. 9. The medication delivery device of any one of claims 2 to 8, wherein the drive tube (180, 280) comprises a corresponding guide structure (182, 189, 282, 287) adapted to cooperate with the guide structure (156, 157, 256, 257) of the housing assembly.

10. 10. The medication delivery device of claim 9, wherein the guide structure (182, 189, 282, 287) of the drive-tube comprises an axial portion (182, 282) and a helical portion (189, 289).

11. 11. The drug delivery device of claim 10, wherein when the drive tube (180, 280) is in a first position, the axial portions (156, 256, 182, 282) of the housing assembly and the guide structure of the drive tube abut and the helical portions (157, 257, 189, 289) of the housing assembly and the guide structure of the drive tube abut, and when the drive tube is in a second position, an axial clearance is provided between the housing assembly and the axial portions (156, 256, 182, 282) of the drive tube, thereby allowing the helical portion of the drive tube (189, 289) to slide over the helical portion (157, 257) of the housing assembly.

12. 12. A medication delivery device according to any one of claims 1 to 11, wherein the drive spring is pre-tensioned to deliver the predetermined multiple doses using a constant force, the force being measurable as an axial force transmitted from the piston rod, the constant force being defined as a force that varies by less than 20 percent between the first dose and the last dose.

13. 13. A drug delivery device as claimed in any one of claims 1 to 12, wherein the drug delivery device comprises a drug-filled cartridge (135, 235) having a proximally disposed piston (136, 236), the piston rod (109, 209) being operatively arranged to advance the piston.

14. 14. The drug delivery device of claim 1, wherein the drug delivery device comprises an integrated needle (124, 224), and the actuation mechanism comprises a needle shield (110, 210) axially movable to cover and uncover the needle, the shield adapted to activate the drive mechanism in response to proximal movement to uncover the needle.

15. 15. A medication delivery device according to any one of claims 1 to 14, wherein the medication delivery device comprises a needle mount for an injection needle, and the activation mechanism comprises an axially movable release button adapted to activate the drive mechanism in response to axial movement thereof.

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