Reusable torsion spring driven injection unit

Abstract

The present invention relates to an injection device in which a drive element transmitting rotation to a piston rod is divided into two elements which are axially movable relative to each other so that the drive mechanism can be released to allow a user to reset the piston rod and replace the cartridge.

Description

Technical Field

[0001] The present invention relates to a torsion spring driven injection device for delivering several doses of a liquid drug. More particularly, the present invention relates to such a torsion spring driven injection device, wherein a user is able to replace an empty cartridge with a new one and thereafter use the injection device multiple times. Background Art

[0002] WO 2020 / 089167 in Figures 1 to 3 A preloaded torsion spring driven automatic injection device manufactured by Novo Nordisk A / S is disclosed under the trade name The drive mechanism comprises a piston rod driver (65) which engages a longitudinal track in the piston rod (30). The piston rod driver (65) may also be connected to a torsion spring (45) which rotates the piston rod driver (65) during the dose discharge. The connection to the torsion spring (45) is via a clutch (60) which may be displaced in the axial direction by a user pushing the injection button (5). The piston rod (30) is further threadedly connected to the housing via a nut portion (70) so that the rotation of the piston rod (30) transmits the piston rod (30) helically in the axial direction. Once the contents of the cartridge (80) have been discharged and the piston rod (30) has moved to its most distal position, it is not possible to move the piston rod (30) back to its initial position. The injection device is therefore classified as a pre-loaded injection device and is discarded once the contents have been discharged.

[0003] US10,537,684 discloses a manually operated injection device in which a user can replace a cartridge. A drive mechanism causes a drive nut to be threadedly connected to a piston rod, and the piston rod is keyed to a lead guide anchored in a housing. When the drive nut is rotated, the piston rod is thereby translated in a distal direction (i.e., does not rotate). When the user removes the cartridge and the cartridge holder, a compression spring pushes the lead guide out of engagement with the housing in a distal direction. When the lead guide is disengaged from engagement with the housing, the lead guide can rotate with the piston rod. During this rotation, the piston rod moves spirally in a proximal direction due to engagement with an internal thread on the drive nut. When the piston rod has moved back to its initial position, the user can insert a new cartridge, which pushes the lead guide back into the engagement in the housing, and the user can reuse the injection device. Summary of the invention

[0004] It is an object of the present invention to provide a torsion spring driven injection device having a very simple and improved mechanism for releasing the piston rod when changing a cartridge.It is another object to provide such a release mechanism suitable for a torsion spring driven injection device.

[0005] Therefore, in one aspect, the present invention relates to a reusable torsion spring driven injection device for expelling several doses of a liquid drug from a loading cartridge. The injection device comprises:

[0006] A piston rod having an outer surface with an external thread extending helically in a longitudinal direction and further provided with a longitudinally extending engagement surface, such as a track or a groove,

[0007] A housing structure, the housing structure comprising:

[0008] a base part having a torsion spring driven discharge mechanism for axially driving the piston rod, and

[0009] - A removable cartridge holder part which holds the cartridge and is connectable to the base part.

[0010] The torsion spring driven discharge mechanism comprises:

[0011] a rotatable piston rod driver engaging an engagement surface of the piston rod such that a rotation of the rotatable piston rod driver is transferred into a similar rotation of the piston rod,

[0012] internal threads associated with the housing structure and engaging external threads on the piston rod such that the piston rod moves helically when rotated, and

[0013] A strained torsion spring which maintains a torque for rotating the rotatable piston rod driver during dose expelling.

[0014] The rotatable piston rod driver further comprises an outer element and an inner element releasably coupled together:

[0015] the outer element remains fixed during dose setting and rotates by the torque of the torsion spring during dose expulsion, and the inner element is axially movable relative to the outer element between a first uncoupled position and a second coupled position,

[0016] The first uncoupled position is a position where the inner element is uncoupled from the outer element so that the inner element can rotate independently of the outer element, and the second coupled position is a position where the inner element is coupled to the outer element to follow the rotation of the outer element.

[0017] According to the invention, a movable element operatively connected to the inner element is axially movable to axially move the inner element from a first uncoupled position to a second coupled position.

[0018] By dividing the piston rod driver into two separate elements that can slide axially relative to each other, a very simple and reliable release mechanism can be obtained, which is very suitable for torsion spring driven injection devices. In torsion spring driven injection devices, the torque in the torsion spring is preferably fixed between injections, and when the torque is fixed, the user can therefore manipulate the piston rod driver without releasing the torque in the torsion spring. Therefore, making the piston rod driver a two-part construction allows one part to move axially without actuating the other part, which can then remain connected to the torsion spring driven expulsion mechanism.

[0019] This solution is particularly suitable for drive mechanisms of this type, wherein the piston rod is rotated by the piston rod driver during an injection, so that a part of the piston rod driver can slide in translation relative to the piston rod when changing a cartridge.

[0020] The movable element is operably connected to the inner element to move the inner element axially. Such movable elements can be actuated manually by a user or by attachment of a cartridge holder part. In the latter case, the movable element can be triggered by the cartridge holder part itself or by the actual cartridge.

[0021] In one example, the movable element is an element that is axially movable relative to the housing structure.Such an element may be arranged on an outer surface of the injection device or inside the injection device.

[0022] The movable element is operably connected to the inner element so that any axial movement of the movable element is converted into axial movement of the inner element. However, the movable element does not need to be directly connected to the inner element; the connection is operably, meaning that the movement of the movable element is converted into the movement of the inner element, for example through a different element. The term operably connected also means that the movable element and the inner element are separate parts, but they are connected.

[0023] In one example, the movable element and the inner element move in unison so that any movement of the movable element is transferred one-to-one to the inner element. In a different example, a transmission may be provided between the movable element and the inner element.

[0024] In the opposite direction, the inner element is preferably moved distally to the first uncoupled position by spring means. Such spring means is preferably a compression spring arranged between the housing part and the inner element. The compression spring preferably pushes the movable element in the distal direction, the inner element coupled to the movable element following this movement.

[0025] The movable element and thus the inner element is moved proximally to the second coupling position by engagement with the cartridge holder part or by engagement with the cartridge itself.Alternatively, the movable element is moved manually by a user.

[0026] In the latter example, the movable element is a sleeve or sleeve-like element, which is telescopically movable relative to the housing structure and preferably manually movable by a user. In order for the user to operate the sleeve, the sleeve is arranged outside the housing structure and thus slides axially on the outside of the housing structure.

[0027] By sleeve is here meant a tubular element surrounding the injection device. However, the sleeve does not necessarily have to completely surround the injection device. It can also be a sleeve-like element covering less than 360 degrees and can therefore have many different appearances. The purpose of the sleeve or sleeve-like element is to transmit the axial movement to the inner element and is preferably accessible by the user from the outside on the housing structure.

[0028] Inside the housing structure, the sleeve is connected to the inner element such that an axial movement of the sleeve is converted into an axial movement of the inner element.

[0029] The sleeve is preferably arranged so that the sleeve abuts the cartridge holder part when installed. If the user does not manually move the sleeve proximally for some reason, this will be done automatically once the user installs the cartridge holder part to the remaining housing structure.

[0030] In another example, a compression spring is enclosed between the sleeve and the housing structure such that the sleeve automatically moves in the distal direction when the cartridge holder part is removed.

[0031] In one example, the movable element is connected to the inner element via an inner ring arranged between the movable element and the inner element. In this example, a spring device such as a compression spring may be arranged between the movable element and the housing portion, the housing portion being for example a nut member fixed in a base portion of the housing structure.

[0032] In one example, such a nut member can be press-fitted into the housing structure and preferably has an internal thread for helically moving the piston rod. Thus, the movable element can be operated by a nut member provided with an axial leg, which is operated through an opening in the nut member. The compression spring is thus located on the distal side of the nut member, while the piston rod driver is arranged on the proximal side of the nut member.

[0033] definition:

[0034] An "injection pen" is generally an injection device having an oblong or elongated shape, somewhat like a pen used for writing. While such pens generally have a tubular cross-section, they can easily have a different cross-section, such as triangular, rectangular or square or any variation around these geometric shapes.

[0035] The term "needle cannula" is used to describe the actual catheter that performs the skin penetration during an injection. The needle cannula is usually made of a metallic material such as stainless steel and is preferably connected to a needle hub made of a suitable material such as a polymer. However, the needle cannula can also be made of a polymer material or a glass material. The needle hub and the needle cannula are often referred to together as a "needle assembly". The needle hub usually has a connection device for connecting the needle assembly to the injection device. The "connection device" can be, for example, a Luer connector, a bayonet connector, a threaded connector, or any combination thereof.

[0036] As used herein, the term "liquid drug" is intended to encompass any flowable medicament containing a drug, such as a liquid, solution, gel, or fine suspension, that can be passed through a delivery device such as a hollow needle cannula in a controlled manner. Representative drugs include drugs such as peptides, proteins (e.g., insulin, insulin analogs, and C-peptide), hormones, biologically derived or active agents, hormone- and gene-based agents, nutritional formulas, and other substances in solid (dispensed) or liquid form.

[0037] "Cartridge" is a term used to describe the container that actually contains the drug. Cartridges are usually made of glass, but can also be molded from any suitable polymer. The cartridge or ampoule is preferably sealed at one end by a pierceable membrane called a "septum", which can be pierced, for example, by the non-patient end of a needle cannula. Such a septum is usually self-sealing, which means that once the needle cannula is removed from the septum, the opening created during penetration automatically seals by inherent elasticity. The opposite end of the cartridge is usually closed by a plunger or piston made of rubber or a suitable polymer. The plunger or piston can be slidably movable inside the cartridge. The space between the pierceable membrane and the movable plunger contains the drug, and the drug is pressed out when the plunger reduces the volume of the space containing the drug.

[0038] Cartridges for both prefilled injection devices and for durable injection devices are typically filled with a predetermined volume of liquid drug at the factory by the manufacturer. A large number of cartridges currently available contain 1.5 ml or 3 ml of liquid drug.

[0039] Since the cartridge generally has a narrow distal neck into which the plunger cannot move, not all of the liquid drug contained in the cartridge can actually be expelled. The term "initial amount" or "substantially used" therefore refers to the injectable contents contained in the cartridge and therefore does not necessarily refer to the entire contents.

[0040] The term "prefilled" injection device refers to an injection device in which a cartridge containing a liquid drug is permanently embedded in the injection device so that it cannot be removed without permanently destroying the injection device. Furthermore, in a prefilled device it is usually not possible to move the piston rod back to its initial position and therefore such prefilled injection devices can only be used if the piston rod is moved in a direction to empty the cartridge. Once the prefilled amount of liquid drug in the cartridge has been used, the user typically discards the entire injection device. Typically, a cartridge filled with a specific amount of liquid drug by the manufacturer is fixed in a cartridge holder which is then permanently connected to the housing structure so that the cartridge cannot be replaced.

[0041] This is in contrast to a "durable" injection device in which the user can move the piston rod back to its initial position himself and replace the cartridge containing the liquid drug when the cartridge is empty. Therefore, the injection device can be reused many times. Prefilled injection devices are usually sold in packages containing more than one injection device, while durable injection devices are usually sold one at a time. When using prefilled injection devices, the average user may need as many as 50 to 100 injection devices per year, while when using a durable injection device, a single injection device can last for several years, however, the average user may need 50 to 100 new cartridges per year.

[0042] "Scale drum" refers to a preferably cylindrical element with markings that indicate to the user of the injection pen the size of the selected dose. The cylindrical element constituting the scale drum may be solid or hollow. "Markings" refers to the incorporation of any kind of printed or otherwise provided symbols, such as engraved or pasted symbols. These symbols are preferably, but not exclusively, Arabic numerals from "0" to "9". In different examples, letters of the alphabet from any available alphabet may be used. However, the symbol may also be a graphic image indicating a specific situation or a specific use, such symbols may be, for example, a key, a lock, a teardrop or similar symbol that provides user information related to the use of the injection device. In conventional pen constructions, the markings are visible through a window or opening provided in the housing structure.

[0043] The term "automatic" used in conjunction with an injection device means that the injection device is capable of performing an injection without the need for the user of the injection device to transmit the force required to expel the drug during the administration process. This force is usually transmitted automatically by a motor or spring driver. The spring used for the spring driver is usually tensioned by the user during dose setting, however, such springs are usually pre-tensioned to avoid problems with delivering very small doses. Alternatively, the manufacturer may fully pre-load the spring with a pre-load force sufficient to empty the entire cartridge through multiple doses. Typically, the user activates a latch mechanism provided on the surface of the housing or at the proximal end of the injection device to fully or partially release the force accumulated in the spring when an injection is performed.

[0044] The term "protective cap" in this article means a cover or sleeve-like structure that is installed at the distal end of the injection device between injections. Such a cover or sleeve-like structure is usually closed at the distal end to completely enclose the distal part of the injection device. Therefore, the protective cap is fixed to the distal end of the injection device and protects the distal end of the injection device between injections. If the needle cannula is permanently or replaceably mounted to the distal end of the injection device, such needle cannula is also protected by the protective cap thereafter. Since the protective cap is installed each time an injection is performed, the term "reinstallation" can also be used to describe the installation of the protective cap. In addition, since the housing structure of the injection device usually has a window through which the user can visually inspect the liquid drug, the protective cap is also used to protect the liquid drug from prolonged exposure to light, because some liquid drugs are sensitive to light, especially light in the UV range.

[0045] The terms "permanently connected" or "permanently embedded" as used in this specification are intended to mean that the components of the cartridge implemented in this application as permanently embedded in the housing require the use of tools to separate and if the components are separated, at least one of the components will be permanently damaged.

[0046] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference in their entirety to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0047] All headings and sub-headings are used herein for convenience only and should not be construed as limiting the invention in any way.

[0048] Unless otherwise stated, the use of any and all examples or exemplary language (such as) provided herein is intended only to better illustrate the present invention, rather than to limit the scope of the present invention. Any language in this specification sheet should not be construed as indicating that any undeclared element is essential to the practice of the present invention.

[0049] The citation and incorporation of patent documents herein is for convenience only and does not reflect any view of the validity, patentability, and / or enforceability of such patent documents.

[0050] This invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The present invention will be explained more fully below in conjunction with preferred embodiments and with reference to the accompanying drawings, in which:

[0052] Figure 1 An exploded view of an example of a prior art torsion spring driven pre-filled injection device is shown.

[0053] Figure 2Shows that during dose setting Figure 1 A cross-sectional view of the proximal portion of a prior art torsion spring injection device.

[0054] Figure 3 Shows that during dose expulsion Figure 1 A cross-sectional view of the proximal portion of a prior art torsion spring injection device.

[0055] Figure 4 An exploded view of a first example of an injection device according to the invention is shown.

[0056] Figure 5 A cross-sectional view of a first example is shown, wherein the cartridge holder is attached to an injection device.

[0057] Figure 6 A cross-sectional view of a first example is shown, wherein the cartridge holder is attached to an injection device and comprises a release spring.

[0058] Figure 7 A cross-sectional view of the first example is shown with the release mechanism in the second locked position and the piston rod extended.

[0059] Figure 8 A cross-sectional view of a first example is shown with the release mechanism in a first, unlocked position and the piston rod extended.

[0060] Fig. 9 A cross-sectional view of a first example is shown with the release mechanism in a first, unlocked position and the piston rod retracted.

[0061] Fig.10 A cross-sectional view of the first example is shown with the release mechanism in the second locked position and the piston rod retracted.

[0062] Fig.11 The piston rod driver is shown in a disengaged state, ie a first position, in which the inner element is uncoupled from the outer element.

[0063] Fig.12 The piston rod driver is shown in an engaged state, ie a second position, wherein the inner element and the outer element are coupled together.

[0064] Fig.13A An exploded view of a second example of an injection device according to the invention is shown.

[0065] Fig. 13B An exploded cross-sectional view of a second example of an injection device according to the invention is shown.

[0066] Fig. 13C As indicated by the dashed line Fig.13A The cut out portion.

[0067] Fig.14 A cross-sectional view of the second example is shown with the release mechanism in a first, unlocked position.

[0068] Fig.15 A cross-sectional view of a second example is shown with the release mechanism in a first, unlocked position and contact between the plunger and the piston rod foot.

[0069] Fig.16 A cross-sectional view of the second example is shown with the release mechanism in a second locked position.

[0070] Fig.17A An exploded view of a third example of an injection device according to the invention is shown.

[0071] Fig. 17B An exploded cross-sectional view of a third example of an injection device according to the present invention is shown.

[0072] Fig.18 A cross-sectional view of the third example is shown with the release mechanism in a first, unlocked position.

[0073] Fig.19 A cross-sectional view of the third example is shown with the release mechanism in a second locked position.

[0074] Fig. 20 A cross-sectional view of a fourth example of an injection device according to the invention is shown with the cartridge holder removed and the release mechanism in a first, unlocked position.

[0075] Fig.21 A cross-sectional view of a fourth example of an injection device according to the invention is shown with a cartridge holder attached and the release mechanism in a second locked position.

[0076] Fig. 22 An exploded view of the release mechanism is shown.

[0077] Fig.23 A perspective view of the release mechanism is shown in a first, unlocked position.

[0078] Fig.24 A perspective view of the release mechanism is shown in a second locked position.

[0079] For the sake of clarity, these figures are schematic and simplified, and they merely show details which are essential to the understanding of the invention, while other details are omitted. Throughout, the same reference numerals are used for the same or corresponding parts. DETAILED DESCRIPTION

[0080] When using the following terms such as "upper" and "lower", "right" and "left", "horizontal" and "vertical", "clockwise" and "counterclockwise" or similar relative expressions, these terms are only used with reference to the drawings and not to actual usage. The drawings shown are schematic representations and for this reason the configuration of the different structures as well as their relative sizes are used for illustrative purposes only.

[0081] In this context, it may be convenient to define the term "distal end" in the drawings to mean the end of the injection device which holds the needle cannula and which points toward the user during injection, whereas the term "proximal end" means the opposite end which typically carries the injection button, e.g. Figure 1 Distal and proximal refer to axial directions extending along the longitudinal axis (X) of the injection device, also referred to as Figure 2 In the public.

[0082] When referring to clockwise and counterclockwise in the following examples, it should be understood that the injection device is viewed from its distal side, i.e. from a position distal to the injection device. Thus, clockwise is a rotation towards the right like the arm of a clock, while counterclockwise is a rotation towards the left.

[0083] In order to explain the various movements that occur in the described injection device, the following terminology is used throughout the following examples;

[0084] "Translational motion" refers to strictly linear motion in the axial direction, but without any rotation.

[0085] A "rotational movement" is any rotational movement about a center, which may be a central point, ie in one plane, or a central axis, ie having a longitudinal extension.

[0086] "Axial motion" means any motion in an axial direction, for example along a central axis. This motion may be strictly translational, or include rotational motion, making it a "helical motion", as this implies a combination of translational and rotational motion.

[0087] "Telescopic" is intended to cover the situation where the movable element moves out of and / or into the base element. The movement may be translational, ie without any rotation, or the movement may include rotation, so that the telescopic movement is helical.

[0088] Examples of prior art

[0089] Figure 1 , 2 and 3 discloses also in WO 2020 / 089167 Figure 1 , 2 The torsion spring driven injection device disclosed in and 3. The automatic injection device is manufactured by Novo Nordisk A / S and is marketed under the trade name sell.

[0090] The following table identifies Figure 1 , 2 and 3. The various parts of the prior art injection device disclosed in FIG.

[0091]

[0092]

[0093] The dose setting and injection mechanism is built into a housing structure, which basically comprises a base portion 55 and a cartridge holder 85. A cartridge 80 containing a liquid drug is fixed in the cartridge holder 85 locked by a nut portion 70. The base portion 55 is closed at the proximal side by a spring seat 20. In the disclosed example, the four parts of the spring seat 20, the base portion 55, the nut portion 70 and the cartridge holder 85 together constitute the housing structure. The housing structure can alternatively be made of other parts that can be connected in many different ways. It is also possible to make the housing structure from a different number of parts, or even to mold the housing structure as one unit.

[0094] The disclosed torsion spring 45 is a helical metal coil spring contained between a spring seat 20, which is a non-rotatable part of the housing structure, and a rotatable ratchet tube 50. When the ratchet tube 50 rotates relative to the housing structure, torque is thereby established and stored in the torsion spring 45.

[0095] Dose setting

[0096] exist Figure 2 Dose setting is disclosed in . Whenever the user wants to set the dose size of the liquid drug to be discharged, the user rotates the dose dial 15. The dose dial 15 is connected to the toothed interface 16, 26 (see for example Figure 1 ) is rotationally coupled to the reset tube 25 so that the dose dial 15 and the reset tube 25 rotate together during dose setting.

[0097] The reset tube 25 is further rotationally coupled to a ratchet tube 50, which therefore also rotates with the dose dial 15 and the reset tube 25 during dose setting. The coupling between the ratchet tube 50 and the reset tube 25 is preferably such that the two parts 25, 50 are axially locked to each other, but can be rotated a few degrees relative to each other to reduce the set dose, as will be explained. However, the two parts 25, 50 may alternatively be molded as one integral part, in which case it is not possible to regret and reduce the set dose.

[0098] like Figures 1 to 3 As shown in FIG. 1 , the clutch 60 is provided with a plurality of outwardly directed teeth 61 on the outer surface, which are engaged during dose setting ( Figure 2), which teeth are engaged by similar teeth 56 provided inside a base portion 55 of the housing structure, such that the clutch 60 is held non-rotatable during dose setting.

[0099] The clutch 60 is snap-fitted to the collar 53 provided on the ratchet tube 50 in the axial direction so that the ratchet tube 50 and the clutch 60 move axially together. However, the snap-fit ​​is designed so that the clutch 60 can rotate relative to the clutch 60.

[0100] The clutch 60 is internally provided with a toothed ring 62 which is engaged by flexible arms 51 provided distally on the ratchet tube 50 (any number of flexible arms 51 may be provided). This engagement allows the ratchet tube 50 to rotate in only one direction (relative to the clutch 60 which is anchored in the housing structure during dose setting). In the figures, this allowed direction is counterclockwise (when viewing the injection device from the distal side), however this is only in the given example and the opposite direction may be possible if desired. Figure 1 The permitted direction indicated by arrow "A" in FIG. 1 is the direction in which the torsion spring 45 is tensioned, which is included between the spring seat 20 and the ratchet tube 50. Torque is therefore stored in the torsion spring 45 during rotation of the dose dial 15, and the engagement between the flexible arm 51 on the ratchet tube 50 and the toothed ring 62 inside the clutch 62 prevents this torque from being released.

[0101] The spring seat 20 is non-rotatably fixed to the base portion 55 of the housing structure so that the torsion spring 20 is tensioned when the ratchet tube 50 is rotated in the counterclockwise direction.

[0102] The ratchet tube 50 is provided with ridges 52 on the outer surface which engage corresponding longitudinal recesses 41 provided on the inner surface of the scale drum 40. This interface forces the scale drum 40 to rotate with the ratchet tube 50 at all times.

[0103] The scale drum 40 is also provided with a helical thread 42 on the outer surface which engages an internal thread 57 inside the base portion 55 of the housing structure so that the scale drum 40 moves helically when rotated. This helical movement of the scale drum 40 brings the markings 43 printed in a spiral pattern into the confines of a window 58 in the base portion 55 so that the user can visually follow the dose setting.

[0104] If the user accidentally sets the dose size to be higher than the dose actually required, the set dose can be reduced by rotating the dose dial 15 in the opposite direction, as described below.

[0105] Dose reduction

[0106] When the user regrets the set dose and wants to lower the set dose, the user rotates the dose dial 15 in a clockwise direction (also when viewed from the distal side), which rotation is converted into a rotation of the reset tube 25 also in a clockwise direction.

[0107] The reset tube 25 is coupled to the ratchet tube 50 such that the two elements 25 , 50 are axially locked to one another but can rotate a few degrees relative to one another.

[0108] However, the ratchet tube 50 is engaged with the clutch 60 by means of the flexible arm 51 engaging the toothed ring 62 of the clutch 60, and the clutch 60 is rotationally fixed in the housing structure by means of the interface between the outwardly directed teeth 61 and the inwardly directed teeth 56 in the base portion 55 of the housing structure. The ratchet tube 50 is therefore not immediately rotatable in a direction to reduce the set dose.

[0109] The reset tube 25 is provided on the distal side with an axially extending key 27 which engages on the outside of the flexible arm 51, and when the reset tube 25 is rotated a few degrees clockwise relative to the ratchet tube 50, the flexible arm 15 is pressed towards the center line X to thereby reduce the set dose. This dial-down mechanism is described in more detail in, for example, US 9,132,239.

[0110] The influence of the key 27 on the flexible arm 51 thus forces the flexible arm 51 to disengage from the clutch 60, so that the torque of the torsion spring 80 can rotate the ratchet tube 50 in a clockwise direction. Since the rotation speed of the ratchet tube 50 when affected by the torque of the torsion spring 45 is higher than the rotation speed of the reset tube 25 operated by the user, the flexible arm 51 reengages the first previous tooth in the toothed ring 62. The set dose size can thus be gradually reduced by rotating the dose dial 15 in the opposite direction to that used when setting the dose (i.e., clockwise in the example).

[0111] Both during dose setting and when regretting a set dose, the scale drum 40 is forced to helically rotate by engagement with the ratchet tube 50 so that the user can check the resulting set dose in the window 58 at any time.

[0112] Once the correct dose has been reached, the user inserts the pen needle through the skin and injects the set dose.

[0113] injection

[0114] The injection is performed by pushing the injection button 5 in the distal direction against the bias of the return spring 10 by a distance determined by Figure 2 and Figure 3 The dotted line "P" indicates.

[0115] The injection button 5 snaps into the reset tube 25, as shown in FIG. Figure 3, which shows the situation during injection. The injection button 5 thus also moves the reset tube 25 in the distal direction.

[0116] like Figure 3 As also seen in FIG. 1 , the ratchet tube 50 is axially coupled to the reset tube 25, and the clutch 60 is coupled to the ratchet tube 50. The result is that both the ratchet tube 50 and the clutch 60 move in the distal direction when the user pushes the injection button 5 and the reset tube 25 distally.

[0117] Distal movement of the clutch 60 disengages the outwardly directed teeth 61 on the clutch 60 from the teeth 56 inside the base portion 55 of the housing structure, as shown in FIG. Figure 3 . Therefore, when the injection button 5 is pushed distally, there is nothing to keep the torque stored in the torsion spring 45. Therefore, the torque of the torsion spring 45 rotates the ratchet tube 50, and the flexible arm 51 provided on the ratchet tube 50 converts this rotation into a rotation of the clutch 60. The reset tube 25 also rotates with the ratchet tube 50. In the disclosed example, this rotation occurs in a clockwise direction.

[0118] like Figure 1 As shown in , the reset tube 25 engages the dose dial 15 with a toothed engagement 16, 26 such that when the reset tube 25 moves distally, the engagement disengages such that the dose dial 15 does not follow the rotation of the reset tube 25 during an injection.

[0119] However, the scale drum 40 is always engaged with the ratchet tube 50 so that when the ratchet tube 50 is rotated during an injection, the scale drum 40 is spirally rotated back to its initial position. Figure 2 and Figure 3 Both show the scale drum 40 in the "zero" position.During dose setting, the scale drum 40 is moved helically in the distal direction.

[0120] When the ratchet tube 50 together with the clutch 60 moves distally out of engagement with the base portion 55 of the housing structure, the outwardly directed teeth 61 provided on the clutch 60 move axially into engagement with corresponding teeth 66 provided on the piston rod driver 65 .

[0121] Therefore, the torque of the torsion spring 45 is converted into a rotation of the piston rod driver 65, which is also provided with one or more one-way arms 67, which engage the toothed periphery 59 inside the base part 55 of the housing structure, thereby allowing the piston rod driver 65 to rotate in only one rotational direction (clockwise in the example of the present disclosure when viewed from the distal side).

[0122] The piston rod driver 65 is internally provided with one or more inwardly directed ridges 68 which engage the longitudinal grooves 31 in the piston rod 30 such that the piston rod 30 is forced to rotate with the piston rod driver 65 during injection.

[0123] Due to the engagement between the threads 71 ​​of the nut portion 70 and the threads 32 of the piston rod 30, the rotation of the ratchet tube 50, the scale drum 40, the clutch 60 and the reset tube 25 under the torque of the torsion spring 45 and the resulting rotation of the piston rod 30 causes the piston rod 30 to spirally rotate in the distal direction.

[0124] The piston rod 30 pushes the piston rod foot 75 distally, which translates the forward movement of the piston rod 30 into forward movement of the plunger 81 inside the cartridge 80 , which again forces a volume of liquid drug to exit through the lumen of the pen needle.

[0125] like Figure 1 As best shown in FIG. 1 , the scale drum 40 carries a plurality of markings 43 printed on the outer surface in a spiral row. These markings 43 pass through windows 58 in the housing structure during dose setting, dose reduction and injection. Any random number of markings 43 may be provided and may be used in any manner. Figure 1 In the disclosed example, these markings 43 are Arabic numerals ranging from 0 to 80. Typically, these numbers indicate some kind of unit related to the liquid drug contained in the cartridge 80, but obviously any kind of markings may be used.

[0126] The scale drum 40 is fixed to the ratchet tube 50 in the longitudinal direction and is threadedly connected to the base portion 55 of the housing structure so that when the ratchet tube 50 is rotated as explained, the scale drum 40 moves helically. When the dose desired to be expelled has been reached, the user pushes the injection button 5 in the distal direction to thereby expel the set dose. Figures 1 to 3 In the example disclosed in , for any given dose size, the injection button 5 together with the reset tube 25 and the ratchet tube 50 are movable in the distal direction.

[0127] Furthermore, a content stop and safety nut 35 is provided, the use of which is explained in EP 1,869,870 and EP 1,869,871.

[0128] Example:

[0129] The present invention relates to a mechanism for releasing a piston rod when replacing a cartridge in an injection device. The release mechanism is disclosed in the context of, however, the release mechanism is not limited to this particular injection device but may be used with any kind of related injection device.

[0130] By incorporating a release mechanism as described herein into an injection device (e.g. ), the resulting injection device can be used multiple times because the cartridge can be replaced. Therefore, the injection device according to the present invention is a durable injection device.

[0131] First Example of the Invention

[0132] In the following example, Figures 1 to 3 Each physical element that is identical or similar in the injection device disclosed in the invention is referenced by the same reference numeral preceded by a "1". Figures 4 to 12 In the following example in FIG. 1 , the piston rod is provided with reference number “ 130 ”.

[0133] For example Figure 4 and Figure 5 As can be seen in the figure, the piston rod 130 is provided with a longitudinal track structure 131 and an external thread 132. A well-known content termination nut is spirally guided by the external thread 132.

[0134] The housing structure comprises a base portion 155, a cartridge holder portion 185 and a nut element 170. The base portion 155 is provided with one or more guide projections 154 which engage an internal track 186 provided inside the cartridge holder portion 185 so that together they form a bayonet coupling, although other kinds of connections may be used to connect the cartridge holder portion 185.

[0135] The nut element 170 is irreversibly connected to the base portion 155 of the housing by a snap-fit ​​interface, or alternatively molded as an integral part of the base portion 155 of the housing structure. The nut element 170 is provided with an internal thread 171 on the inner surface, which cooperates with the external thread 132 of the piston rod 130 so that the rotation of the piston rod 130 transmits the piston rod 130 helically in the axial direction.

[0136] The nut element 170 further holds a clamp 187, for example made of metal, which in the disclosed example is provided with three proximally directed legs 188, which engage the nut element 170 such that the clamp 187 can be moved axially without being disengaged from the nut element 170. The clamp 187 is urged in the distal direction by a compression spring 189, which is enclosed between the nut element 170 and the metal clamp 187. The purpose of this clamp 187 is to urge the cartridge 180 in the distal direction such that a shoulder of the cartridge 180 abuts the cartridge holder 185 at its distal end.

[0137] The ejection mechanism includes a torsion spring 145, such as Figure 5As disclosed in , the torsion spring rotates the piston rod driver 165 during dose expulsion. As also disclosed in prior art examples, when the user pushes the injection button 105, the clutch 160 may move in the distal direction and disengage from the teeth 156 inside the housing portion 155.

[0138] The piston rod driver 165 is composed of Fig.11 and Fig.12 The invention consists of two elements disclosed in the invention: an inner element 190 engaging the piston rod 130 and an outer element 195 engaged by the clutch 160 at least during dose expulsion.

[0139] The inner element 190 is internally provided with one or more inwardly directed ridges 191 which engage longitudinal tracks 131 provided in the piston rod 130 so that rotation of the inner element 190 is translated into a similar rotation of the piston rod 130. The inner element 190 is also provided with a plurality of outwardly directed teeth 192 on its outer surface.

[0140] These teeth 192 cooperate with similar inwardly directed teeth 196 disposed on the interior of the outer member 195. The outer member 195 also includes any number of radial snapping arms 197 and a plurality of axially extending arms 198.

[0141] The radial snapping arms 197 ride on internal teeth provided in the base portion 155 of the housing structure, so that different sounds are emitted when the outer element 195 is rotated. The engagement with the base portion 155 of the housing structure is preferably formed so that the outer element 195 can only rotate in one rotational direction relative to the housing structure. The allowed direction is the direction that moves the piston rod 130 towards the distal end of the housing structure.

[0142] The outer element 195 is preferably fixed in its axial position by the nut element 170, so that the outer element 195 cannot move axially, but can only rotate.

[0143] The axially extending arm 198 engages the spring drive mechanism during dose expulsion as known from examples of the prior art so that torque can be transferred from the torsion spring 145 to rotation of the outer element 195 of the piston rod driver 165 during dose delivery. As in the prior art examples, the outer element 195 engages the clutch 160 of the spring drive mechanism at least during dose expulsion so that the outwardly directed teeth 161 provided on the clutch 160 drive the axially extending arm 198 on the outer element 195.

[0144] The inner member 190 can also be moved in translation to engage and disengage with the outer member 195, such as Fig.11 As shown by arrow “D” in FIG.

[0145] In the first position, Fig.11When the inner element 190 and the outer element 195 are not coupled, the inner element 190 is free to rotate independently of the outer element 195.

[0146] In the second position, Fig.12 When the inner element 190 disclosed in is coupled to the outer element 195 , the inner element 190 will follow any rotation of the outer element 195 , such that a rotation of the outer element 195 will be transferred into a similar rotation of the piston rod 130 .

[0147] The nut element 170, which is irreversibly fixed to the housing structure, is surrounded by a movable sleeve 100. The movable sleeve 100 can slide axially along the housing structure without rotation. To accommodate axial movement, the base portion 155 of the housing structure and the nut element 170 are both provided with one or more longitudinal slits or openings.

[0148] On the inner surface, the movable sleeve 100 carries a ring element 101 which snap-fits into the movable sleeve 100 and thus follows the axial movement of the sleeve 100 .

[0149] like Figure 5 As can be best seen in FIG. 1 , this ring element 101 engages an inner element 190 of the piston rod driver 165 such that the inner element 190 moves axially together with the movable sleeve 100 .

[0150] Figure 7 The situation that the piston rod 130 has moved to a certain position and the user wishes to replace the cartridge 180 is disclosed. Figure 7 In the embodiment, the cartridge 180 and the cartridge holder portion 145 have been removed, but the inner element 190 remains as shown. Fig.12 The middle is connected to the outer element 195.

[0151] exist Figure 8 In FIG. 1 , the user has moved the movable sleeve 100 in the distal direction, as indicated by arrow "B". Since the movable sleeve 100 is connected to the ring element 101, this element has also been moved in the distal direction. As the movable sleeve 100 and the ring element 101 move, they pull along the inner element 190 in the distal direction, so that the inner element 190 is not coupled to the outer element 195.

[0152] Once the inner member 190 and the outer member 195 have been Figure 8 (as well as Fig.11 ) disclosed in the foregoing, the inner element 190 is free to rotate. Uncoupling here means that the teeth 192 on the inner element 190 have moved out of engagement with the inwardly directed teeth 196 on the outer element 195. Therefore, when the inner element 190 now follows the rotation of the piston rod 130, the user can rotate the piston rod 130 back in the threads 171 in the nut member 170.

[0153] Once the piston rod 130 has rotated back to Fig. 9 From the starting position disclosed in the figure, the user can move the movable sleeve 100 in the proximal direction to thus move the inner element 190 proximally. Since the inner element 190 is guided in the longitudinal track 131 in the piston rod 130, the inner element 190 can be moved in translation without affecting the rotational position of the piston rod 130.

[0154] exist Fig.10 In the embodiment of the present invention, the movable sleeve 100 has moved back to the second position, wherein the inner element 190 is again coupled to the outer element 195 to follow the rotation of the outer element 195. Fig.10 Indicated by the arrow "C" in the figure.

[0155] In this second position, the clutch 160 , when rotated by the torsion spring 145 , rotates the outer element 195 , which again rotates the inner element 190 and thereafter also the piston rod 130 .

[0156] If the user is not in the Fig.10 This will occur automatically when the user mounts the cartridge holder 185 onto the base portion 155 of the housing structure by moving the movable sleeve 100 in the proximal direction as shown. Figure 5 As best seen in FIG. 1 , the cartridge holder portion 185 abuts the movable sleeve 100 and forces the movable sleeve 100 to its proximal position when installed.

[0157] exist Figure 6 In another example disclosed in , a compression spring 109 may be provided between the base portion 155 of the housing structure and the movable sleeve 100 , so that when the user removes the cartridge holder portion 185 , the movable sleeve 100 is automatically moved in the distal direction.

[0158] Second Example of the Invention

[0159] Each physical element in this example that is identical or has a similar function to that of the previously disclosed injection device is referenced by the same reference numeral preceded by a "2". Fig.16 In the following example in FIG. 1 , the piston rod is provided with reference mark “ 230 ”.

[0160] like Fig.13A As shown in FIG. 2B , the piston rod 230 is provided with an external thread 132 and a longitudinal track structure 231 .

[0161] The rotatable piston rod driver 265 is divided into an inner part 290 engaging the track structure 231 of the piston rod 230 and an outer part 295 engaging the drive mechanism at least during dose expelling.

[0162] In this example, the housing structure further comprises a nut member 270 which is irreversibly connected to the base portion by a snap-fit ​​engagement. The nut member 270 is internally provided with a thread 271 which engages the external thread 232 of the piston rod 230 .

[0163] In this example, the nut member 270 is provided with an inner track 272 that can engage with an outwardly directed protrusion 284 provided on the cartridge holder portion 280. The engagement between the nut member 270 and the cartridge holder portion 280 is preferably a bayonet coupling. In the disclosed example, two such tracks 272 and two protrusions 284 are shown, however any number may be present.

[0164] The compression spring 289 is enclosed between the nut member 270 and the sleeve element 287 so that the sleeve element 287 is urged in the distal direction. The sleeve element 287 has an outwardly directed flange 287a and an inwardly directed flange 287b (see Fig.16 ). The outwardly directed flange 287a is engaged by the compression spring 289 and the inwardly directed flange 287b engages the release element 200.

[0165] exist Fig. 13C The release element 200 disclosed in an enlarged form in FIG. 2 is provided proximally with a flange 201 which connects the release element 200 to the inner element 290 such that the release element 200 and the inner element 290 move together in the axial direction.

[0166] The release element 200 further comprises a set of outer arms 202 and a set of inner arms 203. The outer arms 202 terminate distally in an inclined surface 206 and the inner arms 203 terminate distally in a hook 204. These arms 202, 203 are preferably provided in pairs, but other numbers are contemplated.

[0167] Also like Fig. 13C As seen in FIG, the inner element 290 is provided with a ring of outwardly directed teeth 292 and the outer element 295 is provided with a similar ring of inwardly directed teeth 296.

[0168] In a similar Fig.11 In the first position of the disclosure, the inner element 290 is not coupled to the outer element 295, so that the inner element 290 can rotate freely and in a position corresponding to Fig.12 In the second position, the inner element 290 is coupled to the outer element 295 so that they rotate together. This engagement is preferably achieved by engagement between the teeth 292 on the inner element 290 and the teeth 296 on the outer element 295.

[0169] Fig.14The state that the user has inserted a new cartridge 280 into the cartridge holder portion 285 and has begun to connect the cartridge holder portion 285 to the base portion 255 of the housing structure is disclosed. In this state, the outwardly directed protrusion 284 is aligned with the start of the internal track 272 in the nut member 270.

[0170] In this state, when the cartridge holder part 285 is not yet attached, the compression spring 289 pushes the sleeve element 287 in the distal direction. The sleeve element 287 is snapped onto the hook 204 of the release element 200, so that the release element 200 is also pulled in the distal direction.

[0171] Since the release member 200 is connected to the inner member 290 via the flange 201 , in this state the inner member 290 is pulled out of engagement with the outer member 295 .

[0172] Thus, when the cartridge holder portion 285 is not attached, the compression spring 289 pulls the inner element 290 distally to a first position in which the inner element 290 is free to rotate.

[0173] When the user begins to rotate the cartridge holder portion 285 in the bayonet coupling so that the outwardly directed protrusions 284 slide into the tracks 272, the sleeve element 287 is forced as Fig.15 As disclosed in the foregoing, the cartridge 280 moves in the proximal direction as the cartridge 280 is pulled in the proximal direction and the proximal end of the cartridge 280 abuts against the distal end of the sleeve 287. However, in this state, when the sleeve 287 slides on the inner arm 203 of the release element 200, no force is applied to the release element 200. Therefore, the release element 200 remains in its position, and since the release element 200 does not move, the inner element 290 does not move either. Due to this, a proper connection can be obtained between the plunger 281 inside the cartridge 280 and the piston rod 230, which in the disclosed example is provided with a piston rod foot 233, before the release mechanism actually locks the inner part 290 to the outer part 295. Fig.14 and Fig.15 The perforated line “E” in FIG. 2 indicates the abutment between the plunger 281 and the piston rod foot 233 .

[0174] Track 272 in nut member 270 terminates in a more straight path, and as outwardly directed protrusion 284 enters the straight path, protrusion 284 abuts inclined surface 206 on release element 200. Continued rotation of outwardly directed protrusion 284 in the straight path forces release element 200 to move in a proximal direction due to the increased force applied to inclined surface 206.

[0175] like Fig.16, the proximal movement of the release element 200 in the proximal direction is transmitted as a similar movement in the proximal direction of the inner element 290. Therefore, as a result of this movement of the inner element 290, the teeth 292 on the inner element 290 engage with the teeth 296 on the outer element 295, and the inner element 290 is thus locked to the outer element 295.

[0176] Thus, it is the contact between the outwardly directed protrusion 284 and the inclined surface 206 that locks the inner element 290 to the outer element 295 rather than the actual position of the plunger 281 and the piston rod foot 233 .

[0177] Each time an injection is performed thereafter, the clutch 260 rotated by the torsion spring 245 rotates the outer element 295 and thus the inner element 290 , thereby rotating the piston rod 230 again.

[0178] Third Example of the Invention

[0179] Each physical element in this example that is identical or has a similar function to that of the previously disclosed injection device is referenced by the same reference numeral preceded by a "3". Fig.19 In the following example in FIG. 1 , the piston rod is provided with reference mark “ 330 ”.

[0180] like Fig.17A As shown in FIG. 3-B, the piston rod 330 is provided with an external thread 332 and a longitudinal track structure 331.

[0181] The rotatable piston rod driver 365 is divided into an inner part 390 engaging the track structure 331 of the piston rod 330 and an outer part 395 engaging the drive mechanism at least during dose expelling.

[0182] In this example, the housing structure further comprises a nut member 370 which is irreversibly connected to the base portion 355 by a snap-fit ​​engagement. The nut member 370 is internally provided with an insert 300 with threads 307 engaging the external threads 332 of the piston rod 330.

[0183] In this example, the nut member 370 is provided with an inner track 372 that can engage with an outwardly directed protrusion 384 provided on the cartridge holder portion 380. The engagement between the nut member 370 and the cartridge holder portion 380 is preferably a bayonet coupling. In the disclosed example, two such tracks 372 and two protrusions 384 are shown, however any number may be present.

[0184] The compression spring 389 is enclosed between the nut member 370 and the insert 300 so that the insert 300 is urged in the distal direction. The insert 300 has an outwardly directed flange 308 against the compression spring 389. On the proximal side, the insert 300 is provided with a second flange 309 which can rotationally connect the insert 300 to the inner element 390 so that the insert 300 and the inner element 390 move together in the axial direction but can rotate relative to each other. The insert 300 is further guided in translation in the nut member 370. The thread 307 is rotationally fixed relative to the nut member 370 and therefore relative to the base portion 355 of the housing structure. The internal thread 307 is therefore associated with the housing structure.

[0185] like Fig.18 As disclosed in Fig.11 In the corresponding first position, the compression spring 389 pushes the inserter 300 and the inner element 390 in the distal direction.

[0186] Once the user inserts the cartridge 385 into the cartridge holder portion 380 and connects the cartridge holder portion 385 to the nut member 370, as shown in FIG. Fig.19 As seen in FIG. 3 , the cartridge 380 engages the insert 300 and moves the insert 300 in the proximal direction. This movement translates into a similar movement of the inner element 390. Thereafter, the outwardly directed teeth 392 on the inner element 390 move into engagement with the inwardly directed teeth 396 on the outer element 395.

[0187] During injection, when the clutch 360 rotates the outer element 395 , this rotation is translated into a similar rotation of the inner element 390 and the piston rod 330 .

[0188] Since the insert 300 is in this example a slidable element and is threadedly connected to the piston rod 330, the piston rod 330 also slides axially together with the insert 300 and the inner element 390. This has the following effect: once the plunger 381 inside the cartridge 380 reaches contact with the piston rod 330 or the piston rod foot 333, both the insert 300 and the piston rod 330 move proximally until the inner element 390 comes into contact with the outer element 395. This ensures that proper contact is established before the inner element 390 is locked to the outer element 395.

[0189] Thus, it is the contact between the cartridge 380 and the insert 300 that locks the inner element 390 to the outer element 395 rather than the position of the plunger 381 and the piston rod foot 333 .

[0190] Fourth Example of the Invention

[0191] Each physical element in this fourth example that is identical or has a similar function to that of the previously disclosed injection device is referenced by the same reference numerals preceded by a "4". Figure 20 to Figure 24 In the following examples disclosed in , the piston rod is provided with a reference mark “ 430 ”.

[0192] Fig. 20 The dose engine is disclosed in a state where no cartridge 480 or cartridge holder 485 is attached, and Fig.21 The injection device is disclosed once the cartridge 480 and the cartridge holder 485 are attached.

[0193] The outer threads 432 on the piston rod 430 engage the inner threads 471 in the nut element 470 so that when the inner element 490 engaging the piston rod 430 is rotated by the outer element 495 which is again rotated by the torsion spring 445, the piston rod 430 is helically moved in the distal direction. The nut element 470 is preferably press-fit into the base portion 455 of the housing structure so that the nut element 470 is non-rotatably fixed relative to the base portion 455. Alternatively, the nut element 470 may be molded as an integral part of the base portion 455.

[0194] As can be seen from the engagement between the outwardly directed teeth 461 on the clutch 460 and the inwardly directed teeth 456 inside the base portion 455, the clutch 460 remains non-rotatable during replacement of the cartridge 480. Only when the clutch 460 moves in the distal direction and disengages from the inwardly directed teeth 456 of the base portion 455 does the clutch 460 allow the outer element 495 to rotate freely.

[0195] Release mechanism in Fig. 22 , Fig.23 and Fig.24 Best seen in . Fig. 22 , the piston drive element 465 comprises an outer element 495 and an inner element 490 as in the previous examples. The inner element 490 is coupled to the metal clip 400 via an inner ring 401 .

[0196] The metal clip 400 is provided with a plurality of axial legs 402 that engage the inner ring 401 so that the metal clip 400 and the inner ring 401 operate in unison. In the disclosed example, radial openings in the axial legs are connected to a plurality of outwardly directed protrusions on the inner ring 401. Fig.23 and Fig.24 As best seen in FIG. 1 , the ring element 401 engages the inner element 490 of the piston rod driver 156, causing the inner element 190 to move axially with the metal clip 400 and the inner ring 401. Preferably, the inner element 490 is snap-fit ​​to the inner ring 401, causing the inner element 490 to move distally and proximally with the inner ring 401.

[0197] The axial leg 402 of the metal clip 400 operates through the opening in the nut element 471, as shown in FIG. Fig. 20 and Fig.21 The distal portion of the metal clip 400 is thus located distally of the nut element 471, while the ring element 401 is positioned proximally of the nut element 470. When the cartridge 480 is inserted, the proximal end of the cartridge 480 is thus pushed on the distal end of the metal clip 400, as shown in FIG. Fig.21 As disclosed in.

[0198] The inner element 490 is internally provided with inwardly directed ridges 491 which engage longitudinal tracks 431 provided in the piston rod 430 such that rotation of the inner element 490 is translated into a similar rotation of the piston rod 430. The inner element 490 is also provided with a plurality of outwardly directed teeth 492 on its outer surface.

[0199] These outwardly directed teeth 492 are capable of engaging with similar inwardly directed teeth 496 disposed within the outer member 195. The outer member 195 also includes a plurality of radial snapping arms 497 and a plurality of axially extending arms 498.

[0200] The radial snapping arms 497 operate with a toothed ring provided on the inner surface of the base portion 455 so that the outer element 495 can only rotate in one rotational direction. The allowed direction is the direction that moves the piston rod 430 distally.

[0201] exist Fig. 20 and Fig.23 In the unlocked position disclosed in FIG. 4 , the compression spring 489 pushes the metal clip 400 in the distal direction. When the metal clip 400 is connected to the inner ring 401 which is again connected to the inner element 490, the inner element 490 is pulled in the distal direction by the compression spring 489. Fig.23 As can be seen in FIG. 4 , the outwardly directed teeth 492 on the inner element are pulled free of the inwardly directed teeth 496 on the outer element 495 , allowing the inner element 490 to rotate with the piston rod 430 .

[0202] During axial movement of the inner element 490 , the inwardly directed ridges 491 move axially in a longitudinal track 431 provided in the piston rod 430 .

[0203] Once the inner element 490 is released from the outer element 495 , the user may rotate the piston rod 430 proximally into the base portion 455 until the piston rod 430 returns to its starting position and a new cartridge 480 may be inserted.

[0204] exist Fig.21 and Fig.24 In the locked position disclosed in , the cartridge 480 has been inserted into the cartridge holder 485 and the cartridge holder 485 has been attached to the base portion 455, preferably by a bayonet interface.

[0205] like Fig.21 As best seen in FIG. 4 , the cartridge 480 pushes the metal clip 400 in the proximal direction against the bias of the compression spring 489. When the metal clip 400 is connected to the inner ring 401 which is again coupled to the inner element 490, the inner element 490 moves proximally to engage with the outer element 495.

[0206] Once the outwardly directed teeth 492 are Fig.24 496, the torque stored in the torsion spring 445 can be released by moving the clutch 460 out of engagement with the base portion 455, as previously explained, thereby rotating the piston rod guide 465, i.e., the outer element 495 and the inner element 490. The simultaneous rotation of the outer element 495 and the inner element 490 is converted into a similar rotation of the piston rod 430, which is thus helically moved in the distal direction due to the threaded connection 432, 471 between the piston rod 430 and the nut element 470.

[0207] Therefore, the fourth example is also based on a movable element (metal clip 400) operatively connected to the inner element 490 to axially move the inner element 490 from a first uncoupled position to a second coupled position.

[0208] Some preferred embodiments have been shown above, but it should be emphasized that the invention is not limited to these preferred embodiments, but can be embodied in other ways within the subject matter defined in the following claims.

Claims

1. A reusable torsion spring driven injection device for expelling several doses of a liquid drug from a loading cartridge (180, 280, 380, 480), comprising: A piston rod (130, 230, 330, 430) having an outer surface, the outer surface having an outer thread (132, 232, 332, 432) extending helically in a longitudinal direction, and the outer surface is also provided with a longitudinally extending engagement surface (131, 231, 331, 431), so that the outer surface of the piston rod (130, 230, 330, 430) has a non-circular cross section, A housing structure, the housing structure comprising: - a base portion (155, 255, 355, 455) comprising a torsion spring driven discharge mechanism for axially driving the piston rod (130, 230, 330, 430), and - a removable cartridge holder part (185, 285, 385, 485) which holds the cartridge (180, 280, 380, 480) and is releasably connected to the base part (155, 255, 355, 455), The torsion spring driven discharge mechanism comprises: a rotatable piston rod driver (165, 265, 365, 465) engaging an engagement surface (131, 231, 331, 431) of the piston rod (130, 230, 330, 430) such that a rotation of the rotatable piston rod driver (165, 265, 365, 465) is transferred into a similar rotation of the piston rod (130, 230, 330, 430), internal threads (171, 271, 307, 471) associated with the housing structure and engaging external threads (132, 232, 332, 432) on the piston rod (130, 230, 330, 430) such that the piston rod (130, 230, 330, 430) moves helically when rotated, and a strain torsion spring (145, 245, 345, 445) which maintains a torque for rotating the rotatable piston rod driver (165, 265, 365, 465) during dose expulsion, and wherein the rotatable piston rod driver (165, 265, 365, 465) comprises an outer element (195, 295, 395, 495) and an inner element (190, 290, 390, 490) which are releasably coupled together, The outer element (195, 295, 395, 495) remains stationary during dose setting and rotates during dose expulsion by the torque of the strain torsion spring (145, 245, 345, 445), and The inner element (190, 290, 390, 490) is axially movable relative to the outer element (195, 295, 395, 495) between a first uncoupled position and a second coupled position, The first uncoupled position is a position in which the inner element (190, 290, 390, 490) is uncoupled from the outer element (195, 295, 395, 495) so that the inner element (190, 290, 390, 490) can rotate independently of the outer element (195, 295, 395, 495), and The second coupling position is a position where the inner element (190, 290, 390, 490) is coupled to the outer element (195, 295, 395, 495) to follow the rotation of the outer element (195, 295, 395, 495), And among them A movable element (100, 200, 300, 400) operably connected to the inner element (190, 290, 390, 490) is axially movable to axially move the inner element (190, 290, 390, 490) from the first uncoupled position to the second coupled position.

2. A reusable torsion spring driven injection device according to claim 1, wherein the movable element (100, 200, 300, 400) and the inner element (190, 290, 390, 490) move in unison.

3. A reusable torsion spring driven injection device according to claim 1 or 2, wherein the inner element (190, 290, 390, 490) is moved distally to the first uncoupled position by spring means (109, 289, 389, 489).

4. A reusable torsion spring driven injection device according to claim 1 or 2, wherein the movable element (100, 200) and the inner element (190, 290) are moved proximally to the second coupling position by engaging with the cartridge holder part (185, 285).

5. A reusable torsion spring driven injection device according to claim 3, wherein the movable element (300, 400) and the inner element (390, 490) are moved proximally to the second coupling position by engagement with the cartridge (380, 480).

6. A reusable torsion spring driven injection device according to claim 3, wherein the movable element is a sleeve which is telescopically movable relative to the housing structure.

7. A reusable torsion spring driven injection device according to claim 6, wherein the sleeve slides axially outside the housing structure.

8. A reusable torsion spring driven injection device according to claim 6, wherein the sleeve is connected to the inner element (190).

9. A reusable torsion spring driven injection device according to claim 6, wherein the sleeve abuts the cartridge holder portion (185) when installed.

10. A reusable torsion spring driven injection device according to claim 6, wherein the spring means is a compression spring, the compression spring being enclosed between the sleeve and the housing structure so as to urge the sleeve in the distal direction.

11. The reusable torsion spring driven injection device according to claim 5, wherein the movable element (400) is connected to the inner element (490) via an inner ring (401 ).

12. A reusable torsion spring driven injection device according to claim 11, wherein the spring means (489) is enclosed between the movable element (400) and a nut member (470) fixed in a base portion (455) of the housing structure.

13. A reusable torsion spring driven injection device according to claim 12, wherein the nut member (470) is provided with an internal thread (471 ) for the piston rod (430).

14. A reusable torsion spring driven injection device according to claim 12 or 13, wherein the movable element (400) is provided with an axial leg (402) operable through an opening in the nut member (470).

Images