Torque spring driven fixed dose injection device

Abstract

This invention relates to a medical injection device for dispensing substantially equal dose volumes of liquid medication. Injection is driven by a torsion spring, which is tensioned prior to each dose release by rotation of a connector element connected to a rotary drive structure. Dose release is controlled by the axial movement of the rotary drive structure, which is only capable of axial movement when the connector element has rotated to a specific rotational position.

Description

Technical Field

[0001] The present invention relates to a torsion spring driven injection device for dispensing multiple substantially equal dose volumes of liquid medicine, and particularly to a torsion spring driven injection device wherein the dose to be dispensed is predetermined by the manufacturer of the injection device and the volume is fixed such that each individual dose has substantially the same volume. Background Technology

[0002] Spring-driven injection devices for automatically dispensing dose volumes of liquid medications are well known in the art. Some of these devices use compression springs to dispensing the dose volume, while others use torsion springs.

[0003] When injecting a liquid solution containing insulin, it is generally considered important that the user has a variety of different dose volumes to choose from in order to accurately deliver the necessary dose volume for each individual user. Therefore, injection devices such as those illustrated, for example, in US 6,899,699, are equipped with a dose setting mechanism through which the user incrementally selects the individual size of the dose volume to be injected. The dose dispensing mechanism in US 6,899,699 is automatic and driven by a spring, which may be a compression spring or a torsion spring.

[0004] However, for other types of liquid medications, such as GLP-1, it is necessary to inject the same dose volume in each injection. Such injection devices are usually referred to as fixed-dose devices because the dose volume is fixed by the manufacturer of the injection device.

[0005] On the one hand, this can be accomplished using a disposable injection device capable of dispensing a single dose volume of a predetermined and fixed size. The user thus administers the injection and discards the disposable injection device once it has been used.

[0006] However, an alternative to using multiple such single-use fixed-dose devices is to use a single injection device dedicated to dispensing multiple predetermined dose volumes of equal size. Such an injection device is sometimes referred to as a multiple-use fixed-dose injection device.

[0007] Examples of such a reusable fixed-dose device for discharging multiple predetermined dose volumes of equal size are disclosed in WO 2017 / 098460, WO 2018 / 007259 and WO 2020 / 089167.

[0008] What these injection devices have in common is that the user must rotate a dose selection button before each injection. This button selects a predetermined dose volume and also tensions a spring, allowing force to accumulate and be stored within it. Therefore, the user needs to manually tension the spring to rotatably prepare the injection device for a single injection at that moment.

[0009] In WO 2020 / 089167, the user tensions the torsion spring by rotating the dose selection button and pushes the injection button located on the proximal side of the injection device to release the torque stored in the torsion spring. The torque then drives the piston rod in the distal direction, causing a predetermined dose volume to be expelled from the injection device.

[0010] However, the multiple-use fixed-dose injection device disclosed in WO 2020 / 089167 includes a large number of complex components. Summary of the Invention

[0011] Therefore, the object of the present invention is to provide a reusable fixed-dose injection device with a simpler structure.

[0012] The invention is defined in claim 1. Advantageous embodiments are further defined in the dependent claims.

[0013] Therefore, in one aspect of the invention, a torsion spring-driven injection device for dispensing a plurality of predetermined and substantially equal fixed dose volumes of liquid medication comprises:

[0014] A shell structure that securely holds the cartridge containing the liquid drug to be dispensed.

[0015] A piston rod, preferably used to displace the liquid drug from the cartridge by moving the piston rod in a distal direction.

[0016] A rotatable drive structure engages the piston rod such that the piston rod rotates together with the rotatable drive structure during drug administration.

[0017] A nut element, which is secured to the housing structure at least during drug administration and threadedly connected to the piston rod, such that the piston rod moves helically as the piston rod rotates relative to the nut element.

[0018] A connector element, which is coupled to the housing structure via a ratchet interface, allows the connector element to rotate relative to the housing structure.

[0019] A torsion spring, operably coupled between the rotatable drive structure and the connector element, such that torque accumulates in the torsion spring through rotation of the connector element relative to the rotatable drive structure, and wherein the ratchet interface between the housing structure and the connector element is capable of resisting the torque of the torsion spring to hold the connector element in its rotatable position.

[0020] The rotatable drive structure can move axially between a first position and a second position, wherein

[0021] The first position is the locked position, wherein the rotatable drive structure is non-rotatably fixed to the housing structure, and

[0022] The second position is the release position, wherein the rotatable drive structure is released from the housing structure and is able to rotate under the influence of the torque stored in the torsion spring.

[0023] When the rotatable drive structure is held in the first position, and one of the plurality of predetermined and substantially equal fixed dose volumes is selected by rotation of the connector element relative to the rotatable drive structure, the torsion spring is tensioned; the connector element can rotate from the initial position to the dose position, and

[0024] When the rotatable drive structure moves axially from the first position to the second position, thereby allowing the rotatable drive structure to rotate from the dose position to the initial position under the influence of the torsion spring, a selected one of the plurality of predetermined and substantially equal fixed dose volumes is individually released, and wherein,

[0025] The rotatable drive structure and the connector element are provided with means that allow the rotatable drive structure to move axially from the first position to the second position when the rotatable drive structure has been rotated to and positioned in the dosage position.

[0026] Therefore, the fixed dose to be discharged is selected by rotating the connector element relative to the rotary drive structure, thereby tensioning the torsion spring. For this purpose, the rotary drive structure and the connector element are provided with means that, when aligned, allow the rotary drive structure to move from the first position to the second position. Such means, in one example, could be a track and protrusion on either component, or the means could simply be protrusions on both components. Other kinds of mechanical devices are conceivable, as long as the rotary drive structure is only allowed axial movement in the correct rotational position (i.e., in the defined dose position). Therefore, it is impossible to move the rotary drive structure to the second release position during rotation. Only when the entire fixed dose has been selected and the connector element has been rotated to the specific dose position is it possible to move the rotary drive structure from the first locked position to the second release position, and thus release the fixed dose.

[0027] Therefore, two relative rotational positions (initial position and dose position) of the connector element and the drive structure are specified, and the magnitude of the dose is predetermined by the rotational distance between these two positions; thus, the initial position and the dose position define the magnitude of the fixed dose.

[0028] Therefore, during dosage setting, the user rotates the connector element from the initial position to the dosage position, while the rotary drive structure is locked to the housing. This rotation tensions the torsion spring. During dosage release, the connector element locks to the housing, and the rotary drive structure rotates from the dosage position and returns to the initial position via the torsion spring.

[0029] It should be understood that, in this document, "fixed dose volume" refers to a fixed metric volume of a liquid drug. However, certain tolerances apply, making small variations in the volume of each fixed dose acceptable under the terminology's definition of a fixed dose volume.

[0030] To provide a better grip for the user, a rotary selection element for rotating to select a fixed dose to be dispensed is preferably provided at the proximal end of the housing structure. In one example, the rotary selection element is rotatably locked to a connector element such that when the user selects a fixed dose by rotating the rotary selection element, the connector element and the selection element rotate together one-to-one. The selection element can be further axially moved relative to the connector element, allowing the selection element to move axially relative to the connector element.

[0031] The rotary selection element can be further used as a dose release element by being axially coupled to the rotary drive structure, such that the selection element and the rotary drive structure move together in the axial direction to move the rotary drive structure from a first position to a second position, thereby releasing the rotary drive structure, and wherein the selection element and the rotary drive structure are allowed to rotate relative to each other. Thus, the rotary drive structure can be moved from a locked position to a released position by axially pushing the rotary selection element. The connection between the rotary selection element and the rotary drive structure can be any type of connection that allows relative rotation between the two components but locks them to move axially in unison. This can be, for example, a ridge that engages or clamps behind a flange, and in one example may include needle rollers or ball bearings or other devices to reduce friction during relative rotation between the two components.

[0032] To move the rotary drive structure back to the first locked position, a compression spring is preferably provided, which pushes the rotary selection element and the rotary drive structure in the proximal direction. Furthermore, a guide device for guiding the selection element is preferably disposed within the housing structure. Such a guide device is preferably a spline guided in one or more tracks.

[0033] In one specific example, the rotary drive structure includes a longitudinal drive tube provided with a radial protrusion as one of the means for allowing the drive tube to move axially from a first position to a second position. The tube herein refers to a longitudinally shaped element, which is preferably, but not necessarily, hollow or at least partially hollow. The radial protrusion is preferably located on the outer surface and preferably near the proximal end of the drive tube.

[0034] Preferably, the drive tube extends through the connector element such that the radial protrusion can engage the connector element.

[0035] In another example, the connector element is provided with a first axial opening as one of the means to allow the drive tube to move axially from a first position to a second position. When the first axial opening and the radial protrusion are aligned (dose position), the radial protrusion on the drive tube can move through the first axial opening, thereby initiating discharge. Therefore, in this particular dose position, it is possible to move the drive tube from a first locked position to a second released position.

[0036] The connector element preferably also has a second axial opening, such that when the second axial opening and the radial protrusion are aligned at the end of discharge (initial position), the radial protrusion on the drive tube can axially pass through the second axial opening in the connector element. Therefore, the drive tube can move from the second release position to the first locking position from this initial position after a fixed dose of discharge.

[0037] The piston rod for discharging a fixed dose is preferably provided with a helical external thread and a longitudinal guide structure such as a groove or a flat surface. In such a configuration, the piston rod can be rotated by engaging the longitudinal guide structure with an element such as a drive structure in a key-like manner, so that the piston rod rotates together with the drive structure.

[0038] As the piston rod rotates, it moves in the distal direction by engaging with a nut element carried by the housing structure. The nut element has an internal thread that engages with the external thread on the piston rod, and the piston rod is helically screwed forward in the distal direction whenever the drive tube, which is provided with an engagement device that engages with the longitudinal guide structure on the piston rod, rotates.

[0039] In one example, the nut element is axially movable and coupled to the drive tube to move axially together with the drive tube. Thus, a so-called floating nut can be obtained, which can be coupled to and detached from the housing. The principle of such a floating nut is described in further detail in EP 2,906,271. However, the nut element can also be permanently attached to the housing.

[0040] By attaching the nut element to the drive tube, it is possible to rotate the nut element out of the housing structure in a first position of the drive tube and rotate it back into the housing structure in a second position of the drive tube. Therefore, the nut element is only attached to the housing during dose dispensing, but rotates freely during dose selection and cartridge replacement.

[0041] definition:

[0042] "Injection pens" are typically injection devices with an elongated oval or slender shape, somewhat like pens used for writing. While such pens usually have a tubular cross-section, they can easily have different cross-sections, such as triangles, rectangles, or squares, or any variation around these or other geometries.

[0043] The term "needle cannula" is used to describe the actual catheter used to perform skin penetration during injection. Needle cannulas are typically made of a metallic material such as stainless steel and are preferably attached to a needle hub made of a suitable material such as a polymer. However, needle cannulas can also be made of polymeric or glass materials. The needle cannula, which is mounted in the needle hub and referred to as the injection needle or needle assembly, can be replaceable or permanently attached to the injection device. A particular type of needle assembly is the so-called "pen needle," in which a portion of the needle cannula extends proximally from the base of the needle hub, allowing this proximal portion to penetrate into the cartridge once the pen needle is attached to the injection device.

[0044] As used herein, the term "liquid drug" is intended to cover any flowable pharmaceutical agent containing a drug, such as a liquid, solution, gel, or fine suspension, that can be passed in a controlled manner through a delivery device such as a hollow needle cannula. Representative pharmaceutical agents may include such drugs as peptides, proteins (e.g., insulin, insulin analogs, and C-peptides), hormones, bioderived or active agents, hormone- and gene-based reagents, nutritional formulations, and other substances in both solid (dispensing) and liquid forms.

[0045] "Cartridge" is a term used to describe the main container that actually contains a liquid medication. Cartridges are typically made of glass such as borosilicate glass, but can alternatively be molded from any suitable polymer. The cartridge or ampoule is preferably sealed at one end by a puncturable membrane called a "septum," which can be punctured, for example, by the non-patient end of a needle cannula. Such a septum is typically self-sealing, meaning that once the needle cannula is removed from the septum, the opening created during penetration is automatically sealed by its inherent elasticity. The opposite end of the cartridge is typically closed by a plunger or piston made of a rubber composition or a suitable polymer. The plunger or piston can be slidably moved inside the cartridge. The space between the puncturable membrane and the movable plunger contains the liquid medication, which is expelled as the plunger reduces the volume of the space containing the liquid medication.

[0046] Because cartridges typically have a narrow distal neck into which the plunger cannot move, not all the liquid medication contained within the cartridge can actually be expelled. Therefore, the terms "initial volume" or "essentially used" refer to the injectable contents contained in the cartridge and therefore not necessarily the entire contents. The injectable contents in the cartridge must be at least equal to the volume constituting the multiple predetermined dose volumes to be expelled. In one example, if we assume a multi-use fixed-dose injection device contains three fixed doses, each with a volume of, for example, 0.3 ml, then the injectable contents of the cartridge need to be at least 0.9 ml, and the total volume of the cartridge must therefore be larger to include the volume that cannot be expelled due to the narrow neck portion.

[0047] The term "pre-filled" injection device refers to an injection device in which a cartridge containing a liquid medication is permanently embedded in the device, making it impossible to remove without permanently damaging the device. Once the predetermined amount of liquid medication in the cartridge has been used, the user typically discards the entire injection device. Typically, the cartridge, pre-filled with a specific amount of liquid medication by the manufacturer, is secured in a cartridge holder, which is then permanently attached to the housing structure, preventing cartridge replacement.

[0048] This contrasts with "durable" injection devices, where users can replace the cartridge containing liquid medication themselves when it's empty. Pre-filled injection devices are typically sold in packages containing more than one injection device, while durable injection devices are usually sold one at a time. When using pre-filled injection devices, the average user may need up to 50 to 100 injection devices per year, while with durable injection devices, a single injection device can last for several years, however, the average user may need 50 to 100 new cartridges per year.

[0049] A "reusable fixed-dose" injection device defines an injection device capable of delivering a predetermined number (i.e., more than one) doses of substantially the same volume. Thus, the initial amount of liquid medication contained in the cartridge is dispensed in multiple substantially identical dose volumes. In one example, the cartridge may have an initial injectable volume of, for example, 3 ml of liquid medication, which may be dispensed, for example, in six identical doses (0.5 ml each). The number of equal-sized dose volumes is typically 2 to 8, preferably 4 to 6 identical dose volumes. The reusable fixed-dose injection device may be pre-filled, such that the entire injection device is discarded after a predetermined number of dose volumes have been dispensed, or it may be a durable injection device, allowing the user to replace the cartridge and dispense a new series of equal-sized dose volumes from the new cartridge.

[0050] The term "automatic" in conjunction with the use of injection devices refers to the ability of the injection device to perform injections without requiring the user to exert the force needed to expel the liquid medication during administration. This force is typically transmitted automatically by an electric motor or spring actuator. The actual spring used for the spring actuator is tensioned by the user, for example, during dose setting; however, such springs are usually pre-tensioned with a small force to avoid the problem of delivering very small doses. Alternatively, the manufacturer can fully preload the spring with a preload force sufficient to expel the entire initial contents (i.e., the entire injectable contents) of the liquid medication contained in the cartridge through multiple doses. Typically, the user activates a release mechanism located on the surface of the housing or proximal to the injection device to partially release some of the force accumulated in the spring during injection. Alternatively, a shield can trigger the injection device, such that activation of a movable shield releases the force required to expel the dose.

[0051] The terms “permanently connected” or “permanently embedded” as used in this specification are intended to refer to a component, in particular a cartridge permanently embedded in the housing structure, which requires the use of tools for separation, and which, if separated, will permanently damage at least one of the components, rendering the injection device inoperable.

[0052] All references cited in this article (including publications, patent applications and patents) are incorporated into this article in their entirety by reference, to the same extent that each reference is individually and specifically indicated by reference and fully elaborated in this article.

[0053] All headings and subheadings are used herein for convenience only and should not be construed as limiting the invention in any way.

[0054] Unless otherwise stated, the use of any and all examples or exemplary language (such as, for example, such as) provided herein is intended only to better illustrate the invention and not to limit the scope of the invention. No language in this specification should be construed as indicating that any unstated element is essential to the practice of the invention.

[0055] The patent references and inclusions in this article are for convenience only and do not reflect any view on the validity, patentability and / or enforceability of such patent references.

[0056] This invention includes all modifications and equivalents of the subject matter described in the appended claims as permitted by applicable law. Attached Figure Description

[0057] The present invention will now be explained more fully with reference to preferred embodiments and the accompanying drawings, wherein:

[0058] Figure 1 An exploded view of an injection device according to a disclosed example of the invention is shown.

[0059] Figure 2A -B shows Figure 1 A cross-sectional view of the injection device disclosed in the paper. Figure 2B yes Figure 2A An enlarged view of the circled portion.

[0060] Figure 3A -B shows two different perspective views of the connector components. Figure 3A It was observed from the proximal position.

[0061] Figure 4 A perspective view of the drive tube is shown.

[0062] Figure 5A -B shows two different views of the selector element. Figure 5A It is a cross-sectional view.

[0063] Figure 6A -B shows two different perspective views of the interface between the housing component and the connector element.

[0064] Figure 7 A cross-sectional view of the drive mechanism is shown.

[0065] For clarity, these figures are schematic and simplified, and they show only the details essential for understanding the invention, while other details are omitted. Throughout the text, the same reference numerals are used for the same or corresponding parts. Detailed Implementation

[0066] When using terms such as “up” and “down,” “right” and “left,” “horizontal” and “vertical,” “clockwise” and “counterclockwise” or similar relative expressions, these terms are for reference only with respect to the accompanying drawings and are not necessarily actual usage. The accompanying drawings are schematic representations, and for this reason, the configurations of different structures and their relative dimensions are for illustrative purposes only.

[0067] In this context, it is convenient to define the term "distal" in the accompanying drawings as referring to the end of the injection device that typically carries the needle cannula, and the term "proximal" as referring to the opposite end that typically carries the dose selection button, such as... Figure 2A As depicted in the text. Distal and proximal refer to the axial orientation extending along the longitudinal axis (X) of the medical container, as well as... Figure 2A As shown in the image.

[0068] When clockwise and counterclockwise are mentioned in the following examples, it should be understood that the injection device is viewed from a position at its far side. Therefore, clockwise is the rotation of the arm on a regular clock, while counterclockwise is the rotation in the opposite direction.

[0069] To explain the various movements that occur in the injection device described in the example, the following terminology will be used throughout the detailed description below;

[0070] "Translation" refers to strictly linear motion without any rotation.

[0071] "Rotational motion" is any rotational motion about a center, which can be a center point (i.e., in a plane) or a central axis (i.e., having a longitudinal extension).

[0072] "Axial motion" refers to any motion in the axial direction. This motion can be strictly translational, or it can include rotational motion, thus making it "helical motion," because it implies a combination of axial and rotational motion.

[0073] The term "telescopic" is intended to cover situations where a movable element moves out of and / or into a base element. Telescopic movements can be translational or include rotation, thus making the telescopic movement helical.

[0074] Figure 1 An exploded view of an injection device according to a first example of the present invention is disclosed, and Figure 2A The same injection device is shown in a cross-sectional view.

[0075] The injection device includes a housing structure comprising a housing component 1 and a cartridge holder 20. The housing component 1 includes... Figure 2B The drug delivery mechanism is shown in enlarged view, and the cartridge holder 20 includes the cartridge 10. The housing part 1 and the cartridge holder 20 are either permanently attached to form a pre-filled injection device, or the cartridge holder 20 can be removed from the housing part 1 for replacing the cartridge 10. This would thus be a durable injection device.

[0076] In the disclosed example, the injection device is a durable injection device, and the cartridge holder 20 has an annular element 21 on its proximal side, which forms an integral part of the cartridge holder 20, and in one example, can be molded integrally with the rest of the cartridge holder 20. The inner surface of the cartridge holder 20, or more precisely, the annular element 21, is provided with a track 22, which can engage with a guide protrusion 2 provided on the housing component 1, thereby forming a bayonet connection. Both the track 22 and the guide protrusion 2 are preferably provided in pairs. The user can then detach the cartridge holder 20 from the housing component 1 when changing the cartridge 10.

[0077] In the disclosed example, cartridge 10 is a standard glass cartridge sealed distally by a puncturable diaphragm 11 and proximally by a movable plunger 12. In the disclosed example, cartridge 10 has an adapter top 13 on its distal side that carries a thread 14, allowing a pen-type needle (not shown) to be attached to the thread 14. It is well known in the art that the adapter top 13 is preferably press-fitted to cartridge 10 and is non-rotatably secured by cartridge retainer 2 during installation. Alternatively, the thread 14 may be provided on the housing structure of the injection device. The thread 14 may be further replaced by alternative coupling devices, such as bayonet couplings or Luer couplings, for attaching the pen-type needle to cartridge 10 or the housing structure.

[0078] During installation, the cartridge 10 is pushed in the distal direction by a distal compression spring 71 to abut against the cartridge holder 20. The distal compression spring abuts the slider 70 distally and against the housing structure proximally. This slider 70 is provided with a pair of radial arms 72 that engage a longitudinal track 3 in the housing component 1 (see, for example...). Figure 7 This allows the slider 71 to slide only relative to the housing component 1 but not to rotate.

[0079] The drive mechanism within the housing component 1 includes a piston rod 15, which is movable in a distal direction, thereby moving the movable plunger 12 forward within the cartridge 10. A piston rod base 18 may be disposed between the piston rod 15 and the movable plunger 12 to better distribute force onto the movable plunger 12. In the disclosed example, the piston rod base 18 is made of two components radially snapped onto the distal end of the piston rod 15.

[0080] The piston rod 15 has an external thread 16 and a longitudinal track structure 17 on its outer surface. Figure 7 (Best shown in the diagram). The external thread 16 on the piston rod 15 engages with the internal thread 26 provided in the nut element 25, such that when the piston rod 15 rotates relative to the nut element 25, the piston rod 15 moves helically, as will be explained.

[0081] The longitudinal track structure 17 in the piston rod 15 is engaged by a dose tube 30, which has an internal engagement device for engaging the longitudinal track structure 17 such that the piston rod 15 rotates together with the dose tube 30 whenever the dose tube 30 rotates. In one example, the track structure 17 includes a flat surface engaged by the dose tube 30 in a keyed structure.

[0082] Figure 4 The dose tube 30 disclosed herein has a circular ridge 31 on its proximal side, which is engaged by a dose selector 40. For this purpose, Figure 5A The dose selector 40 disclosed in -B has a plurality of proximal snap-fit ​​arms 41 internally, which engage with a circular ridge 31 on the dose tube 30, such that the dose selector 40 and the dose tube 30 can move axially together but can rotate relative to each other.

[0083] On the distal side, the dose selector 40 is provided with a plurality of distal elastic arms 42 that engage with the housing component 1, allowing the dose selector 40 to slide axially relative to the housing component 1, but preventing complete release from the housing structure. Preferably, these elastic arms 42 engage behind a plurality of outwardly pointing ribs 5 on the housing component 1, which will explain their use.

[0084] The dose selector 40 is pressed proximally by a compression spring 90, which surrounds the dose selector 40 between the dose selector 40 and the connector element 50, and forces the distal elastic arm 42 to abut against the proximal surface of the outwardly pointing rib 5, as... Figure 2B The best result is shown in the middle.

[0085] Figure 3AThe connector element 50 disclosed in -B is connected to a torsion spring 95, which is coupled to a drive tube 30 at its opposite distal end, such that when the connector element 50 and the drive tube 30 rotate relative to each other, torque accumulates in the torsion spring 95, as will be explained.

[0086] Both connector element 50 and drive tube 40 are provided with L-shaped tracks 96, 97 for fixing torsion spring 95. For this purpose, the end of torsion spring 95 is preferably provided with an inwardly pointing hook, which can be guided to translate through the longitudinal portion of L-shaped tracks 96, 97 and rotated to engage with the corresponding portion.

[0087] The engagement between connector element 50 and housing component 1 is Figure 6A Disclosed in -B. As shown, the housing component 1 is provided on the proximal side with a plurality of outwardly pointing ribs 5 axially separated by guide rails 6, which are capable of guiding the translation of the dose selector 40 during injection.

[0088] At the proximal end of the housing component 1, a plurality of axially oriented proximal V-shaped ratchet teeth 7 are provided. These plurality of axially oriented proximal V-shaped ratchet teeth engage with a plurality of similar distal ratchet teeth 51 disposed on the distal surface of the connector element 50, such as... Figure 3B As shown in the best example. When the compression spring 90 pushes the connector element 50 against the housing component 1, the ratchet interface (7, 51) between the axially pointing proximal V-shaped ratchet teeth 7 and the distal ratchet teeth 51 provided on the connector element 50 can maintain the torque of the torsion spring 95, as will be explained.

[0089] Drive mechanism in Figure 7 The invention discloses and includes a piston rod 15, a drive tube 30, and a nut component 20.

[0090] exist Figure 4 The drive tube 30, disclosed in further detail, has a plurality of radial teeth 32 on its distal side, which engage between injection points with similar teeth 8 disposed on the inner surface of the housing component 1. This engagement (32, 8) secures the drive tube 30 to resist rotation relative to the housing component 1.

[0091] A nut component 25, internally threaded with an external thread 16 and an internal thread 26 that connects to the piston rod 15, is connected to the drive tube 30 via a snap-fit ​​element 60. This allows the nut component 25 to move axially with the drive tube 30 but rotate relative to it. For this purpose, the snap-fit ​​element 60 is provided with a plurality of proximal snap-fit ​​arms 61 that grip the rear of a distal shelf 33 disposed on the drive tube 30, such as... Figure 4 neutralization Figure 7 It is publicly available in China.

[0092] On its outer surface, the nut element 25 is provided with a plurality of splines 27, which are capable of engaging similar internal splines 76 provided in the housing ring 75, which is rotatably and axially fixed in the housing component 1 and thus included in the housing structure. (As in...) Figure 1 and Figure 2B As shown in the optimal embodiment, the housing ring 75 is attached to the housing component 1 via a tenon and groove connection. In an alternative embodiment, the housing ring 75 is molded as an integral part of the housing component 1.

[0093] Between injections, the nut element 25 is not fixed and can rotate freely. Therefore, the piston rod 15, connected to the threaded connection (16, 26) to the nut element 20, moves freely axially. Between injections, the drive tube 30 is fixed to resist rotation by the engagement of radial teeth 32 on the drive tube 30 with internal teeth 8 in the housing component 1, and translational movement (without rotation) of the piston rod 15 is possible. During this translation of the piston rod 15, the nut element 25 is forced to rotate and also rotates freely. Therefore, if the contents of the cartridge 10 expand, for example, due to exposure to frost, the piston rod 15 can move proximally through the movable plunger 12 inside the cartridge 10.

[0094] During injection, the drive tube 30 is pushed distally out of engagement with housing component 1 (32, 8), as will be explained. The nut component 25, axially coupled to the drive tube 30, follows the axial movement of the drive tube 30 and is coupled to the housing ring 75 via splines (27, 76). As the drive tube 30 moves out of engagement with housing component 1, the torsion spring 95 rotates the drive tube 30. Due to the threaded engagement (16, 26) with the nut element 20, the rotation of the drive tube 30 and thus the piston rod 15 in this case causes the piston rod 15 to move helically forward (i.e., distally), the nut element being non-rotatably secured by its engagement (27, 76) with the housing ring 75.

[0095] exist Figure 3A The connector element 50, shown in further detail in section B, surrounds, as... Figure 6A The drive tube 30 disclosed in the paper has multiple outwardly pointing teeth 52 separated by rectangular openings 53 on its outer surface.

[0096] These rectangular openings 53 are set by... Figure 5A The internal spline 43 of the dose selector 40 disclosed in -B engages such that rotation of the dose selector 40 is converted into a similar rotation of the connector element 50. The engagement between the rectangular opening 53 and the internal spline 43 allows the dose selector 40 and the connector element 50 to rotate together one-to-one in two rotational directions; however, the dose selector 40 is capable of translational movement relative to the connector element 50.

[0097] Connector element 50 is further provided with internal ribs 54 and longitudinal flanges 55, such as Figure 3A Disclosed in -B. The opening region between the longitudinal flange 55 and the inner rib 54 defines two openings 56, 57. A first injection opening 56 and a second release opening 57, the use of which will be explained below. Both the injection opening 56 and the release opening 57 have a width that allows a radial protrusion 35 disposed on the proximal side of the drive tube 30 to translately pass through these openings 56, 57.

[0098] To administer the injection, the user first needs to insert the cartridge 10 into the cartridge holder 20 and connect the cartridge holder 20 to the housing component using the bayonet connectors (22, 2). Once the cartridge 10 containing the liquid medication is inserted, the injection device is ready for use.

[0099] When the injection device is ready for dose selection, the proximal compression spring 90 pushes the dose selector 40 and the drive tube 30 in the proximal direction, causing the radial teeth 32 on the drive tube 30 to engage the internal teeth 8 inside the housing component 1, thereby fixing the drive tube 30 against rotation. This position is... Figure 7 It is publicly available in China.

[0100] When viewed from the distal end of the injection device, the user then rotates the dose selector 40 and connector element 50 counterclockwise. This is achieved by... Figure 6A The arrow "D" in -B indicates that the dosing mechanism is viewed from a position near the injection device, thus pointing the arrow clockwise.

[0101] Figure 6B The radial protrusion 35 is disclosed to be located above the release opening 57 and adjacent to the flange 55 on the first side (initial position). During rotation (“D”) of the connector element 50 away from this initial position, the rib 54 on the connector element 50 slides beneath the radial protrusion 35 on the drive tube 30, preventing the user from moving the drive tube 30 in the distal direction. Since the torsion spring 95 operates between the connector element 50 and the drive tube 30, the rotation of the connector element 50 while the drive tube 30 is locked to the housing component 1 tensions the torsion spring 95, causing torque to accumulate in the torsion spring 95.

[0102] As previously described, the torque accumulated in the torsion spring 95 is secured by engagement between the V-shaped ratchet teeth 7 on the housing component 1 and the distal ratchet teeth 51 disposed on the distal side of the connector element 50. The connector element 55 is pressed against the housing component 1 by a compression spring 90 operating between the dose selector 50 and the connector element 50.

[0103] Once the rib 54, flange 55, and injection opening 56 have been rotated to a position where the radial protrusion 35 on the drive tube 30 aligns with the injection opening 56 (dose position), it is possible to translate the drive tube 30 in the distal direction. In this injection position, the radial protrusion 35 preferably abuts the flange 55 on the second opposite side 55a of the flange 55. The injection position or dose position is... Figure 3A As shown in the figure, the radial protrusion 35 is indicated by a dashed line.

[0104] When the injection opening 56 and the radial protrusion 35 are aligned, a predetermined fixed dose has been selected. To dispense the selected fixed dose, the user presses the dose dial 40 in the distal direction. During this translational movement of the dose dial 40, the internal spline 43 engages the axial guide rail 6 in the housing component 1, which protects both the dose selector 40 and the connector 50 from rotation relative to the housing structure during dose dispensing.

[0105] The distal movement of the dose selector 40 is transmitted as a similar translational movement of the drive tube 30, causing the radial teeth 32 to disengage from the internal teeth 8 in the housing component 1. Simultaneously, the spline 27 on the nut element 25 engages with the internal spline 76 in the housing ring 75, thereby locking the nut element 25 to the housing component 1.

[0106] When the radial tooth 32 disengages from the internal tooth 8 in the housing component 1, the torque stored in the torsion spring 95 causes the drive tube 30 to rotate. When the connector element 50 is secured to the housing component 1 during dose dispensing by simultaneously engaging both the rectangular opening 53 in the connector element 50 and the guide rail 6 in the housing component 1 via the internal spline 43 on the dose selector 40, the torque stored in the torsion spring 95 is transmitted as rotation of the drive tube 30. Furthermore, the connector element 50 is firmly pressed against the housing component 1, thus completely securing the interface between the proximal V-shaped ratchet tooth 7 and the distal ratchet tooth 51 on the connector element 50.

[0107] When the drive tube 30 has been set to free rotation by the torsion spring 95, the drive tube 30 will continue to rotate until the radial protrusion 35 again abuts the flange 55. In this position, and when the user removes their finger from the dose selector 40, the protrusion 35 will move proximally upward through the release opening 57 by the proximal compression spring 90, pushing the drive tube 30 and the dose selector 40 in the proximal direction. The end position is... Figure 6B As shown in the diagram. In addition to serving as the end point of the injection, it is also the starting point for selecting a new fixed dose to be delivered, and is therefore also referred to as the initial position.

[0108] Therefore, for each dose selection, the rotation of the drive tube 30 is slightly less than 360 degrees, and the volume of the fixed dose is determined by the manufacturing of the injection device via the selection of the pitch on the threaded engagement (16, 26) between the piston rod 15 and the nut element 25. This selection determines the distance the piston rod 15 moves in the distal direction for each dose release.

[0109] Once the piston rod 15 and plunger 12 have moved to the distal end of the cartridge 10 and the contents of the cartridge 10 have been expelled, the user must replace the cartridge 10 with a new full cartridge 10. This is done by first removing the cartridge holder 20 and discarding the empty cartridge 10. Afterward, a new cartridge 10 must be inserted into the cartridge holder 20 and the piston rod 15 must be pushed back to its initial position.

[0110] When the piston rod 15 is pushed in the proximal direction, the keyed engagement between the piston rod 15 and the drive tube 30 ensures that the piston rod 15 translates without rotating. This is due to the toothed engagement (8, 32) between the drive tube 30 and the housing component 1, which prevents the drive tube 30 from rotating.

[0111] During the non-rotational translational motion of the piston rod 15 in the proximal direction, the nut element 25 is forced to rotate due to the threaded engagement (16, 26) between the external thread 16 on the piston rod 15 and the internal thread 26 in the nut element 25.

[0112] Normally, the user pushes the piston rod 15 proximally with their finger, pushing it only to a position where the piston rod base 18 aligns with the housing component 1. When the cartridge holder 20 is subsequently attached to the housing component 1 via the bayonet couplings (2, 22), the helical engagement between the helical track 22 and the guide protrusion 2 causes the plunger 12 inside the cartridge 10 to push the piston rod 15 a final distance, such that the piston rod base 18 abuts the plunger 12 in the initial position of the new cartridge 10, thereby avoiding any air gaps and eliminating the need for subsequent air venting.

[0113] Some preferred embodiments have been shown above, but it should be emphasized that the invention is not limited to these, but can be implemented in other ways within the scope defined by the following claims.

Claims

1. A torsion spring-driven injection device for dispensing a plurality of predetermined and equal-sized fixed-dose volumes of liquid medication, comprising: A housing structure (1, 20) that holds a cartridge (10) containing the liquid drug to be dispensed. A piston rod (15) for discharging the liquid drug from the cartridge (10). A rotatable drive structure (30) operatively engages the piston rod (15) such that the piston rod (15) rotates together with the rotatable drive structure (30) at least during drug administration. A nut element (25), which is secured to the housing structure (1, 20) at least during drug administration and threadedly connected (16, 26) to the piston rod (15), such that the piston rod (15) moves helically as the piston rod (15) rotates relative to the nut element (25). A connector element (50) is connected to the housing structure (1, 20) via a ratchet interface (7, 51), allowing the connector element (50) to rotate relative to the housing structure (1, 20). A torsion spring (95) is operably coupled between the rotatable drive structure (30) and the connector element (50) such that torque accumulates in the torsion spring (95) by rotation of the connector element (50) relative to the rotatable drive structure (30), and wherein the ratchet interface (7, 51) between the housing structure (1, 20) and the connector element (50) is capable of resisting the torque of the torsion spring (95) to hold the connector element (50) in its rotatable position. The rotatable drive structure (30) can move axially between the first position and the second position; The first position is the position where the rotatable drive structure is non-rotatably fixed to the housing structure (1, 20), and The second position is the position where the rotatable drive structure is released from the housing structure (1, 20) and is able to rotate under the influence of the torque stored in the torsion spring (95). When the rotatable drive structure (30) is maintained in the first position, and one of the plurality of predetermined and equal-sized fixed dose volumes is selected by rotation of the connector element (50) relative to the rotatable drive structure (30), the torsion spring (95) is tensioned; the connector element (50) can rotate from the initial position to the dose position, and When the rotatable drive structure (30) moves axially from the first position to the second position, thereby allowing the rotatable drive structure (30) to rotate from the dose position to the initial position under the influence of the torsion spring (95), a selected one of the plurality of predetermined and equal-sized fixed dose volumes is individually released, wherein, The rotatable drive structure (30) and the connector element (50) are provided with engagement devices (35, 56). The rotatable drive structure (30) is allowed to move axially from the first position to the second position only when the engagement devices (35, 56) provided on the rotatable drive structure (30) and the connector element (50) are aligned respectively, and the rotatable drive structure (30) has been rotated to and positioned in the dosage position.

2. The torsion spring driven injection device according to claim 1, wherein a rotational selection element (40) is provided at the proximal end of the housing structure (1, 20), the rotational selection element being used to rotationally select one of the plurality of predetermined and equal fixed dose volumes to be discharged.

3. The torsion spring driven injection device according to claim 2, wherein the rotary selection element (40) is rotatably coupled to the connector element (50) such that the connector element (50) rotates together with the selection element (40) when the predetermined and equal fixed dose volume is selected, and wherein the selection element (40) is axially movable relative to the connector element (50) such that the selection element (40) is allowed to move axially relative to the connector element (50).

4. The torsion spring driven injection device according to claim 2 or 3, wherein the rotary selection element (40) is axially coupled to the rotatable drive structure (30) such that the selection element (40) and the rotatable drive structure (30) move together in the axial direction to move the rotatable drive structure (30) from the first position to the second position, thereby releasing the rotatable drive structure (30), and wherein the selection element (40) and the rotatable drive structure (30) are allowed to rotate relative to each other.

5. The torsion spring driven injection device according to claim 2 or 3, wherein the compression spring (90) pushes the selection element (40) and the rotatable drive structure (30) in the proximal direction.

6. The torsion spring driven injection device according to claim 2 or 3, wherein the rotating dose selection element (40) is axially guided by the guide device (5, 6) in the housing structure (1, 20).

7. The torsion spring driven injection device according to claim 2 or 3, wherein the rotatable drive structure (30) includes a longitudinal drive tube (30) provided with radial protrusions (35) as one of the engagement devices (35, 56).

8. The torsion spring driven injection device according to claim 7, wherein the connector element (50) is provided with a first axial opening (56) as one of the engagement devices (35, 56).

9. The torsion spring driven injection device according to claim 8, wherein when the first axial opening (56) and the radial protrusion (35) are aligned, the radial protrusion (35) disposed on the drive tube (30) can axially pass through the first axial opening (56) in the connector element (50) to initiate discharge.

10. The torsion spring driven injection device according to claim 9, wherein the connector element (50) is provided with a second axial opening (57).

11. The torsion spring driven injection device according to claim 10, wherein when the second axial opening (57) and the radial protrusion (35) are aligned at the end of discharge, the radial protrusion (35) disposed on the rotatable drive tube (30) is axially able to pass through the second axial opening (57) in the connector element (50).

12. The torsion spring driven injection device according to claim 7, wherein the piston rod (15) is provided with external threads (16) and longitudinal guide surfaces (17) such as grooves.

13. The torsion spring driven injection device according to claim 12, wherein the housing structure internally carries a nut element (25) having an internal thread (26) engaging the external thread (16) on the piston rod (15), and wherein the rotatable drive tube (30) is provided with an internal engagement device that engages the longitudinal guide surface (17) on the piston rod (15) such that the piston rod (15) can rotate together with the rotatable drive tube (30) and move helically when the drive tube (30) and the piston rod (15) rotate relative to the nut element (25).

14. The torsion spring driven injection device according to claim 13, wherein the nut element (25) is axially movable and coupled to the rotatable drive tube (30) to move axially together with the drive tube (30).

15. The torsion spring driven injection device according to claim 14, wherein the nut element (25) is rotatably released from the housing structure in the first position of the rotatable drive tube (30) and rotatably fixed to the housing structure in the second position of the rotatable drive tube (30).

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