TW202434323A - Injection device with an improved needle guard lockout mechanism - Google Patents

Abstract

The invention relates to an injection device comprising a housing (3), a needle guard (20), an injection drive mechanism for driving a plunger within a medicament container (5) and thus expelling the medicament, the drive mechanism including o a plunger rod (31) biased by an injection spring (34); o a retaining member (33) for initially retaining the plunger rod (31) in its proximal position; and o a trigger member (35), mounted onto the retaining member (33). The retraction of the needle guard (20) causes the trigger member (35) to move proximally and thus causes the release of the plunger rod (31). The device (1) further comprises a lockout mechanism for preventing retraction of the needle guard (20) after use of the device, the lockout mechanism comprising a cam system provided on the trigger member (35) and the retaining member (33), that prevents the trigger member from rotating as the needle guard (20) is retracted and that is caused to rotate into a blocking position when the needle guard (20) is returned to its extended position after firing of the device.

Description

Injection device with improved needle protection locking mechanism

The present invention relates to injection devices, in particular to so-called "needle guard activated" auto-injectors which can be activated by the user pressing the device onto an injection site.

This type of device is usually preferred for injecting a drug to be administered in an emergency situation. In particular, the emergency device needs to be not only strong and reliable, but also easy to use with a minimum of steps.

In some devices known from the prior art, such as WO 2009/114542, a removable safety member is provided, which prevents accidental activation of the device during handling of the device. For this purpose, when the device is pressed against the injection site, the safety member blocks the trigger member that can be activated when the needle guard is retracted. Before activating the device for performing an injection, the safety member needs to be removed by the user. Devices of this type also include a cap that is detachably arranged at the distal end of the device housing, which is used to cover the needle guard and maintain it in an extended position, thereby preventing accidental activation during transportation, for example due to vibrations. The cap is also provided with the feature of clamping a sheath that typically protects the needle of a drug container, whereby the sheath is removed simultaneously with the cap.

Another safety feature is provided which locks the needle guard in the extended position after use of the device (after an injection) and thereby prevents any further retraction of the needle guard. This is to prevent repeated use of the device and potential injuries with the needle.

This safety feature is achieved by an additional safety component in the device that is movable and deformable within the device housing. This additional component increases the complexity and manufacturing cost of the device. It may also increase the risk of defects.

Therefore, the object of the present invention is to reduce the number of components while achieving this locking safety function in a robust and reliable manner.

According to the present invention, an injection device is provided, comprising: - an elongated housing extending along a longitudinal axis (X) and constructed to accommodate a drug container, the drug container being provided with a barrel containing a drug, a needle attached thereto, and a plunger displaceable in the barrel to discharge the drug through the needle; - a needle guard telescopically mounted in the housing and axially movable between an extended position and a retracted position, wherein in the extended position the needle guard protrudes distally from the housing and surrounds the needle, and the retracted position is proximally spaced from the extended position, corresponding to the condition of pressing the device against an injection site for activating the injection device; - a needle guard spring to bias the needle guard in a distal direction; - an injection drive mechanism for driving the plunger in the barrel and thereby expelling the drug, the injection drive mechanism comprising: a plunger rod axially movable within the housing between a proximal position and a distal position for driving the plunger in the barrel; an injection spring configured to bias the plunger rod to its distal position; A retaining member fixed in the housing, used to hold the plunger rod in its proximal position against the biasing action of the injection spring in the initial state of the injection device, the retaining member and the plunger rod having corresponding latching features, the latching features including a stop surface and a corresponding radially deflectable elastic arm formed with a protrusion, whereby the plunger rod is held in its proximal position by the engagement of the protrusion with the stop surface; and A trigger member comprising a blocking feature, and the blocking feature can be axially displaced from the blocking position to a release position when the needle guard is moved from its extended position to its retracted position, in which the blocking feature prevents radial deflection of the elastic arm, thereby preventing the protrusion from disengaging from the corresponding stop surface, and in the release position, the elastic arm is free to deflect radially, thereby the protrusion is disengaged from the corresponding stop surface under the biasing action of the injection spring; wherein the retraction of the needle guard causes the trigger member to move proximally, thereby causing the release of the latch feature and thereby causing the activation of the injection device, The injection device further comprises a locking mechanism for preventing the needle guard from retracting once the device has been activated and once the needle guard has returned to its extended position by the needle guard spring, wherein the trigger member is capable of rotating relative to the retaining member depending on the axial displacement and position of the needle guard, and the locking mechanism comprises: - a cam system, provided on the trigger member and the retaining member, which prevents the trigger member from rotating when the needle guard is retracted and causes the needle guard to rotate into a blocking angular position when it returns to its extended position after activating the device; and The stop feature is disposed on the trigger member such that the stop feature is outside the axial path of the needle guard during retraction of the trigger device and interferes with the needle guard in the blocking angle position of the trigger member.

With this design, the latching safety function is combined with the triggering function in the sense that the latching feature is provided on the trigger member, thereby eliminating the need for an additional component dedicated to the latching function. This design achieves the latching function in a simple and reliable manner, allowing the number of components to be reduced.

Preferred embodiments may include one or more of the following features: -The needle guard has a sheath portion for surrounding the needle in the extended position, the sheath portion having a through hole at the distal end for passing the needle when the needle guard is retracted, and a leg protruding axially and proximally from the sheath portion, the leg having a free end for engaging and displacing the trigger member when the needle guard is retracted; -The cam system includes a cam track provided on the trigger member, and a tip provided on the retaining member and defining a cam follower, the tip being used to engage in the cam track; - the retaining member has a substantially cylindrical hollow body, and the trigger member has a sleeve body mounted on the cylindrical hollow body, so that the sleeve body can slide or rotate relative to the cylindrical hollow body depending on the axial displacement and position of the needle guard; - the sleeve body is provided with a first rib for engaging with the free end of the leg when the needle guard is retracted, thereby causing the trigger member to shift proximally; - the sleeve body is provided with a cam track on its inner surface for receiving a tip, which protrudes radially and inwardly from the cylindrical hollow body, and the cam track has a transversely oriented terminal channel connected to an axial channel extending in the proximal direction, and the axial channel has an open distal end; - the stop feature comprises a second rib radially projecting from the sleeve body, the second rib being adapted to selectively engage with the needle guard to prevent the needle guard from retracting proximally; - the second rib being distally spaced from the first rib; - the leg having a recess distally spaced from the free end of the leg and forming a transverse edge, the transverse edge defining a stop surface for preventing the needle guard from retracting proximally in the final state of the injection device after injection; - the tip is biased towards this terminal passage, thereby causing the trigger member to rotate and the second rib to engage the lateral edge of the leg when the needle guard moves back to the extended position corresponding to the final state of the device after injection under the action of the needle guard spring; - the trigger member and the housing include corresponding locking features in a mutually releasable engagement for maintaining the trigger member in its blocking position, and wherein the locking features are designed to be released when the needle guard moves from its extended position to its retracted position, whereby the retraction of the needle guard causes the release of the locking features, the release of the latching features, and thus the activation of the injection device; - the leg has an axial edge having a section extending between the sheath portion and the recess, defining a guide element that slidably engages with a corresponding guide element (113) of the retaining member (33) during axial displacement of the needle guard (20); - a second rib is arranged on the sleeve body for engaging the transverse edge of the leg in the final state of the injection device after injection and thereby preventing the needle guard from retracting proximally; - the latching feature comprises a pair of elastic arms formed on the proximal end of the plunger rod and an axially extending, respective projection formed at the free end of each elastic arm; - the retaining member comprises a radial wall with an axial hole having a peripheral edge defining a stop surface of the latching features; - the projections project radially and outwardly from respective resilient arms which project axially from the radial wall through the hole so as to engage the projections with the stop surface when the plunger rod is in its proximal position; - the blocking feature comprises an axial latch which, in the blocking position of the trigger member, prevents inward deflection of the resilient arms and thus prevents the projections from disengaging from the stop surface; -The housing includes at least one recess, and the trigger member includes a sleeve body and at least one cantilevered flexible arm protruding outward from the sleeve body, the cantilevered flexible arm having a radial ear piece at its free end for releasably engaging with the recess of the housing, and the locking features include the ear piece and the corresponding recess; -The ear piece is biased to engage in the recess by the cantilevered flexible arm, and the cantilevered flexible arm can be deflected inwardly by the needle guard to release the ear piece from the recess; -The cantilevered flexible arm includes a slope for engaging with the needle guard, and when the needle guard moves in the proximal direction, the profile of the slope determines the inward deflection of the cantilevered flexible arm caused by the axial displacement of the needle guard; -The housing and the trigger member respectively have a pair of recesses relative to each other in the radial direction and corresponding cantilevered flexible arms; -The device further includes a trigger spring disposed between the housing and the trigger member, for biasing the trigger member distally, whereby the trigger member is biased to its blocking position in the initial state of the injection device; and -The injection spring is designed to impart a force to the plunger rod in its proximal position that overcomes the retaining force of the interengaging latching features, whereby release of the blocking features causes these latching features to disengage and cause the injection spring to drive the plunger rod to its distal position.

Definition

The following definitions will be used in this specification and claim: -The term autoinjector refers to an injection device in which the force used to expel medication from a medication container is provided by an energy source of the device, which is triggered by the user, as opposed to a device that uses manual force from the user to expel medication. In this specification, the term autoinjector covers syringes with fixed needles and those with automatic penetration features, in which the needle is moved and inserted into the injection site by the energy source of the device before the medication is expelled; -The term "distal" means a position or direction close to, or oriented toward, the exit opening of the cartridge contents when the cartridge is received in the injection device. The term "distal" position and direction may also be referred to as the "forward" position and the "forward" direction, respectively; and - The term "proximal" means a position or direction opposite to the distal position or direction and/or close to or directed toward the grip of the injection device. The term "proximal" position and direction may also be referred to as the "rearward" position and the "rearward" direction, respectively.

The present invention will now be further described by the following preferred embodiments shown in the drawings (FIGS. 1-10).

The injection device depicted in the figure is a disposable autoinjector.

1, 2 and 2A, the injection device 1 comprises an elongated housing 3 extending along a longitudinal axis X and configured to receive a drug container 5. In the illustrated embodiment, the housing 3 is made of two parts, including a front housing 3a and a rear housing 3b coaxially and fixedly attached. However, in other embodiments, the housing 3 may be integrally made as a one-piece component.

In the illustrated embodiment, the drug container 5 is a prefilled syringe having a barrel 6 containing a drug 7, a needle 8 attached thereto, and a plunger 9 displaceable within the barrel 6 to expel the drug through the needle. The barrel 6 is formed with a flange 10 at its proximal end, connected to the tip of the needle 8 at its distal end, the tip presenting a reduced diameter and thereby forming a front shoulder 11. The barrel 6 is made of glass, but in other embodiments it may be made of a plastic material. The syringe 5 is further provided with a removable protective sheath 15 surrounding the needle 8 and including an enlarged base portion 17 at its proximal end. The sheath 15 is typically at least partially made of an elastomeric material such as rubber. As will be described in detail below, the syringe 5 is fixedly mounted in the front housing 3a.

The device 1 further comprises a needle guard 20 which is telescopically mounted in the housing 3 and can move axially between an extended position and a retracted position. In the extended position, the needle guard 20 protrudes distally from the distal end of the housing 3 and surrounds the needle 8, whereby the needle is hidden from the user's sight and protected. The retracted position is proximally spaced from the extended position and corresponds to the condition in which the device is pressed against an injection site for activation of the device.

In association with the needle guard 20, the device comprises a needle guard spring 21, which in the present embodiment is a helical compression spring and is axially arranged between the housing 3 and the needle guard 20 for biasing the needle guard in a distal direction.

The device 1 further comprises a cap 22 detachably mounted on the distal portion of the housing 3 for covering the needle guard 20 and limiting its axial movement. As will be seen below, the cap 22 is also provided with a grip feature for removing the needle sheath 15 when the cap 22 is removed from the housing 3.

In order to drive the plunger 9 in the barrel 6 and thus expel the drug 7 through the needle 8, the device 1 further comprises an injection drive mechanism 25 arranged in the housing 3.

The injection drive mechanism 25 includes a plunger rod 31 that can move axially in the housing 3 to drive the plunger 9 in the barrel 6, a retaining member 33 fixed in the housing 3, an injection spring 34 in the form of a spiral compression spring axially arranged between the retaining member 33 and the plunger rod 31 to bias the plunger rod 31 forward, and a trigger member 35 that can move axially in the housing 3 to trigger the injection stage when moving backward.

Furthermore, the device 1 comprises a trigger spring 37 in the form of a helical compression spring arranged axially between the housing 3 and the trigger member 35 for biasing the trigger member 35 distally.

3, 3A and 3B, it will be seen that the front housing 3a has an elongated cylindrical outer wall 41, a coaxial cylindrical inner wall 42 forming a housing for the syringe barrel 6, and a coaxial front sleeve 43 for detachably connecting to the cap 22. The front housing is further provided with radial connecting ribs 44, four in number in the illustrated embodiment, which firmly connect the outer wall 41 to the inner wall 42 and are regularly distributed around the longitudinal axis X.

In the embodiment shown, the outer wall 41 is generally elliptical in cross section, thereby preventing the device from rolling on a flat surface. It includes a pair of facing apertures 45 in the rear portion for firmly attaching the rear housing 3b to the front housing 3a. On its inner surface, the outer wall 41 is formed with a stop surface 46 for engaging with a complementary feature of the needle guard 20, thereby limiting the displacement of the needle guard 20 in the distal direction. The outer wall 41 is also provided with ridges 47 or grooves on the outer surface of its front portion for enhancing the operability of the user.

The inner wall 42 is generally circular in cross section, sized to match the outer dimensions of the syringe barrel 6, and provided with a smaller diameter stop portion 48 at the front. The stop portion 48 is provided to engage the shoulder 11 of the syringe barrel 6, whereby the syringe 5 can be coaxially inserted into the front housing 41, received in the cavity defined by the inner wall 42 and held in an axial position by the stop portion 48 to prevent forward movement.

The front sleeve 43 defining the distal end of the housing 3 has a ribbed thread section 49 for cooperating with complementary features of the cap 22, those connecting features being designed so that the cap 22 can be removed from the front housing 41 by rotating the cap a fraction of a turn and then removing it axially.

Preferably, the front housing 41 is integrally formed by forming a synthetic material.

1 and 4, the needle guard 20 has a sheath portion 50 with a front annular edge 51 for surrounding the needle 8 in its extended position, and a pair of opposed legs 52 projecting axially and proximally from the sheath portion 50.

The sheath portion 50 is formed as a cylinder and has a through hole 53 defined by an edge 51 at its distal end for the needle 8 to pass through when the needle guard 20 is retracted into the housing 3. The sheath portion 50 is also provided at its distal end with a pair of radial projections 54 that are opposite in the radial direction and are designed to engage with complementary features of the cap 22 to limit axial movement of the needle guard 20 when the cap 22 is attached to the housing 3. This configuration is intended to prevent accidental triggering of the device, for example in the event of a shock.

Each leg 52 has a free end 55 for engaging and displacing the trigger member 35 when the needle guard 20 is retracted into the housing 3 as will be described below. Each leg 52 is formed with a notch spaced distally from the free end 55 and forming a transverse edge 56, and an axial edge having a section 57 extending between the sheath portion 50 and the notch.

The transverse edge 56 defines a stop surface for preventing the needle guard 20 from retracting proximally in the final state of the injection device after injection. The section 57 of the axial edge defines a guide element for engaging with a corresponding feature of the retaining member 33 during the axial displacement of the needle guard 20.

Each leg 52 is further provided with a flexible deflectable wing 58 having a radially protruding front wing edge 59 for engaging with a corresponding stop surface 46 of the outer wall 41, as can be seen in Figure 2. The engagement of the wing 58 with the stop surface 46 defines the extended position of the needle guard 20 relative to the housing 3 and prevents further distal relative displacement of the needle guard 20.

As can be seen in FIGS. 2 and 2A , the needle guard spring 21 disposed between the needle guard 20 and the housing 3 is supported at the proximal end on the stop portion 48 of the front housing 3 a and at the distal end on the annular edge 51 .

1, 2 and 2A, the cap 22 includes a substantially cylindrical wall 61 designed to fit over the front sleeve 43 of the front housing 2a and partially close the front end annular wall 63 of the cylindrical wall 61. The inner surface of the cylindrical wall 61 is formed with a recess 64, which is formed for threaded connection with the complementary features of the rib thread section 49.

The cap 22 further comprises a coaxial gripping sleeve 65 extending rearwardly from the front end wall 61 for engaging the needle sheath 15. At the free end (proximal end), the gripping sleeve 65 is formed with a pair of opposing clamping claws 67, which engage the rear annular surface of the enlarged base 17 of the needle sheath 15 when the cap 22 is attached to the housing 3 (FIG. 2), so that when the cap 22 is removed from the housing 3, the sheath 15 is removed from the syringe 5.

On the outer surface of the cylindrical wall 61, the cap 22 is provided with a main rib 68 extending from the front end to the rear end of the cylindrical wall 61, and a ridge surface 69, wherein the rib 68 is continuously formed with a substantially axial portion and a substantially spiral portion. The main rib 68 and the ridge surface 69 are designed to enhance the user's operation, in particular to make it easier for the user to rotate the cap 22 a fraction of a turn (e.g., 1/4 turn) corresponding to the threaded connection between the cap 22 and the housing 3, and then axially pull the cap 22 for removing the cap from the housing. Together with the ridge 47 of the front housing 3a, the ridge surface 69 can also define a visual indicator of the angular position of the cap 22 relative to the housing 3.

In the illustrated embodiment, the cap 22 is formed as a one-piece piece of synthetic material. In particular, the grip sleeve 65 is formed as a one-piece piece with the rest of the cap 22. However, in other embodiments, the grip sleeve 65 may be a separate component from the rest of the cap and attached thereto. The grip sleeve may also be formed of a different material, such as metal.

The inner surface of the cylinder 61 is formed with a constriction 70 defining a stop surface for engaging with the radial protrusion 54 of the needle guard to prevent the needle guard 20 from retracting when the cap 22 is attached to the housing 3. In this configuration, the axial displacement of the needle guard is therefore limited to a small distance between the constriction 70 and the front annular wall 63 (FIG. 2A).

Still referring to Figures 1, 2 and 2A, the rear housing 3b is formed as a plug for closing the internal volume defined by the front housing 3a at its rear end. It mainly comprises a substantially cylindrical body 71 fitted in the outer wall 41 of the front housing 3a, and a radial closing wall 73 at its proximal end. The outer surface of the cylindrical body 71 is formed with a pair of radial latches 75 facing each other, which are used to engage with the respective holes 45 and firmly attach the rear housing 3b to the front housing 3a.

The inner surface of the cylindrical body 71 of the rear housing 3b is formed with facing recesses 77, which are provided to engage with complementary features of the retaining member 33 for firmly attaching it to the rear housing 3b. The inner surface of the body 71 of the rear housing 3b is further formed with facing recesses in the radial direction, which define radial stops 79 for engaging with features of the trigger member 35, as will be seen below.

Still referring to Figures 1, 2 and 2A, the plunger rod 31 is formed as a one-piece part having a main elongated solid body 81 with a radial plate 83 at its distal end, and a pair of parallel elastic arms 85 extending axially and proximally from the solid body 81. The plate 85 is designed to engage the plunger 9 and transmit the expelling force of the injection spring 34 to the plunger 9.

The arms 85 are spaced apart from one another to define a gap 87 and are flexible so that they can deflect inwardly in a radial direction. Each arm 85 is formed at its free proximal end with a projection 89 for engaging with a stop surface of the retaining member 33. The projection 89 projects radially and outwardly from the respective resilient arm 85. The resilient arms 85 define a latching feature for axially retaining the plunger rod 31 against the biasing action of the injection spring 34.

1, 2, 2A and 5. The retaining member 33 comprises a substantially cylindrical hollow body 101 and a radial wall at its proximal end which forms a central axial hole 102 having a peripheral edge 103. The edge 103 defines a stop surface for engaging the projection 89 (as can be seen in FIG. 2) and thus defines a corresponding latching feature.

The cylindrical hollow body 101 is designed to accommodate the injection spring 34, and the radial wall defines a seat for the injection spring 34. As can be seen in FIG. 2, in the initial state illustrated in this figure, the compressed injection spring 34 is supported at its distal end on the plate 83 of the plunger rod 31 and at its proximal end on the radial wall of the hollow body 101.

The injection spring 34 and the latching feature defined by the resilient arm 85 and the protrusion 89 on the one hand and by the edge 103 on the other hand are designed so that when engaged with each other, if the resilient arm 85 is not prevented from deflecting inwardly, the force imparted to the plunger rod 31 by the injection spring 34 in its proximal position (the same position as in FIG. 2 ) overcomes the retaining force of the latching feature.

The cylindrical hollow body 101 is formed with a tip 105 protruding radially and outwardly therefrom, and the tip 105 defines a cam follower for engaging with a corresponding feature of the trigger member 35.

The retaining member 33 further includes a pair of opposite fixing buckles 107, which extend radially from the hollow body 101 and engage with the corresponding recesses 77 (as shown in FIG. 2A ) for locking the retaining member 33 to the rear housing 3 a.

The retaining member 33 also comprises a pair of parallel branches 108 which protrude axially from the hollow body 101 in the distal direction and are symmetrically spaced by the central axis X. Each branch is provided at its free distal end with a beveled edge 109 designed to bear against and press against the syringe flange 10. The branches 108 and the respective beveled edge 109 provide a degree of elasticity which absorbs possible residual play between the syringe and the device components due to manufacturing tolerances. The branches 108 and the edge 109 are also designed to absorb shocks in the event that the device is dropped in a "needle-up" orientation and to minimize the impact forces on the glass constituting the syringe barrel 6.

Furthermore, the retaining member 33 has an annular support flange 111 extending radially from the hollow body 101 for slidably supporting the leg 52 of the needle guard 20, and two pairs of opposite guide walls 113 further protruding outward from the support flange 111, each pair of guide walls 113 defining a passage for a respective leg 52. The guide walls 113 are constructed to slidably cooperate with the corresponding leg 52 so as to allow the needle guard 20 to slide axially and prevent relative rotation.

Referring now to FIGS. 1, 2, 2A, 6 and 6A, it will be seen that the trigger member 35 comprises a hollow sleeve body 131 which is open at its distal end and closed at its proximal end by a proximal closing wall 133. The sleeve body 131 is fitted over the cylindrical hollow body 101 of the retaining member 33 so that the sleeve body 131 can slide or rotate relative to the cylindrical hollow body 101 depending on the axial displacement and position of the needle guard 20. The movement of the trigger member 35 relative to the retaining member 33 will be explained below.

The trigger member 35 includes an axial pin 135 protruding distally from the closing wall 133, so that in the initial configuration illustrated in Figures 2 and 2A, the pin 135 is inserted into the gap 87 between the elastic arms 85 of the plunger rod 31, thereby preventing the elastic arms 85 from deflecting radially inward and thus preventing the protrusion from disengaging from the stop surface of the edge 103.

The latch 135 thus defines a blocking feature which can be displaced axially together with the trigger member 35 by the needle guard 20 when moving from its extended position to its retracted position. When the trigger member 35 is moved proximally from the blocking position in which the latch 135 blocks the inward deflection of the arm 85, the latch 135 is removed from the gap 87, whereby it no longer interferes with the arm 85 and no longer blocks the deflection of the arm. This corresponds to a released position of the trigger member 35 in which the elastic arm 85 is free to deflect radially. Thus, under the biasing action of the injection spring 34, the projection is disengaged from the corresponding stop surface formed by the edge 103.

The trigger member 35 further comprises a pair of opposing cantilevered flexible arms 137 projecting outwardly from the sleeve body 131, each cantilevered flexible arm being provided with a radial tab 139 at its free end. The tabs 139 are provided for releasably engaging respective radial stops 79 formed by recesses of the rear housing 3b (Fig. 2).

Each tab 139 is biased into engagement in a corresponding recess by a respective flexible arm 137, which can be deflected inwardly by the needle guard 20 for releasing the tab 139 from the recess. Each cantilevered flexible arm 137 includes a ramp 141 for engaging with a corresponding leg 52 of the needle guard 20. The profile of the ramp 141 determines the inward deflection of the cantilevered flexible arm 137 caused by axial displacement of the needle guard 20 when the needle guard is moved in the proximal direction.

The tabs 139 and the corresponding radial stops 79 define mutually releasably engaging locking features. These locking features are designed to maintain the trigger member 35 in its blocking position and can be released by the needle guard 20 when the needle guard 20 moves from its extended position to its retracted position. The retraction of the needle guard 20 causes the release of the locking features 79, 139, the release of the latching features 89, 103, and thus the activation of the injection device.

The trigger member 35 further includes a first rib 143 radially and outwardly protruding from the sleeve body 131, and a second rib 145 spaced apart from it. In the illustrated embodiment, the trigger member 35 includes a pair of first ribs 143 that are opposite in the radial direction, and a pair of second ribs 145 that are also opposite in the radial direction.

The first rib 143 is provided for engaging with the corresponding free end 55 of the leg 52 when the needle protector 20 is retracted, thereby causing the trigger member 35 to be displaced proximally.

The first rib has a stop surface slightly spaced distally from the ear 139 for engaging with the free end 55 of the leg 52 at an axial position corresponding to the apex of the ramp 141, so that retraction of the needle guard 20 sequentially causes deflection of the cantilever 137 and engagement of the free end 55 of the leg 52 without contacting the ear 139.

A second rib 145 is provided for engaging a corresponding guide element defined by the axial edge 57 of the leg 52 during retraction of the needle guard 20 towards its retracted position and, in the final state of the injection device after injection, for engaging a corresponding transverse edge 56 of the leg 52 and thereby preventing the needle guard 20 from retracting proximally.

Thus, the second rib 145 provides a stop feature that selectively engages the needle guard 20, allowing axial displacement of the needle guard 20 in the first stage of operation of the device, and preventing the needle guard 20 from retracting proximally in the final state of the device. This will be further explained below.

The sleeve body 131 of the trigger member 35 is also provided with a cam track 150 on its inner surface for receiving the tip 105 of the retaining member 33. The cam track 150 has an axial channel 151 extending proximally from the open distal end 151 and a transversely oriented terminal channel 155 connected to the axial channel 151. As can be seen in FIG. 6A, the inner rear wall of the terminal channel 155 is inclined relative to the main axis X, while the inner front wall is perpendicular to the main axis X.

The locking feature of the locking mechanism defined by the cam system formed by the tip 105 and the cam track 150 is used to lock the needle guard 20 in an extended position corresponding to the final state of the device after injection, that is, to prevent the needle guard 20 from retracting once the device has been activated and once the needle guard 20 has returned to its extended position by the needle guard spring 21.

Furthermore, the sleeve body 131 is provided in the proximal region with a stop member in the form of a shaft ring 160 protruding radially therefrom, which shaft ring 160 defines a seat for the trigger spring 37.

As can be seen in Figures 2 and 2A, the trigger spring 37 disposed between the needle guard 20 and the housing 3 is supported on the closing wall 73 of the rear housing 3b at the proximal end and on the shaft ring 160 at the distal end.

Beginning with the initial configuration of the injection device 10 (as stored) illustrated in FIGS. 2 and 2A , the major steps for operating the device will now be described with reference to FIGS. 7-11 .

2, 2A, it will be noted that the plunger rod 31 is held in its proximal position by engagement of the stop surfaces of the projection 89 and the edge 103 against the biasing action of the pre-compression injection spring 34. The resilient arms 85 protrude axially through the holes 102 so that the stop surfaces of the projection 89 and the edge 103 engage each other and engage the latch 135 between the resilient arms 85 to prevent inward deflection.

In this initial configuration, the trigger spring 37 is compressed between the rear housing 3 b and the trigger member 35 , whereby the trigger member 35 is biased to its blocking position, wherein the latch 135 engages the gap 87 between the resilient arms 85 .

The trigger member 35 is held in this blocking position by the releasable engagement of the locking features formed by the tabs 139 and the radial stop 79, which prevents the axial displacement of the trigger member 35 in the proximal direction in this position. Obviously, the trigger member 35 is also prevented from moving distally by the wall 73 arm 85 that stops the trigger member 35.

In this initial configuration, the needle guard 20 is prevented from moving distally by the wing edge 59 engaging the stop surface 46. Due to the interaction of the projection 54 and the constriction 70 of the cap 22, the needle guard 20 also has a limited ability to resist the proximal displacement of the biasing action of the needle guard spring 21.

Before using the device 1, the user needs to remove the cap 22 by twisting it, for releasing the threaded connection 49, 64 between the cap 22 and the front housing 3a, and then axially disassemble the cap 22 from the front housing 3a. In doing so, the user removes the sheath 15 from the needle 8, which is retained in the grip sleeve 65 of the cap. The needle 8 is still protected by the needle guard 20, which is then in its fully extended position and is not exposed.

The device is then ready for injection. When uncapped, the device is in the same configuration as shown in Fig. 2, 2A, with only the cap 22 and sheath 15 removed and the needle guard 20 free to move further proximally.

In order to trigger the device 1 and inject the medicine 7 contained in the medicine container 5 (syringe), the user needs to press the distal end of the device, i.e. the tip formed by the annular edge 51 of the needle guard 20, against the injection site. When pressed against the action of the needle guard spring 21, the needle guard 20 begins to partially retract into the housing 3.

In the configuration illustrated in FIGS. 7, 7A, and 7B, the needle guard is partially retracted into the housing 3, thereby exposing the tip of the needle 8 that penetrates the user's tissue.

The legs 52 are axially guided between the guide walls 113 so that the axial edges 57 slide on the respective second ribs 145 of the trigger member 35. During this phase, the legs 52 slide over the respective inclined surfaces 141 of the cantilever arms 137, thus deflecting the cantilever arms 37 inwardly and releasing the tabs 139 from the corresponding radial stops 79 of the housing 3. In this configuration, the trigger member 35 does not move axially or rotationally relative to the initial configuration. The prongs 105 are engaged in the cam track 150 and are positioned in the rearmost portion of the axial channel 153.

In this partially retracted configuration, it will be noted with reference to FIG. 7 that when these locking features 79, 139 are released, the trigger member 35 remains in its axial blocking position, wherein the latch 135 is inserted into the gap 87 and prevents the inward deflection of the resilient arm 85, thereby preventing the projection 89 from disengaging from the stop surface of the edge 103. The trigger member 35 is maintained in its blocking position under the bias of the trigger spring 37.

By continuing to apply pressure to the device 1 against the injection site, the needle guard is further retracted into the housing until it reaches its fully retracted position, thereby exposing the entire length of the needle to be inserted into the user's tissue. This configuration is shown in Figures 8, 8A, 8B.

To reach this configuration, the needle guard 20 is retracted so that the free ends 55 of the legs 52 bear on the respective first ribs 143 and thereby in turn push the trigger member 35 in the proximal direction against the action of the trigger spring 37. Thus, the latch 135 is disengaged from the gap 87 in the fully retracted position of the needle guard 20 (as shown in FIGS. 8, 8A, 8B), thereby releasing the latching features 89, 103.

This configuration corresponds to the released position of the trigger member 35, in which the resilient arms 85 are free to deflect inwardly and in which the projections 89 are disengaged from the stop surfaces of the edge 103 under the action of the injection spring 34.

During the operating phase, the trigger member 35 is still prevented from rotating over the retaining member 33 due to the engagement of the tip 105 in the axial channel 153. In the fully retracted position of the trigger member 35, the tip 105 is seated at the open end 151 of the cam track 150, at least partially within the axial channel 153, and thus the trigger member 35 is still prevented from rotating relative to the retaining member 33.

When these latching features are released, the plunger rod 31 can be driven forward to its distal position (as shown in FIG. 9 ) under the action of the injection spring 34 , thereby pushing the plunger 9 forward in the drug container and expelling the drug.

It will therefore be appreciated that retraction of the needle guard 20 sequentially causes the release of the blocking features 79, 139 and then, upon further retraction, causes the trigger member 35 to be axially displaced from its blocking position to its released position. This in turn causes the latching features 89, 103 to be released and activate the injection device, wherein the injection spring 34 drives the plunger rod 31 to its distal position, thereby injecting the drug.

The presence of the trigger spring 37 ensures that the free end 55 of the leg 52 and the first rib 143 remain engaged with each other after the blocking features 79, 139 are released. This ensures that the release of the latching features 89, 103 - and therefore the activation of the device - occurs at the appropriate needle insertion depth, corresponding to the fully retracted position of the needle guard 20.

The configuration illustrated in Figures 9, 9A, 9B corresponds to the user starting to release the pressure on the device once the injection has been completed. The plunger rod 31 is in its distal position and the needle guard 20 returns to a partially extended position under the action of the needle guard spring 21.

To reach this arrangement, the leg 52 slides back distally over the ramp 141, thereby releasing the cantilever 137, which can bend outwardly back to its initial position when the trigger member 35 is biased in the distal direction by the trigger spring 37. Under the action of the trigger spring 37, the trigger 35 is thus moved axially forward, thereby moving the axial channel 153 to receive the tip 105. In this relative movement, the tip 105 is brought into engagement with the transverse surface of the terminal channel 155 at the end of the axial channel 153 (as can be seen in FIG. 7B ).

Under the action of the trigger spring 37, the mutual engagement of the tip 105 and the cam track 150 causes the tip 105 to be biased toward the terminal passage 155. However, relative rotation of the trigger member 35 and the retaining member 33 is prevented when the second rib 145 bears on the axial edge 57 of the leg 52. This relative rotation is prevented until the needle guard 20 returns to its fully extended position, corresponding to the second rib 145 reaching the proximal end of the edge 57.

In the final state of the device after injection, and once the user has completely withdrawn the device from the injection site and completely released the pressure on the device, the needle guard 20 returns to its fully extended position, also corresponding to the position of FIG. 2 , in which it completely covers the needle 8 .

This final structure is illustrated in Figures 10, 10A, and 10B.

To reach this configuration, the needle guard 20 has been moved distally a distance so that the axial edge 52 reaches a position after sliding on the second rib 145, wherein the notch 56 is positioned corresponding to the second rib 145, thereby allowing the trigger member 35 to rotate.

Under the action of the trigger spring 37 and the mutual engagement of the cam follower (tip 105) in the cam track 150, the trigger member 35 is caused to rotate, so that the inclined rear wall of the terminal channel 155 is forced to slide on the tip 105. The second rib 145 then engages the corresponding transverse edge formed by the notch 56, thereby locking the needle guard 20 in its fully extended position. This prevents the needle guard 20 from being retracted again and acts as a safety measure to prevent the needle from being exposed to avoid the risk of injury.

It will be appreciated that the cam systems 105, 150 allow or prevent relative displacement, either axially or rotationally, of the trigger member 35 relative to the retaining member 33, depending on the axial displacement and position of the needle guard 20.

The trigger member 35 is prevented from rotating by the tip 105 riding in the axial channel 153. In both the blocking position and the release position of the trigger member 35, the tip 105 is engaged in the axial channel 153 to prevent relative rotation.

In order for the trigger member 35 to be able to rotate during the locking period, the trigger member 35 must move distally under the action of the trigger spring 37 until the tip 105 completely leaves the axial channel 153. This state shown in FIG. 9B can only be achieved once the plunger rod 31 is released. Once the arm 85 can no longer interfere with the trigger member 35, the trigger member 35 will be able to move distally beyond its initial position (as shown in FIG. 2), and the tip 105 will eventually leave the axial channel 153. This occurs just before the tip 105 comes into contact with the terminal channel 155. Once the tip 105 leaves the axial channel 153 and contacts the terminal channel 155, the second rib 145 will come into contact with the axial edge 57 of the needle guard 20, preventing rotation of the trigger member 35 until the needle guard has returned to its fully extended state.

If the user pushes on the needle guard 20 in this state of the device, the transverse edge 56 of the needle guard 20 contacts the second rib 145 and the front wall of the terminal channel 155 is then pushed against the tip 105, which is firmly fixed to the housing 3. The front wall of the terminal channel 155 is oriented so that no relative rotation can be caused by the front wall of the terminal channel 155 pressing axially on the tip 105. In the illustrated embodiment, this is achieved by the front wall of the terminal channel being perpendicular to the main axis X.

In an alternative embodiment (not shown), the cam system may be inverted so that the cam follower is provided on the trigger member and the cam track is provided on the retaining member. In such an arrangement, the cam follower may be in the form of a prong protruding radially and inwardly from the sleeve body of the trigger member. The illustrated embodiment is preferred, although it is more easily manufactured as a component by conventional injection molding methods.

In a further alternative embodiment (not shown), the locking features corresponding to the radial stop 79 and the tab 139 may be provided in a different configuration, wherein the radial stop is formed by a recess in the retaining member and the tab is formed on a cantilever projecting radially inwardly from the sleeve body of the trigger member. In such embodiments, the legs of the needle guard are radially slidably engaged between the retaining member and the trigger member. In the described case, retraction of the needle guard causes an outward deflection of the cantilever (as opposed to the inward deflection in the described preferred embodiment) and release of the locking feature. Moreover, in these embodiments, the first rib and the second rib corresponding to the ribs 143, 145 protrude radially inward from the sleeve body of the trigger component.

It will be appreciated that the device according to the present invention includes safety features, such as preventing accidental activation, which are achieved by relatively simple means, eliminating the need for additional parts and processing steps. The present invention provides a high degree of durability and reliability, which is particularly important for emergency devices used in conjunction with life-saving drugs.

1: injection device 2a: front housing 3: elongated housing 3a: front housing 3b: rear housing 5: drug container 6: barrel 7: drug 8: needle 9: plunger 10: flange 11: front shoulder 15: sheath 17: base 20: needle guard 21: needle guard spring 22: cap 25: injection drive mechanism 31: plunger rod 33: retaining member 34: injection spring 35: trigger member 37: trigger spring 41: outer wall 42: inner wall 43: sleeve 44: radial connecting rib 45: Orifice 46: Stop surface 47: Ridge 48: Stop portion 49: Rib thread section 50: Sheath section 51: Front annular edge 52: Leg 53: Through hole 54: Protrusion 55: Free end 56: Transverse edge 57: Segment 58: Wing 59: Front wing edge 61: Cylindrical wall 63: Front annular wall 64: Recess 65: Gripping sleeve 67: Clamping claw 68: Main rib 69: Ridge surface 70: Constriction 71: Cylindrical body 73: Radial closing wall 75: Radial latch 77: Recess 79: Radial stop 81: Solid body 83: Radial plate 85: Flexible arm 87: Gap 89: Protrusion 101: Hollow body 102: Central axial hole 103: Circumferential edge 105: Point 107: Fixed snap-fitting part 108: Branch 109: Inclined edge 111: Support flange 113: Guide wall 131: Sleeve body 133: Closing wall 135: Latch 137: Cantilevered flexible arm 139: Radial ear 141: Inclined surface 143: First rib 145: Second rib 150: Cam track 151: Axial channel 153: Axial channel 155: Terminal channel 160: Shaft ring

The preferred embodiment of the present invention will now be described in more detail with reference to the following figures, wherein: [FIG. 1] is an exploded perspective view of an injection device according to a preferred embodiment of the present invention; [FIG. 2] is a cross-sectional view of the device of FIG. 1 assembled in a storage structure before use in a first axial plane; [FIG. 2A] is a cross-sectional view of the device in the structure of FIG. 2 in a vertical axial plane; [FIG. 3] is a front view of a single front housing of the device of FIG. 1; [FIGS. 3A and 3B] are a side view in direction 3A and a cross-sectional view in axial plane 3B-3B from FIG. 3, respectively; [FIG. 4] is a perspective view of a single needle guard of the device of FIG. 1; [Figure 5] is a top view of a single retaining member of the device of Figure 1; [Figure 6] is a top view of a single trigger member of the device of Figure 1; [Figure 6A] is a cross-sectional view from the axial plane 6A-6A of Figure 6; [Figure 7] is a cross-sectional view of the device of Figure 1 in the plane of Figure 2 in the first step of triggering the device, wherein the needle guard is partially retracted, corresponding to the user starting to press the device against the injection site; [Figures 7A and 7B] are partial exploded views of the device in the assembly of Figure 7 without the outer shell, which are front view and top view respectively; [Figure 8] is a cross-sectional view of the device of Figure 1 in the plane of Figure 2 in the second step of triggering the device, wherein the needle guard is fully retracted, corresponding to the complete insertion of the needle at the injection site; [Figures 8A and 8B] are partial exploded views of the device in the configuration of Figure 8 without the outer shell, which are a front view and a top view respectively; [Figure 9] is a cross-sectional view of the device of Figure 1 in the plane of Figure 2 in the first locking step of the device, wherein the needle guard is returned to a partially extended position, corresponding to the user starting to withdraw the device from the injection site; [Figures 9A and 9B] are partial exploded views of the device in the configuration of Figure 9 without the outer shell, which are a front view and a top view respectively; [Figure 10] is a cross-sectional view of the device of Figure 1 in the plane of Figure 2 in the final locked configuration of the device, wherein the needle guard is returned to its fully extended position, corresponding to the final configuration of the device after use; [Figures 10A and 10B] are partial exploded views of the device in the configuration of Figure 10 without the outer casing, which are front and top views, respectively.

1: Injection device

3: Slim shell

3a: Front shell

3b: Rear shell

5:Medication container

6: Cylinder parts

10: flange

15: Sheath

17: Base part

20: Needle protector

21: Needle guard spring

22: Cap

25: Injection drive mechanism

31: Plunger rod

33: Retaining components

34: Injection spring

35: Trigger components

37: Trigger spring

41: Outer wall

43: Sleeve

45: Orifice

47: Spine

49: Rib thread section

50: Sheath part

52: Legs

54: protrusion

55: Free end

56: Horizontal edge

57: Section

58: Wings

61: Cylindrical wall

65: Grip sleeve

67: Clamping claws

68: Main ribs

69: Ridged surface

71: Cylindrical body

73: Radial closed wall

75: Radial latch

81: Solid body

83: Radial plate

85: Elastic arm

87: Gap

89: protrusion

101: Hollow body

102: Center axial hole

103: Circumferential edge

105: Pointed head

111: Support flange

113:Guide wall

131: Sleeve body

133: Closed wall

139: Radial ear piece

141: Slope

145: Second rib

X: axis

Claims (23)

An injection device comprises: an elongated housing (3) extending along a longitudinal axis (X) and constructed to accommodate a drug container (5), the drug container having a barrel (6) containing the drug (7), a needle (8) attached thereto, and a plunger (9) displaceable within the barrel to expel the drug through the needle; a needle guard (20) telescopically mounted in the housing (3) and axially movable between an extended position and a retracted position, wherein in the extended position the needle guard protrudes distally from the housing and surrounds the needle (8), and the retracted position is proximally spaced from the extended position, corresponding to the condition of pressing the device (1) against an injection site for activating the injection device; A needle guard spring (21) biases the needle guard (20) in the distal direction; An injection drive mechanism (25) for driving the plunger (9) in the barrel (6) and thereby expelling the drug, the injection drive mechanism comprising: A plunger rod (31) axially movable between a proximal position and a distal position in the housing (3) for driving the plunger (9) in the barrel (6); An injection spring (34) configured to bias the plunger rod (31) to its distal position; A retaining member (33) is fixed in the housing (3) and is used to hold the plunger rod (31) in its proximal position against the biasing action of the injection spring (34) in the initial state of the injection device. The retaining member (33) and the plunger rod (31) have corresponding latching features (85, 89, 103), and the latching features (85, 89, 103) include a stop surface (103) and a corresponding radially deflectable elastic arm (85) formed with a protrusion (89), whereby the plunger rod (31) is held in its proximal position by the engagement of the protrusion (89) with the stop surface (103); and A trigger member (35) comprising a blocking feature (135) which can be axially displaced from a blocking position to a release position when the needle guard (20) is moved from its extended position to its retracted position, wherein the blocking feature (135) prevents radial deflection of the elastic arm (85) and thereby prevents the protrusion (89) from disengaging from the corresponding stop surface (103), and in the release position, the elastic arm is free to deflect radially, thereby disengaging the protrusion (89) from the corresponding stop surface (103) under the biasing action of the injection spring (34); wherein retraction of the needle guard (20) causes the trigger member (35) to move proximally and thereby causes the release of the latching features (85, 89, 103) and thereby causes activation of the injection device (1), the injection device (1) further comprising a locking mechanism for preventing the needle guard (20) from retracting once the device has been activated and once the needle guard has been returned to its extended position by the needle guard spring (21), wherein the trigger member (35) is capable of rotating relative to the retaining member (33) depending on the axial displacement and position of the needle guard (20), and the locking mechanism comprises: A cam system (105, 150) disposed on the trigger member (35) and the retaining member (33) prevents the trigger member from rotating when the needle guard (20) is retracted and causes the needle guard (20) to rotate into a blocking angle position when the needle guard (20) returns to its extended position after activating the device; and a stop feature (145) disposed on the trigger member (35) such that the stop feature is outside the axial path of the needle guard (20) during the retraction period for activating the device and interferes with the needle guard (20) in the blocking angle position of the trigger member (35). An injection device as claimed in claim 1, wherein the needle guard (20) has a sheath portion (50) for surrounding the needle (8) in the extended position, the sheath portion (50) having a through hole (53) at the distal end for allowing the needle (8) to pass through when the needle guard (20) is retracted, and a leg (52) protruding axially and proximally from the sheath portion (50), the leg having a free end (55) for engaging and displacing the trigger member (35) when the needle guard (20) is retracted. An injection device as claimed in claim 1 or 2, wherein the cam system includes a cam track (150) disposed on the trigger member (35), and a tip (105) disposed on the retaining member (33) and defining a cam follower, the tip (105) being used to engage in the cam track. An injection device as claimed in claim 3, wherein the retaining member (33) has a substantially cylindrical hollow body (101), and the trigger member (35) has a sleeve body (131) mounted on the top of the cylindrical hollow body, so that the sleeve body (131) can slide or rotate relative to the cylindrical hollow body (101) depending on the axial displacement and position of the needle guard (20). An injection device as claimed in claim 4, wherein the sleeve body (131) is provided with a first rib (143) for engaging with the free end (55) of the leg (52) when the needle guard (20) is retracted, thereby causing the trigger member (35) to shift proximally. An injection device as claimed in claim 4, wherein the sleeve body (131) is provided with a cam track (150) on its inner surface for accommodating the tip (105), the tip (105) protruding radially and inwardly from the cylindrical hollow body (101), the cam track (150) having a transversely oriented terminal channel (155) connected to an axial channel (153) extending in the proximal direction, the axial channel having an open distal end (151). An injection device as claimed in claim 4, wherein the stopping feature comprises a second rib (145) radially protruding from the sleeve body (131), the second rib being used to selectively engage with the needle guard (20) to prevent the needle guard from retracting proximally. An injection device as claimed in claim 5, wherein the stop feature comprises a second rib (145) radially protruding from the sleeve body (131), the second rib being used to selectively engage with the needle guard (20) to prevent the needle guard from retracting proximally, and wherein the second rib (145) is spaced distally from the first rib (143). An injection device as claimed in claim 7, wherein the leg (52) has a recess (56) spaced distally from the free end (55) of the leg (52) and forming a transverse edge, the transverse edge defining a stop surface for preventing the needle guard (20) from retracting proximally in the final state of the injection device (1) after injection. An injection device as claimed in claim 3, wherein the tip (105) is biased toward the terminal channel (155), whereby when the needle guard (20) moves back to the extended position corresponding to the final state of the device after injection under the action of the needle guard spring (21), the trigger member (35) rotates and causes the second rib (145) to engage the lateral edge of the leg (52). An injection device as claimed in claim 10, wherein the trigger member (35) and the housing (3) include corresponding locking features (79, 139) in releasable engagement with each other for maintaining the trigger member (35) in its blocking position, and wherein the locking features are designed to be released when the needle guard (20) moves from its extended position to its retracted position, whereby the retraction of the needle guard (20) causes the release of the locking features (79, 139), the release of the latching features (85, 89, 103), and thus the activation of the injection device. An injection device as claimed in claim 11, wherein the leg (52) has an axial edge (57), the axial edge (57) having a section extending between the sheath portion (50) and the recess (56), which defines a guide element that slidably engages with a corresponding guide element (113) of the retaining member (33) during axial displacement of the needle guard (20). An injection device as claimed in claim 7, wherein the second rib (145) is arranged on the sleeve body (131) to engage the lateral edge of the leg (52) in the final state of the injection device (1) after injection, thereby preventing the needle guard (20) from retracting proximally. An injection device as claimed in claim 1 or 2, wherein the latching features (85, 89, 103) include a pair of elastic arms (85) formed on the proximal end of the plunger rod (31), and axially extending, respective protrusions (89) formed at the free end of each of the elastic arms. An injection device as claimed in claim 14, wherein the retaining member (33) comprises a radial wall having an axial hole (102), the axial hole having a circumferential edge (103) of the stop surface defining the latching features (85, 89, 103). An injection device as claimed in claim 15, wherein the protrusions (89) protrude radially and outwardly from the respective elastic arms (85), and the elastic arms protrude axially from the radial wall through the hole (102), so that when the plunger rod (31) is in its proximal position, the protrusions (89) and the stop surface (103) engage with each other. An injection device as claimed in claim 16, wherein the blocking feature includes an axial latch (135) which prevents the elastic arms (85) from deflecting inward in the blocking position of the trigger member (35) and thereby prevents the protrusions (89) from disengaging from the stop surface (103). An injection device as claimed in claim 1 or 2, wherein the housing (3) includes at least one recess (79), and the trigger member (35) includes a sleeve body (131) and at least one cantilevered flexible arm (137) protruding outward from the sleeve body, the cantilevered flexible arm (137) being provided at its free end with a radial ear piece (139) for releasably engaging with the recess (79) of the housing, and the locking features (79, 139) include the ear piece (139) and the corresponding recess (79). An injection device as claimed in claim 18, wherein the ear piece (139) is biased by the cantilevered flexible support arm to be engaged in the recess (79), and the cantilevered flexible support arm (137) can be deflected inwardly by the needle guard (20) to release the ear piece (139) from the recess (79). An injection device as claimed in claim 18, wherein the cantilevered flexible support arm (137) includes a ramp (141) for engaging with the needle guard (20), and when the needle guard (20) moves in the proximal direction, the profile of the ramp determines the inward deflection of the cantilevered flexible support arm (137) caused by the axial displacement of the needle guard (20). An injection device as claimed in claim 18, wherein the housing (3) and the trigger member (35) respectively have a pair of recesses (79) that are opposite in the radial direction and corresponding cantilevered flexible arms (137). The injection device of claim 1 or 2 further comprises a trigger spring (37) disposed between the housing (3) and the trigger member (35) for biasing the trigger member distally, whereby the trigger member (35) is biased to its blocking position in the initial state of the injection device. An injection device as claimed in claim 1 or 2, wherein the injection spring (34) is designed to impart a force to the plunger rod (31) in its proximal position to overcome the retaining force of the latching features (85, 89, 103) engaging each other, whereby release of the blocking feature (135) causes the latching features (85, 89, 103) to disengage and causes the injection spring (34) to drive the plunger rod (31) to its distal position.

Images