Gap creation device

Abstract

To improve an auto-injector.SOLUTION: There is provided a plunger assembly 100 for use with an auto-injector. The plunger assembly 100 comprises a cartridge 102, and a firing assembly 103 that includes a plunger rod 104 and a drive portion 105, the firing assembly 103 being axially moveable relative to the cartridge 102. The firing assembly 103 is configured to be coupled to the cartridge 102 at a coupling point along a length of the cartridge 102 to fix an axial position of the drive portion 105 relative to the cartridge 102 and wherein the length of the cartridge 102 is configured to be extended in a rearward direction such that the coupling point and a forward end 106 of the plunger rod 104 move rearwards.SELECTED DRAWING: Figure 1a

Description

[Technical Field]

[0001] The present invention relates to power injectors, and more particularly to plunger assemblies for use with power injectors and methods of assembling power injector subassemblies. [Background technology]

[0002] A power injector is a device for receiving a syringe and driving the syringe plunger into the syringe barrel, typically for delivery of medication without any force applied by the user. Typically, a power injector has a plunger driver, often including a spring, arranged to provide the force to drive the syringe plunger into the barrel. The plunger driver is usually activated by the operation of a release mechanism on the power injector, such as a button, or via pressure applied to the injection site via the power injector. A safety power injector may have a shroud that can be deployed into a position covering the needle of a syringe received within the power injector after use of the power injector. The power injector shroud can be deployed under force applied by a driver, which may be the plunger driver or a separate shroud driver.

[0003] A user can be provided with an auto-injector that contains a syringe pre-filled with a substance (such as a medication) so that the auto-injector is ready for use. The auto-injector can thus deliver to the user the substance already contained in the syringe within the auto-injector. The fill volume of the pre-filled syringe can vary depending on the dose of medication to be delivered to the user. Summary of the Invention

[0004] According to a first aspect of the present invention, there is provided a plunger assembly for use with an automatic injector, the plunger assembly comprising a cartridge and a firing assembly comprising a plunger rod and a driver, the firing assembly being axially movable relative to the cartridge, the firing assembly being configured to connect to the cartridge at connection points along the length of the cartridge to fix the axial position of the driver relative to the cartridge, the length of the cartridge being configured to extend rearwardly such that the connection points and a front end of the plunger rod move rearwardly.

[0005] Optionally, the firing assembly is telescopically received within the cartridge.

[0006] Optionally, the plunger assembly further includes a firing assembly locking mechanism configured to engage with the cartridge locking mechanism to couple the firing assembly to the cartridge.

[0007] Optionally, the firing assembly locking mechanism is configured to engage the cartridge locking mechanism under relative rotation between the firing assembly and the cartridge.

[0008] Optionally, the cartridge comprises a first portion and a second portion axially movable relative to the first portion to extend the length of the cartridge rearwardly.

[0009] Optionally, the first portion is forward of the second portion and the launch assembly is configured to couple to the second portion.

[0010] Optionally, one of the first and second cartridge portions includes an angled surface configured to interact with a cartridge follower on the other of the first and second cartridge portions and configured to ride on the angled surface, and extending the cartridge rearward includes rotating the second portion relative to the first portion such that a corresponding mechanism rides on the angled surface.

[0011] Optionally, the first portion further comprises a rotation lock configured to rotationally secure the first portion relative to the housing of the power injector.

[0012] Optionally, the plunger assembly further comprises an actuator axially coupled to the cartridge such that an axial force applied to the actuator inserts the cartridge into the automatic injector, the axial coupling being configured to be overcome upon continued application of the axial force when forward movement of the cartridge is prevented, and the actuator further comprises a cartridge coupler configured to couple the firing assembly to the cartridge upon continued application of the axial force.

[0013] Optionally, one of the actuator and cartridge includes an angled surface configured to interact with a locking follower of the other of the actuator and cartridge to at least partially convert the continuous application of axial force into a rotational force, the angled surface and the locking follower configured to provide an axial coupling.

[0014] Optionally, the actuator includes a sleeve configured to receive the cartridge therein.

[0015] Optionally, the further ramped surface is configured to interact with the locking follower or the further follower to rotate the second part of the cartridge relative to the first part of the cartridge.

[0016] According to a further aspect of the present invention there is provided an automatic injector sub-assembly comprising a plunger assembly according to any one of claims 1 to 13 and further comprising a housing configured to receive the plunger assembly.

[0017] Optionally, the power injector subassembly includes a rotational engagement mechanism configured to engage with the rotational lock.

[0018] Optionally, the power injector subassembly includes an axial end stop configured to receive the plunger assembly and prevent further forward movement of the plunger assembly.

[0019] Optionally, the housing is configured to receive a syringe and further configured to position the syringe so that at least a portion of the syringe forms an axial end stop.

[0020] In accordance with a further aspect of the present invention, there is provided an automatic injector subassembly comprising a plunger assembly and a housing, the plunger assembly comprising a cartridge insertable into the housing, a firing assembly comprising a plunger rod and a driver, the firing assembly being axially movable relative to the cartridge, the firing assembly being configured to couple to the cartridge at connection points along the length of the cartridge to fix the axial position of the driver relative to the cartridge, the cartridge being configured to couple to the housing at a point during its insertion, and at least a portion of the cartridge being configured to be movable rearwardly to cause rearward movement of the connection points and a front end of the plunger rod.

[0021] In accordance with a further aspect of the present invention, there is provided a method of assembling an automatic injector subassembly for use with an automatic injector, the method comprising the steps of at least partially inserting a plunger assembly into a syringe barrel, the plunger assembly comprising a cartridge and a firing assembly, the firing assembly comprising a plunger rod and a driver, the plunger assembly being axially movable relative to the cartridge so that a front end of the plunger rod is aligned with a bung located within the barrel; coupling the firing assembly to the cartridge at a coupling point along the length of the cartridge to fix the axial position of the driver relative to the cartridge; and moving the cartridge at least partially rearwardly so that the coupling point and the front end of the plunger rod move rearwardly.

[0022] Optionally, moving at least a portion of the cartridge rearward comprises extending a length of the cartridge rearward.

[0023] Optionally, the firing assembly further comprises a firing assembly locking mechanism, and coupling the firing assembly to the cartridge comprises engaging the firing assembly locking mechanism with a cartridge locking mechanism of the cartridge.

[0024] Optionally, engaging the firing assembly locking mechanism with the cartridge locking mechanism comprises rotating at least one of the firing assembly and the cartridge relative to the other of the firing assembly and the cartridge.

[0025] Optionally, the cartridge comprises a first portion and a second portion, and the step of extending the cartridge rearward comprises the step of axially moving one of the first portion and the second portion relative to the other of the first portion and the second portion.

[0026] Optionally, one of the first and second cartridge portions includes an angled surface configured to interact with a cartridge follower on the other of the first and second cartridge portions and configured to ride on the angled surface, and extending the cartridge rearward includes rotating the second portion relative to the first portion such that a corresponding mechanism rides on the angled surface.

[0027] Optionally, the method further comprises the step of rotationally fixing the first portion relative to the power injector housing.

[0028] Optionally, the plunger assembly further comprises an actuator axially coupled to the cartridge, and the method further comprises the steps of inserting the cartridge into the automatic injector by applying an axial force to the actuator, preventing further forward movement of the cartridge, and continuing to apply an axial force to the actuator while preventing further forward movement of the cartridge, such that the axial connection between the actuator and the cartridge is overcome and a cartridge coupler of the actuator couples the firing assembly to the cartridge.

[0029] Optionally, the axial coupling comprises an angled surface on the actuator or cartridge configured to interact with a locking follower on the other of the actuator and cartridge, thereby applying a continuous axial force to the actuator to at least partially convert the continued application of the axial force into a rotational force to couple the firing assembly to the cartridge.

[0030] Optionally, the further ramp surface is configured to interact with the locking follower or the further follower, and the step of moving at least a portion of the cartridge rearward comprises the step of causing the ramp surface to interact with the locking follower so as to rotate the second portion of the cartridge relative to the first portion of the cartridge.

[0031] According to a further aspect of the present invention, there is provided a plunger assembly for use with an automatic injector, the plunger assembly comprising a cartridge and a firing assembly comprising a plunger rod and a driver, the firing assembly being axially movable relative to the cartridge, the firing assembly being configured to couple to the cartridge at connection points along the length of the cartridge to fix the axial position of the driver relative to the cartridge so as to establish the axial length of the plunger assembly.

[0032] Optionally, the firing assembly is telescopically received within the cartridge.

[0033] Optionally, the plunger assembly further includes a firing assembly locking mechanism configured to engage with the cartridge locking mechanism to couple the firing assembly to the cartridge.

[0034] Optionally, the firing assembly locking mechanism is configured to engage the cartridge locking mechanism under relative rotation between the firing assembly and the cartridge.

[0035] Optionally, the plunger assembly further comprises an actuator axially coupled to the cartridge such that an axial force applied to the actuator inserts the cartridge into the automatic injector, the axial coupling being configured to be overcome upon continued application of the axial force when forward movement of the cartridge is prevented, and the actuator further comprises a cartridge coupler configured to couple the firing assembly to the cartridge upon continued application of the axial force.

[0036] Optionally, one of the actuator and cartridge is configured to interact with a locking follower of the other of the actuator and cartridge to at least partially convert the continuous application of an axial force into a rotational force, the angled surface and the locking follower being configured to provide an axial coupling.

[0037] Optionally, the actuator includes a sleeve configured to receive the cartridge therein.

[0038] In accordance with a further aspect of the present invention, there is provided a method of assembling an automatic injector subassembly for use with an automatic injector, the method comprising the steps of at least partially inserting a plunger assembly into a barrel of a syringe, the plunger assembly comprising a cartridge and a firing assembly, the firing assembly comprising a plunger rod and a driver, and being axially movable relative to the cartridge so that a front end of the plunger rod coincides with a bung located within the barrel; and coupling the firing assembly to the cartridge at coupling points along the length of the cartridge to fix the axial position of the driver relative to the cartridge so as to establish an axial length of the plunger assembly.

[0039] Optionally, the firing assembly further comprises a firing assembly locking mechanism, and coupling the firing assembly to the cartridge comprises engaging the firing assembly locking mechanism with a cartridge locking mechanism of the cartridge.

[0040] Optionally, engaging the firing assembly locking mechanism with the cartridge locking mechanism comprises rotating at least one of the firing assembly and the cartridge relative to the other of the firing assembly and the cartridge.

[0041] Optionally, the plunger assembly further comprises an actuator axially coupled to the cartridge, and the method further comprises the steps of inserting the cartridge into the automatic injector by applying an axial force to the actuator, preventing further forward movement of the cartridge, and continuing to apply a further forward axial force to the cartridge such that the axial coupling between the actuator and the cartridge is overcome and a cartridge coupler of the actuator couples the firing assembly to the cartridge.

[0042] Optionally, the axial coupling comprises an angled surface on the actuator or cartridge configured to interact with a locking follower on the other of the actuator and cartridge, thereby applying a continuous axial force to the actuator, thereby converting the continued application of the axial force at least in part into a rotational force to couple the firing assembly to the cartridge.

[0043] According to a further aspect of the present invention, there is provided an automatic injector sub-assembly comprising a plunger assembly as claimed in any one of claims 20 to 26, further comprising a housing configured to receive the plunger assembly.

[0044] Optionally, the power injector sub-assembly further comprises an axial end stop configured to prevent further forward movement of the plunger assembly.

[0045] Optionally, the housing is configured to receive a syringe and further configured to position the syringe so that at least a portion of the syringe forms an axial end stop.

[0046] Optionally, the housing is configured to receive a syringe having a barrel and a bung located within the barrel, and the coupling point is located so that the front end of the plunger rod contacts the bung.

[0047] According to a further aspect of the present invention there is provided an automatic injector comprising a plunger assembly as defined in any one of claims 1 to 12 and claims 20 to 26 and / or an automatic injector sub-assembly as defined in any one of claims 13 to 16 and claims 29 to 30. [Brief explanation of the drawings]

[0048] [Figure 1a] FIG. 1a shows an isometric view of a portion of an exemplary plunger assembly. [Figure 1b] FIG. 1b shows a side elevation view of a first portion of an exemplary plunger assembly and a portion of a second portion of a cartridge. [Figure 2] FIG. 2 shows an isometric view of an exemplary plunger assembly. [Figure 3a] FIG. 3a shows a partial cross-sectional view through an exemplary power injector subassembly. [Figure 3b] FIG. 3b shows a partial cross-sectional view through an exemplary power injector subassembly. [Figure 4a] FIG. 4a shows a partial side view of an exemplary plunger assembly in one of different stages of operation. [Figure 4b] FIG. 4b shows a partial side view of an exemplary plunger assembly at one of different stages of operation. [Figure 4c] FIG. 4c shows partial side views of an exemplary plunger assembly at different stages of operation. DETAILED DESCRIPTION OF THE INVENTION

[0049] Typically, a user will be provided with a ready-to-use power injector such that the front end of the plunger rod is held against the bung, which in turn is held against a substance, such as a medicament, contained within the barrel. In the assembled (or ready-to-use / pre-use) configuration, the plunger rod and bung may be held in a position such that rearward movement away from the medicament is not possible.

[0050] The inventors have found that such a configuration does not allow the material contained within the syringe barrel to expand forward of the bung. In certain cases, transporting such a pre-filled syringe in a low-pressure environment (such as at high altitudes) can result in leakage of the medication, because with the plunger rod and bung fixed in a predetermined position, there is no volume available for the medication to expand into other than the front end of the syringe.

[0051] Generally disclosed herein is an exemplary plunger assembly for use with an automatic injector. The exemplary plunger assembly may include a cartridge and a firing assembly including a plunger rod and a driver. In certain configurations, prior to assembly with the automatic injector, the firing assembly is axially movable relative to the cartridge until a relative position of the firing assembly to the cartridge is set during assembly with the automatic injector. After the relative position is set, the firing assembly can be considered coupled to the cartridge in that forward movement of the cartridge results in forward movement of the plunger rod. In exemplary configurations, coupling of the firing assembly to the cartridge fixes the axial position of the driver relative to the cartridge. In some exemplary configurations, a syringe can be retained in a housing of the automatic injector. The plunger assembly can be inserted into the housing, and the plunger rod is then inserted into the barrel of the syringe during assembly with the automatic injector. The forward end of the plunger rod can contact the bung, and the firing assembly is axially movable relative to the cartridge, so that the forward movement of the plunger rod is restrained by the bung, while the cartridge continues to move forward until it is properly seated or secured within the housing. At this point, the firing assembly and / or cartridge are configured to couple together, at least axially, at a coupling point, and the plunger rod is long enough to contact the bung. The cartridge is configured so that the coupling point can be moved rearward. As the coupling point moves rearward, the plunger rod moves rearward, thereby moving the forward end of the plunger rod away from the bung, creating a separation therebetween. In an exemplary configuration of the plunger assembly, the length of the cartridge can be increased. The length of the cartridge can be increased rearward so that the coupling point moves rearward.

[0052] When the exemplary plunger assembly is used with a power injector, a separation is defined between the bung and the front end of the plunger rod when the power injector is in an assembled state. The separation between the bung and the front end of the plunger rod accommodates expansion of the medication within the barrel of the pre-filled syringe, thereby preventing leakage.

[0053] Throughout this specification, the term "forward" refers to the end of the power injector from which medication is delivered. In other words, the front end of the power injector is the end that is proximal to the injection site during use. The terms "rear" or "rearward" refer to the plunger end of the power injector or a component thereof. In other words, the term "rearward" means further away or away from the injection site during use. Other relative terms, such as axial or longitudinal, are used to aid in the description of the device and should not be considered as limiting the scope of the claimed invention.

[0054] The term "cartridge" may encompass any sleeve, collar, or other component capable of receiving a firing assembly, for example, a sleeve, collar, or other component configured to telescopically receive the firing assembly such that the firing assembly is movable therein.

[0055] 1a illustrates an exemplary plunger assembly 100. Plunger assembly 100 includes a cartridge 102 and a firing assembly 103 including a plunger rod 104 and a driver 105. Firing assembly 103 is axially movable relative to cartridge 102. Plunger rod 104 is axially movable relative to cartridge 102.

[0056] Plunger rod 104 may be coupled to driver 105 such that axial movement of plunger rod 104 causes axial movement of driver 105, and vice versa. Movement of firing assembly 103 relative to cartridge 102 also includes movement of plunger rod 104 relative to cartridge 102.

[0057] In an exemplary configuration, the firing assembly 103 can further include a delivery driver disposed between the driver 105 and the plunger rod 104. The delivery driver can bias the plunger rod 104 forward relative to the driver 105. Under the bias of the delivery driver, the plunger rod 104 can be movable relative to the driver 105 on a delivery stroke upon decoupling of the plunger rod 104 and the driver 105.

[0058] In the illustrated example, firing assembly 103 is received within cartridge 102. A forward end 106 of plunger rod 104 extends from a forward end 108 of cartridge 102. Plunger rod 104 is telescopically received within cartridge 102 such that the extent to which forward end 106 of plunger rod 104 extends from forward end 108 of cartridge 102 can be varied.

[0059] Those skilled in the art will appreciate that alternative configurations may be utilized to allow relative axial movement between firing assembly 103 and cartridge 102. For example, in an alternative configuration, cartridge 102 and firing assembly 103 may be arranged to slide along one another. Additional configurations will be apparent to those skilled in the art.

[0060] Firing assembly 103 may include firing assembly locking mechanism 110 (best shown in FIG. 1b). Firing assembly locking mechanism 110 may be configured to engage cartridge locking mechanism 112 to couple plunger rod 104 to cartridge 102. Firing assembly locking mechanism 110 may be configured to engage cartridge locking mechanism 112 at a coupling point. In the exemplary plunger assembly 100, firing assembly 103 may be coupleable to cartridge 102 at multiple locations along the length of cartridge 102. The term "coupling point" encompasses one of multiple locations along the length of cartridge 102 at which firing assembly 103 couples to cartridge 102. The axial position of driver 105 and / or plunger rod 104 relative to cartridge 102 can be fixed when firing assembly 103 and cartridge 102 are coupled, for example, when firing assembly locking mechanism 110 engages cartridge locking mechanism 112.

[0061] In the exemplary plunger assembly 100, the driver 105 includes a firing assembly locking mechanism. In such a configuration, engagement of the firing assembly locking mechanism 110 with the cartridge locking mechanism 112 can fix the axial position of the driver 105 relative to the cartridge 102. As described above, in a configuration in which the plunger rod 104 is coupled to the driver 105, fixing the axial position of the driver 105 relative to the cartridge 102 fixes the axial position of the plunger rod 104 relative to the cartridge 102.

[0062] In the exemplary plunger assembly 100 of FIGS. 1a and 1b, the firing assembly locking mechanism 110 and the cartridge locking mechanism 112 include teeth. The teeth of the firing assembly locking mechanism 110 and the teeth of the cartridge locking mechanism 112 can be configured to interlock upon coupling of the firing assembly 103 and the cartridge 102. In the exemplary configuration shown in FIGS. 1a and 1b, the teeth of the firing assembly 103 and the teeth of the cartridge 102 can be angled rearward to ensure that the teeth can interlock regardless of the axial position of the firing assembly 103 relative to the cartridge 102 prior to coupling. That is, if the teeth of the firing assembly locking mechanism 110 and the teeth of the cartridge locking mechanism 112 are misaligned prior to engagement, the rearwardly angled teeth serve to guide the respective teeth into alignment.

[0063] Those skilled in the art will appreciate that alternative firing assembly locking mechanisms 110 and cartridge locking mechanisms 112 may be utilized, such as lug and recess configurations, clips, magnet configurations, and / or ratchet configurations. Additional configurations may be envisioned by those skilled in the art. Those skilled in the art will also appreciate that while the exemplary locking mechanisms 110 and 112 shown in FIGS. 1a and 1b provide discrete locations along the length of the cartridge 102 to which the firing assembly 103 may couple, continuous coupling configurations may be provided such that the firing assembly 103 may couple to the cartridge 102 at virtually any point along the length of the cartridge 102.

[0064] In the exemplary configurations of FIGS. 1a and 1b, cartridge 102 and firing assembly 103 include linear tracks of teeth that extend along at least a portion of the length of cartridge 102 and firing assembly 103, respectively. In the configurations of FIGS. 1a and 1b, the linear tracks of teeth extend along at least a portion of the length of drive section 105 of firing assembly 103. Those skilled in the art will appreciate that other tooth configurations are possible, provided that the teeth of firing assembly 103 can intermesh with the teeth of cartridge 102 at multiple points along the length of cartridge 102. The tooth pitch of the linear tracks of cartridge 102 and firing assembly 103 can be equal. In the exemplary plunger assembly 100, the length of the linear track of teeth of cartridge 102 can be greater than the length of the linear track of teeth of firing assembly 103.

[0065] Those skilled in the art will appreciate that the number of teeth and tooth pitch can be varied depending on the number of potential attachment points desired along the length of cartridge 102. Thus, by varying the number of teeth and / or tooth pitch, the number of potential attachment points can be varied.

[0066] Firing assembly 103 may include a protrusion 114. In the exemplary configuration shown in FIGS. 1a and 1b, driver 105 includes protrusion 114. Protrusion 114 may be configured to interact with cartridge 102 to prevent relative rotation between firing assembly 103 and cartridge 102 in a first direction. In the exemplary configuration of FIGS. 1a and 1b, protrusion 114 is received within track 116 of cartridge 102. An edge of track 116 may include stop surface 118. When protrusion 114 abuts stop surface 118 of cartridge 102, relative rotation between firing assembly 103 and cartridge 102 in the first direction may be prevented.

[0067] Track 116 of cartridge 102 may be an axial (or vertical) track disposed substantially parallel to the longitudinal axis of cartridge 102. Track 116 of cartridge 102 may act as a guide for axial movement of firing assembly 103 relative to cartridge 102. In the exemplary configuration of FIGS. 1a and 1b, protrusion 114 may be configured to ride along stop surface 118 of track 116 when firing assembly 103 is moved axially within cartridge 102.

[0068] 1a and 1b, the firing assembly locking mechanism 110 can be positioned such that relative rotation between the firing assembly and the cartridge 102 engages the firing assembly locking mechanism 110 and the cartridge locking mechanism 112. The relative rotation to engage the firing assembly locking mechanism 110 and the cartridge locking mechanism 112 can be in a second direction opposite the first direction.

[0069] Firing assembly 103 may further include coupling surface 120. In the exemplary configuration of Figures 1a and 1b, protrusion 114 includes coupling surface 120, although in alternative configurations, coupling surface 120 may be separate from protrusion 114. Coupling surface 120 may be configured to interact with cartridge 102 to rotationally couple firing assembly 103 to cartridge 102. In the example shown in Figures 1a and 1b, driver 105 includes coupling surface 120.

[0070] 1a and 1b, a linear track of teeth forming at least a portion of firing assembly locking mechanism 110 may extend from protrusion 114. The teeth of firing assembly 103 may extend from a mating surface 120 of protrusion 114 that faces a surface of protrusion 114 configured to interact with stop surface 118 of track 116. Relative rotation between firing assembly 103 and cartridge 102 in a second direction may cause corresponding teeth of firing assembly 103 and cartridge 102 to interlock.

[0071] Generally, at least a portion of cartridge 102 is movable rearward to move the connection point rearward after connection of firing assembly 103 and cartridge 102. In exemplary cartridges 102, the length of the cartridge may be increased or extended rearward.

[0072] The exemplary cartridge 102 of FIGS. 1a and 1b includes a first portion 122 and a second portion 124. At least one of the first portion 122 and the second portion 124 may be axially movable relative to the other of the first portion 122 and the second portion 124. Relative axial movement between the first portion 122 and the second portion 124 may cause rearward extension of the cartridge 102. In the exemplary configuration of FIGS. 1a and 1b, relative rotation between the first portion 122 and the second portion 124 may cause relative axial movement between the first portion 122 and the second portion 124.

[0073] At least one of the first portion 122 and the second portion 124 may include an angled surface 126 configured to interact with a cartridge follower 128 on the other of the first portion 122 and the second portion 124. In the exemplary configuration of FIGS. 1a and 1b, the first portion 122 is forward of the second portion 124 and includes the angled surface 126. The second portion 124 includes the cartridge follower 128. In alternative configurations, those skilled in the art will appreciate that the first portion 122 can include the cartridge follower 128 and the second portion 124 can include the angled surface 126. The cartridge follower 128 can be configured to ride over the angled surface 126 upon relative rotation between the first portion 122 and the second portion 124. Those skilled in the art will appreciate that the term "ride over" encompasses movement of a corresponding mechanism along the angled surface and is not intended to impose a positional restriction. 1a and 1b, the cartridge follower 128 comprises a protrusion. In alternative configurations, the cartridge follower 128 may comprise a peg or lug, a corresponding angled surface, or any other mechanism that can ride up onto the angled surface 126 upon relative rotation between the first portion 122 and the second portion 124. In alternative configurations, the angled surface 126 and the cartridge follower 128 may comprise corresponding threads.

[0074] The angled surface 126 is angled rearward. Thus, as the cartridge follower 128 rides up the angled surface 126, the second portion 124 is moved axially rearward relative to the first portion 122. The angled surface 126 converts a rotational force into an axial force upon relative rotation between the first portion 122 and the second portion 124. Those skilled in the art will appreciate that other methods of producing relative axial movement between the first portion 122 and the second portion 124 may be utilized in alternative configurations. For example, the biasing member may be configured to release when released from the first condition to bias the first and second portions away from each other. Those skilled in the art will appreciate other configurations. Additionally, those skilled in the art will appreciate that the cartridge 102 itself may be moved rearward after coupling the cartridge 102 to the plunger rod 104.

[0075] The cartridge 102 may include a rotation lock. The rotation lock may be configured to rotationally lock at least one of the first portion 122 and the second portion 124 relative to a housing of an automatic injector into which the exemplary plunger assembly 100 may be inserted. In the configuration shown in FIGS. 1a and 1b, the rotation lock is configured to rotationally lock the first portion (or front portion) 122 relative to the housing (described in more detail below). The rotation lock may include arms 130a, 130b. The arms 130a, 130b may extend radially outward from the first portion 122. The arms 130a, 130b may be configured to interact with corresponding features on the housing of the automatic injector to prevent relative rotation between the housing and the first portion 122. For example, the arms 130a, 130b may be configured to interact with a protrusion, such as a track, located on or coupled to the housing. One skilled in the art will appreciate that alternative rotation locks may be utilized. For example, the housing may include a keyed opening into which the first portion 122 is received. Those skilled in the art will be able to envision alternative possibilities. In a further alternative configuration, the rotation lock may be arranged to rotationally fix the second (rear) portion 124 relative to the housing instead of the first portion 122.

[0076] In the example plunger assembly 100, the second portion (or rear portion) 124 may include the cartridge locking feature 112, the track 116, and the stop surface 118. In the example plunger assembly 100, the firing assembly 103 may be configured to couple to the second portion 124, such that the coupling point is on the second portion 124.

[0077] The track 116 extends along substantially the entire length of the second portion 124. As mentioned above, in the exemplary configuration shown in FIGS. 1 a and 1 b, the cartridge locking mechanism 112 includes teeth. The teeth may be located on a radially inner surface of the second portion 124. In the exemplary configuration of FIGS. 1 a and 1 b, the teeth are disposed proximal to an edge of the track 116. The teeth may be disposed on an edge of the track 116 opposite the edge of the track 116 that includes the stop surface 118. The linear track of teeth of the cartridge locking mechanism 112 may extend along substantially the entire length of the second portion 124.

[0078] In alternative configurations, the power injector housing into which the plunger assembly 100 is inserted may include one or more of several features of the first portion 122. For example, the first portion 122 may be integral with the power injector housing and configured to interact with the second portion 124 upon insertion of the cartridge 102 into the housing. In other configurations, the housing may include alternative features configured to interact with the cartridge 102 to rearwardly move the coupling point after coupling of the firing assembly 103 and the cartridge 102. For example, one of the housing and the cartridge 102 may include a surface configured to interact with a corresponding feature on the other of the housing and the cartridge 102 at a point during insertion of the plunger assembly 100 to cause rearward movement of the cartridge 102 within the housing. This surface may be an angled surface (e.g., as described above), and the interaction may result in relative rotation between the cartridge 102 and the housing (and firing assembly 103, etc.) and rearward movement of the coupling point. In such a configuration, the cartridge 102 may comprise one of a first portion 122 and a second portion 124 .

[0079] The plunger assembly 100 may further include an actuator 136 (shown in FIG. 2), which may be axially movable relative to the cartridge 102 upon application of an axial force to the actuator 136.

[0080] Actuator 136 can be configured to cause relative rotation between first portion 122 and second portion 124 upon application of an axial force to actuator 136. The axial force can be a forward force. For example, the axial force can be applied during insertion of plunger assembly 100 into the housing of an autoinjector.

[0081] As described above, relative rotation between the first portion 122 and the second portion 124 may engage the firing assembly locking mechanism 110 and the cartridge locking mechanism 112. In an exemplary configuration, relative rotation between the first portion 122 and the second portion 124 may additionally or alternatively cause relative axial movement between the first portion 122 and the second portion 124.

[0082] In the exemplary configuration of FIG. 2 , the actuator 136 includes a cartridge coupler configured to couple the cartridge 102 to the firing assembly 103 upon application of an axial force to the actuator 136. The cartridge coupler may include a ramped surface 142 configured to interact with a lock follower (not visible in FIG. 2 ) located on the second portion 124 of the cartridge 102. Those skilled in the art will appreciate that in alternative configurations, the second portion 124 of the cartridge 102 may include the ramped surface and the actuator may include the lock follower. While in the exemplary configuration of FIG. 2 the lock follower includes a corresponding ramped surface, those skilled in the art will appreciate that in alternative configurations the lock follower may include a lug, protrusion, or peg, or any other component capable of riding up onto the ramped surface. The ramped surface 142 may extend rearward. The lock follower may be configured to be located at a forward-most position of the ramped surface 142 in the initial configuration of the plunger assembly 100.

[0083] 2, actuator 136 includes a sleeve 144. The actuator may further include an end cap 146. End cap 146 may be configured to abut a rear surface of the power injection device housing when plunger assembly 100 is fully inserted therein.

[0084] 2, the sleeve 144 extends from the end cap 146. The sleeve 144 can be configured to receive the cartridge 102. In the exemplary actuator 136, the sleeve 144 is configured to receive the second portion 124 of the cartridge 102. In such a configuration, the sleeve 144 can include the angled surface 142 (or, in a configuration in which the second portion 124 includes the angled surface 142, the sleeve 144 can include a locking follower).

[0085] Figures 3a and 3b show a power injector subassembly 300. The power injector subassembly 300 comprises the plunger assembly 100 of Figures 1a, 1b and 2 and a housing 350. The plunger assembly 100 may be configured for insertion into the housing 350.

[0086] The housing 350 may include a rotational engagement mechanism 352. The rotational engagement mechanism 352 may be configured to engage with a rotational lock of the cartridge 102. The rotational engagement mechanism 352 of the housing 350 may be configured to engage with a rotational lock of the first portion 122 of the cartridge 102 to prevent rotation of the first portion 122 relative to the housing 350.

[0087] 2, 3a, and 3b, the rotational engagement feature 352 comprises an inwardly extending protrusion. Those skilled in the art will appreciate that alternative rotational engagement features 352 may be used to prevent rotation of the first portion 122 relative to the housing 350. For example, in alternative configurations, the housing may include a keyed opening configured to receive the first portion, or a high-friction material disposed on the interior surface of the housing configured to engage a surface of the first portion to resist rotation thereof. Those skilled in the art will be able to envision additional configurations.

[0088] The protrusion may extend along at least a portion of the length of the housing 350 to form a track. In such a configuration, the rotational lock of the first portion 122 of the cartridge 102 may engage with the rotational engagement feature 352 upon insertion of the plunger assembly 100 into the housing 350. In an alternative configuration, the rotational engagement feature 352 may comprise a separate protrusion positioned to engage with the rotational lock of the cartridge 102 when the plunger assembly 100 is fully received within the housing 350.

[0089] 3a and 3b, the protrusion can be configured to interact with one of the arms 130a, 130b of the first portion 122 of the cartridge 102. In the exemplary configuration of FIGS. 3a and 3b, the rotational engagement mechanism 352 includes two inwardly extending protrusions. The two inwardly extending protrusions are opposed and can be configured to engage with corresponding arms 130a, 130b of the first portion 122. Rotation of the first portion 122 relative to the housing 350 can be prevented in a first direction by engagement of the first protrusion with the first arm 130a, and rotation of the first portion 122 opposite the first direction can be prevented by engagement of the second protrusion with the second arm 130b.

[0090] The power injector sub-assembly 300 may include an axial end stop 358. The axial end stop 358 may be configured to prevent forward movement of the plunger assembly 100 when the plunger assembly 100 is engaged with the axial end stop 358. The plunger assembly 100 may be configured to engage the axial end stop 358 during insertion of the plunger assembly 100 into the housing 350.

[0091] The housing 350 can be configured to receive a syringe 360. In the exemplary configuration shown in FIGS. 3a and 3b, a portion of the syringe 360 ​​forms an axial end stop 358. Those skilled in the art will appreciate that in alternative configurations, alternative axial end stops 358 can be utilized. For example, the axial end stop 358 can comprise an inwardly extending protrusion or lip located on the housing and configured to engage a corresponding feature of the plunger assembly 100 to prevent forward movement within the housing 350.

[0092] The front end of the cartridge 102 may be configured to abut the syringe 360 ​​during insertion of the plunger assembly 100 within the housing 350. In the exemplary configuration of Figures 3a and 3b, the first portion 122 may be configured to abut the syringe 360. In an alternative configuration, the first portion 122 may be configured to abut a component disposed between the syringe 360 ​​and the first portion 122. When the first portion 122 and the syringe 360 ​​abut, further forward movement of the plunger assembly 100 is prevented.

[0093] The operation of plunger assembly 100 will now be described with reference to Figures 2, 3a and 3b and 4a-4c.

[0094] FIG. 2 shows plunger assembly 100 in an initial position. In the initial position, firing assembly 103 and cartridge 102 are decoupled, and firing assembly 103 is axially movable relative to cartridge 102. In an exemplary configuration, in the initial position, actuator 136 and cartridge 102 may be axially coupled such that axial movement of one of actuator 136 and cartridge 102 causes axial movement of the other of actuator 136 and cartridge 102. An axial force may be applied to actuator 136 to insert cartridge 102 into the automatic injector. In the example shown in FIGS. 3a and 3b, a linear force is applied to actuator 136 to insert cartridge 102 into housing 350.

[0095] The plunger assembly 100 may be inserted into the barrel of the syringe 360. In the exemplary configuration shown in Figures 3a and 3b, inserting the plunger assembly 100 into the barrel of the syringe 360 ​​comprises inserting the plunger assembly 100 into the housing 350.

[0096] Insertion of plunger assembly 100 into housing 350 may engage a rotation lock on cartridge 102 with a rotation engagement feature 352 on housing 350. In the exemplary configuration shown in Figures 3a and 3b, insertion of plunger assembly 100 into housing 350 causes arms 130a, 130b on first portion 122 of cartridge 102 to engage with corresponding protrusions on housing 350. Engagement of arms 130a, 130b with corresponding protrusions prevents rotation of first portion 122 relative to housing 350.

[0097] Plunger assembly 100 can be moved forward within housing 350. In an exemplary configuration, plunger assembly 100 can be moved forward by applying an axial force to actuator 136. Because actuator 136 is axially coupled to cartridge 102, application of an axial force to actuator 136 moves cartridge 102 and firing assembly 103 forward within housing 350.

[0098] At some point during the forward movement of plunger assembly 100, front end 106 of plunger rod 104 may contact a bung located within the barrel of syringe 360. Those skilled in the art will appreciate that syringe 360 ​​may be a pre-filled syringe, and the point at which plunger rod 104 contacts the bung will depend on the fill volume of the pre-filled syringe.

[0099] Once plunger rod 104 contacts the bung, further forward movement of firing assembly 103 is prevented. Further forward force applied to plunger assembly 100 causes relative axial movement between plunger rod 104 and cartridge 102.

[0100] 3a and 3b, because the actuator 136 and cartridge are coupled, further forward movement of the actuator under axial force causes further forward movement of the cartridge 102. Thus, the cartridge 102 continues to move forward within the housing 350, while the firing assembly 103 remains in substantially the same axial position relative to the housing 350. As a longer length of the plunger rod 104 is received within the cartridge 102, the extent to which the forward end 106 of the plunger rod 104 extends past the forward end 108 of the cartridge 102 begins to decrease.

[0101] The cartridge 102 may be moved further forward until the plunger assembly 100 engages the axial end stop 358. Once the plunger assembly 100 engages the axial end stop 358, further forward movement of the cartridge 102 is prevented. In the exemplary configuration shown in FIGS. 3 a and 3 b, the syringe 360 ​​forms the axial end stop 358, and the plunger assembly 100 may be moved further forward until the cartridge 102 is engaged with the syringe 360. In the exemplary configuration, the plunger assembly 100 may be moved forward within the housing 350 until the cartridge 102 abuts the syringe 360, e.g., until the first portion 122 of the cartridge 102 abuts the syringe 360.

[0102] Continued application of an axial force to the actuator 136 when forward movement of the cartridge 102 is prevented may overcome the axial coupling between the cartridge 102 and the actuator 136. Further application of an axial force to the actuator 136 after the axial coupling has been overcome may couple the firing assembly 103 to the cartridge 102 at the cartridge coupler of the actuator 136. The axial coupling, or the mechanism providing the axial coupling, may include an angled surface 142 on the actuator 136 and a locking follower on the cartridge 102. In such a configuration, when the cartridge is free to move forward, application of an axial force to the actuator 136 may cause corresponding axial movement of the cartridge. In such a configuration, when the cartridge 102 is free to move forward, the locking follower may not move along the angled surface 142. However, when forward movement of the cartridge 102 is prevented, continued application of an axial force to the actuator can cause the lock follower to move along the angled surface 142 to at least partially convert the continued application of the axial force into a rotational force. That is, the axial coupling can be overcome upon continued application of an axial force to the actuator when forward movement of the cartridge is prevented.

[0103] Those skilled in the art will appreciate that the connection point at which firing assembly 103 connects to cartridge 102 may depend on the location of the bung within the syringe barrel. That is, the lower the fill volume of the syringe, the further forward the bung will be within the syringe barrel, and therefore the further forward the connection point will be.

[0104] In the exemplary configuration of Figures 3a and 3b, relative rotation between cartridge 102 and firing assembly 103 couples firing assembly 103 to cartridge 102. When firing assembly 103 is coupled to cartridge 102, the axial position of firing assembly 103 relative to cartridge 102 is fixed. In the example shown in Figures 3a and 3b, the axial position of driver 105 is fixed relative to cartridge 102. The axial position of firing assembly 103 (or specifically driver 105) relative to cartridge 102 can be fixed such that front end 106 of plunger rod 104 contacts the bung.

[0105] 3a and 3b, relative rotation between the cartridge 102 and the firing assembly 103 to couple the cartridge 102 to the firing assembly 103 is caused by interaction between the actuator's ramped surface 142 and the locking follower on the second portion 124 of the cartridge 102. Because the cartridge 102 cannot move further forward, additional axial force applied to the actuator 136 overcomes the axial coupling between the actuator 136 and the cartridge 102. Upon overcoming the axial coupling, the locking follower on the second portion 124 of the cartridge 102 rides up onto the actuator's ramped surface 142. This disengages the cartridge 102 from the actuator 136 and rotates the second portion 124 relative to the actuator 136. This, in turn, causes relative rotation between the second portion 124 and the firing assembly 103. The cartridge locking mechanism 112 is engaged with the firing assembly locking mechanism 110. In the configuration shown in Figures 3a and 3b, engaging the cartridge locking mechanism 112 and the firing assembly locking mechanism 110 comprises meshing corresponding teeth.

[0106] The rotation lock of the first portion 122 of the cartridge 102 engages the rotation engagement mechanism 352 so that the second portion 124 also rotates relative to the first portion 122 .

[0107] In an alternative configuration, relative rotation between the cartridge 102 and the firing assembly 103 can be caused by rotating the housing 350 relative to the cartridge 102. In such a configuration, the cartridge 102 can include a coupling mechanism configured to couple the cartridge 102 to the housing 350 when the cartridge 102 is inserted into the housing 350. In such a configuration, rotation of the housing 350 can cause the coupling mechanism on the cartridge to engage a corresponding coupling mechanism on the housing 350, such that rotation of the housing 350 causes rotation of the cartridge 102 relative to the firing assembly 103. Relative rotation between the firing assembly 103 and the cartridge 102 can engage the firing assembly locking mechanism 110 and the cartridge locking mechanism 112. One skilled in the art will appreciate that such a configuration may not include an actuator 136. In this manner, cartridge 102 and firing assembly 103 may be axially inserted into housing 350 and the housing may be rotated to couple firing assembly 103 to cartridge 102 and / or move the coupling point rearward.

[0108] 4a-4c show the relative positions of the first portion 122 and the second portion 124 at various points during the rotation of the second portion 124. FIG.

[0109] FIG. 4a shows the relative positions of first portion 122 and second portion 124 before cartridge 102 and firing assembly 103 are coupled (and, for example, before second portion 124 begins to rotate relative to firing assembly 103 and first portion 122).

[0110] Rotation of second portion 124 relative to firing assembly 103 to couple cartridge 102 and firing assembly 103 causes cartridge follower 128 of second portion 124 to rotate toward angled surface 126 of first portion 122. Figure 4b shows the relative positions of first portion 122 and second portion 124 at the point where firing assembly 103 and cartridge 102 couple to one another, i.e., the point where firing assembly locking mechanism 110 and cartridge locking mechanism 112 engage.

[0111] After the firing assembly is coupled to the cartridge 102, further rotation of the second portion 124 relative to the first portion 122 causes the cartridge follower 128 of the second portion 124 to ride up against the angled surface 126 of the first portion 122, which causes the second portion 124 to move rearward relative to the first portion 122. Because the connection point between the firing assembly and the cartridge is on the second portion 124, the rearward movement of the second portion 124 also causes the connection point and, therefore, the plunger rod 104 to move rearward relative to the bung, establishing a separation between the plunger rod 104 and the bung. FIG. 4c shows the relative positions of the first portion 122 and the second portion 124 when the cartridge follower 128 of the second portion 124 rides up against the angled surface 126 of the first portion 122 and the second portion 124 moves axially rearward relative to the first portion 122.

[0112] Those skilled in the art will appreciate that by utilizing the plunger assembly 100 described above, a consistent separation between the plunger rod 104 and the bung in the syringe 360 ​​can be established regardless of the fill volume of the syringe 360. This is because the plunger rod 104 is first brought into contact with the bung, then coupled to the cartridge, which is then moved axially rearward a predetermined distance. The plunger assembly 100 can be used with syringes of a variety of different fill volumes.

[0113] It should be noted that many of the features of the exemplary plunger assembly described above and shown in the drawings may be included in other exemplary devices. Different drawings are not necessarily considered separate embodiments, and features described in one drawing may be transferred to the device of another drawing. Those skilled in the art will be able to envision other plunger assemblies and their features without departing from the scope of the appended claims.

Claims

1. 1. A plunger assembly for use with a power injector, comprising: The plunger assembly includes: A cartridge and a firing assembly including a plunger rod and a driver, the firing assembly being axially movable relative to the cartridge, the firing assembly being configured to couple to the cartridge at connection points along the length of the cartridge and to fix the axial position of the driver relative to the cartridge; a firing assembly configured to extend the length of the cartridge rearward such that the connection point and the front end of the plunger rod move rearward.

2. The plunger assembly of claim 1 , wherein the firing assembly is telescopically received within the cartridge.

3. The plunger assembly of claim 1 or 2, further comprising a firing assembly locking mechanism configured to engage a cartridge locking mechanism to couple the firing assembly to the cartridge.

4. The plunger assembly of claim 3 , wherein the firing assembly locking mechanism is configured to engage the cartridge locking mechanism under relative rotation between the firing assembly and the cartridge.

5. A plunger assembly according to any preceding claim, wherein the cartridge comprises a first portion and a second portion axially movable relative to the first portion to extend the length of the cartridge rearward.

6. 6. The plunger assembly of claim 5, wherein the first portion is forward of the second portion, and the firing assembly is configured to couple to the second portion.

7. one of the first and second portions of the cartridge includes an angled surface configured to interact with a cartridge follower on the other of the first and second portions of the cartridge and configured to ride on an angled surface; 7. The plunger assembly of claim 5 or 6, wherein extending the cartridge rearward comprises rotating the second portion relative to the first portion such that a corresponding feature rides up against the angled surface.

8. 8. The plunger assembly of claim 7, wherein the first portion further comprises a rotation lock configured to rotationally secure the first portion relative to a housing of the power injector.

9. the plunger assembly further comprising an actuator axially coupled to the cartridge such that an axial force applied to the actuator inserts the cartridge into the power injector; the axial coupling is configured to be overcome upon continued application of the axial force when forward movement of the cartridge is prevented; 9. The plunger assembly of claim 1, wherein the actuator further comprises a cartridge coupler configured to couple the firing assembly to the cartridge when the axial force is continued.

10. one of the actuator and cartridge comprising an angled surface configured to interact with a locking follower of the other of the actuator and cartridge and at least partially converting the continuous application of the axial force into a rotational force; The plunger assembly of claim 9 , wherein the angled surface and the lock follower are configured to provide the axial connection.

11. 11. A plunger assembly according to claim 9 or 10, wherein the actuator comprises a sleeve configured to receive the cartridge therein.

12. A plunger assembly as described in any one of claims 9 to 11 when directly or indirectly dependent on claim 7, wherein a further ramp surface is configured to interact with the locking follower or a further follower to rotate the second part of the cartridge relative to the first part of the cartridge.

13. 13. An automatic injector subassembly comprising the plunger assembly of any one of claims 1 to 12, said automatic injector subassembly further comprising a housing configured to receive said plunger assembly.

14. 14. The power injector subassembly of claim 13, comprising the plunger assembly of claim 8, comprising a rotational engagement mechanism configured to engage with the rotational lock.

15. 15. The power injector subassembly of claim 13 or 14, comprising an axial end stop configured to receive the plunger assembly and prevent further forward movement of the plunger assembly.

16. 16. The automatic injector subassembly of claim 15, wherein the housing is configured to receive a syringe and further configured to position the syringe so that at least a portion of the syringe forms the axial end stop.

17. An automatic injector subassembly comprising a plunger assembly and a housing, The plunger assembly includes: a cartridge insertable into the housing; and a firing assembly comprising a plunger rod and a driver, the firing assembly being axially movable relative to the cartridge, the firing assembly being configured to couple to the cartridge at connection points along the length of the cartridge to fix the axial position of the driver relative to the cartridge, the cartridge being configured to couple to the housing at a point during insertion into the housing, and at least a portion of the cartridge being configured to be movable rearwardly to cause rearward movement of the connection points and a front end of the plunger rod.

18. 1. A method of assembling a power injector subassembly for use with a power injector, comprising: The method comprises: inserting a plunger assembly at least partially into a barrel of a syringe, the plunger assembly including a cartridge and a firing assembly, the firing assembly including a plunger rod and a driver, the firing assembly being axially movable relative to the cartridge such that a front end of the plunger rod is aligned with a bung located within the barrel; connecting the firing assembly to the cartridge at connection points along the length of the cartridge to fix the axial position of the drive relative to the cartridge; and moving at least a portion of the cartridge rearward such that the connection point and the front end of the plunger rod move rearward.

19. 20. The method of claim 18, wherein moving at least a portion of the cartridge rearward comprises extending a length of the cartridge rearward.

20. 1. A plunger assembly for use with a power injector, comprising: The plunger assembly includes: A cartridge and A firing assembly comprising a plunger rod and a driver, the firing assembly being axially movable relative to the cartridge, the firing assembly being configured to couple to the cartridge at connection points along the length of the cartridge to fix the axial position of the driver relative to the cartridge so as to establish the axial length of the plunger assembly.

21. 21. The plunger assembly of claim 20, wherein the firing assembly is telescopically received within the cartridge.

22. 22. The plunger assembly of claim 20 or 21, wherein the plunger assembly further comprises a firing assembly locking mechanism configured to engage a cartridge locking mechanism to couple the firing assembly to the cartridge.

23. 23. The plunger assembly of claim 22, wherein the firing assembly locking mechanism is configured to engage the cartridge locking mechanism under relative rotation between the firing assembly and the cartridge.

24. the plunger assembly further comprising an actuator axially coupled to the cartridge such that an axial force applied to the actuator inserts the cartridge into the power injector; the axial coupling is configured to be overcome upon continued application of the axial force when forward movement of the cartridge is prevented; 24. The plunger assembly of any one of claims 20 to 23, wherein the actuator further comprises a cartridge coupler configured to couple the firing assembly to the cartridge upon continued application of the axial force.

25. 25. The plunger assembly of claim 24, wherein one of the actuator and cartridge comprises an angled surface configured to interact with a locking follower of the other of the actuator and cartridge and to convert the continuous application of the axial force at least partially into a rotational force, the angled surface and the locking follower configured to provide the axial coupling.

26. 26. A plunger assembly according to claim 24 or 25, wherein the actuator comprises a sleeve configured to receive the cartridge therein.

27. 27. An automatic injector subassembly comprising a plunger assembly according to any one of claims 20 to 26, said automatic injector subassembly further comprising a housing configured to receive said plunger assembly.

28. 28. The power injector subassembly of claim 27, wherein the power injector subassembly comprises an axial end stop configured to prevent further forward movement of the plunger assembly.

29. 29. The automatic injector subassembly of claim 28, wherein the housing is configured to receive a syringe and further configured to position the syringe so that at least a portion of the syringe forms the axial end stop.

30. 30. The automatic injector subassembly of any one of claims 27 to 29, wherein the housing is configured to receive a syringe having a barrel and a bung located therein, and the connection point is located so that a front end of the plunger rod contacts the bung.

31. An automatic injector comprising a plunger assembly according to any one of claims 1 to 12 and claims 20 to 26, and / or an automatic injector sub-assembly according to any one of claims 13 to 17 and claims 29 to 30.

Images