Universal plunger rod and method for connecting and disconnecting the plunger rod and the plunger stopper

Abstract

The present invention relates to a plunger rod (1) connected to a plunger stopper (100), and includes a rod (2) and a sleeve (9), the sleeve (9) having a movable part (16) movable from a first radial direction position to a second radial direction position under the influence of centrifugal force applied thereon. The rod (2) can translate and slide within the sleeve (9) from a first axial position to a second axial position under the influence of end pressure applied to its proximal end (3), and is provided with releasable locking means (7, 14) configured to temporarily lock the rod (2) in the second axial position. The present invention also relates to a method for attaching and detaching the plunger rod and the plunger stopper.

Description

Technical Field

[0001] The present invention relates to a plunger rod intended to be connected to a plunger stopper for discharging or reconstituting a product such as a drug present in a container of an injection device.

[0002] In the present application, the distal end of a component or device means the end furthest from the user's hand when the component or device is in the use position, and the proximal end means the end closest to the user's hand. Similarly, in the present application, the terms "distally" and "distal" mean the direction of injection, and the terms "proximally" and "proximal" mean the direction opposite to the direction of injection.

Background Art

[0003] Injecting instruments such as syringes are well known. Many different types of injection devices have been designed for administering pharmaceuticals. An injection device typically comprises a container for receiving the pharmaceutical or product to be injected and a plunger rod for moving a plunger stopper within the container. The plunger stopper may be moved distally to discharge the product during injection. Alternatively, the plunger stopper may be moved proximally to withdraw a product from, for example, another vial and transfer it into the container of the injection device. Empty and prefilled disposable syringes are commercially available and may be used directly in emergency situations because they are convenient, safe and efficient.

[0004] Prefilled syringes are filled with a drug such as a pharmaceutical and after being packaged for use are typically stored in a hospital or clinic until the need for use arises. For the purpose of ensuring that the formulation within the container does not leak externally during storage, the container is closed at its distal end by a rubber cap and at its proximal end by a plunger stopper.

[0005] In some cases, the plunger rod is connected to the plunger stopper of the prefilled injection device. However, in such a state, the prefilled syringe will take up a considerable amount of storage space. The required storage space is an important feature for prefilled injection devices. This is particularly important when the drugs contained in these devices have to be stored and transported at low temperatures.

[0006] In hospitals and pharmacies, the storage space for pharmaceuticals is limited. Therefore, it is desirable that the prefilled injection device occupies as little volume as possible during transportation and / or storage.

[0007] From such a perspective, prefilled injection devices are often provided without a plunger rod, and the proximal end portion of the injection device is sealed by the plunger stopper itself. In such cases, a separate plunger rod is provided, and the plunger stopper is provided with connecting means intended to cooperate with complementary connecting means arranged on the plunger rod, and when the time comes to proceed with the injection, the plunger stopper and the plunger rod are connected together. In the conventional method, these connecting means are cooperating screws or hooks, a cavity having an internal thread is provided at the proximal end portion of the plunger stopper, and an external thread capable of cooperating with the internal thread of the cavity of the plunger stopper is provided at the distal end portion of the plunger rod for the purpose of screwing the plunger rod into the plunger stopper.

[0008] Regardless, as the development of pharmaceuticals and injection device manufacturers worldwide progresses, the internal thread design and dimensions of the plunger stopper, as well as the material forming the plunger stopper, may vary, and in some cases, some plunger rods may not be compatible with the plunger stopper that seals the proximal end of the prefilled injection device. Incompatibility between the plunger rod and the plunger stopper may cause bending and / or breakage of the plunger rod during the step of screwing the plunger rod into the plunger stopper, and / or may affect the integrity of the container closure, and there is a possibility that the injection of the product may not be carried out in a safe manner. Also, if there is no compatibility between the plunger stopper and the plunger rod, it may not be possible to withdraw, and there is a possibility that reconstitution may not be carried out properly.

[0009] Therefore, regardless of the specific characteristics, design, and / or dimensions of the connecting means such as the internal thread or hook space of the cavity of the plunger stopper, and regardless of the material of the plunger stopper, a plunger rod that is compatible with any plunger stopper is required in a way that the user can be confident that the connection between the plunger rod and the plunger stopper is effective and reliable.

[0010] Furthermore, the plunger rod is usually made of plastic. The plunger rod is generally for single use and is discarded together with the prefilled syringe when the injection is completed. The plastic plunger rod has contributed to the global plastic waste generated in the medical device field.

[0011] Therefore, not only is it necessary to be able to achieve a safe connection with any plunger stopper of the injection device regardless of the design and / or material of the plunger stopper, but also a plunger rod that is removable from the plunger stopper and reusable with the plunger stopper of another prefilled injection device multiple times is further required. SUMMARY OF THE INVENTION

[0012] A first aspect of the present invention is a plunger rod intended to be connected to the proximal cavity of a plunger stopper of an injection device, the plunger rod comprising: - A rod having a proximal end portion and a distal end portion; - A sleeve configured to receive at least the distal end portion of the rod, the sleeve having at least one movable portion at its distal portion that is movable from a first radial position to a second radial position under the influence of a force applied to the movable portion; - The rod is configured such that the distal end portion of the rod is not in contact with the movable portion, the movable portion is in its first radial position, and the distal portion of the sleeve can freely enter and exit the proximal cavity of the plunger stopper from a first axial position. From this position, the distal end portion of the rod applies a force to the movable portion to move the movable portion to its second radial position, and the movable portion harpoons the inner wall of the proximal cavity of the plunger stopper to connect the plunger rod to the plunger stopper. The rod is configured to translate and slide within the sleeve from the first axial position to the second axial position where this is possible, and the rod is configured to translate from its first axial position to its second axial position under the influence of a terminal pressure applied to its proximal end portion. - Removable locking means configured to temporarily lock the rod in its second axial position; Comprising.

[0013] In an embodiment, the plunger rod may further comprise biasing means configured to automatically move the rod from its second axial position to its first axial position when the removable locking means is released.

[0014] The plunger rod of the present invention may be connected to the proximal cavity of the plunger stopper, and the design of the inner wall of the cavity does not matter. In particular, the inner wall of the proximal cavity may be provided with threads of any dimension or design, and the movable part of the plunger rod of the present invention abuts against the inner wall of the cavity when moving from its first radial position to its second radial position, and thus, the plunger rod is interference-fitted or attached to the plunger stopper by a hook, rather than being attached by screwing. The plunger rod of the present invention is thus not screwed into the plunger stopper, but is fixed to the plunger stopper by the movable part abutting against the inner wall of the cavity. In fact, the plunger stopper is usually made of an elastomeric material such as rubber, and the movable part can easily abut against a wall made of such a material.

[0015] The plunger rod of the present invention thus makes it possible to simplify the connection step between the plunger rod and the plunger stopper. In particular, thanks to the plunger rod of the present invention, the end user does not need to screw the plunger rod into the plunger stopper. As a result, the risk of the plunger rod bending and / or breaking during the connection step with the plunger stopper is significantly reduced. The plunger rod of the present invention further makes it possible to eliminate one processing step when the plunger rod is assembled with high-speed machines at the customer's site.

[0016] Furthermore, thanks to the plunger rod of the present invention, it is possible to use a single plunger rod in an injection device having a plunger stopper provided with connection means such as internal threads made of different materials and / or having different designs. The plunger rod of the present invention thus serves to rationalize not only the packaging, transportation and storage processes of prefilled injection devices, but also the use of such prefilled injection devices by end users in medical facilities such as hospitals.

[0017] Furthermore, the plunger rod of the present invention may be easily detached from the plunger stopper attached as described above. Thanks to the biasing means of the plunger rod of the present invention, the movable part may be easily removed from the inner wall of the cavity to which it is fixed. The movable part can be returned to its initial radial position, and the rod may be easily removed from the proximal cavity of the plunger stopper. Therefore, the end user does not need to perform the step of unscrewing for the purpose of detaching the plunger rod from the plunger stopper. Thanks to the plunger rod of the present invention, the detachment operation becomes very simple.

[0018] The plunger rod of the present invention thus further helps to reduce the global plastic waste generated in the medical field and is therefore environmentally friendly. In fact, thanks to the plunger rod of the present invention, it is possible to reuse the same plunger rod in a plurality of prefilled injection devices, thereby significantly saving the plunger rod and avoiding unnecessary plastic waste.

[0019] In an embodiment, a button cap is provided at the proximal end of the rod, a radial flange is provided at the proximal part of the sleeve, and the biasing means comprises a coil spring that abuts against both the proximal surface of the radial flange and the distal surface of the cap. The coil spring is movable from a rest position where the rod is in its first axial position to a stressed state where the rod is in its second axial position. Such an embodiment makes it possible to connect the plunger rod and the plunger stopper in a simple way, and the end user only needs to push the cap of the plunger rod to the end to achieve the connection.

[0020] In an embodiment, the rod is configured to rotate relative to the sleeve, and the releasable locking means comprises at least one hook extending distally from the cap and at least one partial circumferential groove located on the radial flange. The hook and the partial circumferential groove are - When an end pressure is applied to the cap so as to put the coil spring in its stress state, they engage with each other to lock the rod in its second axial position. Further, when the rod is rotated in a first direction with respect to the sleeve, they engage with each other, - When the rod is rotated with respect to the sleeve in a direction opposite to the first direction and the end pressure applied to the cap is released, they disengage from each other to release the rod from its second axial position and are configured to automatically move it to its first axial position.

[0021] Such an embodiment enables the plunger rod to be locked in a connection configuration with the plunger stopper in a simple manner. The end user can thus be confident that the connection between the plunger rod and the plunger stopper is efficient and reliable and that the injection step can be performed safely. Such an embodiment further enables the plunger rod to be unlocked from the plunger stopper in a very simple manner.

[0022] In an embodiment, an extension portion configured to apply a radial force to the movable part is provided at the end end of the rod when the rod moves from its second axial position back to its first axial position, so as to move the movable part from its second radial position to its first radial position. Such an extension portion may be disposed at the end from the movable part, and may be provided with an inclined surface that can cooperate with a complementary inclined surface disposed on the movable part for the purpose of moving the movable part in the centripetal direction when the extension portion is moved in the proximal direction as the rod moves from its second axial position back to its first axial position.

[0023] The end portion of the sleeve may be provided with more than one, for example, two, three, or four movable parts, which may be regularly distributed on the circumference of the sleeve. In an embodiment, two movable parts are provided at the end portion of the sleeve, which are diametrically opposed. Such an embodiment enables a reliable and stable connection between the plunger rod and the plunger stopper because the two movable parts are fixed to the inner wall of the proximal cavity of the plunger stopper.

[0024] In an embodiment, the plunger rod may further include a sheath sized to surround the sleeve except for the movable parts, and the sheath has an outer diameter substantially equal to the outer diameter of the end portion of the sleeve when the movable parts are in their first radial position. The sheath is preferably translationally fixed relative to the sleeve. In such an embodiment, the outer surface of the end portion of the sleeve is in the same plane as the outer surface of the sheath when the movable part(s) is / are in its / their first radial position, and thus the movable part(s) does not project radially outward from the sheath, and accordingly the sleeve is protected. Such an embodiment is particularly convenient and user-friendly because there is no need to take care not to touch the sleeve and / or damage the sleeve when handling the plunger rod.

[0025] In an embodiment where the plunger rod includes a sheath, a cap may be provided at the proximal end portion of the rod, a radial flange may be provided at the proximal portion of the sheath, and the biasing means may include a coil spring supported on the one hand on the proximal surface of the radial flange and on the other hand on the distal surface of the cap, and the coil spring is movable from a rest state in which the rod is in its first axial position to a stressed state in which the rod is in its second axial position.

[0026] In such an embodiment, the rod may be configured to rotate relative to the sheath, and the releasable locking means may comprise at least one hook extending from the cap towards the end and at least one partial circumferential groove located on the radial flange, and the hook and the partial circumferential groove are configured as follows: - When an end pressure is applied to the cap so as to put the coil spring in its stressed state and the rod is further rotated in a first direction relative to the sheath, they engage with each other so as to lock the rod in its second axial position, - When the rod is rotated relative to the sheath in a direction opposite to the first direction to release the end pressure applied to the cap, they disengage from each other to release the rod from its second axial position and automatically move it to its first axial position.

[0027] In an embodiment, the end portion of the sleeve comprises at least one radially outwardly flexible leg, and the end end of the radially outwardly flexible leg forms the movable part. Alternatively, the end portion of the sleeve may comprise two radially outwardly flexible legs facing each other in the radial direction, and the end end of each radially outwardly flexible leg may form a movable part. Alternatively, the end portion of the sleeve may comprise three radially outwardly flexible legs regularly arranged in the circumferential direction, and the end end of each radially outwardly flexible leg may form a movable part. In such an embodiment, the movable part may be, for example, in its first radial position when the flexible leg is in its stationary state and in its second radial position when the flexible leg moves radially outwards under the pressure applied by the end end of the rod. When the end end of the rod returns to its first axial position, the flexible leg naturally returns to its stationary state, thereby causing the movable part to automatically move from its second radial position to its first radial position. Such an embodiment is therefore very easy to manufacture and may be easily implemented industrially.

[0028] In an embodiment, the movable part comprises an outer radially projecting portion. Such an outer radially projecting portion is preferably configured to be fixed to the inner wall of the proximal cavity under the centrifugal force applied to the movable part by the distal end of the rod.

[0029] Another aspect of the invention is a method for connecting a plunger rod as described above to the proximal cavity of a plunger stopper of an injection device, the method comprising: - providing the rod with the plunger rod in its first axial position; - inserting a distal portion of the sleeve into the proximal cavity of the plunger stopper; - applying a terminal pressure to the proximal end of the rod to guide the rod to its second axial position; - actuating locking means to temporarily lock the rod in its second axial position. The method includes the steps above.

[0030] Another aspect of the invention is a method of disconnecting a plunger rod as described above connected to the proximal cavity of a plunger stopper according to the above connection method, the method comprising: - deactivating the locking means; - releasing all terminal pressure applied to the proximal end of the rod to place the rod in its first axial position; - removing the distal portion of the sleeve from the proximal cavity of the plunger stopper. The method includes the steps above.

[0031] The present invention and the advantages arising therefrom will become apparent from the following detailed description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032]

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DETAILED DESCRIPTION OF THE INVENTION

[0033] Shown with reference to Figure 1 is the plunger rod 1 of the present invention intended to be connected to the plunger stopper 100. The plunger stopper 100 is adapted to be inserted into the container 111 of the injection device 110 shown by the dotted line in Figure 1. The plunger stopper 100 is usually made of an elastomeric material such as rubber and is used to seal the proximal end of the container 111.

[0034] When the container 111 of the injection device stores the product to be injected, the plunger stopper 100 may be pushed at the end for the purpose of discharging the product from the injection device 110 through the injection needle 112. When the container 111 is empty, as shown in FIG. 1, the plunger stopper 100 may be moved in the proximal direction, causing the needle 112 to suck the product stored in another vial into the container 111.

[0035] The plunger rod 1 is intended to be connected to the plunger stopper 100 in a fixed state for the purpose of enabling the end user to move the plunger stopper 100 confidently in the distal direction and / or the proximal direction according to the purpose of use.

[0036] Referring to FIGS. 3 and 8, the plunger stopper 100 is provided with a proximal opening cavity 101. Although not shown in the figure, the inner wall 102 of this proximal cavity may be provided with an internal thread, similar to the case of a commercially available plunger stopper. In the illustrated example, the inner wall 102 of the proximal cavity 101 is provided with a proximal internal rib 103 that forms a contact surface 104.

[0037] Referring to FIGS. 1 to 10, the plunger rod 1 has a longitudinal axis A and includes a rod 2 aligned on the axis. The rod 2 has a proximal end portion 2a and a distal end portion 2b. In the illustrated example, the proximal end portion 2a of the rod is provided with a cap 3 formed by a transverse wall 4, from which a tubular wall 5 extends in the distal direction. As will be described later, the proximal end surface of the transverse wall 4 may form a pressing surface 4a for the end user to move the plunger rod 2 in the distal direction.

[0038] The tubular wall 5 is provided with an internal rim 6 that forms a proximal contact surface 6a at its distal end portion 5b. The distal end portion 5b of the tubular wall 5 is further provided with two (see FIG. 1) distal hooks 7 that are diametrically opposed, and their functions will be described later.

[0039] In the illustrated example, the end portion 2b of the rod 2 is provided with an end portion 8 having an outer diameter larger than the outer diameter of the remaining portion of the rod 2. In an embodiment not shown, the end portion 2b of the rod 2 can have the same outer diameter dimension as the remaining portion of the rod, as long as the outer diameter dimension of the end portion 2b of the rod 2 allows the outer protrusion 16 of the flexible leg portion 15 of the sleeve 9 (see FIG. 7) to move in the centrifugal direction.

[0040] The plunger rod 2 further includes a sleeve 9 having a proximal end portion 9a and a distal end portion 9b. The sleeve 9 has a shape and dimensions for receiving the distal region of the rod 2 and at least the distal end portion 2b of the rod 2. A radial flange 10 is provided at the proximal end portion 9a of the sleeve 9, and a tubular wall 11 extends from there in the proximal end direction. An outer rim 12 forming a distal abutment surface 12a is provided at the proximal end of the tubular wall 11.

[0041] The radial flange 10 is provided with two diametrically opposed through holes 13 (only one is visible in FIG. 10) dimensioned to allow the distal hook 7 to pass therethrough, and two adjacent partial circumferential grooves 14 forming a distal abutment surface 14a.

[0042] In the illustrated example, the distal end portion 9b of the sleeve 9 is provided with three flexible leg portions 15 that can bend radially outward under the influence of centrifugal force acting thereon. The flexible leg portions 15 are regularly distributed along the circumference of the sleeve 9. In an embodiment not shown, the number of flexible leg portions 15 can be less than three, for example one or two, or more than two, for example four. An outer protrusion 16 is provided at the distal end of each flexible leg portion 15. Each outer protrusion 16 thus forms a movable part that can move from a first radial position to a second radial position when centrifugal force is applied to the flexible leg portion 15.

[0043] A coil spring 17 is further provided between the radial flange 10 of the plunger rod 2 and the transverse wall 4 of the cap 3. The proximal end portion of the coil spring 17 is supported on the end surface of the transverse wall 4, and the distal end portion of the coil spring 17 is supported on the proximal end surface of the radial flange 10.

[0044] As will be apparent from the following description, the rod 2 is slidably received within the sleeve 9 and can translate under the influence of an end pressure applied by the end user to the pressing surface 4a from a first axial position as shown in FIGS. 1-5 to a second axial position spaced from the first axial position towards the end as shown in FIGS. 6-10.

[0045] The connection of the plunger rod 1 to the plunger stopper 100 will now be described with reference to FIGS. 1-10.

[0046] Referring to FIGS. 1-5, the plunger rod 1 is not connected to the plunger stopper 100 and the rod 2 is in its first axial position. In such a position, the coil spring 17 is in a static state, the distal end portion of the tubular wall 5 of the cap 3 does not contact the proximal end surface of the radial flange 10, and the coil spring 17 couples the rod 2 to the sleeve 9 by the distal abutment surface 12a of the outer rim 12 of the tubular wall 11 of the radial flange 10 resting on the proximal abutment surface 6a of the inner rim 6 of the tubular wall 5 of the cap 3 (see FIG. 4). In this position, the distal end portion 2b of the rod 2 does not contact the distal end portions of the flexible legs 15 and these flexible legs 15 are in a static state. As a result, the outer protrusion 16 is in a first radial position. As a result, the outer diameter dimension of the distal portion 9b of the sleeve 9 is smaller than the inner diameter dimension of the inner wall 102 of the proximal end opening cavity 101 of the plunger stopper 100. The distal portion 9b of the sleeve 9 can thus be easily inserted into the proximal end opening cavity 101 of the plunger stopper 100 as seen in FIGS. 2 and 3.

[0047] When the end portion 9b of the sleeve 9 is inserted into the proximal opening cavity 101 of the plunger stopper 100, an end user who wants to connect the plunger rod 1 to the plunger stopper 100 simply applies an end pressure to the pressing surface 4a of the transverse wall 4 of the cap 3 of the plunger rod 2. Under this end pressure, the end end of the tubular wall 5 of the cap 3 contacts the base end face of the radial flange 10, and the coil spring 17 transitions to its stressed state. The end movement of the rod 2 causes the rod 2 to move from its first axial position to its second axial position, as shown in FIGS. 6 - 10. The end portion 8 of the end end 2b of the rod 2 contacts the end ends of the flexible legs 15, applying a centrifugal force to the end ends of these flexible legs 15 and causing these flexible legs 15 to deflect radially outward. This causes the outer protrusions 16 to move from a first radial position to a second radial position, as shown in FIG. 8. In this second radial position, each outer protrusion 16 harpoons the inner wall 102 of the proximal opening cavity 101 of the plunger stopper 100, thereby achieving a secure connection between the plunger rod 2 and the plunger stopper 100. Thanks to the centrifugal force applied to the outer protrusions 16 by the end portion 8, the outer protrusions 16 are fixed to the inner wall 102 of the proximal opening cavity 101, independent of the design of the inner wall 102 and in particular independent of any internal threads that may be present in the inner wall 102. The efficiency of the connection may be enhanced by the presence of the abutting surface 104 of the internal rim 103 of the plunger stopper 100, which prevents the outer protrusions 16 from moving in the proximal direction.

[0048] When the end end of the tubular wall 5 of the cap 3 contacts the base end surface of the radial flange 10, each end hook 7 passes through the corresponding through hole 13. As a result, for the purpose of locking the rod 2 in its second axial position, the end user only needs to rotate the cap 3 in a first direction with respect to the sleeve 9 so that the end hook 7 contacts the abutting surface 14a of the partial circumferential groove 14, as shown in FIG. 10. The coil spring 17 in that stress state and the end hook 7 engaged with the abutting surface 14a of the partial circumferential groove 14 form a releasable locking means for the rod 2 in its second axial position. The end user can be confident that the connection between the plunger rod 1 and the plunger stopper 100 is efficient and reliable, and can safely operate the plunger rod 1 for the purpose of moving the plunger stopper 100 within the container 111 of the injection device 110.

[0049] When the end user wants to disconnect the plunger rod 1 from the plunger stopper 100, it is only necessary to rotate the cap 3 in the direction opposite to the first direction used previously with respect to the sleeve 9 so that the end hook 7 disengages from the partial circumferential groove 14. The end user then releases the end pressure applied to the pressing surface 4a of the cap 3, and the rod 2 automatically returns to its initial axial position, as shown in FIG. 2, under the effect of the coil spring 17 naturally transitioning to its rest state. During this operation, the end portion 8 of the end end 2b of the rod 2 is separated from the end end of the flexible leg 15 that has returned to the rest state. The external protrusion 16 has thus moved from the second radial position to the first radial position, as shown in FIG. 3, and the plunger rod 1 can be easily disconnected from the plunger stopper 100 by simply removing the end portion 9b of the sleeve 9 from the base end opening cavity 101 of the plunger stopper 100.

[0050] FIGS. 11 to 16 relate to a second embodiment of the plunger rod 1 of the present invention, in which the flexible leg and the external protrusion are replaced by a non-flexible movable part. The same elements as those of the plunger rod 1 in FIGS. 1 to 10 are designated by the same reference numerals.

[0051] Referring to these figures, at the end of the rod 2, an extension 18 is provided which shows a hollow conical surface 18a extending in the proximal direction. The end region of the rod 2 further comprises an outer conical portion 19 which is tapered in the distal direction and the said outer conical portion 19 is located proximally with respect to the extension 18. The sleeve 9 receives, at its end portion 9b, two diametrically opposed movable parts 20, and each movable part 20 comprises a proximal inclined surface 20a and a distal inclined surface 20b. Two diametrically opposed windows 21 are provided in the wall of the sleeve 9, and each window 21 faces the movable part 20. The movable parts 20 and the windows 21 of the sleeve 9 are axially arranged between the extension 18 and the outer conical portion 19 of the rod 2.

[0052] The rod 2 is in its first axial position in FIGS. 11 to 13 and in its second axial position in FIGS. 14 to 16.

[0053] Referring to FIGS. 11 to 13, the outer conical portion 19 of the rod 2 is not in contact with the movable part 20 and they are all located within the wall of the sleeve 9. The outer diameter dimension of the end portion 9b of the sleeve 9 is smaller than the inner diameter dimension of the proximal opening cavity 101 of the plunger stopper 100.

[0054] When the end user wants to connect the plunger rod 1 to the plunger stopper 100, he applies pressure to the transverse wall 4 of the cap 3 of the plunger rod 1 as described above. When the rod 2 moves to its second axial position, as shown in FIGS. 14 to 16, the outer conical portion 19 comes into contact with the proximal inclined surface 20a of the movable part 20, centrifugal force is applied to these surfaces, thereby moving the movable part 20 in the centrifugal direction. Accordingly, the movable part 20 moves from the first radial position as shown in FIGS. 12 and 13 to the second radial position as shown in FIGS. 15 and 16. The movable part 20 thus protrudes from the windows 21 in the wall of the sleeve 9 and they bite into the inner wall 102 of the proximal opening cavity 101 of the plunger stopper, thereby realizing the connection between the plunger rod 1 and the plunger stopper 100.

[0055] At this position, the end user may lock the rod 2 in its second axial position in the same manner as described above with reference to FIGS. 1-10.

[0056] If the end user wishes to disconnect the plunger rod 1 from the plunger stopper 100, he releases the coil spring 17 as described above with reference to FIGS. 1-10.

[0057] When the rod 2 moves proximally from its second axial position to its first axial position, the extension portion 18 also moves proximally, and its hollow conical surface 18a contacts the end inclined surface 20b of the movable part 20 (see FIG. 15). The hollow conical surface 18a slides on the end inclined surface 20b of the movable part 20, thereby applying a centripetal force to these surfaces and causing the movable part 20 to move rearward in the direction of their first radial position. As a result, the movable part 20 is drawn into the interior of the sleeve 9 as shown in FIG. 13. The end user may thus easily disconnect the plunger rod 1 from the plunger stopper 100 by removing the end portion 9b of the sleeve 9 from the proximal opening cavity 101 of the plunger stopper 100.

[0058] FIGS. 17-25 are similar to FIGS. 1-10 and relate to a third embodiment of the plunger rod 1 of the present invention with an outer sheath surrounding the sleeve. The same elements as the plunger rod 1 of FIGS. 1-10 are given the same reference numerals.

[0059] Referring to these figures, the plunger rod 1 includes the same rod 2 as in FIGS. 1-10 and includes a cap 3 and an end portion 8. The plunger rod 1 further includes a sleeve 9, and two flexible legs 15 diametrically opposed are provided at its end portion 9b. An external protrusion 16 is provided at the end end of each flexible leg 15. Contrary to the embodiment of FIGS. 1-10, the proximal end portion of the sleeve 9 does not have a radial flange and includes an external rim 9c.

[0060] The plunger rod 1 of FIGS. 17 to 25 further includes an outer sheath 22 that surrounds the sleeve 9 except for the external protrusion 16. A radial flange 23 is provided at the proximal end portion of the outer sheath 22, and the outer rim 9c of the sleeve 9 is fixed thereto. The sleeve 9 and the outer sheath 22 are fixed to each other. Referring to FIG. 19, the outer sheath 22 has an outer diameter that is substantially equal to the outer diameter of the end portion 9b of the sleeve 9 when the external protrusion 16 is in its first radial position.

[0061] The radial flange 23 is similar to the radial flange 10 of the embodiments of FIGS. 1 to 10, except that it is provided at the proximal end portion of the outer sheath 22 rather than at the proximal end portion of the sleeve 9. As a result, the radial flange 23 is provided with two diametrically opposed through holes 24 (only one is visible in FIG. 23) sized to allow the end hook 7 to pass therethrough, and two adjacent partial circumferential grooves 25 that form the end abutment surface 25a. The radial flange 23 is further provided with a tubular wall 26 that extends in the proximal direction. At the proximal end portion of the tubular wall 26, an outer rim 27 is provided that is intended to cooperate with the inner rim 6 of the cap 3 for the purpose of maintaining the coil spring 17 in its stationary state (see FIG. 18).

[0062] The method for connecting the plunger rod 1 of FIGS. 17 to 25 is the same as that described above for the embodiments of FIGS. 1 to 10. The plunger rod 1 of FIGS. 17 to 25 has the advantage that the sleeve 9 is protected by the outer sheath 22 during the connection and disconnection operations. In particular, as seen in FIG. 19, the outer surface of the external protrusion 16 is flush with the outer surface of the outer sheath 22. This is very convenient for end users who do not need to take care not to touch the sleeve or the external protrusion when operating the plunger rod 1.

[0063] Referring to FIGS. 17 to 20, the plunger rod 1 is not connected to the plunger stopper 100, and the rod 2 is in its first axial position. In such a position, the coil spring 17 is in a stationary state, the end end of the tubular wall 5 of the cap 3 does not contact the base end face of the radial flange 23, and the coil spring 17 is such that the outer rim 27 of the tubular wall 26 of the radial flange 23 rests on the inner rim 6 of the tubular wall 5 of the cap 3, thereby coupling the rod 2 to the outer sheath 22 (see FIG. 18). In this position, the end end 2b of the rod 2 does not contact the end end of the flexible leg 15, and these flexible legs 15 are in a stationary state. As a result, the outer protrusion 16 is in a first radial position, as shown in FIG. 19. The outer diameter dimensions of the end portion 9b of the sleeve 9 and the end portion of the outer sheath 22 are smaller than the inner diameter dimension of the inner wall 102 of the base end opening cavity 101 of the plunger stopper 100. Therefore, the end portion 9b of the sleeve 9 can be easily inserted into the base end opening cavity 101 of the plunger stopper 100, as seen in FIG. 17.

[0064] As described above, when the end user applies an end pressure to the cap 3, the coil spring 17 transitions to its stressed state, and the end portion 8 of the end end 2b of the rod 2 contacts the end end of the flexible leg 15, applying a centrifugal force to the end ends of these flexible legs 15 and causing these flexible legs 15 to deflect radially outward. The outer protrusions 16 move from the first radial position to the second radial position, as shown in FIG. 25, where they then protrude from the outer sheath 22. Thanks to the centrifugal force applied to the outer protrusions 16 by the end portion 8, the outer protrusions 16 are fixed to the inner wall 102 of the base end opening cavity 101 regardless of the design of the inner wall 102 and, in particular, independently of the internal threads that may be present on the inner wall 102. The efficiency of the connection may be enhanced by the presence of the abutting surface 104 of the inner rim 103 of the plunger stopper 100, which prevents the outer protrusions 16 from moving in the base end direction.

[0065] The locking of the rod 2 in this second axial position (shown in FIGS. 21 to 25) may be performed in the same manner as previously described for the embodiments of FIGS. 1 to 10. For this purpose, the end user only needs to rotate the cap 3 in the first direction with respect to the outer sheath 22 so that the end hook 7 contacts the abutment surface 25a of the partial circumferential groove 25, as shown in FIG. 25. The end user can be confident that the connection between the plunger rod 1 and the plunger stopper 100 is made efficiently and reliably, and that the plunger rod 1 can be safely operated for the purpose of moving the plunger stopper 100 within the container 111 of the injection device 110.

[0066] For the purpose of disconnecting the plunger rod 1 from the plunger stopper 100, the end user only needs to rotate the cap 3 in the opposite direction to the previously used first direction with respect to the outer sheath 22 so that the end hook 7 disengages from the partial circumferential groove 25. Then, the end user releases the end pressure applied to the pressing surface 4a of the cap 3, and the rod 2 automatically returns to its first axial position under the effect that the coil spring 17 naturally shifts to its stationary state, as shown in FIG. 17. During this step, as shown in FIG. 19, the flexible legs 15 return to their stationary state and the outer protrusions 16 return to their first radial position. Therefore, the end user can easily disconnect the plunger rod 1 from the plunger stopper 100 by removing the end portion of the outer sheath 22 from the proximal cavity 101 of the plunger stopper 100.

[0067] The plunger rod of the present invention thus makes it possible to simplify the step of connecting the plunger rod to the plunger stopper. Further, the plunger rod of the present invention may be safely connected to any plunger stopper regardless of the material of the plunger stopper and the design of the inner wall of the cavity of the plunger stopper. A single plunger rod may be used for a plurality of plunger stoppers and / or injection devices, thereby contributing to the reduction of plastic waste generated in the field of medical instruments.

Claims

1. A plunger rod (1) intended to be connected to a proximal cavity (101) of a plunger stopper (100) of an injection device (110), wherein the plunger rod (1) comprises: - a rod (2) having a proximal end portion (2a) and a distal end portion (2b); - a sleeve (9) configured to receive at least the distal end portion (2b) of the rod (2), wherein a movable portion (15, 16) movable from a first radial position to a second radial position under the influence of a force applied to at least one movable portion (15, 16) is provided at a distal portion (9b) of the sleeve (9); - the rod (2) is configured to translate and slide within the sleeve (9) from a first axial position in which the distal end portion (2b, 8; 19) of the rod (2) does not contact the movable portion (15, 16; 20) and the movable portion (15, 16; 20) is in its first radial position and the distal portion (9b) of the sleeve can freely enter and exit the proximal cavity (101) of the plunger stopper (100), to a second axial position in which the distal end portion (2b, 8; 19) of the rod (2) applies a force to the movable portion (15, 16; 20) to move the movable portion to its second radial position, and the movable portion (15, 16; 20) abuts against an inner wall (102) of the proximal cavity (101) of the plunger stopper (100) to connect the plunger rod (1) to the plunger stopper (100), and the rod (2) is configured to translate from its first axial position to its second axial position under the influence of a distal pressure applied to its proximal end portion (2a, 3, 4, 4a); - a releasable locking means (7, 14, 14a; 25, 25a) configured to temporarily lock the rod (2) in its second axial position.

2. The plunger rod (1) according to claim 1, further comprising a biasing means (17) configured to automatically move the rod (2) from its second axial position to its first axial position when the releasable locking means (7, 14, 14a; 25, 25a) is released.

3. A button cap (3) is provided at the proximal end portion (2a) of the rod, a radial flange (10) is provided at the proximal end portion (9a) of the sleeve (9), and the biasing means includes a coil spring (17) that abuts against both the proximal end surface of the radial flange (10) and the distal end surface of the cap (3). The plunger rod (1) according to claim 1 or 2, wherein the coil spring (17) can shift from a stationary position where the rod (2) is in its first axial position to a stressed state where the rod (2) is in its second axial position.

4. The rod (2) is configured to rotate relative to the sleeve (9), and the releasable locking means includes at least one hook (7) extending from the cap (3) towards the end and at least one partial circumferential groove (14) located on the radial flange (10). The hook (7) and the circumferential groove (14) are - When an end pressure is applied to the cap (3) to stress the coil spring (17) and the rod (2) is further rotated in a first direction relative to the sleeve (9), they engage with each other to lock the rod (2) in its second axial position, and - When the rod (2) is rotated in a direction opposite to the first direction relative to the sleeve (9) to release the end pressure applied to the cap (3), they disengage from each other to release the rod (2) from its second axial position and automatically move it to its first axial position. The plunger rod (1) according to claim 3, which is configured as such.

5. Two diametrically opposed movable parts (20) are provided at the end portion (9b) of the sleeve (9). The plunger rod (1) according to any one of claims 1 to 4.

6. An extension part (18) is provided at the distal end portion (2b) of the rod (2), which is configured to apply a radial force to the movable part (20) to move the movable part (20) from its second radial position to its first radial position when the rod (2) returns from its second axial position to its first axial position. The plunger rod (1) according to any one of claims 1 to 5.

7. The plunger rod (1) according to claim 1 or 2, further comprising a sheath (22) dimensioned to surround the sleeve (9) excluding the movable part (16), the sheath (22) having an outer diameter substantially equal to the outer diameter of the end part (9b) of the sleeve (9) when the movable part (16) is in its first radial position.

8. A cap (3) is provided at the proximal end portion (2a) of the rod (2), a radial flange (23) is provided at the proximal end portion of the sheath (22), and the biasing means comprises a coil spring (17) supported on one hand on the proximal end surface of the radial flange (23) and on the other hand on the end surface of the cap (3), the coil spring (17) being movable from a stationary state in which the rod (2) is in its first axial position to a stressed state in which the rod (2) is in its second axial position, the plunger rod (1) according to the claim.

9. The rod (2) is configured to rotate relative to the sheath (22), and the releasable locking means comprises at least one hook (7) extending distally from the cap (3) and at least one partial circumferential groove (25) located on the radial flange (23), the hook (7) and the partial circumferential groove (25) being - when an end pressure is applied to the cap (3) to stress the coil spring (17) and the rod (2) is further rotated in a first direction relative to the sheath (22), engage with each other to lock the rod (2) in its second axial position, - when the rod (2) is rotated relative to the sheath (22) in a direction opposite to the first direction and the end pressure applied to the cap (3) is released, disengage from each other to release the rod (2) from its second axial position and automatically move it to its first axial position The plunger rod (1) according to the claim, configured as such.

10. The end portion (9b) of the sleeve (9) comprises at least one radially outwardly flexible leg (15), and the end end (16) of the radially outwardly flexible leg (15) forms the movable part, the plunger rod (1) according to any one of claims 1 to 4 and 7 to 9.

11. The end portion of the sleeve (9) comprises two diametrically opposed outwardly radial flexible legs (15), and the end end (16) of each outwardly radial flexible leg (15) forms a movable part, the plunger rod (1) according to claim 10.

12. The end portion (9b) of the sleeve (9) comprises three outwardly radial flexible legs (15) regularly arranged in the circumferential direction, and the end end (16) of each outwardly radial flexible leg (15) forms a movable part, the plunger rod (1) according to claim 10.

13. The movable part comprises an external radial projection (16), the plunger rod (1) according to any one of claims 1 to 12.

14. A method for connecting the plunger rod (1) according to any one of claims 1 to 13 to the proximal cavity (101) of the plunger stopper (100) of an injection device, the method comprising: - providing the plunger rod (1) with the rod (2) in its first axial position; - inserting the end portion (9b) of the sleeve (9) inside the proximal cavity (101) of the plunger stopper (100); - applying an end-side pressure on the proximal end (2a, 3, 4, 4a) of the rod (2) to guide the rod (2) to its second axial position; - actuating the locking means (7, 14, 14a; 25, 25a) to temporarily lock the rod (2) in its second axial position; comprising a method.

15. A method for disconnecting the plunger rod (1) according to any one of claims 1 to 13 connected to the proximal cavity (101) of the plunger stopper (100) by the method according to claim 13, - deactivating the locking means (7, 14, 14a; 25, 25a); - releasing all end pressures applied to the proximal end (2a, 3, 4, 4a) of the rod (2) to place the rod (2) in its first axial position; - removing the end portion (9b) of the sleeve (9) from the proximal cavity (101) of the plunger stopper (100); comprising a method.

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