Injection device for injecting a composition contained in a medical container

An injection device for injecting a composition contained in a medical container comprising: a body configured to receive the medical container in a fixed position relative to the body, spring-loaded piston rod translationally movable inside the body along a spring axis, between a proximal rest position and a distal operative position wherein the spring-loaded piston rod engages a stopper of the medical container, and a selective blocking mechanism comprising a braking member selectively tiltable relative to the piston rod between a blocking position wherein the braking member impinges on the piston rod so as to prevent any translational movement of the spring-loaded piston rod in a distal direction by a bracing effect and a releasing position wherein the braking member disengages from the piston rod so as to allow the piston rod to move towards the distal operative position under the spring force.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the United States national phase of International Application No. PCT/EP2019/052393 filed Jan. 31, 2019 and claims priority to European Patent Application No. 18305109.3 filed Feb. 2, 2018, the disclosures of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD OF THE INVENTION

The invention relates to an assisted injection device for injecting a composition contained in a medical container. The injection device allows the user to control the injection by selectively allowing or stopping the injection, and makes the injection easier for a user who needs to provide less effort for injecting the composition, especially a composition with a high viscosity.

TECHNICAL BACKGROUND

Prefilled injection devices are common containers to deliver drugs or vaccines to patients and include syringes, cartridges and autoinjectors or the like. They usually comprise a sealing stopper in gliding engagement into a container, the container being filled with a pharmaceutical composition in order to provide the practitioners with a ready-to-use injection device for patients.

A container has a substantially cylindrical shape, and comprises a proximal end able to be stoppered by a sealing stopper, a distal end wherein the pharmaceutical composition is expelled from the container, and a lateral wall extending between the proximal end and the distal end of the container. In practice, the sealing stopper is aimed at moving, upon the pressure exerted by a piston rod, from a proximal end of the container towards the distal end of the container, thereby expelling the drug contained into the container.

When compared to empty injection devices that are filled with a vial-stored pharmaceutical composition just prior to the injection to the patient's body, the use of prefilled injection devices leads to several advantages. In particular, by limiting the preparation prior to the injection, the prefilled injection devices provide a reduction of medical dosing errors, a minimized risk of microbial contamination and an enhanced convenience of use for the practitioners. Furthermore, such prefilled containers may encourage and simplify self-administration by the patients which allows reducing the cost of therapy and increasing the patient adherence. Finally, prefilled injection devices reduce loss of valuable pharmaceutical composition that usually occurs when a pharmaceutical composition is transferred from a vial to a non-prefilled injection device. This results in a greater number of possible injections for a given manufacturing batch of pharmaceutical composition thus reducing buying and supply chain costs.

In certain cases, the injection of the pharmaceutical composition contained in the container with a manual injection device, such as a syringe, can be difficult to carry out, due to the force that needs to be applied onto the piston rod for expelling it. This occurs for example when the pharmaceutical composition has a high viscosity, and/or when the injection is carried out manually by a user that cannot push on the piston rod strongly enough with his fingers, for example when suffering from rheumatoid arthritis or from any type of disease affecting the user's hand or fingers. The injection may be a self-injection or may be performed by a user, such as a health care professional, to another person. In the case of healthcare professionals performing repetitive injections of viscous drugs to patients, the repetition of the same gesture requiring high force applied on the plunger rod to make the injection may cause repetitive strain injuries.

Autoinjectors can assist the user in performing an automatic injection of the pharmaceutical composition. They usually comprise an injection button the user needs to press in order to start the injection.

The injection carried out with an autoinjector is automatic, which means that once the user has pressed the injection button to move the piston, the injection starts and keeps going until the entirety of the pharmaceutical composition is injected.

A consequence is that once the user has triggered the injection by pushing the button, the injection cannot be stopped and restarted again. In particular, carrying out multiple injection sequences of fractions of the pharmaceutical composition while stopping the injection between two consecutive sequences is also not possible.

This lack of control of the injection can generate pain and anxiety to the user, and may lead the user to be unable to perform the injection correctly.

Moreover, similarly to manual injection devices, autoinjectors can encounter difficulties for injecting a pharmaceutical composition with a high viscosity, mainly due to an insufficient force applied to the piston by the injection mechanism. Hence, the pharmaceutical composition is not expelled from the container, or at most expelled at a very low speed.

BRIEF DESCRIPTION OF THE INVENTION

In view of the foregoing, an object of the invention is to provide an assisted injection device for injecting a pharmaceutical composition contained in a medical container that overcomes the drawbacks of the known devices.

The invention aims to provide an injection device which allows the user to control the injection, in particular to stop the injection then starting it again and to adjust the injection rate while performing the injection.

The invention aims also to provide such a device that allows for an easier injection of the pharmaceutical composition compared to the existing injection devices, in particular when the pharmaceutical composition has a high viscosity and/or when the user has a reduced physical strength.

One object of the invention is an injection device for injecting a composition contained in a medical container, comprising:a body configured to receive the medical container in a fixed position relative to the body,a spring-loaded piston rod translationally movable inside the body along a spring axis, between a proximal rest position and a distal operative position wherein the spring-loaded piston rod engages a stopper of the medical container, anda selective blocking mechanism comprising a braking member selectively tiltable relative to the piston rod between a blocking position wherein the braking member impinges on the piston rod so as to prevent any translational movement of the spring-loaded piston rod in a distal direction by a bracing effect and a releasing position wherein the braking member disengages from the piston rod so as to allow the piston rod to move towards the distal operative position under the spring force.

The blocking of the piston rod by the braking member being in a given tilted position relies on a bracing effect.

By “bracing effect” is meant in the present text a blocking of a first part in sliding engagement with a second part along an axis due to friction, even if a force is applied to the first part in the axial direction. In the present case, the first part is the piston rod and the second part is the braking member, which, when tilted in the blocking position, exerts a friction force onto the piston rod sufficient to generate said bracing effect.

The bracing effect results from a torque that urges the braking member in rotation relative to an axis that is preferably perpendicular to the spring axis. This causes the braking member to abut the plunger rod in at least two diametrically opposite points of the plunger rod.

In this application, the “distal direction” is to be understood as meaning the direction of injection, with respect to the medical container the device of the invention is to be mounted on. The distal direction corresponds to the travel direction of the piston rod during the injection, the pharmaceutical composition contained initially in the medical container being expelled from said medical container. The “proximal direction” is to be understood as meaning the opposite direction to said direction of injection.

In this application, the term “orthogonal” designates two axes—extending in a three-dimensional space—that are parallel to respective axes that intersect at a right angle. Said orthogonal axes may belong to a same plane and thus intersect (in this case they are perpendicular), or not.

In this application, a “selective blocking mechanism” refers to a mechanism that may be moved from the blocking position to the actuating position or conversely by the user, during the use of the injection device, to either proceed to the injection or stop the injection. Hence, by selectively actuating or blocking the selective blocking mechanism, the user can start or stop the injection of the composition contained in the medical container at any time of the injection.

According to other optional features of the device of the invention:

The selective blocking mechanism further comprises:a lever pivotably mounted on the body about a pivot axis orthogonal to the spring axis, comprising an actuation zone at a first distance from the pivot axis, anda connecting rod including a first end coupled to the lever by a pivot axis opposite the actuating zone relative to the pivot axis, at a second distance from the pivot axis, and a second end coupled to the braking member,the lever being pivotable between a rest position wherein the connecting rod constrains the braking member in the blocking position, and an actuating position wherein the connecting rod releases the braking member to the releasing position.

The selective blocking mechanism thereby provides a lever effect, which facilitates the injection of high viscosity compositions and/or reduce the force required for the user to carry out the injection. The user may inject the composition or stop the injection at any time by either pushing the lever or releasing the lever respectively.

The lever is coupled to the spring loaded piston rod such that the spring force urges the lever to the rest position. Hence, the spring force of the spring loaded piston rod is used for both moving and blocking the piston rod so as to respectively start and stop the injection.

The first distance is advantageously greater than the second distance, preferably at least twice greater than the first distance.

The selective blocking mechanism further comprises a spring member configured to exert a spring force on the braking member so as to constrain the braking member in the blocking position. Hence, the spring force of the spring loaded piston rod is used only to move the piston rod.

The spring member is connected to the body and to the connecting rod.

The spring member is connected to the body and to the braking member.

The braking member comprises an actuation zone configured for moving the braking member from the blocking position to the releasing position, the selective blocking mechanism further comprising a spring member that urges the braking member to the blocking position.

The spring member is arranged around the piston rod directly in contact with the braking member.

The braking member is preferably a plate provided with a through hole and the spring-loaded piston rod extends through said hole, the inner surface of the hole being configured to impinge on the piston rod when the plate is in the blocking position.

The through hole has a dimension greater than the piston rod, said dimension being configured such that when the braking member is tilted in the blocking position, at least a part of the circumference of the through hole contacts an outer wall of the piston rod.

In the releasing position, the plate is orthogonal to the spring axis.

The body comprises a container holder system configured to receive at least a portion of the medical container and to hold the medical container aligned with the movement direction of the spring-loaded piston rod so that when moving from the proximal rest position to the distal operative position, the spring-loaded piston rod engages the stopper of the medical container and pushes the stopper in the medical container to inject the composition.

The container holder system comprises:an opening provided in the distal wall of the body that leads to a housing adapted to receive at least a portion of the medical container in a position aligned with the movement direction of the spring-loaded piston rod,a slot provided in the outer wall of the body that leads to the housing, andan insert adapted to be inserted in the slot to contact the medical container and to maintain the medical container in a fixed position in the housing.

The container holder system comprises:a slot provided in the outer wall of the body that leads to a housing, configured to receive at least a portion of the medical container and to maintain the medical container in a fixed position aligned with the movement direction of the spring-loaded piston rod, anda through groove provided in the distal wall of the body, continuous with the slot and extending in the distal wall from the slot, the groove being configured to guide the medical container inserted via the slot to the housing.

The injection device is advantageously configured to be handheld.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention proposes an injection device for injecting a composition contained in a medical container.

Prior to the injection, the medical container is filled with the composition intended to be injected, and stoppered with a stopper inserted therein. The stoppered medical container is then mounted on the device, and the injection of the composition can be carried out.

A first embodiment of the injection device is represented inFIGS.1,2, and3A-B. According to this embodiment, the injection device1comprises a body2adapted to be held by a user's hand. To this end, the body2has preferably a cylindrical shape so as to make its handling easier, and is preferably made of a grip material that makes the user's hand adhere to the body. That way, the user can firmly handle the device throughout the injection of the composition.

The body2of the device further comprises a container holder system70configured to receive and to maintain the medical container60in a fixed position while performing the injection.

The medical container60comprises a body61including a proximal end62preferably provided with a flange, and a distal end having a tip63and a needle64extending from thereon. The needle64may be covered by a cap (not represented) to prevent any injury when handled before use.

According to a first embodiment illustrated onFIGS.1and2, the container holder system70includes an opening71provided at the distal end of the body2that leads to a housing72adapted to receive the proximal end62of the medical container60. The container holder system further includes a slot73provided in the outer wall of the body2in communication with the housing, and an insert74adapted to be inserted into the slot73until coming into contact with the proximal end62of the medical container for securing it in the housing72. The insert74is advantageously in the form of a fork with two branches so as to grip the body61of the container inserted in-between. The proximal end of the container then abuts the insert thereby avoiding the container to fall off the device.

In a practical way, the proximal end of the container60is inserted through the opening71and moved in a proximal direction until being positioned in the housing72and the insert74is then inserted radially in the slot73to secure the medical container60in a fixed position relative to the body2.

This embodiment is particularly useful when the container is a syringe or the like as the proximal end of the container is a flange adapted to abut the insert.

Alternatively, when the container is a cylinder or the like (with no proximal flange), the configuration of the container holder system of the first embodiment may be adapted accordingly. According to a preferred embodiment (not represented), the housing extends distally in a portion of the body of the device, and is configured to receive the entire body of medical container. Advantageously, in this situation, only the tip and a needle of the medical container project distally out of the body of the device. Of course, this preferred embodiment may also be appropriate when the medical container is a syringe or the like, the housing being adapted accordingly to accommodate the flange of the medical container.

In a practical way, the container is inserted in the housing through a lateral opening (not represented) provided in the peripheral surface of the body. To that end, the dimensions of the lateral opening correspond substantially to the dimensions of the body of the medical container. The insert is then inserted in the slot until being in contact with a shoulder extending between the distal end of the body and the tip of the medical container. Hence, the shoulder abuts the insert, which thereby maintains the container in a fixed position in the housing.

According to a second embodiment illustrated onFIG.2A, the container holder system70includes a slot75provided in the outer wall of the body2that leads to a housing76adapted to receive the proximal end62of the medical container60.

The container holder system70further includes a through groove77provided in the distal wall of the body, continuous with the slot75and extending in the distal wall from the slot75. In a practical way, the proximal end of the container is inserted through the slot75and moved in a radial direction along the groove77until being positioned in the housing76where the medical container60is maintained in a fixed position relative to the body2. The groove77separates two projecting parts78against which the proximal end of the medical container can abut, thereby preventing the container from falling off the groove.

To this end, the inner surface of the groove77contacts the body61of the container60. In particular, the groove77can be configured to prevent the container60inserted herein from moving radially, unless the container is moved by a user. The groove is preferably made of a rigid and smooth material, such as rigid plastic or metal (e.g. aluminum, stainless steel) for example, for making the insertion of the container therein easier, as well as contributing to maintain the container in a fixed position in the housing76during the injection.

This embodiment is particularly useful when the container is a syringe or the like as the proximal end of the container is a flange adapted to abut the projecting parts.

Alternatively, when the container is a cylinder or the like (with no proximal flange), the configuration of the container holder system of the second embodiment may be adapted accordingly.

The injection device1further comprises a spring-loaded piston rod3that extends inside the body2along a longitudinal axis (A), called spring axis. The spring4of the piston rod is arranged inside the body2, coaxially and in contact with the piston rod3. The medical container60maintained in the container holder system70is aligned with the axis (A). In that way, the spring-loaded piston rod3is translationally movable inside the body2of the device under the force of the spring4along the axis (A), between a proximal rest position and a distal operating position wherein the piston rod3engages the stopper65of the medical container60and pushes said stopper into the medical container.

The injection device1also comprises a selective blocking mechanism for selectively blocking or releasing the piston rod3based on a bracing effect.

According to the first embodiment of the device, the selective blocking mechanism comprises a lever30pivotably mounted on the body2, preferably on a proximal side of the body, about a pivot axis (B) orthogonal to the spring axis (A). The lever30is preferably mounted on an intermediate piece80of the body2of the device, which includes mechanical means for mounting the lever30thereon. The intermediate piece80may be adapted to be mounted on the body2, or may be made from a single piece with the body.

An actuation zone31is provided on the lever30, at a first (non-zero) distance from the pivot axis (B). The actuation zone31is integral with the lever30and constitutes a button intended to be pushed by the user in a distal direction, in order to move the lever30in a tilting motion about the pivot axis (B), from a first position called rest position to a second position called actuating position.

The selective blocking system further comprises a connecting rod40including a first end41pivotably coupled to the lever30according to a pivot axis (C) opposite the actuating zone31relative to the pivot axis (B), at a second distance from the pivot axis (B). The pivot axis (C) is orthogonal to the spring axis (A). The coupling of the lever30and the connecting rod40is preferably achieved by a stud (not represented) provided on one of the lever30or the connecting rod40and corresponding holes (not represented) provided on the other one adapted to receive the stud.

The selective blocking mechanism further comprises a braking member10.

According to a preferred embodiment, and as illustrated inFIGS.1and2, the braking member10is a plate that extends radially, that is, in a direction substantially orthogonal to the spring axis (A). The plate10is provided with a hole11configured to receive the piston rod3. This way, the piston rod3crosses the plate via the hole11, and an inner surface12of the hole faces the piston rod3.

The plate defines a first portion13pivotably coupled to the second end42of the connecting rod40, and a second portion14, opposite the first portion13relative to the spring axis (A) of the piston rod3, configured to be supported by a supporting surface6of the body2of the device.

The plate10is selectively tiltable relative to the piston rod3, by selectively moving the connecting rod40, between a blocking position and a releasing position. In the blocking position, the plate10is tilted relative to the piston rod3, and impinges on the piston rod3via a contact surface between the inner surface12of the hole11at the first and second portions13,14of the plate and the piston rod3. At the same time, the second portion14bears onto the supporting surface6. Hence, the plate10prevents the piston rod3from moving translationally in the distal direction along the axis (A) thanks to the bracing effect. In the releasing position, the plate10disengages from the piston rod3, so that there is no more contact between the plate10and the piston rod3. Hence, the piston rod3is allowed to move towards the distal operative position under the spring force.

By selectively pushing or releasing the actuation zone31of the lever30, the user can start or stop the injection of the pharmaceutical composition contained in the medical container.

As illustrated inFIG.3A, when the actuation zone31is released, the lever30is in the rest position. The spring4is in a compressed state and tends to move to a released state, thereby pressing onto the lever30via its proximal end5. The pressure applied by the spring4onto the lever30, constrains said lever in the rest position. The lever30presses onto the connecting rod40via their connection according to the axis (C), and the connecting rod40presses onto the first portion13of the plate10. The first portion13of the plate10offsets longitudinally relative to the second portion14, making the plate10itself offset relative to the piston rod3. This situation is illustrated inFIG.3Awith a plane P, containing the plate10, close to but not orthogonal to the spring axis (A).

In this situation, a torque defined by two forces of opposite direction, that may be represented by two opposite forces parallel to the spring axis (A) and applied onto the first portion13and the second portion14respectively of the plate10, urges the plate10in rotation relative to an axis that is perpendicular to the plane of the sheet ofFIG.3Aand to the spring axis (A). This causes the plate10to abut the plunger rod at two diametrically opposite points of the plunger rod, the contacting points D1and D2, by a bracing effect.

The plate10is thus constrained in the blocking position by the connecting rod40, wherein the inner surface12of the plate contacts and blocks the piston rod3by friction via the contacting points D1and D2.

As illustrated inFIG.3B, when the user pushes the actuation zone31in a distal direction, the lever30moves in a tilting motion about the pivot axis (B) and pulls the connecting rod40via their connection according to the axis (C) in a proximal direction. By moving to the proximal direction, the connecting rod40pulls the first portion13of the plate10in the proximal direction. The second portion14is pressed in a distal direction against the supporting surface6of the body2. This causes the plate10to move in a tilting motion relative to the piston rod3, thereby cancelling the offset between the first and second portion13,14of the plate10. This situation is illustrated inFIG.3Bwherein the plane P containing the plate10is orthogonal to the spring axis (A).

The plate10thus disengages from the piston rod3, moving from the blocking position to the releasing position. As there is no more contact between the plate10and the piston rod3, said piston rod is allowed to move translationally with the spring force of the spring4in a distal direction, to a distal operative position wherein the piston rod3engages the stopper64and pushes said stopper in the medical container60. The composition is thus expelled from the medical container. In this position, the spring4is at least partially released.

The braking member moves in a tilting motion about a tilting point that may be aligned with the spring axis (A), or remote from the spring axis (A), thereby describing a corresponding tilting angle. In the situation of the first embodiment, as well as the following second embodiment, the plate10is partially supported by the supporting surface6, such that the tilting point is located in the vicinity of the contact surface between the second portion14of the braking plate10and the supporting surface6.

The tilting angle mainly depends on the shape of the braking member, in particular the shape of the surface of the braking member configured to contact the piston rod, and the configuration of the braking member in the device.

As long as the user keeps pushing the actuation zone31, the plate40remains in the releasing position, disengaged from the piston rod3, the piston rod3keeps moving with the release of the spring4, and the injection continues.

During injection, when the user releases the actuation zone31, the lever30moves back in a tilting motion to its rest position thanks to the spring force of the spring4, the plate10moves back in the blocking position thereby re-impinges on the piston rod3, and the device1returns in the situation described previously, the piston rod3being in a more distal position than previously.

As such, the user can start or stop the injection simply by pressing the actuation zone31during a certain amount of time or by releasing it.

As described previously, when the user pushes the actuation zone31, the lever30moves from the rest position to the actuating position, and the piston rod3is moved by the spring force of the spring4. Therefore, the spring force is used for both moving and blocking the piston rod3so as to respectively start and stop the injection.

The bracing effect mainly depends on:the force applied onto the braking member for maintaining it in the blocking position. This force is applied in a direction parallel to the spring axis (A), towards the braking member, and the intensity of said force needs to be sufficient in order to achieve an effective blocking of the piston rod. According to the first embodiment, this force is applied by the connecting rod40onto the first portion13of the plate10, and corresponds to the elastic force of the spring4that is transmitted to the connecting rod40by the lever30;the position of the tilting point of the braking member relative to the spring axis (A). In order to achieve an effective blocking of the piston rod, the tilting point is positioned so that the force applied onto the braking member is as explained above. In particular, the greater the distance between the tilting point and the axis (A), the greater the force applied onto the braking member;the friction between the braking member and the piston rod. Such friction depends on structural features of the braking member and the piston rod, in particular their shape (that may be adjusted to maximize their contact surface) and their mechanical properties such as their constitutive material (that may be selected depending on their coefficient of friction) for example; andthe tilting angle of the braking member relative to the spring axis (A). Such tilting angle depends on the structural features of the braking member. According to the first embodiment, the tilting angle depends on the difference between the diameter of the hole11of the plate10and the diameter of the piston rod3.

Moreover, the selective blocking mechanism provides a lever effect. To illustrate this, the position XActof the actuation zone31, the position XBof the pivot axis (B), and the position XCof the pivot axis (C) are represented inFIG.3Aon an axis (X) extending along the lever30, and sensibly orthogonal to the spring axis (A). XActand XCare projections in a direction parallel to the axis (A) of the central point of the actuation zone31and the axis C respectively on the axis (X). XBis the intersecting point of the axis (B) with the axis (X).

The distance DXAct-XBbetween XActand XBis greater than the distance DXC-XBbetween XCand XB, along the axis (X). This induces a lever effect that allows the user to push the actuation zone31with a reduced force compared to the braking force.

The lever ratio LR is defined as follows:

It follows from this formula that the greater the distance DXAct-XBrelative to the distance DXC-XB, the lower the lever ratio, and the greater the lever effect.

The lever effect is also observed for the transmission of the elastic force of the spring4to the connecting rod40via the lever30. Indeed, in reference toFIG.3A, the spring4is connected to the lever30between XActand XB, whereas the connecting rod40is connected to the lever30between XBand XC. Therefore, the force applied by the connecting rod40onto the plate10is greater than the force applied by the spring4onto the lever30. Hence, the braking force is greater than the spring force.

This lever effect is particularly advantageous, since a spring with a high elastic force may be used to facilitate the injection of high viscosity compositions, while still ensuring the blocking of the piston rod and requiring a limited force to use the device.

The bracing effect and the lever effect presented above in reference to the first embodiment of the device also apply to the second embodiment presented below, notwithstanding the structural and functional differences between said embodiments.

According to a second embodiment, the selective blocking mechanism comprises a spring member50, configured to exert a spring force on the braking member10so as to constrain the braking member in the blocking position. In that manner, the spring4of the piston3allows for pushing the piston rod3from the proximal rest position to the distal operative position to carry out the injection of the composition, whereas the spring member50allows for pressing the braking member10so as to constrain said braking member10in the blocking position. In other terms, contrary to what was previously described in the first embodiment, the spring4of the piston3is no longer involved in the constraining of the braking member10in the blocking position, and the spring force is used only to move the piston rod3. However, the elastic force of the spring member50contributes to the above-described bracing effect.

Different configurations of the spring member50in the device are possible, among which a first, a second, a third and a fourth configuration are detailed in the following. In these configurations, the spring4of the piston rod3is not connected to the lever30but to other elements of the device. Hence, the spring4does not press the lever30, but pushes the piston rod3when the plate10is in the releasing position to carry out the injection.

According to a first configuration of the second embodiment, one end of the spring member50is connected to the body2of the device and the other end is connected to the connecting rod40. According to the embodiment illustrated inFIG.4A, the spring member50is connected to the intermediate piece80of the body, and to a flange43of the connecting rod40. According to the embodiment illustrated inFIG.4B, the spring member50is connected to a surface of an intermediate element9of the body2located between the proximal end and the distal end of the body, and to the flange43provided in the connecting rod40. An advantage of the embodiment ofFIG.4Bis that spring members of reduced length can be used. Moreover, the distance between the intermediate element9and the proximal and distal ends of the body2may be adapted so as to adjust the length of the spring member50in the compression state and the resulting spring force.

In this first configuration, the spring member50is preferably arranged around the connecting rod40, so as to simplify the structure and to achieve an optimum stability of the spring member50.

In this first configuration, the spring member50exerts a spring force onto the connecting rod40, which presses the first portion13of the plate in the distal direction, thereby constraining the plate10in the blocking position.

According to a second configuration of the second embodiment, one end of the spring member50is connected to the body2of the device and the other end is connected to the braking member10. According an embodiment (not represented), the spring member is connected to the intermediate piece80of the body, and to the first portion of the plate. According to the embodiment illustrated inFIG.4C, the spring member50is connected to the intermediate element9of the body located close to the distal end of the body, and to the first portion13of the plate10. An advantage of the embodiment ofFIG.4Cis that spring members of reduced length can be used. Moreover, the distance between the intermediate element9and the proximal and distal ends of the body2may be adapted so as to adjust the length of the spring member50in the compression state and the resulting spring force.

In this second configuration, the spring member50may be arranged around the connecting rod40or at a distance from the connecting rod, depending on the structural features of the connecting rod40and the braking member10, as well as the desired location of the connecting point of the spring member onto the braking member.

According to a third configuration of the second embodiment (not represented), one end of the spring member is connected to the lever, at a distance from the position XBof the pivot axis (B) along the axis (X), and the other end is connected to the body of the device, in particular to the proximal end of the body. In this configuration, the spring member exerts a spring force on the lever so as to constrain the lever in the rest position, thereby pressing the first portion of the plate in the distal direction, and constraining the plate in the blocking position. The force applied by the connecting rod onto the plate is greater than the force applied by the spring member onto the lever. Hence, the braking force is greater than the spring force of the spring member. When the user presses the actuation zone of the lever against the spring force of the spring member, the connecting rod pulls the plate in the proximal direction to the releasing position and the spring pushes the piston rod in the distal direction to carry out the injection.

According to a fourth configuration of the second embodiment, illustrated inFIGS.5and6, the spring member50is mounted on the braking member10, coaxially with the piston rod3. In this configuration, the braking member10is directly actuated by the user that pushes thereon to block or release the piston rod3.

In more details, the braking member10has the general shape of a plate that extends in a substantially radial direction relative to the piston rod. The plate10is provided with a hole11configured to receive the piston rod3. This way, the piston rod3crosses the plate via the hole11, and an inner surface12of the hole faces the piston rod3.

The plate10defines a first portion16which extends radially from the body2of the device, and a second portion17opposite the first portion16relative to the spring axis (A) of the piston rod3, configured to be supported by a supporting surface7of the body2of the device.

The spring member50includes one end mounted on the body2of the device, and another end mounted on the plate10. Preferably, the spring member50is mounted coaxially with the piston rod3, around said piston rod, the first end of the spring50being mounted on the plate10so as to surround the hole11of the plate. The spring member50is in a compressed state, and configured to urge the plate10to the blocking position.

As illustrated inFIG.5, one end of the spring member50may be mounted on a surface of an intermediate element8of the body2located between the proximal end and the distal end of the body. In that manner, springs of reduced length can be used. Moreover, the distance between the element8of the body and the first and second ends of the body2may be adapted so as to adjust the length of the spring50in the compression state and the resulting spring force.

The first portion16is provided with an actuation zone32at a first (non-zero) distance from the spring axis (A). The actuation zone32is integral with the first portion16of the plate and constitutes a button intended to be selectively pushed or released by the user in order to selectively move the plate10in a tilting motion relative to the spring axis (A), between a blocking position and a releasing position.

In the blocking position, the plate10is tilted relative to the piston rod3, and impinges on the piston rod3via a contact surface between the inner surface12of the hole11at the first and second portions16,17of the plate and the piston rod3. Hence, the plate10prevents the piston rod3from moving translationally in the distal direction along the axis (A) by the bracing effect. In the releasing position, the plate10disengages from the piston rod3, so that there is no more contact between the plate10and the piston rod3. Hence, the piston rod3is allowed to move towards the distal operative position under the spring force.

The plate10illustrated inFIG.5is arranged distally from the spring member50. As such, the user needs to push the actuation zone32in the proximal direction in order to move the plate10from the blocking position to the releasing position. However, other arrangements of the plate10and the spring member50are possible, without departing from the scope of the invention.

By selectively pushing or releasing the actuation zone32, the user can start or stop the injection of the pharmaceutical composition contained in the medical container.

As illustrated inFIG.7A, when the actuation zone32is released, the plate10is constrained in the blocking position by the spring force of the spring50. The first portion16of the plate10is longitudinally offset relative to the second portion17, making the plate10itself offset relative to the piston rod3. This situation is illustrated inFIG.7Awherein a plane P containing the plate10is close to but not orthogonal to the spring axis (A).

As illustrated inFIG.7B, when the user pushes the actuation zone32in a proximal direction, the first portion16of the plate10moves in a proximal direction, while the second portion17is pressed in a distal direction against the supporting surface7of the body2. This causes the plate10to move in a tilting motion relative to the piston rod3, thereby cancelling the offset between the first and second portion16,17of the plate10. This situation is illustrated inFIG.3Bwherein the plane P containing the plate10is orthogonal to the spring axis (A).

The plate10thus disengages from the piston rod3, moving from the blocking position to the releasing position. As there is no more contact between the plate10and the piston rod3, said piston rod is allowed to move translationally with the spring force of the spring4in a distal direction, to a distal operative position wherein the piston rod3engages the stopper64and pushes said stopper in the medical container60. The composition is thus expelled from the medical container. In this position, the spring4is at least partially released.

As long as the user keeps pushing the actuation zone32of the plate10, said plate10remains in the releasing position, disengaged from the piston rod3, the piston rod3keeps moving with the release of the spring4, and the injection continues.

During injection, when the user releases the actuation zone32, the plate10moves back in a tilting motion to the blocking position thanks to the spring force of the spring50, thereby re-impinges on the piston rod3, and the device1returns in the situation described previously, the piston rod3being in a more distal position than previously.

As such, the user can start or stop the injection simply by pressing the actuation zone32during a certain amount of time or by releasing it.