WO2006111860A1

WO2006111860A1 - Injection set and injection assistance device

Info

Publication number: WO2006111860A1
Application number: PCT/IB2006/001351
Authority: WO
Inventors: Jean-Pierre Grimard; Frédéric PEROT
Original assignee: Becton Dickinson France
Priority date: 2005-04-20
Filing date: 2006-04-18
Publication date: 2006-10-26
Also published as: WO2006111861A2; FR2884722A1; WO2006111861A3; WO2006111859A1

Abstract

The present invention relates to an injection assistance device (1) for an injection device (3) comprising one body (2) one needle (7) and one piston plunger (26) characterized in that the it comprises at least: a hollow sleeve (4) receiving the body (2) and being arranged in such a way as to allow its axial mobility between an initial position and an insertion position, a sleeve tube (6) able to move with respect to the said sleeve (4) and comprising at least one region for holding (8) intended to be grasped by the user's hand in order to urge the said sleeve tube (6) axially towards an injection site (27), retaining means (16, 17, 12, 14) to keep the sleeve tube (6) in the initial position, and to release the sleeve tube (6) when the axial force exerted on it reaches a predetermined value, said retaining means comprise one peg (16) housed in a cam (17), being able to move with respect to the other and urged by at least a first elastically deformable element (15) . The invention also relates to an injection set comprising this assistance device (1) and an injection device (3) .

Description

Injection set and injection assistance device

The present invention relates to an injection assistance device for an injection device and to an injection set provided with the said injection assistance device, these devices making it easier and safer to inject a product into an injection site.

In this application, the distal end of a component or of a device is to be understood as meaning the end furthest from the user's hand and the proximal end is to be understood as meaning the end closest to the user's hand. Likewise, in this application, the "distal direction" is to be understood as meaning the direction of injection, and the "proximal direction" is to be understood as meaning the opposite direction to the direction of injection.

In order to administer a medicinal product by injection to a body, particularly the human body, there are various possible routes depending on the place in the body at which the said product is to be injected: thus, the product may be injected intravenously, intramuscularly, subcutaneously, into a joint, or else intradermally . In many of these cases, and, particularly when injecting subcutaneously, the depth to which the needle is inserted and therefore at which the product is injected is particularly significant.

Thus, it is possible to observe an adverse immunological reaction if, for example, a product that should have been injected into the subcutaneous tissues is finally injected into the intradermal tissues.

The operation of injecting a product using a syringe is particularly delicate. The patient may make an unforeseen movement or alternatively the person administering the injection might make a wrong move. Thus, errors in the depth to which the needle is inserted are particularly difficult to avoid and discrepancies of just a few millimetres may, themselves alone, lead to errors in injection depth.

As far as subcutaneous injection is concerned, there are various injection techniques currently used. Some users prefer to pinch the skin before inserting the needle, others prefer not to, and still others angle the syringe before inserting it into the skin, it being possible for this angle to vary from one user to another. The result of all this is that the depth to which the needle is inserted and therefore at which the product is injected may itself also vary, with the unpleasant consequences mentioned above.

Furthermore, in this kind of operation, it is also important to avoid any needlestick injury due to the exposed needle, whether this be before or after injection.

In addition, to limit the apprehension felt by the patient, particularly in the case of injections administered by the patient himself, it is desirable for the injection device not to look like a conventional syringe and/or for the needle not to be visible or to be visible only a little prior to insertion.

Finally, injecting a product using traditional injection devices generally entails at least two manual steps. For example, in the case of syringes, one manual step is to hold the body of the syringe in order to insert the needle into the injection site, another step consists in pressing on the piston rod in order to administer the injection, the progression from one step to the other generally entailing moving the fingers with respect to the syringe.

There therefore remains a need for an injection assistance device and for an injection set which are made safe, that is to say which make it possible to limit the impact of undesired movements of the patient and/or of the user in order to prevent a variation in the depth to which the needle is inserted when administering the injection so as to avoid unintentionally injecting the said product at an inadequate depth, limiting the risk of needlestick injury both to the patient and to the person administering the injection, limiting the apprehension felt by the patient and making the giving of the injection easier. There also remains a need for such an injection assistance device and an injection set that allow the user to be certain of causing the needle to penetrate the injection site to a predetermined insertion depth in order to avoid unintentionally injecting the said product at an inadequate depth.

There also remains a need for such an injection assistance device and an injection set that are cheap, easy to manufacture and assemble.

The present invention remedies these needs by proposing an injection assistance device for an injection device for injecting a product into an injection site, this injection device comprising at least one hollow body intended to receive a product that is to be injected, at least one hollow injection needle intended to penetrate the injection site, and at least one piston plunger housed in the said body, the said body and the said piston plunger being able to be moved in axial translation one with respect to the other, characterized in that the said injection assistance device comprises at least: a hollow sleeve provided with at least one bearing surface intended to come into contact with the surface of the said injection site, the said sleeve being intended to receive, at least in part, the said body and being arranged in such a way as to allow its axial mobility between at least a first position known as the initial position in which the said needle is not exposed over its insertion length, and a second position known as the insertion position in which the said needle is exposed by a predetermined insertion length L, a sleeve tube able to move with respect to the said sleeve and comprising at least one region for holding intended to be grasped by the user's hand in order to urge the said sleeve tube axially towards the said injection site, the said sleeve tube also comprising coupling means intended to connect the said region for holding to the said piston plunger or to the said body at least in terms of axial translation, at least from the said initial position to the said insertion position so as to allow at least the said insertion with just one hand and in just one unidirectional axial movement,

- retaining means arranged in such a way as to at least attempt to keep the said sleeve tube in the said initial position, and to release the said sleeve tube when the said axial force exerted on it reaches a predetermined value,

- said retaining means comprise at least one peg housed in a cam, the said peg and the said cam being secured one of them to the said sleeve and the other to the said sleeve tube, at least one of the said peg and cam being able to move with respect to the other and urged by at least a first elastically deformable element.

The injection assistance device and the injection set of the invention imply a limited number of parts to be manufactured and assembled. The injection assistance device and the injection set of the invention are therefore cheap and cost effective devices that are easy to manufacture and assemble.

As a preference, the said sleeve is arranged in such a way as to allow axial mobility of the said body at least between an injection position and a position "" O ~^* known as the final protection position in which the said needle is covered by the said sleeve.

As a preference, the said sleeve tube is arranged in such a way as to allow axial mobility of the said sleeve at least between the said insertion position and a position known as the final protection position in which the said sleeve covers the said needle.

Advantageously, the said injection assistance device comprises at least one second elastically deformable element intended to bear between the said sleeve and the said body or the said sleeve tube so as to urge the said body or the said sleeve with respect to the said sleeve tube from the said injection position to the said protection position once the said axial force on the said sleeve tube has been released and without additional manual intervention on the part of the user.

As a preference, the device according to the invention comprises locking means arranged in such a way as to at least limit the translational movement of the said sleeve or of the said body with respect to the said sleeve tube once the said protection position has been reached.

Advantageously, the said sleeve tube is designed to prolong the movement of the said piston from the said insertion position to an end-of-injection position, the said coupling means being arranged in such a way as to remain coupled to the said piston at least in the distal direction during this axial movement.

The injection assistance device according to the invention may comprise at least one intermediate ring intended to be attached to the said body in such a way as to be blocked in terms of translation with respect to the said body at least in the proximal direction. As a preference, the said intermediate ring is intended to act as a bearing surface for at least one of the said first, second elastically deformable elements.

In one embodiment of the invention, the said intermediate ring is provided with the said peg or with the said cam.

In one embodiment of the invention, the said sleeve tube defines a longitudinal skirt of which the distal part covers the proximal part of the said sleeve, at least in the insertion position.

Alternatively, the said sleeve defines a discontinuous longitudinal skirt in the proximal part of which the distal part of the said sleeve tube becomes inserted, at least in the insertion position, the solid parts of the said skirt then partially covering the said sleeve tube and the open parts allowing the said sleeve tube, and therefore the said injection set to be held.

In a preferred embodiment of the invention, the injection assistance device comprises control means arranged in such a way as to delimit the said insertion position of the said body.

As a preference, the said control means comprise at least one axial stop provided in the said sleeve and intended to have bearing against it at least one of the elements chosen from the group comprising the said body, the said sleeve tube, one of the said first, second elastically deformable elements.

As a preference, the said sleeve tube is arranged in such a way as to move distally until it comes into contact with the injection site in such a way as to delimit the said control means.

Advantageously, the said cam comprises an offset widened portion giving rise to a discontinuity in the path of the said peg and arranged in such a way as to block the said peg and at least partly define the said locking means.

As a preference, the said sleeve or the said sleeve tube comprises a flexible tab arranged in such a way as to be flexed, the said flexible tab bearing respectively on the said sleeve tube or on the said sleeve before the said protection position, the said flexible tab also being arranged in such a way as to straighten out when the said protection position is reached so as to define a stop at least partly forming the said locking means.

Advantageously, at least one of the said first or second elastically deformable elements is chosen from the group comprising a helical spring, a leaf spring, an element made of an elastically deformable material, a more or less sealed gas chamber.

The present invention also solves the aforementioned needs by proposing an injection set for injecting a product into an injection site, this injection set comprising at least: - an injection device as hereinabove comprising at least: a hollow body intended to receive a product that is to be injected, the said body being equipped with at least one region for holding and with a hollow injection needle intended, during a first phase known as the insertion phase, to penetrate an injection site and, during a second phase known as the injection phase, to channel the said product from the said body towards the said injection site, at least one piston plunger housed in a more or less sealed fashion in the said body and intended to be moved in the distal direction by movement means in the said injection phase during which it drives the said product through the said needle, characterized in that it comprises at least one injection assistance device as described hereinabove in the sleeve of which the said body is placed and the sleeve tube of which is linked at least in terms of axial translation to the said piston plunger or to the said body at least from the said initial position to the said insertion position.

As a preference, the said region for holding comprises a flange.

Advantageously, the injection set is in the form of a kit that can be assembled prior to use.

As a preference, the force to overcome the stiction of the said piston plunger in the said body is designed to be greater than the resultant of the force of compression of the said first elastically deformable elements and the force to cause the said needle to penetrate the said injection site.

In one embodiment of the invention, the said piston is coupled to a piston rod arranged in such a way as to form the said sleeve tube.

Other advantages and alternative forms of the present invention will now be specified with the aid of the description which will follow and of the attached drawings in which:

Figure 1 is an exploded perspective view of an injection set according to the invention,

- Figures 2 to 5 are sectioned views of the injection set of Figure 1 in the following positions: initial, needle insertion, end of injection of the product and final protection once the needle has been withdrawn from the injection site .

To make the invention easier to understand, the injection assistance device is described assembled with an injection device with which it forms an injection set .

Reference is made to Figures 1 to 5 which depict an injection set 100 according to the invention comprising an injection assistance device 1 for an injection device 3 comprising a hollow body 2 provided with a flange 10 and intended to receive a product 25 that is to be injected, a hollow injection needle 7 and at least one piston plunger 26 able to move in axial translation in a more or less sealed fashion inside the said body 2. The flange 10 can be part of the body or fastened to it by any suitable means .

The injection assistance device 1 comprises a hollow sleeve 4 provided with a bearing surface 5 intended to be pressed against the injection site 27, a sleeve tube

6 able to move with respect to the said sleeve 4 and comprising a region for holding 8 intended to be grasped by the user' s hand, an intermediate ring 24 attached to the flange 10 of the body 2 and a spring 9 arranged between the intermediate ring 24 and the sleeve 4.

As is apparent from Figures 1 to 5, the sleeve 4 houses the body 2 in such a way that the body 2 is able to move in translation, on the one hand, between an initial position (Figure 2) in which the needle 7 is not exposed and an insertion position (Figures 3 and 4) in which the needle 7 is exposed and inserted into the injection site 27 and, on the other hand, between the insertion position and a final protection position in which the sleeve 4 entirely covers the needle 7 (see Figure 5) . As will be obvious from Figure 5, the sleeve 4 is urged into the final protection position by return means, in the form of the spring 9 in the example depicted.

As is clear from Figures 2 to 5, the sleeve 4 comprises a radial stop 12 situated on the internal wall of its distal part and a radial step 14 situated on the internal wall of its proximal part. The radial stop 12 may be in the form of a continuous or discontinuous annular bulge or alternatively in the form of at least one radial projection. Likewise, the radial step 14 may be in the form of a continuous or discontinuous annular bulge or alternatively in the form of at least one radial rim.

In Figures 1 to 5 the sleeve 4 comprises a tab 15 formed in the wall of its proximal part, the said tab

15 being elastically deformable and able to deflect tangentially . The tab 15 at its proximal end comprises a peg 16.

The sleeve tube 6 defines a longitudinal skirt 47 of which the distal part, at least in the insertion position (see Figure 3) covers the proximal part of the said sleeve 4.

In these figures also, the sleeve tube 6 accommodates the sleeve 4 and its wall comprises a cam 17 in the overall shape of a crescent moon running longitudinally and comprising a distal end 18, a proximal end 19 and, approximately mid-way along, a lateral step 21. The peg

16 coupled to the sleeve 4 via the tab 15 is housed in this cam 17.

The spring 9 comprises a distal end 22 and a proximal end 23.

The way in which the injection set 100 works when injecting a product 25 in an injection site 27 will now be explained with reference to Figures 2 to 5. The injection assistance device 1 comes in an initial position depicted in Figure 2.

In this initial position, the body 2 comprises the product 25 that is to be injected and is closed off, at the opposite end to the needle 7, by a piston plunger 26 connected to the distal end of a piston rod 46 coupled to, or integral with, the sleeve tube 6. In this initial position, before the injection assistance device 1 is used, the sleeve 4 entirely covers the needle 7. It is possible to keep a gap between the sleeve 4 and the piston plunger 26 so as to prevent the product 25 from being pressurized in the body 2 while the injection set 100 is being stored and/or transported.

The sleeve 4 is retained in terms of translation with respect to the body 2 by means, on the one hand, of the spring 9 of which the distal end 22 bears against the radial stop 12 and of which the proximal end 3 bears against the distal face of the intermediate ring 24 and, on the other hand, of the radial step 14 which blocks the intermediate ring 24 in terms of translation in the proximal direction.

In another embodiment, not depicted, the assistance device 1 comprises no intermediate ring 24 and the proximal end 23 of the spring 9 bears against the distal face of the flange 10, the said flange 10 being blocked in terms of translation in the proximal direction by the radial step 14.

In this protected initial position the peg 16 is blocked in a narrowing (not depicted) provided in the distal end 18 of the cam 17 as depicted in Figure 2.

In this pre-use protected initial position of the injection device 3, the risks of needlestick injury are minimized, the needle 7 being entirely covered by the sleeve 4. The injection device 3 is thus completely safe.

The user then grasps hold of the injection assistance device 1 and places the bearing surface 5 of the sleeve 4 at right angles onto the surface of the said injection site 27, as shown in Figure 2.

Whilst the injection assistance device 1 is positioned in the desired location for the injection, the user exerts an axial force in the distal direction on the region for holding 8 of the sleeve tube 6 in order to perform the phase of inserting the needle 7 into the injection site 27.

As the force required to overcome the stiction of the piston plunger 26 is greater than the compression force of the said spring 9 combined with the force to overcome the friction of the penetration of the needle 7 into the injection site 27, the body 2 and sleeve tube 6 assembly moves in the proximal direction under the action of the axial thrust, without the piston plunger 26 being moved within the body 2, as shown in Figure 3. This movement causes the spring 9 to be compressed, the peg 16 to advance towards the proximal end 19 of the cam 17 and, because of the crescent shape of the cam 17, causes the tab 15 to flex tangentially.

Still under the action of the axial force exerted on the region for holding 8 of the sleeve tube 6, the needle 7 penetrates the injection site 27, and does so until the intermediate ring 24 comes into abutment against the radial stop 12. If, and this scenario is not depicted, the assistance device does not have an intermediate ring, the flange comes into abutment against the radial stop 12 via the spring 9.

Thus, the body 2 is in the insertion position, the needle 7 has penetrated the injection site 27 to a perfectly defined insertion depth L as can be seen in Figure 3. By virtue of the radial stop 12, it is then no longer possible to cause the needle 7 to penetrate the injection site 27 any further. The insertion depth L is thus perfectly controlled.

In order to progress to the injection phase, the user continues to exert axial force on the region for holding 8 of the sleeve tube 6 and therefore overcomes the stiction of the piston plunger 26 which, under the pressure of the sleeve tube 6, drives the product that is to be injected through the needle 7 and then into the injection site 27. During this injection phase, the peg 16 continues to progress along the cam 17 in the proximal direction until the piston plunger 26 comes into abutment in the closed end of the body 2.

In the end-of-injection position, as shown in Figure 4, the depth of insertion of the needle 7 has not varied, the piston plunger 26 is at the end of its travel and the spring 9 is still in the compressed state.

To finish off the operation and make the injection assistance device 1 safe, the user then releases the force on the region for holding 8 of the sleeve tube 6 and withdraws the injection assistance device 1 from the injection site 27. As the pressure previously applied on the spring 9 is suppressed, the spring 9 automatically expands to return to its initial slightly compressed state as depicted in Figure 5, as a result causing the deployment of the sleeve 4 which comes to cover the needle 7 in the final protection position. As the spring 9 turns to its initial state and the sleeve 4 deploys, the peg 16 has advanced along the cam 17 in the distal direction, causing the tangential flexing of the tab 15. Having arrived at the lateral step 21, the elastic return of the tab 15 from its flexed state to its unflexed state drives the peg 16 into this lateral step 21 in which it finds itself blocked, as shown in Figure 5.

Thus, in the final protection state depicted in Figure 5, the injection assistance device 1 is perfectly safe. Indeed, because of the blocking means in the form of the peg 16 and of the lateral step 21 in the cam 17 which are associated with the return of the tab 15 to the undeflected state, the sleeve 4 is blocked in terms of translation in both directions with respect to the body 2 and so the needle 7 can no longer be exposed and any needlestick injury is avoided.

The injection set 100 can then be discarded by the user.

In an embodiment, not depicted, of the invention, the sleeve tube 6 is housed inside the said sleeve 4, the said tab then being formed in the wall of the distal part of the said sleeve tube and the said cam being formed in the wall of the proximal part of the sleeve 4. In another embodiment, not depicted, of the invention, the said tab is replaced by a rigid radial finger and the said cam is V-shaped. The retaining means are then formed by the said radial finger coming into abutment against the proximal end of the first branch of the said V-shaped cam. During the injection phase, the radial finger, which is situated on the sleeve tube, travels along the first branch of the V as far as the distal vertex of this V. As the needle is withdrawn and the sleeve is deployed by the return of the spring to the initial state, the radial finger travels along the second branch of the V. The blocking means then comprise the radial finger coming into abutment against the proximal end of the second branch of the said V-shaped cam, after the sleeve has rotated with respect to the sleeve tube.

In another embodiment, not depicted, the slot has a rectilinear shape and is inclined with respect to the axis of the device.

In yet another embodiment, not depicted, the peg is urged laterally by an elastically deformable element replacing the deflecting tab, for example a spring, an elastomer or any other equivalent means.

In other forms of embodiment, not depicted, the helical spring may be replaced by leaf spring, pieces of elastomer, sealed gas chambers inside which the gas can be pressurized and expanded in succession, or any other equivalent means.

The injection set and the injection assistance device according to the invention are particularly simple to use and are perfectly safe. The entire injection operation can easily be performed by a single unidirectional axial movement, with just one hand. Moreover, the injection set and the injection assistance device of the invention are made of a limited number of elements and they are very easy to manufacture and assemble.

Claims

1. Injection assistance device (1) for an injection device (3) for injecting a product (25) into an injection site (27), this injection device (3) comprising at least one hollow body (2) intended to receive a product (25) that is to be injected, at least one hollow injection needle (7) intended to penetrate the injection site (27), and at least one piston plunger (26) housed in the said body (2), the said body

(2) and the said piston plunger (26) being able to be moved in axial translation one with respect to the other, characterized in that the said injection assistance device (1) comprises at least: - a hollow sleeve (4) provided with at least one bearing surface (5) intended to come into contact with the surface of the said injection site (27), the said sleeve (4) being intended to receive, at least in part, the said body (2) and being arranged in such a way as to allow its axial mobility between at least a first position known as the initial position in which the said needle (7) is not exposed over its insertion length, and a second position known as the insertion position in which the said needle (7) is exposed by a predetermined insertion length L, a sleeve tube (6) able to move with respect to the said sleeve (4) and comprising at least one region for holding (8) intended to be grasped by the user's hand in order to urge the said sleeve tube (6) axially towards the said injection site (27), the said sleeve tube (6; 106) also comprising coupling means (46) intended to connect the said region for holding (8) to the said piston plunger (26) or to the said body (2) at least in terms of axial translation, at least from the said initial position to the said insertion position so as to allow at least the said insertion with just one hand and in just one uni-directional axial movement, - retaining means (16, 17, 12, 14) arranged in such a way as to at least attempt to keep the said sleeve tube (6) in the said initial position, and to release the said sleeve tube (6) when the said axial force exerted on it reaches a predetermined value,

- said retaining means comprise at least one peg (16) housed in a cam (17), the said peg (16) and the said cam (17) being secured one of them to the said sleeve (4) and the other to the said sleeve tube (6), at least one of the said peg (16) and cam (17) being able to move with respect to the other and urged by at least a first elastically deformable element (15) .

2. Injection assistance device (1) according to Claim 1, characterized in that the said sleeve (4) is arranged in such a way as to allow axial mobility of the said body (2) at least between an injection position and a position known as the final protection position in which the said needle (7) is covered by the said sleeve (4 ) .

3. Injection assistance device (1) according to Claim 1, characterized in that the said sleeve tube (6) is arranged in such a way as to allow the axial mobility of the said sleeve (4) at least between the said insertion position and a position known as the final protection position in which the said sleeve (4) covers the said needle (7) .

4. Injection assistance device (1) according to Claim 2 or 3, characterized in that it comprises at least one second elastically deformable element (9) intended to bear between the said sleeve (4) and the said body (2) or the said sleeve tube (6) so as to urge the said body (2) or the said sleeve (4) with respect to the said sleeve tube (6) from the said injection position to the said protection position once the said axial force on the said sleeve tube (6) has been released and without additional manual intervention on the part of the user.

5. Injection assistance device (1) according to Claim 2 or 3, characterized in that it comprises locking means (15, 16, 17, 21) arranged in such a way as to at least limit the translational movement of the said sleeve (4) or of the said body (2) with respect to the said sleeve tube (6) once the said protection position has been reached.

6. Injection assistance device (1) according to Claim 1, characterized in that the said sleeve tube (6) is designed to prolong the movement of the said piston (26) from the said insertion position to an end-of- injection position, the said coupling means (46) being arranged in such a way as to remain coupled to the said piston (26) at least in the distal direction during this axial movement.

7. Injection assistance device (1) according to Claim 1, characterized in that it comprises at least one intermediate ring (24) intended to be attached to the said body (2) in such a way as to be blocked in terms of translation with respect to the said body (2) at least in the proximal direction.

8. Injection assistance device (1) according to at least one of Claim 7, characterized in that the said intermediate ring (24) is intended to act as a bearing surface for at least one of the said first, second elastically deformable elements (9, 15).

9. Injection assistance device (1) according to Claim 7, characterized in that the said intermediate ring (24) is provided with the said peg (16) or with the said cam (17) .

10. Injection assistance device (1) according to Claim 1, characterized in that the said sleeve tube (6) defines a longitudinal skirt (47) of which the distal part covers the proximal part of the said sleeve (4), at least in the insertion position.

11. Injection assistance device (1) according to Claim 1, characterized in that the said sleeve (4) defines a discontinuous longitudinal skirt in the proximal part of which the distal part of the said sleeve tube (6) becomes inserted, at least in the insertion position, the solid parts of the said skirt then partially covering the said sleeve tube (6) and the open parts allowing the said sleeve tube (6) to be held.

12. Injection assistance device (1) according to Claim 1, characterized in that it comprises control means (12, 24) arranged in such a way as to delimit the said insertion position of the said body (2) .

13. Injection assistance device (1) according to Claim 12, characterized in that the said control means comprise at least one axial stop (12) provided in the said sleeve (4) and intended to have bearing against it at least one of the elements chosen from the group comprising the said body (2), the said sleeve tube (6), one of the said first, second elastically deformable elements (9, 15) .

14. Injection assistance device (1) according to Claim 12, characterized in that the said sleeve tube (6) is arranged in such a way as to move distally until it comes into contact with the injection site in such a way as to delimit the said control means.

15. Injection assistance device (1) according to Claim 4, characterized in that the said cam (17) comprises an offset widened portion (21) giving rise to a discontinuity in the path of the said peg (16) and arranged in such a way as to block the said peg (16) and at least partly define the said locking means.

16. Injection assistance device (1) according to Claim 5, characterized in that the said sleeve (4) or the said sleeve tube (6) comprises a flexible tab arranged in such a way as to be flexed, the said flexible tab bearing respectively on the said sleeve tube (6) or on the said sleeve (4) before the said protection position, the said flexible tab also being arranged in such a way as to straighten out when the said protection position is reached so as to define a stop at least partly forming the said locking means.

17. Injection assistance device (1) according to one of the preceding claims, characterized in that at least one of the said first or second elastically deformable elements (9, 15) is chosen from the group comprising a helical spring, a leaf spring, an element made of an elastically deformable material, a more or less sealed gas chamber.

18. Injection set (100) for injecting a product (25) into an injection site, the said injection set (100) comprising at least: an injection device (3) comprising at least: a hollow body (2) intended to receive a product (25) that is to be injected, the said body (2) being equipped with at least one region for holding (10) and with a hollow injection needle

(7) intended, during a first phase known as the insertion phase, to penetrate an injection site (27) and, during a second phase known as the injection phase, to channel the said product (25) from the said body (2) towards the said injection site (27), at least one piston plunger (26) housed in a more or less sealed fashion in the said body (2) and intended to be moved in the distal direction by movement means in the said injection phase during which it drives the said product (25) through the said needle (7), characterized in^ that it comprises at least one injection assistance device (1) according at least to Claim I₁ in the sleeve (4) of which the said body (2) is placed and the sleeve tube (6) of which is linked at least in terms of axial translation to the said piston plunger (26) or to the said body (2) at least from the said initial position to the said insertion position.

19. Injection set (100) according to Claim 18, characterized in that the said region for holding comprises a flange (10).

20. Injection set (100) according to Claim 18, characterized in that it is in the form of a kit that can be assembled prior to use.

21. Injection set (100) according to Claims 4 and 18, characterized in that the force to overcome the stiction of the said piston plunger (26) in the said body (2) is designed to be greater than the resultant of the force of compression of the said first elastically deformable elements (15) and the force to cause the said needle (7) to penetrate the said injection site (27).

22. Injection set (100) according to Claim 18, characterized in that the said piston (26) is coupled to a piston rod (46) arranged in such a way as to form the said sleeve tube (6) .