RS49682B - SINGLE USE INJECTION DEVICE - Google Patents

Abstract

Disposable injection device having one syringe (1) provided with a front projection (1a) carrying a needle (2) and one rear edge (1b), said syringe having a chamber filled with a single dose of injection fluid, which is closed with a piston (4 ) connected to one end of the plunger lever (5) provided with a push-button (6) at the height of its opposite end, said injection device comprising a protection device after use of the syringe (1), comprising : - protective sleeves (7) composed of two tubular bodies (8, 9), called the front body and the rear body, which are provided with means of connection (12, 18) which allow them to be joined in extension of one another, the front body (8 ) has a diameter aligned with the diameter of the syringe (1), and a length that is adapted to accommodate said syringe in part, and the rear body (9) has a diameter greater than the diameter of the rear edge (1b) of said syringe and has supporting bodies (23). fingers, - a ring (24) housed in the rear body (9) and having means (29, 31) for securing the rear edge (1b) of the syringe (1) to allow said syringe (2) to be inserted by pointing the needle relative to the rear body (9) the sleeves (7), - the ring (24) and the rear body (9) consist of: ● first means (20, 22, 27) for relative fixation in the direction of translation capable of allowing said ring to be inserted into said rear body by pointing it toward the side joining with the front body (8) and defining a first fixation position, namely injection, thereby allowing injection when the injection device is coupled, ● other means (20, 22, 28) for relative fixation in the translation direction that define a second fixation position, namely after use protection, which is achieved by moving the ring (24) backwards inside the rear body (9), in which position the injection needle (2) is tucked inside the front body (8), - the ring (24) and the front body (8) equipped with means (10 a, 31) for a support capable of holding the elastic means (42) compacted in the first injection fixation position, - and the ring (24) or rear body (9) has one rear portion (26) which is radially flexible and carries the first means (27) ) for fixation in the direction of translation, which are capable of deforming by the push-button (6) of the piston rod (5) at the end of its stroke, so as to release said first fixation bodies and allow the ring (24) to move to the second fixation position during protection after use. The application contains 12 additional dependent claims.

Description

The invention relates to a disposable injection device which is

intended to be pre-filled with one dose of liquid to be injected.

The single-use injection devices now traditionally used consist of a pre-filled syringe equipped with a single cap designed to protect the needle before use, which is then removed before injection, and finally put back in place after injection, to avoid the risk of a subsequent puncture with a dirty needle.

It has always been shown that such a conception leads to a significant inconvenience resulting in the fact that when recapting the needle, the cap must be oriented in relation to the tip of this needle. This obligation, as it turns out, is the cause of relatively frequent needlestick accidents with all the risks posed by such dirty-needle injections. In addition, such syringes do not provide any security in terms of preventing their reuse, and therefore become subject to special obligations in terms of their

destruction.

In order to avoid these inconveniences, the usual planting technique consists in this

to provide the injection device with a protective sleeve, which is able to slide along the body of the syringe and into which the syringe can be retracted, so that either the injection position is obtained in which the injection needle is pulled out, or the protective position in which, after use, this injection needle is retracted and protected inside the protective sleeve.

According to this principle, the classic solution consists in creating devices for

injection that have elastic means inserted between the body of the syringe and the protective sleeve, which

can be compressed and ensure the placement of the protective sleeve and the syringe in their positions for injection both before and during the injection, as well as to relax and lead automatically to the movement of the said protective sleeve and the said syringe into their protective positions after use,

at the end of the injection.

This solution makes it possible to realize injection devices as described in the international patent applications WO-91.13634, WO-93.23089, WO-93.25254 and European EP-446.551 and EP-307.367, guaranteeing on the one hand security against all risks of accidental stabbing before and after injection, apparently due to the fact that the protective sleeve and the syringe are forced to start automatically way after the injection, thanks to the action of the elastic means, and on the other hand to prevent any reuse of the syringe.

However, it turns out that such injection devices require a specific design of syringes with a price significantly higher than that of conventional syringes, such as glass syringes that are now produced in very large series at a very low cost.

In fact, no solution has been found to the problem of obtaining an injection device of this type which cannot be used after injection and which is equipped with a conventional syringe.

Current injection devices of this type also show another disadvantage arising from the fact that during the release of the elastic means, which is activated by means of unlocking located on the piston lever, there is no guarantee that the syringe has been completely emptied, due to the permitted tolerances related to the length of the syringe during their production. Therefore, such injection devices which are specifically designed to be used for injections of very small doses of liquid (of the order of a cubic millimeter) where very strict adherence to the given amount is mandatory, this technical solution proves to be unable to satisfy the set requirements.

The present invention aims to overcome these drawbacks and has as its main objective to provide an injection device which is easy to manufacture and which consists of a conventional syringe and which cannot be reused after injection.

Another object of the invention is to provide an injection device that guarantees the injection of the entire dose of liquid.

For this purpose, the invention envisages a single-use injection device consisting of a syringe equipped with a front protrusion on which the injection needle is located and a rear edge, wherein said syringe has one chamber filled with a dose of liquid to be injected, which is closed by a piston connected to one end of a khpne lever, equipped at the opposite end with a push button.

According to the invention, this injection device has a device for the protection after the use of the syringe, which consists of: - a protective sleeve composed of two tubular bodies, called the front body and the back body, equipped with folding means that allow them to be joined by continuing one on top of the other, the front body having a diameter corresponding to the diameter of the syringe and a length adapted to physically accept said syringe, and the rear body having a diameter greater than the diameter of the rear edge of said syringe, and has means for supporting the fingers, - a ring placed on the rear thread which has means for fixing the rear edge of the syringe capable of allowing the said syringe to be retracted by directing the needle in relation to the rear body of the protective sleeve,

- ring and rear body have:

first means for fixing in the direction of translation which enable said ring to be drawn into said rear body by directing it towards the side of folding the same with the front body, defining a first position of fixation, namely injection, enabling a single injection when the injection device is folded, second means for fixing in the direction of translation which define another position of fixation, namely protection after application, which is obtained after moving back the ring inside the rear body, in which the injection needle is located retracted into the front body, - the ring and the front body are equipped with support means capable of holding the elastic means compressed in the first injection fixation position, - and the ring or rear body has a rear part which is radially elastic and carries the first fixation means in the direction of translation, positioned to be deformed by the push button on the piston lever at the end of its stroke, so as to release said first fixation means and allow the movement of the ring towards the second fixation position for protection after application.

The device for protecting the syringe according to the invention therefore has four main elements (ring, front and back body of the protective cover and elastic means) intended to be assembled in such a way as to form one pre-assembled assembly into which the classic syringe will then be inserted, which then ensures the protection of the needle after application and completely prevents re-use.

In addition, the assembly of the protection device is achieved in a very simple way in stages that can be easily automated. Namely, this assembly is accomplished in the following stages: - pulling the ring into the rear body of the protective cover until it is brought to the first fixation position,

- placement of elastic means in place in the ring in an uncompressed state,

- connecting the rear and front body by compressing the elastic means by the means for supporting the said front body and the ring.

This pre-assembled assembly enables the later installation of a pre-filled classic syringe, which is fixed after this installation in place at the height of its rear edge, in the injection position, and then automatically retracts into a protective position after the injection, completely preventing reuse.

According to one preferred embodiment, the ring is made of a material of a different color compared to the color of the protective cover, primarily for security reasons, so as to enable the identification of a device that has already been used.

In addition, it is convenient for the front body of the protective cover to be made of a transparent material, so that the syringe can be seen.

The rear body of the protective cover itself is preferably made of an opaque material so as to obscure the trigger mechanism from view, which can be reassuring for the medical practitioner and the patient.

In addition, in a suitable embodiment, the means for fixation in the direction of translation of the ring and the rear body of the protective cover consist of: - at least one internal longitudinal groove made in the rear body, which extends into one rear fixation cavity, - for each groove, two front and rear fixation teeth made on the ring and adapted to slide inside the said groove and to be drawn into the fixation cavity.

This construction enables, in addition to defining the first and second fixation positions in the direction of translation, relative fixation in terms of rotation of the ring relative to the rear body.

Furthermore, each cavity for fixation consists in the most suitable design of an opening made in the peripheral wall of the rear body, which opening is bounded on the rear side by an internal outlet, and on the front side by an internal tooth in the form of an asymmetric tooth whose front side is beveled, and which is located on an elastic tongue made in the said peripheral wall of the rear body.

In addition, according to one preferred embodiment, the means for connecting the front and rear bodies of the protective cover have one internal annular notch in the rear body and one external locking outlet formed on the front body.

Furthermore, in a suitable embodiment, the front body of the protective cover has, for each groove of the rear body, one external guide that can enter the said groove. This construction ensures the achievement of relative fixation in terms of mutual rotation of the two bodies of the protective cover.

As for the means for fixing the rear edge of the syringe, they have at least one inner rear tooth made in a ring, which consists of

one non-symmetrical tooth with one bevelled rear side and one internal front outlet made in a ring at a distance from each tooth equal to the thickness of said rear edge.

As for the means for supporting the elastic means, they conveniently consist of said outlet on the ring and an internal outlet in the front body at the height of one of its rear parts with an internal diameter greater than its normal internal diameter.

In addition, according to a preferred embodiment, the elastic parts that carry the first translational fixing means consist of two Radially flexible Paws located on the rear extension of the ring, and on which a rear fixing tooth is placed.

Furthermore, each rear fixation tooth is placed in the most convenient way in the middle along the length of the paw, so that behind those teeth there is a bevel made that allows, at the end of the injection, when force is applied to the push button, to absorb the differences in the length of the syringe, so as to guarantee the injection of the total dose of liquid.

In addition, in a preferred embodiment, the push button of the piston rod has the shape of a single dome with an edge having a chamfered profile, and each paw has a rear edge with a complementary chamfered profile.

Other features, objects and advantages of the invention will be apparent from the following detailed description with reference to the accompanying drawings, which show, by way of example, without limitation, one preferred embodiment. In those drawings: - figure 1 is a longitudinal section in one plane along the axis of an injection device according to the invention, shown before use,

- figure 2 perspective view of the protective cover of this injection device,

- picture 3 is a longitudinal section of a plane A along the axis of this protective cover,

- picture 4 is a longitudinal section of a plane B along the axis of this protective cover,

- picture S is a cross-section of one plane C of this protective cover,

- picture 6 is a cross-section of one plane D of this protective cover,

- figure 7 is a longitudinal section through a plane E along the axis of the ring for locking this injection device,

- figure 8 is a perspective view of this locking ring,

- figure 9 is a longitudinal section of one plane F along the axis of the cartridge with claws for this injection device,

- picture 10 is a perspective view of this insert with claws,

- figures 11a to llf are schematic views of the successive stages of the production of this injection device, - figure 12 is a longitudinal section along an axial plane of this device showing the initial stage of removing the protective cap, before applying said injection device, - figure 13 is a longitudinal section in one axial plane showing the injection device at the end of the injection, - and figure 14 is a longitudinal section in one axial plane showing the injection device in a protective position after applications.

The injection device according to the invention shown in figure 1 has, in the first place, a syringe 1 of a traditional type that is pre-filled, such as for example a glass one, which has in a classical way a protrusion la on the front side on which the needle 2 is mounted, and a rear edge lb at the height of its rear end.

This syringe 1 also has, in a classic manner, a protective cap 3 for the needle 2, which is adjusted to be placed sealed on the front outlet 1a of said syringe.

It also has, in the classic way, a piston 4 that delimits a chamber filled with a single dose of liquid, and which is bored with a threaded hole, into which the threaded end S of a lever S of the piston S, which has a push button 6 at the opposite end, is inserted.

According to the invention, this push button 6 has the shape of a single dome with an edge 6a having a beveled profile with spaced ends.

The injection device according to the invention also has a syringe protection assembly 1 suitable to be completely pre-assembled before said pre-filled syringe is placed in its place in said protection assembly.

That protective assembly has first of all a protective cover 7 shown in figures 2 to 6 and composed of two tubular bodies, the front 8 and the rear 9, which are set to fit one in the extension of the other.

The front body 8 has an inner diameter matched to the outer diameter of the syringe 1 and a length suitable to accommodate the needle 2 equipped with its protective cap 3 and about 80% of the length of the syringe 1.

At the height of its rear end, this front body 8 has a rear part 8a with an approximately ovoid shape and an outer diameter greater than the outer diameter of the rest of said front body, which is internally widened so as to have longitudinal ribs 10 defining an inner diameter equal to the inner diameter of the rest of this front body 8.

Each of these ribs 10 has, among other things, an outlet 10a which delimits a part of the rear end with an inner diameter significantly larger than the diameter of the syringe 1.

On the outside, this rear part 8a has an annular notch 11 bordered by a rear outlet 12 for blocking. Furthermore, as seen in Figure 5, this notch 11 is interrupted by two guides 13 which are diametrically opposite and protrude radially in relation to the outlets 12 for locking.

At the height of its front end, the front body 8 has a detachable front part 8b bounded by an annular tearable zone 14, which is located so as to be at the height of the front projection la of the syringe 1 when it is placed in its place.

This detachable part 8b has inside at the height of its rear end a beveled profile 15, which forms a slope that delimits a rear part in the form of a narrowing 50 with a diameter significantly smaller than the inner diameter of the rest of the front body 8.

In front of this rear part, the detachable part 8b has, among other things, a number of longitudinal notches 16 distributed along the periphery of the inner side of said detachable part, which delimit an inner diameter equal to the black one in said rear part, so that the bottoms of said notches define an outlet 17 with the front end of this rear part.

Finally, as regards this detachable part 8b, its front part located in front of the notch 16 has an inner diameter equal to the diameter separating the bottoms of the notch.

The rear body 9 has a generally ovoid shape aligned with that of the rear portion 8a of the front body 8, and adapted to fit onto said rear portion 8a.

For this purpose, this rear body 9 has, first of all, an annular internal notch 18 adapted to receive the outlet 12 for locking. It has, among other things, two diametrically opposite longitudinal grooves 19, each of which can receive one guide 13, so as to ensure fixation in terms of rotation of the two bodies 8,9, wherein said grooves are interrupted at a small distance from the rear end of this rear body 9, so that it has one internal outlet 20 opposite the end of these grooves 19.

As shown in Figure 7, the ribs 19 are made according to the largest diameter of the rear body 9, so as to minimize the thickness of the walls of said rear body.

The rear body 9 has, among other things, two flexible tongues 21, each of which is made in one of the grooves 19 at the height of its rear end and each is formed by making a U-shaped cutout in the wall of the said rear body.

Each of these tongues 21 has at the height of its rear end a transverse hook 22 which protrudes into the interior of the rear body 9. Each of these hooks has a rear side 22a which is essentially radial and which prevents return, and a front beveled side 22b which forms a slope.

Finally, the rear body 9 has a classic outer ring 23 for resting the fingers.

The protective assembly has, on the other hand, a locking ring 24 in a shape adapted to be inserted into the rear body 9, showing against its front side.

This locking ring 24 with a length adapted to be inserted into the rear body 9 has the form of a cylindrical sleeve 25 extended at the rear with two paws 26 which are diametrically opposed in the form of a cylinder sector.

Each of these two paws 26 has, first of all, at the rear end 26a a chamfered profile which is complementary to that on the edge 6a of the push button 6 of the piston lever 5.

Each of these paws 26 has, among other things, essentially in the middle of its length, one transverse tooth 27 on the outside, adapted to be able to move through one of the grooves 10 of the rear body 9.

The cylindrical sleeve 25 of this locking ring 24 has on it two transverse teeth 28 with the same generatrix as the transverse teeth 27, which are also adapted to be able to move within the grooves 10 of the rear body 9, and are placed at the height of the front end of the said sleeve.

This cylindrical sleeve 25 also has, essentially in the middle of its length, axially in line with the previously mentioned teeth 27, 28, two internal teeth 29, which are diametrically opposed to each other and under which there is one opening 30 in the wall of the said sleeve.

Each of these internal teeth 29 has a rear side 29a with an inclined profile forming a slope and a radial front side 29b which provides blocking of backward movement.

Finally, the cylindrical sleeve 25 has behind the opening 30, at a distance from the inner teeth 29 which is matched with the thickness of the rear edge lb of the syringe 1, an inner annular protrusion 31.

The injection device according to the invention has, finally, one insert 32 with claws shown in figures 9 and 10 which is intended for covering the protective cap 3 and for its withdrawal after tearing the tearable zone 14 of the front body 8 of the protective sleeve 7.

This insert 32 with claws has a frontal cylindrical wall 33, the diameter of which is coordinated to enter the detachable part 8b, and on the periphery of which there are essentially vertically placed four separated longitudinal paws 34, 35, 36, 37 evenly distributed in relation to the axis of the mentioned wall: - two paws 34, 35 which are diametrically square to each other and have at the height of their free ends two lateral claws 38, 39 each, which are adapted to be able to be inserted into the protective cap 3, - two other paws 36, 37 which are diametrically opposite to each other have, in the middle of their length, each an external protrusion 40 with serrated teeth 41 on their outer side, which correspond to the teeth 16 on the detachable part 8b. Furthermore, each protrusion 40 has a rear cylindrical part 40a, in front of which there is a front beveled part 40b forming a bevel.

It should be noted, among other things, that during casting, as shown in Figure 9, the paws 34-37 are made in a position that is noticeably "open", that is, beveled outwards in relation to the axis of the front wall 33.

The manufacture of the injection device described above as well as the joining of the various organs of the constituent elements is further set forth with reference to Figures 1la to 1lf.

The first stage consists in inserting the locking ring 24 into the interior of the rear body 9 of the protective sleeve 7, placing the latter in the direction of the front side of said rear body, until the teeth 27 rest on the outlet 20 (fig. 11a). It should be noted that this positioning is made possible by the elasticity of the tongues 21 and the shape of the front side 22b of the hooks 22, which form an inclined ramp that allows the release of the mentioned teeth.

It should also be noted that once the locking ring 24 is in place, it is fixed in terms of rotation relative to the rear body 9 due to the engagement of the teeth 27 in the grooves 19.

The second stage consists in the helical insertion of a spiral spring 42 into the interior of the locking ring 24, bringing it towards the front of said ring until it rests with one of its ends on the outlet 31 (Fig. 1 lb).

The third stage consists in locking the front body 8 to the rear body by the joint action of the locking outlet 12 with the notch 18 (Fig. 11c). During this operation, the spring 42 is automatically compressed between the outlet 10a of the ribs 10 and the outlet 31. Furthermore, the front body 8 and the rear body are fixed in terms of relative rotation due to the insertion of the guides 13 into the grooves 19.

At the end of these three operations, which can easily be automated, a fully assembled protective assembly is obtained, into which the pre-filled syringe 1 can then be inserted, as will be described further on.

Prior to this retraction, as shown in Figure lld, the clawed insert 32 is placed on the protective cap 3 of the syringe 1, which is at this stage without the piston lever 5. During this installation, the paws 34-37 of the clawed insert 32 are only brought around the protective cap 3, without the risk of pressing it and damaging the needle 2 and/or disrupting the seal.

The syringe 1 equipped with an insert 32 with claws is then pulled into the rear body 9 of the protective sleeve 7 until the edge lb is fixed between the teeth 29 and the outlet 31 (figure lle). It should be noted that this retraction is made possible by the ability of the teeth 29 to bend elastically and by the shape of the slope of the rear side 29a of these teeth 29, which enables their release in relation to the edge lb.

Furthermore, during this retraction, the insert 32 with claws is brought to lock on the protective cap 3 by passing its protrusions 40 at the level of the slope 15 of the detachable part 8b and the narrowing 50, which passage is facilitated, among other things, by the shape of the ramp of the front part 40b of the aforementioned protrusions.

It should be noted, among other things, that the claws 38, 39, as shown in Figure 1, when they are locked, enter the protective cap 3 behind the glass cone where the front protrusions of classic syringes 1 are traditionally located, which serve to ensure sealing. Therefore, all risks of pushing the protective cap 3 and thus damaging the needle 2 and/or disrupting the sealing have been eliminated.

When this stage is completed, it should be noted that the cartridge 32 with claws and the protective cover 7 are fixed in terms of rotation due to the mutual action of their respective teeth 16, 41. Furthermore, on the one hand, the protective cap 3 is fixed in terms of rotation in relation to the cartridge 32 with claws due to the penetration of the claws 38, 39, and on the other hand, the cartridge 32 with claws, the protective sleeve 7 and the locking ring 24 are also mutually fixed in terms of rotation, as set forth above.

The last stage shown in Figure 11f consists in finally connecting the lever 5 and the piston 4 in a classical manner. Thus, a ready-to-use injection device is obtained, the use of which is described below with reference to Figures 12 to 14.

First of all, as shown in Figure 12, the initial stage consists in breaking the breakable zone 14 in a classic way by subjecting the detachable part 8 to a rotational movement and pulling it. With this movement, since the assembly of elements (protective cap 3, protective sleeve 7, locking ring 24) is mutually fixed in terms of rotation, the protective cap 3 is first turned, thereby facilitating its separation, then the cartridge 32 with claws is fixed in the direction of translation relative to the detachable part 8b by the engagement of the protrusion 40 with the outlet 17, so that the protective cap 3 separates simultaneously with the insert 32 with claws and with the mentioned detachable part.

Then the injection can be performed in the classic way by acting in opposite directions on the push button 6 and on the finger support 23. At the end of the injection, as shown in Figure 13, the profiled edge 6a of the pressure button 6 will act together with the profiled edge 26a of the paws 26 on the locking ring 24, performing a deformation radially towards the inside of said paws 26 until the release of the teeth 27 is ensured.

It should be noted, among other things, that the teeth 27, which are placed in the middle of the paws 26, also have a rear oblique ramp that allows them to absorb tolerance deviations during the manufacturing of the syringes 1 and to guarantee the extrusion of the entire dose of liquid.

As shown in Figure 14, when the injection is finished and when the pressure on the push button 6 is stopped, the locking ring 24 driven by the spring 42 is pushed into the interior of the protective cover 7 pulling the syringe 1, until the teeth 28 release the ramp 22b of the teeth 22 and are fixed between said teeth 22 and the outlet 20, thus preventing the subsequent use of the injection device.

Finally, according to one suitable embodiment, the front body 8 of the protective cover 7 is made of transparent material so that the syringe 1 can be seen.

The locking ring 24 is made of a material of a different color than the material of the rear body 9, so that it enables the identification of an injection device that has already been used.

Claims (1)

1/ - A disposable injection device having a syringe (1) equipped with a front protrusion (la) carrying a needle (2) and a rear edge (lb), said syringe having a chamber filled with a dose of liquid for injection, which is closed by a piston (4) connected to one end of a piston rod (S) equipped with a push button (6) at the height of its opposite end, said device for injection^ is indicated by the fact that it consists of a device for protection after the use of a syringe (1), which consists of: - a protective sleeve (7) composed of two tubular bodies (8, 9), called the front body and the rear body, which are equipped with connecting means (12, 18) that allow them to be connected in extension to one another, the front body (8) has a diameter matched to the diameter of the syringe (1), and a length adapted to accept the partially mentioned syringe, and the rear body (9) has a diameter that is greater than the diameter of the rear edge (lb) of the said syringe and has organs (23) for the support of the fingers, - a ring (24) located in the back body (9) and which has means (29, 31) for fixing the back edge (lb) of the syringe (1) which enable the insertion of the said syringe (2) directing the needle in relation to the back body (9) protective covers (7), - the ring (24) and the back body (9) consist of: • the first means (20, 22, 27) for relative fixation in the direction of translation capable of enabling the insertion of said ring into said rear body by directing it towards the side of the connection with the front body (8) and defining a first position of fixation, namely injection, thus enabling injection when the injection device is assembled, • other means (20, 22, 28) for relative fixation in the direction of translation that define another position of fixation, namely protection after use, which is reached by moving the ring (24) backwards inside the rear body (9), in which position the injection needle (2) is inserted inside the front body (8), - the ring (24) and the front body (8) which are equipped with support means (10a, 31) capable of holding the elastic means (42) compressed in the first position of fixation and<n>jection, - and the ring (24) or the rear body (9) has a rear part (26) which is radially flexible and carries the first means (27) for fixation in the direction of translation, which are capable of being deformed by the push button (6) of the piston lever (5) at the end of its stroke, so as to release the mentioned first fixation means and allow the movement of the ring (24) towards the second fixation position during protection after use. 21- The injection device according to claim 1, characterized in that the ring (24) is made of a different color than the color of the protective sleeve (7). 3/ - Injection device according to one of claims 1 or 2, characterized in that the front body (S) of the protective cover (7) is made of transparent material. 4/ - Injection device according to one of claims 1 to 3, characterized in that the rear body (9) of the protective cover (7) is made of opaque material. 5/ - An injection device according to one of the previous claims, characterized in that the means for assembling the front body (8) and the rear body (9) of the protective cover (7) consist of an internal annular notch (18) made in the rear body (9) and an external outlet (12) for locking made on the front body (8). 6/ - An injection device according to one of the overriding requirements, indicated by the fact that the means for fixation in the direction of translation of the ring (24) and the rear body (9) of the protective cover (7) consist of: - at least one internal longitudinal groove (19) made in the rear body (9), which extends into the rear cavity (20, 22) for fixation, - for each groove (19) of two teeth for fixation and that of the rear (27) and front (28) made on the ring (24) and adjusted so that they slide inside the mentioned groove and enter the fixation cavity. II- Injection device according to claim 6, characterized in that each fixation cavity consists of one opening in the peripheral wall of the rear body (9), which is bounded on the back side by an internal outlet (20) and on the front side by an internal tooth (22) in the form of an asymmetrical tooth equipped with a beveled front side (22b), which is located on the elastic tongue (21) made on the mentioned peripheral wall of the rear body (9). 8/ - Device for injection according to one of claims 6 and 7, characterized in that the front body (8) of the protective covers (7) has for each of the grooves (19) of the rear body (9) one external guide (13) that can be placed in said groove. 91 - Device for injection according to one of the preceding claims, characterized in that the means for fixing the edge (lb) of the syringe (1) have at least one rear internal tooth (29) made in a ring (24) and consisting of one asymmetric tooth equipped with one beveled rear side (29a) and one front internal outlet (31) made on the ring (24) at a distance from each tooth (29) that is equal to the thickness of the mentioned edge. 10/ - Injection device according to claim 9, characterized in that the means for supporting elastic means (42) consist of an outlet (31) made in the ring (24) and an internal outlet (10a) made in the front body (8) at the height of one rear part (8a), whose inner diameter is greater than its inner diameter on the rest of the part. 11/ - Device for injection according to one of claims 6 or 7, characterized in that the flexible parts that carry the first organs (27) for fixation in the direction of translation consist of two radially flexible paws (26), which are located on the rear extension of the ring (24), and on which one rear tooth (27) is placed for fixation. 12/ - Injection device according to claim 11, characterized in that each rear tooth (27) for fixation is placed in the middle along the length of the paw (26). 13/ - An injection device according to one of claims 11 or 12, characterized in that the push button (6) on the piston lever (5) has the shape of a dome whose edge (6a) has a bevelled profile, and each paw (26) has one rear edge (26a) with a complementary bevelled profile.