IE65414B1 - Single-use hypodermic syringe - Google Patents

Description

Although this syringe, which ls very widely used and of which tens of millions are manufactured and used each year, is a so-called disposable syringe, nothing in the structure of this syringe renders it unusable after a first use.

This known syringe is considered as a disposaDle syringe rather than a single-use syringe because it is principally produced from synthetic material and cheap and not like the old syringes which were not disposable and of which only the needle was changed.

Nowadays, with the development of serious blood-transmitted diseases, it has become necessary to provide a syringe which, by virtue of its construction, cannot be re-used.

A disposable syringe of the above type already exists (US-A4 687 467). This syringe has a rear cutting extension, at the needle, projecting into the cylinder. When the plunger comes to the end of its travel, when the liquid is ejected, its cap is impaled on the rear cutting end of the needle.

Due to the hollow structure of the retaining stud, the two chambers of the cylinder communicate, which prevents any re-use of the syringe.

This syringe can also be re-used if the first user (voluntarily or involuntarily) does not completely empty the syringe, that is to say draws in a volume of liquid greater than that to be injected.

Furthermore, this syringe necessitates a particular construction of the rear part of the needle, of the cap and above all a complicated shape of the plunger, that ls to say of the retaining stud and the head thereof. -7.A single-use hypodermic syringe is already known which comprises: a cylinder receiving a plunger provided with a cap in the form of a hollow cylindrical body having a peripheral wall ensuring sealing with regard to the cylinder, a closed.front face, a rear face provided with an opening for fixing the cap on the plunger, the closed front face of the cap having a wall Intended to be pierced by a pin carried by the plunger under the action of the pressing movement of the plunger, the plunger has a flange against which the cap rests under the effect of the pressure of the plunger, the plunger has a retaining stud with a head receiving the cap and carries the pin on its head.

Such a syringe is described in the document EP- 0 345 159 (CLOTTEAU/POZZI) which represents an item of prior art in accordance with Article 54(3.). However, although this syringe is really tor single use, since the least pressure exerted on the plunger in order to expel the liquid from the syringe splits the wall by the pin (Figures 7, β) and renders the syringe unusable a second time, this is a theoretical solution which does not function in practice since under the effect of the pressure exerted by the plunger on the liquid, this liquid escapes through the epllt in the wall and the channels of the stud and those of the plunger. As there are no sealing means downstream of the split, this syringe is unusable.

The present invention alms to remedy these shortcomings of the known solutions and proposes the development, from the s Κί I? S - 3 usual syringes, of a syringe which Is really for one use, whilst enabling it to benefit from the particularly efficient and economical conditions of manufacturing known syringes.

To this end the Invention relates to a syringe ot the above type, characterised by the characterising features of the characterising portion of Claim 1.

The syringe according to the invention is intrinsically a single-use syringe because as soon as the user exerts a pressure on the shank of the plunger the pin splits the front face of the cap. This consequence is inevitable whatever provisions are made by the user, even with malicious intent, who might wish to be able to re-use the syringe or to use a syringe which has been disposed of.

Other characteristics of the invention are the subject of the dependent claims. given with reference to the drawings in which: a view of a syringe according to the invention; a partial view on a larger scale than Figure 1; a rear view of the cap; a partial view of the open front end of the a view following the arrow V of Figure 4; The invention will be better understood upon reading the description Figure 1 is 20 Figure 2 is Figure 3 is Figure 4 is cylinder; Figure 5 is . Figure 6 shows schematically the assembly of the syringe according to the invention; Figure 7 is a view of a variant of the construction of the syringe according to the invention; Figure β is a view according to the arrow VIII of Figure 7; 30 Figure 9 is a sectional view of the syringe according to a second variant of the construction. isi $ $ 'i.

Figure 1 shows the hypodermic syringe which ha6 a cylinder 1, one open end of wnich is bordered by a flange 19; the other end has a conical base 13 which ends in an open heck 14 of small dimensions which is intended to receive the needle 5.

The cylinder 1 receives an axially movable plunger 2; the plunger has a plane face 21, on which the user of the syringe acts, outside the cylinder; the end thereof situated in the cylinder 1 has a retaining stud 4 by which the plunger bears a hollow cap 3.

The cap 3 made from a deformable material lies flat with its external periphery against the internal wall of the cylinder 1 and divides the latter in a sealed manner into two chambers 11, 12.

According to Figure 2, the retaining stud 4 of the plunger 2 has in succession: a transverse flange 22, a shank 41 which extends from the flange 22 in the longitudinal axis of the syringe towards the front end 2o of the syringe, at the end of the shank 41 a head 43, of a generally conical or cylindro-conical shape, having on the rear side a transverse face 42 and on the front side a pin 44.

The cap 3 made from deformable material, for example a rubbery material, has the overall shape of a hollow cylinder, the front face 31 of which is closed whilst the rear face 32 has an axial opening 33 having a diameter approximately equal to that of tne shank 41 of the retaining stud30 The closed front face 31 of the cap 3 has a variable ¢r· & y3» thickness: the central part 34 thereof has a small thickness so as to be easily torn or pierced. This fragile part 34 Is obtained either In one single piece by moulding a thin wall or by producing a cap having an opening in the central part 34 of the front face and by placing over this opening a fragile thin wall, of the paten type, for example using ultrasonic welding or any other known means.

The face 32 has openings 35 of which there are three in this case.

As Figure 3 shows, these openings 35 are distributed circumferentially and are centered on a mean circumference between the disc covered by the flange 22 and that covered by the transverse face 42 of the head 43.

The thickness of the rear wall 36 of the cap 3 is substantially smaller than the length of the shank 41 in order to permit an axial movement of the cap along the shank between the flange 22 and the face 42. Thus, for a specific portion of the cap in the syringe, the plunger can move freely between two ends of the shank 41. 2q The syringe is manufactured and sold with the plunger 2 pushed into the cylinder so that the cap 3 has its face 31 close to the base 13 of the said cylinder.

During the first use, the plunger 2 is pulled in the direction tending towards leaving the cylinder 1 in order to draw in the liquid to be injected. In the course of this phase, the cap 3 is resting with its face 32 against the face of the retaining stud 4.

When the plunger is then pushed in the direction of the base 13 of the cylinder, first of all a movement of the plunger 2 is produced relative to the cap 3 until the plunger 2 rests with its flange 22 on the face 32 of the cap.

In the course of this relative movement of the plunger and the retaining stud with respect to the cap 3, the pin 44 situated initially a short distance from the face 31 comes to perforate the fragile portion 34 of th face 31 of the cap 3. The piercing is further ensured by the deformation of the face 31 due to the resistance which the liquid exerts against it when the plunger is pushed.

During the movement of the piston 2 towards the base of the cylinder, the flange 22 is in contact with the face 32 of the cap and thus closes the openings 35, and thus the syringe functions like a syringe of the known type and expels the liquid contained in the chamber 11 through the needle 5.

Up to this point the functioning of the syringe has been, at least from the point of view of the user, the same as that of a syringe of known type. However, without the user being aware of it and having caused it and, moreover, in an interesting manner without the user being able to avoid it, the cap 3 has been pierced by the pin 44.

In order to ensure the seal between the flange 22 and the face 32, it is necessary for the openings 35 to be closed ln a secure manner. If required, it is possible to provide a collar extending beyond the face 32 and turned towards the flange 22; the collar has a sufficient diameter to hide the openings 35.

The syringe cannot be re-filled with liquid since the cap 3 places the two chambers 11, 12 in communication, and therefore the syringe cannot be re-used.

In order to prevent the ueer from withdrawing the plunger 2 In order to fill the cylinder 1 through Ite open end, locking means ere provided In the cylinder on the elde of Its open end.

Ae illustrated In Figures 4 and 5, these locking means can take the form of tabs 15 obtained from splits In the wall of the cylinder 1; these tabs are distanced from the wall towards the axis of the cylinder whilst coming closer to the base of the eald cylinder.

The tabs 15 are resilient, which enables them to be moved aside in order for the plunger 2 to enter the cylinder, then, once the flange 22 is positioned between the said tabs and at the base of the cylinder, all movement tending to cause the plunger to come out of the cylinder will be stopped by the said flange 22 coming into abutment against the tabs.

As shown in Figure 5, as the plunger 2 has in its running part a transverse section in the form of a cross there can be four tabs, each being situated in a quadrant left free by the plunger.

The stopping means could, naturally, be of any other design. By way of example, it is possible to create a flange inside the cylinder 1. To this end, the collar 19 of the cylinder 1 is set off on the end of the latter and has an internal circumference exceeding the interior of the cylinder which may be resilient in order to permit the insertion of the plunger 2 when it is put in place.

The syringe can in no way be filled again when It has already been used a first time since the cap no longer ensures sealing of the plunger in the cylinder.

In order even more reliably to prevent the re-use of the syringe there Is provided. In addition to the piercing of the cap preventing Intake of the liquid, means for partial destruction of the syringe.

To this end the plunger 2 has, a short distance from the end flange 22, a circumferential groove 23 which renders the plunger fragile and permits the user to break it after the perfusion. Once the portion of the plunger 2 coming outside the cylinder is broken it becomes impossible to move the remaining portion bearing the cap 3 in the direction necessary to draw in the liquid.

A manner of manufacturing the syringe will be described below. It is essential for the assembly to be carried out with a great deal of care in order not to pierce the fragile wall 34.

In a first embodiment, illustrated In Figure 6, the cylinder 1 ls provided in two parts, one part 16 of email length at the front of the syringe and having the base 13 and the nose 14, and the other part 17 being larger and having the cylindrical tube, the open rear end and the collar 19 which surrounds it.

The plunger 2 Is Introduced into the portion 17 until Its transverse face 22 lies flush with the front end face of the said portion 17 of the cylinder 1. The cap 3 ls then mounted on the retaining stud 4, the length of the pin 44 ls provided ln such a way that at rest It ls a sufficient distance from the fragile wall 34. In order to be certain not to push ln the cap 3 until it Is against the flange 22, which would risk causing the pin 44 to pierce the fragile wall 34, a template which stops the movement can be placed on the shank.

It ls also possible to provide a cap of substantially greater length than the length of the pin 44, such that the fragile wall 34 remains remote from the pin. As a variant, it is possible to provide a cap of which the membrane has at the front an orifice and, after mounting on the retaining stud, to set a fragile wall 44 in this orifice.

Once the cap 3 is thus put in place on the plunger 2, the template is removed if one has been used, then the said cap is topped with the cylindrical portion 16 which is fixed on the portion 17 by any known means such as glueing, ultrasonic welding...

It will be seen that the portion 16 has a length slightly greater than the cap 3 in order that the latter may be close to the base 13 but does not touch it so as not to risk piercing the wall 34 and thus rendering the syringe unusable .

In order not to risk untimely manipulation of the plunger, for example in the direction of the base 13 of the syringe, which would split the wall 34 before use of the said syringe, stopping means 18, 24 are provided in such a way that it is necessary to follow a precise procedure when using the syringe in order to move the plunger 2.

As can be seen in Figures 7 and 8, the stopping means can be formed by a lug 18 integral with the cylinder 1 and positioned in a recess 24 of the plunger 2. When the plunger 2 is positioned in the position shown by solid lines in Figure 8, it is impossible to move it axially in the cylinder. In order to use the syringe it is necessary to make the plunger 2 turn on itself in order to bring it into the position shown by dotted lines in Figure 8 for which the lug 18 no longer co-operates with the recess 24.

Preferably, in the illustrated embodiment, the plunger has the shape of a cross, each arm has a recess 24 and the lug - 10 has a triangular shape with the angle at the apex slightly less than 90°. Thus the unlocking of the plunger only occurs after a significant rotation, 90° at the maximum, which avoids inadvertent unlocking.

The syringe according to the invention is produced with the usual materials already approved by the medical authorities without the need for new choices. In particular, the pin 4-4or the needle can be made from a synthetic material, Identical to that of the body of the plunger. Thus it is certain that these materials are adapted to the medical use to which they are to be put.

Claims (9)

1) A single-use hypodermic syringe comprising: - a cylinder (1) receiving a plunger (2) provided with a cap (3) in the form of a hollow cylindrical body having a peripheral wall assuring water-tightness with regard to the cylinder (1), a closed front face (31), a rear face (32) provided with an opening (33) for fixing the cap (3) on the head (43) of a retaining stud (4) of the plunger (2), the closed front face (31) of the cap (3) having a wall (34) intended to be pierced by a pin (44) carried by the plunger (2) under the action of the pressing movement of the plunger (2), - the plunger (2) comprises a retaining stud (4) having a head (43) receiving the cap (3), characterised in that: - the retaining stud (4) carries the pin (44) on its head (43), - the rear face (32) of the cap comprises in addition to the opening (33) at least one other opening (35) situated outside the field of contact of the retaining stud (4) but on the inside of the disc covered by a disc (22), - the opening (35), placing the inside of the cap (3) in communication with a rear chamber (12) of the cylinder (1) when traction is exerted on the plunger.

2. ) A syringe according to claim 1, characterised in that the retaining stud (4) comprises a shaft (41) connecting the head (43) to an end disc (22) of the plunger (2).

3. ) A syringe according to claim 2, characterised in that the shaft (41) of the retaining stud (4) is substantially longer than the thickness of the cap (3) so that the cap (3) moves between a first position for which position its rear face (32) comes against the transverse face (42) of the head (43) of the retaining stud (4) at the moment of filling traction exerted on the plunger and another position for which position the rear face (32) is brought against the end disc (22) when the liquid is expelled out of the syringe at the moment of injection.

4. ) A syringe according to claim 3, characterised in that the pin (44) perforates the fragile wall (34) at the moment of expulsion pressure exerted by means of the plunger on the liquid in the syringe, the water-tightness of the cap being assured by the sealing of the openings (35) by the end disc (22) although in the position of retraction when a traction is exerted on the plunger the pin (44) is at a safe distance from the fragile wall (34).

5. ) A syringe according to any one of the claims 1 to 4, characterised in that it comprises the means of stopping (15) π?# ι >.y»τ which prevent the retraction of the plunger (2) to the exterior of the cylinder (1).

6. ) A syringe according to any one of the claims 1 to 5, characterised in that the plunger (2) is rendered fragile by 5 a circumferential groove (23) allowing the plunger to be g broken. I

7. ) A syringe according to any one of the claims 1 to 6, characterised in that the cylinder (1) is produced in two parts (16, 17) assembled one onto another. 10

8. ) A syringe according to any one of claims 1 to 7, characterised by the means of stopping (18, 24) which block any movement of the plunger (2) as long as a process of implementation has not been followed.

9. ) A single-use hypodermic syringe according to claim 1, substantially as hereinbefore described with particular reference to and as illustrated in the accompanying drawings.