Selflocking syringe

Abstract: The invention regards a selflocking syringe. The syringe rod is equipped with an extractor which, when the syringe plunger is pushed to the end of the stroke, hooks the needle and withdraws it by means of a preloaded spring to the inside of the rod, into a protected and inaccessible position, thus making the syringe unserviceable already after its first use.

Description: The present invention relates to selflocking syringes, and more particularly to a syringe with a needle which disappears thus becoming inaccessible after the use of the syringe. The dangers originating from the reutilization of already used syringes and the problems caused by the abandonment in public places of used syringes complete with needle are well-known, especially the damages which any prick of these syringes may cause to anybody who picks up and inadvertently handles abandoned syringes. In order to obviate these problems, injection syringes have already been proposed wherein the needle is automatically retractable after its use. One of these syringes is known from WO-A-90 06 146 (on which the preamble of claim 1 is based) and it comprises: a hollow syringe cylinder body defining a hollow cylindrical nose end; a cylindrical needle holder positioned in said nose end said needle holder having an interior end defining a step surrounding a needle holder interior cavity and said nose end having an interior step surface preventing said needle holder from moving in an outward direction and allowing said needle holder to be extracted from inside of said hollow cylinder body: a plunger positioned within said cylinder body: a rod connected to said plunger and extending into said cylinder body, wherein each of said rod and said plunger has an axial hole passing therethrough; a sliding extractor is positioned within said axial hole of said plunder and within said hole of said rod: a recovery tension spring is positioned within said hole of said rod and connected to said sliding extractor; said extractor being movably displaceable from an advanced position, surrounded by said plunger with a portion protruding from said plunger in the needle holder direction, and a retracted position, fully retracted into said rod, positioned away from said needle holder, said extract or having a hooking head protruding from said plunger in said advanced position to engage said interior covity of said needle holder to join said extractor to said needle holder; and hooking means defining a connection between said rod and said extractor to maintain said extractor in said advanced position and recovery spring under tension, a plug being applied to a free end of said rod with said spring positioned between said plug and said extractor. But such a syringe is relatively complicated and it cannot be assembled mechanically. It is one object of the invention to provide a selflocking syringe which, besides to solve the above-mentioned problems, is simpler in its constuctive features and may be mechanically assembled due to a new and original combination of components, namely plunger, plunger rod and spring retracting means associated thereto. The selflocking syringe of the present invention solves the above problems in accordance with the characterizing part of claim 1. It becomes substantially unserviceable after its first use as the syringe needle disappeared in the cylinder body, thus preventing it from remaining exposed and representing a potential danger when the syringe is abandoned. Further details of the invention will be more evident in the description given below which refers to the enclosed drawing showing an indicative and non-limiting example of practical realization of the selflocking syringe. In this drawing: the picture 1 shows, in longitudinal section, the syringe before use and with needle protected by means of a cap; the picture 2 shows, in longitudinal section, the syringe in use conditions; the picture 3 shows a magnified detail of a part of the syringe marked with a circle in the picture 1; the picture 4 shows, in longitudinal section, the syringe after use, that is with withdrawn needle; the picture 5 shows an example of the equipment used to make ready the plunger with extractor rod and recovery spring. The syringe at issue essentially consists of a hollow cylinder 10, a needle 11 and a plunger 12 with a respective operation rod 13. The cylinder 10 shows at the back a seizing flange 10a and ends on the front side by a nose 10b to which the needle 11 is applied. This needle is applied to a needle-holder 11a which is introduced like a plug into a seat defined by the nose 10b from the inside of the cylinder 10 and which is extractable, as stated below, towards the inside of the cylinder. The plunger 12 slides with tightness into the cylinder 10 and is steadily constrained, in 12a, to the rod 13 which extends and protrudes towards the rear side of the cylinder, beyond the seizing flange 10a. The rod 13 and the plunger 12 are provided with an axial through hole 14 in which an extracting element 15 and a recovery spring 16 are assembled. The extractor 15 can slide in this through hole 14 and shift from an advanced position, at the same level as the plunger 12, to a back position, far from the plunger. The opposite ends of the recovery spring 16 are respectively fastened to the extractor 15 and to a plug 17 applied on the free, that is rear, end of the rod 13. Advantageously, the forging ends of the recovery spring 16 are let, and so fastened, into the material composing the extractor 15 and the end plug 17. Therefore, the three component parts 15, 16, 17 remain permanently connected and can be handled and assembled jointly and easily. In its advanced position, the extractor 15 is integral with the rod 13 and keeps the spring 16 loaded since the latter is stretched, having its opposite end fastened and clamped with the plug 17, as it is possible to infer from the pictures 1 and 2 of the drawing. For its stop in the advanced position, the extractor 15 is provided with a peripheral step 15a - picture 3 - which engages itself in the shoulder collar 14a obtained in the hole 14 of the rod 13 thus normally preventing the extractor 15 from shifting backwards. Furthermore, this extractor is equipped with a hooking head 15b, for example in the shape of a mushroom, turned towards the needle-holder 11a and protruding from the piston 12 when the extractor is in the advanced position. The hooking head 15b of the extractor 15 must get constrained with the needle-holder 11a when the plunger is pushed deeply into the cylinder. For this constraint, the needle-holder 11a is provided with a rear notch 18 having at least an inner projection 18a, for example annular, with which the hooking head 11b spring joins together when the plunger reaches the end of the stroke. In the end, it should be noted that the shoulder collar 14a in the hole 14 of the rod 13 must become deformed, be drawn and destroyed on the step 15a of the extractor 15 when the plunger 12 is pushed deeply into the cylinder and the extractor 15 is hooked to and supported against the needle-holder 11a. In the syringe described above, the extractor 15, the spring 16 and the plug 17, connected one with the other, are previously assembled into the rod 13 by means of an equipment 19 such as the one represented in the picture 5 so that the extractor 15 is hooked in the advanced position and the spring 16 is loaded, that is under tension. Such an assembly is carried out with the help of a thrust tool 20 which passes through a hole 17a obtained in the plug 17 and which is supported and pushes against the extractor until it gives rise to the hooking of the latter one to the collar 14a and the introduction of the spring and plug into the rod. The hole 17a of the plug 17 can be closed. Subsequently, after applying the plunger 12 to the rod provided with the described equipment, the whole is introduced into the cylinder 10 already equipped with needle 11. The syringe is now ready for packaging and for a following use as a normal syringe. However, with this syringe, the needle 11 is withdrawn upon its use to the inside of the rod 13 thus making the syringe unserviceable and the needle inaccessible. As a matter of fact, when the plunger, advancing during the injection, reaches the end of the stroke, the head 15b of the extractor 15 spring hooks the needle-holder and, when pushing on the rod deeply, the collar 14a in the rod 13 on the step 15a of the extractor itself becomes deformed and is drawn. Then, the extractor, no longer constrained to the rod 13, is shifted to the back position by means of the preloaded recovery spring 16 and pulls away the needle hooked through the needle-holder, as shown in the picture 4 of the drawing.

Claims: A selflocking syringe, comprising: a hollow syringe cylinder body (10) defining an hollow cylindrical nose end (10b); a cylindrical needle holder (11a) positioned in said nose end (10b), said needle holder (11a) having an interior end defining a step (18a) surrounding a needle holder interior cavity and said nose end (10b) having an interior step surface preventing said needle holder from moving in an outward direction and allowing said needle holder to be extracted from inside of said hollow cylinder body; a plunger (12) positioned within said cylinder body: a rod (13) connected to said plunger and extending into said cylinder body, wherein each of said rod (13) and said plunger (12) has an axial hole (14) passing therethrough; a sliding extractor (15) is positioned within said axial hole (14) of said plunger (12) and within said hole of said rod; a recovery tension spring (16) is positioned within said hole of said rod and connected to said sliding extractor (15); said extractor (15) being movably displacable from an advanced position, surrounded by said plunger with a portion protruding from said plunger in the needle holder (11a) direction, and a retracted position, fully retracted into said rod, positioned away from said needle holder (11a), said extractor (15) having a hooking head (15b) protruding from said plunger in said advanced position to engage said interior cavity of said needle holder (11a) to join said extractor to said needle holder, and hooking means defining a connection between said rod (13) and said extractor (15) to maintain said extractor in said advanced position and recovery spring under tension, a plug (17) being applied to a free end of said rod (13) with said spring positioned between said plug (17) and said extractor (15), characterized in that said hooking means include a peripheral step (15a) formed on a peripheral surface of said extractor (15) and a shoulder collar (14a) formed on an interior surface of said rod (13). The selflocking syringe as claimed in claim 1, wherein said plug (17) has a hole (17a) allowing access to an interior of said rod for passage of a thrust tool (20) for manipulating said extractor and for loading said recovery spring, and wherein the opposite ends of said recovery spring (16) are fastened into material composing said extractor (15) and into material composing said end plug (17) to define a three component part set including said extractor, said spring and said plug which remain permanently connected thereby facilitating handling and assembling.

Inventors: MAZZARA ISIDORO, MAZZARA, ISIDORO
Applicants: PROFARM SPA, PROFARM S.P.A.
Application year: 1992
Main classification: A61M5
IPC codes: A61M5, A61G12