Syringe

Details Syringe Syringe

1990-05-16

1991-07-16

Yasko, John D.

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

604228, A61M 500

Patent

active

050321145

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a syringe, and more particularly but not exclusively, to a hand-operated syringe of the kind which comprises a container, a needle which cooperates with one end of the container, a plunger which is located inside the container and which co-acts sealingly with the inner surface thereof, and a rod-shaped element which co-acts with the plunger for reciprocating plunger movement in said container. The rod-shaped element is capable of being displaced rectilinearly relative to the container, such that linear movement of said element in a first direction from said one end causes the container to be filled with liquid to be injected, while linear movement of the element in a second direction causes the liquid to be emptied from the container through the needle.
The present invention is concerned primarily with a disposable-type syringe, by which is meant a syringe whose container can be filled with injection liquid only once, i.e. after being once filled it can never be filled again.


BACKGROUND PRIOR ART

Several variants of syringes of this kind are known to the art.
In a first variant of these known syringes the mutual co-action of the plunger and the rod-shaped element is facilitated with the aid of means located between said plunger and said element, this means holding the plunger to the rod-shaped element during linear movement of the element in said first direction and also during linear movement of the element in said second direction. Thus, there is no detachable connection between the plunger and the rod-like element and the plunger will thus be moved backwards and forwards in the container in precise response to the direction of movement of the rod-shaped element.
This means that the container can be filled with liquid each time the plunger is moved away from the needle, and emptied of liquid each time the plunger is moved towards the needle, thereby enabling the syringe to be used over and over again.
The repeated use of one and the same syringe has proven to constitute a serious risk of spreading disease, such as AIDS.
Consequently, single-shot syringes have been proposed, which can be used only once for injection purposes, after which the container can no longer be filled.
An example of such single-shot syringes is described and illustrated in European Patent Application Ser. No. 0 229 017, in which syringe the plunger and rod-shaped element co-act with one another through the intermediary of hook-shaped members which are moved out of engagement with the plunger upon movement of the rod-shaped element towards the needle.
The Swedish Patent Specification Publ. No. 413 838 describes and illustrates a so-called single-shot syringe in which the rod-shaped element incorporates a weakening at a location adjacent the plunger, and in which means are provided for twisting the element relative the plunger subsequent to completing an injection, thereby fracturing the rod-shaped element at the weakened location.
The Swedish Patent Specification Publ. No. 438 598 also teaches a single-shot, or disposable, syringe.


SUMMARY OF THE INVENTION



TECHNICAL PROBLEMS

When viewing the earlier prior art it will be seen that a technical problem is one of providing a syringe which can be filled with injection liquid in a conventional manner and in which when the plunger is moved towards the needle there is activated a means which renders it impossible to refill the container with liquid, since the ability of the syringe to draw in liquid by suction is placed out of function, irrespective of how careful the plunger is moved towards the needle.
It must also be considered a qualified technical problem to provide a disposable, or single-shot hypodermic syringe which is so constructed as to render it impossible to use the syringe more than once, even though conscious efforts are made to do so.
Another qualified technical problem resides in the realization that a syringe which is to resolve the aforesaid technical problems should be provided between the plunger and the rod-sha

REFERENCES:
patent: 4391272 (1983-07-01), Staempfli
patent: 4699614 (1987-10-01), Glazier
patent: 4861338 (1989-08-01), Mathiesen et al.
patent: 4906231 (1990-03-01), Young
patent: 4908020 (1990-05-01), Pettersen
patent: 4950243 (1990-08-01), Estruch

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