Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Patent
1989-11-21
1990-11-27
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
049733095
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a disposable syringe of the type comprising a cylindrical body inside which moves a plunger which, with the end of the body comprising a needle support, sealingly defines an inner chamber of variable volume, the plunger being connected to the inner end of a plunger stem allowing same to be moved.
Syringes of such type are used in the medical field. They are supplied in sterile condition and are normally intended for once only use in order to avoid any risk of contamination. These syringes are generally sold with their plungers in the filling position, that is to say pushed to the end of the stroke inside the body.
However, these syringes have one major disadvantage: their technical structure does not make it possible to prevent a contaminated syringe from being reused. This phenomenom is especially common in risk groups such as drug addicts, where one syringe can be used for several injections for one person or for different persons. Furthermore, it is not unfeasible that repeated use could occur inadvertently in hospitals.
Now, such practices create conditions which are very favourable for the propagation of very serious infectious diseases such as AIDS or hepatitis B.
In order to overcome these drawbacks, the idea was conceived to make disposable syringes.
Document EP-A-0 229 017 relates to a syringe of this type in which the plunger stem is detachably coupled to the plunger so as to ensure that the stem and the plunger are disconnected when a pulling action is exerted on the stem after the first injection. To this end, the plunger is extended on the side of the stem by a conical part followed by a cylindrical part and a disk having a peripheral flange. The plunger stem itself is provided with several tabs which, acting on the edges of the disk like a clamp, have areas of reduced thickness or break lines at the point of connection to the stem. When the injection is completed, the tabs come to rest on the conical part and spread apart, which results in that they break or become sufficiently deformed so as to be no longer able to grip the edge of the disk.
However, this solution is not satisfactory. In fact, the force acting on the gripping tabs is variable depending on several parameters: the viscosity, the diameter of the needle and the injection speed. A low viscosity of the fluid, a low injection speed, or a large diameter of the needle do not generate sufficient resistance to cause breaking of the tabs during the injection. The reliability of thys syringe is therefore risky. Besides, it is possible before the first use to dismantle the syringe and to block the tabs by surrounding them, for example with adhesive tape, which makes it impossible subsequently to spread them apart and thus to break them.
The essential purpose of the present invention is to overcome this drawback by providing a disposable syringe which allows only a single injection by preventing in a reliable and irreparable manner that the inner chamber of the syringe is filled for a second time.
To this end, this syringe of the type comprising a cylindrical hollow body inside which moves a plunger which, with the end of the body comprising a needle support, sealingly defines an inner chamber of variable volume, the plunger being connected to the inner end of a plunger stem allowing same to be moved, and means which make it possible, on the one hand, to make the plunger integral with the inner end of the plunger stem during the first filling of the inner chamber and, on the other hand, to cause the disconnection of the plunger from the inner end of the plunger stem upon any attempt to refill the inner chamber, is characterized in that the connecting means between the plunger and the stem comprise an intermediate memorization member which is formed such that, during filling, it ensures the integration between these two elements, while the injection, that is to say the pressure on the plunger stem, causes the intermediate member to be displaced relative to these two elements so that they will come apart upon
REFERENCES:
patent: 4144885 (1979-03-01), Stait
patent: 4699614 (1987-10-01), Glazier
patent: 4713056 (1987-12-01), Butterfield
patent: 4883466 (1989-11-01), Glazier
patent: 4915692 (1990-04-01), Verlier
patent: 4932941 (1990-06-01), Min et al.
Microtechnic
Yasko John D.
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