Single use syringe

Details Single use syringe Single use syringe

1990-12-21

1992-02-25

Yasko, John D.

Surgery

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

Treating material introduced into or removed from body...

604222, 604228, A61M 500, A61M 5315

Patent

active

050909614

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates generally to medical engineering and, more specifically, to disposable syringes applied for injections.


PRIOR ART

Some disposable syringes for injections known to be in widespread use nowdays comprise a cylindrical housing, a piston with a rod accommodated in said housing, and a needle fixing device (cf., e.g., disposable syringes available from Trumo Europe Co., Belgium). The syringes in question differ practically in nothing from disposable syringes now in extensive use in modern medical practice, the sole exception residing in that they are made of a cheaper material (i.e., polymer) and therefore are not subject to sterilization. This means that the construction of the known disposable syringes enables one to make repeated use of them, which may occur on account of inattention or unscrupulousness on the part of medical staff, or when injections are made by those who are in narcotic or alcoholic intoxication. All stated above proves to be of importance, since such cases are fraught with a danger of infection with the virus of AIDS, that of infections hepatitis, and of some other diseases.
One more prior-art disposable syringe is known to comprise a cylindrical housing accommodating a piston with a rod, and a needle fixing device (EP, A, 0282097).
The syringe under discussion features its needle fixed in a washer situated in the front portion of the syringe housing and capable of reciprocating lengthwise the axis of the housing. The piston disposed past the washer in the syringe housing and rigidly coupled to the rod is not engaged with the washer but has catches adapted for the piston to engage the washer when both of them interact with each other through their end faces. At the end of the injection when the piston and the washer get in contact with each other through their end faces, the piston becomes engaged rigidly, by means of the catches, with the washer, wherein the needle is fixed, with the result that any attempt to repeatedly draw a fresh portion of injectant substance in the syringe, the washer together with the needle is entrained by the piston into the housing of the syringe. As soon as the needle gets inside the housing it is offset with respect to the axis of the housing so that any attempt to perform an injection results in breakade of the injection needle.
However, the aforedescribed construction leaves room for reusing a syringe, since the piston gets engaged with the washer only when in its fully advanced position in the front portion of the housing. This causes the needle to be retracted into the housing, whereby the syringe gets unfit for further use. Should the piston be not brought to the fully advanced position during injection, the syringe can be applied for making an unlimited number of injections involving almost complete utilization of the holding capacity of its housing.


DISCLOSURE OF THE INVENTION

It is a primary and essential object of the invention to develop such a construction of a disposable syringe for injections that would prevent any possibility of reusing such a syringe.
The essence of the invention resides in the fact that in a disposable syringe for injections, comprising a cylindrical housing, which accommodates a piston with a rod and a needle fixing device, according to the invention, the piston and the rod are mechanically disengaged from each other, the diameter of the rod is less than the piston diameter and the rod is provided with an annular two-stepped slot, wherein its lower-depth portion is situated closer to the rod end facing the piston, a sealing cup made of an elastic material is located in said slot portion, the inside diameter of said cup being lesser that the rod diameter at the place where said lower-depth slot portion is situated, while the depth of said cup exceeds a clearance between the slot bottom in its lower-depth portion and the inner surface of the housing.
It is expedient that the rod diameter `d` be so selected as to satisfy the ratio d/D=0.9, where D stands for the rod diameter.
The dispo

REFERENCES:
patent: 4233975 (1980-11-01), Yerman
patent: 4687467 (1987-08-01), Cygielski
patent: 4775363 (1988-10-01), Sandsdalen
patent: 4923443 (1990-05-01), Greenwood et al.
patent: 4973308 (1990-11-01), Borras et al.

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