Hypodermic syringe

Details Hypodermic syringe Hypodermic syringe

1996-11-29

1999-11-09

Stright, Jr., Ronald K.

Surgery

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

Treating material introduced into or removed from body...

604195, 604218, 604241, A61M 500

Patent

active

059804874

DESCRIPTION:

BRIEF SUMMARY
FIELD OF INVENTION

This invention relates to hypodermic syringes and similar devices such as are utilised both for the injection of medicine into the body tissues of, and the taking of fluid samples from, human and animal patients. Thus it may also be applied to additional equipment requiring a similar function. It is particularly concerned with reducing the risk of cross infection through contact with or use of such syringes.
Disposable syringes are used throughout medicine and once used are usually discarded. However, the used needles are notoriously difficult to deal with; unsheathed they easily puncture bags and even when replaced within their originally sterile protective sheaths, they can fall out and present a hazard. This invention addresses the problems of inadvertent stick injuries caused to health workers with contaminated needles after use, particularly when they are being re-sheathed prior to disposal and, after disposal, to ancillary personnel such as cleaners, the prevention of unauthorised re-use of syringes and the ease of transportation of used devices.


BACKGROUND OF THE INVENTION

If problems such as those typified in the field of invention are to be overcome, needle and syringe combinations must be inexpensive to produce, easy to operate and should conform to applicable standards in order that they be widely utilised in the avoidance of such problems.
UK Patent Application GB 2 266 667 A describes such a combination wherein a standard needle is coupled to a detachable end-piece which is affixed to a syringe barrel. A flanged plunger which runs within guides integral to the barrel may, upon termination of use, be engaged into said endpiece by means of rotation in the manner of a bayonet type fixing. Having achieved engagement between said plunger and endpiece the combination is withdrawn within the barrel of the syringe thus shielding the needle.
This system suffers from the fact that as the plunger may be repeatedly moved to the extremes of axial travel allowing both the intake and expulsion of fluids, an unavoidable volume (`dead-space`) of unexpelled fluid is inevitable since a further rotary motion is required in order to engage to the endpiece and there is also no means provided of evacuating fluid from within the central bore of the endpiece. It may be noted that such a dead-space is undesirable and, whilst this cannot be completely eliminated, it is preferred that this unexpelled volume be minimised.
Furthermore this syringe requires that both the plunger and endpiece are sealed to the barrel in order to eliminate the leakage of fluid. This is achieved by the use of separate compressible sealing components which are captured between the components to be sealed. Whilst the same compressible component is utilised twice to serve this purpose, there is undesirable additional cost associated with this solution.
Additionally it may be noted that this syringe utilises an annulus of perforations which are required to break or tear tangentially upon rotation of the plunger. This requires that the detachable portion of the endpiece and its support structure are formed integrally to each other as one component.
The device is such that tearing force occurs in one direction and in one plane. It has been observed that this single action does not provide the optimum method of plunger/endpiece
eedle. Furthermore it is identified that components incorporating such break-off features are sometimes difficult and expensive to develop and may exhibit varying properties which may affect their performance.
Additionally, whilst the syringe provides a means of attaching the plunger/endpiece
eedle combination to the barrel upon full retraction of the needle, there is little to inhibit the complete withdrawal of this combination from the barrel component, whereupon it would be re-exposed. In this eventuality the needle is once again undesirably exposed and/or subject to interference.
GB 2 266 667 A represents the closest prior proposal currently known to the applicant and the present invention was deve

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patent: 5256151 (1993-10-01), Chul
patent: 5263933 (1993-11-01), Novacek et al.

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