Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Patent
1993-10-12
1995-04-18
Yasko, John D.
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
604110, A61M 500
Patent
active
054074363
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to protection against accidental skin piercing by needles of used hypodermic syringes or medical samplers, or the like.
A used such needle poses a health hazard and considerable attention has been directed to reducing the hazard by disposal regimes and means of sheathing the needle tip after use. Also, numerous proposals have been made for automatic retraction of a needle after one use, but to date no-one appears to have put forward a practical proposal that is reliable and commercially viable to make, certainly not so that production costs are reasonable compared with the costs of existing products without needle retraction.
The present invention aims to improve practicality and viability in providing for reliable automatic needle retraction.
It is standard for a syringe or sampler construction to include a hollow cylindrical body, a plunger slidable in the body, and a seal between the plunger and the body effective during sliding of the plunger to express syringe or sampler contents and/or to draw them in before sample expression. Hitherto, acceptedly satisfactory seals have been expensive items made of rubber.
According to one aspect of this invention, there is provided a hypodermic syringe or sampler body and slidable plunger construction that permits direct sealing between the plunger and the body, at least for operation only once but including a number of movements at least for initial entry, retraction to load, and pressing down to express. A suitable construction comprises a hollow cylindrical body, preferably circular cylindrical, and a plunger having at least a hollow head with a continuous outer rim to engage the body internally when slid therein; the plunger head rim, as made, being nominally of greater external size than internal size of the body, but being radially inwardly deformable by the body when slid therein, preferably with some temporary radially outward deformation of the body itself as the plunger head travels along the interior surface of the body.
Satisfactory mouldable synthetic plastics materials for the plunger head, preferably the entire plunger, and the body, can have different resistances to deformation, typically less resistance for the plunger head and more resistance for the body, at least for both as made. Inherently softer or more deformable and harder or less deformable materials for the plunger and the body, respectively, include, for the body, polypropylene, preferably nucleated (at least 0.2% preferably 0.3-0.35%) polypropylene having good clarity/transparency, strength and resistance to shrinkage/warpage during moulding (homopolymer having proved promising in prototypes); and, for the plunger, polyethylene, preferably high-density to give good seal performance and stability (Melt 7 having proved promising in prototypes). At least for such specified materials, the difference in nominal diameters of body interior and plunger head exterior can be up to 50 microns or more, preferably at least 25 microns.
Direct sealing between such a plunger head and body that is satisfactory for intended single use of a hypodermic syringe or sampler eliminates separately made and hitherto relatively expensive seal provisions.
A large number of generally impractical or uncommercial prior proposals for hypodermic syringes with automatic needle retraction after use have been considered. They typically require the hollow needle to be fixed to a holder, commonly called a `hub`, and for such hub to be acted upon by a compression spring and by releasable detent or trigger means to release spring action and forcibly send the needle and its holder into the interior of the syringe or sampler, often into the plunger which will be hollow at least for that purpose. Generally, however, such provisions, including detent or trigger means, involve or are involved in an assembly attachable to the forward end of the syringe or sampler body and/or plunger, and/or in a part or parts fitted interiorly of the body, whether to the body or to the plunger or to both.
REFERENCES:
patent: 772114 (1904-10-01), Pappenheim
patent: 2037768 (1936-04-01), Dickenson
patent: 4838869 (1989-06-01), Allard
patent: 4994034 (1991-02-01), Botich et al.
patent: 5049133 (1991-09-01), Pascual
patent: 5211629 (1993-05-01), Pressly et al.
Jeffrey Peter
Toft John F.
Safe-T-Limited of Laurel House
Yasko John D.
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