Syringe with self-retracting needle

Details Syringe with self-retracting needle Syringe with self-retracting needle

1992-09-04

1993-12-07

Yasko, John D.

Surgery

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

Treating material introduced into or removed from body...

604263, A61M 532

Patent

active

052679764

DESCRIPTION:

BRIEF SUMMARY
This invention relates to medical syringes, i.e. devices serving to inject, by means of a hollow needle, a substance which is usually medicinal, into the body of the patient by intramuscular, hypodermic or intravenous path. This operation is carried out either by a medical functionary or by the patient himself, in which case it is referred to as self-injection.
The utilization of so-called once-only syringes is now generalized. These are sold sterile in a sealed packet and are not to be reused in order to avoid all risks of accidental contamination from one patient to another. However, this very commonplace piece of equipment does not protect medical staff from accidental pricking and does not materially prevent the syringe being reused if the user does not voluntarily destroy it after use.
European patent application No. 0,307,367 describes a syringe with a self-retracting needle, comprising a body carrying at one end a means for supporting an injection needle, a plunger which is mobile within said body, a protective sheath within which said body can slide, and a spring disposed between the sheath and the body. There is also provided a sheath catching means on the body comprising first and second shoulders on the outer wall of the body and at least one flexible toe borne by the sheath so as to cooperate in abutment with the first shoulder for defining a first position of the body in relation to the blocking sheath in a first direction, the spring being compressed and the needle protruding from the sheath in this first position, and with the second shoulder for defining a second blocking position in the same direction, the spring being at least partially released and the needle being withdrawn inside the sheath in this second position. The transition from the first position to the second position is made by cooperation of the plunger with said first flexible toe for freeing the toe of the first shoulder at the end of travel of said plunger, thereby causing the body to retract into the sheath under the effect of the spring until it blocks in the second position.
Such a construction gives partial satisfaction in that, subsequent to injection, the needle is in fact retracted into its sheath. However, this syringe is quite complicated to manufacture, whence a negative impact on its price, and, moreover, is not very reliable. Indeed, the plunger does not cooperate directly with the blocking toes, but through the intermediary of an additional part comprised of an elastic ring, that unscrupulous people can deform to render it usable.
Furthermore, according to the document quoted, the needle is prevented from coming back out by providing a very small sheath hole, just wide enough for the needle which is pre-oriented slantwise to prevent it from coming back out of said hole once it has retracted into the sheath. Such an arrangement has the disadvantage of it being impossible to provide a syringe with interchanging needles since the connection ends of these needles would not be able to get by the sheath hole. In fact, it is often practical for medical staff to be able to adapt a needle of its choosing onto the syringe, e.g. a needle of large diameter to draw liquid into the syringe, and a needle of lesser diameter for injection proper.
The main object of this invention is to provide a new syringe devoid of this disadvantage.
Accordingly, the syringe according to the invention is of the general type, known to the above-mentioned document and recalled above. It differs from the aforesaid in that it comprises at least a second flexible toe and a third shoulder, respectively in the opposite direction to the first flexible toe and two first shoulders, respectively positioned on the sheath and wall of the body for blocking the body in the sheath when it is in the second blocking position, in the opposite direction to the first direction.
In this way, due to this second toe and third shoulder, the blocking of the body in the sheath to prevent the needle from coming back out no longer requires that the sheath exit hole be l

REFERENCES:
patent: 4664654 (1987-05-01), Strauss
patent: 4813940 (1989-03-01), Parry
patent: 4911693 (1990-03-01), Paris

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