Automatic cannula withdrawing device for injection syringes

Details Automatic cannula withdrawing device for injection syringes Automatic cannula withdrawing device for injection syringes

1997-12-12

2000-01-18

McDermott, Corrine

Surgery

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

Treating material introduced into or removed from body...

604110, 604198, 604136, 604137, A61M 532

Patent

active

060153962

DESCRIPTION:

BRIEF SUMMARY
The invention concerns a hollow needle consisting of a hollow needle, a device housing and a device by means of which the needle, after being used, can be retracted back into the housing. The complete retraction of the needle into the housing after use will prevent unintentional injury to the user or another person.
In the state of current technology a hollow needle device of this type is known from WO 92/16248. An injection needle is placed prior to use on an hypodermic needle cylinder. Inside the housing the hollow needle is secured by means of a part which during the injection is dissolved or softened. The hollow needle is tensioned for retraction by a pressure spring inside the housing. If the above named part is dissolved or softened by the injection fluid, the fixing of the needle inside the housing is removed and the needle is returned into the housing by the pressure spring. There is the problem with this type of hollow needle that the timing of the initiation of the retraction is not exactly defined. It is also difficult to find a substance that, on the one hand, can be dissolved or softened by the injection fluid and, on the other hand, can unhesitatingly mix with the injection fluid. Probably for these reasons this hollow needle has not met with success in practice.
Another hollow needle device of this type became known in WO 92/05818. In this version the end of the hollow needle is fixed to a holding piece formed on the hypodermic needle cylinder. At the end of the piston stroke this holding piece with a cutting edge attached to a piston is separated from the hypodermic needle cylinder. The base of the hypodermic needle is simultaneously cut through by the cutting edge. Retraction then occurs by means of a pressure spring located in the housing. Tests have shown, that very strong forces are required to cleanly cut through both parts which are made of plastic and rubber. There thus arises a contradiction between the required thin wall of the injection base and the required wall strength to preclude the cold flow of plastic parts under stress to support the spring force. The required wall strength may not exceed a given amount when the long storage time of the hollow needles is taken into consideration.
Although the urgent need for such a hollow needle has been proven, in practice no such needle has as yet proven itself viable.
It is the task of this invention to create a hollow needle of this type which will avoid the above described disadvantages.


SUMMARY OF THE INVENTION

The task is solved for a hollow needle device of the type described by having the device incorporate a selector switch device which can be set to needle retraction after its use. In the hollow needle of this invention the retraction is initiated by the selector switch device. With such a selector switch device the activation timing for retraction can be determined exactly. Separation of plastic parts or a dissolution of substances by the injection fluid is not required with the hollow needle of this invention. The initiation force can be kept very small and the manner of construction can be appropriate for the material involved.
The hollow needle of this invention is envisioned in particular as an injection needle for a hypodermic needle. It can incorporate a Luer's attachment and be made inseparable from the hypodermic needle when placed on it. The hollow needle can, however, be permanently attached to the hypodermic needle from the very outset.
It is essential, that the customary norm requirements be satisfied by the hollow needle of this invention. There thus results a compatibility with standard hollow needles and standard hypodermic needles for emergencies, i.e., when due to circumstances no hypodermic needles or hollow needles of the type of this invention are available. In addition, the selector switch device can be located in a comparably small housing, so that externally the hollow needle can hardly be differentiated from a customary hollow needle. The extractor hollow needles customarily used in hospitals can be r

REFERENCES:
patent: 4747831 (1988-05-01), Kulli
patent: 5114404 (1992-05-01), Paxton et al.
patent: 5180369 (1993-01-01), Dysarz

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