Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Patent
1993-08-02
1995-02-21
Weiss, John G.
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
604135, 604136, A61M 520
Patent
active
053911512
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a subcutaneous injector of the disposable automatic or `one-shot` kind, that is to say, designed to discharge its contents into the user's body automatically and then to be thrown away. Such injectors are of great benefit in epidemics, and in third-world countries, and under battle conditions.
There have been many proposals for injectors involving a needle initially sealed within the body of the injector and acted on by a powerful spring released by an action on the part of the user, or by the act of placing the injector against the user's body (after release of a safety catch or pin), and the spring simultaneously acts on a piston to discharge the medicament or other contents through the needle.
Generally speaking these have involved a separate casing and spring mechanism into which is inserted a sealed ampoule or cartridge containing the medicament as well as the needle. After use the cartridge is thrown away and the injector is filled with a fresh cartridge, the spring being first re-compressed. Examples of such devices as shown in U.S. Pat. No. Nos. 2,832,339, 2,866,458 and 3,136,313. However fully disposable injectors or syringes are also known, i.e. ones in which the entire device is thrown away after use, and in these there is no separate cartridge. An example of a non-automatic injector of such a construction is shown in U.S. Pat. No. 4,059,109.
In the design of a disposable syringe or injector there are certain essential requirements, the most important being that of sterility and another important one is shelf life, i.e. a guarantee that there will be no corrosion, contamination, leakage or loss of sterility over a long period of storage. In the known disposable syringes and in the known disposable cartridges this is achieved by ensuring that the needle is in a wholly sterile environment, isolated from the atmosphere, right up to the moment of use. Generally speaking the needle is contained within a sheath and it penetrates the wall of this sheath as it advances under the force, direct or indirect, of the spring.
In some arrangements, e.g. that shown in U.S. Pat. No. 3,882,863, the needle is immersed in the medicament itself within the sheath, which in this case forms part of a cartridge. In others there is a piston carrying the needle, the medicament being behind the piston and the needle being in air, but still cut off from atmosphere.
In most of the known arrangements the injection of the medicament starts as soon as the needle penetrates the seal at the end of the sheath or the end of the barrel of the injector. Thus, from the moment the needle enters the user's body medicament is being dispensed. This is generally undesirable as what is really wanted is that the medicament should all, or substantially all, be placed below the skin.
The aim of the present invention is to overcome this problem and achieve a still further improvement in simplicity and reliability in a disposable syringe or injector.
According to the present invention there is provided a subcutaneous injector comprising;
a barrel having a chamber therein;
a first and second piston within the barrel each arranged to be slidable within the chamber the second piston carrying or being associated with an injection needle projecting away from the first piston;
a stop to restrain travel of the second piston towards an end of the barrel;
a releasable drive means; and
injection fluid substantially wholly contained in the portion of the chamber between the first and second pistons;
wherein upon its release the drive means urges the first piston towards the second piston so as to first cause the fluid contained therebetween to urge the second piston to move towards the end of the barrel, causing the injection needle to project therefrom, movement of the second piston eventually being restrained by the stop, further movement of the first piston then causing the injection fluid to be urged out through the injection needle.
According to another aspect of the invention we propose that a disposable subcutaneous injecto
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patent: 4178928 (1979-12-01), Tischlinger
patent: 4227528 (1980-10-01), Wardlaw
patent: 4258713 (1981-03-01), Wardlaw
patent: 4553962 (1985-11-01), Brunet
patent: 4983164 (1991-01-01), Hook et al.
Survival Technology Inc.
Weiss John G.
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