Single use injection device

Details Single use injection device Single use injection device

1995-01-09

1997-03-25

McDermott, Corrine M.

Surgery

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

Treating material introduced into or removed from body...

604218, A61M 500

Patent

active

056139519

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention pertains to an injection device and more particularly to a single use injection device.
In the case of a known injection device--in accordance with FR-A-26 32 190--an anti-reuse device is used for the prevention of the multiple use of the injection device. This anti-reuse device is placed between the piston-receiving inner space of the injection device and the injection needle, and exhibits a cage and a retaining member for a switching member that is provided in the direction of the piston-receiving inner space of the injection cylinder with a flow-through opening, the diameter of which is smaller than a diameter of the switching member, which is configured as a ball. The retaining member, which is placed on the face of the cage that is turned towards the injection needle, is in the present case an elastically deformable disk with a bore that has an inside diameter that is smaller than the outside diameter of the ball. If now, after the injection medium has been drawn up into the inner space of the injection cylinder, this injection medium is expressed through the injection needle, the full injection pressure acts upon the switching member that is adjacent to the elastically deformable disk, the result of which, because of the large surface of the ball that forms the locking member, this ball, in conjunction with the elastic expansion of the opening of the disk, is pressed through this disk and falls into an intermediate chamber that is connected to it. After the ball has passed through the opening in the elastic disk, the injection medium can now enter past the ball into the hollow needle, or more specifically, the longitudinal bore of the injection needle, and thus be injected. If an additional injection medium were now supposed to be drawn up by the injection device, the piston creates inside the injection needle a negative pressure which, because of the large surface of the ball, acts in such a way that the locking member is now advanced from the injection needle to the elastically deformable disk and lies against it, thus forming a sealing closure. In this way, any further drawing of an injection medium into the inner space of the injection cylinder is prevented. In the area of the cage and in the area of the intermediate chamber that receives the ball after it has passed through the elastic disk, there are, in the direction of the longitudinal axis of the injection device, fixed links or continuations and projecting parts in order to ensure a proper flow- through of the injection medium into the various locations of the locking member when the injection medium is drawn into the inner chamber before the use of the injection device and during the expression of the injection medium through the injection needle during the injection. With an appropriately longer configuration of that part of the intermediate chamber which is located between the cage and the injection needle, an aspiration can be made possible that is dependent on the movement space of the ball in the direction of the longitudinal axis of the injection device. What is disadvantageous about this configuration is the fact that the sure functioning of the injection device is not ensured through the use of an elastic disk, and different mounting parts are needed for each size of injection device.
An additional known injection device of the same type--in accordance with WO-A-92/04064--likewise exhibits an anti-reuse device for the prevention of multiple use of the injection device. The anti-reuse device is again located between the piston-receiving inner space of the injection device and the injection needle, and exhibits a cage that is made of an elastically deformable material, for example, an elastomer, for the retaining member, which is formed by means of a ball. In the cage, a retaining member is formed that is made from a circumferential sealing projection, in conjunction with which a diameter of the bore that is surrounded by the retaining member is smaller than the outside diameter of the ball. This

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