Patent ID: 7331936

Claim:
A cylindrical pushrod for the syringe needle-retracting safety injector, wherein the cylindrical pushrod comprises an outer cylinder, an inner cylinder, a push pole and an underpinned piece; the head of outer cylinder is provided with a sealing gasket; the push pole is set at the front end of chamber of outer cylinder, the front end of push pole closes the frontend opening of outer cylinder and outstands outside of the seal gasket, and appears as a tubular shape or projects partially in longitudinal direction, and the back end of said push pole is supported on the underpinned piece; the underpinned piece has a through hole for allowing the push pole to pass through and a underpinned patch for opening or closing the through hole, and the underpinned patch is set at the front end of the chamber of outer cylinder and supports the push pole; the inner cylinder is set inside the outer cylinder with its front end opened and its back end closed, and the top end surface of its cylinder wall supports the underpinned piece or the underpinned patch thereof to close the through hole; the tail of cylindrical pushrod is provided with a clamping structure for clamping the inner cylinder and the outer cylinder in a releasable manner, the clamping structure, after it is released, may make the inner cylinder slide backward to a distance for allowing the push pole pass through after opening the through hole under the action of retractive force of the needle, and is clamped within the outer cylinder again cylinder wall.