| 摘要 |
A single use syringe including shoot back, or retraction, mechanism for biasing a needle, retained in needle holder, back into the interior of the syringe body after use. The needle holder is urged, by a spring in the front of the syringe body, to pass through a piercable seal formed in the front fact of the piston. The needle holder comprises an inner part containing the needle, an outer part engaging the interior wall of the syringe, and a frangible portion joining the inner and outer parts. A raised portion, or bump, is formed partially about the outer part of the needle holder, facing the seal in the piston. The raised portion provides an initial contact area with the plunger, to reduce the force required to break the frangible portion and trigger the shoot-back mechanism. The raised portion may consist of an uppermost portion for contact with the plunger, and a shoulder portion adjacent the uppermost portion to reduce dead space. The edge portion of the seal is thickened, and is relatively compressible, to reduce the dead space prior to triggering the shoot-back mechanism.
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