US Patent 7267664 Self-locking safety disposable syringe with needle protection after use

The invention refers to the field of self-locking safety disposable syringes with needle protection after use. The syringe comprises a hollow barrel (1) ending on its lower side with an internal seat (2) adapted to receive a hub (3) carrying a cannula (4). A hollow driving rod (5) adapted to house a spring (6) is inserted in the hollow barrel. Such rod is closed at its lower end by an extracting element (8) that can slide into the hollow driving rod. The extracting element has an annular notch (9) in which a sealing ring rubber gasket (10) is housed that seals the internal wall of the hollow barrel (1). The extracting element (8) with related sealing ring gasket (10) form a liquid sucking and compressing plunger.