Syringe

Claim 1

A syringe comprising a container, a needle capable of co-acting with one end of the container, a plunger which is located inside the container and which co-acts sealingly with the inner surface thereof, and a rod-shaped element which co-acts with the plunger and which is arranged for rectilinear reciprocating movement relative to the container, such that linear movement of said element in a first direction from said one end causes the container to be filled with liquid to be injected, while linear movement of the element in a second direction causes the liquid to be emptied from the container through the needle, there being provided between the piston and the rod-shaped element, for their mutual co-action, a means which during linear movement of said element in said first direction holds the plunger against the rod-shaped element and which upon linear movement of the element and the plunger in the opposite direction takes an inactive state in which co-action between the rod-shaped element and the plunger is discontinued, therewith to prevent further liquid from being drawn into the container upon renewed linear movement of the rod-shaped element in the first direction, characterized in that means are provided for imparting rotational movement to the rod-shaped element relative to the plunger upon linear movement of said element; and in that the rod-shaped element and the plunger mutually co-act through the intermediary of a screwthread.