Vacuum syringe

Claim 1

A sampling syringe for the withdrawal and storage of blood and the like, the syringe including: (a) an outer housing of generally tubular configuration and having an inner bore of a generally constant cross section and with at least one bypass recess formed in the inner bore, said bypass recess positioned at a determined distance from and near an open rear end of the housing, the housing having a front partially closed other end and a passageway therethrough; (b) meAns for selectively closing the passageway of the partially closed front end of the housing so as to prevent the passage of air, fluids and the like; (c) a test tube of integral construction and having a closed rear end and having a main portion of generally tubular configuration, the test tube slidable in the bore of the outer housing, and (d) a resilient piston mounted in and closing the front end of the test tube, said piston having a plurality of ringlike sealing surfaces sized so as to be slidable in the bore of the outer housing while engaging said bore in a fluid-flow sealing manner, the piston having at least one fluid-flow passageway provided through the wall of the piston with one end of the passageway opening to the interior of the plunger and the other end terminating at the piston outer surface and between adjacent ringlike sealing surfaces, said sealing surfaces disposed to provide a sealing extent to the rear of the outer surface flow passageway termination of the piston so that when this passageway termination is brought in way of the housing bypass recess this sealing extent of the piston to the rear of the termination extends beyond the bypass and into the bore of the outer housing so as to seal the bore from any unwanted flow of air, fluid and the like from and to the open end of the outer housing.