Disposable syringe with slit valve

Claim 1

A syringe assembly for injection comprising: inner and outer tubular members with the inner member having an outer wall to wall dimension less than the inner wall to wall dimension of the outer tubular member to enable the inner tubular member to be telescoped within the outer tubular member; a rupturable closure sealing the forward end of the outer tubular member; a flexible closure secured at its outer end portions to a narrow neck portion on the forward end of the inner tubular member with the central portion of said flexible closure normally extending straight across and adjacent the neck portion of the open end of the inner tubular member; a slit in the relatively small central portion of the flexible closure which is not secured to the neck portion and which opens to provide a passage communicating the interior of the inner tubular member with the interior of the outer tubular member in response to pressure from within the inner tubular member, which flexes the central portion of the closure outwardly from its normal straight across position, and which remains in or returns to the normal straight across position to close the passage in the absence of said internal pressure; a piston ring portion on the forward end of the inner tubular member in sliding engagement with the inner walls of the outer tubular member; a piston plug slidably received within the inner tubular member in sealing engagement with the inner wall of the inner tubular member; means connected to the piston plug and extending rearwardly beyond the inner tubular member for actuating the piston plug axially relative to the inner tubular member; a hypodermic needle; collapsible means on the forward end portion of the outer tubular member supporting the needle with the rearward end of said needle terminating a short distance in advance of the rupturable closure when in uncollapsed position and penetrating through the rupturable closure when in collapsed position; and actuating means for axial displacement of the inner tubular member into the outer tubular member for displacement of fluid from within the outer tubular member.