Replaceable cartridge hypodermic syringe having sterile maintenance of needle

Claim 1

A hypodermic syringe comprising a cylindrical barrel provided at its proximal end with a removable cartridge clamping means including a cartridge plunger-actuating rod, a cartridge in said barrel containing a reciprocable plunger actuatable by said rod, said barrel having its distal end internally threaded for removably attaching a needle assembly thereto, said cartridge being sutstantially cylindrical throughout its length, said barrel having an aperture, said aperture having a length and width sufficient to permit the ready insertion of said cartridge, said barrel being adapted to house said plunger-containing cartridge intermediate its ends in peripherally spaced relation thereto throughout its length and being constructed to permit the ready insertion and removal of said cartridge into and out of said barrel, said cartridge being provided with a penetrable seal at its distal end and with said reciprocable plunger normally positioned adjacent its proximal end, the distal end of said plunger-actuating rod being provided with means for operable connection with the plunger of said cartridge when said cartridge is housed within said barrel, a needle assembly including a central body provided with an external flange seated against the distal end of said syringe barrel, a tapered stud of reduced dimensions projecting from the outer end of said central body and having a longitudinal axis forming an extension of the central axis of said body, an annular wall projecting from the inner end of said central body and having a central longitudinal axis forming an extension of the central axis of said body, said annular wall being located within the distal end of said barrel and closing the distal end of said cartridge in the barrel, said distal end of said barrel seated against the inner end of said central body, said distal end of said cartridge being in nonfluid tight peripherally spaced relation with respect to said annular wall, and the periphery of said annular wall being in threaded engagement with the internal thread at the distal end of said barrel for removably attaching said needle assembly to said barrel, said central body, tapered stud and annular wall being of a one piece plastic construction, a double-ended hypodermic needle having an intermediate portion axially embedded within said body and said tapered stud, the proximal end of said needle projecting axially into the space defined by said annular wall and the distal end thereof extending beyond the outer end of said tapered stud, and the projecting proximal end of said needle penetrating through the penetrable seal at the distal end of the cartridge seated against said central body and enclosed by said annular wall, the projecting proximal end of said needle being of a length less than that of the projecting distal end thereof and less than longitudinal length of said annular wall.