Abstract: A needleless hypodermic injector has a first substantially cylindrical section and a second substantially cylindrical section movably mounted in a first end of the first section. The first section comprises a hollow cylinder defining a chamber for a substance to be administered, the chamber having therein an externally communicating orifice at a second end of the first section and a piston slidably mounted in the hollow cylinder. The second section comprises spring means in the form of a coil spring and a plurality of disc springs arranged in an axial row for driving the piston in the first section from a retracted position in which the hollow cylinder contains the substance to be administered to an extended position in which the substance is substantially completely discharged through the orifice from the chamber. A bushing is slidably mounted between the piston and the spring means and is capable of engaging the piston as it travels from the retracted position to the extended position.

Abstract: A disposable plastic adaptor connects a medicine vial to a needleless injector. It includes a hollow, generally cylindrical body member having a top end and a bottom end, with a wall dividing said hollow body into a generally cylindrical top end cavity and bottom end cavity. The bottom end cavity is adapted to slide over the top end of a medicine vial and the cavity wall includes a plurality of detents which prevent removal of the adaptor from the vial. The top end cavity is adapted to be twist connected to the end of a needleless injector. A fluid connector member is mounted within the body member and it comprises a sharp tipped probe extending axially downwardly within the bottom end cavity and an axial projection with a concave end face extending axially upwardly within the top end cavity. An axial bore extends through the fluid connector member to flow connect the concave end face and the probe tip.

Abstract: A needleless hypodermic injector includes an elongated cylindrical casing defined by front and rear telescoping sections, with an injection orifice at the closed front end of the front section and a push button trigger at the rear end of the rear section. A piston slidably mounted in a cylinder in the front section of the casing moves rearwardly to define a medicine chamber for receiving medicine from a bottle directly or through a valve incorporated in the front end of the front casing section. The piston is moved rearwardly by an internally threaded collar on the externally threaded cylinder, the collar pressing against a bushing, which presses against disc springs in the rear section of the casing. A latch mechanism retains the bushing against the springs until the trigger is pressed, at which time the springs drive the piston forward to discharge the medicine from the chamber through the injection orifice.