Injector for liq. medicament- esp. vaccine-hand gun - of simple trouble free, inexpensive design to suit mass vaccination

摘要

A pressure injector of measured doses of liq. medicament, partic. a vaccine injection gun. The injector comprises a cylindrical chamber with movable piston to discharge liq. through a nozzle at one end of the chamber. The piston is grooved longitudinally for a distance starting from its front face. As the piston is retracted from the nozzle end of the cylinder, liq. is sucked in via the longitudinal groove which is aligned with a cylinder wall inlet as the piston is advanced on the delivery stroke, it is rotated slightly so that the piston groove no longer coincides with the inlet orifice. The piston may have a number of grooves evelyn pitched atound its circumference; means are provided to rotate the piston thro. half one pitch in the same direction at the end of both suction and delivery strokes. Alternatively, the piston may have a single longitudinal groove; in this case the piston is rotated to align the groove with the inlet orifice with piston fully advanced, and to obscure the orifice before the delivery stroke starts. Used for subcutaneous and intradermic injections of liq medicament, esp. vaccines. Partic. suitable for mass vaccination programmes, e.g. in underdeveloped countries. The injector takes the form of a lightweight, inexpensive and uncomplicated hand gun. It is partic. reliable, robust and trouble free.