GB879427A - Improvements in or relating to inoculant injector instruments with adjustable ejection pressure control - Google Patents

Abstract

879,427. Hypodermic syringes. WALKER, G. W., ZIHERL, F., and ZIHERL, L. A. Dec. 31, 1957, No. 40441/57. Class 81 (2). A surgical injector comprises a body with a medicament chamber 21 at one end and a movable ejector 38 for discharging medicament therefrom, the ejector being retracted by fluid pressure and the chamber being recharged with medicament from a reservoir 49 which communicates with the chamber through the body and which extends externally of the body. A stainless-steel medicament chamber 21, having a small discharge aperture 27 is secured in a holder 20 attached to the body 11, by an apertured cap 22 which carries a resilient skin contact member 24. The forward end 41 of a hollow plunger 38 is moved into the chamber 21 to discharge medicament. A conventional hypodermic syringe 49 is secured to the rear end of the plunger 38 within the body 11. The chamber 21 is charged with medicament from the syringe 49 by operating the syringe plunger 52, a non-return ball check valve 43 in the hollow plunger 38 preventing back flow of medicament. A piston 14 slidable within bores 12, 13 in the body 11 is secured around the plunger 38, an accumulator spring 15 being disposed around the rear end of the plunger 38 between the rear face of the piston 14 and a sleeve 32 which is axially adjustable by a knob 33. Fluid is pumped from a reservoir 54 by a piston 61 reciprocated by a lever 64 into the bore 13 of the body 11, the fluid forcing the piston 14 and the plunger 38 rearwardly to compress the spring 15, ball check valves preventing back flow of fluid. The spring 15 may be compressed additionally by rotating knob 33 to displace the sleeve 32 forwardly if the plunger 38 is retracted only partially for injection of a volume of medicament which is less than the full capacity of the chamber 21. On pressing a trigger on the outside of the instrument, a valve stem 78 unseats a ball valve to allow fluid to flow from the bore 13 to the reservoir 54 so that the spring 15 is released and the plunger 38 forces medicament from the chamber 21 to an injection. The point of registry of indicia 50 on the syringe 49 with the knob 33 when the sleeve 32 is retracted gives the effective capacity of the chamber 21. Reference has been directed by the Comptroller to Specifications 798,826 and 798,827.