GB724974A - Improvements in hypodermic injection apparatus - Google Patents

Abstract

724,974. Hypodermic injection devices. BECTON, DICKINSON & CO. March 18, 1953, No. 7516/53. Class 81 (2). A hypodermic injection device is provided with a tubular member adapted to contain gas under pressure and slidably mounted for retraction and projection within a hollow casing having a medicament, chamber adjacent its outer end, the tubular member having means movable therewith to expel medicament from the medicament chamber, a plunger being mounted on or abutting against the rear end of the casing and extending into the tubular member and movable means mounted on the casing and operable to retract the tubular member relative to the plunger thus increasing the pressure of gas within the tubular member and serving as a reaction member for the gas to move the tubular member to its projected position. The tubular member 22 is slidable within a casing 5 which is provided with a nose piece 6 having a rubber lined bore 8 for receiving a charge of medicament in an ampoule 11. A loading cap 7 is provided with a nozzle 14 having an orifice 16 fitted with a cannula 17 through which medicament may be discharged. A plunger 18 with a rubber or the like extension 19 is secured to the tubular member 22 and may slide within a bore in the nose piece 6 to contact a piston-stopper 12 of the ampule 11. A hollow stem portion 35 is mounted within the rear end of the casing 5 so that it abuts against a closure plug 34. and extends within the bore of the tubular member 22, a bushing 36 and packing. rings 37 being disposed between them. On removal of a cap 39 in the closure plug 34 and loosening of a plug 40 in the stem 35, the tubular member 22 and hollow part of the stem 35 are charged with compressed gas, e.g. nitrogen (apparatus not shown), the tubular member being in projected position. The cap 39 and plug 40 are then replaced and the device is cocked by turning the shaft of a pinion 25 with a wrench (not shown), so that a rack 26 and the tubular member 22 on which the rack is mounted are moved rearwardly to compress the charge of gas further. The tubular member 22 and rack 26 are held in cocked position by the pinion 25 which is secured against rotation by a spring-pressed ratchet 29. When an injection is to be made, the ratchet 29 is released by a handle 33 and the tubular member 22 is then projected by the charge of compressed gas so that the plunger 18 moves forwardly to eject medicament from the ampoule 11. A protective covering 51 of rubber or similar material is applied over the loading cap 7. Reference has been directed by the Comptroller to Specifications 568,237 and 697,643.