GB729316A - Improvements in hypodermic syringes - Google Patents

Abstract

729,316. Hypodermic syringes. NATIONAL RESEARCH DEVELOPMENT CORPORATION, June 19, 1953 [March, 24, 1952], No. 7574/52. Class 81 (2). A piston type hypodermic syringe is provided with valve means and medicament and cleansing liquid supply conduits and a spring controlled piston movable within a barrel such that by successive operation of the valve means the syringe may be charged, discharged, and the nozzle and needle assembly flushed for cleansing. The apparatus shown comprises barrel 3 containing a piston 4 with a spring 5 at the front thereof, a needle nozzle 6, a brass cylinder 7 with an axial passage 8 and radial passage 9 the passage 8 carrying a rod 12 which may be set by a threaded plug 10 to limit the stroke of the piston 4, and a pistol type handle 1 associated with a valve 14 manipulation of which, by lever rods 32, 33, effects the various operations of the syringe. A conduit 24 supplies cleansing fluid to the syringe whilst conduit 23 supplies the medicament. The syringe is operated as follows. Assume the valve is in position Fig. 4 with piston in position Fig. 3. The valve is open through duct 20, passage 27, passage 28, ducts 15, 16, leading to passage 16a and to inlet tube 13 and barrel 3. The piston 4 has moved under the action of spring 5 into contact with stop rod 12 and drawn in a charge of medicant from the supply through conduits 21, 23. When the trigger 32 is depressed the valve is rotated anticlockwise to position Fig. 5. The valve is now open through ducts 16, 15, passages 27, 29, to duct 19 and passage 19a and thence to the nozzle 6. The pressure of the medicament supply is transmitted through conduits 23, 22, passages 9, 8, to the rear of piston 4 which is forced forward against spring 5 to expel the medicament in front of the piston through the valve and nozzle 6 and hence through the needle. The piston comes to rest against tube 13 with the spring 5 compressed. When the trigger 32 is released the valve spring 36 returns the valve to position Fig. 4. Depression of trigger 33 rotates the valve clockwise to the. position shown in Fig. 6. The valve is now open through duct 18, passage 30, duct 19 and passage 19a to the nozzle 6. In this position cleansing fluid passes from the conduit 24 to the nozzle and needle. Release of the trigger 33 causes the valve to return to its Fig. 4 position and the piston is moved by expansion of the spring 5 to draw in another charge of medicament from the supply. The quantity of charge may be varied by the plug 10 as shown or an external screw-threaded nut may be arranged to push or pull the rod 12 into the required position. The syringe may be constructed so that when the trigger 32 is held in its depressed position after discharging the syringe, medicament from the barrel under pressure of the supply may be allowed to leak slowly past the piston out through nozzle and needle and thus reduce the risk of cross-infection between successive injections.