GB731572A - Improvements in hypodermic injection apparatus - Google Patents

Abstract

731,572. Hypodermic syringes. HEIN, G. N. May 29, 1953, No. 15056/53. Class 81 (2). In a hypodermic injection device in which medicament is expelled from a chamber by a reciprocable member a fluent medium is employed to increase the pressure of a pressure accumulator used as the power source to drive the member in its ejecting stroke when the reciprocable member is retracted into its "predevice use" position. The needle-less injector shown comprises a casing 20 to the ends of which are secured a nozzle assembly and a control-mounting plate 21 respectively. The casing contains a hollow piston member 27 which carries a plunger 25 and is filled with a compressed gas the pressure of which is increased by the inward movement of a rubber diaphragm 76 which closes its rear end. This diaphragm is clamped in position by a hollow cylindrical member 49 which forms a rearward extension of the piston and is formed with a rack 50 which engages a pinion 52 carried by the casing. The member 49 is slidable on a hollow piston 57 which is fixed axially by the plate 21 but may be rotated angularly between limits by a trigger 59 which protrudes from the rear end of the casing. In the injector 'charged' position shown in Fig. 2, the spaces within the diaphragm 76 and the piston 57 are filled with grease but these connected spaces are isolated from one another by a valve comprising a head 69 and a square-sectioned rod 68 which is threaded through similarly sectioned apertures in the member 49 and piston 57. Grease may flow between the said spaces through apertures 67, 75, and the valve head 69 is so notched that when the rod 68 is turned from its position of Fig. 2 by rotation, through the trigger 59, of the piston 57, the aperture 75 is uncovered. The nozzle assembly comprises inter-screwed bored members 23, 24, the latter member carrying an ampoule 34, jet nozzle 30, cannula 33 and ampoule-cushioning member 29 whilst the bore of member 23 carries a mass 38 of semisolid flowable material such as grease. The plunger 25 carried by the piston 27 slidably fits within the latter bore, this plunger carrying at its tip means for gaseous re-charging etc. of the interior of the piston. Fig. 5 shows the injector in its 'discharged' position the ampoule piston having been moved by the plunger 25 through the intermediary of the flowable mass 38. In this position some grease from the spaces within the diaphragm 76 and piston 57 has passed to the interior of the member 49. For re-charging, the pinion 52 is rotated such that it moves the member 49 rearwardly the relative movement of the fixed piston 57 causing the diaphragm 76 to be 'blown out' with grease thus further compressing the gas within the piston 27. This forward flow of grease holds the valve head 69 clear of the aperture 75 until on cessation of such flow the gas pressure on the diaphragm causes the valve to close. A safety catch 63, for preventing rotation of the piston 57 and hence the valve, is provided at the rear end of the injector. The apparatus is operated by movement of the catch and trigger 59 whereupon the gas pressure within the piston 27 causes rearward movement of the diaphragm 76 and hence the grease which may only flow to fill the space within the member 49 this causing movement of the member, piston 27 and plunger 25 forwardly from the piston 57 and hence expulsion of medicament from the ampoule. The amount of rotation imparted to the piston 57 and valve head 69 may be regulated by restricting the angular movement of the trigger 63 by means of a stud screwed into the rear end of the injector to abut the trigger. Fig. 10 shows a modified injector in its 'charged' condition, grease in the space within the diaphragm 83 being compelled to flow rearwardly into the space in the member 82 when the pawl 93 is lifted by rotation of the rod 95 to release the pinion 90. This grease flow causes relative rearward movement of the fixed piston 85 and the plunger 48 carried by the piston 80 moves forwardly to expel medicament from the ampoule. This ampoule comprises cup portion 42 and integral stem portion 41 movement of the stem into the cup forcing the latter to involute upon the former. In a further modification (Fig. 13)-similar in many respects to that illustrated in Figs. 2 and 5- the parts are so arranged that during the working stroke of the injector the moving parts will be automatically adjusted to ensure a predetermined speed of operation. This is effected by allowing the fixed piston 105 limited axial movement against a spring 112 the tension of which may be adjusted if necessary. Thus on movement of the lever 116 the valve 110 will uncover the passage 109 and grease from the space within the diaphragm will move the piston 105 relatively rearwardly and the member 101 forwardly. If the pressure is sufficient the spring 112 will compress and the piston 105 move rearwardly, the movement causing through the interengagement of a helical groove 120 in a flange formed with the piston and a pin 119 limited rotation of the piston resulting in a partial closure by the valve 110 of the passage 109. Consequently the movement of parts will be slowed and the spring 112 will thrust the piston forward to cause the valve to re-open the passage such that the cycle of partial closure and re-opening may be repeated continuously during the working stroke. The gaseous pressure accumulator structure employed in the above embodiments may be replaced by spring means.