GB798826A - Improvements in needle-less hypodermic injectors - Google Patents

Abstract

798,826. Hypodermic injection devices. Z. & W. MACHINE PRODUCTS, Inc. Aug. 27, 1954, No. 24987/54. Class 81 (2). [Also in Group XXVIII] A needleless hypodermic injector has an actuator and a plunger by which the contents of a medicament chamber may be discharged, and fluid pressure means for withdrawing the plunger and thereby energizing the actuator. In a device for single shot operation, a piston 13 is slidable within a cylinder 10 and secured to a plunger 6 and an extension rod 15. A compression spring 19 is disposed within the cylinder 10 and tends to urge the piston 13 and plunger 6 forwardly. A fluid pump is housed in a handle 1 and consists of a reservoir 37 connected by a channel 69 containing a ball valve 71 to a cavity 39 housing a pump piston 40 which may be reciprocated by a lever 42 pivoted to the handle 1. On reciprocation of the lever 42, fluid, e.g. mineral oil, is drawn from the reservoir 37 and pumped via a channel containing a ball valve 70, a chamber 54 and a passage 66 into the cylinder 10. The piston 13 is retracted against the spring 19 which thus becomes energized. A charged ampoule c, Fig. 7, is held between jaws 23 at the front of the device. The ampoule c has an aperture 83 of about 0.003 inch diameter at the front and is closed at the rear by a piston 85. The plunger 6 bears against the ampoule piston 85. To make an injection, button 62 is depressed which lifts the head 59 of a valve stem 58 thus connecting the cylinder 10 and passage 66 with the reservoir 37 via a channel 68. Fluid then recirculates to the reservoir 37 to release the spring 19 which drives the piston 13 and plunger 6 forwardly with the resultant ejection of inoculant through the ampoule aperture 83 at a pressure sufficient to pentrate body tissues. The ampoule c may be removed from the jaws 23 on retraction of a sleeve 28, which surrounds a collet 21 forming the jaws 23, by means of a trigger 36. The jaws 23 then expand radially to release the ampoule c. A plate 74 is provided at the rear of the injector body for holding the extension rod 15 and the piston 13 in retracted position after the spring 19 has been energized. The narrow portion of a keyhole slot in the plate 74 is arranged to surround a narrow portion 72 of the extension rod 15. The extension rod 15 has a rearwardly projecting threaded portion 16 which is provided with a longitudinally extending flat 79 carrying indicia 80. An adjusting nut 17 is threaded on the extension rod 15 to coincide with one of the indicia 80 so that on projection of the plunger 6, the stroke is limited by the abutment of the nut 17 against the plate 74. Specification 798,827 is referred to.