GB681098A - Hypo-jet injector - Google Patents

Abstract

681,098. Hypodermic injectors. DEHN, S. G. (Scherer Corporation, R. P.). July 7, 1949, No. 18014/49. Class 81 (ii). A hypodermic injector for injecting medicament without the aid of a tissue piercing needle comprises mechanism for operating the plunger whereby a two stage medicament jet is projected the first stage being at a higher velocity than the second stage, and the second stage being sufficient to effect injection at a lower pressure than the first stage. As shown, Fig. 1, the hypo-jet injector comprises a barrel 34 having a lower head 36 connected thereto by screw threads 38. A recess 40 in the head 36 receives the flange 14 of an ampoule A which is held by a retainer plate 42 pivoted at 44 and latched at 46. From a primary cup 54, slidable within the barrel 34 and normally urged downwardly by a spring 56, depends a primary plunger 62. This plunger is slidable through a tubular member 64 which is an extension of a secondary cup 60 slidable in the head 36 and forms the secondary plunger. This plunger 64 is biased upwardly by a light spring 68. A pull rod 70 connected to the cup 54 and having a latch shoulder 74 is provided for compressing the spring 56 to the position shown in Fig. 1. The shoulder 74 is engaged by a latch plate 76 biased to coact by a spring 78. In operation the injector is usually held at right angles to the skin surface and the ampoule is pressed against the epidermis in order to effect a hydraulic seal between the edge of the jet orifice 16 and the epidermis. On release of the latch shoulder 74 the spring 56 propels the primary cup 54 until it strikes the secondary cup 60 and during this time the primary plunger 62 is acting on the follower F, causing a very high pressure tissue piercing jet to issue from the orifice 16. This high pressure drops when the cup 54 strikes the cup 60 as the spring 56 then moves both primary and second ary plungers in unison. Injection is complete when the cup 60 abuts the upwardly projecting boss 65 formed in the head 36. In a modification the cup 54 is held higher in the barrel 34 than is shown in Fig. 1, when the injector is cocked, thereby raising the primary plunger 62 out of contact with the follower F. On release of the cup 54 the travel of the plunger 62 produces an impact against F which is added to the initial high pressure stage of the operation. The primary plunger 62 may have a bullet-shaped end for engaging the follower F. In a further embodiment, Fig. 9, a single plunger 63 is used, the two stage jet action being effected by very stiff spring discs 90 and the spring 56. This embodiment may be modified by utilising a heavy coiled spring in lieu of the discs 90. Specifications 568,237 and 681,097 are referred to.