Patent GB-766431-A (GB)
Title: Improvements relating to hypodermic injection apparatus
Inventor: SADD JOHN AMBROSE
IPC: A61M5/30
Filed: 1953-02-11
Abstract: 766,431. Hypodermic injection appliances. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Feb. 11, 1954 [Feb. 11, 1953], No. 3815/53. Class 81(2) A needle-less hypodermic injection appliance is characterized in that a hammer is adapted to strike a plunger with repeated imp'acts under the action of a compressed coiled spring. The apparatus shown in Fig. 1 is in "charged" position, i.e. a coiled spring 18 is compressed and held and a chamber 6 is filled with medicament. On depression of a lever 43 a sear 44 allows a hammer 9 to spring forward to strike a plunger 7 thus causing a high speed jet of medicament to issue from a nozzle 4. The plunger, hammer and springs are so relatively designed as to weight and resiliency that the hammer 9 makes repeated impacts on the plunger 7 until the medicament is fully discharged. To charge the apparatus a cock 34 is turned such that a compressed medicament supply 38a is put in communication with the chamber 6 via a two-way cock 5 whilst a compressed air supply 39a is allowed to communicate with an enclosed space between a circular insert in a circular member 20 and a piston 26 which is slidable within a cylinder 22. The air moves the piston such that it pushes the hammer 9 rearwardly, thus compressing the spring 18, through interengagement with the head 16 of the latter until the head becomes held by the spring-biased sear 44. Integrally formed with the piston is a sleeve 25 around which and located between a collar 27 and the member 20 is a spring 28 which also becomes compressed due to the rearward travel of the piston. If the air pressure is not sufficient to move the piston rearwardly a handle 47 may be attached to the head 16 such that the hammer may be manually retracted. The capacity of the chamber 6 is adjusted by control via a stop member 8 of the rearward travel of the plunger 7. When the chamber 6 is full and the hammer retracted, the cock 34 is rotated to cut-off medicament and air supplies. The spring 18 then causes the piston 26 to move away from the head 16 to its position as shown in Fig. 1, the air in the enclosed space draining to atmosphere through supply duct 41 and suitable porting arrangements associated with the cock. By turning cock 5 and depressing lever 43, the apparatus is ready for injection. In a modified form of this apparatus, the cocks 5 and 34 are linked with the lever 43 to enable a single combined lever to be used for complete operation of the apparatus. In the apparatus shown in Fig. 2, the medicament chamber 56 has been filled from a reservoir 96a through a cock 90 and a piston 86 with associated parts 81, 84 and head 83 is about to be driven forwardly by compressed air passing from a supply box 98a through a cock 91 to a space at the rear end of the apparatus. An electric lamp 61 is used to indicate a full chamber 56. A hammer 65 having an enlarged end 80 slidably engaged within a hollow core 82 of the piston 86 has screwed thereto and thereon a member 67 which carries sears 75 and 76 respectively engaging, as shown, slots 77, 78, in the casing 51 of the apparatus. By moving the cock 91 such that air may pass to the rear of the piston 86 the piston, parts 81, 84 and head 83 are driven forwardly compressing thereby a main spring 88. On contact of head 83 and member 67, the sears 75, 76, are disengaged from their respective slots and the hammer is caused under the action of the spring 88 to bound forward and strike the plunger which expels the medicament from the chamber 56. This forward movement of the hammer tensions a spring 79 which on rotation of the cock 91, such that air may drain from behind the piston 86 to atmosphere, forces the member 67 and hence the hammer to return to its position shown in Fig. 2. The piston 86 through its interconnection via the spring 88 with the member 67 is also forced rearwardly to its position of Fig. 2. In a modification of this apparatus the cocks 90, 91 are replaced by a single cock the initial rotation of which allows the chamber 56 to fill whilst subsequent rotation of which admits compressed air to behind the piston 86. In a further alternative form, the cock 90 may be omitted and replaced by a cock similar to, and in the position of, cock 5 in Fig. 1. In the apparatus shown in Figs. 3 and 4 vaccine and air supplies are controlled by a spring-loaded lever 166 which simultaneously operates a needle-valve 162 and a spring-loaded plunger 172. The hammer head 137 is held by a spring-loaded lever 144 in the position shown in the Figures. On depression of the lever 166, the valve 162 is withdrawn and vaccine flows from reservoir 117 to the medicament chamber forcing the plunger 149 backwards until a lug 155 carried thereby contacts a stop 154. Simultaneously any air between the rear plate 132 of the apparatus and the piston 139 is drained to atmosphere via tube 173, duct 175 and orifice 178. Release of the lever 166 cuts off the vaccine source and allows, as the plunger 172 has returned to its position of Fig. 4, compressed air to pass to the rear of the piston 139 from reservoir 121 and thus compress springs 142,143 in moving the piston to the shoulder 129. The hammer head 137 is then under considerable tension release of which is effected by depression of lever 144 After injection the lever 166 is again depressed causing the medicament chamber to be refilled and allowing, by movement of plunger 172, such that the tube 173 again communicates with atmosphere via 178, the spring 142 to return the hammer head 137 and piston 139 to the position of Fig. 4 and the re-engagement of lever 144 with the head. 150,151, indicates a non-return valve controlling the vaccine flow to the nozzle 153. Another embodiment differs from that shown in Figs. 3 and 4 solely by utilizing the compressed air supply to rotate the needle valve 162 and to compress the springs 142, 143. The lever 166 is replaced by a spring-loaded crank, which is rotated when necessary by an air-operated piston controlled by a push-button which' also controls the air supply to the piston 139. Fig. 7 shows a modification which may be applied to either the Fig. 4 apparatus or its air-plunger operated derivative in which two springs 143, 196 are used to control the rebounding action of the hammer head 137 the spring 143 being limited in its forward travel by a collar 197 such that it only operates during the medicament skin penetrative phase of the injection continued forward hammer movement being under the action of a follower spring 196. Reference has been directed by the Comptroller to Specification 568,237.