Patent GB-685178-A (GB)
Title: Improvements relating to hypodermic injection apparatus
IPC: A61M5/20
Filed: 1951-01-10
Abstract: 685,178. Hypodermic injection devices. BECTON, DICKINSON & CO. Jan. 10, 1951 [Jan. 17, 1950], No. 739/51. Class 81 (ii). A hypodermic injection device has a needle projectable into body tissues, mechanism for projecting and retracting the needle and mechanism for ejecting medicament from a medicament - receiving chamber into the puncture in the body tissues. The device comprises a casing 10 in the forward part of which is a medicamentreceiving chamber containing an ampoule 20 having stoppers 21, 22, the rear stopper 21 carrying a stylet 24 which projects into the ampoule. Surrounding the medicament-receiving chamber at the forward part of the device is an electromagnet 14 controlled by a switch 15. An armature 16 is normally held in retracted position against a rear cap 13 by a spring 17. A central bore of the armature houses a tube 34 integral with a rod 35 and held against movement relative to the armature by a spring 38. A tension spring 33 is attached at one end within the tube 34 and at the other to a pair of jaws 30 surrounded by a sleeve 32 so that they grip the stylet 24. The jaws 30 are prevented from moving rearwardly by a latch 39 pivoted to the armature 16. In use the forward end of the device is held against the skin and the electromagnet 14 is energised. The armature 16 is thus moved forwardly carrying with it the jaws 30 and the stylet 24 which penetrates the forward stopper 22 of the ampoule and emerges to puncture the skin. When the latch 39 bears against a shoulder 42 of the casing 10 it moves against a leaf spring 41 attached to the armature 16 and releases the jaws 30 which are then retracted by the tension spring 33 and with draw the stylet 24 into the ampoule. With continued forward movement, the armature 16 bears against a stopper 21 of the ampoule and causes ejection of medicament into the puncture made by the stylet 24. The switch 15 is such that the electromagnet 14 remains energised until all the medicament is expelled. As soon as it is de-energised the armature 16 is retracted by the action of the spring 17. The tension spring 33 holds the jaws 30 against the forward part of the tube 34, the sleeve 32 abutting against a shoulder 43 within the central bore of the armature 16 so that it slides relative to the jaws 30, allowing them to release the stylet 24. The spent ampoule and stylet 24 may then be removed and a new one inserted. In order that the jaws 30 may grip the new stylet 24, the rod 35 is pushed into the armature 16 against the action of the spring 38 so that the jaws 30 receive the stylet 24. The sleeve 32 moves along the jaws 30 owing to friction between it and the central bore of the armature 16 thus causing the jaws 30 to grip the stylet 24. As the jaws 30 are moved forwardly, the sleeve 22 overrides the latch 39 which then prevents upward movement of the jaws 30 until the armature 16 is again moved by the action of the electromagnet 14. The rod 35 is then pulled out to its initial position. In an 'alternative construction (not shown) the jaws gripping the stylet are attached to an armature which is moved forwardly by a second electromagnet so that the stylet pierces the skin. A single control unit for energising both electromagnets is provided.