Patent GB-686342-A (GB)
Title: Improvements relating to hypodermic injection apparatus
IPC: A61M5/30
Filed: 1950-09-08
Abstract: 686,342. Hypodermic injection apparatus. HEIN, G. N. Sept. 8, 1950, No. 22217/50. Class 81 (ii). Hypodermic injection apparatus is provided with movable means for forcibly expelling medicament and controlling mechanism for preventing the transmission of force to the medicament expelling means in excess of a predetermined amount. A needleless hypodermic injection device is provided with a barrel 10 within which an actuating member 14 may be reciprocated. The actuating member 14 is provided at its forward end with a plunger 15 having a central axial bore 32 connecting an ampoule 26 carried by the actuating member 14 with a medicamentreceiving chamber in the form of a rubber cup 20, having an integral sleeve portion 22 secured to the plunger 15. The forward end of the barrel is fitted with a nozzle 18 having a bore 19. The ampoule 26, is placed on the actuating member 14 through an opening 25 in the barrel 10, an extension 30 of the plunger 15 projecting through an apertured stopper 28 and displacing a plug 31 closing the aperture of the stopper 28. Rotation of the barrel 10 relative to the actuating member 14 closes the opening 25. A piston rod 38 is axially slidable within the rear portion of the barrel 10 and when the ampoule 26 is in operative position it is caused to bear against a stopper 27 of the ampoule 26 and displace it with the resultant transfer of liquid from the ampoule to the medicament-receiving cup 20. The medicament-receiving cup 20 is discharged by forcng the actuating member 14 and the plunger 15 forwardly under the action of a lever 49 which is operated by hand or foot control. The lever 49 and the actuating member 14 are returned to inoperative position by a spring 51. A plate 44 encircling the piston rod 38 is rockably carried by the actuating member 14, the rear portion of which supports a spring 43 which bears against the plate 44. As the actuating member 14 is moved forwardly for discharge of the medicament, the piston rod 38 is gripped by the plate 44 and moves forwardly with it into the ampoule 26. As the actuating member 14 is returned to the piston rod 38 and stopper 27 are prevented from being moved rearwardly by the clamping plate 47 which surrounds the piston rod 38 and is rockably mounted within the barrel 10 while the ampoule 26 moves rearwardly with respect to the stopper 27 so that a further change of medicament is forced from the ampoule 26 to the medicamentreceiving cup 20 in readiness for the next injection. When the ampoule 26 is to be replaced the plates 44, 47 are pressed forwardly so that they no longer grip the piston rod 38 which may then be withdrawn from the ampoule 26. If too great a pressure is applied to actuate the operating lever 49 a resilient arm 55 attached to the lower end of the lever 49 is flexed and causes a brake shoe 57 to bear against a braking surface 58. The lever 49 may be connected at its lower end to a foot control unit by a Bowden cable 59. In one form of foot control (Fig. 2) the Bowden cable 59 is connected to the outer arm of a bell crank lever 60 of the foot control unit. A foot operated lever 65 having a foot pedal 67 and a pivot 66 is depressed to apply a downward pressure to the outer arm of the bell crank lever 60 which is transmitted to the Bowden cable 59. In the event of too great a pressure being applied to the foot pedal 67, brake shoes 63 on the bell crank lever engage braking surfaces 62 of a slot 61 through which the outer arm 60 the bell crank lever projects. In another form of foot control unit (Fig. 5) pressure is applied to the Bowden cable 59 on depression by the foot of a lever 72 pivoted at one end and attached at the other to the Bowden cable 59 through a spring 79. The spring 79 is so tensioned that excess pressures are not transmitted by it to the cable 59.