Patent GB-669053-A (GB)
Title: Injection device
IPC: A61M5/20
Filed: 1949-01-27
Abstract: 669,053. Hypodermic syringes. BECTON, DICKINSON & CO. Jan. 27, 1949 [Jan. 31, 1948], No. 2323/49. Class 81 (ii). Apparatus for hypodermically injecting liquid medicament without the use of a piercing needle has moving expressing means capable of causing the discharge of substantially all the medicament and arresting means for co-operating with and arresting the expressing means before the completion of its movement. A flask 17 containing compressed gas is housed at the rear end of the device beneath a removable cap 16. The sealed neck of the flask 17 is pierced by a cannula 19 as the cap 16 is screwed into position. The interior of the cannula. 19 is connected through a valve mechanism with a cylinder 23 within which a piston 24 can move. The piston 24 is attached to a plunger 25 the forward end of which engages a stopper 52 of an ampoule 51 contained within the forward end of the apparatus.. A cannula 54 carried by a cap 55 at the forward end of the apparatus pierces a second stopper 53 of the ampoule 51 when the cap 55 is screwed into position. The bore of the cannula 54 is connected with the orifice through which the medicament is expelled. On releasing the valve mechanism compressed gas passes from the flask 17 into the cylinder 23 so that the piston 24 and plunger 25 move forward to discharge medicament from the ampoule 51. The stroke of the piston may be arrested at one of several preselected positions so that only a portion of the medicament contained in the ampoule 51 is discharged. For this purpose several oppositely disposed pairs of abutments 42, Fig. 2, are arranged on the plunger 25. A ring 43 carrying a pair of abutments 48 which project into the cylinder 23 may be rotated into such positions that the abutments 48 engage one preselected pair of abutments 42 on the plunger 25 which is thus arrested. In a modification, Fig. 8, the rear part 79 of the plunger 77 is enlarged and the stroke of the plunger is arrested by engagement between this enlarged portion 79 and a sleeve 72 disposed in the plunger cylinder. The sleeve is provided with a helical thread 73 which fits within a corresponding helical groove 71 in the cylinder wall. A series of gear teeth (not shown) are also disposed around a portion of the sleeve 72 for engagement with an adjustable gear wheel 78 which projects through the casing of the apparatus and may be held in position by a catch 80. By rotation of the gear wheel 78 the sleeve 72 is rotated and thus moved axially within the cylinder so that the plunger stroke may be varied. The valve mechanism used between the gas flask and the plunger cylinder consists of two transverse passages 27, 28, Fig. 11, one passage 27 being connected with the cannula 19 and the other passage 28 being connected with the cylinder 23. These passages 27, 28 are interconnected by a passage 29 the entry to which from the first passage 27 is normally closed by a needle valve 30 having a stem 31 which projects through the body of the device. The other passage 28 is connected with the atmosphere at one end but may be sealed from it by a needle valve 34 which is provided with a stem 35 which projects through the casing of the device and which slides on a pin 41 on a handle 38 on the outside of the casing. When an injection is made the handle 38 is pressed towards the casing against a spring 39 so that it engages the stem 31 of the valve 30 which is thus unseated to allow gas to flow from the flask to the cylinder 23. At the same time the stem 35 of the other valve 34 is pressed inwardly thus sealing the passage 28 from the atmosphere. On releasing the handle 38 the supply of gas is again cut off and the passage 28 is connected with the atmosphere.