GB662943A - Injection device - Google Patents

Abstract

662,943. Hypodermic syringes. BECTON DICKINSON & CO. Jan. 27, 1949 [Jan. 30, 1948], No. 2322/49. Class 81 (ii) A hypodermic injector has an orifice through which medicament can be discharged at skinpenetrating velocities and pressures without the use of a piercing needle, a medicamentreceiving chamber is disposed between a cylinder and the said orifice, a passage communicates with the cylinder for the introduction thereinto of gas under pressure and valve mechanism is provided for governing the flow of gas through said passage. A flask 12 containing compressed gas, preferably CO 2 is housed at the rear end of the device beneath a removable cap 11. The sealed neck of the flask 12 is pierced by a cannula 14 as the cap is screwed into position. The interior of the cannula 14 is connected, through a valve consisting of a rotatable body 16 having a passage 17, with a cylinder 21 containing a piston 22 and plunger 24. When the injection device is inoperative the piston 22 and plunger 24 are at the rear of the cylinder 21 and the closed end of an ampoule 29 is held against the plunger 24 by a cap 26 at the forward end of the device. The cap 26 carries a post portion 27, the rear end of which bears against the stopper 31 of the ampoule 29 and through which is disposed a cannula 28 the rear end of which pierces the stopper 31 and the front end of which forms an orifice 40 through which medicament may be injected. To make an injection, the body 16 of the valve is rotated so that gas flows under pressure from the flask 12 to the cylinder 21 to move the piston 22 forwardly. The ampoule 29 is moved forwardly. the post portion 27 and the stopper 31 remaining stationary so that liquid is ejected through the orifice 40. In one modification (Fig. 6) in which the risk of fracture of the ampoule is minimised the post portion 27 of the cap 44 is omitted and channels 46 are provided in the interior surface of the lower part of the cylinder 21. When the device is being used, gas entering the cylinder 21 from the flask 12 moves the piston 22 and plunger 24 forwardly so that the ampoule 41 is forced against the cap 44, the cannula 43 being thrust within the ampoule 41. The piston having reached its most forward position, gas is able to flow round it through the passages 46 to the forward side of the ampoule stopper 42 which is pushed against the closed end of the ampoule 41 with the consequent discharge of medicament through the orifice in the cap. In another modification Fig. 5 (not shown), an ampoule sealed at both ends is used and the post portion 27 of the cap is omitted so that the front of the ampoule bears directly against the cap. When the piston is moved forwardly the stopper in contact with it is pushed within the ampoule to expel the medicament, the ampoule remaining stationary. After the injection has been made, the valve connecting the flask 12 with the cylinder 21 is closed and the cylinder 21 is connected with the atmosphere by a passage 18 on the rotatable body 16 of the valve leading to a duct 25 in the casing of the device. An alternative form of valve (Fig. 11) consists of two transverse passages 47, 52, one passage 47 being connected with the cannula 14 and the other passage 52 being connected with the cylinder 21. These passages 47, 52 are interconnected by a passage 57, the entry to which from the first passage 47 is normally closed by a needle valve 48 having a stem 51 which projects through the body of the device. The other passage 52 is connected with the atmosphere at one end but may be sealed from it by a needle valve 53 which is provided with a stem 56 which projects through the casing of the device and which may slide on a pin 61 on a handle 58 on the outside of the casing. When an injection is made the handle 58 is pressed towards the casing against a spring 59 so that it engages the stem 51 of the valve 48 which is unseated to allow gas to flow from the flask 12. to the cylinder 21. At the same time the stem 56 of the other valve 53 is pressed inwardly thus sealing the passage 52 from the atmosphere. On releasing the handle 58, the supply of gas is again cut off and the passage 52 is connected with the atmosphere. Specification 568,237 is referred to.