GB732508A - Improvements in hypodermic injection apparatus - Google Patents

Abstract

732,508. Hypodermic injection apparatus. HEIN, G. N. March 12, 1953, No. 6880/53. Class 81 (2). Hypodermic injection apparatus has means for expelling medicament from a chamber or ampoule which is actuated by a pressure accumulator provided with mechanism for increasing the pressure in two stages, relea,sable locking means being associated with said mechanism for preventing release of pressure at the completion of one pressure increasing stage to permit the mechanism to be actuated to effect the second stage of pressure increase. The syringe is provided with a casing 10 fitted at the forward end with a nose-piece 11 which, together with a loading cap 12 forms a medicament chamber having a rubber liner 14 for receiving an invertible medicament receiving cup 15 of rubber. A nozzle 19 in the loading cap 12 has an axial bore 20 defining an orifice having a diameter of the order of 0.003 to 0.012 inch. A plunger 13 for expelling medicament by inverting the cup 15 is secured to a tube 23 disposed within the casing 10. Two accumulator springs 24, 25 bear against the plunger 13, one of the springs 25 being disposed within the tube 23 and the other in a space between the tube 23 and the casing 10. At the rear end of the casing 10, the latter spring 24 bears against a closure cap 26. A rotatable cooking sleeve 29 is mounted on the rear end of the casing 10 and is secured to a screw-threaded shaft 32 which passes through a screw-threaded bore in the closure cap 26 and is associated at its forward end with a locking device within the tube 23. The locking device (Fig. 4) comprises a slotted spool shank 28 for receiving a rubber block 36. The shank and block are covered by a rubber sleeve 38 enclosed by two arcuate brake shoes 39, 40, each formed by two semicircular metal sections. The spool is provided with a forward head portion 27 against which the rear end of the inner accumulator spring 25 bears and a rear head portion 34 against which one end of the shaft 32 bears, a bearing assembly 33 being provided between them. Plungers 43, 45 pass through the centre of the shaft 32 and the rear spool head portion 34 and, on projection, the plungers 43, 45 radially displace the block 36 of the locking device which causes the metal sections of the brake shoes 39, 40 to move outwardly and frictionally grip the interior surface of the tube 23 so that the locking device becomes fixed relative to the tube 23. Projection and retraction of the plungers 43, 45 is brought about by manual rotation of a cam 47 on a shaft 48 by a crank 49, the plunger 45 being provided with a head 46 for engaging the cam 47. In operation, the inner spring 25 is compressed by rotation of the sleeve 29 which moves the shaft 32 and the locking device forwardly relative to the casing 10. The plungers 43, 45 are then projected so that the locking device is fixed and the spring 25 is held in compressed position. The sleeve 29 is then rotated in the opposite direction so that the shaft 32 is moved rearwardly relative to the casing 10. This causes the locking device, tube 23 and plunger 13 to be retracted so that the outer spring 24 becomes compressed. A fresh supply of medicament is then placed in the medicament chamber. In order to make an injection, the nozzle 19 is placed in contact with or adjacent the site of the injection and the locking device is released by rotating the crank 49. The plunger 13 is then projected into the medicament chamber under pressure produced by the expansion of the accumulator springs 24, 25 which pressure is sufficient to force medicament into the tissues without a skin-piercing needle. In an alternative construction (Fig. 5) the plunger 13 is integral with a cylinder 55 containing compressed gas, the cylinder 55 being slidable within the casing 10. A screw-threaded shaft 66 secured to a rotatable cocking sleeve 80, plungers 76, 77 within the shaft 66 and a locking device for receiving the shaft 66 relative to a tube 67 are provided as in the first-described construction. A piston 69 is located within an extension 68 of the tube 67 which is closed by a plug 71 having a bore 72. The rear end of the cylinder 55 is fitted to a collar 59 which with a packing ring 57 serves to secure an expansible diaphragm 56 which extends into the bore of the cylinder 55. The collar 59 is also secured to the tube 67, this portion of the collar being provided with holes 63. A sleeve 61 is located between the rear ends of the collar 59 and the tube 67 and is secured to or bears against the rear closure cap 60. Oil or grease is contained within the diaphragm 56 and, before the syringe is cocked, on the forward side of the piston 69 and between the sleeve 61 and the portion of the collar 59 which is secured to the tube 67. To prepare the syringe for an injection, the cocking sleeve 80 is rotated so that the shaft 66 moves forwardly relative to the casing 10. This causes the projection of the piston 69 so that oil or grease is forced through the bore 72 in the plug 71 at the forward end of the tube 67 into the space between the diaphragm 56 and the tube 67, causing compression of gas in the cylinder 55. The tube 67 is then locked relative to the shaft 66 by the locking device. The cocking sleeve 80 is then rotated in the opposite direction so that the tube 67, collar 59, cylinder 55 and plunger 13 are retracted with the shaft 66 further compressing the gas in the cylinder 55 by the expulsion of oil or grease forwardly through the holes 63 in the collar 59. A fresh ampoule of medicament is then inserted. To make an injection, the locking device is released so that the compressed gas in cylinder 55 compresses the diaphragm 56 so that oil or grease is forced back within the tube 67 causing retraction of the piston 69 and also backwardly through the holes 63 in the collar 59, so that the plunger 13 is urged forwardly to expel medicament from the ampoule. Reference has been directed by the Comptroller to Specification 568,237.