Patent GB-1149041-A (GB)
Title: Improvements in or relating to hypodermic injection apparatus
Inventor: SINCLAIR KENNETH
IPC: A61M5/32
Filed: 1964-12-11
Abstract: 1,149,041. Hypodermic injection apparatus. DEFENCE SECRETARY OF. 8 March, 1966 [11 Dec., 1964], No. 50617/64. Heading A5R. A liquid-containing sealed collapsible capsule includes a hypodermic needle which is adapted for passage of liquid therethrough and which is disposed, prior to discharge of the capsule, through almost the full length of the interior of the capsule. The capsule has a puncturable forward end to which a pointed forward end of the needle is directed and a rear end which has a non- collapsible portion defining a tubular well opening into the capsule. Positioned in the entrance to the well to bear on the rear end of the needle to hold the needle away from the rear end of the capsule is a deformable plunger which is displaceable into the well by the rear end of the needle if the needle is subjected to a predetermined axial force; the plunger will be so displaced into the well if the needle is 'subjected to such force during an injection operation, for example as a result of contacting gristle or bone, and the non- collapsible portion of the capsule continues to be driven forward relative to the needle. As illustrated in Figure 4, the capsule comprises a circumferentially corrugated side wall 12 which is made of tin and to which is sealed a non-collapsible portion defining a well 13. Positioned in the mouth of the well is a cupshaped plunger 30 which has a side wall provided with a plurality of longitudinally-extending projections or bulges 31 such that the maximum outside diameter of the plunger is just greater than the bore of the well in the non- collapsible portion of the capsule; the side wall is capable of buckling to allow the plunger to be displaced into the well. Extending through the plunger is a bore 32 which provides communication between the well and the recess formed in the plunger. Located in the recess formed in the plunger is the rear end of a hollow needle 33 the pointed forward end of which rests against the puncturable forward end of the capsule; the needle is retained in a position to extend along the axis of the capsule by a ring 34. A rubber pad 35 may extend about the forward end of the capsule. Except for the interior of the well and of the recess formed in the plunger, the capsule is filled with an injection liquid. The capsule is intended for use in and may form part of a hypodermic syringe which comprises a syringe casing having a forward end for contacting a patient, the capsule being housed in a forward end portion of the casing. The syringe also comprises main spring means located in the casing behind the capsule to act on the rear end of the capsule, a release mechanism located in the casing to retain the main spring means until it is released, and a secondary spring positioned between the casing and the capsule in a manner such that it is capable of urging the forward end of the capsule in a rearward direction; the main spring means has sufficient power and throw, when released, to drive the rear end of the capsule forward against the reaction of the secondary spring and to compress and partially collapse the capsule thereby to inject the needle and some of the liquid in the capsule into the body of the patient, the secondary spring being sufficiently powerful thereupon to drive the forward end of the capsule rearward until the collapse of the capsule is completed. The forward end of the capsule preferably is held by the secondary spring in a position to the rear of the forward end of the casing, the main spring means having sufficient power and throw, when released, initially to drive the whole capsule forward to contact the body of a patient positioned at the forward end of the casing of the syringe whilst simultaneously increasing the loading of the secondary spring. The main spring means and the release mechanism preferably comprise a compression spring, a capsule-contacting plunger having a sleeve provided with a recess, a dent body integral with the casing and provided with a detent which can engage in the recess in the sleeve of the plunger, and a pushbutton projecting from the rear of the casing and cooperating with a shaft located within the casing, the shaft being capable of holding the detent in engagement with the 'recess in the sleeve of the plunger and being provided with a recessed portion which, on depression of the push button, aligns with the detent to allow the detent to move out of engagement with the recess in the sleeve of the plunger thereby to release the compression spring. The casing preferably is detachable into two parts, a rear part housing the main spring means and the release mechanism and a forward part housing the capsule and the secondary spring, whereby, after discharge of the capsule, the two parts of the casing may be separated, the main spring means reloaded, and the spent capsule replaced with a new capsule. A syringe of this construction, in combination with a liquid-containing sealed collapsible capsule containing a hypodermic needle and having a puncturable end to which a pointed end of the needle is directed, is described, illustrated and claimed in Specification 1149042.