Patent GB-1140490-A (GB)
Title: Injection device
IPC: A61M25/06
Filed: 1967-03-09
Abstract: 1,140,490. Intravenous device comprising needle and cannula. JOHNSON & JOHNSON. 9 March, 1967 [22 March, 1966], No. 11059/67. Heading A5R. An intravenous device, for infusing fluid into or removing fluid from a blood vessel or body cavity, comprises a rigid, preferably hollow, needle partly surrounded by a flexible hollow cannula which preferably is made of a plastics material, for example polyvinyl chloride or polyethylene. As illustrated in Figure 2 (wherein the needle and cannula are shown separated prior to assembly of the device), the needle 11 comprises a sharp pointed front end which adjoins a needle head 18 which adjoins an elongated intermediate section 17 which adjoins a needle shank which adjoins the rear end of the needle, the diameter of the intermediate section of the needle being smaller than the diameter of the head and the shank of the neeedle. The cannula 12 is shrunk into intimate contact with the outer surfaces of the intermediate section and the shank of the needle, the thickness of the wall of the cannula being equal to the difference between the external radii of the intermediate section of the needle and the head of the needle so that the overall external diameter of the intermediate section of the needle and the surrounding cannula is equal to the outer diameter of the head of the needle. The cannula is adapted to flex and slide over the head of the needle when the needle is withdrawn through the cannula after the device has been positioned in the blood vessel or body cavity. The rear end of the needle is attached to a needle fitting which allows the needle to be mounted on for example a hypodermic syringe; the rear end of the cannula is attached to a cannula fitting which is adapted to be connected to tubing (not shown) for infusion or removal of liquid. As illustrated, the needle fitting is in the form of a hub 13 having a tapered socket adapted to fit over a tapered fitting 17a at the end of hypodermic syringe 15 and a tapered extension 16a adapted to mate with a corresponding tapered socket of the cannula fitting which is in the form of a hub 14 attached to the rear end of the cannula. As illustrated in Figure 4, the external surface of the intermediate section of the needle is connected to the head and the shank, respectively, of the needle by smoothly tapered front and rear annular fairing surfaces 21 and 22, the front end 23 of the cannula fitting over the front fairing surface of the needle and being tapered to conform generally to the taper thereof so that the front end of the cannula does not protrude radially outwardly of the needle head thereby to impart maximum flexibility to the front end of the cannula and to facilitate flexure of the cannula over the head of the needle when the needle is withdrawn through the cannula. The wall of the cannula preferably is of uniform thickness throughout the length of the cannula when the cannula is shrunk onto the needle, the front end of the cannula thereafter being ground or cut down to reduce its outer diameter to the diameter of the head of the needle and to provide the taper at the front end of the cannula; alternatively, the taper at the front end of the cannula may be provided prior to shrinking the cannula on to the needle. The intermediate section of the needle prefrably is at least twice as long as the head of the needle to ensure that the portion 24 of reduced diameter of the cannula can be positioned properly in the blood vessel or body cavity prior to removal of the needle through the cannula. When the needle is hollow, the reduction in the external diameter of the intermediate section of the needle preferably is obtained by applying pressure to the needle as it is rotated, reduction in the internal diameter of the intermediate section and formation of the front and rear fairing surfaces simultaneously being obtained; the bore of the intermediate section of the needle preferably is reduced to a diameter of not less than 0.01 inch.