GB847913A - Sterilizable and sterilized hypodermic syringe assembly - Google Patents

Abstract

847,913. Hypodermic syringes. WILBURN, E. H. March 14, 1958. [March 20, 1957]. No. 8224/58. Class 81(2). A hypodermic syringe comprises a barrel 450 with an open rear and a front liquid outlet having a protective cap 469 with a passage 490 which communicates with the surrounding atmosphere through a filter 491, and a reciprocable plunger 476 which in its forward position seals the rear of the barrel from the surrounding atmosphere. The syringe barrel 450 has a bored boss 453 which supports a hypodermic needle 455. The protective cap 469 carries the needle and is mounted on the boss, the external diameter of the cap being slightly larger than the internal diameter of an annular flange 457 which projects forwardly from the barrel and surrounds the boss. For sterilising the syringe, fluid under pressure passes through the aperture 490 in the cap and a cotton wad 491 which after sterilisation prevents the entry of airborne bacteria. A rubber piston 479 has deformable peripheral ribs 487 which normally contact the interior wall of the barrel to form a fluid-tight seal but which are deformed when subjected to a high pressure differential e.g. 737 mm mercury, to permit the passage of sterilising fluid between the barrel and the surrounding medium. The plunger stem 476 is secured at its rear to a hood 482 which is slidable telescopically over the barrel as the plunger is moved. In the most forward position of the plunger, the rear edge 468 of the barrel is plugged into an annular groove 484 formed between the plunger stem and the hood to form a fluid-tight seal, which may be broken when subjected to a pressure differential to allow passage of sterilising fluid from the barrel. The syringe may be sterilised with the plunger retracted or projected. The barrel, protective cap, plunger and hood may be made of polyethylene, the piston being rubber. Specification 847,914 is referred to.