Patent GB-779763-A (GB)
Title: Improvements in and relating to gasket or like packings
IPC: G01M3/02
Filed: 1954-09-20
Abstract: 779,763. Piston and stuffing-box packing. CROSSLEY, A. Sept. 13, 1955 [Sept. 20, 1954], No. 27171/54. Classes 122 (1) and 122 (5). A packing for sealing the joint between a shaft and chamber, which members may be relatively rotatable or fixed, or between the cylinder and piston or plunger of a pump or engine, comprises a deformable annular gasket 5 of modified rectangular shape in cross-section with one corner truncated to provide a chamfered surface, and a metal ring 6 of rightangled triangular shape in cross-section disposed with its hypotenuse upon the chamfered surface of the gasket. For sealing the entry of a tube 1, Fig. 1 (left-hand side), into a pressure chamber 2, the entry end of the latter is provided with an annular rebate 3 for receiving the gasket 5 which is of rectangular or square cross-section with truncated corners to accommodate steel rings 6, 6a, 6b, 6c, although the ring 6 may be omitted; these rings are of triangular cross-section and are split at one or more points on oblique lines to provide scarf joints. Axial pressure to form the seal is effected by a flanged collar 4 with the aid of set-screws, or spring washers or helical springs backed by a fixed or adjustable abutment. The piston or plunger 8, Fig. 8, of a pump or engine may be sealed by two packings of this form which are clamped by discs 4a, 4b in rebates 9, 10 of the piston. A packing for use in a chamber 2 for testing a tube 1 under high pressure is received in a cap 4c, Fig. 1 (right-hand side), screwed on to the chamber and provided with either a single ring 6a or two rings 6, 6a (as shown) on the corresponding truncated corners of the gasket; the face of the gasket opposite the rings and nearer the chamber is formed with a V-shaped groove 5f which under the high pressure in the chamber serves to expand the packing to form the seal. This type of packing with two rings 6b, 6c may be housed in a rebate in a pressure chamber receiving a shaft or tube 1 as shown in Fig. 13, the packing being disposed between a pressure-applying gland 4 and an abutment ring 11 of form complementary to the V-groove 5a; a number of interfitting rings of chevron cross-section may be provided between the packing and abutment ring. The packing shown in Fig. 9 for a pressure chamber 2 and relatively rotatable shaft 1 comprises a gasket 5 of generally right-angled triangle cross-section with truncated corners 5c, 5d surrounded by a single ring 6 of right-angled triangle cross-section; a gland 4 screw-threaded on the shaft urges the packing against a flange 1a on the shaft; alternatively, this packing may be clamped in a rebate in the chamber, the disposition of the gasket and ring then being reversed. The gasket may be formed of natural or synthetic rubber, polytetrafluorethylene or nylon, and may incorporate fillers and plasticizing agents; in one example, woven asbestos cloth impregnated with neoprene is folded and die-pressed to the desired form to receive the rings. The rings and gasket may be constructed as a self-contained unit, although when the ring has only a single split it may be separate from the gasket. These self-contained units may be formed by vulcanizing or bonding the rings to the gaskets and/or forming the rings with studs, lugs or holes for providing a key with the gaskets.