GB1012451A - Improvements relating to piston sealing means - Google Patents

Abstract

1,012,451. Piston and stuffing-box packings. J. L. GRATZMULLER. May 25, 1962 [May 26, 1961; May 8, 1962], No. 20223/62. Addition to 814,830. Headings F2B and F2T. [Also in Division F1] A seal assembly between two relatively displaceable inner and outer members 1, 2, Fig. 2, comprises at least two axially stacked rings 12, 13 of differing hardness which are continuously axially compressed in a space between facing cylindrical surfaces of the members against a radial surface of one of the members by means of a spring-loaded metal ring 7, the harder ring 12 being positioned between the ring 13 and the radial surface and being made of a material having self-lubricating properties which on sliding engagement with the surface of the other member deposits thereon a thin continuous film preventing or minimizing direct frictional contact between that surface and the ring 13. The members 1, 2 constitute the piston and cylinder of an oleo-pneumatic accumulator. The spring 8 is seated at one end against the ring 7 bearing and at the other end against a disc retained on the piston-rod by a spring clip. The ring 12 may be made from P.T.F.E. or polytrifluorochloroethylene and the ring 13 of an elastomer, e.g. neoprene, having a Shore hardness number of 60-80. When gas is introduced in the compartment 4 of the cylinder with the piston bearing against the cylinder end plate 26 on the oil-filled side, the ring 12 undergoes a slight degree of flow as at 12<SP>1</SP> and prevents any extrusion of the ring 13 between the piston and cylinder. In a modification, Fig. 3, the seal assembly comprises a ring 14 of non-binding metal, a ring 12 of P.T.F.E., two or more elastomer rings 15, 16 of different hardness, e.g. as a function of temperature, and a spring-seating ring 17 of non-binding metal. The spring 8 compresses the assembly through a sleeve 19 which has a tubular extension 20 abutting against the spring-retaining washer 9. In the uppermost position of the piston, when no gas is present above it, the washer 9 engages a shoulder 22 on the cylinder end 21 and transmits through the sleeve 19 to the seal assembly the entire oil pressure exerted on the piston. The retainer ring 10 for the washer 9 may be formed of piano wire and may be contained within a channel surrounding the piston rod and formed between facing bevelled portions at the inner peripheries of a pair of superimposed annular members secured together by crimping a flange of one on top of the other. In Fig. 5, the seal assembly forms part of a stuffing-box 28 secured to one end of a high-pressure cylinder 30 around a slidable rod 27. The ring 14 in that case also serves as a guide to the rod. A ring 31 of plastic material is provided to wipe off dirt from the rod.