GB2197916A

GB2197916A - Sealing ring seals

Info

Publication number: GB2197916A
Application number: GB08628141A
Authority: GB
Inventors: Terence Peter Nicholson
Original assignee: Heat Transfer Technology Ltd
Current assignee: Heat Transfer Technology Ltd
Priority date: 1986-11-25
Filing date: 1986-11-25
Publication date: 1988-06-02
Anticipated expiration: 2006-11-25
Also published as: GB2197916B; GB8628141D0

Abstract

A hollow metallic sealing ring 4 for forming a fluid tight seal in a cylinder (1) and piston (2) assembly has an open end and a closed end and is characterised by having a radial section profile which comprises a radially inner part (4a) shaped as apart of an ellipsoid, and a radially outer part (4b) of serpentine shape having a lesser diameter outwardly convex bend (4c) nearest the closed end of the ring and a greater diameter outwardly convex bend (4d) nearest the open end of the ring. <IMAGE>

Description

t ROVED CYLINDER AND PLUG SEALING RING This invention relates to the formation of a fluid tight seal in a cylinder and plug (piston) assembly by means of a metallic hollow sealing ring having a novel and characteristic radial section profile.

In static sealing installations or assemblies, as for instance shaft sealing assemblies, it has already been proposed and found satisfactory to use metallic hollow sealing rings of simple C-shaped, U-shaped or part-elliptic-shaped radial profile installed with their open faces directed radially inwards or outwards.

Attempts to use such rings in dynamic sealing installations such as cylinder and plug assemblies wherein their open faces have to be directed axially of the components have however proved less satisfactory because the ring tends to act as a rigid tube, develops hoop strength and becomes less resilient, which is undesirable.

The present invention has been devised with the object of providing a metallic hollow sealing ring which does not have the above mentioned disadvantage.

In accordance with the invention a metallic hollow sealing ring for the above specified purpose has an open end and a closed end and is characterised by having a radial section profile which comprises a radially inner outwardly convex part shaped as a part of an ellipse and a radially outer part of serpentine shape having a lesser diameter outwardly convex bend nearest the closed axial end of the ring and a greater diameter outwardly convex bend nearest the open axial end of the ring.

The invention also consists in a cylinder and plug (piston) assembly wherein a sealing ring as above defined is located in a circumferential groove formed around the plug (piston) and such that the said greater diameter outwardly convex bend slidably engages the inside wall surface of the cylinder.

The invention is hereinafter explained by reference to the accompanying drawing of a preferred embodiment.

In this drawing: Fig. 1 is a central longitudinal section of a cylinder and plug (piston) assembly incorporating a hollow metallic sealing ring according to the invention; and Fig. 2 is an enlarged view of part of Fig 1.

Referring now to the drawings there is shown a cylinder 1 which contains a slidable plug (piston) 2 intended to move continuously or to be otherwise adjusted for position therein. The plug 2 has a top plate 5 which partly defines an outside circumferential groove 3 which contains a hollow metallic sealing ring 4 having the characteristic features of the invention.

The upper end of the sealing ring 4 is closed and the lower end of the sealing ring 4 is open but conceivably the sealing ring could alternatively be disposed with its open end at the top and its closed end at the bottom of the groove 3.

The sealing ring 4 which is normally at least partly coated with low friction material comprises a radially inner outwardly convex part 4a shaped as part of an ellipse and a radially outer part 4b of serpentine shape. This radially outer part 4b has a lesser diameter outwardly convex bend 4c nearest the closed face of the ring 4 and a greater diameter outwardly convex bend 4d nearest the open face of the ring.

In operation, the hoop strength inherent in the part 4a establishes a rigid seal between the plug 4 and the top plate 5. However the adjoining parts 4c, 4t and 4d collectively are extremely flexible because the part 4d is an interference fit with the cylinder wall. In this instance a ring of C-shaped, U-shaped or exclusively part-elliptic section would be so rigid and hard that the contact pressure, i.e. the load between the ring and the cylinder when attempting to move the plug along the cylinder, would be so great as to be self-destructive.

The sealing ring of the present invention is such that when the plug is stationary it has an extremely high sealing efficiency, yet when it is moved in either direction a rolling action removes any excessive contact load. This effect and the low friction material coating allows the plug to move freely in either direction and imparts an extremely long operating life.

The sealing rings according to the present invention will usually be manufactured from work hardened stainless steel for less arduous and short term operational conditions. For more extreme environmental or operational conditions they will be manufactured from high grade alloys such as Nimonics, Inconels, Waspalloy, Hastalloy and so forth which can be heat treated to meet various strength, resilience and corrosion resistance requirements. In general, the ring part 4a will be coated on its outside surface with a soft facing material, such as for instance gold, silver or nickel to create the permanent seal when in its static position whereas the outside surface of the parts 4b, 4c and 4d will be faced with a low friction coefficient material such as P.T.F.E., Molybdenum disulphide (Electroless Nickel) or one of the many presently available proprietary low friction materials to reduce both the torque and the wear during operation.

Claims

1. A metallic hollow metal sealing ring for use with a plug or piston and cylinder assembly has an open end and a closed end and is characterised by having a radial section profile which comprises a radially innere outwardly convex, part shaped as a part of an ellipse; and a radially outer part of serpentine shape having a lesser diameter outwardly convex bend nearest the closed end of the ring and a greater diameter outwardly convex bend nearest the open end of the ring.

2. A sealing ring as claimed in Claim 1 in which the radially inner outwardly convex part is externally coated with a soft metallic facing material.

3. A sealing ring as claimed in Claim 1 or 2 in which the radially outer part is externally coated with a low friction material.

4. A cylinder and plug assembly wherein a hollow metallic sealing ring as claimed in any of Claims 1, 2 or 3 is located in a circumferential groove formed around the said plug or piston and such that the said greater diameter outwardly convex bend slidably engages the inside wall surface of the cylinder.

5. A metallic metal sealing ring formed substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

6. A cylinder and plug assembly incorporating a hollow metallic sealing ring substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.