GB2115518A

GB2115518A - Sealing means

Info

Publication number: GB2115518A
Application number: GB08204501A
Authority: GB
Inventors: John Harbidge
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-02-16
Filing date: 1982-02-16
Publication date: 1983-09-07

Abstract

Sealing means for relatively slidable members such as a piston (2) and cylinder (3) consists of a sealing member or ring (1) (e.g. of PTFE) in a groove (21) which is urged in axial and radial directions by resilient means shown in the form of an O-ring (4) of rubber or the like acting against an inclined rear end of the ring (1). The rear end is provided with a trailing lip (10) for low pressure sealing with minimum friction under the action of fluid under pressure acting on said end of the ring (1). The ring (1) is also arranged to be acted upon by fluid under pressure ducted radially (22) into the groove (21 at 214) for radially and axially thrusting the ring (1) for high pressure sealing. The forward end (12) of the ring (1) is inclined for co-operation with an inclined end (212) of the groove (21) whereby the ring (1) is thrust radially in the sealing direction. A forward member (11) of metal or other suitable hard material is provided at the forward end of the ring (1) either bonded to it or separate therefrom and is for preventing extrusion of the ring (1) between the piston (2) and cylinder bore (30) under conditions of high fluid pressure. In alternative embodiments the forward member 11 is differently shaped. <IMAGE>

Description

SPECIFICATION Sealing means The object of this invention is to provide improved sealing means for use between a piston and cylinder bore or for similar purposes, e.g.

between a piston rod and cylinder end cap or head whereby effective sealing under both very high and low pressure conditions is obtained. Practical advantages in this respect will be apparent from the following disclosure.

According to this invention sealing means comprises a sealing member or ring which in use is received by a groove or recess in one member of a pair of relatively slidable members such as a piston and cylinder, and resilient means which is also received by the groove or recess for urging the sealing means or ring in axial and radial directions in effecting sealing contact between the relatively slidable members.

The groove or recess may be also arranged to receive fluid under pressure ducted to it for urging the sealing member or ring at least in a radial direction for said sealing contact.

The sealing member or ring is preferably arranged to co-operate with corresponding formation of the groove or recess for effecting radial or outward movement of the sealing member or ring as the latter is urged axially.

Practical examples of the sealing means are shown in the accompanying drawings in which: Figure 1 is a detail axial plane section of the sealing means between a piston and cylinder bore, and Figures 2 and 3 are views similar to Figure 1 but each showing a modification.

Referring to Figure 1 the sealing member or ring 1 is shown carried by the piston 2 for sealing contact with the bore wall 30 of the cylinders 3 and is received by an annular groove 21 in the periphery 20 of the piston 2. Clearance between the periphery 20 of the piston and bore wall 30 has been exaggerated in the drawings for clarity.

That end of the ring 1 subject to operative fluid under pressure P (e.g. hydraulic or pneumatic) is provided with an outwardly directed trailing lip 10 primarily for low pressure sealing. The lip 10 is urged into sealing contact with the bore wall 30 by resilient means shown consisting of an O-ring 4 of rubber or other suitable resilient material accommodated in a deeper portion 214 of the annular groove 21. The O-ring 4 does not perform a sealing function but operates as a spring for urging the lip 10 radially outwardly and also for axially urging the ring 1 forwardly in the direction of fluid pressure applied thereto for a purpose later described. Other suitable spring loading may be employed.

The annular groove 21 also receives fluid under pressure ducted at 22 to it, i.e. to the deeper portion 214 so that the fluid under pressure can act between the base of the groove 21 and the ring 1 in order to thrust the entire ring 1 radially outwardly for intimate sealing contact with the bore wall 30, i.e. under condition of high pressure operation.

The forward end of the ring 1 is shown provided with an inclined or tapered face 1 2 for cooperation with a correspondingly inclined end wall 212 of the groove 21 so that, due to the axial spring loading provided by the O-ring 4 and also due to fluid pressure acting on the rear end of the ring 1, the front face 12 rides up the inclined wall 212 to ensure sealing contact with the bore wall 30 at the forward end of the ring.

For an effective anti-friction sealing action the ring 1 including the lip 10 is preferably made of polytetrafluoroethylene (PTFE) or like material e.g.

having a suitable filling and in order to prevent or minimise extrusion of the material between the forward peripheral land 20' of the piston 2 and the bore wall 30, the ring 1 is shown provided with a forward annular member 11 of metal or other suitable hard material which may be bonded or otherwise secured to the ring 1 or may be a separate member as shown in Figure 2.

Under low pressure conditions of operation the lip 10 mainly provides the sealing function with face sealing contact of the ring 1 with the bore wall 30 also obtained by the axial thrust due to the O-ring 4 and applied fluid pressure P and the cooperation of the forward inclined face 12 with the inclined end wall 212 of the groove 21. Such low pressure sealing is obtained with minimum friction.

As the pressure P is increased fluid under pressure ducted at 22 into the groove 21 at 24 radially thrusts the ring 1 against the bore wall 30 for obtaining a higher degree of sealing which radial pressure increases with the applied pressure. Effective sealing can be obtained in this way under very high applied pressures, e.g. of the order of 15,000 p.s.i. (1000 bar).

In some instances the forward end of the sealing ring 1 or forward member 11 thereat may be radial, i.e. at right angles to the piston axis for co-operation with a corresponding radial end wall of the groove 21.

Referring to Figure 2 the construction and operation is the same as that already described except that the forward member 11 is separate or loose in relation to the ring 1 and has a forward inclined face 112 co-operating with the inclined wall 212 of the groove 21 and also a rear correspondingly inclined face 11 3 co-operating with an inclined leading face 13 of the PTFE ring 1 in a parallel manner.

The co-operation of the inclined faces 112, 212 and 113, 13 is such that on forward axial thrust of the ring 1, the separate forward member 11 is thrust radially outwardly to prevent or minimise extrusion between the piston land 20' and cylinder bore 30.

In a modification of this arrangement shown in Figure 3 a radial forward face 14 of the ring 1, i.e.

at right angles to the piston axis may abut a corresponding radial rear face 114 of the forward member 11.

In any of the arrangements of the sealing means herein described, the axial extent of the ring 1 together with any forward member 11 is such that when under pressure it provides firm radial support of the piston 2 in the cylinder 3.

If desired the sealing means may be employed in a complementary manner in a groove in the bore wall 30 of the cylinder 3, i.e. for co-operation with a plain peripheral portion of the piston 2. The sealing means may be used in any of the ways described in similar applications such as between a piston rod and bore of a cylinder end cap or head and with the same advantages.

Claims

1. Sealing means comprising a sealing member or ring which in use is received by a groove or recess in one member of a pair of relatively slidable members such as a piston and cylinder, and resilient means which is also received by the groove or recess for urging the sealing means or ring in axial and radial directions in effecting sealing contact between the relatively slidable members.

2. Sealing means according to Claim 1 wherein that end part of the sealing member or ring which in use is subject to operative fluid under pressure is provided with an outwardly directed trailing lip which is thrust by said fluid under pressure and by the resilient means against a co-operating surface of one of the relatively slidable members primarily for effecting low pressure sealing.

3. Sealing means according to Claim 1 or 2 wherein the sealing member or ring is arranged to be acted upon by fluid under pressure radially ducted into a said groove receiving the sealing member or ring whereby the ring is thrust radially against a co-operating surface of one of the relatively slidable members primarily for effecting high pressure sealing.

4. Sealing means according to Claim 1,2 or 3 wherein that end part of the sealing member or ring which in use if subject to operative fluid under pressure is formed or inclined for co-operation with the resilient means whereby the sealing member or ring is urged thereby in axial and radial directions for sealing contact between the relatively slidable members.

5. Sealing means according to Claims 3 and 4 wherein said forward or inclined end of the sealing member or ring is arranged to be subjected to fluid under pressure when radially ducted into a said groove receiving the sealing member or ring whereby the ring is thrust radially and axially primarily for effecting high pressure sealing.

6. Sealing means according to any of the preceding claims wherein the forward end of the sealing member or ring in relation to the direction of fluid under pressure acting on the other end of the sealing member or ring when in use, is inclined or tapered for co-operation with corresponding formation of the adjacent end of a said groove in thrusting the forward end part of the sealing member or ring radially for sealing contact between the relatively slidable members.

7. Sealing means according to any of the preceding claims wherein the forward end of the sealing member or ring in relation to the direction of fluid under pressure acting on the other end of the sealing member or ring when in use, is provided with a forward member of metal or other suitable hard material to prevent or minimise extrusion of the material of the sealing member or ring between the relatively slidable members under conditions of high fluid pressure.

8. Sealing means according to Ciaims 6 and 7 wherein the forward end of said forward member of metal or other suitable hard material is inclined or tapered for co-operation with corresponding formation of the adjacent end of a said groove whereby said forward member is thrust radially in a direction for sealing contact between the relatively slidable members.

9. Sealing means according to Claim 7 or 8 wherein the forward member of metal or other suitable hard material is bonded or otherwise secured to the sealing member or ring.

10. Sealing means according to Claim 7 or 8 wherein the forward member of metal or other suitable hard material is a separate member in abutment with the forward end of the sealing member or ring whereby said forward member is subject to radial thrust in a sealing direction with or relative to the sealing member or ring.

11. Sealing means according to Claim 10 wherein abutting faces of the forward end cf the sealing member or ring and the forward member of metal or other suitable hard material are radially arranged or inclined.

12. Sealing means according to any of the preceding claims wherein the resilient means consists of a member of rubber or other suitable resilient material.

13. Sealing means according to Claim 12 wherein the resilient means consists of an O-ring.

14. Sealing means according to any of the preceding claims wherein the sealing member or ring is made mainly or wholly of anti-friction material such as polytetrafluoroethylene (PTFE) e.g. having a suitable filling.

1 5. Sealing means substantially as herein described with reference to Figure 1,2 or 3 of the accompanying drawings.

1 6. An assembly of relatively slidable members such as a piston and cylinder when provided with sealing means according to any of the preceding claims.