SEAL WITH BACK-UP RING

Abstract

A back-up ring (1) for a gland seal includes at least two part ring portions (2,4). Each part ring portion comprises first (6, 10) and second (8, 12) ends. Each end has an undulating surface (22, 24) for overlapping in engagement with a corresponding undulating surface on an end of another part ring portion, to form the back-up ring (1). When the part ring portions (2,4) are assembled to form the back-up ring (1) and are held together by axial and/or radial compression, the engagement of the undulating surfaces (22, 24) restricts relative movement between the part ring portions. A seal assembly (34) including the back-up ring (1) is also disclosed.

Claims

1. A back-up ring for a gland seal comprising: at least two part ring portions, wherein each part ring portion comprises first and second ends, each end having an axially facing undulating surface for overlapping in engagement with a corresponding axially facing undulating surface on an end of another part ring portion, to form the back-up ring; and wherein, when the part ring portions are assembled to form the back-up ring and are held together by axial and/or radial compression, the engagement of the undulating surfaces restricts relative movement between the part ring portions.

2. The back-up ring of claim 1 wherein the back-up ring comprises only two part ring portions.

3. (canceled)

4. The back-up ring of claim 1 wherein the undulating surfaces of the first and second ends of each ring portion are formed on the same axially facing surface of the respective part ring portion.

5. The back-up ring of claim 1 wherein the axially facing undulating surfaces of the first and second ends of each ring portion are formed on opposite axially facing surfaces of the respective part ring portion.

6. (canceled)

7. (canceled)

8. (canceled)

9. The back-up ring of claim 1 wherein the assembled back-up ring has a uniform thickness in the axial direction.

10. The back-up ring of claim 1 wherein the assembled back-up ring has a uniform thickness in the radial direction.

11. The back-up ring of claim 9 wherein the axially opposed surfaces of the ring are planar and parallel to each other.

12. The back-up ring of claim 1 wherein the first and second ends of each part ring portion are of a uniform thickness along their length, apart from projections and depressions forming the undulations of the undulating surfaces.

13. The back-up ring of claim 1 wherein each first and second end of each part ring portion tapers towards its respective extreme end.

14. The back-up ring of claim 1 wherein each part ring portion forming the back-up ring is identical to the other or others.

15. The back-up ring of claim 1 wherein the undulating surfaces that overlap in engagement have complete contact, without spaces in between.

16. The back-up ring of claim 1 wherein each undulating surface comprises or consists of a series of peaks and troughs alternating circumferentially along the undulating surfaces of the at least two part ring portions.

17. The back-up ring of claim 16 wherein the axially facing undulating surfaces have peaks and troughs that extend generally radially from the outer circumferential edge of a respective part ring portion to the outer edge of a hole in the ring.

18. (canceled)

19. The back-up ring of claim 16 wherein the peaks and troughs have smooth shape in cross section.

20. The back-up ring of claim 1 wherein the part ring portions comprise a polyaryletherketone (PAEK) or a reinforced polyaryletherketone material.

21. The back-up ring of claim 20 wherein the part ring portions comprise one or more of: a polyetherketone (PEK); a polyetheretherketone (PEEK); a polyetherketoneketone (PEKK); and a polyetherketoneetherketoneketone (PEKEKK).

22. A seal assembly for a gland comprising: a resiliently deformable sealing member; and a back-up ring, wherein the back-up ring comprises at least two part ring portions, wherein each part ring portion comprises first and second ends, each end having an axially facing undulating surface for overlapping in engagement with a corresponding axially facing undulating surface on an end of another part ring portion, to form the back-up ring; and wherein, when the part ring portions are assembled to form the back-up ring and are held together by axial and/or radial compression, the engagement of the undulating surfaces restricts relative movement between the part ring portions.

23. A part ring portion for a back-up ring for a gland seal comprising first and second ends, each end having an axially facing undulating surface for overlapping in engagement with a corresponding axially facing undulating surface on an end of another part ring portion, to form the back-up ring in use.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] FIGS. 1A and 1B show a back-up ring in schematic elevation and plan views respectively;

[0048] FIG. 2 shows, in schematic cross section, the use of a seal assembly including a back-up ring;

[0049] FIGS. 3A, 3B, and 3C show in schematic cross section the ends of part ring portions;

[0050] FIG. 4A shows in plan view a part ring portion for a back-up ring;

[0051] FIG. 4B shows in plan view a back-up ring using the part ring portion of FIG. 4A; and

[0052] FIGS. 5A and 5B show back up rings in schematic perspective views.

DETAILED DESCRIPTION OF THE DRAWINGS

[0053] A back-up ring 1 is shown in schematic elevation in FIG. 1A and schematic plan view in FIG. 1B. FIG. 1A views the back-up ring of FIG. 1B in direction X. Referring to these figures the back-up ring 1 is formed of part ring portions 2,4. The first part ring portion 2 has first and second ends 6,8 and the second part ring portion 4 has first and second ends 10,12. A circular hole 14 having a circumference 16 is defined by the part ring portions as is the outer circumferential edge 18 of the back-up ring 1.

[0054] The back-up ring 1 has a principal axis A shown in FIG. 1A, normal to the diameter of the ring. The back-up ring 1 has a uniform axial thickness TA defined by the axially opposed surfaces 20,21 (upper and lower surfaces as depicted) which are planar and parallel in this example. The back-up ring has a uniform radial thickness TR.

[0055] The first and second ends 6,8,10,12 of the part ring portions 2,4 have smooth undulating axially facing surfaces that engage with each other so as to be fully in contact, without spaces in between in this example. Two of the undulating surfaces 22,24 are visible in FIG. 1A. The peaks and troughs of the undulating surfaces are smooth in cross section and are radially extending (see FIG. 4A).

[0056] In this example the first and second ends 6,8,10,12 of the part ring portions 2,4 taper, getting thinner as they extend to their extreme ends 26,28,30,32.

[0057] FIG. 2 shows in schematic cross section view the use of a back-up ring 1 in an O ring assembly 34. A tubular 36 has an external circumferential groove 38 into which an elastomeric O ring 40 has been fitted. The O ring 40 is compressed into sealing contact with a larger tubular 42 fitting around the tubular 36. Back up ring 1 is provided in the groove 38 to prevent axial (direction A) extrusion of the O ring 40 from its groove 38 when subjected to pressure P.

[0058] FIGS. 3A, 3B and 3C show some alternative undulating surface arrangements in partial elevation views of an end 6 of part ring portions 2. In each case the undulating surfaces comprise radially extending peaks 44 and troughs 46. As depicted the dashed line indicates the general outline of another part ring portion 4 that would have an end to overlap with and engage the undulating surfaces 22 depicted.

[0059] In FIG. 3A generally square or rectangular in cross section peaks and troughs are employed in the undulating surface 22 of an end 6 that otherwise has a uniform thickness i.e. the end 6 is not tapered.

[0060] A similar arrangement is shown in FIG. 3B except that the undulating surface 22 has smooth peaks and troughs 44,46.

[0061] In FIG. 3C the undulating surface 22 has triangular “teeth” as peaks 44. The end 6 is tapered in this example.

[0062] FIG. 4A shows a part ring portion 4 in plan view and FIG. 4B shows a back-up ring 1 formed of two part ring portions 2,4 made up from two part ring portions identical to that shown in FIG. 4A.

[0063] In this example the part ring portions 2,4 take the same general form as those depicted in FIGS. 1A and 1B except that the axially facing undulating surfaces of the first and second ends are on opposite axially facing surfaces. In the view FIG. 4A, first end 10 has the undulating surface 24 uppermost and second end 12 has the undulating surface 24 beneath. The peaks on these surfaces are suggested by the pairs of lines 48 (not shown in FIG. 4B).

[0064] Thus when the two part ring portions 4,2 are assembled as depicted in FIG. 4b the extreme ends 26,32 visible on upper surface 20 are diametrically opposite on the back-up ring 1.

[0065] FIGS. 5A, and 5B show in schematic perspective, alternative back-up rings 1. In these rings the undulating surfaces are provided on radially facing surfaces of the first and second ends of part ring portions that taper (decrease) in thickness towards the extreme end.

[0066] In FIG. 5A a back-up ring 1 comprises two part ring portions 2,4. The part ring portions 2,4 have first and second ends 6,8,10,12. In this example the ends taper to the extreme ends 26,28,30,32 like those in the back-up ring of FIG. 1, but the undulating surfaces 22, 23,24,25 are radially facing. In FIG. 5A the undulating surfaces 22,25 of the first part ring portion 2 are both radially facing outwards (away from the centre of the ring) and extend axially. The undulating surfaces 23,24 of the second part ring portion 4 are both radially facing inwards (towards the centre of the ring) and extend axially. Part ring portions in FIG. 5A therefore have different forms, that complement each other to form the back-up ring 1.

[0067] In FIG. 5B a back-up ring 1 comprises two part ring portions 2,4. The part ring portions 2,4 have first and second ends 6,8,10,12. In this example the ends taper to the extreme ends 26,28,30,32 like those in the back-up ring of FIG. 1, but the undulating surfaces 22, 23,24,25 are radially facing. In FIG. 5B one of the undulating surfaces 25 of the first part ring portion 2 is radially facing outwards and the other 22 is radially facing inwards. The undulating surfaces 23,24 of the second part ring portion 4 are also facing one (24) radially inwards and the other (23) radially outwards. Part ring portions 2,4 in FIG. 5B have the same shape and can be used interchangeably.