GB2199101A

GB2199101A - Ball and socket joint

Info

Publication number: GB2199101A
Application number: GB08627091A
Authority: GB
Inventors: Keith Shotbolt
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-11-13
Filing date: 1986-11-13
Publication date: 1988-06-29
Also published as: GB8627091D0

Abstract

A coupling member has an enlargement 1 with spherical surfaces 5 and 6, of which surface 6 has a radius of curvature which is smaller than the radius of surface 5. A metal seal ring 7 is connected to a hub 8 by screws 9 prior to inserting enlargement 1 into socket 3. The outer surface of seal 7 is part of a cone and mates with surface 10 inside the socket 3. A preload force generated by tightening nuts 11 on studs 12 pushes the hub 8, enlargement 1 and seal 7 towards the socket 3 and the seal ring 7 is compressed between surface 6 and surface 10. <IMAGE>

Description

BALL M;D SOOKET JOINT This invention relates to a ball and socket joint for connecting pipes which may be initially misaligned,.or which may be displaced from exact alignment during service by expansion or other pipe movement and the potential increase in pipe bending stress can be relieved by joint swivelling.

Previous ball and socket joints of this type are described in U.K. patents 1,558,763; 1,596,794 and 2,095,352.

According to the present invention there is provided a ball and socket joint comprising:two coupling members each of which is attachable at one end thereof to a respective one of two pipe ends to be joined, the first of said two coupling members having, adjacent to the other end thereof, a radial enlargement having larger and smaller radius concentric sspherical outer surface portions, the spherical outer surface portion with larger radius of curvature faces rearwards, that is towards said one end of the first coupling member, the spherical outer surface portion with smaller radius of curvature faces forwards, that is away from said one end of the first coupling member, a seal ring which is disposed around said forward facing part-spherical surface, a hub which is disposed around said rearward facing part-spherical surface, means to hold the seal ring and hub together in assembled relationship around the radial enlargement, the other of said two coupling members having at the other end thereof, a socket for receiving said seal ring therein and said seal ring being such that at least before it is received in the socket, the seal ring and hub are able to swivel with respect to the radial enlargement, and securing means for ap#lving to said hub a preload force which tends to Fush the hub, enlarged portion and seal forwardly into the socket, and hence maintains the seal ring in the socket.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1 shows a cross-sectional view of the assembled ball and socket joint.

In Fig.l a first coupling member with radial enlargement 1 is attached at one end to one of the pipes to be connected 2. The second coupling member which includes a socket 3 is attached at one end to the other of the pipes to be connected 4. The radial enlargement 1 has a rearward facing spherical surface portion 5 and a forward facing spherical surface portion 6 which has a smaller radius of curvature than surface portion 5. Advantageously the radius of surface 6 will be at least 4 per cent smaller than the radius of surface 5. A metal seal ring 7, which may include annular resilient seals (for example 'O'-ringc) and may zonal in two spaced locations with an intermediate pressure-test ort, is shaped internally to mate with spherical surface 6.A hub 8 is shaped internally to mat with spherical surface 5 and the seal ring 7 and hub c have a transition fit between them and are connected together by a plurality of screws 9 (only one shown).

The metal seal ring 7 uses a similar principle to the Laurent seal frequently installed in National wellhead connectors. In this case, the outer surface of the seal ring and the inner mating surface 10 of the socket 3 may form part of a conical surface having rn angle of approximately 10 agrees to the major axis. The angle of the tangent to the inner spherical surface (mating with surface 6) adJoining the front oç the seal ring will be artroximately 20 degrees. This difference in angles rroduces the pressure enerclsed wedge action of the Laurent seal ring.

The outer parts of hub c and socket 3 may form flanges containing a plurality of holes to permit assemhiy.of studs 11 and nuts 12. Wben tightened , the nuts 12 apply a sustained axial preload force to hub 9 which in turn pushes enlargement 1 towards the socket 3 and seal ring 7 is compressed between surface 6 and surface 10. There. are a number of alternative methods of applying the required preload force, some of which are described in the above-referenced patents.

Before assembling the enlargement into the socket, the seal ring and hub are not tightly connected by screws 9 and are able to swivel about any diametral axis which is perpendicular to the major axis through the enlargement. If the two pipes 2 and 4 are angularly misaligned (up to a certain limit) the hub and seal assembly can swivel to become correctly aligned with the socket prior to applying the preload force during assembly of the joint.

Claims

CLAIMS.

1. A ball and socket joint comprising two coupling ~embers each of which is attachable at one end thereof to a respective one of two pipe ends to be joined, the first of said two coupling members having, adjacent to the other end thereof, a radial enlargement having larger and smaller radius concentric spherical outer surface portions, the spherical outer surface portion with larger radius of curvature faces rearwards, that is towards said one end of the first coupling member, the spherical outer surface portion with smaller radius of curvature faces forwards, that is away from said one end of the first coupling member, a seal ring which is disposed around said forward facing part-spherical surface, a hub which is disposed around said rearward facing part-spherical surface, means to hold the seal ring and hub together in assembled relationship around the radial enlargement, the other of said two coupling members having at the other end thereof, a socket for receiving said seal ring therein and said seal ring being such that at least before it is received in the socket, the seal ring and hub are able to swivel with respect to the radial enlargement, and securing means for applying to said hub a preload force which tends to push the hub, enlarged portion and seal forwardly into the socket, and hence maintains the seal ring in contact with the socket.

2. A Joint according to claim 1, constructed such that the application to said hub of said preload force which tends to push the hub forwardly towards the socket causes the seal ring and the hub to move towards one another to come into tighter engagement with said radial enlargement and to clamp said radial enlargement within said seal ring and said hub.

3. A joint as claimed in claims 1 or 2 including means for locating the relative position of said seal ring with said hub in a plane perpendicular to their major axes.

4. A joint as claimed in any preceding claim, wherein at least a portion of the seal ring adjoining the front thereof has an external surface which becomes smaller in diameter proceeding towards the front of the seal ring.

5. A joint as claimed in claim 4, wherein said external surface is frusto-conical.

6. A joint as claimed in any preceding claim, wherein an internal surface of said socket and an external surface of said seal ring are adapted for mating with one another.

A Ajoint as claimed in any preceding claim, wherein said securing means is such as to engage a rear surface of said hub.