GB2202020A - Pipe joints - Google Patents

Abstract

A pipe, particularly for pipe jacking, has at both ends an outer rebate 5 to receive a coupling sleeve 9, an inner rebate 7, and an L-section ring 10 on the pipe end, with one limb 13 acting as a spacer between adjacent pipe lengths, and the other limb 14 overlying the rebate 7 to form a groove accommodating a sealing ring 8. <IMAGE>

Description

PIPE JOINTS This invention relates to pipe joints, in particular but not exclusively, to joints for pipes to be laid by the technique known as pipe jacking or thrust jacking.

Pipe jacking is a technique used to lay pipes without trenching. Pipes are thrust axially through the earth by the application of jacking forces to the rearmost pipe.

In pipe jacking, substantial axial thrust loads are transmitted from one pipe to the next. It is also necessary to provide for sealed joints between the pipes.

In one known arrangement, at each pipe joint, one of the pipes has a rebated end and the adjacent pipe has a socket which fits over the rebated end, a seal ring being trapped radially between the socket and the external surface of the rebated pipe end. In one such pipe joint for jacking pipes the socket is formed by a steel or other hoop fitted onto a rebated portion of the end of the second pipe, so that the overall diameter of the pipe joint is no greater than the diameter of the pipes themselves. Commonly, the first rebated pipe end has an annular groove to accommodate the seal ring, in the rebated region. It is also known, to instal a cushion ring between the adjacent pipe ends.

In another possible arrangement, at each joint both pipe ends have rebates with seal rings, and the pipes are joined by a coupling sleeve which fits over both rebated pipe ends.

The described joint in which a seal ring is received in an annular groove in the rebated pipe end provides excellent sealing and reliable location of the seal ring, but is difficult and costly to produce especially in the case of clayware pipes, because the groove has to be formed by a machining operation.

In our British Patent Application 8629775, we have described and claimed a pipe having at an end thereof a spigot region for making a spigot and socket joint with a socket provided at an end of a further pipe; said spigot region having a circumferential groove thereon for accommodating a sealing ring, which groove is defined between an abutment on the spigot region and an L-section ring fitted on the end of the spigot region with a first limb of the L overlying the end face of the pipe and with the second limb of the L overlying the periphery of the spigot region, the said second limb having its end facing and spaced from the abutment thereby defining the said groove.

Also according to GB 8629775 a pipe joint, intended particularly for jacking pipes, comprises a first pipe end provided with an axially projecting socket, and a mating pipe end which has an external rebate, a spacer or cushion ring between the adjacent pipe ends, which ring has (in cross section) a first limb extending between axially adjacent end surfaces of the respective pipes to act as a spacer or cushion, and a second limb which overlies the outer surface of the rebated pipe end and which has an end surface that forms, with a further surface of the rebate, an annular external groove in the rebate, and a seal ring to be accommodated in the said groove between it and the internal surface of the socket.

The embodiment described in GB 8629775 comprises a pipe length with the said spigot sealing ring and L-section ring at one end, and a mating socket at the other end.

The present invention resides in a pipe having at each end thereof a spigot region, said spigot region having a circumferential groove thereon for accommodating a sealing ring, which groove is defined between an abutment on the spigot region and a ring of angular cross-section fitted on the end of the spigot region with a first limb of the ring overlying the end face of the pipe and with a second limb of the ring overlying the periphery of the spigot region the said second limb having its end facing and spaced from the abutment thereby defining the said groove.

Pipes of this nature can be jointed by means of separate coupling sleeves which receive respective ends of adjacent pipes and replace the above-mentioned sockets.

In one possible arrangement, each pipe has a said spacer or cushion ring at one end, but such ring at the other end.

In another possible arrangement, each pipe has a said spacer or cushion ring at each end. Thus, the pipes are all identical and symmetrical, which facilitates manufacture, storage, and use.

In yet another possible arrangement, pipes provided with spacer or cushion rings at both ends, are used in ultimation with pipes not provided with such spacer or cushion rings.

Preferably, the rebate has a stepped profile, comprising a first region adjacent to the pipe end, on which is fitted the said second limb of the spacer or cushion ring and which with the latter defines the annular groove, and a further region adjoining the first region, of greater diameter and further from the end of the pipe, to receive the thickness of the socket.

The seal ring is preferably, but not necessarily, an O-ring.

The spacer or cushion ring can be made of any suitable material for example high-grade (floor-grade) chip board, hard rubber, or synthetic resin material.

Preferably, the socket comprises a band of stiff material, fitted on a rebate formed on the first pipe end and projecting therefrom. In a preferred construction, the band is of a thermo set resin material reinforced with wound glass fibre and/or with wound steel or other metal tape.

The invention will be further described with reference to the accompanying drawing which is an exploded axial cross section of a jacking pipe joint embodying the present invention.

The drawing shows first and second pipe ends 1, 2 for example of concrete or fired clay, to be laid by pipe jacking. The pipe ends are jointed together, in abutment, by a sleeve or band 9 of substantially rigid material, into opposite sides of which the pipe ends fit. The band 9 can for example be made of plastics material, glass fibre and/or metal strip-reinforced resin, steel or other metal. It should be sufficiently rigid to prevent any substantial lateral or angular misalignment between adjacent pipes.

Each end of each pipe has an external rebate 4, of a diameter substantially equal to or somewhat smaller than that of the coupling sleeve 9, and of a length sufficient to accommodate the sleeve. Longitudinal dimensions of the sleeve 9 and rebates 4 may be such that the shoulders formed at the ends of the rebates abut on the ends of the sleeve 9, so that during pipe jacking at least part of the axial load is transmitted through the sleeve 9. Alternatively the sleeve 9 may be somewhat shorter so that there is a gap between it and the shoulders of the rebates 4. The sleeve 9 does not project radially beyond the external surfaces of the pipes.

In the external surface of the rebate 4, is an annular circumferential groove which accommodates an O-ring seal 8. When the end of the pipe is inserted in the sleeve 9, the O-ring 8 is trapped and compressed between the internal surface of the sleeve 9 and the surface of the pipe.

At each pipe end is a spacer ring 10 which transfers jacking forces between pipes, and compensates for limited angular misalignment of the pipes and for irregularities in their end surfaces.

Conventionally, it was necessary to form the groove by a special cutting or grinding operation, adding to the cost of manufacture.

In accordance with the present invention, the "nib" on the end of the pipe 2, which conventionally defines one side of the groove, is omitted, so that the end of the pipe has a double rebate comprising an axially inner and radially outer region 5 corresponding in diameter to the sleeve 9, and an axially outer region 7 of smaller external diameter extending to the end of the pipe 2.

A shoulder 12 is formed where the region 7 ends.

In the pipe joint according to the drawing, each hard rubber spacer ring 10 is of L-section, with a radial inner limb 13 adjacent the end surface of the pipe, so as to act as a spacer or cushion between the pipe ends when the pipes are jointed together. The spacer has an outer axially extending limb 14 which overlies the end region of the rebate 7 and has an external diameter similar (but not necessarily identical) to that of the rebate 5. The limb 14 is shorter than the rebate 7, so that an annular groove, to receive the sealing ring 8, is formed between the shoulder 12 of the pipe, and the end of the limb 14 of the spacer ring.

The rebate 7 is easier to produce, during manufacture of the pipe, than an annular groove in the pipe material, since it can be formed as part of the pipe spinning or moulding process. Particularly in the case of clayware pipes, the pipes can be made to shape, in the green condition. The rebated region of the pipe is preferably ground to size after firing, to compensate for ovality and dimensional tolerances arising in manufacture of the pipe.

The L-section spacer 10 can be produced substantially as easily and cheaply as a flat spacer ring. It can be fitted to the ends of a pipe 2 very easily either at the factory or on site. The jacking pipe joint is therefore cheap. Additionally, it has a number of practical advantages. Because there is the deformable limb 14 between the end of the pipe 2 and the sleeve 9, the joint shown is tolerant of eccentricity and angular errors. The limb 14 provides good location of the spacer on the end of the pipe, reducing assembly errors, if the spacer is fitted to the pipe end on site. Preferably, the spacer is factory fitted, and in this case it provides protection for the end of the pipe, during handling, transportation and storage.

These substantial advantages are obtained at no extra cost for the pipe joint as a whole.

The spacer 10 can be an interference fit on the pipe, and/or can be held in place on the pipe end by an adhesive. A further possibility, is to mould the spacer 10 directly onto the end of the pipe 2, for example by injection moulding, compression moulding or transfer moulding.

If the spacer 10 is installed on site, it can be fitted to the end of the pipe before or after the seal ring 8 is fitted over the pipe end.

In the illustrated embodiment, the end of the pipe has a stepped rebate 5, 7. Alternatively, it may have a simple rebate, of diameter corresponding to that of the rebate 7, the seal ring 8 being placed between the end of the simple rebate, and the end of the spacer ring limb 14.

The illustrated embodiment uses L-section spacer rings. Alternatively, T-section spacer rings can be used, arranged so that the stem of the T lies between the abutting pipe ends, and the cross-piece of the T overlies the outer surfaces of the rebates on the respective pipe ends.

In the described embodiment, the coupling sleeve 9, in use, is substantially flush with the external surfaces of the pipes. However, depending on the design and the circumstances of use, a coupling sleeve standing out radially from the pipe surfaces may be used.

In the described embodiment, identical symmetrical pipes are jointed by means of separate coupling sleeves. Alternatively, however, symmetrical pipes provided with spacer rings at both ends, can be used in alternation with symmetrical pipes each provided with a coupling socket at each end. Each such coupling socket may for example comprise a sleeve or band corresponding to the sleeve 9, fitted onto the respective pipe end and projecting from it, to form a socket. The pipe end is preferably rebated to accommodate the socket-forming band substantially flush with the external pipe surface. The socket-band can be made of any of the materials previously described. Alternatively, it may comprise thermo-plastic material shrink-fitted or otherwise thermally fitted onto the pipe end for example as described in our GB 8629775.

Claims (7)

1. A pipe having at each end thereof a spigot region, said spigot region having a circumferential groove thereon for accommodating a sealing ring, which groove is defined between an abutment on the spigot region and a ring of angular cross-section fitted on the end of the spigot region with a first limb of the ring overlying the end face of the pipe and with a second limb of the ring overlying the periphery of the spigot region, the said second limb having its end facing and spaced from the abutment thereby defining the said groove.

2. A pipe as claimed in claim 1 in which the said abutment is formed by one end of a rebate formed on the spigot region.

3. A pipe joint comprising a first pipe end and a mating pipe end each with an external rebate, on each rebate a spacer or cushion ring which ring has (in cross section ) a first limb extending between axially adjacent end surfaces of the respective pipes to act as a spacer or cushion, and a second limb which overlies the outer surface of the rebated pipe end and which has an end surface that forms, with a further surface of the rebate, an annular external groove in the rebate, and a seal ring to be accommodated in the said groove; and a coupling sleeve for receiving in opposite ends thereof the said pipe ends, said seal rings providing sealing between the pipe ends and the interval surface of the sleeve.

4. A pipe according to claim 2 or a pipe joint according to claim 3 in which the rebate has a stepped profile, comprising a first region adjacent to the pipe end, on which is fitted the said second limb of the spacer or cushion ring and which with the latter defines the annular groove, and a further region adjoining the first region, of greater diameter and further from the end of the pipe, to receive the thickness of the socket.

5. A pipe or pipe joint according to any preceding claim in which the said ring is made of hard rubber, high-grade chip board, or synthetic resin material.

6. A pipe with two spigot end regions substantially as herein described with reference to the drawing.

7. A pipe joint substantially as herein described with reference to the drawing.