GB2584267A

GB2584267A - Pipe clamp

Info

Publication number: GB2584267A
Application number: GB1816101.8A
Authority: GB
Inventors: Richard Webb Ian; Richard Webb Christopher
Original assignee: Taylor Kerr Couplings Ltd
Current assignee: Taylor Kerr Couplings Ltd
Priority date: 2018-10-02
Filing date: 2018-10-02
Publication date: 2020-12-02
Anticipated expiration: 2038-10-02
Also published as: GB2584267B

Abstract

A pipe clamp 100 or pipe coupling for holding the ends of two pipes, comprises a tubular casing 102 with a longitudinal gap 118 between two free ends 112, 116, for fitting around a pipe. The clamp further comprises a tensioning system 104 for tightening the casing around the outer surface of the pipe. The tensioning system comprises at least one tensioner 124, 126 for drawing the first free end and the second free end towards one another. The clamp also features a bridge member 106 which circumferentially spans the longitudinal gap, with an outwardly facing surface of the bridge member engaging the tensioner to resist outward movement of the bridge member during tightening. The bridge member can comprise a radially extending protrusion, or it can comprise a radially extending fin 132, the fin comprising an aperture 134 through which the tensioner passes. The clamp can further comprise a retainer to retain the bridge member in a central position prior to use.

Description

PIPE CLAMP

The present invention relates to a pipe clamp or pipe coupling for holding the ends of two pipes. In particular, the invention relates to a pipe clamp or pipe coupling comprising a tubular casing for fitting around a pipe and a tensioning system for tightening the casing around the outer surface of the pipe.

In construction and civil engineering projects it is generally necessary to provide utilities such as gas, potable water and sewage removal at a site by laying subterranean pipes or to replace aging or broken pipework with new pipework. Such pipes generally come in standard lengths and are connected together at site. An efficient and economical method of connecting pipes is to use pipes with plain ends as this avoids the need for pipe preparation compared to other methods such as welding, screw threading, flanging, grooving or shouldering.

The pipe connection generally needs to withstand the fluid pressure of the application in which it is being used and also achieve a fluid-tight seal in order to avoid leaks and prevent the ingress of contaminants. This latter requirement is particularly important in the supply of potable water to previously industrial sites, so-called "brownfield" sites. The ground at such sites is often contaminated with industrial pollutants and otherwise undesirable materials. In addition, it is necessary for the pipe itself to resist the permeation of pollutants into and out of the pipe.

When supplying potable water to brownfield sites and other sites where there is an increased risk of contamination, for example, near agricultural land, landfill sites and petrol stations, it is generally advised to use barrier pipe, an example of which is shown in Figure 1. Barrier pipe 1 typically comprises a multi-layer construction having an inner polymer layer 3 for containing the fluid being transported, a fluid impermeable layer 5, such as a layer of aluminium, for preventing contaminants from passing through it and an outer polymer layer 7 to provide a further layer of protection. Adhesive layers 9 may bond the respective layers 3, 5 and 7 together. Suitable types of barrier pipe include those according to British Standard BS 8588 and are available from a variety of manufacturers or distributors.

A problem with barrier pipe is that the ends are not sealed and therefore contaminants may penetrate the layers of the barrier pipe from its cut or free end, thereby rendering it ineffective.

This can be particularly problematic when connecting lengths of pipe together as the connections represent points where contaminants may penetrate the layers of the barrier pipe. Furthermore, non-uniform stress applied to the circumference of the barrier pipe in the region of the connection can cause the ends of the pipe to deform and the layers of the pipe to separate, which may also allow contaminants to penetrate between the layers.

The present invention has been devised with the foregoing in mind.

According to an aspect of the present invention, there is provided a pipe clamp or pipe coupling for holding the ends of two pipes, the pipe clamp or pipe coupling comprising: a tubular casing for fitting around a pipe, the tubular casing having a longitudinal gap between a first free end and a second free end; a tensioning system for tightening the casing around the outer surface of the pipe, the tensioning system comprising at least one tensioner for drawing the first free end and the second free end towards one another; a bridge member configured to circumferentially span the longitudinal gap, wherein an outwardly facing surface of the bridge member is arranged to engage the at least one tensioner to resist outward movement of the bridge member during tightening.

The pipe clamp or pipe coupling of the present invention can be applied to a barrier pipe connection. For example, two plain-ended barrier pipes may be connected by using an internal pipe stiffener in the form of a double-ended male connector, each end of which is inserted into a respective end of the two pipes to be connected. The pipe clamp or pipe coupling of the present invention is fitted externally around the connection and applies a circumferential clamping force which holds the layers at the free ends of the pipes firmly together, thereby reducing the likelihood of the ingress of contaminants. In connections using a pipe stiffener, the pipe clamp or pipe coupling presses the internal circumference of the two pipes against the external circumference of the pipe stiffener such that the layers at the free ends of the pipes are firmly held together between the clamp or coupling and the pipe stiffener.

An advantage of the tubular casing of the pipe clamp or pipe coupling of the present invention is that it assists in providing a uniformly distributed compressive force around the whole circumference of the pipe. The bridge member provides the uniformly distributed compressive force in the region of the longitudinal gap between the two free ends of the tubular casing.

This arrangement helps to hold the layers of the barrier pipe together around the whole circumference of the free ends of the pipes and reduces deformation of the pipe ends and the likelihood of contaminants penetrating the pipe layers.

By arranging an outwardly facing surface of the bridge member to engage or abut the at least one tensioner, outward movement of the bridge member during tightening of the tensioning system can be inhibited. This helps to reduce deformation of the bridge member which may otherwise crimp or fold during tightening of the clamp or coupling. The tensioner applies a resistive or reaction force to the bridge member and therefore reduces its tendency to move outwards during tightening, e.g. by crimping or folding. An advantage of this arrangement is that it assists in maintaining the bridge member in position against the pipe. This allows the clamp or coupling to provide a uniformly distributed compressive force around the whole circumference of the pipe, including in the region of the longitudinal gap, which helps to hold the layers of the barrier pipe together and reduce deformation of the pipe even in the region of the longitudinal gap.

As used herein, the term "pipe clamp" refers to a device which holds the ends of two pipes by applying a circumferential clamping force to both ends of the pipe.

As used herein, the term "pipe coupling" refers to a device which holds the ends of two pipes to connect the two pipes in a fluid tight manner. In addition to providing a circumferential clamping force, the coupling also provides a fluid seal around the pipes and resists axial movement of the two pipes to assist in maintaining the integrity of the connection.

As used herein, the term "longitudinal" means a direction parallel, or substantially parallel, to the length or longest axis of the pipe or pipe clamp or pipe coupling. With respect to the term "longitudinal gap", the gap is longitudinal in the sense that it extends longitudinally along the length of the pipe clamp or pipe coupling. However, the skilled person will appreciate that the gap refers to the circumferential gap in the tubular casing, i.e. the circumferential space or distance between the two free ends of the tubular casing.

As used herein, the term "outward" refers to points located outside the central longitudinal axis of the pipe or pipe clamp or pipe coupling or a direction from a central longitudinal axis towards an outer point. The term "outwardly" should be interpreted accordingly.

The bridge member may comprise a radially extending protrusion in which an outwardly facing surface of the protrusion is arranged to engage the at least one tensioner. The protrusion allows for the arrangement in which the tensioner is spaced some distance from the outer circumference of the pipe or tubular casing. The protrusion can be sized such that it extends to the point where it engages the tensioner.

The bridge member may comprise a radially extending fin, wherein an outwardly facing surface of the fin is arranged to engage the tensioner. The fin allows for the arrangement in which the tensioner is spaced some distance from the outer circumference of the pipe or tubular casing. The fin can be sized such that it extends to the point where it engages the tensioner. The fin may also assist in providing stiffness to the bridge member in the plane of the fin.

Optionally, the fin may comprise an aperture through which a respective one of the at least one tensioner passes and wherein an outwardly facing surface of the aperture engages the tensioner. This arrangement means that the fin can extend to the outer dimensions of the pipe clamp or pipe coupling such that a relatively tall fin can be used without having to increase the overall size of the clamp or coupling. This is because the aperture can pass through the fin at some point along its height. Furthermore, the bridge member may be a loose component (i.e. not attached or held to the pipe clamp or pipe coupling) until the pipe clamp or pipe coupling is installed. This arrangement also prevents longitudinal movement or slippage of the bridge member because the bridge member is held in position by the tensioner passing through the aperture. In addition, the arrangement helps retain the bridge member with the other components of the pipe clamp or pipe coupling until installation.

Optionally, the aperture may comprise an outwardly extending slot. This arrangement allows for movement of the tensioner within the slot as the tensioning system is tightened. Furthermore, it allows for bridge members of different thicknesses or multiple bridge members to be used.

The fin or protrusion may comprise a recess, wherein an outwardly facing surface of the recess engages a respective one of the at least one tensioner. This arrangement also prevents longitudinal movement or slippage of the bridge member due to the outwardly facing surface of the recess engaging the tensioner.

The fin may be attached to the bridge member. Any suitable method of attachment may be used, for example, welding.

The bridge member may comprise first and second bridge member parts. Optionally, the first and second bridge member parts each comprise a bridge portion and a fin portion. In this arrangement, the two fin portions are placed side by side with the each bridge portion of the first and second bridge portions being located on either side of the fin. This provides a double material thickness fin, which increases the strength and stiffness of the fin compared to a single material thickness fin.

The bridge member may comprise a first bridge member and the pipe clamp or coupling may further comprise a second bridge member, wherein the second bridge member is arranged inwardly of the first bridge member. The second bridge member helps provide additional clamping force in the region of the longitudinal gap.

The tensioning system may comprise a single tensioner and the fin may comprise a single aperture or recess. In another embodiment, the tensioning system may comprise first and second tensioners and the fin may comprise respective first and second apertures or recesses. This arrangement provides a tensioner for each pipe end and the first and second tensioners may be spaced apart in a longitudinal direction of the pipe, such that the first tensioner overlies a first pipe end region and the second tensioner overlies a second pipe end region. This assists the pipe clamp or pipe coupling to hold both ends of the pipes and helps to provide a uniform clamping force along the length of the clamp or coupling. Alternatively, the tensioning system may comprise more than two tensioners and the fin may comprise a corresponding number of respective apertures or recesses.

The at least one tensioner may comprise a fastener. As used herein, the term 'fastener' refers to any suitable means for applying a compressive force to draw together the first pivoting member and the second pivoting member, and includes screws, bolts used with either a standard nut or a clinch nut, rivets, clamps or latches, clips or ratchet-based fasteners. Bolts or screws have been found to be particularly suitable tensioners as they can apply a continuous increase or decrease in tensile force. However, other suitable tensioners or fasteners such as the aforementioned may be used.

The bridge member may be attached to the tubular casing. The bridge member may be attached to only one free end of the tubular casing. This reduces the likelihood of the bridge member being lost or accidentally separated from the remainder of the pipe clamp or pipe coupling prior to installation. By attaching the bridge member to only one free end of the tubular housing, the bridge member is free to move and slide under the other free end of the tubular casing when the tensioning system is tightened. The bridge member may be spot welded to the tubular casing. Spot welding has been found to be a particularly suitable way of attaching the bridge member to the tubular casing, although other suitable methods of attachment may be used.

The pipe clamp or pipe coupling may further comprise a retainer for retaining the bridge member in a central position prior to use. In particular the retainer may assist in keeping the bridge member centred in the longitudinal gap prior to installation such that it is in the correct position when the pipe clamp or pipe coupling is installed. The retainer may also assist in for retaining the tensioner in the tensioning system prior to use. The retainer may comprise an 0-ring. However, other suitable retainers may be used.

s The tensioning system is preferably provided on the tubular casing. Any suitable tensioning system or means may be used. The tensioning system may be formed by folding the free ends of the tubular casing back on themselves and welding the ends to the tubular casing to form a loop at each free end. A pin is inserted into each loop. At least one fastener, such as a screw, is passed through transverse holes in one of the pins into tapped transverse holes in the other of the pins, so as to interconnect the two free ends of the tubular casing. Such a tensioning system or means is described in our patent specifications EP-A-0542779 and EP-A-0900346.

The pipe clamp or pipe coupling may be sized to accommodate any pipe having an external diameter of between about 21 mm and about 630 mm, although the skilled person will appreciate that the pipe clamp or pipe coupling may be used with other pipe diameters. The pipe clamp or pipe coupling of the present invention also accommodates typical pipe tolerances in accordance with, for example, BS EN 877:1999.

The pipe clamp or pipe coupling of the present invention is suitable for use in holding pipes formed from a variety of plastic materials including but not limited to polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), high density polyethylene (HDPE), medium density polyethylene (MDPE), polypropylene (PP), acrylonitrile butadiene styrene (ABS) or multi-layer pipes comprising layers of one or more of the aforementioned materials in addition to an impermeable barrier layer such as aluminium. The pipe clamp or pipe coupling of the present invention is also suitable for use in holding metal pipes.

According to a second aspect of the invention, there is provided a pipe coupling for coupling together two pipes in a fluid-tight manner, the pipe coupling comprising: a tubular casing for fitting around a pipe, the tubular casing having a longitudinal gap between a first free end and a second free end; a tubular sealing gasket disposed within the tubular casing; a tensioning system for tightening the casing around the tubular sealing gasket, the tensioning system comprising at least one tensioner for drawing the first free end and the second free end towards one another; a bridge member configured to circumferentially span the longitudinal gap, wherein an outwardly facing surface of the bridge member is arranged to engage the at least one tensioner to resist outward movement of the bridge member during tightening.

The tubular casing may comprise an outer tubular casing and an inner tubular casing, wherein the inner tubular casing fits inside the outer casing. The tubular sealing gasket may be disposed within the inner tubular casing. Each of the inner and outer tubular casing may have a longitudinal gap, which longitudinal gaps may be substantially circumferentially aligned. The tensioning system may be provided on the outer tubular casing.

It should be appreciated that particular combinations of the various features described and defined in any aspect of the invention can be implemented and/or supplied and/or used 10 independently.

The invention will be further described, by way of example only, with reference to the accompanying drawings in which: * Figure 1 is perspective partial cutaway view of an example barrier pipe.

* Figure 2 is a side view of an example pipe connection.

* Figure 3 is a perspective view of a pipe clamp in accordance with an embodiment of the present invention.

* Figure 4 is an end view of the pipe clamp of Figure 2.

* Figure 5 is a plan view of the pipe clamp of Figure 2 showing the clamp installed around a pipe connection.

* Figure 6 is a perspective view of a bridge member in accordance with an embodiment of the present invention.

* Figure 7 is a perspective view of a bridge member in accordance with another embodiment of the present invention.

* Figure 8 is a perspective view of a bridge member in accordance with another embodiment of the present invention.

* Figure 9 is a perspective view of a bridge member in accordance with another embodiment of the present invention.

* Figure 10 is a perspective view of a bridge member in accordance with another embodiment of the present invention.

* Figure 11 is a perspective view of the tensioning bolts and bridge member of a pipe clamp in accordance with an embodiment of the present invention showing retaining 0-rings for keeping for the bridge member centred prior to installation.

* Figure 12 is a perspective view of a pipe clamp in accordance with another embodiment of the present invention.

* Figure 13 is a perspective view of a pipe coupling in accordance with an embodiment of the present invention.

Figure 2 shows a side view of an example pipe connection 10. The internal detail of the pipe connection 10 is shown in dashed lines. The pipe connection 10 comprises a first pipe 2 and a second pipe 4 connected by a pipe stiffener 6 in the form of a double-ended male connector. A first end 6a of the pipe stiffener 6 has been inserted into the opening formed in the end 2a of first pipe 2. A second end 6b of the pipe stiffener 6 has been inserted into the opening formed in the end 4a of second pipe 4. The pipe stiffener 6 forms an interference fit with the pipe to hold the pipe stiffener 6 securely within the pipe and the two ends 2a, 4a of the first 2 and second 4 pipes together.

Figure 3 shows a pipe clamp 100 according to an embodiment of the present invention. The pipe clamp 100 comprises a tubular casing 102, a tensioning system 104 and a bridge member 106. The tubular casing 102 is formed of a rolled steel strip, formed into a tube. The ends 108 of the steel strip have been folded back on themselves away from the interior of the tubular casing 102 and welded to the outside surface of the tubular casing 102 to form a first loop 110 at a first free end 112 of the tubular casing 102 and a second loop 114 at a second free end 116 of the tubular casing 102. A longitudinal gap 118 extends along the length of the pipe clamp 100 between the first 112 and second 116 free ends of the tubular casing 102.

The tensioning system 104 comprises a first pin 120 inserted into the first loop 110 and a second pin 122 inserted into the second loop 114. The pins 120, 122 extend the full length of the pipe clamp 100 at the first 112 and second 116 free ends of the tubular casing 102. The tensioning system 104 further comprises first 124 and second 126 tensioning bolts. The tensioning bolts 124, 126 pass through transverse holes (not shown) in the first pin 120 into tapped or threaded transverse holes (not shown) in the second pin 122, so as to interconnect the two free ends 112, 116 of the tubular casing 102. In use, the tensioning bolts 124, 126 can be turned to draw the two free ends 112, 116 towards one another to tighten the tubular casing around a pipe. The tensioning bolts 124, 126 therefore act as tensioners for the tensioning system 104. Slots 128 are cut in the loops 110, 114 so as to provide clearance for the tensioning bolts 124, 126.

The bridge member 106 is formed of a rolled steel strip and has an arcuate part 130 and a fin 132, which extends outwardly from and longitudinally along a mid-point of the arcuate part 130. The arcuate part 130 has the same or a similar radius of curvature similar as the tubular casing 102 and subtends an angle of approximately 120 degrees at the pipe axis. The fin 132 extends outwardly to approximately the same distance as the loops 110, 114 and has two transverse apertures or slots 134 through each of which respective ones of the tensioning bolts 124, 126 pass.

Without the fin, there may be a tendency for the bridge member to move outwards by folding or crimping in the region of the longitudinal gap as the two free ends of the tubular casing are drawn together during tightening of the clamp. However, in the embodiment of Figure 3, an outwardly facing surface (for example, an outwardly facing internal wall) (not shown in Figure 2 but see Figure 6) of each of the transverse slots 134 formed in the fin 132 is configured to engage or abut its respective tensioning bolt 124, 126 so that, as the clamp 100 is tightened, the tensioning bolts 124, 126 provide a reaction force to the outward movement of the bridge member 106 caused by the compressive force of the clamp 100 being tightened. This helps in maintaining the bridge member 106 in position against the pipe so that the clamp 100 may provide a more uniformly distributed compressive force around the circumference of the pipe, including in the region of the longitudinal gap 118.

Figure 4 shows an end view of the pipe clamp 100 of Figure 3. The tensioning bolts 124, 126 (only the second tensioning bolt 126 is visible in Figure 4) have been adjusted to draw the two free ends 112, 116 of the tubular casing 102 towards one another, thereby closing or narrowing the longitudinal gap 118.

Figure 5 shows a plan view of the pipe clamp 100 of Figure 3 installed around the pipe connection 10 of Figure 2 and overlying the pipe stiffener 6. The internal details of the two pipes 2, 4 within the clamp 100 and the pipe stiffener 6 within the two pipes 2, 4 are shown in dashed lines. The tensioning bolts 124, 126 have been adjusted to draw the two free ends 112, 116 of the tubular casing 102 towards one another, thereby closing or narrowing the longitudinal gap 118 to hold or grip the ends 2a, 4a of the two pipes 2, 4. The first tensioning bolt 124 overlies the first pipe 2 in a region near first pipe end 2a and the second tensioning bolt 126 overlies the second pipe 4 in a region near second pipe end 4a. The pipe clamp 100 has been installed such that the interface of the two pipe ends 2a, 4a is arranged approximately midway in a longitudinal direction between the two tensioning bolts 124, 126. The pipe clamp 100 provides a circumferential clamping force around the pipe connection 10 and holds the ends 2a, 4a of the two pipes 2, 4 against the pipe stiffener 6.

Figures 6-10 respectively show five different embodiments of bridge member. Referring to Figure 6, this shows an embodiment in which the bridge member is formed as a single piece or part and corresponds to the bridge member 106 used in the clamp 100 of Figure 3. As discussed above, the bridge member 106 comprises an arcuate part 130 and a fin 132, which extends radially or outwardly from and longitudinally along a mid-point of the arcuate part 130. The fin 132 is attached to the arcuate part 130, for example, by welding, such that the bridge member 106 forms a single piece or part. The fin has two transverse, radially extending apertures or slots 134 which are formed through the thickness of the fin 132 and each slot 134 is positioned such that a respective one of the tensioning bolts (not shown) can pass through its respective slot 134. Each slot 134 has an outwardly facing surface 134a, for example, an outwardly facing internal wall of the slot, which in Figure 5 is the lower curved part of the slot 134. This outwardly facing surface 134a is configured to engage or abut its respective tensioning bolt (not shown) so that, as the clamp 100 is tightened, the tensioning bolts provide a reaction force to the outward movement of the bridge member 106 caused by the compressive force of the clamp being tightened. This helps in maintaining the bridge member 106 in position against the pipe so that the clamp may provide a more uniformly distributed compressive force around the circumference of the pipe, including in the region of the longitudinal gap.

The bridge member 206 of Figure 7 is substantially the same as that of Figure 6 with the exception that it is formed from two pieces or parts, i.e. a first bridge member part 206a and a second bridge member part 206b. Each bridge member part 206a, 206b comprises a bridge or arcuate portion 230 and a fin portion 232. The fin portions 232 are formed by bending a portion of each bridge member part 206a, 206b such that it extends radially or outwardly, i.e. perpendicularly to the tangent of the arcuate portion 230 at the location of the bend. Each fin portion 232 has two transverse, radially extending slots 234 which are formed through the thickness of the fin portions 232. Each slot 234 has an outwardly facing surface 234a, which is configured to engage or abut its respective tensioning bolt. The fin portions 232 of the first 206a and second 206b bridge member parts are arranged adjacent to one another such that their outer profiles and the slots 234 are aligned and are attached together by spot welding, although any suitable member of attachment could be used. However, the fin portions 232 do not necessarily need to be attached together to serve their purpose.

The bridge member 306 of Figure 8 is substantially the same as that of Figure 7 and comprises a first bridge member part 306a and a second bridge member part 306b, which together form a first bridge member. However, the bridge member 306 also comprises a further or second bridge member 336 which is arranged inwardly of the first bridge member, i.e. inwardly of the first 306a and second 306b bridge member parts. The bridge member 306 of Figure 8 therefore comprises three parts. The second bridge member 336 is formed of a rolled steel strip and is arcuate in form, having the same or a similar radius of curvature similar as the tubular casing of the pipe clamp. The second bridge member 336 subtends a smaller angle compared to the first bridge member, for example, an angle of approximately 90 to 100 degrees at the pipe axis. For clarity, the second bridge member 336 is shown spaced apart from the first bridge member. However, in use, the second bridge member 336 will be held in contact between first bridge member and the pipe. The second bridge member helps provide additional clamping force in the region of the longitudinal gap.

Figure 9 shows another embodiment of the bridge member in which the bridge member 406 is formed as a single piece or part and comprises an arcuate part 430 and an outwardly or radially extending protrusion 438. The radially extending protrusion 438 has a substantially inverted U shape which extends longitudinally along a mid-point of the arcuate part 430. The radially extending protrusion 438 is formed by bending the steel strip in the region of the midpoint of the arcuate part 430. An outwardly facing surface 438a of the radially extending protrusion is configured to engage or abut the tensioning bolts.

Referring to Figure 10, this shows another embodiment in which a bridge member 506 is formed as a single piece or part and comprises an arcuate part 530 and a fin 532, which extends radially or outwardly from and longitudinally along a mid-point of the arcuate part 530. The fin 532 is attached to the arcuate part 530, for example, by welding, such that the bridge member 506 forms a single piece or part. The fin has two recesses 534 which are formed in a outwardly extending surface of the fin 532 and each recess 534 is positioned such that, in use, at least a portion of a respective one of the tensioning bolts (not shown) would be located within its respective recess 534. Each recess 534 has an outwardly facing surface 534a, for example, an outwardly facing internal wall of the recess, which in Figure 9 is the lower curved part of the recess 534. This outwardly facing surface 534a is configured to engage or abut its respective tensioning bolt (not shown).

Figure 11 shows a perspective view of the tensioning bolts 624, 626 and bridge member 606 of a pipe clamp in accordance with an embodiment of the present invention. The other features of the pipe clamp have been omitted for clarity. The bridge member 606 of Figure 11 is substantially the same as the three-part bridge member of Figure 8. Each tensioning bolt 624, 626 passes through a respective slot 634 formed in each fin portion 632 and bears two 0-rings; one on either side of the two fin portions 632 (only the 0-rings on one side of the two fin portions 632 are visible in Figure 11). The 0-rings are located approximately mid-way along the length of the thread of the tensioning bolts 624, 626 and assist in retaining the bridge member 606 centred in the longitudinal gap prior to installation such that it is in the correct position when the pipe clamp is installed. In Figure 11, a second bridge member 636 can be seen in contact between the bridge member 606, i.e. the first bridge member, as it would be in use.

Figure 12 shows a pipe clamp 700 in accordance with another embodiment of the present invention. The construction of pipe clamp 700 is substantially the same as pipe clamp 100 shown in Figure 3 with the exception that the tensioning system 104 only comprises a single tensioning bolt 724 and the clamp 700 comprises a three piece bridge member arrangement similar to the bridge member 306 shown in Figure 8. As the tensioning system 104 only comprises a single tensioning bolt 724, the pipe clamp 700 is shorter in the longitudinal direction than pipe clamp 100 of Figure 3.

The bridge member arrangement comprises a first bridge member 706 having first 706a and second 706b bridge member parts and a second bridge member 736 arranged inwardly of the first bridge member 706, i.e. the second bridge member 736 is arranged inwardly of the first 706a and second 706b bridge member parts. As the tensioning system 104 only comprises a single tensioning bolt 724, each fin portion of the first 706a and second 706b bridge member parts only has a single transverse, radially extending slot 734, which is formed through the thickness of the fin portions. An outwardly facing surface (not shown) of the slot 734 is arranged to engage the tensioning bolt 724. Furthermore, the bridge member arrangement of Figure 12 is shorter in the longitudinal direction than pipe clamp 100 of Figure 3 and has a length substantially corresponding to the that of the pipe clamp 700.

It will be appreciated that modified versions of the various embodiments of bridge member shown in Figures 6 to 10 can all be used with the pipe clamp 700 of Figure 12. Such various embodiments of bridge member only need to be modified to reduce their length to correspond to the length of pipe clamp 700 and, where apertures or recesses are present in the bridge member, to only have a single aperture or recess.

Figure 13 shows a pipe coupling 800 in accordance with another embodiment of the present invention. The pipe coupling 800 comprises an outer tubular casing 802a, an inner tubular casing 802b, a tubular sealing gasket 805, a tensioning system 804 and a bridge member arrangement. The outer tubular casing 802a is formed of a rolled steel strip, formed into a tube. The ends 808 of the steel strip have been folded back on themselves away from the interior of the outer tubular casing 802a and welded to the outside surface of the outer tubular casing 802a to form a first loop 810 at a first free end 812 of the tubular casing 802 and a second loop 814 at a second free end 816 of the outer tubular casing 802a. A longitudinal gap 818a extends along the length of the outer tubular casing 802a between its first 812 and second 816 free ends. The axial end margins of the outer tubular casing 802a are bent inwardly at right angles to form annular flanges 807.

The inner tubular casing 802b is formed of rolled steel and has a longitudinal gap 818b. The axial end margins of the inner casing 802b are bent inwardly at right angles to form annular flanges 809. The inner casing 802b fits inside the outer casing 802a, the axial length of the inner casing 802b being slightly less than that of the outer casing 802a so that the flanges 809 fit inside the flanges 807.

The tubular sealing gasket 805 fits within the inner tubular casing 802b and is formed of an elastomeric material, for example rubber or synthetic rubber. The tubular sealing gasket 805 comprises a series of ribs 811 to achieve a seal which is effective at high hydrostatic pressures, for example 32 bar or even 64 bar. However, the axial length of the gasket that is exposed to the hydrostatic pressure is small compared with the overall axial length of the coupling.

The tensioning system 804 comprises a first pin 820 inserted into the first loop 810 and a second pin 822 inserted into the second loop 814. The pins 820, 822 extend the full length of the pipe coupling 800 at the first 812 and second 816 free ends of the outer tubular casing 802a. The tensioning system 804 further comprises first 824 and second 826 tensioning bolts.

The tensioning bolts 824, 826 pass through transverse holes (not shown) in the first pin 820 into tapped or threaded transverse holes (not shown) in the second pin 822, so as to interconnect the two free ends 812, 816 of the outer tubular casing 802a. In use, the tensioning bolts 824, 826 can be turned to draw the two free ends 812, 816 towards one another to tighten the outer tubular casing 802a around the tubular sealing gasket 805. The tensioning bolts 824, 826 therefore act as tensioners for the tensioning system 804. Slots 828 are cut in the loops 810, 814 so as to provide clearance for the tensioning bolts 824, 826.

The shaping of the outer tubular casing 802a and inner tubular casing 802b are smooth and identical so that a low friction surface is provided for easy sliding when closing the coupling.

This is important because a coupling which has only one casing will not provide low friction surfaces between the steel casing and the rubber gasket or sealing sleeve. The longitudinal gaps 818a, 818b of the outer tubular casing 802a and inner tubular casing 802b respectively are aligned and a bridge member arrangement is provided to complete the circumferential band.

The pipe coupling 800 comprises a three piece bridge member arrangement similar to the bridge member 306 shown in Figure 8. The bridge member arrangement of pipe coupling 800 comprises a first bridge member 806 having first 806a and second 806b bridge member parts and a second bridge member 836 arranged inwardly of the first bridge member 806, i.e. the second bridge member 836 is arranged inwardly of the first 806a and second 806b bridge member parts. Each fin portion of the first 806a and second 806b bridge member parts has two transverse, radially extending slots 834 which are formed through the thickness of the fin portions and each slot 834 is positioned such that a respective one of the tensioning bolts 824, 826 can pass through its respective slot 834. Each slot 834 has an outwardly facing surface (not shown), which is configured to engage or abut its respective tensioning bolt 824, 826.

The fin portions of the first 8206a and second 806b bridge member parts are arranged adjacent to one another such that their outer profiles and the slots 834 are aligned.

The outwardly facing surface of each of the transverse slots 834 formed in the first bridge member 806 is configured to engage or abut its respective tensioning bolt 824,826 so that, as the tensioning system 804 is tightened, the tensioning bolts 824, 826 provide a reaction force to the outward movement of the first bridge member 806 caused by the compressive force of the clamp 100 being tightened. This helps in maintaining the second bridge member 836 in position against the tubular sealing gasket 805 so that the pipe coupling 800 may provide a continuous seal around the circumference of the pipe, including in the region of the longitudinal gaps 118a, 118b.

It will be appreciated that the various embodiments of bridge member shown in Figures 6 to 10 can all be used with the pipe coupling 800 of Figure 13.

The pipe coupling 800 further comprises a pair of frusto-conical gripping rings (not shown). Each ring is provided in a corresponding slot formed in the outer surface of the tubular sealing gasket 805 at each axial end. The outer end of each slot lies at the axial end of the outer surface. The slope of the slot is such that the inner end is nearer the axial middle of the gasket 805 than the outer end. Each ring is formed from a pair or arcuate segments, and comprises a set of hard teeth to penetrate through the gasket 805 at the bottom of the slot and bite into the surface of the pipe, thereby providing locking of the coupling to the pipe against axial movement. The teeth are designed to make contact at approximately 5mm centres around the circumference with a width of approximately 2mm for each tooth, giving approximately 40% contact around the periphery of the pipe.

Claims

Claims 1 A pipe clamp or pipe coupling for holding the ends of two pipes, the pipe clamp or pipe coupling comprising: a tubular casing for fitting around a pipe, the tubular casing having a longitudinal gap between a first free end and a second free end; a tensioning system for tightening the casing around the outer surface of the pipe, the tensioning system comprising at least one tensioner for drawing the first free end and the second free end towards one another; a bridge member configured to circumferentially span the longitudinal gap, wherein an outwardly facing surface of the bridge member is arranged to engage the at least one tensioner to resist outward movement of the bridge member during tightening.
2. A pipe clamp or pipe coupling according to claim 1, wherein the bridge member comprises a radially extending protrusion and wherein an outwardly facing surface of the protrusion is arranged to engage the at least one tensioner.
3. A pipe clamp or pipe coupling according to claim 1 or 2, wherein the bridge member comprises a radially extending fin and wherein an outwardly facing surface of the fin is arranged to engage the at least one tensioner.
4. A pipe clamp or pipe coupling according to claim 3, wherein the fin comprises at least one aperture through which the, or a respective one of the, at least one tensioner passes, wherein an outwardly facing surface of the aperture engages the tensioner.
5. A pipe clamp or pipe coupling according to claim 4, wherein the aperture comprises an outwardly extending slot.
6. A pipe clamp or pipe coupling according to claim 3, wherein the fin comprises a recess, wherein an outwardly facing surface of the recess engages a respective one of the at least one tensioner.
7. A pipe clamp or pipe coupling according to any of claims 3 to 6, wherein the fin is attached to the bridge member.
8. A pipe clamp or pipe coupling according to any preceding claim, wherein the bridge member comprises first and second bridge member parts.
9. A pipe clamp or pipe coupling according to claim 8, wherein the first and second bridge member parts each comprise a bridge portion and a fin portion.
10. A pipe clamp or pipe coupling according to any preceding claim, wherein the bridge member comprises a first bridge member, the pipe clamp or pipe coupling further comprising a second bridge member, wherein the second bridge member is arranged inwardly of the first bridge member.
11. A pipe clamp or pipe coupling according to any of claims 3 to 10, wherein the tensioning system comprises a single tensioner and the fin comprises a single aperture or recess.
12. A pipe clamp or pipe coupling according to any of claims 3 to 10, wherein the tensioning system comprises first and second tensioners and the fin comprises respective first and second apertures or recesses.
13. A pipe clamp or pipe coupling according to any preceding claim, wherein the at least one tensioner comprises a fastener.
14. A pipe clamp or pipe coupling according to any preceding claim, wherein the bridge member is attached to the tubular casing.
15. A pipe clamp or pipe coupling according to claim 14, wherein the bridge member is spot welded to the tubular casing.
16. A pipe clamp or pipe coupling according to any preceding claim, further comprising a retainer for retaining the bridge member in a central position prior to use.
17. A pipe clamp or pipe coupling according to any preceding claim, wherein the retainer comprises an 0-ring.