PIPE COUPLINGS

Abstract: The invention relates to pipe couplings and particularly to the provision of a welded connection between adjacent pipe lengths (1, 2) of plastics material. In this regard such techniques as butt welding and electrofusion welding are widely known and practised, at their cost, but necessary when it is the supply of gas that is involved. The object of the present invention is to provide a welded connection suited to the less exacting conditions of pipe lines for trunking or for the supply of water, which objet is met by a method comprising locating over the adjacent ends of the pipe lengths, a coupling sleeve (3) of a coupling sleeve and the external diameters of the pipes being such that the coupling sleeve is a close sliding fit on the ends of the pipes, applying an external drive (6) to the coupling sleeve to rotate the coupling sleeve on the pipe ends at a rate such that heat generated by friction melts the interface between the coupling sleeve and the pipe ends, and whereby following cessation of rotation, and on cooling, an effective weld is formed between the coupling sleeve and each pipe end.

Description: PIPE COUPLINGS This invention relates to pipe couplings and is particularly concerned with a method and apparatus for connecting adjacent ends of plastics pipes. There is the growing employment of plastics pipes in such as the gas and water supply industries and in other sectors such as the electricity and telecommunications fields, and whereby the supply or service can be provided belo ground. The employment of plastics pipes for the supply of gas or water, or along which appropriate cables, wires, carbon fibres or the like can pass, has many advantages in combining long life, strength and flexibility, but plastics pipes are produced in finite lengths, with the attendant problem of connecting one pipe length to another, and with one pipe length at least already laid in a trench. With such as the supply of gas, there is the essential need for a gas-tight joint between one pipe length and the next, and which has led to the development of portable equipment enabling the butt welding of one pipe end to the next. Whilst not involving the same degree of danger to the public there is the need to prevent the ingress of water at a joint between cables and where pipes are used as trunking for other services, the need to have a joint able to prevent ingress of water and soil. The object of the present invention is to provide a method and equipment for the welding of one pipe end to another that, whilst perhaps not able to meet those most exacting requirements for the supply of gas, is more than sufficient to provide a welded connection for pipes for use as trunking, or even the supply of water. According to one aspect of the present invention, a method of securing the end of one plastics pipe length to the adjacent end of a next plastics pipe length comprises locating over the adjacent ends of the pipe lengths, a coupling sleeve of a compatible plastics material, the internal diameter of the coupling sleeve and the external diameters of the pipes being such that the coupling sleeve is a close sliding fit on the ends of the pipes, applying an external drive to the coupling sleeve to rotate the coupling sleeve on the pipe ends at a rate such that heat generated by friction melts the interface between the coupling sleeve and the pipe ends, and whereby following cessation of rotation, and on cooling, an effective weld is formed between the coupling sleeve and each pipe end. To guard against any ovality of the pipe ends or coupling sleeve, or deviation in wall thickness introduced during their production, it is desirable to form an internal taper extending inwardly of each end of the coupling member, or an external taper extending away from each pipe end, and as rotation of the coupling member is effected, to urge the pipe ends inwardly of the coupling member and compress the outside of each pipe end against the inside of the coupling member, and whereby contact and hence melting and welding around the full periphery of the pipe ends can be substantially assured. Thus, equipment can be provided to be assembled e.g. in a trench, to encircle the pipe ends and apply a rotation to the coupling sleeve. However, it is most desirable that equipment for the rotation of the coupling sleeve is portable and able to be applied to and removed from the coupling sleeve from one side. Consequently, and in accordance with a second aspect of the present invention, equipment for effecting the method first above defined comprises a portable motor, a drive means attached to the motor shaft and formed such as to be able to engage co-operating formations externally of the coupling sleeve and whereby with the drive means applied against one side of the coupling sleeve, the coupling sleeve is caused to rotate. Thus in one relatively simple form, the coupling sleeve can be formed with axial gear tooth formations, and the motor provided with a gear tooth drive member having an axis at parallel to the motor drive shaft, and whereby the gear tooth drive can be held against the toothed coupling sleeve to cause its rotation. Alternatively, an intermediary drive member may be provided to encircle the coupling sleeve, there being a positive means of connection as between the drive member and the coupling sleeve such as by providing ribs and slots respectively on the outer periphery of the coupling member and in a bore of the drive member, the outer periphery of the drive member being formed with axial gear tooth formations for engagement with a gear tooth drive member. Therefore, in accordance with a still further aspect of the invention, equipment for carrying out the method first above defined, comprises a portable motor, a gear tooth drive member on the motor drive shaft, two arms pivotally secured with respect to the motor, and with freely rotatable rollers at the opposite ends thereof, and a toothed belt wrapped around the drive member and the freely rotatable rollers such that the teeth of the belt are in engagement with the drive member and the plain face of the belt in contact with the freely rotatating rollers, and when the length of belt extends across the outermost rollers has the teeth outermost and for presentation to and engagement with transverse teeth formed on the coupling member. Such an arrangement may have the lengths of the two pivotal arms to suit a particular diameter of coupling sleeve and when in position, locate the outermost rollers beyond the top and bottom dead-centres of the coupling sleeve. Thus, when the equipment is presented to the sleeve minimal force is required to cause inward force on the arms and cause them to close on to the coupling sleeve, and when the toothed belt is in enagement with a substantial proportion of the periphery of the coupling sleeve. However, to enable the equipment to be used on a variety of pipe diameters, and to avoid the problems of slack belt when the equipment is not in use, each arm can be both slidable and pivotally mounted, and spring-loaded rearwardly of the drive means. Thus, when not in use, the pivotal arms are in a rearward position the extended length between each rearmost roller and the drive member taking up a considerable part of the length of the belt and holding the belt relatively taut between the outermost rollers. On presentation of the equipment to a toothed coupling sleeve, it is urged against the sleeve and when the force applied to the belt is transmitted by the belt through the outermost rollers to the innermost rollers to cause the arms to slide in relation to the motor until the outermost rollers are beyond the dead- centre of the coupling sleeve, and when the arms are closed on to the sleeve to put the toothed belt in contact with the toothed sleeve over a substantial proportion of its periphery. Following termination of rotation of the sleeve, the equipment of the invention can simply be drawn from the sleeve and transported with ease to its next point of use. Equipment able to draw the pipe ends towards each other and inwardly of the coupling sleeve is already known, and such as is described in EP Patent Application 89313285.2. The invention also embraces a coupling sleeve formed with external transverse teeth for use with the equipment of the invention. Two embodiments of the invention will now be described in greater detail, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a part-sectional perspective view of a first embodiment of the invention; and Figure 2 corresponds to Figure 1 but shows a second embodiment of the invention; Figure 3 is a side elevation of an alternative construction of drive mechanism according to the invention; and Figure 4 is a schematic representation of the mechanism of Figure 3 in use. In Figure 1, the ends of respective pipe lengths 1, 2, are inserted into the opposite ends of a coupling member 3, and to butt against an internal shoulder 4 in the coupling member. The outside diameter of the pipe ends and the inside diameter of the coupling member are such that the pipe ends are an interference fit within the coupling member. The coupling member is provided on its periphery with axial gear tooth formations 5 for engagement with a gear tooth drive member 6 on a shaft 7 for connection to an appropriate portable drive motor (not shown). On activation of the motor, the connection between the gear tooth drive member 6 and the axial gear tooth formations 5 causes the coupling member 3 to rotate at high speed and when the friction at the interface as between the coupling member and the pipe ends causes the melting of the inside face of the coupling member and the outer face of the pipe ends. Following the cessation of rotation immediate and relatively rapid cooling takes place and with the consequent generation of a most effective weld as between the coupling member and the pipe ends. Thus, even with the respective pipes 1 and 2 laid in a trench it is a relatively simple matter to hold the pipe ends and the coupling member clear of the ground and to bring the gear tooth drive member into contact with the axial gear tooth formation on the coupling sleeve. In Figure 2, a similar arrangement is displayed, where again the ends of respective pipes 1, 2, are an interference fir within a coupling member 2. the pipe ends being mserte-:; into the coupling member 2 to butt against an internal member 4. In this embodiment, the outer periphery of the coupling member is provided with a series of parallel slots 8. Encircling the coupling member is a two-piece intermediary drive member 9, the two halves being detachably secured together by connecting elements 10, the bore of which is provided with a series of parallel ribs 11 to engage with the series of parallel slots 8 on the coupling sleeve. On the outer periphery of the intermediary drive member are formed parallel axial gear tooth formations 11 for engagement by the gear tooth drive member 6. Here again, and with the shaft 7 of the gear tooth drive member 6 extending to an apropriate motor, the coupling member 3 can be caused to rotate at high speed with the melting of plastics material at the interface between the coupling member and the pipe ends and which, on cooling, generates an effective weld. With this second embodiment of the invention, there is avoided the cost of producing axial gear tooth formations on every coupling member. In the alternative form of construction shown in Figures 3 and 4, pipe ends are provided as an interference fit in a coupling member, and either the coupling member formed with axial tooth formations as in Figure 1, or provided with an encircling intermediary drive member on which the tooth formations are provided, and as is shown in Figure 2. In this form of construction, the rotational force is derived from a toothed drive belt 12 that wraps around a substantial proportion of the periphery of the coupling sleeve or the intermediary drive member, and whereby to avoid side loading applied to the area of the welded coupling. Thus, a mounting block 13 is provided with a support arm 14 for attachment to the casing of the drive motor, the mounting block supporting pivotal arms 15, 16 having end rollers 17 and intermediary rollers 18. Supported on the block 13 is a toothed drive roller 19 on which a drive gear 20 is provided, to be driven by the motor. Thus, as is shown schematically in Figure 4, the belt is wrapped around the end rollers 17, and the intermediary rollers 18 such that it wraps around the drive roller with its teeth in contact with the teeth of the drive roller 19, and in the run of the belt extending between the end rollers 17, the teeth of the belt are exposed. With then the belt presented to either a toothed coupling sleeve or a toothed intermediary drive member, the urging of the belt against it causes the arms to swing until lateral movement carries the outer rollers 17 beyond the dead centre of the coupling sleeve and when further lateral movement causes a force to act through the belt and on to the pivotal arms to draw the end rollers inwardly, and results in the belt wrapping around the coupling sleeve or the intermediary drive member over more than 50% of its periphery. Activation of the motor then causes the belt to drive the coupling member or the intermediary drive member to a degree to cause melting of the interface between the coupling sleeve and the pipe ends as previously described, but in the absence of side loadings on the coupling sleeve or on the intermediary drive member during rotation.

Claims: CLAIMS 1. A method of securing the end of one plastics pip length to the adjacent end of a next plastics pipe lengt characterised by locating over the adjacent ends of the pip lengths (1, 2), a coupling sleeve (3) of a compatible plastic material, the internal diameter of the coupling sleeve (3) an the external diameters of the pipes (1, 2) being such that th coupling sleeve (3) is a close sliding fit on the ends of th pipes (1, 2), applying an external drive to the couplin sleeve (3) to rotate the coupling sleeve (3) on the pipe end (1, 2) at a rate such that heat generated by friction melt the interface between the coupling sleeve (3) and the pip ends (1, 2), and whereby following cessation of rotation, an on cooling, an effective weld is formed between the couplin sleeve (3) and each pipe end (1, 2). 2. A method as in Claim 1, characterised in that a internal taper is provided within each end of the couplin member (3) or an external taper is provided on each pipe end and the pipe ends are urged inwardly of the coupling membe (3) to compress the outside of each pipe end against th inside of the coupling member during rotation of the couplin member. 3. Equipment for performing the method of Claim 1 o Claim 2, characterised by a portable motor, a drive means (6 attached to the motor shaft (7) and formed such as to be abl to engage co-operating formations (5) formed externally of th coupling sleeve (3) and whereby with the drive means applie against one side of the coupling sleeve (3), the coupling sleeve (3) is caused to rotate. 4. Equipment as in Claim 3, characterised in that the coupling sleeve (3) is formed with axial gear tooth formations (5) and the motor provided with a gear tooth drive member (6) . 5. Equipment as in Claim 3, characterised in that the coupling sleeve (3) is formed with means (8) to engage with co-operating means (10) in the bore of an intermediary drive member (9) encircling the coupling sleeve (3), the periphery of the intermediary drive member being formed with axial gear tooth formations (11) to engage the gear tooth drive member (6). 6. Equipment as in Claim 5, characterised in that the intermediary coupling member is of two-piece construction detachably secured to each other and whereby to enable the intermediary coupling member (9) to be positioned around the coupling sleeve (3). 7. Equipment for performing the method of Claim 1 or Claim 2, characterised by a portable motor, a gear tooth member on a motor drive shaft, two arms pivotally secured with respect to the motor and with freely rotatable rollers at the opposite ends thereof, and a toothed belt wrapped around the drive member and the freely rotatable rollers such that the teeth of the belt are in engagement with the drive member and the plain face of the belt is in contact with the freely rotatable rollers and when the length of belt extending across the outermost rollers has its toothed face outermost and whereby the toothed belt can be presented to the coupling member and to cause rotation thereof. 8. Equipment as in Claim 7, characterised in that the lengths of the pivotal arms are selected to suit a particular diameter of coupling sleeve and whereby to locate the outermost rollers beyond the top and bottom dead centres of the coupling sleeve when the toothed belt is applied against the coupling member. 9. Equipment as in Claim 7, characterised in that the two arms are both pivotally and slidably mounted, and spring- loaded in a direction rearwardly of the drive means.

Inventors: BRIDGSTOCK ERIC, BRIDGSTOCK, ERIC
Applicants: FUSION GROUP PLC
Application year: 1992
Main classification: B29C65
IPC codes: B29C65, B29L23, F16L47