GB2034618A

GB2034618A - A method and apparatus for forming a circumferential groove around a workpiece

Info

Publication number: GB2034618A
Application number: GB7939465A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-11-17
Filing date: 1979-11-14
Publication date: 1980-06-11
Also published as: DK489179A; DE2946082A1; SE7811904L; FR2441441A1; IT1119494B; FI793569A; NO793705L; IT7969226A0

Abstract

In a method of forming a circumferentially extending groove (43) in a circular peripheral surface of a workpiece (44), particularly a pipe, the groove is formed by means of a tool (42) having at least two engagement means (47, 48) for co-operation with the workpiece, at least one of the engagement means comprising a groove- forming roller (48). The engagement means are pressed radially against the workpiece (44) so that the workpiece is clamped between them, and the tool (42) and the workpiece (44) are rotated relative to one another through an angle necessary for the groove forming roller (48) or rollers to describe a groove around the workpiece. The rotary movement is repeated while progressively decreasing the distance between the groove forming engagement means (48) and the centre of the workpiece until the groove is formed to the desired depth. <IMAGE>

Description

SPECIFICATION A method and apparatus for forming a circumferential groove around a workpiece The present invention relates to a method of forming a circumferentially extending groove in a circular peripheral surface of a workpiece, and is particularly concerned with the use of the method for connecting and mounting purposes, such as in the joining of pipes. The invention also relates to a tool for forming such circumferential grooves in workpieces. As used herein the process of forming a groove is to be interpreted as a process by which the material of the workpiece is plastically deformed to form an external groove and, in the case of hollow workpieces, also a corresponding internal bead.

In present day engineering techniques, pipes and tubes are usually joined together by means of welding or soldering operations. Cold joining techniques are also used, although these techniques require the provision of relatively expensive couplings or screw-thread forming operations. A common feature of these known methods is that they are extremely time consuming and, in certain cases, difficult to carry out when the work required must be done in confined spaces. Problems also occur when pipes or tubes made of different materials are to be joined together, for example because the pipes cannot be worked or treated in a mutually similar manner because of the different materials from which they are made, or because the pipes cannot be connected directly together because of the risk of corrosion resulting from galvanic currents.Neither do present day joining methods lend themselves to surface-coated pipes or tubes, for example chromium plated pipes or tubes. In the case of pipes or tubes which are coated with a plastics material, it is normally necessary first to remove the covering before joining the pipes together. Difficulties are also encountered when joining plastics pipes together, and when connecting plastics pipes to metal pipes.

The present invention is based on the concept that circumferentially extending grooves can be formed in pipes, or other workpiece having a circular peripheral surface, extremely accurately without employing cutting operations, by forcing a forming tool, such as a roller or ball, radially against the surface of the workpiece and causing the tool to pass peripherally around the workpiece with a progressively decreasing distance between the forming surface of the tool and the centre of the workpiece.

Thus, the forming tool will produce a groove of progressively increasing depth during plastic deformation of the material of the workpiece, and in the case of pipes will also give rise to a corresponding, regularly formed, bead on the inside of the pipe. The ability to form such grooves and beads in pipes in a simple and inexpensive manner on site will enable various different pipe connections to be made as will be described later in more detail, without any of the drawbacks referred to above.

According to one aspect of the present invention therefore, a method of forming a circumferentially extending groove in a circular peripheral surface of a workpiece comprises locating the workpiece between the engagement means of a tool having at least two engagement means, at least one of the engagement means comprising a groove-forming roller or ball, pressing the engagement means radially against the circular peripheral surface of the workpiece so that the workpiece is clamped between the engagement means, rotating the tool and the workpiece relative to one another whereby a circumferential groove is formed in the circular peripheral surface of the workpiece by the groove forming engagement means, and repeating the relative rotary movement of the tool and the workpiece while progressively decreasing the distance between the groove forming engagement means and the centre of the workpiece until the groove is of the required depth.

The method in accordance with the invention differs markedly from known techniques for producing grooves, these techniques either relying on a cutting operation, in which case no internal bead is obtained in the case of pipes, or comprising locally pressing-in the wall of a pipe against a bead-forming means arranged within the pipe and serving as an anvil surface. This latter technique is not suited for thick-walled pipes and only permits a groove to be formed adjacent the ends of the pipe, since the anvil surface must be arranged internally of the pipe and must be removed afterwards. In the case of thinwalled pipes it has also been proposed to use rollers for deforming the pipe, the rollers being mounted on arms rotating around the pipe. Furthermore, a common feature of most of these known methods is that none can be carried out on site.Since they require the use of complicated tools or machines especially constructed for the purpose.

For the purpose of avoiding cutting the workpiece when carrying out the method in accordance with the invention, preferably the groove forming engagement means comprises a roller having a groove forming part with an arcuate profile having a radius of curvature which when grooving a pipe is at least equal to the wall thickness of the pipe. The groove is preferably therefore formed to a depth which corresponds substantially to the wall thickness of the pipe.

As a result of forming the groove progressively in the described manner there is obtained on the inside of a pipe a regular bead without the use of any form of anvil or reaction surface within the pipe. Thus, grooves can be formed at any desired position along a pipe, which renders the method suitable, inter alia, for use in the technique of joining and connecting pipes which is described below. The method can also be applied to all types of material known today and also in joining together workpieces of mutually different materials. Surface-coated pipes, such as chromium-plated pipes, can also be provided with grooves by the method in accordance with the invention.

As mentioned above, the groove-forming method in accordance with the invention can be used with advantage when desiring to form a tight connection between two pipes. For example, in a method of forming a sealed joint between two pipe sections having different diameters such that one section will fit into the other, the larger pipe section being made of metal, one end of the smaller pipe is inserted into the larger pipe section so that there is a ring of resilient material capable of serving as a sealing material around the smaller pipe section adjacent the inner surface of the larger pipe section, and a groove is formed in the outer surface of the larger pipe section by the method in accordance with the invention so as to form on the inner surface of the larger pipe section a bead which presses into and co-acts in a sealing fashion with the resilient material.When the smaller pipe section is made of metal and has no plastics covering, the smaller pipe section is first provided with an external groove and the ring of resilient sealing material is arranged in this groove. On the other hand, when the smaller pipe section is made of a plastics material, the plastics material can itself serve as the resilient sealing material, and in this case an internal support sleeve, for example a metal sleeve, needs to be arranged in the end of the plastics pipe section before the pipe section is inserted into the larger pipe section.

Using the invention, for instance, in connecting copper pipes is very advantageous as the pipes do not have to be heated, which otherwise would impair the strength of the material.

Furthermore, in the case of metal workpieces, the progressive plastic deformation of the metal as the groove is formed results in a certain degree of cold hardening of the metal in the groove, and the groove will also have a high surface fineness. Hence, in addition to its use in the joining of pipes, the method in accordance with the invention can also be used for forming grooves which are to be used as races for ball bearings.

According to a further aspect of the invention, a tool for forming a circumferentially extending groove in a circular peripheral surface of a workpiece comprises at least two engagement means mounted so that the workpiece can be clamped between them with the engagement means pressed radially against the circular peripheral surface of the workpiece and whereby relative rotary movement can be effected between the engagement means and the workpiece, at least one of the engagement means comprising a groove-forming roller or ball, and means for progressively decreasing the distance between at least one of the engagement means and the point which, in use, is occupied by the centre of the workpiece.

The tool may have the form of a practical hand tool which, inter alia, permits pipes or tubes to be readily joined together on site, even though the pipes or tubes are located in extremely confined spaces. The forces exerted on the pipe or tube are balanced out in the tool.

In one example of the tool in accordance with the invention the tool includes a stirrup-shaped holder in which the engagement means are mounted, and at least one of the engagement means is adjustable in the radial direction by means of a spindle in screw engagement with the stirrup-like holder, while the or each other engagement means is fixedly connected to the holder.

In order to reduce the angle through which the tool and the workpiece must be rotated relative to each otherfora groove to be formed by the grooveforming engagement means, the tool may have a multiplicity of groove-forming engagement means arranged to contact the workpiece at different locations around its periphery. These engagements means may conveniently be mounted on a carrier which is capable of adapting its shape to the shape of the workpiece and which comprises a plurality of pivotally connected links, for example in the form of a roller chain.

In addition to joining pipes and tubes in civil engineering projects, the groove-forming technique of the invention can also be used in joining together pipes and round workpieces in the manufacture of, for example, tubular structures, stanchions, furniture framestructures and fences. Another use of the method in accordance with the invention is that the formation of a groove and bead in a pipe or tube can form a stop member or a locking member in tubular structures, or a member for mounting an element, such as a valve, in a pipe-line. Afurther important advantage afforded by the groove-forming method in accordance with the invention is that it can also be applied, without limitation, under water and in places where serious problems may exist in carrying out welding and soldering operations.Furthermore the workman carrying out the method need have no specialized instruction in how the method should be carried out.

With the invention, it is possible to produce either sealed or non-sealed pipe joints. Also, it is possible to provide even thin-walled tubes with screwthreaded tube parts for the simple connection of the same.

Various embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figures la and it are part elevation and part sectional views illustrating one form of pipe joint which can be produced using the present invention; Figures 2a, 2b and 3 to 5 are part elevation and part sectional views illustrating five further forms of pipe joint which can be produced using the invention; Figure 6 is a perspective view of one form of a handtool for forming a groove in accordance with the invention.

Figure 7 is a part elevation and part sectional view of a component of the tool shown in Figure 6; Figures 8a to 8f are views illustrating different forms of groove-forming rollers which may be used in a tool in accordance with the invention; Figure 9 is an elevation of another example of a tool in accordance with the invention; and, Figure 10 is a view similar to Figure 9 but showing yet another example of a groove-forming tool.

Figure la shows two metal pipes 1 and 2 which are to be joined together and of which the pipe 1 has a smaller diameterthan the pipe 2. In the pipe 1 there is first formed a circumferentially extending groove 3, and a seal 4 is arranged in the groove, the seal suitably having the form of a resilient O-ring Dshaped sectional profile. The grooved pipe 1 is then inserted into the pipe 2 and, as illustrated in Figure 1b, a groove 5 is then formed in the outer pipe 2 opposite the groove 3 in the inner pipe 1. The groove 5 is formed by a method in accordance with the invention, at least one groove-forming roller or ball being pressed against the wall of the pipe 2 while relative rotary movement is effected between the groove-forming device and the wall of the pipe.This rotary movement is repeated while progressively decreasing the distance between the grooveforming device and the central axis of the pipe until the groove has obtained the desired depth. Since the groove 5 is formed by plastic deformation of the material of the pipe, there is formed on the inside of the pipe 2 a bead which forces the seal 4 into sealing engagement with both the inner pipe 1 and the outer pipe 2. At the same time the pipes 1 and 2 are locked against mutual displacement in the axial direction.

The groove-forming roller is pressed against the pipe whilst using an externally located reaction surface or anvil, and hence no such surface or anvil need be arranged inside the pipe. Nevertheless, the progressive working of the material in the groove ensures that a regular internal bead is formed, guaranteeing uniform sealing around the pipe.

Although not clearly shown in the drawing, the depth of the groove 5 should correspond substantially to the wall thickness of the pipe 2. The seal 4, although a ring of resilient material in the present case, may be any suitable element and in its simplest form may comprise a loop of tape or a ring of nonhardening sealing paste.

While Figures 1a and 1b illustrate the joining of two metal pipes of different diameters, Figures 2a and 2b illustrate two alternative ways of joining together two metal pipes 6 and 7 having the same diameter as each other. In the embodiment of Figure 2a adjacent ends of the pipes 6 and 7 are first provided with a groove 8 and 9 respectively, and sealing elements 10 and 11 are located in the grooves. These ends of the pipes are then inserted into an outer sleeve 12, and two sealing grooves 13 and 14 are formed in the sleeve 12 opposite the grooves 8 and 9 in the same manner as that described with reference to Figures 1.

As shown in Figure 2b a joint having a substantially smooth outer surface can be obtained by using an internal joining sleeve 15 having two grooves 16 and 17 containing sealing means 18 and 19 respectively.

The sleeve 15 is inserted in the adjacent ends of the two pipes 6 and 7 to be joined, and two outer sealing grooves 20 and 21 are then formed in the pipes 6 and 7 respectively opposite the grooves 16 and 17 as described above.

Figure 3 illustrates how two plastics pipes 22 and 23 of the same diameter can be connected together.

The material from which the pipes are made is sufficiently resilient to serve as a sealing material, and therefore no separate sealing ring is required as in the previous examples. In this case an inner support sleeve 24, preferably made of metal, is inserted in each of the two adjacent ends of the pipes to be connected, and the two ends of the pipes are inserted into a single external metal sleeve 25. The metal sleeve 25 is then provided with grooves 26 and 27 in the manner described above, the grooves extending circumferentially of the pipes 22 and 23 being joined together. As will be seen, the internal bead created when forming the groove 27 in the sleeve 25 will be pressed sealingly into the material of the plastics pipe 23, and in a similar manner the bead formed by the groove 26 will be pressed into the material of the pipe 22.The sleeve 25 is thus capable of transferring tension forces between the two pipes. As will be readily understood, the two sleeves 24 may be replaced by a single internal support sleeve which is common to both pipes.

In Figure 4 there is illustrated a joint in which two metal pipes 28 and 29 are joined together but are not in direct contact with one another, since the material from which the pipes are made may give rise to galvanic currents therebetween. Consequently, in this case each pipe is provided with an external groove 30, and a sleeve 31 made of plastics or some other suitable insulating material is arranged over its end and covering the groove. If preferred, a single plastics sleeve common to both pipes may be used.

The sleeved ends of the two pipes are then inserted into an outer metal sleeve 32 in which, similar to the Figure 3 embodiment, two sealing grooves 33 and 34 are formed, the material of the insulating plastics sleeves 31 being forced into the grooves 30 by the beads resulting from the formation of the grooves 33 and 34to provide a sealing connection.

Figure 5 illustrates a joint in which two pipes covered with a plastics material are joined together, each of the pipes comprising an inner copper pipe 35, 36 and a plastics coating 37, 38 respectively.

Such pipes can be joined together by simply inserting the pipe ends into an outer metal sleeve 39 and forming a pair of grooves 40 and 41 in the sleeve by the method in accordance with the invention, the grooves 40, 41 giving rise to corresponding beads which bite in a sealing manner into the plastics layers 37 and 38 of the two pipes.

The figures of the drawings so far described merely illustrate a few of a large number of sealed joints and connections which can be created by using the present invention. However, as will be understood, the invention can also be used in the formation of non-sealed joints and to provide internal beads which can be used as stop means and mounting shoulders for a large number of different purposes.

Figure 6 illustrates the use of a simple hand-tool 42, constructed in accordance with the invention, to form a peripheral groove 43 in the outer of two pipe sections 44 and 45 which are to be joined together.

The tool 42 includes a stirrup-like member 46 having a fixed leg in which a pair of support rollers 47 are rotatably mounted. In screw-threaded engagement with the other leg of the stirrup-like member 46, opposite the support rollers 47, is a spindle 47a carrying at one end thereof a rotatable, grooveforming roller 48. The roller 48 is provided with an active groove-forming part having a substantially circular-arcuate profile with a radius of curvature which is at least equal to the wall thickness of the pipe. This active part of the roller 48 merges with two lateral support surfaces which serve to limitthe depth to which the groove can be formed. The roller is conveniently made of a tough, hardened material.

The force with which the roller 48 can be pressed against the wall of the pipe can be readily controlled in a known manner by means of a knob 49 which operates the spindle 47a.

Preferably, the roller 48 and its holder 50 form a separate member which is mounted on a stud 51 extending from the screw spindle 47a. This permits the same tool to be used for different purposes by means of a simple exchange of the roller member.

In Figure 7, the holder 50 and the roller 48 is shown partly in section, and it will be realized that the holder 40 is provided with a cavity 42 adjacent the roller 48. The cavity is filled with a porous material 53, such as foam rubber, which is intended to effect a cleaning and lubricating operation on the roller 48.

The material can be exchanged through the mounting stud 51 socket provided in the holder 50.

The tool 42 can be readily handled and, since no internal anvil surface needs to be provided in the pipe, can be used to form a groove in a pipe which, for example, is to be joined to another pipe on the working site. The support rollers 47 may optionally be replaced with groove-forming rollers, meaning that a peripherally extending groove can be formed by simply rotating the tool 42 backwards and forwardsthrough an angle of about 1800. However, the use of support rollers causes the material adjacent the edges of the groove to be pressed flat, resulting in a very smooth surface adjacent the groove.

A similar tool may also be constructed in the form of, for example, an adjustable spanner or a pipe wrench, wherein one or more groove-forming rollers or balls are arranged on the inner surfaces of the spanner jaws. By means of a tool designed in this way it is possible to form circumferentially extending grooves in pipes located in very confined spaces.

Figures 8a to 8f illustrate different designs of groove forming rollers. The rollers shown in Figures 8a to c form grooves having different relationships between depth and width. The roller shown at 8d forms two grooves simultaneously, and the rollers shown at 8e form an asymmetrical groove (and corresponding bead inside the pipe) such as can be used, for instance, in the manufacture of nozzles.

The roller shown at 8f is provided with a conventional screwthread and can be used for forming a helical groove, for instance an external thread to be used for connecting purposed. Thus, by means of the invention, an accurate thread can be formed without employing cutting operations. When forming a thread, preferably at least three rollers of the type shown at 8fare used without any plane support rollers. The number of turns of the thread on each roller can be varied.

The tool illustrated in Figure 9 corresponds in all essential respects to the tool of Figure 6. However, the tool of Figure 9 is provided with a telescopic handle comprising a shaft portion 54, and a knob 55 rotatably mounted on the shaft. By means of this handle, the tool 42 can be easily rotated around a workpiece.

Figure 10 illustrates an example of a grooveforming tool in accordance with the invention comprising a roller chain 56 having alternating grooveforming rollers 57 and support rollers 58. A pipe 59 can be clamped between the rollers 57 and 58 and two further support rollers 60 by means of a knob or handle 62 in screw-engagement with a holder 61. A circumferentially extending groove can be formed in the pipe 59 by moving the tool through only a relatively small angle, and the tool is therefore suited for use when forming grooves in pipes located in pipe trenches. The chain 56 illustrated may, of course, be provided with any desired number of groove-forming rollers 57 and support rollers 58.

A tool in accordance with the invention may be modified in several respects, but its most important feature is that it includes at least one groove-forming roller or ball and at least one external anvil surface which enables the pipe to be clamped within the tool and the roller or ball to be progressively urged against the wall of the pipe. As previously mentioned, the anvil surface may also comprise grooveforming rollers or balls. Other combinations of groove-forming rollers or balls and support rollers are also possible. When both groove-forming rollers and support rollers are mounted on a chain, it is preferred that the groove forming rollers have a larger diameter than the support rollers.

Since it is only necessary to provide for relative rotation between the workpiece and the grooveforming roller or ball, a tool in accordance with the invention need not be solely a hand operated tool, but may be one which can be used in a lathe, a screw-cutting machine, or some other similar machine, the forces being balanced in the tool.

Claims

1. A method of forming a circumferentially extending groove in a circular peripheral surface of a workpiece, comprising locating the workpiece between the engagement means of a tool having at least two engagement means, at least one of the engagement means comprising a groove-forming roller or ball, pressing the engagement means radially against the circular peripheral surface of the workpiece so that the workpiece is clamped between the engagement means, rotating the tool and the workpiece relative to one another whereby a circumferential groove is formed in the circular peripheral surface of the workpiece by the groove forming engagement means, and repeating the relative rotary movement of the tool and the workpiece while progressively decreasing the distance between the groove forming engagement means and the centre of the workpiece until the groove is of the required depth.

2. A method according to claim 1, in which the workpiece is a pipe and the groove forming engagement means comprises a roller having a groove forming part with an arcuate profile having a radius of curvature which is at least equal to the thickness of the pipe.

3. A method of forming a sealed joint between two pipe sections having different diameters such that one section will fit into the other, the larger pipe section being made of metal, the method comprising inserting one end of the smaller pipe section into the larger pipe section so that there is a ring of resilient material capable of serving as a sealing material around the smaller pipe section adjacent the inner surface of the larger pipe section, and forming a groove in the outer surface of the larger pipe section by a method according to claim 1 so as to form on its inner surface a bead which presses into and sealingly coacts with the resilient material.

4. A method according to claim 3, in which the smaller pipe section is made of metal, and the ring of resilient material is located in a groove which has been formed previously in the outer surface of the smaller pipe section.

5. A method according to claim 3, in which the smaller pipe section is made of a plastics material and itself forms the ring of resilient sealing materia, and there is provided in the end of the smaller pipe section a rigid inner support sleeve.

6. A method according to claim 5, in which the inner support sleeve is made of metal.

7. Atool for forming a circumferentially extending groove in a circular peripheral surface of a workpiece, the tool comprising at least two engagement means mounted so that the workpiece can be clamped between them with the engagement means pressed radially against the circular peripheral surface of the workpiece and whereby relative rotary movement can be effected between the engagement means and the workpiece, at least one of the engagement means comprising a groove-forming roller or ball, and means for progressively decreasing the distance between at least one of the engagement means and the point which, in use, is occupied by the centre of the workpiece.

8. Atool according to claim 7, in which the engagement means are mounted in a stirrup-like holder, and at least one of the engagement means is adjustable in the radial direction by means of a spindle in screw-engagementwith the stirrup-like holder.

9. A tool according to claim 7 or claim 8, in which there are two engagement means, one of which comprises a freely rotatable groove-forming roller or ball, and the other of which comprises a pair of support rollers arranged diametrically opposite the roller or ball.

10. Atool according to claim 7, in which at least one of the engagement means is carried by a holder comprising a plurality of pivotally connected links whereby the holder is capable of adapting to the shape of the workpiece.

11. A tool according to claim 10, in which the holder comprises a roller chain carrying freely rotatable groove-forming rollers.

12. Atool according to claim 7, substantially as described with reference to Figures 6 and 7, Figure 9, or Figure 10, and having a groove forming roller substantially as described with reference to any one of Figures 8a to 8f of the accompanying drawings.

13. A method of forming a circumferentially extending groove in a workpiece according to claim 1, in which the groove is formed using a tool according to claim 12.

14. A method according to claim 3, substantially as described with reference to Figures 1 a and 1b, or any one of Figures 2a, 2b and 3 to 5 of the accompanying drawings.