PIPΞ DEPOBMHTG METHOD JTO APPARATUS

TECHNICAL FIELD

5 This invention relates to apparatus and methods for deforming pipes, for example by curving, coiling or thickening.

BACKGROUND ART It has been proposed to curve metal, steel or 0 other alloy pipes of diameters of between 100 and 1600mm and of wall thicknesses of between 6 and 100mm on a machine of the kind in which a pipe to be curved is fed through a heating station where it is heated locally and is constrained to move in a curved path downstream of the

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heating station. In the operation of this kind of machine the pipe wall is deformed where locally heated at the heating station to produce the required curvature and it rapidly sets in the deformed condition as it cools on- leaving the heating station. In proposed machines of this kind, the pipe is heated evenly around its circumference at the heating station, for example by an electrical induction coil designed to completely encircle the pipe. Heating in this way produces satisfactory curving but it results in a thinning of the pipe wall on the outside of the curve. More particularly there is a longitudinal contraction and radial thickening of the pipe wall at the inside of the ^" curve and a corresponding longitudinal extension and radial thinning of the pipe wall at the outside of the curve. The thinning of the pipe wall causes localized weakness and in many applications it is necessary to use a heavier duty pipe for curved sections than for straight sections, with significant cost penalties. The thinning of a pipe curved on a machine of this kind ^" is minimized by pushing rather than pulling the pipe through the heating station, by heating only a small section of the pipe at any one time and by forming the bend in one continuous operation. Nevertheless, while a machine of this kind may reduce the number of welds required in a pipe length, if the pipe wall thickness has to be increased to accommodate the pipe curves cost savings are reduced. It is also to be noted that the proposed machines of this kind are limited to curves of a maximum of 180°. It is a further consideration when selecting pipe wall thicknesses for a particular application that the pipe, whether straight or curved, will almost certainly require to be attached to an adjacent unit, such as to another pipe length whether in end-to-end relationship or at a T-junction or to an end piece, and

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this may require a particular minimum thickness of wall material in the pipe to accommodate a weld or screw- thread. Under these circumstances it has been necessary to use this minimum pipe wall thickness for the whole length of the pipe or an even greater wall thickness if the join is to be on a curve. Additionally where a T- junction is to be provided in the pipe it has been necessary to divide the pipe length, join a T-piece to each divided end, for example by welding, and then join the desired unit to the T-piece usually also be welding. Such numerous joins are both labour intensive and expensive.

STATEMENTS OF THE INVENTION It is an object of a first aspect of the present invention to provide an improved method and machine for curving pipes whereby thinning of the pipe wall along the curve can Joe substantially eliminated.

According to the first aspect of the invention there is provided a pipe curving ^' machine comprising: pip≤ heating means disposed at a pipe heating station; pipe feed means to feed a length of pipe to be curved through the pipe heating station for localized heating of the pipe at that station; and pips guide means for guiding the pipe in a curved path downstream of the heating station; wherein the pipe heating means is such as to preferentially heat the pipe wall to the inside of the pipe curve whereby the pipe curves into said path substantially by thickening of the pipe wall on the inside of the curve without a corresponding thinning of the wall on the outside of the curve.

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The pipe feed means may comprise a pusher operable to push the length of pipe through the heating station.

The pipe guide means may comprise a pivot arm for attachment to the pipe downstream of the heating station and pivotable so as to then constrain the pipe to move in said path.

The pipe heating means may comprise an electrical induction coil to encompass the pipe and having a lobed interior so as to define a pocket between the coil and the pipe at the outside of the curve.

The heating means may further comprise a cooling pad extending within the lobed interior of the coil and provided with means for circulation of a cooling fluid therethrough.

The coil may be shaped so that the pocket is crescent-shaped and the cooling pad may be of crescent- shaped cross-section to substantially fill the pocket.

Generally an air blast plenum will be located immediately upstream of the heating station, the plenum having apertures therein to direct air blasts at the pipe as it passes through the heating station and thereby remove gases and other products of the heating. Further, quenching means will usually be provided immediately downstream of the heating station to cool the pipe wall as soon as it has been curved at the heating station by the guide means and .thereby alleviate non-desired deformation of the pipe.

Preferably the machine in accordance with the first aspect of the present invention has a T-shaped plan, with the feed means being displaceable along the bottom of the T-shape, the pipe heating station being located at the junction of the bottom and the cross-piece of the T-shape, and the pivot arm being displaceable along the cross-piece and pivotable therefrom.

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Further according to the first aspect of the present invention there is provided a method of curving a pipe which comprises feeding a length of pipe to be curved to a pipe heating station, preferentially heating the pipe wall to one side as the pipe length passes through the heating station, quenching the pipe length immediately downstream of the heating station, and guiding the pipe length in a curved path downstream of the heating station with the inside of said curved path being on said preferentially heated side of said pipe wall whereby the pipe curves into said path substantially by thickening of the pipe wall on the inside of the curve without a corresponding thinning of the wall on the outside of the curve. Still further according to the first aspect of the present invention there is provided a pipe when curved by the method of the immediately preceding paragraph.

It is an object of a second aspect of the present invention to extend pipe.curving facilities to enable a pipe to be coiled. Hitherto pipe coils have been formed by forming 180° curves in pipe lengths, suitably shaping the pipe ends and welding the lengths together. Alternatively a pipe length has been manually heated and bent around a former. Both the above known methods are extremely laborious- and therefore expensive. According to _. the second aspect of the present invention there is provided a method of coiling a length of pipe which comprises: feeding the pipe length through a heating station to locally heat the pipe length;

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guiding a portion of the pipe length downstream of the heating station in a curved path in the plane of the pipe length as the pipe length is fed through the heating station, said curved path being along an arc of up to 90° taken on a constant radius about a fixed locus; rotating the pipe length about the axis of the pipe length upstream of the heating station to displace the curved path of said pipe portion into the coil path at the desired pitch; and feeding at least part of the pipe length upstream of the heating station through the heating station and directing said at least part of the pipe length along the coil path to coil the pipe length.

Further according to the second aspect of the present invention there is provided a coiled pipe when formed by the method described in the immediately preceding paragraph.

The curved path may be relatively short, extending for example through an arc of 20°, but should be not more than 90° since otherwise the desired pitch of the coiled pipe may not be obtainable by merely rotating the pipe length.

Still further according to the second aspect of the present invention there is provided a pipe coiling machine comprising: pipe heating means disposed at a pipe heating station; pipe feed means to feed a length of pipe to be coiled through the pipe heating station for localized heating of the pipe at that station; pipe guide means capable of guiding a portion of the pipe length in a curved path downstream of the heating station in the plane of the pipe length, said curved path being along an arc of up to 90 taken on a constant radius about a fixed locus; and

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means to support the curved pipe length in a coil path when the pipe length upstream of the heating station is rotated about its axis to displace the curved pipe length out of said plane, said supporting means being capable of directing the pipe length along the coil path when the pipe length upstream of the heating station is fed through the heating station.

The pipe directing means may be any means which ensures that the pipe length follows the coil path as it leaves the heating station, and is preferably fixed in use to permit the free passage of the directed pipe length therethrough.

The pipe guide means ^" conveniently comprises a pivot arm having a pivot axis perpendicular to said plane of the pipe length and clamping means carried by the pivot arm to receive the portion of the pipe length downstream of the heating station and displaceable along the curved path by pivoting motion of the pivot arm. Thus the preferred method of coiling comprises clamping the portion of the pipe length to means displaceable along the curved path during said guiding step, releasing the portion of the pipe length from said clamping means/ performing said rotating step, and directing the pipe length through fixed directing means on the coil path while heating the pipe length at the heating station during the guiding and feeding steps. It has been found that the pipe follows the coil path very accurately and the pipe directing means may be located immediately downstream of the heating station or angularly displaced therefrom by up to 90° or more.

The pipe heating station will include pipe heating means which may heat the pipe evenly around the circumference, but this tends to lead to a thinning of the pipe wall on the outside of the curve by longitudinal extension and radial thinning so that a heavier duty pipe

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length may be required. Accordingly, it is preferred that the pipe heating means is such as to preferentially heat the pipe wall to the inside of the pipe curve whereby the pipe curves into said path substantially by 5 thickening of the pipe wall on the inside of the curve without a corresponding thinning of the wall on the outside of the curve.

In essence it is preferred that the pipe coiling machine of the second aspect of the present

10 invention includes a pipe curving machine in accordance with the first aspect of the invention. In a preferred embodiment the clamping means carried by the pivot arm is replaced by the pipe directing ^" means which may, for example, be a set of rollers or wheels to embrace the

15 curved pipe length, and whose central axis is offset relative to the clamping means to allow for the rotational displacement of the pipe length out of the curved path into the coil path.

A small diameter pipe may be rotated from the

20 curved path into the coil path by hand but the pipe coiling machine may include pipe turning means for rotating the pipe length about the axis of the pipe length upstream of said pipe portion whereby to displace the curved path of said pipe portion into the coil path

25. at the desired pitch.

The pipe length may be rotated about its axis by suitable means associated with the feed means, for example a geared clamp engageable around the periphery of the pipe length and rotatable by correspondingly geared

30 drive means including a motor. In a simple alternative arrangement the rotating means may comprise a chain locked around the pipe periphery with one free end extending part way around the periphery and tangentially therefrom, such that longitudinal displacement of the

35 free end will cause rotation of the pipe length. The

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amount of rotation will depend on the desired pitch of the coiled pipe and this will be at least partly dependent upon the diameter of the pipe length and the diameter of the coiled pipe. Thus the pitch of a coiled pipe where the diameter of the pipe is 600mm and the diameter of the coil is 2000mm must be considerably greater than where the pipe diameter is 50mm and the coil diameter is 3500mm, although the pitch of the latter coiled pipe may optionally be selected the same as that of the former.

It is an object of a third aspect of the present invention to provide for the thickening of a pipe wall section over a predetermined portion of a pipe length to facilitate joining of the pipe length to other units without having to use that wall thickness along the whole length of the pipe where such joins are not envisaged.

According to the third aspect of the present invention there is provided apparatus for thickening a pipe comprising: pipe heating means disposed at a pipe heating station; pipe pusher means to push a length of pipe through the pipe heating station for localized heating of the pipe at that station; and pipe restraint means to engage ^" the pipe downstream.of the heating station and to provide resistance to the movement of the pipe caused by the pusher means so as to reduce the speed of pipe movement downstream of the heating station and to cause thickening of the pipe wall by deformation of the heated pipe wall at the heating station.

This third aspect of the present invention has particular application to the production of pipe lines in which nozzles or branch lines extend from main pipe

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sections. Conventionally, this requires the welding of nozzles or junction pieces into the main pipe segments which is laborious and expensive. The apparatus of the present invention enables a pipe wall to be appreciably thickened over any required length and this in turn makes it possible to form nozzles and junctions by extrusion from the pipe wall. The invention is not limited to this application, however, and there are many other circumstances in which localized thickening of a pipe wall would be an advantage. For example, pipe ends could be thickened preparatory to being screw-threaded.

Further according to the third aspect of the present invention there is provided a method of forming a T-junction in a pipe for connection of an adjacent unit, which comprises thickening the pipe wall of a preselected section of the.pipe using the apparatus of the third aspect of the invention, forming a bore through the thickened pipe wall at the desired location of the T- junction, said bore being undersized compared to the desired cross-sectional area of the T-junction, providing an extrusion member within the pipe, said extrusion member being of substantially the desired cross-sectional area of the T-junction, and withdrawing the extrusion member through the bore to thereby extrude the pipe wall material around the bore into an integral T-junction collar to which the adjacent unit may be fastened.

This method allows branch fitting without expensive T-pieces, saves the labour of two additional welds in joining a T-piece, alleviates the need for reinforcing pads at the joins and, as indicated previously, allows for the selection of the minimum pipe thickness along the remainder of the pipe. Furthermore, because of the increased pipe wall thickness, the integrity of the branch or T-junction may be higher than the original pipe. A branch pipe or other unit may be

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connected to the T-junction collar by, for example, welding or screw-threading once the collar has been threaded.

The pipe restraint means of the pipe thickening apparatus may be effective to provide a fluid pressure resistance to the forward movement of the pipe. It may for example comprise an hydraulic resistor. More particularly, it may comprise an hydraulic cylinder unit. This arrangement may be used where the pipe length to be thickened is straight, with the pipe section being allowed to move downstream of the heating station more slowly than upstream of the heating station. However, it is considered particularly applicable where the pipe wall to be thickened is in a curved section of the pipe, in which case the apparatus may include pipe guide means for guiding the pipe in a curved path downstream of the heating station with the pipe restraint means acting on the pipe guide means. In one embodiment the pipe heating means, the pipe pusher means and the pipe guide means form part of a pipe curving machine in accordance with the first aspect of the present invention, with the pipe guide means comprising a pivot arm for attachment to the- pipe to constrain the pipe to move in the curved path.

In a preferred embodiment the pusher means and the restraint means are directly opposed to one another respectively to cause and to restrain movement along a linear path. This configuration will be used for producing wall thickening in a straight pipe. The restraint means may restrain any section of the pipe so that the wall thickening may be at one end, between the ends of the pipe or at several locations along the pipe length. Preferably, where the wall thickening is to be performed on a straight pipe, the pipe restraint means is fixed downstream of the heating station to hold the pipe at the desired location downstream of the heating station

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and the heating station is itself moved linearly upstream away from the pipe restraint means as the pusher means acts to displace the pipe length through the heating station. The pipe is only thickened where it is heated by the heating means and control is provided by the relative displacements of the pusher means and heating station towards each other. The heating station will generally include quenching means immediately downstream of the heating means to minimise unwanted distortion of the pipe. It may also be desirable to include guide rollers or similar means on either side of the heating station to maintain the configuration of the pipe as the heating station effectively moves along its length.

It will be appreciated that the apparatus in accordance with the third aspect of the invention may also be used for thickening non-tubular sections, that is it may be used for increasing the σross-sectional area of solid lengths of material, and reference to the thickening of pipe sections herein should be construed accordingly where applicable.

BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of a pipe curving machine in accordance with a first aspect of the present invention, together with modifications thereto to permit use of the machine for pipe coiling and pipe thickening will now be described by way of example only with reference to the accompanying drawings, in which:

Fig. 1 is a plan view of the pipe curving machine; Fig. 2 is a partial enlarged plan view of the machine of Fig. 1 with part of the view broken away for clarity;

Fig. 3 is a partial enlarged side view of the machine of Fig. 1 taken on the line 3-3;

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Fig. 4 is a partial enlarged side view of the machine of Fig. 1 taken on the line 4-4;

Fig. 5 is a sectional view taken on the line 5-5 in Fig. 3; Fig. 6 is an enlarged detailed view of the view in Fig. 2;

Fig. 7 is a sectional view taken on the line 7-7 in Fig. 6, but showing a pivot arm and cross-member aligned; Fig. 8 is a side view, partly broken away, taken on line 8-8 in Fig. "6;

Fig. 9 is a view taken on line 9-9 in Fig. 6;

Fig. 10 is a partial view on line 10-10 of Fig. 6; Fig. 11 is a cross-sectional view of a pipe length which has been curved on the machine of Fig. 1;

Figs. 12 and 13 show different plan views similar to Fig. 2 but with the machine modified to perform thickening of the pipe wall in straight pipe lengths; the different views showing different stages of the pipe thickening process;

Fig. 14 shows a cross-section of a pipe whose wall has been thickened on the machine of Figs. 12 and 13; and Figs. 15, 16 and 17 show three stages in a pipe coiling operation carried out on the machine of Fig. 1 suitably modified in Figs. 16 and 17.

DETAILED DESCRIPTION OF THE DRAWINGS The pipe curving machine illustrated in Figs. 1 to 9 comprises a pipe feed means denoted generally as 11 for feeding a length of pipe 12 through a heating station 13 and a pipe guide -means denoted generally as 14 for guiding the pipe in a curved path downstream of the heating station 13.

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Pipe feed means 11 comprises a pusher 15 mounted on track rails 16 and movable along those rails by operation of two hydraulic cylinder arrangements 17 connected to the pusher. Heating station 13 is defined by an electrical induction heater 19 which encircles the pipe to provide localized heating of the pipe wall at the heating station.

Pusher rails 16 are mounted on a pair of massive I-beams 21 forming part of a main frame of the machine. This frame is generally T-shaped with the I- beams 21 forming the stem of the T and further structural sections being welded together to form a massive generally angle-shaped cross-member 22 of the frame. I- beams 21 carry the induction heater and associated transformer equipment (not shown) and cross member 22 carries a pair of pipe guide rollers 23 movable towards and away from one another so as to be adjustable to form a guide for the pipe immediately in advance of the induction heater.

Pipe guide means 14 comprises a clamp head 24 which can be clamped onto the pipe and which is carried on a massive pivot arm 25 extending from an arm pivot 26. The arm pivot is rotatable on a platform 27 ^" which is mounted by slides 28 on a pair of rails 29 extending along the cross member 22 of the main frame. Pipe clamp 24 is mounted by slides 31 on rails 32 extending along the pivot arm whereby it can be moved in and out along the arm. In operation of the machine, for curving a pipe, the pivot arm 25 is initially set so that the pipe clamp head 24 can be clamped around the pipe immediately downstream of the induction heater 19 as indicated in Figure 4 and with the clamp head positioned on the pivot arm at an appropriate radius so that as the pipe is fed

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through the heating station 13 by pusher 15 it is constrained by the pivot arm to move in a curved path of the required curvature as indicated in broken outline in Figure 2. Appropriate means described hereinafter are provided to enable the pipe clamp 24 to be restrained at the appropriate radius to the pivot arm and to restrain the pivot mounting platform 27 at the appropriate location along the rails 29.

As the pipe 12 passes through the induction heater 19 its wall is heated locally to enable the deformation required for it to move in the curved path defined by the pivot arm. Deformation occurs only at the heating station and the deformed wall will rapidly set in the deformed condition as it cools on leaving the heating station.

In conventional pipe curving machines, the induction heater 19 would heat the pipe evenly around its circumference with consequent thinning of the pipe wall at the outside of the curve, as has been discussed above. In accordance with the first aspect of the present invention, however, induction heater 19 is designed to preferentially heat the pipe wall to the inside of the pipe curve whereby the pipe curves substantially by thickening of the pipe wall on the inside of the curve without a corresponding .thinning of the wall on the outside of the curve. Details of the induction heater 19 are illustrated in Figure 10 and will be described in detail hereinafter.

Referring now in detail to the drawings and in particular to Figures 1 to 5, the parallel massive I- bea s 21 are supported on the ground 18 by steel pads 20 which are bolted by means not shown on opposed sides to spaced concrete footings 30 and to the I-beams 21. A series of spaced steel spacer members 33 are welded or bolted between the I-beams 21.

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Rails 16 are welded or otherwise fastened to the exterior surface of the web of respective I-beams 21 and extend from adjacent the cross-member 22 to the remote end 34 of the beams. At the remote end 34, a transverse stop member 35 is bolted to the I-beams and to the adjacent steel pad 20.

Hydraulic cylinder arrangements 17 are mounted in spaced parallel disposition on three carriages 36 slidingly supported on the rails 16. Each carriage 36 comprises a massive steel structure of generally H cross-section as shown in Figure 5. The cross-piece 37 of the H-shapε extends across the top of the I-beams 21, the upper legs 38 of the H-shape define platforms 39 to which the hydraulic cylinder arrangements 17 are respectively bolted, and the lower legs 40 carry respective roller assemblies 41 to slidingly mount the carriage on the rails 16 with minimal lateral play. The roller assemblies 41 may take any suitable known form and will not be described further. The three carriages 36 are rigidly spaced from one another along the I-beam 21 by their engagement with the two hydraulic cylinder arrangements 17.

Each hydraulic cylinder arrangement 17 comprises two back to back hydraulic cylinder units 42 both supported on the central carriage 36 and on the respective outer carriages.. Each hydraulic cylinder unit 42 has a single piston 43, the right-hand end ones of which (in Figure 1) carry end plates 44 which are bolted to the transverse stop member 35, and the left-hand end ones of which (in Figure 1) carry end plates 45 which are selectively engaged with the pusher 15.

The hydraulic arrangements and controls for displacement of the piston rods 43 are not shown and it is believed they will be readily understood by the expert in the field. In order to improve control over the

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heating of the pipe at the heating station 13, it is important that the pipe be displaced through the heating station at a constant rate and it is for this reason that two pairs of identical back to back hydraulic cylinder units 42 are used to displace the pusher 15. The piston rods 43 of each hydraulic cylinder arrangement 17 may be controlled to extend together or successively, provided in the latter case there is no change in rate in transferring hydraulic fluid flow from one hydraulic cylinder unit 42 to the other, and the hydraulic controls are relatively straight forward. In contrast, a single hydraulic cylinder unit with a multiple stage piston rod may be used but the control over the hydraulic flow required to ensure a constant rate of extension is more complicated.

Pusher 15 comprises a carriage 46 slidingly mounted on the rails 16 in the same manner as the carriages 36. Carriage 46 comprises a cross-piece 47 extending across the top of the I-beams 21 and supporting spaced pillars 48, each of which supports an end plate 45 of the adjacent piston rods 43. As shown, the pusher 15 has front and rear cover plates 49 and 50 extending across the pillars 48, at least the pillar 49 having a sufficient cross-sectional area to bear against the end face of a pipe 12 to be curved on the machine to urge the pipe through the heating station 13 as the hydraulic cylinder arrangements 17 are actuated. Spaced support members 51 are mounted on the front plate 49 and project towards the heating station 13 about a lower arc to define a support for the end of the pipe at the height at which the pipe is intended to pass through the heating station. Different front plates 49 may be provided to accommodate different diameter pipes.

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In modifications not shown, the front plate 49 may be totally removed from the pusher 15 and replaced by a clamp arrangement supported on the cross-piece 47 between the pillars 48 and, for example, essentially identical to the clamp arrangement in the clamp head 24 to be described hereinafter. Such an arrangement permits a pipe to extend through the pusher 15, including the back plate 50, between the hydraulic cylinder arrangements 17 and as far back as the stop member 35. If the maximum travel of the hydraulic cylinder arrangements 17 is achieved before the full length of the pipe has been passed through the heating station, the pusher 15 may be released from the pipe and the hydraulic cylinder arrangements retracted to a more rearward position on the pipe before recommencing the bending operation. This arrangement also permits multiple lengths of pipe to be welded together on the machine and to be successively curved as desired. In a second modification, the pillars 48 may carry tie rods (not shown) which extend rearwardly towards the stop member 35 and carry a bearing plate (also not shown) which is intended to engage the trailing end of the pipe, the pipe again extending through the pusher 15.

With reference now also to Figures 6 and 9, the rollers 23 are designed to guide and support the pipe 12 as it passes through the heating station 13. Each roller 23 has an externally concave configuration and is mounted for rotation about a vertical axis. Each roller is mounted on a support 52 slidably carried in a frame 53. The frames 53 are bolted to the upper edge of a massive I-beam 54 forming part of the cross-member 22. Each frame 53 comprises a box section, the two box sections opening towards each other to receive the associated support member 52. Each support member is engaged with a screw-threaded adjustment member 55 which is rotatable

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relative to the support member and which screw-threadably engages v/ith the opposite closed end 56 of the box frame 53. Rotation of the adjustment member 55 by means of the wheel 57 causes the support member 52 and therefore the associated roller 23 to project to a greater or lesser extent from the box frame 53. The support member 52 comprises a box structure which slidingly engages the inner surface of the box frame 53 and has vertically spaced support arms extending outwardly therefrom which at their distal nds receive the roller axles 59. A screw-threaded locking device 60 is carried by the box frame 53 and is adjustable to abut the support member 52 to lock the support member relative to the box frame. If desired the rollers 23 may be exchanged for ones having different radii of curvature to accommodate pipes of different diameter, or they may be removed altogether if necessary.

The heating station 13 is mounted on a carriage 61 slidably supported on the rails 16 for displacement along the I-beams 21. For normal curving operations on the machine, the position of the heating station 13 is fixed with the heater 19 immediately downstream of the rollers 23. -However, for certain operations such as pipe thickening to be described hereinafter, it may be desired to displace the heating station along the I-beams 21 and it is for this purpose that the rollers 23 and possibly the box frames 53 may need to be removed.

The carriage 61 is identical to the carriages 36 and carries on the upper surface of the upper legs 62 respective pillars 63 which are sufficiently laterally spaced to permit the pipe to pass therethrough. The pillars 63 extend to a greater height than that of the proposed maximum diameter pipe to be deformed on the machine and support cantilevered arms 64 which in normal usage for curving pipes extend over the rollers 23 and

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associated assemblies. The remote end of the cantilevered arms carry in suspended manner the heater 19, an air blast ring 65 immediately upstream of the heater 19 and a quenching ring 66 immediately downstream of the heater 19.

Carriage 61 carries on platforms (not shown) adjacent to the pillars 63 transformers for the heater 19 as well as supply connections for air and water to the rings 65 and 66, with the various supplies being channelled up the pillars 63 and along the cantilevered arms 64.

With particular reference to Figure 10, heater 19 comprises an induction coil 67 and a water cooled pad 68 having water supply channels 69 therethrough. Instead of being of completely circular cross-section so as to encircle the pipe 12 with a small clearance completely around the circumference as in the case of the induction coils of previously proposed curving machines, induction coil 67 is of lobed configuration so as to define a substantial crescent shaped pocket between the coil and the pipe 12 on the side of the pipe disposed to the outside of the intended pipe curve. The cooling pad 68 fits within this pocket and is crescent shaped so as to substantially fill it. The water supply pipes 69 are also supplied from a connection with a source on the carriage 61. The induction coil 67 is supported from the cantilevered arms 64 by respective branch members 64' which carry the electrical and water supply.

Because of the substantial gap between the induction coil 67 and the outside of the pipe, and the extraction of heat from this gap by the water cooling, the pipe wall at the outside of the curve is not heated sufficiently to be deformed by thinning. The inside of the pipe is heated to elevated temperatures by the induction coil 67 and is able to contract longitudinally

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with consequent thickening to enable the pipe to curve to the degree determined by pivot arm 25 as described hereinafter. Consequently, the pipe curves with no appreciable thinning of the wall at the outside of the curve. In effect the natural axis of the pipe curvature is shifted from the central axis of the pipe toward the outer wall so that substantially all permanent deformation takes place on the inside of the pipe.

The desired temperature of the pipe wall at which optimum bending of the pipe occurs will depend upon the material of the pipe and these temperatures have previously been well established, although clearly in accordance with the first aspect of the present invention, the temperature will only be required on the inside of the curve. The inductive power for the coil 67 to provide such temperature will vary according to at least the pipe diameter and wall thickness but is likely to be between 240 and lOOOKw. The ring 65 provided upstream of the heater 19 has apertures on its radially inner surface and closely surrounds the pipe 12. During heating, air is blasted through the apertures to, inter alia, remove noxious gases and maintain a substantially constant atmosphere between the induction coil and the pipe. Ring 66 located downstream of the heater 19 is provided for quenching purposes and is adapted to inject water, air and/or other cooling fluid around the pipe surface immediately after it has passed through the induction coil 67. The type of quench required will depend upon the material of the pipe. Thus for example, for normal carbon steel a controlled water cooling quench is used which refines the grain structure and improves the mechanical properties. In some steels for example API5LX42 up to and including X70, water and air is used for the quench to ensure maximum ^" ductility at low temperatures. In low alloy steel, including manganese

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and molybdenum steels, air cooling eliminates the need for additional heat treatment after bending. Chrome molybdenum and other high alloy steels may be heat treated after bending, and for stainless steels cooling with controlled water allows for an economical process for bending and quenching in one operation, equivalent to heat treatment. In any event, quenching occurs substantially immediately the pipe section leaves the induction coil 67 and bending or other deformation takes place substantially only within the induction coil.

The cross-member 22 comprises not only the I- beam 54 mounted on concrete footing 30 and steel pad 20 to be at the same height as the I-beams 21, but also a low section I-beam 70 supported on the ground by a concrete footing 71 and a steel pad 72, the steel pad 72 being bolted to both the I-beam 70 and the concrete footing by means not shown. The I-beam 70 carries on the external surface of the uprights thereof the rails 29 and, on the cross-piece thereof, a screw-threaded rod 73 which is supported for rotation relative thereto as at 74 (Figure 6) , the rod 73 being selectively rotated by means of an electric motor 75. Two such rods 73 are provided along the length of the I-beam 70, each such rod having its respective motor 75 and the rods being separated by a short distance at the centre of the beam 70.

The carriage 27 carries depending members 76 on which the three roller assemblies 28 associated with each rail are supported as shown in Figure 7. The carriage 27 also carries a depending rigid screw-threaded nut 77 which engages with the screw-threaded rod 73 and which .on rotation of the rod 73 is displaced with the carriage along the I-beam. The nut 77 may be automatically transferred from the one screw-threaded rod 73 to the other when the carriage 27 is displaced to the

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longitudinal centre of the I-beam 70. The nut 77 is displaceable along a bearing surface 78 provided on the cross-piece of the I-beam 70.

The carriage 27 also carries the pivot 26 by which the arm 25, which comprises a further I-beam, is pivotally mounted relative to the carriage 27. A bearing member 79 is supported on the carriage 27 around the pivot post 27 and a roller bearing assembly 80 is located between the upper surface of the bearing member and the pivot arm 25. Thus, the pivot arm 25 is free to pivot relative to the carriage from substantially any position along the I-beam 70.

The parallel cylindrical rails 32 mounted along substantially the full length of the I-beam 25 receive the horse shoe cross-section slides 31 thereon, the slides depending from a platform 81 of the clamp head 24. The I-beam 25 also carries a screw-threaded rod 82 rotatably mounted relative to the I-beam on bearings 83. The rod 82 is adapted to be rotated by an electric motor 84 provided at the distal end of the pivot arm 25. The screw-threaded rod 82 is located between the rails 32 and a screw-threaded nut depends in rigid manner from the carriage 81 between the slides 31 to screw-threadably receive the rod whereby the carriage may be displaced along the rails 32 and I-beam 25 on rotation of the rod

82.

The clamp head 24 is mounted on the platform 81 in off-set manner whereby, with reference to Figure 4, when the arm 25 is aligned along the I-beam 70, in which position the arm 25 engages a stopper 85 mounted on the I-beam 54 (Figure 7) the platform 81 substantially abuts the I-beam 54 and the clamp head 24 is disposed in a plane immediately downstream of the plane of the heater 19 and quench ring 66. In order to begin bending the pipe, the clamp head 24 is set at the desired radius of

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curvature relative to the pivot post 26 by actuating the motor 84 and the arm 25 is then displaced along the I- beam 70 by actuation of the motor 75 until the clamp head is aligned with the axis of the pipe 12 to be curved. With reference to Figure 8, the pivot arm 25 carries a ground engaging wheel assembly 86 adjacent its remote end in order to ensure the horizontal attitude of the arm.

Also with reference to Figure 8, the clamp head 24 carried by the platform 81 is in the form of a box frame comprising opposed upright members 87, identical bottom plates 88 having concave cut-out portions in their upper surfaces and welded to respective sides of the two upright members 87, and a top member 89 pivotally mounted at 90 to one of the upright members 87 and selectively lockable with the other upright member by a simple locking arrangement comprising a pivoted screw-threaded bolt 91 on the other upright member 87 engageable in a slot formed in the top member 89 (not shown) with a - ^' ■--.■-,,-•-" screw-threaded nut 92 on the bolt 91 which may be screwed ^" down onto the surface around the slot. A bottom clamp member 93 having a cut-out of equal radius to the radius of the pipe is located between the identical bottom plates 88 and is held therebetween. A top clamping member 94 also having an arcuate cut-out of radius equal to that of the pipe 12 is supported from the top member 89 by a pivot location 95 and is loσatable over the bottom clamping member -93 by slide plates 96 provided on opposed sides of each upright member 87. In normal usage the bottom and top clamp members 93 and 94 do not abut, thereby permitting the clamp head 24 to be tightened on a pipe 12 by means of the locking nut and bolt assembly 91 and 92.

OMPI

If a different diameter pipe is to be curved, it is necessary to provide different diameter bottom and top clamping members 93 and 94, different diameter induction coil 67 and rings 65 and 66, and to adjust the rollers 23. If the pipe is to extend through the pusher 15, it may also be necessary to provide a different clamping arrangement therein substantially in accordance with the clamp head 24.

As previously explained, and with reference to Figure 11, when a pipe is curved on the machine, of

Figures 1 to 10 the thickness of the outside portion of the wall on the curve is substantially retained as before whereas the thickness along the inner portion of the curve is increased. As illustrated in Figure 2, with suitable adjustment of the pivot arm 25 along the I-beam 70 a pipe 12 may be curved in a clockwise or anticlockwise manner relative to the heating station 13. Such curve may be up to 180 and may, if desired, be followed by a curve in a different plane by suitably rotating the pipe about its unbent axis. The metal bending temperature, bending speed and bending force are partly dependent upon the pipe thickness and are advantageously controlled by means of a microprocessor which monitors the pipe thickness prior to the heating zone. The known pipe diameter which may be accommodated on the machine is from 50mm to 760mm with a wall thickness from 3mm to 75mm. In a proposed embodiment, the bending radius range is from 75mm to 5000mm and it is to be noted that with suitable adaptation the machine can accommodate non-circular hollow sections or profiles.

Referring now to Figures 12 to 14, the machine of Figures 1 to 10 is modified to provide thickening of the pipe wall along a linear axis. The sole variations to the machine are that the pivot arm 25 is aligned with the I-beam 70 and restrained from movement in this

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position, that is abutting the stop member 85 with the clamp head aligned with the axis of the pipe; the clamp head is adjusted so that the pipe cannot pass therethrough, and this may be by clamping the pipe if the pipe thickening is to be intermediate the ends of the pipe or by abutting the pipe against the clamp member if the pipe thickening is to be at that end; and by providing a circular induction heater 19 instead of the lobed coil 67 so that the pipe 12 is heated evenly around its circumference.

In this- rocess, the hydraulic cylinder arrangements 17 are actuated at the same time as the heating station is slowly displaced towards the pusher 15 by displacement along the rails 16 of the I-beams 21. Such displacement is advantageously by means of an electric motor (not shown) in the same manner as adjustment is provided for the pivot arm 25 along the I- bea 70, that is by means of a motor driven rotatable screw-threaded rod which drivingly engages a nut on the carriage 61 of the heating station.

As the heating station moves between the rollers 23, it will be necessary to retract the rollers and separate locating means (not shown) may be provided along the length of the pipe 12. Control of the pipe thickening will be provided in a similar manner to the control for the pipe curving and the pipe will be quenched immediately downstream of the heater 19.

Figure 14 illustrates the thickening of the pipe performed in this manner and this facilitates the screw-threading of the pipe end or the provision of T- junctions in the manner previously described.

Pipe thickening may also be performed on a linear pipe by fixing the position of the heating station 13 and restraining movement of the pipe through the heater 19. This may be provided by a hydraulic ram

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engaging the leading end of the pipe and providing for controlled retraction of the ram. For pipe thickening in a curved pipe, the heating station 13 may be fixed and movement of the pivot arm 25 in the machine of Figures 1 to 10 may be restrained by a hydraulic arrangement.

An arrangement for thickening a linear pipe in which a hydraulic ram is provided downstream of the heating station to restrain movement of the pipe through the heating station is disclosed in Australian provisional patent application No. PF 9842, the disclosure of which is included herein by reference.

Referring now to Figures 15 to 17, the machine of Figures 1 to 10 is modified to allow for coiling of the pipe after curving the pipe through an arc of up to 90 . Figure 15 illustrates the pipe having been curved on the machine, following which the pipe is released from the clamp head 24 by disengagement of the locking assembly 91, 92, raising the top member 89 and thereby removing the top clamp 94. The pipe is then rotated about its linear axis by the desired amount to define the pitch of the coil to be formed. As shown in Figure 16, the pitch is a few degrees. The clamp head 24 is then replaced by a series of rollers 101 supported in the box frame carried by the pivot arm 25, the rollers 97 supporting the pipe at the desired position defining the pitch. Such support need not be with the pivot arm at 90° relative to the I-beam 70 and may be for example as little as 20° relative thereto. The rollers 97 must rotate about axes at 90 to the plane of the pitch of the pipe and they must therefore be slightly tilted.

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Once the pitch angle has been set, the pusher 15 and heating station 13 are reactuated and it has been found that the pipe automatically follows the pitch path as it is bent at the heating station, as shown in Figure 17.

A small pipe 12 may be rotated by hand to define the coil path, or suitable mechanical means may be provided. If it is desired to have a pipe coil of length (along the coil) greater than the length of one pipe length, additional pipe lengths may be welded to the previously coiled portion during the process.

Control arrangements for the pipe coiling process are as for the pipe curving process.

It will be appreciated that the machine of the present invention, together with its modifications, provide many advantages over the prior proposals, but other modifications not described herein and falling within the scope of the invention as defined by the claims will be apparent to those experienced in the art.