For a variety of reasons, in the fabrication of pipe and tubing by rolling up a tubular form from a flat strip or skelp and seam welding the abutting edges, it is impossible to maintain precise control of the finished diameter. Particularly in larger diameters and where lighter gauge material is used, for example in diameters above 150 millimetres or where the wall thickness is less than 2% of diameter, pipe and tubing fabricated in this way may not be perfectly round. Some variation from straightness is also frequently experienced. It is well known that standards for some forms of pipe and tubing prescribe quite liberal tolerances.

Many applications exist in which pipe and tubing must meet precise specifications in relation to diameter, roundness and straightness and a variety of methods has therefore been developed to correct defects in these criteria. Where the diameter of pipe or tubing has to be increased, it is common to pass a cylindrical die of some suitable hard material and having an external diameter somewhat greater than the internal diameter of the pipe or tube through the lumen of the pipe or tube to stretch it.

Where more than a minor correction is required, consecutive passes of dies of increasing diameter may be required, the internal surfaces of the

pipe or tube lumen may require lubrication, scoring of the internal surfaces is common and some degree of wall thinning will occur. The process has the advantage of being operable on a continuous basis. In another method, the internal diameter of pipe or tubing is increased by subjecting the interior of short lengths to hydraulic pressure to expand it into an enclosing female die. Use of this method is normally confined to short lengths of pipe or tubing and has the disadvantages of slowness and the fact that it cannot be operated on a continuous basis. Both methods are well known in the art.

Where the diameter of pipe or tubing is required to be decreased, it is common to roll it down by passing the pipe or tubing through a plurality of concave rollers arranged such that their diameters extended meet at a common point and with their collective concavities more or less forming a complete circle slightly smaller than the final diameter of pipe or tubing required. Equally-spaced rollers are supported on shafts parallel to tangents to the surface of the pipe and tubing and are driven in rotation while the pipe or tubing to be resized is fed between them and is thereby cold worked to a smaller diameter. Unless the pipe or tubing is stretched at the time, some degree of wall thickening will occur. An example of this method is that taught by United States Patent No. 5,533, 370. This method appears intended for use with only pipe or tubing of smaller diameters and the fact that the method includes provision for final sizing to be performed by drawing the rolled pipe or tube through a female sizing die is indicative SUBSTITUTE SHEET (RULE 26)

of the limited control of worked diameter available. Disadvantages of this method are the fact that only relatively small decreases in diameter may be achieved in a single pass, normally of the order of 0.2 to 0. 4mm, that what is effectively a wiping action of the sides of the roller concavities may scuff or mar the external surfaces of pipe or tubing (an important factor in stainless steel products), and the fact that the method is relatively ineffective in large, relatively thin-walled pipe or tubing. The scuffing or marring of external surfaces is particularly pronounced in larger diameter pipe or tubing where the method is normally performed using only two rollers having deep concavities. Obviously, as suggested in the example cited, the diameter of pipe or tubing may be reduced by drawing it through a female sizing die. Where this method is employed, the pipe or tube may require lubrication, the external surface of the pipe or tubing is frequently scored by asperities in the die or picked up by the die and some wall thickening and elongation may occur. An example of this method is that taught by United States Patent No. 4,057, 992 in which both internal and external dies are used in what is normally a second or third manufacturing operation.

Another example of diametral reduction by rolling, in this case described at spin forming, is that taught by United States Patent No.

6,233, 991 in which a short length of pipe or tubing is rotationally supported by clamps only at the ends and a plurality of cylindrical rollers is brought to bear against the outer surface of the length of pipe or tubing while it is rotated, thereby reducing its diameter and, if required, rendering SUBSTITUTE SHEET (RULE 26)

it into tapered form. The method is applicable only to short lengths of pipe or tubing and obviously cannot be operated as a continuous process.

Of relevance to the present invention is United States Patent No.

4,242, 894 in which thin-walled metallic tubing is formed from a solid blank in an Assel rolling mill. In this case, provision is made to vary the wall thickness of the formed tubing by adjusting the radial positions of a plurality of forming rollers. Adjustment is effected by increasing the skew of short shafts upon which the forming rollers are rotationally supported, thereby radially displacing the rollers inwardly or outwardly. The ends of the short shafts are rotationally supported in suitable bearings accommodated within the ball parts of ball and socket joints, which ball parts move in complementary sockets to permit skewing of the shafts.

The rollers are short and are provided with shoulders which work on the blank from which the tubing is formed.

In many tube rolling methods, such as that taught by United States Patent No. 4,827, 749, a mandrel is inserted into the lumen of a tube to be rolled and the tube worked by a plurality of rollers against the mandrel.

Applications are also common in which laminated pipe or tubing is made by drawing one piece of pipe or tubing into the lumen of another.

Where, for example, the inner pipe or tube is made from a polymer material, it is common to temporarily reduce its diameter by passing it between concave rollers or through a female sizing die in the manner described and, when positioned inside a pipe or tube of larger diameter, expanding it by the application of internal fluid pressure to make a tight fit SUBSTITUTE SHEET (RULE 26)

within the outer pipe or tube. Additionally, to ensure a more secure capture of the inner pipe or tube, the outer pipe or tube may subsequently be reduced in diameter using one of the methods described. Where both the inner and outer pipes or tubes are of metal, the inner is captured simply by reducing the diameter of the outer.

The object of the present invention is to provide a method and apparatus for reducing the diameter of pipe or tubing; which may readily be precisely adjusted to produce an accurate finished diameter; which may be operated on continuous or discrete lengths of pipe or tubing; which may be made self-correcting ; which may also provide a straightening effect; which acts without marring the external surface of the pipe or tubing; which is capable of effecting a greater degree of reduction in diameter in a single pass than other systems; which leaves the pipe or tubing properly round ; which may be ganged into a multi-stage operation ; which acts without the necessity to lubricate the pipe or tubing; and which is effective in treating a full range of diameters in both thin and thick-walled pipe or tubing.

According to the present invention, the diameter of pipe or tubing is reduced by passing it through a rotating apparatus comprising a supporting cylinder in which is provided a plurality of closely and equally- spaced, skewed, long, narrow, parallel cylindrical rollers of a rigid, hard material which are brought to bear on the external surface of the pipe or tubing as it passes through said apparatus. Said rollers are supported in a cylindrical array with their ends on pitch circles of equal diameter and are SUBSTITUTE SHEET (RULE 26)

rotationally supported in suitable bearings provided in the end flanges of said supporting cylinder, said end flanges being provided with apertures to permit the ingress and egress of the pipe or tubing to be treated. One or both or said end flanges are capable of rotational displacement within the ends of said supporting cylinder, thereby adjusting the degree of skew of said rollers which, although they are displaced relative to the longitudinal axis of said supporting cylinder, remain in planes parallel to said longitudinal axis. Said bearings of said rollers are themselves supported in part-spherical bushings which are, in turn, accommodated within complementary cups formed in said end flanges such that said rollers may continue to be rotationally supported in said end flanges when in their skewed positions. Said supporting cylinder is itself rotationally supported in one or more bearings which permit it to rotate about its longitudinal axis, driven by a suitable driving motor. In operation, the degree of skew of said rollers is adjusted to bring narrow, centrally-located contact zones of the rollers to bear against the outer surface of the pipe or tubing with a desired force. As said pipe or tubing passes at a steady speed through said cylindrical array of rollers, said supporting cylinder is rotated by its driving motor, causing said contact zones of said rollers to describe continuous, parallel, overlapping, helical paths along the external surface of said pipe or tubing, locally applying a compressive force to said pipe or tubing in excess of the yield stress of its material and thereby causing said pipe or tubing to adopt a set at a smaller diameter. The passage of said contact zones of said rollers over the outer surface of said pipe or tubing causes SUBSTITUTE SHEET (RULE 26)

the surface to be attractively burnished without marring, any out-of- roundness of said pipe or tubing is simultaneously corrected and, should said pipe or tubing require straightening, its restraint in correct alignment as it passes through said rollers will effect this.

The various aspects of the present invention will be more readily understood by reference to the following description of preferred embodiments given in relation to the accompanying drawings in which: Figures la, lb and le are partial cross-sectional views of said supporting cylinder showing various positions of one of said cylindrical array of said rollers; Figure 2 is a partial cross-sectional view of said supporting cylinder and said pipe or tubing to be treated showing the arrangement of some of said cylindrical array of said rollers in relation to said pipe or tubing to be treated; Figure 3 is a longitudinal cross-sectional view of said supporting cylinder, its supporting bearing and said pipe or tubing to be treated, said rollers having been deleted for clarity of presentation; Figure 4 is an end view of the components depicted in Figure 3; Figure 5 is a longitudinal cross-sectional view of supporting means at one end of one of said rollers; Figure 6 is a side view of the complete apparatus with said pipe or tubing to be treated passing through it; SUBSTITUTE SHEET (RULE 26)

Figure 7 is a longitudinal cross-sectional view of an alternative means of supporting said rollers; Figure 8 is an end view of said supporting cylinder showing calibration detail; Figure 9 is a partial side view of the central part of one said roller showing alternative shaping detail; Figure 10 is a partial side view of the central part of one said roller showing another alternative shaping detail; Figure 11 is a side view of a typical set of said rollers in cylindrical array with all supporting means deleted for clarity of presentation; Figure 12 is an end view of the set of said rollers depicted in Figure 11.

With reference to Figure la, roller 3 is rotationally supported within supporting cylinder 1 with its axis positioned on pitch circle 2 and parallel to the axis of said supporting cylinder. With reference to Figure lb, the same roller is shown with its ends skewed 15° either side of the previous position. It can be seen that the distance 4 from the centre 5 of said supporting cylinder to contact zone 6 of said roller has been reduced.

With reference to Figure 1 c, said roller is shown with its ends skewed a further 15° and distance 4 can be seen to have been further shortened. It may be appreciated from the figures that skewing of said rollers may be employed to bring their central contact zones into forceful contact with the outer surface of said pipe or tubing to be treated. Obviously, said rollers SUBSTITUTE SHEET (RULE 26)

may be made solid throughout their lengths or made with solid ends and partially hollow in their middle parts.

With reference to Figures 2,11 and 12, partial and complete sets of rollers 3 in cylindrical array are depicted, said rollers being rotationally supported within supporting cylinder 1 with their axes ends positioned on pitch circles 2 of equal diameter. Skewing of said rollers has brought contact zones 6 into contact with the external surface of pipe or tubing to be treated 7. In the preferred embodiment, said rollers are made with a minimum practical diameter commensurate with a particular application in order to provide the maximum number of rollers in each said cylindrical array. This normally results in said rollers having a diameter approximately 20% of that of the pipe or tubing to be treated, for example, 18 rollers with a diameter of 28 millimetres are used in an arrangement to treat pipe or tubing with a diameter of 150 millimetres.

With reference to Figure 3, pipe or tube to be treated 7 is depicted passing through apertures 8 in end flanges 9,19 of supporting cylinder 1 in the direction shown by arrow 23. A typical position of the axis of one of a said cylindrical array of rollers is depicted by broken line 18, supporting provisions for this roller in end flanges 9,19 having been cut away in the figure. End flange 19 is fixed in one end of said supporting cylinder and end flange 9 is captured in the other end of said supporting cylinder between shoulders 20,21 while remaining free to be displaced in a rotational sense to effect skewing of said rollers. Supporting provisions (not shown) for the ends of said rollers are accommodated in apertures 10

provided in said supporting cylinder end flanges. Bearing 15 is positioned on or close to a plane passing through the contact zones of said rollers.

Mounting flange 12 is provided on the mid exterior surface of said supporting cylinder and attached to this with suitable fastening means is radial web 13, the periphery of which is formed into an inner part of a housing for bearing 15. Cylindrical pulley 14 is formed on one side of said radial flange positioned towards its periphery. Radial mounting flange 22 is provided with holes 17 for mounting attachments (not shown) and its inner periphery is formed into a cylindrical extension 16 which incorporates an outer part of a housing for bearing 15. Mounting flange 22 is fixed with suitable fastenings to a supporting structure (not shown) and supporting cylinder 1 is driven in a rotational sense by drive forces applied to pulley 14 through a suitable belt (not shown). In alternative embodiments, said pulley is replaced with a sprocket or gear (not shown) and said supporting cylinder is driven in a rotational sense by drive forces applied through one or more suitable chains or gears. As pipe or tubing to be treated 7 passes through the interior of said supporting cylinder and through said rotating cylindrical array of rollers (not shown), said contact zones of said rollers pass over the external surface of said pipe or tubing following continuous, parallel, overlapping, helical paths a typical one of which is indicated by arrow 24. It ca be readily demonstrated that the power required to drive said rollers against said pipe or tubing is quite low and, even when said pipe or tubing is being heavily worked, is normally considerably less than the power required by conventional methods.

SUBSTITUTE SHEET (RULE 26)

With reference to Figure 4, end flange 9 is restrained in a rotational sense by adjustable-length struts 33, the inner ends of which are pivotally attached to short shafts 34 formed on end flange 9 and the outer ends of which are pivotally attached to short shafts 35 formed on the ends of posts 32 fixed to the end exterior surfaces of said supporting cylinder. Skewing of said rollers is effected by lengthening or shortening said struts, thereby displacing end flange 9 in a rotational sense relative to said supporting cylinder.

With reference to Figure 5, the ends of rollers 3 are provided with tapered section 27, the end of which is formed into shaft 28. Shaft 28 is rotationally accommodated in needle bearing 29 which is, in turn, accommodated within part-spherical bushing 26. Part-spherical bushing 26 is accommodated within split cup 25 which is, in turn, accommodated within aperture 10 provided in end flange 9. Bearing 29 is captured on shaft 28 between shoulder 36 and retaining cap 30, said retaining cap being fixed to the end of said shaft by suitable fastening 31. Suitable means (not shown) are provided for the lubrication of said roller support means. Said split cup is provided with external flange 37 by means of which said split cup is retained in place in aperture 10 by suitable attachment means (not shown). The openings on either side of said split cup are suitably relieved to provide the requisite freedom of movement of roller 3. Shaft 28 and needle bearing 29 are made sufficiently long to accommodate the axial displacement of roller 3 caused by an increase or decrease in its degree of skewing. In an alternative embodiment (not SUBSTITUTE SHEET (RULE 26)

shown), shaft 28 and needle bearing 29 are positively captured in part- spherical bushing 26 and the axial displacement of roller 3 caused by an increase or decrease in its degree of skewing is accommodated by axial displacement of end flange 9 within the end of supporting cylinder 1, said end flange being restrained against rotational displacement relative to said supporting cylinder by suitable splines, lugs or the like (not shown) on one engaging complementary provisions on the other.

With reference to Figure 6, the assembly depicted in Figures 3 and 4 are mounted in moving frame 38. Said moving frame is slidingly supported by brackets 43,44 bearing upon linear bearings 41,42 travelling on rails 39, 40 fixed to upper surfaces of fixed frame 45. Pipe or tubing to be treated 7 is depicted passing through supporting cylinder 1 and its extension is supported on suitable supports (not shown). Pivot shaft 46 is fixed to a lower structural member of said moving frame towards one of its sides and valve 48 is fixed to a lower structural member of said fixed frame towards the second side of said moving frame. Link 49 connects the operating lever of said valve to said pivot shaft such that, as said moving frame is displaced along rails 39, said valve is progressively opened, said valve being fully closed at the left-hand limit of travel (as depicted) of said moving frame. A supply of compressed air at a suitable pressure is connected to said valve through air line 47 and air is supplied from said valve through flexible air line 50 to air motor 51. Said air motor drives pulley 52 through reduction gearbox 54, said pulley being connected to pulley 14 by belt 53 to drive supporting cylinder 1 in a SUBSTITUTE SHEET (RULE 26)

rotational sense. Suitable gusseting is provided, as required, to stiffen said moving and fixed frames. In operation, as said pipe or tubing passes into said apparatus from a tube forming mill, frictional forces applied through the contact zones of said rollers act to displace said moving frame along rails 39,40, thereby partially opening valve 48 and actuating air motor 51 to drive supporting cylinder 1 in a rotational sense. Progressive displacement of said moving frame occurs until said air motor has reached a speed of operation matched to the speed of advance of said pipe or tubing. Further displacement of said moving frame then ceases. If the speed of advance of said pipe or tubing is reduced for some reason, the forces generated by said rollers upon said pipe or tubing act to displace said moving frame back towards its rest position, thereby closing valve 48 somewhat and reducing the speed of operation of air motor 51 and thereby the speed of rotation of supporting cylinder 1.

With reference to Figure 7, in an alternative embodiment, rollers 3 are rotationally supported in needle bearings 56 accommodated in bores 73 provided in shoulders 58 formed on the ends of mounting yokes 59.

Each said mounting yoke is supported on shaft 64 pivotally supported in bearing 63 provided in the wall of supporting cylinder 1 and is retained in place by belville washers 65, washer 66 and circlip 67 or other suitable fastening. The rollers in said cylindrical array are simultaneously skewed by force applied through skewing rings 60 which are pivotally connected to pivots 61 provided on the ends of said yoke and retained in place by circlips 62. Thrust washers 57 are provided between the ends of rollers 3

and the inner surfaces of shoulders 58. Said supporting cylinder is increased in diameter as required to accommodate the arrangement described. The arrangement described is obviously suited for treating only one diameter of pipe or tubing and, in an alternative embodiment (not shown) used to treat differing diameters, the outer parts of shafts 64 are suitably threaded to engage ball nuts which are actuated by one or more suitable stepper motors to simultaneously displace all said rollers radially inwards or outwards. The use of ball screw and nut arrangements in such applications is well known and obvious.

With reference to Figure 8, index mark 68 is provided on the face of end flange 9 and calibration marks 69 are provided on the end of supporting cylinder, said marks facilitating the adjustment of skew of said rollers. Obviously, the arrangement described is optionally able to be reversed.

With reference to Figure 9, in an alternative embodiment, shaft 3 is provided with a centrally-located, narrow, convex part 70 to permit a more localised force to be provided by said roller to said pipe or tubing to be treated.

With reference to Figure 10, in an alternative embodiment, shaft 3 is provided with a centrally-located, concave part 72 to permit a more dispersed force to be provided by said roller to said pipe or tubing to be treated.

With further reference to Figure 6, said fixed frame is fixed to floor 74 with suitable fastenings. Where required, said fixing provisions SUBSTITUTE SHEET (RULE 26)

incorporate jacking means (not shown) to precisely align the apparatus with the axis of pipe or tubing 7 emerging from a tube forming mill (not shown). Said jacking means may be operated to create a straightening effect of said pipe or tubing. In a first embodiment, said jacking means are manually operated. In an alternative embodiment, sensors (not shown) are employed to detect the straightness or not of said pipe or tubing and, as required, one or more stepper motors (not shown) are employed to operate said jacking means to correct any deviation from straightness. A programmable logic controller or other microprocessor-based device is employed to process data from said sensors and control the operation, as required, of said stepper motors. In another alternative embodiment (not shown), said fixed frame is permanently fixed to floor 74 and mounting flange 22 is supported on linear bearings slideably travelling on rails fixed to the vertical members of said moving frame, said linear bearings being displaced by ball screw and nut arrangements driven by one or more stepper motors. Said stepper motors are employed to drive said ball screw and nut arrangements to correct any deviation of said pipe or tubing from straightness. A programmable logic controller or other microprocessor- based device is employed to process data from said sensors and control the operation, as required, of said stepper motors.

With reference to Figures 3 and 6, in an alternative embodiment (not shown), air motor 51 is mounted directly to cylindrical extension 16 and drives supporting cylinder 1 in a rotational sense through one or more belts, chains or gears engaging pulleys, sprockets or gears formed on SUBSTITUTE SHEET (RULE 26)

pulley 14 or on the external surface of supporting cylinder 1. In this embodiment, said moving frame is redundant and said apparatus is simply fixed to vertical members of said fixed frame. In other alternative embodiments (not shown), said air motor is replaced by another form of drive motor in the form of an hydraulic motor, a stepper motor or other form of speed-controllable electric motor. In this arrangement, the speed of advance of said pipe or tubing is detected by one or more encoders attached to forming rollers on said tube forming mill or on a jockey wheel which travels on said pipe or tubing. A programmable logic controller or other microprocessor-based device is employed to process data from said encoders and control the operation, as required, of said drive motor driving said supporting cylinder in a rotational sense.

In an alternative embodiment (not shown), said apparatus is made in multi-stage form with two or more of said units operated in tandem such that one of each or all units are employed to reduce the diameter of said pipe or tubing, correct its out-of-roundness or straighten it. Said units are optionally operated with a common direction of rotation or with alternate units rotating in the opposite sense. It will be appreciated from further inspection of Figures la, lb, lc and 2 that the axes of said cylindrical arrays of rollers of consecutive units, regardless of their adjustments, will always be collinear. At the same time, the speed of advance of said pipe or tubing through consecutive units will be correct regardless of said skewing adjustment of said rollers. This is a result of the fact that, as the degree of skew of said rollers is increased, which SUBSTITUTE SHEET (RULE 26)

would tend to increase the axial component of the vector triangle representing speed of advance of said pipe or tubing, the rotational component is automatically decreased in compensation. As a result, the said apparatus is very well suited for operation in multi-stage form. It should be noted also that the axial forces imparted to said pipe or tubing by operation of the said apparatus are high and no other means of propulsion or urging in an axial sense are required to be applied to said pipe or tubing during its passage through said apparatus. In multi-stage arrangements of said apparatus, the axial forces applied by it to said pipe or tubing are optionally employed to draw material through a tube forming mill positioned upstream of said apparatus and significantly reduce the power required to drive said tube forming mill. Obviously, said apparatus may optionally be employed to work upon continuous lengths of pipe or tubing delivered directly from a tube forming mill or upon discrete lengths of pipe or tubing loaded sequentially into said apparatus.

With further reference to Figure 4, in an alternative embodiment (not shown), one or more stepper motors mounted on the external surface of supporting cylinder 1 are employed to adjust the lengths of suitable ball screw and nut arrangements (not shown) used in place of adjustable-length struts 33. Sensors are provided to detect the precise corrected diameter of said pipe or tubing and a programmable logic controller or other microprocessor-based device is employed to process data from said sensors and control the operation, as required, of said stepper motors.

Power and control signals are supplied to said stepper motors through slip- SUBSTITUTE SHEET (RULE 26)

ring provisions and control signals are optionally transmitted through wireless connections.

Sensing means in the form of opposed pairs of rollers attached to the inner ends of radially-arranged linear transducers are employed to measure the finished diameter of said pipe or tubing emerging from said apparatus, said rollers being urged into contact with said pipe or tubing by suitable springs. In a second embodiment, sensing means in the form of a laser micrometer are employed to measure the finished diameter of said pipe or tubing emerging from said apparatus. In a third embodiment, sensing means in the form of opposed pairs of proximity sensors, each said sensor measuring the gap between its reference surface and the external surface of said pipe or tubing are employed to measure the finished diameter of said pipe or tubing emerging from said apparatus.

With further reference to Figure 3, it will be readily appreciated that supporting cylinder 1 with its said roller array may be made to be readily detachable from radial web 13 through the use of quick-release attachments (not shown) and a replacement said supporting cylinder with its said roller array installed in its place to accommodate said pipe or tubing of a different diameter.

The rolling process performed by said apparatus provides accurate control of the external diameter of pipe or tubing; it requires no lubrication of said external surface of said pipe or tubing; it requires only low power for its operation; it leaves said external surface of said pipe or tubing

burnished and easily polished; it is not limited by the diameter, length or wall thickness of said pipe or tubing; it may be operated with a greater lineal speed of said pipe or tubing than the output speed of a tube forming mill and the two may thus be operated in conjunction; it may be performed by multiple said rolling units operated in tandem; it exerts a rounding and straightening effect upon said pipe or tubing; it may be operated under automatic control; it may be employed with continuous lengths of said pipe or tubing or with discrete lengths; and it provides a greater reduction in external diameter of said pipe or tubing per pass than conventional rolling processes.