Tandem roller pipe bender

Abstract: A pipe bender (100) comprises a base (111), a former (132) on the base and having a former surface extending angularly at a fixed radius about a bending axis (114). The former surface is provided to engage a length of pipe (133) to be bent to conform to at least a portion of the length of the former surface. A bending arm (113) is pivotally mounted on the base (111) for pivoting movement about the axis (114). A bending assembly (115) is mounted on the arm (113) and includes two deforming rollers (123,125) rotatably mounted for movement about an axis which is parallel to the bending axis (114) and spaced radially outwardly of the bending surface. The rollers (123,125) are adapted to engage the length of pipe (133) to cause bending thereof as it is moved angularly about the axis (114). The rollers (123,125) are substantially co-extensive, with one of the rollers being positioned radially with respect to the bending axis (114) so that in use the one roller is positioned at approximately the bending point of the pipe, the other roller being spaced angularly forward of the one roller and radially further from the bending axis (114) than one roller. A hydraulic ram (126) is provided to cause angular movement of the arm (113) about axis (114) to thereby move the roller and deform the pipe.

Description: The invention pertains to pipe bending and more particularly to an apparatus and method for bending pipe using at least two means for exerting pressure against an inside former. BACKGROUND OF THE INVENTION There are many known apparatuses for pipe bending, each with its own particular method of use and each with its own limitations. Certain features are commonly considered to be unacceptable in a bent section of pipe. Kinking of the surface of the section is usually found on the inside of the bend. It is considered a major fault. Wrinkling of the surface of this section is also usually found on the inside of a bend. Wrinkling is like small but repeated kinks and is often not acceptable. Distortion of the original shape of the cross-sectional profile in the form of a flattening found at the outside of the bend is sometimes acceptable if only minor by visual inspection. Marks, dents or bulges left in the surface of the section by the bending apparatus is usually considered a minor fault from a mechanical standpoint but may be very significant in a visual sense. In recent times, pipe and RHS have been available in C350 grade steel, which is stronger than previously supplied steels. This grade of steel is work hardened when it is cold formed into pipe. It is also welded at the seam by electric resistance welding. The resulting pipe and RHS section is stronger and much more resistant to deformation. However bending is itself a form of controlled deformation. Further, sections are now offered with thinner wall thicknesses to give a section of similar strength lower weight than previous sections. While the strength, section thinness and lower weight may be advantagous to most users, problems involving all of the bending faults mentioned above are encountered when using conventional bending devices which were designed for sections produced by prior means. Most existing pipe benders use a rigid, curved former which controls both the cross-sectional profile of the section and the radius of the bend. One simple type of bender users two fixed posts to apply a reaction force, while the inner former is forced into the pipe section between the posts to create the bend. The bend starts at the centre and progresses in both directions along the section as the former is progressively advanced between the posts. This type of bender is usually referred to as a "fixed post bender". Because the reaction points are widely spaced (to allow the former to pass between them) the force applied is relatively low allowing easy bending. However, high former contact pressure is desireable to prevent wrinkling of the bend, particularly with C350 grade sections which are in use today. Severe kinking is usually experienced with C350 grade pipe in conventional formers with a radius of bend of approximately three times the diameter of the pipe. There have been attempts to avoid this by increasing the former radius from three diameters to four diameters and by making the former tighter on the pipe, even to the point of having the pipe squeeze into the former. It is intended that this grip in the former will stop the pipe rising out of the former at the point of bend and allow a kink to form. These measures are successful on some types of pipe and in most cases kinking is not found while flattening and wrinkling are only minor. However, many users do not like the swept bend appearance of a four diameter bend as it affects design from both a mechanical point of view as well as aesthetic considerations. Also, variations in pipe quality, bending technique and former specifications all cause serious bending faults. A fairly recent variation of the fixed post bender allows the reaction points to be kept fairly close to the point of bond while also providing for them to move outward as bending progresses. This is done by mounting a roller on each of two pivotting arms. The arms move apart as the former is driven between them. However, this method still results in some problems with extra light wall sections where some wrinkling still occurs and outside flattening is noticeable. Certain more effective and also more complex and expensive benders are referred to as draw benders. They are arranged to start the bend at a predetermined point and progressively bend this section around a former in one direction only. This is usually done by providing a fixed inside former, with one reaction point also fixed. Bending is achieved by a sliding or rolling outside former following an arc concentric with the inside former's shape. This allows the reaction point to be kept relatively close to the actual point of bend at all times and high former contact pressure is maintained. This tends to minimise wrinkling. However, with some extra light wall sections, wrinkling is still encountered with considerably flattening around the outside of the bend. Draw benders are usually arranged to make a bend progressively in one direction from a start point, by engaging the pipe to be bent between a fixed reaction point, a fixed inside former and a movable outside member which is attached pivotally at the centre of the fixed former. Some variations use a fixed outside member and an inside former and clamping reaction member that rotate together pulling the pipe around the bend. On fixed inside former types the outside member is usually a shaped roller that moves at a constant radius to the fixed inside former which has a curved groove to shape and support the pipe as it is bent. In US Patent No. 4 012 933 there is disclosed a pipe bender comprising a base, a former mounted on the base and having a former surface extending angularly at a fixed radius about a bending axis, said former surface being provided to engage a length of pipe to be bent to conform to at least a portion of the length of said former surface; a bending arm pivotally mounted on said base for pivotting movement about said axis; a bending assembly mounted on said arm, said assembly includes two deforming rollers rotatably mounted for movement about an axes parallel to said bending axis, and spaced radially outwardly of said surface, said rollers being adapted to engage said length of pipe to cause bending thereof as it is moved angularly about said axis; said roller being substantially co-extensive with one roller being positioned radially with respect to said bending axis, so that in use said one roller is positioned at approximately the bending point of the pipe, the other roller being spaced angularly forward of said roller and radially further from said bending axis than said one roller; and motor means to cause angular movement of said arm about said axis to thereby move said roller to deform said pipe. The two rollers are mounted for movement at constant radii, the leading roller having a larger radius. OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to substantially ameliorate some of the disadvantages associated with prior art pipe benders. In accordance with the invention the two deforming rollers are rotatably mounted on a flange which is pivotally supported by said bending arm. BRIEF DESCRIPTION OF THE DRAWINGS A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings wherein: Figure 1 is a front elevation of a prior art fixed post bender; Figure 2 is a front elevation of a prior art bender with pivotted arms; Figure 3 is a front elevation of a prior art draw bender; Figure 4 is a front elevation illustrating a source of defects in conventional pipe benders; Figure 5 is a front elevation of a tandem roller pipe bender according to the teachings of the present invention; Figure 6 is a front elevation of a bending apparatus incorporating a tandem roller arrangement; Figure 7 is a schematic perspective view of a pipe bender; Figure 8 is a schematic sectioned side elevation of a portion of the pipe bender of Figure 7; Figure 9 is a schematic sectioned side elevation of the pipe bender of Figure 7; and Figures 10 to 13 are schematic plan views of the pipe bender of Figure 7 in progressive modes of operation. BEST MODE AND OTHER EMBODIMENTS OF THE PRESENT INVENTION As shown in Fig. 1, a conventional fixed post bender 10 uses a rigid, curved former 11 which controls both the cross-sectional profile of the section and the radius of the bend. Fixed posts 12 are set apart while the former 11 is forced into the section between the posts to create the bend. Fig. 2 Illustrates a variant of a conventional fixed post bender which allows the reaction points 13 to be kept fairly close to the point of the bend while also allowing them to move outwards (in the direction of the arrows 14) as bending progresses. This is done by mounting rollers 15 on each of two pivotted arms 16. Fig. 3 illustrates a prior art induction bender 20. A fixed inside former 21 cooperates with a sliding or rolling outside former 22. Each of these prior devices has been briefly described and their limitations partially discussed in the BACKGROUND OF THE INVENTION. It is believed that wrinkling occurs in these and other devices because the actual point of bend can lag behind the point of maximum contact pressure. This causes the pipe or section being formed to be lifted out of the inside former by leverage from the reaction point and the point of maximum contact pressure. This concentrates the bend momentarily until a new bend point is established at the contact point. The cycle continues, thus causing wrinkles. This is shown in Fig. 4, wherein A represents the reaction point, B represents the point of maximum contact pressure and C represents the point of bending. It is possible to avoid the cycle of wrinkle formation by providing a second point of contact pressure at the point of bend. A device for achieving this result is illustrated in Fig. 5. As shown In Fig. 5, an inside former 50 includes a peripheral channel 51 which conforms to the shape of the section 52 being bent. Generally, the section 52 will be a round pipe and the cross-section of the channel 51 will correspond to about one half of the circumference of the pipe. However, It should be appreciated that the teachings of the present invention are not limited to bending of round pipes. The inside former 50 works in cooperation with an outside former 53. The outside former 53 comprises at least two means for exerting pressure on the section 52. For the purpose of the present example, the means for exerting pressure are rollers 54. However, the means need not be rollers, as sliding shoes or various other pressure exerting devices could be used in place of the rollers 54. The rollers 54 are mounted on a pivotting cradle 55. The cradle 55 pivots about an axis 56. Preferably, the rollers 54 have concave peripheral grooves or channels which match the profile of the section being bent. Because the cradle is pivotting, the reaction force exerted against the first roller 57 is reflected or transmitted to the second roller 58 which is located at or near the point of bend. This keeps the pipe or material at the point of bend fully seated in the inside former 50, thus prevent the point of bend from lagging the point of maximum pressure. Thus, bending will be continuous without the wrinkle cycle being encountered. One advantage of this system is that the grip of the inside former 50 is not relied upon to keep the material at the point of bend seated. Because former squeeze is not required, the profile shape of the formers is less critical. By reducing the inside former coverage to one half pipe diameter and having the point of bend outside former 54 with half pipe diameter coverage also, the profile of the pipe will be fully contained at the point of bend and outside flattening will be minimized. This allows former radius to be reduced while maintaining a good quality of bend on a wide range of sections. It can be appreciated that the leading outside former 57 applies the bending force as a moment and that the trailing outside former 58 applies a force to the material to contain and control the shape of material in the inside former 50. It is preferred that the trailing outside former 58 be located at or near the point of bend. The trailing outside former 58 need not be located precisely at the point of bend. In a preferred embodiment, a gap of several millimeters is left between the outside diameter of the trailing former end the outside diameter of the inside former. This ensures that the pressure exerted by the trailing edge former is also exerted onto the section or pipe being bent and not transmitted directly onto the inside former. The distance separating the two outside formers could vary greatly so that the contact they have with the material being bent could be very close or quite distant. Further, the two outside formers, while preferably mounted on a common pivotting carriage, could be moved into and out of position by separate means. Hydraulic, pneumatic, electrical, magnetic or mechanical devices can be used to move each outside former into and out of position independent of the other outside formers. In this regard it should also be noted that the pivot point 56 of the carriage 55 can be moved relative to the rotational centres of the outside formers to as to vary the geometry and hence the contact pressure exerted by the trailing outside former 58. It should be appreciated that the advantages of the present invention are obtained regardless of whether the rollers and cradle 55 rotate with respect to the centre of the inside former or whether the former and section being bent rotate with respect to a fixed set of outside formers. Similarly the rollers or other means for exerting pressure may be mounted on a rotating arm or urged into position in other suitable ways. To speed the rate at which sections can be bent, two pairs of outside formers could be located to allow bending to proceed around the inside former in opposite directions and simultaneously. Fig. 6 illustrates an example of a pipe bending apparatus 60 utilizing tandem rollers 61 as disclosed with reference to Fig. 5. Note that the rollers 62 are mounted on a common cradle 63 which rotates about a pivot point 64. The cradle 63 pivots with respect to an arm 65 which rotates about the centre 66 of the inside former 67. A central post 68 to which the inside former is mounted also bears an arm 69 which provides a fixed reaction point 70 for the material which is being bent 71. A hydraulic cylinder 72 in combination with a link mechanism 73 allows the arm 65 to be rotated at least 180° with respect to the inside former. This particular arrangement for rotating the arm 65 is described more completely in Australian Patent Application No. 58906/90. In Figures 7 to 13 of the accompanying drawings there is schematically depicted a pipe bender 110. The bender 110 has a base 111 from which there extends legs 112 to support the base 111 on a ground surface. The base 111 is basically a hollow housing which pivotally supports an arm 113 for pivotting movement about a generally vertical axis defined by the main pin 114. Mounted on the radial extremity of the arm 113 is a bending assembly 115 which includes a carriage 116. The carriage 116 is slidably mounted on the arm 113 for longitudinal movement relative thereto. This movement is effected by means of a threaded shaft 117 provided at its outer end with an adjustment wheel or lever 118. The shaft 117 threadably engages a threaded passage 119 formed in the arm 113. The bending assembly 115 further includes a roller support 120 pivotally mounted by means of a secondary pin 140. The support 120 co-operates with a pair of vertically spaced generally horizontal flanges 121 to support two or more rollers. In this particular embodiment two rollers 122 and 123 are provided. The flanges 121 are joined by means of a handle 124 which is pivotally supported by passing through a passage in the support 120. The rollers are each supported by means of a pin 125. The roller 122 is positioned at the point of bending and the roller 123 is positioned forward thereof. The roller 123 is located angularly forward of and radially further out than the roller 122, relative to the bending axis. Mounted within the base 111 is a hydraulic ram 126 having a cylinder 127 pivotally mounted at one end by means of a pin 145. The ram 126 has a piston rod 129 terminating with a yolk 128. The yolk 128 is pivotally attached to a link 129 by means of a pin 130. The other end of the link 129 is pivotally attached to the arm 113 by means of a pin 131. The arm 113 is also provided with a socket 146 which receives the pin 130 during various phases of movement of the arm 113 about the pin 114. Also mounted on the base 111 is a former 132 which is provided with a former surface 133 which extends angularly about the pin 114, at a generally constant radius. In this particular embodiment, the former surface 132 is concave in transverse cross-section. In this regard it should be appreciated that a length of pipe 134 to be deformed by the bender 110, is bended to generally conform to the surface 132 and therefore the pin 114 also defines the bending axis about which the pipe 134 is bent. The hydraulic ram 126 is controlled in its movement by means of a spool valve 135, operated by means of a lever 136 extending upwardly through the base 111. The spool valve 135 receives hydraulic fluid under pressure and delivers it to the cylinder 127. When the spool valve 135 is moved in a first direction by means of the lever 136, hydraulic fluid under pressure is delivered to the cylinder 127 to cause the piston rod 129 to telescopically extend from within the cylinder 127. This telescopic movement commenced from when the hydraulic ram 126 is configured as shown in Figure 4. As the piston rod 127 extends, the arm 113 is caused to pivot due to engagement of the pin 130 with the socket 132. This continues until the arm 113 has reached the position depicted in Figure 6. At this position, the arm 113 pivots to remove the pin 130 from contact within the socket 146. However the arm 113 continues to pivot due to the force being applied to the arm 113 via the link 129. The spool valve 135 has a cam follower 136 which engages a cam 137 fixed to the arm 113 (via the pin 125) so as to rotate with the arm 113. The cam 137 Is adjustable to return the spool valve 135 to the start position and/or to cause the spool valve 135 to return the arm 113 to the start position. Accordingly, the cam 137 can be used to govern the angle through which the pipe 134 is bent. The former 132 is mounted on the pin 114 but is removable. This enables formers of various sizes to be used so that varying radii may be produced. The former 132 has a rear recess 139 which engages a projection 140 on the base 111, so that the former 132 is held stationary during operation. Also mounted on the base 111 is a pipe support 141 which engages the pipe 134 to retain one portion stationary with respect to the base 111 during bending. In operation of the above described bender 110, it should be appreciated that the bender 110 is described as bending in one predetermined direction. However it should be appreciated that bending can take place in the reverse direction. This is achieved by removing the former 132. Thereafter, the lever 136 is removed together with the cam 137 by release of the bolt 138. The handle 118 is then rotated to remove the bending assembly 115. Next the main pin 114 is removed which enables the arm 113 to be pulled from within the base 111. This is achieved by telescopic movement of the piston rod 127 outwardly with respect to the cylinder 127. Thereafter, the arm 113, link 129 and piston rod 127 are rotated about the axis of the piston rod 127, through 180°. Thereafter, the above steps are reversed. This then locates the hydraulic ram 126 and link 127 on the other side of the lever 136. The bender 110 will then operate to move the arm 113 clockwise about the pin 114 as opposed to anti-clockwise as described with reference to Figures 4 to 7. To accommodate the reverse movement, there is provided a pin 143 which is locatable in either of recesses 142 to hold the support 120 in the correct position. It should be appreciated that the handle 118 is rotated in order to move the rollers 122 radially with respect to the pin 114, in order to accommodate pipes of different diameters. It should further be appreciated that two or more rollers 122 may be employed, with one of the rollers being positioned at the point of deformation of the pipe 134.

Claims: A pipe bender comprising a base (111) a former (132) mounted on the base and having a former surface (133) extending angularly at a fixed radius about a bending axis (114), said former surface being provided to engage a length of pipe (134) to be bent to conform to at least a portion of the length of said former surface; a bending arm (113) pivotally mounted on said base for pivotting movement about said axis; a bending assembly (115) mounted on said arm, said assembly including two deforming rollers (122,123) rotatably mounted for movement about an axes parallel to said bending axis, and spaced radially outwardly of said surface, said rollers being adapted to engage said length of pipe to cause bending thereof as it is moved angularly about said axis; said roller being substantially co-extensive with one roller being positioned radially with respect to said bending axis, so that in use said one roller is positioned at approximately the bending point of the pipe, the other roller being spaced angularly forward of said roller and radially further from said bending axis than said one roller; and motor means to cause angular movement of said arm about said axis to thereby move said roller to deform said pipe, characterised in that; said two deforming rollers are rotatably mounted upon a flange (121) which is pivotally supported by said bending arm. The pipe bender of claim 1 further comprising a reaction member (141) mounted on said base and adapted to engage said length of pipe during bending thereof and retain a bent portion of said length of pipe in contact with said former surface. The pipe bender of claim 1 or claim 2 wherein said bending arm comprises means (116) for selecting a radial location of the bending assembly relative to said surface. The pipe bender of any one of the preceding claims wherein said motor means comprises a hydraulic ram (127) pivotally mounted to the base at one end thereof, and at the other end pivotally associated with said bending arm. The pipe bender of claim 4 wherein said other end of the hydraulic ram is pivotally connected to a link (129) by way of a pin (130), the link in turn being pivotally connected to the bending arm and wherein said pin is adapted to form contact within a socket (146) of the bending arm during at least a portion of pivotal rotation of said bending arm. The pipe bender of claim 4 or claim 5 further comprising an abutment mounted on the base to provide means by which the angle through which the hydraulic ram may pivot is limited. The pipe bender of claim 5 or claim 6 wherein the arm, link and hydraulic ram may be rotated about an axis of the hydraulic ram through 180° so as to allow the pipe bender to operate in a reverse direction. The pipe bender of any one of the preceding claims further comprising a spool valve (135) having a cam follower (136) which engages a cam (137) fixed to the bending arm, the cam being adjustable to cooperate with said spool valve thus governing an angle through which said length of pipe is bent. The pipe bender of any one of the preceding claims wherein the former is removable so as to be replaced by formers of varying radii. The pipe bender of any one of the preceding claims wherein the former comprises a recess adapted to cooperate with a projection (140) on the base, cooperation of the projection with the recess holding said former stationary relative to the base during operation.

Inventors: DIRCKS ROBERT ALEXANDER, DIRCKS, ROBERT ALEXANDER
Applicants: DIRCKS ROBERT ALEXANDER, DIRCKS, ROBERT ALEXANDER
Application year: 1991
Main classification: B21D7
IPC codes: B21D7