Roller mount with three-axis freedom

Abstract: A roller mounting arrangement for a machine in which elongated material is shaped by rollers as the material progresses along a pathway. The rollers (9) are mounted so that they are free to pivot and distribute forming pressure over a wider area of the material being shaped. The rollers (9) have freedom to pivot about a plurality of axes. In a tandem mounting arrangement, the rollers have 3-axis freedom.

Description: BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates to a mounting arrangement for a roller used in the processing of an elongated piece of material. In particular, the invention has application in the support for rollers used in the manufacture of welded steel pipes. For many years, steel pipe has been produced by bending a sheet of steel into a tubular form and then welding the edges of the strip along a seam. Equipment utilizing various series of breakdown rolls, cage rolls and fin-pass rolls are in widespread use. For example, reference may be made to U.S. Patent No. 5,140,123 which shows a method and apparatus for continuously manufacturing a metal tube. An earlier example of such machinery and techniques is shown in U.S. Patent No. 4,709,845. Refinements of the types of machines shown in the foregoing patents are described in U.S. Patents Nos. 5,607,098; 5,673,579; and 5,784,911. In traditional tube forming machinery in which rollers of various shapes are used to bend sheet steel into a tubular shape, it has been assumed that the precise position of each roller should be set and held fixed. In conventional machines, the horizontal and vertical location of the rolls, along with the angular position of the axis of the forming rolls, has been adjusted and set to a specific value depending upon such factors as the particular thickness of the sheet being processed, the type of steel (i.e., stainless, etc.), the hardness and quality of the material, and the shape of the desired end product. In situations where the steel to be processed through the tube forming machines is of lower and more variable quality, the fixed position of the rolls can create difficulties relating to twisting, excessive loading of the rollers, threading of the strip through the machine and marking of the surface of the steel processed by the machine. If the steel processed by the machine varies from sheet to sheet because, for example, of variations in the processes used to make the steel which comprises the sheet, such variations can create significant handling difficulties when such sheets are used to make tubes. Variations in properties such as hardness and surface characteristics may mean that frequent adjustments in the positions of the rolls used to process such material are required. In a continuous tube forming process, stoppage of the process to adjust the positions of the forming rolls is quite problematic. As an alternative to stopping the machine in order to make adjustments, forcing the material through the machine can result in excessive loading of the rolls, resulting in excessive wear of both the rolls and the bearings for the rolls, and the creation of roll marks on the surface of the tube being processed. Another difficulty associated with the use of rolls with positions which are fixed is that threading of the sheet through the machine for purposes of initial start-up can be difficult, particularly where the material of the sheet has inconsistencies in the properties of the material. With certain materials, the sheet when held by fixed rolls will tend to twist and distort, making threading of the sheet through the machine very difficult. US-A-4,776,194, which forms the basis for the preamble of claim 1, discloses a pipe mill and method comprising certain improvements in pipe mills of cage-type. Edge forming roll sets, usually mounted immediately downstream of the break-down passes, are mounted for lateral movement to compensate for strip camber or lateral creep. In one form of the mill disclosed in this document the edge forming rolls are adjustably fixed with respect to each other on a mounting plate which is suspended on a pivot. Movement of the edge forming rolls from side-to-side about the pivot is obtained by power steering each edge forming roll housing with the steering pivot located at the center of pressure of the edge forming roll set. The steering is controlled by a closed loop system utilizing sensors with a microprocessor. A taper pin lock holds the plate centered and against movement for threading purposes. Side push cylinder assemblies may be employed to center the plate for locking. At least some of the foregoing problems and disadvantages of conventional tube forming machinery are solved by use of the present invention wherein rolls in the cage zone of a tube forming machine are flexibly supported such that they are free to rotate about a plurality of axes. A roller mount of the present invention includes a typical vertical frame for supporting a cage roll. However, the roller itself is mounted so that it is free to pivot in an X-Y plane. In addition, the roller may be mounted on a swivel bearing carried by the main vertical frame so that the angular position of the axis of the roller is free to pivot in a Y-Z plane of the machine, as well, which is explained more fully below. The pair of cage rolls are additionally mounted so that they are free to pivot in an X-Z plane of the machine. Thus, using a conventional tube-forming machine construction wherein a pair of cage rollers is used, the cage rolls may be mounted so that they have freedom of movement about three axes. The present invention provides a roller assembly having the features set out in the accompanying claim 1. Advantageous further features are set out in sub-claims 2 to 5. The invention extends to a tube-making machine having a roller assembly having the features set out in any one or more of claims 1 to 5. The advantages of the present invention will be better understood upon a reading of the following specification, read in conjunction with the accompanying drawings, wherein: BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side elevational view showing the overall layout of a continuous tube making machine; Figure 2 is a side elevational view of an alternative layout of a continuous tube making machine; Figure 3 is an end elevational view, in partial section, of a cage roll stand embodying an example of the present invention; Figure 4 is a top plan view of the cage roll stand shown in Figure 3; Figure 5 is a front elevational view, in partial section, of two rollers in a cage roll stand; Figure 6 is a top plan view of the components used to support the forming rolls in a manner in accordance with the present invention; Figure 7 is a front elevational view of the forming rolls shown in Figure 6; Figure 8 is an end view of the forming roll support components shown in Figures 6 and 7; Figure 9 is a schematic diagram of a cage roll arrangement of the prior art; Figure 10 is a schematic diagram of a forming roll mounting arrangement embodying the present invention; Figures 11 and 12 are schematic diagrams showing the interaction between the flexibly mounted rolls of the present invention and the sheet being processed by such rolls; Figures 13 through 15 are schematic diagrams of a prior art mounting arrangement for forming rolls; Figure 16 is a schematic diagram showing the flexibility of the mounting arrangement of the present invention. DETAILED DESCRIPTION OF AN EXAMPLE OF THE INVENTION As used herein, the axes of a tube forming machine are the X, Y and Z axes, and those axes are defined as follows: the Z-axis is the longitudinal axis, i.e., the one which corresponds to the direction of movement of a sheet along a pathway through the machine; the X-axis is the horizontal axis, which is transverse to the Z-axis; and the Y-axis is the vertical axis, which is also transverse to the Z-axis. These axes are also used to define planes discussed herein, e.g., X-Y planes, which are generally perpendicular to both the Z-axis and the direction of work movement; Y-Z planes, which are vertically oriented and longitudinally extending planes; and X-Z planes, which are horizontally oriented and longitudinally extending planes. Figure 1 is a side-elevational view of one type of a tube forming machine in which the present invention is useful. In the machine shown in Figure 1, a steel strip is first engaged by a series of two breakdown roll stands 2. Generally, one or more of the breakdown rolls are driven by motors to provide the driving force which pushes the steel strip through the machine. In this example, there are two breakdown roll stands. However, in other machines, a different number of breakdown roll stands may be used, and one or more may be equipped with motors for purposes of driving the strip through the machine. In the example shown in Figure 1, five cage roll stands 3 then work on the strip in series, each having a pair of forming rolls 9. In each cage roll stand 3, there is a pair of forming rolls 9 mounted on each side of the cage roll stand 3 by a mounting mechanism 8 with three-axis freedom. After the vertically mounted forming rolls 9 complete their processing, the strip is fed to the fin pass roll stands 4 of which there are three shown in the machine shown in Figure 1. After the fin pass roll stands 4, the edges of the strip are welded together by a high frequency welder 5, and in the final step, are processed by a squeeze roll stand 10. Because tubes manufactured by a machine embodying the present invention may have walls of different thickness, may have different diameters, and may be made of various materials, the machines may have alternative combinations of forming rolls, such as is shown in Figure 2. In Figure 2, a series of alternating horizontally and vertically mounted rollers are used to form a strip into a tube. Initially, as shown in Figure 2, a breakdown roll stand 2 is followed by a side roll stand 6 in which forming rolls 9 are held by a mechanism 8 with three-axis freedom. The third roll stand is another breakdown roll stand 2, which is, in turn, followed by a second side roll stand 6. Then, another breakdown roll stand 2 with horizontally mounted rollers, is followed by two cluster roll stands 7 in series, each stand having pairs of adjacent forming rolls 9, and each pair of forming rolls 9 being held by a mechanism 8 with three-axis freedom. Again referencing Figure 2, four thin pass roll stands 4 are used to bring the edges of the strip together, after which they are welded by the high frequency roller 5 and finally processed by the squeeze roll stand 10. It should be noted that the diagrams of Figures 1 and 2 show the vertically oriented forming rolls 9 as a pair. However, for each pair of vertically mounted forming rolls 9 shown in Figures 1 and 2, there is a pair of opposing rolls which are not shown. Figure 3 is an end view in partial section of the pathway of a tube forming machine at a location where a strip is contacted by a pair of opposing forming rolls 9. The forming rolls 9 are held in place by the main vertical frames 14 of which two are shown in Figure 3. The two main vertical frames and related components thereof are mirror images of one another, one on each side of the strip being processed. With reference to Figure 3, the mechanisms 8 with three-axis freedom which are used to support the forming rolls 9 are mounted to a vertical slide frame 35 by a swivel bearing 40. The slide frame 35 moves along a vertical slide rail 36 by the use of vertical slide bearings 36a. A vertical sleeve frame 36b has a nut 37 mounted at the lower end thereof, which surrounds a rotatable male screw shaft 38, the rotation of which causes upward and downward adjustment of the height of the forming roll 9. The height adjustment motor 25 causes simultaneous rotation of the screw shafts 38 on the right and left side of the cage roll stand 3. The width adjusting motor 26, which is supported on a base 24, is used to adjust the extent to which the forming rolls 9 in a particular cage roll stand are separated. The height and width adjusting motors 25 and 26, respectively, are connected to the main vertical frames 14 by the height and width adjusting shafts 28 and 27, respectively, with shaft 28 being a spline shaft and shaft 27 being a screw shaft. Width adjustment results from rotation of the threaded shaft 27 within the screw rings 31 connected to the base 14a. The weight of the compoents mounted to the main vertical frame 14 is transferred to the main horizontal slide rail 30 by the horizontal slide bearing 14c. The bottom roll 12 has a height adjusting motor 20 which is connected by drive shaft 21 to a worm and worm wheel gearbox 18 to cause rotation of male screw shaft 19 within the nut 17, which results in upward or downward movement of the bottom roll holder 13. The male screw shaft 19 and nut 17 are contained within the sleeve frame 16. With reference to Figures 3, 4 and 5, the width and height adjustment drive shafts extend through the main horizontal frame 11. A guide sleeve 15 surrounds the guide rod 22 as part of the height adjustment of the bottom roll 12. Figures 6, 7 and 8 are top, side and end views (with Figures 7 and 8 in partial section) of the mechanism 8 with three-axis freedom used to flexibly support the forming rolls 9 as they engage a strip being processed by the machine shown in Figures 1, 2 and 3. Each forming roll 9 has a roll shaft 47, the ends of which are held by a roll holder 45. A roll shaft keeper plate 51 is used to secure the shaft 47 in position within the roll holder 45. The roll holder 45 is rotatably mounted to a pivot frame 43 by swing shaft bearings 44, each of which surrounds and supports a roll holder swing shaft 46. The pivot frame 43 is mounted by the pivot shaft 42 to the swivel bearing 40 by the pivot shaft holder 41. The pivot frame 43 is rotatable about the pivot shaft 42, as indicated by the unnumbered arrows in Figure 6, providing the forming rolls 9 with freedom to move in an X-Z plane. A pivot shaft keeper plate 52 fits into a keeper plate groove 42a on the pivot shaft 42. Similarly, the roll shaft keeper plate 51 fits into a keeper plate groove 47a on the roll shaft 47. As can be seen in Figure 7, the roll bearings 50 allow free rotation of the forming rolls 9 about the roll shafts 47. A stopper bar 53 limits the movement of the pivot frame 43 in the directions shown by the unnumbered arrows in Figure 5, i.e., movement in Y-Z planes. With reference to Figure 8, the dotted line position of the forming roll 9' and the unnumbered arrow in Figure 8, indicate the moveability of the forming roll 9 in the X-Y plane. The movement of the pivot frame 43 about the pivot shaft 42 provides the forming rolls 9 with freedom to move in X-Z planes, and movement of the pivot frame 43 within the swivel bearing 40 about the pivot shaft holder 41 provides the forming rolls with freedom to move in Y-Z planes. Thus, the forming rolls have three-axis freedom. Figures 9 and 10 contrast the conventional or fixed mounting arrangement of forming rolls of the prior art as compared with the flexible mounting of forming rolls in accordance with the present invention. The ability of the forming rolls 9, as shown in Figure 10, to assume a position in which forces acting on the roller by virtue of the tendency of the strip to resist bending, results in the forming rolls 9 assuming a position in which the loading is spread to a plurality of points on the work surface of the forming roll 9, thus avoiding the concentrated loading, unbalanced force distribution, and excessive wear and roll marks which tend to occur with conventional machinery. Comparison of Figures 11 and 12 with Figures 13, 14 and 15 shows the advantage of mounting the forming rolls 9, as a pair, onto a pivoting frame 43. This arrangement allows an even distribution of force to be applied, thus avoiding concentrated loads and the resulting roll marks which occur with the conventional arrangement as is shown in Figures 13, 14 and 15. While it should be recognized that certain advantages of the present invention can be achieved by simply mounting a single roller with the freedom of rotation which is shown in Figure 10, mounting a pair of rollers with three-axis freedom as shown in Figures 11 and 12 (as well as being shown in Figures 6 through 8) is a particularly advantageous embodiment of the present invention. Figure 16 shows the independent moveability of the two forming rolls 9 mounted on a single pivot frame. Each of the forming rolls mounted within a pivot frame of the present invention is free to assume an orientation in the X-Y direction depending upon the particular interface of that roller with a strip as it passes through a cage roll stand. This independent rotatability of the forming rolls results in substantially reduced tendency for the strip to engage in a twisting deviation from the planned pathway. The moveability of the pivot frame 43 about the swivel bearing 40 results in much improved threading of a strip through the machine at the start up phase of a tube forming operation. Finally, the three-axis freedom with which the forming rolls of the present invention are mounted results in a substantial reduction in the extent to which tubes are marked with roll marks of the type which are typically imparted to a tube with forming rolls which are fixed in a position in accordance with conventional tube forming machinery. Although the invention claimed below has been described with reference to a specific mounting arrangement and components, other arrangements and components equivalent to those described herein may be substituted, and portions of the machines shown and described herein may be employed to practice the invention in other ways. Indeed, numerous variations, modifications and alternatives will be apparent to persons of skill in the art, and all such variations, modifications and alternatives are intended to be included within the scope of the invention in so far as they are covered by one or more of the appended claims.

Claims: A roller assembly (8) for a tube making machine having a longitudinal axis defined by a pathway and the direction along which sheet material moves along that pathway, the assembly (8) comprising at least two sheet rollers (9) having respective sheet engaging surfaces, said rollers (9) being supported by and rotatable on respective roller shafts (47), said roller shafts (47) defining respective roller axes, said shafts (47) being supported by respective shaft holders (45), said shaft holders (45) allowing said rollers (9) to rotate about said respective roller axes, characterised in that said shaft holders (45) are rotatable about respective shaft holder axes (46) for movement in respective planes which are generally perpendicular to the said longitudinal axis when the assembly is present in such a machine, said shaft holder axes being generally perpendicular to said roller axes, said shaft holders (45) are supported by a roller assembly frame (43), and said roller assembly frame (43) is pivotable about a roller assembly pivot axis (42), such that each of said rollers is free to rotate about a roller axis and is free to pivot about a shaft holder axis and said roller assembly pivot axis whilst it engages such material. A roller assembly according to claim 1, characterised in that said shaft holders (45) are adjacent to each other and said shaft holder axes are generally co-linear. A roller assembly according to claim 1, characterised in that each said roller shaft (47) is supported on opposite ends of its roller (9), and said shaft holder (45) includes a roll frame (45) with swing shafts (46) on opposite sides of said roll frame (45), said swing shafts defining said shaft holder axes. A roller assembly according to claim 2, characterised in that said shaft holders (45) include respective roll frames (45), said roll frames being rotatably supported by respective pairs of swing shafts, said pairs of swing shafts being generally coaxial and being supported by said roller assembly frame (43). A roller assembly according to claim 1, characterised in that said roller assembly frame (43) pivots on said roller assembly pivot axis (42) about a main pivot shaft (42), said main pivot shaft (42) being carried by a swivel bearing (41), said swivel bearing (41) allowing rotational movement of said roller assembly frame (43) about a swivel axis, said swivel axis being transverse to said roller assembly pivot axis (42). A tube making machine having a roller assembly as claimed in any preceding claim.

Inventors: KUSAKABE YUKIO, MORI KIROKAZU, OMURA KAZUO, KUSAKABE, YUKIO, MORI, KIROKAZU, OMURA, KAZUO
Applicants: KUSAKABE ELECTRIC & MACHINERY, KUSAKABE ELECTRIC & MACHINERY CO., LTD.
Application year: 1999
Main classification: B21C37
IPC codes: B21C37, B23K13, B21D5