METHOD AND FORMING MACHINE FOR DEFORMING A HOLLOW WORKPIECE

Abstract: The invention relates to a method and a forming apparatus (1) for deforming a hollow tubular workpiece (4), wherein the workpiece is clamped down in a clamping device, a first forming tool is placed into contact with the outer surface of the workpiece, the tool is rotated about an axis of rotation relative to the workpiece and one end of the workpiece is deformed by means of said first tool. A second forming tool is placed into contact with the outer surface of the workpiece and is rotated relative to the workpiece about an axis of rotation. The other end of the workpiece is deformed by means of said second tool and at least one of said tools is moved relative to the workpiece during said deformation and/or between deforming steps (on the same workpiece), wherein the axis of rotation of said tool is translated and/or pivoted about an axis with respect to said workpiece.

Description: Method and forming machine for deforming a hollow workpiece The invention relates to a method for deforming a hollow tubular workpiece, wherein the workpiece is clamped down in a clamping device, a first forming tool is placed into contact with the outer surface of the workpiece, said tool is rotated about an axis of rotation relative to the workpiece and one end of the workpiece is deformed by means of said first tool. The invention furthermore relates to a forming machine in accordance with the preamble of claim 7. Such a method and forming machine are known, for example from European patent application no. EP 0 916 428. Said publication discloses a method and a forming machine, comprising a forming head fitted with a number of rollers, by means of which the diameter of one end of a cylindrical metal element is reduced and moreover bent through an angle. To this end, the metal cylinder is clamped down and said cylinder and said forming head are rotated relative to each other about an axis of rotation, whereupon said end is deformed by pressing said rollers in radial direction against the outer surface of said cylinder and moving them along said outer surface in a number of cycles, whereby the radial distance between the rollers and the axis of rotation is decreased with each cycle, as a result of which a reduction of the diameter is obtained. Since the axis of rotation is at an angle with the central axis of the metal cylinder, the end of the cylinder is not only reduced as a result of the movement in radial direction of the rollers, but in addition said end will also be positioned at an angle. Due to the use of the aforesaid cycles, the workpiece assumes the shape of the final product step by step. EP 0 916 426 discloses a comparable method and forming machine, wherein the axis of rotation is eccentrically offset from the central axis of the metal cylinder. Thus a product is invention makes it possible to deform materials having a smaller wall thickness of, for example, 1.2 mm or less. The invention furthermore relates to a hollow tubular workpiece having a continuous wall and two open ends, which have been deformed in such a manner that the projections of said ends on a plane straight through an undeformed part of the metal workpiece are at an angle of less than 180° with each other, as well as to a catalytic converter for a vehicle, such as e.g. a car, comprising such a workpiece. The invention will now be explained in more detail with reference to the appended figures, which show an embodiment of the method and the forming machine according to the present invention. Fig. 1 is a schematic top plan view, partially in section, of a forming machine according to the present invention, comprising two forming heads. Fig. 2 is a side elevation of the forming machine of Fig. 1. Fig. 3 is a side elevation of the forming machine of Fig. 1, wherein a part of the forming machine is turned through an angle of 90° . Figs. 4 and 5 schematically show a number of stages of a method according to the present invention, carried out on the forming machine of Fig. 1. Parts corresponding to each other or having substantially the same function will be indicated by the same numerals in the various figures. Fig. 1 shows a forming machine 1 comprising a first forming head 2 , a second forming head 3 and a chuck 4 for clamping down the workpiece, for example the illustrated, already deformed, metal cylinder 5. The two forming heads 2, 3 comprise a baseplate 6 on which two guide rails 7 are mounted. Guides 8 extend over said rails 7 on which guides a second set of guide rails 9 is mounted, which extend at right angles to • outward direction, that is, in radial direction away from the cavity 5 defined by workpiece 5, by means of said inside roller 19. Forming rollers 13 and inside roller 19 often lie in the same plane, which plane extends perpendicularly to axis of rotation 17 in this embodiment, so that the wall is confined between said rollers 13, 19 at the location of the deformation. Assembly 12 comprises an external gear 25 on a side remote from rollers 13, 19, which gear mates with a pinion 26 mounted on the end of a drive shaft 27 of an electric motor 28. Thus, the assembly 12 can be rotated by means of electric motor 28. Assembly 12 furthermore comprises a hydraulic cylinder 29, which is capable of moving ring 18, and thus forming rollers 13, in radial direction by means of a piston 30, a piston rod 31 and a pressure plate 32. Within the framework of the present description, the radial movement of the forming rollers 13 will be indicated as the Z-direction. Ring 22, and thus inside roller 19, can be moved in radial direction by means of a hydraulic cylinder 33 and a hollow piston rod 34, whilst housing 11 can be moved along said guide rails 7 and 9 in its entirety by means of hydraulic cylinders 35 and 36. Within the framework of the present description, the radial movement of inside roller 19 will be indicated as the W-direction. Movements of housing 11 parallel to axis of rotation 17 and perpendicularly to said axis 17 will be indicated as the X-direction and the Y-direction, respectively. Second forming head 3 is practically identical to forming head 2, but it is furthermore capable of pivoting movement about a pivot point 37, so that the end of workpiece 5 that is being worked by said forming head 3 can be deformed through an angle of 90 , for example. In addition, an assembly 38 is provided, by means of which axis 37 can be moved, as will be explained in more detail hereafter. Figs. 4 and 5 schematically show in 25 steps the manner in which an open end of a metal cylinder 5 can be deformed by means of forming head 3 of forming machine 1 according to Fig. 1. At the same time, the other end of cylinder 5 can be worked by means of forming head 2. Step 1 shows the starting position, wherein workpiece 5 is clamped down in a chuck 4. Said end, which has already undergone a machining step and which has a smaller diameter than the other part of cylinder 5, is then (step 2) deformed by rotating assembly 12 and placing the forming rollers 13, 19 into contact with, respectively, the outer surface and the inner surface of cylinder 5 and moving said rollers radially towards axis of rotation 17 and away from axis of rotation 17, respectively, and simultaneously pivoting the forming head through an angle β about pivot point 37. The various driving means are thereby controlled in such a manner that a composite, flowing movement of the forming rollers 13, 19 (in Z-direction and W-direction) , assembly 13 (in X- direction and Y-direction) and the forming head (through an angle β) is obtained, as a result of which a bent portion 40 is formed. After forming head 3 has been pivoted through an angle β, the movement of the assembly 12 in the X-direction is continued (step 3) , so that a cylindrical portion 41 remains, which portion has a smaller diameter than the original open end of cylinder 5 and which extends at an angle β relative to the other part of cylinder 5. Then (step 4) the forming rollers 13, 19 are moved radially outwards and radially inwards, respectively, so that the contact between said rollers 13, 19 and, respectively, the outer surface and the inner surface of the wall of cylinder 5 is broken. Assembly 12 is moved back along cylindrical portion 41 in the X-direction and the Y-direction until the transition between the bent portion 40 and said cylindrical portion 41. The above cycle is repeated by pivoting forming head 3 through an angle β and translating and adjusting assembly 12 (step 5, which is substantially identical to step 2) and translating assembly 12 in the X-direction and the Y-direction (step 6, which is substantially identical to step 3) , wherein the diameter of the cylindrical portion 41 is further reduced. Then the contact between said rollers and said cylindrical portion 41 is broken, and the assembly is returned to the transition area between bent portion 40 and cylindrical portion 41 (step 7, which is substantially identical to step 4) . Depending on the characteristics of the workpiece, such as the wall thickness, the mechanical strength and stiffness and the elastic elongation, steps 2 - 4 are repeated until the desired reduction of the diameter and the desired angle, for example of 90 , have been obtained. If the nature of the workpiece involves that the angle β must not be larger than, for example, 15 or 8 per cycle, a total number of, respectively, 6 and 12 cycles will be required for the said deformation. After the operations that are shown in Fig. 4 have been carried out, pivot point 37 is moved by means of assembly 38 to the starting position as shown in Fig. 5 (step 13) . The operation of Fig. 4 (steps 2 - 12) are repeated (steps 14 - 25) , wherein the angle β is of opposite sense, however, so that an S-bend is obtained in the end of cylinder 5. As is shown in Fig. 3, the forming head 3 of forming machine 1 is furthermore capable of pivoting movement about axis of rotation 17 of forming head 2, so that the bending of workpiece 5 is not limited to bending in one and the same imaginary plane. Pivoting of forming head 3 about axis of rotation 17 between or during operations enables the central axis of the deformed portion of workpiece 5 to assume a three- dimensional shape. As a matter of course the forming machines according to the present invention can be operated by a person as well as by IX) o

Claims: . CQ Pi Φ JJ CQ Cn β -H ε 0 4H Φ TJ β Φ Φ 3 JJ Φ O H 0 \. TJ β rd β 0 -H JJ rd S εH 0 4H φ TJ TJ -H fd CQ 5. A method according to any one of the preceding claims, wherein the larger part of the operation is carried out in one flowing movement. 6. A method according to any one of the preceding claims, wherein at least one inside forming tool (19) is placed into the cavity defined by the workpiece (5) , at the location of at least one of the ends thereof, into contact with the inner surface of the hollow workpiece (5) , and wherein the workpiece (5) is deformed by means of said second tool (19) . 7. A forming machine (1) at least comprising a clamping device (4) for clamping down a hollow tubular workpiece (5) to be deformed, a first forming tool (13) which can be placed into contact with the outer surface of the workpiece (5) while the workpiece (5) is being worked and by means of which one end of the workpiece (5) can be deformed, driving means (25, 26, 28) for rotating said tool (13) relative to said workpiece (5) and means (35, 36) for moving said tool (13) relative to said workpiece (5) in such a manner that said tool (13) can follow one or more desired paths with respect to the workpiece (5) so as to work said workpiece (5) , characterized in that said forming machine (1) comprises at least one second forming tool (13) , which can be placed into contact with the outer surface of the workpiece (5) during the machining of the workpiece (5) , and by means of which the other end of the workpiece (5) can be deformed, as well as driving means (25, 26, 28) for rotating said tool (13) relative to said workpiece (5) and means (35, 36) for moving said tool (13) relative to said workpiece (5) in such a manner that said tool (13) can follow one or more desired paths with respect to the workpiece (5) so as to work said workpiece (5), wherein at least one of said tools (13, 13') can be moved relative to the workpiece (5) during said deformation and/or between deforming steps (on the same workpiece) in such a manner that the axis of rotation (17, 17') of said tool (13, 13') is translated and/or pivoted about an axis (37) relative to said workpiece (5) . 8. A forming machine (1) according to claim 7, wherein both tools (13, 13') can be moved relative to the workpiece (5) during said deformation and/or between deforming steps (on the same workpiece), wherein the axes of rotation (17, 17') of said tools (13, 13') are translated and/or pivoted about an axis (37) . 9. A forming machine (1) according to claim 7 or 8 , wherein at least one of said tools (13, 13') can be pivoted about at least two axes (37, 17) relative to the workpiece (5) during said deformation and/or between deforming steps (on the same workpiece) , wherein at least two of said axes (37, 17) or projections of each of said axes (37, 17) on a common plane are at an angle with respect to each other. 10. A forming machine (1) according to any one of claims 7-9, wherein at least one of said axes (37) can be moved during said deformation and/or between deforming steps. 11. A hollow tubular workpiece (5) having a continuous wall and two open ends, which have been deformed, preferably by means of the method according to any one of the claims 1 - 6, in such a manner that the projections of the central axes of said ends on a plane straight through an undeformed part of the metal workpiece are at an angle of less than 180° with respect to each other. 12. A catalytic converter for a vehicle, such as e.g. a car, comprising a workpiece according to claim 11.

Inventors: MASSEE JOHAN, MASSEE, JOHAN
Applicants: MASSEE JOHAN, MASSEE, JOHAN
Application year: 2001
Main classification: B21D22
IPC codes: B21D22, B21D41, B21D53