GB2365375A

GB2365375A - Bending elongate members

Info

Publication number: GB2365375A
Application number: GB0117188A
Authority: GB
Inventors: Nobuyoshi Masumoto; Tatsushi Itou
Original assignee: Komatsu Ltd
Current assignee: Komatsu Ltd
Priority date: 2000-07-13
Filing date: 2001-07-13
Publication date: 2002-02-20
Anticipated expiration: 2021-07-13
Also published as: CN1333095A; KR20020006584A; JP2002028731A; GB0117188D0; GB2365375B; US20020029604A1; US20040011115A1

Abstract

A method of bending an elongate member and a bending apparatus which can resist the occurrence of wrinkles in flanges of the elongate member. The elongate member is approximately L-shaped or U-shaped in cross section and has a generally flat bottom portion and upstanding flanges at the edges of the bottom portion. The method uses an inner forming assembly (20) for forming an inner curved shape in the elongate member, an outer forming assembly (6) having a forming pad (9) which can be caused to project and retract so as to form an outer curved shape in the elongate member and die plates (10) which are rotatable in response to movement of the forming pad and sidewall (8) provided in the longitudinal direction of the outer forming assembly. By pressing the elongate member against the outer forming assembly with the inner forming assembly and by pressing the flanges against the sidewall and the inner forming assembly, the occurrence of wrinkles in flanges is resisted. Buckling of the free end sides of the flanges is prevented by extending gradually a bending fulcrum through a retraction of the forming pad and rotation of the die plates. Further, by installing a moving mechanism to the sidewall, setting and taking out the long length of the member is facilitated.

Description

<Desc/Clms Page number 1> A Method of Bending an Elongate Member and a Bending Apparatus for Use in Such Method. DETAILED DESCRIPTION OF THE INVENTION Field of the invention The present invention relates to a method of bending an elongate member which is approximately L-shaped or U-shaped in cross section in its longitudinal direction and a bending apparatus for use in such method.

Prior Art and Problems to be resolved by the Invention It is difficult to forin as a unitary member an elongate member which is approximately L-shaped or U-shaped in cross section and also curved in the direction of the length thereof, and therefore, in conventional methods, such a member is manufactured by dividing the member into a plurality of parts in the longitudinal direction and by welding the bent parts after bending the divided parts separately. That is, as shown in Figure 9, an elongate member having such a shape as described above is manufactured as the whole member by dividing the member into a member (31) which is not bent in the longitudinal direction, a member (32) having a relatively large curvature in the longitudinal direction and a member (33) having a relatively small curvature in the longitudinal direction, manufacturing parts having these divided shapes separately and welding together Z=1 I

the manufacture parts. Therefore, to manufacture th:-- elongate member having such a shape as described above, many steps are required and the manufacturing cost is high. Accordingly, to reduce the manufactufing cost of the above- mentioned long length of the member, it is required to research forming it unitary member. Currently, as a method of forming a long length of a member as a unitary member, there are methods utilizing draw forming or bending divided into processes, that is to say bending in the direction of the cross section and bending in the longitudinal direction. However, in draw forming, draw forming must be carried out using steel plate having a dimension sufficiently larger than the steel plate to which completed products is spread because steel plate must restrained in machining, and excessive parts must be eliminated by laser cutting or plasma cutting after the draw forming. Therefore, there is a defect that material yield decreases in draw forming. Further, draw forming is usually carried out with a thin plate (thickness is 0.6 mm. to 2.3 mm). It is said that it is difficult to draw form a thick plate (for example, thickness of 4.5 mm. or more). If draw forming of the thick plate is performed, facilities which have the capability of pressing and draw forming the thick plate and the molds with the corresponding high hardness are required, and therefore the cost of equipment required becomes enormous. Accordingly, it is impossible to reduce the manufacturing cost in bending the long length of the

member described above by draw forming. On the other hand, in a method of bending divided into two processes, a shape in transverse cross section is first formed by a first bending process, and then a shape in the longitudinal direction is formed by a second bending process. The bending method of the second process is shown in Figure 10. The bending of the second process is intended to carry out the bending by supporting both ends of the long length of the member by a lower mold (35) and forming a bend in the elongate member by pressing a part (43) of the platelike bottom portion (41) which is by an upper mold (36) forming an inner bent shape of the elongate member. However, in such a bending method, there is a problem of buckling caused in the free end side of the flanges (42) in which the large deformation is produced due to contraction. The occurrence of buckling is pronounced particularly when a long length of a member is given a large curvature. Accordingly, to reduce the manufacturing cost, it is required to provide a machining method in which, in a method of bending divided into two processes, Z-1 buckling does not occur in free end of flange (42) in bending in the longitudinal direction. This invention has been developed to resolve the above-mentioned conventional defects and it is an object of the

_nvention tonrovide a method of bending an elongate nimber and a bending apparatus which are capable of resisting wrinkles -rom occurring in flanges of a Long length of a member due to buckling of f7ree end sides of the flanges in bending zhe long 'engzh of the member in the longitudinal direction. Also an object of the invention is to provide a method of bending an elongate member and a bending apparatus which are capable of setting and taking out the elongate member easily in the bending method described above.

Means of Solving the Problems and Effects of the Invention And so, a method of bending a long length of a member of claim 1 is the method of bending, wherein, in a long length of a member which has a plateiike bottom portion 1 and flanges 2 installed In a standing manner at the end of the platelike bottom portion 1, free end sides of the flanges 2 shrink and platelike bottom portion I sides of the f langes 2 expand, characterized in that, in bending the long length of the meznbe-- by using an inner forming assembly 20 forming an inner bent shape of the long length of the member and an outer forming assembly 6 f orming an outer bent shape of the long length of themeinber andby pressing the platelike bottom portion 1 in the above-mentioned outer

forming assembly 6 with the above-mentioned inner forming assembly 2 0, the above-me=ioned f !a.n.ges 2 arepressed from both, sides thereof between a sidewall 6 of the above-men'#:ioned outer -orming assembly 6 and the above-ment _-'oned inner or=ing assembly 20, respectively, and bend-4---g is carried out w#ii:.e doing the ,'-on_'ngof the above-mentioned flanges 2 with the above-mentJ oned sidewall 8 and the above -ment i oned inner forming assembly 20. And, a bend4ng apparatus for a long length of a member of claim 2 is the bending apparatus for carrying out the bending _n which, in a long length of a member having a platelike bo-.tom portion 1 and flanges 2 installed in a standing manner at the end of the platelike bottom portion 1, free end sides of the flanges 2 shrink and platelike bottom portion I sides of the flanges 2 expand, including an inner forming assembly 20 forming an inner bent shape of the long length of the member and an outer f orming assembly 6 forming an outer ben:: shape of the long length of t.he riember, bendi.ng the Long length of the member by pzessing the platelike bottom portion 1 in the above-mentioned outer forming assembly 6 with the above-mentioned inner for-ling assembly 20, characterized in that the above-mentioned flanges 2 are pressed 11--omboth sides thereof between a sidewall 8 provided in the above-ment-Joned outer forming assembly 6 and the above-mentioned inner forming assembly 20, respectively, and the bending is carried out so as to do the ironing of the above -ment -ioned flanges 2 with the above-mentioned 5idewall 8

and the above-mentioned inner forming assembly 20. in accordance with t"e above-men7c#ioned method o-f bending a long length of a member of claim I and the above-mentioned bending apparatus fo_- a -Iong length of a member of claim 2, it is possible to restrain the occurrence of wrinkles effeczively, which are going to be produced at flanges 2 due to bending the long length of the member. That is, by pressing the platelike bottom portion I of the long length of the member in the outer forming assembly 6 by the inner forming assembly 20, the deformation that f ree end s idea of f langes 2 shrink and platel i ke bottom port4on I sides of the flanges 2 expand is produced in the longitudinal direction of the long length of the member. The wrinkles resulting from buckling are going to be produced at f langes 2 due to the def ormation. However, since the sidewalls 8 provided in the longitudinal direction of the outer -forming assembly 6 press respective flanges 2 against the inner forming assembly 20, and the sidewall 8 and the inner forming assembly 20 do the ironing of the flanges 2, it is possible to restrain the occurrence of wrinkles. And, a bending apparatus for a long length of a member of claim 3 has a forming pad 9 and die plates 10 in the longitudinal direction in such a way that an outer forming assembly 6 forms an outer bent shape of the long.length of the member, and is characterized in that the above-mentioned forming pad 9 is installed so as to be capable of projecting and ret-racting by

.being aDplied with a force toward the direction of "-::"ie above-mentioned inner f-orming assembly 20 by a means '.6 of applying a force and -z:he sides of the above -mer.tio,ned forming pad 9 of the above -mentloned dle plates '. 0 are inst'alled ro#:azably following a projection/re-z-raction of the above -ment _4 oned forming pad 9. In accordance with the bending apparatus for a long length of a member of claim 3, by pressing the platelike bottom portion I of the long length of the member by the inner forming assembly 2 0, the f orming pad 9 retracts and the sides of the f orming pad 9 of the die plates 10 are rotated to the direction of a retract Ion of the forming pad 9, and a bending fulcrum of the long length of the member is extended gradually toward both ends of t.1--e long length of the member and a largely bending part 3 is formed gradually. Thereby, since free end sides of the flanges 2 of the largely bending part- 3 shrink gradually, it is possible to prevent f ree end sides of the f langes 2 f rombuckling ef f ectiveiy. Furthermore, as the forming pad 9 retracts, the ironing is applied to each flange 2 of the long length of t.-.e member through a side face of the sidewall 8 and the inner forming assembly 20. As the forming pad 9 retracts, the sides of the forming pad 9 of the die plates 10 are rotated to the direction of a retraction of the forming pad 9,. and therefore the flanges 2 applied with the ironing is extended gradually toward both ends of the long length of the member and this results in the Ironing

of the whole flange 2, and so it is possible to restrain the occurrence of wrinkles further. The bending apparatus for a long length of a member of claim 4 is characterized in that the bending apparati.#s have a -moving mechanism for moving the sidewalls 8 provided in the longit'.:dinal direction of an outer forming assembly 6 away from flanges 2. In accordance with the above-mentioned bending apparatus for a long length of a member of claim 4, when the long length of the member is set to the outer f orming assembly 6, the long fo=4 ength of the member may be set to the outer _ng assembly 6 easily since the sidewalls 8 position on the outer sides, and when bending, +.-he sidewalls 8 press the flanges 2 against the inner f orming assembly 20 andbending is carried out whi _-'e doing the ironing of the flanges 2 with the sidewall 8 and the inner forming assembly 20, and after bending is completed, the long length of the member may be taken out from the outer forming assembly 6 easily since the sildewalls B move away fromthe f -'anges 2. BRIEF DESCRIPTION OF THE DRAWINGS Figure I is a perspective view illustrating one example of an elongate member which is approximately U-shaped in cross section. Figure 2 shows an outer forming assembly in an embodiment of a bending apparatus for bending an elongate member in accordance with

the invention

Figure 2(a) being a top plan view, Figure 2(b) a sectional front elevation view and Figure 2(c) a sectional side elevation view.

Figure 3 shows an inner forming assembly in an embodiment of a bending apparatus for bending an elongate member in accordance with the invention, Figure 3(a) being a bottom plan view, Figure 3(b) a front elevation view and Figure 3(c) a sectional side elevation view.

Figure 4 is a view illustrating a stage 'In a method of bending the elongate member according to the invention and shows a sectional diagrammatic sketch of a machining step at the start of bending, Figure 4(a) being a sectional front elevation diagrammatic sketch, and Figure 4(b) a sectional side elevation diagrammatic sketch.

Figure 5 is a view illustrating a stage in the method of bending the elongate member and shows a sectional diagrammatic sketch of a machining step subsequent to the machining step of Figure 4, Figure 5(a) being a sectional front elevation diagrammatic sketch and Figure 5(b) a sectional side elevation diagrammatic sketch.

Figure 6 is a view illustrating a stage in the method of bending the elongate member and shows a sectional diagrammatic sketch of a machining step subsequent to the machining step of Figure 5, Figure 6(a) being a sectional front elevation diagrammatic sketch and Figure 6(b) a sectional side elevation diagrammatic sketch.

Figure 7 is a view illustrating a stage in the method of bending the elongate member and shows a sectional diagrammatic sketch of a machining step subsequent to the machining step of Figure 6, Figure 7(a) being a sectional front elevation diagrammatic sketch and Figure 7(b) a sectional side elevation diagrammatic sketch.

Figure 8 is a view illustrating a stage in the method of bending the elongate member and shows a sectional diagrammatic sketch of a machining step at the end of bending, Figure 8(a) being a sectional front elevation diagrammatic sketch and Figure 8(b) a sectional side elevation diagrammatic sketch.

Figure 9 is a view illustrating a conventional manufacturing process of an elongate member which is approximately U-shaped in cross section, and Figure 10 is a view illustrating a second conventional bending process in which the bending of the elongate member which is approximately U-shaped in C, cross section is divided into two processes. Embodiments of the Invention Next, referring to the drawings, there is illustrated in detail a specific embodiment of a method of bending an elongate member and a bending apparatus for carrying out the method. The present embodiment shows the method of bending an elongate member A and the bending ZD

apparatus f or use in such method as shown in Figure as one example of a method of bending an elongate member and a bending apparatus for use in such method. First, a bending apparatus for an elongate member A wi I I be described. The bending apparatus for the elongate member A includes an outer f orming assembly 6 and an inner forming assembly 20. Referring to the outer forming assembly 6, Figures 2 shows the whole view of the outer forming assembly 6 and Figure 2 (a) is a top plan view, (b) is a sectional front elevation view and (c) is a sectional side elevation view. The outer forming assembly 6 has a base 7, sidewalls 8, a forming pad 9 and die plates 10. The base 7 is approximately rectangular and has a groove 11 extending in the longitudinal direction at the midsection thereof. A pair of sidewalls 8 opposed to each other is provided in the groove 11. The sidewalls 8 are approximately in forms of a landscape rectangular plate, placed and held on a bottom surface of the groove 11 and installed upright in the transverse direction of -:he groove 11 and arranged in such a way that outer side faces of -respective sidewalls 8 abut against inner side faces of the groove 11. The sidewalls 8 are installed in such a way that the height thereof is nearly equal to the height of the side f aces of the groove A rectangular cavity 12 extending upward is provided at the midsection of a bottom f ace of the groove libetween the sidewalls

8. The forming pact 9 is i,-.serted movably up and down the rectangular cavity 12. --he die plates 10 are installed on bot.#-i sides of the forming pad 9. Gaps 13 are provided #between the s-'ciewall 8 and the fc)_rming pad 9 and between t!7ie sidewall 8 and the die plate 1-0. The gaps 13 are provided to enable the sidewalls 8 to move. The die plates 10 are supported by pins 14 on the outer sides relative to the base 7 and installed rotatably up and down on the inner sides. There is the following re-lation between the forming pad 9 and the die plates 10 described above. That is, the forming pad 9 has inclined portions 15 which are inclined downwardly on the sides of respective die plates 10 and respective tips of the inner sides of the die plates 10 are placed and held on the inclined port-Lon 15. Therefore, there -'s the relation that the forming pad 9 sides of the die plates IQ rotate up and down following the up-and-down movements of the forming pad 9. Further, a spring 16 is installed at a bottom face of t-'-.e forming pad 9, and this applies an upward force to the forming pad 9. Accordingly, the die plates 10 placed and held on the inc _1 ined portion 15 of the forming pad 9 assume a state in which the inner sides of the die plates 10 is rotated upward since t'--e forming pad 9 sides project upward, and bottom faces of the die plates 10 and a top f ace of the base 7 are in a condition of not being in contact Further, a top face of the forming pad 9 and top faces of the die plates 10 are installed so as to be lower than the height of the sidewalls 8.

Figure 3 shows the whole view of the inner for-ming assembly 20 and Figure 3 (a) is a bottomplan view, (b) I's a f-ront, elevation view and (c) is a sectionai side elevation view. -.:he inner forming assembly 20 has a base 21, a punch. 22 and wedge plates 23. The base 21 is approximately rectangular a.-.d the punch 22 is attached to a bottom face thereof and a pair of wedge plates 23, 23 are installed on both sides of the punch 22. The punch 22 has a configuration of which a midsection pro.jects downward, and a lower portion thereof forms a shape corresponding to the desired bend of the elongate member A. Respective wedge plates 23 are approximately in the form of a landscape rectangular plate and include the wedge portion 23a located at a front-end thereof and a restraining portion 23b located above the wedge po--4.- ion. The wedge plates 23 are attached to a bottom face of t-he base 7 so as to extend vertically downward in the direction of the plate thickness. When the inner forming assembly 2C -'s fitted into the outer forming assembly 6, the punch 22 is inser-zied between the sidewalls 8 of the outer forming assembly 6. The punch 22 abuts against the top f ace of the forming pad 9 insta "Lled between the sidewalls 8 and the forming pad 9 is lowered by the pressing force of the punch 22. AS the forming pad 9 4s lowered, the 4.4 - .6 inner end sides of the die plates 10 are rotated downward and * bottom face of the die plates 10 abuts against a top face of * base 7 at the lowest end of the forming pad 9. At this time, the top face of the forming pad 9 and the tot) face of the die

plate (10) are arranged so as to form the desired outer shape of the elongate member A. That is, the top face of the forming pad (9) has a concave portion for forming a relatively large curvature in the longitudinal direction and the top face of the die plate (10) has a concave portion for forming a relatively small curvature in the longitudinal direction.

Here, a moving mechanism for the sidewalls (8) will be illustrated. Vertical grooves (17), which are approximately U-shaped in cross section and extend vertically are formed beside the groove (11) of the outer forming assembly (6). The vertical grooves are provided to permit insertion of the wedge plates (23) installed on the inner forming assembly (20). On the other hand, tip thickness of the wedge portion (23a) of the wedge plate (23) installed on the inner forming assembly (20) is set to a dimension smaller than the depth of the vertical groove (17) and the thickness of the restraining portion (23b) is set to a dimension larger than the depth of the vertical groove (17). Further, the difference between the thickness of the restraining portion (23b) of the wedge plate (23) and the depth of the vertical groove (17) is set so as to be nearly equal to the width of a gap (13) provided between the sidewall (8) and the forming pad (9) and between the sidewall (8) and the die plate (10).

When the inner forming assembly (20) is lowered together with the start of the bending, the wedge plates (23), respectively, installed on the inner forming assembly (20) are inserted into the vertical groove (17) provided in the outer forming assembly

6. When the wedge portions 23a of the wedge plates 23 are i:nserted into the vertical groove 17 to some extent, the wedge portions 23a abut against a bottom face of the vertical groove 17 and side faces of sidewalls 8. And so, the sidewalls 8, placed and held on a bottom surface of the groove 11 of a top face of the base 7 and not secured, move inside gradually. Next, a method of bending the elongate member A will be described. Figures 4 to 8 show sectional diagrammatic sketches representing stages in the bending of the elongate member A. In each drawing, drawing number (a) indicates a sectional front elevat i4on view and (b) indicates a sectional side elevation view. First, the elongate member A formed to have a predetermined shape in a transverse cross section is carried between the sidewalls 8 of the outer f orining assembly 6 with the free end sides of flanges 2 up and set on the top facesof the forming pad 9 andthe die plates 10 installed between the sidewalls 8. At this time, the sidewalls 8 are positioned on the outer sides, the forming pad 9 receives an upward force from the spring 16 provided at the bottom face of the forming pad 9 and the inner sides of the die plates 10 are rotated upward following the forming pad 9. By lowering the inner forming assembly 20, the wedge portions 23a of the wedge plates 23 installed as the inner forming assembly 20 are inserted into the vertical groove 17 provided in the outer forming assembly 6. When the wedge portions 23a of the wedge

plates 23 are inserted into the vertical groove 17 to the snecif ied depth, the wedge portions 23a abut against the bottom face of the vertical groove 17 and the side faces of sidewails 8. The sidewalls 8 are placed and held on a bottom surface of the groove 11 provided on the top face of -zne base 7 of the outer forming assembly 6 and are not secured. T-herefore, the sidewalls 8 are pressed by the wedge portions 23a to move inside (Figure 4). By lowering the inner forming assembly 20 fu--ther, the restraining portions 23b of the wedge plates 23 installed on the inner forming assembly 20 are inserted into the vertical groove 17 of the outer forming assembly 6, and the side faces of the sidewalls 8 are pressed against the side faces of the forming pad 9 and the die plates 10. The punch 22 attached to the inner forming assembly 20 is inserted between the sidewalls 8 of the outer forming assembly 6 and the lower surface of the punch 22 contacts the inside of the elongate member A. By pressing a part which is to be a relatively large curvature part 3 of the platelike bottom portion i of the elongate member A by the punch 22, the elongate member A is bent as a bending fulcrum of both sides of a concave portion for largely bending of a top face of the f orming pad 9. The forming pad 9 is lowered and the sides of the forming pad 9 of the die plates 10 are rotated downward following a descent of the forming pad 9 caused by the pressing force of the punch 22 (Figure 5). When the inner forming assembly 20

is lowered further, by pressing a part which is to be the relatively large curvature part (3) of the platelike bottom portion (1) of the elongate member A by a tip of the punch (22) keeping the sidewall (8) restrained, the forming pad (9) is lowered further and the die plates (10) are rotated downward. Thereby, a bending fulcrum of the elongate member A is extended from both sides of a concave portion for largely bending of a top face of the forming pad (9) to the sides of the die plates (10) depending on bending in the longitudinal direction and a large curvature part (3) of the elongate member (A) is formed gradually.

Conventionally this deformation has caused the free end sides of flanges (2) to shrink and platelike bottom portion (1) sides of the flanges (2) to expand in the longitudinal direction of the elongate member, and this can result in wrinkles being produced gradually at flanges (2). However, since respective flanges (2) are pressed against side faces of the punch (22) by side faces of the sidewalls (8), the occurrence of wrinkles is resisted in the present method (Figure 6).

When the inner forming assembly (20) is lowered further, the lower surface of the punch (22) presses the platelike bottom portion (1) of the elongate member A further while side faces of the sidewalls (8) press respective flanges (2) against side faces of the punch (22), the forming pad (9) is lowered and the die plates (10) are rotated downward. Therefore, the bending fulcrum of the elongate member A is extended to both sides thereof. By this bending, wrinkles would normally be produced at flanges (2). However, since respective flanges (2) are pressed against the side faces of the punch (22) by the side faces of the sidewalls (8), the occurrence of wrinkles is resisted (Figure 7).

Here, as the forming pad (9) is lowered, pressing or ironing is applied to each flanges (2) of the elongate member A through the side faces of the sidewall (8) and the side faces of the punch (22). As the forming pad (9) is lowered, the sides of the fon-ning pad (9) of the die plates (10) are rotated downward, and therefore the flanges (2) applied with the ironing is extended gradually toward both ends of the elongate member A and this results in the ironing or pressing of the whole flange (2). Therefore, it is possible to resist the occurrence of wrinkles further.

When the inner forming assembly (20) is lowered further, the lower surface of the punch (22) presses the part to be the relatively large curvature part (3) of the platelike bottom portion (1) of the elongate member A while the side faces of the sidewalls (8) press the respective flanges (2) against side faces of the punch (22), the forming pad (9) reaches its lowest point and a bottom face of the die plates (10) abuts against a top face of a base (7). At this time, a top face of the forming pad (9) and a top face of the die plate (10) form an outer shape of the elongate member A and the elongate member A is forcedly pressed against the top face of the forming pad (9) and the top face of the die plate (10) by the punch (22). Thereby the elongate member A is pressed against a concave portion for forming a large curvature provi I In on the top face of the forming pad (9) and a concave portion for C forming a small curvature provided on the top face of the die plate (10), and therefore a relatively large curvature part (3) and a relatively small curvature part of the elongate member A are formed in the longitudinal direction and the bending Z#' of the elongate member A is completed (Figure 8).

After the completion of the bending, the inner forming assembly (20) is raised, the punch (22) is drawn from between the sidewalls (8) and the wedge plates (23) are drawn from the vertical groove (17). Accordingly, the sidewalls (8) are freed from the constraints of the wedge plates (23) and the distance between the sidewalls (8) is expanded outward of itself. Since the distance between the sidewalls (8) is expanded, the elongate member A may be taken out from the outer forming assembly (6) easily after the completion of the bending.

In accordance with the above-mentioned method of bending an elongate member A and the above-mentioned bending apparatus, it is possible to resist the occurrence of wrinkles effectively, which wrinkles are usually produced at flanges (2) due to bending the long length of the member A. That is, by pressing a relatively large curvature part (3) of the platelike bottom portion (1) of the elongate member A by the punch (22) provided in the inner forming assembly (20),

'##he deformation t'-at free end sides flanges 2 ghr'Ink and platelike bottom port-'on 1 s_#des of the Z la.'Iges 4 exQanc is produced in the longitudinal direction of the elongate member A. Wrinkles are usually produced at flanges 2 due to such deformation. However, since a side face of the sidewa--L.Is 6 oress respective flanges 2 against a side face of --he punch 22, and the side face of the sidewall 8 and the side faceof the punch 22 do the ironIngof the flanges2, it -'spossible to resist the occ,-,rrence of wrinkles. And, in the outer forming assembly 6, -the forming pacL ti is subject to an upward force by a spring 16, or a means for applying aforce, provided at the bottom face and the die plates 1.0 supported by pins 14 are installed on both sides of the 'ffo::rr.ing -pad 9. The die plates 10 are placed and he.Ld or. an inclined portion 15 provided on the forming pad 9 at a tip o-f the bottom face zhezeof and installed rotatably so as to follow up-and-down movements of the forming pad 9. Therefore, by nressinc- a part to be a relatively large curvature part 3 of the platelike bottom portion 1 of the elongate member A by the punch 22 installed in the ..ner forming assembly 20, the f orming pad 9 J s lowered and -he - sides of the fo_rmingpad 9 of the die plates 10 are rozazed downward, and a bending -fulcrum of the elongate member A is extended gradually toward both ends of the elongate member A and a relatively large curvature part 3 is formed gradually. Thereby, since free end sides of the flanges 2 of the relatively large curvature part 3

shr-'.-.k gradual ly, L't is possible to prevent effectively the occurrence of buckling of the flanges 2. Here, as z;-e f:0--ming pad 9 is lowered, the Ironing- or pressing is applied to each flange 2 of the elongate member A through the side faces of the sidewal7m. 8 and the side faces of t-'-.e ourich 22. As the ffozming pad 9 _Js lowered, the sides of --he fo-nning pad 9 of t.I-,4e die iDlates 10 are rotated downward, and therefore the flanges 2 applied with. the ironing is extended gradually toward both ends of the elongate member A and this results in the _4rcn_i.n.g of the whole f lange 2, and so _-z is possible to restrain the occurrence of wrinkles further. Further, each 5idewall 8 provided -I-- the outez ,fforming assembly 6 has a moving mechanism formnoving inside. The-refore, wher, the elongate member A is set 'zo the outer --forming assembly 6, the elongate member A may be set to the ouzer forming assembly 6 easily since r--'-e s_#dewa- . Is 8 pos-4tion on outer sides, and when bending, the punch 22 is inserted between #he sidewalls 8 and the sidewal--s 8 are moved :o innez s-4des by the wedge plates 23 and abut 2 against the flanges 2, and bending is carried out while doing the pressing of the flanges 2 wi±-.'- the side faces of the sidewalls 8 and the s_`-.4,e *faces of -:#he punch 22, and after bending is completed, t1ne punch. 22 is withdrawn from between the sidewalls 8 and the wedge plates 23 are withdrawn from the vertical groove 17, and the sidwqlls 8 are freed from the contraints of the wedge plates 23 and move so as to

expand the d-4stance between the sidewalls 8 outward of itself. Accordingly, t-;-'#e elongate meriber A may be taken out from the ourer forming assembly 6 easi-2y.

Claims

Claims: 1. A method of bending an elongate member which has a generally flat bottom portion (1) and upstanding flanges (2) at the edges of the bottom portion (1), comprising bending the elongate member by using an inner forming assembly (20) to form an inner curved shape in the elongate member and an outer forming assembly (6) to form an outer curved shape in the elongate member by pressing the bottom portion (1) against said outer forming assembly (6) with said inner forming assembly (20), said flanges (2) being pressed from both sides thereof between a sidewall (8) of said outer forming assembly (6) and said inner forming assembly (20), whilst said bending is carried out .
2. A bending apparatus for bending an elongate member which has a generally flat bottom portion (1) and upstanding flanges (2) at the edges of the bottom portion (1), said apparatus including an inner forming assembly (20) for forming an inner curved shape in the elongate member and an outer forming assembly (6) for forming an outer curved shape in the elongate member, bending the elongate member being carried out, in use, by pressing the bottom portion (1) against said outer forming assembly (6) with said inner forming assembly (20), characterized in that said outer forming assembly (6) includes a

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sidewall (8) the arranclement being such that in use, during bending, the flanges (2) are pressed between the sidewalls (8) and the outer forming assembly (6) in order to resist wrinkling of the flanges during bending of the elongate member.
3. A bending apparatus according to claim 2, including a forming pad (9) and die plates (10) extending in a longitudinal direction in such a way that said outer forming assembly (6) forms an outer curved shape for the elongate member, characterized in that said fori-ning pad (9) is arranged so that it can project and retract in response to a force acting toward the direction of said inner forming assembly (20) and generated by a force applying means (16), said die plates (10) being located adjacent the sides of the forming pad and being pivotably mounted such that they can rotate in response to movement of the forming pad (9).
4. A bending apparatus according to either claim 2 or claim 3), including a moving mechanism for moving said sidewalls (8) away from said flanges (2).