This invention relates to a method of bending a sheet-metal section, which includes alternating long¬ itudinal ridges and troughs , and the lateral portions of which also are the lateral portions of the ridges . about an axis, which extends perpendicularly to the longitudinal direction of the ridges and troughs and is in parallel with the plane of the sheet. The invent¬ ion also relates to ^* a device for carrying out the method. It is previously known at the bending of such sectional or corrugated sheet about an axis extending perpendicularly to the corrugations and in parallel with the plane of the sheet to form in the corrugat¬ ions, which with their tops are located closest to said axis, strip-shaped protrusions in the direction of the axis which project from one and the same side of the sheet, in such a manner, that each such pro¬ trusion extends at least partially over the sides of a corrugation and the intermediate portion uniting the sides, and the protrusions are given such a shape that the sheet shrinks more closest to the axis than farthest away therefrom. By this way of bending a sectional sheet an accumulation of material is ob¬ tained in the trarisistion area between the side and the intermediate portion of -a corrugation, which accumulation renders it impossible to bend a sec-

tional sheet provided with a surface-covering coat without damaging the coat in one way or the other.. It is not possible, either, by said known bending method to bring about a bend with a radius below 750 mm, which

5 reduces substantially the applicability of this bending method.

It is further known to bend a sheet-metal section about an axis, which extends perpendicularly to the longitudinal direction of the corrugation and in

^■ * 0 parallel with the plane of the- sheet, by a method, according to which impressions are made in radial direction from the axis only in "those portions of the corrugations of the sheet which face toward the said axis. Said impressions are made in consecutive steps

^5 until the desired bending angle has been obtained. By this known method it is possible, contrary to said firstmentioned bending method, to bend also a section¬ al sheet, which is provided on one and/or the other side with a surface-covering coat, without damaging

20 the coat on either side, provided that the sheet -at the moment when the impressions are being made is not clamped on either side of the place of impression, but can move freely relative thereto. Even -when the sheet is clamped only on one side of the place of impression,

25 the lastmentioned method of bending a sheet-metal sec¬ tion involves a certain risk, that the sheet in certain parts is subjected to stretching, whereby a possible surface coat will be damaged and also the bending result will be deteriorated, i.e. the bending or deflection

30 line will be more or less discontinuous.

The present invention, therefore, has the object to overcome the disvantages involved whith the last¬ mentioned method of bending sheet-metal sections, especially when it concerns the bending of clamped

35 sheet metal, and at the same time to bring about a method and a device, which render it possible to bend

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sectional sheets with a. radius, which is substantially smaller than heretofore possible, whithout damaging the sheet even when it is surface-coated. This object is - ---achieved in- that -the -method -and. the. device according to 5 the present invention have been given the characteriz¬ ing features defined in the attached claims.

The invention is described in greater detail in the following, with reference to the accompanying drawings, in which 10 Fig. 1 is a section of a bending tool for bending a trapezoid sectional metal sheet according to the in¬ vention, shown in a schematic way,

Fig. 2 is a section along the line II-II in Fig. 1 through the lower portion of the bending tool formed as 15 a pressing bar,

Fig. 3 is an end view of a bending die comprised in the upper portion of the bending tool and acting as a dolly member,

Fig. 4 is a lateral view of the bending die shown 20 in Fig. 3,

Figs. 5 and 6 are an end view and, respectively, a lateral view of an alternative embodiment of the bending die shown in Figs. 3 and 4,

Figs. 7 and 8 are an end view and, respectively, 25 a lateral view of a futher embodiment of the bending die according to the invention.

Fig. 9 is a view seen substantially along the line IX-IX in Fig. 8,

Fig. 10 is a view for illustrating the applying 30 of a bending die, more precisely the bending die shown in Figs. 7-9, against a sheet,

Fig. 11 is a section through a bending frame supporting the bending tool, shown in a schematic way, Fig. 12 is a perspective and schematic view of a 35 bending tool according to the invention for bending a sinusoidal sectional sheet, the upper and the lower

-portion of the tool being shown separated by a sheet being bent, which sheet is provided with only two ridges and located between said portions, and

Fig. 13 is a perspective and schematic view of a bending tool according to the invention for bending a substantially U-shaped metal sheet section with great section height and reinforced lateral portions, the upper and the lower portion of the tool being shown separated and a U-shaped section being bent located therebetween.

In Fig. 1 the numeral 1 designates a trapezoid sectional metal sheet, which is shown disposed for being bent between the upper and the lower portion 2 and, respectively, 3 of a bending tool. The portions 2 and 3 are individually movable toward and. from one another and arranged in a bending frame 4, which may be comprised in a bending machine, which includes two such bending frames movable relative to each other for bending a sectional metal sheet simultaneously about to parallel axes, which extend perpendicularly to the longitudinal direction of the profile, i.e. of the ridges 1a and the troughs lb, and are in parallel with the plane of the sheet. Each- such bending frame 4, as schematically shown in Fig. 11, is pivotal about a shaft 6 mounted in the stand of the bending machine

(not shown) by electrically, pneumatically or hydraulic- ally controlled drive means 5, for example a piston- -cylinder means. Said shaft 6, thus, supports the bend¬ ing frame 4 and is in parallel with the axis, about which the sheet is to be bent.

The upper portion 2 of the bending tool comprises a number of bending dies 8 mounted in a holder 7 and corresponding at least to the number of troughs 1 in a sheet. The dies project from the holder 7 -through a distance corresponding at least to the height of the sheet section and have at their lower portion a shape

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corresponding substantially to the r-e.spec.tive cross- -sectional shape, in such a manner, that in the case of a trapezoid sheet section the die end 9 facing to the sheet shall have a. width.,-./which must not be greater.than the smallest width of the trough bottom between the lateral portions 1c, as is apparent ^' especially from Fig. 10. Every die is provided in the cross-section with a groove 10, which extends across the entire width of the die and has a depth corresponding to the intended impression depth in the sheet. The portions 11 enclosing the groove 10 and formed with end profile are intended to support the sheet at the moment of bending, as will become more evident from the following. The lower portion 3 of the bending tool is in¬ tended to cooperate with the upper bending dies and comprises a pressing bar 13, which is supported by a holder 12 and has a pressing portion 15 tapering to a rounded end profile 14. The pressing portion is intended to be pressed into the grooves 10 of the dies and thereby into the lower surface of the sheet lying therebetween, which surface consists of the trough bottoms, and to form impressions extending across the entire width of the trough bottoms and being corresponded by protrusions on the other side of the trough bottoms. For each such effected im¬ pression across the entire width of the sheet, the sheet is bent through a definite predetermined angle. By effecting several such impressions conse- cutively in rows and in spaced relationship, either by moving the sheet 1 in steps relative to the bend¬ ing tool or by moving said tool relative to the sheet, the sheet can be bent through at least 180 and even to a radius as small as 30 mm, depending on the section heigh ^' t and impression depth.

In order to eliminate stretchings in the sheet

at each such impressing, even when the sheet is rigidly clamped on one side of the bending tool, for example at the sheet support 16 in Fig. 11, accord¬ ing to the present invention the lateral portions 1c of each.trough are subjected to an outwardly directed pressure, prior to or simultaneously with the effect¬ ing of an impression. This pressure is brought about, at the embodiments shown in Figs. 1-11, by means of protrusions 17 projecting from each die 8, which protrusions at the lowering of the upper tool portion 2 are caused so to contact the lateral portions 1c of a trough (Fig. 10)j that they press the lateral portions lc of the trough in the direction away from each other by a definite predetermined force, at the latest when each die 8 with its support member 11 abuts the sheet and acts as a support therefor. When the pressing bar 13 is pressed in against the sheet portions -located between the support members 11 of the dies in order to effect said impressions, the lateral portions lc are caused by said laterally * ^' directed forces to bulge outward in the area about the ends of the protrusion formed in the upper sur¬ face of the trough bottom" by the impression and here¬ by are given a permanent, softly outwardly bulging "natural defomation" in said area of the lateral portions 1c, which receives the surplus material formed at every impressing, without giving rise to sharp folds or stretchings, which may cause crack

- formation or other damages in a possible surface coat on the sheet.

At the embodiment shown in Figs. 3 and 4, the pressure exerting protrusions 17 of the dies have the form of balls 20 rotatably mounted in the sides 18 of the dies extending to the end 9, and at the embodiment shown in Figs. 5 and 6 the said pro ^' tru- sions have the form of pins 21 fastened in said

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sides 18 of the dies and having an end surface 22, which is substantially in parallel with the lateral portions lc of the trough for bringing about a - pressu-re-substan=tiail-y perpendicular to said- portions.

5 The protrusions 17, irrespective of whether they are in the form of balls or pins, shall be located centri- cally in relation to the groove, and their lower point be on the same level as or slightly above the level of the groove 10. The balls 20 as well as the pins

10 21 preferably are made of plastic or another easily sliding material, preferably with self-lubricating properties, which especially applies to the pins, because the balls by their rotatability roll against the lateral portions of the troughs when the die is

15-being applied, so that the balls do not give rise to scratches or the like in a possible surface coat, even if the coat consists of a steel material. The protrusions 17 of the dies also may have the form of a rotatably mounted cylinder, though this is not 0 shwon in the drawings.

At the embodiment of the die according to the invention shown in Figs. 7-9 the protrusions 17 are designed integral with the die 8. Also at this embodiment each such protrusion 17 is located 5 symmetrically in relation to the groove 10 of the die, and its downwardly directed end surface 24, as shown in Fig. 7, is rounded and lies in the same plane as and substantially in parallel with the bottom surface 25 of the groove. Said end surface 0 24 then transforms into a rounded lateral surface 26 and forms a rounded corner 27. The corners 27 of ^• these protrusions constitute the pressing part of the bending die in order to effect the said later¬ ally directed forces against the lateral portions 5 1c of a trough when the die is applied to -the sheet, and thereby for obtaining at least an outwardly

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directed prestressing of these latera-1 portions lc before the impression proper of the trough bottom 1b is effected by means of the pressing bar 13 in co¬ operation with bending die 8. At ^" the bending machine shown schematically in Fig. 11, it is the bending tool located in the bend¬ ing frame 4 which for each impression is moved in steps relative to the sheet 1 to be bent. Said move¬ ment at the embodiment shown takes place in the form of a stepped pivotal movement about the axle 6, start¬ ing from a substantially upright position, in which the frame 4, however, should have a certain inclin¬ ation relative to the normal plane of the sheet, so that the sheet, i.e. the portion 28 thereof, is bent in the right direction, i.e. downward in Fig. 11, already at the first impression. The inclination of the frame in starting position may correspond to an angle being half the angle, through which the frame is pivoted at each bending step, and which is a multiple of the final bending angle.

As already mentioned, the stepped rotation of the frame 4 about the axle 6 is effected by the drive means 5. Said drive means 5, which in Fig. 11 is shown in the form of a hydraulically or pneumatic- ally operated piston-cylinder means, according to the invention is controlled so in dependency on the lower portion of the bending tool, that it is either, entirely disengaged when the pressing bar 13 of the bending tool contacts the sheet 1 , so that the frame 4 during the impression moment proper is freely movable relative to the axle 6 and can be caused to carry out a short return movement, or said drive means forcibly effects the return or spring-back movement of the bending frame relative to the sheet 1. This return or spring-back movement very efficiently con¬ tributes to prevent the material in the sheet from

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being stretched in a damaging way. ^"

Fig. 12 shows an embodiment of the bending tool according to the invention which is intended to bend - sinusoidal sectional sheet metal. The tool comprises a lowe -portion 30, which at the embodiment shown is intended to be stationary mounted, for example on a pressing table (not shown) of a press known per se, and an upper portion 31 , which shall be connected to the movable part of the press for being moved toward and from the lower portion 30 of the tool and thereby in cooperation with said lower portion to bend a sheet 32 inserted between the tool portions 30, 31 about an axis, which extends perpendicularly to the profile of the sheet and in Fig. 12 lies above the sheet 32, by effecting consecutive parallel impressions 34 in the portions 33 of the sheet which are located closest- to said portion. Hereby the sheet is advanced in steps, instead of the tool as described above, but the tool according to Fig. 12 and also according to Fig. 13 can be used in a bending frame 4 pivotal in steps. It should further be mentioned that the lower and the upper portion of the tool shown in Fig. 12 can change place, so to say, so that the lower portion acts as upper portion and the upper portion acts as lower portion, in which case, however, the bending will take place about an axis lying beneath the sheet, as at the embodiment according to Figs. 1 and 11. This possibility of place interchange between the upper and the lower portion of the tool applies generally to the tool according to the invention and, thus, applies to the embodiment according to Figs. 1-11 as well as to Fig. 13.

At the embodiment shown in Fig. 12, disting¬ uishing from the embodiment described above and shown in the drawings, -the pressing bar 13 is loc¬ ated in the upper portion 31 of the tool and the

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dies 8 are located in the lower portion 30 of the tool. The dies are shown coherent, with an outline corres¬ ponding to the cross-sectional shape of the sheet, and are formed of two plates 35, which have said out- line and between which a spacer 36 is located to form the groove TO of the dies between the support members 11, into which groove the pressing bar 13 is intended to press the sheet portions located between the support members 11 and thereby to form the impressions 34. The depth of the groove is determined by a surface 37 of a boss 38 provided on the spacer 36 between the support members 11 of each die. The end portions of the boss lying outside the outline of the support members form protrusions 39, which like the protrusions 17 at the embodiment ^' according to Figs. 7-9 are intended upon application of the upper portion 31 of the tool against the sheet 32 supported by the lower portion 30 of the tool to exert the pressure forces directed to the lateral portions 32c of the corrugations in order to form in the lateral portions 32c of the corrugations outward bulgings 40 in the same plane as the impress¬ ions and at the ends thereof, - in such a manner, that each impression 34 at its ends transforms to an outward bulding 40 and to some extent is extended therethrough. Each protrusion 39 is located symmetrically in relation to the groove 10 of the die, and its end sur¬ face 41 constituting an extension of the bottom sur¬ face 37 of the groove is rounded convex and transforms to a convex rounded, inwardly inclined lateral surface 42 via a well-rounded corner 43.

The upper portion 31 at the embodiment according to Fig. 12 is provided with clamping members 44 loc¬ ated on both sides of the pressing bar 13 and directly in front of -each other. The configuration of the clamp- ing members corresponds to that of the corrugations, so that the clamping members upon application of the

upper portion 31 against the lower portion 30 press the sheet against the surface 45 of the plates 35 loc¬ ated between the support members 11 and thereby act as dolly for the sheet on both sides of the protrusions 39. Said clamping members 44, like the plates 35, may be formed coherent and have an outline corresponding to the cross-sectional shape of the sheet.

The portions of the pressing bar 13 for effecting the impressions -34 may have convex arc-shape as in- dicated in Fig. T2, and the surface 37 constituting the bottom of the groove 10 has a corresponding con¬ cave arc-shape.

In Fig. 13 is shown in a schematic manner that it is .possible, according to the basic principles on which the present invention is based, also to bend a sheet 50, which has trapezoid section and a great section height and is provided with both stiffening grooves 51 and reinforcing folds 52. For reasons of simplicity, only one corrugation is shown in Fig. 13. As in Fig. 12, the pressing bar 13 also in Fig. 13 is provided in the movable upper portion 54 of the tool and the dies 8 are provided in the stationary lower portion 55 of the tool, but also in this case it is possible to position the pressing bar 13 in the lower portion and the dies 8 in the upper portion of the tool.

At the embodiment according to Fig. 13, each die 8 has a configuration corresponding to the inner cross- -sectional shape of the corrugations of the sheet, and protrusions 56 protruding on both sides, which protru- sions distinguished from the protrusions 17 at previous embodiments extend along the entire height of the die from the bottom of the groove 10 in each die, and which with their convex rounded lateral surface 57 are in parallel with the closest side 58 of the die, except for its portion located closest to the groove 10 whic is rounded to the bottom of the groove.

The protrusions 56, thus, increase the width of the dies, so that a sheet 50 applied on the dies 8 in the lower portion 55 of the tool will rest with its lateral portions 50c against the protrusions 56 and be support- ed by the at a distance above the supporting members of the dies located on both sides of the groove 10. In order to prevent the lateral portions 50c of the sheet from springing out when the sheet is pressed down on the dies 8 of the lower portion, the upper portion of the tool is provided with counter-hold members 64 to support the lateral portions 50c of the sheet on the opposite side of each such portion, against which a protrusion 56 acts to form outward bulgings 58 in the lateral portions 50c, at the same time when the upper portion 54 of,the tool is pressed down against the sheet applied on the lower portion 55 for effecting the impression 59 in those portions 60 of the sheet which are located closest to the axis, about which the sheet is to be bent. In order to render possible the formation of the outward bulgings 58, the counter- -hold members are provided with grooves 65 located in the same plane as the pressing bar 13. Each inter¬ mediate space between two counter-hold members 64, furthermore, is so formed that the support surfaces 61 of the counter-hold members which face toward each other and have a form corresponding to the form of the lateral portions, substantially completely abut the lateral portions of the sheet first when the pressing bar 13 located in each intermediate space between two counter-hold members 64 has been pressed- -in through the intended distance and formed an im¬ pressions in-the sheet which, thus, extends also over the outward bulgings wherat, however, certain folds are formed in the break between impression and out- ward bulging.

The counter-hold members preferably can be given

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a configuration corresponding to the cross-sectional shape of the corrugations of the plate, in the inter¬ mediate portions 60 of which no impression takes place-. For the—stiffening grooves 51 of these inter- mediate-portions, both each die 8 and each counter- -hold member 64 are formed at their end with a de¬ pression 62.

The present invention is not restricted to what is described above ^" and shown in the drawings, but can be altered and modified in many different ways within the scope of the invention idea defined in the attach¬ ed claims.