IE49756B1 - Method and device for bending corrugated sheet metal - Google Patents

Description

This invention relates to a method of bending corrugated sheet metal, which includes alternating longitudinal crests and valleys, about an axis which extends transversely of the longitudinal direction of the crests and valleys and parallel to the plane of the sheet. The invention also relates to a device for carrying out the method.

In the following description and in the claims the corrugations will for convenience be considered as comprising alternating crests and valleys having common side walls.

It should be understood that this definition depends on the sheet being viewed at all times from one side and that, if the sheet is viewed from the other side, the crests will become valleys and the valleys will become crests. The corr ugations may be of any cross-section even if this means ; that the boundaries between the side walls and the crests and valleys are not clearly defined.

It is previously known, when bending such sectional or corrugated sheet about an axis extending on one side of the sheet transversely of the corrugations and parallel to the plane of the sheet, to farm in the corrugations having their apices nearest the axis rib formations parallel to the axis and projecting from one and the same side of the sheet, each rib formation extending over at least part of the sides of a corrugation and at least part of the intermediate portion between the two sides. The rib formations are shaped so as to enable the sheet to shrink more in the parts closest to the axis than in the parts farthest away from the axis during bending. By this method of bending corrugated sheet an accumulation of material is obtained in the transition areas between the sides and the intermediate portion of a corrugation, which accumulation renders it impossible to bend a corrugated sheet provided with a surface-covering layer without damaging the layer in one way or another. It is not possible, either, by this known bending method to bring about a bend with a radius below 750 mm, which reduces substantially the applications of this bending method.

It is further known to bend corrugated sheet metal about an axis extending transversely of the longitudinal direction of the corrugaticns and parallel to the plane of the sheet by a method according to which identations are formed in radial directions from the axis only in those portions of the corrugations which face directly towards the axis. These indentations are formed in consecutive steps until the desired bending angle has been obtained. By this known method, contrary to the first-mentioned bending method, it is possible to bend a corrugated sheet which is provided on one or both sides with a surface-covering layer without damaging the layer on either side, provided that the sheet is not clamped on either side of each indentation at the instant when the indentations are being formed, but can move freely relative thereto. Even when the sheet is clamped only on one side of the indentation, this method of bending corrugated sheet metal involves a certain risk due to the sheet being subjected to stretching in certain parts, whereby the surface layer may possibly be damaged and also the resultant bending may deteriorate, i.e., the bending or deflection line may be more or less discontinuous.

It is an object of the present invention, therefore, to overcome the disadvantages involved in the lastmentioned method of bending corrugated sheet metal, especially as it concerns the bending of clamped sheet metal, and at the same time to provide a method and a device which - 4 render it possible to bend corrugated sheets with a radius which is substantially smaller than heretofore possible, without damaging the sheet even when it is surface-coated.

According to the invention there is provided a method of bending corrugated sheet metal about an axis on one side of the sheet extending transversely of the corrugations and parallel to the plane of the sheet, the corrugations forming alternating crests and valleys having common side walls when viewed from said one side of the sheet, which method comprises forming indentations in the crests transversely of the corrugations by pressing portions of the crests into grooves in counter-hold members provided on the opposite side of the sheet, and forming outward bulges in the side walls of the corrugations on said one side of the sheet by means of projecting protrusions provided on the side walls of counter-hold members, the protrusions acting on said opposite side of the sheet to exert outwardly directed forces in the plane of the indentations on the side walls of the corrugations.

The invention also provides a device for carrying out this method comprising a tool, which consists of an upper portion and a lower portion, one of which is formed with at least one pressing bar for extending transversely of the corrugations in the sheet, and the other of which is formed with the counter-hold members including grooves, into which the pressing bar is intended to press the sheet to be bent, each side wall of each counter-hold member being provided with a projecting protrusion for acting on said opposite side of the sheet, at least on application of the pressing bar against the sheet, to exert an outwardly directed force on the corresponding side wall of the corrugation to form the outward bulges in the side walls of the corrugations.

In order that the invention may be more fully understood, reference will now be made by way of example, to the accompanying drawings, in which: - 5 Figure 1 is a section through a bending tool for bending a trapezoidal section metal sheet according to the invention, shown schematically, Figure 2 ia a section along the line II-II in Fig. 1 through the lower portion of the bending tool formed as a pressing bar, Figure 3 is an end view of a bending die forming part of the upper portion of the bending tool and acting as a dolly, Figure 4 is a lateral view of the bending die shown in Fig. 3, Figures 5 and 6 are an end view and a lateral view of an alternative embodiment of the bending die to that shown in Figs. 3 and 4, Figure 7 and 8 are an end view and a lateral view of a further embodiment of the bending die, Figure 9 is a view seen substantially along the line IX-IX in Fig. 8, Figure 10 is a view for illustrating the applying of a bending die, more precisely the bending die shown in Figs. 7 to 9, against a sheet.

Figure 11 is a section through a bending frame supporting the bending tool, shown schematically, Figure 12 is a perspective and schematic view of a bending tool for bending a sinusoidal sectional sheet, and Figure 13 is a prespective and schematic view of a bending tool for bending a substantially U-shaped metal sheet section with relatively great sectional height and reinforced side walls.

In Fig. 1 the numeral 1 designates a trapezoidal - 6 sectional metal sheet which is shown disposed for being bent between the upper and lower portions 2 and 3 of a bending tool. The portions 2 and 3 are individually movable towards and away from one another and arranged in a bending frame 4, which may form part of a bending machine which includes two such bending frames movable relative ; to each other for bending a sectional metal sheet simultaneously about two parallel axes, which extend perpendicularly to the longitudinal direction of the profile, i.e.,; of the crests la and the valleys lb, and are parallel tothe 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 hydraulically controlled drive means 5,: for example piston-cylinder means. Said shaft 6 thus ! supports the bending frame 4 and is parallel to the axis;, i 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 corres ponding at least to the number of valleys lb in a sheet.

The dies project from the holder 7 by a distance correspond ing at least to the height of the sheet section and have in their lower region a shape corresponding substantially to the respective cross-sectional shape of the sheet, so that in the case of a trapezoid sheet section the die end 9 , facing to the sheet will have a width not greater than the smallest width of the valley bottom between the side walls lc, as is apparent especially from Fig. 10. Every die is provided in cross-section with a groove 10 which extends across the entire width of the die and has a depth corresponding to the intended indentation depth in the sheet. The portions 11 (see Fig. 3) enclosing the groove 10 and formed with an 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 intended - 7 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, as shown in Fig. 2. 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 valley bottoms, and to form identations extending across the entire width of the valley bottoms and corresponding protrusions on the other side of the valley bottoms. For each such effected line of indentations across the entire width of the sheet, the sheet is bent through a definite predetermined angle. By effecting several such lines of indentations consecutively and in spaced relationship, either by moving the sheet 1 in steps relative to the bending tool or by moving said tool relative to the sheet, the sheet can be bent through at least 18q° and even to a radius as small as 30 mm, depending on the section height and impression depth.

In order to eliminate stretching of the sheet at each such impressing step, even when the sheet is rigidly clamped in one side of the bending tool, for example at the sheet support 16 in Fig. 11, the side walls lc of each corrugation are subjected to an outwardly directed pressure prior to or simultaneously with the effecting of an impression. This pressure is brought about, in 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 side walls lc of a corrugation (Fig. 10) that they press the side walls lc of the corrugation in directions away from each other with 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 against the sheet portions located between the support members 11 of the dies in order to effect said indentations, the side walls lc are caused by - 8 said laterally directed forces to bulge outward in the area about the ends of the protrusion formed in the upper surface of the valley bottom by the indentation and thereby are given a permanent, gradually outwardly bulging natural deformation in said area of the side walls lc which receives the surplus material formed at every impressing step without giving rise to sharp folds or stretching, which may cause crack formation or other damage in a possible surface layer on the sheet.

In 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 in the embodiment shown in Figs. 5 and 6, the said protrusions have the form of pins 21 fastened in said sides 18 of the dies and having end surface 22 which are substantially parallel to the side walls lc for exerting pressure substantially perpendicular to said walls. The protrusions 17, irrespective of whether they are in the form of balls or pins, are located centric20 ally in relation to the groove, and their lower point is on the same level as, or slightly proud of, the level of the groove 10. The balls 20, as well as the pins 21, preferably are made of plastics or another easily sliding material, preferably with self-lubricating properties, which espegial25 ly applies to the pins, because the balls by their rotatability roll against the side walls lc of the corrugations when the die is being applied, so that the balls do not1 give rise to scratches or the like in a possible surface layer, even if the layer consists of a steel material. The protrusions 17 of the dies also may have the form of rotatably mounted cylinders, though this is not shown in the drawings.

In the embodiment of the die shown in Figs. 7-9, the protrusions 17 are designed integral with the die 8.

Also, in this embodiment, each protrusion 17 is located symmetrically in relation to the groove 10 of the die, and - 9 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 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 laterally directed forces against the side walls lc of a corrugation when the die is applied to the sheet, and thereby obtaining at least an outwardly directed prestressing of these side walls lc before the impression proper of the valley bottom lb is effected by means of the pressing bar 13 in cooperation with bending die 8.

In the bending machine shown schematically in Fig. 11, it is the bending tool located in the bending frame 4 which for each impression is moved in steps relative to the sheet 1 to be bent. Said movement in the embodiment shown takes place in the form of a stepped pivotal movement about the axle 6, starting from a substantially upright position, in which the frame 4, however, should have a certain inclination 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 its starting position may correspond to an angle which is half the angle through which the frame is pivoted at each bending step, and which is a fraction 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 hydraulically or pneumatically operated piston-cylinder means, is controlled in relation to the lower portion of the bending tool, so that either it is entirely disengaged when the pressing bar 13 of the bending tool contacts the sheet 1, so that the frame 4 during the impression moment - 10 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 movement of the bending frame relative to the sheet 1. This return movement very efficiently contributes to prevent the material in the sheet from being stretched in a damaging way.

Fig. 12 shows an embodiment of the bending tool which is intended to bend sinusoidal sectional sheet metal. The tool comprises a lower portion 30, which in the embodiment shown is intended to be fixedly mounted, for example on a pressing table (not shown) of a press known per se, and an upper portion 31, which is connected to the movable part of the press for being moved towards and away from . the lower portion 30 of the tool, 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 axis whilst the sheet is advanced in steps. The tool according to Fig. 12 and also the tool according to Fig. 13 can be used in a bending frame 4 pivotal in steps. It should further be mentioned that the lower and upper portions of the tool shown in Fig. 12 can change place, 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 in the embodiment according to Figs. 1 and 11. This possibility of interchanging between the upper and the lower portions 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.

In the embodiment shown in Fig. 12, by contrast with the embodiment described above, the pressing bar 13 is located in the upper portion 31 of the tool and the dies 8 are located in the lower portion 30 of the tool. - 11 The dies are shown coherent, with an outline corresponding to the cross-sectional shape of the sheet, and are each formed of two plates 35, which have said outline and between which a spacer 36 is located to form the groove 10 of the die between the support members 11, into which groove the pressing bar 13 is intended to press the sheet portion located between the support members 11 and thereby to form the indentations 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 in 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 against the side walls 32c of the corrugations in order to form in the side walls 32c of the corrugations outward bulges 40 in the same plane as the indentations and at the ends thereof, in such a manner that each indentation 34 at each end transforms to an outward bulge 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 surface 41 constituting an extension of the bottom surface 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 in the embodiment according to Fig. 12 is provided with clamping members 44 located on both sides of the pressing bar 13 and directly in front of each other. The configuration of the clamping 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 located between the support members 11 - 12 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 coherent and'have an outline corresponding to the cross-sectional shape of the sheet.

The portions of the pressing bar 13 for effecting the indentations 34 may have a convex arc-shape as indicated in Fig. 12, and the surface 37 constituting the bottom of the groove 10 has a corresponding concave arc-shape.

In Fig. 13 an arrangement is shown in a schematic manner for bending a sheet 50 which has a trapezoid section and a relatively great sectional 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 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.

In 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 protrusions, in contrast to the protrusions 17 in the previous embodiments, extend over the entire height of the die from the bottom of the groove 10 in each die, and which have their convex rounded lateral surface 57 parallel to the sides 58 of the die, except for the portions located closest to the groove 10 which are 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 the side walls 50c of its corrugations against the protrusions 56 and be supported by them at a distance above the supporting members of the dies located on both sides of the groove 10. In order to prevent the side walls 50c of the corrugations from springing - 13 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 side walls 50c of the sheet on the opposite side of each such portion, against which a protrusion 56 acts to form outward bulges 58 in the side walls 50c, at the same time as the upper portion 54 of the tool is pressed down against the sheet applied on the lower portion 55 for effecting the indentations 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 bulges 58, the counter-hold members are provided with grooves 65 located in the same plane as the pressing bar 13. Each intermediate space between two counter-hold members 64, furthermore, is so formed that the support surfaces 61 of the counter-hold members, which face towards each other and have a form corresponding to the form of the side walls 50c substantially completely abut the sidewalls 50c of the sheet first when the pressing bar 13 located in each intermediate space between two counterhold members 64 has been pressed in through the intended distance so as to form indentations in the sheet which thus extends also over the outward bulges. However, folds are formed at the boundary between indentation and outward bulge.

The counter-hold members are preferably given a configuration corresponding to the cross-sectional shape of the corrugations of the plate, in the intermediate portions 60 of which no impression takes place. For the stiffening grooves 51 of these intermediate portions, both each die 8 and each counter-hold member 64 are formed at their end with a depression 62.

Claims (10)

1. A method of bending corrugated sheet metal about an axis on one side of the sheet extending transversely of the corrugations and parallel to the plane of the sheet, the corrugations forming alternating crests and valleys having common side walls when viewed from said one side of the sheet, which method comprises forming indentations in the crests transversely of the corrugations by pressing portions of the crests into grooves in counter-hold memhers provided on the opposite side of the sheet, and forming outward bulges in the side walls of the corrugations on said one side of the sheet by means of projecting protrusions provided on the side walls of the counter-hold members, the protrusions acting on said opposite side of the sheet to exert outwardly directed forces in the plane of the indentations on the side walls of the corrugations.

2. A method as defined in claim 1, wherein a pressing member cooperates with the counter-hold members for effecting the impressions, and the counter-hold members are caused to perform a return movement during the final phase of the impressing movement of the pressing mamber.

3. A method as defined in claim 2, wherein the return movement is brought about in response to movement of the pressing member against the counter-hold members by drive means provided for stepped advancing of the bending tool comprising the counter-hold and impressing members.

4. A device for carrying out the method according to claim 1, comprising a tool, which consists of an upper portion and a lower portion, one of which is formed with at least one pressing bar for extending transversely of the corrugations in the sheet, and the other of which is formed with counter-hold members including grooves, into which the pressing bar is intended to press the sheet to be bent, each side wall of each counter-hold member being provided - 15 with a projecting protrusion for acting on said opposite side of the sheet, at least one application of the pressing bar against the sheet, to exert an outwardly directed force on the corresponding side wall of the corrugation to form the outward bulges in the side walls of the corrugations.

5. A device as defined in claim 4, wherein the protrusions are integral with the counter-hold members.

6. A device as defined in claim 4, wherein the protrusions consist of rotatably mounted balls or cylindrical rollers, for example of plastics material.

7. A device as defined in claim 4 or 5, wherein the tool portion supporting the pressing bar is provided with counter-hold members formed with grooves located in the same plane as the pressing bar for supporting the side walls of the corrugations during pressing-out of the outward bulges.

8. A device as defined in any one of claims 4 to 7, wherein the upper and the lower portions of the tool are located in a bending frame pivotal about an axle parallel to the bending axis, and means are provided to maintain the bending frame freely pivotal about its axle at the moment of impression, in such a manner that the frame is caused to perform a return movement during the final phase of the impressing movement.

9. A method of bending corrugated sheet metal substantially as hereinbefore described with reference to the accompanying drawings.

10. A device for bending corrugated sheet metal substantially as hereinbefore described with reference to the accompanying drawings.