EP0146352A2

EP0146352A2 - A method and apparatus for bending a corrugated sheet

Info

Publication number: EP0146352A2
Application number: EP84308696A
Authority: EP
Inventors: Karl Allan Esse Erixon
Original assignee: Granges Aluminium AB
Current assignee: Granges Aluminium AB
Priority date: 1983-12-16
Filing date: 1984-12-13
Publication date: 1985-06-26
Also published as: SE8306988D0; SE8306988L; EP0146352A3; SE445309B

Abstract

A method of and apparatus for bending a corrugated sheet transversely of the direction of corrugation, the corrugated sheet being of the type having a plurality of parallel ridges and troughs formed by ridge tops (17) connected to ridge bottoms (18) by intermediate side walls (19 and 20). The apparatus comprises a first tool (11) in the form of a pressure bar formed along the length thereof with alternating projections (16A) and notches (16B) and a second tool (10) in the form of an elongate member (12) carrying a plurality of projections (13), a channel (14) being provided in each projection (13) to receive the first tool (11) in use of the apparatus. In use of the apparatus, a corrugated sheet is pressed between the first and second tools so that each projection (13) of the second tool (10) enters a respective valley between two ridge tops (17) of the corrugated sheet and the first tool (11) enters the channels (14) of the projections (13) to form a fold (22) extending transversely of the corrugations and into the valleys of the corrugated sheet. The trough bottom (18) of each corrugation is brought into contact with the base of the respective notch (16B) during the pressing operation and at the same time the side walls (19 and 20) of the respective valley contact the edges of the notch (1 6B) whereby the portions (19A and 20A) of the side walls between the point of contact with the notch edge and the trough bottom (18) are moved away from the valley (21) and the portions (19B and 20B) of the side walls between the point of contact and the ridge top are moved into the valley.

Description

THIS INVENTION relates to a method and apparatus for bending a corrugated sheet transversely of the direction of corrugation.
Published Swedish Patent Specification 7514338-8 discloses a method of bending corrugated sheet and a machine for carrying out the method. According to the disclosed method, an elongate pressure bar is positioned on one side of the corrugated sheet and a channelled member is positioned on the other side of the sheet so that the pressure bar and the channelled member both extend transversely of the direction of the corrugations. When the pressure bar and the channelled member are forced against another, one or more successive transverse folds are formed in each of the troughs of the corrugated sheet in an area where the sheet is to be bent so that the sheet is bent through a desired angle. During the formation of the folds, the side walls of the corrugations between the toughs and the ridges thereof in the bending area are deformed, so that portions of the side walls extend away from the valleys therebetween forming indentations in the side walls.
The method described in Swedish Patent Specification No. 7514338-8 makes it possible to bend corrugated sheet transversely of the direction of the corrugations to produce a bend having a small radius of curvature and a large bending angle. However, the method has the disadvantage that for some corrugation shapes and some materials, particularly aluminium sheet having trapezoidal cross-section corrugations, the width of sheet in the bending area is increased during the bending process. This increase in sheet width is due to the fact that the deformation of the side walls during the depression of the folds forces the ridge tops of the corrugatibns in the bending area away from one another, thus causing an increase in the total width of the sheet. The increase in the width of the corrugated sheet can amount to 10 to 20 millimetres in, for example, aluminium sheet formed with trapezoidal cross-section corrugations, which prevents the method being used for bending corrugated sheets of the above-mentioned type when the bent corrugated sheets are intended to be overlapped with one another in order to cover a large area.
It is an object of the present invention to overcome or at least mitigate the disadvantage of the above-described previously proposed method.
According to one aspect of the present invention, there is provided a method of bending a corrugated sheet transversely of the direction of corrugation, the corrugated sheet having a plurality of substantially parallel ridges and troughs defined by ridge tops and trough bottoms connected by side walls, which method comprises pressing the corrugated sheet between first and second tools to form a fold extending transversely of the direction of corrugation and into the valleys between adjacent ridge tops of the corrugated sheet, the side walls of the corrugation being deformed during the formation of the fold in such a way that a first portion of each side wall is moved away from the valley between adjacent ridge tops and a second portion of each side wall is moved into the valley between adjacent ridge tops.
In another aspect, the present invention provides a method of bending a corrugated sheet transversely of the direction of corrugation, the corrugated sheet having a plurality of substantially parallel ridges and troughs defined by ridge tops and trough bottoms connected by side walls, which method comprises pressing a corrugated sheet between a first tool and a second tool so that each of a plurality of notches of the first tool receives a respective trough bottom of the corrugated sheet and each of a plurality of projections of the second tool enters a respective valley between adjacent ridge tops of the corrugated sheet, the first tool entering a respective channel formed in each of the projections of the second tool to form a fold extending transversely of the direction of corrugation and into the valleys between adjacent ridge tops of the corrugated sheet, and the side walls of each valley between adjacent ridge tops contacting respective edges of the associated notch so that a first portion of each side wall is moved into the valley and a second portion of each side wall is moved away from the valley.
Preferably, each notch of the first tool is so dimensioned that a selected point on each side wall of the valley received in the notch contacts a respective free edge of a side wall of the notch during the pressing of the corrugated sheet between the first and second tools.
Conveniently, the movements of the first and second portions of the side walls are arranged to compensate for one another so that the distance between the ridge tops of the corrugated sheet in the region of the fold is substantially unchanged after the corrugated sheet has been folded.
Usually, the portions of the side walls adjacent the respective trough bottoms are moved away from the valleys between the ridge tops and the portions of the side walls adjacent the ridge tops are moved into the valleys between the ridge tops during the formation of a fold.
The present invention also provides apparatus for bending a corrugated sheet transversely of the direction of corrugation, the sheet having a plurality of substantially parallel ridges and troughs defined by ridge tops and trough bottoms connected by side walls, which apparatus comprises a first tool formed with a plurality of notches for each receiving a respective trough bottom of a corrugated sheet, and a second tool formed with a plurality of projections for each entering a respective valley between adjacent ridge tops of a corrugated sheet, the projections of the second tool having free ends formed with channels whereby, in use of the apparatus, when a corrugated sheet is pressed between the first and second tools, the first tool enters the channels in the projections of the second tool to form a fold extending transversely of the direction of the corrugation and into the valleys between adjacent ridge tops of the corrugated sheet and the side walls of each valley between adjacent ridge tops each contact an edge of a respective notch of the first tool so that a first portion of each side wall is moved into the valley and a second portion of each side wall is moved away from the valley.
In another aspect, the present invention provides apparatus for bending a corrugated sheet of the type having a plurality of substantially parallel ridges and troughs with intermediate side walls transversely of the direction of corrugation, which apparatus comprises a first tool in the form of a pressure bar arranged to extend over substantially the entire width of the sheet transversely of the direction of corrugation and to be positioned against one surface of the sheet to abut the bottom of the troughs of the corrugations of the corrugated sheet, and a second tool provided with projections extending into the valleys between adjacent tops of the ridges of the corrugated sheet and adapted to be positioned against the other surface of the sheet so that the projections abut the inner surfaces of the valleys defined between adjacent ridge tops, the projections of the second tool each being provided at a free end thereof with a channel having a width that is at least equal to the sum of the thickness of the pressure bar and twice the thickness of the corrugated sheet so that the pressure bar can be forced into the channels of the projections to form folds in the troughs of the corrugated sheet, in which apparatus the pressure bar is provided along the length thereof with projections and notches matched to the corrugation shape of the sheet to be bent so that, in use of the apparatus, when a corrugated sheet is pressed between the first and second tools, the notches abut the outer surfaces of the trough bottoms of the corrugated sheet and the projections of the pressure bar abut the corresponding side walls of the corrugated sheet whereby deformation of the side walls can be controlled during the formation of a fold in the corrugated sheet.
Preferably, each notch of the first tool is dimensioned so that when the trough bottom of a respective corrugation contacts a floor of the notch, the corresponding side walls of the corrugated sheet simultaneously contact respective edges of the notch. Generally, the projections and notches of first tool are substantially rectangular.
Usually, when the corrugated sheet to be bent has trapezoidal cross-section corrugations, the projections of the second tool are substantially trapezoidal and the notches of the first tool have a depth which is substantially equal to from 20% to 60% of the perpendicular distance between a ridge top and a trough bottom of the corrugated sheet so that, in use of the apparatus, when a corrugated sheet having trapezoidal cross-section corrugations is pressed between the first and second tools, the portions of the side walls of each valley adjacent the trough bottom thereof are moved away from the valley and the portions of the side walls adjacent the ridge top are moved into the valley.
Preferably, the notches of the first tool have a depth which is substantially equal to between 30% and 40% of the perpendicular distance between a ridge top and a trough bottom of a corrugated sheet so that, in use of the apparatus, when a corrugated sheet is pressed between the first and second tools, the movements of the first and second portions of the sheet compensate for one another and the width of the corrugated sheet in the region of the fold remains substantially unchanged.
Thus, the present invention enables the provision of a method and apparatus for bending corrugated sheet transversely of the direction of corrugation which prevent or at least hinder changes in the width of the corrugated in the bending area during bending.
As will be appreciated from the above the fact that in use of apparatus and/or a method embodying the present invention the portions of the side walls connecting the ridge tops with the trough bottoms in the region where a fold is being formed contact the edges of the respective notches of the first tool during the bending process so that a portion of each side wall is moved away from the valley between adjacent ridges tops and another portion of each side wall is moved into the valley between the ridge tops enables the movements of the side walls to be adjusted so that they compensate for one another to a desired extent to enable changes in the width of the sheet in the bending area to be controlled. This feautures also allows the sheet to be bent through a large bending angle to form a bend having a small radius of curvature with no substantial change in the width of the sheet in the bending area. It is also possible to provide for controlled increases or decreases of the sheet width in the bending area if desired for any reason.
For a better understanding of the present invention, and to show how the same may be put into effect, reference will now be made, by way of example, to the accompanying drawing, in which:

FIGURE I is a diagrammatic view of apparatus embodying the invention;
FIGURE 2, is a vertical section through the apparatus shown in Figure I taken along line II-II of Figure I;
FIGURE 3 is an end view of a portion of a corrugated sheet having trapezoidal cross-section corrugations and showing in dashed lines the deformation of side walls of the corrugations produced by apparatus embodying the present invention; and
FIGURE 4 is a side elevational view of part of a side wall of a corrugated sheet after a bending operation.

As mentioned hereinbefore, a machine for bending a corrugated sheet transversely of the direction of corrugation is disclosed in published Swedish Patent Specification No. 7514338-8. The machine comprises a table having two rotatably mounted press heads which can be moved in a stepwise manner to different angular positions with respect to the plane of the table. Each press head comprises a first tool in the form of a pressure bar and a second tool which are adapted to be pressed against respective opposite sides of a corrugated sheet located on the table in order to bend the sheet by forming a number of folds extending transversely of the corrugations of the sheet.
Referring now to the drawings, there is shown apparatus in accordance with the present invention which is suitable for use in place of the first and second tools of the above-described machine. As shown in Figure I, the apparatus comprises a top tool 10 and a bottom tool 11. The top tool 10 comprises a rectangular cross-section elongate member 12 having the shape of a cushion or bolster. As shown by Figures I and 2, two parallel spaced-apart rows of trapezoidal projections or teeth 13 extend perpendicularly of the elongate member 12. In the arrangement shown, the two rows of teeth or projections 13 are formed by trapezoidal plates 13A and 13B which are spaced apart by a spacer 15 attached to the elongate member 12 to define a space 14 between the plates 13A and 13B. The bottom tool I I consists of a pressure bar 16 in the form of an elongate steel ruler having a castellated edge formed by rectangular projections 16A and notches 16B. The pressure bar 16 has a length which is approximately equal to the width of the sheet to be bent. The space 14 between the plates 13A and 13B has a width that is at least equal to the sum of the thickness of the bar 16 and twice the thickness of the sheet to be bent.
The apparatus shown in Figure I is particularly suited for bending a corrugated sheet having trapezoidal cross-section ridges and troughs extending parallel to one another along the length of the sheet. As shown in bold lines in Figure 3 such a corrugated sheet comprises a plurality of substantially planar ridge tops 17 and a plurality of substantially planar trough bottoms 18. Each trough bottom 18 is connected to one adjacent ridge top 17 by a first side wall 19 and to the other adjacent ridge top 17 by a second side wall 20 so that each trough bottom 18 and the associated side walls 19 and 20 define a trapezoidal cross-section valley 21 having the same shape as the projections 13 enabling each projection 13 to extend into a respective valley 21 so that the free edge 13C of the projection, that is the shorter of the two parallel edges thereof, abuts the respective trough bottom 18 and the elongate member 12 abuts the ridge tops 17.
The rectangular shaped notches 16B of the pressure bar 16 each have a width B which is greater than the length of a free edge 13C of a projection 13, and a depth D such that the edges of each notch 16B, which also form respective edges of the adjacent projections 16A, abut the side walls 19 and 20 of a corrugated sheet when each trough bottom 18 of the corrugated sheet contacts the floor of a respective notch 16B in the pressure bar . By varying the width B of the notches 16B and/or the depth D thereof, the point at which the edges of the notches 16B of the pressure bar abut the side walls 19 and 20 of the corrugated sheet when the trough bottoms 18 of the corrugated sheet contact the floors of the notches 16B can be moved along the length of the side walls 19 and 20 as will be explained further below.
In order to bend a corrugated sheet using the apparatus described above, the top tool 10 and the bottom tool I are first positioned against respective surfaces of the corrugated sheet so that the corrugated sheet is sandwiched between the first and second tools and the projections 13 of the top tool 10 are aligned with the valleys 21 of the corrugated sheet while the notches 16B of the bottom tool 11 are aligned with the trough bottoms 18 of the corrugated sheet. When the top tool and the bottom tool are forced against one another, each projection 13 of the top tool extends into a respective valley 21 of the corrugated sheet and each trough bottom 18 of the corrugated sheet contacts the floor of a respective notch 16B of the bottom tool so that the bottom tool extends into the space 14 between the plates 13A and 13B forming the projections 13. At the same time, the side walls of each valley 21 contact the edges of the respective notch 16B of the pressure bar.
When the bottom tool I I is introduced into the space 14, a fold 22 (Figure 4) extending transversely of the corrugations and into the valleys 21 between the ridge tops 17 is produced in the trough bottoms 18 of the corrugated sheet. The fold 22 preferably lies on a line perpendicular to the direction of corrugation of the corrugated sheet. By repeating the above described operation at different positions spaced apart along the length of the corrugations, a plurality of folds parallel to one another and spaced apart along the length of the corrugations can be formed and the sheet can be bent through a large angle so that a bend having a small radius of curvature can be produced.
As a fold 22 is produced in the corrugated sheet in the manner described above, portions of the side walls 19 and 20 of each valley 21 adjacent the fold 22 are deformed, the portion of each side wall between the point of contact with the edge of the respective notch 16B and the respective ridge top 17 being moved into the valley and the portion of each side wall between the point of contact with the edge of the notch 16B and the trough bottom 18 being moved from the valley. By selecting the width B and depth D of the notches 16B appropriately, the edges of the notches 16B will be brought into contact with particular points on the side walls 19 and 20, for example the points P and Q shown in Figure 3. Thus when a fold 22 is produced, the side walls 19 and 20 are deformed in such a way that the portions 19A and 20A of the side walls of each valley below the contact points P, Q, that is the portion of the side walls adjacent the trough bottoms 18, will be moved away of from the valley 21 and the portions of the side walls 19B and 20B above the contact points P and Q, that is the portions of the side walls adjacent the ridge tops 17, will be moved into the valley 21 as shown by means of dashed lines in Figure 3.
As described above the deformation of the side walls 19 and 20 can be controlled by altering the points of contact of the side walls of each valley with the edges of the respective notch 16B by changing the dimensions of the notches. Thus if the points P and Q are positioned close to the trough bottoms 18, the larger portion of each. side wall of a valley, that is the portions 19B and 20B above the contact points P and Q, will be moved into the valley when the sheet is deformed during the bending operation and the ridge tops 17 of the corrugated sheet will thus be pulled together causing the width of the corrugated sheet in the bending area to be decreased. Alternatively, if the contact points P and Q are positioned closer to the ridge tops, 17 the larger portions of the side walls will be the portions 19A and 20A adjacent the trough bottoms 18 so that the ridge tops 17 will be moved away from each other during the bending process, so increasing the width of the sheet in the bending region. Thus, by selecting the points P and Q appropriately, the movement of the upper portions 19B and 20B and the lower portions 19A and 20A of the side walls respectively, can be made to compensate or balance one another so that no movement of the ridge tops, and consequently no change in the width of the sheet, in the bending region occurs during a bending operation. As mentioned above, the position of the contact points P and Q on the side walls 19 and 20 is determined by the relative dimensions of the width and depth of the notches 16B of the bottom tool. Assuming that the width of the notches 16B remains constant, the depth thereof should preferably be equal to between 20 and 60% of the perpendicular distance H between the ridge tops 17 and the trough bottoms 18 of the corrugated sheet. For full compensation of the movements of the respective upper and lower portions of the side walls, that is so that substantially no change in the sheet width occurs during a bending operation, the notches 16B should have a depth of about 30 to 40% of the distance H between the ridge tops 17 and the trough bottoms 18 of the sheet to be bent. Of course, the depth of the notches will depend upon the shape of the corrugations and the thickness, quality and material of the sheet. However, the correct values for the depth of the notches can easily be obtained experimentally.
As shown in dashed lines in Figure 3, when a corrugated sheet is bent using the apparatus described above, the portions 19B and 20B of the side walls 19 and 20 above the contact points P and Q form smoothly curved or "soft" substantially oval cross-section projections extending into the valleys 21 of the sheet, while the portions 19A and 20A of the side walls below the contact points P and Q are deformed so as to extend away from the valleys 22 and have a comparatively angular or pointed cross-sectional shape as illustrated schematically in Figure 3.
While only one embodiment of the apparatus and only one example of the method according to the invention have been described above and illustrated in the drawings, it is obvious that many variations and modifications are possible within the scope of the invention. For example, the projections of the top tool do not need to have a shape which is in complete agreement with the shape of the valleys between the ridge tops and some discrepancies are possible. Furthermore,the notches and the projections of the bottom tool do not need to be of rectangular shape, and many other shapes are possible. For example, the projections of the bottom tool may have rounded or bevelled corners where the projections meet the notches for providing a softer abutment against the side walls of the sheet. Also, during use of the apparatus, the positions of the top and bottom tools may be reversed so that the top tool 10 is positioned beneath the sheet and aligned with the valleys defined by the ridge tops 17 and side walls 19 and 20. Moreover instead of forming the projections 13 of the top tool 10 by means of two spaced plates, each projection 13 may consist of a block having a similar shape to the two plates and formed with a channel in the free edge thereof opposite the elongate member to replace the space 14 between the two plates.
Also, the top and bottom tools may alternatively be designed so that the portions of the side walls closest to the ridge tops 17 of a corrugated sheet are pushed away from the valleys between the ridge tops and the portions of the side walls closest to the trough bottoms 18 are pushed into the valleys between the ridges during a bending operation that is, so that the upper portions 19B and 20B and the lower portions 19A and 20A of the side walls of the corrugated sheet move in directions opposite to those described above and illustrated in Figure 3. Also, the apparatus and method described may be used to bend corrugated sheet having other than trapezoidal cross-section corrugations, for example sheets having sinusoidal corrugations.
The features disclosed in the foregoing description, in the following claims and/or in the accompanying drawings may, both separately and in any combination thereof, be material for realising the invention in diverse forms thereof.

Claims

I. A method of bending a corrugated sheet transversely of the direction of corrugation, the sheet having a plurality of substantially parallel ridges and troughs defined by ridge tops and trough bottoms connected by side walls, which method comprises pressing the corrugated sheet between first and second tools to form a fold extending transversely of the direction of corrugation and into the valleys between adjacent ridge tops of the corrugated sheet, the side walls of the corrugation being deformed during the formation of the fold in such a way that a first portion of each side wall is moved away from the valley between adjacent ridge tops and a second portion of each side wall is moved into the valley between the adjacent tops.
2. A method of bending a corrugated sheet transversely of the direction of corrugation, the corrugated sheet having a plurality of substantially parallel ridges and troughs defined by ridge tops and trough bottoms connected by side walls transversely of the direction of corrugation , which method comprises pressing a corrugated sheet between a first tool and a second tool so that each of a plurality of notches of the first tool receives a respective trough bottom of the corrugated sheet and each of a plurality of projections of the second tool enters a respective valley between adjacent ridge tops of the corrugated sheet, the first tool entering a respective channel formed in each of the projections of the second tool to form a fold extending transversely of the direction of corrugation and into the valleys between adjacent ridge tops of the corrugated sheet and the side walls of each valley between adjacent ridge tops contacting respective edges of the associated respective notch so that a first portion of each side wall is moved into the valley and a second portion of each side wall is moved away from the valley.
3. A method according to Claim 2, wherein each notch of the first tool is so dimensioned that a selected point on each side wall of the valley received in the notch contacts a respective free edge of a side wall of the notch during the pressing of the corrugated sheet between the first and second tools.
4. A method according to claim I, 2 or 3 wherein the movements of the first and second portions of the side walls are arranged to compensate for one another so that the distance between the ridge top of the corrugated sheet in the region of the fold is substantially unchanged after the sheet has been folded.
5. A method according to claim 1,2,3 or 4 wherein the portions of the side walls adjacent the respective trough bottoms are moved away from the valleys between adjacent ridge tops and the portions of the side walls adjacent the ridge tops are moved into the valleys between adjacent ridge tops during the formation of a fold.
6. Apparatus for bending a corrugated sheet transversely of the direction of corrugation, the sheet having a plurality of substantially parallel ridges and troughs defined by ridge tops and trough bottoms connected by side walls, which apparatus comprises a first tool formed with a plurality of notches for each receiving a respective trough bottom of a corrugated sheet, and a second tool formed with a plurality of projections for each entering a respective valley between adjacent ridge tops of a corrugated sheet, the projections of the second tool having free ends formed with channels whereby, in use of the apparatus, when a corrugated sheet is pressed between the first and second tools, the first tool enters the channels in the projections of the second tool to form a fold extending transversely of the direction of the corrugation and into the valleys between adjacent ridge tops of the corrugated sheet and the side walls of each valley between adjacent ridge tops each contact an edge of a respective notch of the first tool so that a first portion of each side wall is moved into the valley and a second portion of each side wall is moved away from the valley.
7. Apparatus according to Claim 6, wherein each notch of the first tool dimensioned so that, when the trough bottom of a respective corrugation contacts a floor of the notch, the corresponding side walls of the corrugated sheet simultaneously contact respective edges of the notch.
8. Apparatus according to claim 6 or 7 wherein the notches of first tool are substantially rectangular.
9. Apparatus according to claim 8 suitable for bending a corrugated sheet having trapezoidal cross-section corrugations, wherein the projections of the second tool are substantially trapezoidal and the notches of the first tool have a depth which is substantially equal to from 20% to 60% of the perpendicular distance between a ridge top and a trough bottom of the corrugated sheet so that, in use of the apparatus, when a corrugated sheet having trapezoidal cross-section corrugations is pressed between the first and second tools, the portions of the side walls of each valley adjacent the trough bottom thereof are moved away from the valley and the portions of the side walls adjacent the ridge top of the valley are moved into the valley.
10. Apparatus according to claim 9, wherein the notches of the first tool have a depth which is substantially equal to between 30% and 40% of the perpendicular distance between a ridge top and a trough bottom of the corrugated sheet so that, in use of the apparatus, when a corrugated sheet is pressed between the first and second tools, the movements of the first and second portions of the sheet compensate one another and the width of the corrugated sheet in the region of the fold remains substantially unchanged after the formation of the fold.