GB2249506A

GB2249506A - Method of bending L or channel sections

Info

Publication number: GB2249506A
Application number: GB9024218A
Authority: GB
Inventors: Charles Edward Harris; Ronald Charles Sammons
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-11-07
Filing date: 1990-11-07
Publication date: 1992-05-13
Anticipated expiration: 2010-11-07
Also published as: GB2249506B; GB9024218D0

Abstract

The section is placed in a die 3 having a base having an internal profile corresponding to the desired bending angle e.g. V shaped. A punch 9 with an external profile corresponding to the desired bending angle and which matches the internal profile of the die is directed into the die. The punch has at least one side forming insert 11, 12 attached to its side which has a thickness corresponding to that of the section wall 18, 19 and which has a substantially round leading edge profile. When the punch 9 is directed into the die 3, the leading edge of the insert 11, 12 drives the respective section edge into the space between the sides of the punch and side plates 13, 14 on the inserts 11, 12 before the nose of the punch acts on the base 17 of the section. The section may be metal or synthetic polymer which has been bent or extruded to provide a cross section which is 'U', V', 'L' shaped or rectangular, preferably of stainless steel or galvanised iron. The punch and die used to form the bend are matched to form preferably a right angle. <IMAGE>

Description

METHODS OF BENDING CHANNEL SECTIONS This invention relates to a method of bending ehannel sections, particularly metal channel sections, and to channel sections having bends formed by the method.

It is well known that due to its ductility many types of metal bar, and some made of synthetic polymers, may be bent accurately by the application of pressure when the bar is placed over a jig or former having the necessary profile.

However when channel sections are bent problems arise due to the sides of the channel which tend to buckle. These problems may be overcome by cutting a 'V' shaped slot from the edges of the channel at the bending point and joining the edges of the slot after bending by welding. Alternatively the edge of the channel at the bending point may be slit and the flange formed after bending folded under the base of the channel. Both these Operations require additional manufacturing steps when bending channel and a welding or other securing operation on the bent channel.

When channel is to be used as a load supporting element, for instance when used in joist hangers, the existing methods of bending channel section are unsatisfactory.

According to the present invention there is provided a method of bending channel section characterized in that the channel section is placed in a die having vertical walls adapted to support the channel sides and a base having an internal profile corresponding to the desired bending angle, a punch having an external profile corresponding to the desired bending angle and matching the internal profile of the die is directed into the die, the punch having at least one side forming insert attached to the side of the punch which has a thickness corresponding to that of the channel wall and which has a substantially round leading edge profile whereby, when the punch is directed into the die1 the leading edge of the insert drives the edges of the channel into the space between the sides of the punch and the die wall before the nose of the punch acts on the base of the channel section.

The term channel refers to metal or synthetic polymer which has been bent or extruded to provide a cross section which is 'U', 'V', 'L' shaped or rectangular.

The punch and die used to form the bend may be matched to form a right angle, for instance when making a bracket or the stirrup of a joist hanger. However channel sections may be bent over a wide range of angles both greater and less than a right angle when required.

The die used will preferably be formed with a well corresponding to the bending angle and a surface profile to match the base of the channel section to be bent. If the channel section is rectangular then the surface of the die will be flat. In the case of a U-shaped channel the surface of the die will be formed as a matching concave furrow.

The punch has a leading edge and nose which match the contour of the die well. The surface of the punch will similarly match the surface of the die. Each side of the punch will carry an insert spaced from the nose by an amount dependent upon the height of the side walls of the channel to be bent. The location of the insert must be such that it makes contact with the upper edge of the side wall before the nose of the punch reaches the base of the channel. In order to prevent the side wall buckling the punch carries a side plate which covers the side wall of the channel before the insert reaches it. The restraining action of the side wall is preferably enhanced by at least one block spaced from the die and rigidly fixed to the base of the press.

If the channel is assymetric, e.g. an L-shaped channel then only one insert will be required. Most forms of channel are symmetrical however and an insert is required on both sides of the central portion of the punch together with side plates.

The invention is particularly useful with metal channel such as stainless steel or galvanised iron channel. The invention may also be performed with other materials such as synthetic polymers.

In order that the invention may be clearly understood it will now be described with reference to the accompanying drawings in which: Figure 1 is a schematic end view of a press showing a punch and die used in bending channel sections according to the invention, Figure 2 is a side view of the press shown in Figure 1 with certain elements removed to improve clarity, Figure 3 is an enlarged cross sectional view of part of the press shown in Figure 1, and Figure 4 is a schematic side view of the punch and die of Figure 1 acting on a piece of channel section.

A press 1, see Figure 1, has a bottom bolster plate 2 carrying a centrally positioned die 3. The plate 2 also carries two heel blocks 4 and 5 spaced from the sides of the die 3 and rigidly held in position by two further blocks 6 and 7. Above the die 3 is positioned a matching punch 8 carried by driving means, not shown, which enables the punch 8 to be raised and lowered vertically as indicated by the arrow. The punch 8 comprises a central portion 9 and two side inserts 11 and 12. On each side of the central portion 9 are attached side plates 13 and 14 spaced from the side faces of the central portion 9 by the inserts 11 and 12. The outer faces of the side plates 13 and 14 fit between the inside faces of the blocks 4 and 5.

The die 3, see Figure 2, has a central V-shaped well 15 adapted to receive and mate with nose 16 of the central portion 9 of the punch 8 As illustrated the profiles of the punch 8 and the die 3 provide a 90 degree bend. For purposes of clarity the side plate 13 has been omitted from the figure. The lower portion of the insert 11 has a rounded profile.

A piece of rectangular channel to be bent through 90 degrees, see Figure 3, is placed with its base 17 lying on the upper surface of the die 3 with side walls 18 and 19 vertical. To form a right angle bend the punch 8 is driven towards the die 3 Before the nose 16 touches the base 17 of the channel the inserts 11 and 12 engage the upper edges of the side walls 18 and 19 respectively. As pressure increases an indentation is made into each of the side walls 18 and 19 driving the metal away from the point of bending. The side face of the central portion 9 of the punch and the presence of the side plates 13 and 14 within the blocks 4 and 5 ensures that the metal displaced by the insert 11 is prevented from wrinkling or buckling outwardly.

The punch 8 continues to move downwards so that the nose 16 engages the base of the channel 17 and drives it into the well 15 of the die 3. Pressure is continued until the punch 8 reaches the end of its travel. When the punch is withdrawn it is found that the channel has been bent into and angle corresponding substantially to that between the sides of the well 15. The side walls 18 and 19 carry indentations corresponding to the front profile of the inserts 11 and 12. The side walls 18 and 19 will be slightly thickened around the area adjacent to the indentation due to the presence of displaced metal.

In practice the profile of the central portion 9 of the punch 8 and the well 15 of the die 3 will exceed 90 degrees when a metal channel is being bent as to ensure that the metal is bent passed its elastic liflilt and does not spring back to an angle less than 90 degrees when the bending pressure is released.

The double action of the punch 8 on the channel is illustrated in Figure 4 in which the side plates 13 and 14 have been omitted for clarity. When the punch is driven downwards the leading edge of the insert 11 first makes contact with the upper edge of the sieve wall 18 of the rectangular channel. The leading; ~'-~- the insert forms an indentation in the side wall 18 firlvlr. the metal out of the area. When the nose 16 of the punch 8 reaches the base 17 of the channel the insert 11 will have caused an appreciable indendation into the side wall 18 so that it does not resist the bending of the base 17. This indentation will be further increased as the nose 16 drives the base 17 into the well 15 of the die 3. When the punch is withdrawn the side view of the channel will be as shown in Figure 4 (b). The base 17 will be bent through a right angle 21 and the side wall 18 will carry an indentation 22 in the portion adjacent to the right angle bend 21.

Claims

1. A method of bending channel section characterized in that the channel section is placed in a die having vertical walls adapted to support the channel sides and a base having an internal profile corresponding to the desired bending angle, a punch having an external profile corresponding to the desired bending angle and matching the internal profile of the die is directed into the die, the punch having at least one side forming insert attached to the side of the punch which has a thickness corresponding to that of the channel wall and which has a substantially round leading edge profile whereby, when the punch is directed into the die, the leading edge of the insert drives the edges of the channel into the space between the sides of the punch and the die wall before the nose of the punch acts on the base of the channel section.

2. The method of bending channel section according to claim 1, characterized in that the channel is metal or synthetic polymer which has been bent or extruded to provide a cross section which is 'U' shaped or rectangular.

3. The method of bending channel section according to either claim 1 or claim 2, characterized in that the metal channel comprises stainless steel or galvanised iron.

4. The method of bending channel section according to any of the preceding claims, characterized in that the punch and die used to form the bend are matched to form a right angle.

5. The method of bending channel section according to any of the preceding claims, characterized in that: the die is formed with a well corresponding to the bending angle and a surface profile to match the base of the channel section to be bent.

6. The method of bending channel section according to any of the preceding claims, characterized in that the punch has a leading edge and nose which match the contour of the die well.

7. The method of bending channel section according to claim 6, characterized in that the side of the punch carries an insert spaced from the nose by an amount dependent upon the height of the side walls of the channel to be bent.

8. The method of bending channel section according to claims 6 or 7, characterized in that the insert is located so that it makes contact with the upper edge of the side wall before the nose of the punch reaches the base of the channel.

9. The method of bending channel section according to any of the claims 6 to 8, characterized in that the punch carries a side plate which covers the side wall of the channel before the insert reaches it

10. The method of bending channel section according to claim 9, characterized in that the side wall is at least one block spaced from the die and rigidly fixed to the base of the press.

11. Methods of bending channel section according to claim 1 and as herein described.

12. Methods of bending channel section as herein described with reference to the accompanying drawings.

13. Channel sections whenever made by the method of any of the claims 1 to 12.