GB2166986A - A workpiece support device for a bending machine - Google Patents

Abstract

The support comprises a structure 48 having a recess 50, and a jaw or two jaws 58, 60 mounted in the recess for pivotal movement between two positions. In the first position (shown in solid line) the jaw cooperate, or the single jaw cooperates with a wall of the recess, to engage a workpiece. In the second position (shown in broken line) a workpiece is readily removable from or insertable into the recess. Preferably means such as a spring 74 resiliently urge the jaws to the second position so as to assist removal of the workpiece. The support is a backguide or an inter clamping die for hollow-section workpieces to be bent in a down-bending machine, or is used in a compression-bending machine as a guide or a clamp. <IMAGE>

Description

SPECIFICATION A workpiece support device for a bending machine This invention is concerned with a workpiece support device for a bending machine and with a bending machine including such a device.

Bending machines currently available can be divided into three main groups: 1) rotary draw bending; 2) compression bending and, 3) roll bending.

Rotary draw bending is the most widely used method and the machines range from the manually operated to hydraulically pneumatically or electromechanically powered machines with varying degrees of automacity using NC or CNC. In a rotary draw bending machine there is a rotatable bend former, a clamping die and a back die or guide. A part of the workpiece is clamped between the clamping die and a part of the bend former. As the bend former rotates and bends the workpiece about itself, the back guide moves with the part of the unbent workpiece and takes up the reaction. A mandrel may be used to prevent wall collapse and on the smaller radii thin walled tubes a wiper die may be used.

Compression bending may be divided into two methods: a first in which there is a stationary bend former, a clamp or stop which holds the workpiece and a guide which urges the workpiece around the former. In the second method, also known as ram or three point bending, two dies support the workpiece and a former is forced onto the workpiece to make the bend.

Both rotary draw bending and compression bending can be used to bend hollow section without a mandrel, known as "empty" bending, as well as bending open or slotted sections.

In roll bending there are three rolls arranged with their axes on the apices of a triangle. The workpiece is passed between the rolls. One roll is adjustable to control the bend radius and the other two are driven.

There are many not so commonly employed other methods of bending.

The invention provides a workpiece support device for a bending machine comprising a device having a support structure with a recess, and a jaw positioned in the recess, the jaw being mounted for pivotal movement between first and second positions, the first position being one in which the jaw co-operates either with another jaw pivotally mounted in the recess or with a wall of the recess to engage a workpiece and the second position being one in which the workpiece is readily removable from or insertable into the recess.

Preferably the device includes means, such as a spring located in the base of the recess, resiliently urging the jaw to the second position so as to assist removal of the workpiece.

Either the jaw or a side wall of the recess may have an edge providing an axis about which the jaw can pivot.

For a curved section workpiece, the jaw may have an engagement surface which is, in cross-section, a curve and, for example, may be a longitudinal part of the surface of a cylinder. Other curved surfaces are possible including single and multi-radiused curves, as well as ellipses and the like.

For a rectangular section workpiece, the jaw may have two flat engagement surfaces arranged substantially perpendicular to each other.

Preferably, the device also includes another jaw pivotally mounted in the recess, the two jaws being shaped and disposed symmetrically about a plane.

The invention also provides a bending machine having a workpiece support device according to the invention.

In a rotary draw bending machine for bending hollow section tube, the machine comprising a bend former and a back guide, the back guide may be a workpiece support device according to the invention.

In a rotary draw bending machine for bending angle section, singly or in pairs, hollow rectangular section, slotted hollow rectangular section and open channel rectangular section in which the open side of the channel is to be on the outside of the bend or on either side of the bend, the machine comprising a bend former and a back guide, the bend former may have a plain cylindrical surface with no lateral locating flanges and the back guide may be a workpiece support device according to the invention.

In a rotary draw bending machine for bending angle section, singly or in pairs, and open channel rectangular section in which the open side of the channel is to be on the inside of the bend, the machine comprising a bend former and a back guide, the bend former may have a plain cylindrical surface with no lateral locating flanges but may have an annular central flange for extending into the open side of the channel during bending, and the back guide may be a workpiece support device according to the invention.

In a rotary draw bending machine for crush bending hollow section, the machine comprising a bend former and a back guide, the bend former may have a plain cylindrical surface with no lateral locating flanges but may have an annular central flange for forming the crush, and the back guide may be a workpiece support device according to the invention.

In a compression bending machine comprising a bend former and a guide or die, the guide or die may be a workpiece device according to the invention.

In a compression or rotary bending machine further including a clamping die, the clampind die may be a workpiece support device according to the invention.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, of which: Figure 1 is an end view of one embodiment of a workpiece support device according to the invention for a machine for bending hollow rectangular section, slotted hollow rectangular section and open channel rectangular section; Figure 2 is an end view of a second embodiment of a workpiece support device according to the invention for a machine for bending hollow round, oval or elliptical section with or without (empty) a mandrel; Figures 3A and 3B are schematic plan and end views respectively of a conventional hollow square and rectangular section rotary draw bending machine;; Figures 4A and 4B are schematic plan and end views respectively of a hollow square and rectangular section rotary draw bending machine according to the invention; Figures 5A and 5B are schematic plan and end views respectively of a conventional machine for the rotary draw "crush" bending of hollow rectangular section; Figure 6A and 6B are schematic plan and end views respectively of a machine according to the inventionforthe rotary draw "crush" bending of hollow rectangular section; Figures 7A and 7B are schematic plan and end views respectively of a conventional machine for the rotary draw "empty" bending of hollow circular section tube;; Figures 8A and 8B are schematic plan and end views respectively of a machine according to the invention for the rotary draw "empty" bending of hollow circular section tube; Figures 9A and 9B are schematic plan and end views respectively of a conventional machine for the power assisted back guide (boost) rotary draw bending of hollow circularsection tubing; Figures 10A and 108 are schematic plan and end views respectively of a conventional machine for the rotary draw bending of open channel rectangular section with the open side on the inside of the bend;; Figures 11A and 11B are schematic plan and end views respectively of a machine accoridng to the invention for the rotary draw bending of open channel rectangular section with the open side on the inside of the bend; Figure 12 is an end view of a slotted or open sided hox section; Figures 13A and 13B are schematic plan and end views of a machine for bending the slotted or open sided box section shown in Figure 12; and Figures 14 and 15 are schematic views of the two basic types of compression bending machines.

The workpiece supporting device shown in Figure 1 comprises a support structure 20 having a recess 22 with a base wall 24 and side walls 26 and 28. Side wall 28 and back wall 24 are perpendicular to each other. Side wall 26 forms an obtuse angle with back wall 24. Mounted in the recess 22 is a jaw 30 having two limbs 32 and 34 extending substantially perpen dicular to each other. The two limbs provide two flat engagement surfaces 36 and 38 extending substantially perpendicular to each other. Limb 32 of jaw 30 has two angled surfaces providing an edge 40 which sits on side wall 26.The jaw 30 is thus pivotally mounted for movement between first and second positions: the first position being shown in solid line in which side wall 28 and engagement surfaces 36 and 28 co-operate to make-up the three sides of a rectangle in order to engage a rectangular section workpiece; the second position being shown in broken line in which the workpiece is readily removable from or insertable into the recess 22 with the engagement surface 36 extending substantially parallel to side wall 26. A screw-threaded element 42 extends through the structure 20 and into a recess in limb 32 in order to hold the jaw 30 in the recess. A spring 44 is located in a slot 46 in base wall 24 and resiliently urges the jaw 30 into the second position so as to assist removal of a workpiece.When a workpiece is inserted into the recess it engages the engagement surfaces 36 and 38 of the jaw 30. Force is then required to push the workpiece in and the jaw 30 to its first position against the action of the spring 44.

The device shown in Figure 1 can be modified by the side wall 26 having two angled surfaces to provide an edge instead of limb 32, the latter then having one flat surface to contact the edge. The spring 44 could be located in a recess in side wall 26 so as to engage the inner most one of the two angled surfaces of the limb 32 of the jaw 30.

Figure 2 shows a workpiece supporting device for use in bending hollow curved section. It comprises a support structure 48 having a recess 50 with a base wall 52 and side walls 54 and 56 diverging from each other as they extend from the base wall to the mouth of the recess. Two jaws 58 and 60 are mounted in the.

recess 50 and are shaped and disposed symmetrically about a longitudinal plane extending midway between them. Each jaw sus, 60 has an engagement surface 62, 64 respectively which is a longitudinal part of the surface of a cylinder. Each jaw 58, 60 has two angled surfaces providing an edge 66, 68 respectively which sits on the respective side wall 54, 56. Each jaw sus, 60 is thus pivotally mounted for movement between first and second positions: the first position being shown in solid line in which the jaws 58 and 60 co-operate to engage a workpiece; the second position being shown in broken line in which the workpiece is readily removable from or insertable into the recess 50.The radii of the engagement surfaces 62 and 64 are the same as each other and are appropriate for the circular section workpiece to be bent. In the first position, the axes of the engagement surfaces 62 and 64 are not coincident but parallel to and spaced from each other. Screw threaded elements 70 and 72 extend through the structure 48 and into recesses in respective jaws 58 and 60 in order to hold the jaws in the recess 50. A spring 74 is located in a slot 76 in the base wall 52 of the recess 50 and resiliently urges the two jaws 58 adn 60 into the second position so as to assist removal of a workpiece. When a workpiece is inserted into the recess it engages the engagement surfaces 62 and 64 of the jaws 58 and 60. Force is then required to push the workpiece in and the jaws 58 and 60 to their first positions against the action of the spring 74.

The modifications applicable the device shown in Figure 1 are also applicable to the device shown in Figure 2. Further, the device shown in Figure 1 can be constructed as a two jaw device similar to that shown in Figure 2, and the device shown in Figure 2 can be constructed as a single jaw device similar to that shown in Figure 1. In the latter modification, one of the side walls would have to be curved and positioned in the same place as the engagement surface of the jaw it replaces when in its first position.

Figures 3A and 3B show the essential elements of a conventional rotary draw bending machine for bending hollow square and rectangular section. The machine comprises a bend former 78 with an inner clamping die 80, an outer clamping die 82 and a back guide 84. A hollow rectangular section workpiece 86 is shown in broken line in Figure 3B. The bend former 78, clamping dies 80 and 82 and back guide 84 are grooved to take half the depth of the workpiece. The bend former 78 therefore has annular lateral locating flanges 88 and, to enable the workpiece to be removed after the bending operation, can be split to space the flanges further apart.

On automatic bending machines of this type there is the added problem of clearance iftheworkpiece has to be rotated (after called planing).

Figures 4A and 4B show the essential features of a rotary draw bending machine according to the invention with a bend former 90 having a plain cylindrical surface with no lateral locating flanges.

The machine also has a back guide 92 similar to the workpiece support device shown in Figure 1 with a right angled jaw 94 pivotally mounted in a recess in a support structure 96. This gives the following advantages over the machine shown in Figures 3A and 3B: a) any variation in workpiece size can be accommodated; b) the clamping operation involved with the bend former 78 due to its locating flanges 88 is eliminated; c) rapid removal of the workpiece; d) an uncluttered bending area eases the problem of rotating (planing) the workpiece for another bend; e) tool manufacture is simplified; f) ease of spring back correction due to simple remachining of a plain cylinder rather than several compound shapes; g) tool wear can be taken up; h) production rate is increased.

The machine in Figures 4A and 4B can also be used to bend an open channel rectangular section workpiece with the open side being on the outside of the bend, or on either side of the bend, as well as for bending angle section either singly or in pairs.

Figures 5A and 5B show the essential features of a conventional rotary draw bending machine for the crush bending of hollow rectangular section. The machine comprises a bend former 98 with an inner clamping die 100, an outer clamping die 102 and a back guid 104. A hollow rectangular workpiece 106 is shown in broken line in Figure 5B. the bend former 98, inner and outer clamping dies 100 and 102 and back guide 104 are grooved to take the shape of the workpiece. The bend former 98 has annular lateral locating flanges 108 which are movable apart from each other to enable the workpiece to be removed after the bend has been completed. The bend former 98 also has a central annular flange 110 for producing the crush.Dependant upon the tube shape, there may be the additional problem of rotating (planing) the workpiece between bending operations.

Figure 6A and 6B show the essential features of a rotary draw bending machine according to the invention with a bend former 112 having a plain cylindrical surface with only a central annular flange 114 for producing the crush and no lateral annular locating flanges. The machine also has a back guide 116 which is a workpiece support device similar to that shown in Figure 1 with a right angled jaw 118 pivotally mounted in a recess in a support structure 120.This machine provides the following advantages over the machine shown in Figures 5A and 5B: a) any variation in workpiece size can be accommodated; b) the clamping operation involved with the bend former 98 due to its locating flanges 108 is eliminated; c) rapid removal of the workpiece; c) an uncluttered bending area which eases the problem of rotating (planing) the workpiece between bending operations; 3) tool manufacture is simplified; f) tool wear can be taken up; and g) production rate is increased.

Figures 7A and 7B show the essential features of a conventional rotary draw bending machine for the bending of curved section hollow tube without using a mandrel, often known as empty bending. The machine comprises a bend former 122 with an inner clamping die 124, an outer clamping die 126 and a back guide 128 each grooved to accommodate the workpiece. A hollow circular section workpiece 130 is shown in Figure 7B. The bend former 122 and back guide 128 are of a split type in order to facilitate manufacture of the multiradiused grooves necessary. In this method of bending the tube is reformed to an oval shape. The top half of the bend former 122 is vertically movable to assist in forming the oval shape and releasing the tube after bending. The main disadvantages of these tools are the cost of manufacture and the lack of fine adjustment after assembly.

Figures 8A and 88 show the essential features of a rotary draw bending machine according to the invention forthe bending of curved section hollow tube without using a mandrel. The machine comprises a bend former 131- a conventional round-grooved former- and a back guide 132 which is similar to the workpiece support device shown in Figure 2. The back guide 132 comprises a support structure 134 having a recess and two jaws 136 each pivotally mounted in the recess, each jaw having a curved engagement surface.This machine provides the following advantages over the machine as shown in Figures 7A and 7B: a) any variation in tube size can be accommodated; b) the clamping operation involved with the bend former 122 is eliminated; c) rapid removal of the workpiece; d) the manufacture of the bend former is simplified; e) the ability to vary the sectional shape of the tube by altering the amount of back pressure applied to the rear of the back guide; f) tool wear can be taken up; and g) the back guide according to the invention can be used with the conventional "empty" bend former 122 to give greater control over the quality of the finished workpiece.

Figures 9A and 9B show the essential features of a conventional rotary draw bending machine having a power assisted back guide (commonly referred to as boost). This method is suitable for all tubes (eg circular) and most sections (eg rectangular) and is illustrated for a hollow circular section tube. The machine comprises a bend former 138 with an inner clamping die 140, an outer clamping die 142, a back guide 144 and a thrust ram 146. The bend former 138 and back guide 144 are grooved to accept a workpiece 148 shown in broken line in Figure 9B. In this method a direct thrust is applied by the ram 146 to the end of the back guide 144 in the direction of travel. This is to help overcome the drag forces set up during bending and is dependent upon the friction between the tube and the back guide.The main problem with this method is to synchronise the movement of the back guide 144 with the peripheral speed of the bend former 138. According to the invention, the back guide 144 and ram 146 are replaced by a workpiece support device similar to that shown in Figure 2 so that the machine resembles that shown in Figures 8A and 8B. Back pressure on the back guide/workpiece support device clamps the workpiece in the device ensuring synchronisation: the effect is similar to that of a rack and pinion.

In extreme cases, should a thrust ram prove necessary, greater lattitude in setting would be available as a greater load could now be applied with no fear of the back guide slipping along the tube.

Figures 1 OA and 1 OB show the essential features of a conventional rotary draw bending machine for bending open channel section with the open side on the inside of the bend. The machine comprises a bend former 150 with an inner clamping die 152, an outer clamping die 154 and a back guide 156. The bend former 150 is of the split variety comprising numerous parts in order to completely contain and release the workpiece. This makes the bend former 150 cumbersome to use and expensive to manufacture. The back guide 156 provides a flat abutment surface.

The machine according to the invention shown in Figures 11A and 11 B is a rotary draw bending machine for bending open channel section with the open side on the inside of the bend. The machine comprises a bend former 158 with an inner clamping die 160, an outer clamping die 162 and a back guide 164. The bend former 158 has a plain cylindrical surface with a single central flange 166 for extending into the open side of a workpiece 168 shown in broken line. The back guide 164 is a workpiece support device of a construction similar to that shown in Figure 1 and comprises a support structure 170 having a recess and a right-angled jaw 172 pivotally mounted in the recess.

The advantages which this machine provides over the machine shown in Figures 1 OA and 10B are: a) an exact fit of the tools to the section; b) tool wear can be taken up; c) the "nipping" pressure of the back guide 164 is variable so giving a precise control over the quality of the bend; d) the synchronisation of movement between the back guide 164 and the bend former 158 is ensured; e) rapid release of the workpiece after bending; f) by virtue of the bend former 158 drawing the section in a rotary direction from the workpiece support device/back guide 164, a wiping action occurs which has the effect of stretching the workpiece on the outside of the bend thus assisting bending. This feature eliminates the need for a pre-loading or stretch forming facility; and g) the production rate is increased.

Figure 12 shows an open sided or slotted box section. This section is virtually impossible to bend by conventional means, even with the use of highly sophisticated tooling. The usual approach is for a complete box section to be bent and then the required slot is then machined in a separate operation.

Figures 13A and 13B show a bending machine according to the invention which can be used to bend the section of Figure 12. This apparatus is very similar to that shown in Figures 4A and 4B with the addition of a special mandrel 174. By using this machine according to the invention not only do the advantages mentioned in relation to the machine of Figures 11A and 11 B accrue but also that bends can be produced in any plane and that there are obvious cost savings by forming a bent slotted box section in one operation.

In relation to Figures 4A and 4B, Figures 6A and 6B, Figures 8A and 8B, Figures 1 IA and 11 B, and Figures 13A and 138, the outer clamping die can be a workpiece support device according to the invention and constructed similar to that shown in Figure 1 or Figure 2 depending upon the cross-section of the workpiece.

Also the outer clamping die on a conventional machine can be replaced by a workpiece support device according to the invention. The benefits of ths over a conventional outer clamping die are: a greater clamping force can be used; the clamped length can be kept to a minimum for the straights between bends; rapid release of the workpiece, and the fact that tool wear can be taken up.

The machine shown in Figure 14 is a compression bending machine comprising a stationary bend former 176, a clamp or stop 178 holding workpiece 180 and a guide 182. According to the invention the guide 182 is a workpiece support device of a similar construction to that shown in Figures 1 or 2, as can also be the clamp or stop 178.

Figure 15 shows another type of compression bending machine in which a workpiece 184 is supported by two spaced dies 186 and a ram bend former 188 is applied to the workpiece to form the bend. According to the invention, the dies are workpiece support devices of a similar constructions to those shown in Figures 1 and 2, depending upon the cross-section of the workpiece.

Claims (17)

1. A workpiece support device for a bending machine, the device having a support structure with a recess, and a jaw positioned in the recess, the jaw being mounted for pivotal movement between first and second positions, the first position being one in which the jaw cooperates either with another jaw pivotally mounted in the recess or with a wall of the recess to engage a workpiece and the second position being one in which the workpiece is readily removable from or insertable into the recess.

2. A device as claimed in Claim 1 and including means resiliently urging the jaw to the second position so as to assist removal of the workpiece.

3. A device as claimed in Claim 2, wherein the means is a spring located in the base of the recess.

4. A device as claimed in Claim 1,2 or 3, wherein the jaw has an edge providing an axis about which it can pivot.

5. A device as claimed in Claim 1,2 or 3, wherein a side wall of the recess has an edge providing an axis about which the jaw can pivot.

6. A device as claimed in any preceding claim, wherein the jaw has an engagement surface which is in cross-section, a curve.

7. A device as claimed in any one of Claims 1 to 5, wherein the jaw has two flat engagement surfaces arranged substantially perpendicular to each other.

8. A device as claimed in any preceding claim, wherein another jaw is pivotally mounted in the recess, the two jaws being shaped and disposed symmetrically about a plane.

9. A workpiece supporting device for a bending machine substantially as herein described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.

10. A bending machine having a workpiece supporting device as claimed in any preceding claim.

11. A rotary draw bending machine for bending hollow section tube, the machine comprising a bend former and a back guide, wherein the back guide is a workpiece support device as claims in any one of Claims 1 to 6,8 and 9.

12. A rotary draw bending machine for bending angle section, singly or in pairs, hollow rectangular section, slotted hollow rectangular section and open channel rectangular section in which the open side of the channel is to be on the outside of the bend or on either side of the bend, the machine comprising a bend former and a back guide, wherein the bend former has a plain cylindrical surface with no lateral locating flanges and the back guide is a workpiece support device as claimed in any one of Claims 1 to 5,7,8and9.

13. A rotary draw bending machine for bending angle section, singly or in pairs, and open channel rectangular section in which the open side of the channel is to be on the inside of the bend, the machine comprising a bend former and a back guide, wherein the bend former has a plain cylinderical surface with no lateral locating flanges but has an annular central flange for extending into the open side of the channel during bending, and the back guide is a workpiece support device as claimed in any one of Claims 1 to 5,7,8 and 9.

14. A rotary draw bending maching for crush bending hollow section, the machine comprising a bend former and a back guide, wherein the bend former has a plain cylindrical surface with no lateral locating flanges but has an annular central flange for forming the crush, and the back guide is a workpiece support device as claimed in any one of Claims 1 to 5,7,8and9.

15. Acompression bending machine comprising a bend former and a guide or die, wherein the guide or die is a workpiece supporting device as claimed in any one of Claims 1 to 9.

16. A compression or rotary draw bending machine as claimed in any one of Claims 11 to 15, the machine further including a clamping die, wherein the clamping die is a workpiece support device as claimed in any one of Claims 1 to 9.

17. A bending machine substantially as herein described with reference to and as shown in Figures 4A and 4B, or with reference to and as shown in Figures 6A and 6B, or with reference to and as shown in Figures 8A and 8B, or with reference to and as shown in Figures 11A and 11 B, or with reference to and as shown in Figures 13A and 13B, or with reference to and as shown in Figure 14 or with reference to and as shown in Figure 15 of the accompanying drawings.