Bending Machines

A bending machine for forming bends in a sheet material. The bending machine has a pair of spaced relatively fixed forming tools for movement with respect to an unclamped portion of the sheet material to effect corresponding bends in the sheet material.

This invention relates to an improved bending machine for forming bends on 
the edges of sheet metal panels. 
The most generally used method of forming bends in sheet material is by 
means of male and female vee shaped tools in a conventional press brake 
whereby the sheet material is fed into the tools in a horizontal plane and 
the sheet at each side of the fold line is raised upwards as the bend 
progresses. 
In the case of a narrow fold on the edge of a large panel it is necessary 
to manually support the main body of the panel throughout the bending 
process and also when the tools retract and leave the workpiece 
unsupported. Handling problems are also caused when successive bends in 
opposite directions are required, entailing sheet turnover between bending 
operations. A further disadvantage of the vee tool method is the damage to 
the sheet surface which commonly occurs where the point of the male vee 
and the two corners of the female vee contact the material. 
A method commonly used in presswork to form one or more edges of a panel 
simultaneously is to clamp the main body of the sheet and apply a force 
perpendicular to its surface at or near the point where the bends are to 
be formed until the sheet material bends. This method normally requires a 
special tool for each different size of panel and may also result in 
marking of the material where there has been a peak of pressure applied in 
forming the bend. 
One bending machine which uses this method of bending sheet material is 
described in UK Patent Publication No. 2004216A. The machine is a fully 
automatic bending machine requiring no manual intervention and is designed 
primarily for bending the edges of sheet material to form a shallow 
rectangular box, tray or panel. The sheet of metal is held in its centre 
by a vice which is used to slide the sheet material towards a forming tool 
and is also used for rotating the sheet of material so that a different 
edge of the sheet material is facing the forming tool. 
The machine includes a bending press which includes two vertically facing 
bending blades which have a reciprocating motion so that the bending 
blades pass towards and through the plane of the sheet material to form a 
bend. The face of each bending blade is planar and so as the blade comes 
into contact with the sheet material it has a tendancy to slide along the 
material which can cause marking of the material. The application of the 
load is at one point and thus as the bending blade moves towards and 
through the plane of the sheet material the force on the sheet material is 
not constant. In cases where the sheet material has a treated surface such 
as a plastic coating this will cause creasing and marking which is 
unsatisfactory. 
An improvement to the bending maching is enclosed in European Patent 
Publication No. 23894. In this machine at least one of the bending blades 
is adjustably movable towards and away from the clamp which holds the 
sheet material so that a first portion of the bend is carried out by 
applying force at a first distance from the bend and then the bending is 
completed by applying force at a second position closer to the clamp means 
and the finished bend. However the apparatus required for achieving this 
movement of the bending blade towards and away from the bend is very 
complicated and makes the finished machine very costly. 
The bending blades of this bending machine are mounted on a C-shaped 
mounting tool. This means that the distance of the bend to the edge of the 
material is limited by the depth of the throat of the C-shape mounting 
tool. This means that the machine can only be used for forming bends very 
close to the edge of the sheet of material. Additionally the depth of 
throat restriction prevents the use of a variable position back stop. 
According to this invention there is provided a bending machine for forming 
bends in sheet material including clamp means for clamping part of the 
sheet material and a forming tool with which force is applied to the 
unclamped part of the sheet material to effect a bend, characterised in 
that the forming tool has a curved forming surface extending from the end 
of the tool along the side of the tool closest to the clamp means such 
that as the forming tool moves towards and through the plane of the sheet 
material the point of application of the load moves along the sheet 
material from the point of first contact with the forming tool towards the 
clamp, the curve of said surface being such that a substantially constant 
load is applied by the forming tool on the sheet material. 
Thus as the forming tool moves the sheet material is gradually bent such 
that the load applied remains substantially constant so that the material 
surface is not damaged. 
It has been found that an optimum forming tool is produced if the curve is 
arranged such that for each constant increment of the forming tool 
movement, the tangent to the curve at the point of application of the load 
moves through a constant angle. 
However an effective forming tool is produced with a simple curved surface 
with a single radius. With such a curve, the load applied by the tool 
remains substantially constant and the point of application of the load 
moves towards the clamp means as the bend is formed. Thus the effect is 
that the forming tool rolls into contact with the sheet material which 
prevents marking of the surface of the material. Also this rolling contact 
considerably reduces the sliding of the tool along the sheet surface 
exhibited when the forming tool has a planar face. Thus the tendancy to 
mark the surface of the sheet material is substantially reduced. 
With such a tool an effective bend may be formed with substantially no 
peaks of load applied, so that bends in material with treated surfaces may 
easily be formed by using forming tools which only display reciprocating 
movement, thus obviating the requirement for complicated movement of the 
forming tool during formation of the bends. 
Preferably the bending machine includes two forming tools which are 
co-linear and facing each other, positioned above and below the clamping 
means so that bends may be formed in either direction. Preferably the two 
forming tools are connected together in a mounting frame and move in a 
reciprocating motion. 
Preferably the two forming tools and mounting frame extend along the length 
of the sheet material and are connected together only at their ends to 
define a "letterbox" like slot through which sheet material is fed. 
Thus the bending machine in accordance with the invention may be used to 
form bends at any position in the sheet material since the sheet material 
may be fed through the mounting frame up to a variable position back stop 
without obstruction. 
Preferably the direction of the reciprocating motion of the forming tools 
may be varied so that the direction of the force applied may be varied. 
When forming a bend of angle .psi. the material has to be bent to an angle 
of .psi.+.delta. since the sheet material invariably springs back slightly 
the distance .delta.. Thus when a bend of 90.degree. is to be formed a 
reciprocation motion perpendicular to the sheet material is not sufficient 
to form the required bend. Thus it is important that the direction of the 
reciprocating motion of the bending tools may be varied. 
In all cases the angle of the bend produced by the bending machine is 
dependant on the distance moved by the forming tool. Preferably the extent 
of the reciprocating motion may be limited by adjustable stops so that 
bends of substantially different angles may be formed. 
Preferably the clamp means also has means to limit its movement to clamp 
the material so that if it is required to form a flattened or partially 
flattened hem out of the edge of the sheet material the edge of the 
material is moved so that it is beneath the clamp and the clamp is moved 
towards the sheet material to a position just above the sheet material so 
that the edge of the material is flattened into a hem. This is preferably 
in a form of a stop against which the clamp means bears to prevent further 
movement towards the sheet material of the clamp and is known as a 
"scotch". 
Preferably the bending machine includes stops behind the clamp means and in 
front of the clamp means to engage the leading edge and trailing edge of 
the sheet material so that the position of the bend to be formed may be 
accurately controlled. The stops which are positioned behind the clamp 
means may be in the form of contact pads which provide an electrical 
signal when contacted by the edge of the sheet material. This may be by 
closing a circuit on the contact pad, or a circuit between the contact, 
the sheet material and the clamping means of the machine. However when 
used on a surface coated with a non-conducting material a mechanical 
contact such as a microswitch is required. Preferably the machine includes 
at least two back gauge contacts which are slidably mounted on a lateral 
rail running parallel to the bending tools so that accurate measurement is 
achieved with any size of sheet material. 
Preferably the front stops are in the form of disappearing pawl stops which 
are pivoted so that the sheet material may be fed forwards across the 
stops towards the clamp means but cannot be moved backwards from the clamp 
means since the front stops will have rotated back to the position where 
the pawl forms a stop. Preferably the front stops are movable so that 
sheet material of different sizes may be handled. The use of both front 
and back gauges means that the sheet material may be bent very accurately 
taking into account any discrepancies in the starting sheet of material. 
Preferably the bending machine also includes a movable side guide which 
along which the sheet material may be fed towards the clamp means. 
Preferably the distance of the mounting frame on which the bending tools 
are mounted from the clamp means may be variable so that different 
thicknesses of sheet material may be handled. 
Preferably the bending machine is programmable so that a series of bends 
may be formed with either the top or bottom forming tool each operating in 
different sequences and each capable of moving at a variety of different 
angles and each capable of variable stroke length limitation. 
The position of the back and front stops are variable and programmable so 
that the position of each bend may be controlled by a microprocessor. Some 
or all of the functions of the bending machine may be programmed. 
The apparatus described may be used to bend a sheet of material at any 
position on the material by choosing different positions of back and front 
stops. 
However a particularly useful embodiment of the invention has been 
developed which is useful for forming a shallow rectangular box, tray or 
panel. 
In such apparatus two parallel sides of the tray or box are formed and then 
one perpendicular edge is bent. In this case the edges of the clamp are 
shaped to allow the formed edges to slide onto the clamp. 
The edge of the clamp running parallel to the forming tool has to equal the 
width of the sheet material. Preferably the clamp may be contracted 
laterally to facilitate removal of the half-finished, or finished box or 
tray from the machine when the bend has been completed. 
Preferably this contracting and expanding of the clamp may be programmable. 
To allow the machine to be used to make different sized boxes or trays, 
preferably the uncontracted width of the clamp may be variable. This may 
be in the form of removable spacers. 
The bending machine may be hydraulically or mechanically operated, or a 
combination thereof.

In FIGS. 1, 2 and 3 the bending machine is shown including two forming 
tools 2 and 3. The bending machine shown in the other figures is exactly 
the same as the first example but includes only one forming tool 3. 
Components of the second machine will have the same reference numbers as 
corresponding components of the first machine. 
A first bending machine 1 includes two forming tools 2 and 3 between which 
is defined a longitudinal slot 4 through which the sheet material 5 may be 
fed up to a back stop 6 and up to a front stop 7. When the sheet material 
5 is in position it is clamped using clamp 8 which is controlled by 
hydraulic cylinders 9. 
Forming tools 2 and 3 extend across the length of the sheet material 5 and 
are connected together at each end to a reciprocating support 10. The 
movement of support 10 is controlled by hydraulic cylinders 11. A 
reciprocating support guidance 12 is pivotally mounted via pivot means 13 
so that the angle of load application may be varied. The angular movement 
of the guidance means 12 is controlled by hydraulic cylinders 14. 
Each forming tool 2 and 3 has a forming surface 15 which extends from the 
tip 16 of the tool 2 or 3 along the side of the forming tool 2 or 3 
closest to the clamp 8. The curve 15 is such that for a constant increment 
of the forming tool movement the tangent of the curve at the point of 
application of the load varies by a constant angle. This means that the 
load applied at each point of application is substantially constant and a 
smooth bend is formed. The operation of the formation of the bend is shown 
in detail in FIG. 1. As forming tool moves distance x the tangent of the 
curve increases by .theta., so that the vertical component of the force 
applied by the forming tool 3 gradually decreases. As the forming tool 
moves the point of application of the load moves towards clamp means 8 
therefore nearer to the bend. Thus the effective load on the sheet 
material 5 remains substantially constant. The forming tool rolls into 
contact with the sheet material 5 so that the surface of sheet material 5 
is not damaged and will not have any marks or creases on it. 
The bending machine includes a microprocessor 17 which is coupled to the 
hydraulic cylinders 11, hydraulic cylinders 9 and the front stop 7 and 
rear stops 6 so that the operation of the bending machine may be 
controlled. 
In the second bending machine 18 there is only one bending tool 3. The back 
gauge 6 comprises two electrical probes 61 which are coupled to the 
machine by cables 62. When sheet material 5 contacts stop 61 power is 
supplied to cable 62 to initiate the bending cycle. The probes 61 are 
slidable along lateral rod 63 so that the probes 61 may be spaced apart if 
the sheet material 5 is wider. The rod 63 is coupled via screw box 64 to 
cog 65 to drive belt 66. Movement of drive belt 66 causes rotation of cog 
65 and movement of lateral rod 63 in a direction towards and away from 
clamp means 8. 
A motor (not shown) drives the drive belt 66 via an encoder 67. The encoder 
67 is coupled to the microprocessor 17 and is used to control the position 
to which the lateral rod 63 is moved. 
Front stops 7 comprise a plurality of disappearing stops 71 which comprise 
pivotally mounted pawls 72 which are biased upwards. When sheet material 6 
is fed forwards towards the clamp 8 the pawls 72 are pushed downwards to 
allow the sheet to move forwards. The pawls then release to form a stop 
against which the material 5 cannot move. Thus the position of the 
trailing edge of the sheet is fixed. The front stop 7 includes 4 rows 73 
of stops 71. Three of the rows 73 include three stops 71 and a middle one 
74 includes seven stops 71. The rows 73 are connected to each other by 
framework 75 which is movable towards and away from the clamp means 8. The 
distance movable by the framework 75 is greater than the distance between 
two adjacent stops 71 so that the position of the front stop 71 can be 
varied up to the full length of the longer member 74. 
The movement of the frame 74 is similar to the movement of lateral slide 
rods 63 described above. 
The position of the main motor 19 is shown clearly in FIG. 9. The motor is 
any standard A C Squirrel cage motor. The motor 19 is coupled via a bell 
housing 191 to an hydraulic pump 192. The hydraulic pump 192 supplies 
hydraulic power for actuation of all the control and operating cylinders. 
Clamp 8 comprises an upper clamp member 821 and a lower member 822. The 
upper clamp member 821 comprises a plurality of spacer members 81 and two 
outer members 82. In order to accommodate the shape of the box produced by 
the sheet material the clamp 8 includes a foot 83 facing towards the 
forming tool 3. Also the two end members 82 include laterally extending 
feet 84 which accommodate two completed parallel sides of a box when a 
perpendicular to the parallels is being formed. Within each of end members 
82 is a hydraulic cylinder 85 which when actuated bears against auxiliary 
spacer members 81 urging the two end members 82 towards each other. A 
wedge shaped member 86 is movable into a wedge shaped hole 87 formed in 
two inner members 88. Hydraulic cylinder 89 is pivotally connected to 
mounting means 891 which is pivotally connected to wedge shape member 86. 
When hydraulic cylinder 89 is actuated the mounting means 891 rotates and 
forces the wedge shape member 87 between inner members 88. If pressure is 
released from hydraulic cylinder 89 the wedge shaped member 87 moves away 
from inner members 88. Pressure is applied to hydraulic cylinders 85 which 
allow the end members 82 to move inwards to allow the clamp to contract. 
Hydraulic leads 851 to the cylinders 85 and hydraulic leads 892 to 
hydraulic cylinder 89 are coupled so that the operation of the cylinder is 
synchronized. The width of the clamp 8 produced by inner members 88 spacer 
members 81 and end members 82 can be varied by adding further spacer 
members 81 between the inner member 88 and the end member 82. The clamp 8 
is mounted on a lateral mounting means 811 which extends across the width 
of the machine and includes groove 812 into which the spacer members 81 
fit. Each spacer member 81 includes a lateral groove 813 which is 
engagable by a pivoting clamp 814 pivotally mounted on pin 815 which runs 
laterally over the machine. Handle 816 is used to pull clamp means 814 out 
of contact with the spacer means 81 to allow changing of the spacer 
members 81 along the width of the machine. The feet 83 of the spacer means 
81 are replacable since they are fixed to the spacer means 81 by means of 
screws 817 which are easily removable. 
Sheet material is fed into the bending machine on a mounting table 21 
including a plurality of bearing 22 to allow the sheet material 5 to roll 
easily into position. 
The table 21 is movable from a first raised position (A) level with lower 
clamp 822 to a second lowered position (B) beneath the level of the clamp 
822. 
The sheet material 5 is fed forwards into position with the table 21 raised 
to clear the front stops 7. The table 21 is then lowered and the sheet 
material bears on the frame 75 of the front stops. 
The clamp 8 includes mean 91 for limiting the downward stroke of hydraulic 
cylinder 9. Stop 91 is connected to hydraulic cylinder 92 so that it is 
movable from a position where it interferes with the downward stroke of 
cylinder 9 to a position where it is retracted and does not interfere with 
this movement. In normal operation of the machine scotch 91 is fully 
retracted and hydraulic cylinders 9 cause the clamps to clamp firmly on 
the sheet material 5. However when it is required to form a hemmed edge 
the edge of the material 5 is placed under the clamp 8 and hydraulic 
cylinder 92 pushes scotch 91 into position. The hydraulic cylinder 9 then 
moves downwards until it contacts scotch 91 whereupon movement downwards 
of clamp 8 stops. A rotatable gauge 93 is used for finely adjusting the 
effect of scotch 91 on the movement of the clamp. 
The angle of approach of bending tool 3 may be varied by a movement of 
lever 31 which is coupled to reciprocating support 10 which controls the 
angle of the reciprocating movement of bending tool 3. 
Rotation of lever 31 rotates an eccentric shaft 311 running laterally of 
the machine. Shaft 311 is connected via link 322 to reciprocating support 
10. The rotation of shaft 311 causes link 312 to reciprocate and causes 
support 10 to pivot about pivot point 11. This changes the angle of 
approach of bending tool 3. 
Handle 32 is used to vary the distance of bending tool 3 from clamp means 8 
by movement of pivot point 11. A shaft 321 is slightly eccentric with 
respect of pivot point 11. Rotation of handle 32 relates shaft 321 which 
causes slight movement of bending tool 3 with respect to the clamp 8. Thus 
different thicknesses of material 5 may be accommodated. 
A further handle 33 is used for varying the movement of the bending tool 3 
by varying the stroke of hydraulic cylinder 11 which controls movement of 
forming tool 3. Within the cylinder 11 is a bore 111 through which runs a 
lateral shaft 33 connected via a chain drive (not shown) to handle 33. The 
lateral shaft 33 includes an eccentric portion 332 within bore 111 so that 
rotation of handle 33 moves the cylinder 11 vertically which changes the 
position of the stroke of the cylinder 11. This means that the position of 
the movement of the bending too 3 changes so that the end position of the 
movement changes to allow a different angled bend to be formed. 
Preferably the positions of the stops and the angle and position of the 
reciprocating motion of the bending tool 3 are preprogrammed to the 
microprocessor 17 for each particular shape required to be made by the 
bending machine. The operator of the machine signals to the microprocessor 
that the first bend is to be made which sets the first rear stop to its 
required position and the position and extent of movement of the forming 
tool is preprogrammed. The operator then feeds the sheet material into the 
back stop and the bend is effected at the required position. 
A side guide 26 is positioned at the front of the machine. It is used to 
guide one side edge of the sheet material 5 towards the bending tool 3. 
The side guide 26 is slidable across the front of the machine so that 
different widths of material may be handled. The movement of side guide 26 
is controlled in a similar manner to the movement of back stops 6 and 
front stops 7. 
Across the front of the machine is a photoelectric guard (not shown) which 
automatically shuts off operation of the machine if any foreign body (for 
example, a hand) passes through the guard. 
FIG. 21 shows schematically how a hemmed safe edge may be formed using the 
scotch limiting the clamps movement. The edge of the sheet material is 
bent to an angle of over 90.degree. in two steps. The sheet material is 
then pulled so that the end of the material is under the clamp 8 and the 
clamp 8 is brought downwards to form a hemmed edge 23. 
A method of making box 24 from blank 25 will now be described to clarify 
the operation of the machine. The machine may be used to make any number 
and shape of bends according to the programme in the microprocessor 17. 
1. Sheet 25 is loaded such that edge A contacts back guage 61 and side B is 
in contact with the side guide 26. 
2. Clamp 8 descends to its clamped position. 
3. Back gauge 61 is retracted. 
4. Bending beam 3 is raised to produce its first bend. 
5. Bending beam 3 is then lowered. 
6. The sliding rod 63 carrying the back gauges is then moved to its second 
position. 
7. Clamp 8 is raised to clear the component. 
8. The back of the component is fed towards the back gauge 61 to A1. 
9. Clamp 8 is lowered. 
10. Back gauge 61 is retracted. 
11. Bending beam 3 is raised. 
12. Bending beam 3 is lowered. 
13. Clamp 8 is raised to clear the component. 
14. The component 5 has to then be pushed inwards to clear the foot 83 of 
the clamp. 
15. Clamp 8 is fully raised. 
16. Slide guide 26 is moved to its extreme left. 
17. Table 21 is raised so that the component may slide easily out of the 
clamp over bearings 22 and is then rotated through 180.degree.. 
18. The side guide 26 is returned to its first position. 
19. The front gauge 71 is moved to its first position. 
20. Table 21 is lowered. 
21. Component is located with A2 against front gauge 61 so that the 
distance between the bend A2 and the bend C1 to be formed is exactly as 
required. Side D is now fed along the side guide 26. 
22. Clamp 8 is lowered. 
23. Bending tool 3 is raised. 
24. Bending tool 3 is lowered. 
25. Clamp 8 is raised to clear the component. 
26. The front gauge is moved to its second position. 
27. Edge D is maintained in contact with the side gauge and A2 with the 
front gauge 71. 
28. Clamp 8 is lowered. 
29. Bending beam 3 is raised. 
30. Bending beam 3 is lowered. 
31. Clamp 8 is raised to clear the component. 
32. The component is pushed inwards to the foot 83 of the clamp 8. 
33. Top clamp is raised fully. 
34. Side gauge is moved to its next position. 
35. Table 21 raised. 
36. Component withdrawn and rotated through 90.degree.. 
37. Back gauge 71 is moved to its next position. 
38. Table 21 lowered. 
39. C2 is placed against the side guide 26 and B is located on back guage 
71. 
40. Clamp 8 descends. 
41. Back guage 71 retracts. 
42. Forming tool 3 is raised. 
43. Forming tool 3 is lowered. 
44. Back gauge 71 to its next position. 
45. Clamp 8 is raised to clear component. 
46. B1 is located against back gauge 71. 
47. Clamp 8 is lowered. 
48. Back gauge 71 retracted. 
49. Bending tool 3 raised. 
50. Bending tool 3 lowered. 
51. Clamp 8 is raised to clear component. 
52. Component pushed forwards to clear foot 83. 
53. Clamping tool 81 contracted by hydraulic cylinders 85 and 89 to allow 
feet 84 to clear sides C and A of the box. 
54. Clamp 8 fully raised. 
55. Table 21 raised. 
56. Component withdrawn and rotated through 180.degree.. 
57. Front gauge 71 to next position. 
58. Table 21 lowered. 
59. Component fed in with A2 to side guide 26 and B2 against front gauge 
71. 
60. Clamp 8 lowered. 
61. Forming tool 3 raised. 
62. Forming tool 3 lowered. 
63. Clamp 8 raised. 
64. Front gauge 72 to next position. 
65. A2 is maintained against side guide 26 and B2 at front gauge 71. 
66. Clamp 8 lowered. 
67. Forming tool 3 raised. 
68. Forming tool 3 lowered. 
69. Clamp 8 raised to clear component. 
70. Clamping tool retracted so that component clear feet 84 of clamp. 
71. Component pushed inwards to clear foot 82. 
72. Top clamp 8 fully raised. 
73. Table 21 raised. 
74. Finished component withdrawal. 
75. Table 21 lowered. 
76. Back gauge and side guide returned to first position. 
77. Top clamp expanded to its original size.