GB2160799A - A bending machine and a die changing system therefor - Google Patents

Abstract

A bending machine comprises a lower die 21F or 21R for supporting a sheet metal workpiece, an upper die 41F or 41R for gripping the workpiece by pressing the same against the lower die, the upper die being mounted on a lower part of a vertically movable ram 27, a vertically movable bending beam 47F or 47R for upwardly bending one edge of a workpiece gripped between the upper and lower dies, and a tapered guide member 111F or 111R mounted on the ram for guiding the bending beam towards the upper die during a bending stroke. The machine can bend both edges of sheet metal in two stages by the sets of dies, rams and guide members. The guide members are adjustable by means 115. The upper dies can be supplied from elevator- supported storage racks having a plurality of stages. Any desired combination of upper die elements can be transferred from the racks to form an upper die 41F or 41R to suit the width of sheet metal. <IMAGE>

Description

SPECIFICATION A Bending Machine and a Die Changing System Therefor This invention relates to a bending machine for bending a sheet metal workpiece and to a die changing system therefor, and, in particular, to a machine which maintains a sheet metal workpiece in a horizontal plane so that it can be conveyed, for example in a horizontal direction, and which bends the edge of the workpiece in, for example, an L-shape and to a die exchange system for such a bending machine which is capable of quickly changing a die made up of separate sections assembled to a length corresponding to the width of the workpiece.

A previously proposed machine which holds a workpiece horizontally and bends an edge of that workpiece into an L-shape is called a tangent bender and is provided with a bottom die which supports the workpiece from the bottom and a freely vertically movable top die which presses the workpiece from the top against the bottom die, as well as a freely rotatable bending beam which bends the edge of the workpiece upwards while the workpiece is secured by the application of pressure between the bottom die and the top die. Generally, the bending beam is supported at each end, so that when the workpiece is being bent there is a tendency for inflection to occur near the centre of the bending beam because of the drag of the workpiece, making it difficult to carry out the bending operation with a satisfactory degree of precision.Accordingly, to prevent this inflection, the width of the bending beam is increased near the centre thereof. Thus, because of the bending beam of a conventional tangent bender is comparatively wide near the centre thereof, if a workpiece is conveyed whilst the tangent bender is positioned in the process line where the bending operation is to be carried out, the wide part of the bending beam hinders positioning on the transportation roller. This is disadvantageous for a process line where the object is a workpiece of comparatively small width.

Also, in a process where one edge and then the other edge of a sheet-like workpiece are to be bent continuously, when a pair of tandem benders are positioned in opposition with the process line therebetween, it is necessary to separate the bender beams of the tandem benders by a comparatively large distance to prevent interference therebetween which is not a desirable situation.

In addition, the top die in a conventional tangent bender is mounted on the bottom of a free vertically movable ram, is intended to conform to sheet metal workpieces of diverse widths and generally comprises a divided die which can be assembled in diverse selected lengths. More specifically, this top die is made up of a plurality of divided leaves which can be appropriately combined in diverse lengths. In order to change this top die to conform to the width of a workpiece, a die-changing robot may be used, and each split leaf can be mounted on or removed from the ram. Accordingly, a considerable amount of time is used in mounting the top die on the ram when making a change therein, making it difficult to improve operating efficiency.

It is an object of the present invention to enable the provision of a bending machine and a die changing system therefor whereby the above disadvantages may be overcome or at least mitigated.

According to a first aspect of the present invention, there is provided a bending machine, comprising upper and lower dies for gripping a sheet workpiece therebetween, a bending beam for bending an edge of a workpiece gripped between the upper and lower dies, and guide means for guiding the bending beam during a bending operation, wherein the guide means is connected to the die which is on the other side of the workpiece from the bending beam during bending operations.

According to a second aspect of the present invention, there is provided a die changing system for a bending machine, comprising a plurality of elevator means, each of which comprises a plurality of stages for storing dies separately, means for moving the elevator means individually so as to obtain any desired combination of the dies stored on the stages, and means for disposing a desired combination of dies in a desired position in a bending machine by transferring the same from the stages.

The present invention thus enables the provision of a bending machine which can be equipped with a narrow bending beam to bend the edge of a sheet metal workpiece secured to the top of a bottom die by means of a top die.

The present invention also enables the provision of a bending machine which can simultaneously bend edges of a sheet metal workpiece.

The present invention further enables the provision of a bending machine which is capable of bending the edge of a workpiece at a desired angle.

The present invention still further enables the provision of a bending machine which is capable of easily adjusting the clearance between the top die and the bending beam in accordance with the thickness of the workpiece.

The present invention still further enables the provision of a die changing system which allows easy changing of the top die of a bending machine, whereby the top die can be assembled in desired lengths.

The present invention still further enables the provision of a die changing system which allows simultaneous changing of a plurality of top dies provided in parallel on the bending machine.

According to a preferred aspect of the present invention, a bending beam is constructed in such a way as to bend the edge of a sheet metal workpiece upwards from below, while the sheet metal workpiece is secured by being pressed between a bottom die and a top die. The bending beam is constructed so that its upper position and the distance between the bending beam and the top die are freely adjustable. In addition, the bending machine is constructed symmetrically, with pairs of bottom dies, top dies, and bending beams being positioned in parallel. Also, a storage section, which stores a plurality of top dies divided into diverse lengths, is provided with a plurality of rows and stages. Because the plurality of diverse rows of the storage section can be assembled in diverse ways, the top die can be assembled in appropriate desired lengths.A configuration linking a plurality of diechanging mechanisms allows them to be used simultaneously.

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 drawings, in which:~ Figure 1 is a front elevational view of a bending machine in accordance with the present invention, Figure 2 is a sectional view taken along the line Il-Il of Figure 1, Figure 3 is an enlarged sectional view taken along the line Ill-Ill of Figure 1, Figure 4 is an enlarged sectional view taken along the line IV~IV of Figure 1, Figure 5 is a partial sectional view taken along the line V-V of Figure 4, corresponding to Figure 2, Figure 6 is an enlarged sectional view taken along the lineVI-VI of Figure 1, Figure 7 is an enlarged sectional view taken along the lineVIll-VIll of Figure 1, Figure 8 is an enlarged drawing of the part indicated by an arrow VIII in Figure 2, and Figure 9 is a sectional view taken along the line IX-IX of Figure 8.

Referring first to Figures 1 and 2, a bending machine 1 for bending the edge of a sheet metal workpiece W comprises a frame body 3 having a base 5, a left side frame 7 and a right side frame 9, which are erected on the base 5 to form the sides of the frame body 3, and a plurality of upper beam members 11 F and 11 R, which are supported on the side frames 7 and 9 at the left and right edges thereof and separated from front to rear.

Close to the centre of the base 5 are erected support plates 13A and 13B and both edges of the support plate 13B, which extends to the left and to the right, are connected to the side frames 7 and 9. A horizontal plate 15, connected to the left and right edges of the side frames 7 and 9, is supported on the upper section of both support plates 13A and 13B. A plurality of die support plates 1 7F and 1 7R, of which the left and right edges are connected to the side frames 7 and 9, are erected on the upper surface of the horizontal plate 15 with a suitable distance between then from front to rear. The front and rear die support plates 17F and 17R are mutually connected by means of a plurality of connecting members 19 which are elongated in the front and rear directions.A plurality of front and rear bottom dies 21 F and 21 R, of which both edges are connected to the side frames 7 and 9, are respectively supported on the upper sections of the connecting members 19.

These bottom dies 21 F and 21 R support the workpiece W. On their respective suitable surfaces, front and rear, a plurality of suitable sensors 23F and 23R such as, for example, limit switches or proximity switches for detecting the width of the workpiece W, are mounted at suitable intervals. The sensors 23F and 23R are installed to conform to a plurality of rotary activators 25F and 25R, which will subsequently be explained. The sensors 23F and 23R, by detecting the presence or absence of the workpiece W, act to control the actions of the conforming rotary actuators 25F and 25R.

In addition, as can be understood from Fig. 1 and Fig. 2, in the upper position of the bottom dies 21 F and 21 R, a ram 27 is positioned so that it may move freely in the vertical direction. The front and rear width of the ram 27 is a larger distance than the front and rear distance of the bottom dies 21 F and 21 R, and is extended a larger distance in the left and right direction. Both sides of the ram 27 in the left and right directions are rotatably connected to a piston rod 31 R of an elevating cylinder 31 mounted through a bracket 29 on the inside surfaces of the side frames 7 and 9. Accordingly, the ram 27 is caused to move in the vertical direction by the action of the elevating cylinder 31.

Superpositioned on the ram 27 to guide it, a guide block 33 is mounted superpositionedly on the center section of the rear surface of the upper beam member 11 F. A trapezoid-shaped guide bracket 35 is vertically mounted on the central upper surface of the ram 27. A plurality of roller brackets 39, which provide for the free rotation of a guide roller 37 which moves in a freely rolling manner on the superpositioned surface of the guide block 33, are mounted on the guide bracket 35. Accordingly, the ram 27 is guided in the side block 33, and moves superpositionedly in the vertical direction.

In the front and rear sections of the bottom surface of the ram 27, as previously outlined, the top dies 41 F and 41 R, which secure the workpiece W by pressing it against the bottom dies 21 F and 21 R, are respectively installed in a freely dismountable manner. These top dies 41 F and 41 R are made up of a plurality of split leaves of appropriate dimensions divided into a large number of parts which are assembled and used in appropriate lengths to conform to the width of the workpiece W. A plurality of pressure cylinders 43F and 43R, which are used for applying pressure to the ram 27 when the workpiece W is pressed against the bottom dies 21 F and 21 R by the top dies 41 F and 41 R, is installed so that the pressure cylinders 43F and 43R are spaced at suitable intervals on the bottom surfaces of the upper beam members 11 F and 11 R. On the upper surface of the ram 27, the rotary actuators 25F and 25R are mounted to conform to each of the pressure cylinders 43F and 43R. On the rotational axis of each of the rotary actuators 25F and 25R a plurality of L-shaped movable blocks 45F and 45R is mounted so that the blocks 45F and 45R can freely move to a position directly under the pressure cylinders 43F and 43R and a position separated from the position directly under the pressure cylinders 43F and 43R.

As a result of this construction, only the equivalent rotary actuators 25F and 25R act according to the action of the sensors 23F and 23R which have detected the workpiece W. Accordingly, only some members of the movable blocks 45F or 45R which conform to the position of the workpiece W is positioned directly under the pressure cylinders 43F and 43R. Only the part of the ram 27 which corresponds to the workpiece W is pressed down by the pressure cylinders 43F and 43R.

Accordingly, even in the case where there is uneven distribution on one side of the workpiece W, the workpiece W can be pressed uniformly, and a uniform bending is carried out, further improving the precision of the operation.

In order to bend upward the edge of the workpiece W, which is secured by the pressure of the top dies 41 F and 41 R against the bottom dies 21 F and 21 R, a plurality of bend-beams 47F and 47R are provided on the inner sides of the bottom dies 21 F and 21 R so that they can move freely in the vertical direction. More specifically, the bend-beams 47F and 47R are mounted on the upper portion of a plurality of bending rams 49F and 49R which are installed so that they have unrestricted vertical movement. On the lower portion of each of the bending rams 49F and 49R, a plurality of eccentric shafts 53F and 53R, which are suppnrted in a freely rotatable manner on the horizontal plate 15, are matingly supported at their eccentric section through a plurality of brackets 51 F and 51 R.

Accordingly, the eccentric shafts 53F and 53R rotate in a suitable manner, causing the bending rams 49F and 49R to be elevated. It will now be understood that by the elevation of the bending beams 47F and 47R beyond the upper surfaces of the bottom dies 21 F and 21 R, the edge of the workpiece W, which is pressed against the bottom dies 21 F and 21 R by the top dies 41 F and 41 R, will be bent in the upward direction.

These bending rams 49F and 49R, are forced in the inner direction by means of suitable metal springs 55F and 55R, such as coil springs, mounted elastically between the die support plates 17F and 17R. However, a large inclination to the inner direction of the bending rams 49F and 49R is regulated by a plurality of regulating members 57F and 57R provided on the connecting member 19 which is fitted so that it pierces a cut-out section 49N in the bending rams 49F and 49R.

A plurality of arm members 59F and 59R are integrally and respectively mounted on the eccentric shafts 53F and 53R to rotate these eccentric shafts 53F and 53R. The leading sections of a plurality of piston rods 63F and 63R of a plurality of bending cylinders 61 F and 61 R are pivotally connected to and supported on the leading section of these arm members 59F and 59R. Accordingly, it will now be understood that the eccentric shafts 53F and 53R are caused to rotate by means of the reciprocating action of the piston rods 63F and 63R of the bending cylinders 61 F and 61 R.

The bases of the bending cylinders 61 F and 61 R are pivotally attached to a plurality of brackets 65F and 65R which are secured to the base 5. These bending cylinders 61 F and 61 R are constructed so that they freely vary position proportional to the stroke of the piston rods 63F and 63R. Specifically, as is shown clearly in Fig.3, a cylinder cap 69 is integrally mounted on one end of the cylinder body 67 of the bending cylinders 61 F and 61 R, and at the shaft center of this cylinder cap 69, a rotating rod 73 is removably and rotatingly supported by a plurality of bearing 71.The inner end section of the rotating rod 73 extends close to the other end of the cylinder body 67, and, a communication hole 77, which communicates with a port 75 formed in the cylinder cap 69, is pierced at the center section of the shaft. A guide key 79 is integrally mounted on the rotating rod 73, and mates with a cuffnut member 81 in a freely slideable manner. In addition, a spherical washer 85, which can freely throttle the aperture 83 of the communication hole 77 which communicates with the cylinder body 67, is mated in a freely slideable manner with the inner end section of the rotating rod 73.

The nut member 81 is screwed into a female screw section 87, which is formed in the inner circumferential surfaces of the cylindrically formed piston rods 63F and 63R. The nut member 81 is prevented from coming out of the female screw section 87 by a stopper ring 89, which is secured on the inner ends of the piston rods 63F and 63R. A spring casing 93, into which is fitted a spring 91, such as an initially coned disc spring, is installed on the outside of the end section of the rotating rod 73, and a needle 95 is integrally mounted on that spring casing 93. This needle 95 is formed to press a ball-shaped check valve 99 which is positioned inside a drain port 97 formed in the cylinder cap 69.

In addition, a pulley 101 is mounted on the outside end section of the rotating rod 73. A belt 103 runs between this pulley 101 and a pulley 107 mounted on the output shaft of a motor 105, such as a pulse motor or a servo motor. This motor 105 is supported by a bracket 109 on the cylinder body 67.

From this configuration, the rotating rod 73 is driven by the motor 105, causing it to rotate, upon which the nut member 81 is rotated against the piston rods 63F and 63R, and moves along with the female screw section 87. Accordingly, after the nut member 81 is suitably positioned, the piston rods 63F and 63R are caused to protrude by feeding pressurized oil from the port 75.

By means of the protruding action of the piston rods 63F and 63R, the nut member 81 comes into contact with the spherical washer 85, upon which the spherical washer 85 moves in the direction of the shaft. The aperture 83 is throttled so that the protruding action of the piston rods 63F and 63R is reduced in speed. Subsequently, when the piston rods 63F and 63R next protrude they encounter resistance by the spring 91, and the rotating rod 73 moves in the direction of the shaft. The needle 95 presses against the check valve 99 and because one part of the oil pressure in the cylinder 67 is discharged, the protruding action of the piston rods 63F and 63R is halted.

As has already been explained, the strokes of the piston rods 63F and 63R in the bending cylinders 61 F and 61 R can be optionally adjusted by adjusting the position of the nut member 18 under the control of the motor 105. Therefore the amount of rotation of the eccentric shafts 53F and 53R can be adjusted.

Specifically, by adjusting the amount of rotation of the eccentric shafts 53F and 53R the amount of elevation of the bend-beams 47F and 47R can be adjusted, and the bending angle of the edge section of the workpiece W can be adjusted.

Now referring to Fig. 2,4 and 5, when the edge of the workpiece W is bent by the bend-beams 47F and 47R, the wedge-shaped guide members 111 F and 111 F, by which the bend-beams 47F and 47R are steered in the direction of the top dies 41 F and 41 R, are mounted in a position on the lower surface of the ram 27 which is freely adjustable vertically.

More specifically, a plurality of guide section 113, which are separated in suitable spacing in the left and right direction, are mounted vertically in the central section of the front and rear direction of the ram 27. The wedge-shaped guide members 111 F and 111 F are moved to contact the front and back surfaces of these guide sections 113. Each of the wedge-shaped guide members 111 F and 111 R is formed as a slanting surface, in a position opposite the bend-beams 47F and 47R, slanting to the upper side approaching the side of the top dies 41 F and 41 R.Accordingly, when the bending-beams 47F and 47R are elevated to bend the end of the workpiece W by the action of the bending cylinders 61 F and 61 R, the bend-beams 47F and 47R are steered toward the top dies 41 F and 41 R by the wedge-shaped guide members 111 F and 111 R, and the edge of the workpiece W is bent.

As has already been explained, when the edge of the workpiece W, which is secured by being pressed against the bottom dies 21 F and 21 R by the top dies 41 F and 41 R, is bent by the bend-beams 47F and 47R,the force exerted on the bend-beams 47F and 47R is received by the guide section 113 of the ram 27. Accordingly, a companion force is transmitted to the top dies 41 F and 41 R through the ram 27 so that the forces exerted to the top dies 41 F and 41 R, and the bend-beams 47F and 47R are balanced, and precision in the bending process is easily obtained.

Referring again to Fig. 2,4 and 5, a screw section 115S formed on the lower end of each of a plurality of adjustment frames 115, supported in a freely rotatable manner on the ram 27, is screwed into each of the respective guide members 111 F and 11 R. Also, a plurality of worm gears 1 17F and 1 17R is fixed on the respective upper ends of each adjustment frame 115.A plurality of worms 121 F and 121R, to which the rotating shafts 119F and 1 19R are fixed, engage the worm gears 1 17F and 117R. Each of the rotating shafts 1 19F and 119R is supported horizontally in a freely rotatable manner on the upper surface of the ram 27 by a plurality of bearing blocks 123F and 1235. A plurality of pulleys 127F and 127R is mounted on the ends of the rotating shafts 1 19F and 119R, and each of the pulleys 127F and 127 is fitted with a chain or belt 125R interconnectively linking the rotating shafts 1 19F and 1 19R. In addition, one of the rotating shafts 121R, is interconnectively linked to a motor 133 mounted on the ram 27, by the pulley 129 and the belt 131. Further, each of the wedge-shaped guide members 111 F and 111 R is formed so that they interlock with one another, and simultaneously move the same amount in the vertical direction.

As has already been made clear, it is possible to adjust the vertical position of each wedge-shaped guide member 111 F and 111 F, simultaneously and in the same amount, by the drive action of the motor 133, and to adjust the amount of steering in the direction of the top dies 41 F and 41 R can be adjusted to correspond to the thickness of the workpiece W, over the complete range of thicknesses.

In this embodiment of the workpiece W between the bottom die 21 F and the top die 41 F, the bending machine 1 bends the edge of one side of the workpiece W (the right-hand edge in Fig. 2).

Subsequently, the ram 27 is elevated and the workpiece W is released. The workpiece W moves in the right hand direction in Fig. 2, and after the workpiece W is secured between the bottom die 21 R and the top die 41 R, the other edge of the workpiece W (the left-hand edge in Fig. 2) is bent. A plurality of positioning devices 135 are provided for positioning both edges of the workpiece Was outlined above. A specific drawing is omitted, however, but the above positioning devices 135 are positioned with a suitable spacing between the bend-beam 47F or 47R.A stopper 137 on the positioning device 135, which is for positioning the edge of the workpiece W, moves in the right and left directions in Fig. 2, and, as well as being provided in a freely positionable manner, it does not cause interference when the workpiece W is passing, while causing an impasse on the pass-line of the workpiece W for positioning when the workpiece is processed.

The length of the top dies 41 F and 41 R is intended to be variable to comply with the width of the workpiece W, and these top dies 41 F and 41 R are supported so as to move freely in the left and right directions of the ram 27. Also, a rack device 139 is installed on one side of the frame 7 to provide a plurality of storage sections where the top dies 41 F and 41 R can be freely stored.

As is made clear in Fig. 1,6, and 7, a plurality of guide rails 143F and 143R, and 145F and 145R, are perpendicularly mounted on the front and back surfaces of a perpendicularly mounted support frame 141 on the outside surface of the frame 7.A plurality of first elevating racks 147F and 147R are supported in a freely elevatable manner on the guide rails 143F and 14so. Also, a plurality of second elevating racks 149Fand 149R, which are positioned adjacent to the first elevating racks 1 47F and 147R, are supported in a freely elevatable manner on the guide rails 145F and 145R. Each of the first elevating racks 147F and 147R are connected by a plurality of vertical ropes or chains 153U and 153L running between a plurality of pulleys or sprockets 151 U and 151 L, which are installed in a freely rotatable manner on the upper and lower sections of the support frame 141. In addition, each of the second elevating racks 149F and 149R, are, in the same manner, connected by a plurality of vertical ropes or chains 157U and 157L running between a plurality of pulleys or sprockets 155U and 155L, which are installed in a freely rotatable manner on the upper and lower sections of the support frame 141.

Accordingly, the first elevating racks 147F and 147R and the second elevating racks 149F and 149R are respectively linked and move vertically. For example, when the front elevating racks 147F and 147R are elevated, the back elevating racks 149F and 149R are made to descend.

In order to move the first elevating racks, 147F and 147R, and the second elevating racks, 149F and 149R, individually in the vertical direction, a first elevating screw frame 1,57 and a second elevating screw frame 159 are supported in a freely rotatable manner on the support frame 141. These first and second elevating screw frames 157 and 159 are interconnectively linked to a plurality of first and second control motors 161 and 163 mounted on the support frame 141. In addition, a plurality of nut members 165 and 167, which are screwed to the first and second elevating racks 147F and 149F.

Accordingly, the first elevating racks 1 47F and 147R and the second elevating racks 149F and 149R can be individually elevated by the individual action of each control motor 161 and 163.

A plurality of stages of storage sections 169a to 169f, and 171Ato 171Fare respectively provided in each of the first and second elevating racks 147F and 147F, and 149R, to support the storage of a suitable number of the top dies 41 F and 41 F. On each storage section 169a to 169f in the front first elevating rack 147F, a variety of lengths of top dies 41 F are stored in order from the bottom stage while the equivalent top dies 41 R in the rear first elevating rack 147R are stored in order from the bottom stage.

In the same way, on each storage section 169A to 169F in the front second elevating rack 149F, a variety of lengths of top dies 41 F are stored in order from the bottom stage, and on each storage section 169A to 169F in the rear first elevating rack 149R the equivalent top dies 41 R are stored in order from the bottom stage.

Accordingly, the length of the top die 41 F should be variable to comply with the width of the workpiece W, and in both the first elevating rack 147F and the second elevating rack 149, when the assembly of each storage section 169a to 169f and 171A to 171 F is chosen optionally, the assembly of both the storage sections 1 69a to 1 69f of the first elevating rack 147R, and the storage sections 169A to 169F of the second elevating rack 149R, is the same for the rear as the front side. Therefore, the top dies 41 F and 41 R for both front and rear can be changed simultaneously.

A plurality of die exchange systems 173F and 173R are provided on the front and back surfaces, respectively, of the ram 27 to simultaneously change the front and rear top dies 41 F and 41 R which are supported on the front and rear sections of the ram 27. More specifically, a plurality of guide rails 175f and elongated in the front and rear surfaces of the ram 27.The die exchange systems 173F and 173R are supported on these respective guide rails 175F and in a freely movable manner.A plurality of pulleys 177F and 179F, and 177R and 179R (not shown on the drawings) are supported in a freely rotatable manner on the back and rear surfaces of the ram 27 in order to move the die exchange systems 173F and 173R along the guide rails 175F and 175R in the left and right directions. A plurality of belts 181F and 181 F, such as timing belts, are fitted between the pulleys 177F and 179F, and 177R and 179R, respectively, and the respective die changing system 173F and 173R are connected to the belts 181F and 181R. The pulleys 179F and 179R are integrally mounted on the through shaft 183 which penetrates the ram 27 in the front and rear direction.The through shaft 183 is interconnectively linked with a control motor 187, such as a servomotor or pulse motor, installed on the ram 27 through a bracket 185.

Through this configuration, when the control motor 187 rotates, the front and rear die changing systems 173F and 173R move along the guide rails 175F and 175R simultaneously in the left and right direction. Now referring to Fig. 8 and Fig. 9, the movable block 189, which is freely movable in the left and right direction along the guide rail 175F in the die changing system 173F, is connected to the belt 181f using a suitable connecting tool 191. A nose section 193 which can penetrate the through- hole 7H which pierces the frame 7 and protrudes through the side of the rack device 139 is formed in the movable block 189. A guide rail 195, parallel to the direction of movement of the movable block 189, is formed on this nose section 193.A slide member 199, which supports a mini-cylinder 197 on its leading section, is supported in a freely movable manner on the guide rail 195. This slide member 199 is connected to a piston rod 201 R of a retractable cylinder 201 supported on the movable block 189.

Accordingly, by a suitable action of the retractable cylinder 201, the slide member 199 carries out a reciprocal action in opposition to the block 189.

As shown in Fig. 9, the mini-cylinder 197 provides a corresponding hole 41 H formed in the front side surface of each top die 41 F and a detachable piston rod 197R.A rectangular cutout section 41N elongated in the left and right direction is formed in the front surface of the top die 41 F. The top die 41 F is supported by engagement of the cutout section 41 N with a support bar 203. The support bar 203 is elongated in the long direction of the ram 27, and is supported on a supporting member 205 secured to the lower surface of the ram 27 by a plurality of bolts 207 and a spring 209, such as a coil spring. A stage 415 is formed on the rear surface of the top die 41 F, along with a slanting section 41 B.The stage 415 of the top die 41 F is supported on a support bar 211 provided on the ram 27 in parallel with the support bar 203. A slanting section 41 B makes contact with a slanting section 213B which is formed on a clamp member 213 which is provided with free vertical movement at an appropriate number of locations on the ram 27. This clamp member 213 is connected to a piston rod 215R in a cylinder 215 mounted on the ram 27.

The clamping force employed on the slanting member 41 B of the top die 41 F is applied in the left direction in Fig. 9. When the edge of the workpiece W is being bent, the direction in which the pressure is applied is in the same direction thereby when the bending process is taking place, the securing of the top die is not loosened, and it is enable for the clamping force on the top die 41 F to be low.

In this configuration, the top die 41 F is made to move integrally with the movement of the movable block 189 in the status where the piston rod 197R in the mini-cylinder 197, corresponds to the correspondent hold 41 H in the top die 41 F, and the changing of the top die 41 is carried out. At this time, by the action of the retractable cylinder 201 and the positioning of the movable block 189 at a suitable distance from the rack device 139, the top die 41 F can be moved toward the ram 27.

As can be understood from the above explanation, by means of the present invention, when the edge of the workpiece, which is held in a fixed position by the pressure of the top die against the bottom die, is bent by the bent-beams, the force used by the bend-beams is received from the ram and transmitted to the top dies, so that the forces are balanced and highly precise processing is obtained.

In addition, the adjustment of the clearance between the bend-beams and the top dies to correspond to the plate thickness of the workpiece can be easily performed. The adjustment of the bending angle of the workpiece is also easy.

Furthermore, the securing of the workpiece by pressure is carried out uniformly, and the precision of the bending process is improved.

The process of bending both edges of the workpiece is also improved. Also, it becomes of bending both edges of the workpiece is also improved.

Furthermore, it becomes easy to select the length of the front and rear section of the top die to match the width of the workpiece, and, at the same time, both sides of the top die can be changed simultaneously, giving improved operating efficiency.

Claims (18)

1. A bending machine, comprising upper and lower dies for gripping a sheet workpiece therebetween, a bending beam for bending an edge of a workpiece gripped between the upper and lower dies, and guide means for guiding the bending beam during a bending operation, wherein the guide means is connected to the die which is on the other side of the workpiece from the bending beam during bending operations.

2. A bending machine according to Claim 1, wherein the guide means is connected to a movable one of the upper and lower dies.

3. A bending machine according to Claim 1 or 2, wherein one of the upper and lower dies is movable towards and away from the other of the upper and lower dies by a ram.

4. A bending machine according to Claims 2 and 3, wherein the guide means is mounted on the ram.

5. A bending machine according to any one of the preceding claims, wherein the upper die is movable towards and away from the lower die.

6. A bending machine according to any one of the preceding claims. wherein the guide means comprises a cam surface.

7. A bending machine according to any one of the preceding claims, wherein the guide means is arranged substantially to rotate the bending beam about the point at which the workpiece is gripped during a bending stroke.

8. A bending machine comprising a lower die for supporting a sheet metal workpiece, an upper die for gripping the workpiece by pressing the same against the lower die, the upper die being mounted on a lower part of a vertically movable ram, a vertically movable bending beam for upwardly bending one edge of a workpiece gripped between the upper and lower dies, and tapered guide members mounted on the ram for guiding the bending beam towards the upper die during a bending stroke.

9. A bending machine according to Claim 8, wherein the positions of the guide members are freely vertically adjustable.

10. A bending machine according to Claim 8 or9, wherein the elevation of the bending beam is freely adjustable.

11. A bending machine according to Claim 10, wherein the elevation of the bending beam is adjustable by means of an hydraulic cylinder, the stroke of which is freely adjustable.

12. A bending machine according to any one of Claims 8 to 11, comprising a plurality of pressure cylinders spaced along the length of the upper die, a plurality of movable blocks, and means for moving each movable block into and out of a position in which the same can be acted on by a respective said pressure cylinder.

13. A bending machine according to Claim 12, further comprising means for detecting the width of a workpiece to be bent and means responsive to the detecting means for controlling the means for moving each movable block.

14. A die changing system for a bending machine, comprising a plurality of elevator means, each of which comprises a plurality of stages for storing dies separately, means for moving the elevator means individually so as to obtain any desired combination of the dies stored on the stages, and means for disposing a desired combination of dies in a desired position in a bending machine by transferring the same from the stages.

15. A die changing system according to Claim 14, wherein a said elevator means is provided with a pair of sets of stages on which dies can be arranged symmetrically with respect to a vertical plane.

16. A bending machine, substantially as hereinbefore described with reference to, and as shown in. the accompanying drawings.

17. A die changing system for a bending machine, substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.

18. Any novel feature or combination of features described herein.