The present invention relates to a support device in a press brake, adapted to follow the movement of a sheet or the like to be bent during a press brake operation.

This type of support device is manufactured e.g. by a Swedish company called Infer Ab. Enclosed is a copy of a brochure describing the support device and its operation. However, the construction of this support device is unsatisfactory since the propagation of a bending operation as well as pivoting of the device together with a sheet being bent as the bending advances are not linked in any way to each other. The support device has an unfabourably selected centre of pivoting, a consequence of which is that, as the bending operation advances, the sheet has just one point of support or fulcrum.

An object of this invention is to eliminate the above drawbacks. In order to achieve this object, a support device of the invention is principally characterized in that a means producing the movement of the support device at least during a bending operation is adapted to be controlled by means of a control element mounted in connection with a movable bending tool and following the movement thereof. One benefit offered by this solution is that the support device remains in contact with a sheet to be bent all the time during a press brake operation. The return movement of the support device can be adapted to be carried out independently of the movement of a bending tool.

According to one preferred embodiment, the centre of rotation or fulcrum of a support device is the edge of a slot-shaped bending tool which faces the support device. One of the benefits gained by this solution

is that the support device carries a sheet over an extensive area so as to eliminate the drawbacks caused by support forces acting locally on a sheet, such as unnecessary sheet bendings during a press brake operation.

It is preferable that a means reponsible for the pivoting movement of the support device is adapted to be movable in the traveling direction of a movable bending tool. A benefit gained by this solution is that the control element may comprise e.g. a linear sensor or a beam based on the balance of moments.

Particularly in support equipment according to the above embodiment, it is preferable to arrange the attachment between the support device and a means responsible for the rotating motion of the support device to be movable in the direction of the radius of the centre of rotation or fulcrum of the support device. On the other hand, this solution makes it possible for a support device to rotate around a stationary fulcrum at the same time as the movement of a means responsible for the pivoting motion of the support device proceeds in the traveling direction of a bending tool.

It is also preferred that the driving mechanism of a press brake machine, preferably a two-handed release mechanism, be mounted in connection with the support device. This solution provides for a safe operation of the support device. At the same time, it increases the efficiency and reduces the physical stress caused by the work.

Other preferred embodiments of the invention are set forth in the annexed subclaims.

The invention will now be described in more detail in the following specification with reference made to the embodiments shown in the accompanying drawings. Figures 1 - 3 show schematically three different embodiments of the invention.

The principal components of an apparatus shown in the drawings include a press brake 1 , a support device 2 such as a working level, control elements 3 for a ipivot- i- ^τ -'_ ^~ ; ^■ motion of the support device as well as means 4 responsible for the movement of the support device.

The press brake 1 comprises a vertically movable upper tool 5 as well as a slot-shaped fixed lower tool 6. These features of a press brake are known as such and, thus, it is not necessary to describe them further in this context, being familiar to a person skilled in the art.

The top surface of a support device 2 is flat and adapt¬ ed to pivot around the front edge 6" of a slot 6' made in said lower tool 6. In the drawings, a support device is shown to be mounted on the front side of a press brake. It is.completely possible to mount a similar support de¬ vice also on the rear side of a press brake, whereby the fulcrum would be respectively the rear edge 6"' of slot 6' . In order to control the pivotingmovement of a support device, the movable section of a support device is pro¬ vided with a control arc 7, the centre of its radius be¬ ing 6" and wherein a control pin 8 fixed to the body 1 of support device 2 controls thepivoting movement of said support device. In fig. 1, the dash-and-dot lines in-

dicate support device 2 as well as means 4 responsible for its movement in the upper position. The support device 2 further includes a driving gear 9, e.g. a two- handed release mechanism, for operating the press brake and at the same time the support device.

The movable upper tool 5 is provided with a spring- loaded 10 pin 11, which travels therealong and which, as the upper tool reaches a sheet to.be bent and placed upon support device 2, at the same time responds to a lever 13 journalled at 12 to the body of a press brake. On the opposite side of journalling 12 relative to the point of contact of pin 11 said lever 13 is provided with a sliding contact 14 to the piston rod 16 of a hydraulic cylinder 15. The cylinder has a fluid chamber 17 which communicates through a pressure line 18 with the pressure chamber 20 of a cylinder 19 providing a means responsible for thepivoting movement of support device 2. The cylinder has a piston rod 21 adapted to be movable in the traveling direction of upper tool 5 or in vertical direction and its head 22 is in contact with the bottom surface of a working level providing said support device 2.

The purpose of this embodiment of the invention is to translate the pivoting movement of the lever produced by pin 11 through the intermediary of lever 13 into such a vertical movement of piston rod 21 that the po¬ sition of support device 2 matches the position of each bending stage of a sheet.

Particularly the detail 0 in fig. 1 illustrates that both the leverage and angle of bending change during a press* brake operation. At the initial stage of bend¬ ing, there is a lever B-c between the point of movable

upper tool 5 and the front edge 6" of lower tool slot 6'. As the bending proceeds, the lever in reference to detail 0 will be H-C, K-C, L-C etc. up to the dimension of the side face of slot 6* . Although the operating distance of the tool remains unchanged, the angle is changing. In other words, although distances B-H and, on the other hand, H-K are equal, angles BCH and, on the other hand, HCK are unequal.

The above geometric principle is applied on point C or on the front edge 6" of slot 6' of lower tool 6. Par¬ ticularly the embodiment shown in fig. 1 employs two fulcrums, the first being provided by the head 22 of piston rod 21 of cylinder 19. A spacer block 23 is used to provide piston rod 21 with a rack 24 which is in contact with a pair of gears 25a and 25b, whose gear ratio is the ratio C-E and C-F. The vertically movable rack 24 drives through the intermediary of the pair of gears 25a and 25b a cogged belt 26 which drives a gear 25c in contact with a second rack 27. The end 28 of this second rack is in contact with the bottom surface of a working level providing said support device 2. Head 22 and end 28 are capable of moving relative to the bottom surface of the support device with the latter pivoting around edge 6". Thus, the fulcrum shifts in the radial direction of the centre of rotation of a sup¬ port device as piston rod 21 and rack 27 perform a linear movement and said support device 2 pivots around front edge 6". The transmission ratio of gears 25b and 25c connected by cogged belt 26 is 1:1. The points E and F marked in fig. 1 rise in correlation to distances C-E and C-F.

The lever 13 operates also on the principle of the above- described varying angle and leverage. The pin 11 func-

tions as a means slidable relative to the top surface of the lever, as shown in the figure. A similar func¬ tion relates to sliding contact 14, a pin 14' fixed to the piston rod being capable of sliding in a groove 14" at the end of lever 13. Thus, the action between the point of pin 11 and the journalling corresponds to that of detail 0 shown in fig. 1 and the distance between pin 14 ^r and journalling 12 corresponds to the action between points C-F. The ratio of operating distances can of course be varied by changing the diameters of cylinders 15 and 19 as well as by adjusting the distance between pin 11 and fulcrum 12.

The press brake operating mechanism, particularly a two-handed release mechanism, refers in this contaxt to a mechanism and disposition fulfilling the requirements specified in Safety Code 3:1 of the Labour Safety Board on hydraulic and pneumatic presses. The two-handed release mechanism is a separate unit and fitted with guide rails with a locking recess. The locking mecha¬ nism is located in guide holes made in a working level forming said support device 2. Thus, the two-handed release mechanism can be removed from support device 2. This offers a particular adavantage whenever a support device 2 is provided e.g. with a telescopically exten¬ sible member. Thus, the pivoting section of a support device can be provided with extensions for flexibly changing the size of a support device according to the size of a sheet to be bent. The two-handed release mechanism can be mounted on the sides of a support de¬ vice or in connection with the outermost extension. Such various alternative positions of a two-handed re¬ lease mechanism, together with flexible size variations of a support device, provide particularly preferred and short distances of manual operation as the hands are

moved over to the release mechanism after setting a piece in position. This embodiment provides a safe and economical way of operating a two-handed release mechanism.

Fig. 2 shows a basic view of a second embodiment of the invention provided with a controlled descent for a workpiece, said descent being independent of the return movement of a movable bending tool. In fig. 2, the same reference numerals indicate those functional parts which are similar to those in the embodiment of fig. 1.

As the movable upper tool 5 of a press brake comes into contact with a sheet to be bent, the pin 11 is also set so as to engage lever 13. A limit switch 34 associated with pin 11 energizes the coil of valve 30 resulting in oil flowing through valve 33 and 32 over to the side of the piston rod 16 of cylinder 15. The pressure of valve 33 is set lower than the pressure required in cylinder 19 for lifting the pivoting support device. The rest of the pressure required in cylinder 19 generates through the intermediary of lever 13 from upper tool 5. However, if the oil pressure setting on valve 33 is sufficiently high to raise piston rod 16 more rapidly than what is achieved by lever 13, the result is a flow- restricting effect on the part of valve 32 so as to de¬ crease the pressure in cylinder 15 on the piston rod side, as a consequence of which the pin 11 re-establishes a contact with lever 13. The solution requires that the valve 32 and operating lever 29 be supported on piston rod 16 and that piston rod 16 has a sliding engagement with lever 13. By means of the above procedure, the loading on lever 13 can be made very light indeed.

When the upper tool 5 has reached the lower tool to com-

mence the pressing stage in a press brake operation, a means (limit or pressure switch) controlling movement of the upper tool switches off the control current from the coil 9 of valve 30. Upon the commencement of the return movement of upper tool 5, said tool (or an elec¬ trical device, e.g. electric time relay, associated therewith) provides a control current to the coil b of valve 31 for allowing the passage of oil pressure onto the side of piston rod 21 of cylinder 19, whereby the support device 2 commences its descent and at the same time lowers a sheet that has been bent. Timing of the descent movement of the support device relative to the return movement of the upper tool can be controlled e.g. by means of a time relay and the rate of descent of the support device can be likewise controlled e.g. by means of a flow-resistance valve 35. With support device 2 in a horizontal lower position, said device can provide (e.g. limit switch) the switch-off of a control current to the coil of valve 31.

Fig. 3 illustrates one embodiment of a support device of the invention which employs a linear sensor 36 mount¬ ed in connection with a movable bending tool 5. The linear sensor issues a message to a press brake program¬ ing unit 37 which is adapted to control e.g. a propor¬ tional valve 38. On the other hand, valve 38 controls a cylinder 19 by means of a pressure 39 issuing e.g. from the hydraulics of a press brake.