Patent Description:
Bending machines, such as for example press brakes, are often designed for operation with different bending tools, which implement the bending of a corresponding workpiece during operation.

The exchange of bending tools requires the opening or closing of a corresponding holding device on the bending machine. In the prior art, holding devices are known that must be opened or closed manually by a human operator. Such manual holding devices require the physical effort of the operator and require long changeover times for the bending tools.

Automatic holding devices are also known from the prior art, in which, with a suitable actuator, the holding device can be released to remove the bending tool or closed to fix the bending tool. For example, hydraulic, pneumatic, or electromechanical actuators are used as actuators. Automatic holding devices relieve the human operator, but result in high manufacturing costs and are prone to errors.

<CIT> discloses a press brake in which a bending tool is releasably clamped in a tool holder via a hydraulically or pneumatically pressurisable swellable body. <CIT> discloses a bending press with a clamping device for the releasable fastening of a tool, wherein the clamping device is hydraulically operable.

<CIT> describes a tool holder in which the tool is fixed using a clamping device that is actuated by a cylinder pressurised with compressed air.

Document <CIT> discloses a clamping device for clamping a tool in a press brake according to the preamble of claim <NUM>. The clamping device includes a part receiving the tool as well as an actuated member and an engaging member to be brought into contact with the tool. The clamping device is provided with a transmission placed between the actuated member and the engaging member. The actuated member can be pneumatically or electrically or hydraulically driven. The transmission can include a wedge-shaped member or a lever.

Document <CIT> discloses a bending machine for metal sheets comprising a punch means which includes an upper tool-holding cross piece. The cross piece comprises a locking means having a plurality of movable locking elements and configured to engage and lock upper bending tools in a locking configuration so as to prevent any movement of the upper bending tools. The locking elements are driven linearly between the locking configuration and a releasing configuration in which the locking elements do not engage and lock the upper bending tools.

The object of the invention is to provide a bending machine having a holding device for bending tools, wherein the holding device enables an automatic fixing and release of the bending tools in a simple manner.

This object is achieved by the bending machine according to patent claim <NUM>. Further developments of the invention are defined in the dependent claims.

The bending machine according to the invention has a bending beam which can be moved in at least one working direction of the bending machine to form a workpiece by bending along a bending line, wherein the bending line runs in a width direction of the bending machine. The bending machine contains a holding device for fixing at least one bending tool on the bending machine. A release means is also provided on the bending machine which, when it is actuated, transfers the holding device from a closed position in which the at least one bending tool is fixed to an open position in which the at least one bending tool is released. The bending machine according to the invention is designed such that a movement of the bending beam towards a predetermined release position actuates the release means when the predetermined release position is reached.

The bending machine according to the invention has the advantage that the movement of the bending beam is used not only for the purposes of the bending of the workpiece, but also to release bending tools held in the bending machine. In this way, a simple mechanism is created to allow a changing of bending tools on the bending machine.

In a preferred embodiment of the bending machine according to the invention, the at least one bending tool is held on the bending beam when the holding device is in the closed position. Nevertheless, it is also possible that the at least one bending tool is held on a bending beam other than the bending beam, the movement of which actuates the release means.

The at least one bending tool can be fixed in different ways depending on the design of the bending machine. In a preferred variant, the holding device provided in the bending machine is designed for fixing the at least one bending tool in a positive and/or non-positive manner. A form-fitting fixing can be effected, for example, via a slide control. In the case of a non-positive fixing, the holding device exerts a holding force on the at least one bending tool to fix same on the bending machine, wherein the holding force on the at least one bending tool is terminated when the release means is actuated and the holding device is thereby brought into the open position in which the at least one bending tool is released.

In a further embodiment, the bending machine according to the invention is designed such that when the predetermined release position is reached, the movement of the bending beam generates a release force which is exerted on the holding device by the release means to cancel the fixing of the at least one bending tool. This variant of the invention is preferably combined with a non-positive fixing of the at least one bending tool, so that the release force terminates the holding force exerted by the holding device on the at least one bending tool.

In a variant of the embodiment just described, the release means can generate the release force directly by mechanical action on the holding device. Nevertheless, it is also possible for the release means to comprise a hydraulic circuit, for example, which is switched on when the release position is reached and then generates the release force via hydraulic pressure.

In a further preferred embodiment, the bending machine according to the invention is designed such that the movement of the bending beam towards the predetermined release position is a movement in the working direction of the bending machine. This embodiment is preferably used when the bending machine is a press brake. In a modified embodiment it is also possible that the movement of the bending beam towards the predetermined release position is a movement in a direction deviating from the working direction, wherein the deviating direction preferably corresponds to the width direction of the bending machine. This variant is preferably used when the bending machine is a panel bender.

In a further embodiment, the release means is immovably attached to the bending machine, whereas the holding device together with the bending beam can be moved towards the predetermined release position. With this variant, the interaction of the release means with the holding device is implemented in a simple manner. The holding device is preferably provided on the bending beam, the movement of which actuates the release means, to hold the at least one bending tool on this bending beam. Nevertheless, instead of the holding device, the release means can also be movable with the bending beam, the movement of which actuates the release means, whereas the holding device is immovably attached to the bending machine to hold the at least one bending tool on a (stationary) bending beam other than the bending beam, the movement of which actuates the release means.

In a further variant of the bending machine according to the invention, the release means contains one or more contact elements, preferably one or more wedges. These contact elements are arranged such that when the predetermined release position is reached, they mechanically contact the holding device and thereby terminate the fixing of the at least one bending tool. With this variant, the release of the at least one bending tool can be achieved by a simple mechanical structure. In a preferred embodiment, the exertion of a holding force generated by the holding device on the at least one bending tool is terminated by means of the contact element or elements.

In a preferred variant, a respective contact element is designed such that when the predetermined release position is reached, it presses against at least one contact surface of the holding device and in this way triggers a movement on the holding device, whereby the fixing of the at least one bending tool is terminated. The exertion of a holding force generated by the holding device on the at least one bending tool is preferably terminated.

In a further preferred configuration, the holding device is a clamping device which is designed so as to exert a holding force in the form of a clamping force on the at least one bending tool to fix the at least one bending tool.

In a further preferred embodiment, the holding device comprises one or more elastic means, which are pretensioned in the holding device to generate thereby a holding force for fixing the at least one bending tool. The elastic means can be configured differently, for example as one or more springs, such as for example disc springs, and/or as one or more elastomers and the like.

To ensure that the at least one bending tool does not fall out of the holding device when in the open position, in a preferred variant the holding device comprises one or more loss prevention devices to hold the at least one bending tool loosely in the holding device when the holding device is open.

To ensure a correct alignment of the at least one bending tool when it is fixed, in a further variant the holding device comprises one or more positioning means to ensure that the at least one bending tool moves into a predetermined position when the predetermined release position is reached, in which the at least one bending tool is held by the holding device.

In a further variant, a sensor system is provided in the bending machine according to the invention, which is configured to detect the approach of the bending beam towards the predetermined release position as a detection event. The bending machine is preferably designed such that when the detection event is detected, a message is output via a user interface of the bending machine, such as for example a display. In this way, an operator of the bending machine is informed that the bending machine is in a state in which the bending tools can be changed.

In a further embodiment of the bending machine according to the invention, the release means can be moved into a parked position on the bending machine, in which the release means cannot be actuated by moving the bending beam. In this way, an unintentional loosening of the fixing of the at least one bending tool can be prevented.

In one embodiment, the bending machine according to the invention is a press brake for freely bending a workpiece between a movable upper beam and a stationary lower beam. The bending beam, the movement of which actuates the release means, is the upper beam.

In a particularly preferred variant of the bending machine designed as a press brake, the holding device is provided on the upper beam to hold the at least one bending tool on the upper beam, wherein the release means is arranged to be immovably adjacent to the upper beam and the predetermined release position is reached due to the movement of the upper beam in the working direction away from the lower beam. As a result, the movement of the upper beam that is already present for bending the workpiece is also used to release the at least one bending tool in a simple manner.

In a further embodiment, the bending machine according to the invention is a panel bender, which is configured such that the workpiece-in contrast to free bending in a press brake-is fixed during bending.

In a particularly preferred variant of the bending machine designed as a panel bender, the holding device is provided on the bending beam, the movement of which actuates the release means to hold the at least one bending tool on this bending beam, wherein the predetermined release position is outside a working area in which the bending by the bending beam takes place. In this case, the bending beam can preferably be moved into the predetermined release position in the width direction of the panel bender.

In a preferred embodiment of the panel bender described above, this includes a primary bending beam, which is movable exclusively in the working direction and perpendicular to the plane spanned by the working direction and the width direction, and a secondary bending beam, which is the bending beam, the movement of which actuates the release means, wherein the secondary bending beam is movably arranged on the primary bending beam in the width direction. The secondary bending beam thus follows the movement of the primary bending beam, but can also be moved in the width direction relative to the primary bending beam.

In a preferred embodiment, the primary bending beam comprises one or more bending tools which are firmly connected thereto and cannot be exchanged without additional aids. In contrast, corresponding bending tools can be changed on the secondary bending beam. The secondary bending beam is therefore always used as required when bending processes must be carried out on the workpiece with specific bending tools.

Exemplary embodiments of the invention are described in detail below with reference to the accompanying figures.

In all of the figures described below, the spatial orientation of the corresponding bending machine is illustrated by a Cartesian coordinate system with an x-axis, y-axis and z-axis. The z-axis represents the height direction, the y-axis represents the width direction of the bending machine in which the bending line runs, and the x-axis represents the direction perpendicular to the y-axis and z-axis. In the direction of the x-axis, the workpiece to be bent is introduced into the bending machine by an operator or, in some cases, automatically.

A first embodiment of a bending machine according to the invention in the form of a press brake is described below. This press brake is shown in plan view in <FIG> and in perspective view in <FIG> and is indicated by the symbol <NUM>. Only the components of the press brake that are essential to the invention are shown.

The press brake <NUM> comprises a machine body <NUM> fixed to the floor, which comprises two side stands <NUM>, <NUM> and a front plate <NUM>. A stationary lower beam <NUM> and an upper beam <NUM> that can be moved in the z-direction extend in a manner known per se between the side stands <NUM> and <NUM>. In the embodiment described here, the upper beam represents a bending beam within the meaning of the claims. On the upper side of the lower beam <NUM> there is a tool holder <NUM>, on which suitable lower tools are fastened during operation of the bending machine. Analogously, bending tools are fixed to the underside of the upper beam <NUM> for the corresponding bending process, wherein two such bending tools <NUM> are provided according to <FIG> and <FIG>.

The press brake <NUM> is used for bending sheet metal. The sheet metal is introduced along the x-axis into the working area between lower beam <NUM> and upper beam <NUM>, and then the upper beam <NUM> is moved downwards to form the sheet metal, so that the bending tools <NUM> press into the sheet metal and form it appropriately. The movement of the upper beam <NUM> is effected by means of hydraulics in the form of two hydraulic cylinders <NUM>, <NUM>', which can be seen from the rear view of <FIG>. To control and monitor the bending process carried out by the press brake are provided a control device <NUM>, indicated only schematically in <FIG>, and a user interface <NUM> in the form of a touch display, which is arranged in the right-hand area of the press brake on the front plate <NUM>.

Since large forces act on the sheet during the bending process, the corresponding bending tools <NUM> must be firmly fixed in the upper beam <NUM>. At the same time, however, it must also be ensured that the bending tools <NUM> can be exchanged. This is ensured by a holding device <NUM> which fixes the corresponding bending tools <NUM> to the upper beam <NUM>, wherein it is possible for the holding device to be opened with a release means <NUM> to remove the bending tools.

The construction and functioning of the holding device <NUM> and the release means <NUM> are explained in more detail below with reference to <FIG>. <FIG> shows a press brake <NUM> in a plan view from the rear. <FIG> shows the already mentioned hydraulic cylinders <NUM> and <NUM>', which act in a manner known per se on the edge regions of the upper beam <NUM> and thereby move the upper beam up or down. <FIG> also shows the above-mentioned holding device <NUM>, which in the embodiment described here is designed as a clamping device. The holding device <NUM> comprises a clamping plate <NUM> which extends along the width direction y of the press brake and, in the closed state, exerts a clamping force on the bending tools <NUM> in the direction of the x-axis. The clamping plate is held on the lower end of the upper beam <NUM> by a large number of fastening means <NUM> in the form of screws. For reasons of clarity, only some of these fastening means are labelled with reference symbol <NUM>.

A release means <NUM> is used to open the holding device <NUM> and thereby release the fixing of the bending tools <NUM> in the holding device, which in the embodiment described here includes a total of eight contact elements <NUM> in the form of corresponding wedges which are fastened along the y-direction to a transverse strut <NUM>, which in turn is attached to the machine body <NUM> via fastening means <NUM> in the form of screws. The transverse strut, which is located adjacent to the upper beam <NUM> in the x-direction, is thus arranged in a stationary manner on the press brake <NUM> and consequently cannot be moved together with the upper beam. When the upper beam <NUM> moves upwards, the contact elements <NUM> penetrate the holding device <NUM>, as a result of which the latter is opened and the clamping of the bending tools <NUM> is released, as will be described in more detail below.

<FIG> also shows a sensor system <NUM> that is indicated only schematically. This sensor system detects when the contact elements <NUM> are in a position within the holding device <NUM> due to an upward movement of the upper beam <NUM>, so that the clamping of the bending tools <NUM> is released. When this position is detected, a corresponding message is generated on the user interface <NUM> so that the operator knows that the bending tool <NUM> is now released and can be removed. In the same way, a message can be output via the user interface <NUM> if the sensor system <NUM> detects that, due to the downward movement of the upper beam <NUM>, the contact elements <NUM> have moved so far out of the holding device <NUM> that they can no longer effect the opening of the holding device <NUM>, and the bending tools <NUM> are fixed to the upper beam <NUM>. The corresponding message shows the user that the corresponding bending process can now be carried out.

<FIG> show sectional views in the closed state of the holding device <NUM>, wherein the section in <FIG> in the xz-plane runs centrally through the left-hand bending tool <NUM> in <FIG>, whereas the section in <FIG> in the xz-plane runs centrally through the left-most wedge <NUM> of <FIG>. As can be seen from <FIG>, the contact element <NUM> is fastened to the transverse strut <NUM> via fastening means in the form of screws <NUM>. At lower end thereof, the contact element <NUM> has a wedge-shaped tip which is moved into the holding device <NUM> to open it, as will be described in more detail further below.

The holding device <NUM> comprises the clamping plate <NUM>, which is formed from a front section 114a and a rear section 114b, which are firmly connected to one another, for example via a screw connection. The rear section 114b is arranged in a recess at the lower end of the upper beam <NUM> and is held there together with the front section 114a via the fastening means <NUM> on the upper beam <NUM> already mentioned above. In the embodiment described here, the fastening means <NUM> is a screw which extends from an opening in the front section 114a of the clamping plate <NUM> through a bore in the rear section 114b of the clamping plate <NUM> into a threaded bore in the upper beam <NUM>. The screw comprises a rear threaded section 115b, which is screwed to the upper beam <NUM>, and a cylindrical section 115a, on which is arranged an elastic means <NUM> which is formed from plate fields in the embodiment described here. Furthermore, the fastening means <NUM> has a head 115c which presses against the elastic means <NUM> so that a pretensioning force is generated. This pretensioning force presses the rear section 114b of the clamping plate <NUM> against the bending tool <NUM>, which is accommodated in a gap between the upper beam <NUM> and the rear section 114b. As a result, the bending tool <NUM> is fixed in the holding device <NUM>.

The correct positioning of the bending tool <NUM> in the holding device <NUM> is achieved with the aid of a positioning means <NUM> in the form of an adjusting wedge, the triangular tip of which engages in a corresponding recess <NUM> in the bending tool <NUM>. When the holding device <NUM> is closed, this adjusting wedge slides into the recess <NUM> and thus ensures that the bending tool <NUM> is correctly arranged on the upper beam <NUM>. In addition, at the upper end of the bending tool <NUM> there is a loss prevention device <NUM> in the form of a tongue or groove, into which an undercut <NUM> of the bending tool <NUM> engages. When the holding device <NUM> is opened, in which the rear section 114a of the clamping plate <NUM> moves away from the bending tool <NUM>, the engagement of the loss prevention device <NUM> in the undercut <NUM> ensures that the bending tool <NUM> is lodged on the upper beam <NUM>. Subsequently, the bending tool <NUM> can be removed from the upper beam <NUM> manually by an operator via a corresponding tilting movement.

It can be seen from <FIG> that in the sections of the clamping plate <NUM> on which a corresponding contact element <NUM> is located, a pocket <NUM> is formed between the front section 114a and the rear section 114b of the clamping plate. In the area of this pocket there is also an opening in the rear clamping plate 114b, in which a contact block <NUM> with a bevelled contact surface <NUM> is inserted. The contact surface <NUM> comes into contact with the contact element <NUM>. Furthermore, an inclined contact surface <NUM> for the contact element <NUM> is provided on the front section 114a. When the holding device <NUM> is opened, the contact element <NUM> is inserted into the pocket <NUM> from above, wherein the contact element <NUM> is not yet inserted so deeply in the state of <FIG> that the holding device is opened.

<FIG> shows a sectional view analogous to <FIG> with the holding device <NUM> open. In the same way, <FIG> shows a sectional view analogous to <FIG> with the holding device <NUM> open. To open the holding device <NUM>, the upper beam <NUM> is moved a little further upwards compared to <FIG>, so that the contact elements <NUM> penetrate deeper into the corresponding pockets <NUM> compared to <FIG>. As a result, the clamping plate <NUM> is moved to the right, whereby the elastic means <NUM> is compressed and thereby the clamping force acting on the bending tool <NUM> is released. The release means thus generates a release force acting against the clamping force.

As can be seen from <FIG>, when the holding device <NUM> is in the open position, the rear section 114b of the clamping plate <NUM> no longer presses against the bending tool <NUM>. Consequently, the bending tool <NUM> is only loosely held on the upper beam <NUM> by the loss prevention device <NUM> and can be exchanged by an operator. To fix the exchanged bending tool, the upper beam <NUM> is moved down again, which means that the contact elements <NUM> move out of the respective pockets <NUM> and the clamping plate <NUM> presses against the bending tool <NUM> again via the elastic means <NUM>, thereby fixing it. A corresponding bending process can then be effected by moving the upper beam <NUM> further down towards the workpiece which is located between the upper beam <NUM> and the lower beam <NUM>.

A second embodiment of a bending machine according to the invention is described below with reference to <FIG>. This bending machine is denoted by reference number <NUM> in the perspective view of <FIG>. This is what is termed a panel bender, which is used to bend metal sheets in the same way as press brakes, wherein unlike press brakes, the metal sheets are fixed during the bending process.

The panel bender <NUM> comprises a machine body <NUM>, which has two side stands <NUM> and <NUM>, among other things. An upper hold-down device <NUM>, which can be moved in the vertical direction, and a stationary lower hold-down device <NUM> extend between the side stands. A hold-down tool <NUM> is provided at the lower end of the upper hold-down device <NUM>. Analogously, a hold-down tool <NUM> is provided at the upper end of the lower hold-down device <NUM>. For a bending process, the workpiece or sheet metal to be bent is fixed between the two hold-down tools <NUM> and <NUM>. For this purpose, the upper hold-down device <NUM> moves downwards so that the workpiece is clamped between the hold-down devices <NUM> and <NUM>. The movement of the upper hold-down device <NUM> is preferably effected via hydraulics, which cannot be seen from the figures.

A primary bending beam <NUM> and two secondary bending beams <NUM>, <NUM>' are provided in the panel bender <NUM> for bending the sheet metal fixed between the hold-down tools <NUM> and <NUM>. A respective secondary bending beam represents a bending beam within the meaning of the patent claims. The primary bending beam <NUM> extends along the hold-down devices <NUM> and <NUM> in the width direction (i.e., the y-direction) of the panel bender. An upper bending tool <NUM> and a lower bending tool <NUM> are permanently attached to the primary bending beam, i.e., these bending tools cannot be exchanged without additional aids. The primary bending beam <NUM> can be moved in the z-direction and the x-direction and can thereby use the bending tools <NUM> and <NUM> to bend the sheet metal that is fixed between the hold-down tools <NUM> and <NUM>.

To carry out specific bending processes, the two secondary bending beams <NUM>, <NUM>' are used in the panel bender <NUM>. These bending beams are arranged on the primary bending beam <NUM> and follow the movement of the primary bending beam in the x-and z-directions. In addition, the secondary bending beams <NUM>, <NUM>' can be moved in the y-direction relative to the primary bending beam <NUM>. Corresponding extension sections <NUM> and <NUM>' in the form of profiles are attached on each side of the primary bending beam <NUM>, wherein the secondary bending beam <NUM> can be driven into the extension section <NUM> and the secondary bending beam <NUM>' can be driven into the extension section <NUM>'. According to <FIG>, the secondary bending beams <NUM>, <NUM>' are also located in the extension sections <NUM>, <NUM>'. The movement of the secondary bending beams <NUM>, <NUM>' relative to the primary bending beam <NUM> is effected via belt drives which comprise rotary drives <NUM>, <NUM>', deflection rollers <NUM>, <NUM>' and toothed belts <NUM>, <NUM>'. The structure of the belt drives is explained in more detail below with reference to <FIG>.

In contrast to the primary bending beam <NUM>, corresponding bending tools are fastened to the secondary bending beams <NUM>, <NUM>' in an exchangeable manner. Two bending tools <NUM> are shown as an example in <FIG>, which are held on the secondary bending beam <NUM> or on the secondary bending beam <NUM>' via holding devices <NUM>, which are described further below. To bend a metal sheet, the secondary bending beam <NUM> or <NUM>' can be moved into the primary bending beam <NUM> by the extension sections <NUM> or <NUM>'. The movement of the primary bending beam <NUM> can then cause the corresponding secondary bending beam to also move and the bending tools <NUM> to interact with the metal sheet. After completion of the bending process, the secondary bending beam used is moved back into the extension section <NUM> or <NUM>'. When a respective secondary bending beam <NUM>, <NUM>' is moved into a specific tool change position within the extension sections <NUM>, <NUM>', a release means <NUM> (see <FIG>) interacts with the holding device <NUM>, whereby the bending tools <NUM> are released from the holding device <NUM> as described in more detail below.

<FIG> shows the structure of the primary bending beam <NUM> and the secondary bending beams <NUM>, <NUM>' in a plan view from the front. To move the secondary bending beam <NUM> from the corresponding extension section <NUM> into the primary bending beam <NUM>, use is made of the upper rotary drive <NUM> which drives the toothed belt <NUM>, which is deflected via the deflection roller <NUM> and guided back to the rotary drive <NUM>. The secondary bending beam <NUM> is connected to the toothed belt <NUM>, so that the movement of the toothed belt causes the movement of the secondary bending beam in the y-direction via the rotary drive <NUM>. Analogously, the lower rotary drive <NUM>' is provided for moving the secondary bending beam <NUM>', which is deflected back to the rotary drive <NUM>' via the deflection roller <NUM>'. The toothed belt <NUM>' is connected to the secondary bending beam <NUM>', so that the movement of the toothed belt leads to the movement of the secondary bending beam <NUM>' in the y-direction. For the movement of the bending beams <NUM> and <NUM>', two guide rails <NUM> are provided, which extend over the length of the primary bending beam <NUM> and the two extension sections <NUM>, <NUM>'.

<FIG> shows a perspective detailed view of the area of the left secondary bending beam <NUM> from <FIG>. As can be seen, the secondary bending beam <NUM> has a U-shaped profile which is incorporated into a corresponding U-shaped profile of the extension section <NUM>. The secondary bending beam <NUM> is slidably guided along the guide rails <NUM> via two upper and two lower guide carriages <NUM> (see <FIG>). <FIG> also shows that two holding devices <NUM> (an upper and a lower holding device) are provided for the secondary bending beam <NUM>, each of which comprises a front clamping bar <NUM>, via which bending tools are clamped to the secondary bending beam <NUM>.

In addition, the release means <NUM>, which is not visible per se and which opens the corresponding holding device, is shown with dashed lines for both holding devices <NUM>. The release means for the upper holding device comprises two contact elements <NUM> in the form of wedges which are fastened and in particular screwed to the underside of the upper leg of the extension section <NUM>. Furthermore, a wedged strip <NUM> is provided, which is movably arranged between the upper leg of the extension section <NUM> and the upper leg of the bending beam <NUM>. The wedged strip <NUM> interacts with the contact elements <NUM>, as will be described further below. Corresponding contact elements <NUM> in the form of wedges are also provided on the upper side of the lower leg of the extension section <NUM>, which in turn interact with a wedged strip <NUM>, which is movably arranged between the lower leg of the extension section <NUM> and the lower leg of the bending beam <NUM>.

<FIG> show in detail the structure of the upper holding device <NUM> and the associated release means <NUM> of the bending beam <NUM> in a state in which the bending tool <NUM> is fixed by the holding device <NUM>. <FIG> shows a plan view of a plane in which are located the two contact elements <NUM> and the wedged strip <NUM> for the upper holding device. The secondary bending beam <NUM> is in a position which is outside of the primary bending beam <NUM>, but does not yet correspond to a release position further to the left in <FIG>, in which the holding device <NUM> is open. As can be seen from <FIG>, the wedged strip <NUM> has two inclined contact surfaces <NUM> which, in the position shown in <FIG>, do not yet interact with opposite inclined surfaces of the contact elements <NUM>. In addition to the front clamping bar <NUM>, <FIG> shows several fastening means <NUM> in the form of screws, several elastic means <NUM> in the form of disc springs, a rear clamping bar <NUM> and further fastening means <NUM>. These components are described below with reference to <FIG>.

<FIG> shows a section in the xz-plane from <FIG> at the position of the bending tool <NUM>. As can be seen, the fastening means <NUM> is screwed to a holding means <NUM> in the form of a cylindrical pin, with the holding means <NUM> in turn being inserted into a bore in the wedged strip <NUM> and thereby producing a rigid connection via the further fastening means <NUM> between the wedged strip <NUM> and the holding means <NUM>. The holding means <NUM> holds the wedged strip <NUM> between the upper leg of the extension section <NUM> and the lower leg of the bending beam <NUM>. In addition, it can be seen in <FIG> that the rear clamping bar <NUM> is located behind the front clamping bar <NUM> and is firmly connected to the upper leg of the bending beam <NUM>, for example via a screw connection. The rear clamping bar <NUM> has a bore in which there is a socket <NUM> through which the holding means <NUM> extends. The socket and a section on the back of the rear clamping bar <NUM> press against the elastic means <NUM> in the form of disc springs. A section of the elastic means <NUM> is arranged in a receptacle of the clamping bar <NUM>, so that the clamping bar <NUM> constitutes an abutment for the elastic means <NUM>, which is placed under pretensioning force.

The distance between the front clamping bar <NUM> and the rear clamping bar <NUM> is so small in <FIG> that the bending tool <NUM> is clamped between the two clamping bars. Similar to the first embodiment described above, a positioning means <NUM> in the form of an adjusting wedge is again provided, which engages in a corresponding recess <NUM> of the bending tool <NUM>. Furthermore, just as in the first embodiment, a loss prevention device <NUM> is provided in the form of a tongue or groove, into which an undercut <NUM> of the bending tool <NUM> engages.

To release the fixing of the bending tool <NUM> in the holding device <NUM>, the secondary bending beam <NUM> is moved further to the left in the y-direction until it reaches the release position shown in <FIG> shows a plan view analogous to <FIG> and <FIG> shows a section analogous to <FIG>. As can be seen from <FIG>, when the release position is reached, the front inclined section of the corresponding contact elements <NUM> interacts with the opposite inclined contact surfaces <NUM> of the wedged strip <NUM>. As a result, under compression of the elastic means <NUM>, the wedged strip <NUM> slides forward together with the holding means <NUM> and the front clamping bar <NUM> (i.e., to the right in the sectional view of <FIG>), thereby enlarging the distance between the front clamping bar <NUM> and the rear clamping bar <NUM>, and the clamping of the bending tool <NUM> in the holding device <NUM> is thereby released. The bending tool <NUM> is still held in the holding device via the loss prevention device <NUM>, but can be removed from the holding device by an operator via a corresponding tilting movement.

Embodiments of a bending machine have been described above, in which the fixing of the bending tools in a corresponding holding device is ensured via an elastic means and this fixing is released in a purely mechanical manner by generating a corresponding release force. Nevertheless, it is also possible for the bending tools to be fixed in some other way, for example hydraulically, and for the corresponding release force to release the fixing also to be generated hydraulically.

If hydraulic clamping is used in the panel bender described above instead of mechanical clamping, this has the disadvantage that hydraulic hoses, for example via energy chains, must be routed over the entire bending length. To avoid this disadvantage, a hydraulic clamping bar having a closed hydraulic circuit can be used. The secondary bending beam has two positions, a parked position and a tool change position. The bending tool is still clamped in the parked position, whereas this clamping is released in the tool change position. In the tool change position, a quick-release coupling of the otherwise self-sufficient hydraulic circuit of the clamp is connected to a controlled circuit and the pressure of the clamp for disengaging or clamping the bending tools is controlled directly. A hydraulic pump can also be provided for this.

If the secondary bending beam is in the parked position, the hydraulic pressure in the self-sufficient hydraulic circuit is constant and the bending tools are held in the clamping unit. There is no connection to the controlled hydraulic circuit. If the secondary bending beam is moved to the tool change position, it is coupled to the controllable hydraulic circuit via the quick coupling. The hydraulic pressure in the controlled hydraulic circuit can then be reduced thereby to effect release of the clamp. On the other hand, the pressure for effecting the clamping is increased again. If the secondary bending beam is then moved from the tool change position to the parked position after a tool change, the controllable hydraulic circuit is decoupled again, wherein a non-return valve keeps the pressure within the clamp constant. The clamping is then self-sufficient again.

Claim 1:
A bending machine, the bending machine (<NUM>; <NUM>) having a bending beam (<NUM>; <NUM>, <NUM>') which can be moved at least in one working direction (z) of the bending machine (<NUM>; <NUM>) to form a workpiece by bending along a bending line which runs in a width direction (y) of the bending machine (<NUM>; <NUM>), the bending machine (<NUM>; <NUM>) containing a holding device (<NUM>; <NUM>) to mount at least one bending tool (<NUM>; <NUM>) on the bending machine (<NUM>; <NUM>), and a release means (<NUM>; <NUM>) being provided on the bending machine (<NUM>; <NUM>) to move the holding device (<NUM>; <NUM>) from a closed position in which the at least one bending tool (<NUM>; <NUM>) is fixed into an open position releasing the at least one bending tool (<NUM>; <NUM>),
characterised in that
the bending machine (<NUM>; <NUM>) is designed such that a movement of the bending beam (<NUM>; <NUM>, <NUM>') towards a predetermined release position actuates the release means (<NUM>; <NUM>) when the predetermined release position is reached.