EP0703020A2 - Processing machine with movable work piece holding devices - Google Patents

Abstract

The machine, in particular, in the form of a punching machine incorporates a toolhead (7) and a workpiece guide unit (4) which is movable relative to the toolhead, and has at least two workpiece holding elements (20). The drives of the holding elements are joined to the energy source via a switch (22) which moves together with the workpiece (5), and interacts with a stationary stop (21). The switch (22) is connected to the respective holding element (20), and is provided with a slider which in the position at the stop (21) is pressed against the latter. At least in one position, of the slider, the drive of the respective holding element is connected to the energy source. Analogously, at least in one other position of the slider, the drive of this holding element is disconnected from the energy source.

Description

The invention relates to a processing machine, in particular a punching machine, with a processing head and a workpiece guide which can be moved relative to the workpiece, on which at least two holding devices for the workpiece, which can be fixed in a controlled manner on the workpiece and can be moved relative to the workpiece and the workpiece guide by means of an energy source are provided, the drive means of the holding devices being connected to the energy source via at least one switching element which can be coupled to the workpiece, and the switching element being associated with a stop which is stationary relative to the machining head and the holding device in question when the switching element has hit the stop into a workpiece releasing position is controlled and moved relative to the workpiece in a position with a safety distance from the machining head.

On a processing machine of this type, the workpiece to be processed is fed mechanically or automatically relative to the processing head. The holding devices serve to fix the workpiece in a defined position both during the infeed movement and during the machining process. At the same time, the entire workpiece must be accessible to the machining head in order to avoid material losses. This also applies in particular to the workpiece area covered by the holding devices fixed to the workpiece.

This results in the need to be able to control the individual holding devices into a position releasing the workpiece and to be able to move them relative to the workpiece, in order to thereby enable processing of the workpiece area that is otherwise covered by the relevant holding device. So that the workpiece can be moved even when the holding device is released and held in a defined processing position, at least one of the holding devices provided on the processing machine must always be fixed on the workpiece.

By means of the stop, which is stationary relative to the processing head, the so-called dead-area link, an area is defined on the processing machine around the processing head from which the holding devices must be kept away, in particular to avoid damage. The above-described movement of the holding devices controlled in the release position relative to the workpiece must accordingly be triggered as soon as the holding device in question reaches the limit of the danger zone around the machining head in the course of the feed movement of the workpiece.

For this purpose, an electrical switch connected to the workpiece guide is provided on a known processing machine, which switches an electrohydraulic valve when approaching a dead zone gate, via which a displacement drive for the associated holding device is actuated in the form of a hydraulic piston-cylinder unit. The holding device is moved into an end position remote from the machining head by means of the hydraulic drive. As soon as the workpiece guide has reached a position in the course of its infeed movement relative to the machining head in which the contact between the electrical switch and the dead zone link is removed, the electrohydraulic valve is switched to a switching position in which the hydraulic drive of the holding device moves it back into its initial position . Clamping jaws provided on the holding device for the workpiece are controlled mechanically coupled with the displacement drive.

Due to the described functional sequence comprising several switching operations, the known processing machine results in a relatively slow actuation of the holding devices. Since the contact between the electrical switch attached to the workpiece guide and the associated dead zone link is maintained regardless of the movement of the holding devices, as long as the switch is in contact with the Dead area backdrop, the holding devices are moved after their release from the workpiece by a uniform, always constant path length into their end position determined by the design of the piston-cylinder unit of the displacement drive. Accordingly, the holding devices bypass the processing head on the known processing machine relatively widely, and it takes a relatively long time before the holding devices can be fixed on the workpiece again after passing through the processing head. Due to the circumstances mentioned, short processing times can disadvantageously not be achieved in the known processing machine.

The object of the invention is to provide a processing machine which allows workpiece processing to be accelerated compared to the known processing machine.

This object is achieved in that on a processing machine of the type mentioned, the switching element is connected to the associated holding device and has a slide switch, which is supported in the position in the position of the stop in the direction of the stop, the slide switch in at least one slide position connects the energy source to the drive means of the associated holding device and interrupts this connection in at least one further slide position. On such a processing machine, the drive means by means of which the holding devices are moved relative to the workpiece are switched directly by the switching element. Further switching operations associated with additional switching times are eliminated. In addition, the switching of the switching element is directly coupled to the relative movement of the associated holding device relative to the workpiece. If, for example, the switching element with the slide switch runs onto the stop which defines the danger area around the processing head, the switching slide is transferred to a switching position in which the drive means move the relevant holding device away from the processing head. As soon as the holding device reaches a position outside the danger zone around the machining head during its movement, the slide switch moved with the holding device assumes a slide position in which the holding device is stopped. After passing through the processing head, the switch slide of the switching element is shifted in the opposite direction of its previous movement with a corresponding design of the stop serving as a dead zone link and finally assumes a switching position in which the holding device in question is moved back into its starting position on the workpiece. Accordingly, the holding devices on the known processing machine are only moved away from the workpiece by the distance that is absolutely necessary for safely moving around the processing head. The holding devices on the processing machine according to the invention accordingly bypass the processing head directly adjacent to the boundary of its danger zone and can therefore be fixed on the workpiece again within a very short time after passing the processing head. All in all, the inventive method Processing machine therefore realize high processing speeds.

In principle, the advantages of the processing machine according to the invention described above can also be achieved in cases in which the holding devices are moved relative to the workpiece and the workpiece guide by means of electrical drive means. In a preferred embodiment of the processing machine according to the invention, however, the holding devices can each be displaced relative to the workpiece and the workpiece guide by means of a displacement drive with at least one drive piston-drive cylinder unit as the drive means. In this case, the advantageous effects described above can expediently be achieved in that the drive piston-drive cylinder unit is connected to a drive pressure source via the switching element, with a directional valve with a valve slide being provided as the switching slide as the switching element, which in at least one slide position Releases connection between the drive pressure source and the drive piston-drive cylinder unit and locks in at least one further slide position.

In an advantageous embodiment of the invention, the drive cylinder is connected to the holding device on a processing machine of this type, the drive piston is designed as a double-acting piston and connected to the workpiece guide via a piston rod, the annular space of the drive cylinder is permanently connected to the drive pressure source and the cylinder space at the the side of the drive piston facing away from the annular space can be connected to the drive pressure source or an unpressurized space via the directional valve. In at least one slide position, the valve slide releases the connection between the drive pressure source and the cylinder space on the side of the drive piston facing away from the annular space; in a further slide position, it blocks this connection and releases the connection between the cylinder space on the side of the drive piston facing away from the annular space and the unpressurized space. In a slide position in which the valve slide releases the connection between the drive pressure source and the cylinder space on the side of the drive piston facing away from the annular space, the associated holding device is in its initial position on the workpiece. If the valve slide now runs on the stop marking the danger area around the machining head, the valve slide is moved into a slide position in which it blocks the connection between the drive pressure source and the cylinder space on the side of the drive piston facing away from the annular space and the connection of this cylinder space with releases the unpressurized space. Accordingly, the drive cylinder with the holding device connected to it is displaced relative to the drive piston by means of the drive pressure permanently present in the annular space of the drive cylinder. The drive piston displaces the pressure medium present in the cylinder space on the side of the drive piston facing away from the annular space into the unpressurized space and the holding device finally assumes its position remote from the machining head. After the holding device has passed the processing head and the valve slide on the stop is released, the valve slide moves back to its starting position. Now the cylinder space on the side of the drive piston facing away from the annular space is again connected to the drive pressure source. Accordingly, a pressure builds up in this cylinder space, by means of which the drive cylinder is pushed back into its starting position, in which the holding device in question is in its starting position on the workpiece.

The displacement drive described above can be designed both as a pneumatic and as a hydraulic drive system. The last-mentioned embodiment is found in a preferred design of the processing machine according to the invention, on which a hydraulic directional control valve is provided as the switching element. The hydraulic displacement drive can be switched directly by means of the hydraulic directional valve.

In a further advantageous embodiment of the invention it is provided that the valve slide is acted upon by a spring element in the direction of the stop. A spring element offers a structurally simple and easy-to-maintain option for applying force to the valve spool. In addition or as an alternative to the action by means of a spring element, the valve slide can be acted upon by means of the drive pressure source in the direction of the stop.

In addition to driving the holding devices relative to the workpiece and the workpiece guide, the control of the fixing of the holding devices on the workpiece or the release of the holding devices from the workpiece also offers a possibility of increasing the speed of the workpiece machining. The faster the holding device moved with the workpiece guide in the direction of the machining head can be detached from the workpiece before reaching the machining head, and the faster the released holding device can be fixed on the workpiece again after passing through the machining head, the faster the workpiece can be delivered to the machining head be without affecting the security of its fixation on the workpiece guide.

In the case of a preferred embodiment of the processing machine according to the invention, it is therefore provided that the holding devices can be fixed on the workpiece in a controlled manner by means of the respectively assigned switching element. The mechanical inertia associated with a direct mechanical coupling of the movement of the holding devices relative to the workpiece and the workpiece guide and the fixing or releasing of the holding devices is avoided in this way. With a corresponding design of the switching element, the functions "moving the holding devices" and "setting or releasing the holding devices" can be parallelized in time or at least carried out in succession in close succession.

Another embodiment of the processing machine according to the invention, on which the holding devices each have at least two clamping jaws, between which the fixed workpiece is held in a clamped manner and at least one of which is rotatably mounted about an axis of rotation and wherein a directional valve with a valve slide is provided as the switching element characterized in that the rotatably mounted clamping jaws on the side of the axis of rotation facing away from the workpiece protrudes from this and is supported on a control cam which rises in the opposite direction of the workpiece and which is connected to a control piston guided in a control cylinder and can be displaced parallel to the workpiece plane thereon, and in that the control cylinder can be connected to a control pressure source via the directional control valve, the valve slide of the directional control valve releasing a connection between the control cylinder and the control pressure source in at least one control position and in at least one position ner further control position blocks this connection. On such a processing machine, one and the same switching element can be used to control the assigned holding device into the position releasing the workpiece or into the position defining the workpiece and for actuating the drive for the movement of the holding device in question relative to the workpiece and the workpiece guide. The use of control piston control cylinder units which can be acted upon separately with a control pressure opens up the possibility of fixing or detaching the holding devices on the workpiece, decoupled from their relative movement relative to the workpiece and the workpiece guide. With an appropriate arrangement of the control edges on the valve slide of the directional valve, it is ensured that that the functions "release workpiece", "move the holding device away from the workpiece", "move the holding device towards the workpiece" and "set the holding device" can run in close succession in time.

In an advantageous embodiment of a processing machine according to the invention of the type described it is provided that the control piston is designed as a differential piston and that the space of the control cylinder delimited by the smaller piston area is permanently connected to the control pressure source and the space of the control cylinder delimited by the larger piston area via the directional control valve the control pressure source or an unpressurized space can be connected, the valve spool in a control position releasing the connection between the control pressure source and the control cylinder space delimited by the larger piston area and in at least one further control position blocking this connection and releasing the connection to the unpressurized space.

To simplify the construction, the drive pressure source is provided as a control pressure source in a further preferred embodiment of the processing machine according to the invention.

If the rotatably mounted clamping jaws are supported on the cam by means of a support roller, the friction occurring at the contact surface between the cam and the associated clamping jaw is reduced, and there is a smooth mechanical pivoting drive for the clamping jaw.

So that the workpiece to be machined can be fixed to the workpiece guide as simply and time-saving as possible before the start of the machining process on the machine tools according to the invention, it is provided in an expedient embodiment of the invention that the valve spool is acted upon by a bridging control pressure in a connection that releases the connection between the control cylinder and the control pressure source / or can be moved into a position blocking this connection. By means of the bridging control pressure, the holding devices can be controlled into the position in which they release the workpiece, regardless of a contact between the switching element and the stop which is stationary with respect to the machining head. In this position of the holding devices, the workpiece to be machined can be inserted into the holding devices in preparation for the machining process. The bypass valve of all switching elements can expediently be acted upon simultaneously with the bypass control pressure, so that the workpiece to be machined can be inserted into all holding devices at the same time. The minimization of the set-up times of the processing machine that can be achieved in this way contributes to a minimization of the total duration of the workpiece processing.

In the case of a further preferred embodiment of the processing machine according to the invention, the control of the holding devices is provided independently of a contact between the valve slide and the stop which is stationary with respect to the processing head, that the valve slide has two telescopic slides which are guided towards each other in the direction of displacement, which are displaceable against each other against a restoring force, the first slide valve being assigned to the stop which is stationary relative to the machining head and the second slide valve is actuated by means of the bridging control pressure relative to the first slide valve in which the connection between the control cylinder and the control pressure source is released and / or in which this connection is blocked Position is displaceable.

Fig. 1

eine Stanzmaschine mit Werkstückführung in der Seitenansicht,

Fig. 2

eine ausschnittsweise Draufsicht auf die Werkstückebene in Fig. 1,

Fig. 3

das hydraulische Schaltscheme einer Werkstück-Haltevorrichtung an der Stanzmaschine nach den Fign. 1 und 2,

Fig. 4

eine Schnittdarstellung einer Werkstück-Haltevorrichtung an der Stanzmaschine nach den Fign. 1 und 2 einschließlich des Schaltelements der Werkstück-Haltevorrichtung,

Fig. 5

eine vergrößerte Schnittdarstellung des Schaltelements nach Fig. 4 und

Fig. 6a bis Fig. 6c

den Ausschnitt A aus Fig. 5 in verschiedenen Schaltstellungen.

The invention is explained in more detail below with the aid of schematic representations of an exemplary embodiment. Show it:

Fig. 1

a punching machine with workpiece guide in side view,

Fig. 2

2 shows a partial plan view of the workpiece plane in FIG. 1,

Fig. 3

the hydraulic circuit diagram of a workpiece holding device on the punching machine according to FIGS. 1 and 2,

Fig. 4

a sectional view of a workpiece holding device on the punching machine according to FIGS. 1 and 2 including the switching element of the workpiece holding device,

Fig. 5

an enlarged sectional view of the switching element according to FIGS. 4 and

6a to 6c

the section A from Fig. 5 in different switching positions.

As the fig. 1 and 2, the processing machine shown comprises a stand 1 with an upper machine part 2 and a lower machine part 3. In the space between the upper machine part 2 and the lower machine part 3, a workpiece guide 4 is arranged, by means of which a workpiece in the form of a metal sheet 5 in a horizontal plane can be moved relative to a punching station 6 at the front end of the stand 1.

The punching station 6 essentially consists of a machining head 7 mounted on the machine upper part 2 with a plunger 8 that can be moved up and down, and a die holder 9 supported on the machine bottom part 3, in which a die, not shown, is held. The workpiece guide 4 comprises a guide carriage 10 which is driven in the direction of a double arrow 12 by means of a motor 11. For this purpose, a pinion mounted on the drive shaft of the motor 11 meshes with a toothed rack 13 attached to the lower machine part 3. A transverse rail 14 is guided on the guide carriage 10 such that it can be displaced transversely to the direction of movement thereof in the direction of a double arrow 15. The cross rail 14 is driven by a motor 16 which acts on a toothed rack 18 which is fixedly connected to the cross rail 14 via a drive pinion 17.

On the side facing the punching station 6, a total of six guide housings 19 are rigidly connected to the cross rail 14. In the interior of the guide housing 19, a holding device in the form of a claw 20 is displaceably guided relative to the guide housing 19 in the direction of the double arrow 12. 2, only four of the total of six guide housings 19 or claws 20 are shown. A stop designed as a dead zone link 21 is firmly connected to the die holder 9 and defines a danger zone around the machining head 7. The dead zone link 21 is assigned a switching element 22, which is displaceably attached to each of the claws 20.

As can be seen in particular from FIG. 2, seamless machining of the edge regions of the metal sheet 5 is only possible if the individual holding devices 20 are temporarily detached from the metal sheet 5. Only under this condition is the area of the metal sheet 5 otherwise covered by the relevant holding device 20 accessible for the punch 8 of the machining head 7.

If the sheet metal plate 5 is moved upward by moving the cross rail 14, for example in FIG. 2, then the switching element 22 of the lower claw 20 adjacent to the machining head 7 in FIG. 2 runs onto the dead zone link 21. As a result, this claw 20 is opened and moved linearly in the direction of the cross rail 14 relative to the workpiece and the associated guide housing 19. The claw 20 maintains this retracted position as long as the switching element 22 with the dead zone link 21 is in contact. The metal sheet 5 is fixed to the workpiece guide 4 during this time by means of the remaining claws 20. As soon as the lower claw 20 in FIG. 2 has passed the machining head 7 of the punching machine at a distance predetermined by the dead area link 21, the contact between the relevant switching element 22 and the dead area link 21 ends, and the claw 20 becomes its starting position on the metal sheet 5 process back and fixed on this.

The technical means which enable the functional sequence described above and their interaction are illustrated in principle in FIG. 3 and in particular in FIG. 4 in detail.

A hydraulic directional control valve with a valve spool 23 is used as the switching element 22, which is supported with a corresponding arrangement of the associated claws 20 relative to the machining head 7 via a feeler roller 24 on the dead zone link 21. The valve spool 23 can have five spool positions I, II, III, IV, V.

To move the claw 20 relative to the sheet metal plate 5 and the guide housing 19 and thus relative to the workpiece guide 4, a drive piston-drive cylinder unit 27 consisting of a drive piston 25 and a drive cylinder 26 is used. The drive piston 25 is designed as a double-acting differential piston and via a Piston rod 28 on the guide housing 19 set. The drive cylinder 26 is connected to the claw 20.

The annular space of the drive cylinder 26 is connected via a central bore 29 to a hydraulic pump 30 serving as a drive pressure source and is continuously acted upon by this with hydraulic fluid under drive pressure. The cylinder space of the drive cylinder 26 on the side of the drive piston 25 facing away from the annular space is connected via a hydraulic line 31 to a working connection of the directional control valve 22.

A control cylinder 32 and a control piston 33 form a control piston-control cylinder unit 34. The control piston 33 is also designed as a double-acting differential piston. The control cylinder space delimited by the smaller piston area is permanently connected to the hydraulic pump 30, which is also used as a control pressure source, via a pressure line 35, which runs partly as a central longitudinal bore inside a guide rod 36 connected to the guide housing 19. A hydraulic line 37 connects the control cylinder space delimited by the larger area of the control piston 33 to the second working connection of the directional control valve 22.

The directional control valve 22 is finally connected to the hydraulic pump 30 via a pump line 38 and connected via a tank line 39 to a pressure-free hydraulic tank, not shown, in the sense of being under ambient pressure.

A control piston 33 is formed in one piece with the control piston 33 and is provided on its wedge-shaped end facing away from the control piston 33 with a control curve 41 rising in the direction of the control piston 33. A clamping jaw 43 of the claw 20 is supported on the control cam 41 by a support roller 42. The clamping jaw 43 is rotatably mounted about an axis of rotation 44 and is acted upon on the side remote from the support roller 42 by a compression spring in the form of an expansion spring 45. A rigid clamping jaw 46 of the claw 20 serves as a support for the metal sheet 5 and as an abutment for the spreading spring 45.

In the in Figs. 3 and 4 shown starting position the claw 20 is clamped to the metal sheet 5. The valve spool 23 is in the slide position I, in which it the hydraulic pump 30 via the pump line 38 and the hydraulic lines 31, 37 with the space of the drive cylinder 26 on the side of the drive piston 25 facing away from the annular space or with the larger area of the Control piston 33 connects limited space of the control cylinder 32. The tank line 39 is blocked. The same pressure, namely the drive pressure generated by the hydraulic pump 30, is present in the drive cylinder 26 on both sides of the drive piston 25. Due to the different size of the piston or cylinder surfaces acted upon by the drive pressure, however, the drive cylinder 26 is shown in FIGS. 3 and 4 move right end position. The same applies to the claw 20 connected to the drive cylinder 26. Due to the corresponding pressure-area ratios on the control piston-control cylinder unit 34, the latter takes on the control piston 33 one-piece tensioning pistons 40 are also shown in FIGS. 3 and 4 right end position. In this position, the tensioning piston 40 acts on the clamping jaw 43 in the closing direction via the control cam 41.

If the valve slide 23 now runs with the feeler roller 24 arranged at its front end in the course of the movement of the sheet metal plate 5 accomplished by means of the workpiece guide 4 onto the dead zone link 21, then it is first shifted into the slide position II. In the slide position II, the space of the drive cylinder 26 is still connected to the hydraulic pump 30 on the side of the drive piston 25 facing away from the annular space. In the slide position II, the connection of the hydraulic pump 30 that can be established via the pump line 38 to the control cylinder space delimited by the larger area of the control piston 33 is blocked.

A continued movement of the directional valve 22 in the direction of the dead zone link 21 leads to a displacement of the valve slide 23 into its slide position III. In the slide position III, the valve slide 23 connects the control cylinder space delimited by the larger area of the control piston 33 via the hydraulic line 37 and the tank line 39 to the unpressurized hydraulic tank. In this switching position of the directional control valve 22, the control piston 33 displaces the hydraulic fluid from the control cylinder space delimited by the larger area of the control piston 33 under the action of the hydraulic pressure present in the annular space of the control cylinder 32. This is associated with a shift of the tensioning piston 40 in FIGS. 3 and 4 to the left. Actuated by the spreading spring 45, the clamping jaw 43 can now pivot into its open position, in which it releases the metal sheet 5.

With continued movement of the workpiece guide 4 in the direction of the dead zone link 21, the valve slide 23 is moved into its slide position IV. In the slide position IV, the connection that can be established via the pump line 38 between the hydraulic pump 30 and the space of the drive cylinder 26 on the side of the drive piston 25 facing away from the annular space is blocked. The claw 20 is still controlled in the open position.

When the valve slide 23 continues to run onto the dead zone link 21, the space of the drive cylinder 26 on the side of the drive piston 25 facing away from the annular space is finally connected to the unpressurized tank line 39 via the valve slide 23. In this switching position V of the directional control valve 22, the drive piston 25 can displace the hydraulic fluid present on the opposite side under the effect of the drive pressure present in the annular space and generated by the hydraulic pump 30. Accordingly, the drive cylinder 26 moves together with the claw 20 connected thereto in the FIGS. 3 and 4 to the left. The previously opened claw 20 is consequently moved away from the metal sheet 5 and retracted relative to the processing head 7 of the punching station 6. This retraction movement ends as soon as the valve slide 23 moved with the claw 20 is so far away from the dead zone link 21 that it is out of the force a symbolized spring 47 is pushed back from slide position V to slide position IV.

The dead zone link 21 is mounted opposite the machining head 7 in such a way that the claw 20 is always kept outside the danger zone around the machining head 7. In addition, the dead zone link 21 is designed such that the contact with the valve slide 23 ends as soon as the claw 20 has passed the machining head 7 with a certain safety distance. As soon as the claw 20 has reached this position, the valve slide 23 is released and this then first passes through the slide positions III and II, in which the opened claw 20 is moved back to the metal plate 5, before it takes up the slide position I again, in which the claw 20 is closed and fixed to the metal sheet 5.

A reciprocating-piston-cylinder unit 48 indicated in FIG. 3 serves to raise and lower the dead-area link 21. Lowering the dead-area link is possible, for example, in cases in which the machining tools at the punching station 6 can be changed with the aid of the workpiece guide 4 and closed For this purpose, the workpiece guide 4 must be moved into the vicinity of the machining head 7 or the die holder 9. The dead area link 21 is indicated in dashed lines in FIG. 3 in the lowered position.

The claws 20 must be switched to the open position so that the workpiece guide 4 can be loaded with the metal sheet 5 to be machined before the machining process begins, or so that the metal sheet 5 can be removed from the workpiece guide 4 after the machining has ended. This is by means of the in Figs. 5 and 6 shown devices possible regardless of contact between the valve spool 23 and the dead zone gate 21.

As shown in FIG. 5, the valve spool 23 is composed of two part spools 49, 50 which are telescopically guided in the direction of displacement. The part spool 49 is assigned to the dead zone link 21 and is moved onto it when it approaches it. This results in the switching operations described above.

The partial slide 50 guided in the interior of the partial slide 49 can be acted upon by a pneumatic bypass control pressure on a piston 51 via a pressure line 52. Control edges 53, 54 of the inner slide member 50 are assigned control edges on the outer slide member 49.

6a shows the mutual arrangement of the control edges 53, 54 on the inner slide part 50 compared to the assigned control edges on the outer slide part 49 in the starting position of the switching element 22. In this starting position, the switching element 22 assumes the switching position I according to FIG. 3, ie the associated claw 20 is in its away from the cross rail 14 End position shifted and controlled in the closed position. If the claw 20 is now to be opened in order to make it possible to insert a workpiece to be machined, the inner slide part 50 on the piston 51 is acted upon by pneumatic bypass control pressure. As a result, the inner slide member 50 moves relative to the outer slide member 49, which, as shown in FIG. 5, is supported on the housing of the control valve 22 until the control edges 53, 54 assume the position shown in FIG. 6b. In this position, the control edges 53, 54 block the hydraulic line 37 against the pump line 38 and at the same time release the connection between the hydraulic line 37 and the tank line 39. Accordingly, the control piston 33 can be displaced to the left in FIG. 3 under the effect of the pressure which is permanently present in the space of the control cylinder 32 which is limited by its smaller area. As already described above, this is associated with a rectified movement of the tensioning piston 40 and consequently a pivoting of the rotatably mounted clamping jaw 43 into the open position. Now the workpiece to be machined can be placed on the rigid jaws 46 of the claw 20.

As a result of the piston 51 being relieved of the pneumatic bridging control pressure acting previously, the inner slide member 50 moves back into its starting position, in which the control edges 53, 54 assume the position shown in FIG. 6a. The pump line 38 is now connected again to the hydraulic line 37, and the hydraulic pump 30 acts on the space of the control cylinder delimited by the larger area of the control piston 33 32. As a result, the control piston 33 is pushed back into the starting position shown in FIG. 3, in which the pivotable clamping jaw 43, actuated via the clamping piston 40, acts on the workpiece to be machined.

For the sake of completeness, the position of the control edges 53, 54 of the inner slide valve 50 in the operating state of the directional control valve 22 is shown in FIG. 6c, in which the inner slide valve 50 is unloaded and the outer slide valve 49 that has run onto the dead zone link 21 in its position relative to the control cylinder 32 leading hydraulic line 37 locking position is shifted.

Claims (13)

Processing machine, in particular punching machine, with a processing head (7) and a workpiece guide (4) which can be moved relative to it, on which at least two drive means can be fixed in a controlled manner on the workpiece (5) and are connected to an energy source in relation to the workpiece (5) and the workpiece guide (4) is provided with movable holding devices (20) for the workpiece (5), the drive means of the holding devices (20) being connected to the energy source via at least one switching element (22) which can be moved and coupled to the workpiece (5) and the switching element (22) is assigned a stop (21) which is stationary relative to the machining head (7) and the holding device (20) in question is moved into a position releasing the workpiece (5) when the switching element (22) has run onto the stop (21) and moved relative to the workpiece (5) into a position at a safe distance from the machining head (7) , characterized in that the switching element (22) is connected to the associated holding device (20) and has a slide switch which, in the position which has run onto the stop (21), is supported on the stop (21) in the direction of the stop (21), whereby the switch slide connects the energy source with the drive means of the associated holding device (20) in at least one slide position and interrupts this connection in at least one further slide position. Processing machine according to claim 1, wherein the holding devices (20) can each be displaced relative to the workpiece (5) and the workpiece guide (4) by means of a displacement drive with at least one drive piston-drive cylinder unit (27), characterized in that the drive pistons -Drive cylinder unit (27) is connected via the switching element (22) to a drive pressure source (30), the switching element (22) being a directional valve (22) with a valve slide (23) as the switching slide, which is in at least one slide position (I, II, III) releases the connection between the drive pressure source (30) and the drive piston-drive cylinder unit (27) and blocks it in at least one further slide position (IV, V). Processing machine according to claim 2, characterized in that the drive cylinder (26) is connected to the holding device (20) and the drive piston (25) is designed as a double-acting piston and is connected to the workpiece guide (4) via a piston rod (28) and in that the annular space of the drive cylinder (26) is permanently connected to the drive pressure source (30) and the cylinder space on the side of the drive piston (25) facing away from the annular space can be connected to the drive pressure source (30) or an unpressurized space via the directional control valve (22), whereby the valve spool (23) in at least one spool position (I, II, III) the connection between the drive pressure source (30) and the cylinder space on the side facing away from the annular space releases the drive piston (25) and in a further slide position (V) blocks this connection and releases the connection between the cylinder space on the side of the drive piston (25) facing away from the annular space and the unpressurized space. Processing machine according to claim 2 or 3 with a hydraulic displacement drive, characterized in that a hydraulic directional valve (22) is provided as the switching element (22). Processing machine according to one of claims 2 to 4, characterized in that the valve slide (23) is acted upon by a spring element in the direction of the stop (21). Processing machine according to one of claims 2 to 5, characterized in that the valve slide (23) is acted upon by means of the drive pressure source (30) in the direction of the stop (21). Processing machine according to one of claims 1 to 6, characterized in that the holding devices (20) can be fixed on the workpiece (5) in a controlled manner by means of the respectively assigned switching element (22). Processing machine according to claim 7, wherein the holding devices (20) each have at least two clamping jaws (43, 46), between which the fixed workpiece (5) is held clamped and at least one of which is rotatably mounted about an axis of rotation (44) and wherein as Switching element (22) a directional control valve (22) with a valve slide (23) is provided, characterized in that the rotatably mounted clamping jaws (43) on the side of the axis of rotation (44) facing away from the workpiece (5) projects beyond it and engages in one Supporting opposite direction of the workpiece (5) rising control cam (41) which is connected to a control piston (33) guided in a control cylinder (32) and displaceable thereon parallel to the workpiece plane and that the control cylinder (32) via the directional control valve (22) can be connected to a control pressure source (30), the valve spool (23) of the directional control valve (22) in at least one control position (I) connecting the control cylinder he (32) and the control pressure source (30) releases and blocks this connection in at least one further control position (II, III, IV, V). Processing machine according to claim 8, characterized in that the control piston (33) is designed as a differential piston and that the space of the control cylinder (32) delimited by the smaller piston area is permanently connected to the control pressure source (30) and the space delimited by the larger piston area Control cylinder (32) via the directional valve (22) with the control pressure source (30) or a pressure-free space can be connected, wherein the valve spool (23) releases the connection between the control pressure source (30) and the control cylinder space delimited by the larger piston area in a control position (I) and blocks this connection in at least one further control position (III, IV, V) and the connection to the unpressurized one Frees space. Processing machine at least according to claims 2 and 8, characterized in that the drive pressure source (30) is provided as the control pressure source (30). Processing machine according to one of claims 7 to 10, characterized in that the rotatably mounted clamping jaws (43) are supported on the control cam (41) via a support roller (42). Processing machine according to one of claims 8 to 11, characterized in that the valve slide (23) can be moved by means of a bridging control pressure into a position which releases the connection between the control cylinder (32) and the control pressure source (30) and / or into a position blocking this connection . Processing machine according to claim 12, characterized in that the valve slide (23) has two telescopic slides (49, 50) which are telescopically guided in the direction of displacement and which can be displaced against one another against a restoring force, the first partial slide (49) being opposite the machining head (7) assigned to the fixed stop (21) and the second slide valve (50) is acted upon by the bridging control pressure relative to the first slide valve (49) into which the connection between the control cylinder (32) and the control pressure source (30) is released and / or released this connection blocking position is displaceable.

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