EP3695125A1

EP3695125A1 - Valve arrangement and control method

Info

Publication number: EP3695125A1
Application number: EP18812035.6A
Authority: EP
Inventors: Stefan Tadje
Original assignee: Aventics GmbH
Current assignee: Aventics GmbH
Priority date: 2017-10-10
Filing date: 2018-10-03
Publication date: 2020-08-19
Anticipated expiration: 2038-10-03
Also published as: WO2019072328A1; CN111656021A; US20200240444A1; DE102017009374B4; EP3695125B1; US11359650B2; DE102017009374A1; CN111656021B

Abstract

The aim of the invention is to provide a valve arrangement for controlling pneumatic drives, with protection against sudden unprompted changes to the initial switching position without reception of an input signal there is a fault in a restoring element of a pilot stage, and subsequent effective fault detection by purely pneumatic means. According to the invention, the valve arrangement comprises a first and a second working connection (1; 2) that can be connected to a drive and a first and a second electropneumatically pilot-operated directional control valve, one or both directional control valves being mounted upstream of the working connections (1; 2) for action upon and ventilation of same. The pilot stages of both directional control valves are designed as self-restoring entities and the second direction control valve is designed to alternate between a rest position and a switching position. The pilot stage of the first directional control valve has an external control connection (8, 8') which can be acted upon by the second directional control valve to achieve its switching position and can be ventilated by the second directional control valve to achieve its rest position. The second directional control valve has an air spring (19) as a restoring element for the main stage (14) and said air spring can be acted upon and ventilated externally via the first directional control valve. A change of state between action upon or ventilation of the air spring (19) takes place once the first directional control valve is in a switching position and only when the first directional control valve changes switching state. A change of state between action upon or ventilation of a working connection (1; 2) takes place after an action upon or ventilation which is brought about when the second directional control valve is in the switching position and only when the second directional control valve is in the rest position.

Description

Valve arrangement and control method

Technical area

The invention relates to a valve arrangement and a control method for the safe control of pneumatic drives.

State of the art

For the use of pneumatically pilot-operated valves in controls for pneumatic drives, there are operational safety requirements in certain areas of application, which, for example, are derived from the provisions of Directive 2006/42 / EC

(Machinery Directive) or the safety-related standard EN ISO 13849. For example, in the case of door controls in machine tools, an unexpected movement of the drive cylinder must be reliably prevented during manual intervention by the operator. According to ISO 13849-2: 2012, this implies, among other things, the requirement of fault exclusion for valves "Automatic change of the output switching position without

Input signal ".

To control pneumatic drives, such as a double-acting pneumatic cylinder, the use of electropneumatically pilot operated valves with an electrically directly operated preliminary stage (pilot valve, pilot valve) and indirectly via the precursor pneumatically actuated main stage (main valve) is known in the art. Such pneumatically piloted valves are also referred to as multi-stage valves and include, for example, as a precursor an electrically operated 3/2-way pilot valve in poppet design (also as

"Pilot solenoid valve") with a mechanical spring return and as a main stage a pneumatically operated also against a mechanical spring 5/2-way Slide valve in longitudinal or piston valve design. The construction of such electropneumatically pilot operated valves is for example from that of the

Publications EP 0 846 873 A2 or EP 0 463 394 Bl disclosed prior art. In this case, the electrically operated 3/2-way pilot solenoid valve as a precursor switches the control air applied to its input to the also spring-loaded longitudinal or piston slide of the main stage. The control air can be obtained from the pilot valve either internally via the compressed air connection of the multi-stage valve (ie the compressed air supply switched from the main stage to the working connections of the drive), or externally via a separate control air connection. An external one

Supply of the control air is used, for example, when the main stage is to switch only very low pressures that are not sufficient for actuating the drive piston itself. When used in safety-related applications such pilot-operated valves have the disadvantage that a possible breakage of the spring of the

Pilot valve whose closing force decreases and the applied air pressure

Press the pilot valve to allow control air to reach the drive slide or piston of the main stage. This can switch the main stage and apply the pneumatic drive unexpectedly automatically.

To overcome this disadvantage for safety-related functions, it is generally known in the art to use the possibility of external supply of the control air for a redundant circuit. Such known in the prior art redundant valve assembly with the two valves 101 and 102 is shown in the circuit diagram Fig. 10 in its unactuated (de-energized) starting position with the valves 101 and 102 in their rest position. The two valves 101 and 102 are each formed with a mechanical spring return in their pre- and main stage. The designed as electropneumatically pilot operated 5/2-way valve valve 101 is directly the

Work ports 103 and 104 upstream, which it in a rest and a

Switching position alternately opposite to the compressed air connection 105 and one of the compressed air outputs 106 or 107 (also referred to as exhaust ports) connects. The two chambers of one connected to the working ports 103 and 104

double-acting pneumatic actuator are so alternately via the valve 101 in its two switching states (rest position on the one hand and switching position on the other hand) acted in opposite directions and vented. The control air supply of the pilot valve 108, which required for acting on the main stage 109 of the valve 101

Provides control air, the valve 102 is connected upstream, which is designed as an electropneumatically pilot-operated 3/2-way valve 102 with the pilot valve 110. The pilot valve 1 10 receives the control air switched by him internally via the

Compressed air connection 1 11. The valve 102 supplies the compressed air supply for the

Pilot valve 108 of the valve 101 is free in its switching state and locks it in its rest position. It is therefore always necessary to switch both valves 101 and 102 simultaneously in order to be able to bring about a change of state at the working connections 103 and 104. Such a circuit has the advantage that a spring break in one of the two pilot valves 108 or 110 alone without input signal to a

State change can lead to the working ports 103 and 104. So can one

Although spring break in the pilot valve 1 10 may lead to switching the main stage 1 12 of the valve 102, which would have the provision of a control pressure at the pilot valve 108 result. However, since this does not switch for lack of an electrical control signal, the valve 101 does not change its switching state. Conversely, a spring break in the pilot valve 108 alone can not lead to the switching of the valve 101, because at

Pilot valve 108 is applied no control pressure, since the valve 102 does not switch for lack of an electrical control signal. A disadvantage of such a circuit, however, that a spring break in each case only one of the two pilot valves 108 or 1 10 during operation can not be detected. Thus, the two valves 101 and 102 would switch in these two cases when applying an electrical control signal because the pilot valves 108 and 1 10 are electromagnetically direct switching and change their position each without drag. Furthermore, the valve 101 would always switch back in the removal of the control signals in these two cases, because either by the return of the

Valve 102 (with undamaged return spring) in its rest position on the pilot valve 108 no spring-loaded main stage 109 counteracting control pressure is applied (= break the spring of the pilot valve 108) or in the other case, the undamaged valve 101 anyway returns to its rest position (= breakage of the spring of the pilot valve 1 10). Since the valve 101 thus returns to its rest position, in each case in both cases of error, the working connections 103 and 104 also each again come to a standstill

Change of state (reverse ventilation / impingement), which is why one with the Working connections 103 and 104 connected pneumatic drive would also change its state again. The operation of a double-acting pneumatic actuator connected to the working ports 103 and 104 would therefore occur in both

Error cases - if perceptible from the outside - continue unimpaired, which is why such individual errors in operation therefore remained undetected without additional facilities. With the help of expert considerations, this could be achieved through integration

corresponding electronic monitoring measures, such as the use of position sensors to query the switching position of the valves and staggered

Circuit signals and a corresponding evaluation within a

higher-level control can be achieved, but with a corresponding

Design and implementation effort is connected, which significantly exceeds the cost of the actual valve function in practice.

From WO 03/004194 AI a valve assembly with two series-connected, automatically resetting main valves and their respective associated pilot valves is known, which can serve for example the control of a double-acting pneumatic cylinder. The main valves are for alternately opposing loading and venting of the two chambers of the working cylinder in a rest and a

Switching position arranged, wherein for taking the switching position both

Main valves must switch. To implement a security function, the

Main valves are each designed to operate switches that allow an external actuation of an electrical actuation of the electrically operated pilot valves. An electrical actuation takes place only when both main valves are in their rest position and the switches are closed. If a fault occurs when the main valves are diverted back by not returning one of the main valves, the circuit will be cut off, making re-operation impossible. This requires the integration of a corresponding electrical circuit with switches and relays, which creates a corresponding design and cost. DE 10 2007 041 583 A1 discloses a valve arrangement with a first main valve controlled by a first pilot valve and one via a second one

Pilot valve controlled second main valve, which interconnects with each other are that with simultaneous control of the two main valves by means of pilot valves, a switching operation from a basic position takes place in a working position, whereby in the basic and in the working position, two working ports are alternately acted upon in opposite directions and vented. To realize a safety function to prevent a load change at the working ports in the control of only one of the two main valves, a pneumatic circuit with two pilot valves each upstream upstream shuttle valves each provided with three connections, which is relatively complex and a relatively complex pneumatic ducting and interconnection with a correspondingly large space required.

DE 10 2009 037 120 A1 discloses a pneumatic safety valve device with two bistable main valves which can each be actuated by a pilot valve in order to be able to be switched to a working position in which they cause a pneumatic pressure to be applied to two working ports. The structural design of the

Safety valve device causes a switching of the main valves in the

Working position only if the two pilot valves are actuated substantially synchronously. If only one of the main valves is switched to the working position with only asynchronous actuation, this error state remains stored until a

Reset by means of a separate return valve device takes place. The

pneumatic interconnection of the safety valve device is relatively complex due to its purpose to provide a pneumatic fault storage and requires a relatively complex pneumatic ducting and interconnection with a correspondingly large space.

Disclosure of the invention

The invention is based on the object to avoid the disadvantages shown. In particular, a structurally simple valve assembly for the safe control of pneumatic actuators is to be created, which provides protection against a sudden automatic change of the output switching position without input signal in the event of a fault in a restoring device of a precursor and allows effective error detection by purely pneumatic means in this case. The object is achieved by a valve arrangement according to claim 1, advantageous embodiments are described in the subclaims. The core of the invention forms a valve assembly, comprising a first and a second, connectable to a pneumatic actuator working port and a first and a second, each electropneumatically pilot-controlled directional valve, in which one or both directional valves upstream of the working ports for their admission and venting or are , wherein the precursors of both directional control valves are formed automatically resetting and the second directional control valve for alternately taking a rest and a switching position is formed and the precursor of the first directional control valve has an external control port which can be acted upon via the second directional control valve in its switching position and vented in its rest position is, wherein the second directional control valve as a back-up device for the main stage an externally via the first directional control valve

acted upon and ventilated air spring and a state change between loading or venting of the air spring of the second directional control valve after the

Taking a switching position by the first directional control valve only in response to the change in the switching state of the first directional control valve and a state change between loading or venting on one of the two working ports after a previously made with the taking of the switching position by the second directional control valve or vent only in dependence from the taking of the rest position by the second directional valve takes place. With the valve assembly, a structurally simple control for a double-acting pneumatic actuator is provided, which provides effective protection against a sudden automatic change in the

Output switch position without input signal in case of a fault in one

Provision device provides a precursor and allows for this case at the same time an effective error detection by purely pneumatic means. In operation, the valve arrangement causes the change-sensed loading and venting of the

Working connections and thus the control of a connected to the working ports double-acting pneumatic actuator in its two directions of movement.

Due to the redundant arrangement of the two-way valves is first the

Basic fault exclusion ensures that an error in the restoring device one of the two precursors (for example, a spring break in a pilot valve) does not lead to an unintended change of state at the working connections. It is always necessary to switch both directional control valves in order to be able to bring about a change of state at the working connections (opposite venting / admission). Although an error in the preliminary stage of the second directional control valve in the unactuated (idle) rest position can lead to switching its main stage, which provides the provision of a control pressure on

Control connection of the first-way valve would result. However, since this does not switch for lack of an electrical control signal, the first directional control valve does not change its

Switching state. Conversely, an error in the preliminary stage of the first directional valve in the unactuated rest position can not lead to switching its main stage, because at its precursor no control pressure is applied, since the second directional control valve without electric

Control signal does not switch. In addition, however, the valve assembly has the further advantage that an error in one of the two precursors of the two-way valves is reliably detected during operation from the outside. For example, the two-way valves switch when applying electrical control signals in the event of a fault in the

Rear part device in one of the two pilot valves initially normal, because the electrically operated (for example, by solenoids) operated precursors change their position in each case without counterforce of an automatic return device (for example, a mechanical spring). However, a connected to the working ports pneumatic drive would not go back in these error cases in the renewed removal of electrical control signals. Because due to the cross shading always both directional control valves must leave their previously assumed switching state (switch back), so that a renewed change of state (reverse opposing admission / venting of the working connections) can occur at a connected pneumatic drive. Changes only the first directional valve on removal of the electrical input signal its switching position (= error in the restoring device of the precursor of the second directional control valve), occurs at the connected cylinder no change of state, because of a previously made with the taking of the switching position by the second directional valve acted upon or vented working connection no renewed change of state between admission or venting takes place. The

In this case, the main stage of the second directional valve can not return to its rest position even when the air spring is acted upon by the first directional control valve, because due to the defective pilot valve, which can not switch back, continues to be applied to the return movement of the main stage counteracting control pressure (which, in contrast to the operation of the first-way valve is not controlled externally). Consequently, the state of a connected to the affected working port chamber of the pneumatic drive can not change from being applied to venting or vice versa, the movement of the pneumatic drive is blocked. The pneumatic drive can not retract, the error is detected. In the opposite case (= error in the return device of the precursor of the first-way valve), neither return the first, nor the second way valve in its rest position, because they block each other. The main stage of the first directional control valve can not switch back as long as the second directional control valve has not switched back, because via the control connection and the defective preliminary stage of the first directional control valve, one of the return movement of its

Main stage counteracting control pressure is applied. The main stage of the second

Directional valve, in turn, can not switch back, as long as the main stage of the first directional control valve has not switched back, because the externally acted on the first directional control valve in its rest position air spring builds up pressure. Because of the

Arbeitsanschlüssen no change of status and thus also on one

When the pneumatic drive connected does not change state again (reversed countermeasure / venting), a pneumatic drive connected to the working connections can not retract and the error is detected. A pneumatic drive connected to the working connections can therefore not change its state in both fault cases. Both fault cases are therefore recognizable from the outside based on the unchanged position of the drive after switching. In a structurally simple embodiment with commercially available and economically available pneumatic components, the main stages of the two-way valves in slide and / or the precursors of the two-way valves are designed in seat design.

Starting from the basic configuration of the valve arrangement, the realization of different valve functions is achieved in different detail embodiments: In a structurally simple design for alternating opposing

Loading and venting of the chambers of a double-acting pneumatic actuator (eg., A double-acting cylinder) is the first directional control valve for alternately taking a rest and a switch position formed with an automatically resetting main stage, wherein the second directional valve external

Control terminal of the first directional control valve in its switching position via a control line with a compressed air source and in its rest position with a compressed air outlet connects and its air spring acted on the first directional control valve in its rest position and vented in the switching position, and wherein the first directional control valve the two

Working connections is arranged upstream and in the switching position connects the first working port with a compressed air source and the second working port with a compressed air outlet and connects in the rest position the second working port with a compressed air source and the first working port via a connecting line with the control line, wherein in the connecting line in the opposite direction blocking

Check valve is arranged and / or the compressed air connection of the second

Directional valve upstream of a throttle device or are. With this embodiment of the valve assembly, a structurally simple control for a double-acting pneumatic actuator is provided, which provides effective protection against a sudden automatic change of the output switching position without input signal in the event of a fault in a restoring device of a precursor and in this case also an effective error detection made possible by purely pneumatic means. In operation, the valve assembly causes in the parallel rest and switching positions of the two-way valves, the alternating opposite direction and ventilation of the working ports and thus the control of a connected to the working ports double-acting pneumatic actuator in the two directions of movement. Due to the

Redundant arrangement of the two-way valves is initially the basic

Fault exclusion ensures that an error in the return device of one of the two precursors (for example, a spring break in a pilot valve) does not lead to an unintended change of state at the working connections. It is always necessary to switch both directional control valves together in order to be able to bring about a change of state (opposing admission / venting) at the working connections. An error in the return device of the precursor of the second directional valve in its unactuated Although the (non-energized) rest position can lead to switching its main stage, which would result in the provision of a control pressure at the control port of the first-way valve. However, since this does not switch for lack of an electrical control signal, the first directional control valve does not change its switching state. At the same time prevent or delay in this case of error, the check valve or the throttle device acting on the first working port via the control line, the connecting line and located in the rest position first way either completely, or at least such that this does not lead to a dangerous - sudden - movement of an the working connection connected pneumatic drive can lead. Is the

Valve arrangement instead of a check valve exclusively with a

Compressed air connection of the second directional control valve upstream throttle device is executed, in the case of a fault in the return device of the precursor of the second

Directional valve in the unactuated rest position - depending on the nature of a connected to the working connections pneumatic drive - a change of state (admission) of the first working port is not complete in every case

prevented. Since in this case of error, however, the second working port is simultaneously acted upon via the first directional control valve and the compressed air source, there is basically one of the unintentional change in position of a connected to the working ports

pneumatic actuator counteracting back pressure. In the case of any, depending on the nature of a connected to the working connections pneumatic drive force differences is ensured due to the throttle device, however, that a change in position may occur at most with a significantly reduced speed, which meets existing practical requirements for reliability as a rule and at the same time also recognizability ensures the error. Conversely, an error in the return device of the precursor of the first

Directional valve in the unactuated (powerless) rest position does not lead to switching its main stage, because at its precursor no tax pressure is applied, since the second

Directional valve without electrical control signal does not switch. In addition, however, the valve assembly has the further advantage that a fault in the rear part of one of the two precursors (eg. A spring break in a pilot valve) of the two-way valves is reliably detected during operation. In these two cases, the two-way valves switch when applying electrical control signals initially normal, because the electric actuated precursors change their position in each case also without counter force of the return part devices (for example, mechanical springs). The first directional valve connects in the

Switch position the first working port with the compressed air source and the second working port with a compressed air outlet, one with the working ports

connected pneumatic drive changes its position. However, a connected to the working ports pneumatic drive would not go back in these error cases in the removal of electrical control signals. Because of the crosswise interconnection, always switch both directional control valves back so that a new change of state (reverse opposing admission / venting of the working connections) can occur at the connected cylinder. If only the first directional valve without electrical input signal returns to the rest position (= error in the return device of the precursor of the second directional control valve), no renewed change of state occurs at the connected cylinder because either the check valve (if present) or the first working connection (if there is only one) Throttle device) is still acted upon via the second directional control valve and the first working port and the associated chamber of the pneumatic drive is not vented. The

Main stage of the second directional control valve can not return to its rest position in this case of failure despite acting on the air spring, because on the defective preamp continues to counteract the return movement of its main stage control pressure (in contrast to the operation of the first-way valve is not controlled externally). If the valve arrangement is designed instead of a check valve exclusively with a throttling device upstream of the compressed air connection of the second directional control valve, no renewed change of state occurs at the connected cylinder because the first working connection and the associated chamber of the pneumatic drive are still acted on by the second directional control valve and not be vented. There is basically a change in the position of a counteracting to the working connections pneumatic actuator counteracting back pressure. A movement of a connected to the working connections pneumatic drive is not completely prevented in this case of error - depending on the nature of the pneumatic drive - in any case. In the case of any, depending on the nature of a force associated with the working connections pneumatic drive force differences is ensured due to the throttle device, however, that a change in position at best with a significantly reduced speed can occur, what existing practical requirements for the reliability generally sufficient and at the same time also ensures the recognizability of the error. In the opposite case (= error in the

Restoring the precursor of the first-way valve), return neither the first, nor the second way valve in its rest position, because they block each other. The main stage of the first directional control valve can not switch back as long as the second directional control valve has not switched back, because via the external control connection continues to be applied to the return movement of its main stage counteracting control pressure. The main stage of the second directional control valve, in turn, can not switch back as long as the main stage of the first directional valve has not switched back, because the externally acted upon via the first directional control valve only in its rest position air spring builds up pressure. Since no change of state occurs at the working connections, a pneumatic drive connected to the working connections can not retract and the error is recognized.

In a structurally simple embodiment of the above embodiments, the second directional control valve is designed as a 3/2-way valve and formed as a back-up device for the main stage with an externally acted upon and vented via the first directional valve air spring.

In a structurally simple embodiment of the foregoing, the second directional control valve is designed as a 4/2-way valve and designed as a return device for the main stage with an externally acted upon and vented via the first directional valve air spring.

In an alternative embodiment for alternately counteracting and venting the chambers of a double-acting pneumatic drive (eg a double-acting cylinder) with a modified channel guide, the first directional control valve is designed for alternately taking a rest position and a switching position with an automatically resetting main stage the second directional control valve the external

Control connection of the first directional control valve in its switching position via a control line with a compressed air source and in a rest position with a compressed air outlet connects and its air spring is acted upon by the first directional control valve in its rest position and vented in the switching position, and wherein the first directional control valve to the first

Work connection is arranged upstream and this connects in the switching position with a compressed air source and in the rest position with a compressed air outlet and wherein the second directional control valve is upstream of the second working port and connects it in the rest position with a compressed air source and in the switching position with a compressed air outlet. In this embodiment, the arrangement of a check valve or a compressed air connection of the second directional valve upstream throttle device is due to the changed channel management while maintaining the desired safety features

dispensable. Due to the redundant arrangement both the formed with the external control port precursor of the first directional control valve, as well as the precursor of the second directional valve must switch to the two working ports a

Change of state (opposing ventilation / admission) to bring about. In the case of a fault in the return device of the precursor of the second directional valve occurs at the two working connections no change in state (opposing

Venting / admission), because the first-stage valve precursor does not switch without an electrical control signal. Although the error in the return device of the precursor of the second directional control valve can lead to switching its main stage, but this leads only to the additional venting of the second working port. The first work connection remains vented in this case on the remaining in its rest position the first directional control valve. One with the two working connections

connected pneumatic drive remains in its position. Even in the case of an error in the return device of the precursor of the first-way valve occurs at the two working connections no change in state (reverse vent / impingement), because at its precursor no control pressure is applied because the second directional control valve does not switch without electrical control signal. The first working port remains vented via the first directional valve, the second acted upon by the second directional control valve. A connected to the two working ports pneumatic drive remains in its position. In addition, the valve assembly also has the other in this embodiment

Advantage that an error in the return device of one of the two precursors of the two-way valves is always reliably detected during operation. One with the work connections Connected pneumatic drive would not go back into these error traps when removing the electrical control signals again. Because of the crosswise interconnection, both directional control valves always have to switch back, so that a renewed change of state (reverse opposing

Pressurization / bleeding of the working connections) may occur. After the previous taking of the switching position, only the first directional control valve without electrical input signal returns to the rest position (= error in the return device of the

Pre-stage of the second directional control valve), occurs at the connected cylinder no renewed state change, because the second working port continues on the second

Directional valve is vented. Also, the first working port is vented in this case on the returned to its rest position first way valve. One with the two

Working connections connected pneumatic drive remains in its last occupied position. In the opposite case (= error in the return device of the precursor of the first-way valve), neither return the first, nor the second way valve in its rest position, because they block each other. The main stage of the first directional valve can not switch back, as long as the second directional control valve is not

has switched back because of the external control port continues to be one of

Return movement of its main level counteracting control pressure is applied. The main stage of the second directional control valve, in turn, can not switch back as long as the main stage of the first directional valve has not switched back, because the externally acted upon via the first directional control valve only in its rest position air spring builds up pressure. The first working port remains pressurized via the first directional control valve and the second

Working port vented via the second directional control valve. Since at the working connections therefore no renewed change of state (opposite venting / admission) occurs, connected to the working ports pneumatic drive can not

go back and the error is detected.

In a structurally simple embodiment of the above embodiments, the first directional control valve is designed as a 5/2-way valve.

In an alternative embodiment to allow a two-sided venting of the two working ports, the first directional control valve is electropneumatic on both sides vorgesteuertes 5/3 way valve configured with a double-sided automatically resetting main stage and designed to take a vented center position as a rest position, and a first and a second switching position, wherein the capture of the first switching position in the operation and admission of the external

Control terminal formed precursor, and wherein the second directional control valve, the external control port of the first directional control valve in its switching position via a control line with a compressed air source and in a rest position with a

Compressed air outlet connects and its air spring via the first directional control valve in its second switching position acted upon and vented in the first switching position and rest position, and wherein the first directional control valve upstream of the first working port and this in the first switching position with a compressed air source and in the second switching position and the Resting position with a compressed air outlet connects and wherein the second directional control valve is arranged upstream of the second working port and this in the rest position with a compressed air source and in the switching position with a

Compressed air outlet connects. In this design is due to the changed

Channel management while maintaining the desired safety features, the arrangement of a check valve or the compressed air connection of the second directional valve upstream throttle device dispensable. Due to the redundant arrangement both the formed with the external control port precursor of the first directional control valve, as well as the precursor of the second directional control valve must be able to bring about a change in state (opposing vent / impingement) at the two working ports. In the case of a fault in the rear part of the precursor of the second directional valve occurs at the two working ports no change in state (opposite direction ventilation / admission), because the precursor of the first-way valve does not switch without electrical control signal. Although the error in the return device of the precursor of the second directional control valve can lead to switching its main stage, but this leads only to the additional venting of the second working port. The first work connection remains vented in this case on the remaining in its rest position the first directional control valve. A connected to the two working ports pneumatic drive remains in its position. Even in the case of a fault in the rear part of the precursor of the first-way valve occurs

Starting position at the two working connections no change of state (Opposite venting / admission), because at its precursor no control pressure is applied, since the second directional control valve does not switch without electrical control signal. The first working port remains vented via the first directional valve, the second acted upon by the second directional control valve. One connected to the two work ports

pneumatic drive remains in its position. In addition, the

Valve arrangement in this embodiment, the further advantage that an error in the return device one of the two precursors of the two-way valves is reliably detected during operation. A connected to the working ports pneumatic drive would not go back in these errors in the removal of electrical control signals again. Because of the crosswise interconnection always both have to

Directional valves change their previously assumed switching state again, so that at a connected pneumatic drive a new state change

(reverse opposing loading / bleeding of the working connections) and the drive can drive back again. The reverse inverted in opposite directions

Actuation / venting of the working connections after a previously with the receipt of the first switching position by the first directional valve and the switching position by the second directional valve made opposing action and venting takes place only with the common assumption of the second switching state by the first directional control valve and the switching back of the second directional control valve.

In a structurally simple embodiment of the above embodiments, the second directional control valve is designed as a 5/2-way valve and designed as a return device for the main stage with an externally acted upon and vented via the first directional valve air spring, if no configuration than 3 / 2- or 4/2 -Wegeventil is provided.

To increase the vibration and operational stability of the return device of the main stage of the first-way valve is formed in parallel with a mechanical spring and an air spring, wherein the air spring is acted upon externally via the second directional valve in its rest position and its switching position is vented, if the first

Directional valve is designed as a directional control valve for taking two switching states (a rest position and a switching position). The second directional valve is here as 5/2 Directional valve designed.

If in one of the preceding embodiments of the valve arrangement, the first directional control valve for alternately taking a rest and a switching position formed with an automatically resetting main stage and designed as a 5/2-way valve, and is arranged upstream of the two working ports and in the switching position the first

Connect working port with a compressed air source and the second working port with a compressed air outlet and connects in the rest position the second working port with a compressed air source and the first working port via a connecting line to the control line, wherein the compressed air connection of the second directional valve upstream of a throttle device and in the connecting line no check valve is arranged, an additional valve function by a special

Control method achieved, in which the precursors of the two-way valves both electrically together and individually switchable. Based on the working connections, the valve arrangement is hereby a total of 5/3 way valve with an open

Mid-position (both working connections applied) controllable. The control position corresponding to a 5/3 way valve in its open center position corresponds to the switching position of only the second directional control valve (while the first directional control valve in

Resting position is located).

If in one of the above embodiments of the valve arrangement, the first directional control valve for alternately taking a rest and a switching position formed with an automatically resetting main stage and configured as a 5/2-way valve, and the first working port is upstream and this in the switching position with a

Compressed air source and in the rest position with a compressed air outlet connects, while the second directional control valve upstream of the second working port and this in the rest position with a compressed air source and in the switching position with a

Compressed air output connects, an additional valve function is achieved by a special control method, in which the precursors of the two-way valves are both electrically controlled together and individually. Based on the working connections, the valve assembly is thereby controllable as a total 5/3 way valve with a vented center position (both working ports vented). The a 5/3 way valve in its vented center position corresponding control position corresponds to the switching position only the second directional control valve (while the first directional control valve is in rest position). Further advantages of the invention will become apparent hereinafter from the description of preferred embodiments of the invention with reference to FIGS. 1 to 10. Shown are: A schematic circuit diagram of a valve arrangement according to the invention according to a first embodiment. a schematic diagram of a valve assembly according to the invention according to a second embodiment. a schematic circuit diagram of a valve arrangement according to the invention according to a third embodiment. a schematic diagram of a valve arrangement according to the invention according to a fourth embodiment. a schematic diagram of a valve assembly according to the invention according to a fifth embodiment.

Fig. 6 is a schematic circuit diagram of a valve arrangement according to the invention according to a sixth embodiment.

Fig. 7 is a schematic circuit diagram of a valve arrangement according to the invention according to a seventh embodiment. Fig. 8 is a tabular representation of switching positions of the valve assembly of FIG. 2 in comparison with the switching positions of a 5/3 -Wegeventils with an open center position. Fig. 9 is a tabular representation of switching positions of the valve assembly of FIG. 6 in comparison with the switching positions of a 5/3 -Wegeventils with a vented center position.

10 is a schematic circuit diagram of a known valve arrangement (state of

Technology).

Fig. 1 shows an exemplary embodiment of a valve assembly according to the invention in the unactuated (de-energized) starting position with all the valves in their

Rest. According to FIG. 1, the valve arrangement comprises a first working connection 1 and a second working connection 2, which are connected to a pneumatic drive designed as a double-acting pneumatic working cylinder 3. Further, the valve assembly comprises a first electropneumatically pilot-operated directional control valve, which is designed as a pilot-operated 5/2-way valve 4 and as a return device comprises a mechanical spring 5, which automatically spring-loaded by them main stage 6 of the 5/2-way valve 4 in the de-energized state Rest position returns. As a pilot control device, the 5/2-way valve 4 is formed with an electromagnetically actuated, automatically resetting pilot valve 7, which switches the main stage 6 of the 5/2-way valve 4 on actuation and concern of a control pressure at the control terminal 8 from the rest position to a switching position. The 5/2-way valve 4 is the two working ports 1 and 2 upstream and connects in the rest position the

In the switching position, the 5/2-way valve 4 connects the working port 1 with the compressed air source 10 and the working port 2 with the compressed air output 1 1. The control port 8 is a second electro-pneumatically pilot-operated Directional control valve, which is also designed as a pilot operated 5/2-way valve 12, upstream. When

Pilot control device, the 5/2-way valve 12 is also formed with an electromagnetically actuated, automatically resetting pilot valve 13, which the

Main stage 14 of the 5/2-way valve 12 switches on actuation and concerns a control pressure from the rest position to a switching position, wherein the pilot valve 13, the required control pressure for actuating the actuator of the main stage 14 internally over the compressed air connection 15 refers. The 5/2-way valve 12 connects the control line 16 and the control port 8 in switching position with the compressed air source 10 and in

Rest position with the compressed air outlet 17, wherein the arranged in the connecting line 9 check valve 18 upon actuation of the control line 16 by the 5/2-way valve 12 blocks. In the rest position, the left chamber of the pneumatic drive via the 5/2-way valve 4, the connecting line 9 and the 5/2-way valve 12 is simultaneously connected to the compressed air outlet 17 and therefore vented, since the check valve 18 blocks only in the opposite direction. As a return device, the 5/2-way valve 12, an air spring 19, which switches the spring-loaded by them main stage 14 of the 5/2-way valve 12 in the de-energized state in a rest position, when applied to the air spring 19, a control pressure. For this purpose, the air spring 19 is acted upon externally via the 5/2-way valve 4 in its rest position via the supply line 2 arranged parallel to the working connection 2. Due to the redundant arrangement of the two 5/2-way valves 4 and 12, the basic fault exclusion is initially ensured with the valve arrangement that an error in the return device of one of the two pilot valves 7 or 13 (for example a spring break) does not lead to an unintentional movement of one the working connections 1 and 2 connected pneumatic drive leads. Both 5/2-way valves 4 and 12 must always be switched together in order to change the state of the working connections 1 and 2 (opposite directions of the

Admission / venting) to bring about. Although a spring break in the pilot valve 13 in the de-energized idle position can lead to switching of the main stage 14 of the 5/2-way valve 12, which would have the provision of a control pressure at the pilot valve 7 result. However, since this does not switch for lack of an electrical control signal, the 5/2-way valve 4 does not change its switching state. At the same time prevents in this case of error, the check valve 18 is an admission of the left chamber of the pneumatic cylinder 3 via the control line 16 and at rest 5/2-way valve 4. Conversely, a spring break in the pilot valve 7 in the de-energized state not to switch the 5 / 2-way valve 4 lead, because the pilot valve 7 no control pressure is applied, since the 5/2-way valve 12 does not switch for lack of an electrical control signal. In addition, however, the valve assembly has the further advantage that a fault, such as. A spring break, in one of the two pilot valves 7 or 13 is reliably detected during operation. In these two cases the two 5/2-way valves 4 and 12 initially switch normally when applying electrical control signals, because the electromagnetically controlled pilot valves 7 and 13 change their position even without counterforce by a mechanical spring. The 5/2-way valve 4 connects in the switching position the working port 1 with the compressed air source 10 and the working port 2 with the compressed air output 1 1, the pneumatic cylinder 3 extends. However, in the event of a spring break in one of the two pilot valves 7 or 13, the pneumatic power cylinder 3 does not retract when the control signals are removed. Because due to the crosswise shading of the two 5/2-way valves 4 and 12 must always switch back both pilot valves 7 and 13 so that at the working ports 1 and 2 a new state change (opposing

Venting / admission) may occur. Switches only the 5/2-way valve 4 (=

Spring break in the pilot valve 13) back, the pneumatic cylinder 3 can not retract because the check valve 18 via the 5/2-way valve 12 and the control line 16 is still applied and the left chamber of the pneumatic cylinder 3 is not vented. The main stage 14 of the 5/2-way valve 12, despite applying the air spring 19 does not switch back, because of the defective pilot valve 13, which relates the control pressure internally via the compressed air port 15, continues to the main stage 14 counteracting control pressure. In the opposite case (= spring break in

Pilot valve 7) switch neither the 5/2-way valve 4, nor the 5/2-way valve 12, because they block each other. The main stage 6 of the 5/2-way valve 4 can not switch back, as long as the 5/2-way valve 12 has not switched back, because of the defective pilot valve 7 continues one of the spring-loaded main stage. 6

counteracting control pressure is present. The main stage 14 of the 5/2-way valve 12, in turn, can not switch back as long as the main stage 6 of the 5/2-way valve 4 has not switched back, because the air spring 19 does not build up pressure. Because of the

Working connections 1 and 2 no change of state occurs, the remains

Working cylinder 3 extended and the error is detected.

Fig. 2 shows an alternative embodiment of the valve arrangement according to the invention in the unactuated (de-energized) starting position with all the valves in their rest position. In the case of the valve arrangement otherwise identical to the valve arrangement according to FIG. 1, in contrast to the valve arrangement according to FIG Check valve arranged in the connecting line 9. Instead, that is

Compressed air connection 15 in the valve arrangement according to FIG. 2 upstream of a throttle device which is formed in the supply line 21 to the compressed air port 15 of the 5/2-way valve 12 as a constant cross-sectional constriction 22. Furthermore, instead of a constant cross-sectional constriction 22, the throttle device may also be designed as a variable cross-sectional constriction, for example as a throttle valve. The design as a constant cross-sectional constriction 22 offers a high reliability, since it contains no moving parts, but only a constriction of the respective line cross-section, either in the formation of the line or as

subsequently used, the cross-section narrowing aperture can be executed. Is the valve assembly formed as a modular unit with a common base plate for the lines (air ducts and electrical conductors) and connections and placed on the base plate valve modules or valve bodies, as for example from the EP 0 463 394 Bl or DE 39 27 637 Cl According to the prior art disclosed, the cross-sectional constriction 22 can also be designed in a structurally simple way

As a section with a smaller diameter in the course of the corresponding channel bore or -opening be performed in the base plate. In switching position, the 5/2-way valve 12 - as in the valve assembly of FIG. 1 - acts on the control port 8 of the 5/2-way valve 12 by the control line 16 with the

Compressed air source 10 connects. A spring break in the pilot valve 13 in de-energized rest position can lead to switching of the main stage 14 of the 5/2-way valve 12 in this embodiment of the valve assembly (as shown in FIG. 2), which would result in the provision of a control pressure on the pilot valve 7. However, since this does not switch for lack of an electrical control signal, the 5/2-way valve 4 does not change its

Switching state. Since, however, in the embodiment according to FIG. 2, no check valve is arranged in the connecting line 9, this leads in the de-energized idle position simultaneously to an admission of the valve port 23 of the 5/2-way valve 4 (which does not switch) and thereby to an admission of the left chamber of the working cylinder 3 via the control line 16 and the connecting line 9. The same situation would exist in the valve assembly of FIG. 1 in the case of a simultaneous spring break in the

Pilot valve 13 and a failure (failure) of the check valve 18. Since in this state at the same time the right chamber of the pneumatic drive 3 via the 5/2 Directional valve 4 is acted upon by the compressed air source 10, in this case of error is in principle a counteracting the unintentional extension of the pneumatic drive 3 counter-pressure. If a piston rod-less pneumatic drive is controlled with the valve arrangement, this is pressure-balanced in the case of the simultaneous admission of both chambers and does not move. Is however - according to the embodiments of FIGS. 1 and 2 - with the valve assembly a

Piston rod cylinder driven (with a piston on one side piston rod), act due to different loading surfaces on both sides of the piston at the same pressure in each case different moments of force, as these respectively

p

are determined and defined by the pressure acting on the existing surface (p = -). The piston surface occupied by the piston rod causes a force difference. This force difference may be about 10% of the maximum force of the cylinder in practice for ISO cylinders, depending on the diameter of the piston rod:

By the compressed air connection 15 of the 5/2-way valve 12, the cross-sectional constriction 22 upstream, is ensured in such an error case that the piston rod not only with a (compared to the normal operation) reduced force (corresponding to the applied force difference), but in addition also a reduced Speed extends. If the extension of the working cylinder 3 is not completely prevented in this case of error, however, the execution of a dangerous - sudden - movement is prevented, which satisfies the extent existing practical requirements for the reliability of such pneumatic actuators as a rule. Fig. 3 shows an alternative exemplary embodiment of the valve assembly according to the invention in the unactuated (de-energized) starting position with all the valves in their rest position. In the otherwise identical with the valve assembly of FIG. 1 valve assembly is the compressed air port 15 of the 5/2-way valve 12 in the

Valve arrangement according to FIG. 3 additionally arranged upstream of a throttle device, which is designed as a in the supply line 21 to the compressed air port 15 of the 5/2-way valve 12 arranged constant cross-sectional constriction 22. This embodiment of the valve assembly according to the invention thus provides a combined protection against various, in the context of a spring break in the pilot valve 13 and in addition a simultaneous failure of the check valve 18 conceivable failure cases. In the event of a spring break only in the pilot valve 13, the check valve 18 prevents exposure of the left chamber of the pneumatic working cylinder 3 via the control line 16 and the at-rest 5/2-way valve 4. In the case of a simultaneous error (failure) of the check valve 18 is at the control of a piston rod cylinder (with a piston formed on one side piston rod) ensures that the piston rod extends only at a reduced speed, because the compressed air port 15 of the 5/2-way valve 12 the

Sectional constriction 22 upstream.

Fig. 4 shows an alternative embodiment of the valve assembly according to the invention in the unactuated (de-energized) starting position with all the valves in their rest position. In the otherwise identical with the valve assembly of FIG. 1 valve assembly is in contrast to the valve assembly of FIG. 1, on the one hand, the rear part of the 5/2-way valve 4 not as a mechanical spring, but as

Air spring 24 is formed, which is acted upon externally constant by the pressure medium source 10. In this version, in addition, the risk of a spring break in the

Rear part of the main level 6 excluded. On the other hand that relates

Pilot valve 13, the required for actuating the actuator of the main stage 14 control pressure, unlike the valve assemblies of FIG. 1 to 3 not internally via the compressed air connection 15, but externally from the compressed air source 10. In this way, the valve assembly with two identically designed valve types is possible , The external control air supply of the pilot valve 13 is also not switched in this case, but constantly externally connected to the compressed air source 13. For the

Operation of the valve assembly, this is not relevant, but leads to the possibility of the same parts use (here the valves 4 and 12) in the production. The relevant in the context of the application operation of the valve assembly of FIG. 4 is in

Incidentally identical to the operation of the valve assembly of FIG. 1.

Fig. 5 shows an alternative exemplary embodiment of the valve assembly according to the invention in the (unactuated) energized starting position with all the valves in their rest position. In the otherwise identical with the valve assembly of FIG. 1 valve assembly is in contrast to the valve assembly of FIG. 1 the

Rear part of the 5/2-way valve 4 additionally formed parallel to the mechanical spring 5 with the air spring 24, the externally via the 5/2-way valve 12 in the

Rest position is applied and its switching position is vented via the compressed air outlet 25. This embodiment serves to increase the vibration and operational stability of the valve assembly by the force exerted on the 5/2-way valve 4 restoring force is increased by the two parallel executed back part means. Furthermore, this embodiment provides additional security in the event of breakage of the spring 5 of the main stage 6, in which the provision is still ensured by the air spring 24. The relevant in the context of the application operation of the valve assembly of FIG. 5 is in

Incidentally identical to the operation of the valve assembly of FIG. 1.

Fig. 6 shows an alternative embodiment of the valve assembly according to the invention in the unactuated (de-energized) starting position with all the valves in their rest position. The valve assembly has an otherwise identical structure a relation to the valve assembly of FIG. 1 changed channel guide. The first electropneumatically piloted 5/2-way valve 4 is upstream of the first working port 1 and connects it in the rest position with the compressed air outlet 26 and in switching position with the compressed air source 10. The second electropneumatically piloted 5/2-way valve 12 is the second working port 2 upstream and connects it via the supply line 27 in the rest position with the compressed air source 10 and in

Switching position with the compressed air outlet 25. The air spring 19 is externally connected via the 5/2 Directional valve 4 is acted upon in the rest position via the supply line 28. In this embodiment, due to the changed channel management while maintaining the

desired safety features both the arrangement of a check valve in the connecting line 9, as well as a compressed air connection 15 of the second 5/2-way valve 12 upstream throttle device dispensable. Due to the redundant arrangement, both with the external control terminal 8 trained

Pilot valve 7 of the first 5/2-way valve 4, as well as the pilot valve 13 of the second 5/2-way valve 12 switch so that at the two working ports 1 and 2, a change in state (reverse venting / admission) occurs. An error in the return device of one of the two pilot valves 7 or 13 (for example, a spring break) can not lead to an unintentional movement of a connected to the working ports 1 and 2 pneumatic drive. In case of a spring break in the

Pilot valve 13 occurs at the two working ports 1 and 2 no change in state (opposite direction ventilation / admission), because the pilot valve 7 does not switch without electrical control signal. Although a spring break in the pilot valve 13 may lead to switching its main stage 14, but only for additional

Vent also the second working port 2 via the compressed air outlet 25 leads. The first working port 1 remains vented in this case on the remaining in its rest position first 5/2-way valve 4. The working cylinder 3 connected to the two working connections 1 and 2 remains in its position. Also in the case of a spring break in the pilot valve 7 occurs at the two working ports 1 and 2 no

Change of state (opposing venting / admission), because at the pilot valve 7 no control pressure is applied, since the second 5/2-way valve 12 does not switch without electrical control signal. The first working port 1 remains vented via the remaining in its rest position first 5/2-way valve 4, the second working port 2 via the second 5/2-way valve 12 is applied. The working cylinder 3 connected to the two working connections 1 and 2 remains in its position. In addition, the valve assembly also has the further advantage in this embodiment that a fault in the return device of one of the two pilot valves 7 or 13 (eg. A spring break) is detected in each case safe operation. One with the working connections 1 and 2

Connected pneumatic drive would not go back in these errors in the removal of the electrical control signals. Because of the criss-cross Shading of the two 5/2-way valves 4 and 12 must always switch back both pilot valves 7 and 13, so that at the working ports 1 and 2, a new state change (opposite direction ventilation / admission) may occur. Switches only the 5/2-way valve 4 after the previous assumption of switching position in the removal of the electrical input signal back to its rest position (= spring break in the pilot valve 13), the pneumatic working cylinder 3 can not retract, because the second working port 2 continues over the second 5/2-way valve 12 and the compressed air outlet 25 is vented. The main stage 14 of the 5/2-way valve 12, despite applying the air spring 19 does not switch back because of the defective

Pilot valve 13, which receives the control pressure internally via the compressed air connection 15, continues to be applied to the main stage 14 counteracting control pressure. Also, the first working port 1 is vented in this case on the returned to its rest position 5/2-way valve 4. The pneumatic cylinder 3 remains extended. In the opposite case (= spring break in the pilot valve 7), neither the 5/2-way valve 4, nor the 5/2-way valve 12, because they block each other. The main stage 6 of the 5/2-way valve 4 can not switch back as long as the 5/2-way valve 12 has not switched back, because of the defective pilot valve 7 continues to be one of

spring-loaded main stage 6 counteracting control pressure is applied. The main stage 14 of the 5/2-way valve 12, in turn, can not switch back as long as the main stage 6 of the 5/2-way valve 4 has not switched back, because the air spring 19 does not build up pressure. Since at the working ports 1 and 2 no renewed change of state occurs, the pneumatic cylinder 3 is extended and the error is detected. The first working port 1 remains pressurized via the first 5/2-way valve 4 and the second working port is vented via the second 5/2-way valve 12. Because of the

Working connections 1 and 2 thus no change of state (opposing

Venting / admission) occurs, the pneumatic cylinder 3 can not go back and the error is detected. Also in this embodiment, the

Rückstellelleinrichtung the main stage 6 of the 5/2-way valve 4 is additionally formed parallel to the mechanical spring 5 with an air spring according to the embodiment of FIG. This air spring is this via a branch with the

Supply line 27 connected and also externally via the 5/2-way valve 12 in acted on its rest position and vented its switching position via the compressed air outlet 25.

Fig. 7 shows an alternative embodiment of the valve assembly according to the invention in the unactuated (non-energized) starting position with all the valves in their rest position. 6, the first electropneumatically pilot-operated valve is configured as a double-electropneumatically pilot-operated 5/3-way valve 29 with a main stage on both sides automatically resetting and for taking a vented center position as in the otherwise identical with the valve arrangement shown in FIG Resting position, as well as a first and a second switching position formed, wherein the capture of the first switching position in the operation and admission of the external control terminal 8 '

trained pilot valve 7 'takes place. The 5/3 way valve 29 is the first

Working connection 1 upstream and connects this in the first switching position (switching the pilot valve 7 ') with the compressed air source 10 and in the second switching position (switching the pilot valve 30) and the rest position with the compressed air output 26. The electropneumatically piloted 5/2-way valve 12 is upstream of the second working port 2 and connects it via the supply line 27 in the rest position with the compressed air source 10 and in switching position with the compressed air output 25. The air spring 19 of the 5/2-way valve 12 is externally via the 5/3 way valve 29 in the second

Switched position (switching of the pilot valve 30) via the supply line 28 and vented in the first switching position (switching the pilot valve 7 ') and rest position. In this version is - as in the execution acc. Fig. 6 - due to the changed channel management while maintaining the desired safety features both the arrangement of a check valve in the connecting line 9, as well as a compressed air connection 15 of the second 5/2-way valve 12 upstream

Throttle dispensable. Due to the redundant arrangement, both the control valve 7 'of the 5/3 way valve 29, which is formed with the external control connection 8', and the pilot control valve 13 of the second 5/2-way valve 12 must switch, so that a change of state occurs at the two working connections 1 and 2 (in opposite directions

Venting / admission) occurs. An error in the return device of one of the two pilot valves 7 'or 13 (for example, a spring break) can in the starting position do not lead to an unintentional movement of a connected to the working ports 1 and 2 pneumatic drive. In case of a spring break in the

Pilot valve 13 occurs at the two working ports 1 and 2 no change in state (opposing vent / impingement), because the pilot valve 7 'does not switch without electrical control signal. Although a spring break in the pilot valve 13 may lead to switching its main stage 14, but only for additional

Vent also the second working port 2 via the compressed air outlet 25 leads. The first working port 1 remains vented in this case on the remaining in its rest position 5/3 -way valve 29. The working cylinder 3 connected to the two working connections 1 and 2 remains in its position. Also in case of a spring break in the

Pilot valve 7 'occurs in the starting position at the two working ports 1 and 2 no change in state (reverse venting / admission), because on

Pilot valve 7 'no control pressure is applied because the second 5/2-way valve 12 does not switch without electrical control signal. The first working port 1 remains vented via the remaining in its rest position 5/3 - way valve 29, the second working port 2 via the second 5/2-way valve 12 is applied. The working cylinder 3 connected to the two working connections 1 and 2 remains in its position. In addition, the valve arrangement also has the further advantage in this embodiment that a fault in the rear part of one of the two pilot valves 7 'or 13 (eg. A spring break) in each case reliably detected. One with the working connections 1 and 2

Connected pneumatic drive would not go back in these errors in the removal of the electrical control signals. Because due to the crosswise interconnection of the two-way valves 29 and 12 always both pilot valves 7 'and 13 must change their previously assumed switching state again, so at the working ports 1 and 2 a new change of state (opposing

Venting / admission) occur and the drive can drive back again. Switches only the 5/3 way valve 29 after the previous taking the switch position in the removal of the electrical input signal back to its rest position (the vented center position) back (= spring break in the pilot valve 13), the pneumatic cylinder 3 can not retract, because the second Working port 2 is still vented via the second 5/2-way valve 12 and the compressed air outlet 25. The main stage 14 of the 5/2-way valve 12 can not switch back despite applying the air spring 19, because of the defective pilot valve 13, which controls the pressure internally over the

Compressed air connection 15 refers, continues to be applied to the main stage 14 counteracting control pressure. Also, the first working port 1 is vented in this case on the returned to its rest position (the vented center position) 5/3 -way valve 29. The pneumatic cylinder 3 remains extended. In the opposite case (=

Spring break in the pilot valve 7 ') switch neither the 5/3-way valve 29, nor the 5/2-way valve 12, because they block each other. The main stage 6 'of the 5/3-way valve 29 can not switch back as long as the 5/2-way valve 12 has not switched back, because on the defective pilot valve 7' continues to apply a spring-loaded main stage 6 'counteracting control pressure. The main stage 14 of the 5/2-way valve 12, in turn, can not switch back, as long as the main stage 6 'of the 5/3 -Wegeventils 29 does not switch to its second switching position (switching the pilot valve 30), because the air spring 19 does not build up pressure. Since at the working ports 1 and 2 no renewed change of state occurs, the pneumatic cylinder 3 is extended and the error is detected. The first working port 1 remains pressurized via the first 5/3 -way valve 29 and the second working port is vented via the second 5/2-way valve 12. Since at the working ports 1 and 2, therefore, no renewed change of state (opposing vent / admission) occurs, the pneumatic cylinder 3 can not go back and the error is detected. The valve arrangements of FIGS. 6 and 7 can be produced on the basis of the identical ducting in the construction as a modular unit with a base plate and on these valve modules or valve bodies with a same base plate. This allows the same part usage of the base plate in the manufacture of both

Valve arrangements of Fig. 6 and 7. The different valve function results only from the different configuration of the first directional valve, which can be replaced by replacing the same base plate.

Fig. 8 shows a tabular representation of switching positions of the valve assembly of FIG. 2 in comparison with the switch positions of a commercially available on both sides electropneumatically piloted 5/3 -Wegeventils 29 'with an open

Middle position (both working connections applied). By the pilot valves 7 and 13 of the valve assembly of FIG. 2 both together, and individually electrically are formed switchable, with the thus enabled control positions an additional valve function is achieved. The possible control positions are shown in the rows of the table Fig. 8, wherein the information of the first column, the respective

Designate switching positions of the pilot valve 7 and the information in the second column denote the respective switching positions of the pilot valve 13, both in each case based on the design of the valve assembly according to. In each case the indication "on" designates the actuation of the corresponding pilot valve, whereby the directional valve pneumatically piloted by it assumes its switch position. "Off" designates respectively the non-actuation of the corresponding pilot valve, whereby the directional valve pneumatically piloted by it retires. With reference to the working connections 1 and 2, the valve arrangement according to FIG. 2 with these control positions in total corresponds to the mode of operation of a

commercially available 5/3-way valve 29 'with an open center position (both

Working connections applied) controllable. The specified in Fig. 8

Control positions of the valve assembly acc. Fig. 2 respectively

Switching states of a 5/3 way valve 29 'are shown in the third column and indicated in the fourth column with Kurzangaben. The 5/3 way valve 29 'in its open center position (this is the rest position of the 5/3-way valve 29', both precursors are inactive) corresponding control position of the valve assembly acc. FIG. 2 is shown here in the second line of the table FIG. 8. Here's just that

Pilot valve 13 is actuated, wherein the 5/2-way valve 12 assumes its switching position (while the first 5/2-way valve 4 is in the rest position).

Fig. 9 shows a tabular representation of switching positions of the valve assembly of FIG. 6 in comparison with the switch positions of a commercially available on both sides electropneumatically piloted 5/3 -Wegeventils 29 "with a vented

Middle position. By the pilot valves 7 and 13 of the valve assembly shown in FIG. 6, both jointly, and individually formed electrically switchable, an additional valve function is achieved with the thus enabled control positions. The possible control positions are shown in the rows of the table Fig. 9, wherein the information of the first column indicate the respective switching positions of the pilot valve 7 and the information in the second column, the respective switching positions of Pre-control valve 13 denote, both in each case based on the execution of the valve assembly acc. In each case the indication "on" designates the actuation of the corresponding pilot valve, whereby the directional valve pneumatically piloted by it assumes its switching position. "Off" designates respectively the non-actuation of the corresponding pilot valve, whereby the directionally controlled pilot valve retires. Related to the

Working connections 1 and 2 is the valve arrangement according to FIG. 6 with these

Control positions in total according to the operation of a commercially available 5/3 -Wegeventils 29 "with a vented center position (both working ports vented) controllable The specified in Fig. 9 control positions of

Valve arrangement acc. 6 each corresponding switching states of a 5/3 -Wegeventils 29 "are shown in the third column and referred to in the fourth column with Kurzangaben.Die the 5/3 -Wegeventil 29" in its vented center position (this is the rest position of the 5/3-way valve). 3-way valve 29 ", both precursors are inactive) corresponding control position of the valve arrangement according to Fig. 6 is shown here in the second line of the table Fig. 9. Here, only the pilot valve 13 is actuated, the 5/2-way valve 12 its Switching position occupies (while the first 5/2 way valve 4 is in the rest position).

LIST OF REFERENCE NUMBERS

First work connection

Second work connection

working cylinder

, 12 5/2-way valve

, 5 ', 5 "spring

, 6 ', 14, 109, 112 main stage

, 7 ', 13, 30, 108, 1 10 pilot valve

, 8 'control connection

Connection line0 Compressed air source

1, 17, 25, 26 106, 107 Compressed air outlet 5, 105, 111 Compressed air connection6 Control line

8 Check valve9, 24 Air spring

0, 28 supply line

1, 27 supply line2 cross-sectional constriction3 valve connection

01, 102 valve

03, 104, 111 working connection 9, 29 ', 29 "5/3 way valve

Claims

claims

Valve arrangement, comprising a first and a second, connectable with a pneumatic actuator working port (1, 2) and a first and a second, each electropneumatically pilot-operated directional control valve, in which one or both valves the working ports (1, 2) for their admission and venting is preceded or are, wherein the precursors of both valves are formed automatically resetting and the second directional control valve for alternately taking a rest and a switching position is formed and the first stage of the first-way valve, an external control terminal (8, 8 '), which via the second Directional valve in its switching position can be acted upon and vented in its rest position, characterized in that the second directional control valve as a return device for a

Main stage (14) has an externally acted upon via the first directional valve and can be vented air spring (19) and a state change between loading or venting of the air spring (19) of the second directional control valve after taking a switching position by the first directional control valve only in response to the change of the switching state the first directional control valve and a state change between loading or venting at one of the two working connections (1, 2) after a loading or venting has previously taken place with the taking of the switching position by the second directional control valve only as a function of the intake of the

Rest position by the second directional valve takes place.

Valve arrangement according to claim 1, characterized in that main stages (6, 6 '; 14) of the two-way valves in slide and / or the precursors of the two

Directional control valves are designed in seat construction.

Valve arrangement according to claim 1 or 2, wherein the first directional control valve for

formed alternately taking a rest and a switch position with an automatically resetting main stage (6), characterized in that the second directional control valve the external control port (8) of the first directional control valve in its switching position via a control line (16) with a compressed air source (10) and in its rest position with a compressed air outlet (17) connects and its air spring (19) via the first directional control valve is acted upon in its rest position and vented into its switching position, and wherein the first directional control valve is arranged upstream of the two working connections (1; 2) and in the switching position the first working connection (1) with a compressed air source (10) and the second working connection ( 2) with one

Compressed air outlet (1 1) connects and in the rest position, the second working port with a compressed air source (10) and the first working port (1) via a

Connecting line (9) connects to the control line (16), wherein in the

Connecting line (9) is arranged in the opposite direction blocking check valve (18) and / or the compressed air connection (15) of the second directional control valve, a throttle device is arranged upstream or are.

Valve arrangement according to one of claims 1 to 3, characterized in that the second directional control valve is designed as a 3/2-way valve.

Valve arrangement according to one of claims 1 to 3, characterized in that the second directional control valve is designed as a 4/2-way valve.

formed alternately taking a rest and a switch position with an automatically resetting main stage (6), characterized in that the second directional control valve the external control port (8) of the first directional control valve in its switching position via a control line (16) with a compressed air source (10) and in a rest position with a compressed air outlet (17) connects and its air spring (19) acted on the first directional valve in its rest position and vented in the switching position, and wherein the first directional control valve upstream of the first working port (1) and this in the switching position with a compressed air source (10) and in the rest position with a compressed air outlet (1 1) connects and wherein the second directional control valve upstream of the second working port (2) and this in the rest position with a compressed air source (10) and in the switching position with a compressed air outlet ( 25) connects.

Valve arrangement according to one of claims 1 to 6, characterized in that the first directional control valve is designed as a 5/2-way valve (4).

8. Valve arrangement according to claim 1 or 2, wherein the first directional control valve as

on both sides electropneumatically piloted 5/3 way valve (29) configured with a double-sided automatically resetting main stage (6 ') and designed to take a vented center position as a rest position, and a first and a second switching position, wherein the capture of the first switching position during actuation and loading with the external control terminal (8 ')

trained precursor, characterized in that the second directional control valve connects the external control port (8 ') of the first directional valve in its switching position via a control line (16) with a compressed air source (10) and in a rest position with a compressed air outlet (17) and its air spring (19) about the first

Directional valve acted upon in the second switching position and in the first

Switched position and rest position is vented, and wherein the first directional control valve upstream of the first working port (1) and this connects in the first switching position with a compressed air source (10) and in the second switching position and the rest position with a compressed air outlet (26) and wherein the second Directional valve upstream of the second working port (2) and this in the rest position with a

Compressed air source (10) and in the switching position with a compressed air outlet (25) connects.

9. Valve arrangement according to one of claims 1 to 3, 6, or 8, or one of

Claims 1 to 3 or 6 in each case in conjunction with claim 7, characterized

in that the second directional valve is designed as a 5/2-way valve (12).

10. Valve arrangement according to one of claims 1 to 3, 6 or 7 respectively in conjunction with claim 9, characterized in that the return means of

Main stage (6) of the first directional valve is formed in parallel with a mechanical spring (5) and an air spring (24), wherein the air spring (24) acted externally via the second directional control valve in its rest position and the switching position is vented.

1 1. Control method for a valve assembly according to claims 3 and 7, or the Claims 3 and 7 in conjunction with each of claims 4, 5 or 9, or claims 3 and 7 and claim 10, or claims 3, 7, 9 and 10, wherein the compressed air connection (15) of the second directional valve upstream of a throttle device is and in the connecting line (9) no check valve is arranged, characterized in that the precursors of the two-way valves are formed both jointly, as well as individually electrically switchable.

12. Control method for a valve assembly according to claims 6 and 7, or claims 6, 7 and claim 9, or claims 6, 7, 9 and 10, characterized in that the precursors of the two-way valves both jointly, and individually electrically are formed switchable.