Valve arrangement and control method

Abstract

For the purpose of providing a valve arrangement for controlling pneumatic drives with protection against a sudden automatic change in the initial switching position without an input signal in the event of a fault in a resetting device of a pilot stage and, for this situation, effective fault identification by purely pneumatic means, said valve arrangement comprises a first and a second working connection (), which can be connected to a drive, and a first and a second electropneumatically pilot-controlled directional valve, in which valve arrangement one or both directional valves is or are arranged upstream of the working connections () for the purpose of influencing and venting said working connections, wherein the pilot stages of both directional valves are of automatically resetting design and the second directional valve is designed for alternately assuming an inoperative position and a switching position and the pilot stage of the first directional valve has an external control connection (') which can be influenced by means of the second directional valve in its switching position and can be vented by means of said second directional valve in its inoperative position, wherein the second directional valve has, as a resetting device for the main stage (), an air spring () which can be influenced and can be vented externally by means of the first directional valve, and a change in state between influencing or venting of the air spring () after the first directional valve assumes a switching position takes place only depending on the change in the switching state of the first directional valve, and a change in state between influencing or venting at one working connection () after previous influencing or venting which took place with the second directional valve assuming the switching position takes place only depending on the second directional valve assuming the inoperative position.