| 摘要 |
<p>An actuating device for an on/off valve having a pneumatic drive that is connected to a compressed air supply by a solenoid valve, wherein when driven with a control voltage, the solenoid valve ventilates the pneumatic drive with the compressed air and, when the control voltage is not present, vents the pneumatic drive. The pneumatic drive moves the on/off valve into an operating position during ventilation and moves it into a safety position during venting. To permit the performance of partial-stroke tests in the simplest way possible, a device for performing the partial-stroke test includes a controllable switch which is closed in a quiescent state, and in this case supplies the control voltage to the solenoid valve. The controllable switch is opened by a control signal that is generated to perform the partial-stroke test. The control signal is supplied to the controllable switch by a position switch that is closed in the operating position of the on/off valve and is opened when the on/off valve reaches a predefined position in the direction of the safety position.</p> |
