Vorrichtung zur Regelung einer am Ablauf eines Prozesses beteiligten physikalischen Grösse

摘要

943,335. Fluid-pressure servomotor control systems. UNILEVER Ltd. June 16, 1960 [June 26, 1959], No. 22106/59. Heading G3P. On interruption of the process in a pneumatically operated process control system the regulating element is either locked at its instant position or is moved therefrom to an end position and on resumption of control is unlocked or moved back to the same instant position. A pneumatic proportional and reset controller, Fig. 1, is connected in operation to a regulating element 11 through a changeover valve 1. A pivoted arm 51 carries a microswitch 5 the operating arm of which engages a stop 21 on a rod 22 of the regulating element. When the control action is interrupted by operation of the switch 18,19 the relay coil 9 is de-energized to close the contacts 12,13 and energize the coil 11 of an electromagnetic clutch 4 which locks the arm 51. The changeover valve 1 is moved so that the regulating element 11 is connected to the supply 30 via valves 2,1 and is therefore moved to an extreme position and the microswitch 5 closes contact Y. On depression of the button 7 to restart the process the coils 21, 8 are energized and contacts 16,17 closed. The changeover valve 2 is actuated to connect the regulating element 11 to exhaust via valves 1 and 2 so that it starts to return to the position it had on interruption of the process when it actuates the switch 5 to de-energize the clutch 4. In another example Fig. 2, the pneumatic controller includes proportional, desired value, measured value and reset bellows which act on a disc 101 which cooperates with a nozzle 102 the back pressure of which is fed to a relay 107 the output of which is fed to the regulating element 112. Normally an arm 122 freely follows the rod 119 connected to a rod 115 of the regulating element. On interruption of the process the arm 122 is locked by an electromagnetic clutch 123. Any leakage of air from the regulating element 112 results in operation of the microswitch 125 and a valve 126 in the supply line is opened to provide a compensating amount of air sufficient to keep the regulating element in its position.