GB693352A - Improvements in or relating to electrical apparatus for controlling cyclic operationof multi-unit apparatus - Google Patents

Abstract

693,352. Timed control of electric circuits. POWER - GAS CORPORATION Ltd., and WRIGHT, G. July 28, 1950 [July 30, 1949]. No. 20056/49. Drawings to Specification. Class 118 (ii) [Also in Groups XXVII and XXXVII] A control system for effecting timed and sequential operation of a number of similar units such as a series of dust extraction units which require to be shut down, cleaned and returned to service in succession, includes electrically driven timing devices, one of which times the operation and the other the interval between successive operations, the first device being brought into action on cessation of operation of that unit and initiating operation of the next unit. The system may comprise a common control equipment, including the timers, and local control equipment for the individual units, the several local equipments. being connected to the common equipment by a "start" line and a ".stop " line over which electric impulses, controlled by the timers, are passed to the local control equipments. Each local equipment includes a sequence relay which is actuated on completion of the operation of the associated unit and prepares the local equipment of the next unit for response to the control impulses, whilst simultaneously rendering the former unit insensitive to further impulses. When all the units have operated a common tripping circuit for the several sequence relays is completed to initial another cycle of operations. Each local equipment may include means for de-energizing the associated unit and removing it from the sequence. The system may also include alarm apparatus responsive to faulty operation of the units or power supply failure. Means may also be provided for temporarily cutting out the interval between successive operations. As applied to a dust .extraction plant, each local control equipment also comprises a torque motor which, under the control of an impulse from the. central equipment, closes the exhaust valve, a limit switch associated with which brings about 'operation of a shaker motor for the filter bag and operation of the sequence relay for preparing the starting circuit of the next unit. A " stop " pulse subsequently causes the torque motor to re-open the exhaust valve and stop the shaker motor. The next impulse from the central equipment passes to the following unit, which performs a similar series of operations.