Patent GB-486324-A (GB)
Title: Improvements relating to the operation and control of water filtering systems
IPC: B01D37/04
Filed: 1937-01-02
Abstract: 486,324. Filters. PERMUTIT CO., Ltd. Jan. 2, 1937, No. 142. Convention date, Jan. 2, 1936. [Class 46] [Also in Group XXIX] In a water-filtering system comprising a battery of filter units with separate valves for controlling the flow through the individual units and one or more master valves for controlling the flow through the battery as a whole, control means are provided for effecting co-ordinated operation of the valves. There may be a single multi-way master valve and the valves for the units may each have its own pilot operating valve. Fig. 1 shows an arrangement of four filters to which water is supplied through a master valve V7C, the filtrate being passed to service through a valve V5. For back-flushing unfiltered water is supplied to the bottom of each filter through a master valve V7A. and the water after passing upward through the filter is led to waste through a master valve V7B. Valves V1 ... V4 at the top of the elements are operated so that the elements are flushed successively one at a time. After back-flushing there may' be a period of filtering to waste, the filtrate being discharged through a master valve V6, before normal filtration is started. Each of the valves is opened and closed by a piston working in a cylinder to which pressure fluid is admitted and from which it is discharged under control of a rotary pilot valve PV which has the necessary ports and connections for operating the valves successively as required to carry out the series of operations described above. Diaphragms moved in one direction by a spring and in the other by pressure fluid may be used instead of pistons for operating the valves. An alternative arrangement of connections is described to allow of back-flushing of each filter by filtered water from the other filters. In such an arrangement two valves are provided at the top of each filter, one controlling the supply pipe for water to be filtered and the other a branch pipe for leading flushing water to waste. The valve PV may be turned by an electric motor the circuit of which is closed initially to start a regenerative cycle by a constant speed timing motor driving a rotary switch member. The shaft of the valve carries the moving member of a circuit breaker which ensures that the valve PV is brought to rest in correct position for each regenerative step. Separate timing motors are provided to time the period of flushing for each filter and of filtering to waste and to close the circuit of the driving motor at the end of each such period, so that the valve is moved on a further step. In the arrangement shown in Fig. 18, a single rotary multi-way master valve MV is used, and each of the valves for the individual filters, whether piston-operated or diaphragm operated, has associated with it a pilot-valve operated by a solenoid S1, S2 or S3. The valve MV is operated electrically, as described above in connection with the valve PV. When the valve is in position for back-flushing the circuits of the solenoids are closed successively for periods each determined by its own timing motor. Specification 482,955 is referred to.