GB531444A - Improvements in or relating to compressor plants of variable delivery of pressure fluid - Google Patents

Abstract

531,444. Fluid-pressure servomotors. SCHWEIZERISCHE LOKOMOTIV-UND MASCHINENFABRIK. July 22, 1939, No. 21365. Convention date, July 25, 1938. [Class 135] A control device for a rotary fluid compressor device comprising a rotor 1, suction pipe 2, and pressure pipe 3 is adapted to cut off the driving- motor when the pressure in pipe 3 reaches a given maximum value and to bring in the driving-motor automatically when the pressure drops to a certain value. The pressure pipe 3 is fitted with a non-return valve 9 and is connected via a pipe 14 to a cylinder 14a containing a piston 12 loaded by a weight 10. At a given pressure the piston 12 rises to the dotted line position, and the fluid passes through a pipe 17 and acts upon a piston 13 loaded with a weight 11 of less mass than 10, so that the piston 13 rises to the position shown by dotted lines and by linkage 18 acts upon a mercury switch 19 to de-energize a solenoid 22 and open a switch 25 to stop the driving-motor. At the same time the pressure fluid passes via pipes 17, 17a, 15 to an accumulator 16 and thence to the cylinder 5c so as to depress a plunger 5 and an associated valve 4 against the action of a spring 6 and cut off the compressor 1 from the suction conduit. At the same time a valve 7 is opened to connect the pressure side to atmosphere or to the suction conduit. As the pressure drops the fluid leaves the cylinder 5 and passes finally out of pipe 15d until the piston 13 drops to cut off this flow and energize the solenoid 22 to throw-in the motor. The valve 4 meanwhile returns to its open position under the action of spring 6. The pipe 15 may be fitted with a narrow gauged orifice to retard the closing of the valve 4. The retarded opening of the valve 4 may be effected by an electric time lag relay, or by a plunger oil baffle connected to the plunger 5.