Patent GB-1028286-A (GB)
Title: Rotary compressor
IPC: F04C28/06
Filed: 1964-08-04
Abstract: 1,028,286. Rotary compressors. JAEGER MACHINE CO. Aug. 4, 1964 [Oct. 3, 1963], No. 29265/64. Heading F1F. In a rotary positive-displacement, oil-cooled compressor having an unloading system whereby the power required to drive the compressor in its unloaded state is greatly reduced, as described in Specification 1,028,285. The pressure switch PS subjected to the pressure in a line 48, Fig. 1, connected to the air service conduit 25, controls a solenoid-actuated valve Sl in a line 27 carrying oil from the air-oil separator 24 to the upstream end of the interstage manifold 14 through a strainer 28 and check valve 29 as well as a solenoid-actuated valve S2 which besides supplying air to and exhausting air from the piston-actuator controlling the air-intake valve 16 also through the valve S2 controls further solenoid-actuated valves S3, S4 which in turn control an airpressure actuated five-way control valve 50. As described in Specification 1,028,285, thermal switches TH1 and TH2 and a flow switch FLS are fitted. In the inoperative position of the compressor, the solenoids of the valves Sl, S2 are both de-energized such that the valve Sl is closed and the valve S2 positioned to vent the piston-actuator to atmosphere to allow the valve 16 to open. Both the valves S3 and S4 are vented to atmosphere so that the valve 50 is in its central position under the action of its springs and blocks all its ports. On the closing of a three-pole switch and the subsequent momentary depression of a starter switch in the electric circuit, a circuit is energized to start the compressor motor 11 and energize the solenoid of the valve S3 so that air from the service line 25 passes through lines 48, 45 and 53 to actuate an air actuator 50b and at the same time vent an actuator 50a through the line 44 to shift the valve 50 leftwardly. With the valve 50 thus shifted a line 54 from the compressor is still blocked, lines 56, 59 are inter-connected to form a closed path through a cyclone oil separator 57 and a line 55 from the oil reservoir 23 is connected to a line 60 leading to a thermally-actuated, by-pass valve 40. The valve 40 is connected to the oil cooler by the line 38 and to the pump 30 by the line 39 until such time as the temperature of the oil rises. The switch PS is maintained in its initial position in which the solenoid of the valve Sl is energized to open the valve whence separated oil from the separator flows into the upstream end of the manifold 14. With the compressor and oil pump operating normally, air is drawn into the compressor through the inlet valve 16 and discharged therefrom through the line 20 into the receiver 21 and the service line 25 and this continues whilst there is a demand for air and the operating pressure is below 105 p.s.i.g. On reaching this pressure the switch PS operates to energize the solenoid of the valve S2 to direct air to close the valve 16. At the same time air is directed to the actuator 50a and the actuator 50b is vented to move the valve 50 rightwardly so that the lines 54 and 59 are inconnected to discharge air through the exhaust silencer 58. During unloaded condition of the compressor, the air-oil mixture from the compressor is predominantly oil, only scavenging air entering the line 18 and passing through the manifold and the high pressure stage. The amount of oil remains substantially the same whether the compressor is loaded or unloaded, it being necessary for the cyclone separator 57 to be of sufficient capacity to deal with the oil in the unloaded condition of the compressor so that the oil is not lost. At this time the line 55 from the reservoir 23 is closed by the valve 50 and the line 27 blocked by the valve S1 to retain the oil to the system. Compressed air in the air-receiver 21 is retained on the closure of the check valve so that time is saved when the compressor is again loaded. On the pressure in the service line falling to 90 p.s.i.g. the pressure switch is returned to its position for further loading of the compressor. Restricted by-passes 43, 52 associated with the valves 16 and S4 respectively prevents instantaneous operation of the valves 16, 50 for protection of the compressor. As in Specification 1,028,285 an automatic stopping and starting circuit is included which can operate due to delay circuits up to a maximum of four times per hour.