GB583938A - Improvements in fluid pressure supply systems - Google Patents

Abstract

583,938. Rotary compressors. BENDIX-WESTINGHOUSE AUTOMOTIVE AIR BRAKE CO. July 27, 1944, No. 14394. Convention date, Aug. 4, 1943. [Class 110 (ii)] Also in Group XXIX] A rotary compressor is controlled by a single valve responsive to the pressures in a high pressure reservoir and in a low pressure reservoir whereby the compressor can transfer fluid from the low pressure reservoir to the high pressure reservoir or can supply either reservoir direct from the atmosphere in order to maintain the pressures in the reservoirs within predetermined limits. The system shown in Fig. 1 comprises a compressor 8, a high pressure reservoir 6, a low pressure reservoir 7, two pressure responsive governors 37, 68, a relay valve mechamism 38, and fluid pressure actuator mechanism 39. The compressor shown is of the rotary sliding blade type and has an inlet port 13 and a discharge port 14. Air can be drawn into the inlet port 13 past a check valve 17 from an aperture 16. Compressed air passes out of the discharge port 14 past a check valve 22 and a conduit 21 to the high pressure reservoir 6. The discharge port 14 also leads by a port 27 and a passage 28 to a chamber 25. The latter communicates by a conduit 29 with the low pressure reservoir 7 and by a port 26 and a passage 30 with the inlet side of the compressor. The chamber 25 contains a shuttle valve 32 carried on a stem 33 with a collar 36 against which bears a spring 35 urging the valve to close the port 27. The stem 33 is pivoted centrally to a lever 50 which is pivotally connected at its opposite ends to piston rods 45, 49, the pistons 44, 48 thereof moving in cylinders 42, 46 within limits defined by stops 54, 55. Compressed air from the high pressure reservoir 6 is supplied to both cylinders 42, 46 from a conduit 41, the latter being supplied directly by a conduit 67 and the former indirectly through the relay valve mechanism 38 and a conduit 57. The pressure responsive governors 37, 68 are similar and of well-known type in which when a predetermined pressure is reached in the relevant reservoir operate to connect a conduit 40 or 69 with a conduit 41 or 70 and to cut off the connection between the conduit 41 or 70 with the atmosphere. The relay valve mechanism 38 comprises a casing with chambers 56, 58 connected by a port 59, a valve member 63 which opreates in the chamber 56 between the port 59 and a vent port 61, and a spring loaded piston 64 which is operated by the pressure in the conduit 70 and is connected to the valve 63 by a stem 62. In operation air is drawn in through the atmospheric port 16 and passed to the high pressure reservoir 6 past the check valve 22 as above described. This continues until the pressure in the reservoir 6 attains a predetermined value say 600 lbs. per sq. inch, when the governor 37 operates to admit pressure to the conduit 41. As the relay valve is then in the position shown, air pressure is admitted to both cylinders 42,46, whereupon the valve 32 is raised to close the port 26 and open the port 27. Air pressure is now admitted to the low pressure reservoir 7 by the conduit 29. When the pressure in the reservoir 7 reaches a predetermined value say 100 lbs. per sq. inch, the governor 68 operates to admit pressure to the piston 64 which causes the valve 63 to close the port 59 and open the port 61 thus venting the cylinder 42. The valve 32 therefore moves down to an intermediate position in which both ports 26, 27 are open and the compressor is unloaded with air passing idly from the inlet port 13 to the outlet port 14 and returning via the passage 28, port 27, chamber 25, port 26 and passage 30. If due to leakage from the system the pressure in the high pressure reservoir 6 falls below the predetermined value, the cylinder 46 is vented and the valve 32 closes the port 27. The compressor now draws air from the reservoir 7 to replenish the reservoir 6 and eventually the pressure in the reservoir- 7 falls below its predetermined value. When this happens the relay valve mechanism 38 and the mechanism 39 resume the position shown. When the pressure in the reservoir 6 has reached its predetermined value again, the valve 32 is moved to close the port 26 once more and air to replenish the reservoir 7 is drawn in from the atmospheric port 16. As shown the high pressure from the reservoir 6 is used to operate an actuator 72 under the control of a self-lapping valve mechanism 77 as described in Specification 543,778, [Group XXIX], exhausted fluid being returned to the reservoir 7. In a modification, the relay valve mechanism is dispensed with and the two pistons of the fluid-pressure actuator mechanism operate in opposite directions on one end of the lever 50.