GB1160161A - Rotary Sliding Vane Compressor - Google Patents

Abstract

1,160,161. Rotary positive-displacement compressors. WORTHINGTON CORP. Oct. 4, 1966 [April 4, 1966], No.44221/66. Heading F1F. A rotary compressor for a refrigeration system comprises a rotor 52, Figs. 1 and 2, having two sets of radial vanes 60, 64 slidably lodged in slots 58, 62 and engaging with liners 44, 46 within a casing 34, which liners are separated from each other by a fixed wall 38 so as to form two stages 40, 42, the rotor being driven by an electric motor 20, and the wall 38 being furnished with a plurality of assemblies 114, 116, 118, 120 to effect unloading of the low-pressure stage 40 in accordance with the difference between the pressures at a plurality of inlets 32 for the refrigerant vapour and the interior of a further casing 18 into which the compressed vapour is discharged from the high-pressure stage 42 through a passageway 102. Each of the assemblies aforesaid includes a plunger 122 that engages with a compression spring, abuting the liner 44, a chamber 124 adjacent the plunger being connected by a conduit 136 or 158 to one or other of two control devices 138, which detects the beforementioned pressure difference and normally renders the plunger adjacent the liner 44. When the said pressure difference becomes excessive, the plunger 122 in one of the assemblies is retracted so as to allow compressed vapour in the low-pressure stage to escape into one or both of two passageways 66, 68 that connect the inlets 32 to inlet ports in the form of a plurality of slots 70, 72, which are located between outlet ports in the form of a plurality of slots 74, 76. The assemblies 114, 116 are controlled by one of the devices 138 and the assemblies 118, 120 are controlled by the other of these devices, the plungers in the assemblies 114, 118 being the first to be operated when the pressure difference becomes excessive and the plungers of the other assemblies being operated thereafter if the pressure difference continues to increase. If the pressure in the working chambers 50, 54 exceeds a predetermined value, the plungers 122 serve as safety valves. The rotor is driven by an electric motor 20 that is cooled by the low-pressure vapour flowing therethrough from an inlet 24 to the inlets 32. Oil in a reservoir 186 is directed into the slots 58, 62 by a pump 196 through a passageway 200 to lubricate the vanes. Each of the control devices includes a spring- loaded piston 142, Fig. 6, within a cylinder 140 having its ends connected by conduits 148, 156 to the inlets 32 and either the interior of the casing 18 or the high-pressure end of the low-pressure stage, respectively, the piston being moved in accordance with the changes of pressure at the ends of the cylinder. The conduits 136, 158 are connected by a conduit 157 to the interior of the casing so that when the piston is in the position shown the pressure in the chamber 124 of each of said assemblies is sufficient to keep the plunger 122 against the liner; and when the piston moves to uncover the end of one or each of the conduits 136, 158, the consequent reduction of pressure in the associated chambers 124 effects a corresponding reduction in the loading of the compressor. An alternative control device (160, Fig. 7 not shown), is generally similar to that shown save that the piston is modified to prevent unloading of the compressor until a predetermined pressure difference arises. The working fluid of the alternative control device and the beforementioned assemblies is oil, which is stored in a reservoir (186) and pressurized by a pump (188). A second embodiment, Fig. 5 (not shown), has assemblies similar to those shown at either end of a casing for a single rotor.