GB1031991A - Improvements in or relating to apparatus for compressing air or other gas - Google Patents

Abstract

1,031,991. Rotary compressors and vacuum pumps. BYRAN DONKIN CO. Ltd. March 4, 1962, No. 8378/62. Heading F1F. In a rotary compressor or vacuum pump, a primary rotor 34 (Fig. 2, not shown) has two diametrally-opposed lobes 38, 40 and engages with a secondary rotor 36 having two diametrally-opposed lobe-receiving pockets 42, 44, the rotors being mounted on parallel shafts 54, 56 (Fig. 1, not shown) which are coupled to one another by gears 66, 68 lodged in an end cover 76 attached to an end plate 60 of a stationary casing 30 for the rotors. In operation, gas is drawn into the casing through an inlet 46 and compressed in a space or chamber 32 between the rotor 34 and the casing, the compressed gas being ejected through an outlet port 50 controlled by a valve 52 which remains closed until the pressure in said chamber is equal to that in an outlet duct 48. Alternatively, the primary rotor may comprise a single lobe (Fig. 11, not shown) or three lobes (Fig. 12, not shown), the secondary rotor having a corresponding number of lobereceiving pockets. An arcuate recess or depression 150 is formed in each of the end plates 60, 62 to allow compressed gas trapped in the lobe-receiving pocket in the rotor 36 which is mating with a lobe on the rotor 34 to escape into the other lobe receiving pocket so as to reduce vibration caused by low-pressure gas being conveyed by the lobe-receiving pockets from the region of the inlet 46 to the chamber 32. The compressor may be modified to include a port 208 (Fig. 13, not shown) to effect communication between a lobe-receiving pocket, which is approaching the chamber 32, and the outlet duct 48 so as to equalize the pressure in said pocket with that in said chamber and thereby reduce vibration. The port 208 may be provided in addition, or as an alternative, to the recesses 150, and may be included in any of the preferred embodiments. A pump 72 (Fig. 1) driven by the shaft 56 draws cooling oil from a sump (not shown) and delivers it to a port 74 communicating with a non-return valve 78 for conduits 80 82, 84 leading to transverse bores in the shafts 54, 56 through which the oil is ejected into cavities 88 in the rotors. The oil returns to the sump from said cavities through bores 90 and annular passages 92 surrounding the conduits 80, 84. When the rotors are stationary, oil is retained in the rotors by spring-biased valvemembers 94 abuting the ends of the passages 92. When the end cover 76 is removed, oil is retained in the rotors by spring-biased sleevemembers 106 closing holes 110 in the conduits 80, 84. The apparatus may comprise two stages constituted by two primary rotors 160, 162 (Fig. 10, not shown) which engage with a single secondary rotor 166, bores 172, 174 containing the primary rotors being in communication with one another through a valve 194 and an inter-cooler 178. The outlet duct duct 196 for the bore 174 is controlled by a further valve 194, both of said valves being similar to the valve 52.