GB1349317A - Screw compressor - Google Patents

Abstract

1349317 Rotary positive-displacement compressors GARDNER-DENVER CO 12 June 1972 [23 Aug 1971] 27365/72 Heading F1F A screw-compressor comprises male and female inter-engaging rotors 12, 14 located in parallel intersecting bores 18, 20 of a rotor housing 16, a bearing housing 34 attached to the low-pressure end of housing 16 and having an inlet port 36, an intermediate housing 30 attached to the other end of housing 16 and having highpressure outlet port 78, and low-pressure casing means 98 removably attached to intermediate housing 30 so as to surround rotor 16 and define therewith a cavity 102 in communication with inlet 36, a flanged gas inlet 100 in casing 98 leading to the cavity 102. A movable wall portion 42 of the working chamber serves as valve means to selectively vent gas trapped between rotors 12, 14 back into cavity 102 thus to regulate the compressor capacity. Intermediate housing has bearings 54 for the high-pressure ends of rotors 12, 14, a high-pressure casing 114 being removably attached to housing 30. Casing 114 defines a cavity 116 in communication with outlet 78 and has an outlet 120 for the compressed gas. A piston 72 is attached via webs 74 to movable wall portion 42. Normally, highpressure in chamber 76 serves to move piston 72 and portion 42 to the right as in Fig. 3 due to the larger surface area of piston 72. A spring 90 also biases portion 42 to the right thus creating a vent between an edge 44 of housing 16 and portion 42. Hydraulic fluid from the lubrication and cooling system can be fed to chamber 70 to close the vent. A piston 62 attached to end 63 of rotor 12 is acted upon by pressure from the lubricating system in chamber 60 so as to balance fluid-pressure forces on the highpressure end 64 of rotor blades 22. The casing can be fixed in position relative to a prime mover which drives end 66 of rotor 12. It can be maintained in this position while the rest of the compressor is detached therefrom for servicing. The lubrication system, which is also used to inject liquid into the working chamber to cool the gas being compressed, is described in detail particularly with reference to Figs. 7 and 7A (not shown).