GB1048446A - Screw rotor machine - Google Patents

Abstract

1,048,446. Rotary compressors and motors. SVENSKA ROTOR MASKINER A.B. May 14, 1964, No. 20066/64. Heading F1F. A rotary compressor or motor of the meshing screw type comprising a housing 10, Figs. 1, 2, having intersecting cylindrical bores 12, 14 to form a working space having low and high pressure ports 50, 48 located on opposite sides of a plane in which lie the axes of the bores and co-operating male and female helically-threaded rotors 34, 38, includes a working section 61 extending from the low pressure end K of the housing to a point L corresponding to that end of the high pressure port nearest to the low pressure port and a high pressure section 63 extending from the point L to the high pressure end M of the housing 10 and also within the working section 61, the profile of the threads of the male rotor in transverse cross-section include a tip portion 53, Fig. 7, concentric with the bore 12 of substantially constant width throughout the length of the working section 61 and generated flank portions 47 and within the high pressure section 63 the profile of the threads of the male rotor include a circular tip portion 51, Fig. 21 and generated flank portions 59. The flank portions in each instance are generated by the crest edges of the female rotor threads and the centres of curvature of the circular tip portions lie substantially on the pitch circle 82 of the male rotor 34. The male rotor threads co-operate with the troughs of the female rotor to form the envelope of the male rotor thread profile during rotation of the rotors with the trough of the female rotor at the high pressure end being fully circular. An unbroken seal is formed in the working section 61 by the co-operation of the crest edges and roots of the respective rotors. As shown in Figs. 1 and 2, the high pressure section is gradually tapered with the tip portions of the male rotor gradually changing from a generator form 53 to a circular form 51 with the elimination of the sealed pockets so that an open pocket is provided at the point M to prevent further compression with consequent damage to the compressor and to reduce noise, temperature and bearing loads. The male rotor is preferably provided with three threads and the female rotor with four threads with timing gears 42, 46 keeping the rotors in timed relation with each other. In another embodiment, Fig. 24 (not shown) a sharp step is provided between the working and high pressure sections instead of the merging of parallel and tapered portions of the rotors.