GB1085821A - Helically threaded rotors for screw type pumps, compressors and similar devices - Google Patents

Abstract

1,085,821. Rotary intermeshing screw machines. J. E. WHITFIELD. Feb. 5, 1965 [March 13, 1964], No. 5065/65. Heading F1F. In an intermeshing screw machine operable as a pump, compressor, pneumatic or hydraulic motor, I.C. or steam engine or a meter comprises a housing 10, Figs. 1, 2, having a pair of parallel intersecting bores 12, 14 mounting respectively main and gate complementary mating helically threaded rotors 34, 38 which together with the housing form pockets at the suction end 60 which as the rotors revolve in opposite directions about their axes advance towards the discharge end 58 and with the threads of each rotor co-operating with the troughs of the mating rotor and the housing to provide close running clearances. Each rotor includes a uniform section 54 extending from the suction end to a point short of the discharge end wherein the threads and troughs are of uniform shape and size and a non-uniform section 55 extending from said point to the discharge end wherein the threads and troughs are of non-uniform shape and size. The main rotor 34 includes lands at the roots of the threads which are cylindrical and substantially uniform throughout the whole length of the rotor and lands 72, Fig. 29 at the tips of the threads extending from said point to the discharge end which are inclined and of gradually increasing width with the crest edges 76 rounded and tangential to the inclined tip land 73 and to the generated sides 78 of the threads. The gate rotor 38 includes lands 70, Fig. 30 at the tips of the threads which are cylindrical and substantially uniform throughout the length of the rotor and concave troughs uniform throughout the uniform section 54 and concave troughs having concave inclined lands at the bottom and of gradually decreasing depth from said point to the discharge end 58. The crest edges of the lands 70 are rounded, generated by the crest edges 76 of the rotor 34 and tangential to the lands 70 and may be sharp with respect to the flanks of the concave trough or the sharp edges may be rounded to be tangential to the flanks. The trough 66 of the main rotor 34 and the trough 68 of the gate rotor 38 at the discharge end of the rotors are approximately half what they are over the uniform sections 54 of the respective rotors. With this arrangement the threads of the two rotors are completely generated, an unbroken seal is maintained between the threads of the two rotors and the housing and the pockets as they approach the discharge end of the device are gradually unsealed to eliminate excessive pressure, noise and temperature and vent the pockets at high speeds of rotation of the rotors. Timing gears 37, 41 are fitted on the shafts 36, 40 of the main and gate rotors respectively to permit of slight working clearances between the rotors and housing. The timing gear 41 is made adjustable with respect to a hub 39 fixed to the shaft 40 of the gate rotor to permit of correct timing. The main rotor 34 is driven and drives through the gearing and the helical threads of the two rotors the gate rotor 38. The tips of the threads of the gate rotor may include shallow slots fitted with sealing material to reduce leakage. The non-uniform end of the gate rotor may be enlarged to provide for cooling liquid at the high temperature end of the device where extra cooling is necessary.