GB1301475A - - Google Patents

Abstract

1301475 Screw rotor machines SVENSKA ROTOR MASKINER A B 10 July 1970 [14 July 1969] 35360/69 Heading F1F In a meshing screw rotor machine comprising a housing rotatably mounting at least two intermeshing screw rotors, one at least of said rotors is journalled in bearing assemblies including two axially spaced thrust bearing means, one being of the double-acting type capable of supporting axial loads in either direction and the other supporting axial loads in the same direction as those imparted to the rotor during machine operation with a pre-loaded spring means inserted in series with the said other thrust bearing means to transfer thrust from the rotor to the housing. During operation of screw rotor machines of the kind in which oil is injected into the working space and the female rotor is driven by the male rotor by direct contact between their flanks besides the large axial loads acting on the rotors resulting from the pressure difference of the working medium at the low and high-pressure ends of the machine, axial loads also result from direct contact between the rotor flanks being added to the pressure difference loads in the case of the male rotor and subtracted therefrom in the case of the female rotor. As shown in Fig. 1, the male rotor 28 of a single stage compressor is supported at the high-pressure end of the machine by a double-acting thrust bearing comprising inner and outer ball bearings 34 and at the lower pressure end by a roller bearing 32 and a further thrust bearing 38 whose inner race abuts an axially-slidable sleeve 44 constituting an abutment for a pre-loaded helical spring 46 which at its other end abuts a nut 42 carried by the rotor. When the machine is inoperative, the spring 46 removes axial load from the outer bearing 34. On starting the compressor the spring force has first to be removed before the thrust bearings commence to take axial load. The loading of the spring will determine the load which can be transferred to the bearing 38, any further increase then being taken by the inner bearing 34. The invention may also be applied to a two-stage compressor having additional low-pressure male and female rotors (28A, 30A), Fig. 3 (not shown). The male rotors are in alignment and connected together by a splined coupling comprising elements (62, 64) splined internally and externally and an internally splined coupling sleeve (60). The spring 46 in this case is interposed between the elements (62, 64) and the thrust bearings located at the lowpressure end of the low pressure stage and the high-pressure end of the high-pressure stage. For modifications to the arrangement and disposition of the spring 46 both in single-stage and double-stage compressors reference should be made to the Specification.