GB1220054A - Two-stage compressor of the meshing screw rotor type - Google Patents

Abstract

1,220,054. Rotary compressors. SVENSKA ROTOR MASKINER A.B. Feb. 2, 1968 [Feb. 6, 1967], No. 5592/67. Heading F1F. A two-stage rotary compressor of the meshing screw rotor type comprises a housing having first and second barrel members 10, 12, Fig. 1, separated by a partition 16 and each formed with a pair of overlapping parallel bores housing intermeshing male and female rotar elements to form first and second stage compressors having working spaces 20, 22 respectively closed at their outer ends by end-plates 18, 14. The bores are all of the same diameter with the male and female rotors 40, 42 in the first stage axially aligned with the male and female rotors 44, 46 in the second stage. The female, or preferably, the male rotors are connected together to form a torsionally and axially rigid rotor unit which is supported in the end-plate 18 by a radial bearing 62 and in the end-plate 14 by a combined radial and thrust bearing 66, 68. The male rotor 40 is provided with a shaft 48 on which the male rotor 44 is shrunk after the passage of the shaft through the partition 16 The shaft 48 is formed with an axial bore 58 and radial bores 60. Fig. 2, into which high pressure liquid may be introduced to mullify the interference between the rotor 44 and the shaft 48 if it should be necessary to remove the rotor 44. Chevron-shaped compression chambers in the two stages are oppositely directed with inlet ports 24, 34 to the two stages on opposite sides of the partition 16 and outlet parts 30, 36 adjacent the end-plates 18, 14, so that axial loads acting on the shaft 48 as the result of compression of the fluid in the one stage are partially balanced as the result of the compression of the fluid in the other stage. Radial forces tending to separate and deflect the pairs of intermeshing rotors are greatest adjacent the outlets and the male rotors are radially supported at these points. The radial forces acting on the female rotors are greater than on the male rotors and the moments of inertia of these rotors are less than the male rotors hence the resistance to bending and torque is less and in consequence the rotors 42, 46 are mounted on separate shafts radially supported in the partition 16 and supported against both radial and axial loads in the end-plates 18, 14. To reduce housing deformation oil under pressure is admitted to a channel 82, Fig. 2, and is distributed to the working spaces 20, 22 through injection openings 84, 86 to cool the rotors and the housing and also act as a liquid seal therebetween. The oil also seals the two stages from each other, lubricates the bearings and passes to a space in a cover 64, the pressure therein acting on the end of the shaft 48 to further balance the axial loads on the shaft.