Patent GB-1010665-A (GB)
Title: Improvements in and relating to rotary piston machines of the intermeshing screw type
IPC: F04C18/16
Filed: 1962-05-10
Abstract: 1,010,665. Rotary piston machines. SVENSKA ROTOR MASKINER A.B. May 10, 1962 [May 20, 1961], No. 17973/62. Heading F1F. In a rotary piston machine comprising male and female rotors 22, 36, Fig. 2, having respectively intermeshing helical lands and grooves 46, 52 and a casing 24 having intersecting parallel bores 28, 30 in which the rotors on rotation form variable volume chevron-shaped working chambers, the major portions of the convex flanks of the male rotor lands and the major portions of the concave flanks of the female rotor grooves lie outside their respective pitch circles, with at least one flank of each female groove 52 having a portion extending radially outwardly from a point of the flank defined by a continuously increasing radius vector swung from the point of intersection with the pitch circle of a radial line drawn from the rotor centre, and the profiles of the male rotor lands being the envelopes developed by the said female rotor grooves as the grooves and lands pass into and out of mesh with each other. Operating as a compressor as the rotors rotate, the working chambers between the rotors gradually decrease in size from the inlet low pressure end 42 of the casing to the outlet high pressure end 44 to give a gradual increase in pressure and acceleration of the gas with a consequent small leakage between the pockets and reduction in noise. In one embodiment, Fig. 2a, the male lands 46 and female grooves 52 are symmetrically disposed in relation to each other. The contact point 54 between the rotors travelling continuously to carry out a combined rolling and sliding movement as shown in Figs. 4, 6, 8. In this embodiment synchronizing gears between the rotors are dispensed with. In a modification, the male lands and female grooves are asymmetrically disposed with respect to each other. In a further embodiment, the machine is provided with liquid injection to lubricate the rotors. Oil is injected under pressure into a chamber 66, Fig. 14, and is forced through channels 70 connecting the chamber with the working spaces between the rotors. The outlets of the channels being disposed at or adjacent to the intersection line of the casing bores and directed towards the high pressure port 44. Also in this embodiment, the female grooves 52, Fig. 15a are made in two portions with a circular part and straight edge parts which co-operate with circular crests on the male lands 46 and flank portions generated by the straight parts of the female groove. In a still further embodiment, which in this case includes synchronization gearing, the two rotors are disposed so that there is never any direct mechanical contact between them. In this embodiment, each male rotor flank is composed of an inner portion 82, Fig. 17, produced by travelling generation and an outer portion 84 generated by a point 86 on the female rotor flank. Each female rotor flank includes a portion 88 outside the point 86 which is produced by travelling generation along the portion 82. The sealing line between the rotors having profiles according to the invention is shorter than the sealing line with rotors having circular contact or point contact and all sharp corners on the line are eliminated.