GB891524A - Improved pumps, motors and driving units of the rotor type - Google Patents

Abstract

891,524. Rotary pumps and motors. SOC. D'ETUDES ET D'EXPLOITATION DU GENERATEUR A PISTON LIBRE. April 3, 1958 [April 8, 1957], No. 10895/58. Class 110 (2). A rotary pump or motor of the Roots type comprises two-lobed rotors rotatable in a bicylindrical casing having oppositely disposed inlet and outlet opening into the casing at the intersection of the cylinders, in which each rotor is formed integral with journal bearings, one on either side, and each bearing is rotatable in a smooth bearing surface in the casing and formed around its periphery with a pair of arcuate recesses separated by plane portions, such that the smooth bearing surfaces on the sides of the rotors opposite to the inlet communicate with the inlet and the smooth bearing surfaces on the sides of the rotors opposite to the outlet communicate with the outlet in order that the rotors together with the journal bearings are in substantial hydraulic lateral balance. As shown in Fig. 5, a pair of interengaging two-lobed rotors 12, 12<SP>1</SP> are formed integral with journal bearings 10, 11, Fig. 4, having arcuate recesses 14, 15 opposite to which in the three-part casing 1, 2, 3 open passages 18, 19 communicating through passages 18<SP>1</SP>, 191 with the inlet 9 and outlet 8 respectively. The passages 18, 19 also communicate through longitudinal casing grooves 22, 23 with arcuate casing recesses 16, 17. Thus the radial thrusts acting on the bearing can be made to substantially balance the radial thrusts acting on the rotors by predetermining the widths of the recesses 14, 15, 16, 17 in accordance with the axial lengths of the rotors. To effect automatic centring of the rotors with respect to the casing to produce axial balance of the rotors, recesses 28, 29, Fig. 8, in the rotor side faces communicate through calibrated orifices 30, 31, passages 32, 33 and one or other of non-return valves 34, 35 with one of the journal bearings. Leakage through the orifices creates a pressure in the recesses 28, 29 related to the clearance between the rotors and the casing so that the rotors " float " between the casing walls. Dowel pins 26 carried by the bearing 10 transmit torque to a gear 13 which meshes with a similar gear on the other rotor to synchronize the movements of the rotors. In eases where it is necessary to drive two driven units simultaneously in opposite directions, e.g., electric machines, twin propellers, rolling mills, &c., two pairs of rotors 38, 39, Fig. 9, are arranged in separate cells with one pair of rotors disposed at 90 degrees to the other. Synchronization is achieved by intermeshing gears 46, 47. To cause the driving rotors to rotate more rapidly than the driven units one rotor shaft mounts a pinion 44 meshing with an internally toothed wheel 42 driving a shaft 40 which is coaxial with another shaft 41 driven by the rotors through a further pinion 45 and internally-toothed wheel 43. In an alternative arrangement two pairs of rotors arranged as in Fig. 9 may be coupled by gearing to drive a single shaft coaxial with one of the rotor shafts. Valves 73, 74, Fig. 12, slidable in a valve casing and connected to pistons 75, 76 respectively subjected on their smaller inner faces to high pressure admitted through chambers 71, 72 and on their larger outer faces alternatively to high and low pressures through remotely controlled lines 77, 78 to connect one of the passages 66, 67 with high pressure and the other passage with low pressure in accordance with the desired direction of rotation of the rotors. The bores in the casing in which the journal bearings 10, 11 rotate are surface hardened, e.g., by nitriding, chroming or cementating.