GB636764A - Improvements in meshing-screw pumps or engines - Google Patents

Abstract

636,764. Meshing - screw pumps or engines. WHITFIELD, J. E. Aug. 1, 1947, No. 20953. Convention date, May 11, 1943. [Class 110(ii)] The pump or engine has male and female rotors 32, 30, provided with running clearance with the walls of the casing 20, and inlet and outlet ports diagonally disposed with respect to one another in the casing, the edges of each port opening matching the remote crest edges of the threads of the rotors. These edges meet to form an apex at the adjacent intersection of the cylindrical chambers 23, 24, and each pocket formed by meshing threads is sealed by the wall of the casing at one port opening at the same instant that the pocket is opened to the other port opening. The initial opening of an outlet port (for a pump) may be by way of a channel such as 58, 62 or 68, the cross-sectional areas of which may be fixed or variable. This channel prevents the sudden evening out of pressures and consequent noise caused when a pocket is opened to discharge all at once. The male rotor has a pitch circle of diameter less than the root diameter and the female rotor a pitch circle which is greater than its outside diameter. The sides of the male threads are shaped by helical surfaces generated by the crest edges of the threads of the female rotor. Fig. 1 shows one construction with gears 36, 37, of 2:1 ratio coupling the rotor shafts 31, 29. Vents 34 lead from fluid seals 35, around the shafts, to the atmosphere to prevent any intercommunication between the fluid in the working chamber and the bearing lubricating system. The inlet port is defined by a recess 43, in an end wall 22, and dotted lines 44, 46, 45 connected with an opening 42. The outlet port connected to an opening 50 comprises a recess 51, in an end wall 21, and boundaries 52, 53, 55, 54. To prevent power loss and noise due to sudden discharge of fluid from a pumping space, a connecting channel 58, Fig. 1, is formed by cutting away a portion of the intersection on the casing, at a cusp formed by the rotor bores to make an initial opening to the outlet port from the pumping chamber. The channel may be tapered or, as shown in Fig. 8, may be replaced by a shutter 63, triangular in shape. The shutter may be adjusted to any position and secured by set screws 65. Alternatively a slot 66, Fig. 9 (not shown), may be cut in the casing wall to form a continuation of the final port lines 56, 57, especially where dense liquids are pumped or fluids are pumped at high speed. Fig. 12 shows another device in which a plug 67 may be adjusted to open a channel. A further arrangement has a rotary valve in the channel, with a segmental piece cut out of it. The valve may be tapered. More than two rotors may be used in the pump or engine. Specifications 558,740 and 636,417, [Group XXIV], are referred to.