Patent GB-974080-A (GB)
Title: Variable capacity gear pumps or motors
IPC: F04C2/18
Filed: 1960-12-20
Abstract: 974,080. Gear pumps and motors. W. REINERS, and G. WIGGERMANN, [trading as FIRMA REINERS & WIGGERMANN GETRIEBE-UND MASCHINENBAU]. Dec. 20, 1960 [Dec. 21, 1959; Feb. 6, 1960], No. 43737/60. Heading F1F. In a variable capacity gear pump or motor having a gear train comprising three intermeshing gear wheels rotatably supported in a housing with the intermediate wheel radially movable within a housing cavity so that its axis is stoplessly movable within limits with respect to the axes of the outer wheels thereby to adjust the depth of tooth engagement and the quantity and flow direction of the liquid, the outer gear wheels are additionally coupled by auxiliary gearing comprising a gear train having two outer wheels fixed to or formed by the two outer pump or motor wheels and an intermediate wheel displaceable under the delivery pressure (pump) or inlet pressure (motor) both radially and substantially perpendicular to a line joining the axes of the outer wheels, so that torque may be transmitted to that outer wheel whose teeth in mesh with those of the intermediate wheel are moving towards the pressure side of the pump to counteract any disengagement of the teeth. Described as a pump, outer gears 7, 8, Fig. 1, keyed respectively to a driving shaft 3 and a freely rotatable countershaft 4 engage an intermediate gear 9 mounted on the eccentric 6 formed on a shaft 5 fitted with a lever 12 to adjust the position of the gear 9 with respect to the gears 7, 8. Fig. 2 shows the gear 9 moved closer to the gear 7 and farther from the gear 8 and with the wheels rotating in the direction shown space 10a on one side of the gear 9 becomes the suction chamber and the space 10b on the other side of the gear 9 the delivery chamber. An auxiliary gear train separated from the gears 7, 8, 9 by a casing partition 1c comprise outer gears 13, 14 secured to the driving and countershafts respectively and an intermeshing gear 15 secured to a sliding bearing 16 freely rotatable on a pin 17. The pin 17 is connected to a piston 18, Fig. 3, subjected on opposite faces through ducts 21a, 21b, to the pressures in the spaces 10a, 10b, so that the piston is moved in accordance with the pressure difference in these spaces to move the gear 15 transversely, Fig. 2, into closer meshing engagement with the gears 13, 14 to superimpose torques on the gears 7 and 8. As shown, the torque superimposed on the outer gear 8, i.e., that gear whose teeth are moving towards the delivery chamber, opposes the direction of rotation of that gear to compensate for the hydrostatic torque tending to move the gear teeth out of intermeshing engagement with each other. A spring 22 abutting a screw-plug 20 and loading the piston 18 ensures positive loading of the tooth flanks. In practice it is found that when the greater distance occurs between the intermediate gear and the driving gear, viz gear 7, the compensating effect of the auxiliary gearing can be dispensed with, hence the piston 18 on the spring side may be lengthened so that it abuts the screw-plug 20 and the auxiliary gearing is disconnected when space 10a is the delivery chamber and space 10b the suction chamber. In a modification, the bearing 16, pin 17 and pistons 18 are omitted, the intermediate gear 15 of the auxiliary gear train being supported only by the intermeshing between it and the gears 13, 14, and by the end 1a of the casing and the partition 16. Spaces on either side of the gear 15 are connected to the pump spaces 10a, 10b so that the pressures in these spaces act directly on the gear 15. A non-return valve may be fitted to prevent flow from the space 10a to the associated auxiliary gear space to disconnect the auxiliary gearing as is the case with the lengthened piston. Alternatively the gear 15 may be freely mounted on a bush having a rectangular slot engageable with a fixed guide on the casing to permit transverse movement of the gear 15. In another embodiment the auxiliary gearing may be disposed in the pump chamber. The intermediate gear 15 being mounted with clearance on the eccentric shaft 5 and the gears with which it meshes being extensions of the gears 7, 8.