GB1129534A - Hydraulic transmission systems - Google Patents

Abstract

1,129,534. Hydrostatic transmissions. JOSEPH LUCAS (INDUSTRIES) Ltd. 4 Oct., 1966 [15 July, 1965], No. 30021/65. Heading F2D. In a hydrostatic transmission for vehicles, wherein the swash plate angles of a variable displacement swash plate pump and a variable displacement swash plate motor are respectively varied by fluid servo motors controlled by spool valves, and the spools 13, 12 of said valves are connected to arms of a rotatable control member 19, the valve spools are both permitted limited ineffective movement such that rotation of the member 19 in one direction from apredetermined position (Fig. 1, not shown) changes the motor displacement without substantially changing the pump displacement (for overdrive), and in the other direction from said predetermined position reduces the pump displacement without substantially changing the motor displacement. The servo motors are of the follow-up type and comprise axially stationary pistons and-movable cylinders 11, 10 connected to the pump. and motor swash plates (9), (8) respectively. The valve bores are integral with the cylinders 11, 10. Each of the spools 13, 12 has a pair of lands which may simultaneously close passages 14, 15 leading to opposite ends of the cylinder. When, e.g. the cylinder 10 is limited in its further rightward movement the valve spool 12 may move further rightwards ineffectively. The control member 19 is rotatable about a fixed hub 20 by a rod 26 acting through a lever 23 which is pivoted on a pin 22 eccentric to the hub 20 and is connected to the member 19 by a slot and pin 25, 24. The transmission provides Forward (Fig. 1, not shown), Overdrive, Neutral (as shown) and Reverse (Fig. 3, not shown). A spring-loaded detent (not shown) is provided to hold the lever 23 in Neutral. The whole assembly is enclosed in a casing containing circulating liquid.