Hydraulic Apparatus

1,154,185. Regulating. DOWTY HYDRAULIC UNITS Ltd. March 22, 1968 [April 11, 1967], No.16578/67. Heading F1B. [Also in Division F2] A closed circuit hydrostatic transmission employing a make-up pump is driven by a variablespeed engine, and should the make-up pump pressure fall below a predetermined value the engine speed is automatically increased. As shown a variable-displacement pump 1 supplies a constantdisplacement motor 2 and make-up liquid is supplied by an input driven pump 6 through a cooler 9 and a filter 11 to a pipe network 12 in which the pressure is maintained at a predetermined value by a relief valve (not shown). The network pressure 12 is applied to a servo 15 adjusting the loading of a governor of the engine fuel pump 19, so that should the network pressure 12 fall, the servo spring adjusts the governor to increase the engine speed. The engine speed is manually controlled by a link 22 and a lever 21. In a modification a spring- loaded lost motition is provided between the link 22 and the lever 21 so that movement of the servo 15 will not alter the manual control. In another modification the servo and the manual control link act on opposite ends of a floating lever the mid-point of which is linked to the governor control so that movement of either the servo or the manual control will not affect the other control.