Hydraulic control mechanism for mechanical excavator

摘要

Hydraulic control system which is particularly suitable for use in movable earth-working machines such as mechanical excavators equipped with a displacement mechanism and with a working mechanism. The hydraulic control system is arranged for supplying the flows of pressurised fluid from a pair of main pumps separately to displacement control valves and to working-component- control valves by means of a confluence selector valve mechanism with the aim of supplying one or a number of particular control valves requiring a greater supply of fluid, thereby improving the rate of work of one or a number of actuating devices at the same time as the straight-line displacement capacity is maintained. In addition, provision has been made for a path-limitation mechanism for a working-component-control valve in communication with an actuation device subject to a variable load, with the aim of limiting the travel of the ratchet of the control valve and causing the fluid discharged from the actuating device to return to it in order to increase the rate of work of the actuating device. <IMAGE>