Valve apparatus and hydraulic drive system

A hydraulic drive system comprising a hydraulic pump, a plurality of hydraulic actuators driven by hydraulic fluid delivered from said hydraulic pump, a plurality of directional control valves of closed center type for respectively controlling flows of the hydraulic fluid supplied to said plurality of actuators from said hydraulic pump, and pressure compensating means for retaining a differential pressure between a delivery pressure of said hydraulic pump and a maximum load pressure of said actuators, to a prescribed value,

• wherein said hydraulic drive system includes a valve apparatus which comprises a casing formed therein with at least one pair of spool bores arranged in juxtaposed relation to each other, the pair of spool bores having axes in a plane, a single common pump port connected to said hydraulic pump, at least one tank port including a pair of actuator ports connected to each of said plurality of actuators and communicating with each of said spool bores, and at least one corresponding pair of spools arranged in juxtaposed relation to each other and slidably inserted respectively in said spool bores in said casing, each of said spools controlling communication between said common pump port and tank port and the corresponding pair of said actuator ports, said common pump port communicating with a common pump line formed in the casing between the pair of spool bores and spools arranged in juxtaposed relation so as to perpendicularly intersect the plane in which the axes of the pair of spool bores extend, whereby said valve apparatus provides said plurality of directional control valves of closed center type.