Patent ID: 12012724

Abstract:
A hydraulic excavator drive system (1) includes an arm control valve (31) and an arm switching valve (41). The arm switching valve (41) is connected to an arm pushing supply line (34) by a rod-side line (42) and to an arm crowding supply line (35) by a head-side line (43). The arm switching valve (41) is switched between a neutral position, a recycling position in which the arm switching valve (41) allows the rod-side line (42) to communicate with the head-side line (43) and a second tank line (44), and a meter-out control position in which the arm switching valve (41) allows the head-side line (43) to communicate with the tank line (44). The arm switching valve (41) incorporates therein a check valve (45) that allows a flow from the rod-side line (42) toward the head-side line (43) when the arm switching valve (41) is in the recycling position.