BOOM CYLINDER CONTROL CIRCUIT OF WORKING MACHINE

摘要

A boom cylinder control circuit of a working machine, wherein, when a stone crushing operation by a breaker or an operation to move a bucket longitudinally along the ground is performed, a lowering side delivery oil passage (E) and a rising side delivery oil passage (F) allowing those oils contained in a head side oil chamber (10b) and a rod side oil chamber (10a) of a boom cylinder (10) to flow to an oil tank (12) without passing a control valve (13) are provided in a control circuit of the boom cylinder (10) so as to facilitate a boom operation, and a second solenoid valve (21) and a third solenoid valve (22) operated to open and close these delivery oil passages are provided also in the control circuit of the boom cylinder (10).