Hydraulic system for bucket self-leveling during raising and lowering of boom

摘要

A hydraulic system having a first bucket leveling circuit for controlling leveling of the bucket during raising of the boom and a second bucket leveling circuit for controlling leveling of the bucket during lowering of the boom. The second bucket leveling circuit includes a motor-type flow divider having first and second shaft connected motor sections. Controls are operative when the boom control valve supplies fluid under pressure to the rod end of the boom cylinder for passing fluid from the piston end of the boom cylinder to the inlet of the first and second sections of the motor-type flow divider, and for preventing passage of fluid from the piston end of the boom cylinder to the inlet of the first flow divider. Although the pressure at the piston end of the boom cylinder is low during lowering of the boom, the motor-type flow divider is operative to supply fluid to the rod end of the bucket cylinder at a pressure that is substantially higher than the pressure at the piston end of the boom cylinder during lowering of the boom, and sufficient to move the bucket at a rate to maintain the latter substantially level.