Patent ID: 7059237
Filing Date: 2006-06-13
Classification: E02F,F15B

Abstract:
1. A multiple-directional switching valve, including a pump port connecting with an oil pressure source, an unloading passage connecting with the pump port, a tank port connecting with a tank, a tank passage connecting with the tank port, a directional switching valve for boom connecting with the unloading passage and operative to control a supply of a pressured oil from the pump port to a boom cylinder, a directional switching valve for bucket connecting with the unloading passage and operative to control a supply of a pressured oil from the pump port to a bucket cylinder, a merged passage operative to supply a part or a whole part of a return pressured oil which is drained from a rod-side chamber of the boom cylinder via the directional switching valve for boom to a head-side chamber of the bucket cylinder, and a flow divider system operative to divide the return oil drained from the rod-side chamber of the boom cylinder into a flow to the merged passage and a flow to the unloading passage, and having a bucket-leveling function in which a bucket is maintained at a level position by supplying the return pressured oil drained from the rod-side chamber of the boom cylinder to the head-side chamber of the bucket cylinder when a boom is raised by supplying the pressured oil to the head-side chamber of the boom cylinder and the directional switching valve for boom is configured so as to disconnect the boom cylinder with the merged passage in a neutral position thereof, the multiple-directional switching valve comprising: a diverged passage which is diverged from said merged passage at a location upstream of said flow divider system and connects with said unloading passage or said tank passage; a switching valve operative to connect and disconnect said diverged passage, the switching valve being provided so as to connect and disconnect the diverged passage independently from operation of said directional switching valve for a boom, wherein said switching valve is switched to a connecting position thereof such that said return pressured oil which is drained from the rod-side chamber of the boom cylinder via the directional switching valve for the boom to be supplied to said merged passage flows in said diverged passage and is prevented from being supplied to said head-side chamber of the bucket cylinder.