HYDRAULIC CONTROL DEVICE OF HYDRAULIC WORKING MACHINE

Title:

HYDRAULIC CONTROL DEVICE OF HYDRAULIC WORKING MACHINE

Document Type and Number:

WIPO Patent Application WO/2004/076334

Kind Code:

A1

Abstract:

A hydraulic control device of a hydraulic working machine, comprising a derricking cylinder (7) rotating the free end of a boom in a derricking direction, an attachment rotatably fixed to the tip part of the boom, a tilt cylinder (8) vertically rotating the attachment relative to the boom, and a leveling cylinder (9) extending/retracting in conjunction with the derricking operation of the boom to hold the vertical angle of the attachment at a preset angle according to a variation in the derricking angle of the boom, wherein when the working pressure of the derricking cylinder (7) is increased to a pressure higher than a preset pressure in boom raising operation, a pipeline (35) for performing the extending operation of the derricking cylinder (7) is allowed to communicate with a pipeline (33) for performing the extending operation of the leveling cylinder (9). This communication is performed by a pipeline (37) installed between the pipelines (35) and (33) and first and second selector valves (21) and (20) switching the circuit of the pipeline (37).

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Inventors:

SATO KENSUKE (JP)
TOYOOKA TSUKASA (JP)

Application Number:

PCT/JP2004/002380

Publication Date:

September 10, 2004

Filing Date:

February 27, 2004

Export Citation:

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Assignee:

HITACHI CONSTRUCTION MACHINERY (JP)
SATO KENSUKE (JP)
TOYOOKA TSUKASA (JP)

International Classes:

B66F9/065; B66F9/22; E02F3/43; (IPC1-7): B66F9/22; B66F9/06; B66F9/065

Foreign References:

JP2003034494A	2003-02-07
JPH0365765U	1991-06-26
JPH061397U	1994-01-11
US4822237A	1989-04-18

Other References: