Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Reexamination Certificate
2007-04-24
2007-04-24
Leslie, Michael (Department: 3745)
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
C091S448000
Reexamination Certificate
active
11302704
ABSTRACT:
A hydraulic control device for controlling a boom-arm combined operation in an excavator includes a boom low-speed control spool and an arm high-speed control spool provided on parallel lines for receiving hydraulic flow from a second hydraulic pump via the parallel lines. A boom priority valve is provided on the parallel line interconnecting the second hydraulic pump and the arm high-speed control spool for throttling the parallel line to cause the hydraulic flow of the pump to be supplied to the boom low-speed control spool prior to the arm high-speed control spool. The boom priority valve has a pressure receiving part remaining in fluid communication with a boom pilot valve through a boom priority control signal line and a variable orifice section for reducing an opening area of the parallel line in proportion to the magnitude of a boom priority control signal pressure delivered to the pressure receiving part.
REFERENCES:
patent: 5673558 (1997-10-01), Sugiyama et al.
patent: 01158123 (1989-06-01), None
Doosan Infracore Co., Ltd.
Lee Hong Degerman Kang & Schmadeka
Leslie Michael
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