Hydraulic device for construction machinery

Details Hydraulic device for construction machinery Hydraulic device for construction machinery

1994-09-07

1996-11-05

Melius, Terry Lee

Excavating

Ditcher

Condition responsive

91421, 60452, G05D 102

Patent

active

055712266

ABSTRACT:
A hydraulic device for construction machinery includes a hydraulic pump; a hydraulic actuator having two fluid chambers; actuator fluid lines leading from each of the fluid chambers; pump fluid line leading from the pump; fluid tank fluid line leading to the fluid tank; operating lever to be operated by an operator; a direction switching unit connected to the actuator lines, the fluid tank fluid line, and the pump fluid line, and which is controlled in accordance with the direction of operation of the operating lever; inflow variable restriction located between the pump and the actuator fluid lines and whose restriction area is controlled in accordance with the degree of operation of the operating lever; outflow variable restriction located in between the fluid tank and the actuator fluid lines; and a pressure difference controller for controlling the difference in pressure between the inlet and exit ports of the inflow variable restriction. The restriction areas of the inflow and outflow variable restrictions may be controlled independently and the outflow variable restriction is controlled in accordance with fluctuations in the fluid pressure of the inlet chamber of the actuator thereby preventing the occurrence of cavitation whilst still ensuring the desirable control characteristic that the actuator drive speed corresponds to the degree of operation of the operating lever.

REFERENCES:
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