Power plants – Pressure fluid source and motor – Condition responsive control of motive fluid flow
Patent
1990-12-14
1991-11-12
Look, Edward K.
Power plants
Pressure fluid source and motor
Condition responsive control of motive fluid flow
91461, F15B 2108
Patent
active
050637410
ABSTRACT:
A hydraulic circuit suitable for use in a hydraulic operating circuit of a power shovel includes a hydraulic cylinder for driving a working component and a hydraulic change-over valve for selectively supplying the cylinder with a discharge oil pressure of a hydraulic pump driven from an engine. The hydraulic circuit prevents cavitation in an oil chamber of the cylinder and includes a pair of first signal receiving portions provided in the hydraulic change-over valve for moving the spool thereof in the forward and reverse directions away from a netural position, respectively, and a second signal receiving portion for pulling back the spool toward said neutral position. A pressure detector produces a signal commensurate with the pressure in an oil chamber of the cylinder opposing an oil chamber where vacuum pressure is developed by the weight of the working component and a signalling device produces a signal indicating the extent of pulling back the spool toward the neutral position on receipt of the results of detection by the pressure detector, thereby supplying the signal to the second signal receiving portion of the hydraulic change-over valve.
REFERENCES:
patent: 4694927 (1987-09-01), Nagae
patent: 4718329 (1988-01-01), Nakajima et al.
patent: 4747335 (1988-05-01), Budzich
patent: 4881450 (1989-11-01), Hirata et al.
Kabushiki Kaisha Kobe Seiko Sho
Kapsalas George
Look Edward K.
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