Motors: expansible chamber type – With motive fluid valve – Contracting chamber exhaust valve controlled by expanding...
Patent
1989-03-20
1991-04-09
Look, Edward K.
Motors: expansible chamber type
With motive fluid valve
Contracting chamber exhaust valve controlled by expanding...
91461, F15B 1104, F15B 13043
Patent
active
050054660
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 neutral 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: 3630121 (1971-12-01), Landaeus et al.
patent: 4185660 (1980-01-01), Faix
patent: 4411189 (1983-10-01), Miller
patent: 4700610 (1987-10-01), Bauer et al.
patent: 4718329 (1988-01-01), Nakajima et al.
patent: 4747335 (1988-05-01), Budzich
patent: 4757685 (1988-07-01), Burckhartzmeyer
patent: 4840111 (1989-06-01), Garnjost
Kabushiki Kaisha Kobe Seiko Sho
Kapsalas George
Look Edward K.
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