Motors: expansible chamber type – With motive fluid valve – Pilot valve
Patent
1980-06-16
1982-12-07
Cline, William R.
Motors: expansible chamber type
With motive fluid valve
Pilot valve
137113, 13750518, 91436, F15B 1116
Patent
active
043620892
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to valve systems, and in particular to pressure regulating valves for use in load controls.
2. Background Art
In one conventional system for controlling a fluid motor, such as used in lifting a load in a vehicle such as an earthworking machine, fluid pressure is delivered to a piston cylinder through a main control valve which is conventionally controlled by a pilot valve. The pressurized fluid is provided from a suitable high pressure pump which is driven when the apparatus is in operation. It is desirable to provide a pressure regulating means for regulating the pressure of the fluid delivered to the pilot valve, and for this purpose, pressure regulating valves have conventionally been employed.
The regulated pressure fluid is delivered to the pilot valve for modulation thereby in effecting the shifting of the main valve to provide the desired control of the fluid motor.
At times, it is necessary to operate the fluid motor in the absence of fluid pressure from the pump. Thus, at times, it may be desirable to lower the load at the time of an engine failure and the pressure source is de-energized such that the normal control of the piston cylinder is no longer available. To permit the controlled lowering of the load under such conditions, it has been conventional to provide a selector and a second valve which is arranged to provide controlled fluid pressure to the pilot valve by suitably controlling the fluid relieved from the piston cylinder.
A number of fluid systems have been developed for use in controlling such loads. Illustratively, in U.S. Pat. No. 3,703,850, of Don R. Honeycutt, a hydraulic control system is disclosed utilizing dump valves controlled by the hydraulic fluid of the system for removing from the system returning hydraulic fluid so as to eliminate the need for delivering the returning fluid back through a substantial length of the system and thereby providing a faster response time.
In U.S. Pat. No. 3,766,944, Josef Distler shows a pilot controlled fluid flow regulating valve wherein the pressure reducing signal is developed by a pilot valve. The flow regulating valve has a chamber receiving pressurized fluid from the pump through a pilot valve for moving the spool of the regulating valve from a neutral position to an intermediate position and thereupon to any one of several operative positions. A control piston is displaced by a manually operated handle in effecting the desired control of the fluid system.
In U.S. Pat. No. 3,840,049, of Jesse L. Field, Jr., which patent is owned by the assignee hereof, a fluid motor control system is provided having a float position. The control valve includes a spool and means for selectively shifting the spool in response to fluid pressure signals from a manually operated pilot valve. The valve has make-up valve means which automatically opens a bypass passage between the fluid motor ports and fluid return passage when necessary to prevent cavitation of the motor such as during an overrunning condition from the external load force. In the Field, Jr. patent, the spool of the pilot valve has four positions, including a float position interconnecting the two motor ports and the fluid return passage so that the motor may move in either direction, as determined by external load forces. The pilot valve is anually actuated and utilizes a smaller pool than that of the directional valve.
In a second U.S. Letters Patent owned by the assignee hereof, Eugene E. Latimer discloses, in U.S. Pat. No. 3,987,703, a hydraulic control system wherein the load lifting hydraulic motor is controlled from a source of pressurized fluid through a pilot-operated directional control valve having a combined restrictor and shuttle valve assembly. This assembly is operative to direct pressurized fluid from the pump for pilot operation of the main control valve when the pump is in operation. However, upon failure of the pump system to provide the desired pressure, the assembly provides an emergency source of hydraulic fluid for
REFERENCES:
patent: 868219 (1907-10-01), Pietzuch et al.
patent: 3103230 (1963-09-01), Kutschie
patent: 3576194 (1971-04-01), Christensen
patent: 3703850 (1972-11-01), Honeycutt
patent: 3766944 (1973-10-01), Distler
patent: 3840049 (1974-10-01), Field, Jr.
patent: 3874269 (1975-04-01), Walters
patent: 3987703 (1976-10-01), Latimer
patent: 4240457 (1980-12-01), Riediger
Earley Robert W.
Melocik Kurt B.
Caterpillar Tractor Co.
Cline William R.
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