US 3,943,825 AGranted

Hydraulic control system for load supporting hydraulic motors

AssigneeCaterpillar Tractor Co.

InventorsDonald L. Bianchetta, Kenneth R. Lohbauer, Sammy J. Rhodes

Life of this patent

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Abstract

A load supporting hydraulic system having a pilot operated main control valve is provided with pilot controlled load check valve operative to permit free flow of fluid from said control valve toward the load supporting means of the system in response to pilot pressure and to block fluid flow from the load supporting means toward the control valve. The system includes valve means operative independent of the main control valve to permit the load check valve to be opened by fluid pressure in the load supporting means to allow fluid flow therefrom to the reservoir. The system further includes safety valve means for blocking fluid flow to pilot control means.

Claims6

Dependent claims

A fluid control system comprising:

a source of pressurized fluid including a reservoir;
a load supporting fluid motor having a load supporting chamber and an opposed chamber defined by a piston received in a cylinder;
a pilot actuated main control valve responsive to a predetermined minimum pilot pressure to control cummunication between said main source of fluid pressure and said load supporting chamber of said fluid motor for alternately establishing communication of said main source with said load supporting chamber and communication of said load supporting chamber with said reservoir;
a pilot control system including a source of pilot fluid and means including a pilot control valve connected to operate said main control valve;
a relief valve for establishing a predetermined pilot fluid pressure in said pilot control system and including pressure responsive means responsive to said predetermined fluid pressure to open said relief valve and bypass fluid from said pilot control system to said reservoir;
a safety valve disposed in fluid flow controlling relation between said source of pilot fluid and said pilot control valve and having an operative position to permit operation of said pilot system with said predetermined minimum pilot pressure and a safety position to render said pilot control system inoperative;
a load check valve having a control chamber and disposed between said load supporting chamber of said fluid motor and said main control valve so as to permit free flow of fluid from said control valve toward said load supporting end and to normally block fluid flow from said load supporting end toward said control valve;
means responsive to said pilot control system for opening said load check valve in response to pilot actuation of said main control valve to allow fluid flow from said load supporting chamber toward said control valve and said reservoir;
and,
bypass vent means manually positionable for venting said control chamber via said pilot control valve and permit said load check valve to open in response to fluid pressure in said load supporting chamber in the absence of pilot pressure for actuation of said main control valve.

7 more elements

Dependencies are inferred from the claim text.

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Abstract

A fluid control system comprising:

a source of pressurized fluid including a reservoir;
a load supporting fluid motor having a load supporting chamber and an opposed chamber defined by a piston received in a cylinder;
a pilot actuated main control valve responsive to a predetermined minimum pilot pressure to control cummunication between said main source of fluid pressure and said load supporting chamber of said fluid motor for alternately establishing communication of said main source with said load supporting chamber and communication of said load supporting chamber with said reservoir;
a pilot control system including a source of pilot fluid and means including a pilot control valve connected to operate said main control valve;
a relief valve for establishing a predetermined pilot fluid pressure in said pilot control system and including pressure responsive means responsive to said predetermined fluid pressure to open said relief valve and bypass fluid from said pilot control system to said reservoir;
a safety valve disposed in fluid flow controlling relation between said source of pilot fluid and said pilot control valve and having an operative position to permit operation of said pilot system with said predetermined minimum pilot pressure and a safety position to render said pilot control system inoperative;
a load check valve having a control chamber and disposed between said load supporting chamber of said fluid motor and said main control valve so as to permit free flow of fluid from said control valve toward said load supporting end and to normally block fluid flow from said load supporting end toward said control valve;
means responsive to said pilot control system for opening said load check valve in response to pilot actuation of said main control valve to allow fluid flow from said load supporting chamber toward said control valve and said reservoir;
and,
bypass vent means manually positionable for venting said control chamber via said pilot control valve and permit said load check valve to open in response to fluid pressure in said load supporting chamber in the absence of pilot pressure for actuation of said main control valve.

7 more elements