G - Physics
05
D
137/95
G05D 11/00 (2006.01) F15B 13/02 (2006.01) G05D 7/01 (2006.01)
Patent
CA 1237632
A PRIORITY VALVE Abstract of the Disclosure A priority valve is disclosed for controlling fluid flow between a power source and functions operated by the power source, one of the functions being a priority function and at least one other function being a secondary function. The priority valve includes a housing having first and second bores formed therein. An inlet passage connects the power source to the first bore while first and second outlet passages connect the first bore to the primary and secondary functions respectively. A valve spool is positioned in the first bore and is movable between first and second ends of the first bore. The valve spool has an annular groove which is in constant communication with the inlet passage and at least one of the outlet passages. The valve spool further includes a passageway formed therein which constantly connects the first end of the first bore to the first outlet passage. The valve spool is movable between a first position permitting fluid flow from the inlet passage to the first outlet passage while blocking fluid flow to the second outlet passage and a second position permitting fluid flow from the inlet passage to the second outlet passage while blocking fluid flow to the first outlet passage. A pin is movably positioned in the second bore and has an enlarged end which extends into the first bore. Springs are present for urging the valve spool toward the first position and the pin toward the spool valve. The priority valve further includes a load signal passage connecting the priority function to the second end of the first bore. When full fluid flow is demanded by the priority function, the pressure difference between the load signal passage and the inlet passage decreases causing the valve spool 38 to move toward its first position. When the priority valve demands less than full flow, the pressure difference between the load signal passage and the inlet passage increases and the spool valve is allowed to move toward its second position. Should a situation occur wherein the priority function demands pressure approaching a maximum pressure value which can be delivered by the power source, the pressure within the load signal passage increases and this pressure causes the enlarged end of the pin to contact the valve spool and force it toward its second position thereby assuring fluid flow between the power source and the secondary functions.
481405
Miller James A.
Wittren Richard A.
Borden Ladner Gervais Llp
Deere & Company
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