Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
2004-12-16
2008-09-09
Rivell, John (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C137S625680, C137S625690, C251S030040
Reexamination Certificate
active
07422033
ABSTRACT:
A spool type control valve is operated by an electrically driven pilot valve. A pilot piston is attached to the control spool. As an electrical actuator moves the pilot spool, a greater pressure is applied to one side of the pilot piston than the other side, which causes movement of the control spool. When the control spool reaches the desired position, its positional relationship to the pilot valve defines a pressure differential across the pilot piston which exerts a net force on the control spool that counterbalances a spring force acting on the control spool. This defines an equilibrium position at which the control spool remains until subsequent motion of the pilot spool occurs which alters the pressure differential across the pilot piston.
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Haas George E.
HUSCO International Inc.
Quarles & Brady
Rivell John
Schneider Craig M
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