THEORY OF OPERATION - CONTINUED
BRAKE AND HYDRAULIC FAN SYSTEM - CONTINUED
High pressure cutoff in a piston pump limits maximum pressure at any pump displacement. During normal
piston pump operation, pressure compensator spool is forced down by cutoff spring.
As pressure in pump pressure passage increases, oil flows through spool control orifice into cavity for cut-
off spool. As oil pressure in cavity increases, force behind cutoff spool also increases, moving cutoff spool
against force of cutoff spring.
As pressure behind cutoff spool becomes greater than force of cutoff spring, cutoff spool overrides spring
and spool moves up, allowing oil to flow around spool. Oil will flow through signal passage, extending
actuator piston. Swashplate angle will decrease, causing pump to maintain cutoff pressure.