FRAME AR-LOADER 3119003 - Caterpillar

Illustration 2 g06288267
Travel counterbalance valve (level travel)
(1) Travel counterbalance valve
(2) Crossover relief valve
(3) Port (supply port for reverse travel)
(4) Port (supply port for forward travel)
(5) Travel motor
(6) Crossover relief valve
(9) Spool
(10) Passage
(12) Passage
(13) Damper
(14) Parking brake
(15) Damper
(16) Passage
(17) Passage
(18) Passage
(19) Displacement change valveDuring forward travel on level ground, pump oil is supplied to port (3). The oil flows through passage (17) through the check valve and onto the right side of spool (9). The oil pushes the spool to the left against spring pressure. The orifice on the opposite side of the spool near passage (18) dampens the shifting of the spool for smoother operation.Once shifted, oil flows through the spool to passage (16) and onto travel motor (5).The shifted spool creates a path for oil to simultaneously flow through the spool and up to passage (10). Oil in passage (10) flows to the parking brake (14). The oil acts on the brake piston and forces the spring to retract allowing the brake to release. The travel motor now begins to turn and return oil flows back through passage (12). The return oil has a path back to tank through spool (9) and exits the motor at port (3).Counterbalance Valve Operation During Slope Travel
Illustration 3 g06288269
Travel counterbalance valve (slope travel)
(1) Travel counterbalance valve
(2) Crossover relief valve
(3) Port (supply port for reverse travel)
(4) Port (supply port for forward travel)
(5) Travel motor
(6) Crossover relief valve
(9) Spool
(10) Passage
(12) Passage
(13) Damper
(14) Parking brake
(15) Damper
(16) Passage
(17) Passage
(18) Passage
(19) Displacement change valveWhen the machine travels down a slope, the travel motors rotate at a higher speed. The higher speed is due to the mass (weight and size) of the machine. When this condition occurs, the pumps cannot maintain the oil supply to the travel motors. The pressure decreases at port (4) decreasing the pressure to the right side of spool (9).The decreased pressure allows spring pressure to move spool (9) to the right. The passage through the spool to port (3) begins to close. This blocks oil flow to the hydraulic tank. The return oil from the travel motor and