V-BELT 7W5259 - Caterpillar

Illustration 1 g00671132
(1) Travel brake valve (2) Counterbalance valve "CT1" (top) (3) Counterbalance valve "CT2" (bottom)Counterbalance valve "CT1" (2) and counterbalance valve "CT2" (3) are located in travel brake valve (1).
Illustration 2 g00671057
(1) Travel brake valve (2) Counterbalance valve "CT1" (3) Counterbalance valve "CT2" (4) Large travel motor (5) Small travel motor (6) Passage (7) Check valve (8) PassageEach travel brake valve contains two counterbalance valves (2) and (3). The counterbalance valves prevent the occurrence of a shock load during a travel stop. The counterbalance valves also prevent cavitation and overrun.Slope Travel
Note: Explanations of slope travel are relative to the forward direction.When the machine moves down a slope, travel motors (4) and (5) rotate at a higher speed. The higher speed is due to the mass of the machine. The pumps cannot maintain the oil supply to the motors. The lack of oil supply will cause cavitation in the travel motors.The counterbalance valves require pilot pressure in order to open. When the machine moves down a slope, the pump cannot supply enough pilot pressure to counterbalance valve "CT2" (3). Pilot pressure is supplied by pump oil and the pilot pressure is sent through passage (8). The pilot pressure drops when the travel motors begin to cavitate. This drop in pressure causes counterbalance valve "CT2" (3) to close. The return oil flow to the hydraulic tank is restricted. The oil flow to the suction port of the travel motor is restricted. The rotation of the travel motor will slow down.When the pilot pressure in line (8) increases, counterbalance valve "CT2" (3) opens. The oil is able to return to the hydraulic tank. The motors rotate according to the output of the pump. This prevents the motors from cavitating.