CABLE AS 1935920 - Caterpillar

Illustration 1 g02219936
Right travel motor and counterbalance valve
(17) Port
(20) Port
(25) Travel counterbalance valve
(26) Brake valve
(27) Travel motor The travel counterbalance valve is bolted to the travel motor. Pump oil from the main control valve enters travel counterbalance (25) and flows to travel motor (27). When the travel control valves are in the NEUTRAL position, oil that is inside the travel motors is trapped by the counterbalance valves. Trapping the oil in the travel motors hydraulically locks the travel motors.The travel counterbalance valve has the following four functions:
The valve prevents a shock load when travel is stopped.
The valve prevents overspeed while the machine is traveling down a slope.
The valve prevents cavitation.
The valve routes a portion of the pump oil to the travel parking brake in order to release the brake.Note: The conditions listed below are for forward travel. Reverse travel functions in the same manner.Counterbalance Valve Operation During Level Travel
Illustration 2 g03643058
Sectional view of travel counterbalance valve and partial schematic
(1) Passage
(2) Port
(4) Passage
(5) Port
(6) Passage
(7) Orifice
(8) Valve
(9) Spring chamber
(10) Spring
(11) Guide chamber
(12) Ball
(13) Guide
(14) Passage
(15) Passage
(16) Check valve
(17) Port
(18) Passage
(19) Passage
(20) Port
(21) Check valve
(22) Passage
(23) Spring
(25) Travel counterbalance valve Counterbalance valve (25) consists of valve (8), check valve (16), check valve (21), spring (10) and spring (23). During a forward travel operation, pump oil is supplied to port (17). The oil flows through passage (18) and opens check valve (16) in valve (8). Port (17) is also connected to the travel motor through passage (18), passage (1), and port (2).At the same time, pressure oil from passage (18) enters passage (15) and spring chamber (9). The oil flows through passage (14) and opens ball (12). The oil enters guide chamber (11).With pressure oil in spring chamber (9) and guide chamber (11), valve (8) is moved to the right against the force of spring (23). This action opens passage (4).Pressure oil flows through brake valve (26) and unclamps the parking brake.Return oil from the travel motor flows into port (5), passage (6), passage (4), passage (19), and port (20). The travel motor circuit is complete and the travel motor rotates.When the oil flow to port (17) is blocked, the pressure in spring chamber (9) and guide chamber (11) decreases. The force of spring (23) shifts valve (8) to the left. Passage (4) is closed. Return oil from the travel motor is blocked and the rotation of the travel motor stops.When the direction of travel is reversed, pump oil enters port (20). During reverse travel, the travel counterbalance valve operates in the same manner as the forward travel operation. Valve (8) is moved to the left so that the return oil from the motor is discharged through port (17). Counterbalance Valve Operation During Slope Travel
Illustration 3 g03643063
Schematic and sectional view of travel counterbalance valve
(1) Passage
(2) Port
(4) Passage
(5) Port
(6) Passage
(7) Orifice
(8) Valve
(9) Spring chamber
(10) Spring
(11) Guide chamber
(12) Ball
(13) Guide
(14) Passage
(15) Passage
(16) Check valve
(17) Port
(18) Passage
(19) Passage
(20) Port
(21) Check valve
(22) Passage
(23) Spring
(25) Travel counterbalance valve When the machine travels down a slope, the travel motors rotate