FRAME AS-CARBODY 1723089 - Caterpillar

When 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 lack of oil supply will cause cavitation in the travel motor. A pressure decrease occurs at port (24). A pressure decrease occurs in spring chamber (19) as well.The force of spring (22) moves spool (17) to the left. Passage (13) begins to close. This blocks oil flow between passage (27) and passage (30). The return oil from the travel motor and the oil flow to the supply port of the travel motor are restricted. The rotation of the travel motor slows down.The pressure of the oil delivery from the idler pump at port (24) increases. Part of the oil flows through passage (20). Spool (17) shifts to the right. Passage (13) opens. Return oil from the travel motor flows through port (29). The modulation of spool (17) maintains the proper opening of passage (13) when the machine travels down a slope. The travel motor begins to rotate in accordance with the amount of pump oil supply. This action prevents cavitation in the travel motors.When the machine is traveling down a slope, or the machine is suddenly stopped, spool (17) suddenly closes passage (13). This action causes a hydraulic pressure spike to occur. A damper is provided at both ends of spool (17) in order to prevent hydraulic pressure spikes. As spool (17) shifts to the left, the oil in spring chamber (19) is pressurized. Ball (15) moves to the right. The oil in spring chamber (19) flows through passage (20) and orifice (14) into passage (23). Spool (17) slowly moves to the left. passage (13) slowly closes. The size and the position of orifice (14) maintains the proper shock damper.The sudden pressure spikes in passage (11) and passage (13) are controlled by valve (3) and valve (7). As pressure spikes are eliminated by valve (3) and valve (7), the oil in passage (35) and passage (40) shift damper piston (37) upward and downward. This action provides smooth opening of valve (3) and valve (7).Operation Of Travel Crossover Relief Valves During Travel Stop
Illustration 4 g02546261
Travel counterbalance valve (travel stop)
(1) Crossover relief valve (reverse travel)
(2) Spring
(3) Valve
(4) Passage
(5) Passage
(6) Passage
(7) Valve
(8) Spring
(9) Crossover relief valve (forward travel)
(10) Passage
(11) Passage
(12) Passage
(13) Passage
(14) Orifice
(15) Ball
(16) Spring
(17) Spool
(18) Spring
(19) Spring chamber
(20) Passage
(21) Passage
(22) Spring
(14) Passage
(21) Passage
(22) Port (supply port for forward travel)
(23) Passage
(24) Port
(25) Check valve
(25) Passage
(26) Passage
(27) Port
(28) Passage
(29) Check valve
(29) Passage
(30) Port
(31) Passage
(32) Travel counterbalance valve
(33) Counterbalance valve
(34) Left travel motor
(35) Passage
(36) Orifice
(37) Damper piston
(38) Chamber (damper piston)
(39) Orifice
(40) Passage If the travel levers/pedals are returned