VALVE GP- 3148808 - Caterpillar

Counterbalance Valve Operation During Level Travel
Illustration 2 g02161703
Travel counterbalance valve (level travel)
(2) Counterbalance valve
(3) Crossover relief valve (forward travel)
(4) Port (supply port for reverse travel)
(5) Port (supply port for forward travel)
(6) Crossover relief valve (reverse travel)
(7) Spool
(8) Check valve
(9) Check valve
(10) Spring
(11) Spring
(12) Passage (oil flow to rotary group during reverse travel)
(13) Passage
(14) Spring chamber
(15) Passage
(16) Ball
(17) Damper chamber
(18) Throttling slots
(19) Passage (return oil flow from rotary group during reverse travel)
(20) Passage
(21) Passage
(22) Spring chamber
(23) Passage
(24) Spring chamber
(25) Damper piston
(26) Spring
(27) Spring chamber
(39) Passage (parking brake release oil) Counterbalance valve (2) consists of spool (7), check valve (8), check valve (9), spring (10) and spring (11). During reverse travel, pump oil is supplied to port (4). The oil flows through port (4) and opens check valve (9) in spool (7). The oil also flows through passage (12) to the rotary group of the travel motor.A portion of the pump oil in port (4) flows through passage (13). The oil enters spring chamber (14). This pump oil flows through passage (15). Ball (16) shifts. This allows pump oil to flow through the orifice and into damper chamber (17). Oil also flows from spring chamber (14) to damper chamber (17). The pressure oil in spring chamber (14) and the pressure oil in damper chamber (17) shifts spool (7) to the left against the force of spring (10). Throttling slot (18) now opens.Pressure oil also flows through passage (21), spring chamber (22) and passage (23). The oil now enters spring chamber (24). The pressure oil shifts damper piston (25) to the right against the force of spring (26). The movement of damper piston (25) against spring (26) dampens the force of the sudden increase in pressure at travel crossover relief valve (6).As spool (7) shifts to the left, throttling slots (18) open. Return oil from the travel motor flows through passage (19), throttling slots (18) and port (5) to the hydraulic tank. The oil in spring chamber (27) and passage (20) will be the same pressure as the return oil.When the oil flow from port (4) is blocked, the pressure in spring chamber (14) and damper chamber (17) decreases. The force of spring (10) shifts spool (7) to the right. Throttling slots (18) close. Return oil from the travel motor at passage (19) is blocked and the rotation of the travel motor stops.When the direction of travel is reversed, pump oil flows to spool (7) through port (5). The return oil flows through port (4). During forward travel, the travel counterbalance valve operates in the same manner as the reverse travel operation.Counterbalance Valve Operation During Slope Travel
Illustration 3 g02161740
Travel counterbalance valve (slope travel)
(2) Counterbalance valve
(3) Crossover relief valve (forward travel)
(4) Port (supply port for reverse travel)
(5) Port (supply port for forward travel)
(6) Crossover relief valve (reverse travel)
(7) Spool
(10) Spring
(13) Passage
(14) Spring chamber
(15) Passage
(16) Ball
(17) Damper chamber
(18) Throttling slots
(19) Passage When the machine travels down a slope, the travel motors rotate at a higher speed. The higher speed is due to the mass (weight