COUNTERWEIGHT GP 2447938 - Caterpillar

Counterbalance Valve
Illustration 1 g03350354
(1) Counterbalance valve
(2) Check valve
(3) Spring
(4) Passage (parking brake)
(5) Spool (counterbalance valve)
(6) Spring
(7) Check valve
(8) Port
(9) Port
(10) Orifice
(11) Cover (motor) Each travel motor contains a travel brake valve. The travel brake valve consists of counterbalance valve (1), check valve (2), and check valve (7). The travel brake valve prevents the occurrence of a shock load during a travel stop. The travel brake valve also prevents cavitation and overrun. The travel brake valve sends oil to the parking brake in order to release the brake. This action occurs before the start of the machine movement.Counterbalance Valve Operation During Level Travel
Illustration 2 g02927816
Counterbalance valve (level travel)
(3) Spring
(4) Passage (parking brake)
(5) Spool
(7) Check valve
(8) Port
(9) Port
(10) Orifice
(11) Cover (motor)
(12) Spool chamber
(13) Passage
(14) Throttle slot
(15) Passage
(16) Passage
(17) Motor rotary group Pump oil enters the counterbalance valve through port (9) and opens check valve (7). The oil then goes through passage (15) to motor rotary group (17). A portion of the pump oil from port (9) goes through orifice (10), of spool (5), and passage (13) into spool chamber (12). The oil pressure in spool chamber (12) shifts spool (5) to the right. Throttle slot (14) opens. Return oil from motor rotary group (17) flows through passage (16), through throttle slot (14) and through port (8). From port (8), the oil flows back to the hydraulic tank.When spool (5) moves to the right, passage (4) opens. Oil flows from port (9) to the parking brake. The parking brake is released and motor rotary group (17) is allowed to rotate.When pump oil is supplied through port (8), spool (5) moves to the left. Motor rotary group (17) rotates in the reverse direction.Counterbalance Valve Operation For Stopping The Machine
Illustration 3 g02927818
Counterbalance valve (travel stop)
(5) Spool
(6) Spring
(8) Port
(9) Port
(10) Orifice
(12) Spool chamber
(13) Passage
(14) Throttle slot
(16) Passage
(17) Motor rotary group When oil flow from port (9) is blocked, the pressure decreases in spool chamber (12). Spool (5) is returned to the left (NEUTRAL position) by the force of spring (6). When spool (5) returns, oil flow from spool chamber (12) is restricted at orifice (10) and passage (13). This restriction causes a slight pressure increase in spool chamber (12). This resistance causes slow movement of spool (5) to the NEUTRAL position. Throttle slot (14) closes at a controlled speed.When no pump oil is supplied to port (9), the travel motor is still rotating because of the mass (weight and size) of the machine. Return oil flow from motor rotary group (17) flows through passage (16) and flows through throttle slot (14). The return oil flow is restricted at throttle slot (14). The rotation of motor rotary group (17) slows at a controlled speed. When spool (5) is returned to the NEUTRAL position, throttle slot (14) closes completely. Return oil flow from the motor is blocked and the rotation of the motor stops smoothly.When pump oil is blocked at port (8), spool (5) is returned to the right. The travel stops with minimal shock load.Counterbalance Valve Operation During