PLATE AS 1671168 - Caterpillar

Isolator Compensator Explanation
Note: For this explanation of the isolator compensator assembly, the Tilt Cylinder Control Spool will be used. The isolator compensator assembly for the Lift Cylinder Control Spool and the isolator compensator assembly for the auxiliary control spool work in the same manner.
Illustration 20 g01341848
(6) Isolator compensator assembly for the auxiliary function (7) Isolator compensator assembly for the tilt cylinders (8) Isolator compensator assembly for the lift cylinders (9) Isolator compensator assembly for the secondary auxiliary function (21) Secondary auxiliary control spool (20) Lift cylinder control spool (19) Tilt cylinder control spool (18) Auxiliary control spool (48) Bridge passage for the tilt cylinder control spool (49) Passage to the bottom of the compensator spool (61) Load sensing passage (62) Auxiliary pump passage
Illustration 21 g01342156
(63) Spring (64) Orifice in isolator spool (65) Spring (66) Cross drilled hole (67) Compensator spool (68) Isolator spool
Illustration 22 g01342154
Section view that shows the tilt cylinder control spool (19) Tilt cylinder control spool (23) Central return passage (24) Central supply passage from the hydraulic pump (43) Working port "A" (45) Working port "B" (48) Bridge passage (49) Passage to the bottom of the compensator spool (61) Load sensing passage (62) Auxiliary pump passageSingle Function
Shifting the spool will connect work port "A" (43) or work port "B" (45) to the bridge (48). Shifting the spool will also connect the central pump supply passage (24) to passage (49). Passage (49) connects passage (24) to the bottom of the compensator spool (67) . Working pressure is communicated through a small cross drilled hole (66) in the upper portion of the compensator spool (67). Working pressure acts on the top of the compensator spool (67) and on the bottom of the isolator spool (68). The pressure on the bottom of the isolator spool will lift the isolator spool. Shifting up the isolator spool meters oil from the auxiliary pump passage (62) into the load sensing passage (61). Oil in the load sensing passage creates a load sensing signal to the hydraulic pump controller. If working pressure is greater than hydraulic pump pressure, the compensator spool (67) remains shut for the load check function of the compensator. When the pump pressure exceeds the working pressure, pump pressure will shift up the compensator spool (67) against the isolator spool (68) .The isolator compensator is designed to maintain a 24 bar (348 psi) margin between the hydraulic pump pressure and working pressure. Hydraulic pump pressure must be greater than working pressure. Multifunction
Each command function will generate an independent load sensing signal. Refer to "Single Function ".Load sensing pressure is communicated to the top of each isolator spool through an orifice (64) in the spool. The isolator spool with the highest pressure creates the load sensing signal. This load sensing signal is sent to the hydraulic pump controller. This load sensing signal is also sent to the top of each of the other isolator spools.The isolator spools with working pressures that are less than load sensing pressure are pushed