LABEL 0992425 - Caterpillar

Illustration 1 g00870367
Steering metering pump
(1) Inlet port for the pilot oil
(2) Return port to the hydraulic tank
(3) Outlet port to the right neutralizer valve
(4) Outlet port to the left neutralizer valve
Illustration 2 g00870368
Section A-A
(A) Control section
(B) Metering section
(5) Drive shaft
(6) Oil passage
(7) Spool
(8) Centering springs
(9) Pin
(10) Oil passage for left turn
(11) Oil passage for right turn
(12) Sleeve
(13) Oil passage to metering section
(14) Stator
(15) Rotor The steering metering pump is made up of two sections: control section (A) and metering section (B). The two sections send pilot oil to the steering neutralizer valves. From the neutralizer valves, the oil flows to the steering control valve. These components control the speed and direction of a turn.Metering section (B) is a small hydraulic pump. The metering section produces a specific amount of metered oil flow. Then, the metered oil is directed by control section (A). The metered oil flows to either the outlet port to the right neutralizer valve or to the outlet port to the left neutralizer valve.The steering wheel is connected to spool (7) by a splined shaft assembly. When the steering wheel is not being turned, the control section is in the No Steer position. When the steering wheel is not being turned , most of the flow is blocked by spool (7) and sleeve (12). A small amount of oil leaks past the spool and back to the hydraulic tank. This ensured that a supply of oil that is at operating temperature is always available at the metering pump. The pilot oil cannot flow through the metering pump until the steering wheel is turned.The following components will turn when the steering wheel is rotated: drive shaft (5), spool (7), pin (9), and sleeve (12). These components turn in relation with each other. Sleeve (12) and spool (7) do not begin turning at the same time.
Illustration 3 g00870369
Spool and sleeve
(7) Spool
(12) Sleeve
(16) Slots for the centering springs
(17) Grooves for oil flow
(18) Hole in spool for the pin
(19) Orifices for oil flow
(20) Hole in sleeve for the pin The rotation of sleeve (12) is slightly delayed because hole (18) is elongated in spool (7). Also, the force of centering springs (8) prevent sleeve (12) from turning too rapidly. At this point, both spool (7) and sleeve (12) turn as a unit.Spool (7) is permitted to rotate slightly in sleeve (12). This causes orifices (19) in sleeve (12) to align with grooves (17) in spool (7). This provides a path for the pilot oil to flow to metering section (B). The pilot oil then flows to either the right or the left neutralizer valve. The pilot oil then flows to the steering control valve.When the steering wheel is no longer turning, centering springs (8) will bring spool (7) and sleeve (12) back to a No Steer position. This prevents the orifices in sleeve (12) from aligning with grooves in spool (7). This blocks the flow of oil to metering section (B). This causes the steering cylinders to remain in their current position.When the