938G Series II Wheel Loader and IT38G Series II Integrated Toolcarrier Hydraulic System Piston and Vane Pump (Implement Section) Caterpillar


Piston and Vane Pump (Implement Section)
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1.1. Operation of the Implement Section



Illustration 1g00928400

Piston and Vane Pump

(1) Steering section. (2) Implement section (vane). (3) Braking section. (4) Coupling. (5) Rotor. (6) Cam ring.

The hydraulic pump group consists of three pump sections. Steering section (1) is a load sensing axial piston type pump. The steering section provides the oil that is needed to operate the steering system. The steering section is also the source for the pilot system oil.

Brake section (3) is a vane pump. The brake section provides the oil that is needed to operate the service brake circuit and the parking brake circuit.

Implement section (2) is a fixed displacement vane pump. The implement section provides the oil that is needed to operate the cylinders for the work tool. In the IT38G Series II Integrated Toolcarrier, the implement section also supplies oil to the auxiliary function and/or the coupler cylinder.

All three pump sections rotate through a common shaft. The implement section is driven by coupling (4). The steering section and the implement section share a common inlet. Each pump section has a separate outlet.

Brake pump section (3) has a separate inlet as well as an outlet.

Operation of the Implement Section




Illustration 2g00928450

Sectional View of the Pump Cartridge

(5) Rotor. (6) Cam ring. (7) Outlet. (8) Passage. (10) Inlet. (11) Vanes. (12) Outlet.

The following components are the components of the implement pump section: a plate, adapter, seal packs, rotor (5), cam ring (6) and vanes (11) .

First, vanes (11) are pushed against cam ring (6) by centrifugal force. Oil pressure in passage (8) pushes the vanes against the cam ring. Both ends of the vanes are connected by the passages. This oil maintains an even pressure on both ends of the vanes. This oil also permits the oil behind the vanes to escape as the vanes are pushed induring rotation.

As rotor (5) turns, the vanes in locations (F) and (G) move outward. The vanes follow the shape of cam ring (6). As the chamber area between the vanes increases, a low pressure or a low vacuum is created in the chamber. This pressure difference causes oil to flow from the hydraulic oil tank through inlets (9) and (10). The oil fills the space between the vanes at locations (F) and (G). The oil continues to fill the space through locations (E) .

The oil between the vanes at locations (E) and (A) will be trapped when the vane at location (E) passes the end of inlet (10). As rotor (5) continues to rotate, the vanes are pushed inward by the contour of cam ring (6). The chamber area between the vanes now decreases. The oil between the vanes at locations (A) and (C) is pushed into outlet (7). The displacement of the pump is determined by the difference in volume of the inlet chamber and the outlet chamber, multiplied by the number of chambers. A chamber is the area between one vane and the next vane.

The oil continues to be pushed through locations (C) and (D). When the vane at location (C) passes the end of outlet (8), the cycle is completed.

Reference: For additional information about specifications for the implement pump, refer to the Service Manual module Specifications, "Piston and Vane Pump - (Implement Section)".

Reference: For additional information on vane pumps, refer to Special Instruction, SMHS7047, "Special Disassembly and Assembly Procedures for Sperry Vickers Pumps with New Type Cartridges ".

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