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Section E
5 - 1
Component Key:
A
Spur Gear - Idler
B
Spur Gear - Driven
C
Channel
D
Recess
P1 Main Section
P2 Secondry Section
9803/3280
Hydraulics
Circuit Descriptions
Purchased from www.WorkshopManuals.co.uk
Hydraulic Pump - Fixed Flow
Single Pump - Operation
The hydraulic pump is a gear type. The basic principle of the
pump depends on the meshing of the two spur gears A and
B, one of which is engine-driven whilst the other is an idler.
Oil is picked up on the inlet side of the pump by the gears
and carried round between the gear teeth and the pump
body. As the gears come into mesh the oil is forced through
the pump outlet port.
Lubrication is provided by the hydraulic oil which is directed
around the unit, via special oil ways, by the motion of the
meshing gears.
Double Pump - Operation
Both sections P1 and P2 operate as described below:
The basic principle of the gear pump depends on the mesh-
ing of two spur gears A, one of which is engine driven while
the other is an idler.
Oil is picked up by the gear teeth on the inlet side of the
pump and carried around betwwen the teeth and the pump
body. As the gears come into mesh, the space carrying the
oil is filled by a gear tooth on the mating gear, forcing the oil
out of the space and the through the pump outlet.
The wear plates B are loaded towards the gears by pres-
surised oil which is fed to the backs of the wear plates via
channels C. This ensures that the clearance between the
wear plates and gears is prevented from becoming exces-
sive as outlet pressure rises.
The side of each wear plate that faces the gears has two
recesses D. The recess on the inlet side of the pump assists
the flow of oil into the gear spaces, thus raising the cavitation
threshold of the pump. The recess on the outlet side vents oil
trapped between meshing gear teeth to prevent compres-
sion loads on the bearings.
Section E
5 - 1
Issue 1
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