DRESSTA TD-25M EXTRA, Service Manual

Page: 368 / 595

SECTION 10A
PUMPS
Page 2
TD-25M EXTRA DRESSTA
EQUIPMENT PUMP
2. DESCRIPTION AND OPERATION (Refer to Fig. 10A.7)
The equipment pump rotary vane type consists principally of an inlet housing, three outlet bodies,
a drive shaft and three pumping cartridges. The single inlet port feeds all three pumping cartridges.
Front and Center Pumping Cartridges
The principle components of a cartridge are an elliptical rotor ring, a slotted rotor splined to the
drive shaft, an inlet and outlet support plate fitted with four special seal pack subassemblies, two
flex side plates and ten vanes and inserts fitted to the rotor slots. Fluid enters the cartridge through
the inlet port and is discharged through the outlet of flex side plate and support plate to the outlet
ports.
The rotor is driven within the rotor ring by the pump driveshaft, which is coupled to the torque
converter accessory drive gear. As the rotor turns, centrifugal force on the vanes, aided by under
vane pressure fed from the outlet port, causes the vanes to follow the elliptical inner surface of the
rotor ring. Radial movement of the vanes and turning of the rotor causes the chamber volume
between the vanes to increase as the vanes pass the inlet sections of the rotor ring. This results in
a low pressure condition which allows atmospheric pressure to force fluid into the chambers. An
additional inlet fluid exists through a drilled hole in the rotor ring. This hole connects the inlet port
directly to the inlet areas of the rotor ring and provides an additional flow path for fluid to get into
the cartridge.
Fluid is trapped between the vanes and carried past a sealing land to the outlet section of the rotor
ring. As the outlet section is approached, the chamber volume decreases and fluid is forced out
into the system. System pressure is fed under the vanes, assuring their sealing contact against the
rotor ring during normal operation. In the intra-vane cartridge, full system pressure is continuously
applied only to the area between the vane and insert. This area is small and thrust is
correspondingly light. During vane travel through pressure areas, full system pressure is applied
against the bottom area of the outer vane. The valving of pressure to and from the bottom area of
the vane is through holes drilled in the rotor. This selective application of pressure maintains the
vane in substantially constant radial hydraulic balance in all positions. Vane tip wear is
compensated automatically.
As the vane wears, pressure moves the vane father out in the rotor slot holding the vane
tip against the rotor ring. The pump ring is shaped so that two pumping chambers are formed
180 [
o
] apart. Thus, opposing hydraulic forces which develop side loads on the shaft cancel out
to form a hydraulic balance.
The flex side plates for both inlet and outlet are symmetrical. Pressure is fed behind each side
plate into two kidney shaped cavities, which are sealed by special seal pack subassemblies.
The two flex side plates and their associated kidney shaped cavities function in the following
manner. As pressure also builds up in the outlet, pressure also builds up in the cavities. The
pressure in the cavities hold the flex side plates in hydraulic balance against the rotor and provide
optimum running clearance for minimum internal leakage and minimum friction. The flex side
plates also provide passages for feeding under vane pressure to the space between the vane and
insert. The bronze faces of the flex side plates ride next to the rotor and provide excellent wear and
cold start characteristics. The inlet and outlet support plates hold the flex side plates in position and
contain passages which allow fluid pass from the inlet to the pumping cartridge and from the
cartridge to the outlet port.