Meyer E-58H, Service Manual

Page: 18 / 78

Under a condition, such as when a hydraulic cylinder
is extended to the end of its stroke, eliminating
additional space for the pressurized hydraulic oil to
be pumped into, the alternate opening and closing
of the poppet valve controls the pump’s pressure
output and provides an escape for the pressurized
hydraulic fluid.
The pressure relief valve used in the E-58H, E-78 &
E-88 pump, while more sophisticated than the one
described, functions in the same manner. The pump
pressure relief valve may be adjusted to the specified
pressure of 2000 P.S.I. by adjusting the set screw after
installing a suitable pressure gauge of 2500 P.S.I. in
the circuit.
SOLENOID VALVES
Hydraulic valves are simple in concept and all have the
same basic function: Control the direction of oil flow.
Each Solenoid Valve consists of two components: the
Cartridge and the Coil.
Cartridge
The Cartridge consists of the hydraulic valve
mechanism and an armature which enables the
valve mechanism to be operated and controlled
electrically. The Cartridge is designed to screw in
and out of the E-58H, E-78 & E-88 units much like
the typical “spark plug”.
FIGURE 1-13
COIL
VALVE SPOOL
WINDING
ARMATURE
FIGURE 1-11
ELECTRO LIFT® UNIT COMPONENTS
FIGURE 1-12
-16-
E-58H, E-78 & E-88 UNIT COMPONENTS
MOTOR (4-1/2”)
Iskra - Two terminal
The Iskra motor is a four pole, electromagnet motor
which consists primarily of a 4-1/2” diameter solid
steel frame, armature, brushes, field coils and pole
pieces. This motor can be used on vehicles with either
the common negative ground electrical system or the
positive ground electrical system.
HYDRAULIC PUMP
The pump in a hydraulic system employs an external
source of power to apply a force to a liquid. A pump
develops no power of its own. It simply transfers power
from an external source (the electric motor on the E-
58H, E-78 & E-88 unit) to the liquid in the hydraulic
system.
The basic operating principles of the hydraulic
pump used in the E-58H, E-78 & E-88 units are quite
simple. Figure 1-11 illustrates the basic components
of a positive displacement gear type pump and their
functions. The pumping action takes place within the
pump chamber which is connected to the reservoir by
the intake line. The pump chamber has an outlet line
in which the liquid under motion and pressure leaves
the pump to perform work.
PRESSURE RELIEF VALVE
A basic pressure relief valve is shown in
Figure 1-12. It consists of a poppet valve and a valve
spring. Both are located in a passage which connects
the inlet passage to the outlet passage. The poppet
valve is normally held closed by the valve spring,
sealing the connecting passage from the pressurized
outlet passage. The poppet valve, being a piston, is
exposed to the pressurized hydraulic fluid in the outlet
passage. Whenever the hydraulic pressure against
the poppet valve becomes greater than the pressure
being exerted on the poppet valve from the opposite
direction by the valve spring, the poppet valve will
open. This allows some of the pressurized hydraulic
fluid to flow through the connecting passage to the
non pressurized inlet passage. The effect is to lower
the pressure in the outlet passage which will allow the
valve spring to close the poppet valve again.