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2. 3-way (single check valve type) mini-valve.
3. Manually controlled emergency brake re-
lease.
4. Plumbing terminal, flexible hoses, copper
lines and "O" rings.
5. Portions of the electrical system.
Figure 1-15. Brake System Block Diagram
Each corner of the cast-iron table base has a hydrau-
lic brake cylinder. These single action cylinders are
hydraulically connected in parallel to the mini-valve
and all four are activated together. It is normal for
one corner of the table to raise before the others
due to the weight distribution of the table.
An electronic timer in the relay box is activated when
any function on the pendant control is pushed
momentarily. The pump/motor and brake system
mini-valve are activated and the brake cylinders
are completely set. The electronic timer runs for
approx. 8-10 seconds.
The brakes are released by pushing the BRAKE
UNLOCK button momentarily. An electronic timer in
the relay box activates the brake function hydraulic
mini-valve and pump/motor.
Figure 1-14. Elevation Return Circuit
f. Brake System
The brake system consists of the following compo-
nents: (figure 1-15)
1. Single action slave cylinders (4 each).
e. Elevation Cylinder Return Circuit
A three-way (single check valve type) mini-valve
controls both the elevation and return circuits. The
elevation circuit operation within the mini-valve is
identical to the operation of the four-way valves
previously described (inlet pressure opens the
check valve allowing the oil to enter the cylinder). In
the return position, inlet pressure pushes the pilot
plunger up and opens the return check valve. See
figure 1-14. The open check valve allows a path
for the oil in the elevation cylinder to return to the
reservoir. When the pilot plunger valve is opened,
the continuing pump pressure opens the pres-
sure relief valve which provides a return oil path
to the reservoir.
The mini-valve used in the elevation circuit contains
only one check valve (all four-way mini-valves use
two check valves). The check valve is used to trap
the oil in the elevation cylinder thereby supporting
the table top. When the top is being lowered the
check valve is mechanically held open by the pilot
plunger through pump pressure.
041905.029
TO RESERVOIR THROUGH
PRESSURE RELIEF VALVE
INLET
RETURN TO
RESERVOIR
041905.028
MOTOR/PUMP
ASSEMBLY
PLUMBING
TERMINAL
BRAKE
BRAKE
BRAKE
BRAKE
EMERGENCY
BRAKE RELEASE
PRESSURE
RELIEF
VALVE
BRAKE
MINI-VALVE
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