Minster IOI, Service Manual

Page: 42 / 92

COUNTERBALANCE SYSTEM
Theory of Operation
Counterbalances on mechanical power presses are
used to offset or counterbalance the weight of the press
slide and upper die. Air counterbalances are usually air
cylinders mounted in the press frames and connected
by the cylinder rod or rod brackets to the press slide.
(See Figure 6E.) Included in the system is a safety pop-
off valve, fusible plug and water drain plumbed to the
cylinders. (See Figure 2E.) A check valve is usually
found within the system to prevent a sudden loss of
pressure (located just after the regulator.) A pressure
switch or transducer should also be included (also
located after the regulator) to detect when the pressure
falls below a minimum level to prevent press operation.
As the counterbalance piston travels down in the stroke
the volume decreases therefore pressure increases
taking out the slide’s bearing clearances. As the piston
travels up in the stroke the volume increases thus
decreasing pressure allowing lubrication of the bear-
ings to occur.
The counterbalance system assists in the following:
•
Maintains and reduces bearing clearance
•
An aid to maintain main to pinion gear contact
•
Aids press drive to overcome slide dynamics
•
Aids shutheight adjust mechanism to raise or
lower the slide
IMPORTANT:
Before making any shutheight adjustments,
make certain air pressure to the counterbal-
ance has been properly set to balance the
weight of the slide and attached die. Failure to
properly adjust counterbalance air pressure
may result in damage to the slide adjust mech-
anism.
NOTE: If no die is installed, counterbalance air pres-
sure should be set at balance point (0 die
weight.)
CAUTION
NEVER OPERATE A COUNTERBALANCED PRESS
WITHOUT PROPER AIR PRESSURE APPLIED TO
THE COUNTERBALANCE SYSTEM.
E - 7
Counterbalance Plate
Counterbalance Rod
.375” - 16 Hex. Nuts
Air Cylinder Cover
Seal
Cylinder
Air Cylinder Head Pin
Air Cylinder Head
Piston Plate
Piston
Bushing
Piston Rod
Figure 6E. Counterbalance cylinder.
!