JLG 20VP (3120728) Service Manual - Manual (Page 25)

SECTION 2 - SERVICE PROCEDURES
3120728 – JLG Lift – 2-7
Operation (See Figure 2-4. & Figure 2-5.)
When the magnetic coil is not energized (brake on), the
armature plate is pushed away from the magnetic coil sur-
face by heavy springs internally mounted in the magnetic
coil housing. This pressure forces the armature plate
against the friction brake disk holding it tight between the
armature plate and the mounting plate. The brake is not
released until either the magnetic coil is energized pulling
the armature plate away from the friction brake disk or the
brake is manually released using the manual brake
release handle.
A correctly adjusted brake will ideally have a measurment
of approximately .006" (but will operate normally at .004" to
.010") between the armature plate and magnetic coil
housing surface when the brakes are ENGAGED (brakes
on).
Never allow any type of lubricant (oil, grease, hydraulic
fluid, etc.) to come in contact with the brake friction disk or
it’s contacting surfaces. Also if the brake becomes
clogged with debris or dirt the brake may not release
properly.
Checking/Adjusting Armature Plate Gap Setting
1. First inspect that all parts of the brake assembly are
tight and secure. Tighten as necessary.
2. Inspect the brake for any debris which may be
lodged in the air gap between the armature plate
and magnetic coil when the brakes are ENGAGED
(brakes on); on either side of the friction disk when
the brake is RELEASED (brakes off); or any dirt or
debris lodged between the manual release arm and
the magnetic coil housing. Clean and remove debris
as necessary.
3. With the brakes ENGAGED measure the air gap
between the armature plate and the magnetic coil
housing. The correct setting should be .006", how-
ever the brakes will operate properly if the measure-
ment is a minimum of .004" and a maximum of .010".
(See Figure 2-5.)
4. If the air gap falls outside the maximum allowable
setting of .010" the friction disk has worn. To correct
this replace the disk with a new one.
5. It the air gap is below the minimum allowable setting
of .004", recheck the areas between the magnetic
coil housing, armature plate, friction disk and
mounting plate for debris. Clean as neccessary. Also
check that the manual release arm screws are not
tightened to tight.
Manual Release Arm - Screw Adjustment
NOTE: Always check the armature plate gap setting is within
spec before attempting to adjust the manual release
arm screw adjustment.
1. With the brakes ENGAGED (brakes on) the air gap
under the head of the manual release arm screw to
the surface of the armature plate should be set at
.020". Adjust using the locknut on the release arm
end of the screw.
2. With the brakes electrically RELEASED (brakes off)
the air gap under the screw head increases to
approximately .026" due to the armature plate move-
ment towards the magnetic coil, releasing the fric-
tion brake disk. When the brakes are RELEASED
(brakes off) manually the screw head pulls in against
the armature plate releasing the friction brake disk.
Figure 2-5. Brake Armature Plate & Brake Disk Adjustment.
FRICTION BRAKE DISK FRICTION BRAKE DISK
ARMATURE PLATE ARMATURE PLATE
MAGNETIC COIL
(Not Energized)
MAGNETIC COIL
(Energized)
MANUAL
RELEASE ARM/
ADJUSTMENT
SCREW
MANUAL
RELEASE ARM/
ADJUSTMENT
SCREW
GAP SETTINGS - BRAKE ON
(Magnet Not Energized)
GAP SETTINGS - BRAKE RELEASED
(Magnet Energized)
0.006” GAP
BETWEEN
ARMATURE
PLATE AND
MAGNETIC COIL
0.006” GAP
BETWEEN
FRICTION
DISK AND
ARMATURE
PLATE
0.020” GAP
UNDER
SCREW HEAD
BETWEEN
ARMATURE
PLATE
0.026” GAP
UNDER
SCREW HEAD
BETWEEN
ARMATURE
PLATE
MOUNTING PLATE MOUNTING PLATE