JLG 450A_AJ Series II Service Manual - Manual (Page 274)

SECTION 4 - BOOM & PLATFORM
4-8 – JLG Lift – 3121180
4.2 ROTATOR
Theory of Operation
See Figure 4-6., Rotator Assembly - Cutaway
Fluid entering Port P2 under pressure will bear on the pis-
ton (4) and force piston sleeve (3) upwards. The left-
handed spline of piston sleeve (3) will combine with right-
handed spline of shaft (2A) and cause rapid counter-
clockwise rotation of shaft and flange (2B) (looking down).
Fluid entering Port P1 will reverse rotation.
Displacement and torque are identical for clockwise and
counterclockwise rotation.
Shaft (2A) is integral with shaft flange (2B) and bearing
tube (2C). The shaft is supported radially by the large
upper radial bearing (19) and lower radial bearing (18).
Axially, shaft is separated from housing by upper and
lower thrust rings (20). End cap (5) is adjusted for axial
clearance and locked in position by cap screws (7).
Disassembly and Inspection
Place on a clean workbench with room to place internal
parts as they are removed. Remove all hydraulic fittings
Loosen cap screws(7) and unscrew locknut (6) and end
cap (5). Shaft is now free to move up and out of engage-
ment with piston sleeve (3). Note orientation between
spline teeth (see Figure II), as this will greatly simplify
actuator timing upon reassembly.
After removing shaft, piston sleeve, and piston assembly
can now be moved down and out of housing. Remove all
seals and bearings from their grooves, except static piston
seals (9) and (11). These seals generally do not require
replacement. Clean all parts thoroughly and inspect for
wear. A small amount of wear in spline teeth has little
effect on actuator strength. New spline sets are manufac-
tured with a backlash of about 0.005" (0.127 mm) per mat-
ing set. After long service, a backlash of about 0.015"
(0.381 mm) per set may still be acceptable in most cases,
depending on required accuracy of application.
Item (1) is the integral housing and ring gear. Check ring
gear for wear and weld damage to the pins. Inspect cylin-
der bore for wear and scratches. Surface finish should be
32 RMS or better; re-hone if necessary. Radial bearings
(18) and (1 9) and piston bearings (17) have a maximum
radial clearance of 0.006" (0.152 mm). Clearance in
excess of 0.008" (0.203 mm) requires bearing replace-
ment. Rough and grooved shaft journals require shaft
replacement.
Assembly and Testing
Wash all parts thoroughly in cleaning solvent and blow
dry. Coat all sealing and working surfaces with a good
grade hydraulic oil. Install seals and bearings in piston
sleeve, piston, shaft, and end cap. Exclusion seal lips (16)
face outward, and high pressure seal lips face inward.
Place actuator in a vertical position, install piston sleeve
(3) in timed relation to housing, applying firm pressure as
new seals and bearings enter housing and become com-
pressed by housing chamber.
DO NOT MISALIGN SLEEVE TOO MUCH ANY ONE WAY, AS IT
WILL MAR CYLINDER BORE. TIMING MARKS (SMALL PUNCH
MARKS ON FACE OF EACH GEAR), MUST BE ALIGNED FOR
PROPER SHAFT ORIENTATION. REFER TO FIGURE 4-5., TIMING
MARKS.
1. Integral Housing & Ring Gear
2. Shaft
3. Piston Sleeve
Figure 4-5. Timing Marks