JLG 660SJ Service Manual - Manual (Page 194)

SECTION 4 - BOOM & PLATFORM
4-22 – JLG Lift – 3121202
3. Install new seals (11), back-up ring (12), cap bearing
(13), bearing packing (14) and thrust ring (10) on
end cap (5).
4. Place the actuator in the vertical position, install the
piston sleeve (3) in timed relation to the housing (1).
DO NOT MISALIGN THE SLEEVE TOO MUCH ANY ONE WAY, AS IT
WILL MARK THE CYLINDER BORE.
NOTE: The timing marks (the small punch marks on the
face of each gear), must be aligned for proper shaft
orientation. (See Actuator Timing.)
5. Install the shaft (2) into housing (1) by aligning the
proper punched timing marks. (See Actuator Tim-
ing.)
6. Temporarily tape the threaded portion of the shaft
will help installation past the shaft seals (masking
tape).
7. The end cap (5) is torqued to 40 - 50 ft. lbs. (54 - 68
Nm), such that the actuator begins rotation at
approximately 100 psi (6.895 Bar) pressure.
8. The end cap must be secured against the shaft by
installing axial set screws (4).
4.10 ROTARY ACTUATOR (S/N 0300130779
TO PRESENT)
Theory of Operation
The L20 Series rotary actuator is a simple mechanism that
uses the sliding spline operating concept to convert linear
piston motion into powerful shaft rotation. Each actuator is
composed of a housing with integrated gear teeth (01)
and only two moving parts: the central shaft with inte-
grated bearing tube and mounting flange (02), and the
annular piston sleeve (03). Helical spline teeth machined
on the shaft engage matching splines on the in- side
diameter of the piston. The outside diameter of the piston
carries a second set of splines, of opposite hand, which
engage with matching splines in the housing. As hydraulic
pressure is applied, the piston is displaced axially within
the housing - similar to the operation of a hydraulic cylin-
der - while the splines cause the shaft to rotate. When the
control valve is closed, oil is trapped inside the actuator,
preventing piston movement and locking the shaft in posi-
tion.
The shaft is supported radially by the large upper radial
bearing and the lower radial bearing. Axially, the shaft is
separated from the housing by the upper and lower thrust
Figure 4-29. Actuator Timing Bars indicate starting posi-
tions of piston and shaft.
Arrows indicate direction they
will rotate. The housing with
integral ring gear remains sta-
tionary. As fluid pressure is applied,
the piston is displaced axially
while the he lical gearing
causes the piston and shaft to
rotate simultaneously. The
double helix design com-
pounds rotation: shaft rota-
tion is about twice that of the
piston.