JLG 600SC_660SJC Service Manual - Manual (Page 245)

SECTION 7 - BOOM & PLATFORM
3121157 – JLG Lift – 7-19
8. The end cap must be secured against the shaft by
installing axial set screws (4).
7.9 ROTARY ACTUATOR (S/N 0300132437
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
washers. The end cap is adjusted for axial clearance and
locked in position by set screws or pins.
Figure 7-26. Actuator Timing
Bars indicate starting posi-
t i o ns o f p i s t o n a n d s h a f t .
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
w h i l e t h e h e l i c a l g e a r i n g
causes the piston and shaft to
rotate simultaneously. The
d o u b l e h e l i x d e s i g n c o m -
pounds rotation: shaft rota-
tion is about twice that of the
piston.