JLG 1100SB Service Manual - Manual (Page 221)

SECTION 4 - BOOM & PLATFORM
3121265 – JLG Lift – 4-51
4.10 ROTARY ACTUATOR
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.
Required Tools
Upon assembly and disassembly of the actuator there are
basic tools required. The tools and their intended func-
tions are as follows:
1. Flashlight - helps examine timing marks, component
failure and overall condition.
2. Felt Marker - match mark the timing marks and out-
line troubled areas.
3. Allen wrench - removal of port plugs and set screws.
4. Box knife - removal of seals.
5. Seal tool - assembly and disassembly of seals and
wear guides.
6. Pry bar - removal of end cap and manual rotation of
shaft.
7. Rubber mallet- removal and installation of shaft and
piston sleeve assembly.
8. Nylon drift - installation of piston sleeve
9. End cap dowel pins - removal and installation of end
cap (sold with Helac seal kit).
The seal tool is merely a customized standard flat head
screwdriver. To make this tool you will need to heat the flat
end with a torch. Secure the heated end of the screwdriver
in a vice and physically bend the heated end to a slight
radius. Once the radius is achieved round off all sharp
edges of the heated end by using a grinder. There may be
some slight modifications for your own personal prefer-
ence.
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.