JLG 450A_AJ Series II Service Manual - Manual (Page 277)

SECTION 4 - BOOM & PLATFORM
3121180 – JLG Lift – 4-11
4.3 ROTARY ACTUATOR (S/N 0300130812
AND 1300006433 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 inside diameter
of piston. Outside diameter of 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 operation of a hydraulic cylinder - while splines cause
the shaft to rotate. When the control valve is closed, oil is
trapped inside actuator, preventing piston movement and
locking shaft in position.
Shaft is supported radially by large upper radial bearing
and lower radial bearing. Axially, shaft is separated from
housing by upper and lower thrust washers. The end cap
is adjusted for axial clearance and locked in position by
set screws or pins.
Required Tools
Basic tools required for assembly and disassembly of the
actuator and their intended functions are as follows:
1. Flashlight - helps examine timing marks, component
failure, and overall condition.
2. Felt Marker - match mark timing marks and outline
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 - end cap removal 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 a customized flat-head screwdriver. To
make this tool, heat flat end with a torch and bend to a
slight radius in a vice. Round off sharp edges with a grinder.
Bars indicate starting posi-
tions of piston and shaft.
Arrows indicate direction they
rotate. Housing with integral
ring gear remains stationary. As fluid pressure is applied,
piston is displaced axially
while helical gearing causes
piston and shaft to rotate
simultaneously.
The double helix design com-
pounds rotation: shaft rota-
tion is about twice that of the
piston.