JLG 600SC_660SJC Service Manual - Manual (Page 120)

SECTION 4 - BOOM & PLATFORM
4-18 – JLG Lift – 3121607
4.9 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
integrated bearing tube and mounting flange (02), and the
annular piston sleeve (03). Helical spline teeth machined on
the shaft engage matching splines on the piston inside diame-
ter. The piston outside diameter carries a second set of oppo-
site direction splines which engage with matching splines in
the housing.
As hydraulic pressure is applied, piston is displaced axially
within the housing - similar to operation of a hydraulic cylin-
der - while splines cause shaft to rotate. When control valve is
closed, oil is trapped inside the actuator, preventing piston
movement and locking the shaft in position. The shaft is sup-
ported radially by the large upper radial bearing and lower
radial bearing. Axially, the shaft is separated from the housing
by upper and lower thrust washers. End cap is adjusted for
axial clearance and locked in position by set screws or pins.
Required Tools
1. Flashlight - Examine timing marks, component failure,
and overall condition.
2. Felt Marker - Match mark timing marks and outline trou-
bled areas.
3. Allen wrench - Remove 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 - Piston sleeve installation.
9. End cap dowel pins - removal and installation of end cap
(sold with Helac seal kit).
The seal tool is a customized standard flat head screwdriver. To
make this tool, heat flat end with a torch. Secure heated end of
screwdriver in a vice and bend to a slight radius. Once radius is
achieved, round off all sharp edges using a grinder. There may
be some slight modifications for your personal preference.
Bars indicate starting positions
of piston and shaft. Arrows indi-
cate direction they will rotate.
The housing with integral ring
gear remains stationary. As fluid pressure is applied, the
piston is displaced axially while
helical gearing causes the piston
and shaft to rotate simultane-
ously. The double helix design
compounds rotation: shaft rota-
tion is about twice of the piston.