JLG 510AJ Service Manual - Manual (Page 207)

SECTION 4 - BOOM AND PLATFORM
3121181 – JLG Lift – 4-9
4.3 ROTARY ACTUATOR
(S/N 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 com-
posed 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 annular piston sleeve (03).
Helical spline teeth machined on the shaft engage matching
splines on the in- side diameter of piston.
The 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 dis-
placed axially within the housing - similar to the operation of a
hydraulic cylinder - while splines cause shaft to rotate. When
control valve is closed, oil is trapped inside the actuator, pre-
venting piston movement and locking the shaft in position.
The shaft is supported radially by the large upper radial bear-
ing and the lower radial bearing. Axially, shaft is separated
from 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
Upon assembly and disassembly of actuator there are basic
tools required. The tools and their intended functions are as
follows:
1. Flashlight - helps examine timing marks, component
failure and overall condition.
2. Felt Marker - match mark the 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 - removal of end cap and manual rotation of
shaft.
7. Rubber mallet- removal and installation of shaft and pis-
ton 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 screw-
driver. To make this tool you will need to heat the flat end with
a torch. Secure heated end of screwdriver in a vice and physi-
cally bend heated end to a slight radius. Once 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 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, pis-
ton 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 that of piston.