Rotary Actuator; Theory Of Operation; Tools Required For Assembly/Disassembly - JLG E450A Service And Maintenance Manual

SECTION 4 - BOOM & PLATFORM

4.11 ROTARY ACTUATOR

Theory Of Operation

The rotary actuator is a simple mechanism that uses the slid-
ing 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). Heli-
cal 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 oppo-
site 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 cyl-
inder while the splines cause the shaft to rotate. When the
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, 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 setscrews or pins.
NOTE: Bars indicate starting positions of piston and shaft.
Arrows indicate direction they will rotate. The hous-
ing with integral ring gear remains stationary.
As fluid pressure is applied, the piston is displaced
axially while the helical gearing causes the piston
and shaft to rotate simultaneously. The double helix
design compounds rotation: shaft rotation is about
twice that of the piston.
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Tools Required for Assembly/Disassembly

Upon assembly and disassembly of the actuator
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 outline
troubled areas.
3. Allen wrench- removal of port plugs and setscrews.
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 headscrew-
driver. 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 preference.
there are
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