Upright SB-80, Service & Parts Manual

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3-26 SB80 Work Platform - European
M
AINTENANCE
Section
3.19
3.19 R
OTARY
A
CTUATOR
Theory of Operation
The HP-9K Series rotary actuator is a simple mecha-
nism that uses the sliding spline operating concept to
convert linear piston motion into powerful shaft rota-
tion. Each actuator is composed of a housing (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 inside diameter of the piston. The outside diame-
ter 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 cylinder - 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 bearing (302) and the lower radial bearing
(303). Axially, the shaft is separated from the housing
by the upper and lower thrust rings (304). The end
cap (04) is adjusted for axial clearance and locked in
position by set screws (105).
Displacement and torque are identical for clockwise
and counter-clockwise rotation.
Disassembly and Inspection
Place on a clean workbench with ample room for all
internal parts as they are removed. Remove all
hydraulic fittings. Loosen set screws (105) and
unthread end cap (04). Use a small grinder to
remove the set screw thread stakes if necessary.
Remove the stop tube (400), if furnished. The shaft is
now free to move up and out of engagement with the
piston sleeve (03). Note the timing marks on the
spline teeth - small punch marks on the face of each
gear (see Figure 3-32). Correct orientation of the
marks will greatly simplify actuator timing upon reas-
sembly. Do not remove any component without first
locating the timing marks.
After removing the shaft, the piston sleeve (03) can
now be moved down and out of the housing. Remove
all seals and bearings from their grooves. Clean all
parts thoroughly and inspect for wear. A small
amount of wear in the spline teeth will have little
effect on the actuator strength. New spline sets are
manufactured with a backlash of about ,127 mm
(.005”) per mating set. After long service, a backlash
of about ,381 mm (.015”)per set may still be accept-
able in most cases, depending on the required accu-
racy of the application.
Check the housing ring gear for wear. Inspect the cyl-
inder bore for wear and scratches. The surface finish
should be 32 RMS or better; rehone if necessary.
The wear rings (302) (303) should have a maximum
radial clearance of ,152 mm (.006”). A clearance in
excess of ,2 mm (.008”) requires replacement.
Rough and grooved shaft journals require shaft
replacement.
Assembly and Testing
Wash all parts thoroughly in cleaning solvent and
blow dry. Coat all sealing and working surfaces with a
good grade hydraulic oil. Install seals and bearings in
the piston sleeve, shaft, and end cap oriented as
seen in (see Figure 3-34). The gap on the wear rings
(302)(303) should not exceed 3,175 mm (.125”).
Place the actuator in a vertical position and install the
piston sleeve (03) in timed relation to the housing.
Apply firm pressure as the new seals enter the hous-
ing and become compressed by the housing cham-
ber.
CAUTION: Take care to insure the piston sleeve
does not mar the cylinder bore. The timing
marks must be aligned for proper shaft orienta-
tion (see Figure 3-32).
The shaft (02) is installed by again aligning the
proper punched timing marks (see Figure 3-32). Use
masking tape to temporarily tape the threaded por-
tion of the shaft to help clear the piston seal (200).
Turn the actuator upside-down and install the stop
tube (400), if furnished.
Apply antiseize to threaded and surrounding areas of
the end cap (04) and thread onto the shaft. Torque
the end cap to 81,3 Nm (60 ft./lb)
Figure 3-32: Rotary Actuator