Upright SB60 Service & Parts Manual page 40

Section
3.19
3.19 Rotary Actuator
Theory of Operation
The HP-9K 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 (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 inside diameter of the
piston. The outside diameter 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, preventing 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 hydrau-
lic 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 3-27. Correct orienta-
tion of the marks will greatly simplify actuator timing
upon reassembly. 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 .005" per mating set. After long
service, a backlash of about .015" per set may still be
acceptable in most cases, depending on the required
accuracy of the application.
3-26
Maintenance
Check the housing ring gear for wear. Inspect the
cylinder 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 .006". A clearance in excess of .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
Figure 3-25. The gap on the wear rings (302) (303)
should not exceed .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 housing and become compressed by the
housing chamber. 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 3-27.
The shaft (02) is installed by again aligning the proper
punched timing marks, see Figure 3-27. Use masking
tape to temporarily tape the threaded portion of the
shaft to help clear the piston seal (200). Turn the actua-
tor 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 60 ft/lb.
Figure 3-25
SB60 Work Platform