ROTARY JOINTS
SUB-SECTION 4C
lift the hydraulic swivel straight up until it clears the stem
7. Turn the assembly over, and install the retaining snap
of the collector, and remove the hydraulic swivel to a suit-
ring.
able repair area.
INSTALLATION. To install a rotary joint that has been
removed from the machine, proceed as follows:
OVERHAUL. Overhaul of the rotary joint consists only of
seal replacement. To replace the rotary joint seals, proceed
1. Carefully install the hydraulic swivel over the collector
as follows (see Figure 4C-1):
stem. Position the swivel so that port #4 on the Inner stem
is facing toward the front of the carrier. Then install the
1. Remove the snap ring at the top of the hydraulic rotary
capscrews which connect the collector assembly to the bot-
joint.
tom of the swivel.
2. Carefully remove the outer body from the inner stem.
2. Turn the outer body as required to position the swivel
3. The outer body bore should be thoroughly washed with
with the ports facing the rear of the revolving frame. lnstall
a suitable cleaning solvent or diesel fuel, and inspected for
the capscrews and lockwashers which secure the swivel to
signs of scoring or deep scratches. If excessive scoring or
the revolving frame deck.
deep scratches are found, the entire rotary joint should be
3. Install the O-ring elbow fittings on the lower portion of
replaced.
the inner stem.
NOTE
4. Attach the hoses to the O-ring fittings on the lower
portion of the inner stem.
Excessive scoring or deep scratches are usually caused
by foreign material in the hydraulic system. If these
5. Reconnect the hydraulic lines to the outer body of the
defects are found, the hydraulic system should be
swivel.
checked for foreign material.
6. Install the junction box on the top of the swivel, and
4. The inner stem should be thorougly washed with a
tighten the setscrews in the collar at the bottom of the
suitable solvent or diesel fuel. The teflon seals should then
junction box.
be inspected for deep scratches or severe damage.
7. Reconnect the throttle cable and electrical wires.
NOTE
9. Reconnect the ground cable to the battery. Then start
the engine and check for leakage while opearating all
The teflon seals and the loading O-rings under the
machine functions.
seals should not be removed unless the seals show
signs of deep scratches or severe damage, since re-
moval of these seals will damage them beyond use.
ROTARY JOINT (979J30)
GENERAL. The rotary joint is mounted on the center of
In the event a seal must be replaced, use the following
the upper, and is the means by which the hydraulic and
procedure:
electrical circuits in the upper are connected to their re-
A. Generously lubricate the spool with clean hydraulic
spective circuit in the carrier.
oil.
The hydraulic swivel consists of an outer body fixed to the
B. Carefully install a new loading O-ring in the seal
deck of the revolving frame and an inner stem fixed to the
groove.
carrier deck. This arrangement allows the upper to rotate
on the carrier without breaking a hydraulic connection.
C. Walk a new seal into place in the same manner the
bead of a tire is walked onto a wheel rim.
The electrical swivel consists of a set of fixed circular
conductors and a set of collectors that make contact with
D. Knead the seal by hand to squeeze it into the seal
the conductors. The conductors are connected to the inner
groove.
stem of the hydraulic swivel so that the conductors will
rotate with the hydraulic swivel whenever the upper is
5. Generously lubricate the outer body bore and inner
rotated. This maintains a continuous electrical connection
stem with clean hydraulic oil.
between the upper and carrier, regardless of the position of
6. Place the outer body in a vertical position with the bot-
the upper.
tom of the body up. Insert the top of the inner stem into
REMOVAL. The rotary joint must be removed to perform
the body bore, and while the stem is being lowered into the
any repairs. Remove the rotary joint as follows (see Figure
body compress the teflon seals by hand as they enter the
4C-2):
bore.
4C-2
