the jaw. A timing bracket ensures that the wedge and
jaw are moved at the proper time.
Placing the lock control handle in the unlocked posi-
tion moves the wedge away from the jaw. This action
unlocks the jaw so that it can be moved by the trailer
kingpin. When the tractor is moved out from under
the trailer, the kingpin moves the jaw until the kingpin
is out of the mechanism. With the jaw in the un-
locked position, the lock control handle will remain in
the unlocked position until manually moved by the
operator.
During coupling (
Fig. 10.15
), the motion of the king-
pin entering the jaw will actuate the jaw and wedge.
The jaw will move behind the kingpin, followed by the
wedge. The purpose of the wedge is to reinforce the
jaw and take up slack around the pin. Any wear on
the jaw is immediately taken up by the wedge so
there is no slack in the connection.
Fifth Wheel Locking Operation
Locking the Fifth Wheel Lock Mechanism
NOTICE
Before attempting to lock or unlock the fifth
wheel lock mechanism of a sliding type fifth
wheel, the slide release pull handle, if so
equipped, and the slide locking wedges must be
in the locked position. This prevents the sliding
member from moving rapidly to the far forward or
rearward position, which could damage the fifth
wheel member or kingpin.
1.
Chock the front and rear of the trailer tires to
prevent the trailer from moving.
WARNING
Keep the fifth wheel plate lubricated to prevent
binding between the tractor and trailer. A binding
fifth wheel could cause erratic steering and loss
of vehicle control, possibly resulting in serious
personal injury or death.
2.
The kingpin lock mechanism must be fully open,
the fifth wheel plate must be completely lubri-
cated with chassis grease. For lubrication in-
structions, see Group 31 of the
Century Class
Trucks Maintenance Manual
.
3.
Position the tractor so that the fifth wheel lock
opening is in line (both vertically and horizontally)
with the trailer kingpin. The kingpin should be in
a position to enter the throat of the locking
mechanism (
Fig. 10.15
). Adjust the trailer landing
gear to give enough alignment height for positive
kingpin lockup.
4.
With the fifth wheel lock opening aligned with the
trailer kingpin, back the tractor slowly toward the
trailer, making sure that the kingpin enters the
throat of the locking mechanism. Continue back-
ward motion until positive lockup occurs.
5.
Apply the tractor parking brakes.
6.
Make a visual and physical check for positive
kingpin lockup. When lockup has occurred, the
fifth wheel control handle will have moved to the
locked position. Make sure that the safety latch
is down over the lock control handle. See
1
2
A
3
B
C
10/26/2010
f310184c
A. Unlocked Position
B. Locking
C. Locked
1.
Wedge
2.
Jaw
3.
Trailer Kingpin
Fig. 10.15, Fontaine Kingpin Lock Mechanism
Fifth Wheels and Trailer Couplings
10.12