Fifth Wheel Lock Mechanism for Trailer
Kingpin
(Fig. 10.10)
The Castloc II and Simplex Series fifth wheel lock
mechanism consists of a rotating jaw and a spring-
actuated lock that grips the trailer kingpin. The jaw
rotates on an eccentric pin during coupling and un-
coupling operations. The spring-actuated lock holds
the jaw in the locked position once kingpin lockup
has occurred.
In the locked position, there is approximately 1/16-
inch (1.6-mm) clearance between the jaw and king-
pin. The jaw eccentric pin can be removed and ro-
tated to compensate for wear and maintain an
approximate 1/16-inch (1.6-mm) clearance during
service.
Placing the operating rod in the lockset position
moves the lock away from the jaw. This action un-
locks the jaw so that it can be rotated by movement
of the kingpin. When the tractor is moved out from
under the trailer, the kingpin will rotate the jaw until
the jaw is in the unlocked position, allowing the king-
pin to move out of the mechanism. With the jaw in
the fully open position, the operating rod drops out of
the lockset position, and the fifth wheel is ready for
coupling. See Fig. 10.11.
During coupling, the kingpin contacts and rotates the
jaw into the locked position. This action automatically
moves the operating rod into the locked position.
This securely locks the jaw around the kingpin. In the
locked position the safety latch swings freely over the
operating rod. See Fig. 10.12.
Fifth Wheel Locking and Unlocking
Locking the Fifth Wheel Lock Mechanism
1.
Chock the front and rear of the trailer tires to
prevent the trailer from moving.
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
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1
2
3
4
A
B
C
5
6
A. Locked Position
B. Jaw movement compresses spring.
C. Fully open.
1. Operating Lever
2. Safety Latch
3. Jaw
4. Jaw Eccentric Pin
5. Lock
6. Spring
Fig. 10.10, ASF Castloc II and Simplex Series Kingpin
Locking Mechanism Operation
1
1
2
3
11/02/2010
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1. Safety Latch
2. Operating Rod (locked)
3. Operating Rod (unlocked)
Fig. 10.11, Simplex Kingpin Locking Mechanism,
Locking and Unlocking
Fifth Wheels and Trailer Couplings
10.7
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