Fifth Wheels the jaw. A timing bracket ensures that the wedge and jaw are moved at the correct time. 2 A Placing the lock control handle in the unlocked position moves the wedge away from the jaw. This action un- locks the jaw so that it can be moved by the trailer king- pin. 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 unlocked posi- tion, the lock control handle will remain in the unlocked position until manually moved by the operator. 1 During coupling ( Fig. 11.5 ), the motion of the kingpin 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. 3 B C Fifth Wheel Locking Operation 01/04/95 f310184c NOTE: Kingpin correctly entering the lock. Note how the steel tongue allows lock halves to close completely around the neck and shoulder of the kingpin. Locking the Fifth Wheel Lock Mechanism 1. Chock the front and rear of the trailer tires to pre- vent the trailer from moving. A. Unlocked Position B. Locking C. Locked 2.
The kingpin lock mechanism must be fully open, the fifth wheel plate must be completely lubricated with chassis grease. For lubrication instructions, refer to Group 31 of the Cargo Maintenance Manual. 1. Wedge 2. Jaw 3. Trailer Kingpin Fig. 11.5, Fontaine Kingpin Lock Mechanism 11.7