General Information

The Fontaine sliding fifth wheel mount is designed to provide optimum axle loading for maximum tractor use with different lengths and types of trailers. The sliding fifth wheel mount is used with the Fontaine H5092 series, and 6000/7000 No-Slack II series fifth wheels, and is equipped with either an air-operated release slide (AWB or HAWB models), or a manual release slide (MWS or HMWS models).

On Fontaine fifth wheels kingpin release is accomplished by activating a manual lock control handle located on either the right side or left side of the fifth wheel. Kingpin lockup occurs when the kingpin is forced into the jaws and the lock control handle moves to the locked position.

The fifth wheel top plate is mounted on a slide assembly, which is attached to slide rails that are mounted on the vehicle frame. The slide rails permit forward and rearward movement of the slide assembly, allowing for optimum weight distribution over the tractor axles.

Slots are evenly spaced along the slide rails, and retractable tapered wedges are positioned through the slots to hold the fifth wheel in the desired position. See Fig. or see Fig..

Locking Wedge

Air Cylinder

Fig. 1, Air-Operated Sliding Fifth Wheel Mount, AWB Model

Locking Wedge

Slide Release Pull Handle

Fig. 2, Manual Release Sliding Fifth Wheel Mount, MWS Model

The slide portion of the sliding model may be attached to either an air-operated release slide, or a manual release slide.

The air-operated release slide contains an air cylinder that locks and unlocks the fifth wheel slide. See Fig.. The air cylinder is activated by a two-position air-control valve in the tractor cab.

The manual release slide contains a slide release pull handle, located on the left side of the fifth wheel, which locks or unlocks the fifth wheel slide. See Fig..

Fifth Wheel Lock Mechanism for Trailer Kingpin (see Fig.).

Unlocked Position

Locking

Locked

Wedge

Jaw

Trailer Kingpin

Fig. 3, Fontaine Kingpin Lock Mechanism

The Fontaine fifth wheel lock mechanism for the trailer kingpin consists of a spring-loaded jaw and a sliding wedge.

The jaw and wedge each have a pin permanently attached. The pin on the jaw and the pin on the wedge fit into elongated notches in the lock control handle. The notches in the handle control the limit of movement for both the jaw and wedge. The notches are arranged so that the wedge is actuated first during release of the kingpin.

During lockup, the jaw is moved first with the spring-loaded wedge being allowed to slip in place against 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 position 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 unlocked position, the lock control handle will remain in the unlocked position until manually moved by the operator.

During coupling (see Fig.), 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.