General Information
The ASF Castloc® II and Simplex® series fifth wheels are used for pulling trailers having the standard 2-inch (51-mm) diameter kingpin. When installed as a stationary fifth wheel (see Fig.), they are bracket-mounted to the tractor frame in a position that best distributes the trailer load over the tractor axles. When used as a sliding fifth wheel (see Fig.), they are mounted on the Taperloc® sliding mount (air-operated or manual release).
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Lubricant Grooves
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Safety Latch
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Operating Rod
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Mounting Bracket
Fig. 1, Simplex Stationary Fifth Wheel
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Baseplate
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Bolted Stop
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Baseplate Rail
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Fifth Wheel Mount
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Slider Saddle Plate
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Safety Latch
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Operating Rod
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Operating Lever
Fig. 2, Taperloc Slide, Manually-Operated Release
The fifth wheel lock mechanism for the trailer kingpin consists of a rotating jaw that grips the trailer kingpin and a spring-actuated lock. The jaw rotates on a jaw pin during coupling and uncoupling operations. Kingpin lockup occurs when the kingpin is forced into the jaw and the operating rod handle moves to the locked position. The kingpin is released either by activating a manual operating rod, or if equipped with Touchloc®, by a dash mounted release-knob, which activates an air cylinder underneath the top plate. The air cylinder activates the operating rod. The operating rod is located on the left side of the fifth wheel for Castloc II and Simplex II fifth wheels, and on the right side for the Simplex fifth wheel assembly.
On sliding fifth wheels, the top plate is mounted on a sliding saddle plate, which slides along the baseplate attached to the tractor frame. The baseplate rails allow forward and rear movement of the slide assembly, for optimum weight distribution over the tractor axles.
Tapered slots in the baseplate rails, aligned in 4-inch (102-mm) increments, provide for location of the fifth wheel along the baseplate. Retractable, spring-actuated lockpins are positioned through the slots to hold the fifth wheel in the desired position. The lockpins are retracted either manually or by an air-operated cylinder controlled from the cab.
The manually-operated slide contains an operating rod (see Fig.) which unlocks both sides of the plate at the same time.
The air-operated sliding saddle plate contains an air cylinder which moves the operating lever to unlock both sides of the plate at the same time. The air cylinder is activated by a two-position air-control valve in the tractor cab.
Fifth Wheel Lock Mechanism for Trailer Kingpin (see Fig.)
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Locked Position
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Jaw movement compresses spring.
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Fully open.
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Operating Lever
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Safety Latch
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Jaw
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Jaw Eccentric Pin
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Lock
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Spring
Fig. 3, ASF Castloc II and Simplex Series Kingpin Locking Mechanism Operation
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 uncoupling 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 kingpin. The jaw eccentric pin can be removed and rotated 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 unlocks 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 kingpin 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..
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Safety Latch
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Operating Rod (locked)
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Operating Rod (unlocked)
Fig. 4, Simplex Kingpin Locking Mechanism, Locking and Unlocking
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..
