Abstract

A rotatable fifth wheel mechanism for use on converter dollies, truck tractors, and permanently attached dollies. The mechanism includes: a fifth wheel supported on a frame for rotation about a vertical axis; and a clutch secured between the fifth wheel and the frame, to control rotation of the fifth wheel relative to the frame. The clutch includes a drum secured to the fifth wheel, friction pad completely surrounding the drum and an inflatable bladder for applying pressure to the friction pad. The fifth wheel mechanism also includes apparatus for increasing or decreasing the pressure in the bladder to selectively vary the engagement force between the drum and friction pads. The apparatus for selectively increasing or decreasing pressure includes at least a pair of electrically operated air valves. The fifth wheel includes at least one spring biased key (coupled to an automatic sensing device) which, when the fifth wheel is in proper alignment with the fifth wheel plate on a semi-trailer, engages with a mating slot in the fifth wheel plate. An electronic control package is also disclosed which includes apparatus for initiating a command, apparatus for encoding the command, apparatus for decoding the command and apparatus for implementing the command. The apparatus for encoding and the apparatus for decoding are interconnected by only a single wire (not counting the ground).