Uni-directional mechanism

A uni-directional mechanism, comprising:

• a. a rotatable input element in the form of a wheel with a generally cylindrical periphery,
• b. a rotatable output element in the form of a housing having a cylindrical bore whose surface lies adjacent to the periphery of the wheel,
• c. a dog mounted in the output element, the dog mounted in a generally radial recess in the housing, the inner end of the dog is semi-cylindrical, the recess having two parallel spaced sides between which the dog is slidably mounted, one of the said sides of the recess is joined to the surface of the cylindrical bore by a plane surface which is inclined at a substantial angle to the radial,
• d. notches formed on the input element, each notch consisting of two plane surfaces lying symmetrically to a radius and meeting at an angle of about 90.degree., the wheel being provided with a substantial land between successive pairs of notches and the dog being provided with a broad surface that slides on successive lands and is large enough to bridge each notch, and
• e. a coil spring for biasing the dog toward the said input element, the coil spring being located in the recess and compressed between the inner end of the recess and the inner end of the dog, the dog being movable automatically from a first aspect where it does not engage a surface of a notch when the input element is rotated in one direction to a second aspect where a portion of said semi-cylindrical inner end of the dog engages one of the spaced sides of the recess and a surface of the dog engages the inclined surface of the recess so that the dog does engage a surface of a notch in driving relationship when the input element is rotated in an opposite direction.