Motor and gearbox for actively driven caster wheel of a utility vehicle

A method of using a gearbox for an actively driven caster wheel system, comprising

• providing a gearbox for an actively driven caster wheel system, the gearbox having
• a housing defining a set of operational surfaces, the set of operational surfaces,
• being identical to its own mirror image,
• having an input shaft engagement aperture elongated to define an input axis, and
• having an output shaft engagement aperture elongated to define an output axis,
• a transmission operationally engaged with the operational surfaces of the housing, the transmission having,
• an input shaft assembly having
• an elongated input shaft and
• a set of input shaft bearings, and
• an input gear engaged with the input shaft, and
• an output shaft assembly having
• an elongated output shaft and
• a set of output shaft bearings,
• an output gear engaged with the output shaft, and
• wherein the input shaft assembly is installed in the input shaft engagement aperture such that the input gear is adapted to rotate about the input axis during operation,
• wherein the output shaft assembly is installed in the output shaft engagement aperture such that the output gear is adapted to rotate about the output axis during operation, and
• wherein the input gear is operationally engaged with the output gear such that mechanical work is transmitted therebetween during operation;
• operationally engaging a motor to the input shaft of the gearbox;
• operationally engaging a steering axis of a caster wheel to the output shaft of the gearbox;
• transmitting work from the motor to the input shaft of the gearbox;
• and
• transmitting work from the output shaft of the gearbox to the steering axis of the caster wheel to steer the caster wheel.

An actively driven caster wheel system, comprising

• a gearbox, the gearbox comprising
• a housing defining a set of operational surfaces, the set of operational surfaces,
• being identical to its own mirror image,
• having an input shaft engagement aperture elongated to define an input axis, and
• having an output shaft engagement aperture elongated to define an output axis,
• a transmission operationally engaged with the operational surfaces of the housing, the transmission having,
• an input shaft assembly having
• an elongated input shaft and
• a set of input shaft bearings, and
• a worm gear engaged with the input shaft, and
• an output shaft assembly having
• an elongated output shaft and
• a set of output shaft bearings,
• a helical gear engaged with the output shaft, and
• wherein the input shaft assembly is installed in the input shaft engagement aperture such that the worm gear is adapted to rotate about the input axis during operation,
• wherein the output shaft assembly is installed in the output shaft engagement aperture such that the helical gear is adapted to rotate about the output axis during operation, and
• wherein the worm gear is operationally engaged with the helical gear such that mechanical work is transmitted therebetween during operation;
• an electric motor operationally engaged with the input shaft such that mechanical work may be transmitted therebetween;
• a caster wheel assembly having a steer axis, the steer axis being operationally engaged with the output shaft of such that the steer axis is coaxial with the output shaft, and mechanical work may be transmitted between the steer axis and the output shaft;
• an encoder operationally engaged with the output shaft and adapted to output a signal representative of the angular position of the output shaft;
• wherein the worm gear has a lead angle, and the lead angle has a tangent;
• wherein there is a coefficient of friction between the helical gear and the worm gear;
• and
• wherein the coefficient of friction between the helical gear and the worm gear is between 95% and 99% of the tangent of the lead angle of the worm gear;
• wherein the transmission has a mechanical advantage between 5:1 and 150:1;
• and
• wherein total backlash at the output shaft is less than 0.7 degrees.