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A roller board includes a base plate with a cam retaining bore and an accommodating chamber. A roller unit includes a caster mounted rotatably to the base plate underneath the retaining bore, and a roller journalled to the caster. A cam, in the form of a rotatable shaft, is connected to the caster,

A roller board includes a base plate with a cam retaining bore and an accommodating chamber. A roller unit includes a caster mounted rotatably to the base plate underneath the retaining bore, and a roller journalled to the caster. A cam, in the form of a rotatable shaft, is connected to the caster, extends into the chamber via the retaining bore in the base plate, and has a top end which defines an annular cam face with a pair of diametrically opposite lowermost points and a pair of diametrically opposite uppermost points between the lowermost points. A cam follower is disposed within the chamber, and includes an urging spring that has a first end fixed to the base plate and a second end disposed above and abutting against the cam face for urging the cam in an axial direction relative to the cam.

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1. A roller board comprising:a base plate having a cam retaining bore and an accommodating chamber surrounding said cam retaining bore; a roller unit including a caster mounted rotatably to said base plate underneath said cam retaining bore, and a roller journalled to said caster; and a cam mechanis

1. A roller board comprising:a base plate having a cam retaining bore and an accommodating chamber surrounding said cam retaining bore; a roller unit including a caster mounted rotatably to said base plate underneath said cam retaining bore, and a roller journalled to said caster; and a cam mechanism including a cam in the form of a rotatable shaft that is connected to said caster and that extends into said accommodating chamber via said cam retaining bore in said base plate, said cam having a top end which defines an annular cam face with a pair of diametrically opposite lowermost points and a pair of diametrically opposite uppermost points between said lowermost points, and a cam follower disposed within said accommodating chamber and including an urging spring that has a first end fixed to said base plate and a second end disposed above and abutting against said cam face for urging said cam in an axial direction relative to said cam, said cam being rotatable along with said caster between a first position, in which said second end of said urging spring abuts against said cam face at one of said lowermost points for urging said caster to be maintained in a travelling direction parallel to a longitudinal axis of said base plate, and a second position, in which said second end of said urging spring abuts against said cam face at one of said uppermost points for urging said caster to be maintained in a transverse direction relative to said longitudinal axis of said base plate, rotation of said cam between said first and second positions resulting in upward and downward movements of said second end of said urging spring in said axial direction.