Positioner and guiding device having positioner

A positioner, comprising:

• a base, a first slider protruding from the bottom of the base, a limiter being provided on the upper side of the base, and two supports being formed on the base laterally opposed to each other, wherein the limiter is interposed between the supports, and the base forms two cavities, with each of the cavities forming a baffle wall at the front side;
• a shaft standing upright on the base, and the limiter forming a restriction on the diametrical outer circumference of the shaft;
• a bearing block located at the bottom of the base, and the bearing block being located at the axial extension of the shaft, with the bearing block having two bearing faces located on each of the two sides at the top of the bearing block;
• a bolt axially connecting the bearing block and the shaft, causing the shaft to move the bearing block and being positioned at a first position or a second position, the first position being lower than the second position;
• a pivot pivotally passing through the shaft along the diameter of the shaft;
• a brake structure including a handle, two first cams, and two second cams, wherein the handle extends to form each of the first cams, and the first cams are laterally opposed to each other;
• each of the second cams is axially connected to each of the first cams, and each of the first cams is located between the second cams;
• the pivot axially passes through each of the first cams and each of the second cams, allowing the brake structure to rotate with the pivot as a center;
• and each of the second cams abuts against each of the supports;
• and
• a front seat located at the front side of the base, the front side of the front seat forming an abutting side, and the rear side of the front seat being opposite to each of the first cams;
• a second slider protruding from the bottom of the front seat, and two hooks protruding from the rear side of the front seat, with each of the hooks entering each of the cavities, and each of the baffle walls forming an obstacle against each of the hooks;
• each of the cavities having a length along the direction toward the front side and the rear side of the base that is greater than the length of the hook, thereby allowing the base and the front seat to be connected in a relatively front-to-back sliding manner;
• wherein, each of the first cams protrudes at its circumferential edge to form a pressing surface, and each of the first cams urges the front seat to move forward through each of the pressing surfaces;
• each of the second cams protrudes at its circumferential edge to form an abutting surface, and each of the second cams presses against each of the supports through each of the abutting surfaces, thereby restricting the shaft from moving upward;
• when the bearing block is positioned at the first position, the front seat is adjacent to the base and the brake structure restricts the shaft from moving upwardly through the pivot, and when the bearing block is positioned at the second position, the pressing surface urges the front seat to move in the direction away from the base.