| 摘要 |
PURPOSE:To unify a load torque at the time of running on a slanting surface of the cam surface of a step cam by increasing gradually an elevation angle of the slanting surface in proportion as a diameter becomes smaller. CONSTITUTION:The cam surface of the step cam 15 is formed with the corresponding number of steps 15b... to the number of tracks of a medium applied on a spindle shaft side in their concentric circular arc surfaces respectively and the slanting surfaces 15c..., each between the steps adjacent to each other from the step on the larger diameter side to the step on the smaller diameter side, thus forming a spiral pattern as a whole. A fall (a) between the steps adjacent to each other is constant with all other falls, corresponding to the moving amt. of a magnetic head by one track. Each set of forming the slanting surface with the step on the large diameter side and the step on the smaller diameter side has an angle to suit a step cam motor, e.g. the same central angle of 7.5 deg. is made. The elevation angle theta made by each of the individual slanting surfaces 15c... and a tangential line at the point of intersection with the step on the smaller diameter side is gradually increased in accordance with its positional change from a larger diameter part to a smaller diameter part of the step cam.
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