| 摘要 |
PROBLEM TO BE SOLVED: To reduce backlash by forming two side wall surfaces of a cam groove into a tapered shape broadening towards an opening side, and forming an outer peripheral surface of the cam follower into a tapered shape narrowing towards its front end. SOLUTION: When a needle bar moves vertically in synchronization with the rotation of a main shaft 50, a link 22 swings via a follower 28 engaging with a cam groove 53 provided in one surface of a cam 52 for driving a cloth- pressing member rotating along with the ration of the main shaft 50. In such a cam mechanism, a working face of a side wall surface 53a of the cam groove 53 of the driving cam 32 is formed into a slanting wall with an opening angleθfixed to about 2 to 10 degrees. On the other hand, an outer peripheral surface of the cam follower 28 is formed into a tapered surface corresponding to the opening angleθof the side wall surface 53a. As a consequence, in assembly operation, the driving cam 52 and the cam follower 28 can be assembled without backlash therebetween only by inserting the cam follower 28 in slight contact with the side wall surface 53a.
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