| 摘要 |
PROBLEM TO BE SOLVED: To automatically set up a sewing length of a buttonhole corresponding to size of the button by a simple mechanism with less parts, improved operability and an accurate and simple control. SOLUTION: While installing a reflection board 15 in an operation wall 13b of a button holder 13, a light sensor 16 having a light emitter and a light acceptor is installed in a side wall of a press holder 18. The initial distance corresponding to detected signals when a button 35 is not kept in the button holder 13 is calculated. The distance from a determined standard spot P0 of the press holder 18 to the reflection board 15 is calculated based on the strength of reflected light received by the light acceptor when the sewing is under the condition of the button 35 kept at the button holder 13. Based on these distances, a cloth is reversed only when the determined length is sewn.
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