| 摘要 |
To determine the thread supply on a lower-thread bobbin ( 17 ), holes ( 19 ) are arranged in the shape of a spiral in a flange ( 21 ) of the bobbin. Light from a light source ( 35 ), which is directed towards the flange ( 21 ), is reflected only by those holes ( 19 ), behind which there is no longer any thread, so that the light beams ( 36 ) reach the rear flange ( 22 ) and can be reflected therefrom and received by the light receiver ( 39 ).
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