| 摘要 |
<p>A bobbin run-out detector for a lockstitch sewing machine is responsive to thread tension for sensing when the bobbin is empty of thread. The thread tension is sensed by a hook member (168; 332) engageabie with the thread extending from the bobbin, the hook member (168; 332) being moved by a resilient bias as a result of loss of thread tension consequent on emptying of the bobbin. The hook member (168, 332) is linked to a shutter (174; 334) which moves with the hook member (168; 332) in order to influence a light beam, light receiving means (202) being responsive to such influence to produce a signal indicative of bobbin run-out. The signal may stop the machine and/or actuate an alarm. Alternatively, the signal may actuate a bobbin change device (2, 4, 14, 16) for removing the empty bobbin and for inserting a previously wound bobbin, to permit sewing to resume. </p> |
