| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect the amount of remaining bobbin thread on a bobbin in a sewing machine in a non-contact manner.SOLUTION: In a state in which first, second and third measuring apertures 13, 16 and 19 provided in a bobbin case 3, an inner hook 6 and an outer hook 9, respectively, communicate with each other, thereby forming a communicating measuring aperture 22, irradiation light is applied from an irradiation part 23 of an optical measuring instrument 21 to an outer peripheral surface 27 of a thread-winding part 26 of a bobbin through the communicating measuring aperture 22. Reflected light from the outer peripheral surface 27 is received by a light-receiving part 30 of the optical measuring instrument through the communicating measuring aperture 22. According to the principle of triangulation distance measurement based on information about a light-receiving position output from the light-receiving part 30, the position of the outer peripheral surface 27 of the thread-winding part 26 of the bobbin is measured. A plurality of measurements are made to detect a minimum measurement value as the position of the outer peripheral surface 27 of the thread-winding part 26. It is determined by a determination device whether the amount of remaining bobbin thread detected based on the minimum measurement value satisfies the required amount of the bobbin thread allowing one sewing operation by a sewing machine. During the measurements, an air blow device 31 blows air on the outer peripheral surface 27. |
