A Measuring Method and an Apparatus to Detect the Strain of the Tension Spring Produced by the Bobbin Thread in a Lock Stitch Sewing Machine

摘要

In this report, a method of measuring the strain of the tension spring produced by the bobbin thread in a sewing machine is proposed. To overcome the difficulty due to the intrinsic mechanism of lock stitch formation, a pair of intermittently working of brush-terminal combinations was attached to the body of the bobbin case to establish the bridge circuit ina measuring system. The effect of the brush on the speed limit of the system was evaluated and it was confirmed to have the ability to measure the strain of the tension spring at low speed sewing. Also, it was found that the setting time of the tension spring depended on it sown rigidity and it had considerable influence on the dynamic characteristics of the apparatus.