Abstract
This paper deals with the behavior of forces produced in the feed mechanism of industrial sewing machine during the operation of the presser foot mechanism. As a result, the followings are made clear. (1) As for the force P produced in the feed bar by the presser foot and the torque T produced in the arm shaft, the theoretical values agree with the experimental values. Therefore this theory which supposes the presser mechanism to be the forced vibration system of one-degree-of-freedom supported by the presser bar spring and the "apparent spring of the feed bar" is found to be valid. (2) About half of the torque T is the torque T3 produced by the friction of the arm shaft bearings. The intensity of the torque T3 is due to the remarkable increase of the component force F5b of the feed lifting mechanism applied to the arm shaft. (3) Dynamic load factor of the force P to the pre-load of the presser bar spring is roughly in proportion to the moving weight W9 of the presser foot mechanism. This factor reduces exponentially with the increase of the spring constant of the presser bar spring and is less than 2 in the range where the spring constant is more than kM of the testing machine. (4) It is possible to estimate the force P during sewing operation according to this study by assuming that the "apparent spring constant k8 of the feed bar" is reduced by the insertion of the sewing materials.
