A preventive method against seam puckers by using a differential feed in the lookstitch sewing machine has been studied. The results obtained were as follows :(1) The differential feed mechanism was effective on the prevention of seam puckers. The seam shrinkage ratio was affected by the differential feed ratio and the pressure of a presser foot. Especially in the case of fabrics with a stretchability the satisfied results were obtained. But the feed marks were observed near a seam line in the

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... ase that the fabrics have low elastic recovery and high movability of woven yarns. (2) As shown in Figs. 4((i )-(iii)), the shapes of feed dogs were changed so that the differential feed effect concentrates on a seam line. These feed dogs were very effective on the preventions of seam puckers and feed marks. (3) The uniformity of stitch pitch in a seam was not degraded by using the feed dogs mentioned above.