Cluett, Peabody & Co., Inc.

John H Blum

John L Rockerath

The disclosure is directed to a method and means for detecting a skipped stitch, in the absence of a thread break, on a chain stitch sewing machine or the like. The detector system includes a secondary thread tension system which functions to provide lateral pressure against an unbroken thread in the region between the primary thread tension means and the sewing needle. Whenever, during the course of the sewing operation, there occurs a momentary malfunction in the chain stitch operation, a momentary variation in tension in the unbroken thread occurs in the region between the needle and the primary tension device. This momentary reduction in tension enables a yieldable member to momentarily displace or deflect the thread. The sensing device detects such momentary deflection of the thread and initiates an appropriate control function. A particularly advantageous such control function is the marking of the fabric in the area of the skipped stitch so that the defect may be easily observed and repaired in a subsequent inspection operation. Appropriate for this purpose is the use of one-shot pulse control, in conjunction with an extendable marking device. When a momentary loss of tension is detected, the marking device is momentarily actuated to imprint a mark on the fabric which can be easily detected later on by an inspector.

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Cold Brook, NY, United States of America

John H Blum