| 摘要 |
A looper operating device for sewing machines in which the looper is provided with forward movement and the machine's needle possesses work feeding movement which is synchronized and caused to perform its intended function simultaneously with the machine's feed dog. The device includes a lever member having an upper fulcrum to which actuating linkage for the looper are connected. The opposite end of the lever member includes a lower fulcrum 25 connected to a lever element mounted on a shaft that is operatively connected to and simultaneously actuates both the feed dog and needle. This lever element is stationary when the stitch length is zero or is oscillating with an amplitude proportional to the stitch length. The lever member includes an intermediate fulcrum 27 connected to an oscillating member of constant amplitude which is equivalent to the oscillation of the looper whereby for a zero stitch length, the start of the arc defined by the tip of the looper is fixed, and when increasing the stitch length, the start of the arc is proportionally moved from the vertical that passes through the lower dead point of the needle and occurs in a reverse manner when the stitch length is reduced.
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