Sewing machine with mechanism for retracting feed dog away from upper surface of needle plate

Abstract

An electrically controlled sewing machine includes a needle bar, a needle plate, a feed dog, a feed dog vertical drive mechanism, a feed dog front/rear drive mechanism, an embroidery drive mechanism, and a feed dog retraction mechanism. The feed dog retraction mechanism includes a switching operation lever. The feed dog vertical drive mechanism includes a normal sewing drive cam and a retraction drive cam, which are switched between using the switching operation lever. The retraction drive cam drives the feed dog to rise upward by about 1 mm when the upper thread is being tightened, that is, at about 40.degree. to 90.degree. phase at the end of the thread tightening operation by the upper thread take-up lever. Because the feed dog moves upward only about 1 mm, it remains retracted below the level of the needle plate and will not interfere with movement of a workpiece cloth mounted in an embroidery frame. However, because the feed dog moves upward, the lower thread and the upper thread loop, which is being tightened at this point, can easily be pulled through the space between the connection portion at the front end of the feed dog and the vertical axis oscillating shuttle position beneath the connection portion of the feed dog. The lower thread and the upper thread loop can pass through the space without any resistance. Therefore, the thread tension will not degrade, so that attractive stitches can be formed.

Dependencies are inferred from the claim text.