Automatic bottom thread breaking method for sewing and sewing machine thereof

Abstract

The invention discloses an automatic bottom thread breaking method for sewing and a sewing machine thereof. The method includes the steps that step S1, during sewing, a thread bonding mechanism acts to tension an upper thread on a sewing material side and bring a bottom thread or a bottom thread end to a sewing material, and at the same time, the upper thread in a machine head thread channel is loosened to supply enough upper thread quantity; step S2, a feed dog or a cloth conveyor on the sewing machine drives the upper thread or / and the bottom thread or / and the bottom thread end on the sewing material side to feed forwards through cloth, a cutting edge arranged on a presser foot at the lower side of the sewing machine cuts off the upper thread or / and the bottom thread or / and the bottom thread end at the lower side of the top end of a machine needle or an electric heating blade irons off the upper thread or / and the bottom thread or / and the bottom thread end, and automatic breaking treatment of the upper thread, or / and the bottom thread, or / and the thread end of the bottom thread in the sewing process is finished; and step S3, through the reciprocating operation of actions, the upper thread or / and the bottom thread or / and the bottom thread end in sewing can be continuously and automatically cut.

Description

【Technical field】 [0001] The invention relates to sewing technology, in particular to an automatic bobbin thread cutting method for sewing and a sewing machine thereof. 【Background technique】 [0002] Lockstitch is a sewing machine that connects the upper thread and the lower thread in series on the sewing material according to certain rules, and forms a firm and beautiful stitch. It is often used to sew two pieces of sewing material to each other. Such as figure 1 As shown, the formation process of the lock stitch includes the following six stages: stabbing material stage, thread loop formation stage, thread loop expansion stage, loop stage, thread loop contraction stage, and seam forming stage, figure 1 The middle stages a to e are respectively the thread loop forming stage, the thread loop expanding stage, the collar stage, the thread loop shrinking stage and the seaming stage; wherein, in the seaming stage, the thread take-up takes up the thread so that the thread forme...

AI Technical Summary

Problems solved by technology

[0003] When sewing on a sewing machine, the bottom thread is set in the rotary hook of the sewing machine, and the fabric is sewed by interweaving with the upper thread. When the last stitch is sewn, the upper thread and the lower thread will be interwoven under the needle plate. The upper thread and lower thread are cut off. The common method is to pull out the intertwined upper thread and lower thread and cut it off. However, this method will make the thread ends of the lower thread and upper thread longer and stay in front of the seam starting point. If the length of the thread is too long, it is not beautiful; if the length is too short, the thread is easy to loose and affect the appearance quality of the product

At this time, it is necessary to manually trim the thread ends of the bottom thread and the upper thread, which increases the process and manpower, thereby increasing the production cost; some people use manual methods to pull the thread braid back into the guide groove of the needle plate, and when the next work, this section is old. Thread ends will be wrapped in new braids, but this solution is still inefficient and also labor intensive

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