Automatic thread trimmingmechanism of sewing machine and sewing machine

Abstract

The invention provides a sewing machine automatic thread trimming mechanism. The mechanism includes a lower shaft, a thread trimming drive cam, a moving cutter assembly, a crankshaft, a thread trimming drive assembly, a thread trimming crank and a thread trimming connecting rod, wherein the thread trimming drive cam is fixed on the lower shaft, the moving cutter assembly can swing around the lower shaft and includes at least one moving cutter and a moving cutter frame, the thread trimming drive assembly is installed at one end of the crankshaft, and the thread trimming crank is fixed at the other end of the crankshaft; the thread trimming drive assembly includes a first extending arm, the end portion of the first extending arm is connected with a rotor, the two ends of the thread trimming connecting rod are hinged to the thread trimming crank and the moving cutter frame respectively, the distance between the crankshaft and the hinged point of the thread trimming crank and the thread trimming connecting rod is L1, the distance between the lower shaft and the hinged point of the moving cutter frame and the thread trimming connecting rod is L2, the ratio of the L1 to the L2 is not smaller than 2.5, and the transmission angle gamma of the thread trimming connecting rod relative to moving cutter frame is not smaller than 40 degrees; during thread trimming, the rotor is matched with a thread trimming contact surface on the periphery of the thread trimming drive cam. The structure and transmission chains of the sewing machine automatic thread cutting mechanism are simplified, the number of complicated parts in an original mechanism is reduced, the cost is reduced, and the assembling time is reduced.

Description

technical field [0001] The invention relates to a sewing device, in particular to an automatic thread trimming mechanism of a sewing machine and a sewing machine. Background technique [0002] At present, sewing machines (especially lockstitch machines) are equipped with an automatic thread trimming mechanism, which is used to cut off the bottom thread and the upper thread at the rotary hook after each sewing. Such as figure 1 As shown, the automatic thread trimming mechanism in the existing sewing machine generally includes a rotatable lower shaft 100, a cam 200 fixed on the lower shaft 100, a thread trimmer shaft 300 parallel to the lower shaft 100, a swingable thread trimmer crank assembly 400, The disc 500 positioned at one end of the thread-cutting shaft 300, the thread-cutting crank 600 fixed at the other end of the thread-cutting shaft 300, the thread-cutting connecting rod 700, the moving knife rest 800, the moving knife 900 fixed on the moving knife rest 800, and t...

AI Technical Summary

Problems solved by technology

Therefore, in the above-mentioned automatic thread trimming mechanism of the sewing machine, the thread trimming crank assembly includes three extension arms, and it cooperates with the thread trimming shaft through a sliding pair, which makes the overall structure of the automatic thread trimming mechanism complex and requires high machining accuracy of the parts. The processing cost is high, and due to the large number of parts, the assembly is inconvenient and the working hours are long

[0004] go a step further, figure 1 and figure 2 In the existing automatic thread trimming mechanism shown, in the thread trimming actuator ABCD composed of the thread trimming crank, the thread trimming conn

Images