The continuous stitches sewn by a straight stitch sewing machine have the same shape on the front and back, like a dotted line. The stitches are densely distributed, and the sewing fastness generally exceeds that of manual sewing. It is suitable for sewing cotton, linen, silk, wool, chemical fiber inelastic interwoven fabric or leather and other clothing and household products. The sewing thickness can range from two layers of silk to 5mm thick free-form woolen cloth. After installing the special accessories, it can be used for embroidery, crimping, embossing, tucking, embedding, buttonholes, etc.
The straight stitch sewing machine is composed of a machine head, a frame and a table. The head is the main part of the sewing machine . It is composed of 4 mechanisms including puncturing, thread hooking, thread take-up and feeding, and winding auxiliary mechanism. The movement of each mechanism is reasonably coordinated, working in cycles, and forming stitches.
① Stabbing mechanism: It is composed of crank slider mechanism. The crank is driven by the main shaft. The needle bar with the organic needle is connected with the small connecting rod. When the main shaft rotates once, the needle bar moves up and down once, so that the machine needle completes the action of piercing the material and leading the suture.
②Thread hook mechanism: three types: shuttle type, shuttle type and rotary shuttle type. The shuttle hook thread mechanism is composed of a crank rocker mechanism and a swing guide rod mechanism. The main shaft (crank) is connected with the Dalian rod and is the input rod of this mechanism. The shuttle holder is connected with the rocker (lower shaft crank) of the swing guide rod mechanism and is the output rod of this mechanism. The final execution component of the hook thread mechanism is the shuttle, and there is a certain gap between the shuttle and the shuttle holder. In each movement cycle, the shuttle holder pushes the shuttle to rotate and swing at an angle of 206° to 210°, which plays the role of hooking, dividing, unthreading, outgoing, and supplying shuttle threads.
③Thread take-up mechanism: There are link type, cam type, etc. The link type thread take-up mechanism is composed of a four link mechanism. The crank (thread take-up eccentric wheel) is connected with the main shaft and is driven by the main shaft. It is the input rod of this mechanism; the lead rod, which is the same rigid body as the thread take-up rod, is the output rod of the thread take-up mechanism. There is a threading hole on the top of the thread take-up lever, and its up and down movement plays the role of retracting and releasing the suture.