Seal cutter for plastic bag

A seal cutter for a plastic bag, comprising a folding device, a conveyor device, a point cut-off device, a tension control device, and a coreless winding device, wherein:

• the folding device includes a fixing seat including two opposite fixing racks which are combined with each other by a fixing plate and a roller, a first connecting plate is secured on a bottom of the fixing plate, a rectangular guide plate is mounted on the first connecting plate in an inclined manner, and is provided with a protruding block secured on the first connecting plate, a triangular guide plate is provided with a link secured on one of the two opposite fixing racks, so that the triangular guide plate is rested on the rectangular guide plate, a second connecting plate is secured on the other one of the two opposite fixing racks, a fixing rod is secured on a bottom of the second connecting plate, an oblique drive rod is secured on one end of the fixing rod, and is located above the triangular guide plate;
• the conveyor device includes two opposite U-shaped seats for securing a drive rubber wheel, two opposite first slide blocks for securing a driven rubber wheel, two opposite second slide blocks for securing an eccentric shaft, two cover plates for securing the first and second slide blocks on the U-shaped seat, and two adjusting knobs each extended through a respective cover plate to adjust a tension between the first and second slide blocks;
• the point cut-off device includes a blade seat, a point cut-off blade, and two press plates, the blade seat has a bottom end formed with multiple spring support seats, and has a top end formed with multiple screw bores, the point cut-off blade is formed with multiple slots aligning with the multiple spring support seats of the blade seat for mounting multiple springs, each of the springs has a top urged on a respective spring support seat of the blade seat and has a bottom urged on the two press plates, the point cut-off blade is formed with multiple step portions, each of the two press plates is mounted on the point cut-off blade by multiple screws which extend through the two press plates and through multiple sleeves between the two press plates, each of the multiple sleeves is rested on a respective step portion of the point cut-off blade;
• the tension control device includes a fixed roller set, a movable roller set, and a chain set for moving the movable roller set to engage the fixed roller set;
• the coreless winding device includes a piston rod structure, and a clamping structure, wherein:
• the piston rod structure includes an outer tube, and a gas pressure cylinder mounted on a rear end of the outer tube, the gas pressure cylinder has a front end secured with a bearing disk, the gas pressure cylinder has a gas pressure rod extended into the outer tube through a bearing hole in the bearing disk, and pivotally connected with a first end of a sleeve which has a second end formed with an elongated through hole, an inner tube is mounted in the bearing hole and the outer tube for receiving the gas pressure rod, two opposite piston rods mounted in the inner tube and protruding outward from an elongated through hole formed in the inner tube, one of the two piston rods is fixed, and the other piston rod is movable;
• and
• the clamping structure including two shafts each mounted on a support base and each having two ends each provided with a gear, two inverted U-shaped clips each mounted on one of the two shafts, two gas pressure cylinders each pivotally mounted on the support base and each pivotally mounted on the gear of one of the two shafts, and a gas pressure cylinder mounted on a bottom of the support base for lifting the support base, one of the two inverted U-shaped clips is provided with two opposite small gas pressure cylinders each having a gas pressure rod for driving a drive bar pivotally mounted on a side portion to rotate relatively.