A projectile loom is a kind of shuttleless weaving machine, and its mechanism mainly includes shedding, picking, weft insertion, beating-up, warp let-off and cloth take-up. The specific introduction is as follows:
Shedding mechanism: Projectile looms are usually equipped with positive cam or rotary dobby systems. When a positive cam rotates, it oscillates a roller lever horizontally. This horizontal motion is transmitted to the heald shafts through links, causing them to move up and down vertically, thus forming a shed for the weft to pass through.
Picking mechanism: The unique feature of a projectile loom is its torsion-rod picking mechanism. The energy required for picking is built up and stored in a specially made torsion rod. During picking, the torsion rod is suddenly released, making the picking arm hit the projectile. The projectile is accelerated and travels to the other end of the machine through the rake-shaped projectile guides.
Weft insertion mechanism: It consists of several sequential operations. First, the projectile moves to the picking position. Then, the projectile feeder opens after gripping the weft end. Next, the picking arm hits the projectile, and the projectile draws the weft through the shed. After that, the projectile is stopped at the receiving end, and the weft tensioner holds the thread lightly stretched. The feeder grips the thread again, and the selvedge grippers secure the weft at both sides of the cloth. Finally, the weft is severed by a scissor on the picking side, and the projectile on the receiving side releases the weft and is conveyed back to the picking position.
Beating-up mechanism: As the projectile moves through the guide with the weft yarn, the yarn is laid into the guide. Two antifriction rollers follow two cams. The nose of one cam exerts pressure on one of the antifriction rollers in the leftward direction. At a specific moment, the antifriction roller moves downward due to the cam's curvature, causing the sley to shift to the right. This facilitates the release of the weft yarn from the guide through the slot in the guide. Meanwhile, the reed beats up the newly inserted weft, ensuring it is firmly placed at the fell of the cloth.
Warp let-off mechanism: In earlier versions of projectile weaving machines, the warp let-off was controlled mechanically, using a worm and worm wheel to drive the beam, with the tension in the warp monitored and transmitted to a ratchet to control the beam's rotation. In later versions, it is electronically controlled. A back-rest roller serves as an automatic control device. The control unit adjusts the speed of the warp let-off motor according to the back-rest roller's position sensed by a sensor.
Cloth take-up mechanism: The cloth take-up mechanism in a projectile loom is responsible for taking up the woven fabric at a constant speed to ensure the uniformity of the fabric's density and width. It typically consists of a take-up roller and a drive mechanism. The drive mechanism can be mechanical or electronic, which is connected to the main shaft of the loom or other power sources to obtain power and drive the take-up roller to rotate.