Weft insertion mechanism – rapier weft insertion device
The components of the rapier weft insertion mechanism include rapier heads, rapier belts, rapier wheels and guide devices.
1. Rapier belt
Rigid rapiers should be made of light but strong materials. Aluminum alloy rods, thin-walled steel pipes, carbon fiber or rapiers made of laminated materials can be used.
Flexible sword belts are now mostly made of multi-layer laminated materials. It is made of multi-layer high-strength filament fabric as the base, impregnated with resin and laminated, and the surface is covered with a wear-resistant layer. Generally thick 2.5 ~ 3mm. The sword belt must withstand repeated bending deformation during operation, requiring good elastic recovery performance, wear resistance, and sufficient strength. During the working life, the belt edge shall not be damaged, the surface shall not peel, and the belt body shall not delaminate or break. . Some flexible sword belts use steel belts as materials. The steel belts have good rigidity and elasticity, and no guides are needed in the shed. However, the steel belts are difficult to open and cannot be driven by gear teeth, so the effective width of weft insertion is limited. Similar to the steel belt, the sword belt is made of carbon fiber. It has the advantages of the steel belt and is lightweight, but it is more expensive.
2. Rapier head
The function of the rapier head is to clamp and bring the weft yarn through the shed. The function of the rapier head of the weft feeding rapier is to pick up and hold the weft yarn before entering the shed, and place it on the yarn clamp. A short section of weft yarn is overhead on the rear side as a feeding section, which is picked up by the weft-picking sword hook; the function of the weft-picking sword head is to hook and clamp the weft yarn, and after exiting the shed, the weft yarn is released by the action of the opening sword plate. Clamp-on sword heads can be divided into two types: positive and negative.
(1) Fork-type rigid rapier (rapier head): It uses a fork-shaped weft feed rapier head to introduce the weft yarn unwound from the package into the shed. In the middle of the reed width, the weft yarn head end yarn loop is The hook-shaped weft-joining rapier hooks the lead-out shed. Since the weft yarn is not cut and is connected to the fabric, double weft yarns are introduced each time. This rapier is suitable for weaving double weft fabrics, such as canvas, conveyor belt core, etc. When using this kind of rapier for weft insertion, the weft yarn will be rubbed by the fork and hook head, and the weft yarn extraction speed is fast, twice that of the rapier. Therefore, the weft yarn is required to have high strength and wear resistance.
(2) Clamping rigid rapier (rapier head): The clamp on the weft feed rapier head of this mechanism actively opens and closes by the weft feed side opener to hold the weft yarn into the shed. There is a reed holder in the center. The handover finger controls the opening and closing of the weft-feeding sword and the weft-receiving sword clamps. Actively control the weft yarn transfer, send the weft sword in the middle of the shed to transfer the weft yarn head to the jaws of the weft receiving rapier head, continue to guide the weft yarn through the shed, and when the weft connecting sword comes out of the shed, actively open the weft side opener and By closing the jaws of the weft-feeding rapier head, this device enables weaving of weft yarns of various thicknesses and colors.
The rigid rapier can be hung in the shed during weft insertion without contacting the lower warp yarns, which reduces the friction on the warp yarns and is conducive to variety adaptability. However, the width of the rigid rapier is at least half of the effective width of the fabric reed. Therefore, for wide-width fabrics, the area occupied by the loom is significantly increased, which greatly reduces its application range.
(3) Flexible rapier clamping rapier head: Flexible rapier generally adopts a clamping rapier head, using two flexible rapier straps that can be bent. Generally used rapier belts are often punched with perforations, and the perforations mesh with the teeth on the rapier wheel during operation. The rapier wheel rotates back and forth, allowing the rapier belt to move in and out of the shed for weft insertion. After the rapier belt exits the shed and goes around the rapier wheel, it can be bent and extended below the loom, thus reducing the area occupied. The clip-on sword head is shown in Figure 1-1.
3. The sword wheel
The sword wheel rotates back and forth to drive the flexible sword belt in and out of the shed. When drawing the sword at high speed, the sword wheel is required to be light and have sufficient strength. The material can be aluminum alloy or high-strength laminating material, such as nylon and reinforced with graphite carbon fiber filling. The diameter of the sword wheel is generally 250~450mm, and the pitch of the wheel teeth and the sword belt hole should match each other. In recent years, in order to improve the transmission accuracy of the sword transfer system and reduce the speed-increasing transmission ratio of the sword transfer mechanism to the sword wheel, larger sword wheels tend to be used.
4. Guide devices
Guide devices include sword guide hooks and sword guide plates (velvet pads). For narrow sword belts (16mm), sword guide hooks are used on both sides. For wider sword belts (24 mm), sword guide hooks are used on both sides. ~30mm) often has a guide hook only on the side of the fabric opening. Some looms do not have guide hooks. The guide device of the sword belt in the shed plays two roles. One is to stabilize the sword head and sword belt in the shed; the other is to hold up the sword belt and reduce the friction between the sword head, sword belt and warp. In order to reduce the friction between the sword belt and the warp yarns, some looms make the sword guide hook into a floating guide hook, which slightly holds up the sword belt and “floats” about 1 to 3 mm above the lower warp yarns. As shown in Figure 1-2.
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