Technical Articles

The rapier loom's main transmission rotates the sprocket driving wheel so that the rapier head and the rapier tape proceed weft insertion. Here is something you need to know about the sprocket wheel.

1 The Function and Criteria of Sprocket Driving Wheel
1) The function of the sprocket wheel. The sprocket wheel is the main part of the rapier loom that completes the weft insertion movement. There are two identical sprocket wheels on a rapier loom, installed on the left and right sides of the loom. It reciprocates and controls the rapier tape sheathed on the sprocket wheel teeth. When the rapier tape runs from the sprocket wheel teeth into the fixed guide rail, the movement of the rapier tape is converted from curvilinear motion to linear motion. Meanwhile, the rapier heads that are set on the left and right rapier tapes handover the weft and finishes weft insertion.

2) The criteria of the sprocket wheel.
a. The surface of the sprocket wheel, including teeth, should be smooth and free of waste edges, burrs sinks, or bubbles to avoid interference in the cooperation with rapier tape.
b. The performance of the sprocket wheel should be stable, reliable, and flexible. The radial runout of sprocket wheel tooth, tolerance of the tooth shape, tolerance of the inner diameter of the sprocket wheel, and concentricity must meet the drawing's requirements. The installation should ensure that the sprocket wheel is locked firmly by the clamp to avoid loosening and slipping.
c. The sprocket wheel should have excellent wear resistance and long service life. The material selection, accurate processing technology, heat treatment, surface treatment, adjustment of the proportion of carbon fiber, reinforced nylon, and glass fiber are critical to the service life of the sprocket wheel.

2 Classification and Technical Requirements of the Sprocket Wheel
1) Classification of sprocket wheels. According to the materials used, sprocket drive wheels are classified into carbon fiber composite sprocket wheels and all-metal sprocket wheels. Some sprocket wheel classification is shown below.

The choice of the sprocket wheel should match with the rapier loom. Each sprocket wheel is used on a specific loom. The size, shape, and specifications are different, so sprocket wheels must be purchased according to the part number in the loom model.

2) The technical requirements of the sprocket wheels. The sprocket wheel's technical specifications are generally proposed by the rapier loom manufacturer as per the loom performance. The main technical requirements are outer diameter, inner diameter, number of teeth, radial runout, concentricity, surface roughness, tooth side roughness, hardness, resistance value(for carbon fiber sprocket wheels), etc. The dimensional parameters of some sprocket wheels are shown below.


Regarding the specific technical parameters of the metal sprocket wheel, each loom manufacturer has its requirements. The general standard is shown below.


3 Application of Sprocket Wheel
As there are many types of sprocket wheels, each loom manufacturer has different requirements and instructions in their adjustment and maintenance manuals. However, the matters needing attention in the application are similar, only differ in some specific parameters in the adjustment. Here are some tips for the use of the sprocket wheel
1) Check the appearance of the sprocket wheel by visual inspection and hand feel, whether it is smooth, with waste edges, burrs, or cracks.

2) Sheathe the rapier tape on the sprocket wheel to stimulate the running condition, and observe whether the teeth contacting area fits well. Analyze the reason if they do not fit well.

3) During the adjustment, it must be ensured that the thickness of the rapier tape cannot be higher or lower than the tooth height of the rapier sprocket wheel. Adjust the clearance value of rapier tape and tape block as per the manual from the loom manufacturer till the traverse is smooth. If the clearance value is too small, the transmission resistance of the sprocket wheel is vast; if it is too big, the rapier tape will jump, affecting the delivery of weft and even cause rapier head damage.

4) Generally, the sprocket wheel used twice by changing a 180° angle.

4 Maintenance and Management of Sprocket Wheel
1) The sprocket wheel should be stored in a packaging box laid flat, avoid squeeze and deformation, and keep in a dry place.

2) Sprocket wheels should be checked before use. Remove dirt and fluff, and check whether any injury on the surface of the wheel tooth. If any, the sprocket wheel should be dismantled and repaired promptly.

3) Generally, the sprocket wheel's maintenance cycle is one month; the integrity of the sprocket wheel should be checked monthly.

4) Acceptance inspection should be carried out for the newly purchased sprocket wheel. The following process can be conducted to check the qualification of the recently purchased parts.
a. The delivered goods must be packed well in carton, with reliable outer packaging to avoid damage during transportation. Product certificate indicating production year, month, and date should be placed in the carton.

b. Check and conduct random or full inspection about the model, specification, and quantity indicated in the packing list. Quality check can be done by experienced mechanician, by visual inspection or hand feel, to check the appearance and the tooth profile is smooth or not. Also can use rapier tape to stimulate the working condition to judge their inosculation.

c. Sprocket drive wheels with different specifications should be placed in different areas to avoid mixing. When dispatching, the earlier comer should be used first to avoid long storage time.