Weft pattern chain preparation for Crompton and knowel's drop box motion:
The selection of shuttle boxes is performed by either separate pattern chain and cylinder or by dobby and Jacquard.
The separate selection mechanism is used in the loom having tappet shedding. The pattern capacity of a separate selection mechanism is limited. A chain of plates and cylinder are used in a separate selection mechanism. One pattern chain plate is used for two picks. The shuttle box position from 1 to 4 is avoided.
The box selection is performed in the dobby and Jacquard loom by using separate jack levers or hook. The figuring capacity of dobby or Jacquard gets reduced in this situation. The no. Of picks in the weft pattern gets increased in this situation.
Meaning of different chain's plates for Crompton and knowel's drop box motion:
You can understand the meaning of each plate to be used for different shuttle box as shown in below picture:
Weft pattern chain preparation for given weft pattern for Crompton and knowel's dropbox motion: