Every loom lifts part of the warp so that the weft can pass through. A dobby does this not thread by thread but with heddle shafts. That makes it a simple and fast pattern machine.
Heddle shafts
A heddle shaft is a rectangular frame that carries many heddle wires. Every warp thread passes through the eye of one heddle. When a shaft lifts, all the threads on it lift together.
In the drawing, 16 warp threads are drawn in turn through 8 shafts: thread 1 goes to shaft 1, thread 2 to shaft 2, and thread 9 starts again on shaft 1. The plan that shows which thread goes to which shaft is called the draft.
The pattern chain: which shafts lift?
The dobby sits beside the loom and chooses which shafts lift for every pick. On a classic dobby the choice is made by a chain of pegged bars. Each bar is one pick, and its pegs mark the shafts that lift for that pick. As the chain turns, the next bar is read.
On the chain beside the drawing, the pegs match the shafts that lift, and the line underneath lists them. Today electronic dobbies make the same choice and the pattern file is loaded straight into the machine.
What happens in one pick
- The shed opens: the chosen shafts rise and the others drop. The gap between the raised and lowered threads is called the shed.
- The weft goes in: the shuttle travels across the shed and back, leaving the weft thread in the shed.
- The reed beats: the reed swings forward and packs the new pick against the edge of the cloth.
- The shed closes: the shafts return and the chain moves on to the next pick.
Press "Start the loom" and it begins to weave. The buttons below it pause, speed up or slow down the loom, and the arrow keys move it one pick at a time.
