Adjustment of weft yarn stretch in a shed of an air jet loom

A method of controlling an air jet loom including at least one main blowing nozzle for picking a weft yarn into a shed of warp yarns and a plurality of groups of relay nozzles disposed across the shed;

• said method comprising the steps of
• detecting the arrival of a picked weft yarn at a shed-end weft stop motion and emitting a first signal in response thereto;
• detecting a stop shock in the picked weft yarn in a shed-entry weft stop motion and emitting a second signal in response thereto;
• and
• measuring the time difference between said signals to obtain a parameter for controlling at least one of the blowing pressure and the blowing time of at least said groups of relay nozzles.

In an air jet loom, the combination comprising

• a main blowing nozzle for picking a weft yarn into a shed of warp yarns;
• a plurality of groups of relay nozzles disposed across said shed for blowing a weft yarn along in said shed;
• a shed-end stop motion for detecting the arrival of a picked weft yarn at the end of said shed and emitting a first signal in response thereto;
• a shed-entry stop motion for detecting a stop shock in a weft yarn and emitting a second signal in response thereto;
• at least one pressure valve for controlling the blowing pressure of said relay nozzles;
• a plurality of timing valves, each said timing valve being connected with a respective group of relay nozzles for controlling the blowing time of said respective group of relay nozzles;
• and
• a loom control system connected to each said stop motion to receive said first and second signals therefrom and to said valves for controlling the subsequent operation of said valves in dependence on a time difference in said signals for a given number of picks.