Abstract
In order to fly the weft straight with no crooks, long nozzles were studied to find the following results:
1) So far as the outlet of the yarn guide pipe was downstream of the geometrically joining point of air supplied to the nozzle, the high velocity region effective to accelerate the weft could be wide axially if the yarn were started from the deeper point of a nozzle as long as possible.
2) The demerit of slow speed-up of a long yarn due to a long nozzle could be overwhelmed with the merit of high velocity given by the long duration of yarn acceleration. Velocity higher than 100m/sec could be obtained by the numerical calculation at the exit of a long nozzle.
3) A device to measure the yarn speed photoelectrically without touching the yarn was used to prove that, the deeper the point of yarn start in the long nozzle, the higher the yarn speed when its front end leaves the nozzle.
4) Although the way to measure and express numerically the deviation of yarn passage was devised, it did not verify that the deviation would be smaller if the yarn were started from the deeper point of the nozzle, in case where there were no substreams added from outside of the shed.
