Air weft insertion system

In a method of inserting a weft strand into the warp shed of a loom in which a nozzle is located adjacent one side of the shed, said nozzle converging to a minimum cross-sectional area and one end of a length of said strand is delivered to the nozzle for insertion in the shed, the improvement comprising:

• (a) providing a source of a compressible medium under a pressure in excess of that required to choke said nozzle and with a supply capacity substantially exceeding the flow rate of said nozzle, and
• (b) delivering said pressurized medium to said nozzle from said source at a flow rate capability exceeding the actual flow rate possible at said pressure through the minimum area of the nozzle to induce at the minimum area of the nozzle a choked condition of said medium and continuing delivery of said medium to said nozzle to substantially sustain its choked condition for a time exceeding the time required for said choked condition to be achieved, whereby a pulse of pressurized medium of at least supersonic velocity is emitted from said nozzle with consequential projection of said strand length from said nozzle into said shed.

The method of claim 27 wherein said pulse has a duration of at least about 10 millisec and said delivery pressure is in the range of about 50-80 psig.

A loom in which a weft strand is inserted into a shed of warp threads comprising a nozzle in proximity to the shed and opening into the shed to serve as a guide for a weft strand passing therethrough, means for delivering to the nozzle a gaseous medium at an operating pressure having a ratio to the atmosphere ambient to said shed of at least about 2.7:1, and means for abruptly expelling from said nozzle a sustained pulse of said gaseous medium, said pulse having a supersonic velocity and being directed toward the shed to thereby project said weft strand through at least a portion of the shed.

In a loom comprising a nozzle located adjacent one side of the loom shed, said nozzle converging to a minimum cross-sectional area and means for delivering one end of a length of a weft strand to the nozzle for insertion in the shed, the improvement comprising:

• (a) means for providing a source of a compressible medium under a pressure in excess of that required to choke said nozzle by said medium and with a supply capacity substantially exceeding the flow rate of said nozzle, and
• (b) means for delivering said pressurized medium from said source at a flow rate capability exceeding the actual flow rate possible at said pressure through the minimum area of the nozzle to induce at the minimum area of the nozzle a choked condition of said medium, and
• (c) control means for continuing delivery of said medium to said nozzle to substantially sustain its choked condition for a time exceeding the time required for said choked condition to be achieved, whereby a pulse of pressurized medium of at least supersonic velocity is emitted from said nozzle with consequential projection of said strand length from said nozzle into said shed.

A method of inserting a weft strand into the shed of a cyclically operating weaving machine, said shed having a length of at least about 48 inches, comprising the steps of:

• providing a nozzle in proximity to one side of said shed for guiding the free end of a weft strand toward said shed, providing in said shed an elongated weft confining zone at least partially open to atmosphere along its length, and creating a pulse of a pressurized gaseous medium of a duration corresponding to a fraction of the machine operating cycle passing through said nozzle and across said shed to the other side thereof, the magnitude of said medium pressure and said pulse duration being sufficient to impart to said strand end energy adequate to transport the same across said shed to said opposite shed side, and the magnitude of said pulse pressure being selected to deliver the pulse front to said opposite shed side before the arrival thereat of the leading strand end.