Method and apparatus for controlling yarn plug length

Abstract

A continuous synthetic filament yarn is processed by crimping, entangling, and straightening the yarn. The yarn is straightened by heating under tension, resulting in a yarn that can be used in its straightened form and later bulked by a subsequent process such as dyeing, boiling, heating, etc. The length of a yarn plug formed by crimping is controlled by controlling the temperature of the yarn.

What is claimed is: 
     
       1. A method for controlling a yarn plug length in a crimping zone which comprises: feeding a yarn to a heating zone .Iadd.comprising a first heated roll.Iaddend., thereafter feeding the yarn to a yarn crimping zone and producing a yarn plug therein;   monitoring the length of said yarn plug produced in said crimping zone;   increasing the temperature of the yarn in said heating zone .Iadd.by increasing the temperature of the first heated roll .Iaddend.if the plug length is too long;   decreasing the temperature of the yarn in said heating zone .Iadd.by decreasing the temperature of the heated roll .Iaddend.if the plug is too short.   
     
     
       2. The method of claim 1 wherein the .[.temperature of the yarn is controlled by controlling the temperature of the yarn in a yarn feeding zone, said yarn feeding zone for feeding the yarn to the crimping zone.]. .Iadd.heating zone comprises said first heated roll and a second heated roll wherein said first heated roll is positioned downstream of said second heated roll and is operated at a higher peripheral speed as compared to said second heated roll so that the yarn is drawn.Iaddend.. .[.3. The method of claim 1 wherein the temperature of the yarn is controlled by controlling the temperature of a yarn drawing zone, said yarn drawing zone for drawing the yarn and feeding the drawn yarn to the 
     
     
        crimping zone..]. 4. An apparatus for controlling the plug length of a yarn produced by a crimping means comprising: .Iadd.a heated feed roll; .Iaddend.   crimping means for producing a yarn plug;   monitoring means for monitoring the length of the yarn plug;   temperature control means; and   coupling means coupling said monitoring means with said control means for controlling the temperature of the yarn upstream of the crimping means .Iadd.by controlling the temperature of the heated feed roll.Iaddend., said control means causing the temperature of the yarn to increase when said monitoring means detects a length of yarn plug which is too long and to decrease when the monitoring means detects a length of yarn plug which   
     
     
        is too short. 5. The apparatus of claim 4 wherein said monitoring means 
     
     
        comprises an electric eye. 6. The apparatus of claim 4 wherein said crimping means comprises a fluid jet. .Iadd.7. The apparatus of claim 6 wherein the fluid is steam. .Iaddend..Iadd.8. The apparatus of claim 4 further comprising a heated draw roll positioned downstream of the heated feed roll. .Iaddend.