Apparatus for straightening fabric

Abstract

An apparatus for correcting skew and/or bow distortions in woven or knitted fabrics during tentering in which the relative speed of two laterally spaced, driven fabric-engaging means or tenter chains is varied without altering the mean speed of the two fabric-engaging means to thereby obtain a straightened fabric of substantially uniform yield.

That which is claimed is: 
     
       1. In a tenter having a pair of laterally spaced, elongate and longitudinally movable first and second fabric-engaging tenter chains for moving a fabric forwardly while applying lateral tension to the fabric therebetween; the combination therewith of a. .[.tenter chains.]. .Iadd.means .Iaddend.for driving said .[.fabric-engaging means.]. .Iadd.tenter chains .Iaddend.to move at least the longitudinal center of the fabric therebetween at a predetermined substantially constant lineal speed and including a rotary input element adapted to be driven forwardly at a constant speed,   b. detecting means for detecting and producing a signal in response to a skew distortion in the forwardly moving fabric in which one side edge portion of the fabric is skewed forwardly of the opposite side edge portion thereof, and   c. responsive means interposed in said driving means and responsive to a skew correction signal of said detecting means for oppositely varying the lineal speed of said pair of fabric-engaging tenter chains in direct proportion to each other to correct the skew distortion without altering said constant lineal speed of the longitudinal center of the fabric, said responsive means comprising 1. first and second differential units including respective first and second rotary input portions driven by said input element, first and second rotary output portions on the respective first and second differential units drivingly connected to the respective first and second tenter chains, said first and second differential units also including first and second normally stationary rotary .[.housings.]. .Iadd.members.Iaddend., planetary gear means .[.in each housing.]. .Iadd.carried by each rotary member.Iaddend., and sun gears fixed on the input portion and the output portion, respectively, of each differential unit and meshing with the respective planetary gear means whereby each output portion is driven at a constant speed by said rotary input element while the respective .[.housings.]. .Iadd.rotary members .Iaddend.are stationary, and   2. reversible means under control of said detecting means for rotating said first and second .[.housings.]. .Iadd.rotary members .Iaddend.simultaneously in .[.opposite.]. directions .[.relative to each other whereby, when either housing rotates in a forward direction,.]. .Iadd.required to increase and decrease by corresponding amounts .Iaddend.the .[.speed.]. .Iadd.speeds .Iaddend.of the output .[.portion.]. .Iadd.portions .Iaddend.of the respective differential .[.unit is reduced and the other housing is rotated in a reverse direction to increase the speed of the output portion of the other differential unit.]. .Iadd.units.Iaddend..     
     
     
       2. Apparatus according to claim 1, wherein said input element includes a drive shaft extending through and supporting both of said first and second differential units thereon, and means securing said first and second rotary input portions on said drive shaft. 
     
     
       3. Apparatus according to claim 1, wherein said reversible means comprises a reversible electric motor, common to both of said first and second .[.housings.]. .Iadd.rotary members .Iaddend.and being electrically connected to said detecting means, and transmission means for transmitting rotation from said motor to said first and second .[.housings.]. .Iadd.rotary members .Iaddend.simultaneously in opposite directions relative to each other upon said detecting means detecting a skewed distortion in the fabric. 
     
     
       4. Apparatus according to claim 1, wherein said first and second differential units are arranged with the axes of their respective .[.housings.]. .Iadd.rotary members .Iaddend.disposed in laterally spaced, substantially parallel relationship, said input element comprising a drive shaft disposed in spaced substantially parallel relation from said .[.housing.]. .Iadd.rotary members .Iaddend.and driving connections between said drive shaft and the input portions of said first and second differential units. 
     
     
       5. Apparatus according to claim 1, including a. advancing means driven by said drive means for engaging the width of the fabric and advancing the same forwardly away from said fabric-engaging tenter chains,   b. said detecting means including means for detecting a bowed distortion in the forwardly moving fabric, and   c. a third differential unit comprising 1. a third rotary input portion driven by said input element,   2. a third rotary output portion drivingly connected to said advancing means, and   3. a third normally stationary rotary .[.housing.]. .Iadd.member .Iaddend.having planetary gear means in said .[.housing.]. .Iadd.member.Iaddend., and sun gears fixed on the input portion and output portion, respectively, and meshing with the planetary gear means for normally transmitting substantially constant-speed rotation from said third input portion to said third output portion while the .[.housing.]. .Iadd.member .Iaddend.is stationary, and     d. additional reversible means responsive to said detecting means detecting a bowed distortion in the fabric for driving said third .[.housing.]. .Iadd.member .Iaddend.in a direction corresponding to the direction of the bowed distortion being detected to vary the speed of said advancing means to thereby correct the bowed distortion in the fabric.   
     
     
       6. In a tenter having a pair of laterally spaced, elongate and longitudinallly movable first and second fabric-engaging means for moving a fabric forwardly while applying lateral tension to the fabric therebetween; the combination therewith of a. means for driving said fabric-engaging means to move at least the longitudinal center of the fabric therebetween at a predetermined substantially constant lineal speed,   b. advancing means driven by said drive means for engaging the width of the fabric and advancing the same forwardly away from said fabric-engaging means,   c. detecting means for detecting and producing a signal in response to a skew distortion in the forwardly moving fabric in which one side edge portion of the fabric is skewed forwardly of the opposite side edge portion thereof and for detecting and producing a bow correction signal in response to a bowed distortion in the forwardly moving fabric,   d. first responsive means interposed in said driving means and responsive to a skew correction signal of said detecting means for oppositely varying the lineal speed of said pair of fabric-engaging means in direct proportion to each other to correct the skew distortion without altering said constant lineal speed of the longitudinal center of the fabric, and   e. second responsive means interposed in said driving means and responsive to a bow correction signal of said detecting means in which the central portion of the fabric is lagging or leading the opposite side edge portions thereof, for compensatively varying the speed of said advancing means to correct the bowed condition of the fabric.   
     
     
       7. Apparatus according to claim 6, wherein said means for compensatively varying the speed of said advancing means comprises a. a speed variator having 1. a driven rotary input portion,   2. a rotary output portion drivingly connected to said advancing means, and   3. movable means under control of said detecting means detecting a bowed distortion in the fabric for varying the speed of said output portion relative to the speed of said input portion.     
     
     
       8. Apparatus according to claim 7, wherein said speed variator comprises a differential unit and said lastnamed movable means comprises a normally stationary rotary housing having planetary gear means therein for transmitting rotation from said input portion to said output portion, and reversible means under control of said detecting means for rotating said housing in response to detection of a bowed distortion being detected to vary the speed of said advancing means and thereby correct the bowed distortion in the fabric. 
     
     
       9. In a tenter having a pair of laterally spaced, elongate and longitudinally movable fabric-engaging means for moving forwardly a fabric held therebetween; the combination therewith of a. drive means drivingly connected to and normally imparting substantially constant forward lineal speed to said pair of fabric-engaging means and including a rotary input element adapted to be driven forwardly at a constant speed,   b. detecting means responsive to detection of skew distortions in the fabric for producing skew correction signals, and   c. a pair of separate differential units for the respective fabric-engaging means, each differential unit including 1. an input portion driven by said input element,   2. an output portion drivingly connected to the respective fabric-engaging means, and   3. a normally stationary rotary member having planetary gear means for normally transmitting substantially constant-speed rotation to said output portion from said input portion, and     d. .[.a.]. normally inactive reversible electric motor .Iadd.means .Iaddend.responsive to said skew correction signals for rotating one of said rotary members in that direction required to .[.correct a corresponding skew distortion in the fabric.]. .Iadd.increase the speed of the output portion of its differential unit by a predetermined amount .Iaddend. and .Iadd.for .Iaddend.simultaneously rotating the other of said rotary members in .[.the opposite.].  .Iadd.that .Iaddend.direction .[.from said one of said rotary members, so that, when either housing rotates in a forward direction, the speed of the output portion of the same differential unit is reduced as the other housing rotates in a reverse direction to increase the speed of the output portion of the respective other differential unit.]. .Iadd.required to reduce the speed of the output portion of its differential unit by a corresponding predetermined amount, .Iaddend.whereby whenever the speed of either fabric-engaging means is increased to correct a skewed distortion in the fabric, the speed of the other fabric-engaging means is correspondingly reduced, such that the sum of the speeds of the two fabric-engaging means is equal to said constant forward speed to thereby vary the forward speed of opposite side edge portions of the fabric for correcting a skewed distortion thereof without altering the mean forward speed of the fabric.   
     
     
       10. In a tenter having a pair of laterally spaced, elongate and longitudinally movable fabric-engaging means for moving forwardly a fabric held therebetween; the combination therewith of a. drive means drivingly connected to and normally imparting substantially constant forward lineal speed to said pair of fabric-engaging means and including a rotary input element adapted to be driven forwardly at a constant speed,   b. detecting means responsive to detection of skew and bow distortions in the fabric for producing skew correction signals and bow correction signals,   c. a pair of separate differential units for the respective fabric-engaging means, each differential unit including 1. an input portion driven by said input element,   2. an output portion drivingly connected to the respective fabric-engaging means, and   3. a normally stationary rotary member having planetary gear means for normally transmitting substantially constant-speed rotation to said output portion from said input portion,     d. reversible means for, at times, rotating both of said rotary members simultaneously in opposite directions relative to each other so that, when either housing rotates in a forward direction, the speed of the output portion of the same differential unit is reduced as the other housing rotates in a reverse direction to increase the speed of the output portion of the respective other differential unit whereby whenever the speed of either fabric-engaging means is increased to correct a skewed distortion in the fabric, the speed of the other fabric-engaging means is correspondingly reduced, such that the sum of the speeds of the two fabric-engaging means is equal to said constant forward speed to thereby vary the forward speed of opposite side edge portions of the fabric for correcting a skewed distortion thereof without altering the means forward speed of the fabric, e. bow correction means including advancing means for advancing the fabric forwardly away from said fabric-engaging means and having an additional differential unit also comprising   1. an input portion driven by said input element,   2. an output portion drivingly connected to said advancing means, and   3. an additional normally stationary rotary member having corresponding planetary gear means for normally transmitting substantially constant-speed rotation to the last-named output portion from the last-named input portion, and     f. a normally inactive reversible electric motor responsive to said bow correction signals for rotating said additional rotary member in that direction required to alternatively increase and decrease the speed of said advancing means for correcting bowed distortions in the fabric.   
     
     
       11. In a tenter having a pair of laterally spaced, elongate and longitudinally movable first and second fabric-engaging means for moving a fabric forwardly while applying lateral tension to the fabric therebetween; the combination therewith of a. means for feeding fabric to said fabric-engaging means,   b. control means for said feeding means including 1. sensing means adjacent said fabric-engaging means for sensing variations in density of forwardly moving fabric; and   2. means responsive to said sensing means for varying the speed of said feeding means in accordance with density variations being sensed by said sensing means,     c. means for driving said fabric-engaging means to move at least the longitudinal center of the fabric therebetween at a predetermined substantially constant lineal speed,   d. detecting means for detecting and producing a signal in response to a skew distortion in the forwardly moving fabric in which one side edge portion of the fabric is skewed forwardly of the opposite side edge portion thereof,   e. responsive means interposed in said driving means and responsive to a skew correction signal of said detecting means for oppositely varying the lineal speed of said pair of fabric-engaging means in direct proportion to each other to correct the skew distortion without altering said constant lineal speed of the longitudinal center of the fabric,   f. advancing means disposed on the output side of said fabric-engaging means and adapted to engage the corrected fabric for positively and continuously advancing the corrected fabric away from said fabric-engaging means,   g. delivery means disposed on the opposite side of said advancing means from said fabric-engaging means and in spaced relation to said advancing means and adapted to receive the corrected fabric from the advancing means and to continuously deliver the fabric therefrom,   h. said detecting means being positioned between  said advancing means and said delivery means adjacent the path of fabric movement therebetween for detecting skew distortions in the fabric while in relaxed state, and   i. drive means connected to said advancing means and said delivery means for continuously driving the same at lineal speeds sufficient to advance the corrected fabric past said detecting means under minimal tension whereby the corrective action on the fabric is substantially improved.   
     
     
       12. Apparatus according to claim 11, wherein said control means further comprises a drive shaft adapted to be driven at a constant speed, and said means responsive to said sensing means comprises a. a differential gear unit including 1. an input portion operatively connected to and driven by said drive shaft,   2. an output portion drivingly connected to said feeding means, and   3. a normally stationary rotary housing having planetary gear means therein normally transmitting constant-speed rotation to said output portion from said input portion, and     b. reversible means responsive to said sensing means sensing other than a predetermined normal density of the fabric for rotating said housing in a direction required to vary the rate of feed of the fabric to return the same to said normal density.