Method and apparatus for guiding side edges of continuously running web

Abstract

The present invention is to provide a method and an apparatus facilitating side edges of a web continuously running in a machine direction to be quickly corrected when these side edges are detected to be out of coincidence with a positions in a cross direction orthogonal to the machine direction. Roll means rotating about a shaft extending in a direction defined between a machine direction and a cross direction are put in contact with side edge of a web continuously running in the machine direction. The shaft is mounted on an arm adapted to rotate back-and-forth so that the shaft can swing in- and outward in the cross direction. Downstream of the roll means, the side edge is position-detected and the arm is made swing by a desired angle determined on the basis of a difference between the actual position and a desired position.

1 . A method for guiding a web continuously running in a machine direction and having a pair of side edges opposed to each other in a cross direction orthogonal to said machine direction so that at least one of said side edges is guided to a predetermined position in said cross direction by putting roll means rotating about a shaft extending in a direction defined between said machine direction and said cross direction in contact with a vicinity of at least one of said side edges, said method comprising the steps of: 
 mounting an arm having a proximal end and a distal end opposed to said proximal end at said proximal end on a pivot pin adapted to rotate back-and-forth so that said arm swings around said pivot pin in- and outward as viewed in said cross direction;    supporting said shaft of said roll means by said distal end of said arm so that said roll means also swing about said pivot pin in- and outward;    detecting, at downstream of said roll means, a position of said one side edge after this side edge has been guided; and    driving said arm by driving means adapted to operate on the basis of a difference between said position detected in this manner and said desired position so that said arm swings in- or outward in said cross direction by a predetermined angle.    
   
   
       2 . The method according to  claim 1 , wherein said driving means comprises an extensible/retractable arm operatively associated with a servomotor adapted to rotate in a direction and at a rotational frequency depending on the difference between said detected position and said desired position and thereby to extend or retract said extensible/retractable arm so that said side edge is guided to said desired position.  
   
   
       3 . The method according to  claim 1 , wherein said roll means is put in contact with at least one side of said web.  
   
   
       4 . The method according to  claim 1 , wherein said roll means comprises a pair of rolls extending in parallel to each other and adapted to nip at least said one side edge and the vicinity thereof.  
   
   
       5 . The method according to  claim 1 , wherein said roll means are provided in vicinities of a pair of said side edges to guide these side edges to respective said desired positions.  
   
   
       6 . An apparatus for guiding a web continuously running in a machine direction and having a pair of side edges opposed to each other in a cross direction orthogonal to said machine direction so that at least one of said side edges is guided to a predetermined position in said cross direction by putting roll means rotating about a shaft extending in a direction defined between said machine direction and said cross direction in contact with a vicinity of at least one of said side edges, said apparatus further comprising: 
 said shaft of said roll means being supported on a distal end of an arm which has a proximal end and said distal end opposed to said proximal end;    said proximal end of said arm being mounted on a pivot pin adapted to rotate back-and-forth so that said arm swings about said pivot pin in- and outward as viewed in said cross direction;    detector means being provided downstream of said roll means in said machine direction to detect a position of said one side edge immediately after said one side edge has been guided; and    said arm being operatively associated with driving means adapted to operate on the basis of a difference between said position detected by said detector means and said desired position so that said arm swing in- or outward in said cross direction by a desired angle.    
   
   
       7 . The apparatus according to  claim 6 , wherein said driving means comprises an extensible/retractable arm operatively associated with a servomotor.  
   
   
       8 . The apparatus according to  claim 6 , wherein said roll means is put in contact with at least one side of said web.  
   
   
       9 . The apparatus according to  claim 6 , wherein said roll means comprises a pair of rolls extending parallel to each other and adapted to nip at least said one side edge and the vicinity thereof.  
   
   
       10 . The apparatus according to  claim 6 , wherein said roll means are provided in vicinities of a pair of said side edges to guide these side edges to respective said predetermined positions.