The present invention relates to a moving web expanding and guiding apparatus and more particularly it relates to improvements in an apparatus wherein various webs such as woven fabrics, knitted fabrics, paper, and films are prevented by the expanding action of an expander device from becoming rolled at the selvages, wrinkled, or contracted during their movement and zigzag deviation of moving webs is corrected by the centering action of a guide device.
Conventionally, such moving web expanding and guiding apparatus, as disclosed for example in U.S. Pat. No. 4,224,724, is of the type comprising, in combination, an expander device having at least two expanding screw rolls diposed parallel to each other, of which one screw roll is designed so that the amount of its push-in with respect to the moving web is adjustable so as to adjust the amount of expansion of the web, and a guide device having at least two centering rolls disposed parallel to each other and designed so that when the moving web deviates, the centering rolls are tilted in the direction which corrects the deviation of the web.
In the aforesaid apparatus, however, the expanding action of the screw rolls is still insufficient and there is a serious drawback that even if the moving web excessively zigzag deviates to one side for one cause or another to the extent of causing the guide device to reach the limit of its deviation correcting action, it is impossible to prevent the moving web from being caught on one end of a screw roll and damaged since the screw rolls are designed to continue to be rotated by a motor.
Further, when the moving web excessively zigzag deviates to one side to the extent of causing the guide device to reach the limit of its deviation correcting action, as described above, the position of the centering rolls is such that they are greatly tilted to the limit position, and since the centering rolls are designed so that they are stopped at such limit tilted position, much labor and time are required to restore the deviated web to its normal position by hand before the machine can be restarted, thus producing a drawback that the machine cannot be restarted efficiently.