There is conventionally known a roller for properly adjusting the width of a travelling web by expanding or contracting the web to a predetermined position whereby the web undergoes a change in width. The roller of the type abovementioned includes a core roller, a pair of inclinedly movable tension setting members of short cylindrical shape disposed at the ends of the core roller, and a plurality of elastic bands having a proper amount of surface frictional resistance axially arranged in the cylindrical shape around the circumference of the core roller between the tension setting members.
The cylindrically arranged elastic bands are axially moved in succession according to the inclined movement of the tension setting members, while being rotated by the contact of a travelling web therewith. Thus, the web is expanded or contracted to the predetermined position, whereby the travelling web is properly adjusted in width.
According to the adjusting roller of this type, the elastic bands are connected to the tension setting members with the ends of the elastic bands secured to the peripheries of the tension setting members. It is therefore unavoidable that the joint ends of the elastic bands will be bent or twisted, as the elastic bands are axially moved expanded or contracted, according to the inclined movement of the tension setting members when adjusting the web width. This presents disadvantages as follows:
(1) Since rotating torque greater than necessary is required for rotating the roller, no smooth width adjustment of a travelling web can be performed.
(2) The bent or twisted portions of the elastic bands are apt to be damaged. When the elastic bands are repeatedly bent or twisted, they are broken, thereby to reduce the life-time of the adjusting roller.
(3) When the elastic bands are broken, there is produced powder from the material forming the elastic bands, such as rubber powder. Such powder sticks to the web, and the web is subsequently contaminated.