Peel off device for unwinding a web of material from a roll

Abstract

Peel off device ( 4 ) for unwinding a web of material ( 2 ) from a stock roll ( 1 ), especially for high speed unwinding a web of a thin polymer film or the like, comprising a base ( 5 ) associated to the roll ( 1 ), a linear guiding device ( 6 ) mounted on the base ( 5 ), an idler support ( 7 ) linearly guided on the base ( 5 ) in a direction towards the roll ( 1 ), and a pair of idlers ( 9, 10 ) for the web ( 2 ) to be unwound. The idlers ( 9, 10 ) are mounted offset with respect to each other on the idler support ( 7 ) to provide for a meandering path of the web between the idlers ( 9, 10 ). The axes of rotation (A 9 , A 10 ) of the idlers ( 9, 10 ) are parallel to the bearing axis (A 3 ) of the roll ( 1 ). The first idler ( 9 ) is pushed towards the roll to maintain a contact force (F) between the first idler ( 9 ) and the surface of the roll ( 1 ) while the web ( 2 ) is peeled off the roll ( 1 ).

What is claimed is: 
     
         1 . A peel off device for unwinding a web of material from a stock roll, said device comprising:
 (a) a base associated to the roll,   (b) a linear guiding device mounted on the base,   (c) an idler support linearly guided on the base in a direction towards the roll, and   (d) a first idler and a second idler for the web to be unwound, wherein
 the first and second idlers are mounted offset with respect to each other on the idler support to provide for a meandering path of the web between the first and second idlers, 
 the axes of rotation of the first and second idlers are parallel to the bearing axis of the roll, and 
 the first idler is pushed towards the roll so that a contact force is maintained between the first idler and a surface of the roll while the web is peeled off the roll. 
   
     
     
         2 . A peel off device according to  claim 1 , wherein the idler support pushes the first idler towards the roll to generate the contact force. 
     
     
         3 . A peel off device according to  claim 2 , wherein the idler support is powered by a pneumatic drive system. 
     
     
         4 . A peel off device according to  claim 3 , wherein the pneumatic drive system comprises a pressurized air cylinder. 
     
     
         5 . A peel off device according to  claim 1 , wherein the idler support is guided along the linear guiding device by a stepper motor. 
     
     
         6 . A peel off device according to  claim 1 , wherein the contact force between the first idler and the surface of the roll has a value of from between about 2 N and about 5 N in a direction towards the roll. 
     
     
         7 . A peel off device according to  claim 1 , wherein the peel off device further comprises a position tracking system for the position of the idler support. 
     
     
         8 . A peel off device according to  claim 7 , wherein the position tracking system is a magnetic position tracking system. 
     
     
         9 . A peel off device according to  claim 1 , wherein the linear guiding device is a guiding rail. 
     
     
         10 . A peel off device according to  claim 9 , wherein the idler support is mounted on a guide block engaging with the guiding rail. 
     
     
         11 . A peel off device according to  claim 1 , wherein the angle between the tangent of the surface of the roll at the point of contact with the first idler and the line passing through the centers of the first and second idlers is from about 300° to about 360°. 
     
     
         12 . A peel off device according to  claim 2 , wherein the idler support is pushed by a force impulse exceeding the continuous contact force in a direction towards the roll in case of blocking of the normal movement of the idler support. 
     
     
         13 . A peel off device according to  claim 1 , wherein the first and second idlers have a center to center distance which is a multiple of a diameter of the first idler. 
     
     
         14 . A peel off device according to  claim 1 , wherein the first idler is supported on a lever arm, which is pivotably mounted on the idler support and biased towards the roll to generate the contact force. 
     
     
         15 . A peel off device according to  claim 14 , wherein a pivot axis of the lever aim is parallel to an axis of rotation of the first idler. 
     
     
         16 . A peel off device according to  claim 14 , wherein the peel off device further comprises a rotary pneumatic cylinder mounted on the idler support for biasing the lever arm and the first idler towards the roll. 
     
     
         17 . A peel off device according to  claim 14 , wherein the peel off device further comprises stoppers at the idler support to limit the pivot range of the lever arm. 
     
     
         18 . A peel off device according to  claim 14 , wherein the peel off device further comprises position sensors for a pivot position of the lever arm. 
     
     
         19 . A method for unwinding a web of material from a stock roll, said method comprising the steps of:
 providing a peel off device comprising a base associated to the roll, a linear guiding device mounted on the base, an idler support linearly guided on the base in a direction towards the roll, and a first idler and a second idler for the web to be unwound, wherein the first and second idlers are mounted offset with respect to each other on the idler support to provide for a meandering path of the web between the first and second idlers, the axes of rotation of the first and second idlers being parallel to a bearing axis of the roll, and   pushing the first idler towards the roll to maintain a contact force between the first idler and a surface of the roll while the web is peeled off the roll.   
     
     
         20 . A method for the continuous converting a web of material from a stock roll into an absorbent article, wherein the web is unwound according to the method for unwinding the web of material from the stock roll of  claim 19 .