Web tensioning device

Abstract

A web tensioning device utilizes a dancer arm which is pivoted by a servo motor controlled in a feedback mode. The controller for the servo motor receives an input signal based on the acceleration (positive or negative) of the dancer arm and implements a position adjustment necessary to maintain predetermined web tension.

I claim:  
     
         1 . A web tensioning device which comprises: 
 a base;    a dancer arm for engaging the web to be tensioned, having a free end portion with a dancer mounted thereon and a fixed end portion pivotably mounted to the base;    a servo motor operably associated with the dancer arm for pivotally positioning the dancer arm in response to a control output signal; and    a controller operably associated with the servo motor for generating the control output signal in response to a web tension requirement.    
     
     
         2 . The web tensioning device in accordance with  claim 1  wherein the controller generates a control output signal in response to movement of the dancer arm.  
     
     
         3 . The web tensioning device in accordance with  claim 1  wherein the controller generates a control output signal in response to web feed rate.  
     
     
         4 . A web tensioning device which comprises: 
 a base;    an angular position sensor;    a dancer arm for engaging the web to be tensioned, having a free end portion with a dancer mounted thereon and a fixed end portion pivotably mounted to the base so as to coact with the angular position sensor and indicate relative angular displacement of the dancer arm as a web in contact with the dancer is maintained in tension;    a servo motor operably associated with the dancer arm for pivotally positioning the dancer arm in response to a control signal; and    a controller for generating the control output signal in response to movement of the dancer arm due to changes in web tension as detected by the angular position sensor.    
     
     
         5 . The web tensioning device in accordance with  claim 4  wherein the angular position sensor is an encoder operably associated with the fixed end portion of the dancer arm and senses relative angular displacement of the dancer arm.  
     
     
         6 . The web tensioning device in accordance with  claim 4  wherein the encoder is an incremental rotary optical encoder.  
     
     
         7 . The web tensioning device in accordance with  claim 4  wherein the servo motor is an electric motor.