Automatically-adjusting web media tensioning mechanism

A method for automatically adjusting a level of tension in web media being transported in a roll-fed web media transport system, the web media having a width, comprising:

• receiving web media into an automatically-adjusting tensioning mechanism from a source roller, the automatically-adjusting tensioning mechanism including:
• a bracket assembly mounted to a frame and adapted to freely pivot around a pivot axis through a range of pivot angles, the pivot axis being oriented in a direction across the width of the web media;
• a first tensioning shoe extending in a lengthwise direction across the width of the web media and having a first curved surface around which the web media slides, the first tensioning shoe being attached to the bracket assembly;
• and
• a second tensioning shoe extending in a lengthwise direction across the width of the web media and having a second curved surface around which the web media slides, the second tensioning shoe being attached to the bracket assembly at a fixed distance from the first tensioning shoe;
• and
• a weight attached to the bracket assembly or one of the tensioning shoes using a cable to provide a torque on the bracket assembly;
• feeding the web media through an S-shaped media path in the automatically-adjusting tensioning mechanism where the web media is wrapped around the first curved surface of the first tensioning shoe and is wrapped around the second curved surface of the second tensioning shoe such that a frictional drag is produced as the web media slides around the first and second curved surfaces resulting from friction between the web media and the first and second curved surfaces, thereby providing a tension in the web media as it exits the automatically-adjusting tensioning mechanism, the web media being in contact with the first curved surface for a first contact distance and being in contact with the second curved surface for a second contact distance, wherein the torque provided by the weight opposes a torque on the bracket assembly provided by the frictional drag produced as the web media slides around the first and second curved surfaces, and wherein the pivot angle of the bracket assembly automatically adjusts as the web media passes through the automatically-adjusting tensioning mechanism in response to differences in a coefficient of friction between the web media and the first and second tensioning shoes such that the tension in the web media as it exits the automatically-adjusting tensioning mechanism has a reduced level of variability as a function of the coefficient of friction relative to configurations where the bracket assembly is held in a fixed position;
• and
• pulling the web media through the automatically-adjusting tensioning mechanism using a feed mechanism provided downstream of the automatically-adjusting tensioning mechanism.