Film web motion control system

摘要

A web motion control system for controlling the tension in a web advanced at a preset velocity in a web transport path between a supply reel and a take-up reel without the use of tension loops, particularly for use in transporting spliced together, developed filmstrips through a film preparation work station. The web (film) is advanced in the web transport path in either a forward or rewind direction in either a velocity mode or a position mode by a motor driven capstan roller. The supply and take-up reels have a hub over which the web is wound in unknown supply and take-up web winding diameters. Take-up and supply reel motors and encoders are attached to the take-up and supply reels for imparting torques to the reels in response to motor torque signals to prevent slack in the film segments between the reels and the capstan roller and to provide reel encoder output signals on at least each 360 DEG rotation of the reels. A metering encoder rotated with the capstan roller is employed to develop an encoder count signal. The web winding radii are calculated from the differential encoder counts at successive reel encoder output signals, and appropriate motor torque signals are developed. The encoder count is also employed in the position mode to control the stopping of the web after a predetermined advancement.