Patent Document ID: 4743811
Application ID: 07098647
Patent Flag: 1

Claim One:
1. An apparatus for transporting a web between supply and takeup reels comprising: a supply brushless direct current (DC) motor connected to said supply reel; a takeup brushless DC motor connected to said takeup reel; a supply Hall device assembly mounted on said supply motor for producing supply Hall signals; a takeup Hall device assembly mounted on said takeup motor for producing takeup Hall signals; control means for producing from said supply Hall signals and said takeup Hall signals, both commutation control signals and servo voltage signals for controlling the rotation of said supply and takeup motors to effect transport of said web between said supply and takeup reels; wherein each of said Hall device assemblies includes at least two angularly spaced Hall devices and wherein said Hall signals produced by said Hall devices are out of phase with each other such that the period between changes in signal value between two consecutive Hall signals is a measure of the radial velocity of the respective motor; and wherein said control means applies a correction factor to said Hall periods to correct for any misplacement in the angular position of said Hall devices.