Patent ID: 8733687
Filing Date: 2014-05-27
Classification: B65H

Abstract:
1. An apparatus for reducing feed rate variations in a web material when unwinding a parent roll on an unwind stand about a longitudinal axis to transport the web material away from the parent roll at a web takeoff point, the apparatus comprising: a rotational position and speed determining device associated with a shaft of the parent roll for determining the rotational position and speed of the parent roll; a drive system associated with a driving mechanism for imparting rotational movement to the parent roll on the unwind stand, the drive system causing the driving mechanism to drive the parent roll at a drive point located on the outer surface of the parent roll; a measuring device associated with the unwind stand for measuring the radius of the parent roll on the unwind stand; and a programmable logic device for generating an ideal speed reference signal, SRS the programmable logic device being associated with: i) the rotational position and speed determining device for receiving the rotational position and speed of the parent roll; ii) the drive system for initially controlling the speed of the driving mechanism based upon the ideal speed reference signal, SRS iii) the measuring device for receiving the measured radius for the parent roll; the programmable logic device being programmable to divide the parent roll about the longitudinal axis into a selected number 1, 2, . . . n, of data collection sectors to be analyzed; the programmable logic device initially being operable to control the drive system such that the driving mechanism drives the parent roll at a location on the outer surface at the drive point at a driving speed, M the programmable logic device creating a data table having a sector column for entering a sector number for each of the data collection sectors, 1, 2, . . . n, the data table also having a column for entering a drive point radius, R the programmable logic device correlating each of the data collection sectors, 1, 2, . . . n, at the web takeoff point with a corresponding one of the data collection sectors, 1, 2, . . . n, at the drive point; the programmable logic device receiving data from the rotational position and speed determining device to determine a rotational speed for each of the data collection sectors, 1, 2, . . . n, while at the drive point, as the parent roll is being driven; the programmable logic device calculating the drive point radius, R where M i is the driving speed for the parent roll and Ω i (1, 2, . . . n) is the rotational speed when each of the data collection sectors, 1, 2, . . . n, is at the drive point; the programmable logic device entering the drive point radius, R the programmable logic device calculating an ideal drive point radius, R the programmable logic device calculating the drive point correction factor, C where R dp (1, 2, . . . n) is the drive point radius for each of the data collection sectors, 1, 2, . . . n, and R dpi is the ideal drive point radius; the programmable logic device entering the drive point correction factor, C the measuring device measuring the web takeoff point radius, R the programmable logic device calculating an ideal web takeoff point radius, R the programmable logic device calculating the web takeoff point correction factor, C where R tp (1, 2, . . . n) is the web takeoff point radius for each of the data collection sectors, 1, 2, . . . n, and R tpi is the ideal web takeoff point radius; the programmable logic device entering the web takeoff point correction factor, C the programmable logic device calculating the total correction factor, C where C dp (1, 2, . . . n) is the drive point correction factor for each of the data collection sectors, 1, 2, . . . n, and C tp (1, 2, . . . n) is the web takeoff point correction factor for each of the data collection sectors, 1, 2, . . . n; the programmable logic device entering the total correction factor, C the programmable logic device multiplying the total correction factor, C the programmable logic device commanding the drive system to adjust the driving speed, M