Alternative method for reducing web feed rate variations induced by parent roll geometry variations

摘要

A method is disclosed for reducing feed rate variations when unwinding a web material to transport the web material away from the parent roll at a web takeoff point where the feed rate variations are induced by parent roll geometry variations. The method utilizes calculated and/or measured data to make suitable adjustments in the driving speed for an out-of-round parent roll to get closer to a relatively constant feed rate. By dividing the parent roll into 1, 2, . . . n sectors, the data can be refined to a relatively high degree taking into account high speed data processing capabilities as well as operating system response times to make appropriate driving speed adjustments.

主权项

1. A method for reducing feed rate variations in a web material when unwinding a parent roll about a longitudinal axis to transport the web material away from the parent roll at a web takeoff point, the method comprising the steps of:
dividing the parent roll into a plurality of angular sectors disposed about the longitudinal axis; using an ideal speed reference signal to drive the parent roll at a driving speed corresponding to a web feed rate of a round parent roll and at a drive point being disposed on the outer surface either coincident with or spaced from the web takeoff point; measuring a web takeoff point radius for each of the sectors by measuring the radius at or near the web takeoff point of the parent roll for each of the sectors as the parent roll is being driven at the drive point; calculating an ideal web takeoff point radius by determining an average for the web takeoff point radii for all of the sectors; calculating a web takeoff point correction factor for each of the sectors as a function of the ideal web takeoff point radius and the web takeoff point radius; multiplying the web takeoff point correction factor for each of the sectors by the ideal speed reference signal to establish an improved speed reference signal for each of the sectors; and adjusting the driving speed of the parent roll for each of the sectors to an improved driving speed as each of the sectors approaches or is at the drive point using the improved speed reference signal to at least reduce fluctuations in the web feed rate caused by variations in the web takeoff point radii.