Method for determination of roll density

• US 20040154391A1
• Filed: 12/11/2003
• Published: 08/12/2004
• Est. Priority Date: 06/15/2001
• Status: Active Grant

• Current Assignee: Valmet Technologies OY
• Original Assignee: Metso Paper Incorporated (Neles Oyj)
• Inventors: Paanasalo, Jari
• Granted Patent: US 6,917,895 B2
• Time in Patent Office: Days
• US Class Current: 73/159
• CPC Class Codes: B65H 18/26 Mechanisms for controlling contact pressure on winding-web package, e.g. for regulating the quantity of air between web layers
• CPC Class Codes: B65H 2515/12 Density
• CPC Class Codes: G01N 33/346 paper sheets
• CPC Class Codes: G01N 9/36 Analysing materials by measuring the density or specific gravity, e.g. determining quantity of moisture methods of measurement in general G01N9/02 - G01N9/32

Abstract

The method concerns a method for determination of roll density, wherein the density of the wound roll is determined in connection with the web reel. The method uses the known relation between the length (l), diameter (D), basis weight (b) and density (ρ) of the wound roll. formula (I). In the method, distortions caused in the measurement results by noise and other disturbances are eliminated by using a recursive time variant least squares method in the processing of the measurement results.

Claims

1. Method for determination of roll density, in which method the density of the wound roll is determined in connection with the web reel, which method uses the known relation between the length (l), diameter (D), initial diameter (D_o), basis weight (b) and density (ρ

) of the wound web,

2. Method according to claim 1, characterized in that a method of mathematical statistics is applied to the least square method, whereby the relation is obtained between the measurement exactness and the method'"'"'s built-in elimination of noise and disturbances.

3. Methods according to claim 1 or 2, characterized in that statistical confidence limits are determined for measurement value.

4. Method according to any preceding claim, characterized in that in the method before measurement occasion (11) the variables are initialized by points (12) determined by the nominal density or by the preceding measurement, that on each measurement occasion the correlation matrix (13) and the regression vector (14) are updated, that the correlation matrix (15) is reversed in order to calculate the paper thickness (16), that the density (17) is calculated based on the paper thickness (16), that the error variance (18) is updated, that the confidence limit is calculated for the desired probability (19), and, when required, the buffer length (20, 21) is changed, and that the speed of oblivion (22) is determined, whereupon the following measurement (23) in the method is carried out after the desired web length.

5. Method according to any preceding claim, characterized in that the method uses the extended time variant Kalman filter for further processing of the measurement results and for measuring the internal stresses of the roll.

6. Method according to any preceding claim, characterized in that in the method the roll diameter is determined by contact-free measurement.

7. Method according to claim 6, characterized in that the diameter is measured by pulse measurement, ultrasound or a laser sensor.

8. Method according to any preceding claim, characterized in that in the method the density is measured separately for each station based on the roll diameter and web length given by a linear sensor.

9. Method according to any claim 1-8, characterized in that the method is applied in connection with winding-in of the web.

10. Method according to any claim 1-8, characterized in that the method is applied in connection with unwinding of the web.

11. Method according to any claim 1-10, characterized in that the method is applied in connect with winding of a paper and board web.