Machine direction sensor system with cross direction averaging

Abstract

Disclosed is a machine direction measurement system having an increased cross direction sampling area (significantly larger than the natural sensor measurement window) to generate a more representative and stable machine direction reading of the process. In effect, the sensor should have as wide a coverage area as possible without having to resort to the expense of measuring the entire width of the sheet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a papermaking machine embodying the present invention.

FIG. 2 is a top view of a preferred sensor system in accordance with the present invention.

FIG. 3 is a side view of the sensor system of FIG. 2.

FIG. 4 is an end view of the sensor system.

FIG. 5 is an exploded orthogonal view of the sensor system.

FIGS. 6-8 show various sensor heads that may be used in the practice of this invention.

Claims

1. A machine direction sensor system with cross direction averaging, for measuring process variables in a continuous flat sheet process having a machine direction and a cross direction, the sensor system comprising: one or more sensors for taking a plurality of measurements along a cross directional section of the continuous flat sheet, and for generating a series of signals representing said measurements; anda controller for receiving said signals and for using said signals to average said measurements into a single reading.

2. A sensor system according to claim 1, wherein said one sensor includes: a sensor head; and a driver for moving the sensor head back and forth across said cross directional section.

3. A sensor system according to claim 2, further comprising a housing extending across said cross directional section of the continuous flat sheet, and wherein said sensor head and said driver are mounted inside the housing.

4. A sensor system according to claim 3, wherein the sensor head includes an infrared optical sensor, and the sensor system further comprises an optical fiber for conducting optical signals from the optical sensor to the controller.

5. A sensor system according to claim 4, wherein: the driver includes an air cylinder to drive the optical sensor back and forth; andthe sensor system further includes:a solenoid for controlling the direction of air flow through the air cylinder; and a cable chain for moving the optical fiber as the sensor head moves back and forth.

6. A sensor system according to claim 5, further comprising a standardization plate supported by the housing, and wherein the optical sensor is supported for movement to a position adjacent the standardization plate to calibrate the sensor head.

7. A sensor system according to claim 6, further comprising a sensor cartridge assembly, and wherein: the sensor cartridge assembly includes the optical sensor, the air cylinder, the solenoid, and the cable chain;the sensor cartridge assembly is releasably secured inside the housing; andthe housing includes a base and a cover, said cover being movably connected to the base to provide access to the interior of the housing.

8. A method for measuring process variables in a continuous flat sheet process, with cross directional averaging, said flat sheet process having a machine direction and a cross direction, the method comprising the steps of: using one or more sensors to take a plurality of measurements along a cross directional section of the continuous flat sheet, and to generate a series of signals representing said measurements; andaveraging said measurements into a single reading.

9. A method according to claim 8, wherein said one or more sensors includes a sensor head, and the using step includes the step of driving the sensor head back and forth across said cross directional section.

10. A method according to claim 9, wherein a housing extends across the cross directional section of the continuous flat sheet, and the method comprises the further step of mounting said sensor head inside the housing.

11. A method according to claim 10, wherein the sensor head is an infrared optical sensor, and the method comprises the further step of conducting optical signals from the optical sensor to a controller to measure moisture content of an area of said continuous flat sheet.

12. A method according to claim 11, wherein a standardization plate is supported by the housing and is located laterally outside said continuous flat sheet, and the method comprises the further steps of: moving the optical sensor to a position adjacent the standardization plate; andusing the standardization plate to calibrate the optical sensor.

13. A sheet making machine comprising: a headbox for receiving and holding a paper slurry;a forming section for receiving the pulp slurry from the headbox and for forming the slurry into a fiber web;a drying section for drying the fiber web; anda sensor system for measuring process variables of the fiber web in a machine direction with cross direction averaging.

14. A sheet making machine according to claim 13, wherein the sensor system includes: one or more sensors for taking a plurality of measurements along a cross directional section of the fiber web, and for generating a series of signals representing said measurements; anda controller for receiving said signals and for using said signals to average said measurements into a single reading.

15. A sheet making machine according to claim 14, wherein said one or more sensors includes: a sensor head; anda driver for moving the sensor head back and forth across said cross directional section.

16. A sheet making machine according to claim 15, wherein: the sensor head includes an infrared optical sensor;the driver includes an air cylinder to drive the optical sensor back and forth; andthe sensor system further includes:an optical fiber for conducting optical signals from the optical sensor to the controller;a solenoid for controlling the direction of air flow through the air cylinder; anda cable chain for moving the optical fiber as the sensor head moves back and forth.

17. A sheet making machine according to claim 16, wherein the sensor system further comprises a standardization plate, and the optical sensor is supported for movement to a position adjacent the standardization plate to calibrate the sensor head.

18. A sheet making machine according to claim 17, wherein: the sensor system further includes a housing extending across said cross directional section of the continuous flat sheet, and a sensor cartridge assembly releasably mounted inside the housing;the sensor cartridge assembly includes the optical sensor, the air cylinder, the solenoid, and the cable chain; andthe housing includes a base and a cover, said cover being movably connected to the base to provide access to the interior of the housing.