Method and apparatus for detecting water on a surface of an object

• US 6,528,790 B2
• Filed: 05/03/2001
• Issued: 03/04/2003
• Est. Priority Date: 05/03/2001
• Status: Expired due to Term

• Current Assignee: Cleveland-Cliffs Steel Technologies Incorporated
• Original Assignee: Bethlehem Steel Corporation (ArcelorMittal SA)
• Inventors: Rudolph, Ralph G.
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): MORAN, TIMOTHY J
• Application Number:
  US09/847,896
• Publication Number:
  US 20020162962A1
• Time in Patent Office: 670 Days
• Field of Search: 250/339.1, 250/341.1, 250/341.8, 250/559.5, 356/429, 356/430, 356/431
• US Class Current: 250/339.1
• CPC Class Codes: G01N 21/3554 for determining moisture content
• CPC Class Codes: G01N 21/3559 in sheets, e.g. in paper

Abstract

A method and apparatus for detecting and removing water from a surface of a moving metal sheet in continuous treatment line to prevent the formation of water stains thereon. A selected surface area of the moving metal sheet is illuminated with infrared radiation having a wavelength substantially absorbed by water, and an optical sensor system is employed to view images reflected off the selected surface area. An optical bandpass filter limits transmission of infrared light to within a specific range of wavelengths known to be strongly absorbed by water. The sensor assembly produces a signal representative of the intensity of the reflected light. If the intensity signal is lower than a predetermined level, water is detected and the signal may be used to trigger a control device that sounds alarms, records the event, or otherwise controls the environment of the object so that detected water may be removed to prevent the formation of water stains. The present invention is particularly suited for detecting the presence of water on a moving steel sheet treated in a continuous coating line.

Claims

1. An apparatus for non-invasive detection of water on a surface of a steel sheet coated in a continuous coating line to prevent the formation of water stains thereon, said apparatus comprising:

a) an infrared light source positioned to transmit a generated infrared light of a predetermined intensity onto a selected surface area of the steel sheet, said generated infrared light having a wavelength substantially absorbed by water;

b) a sensor assembly having a sensor positioned to sense reflected infrared light reflected off said selected surface area, said assembly producing a signal representative of a second intensity of said reflected infrared light for comparison with said predetermined intensity to thereby detect a presence of water on said selected surface area; and

c) a control device to initiate a condition whereby detected water is removed from the surface of the steel sheet before coiling to prevent the formation of water stains thereon.

2. The invention according to claim 1, further comprising:

a) a filter located between said infrared light source and said sensor to limit an amount of said reflected infrared light detected by said sensor within a predetermined wavelength range.

3. The invention according to claim 2, wherein said filter is disposed proximate said sensor and between said select area of said object and said sensor.

4. The invention according to claim 2, wherein said filter limits transmission of infrared light having a wavelength in a range from 2.5 to 3.5 microns.

5. The invention according to claim 2, wherein said filter limits transmission of infrared light having a wavelength in a range from 2.7 to 2.9 microns.

6. The invention according to claim 2, wherein said filter limits transmission of infrared light having a wavelength in a range from 6-7 microns.

7. The invention according to claim 2, wherein said filter limits transmission of infrared light having a wavelength in a range from 1-2 microns.

8. The invention according to claim 2, wherein said sensor is an indium arsenide photovoltaic infrared diode sensitive to infrared wavelengths within a range from 1 to 3.5 microns.

9. The invention according to claim 2, in combination with a rinse section of a steel treatment assembly, wherein said object is a moving sheet of steel conveyed along said rinse section between a drying stage area and a coiler stage of said steel treatment assembly, said infrared light source and said sensor assembly being positioned proximate a roller supporting a turn in said conveyed strip.

10. According to claim 9, wherein said sensor assembly includes a plurality of sensors, said apparatus further comprising:

a) a plurality of rotating polyhedral mirrors disposed between said strip and said sensor assembly and each positioned to scan a portion of an entire width of said strip and direct infrared light reflected off said portion of said strip toward a corresponding one of said plurality of sensors thereby facilitating sensing of said entire width of said strip.

11. The apparatus according to claim 9, wherein said sensor assembly comprises an array of sensors, each of said sensors adapted to sense a width portion of said strip, said array of sensors together sense reflected light across an entire width of said strip.

12. The apparatus according to claim 2, wherein said light source comprises a pair of quartz infrared heaters disposed above said object and each having a parabolic reflector mounted there above to illuminate said select area by infrared radiation.

13. The apparatus according to claim 1, wherein said object is opaque substantially preventing said infrared light from passing through said surface.

14. The invention according to claim 2, wherein said filter limits transmission of infrared light having a wavelength between 1.0 to 2.7 microns and a wavelength between 3.2 to 3.5 microns.

15. An apparatus for non-invasive detection of water on a strip of steel in combination with a rinse section of a steel treatment facility, said strip of steel being conveyed along said rinse section between a drying stage area and a coiler, said apparatus comprising:

a) a detection assembly provided to detect a presence of water on said strip and positioned along said rinse section between said drying stage area and said coiler proximate a roller supporting a turn in said conveyed strip, said detection assembly including;

b) an infrared light source including a pair of quartz infrared heaters disposed above said strip, said heaters having a parabolic reflector to illuminate an entire width of said strip by infrared radiation;

c) a detection box disposed between said pair of quartz infrared heaters and disposed above said strip to detect a reflected portion of said infrared radiation reflected off said strip, said detection box including;

d) an infrared sensor including an arsenide photovoltaic infrared diode sensitive to infrared wavelengths within a range from 1 to 3.5 microns and producing a first signal representative of an intensity of said reflected portion of said infrared radiation;

e) an optical filter disposed between said infrared sensor and said strip limiting transmission of said reflected infrared light to a range from 2.7-2.9 microns;

f) a lens disposed between said optical filter and said infrared sensor to focus said reflected light onto said sensor; and

g) an amplifier receiving said first signal and producing therefrom an amplified voltage signal representative of said intensity of said reflected portion of said infrared radiation.

16. A non-invasive method of detecting water on a surface of a steel sheet coated in a continuous coating line to prevent the formation of water stains thereon, said method comprising the steps of:

directing an infrared light having a wavelength substantially absorbed by water onto a selected surface area of the steel sheet;

sensing a reflected portion of said infrared light from said selected surface area to determine an intensity thereof;

determining the presence of water on said selected surface area by comparing said intensity to a predetermined value; and

providing a condition whereby detected water is removed from the surface of the steel sheet before coiling to prevent the formation of water stains thereon.

17. The method of claim 16, further comprising the step of:

filtering said infrared light to limit transmission thereof to within a pre-described range of wavelengths prior to said step of sensing.

18. The method of claim 17, wherein said pre-described range of wavelengths is within a range from 2.5 to 3.5 microns.

19. The method of claim 17, wherein said pre-described range of wavelengths is within a range from 2.7 to 2.9 microns.

20. The method of claim 19, wherein said step of filtering said infrared light filters said reflected portion of said infrared light.

21. The method of claim 17, wherein said pre-described range of wavelengths is within a range from 6 to 7 microns.

22. The method of claim 17, wherein said pre-described range of wavelengths is within a range from 1 to 2 microns.

23. The method of claim 17, in combination with a method of conveying said object in a rinse section of a steel treatment assembly, wherein said object is a strip of steel;

said method further comprising the steps of;

conveying said strip of steel along said rinse section between a drying stage area and a coiler of said rinse section; and

said step of directing said infrared light and said step of sensing said reflected portion of said infrared light occurring at a location between said drying stage and said coiler proximate a roller supporting a turn in said conveyed strip.

24. The method claim 17, wherein said step of sensing said reflected portion of said infrared light includes the additional step of producing a first signal representative of said intensity of said reflected portion of said infrared light and amplifying and converting said first signal to a second voltage signal and said step of determining the presence of water on said selected includes the step of comparing said second voltage signal to a predetermined threshold value.

25. A method of non-invasively detecting water on a surface of a moving strip of metal conveyed along a rinse section of a manufacturing assembly, said method comprising the steps of:

conveying said strip of metal along said rinse section between a drying stage area and a coiler of said rinse section;

directing an infrared light having a wavelength substantially absorbed by water onto said strip;

filtering said infrared light to limit transmission thereof to within a range of wavelengths from 2.7 to 2.9 microns;

sensing a reflected portion of said infrared light reflected off said select strip to determine an intensity thereof, and producing a first signal representative of said intensity of said reflected portion of said infrared light;

amplifying and converting said first signal to a second voltage signal; and

determining the presence of water on said strip area by comparing said second voltage signal to a predetermined threshold value;

wherein, said step of directing said infrared light and said step of sensing said reflected portion of said infrared light occurring at a location between said drying stage and said coiler proximate a roller supporting a turn in said conveyed strip of metal.

26. Apparatus for detecting the presence water on the surface of a continuous moving metal sheet to prevent the formation of water stains thereon, comprising:

a) an energy source positioned to transmit radiant energy onto a surface target area of the continuous moving metal sheet, said radiant energy having a wavelength substantially absorbed by water;

b) a sensor positioned to receive reflected radiant energy from said surface target area, said sensor generating an output signal indicative of an intensity difference between of said transmitted radiant energy and said reflected radiant energy, a predetermined difference indicating the presence of water; and

c) a control device to initiate a condition whereby detected water may be removed from the surface of the continuous moving metal sheet to prevent the formation of water stains thereon.

27. The invention recited in claim 26, further comprising:

a) a filter located between said reflected radiant energy and said sensor to limit to a selected wavelength the reflected radiant energy received by said sensor.

28. A method for detecting water on a surface of a metal sheet to prevent the formation of water stains thereon, comprising the steps of:

directing radiant energy having a wavelength substantially absorbed by water onto a surface target area of said metal sheet;

sensing a reflected radiant energy from said surface target area to determine an intensity thereof;

determining a presence of water on said surface target area by comparing said intensity to a predetermined value; and

providing a control device to initiate a condition whereby detected water may be removed from the surface of the continuous moving metal sheet to prevent the formation of water stains thereon.

29. A non-invasive method of detecting water on a surface of a strip, said method comprising the steps of:

conveying said strip between a drying stage area and a coiler in a rinse section of a treatment line;

directing an infrared light having a wavelength substantially absorbed by water onto a selected area of the strip;

sensing a reflected portion of said infrared light reflected off said selected surface area to determine an intensity thereof; and

determining the presence of water on said selected area by comparing said intensity to a predetermined value.

30. The method of claim 29 wherein said step directing said infrared light and said step of sensing said reflected portion of said infrared light occurs at a location between said drying stage and said coiler proximate a roller supporting a change in direction of the conveyed strip.

31. The method of claim 29, further comprising the step of:

filtering said infrared light to limit transmission thereof to within a pre-described range of wavelengths prior to said step of sensing.

32. The method of claim 29 wherein the strip is steel and the drying stage area and the coiler are located in the rinse section of a continuous coating line.

33. A non-invasive method of detecting water on a surface of an object, said method comprising the steps of:

rinsing said object;

drying said object;

directing an infrared light having a wavelength substantially absorbed by water onto a select area of said dried object;

sensing a reflected portion of said infrared light from said select area to determine an intensity thereof; and

determining the presence of water on said selected area by comparing said intensity to a predetermined value.

34. The method of claim 33, further comprising the step of:

filtering said infrared light to limit transmission thereof to within a pre-described range of wavelengths prior to said step of sensing.

35. An apparatus for non-invasive detection of water on a continuous strip conveyed along a rinse section and drying section in a treatment line, said apparatus comprising:

a) an infrared light source positioned to transmit a generated infrared light of a predetermined intensity onto a selected surface area of the continuous strip, said generated infrared light having a wavelength substantially absorbed by water; and

b) a sensor assembly having a sensor positioned to sense reflected infrared light reflected off said selected surface area, said assembly producing a signal representative of a second intensity of said reflected infrared light for comparison with said predetermined intensity to thereby detect a presence of water on said surface.

36. The invention according to claim 35, further comprising:

a) a filter located between said infrared light source and said sensor to limit an amount of said reflected infrared light detected by said sensor within a predetermined wavelength range.

37. The invention according to claim 35, wherein

a) said infrared light source and said sensor assembly are positioned proximate a roller supporting a change in direction of said continuous strip conveyed along the rinse section and drying section of the treatment line.

38. The invention according to claim 35, wherein said sensor assembly includes a plurality of sensors, comprising:

a) a plurality of rotating polyhedral mirrors disposed between the continuous strip and said sensor assembly and each positioned to scan a portion of an entire width of said continuous strip and direct infrared light reflected off said selected surface area toward a corresponding one of said plurality of sensors thereby facilitating sensing of said entire width of said continuous strip.

39. The apparatus according to claim 35, said sensor assembly comprises an array of sensors, each of said sensors adapted to sense a width portion of the continuous strip, said array of sensors together sense reflected light across an entire width of the continuous strip.

40. The apparatus according to claim 35, wherein said light source comprises a pair of quartz infrared heaters disposed above the continuous strip and each having a parabolic reflector mounted there above to illuminate said select area by infrared radiation.

41. The invention according to claim 35, wherein the continuous strip is a continuous metal strip.

42. The invention according to claim 35, wherein the continuous strip is a continuous steel strip.

43. In a continuous treatment line that applies a coating to at least one surface of a moving metal strip, the improvement comprising:

an infrared light source, a sensor, and a control device that communicate to illuminate and scan said at least one surface of the moving metal strip with infrared light at a wavelength substantially absorbed by water, and to initiate a condition whereby detected water is removed from said at least one surface to prevent the formation of water stains thereon.