NIP width sensing system and method

• US 20050000303A1
• Filed: 07/30/2004
• Published: 01/06/2005
• Est. Priority Date: 02/19/1998
• Status: Active Grant

• Current Assignee: Robert H. Moore, William B. Kennedy
• Original Assignee: Robert H. Moore, William B. Kennedy
• Inventors: Kennedy, William B., Moore, Robert H.
• Granted Patent: US 7,225,688 B2
• Time in Patent Office: Days
• US Class Current: 73/862.550
• CPC Class Codes: G01B 7/14 for measuring distance or clearance between spaced objects or spaced apertures G01B7/30 takes precedence
• CPC Class Codes: G01L 5/0085 Force sensors adapted for insertion between cooperating machine elements, e.g. for measuring the nip force between rollers

Abstract

Devices for measuring a nip width between rolls of a press nip include one or more sensors adapted to be placed in the nip while the nip is stationary. The electrical resistance of each sensor corresponds to the size of the nip width, whereby a nip width or a nip width distribution may be determined by measuring the sensor resistance(s). Methods of measuring a nip width distribution include providing a plurality of force sensitive resistor sensors each of which respond to pressure applied thereto to provide a variable sensor resistance as a function of the amount of pressure and the area of the pressure exerted on the sensor.

Claims

1. A device for measuring a nip width between two rolls of a press nip, said device comprising:

a) a sensor assembly, said sensor assembly including;

1) a first strip formed of a first electrically conductive material having a resistance, said first strip having a first end and a second end and a first measuring zone between said first and second ends;

2) a second strip disposed adjacent said first strip and formed of a second electrically conductive material, said second strip having a second measuring zone disposed adjacent and substantially coextensive with said first measuring zone;

3) a gap defined between said first and second strips and electrically isolating said first and second strips from one another; and

4) wherein at least one of said first and second strips is deformable such that, when said device is placed in the press nip, pressure from the nip rolls forces portions of said first and second measuring zones into electrically conductive contact with one another, the area of said contact substantially directly corresponding to the nip width; and

b) resistance measuring means for measuring an electrical resistance across said first measuring zone.

2. The device of claim 1 wherein said resistance measuring means includes first and second leads, said first lead connected to a voltage source and to said first strip adjacent said first end, said second lead connected to said first strip adjacent said second end and to a ground.

3. The device of claim 2 wherein substantially no current flows through said second strip when said first and second strips are not in contact.

4. The device of claim 2 wherein said first and second materials are the same.

5. The device of claim 2 wherein said first material has a higher electrical resistance than said second material.

6. The device of claim 2 including at least one compressible edge support operative to maintain said gap when said sensor is unloaded and to allow said first and second strips to make contact when said sensor is placed in the press nip.

7. The device of claim 2 including a strip and a plurality of said sensors mounted thereon.

8. The device of claim 1 including a temperature sensor operative to measure a temperature in the press nip and to generate a temperature compensation signal.

9. The device of claim 1 including means for detecting when an end edge of said sensor assembly is positioned within the press nip.

10. The device of claim 1 wherein said resistance measuring means comprises:

a) a first lead connected to a ground and to said first strip adjacent said first end;

b) a second lead connected to a ground and to said first strip adjacent said second end;

c) a voltage source; and

d) a third lead connected to said voltage source and to said second strip.

11. The device of claim 10 including a first resistor in said first lead between said first strip and ground and a second resistor in said second lead between said first strip and ground.

12. The device of claim 10 wherein substantially no current flows through said second strip when said first and second strips are not in contact.

13. The device of claim 10 wherein said first and second materials are the same.

14. The device of claim 10 wherein said first material has a higher electrical resistance than said second material.

15. The device of claim 10 including at least one compressible edge support operative to maintain said gap when said sensor is unloaded and to allow said first and second strips to make contact when said sensor is placed in the press nip.

16. The device of claim 10 including a strip and a plurality of said sensors mounted thereon.

17. A device for measuring a nip width between two rolls of a press nip, said device comprising:

a) a sensor assembly, said sensor assembly comprising;

1) a first strip formed of a first electrically conductive material;

2) a second strip spaced apart from said first strip and formed of a second electrically conductive material;

3) a third strip mounted on said second strip between said first and second strips and having first and second opposed contact surfaces, said first contact surface facing said first strip and said second contact surface electrically contacting said second strip, said third strip formed of a semiconductor material operative to substantially prevent current flow through said semiconductor material except between said contact surfaces;

4) a gap defined between said first strip and said first contact surface and electrically isolating said first strip and said third strip from one another; and

5) wherein at least one of said first strip and said second and third strips are deformable such that, when said device is placed in the press nip, the nip rolls force portions of said first strip and said first contact surface into electrically conductive contact with one another, the area of said contact substantially directly corresponding to the nip width; and

b) resistance measuring means for measuring a resistance across said first, second and third strips, said resistance measuring means including a voltage source, a first lead connecting said voltage source to said first strip and a second lead connecting said voltage source to said second strip.

18. The device of claim 17 wherein said third strip comprises segments of said semiconductor material insulated from one another.

19. The device of claim 17 wherein said semiconductor material is orthotropic.

20. The device of claim 17 wherein said third strip has a thickness of no greater than 0.2 inch.

21. The device of claim 17 wherein said semiconductor material includes a filled composite comprising a non-conductive medium and conductive particles held in said non-conductive medium.

22. The device of claim 17 further including a fourth strip mounted on said first strip between said first and second strips and having first and second opposed contact surfaces, said first contact surface facing said second strip and said second contact surface electrically contacting said first strip, said fourth strip formed of a semiconductor material operative to substantially prevent current flow through said semiconductor material except between said contact surfaces, and wherein when said device is placed in the press nip, the nip rolls force portions of said first contact surfaces of said third and fourth strips into electrically conductive contact with one another, the area of said contact substantially directly corresponding to the nip width.

23. The device of claim 17 further including spacer means disposed in said gap between said first strip and said first contact surface to maintain said gap when said sensor is not under pressure.

24. The device of claim 17 including at least one compressible edge support operative to maintain said gap when said sensor is unloaded and to allow said first and second strips to make contact when said sensor is placed in the press nip.

25. The device of claim 17 including a strip and a plurality of said sensors mounted thereon.

26. A device for measuring a nip width between two rolls of a press nip, said device comprising:

a) a sensor assembly, said sensor assembly comprising;

1) a first strip formed of a first electrically conductive material;

2) a second strip spaced apart from said first strip and formed of a second electrically conductive material;

3) a third strip mounted on said second strip between said first and second strips and having first and second opposed contact surfaces, said first contact surface facing said first strip and said second contact surface electrically contacting said second strip, said third strip formed of a semiconductor material operative to substantially prevent current flow through said semiconductor material except between said contact surfaces;

4) a force sensitive resistive material layer interposed between said first strip and said first contact surface, said force sensitive resistive material layer operative to electrically isolate said first strip and said third strip from one another when in a relaxed state and to electrically connect said first strip and said third strip when a prescribed pressure is applied to said force sensitive resistive material layer; and

5) wherein at least one of said first strip and said second and third strips are deformable such that, when said device is placed in the press nip, the nip rolls force portions of said first and second strips toward one another, thereby compressing a corresponding portion of said force sensitive resistive material layer, the area of said corresponding portion corresponding to the nip width; and

b) resistance measuring means for measuring a resistance across said first, second and third strips, said resistance measuring means including a voltage source, a first lead connecting said voltage source to said first strip and a second lead connecting said voltage source to said second strip.

27. The device of claim 26 wherein said third strip comprises segments of said semiconductor material insulated from one another.

28. The device of claim 26 wherein said semiconductor material is orthotropic.

29. The device of claim 26 wherein said third strip has a thickness of no greater than 0.2 inch.

30. The device of claim 26 wherein said semiconductor material includes a filled composite comprising a non-conductive medium and conductive particles held in said non-conductive medium.

31. The device of claim 26 further including a fourth strip mounted on said first strip between said first and third strips and having first and second opposed contact surfaces, said first contact surface facing said second strip and said second contact surface electrically contacting said first strip, said fourth strip formed of a semiconductor material operative to substantially prevent current flow through said semiconductor material except between said contact surfaces, and wherein when said device is placed in the press nip, the nip rolls force portions of said first contact surfaces of said third and fourth strips into electrically conductive contact with one another, the area of said contact directly corresponding to the nip width.

32. The device of claim 26 including a strip and a plurality of said sensors mounted thereon.

33. A device for measuring a nip width between two rolls of a press nip for which a largest expected nip width is known, said device comprising a sensor assembly, said sensor assembly having a sensor length and a sensor width and adapted for placement in the press nip such that said sensor length extends across the nip width and perpendicular to the roll axes, said sensor assembly further comprising:

a) a plurality of substantially parallel membrane switches, said membrane switches extending substantially perpendicular to said sensor length and arranged in successive, spaced apart relation along said sensor length, at least two of said membrane switches being spaced apart from one another along said sensor length a distance greater than the largest expected nip width; and

b) a plurality of electrically conductive lead lines, each said lead line connected to a respective one of said membrane switches.

34. The device of claim 33 including a strip and a plurality of said sensors mounted thereon.

35. A device for measuring a nip width between two rolls of a press nip for which a largest expected nip width is known, said device comprising a sensor assembly, said sensor assembly having a sensor length and a sensor width and adapted for placement in the press nip such that said sensor length extends across the nip width and perpendicular to the roll axes, said sensor assembly further comprising:

a) first and second spaced apart lead lines extending along at least a portion of said sensor; and

b) a plurality of membrane switches arranged in successive, spaced apart relation along said sensor length, at least two of said membrane switches spaced apart from one another along said sensor length a distance greater than the largest expected nip width, each of said membrane switches disposed between and electrically connected to each of said first and second lead lines such that each said membrane switch is in electrically parallel relation to each of the other said membrane switches.

36. The device of claim 35 including a plurality of resistors disposed between and electrically connected to each of said first and second lead lines, each said resistor being electrically connected in series relation to a respective one of said plurality of membrane switches.

37. The device of claim 35 wherein said first and second lead lines extend along at least a portion of said sensor length and are spaced apart from one another along said sensor width.

38. The device of claim 35 wherein said membrane switches are spaced apart along said sensor width.

39. The device of claim 35 wherein each of said membrane switches comprises a dot having a diameter greater than the spacing between adjacent said membrane switches along said sensor length.

40. The device of claim 35 including a strip and a plurality of said sensors mounted thereon.

41. A method of measuring a nip width between two rolls of a press nip, said method comprising the steps of:

a) estimating a largest expected nip width between the rolls;

b) selecting and providing a device for measuring the nip width, the device comprising;

1) a plurality of sensor assemblies, each of the sensor assemblies including a force sensitive resistor sensor responsive to pressure applied to the force sensitive resistor sensor to provide a variable sensor resistance as a function of the amount of pressure and the area of the pressure exerted on the sensor, each of the sensors having a sensing length greater than the largest expected nip width; and

2) electronics for determining the sensor resistances of the plurality of sensors;

c) mounting the sensors in the press nip such that each of the sensors extends lengthwise across the nip width, whereby each sensor is subjected to a respective nip pressure over a contact area corresponding to the nip width at the respective sensor'"'"'s location;

d) while the rolls are stationary, determining the sensor resistance of each of the sensors along the nip width;

e) determining a line load between the rolls;

f) scaling each of the sensor resistances as a function of the line load to determine a scaled line load value corresponding to each sensor resistance; and

g) determining a nip width corresponding to each scaled line load value.

42. The method of claim 41 including the step of converting the sensor resistances to corresponding voltage signals, and wherein the steps of determining and scaling the sensor resistances are executed by the electronics using the voltage signals.

43. A method of measuring a nip width between two rolls of a press nip, said method comprising the steps of:

a) estimating a largest expected nip width between the rolls;

b) selecting and providing a device for measuring the nip width, the device comprising;

1) a plurality of sensor assemblies, each of the sensor assemblies including a force sensitive resistor sensor responsive to pressure applied to the force sensitive resistor sensor to provide a variable sensor resistance as a function of the amount of pressure and the area of the pressure exerted on the sensor, each of the sensors having a sensing length greater than the largest expected nip width; and

2) electronics for determining the sensor resistances of the plurality of sensors;

c) characterizing each of the sensors by determining the resistance response of each sensor as a function of pressure and contact area;

d) mounting the sensors in the press nip such that each of the sensors extends lengthwise across the nip width, whereby each sensor is subjected to a respective nip pressure over a contact area corresponding to the nip width at the respective location;

e) while the rolls are stationary, determining the sensor resistance of each of the sensors along the nip width;

f) for each sensor, determining a reference line load corresponding to the determined sensor resistance; and

g) determining a flip width corresponding to each determined reference line load.

44. The method of claim 43 including the step of measuring the line load at a prescribed location along the length of the nip using an auxiliary measuring device, and wherein said step of determining a reference line load includes, for each sensor, scaling the determined reference line load as a function of the line load determined by the auxiliary measuring device, and wherein said step of determining nip width includes estimating the actual nip width corresponding to each scaled reference line load.

45. The method of claim 44 wherein the auxiliary measuring device is selected from the group consisting of a Prescale film, a carbon paper, and an embossed foil.

46. The method of claim 43 including determining and using parameters of the rolls to determine the nip width.

47. A method of measuring a nip width between two rolls of a press nip, said method comprising the steps of:

a) estimating a largest expected nip width between the rolls;

b) selecting and providing a device for measuring the nip width, the device comprising;

1) a plurality of sensor assemblies, each of the sensor assemblies including a force sensitive resistor sensor responsive to pressure applied to the force sensitive resistor sensor to provide a variable sensor resistance as a function of the amount of pressure and the area of the pressure exerted on the sensor, each of the sensors having a sensing length greater than the largest expected nip width; and

2) electronics for determining the sensor resistances of the plurality of sensors;

c) characterizing each of the sensors by determining the resistance response of each sensor as a function of nip width;

d) mounting the sensors in the press nip such that each of the sensors extends lengthwise across the nip width, whereby each sensor is subjected to a respective nip pressure over a contact area corresponding to the nip width at the respective location;

e) while the rolls are stationary, determining the sensor resistance of each of the sensors along the nip width;

f) for each sensor, determining a reference nip width corresponding to the determined sensor resistance.

48. The method of claim 47 including the step of measuring the nip width at a prescribed location along the length of the nip using an auxiliary measuring device, and, for each sensor, scaling the determined reference nip width as a function of the nip width determined by the auxiliary measuring device.

49. The method of claim 48 wherein the auxiliary measuring device is selected from the group consisting of a Prescale film, a carbon paper, and an embossed foil.

50. A device for measuring a nip width between two rolls of a press nip for which a largest expected nip width is known, said device comprising a sensor assembly, said sensor assembly having a sensor length and a sensor width and adapted for placement in the press nip such that said sensor length extends across the nip width and perpendicular to the roll axes, said sensor assembly further comprising:

a) a plurality of sensing lines arranged and configured to measure at least said largest expected nip width;

b) wherein said sensing lines include a force sensitive resistive material having a saturation pressure less than a prescribed nominal pressure whereby, when said device is mounted in the press nip, each sensing line positioned in the nip width will be substantially saturated.

51. The device of claim 50 including a strip and a plurality of said sensors mounted thereon.

52. The device of claim 50 including first and second opposed, flexible film layers, wherein each of said sensing lines includes a first line secured to an inner surface of said first film layer and a second line secured to an inner surface of said second film layer and facing said first line.

53. The device of claim 50 wherein:

said sensing lines are substantially parallel,

said sensing lines extend substantially perpendicular to said sensor length,

said sensing lines are arranged in successive, spaced apart relation along said sensor length, and

at least two of said sensing lines are spaced apart from one another along

said sensor length a distance greater than the largest expected nip width, said sensor assembly further including a plurality of electrically conductive lead lines, each said lead line connected to a respective one of said sensing lines.

54. The device of claim 50 wherein said sensor assembly includes first and second spaced apart lead lines extending along at least a portion of said sensor, and wherein:

said sensing lines are arranged in successive, spaced apart relation along said sensor length,

at least two of said sensing lines are spaced apart from one another along said sensor length a distance greater than the greatest expected nip width, and

each of said sensing lines are disposed between and electrically connected to each of said first and second lead lines such that each said sensing line is in electrically parallel relation to each of the other said sensing lines.

55. The device of claim 54 including a plurality of resistors disposed between and electrically connected to each of said first and second lead lines, each said resistor being electrically connected in series relation to a respective one of said plurality of sensing lines.

56. The device of claim 54 wherein said first and second lead lines extend along at least a portion of said sensor length and are spaced apart from one another along said sensor width.

57. The device of claim 50 wherein:

said sensing lines are substantially parallel,

said sensing lines extend substantially parallel to said sensor length with a uniform offset spacing along said sensor length between respective ends of said sensing lines, and

at least two of said ends of said sensing lines are spaced apart from one another along said sensing length a distance greater than the largest expected nip width,

said sensor assembly further including a plurality of electrically conductive lead lines, each said lead line connected to a respective one of said sensing lines.

58. The device of claim 50 wherein:

said sensing lines are substantially parallel,

said sensing lines extend at an angle with respect to said sensor length with a uniform offset spacing along said sensor length between respective ends of said sensing lines, and

at least two of said ends of said sensing lines being spaced apart from one another along said sensor length a distance greater than the largest expected nip width,

said sensor assembly further including a plurality of electrically conductive lead lines, each said lead line connected to a respective one of said sensing lines.

59. A device for measuring a nip width between two rolls of a press nip for which a largest expected nip width and a largest expected nip pressure are known, said device comprising a sensor assembly, said sensor assembly having a sensor length and a sensor width and adapted for placement in the press nip such that said sensor length extends across the nip width and perpendicular to the roll axes, said sensor assembly further comprising:

a) a plurality of sensing lines, said sensing lines arranged and configured to measure at least said largest expected nip width; and

b) wherein said sensing lines include a force sensitive resistive material having a saturation pressure at least as great as the largest expected pressure in the nip whereby, when said device is mounted in the press nip, each sensing line positioned in the nip width will be partially actuated so that the electrical resistance of said sensing line is representative of the nip pressure on said sensing line.

60. The device of claim 59 including a strip and a plurality of said sensors mounted thereon.

61. The device of claim 59 including first and second opposed, flexible film layers, wherein each of said sensing lines includes a first line secured to an inner surface of said first film layer and a second line secured to an inner surface of said second film layer and facing said first line.

62. The device of claim 59 wherein:

said sensing lines are substantially parallel,

said sensing lines extend substantially perpendicular to said sensor length,

said sensing lines are arranged in successive, spaced apart relation along said sensor length, and

at least two of said sensing lines are spaced apart from one another along said sensor length a distance greater than the largest expected nip width,

said sensor assembly further including a plurality of electrically conductive lead lines, each said lead line connected to a respective one of said sensing lines.

63. The device of claim 59 including first and second spaced apart lead lines extending along at least a portion of said sensor, and wherein:

said sensing lines are arranged in successive, spaced apart relation along said sensor length,

at least two of said sensing lines are spaced apart from one another along said sensor length a distance greater than the largest expected nip width, and

each of said sensing lines are disposed between and electrically connected to each of said first and second lead lines such that each said sensing line is in electrically parallel relation to each of the other said sensing lines.

64. The device of claim 63 including a plurality of resistors disposed between and electrically connected to each of said first and second lead lines, each said resistor being electrically connected in series relation to a respective one of said plurality of sensing lines.

65. The device of claim 63 wherein said first and second lead lines extend along at least a portion of said sensor length and are spaced apart form one another along said sensor width.

66. The device of claim 59 wherein:

said sensing lines are substantially parallel,

said sensing lines extend substantially parallel to said sensor length with a uniform offset spacing along said sensor length between respective ends of said sensing lines, and

at least two of said ends of said sensing lines are spaced apart from one another along said sensing length a distance greater than the largest expected nip width,

said sensor assembly further including a plurality of electrically conductive lead lines, each said lead line connected to a respective one of said sensing lines.

67. The device of claim 59 wherein:

said sensing lines are substantially parallel,

said sensing lines extend at an angle with respect to said sensor length with a uniform offset spacing along said sensor length between respective ends of said sensing lines, and

at least two of said ends of said sensing lines are spaced apart from one another along said sensor length a distance greater than the largest expected nip width,

said sensor assembly further including a plurality of electrically conductive lead lines, each said lead line connected to a respective one of said sensing lines.