BACKGROUND OF THE INVENTION The present invention relates to the measurement and trending of the release line of a paper web or sheet from a paper machine roll and/or clothing. More specifically, the present invention relates to an apparatus for measuring and detecting changes in the release line of a paper web or sheet from a paper machine roll and/or clothing as well as a method for measuring changes in the paper web release line from paper machine rolls and/or clothing.

Papermaking machines include a plurality of press rolls and conveyors such as felt conveyors and wires which transport the formed paper web through the machine.

The angle or line at which the web is released from a roll, felt or wire (or similar rotating device in a papermaking machine) is commonly referred to as a release angle or release line. It is known that the release angle or release line is a function of the draw imposed upon the web or sheet, the furnish, grade changes, or the condition or cleanliness of the felt, wire or the roll.

Accordingly, the release line or release angle is also a function of chemical treatment programs employed to keep the felt, wire and press rolls clean and in optimum working condition.

Further, the release line or release angle is also affected by phenomenon such as picking and the existence of stickies, tackies, hot melt and pitch type contaminant outbreaks on the roll or clothing surface which interfere with the release of the sheet. Picking occurs when the web sticks to the roll or clothing. The presence of stickies, tackies and hot melt outbreaks on the roll or clothing surface are commonly associated with the processing of recycled fiber that contains ink, tars, latex, adhesives and other organic compounds. Obviously, the presence of such materials on the roll or clothing surface will adversely affect the release of the paper web or sheet from the surface.

Accordingly, there is a need for a means for monitoring the release line or the release angle of a paper web or sheet from a rotating device of a papermaking machine such as a press roll, felt or wire.

The use of such a monitoring device or method would provide the papermaker with valuable information on the draw imposed on the web or sheet, the furnish, grade changes, felt and wire cleanliness and conditioning as well as roll cleanliness and conditioning. Still further, such a monitoring device or method would provide the papermaker with the capability to adjust machine draws and chemical treatment programs based upon changes in the release line or release angle. Further, such a device or method would provide the papermaker with an effective means of assessing papermaking machine performance.

SUMMARY OF THE INVENTION The present invention satisfies the aforenoted needs by providing a method and apparatus for measuring the release line of a paper sheet from a rotating device as well as monitoring changes in the release line or release angle of a paper sheet from a rotating device.

In an embodiment, the present invention provides an apparatus for measuring a location of a release line of a paper sheet from a rotating device. Specifically, the paper sheet engages the device and extends around at least part of the device as the device rotates. The apparatus includes a distance measuring device that repeatedly measures the distance between the paper sheet as it passes a fixed point downstream of the rotating device and a measuring device. The measuring device transmits the measured distances to a data acquisition system. The data acquisition system stores the measured distances and calculates changes in the measured distances. The changes in the measured distance are indicative of changes in the release line or release angle of the sheet.

From these calculated changes in the measured distances, the papermaker can evaluate changes in the draw, furnish as well as grade changes. Further, the papermaker can evaluate felt, wire and roll conditioning and cleaning as well as felt, wire and roll chemical treatment programs. As a result of the information provided by the apparatus of the present invention, the papermaker can adjust machine draws and chemical treatment programs based upon changes in the release line and trends in the changes in the release line.

In an embodiment, the measuring device comprises a transmitter and a receiver. The transmitter emits a signal directed at the sheet and at the fixed point downstream of the rotating device. The receiver receives the signal after it is reflected off of the paper sheet.

The measuring device measures the transit time for the signal to travel from the measuring device, to the paper sheet and back to the receiver and thereafter calculates a measured distance from the measured travel time.

In an embodiment, the measuring device is disposed vertically above the paper sheet.

In an embodiment, the measuring device is disposed vertically below the paper sheet.

In an embodiment, the paper sheet extends downward and laterally away from the rotating device as it moves downstream from the rotating device. In this embodiment, the measuring device and rotating device may be disposed in a common horizontal plane.

In an embodiment, the measuring device is disposed in a housing and the housing is connected to an air supply. The housing further comprises at least one port for communicating a flow of air around the measuring device. This embodiment prevents mist, dust and other debris from accumulating in the space disposed between the measuring device and the fixed point or the paper sheet which could otherwise interfere with the signal directed at the paper sheet.

In an embodiment, the measuring device is treated with a water repellent to prevent water from accumulating on the measuring device and interfering with the ability of the measuring device to transmit and receive a signal.

In an embodiment, the measuring device is a laser distance measuring device.

In an embodiment, the data acquisition system includes a display for displaying changes in the measured distance over time.

In an embodiment, the rotating device is selected from the group consisting of a center roll, a third press roll, a felt and a wire.

In an embodiment, the present invention provides a method for measuring the location of a release line of a paper sheet from a rotating device. The paper sheet engages the device and extends around at least part of the device as the device rotates. The method comprises the steps of (a) measuring the distance between a first fixed point and the paper sheet as the paper sheet crosses a second fixed point disposed downstream of the rotating device, (b) storing the measured distance, (c) repeating steps (a) and (b), and (d) calculating a change in the measured distance.

In an embodiment, step (a) of the method of the present invention further comprises placing a distance measuring device at the first fixed point. The measuring device comprises a transmitter and a receiver. The transmitter emits a signal directed at the sheet and the second fixed point. The receiver receives the signal after it is reflected off of the paper sheet. The measuring device measures a transit time for the signal to travel from the measuring device, to the paper sheet and back to the receiver and thereafter calculates a measured distance from the measured transit time.

In an embodiment, the first fixed point is disposed vertically above the paper sheet.

In an embodiment, the first fixed point is disposed vertically below the paper sheet.

In an embodiment, the first fixed point and second fixed point are disposed in a common horizontal plane.

It is therefore an advantage of the present invention to provide a papermaker with a means for monitoring changes in the release line and release angle of a paper web or sheet from a rotating device of a papermaking machine.

Another advantage of the present invention is that the papermaker can use information relating to changes in the release line or release angle of a paper web or sheet from a rotating device of a papermaking machine to evaluate the draw, furnish, grade changes, felt and wire conditioning and cleaning and roll conditioning and cleaning as well as felt, wire and roll chemical treatment programs.

A further advantage of the present invention is that the papermaker can use information relating to the trends and the changes of the release angle or release line of a paper sheet or web from a rotating device of a papermaking machine to change the draw, furnish, grade or felt, wire or roll chemical treatment programs.

Still another advantage of the present invention is that it provides an apparatus and a method to measure how well or poorly a paper web or sheet releases from a roll, felt or wire or other rotating device of a papermaking machine.

Still another advantage of the present invention is that it provides the papermaker with a method and apparatus for measuring how well or poorly a paper web or sheet releases from a roll, felt or wire or other rotating device of a papermaking machine on-line or during operation of the machine.

And another advantage of the present invention is that it provides a papermaker with an apparatus for monitoring changes in the release line of the paper web or sheet from a rotating device of a papermaking machine that can be easily installed on an existing machine without substantially interfering with or the need for changing or altering the machine components.

And another advantage of the present invention is that it provides the papermaker with on-line capability to evaluate the release properties of different materials of construction of press rolls and clothing.

Finally, yet another advantage of the present invention is that it enables the papermaker to evaluate the effectiveness of thick stock coagulant chemistries on flocculating or tying up detrimental substances that can interfere with the release of a paper sheet or web from press rolls and clothing.

Other objects and advantages of the invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The present invention is illustrated more or less diagrammatically in the following drawing wherein: Figure 1 is a schematic illustration of a portion of a papermaking machine equipped with an apparatus made in accordance with the present invention.

It should be understood that the drawing is not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein.

DETAILED DESCRIPTION OF THE INVENTION In Figure 1, a release line monitoring apparatus 10 is illustrated as installed in a section 11 of a papermaking machine. The apparatus 10 includes three different embodiments, or three different possible locations of the distance measuring devices or sensors 12a, 12b and 12c. Referring first to sensor 12a, it will be noted that the sensor 12a is disposed vertically below the rotating device 13 around which a paper sheet or web 14 is being conveyed. The rotating device 13 is rotating in the direction of the arrow 15. It will be noted that the rotating device 13 can be a press roll such as a center roll or third press roll or the rotating device 13 can be a felt or a wire or other conveying device utilized in papermaking machines. As the sheet 14 is transported downstream, or in the direction of the arrow 16 by the rotating device 13, it releases from the device 13 at or around the area indicated at 17 for the sheet 14 shown in solid line or the area shown at 17a for the sheet 14a shown in phantom. As a result, a release angle 0 is indicated for the sheet 14 shown in solid line and a release angle P is indicated for the sheet 14a shown in phantom.

Accordingly, during the operation of the papermaking machine, system parameters may vary which affect the release point or release line of the paper sheet 14. The apparatus 10 is provided to monitor the changes in the release point, line or angle of the paper sheet.

Specifically, the apparatus 10 includes a sensor 12a, 12b or 12c mounted in an appropriate position so that it has an unobstructed view through a fixed point disposed downstream of the rotating device 13. Specifically, referring to the sensor 12a, mounted below the rotating device 13, the sensor 12a emits a signal 18a along a straight line which is crossed by the paper sheet 14 as it moves downstream from the rotating device 13. When the paper sheet 14 is being released at the angle 0, the signal 18a detects the release line at the point indicated at 21.

However, should system parameters change which result in the paper sheet 14 either sticking or adhering to the rotating device 13 resulting in a later release at an angle P, the signal 18a of the sensor 12a will engage the paper sheet 14a at the point indicated at 22. The sensor 12a is a distance measuring device.

Accordingly, the distance between the sensor 12a and the point 21 is measured and transmitted to a data/sensor interface 23. The measured distance is then transmitted to a data acquisition system 24 which may comprise a computer or central processing unit with customized trend software installed thereon for performing statistical analysis. Further, as the release point of the sheet 14 moves from the point indicated at 17 to the point indicated at 17a and the signal 18a engages the sheet 14a at the point 22, the shortened distance between the sensor 12a and the point 22 is measured and transmitted to the data acquisition system 24 through the interface 23. The data acquisition system 24 will then calculate the change and distance between the points 21 and 22 and either display that change or analyze that change with an appropriate trend software package installed on the system 24.

Similarly, a sensor 12b may be mounted in a position that is approximately horizontal with or coplanar with the rotating device 13. Again, a signal 18b is transmitted towards the paper sheet 14 and engages the sheet 14 or 14a at the points indicated at 25,26 respectively. The distances between the sensor 12b and the points 25,26 are measured and transmitted to the data acquisition system 24 through the interface 23 as described above for the sensor 12a. Similarly, a sensor 12c may be disposed vertically above the rotating device 13. The device 12c, like the devices 12a and 12b, direct a signal 18c downward which engages the paper sheet 14 at the points 27,28, depending upon the release angle 6 or respectively.

Referring back to the sensor 12a, it will be noted that the sensor 12a is contained within a housing 31.

The housing 31 is connected to an air control packet 32 which, in turn, is connected to an air supply 33. The housing further includes at least one port 34. Air is communicated from the supply 33 by the control package 32 through the port 34 into the housing 31. The blowing air prevents the accumulation of mist and dust in the space around the sensor 12a. A flow of low pressure air around the sensor 12a enhances the reliability of the signal 18a and reduces the chances of the signal 18a being weakened or otherwise interfered with by mist or dust.

Further, the generation of mist or dust around a press roller can cause water to condense on the sensors 12a, 12b and 12c. To alleviate this problem, the sensors 12a, 12b and 12c may be coated with a water repellent.

The flow of low pressure air around the sensors 12a, 12b and 12c will alleviate this problem as well.

The apparatus 10 of the present invention can be employed on the wire at the couch, at the press section, at the dryer section and at the yankee dryers for tissue machines. The sensors 12 are installed at a fixed position, preferably mounted on a papermaking machine frame or other fixed point on the mill floor with a suitable bracket. The interface 23 and data acquisition system 24 can be installed up to 1,000 meters away, preferably in a controlled room with a controlled temperature and reduced humidity environment.

Two sensors or measuring devices are preferred.

Specifically, the distance measuring device sold under the name DME2000 by Sick Optic Electronic, Inc. of Eden Prairie, Minnesota is a preferred device along with its utility software version 2.1. Another preferred device is sold under the tradename DME3000-211S02, also by Sick Optic Electronic, Inc. of Eden Prairie, Minnesota. Both of these sensors can function adequately up to a distance of 8 meters away from the sheet 14 thereby providing flexibility in terms of the mounting and arrangement of the brackets. Further, these sensors are suitable for use on paper sheets of any color, including red. The DME2000 distance measuring device is a 1 kilowatt laser device; the DME3000 measuring device is a 3 kilowatt laser device. It has been determined that the 3 kilowatt laser devices are more effective and more reliable at distances ranging from 4 meters to 8 meters.

It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be covered by the appended claims.