EP4781022A1 - Seal strip wear monitoring systems and assemblies therefor - Google Patents

Abstract

A seal strip of a suction roll of a paper machine having a wear monitoring system includes: a seal strip having an upper surface; and a wear monitoring system. The wear monitoring system includes a sensor comprising a first conductive layer, a second conductive layer, and a resistive layer, the first and second conductive layers being mounted on the resistive layer, the second conductive layer being separated from the first conductive layer. The wear monitoring system further comprises a signal processor electrically connected to the first and second conductive layers and configured to process signals related to resistance between the first and second conductive layers. The sensor is at least partially embedded in the seal strip.

Description

SEAL STRIP WEAR MONITORING SYSTEMS AND ASSEMBLIES THEREFOR

Related Application

[0001] The present application claims priority from and the benefit of U.S. Provisional Patent Application No. 63/584,626, filed September 22, 2023, the disclosure of which is hereby incorporated herein by reference in full.

Field of the Invention

[0002] The present invention is directed generally to papermaking, and more specifically to suction rolls and equipment within a papermaking machine.

Background of the Invention

[0003] Paper manufacturing inherently requires at many points in the production process the removal of water. In general, the paper pulp (slurry of water and wood and other fibers) rides on top of a felt (in the form of a wide belt) which acts as a carrier for the wet pulp before the actual sheet of paper is formed. Felts are used to carry the pulp in the wet section of the paper machine until enough moisture has been removed from the pulp to allow the paper sheet to be processed without the added support added by the felt.

[0004] Quite commonly on the wet end of a paper machine, initial water removal is accomplished using a suction roll in a press section (be it a couch, pickup, or press suction roll) used in conjunction with a standard press roll without holes (or against a Yankee dryer in a tissue machine) that mates in alignment with the suction roll. The felt pulp carrier is pressed between these two rolls.

[0005] The main component of a suction roll 10 includes a hollow shell 12 (FIG. 1) made of stainless steel, bronze or other metal that has tens of thousands of holes, drilled in a prescribed pattern radially around the circumference of the roll. These holes are gauged in size (ranging from under 1/8" to nearly %") and are engineered for the particular paper material to be processed. It is these holes that form the "venting" for water removal. This venting can typically range from approximately 20 to 45 percent of the active roll surface area. The suction roll shell is driven by a drive system that rotates the shell around a stationary core called a suction box.

[0006] The suction box 20 (FIG. 2) can be thought of as conventional long rectangular box without a lid on the top and with ports on the end, bottom or sides. The end (specifically the drive end) of the box typically has a pilot bearing, of which the inner raceway is a pilot bushing or bearing with a slip fit to a journal on the suction box and the outer raceway is pressed onto the rotating shell. The suction box 20 is connected with a suction source (e.g., a vacuum pump). An exemplary suction box and shell are shown in U.S. Patent No. 6,358,370 to Huttunen, the disclosure of which is hereby incorporated herein in its entirety. [0007] In order to take advantage of the holes in the shell, a vacuum zone 30 must be created using these ports on the inside of the suction roll shell in a zone that is directly underneath the paper pulp that is being processed. This is accomplished by the suction box 20 using a slotted holder 32 which holds a seal along the long axis of the suction box on both sides. FIG. 2 shows the slotted holders 32, and FIGS. 3 and 4 show two varieties of seals 34, 34' which are in the form of strips (hereinafter "seal strips"). In addition to these long seals there are two shorter seals (called end deckles) on the short ends (called tending and drive ends) that permit some axial adjustment as needed to accommodate various sheet widths.

[0008] The seal strips 34, 34' are usually made of rubberized polymerized graphite and are held nearly in contact with the inner surface of the shell 12 during operation (see FIGS. 3 and 4). Between the seal strips 34, 34' a constant vacuum is drawn. This allows the vacuum zone 30 to be created underneath the sheet 40 as is passes over the roll 10. The seal strips 34, 34' are biased upwardly toward the suction roll shell 12 by load tubes 42, which are sealed hoses that run underneath the entire length of the seal strip 34, 34'. Pressure in the load tube 42 expands the load tube 42 (much like air in a balloon) and lifts the seal strip 34, 34' toward the inside surface of the shell 12. This effect, along with help from the system vacuum from the suction box 20 and the laminar flow of lubrication water mentioned previously, forms the seal between the edge of the seal strip 34 and the inside of the shell 12.

[0009] In actual application, in a properly functioning suction roll the seal strips 34, 34' never directly contact the inside of the suction roll shell 12. If the seal strips 34, 34' were to contact the shell 12 they would wear away and would quickly lose their sealing ability. In order to eliminate or significantly reduce this wear and to provide a seal, water is applied along the length of the seal strips 34, 34' with a lubrication shower formed with water flowing through a spray nozzle 24 (see FIG. 2). This shower keeps the seal strips 34, 34' lubricated with a laminar flow of water between the seal surface and the inside surface of the shell 12.

[0010] The amount of water used for lubrication should be gauged properly so that the proper amount of lubrication is applied to keep the seal strips 34, 34' lubricated, but not so much to either become an issue for the pulp being processed or to be wasting water. In addition, process water used in a paper mill may contain chemicals and also significant particulates that may clog the lubrication shower nozzles 24 during normal operation. Since these nozzles 24 are located inside the rotating shell 12 they are not visible to the paper machine operator.

[0011] Seal strips are typically replaced periodically after some degree of wear occurs. However, because the seal strips inside a suction roll are not visible to the operator of the paper making equipment or to anyone trying to view the seal strips, many conditions inside an operating suction roll, including the degree of seal strip wear, are unknown. As such, a reliable method of detecting seal strip wear to inform the operator of the papermaking equipment that maintenance is needed on the equipment before a failure occurs may be desirable.

Summary of the Invention

[0012] As a first aspect, embodiments of the inventions are directed to a seal strip of a suction roll of a paper machine having a wear monitoring system comprising: a seal strip having an upper surface; and a wear monitoring system. The wear monitoring system comprises a sensor comprising a first conductive layer, a second conductive layer, and a resistive layer, the first and second conductive layers being mounted on the resistive layer, the second conductive layer being separated from the first conductive layer. The wear monitoring system further comprises a signal processor electrically connected to the first and second conductive layers and configured to process signals related to resistance between the first and second conductive layers. The sensor is at least partially embedded in the seal strip.

[0013] As a second aspect, embodiments of the invention are directed to a seal strip of a suction roll of a paper machine having a wear monitoring system comprising a seal strip having an upper surface and a wear monitoring system. The wear monitoring system comprises: a sensor comprising a first conductive layer, a second conductive layer, and a resistive layer, the first and second conductive layers being mounted on the resistive layer, the second conductive layer being separated from the first conductive layer; and a signal processor electrically connected to the first and second conductive layers and configured to process signals related to resistance between the first and second conductive layers. The first conductive layer has a free end adjacent the upper surface of the seal strip, the free end defining an edge of the first conductive layer, the edge being generally parallel with the upper surface. The sensor is rolled into a coiled configuration and is at least partially embedded in the seal strip within a hole therein.

[0014] As a third aspect, embodiments of the invention are directed to a seal strip of a suction roll of a paper machine having a wear monitoring system comprising a seal strip having an upper surface and a wear monitoring system. The wear monitoring system comprises: a sensor comprising a first conductive layer, a second conductive layer, and a resistive layer, the first and second conductive layers being mounted on a common surface of the resistive layer, the second conductive layer being separated from the first conductive layer; and a signal processor electrically connected to the first and second conductive layers and configured to process signals related to resistance between the first and second conductive layers. The sensor is at least partially embedded in the seal strip. The first conductive layer has a free end adjacent the upper surface of the seal strip, the free end defining an edge of the first conductive layer, the edge being generally parallel with the upper surface. The first conductive layer narrows in width as the first conductive layer extends from the edge away from the upper surface.

Brief Description of the Figures

[0015] FIG. 1 is a perspective end view of a typical paper machine suction roll.

[0016] FIG. 2 is an enlarged perspective end view of the suction box area of a typical suction roll.

[0017] FIG. 3 is an end view of the suction box area and seal strips of a conventional suction roll.

[0018] FIG. 4 is an end view of the suction box area and seal strips of another conventional suction roll.

[0019] FIG. 5 is a schematic perspective view of a wear sensor for a seal strip according to embodiments of the invention. [0020] FIG. 6 is a schematic perspective view of a wear sensor for a seal strip according to alternative embodiments of the invention.

[0021] FIG. 7 is a schematic perspective view of a wear sensor for a seal strip according to further embodiments of the invention.

[0022] FIG. 8 is a schematic perspective view of a wear sensor for a seal strip according to still further embodiments of the invention.

[0023] FIG. 9 is a schematic partial perspective view of the wear sensor of FIG. 8 in a coiled configuration.

[0024] FIG. 10 is a schematic front section view of the wear sensor of FIG. 8 embedded in a seal strip.

[0025] FIG. 11 is a top perspective view of the seal strip and wear sensor of FIG. 10 embedded in a seal strip.

Detailed Description of the Embodiments

[0026] The present invention will now be described more fully hereinafter, in which embodiments of the invention are shown. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements throughout. Thicknesses and dimensions of some components may be exaggerated for clarity.

[0027] In addition, spatially relative terms, such as "under", "below", "lower", "over", "upper" and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "under" or "beneath" other elements or features would then be oriented "over" the other elements or features. Thus, the exemplary term "under" can encompass both an orientation of over and under. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0028] Well-known functions or constructions may not be described in detail for brevity and/or clarity.

[0029] Referring now to the drawings, a wear sensor for use in a seal strip for papermaking machine is designated broadly at 100 and illustrated in FIG. 5. As used herein, the term "papermaking machine" is intended to include any machine for making paper products, including traditional paper, paperboard/cardboard, tissue, toilet paper, and the like. The sensor 100 includes two conductive layers 102, 104 that are parallel to but spaced apart from each other. A resistive layer 106 is sandwiched between the conductive layers 102, 104. A respective lead 108, 110 is connected with and extends from each of the conductive layers 102, 104. The leads 108, 110 are routed to a device (such as an ohmmeter 114) that detects the resistance across the conductive layers 102, 104. The ohmmeter 114 is operatively connected with a processor 116 that receives signals therefrom and processes the signals into an indication of the extent of wear experienced by the seal strip. [0030] The structure of the sensor 100 is such that, as the area of the layers 102, 104, 106 shrinks (for example, due to wear beginning at the free end F of the sensor 100), the resistance measured between the layers 102 increases. Thus, if a sensor 100 were embedded in a seal strip with the free end F parallel to and at or near the wear surface of the seal strip, wear experienced by the seal strip during operation would also begin to wear away the free end F of the sensor 100, thereby reducing the area of the layers 102, 104, 106 and increasing the measured resistance of the sensor 100. The increase in voltage can be correlated to the extent (e.g., the depth) of wear of the seal strip.

[0031] Referring now to FIG. 6, another embodiment of a sensor is shown therein and designated broadly at 200. The sensor 200 includes two conductive layers 202, 204 separated by a resistive layer 206 and leads 208, 210 similar to the sensor 100. However, as can be seen in FIG. 6, the conductive layers 202, 204 are triangular in shape, as is the resistive layer 206 sandwiched by the conductive layers 202, 204. The leads 208, 210 attach to one of the "points" of the triangle defined by the conductive layers 202, 204. The leads 208, 210 attach to an ohmmeter and processor or the like that detect the resistance between the conductive layers and provides an indication of wear.

[0032] The sensor 200 is embedded in a seal strip with its free end F2 (the side of the conductive layers 202, 204 and the resistive layer 206 opposite the attachment point with the leads 208, 210) positioned parallel to and at or near the wear surface of the seal strip. During operation, wear on the seal strip wears away the free end F2. As this happens, the area of the layers 202, 204, 206 shrinks, thereby increasing the resistance between the conductive layers 202, 204. However, because the end of the sensor 200 adjacent the leads 208, 210 is considerably narrower than the free end F2, the rate at which the area of the layers 202, 204, 206 shrinks is increased compared to that of the sensor 100. As a result, the resistance between the conductive layers 202, 204 increases at a greater rate with a similar depth of wear as compared to the sensor 100. This increase in resistance between the sensors 100, 200 for the same depth of wear can render the sensor 200 more sensitive for small differences in wear depth. [0033] Referring now to FIG. 7, another wear sensor, designated broadly at 300, is illustrated therein. The sensor 300 includes conductive layers 302, 304 that are mounted on a resistive layer 306, but in this embodiment the conductive layers 302,304 are mounted on the same side of the resistive layer 306 and are separated by a gap 314. Leads 308, 310 are connected with, respectively, layers 302, 304. The leads 308, 310 are connected with an ohmmeter/processor as discussed above that can detect the resistance between the conductive layers 302, 304.

[0034] As with the sensors 100, 200, the sensor 300 is mounted within the seal strip so that its free end F3 is parallel to and positioned at or near the wear surface of the seal strip. As the seal strip experiences wear, the free end F3 of the sensor 300 begins to wear away, with an accompanying increase in resistance. Detection of the increase in resistance can then be correlated with the extent of wear of the seal strip in the manner described above.

[0035] This sensor embodiment may have an advantage over the sensors 100, 200 in that, because the conductive layers 302, 304 do not directly overlie each other, the risk of a "short circuit" occurring between the layers 302, 304 is reduced or eliminated, whereas damage to the resistive layer in either of the sensors 100, 200 may result in a short circuit. [0036] Another wear sensor, illustrated in FIG. 8 and designated broadly at 400, has a similar construction to that of sensor 300 in that its conductive layers 402, 404 are mounted on the same surface of the resistive layer 406 rather than on opposite sides. However, the conductive layer 402 is similar to the conductive layer 202 of the sensor 200 in that it is wider at its free end F4 than at the end connected with the lead 408. As a result, as the free end F4 wears away, the resistance detected by an ohmmeter/processor as discussed above attached to the leads 408, 410 will be greater than at the same depth for the sensor 300, thereby potentially providing a more precise/sensitive measurement of wear of the seal strip.

[0037] When installed in a seal strip, any of the sensors 100, 200, 300, 400 may maintain the flat configuration shown in FIGS. 5-8. However, a flat configuration is not required. FIG. 9 illustrates a configuration in which the sensor 400 of FIG. 8 is rolled into a coiled configuration (i.e., the sensor 400 is rolled about an axis that is parallel with the wear axis of the sensor 400), such that the free end F4 of the sensor 400 presents a spiraled arrangement at or near the wear surface of the seal strip.

[0038] FIGS. 10 and 11 illustrate how the sensor 400 can be installed in a seal strip 450. A hole 452 can be drilled or otherwise formed in the seal strip 450, and the sensor 400, with its leads 408, 410, can be inserted into the hole 452. In some embodiments, the hole 452 may be partially or completely filled with a potting compound (e.g., epoxy). The leads 408, 410 extend from the lower end of the hole to attach to an ohmmeter/processor as discussed above. It can also be seen in FIG. 10 that in some embodiments, additional wires may extend between sensors installed at other locations in the seal strip 450 in order to provide a full wear profile across the length of the seal strip 450. Additional discussion about the use of multiple wear sensors and how signals may be extracted therefrom is discussed in U.S. Patent Application No. 18/347,943, filed July 6, 2023, the disclosure of which is hereby incorporated herein by reference in full.

[0039] The sensors 100, 200, 300, 400 may be formed of any materials deemed to be suitable for creating resistance between the conductive layers that can be measured. In some embodiments, the conductive layers (e.g., layers 402 and 404) may be formed from a copper foil. In other embodiments, the resistive layer may be formed of a carbon film. Either or both of these materials have sufficient resilience that, when included as thin sheets, they can easily be coiled into the form of FIGS. 9-11 without fracturing or cracking the sensor. In some embodiments, the conductive layers may be mounted on the resistive layer via a conductive adhesive, such as electrically conductive acrylic (which may be preapplied to a metallic tape, such as copper tape), or an electrically conductive epoxy. The conductive adhesive may provide a conductive boundary layer that can introduce additional resistance.

[0040] Those of skill in this art will appreciate that the sensors illustrated herein may take other forms. For example, although the various leads discussed herein are illustrated as bare wires, in many embodiments the wires may be insulated to prevent damage and/or shorting. Also, the conductive layers 202, 204, 402 are shown as being generally triangular in shape; however, other shapes in which the conductive layer narrows from its free end to its mounting location with its lead may also be employed. As one example, the long edge of the conductive layer 402, which is shown in FIG. 8 as being a straight line, may instead follow an arcuate path (e.g., a logarithmic path), which may enable the sensor to be tuned for optimal precision. Other variations may be contemplated by those of skill in this art.

[0041] Further, in some embodiments the wear sensors 100, 200, 300, 400 may be accompanied by temperature sensors that are also embedded in the seal strip. [0042] The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.

Claims

What is claimed is:

1. A seal strip of a suction roll of a paper machine having a wear monitoring system, comprising: a seal strip having an upper surface; and a wear monitoring system, comprising: a sensor comprising a first conductive layer, a second conductive layer, and a resistive layer, the first and second conductive layers being mounted on the resistive layer, the second conductive layer being separated from the first conductive layer; and a signal processor electrically connected to the first and second conductive layers and configured to process signals related to resistance between the first and second conductive layers; wherein the sensor is at least partially embedded in the seal strip.

2. The seal strip and wear monitoring system defined in Claim 1, wherein the resistive layer has first and second opposed surfaces, and wherein the first conductive layer and the second conductive layer are mounted to the first surface.

3. The seal strip and wear monitoring system defined in Claim 1, wherein the resistive layer has first and second opposed surfaces, and wherein the first conductive layer is mounted to the first surface and the second conductive layer is mounted to the second surface.

4. The seal strip and wear monitoring system defined in Claim 1, wherein the first conductive layer has a free end adjacent the upper surface of the seal strip, the free end defining an edge of the first conductive layer, the edge being generally parallel with the upper surface.

5. The seal strip and wear monitoring system defined in Claim 4, wherein the first conductive layer defines a generally triangular footprint on the resistive layer, wherein the edge of the first conductive layer defines one side of the triangular footprint.

6. The seal strip and wear monitoring system defined in Claim 5, wherein the second conductive layer defines a generally triangular footprint on the resistive layer.

7. The seal strip and wear monitoring system defined in Claim 4, wherein the first conductive layer narrows in width as the first conductive layer extends from the edge away from the upper surface.

8. The seal strip and wear monitoring system defined in Claim 7, wherein the second conductive layer narrows in width as the second conductive layer extends away from the upper surface.

9. The seal strip and wear monitoring system defined in any preceding claim, wherein the first conductive layer comprises a metallic foil.

10. The seal strip and wear monitoring system defined in any preceding claim, wherein the resistive layer comprises carbon film.

11. The seal strip and wear monitoring system defined in any preceding claim, wherein the sensor is rolled into a coiled configuration.

12. A seal strip of a suction roll of a paper machine having a wear monitoring system, comprising: a seal strip having an upper surface; and a wear monitoring system, comprising: a sensor comprising a first conductive layer, a second conductive layer, and a resistive layer, the first and second conductive layers being mounted on the resistive layer, the second conductive layer being separated from the first conductive layer; and a signal processor electrically connected to the first and second conductive layers and configured to process signals related to resistance between the first and second conductive layers; wherein the first conductive layer has a free end adjacent the upper surface of the seal strip, the free end defining an edge of the first conductive layer, the edge being generally parallel with the upper surface; and wherein the sensor is rolled into a coiled configuration and is at least partially embedded in the seal strip within a hole therein.

13. The seal strip and wear monitoring system defined in Claim 12, wherein the resistive layer has first and second opposed surfaces, and wherein the first conductive layer and the second conductive layer are mounted to the first surface.

14. The seal strip and wear monitoring system defined in Claim 12, wherein the resistive layer has first and second opposed surfaces, and wherein the first conductive layer is mounted to the first surface and the second conductive layer is mounted to the second surface.

15. The seal strip and wear monitoring system defined in Claim 12, wherein the first conductive layer narrows in width as the first conductive layer extends from the edge away from the upper surface.

16. The seal strip and wear monitoring system defined in any preceding claim, wherein the first conductive layer comprises a metallic foil.

17. A seal strip of a suction roll of a paper machine having a wear monitoring system, comprising: a seal strip having an upper surface; and a wear monitoring system, comprising: a sensor comprising a first conductive layer, a second conductive layer, and a resistive layer, the first and second conductive layers being mounted on a common surface of the resistive layer, the second conductive layer being separated from the first conductive layer; and a signal processor electrically connected to the first and second conductive layers and configured to process signals related to resistance between the first and second conductive layers; wherein the sensor is at least partially embedded in the seal strip; and

Y1 wherein the first conductive layer has a free end adjacent the upper surface of the seal strip, the free end defining an edge of the first conductive layer, the edge being generally parallel with the upper surface; and wherein the first conductive layer narrows in width as the first conductive layer extends from the edge away from the upper surface.

18. The seal strip and wear monitoring system defined in Claim 17, wherein the first conductive layer comprises a metallic foil.

19. The seal strip and wear monitoring system defined in Claim 17, wherein the first conductive layer narrows in width as the first conductive layer extends from the edge away from the upper surface.

20. The seal strip and wear monitoring system defined in Claim 17, wherein the sensor is rolled into a coiled configuration.