A belt for a pulp or papermaking machine having a sensor for detecting pressure during operation, and a press using the same.

Abstract

The pressure-sensing belt for shoe presses and the like comprises: a substantially cylindrical polymer belt having a longitudinal axis, a radial inner surface, and a radial outer surface; a plurality of widthwise (CD) reinforcing fibers extending along the longitudinal axis for the length of the belt between the inner surface and the outer surface; a plurality of longitudinal (MD) reinforcing fibers extending circumferentially with respect to the longitudinal axis between the inner surface and the outer surface; and a plurality of piezoelectric fibers extending within the belt, each of which has a sensing portion and a signal transmission portion.

Description

Technical Field

[0001] This application claims the priority and benefit of U.S. Provisional Patent Application No. 63 / 501,893, filed on May 12, 2,023, the disclosure of which is incorporated herein by reference.

[0002] The present invention generally relates to nip presses and more particularly to shoe presses.

Background Art

[0003] In a conventional fourdrinier papermaking process, an aqueous slurry or suspension of cellulose fibers (known as paper “stock”) is supplied to the upper run of a woven wire or synthetic material endless belt that moves between two or more rolls. The belt is often referred to as a “forming fabric” and forms a papermaking surface on the upper surface thereof, and the papermaking surface functions as a filter to separate the cellulose fibers of the papermaking from the aqueous medium, thereby forming a wet paper web. The aqueous medium is discharged by gravity or by vacuum on the lower surface of the upper run (i.e., the “machine side”) through the mesh openings (known as drainage ports) of the forming fabric.

[0004] After leaving the forming section, the paper web is sent to the press section of the papermaking machine, where it passes through the nips of one or more presses (often roller presses) covered with another cloth typically referred to as "press felt." The pressure from the press removes further moisture from the web. This moisture removal is often enhanced by the presence of a "batt" layer of press felt. The paper is then sent to the dryer section for further moisture removal. After drying, the paper is prepared for secondary processing and packaging.

[0005] For the past 35 to 40 years, "shoe presses" have been developed for the press section of papermaking machinery. A shoe press comprises a roll or similar structure that mates with an opposing roll or a shoe of the press structure. The surface of the shoe is slightly concave, and its curvature approximates the convex contour of the mating roll. This arrangement widens the nip in the paper transport direction, thereby allowing more moisture to be removed within the nip.

[0006] Endless belts or blankets have traditionally been used in shoe press operations. The belt overlaps and contacts the shoe of the press machine. The press felt overlaps the shoe press belt, and the paper web overlaps the press felt. The shoe press belt and press felt pass through the nip, in which case the paper web is transported to the nip. The press felt moves above a set of rollers arranged around the shoe. In conventional embodiments, the shoe press belt was also driven by a set of drive rollers arranged around the shoe. However, in some recent configurations, the shoe press belt is clamped or fixed to the edges of circular head plates located at both ends of the shoe, so that the shoe press belt rotates and passes through the nip due to the rotation of the head plates.

[0007] Considering performance requirements, shoe press belts must be flexible enough to pass around the drive rollers or head plate and through the shoe, and durable enough to withstand the repeated pressure applied within the nip. For these performance parameters, most endless belts are made entirely or largely from polymer material (often polyurethane). Many shoe press belts also include reinforcing fibers or reinforcing fabric embedded between or within the polymer layers. Additionally, shoe press belts may be configured to allow moisture to permeate easily from the paper web. For this reason, some shoe press belts have grooves or blind-drilled holes on the surface adjacent to the press felt, which serve to drain moisture from the paper as it is discharged from the press felt.

[0008] Understanding the pressure profile applied to the paper web as it is transported through the nip is crucial. Fluctuations in nip pressure can affect the amount of moisture released from the paper web, thereby potentially impacting the moisture content, thickness, and other properties of the final sheet. Excessive nip pressure can cause the web to collapse or tear. Of course, in a shoe press, the pressure typically varies at various points within the nip, both along and transverse to the paper transport direction, and can also vary over time. [Overview of the project] [Problems that the invention aims to solve]

[0009] As a result, it is desirable to have reliable techniques and equipment for determining the pressure distribution and area of ​​the nip in a shoe press. [Means for solving the problem]

[0010] In a first aspect, embodiments of the present invention are directed toward a pressure-sensing belt for shoe presses and the like. The belt comprises a substantially cylindrical polymer belt having a longitudinal axis, a radial inner surface and a radial outer surface; a plurality of reinforcing cross-machine (CD) fibers extending over the length of the belt parallel to the longitudinal axis between the inner surface and the outer surface; a plurality of reinforcing machine direction (MD) fibers extending circumferentially with respect to the longitudinal axis between the inner surface and the outer surface; and a plurality of piezoelectric fibers extending within the belt, each of which has a sensing portion and a signal-carrying portion.

[0011] In a second respect, embodiments of the present invention are directed toward a shoe press that uses the belt described above. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is an end view of the shoe press of the present invention. [Figure 2] Figure 2 is a front cross-sectional view of the lower roll and shoe press belt of the shoe press shown in Figure 1. [Figure 3] Figure 3 is a perspective view of the shoe press belt in Figure 1, in which the outer polymer layer has been removed and the CMD fibers are exposed. [Figure 4] Figure 4 is a partially enlarged end view showing the reinforcing fibers and piezoelectric fibers of the shoe press belt in Figure 1. [Figure 5] Figure 5 is a partially enlarged perspective view of the shoe press belt in Figure 1, in which the outer polymer layer has been removed to reveal the reinforced CMD fibers and piezoelectric fibers. [Figure 6] Figure 6 is a schematic front view of an exemplary piezoelectric fiber used in the shoe press belt shown in Figure 1. [Figure 7A] Figure 7A is a schematic front view of another exemplary piezoelectric fiber that can be used in the shoe press belt of Figure 1. [Figure 7B] Figure 7B is a schematic front view of the piezoelectric fiber shown in Figure 7A, with the piezoelectric core cut. [Figure 8] Figure 8 is a partial perspective view of the shoe press belt in Figure 1, in which the sensing portions of the plurality of piezoelectric fibers, which are shown at different lengths, are capable of sensing different axial positions on the shoe press belt. [Figure 9] Figure 9 is a front cross-sectional view of the shoe press shown in Figure 2, and the processing unit is schematically shown. [Modes for carrying out the invention]

[0013] Herein, the present invention is described in more detail below with reference to the accompanying drawings illustrating embodiments of the invention. However, the present invention may be carried out in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure is thorough and complete and so that those skilled in the art may fully understand the scope of the invention.

[0014] The same number refers to the same element throughout the diagram. In the diagram, the thickness of certain lines, layers, components, elements, or functions may be exaggerated for clarity. Dashed lines indicate arbitrary functions or operations unless otherwise specified.

[0015] The terms used herein are intended solely to describe specific embodiments and are not intended to limit the invention. Where used herein, the singular forms “one” (a, an) and “the” are intended to also include the plural forms unless the context clearly indicates otherwise. Where used herein, the words “~equipped with” and / or “~equipped with” indicate the presence of the described feature, integer, step, operation, element and / or component, but it will be further understood that they do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. Where used herein, the word “and / or” includes any and all combinations of one or more of the associated enumerated items. Where used herein, phrases such as “X~Y” and “about X~Y” should be interpreted as including X and Y. Where used herein, phrases such as “about X to Y” mean “about X to about Y.” Where used herein, phrases such as “about X~Y” mean “about X to about Y.”

[0016] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as generally understood by one of the ordinary people skilled in the art to which this invention pertains. Furthermore, unless expressly defined herein, terms as defined in commonly used dictionaries should be interpreted as having the meaning consistent with their meanings in the context of this application and related art, and should not be interpreted in an idealized or overly formal sense. Well-known functions or configurations may not be described in detail for the sake of brevity and / or clarity.

[0017] When an element is referred to as being "on top of" another element, "attached" to another element, "connected" to another element, "bonded" to another element, or "in contact" with another element, it is possible that the element is directly attached to, connected to, bonded to, or in contact with the other element, or that an intervening element may also be present. In contrast, when an element is described, for example, "directly on top of" another element, "directly attached" to another element, "directly connected" to another element, "directly bonded" to another element, or "in direct contact" with another element, no intervening element is present. Furthermore, a reference to a structure or feature positioned "adjacent" to another feature will be understood by those skilled in the art to mean that it may have a portion that overlaps with the adjacent feature or a portion that lies beneath the adjacent feature.

[0018] Referring to FIGS. 1 and 2, a press is schematically shown at 20. The press 20 includes an upper roll 24 mating with a lower roll 22, defining a nip 25 through which a web or sheet, such as a paper web 37, can pass between the lower roll 22 and the upper roll 24. Each of the lower roll 22 and the upper roll 24 defines an individual axis A1 and A2. The axes A1 and A2 are substantially parallel to each other and substantially perpendicular to the direction MD in which the web 37 moves. As shown in FIG. 1, press felts 35 and 36 are disposed between the lower roll 22 and the upper roll 24. The press felts 35 and 36 are driven around sets of individual drive rollers 35a and 36a by the lower roll 22 and the upper roll 24. The web 37 is conveyed by the press felts 35 and 36 and between the press felts 35 and 36.

[0019] Referring again to FIGS. 1 and 2, the lower roll 22 includes a beam 26 extending parallel to axis A1. The beam 26 includes a circular shaft 28 engaged with and supported by brackets 30 at both of its ends. A shoe 32 having a concave pressing surface 33 extends upward from the beam 26. The shoe 32 is mounted on the beam 26 such that it can be controllably biased upward. The biasing of the shoe 32 can be performed, for example, by a hydraulic system (not shown). A circular head plate 34 is rotatably attached to each shaft 28 spaced from an end of the shoe 26. By bearings 37, the head plate 34 can be rotated on the shaft 28.

[0020] Around each head plate 34, a substantially cylindrical shoe press belt or sleeve 40 is attached such that its longitudinal axis is substantially parallel to axis A1. The shoe press belt 40 is fixed to the head plate 34 (by means of a clamp or the like) so that when the head plate 34 rotates about the shaft 28, the shoe press belt 40 also rotates. Typically, the shoe press belt 40 has a diameter of about 40 to about 84 inches and a length of about 120 to about 480 inches.

[0021] As shown in FIG. 1, the lower roll 22 and the upper roll 24 are arranged relative to each other such that the upper roll 24 deflects the shoe press belt 40 from a cylindrical shape and conforms to the shape of the pressing surface 33 of the shoe 32. The pressing surface 33 of the shoe 32 has a shape that is substantially complementary to the convex shape of the upper roll 24. As a result, the nip 25 has a wide width and extends in the direction MD (this dimension is typically about 3 inches to about 12 inches). Both the shoe 32 and the upper roll 24 can be adjusted so as to be able to control the magnitude and distribution of the pressure in the nip 25. In particular, the shoe 32 may be made rotatable about an axis parallel to axis A1, whereby the pressure can be adjusted along the web travel direction MD. When the shoe press belt 40 rotates together with the head plate 34, a part of it is deflected by the contact surface 24a of the upper roll 24 and contacts the contact surface 33 of the shoe 32.

[0022] Those skilled in the art will recognize that the present invention may be suitable for shoe presses of other configurations. For example, the lower roll 22 may comprise a fixed shaft and a hydraulic shoe (e.g., available from Voith Group, Heidenheim, Germany under the trademark NipcoFlex), or it may be replaced by a shoe alone, where the shoe press belt is guided across the shoe by a set of drive rollers. The upper roll 24 may be hydraulically supported (as in the NipcoFlex press described above), may comprise an adjustable convex shoe (e.g., available from Voith Group under the trademark NipcoFlex), or may not have an adjustment function. Other exemplary shoe presses include those available from Valmet (SymBelt), Bellmer (TURBOPRESS), and Beloit (ENP-C). Furthermore, the lower and upper members may be oriented such that the concave pressing surface of the shoe faces the upper member of the shoe press, and the convex pressing surface faces the lower member of the shoe press. These and other suitable configurations of shoe presses are described and illustrated in Joint Textbook Committee of the Paper Industry, Pulp and Paper Manufacture, Vol. 7, 267-70 (Third Edition, 1991). Alternative configurations should include a shoe with an adjustable concave pressure surface and a mating structure (e.g., rolls or opposing convex shoes) that forms a nip through which the shoe press belt passes.

[0023] Figures 3 to 5 show the shoe press belt 40 in more detail. The majority of the shoe press belt 40 consists of a polymer material, such as polyurethane or rubber, which serves as the matrix 42. Typically, the material constituting the entire matrix 42 is the same, but it does not necessarily have to be the same. The matrix 42 may consist of layers of different materials. An exemplary material for use in the matrix 42 is a polyurethane material having a Shore A hardness value of about 55 to about 100.

[0024] As can be seen in Figure 4, the shoe press belt 40 also includes reinforcing threads or fibers. One set of fibers 44 is routed in the MD direction (i.e., often as a single continuous spirally wound fiber, the shoe press belt 40 extends circumferentially within the matrix 42 of the shoe press belt 40). Another set of fibers 46 is located outside the MD fibers 44 and is routed in the CMD direction (i.e., the shoe press belt 40 extends axially within the matrix of the shoe press belt 40). The fibers 44 and 46 may be any known to be suitable for reinforcement of the shoe press belt 40. The fibers 44 and 46 may be formed in any size and material suitable for use in the shoe press belt. Exemplary fibers include those formed from polyester, nylon, or ultra-high molecular weight polyethylene (UHMWPE), which may be about 1,000 to 1,200 denier and twisted in 2, 3, or 6 plies. Fibers 44 and 46 may be present at any density / frequency, but are typically spaced so that 8 to 12 fibers are present per inch.

[0025] Fibers 44 and 46 are incorporated within the shoe press belt 40 to provide reinforcement in the longitudinal and width directions. When used herein, fibers 44 and 46 are intended to encompass both woven fabrics (e.g., as shown in U.S. Patent No. 5,196,092 to Stigberg) and reinforcing structures, such as those illustrated (including, for example, the structures described and illustrated in U.S. Patent No. 5,525,194 to Jermo), and their disclosures are incorporated herein in their entirety.

[0026] The radially outward-facing surface of the matrix 42 of the shoe press belt 40 may be provided with grooves or the like that can improve the dewatering capacity of the shoe press belt 40. Such grooves are typically MD grooves, but they may also be provided with holes or the like. Exemplary groove patterns are illustrated and described in U.S. Patent No. 8,083,899 to Kawamata, the disclosure of which is incorporated herein by reference in its entirety.

[0027] As shown in Figure 5, the shoe press belt 40 also includes a plurality of piezoelectric fibers 100 that serve as pressure sensors. The plurality of piezoelectric fibers 100 are configured to include a sensing portion 102 that generates a signal under pressure, and a signal transmission portion 104 (see Figure 6) that transmits the signal from the sensing portion 102 to a processing unit 56 (described later). For example, the sensing portion 102 may be made of a piezoelectric material, such as piezoelectric polymers, piezoelectric ceramics, and piezoelectric composites. The signal transmission portion 104 may be any type of communication cable to which the information generated by the sensing portion 102 can be transmitted. Exemplary materials for the signal transmission portion may be magnetic wire or other conductive wire (insulated or non-insulated). In some cases, the piezoelectric fiber 100 may also include a non-conducting portion 106 (see Figure 6) (e.g., polyester fiber) that extends beyond the piezoelectric portion.

[0028] In some cases, the piezoelectric fiber 100 may be one layer or component of a multilayer fiber or a multicomponent fiber. For example, the piezoelectric fiber 100 may be the core of a multilayer fiber that also includes an outer protective sheath made of a different material (see Figure 7A).

[0029] The plurality of piezoelectric fibers 100 are shown herein as CD fibers, but in some embodiments, the piezoelectric fibers may also be included longitudinally. Typically, the plurality of piezoelectric fibers 100 are arranged practically equidistant from one another along the shoe press belt 40. For example, the piezoelectric fibers 100 may be spaced at approximately 15 degrees apart so that the shoe press belt 40 contains 24 piezoelectric fibers 100.

[0030] As shown in the embodiment and in Figure 9, each of the plurality of piezoelectric fibers 100 is configured such that the sensing unit 102 is positioned at a different axial position on the shoe press belt 40. (For example, the first sensing unit 102 may be positioned adjacent to one end of the shoe press belt 100, the second sensing unit 102 may be positioned 12 inches from that end of the shoe press belt 100, the third sensing unit 102 may be positioned 24 inches from that end of the shoe press belt 100, and similarly, they may be positioned along the entire length of the shoe press belt 40. This type of arrangement allows for pressure measurement at different axial positions on the shoe press belt 40, thereby providing the operator with a complete pressure profile along the length of the shoe press belt 400. Such a pressure profile allows the operator to identify and correct problems in the correct position of the papermaking machine. Other configurations may also be used in which the sensing units 102 are typically positioned substantially equidistant from each other along the length of the shoe press belt 40, or where the sensing units 102 are concentrated in one or more areas of particular interest.)

[0031] In one embodiment, each of the plurality of piezoelectric fibers 100 is coexisted with or together with one of the plurality of CD fibers 46. For example, each piezoelectric fiber 100 may be spirally wound around a CD fiber 46, or the piezoelectric fiber 100 may be routed adjacent to a CD fiber 46. This embodiment has the advantage that the existing CD fiber 46 can be used as a supporting "backbone" for the piezoelectric fibers 100, and therefore the piezoelectric fibers 100 do not need to extend along the entire length of the shoe press belt 40. In such embodiments, it may be desirable to fix the ends of the piezoelectric fibers to the CD fibers via an adhesive or the like.

[0032] In another embodiment, each of the plurality of piezoelectric fibers 100 is replaced by one of the plurality of CD fibers 46 in the matrix 42, so that the total number of CD fibers (i.e., the total number of CD fibers 46 and piezoelectric fibers 100) does not change. In such an embodiment, the piezoelectric fibers 100 extend along the entire length of the shoe press belt 100 (see Figures 6 and 7A). In this configuration, each of the plurality of piezoelectric fibers 100 may be modified to have sensing portions at different axial positions along the length of the shoe press belt 40. This can be achieved by replacing the portions of the piezoelectric fibers 100 facing the signal transmission unit 104 with a non-conductive material (shown as 106 in Figure 6). In another embodiment, the piezoelectric core of the multilayer fibers may be cut at a desired position, so that a signal is transmitted only to the portion of the piezoelectric fibers 100' before the cut position (Figure 7B). Other variations may also be possible.

[0033] Each of the plurality of piezoelectric fibers 100 is operably connected to a processing unit (schematically represented by reference numeral 56 in Figure 9). The processing unit 56 may be mounted on one of the plurality of head plates 34, above one end of the shoe press belt 40, or at another convenient location. As one example, the processing unit 56 may be a wireless voltage reader (see Figure 9) mounted directly above one end of the shoe press belt 40, so that the voltage applied to the signal carrier as the signal carrier passes under the voltage reader can be read. Alternatively, the plurality of piezoelectric fibers may be wired to the processing unit 56.

[0034] The processing unit 56 may also include a device or sensor capable of identifying which piezoelectric fiber 100 is generating the signal to be read. This can be achieved in several ways. One example is to attach an RFID tag or transmitter associated with each piezoelectric fiber 100, so that as the shoe press belt 40 rotates during operation, an RFID reader can detect the RFID tag and associate the received signal with the correct piezoelectric fiber 100. Another example is that the piezoelectric fibers 100 may be arranged circumferentially far enough apart from each other that only one fiber is present in the nip at a time, thus simplifying the identification of which fiber 100 is transmitting the signal.

[0035] The processing unit 56 includes a signal transmitter 58 that communicates with a signal receiver 62 located away from the shoe press 20. The signal receiver 62 is wired to a personal computer 64 or other data processing device (e.g., a distributed control system in a paper mill) that can process the signal from the transmitter 58 into useful and understandable information. To transmit data from the processing unit 56 to the receiver 62, a wireless communication mode, such as RF signals (e.g., Bluetooth), is used. 登録商標 It is preferable that the protocol) is used.

[0036] The shoe press belt 40 can be manufactured by any method known for the manufacture of shoe press belts, such as casting, molding, extrusion, etc. One manufacturing method is described in U.S. Patent No. 7,014,733 to Gustafson et al., the disclosure thereof is incorporated in its entirety herein by reference.

[0037] The shoe press belt 40, which includes the plurality of piezoelectric fibers 100 described above, can provide real-time information regarding the operating parameters in the nip, such as the magnitude and distribution of pressure, nip width, strain, and stress. With such information, the operator can adjust the shoe press 20 as needed for the current papermaking process. For example, it may be desirable to adjust the shoe 32 so that the pressure in the nip section 25 is maintained at a constant magnitude. As another example, it may be desirable to adjust the shoe 32 so that the peak pressure generated in the nip section 25 is located at the "downstream" end rather than the center of the nip section 25, thereby improving the quality of the paper formed in the nip section 25.

[0038] Furthermore, the belts of the present invention may be suitable for other uses. These may include, for example, other parts of papermaking machinery (e.g., calendaring belts and clupak blankets), belts for pulp machines, and belts for tissue machines).

[0039] Furthermore, it is conceivable that pressure-sensitive materials other than piezoelectric fibers could be used.

[0040] The foregoing is illustrative of the present invention and should not be construed as limiting. While exemplary embodiments of the present invention are described, those skilled in the art will readily understand that many modifications are possible to these exemplary embodiments without substantially departing from the novel teachings and advantages of the present invention. Accordingly, all such modifications are intended to fall within the scope of the present invention as defined in the claims. The present invention is defined by the appended claims, and equivalents thereof are included in the claims.

Claims

1. It is a pressure-sensing belt, A substantially cylindrical polymer belt having a longitudinal axis, a radial inner surface, and a radial outer surface; A plurality of widthwise (CD) reinforcing fibers extending parallel to the longitudinal axis over the length of the belt between the inner surface and the outer surface; A plurality of longitudinal (MD) reinforcing fibers extending circumferentially with respect to the longitudinal axis between the inner surface and the outer surface; and, A plurality of piezoelectric fibers extending within the belt, each of the plurality of piezoelectric fibers having a sensing portion and a signal transmission portion. The pressure-sensing belt is equipped with the aforementioned features.

2. The belt according to claim 1, wherein the polymer belt includes polyurethane.

3. The belt according to claim 1, wherein the polyurethane has a Shore A hardness value of approximately 55 to 100.

4. The belt according to any one of claims 1 to 3, wherein each of the sensing portions of the plurality of piezoelectric fibers is arranged at a different axial position.

5. The belt according to any one of claims 1 to 3, wherein each of the plurality of piezoelectric fibers has a non-conductive portion and extends over the length of the belt.

6. The belt according to claim 5, wherein each of the plurality of piezoelectric fibers is arranged to replace one of the plurality of CD reinforcing fibers.

7. The belt according to any one of claims 1 to 3, wherein each of the plurality of piezoelectric fibers is located in the same place as one of the plurality of CD reinforcing fibers.

8. The belt according to claim 7, wherein each of the plurality of piezoelectric fibers extends to a length shorter than the length of the belt.

9. The belt according to claim 8, wherein each of the plurality of piezoelectric fibers is spirally wound around a corresponding one of the plurality of CD-reinforced fibers.

10. The belt according to any one of claims 1 to 3, wherein the sensing portion comprises a piezoelectric polymer and the conductive portion comprises a magnetic wire.

11. The belt according to any one of claims 1 to 3, wherein the outer surface is provided with a plurality of recesses for draining water.

12. The belt according to any one of claims 1 to 3, wherein the plurality of piezoelectric fibers are substantially spaced apart from one another along the circumference of the belt.

13. The belt according to any one of claims 1 to 3, further comprising at least one piezoelectric fiber routed in the MD direction.

14. It is a shoe press, A first member having a convex pressing surface; A second member comprising a shoe having a concave pressing surface substantially complementary to the convex pressing surface, the second member further comprising a pair of substantially circular head plates rotatably mounted to axially opposing ends thereof; The belt according to claim 1, attached to the head plate; and A processing unit that communicates with the plurality of piezoelectric fibers, wherein the processing unit processes the signal generated by the sensing unit, The shoe press is equipped with the aforementioned shoe press.

15. The shoe press according to claim 14, wherein the first member comprises an elongated roll.

16. The shoe press according to claim 14, further comprising an endless press felt positioned to be conveyed between the belt and the pressing surface of the second member.

17. The shoe press according to claim 14, wherein the processing unit is mounted above one end of the belt, aligned axially with the shoe.

18. The shoe press according to claim 17, wherein the processing unit comprises a signal transmitter, and the shoe press further comprises a signal receiver and a display device operably associated with the signal transmitter.

19. The shoe press according to claim 17, wherein an identifier is associated with each of the plurality of piezoelectric fibers, and the identifier is configured to provide the processing unit with a signal indicating the indentation of the associated piezoelectric fiber.

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