Fabric for paper-making

Abstract

To provide a fabric for paper-making whose replacement timing can be more accurately determined without shortening its product life.SOLUTION: A fabric for paper-making includes a warp 2 and a weft 3 that interweave with each other. Either one of the yarns 2, 3 that constitute the fabric 1 for paper-making includes a core-sheath yarn with a core-sheath type structure including a core part 6 and a sheath part 7 that covers the periphery of the core part. The core part 6 forms an opaque or colored transparent single layer, and the sheath part 7 forms a colorless transparent single layer. Since the sheath part 7 is colorless transparent, an abrasion state of the sheath part 6 can be confirmed either from a traveling face side or from a paper-making face side.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a papermaking fabric used in a manner in which its surface is exposed.

Background Art

[0002] Examples of papermaking fabrics include a wire used in the wire part of a paper machine, a base fabric of a press felt used in the press part, and a canvas used in the dry part. The wire is substantially entirely composed of a papermaking fabric. The press felt is formed by integrating a base fabric composed of a papermaking fabric and a batt layer made of short fibers by needling. The canvas includes those substantially entirely composed of a papermaking fabric and those in which a base fabric composed of a papermaking fabric and a batt layer made of short fibers are integrated by needling.

[0003] In addition, since a papermaking fabric wears out during use and needs to be replaced when the wear progresses, means for confirming whether the wear has reached a level that requires replacement is necessary. For a papermaking fabric whose surface is not covered by other layers and is used in a manner in which the surface is exposed, such as a wire or a canvas without a batt layer, its surface can be visually inspected. For this reason, it has been proposed to adopt core-sheath yarns as warp and / or weft yarns constituting the papermaking fabric and visually check the wear state.

[0004] For example, Patent Document 1 describes that when the wear of the core-sheath yarns constituting the papermaking fabric progresses and the core part is exposed, a visual change is caused. Patent Document 1, for example, makes the core part a distinct color and includes a white pigment in the sheath part so that the color of the core part is hidden from view until the sheath part is sufficiently worn away and the core part is exposed, and it is described that the wear of the papermaking fabric can be determined by grasping the exposure of the core part by a visual color change in observation from the wear surface side.

[0005] In addition, Patent Document 2 describes that in a papermaking fabric (papermaking machine cloth) containing core-sheath yarns, the sheath part forms a plurality of layers, and the core part and each layer of the sheath part have contrasting colors or reflectivities so that they can be visually distinguished from each other. By grasping which part of each layer of the sheath part and the core part is exposed in the observation from the worn surface side, the degree of wear of the papermaking fabric can be determined.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, in the structures described in Patent Documents 1 and 2, the color change can only be observed from the "worn surface side". In many cases, wear occurs from the running surface side. The running surface side is the inside of the paper machine, where rolls for driving the papermaking fabric, rolls for supporting the papermaking fabric, suction boxes for promoting dehydration, etc. are arranged. Therefore, with the structures of Patent Document 1 and Patent Document 2, it was difficult to observe the worn state visually both spatially and in terms of illuminance.

[0008] Furthermore, when the sheath part contains a plurality of layers like the core-sheath yarns described in Patent Document 2, although the state of wear can be confirmed step by step by the stepwise color change, there was a high risk that the core part would be exposed even if the layers of the sheath part were peeled off and not worn.

[0009] In view of the above background, an object of the present invention is to provide a papermaking fabric that can more accurately determine the replacement time without shortening the life of the papermaking fabric.

Means for Solving the Problems

[0010] In order to solve the above problems, an aspect of the present invention is a papermaking fabric (1, 11) that includes warp threads (2, 12) and weft threads (3, 13) woven into each other, has a running surface side surface (4, 14) and a papermaking surface side surface (5, 15), and is used in a manner in which both surfaces are exposed. Any of the threads constituting the papermaking fabric includes a core-sheath type core-sheath thread including a core part (6, 18, 20) and a sheath part (7, 19, 21) covering the periphery of the core part. The core part forms an opaque or colored transparent single layer, and the sheath part forms a colorless transparent single layer.

[0011] According to this aspect, the presence or absence of the core part (the disappearance timing of the core part) can be confirmed from both the papermaking surface side and the running surface side through the colorless transparent sheath part. Therefore, compared with the case where the wear state can only be confirmed from the wear surface side, the number of surfaces that can be confirmed is doubled, and the replacement timing of the papermaking fabric can be determined more accurately. Further, even when the wear surface side of the papermaking fabric is the running surface side where it is difficult to confirm spatially and in terms of illuminance due to the presence of rolls or suction boxes, the wear state can be confirmed from the papermaking surface side where it is easy to confirm spatially and in terms of illuminance. Therefore, regardless of the structure of the paper machine, the replacement timing of the papermaking fabric can be determined more accurately.

[0012] In the above aspect, one of the warp threads (2, 12) and the weft threads (3, 13) may include the core-sheath thread, and the other of the warp threads and the weft threads may be colorless and transparent as a whole. For example, the weft thread may include the core-sheath thread, and the warp thread may be the colorless and transparent one.

[0013] According to this aspect, since the thread intersecting the core-sheath thread is colorless and transparent, the visibility of the core part of the core-sheath thread is improved when viewed from either the papermaking surface side or the running surface side.

[0014] In the above aspect, the core-sheath thread includes a first core-sheath thread (16) and a second core-sheath thread (17) extending in the same direction as the first core-sheath thread and woven in a different weaving method from the first core-sheath thread. The core parts of the first core-sheath thread and the second core-sheath thread may be different from each other in at least one of hue, chroma, lightness, and transparency.

[0015] According to this aspect, the wear states of two types of yarns can be confirmed.

[0016] In the above aspect, the first core-sheath yarn (16) and the second core-sheath yarn (17) are arranged so as to have a portion overlapping with each other in the thickness direction of the paper-making fabric (11), and the core portions of the first core-sheath yarn and the second core-sheath yarn may be colored and transparent.

[0017] According to this aspect, even if the core portions of the first core-sheath yarn and the second core-sheath yarn have a portion overlapping in the thickness direction of the paper-making fabric, since the sheath portions of the first and second core-sheath yarns are colorless and transparent and the core portions are colored and transparent, not only the wear state from the running surface side but also the internal wear state can be confirmed from both the running surface side and the paper-making surface side. Therefore, the replacement timing of the paper-making fabric can be determined more accurately.

[0018] In the above aspect, the core portion (18) of the first core-sheath yarn may be thicker than the core portion (20) of the second core-sheath yarn, and the visible light transmittance of the core portion of the first core-sheath yarn may be greater than the visible light transmittance of the core portion of the second core-sheath yarn.

[0019] According to this aspect, even if the core portions of the first core-sheath yarn and the second core-sheath yarn have a portion overlapping in the thickness direction, since the core portion of the relatively thick first core-sheath yarn has a relatively large visible light transmittance and can be seen through, the visibility of the core portion of the relatively thin second core-sheath yarn is improved.

[0020] In the above aspect, the core portion (18) of the first core-sheath yarn may be thicker than the core portion (20) of the second core-sheath yarn, and the haze value of the core portion of the first core-sheath yarn may be smaller than the haze value of the core portion of the second core-sheath yarn.

[0021] According to this aspect, even if the core portions of the first core-sheath yarn and the second core-sheath yarn have a portion overlapping in the thickness direction, since the transparency of the core portion of the relatively thick first core-sheath yarn is high, the visibility of the core portion of the relatively thin second core-sheath yarn is improved.

[0022] In the above aspect, one of the warp yarns (12) and the weft yarns (13) includes the first core-sheath yarn (16) and the second core-sheath yarn (17), and the other of the warp yarns and the weft yarns may be colorless and transparent as a whole yarn.

[0023] According to this aspect, in a papermaking fabric having two layers, regardless of whether internal wear or wear on the surface of the papermaking fabric is dominant, it is possible to accurately determine the end of the life of the papermaking fabric due to wear. Further, since the yarn intersecting the core-sheath yarn is colorless and transparent, the visibility of the core portion of the core-sheath yarn is improved when viewed from either the papermaking surface side or the running surface side.

Effect of the Invention

[0024] According to the above aspect, it is possible to more accurately determine the replacement timing of the papermaking fabric without shortening the life of the papermaking fabric.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0026] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a papermaking fabric 1 according to the first embodiment. The papermaking fabric 1 is used as a wire in the wire part of a paper machine.

[0027] The papermaking fabric 1 includes warp threads 2 and weft threads 3 woven into each other, and has a running surface side surface 4 that contacts a roll of a paper machine and a papermaking surface side surface 5 on which wet paper is placed. The papermaking fabric 1 is a single-layer fabric (single warp and single weft) in which both the warp threads 2 and the weft threads 3 are arranged in a single layer. In the illustrated example, the warp threads 2 are woven into the weft threads 3 so as to repeat passing over two weft threads 3 and then passing under the two weft threads 3. However, the texture of the papermaking fabric 1 is not limited to that formed by such a weaving method, and may be, for example, plain weave or twill weave.

[0028] The warp threads 2 are composed of colorless and transparent fibers made of a resin manufactured by extrusion molding or the like. The weft threads 3 are core-sheath type core-sheath yarns made of a resin, including a colored transparent or opaque core part 6 and a colorless and transparent sheath part 7 that covers the entire circumference of the core part 6 in a cross-sectional view, and are manufactured by extrusion molding or the like. In a cross-sectional view, the core part 6 presents a single-layer circular shape, and the sheath part 7 presents a single-layer annular shape. The warp threads 2 and the sheath part 7 of the weft threads 3 are such that the resin itself of the material is colorless and transparent. The core part 6 of the weft threads 3 may be such that the resin itself of the material is colored transparent or opaque, or may be a material obtained by adding a dye or pigment to a colorless and transparent resin. The "colorless and transparent" of the warp threads 2 and the sheath part 7 does not necessarily require a visible light transmittance of 100%. As long as the core part 6 of the weft threads 3 can be visually recognized when viewed from either the running surface side or the papermaking surface side, it may be cloudy. In this specification, the "colorless" thread means a thread to which no coloring additive such as a dye or pigment is added. Also, in this specification, "transparent" means, for example, a haze value of 10% or less. The "opaque or colored transparent" of the core part 6 only needs to be distinguishable from the "colorless and transparent" warp threads 2 and the sheath part 7 when viewed from either the running surface side or the papermaking surface side. For example, the difference between the haze value of the core part 6 and the haze value of the sheath part 7 is 30% or more, or it is colored (adding a coloring additive such as a dye or pigment) regardless of the haze value.

[0029] Figure 2 is a cross-sectional view of the weft yarn 3, showing the progress of wear. In the figure, the lower side is the wear surface side where wear occurs. In the case of the paper-making fabric 1 of single-layer weaving (see Figure 1), the running surface side surface 4 (see Figure 1) that contacts the roll or suction box of the paper-making machine etc. often becomes the surface on the wear surface side. Figure 2(A) shows the state without wear, Figure 2(B) shows the state where the wear has reached the core part 6 and the core part 6 has worn by about 10% of its diameter, Figure 2(C) shows the state where the core part 6 has worn by about half, Figure 2(D) shows the state where the core part 6 has worn by about 90% of its diameter, and Figure 2(E) shows the state where the core part 6 has completely disappeared due to wear.

[0030] Since the sheath part 7 is colorless and transparent and the core part 6 is colored transparent or opaque, if the core part 6 exists, the core part 6 can be visually recognized. In the states shown in Figures 2(A) to (C), the width in the horizontal direction passing through the center of the core part 6 is the same as the initial diameter of the core part 6. Therefore, whether viewed from the wear surface side (the lower side of the figure) or from the opposite side (the upper side of the figure), the width of the visually recognized core part 6 is the same. In the state shown in Figure 2(D), the width of the core part 6 visually recognized from the wear surface side and the opposite side is narrower than the initial width. In the state shown in Figure 2(E), the core part 6 has disappeared and the core part 6 is not visually recognized.

[0031] In other words, in the wear state where the core part 6 is exposed but the cross-sectional area perpendicular to the axis of the core part 6 remains more than half of that before the start of use, regardless of the confirmation direction of the paper-making fabric 1 (paper-making surface side / running surface side), there is no visual change in the appearance of the core part 6, and the core part 6 is visually recognized as a line with a uniform width. When there is a place where the cross-sectional area perpendicular to the axis of the core part 6 has disappeared to less than half of that before the start of use, the same visual change occurs regardless of the confirmation direction (paper-making surface side / running surface side), and a place where the width of the visually recognized line of the core part 6 becomes smaller occurs. Furthermore, when the wear progresses and the disappearance of the core part 6 occurs, the same visual change occurs regardless of the confirmation direction (paper-making surface side / running surface side), and a broken place occurs in the visually recognized line of the core part 6.

[0032] FIG. 3 shows the difference in the appearance of wear between the single-layer papermaking fabric 101 of the prior art and the papermaking fabric 1 according to the first embodiment. As shown in FIG. 3(A), the papermaking fabric 101 shown as a comparative example includes warp threads 102 and weft threads 103 woven into each other, and the weft thread 103 includes a colored (for example, blue) core portion 106 and a sheath portion 107 of an opaque color (for example, white) different from the core portion 106. FIG. (A2) on the running surface side shows a state where FIG. (A1) on the papermaking surface side is rotated 180° about the extension direction of the weft thread 103 as an axis.

[0033] Wear occurs on the running surface side of the knuckle portion 108 (the portion where the warp 102 and the weft 103 overlap each other). The papermaking fabric 101, which is a papermaking wire, is configured to wear the weft 103 first so that the warp 102, which is the lifeline of the lifespan, does not wear. That is, the surface on the running surface side of the weft 103 (the weft 103 of the knuckle portion 108 where the warp 102 is on the papermaking surface side and the weft 103 is on the running surface side) is located more on the running surface side than the surface on the running surface side of the warp 102 (the warp 102 of the knuckle portion 108 where the warp 102 is on the running surface side and the weft 103 is on the papermaking surface side). Similarly, the surface on the papermaking surface side of the weft 103 (the weft 103 of the knuckle portion 108 where the warp 102 is on the running surface side and the weft 103 is on the papermaking surface side) is located more on the papermaking surface side than the surface on the papermaking surface side of the warp 102 (the warp 102 of the knuckle portion 108 where the warp 102 is on the papermaking surface side and the weft 103 is on the running surface side) (the same applies to the positional relationship between the warp 2 and the weft 3 of the papermaking fabric 1 according to the embodiment. See FIG. 1). Therefore, wear occurs on the weft 103 rather than the warp 102. The upper part of FIG. 3(A) shows a state where the weft 103 is worn to the same extent as the weft 3 shown in FIG. 2(B) in the knuckle portion 108 where the weft 103 of the prior art is arranged more on the running surface side than the warp 102. From the papermaking surface side, since the sheath portion 107 is opaque so as to hide the color of the core portion 106, the core portion 106 cannot be visually recognized. From the running surface side, in the knuckle portion 108 where the weft 103 is located more on the running surface side than the warp 102, the core portion 106 is exposed due to the wear of the sheath portion 107, and the core portion 106 is visually recognized. The lower part of FIG. 3(A) shows a state where wear further progresses from the state shown in the upper part, and the weft 103 is worn in the knuckle portion 108 to the same extent as the weft 3 shown in FIG. 2(C). From the papermaking surface side, since the sheath portion 107 is opaque, the core portion 106 cannot be visually recognized, and from the running surface side, the visually recognized core portion 106 is wider than the state shown in the upper part.

[0034] On the other hand, in the papermaking fabric 1 according to the first embodiment, if the wear state of the weft yarn 3 is the initial wear state shown in FIGS. 2(A) to 2(C), the width of the core portion 6 in the knuckle portion 8 can be visually recognized as being the same as the diameter of the initial core portion 6 from either the running surface side or the papermaking surface side. The upper part of FIG. 3(B) shows the state in which the weft yarn 3 has worn to the state shown in FIG. 2(D) in the knuckle portion 8 where the weft yarn 3 is disposed on the running surface side of the warp yarn 2. From either the papermaking surface side or the running surface side, it can be visually recognized that the width of the core portion 6 of the weft yarn 3 is thinner than the portions before and after in the knuckle portion 8. The lower part of FIG. 3(B) shows the state in which wear further progresses from the state shown in the upper part, and in the knuckle portion 8, the weft yarn 3 has worn to the state shown in FIG. 2(E). In the knuckle portion 8, since the core portion 6 has disappeared due to wear, the state in which the core portion 6 is interrupted at the knuckle portion 8 can be visually recognized from either the papermaking surface side or the running surface side. When an operator discovers such a state in which the core portion 6 is partially interrupted, the operator may determine that the life of the papermaking fabric 1 has ended and that it is necessary to replace it.

[0035] As described above, since the sheath portion 7 is colorless and transparent and the core portion 6 is colored transparent or opaque, the wear state can be confirmed from both the papermaking surface side and the running surface side. For this reason, compared with the prior art in which the wear state can be confirmed only from the wear surface side, the number of surfaces that can be confirmed is doubled, and the replacement timing of the papermaking fabric 1 can be determined more accurately. Even when the wear surface side is the running surface side where it is difficult to confirm spatially and in terms of illuminance, the wear state can be confirmed from the papermaking surface side where it is easy to confirm spatially and in terms of illuminance, so the replacement timing of the papermaking fabric 1 can be determined more accurately. Further, since the warp yarn 2 is colorless and transparent, the visibility of the core portion 6 of the weft yarn 3 is improved. Since the core portion 6 and the sheath portion 7 are single-layered, the risk of layer peeling is low, and a decrease in the life of the yarn can be suppressed.

[0036] Next, the papermaking fabric 11 according to the second embodiment of the present invention will be described with reference to FIGS. 4 and 5.

[0037] As shown in FIG. 4, the paper-making fabric 11 includes warp threads 12 and weft threads 13 woven into each other, and has a running surface side surface 14 that contacts the roll of the paper-making machine and a paper-making surface side surface 15 on which wet paper is placed. The weft thread 3 is arranged in a double layer so as to include a first weft thread 16 that is only involved in the formation of the structure on the running surface side and a second weft thread 17 that is only involved in the formation of the structure on the paper-making surface side. The warp thread 12 forms the fabric structure on the running surface side by being woven into the first weft thread 16, and forms the fabric structure on the paper-making surface side by being woven into the second weft thread 17, and is a self-connecting thread that connects both fabric structures. Thus, the paper-making fabric 11 is a triple-woven (two-ply warp and two-ply weft) fabric. In the illustrated example, the number of the second weft threads 17 is twice the number of the first weft threads 16, and the second weft threads 17 are arranged so as to overlap vertically with the first weft threads 16 when viewed from the thickness direction of the paper-making fabric 11 at every other one. The weft thread 13 into which a pair of warp threads 12 is woven alternates between the first weft thread 16 and the second weft thread 17 for every four first weft threads 16 (eight second weft threads 17). The structure on the running surface side is formed by a pair of warp threads 12 cooperating such that one warp thread 12 passes above one first weft thread 16, below one first weft thread 16, and above two first weft threads 16, and then the other warp thread 12 passes below one first weft thread 16 and above three first weft threads 16 repeatedly. The structure on the paper-making surface side is a plain weave.

[0038] Note that the structure of the paper-making fabric 11 is not limited to the illustrated example. For example, the structures on the running surface side and the paper-making surface side may be other fabric structures respectively. There may be a thread that does not have a connecting function as the warp thread 12, that is, a thread that is only woven into the first weft thread 16 or the second weft thread 17. Also, in this case, instead of the self-connecting thread, a connecting thread that connects the structures on the running surface side and the paper-making surface side without forming a fabric structure may be used. The self-connecting thread or the connecting thread may be provided as the weft thread 13 instead of or in addition to the warp thread 12. The ratio of the number of the first weft threads 16 to the number of the second weft threads 17 may be different.

[0039] The warp thread 12 is colorless and transparent, and the manufacturing method and material of the warp thread 12 are the same as those of the warp thread 2 in the first embodiment. The first weft thread 16 includes a colored transparent core portion 18 and a colorless transparent sheath portion 19 that covers the entire circumference of the core portion 18 in a cross-sectional view. The second weft thread 17, similarly to the first weft thread 16, includes a colored transparent core portion 20 and a colorless transparent sheath portion 21 that covers the entire circumference of the core portion 20 in a cross-sectional view. For each of the first weft thread 16 and the second weft thread 17, the manufacturing method and material, as well as the relative arrangement and shape of the core portions 18, 20 and the sheath portions 19, 21, are the same as those of the weft thread 3 in the first embodiment.

[0040] The first weft thread 16 is thicker than the second weft thread 17, and the core portion 18 of the first weft thread 16 is thicker than the core portion 20 of the second weft thread 17. When both the core portion 18 of the first weft thread 16 and the core portion 20 of the second weft thread 20 are colored transparent, it is preferable that the visible light transmittance of the core portion 18 of the first weft thread 16 is greater than the visible light transmittance of the core portion 20 of the second weft thread 17. That is, it is preferable that the color of the thick core portion 18 of the first weft thread 16 is lighter than the color of the thin core portion 20 of the second weft thread 17.

[0041] When both the core portion 18 of the first weft thread 16 and the core portion 20 of the second weft thread 17 are colored transparent, instead of the visible light transmittance, the haze value can be used as an index, and the color of the core portions 18, 20 can be determined so that the haze value of the core portion 18 of the first weft thread 16 is smaller than the haze value of the core portion 20 of the second weft thread 17. The haze value is also called the cloudiness value or turbidity, etc., and is an index representing the degree of cloudiness or the degree of light diffusion of a transparent substance. When the haze value is 0%, it means that the test specimen is completely transparent, and as the haze value increases, it means that the degree of cloudiness of the test specimen increases. The haze value can be obtained from two light transmittances. Let the total light transmittance, which is the transmittance of the light including all of the parallel component and the diffused component among the light rays passing through the test specimen, be Tt, and the diffused transmittance, which is the transmittance of the light (diffused light) excluding the parallel component, be Td. Then, the haze value is expressed as Td / Tt × 100 (%).

[0042] In the case of the triple-woven papermaking fabric 11, the yarns forming the structure on the running surface side and the yarns forming the structure on the papermaking surface side move separately from each other (for example, the first weft yarn 16 and the warp yarn 12, or the warp yarn 12 and the second weft yarn 17), resulting in internal wear where the contact surfaces of these yarns wear against each other. FIG. 5(A) shows, as a comparative example, how the internal wear of the prior art triple-woven papermaking fabric 111 appears. FIG. 5(B) shows how the internal wear is dominant over the wear on the running surface side in the papermaking fabric 11 according to the second embodiment. FIG. 5(C) shows how the wear on the running surface side is dominant over the internal wear in the papermaking fabric 11 according to the second embodiment. In FIG. 5, the warp yarn 12 is omitted in all the figures for illustration purposes. In FIGS. 5(B) and (C), it shows the case where the internal wear of the second weft yarn 17 and the wear on the running surface side or internal wear of the first weft yarn 16 occur at overlapping positions when viewed from the thickness direction of the papermaking fabric 11. However, these wears can also occur at positions shifted from each other in the weft yarn extending direction. For example, when internal wear occurs due to the first weft yarn 16 and the second weft yarn 17 rubbing against each other, the internal wear on the running surface side of the second weft yarn 17 and the internal wear on the papermaking surface side of the first weft yarn 16 occur at overlapping positions when viewed from the thickness direction. Also, for example, when internal wear occurs at the contact surface between the warp yarn 12 (see FIG. 4) and the first weft yarn 16 or the second weft yarn 17, the internal wear of the second weft yarn 17 can occur at a position shifted from the internal wear or the wear on the running surface side of the first weft yarn 16 in the weft yarn extending direction.

[0043] The prior art triple-woven papermaking fabric 111 shown in FIG. 5(A) has the same structure as the papermaking fabric 11 of the second embodiment, but the colors of the first weft yarn 116 (corresponding to the first weft yarn 16 of the second embodiment), which is a core-sheath yarn, and the second weft yarn 117 (corresponding to the second weft yarn 17 of the second embodiment) are different from those of the second embodiment. The core parts (not shown) of the first weft yarn 116 and the second weft yarn 117 are colored, and the sheath parts 119 of the first weft yarn 116 and 121 of the second weft yarn 117 have an opaque color (for example, white) that hides the color of the core part (not shown).

[0044] Internal wear occurs between the yarns forming the structure on the running surface side and the yarns forming the structure on the paper-making surface side due to their independent movement. The upper part of Fig. 5(A) shows the appearance when the second weft yarn 117 of the prior art wears to the same extent as the weft yarn 3 in Figs. 2(A) to (C) on the running surface side due to internal wear. When viewed from the running surface side, the running surface side of the relatively thin second weft yarn 117 is covered by the first weft yarn 116 which is relatively thick and has an opaque sheath part 119 that hides the color of the core part (not shown), so the internal wear on the running surface side of the second weft yarn 117 cannot be confirmed. When viewed from the paper-making surface side, there is no visible change, and the internal wear on the running surface side of the second weft yarn 117 cannot be confirmed. The lower part of Fig. 5(A) shows the appearance when the second weft yarn 117 of the prior art wears to the same extent as the weft yarn 3 in Figs. 2(D) and (E) on the running surface side due to internal wear. When viewed from the running surface side, similar to the upper part of Fig. 5(A), the running surface side of the second weft yarn 117 is covered by the first weft yarn 116, so not only can the replacement time of the paper-making fabric 111 not be timely grasped, but the occurrence of internal wear on the running surface side of the second weft yarn 117 itself cannot be grasped. When viewed from the paper-making surface side, although the width of the second weft yarn 117 itself becomes partially thinner, since the state of the core part (not shown) is unknown, it is difficult to timely grasp the timing of the life of the paper-making fabric 111 due to the internal wear on the running surface side of the second weft yarn 117. Although not shown in the figure, if the worn surface is on the running surface side, wear occurs on the running surface side of the first weft yarn 116 and is visible like the weft yarn 103 shown in Fig. 3(A2).

[0045] The upper part of Fig. 5(B) shows how it looks when the wear on the running surface side due to the internal wear of the second weft yarn 17 of the second embodiment wears to the same extent as the weft yarn 3 in Figs. 2(A) to (C). At this stage, there is no change in the appearance. The middle part of Fig. 5(B) shows how it looks when the wear on the running surface side due to the internal wear of the second weft yarn 17 of the second embodiment wears to the same extent as the weft yarn 3 in Fig. 2(D). At this stage, when viewed from either the running surface side or the paper-making surface side, it can be visually recognized that a part of the core 20 of the second weft yarn 17 has become thinner. The lower part of Fig. 5(B) shows how it looks when the wear on the running surface side due to the internal wear of the second weft yarn 17 of the second embodiment wears to the same extent as the weft yarn 3 in Fig. 2(E), and the wear on the paper-making surface side (internal wear) or the wear on the running surface side (wear due to contact with rolls or suction boxes of the paper-making machine, etc.) of the first weft yarn 16 wears to the same extent as the weft yarn 3 in Fig. 2(D). At this stage, when viewed from either the running surface side or the paper-making surface side, it can be visually recognized that the core 20 of the second weft yarn 17 has disappeared partially and is interrupted, and at the position where this part overlaps, the core 18 of the first weft yarn 16 has become thinner (remains).

[0046] Regarding the wear from the running surface side of the paper-making fabric 11 of the second embodiment shown in Fig. 5(C), the wear of the first weft yarn 16 becomes a problem. The upper part of Fig. 5(C) shows how it looks when the wear on the running surface side of the first weft yarn 16 wears to the same extent as the weft yarn 3 in Figs. 2(A) to (C). At this stage, there is no change in the appearance. The middle part of Fig. 5(C) shows how it looks when the wear on the running surface side of the first weft yarn 16 wears to the same extent as the weft yarn 3 in Fig. 2(D). At this stage, when viewed from either the running surface side or the paper-making surface side, it can be visually recognized that a part of the core 18 of the first weft yarn 16 has become thinner. The lower part of Fig. 5(C) shows how it looks when the wear on the running surface side of the first weft yarn 16 wears to the same extent as the weft yarn 3 in Fig. 2(E), and the running surface side of the second weft yarn 17 wears to the same extent as the weft yarn 3 in Fig. 2(D) due to internal wear. At this stage, when viewed from either the running surface side or the paper-making surface side, it can be visually recognized that the core 18 of the first weft yarn 16 has disappeared partially and is interrupted, and at the position where this part overlaps, the core 20 of the second weft yarn 17 has become thinner (remains).

[0047] When the operator discovers either a state where the core part 20 of the second weft yarn 17 is partially interrupted as shown in the lower part of Fig. 5(B) or a state where the core part 18 of the first weft yarn 16 is partially interrupted as shown in the lower part of Fig. 5(C), it may be determined that the life of the paper-making fabric 11 has ended and that it needs to be replaced.

[0048] As described above, since the sheath parts 19, 21 are colorless and transparent and the core parts 18, 20 are colored and transparent, regardless of whether internal wear or wear from the running surface side is dominant, the wear state can be confirmed from both the running surface side and the paper-making surface side. For this reason, it is easy to confirm the wear state, and the life of the paper-making fabric 11 can be grasped more accurately. Also, since the warp yarn 12 is colorless and transparent, the visibility of the core parts 18, 20 of the first weft yarn 16 and the second weft yarn 17 is improved. Since the core parts 18, 20 and the sheath parts 19, 21 are single-layered, the risk of layer peeling is low, and a decrease in the life of the yarn can be suppressed.

[0049] Since the core part 18 of the relatively thick first weft yarn 16 has a larger value for the visible light transmittance or a smaller value for the haze value than the core part 20 of the relatively thin second weft yarn 17, the visibility of the relatively thin core part 20 can be enhanced, and the life of the paper-making fabric 11 can be judged more accurately without being restricted by the confirmation direction.

[0050] The description of the specific embodiments ends here. However, the present invention is not limited to the above embodiments and modification examples, and can be widely modified and implemented. The paper-making fabric may be a canvas having no bat layer instead of a wire, or a fabric used in a papermaking machine other than a pulp machine, such as a paper-making machine.

[0051] The warp threads may exhibit a colored transparency that does not significantly reduce the visibility of the core part of the weft threads. Instead of or in addition to the weft threads, the warp threads (self - tying threads and / or warp threads without a tying function) or the tying threads may be core - sheath threads that include a core part that is colored transparent or opaque and a colorless transparent sheath part. When using two types of non - overlapping threads as core - sheath threads, the core part may be opaque instead of colored transparent. In this case, it is preferable that the core parts of different types of core - sheath threads differ from each other in at least one of hue, chroma, lightness, and transparency.

[0052] The paper - making fabric may be a double - weave (one - ply warp and two - ply weft, two - ply warp and one - ply weft) in which one of the warp and weft threads is double - ply and the other is single - ply.

Explanation of Symbols

[0053] 1, 11: Paper - making fabric 2, 12: Warp threads 3, 13: Weft threads (core - sheath threads) 6, 18, 20: Core part 7, 19, 21: Sheath part 16: First weft thread (first core - sheath thread) 17: Second weft thread (second core - sheath thread)

Claims

1. A papermaking fabric including warp and weft threads woven into each other, having a running surface side surface and a papermaking surface side surface, and being used in a manner such that both surfaces are exposed, wherein any of the threads constituting the papermaking fabric includes a core-sheath yarn having a core-sheath structure including a core portion and a sheath portion covering the periphery of the core portion, the core portion forms an opaque or colored transparent single layer, and the sheath portion forms a colorless transparent single layer, a papermaking fabric.

2. The papermaking fabric according to claim 1, wherein one of the warp and weft threads includes the core-sheath yarn, and the other of the warp and weft threads is colorless and transparent as a whole thread.

3. The papermaking fabric according to claim 2, wherein the weft thread includes the core-sheath yarn, and the warp thread is colorless and transparent as a whole thread.

4. The core-sheath yarn includes a first core-sheath yarn and a second core-sheath yarn extending in the same direction as the first core-sheath yarn and woven in a different weaving manner from the first core-sheath yarn, wherein the core portion of the first core-sheath yarn and the core portion of the second core-sheath yarn are different from each other in at least one of hue, chroma, lightness, and transparency, the papermaking fabric according to claim 1.

5. The first core-sheath yarn and the second core-sheath yarn are arranged so as to have a portion overlapping with each other in the thickness direction of the papermaking fabric, wherein the core portion of the first core-sheath yarn and the core portion of the second core-sheath yarn are colored transparent, the papermaking fabric according to claim 4.

6. The core portion of the first core-sheath yarn is thicker than the core portion of the second core-sheath yarn, wherein the visible light transmittance of the core portion of the first core-sheath yarn is greater than the visible light transmittance of the core portion of the second core-sheath yarn, the papermaking fabric according to claim 5.

7. The core portion of the first core-sheath yarn is thicker than the core portion of the second core-sheath yarn, wherein the haze value of the core portion of the first core-sheath yarn is smaller than the haze value of the core portion of the second core-sheath yarn, the papermaking fabric according to claim 4.

8. One of the warp and weft threads includes the first core-sheath yarn and the second core-sheath yarn, wherein the other of the warp and weft threads is colorless and transparent as a whole thread, the papermaking fabric according to any one of claims 4 to 7.

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