Patent Grant
7185757
This invention relates to a belt used in a shoe press mechanism such as a shoe press for papermaking, and especially to a belt adapted for use in a closed-type shoe press.
In papermaking, the use of shoe presses is on the increase because they contribute to a reduction in the total manufacturing cost. Furthermore, there is a trend toward the use of a closed type shoe press because it requires less space and avoids scattering of oil.
Compared to conventional belts used in open type shoe presses, belts used in a closed type shoe press are subject to more severe conditions, especially in terms of papermaking speed and nip pressure. Accordingly there has been a strong demand by users for improvement in belt durability.
Among typical technologies used for producing belts for closed type shoe presses, various manufacturing technologies using mandrels are known. For example, Examined Japanese Patent Publication No. 57236/1991, and Unexamined Japanese Patent Publication No. 45888/1989, disclose a manufacturing method using an endless woven fabric as a core member. In addition, Japanese Patent No. 3213589 discloses a manufacturing method using an endless mesh for a core member. However, these manufacturing methods have deficiencies, especially difficulties encountered in adjusting the machine direction dimension of a belt being produced.
In addition, PCT Patent application No. 503315/1989, and Unexamined Japanese Patent Publication No. 209578/1996, disclose a manufacturing method wherein a woven fabric is not used. These manufacturing methods form threads in the axial direction of a mandrel at regular intervals around the entire circumference of the mandrel. However, it is difficult to position the threads substantially parallel to the axial direction of the mandrel, and to avoid loosening of the threads under tensile force. With these methods excessive time is required for forming the threads.
Unexamined Japanese Patent Publication No. 298292/1989, and PCT Patent application No. 505428/1993, disclose a manufacturing method wherein a mat-shaped fiber band or a woven fabric impregnated with uncured resin is wound in a helix and then cured. However, with these manufacturing methods, exfoliation can easily occur at joints of the helix.
a) and 10(b) show a manufacturing method for a conventional shoe press belt. An endless woven fabric C is arranged on two rolls A and B, and impregnated and coated on an external surface of the woven fabric C by a coating apparatus D to form a shoe side layer, which is then cured. After curing of the shoe side layer, the endless woven fabric C is removed from the rolls A and B, turned inside-out, and reset on the rolls with its original inner surface facing outward. The fabric is again impregnated and coated to form a wet paper web side layer. The wet paper web side layer is cured, its thickness is adjusted, and concave grooves G are formed in its outer surface to produce a belt 1 is obtained, as shown in
The above-described conventional method had two principal deficiencies. First, in order to impregnate and coat the shoe side layer E on one surface of the endless woven fabric and the wet paper web side layer F on the other side, the belt needed to be reversed, and reversal caused distortion to occur inside the belt. Second, since the distortion that existed when weaving the endless woven fabric is released as the resin is cured. Release of this distortion results in instability of the form of the belt, enabling flapping of the belt to occur.
Japanese Patent No. 3408416, and Unexamined Japanese Patent Publication No. 303377/2000, disclose a manufacturing method wherein a first resin layer is formed on a mandrel followed by formation of a base body around the external circumference of the resin layer, and formation of another resin layer, which is connected with first resin layer through the base body. According to this manufacturing method, after forming the first resin layer, there is no need to grind or reverse the resin layer, and therefore manufacturing efficiency and productivity can be improved.
The shoe press belt manufactured according to the manufacturing method disclosed in the Japanese Patent No. 3408416 has relatively large undulations at the joints of the warp yarns and weft yarns in the woven fabric used as its base body. In the use of the belt, these undulations result in large stress concentration at the joints of the warp yarns and weft yarns, which can result in cracking of a resin layer, and impairment of the durability of the belt.
In the case of a manufacturing method disclosed in Unexamined Japanese Patent Publication No. 303377/2000, similarly to the methods disclosed in PCT Patent application No. 503315/1989 and Unexamined Japanese Patent Publication No. 209578/1996, threads have to be formed in the axial direction of the mandrel at regular intervals, and be distributed around the entire circumference of the mandrel. The need for this arrangement of threads causes manufacture of the belt to be very time consuming and labor intensive.
It is an object of the invention to address the above-described problems, and to provide a shoe press belt that exhibits high crack resistance, and that can be produced efficiently.
The shoe press belt in accordance with the invention comprises a base body, a wet paper web side layer on one side of the base body and a shoe side layer on the opposite side of the base body. The shoe side layer is formed on a mandrel having a polished surface. The base body comprises a lattice material comprising warp yarns and weft yarns crossing one another at crossing points and joined at the crossing points, and a layer comprising thread wound in a helix.
Preferably the warp yarns are disposed between two layers of weft yarns pinched by the weft yarns, and the warp and weft yarns are joined at the crossing points by an adhesive comprising a resin or by a thermal bond.
The weft yarns of the lattice material preferably have a higher strength than that of the warp yarns, and the weft yarns preferably extend along the axial direction of the mandrel during the formation of the belt. The number of weft yarns of the lattice material is preferably more than double the number of warp yarns in the lattice material.
The lattice material may be wound onto the mandrel in a single sheet having a width slightly greater than the circumference of the shoe side layer on the mandrel. Alternatively, the lattice material can be wound onto the mandrel in a helix, or applied to the mandrel in plural sheets positioned on the mandrel with their edges overlapping one another in the widthwise direction.
Another aspect of the invention is the method of making a belt for use in a shoe press wherein the belt passes between a press roll and a shoe, comprising forming a shoe-side layer on a mandrel having a polished surface, forming a base body on the shoe side layer while the shoe side layer is on the mandrel, by placing, around the mandrel, a lattice material comprising warp yarns and weft yarns crossing one another at crossing points and joined at the crossing points, and also winding thread in a helix about the mandrel, and forming a wet paper web side layer on the base body.
According to the invention, by using the lattice material made by joining the crossing points of warp yarns and weft yarns as a component of the base body, undulations of the warp yarns and weft yarns can be made relatively small. Accordingly, cracking on a resin layer during use of the belt can be prevented and the durability can be improved. In addition, since there is no need to form thread in the axial direction of the mandrel, productivity can be remarkably improved.
a) is a cross-sectional view illustrating the process of forming the shoe side layer of the belt on a mandrel;
b) is a perspective view corresponding to
a) is a cross-sectional view showing the process of manufacturing a conventional shoe press belt; and
b) is a partial cross-sectional view of a shoe press belt produced by the conventional method.
As shown in
The base body 30 comprises a lattice material 40, composed of warp yarns 40A and weft yarns 40B, joined at their crossing points, and a wound layer 50 composed of a thread 50A wound in a helix.
Before the shoe side layer 20 is applied to the mandrel, the mandrel is pre-coated with a suitable remover material, or, alternatively a removing sheet (not shown) is applied to the surface of the mandrel. As shown in
Since the shoe press belt 10 according to the invention, when in use, as shown in
Polishing the surface of the mandrel M not only ensures smoothness of the inner surface of the belt 10, but also for facilitates removal of the shoe press belt from the mandrel. The mandrel M preferably includes a heater (not shown) which facilitates curing of the resin of the belt, including the resin of the shoe side layer 20.
After the shoe side layer 20 is formed on the mandrel, the base body 30 is formed on the external circumference of the shoe side layer 20. For the lattice material 40, which is composed of warp yarns 40A and weft yarns 40B, joined at their crossing points, a material such as disclosed in unexamined Japanese Patent Publication No. 194855/2002 may be used. This patent publication describes a lattice-like material composed of a warp layer disposed between two weft layers, in which the warp includes carbon fiber yarn and alkali-proof organic fiber yarn respectively impregnated with resin, and the weft includes both the carbon fiber yarn and the organic fiber yarn or only the organic fiber yarn.
As shown in
An example of a method of forming the base body 30 will be explained with reference to
To improve the strength of the belt, it is preferable to position the plural sheets of lattice material 40 on the mandrel M so that their lengthwise dimension is parallel to the axis of the mandrel, and so that the edges of the sheets overlap one another in the widthwise direction (that is, the circumferential direction), as shown in
The lattice material 40 of the base body of the belt may be composed of only a single sheet, in which case it can be easier to pull and fix the lattice material under even tensile force by means of a pulling apparatus provided at both ends of the mandrel M. However, as shown in
After forming the wound layer 50, as shown in
In the embodiments described above, one layer of lattice material 40 is provided on the external surface of the shoe side layer 20, and the wound layer 50 is then formed on the external surface of the lattice material 40. However, the invention is not necessarily limited to this arrangement of the lattice material 40 and the wound layer 50. Various other arrangements may used. For example, the wound layer can be formed first, and the lattice material can then be positioned on the outside of the wound layer. Alternatively, plural layers of the lattice material 40 can be provided. In a further alternative, a first wound layer can be formed on the shoe side layer, and then, after positioning the lattice material on the first wound layer, another wound layer can be formed. In still another alternative, a first layer of lattice material can be positioned on the shoe side layer, a wound layer can be formed on the first lattice layer, and then one or more further layers of lattice material can be applied on the outside of the wound layer. Still other variations can be used which are similar to those described, including other variations incorporating plural layers of lattice material. When applying plural layers of lattice material, it is preferable to position then so that, in any given layer, parts of lattice sheets which overlap in the widthwise are not directly over or under overlapping parts of another layer.
Following completion of the base body, an endless wet paper web side layer 60 is formed on the external circumference of the base body. Resin forming the wet paper web side layer 60 flows through the base body 30 comprising the lattice material 40 and the wound layer 50, and connects with the external surface of the shoe side layer 20, thereby integrating the shoe side layer, the base body, and the web side layer. Although the shoe side layer 20 and the wet paper web side layer 60 are usually integrated with each other naturally, the extent of their integration may be improved using a primer or an adhesive agent when necessary.
The resin used for the shoe side layer 20 and the wet paper web side layer 60 can be selected from any of various rubbers or other elastomers. However, polyurethane resin is preferably used. Thermosetting urethane resin is desirable, preferably having a hardness in the range from 80 to 90 degree (JIS-A). The hardness of the shoe side layer 20 and the wet paper web side layer 60 can be different in order to meet various conditions encountered in the use of the belt. However, in some cases, the hardnesses of the two layers can be the same.
In order to give the shoe press belt a high level of strength in the widthwise direction (cross machine direction), relatively thick and rigid yarn as shown in
The material of the weft yarns 40B is preferably synthetic fiber with a high modulus and high elastic modulus, such as nylon, PET, aromatic polyamide, aromatic polyimide, and high strength polyethylene. These fibers enable the base body to achieve durability and dimensional stability during use the belt, and also provide the durability required during removal of the shoe press belt from the mandrel on which it is formed. It is desirable that the strength of the lattice formed by the weft yarns 40B be in the region of 50–250 kg/cm, and that its 1% modulus be in the region of 5–40 kg/cm. In addition, it is also possible to use inorganic fibers such as carbon fiber or fiberglass etc.
When positioning the lattice material 40 on the external circumference of the shoe side layer 20, it is positioned so that its weft yarns 40B extend parallel to the direction of the axis of the mandrel M. This positioning of the lattice material may be achieved by gradually turning the mandrel M before the shoe side layer 20 is completely cured (that is, while the resin forming the shoe side layer is still glue-like At this time, apparatuses (not shown) for pulling and fixing the lattice material 40 are provided at both ends of the mandrel M. With these apparatuses, the lattice material 40, which usually comprises plural sheets, is gripped by gripping members, and is pulled under a uniform tensile force, and fixed to the shoe side layer.
When the lattice material 40 comprises only one sheet, after adjusting its width to an dimension slightly greater than the circumference of the shoe side layer 20, it is wrapped once around the shoe side layer, and its edges are brought into overlapping relationship in the widthwise direction. When the lattice material 40 comprises plural sheets, it is also important to make sure that edges the sheets overlap one another in the widthwise direction. It is to be noted that the term “overlap” includes a case where the opposing protruding yarns of the adjacent lattice materials not only overlap in the widthwise direction, but also overlap when viewed laterally along the plane formed by the adjacent lattice materials.
For the material of thread 50A, which is used for the wound layer 50, monofilament yarn or multifilament yarn comprising synthetic fiber having high strength, high modulus and high elastic modulus, such as nylon, PET, aromatic polyamide, aromatic polyimide and high strength polyethylene etc. may be used. Twisted yarns composed of any of these materials may also be used.
It is desirable to achieve a strength of the finished product in the range from about 100–300 kg/cm, by winding 10–50 pieces/5 cm when the thread 50A is multifilament comprising nylon or PET (7000 dtex) and by winding 10–30 pieces/5 cm when thread 50A is multifilament comprising aromatic polyamide (3000 dtex).
The wet paper web side layer 60 can be formed after winding the thread 50A to form the wound layer 50, but, as an alternative, it may be formed simultaneously with the winding of thread 50A. After forming the wet paper web side layer 60, the shoe press belt 10 is obtained by curing the resin with heat using heating apparatus (not shown) attached to the mandrel M, further polishing the surface to achieve the desired thickness of the shoe press belt, and finishing by producing concave grooves 70, or blind holes, in the paper web-engaging surface, as required.
After completion, the shoe press belt 10 is removed from said mandrel M. Removal can be achieved easily by applying a remover or a removing sheet or similar removing member to the surface of the mandrel M before forming the shoe side layer, and by connecting one end of the belt 10 to a ring R, as shown in
Examples 1–10 of a shoe press belt according to the invention having the above-described structure, and a comparative example 1, were produced following three processes, which will be explained in detail for Example 1. For the other examples, the differences in the processes will be pointed out.
In a first process, a remover (KS-61, from Shin-Etsu Chemical Co., Ltd.) was applied to the polished surface of a rotatable mandrel having a diameter of 1500 mm, using an appropriate driving means. Next, a thermosetting urethane resin, and curing agent were mixed. The mixture was composed of a TDI prepolymer (Takenate L2395 from Takeda Chemicals Co., Ltd.) and a curing agent comprising a DMTDA mixture composed of 3,5-dimethylthio-2,4-toluenediamine and 3,5-dimethylthio-2,6-toluenediamine (ETHAUCURE 300 from Albemarle Corporation). The prepolymer and curing agent were mixed with an H/NCO equivalent ratio of 0.97. The mixture was then applied to the surface of the mandrel to a thickness of 1 mm, using a doctor bar while rotating the mandrel. Then, the mandrel was left at room temperature while still rotating. After 10 minutes, the resin was heated to 70 degrees Celsius for 30 minutes to be cured, using a heating apparatus attached to the mandrel.
In a second process, a lattice material made by sandwiching warp yarns and weft yarns, and joining the crossing points of warp yarns and weft yarns with a urethane type resin adhesive. (The density of the weft yarns is shown in table below. The density of the warp yarns is 1 piece/cm for all the examples.) Twisted yarns of multifilament PET fiber having a fiber thickness of 5000 dtex were used both for the warp yarns and the weft yarns. One layer of the lattice material comprising plural sheets was positioned on the external circumference of the shoe side layer in such a way that weft yarns extended axially along the mandrel. The edges of the sheets overlapped one another in the widthwise direction. The wound layer was formed by winding a multifilament PET yarn having a fiber thickness of 7000 dtex in a helix on the external circumference of said lattice material. The pitch of the wound layer is shown in the table. Following winding of the wound layer, the base body was completed by filling with a coating resin to the extent that the gaps between the lattice material and the wound layer were covered.
In a third process, following completion of the base body, the same thermosetting urethane resin used for the shoe side layer was impregnated and coated onto the wound layer top a thickness of 5.5 mm to form the wet paper web side layer. After curing the resin with heat at 100 degrees Celsius for 5 hours, the surface of the wet paper web side layer was polished until the overall thickness of the belt was brought to 5.0 mm. Then concave groove extending in the machine direction of the belt were formed, using a rotating blade.
In Example 2, the locations of the lattice material and the wound layer in the base body were interchanged. That is, in the second process, after forming a wound layer on the external circumference of the shoe side layer, one layer of lattice material, comprising plural sheets, was positioned on the wound layer in such way that its weft yarns extended along the axial direction of the mandrel, and the edges of the sheets overlapped one another in the widthwise direction.
In Example 3, in the second process, two layers of lattice material, each comprising plural sheets, were positioned on the external surface of the shoe side layer with their weft yarns extending along the axial direction of the mandrel and their edges overlapping in the widthwise direction. Here the overlapping areas of the outer layer were positioned so that they did not overlap the overlapping sections of the inner layer. The wound layer was formed on the exterior of the outer layer of lattice material.
In Example 4, in the second process, after forming a wound layer on the external circumference of the shoe side layer, two layers of lattice material, each comprising plural sheets, were placed on the exterior of the wound layer, with their weft yarns extending along the axial direction of the mandrel. Here, as in Example 3, the edges of the sheets in each layer overlapped one another in the widthwise direction, and the overlapping areas of the outer lattice layer were positioned so that they did not overlap the overlapping sections of the inner lattice layer.
In Example 5, in the second process, a single sheet of lattice material was wound around the shoe side layer in a helix, with the edges of the sheet overlapping in the widthwise direction, and so that the weft yarns of the lattice material extend substantially parallel to the axis of the mandrel. The wound layer was then formed on the external circumference of the lattice layer.
In Example 6, the locations of the wound layer and the helically wound lattice layer as in Example 5 were interchanged. That is, in the second process, after forming the wound layer on the external circumference of the shoe side layer, a single sheet of lattice material was wound in a in helix over the wound layer, with its edges overlapping.
In Example 7, in the second process, a first sheet of lattice material was wound in a helix over the shoe side layer with its edges overlapping in the widthwise direction, and then a second sheet of lattice material was wound in a helix over the first helically wound sheet, again with its edges overlapping in the widthwise direction. Then a wound layer was formed on the external circumference of the second helically wound sheet of lattice material.
In Example 8, in the second process, after forming the wound layer on the external circumference of the shoe side layer, a first layer of lattice material was wound in a helix over the wound layer, with its edges overlapping, and then a second layer of lattice material was wound over the first helically wound layer of lattice material, again with its edges overlapping.
In Example 9, in the second process, after forming a first wound layer on the external circumference of the shoe side layer, one layer of lattice material comprising plural sheets was positioned on the wound layer in such a way that its weft yarns extended along the axial direction of the mandrel and the edges of the sheets overlapped in the widthwise direction. Then, another wound layer was formed on the external circumference of the lattice layer.
In Example 10, in the second process, a single sheet of lattice material, having a width slightly greater than the circumference of the shoe side layer, was placed on the external circumference of the shoe side layer, with its weft yarns along the axial direction of the mandrel and with its two edges overlapping each other in the widthwise direction. A first wound layer was then formed on said external circumference of the lattice, and another single sheet of lattice material, having a width slightly greater than the circumference of the shoe side layer, was placed on the external circumference of the first wound layer, with its weft yarns along the axial direction of the mandrel and with its two edges overlapping each other in the widthwise direction. The overlapping portions of the two lattice layers were positioned so that they did not overlap each other. Finally a second wound layer was formed on the external circumference of the outer layer of lattice material.
In the Comparative Example, as shown in
For all of the examples, physical properties such as cutting strength and crack-resistance were examined. An apparatus used for examining crack-resistance is shown in
Physical properties such as cutting strength and crack resistance, for Examples 1–10 and the Comparative example, are shown in the table below.
The data in the table show that the Examples according to the invention have excellent crack-resistance in comparison with the Comparative example. The Examples may have superior crack resistance because the base body of the Comparative example comprises a woven fabric wherein undulations of the warp yarns and weft yarns are relatively large, allowing cracks to occur more easily, whereas the base bodies of the Examples in accordance with the invention comprise a lattice material as a component, wherein the crossing points of the warp yarns and weft yarns are joined and undulations of the warp yarns and weft yarns are relatively small.
According to the invention as described above, undulations of the warp yarns and weft yarns can be made relatively small by using, as a component of the base body, a lattice material made by joining the crossing points of the warp yarns and weft yarns. By doing so, the occurrences of cracks in the resin layers during use of the belt can be prevented, and the durability of the belt is improved. In addition, since there is no need to form thread in the direction of the mandrel in order to form the base body, a remarkable improvement in productivity can be realized.
Further, it is advantageous that no displacement of the crossing points occurs when the lattice material is wound on the mandrel, since the yarns are bonded at the crossing points.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-091505 | Mar 2004 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4311474 | Standley | Jan 1982 | A |
| 4877472 | Rodal | Oct 1989 | A |
| 5134010 | Schiel | Jul 1992 | A |
| 5943951 | Muellner et al. | Aug 1999 | A |
| 6699368 | Ishii et al. | Mar 2004 | B2 |
| 6736939 | Watanabe | May 2004 | B2 |
| 6921461 | Watanabe et al. | Jul 2005 | B2 |
| 6929718 | Kimura | Aug 2005 | B2 |
| Number | Date | Country |
|---|---|---|
| 64-45888 | Feb 1989 | JP |
| 1-503315 | Nov 1989 | JP |
| 1-298292 | Dec 1989 | JP |
| 3-57236 | Aug 1991 | JP |
| 5-505428 | Aug 1993 | JP |
| 8-209578 | Aug 1996 | JP |
| 2000-303377 | Oct 2000 | JP |
| 3213589 | Jul 2001 | JP |
| 2002-194855 | Jul 2002 | JP |
| 3408416 | Mar 2003 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20050211533 A1 | Sep 2005 | US |
