Patent Grant
7527708
The present invention relates to a support body for an apparatus having an extended nip defined between a contact surface of the support body and an opposed surface.
The previously known presses with an extended press nip have a so-called press shoe, which consists of a metallic material, such as aluminium or steel, and are designed with a press surface, usually a concave press surface, whose profile is very accurately adapted to the opposed counter-pressure surface. Such a press shoe is very complicated to manufacture and therefore involves a very high cost. Due to the fact that it consists of metal, it is relatively rigid and inflexible. The press roll acting as a counter roll of such a shoe press can have a relatively thick cylinder wall which withstands the forces from the press shoe. In accordance with another embodiment of the counter roll, it has a relatively thin cylinder wall and is provided internally with a counter-pressure system for adjustable crowning of the thin and, thus, deformable cylinder wall or shell in dependence of the forces the press shoe has to apply on the counter roll in order to obtain the desired load. Also the press shoe can be crowned in accordance with the crowning of the counter roll, and it will then be usable only in combination with this counter roll. Alternatively, the metallic press shoe can be tilted by means of hydraulic cylinders.
A Yankee cylinder has a cylinder wall or shell which is relatively thin, and which easily is deformed by impression of the press shoe when the Yankee cylinder is used as a counter roll. The deformation of the shell varies in an axial direction from the central region in a direction towards the end walls, where the impression is substantially smaller than within the central region. Therefore, the press shoe will act with a higher pressure at and in the vicinity of the end walls, resulting in an increased wear at the edges of the press felt and an irregular load profile along the press shoe, something which in its turn results in variable paper properties crosswise to the machine direction. It has been proposed to crown the shell of the Yankee cylinder by means of an internal counter-pressure system, or to arrange two or more rows of hydraulic cylinders on the underside of the press shoe for influencing the press shoe to conform to the deformed surface, in both cases in order to achieve a more uniform load profile. Both proposals, however, are complicated and expensive to carry out.
The following documents are examples of presses having extended press nips.
DE 44 05 587 and WO 02/44467 describe a press having a hydrostatic bearing, including a press shoe 3 or double press shoes 3a, 3b of the same design. A press belt 6 rotates on top of a lubricating fluid bed of the press shoe 3 with a very small friction. The press shoe, which is made of metal, has a pressure chamber 10 containing a hydraulic fluid, preferably water. A rectangular pressure-equalizing membrane 20, consisting of a suitable solid material, preferably stainless steel, is fixed on the press nip side of the press shoe. The pressure-equalizing membrane 20 has an outer edge 26, an inner edge 22, and an opening 27 that is defined by the inner edge 22. The pressure-equalizing membrane 20, thus looking like a frame, is flexible so that an edge zone 21, standing in direct contact with the hydraulic fluid, can deflect when pressure differences occur between its two sides. These pressure differences arise when hydraulic fluid happens to leak out through the press nip as a result of irregularities in the paper web and/or in the envelope surface of the counter roll. Thus, the flexible pressure-equalizing membrane 20 creates a self-adjusting nip 2, having no or only a minimum of fluid leakage. Thus, through the opening 27 in the pressure-equalizing membrane 20, the pressure fluid in the pressure chamber 10 stands in direct contact with the movable belt. The complementary addition which has been done in said WO-publication in comparison to said DE-publication is that the flexible membrane has been provided with “pinholes 25” within its free edge zone 21 in order to conduct hydraulic fluid from the pressure chamber 10 to the belt 6 for the purpose of lubricating the belt.
U.S. Pat. No. 5,980,693 describes presses having a tube-shaped or inflatable loading element, but with a metal shoe between the loading element and the inside of the belt. Furthermore, this part of the shoe is constructed in order to provide a slow reduction of the pressure in nip outlet. Normally, an abrupt pressure drop is desired.
U.S. Pat. No. 3,839,147 describes a shoe press having two opposed shoes. Each shoe has a metal bottom and sills, sealing against the inside of the belt. The side of the shoe facing the belt is a perforated diaphragm, which causes the pressure of the hydraulic fluid in a pressure chamber to load the inside of the belt directly. The shoe is of a rather complicated construction with various apertures and reinforcements.
U.S. Pat. No. 5,951,824 describes an ordinary shoe having ordinary hydraulic loading elements. The shoe is coated with a soft and durable layer of polymer or rubber in order to reduce the risk of damages to the belt and shoe from paper wads passing through the press nip.
EP 0 575 353 describes a press having a shoe, which is loaded with bellows being arranged inside a metal cover of the shoe, wherein a belt slides around said metal cover.
U.S. Pat. No. 6,334,933 describes a press having a counterpart of metal, which is provided with a plurality of pressure pockets being sealed by a metal plate and hoses, which also can contribute to loading the opposite portions of the press nip.
U.S. Pat. No. 6,387,216 describes a press having an open fluid chamber, over which a belt is running and which is loading the press nip. The chamber is sealed by means of setting the belt under pressure, so that it is tightened over the edges of the chamber.
EP 1 319 744 describes a method for measuring and regulating the nip pressure in a shoe press, crosswise to and along the web, by means of measuring and continuously adapting the hydraulic static pressure in reference points above measurement holes in the press nip.
DE 30 30 233 describes an elastic slide shoe which is attached to a stand of metal. The slide shoe includes a solid body or a hollow body in the form of a hose which can be filled with a pressure medium. The hose is surrounded by an elastic belt which is attached to the metal stand. The hollow body may be divided into chambers which can be pressurized to different pressures. However, a change of pressure in the chamber or chambers does not result in a change of the loading in the nip because of the fact that the hollow body is permitted to expand laterally during every such increase of pressure.
It is an object of the invention to provide an elastic support body which, in relation to known support bodies, can be manufactured in a more simple way, without any special machining and without any major consideration to the shape of the opposed surface which it is to work against, and which can provide a loading profile in dependence of the pressure in the pressure chamber or pressure chambers in the same way or even in a better way than what is possible with a conventional support body of metal with one or more rows of pressure pockets which are closed by a running belt.
A support body according to one embodiment of the invention is characterized in that it is provided with a holding device arranged to form a counter support for the pressure chamber or the pressure chambers, respectively, except at the side of the pressure chamber or pressure chambers, respectively, facing said contact surface.
The holding device according to the invention is characterized in that it has a space for receiving the support body in order to form an outer counter support for all surfaces of the support body, as seen circumferentially, except its contact surface, and/or is entirely or partially embedded in the support body in order to form an inner counter support for the pressure chamber or the pressure chambers, respectively, except at the side facing said contact surface.
The apparatus according to the invention is characterized in that the support body is provided with a holding device arranged to form a counter support for the pressure chamber or the pressure chambers, respectively, except at the side of the pressure chamber or pressure chambers, respectively, facing said contact surface, whereby, in the operation of said apparatus and the support body being in a nip-forming operation position, the support body is arranged such that a change of the pressure in said pressure chamber or in at least one of said several pressure chambers produces a corresponding change of pressure in the nip with accompanying changed press curve.
A press according to one embodiment of the invention is characterized in that the press body is provided with a holding device arranged to form a counter support for the pressure chamber or the pressure chambers, respectively, except at the side of the pressure chamber or pressure chambers, respectively, facing said press surface, whereby, in the operation of the press and the press body being in a nip-forming operation position, the press body is arranged such that a change of the pressure in said pressure chamber or in at least one of said several pressure chambers produces a corresponding change of pressure in the nip with accompanying changed press curve.
A method of forming an extended nip according to one embodiment of the invention is characterized by the steps of:
A method of controlling the load in an extended nip according to one embodiment of the invention is characterized by the steps of:
The expression “nip” is to be interpreted in its broadest meaning in order to encompass such a nip that is defined by a wire and support body.
Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
The present inventions now will be described more fully hereinafter with reference to the accompanying drawings in which some but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.
The invention will be described in connection with a press for dewatering a fibre web. Naturally, in addition to the press section, the invention can be applied to any suitable apparatus for the treatment of a fibre web, e.g. an apparatus in a drying or forming section of a paper or board machine, and in a calender for surface treatment of the fibre web.
The second press element 2 includes a counter-pressure member being active in the press nip N and having a movable, endless surface 3, which forms an opposed surface or counter-pressure surface 4, which can be curved or linear, within the press nip N. In the shown embodiment of the press, the second press element 2 consists of a counter roll in the form of a press roll. The counter roll also can be a drying cylinder in a conventional drying section, or a drying cylinder in a tissue machine designated Yankee cylinder. In this case, the counter-pressure member includes the cylindrical wall 5 of the counter roll 2 the envelope surface of which forms said movable, endless surface 3, which within the extended press nip N forms said counter-pressure surface 4, which can be at room temperature or a temperature raised by means of heating. Provided that the cylinder wall 5 is thick and stable enough, it constitutes the counter-pressure member as such. In the case when the cylinder wall 5 is thin and deformable, the counter-pressure member further includes an internal supporting system (not shown), which provides the necessary counter-force.
The first press element 1 includes a movable, endless belt 6 of a flexible material, a support body 7 in the form of a press body, a holding device 8 for mounting the press body 7, a support for mounting the holding device 8, and a loading means for activating the press body 7. The movable belt 6 describes a closed loop inside of which the press body 7 and the support are located. Before the press nip N, the movable belt 6 is arranged for meeting a press felt 9 carrying a wet fibre web W which is to be dewatered when it passes through the extended press nip N. The loading means is arranged for being activated in order to influence the press body 7 during the operation of the press for obtaining pressure forces which the press body 7 exerts against the counter roll 2 via the belt 6, the press felt 9 and the web W. The press body 7 is arranged for deciding the length of the extended press nip N, as seen in the machine direction. The press body 7 has a free sliding surface 10 with which the rotating belt 6 is in sliding contact during the operation of the press, whereby the sliding surface 10 entirely or partially forms a contact surface or press surface 13, which together with said counter-pressure surface 4 defines the press nip N. A spraying device 11 is mounted upstream the press body 7 for supplying lubricant on the inside of the belt in order to form a film which reduces the friction between the rotating belt 6 and the press body 7.
In the shown embodiment of the press, the first press element 1 consists of a press roll, the shell of which forms the movable belt 6 which thus describes a substantially circular loop. In an alternative embodiment of the press (not shown), the flexible, movable belt is arranged for running in a non-circular loop, e.g. in a substantially oval loop or in a substantially triangular loop, around the press body and one or several guide rolls. In the embodiment shown, the press roll 1 has two circular, rotatably mounted end walls (not shown), whereby the shell 6 is rigidly mounted to the peripheries of the end walls in order to rotate together with them. The shell 6 and the end walls define a closed space in which the support is located, said support including a stationary supporting beam 12 extending axially between the end walls without touching them. Also the press body 7 and its holding device 8 are extending axially between the end walls without touching them. Alternatively, the second press element 2 can be of the same or substantially the same design as the above-described first press element 1, whereby the press nip thus is formed by two press bodies according to the invention.
The press body 7 is elastically deformable and has its press surface 13 adaptable to the counter-pressure surface 4 in interaction with this. This adaptation takes place under the influence of a load being created by said loading means, on the press body 7 in a direction towards the counter-pressure surface 4 in order to load the entire press nip N correspondingly. The definition that the press body is elastically deformable does not necessarily imply that the entire press body consists of an elastic material, but should in the context of the invention be seen in a broader sense, namely that the press body has at least one functional portion consisting of an elastic material and fulfilling said definition. For practical and production-engineering reasons, and according to the most preferred embodiments the press body is in its entirety made of an elastic material (or several).
According to the invention, the press body 7 includes one or several closed pressure chambers, said pressure chamber or pressure chambers being part of said loading means. In accordance with
As mentioned in the foregoing, the press body 7 is elastically deformable in order to expand, under the influence of an increased pressure in the pressure chamber 14, and bring the top wall 31 with its press surface 13 in a direction towards the counter-pressure surface 4 of the counter roll. As is evident from
The press body 7, being used in the embodiments according to
Also in the embodiment according to
When the support body 7 has a plurality of pressure chambers (as those according to
The support body 7 is an extruded member defining three separate pressure chambers 76, 78, 80 extending in the cross-machine direction and spaced apart in the machine direction. Each of the chambers 76, 78, 80 has a generally rectangular cross-sectional shape. An internal reinforcing tube 82 of generally rectangular cross-sectional shape is embedded within the chamber 76. The reinforcing tube 82 comprises a continuous steel profile. The top wall of the reinforcing tube 82 has holes 83 spaced apart in the cross-machine direction along the tube for communicating fluid pressure from the interior of the tube 82 to the chamber 76.
Similarly, an internal reinforcing tube 84 is embedded within the chamber 78 and has holes 85 in its top wall for communicating fluid pressure from the interior of the tube 84 to the chamber 78, and an internal reinforcing tube 86 is embedded within the chamber 80 and has holes 87 in its top wall for communicating fluid pressure from the interior of the tube 86 to the chamber 80.
Separate sources of fluid can be coupled respectively to the interiors of the reinforcing tubes 82, 84, 86 for pressurizing the chambers 76, 78, 80 independently of one another.
The press body can further include an exchangeable wear protection layer 90 that covers the contact surface of the support body 7. The wear protection layer comprises a flexible sheet of suitable material such as a polymer film. The wear protection layer can be removed and replaced with a new layer when it becomes worn. In this manner, wear of the support body 7 is substantially prevented and the press body can be easily and inexpensively restored to a like-new condition. The upstream edge of the wear protection layer 90 is rigidly affixed to an upstream side of the holding device, such as by fasteners 92 or the like. The downstream edge of the wear protection layer 90 can be left free to follow movement and deformation of the support body 7.
A press body in accordance with a tenth embodiment of the invention is illustrated in
The downstream chamber 94, because of its high aspect ratio, includes a pair of reinforcing tubes 100a and 100b stacked one atop the other and rigidly joined together, such as by welding or the like. Each tube 100a, 100b has a height that is substantially half the height of the chamber 94 in its non-pressurized condition. This arrangement provides increased bending stiffness relative to a single reinforcing tube of full height. Holes 102 are provided between the tubes 100a, 100b for communicating fluid between their interiors. A series of holes 104 are formed in the top wall of the upper tube 100a for communicating fluid from the interiors of the tubes 100a, 100b to the interior of the chamber 94.
The middle chamber 96 includes an internal reinforcing tube 106 having holes 107 in its top wall, and the upstream chamber 98 includes an internal reinforcing tube 108 having holes 109 in its top wall. As in the ninth embodiment, the interiors of each of the reinforcing tubes 100a/b, 106, 108 can be supplied with separate fluid streams, which optionally can have different pressures, for pressurizing the chambers 94, 96, 98 independently of one another.
Finally, an eleventh embodiment of a press body in accordance with the invention is depicted in
The upstream chamber 98 has a stack of five separate reinforcing tubes 108a, 108b, 108c, 108d, 108e stacked one atop another and rigidly joined together. There are holes between the contiguous tubes 108a and 108b, between the contiguous tubes 108b and 108c, between the contiguous tubes 108c and 108d, and between the contiguous tubes 108d and 108e for communicating fluid between the respective interiors of the contiguous tubes. The top tube 108a has holes 109 as in the prior embodiment.
The press body according to the invention has a number of essential advantages of which the following can be mentioned:
The support bodies 7 which are described above and shown in the drawings have been designated press bodies, since they are used in a press apparatus. Naturally, the same embodiments of the press body can be used in other apparatus for the treatment of a fibre web in a paper or board machine, or in a calendar. When the invention is applied to e.g. a wire section, the belt 6 of the first press element 1 in
The load in the nip can vary from 0 to 3000 kN/m.
The support body may have a dimension in the machine direction (width) which typically is 50-500 mm.
The desirable elastic properties of the support body are achieved by means of an elastic material, having a coefficient of elasticity which is substantially lower than that of metal, such as steel and aluminium, so that the support body, depending on the construction of the support body, can be elastically expanded or elastically compressed. Typical hardness values of the elastic material is 50-95 Shore A. The elastic material should also give the support body a sufficient strength/hardness in order to withstand wear, but at the same time make the support body elastically deformable enough in order to obtain the desired function according to the invention. As elastic materials, plastic and rubber materials can be used, such as polymers, composite materials, which can be reinforced with e.g. glass fibres, carbon fibres or textile. At present, polyurethane is a preferred polymer.
In some of the embodiments described above, the holding device 8 functions as an outer counter support for all surfaces, as seen circumferentially, of the support body 7 except its contact surface 13. It can also be designed and arranged such that it functions as an inner counter support which is entirely or partially embedded in the support body at a distance from the pressure chamber or pressure chambers, respectively. Also the combination of an outer counter support and an inner counter support can be used, such as in the embodiments of
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0302767-9 | Oct 2003 | SE | national |
The present application is a continuation-in-part of International Patent Application PCT/SE2004/001485 filed on Oct. 15, 2004, which designated inter alia the United States of America and was published under PCT Article 21(2) in the English language.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3293121 | Martin | Dec 1966 | A |
| 3839147 | Daane | Oct 1974 | A |
| 4468287 | Dahl | Aug 1984 | A |
| 4576682 | Laapotti | Mar 1986 | A |
| 4851119 | Berglöff et al. | Jul 1989 | A |
| 5614064 | Nykopp | Mar 1997 | A |
| 5951824 | Deshpande | Sep 1999 | A |
| 5980693 | Liang et al. | Nov 1999 | A |
| 6334933 | Koski | Jan 2002 | B1 |
| 6387216 | Koski | May 2002 | B1 |
| 6835283 | Weigant et al. | Dec 2004 | B2 |
| Number | Date | Country |
|---|---|---|
| 30 30 233 | Feb 1982 | DE |
| 44 05 587 | Sep 1994 | DE |
| 0 575 353 | Aug 1995 | EP |
| 1 319 744 | Jun 2003 | EP |
| WO 0244467 | Jun 2002 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20060254437 A1 | Nov 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/SE2004/001485 | Oct 2004 | US |
| Child | 11408340 | US |
