Technical field
-
The present invention relates to a fabric edge support device according to the preamble of claim 1. The present invention relates in general to a fabric edge support device for use in connection with an edge of a forming fabric of a fiber web machine fourdrinier section, the fabric edge support device comprising
- a bar, which comprises a cross sectionally a curved surface to provide an edge support surface extending in a machine direction for the forming fabric, the bar is provided to be set at a distance downstream from a headbox to bend the forming fabric edge upwards to prevent fiber stock to flow over the edge of the forming fabric when installed,
- a water channel arranged in operational connection with the edge support surface so as to provide water stream on the edge support surface when in use,
- a holder for supporting the bar and setting the position of the bar, the holder comprising attachment means for attaching the fabric edge support device to a fiber web machine.
Background art
-
A fiber web machine fourdrinier section comprises a forming fabric that forms an endless loop around a plurality of rolls, a substantially horizontal fourdrinier table is provided as a first part of the loop for dewatering the fiber stock flowing from a headbox on to the moving forming fabric. At this stage the fiber stock consists over 95% of water, while the rest is fibers, fillers and chemicals. The fourdrinier table comprises a breast roll and a forming board that are guiding the forming fabric at the position where the fiber stock comes on to contact with the forming fabric. As the stock flow is now laid on an open forming fabric, there the stock flow may spread as a deckle wave toward the edges of the moving forming fabric. To prevent overflow out from the forming fabric there have been used fabric edge support devices such as deckle boards and rulers.
-
Patent document
US 4738751 discloses an apparatus for continually supporting and curling the edge of the fabric so as to prevent loss of pulp mixture off the sides of the fabric and so as to prevent edge wave formation which would require substantial trimmage and waste. The apparatus includes a pair of bars having a wedge-shaped cross-section, one edge of each inserted under one side of the fabric, to cause the edge of the fabric to curl upward. Apparatus is provided to adjust the amount of curl. Several of these curl adjusting apparatuses are placed along the length of the bars so that the amount of curl can be different at different points along the bars.
Patent document
US 5302250 discloses a paper machine deckle defining structure that is protected from fiber accumulations by a uniformly distributed water film that continuously flows from a flat, horizontal upper surface over all smoothly faired lower surfaces of the deckle elements.
Patent document
US 8236139 discloses an apparatus for preventing the creation of non-uniform profiles caused by deckle waves though the use of transforming the deckle boards into active drainage elements in the paper forming area of the paper machine.
-
An object of the invention is to provide a fabric edge support device that is easy to adjust in terms of deckle wave control, prevents accumulation of fibers and makes the forming fabric change easy. Thus a fabric edge support device in which the performance is considerably improved compared to the prior art solutions.
Disclosure of the Invention
-
Objects of the invention can be met substantially as is disclosed in the independent claim and in the other claims describing more details of different embodiments of the invention.
-
According to an embodiment of the invention it is provided a fabric edge support device for use in connection with an edge of a forming fabric of a fiber web machine fourdrinier section, the fabric edge support device comprising
- a bar, which comprises a cross sectionally a curved surface to provide an edge support surface extending in a machine direction for the forming fabric, the bar is provided to be set at a distance downstream from a headbox to bend the forming fabric edge upwards to prevent fiber stock to flow over the edge of the forming fabric when installed,
- a water channel arranged in operational connection with the edge support surface so as to provide water stream on the edge support surface when in use,
- a holder for supporting the bar and setting the position of the bar, the holder comprising attachment means for attaching the fabric edge support device to a fiber web machine,
- the fabric edge support device comprises a fabric guide to support the forming fabric during a fabric change.
-
This provides an effect by means of which the deckle wave can be accurately controlled, the accumulation of the fibers is reduced and the maintenance of the fiber machine fourdrinier section is easier to perform, especially the fabric change (the term "fabric change" refers in this description always to the forming fabric change) can be done in a short time and a risk of forming fabric damage during the fabric change is deminished when there is a denoted fabric guide to support the forming fabric during a fabric change. Thus the performance of the fabric edge support device is considerably improved. In most of the prior art solutions the fabric edge support devices or deckle boards need to be removed for the fabric change. This causes an extra task for the operators in removal of the former fabric but also later a potential quality defect for fiber web to be produced if the settings are not returned after the fabric change to the proper ones. For example the distance of the curved support surface in relation to the forming fabric edge (both in lateral direction and in elevation) must be very precisely set so that the elevation or curl of the forming fabric edge is just right.
-
According to an embodiment of the invention the fabric guide comprises a horizontal surface or plane to support the forming fabric during the fabric change enabling that the forming fabric can be slidden along the fabric guide when installed/removed. As the forming fabric is an endless loop having a weight of several hundreds of kilograms in a modern fiber web machine fourdrinier section it needs to be pushed/drawn on to its place from the tending side of the fiber web machine. The rolls and other structures are supported for the fabric change by special cantilever beams. However, the fabric edge support device is on the way and may prevent smooth fabric change. The fabric guide comprising a substantially horizontal surface or plane carries part of the loose forming fabric weight and guides the forming fabric over the structures of the fabric edge support device and other structures below the level of the fourdrinier table. For example, according to an embodiment, the fabric guide may comprise a bracket plate or rod attached above the holder. According to another embodiment the fabric guide may comprise a part of the bar and/or water channel extending over the holder to form the support for the forming fabric. Still according to another embodiment the holder comprises an integral top surface that has been formed as the fabric guide. Then the holder itself is shaped or formed so that it functions as the fabric guide to form the support for the forming fabric.
-
According to an embodiment, the holder comprises an adjusting device for adjusting the position of the bar in the first direction, preferably an adjustment screw - the first direction being cross direction when installed in the fiber web machine. The bar comprising a cross sectionally a curved surface to provide an edge support surface extending in a machine direction for the forming fabric need to be set precisely in relation to the forming fabric edge. Due to the curved edge support surface, the lateral position (cross directional position) of the bar in relation to the forming fabric edge defines a curl or bend of the forming fabric edge. If the bar is closer to a center line of the fiber web machine, the bar curls or bends the forming fabric edge more. Contrary, if the bar is more distant from the center line of the fiber web machine, the bar bends the forming fabric edge less. As this bending has a significant effect on the deckle wave formation, a precise adjustability is highly appreciated feature. Also the distance in machine direction need to be set properly, thus the bar is provided to be set at a distance downstream from a headbox to bend the forming fabric edge upwards to prevent fiber stock to flow over the edge of the forming fabric. According to an embodiment, the bar comprises a longitudinal slide rail for adjusting the position of the bar in the second direction i.e. machine direction. This is only one option, there are several possibilities to determine the bar position in the machine direction.
-
The fabric edge support device comprises a holder for supporting the bar and setting the position of the bar, the holder comprising attachment means for attaching the fabric edge support device to a fiber web machine. According to an embodiment, the attachment means is a holder frame to be attached to the structures of the fiber web machine. Depending on the length of the bar, the bar is attached to at least two holders, the number of the holders may be two to four, even more depending on the length of the bar. For very short bars, only one holder is enough.
-
The fabric edge support device comprises also a water channel arranged in operational connection with the edge support surface so as to provide water stream on the edge support surface when in use. As the forming fabric edge slides continuously along the bar edge support surface, this sliding contact may cause friction and wear & tear of the forming fabric or the bar. Therefore, a water stream is provided on the surface, it both reduced friction but also keep the bar clean from possible accumulation flocks of fibers, fillers or chemicals. Preferably the water stream is arranged so that there is a continuous water film on the edge support surface, flowing from upper part of the bar downwards. A water channel attached in the vicinity above to the bar and extending along the bar would provide water stream on the edge support surface when in use. It may also be integrated to or with the bar. According to an embodiment the water channel is a tube comprising plurality of openings along the length of the tube, the openings being inclined towards the edge support surface for supplying water on the edge support surface. Still according to another embodiment, it is provided a water tube comprising plurality of openings along the length of the water tube, the openings being set on the upper area of the water tube and being inclined towards the edge support surface for supplying water on the edge support surface. In order to make the gliding contact between the forming fabric and the bar durable and long lasting, the bar material is HDPE. This has good sliding characteristics with current commercially available forming fabric materials and contact surface lubricated with water as explained above.
-
The exemplary embodiments of the invention presented in this patent application are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. In this application the forming fabric refers to a forming wire, which consists of yarns between which water can exit from the web.
Brief Description of Drawings
-
In the following, the invention will be described with reference to the accompanying exemplary, schematic drawings, in which
- Figure 1A illustrates a side view of fiber web machine fourdrinier section,
- Figure 1B illustrates a partial top view of fiber web machine fourdrinier section,
- Figure 2 illustrates a fabric edge support device according to another embodiment of the invention,
- Figure 3 illustrates a fabric edge support device according to still another embodiment of the invention,
- Figure 4 illustrates a fabric edge support device according to still another embodiment of the invention,
- Figure 5 illustrates a fabric edge support device according to still another embodiment of the invention,
- Figure 6A and 6B illustrates a fabric edge support device according to still another embodiment of the invention,
Detailed Description of Drawings
-
Figure 1A depicts schematically a side view example of a fiber web machine 1 fourdrinier section. The forming section comprises a head box 12, forming fabric 10 (or moving wire 10) being in a shape of endless loop, a breast roll 14, forming board 15, and a series of vacuum/suction/foil boxes 16 and rolls 17a, 17b, 17c. At least one of the rolls 17a, b, c being movable so that the forming fabric tension can be adjusted and the tension can be released for the fabric change. In this Fig. 1A the roll 17c in the right bottom is the one that is illustrated to be the movable roll. As the fiber stock FS suspension moves along the forming fabric 10 (in machine direction MD) and over the vacuum/suction/foil boxes 16, the water is removed to form a continuous web. The fiber stock FS flows out of the head box 12 in a flat stream onto the moving forming fabric 10 on a fourdrinier table 101 of a fiber machine. Basically the fourdrinier table 101 is the horizontal part of the fiber web machine 1 fourdrinier section between the breast roll 14 and the roll 17a. In Fig. 1A there is presented a fourdrinier configuration with a top former 18.
-
In Fig 1B it is presented a partial top view of the fiber web machine 1 fourdrinier section of Fig. 1A. The head box 12, breast roll 14, forming board 15 and vacuum/suction/foil boxes 16 are illustrated schematically as well as the forming fabric 10. The fabric edge support device 2 is installed on both sides of the forming fabric 10, both on the drive side DS and tending side TS of the fiber web machine 1. Advantageously the fabric edge support device 2 is positioned so, that its leading edge is after the forming board 15 in machine direction MD. The forming fabric edges 100 cross the fabric edge support devices 2. The fiber web machine 1 cross direction is illustrated with an arrow CD.
-
In Fig 2 it is presented an embodiment of fabric edge support device 2 for use in connection with an edge 100 of a forming fabric 10 of a fiber web machine 1 fourdrinier section (not shown in Fig. 2), the fabric edge support device 2 comprising
- a bar 20, which comprises a cross sectionally a curved surface to provide an edge support surface 201 extending in a machine direction MD for the forming fabric 10, the bar 20 is provided to be set at a distance downstream from a headbox 12 (not shown in Fig. 2) to bend the forming fabric edge 100 upwards to prevent fiber stock FS to flow over the edge 100 of the forming fabric 10 when installed,
- a water channel 21 arranged in operational connection with the edge support surface 201 so as to provide water stream on the edge support surface 201 when in use,
- a holder 22 for supporting the bar 20 and setting the position of the bar 20, the holder 22 comprising attachment means 224 for attaching the fabric edge support device 2 to a fiber web machine 1,
- the fabric edge support device 2 comprises or is provided with a fabric guide 23 to support the forming fabric 10 during a fabric change.
As shown in the Fig. 2, the fabric guides 23 are assembled to the fabric edge support device only on the tending side TS. As during the fabric change, the old forming fabric is slided out from the fiber web machine from the tending side TS and the new forming fabric is also installed from the tending side TS, the fabric guides would be useless on the drive side DS fabric edge support device. The fabric guide 23 comprises a horizontal surface or plane to support the forming fabric 10 during the fabric change enabling that the forming fabric 10 can be slidden along the fabric guide 23 when installed/removed.
-
In Fig 3 it is presented a more detailed embodiment of the tending side TS fabric edge support device 2 of Fig. 2. The fabric guide 23 comprises a substantially horizontal surface or plane to support the forming fabric 10 during the fabric change enabling that the forming fabric 10 can be slidden along the fabric guide 23 when installed/removed. As shown in the Fig. 3, the fabric guides 23 have slight inclinations or ridge shape in cross direction CD, it makes it easier to slide the forming fabric over the fabric guide. However, the levelling of fabric guides in machine direction is preferably even, so that the surfaces of the fabric guides form a straight line and therefore the load between the different fabric guides 23 would be even. According to the embodiment in Fig. 3, the fabric guide 23 comprises a bracket plate or rod attached above the holder 22. This is the preferred place for the fabric guide since the holders 22 may comprise structures that could grab or cut the forming fabric. However, if necessary, fabric guides 23 can also be attached between the holders 22 as shown in Fig. 3. As shown in the embodiment of Fig. 3, the bar 20 is attached to at least two holders 22, the number of the holders 22 may be two to four, even more depending on the length of the bar 20.
-
In Fig. 4 it is presented an embodiment of a fabric edge support device 2 comprising a holder 22 for supporting the bar 20 and setting the position of the bar 20, the holder 22 comprising attachment means 224 for attaching the fabric edge support device 2 to a fiber web machine 1. The attachment means 224 is a holder frame 224 to be attached to the structures of the fiber web machine 1. The attachment means or holder frame construction depends on the actual fiber web machine construction, therefore the embodiment shown in Fig. 4 is only one of the numerous possible alternatives. The holder 22 comprises an adjusting device 221 for adjusting the position of the bar 20 in the first direction i.e. cross direction CD, preferably an adjustment screw.
-
Fig 5 depicts schematically the fabric edge support device 2 comprising a water channel 21 arranged in operational connection with the edge support surface 201 so as to provide water stream on the edge support surface 201 when in use. The water channel 21 is according to an embodiment a tube 21 comprising plurality of openings 211 along the length of the tube 21, the openings 211 being inclined towards the edge support surface 201 for supplying water on the edge support surface 201.
-
In Figure 6A it is presented a side view, parallel to MD, of the fabric edge support device 2 comprising a water channel 21 arranged in operational connection with the edge support surface 201 so as to provide water W stream on the edge support surface 201 when in use. In Fig. 6A it is illustrated a part of the forming fabric 10 supported by the edge support surface 201 bending the forming fabric edge 100 upwards to prevent fiber stock FS to flow over the edge 100 of the forming fabric 10. The position of the bar 20 / edge support surface 201 in relation to the forming fabric edge 100 can be precisely adjusted in the in the first direction i.e. cross direction CD by means of the adjusting device 221, preferably an adjustment screw as shown in Fig. 6A. As the bar 20 is adjusted towards the forming fabric 10, the forming fabric edge 100 bends more i.e. raises upwards.
-
In Figure 6B it is presented a side view, parallel to MD, of the fabric edge support device 2 similar to Fig. 6A provided with an embodiment of a fabric guide 23 to support the forming fabric during a fabric change. The fabric guide 23 comprises a substantially horizontal surface or plane to support the forming fabric 10 during the fabric change enabling that the forming fabric 10 can be slidden along the fabric guide 23 when installed/removed. As shown in the Fig. 6B, the fabric guide 23 is in general horizontal or substantially horizontal, but it has slight inclinations or ridge 230 shape in cross direction CD, it makes it easier to slide the forming fabric over the fabric guide 23. It also has in the first outer end (TS end when installed) a more significant bevelling to prevent forming fabric to grab to the structures of the holder 22. In Fig. 6B it is also presented an embodiment wherein the bar 20 comprises a longitudinal slide rail 202 for adjusting the position of the bar 20 in the second direction i.e. machine direction MD. This can also be the other way around, the slide rail can also be a part of the holder 22 while rail clamps are attached to the bar 20.
-
While the invention has been described herein by way of examples in connection with what are, at present, considered to be the most preferred embodiments, it is obvious to the skilled person that, along with the technical progress, the basic idea of the invention can be implemented in many ways. The invention and its embodiments are thus not limited to the examples and samples described above but they may vary within the contents of patent claims and their legal equivalents. The details mentioned in connection with any embodiment above may be used in connection with another embodiment when such combination is technically feasible.
Part list
-
- 1
- fiber web machine
- 10
- forming fabric
- 100
- forming fabric edge
- 101
- fourdrinier table
- 12
- head box
- 14
- breast roll
- 15
- forming board
- 16
- vacuum/suction/foil box
- 17a, b,c
- roll
- 18
- top former
- 2
- fabric edge support device
- 20
- bar
- 201
- edge support surface
- 202
- slide rail
- 21
- water channel
- 211
- opening
- 22
- holder
- 220
- slide rail clamp
- 221
- adjusting device
- 224
- attachment means, holder frame
- 23
- fabric guide
- 230
- fabric guide ridge
- MD
- machine direction
- CD
- cross direction
- FS
- fiber stock
- DS
- drive side
- TS
- tending side
- W
- water