A multilayer papermaker's press felt fabric comprising in combination a woven first fabric layer, typically a double layer fabric, has a cross machine direction pin seam. A second fabric layer is located on the paper side face of the first fabric layer, and a layer of needled batt is applied to the paper side face of the second layer binding the layers together. A flap comprising a short length of the second fabric layer with attached batt overlays the pin seam area in the first layer. The second layer comprises a plurality of relatively narrow strips, which are located with a lateral edge at a first cant angle of from more than 1° to less than 20° to the machine direction. A third layer, similar to the second layer, can be included on the machine side of the first layer; the strip widths, the cant angles, and the direction of the cant angle relative to the machine direction for each of the two strips need not be the same. The fabric is assembled using a spiral winding technique.
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1. A multilayer papermaker's press felt fabric comprising in combination:
a woven first fabric layer incorporating therein a cross machine direction pin seam,
a second fabric layer on the paper side face of the first fabric layer,
a layer of needled batt applied to the paper side face of the second layer which penetrates into the first fabric layer thereby binding the first and second layer together, and
a flap comprising a short length of the second fabric layer with attached batt overlaying the pin seam in the first layer, wherein:
(a) the second layer comprises a plurality of relatively narrow strips, and
(b) the strips of the second layer are located with a lateral edge at a first cant angle to the machine direction, and
(c) the first cant angle has a value of from more than 1° to less than 20°.
2. A fabric according to
(a) the third layer comprises a plurality or relatively narrow strips, and
(b) the strips of the third layer are located with a lateral edge at a second cant angle to the machine direction, and
(c) the second cant angle has a value of from more than 1° to less than 20°.
3. A fabric according to
4. A fabric according to
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24. A fabric according to
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This application is a cip of U.S. Pat. No. 08/805,202 filed Feb. 27, 1997, now abandoned.
This invention relates to press felts, which are used in the press section of a paper making machine. In this part of the papermaking machine, the paper web, which may contain up to about 85% water, is passed between pairs of opposed rolls so that a large proportion of this water is literally squeezed out of the wet paper web. In this process, the wet paper web is supported by at least one, or conveyed between two opposed fabrics known as press felts. These press felts are generally constructed with a fabric base structure, which has layers of batt needled to at least one, and generally to both, of its surfaces. Several fabric constructions are used for the base fabric structure, including both single layer and double layer woven fabrics, and the fabrics can be woven either flat as a continuous run, or endless as a closed loop. Endless felts require that the press section be opened up to allow their installation. Seamed felts are open ended for installation and the ends are subsequently joined by seaming, for example with a pin seam, on the press section. In either case, in order to be able to install the finished fabric into a press section, it is often advantageous to make provision for a seam that can be closed during installation in the press section.
The seam is the most difficult part of the press fabric to make. For although it is relatively straight forward to create a press felt which will provide the required properties of adequate strength, adequate drainage, and lack of fabric marking, whether or not it can be used depends upon also being able to provide a seam in the fabric which has an adequate life in service, provides the required strength, provides the required drainage, and most importantly does not cause marking of the paper.
The most commonly used seam in press felts is a pin seam, in which monofilament yarns from each of the two ends of the fabric which are to be joined are woven back into the fabric ends to provide a set of small loops. The two fabric ends are joined by interdigitating the two sets of loops, and inserting a pintle across the width of the fabric. This form of seam is most often used in press felts based on double layer woven fabrics. Examples of such seams are shown in EP 0 294 951, U.S. Pat. No. 4,842,925 and U.S. Pat. No. 4,601,785.
These conventional press felts offer the benefits of ease of installation, and ease of seam assembly on the machine. But they have the disadvantages of being limited to applications which can tolerate at least some marking of the paper by the seam, and where the drainage requirements are modest. A further disadvantage is that the applied batt wears more rapidly in the seam area. An area of worn batt cover over the seam area increases the danger of marking, and also accelerates even more the rate of wear in the seam area. This leads to premature press felt failure due to either paper marking problems, or mechanical seam failure, or both.
Several proposals have been made to overcome these difficulties.
One that has been made is to use two woven fabric layers, rather than one, to provide what may be termed a laminated base structure. Fabrics of this type are shown in U.S. Pat. No. 3,086,276, wherein the fabric layers are disposed in a bias relationship, and in U.S. Pat. No. 3,657,068 in which a relatively fine and a relatively coarse fabric are disposed on each side of a layer of batt. An alternative fabric is shown in U.S. Pat. No. 5,110,672. In these references, the layers are laminated together by the batt which in the needling application process is forced into engagement with all of the layers. A problem common to all of these structures is that the cut fabric ends adjacent the seam tend to unravel, thus leaving the batt more or less unsupported in the most important area of the fabric. This leads to marking of the paper, and to premature seam failure.
Alternatively, it has been proposed to use a laminate structure, examples of which are described in U.S. Pat. No. 4,186780 and in U.S. Pat. No. 4,418,726, and to pin seam each of the fabrics in the laminate. Apart from the fact that this does not eliminate any of the difficulties attendant on a single pin seam, it further complicates installation, as there are now two seams to be closed, not one. Such an installation step is difficult, time consuming and defeats the original purpose of the seam, which is to provide ease of installation.
Another proposal is to provide what may be termed a “flap” of batt, which may be reinforced with a portion of the fabric base, that will overlay a conventional pin seam, preferably on the paper side of the fabric. Examples of this are described in CA 1,303,833 and EP 0 294 951 mentioned above. In each of these, in constructing the pin seam, a short flap of batt is provided which is attached to one of the ends to be joined and which is intended to cover the joint after the pin seam has been assembled. In U.S. Pat. No. 4,601,785 it is recommended to attach the batt flap by gluing or needling. In U.S. Pat. No. 4,842,925 it is recommended to use brittle or soluble yarns adjacent the seam. Either during or following the needling step to attach the batt these yarns are removed thus allowing the batt flap to be cut and placed in position. In EP 0 294 951 it is recommended to use an additional layer of machine direction yarns in the base fabric to reinforce the batt flap. Seams such as these are also difficult to assemble, and suffer from the disadvantage that the fabric in the flap supporting the batt also ends to unravel, thus leaving the batt unsupported which results in marking of the paper.
This invention seeks to provide an alternative solution to these problems. A press felt is provided in which a laminate fabric is used as the base fabric, only the first layer of which is joined end-to-end by a pin seam. The second layer is cut to provide a batt carrying flap over the pin seam. The second layer is also canted with respect to the first layer, so that the cut seam is at an angle with respect particularly to the fabric wefts, thus inhibiting the loss of these yarns due to the fabric unravelling. The second fabric is also made in relatively narrow strips, thus further diminishing the possibilities of unravelling.
Thus in a first embodiment this invention seeks to provide a multilayer papermaker's press felt fabric comprising in combination:
In a second the fabric further includes a third layer on the machine side of the first layer wherein:
The invention will now be described in one embodiment by way of reference to the drawings, in which:
In this invention the following terms are of importance:
Referring first to
The upper second fabric on the paper side of the first is a relatively thinner fabric and as shown comprises a simple weave with wefts 13 and warps 14. The manner of construction of this fabric layer is described below. In the region of the seam 2 both the second fabric 4, and the batt 5 are cut at the line 16 (the batt 6 if used is also cut at the line 17) to provide a flap 15. In use, the press felt moves in the direction A, so that the flap 15 is downstream from the line of the seam pintle 10.
In
The fabric of
An alternative fabric is shown in FIG. 3. This fabric is similar to that shown in
The importance of the combination of using a relatively narrow strip for the second layer, or for the second and third layers, which has a lateral edge at a cant angle θ to the machine direction is that when the second fabric is cut to open the seam at any given point there is only a short length of second, and, when used, third, fabric yarn which can unravel when the press fabric is in use. The amount which can unravel is limited by the width X of the narrow strip of the layer, and the value of the cant angle θ.
In experimental fabrics it has been found that cant angles as low as 1.7° (which corresponds to an angle of 3 cm per meter) can be used successfully, up to a maximum angle of about 20° above which the risk of unraveling again appears to become a problem. It appears that a cant angle of less than about 10° is desirable.
The relative widths of the first layer and the strips used for the second and third layers, as appropriate, is at least in part determined by the width of the press section. The strips have to be of adequate width to be woven, and should be significantly narrower than the first layer, since if they are made too wide the amount of yarn that can unravel increases. It appears that a ratio of at least 2:1 is desirable. However for a wide press section it is not possible to maintain such a low ratio, and ratios up to at least about 20:1 appear to be useable. It is also possible to use different width strips when both a second and a third layer are used.
The choice of fabric weave used for each of the layers is open to considerable flexibility, and will mainly be determined by the proposed conditions of use. As a generality, the first layer should be a double layer fabric, mainly to facilitate construction of the pin seam. The second, and where used, third, layer is generally a single layer fabric, and is preferably a different weave in terms of yarns count/cm than the first layer. It can be either a finer weave or a coarser weave, and in some applications a second, or third, layer that is a double layer fabric might be used. The second and third layer fabrics also need not be the same. Furthermore, these fabrics need not be woven ones, and a knitted fabric strip can be used in certain applications.
Fekete, Eugene Z., Perry, Edwin R., Burke, Robert P.
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Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Jun 19 1997 | PERRY, EDWIN R | JWI Ltd | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 020645 | /0730 | |
Jun 23 1997 | FEKETE, EUGENE Z | JWI Ltd | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 020645 | /0730 | |
Jun 23 1997 | BURKE, ROBERT P | JWI Ltd | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 020645 | /0730 | |
Jul 03 2000 | JWI Ltd | ASTENJOHNSON, INC | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 020679 | /0098 | |
Aug 20 2004 | Astenjohnson, Inc. | (assignment on the face of the patent) | / | |||
Nov 08 2007 | ASTENJOHNSON, INC | BANK OF AMERICA, N A , AS COLLATERAL AGENT | NOTICE OF GRANT OF SECURITY INTEREST IN PATENTS | 020986 | /0428 |
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