Patent Application
20070028995
The invention concerns a method of making a low marking, easily joinable pin seam for use in an endless woven type papermakers fabric, particularly for a base fabric for a press felt. It also concerns base fabrics constructed so as to incorporate the seam, and press felts containing the base fabric and seam.
The present invention relates to a novel seam which is intended for use in endless woven type papermakers fabrics, more particularly for base fabrics for press felts. The majority of press felts in use today include base fabrics which are formed either by spirally winding and joining relatively narrow strips of flat woven cloth so as to build up a desired fabric width, flat weaving the base fabric to the desired full width and length of the finished fabric, or by the so-called endless weaving process. Endless woven type base fabrics for press felts are well known in the papermaking industry and have been in widespread use for many years. Regardless of the type of base fabric construction that is employed, it is desirable in certain instances to be able to incorporate into the base fabric means for seaming the fabric to facilitate its installation on the papermaking machine for which it is intended. Approximately 40% of press fabrics manufactured at present contain a seam.
In the endless weaving process, the fabric is woven such that two layers are formed simultaneously, in a manner similar to a tubular garment such as a tube sock. During weaving, a continuous weft yarn is interwoven with the warp yarns somewhat like a spiral, but when the fabric is installed on the papermaking machine, the fabric is rotated such that the weft yarns are oriented in the machine direction (MD) of the fabric, and the warp yarns in the loom become oriented in the cross-machine direction (CD) of the fabric. The endless weaving process produces a fabric whose length is twice the width of the reed on the loom. Although this process uses a single continuous weft yarn, it is known and understood to refer to “weft yarns” as indicative of segments of the weft yarn and their paths in one of the fabric layers, and references herein to “weft yarns” should be understood as having this meaning.
When a seamed endless woven fabric is to be manufactured, the first layer of cloth is anchored at one side of the loom by its weft yarns to a so-called forming wire, so as to form seaming loops; at the opposite side of the loom, the fabric is folded over on itself and the weft yarns are brought back to the forming wire. The manner of weaving the continuous weft yarn across the body of the fabric, around the forming wire and back into the fabric results in a fabric having at least two layers of weft yarns in its construction. In this manner, an endless structure is produced which includes the seam already formed during the weaving process. These manufacturing techniques are well known to those of skill in the art and variants thereto have been described in the patent literature, for example in U.S. Pat. No. 4,896,702 to Crook, U.S. Pat. No. 5,531,251 to Rydin, and U.S. Pat. No. 5,732,749 to Fargeout. It is also known from U.S. Pat. No. 6,508,278 to Kornett, in a system requiring three sets of CD yarns, to modify one or more of the yarn denier, yarn spacing or weave pattern of the yarns in the fabric adjacent to the seam so as to improve the properties of the fabric in that area to be more consistent with the properties of the remainder of the fabric to reduce sheet marking.
However, a problem common to all of the prior art pin seam constructions has been the ability to attain acceptable uniformity of the seaming loops to facilitate installation on the papermaking machine, after the forming wire is removed, and subsequently replaced by a pintle to secure the seam for operation. Theoretically, the manufacturing process should produce uniform seaming loops with little variation in the orientation, size and shape, but this is seldom the case in actual fact. As a result, the seam loops are difficult to mesh together in order to provide a clear and open channel for the pintle.
Various constructions have been suggested, for example in U.S. Pat. No. 6,000,441 and U.S. Pat. No. 6,079,454, both to Lee et al., which have attempted to address the problem of producing more uniform seaming loops. However, none have been entirely successful to date.
The present inventor has discovered that, if the weave pattern of the endless woven base fabric is modified proximate to the forming wire on the loom, such that the double layer construction of the fabric is opened up to provide a loop forming single layer weave construction, then it is possible to form the seaming loops in this single layer area and obtain the desired benefits of improved loop uniformity, reduced loop variation and a generally flatter, low-marking seam than has previously been possible in prior art constructions.
Thus, the present invention seeks to provide a method of making a novel seam for use in an endless woven papermakers fabric construction, a novel seam for an endless woven base fabric, a base fabric incorporating the novel seam, and a press felt including the base fabric and seam. The base fabric is woven according to a weave pattern which requires a multiple of 8 sheds to weave on the loom; thus, 8, 16, 24 etc. shed constructions would be suitable for the practice of the invention, where the weave design includes a set of warp yarns which are interwoven with a continuous weft yarn system which is arranged in two layers.
Adjacent the vertically aligned lateral edges of the fabric, where the seaming loops are to be formed around the forming wire, the weave pattern of the fabric is modified so that the warp yarns separate into upper and lower warp yarns in a seaming portion of the fabric. In the body portion of the fabric, the weft yarns are interwoven with selected ones of the warp yarns to form a continuous double layer structure; but in the seaming portion, the fabric separates into a first (upper) and second (lower) layer. In the upper layer, the weft yarn interweaves with only selected warp yarns which will comprise the upper warp yarns, and in the lower layer, the weft yarn interweaves with only selected warp yarns which will comprise the lower warp yarns. The seaming loops are formed by the weft yarn as it follows a path from the upper layer around the forming wire and continues into a path in the lower layer.
The substantially uniform seaming loops thus formed provide an open channel through which the pintle, which will eventually be used to join the fabric ends together, can be easily inserted.
The invention therefore seeks to provide a method of making a seam for an endless woven multilayer papermakers fabric wherein first and second lateral edges of the fabric are aligned vertically during weaving, the method comprising
(i) selecting a repeating weave pattern including a continuous weft yarn and a plurality of warp yarns so as to provide during weaving
(a) a body portion woven as a double layer;
(b) a shed change for the warp yarns adjacent to the warp yarns of the body portion to provide a first and second seaming portion, such that in each seaming portion the warp yarns are separated into a group of upper layer warp yarns and a group of lower layer warp yarns such that the weft yarn interweaves with each group consecutively to form a distinct upper and lower layer; and
(ii) providing a forming wire at the vertically aligned lateral edges of the fabric whereby in each seaming portion, the weft yarn in sequence interweaves with the upper layer warp yarns to provide the upper layer, forms a seaming loop about the forming wire and interweaves with the lower layer warp yarns to provide the lower layer.
The invention further seeks to provide an endless woven multilayer papermakers fabric made according to the method of the invention. Preferably, the fabric is woven to a pattern requiring an integer multiple of 8 sheds in the loom.
The method and fabrics of the invention are particularly suitable for press felt base fabrics, which can be incorporated into press felts.
The invention will now be described with reference to the drawings, in which
Referring first to
After the desired number of repeats of these steps, the woven fabric can be removed and finished in the usual manner, including the known process of needling with batt in the case of a press fabric, and replacement of the forming wire 122 by a pintle 124 (shown in
This figure illustrates one embodiment of the invention. The worker skilled in the art will recognize that other weave patterns are possible using a multiple of 8 sheds in the loom, depending on the intended end use of the fabric.
Referring to
The separation of the upper and lower layers 112, 116, resulting in an internal channel 115, provides to the seaming loops 305 a degree of flexibility which allows them to move easily, thereby improving interdigitation of the seaming loops 305 and cushioning the seam region, thereby reducing seam marking on the paper sheet.
Further, referring also to
Due to the improved uniformity of the loops formed by the method of the invention, pintle insertion is facilitated during installation in the papermaking machine for which the fabric is intended, in addition to the advantages discussed above in reduction of sheet marking when the fabric is in use.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0515928.0 | Aug 2005 | GB | national |
