Base fabric, press felt and method of forming base fabric with seam

Abstract

The invention relates to a base fabric of a press felt. The base fabric comprises end regions which are provided with seam loops (4). The seam loops are slanted. Further, the invention relates to a press felt and a method of forming the same.

Claims

1. A base fabric for a press felt, wherein the base fabric is a flat formed structure and comprises: several machine direction yarns; several cross machine direction yarns; a first end region and a second end region, wherein said respective first and second end regions of the base fabric are folded in order to form folded fabric sections and adjacent cross machine direction yarns are removed so that the machine direction yarns, which are also folded, form seam loops at the respective first and second end regions; transverse bonding sections at proximity of the end regions for bonding the folded fabric sections together; the seam loops are slanted whereby the folded machine direction yarns forming the seam loops are without alignment at the respective first and second end regions; the machine direction yarns are twisted relative to their longitudinal axis at the respective first and second end regions in order to allow formation of the slanted seam loops; and there are at least two zones provided with the slanted seam loops, the seam loops in one zone differ from the seam loops in the other zone regarding their slanting direction and/or their angle of slant.

2. The base fabric as claimed in claim 1, wherein adjacent seam loops are partly overlapping at the respective first and second end regions.

3. The base fabric as claimed in claim 1, wherein at least some of the seam loops are partly overlapping with themselves.

4. The base fabric as claimed in claim 1, wherein the flat formed structure has a single layer structure, wherefore after folding the base fabric, the basic fabric comprises a two-layer structure.

5. The base fabric as claimed in claim 1, wherein the bonding sections comprise stitches for bonding each folded section.

6. A press felt for a press section of a paper machine, the press felt comprising a base fabric and at least one batt fibre layer attached to the base fabric; wherein the base fabric for the press felt is in accordance with claim 1.

7. A method of forming a base fabric with a seam for a press felt, wherein the method comprises: forming the base fabric of machine direction yarns and cross machine direction yarns by utilizing flat forming technique; connecting transverse ends of the base fabric together for forming an endless fabric structure; determining positions of first and second end regions; removing cross machine direction yarns from the determined respective first and second end regions; folding the basic fabric against itself whereby folded machine direction yarns form seam loops at the respective first and second end regions; and bonding the folded fabric structure together at proximity of the first and the second end regions; forcing the seam loops to a predetermined slanted position at the respective first and second end regions; and twisting the machine direction yarns relative to their longitudinal axis at the respective first and second end regions in order to form the slanted seam loops in such a manner that there are at least two zones provided with the slanted seam loops, the seam loops in one zone differ from the seam loops in the other zone regarding their slanting direction and/or their angle of slant.

8. The method as claimed in claim 7, wherein forcing the seam loops to the desired slanted position and distance from each other by means of at least one template piece having guiding surfaces provided with desired angles.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Some embodiments are described in more detail in the accompanying drawings, in which

(2) FIG. 1 is a schematic perspective view of a press felt provided with a connectable seam and having a shape of an endless loop,

(3) FIG. 2 is a schematic side view of an end region of a press felt seen in the cross machine direction,

(4) FIGS. 3a-3e are schematic views showing manufacturing steps of the press fabric,

(5) FIG. 4 is a schematic top view of a part of an end region of a base fabric provided with slanted seam loops,

(6) FIGS. 5 and 6 are schematic views showing some feasible slanting designs of seam loops,

(7) FIG. 7 is a schematic view of a known base fabric seen in the machine direction and showing aligned seam loops,

(8) FIG. 8 is a schematic view of base fabric seen in the machine direction and being provided with slanted seam loops, and

(9) FIG. 9 is a schematic top view of a part of an end region of a prior art base fabric.

(10) For the sake of clarity, the figures show some embodiments of the disclosed solution in a simplified manner. In the figures, like reference numerals identify like elements.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

(11) FIGS. 1 and 2 show some basic features of a feasible press felt 1. The press felt 1 may comprise a woven base fabric 1a comprising machine direction yarns 2 and cross machine direction yarns 3, which are crossing each other. The base fabric 1a may be flat woven. End regions E1 and E2 of the press felt 1 may be connected to each other for forming a seam S when installed on a press section of a paper machine. The press felt 1 is configured to run in the machine direction MD. The press fabric 1 comprises a paper side surface P against which a paper web to be dried is arranged on the press section. An opposite side is a roll side surface R which is against rolls and other machine elements of the paper machine.

(12) The seam S comprises interdigitated seam loops at both end regions E1 and E2. Principle of the seam loops 4 is shown in FIG. 2. The seam loops 4 are formed of machine direction yarns 2 of the base fabric 1a. The seam loops 4 are formed by folding a flat woven base fabric 1a against itself where after double layer structure is generated and the machine direction yarns 2 are also folded so that they form the seam loops 4. The layers of the base fabric are connected to each other by means of at least one bond 5.

(13) After the base fabric 1a is properly formed and provided with needed means for the seaming, the base fabric 1a is further processed by furnishing it with one or more batt fibre layers 6. Typically, at least the paper side surface P is provided with batt fibre. The batt fibre 6 may be attached in a needling machine to the base fabric 1a.

(14) FIGS. 3a-3e show manufacturing steps A-E of the press felt 1. At first, in a step A a flat base fabric blank is formed by utilizing flat weaving technology, or alternatively, is formed by winding, for example. The flat base fabric 1a has ends 7a and 7b, which are connected to each other in a step B. The connection may be executed by welding technique, such as ultrasonic welding. Then, a welding seam W is formed. Next, the base fabric 1a is folded against itself and one or more cross machine direction yarns 3 are removed YR from the formed end regions E1 and E2 in a step C. The step C further comprises bonding the folded structures at the end regions E1 and E2 together by means of bonds 5.

(15) FIG. 3d discloses a step D comprising manipulation of the formed seam loops 4 by means of a template piece or any other external means so that the seam loops 4 are directed in a desired manner. In FIG. 3e the ends of the base fabric 1a are connected to each other at a seam S. Finally, one or more batt fibre layers are attached to one or both outer surfaces of the base fabric.

(16) FIG. 4 shows that the seam loops 4 are slanted so that when seen above the seam loops 4 do not align with itself but instead their edge surfaces are on different planes, as it is indicated in FIG. 4 by means of reference numeral 8.

(17) FIG. 5 discloses that adjacent seam loops 4a and 4b may be slanted so that their edge surfaces are against each other. At maximum, the adjacent seam loops may be slanted so that they are partly overlapping, which situation is demonstrated by means of broken lines.

(18) FIG. 6 indicates that the amount of slanting of a seam loop 4c may correspond to CMD dimension i.e. width of the MD-yarn. In an alternative solution, slanting of a seam loop 4d may correspond to half of the width of the yarn forming the seam loop.

(19) FIG. 7 discloses a prior art solution concerning an end region of a base fabric. As can be noted, the end region comprises seam loops 4, which are aligned. Then, an imaginary line 9 passing via edge surfaces of the seam loop 4 is perpendicular to an imaginary line 10 passing via an outer surface of the base fabric 1a.

(20) In FIG. 8 seam loops 4 are slanted. Then, the line 9 clearly shows that the seam loop 4 is slanted relative to the line 10. An angular position between the lines 9 and 10 is definitely not perpendicular.

(21) FIG. 9 shows from above a conventional basic fabric which is provided with aligned seam loops.

(22) The drawings and the specification associated thereto is merely intended to illustrate the idea of the invention. The details of the invention may vary within the scope of the claims.