DRYER FABRIC

Abstract

The invention relates to a dryer fabric, which is woven of machine direction yarns (2) and cross machine direction yarns (3). The machine direction yarns (2) have free long float above at least seven cross machine yarns on a paper side (P) of the dryer fabric (1). Further, the fabric has double cloth structure having machine direction yarns in two successive layers (2a, 2b).

Claims

1-8. (canceled)

9. A dryer fabric for a dryer section of a paper machine, the dryer fabric (1) being a woven structure and comprising: a paper side surface (P) that is facing towards a fiber web to be dried during use of the dryer fabric (1); a roll side surface (R) that is facing towards the paper machine during use at the dryer section; a plurality of machine direction (MD) yarns (2), each of the plurality MD yarns (2) having a flat cross section; and a plurality of cross machine direction (CMD) yarns (3), wherein: the dryer fabric (1) has a double machine direction yarn structure comprising MD yarns (2) in two successive layers (2a, 2b); the MD yarns (2) pass above at least seven of the plurality of CMD yarns (3) on at least the paper side (P) of the dryer fabric (1), thereby forming long floats (LF, LFP) on the paper side surface (P) and providing the dryer fabric (1) with a smooth surface on the paper side surface (P) for preventing generation of markings to the fiber web; and the dryer fabric has a double-cloth structure so that the fabric has two independent fabric layers one above the other, the fabric layers being self-stitched to connect the fabric layers together.

10. The dryer fabric as claimed in claim 9, wherein a contact area of the paper side surface (P) of the dryer fabric (1) is 50% or more.

11. The dryer fabric as claimed in claim 9, wherein: the CMD yarns (3) are strongly shrinking yarns, whereby heat treatment of the dryer fabric is configured to cause cross direction shrinkage of the dryer fabric so that adjacent MD yarns (2) are being moved closer to one another; and the shrinkage of the CMD yarn (3) is over 10%; and after weaving, the dryer fabric (1) has shrunk by means of heat treatment at least 10% in the cross machine direction.

12. The dryer fabric as claimed in claim 9, wherein: the flat cross section of the MD yarns (2) is rectangular or substantially rectangular; a width of the MD yarn (2) is 0.6 mm or more; and a height of the MD yarn (2) is 0.4 mm or less.

13. The dryer fabric as claimed in claim 9, wherein the MD yarns (2) pass below at least seven of the plurality of CMD yarns (3) on the roll side surface (R) of the dryer fabric (1), thereby forming long floats (LFT) on the roll side surface (R).

14. The dryer fabric as claimed in claim 9, wherein the MD yarns (2) have long free floats (LF, LFP, LFR) passing over at least eleven of the plurality of CMD yarns (3) on at least one surface of the dryer fabric (1).

15. The dryer fabric as claimed in claim 9, wherein the dryer fabric has at least eight shed weaving structure.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0038] Some embodiments are described in more detail in the accompanying drawings, in which

[0039] FIG. 1 is a schematic perspective view of a dryer fabric provided with a seam and thereby having a shape of an endless loop,

[0040] FIG. 2 is a schematic view of a dryer fabric seen from a paper side surface,

[0041] FIG. 3 shows schematically and seen from the cross machine direction an end portion of a feasible single layer dryer fabric provided with connecting seam loops for allowing formation of a seam,

[0042] FIGS. 4 and 5 are schematic views of a dryer fabric provided with long floats of machine direction yarns on a paper side surface and on a roll or machine side surface,

[0043] FIG. 6 illustrates schematically difference between a prior art solution provided with short floats of MD-yarns and the disclosed solution provided with long floats of MD-yarns,

[0044] FIG. 7 illustrates a surface of a paper side surface of a dryer fabric,

[0045] FIG. 8 illustrates a surface topography of a paper side surface of a dryer fabric and potential surface contact area is shown in the Figure by using different colour, and

[0046] FIG. 9 shows an example of features and properties of a dryer fabric according to the disclosed solution.

[0047] 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

[0048] FIGS. 1 and 2 show some basic features of a feasible drying fabric 1. The dryer fabric 1 may be a woven structure comprising machine direction yarns 2 and cross machine direction yarns 3, which are crossing each other. The dryer fabric may be flat woven and its seam ends SE1 and SE2 may be connected to each other for forming a seam S when installed on a dryer section of a paper machine. The dryer fabric 1 is configured to run in the machine direction MD. The dryer fabric 1 comprises a paper side surface P against which a paper web to be dried is arranged on the dryer section. An opposite side is a roll side surface which is against rolls and other machine elements of the paper machine.

[0049] FIG. 3 shows an end portion of a feasible single layer dryer fabric 1 provided with connecting seam loops 4. A seam S is formed when opposing seam ends SE1 and SE2 are arranged against to each other so that the seam loops 4 at their ends are being interdigitated and a seam channel is formed. A connecting yarns or seam yarn 5 is inserted inside the seam channel for connecting the seam ends SE1 and SE2.

[0050] In FIG. 3 the basic structure of the dryer fabric 1 is single layer fabric, wherein cross machine direction yarns 3a and 3b are in one single layer. The structure may comprise cross machine direction filler yarns 3a and basic cross machine direction yarns 3b. Yarns 3b are connected with the machine direction yarns 2. The machine direction yarns 2 are arranged in two layers 2a, 2b which are one above the other so that the yarns 2a are running on the paper side surface P and the yarns 2b are running on the roll side surface R. Thus, the fabric has double fabric structure comprising a double warp yarn system. The machine direction yarns form seam loops at the seam ends SE1 and SE2. The machine direction yarns 2 have free long floats LFP over seven cross machine direction yarns 3 on the paper side surface P. The roll side surface R may also be provided with the long floats LFR. The number of cross machine yarns 3 passed by the machine direction yarns 2 at the long floats may be the same or it may be different, which means that the structure may be symmetrical or it may be asymmetric. As can be seen in FIG. 3, the dryer fabric has eight shed-weave structure, wherein the machine direction yarn 2 passes above seven CMD-yarns 3, below one CMD-yarn 3 and continues repeating the same pattern. Let it be mentioned that other weave patterns, allowing extremely long floats, may also be used.

[0051] FIGS. 4 and 5 show a dryer fabric 1 having a double cloth structure having CMD-yarns 3 in two layers. In FIGS. 4 and 5 CMD-yarns of a bottom layer are marked with reference numeral 3d. Further, the dryer fabric 1 is provided with long floats FLP of machine direction yarns 2 on a paper side surface P, and also on the roll or machine side surface R. FIG. 4 also illustrates that all the machine direction yarns 2 may have the same weave pattern, but an adjacent MD-yarn pattern comprises a phase shift of one or two CMD-yarn in the same direction.

[0052] FIG. 6 illustrates schematically difference between a prior art solution provided with short floats SF of MD-yarns 2 and the disclosed solution provided with long floats LF of MD-yarns 2.

[0053] FIG. 7 illustrates a surface of a paper side surface P of a dryer fabric 1. In FIG. 8 it is shown a surface topography of a paper side surface P of a dryer fabric 1. Potential surface contact area is shown in the FIG. 8 by using yellow colour. The yellow or lighter colour indicates the potential contact surface areas whereas red or darker colour indicates non contacting areas. As can be easily noted from FIG. 8, the contact areas represent over 50% of the total surface of the dryer fabric 1.

[0054] FIG. 9 shows an example of features and properties of a dryer fabric according to the disclosed solution.

[0055] Both the MD-yarns and CMD-yarns may be monofilaments and are made of plastic material. Flat threads are used as MD-yarns, the cross section of which preferably resembles a rectangle with rounded corners. Such a thread is provided with a larger contact area compared, for example, with flat oval-shaped threads, which can basically also be applied. The cross section of the CMD-yarns may, in turn, be substantially round, in which case the MD-yarns run as smoothly as possible between the CMD-yarns, when passing between paper side P and roll side R of the fabric. Extremely strongly shrinking threads may be employed as the CMD-yarns, meaning that the longitudinal shrinkage of an individual thread is at least 10%. Furthermore the shrinkage in the width direction of the entire dryer fabric is at least 10%.

[0056] This application relates to a dryer fabric used on a dryer section of a paper machine. However, it has been noted that the disclosed fabric structure could also be utilized in filtering devices such as in horizontal belt filters. The disclosed structure may also be beneficial to be used as a conveyor belt in paper machine or in any other machine which processes fibre web.

[0057] 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.