NZ197686A

NZ197686A - Papermakers drier felt with two sets of cross machine yarns

Info

Publication number: NZ197686A
Application number: NZ197686A
Authority: NZ
Inventors: M J Josef; E R Romanski
Original assignee: Albany Int Corp
Priority date: 1980-07-10
Filing date: 1981-07-10
Publication date: 1984-11-09
Also published as: ZA814577B; JPS5742995A; AU7270281A; DE3127359A1; AR228609A1; BR8104388A; BE889574A; CA1148003A; IT8148864A0; GB2080842A; NL8103275A; FR2486549A1; GB2080842B

Description

1 976 io.~r i>o Priority pau^s).

Complete Specification Filed: C,MK \0JcM- Publication Date: P.O. Journal f'*o: ;S# ;N.Z. No. ;NEW ZEALAND ;Patents Act, 1953 ;COMPLETE SPECIFICATION ;"DRYER FELT FABRIC." ;We, ALBANY INTERNATIONAL CORP. a New York Corporation of 1 Sage Road, Menands, New York, 1220], United States of America do hereby declare the invention, for which we pray that a Patent may be. granted to us , and the method by which it is to be performed, to be particularly described in and by the follbwing statement ;- 1 - ;(Followed by 1A.) ;197686 ;IMPROVED DRYER FELT FABRIC ;BACKGROUND OF THE INVENTION ;1. Field of the Invention ;The invention relates to paper machine clothing and more particularly relates to fabrics useful as dryer felts, and their use. ;2. Brief Description of the Prior Art ;The art is replete with descriptions of dryer felts and dryer felt fabrics. In spite of the wide variety of materials available, the ideal dryer fabric is yet to be found. ;In recent years, dryer fabrics have been developed which are constructed partially or entirely from monofilaments. However, such fabrics have .not been entirely satisfactory when employed to fashion dryer felts. The monofilaments are subject to abrasion and moist heat hydrolysis. In the prior art constructions the load bearing machine direction monofilament yarns may be rapidly degraded under some conditions of use so that the life of the dryer felt is shortened. ;With the structured fabrics of the present invention, employed as dryer felts, the cross-machine direction yarns support the paper sheet being dried. The monofilament machine direction yarns are thus protected from direct contact with degradative elements. The overall operating life of the dryer felt is significantly increased'over felts where the ;"1ft ;197686 ;monofilament machine direction yarns are in contact with the paper sheet being dried. ;Representative of the state of the art in regard to dryer fabrics are those described in U.S Patents 3,573,164 and 3,905,863. ;SUMMARY OF THE INVENTION ;The invention comprises a fabric for use as a paper machine dryer felt, which comprises: ;a first sinuous layer of cross-machine direction yarns, providing a fabric first periphery of peaks and valleys wherein a plurality of peaks are in a first outside plane and the valley floors are in a first inside plane, said peaks being flattened by reduction in the cross-section of the yarns to provide 10 to 50 percent of the surface area of the first periphery and 100 percent of the area which will come in contact with a paper sheet to be supported by the fabric on a paper machine; ;a second sinuous layer of cross machine direction yarns, providing a fabric second periphery of peaks and valleys wherein a plurality of peaks are in a second outside plane and the valley floors are in a second inside plane; and a plurality of monofilament machine direction yarns positioned between the first and second outside planes, interweaving the cross-machine direction yarns of the first layer at points which are between the first outside and inside planes and which are spaced inwardly of the first outside plane, and interweaving the cross-machine direction yarns of the second layer. ;197686 ;The invention further comprises a method of making a fabric for use as a paper machine dryer felt, the method comprising the steps of: ;making a fabric comprising: a first sinuous layer of cross-machine direction yarns, providing a fabric first periphery of peaks and valleys wherein a plurality of peaks are in a third outside plane and the valley floors are in a first inside plane; a second sinuous layer of cross-machine direction yarns, providing a fabric second periphery of peaks and valleys wherein a plurality of peaks are in a second outside plane and the valley floors are in a second inside plane; and a plurality of monofilament machine direction yarns positioned between the second and third outside planes, interweaving the cross-machine direction yarns of the first layer at points which are between the third outside plane and the first inside plane and interweaving the cross-machine direction yarns of the second layer; and subsequently, ;flattening the plurality of peaks of the first layer by reducing their cross-section such that they are in a first outside plane, such that said peaks provide 10 to 50 percent of the surface area of the first periphery and 100 percent of the area which will come in contact with a paper sheet to be support by the facric on a paper machine and such that the machine direction yarns interweave the cross-machine direction yarns of the first layer at points spaced inwardly of the first outside plane. ;- 3 - ;197686 ;BRIEF DESCRIPTION OF THE DRAWINGS ;Figure 1 is a cross-sectional, side elevation of a portion of a preferred embodiment fabric of the invention. ;Figure 2 is a schematic view of a portion of a drying section in a paper making machine. ;Figure 3 is a top view of a portion of the fabric of Figure 1. ;DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION ;Figure 1 is an enlarged, cross-sectional, side elevation of a portion of a fabric 10 "of■ the invention. The fabric 10 comprises a first sinuous layer 12 of monofilament cross-machine direction yarns 14. The layer 12 forms a periphery of fabric 10 which in side profile shows peaks 16 and valley floors 18. A plurality of at least two peaks 16 in layer 12 are in a single plane forming an outer periphery of fabric 10. Preferably at least about 50 percent, most preferably all or substantially all of the peaks 16 are in the aforesaid plane. Valley floors 18 are in a separate plane inside of the plane formed by the peaks 16 ;A second sinuous layer 20 of monofilament cross-machine direction yarns 14' forms another periphery of the fabric 10 which also appears, in side profile, as peaks 16' ;197686 ;and valley floors 18'. A plurality of at least two of the peaks 16' are in a- single plane forming the outer periphery (preferably at least about 50 percent, most preferably all of the peaks 16' are in the periphery). Valley floors 18' are in a separate, .single plane inside of the plane formed by peaks 161. ;A plurality of monofilament machine direction yarns 22 are positioned between the outer fabric periphery.formed by the outside planes, formed by the peaks 16 and the peaks ! 16' and interweave with the cross-machine direction yarns i 14, 14' at points between the respective planes of peaks 16, valley floors 18 and peaks 16', valley floors 18'. Thus, as shown in Figure 1, the knuckles of load bearing machine direction yarns 22 are below the peakfe 16, 16' at the point where they interweave with the cross-machine direction yarns 14, 14' and do not come into direct contact with the sheet 24 of paper carried on fabric 10, when fabric 10 is employed as a dryer fabric on a paper making machine. The sheet 24 is supported on the peaks 16 of the cross-machine direction yarn 14. On the side of fabric 10 facing away from the carried sheet, the machine direction yarns 22 are also protected by the outwardly projecting peaks 16' i from contact with elements of the paper making machine which might hasten abrasion or other degradation of the important load bearing machine direction yarns. However, it will be appreciated that the greatest degradation of yarns in a dryer ;19 7686 ;fabric occurs in those monofilament yarns in contact with sheet 24. Thus, it is not critical that yarns 22 be protected ■! ;J ;by peaks 16' on the side of the fabric facing away, from the j ;1 ;I ;carried sheet 24 although such is obviously preferred. Within ! ;j the scope of the invention are fabrics where the yarns 22 are j on the outer periphery of layer 20 where they pass through ] ;| ;layer 20. j ;In the embodiment fabric 10 the machine direction yarns J ;j ;22 within layer 12 are paired with the yarns 22 within layer 20 i and the yarns within the pairs are slightly offset from each j other in regard to vertical alignment, as they knuckle over i the cross-machine direction yarns 14, 14'. There are, in the ! weaving pattern, 4 sets of machine direction yarn 22 pairs. j ;One pair interweaves with every fourth of cross-machine j direction yarns 14, 14' and then the pattern repeats. ;Preferably, the machine direction yarns pass over at least one cross-machine direction yarn, under at least one following cross-machine direction yarn and over at least one further following cross-machine direction yarn of the upper cross-machine direction layer before running down to interconnect the lower cross-machine direction layer with the upper cross-machine direction layer, the machine yarns and cross-machine direction yarns being thus interconnected in a repeat pattern. Of course the weave will be such that the relationship of the machine direction yarns and the upper layer of cross-machine ;<'o ;1 V 7 6 8 6 ;direction yarns will be such that the plane of the upper surfaces of the portions of the cross-machine direction yarns of the upper layer over which the' ;machine direction yarns pass is relatively elevated in a direction away from the plane of the upper surface of the fabric; and the plane of the exposed upper surfaces of the portions of the machine direction yarns in the upper layer under which the cross-machine direction yarns, pass is relatively depressed in the opposite direction, whereby the differences in elevation between the exposed upper surface portions of the machine direction yarns are protected from contact with paper sheet which contacts the surface of the cross-machine direction yarns in the upper layer. ;The yarns 14, 14' and 22 may be monofilaments on any synthetic polymeric resin. The yarns 14 and 14' may also be multifilament yarns. Representative of such multi- and monofilaments are yarns of polyester, polyamide, polyolefin, polyaramid, polyimide and the like. Generally such, yarns having diameters of from 10 to 4 0 mils are advantageously employed in the fabrics of the invention. ;19 7 6 8 6 ;Following the weaving of the fabrics of the invention, they are heat set to stabilize the fabric and to draw the yarns into their desired relative positions. The machine direction yarns 22 are drawn inwardly of the outer surfaces of the fabric 10 and this pressure "crimps" the yarns 18, 18' so that the peaks 16, 16' are displaced to the outside plane of the fabric as previously described. The degree of heat-setting required to achieve the desired structure of the fabric 10 will of course vary depending on the nature of the yarns 14, 14' and 22. However, optimum times, temperatures and tensions placed on the fabric during heat-setting can be determined by those skilled in the art, employing trial and error technique for the different yarn materials. In general, heat-setting may be carried out at temperatures of from about 150°F. to 375°F. for from 15 to 60 minutes. The fabrics of the invention may be woven flat and the ends joined by conventional seaming methods, known to those skilled in the art. The seamed belts so made are readily employed as dryer felts in the dryer section 30 of a paper making machine as shown in Figure 2. As shown in Figure 2, the paper sheet 24 is held against the steam cylinders 32 by the endless belt 34 of fabric 10 during passage of sheet 24 through dryer section 30. ;As shown in Figure 1 and in Figure 3, a top view of the embodiment fabric of Figure 1, the outermost portion or "knuckle" of peaks 16 have been partially abraded away to increase the surface area of the fabric 10 which functions as the support area for the paper sheet 24-. The technique ;* -/- 19 7 6 8 6 of abrading away portions of knuckles on fabrics is well known; see for example U. S. Patents 3,573,164 and 3,905,863. ' < Advantageously, sufficient of the peaks 16 are abraded away to provide peaks 16 with a surface area comprising from about 20 to about 50 percent of the total surface area of the dryer fabric, in the outer periphery of layer 12. Most advantageously, the abraded peaks 16 comprise from 10 to 30 percent of the total surface area. When the peaks 16 provide . the specified surface area of the dryer fabric, the dryer fabric 10 exhibits an improved drying efficiency in operation on a paper making machine. The increased area of contact between the peaks 16 and the paper sheet 24 being dried promotes a faster drying rate and, in many instances, enhances the sheet tensile strengths of the product paper dried thereon.

It is important that the machine direction yarns in the fabric of the invention are not abraded and remain substantially intact, since they are the load-bearing yarns of the fabric 10.

The following example sets forth the best mode contemplated by the inventors of making and using the invention but are not to be considered as limiting.

EXAMPLE 1 A fabric is prepared in a duplex weave of 0.016" diameter polyester monofilament (100 per inch) machine 197686 direction yarns interwoven with 0.016" diameter polyester monofilamenti(44 per inch; 22 top and 22 bottom) filling or cross-machine direction yarns. After heat setting, a fabric is obtained having only cross-machine direction yarns in the outer plane of the fabric. The upper surface of the fabric is subjected to abrasion to remove up to 0.0051 inches of the cross-machine direction knuckles. This leaves the abraded knuckles providing 29.3% of the surface area of the fabric. The percentage of surface area making contact at varying degrees of knuckle abrasion up to 0.0051 inches is shown in the Table 1, below.

TABLE 1 Inches Removed by Sanding Percent Surface Contact 0 (not sanded) 0.0010 0.0019 0.0034 0.0051 4. 3i 7 - 8 13. 6 14. 3 29.3 Both sanded and unsanded fabrics are used to make endless dryer belts and each is tested on a papermakers machine in the dryer section. It is observed that the runs with the sanded fabric of Example 1'improve the drying rate by 2-5 percent over the drying rate achieved using the unsanded fabric. to 197686 Those skilled in the art will appreciate that many modifications of the preferred embodiments described above may be made without departing from the spirit and the scope of the invention. For example, the fabric of the invention may be woven to include various stuffer picks, to obtain fabrics of different permeabilities as will be appreciated by those skilled in the art.

II -Jn6-

Claims

9 l? %Z(p What we claim is:

1. A fabric for use as a paper machine dryer felt, which comprises: a first sinuous layer of cross-machine direction yarns, providing a fabric first periphery of peaks and valleys wherein a plurality of peaks are in a first outside plane and the valley floors are in a first inside plane, said peaks being flattened by reduction in the cross-section of the yarns to provide 10 to 50 per cent of the surface area of the first periphery and 100 per cent of the area which will come in contact with a paper sheet to be supported by the fabric on a paper machine; a second sinuous layer of cross-machine direction yarns, providing a fabric second periphery of peaks and valleys wherein a plurality of peaks are in a second outside plane and tfie valley floors are in a second inside plane; and a plurality of monofilament machine direction yarns positioned between the first and second outside planes, interweaving the cross-machine direction yarns of the first layer at points which are between the first outside and inside planes and which are spaced inwardly of the first outside -12" 0 - i wee plane, and interweaving the cross-machine direction yarns of the second layer.

2. A fabric as claimed in claim 1 in which the cross-machine direction yarns are monofilaments.

3. A fabric as claimed in claim 1 in which the cross-machine direction yarns are multifilament yarns.

4. A fabric as claimed in any preceding claim in which the plurality of monofilament machine direction yarns interweave the cross-machine direction yarns of the second layer at points which are between the second outside and inside planes and which are spaced inwardly of the second outside plane.

5. A fabric as claimed in any preceding claim in which said plurality of peaks of the first layer provide 20. to 50 per cent of the surface area of the first periphery.

6. A fabric as claimed in any of claims 1 to 4 in which said plurality of peaks of the first layer provide 10 to 30 per cent of the surface area of the first periphery.

7. A fabric as claimed in any preceding claim in which the plurality of peaks in the first outside plane are flattened by abrading away portions of the yarns. -13- N.Z. PATENT OFFICE t 197686 '-S<-

8. A fabric for use as a paper machine dryer felt, the fabric being substantially as herein described with reference to and as illustrated by the accompanying drawings. 5

9. A paper machine dryer felt made from a fabric as claimed in any preceding claim. 10. A method of making a fabric for use as a paper machine dryer felt, the method comprising the steps of:

10 making a fabric comprising: a first sinuous layer of cross-machine direction yarns, providing a fabric first periphery of peaks and valleys periphery of peaks and valleys wherein a plurality of peaks are in /a second outside plane and the f valley floors ^are in a second inside plane: and 20 a plurality of monofilament machine direction yarns positioned between the second and third outside planes, interweaving the cross—machine direction yarns of the first layer at points which are between the the third outside plane and 25 the first inside plane and interweaving the cross-machine direction yarns of the second layer: J , . *- ra . • - wherein a plurality of peaks are in'third outside ; ^ r-*S.-5 rSfipPT. plane and the valley floors are in a first inside 15 plane; a second sinuous layer of cross-machine direction yarns, providing a fabric second {*'-.■ wrr-. - K+- N.z. PATENT OFFICE -4 JUL 1984 - IS- - .197686 and, subsequently, flattening the plurality of peaks of the first layer by reducing their cross-section such that they are in a first outside plane, such that said peaks provide 10 to 50 per cent of the surface area of the first periphery and 100 per cent of the area which will come in contact with a paper sheet to be support by the fabric on a paper machine and such that the machine direction yarns interweave the cross-machine direction yarns of the first layer at points spaced inwardly of the first outside plane. •"

11. A method as claimed in claim 10 in which, after flattening, said plurality of peaks of the first layer provide 20 to 50 per cent of the , surface area of the first periphery.

12. A method as claimed in claim 10 in which, after flattening, said plurality of-peaks of the first layer provide 10 to 30 per cent of the surface area of the first periphery.

13. A method as claimed in any of claims 10 to 12 in which the flattening step comprises abrading away portions of the yarns of the first layer.

14. A method of making a fabric for use as a paper machine dryer felt, the method being substantially as herein described with reference to and as illustreated by the accompanying drawings. ALBANY INTERNATIONAL CORP By Their Attorneys HENRY HUGIJES LIMITED Per:/W