WO1999019564A1

WO1999019564A1 - Multi-layer seamed felt with at least two offset seams

Info

Publication number: WO1999019564A1
Application number: PCT/US1998/006362
Authority: WO
Inventors: Glenn C. Townley
Original assignee: Asten Inc
Current assignee: Asten Inc
Priority date: 1997-10-10
Filing date: 1998-04-01
Publication date: 1999-04-22
Anticipated expiration: 2000-04-10
Also published as: ZA989233B; CA2229121A1; AU6944698A

Abstract

A multi-layer papermaking fabric having at least two sets of offset seam loops (26, 27) at each end of the fabric. The respective seam loop sets are joined to render the fabric endless.

Description

MULTI-LAYER SEAMED FELT WITH AT LEAST TWO OFFSET SEAMS BACKGROUND OF THE INVENTION

Field of the Invention The present invention relates to seams for a multi-layer felt for use in a papermaking machine.

Description of the Prior Art

Felts employed in a papermaking machine often comprise a base fabric with batt material attached thereto. Base fabrics are typically woven fabrics which are woven and used as an endless loop or woven open ended wherein the ends of the fabric are joined by a seam to form the endless fabric. A typical seam for a papermaker's base fabric includes a plurality of spaced apart loops on each end of the fabric. The loops are generally mated in an intermeshing relationship to form a substantially tubular channel through which a pintle is inserted to close the seam.

As papermaking machines have developed, machine felt speeds of between 4000 and 5000 feet per minute have become common. Due to such high speeds, and the hostile temperature, pressure and environmental conditions to which the seam is exposed, seam durability is of concern. Several attempts to increase seam strength by increasing the diameter of the pintle have been made. However, a larger pintle requires larger diameter loops which increase felt thickness in the seam area. The increased thickness causes imperfections in the product being produced as well as machine vibrations due to imbalance during running of the machine . Seamed felts often experience other problems, including property variations, such as void volume and permeability, in the seam area. Property variations between the fabric and the seam area can cause undesirable markings on the paper product being produced .

Another attempt to increase seam strength has been the use of a multi-layer fabric with multiple seams. However, it is generally difficult and time consuming to seam multiple seams since the lower seam is often difficult to see and less accessible. Furthermore, the undesirable results caused by property variations are often enhanced in multi-layer fabrics utilizing multiple seams since the effects of the seam are multiplied. Accordingly, it is desirable to provide a multi-layer fabric having multiple seams which are easier to join and are less likely to cause paper marking.

SUMMARY OF THE INVENTION The present invention generally includes a multi-layer papermaking fabric having a plurality of cross machine direction (CMD) yarns interwoven with a first plurality of machine direction (MD) yarns to define first seam loops at each end of the fabric and a second plurality of MD yarns to define second seam loops at each end of the fabric. To join the fabric, both sets of seam loops of one end of the fabric are intermeshed with the corresponding seam loops of the other end of the fabric to define two seam channels. A pintle is inserted into each seam channel to render the fabric endless. To make the seams easier to join and to reduce the effects of the seams, the first and second seams are spaced from each other in the CMD.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a side elevation of two ends of the fabric of the present invention.

Figure 2 is a side elevation of the two ends of the fabric shown in Figure 1 joined together. Figure 3 is a side elevation of an alternate embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiments will be described with reference to drawing figures where the numerals represent like elements throughout.

In the present invention, the woven base fabric 10 has at least four layers of machine direction (MD) yarns 20-23 with two sets of loops 26, 27 extending from each end of the fabric 10. As shown in Figure 1, the preferred base fabric 10 comprises two double-layer fabrics 12, 14 which are laminated together. Lamination of the fabrics 12, 14 will be described in more detail hereinafter. The resultant base fabric 10 has four MD yarn layers 20-23 interwoven with CMD yarns 24 and 25 respectively. First loops 26 are formed from MD yarns 20 and 21 and second loops 27 are formed from MD yarns 22 and 23 at each end of the fabric 10. As shown in Figure 1, seam loop 26 is offset from seam loop 27 at each end of the fabric 10. This offset is preferably produced during laminating of the two fabrics 12, 14. The fabrics 12, 14 are aligned with their ends offset and then laminated together using any known method, such as batt needling. Lamination preferably is accomplished by needling a layer of batt material 30, 32 to each face of the fabric 10. A scrim may be used to initially bond the fabrics 12, 14 in their desired positions. Fabric bonding techniques are disclosed in U.S. Patent Nos. 4,806,413 and 4,830,915. In the preferred embodiment, the batt material

30, 32 is applied to both surfaces of the base fabric 10 prior to seaming thereof. To facilitate seaming, the upper batt layer 30 is cut and flapped and the bottom batt layer 32 is provided with a groove 34, as is known in the art. The upper flap cut is preferably slightly offset from the upper pintle

28 after seaming.

The fabric 10 is joined by intermeshing the two sets of seam loops 26, 27 and inserting a pintle 28, 29 through each channel formed thereby, as shown in Figure 2. In some applications, it may be necessary to delaminate the two fabrics 12, 14 in the areas adjacent the seam loops 26, 27 to make lower seam loops 27 more accessible. Since loops 26 are offset from loops 27, pintle 28 is offset from pintle 29 in the machine direction after seaming. The pintles 28, 29 are preferably offset from one another in a range of one-sixteenth of an inch to one inch. More preferably, the offset is in the range of one-eighth to three-quarters of an inch. The seam offset makes it easier to join the seams since the second seam 27 is more visible and accessible during seaming. Additionally, the seam offset reduces the effects of property variations in the fabric 10. The seam offset effectively spreads the seam zone, thereby dispersing the seam effects over a greater area whereby they are minimized. Furthermore, the upper layers act to mask the lower seam while the lower layers provide a layer of fabric behind the upper seam, rather than a void, to reduce the effects of the upper seam.

In an alternate embodiment, shown in Figure 3, the base fabric 110 is a single, four layer fabric. The seam loops 126, 127 are preferably offset during weaving of the base fabric 110. The fabric structure, layers and weave patterns set forth herein are- merely representative of possible multilayer fabrics. A variety of fabrics can be employed in practicing the present invention.

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Claims

I claim :

1. An improved papermaker's multi-layer fabric of a type having a plurality of cross machine direction (CMD) yarns, a first plurality of machine direction (MD) yarns interwoven with the CMD yarns to define first seam loops at each end of the fabric, a second plurality of MD yarns interwoven with the CMD yarns to define second seam loops at each end of the fabric, the first seam loops at each end of the fabric intermeshed to define a first seam and the second seam loops at each end of the fabric intermeshed to define a second seam, the improvement characterized by: the first and second seams being located in spaced apart vertical planes perpendicular to the fabric and extending in the CMD.

2. The fabric according to claim 1 wherein the first plurality of MD yarns define a first sub-fabric and the second plurality of MD yarns define a second sub-fabric and the two sub- fabrics are laminated together to form the multi-layer fabric .

3. The fabric according to claim 2 wherein the sub- fabrics are laminated together through needling of batt material to the fabric.

4. The fabric of claim 1 wherein batt material is anchored to the fabric .

5. The fabric of claim 1 wherein the vertical planes are spaced from each other by one-sixteenth to three-quarters of an inch.

6. An improved papermaker's multi-layer fabric of a type having a plurality of cross machine direction (CMD) yarns, a first plurality of machine direction (MD) yarns interwoven with the CMD yarns to define first seam loops at each end of the fabric, a second plurality of MD yarns interwoven with the CMD yarns to define second seam loops at each end of the fabric, the first seam loops at each end of the fabric intermeshed to define a first seam and the second seam loops at each end of the fabric intermeshed to define a second seam, the improvement characterized by: the first and second seams being located in CMD vertical planes which extend perpendicular to the fabric and are spaced apart by more than one-eighth on an inch.

7. A method of producing a papermaking fabric having first and second seams located in cross machine direction

(CMD) vertical planes which extend perpendicular to the fabric and are spaced apart by more than one-eighth of an inch, the method comprising the steps of: weaving a plurality of machine direction (MD) yarns with a plurality of CMD yarns to form a first sub-fabric having first and second ends which are spaced at a predetermined distance and include a plurality of seam loops; weaving a plurality of MD yarns with a plurality of CMD yarns to form a second sub-fabric having first and second ends which are spaced at the predetermined distance and include a plurality of seam loops; aligning the first sub-fabric with the second sub-fabric with the first sub-fabric ends offset from the second sub- fabric ends by more than one-eighth of an inch; and laminating the two sub-fabrics together.