TRANSFER BELT

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to paper machinery, and, more particularly, to transfer belts utilized in the process for paper making.

2. Description of the Related Art

Center belts, or transfer belts, are an essential component of a paper making system in that they transfer a fibrous web from one processing station to another. There have been many proposals in the art to provide increased durability and efficiency for such belts.

The International Patent Publication to Carlson WO 03/071030 A1 describes a paper machine belt with a resinous layer on both sides of a cross machine directed (CD) oriented substrate with extra fibrous layers. This is done to minimize, if not eliminate, the possibility of edge curl of the belt during operation. U.S. Patent 5,298,124 to Elklund teaches the possible addition of an inside layer to such a substrate. The several additional approaches have been to utilize singeing of the edge to minimize fiber loss during use in a paper machine system.

The above approaches, while solving some of the problems, still have existing problems, such as limited lifetime, production efficiencies, fibrous web release l

irregularities, high energy consumption, and deteriorating sheet quality, over a long term basis, particularly when the transfer belt is used in a short belt system where the number of rotations the fabric must endure over its service life is considerably greater that current commercial applications.

Thus, a need exists in the art to provide a transfer belt having increased service lifetime and durability.

SUMMARY OF THE INVENTION

The invention, in one form, relates to a transfer belt having a face side layer and a roll side layer with the roll side layer having wear resistance that is at least 1.5 times the wear resistance of the face side layer.

In another aspect of the invention the above variation in wear resistant is determined by the Martindale Wear Test.

An advantage of the present invention is increased service life and durability.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

Fig. 1 illustrates a cross-section view of one form of a transfer belt embodying the present invention; Fig. 2 illustrates an alternative embodiment of a transfer belt embodying the present invention; and Fig. 3 illustrates still another alternative of a transfer belt embodying the present invention.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate several embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to Fig. 1 , there is shown a transfer belt 10 having a face side layer 12, a roll side layer 14 and a base 16 intermediate the face side layer 12 and roll side layer 14. Typically, the face side layer 12 abuts the material being transferred in the paper machine process. This can be a fibrous web in any one of a number of forms. The roll side layer 14 typically comes in contact with driving and supporting rolls in the paper machine process so that force to move the belt 10 is transferred to the roll side layer 14.

In accordance with the present invention, the wear resistance of the roll side layer 14 is at least 1.5 times the wear resistance of the face side layer 12. The difference in wear resistance can be selected through a number of approaches, as illustrated below.

The wear resistance is determined by any one of a number of wear resistances testing systems.

One such wear tester is commonly referred to as the Martindale Method for testing which is a standard test method for abrasion resistance of textile fabrics. There is an ASTM D4966-98 method for defining the testing of the abrasion resistance of fabrics. The substance of the test method is hereby incorporated in its entirety. Another standard for the Martindale Test for Abrasion Resistance of Fabrics is defined in ISC 129471 -(1- ). The substance of this test method is also hereby incorporated in its entirety. It should be apparent to those skilled in the art that other Martindale test procedures may be employed with equivalent results.

For purposes of describing the present invention, the Martindale tester is a device where samples to be tested are placed in a specimen holder so that they are in a planar form relative to the abrasion device. The abrasion device has a predetermined coarseness and it is moved over the surface of the sample to be tested in a Lissajous pattern that covers the surface of the device of a specimen to be tested. The Lissajous pattern is named after Jules Antoine Lissajous who, in 1857, described, in greater detail, the complex harmonic motion curves first developed by Nathaniel Bowditch in 1815.

Using this periodic complex movement, the test is conducted over a predetermined number of cycles and a predetermined weight is applied to the abrasion device to consistently simulate abrasion on the fabric. As illustrated herein, the resistance to

abrasion is determined by the weight loss of the fabric in terms of grams of material loss over the course of the test. IT should be apparent to those skilled in the art, that other measures of abrasion resistance may be employed such as caliper loss for the fabric thickness.

Although exemplary compounds and materials will be described in connection with the face side layer 12 and the roll side layer 14, it should be apparent that other combinations of materials may be employed to also achieve the inventive object of a roll side wear resistance at least 1.5 times the face side resistance.

The materials selected for the various layers may be polyurethane polymers, silicones, and aramids, and combination of such materials, each chosen to achieve the difference in wear resistance. For example, face side layer 12 may be formed from a polyurethane polymer and the roll side layer 14 formed from a polyurethane polymer with a fiber reinforcement. In addition, a woven or non-woven base 16 of appropriate material may be employed intermediate the face side layer 12 and the roll side layer 14. The difference in wear resistance of the face side layer 12 and roll side layer 14 in Fig. 1 is accomplished by the use of reinforcement in the roll side layer 14.

Fig. 2, however, relies on a different mechanism to accomplish the same end. In Fig. 2, a face side layer 18 overlies a base 20. A roll side layer 22 is attached to the opposite side of the base 20. The face side layer 18 is formed from a soft polyurethane polymer and the roll side layer 22 is formed from a harder polyurethane polymer. These polyurethane polymers, with variable hardness, can be readily selected from

commercial manufacturers of such materials. Also in Fig. 2, as in Fig 1 , the base 20 may be formed from woven or non-woven material.

Fig. 3 shows still another way of varying the wear resistance of the roll side and face side layers. In Fig. 3, a face side layer 24 overlies and is connected to a roll side layer

26. As illustrated in Fig. 3, the face side layer 24 is formed from polyurethane having embedded therein relatively fine calcium carbonate. The roll side layer 26 also has polyurethane, but with a coarser calcium carbonate embedded therein to achieve the higher wear resistance set forth in accordance with the present invention. It should also be apparent that the wear resistance of the roll side layer 26 can be achieved with the addition of fiber reinforcements instead of, or in addition to, the calcium carbonate.

The selection of the wear resistance has been illustrated above with the use of polyurethane. It should be apparent to those skilled in the art that the variation in wear resistance may be also achieved by using silicones, aramids or other appropriate materials or combinations of such materials. As used in connection with the Martindale test, the wear resistance of the face side layer is such that the material loss, over the course of the test, is less than 6 grams and the wear resistance of the roll side layer is such that the material loss, over the course of the test, is less than 8 grams with the ratio of wear resistance of the roll side layer being at least 1.5 times the wear resistance of at least the face side layer.

The resultant selection of wear resistance gives increased performance in terms of longevity and durability of the transfer belt

While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.