Endless power transmission belt

ABSTRACT

This invention provides an improved power transmission belt which has a relatively thick rubber backing layer for improved interface with associated pulleys and improved wear resistance. The belt also has an aramid, glass, or other high modulus relatively inextensible cord secured by a layer of fabric.

INFORMATION

DETAILED DESCRIPTION OF THE INVENTION

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view with parts in cross-section, parts in elevation, and parts broken away illustrating one exemplary embodiment of the belt body of the invention.

FIGS. 2-4 are partial views, similar to FIG. 1, illustrating various types of alternative fabric arrangements.

DESCRIPTION OF PREFERRED EMBODIMENTS

As shown in FIG. 1, the endless power transmission belt is shown as a portion of an entire continuous belt adapted to be operated between driving and driven pulleys in an endless manner well known in the art. The belt has a compression section , defined by a plurality of longitudinally extending ribs , each having a trapezoidal cross-section (also referred to as truncated vee ribs) extending partially into the compression section, having inner surfaces and angled side surfaces . The compression section is composed of a rubber material well-known in the art. A tension section , composed of a similar material, is disposed outwardly of the compression section. A load-carrying section is disposed between the compression and tension sections, and is composed of a rubber material well-known in the art. This section also comprises a plurality of longitudinally extending cords or cord windings made of high modulus material, the preferred material being aramid. These cords are imbedded in the section and are utilized as load-carrying cords, and as indicated above, they are stretch-resistant and provide additional improved belt characteristics.

In order to prevent the cords from floating during construction, a backing layer and a fabric layer are formed as part of the belt. The backing layer is disposed outwardly of the tension section and also forms the outer surface of the belt. This surface also has the additional function of acting as a wear surface against a back side idler which is used in some belt drive systems, and provides a higher coefficient of friction than a fabric backing which is frequently used. The backing layer has a thickness ranging from 0.015 to 0.050 inch, and is composed of a special polymeric material such as EPDM (ethylene propylene diene monomer). The fabric layer is disposed in the tension section, preferably adjacent the backing layer and the load-carrying cords, and has been found to work in conjunction with the backing layer to provide the above-mentioned control of the cords. As shown, the backing layer is adjacent the fabric layer, although it may be spaced therefrom. The fabric layer is comparatively thin, ranging from about 0.005 to 0.035 inch. As shown in FIG. 1, the fabric layer is formed of a rubber impregnated square woven fabric having threads made of materials well-known in the art, such as cotton, rayon, nylon, aramid, polyester or fiberglass. The fabric layer is preferable formed of a wide strip of material wrapped around the load-carrying section, and having transversely extending ends and which are overlapped to form a splice . The present construction permits the splice to be thinner than in conventional constructions. As shown in FIG. 1, this avoids misalignment of the strength cords .

Modifications

As alternative forms of the invention, it is contemplated to use other types of fabric instead of the square woven material of layer . FIG. 2 illustrates a belt having a construction similar to belt , except that fabric layer is formed of a knitted material similar to that shown in the Richmond patent. As in FIG. 1, the fabric layer is formed with ends and which have a splice similar to splice .

FIG. 3 illustrates belt similar to belts and , except that the fabric layer is formed of a structure known as “tire cord”, consisting of transversely extending strength cords and weak tie strands which hold the strength cords in a substantially parallel relationship. This type of cord is also shown in the Richmond patent. The fabric layer is also formed with ends and overlapped to form splice similar to the splices and .

FIG. 4 illustrates a belt similar in construction to the other belts, except that fabric layer is formed of a bias laid woven fabric referred to as “stress-relieved”, in which the warp and weft threads are disposed at an angle of 95° to 155° to each other. Such a fabric is shown in the above-referenced Waugh patent. The fabric layer is also formed as a sheet having ends and which are overlapped to form splice , similar to the other splices.

Reference has been made throughout this application to splice thickness. What is meant by splice thickness is the total thickness of the spliced structure at the location of the splice.

The invention described herein comprises a belt structure and method in which the “fabric layer” and the “backing layer” comprise separate and distinct layers, and further are installed in the belt discreetly during the building process. This is distinct from a structure and method in which the “backing layer” is laminated to the “fabric layer” in a separate operation and the resulting composite is then applied to the belt during the building process. This is the primary distinction which ensures that the splice thickness can be minimized—the splice in the “backing layer” can be staggered some distance away from the splice in the “fabric layer”, in which case, the maximum splice thickness will be limited to twice the fabric thickness or twice the backing thickness (whichever is thicker), rather than twice the combined thickness of a composite containing both elements. (This maximum in either case is reached with a plain lap splice; a butt splice or bevel splice—with or without sewing—would have a thickness substantially equal to the structure spliced, whether “backing”, “fabric”, or “composite”. A skived lap splice, in which the rubber “backing” is removed from the ends to be overlapped in the splice, would have a maximum thickness equal to two fabric layers.).

Other modifications are also contemplated. For example, instead of the trapezoidal or truncated vee ribs, fully V-shaped ribs may be utilized, as shown for example in FIG. 5 of the above-referenced Richmond patent. Other modifications are also contemplated as being within the scope of the inventive concept.

CLAIMS

1. In an endless power transmission belt comprising an inner compression section, an outer tension section, and a load-carrying section disposed between said compression and tension sections and having longitudinally extending load-carrying cords; the improvement wherein said load-carrying cords are made of a high modulus material and said belt further comprises a polymeric backing layer disposed outwardly of said tension section and forms the outer surface of said belt, and a fabric layer disposed between said backing layer and said load-carrying cords.

2. The belt of claim 1 wherein said load-carrying cords are composed of aramid.

3. The belt of claim 1 wherein said belt is comprised of a plurality of longitudinally extending ribs in said compression section.

4. The belt of claim 3 wherein said ribs have a trapezoidal cross-section.

5. The belt of claim 1 wherein said backing layer has a thickness between 0.015 and 0.050 inch.

6. The belt of claim 1 wherein said backing layer is composed of ethylene propylene diene monomer.

7. The belt of claim 1 wherein said backing layer is adjacent said fabric layer.

8. The belt of claim 1 wherein said fabric layer comprises a rubber impregnated fabric.

9. The belt of claim 8 wherein said fabric is selected from a group consisting of knitted, square woven, tire cord, or stress-relieved fabrics.

10. The belt of claim 1 wherein said fabric layer has a thickness between 0.005 and 0.035 inch.

11. The belt of claim 1 wherein said fabric layer comprises transversely extending ends joined together by a splice, said splice having a maximum thickness of 0.070 inch.

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