Power transmission belt reinforcing material and power transmission belt constructed therewith

Abstract: A belt reinforcing material of at least two layers where one layer is a twined fabric and the other layer is a woven fabric that are attached to each other such as by needle-punching. A toothed power transmission belt with a plurality of teeth spaced along one side of the belt includes the aforementioned fabric disposed at a peripheral surface that includes the belt teeth.

Description: Background of the Invention The invention relates to a belt reinforcing fabric, but more particularly, the invention relates to a reinforcing fabric particularly useful in reinforcing belt teeth and a toothed power transmission belt made with such fabric. Toothed power transmission belts have a polymeric body such as of a rubber, thermoplastic, or urethane, with a plurality of teeth formed along at least one side of such belts. A tensile member is typically embedded in a body as a load carrying member. It is preferred to have the belt teeth reinforced with a fibrous material to enhance their shear strength and wear-resistance, or to alter their coefficient of friction for engagement with a toothed pulley. Wear-resistant fabrics for belts are of a woven type such as a canvas, a crimped stretchable nylon, and a leno-weave, etc., and may be of a knit fabric such as a 1 x 1 rib knit. Such fabrics are disposed in the belt at a peripheral surface that includes the belt teeth and may be in the form of single layer fabrics, multiple layers of woven fabrics, bonded layers of fabrics, and fabrics with an outer layering of an impervious thermoplastic film. Other fabric reinforcements for reinforcing belt teeth may be of the non-woven type and include a web of discontinuous fibers or a web of fibers that are bonded together by thermal or chemical bonding or needle-punching in known fashion to form a non-woven fabric. Such non-woven belt fabrics are typically embedded in a belt body and may be used to help locate a belt's pitch line diameter (PLD) for a spirally wound tensile cord at lands located between spaced belt teeth. The fabrics are sometimes in an expanded form near a middle portion of the belt tooth where they act as a tooth reinforcement. With some non-woven fabrics, it is difficult to control a requisite thickness for maintaining an acceptable PLD. Some non-woven fabrics are difficult to handle and position at a desired location within belt teeth because of processing limitations of belt manufacture. Examples of fabric reinforcements for belts and belts reinforced therewith are disclosed in the following patents: U.S. Patent No. 3,964,328 (Redmond) discloses a fabric in the preferable form of a stretchable nylon with a thermoplastic layer such as polyethylene bonded to an exterior surface thereof. The fabric is disposed at a peripheral surface of a belt including belt teeth as a wear-resistant fabric and friction modifying reinforcement. U.S. Patent No. 4,099,422 (Cicognai et al.) discloses a rubberized fabric. Two layers of the fabric are disposed along a peripheral surface of a belt including belt teeth for wear-resistance and rigidifying the belt teeth. U.S. Patent No. 4,235,119 (Wetzel) discloses a fabric disposed along a peripheral surface of a belt including belt teeth as a wear-resistant fabric. Discontinuous fibers are compounded into a rubber elastomer of a belt body and are located adjacent the fabric and a tensile member for rigidifying the belt teeth. U.S. Patent No. 4,605,389 (Westhoff) discloses a fabric of the type as used in Redmond '328. The fabric is disposed along a peripheral surface of a belt including spaced belt teeth where the belt teeth are configured flank surfaces having a tractrix curve shape. U.S. Patent No. 4,895,555 (Watanabe et al.) discloses a web of non-woven fabric. The non-woven fabric is used as a reinforcement with a cast urethane belt body and is compressed under a tensile member in a land area of a belt and is diffused in belt teeth as a reinforcing fiber for improving the shear strength of the teeth. U.S. Patent No. 5,362,281 (Dutton) discloses a double woven fabric with two sets of warp yarns and two sets of weft yarns that are tied together to form a single fabric layer. The fabric is used as a reinforcement and is disposed along a peripheral surface of the belt including belt teeth as a wear-resistant fabric and a reinforcement member. The fabric also operates to help locate tensile members of the belt for controlling PLD. The features of the present invention that are know from this document have been placed in the preamble of claim1. U.S. Patent No. 4,392,842 (Skura et al.) discloses a stretchable fabric reinforcement. The reinforcement is used in two layers of a toothed belt where one.layer is disposed at a peripheral surface including the belt teeth and the other layer is embedded as a suspended layer in the belt teeth as a reinforcement. U.S. Patent No. 5,536,214 (Akita et al.) discloses a non-woven fabric where in the prefered form, it is needle punched which bonds discontinuous fibers of the fabric together by entangling some fibers. The non-woven fabric is used as an embedded reinforcement in a toothed belt body of cast urethane. The fabric is disposed in the belt body in a land area between belt teeth where it is compressed to help control PLD and in the belt teeth where it is expanded and serves as an embedded reinforcement for the belt teeth. Summary of the Invention In accordance with the invention, as defined in claim 1, a belt reinforcing material is provided comprising two layers of textile material that are attached to each other. One of the layers is in the form of a twined fabric such as a woven fabric that preferably is stretchable at least along one axis of the fabric. A layer of non-woven material is attached to the twined fabric layer such as by needle-punching. A toothed power transmission belt also in accordance with the invention, as defined in claim 8, is of the type with a polymeric body and a plurality of spaced teeth along at least one side of the belt. The belt includes a wear-resistant fabric disposed at a peripheral surface that includes the belt teeth. A tensile member is embedded in the body. For cast belts, the layered fabric preferably includes an impervious thermoplastic layer at an exterior surface of the twined fabric. The thermoplastic layer is useful in conjunction with a manufacturing process for a belt having a polymeric body of a castable urethane material. Optionally, more than one twined fabric layers may be used in conjunction with one or more layers of non-woven fabric material. A further bothed power transmision belt of the present invention is defined in claim 10. An object of the invention is to provide a belt reinforcing material for a power transmission belt. Another object of the invention is to provide a belt construction with an improved wear-resistant fabric that exhibits improved belt tooth reinforcement and positioning of a non-woven fabric during belt manufacture. Another object of the invention is to provide a belt with a layer of non-woven material that is located and positioned in a belt tooth for enhancing reinforcement of the belt tooth. An advantage of the invention is that a non-woven fabric can be placed in a mold so that it will be in a desired proper position within a tooth of a formed belt. These and other objects and advantages of the invention will be apparent after reviewing the drawings and detailed description thereof wherein: Figure 1 is a perspective view showing a layered fabric of the invention; Figure 2 is an enlarged cross section of fabric taken along the line 2-2 of Figure 1; Figure 3 is a view similar to that of Figure 2 but showing an alternate form of a fabric of the invention; and Figure 4 is an enlarged fragmentary longitudinal view of a side of a toothed belt of the invention with depicted alternate embodiments and wherein a view taken along the line 2' - 2' is a view of fabric similar to Figure 2, and a view taken along the line 3'-3' is a view of fabric similar to Figure 3. Description of Preferred Embodiment Referring to Figures 1 and 2, a belt reinforcement fabric 10 has a non-woven fabric layer 12, a twined fabric layer 14, and optionally, and when for a urethane or cast belt, a thermoplastic layer 16. The non-woven fabric layer is made with discontinuous fibers 18 and may be initially in the form of: a web of unbonded discontinuous fibers of the same or different materials; a web of the same or discontinuous fibers of the same or different materials that are bonded together by needle punching; or a web of dissimilar fibers that have been heat bonded to each other in any desired fashion and sheeted into a fabric of controlled weight and thickness. A wide range of fiber types may be used for the non-woven fabric such as, for example, nylon, polyester, aramid, polypropylene or a combination thereof, or a combination of nylon and polypropylene fibers where the fibers of the fabric have different melting temperatures so they can be thermally bonded to one another. Examples of fiber bonding include: chemical, thermo/pressure, hydroentangled, needle-punch, chemical/thermal or a composite thereof. The twined fabric may be of any suitable fabric such as canvas, crimped fabric that is stretchable in at least one direction, leno weave, knit or the like; and made of any desired fiber including aramid, nylon, polyester, rayon, polypropylene and cotton. The twined fabric illustrated in Figure 2 is of the type disclosed in Dutton US-A-5,362,281 which is a single fabric of a multi-weave type with two sets of warp and weft yarns where in a first woven component 20 has a plurality of warp yarns 22 and a plurality of fill or weft yarns 24. A second woven component 26 has a plurality of warp yarns 28 and weft yarns 30. The woven components are periodically interlaced with tie yarns (not shown) which may be weft or warp yarns. The non-woven fabric is attached to the twined fabric at a plurality of spaced points 32, 34, 36 as is preferably accomplished by needle-punching. A serrated needle of a needle-punch (not shown) hooks fibers of the non-woven fabric or twined fabric or both, and positions the hooked fiber through 38 and into the adjacent fabric layers which entangles 40 fibers and attaches the layers 12, 14 together at spaced points 32, 34, 36. Needle-punching may be directed from either the non-woven fabric side or the twined fabric side. When an unbonded web of non-woven fabric is chosen, it is preferred that needle-punching take place from the non-woven side because the twined fabric serves as a substrate during the needle-punching operation. However, when a bonded layer of non-woven fabric is chosen, it may be optionally used as a substrate and needle-punching may be directed from the twined fabric side. The number of attachment points must be sufficient to hold the fabric layers sufficiently together during a belt manufacturing process. Also, the number of needle-punches per unit area, commonly referred to as needle-punches per square inch or ppsi, has an impact on the thickness 42 of the composite reinforcement fabric 10 1 square inch = 6.45cm 2 . Generally speaking, the higher the density of needle-punching, the thinner the reinforcement fabric. It has been determined that a needle-punch density from about 100 to about 500 ppsi is satisfactory for attaching the non-woven fabric and twined fabric layers together. To complete the illustrated embodiment of the reinforcement fabric 10, a layer of thermoplastic material 16 is applied and bonded to the outer surface of the twined fabric in known fashion. The thermoplastic material may be of any desired type such as polyethylene and include alloys with other thermoplastic materials as desired to modify friction, increase wear-resistance properties, etc. Another belt reinforcement fabric 44 of the invention is illustrated in Figure 3. The fabric is substantially similar to that as shown in Figure 2 except for a thicker layer 46 of a non-woven fabric and a thinner layer 48 of a twined fabric. A layer of thermoplastic material is optionally excluded. The layers of fabric are attached to each other at a plurality of spaced points 52, 54, 56 by needle-punching. Fibers 56 are pushed through the twined textile fabric which entangles 40 fibers between the fabric holding the fabrics together. The twined fabric is woven in a single layer and has warp yarns 58 and weft yarns 60. Referring to Figure 4, a toothed power transmission belt 62 of the invention has a polymeric body 64, a plurality of spaced teeth 66, 68 along at least one surface 70 for engagement with a toothed pulley (not shown), and a wear-resistant fabric 10 or 44 disposed along a periphery 72 that includes the belt teeth. The polymeric body may be of any desired material which includes, by way of example, natural rubbers, synthetic rubbers, and blends thereof; urethanes such as of the liquid cast or millable gum variety; and thermoplastic such as polyester. For the belt tooth 66, a cast liquid urethane body may be used in combination with fabric 10. A tensile member 74 is embedded in the belt body and may be in the form of a spirally wound cord. The pitch line diameter for the cord is at least partially controlled by the thickness 42 of the fabric. As known in the art, a PLD for a belt can be slightly modified by the winding tension of a tensile member during a belt manufacturing process. Optionally, ribs 76 and grooves 78 may be formed on an opposite side of the belt for enhanced flexibility. However, and in some applications, it may be desired for the belt to have a flat surface 80 for engagement with pulleys (not shown). The embedded tensile member 74 is of the endless type such as a spirally wound cord and is made from a material with minimum elongation such as fiberglass, aramid, and carbon fiber. The profile of the belt teeth may be of any desired configuration such as trapezoidal, or with curvilinear flank surfaces such as those shown in U.S. Patent Numbers 3,756,091 (Miller), 4,605,389 (Westhoff), or 4,515,577 (Cathey et al.). The belt tooth profile of Figure 4 has flanks of the curvilinear type. The non-woven fabric layer, being attached to the twined fabric layer, conforms to the peripheral surface including the belt teeth. By following the contour of the belt teeth, the fabric is in a position to enhance reinforcement of belt teeth. In the case of manufacturing a cast urethane belt, the fabric 10 may be pre-pleated before being placed in a mold, or alternatively, the fabric may be pleated while it is being positioned in a toothed mold. The composite fabric 10, 44 eliminates a need for separately handling a non-woven fabric material and positioning it at a strategic location adjacent to a peripheral belt surface. In the case of a belt with a rubber body, the fabric is pretreated in known fashion such as by dipping it into a laytex or elastomeric material solution for adhesion with the rubber body. To illustrate the advantages of the features of the invention, 14mm pitch, curvilinear toothed belts of the invention with polyurethane bodies were tested against similar prior art belts. The belts were constructed in a similar manner except for the wear-resistant fabric. The test conditions for the belts were as follows: 44.7kW (60 horsepower) 32 Toothed sprockets T1 + T2 = 526kg (1160 lbs) All tested belts had a fabric with a thermoplastic layer and the textile portion of each fabric is characterized by the following: Fabric Description Fabric Construction Belt Life Performance Prior Art - single ply twined fabric 308 g/m 2 (13 oz./sq.yd.), multi-warp Warp - 210/2dtex X 118 Count Fill-70/6 dtex X 96 count 25.5 hrs. Prior Art - dual twined fabric 2 ply-209g/m 2 (8.84 oz./sq. yd.), single warp Warp-210/1 dtex X 81 count Fill-70/4 dtex X 74 count 38 hrs. Invention - twined fabric & nonwoven 209g/m 2 (8.84 oz./sq yd.) - single warp Warp-210/1 dtex X 81 Count Fill-70/4 dtex X 74 count 330 gm./m 2 - non woven needle density 171 ppsi (1 square inch = 6.45cm 2 ) 154 hrs. Invention - twined fabric & nonwoven 308g/m 2 (13 oz./sq.yd.), multi-warp Warp-210/1 dtex X 118 count Fill-70/6 dtex X 96 count 50 gm./m 2 - non woven needle density 240 ppsi (1 square inch = 6.45cm 2 ) 350 hrs. Thus, belts of the invention displayed load lives that were from about 6 to 11 times better than that of the prior art belts having prior art fabric reinforcements. It will, of course, be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention as defined in the claims.

Claims: A power transmission belt reinforcing material (10,44) comprising two layers of textile fibrous material with portions of one of the layers attached to the other layer and wherein one of the layers is a twined fabric layer (14,48); and characterised in that the other layer comprises: a non-woven fabric layer (12,46) of material (18) attached to the layer of twined fabric material. The reinforcing material as claimed in claim 1 wherein the non-woven fabric layer (12,46) is a web of non-woven fibrous material (18). The reinforcing material as claimed in claim 1 wherein the non-woven fabric layer (12,46) is a calendered web of heat bonded, non-woven fibrous material (18). The reinforcing material as claimed in claim 1, 2 or 3 wherein the twined fabric layer (14,48) is selected from the group consisting of a woven fabric and a knit fabric. The reinforcing material as claimed in claim 1, 2, 3 or 4 comprising: a layer (16) of thermoplastic material bonded to an exterior facing surface of the twined fabric material. The reinforcing material as claimed in any one of claims 1-5 wherein fibres (40) of one layer are interlaced with fibres of the other layer to attach (32,34,36, 52,54) the layers (12,14,48,46) together. The reinforcing material as claimed in claim 6 wherein the fibres (40) are interlaced by needle-punching. A power transmission belt (62) having a plurality of belt teeth (66,68) reinforced with a reinforcing material (10, 44) according to any one of claims 1-7. A belt as claimed in claim 8 wherein the reinforcing material is disposed along a peripheral edge of the belt that includes the belt teeth. A toothed power transmission belt (62) with a belt body (64) primarily formed of a urethane elastomer and reinforced with a textile fibrous material at a peripheral edge that includes the belt teeth, characterised in that the fibrous material comprises: a non-woven fabric layer (12,46) of material (18) attached to a layer (14,48) of twined fabric material and a layer (16) of thermoplastic material bonded to the layer of twined fabric material on the externally exposed side thereof along the peripheral edge.

Inventors: WESTHOFF WILLIAM L, WESTHOFF, WILLIAM L.
Applicants: GATES CORP, THE GATES CORPORATION
Application year: 1998
Main classification: B32B5
IPC codes: F16G1, B32B5