V-BELT FOR HIGH LOAD POWER TRANSMISSION

Abstract: A power transmission V-belt (10) for transmitting high loads with extended useful life. The por­ tion of the V-belt in which the tensile elements (13) thereof are embedded is formed of a rubber having short reinforcing fibers (17) distributed therein and oriented longitudinally of the belt. Different embodiments of both wrapped and raw edge belts em­ bodying the invention are disclosed. Embodiments in which the outermost portion of the tension sec­ tion and the innermost portion of the compression section are free of the longitudinally extending short fibers are also disclosed. Preferred amounts of the short fiber material and the hard­ ness of the rubber are disclosed.

Description: This invention relates to power transmission belts and in particular to V-belts intended for high power transmission service. In one common form of V-belt for use in transmitting power as between pulleys, a plurality of longitudinally extending tensile cords are em­ bedded in a layer of cushion rubber. An outer tension section of rubber is provided outwardly of the cushion rubber and an inner compression section of rubber is provided inwardly of the cushion rubber. It is further conventional to cover the belt with a fabric, such as canvas. The canvas may completely encircle the belt, or may be applied only to the inner surface and outer surface there­ of, with the sides of the belt defining raw edges. A serious problem arises in the use of such conventional belts where high loads are transmit­ ted. The stresses developed in the belt as a re­ sult of the high load transmission causes cracking to occur. Both longitudinal cracks and side cracks have been found to extend through the cushion rubber in which the tensile cords are em­ bedded. Such cracks propagate to and into both the tension and compression sections of the belt, thereby substantially reducing the useful life of the belt. One attempted solution to this problem has been to provide a distribution of short reinforc­ ing fibers extending transversely across the belt in either or both of the compression and tension sections. Conventionally, approximately 5 to 10 parts by weight of such fibers are provided in such sections. While such a distribution of reinforcing fibers does increase the rigidity in the transverse direction, the use of such fibers has been found to cause the belt to be harder than desired. Because of the increase in the hardness, the prevention of cracks by such means is not completely satisfactory. The inventors hereof have proposed previous­ ly, as disclosed in Japanese Utility Model Appli­ cation No. 60144/1979, the provision of a small amount of such short fibers, such as 0.1 to 3.0 parts by weight, in the compression rubber sec­ tion, as illustrated in Figure 9. It has been found that such construction does provide an im­ proved long life by affording a limited degree of desired rigidity in the compression section. Such structure has been found, however, to be not completely satisfactory in extending the useful life of such belts because of the shifting of the tensile cords so that the spacing therebetween became irregular and some superposition occurred. As seen in Figure 9, the prior art structure re­ quired the conventional use of a cushion rubber layer embedding the tensile cords in addition to the compression section provided with the longi­ tudinally extending short fibers and the conven­ tional outer tension section. The present invention comprehends an improved V-belt structure which overcomes the deficiencies of the prior art structures in a novel and simple manner and provides substantially improved long, troublefree life of such a V-belt, notwithstanding the transmission of high loads thereby. The improved V-belt construction of the pres­ ent invention provides improved resistance to bending and cracking and unexpectedly provides im­ proved transverse stability under severe high load conditions. The belt construction is extremely simple and economical, while yet providing the improved dura­ bility and long life. More specifically, the invention comprehends the provision of such a power transmission V-belt wherein the portion of the belt in which the ten­ sile elements are embedded is formed of rubber having short reinforcing fibers distributed there­ in and oriented longitudinally of the belt. In the present invention, the fibers are present in the ratio of approximately 0.1 to 3.0 parts to 100 parts of the rubber. The rubber in which the tensile cords are embedded is caused to have a Shore A hardness of approximately 70° to 90°. The tensile cords may be formed of conven­ tional strong filamentary material. In the illus­ trated embodiment, the fibers have a length of ap­ proximately 2 mm to 20 mm and may be formed of suitable reinforcing material, such as natural fiber, artificial fiber, synthetic fiber, and in­ organic fiber materials. In the illustrated embodiment, the fibers comprise cut fibers. A rubberized fabric cover may be provided on the inner and outer surfaces and also may be se­ lectively provided on the side edges, as desired. The fabric cover, in the illustrated embodi­ ment, is made up of bias-laid plies, with the warps and wefts thereof disposed at a 90° to 140° crossing angle. The plies are preferably bias-­ laid. In the disclosed embodiments, at least one of the outermost porion of the tension section and the innermost portion of the compression sec­ tion is caused to be free of the longitudinally extending short fibers. The invention comprehends that the entire belt body be formed of rubber having short rein­ forcing fibers distributed therein and oriented longitudinally of the belt, as desired. In all embodiments of the invention, the portion of the belt in which the tensile cords are embedded is provided with the longitudinally extending short fibers. Other features and advantages of the inven­ tion will be apparent from the following descrip­ tion taken in connection with the accompanying drawing wherein: FIGURE 1 is a schematic illustration of a drive belt embodying the invention, as used in transmitting power between a driver pulley and a driven pulley; FIGURE 2 is a fragmentary perspective view of a portion of a belt embodying the invention; FIGURE 3 is a transverse section illustrating a modified form of belt embodying the invention; FIGURE 4 is a transverse section illustrating another modified form of belt embodying the inven­ tion; FIGURE 5 is a transverse section illustrating still another form of belt embodying the inven­ tion; FIGURE 6 is a transverse section illustrating a still further belt embodying the invention; FIGURE 7 is a transverse section illustrating yet another belt embodying the invention; FIGURE 8 is a transverse section illustrating a conventional prior art belt; and FIGURE 9 is a transverse section illustrating a prior art belt developed by applicants herein. In the illustrative embodiments of the inven­ tion as disclosed in the drawing, a power trans­ mission belt generally designated 10 embodying the invention is illustrated as for use in transmit­ ting high loads between a driver pulley 11 and a driven pulley 12. As discussed briefly above, the belt of the present invention is adapted to pro­ vide such high load power transmission with an extended useful life. As shown in Figure 2, power transmission belt 10 comprises a V-belt having a plurality of ten­ sile cords 13 extending longitudinally of the belt in side-by-side spaced relationship transversely thereof. The tensile cords are embedded between an outer tension section 14 and an inner compres­ sion section 15. In the illustrated embodiment, the tension and compression sections are formed of similar rubber and are integrally joined be­ tween the tensile cords, whereby the belt body generally designated 16 comprises an integral uni­ tary construction. As further illustrated in Figure 2, a distri­ bution of short reinforcing fibers 17 is provided throughout the belt body. More specifically, the invention comprehends that the longitudinally ex­ tending short reinforcing fibers be provided in the rubber in which the tensile cords are embedded within the belt body. Belt 10 is provided with an outer cover fab­ ric 18 which may fully encircle the belt and thus cover the top surface 19 of the tension section, the bottom surface 20 of the compression section, and the side edges 21. The belt rubber may com­ prise conventional power transmission belt rubber which may be blend of a natural rubber, chloro­ prene rubber, and/or styrene butadiene rubber. The tensile cords are preferably formed of conventional tensile cord material, such as poly­ ester resin, aliphatic polyamide resin, aromatic polyamide resin, etc. The rubber preferably has a Shore A hardness of 70° to 90°. The short fibers 17 are preferably cut fibers formed of natural fiber, artificial fiber, synthetic fiber, inorganic fiber, etc., and in the illustrated embodiment, have a length of ap­ proximately 2 mm to 20 mm. The cut fibers are provided in the belt 10 in a ratio of approximately 0.1 to 3.0 parts by weight of the rubber. The farbirc 18 may comprise a canvas fabric. The fabric may be formed with one or more plies, with the warps and wefts of the plies being formed of cotton yarns, blended yarns of cotton and nylon yarns, blended yarns of cotton yarns and polyester yarns, etc. The plies are woven at a wide crossing angle of approximately 90° to 140° and, in the illustrated embodiment, are laminated and bonded to the rubber body with rubber in a bias direction. It has been found that by utilizing both the longitudinally oriented short fibers in the rubber in which the tensile cords are embedded, and pro­ viding the rubber as a relatively hard rubber, maximum extension of useful life of the belt is obtained, with minimized cracking and desirable bending durability with reduced belt-degrading heating during use of the drive system. Referring now to the embodiments of Figures 3-7, the invention comprehends a number of modi­ fications within the broad scope thereof providing improved long, troublefree life of the belt under high load conditions. As seen in Figure 3, a modified form of belt generally designated 110 embodying the invention is shown to comprise a belt similar to belt 10 but wherein the innermost portion 122 of the compres­ sion section 115 is free of the longitudinally extending cut fibers 117. Another belt embodying the invention general­ ly designated 210 is shown in Figure 4 to comprise a belt generally similar to belt 10, but wherein both the outermost portion 223 of the tension section and the innermost portion 222 of the com­ pression section are provided free of the longi­ tudinally extending cut fibers 217. As further illustrated in Figure 4, the ex­ tent of the cut fiber-free portions of the tension and compression sections outwardly and inwardly of the portion of the belt in which the tensile cords are embedded may be selected, as desired, within the broad scope of the invention. In Figure 5, still another form of belt gen­ erally designated 310 embodying the invention is shown to comprise a belt similar to belt 10, but wherein the side edges 321 comprise raw edges, with the cover fabric 318 being provided only on the outer surface 319 of the tension section and the inner surface 320 of the compression section. Still another form of the invention generally designated 410 is illustrated in Figure 6 to com­ prise a belt similar to belt 110, but wherein the side edges 421 of the belt comprises raw edges. A belt generally designated 510 is illustra­ ted in Figure 7 to comprise a belt generally sim­ ilar to belt 210, but wherein the side edges 521 thereof comprise raw edges. The unexpected extended useful life of the power transmission belts embodying the invention is illustrated in the following Table 1, wherein the belt 10 is shown to have a substantially in­ creased useful life over the prior art belts of Figures 8 and 9. In determining the comparison of useful life, the belts were driven in a drive system, as shown in Figure 1, wherein the driver pulley was 80 mm in diameter, the driven pulley was 74 mm in diameter, with the driver pulley being rotated at a speed of 3600 rpm. 6 PS of load and 100 kg of initial load were applied. As shown in Table 1, the provision of the longitudinally extending short fibers in the portion of the rubber body in which the tensile cords are embedded provides an unexpectedly sub­ stantial increase in the useful life of the belt. The provision of the longitudinally extending short fibers in the portion of the rubber in which the tensile cords is embedded has been un­ expectedly found to provide desirable transverse side pressure durability under high loads, while yet providing desirable bending and crack resis­ tance under such high loads. By substantially extending the useful life of the belt before side cracking occurs, lowered maintenance and parts costs provide a highly meri­ torious improvement in the power transmission of high loads in such pulley systems. The foregoing disclosure of the specific embodi­ ments is illustrative of the broad inventive con­ cepts comprehended by the invention.

Claims: 1. In a power transmission V-belt for trans­ mitting a high load, said V-belt comprising a belt body having an inner compression section and an outer tension section, and longitudinally ex­ tending tensile elements embedded in said V-belt between said sections, the improvement comprising the portion of said V-belt in which said tensile elements are embedded comprising rubber having short reinforcing fibers distributed therein and orientated longi­ tudinally of the V-belt. 2. In a power transmission V-belt for trans­ mitting a high load, said V-belt comprising a belt body having an inner compression section and an outer tension section, and longitudinally ex­ tending tensile elements embedded in said V-belt between said sections, the improvement comprising the portion of said V-belt in which said tensile elements are embedded comprising rubber having short reinforcing fibers distributed therein and oriented longi­ tudinally of the V-belt, said fibers being present in the ratio of approxi­ mately 0.1 to 3.0 parts to 100 parts of rubber by weight. 3. In a power transmission V-belt for trans­ mitting a high load, said V-belt comprising a belt body having an inner compression section and an outer tension section, and longitudinally ex­ tending tensile elements embedded in said V-belt between said sections, the improvement comprising the portion of said V-belt in which said tensile elements are embedded comprising rubber having short reinforcing fibers distributed therein and oriented longi­ tudinally of the V-belt, said rubber having a Shore A hardness of approxi­ mately 70° to 90°. 4. The power transmission V-belt of claims 1, 2 or 3 wherein said tensile cords are formed of any one of the group of synthetic resins compris­ ing polyester resin, aliphatic polyamide resin, and aromatic polyamide resin. 5. The power transmission V-belt of claims 1, 2 or 3 wherein said fibers have a length of approximately 2 mm to 20 mm. 6. The power transmission V-belt of claims 1, 2 or 3 wherein said fibers are formed of any one of the group of natural fiber, artificial fiber, synthetic fiber, and inorganic fiber. 7. The power transmission V-belt of claims 1, 2 or 3 wherein said fibers comprise cut fibers. 8. The power transmission V-belt of claims 1, 2 or 3 wherein a bias-laid plied rubberized fabric cover is provided on said rubber portion, said fabric cover being formed of yarns formed of any of the group consisting of cotton yarns, blended cotton and nylon yarns, and blended cotton and polyester yarns. 9. The power transmission V-belt of claims 1,2 or 3 wherein at least one of the outermost portions of the tension section and the innermost portion of the compression section is free of said short fibers. 10. The power transmission V-belt of claims 1, 2 or 3 wherein the entire belt body is formed of rubber having short reinforcing fibers distrib­ uted therein and oriented longitudinally of the belt.

Inventors: FUJITA, KUNIHIRO, TANAKA, HIDEAKI
Applicants: MITSUBOSHI BELTING LTD.
Application year: 1986
Main classification: F16G5
IPC codes: F16G5