Abstract: A V-ribbed belt B has bottom and back faces each provided with a plurality of ribs 3, 4 of approximately trapezoidal section which extend in parallel with each other along the belt length. In order to suppressing a discrepancy between respective speed ratios of revolution transmitted from one pulley to the other in normal and reversed positions of the belt B, the belt B is adapted to have a difference of 2 mm or less between a bottom-face-side belt length when the bottom-face-side ribs 3 of the belt B are faced on an inner peripheral side thereof and a back-face-side belt length when the back-face-side ribs 4 of the belt B are faced on the inner peripheral side thereof. The center of a cord 2 embedded inside of the belt B is thereby positioned substantially in the middle of the belt thickness so that the cord 2 has equal distances from both the bottom face and back face of the belt B even if the belt B is in either position.

Abstract: Extruded sections of synthetic fibers extruded from a side face of each rib in a V-ribbed belt are plastically deformed in the shape of sectors gradually broadened toward their distal ends. The extruded sections of the synthetic fibers are not heated beyond their melting point during a grinding process so as to be kept unmelted. The extruded sections of the synthetic fibers are raised from the side face of the rib so that microscopic unevenness is formed over the side face of the rib. The synthetic fiber is formed of nylon with a filament diameter of 20 &mgr;m or more.

Abstract: Toothed belt comprises teeth and bottoms which are alternately formed at one surface of the toothed rubber layer of the toothed belt. A fabric is provided at the outer surface of the teeth and the bottoms. A back rubber layer is integrally provided at the other surface of the toothed rubber layer. A plurality of cords are interposed at the interface between the toothed rubber layer and the back rubber layer. A large number of modified microfibers are intermixed throughout the toothed rubber layer. The modified microfibers consist of a copolymer of polyolefin and nylon fiber. The modified microfibers are oriented in the length direction of the toothed belt as a whole.

Abstract: The invention comprises a cog type belt having a plurality of transverse teeth on an inner surface. The belt comprises an outer extensible elastomeric layer, an inner compression layer and a tensile member. Each tooth further comprises a non-metallic or plastic transverse member, pillar or rod that extends across the width of each tooth. The opposing outer surfaces of each transverse member are inclined to each other and each end approximately equates to an outer surface of the belt body elastomeric. A compressive load between the sheaves is carried by the rod and the sidewall in proportion to the modulus of each component. The transverse members have pegs or legs that allow proper spatial orientation of each transverse member in each tooth during the fabrication process, thus assuring proper operating characteristics, including proper alignment within a pulley.

Abstract: A power transmission belt having a body with a length, a first side, a second side, and laterally spaced side surfaces. The body has cog crests and cog troughs in at least a first layer on the first side of the body and alternating the length of the body. The body further has at least one cushion rubber layer and at least one load carrying cord embedded in the at least one cushion rubber layer and extending lengthwise of the body between the cog crests and the second side of the body. The at least first layer has a first joint that is in a cog crest and does not extend into a cog trough. At least one cushion rubber layer is made from a first material, with the first material from the at least one cushion rubber layer not penetrating the first joint. The invention is also directed to a method of forming a belt of this type.

Abstract: A method of bonding an ethylene•&agr;-olefin rubber composition with a fiber material. The method includes the steps of adhesion treating the fiber material with a resorcinol-formalin-rubber latex with an ethylene•&agr;-olefin elastomer latex and vulcanization bonding the adhesion-treated fiber material together with an unvulcanized ethylene•&agr;-olefin rubber composition.

Abstract: A toothed belt having a body with a length, an inside surface, an outside surface, laterally spaced sides, and a plurality of teeth spaced in a lengthwise direction on the inside of the body. An elongate, load carrying cord extends lengthwise of the body and is embedded in the body. A cloth layer is provided on the inside surface of the body. The load carrying cord has a diameter that is greater than 1.1 mm and not greater than 1.5 mm and is prepared by a) bundling glass fiber filaments each having a diameter of from 5 to 10 &mgr;m into strands, b) gathering and primary twisting a plurality of stands in one twist direction to form strings, and c) gathering and final twisting the strings in a direction oppositely to the one twist direction.

Abstract: A power transmission striated belt including an elastomeric matrix (21) and a lengthwise supporting structure consisting of polyamide 4.6 twisted strands (20). The supporting structure (21) is selected so that the stress-elongation diagram of the belt exhibits an average slope ranging from 12 to 20 daN/% of elongation per width centimeter. The twisted strands are wound with an almost null nominal tension, and the curing operation and the cooling operation after curing are carried out without any belt tensioning.

Abstract: In a V-ribbed belt including short fibers such as carbon fibers in the surfaces of ribs, that is, a contact surface with a pulley, the surfaces of the ribs are coated with a water repellent agent so that the surfaces of the ribs can attain water repellency. Thus, while suppressing performance degradation and increase in manufacturing cost of the belt, the water removing property against water splashed on the belt is improved, so as to prevent slip and an accompanied unpleasant noise from being caused.

Abstract: A drive system having a belt with a length and a plurality of teeth spaced regularly along the length of the belt and a first pulley having a plurality of grooves for receiving the belt teeth with the belt and first pulley in operative relationship. The single pitch difference between the belt teeth and the grooves in the first pulley is between -0.04 mm and 0 mm.

Abstract: The invention concerns a method of manufacturing a ribbed vulcanized transmission belt having an elastomer cushion layer and an elastomer compression layer in which reinforcing fibers are embedded. The method comprises the following steps:a) forming a blank having at least the cushion layer and the compression layer;b) molding said blank under pressure in a mold provided with an imprint of the ribs;c) vulcanizing said blank;d) machining off surplus material so as to uncover protruding ends of the fibers.In the belt of the invention, in the vicinity of the surfaces of the ribs, the mean direction of the reinforcing fibers is substantially tangential to the surfaces of the ribs, and, in at least one region of each of said ribs, said fibers have protruding ends.

Abstract: A component for a power transmission belt. The component is a fiber cord that is treated in a first step with at least one of a) an isocyanate compound and b) an epoxy compound such that after the first step the at least one of the isocyanate compound and epoxy compound is present in solid form in an amount equal to 0.5 to 2.0 weight %. The fiber cord is treated after the first step in a second step with an RFL liquid so that the percentage void in the cord, as determined by the following formula, is not greater than 1.5%:percentage void=100.times.A.sub.y /A.sub.x, where A.sub.x is the total surface area of the cord and A.sub.y is the void area.

Abstract: A conveyor belt is described having a woven fabric backing which includes staple fiber yarn and includes a twill weave with an inclination angle of 10.degree. to 70.degree. relative to the moving direction of the conveyor belt, and in which adjacent yarns have the same direction of lay. In the woven fabric backing the staple fiber yarn is provided as warp yarn, each of which has the same direction of lay in its longitudinal direction, and adjacent yarns of which are alternately S and Z twisted. Additionally, elements which support the tensile forces are arranged in the conveyor belt, the elements being arranged in a woven fabric or being sheathed as threads by staple fibers. Since the staple fiber yarn of the warp of the woven fabric backing extends diagonally over the entire width of the conveyor belt, an endless support results even when the belt runs over an edge, and an absolutely uniform vibration-free conveyor belt movement having a low noise level is achieved even when the belt passes over an edge.

Abstract: An endless power transmission belt construction, cord therefor and methods of making the same are provided, the cord having the yarns and the plies thereof respectively twisted on a 2 for 1 twister so as to cause the longitudinal axes of the fiber filaments to be disposed generally in the longitudinal direction of the cord with the denier of the fiber filaments of each yarn being approximately 1500. The twist multiplier of three plies is 3.7687 as the plies are twisted together at a rate of approximately 2.9 turns per linear inch of the cord, and the twist multiplier for the two yarns is 3.6765 as the two yarns for each ply are twisted together at a rate of approximately 4.9 turns per linear inch of that ply. The twist multiplier for five plies is 3.6986 as the plies are twisted together at a rate of approximately 1.8 turns per linear inch of the cord, and the twist multiplier for three yarns is 3.5838 as the three yarns for each ply are twisted together at a rate of approximately 3.

Abstract: The tension member for a belt of this invention is made from a glass cord. First twist yarns of this glass cord are obtained by paralleling and twisting a plurality of fiber bundles, each including a large number of glass filaments, by a predetermined first twist number. The fiber bundles are previously soaked with a treatment liquid including a mixture of rubber latex and an initial condensation product of resorcinol and formalin as a main component and then heated. The glass cord is fabricated by paralleling a predetermined number of the first twist yarns and twisting them by a predetermined final twist number, so as to squeeze and substantially eliminating spaces among the first twist yarns. Accordingly, the belt including this glass cord as the tension member can achieve good water resistance because externally intruding water is prevented from being held within the belt.

Abstract: A power transmission belt having a body with a length, an inside surface, an outside surface, and laterally spaced side surfaces. A plurality of laterally extending, discrete fibers are embedded in the body and have portions projecting from at least one of the side surfaces of the body. The side surfaces make with each other an angle of 42.degree.-50.degree..

Abstract: A double V-ribbed belt having a body with an inside, an outside, a length, and laterally spaced sides. At least a first rib is exposed on the inside of the body and extends in a lengthwise direction. At least a second rib is exposed on the outside of the body and extends in a lengthwise direction. A substantially inextensible layer resides between the first and second ribs. Laterally extending reinforcing fibers are provided in the body on at least one of the inside and outside of the inextensible layer, with the concentration of reinforcing fibers on the inside of the inextensible layer being different than the concentration of reinforcing fibers on the outside of the inextensible layer.

Abstract: A cover belt for a duct is presented, which can be swung up from a closed position by a deflecting device movable in the longitudinal direction of the duct and falls back in its closed position behind the deflecting device. The cover belt is made of a flexibly deformable material with metallic reinforcements. The cover belt is comprised of a securing strip, a joint strip and a cover strip. The securing strip is secured along the duct, the joint strip connects the securing strip flexibly to the cover strip, and the cover strip spans the duct and is supported on both sides of the duct. At least one belt-shaped textile reinforcement layer with essentially the same overall width as the cover belt is embedded in the flexibly deformable material in the area of the neutral plane of the cover belt.

Abstract: An endless power transmission belt construction, cord therefor and methods of making the same are provided, the cord having the yarns and the plies thereof respectively twisted on a 2 for 1 twister so as to cause the longitudinal axes of the fiber filaments to be disposed generally in the longitudinal direction of the cord with the denier of the fiber filaments of each yarn being approximately 1500, the twist multiplier for the three plies being 3.7687 as the three plies are twisted together at a rate of approximately 2.9 turns per linear inch of the cord, the twist multiplier for the two yarns being 3.6765 as the two yarns for each ply are twisted together at a rate of approximately 4.9 turns per linear inch of that ply, and the fiber filaments comprising p-aramid that comprises co-poly (paraphenylene/3,4' oxydiphenylene terephthalamide).

Abstract: A rubber composition containing a rubber forming a continuous phase of 100 weight parts; a nylon fiber with fine diameter of 1-15 weight parts by the fiber, the nylon fiber being grafted with a molecular of a rubber capable of co-crosslinking to the rubber forming the continuous phase; and a short fiber of 1-30 weight parts is used to at least a part of a rubber of a transmission belt. Thus, high anisotropy in modulus of elasticity in the transmission belt is maintained. Further, stress concentration at an interface of the short fiber and the rubber is distributed to enhance the strength, elasticity and flex fatigue resistance.

Abstract: A power transmission belt having a body with a length and laterally spaced side surfaces, a first plurality of laterally extending discrete fibers embedded in the body and having portions projecting from the side surfaces, and a second plurality of discrete pulp-like fibers intermixed with the first plurality of laterally extending discrete fibers. The fibers in the first plurality of laterally extending discrete fibers have at least one of a) a different composition and b) a different texture than the fibers in the second plurality of discrete fibers.

Abstract: A power transmission belt having a body with a length and laterally oppositely facing pulley engaging surfaces. The body has at least a portion thereof that is made from rubber. Aramid fibers are embedded in the rubber portion of the body in an amount of 5-20 parts by weight, and more preferably 8-15 parts by weight, of aramid fiber per 100 parts by weight of rubber.

Abstract: A method of forming a power transmission belt including the steps of: providing a belt sleeve defining an axis and having a rubber layer with elongate fibers embedded therein and extending generally parallel to each other in a first line; rotating the belt about its axis; providing a grinding element for cutting the rubber layer and fibers to define ribs with oppositely facing flanks; and urging the rotating belt sleeve and grinding element, one against the other in first and second steps and, as an incident thereof, causing the grinding element to define the oppositely facing flanks. The belt sleeve and grinding element are urged one against the other transversely of the first line at a first speed during the first step and at a second speed different than the first speed during the second step.

Abstract: An endless power transmission belt construction, cord therefor and methods of making the same are provided, the cord having the yarns and the plies thereof respectively twisted on a 2 for 1 twister so as to cause the longitudinal axes of the fiber filaments to be disposed generally in the longitudinal direction of the cord with the denier of the fiber filaments of each yarn being approximately 1500, the twist multiplier for the three plies being 3.7687 as the three plies are twisted together at a rate of approximately 2.9 turns per linear inch of the cord, the twist multiplier for the two yarns being 3.6765 as the two yarns for each ply are twisted together at a rate of approximately 4.9 turns per linear inch of that ply, and the fiber filaments comprising p-aramid that comprises co-poly(paraphenylene/3,4' oxydiphenylene terephthalamide).

Abstract: A power transmission belt having a body with a compression section and a length. A first plurality of short fibers is embedded in the compression section of the body aligned to be substantially parallel to the length of the belt. A second plurality of short fibers is embedded in the compression section of the body and aligned to be transverse to the length of the belt.

Abstract: A power transmission belt having a belt body with a length and laterally oppositely facing pulley engaging side surfaces. A first plurality of short fibers, made from a first material, is embedded in the belt body and extends substantially in a lateral direction. A second plurality of short fibers, made from a second material, is embedded in the belt body and extends substantially in a lateral direction. A plurality of the short fibers made from the first material project laterally from at least one of the pulley engaging side surfaces on the belt body.

Abstract: A rubber composition includes hydrogenated acrylonitrile-butadiene rubber (HNBR), a copper dithiocarbamate salt compound and sulfur. The use of the copper dithiocarbamate salt compound results in the vulcanized rubber composition exhibiting improved heat resistance as compared to a rubber material that does not include the copper dithiocarbamate salt compound. Toothed belts and V-ribbed belts can be made using the rubber composition to produce belts exhibiting improved heat resistance.

Abstract: A toothed rubber belt has teeth, a rubber back and a core wire imbedded in the rubber back. The core wire has lower twists of about 10.5 to about 13.5 times/10 cm and an upper twist of about 6.5 to about 9.5 times/10 cm. Preferably, the wire core is made of glass having a construction of ECG 150 3/6 to 3/13. The core wire having the specified number of twists improves the physical properties of the belt.

Abstract: A fiber-reinforced rubber article has a rubber body portion with a fiber reinforcement embedded therein. The fiber reinforcement includes a plurality of tubular braided cords braided by yarns. Each of the tubular braided cords is braided by more than three yarns at a braid angle in a range between 10.degree. and 35.degree., wherein said braid angle is an angle between a yarn of the tubular braided cord and the axial line of the tubular braided cord. Each tubular braided cord also has a fistulous center hole defined by the tubular braided cord.

Abstract: A toothed belt has cores coated with a resorcin-formalin-latex liquid that includes as the latex component at least about 60 wt % of a hydrogenated acrylonitrile-butadiene rubber or a chlorosulfonated polyethylene rubber. The teeth can be covered with a tooth covering fabric that is made from yarns containing at least 50 volume percent of aramid fibers.

Abstract: A power transmission belt having a belt body with an inside surface and an outside surface, with the belt body having a compression section and a tension section, spaced outside of the compression section. At least a first part of the tension section is defined by a chlorosulfonated polyethylene rubber composition having a chlorine content of 15 to 30% by weight. At least a second part of the compression section is defined by a rubber composition that is different than the rubber composition of the first part.

Abstract: A rubber having a fiber reinforcement embedded thereon. The reinforcement comprises a cylindrically braided cords by more than four and even numbered yarns and a center cord provided in a hollow part of it. The twist multiplier K is set lesser than 350, the twist multiplier K being expressed ##EQU1## where T is a number of twists per 10 cm and D is a total denier.

Abstract: A power transmission belt having a length and a lateral extent. The belt consists of a tension layer and a compression layer with the compression layer defined at least partially by acrylonitrile-butadiene copolymer rubber (hydrogenated nitrile rubber), having at least an 80% hydrogen addition rate, and a plurality of substantially laterally oriented fibers in the acrylonitrile-butadiene copolymer rubber in the compression layer. The fibers are treated with one of resorcin-formalin-nitrile rubber latex (RFL) and resorcin-formalin-hydrogenated nitrile rubber latex (RFL) having at least an 80% hydrogen addition rate.

Abstract: A rubber having fiber reinforcement embedded thereon. The reinforcement comprises a cylindrically braided cords of more than four and even numbered twisted yarns. Yarns are right twist oriented and left twist oriented and they are twisted in the reverse direction in an, S-twist and a Z-twist.

Abstract: An aramid fiber cord for use as a component in a power transmission belt, which aramid fiber cord has a plurality of aramid fiber filaments of 300 to 3100 denier adhesively treated and formed into a strand with a primary twist factor (Y) in a range of -1 to 1. A plurality of the strands are formed into the cord with a finishing twist factor (X) in a range of 1 to 4. The primary twist factor (Y) and finishing twist factor (X) satisfy the following equations: Y is .gtoreq. to -0.6X+1.3 and Y is .gtoreq. to -1.5x+5.0.

Abstract: A power transmission belt having an inside surface and an outside surface. The power transmission belt has: a compression section defining a plurality of laterally spaced, longitudinally extending ribs made at least partially of rubber; a plurality of discrete, laterally extending reinforcing fibers in the ribs; a tension section outside of the compression section and defined at least partially by a rubber layer; and a plurality of discrete, laterally extending reinforcing fibers in the rubber layer of the tension section. The length of the reinforcing fibers in the rubber layer of the tension section is greater than the length of the reinforcing fibers in the ribs.

Abstract: A toothed belt of the present invention comprises a back surface section and tooth sections that are made of an acrylonitrile-butadiene copolymer (NBR) with a hydrogenation rate of 90% or more; a tooth cloth that covers the surface of the tooth sections and tooth lands, the tooth cloth being made of an industrial nylon raw fiber with a viscosity relative to sulfuric acid of 2.45 to 2.53, a tensile strength of 5 g/denier or more, and a fineness of single fibers of 5 denier or less and being treated with resorcinol-formaldehyde-latex (RFL) liquid in which resorcinol-formaldehyde resin is mixed with a hydrogenated NBR as a latex component; and core fibers with a core diameter of 0.63 to 0.85 mm, the core fibers being made of twisted bundles of glass fibers of high strength.

Abstract: A power transmission belt having a belt body defining laterally spaced, oppositely facing flank surfaces for engagement with a pulley and at least one fiber within the belt body and extending in a lateral direction. The fiber has a cross-sectional area taken transversely of its length and a surface exposed at at least one of the flank surfaces. The exposed fiber surface is flared to have an area that is greater than the cross-sectional area of the fiber.

Abstract: A fiber reinforced composite belt in which a stainless steel fiber aggregate having a diameter of from 5 to 50 .mu.m and impregnated with 1 to 10% by weight of a thermosetting resin such as an epoxy resin is buried as a reinforcing material in a base material for belt, and a process for preparing the above-mentioned fiber reinforced composite belt are provided. This fiber reinforced composite belt is much more excellent in flex resistance, durability, water resistance and coefficient of linear expansion, as compared with not only a rubber belt and a synthetic resin elastomer belt but also belts reinforced by directly burying a stainless steel fiber and a steel fiber in the rubber.

Abstract: The disclosure is of conveyor belting and a method for its manufacture. The belting comprises a plurality of substantially parallel, uncrimped textile yarns of a specific character, embedded in a matrix of a specific class of ionomer elastomeric resin. The belting of the invention is useful to manufacture conveyor belts which exhibit advantageous properties of wear resistance, flexibility, stability in running, structural integrity and resistance to food, oils, fats, and like staining.

Abstract: A rubber structure has a fiber reinforcement embedded therein. The reinforcement is constructed of cylindrically braided cords braided by yarns, where the number of yarns is an even number in a range of four up to eight. Each cylindrically braided cord has a hollow portion extending in the longitudinal direction at the center thereof. The hollow portion has a small diameter.

Abstract: A V-ribbed belt having a rib rubber layer which includes a plurality of ribs extending under a tension member layer of a power transmission belt along the longitudinal direction of the belt. Short fibers are mixed in the ribs. The direction of orientation of the short fibers is near the longitudinal direction of the belt near the tension member layer and gradually changed toward near the vertical direction of the belt near the rib tops. Through the above arrangement, endurance to the shearing stress can be improved and flexibility is also maintained and consequently, endurance to rib chipping off is improved.

Abstract: A transmission belt having a base section with a plurality of teeth spaced lengthwise of the belt and a canvas layer covering the teeth. The canvas layer has weft yarns extending in a lengthwise direction defined by aromatic polyamide fiber spun yarn twisted with a urethane elastic yarn. The canvas layer further includes warp yarns made by twisting a plurality of filaments, at least one of which is aliphatic mono-filament of 10 to 50 denier, or a plurality of aromatic polyamide multi-filament of 1 to 6 denier.

Abstract: A power transmisison belt having: at least one longitudinally extending rib having laterally spaced, first and second oppositely facing surfaces for reception within a complementary pulley groove; at least one fiber embedded in the one rib and having a length extending transversely to the longitudinal extent of the one rib, with the fiber having a portion projecting outwardly from the one rib beyond one of the first and second surfaces; and a noise suppressing material applied to the one of the first and second surfaces and a portion of the one fiber to inhibit noise generation between a power transmission belt and a cooperating pulley resulting from relative movement of one against the other.

Abstract: An improved cord for use in a power transmission belt. Before an adhesive stretching thermal fixation treatment, the cord, upon being heated, has a ratio of shrinkage percentage to shrinkage stress of less than 12% per g/d. After an adhesive stretching thermal fixation treatment, the heated cord has a ratio of shrinkage percentage to shrinkage stress of less than 6% per g/d.

Abstract: A mechanical component consisting of anti-static material is a compound material of synthetic resin and uniformly dispersed carbon fiber as a conductive filler. The carbon fiber is whisker-shaped and is made of hydrocarbon by means of vapor-phase system where hyperfine particles of high-melting metal and/or its compound is utilized as nuclei. The carbon fiber bestows the mechanical component with superior mechanical properties and uniforms and optimum electric resistivity.

Abstract: A composite material for a transmission belt includes an elastomer matrix forming a basic component of the material. There is included a cross-linking system of the elastomer matrix and at least one fiber reinforcement including fibers with a maximum length of about 30 mm. The fibers are disposed throughout the elastomer matrix and are generally oriented to extend in a first direction of reinforcement. There is at least one thermosetting resin in the elastomer matrix. The elastomer matrix which includes the cross-linking system, the fiber reinforcement and the thermosetting resin has a first equivalent tensile modulus which is calculated for a hypothetical elongation of 100% in the first direction and a second equivalent tensile modulus which is calculated for an actual or hypothetical elongation of 100% in a second direction which is perpendicular to the first direction. A second equivalent tensile modulus is at least 6 MPa.

Abstract: A multiribbed power transmission belt and method of manufacturing the same, wherein an unvulcanized belt preform is provided with transversely extending staple fibers in the compression section thereof. The compression section is caused to be vulcanized while being urged against a mold having projections forming shallow grooves in the inner surface thereof. The grooves have a depth in the range of approximately 20% to 50% of the height of the ribs intended to be formed in the final power transmission belt. The ribs are formed in the belt by removing material from the compression section of the vulcanized preform, such as by the conventional machining operations of grinding, cutting, etc. The angular deflection of the reinforcing fibers in the compression section is caused to be no more than approximately 25% to provide the improved belt construction.

Abstract: In raw-edge power transmission belts the tensile cords is covered with a thinly compressed layer composed of nonwoven fabric and elastomer matrix permeated therethrough at the tooth bottoms, and the nonwoven fabric is diffusedly mixed for reinforcing an elastomer matrix in the tooth parts.In the method of manufacture, the outer cylindrical circumference of the internal die along which toothed faces are formed are covered with nonwoven fabric under non pressure, and the tensile cords are wound spirally. Hereafter, dies are set up and elastomer material is injected and hardened. A transmission belt is drived by slicing roundly a cylindrically shaped body derived in these processes.

Abstract: A V-ribbed belt having a plurality of ribs on a belt base along the lengthwise direction of belt and a method of manufacturing such V-ribbed belt. The belt according to the present invention is used for driving of driers, auxiliary machines for motor cars, washing machines, etc. ribs of the belt are formed solely of rubber and are provided with a surface layer comprising a non-woven fabric at the outer surface thereof. The thickness and the weight per unit area of the non-woven fabric are in the range of between 0.01 and 0.3 mm and between 3 and 100 g/m.sup.2 respectively. The non-woven fabric can contain a coefficient of friction reducing agent, where necessary.