JP3908361B2 - Transmission belt manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a transmission belt, and more specifically, a belt sleeve is sufficiently vulcanized without using a jacket, and a V-ribbed belt, a toothed belt, a flat belt, etc. having good appearance without containing bubbles are manufactured. The present invention relates to a method for manufacturing a transmission belt that can be used.
[0002]
[Prior art]
In the conventional V-ribbed belt manufacturing method, as an example, an adhesive rubber layer is interposed between the compression rubber layer and the stretch rubber layer on the outer peripheral surface of the mold, and the core wire is embedded so as to embed the core wire in the adhesive rubber layer. A cylindrical jacket that can be elastically deformed is fitted concentrically on the outer side of the belt sleeve for vulcanization, and the assembly assembled in the above form is placed on a support base located below in the vulcanization can via an elastic packing material. The uncovered belt sleeve was vulcanized by placing an upper lid on the mold, press-fitting high-pressure steam outside the mold and low-pressure steam inside the drum, respectively.
The obtained vulcanized sleeve was manufactured by a grinder method in which a plurality of V-shaped grooves were ground by a grinding wheel in which a circular tube-shaped surface portion and a portion having a plurality of V-shaped grooves were connected and integrated. (See Japanese Patent Publication No. 7-37084)
[0003]
In the above belt sleeve manufacturing method, the high pressure steam outside the jacket presses the jacket, and then presses the unvulcanized belt sleeve to discharge air existing in the gap between the jacket and the mold and to have a predetermined shape. The rubber was molded and solidified, and it was made dense without containing bubbles to obtain a good quality product.
[0004]
As a manufacturing method of the jacket, a flange comprising an unvulcanized rubber extending outwardly to at least one end edge of the molded body is usually formed by winding an unvulcanized rubber layer of a predetermined thickness around a molding die. After adhering, the other cylindrical jacket is fitted, and this is put into a vulcanizing can and vulcanized, and then the molded body can be extracted from the mold.
[0005]
[Problems to be solved by the invention]
However, in the conventional belt sleeve manufacturing method, it is necessary to prepare a plurality of rubber jackets for various belt sizes and store them constantly, which occupies a large area in the factory. Further, when a special size belt is manufactured, since the jacket is not frequently used, the appearance is visually inspected every time it is used.
[0006]
In addition, whatever size of the product flows from the previous process in any order, it is necessary to take out the corresponding jacket in a short time and insert the jacket into the unvulcanized belt sleeve, In reality, it takes time to put in and out various jackets of different sizes, and there is a loss of setup time including order restrictions and rearrangement.
[0007]
Furthermore, in order to prevent so-called steam leakage, in which steam enters the unvulcanized belt sleeve from the jacket, it is necessary to manage the jacket. For example, after a long period of use, it is necessary to constantly check the aging surface condition of the flanges and inner surfaces of the jacket, the presence or absence of dust adhering to both flanges of the jacket, and changes in the jacket length and circumference. It was. If neglected, steam leakage occurred and the defective belt sleeve containing bubbles was vulcanized.
In addition, when the jacket is replaced, sufficient residual heat is generated in the vulcanizing can before use, and the length and circumference of the jacket are expanded to fit into the unvulcanized belt sleeve. It was necessary to secure appropriate dimensions that were easy to use.
[0008]
The present invention improves various problems when such a jacket is used, enables a production line to be installed in a small space, reduces loss of working time, and vulcanizes at low cost. It is an object of the present invention to provide a method for manufacturing a transmission belt from a belt sleeve of good quality that does not contain bubbles.
[0009]
[Means for Solving the Problems]
That is, in the invention according to claim 1 of the present application, a cylindrical unvulcanized belt sleeve having a core wire embedded in a rubber layer is attached to a mold and vulcanized, and then the surface of the vulcanized belt sleeve is applied. In the manufacturing method of the transmission belt obtained by polishing, after forming at least a part of both side surfaces of the molding die together with the outer peripheral surface of the unvulcanized belt sleeve attached to the molding die by a film body that does not transmit vapor. The mold is placed in a vulcanizing can, vulcanized without vapor entering the film body, the film body is removed from the belt sleeve, and then the surface of the belt sleeve in contact with the film body is polished. In the belt manufacturing method, the film body that does not transmit vapor surely surrounds both the outer peripheral surface of the unvulcanized belt sleeve and part of both side surfaces of the mold , thereby preventing the entry of steam during vulcanization. ,Jacket It can be vulcanized without using it, is suitable for a small space production line, reduces work time loss, can be manufactured at low cost, and the surface of the vulcanized belt sleeve that is in contact with the membrane is Even if it exists, since it grind | polishes with a grinding | polishing wheel, the external appearance favorable transmission belt can be produced.
[0010]
According to the second aspect of the present invention, at least two or more grooves are formed in the longitudinal direction of the sleeve by polishing the back surface of the vulcanized belt sleeve in contact with the film body, and then the V-ribbed belt. It can be manufactured at a low cost by reducing the loss of working time, and even if the surface of the vulcanized belt sleeve that is in contact with the membrane is the ground surface, it is polished into multiple grooves. In addition, a V-ribbed belt with good appearance can be produced.
[0011]
In the invention according to claim 3 of the present application, a vulcanized toothed belt sleeve having teeth and grooves alternately on the inner surface at predetermined intervals is manufactured, and the back surface of the sleeve that is in contact with the film body is polished. A toothed belt having a good appearance can be produced by flatly polishing the back surface in the same manner as in the second aspect of the invention.
[0012]
In the invention according to claim 4 of the present application, a synthetic resin film is used as a film body that does not transmit vapor, and the operation of winding and surrounding the unvulcanized belt sleeve around the outer peripheral surface becomes easy.
[0014]
In the invention according to claim 5 of the present application, the sealing material is mounted on the film body which does not transmit the vapor provided at the upper and lower corner portions of the unvulcanized belt sleeve, thereby preventing the entry of the vapor from the upper and lower corner portions. can do.
[0015]
In the invention according to claim 6 of the present application, since the sealing material is a fiber material selected from at least one layer of rubber-equipped canvas and non-woven fabric, the sealing effect of the upper and lower corner portions is enhanced.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, with reference to the accompanying drawings, a method for manufacturing a power transmission belt of the present invention, particularly a V-ribbed belt, will be described.
FIG. 1 shows a view for producing an unvulcanized belt sleeve constituting a compressed rubber layer, a core wire, and an extended rubber layer on a mold. First, the molding die 1 is installed in a molding machine (not shown), and an unvulcanized rubber sheet 3 and an adhesive rubber layer are formed on the outer peripheral surface of the drum 1 as one or several reinforcing cloths 2 and an extended rubber layer. An unvulcanized rubber sheet 4 is wound, and a core wire 5 made of a cord such as polyester fiber, aramid fiber, or glass fiber is spun from above, and then an unvulcanized rubber sheet 6 that becomes a compressed rubber layer is wound. This forming method is generally called a reverse molding method because the compressed rubber layer is located outside.
[0017]
The rubbers of the unvulcanized rubber sheets 3 and 6 that become the stretched rubber layer and the compressed rubber layer are natural rubber, butyl rubber, styrene-butadiene rubber, chloroprene rubber, ethylene-propylene rubber, alkylated chlorosulfanated polyethylene, hydrogenated For example, para-aramid fiber (trade name: Twaron, Kevlar, Technora), nylon, polyester, or rubber materials such as nitrile rubber, mixed polymer of hydrogenated nitrile rubber and unsaturated carboxylic acid metal salt, or a mixture thereof. In addition, short fibers such as vinylon and cotton are oriented in the belt width direction. The addition amount of this short fiber is 5-40 weight part with respect to 100 weight part of rubber | gum.
The adhesive rubber layer may include the short fibers, but preferably does not include them.
[0018]
The reinforcing cloth 2 is made of cotton, polyester fiber, nylon, or the like, and is a cloth woven into plain weave, twill weave, satin weave, etc., and may be a wide angle canvas in which the crossing angle between the warp and the weft is about 90 to 120 °. The reinforcing cloth 2 is subjected to RFL treatment, and then the rubber composition is subjected to fiction and coating to form a canvas with rubber. The RFL liquid is obtained by mixing an initial condensate of resorcin and formalin into a latex. Examples of the latex used here include chloroprene, styrene / butadiene / vinylpyridine terpolymer, hydrogenated nitrile, NBR, and the like.
[0019]
FIG. 2 shows that the outer peripheral surface 9 of the unvulcanized belt sleeve 7 produced on the mold 1 is being surrounded by a film body 8 that does not allow vapor to pass therethrough. According to this, the film body 8 which does not transmit vapor is formed in a spiral manner across a part of both side surfaces 10 of the mold 1 together with the outer peripheral surface 9 of the unvulcanized belt sleeve 7 of the mold 1 taken out from the molding machine. Wrap. At this time, it is necessary to overlap the end portions of the film body 8 so that the unvulcanized belt sleeve 7 is not exposed. Of course, the film body 8 may be used by overlapping several plies, preferably 2 to 4 plies.
In addition, if the said film | membrane body 8 uses a wide thing, it is not necessary to wind in spiral shape.
[0020]
As shown in FIG. 3, the unvulcanized belt sleeve 7 surrounded by the film body 8 extends over not only the outer peripheral surface 9 but also part of both side surfaces 10 of the molding die, and the corner portion 12 of the molding die 1. To prevent steam from entering during vulcanization.
[0021]
The film body 8 that does not transmit vapor is preferably a synthetic resin film. For example, polymethylpentene, polyvinylidene chloride, polyvinyl chloride, polyethylene, polypropylene, 6 nylon, 6.6 nylon, 6.10 nylon, etc. Made of polyamide, aramid and polyester. Among these, the registered trademark “Saran Wrap”, which is made of a synthetic resin film made of polymethylpentene or polyvinylidene chloride, easily surrounds the unvulcanized belt sleeve 7 and has a small thermal shrinkage during vulcanization. Thus, it can be used safely without being peeled off from the belt sleeve 7 and without generation of toxic gas during vulcanization. The thickness of the film body 8 is not particularly limited, but a thinner one is preferable for the winding operation.
[0022]
The mold 1 equipped with the unvulcanized belt sleeve 7 surrounded by the film body 8 is installed in the vulcanizing device 15 as shown in FIG. In this vulcanizing device 15, a molding die 1 equipped with an unvulcanized belt sleeve 7 surrounded by a film body 8 is placed on a support assembly table 17 positioned below in a vulcanizing can 16, and further a molding die. An upper lid 18 is placed on the mold 1, and high pressure steam is press-fitted on the outside of the mold 1 and low-pressure steam is press-fitted inside the mold 1 to vulcanize the unvulcanized belt sleeve 1. Both the high-pressure steam and the low-pressure steam are introduced from the introduction port 19, and the internal moisture is discharged from the drain port 20.
[0023]
In order to prevent low-pressure steam press-fitted into the mold 1 from entering the side where the unvulcanized belt sleeve 7 exists from the gap between the mold 1 and the support assembly 17, A rubber packing (not shown) may be attached. It is also possible to provide a pipe (not shown) through which the air existing between the mold 1 and the film body 8 or between the upper lid 18 and the mold 1 is communicated to the outside of the vulcanizer 15 during vulcanization.
[0024]
Although the vulcanization conditions are not particularly limited, the vulcanization temperature is adjusted to a temperature at which the film body 8 does not melt. Specifically, 140 to 160 ° C. is preferable.
[0025]
FIG. 4 shows a case where a sealing material 22 is provided in the upper and lower corner parts 12 on the enclosed film body 8 in order to further surround the corner parts 12 of the mold 1. As a result, the upper and lower corner portions 12 of the mold 1 can be reliably sealed. This sealing material 22 is made of polyamide fibers such as 6 nylon, 6/6 nylon, 6/10 nylon, 4/6 nylon, 12 nylon, etc., polyester fibers, filament yarns of polyvinyl alcohol, polyethylene, polypropylene, and spun yarns such as cotton. The canvas is impregnated with rubber, and preferably 1 to 4 ply laminated. Moreover, a nonwoven fabric may be sufficient.
[0026]
When vulcanization is completed, the film body 8 can be easily peeled off from the surface of the mold 1 taken out from the vulcanization can 16. The film body 8 is scrapped. The surface of the belt sleeve 7 extracted from the mold 1 is vulcanized and roughened with the sheet surface immediately after molding as compared with the case where a jacket is used, but there is no occurrence of porous material and the like. Sulfur.
[0027]
The belt sleeve 7 is polished by a polishing wheel 25 as shown in FIG. That is, the belt sleeve 7 is hung on the driving roll 26 and the driven roll 27 so that the compressed rubber layer is located on the surface side, and runs under a predetermined tension. The running speed of the belt sleeve 7 is not particularly limited.
The rotating grinding wheel 25 is arranged on the drive roll 26 or driven roll 27 side, moves so as to contact the running belt sleeve 7, and has a plurality of groove portions of 3 to 100 on the surface of the belt sleeve 7. Polish at once.
The rotation direction of the grinding wheel 25 may be the same direction as that of the belt sleeve 7 or the reverse direction, but in the case of the present embodiment, it is the reverse direction. The rotation speed of the grinding wheel 25 is 400 to 2,000 rpm.
[0028]
Part of the abrasive powder discharged from the grinding wheel 25 adheres to the belt sleeve 7, and the others are sucked from a duct (not shown) surrounding the grinding wheel 25 and released to the outside of the grinding machine. Is done.
On the other hand, the polishing powder adhering to the belt sleeve 7 after polishing is removed by the rotating brush 28 and immediately discharged to the outside of the polishing machine by the operation of the vacuum device 29.
[0029]
The rotating brush 28 is located on the drive roll 26 side and is installed on a support plate 31 connected to the cylinder 30. The rotating brush 28 is connected to the drive motor 33 via the transmission belt 32 and rotates in the direction opposite to the traveling direction of the belt sleeve 7. The rotation speed of the rotary brush is 100 to 800 rpm, and the pressure when the rotary brush 28 contacts the belt sleeve 7 is 2 to 6 kg / cm (linear pressure).
The rotating brush 28 is moved during polishing because it always needs to contact the surface of the belt sleeve 7 with a constant pressure.
[0030]
The rotating brush 15 is obtained by flocking a synthetic fiber filament such as nylon or polyester or a metal wire such as brass on the surface of the rotating shaft.
[0031]
The polishing wheel 25 used here is not particularly limited. For example, as shown in FIG. 7, the polishing wheel 25 alternately includes polishing portions 35 protruding at a constant pitch along the circumferential direction (indicated by the arrow direction in the figure). The polishing portion 35 alternately has rib portions 36 and concave portions 37 having a triangular cross section at a constant pitch in the width direction and along an oblique direction with respect to the rotation axis of the wheel 25. A 100-120 mesh granular material 38 made of diamond or the like is attached to the surfaces of the rib portion 36 and the concave portion 37, and at the same time, a tip surface 40 including an edge 39 in the rib portion 36 of the polishing portion 35, that is, It also adheres to the surface that contacts the belt sleeve 7.
[0032]
The groove-shaped slit portions 41 provided between the polishing portions 35 are regions in which the stress received by the surface to be polished of the belt sleeve 7 is once released during processing to restore deformation. As a result, the surface to be polished is processed again by the polishing section 35 without leaving any distortion, thereby enabling high-precision polishing. For this reason, it is preferable that the number of slit portions 41 is large.
[0033]
In the V-ribbed belt 11 obtained by cutting the belt sleeve 7 to a predetermined width, a plurality of groove portions 43 are polished as shown in FIG. 8, and short fibers are exposed from the surface in contact with the pulley. .
[0034]
Moreover, in this invention, it can apply also to the manufacturing method of a toothed belt. As shown in FIG. 9, first, a cylindrical canvas 51 is inserted and mounted in a molding die 1a having groove portions 52 provided at regular intervals, and a cord forming a core wire 5 is wound around the spiral on the mold 1a. An unvulcanized belt sleeve 54 is produced by laminating an unvulcanized rubber sheet 53 that forms a portion and a back portion, and the outer periphery of the belt sleeve 54 is surrounded by a film body 8 that does not transmit vapor in the same manner as described above. The mold 1a is placed in a vulcanizing can and vulcanized in a state where steam does not enter the inside of the film body to obtain a toothed belt sleeve 58 having teeth 56 and grooves 57 at predetermined intervals on the inside. Thereafter, the film body 8 is removed from the surface of the toothed belt sleeve 58. FIG. 10 is a perspective view of a toothed belt sleeve 58 having a tooth portion 56 and a groove portion 57 at a predetermined interval on the inner side.
[0035]
The toothed belt sleeve 58 taken out from the mold 1a is attached to the two shafts of the processing machine, and the back surface that is in contact with the film body is flatly polished by the rotating polishing wheel while rotating by applying tension. The belt sleeve processed on the back surface is cut into a predetermined width by a cutter to produce a toothed belt.
[0036]
【Example】
Examples of the present invention will be described below.
Example 1
As a core wire, 1,100 denier polyethylene terephthalate fiber is twisted in the up and down direction with an upper twist number of 11.4 times / 10 cm and a lower twist number of 21.0 times / 10 cm to form a 2 × 3 twist structure, total denier 6,600 raw codes were prepared. Next, this untreated cord was pre-dipped with an isocyanate-based adhesive, then dried at about 170 to 180 ° C., immersed in an RFL solution, and then subjected to a stretching and heat setting treatment at 200 to 240 ° C. to obtain a treated cord. .
[0037]
In addition, a plain woven canvas using cotton spun yarn was used as the reinforcing fabric. These canvases were immersed in an RFL solution and then heat treated at 150 ° C. for 2 minutes to obtain treated canvases. Thereafter, a rubber composition was friction coated with these treated canvases to obtain rubberized canvases.
[0038]
A rubber composition made of chloroprene rubber containing short aramid fibers was used for the compression rubber layer and the stretch rubber layer, and a rubber composition made of chloroprene rubber containing no short fibers was used for the adhesive rubber layer.
[0039]
After preparing these materials, add a reinforcing cloth, an unvulcanized rubber sheet with a stretch rubber layer, an unvulcanized rubber sheet with an adhesive rubber layer, a core wire, and an unvulcanized rubber sheet with a compressed rubber layer to a flat mold. Unwrapped belt sleeves were prepared by winding them one after another. Subsequently, a synthetic resin film (trade name: Saran Wrap) is wound on the outer surface of the unvulcanized belt sleeve along a part of both sides of the mold and wound in two plies in a spiral shape. A canvas with rubber was mounted on the surrounding synthetic resin film, and this was placed in a vulcanizing can and vulcanized.
[0040]
After removing the mold from the vulcanization can, the synthetic resin film on the outer surface of the belt sleeve could be easily peeled off. The appearance of the belt sleeve was vulcanized as it was on the sheet surface immediately after molding to form an uneven surface.
[0041]
As shown in FIG. 6, the obtained belt sleeve is hung on a driving roll and a driven roll and run under a predetermined tension, and at the same time, a grinding wheel with diamond attached is rotated by 1,800 rpm in the opposite direction to the belt sleeve. The belt sleeve was polished, and at the same time, a brass rotating brush was rotated at 450 rpm in the direction opposite to the running direction of the belt sleeve, and pressed with a rotating brush pressure of 2.0 kg / cm ² . In addition, the vacuum amount is set to 25 m / sec. Adjusted.
As a result, 80 groove portions on the surface were polished at a time. The depth of the groove portion was about 2 mm, and the polishing time was 3.5 minutes.
[0042]
The polished belt sleeve was cut into 3 ribs to produce a V-ribbed belt. The surface of the obtained V-ribbed belt was sufficiently vulcanized without generation of porosity, and had a good appearance with short fibers protruding from the surface.
[0043]
【The invention's effect】
As described above, in the invention according to claim 1 of the present application, after enclosing at least a part of both side surfaces of the molding die together with the outer peripheral surface of the unvulcanized belt sleeve attached to the molding die by the film body that does not transmit vapor. The mold is placed in a vulcanizing can and vulcanized without vapor entering the film body. After removing the film body from the belt sleeve, the surface of the belt sleeve in contact with the film body is polished. The transmission belt manufacturing method reliably surrounds both the outer peripheral surface of the unvulcanized belt sleeve together with the outer peripheral surface of the molding die by the vapor-impervious film body, and prevents the vapor from entering during vulcanization. Therefore, it is possible to vulcanize without using a jacket, and there is an effect that various problems when using the jacket can be solved.
[0044]
According to the second aspect of the present invention, at least two or more grooves are formed in the longitudinal direction of the sleeve by polishing the back surface of the vulcanized belt sleeve in contact with the film body, and then the V-ribbed belt. Further, in the invention according to claim 3, a vulcanized toothed belt sleeve having alternating teeth and grooves on the inner surface at predetermined intervals is produced, and the back surface of the sleeve in contact with the film body is formed. This is a method for manufacturing a toothed belt that is polished and finished flat, and any belt can be manufactured at a low cost with reduced loss of working time. Since the grooves are polished, a belt having a good appearance can be produced.
[0045]
In the invention according to claim 4 of the present application, the use of the synthetic resin film as the film body which does not transmit vapor facilitates the winding and surrounding work around the outer peripheral surface of the unvulcanized belt sleeve.
[0047]
In the invention according to claim 5 of the present application, it is possible to further prevent the intrusion of vapor from the upper and lower corner portions by mounting the sealing material on the film body provided at the upper and lower corner portions.
[0048]
In the invention according to claim 6 of the present application, since the sealing material is a fiber material selected from at least one layer of canvas with rubber and non-woven fabric, there is an effect of enhancing the sealing effect at the upper and lower corner portions.
[Brief description of the drawings]
FIG. 1 is a diagram showing a process for producing an unvulcanized belt sleeve on a mold in a method for producing a transmission belt according to the present invention.
FIG. 2 is a view showing a state in which an unvulcanized belt sleeve produced on a mold is surrounded by a film body in the method for producing a transmission belt according to the present invention.
FIG. 3 is a view showing a state in which the film body is surrounded not only on the outer surface of the unvulcanized belt sleeve but also on a part of both side surfaces of the molding die in the method for manufacturing a transmission belt according to the present invention. .
FIG. 4 is a view showing a case where a sealing material is provided on the upper and lower corners of a molding die on an enclosed film body in the method for manufacturing a transmission belt according to the present invention.
FIG. 5 is a view showing a state where an unvulcanized belt sleeve mounted on a mold is vulcanized in the method for manufacturing a transmission belt according to the present invention.
FIG. 6 is a front view showing a state in which a belt sleeve is polished in the method for manufacturing a transmission belt according to the present invention.
FIG. 7 is a partial perspective view of a polishing wheel used in the method for manufacturing a transmission belt of the present invention.
FIG. 8 is a partial cross-sectional perspective view of a V-ribbed belt obtained by the transmission belt manufacturing method according to the present invention.
FIG. 9 is a cross-sectional view of a forming die in which a toothed belt sleeve is manufactured in the method for manufacturing a transmission belt according to the present invention.
FIG. 10 is a perspective view of a sleeve for a toothed belt.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Mold 2 Reinforcement cloth 3 Unvulcanized rubber sheet 4 Unvulcanized rubber sheet 5 Core wire 6 Unvulcanized rubber sheet 7 Belt sleeve 8 Film body 11 V-ribbed belt 15 Vulcanizing device 16 Vulcanizing can 22 Sealing material 25 Polishing wheel 58 Toothed belt sleeve

Claims (6)

In a manufacturing method of a transmission belt obtained by attaching a cylindrical unvulcanized belt sleeve having a core wire embedded in a rubber layer to a mold and vulcanizing, and then polishing the surface of the vulcanized belt sleeve After enclosing at least a part of both sides of the molding die together with the outer peripheral surface of the unvulcanized belt sleeve attached to the molding die by a film body that does not transmit vapor, the molding die is placed in a vulcanizing can, A method for producing a transmission belt, comprising: vulcanizing without entering the inside of the film body, removing the film body from the belt sleeve, and then polishing the surface of the belt sleeve in contact with the film body.   The transmission belt according to claim 1, wherein at least two grooves are formed in the longitudinal direction of the sleeve by polishing the back surface of the vulcanized belt sleeve in contact with the film body, and then finished into a V-ribbed belt. Production method.   The transmission belt according to claim 1, wherein a vulcanized toothed belt sleeve having alternating tooth portions and groove portions on the inner surface at predetermined intervals is manufactured, and the back surface of the sleeve in contact with the film body is polished and finished flat. Manufacturing method.   4. The method for producing a transmission belt according to claim 1, wherein the film body which does not transmit vapor is a synthetic resin film. 2. The method of manufacturing a transmission belt according to claim 1, wherein the sealing material is mounted on a film body that does not transmit vapor and is provided at upper and lower corner portions of the unvulcanized belt sleeve. 6. The method for producing a transmission belt according to claim 5, wherein the sealing material is a fiber material selected from at least one layer of rubberized canvas and nonwoven fabric.

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