Conveyor belt

Abstract

To provide a conveyor belt which can maintain flame resistance of the conveyor belt for a long time by more effectively using flame retardants.SOLUTION: A core layer 4 coated with coating rubber 6 is arranged between an upper cover rubber 2 and a lower cover rubber 3, the upper cover rubber 2 and the lower cover rubber 3 are joined to the core layer 4 via the coating rubber 6, and by adding flame retardants to at least an upper coat rubber 6a disposed between the upper cover rubber 2 and the core layer 4 of the coating rubber 6, the upper coat rubber 6a is made into rubber having a higher oxygen index and high flame resistance than the upper cover rubber 2.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a conveyor belt, and more particularly to a conveyor belt that can more effectively utilize a flame retardant and maintain the flame retardancy of the conveyor belt for a long period of time. [Background technology]

[0002] A variety of materials, including mineral resources such as iron ore and limestone, are transported by conveyor belts. The cover rubber of the conveyor belt, especially the upper cover rubber on which the materials are placed, is the part that wears the most over time.

[0003] Depending on the use conditions of the conveyor belt, a flame-retardant (self-extinguishing) conveyor belt is used. In a flame-retardant conveyor belt, a flame retardant is generally compounded in the cover rubber (see, for example, Patent Document 1). The flame retardant compounded in the cover rubber decreases as the cover rubber wears, so the flame retardancy of the conveyor belt decreases over time. Therefore, if the amount of flame retardant compounded is increased in order to ensure flame retardancy even when the cover rubber wears, the material cost increases significantly because the flame retardant is expensive compared to other materials. Furthermore, a problem occurs in that the wear resistance of the cover rubber decreases due to the incorporation of the flame retardant. Therefore, there is room for improvement in effectively utilizing the flame retardant to maintain the flame retardancy of the conveyor belt over a long period of time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-24530 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a conveyor belt that can more effectively utilize a flame retardant and maintain the flame retardancy of the conveyor belt for a long period of time. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a conveyor belt comprising an upper cover rubber, a lower cover rubber, and a coating rubber disposed between the upper cover rubber and the lower cover rubber and coated with the coating rubber. It is composed of the body and mind a traction layer, the upper cover rubber and the lower cover rubber being joined to the traction layer via the coating rubber, and at least a portion of the conveyor belt is made of rubber containing a flame retardant, The upper cover rubber and the core are in contact with each other. Upper coated rubber The upper coating rubber contains flame retardants. has higher flame retardancy than the upper cover rubber. Effect of the Invention

[0007] According to the present invention, at least the upper coat rubber disposed between the upper cover rubber and the core layer has higher flame retardancy than the upper cover rubber. That is, the flame retardant is unevenly distributed in the upper coat rubber compared to the upper cover rubber. Therefore, compared to a conventional flame retardant conveyor belt in which the flame retardant is only mixed in the cover rubber, it is advantageous to suppress the flame retardancy of the conveyor belt from decreasing with the wear of the upper cover rubber. The flame retardant mixed in the upper coat rubber is not lost in the upper cover rubber due to wear, so it is advantageous to maintain the flame retardancy of the conveyor belt for a long period of time. In this way, the flame retardant can be effectively utilized without waste to ensure flame retardancy, so the amount of flame retardant mixed can be suppressed, which is also advantageous to avoid the decrease in the wear resistance of the upper cover rubber caused by the mixture of the flame retardant. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is an explanatory diagram illustrating a side view of a conveyor belt according to the present invention in use. [Diagram 2] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 3] FIG. 2 is an explanatory diagram illustrating an enlarged cross-sectional view of the conveyor belt of FIG. 1. [Figure 4] FIG. 13 is an explanatory diagram illustrating an enlarged cross-sectional view of another embodiment of a conveyor belt. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A conveyor belt according to the present invention will now be described with reference to the embodiments shown in the drawings.

[0010] As shown in Figures 1 and 2, a conveyor belt 1 of the present invention is used by being attached to a conveyor line 7. The conveyor belt 1 is configured by integrating an upper cover rubber 2, a lower cover rubber 3, and a traction layer 4 disposed therebetween by vulcanization adhesion.

[0011] In the conveyor line 7, the conveyor belt 1 is stretched between a driving pulley 8a and a driven pulley 8b and stretched with a predetermined tension. The conveyor belt 1 is supported by a number of support rollers 8c between the pulleys 8a and 8b. In the figure, the arrow W indicates the width direction of the conveyor belt 1, and the arrow H indicates the thickness direction of the conveyor belt 1.

[0012] An object C is put on the conveyor belt 1, and the conveyor belt 1 transports the object C to its destination. Specifically, on the carrier side of the conveyor line 7 (the side on which the object C is placed and travels), the lower cover rubber 3 of the conveyor belt 1 is supported by the support rollers 8c, so that the conveyor belt 1 becomes a trough shape with the center part in the width direction W protruding downward. The object C is put on and transported on the top surface of the upper cover rubber 2. On the return side of the conveyor line 7, the upper cover rubber 2 of the conveyor belt 1 is supported in a flat state by the support rollers 8c.

[0013] Examples of the transported goods C include coke, sintered ore, overburden, ore, etc. When transporting high-temperature transported goods C or in an environment where there is fire nearby, the conveyor belt 1 is required to have high flame retardancy. For this reason, the conveyor belt 1 is flame retardant.

[0014] 3, the conveyor belt 1 has an upper cover rubber 2, a lower cover rubber 3, a traction layer 4 (5a, 5b, 5c) disposed between the upper cover rubber 2 and the lower cover rubber 3, and a coating rubber 6 that covers the traction layer 4. The conveyor belt 1 may be equipped with other members as required.

[0015] A rubber type used in known upper cover rubbers can be used for the upper cover rubber 2. A rubber type having excellent abrasion resistance and cut resistance is generally used for the upper cover rubber 2. The layer thickness of the upper cover rubber 2 is, for example, 3 mm to 25 mm.

[0016] The lower cover rubber 3 may be made of a rubber type that is used for known lower cover rubbers. The upper cover rubber 2 and the lower cover rubber 3 may be made of the same or different rubber types. The layer thickness of the lower cover rubber 3 is, for example, 1.5 mm to 10 mm.

[0017] The core layer 4 is a member that bears the tension for tensioning the conveyor belt 1. The core layer 4 is embedded over almost the entire width of the conveyor belt 1. In this embodiment, the core layer 4 is configured by laminating three layers of band-shaped cores 5 (5a, 5b, 5c). The number of cores 5 is appropriately determined depending on the performance required for the conveyor belt 1, and is, for example, about 1 to 8 layers. The core 5 is a fiber reinforcement member formed from fibers, and for example, canvas is used. The layer thickness of the core 5 is, for example, 2 mm to 14 mm. It is also possible to use a core 5 (core layer 4) configured by arranging a large number of steel cords extending in the belt longitudinal direction in parallel in the belt width direction.

[0018] The traction layer 4 is covered with a coating rubber 6. The upper cover rubber 2 and the lower cover rubber 3 are joined and integrated with the traction layer 4 via the coating rubber 6. It is preferable that not only the upper and lower surfaces of the traction layer 4 but also the left and right sides are covered with the coating rubber 6 so that the entire surface of the traction layer 4 is covered with the coating rubber 6.

[0019] The coating rubber 6 is a rubber with excellent adhesive strength, and a known coating rubber (adhesive rubber) used in a known conveyor belt can be used. The layer thickness of each of the coating rubbers 6a, 6b, and 6c is, for example, 0.2 mm to 1.0 mm, which is thinner than the upper cover rubber 2 and the lower cover rubber 3.

[0020] However, in order to ensure flame retardancy, a flame retardant is blended into at least a part of the coating rubber 6 of the conveyor belt 1. As the flame retardant, various known flame retardants such as organic flame retardants (halogen-based, phosphorus-based, composite type, etc.) and inorganic flame retardants (metal hydroxide, antimony-based, etc.) can be used.

[0021] In this embodiment, the upper core 5a is covered with an upper coating rubber 6a and a middle coating rubber 6c, the lower core 5b is covered with a lower coating rubber 6b and a middle coating rubber 6c, and the middle core 5c is covered with a middle coating rubber 6c and a middle coating rubber 6c. Therefore, the upper and lower surfaces of the core layer 4 are covered with the upper coating rubber 6a and the lower coating rubber 6b, respectively. The cores 5a, 5b, and 5c are joined via the coating rubbers 6 that are adjacently layered.

[0022] In this embodiment, the flame retardant is compounded in the upper coat rubber 6a covering the upper surface of the upper core 5a and the lower coat rubber 6b covering the lower surface of the lower core 5b. The middle coat rubber 6c covering the upper and lower surfaces of the middle core 5c does not contain a flame retardant. The upper coat rubber 6a arranged between the upper cover rubber 2 and the core layer 4 has a higher flame retardancy than the upper cover rubber 2, and the lower coat rubber 6b arranged between the lower cover rubber 3 and the core layer 4 has a higher flame retardancy than the lower cover rubber 3. The upper coat rubber 6a can have a higher flame retardancy than the lower coat rubber 6b or the same. The upper coat rubber 6a has a higher flame retardancy than the upper cover rubber 2, which means that the upper coat rubber 6a has a higher flame retardancy than the upper cover rubber 2 when compared at the same size (same layer thickness). Similarly, the lower coating rubber 6b having higher flame retardancy than the lower cover rubber 3 means that, when compared at the same size (same layer thickness), the lower coating rubber 6b has higher flame retardancy than the lower cover rubber 3. Hereinafter, in the present invention, when one has higher flame retardancy than the other, this means superiority or inferiority of flame retardancy when compared at the same size (same layer thickness).

[0023] The level of flame retardancy (superiority) can be evaluated by the oxygen index value measured based on the test specified in JIS K 7201-2. The higher the oxygen index value, the better the flame retardancy. Therefore, the upper coat rubber 6a arranged between the upper cover rubber 2 and the traction layer 4 has a higher oxygen index than the upper cover rubber 2, and the lower coat rubber 6b arranged between the lower cover rubber 3 and the traction layer 4 has a higher oxygen index than the lower cover rubber 3.

[0024] In the conveyor belt 1, since the transported object C is put and placed on the upper cover rubber 2, it is preferable to prioritize ensuring the flame retardancy of the upper cover rubber 2 side. Therefore, in this conveyor belt 1, at least the upper coat rubber 6a arranged between the upper cover rubber 2 and the core layer 4 of the coat rubber 6 only needs to have a higher flame retardancy than the upper cover rubber 2. Therefore, it is sufficient that the flame retardant is blended at least in the upper coat rubber 6a arranged between the upper cover rubber 2 and the core layer 4 of the coat rubber 6. In other words, it is sufficient that the upper coat rubber 6a arranged between the upper cover rubber 2 and the core layer 4 has a higher oxygen index than the upper cover rubber 2.

[0025] If the oxygen index of this upper coating rubber 6a is greater than that of the upper cover rubber 2, a flame retardant can be compounded in the upper cover rubber 2. Therefore, the specifications may be such that the flame retardant is compounded in at least the coating rubber 6 and the upper cover rubber 2. However, flame retardants are expensive materials, and compounding them carries the risk of reducing the wear resistance of the rubber. Therefore, from the standpoint of reducing material costs and wear resistance, it is preferable to compound the flame retardant only in the coating rubber 6, and not in the upper cover rubber 2 or the lower cover rubber 3.

[0026] As described above, in this conveyor belt 1, the flame retardant is unevenly distributed in the upper coating rubber 6a and the upper cover rubber 2. The flame retardant mixed in the upper coating rubber 6a is not lost with wear of the upper cover rubber 2, which is advantageous in suppressing deterioration of the flame retardancy of the conveyor belt 1 over time compared to a conventional flame-retardant conveyor belt in which the flame retardant is mixed only in the cover rubber. As a result, it becomes possible to maintain the flame retardancy of the conveyor belt 1 for a long period of time.

[0027] By blending the flame retardant in the coating rubber 6 (at least the upper coating rubber 6a) in this way, the flame retardant can be used effectively without waste and flame retardancy can be ensured. Therefore, it is possible to suppress the amount of flame retardant blended into the upper cover rubber 2 to zero or a small amount, which is advantageous in avoiding a rise in material costs and in avoiding a decrease in the abrasion resistance of the upper cover rubber 2 caused by blending the flame retardant.

[0028] In this embodiment, the lower coating rubber 6b disposed between the lower cover rubber 3 and the core layer 4 has higher flame retardancy than the lower cover rubber 3, which is advantageous in suppressing the combustion of the lower core 5b. The flame retardancy of the lower coating rubber 6b is not impaired by wear of the lower cover rubber 3. A flame retardant can be blended into the lower cover rubber 3, but blending increases material costs. A flame retardant can also be blended into the middle coating rubber 6c, but because fire is present outside the conveyor belt 1, the importance (priority) of improving the flame retardancy is lower than that of the upper coating rubber 6a and the lower coating rubber 6b.

[0029] The oxygen index of the upper cover rubber 2 and the lower cover rubber 3 is, for example, 22 to 26. In order to make the upper coat rubber 6a adjacent to the upper cover rubber 2 and the lower coat rubber 6b adjacent to the lower cover rubber 3 exhibit appropriate flame retardancy, it is preferable that the oxygen index of each is somewhat higher than that of the upper cover rubber 2 and the lower cover rubber 3. Therefore, it is preferable that the oxygen index of the upper coat rubber 6a is 5 or more higher than that of the upper cover rubber 2, and the oxygen index of the lower coat rubber 6b is 5 or more higher than that of the lower cover rubber 3. In order to increase the oxygen index, a larger amount of flame retardant needs to be blended, which increases the material cost. Therefore, it is preferable that the oxygen index of the upper coat rubber 6a and the lower coat rubber 6b are each 5 to 10 higher than that of the upper cover rubber 2 and the lower cover rubber 3. The blending amount of the flame retardant may be determined so that the oxygen index value is in a desired numerical range using this oxygen index as an index.

[0030] The embodiment of the conveyor belt 1 illustrated in Fig. 4 differs from the previous embodiment only in the specification of the coating rubber 6. In this embodiment, a flame retardant is blended into the upper coating rubber 6a covering the upper and lower surfaces of the upper core 5a and the lower coating rubber 6b covering the upper and lower surfaces of the lower core 5b. No flame retardant is blended into the middle coating rubber 6c covering the upper and lower surfaces of the middle core 5c. Each of the upper coating rubbers 6a has a higher flame retardancy than the upper cover rubber 2, and each of the lower coating rubbers 6b has a higher flame retardancy than the lower cover rubber 3.

[0031] In this embodiment, both the upper and lower sides of the upper core 5a are covered with highly flame-retardant coating rubber 6a, which is more advantageous in suppressing combustion of the upper core 5a than when only the upper surface of the upper core 5a is covered with highly flame-retardant coating rubber 6a. Similarly, both the upper and lower sides of the lower core 5b are covered with highly flame-retardant coating rubber 6b, which is more advantageous in suppressing combustion of the lower core 5b than when only the lower surface of the lower core 5b is covered with highly flame-retardant coating rubber 6b.

[0032] The various arrangements described in the previous embodiment can also be applied to this embodiment.

[0033] The flame retardancy of the conveyor belt 1 is more significantly affected by the flame retardancy of the rubber arranged closer to the surface of the conveyor belt 1. Therefore, when the traction layer 4 is constructed by laminating a plurality of traction members 5a, 5b, 5c, it is preferable that, among the coating rubbers 6 covering both the upper and lower surfaces of each of the traction members 5a, 5b, 5c, the uppermost coating rubber 6a and the lowermost coating rubber 6b have higher flame retardancy than the other coating rubbers 6c, as in the embodiment illustrated in Fig. 3. By adopting this specification, effective flame retardancy can be ensured while minimizing the amount of flame retardant mixed.

[0034] When the core layer 4 is constructed by laminating a plurality of cores 5a, 5b, 5c, even better flame retardancy can be ensured by using the embodiment illustrated in Fig. 4. That is, among the coating rubbers 6 covering both the upper and lower surfaces of each of the cores 5a, 5b, 5c, both the upper and lower surfaces of the uppermost core 5a are covered with coating rubber 6a having higher flame retardancy than the upper cover rubber 2, and both the upper and lower surfaces of the lowermost core 5b are covered with coating rubber 6b having higher flame retardancy than the lower cover rubber 3. This makes it possible to further improve flame retardancy while suppressing the amount of flame retardant used. EXAMPLES

[0035] As shown in Table 1, conveyor belt test samples were prepared as follows: Example 1 and Conventional Examples 1 to 3 having the laminated structure of Fig. 3, and Example 2 having the laminated structure of Fig. 4. These five test samples were subjected to a flame retardancy test specified in JIS K 6324 to confirm whether they met Class 3 flame retardancy. The results are shown in Table 1.

[0036] The first to sixth layers of the coating rubber in Table 1 are numbered in order of proximity to the top cover rubber, and the coating rubber closest to the top cover rubber is the first layer. In the laminated structure of FIG. 3, the coating rubber has four layers, so the fifth and sixth layers do not exist. The oxygen index in Table 1 is a value measured based on the test specified in JIS K 7201-2. The top cover rubber and the bottom cover with an oxygen index of 24.5 are the same rubber and contain a flame retardant. The coating rubbers with an oxygen index of 33 are all the same rubber and contain a flame retardant. The coating rubbers with an oxygen index of 21 are all the same rubber and do not contain a flame retardant. In addition, the same specification of canvas was used as the core for each test sample. Conventional Examples 1, 2, and 3 are different only in the layer thickness of the top cover rubber. That is, Conventional Examples 1 and 2 can be regarded as reproducing the state in which the top cover rubber of Conventional Example 3 is worn by 2 mm and 1 mm, respectively.

[0037] [Table 1]

[0038] From the results in Table 1, Examples 1 and 2 and Conventional Examples 2 and 3 have Class 3 flame retardancy as specified in JIS K 6324. Conventional Example 1 does not have Class 3 flame retardancy and has poor flame retardancy. From the results of Conventional Examples 1 to 3, it can be seen that the flame retardancy decreases as the upper cover rubber wears. In addition, from the results of Examples 1 and 2 and Conventional Example 1, which have the same layer thickness of the upper cover rubber, it can be seen that even if the upper cover rubber is thin, the flame retardancy of the conveyor belt can be ensured as long as the flame retardancy of the coating rubber is high. [Explanation of symbols]

[0039] 1. Conveyor belt 2 Upper cover rubber 3 Lower cover rubber 4 Cardiac layer 5a Upper central body 5b Lower central body 5c Medial centrum 6 Coated Rubber 6a Upper coated rubber 6b Lower coated rubber 6c Middle coated rubber 7 Conveyor Line 8a Drive pulley 8b Driven pulley 8c Support roller

Claims

1. A conveyor belt comprising an upper cover rubber, a lower cover rubber, and a core layer disposed between the upper cover rubber and the lower cover rubber and composed of a core layer covered with a coating rubber, the upper cover rubber and the lower cover rubber being joined to the core layer via the coating rubber, and at least a portion of the conveyor belt is made of rubber containing a flame retardant, A conveyor belt characterized in that at least the upper coating rubber, which is disposed between the upper cover rubber and the core layer and is in contact with the upper cover rubber and the core layer, contains a flame retardant, and this upper coating rubber has higher flame retardancy than the upper cover rubber.

2. 2. The conveyor belt according to claim 1, wherein a flame retardant is blended into a lower coating rubber, which is disposed between the lower cover rubber and the core layer and is in contact with the lower cover rubber and the core layer, and the lower coating rubber has higher flame retardancy than the lower cover rubber.

3. 3. A conveyor belt as described in claim 1 or 2, wherein the core layer is constructed by stacking a plurality of the cores, and among the core layers, the uppermost core has both upper and lower surfaces covered with the coating rubber containing a flame retardant and having a higher flame retardancy than the upper cover rubber, and this coating rubber abuts against the upper cover rubber and the uppermost core, and the lowermost core has both upper and lower surfaces covered with the coating rubber containing a flame retardant and having a higher flame retardancy than the lower cover rubber, and this coating rubber abuts against the lower cover rubber and the lowermost core.

4. A conveyor belt as described in any one of claims 1 to 3, wherein the core layer is constructed by stacking a plurality of the cores, both the upper and lower surfaces of each of the cores are covered with the coating rubber, and the coating rubber arranged at the top, in contact with the upper cover rubber and the uppermost core, and containing a flame retardant, and the coating rubber arranged at the bottom, in contact with the lower cover rubber and the lowermost core, and containing a flame retardant, have higher flame retardancy than the other coating rubbers.

5. A conveyor belt according to any one of claims 1 to 4, wherein the oxygen index of the upper cover rubber and the lower cover rubber is 22 to 26, the oxygen index of the coating rubber arranged between the upper cover rubber and the core layer and in contact with the upper cover rubber and the core is 5 or more higher than the oxygen index of the upper cover rubber, and the oxygen index of the coating rubber arranged between the lower cover rubber and the core layer and in contact with the lower cover rubber and the core is 5 or more higher than the oxygen index of the lower cover rubber.

6. The conveyor belt according to any one of claims 1 to 5, wherein the flame retardant is compounded only in the coating rubber.

7. The conveyor belt according to any one of claims 1 to 5, wherein the flame retardant is compounded in at least the coating rubber and the upper cover rubber.

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