JPH0543608B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a conveyor belt having one or more layers of core fabric, and particularly to a conveyor belt in which the core fabric has excellent strength and durability. [Prior art] Core fabric has traditionally been used as a reinforcing material for conveyor belts, but in order to improve the strength utilization rate,
A special fabric with no shrinkage is used for the structure of the core fabric. Figures 1A to 1C are diagrams explaining the special weave, in which the warp thread 1 (used in the longitudinal direction of the belt) and the weft thread 2 are simply placed perpendicularly, just like in a normal woven fabric. The warp and weft threads are not intertwined or woven together. In addition to the warp yarns 1 and the weft yarns 2, a leno yarn 3 is entangled with the weft yarns as shown in FIG. 1C to form a cloth-like structure.
Therefore, the warp threads 1 and the weft threads 2 are substantially straight and in a so-called unwavy state, and this weaving method is referred to as a special weave in the present invention. The materials used for the warp threads of special weaves are generally fibers made of ordinary vinylon, polyester, polyamide, etc., but recently aromatic polyamide fibers have also come into use. However, the structure of conventional special weaving is that the warp threads are single-twisted or double-twisted using top and bottom twists, and the twisting structure of the warp threads is also undefined (for example, 1500d x 2 x
6.1500d×3×4), and the twist angle was also inappropriate. Therefore, the power utilization rate is low, and the high power (1000
Not only was it not possible to produce a core of ~2500 kg/cm), but it was also necessary to use a large amount of thread made of aromatic polyamide fibers, which was disadvantageous in terms of cost. [Object of the Invention] The object of the present invention is to eliminate the disadvantages of using a twisted cord of aromatic polyamide fibers as described above, and to maximize the strength utilization rate while providing flexibility due to the twisting effect. It is an object of the present invention to provide a conveyor belt that has been improved to a similar state and that allows a highly durable core to be obtained with a small amount of fibers. [Structure of the Invention] The present invention achieves the above object, in a conveyor belt having one or more layers of core fabric, wherein the core fabric has warp threads and weft threads intersecting each other in substantially straight lines, The warp threads are made of a structure in which entangled threads are entangled with these threads, and the warp threads are: (1) The multifilament threads are pulled into one thread in the first stage, and then the two threads are twisted in the second stage. An aromatic product consisting of a three-stage twisted structure in which two or more of the above-mentioned medium-twisted yarns are pulled together and medium-twisted in the opposite direction of the first-twisted yarn, and then two or more medium-twisted yarns are aligned in the third stage and a final twist is applied in the opposite direction of the medium-twisted yarn. It is a plied yarn of polyamide fibers, and (2) the middle twist angle α between the center axis of the middle twist yarn and the center axis of the first twist yarn is 10° to 30°, and the angle α between the center axis of the first twist yarn and the center axis of the second twist yarn is 10° to 30°. The ply twist angle β is
10° to 20°, and (3) the number of twists of the ply-twisted yarn is 2 or 3. Hereinafter, the present invention will be specifically explained with reference to embodiments shown in the drawings. Figures 2A and B show the center twist angle α of the center twist yarn 5 obtained by aligning a plurality of first twist yarns 4 (four in the figure) with a radius r and applying medium twist to them. FIG. The radius r (mm) of the first twisted yarn and the intermediate twist angle α can be determined by the following equations (1) and (2), assuming that the cross section of the first twisted yarn 4 is circular. 2r=K√...(1) tanα=2πr'/h...(2) However, r': Distance (radius) between the center axis of the middle-twist yarn and the center axis of the bottom-twist yarn (mm) K: Constant (0.011 ρ: Specific gravity of the fiber h: Medium twist pitch (mm) D: Total denier of the first twisted yarn In addition, Figure 3 A and B show the medium twisted yarn with radius R (=r+r') obtained as above. 5 is a diagram illustrating the ply-twist angle β of ply-twisted yarn 6 obtained by arranging a plurality of ply-twisted yarns 6 (three in the figure) and applying ply-twisting to the ply-twisted yarns. The radius R (mm) of this medium-twisted yarn and the twist angle β are as follows, assuming that the cross section of the medium-twisted yarn 5 is a circle.
It can be obtained using the following equations (3) and (4). 2R=K√′......(3) tanβ=2πR'/h...(4) However, R': Distance (radius) between the central axis of the top-twisted yarn and the center axis of the medium-twisted yarn (mm) K: Constant ( (0.011) ρ: Fiber specific gravity h: Ply twist pitch (mm) D': Total denier of medium-twist yarn Figure 4 shows the number of twist stages and the number of ply-twists, where a is the ply-twist yarn and b is the medium-twist yarn. Twisted yarn, c indicates ply-twisted yarn. Therefore, in Fig. 4 A, the number of twist stages and the number of final twists are both 1, B is an example in which both the number of twist stages and the number of final twists is 2, and C is an example in which the number of twist stages is 3 and the number of final twists is 4. . In the present invention, it is necessary to use aromatic polyamide fibers for the warp threads of the core body. Usually, the cutting strength of twisted yarn is determined by the strength of the material used for it. That is, if the strength of the material is high, a twisted yarn with high strength can be obtained. However, there are some fibers in which the inherent strength of the fiber cannot be fully utilized unless an appropriate structure is selected based on the shape of the stress-strain curve of the fiber material. A typical example thereof is aromatic polyamide fiber (eg, "Kevlar" (trademark)). Figure 5 shows stress-strain curves for fibers made of nylon (N), polyester (PE), and aromatic polyamide (K). As seen in the graph, aromatic polyamide fibers have high strength, but their elongation at break is lower than fibers made of polyester or nylon. If you pay closer attention, you will notice that the modulus near the cutting point is small for polyester and nylon fibers (a horizontal curve), whereas for aromatic polyamide fibers it is large and remains almost straight from the initial stage to cutting. It is a stress-strain curve. The modulus near the cutting point is called the terminal modulus, and in general, the smaller the terminal modulus of the fiber, the higher the strength utilization rate, and the opposite is true for aromatic polyamide fibers, so it is necessary to carefully consider the structure of the twisted yarn. Aromatic polyamide fibers can be said to have a high terminal modulus due to their low elongation. Fibers made from polyester and nylon have a low terminal modulus, so the twist structure does not significantly change the strength utilization rate. On the other hand, the special fabric used for the core of the present invention has warp threads and weft threads that intersect in a straight line, and the warp threads and weft threads are bound together by leno threads, so they are similar to ordinary plain weave or twill weave. Since the warp yarns are not crimped, the loss of strength due to friction between the warp yarns and the weft yarns is small, and the strength utilization rate hardly changes depending on the material of the weft yarns. Therefore, other organic synthetic fibers can be used as the weft yarn in the present invention. Only when the special fabric used as the core of the conveyor belt of the present invention satisfies all of the following four items will it exhibit a high strength effect. (1) Medium twist angle (α) is 10° to 30°. (2) The ply twist angle (β) is 10° to 20°. (3) The strands are made up of three tiers. (4) The number of ply twists is 2 or 3. The twisted threads (cords) constituting the core fabric have a three-tiered twist structure as described above, and each has a medium twist angle α of 10° to 30° and a final twist angle β of 10° to 20°. By making the strands (cord)
The direction of the individual constituent filaments constituting the cord is arranged so as to be substantially parallel to the cord axis direction. Therefore, by this arrangement, the strength utilization rate of the aromatic polyamide fiber (filament) can be increased to a state close to the maximum while imparting flexibility due to the twisting effect. Moreover, by limiting the number of twists of the ply-twisted yarn to two or three, the cross-section of the ply-twisted yarn is less likely to deform when stress is applied to these multiple yarns at the same time, and the shape stability is improved. As mentioned above, it can stably maintain the high strength utilization rate that has been raised to a near limit, and can sufficiently withstand large stretches and repeated bending when used in conveyor belts. In addition, since it has a high strength utilization rate, it can be made into a highly durable core for conveyor belts with a small amount of fiber. The above-mentioned effects are reduced when the number of twists of the ply-twisted yarn is increased to four or more because the shape stability of the thread cross section of the ply-twisted yarn against stress gradually decreases. In addition, the medium twist angle α
If the twist angle β exceeds 30 degrees, or the final twist angle β exceeds 20 degrees, the angle of each filament with respect to the cord axis direction gradually increases, and the friction caused by twisting increases, so the strength of the twisted cord gradually decreases. In addition, the medium twist angle α and the final twist angle β are
If the angle is less than 10°, the binding properties of the first-twisted yarn and the middle-twisted yarn will be insufficient, resulting in a decrease in durability against bending. Therefore, it is only when the above-mentioned four requirements (1) to (4) synergize with each other that the desired effect of increasing the strength utilization rate of aromatic polyamide fibers to near the maximum level and increasing durability can be achieved. However, even if each requirement is partially satisfied, the object of the present invention cannot be achieved. Such an effect can be particularly noticeable in the case of thick twisted yarns having a total denier of 10,000 d or more. [Example] Aromatic polyamide fiber (multifilament) with a strength of 23 g/d and a denier of 1500 d (1000 filaments) was prepared with the number of twists, number of twist stages, and twist angle shown in Table 1 (this invention) and Table 1 (this invention), respectively. By making various changes as shown in Table 2 (comparative example), twisted cords with flexibility due to the twisting effect were created, and this was used as warp yarns to create special fabrics. When the strength in the warp direction was measured for each, the results shown in Tables 1 and 2 were obtained.

【table】

〔Effect of the invention〕

Since the present invention is configured as described above, it has the following effects. That is, (1) A durable conveyor belt can be obtained because a core body with high strength utilization rate and high strength can be obtained. (2) The desired strong design can be achieved. (3) The cost of the core is low, which is economically advantageous.

[Brief explanation of the drawing]

Fig. 1 is an organization chart of the special weave, Fig. 1A is a plan view, Fig. 1B is a front view, Fig. 1C is a side view, and Fig. 2A is an explanatory diagram showing the medium twist angle. , FIG. 2B is a plan explanatory diagram of FIG. 2A, FIG. 3A is an explanatory diagram showing the upper twist angle, FIG. 3B is a plan explanatory diagram of FIG. 3A, and FIGS. 4A, B, C. is an explanatory diagram showing the number of twist stages and the number of upper twists, and FIG. 5 is a graph showing a stress-strain curve. 1... Warp thread, 2... Weft thread, 3... Leno thread, 4... Lower twisted thread, 5... Medium twisted thread, 6... Upper twisted thread.

Claims (1)

[Scope of Claims] 1. A conveyor belt having one or more layers of core fabric, wherein the core fabric has warp yarns and weft yarns that intersect with each other in a substantially straight line, and entanglement yarns therewith. (1) In the first stage, the multifilament yarns are pulled together into a single thread, and then two or more of the threads are pulled together in the second stage to form the thread. It is a plied yarn of aromatic polyamide fibers having a three-stage twist structure in which a medium twist is applied in the opposite direction of the medium twist yarn, and two or more of the medium twist yarns are pulled together in the third stage and a final twist is applied in the opposite direction of the medium twist yarn. (2) The middle twist angle α between the center axis of the middle twist yarn and the center axis of the first twist yarn is 10° to 30°, and the final twist angle β between the center axis of the top twist yarn and the center axis of the middle twist yarn is 10° to 30°.
10° to 20°, and (3) a conveyor belt characterized in that the number of twists of the ply-twisted yarns is two or three.