Patent Grant
11293518
This is a U.S. National Phase Application under 35 U.S.C. § 371 of International Application No. PCT/JP2018/016500, filed Apr. 23, 2018, which claims priority to Japanese Application Nos. 2017-085025, filed Apr. 24, 2017 and 2018-079008, filed Apr. 17, 2018, which was published Under PCT Article 21(2), the entire contents of which are incorporated herein by reference.
The present invention relates to a toothed belt containing a back portion and plural teeth integrally molded of a thermoplastic elastomer.
Toothed belts have been used broadly as motive power transmission belts in general industrial machines, agricultural machines, etc. and have come to be applied to heavy transport targets in recent years. For application to heavy transport targets, it is effective to increase the load-bearing capacity by increasing the overall size of a toothed belt (in particular, its tooth height). However, size reduction is also required from the viewpoint of machine installation space; in particular, it is desired to increase the load-bearing capacity while keeping the belt width.
As techniques for increasing the load-bearing capacity while keeping the belt width, a technique of arranging plural core wires in the belt thickness direction (refer to Patent documents 1 and 2); a technique of arranging core wires in the belt width direction densely without gaps; a technique of increasing the diameter of core wires; etc. have been known.
However, Patent documents 1 and 2 have no specific disclosure about the magnitude of belt strength, the structure (pitch and height) of teeth, etc. that are suitable for application to heavy transport targets.
An object of the present invention is to provide a toothed belt that can increase the load-bearing capacity while keeping the belt width and hence is suitable for application to heavy transport targets.
The present invention provides a toothed belt including a belt body including plural core wires that extend in a belt longitudinal direction and are arranged in a belt width direction, a back portion in which the plural core wires are buried, and plural teeth that are opposite to the back portion in a belt thickness direction and arranged in the belt longitudinal direction so as to be spaced from each other, in which the back portion and the plural teeth are molded integrally of a thermoplastic elastomer, having: a belt strength per 1-mm belt width of higher than or equal to 1.85 kN; a pitch of the plural teeth of longer than or equal to 20 mm; a height of each of the plural teeth of greater than or equal to 5 mm; and a thickness of the back portion of larger than or equal to 4 mm.
As described later in Examples, the present invention can provide a toothed belt capable of increasing the load-bearing capacity while keeping the belt width and hence suitable for application to heavy transport targets.
In the present invention, each of the plural core wires may be constituted of a steel cord or a cord produced by twisting at least any of aramid fibers and carbon fibers.
Each of the plural core wires: may be constituted of a steel cord; may have a strength of 7 to 8 kN; and may have a diameter of 2.3 to 2.6 mm. In this case, since a steel cord having features of a low degree of elongation and high strength is used as the core wire, necessary increase of the belt strength per unit width can be realized in an even preferable manner.
The plural core wires: may have a pitch of 3.0 to 3.7 mm; and may have an interval between the plural core wires of 0.4 to 1.4 mm. In this case, as described later in Examples, necessary increase of the belt strength per unit width can be realized in an even preferable manner by employing a preferred combination of the pitch and the interval of the core wires.
The thermoplastic elastomer may be at least one selected from the group consisting of: a polyurethane thermoplastic elastomer; a polyester thermoplastic elastomer; a polystyrene thermoplastic elastomer; a polyolefin thermoplastic elastomer; a polyamide thermoplastic elastomer; and a vinyl chloride thermoplastic elastomer.
The thermoplastic elastomer may be a polyurethane thermoplastic elastomer and may have a hardness of 85 to 95°. In this case, a toothed belt that is superior in mechanical characteristics and durability can be obtained. Furthermore, since a polyurethane thermoplastic elastomer is used universally to form transmission belts and transport belts, toothed belts can be easily manufactured thereof. Still further, the type of polyurethane that constitutes the polyurethane thermoplastic elastomer may be polyether polyurethane, polyester polyurethane, or polycarbonate polyurethane.
The present invention can provide a toothed belt capable of increasing the load-bearing capacity while keeping the belt width and hence suitable for application to heavy transport targets.
As illustrated in
Core wire 1 employed in the present embodiment is constituted of a steel cord (a cord produced by twisting steel fibers together). The plural core wires 1 extend in the belt longitudinal direction and are arranged in the belt width direction.
The plural teeth 3 are opposite to the back portion 2 in the belt thickness direction and arranged in the belt longitudinal direction so as to be spaced from each other. The back portion 2 and the plural teeth 3 are molded integrally of a thermoplastic elastomer. In the present embodiment, the thermoplastic elastomer constituting the back portion 2 and the plural teeth 3 is a polyurethane thermoplastic elastomer that is 85 to 95° in hardness (measured by a type-A hardness meter according to JIS K6253: 2012). Example types of polyurethane that constitutes the polyurethane thermoplastic elastomer include polyether polyurethane, polyester polyurethane, and polycarbonate polyurethane.
It is preferable that the toothed belt 10 satisfies the following requirements.
For example, the toothed belt 10 is used in an elevating transport machine 50 as illustrated in
The elevating transport machine 50 includes toothed pulleys 51 and 53 which are arranged side by side at a top position and toothed pulleys 52 and 54 which are arranged side by side at a bottom position. A toothed belt 10 of open-end is cut into a prescribed width and length, and two end portions in the belt longitudinal direction are fixed to each other with a jig or the like to be endless. The respective resulting belts are wound on the pair of toothed pulleys 51 and 52 and the pair of toothed pulleys 53 and 54, respectively arranged vertically to be opposite to each other. A fixing member 58 for fixing a carrier 57 is attached to each toothed belt 10. Among the four toothed pulleys 51-54, one toothed pulley 52 is driven and the remaining toothed pulleys 51, 53 and 54 are moved synchronously via the toothed belt(s) 10. In the case where the toothed pulley 52 is rotated in the normal direction or the reverse direction in a state that a transport target 59 is put on the carrier 57, the pair of toothed belts 10 are caused to run and the transport target 59 is elevated or lowered vertically.
The toothed belt 10 is preferable for applications to heavy transport targets and can be used in, for example, a use environment in which the weight of the transport target 59 is 5 to 11 t and the maximum tension of 0.20 to 0.25 kN/mm is applied.
The toothed belt according to the present invention may be either an open-end one or an endless one. The toothed belt according to the present invention is not limited to be used in elevating transport machines, and may be used in any machines. Furthermore, the toothed belt according to the present invention may be provided with a reinforcement cloth on the outer circumferential surface and/or the inner circumferential surface of the belt body.
Next, an example of a manufacturing method of the toothed belt 10 will be described.
For example, the toothed belt 10 is manufactured by a manufacturing machine 60 illustrated in
The outer circumferential surface of the shaping drum 61 is formed with grooves at a prescribed interval in the circumferential direction, for forming the teeth 3. The pulley 64 can be moved in the horizontal direction relative to the shaping drum 61 and applies a prescribed tension to the pressing band 65. The pressing band 65 is disposed so as to be wound on approximately half of the outer circumferential surface of the shaping drum 61, and is pressed against the outer circumferential surface of the shaping drum 61 by the tension applied from the pulley 64.
The extruding head 66 supplies thermoplastic elastomer in a state of being melted by heating, to the outer circumferential surface of the shaping drum 61. The core wire-supplying device (not illustrated) supplies plural core wires 1 arranged in the axial direction of the shaping drum 61 to the outer circumferential surface of the shaping drum 61.
As the shaping drum 61 rotates, the thermoplastic elastomer in the melted state and the plural core wires 1 which are supplied to the outer circumferential surface of the shaping drum 61 are caught between the shaping drum 61 and the pressing band 65. During that course, the grooves formed on the outer circumferential surface of the shaping drum 61 are filled with the thermoplastic elastomer by pressing force of the pressing band 65, and thus the teeth 3 are formed in the respective grooves. Furthermore, during that course, the back portion 2 in which the plural core wires 1 are buried is formed between the outer circumferential surface of the shaping drum 61 and the pressing band 65. The thermoplastic elastomer is cooled and solidified while the thermoplastic elastomer is pressed strongly against the outer circumferential surface of the shaping drum 61 by the pressing force of the pressing band 65. The belt body 10a is taken out continuously at the position where the pressing band 65 leaves the shaping drum 61.
According to the present embodiment, as described above and as will be shown by Examples later, the load-bearing capacity can be increased while keeping the belt width W, whereby the toothed belt 10 that is suitable for application to heavy transport targets can be provided.
In the present embodiment, each core wire 1 is constituted of a steel cord and is 7 to 8 kN in a strength and 2.3 to 2.6 mm in a diameter D. In this case, since a steel cord having features of a low degree of elongation and high strength is used as the core wire 1, necessary increase of the belt strength per unit width can be realized more certainly.
In the present embodiment, the pitch Pt of the core wires 1 is 3.0 to 3.7 mm and the interval d between the core wires 1 is 0.4 to 1.4 mm. In this case, as will be shown by Examples later, increase of the belt strength per unit width can be realized more certainly by selecting a preferred combination of the pitch and the interval of the core wires 1.
The present inventors produced toothed belts of Examples 1 to 9 and Comparative Examples 1 to 3 according to the above-described manufacturing method using an AT20 tooth profile (a tooth profile according to ISO 17396: 2014; teeth pitch: 20 mm) and a polyurethane (polyester polyurethane) thermoplastic elastomer, and performed a tension test and a running test on these toothed belts.
The following Tables 1 to 4 show structures of the toothed belts of Examples 1 to 9 and Comparative Examples 1 to 3.
The belt width W of all of the toothed belts of Examples 1 to 9 and Comparative Examples 1 to 3 was set at 135 mm
To enable comparison when the pitch P of the teeth 3 or the belt strength per 1-mm belt width was varied, Table 1 shows the structures of the toothed belts of Examples 1 to 3 and Comparative Examples 1 to 3. To enable comparison when the pitch Pt of the core wires 1 was varied from that of the toothed belt of Example 1, Table 2 shows the structures of the toothed belts of Examples 1, 4 and 5. To enable comparison when the hardness was varied from that of the toothed belt of Example 1, Table 3 shows the structures of the toothed belts of Examples 1 and 6 to 8. To enable comparison when the polyurethane type was varied from that of the toothed belt of Example 1, Table 4 shows the structures of the toothed belts of Examples 1 and 9.
In the running test, a test piece 10x having a width 20 mm and a length 3,700 mm was taken from each of the toothed belts of Examples 1 to 9 and Comparative Examples 1 to 3. As illustrated in
Strengths of test piece 10x before and after the running test (before running and after running) were measured by a tension test and, furthermore, a reduction ratio of the strength of test piece 10x between before and after the running test was calculated for each test piece 10x. Results are shown in items “strength before running” and “strength after running” of the belt, and in item “strength reduction ratio” of Tables 1 to 4.
In the tension test, a tension test piece having a width 20 mm and a length 500 mm was taken from a test piece 10x before running and a test piece 10x after running that were taken from each of the toothed belts of Examples 1 to 9 and Comparative Examples 1 to 3. And each tension test piece was subjected to a tension test using an Amsler's tension tester (pull rate: 50 mm/min) and strength until the tension test piece broke was measured.
After the running test, each test piece 10x was observed. If a defect such as “tooth chipping” or “tooth wear” was found, the state was entered in item “state after running” of Tables 1 to 4. If no such change was found, “no defect” was entered.
Occurrence of a positioning failure with respect to the drive pulley 71 and the driven pulley 72 was judged for each test piece 10x before and after the running test. More specifically, as illustrated in
Based on the results of the above-described running test, the toothed belts of Examples 1 to 9 and Comparative Examples 1 to 3 were given ranks A to D according to criteria shown below in Table 5. Results were entered in item “judgment” of Table 1 to Table 4.
The toothed belts of Examples 1 to 3 in which the teeth pitch P was longer than or equal to 20 mm (the teeth pitch P was relatively long and accordingly the tooth scale (the tooth length in the longitudinal direction and the tooth height h3 of the teeth), associated with the teeth pitch P was large) and the strength was high (higher than or equal to 1.85 kN/mm) were all classified as rank A.
Comparative Example 1 was a toothed belt of high in strength but 14 mm in teeth pitch P (i.e., the tooth scale was a little small). Where the tooth scale associated with the teeth pitch P was small, the resistance against effective tension (load) acting on each tooth was lower than in a large scale tooth. Thus, the teeth were prone to be deformed to a large extent and hence a life end was reached early due to tooth chipping, resulting in incapable of practical use (rank D).
Comparative Example 2 was a toothed belt of 20 mm in teeth pitch P (i.e., the tooth scale was large) but lower than 1.85 kN/mm in belt strength because of the use of core wires which were narrower and lower in strength than in Example 1. In this case, because of the narrow core wires, when a heavy load was exerted on the toothed belt, an extremely large tension acted on each core wire, as a result of which the toothed belt was elongated to cause a positioning failure, resulting in incapability of practical use (rank D).
Comparative Example 3 was a toothed belt of 14 mm in teeth pitch P (i.e., the tooth scale was a little small) and lower than 1.85 kN/mm in belt strength. In this case, tooth chipping occurred early and a positioning failure occurred, resulting in incapability of practical use (rank D).
Examples 4 and 5 were toothed belts of the same in structure as that of Example 1 except that the pitch Pt of the core wires was changed (increased) to decrease the number of core wires buried in the toothed belt, and having the teeth pitch P of 20 mm (the tooth was of a large scale). Although the belt strength was lower than in Example 1 because the number of core wires was decreased, belt strength that was higher than or equal to 1.85 kN/mm was maintained even after running and was free of a defect such as “tooth chipping” or “tooth wear” and a positioning failure. As such, it was confirmed that they were capable of practical use (rank B).
Examples 6 to 8 were toothed belts of the same in structure as that of Example 1 except that the hardness of the material (polyurethane thermoplastic elastomer) constituting the toothed belt was changed, and having the teeth pitch P of 20 mm (the tooth was of a large scale). Example 8 in which the hardness was high (95°) was classified as rank A. However, since in the toothed belts being low in hardness, the teeth were prone to wear because of deformation of the teeth, Example 7 (85°) was classified as rank B and Example 6 (80°) was classified as rank C.
Example 9 was a toothed belt of the same in structure as that of Example 1 except that the polyurethane type which is the material (polyurethane thermoplastic elastomer) constituting the toothed belt was changed, and having the teeth pitch P of 20 mm (the tooth was of a large scale). This case was classified as rank A, like in Example 1.
Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and can be subjected to various design modifications without departing from the scope of the claims.
The toothed belt according to the present invention may be either an open-end belt or an endless belt. Furthermore, the toothed belt according to the present invention is not limited to be used in elevating transport machines and may be used in any machines.
The thermoplastic elastomer is not limited to a polyurethane thermoplastic elastomer and may be, for example, a polyester thermoplastic elastomer, a polystyrene thermoplastic elastomer, a polyolefin thermoplastic elastomer, a polyamide thermoplastic elastomer, a vinyl chloride thermoplastic elastomer, or the like, or a combination of two or more thereof.
The harness of the thermoplastic elastomer is not limited to 85 to 95° and may be out of this range.
The core wire is not limited to be constituted of a steel cord and may be constituted of, for example, a cord produced by twisting aramid fibers or carbon fibers.
A reinforcement cloth may be provided on the outer circumferential surface and/or the inner circumferential surface of the belt body.
The present application is based on Japanese Patent Application No. 2017-085025 filed on Apr. 24, 2017 and Japanese Patent Application No. 2018-079008 filed on Apr. 17, 2018, the disclosures of which are incorporated herein by reference.
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