Patent Application
20220084719
The present application is based on Japanese patent application No.2020-154657 filed on Sep. 15, 2020, the entire contents of which are incorporated herein by reference.
The present invention relates to a cable.
In order to enhance productivity in a factory or the like, the widespread use of industrial robots such as cooperative robots or small articulated robots or the like is expanding. As an example of a cable being used to be wired to a movable part (a part to be subjected to bending or torsion) of such an industrial robot, there is a cable having a braided shield composed of a plurality of metal wires braided together, and a sheath, which in turn have been provided over a periphery of a cable core composed of a plurality of electrical insulated wires stranded together. (See, e.g., JP2015-79574A below.)
[Patent Document 1] JP2015-79574A
In the above mentioned conventional cable wired to the movable part of the industrial robot and the like, however, there has been a problem with a disordered state being caused in the plurality of metal wires of the braided shield by repeated bending of the same cable resulting from the movements of the movable part of the industrial robot and the like, and a subsequent wire break being caused in the plurality of metal wires of the braided shield by more repeated bending of the same cable. The occurrence of the wire break in the plurality of metal wires of the braided shield leads to a degradation in the function of the braided shield acting as a shielding layer.
In light of the foregoing, it is an object of the present invention to provide a cable which is designed to be resistant to the occurrence of a wire break in a plurality of metal wires together constituting a braided shield, when repeatedly bent.
For the purpose of solving the aforementioned problem, the present invention provides a cable, comprising:
According to the present invention, it is possible to provide the cable which is designed to be resistant to the occurrence of a wire break in a plurality of the metal wires together constituting the braided shield, when repeatedly bent.
Next, preferred embodiment according to the present invention will be described with reference to appended drawings, wherein:
An embodiment of the present invention will be described below in conjunction with the accompanying drawings.
The cable 1 is configured in such a manner as to include a cable core 3 having one or more electric wires 2, a braided shield 6, which is covering a periphery of the cable core 3 and including braided metal wires, and a sheath 7, which is covering a periphery of the braided shield 6. In the cable 1 according to the present embodiment, a cushion layer (also referred to as wire break suppressing layer) 5, which is configured to suppress the occurrence of a wire break in the metal wires together constituting the braided shield 6 when the cable 1 is repeatedly bent, is provided between the cable core 3 and the braided shield 6. The detail of the cushion layer 5 will be described later.
The one or more electric wires 2 together constituting the cable core 3 each of which has a conductor 21, and an electrical insulating member 22, which is covering a periphery of the conductor 21. Each of the constituent conductors 21 of the one or more electric wires 2 is composed of a stranded wire conductor produced by stranding together metal wires each made of a tin-plated annealed copper wire or the like. Each of the constituent conductors 21 of the one or more electric wires 2 may be configured with a composite stranded wire produced by using child stranded wires each composed of metal wires stranded together and further stranding a plurality of the child stranded wires together. For the constituent electrical insulating members 22 of the one or more electric wires 2, it is possible to use, e.g., an electrical insulating material made of polyethylene or fluoropolymer resin.
In the present embodiment, the cable core 3 is configured by providing a fibrous filling member 8 composed of rayon yarns (staple fiber yarns) or the like over a center of the cable 1, and stranding a plurality (herein six) of the electric wires 2 together on a periphery of that filling member 8. It should be noted, however, that the configuration of the cable core 3 is not limited to the foregoing, but that the cable core 3 may be configured in such a manner that in place of the fibrous filling member 8, e.g., a linear shape body, a tension member, or the like made of a resin or the like may be provided over the center of the cable 1. Further, the number of electric wires 2 together constituting the cable core 3 is also not limited to the one shown in
A binder tape 4 is helically wrapped around a periphery of the cable core 3. The binder tape 4 acts to hold the strands of the cable core 3 so that the strands of the cable core 3 are not unlaid. For the binder tape 4, it is possible to use, e.g., a tape made of a paper or a nonwoven fabric cloth or the like, or a resin tape made of PE (polyethylene) or the like. Although the details will be described later, because it has been able to be confirmed that when the cable 1 has repeatedly been bent, the occurrence of a disordered state in the metal wires of the braided shield 6 has been able to be suppressed by using the resin tape rather than by using the nonwoven fabric cloth tape, the resin tape may more preferably be used as the binder tape 4. Note that the binder tape 4 is not indispensable, but that it is substitutable by e.g., a thread-like body made of a resin or a cotton or the like being wrapped around the periphery of the cable core 3.
The braided shield 6 acts as a shielding layer to provide a shield against noise coming from outside, and is covering the periphery of the cable core 3. For the cable 1, configuring its shielding layer with the braided shield 6 enables the flexibility of the cable 1 to be enhanced. In the present embodiment, the cushion layer 5 is provided on a periphery of the binder tape 4, and the braided shield 6 is provided on a periphery of the cushion layer 5. Although herein the braided shield 6 constituted by the metal wires braided together is used, the configuration of the braided shield 6 is not limited to the foregoing, but for the braided shield 6, it is also possible to use, for example, a mixed woven braided shield which is produced by weaving metal wires and constituent resin wires made of a resin, such as rayon yarns (staple fiber yarns) or the like, together into a braid. Further, for the metal wires using the braided shield 6, it is also possible to use, for example, a metal wire coated with a lubricating material such as a liquid paraffin or the like. This makes it possible to further suppress the occurrence of an abrasion together of the braided shield 6 and the cushion layer 5. Note that the braid density of the braided shield 6 may be set at not lower than 85 percent, from the point of view of providing a shield against noise coming from outside. For the metal wires together constituting the braided shield 6, it is possible to use, e.g., a tin-plated annealed copper wire.
The sheath 7 is provided over a periphery of the braided shield 6, and acts to protect the braided shield 6 and the cable core 3. The sheath 7 may be configured in such a manner as to be made of, e.g., polyvinyl chloride resin, urethane resin, fluoropolymer resin, fluorine rubber, or the like, or may be configured as the one made of a resin composition containing at least one of these types of resins as a main component (base polymer).
The cushion layer 5 is provided between the cable core 3 and the braided shield 6 (more specifically, between the binder tape 4 and the braided shield 6), and when the cable 1 is bent (especially, when the cable 1 is subjected to repeated sliding movements in a state of being bent in a U-shape), the cushion layer 5 acts to mitigate a lateral pressure applied to the braided shield 6 by the cable core 3 in the bent portion of the cable 1. By allowing the cushion layer 5 to mitigate the lateral pressure applied by the cable core 3 to the braided shield 6, when the cable 1 is repeatedly bent (especially when the cable 1 is subjected to repeated sliding movements in a state of being bent in a U-shape), it is possible to suppress the occurrence of a disordered state in the braid of the metal wires together constituting the braided shield 6, and therefore the metal wires of the braided shield 6 become resistant to abrading each other and, as a result, it is possible to prevent the wire break in the metal wires of the braided shield 6 from being caused by the abrasion together of the metal wires of the braided shield 6. Note that the thickness of the cushion layer 5 may be set at such a thickness as to be able to mitigate the lateral pressure applied from the cable core 3 to the braided shield 6 when the cable 1 is bent, and thereby suppress the occurrence of a wire break in the metal wires together constituting the braided shield 6.
It is also conceivable that the cable 1 is configured in such a manner that, for example, a tape material, which is high in cushioning performance, is used for the binder tape 4 so that the binder tape 4 is used as a substitute for the cushion layer 5 (that is, it is conceivable that the cable 1 is configured in such a manner that the binder tape 4 and the braided shield 6 are brought into contact with each other with no cushion layer 5 being provided between the binder tape 4 and the braided shield 6), but in this case, since the tape material for the binder tape 4 is resistant to following the movement of the braided shield 6, the tape material for the binder tape 4 and the braided shield 6 are rubbed against each other when the cable 1 is repeatedly bent. Further, at this point of time, the occurrence of such a rubbing together of the tape material for the binder tape 4 and the braided shield 6 in an uneven portion of the tape material for the binder tape 4 causes a disordered state in the metal wires of the braided shield 6, which leads to concern that a wire break may occur in the metal wires of the braided shield 6.
Further, it is also conceivable that the cable 1 is configured in such a manner that, for example fiber yarns such as rayon yarns (staple fiber yarns) or the like are wound laterally (wrapped side by side) around the periphery of the binder tape 4 by being helically wound therearound, so that the laterally wound fiber yarns together constitute the cushion layer 5. In this case, however, a misalignment or an overlapping between the side by side fiber yarns together constituting the cushion layer 5 occurs when the cable 1 is repeatedly bent, accompanied by a collapsing in the shape of the cushion layer 5, which leads to concern that the cushioning function of the cushion layer 5 may not be fulfilled.
For the purpose of avoiding the foregoing problems, in the present embodiment, the cushion layer 5 is configured with a braided layer, which is constituted by linear shape fiber yarns braided together. By the cushion layer 5 being configured with the above braided layer constituted by linear shape fiber yarns braided together, when the cable 1 is repeatedly bent, the above configuration of the cushion layer 5 allows the cushion layer 5 to easily follow the movement of the braided shield 6, and the rubbing (sliding) of the braided shield 6 and the cushion layer 5 relative to each other to be minimized and, as a result, it is possible to suppress the occurrence of an abrasion together of the metal wires of the braided shield 6. In the present embodiment, rayon yarns (staple fiber yarns) are used as the fiber yarns together constituting the cushion layer 5. It should be noted, however, that the fiber yarns together constituting the cushion layer 5 are not limited to the foregoing rayon yarns (staple fiber yarns), but that the fiber yarns together constituting the cushion layer 5 may be configured as the ones made of a material designed to suppress the occurrence of a wire break in the metal wires together constituting the braided shield 6, and that for the fiber yarns together constituting the cushion layer 5, it is also possible to use, for example, a nylon yarn or a cotton yarn or the like.
When the rayon yarns (staple fiber yarns) are used as the fiber yarns together constituting the cushion layer 5, the rayon yarns (staple fiber yarns) may be composed of the following type: single yarns or two-ply yarns with a yarn count of from 10 to 60. Preferably, for the rayon yarns (staple fiber yarns), the two-ply yarns with a yarn count of 10, 20, 40, or 60, or the single yarns with a yarn count of 10, or 20 may be used. Further, from the point of view of suppressing the occurrence of a wire break in the fiber yarns together constituting the cushion layer 5, the fiber yarns are configured to preferably have a tensile strength of not lower than 2.5 N and an elongation of not lower than 10 percent. The tensile strengths and the elongations of the fiber yarns can be obtained by using a testing method in compliance with Section 9.5.1 of JIS L 1095 (2010).
Note that the cable 1 may be configured to allow the cushion layer 5 not to completely follow the movement of the braided shield 6 when the cable 1 is repeatedly bent, but that the cable 1 may be configured to allow a slight sliding of the cushion layer 5 and the braided shield 6 relative to each other to occur. For example, if the fiber yarns together constituting the cushion layer 5 and the metal wires together constituting the braided shield 6 are stuck together to cause a disruption to the sliding of the braided shield 6 relative to the cushion layer 5, then a load is applied to the constituent fiber yarns of the cushion layer 5 and the metal wires of the braided shield 6, which leads to concern that a failure such as a wire break or the like in the metal wires of the braided shield 6 may occur. For the purpose of avoiding the foregoing problem, in the present embodiment, the cable 1 may be configured in such a manner that an angle formed by the fiber yarns in the cushion layer 5 with respect to the longitudinal direction of the cable 1 is made smaller than an angle formed by the metal wires of the braided shield 6 with respect to the longitudinal direction of the cable 1. This makes the metal wires of the braided shield 6 resistant to being stuck in the constituent fiber yarns of the cushion layer 5 and, as a result, the sliding of the braided shield 6 relative to the cushion layer 5 is enhanced. The angle formed by the fiber yarns in the cushion layer 5 with respect to the longitudinal direction of the cable 1 is set at, for example, not smaller than 15 degrees and not greater than 30 degrees. In addition, the angle formed by the metal wires in the braided shield 6 with respect to the longitudinal direction of the cable 1 is set at, for example, not smaller than 35 degrees and not greater than 60 degrees.
Further, if the braided constituent fiber yarns of the cushion layer 5 are too low in their braid density, their stitch length is long, which leads to concern that the metal wires of the braided shield 6 may easily get stuck in the constituent fiber yarns of the cushion layer 5. For that reason, the braid density of the cushion layer 5 is preferably set at not lower than 85 percent. By setting the braid density of the cushion layer 5 at not lower than 85 percent, the irregularities on the surface of the cushion layer 5 are reduced to a substantially smoothed surface state and, as a result, it is possible to further enhance the sliding of the braided shield 6 relative to the cushion layer 5. In particular, it is preferable that the braid density of the cushion layer 5 is made higher than the braid density of the braided shield 6. More specifically, the braid density of the cushion layer 5 may be made higher than the braid density of the braided shield 6, in a range of the braid density of the braided shield 6 of not lower than 85 percent and in a range of the braid density of the cushion layer 5 of not lower than 90 percent.
Note that in the present embodiment, the cable 1 is configured in such a manner that the cushion layer 5 and the braided shield 6 are in direct contact with each other, but that the cable 1 may be configured in such a manner that a separate member is interposed between the cushion layer 5 and the braided shield 6. For example, the cable 1 may be configured in such a manner that a tape member such as a resin tape or the like is wrapped around the periphery of the cushion layer 5, followed by the braided shield 6 being provided on a periphery of that tape member.
The cables 1 in Examples 1, 2, and 3 were prototyped, and a U-shape bending test was conducted thereon. In the cable 1 of Example 1, the binder tape 4 was configured with a nonwoven fabric cloth tape, while in the cable 1 of Example 2, the binder tape 4 was configured with a resin tape made of PE (polyethylene). Also, the cable 1 of Example 3 was configured by omitting the binder tape 4 and wrapping a thread-like body around the periphery of the cable core 3 instead, and was configured by wrapping a resin tape made of PE (polyethylene) around the periphery of the cushion layer 5, followed by providing the braided shield 6 on the periphery of that resin tape. In each of Examples 1, 2, and 3, a P/Pd ratio, which referred to a ratio of a twist pitch P of the cable core 3 to a diameter Pd of a circle passing through centers of the respective six constituent electric wires 2 of the cable core 3, was set at 12. Further, in each of Examples 1, 2, and 3, the angle of the respective metal wires in the braided shield 6 with respect to the longitudinal direction of the cable 1 was set at 50 degrees, while the angle formed by the respective constituent fiber yarns in the cushion layer 5 with respect to the longitudinal direction of the cable 1 was made smaller than 50 degrees. Further, in each of Examples 1, 2, and 3, the braid density of the cushion layer 5 was set at not lower than 90 percent, while the braid density of the braided shield 6 was set at not lower than 85 percent, and the braid density of the cushion layer 5 was made higher than the braid density of the braided shield 6.
In the U-shape bending test, as shown in
As a result of the U-shape bending test, in the cables 1 in Examples 1, 2, and 3, no rupture occurred, even when the cables 1 in Examples 1, 2, and 3 were subjected to 27000 times repeated bending. Further, as a result of observing the states of the respective braided shields 6 of the cables 1 in Examples 1, 2, and 3 after having been subjected to the 27000 times repeated bending, it was confirmed that substantially no disordered state was being caused in the braids of the metal wires together constituting the respective braided shields 6 (the disordered states in the metal wires of the respective braided shields 6 were negligible), and that no wire break (rupture) in the metal wires of the respective braided shields 6 due to the disordered states therein was being caused as well. Further, as a result of the U-shape bending test, it was confirmed that among the cables 1 in Examples 1, 2, and 3, the cable 1 in Example 2 using the resin tape made of the PE (polyethylene) as the binder tape 4 was in the most negligible disordered state in the braid of the metal wires together constituting the braided shield 6. In
Also, a cable of a comparative example was made that was the same in configuration as the cable 1 of Example 1 except that the cushion layer 5 was omitted, and the U-shape bending test was conducted in the same manner as in Examples 1, 2, and 3. As a result of that U-shape bending test, in the cable of the comparative example, a rupture occurred at a stage at which that cable was subjected to about 3000 times repeated bending. In
Note that in Example 3, the resin tape was being provided between the cushion layer 5 and the braided shield 6, but that the cable 1 of Example 3 achieved the U shape bending test result analogous to those of Examples 1 and 2 which were not being provided with that resin tape between the cushion layer 5 and the braided shield 6. That is, it was able to be said that even when the resin tape was being interposed between the cushion layer 5 and the braided shield 6, the cushion layer 5 was mitigating the lateral pressure applied by the cable core 3 to the braided shield 6 when the cable 1 was bent. It was able to be said that from the point of view of cost reduction by reducing the number of parts, it was desirable to omit the resin tape between the cushion layer 5 and the braided shield 6, and that it was more desirable that the cushion layer 5 and the braided shield 6 were in direct contact with each other.
As described above, the cable 1 according to the present embodiment is configured in such a manner as to include therein the cushion layer 5 provided between the cable core 3 and the braided shield 6, and the cushion layer 5 is composed of a braid including braided the constituent linear shape fiber yarns together.
The cushion layer 5 is moved in such a manner as to be interlocked with (in such a manner as to follow) the braided shield 6 when the cable 1 is bent, and acts to mitigate the stress (the lateral pressure) applied from the cable core 3 to the metal wires of the braided shield 6 when the cable 1 was bent. Thus, when the cable 1 is repeatedly bent, the cushion layer 5 is able to suppress the occurrence of a disordered state in the braid of the metal wires of the braided shield 6 and, as a result, it is possible to achieve the cable 1, which is resistant to the occurrence of a wire break in a plurality of the metal wires together constituting the braided shield 6, even when the cable 1 was bent. That is, according to the present embodiment, it is possible to achieve the cable 1 designed for a movable part, which is high in bending resistance, and which is greatly enhanced in lifetime.
Further, by the cushion layer 5 being provided between the cable core 3 (the one or more electric wires 2) and the braided shield 6 (more specifically, between the binder tape 4 and the braided shield 6), the cushion layer 5 is able to protect the cable core 3 from being damaged by the braided shield 6. If the cushion layer 5 is not provided between the cable core 3 (the one or more electric wires 2) and the braided shield 6 (more specifically, between the binder tape 4 and the braided shield 6), then there is concern that during the repeated bending of the cable 1, the binder tape 4 and the respective constituent electrical insulating members 22 of the one or more electric wires 2 may be abraded due to the abrasion together of the binder tape 4 and the braided shield 6, and the abrasion together of the respective constituent electrical insulating members 22 of the one or more electric wires 2 and the braided shield 6, but by the cushion layer 5 being provided between the cable core 3 (the one or more electric wires 2) and the braided shield 6 (more specifically, between the binder tape 4 and the braided shield 6), the cushion layer 5 is also able to suppress the occurrence of the above failures.
Note that in the case where the cable core 3 is configured by stranding a plurality of the electric wires 2 together, the load applied to the braided shield 6 by the cable core 3 is considered to become large due to the influence of the irregularities on the surface of the cable core 3, as compared with the case where the cable core 3 is configured with one electric wire 2. The present invention is especially effective in the above case, that is, in the case where the cable core 3 is configured by stranding a plurality of the electric wires 2 together.
Next, the technical ideas grasped from the aforementioned embodiments will be described with the aid of the reference characters and the like in the embodiments. It should be noted, however, that each of the reference characters and the like in the following descriptions is not to be construed as limiting the constituent elements in the appended claims to the members and the like specifically shown in the embodiments.
[1] A cable (1), comprising: a cable core (3) including one or more electric wires (2); a braided shield (6) covering a periphery of the cable core (3) and including braided metal wires (2); a sheath (7) covering a periphery of the braided shield (6); and a cushion layer (5) provided between the cable core (3) and the braided shield (6), the cushion layer (5) comprising a braid including braided linear shape fiber yarns.
[2] The cable (1) as defined in the above [1], wherein the cable core (3) comprises a plurality of the electric wires (2) stranded together.
[3] The cable (1) as defined in the above [1] or [2], wherein the fiber yarns constituting the cushion layer (5) are composed of rayon yarns (staple fiber yarns).
[4] The cable (1) as defined in any one of the above [1] to [3], wherein an angle formed by the fiber yarns of the cushion layer (5) with respect to a longitudinal direction of the cable (1) is smaller than an angle formed by the metal wires of the braided shield (6) with respect to the longitudinal direction of the cable (1).
[5] The cable (1) as defined in any one of the above [1] to [4], wherein the cushion layer (5) comprises a braid density of not lower than 85 percent.
Although the embodiments of the present invention have been described above, the aforementioned embodiments are not to be construed as limiting the inventions according to the appended claims. Further, it should be noted that not all the combinations of the features described in the embodiments are indispensable to the means for solving the problem of the invention. Further, the present invention can appropriately be modified and implemented without departing from the spirit of the present invention.
Although the invention has been described with respect to the specific embodiments for complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art which fairly fall within the basic teaching herein set forth.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-154657 | Sep 2020 | JP | national |
