Twisted string-shaped electric cable for underwater purpose

An electric cable includes at least one electric wire, and a plurality of string-shaped bodies each extending in a longitudinal direction of the electric cable and twisting with one another around the at least one electric wire being a core. The plurality of string-shaped bodies has connection parts twisting with one another excluding the at least one electric wire. The connection parts are connected to a frame of an underwater robot.

BACKGROUND

Technical Field

The present disclosure relates to an electric cable through which an electric current flows.

Description of the Related Art

There has been known an underwater robot that performs operations underwater. For example, as described in PTL 1, an underwater robot is connected with a control device on land through a cable and is remotely operated wiredly by the control device through this cable.

The cable in PTL 1 is composed of multiple optical fiber cords, multiple power wires, an anti-tensile body made of aramid fiber, a jelly-like admixture bonding all of these components together, and a sheath made of elastomer for buoyancy and protection. The optical fiber cord is composed of optical fiber, an anti-tensile body, a sheath, and a reinforce layer. With this composition, the cable has a high tensile strength while protecting its transmission path for power or signals.

CITATION LIST

SUMMARY

The present disclosure offers an electric cable, that protects its transmission path for signals or power and provides a high tensile strength as well as flexibility for free handling.

To fulfil the above-described technological requirements, one aspect of the disclosure provides an electric cable. The electric cable includes at least one electric wire, and a plurality of string-shaped bodies each extending in a longitudinal direction of the electric cable and twisting with one another around the at least one electric wire being a core. The plurality of string-shaped bodies has a connection part twisting with one another excluding the at least one electric wire. The connection part is connected to a frame of an underwater robot.

Another aspect of the disclosure provides an electric cable that includes a plurality of string-shaped structures each extending in a longitudinal direction of the electric cable and twisting with one another. Each of the plurality of string-shaped structures has a plurality of string-shaped bodies each extending in the longitudinal direction and twisting with one another. At least one of the plurality of string-shaped structures has an electric wire. The at least one of the plurality of string-shaped structure having the electric wire has a structure in which the plurality of string-shaped bodies twisting with one another around the electric wire being a core. The plurality of string-shaped bodies has a connection part twisting with one another excluding the electric wire. The connection part is connected to the frame of an underwater robot.

Further another aspect of the disclosure provides an electric cable that includes a plurality of string-shaped structures each extending in a longitudinal direction of the electric cable and twisting with one another. Each of the plurality of string-shaped structures has a plurality of string-shaped bodies each extending in the longitudinal direction and twisting with one another. Each of at least two of the plurality of string-shaped bodies has one electric wire. The string-shaped structure having the one wire has a structure in which the plurality of string-shaped bodies twisting with one another around the one electric wire being a core.

The present disclosure offers an electric cable, that protects its transmission path for signals or power and provides a high tensile strength as well as flexibility for free handling.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An electric cable of one aspect of the disclosure has a plurality of string-shaped structures each extending in the longitudinal direction and twisting with one another. Each of the plurality of string-shaped structures has a plurality of string-shaped bodies each extending in the longitudinal direction and twisting with one another. At least one of the plurality of string-shaped structures includes an electric wire through which an electric current flows, and the plurality of string-shaped bodies twist with one another around the electric wire being a core.

Such a configuration offers an electric cable, that protects its transmission path for signals or power and provides a high tensile strength as well as flexibility for free handling.

For example, two of the plurality of string-shaped structures have electric wires, and each of the two string-shaped structures has one electric wire. This allows the two electric wires to work as a twisted pair wire. Hence, the electric cable has high transmission characteristics.

The string-shaped body is made of a material with a density lower than that of water for example. This allows the electric cable to float in water, and thus to be handled freely in water.

The string-shaped body is made of polypropylene for example. Polypropylene has a density lower than that of water, and a lighter weight and a higher tensile strength than the other synthetic fiber materials. Accordingly, the electric cable floats in water for free handling in water, and is light for free handling on land as well. Furthermore, being made of polypropylene provides a higher tensile strength of the electric cable than a case where the string-shaped body is made of another synthetic-fiber material.

For example, the string-shaped body is formed of multiple fiber threads each extending in the longitudinal direction and twisting with one another. Such an electric cable provides a higher flexibility than a case where the string-shaped body is formed of a single wire, allowing the cable to be handled more freely.

An electric cable of one aspect of the disclosure includes an electric wire through which an electric current flows, and a plurality of string-shaped bodies each extending in the longitudinal direction and twisting with one another around the electric wire being a core.

Such a configuration offers an electric cable, that protects its transmission path for signals or power and provides a high tensile strength as well as flexibility for free handling.

Hereinafter, a detailed description is made of some embodiments with reference to the related drawings as appropriate. However, a detailed description more than necessary may be omitted, such as a description of a well-known item and a duplicate description for a substantially identical component, to avoid an unnecessarily redundant description and to allow those skilled in the art to easily understand the following description.

Note that the inventors provide accompanying drawings and the following description for those skilled in the art to well understand the disclosure and do not intend that the drawings and the description limit the subjects described in the claims.

FIG. 1illustrates an electric cable according to one exemplary embodiment, in a stored state.FIG. 2illustrates a configuration of the electric cable.FIG. 3is a sectional view of the electric cable ofFIG. 2, taken along line3-3.

As shown inFIG. 1, electric cable10in this embodiment is rope-like and flexible enough to be wound around reel100with a small external diameter, and is stored in a state wound around reel100. Electric cable10is partly drawn out from reel100for use.

Concretely, as shown inFIG. 2, electric cable10includes three string-shaped structures12A through12C each extending in the longitudinal direction and twisting with one another. The term “the longitudinal direction” in this description refers to the longitudinal direction of electric cable10, namely the extending direction indicated by arrow L inFIG. 2.

In this embodiment, three string-shaped structures12A through12C twist with one another, and concretely the respective structures extend in the longitudinal direction in a coil form and intertwine with one another. Accordingly, electric cable10is like a three-strand rope.

Each of string-shaped structures12A through12C includes a plurality of string-shaped bodies14each extending in the longitudinal direction and twisting with one another. In this embodiment, each of string-shaped structure12A and12B has six string-shaped bodies14each extending in the longitudinal direction in a coil form and intertwining with one another (like a six-strand rope). String-shaped structure12C has seven string-shaped bodies14each extending in the longitudinal direction in a coil form and intertwining with one another.

In this embodiment, string-shaped body14is made of a material with a density lower than that of water (the reason is described later). In other words, string-shaped body14is made of a material that floats in water. String-shaped body14is made of polypropylene or polyethylene for example. Polypropylene that is light in the weight per unit length and has a high tensile strength and insulation is favorable as a material of string-shaped body14.

String-shaped body14itself may be formed of one fiber thread with a large diameter, or multiple fiber threads with a small diameter each extending in the longitudinal direction and twisting with one another, where the latter has a higher flexibility. For a string-shaped body of multiple fiber threads, they may be either synthetic fiber (e.g., polypropylene) or natural fiber (e.g., hemp).

If string-shaped body14is formed of multiple fiber threads twisting with one another, electric cable10has a characteristic just like a rope. More specifically, string-shaped structures12A through12C correspond to strands of a rope, and string-shaped body14corresponds to yarn of the rope. Hence, if fiber threads forming string-shaped body14is the same as those forming yarn of a rope, electric cable10has a tensile strength and flexibility substantially same as those of the rope. For example, if the fiber thread is made of polypropylene, electric cable10with diameter D1of 9 mm has a tensile strength of approximately 11 kN, like a polypropylene rope with the same diameter.

As shown inFIG. 2, string-shaped structures12A and12B are formed of a plurality of string-shaped bodies14twisting with one another around electric wires16A and16B (through which an electric current flows) being cores. More specifically, at the centers of string-shaped structure12A and12B, electric wires16A and16B respectively extend in the longitudinal direction. Each of a plurality of string-shaped bodies14extend in the longitudinal direction in a coil form with each of electric wires16A and16B being a center. Consequently, electric wires16A and16B are protected by a plurality of string-shaped bodies14. As shown inFIGS. 2 and 3, string-shaped structure12C has string-shaped body14, instead of an electric wire, as a core at the center, and is formed of six string-shaped bodies14twisting with one another around string-shaped body14. String-shaped structures12A through12C are approximately the same in diameter. Here, string-shaped structure12C may be formed of seven string-shaped bodies14.

Electric wires16A and16B of string-shaped structures12A and12B include conducting wire18through which an electric current flows, namely through which signals or power are transmitted, and coating cover20that coats conducting wire18for protection. Conducting wire18is made of a conductive material with a high flexibility, such as copper. Coating cover20is made of polyethylene with a high flexibility and insulation.

Electric cable10of the configuration above protects electric wires16A and16B, which are a transmission path for signals or power, and provides a high tensile strength as well as flexibility for free handling.

In other words, electric cable10plays a role of transmitting signals or power through electric wires16A and16B. Electric cable10has functions substantially the same as those of a rope by means of a plurality of string-shaped bodies14composing string-shaped structures12A through12C by twisting respectively with a plurality of string-shaped structures12A through12C twisting with one another. Accordingly, electric cable10has a tensile strength substantially equivalent to that of a rope, and is flexible enough to be handled freely like a rope.

Electric wires16A and16B of string-shaped structures12A and12B function as a twisted pair wire with high transmission characteristics in transmitting high-frequency signals (e.g., differential signals).

Concretely, each of string-shaped structures12A and12B extends in the longitudinal direction in a coil form and intertwining with the other, and so does each of internal electric wires16A and16B. Thus, electric wires16A and16B form a twisted pair wire. Accordingly, electric wires16A and16B are less subject to the influence of noise than a parallel wire in transmitting signals.

As shown inFIG. 3, a plurality of string-shaped bodies14winds around each of electric wires16A and16B. Further, string-shaped structure12A having electric wire16A and string-shaped structure12B having electric wire16B are twisted with each other. Accordingly, distance D2between electric wires16A and16B is approximately equal to the diameter of string-shaped structures12A and12B, and is approximately uniform regardless of the position in the extending direction of electric cable10. Furthermore, however electric cable10is bent, the distance between electric wires16A and16B hardly changes. In other words, the stray capacitance between electric wires16A and16B hardly changes. Hence, however electric cable10is bent, the transmission characteristics of electric wires16A and16B hardly change. Consequently, electric wires16A and16B function as a twisted pair wire with high transmission characteristics.

Regarding the above, electric cable10in this embodiment is used with part of it wound around reel100as shown inFIG. 1. That is, an electric current flows through the part wound around reel100as well. When electric cable10is wound around reel100, stray capacitance occurs between two parts of a twisted pair wire (i.e., electric wires16A and16B) adjacent to each other on reel100. As shown inFIG. 1, however, electric cable10closely wound around reel100causes the distance between two parts of a twisted pair wire adjacent to each other to be kept approximately equal to diameter D1of electric cable10, which suppresses variations in the stray capacitance between the parts. Consequently, a twisted pair wire inside electric cable10, even if part of electric cable10is wound around reel100, can transmit signals in a stable state of the transmission characteristics.

From here, a description is further made of the functions of electric cable10according to this embodiment referring to its examples of use.

As shown inFIG. 4, underwater robot102, a robot that inspects underwater structures such as a dam and a waterway, is connected to control device104through electric cable10according to the embodiment. Reel100that winds and stores electric cable10and control device104are placed aboard ship106.

Underwater robot102includes lighting unit108illuminating the inside of water, camera110for photographing, thruster112for moving underwater robot102in water, control board116, and frame118as a housing of underwater robot102. Control board116transmits control signals from control device104to lighting unit108, camera110for photographing, and thruster112. This underwater robot102has battery114aboard. For this reason, electric cable10of this example does not transmit power as energy for driving underwater robot102.

Electric cable10connects ship106(control device104) with underwater robot102mechanically and electrically. To mechanically connect electric cable10with ship106and underwater robot102, electric wires16A and16B are separated from electric cable10at the two ends of electric cable10, and the two ends where electric wires16A and16B are not provided are respectively connected to the body of ship106and frame118of underwater robot102. The ends of electric wires16A and16B separated from electric cable10close to reel100are connected to control device104; the ends of electric wires16A and16B close to underwater robot102are connected to control board116of underwater robot102.

Concretely, electric wires16A and16B and six string-shaped bodies14are separated from each other at the two ends of string-shaped structures12A and12B. Each of six string-shaped bodies14where electric wires16A and16B are separated from string-shaped structures12A and12B are twisted with one another to newly form two string-shaped structures where electric wires16A and16B are not provided. The two new string-shaped structures and string-shaped structure12C are twisted with one another to form parts where electric wires16A and16B are not provided at the two ends of electric cable10. Then, the parts where electric wires16A and16B are not provided are respectively connected to the body of ship106and frame118of underwater robot102. The ends of electric wires16A and16B separated are respectively connected to control device104and control board116of underwater robot102.

Connecting in this way prevents a tensile force produced when electric cable10is wound around reel100to pull up underwater robot102from underwater from exerting on electric wires16A and16B.

Control signals are transmitted from control device104to underwater robot102through electric cable10(its electric wires16A and16B). For example, a signal for adjusting the amount of light of lighting unit108, a signal for controlling photographing of camera110, and a signal for controlling output of thruster112are transmitted from control device104to underwater robot102through electric cable10.

Data signals are transmitted from underwater robot102to control device104through electric cable10. For example, image data photographed by camera110and information about the remaining amount of battery114are transmitted as signals from underwater robot102to control device104through electric cable10.

As described above, string-shaped body14of electric cable10is made of a material (e.g., polypropylene) with a density lower than that of water. Hence, even if electric wires16A and16B have a density higher than that of water, the density of entire electric cable10can be made lower than that of water, resulting in electric cable10floating in water.

Concretely, as shown inFIG. 5, if underwater robot102is connected to electric cable510, which is a comparative example, having a density higher than that of water, electric cable510hangs down from underwater robot102, which can cause electric cable510to contact water bottom B. For example, electric cable510can tangle in an obstacle on water bottom B, interfering with inspection by underwater robot102or retrieval of such underwater robot102.

In this way, when used underwater, electric cable10floats in water to allow it to be handled more freely.

Besides, electric cable10can be handled freely like a rope as described above. More specifically, electric cable10bends with a small curvature radius because of its high flexibility. Hence, underwater robot102is not limited in its action by electric cable10, thus freely moving underwater. Further, such electric cable10can be stored in a small space. For example, as in this embodiment, electric cable10can be stored in a state wound around small reel100.

Furthermore, electric cable10has a high tensile strength substantially the same as that of a rope as described above. Concretely, if electric cable10has an external diameter same as that of a rope and the material of string-shaped body14is the same as that of the rope, electric cable10has a tensile strength substantially the same as the rope. Consequently, electric cable10can be used for retrieving underwater robot102in water.

With the embodiment described above, electric cable10protects electric wires16A and16B as a transmission path for signals or power and provides a high tensile strength as well as flexibility for free handling.

Note that the present disclosure is not limited to the embodiment described above. For example, electric cable10of the embodiment described above is formed of three string-shaped structures12A through12C twisting with one another as shown inFIG. 3; besides, two, or four or more, string-shaped structures may be used. It is only required that two or more string-shaped structures are used in order for them to twist with one another. The number of string-shaped structures may be changed in response to a tensile strength required for electric cable10.

In the embodiment described above, as shown inFIG. 3, string-shaped structures12A through12C include six string-shaped bodies14twisting with one another; however, it is only required that two or more string-shaped bodies are used for one string-shaped structure. That is, the number of string-shaped bodies for one string-shaped structure may be changed in response to a tensile strength required for electric cable10.

Furthermore, in the embodiment described above, each of string-shaped structures12A and12B has one electric wire16A and one electric wire16B as shown inFIG. 3, but other cases are accepted. For example, electric cable210according to another embodiment shown inFIG. 6is formed of multiple (three) string-shaped structures212A through212C twisting with one another, and string-shaped structure212A, one of them, is provided with multiple (two) electric wires16A and16B. Electric wires16A and16B are twisted with one another to form a core and are protected by nine string-shaped bodies14twisted with one another around the core as shown inFIG. 6. The core of string-shaped structure212A, formed of two electric wires16A and16B, has a core diameter substantially larger than those of string-shaped structures12A through12C. Accordingly, each of string-shaped structures212B and212C has string-shaped body15with a diameter larger than that of string-shaped body14at the core and nine string-shaped bodies14twisted with one another around the core. Accordingly, three string-shaped structures212A through212C are formed with their diameters substantially equal to one another.

All of the plurality of string-shaped structures may be provided with electric wires. Instead, the number of electric wires included in electric cable10may be changed. For example, underwater robot102of the embodiment described above is controlled by control signals from control device104through control board116. Alternatively, underwater robot102may be controlled by control device104, not through control board116, by connecting the electric wires included in electric cable10directly to thruster112for example to transmit control signals. In this case, the number of electric wires included in electric cable10can be increased in response to the number of devices (e.g., thruster112) controlled by control device104.

In the embodiment described above, electric wires16A and16B of electric cable10are used as a signal line for transmitting signals to underwater robot102; however, may be used otherwise. For example, electric wires16A and16B may be used as a power line for supplying power. In this case, the number and thickness of electric wires provided in string-shaped structures may be changed in response to an application purpose of electric cable10. For example, in electric cable210shown inFIG. 6, string-shaped bodies15positioned at the centers of string-shaped structures212B and212C can be respectively replaced with electric wires17B and17C to transmit control signals using electric wires16A and16B of string-shaped structure212A as well as to supply power using electric wires17B and17C.

Additionally, electric cable10in the embodiment described above is used for underwater robot102that freely moves in water as shown inFIG. 4, and thus its string-shaped body14is made of a material (e.g., polypropylene) with a density lower than that of water; however, another material may be used. For example, if the electric cable is not to be used in water, its string-shaped body may have a density higher than that of water.

Note that, as shown inFIG. 7, the electric cable may be electric cable310that includes electric wires16A and16B through which an electric current flows and a plurality of string-shaped bodies14extending in the longitudinal direction and twisting with one another with electric wires16A and16B being a core. That is, electric cable310corresponds to string-shaped structure212A of electric cable210shown inFIG. 6. Even such electric cable310protects electric wires16A and16B as a transmission path for signals or power and provides a high tensile strength as well as flexibility for free handling.

Then, how to twist a plurality of string-shaped structures, a plurality of string-shaped bodies, and multiple fiber threads (if the string-shaped bodies are formed of multiple fiber threads twisting with one another) is not limited. For example, the plurality of string-shaped bodies may be twisted in an eight-strand rope. Here, the plurality of string-shaped structures, the inside of which electric wires extend, are favorably twisted in a three-strand rope as shown inFIG. 2. This is because string-shaped structures complicatedly twisted can break the internal electric wires.

In the embodiment described above, electric cables10,210, and310are connected to underwater robot102; however, the connection destination of them is not limited to underwater robot102. For example, they can be connected to a flight vehicle for inspecting external walls exposed from the water surface of a bridge pier and a dam for example.

Hereinbefore, the description is made of some embodiments for exemplification of the technologies in the disclosure. For this purpose, detailed descriptions and accompanying drawings are provided. Accordingly, some components described in the detailed descriptions and accompanying drawings may include, besides what is essential for solving problems, what is not essential in order to exemplify the above-described technologies. Hence, the fact that such inessential components are included in the detailed descriptions and accompanying drawings does not mean that such inessential components are immediately acknowledged as essential.

The above-described embodiments are for exemplification of the technologies in the disclosure. Hence, the embodiments may undergo various kinds of change, substitution, addition, and/or omission within the scope of the claims and their equivalent technology.

INDUSTRIAL APPLICABILITY

An electric cable of the present disclosure is applicable to an electric cable that transmits signals or power.