JPS5953771B2 - Tension adjustment device for submarine cables, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tension adjustment device that is mounted on a laying ship and adjusts the tension applied to a submarine cable or the like in order to safely and accurately lay or pull up the submarine cable.

Figure 1 shows an outline of a laying ship equipped with a submarine cable laying machine.

A submarine cable laying machine 2 is mounted on a laying ship 1, and a submarine cable 3 is laid in the sea or lifted out of the sea by this laying machine 2 via a rotatable sheave 4 fixed to the bow or stern of the ship. .

This figure shows the case where the cable is installed.

By the way, when laying or pulling up the submarine cable 3,
Sea swells 5 cause the cable laying ship 1 to pitch vertically (arrow A in the drawing), and the submarine cable 3
A fluctuating tension is applied to the

If the period of this fluctuating tension is synchronized with the natural period of the submarine cable being laid, it will become very large and may cause the submarine cable 3 to break.

As an example of such a problem, Fig. 2 shows an example of an outer diameter of approximately 1
Laying ship 1 pitching a submarine cable 3 with a diameter of 1 mm and an underwater weight of 0.7 kg/m at a period of 6 seconds and an amplitude of 1.5 m.
The results of estimating the relationship between the water depth and the variable tension of a submarine cable when it is installed in

According to this, when the submarine cable 3 is laid on the seabed at a depth of about 1000 m at a ship speed of 8 knots, a very large tension fluctuation is applied to the submarine cable 3 due to the pitching motion of the laying ship 1 and resonance with the submarine cable 3. It is expected that even at a boat speed of 4 knots, a fluctuating tension of about 0.5 tons will be applied at a depth of 1,500 m.

In order to alleviate this fluctuating tension, conventionally, the laying speed of the submarine cable 3 has been adjusted by increasing or decreasing the laying speed of the submarine cable 3 using the laying machine 2 in accordance with the pitching cycle of the laying ship 1.

On the other hand, in order to accurately lay the submarine cable 3 along the seabed surface 6, it is necessary to lay the submarine cable 3 at a preset speed.

However, according to the conventional method of alleviating the fluctuating tension described above, the speed of the submarine cable 3 must be increased or decreased in accordance with the pitching period of the laying vessel 1, and the inertia of the laying machine 2 is large and the pitching period is The installation speed could not follow the current speed, and fluctuating tension remained in the submarine cable.

As described above, the conventional method of adjusting the tension of submarine cables has problems in safely and accurately laying or pulling up cables.

The present invention has been made with the aim of solving the above problems, and the gist thereof is to provide a rotatable sheave that is installed in a laying ship and guides a submarine cable, etc. between a laying machine and the sea, and The present invention relates to a tension adjustment device for submarine cables, etc., comprising a tension adjustment means for moving the sheave up and down in order to correct fluctuations in tension applied to the sheave.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

FIG. 3 shows a schematic configuration of an embodiment of a tension adjusting device according to the present invention installed on the bow of a laying ship, and FIG. 4 shows a plan view thereof.

A groove 8 is formed in the bow of the cable laying ship 1 from below toward the deck 7.
is formed.

9 is the bottom surface of the groove 8. A sheave 4 is housed on the tip side of this groove 8.

This sheave 4 is rotatably attached to the tip of an arm 11 which is rotatably fixed to the hull side at a fulcrum 10.

The other end of the arm 11 is connected to a rod 13 of a hydraulic cylinder 12 installed on the hull side.

14 is a pressure regulating valve for setting the pressure of the hydraulic cylinder 12, and 15 is a hydraulic pump for applying pressure to the hydraulic cylinder 12.

The arm 11, the hydraulic cylinder 12, the pressure regulating valve 14,
The hydraulic pump 15 and the like constitute the tension adjustment means.

Further, 16 is a trough installed on the deck 7 to guide the submarine cable 3, and the end of the trough on the bow side is inclined toward the groove bottom surface 9.

5a and 5b are the valleys and mountains of the sea swell, and in Fig. 3, the solid line indicates when the bow of the laying ship 1 enters the sea swell valley 5a and descends, and the solid line indicates when the bow enters the sea swell peak 5b. The case where the temperature rises is shown by a broken line.

Now, when the bow of the laying ship 1 rises from the lowered state, the tension applied to the submarine cable 3 increases, and a force corresponding to the increased tension is transmitted to the hydraulic cylinder 12 via the sheave 4 and the arm 11. .

Since the force exerted by the hydraulic cylinder 12 is set in advance by the pressure regulating valve 14 so as not to exceed an allowable value that takes into account the tensile strength of the submarine cable 3, the hydraulic cylinder 12 acts in the direction ( It operates in the direction of arrow B in the drawing, displaces the sheave 4 until it balances the preset force, and then stops.

When the bow of the laying ship 1 rises, due to the displacement of the sheave 4, the relative position between the deck 7 and the sheave 4 changes from when it is in the downward surrender state, and the submarine cable 3 moves from the trough 16 to the groove bottom surface 9.
and is laid in contact with the sheave 4.

When the bow of the laying ship 1 descends from the raised state, the tension in the submarine cable 3 begins to decrease, so the hydraulic cylinder 12 operates in the direction of increasing this decreased tension (in the direction of arrow C in the drawing), and operates according to the preset value. The sheave 4 is displaced to a point where it balances the applied force.

In this way, by displacing the sheave 4 by an amount commensurate with the amount of change in tension in response to the pitching cycle of the installation ship 1, the fluctuation of tension in the submarine cable 3 caused by the pitching movement of the installation ship 1 is suppressed. The goal is to correct this.

FIGS. 5 and 6 show other embodiments using other configurations as the tension adjusting means.

In the one shown in FIG. 5, a sheave 4 is rotatably supported at the tip of an arm 18 connected to the rotating shaft of a hydraulic motor 17.
The hydraulic motor 17 rotates to displace the sheave 4.

Also, what is shown in Fig. 6 is a guide groove 19 fixed to the hull.
One end of the wire 20 is attached to the rotating shaft of the sheave 4, which can move vertically, and the other end of the wire 20 is connected to the rotating shaft of the hydraulic motor 17, which is controlled to a constant torque, via a pulley 2 fixed to the hull. Wire 2
By unwinding or winding the sheave 4, the fluctuating tension of the submarine cable 3 is reduced.

In FIGS. 5 and 6, the same members as in the previously mentioned embodiment are designated by the same reference numerals.

In addition, although the above-mentioned embodiment shows the case where the present invention is applied to the bow of the ship, the same applies even if it is applied to the stern of the ship.

Further, in the above embodiments, submarine cables are the objects to be laid or salvaged, but the objects may be other cables or cables.

As described above, according to the tension adjustment device for submarine cables, etc. according to the present invention, the fluctuating tension in submarine cables, etc. caused by the pitching movement of the laying ship can be reduced or corrected by displacing the sheave in accordance with the pitching cycle. Therefore, there is no fear of the submarine cable breaking, and there is no need to change the laying or salvage speed of the submarine cable, etc., making it possible to safely and accurately lay and salvage the submarine cable.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a laying ship equipped with a submarine cable laying machine;
Fig. 2 is an estimated diagram of the relationship between the fluctuating tension of a submarine cable and water depth when the submarine cable is laid by conventional means, and Fig. 3 is a schematic diagram of an embodiment of the present invention applied to a laying ship. FIG. 4 is a plan view thereof, and FIGS. 5 and 6 are schematic views of other embodiments. In the drawing, 1 is a laying ship, 2 is a submarine cable laying machine, 3 is a submarine cable, 4 is a sheave, 11 is an arm, 12 is a hydraulic cylinder, 14 is a pressure regulating valve, 15 is a hydraulic pump, 17 is a hydraulic motor, 18 19 is a guide groove, 20 is a wire, and 21 is a pulley.

Claims (1)

[Claims] 1. A rotatable sheave installed on a laying ship to guide a submarine cable, etc. between a laying machine and the sea, and a tension adjustment means for moving the sheave up and down to correct fluctuations in tension applied to the submarine cable, etc. A tension adjustment device for submarine cables, etc., characterized by comprising: