EP0505264B1 - Capstan for fragile cables - Google Patents

Description

The present invention relates to a capstan for handling cables, comprising a central hub provided with means of rotation about an axis D.

The invention finds an application in the general field of cable handling, and, more particularly, in that of handling fragile cables such as those used in marine seismic.

Marine seismic uses cables, called flutes, of great length which, in operational configuration, are submerged and towed by a ship. At rest, the flutes are stored on drums installed on the deck aft of the ship.

By way of example, reference may advantageously be made to US Pat. No. 4,218,025 which presents, as prior art, a capstan for handling cables, comprising a central hub provided with means for rotation about an axis, said capstan comprising, at the periphery of said central hub, a plurality of modules each comprising a conveyor belt disposed between two parallel cylinders, all of the conveyor belts forming a drum for said capstan and said drum having a winding zone intended to receive turns a cable, one of the cylinders of each recentering module, called the drive cylinder, being driven by a motor so as to move said conveyor belt parallel to the axis of rotation of the central hub to control the position of the cable relative to the drum winding area.

Technological developments are currently tending to increase the length of the flutes and also their number, which raises a number of problems.

On the one hand, the increase in the length of the flutes requires drums fitted with larger cheeks, hence an increase in the volume occupied for the storage of each flute, this volume having to be multiplied by the growing number of flutes simultaneously put in action. This results in such a space requirement of the area of the bridge allocated to the launching of the flutes that should be considered today for using larger ships, with the disadvantage of a higher cost of prospecting programs.

On the other hand, in the storage position, the first layers of coiled cables undergo significant permanent stresses which are due to the winding traction of the cable, to the pressure exerted by the succession of the layers of turns, to the significant curvature to the diameter of the drum barrel, and finally to the connecting elements of the lengths of flutes. These junction elements, of larger diameter, generate additional point stresses detrimental to the components of the streamer cables, and this all the more so as the technology in the field of marine seismics evolves in the direction of better performance, but also of a greater fragility of the internal elements of the flutes.

An ideal solution would be to store the cables inside the vessel, on a drum, in a well or in bulk, under optimal conditions, that is to say without excessive constraints or bends. It still remains to design a handling means for bringing, and vice versa, the cable from its operational configuration to its storage configuration.

Also, the technical problem to be solved by the object of the present invention is to produce a capstan for handling cables, in accordance with the preamble, which, in a reduced footprint, would be suitable for handling cables of new technology, without introducing stresses or bends incompatible with the fragility of the components used.

To this end, the invention provides a capstan for handling cables, comprising a central hub provided with means of rotation about an axis, said capstan comprising, at the periphery of said central hub, a plurality of refocusing modules comprising, each, a conveyor belt disposed between two parallel cylinders, the set of conveyor belts forming a drum for said capstan and said drum having a winding zone intended to receive turns of a cable, one of the cylinders of each module centering, said drive cylinder, being driven by a motor so as to move said conveyor belt in parallel to the axis of rotation of the central means for controlling the position of the cable relative to the winding zone of the drum, characterized in that it further comprises a feeler which, when the cable laterally exceeds a determined average position, controls a power supply box for the drive motor, to center the turns of the cable.

The role of this capstan being only to pull cables for storage at the end of the operation, or on the contrary to bring the cables of the storage in operational configuration, the winding zone, limited to a small number of turns, typically 3 or 4, can be very reduced in size, hence a drum width, and therefore of capstan, much less than that of the drums currently used, which makes it possible to envisage installing on the deck of the ship a plurality of conforming capstans. to the invention for applications in multi-cable marine seismic for example.

On the other hand, since the capstan of the invention does not include cheeks, it is possible to increase the diameter of the drum in order to limit the stress on the constituent elements of the cables. Likewise, the stress on the cables is low, since it is exerted only during the passage over the drum during winding, the storage phase then being carried out with a reduced stress in maintaining the stretched strand.

It will also be noted that the presence of elements for joining the lengths of cables has no effect on the operation of the capstan of the invention. Similarly, no adjustment is necessary for the use of cables of different diameters.

The control of the drive motors by the device for controlling the position of the cable during winding makes it possible to maintain the turns present on the drum in the winding zone, generally the central part of the conveyor belts, despite the phenomenon of pitch screw generated by the winding. This position correction being carried out synchronously, no particular constraint is applied to the cables during the recentering.

The description which follows with reference to the appended drawings, given by way of nonlimiting examples, will make it clear what the invention consists of and how it can be implemented.

Figure 1 is a perspective view of a capstan according to the invention.

FIG. 2 is a side view of a module for refocusing the capstan of FIG. 1.

FIG. 3 is a section through the conveyor belt of the refocusing module of FIG. 2.

FIG. 4 is a side view of a cylinder of the refocusing module of FIG. 2.

Figure 5 is a side view of a capstan according to the invention provided with a pivot means.

FIG. 6 is a top view of the rear deck of a ship on which the capstan of FIG. 5 is installed.

Figure 7 is a view similar to that of Figure 6 in which the capstan is coupled to a storage winch.

Figure 8 is a side view of a capstan according to the invention provided with a pressure wheel.

FIG. 1 shows in perspective a capstan 10 for handling a cable 100, comprising a central hub 200 provided with means of rotation about an axis D constituted by a hydraulic motor 210, for example with cams, mounted directly without reducer on the shaft 220 of said central hub 200. This technique makes it possible to apply to the cable 100 the minimum effort necessary for its handling for the winding configuration. In addition, the hydraulic motor 210 is fitted with safety valves calibrated for the maximum permissible torque by the cable 100. In the event of the cable hanging, the capstan 10 stops at the set torque and can even deviate to avoid any abnormal effort on the cable. The speed of the capstan is independent of the load, even when turning with reduced torque.

As shown in FIG. 1, the capstan 10 comprises, at the periphery of the central hub 200, a plurality of refocusing modules 300, a side view of one of which is given in FIG. 2. Each module recentering comprises a conveyor belt 310 arranged between two parallel cylinders 321 and 322. As can be seen in FIG. 1, all of the conveyor belts 310 form a drum for the capstan 10. This drum is intended to receive in a winding zone Z a limited number of turns 110 of the cable 100, 4 in the case of FIG. 1, this number not being imperative. Said winding zone Z will generally, but not exclusively, be situated around the median plane of the drum, that is to say in a central zone of the conveyor belts 310.

So as to counteract the spiral effect generated by the winding or unwinding of the cable 100 on the capstan drum 10, and therefore to maintain the turns of cable 110 in the winding zone Z, one of the cylinders 321 of each refocusing module 300, called the drive cylinder, is coupled to a drive motor 330 shown in FIG. 1. This drive motor 330 can be a hydraulic motor capable of moving the conveyor belts parallel to the axis D of rotation of the central hub, in both directions as required.

On the other hand, a device 410, 420 for controlling the position of the cable 100 during winding controls, synchronously, said drive motors 330 so as to move the conveyor belts 310 of refocusing modules 300 in order to maintain , by refocusing effect, the turns 110 in the zone Z for winding the capstan drum 10. This refocusing is carried out independently of the direction of rotation of the capstan (winding or unwinding).

As shown in FIG. 1, said position control device comprises a probe 410 which controls a housing 420 for synchronous supply of the drive motors 330 when the cable 100 laterally exceeds a determined average position. The direction of supply of the motors 330 depends on the turning or turning function with respect to the theoretical winding zone (central zone) of the capstan drum.

It is understood that the desired refocusing effect will only be obtained if the speed of the belt drive motors 310 is sufficient relative to the speed of rotation of the central hub 200.

The speed of movement of the conveyor belts is independent of the speed of rotation of the capstan. It is a function of the angular position of the 410-420 control device. The control, proportional to the angle, makes it possible to obtain a very flexible variation of correction with a speed which tends towards zero at the ideal winding position. This technique allows rapid correction of the position in the case of a transient offset phenomenon.

It should also be emphasized that the position control device described with reference to FIG. 1 makes operation independent of the diameter of the cable 100 to be wound up and of punctual variations in shape over the length, due for example to the connection elements. Finally, the large diameter of the capstan drum 10 has the advantage of generating a very reduced speed of movement of the strips 310.

As can be seen in Figures 2 and 3, each conveyor belt 310 comprises, for example, 4 toothed belts 311 separated by trapezoidal guide spacers 312. The belts 311 and the spacers 312, made in particular of polyurethane, are covered with a flexible elastomer 313 with a high coefficient of adhesion to allow winding without risk of deterioration of the fragile elements of the cable and to prevent slipping of the cable during winding.

In accordance with FIG. 3, the elastomeric coating 313 has a slightly convex profile in the convex direction so as to reconstitute the diameter of the capstan drum to be produced.

Figures 2 and 4 show that the toothed belts 311 cooperate with longitudinal notches 330 arranged on said cylinders 321, 322 to ensure the longitudinal drive of the strip 310 according to the conventional principle of a belt. On the other hand, the guide spacers 312 cooperate with annular grooves 340 formed in the cylinders in order to allow the longitudinal guidance of the conveyor belt 310 and to resist the transverse sliding of the belt caused by the starting acceleration during the formation of the first turn.

In order to support the load applied by the cable to the conveyor belts, each refocusing module 300 comprises a fixed counter plate 350 on which the conveyor belt 310 slides, as illustrated in FIGS. 2 and 3. This counter plate 350 can be a polished metal plate.

The hydraulic motor 210 for rotating the capstan preferably includes a backpressure valve on the motor circuit to allow, in a turning or turning configuration, to control the inertia of the drum and to maintain, by forced unwinding on the motor , the cable tension during storage or destocking.

• vitesse maximale à couple réduit
• vitesse réduite à fort couple.

Cette particularité permet, par exemple, de réduire le temps de mise à l'eau des flûtes sismiques suivant les conditions de mer en augmentant la vitesse du navire. Pour cette fonction, le moteur hydraulique 210 de rotation du cabestan est couplé en petite cylindrée, donc vitesse maximale et couple réduit.In addition, the hydraulic motor 210 is equipped with a displacement selection block which allows a dual function of the motor:

• maximum speed at reduced torque
• reduced speed at high torque.

This feature allows, for example, to reduce the time to launch seismic streamers according to sea conditions by increasing the speed of the ship. For this function, the hydraulic motor 210 for rotating the capstan is coupled in small displacement, therefore maximum speed and reduced torque.

When the vessel on which the compliant capstan is installed the invention is subjected to a side wind and / or to a surface current, the winding or unwinding direction of the cable makes a non-zero and essentially variable angle with the axis of said vessel. This is why it is provided, as indicated in FIGS. 5 and 6, that the capstan 10 further comprises a means 500 for pivoting around a direction Δ orthogonal to the axis D of rotation. In the embodiment of FIG. 5, the pivoting means 500 is formed by a stirrup fixed to the capstan 10 and connected at its ends to fixed points by straps 510, 520. It can also be observed in FIG. 5 that the the pivot axis Δ passes through the point T of tangency, at the winding, of the fiber leaving the cable 100.

The capstan of the invention thus made orientable can follow angular variations of the order of 10 to 20 °, which has the advantageous effect of limiting the transverse forces on the refocusing modules resulting from a difference between the effective direction of the cable and nominal direction of unwinding / winding of the capstan.

It is understood that during the winding or unwinding operation, the tension of the cable 100 on the capstan 10 may be sufficient to prevent the capstan from pivoting about the axis Δ under the action of rolling by example. On the other hand, at the end of winding or at the beginning of unwinding, the length of submerged cable being low, the tension on the capstan is less so that the latter becomes more sensitive to roll and can therefore pivot freely with the danger that this represents for personnel responsible for maneuvering the capstan. Also, the invention provides that said pivot means 500 is provided with means for limiting the amplitude of pivoting, provided, for example, by a hydraulic feedback brake. In particular, integral with the pivoting means 500, a mechanical assembly integrating the sensors 410 and 420 equipped at its end with an open fairlead 800 consisting of 3 rollers for example will serve as the cable entry on board. This fairlead 800 will be fitted with sensors integrated in a loop for correcting the angular position of the assembly with the direction of the cable in the water.

As shown in Figure 7, the capstan according to Figures 5 and 6 can be coupled to a winch 600 for storing the cable 100 on wherein said cable is wound under a constant fixed tension. For this purpose, the capstan 10 comprises means for lateral displacement of the pivoting means 500 parallel to the storage winch 600. These means consist of guide tracks 530 in which the straps 510, 520 can slide under the action of a hydraulic synchronous motor.

Finally, FIG. 8 shows an embodiment of the capstan of the invention which is particularly advantageous in that it comprises a pressure wheel 700 pressing on said capstan 10 substantially at the point T of tangency, on winding, of the fiber. outgoing from cable 100, the linear speed of said pressure wheel being at least equal to the linear speed of the capstan. This arrangement enables the cable to be pressed against the recentering modules, in particular at the end of winding and at the start of unwinding.

Claims (15)

1. Capstan (10) for handling cables (100), comprising a central hub (200) provided with means of rotation about an axis (D), the said capstan (10) comprising at the periphery of the said central hub (200), a plurality of centring modules (300) each comprising a conveyor belt (310) disposed between two parallel cylinders (321,322), the assembly of conveyor belts (310) forming a drum for the said capstan and the said drum having a winding zone (Z) intended to receive the turns (110) of cables, one of the cylinders (321,322) of each centring module (300), called the drive cylinder, being driven by a motor provided for displacing the said conveyor belt (310) parallelly to the axis D of rotation of the central hub (200) for controlling the position of the cable relatively to the winding zone of the drum, characterized in that it further comprises a feeler (410) which, when the cable (100) laterally overshoots a predetermined mean position, controls a unit (420) supplying the driving motor to recenter the turns of the cable.
2. Capstan according to Claim 1, characterised in that each conveyor belt (310) comprises a plurality of notched belts (311) working in conjunction with longitudinal notches (330) produced on the said cylinders (321, 322), the said notched belts being separated by longitudinal guidance cross pieces (312) working in conjunction with annular grooves (340) produced in the cylinders (321, 322).
3. Capstan according to Claim 2, characterised in that the said notched belts (311) and the said cross pieces (312) are covered with an elastomer coating (313) with a high coefficient of adhesion.
4. Capstan according to Claim 3, characterised in that the said elastomer coating (313) has a convex profile.
5. Capstan according to any one of Claims 2 to 4, characterised in that each centring module (300) comprises a fixed reinforcing plate (350) over which the conveyor belt (310) slides.
6. Capstan according to any one of Claims 1 to 5, characterised in that the said means of rotation comprise a hydraulic cam motor (210) mounted without reduction gear on the shaft (220) of the said central hub (200).
7. Capstan according to Claim 6, characterised in that the circuit of the said hydraulic motor (210) comprises a counterpressure valve intended to control the inertia of the capstan (10).
8. Capstan according to one of Claims 6 or 7, characterised in that the said hydraulic motor (210) is fitted with a cylinder selection unit allowing a double function: maximum speed at reduced torque and reduced speed at high torque.
9. Capstan according to any one of Claims 1 to 8, characterised in that it furthermore comprises a means (500) of pivoting about a direction A orthogonal to the axis D.
10. Capstan according to Claim 9, characterised in that the said direction A of pivoting passes substantially through the point T of tangency, during winding, of the outgoing strand of the cable (100).
11. Capstan according to one of Claims 9 or 10, characterised in that the said means (500) of pivoting is fitted with means of limitation of the amplitude of pivoting.
12. Capstan according to Claim 11, characterised in that the said means of limitation are constituted by a hydraulic feedback brake.
13. Capstan according to any one of Claims 9 to 12, characterised in that it comprises means (530) of lateral displacement of the means (500) of pivoting parallel to a storage winch (600).
14. Capstan according to any one of Claims 1 to 13, characterised in that it furthermore comprises a pressure wheel (700) pressing on the said capstan (10), the linear speed of the said pressure wheel (700) being at least equal to the linear speed of the capstan (10).
15. Capstan according to Claim 14, characterised in that the said pressure wheel (700) presses on the capstan (10) substantially at the point (T) of tangency, during winding, of the outgoing strand of the cable (100).

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