NO346954B1

NO346954B1 - Bridle block for a deflector

Info

Publication number: NO346954B1
Application number: NO20210287A
Authority: NO
Inventors: Svein Langeland
Original assignee: Seismeq As
Priority date: 2021-03-04
Filing date: 2021-03-04
Publication date: 2023-03-13
Also published as: NO20210287A1

Description

Field of the invention

The present invention relates to a bridle block for a deflector, for adjusting the deflector's angle of attack in the water, said bridle block comprises a bridle block body and a bridle block arm pivotably connected to each other in a pivot axle, the bridle block arm has a first end with an attachment for a towline from a vessel, and the bridle block body has on a first side of the pivot axle an attachment for front bridles running to the deflector, and the bridle block body has on a second side of the pivot axle an attachment for aft bridles running to the deflector.

Background of the invention

In marine seismic survey, it is common to use several long streamers and sources of seismic signals, usually hydrophones or airguns, towed behind a vessel. The seismic signals are reflected from layers in the underground and picked up by the streamers, after which the signals are interpreted, giving information on the geology of the underground. The streamer cables are spanned out by starboard side and port side deflectors, which in turn are towed by the vessel. Each deflector is usually attached to a towing block, called a "bridle block", by bridles connected to the forward and aft ends of the deflector. This bridle block is used for both streamers and gun cables (sources). The bridle block is attached to a towline, also called spurline, from the towing vessel. The deflectors are normally placed on either side of the seismic tow and have such an angle of attack in the water that they pull the towlines and thereby the tow laterally outwards.

Often there is a need to change the lift of the deflectors on the tow, and to control the direction of the tow, which can be done by adjusting the angle of attack of the deflector in the water. The angle of attack can be adjusted by replacing the bridle lines at the forward or aft edge of the deflector with shorter or longer bridle lines, while the rest of the bridle lines are kept unchanged. Another way of adjusting the angle of attack is to replace spacers, which include attachment points for the bridle lines in the bridle block, with shorter or longer spacers, whereas the bridle lines are typically kept in the same lengths.

A commonly used procedure is to pre-set the deflectors' angle of attack manually by manually adjusting the bridle line lengths or to adjust their connectors positions on the bridle block inwardly or outwardly, before the launching of the deflectors.

However, such a manually adapted bridle line length does not allow controlling the deflector's heading during use.

Disclosure of the state of art

GB2399883A relates to controlling the depth of a marine deflector used to laterally space streamers in a seismic survey by varying its tilt angle. A bridle couples the deflector to a lead-in that extends from the towing vessel. Actuators adjust the length of the upper and lower bridle segments resulting in tilting of the deflector and thus control of depth. Other means of adjusting the geometry of the bridle are shown using pulleys, rotatable tow-points and toothed wheels. In an alternate embodiment, moveable flaps on the deflector produce the tilt. The angle of attack of the deflector can be independently controlled.

NO339296B1 (NO20151550A1) relates to a bridle block for a deflector, the bridle block including a stem and a rocker arm pivotably attached to each other on a pivot axle, the stem having an attachment for a towline from a vessel. A forward portion of the rocker arm having an attachment for fore bridle lines of the deflector, and an aft portion of the rocker arm having an attachment for aft bridle lines of the deflector. The bridle block includes a hydraulic cylinder provided with at least one valve, and the hydraulic cylinder being attached to the stem and the rocker arm to hold the stem and the rocker arm in a chosen relative position, wherein the at least one valve is operated directly or indirectly by an electric control signal from a control unit, and the at least one valve takes an open position when a control signal is missing, so that there is an open fluid connection between the piston side of a piston and a reservoir for hydraulic oil or an open fluid connection between the piston-rod side of the piston and the reservoir. A method of using the bridle block to passively guide a deflector into a known angle of attack relative to water when the deflector is being towed through the water is described as well.

NO20191059A1 discloses a bridle block for a deflector.

Objects of the present invention

An object of the invention is to produce a bridle block, which is well suited for controlling a deflector, wherein the bridle block can be remotely controlled in order to adjust the deflector's angle of attack in the water.

At least one object is to provide an alternative bridle block with an electrical motor.

Advantages with an electrical motor as electric actuator is that it is simpler and cheaper than using a hydraulic cylinder. It is simpler in that electric power is on site, and it is not necessary with a power pack for regulation of angle of attack of the deflector.

The deflector is subjected to relatively large uncontrolled forces during use, and by using an electrical motor, such as a geared motor, forces can more easily be absorbed.

Further, an electrical motor is more compact.

Summary of the invention

The above objects are achieved with a bridle block for a deflector, the bridle block comprises a bridle block body and a bridle block arm pivotably connected to each other in a pivot axle, the bridle block arm has a first end with an attachment for a towline from a vessel, and the bridle block body has on a first side of the pivot axle an attachment for front bridles running to the deflector, and the bridle block body has on a second side of the pivot axle an attachment for aft bridles running to the deflector. The bridle block further comprises an electrical motor with a spindle and a nut, said nut being connected to a slider accommodating a second end of the bridle block arm, forcing the second end of the bridle block arm back and forth on the bridle block body, wherein said electrical motor is communicating with a remote controller, and which upon receipt of an electrical signal is activated and regulates the deflector's angle of attack by regulating relative position between the bridle block body and the bridle block arm.

The slider can slidably accommodate the second end of the bridle block arm.

Said electrical motor is preferably a geared motor with an absolute position encoder.

Said electrical motor and electric components can be enclosed in a watertight housing.

The spindle can be running in a longitudinal direction between the attachment for the front bridles and the attachment for the aft bridles.

Said nut connected to the slider accommodating the second end of the bridle block arm can be running back and forth on the spindle in a direction between the attachment for the front bridles and the attachment for the aft bridles, forcing the second end of the bridle block arm to pivot about the pivot axle.

The bridle block arm can be driven to a position providing a small angle of attack of the deflector, in that the second free end is forced in a direction toward the attachment for the aft bridles, and the bridle block arm can be driven to a position providing a large angle of attack of the deflector, in that the second free end is forced in a direction toward the attachment for the front bridles.

Said bridle block arm may be offset attached to the bridle block body in the pivot axle, either closer to the attachment for the front bridles running to the deflector or closer to the attachment for the aft bridles running to the deflector.

Said remote controller can be a control unit on the vessel. Said control unit on the vessel can be a processing unit, such as an iPad<TM >or the vessel's navigation system.

Said electrical motor can upon loss of electrical signals be returned to a fail-safe position.

Description of the figures

Embodiments of the present invention will now be described, by way of example only, with reference to the following figures, wherein:

Figure 1 and 2 shows embodiments of a bridle block according to the invention.

Figure 3-5 shows the bridle block according to the invention, in different positions providing different angle of attack (AOA).

Figure 6 shows an example of a bridle block in a first position and connected to a deflector.

Figure 7 show an example of a bridle block in a second position and connected to the deflector.

Description of preferred embodiments of the invention

The bridle block according to the invention is in this application disclosed used with a deflector for marine survey, but the bridle block may also be suited for use with a trawl door, or for oil skimmer, dirt (plastic) skimmer.

As shown in figures 6 and 7, a bridle block 10 is connected between a towline 32, also called spurline, running from a vessel (not shown) on a water surface and a deflector 40. Front bridles 34 are running from the bridle block 10 and to a first side of the deflector 40, and aft bridles 36 are running from the bridle block 10 and to a second side of the deflector 40. The bridle lines 34,36 can be a single line, a pair of lines, or several lines. By adjusting the bridle block 10 and thereby the tension in the bridles 34,36, angle of attack (AOA) of the deflector 40 in the water is regulated. The dotted lines in figures 6 and 7 indicates how bridles without steering would look like, longer or shorter. In figure 6, the bridle block 10 is adjusted such that the deflector 40 has a large angle of attack (AOA), thereby providing a large lifting force. In figure 7, the bridle block 10 is adjusted such that the deflector 40 has a small angle of attack (AOA), thereby providing a low lifting force. In figures 6 and 7, the direction of lift force is in horizontal direction, and the direction of drag force is in vertical direction.

Operation of the bridle block 10 to provide different angles of attack (AOA) and operation of the deflector can be performed in a known way, and the different operations are therefore not disclosed in detail, as such operations are assumed known for a skilled person.

Figures 1 and 2 shows embodiments of the bridle block 10 according to the invention in detail. Direction of motion in figures 1-5 is should be assumed to be mainly in vertical direction.

The bridle block 10 comprises a bridle block body 12 and a bridle block arm 14 pivotably connected to each other in a pivot axle 38, said pivot axle being for instance a pivot axis. The bridle block body 12 can as shown in figure 1 be a back plate, or the bridle block body 12 can be a housing accommodating the different parts. Figure 2 depicts a housing, but in where only the back plate and a bottom plate is shown. The bridle block arm 14 can as shown be a straight link-arm or leverarm connected in the pivot axle 38, such as a protruding pivot axle fixed to the bridle block body 12 (back plate). The bridle block arm 14 can be offset attached to the bridle block body 12, for instance in that the pivot axle 38 is closer to an attachment 24 for the front bridles 34 running to the deflector 40 or the pivot axle 38 is closer to an attachment 26 for the aft bridles 36 running to the deflector 40. However, the pivot axle 38 of the bridle block arm 14 can also be placed centrally on the bridle block body 12.

The bridle block arm 14 is pivotably engaged in the pivot axle 38 and a first free end 14a, shown as protruding upwards, is equipped with an attachment 22 for the towline 32 from the vessel.

The bridle block body 12 has on a first side of the pivot axle 38, for instance as seen on the left hand side in the figures, the attachment 24 or a connection for the front bridles 34 running to the deflector 40, and the bridle block body 12 has on a second side of the pivot axle 38, for instance as seen on the right hand side in the figures, the attachment 26 or a connection for the aft bridles 36 running to the deflector 40.

The bridle block 10 further comprises an electrical motor 28 with a spindle 18 and a nut 20 providing a ball screw, for regulation of relative position between the bridle block body 12 and the bridle block arm 14. The electrical motor 28 is communicating with a remote controller, which upon receipt of an electrical signal is activating the motor 28, and hence the spindle 18, and regulates the deflector's angle of attack (AOA) in the water.

The nut 20 being driven on the spindle 18 is connected to a slider 16 accommodating a second end 14b of the bridle block arm 14. When the spindle 18 is activated and drives the nut 20, the second end 14b of the bridle block arm 14, shown as protruding downwards, is moved back and forth on the bridle block 10, which regulates the angle of the first end 14a of the bridle block arm 14, with the attachment 22 of the towline 32, and thus regulates the deflector's angle of attack (AOA) in the water.

The spindle 18 is placed running in a longitudinal direction between the attachment 24 for the front bridles 34 and the attachment 26 for the aft bridles 36. The nut 20 connected to the slider 16 is thus running back and forth on the spindle 18 in a direction between the attachment 24 for the front bridles 34 and the attachment 26 for the aft bridles 36, forcing the bridle block arm 14 to pivot about the pivot axle 38.

The bridle block arm 14 can be driven to a position providing a small angle of attack (AOA) of the deflector 40, as shown in figure 3, in that the second free end 14b of the bridle block arm 14 is forced in a direction toward the attachment 26 for the aft bridles 36. A distance A between the attachment 24 for the front bridles 34 on the bridle block body 12 and the attachment 22 for the towline 22 on the first end 14a of the bridle block arm 14 is thus shorter than a distance B between the attachment 26 for the aft bridles 36 on the bridle block body 12 and the attachment 22 for the towline 22 on the first end 14a on the bridle block arm 14.

The bridle block arm 14 can be driven to a position providing a large angle of attack (AOA) of the deflector 40, as shown in figure 5, in that the second free end 14b of the bridle block arm 14 is forced in a direction toward the attachment 24 for the front bridles 34. The distance A between the attachment 24 for the front bridles 34 on the bridle block body 12 and the attachment 22 for the towline 22 on the first end 14a of the bridle block arm 14 is thus larger than the distance B between the attachment 26 for the aft bridles 36 on the bridle block body 12 and the attachment 22 for the towline 22 on the first end 14a on the bridle block arm 14.

In figure 4 the bridle block arm 14 is driven to a position providing a medium angle of attack (AOA) of the deflector 40, in that the second free end 14b of the bridle block arm 14 is forced to a position half way in between the attachment 24 for the front bridles 34 and the attachment 26 for the aft bridles 36. The distance A between the attachment 24 for the front bridles 34 on the bridle block body 12 and the attachment 22 for the towline 22 on the first end 14a of the bridle block arm 14 can in this position be basically similar to the distance B between the attachment 26 for the aft bridles 36 on the bridle block body 12 and the attachment 22 for the towline 22 on the first end 14a on the bridle block arm 14.

The bridle block arm 14 can be driven to any position in between the positions shown in figures 3 and 5, thus providing any desired angle of attack (AOA) of the deflector 40.

The electrical motor 28 is in one embodiment a geared motor with an absolute position encoder, thus ensuring accurate movement of the spindle 18 and nut 20. The electrical motor 28 and electric components can be accommodated in a watertight housing 42.

Further, the electrical motor 28 comprises or is connected to a remote controller connection, which is connected to or communicating with a remote controller on the surface, by either a cable or wireless connection. In case the controller is wireless, a battery (not shown) can be used for delivering energy for driving the electrical motor 28. The remote controller can be a control unit or processing unit on the vessel, such as an Ipad<TM >or the vessel's navigation system.

In case of loss of electrical signal, the electrical motor 28 can move the spindle 18 and the nut 20, and thus the bridle block arm 14, to a non-activated and fail-safe position, for instance a position that provides minimal lift force or drag force on the deflector 40.

Claims

1. A bridle block (10) for a deflector (40), the bridle block (10) comprises a bridle block body (12) and a bridle block arm (14) pivotably connected to each other by a pivot axle (38),

the bridle block arm (14) has a first end (14a) with an attachment (22) for a towline (32) from a vessel,

the bridle block body (12) has on a first side of the pivot axle (38) an attachment (24) for front bridles (34) running to the deflector (40), and the bridle block body (12) has on a second side of the pivot axle (38) an attachment (26) for aft bridles (36) running to the deflector (40), characterized in that

the bridle block (10) comprises an electrical motor (28) with a spindle (18) and a nut (20), said nut (20) being connected to a slider (16) accommodating a second end (14b) of the bridle block arm (14), forcing the second end (14b) of the bridle block arm (14) back and forth on the bridle block body (12),

wherein said electrical motor (28) is communicating with a remote controller, and which upon receipt of an electrical signal is activated and regulates the deflector's (40) angle of attack (AOA) by regulating relative position between the bridle block body (12) and the bridle block arm (14).

2. The bridle block (10) according to claim 1, wherein the slider (16) slidably accommodates the second end (14b) of the bridle block arm (14).

3. The bridle block (10) according to claim 1, wherein said electrical motor (28) is a geared motor with an absolute position encoder.

4. The bridle block (10) according to claim 1, wherein said electrical motor (28) and electric components are enclosed in a watertight housing (42).

5. The bridle block (10) according to claim 1, wherein the spindle (18) is running in a longitudinal direction between the attachment (24) for the front bridles (34) and the attachment (26) for the aft bridles (36).

6. The bridle block (10) according to claim 1, wherein said nut (20) connected to the slider (16) accommodating the second end (14b) of the bridle block arm (14) is running back and forth on the spindle (18) in a direction between the attachment (24) for the front bridles (34) and the attachment (26) for the aft bridles (36), forcing the second end (14b) of the bridle block arm (14) to pivot about the pivot axle (38).

7. The bridle block (10) according to claim 6, wherein the bridle block arm (14) is driven to a position providing a small angle of attack (AOA) of the deflector (40), in that the second free end (14b) is forced in a direction toward the attachment (26) for the aft bridles (36), and the bridle block arm (14) is driven to a position providing a large angle of attack (AOA) of the deflector (40), in that the second free end (14b) is forced in a direction toward the attachment (24) for the front bridles (34).

8. The bridle block (10) according to claim 1, wherein said bridle block arm (14) is offset attached to the bridle block body (12) on the pivot axle (38), either closer to the attachment (24) for the front bridles (34) running to the deflector (40) or closer to the attachment (26) for the aft bridles (36) running to the deflector (40).

9. The bridle block (10) according to claim 1, wherein said remote controller is a control unit on the vessel.

10. The bridle block (10) according to claim 9, wherein said control unit on the vessel is a processing unit, such as an iPad<TM >or the vessel's navigation system.

11. The bridle block (10) according to claim 1, wherein said electrical motor (28) upon loss of electrical signals is returning to a fail-safe position.