WO2019093901A1

WO2019093901A1 - Cleaning device for a submerged surface

Info

Publication number: WO2019093901A1
Application number: PCT/NO2018/050266
Authority: WO
Inventors: Rune RØRSTAD
Original assignee: Plastfabrikken As
Priority date: 2017-11-07
Filing date: 2018-11-07
Publication date: 2019-05-16
Also published as: NO344883B1; NO20181427A1

Abstract

A cleaning device (1) for cleaning a submerged surface (99), the cleaning device (1) being arranged to move along a sloping operative direction of motion (X1 -X4), and the cleaning device (1) further comprising a first reversing device arranged to communicate with the propulsion system (13) so that the cleaning device (1) may switch between the first horizontal direction of motion (A) and the second horizontal direction of motion (B) when a cable (2) subjects the cleaning device (1) to a force (F2) which prevents the cleaning device (1) from following the sloping operative direction of motion (X1 -X4). Further, a fish cage (4) including a plurality of cleaning devices (1) and a method for using the cleaning device (1) are described.

Description

CLEANING DEVICE FOR A SUBMERGED SURFACE

The invention relates to a cleaning device adapted for autonomously cleaning a submerged surface, for example a net belonging to a fish cage. The invention also describes a method for using the cleaning device.

Background of the invention and prior art

A fish-farming cage may comprise a closed enclosure, generally in the form of a net which allows the water to flow freely through the enclosure. Over time, the net will become covered in fouling and the water flow decreases. The oxygen content inside the fish cage will thereby be reduced, which is unfavourable to the wellbeing, health and growth of the fish.

To clean the nets, various cleaning devices that are lowered along the inside or outside of the net may be used. The cleaning devices may include rotating brushes or water under high pressure which is carried up to one or more rotating discs provided with nozzles so that the net is flushed clean.

Patent document US201 1/0185519 discloses an autonomous cleaning device for a net belonging to a fish cage. The cleaning device comprises a frame, buoyancy means, rotating brushes and a battery. The cleaning device is adapted for remote control by an operator above a water surface.

Patent document NO20160677 shows a cleaning device comprising several propulsion devices for positioning and orientation relative to the surface, and a buoyancy structure holding the surface-treating arrangement and the positioning arrangement and providing buoyancy for the cleaning device.

It is common for fish cages to be provided with so-called bird nets to keep predatory birds away from the fish in the enclosure. The bird net is secured to a railing which surrounds the enclosure. To enable cleaning of the net from the inside, the bird net must be loos- ened from the railing as a cleaning device provided with one or more hoses for the supply of water and/or energy is moved sideways along the net wall.

Because of the work of mobilizing a boat and crew for the operation of known cleaning devices, cleaning of the nets will not be carried out until the fouling is relatively extensive. There is therefore a need for simpler solutions which do not presuppose the use of a boat.

General description of the invention

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.

The object is achieved through the features that are specified in the description below and in the claims that follow.

The invention is defined by the independent claims. The dependent claims define advantageous embodiments of the invention.

In a first aspect, the invention relates to a cleaning device for cleaning a submerged surface, the cleaning device comprising a cleaning unit, a propulsion system arranged to move the cleaning device along a first horizontal direction of motion and a second horizontal direction of motion and a first vertical direction of motion and a second vertical direction of motion, and a cable which, at a first end, is connected to a coupling attachment fixed to a holding structure and, at a second end, is connected to the cleaning device. The propulsion system is further arranged to provide a sloping operative direction of motion of the cleaning device along the submerged surface, and the cleaning device further comprises a first reversing device arranged to communicate with the propulsion system so that the cleaning device may switch between the first horizontal direction of motion and the second horizontal direction of motion when the cable subjects the cleaning device to a force which prevents the cleaning device from following the sloping operative direction of motion.

By a submerged surface may be understood herein an enclosure belonging to a fishfarming cage. The submerged surface may be a net. The holding structure may be part of a fish cage. The holding structure may be part of a floating ring belonging to a fish cage. The submerged surface may comprise a rectangular or trapezoidal work area for the cleaning device. The work area may comprise a first lateral boundary, a second lateral boundary, a lower boundary and an upper boundary. The upper boundary may be a water surface. The lateral boundaries may typically have a height of 10 metres and may include a curved sector with a radius that is substantially equal to an extended length of the cable. The upper boundary may typically have a length that is twice the length of the cable, for example 50 metres, if the cable is 25 metres long. The lower boundary typically has a length that is smaller than or equal to the upper boundary.

By a sloping operative direction of motion may be understood herein a direction of motion which is different from perpendicular relative to the water surface. The sloping operative direction of motion may typically have an angle of pitch of between 2 and 5 degrees. The angle of pitch may be smaller than 2 degrees and larger than 5 degrees, but larger than 0 degrees, 0 degrees corresponding to perpendicular.

By the term operative may be understood herein an operative state or a mode of operation in which the cleaning device cleans the submerged surface.

By a cable may be understood a flexible element which connects the cleaning device to the holding structure. The cable may be adapted for conveying energy and/or signals and/or a fluid from a source to the cleaning device. The cable may be a rope, a wire or a hose. The cable may also be referred to as an umbilical. The cable that is described herein may restrict the work area of the cleaning device and hold the cleaning device back when the cleaning device is moving away from the coupling attachment in the first or the second horizontal direction of motion or the second vertical direction of motion. If the cable is, for example, 25 metres long, the cleaning device may move up to 25 metres away from the coupling attachment.

The cleaning device includes a lower end portion and an upper end portion. The cable is advantageously connected to the upper end portion of the cleaning device. In an operative position, the lower end portion may be facing downwards in the water column, independently of whether the cleaning device is moving downwards or upwards along the submerged surface.

The effect of the first reversing device is that the cleaning device can automatically change its horizontal direction of motion when the cleaning device is moving away from the coupling attachment and down a water column and the cable is extended to its maximum length, typically when the cleaning device reaches one of the lateral boundaries of the work area.

The propulsion system is arranged to move the cleaning device along the submerged surface and to or from the submerged surface. When the cleaning device is operative, the propulsion system may give the cleaning device a push force which moves the cleaning device in a desired operative direction of motion and at a desired angle of pitch.

The cleaning device may have a perpendicular position or a slanted position when it is following the operative sloping direction of motion.

When the cleaning device is moving away from the coupling point and the cable is being extended completely, the taut cable will prevent a further movement of the cleaning device away from the coupling attachment. As the cable holds back the cleaning device, a force component forms between the cable and the push force of the propulsion system, and the push force of the cleaning device will give the cleaning device a rotating motion to equalize said force component. The force component will be equalized when the push force is in line with the tensile force on the cable. The reversing device registers that the cable is being stretched or that the cleaning device is rotating and outputs a signal to the propulsion system for the cleaning device to change its operative direction of motion from the first to the second horizontal direction of motion, or vice versa. Thereby the cleaning device can move alternately in a first and a second horizontal direction of motion, while, at the same time, the cleaning device is moving alternately upwards at an angle and downwards at an angle in the water column. By the operative direction of motion being sloped, the cleaning device will move in a V-pattern along the submerged surface when moving along the submerged surface.

The cleaning device may include a second reversing device arranged to switch between the first vertical direction of motion and the second vertical direction of motion of the cleaning device.

The effect of the second reversing device is that the vertical direction of motion of the cleaning device can be changed automatically when the cleaning device reaches a lower boundary or an upper boundary as the distance between the coupling point and the lower or upper boundary is smaller than the length of the cable. This typically happens when the working depth of the cleaning device is restricted to, for example, 10 metres and the cable is 25 metres long.

The vertical reversing device may include a means for registering the depth of the cleaning device below a surface. The means may be a depth sensor. The means may be a distance sensor. The means may be a pressure sensor. The means, referred to as a depth sensor in what follows, may be used to indicate an upper boundary and a lower boundary of the work area. The depth sensor may output a signal to the propulsion system to change the vertical direction of motion of the cleaning device at one or more depths. The lower boundary may be a specified depth. The upper boundary may be a water surface.

The first reversing device may include an orientation sensor.

The effect of the orientation sensor is that the orientation sensor can output a signal to the propulsion system when the orientation of the cleaning device deviates from a programmed orientation as the cleaning device moves along the operative direction of motion. Such a deviation may arise when the cleaning device is held back by the cable. The orientation sensor may, for example, be an angle sensor or a gyro. The orientation sensor may be programmed to communicate with the propulsion system so that the cleaning device can change its direction of motion when the orientation of the cleaning device deviates beyond a specified value.

The first reversing device may include a tension sensor.

The effect of the tension sensor is that the tension sensor may register a tensioning of the cable and output a signal to the propulsion system so that the cleaning device can change its direction of motion when a tensile force on the cable exceeds a given value.

The sloping operative direction of motion may have a constant angle of pitch.

The effect of the constant angle of pitch is that the cleaning device can clean the submerged surface in a V-pattern and thereby ensure that a desired portion of the submerged surface can be cleaned in a specific number of passes by the cleaning device.

The propulsion system may comprise at least two thrusters of variable push force.

By a thruster may be understood, herein, a propeller or a water jet arranged to move a body in a fluid, for example water.

The effect of the variable push force of at least two thrusters is that the cleaning device can be oriented and moved in the water column by varying effect being supplied to the thrusters, especially when the thrusters are arranged parallel to each other at a distance apart, for example on a first side and on a second side of the cleaning device.

In an alternative embodiment, the propulsion system may include at least one rotatable thruster. The effect of the rotatable thruster is that the cleaning device can be oriented and moved in the water column with just one thruster.

In a second aspect, the invention relates to a fish-farming cage including at least one cleaning device for cleaning a submerged surface, the cleaning device comprising a cleaning unit, a propulsion system arranged to move the cleaning device along a first horizontal direction of motion and a second horizontal direction of motion and a first vertical direction of motion and a second vertical direction of motion, and a cable which, at a first end, is connected to a coupling attachment fixed to a holding structure and, at a second end, is connected to the cleaning device. The propulsion system is further arranged to provide a sloping operative direction of motion of the cleaning device along the submerged surface, and the cleaning device further includes a first reversing device adapted for communicating with the propulsion system, so that the cleaning device can switch between the first horizontal direction of motion and the second horizontal direction of motion when the cable subjects the cleaning device to a force that prevents the cleaning device from following the sloping operative direction of motion.

The cleaning device may be in accordance with the first aspect of the invention.

The effect of providing a fish cage with at least one cleaning device as described by the invention is that a net belonging to the fish cage can be cleaned autonomously. A plurality of cleaning devices may be connected to fixed coupling points on the holding structure. In an alternative embodiment, the cleaning devices may be moved from a first coupling point to a second coupling point. The number of cleaning devices in a fish cage may be adjusted to the area that is to be cleaned. If the cleaning device has a reach of 2 x 25 metres, a fish cage with a circumference of 180 metres may include four cleaning devices to cover the entire area.

In a third aspect, the invention relates to a method for cleaning a submerged surface, the method comprising arranging a cleaning device according to the first aspect of the invention in a fish-farming cage, the method comprising the steps of: a) letting the cleaning device move alternately in a sloping, upward operative direction of motion and a sloping, downward direction of motion along a first horizontal direction of motion or a second horizontal direction of motion b) letting the cleaning device switch between the first and the second horizontal direction of motion when the cable subjects the cleaning device to a force that prevents the cleaning device from following the operative direction of motion. The effect of letting the cleaning device move in the way described by the invention is that the cleaning device can move in a V-pattern that forms a movement pattern covering the entire portion of the submerged surface that is to be cleaned.

The method may further comprise using a cleaning device that moves along the sloping operative direction of motion at a constant angle of pitch.

The method may further comprise defining a work area on the submerged surface, wherein the upper and lower depths of the work area are defined by a depth sensor, and wherein the horizontal extent of the work area is defined by the length of the cable.

In what follows, an example of a preferred embodiment is described, which is visualized in the accompanying drawings, in which:

Figure 1 shows a top view of a cleaning device according to the invention;

Figure 2 shows a side view of the cleaning device of figure 1 , the cleaning device being in contact with a submerged surface;

Figure 3 shows, on a smaller scale, a schematic movement pattern for the cleaning device in a work area on a submerged surface;

Figure 4 shows, on a larger scale, a top view of a cleaning device in an operative position;

Figure 5 shows, on a larger scale the cleaning device shown in figure 4;

Figure 6 shows the difference in work width of a cleaning device in a perpendicular operative position and a slanted operative position; and

Figure 7 shows, on a smaller scale and in a view from above, a fish cage including a plurality of cleaning devices and a plurality of work areas.

Figures 1 and 2 show a cleaning device 1 according to the invention. The cleaning device 1 comprises a propulsion system 13, a cleaning unit 12, a cable 2, a first end portion 10 and a second end portion 1 1 . The cleaning device is provided with a first axis 100.

The propulsion system 13 is shown with four propulsion thrusters 14 and two pusher thrusters 15. The pusher thrusters 15 are arranged perpendicularly to the propulsion thrusters 14. The propulsion thrusters 14 are arranged to move the cleaning device 1 along a submerged surface 99 in a desired direction. The pusher thrusters 15 are arranged to move the cleaning device 1 towards and away from the submerged surface 99. Further, the pusher thrusters 15 are arranged to hold the cleaning device 1 up to the submerged surface 99 when the cleaning unit 12 is active, the cleaning unit 12 subjecting the cleaning device 1 to a push force pushing the cleaning device 1 away from the submerged surface 99.

The cleaning device 1 further comprises an orientation sensor 16 which is arranged to register the orientation of the cleaning device 1 in the water column, and a depth sensor 17 which is arranged to register the depth of the cleaning device 1 below a water surface 98. The orientation sensor 16 and the depth sensor 17 are connected to the propulsion system 13.

When the cleaning device 1 is operative, the first end portion 10 will be facing downwards in the water column and the second end portion 1 1 will be facing upwards in the water column, both when the cleaning device 1 is moving downwards in a direction D and upwards in a direction C in the water column.

The first end 21 of the cable 2 is connected to a coupling attachment 31 belonging to a holding structure 3 (figure 3). The cable 2 is shown floating in the water column so that the cleaning device 1 may orient freely in the water column.

Figure 3 shows a principle drawing of a work area 90 of the cleaning device 1 in a fish cage 4. The work area 90 comprises an upper boundary 98, a lower boundary 97, a first lateral boundary 95 and a second lateral boundary 96.

The upper boundary 98 may be a predefined depth. The upper boundary 98 may be a water surface, as shown in figure 3. The lower boundary 97 is a predefined depth. The predefined depths 97, 98 may be programmed into the control system 13.

The first lateral boundary 95 and the second lateral boundary 96 are defined by the length of the cable 2 and form a curve with a radius that is substantially equal to the length of the cable 2.

Figure 4 shows a movement pattern for the cleaning device 1 within the work area 90 on the submerged surface 99. To accentuate the principle, the angle of pitch is substantially larger than it will typically be in actual use. When the cleaning device 1 reaches the first lateral boundary 95 or the second lateral boundary 96, the first reversing device is activated, and the cleaning device 1 changes its horizontal direction of motion from A to B, or vice versa. The angle of the operative direction of motion X is kept constant.

When the cleaning device 1 reaches the upper boundary 98, shown in the figure as a water surface, a reduced buoyancy of the cleaning device 1 will make the cleaning device 1 unstable. The orientation sensor 16 registers the instability and outputs a signal to the propulsion system 13 to change the vertical direction of motion from C to D. If the upper boundary 98 is below the water surface, the depth sensor 17 may register the upper boundary 98 and output a signal to the propulsion system 13 to change the vertical direction of motion from C to D.

When the cleaning device 1 reaches the lower boundary line 97, this is registered by the depth sensor 17, which outputs a signal to the propulsion system 13 to change the vertical direction of motion from D to C.

Figure 5 shows how the cleaning device 1 moves along the submerged surface 99 in a horizontal direction of motion B and down along an operative sloping direction of motion X1 at a constant angle of pitch a. The cable 2 has been extended to a maximum length and prevents a further horizontal movement in the second horizontal direction of motion B.

The cable 2 applies a tensile force F2 to the cleaning device 1 . The propulsion system 13 gives the cleaning device 1 a push force FV which is constant. Because the cable 2 prevents a further horizontal movement by the cleaning device 1 , the push force FV will provide a rotation of the cleaning device 1 in a direction R around the second end 22 of the cable. The rotation R is registered by the orientation sensor 16, which outputs a signal to the control system 13 when the angle a exceeds a given value. The horizontal reversing device is activated, and the propulsion system 13 changes the input effect and pushing direction of the thrusters 14 so that the cleaning device 1 changes its operative direction of motion from the direction X1 to the direction X2 or X3 so that the cleaning device 1 begins to move in the first horizontal direction of motion A towards the coupling attachment 31 . The cleaning device 1 moves in the first horizontal direction of motion A, past the coupling attachment 31 , until, again, the cable 2 is fully extended.

Figure 6 shows alternative orientations of the cleaning device 1 when it is being moved along the sloping operative direction of motion X2. When the first axis 100 of the cleaning device 1 is oriented perpendicularly, the cleaning device 1 will provide a work width W1 which is larger than a work width W2 which is created when the first axis 100 of the cleaning device 1 coincides with the sloping operative direction of motion X2.

Figure 7 shows a fish cage 4 seen from above, the fish cage 4 including four cleaning devices 1 . The four cleaning devices 1 are each attached to the holding structure 3 via a respective coupling attachment 31 . The four cleaning devices 1 each cover a separate sector S1 , S2, S3, S4 of the fish cage 4 so that the four cleaning devices 1 together can clean an upper portion of the net 32 (see figure 3) around the entire fish cage 4.

It should be noted that all the above-mentioned embodiments illustrate the invention, but do not limit it, and persons skilled in the art may construct many alternative embodiments without departing from the scope of the attached claims. In the claims, reference numbers in brackets are not to be regarded as restrictive.

The use of the verb "to comprise" and its different forms does not exclude the presence of elements or steps that are not mentioned in the claims. The indefinite article "a" or "an" before an element does not exclude the presence of several such elements.

The fact that some features are indicated in mutually different dependent claims does not indicate that a combination of these features cannot be used with advantage.

Claims

C l a i m s

1 . A cleaning device (1 ) for cleaning a submerged surface (99), the cleaning device (1 ) comprising:

- a cleaning unit (12);

- a propulsion system (13) arranged to move the cleaning device (1 ) along a first horizontal direction of motion (A), a second horizontal direction of motion (B), a first vertical direction of motion (C) and a second vertical direction of motion (D); and

- a cable (2) which, at a first end (21 ), is connected to a coupling attachment (31 ) fixed to a holding structure (3) and, at a second end (22), is connected to the cleaning device (1 ),

c h a r a c t e r i z e d i n that:

- the propulsion system (13) is further arranged to provide a sloping operative direction of motion (X1 -X4) of the cleaning device (1 ) along the submerged surface (99); and

- the cleaning device (1 ) further comprises a first reversing device arranged to communicate with the propulsion system (13) so that the cleaning device (1 ) may switch between the first horizontal direction of motion (A) and the second horizontal direction of motion (B) when the cable (2) subjects the cleaning device (1 ) to a force (F2) which prevents the cleaning device (1 ) from following the sloping operative direction of motion (X1 -X4).

2. The cleaning device (1 ) according to claim 1 , wherein the cleaning device (1 ) comprises a second reversing device arranged to switch between the first vertical direction of motion (C) and the second vertical direction of motion (D) of the cleaning device (1 ).

3. The cleaning device (1 ) according to claims 1 -2, wherein the first reversing device includes an orientation sensor (16).

4. The cleaning device (1 ) according to any one of the preceding claims, wherein the first reversing device includes a mechanical switch or a valve.

5. The cleaning device (1 ) according to any one of the preceding claims, wherein the sloping operative direction of motion (X1 -X4) has a constant angle of pitch (a).

6. The cleaning device (1 ) according to any one of the preceding claims, wherein the propulsion system (13) includes at least two thrusters (14) of adjustable push force (FV).

7. A fish-farming cage (4) including at least one cleaning device (1 ) for cleaning a submerged surface (99), the cleaning device (1 ) comprising:

- a cleaning unit (12);

- a propulsion system (13) arranged to move the cleaning device (1 ) along a first horizontal direction of motion (A) and a second horizontal direction of motion (B) and a first vertical direction of motion (C) and a second vertical direction of motion (D); and

c h a r a c t e r i z e d i n that:

- the cleaning device (1 ) further comprises a first reversing device arranged to communicate with the propulsion system (13) so that the cleaning device (1 ) can switch between the first horizontal direction of motion (A) and the second horizontal direction of motion (B) when the cable (2) subjects the cleaning device (1 ) to a force (F2) which prevents the cleaning device (1 ) from following the sloping operative direction of motion (X1 -X4).

8. The fish-farming cage (4) according to claim 7, wherein the cleaning device (1 ) includes a vertical reversing device arranged to switch between the first vertical direction of motion (C) and the second vertical direction of motion (D) of the cleaning device (1 ) when the cleaning device (1 ) arrives at a specified depth in the water column.

9. A method for cleaning a submerged surface (99), the method comprising arranging a cleaning device (1 ) according to claim 1 in a fish-farming cage 4, c h a r a c t e r i z e d i n that the method comprises the steps of: a. letting the cleaning device (1 ) move alternately in a sloping, upward operative direction of motion (X1 -X4) and a sloping, downward operative direc- tion of motion (X1 -X4) along a first horizontal direction of motion (A) or a second horizontal direction of motion (B). b. letting the cleaning device (1 ) switch between the first horizontal direction of motion (A) and the second horizontal direction of motion (B) when the cable subjects the cleaning device (1 ) to a force (F2) that prevents the cleaning device (1 ) from following the operative direction of motion (X1 -X4).

The method for cleaning a submerged surface (99) according to claim 9, wherein the cleaning device (1 ) moves along the sloping operative direction of motion (X1 -X4) at a constant angle of pitch (a).

A method for defining a work area (90) on a submerged surface (99) for a cleaning device (1 ) according to claim 1 , wherein the upper and lower depths of the work area (90) are defined by a depth sensor, and wherein the horizontal extent of the work area (90) is defined by the length of the cable (2).