The present invention relates to a closed, spherical cage for rearing fish as set out in the preamble of claim 1.

Background

Industrial fish farming has long been a major "industry" in many countries, and both the size and number of fish farms have grown considerably. The vast majority of cages used commercially are open cages located in the sea and where the fish that are raised are separated from the surroundings by a single layer of seine net that hangs like a large cylinder in the sea, closed in its bottom but open at the top. The net hangs from buoyancy elements, which form a floating ring on the surface. Under ideal conditions, this works well, but it is exposed to damage and loss of fish during storms, and provides little protection against algae and not least salmon lice. Billions of (Norwegian) kroner are lost annually in the form of escaping fish which also leads to an unwanted strain on the wild fish in the form of disease etc.

Existing facilities also contaminate the seabed under the facilities and the surrounding areas, because they lack effective solutions for collecting waste from feed and excrement.

Due to the disadvantages mentioned, a number of measures have been proposed to overcome these problems or disadvantages, such as moving the entire facilities ashore or using facilities that are more closed and can provide better protection against one or more of the mentioned disadvantages. So far, no proposals have been made that have proved sufficiently simple and affordable to realize that they to significant extent have been able to compete with existing facilities, despite the fact that they technically show advantages over the open cages.

From U.S. Patent No. 8424491 B2, a closed, mainly spherical cage construction is known, which is built up by triangular, rigid beam sections based on beam elements of plastic or metal. The beam elements can enclose conduits or inflatable elements. The system is submersible so that the entire cage can be submerged under water if necessary. According to the patent, cages of different sizes can be built up of the same basic components, for example by using from 80 up to 720 composite triangular elements, but since the elements are rigid in nature, extreme precision is required to join these at such an angle that one achieves the desired size. It could therefore be desirable to have a system which is more flexible and which allows the components to be joined together without having to ensure such a high degree of accuracy. In Norwegian patent No. 332518, a spherical cage based on a supporting structure of beams composed of polygons with a net in the form of removable panels is described. Fixed and inflatable buoyancy elements are included in several of the beams, while some beams may contain only fixed buoyancy elements, only inflatable buoyancy elements or no such parts.

Among other technology known in the art, reference is made to SE 450866 and to US 5,251,571 A.

Objectives

It is an object of the present invention to provide a cage for farming fish which is simple in its construction, easy to adapt to different sizes and easy and safe to operate, including exhibiting low operating and maintenance costs, and which withstands storms with minimal risk of damage.

It is a further object to provide a cage which provides good security against escape and which has an inherent ability of protecting fish against lice and against algae in the event of strong algae growth, and which pollutes the environment to a lesser extent.

The present invention

The above object is achieved by the fish cage according to the present invention as claimed in claim 1.

Preferred embodiments of the invention are disclosed by the dependent claims.

By "closed" as used here, is understood that there are both roofs and walls in the cage, however, it should not be understood that any part of it is waterproof or airtight unless it is clearly stated.

The present invention provides a cage which is unique in its construction and which solves the mentioned challenges, among other things in that it can be immersed completely under water which is a great advantage in bad weather or as a measure among others to reduce the nuisance caused by salmon lice.

The submersible function of the cage enables the installation of coastal fish farms, where conventional cage systems are unable to withstand the strong natural forces to which the facilities are occasionally exposed in the form of strong winds and large waves.

The submerged cage according to the invention also offers advantages in farming in that upper water masses can be avoided in critical situations, such as in the case of dangerous algae growth, lice infestations, or in the case of discharges of environmental toxins. Other critical situations can be, for example, oil spills caused by discharges from the oil industry or accidents at sea. Furthermore, the system of adjustable buoyancy / ballast can be controlled so that the cage can be turned in the sea so that any part of the cage can be turned to above water level whenever desired, for example when cleaning, maintaining or installing new equipment or transfer channel for fish or the like.

The present invention consists of a closed cage construction, which provides a number of advantages over currently used conventional cage constructions. The closed design offers obvious advantages over existing solutions used, due to the fact that the risk of escaping farmed fish is significantly reduced through the cage being closed. According to a preferred embodiment, the cage has a double net solution, which, among other things, allows for continuous monitoring of several operating parameters, including damage to the net with the risk of escape The net is divided into panes / sections for each of the cage's construction elements / panes and is individually attached to buoyancy elements. The fact that the net is divided into sections gives a significant advantage over conventional cages with large and heavy nets. The advantage of smaller net sections is that this method provides easier assembly and service due to weight, size and requirements for tools, for otherwise heavy operations as is the case today. If desired, the solution with net sections provides the opportunity to have additional layers of net, or other membrane types if considered expedient.

The cage's construction with the possibility of at least two layers of net (or net plus membrane), means that one can mount a filter function with a cloth/ membrane on the outer layer, as well as the possibility of controlling and monitoring of water masses between outer and inner net section.

The cage's construction makes it possible to move it by towing even if the cage should be filled with fish. Moving cages with fish has proven to be desirable for the industry from an operational and safety perspective.

Size adaption from small to large diameter of the cage, or vice versa, can be done either by selecting (tension) struts and buoyancy tubes of other lengths or by changing the geometry of the finger brackets so that the curvature is generally smaller or larger at each joint, as well as a combination of the two methods.

Compared to the closed structure known from U.S. Pat. No. 8,424,491 B2, the cage of the present invention is lighter, easier to size adapt, and allows the use of more than one layer of net or other type of "membrane" against the environment, if desired. While in each joint of the cage according to US 8424491 there are four or five rigid beam elements which meet, according to the present invention, only three struts meet at each joint and they are easily assembled using a particular sleeve and a prefabricated finger bracket which makes the mounting in principle equally simple as setting up a tent. While the finished cage of the present invention is soft, resilient and flexible, the skeleton of the cage of US 8,424,491 B2 is rigid. It is not a given that one cage is better than the other in all conditions and in all contexts, but they are different and have, despite some common features, fundamentally different properties.

In the following, the present invention will be described in more detail in the form of some selected, non-limiting embodiments, with reference to the accompanying drawings.

Figure 1 is a schematic side view of a cage according to the present invention.

Figure 2 is a schematic side view of a cage according to the present invention during an operation.

Figure 3 is a schematic side view of a cage according to the present invention in a submerged state.

Figure 4 shows an embodiment of the composition of the supporting skeleton of the cage according to the present invention

Figure 5 shows, schematically, details of a buoyancy system comprised by the cage according to the present invention

Figure 6 is a schematic side view of two cages according to the present invention during the execution of an operation.

Figure 1 shows a closed, spherical cage 10 according to the present invention floating deep in the sea, with the top projecting above the water surface. The spherical shape is obtained through a number of struts 11 mounted together in joints 12, which form a grid pattern consisting of polygons 13. In the embodiment shown, the polygons are a combination of pentagons and hexagons. Most of the panes are covered with nets in at least one layer.

The upper pane of the cage is covered by an impermeable plate 14 and the lower pane is covered by a plate 15 provided with further details, including a fastening device 16 to a bottom mooring 17 and a hatch 18 for discharging waste from the cage. A safety line 19 is also shown as a supplement to the mooring 17. A buoy 21 with flag, light or other marking, is attached to the cage to make it easily visible.

As is explained in the following, tubes are arranged in connection with each of the struts, containing buoyancy elements, which make it possible to place the cage high or low in the water. Figure 2 shows the cage from figure 1 in a situation in which a service boat 22 has arrived and connected a drainage hose 23 to the hatch 18 to pump out solid waste from the lower part of the cage. In practice, one end of the drainage hose 23 can normally be connected to the hatch 18 while the other end is attached to the upper part of the cage so that it can be easily connected to the pump on board the boat, without the need for subsea connecting operations. The drainage hose 23 may alternatively be connected to a collection device, for example in the form of an impervious bag/ container on the bottom for temporary collection and storage.

Figure 3 shows a situation where the cage according to the invention has been pulled completely under water by means of a winch 31 and preferably by means of an adapted adjustment of the buoyancy in at least some of the buoyancy elements. In a zone A at the top of the cage, an airtight fabric is arranged to ensure that an air pocket accompanies the cage when it is pulled down. For example, in zone A, solar cell panels can be fitted for storage/ supply of energy so that the cage is at least partially self-sufficient in energy.

At the bottom of the cage, in a zone B, an impermeable fabric is typically arranged to collect solid waste until it is discharged via the hatch 18. In the submerged state a special buoy 32, typically equipped with battery, communication unit and a central control unit 33, have the ability to transfer information to and from the cage, as well as controlling certain parameters on the cage as discussed below. For example, the control unit may be programmed to automatically lower the cage under water when wind strength and/ or wave height exceeds certain levels. This can be done by starting the winch 31 and adjusting the buoyancy using the buoyancy elements described below.

The communication unit in the buoy 32 can provide current information about the condition of the cage and the position of the cage, as well as allowing an operator to override the automation. The buoy 32 is shown connected to the cage with a cable 34 for transmission of current and optionally communication, while communication to the operator preferably takes place wirelessly. The winch 31 can, if desired, be operated manually, but is preferably controlled by the control unit 33 which automatically can implement various measures based on external parameters, such as wind strength, wave height etc.

One or more of the communication unit, the control unit and the battery may also optionally be arranged in a watertight manner on the plate 14.

Figure 4 shows how the struts are connected together at joints 12, as shown more generally in figure 1. A strut 11 is connected at both ends via a sleeve 42 to a Y-shaped finger bracket 43. The sleeve is attached with a through-going rivet or bolt 44 to the finger bracket 43. The strut 11 is attached to the sleeve 42 with a rivet or bolt 45, which has a certain freedom of movement in a longitudinal groove 46 in the sleeve, which allows axial movement of the struts without subjecting the finger brackets 43 or the struts to harmful stress. Thus, the entire construction is flexible and relatively tolerant for forces applied by wave motions.

It is, however, a key element of the present invention that the struts do not operate alone, but in common with tubes containing buoyancy elements. This is shown in figure 5. To a strut 11, a connected and parallel running buoyancy tube 50 is shown. The buoyancy tube 50 can contain a number of functional elements and the most important of these are discussed here. Each buoyancy tube contains a cableway 51 on the inside of the tube wall for transporting air and normally transmission of electrical signals, including a pneumatic pipe 52 for supplying air to a buoyancy element in the form of a bladder 53 as well as a return pipe 54 for releasing air. An electric cable 55 is also shown. A local control unit 56 is shown too; it is in electrical contact at least with the central control unit 33 and optionally with other local control units 56. The local control units 56 need not have their own processor, but may in one embodiment comprise a pressure and a temperature sensor and may comprise a relay or the like, which allows it to control one or more valves for filling or emptying gas from the bladders 53.

The control unit 56 and the bladders 53 may be attached to one or more flanges 57 projecting into the buoyancy tube 50 from its cylindrical wall. It is to be understood that the bladder 53 in the inflated state can extend the entire length of the buoyancy tube and fill the entire diameter of the buoyancy tube. It is typically made of a robust, elastic material that will not be damaged even if it is squeezed against shells, gravel or other particles.

The buoyancy tube 50 is furthermore provided with net fasteners 58 on both sides, serving to hold the pane-shaped net in place. Figure 5 shows an inner net 61 and an outer net 62 with a mutual distance corresponding to the outer diameter of the buoyancy tube. The tube can be equipped with points 59 for lighting and possibly for a camera. Furthermore, it may comprise nozzles for supplying extra air or oxygen to the water body. Figure 5 also shows a fastening point 60 for fastening struts to buoyancy tubes. There will be a number of such fasteners 60 along the length of the buoyancy tubes 50 and the struts 11, depending on the length thereof. The buoyancy tube furthermore has through openings 63 between its outside and its inside, to allow water to pass through, ensuring that the buoyancy is reduced when the amount of air in the bladder 53 is reduced.

The central control unit 33 can be programmed to fill or empty the bladders 53 in each buoyancy tube 50 individually. Alternatively, the buoyancy tubes can be divided into different zones, so that the bladders in each zone are emptied and filled at the same time, but independently of the emptying and filling in other zones. Both of these options allows making parts of the cage light and other parts of the cage heavier, whereby the whole cage can be rotated in the water, so that any part of it may be brought above the water surface, for example for maintenance, repair, cleaning or to and disconnection of equipment.

The buoyancy tubes are typically connected with finger brackets and sleeves that correspond to those shown in figure 4, but with dimensions that are adapted to the diameter of the buoyancy tubes.

The struts 11 can also be designed as - or with - gas-tight, closed sections which give them a certain buoyancy in water, or at least give the strut an effective density close to the density of water, so with regard to buoyancy, they are approximately neutral in the water.

Figure 6 shows schematically how a tubular net 64 can be connected to a respective pane in two closely spaced cages according to the invention. This can be done to move fish from one cage to another, for example when larger maintenance operations are required. The otherwise closed sections 61 and 62 of inner and outer seine nets, respectively, must for the purpose be disconnected, at least partially, in the relevant panes in order to allow the fish to pass.

Feeding of the fish in the cage can in principle take place via any pane, preferably, but not necessarily, near the top of the cage and from a position which during normal operation is above water.