NO346878B1 - Sink-float structure - Google Patents

Description

TECHNICAL AREA

[0001] The present invention comprises a sink-float structure which is able to sink and float in relation to the water surface.

BACKGROUND OF THE INVENTION

[0002] A sinking-floating structure is used for a sinking-floating fishing pond for farming fish and shellfish and an oil containment boom to prevent diffusion into the sea. E.g. patent document 1 discloses a sink-float frame with suspended curtains enclosing four sides, capable of preventing a contaminated area from diffusing into water. A sink-float structure can be positioned at any possible depth in the water. The sinking-floating frame indicated in patent document 1 sinks or floats by exchanging water and air in an airtight chamber. The sinking floating structure may be sunk to the bottom of the water when the water surface is strongly disturbed by a storm, e.g. to avoid destruction and leaching.

Patent Document 1: Japanese Patent No. 3761254

DESCRIPTION OF THE INVENTION

[0004] The sinking floating frame with the design disclosed in Patent Document 1 changes its depth in the water in accordance with the amount of water flowing through a water inlet-outlet part formed on the bottom of the four airtight chambers. In this configuration, if the airtight chambers rather water or air often remain in the airtight chambers. In the case of trying to lower the floating structure, it takes time, if the air remains in the airtight chamber, to lower it or it is impossible to lower it to the desired depth or a position of the structure tends to be unstable even when it is sinking. In case one tries to raise (float) the sinking structure it takes time, if the water remains in the airtight chamber, to raise it or it is impossible to raise it to a desired depth or a position of the structure tends to be unstable even when it flows. In addition, projections formed on the bottoms of the airtight chambers are difficult to get out of the water and can be an obstacle to moving the structure in the water.

[0005] In light of the above-mentioned situation, an objective of the present invention is to provide a sink-float structure that safely fills and empties a fluid, performs safe float or sink movement and promotes control of its position in water by arranging fluid inlets - outlet parts on the upper and lower sides of a hollow element.

[0006] To achieve this objective, the present invention provides a sinking floating structure which is able to sink and float in relation to the water surface.

The present invention thus relates to a sinking floating structure 30 which can be raised and lowered in relation to the water surface where the sinking floating structure includes:

a hollow element 2 divided into several chambers 6,

a water inlet-outlet part 7 through which water flows in and out of the hollow element 2,

an air inlet-outlet part 8 through which air flows in and out of the hollow element 2, and

fluid channels 10 located between adjacent chambers that allow water and air to flow through the adjacent chambers 6, wherein,

if a lower side is defined as the side located on the bottom side of the water in the case where the hollow element floats on the water surface and an upper side is defined as a side opposite to the lower side,

the water inlet-outlet part 7 is on the lower side in the hollow element 2, the air inlet-outlet part 8 is on the upper side in the hollow element 2,

and

The fluid channels 10 located between the adjacent chambers 6 have an inlet-outlet part for water and air 11 located on the upper side of one of the chambers 6, and another inlet-outlet part for water and air 12 located on the lower side 12 in an adjacent chamber 6 , there

several of the hollow elements 2 form a frame 1.

[0007] This configuration prevents air from remaining in each chamber to fill the entire hollow element with water, and prevents water from remaining in each chamber to empty the entire hollow element. This means that water and air are safely filled and emptied, which makes it possible to efficiently use limited space in the hollow element. This performs a quick and safe raising and lowering movement. Present in the divided chambers, water and air do not flow between the chambers, thereby promoting control of the position of the sinking float structure in water.

[0008] In the sink-float structure according to the present invention, it is preferred that the hollow element is an element respectively including the simple water inlet-outlet part and the simple air inlet-outlet part, and several hollow elements configuring a frame. This configuration causes the parts filled with water and air to be dispersively allocated to balance the weight in the frame, which is effective in controlling the position and preventing tilting of the sink-float structure in water.

[0009] An embodiment according to the invention comprises a sink-float structure where the hollow element 2 is preferably arranged to keep the center of gravity of the frame 1 in the central position of the frame while it is filled with water or air. This arrangement further prevents a tilting of the sink-float structure and promotes that the sink-float structure maintains a horizontal state in water.

[0010] Another embodiment according to the invention comprises a sink-float structure where the hollow elements 2 are preferably also arranged to keep an equal distance between the chambers 6 filled with water or air in the peripheral direction of the frame 1 while the hollow elements are filled with water or air. The configuration prevents further tilting of the sink-float structure and promotes the sink-float structure to maintain a horizontal state in water.

[0011] According to the present invention, water and air tend not to remain in the hollow element, which enables efficient use of a limited space into the hollow element. This results in a safe and quick raising and lowering movement. As water or air is filled in the divided chambers, water tends not to flow between the chambers to effect a control of the position of the sink-float structure in water. BRIEF DESCRIPTION OF THE FIGURES

[0012] [Fig. 1] This is a perspective view showing an example of use, as a fishpond, of a sink-float structure according to an embodiment of the present invention.

[Fig. 2] This is a schematic section cut across an axial direction showing a hollow element according to an embodiment of the present invention.

[Fig. 3] This is a perspective view illustrating a communicator according to an embodiment of the present invention.

[Fig. 4] These are schematic sections illustrating the hollow element according to an embodiment of the present invention which is filled with water.

[Fig. 5] These are schematic sections illustrating the hollow element according to an embodiment of the present invention which is filled with air.

[Fig. 6] These are plan views illustrating a first example of the sink-float structure according to an embodiment of the present invention which is filled with water.

[Fig.7] These are plan views illustrating another example of the sink-float structure according to an embodiment of the present invention which is filled with water.

[Fig. 8] This is a schematic section illustrating another example of the communicator according to an embodiment of the present invention.

[Fig. 9] This is a perspective view illustrating another example of the sink float structure according to an embodiment of the present invention.

[Fig. 10] This is a perspective view of an example of the sink-float structure according to an embodiment of the present invention which has a double circular shape.

METHOD(S) OF CARRYING OUT THE INVENTION

[0013] The following describes an embodiment of the present invention with reference to the figures. A sinking-floating structure according to an embodiment of the present invention is first described with reference to Fig. 1. The sinking-floating structure (hereinafter only referred to as the structure) is capable of being raised and lowered in relation to the water surface (e.g. the sea surface) . Fig. 1 is a perspective view illustrating an example of the use of this structure 30 for an embodiment in the form of a fishpond for raising fish and shellfish. The structure 30 includes a frame 1 with netting 20 attached thereto. Fig. 1 illustrates a main part. Although not illustrated in the figures, the structure 30 may include a weight to balance against the buoyancy of the frame 1 and an anchor which is placed on the bottom of the water.

[0014] In the example in Fig. 1, the frame 1 is formed in a circular shape by means of hollow elements 2. Each of the hollow elements 2 includes a water inlet-outlet pipe 3 and an air inlet-outlet pipe 4 separately located at a certain interval. Hereinafter, it is assumed for a simple explanation that a hollow element 2 includes a water inlet-outlet pipe 3 and an air inlet-outlet pipe 4. In the example in Fig. 1, the frame 1 is shaped to have a circular shape by means of four hollow elements 2.

[0015] Each hollow element 2 is provided with the water inlet-outlet pipe 3 and the air inlet-outlet pipe 4. Water is injected into the hollow element 2 by means of forced injection using a pump connected to the water inlet-outlet pipe 3 or spontaneous injection. When water is injected into the hollow element 2 filled with air, the air is emptied through the air inlet-outlet pipe 4. Depending on the amount of water injected into the hollow element 2, the hollow element 2 loses its buoyancy and sinks into the water.

[0016] In contrast, air is injected into the hollow element 2 by means of forced injection using a compressor or a high-pressure cylinder connected to the air inlet-outlet pipe 4. When air is injected into the hollow element 2 filled with water, the water is emptied through the water inlet- the outlet pipe 3. In accordance with the amount of air injected into the hollow element 2, the hollow element 2 achieves its buoyancy and is raised towards the surface of the water.

[0017] The internal structure in the hollow element 2 is described with reference to Fig. 2. Fig. 2 is a schematic section of the hollow element 2 in the axial direction and corresponds to a sectional view along the line AA in Fig. 1. Fig. 2 illustrates one of the hollow elements 2 while the other three hollow elements 2 have the same structure.

[0018] Fig. 2 illustrates the hollow element 2 floating on the water surface. The lower side in Fig. 2 forms the bottom side of the water. Hereinafter, the lower side on the inside of the hollow element 2 means the lowest position of the internal surface of the hollow element 2 against the bottom side of the water or its vicinity. The upper side means the highest position of the inner surface of the hollow element 2 opposite the bottom side of the water or its vicinity.

[0019] The inside of the hollow element 2 is divided into four chambers 6a, 6b, 6c and 6d with partition walls 5. The water inlet-outlet pipe 3 is provided to chamber 6a located at the end of the hollow element 2, while the air inlet-outlet pipe 4 is provided towards chamber 6d located at the other end. The water inlet-outlet pipe 3 has an inlet-outlet part 7 on the lower side of chamber 6a. Water from the water inlet-outlet pipe 3 flows out to chamber 6a through an inlet-outlet part 7. As in each figure in Fig. 5 to be explained later, when air is injected through the air inlet-outlet pipe 4 into the hollow member 2, water in chamber 6a flows in in the water inlet-outlet pipe 3.

[0020] The air inlet-outlet pipe 4 has an inlet-outlet part 8 on the upper side of chamber 6d. Air from the air inlet-outlet pipe 4 flows out to the chamber 6d through an inlet-outlet part 8. As in each of the figures in Fig.6 explained later, when water is injected through the water inlet-outlet pipe 3 into the hollow member 2, air flows into the chamber 6d into the air inlet-outlet pipe 4. The inlet-outlet parts 7 and 8 each only need to have a configuration with an opening to allow water and air to flow in and out, and are not limited to an opening at one end of the corresponding pipe which in Fig. 2, and can e.g. be several small holes. The opening can be a through hole provided in the hollow element 2. With such a through hole formed in the lower side of chamber 6a, the water inlet-outlet pipe 3 is connected to its through hole from the outside of chamber 6a.

[0021] The partition walls 5 are installed with a fluid channel 10. Each fluid channel 10 has the same structure and includes an inlet-outlet part 11 on the upper side of each chamber and an inlet-outlet part 12 on the lower side of each chamber. The inlet-outlet parts 11 and 12 are parts where water or air in each chamber flows in and out.

[0022] Fig. 3 is a perspective view of an example of a fluid channel 10. In the example in Fig. 3, the fluid channel 10 is a tube shaped into a crank shape and is installed in the circular partition wall 5. The opening at one end of the tube is the inlet outlet part 11 and the opening at the other end is the inlet-outlet part 12. The inlet-outlet parts 11 and 12 need only have a configuration with an opening to allow water and air to flow in and out, and is not limited to an opening at the end of the pipe as in Fig. 2 and 3, and can e.g. be several small holes. A through hole provided on the part of the wall 5 can also be used as inlet-outlet part 11. Alternatively, a through hole can be provided on the upper side of one of the adjacent chambers used as inlet-outlet part 11, while another through hole can be provided on the lower side of the second chamber to be used as the inlet-outlet part 12. These two through holes can be connected through a pipe arranged on the outside of the hollow element 2. Another configuration of the fluid channel 10 will be described later with regard to Fig. 8.

[0023] Fig. 4 is a section illustrating the hollow element 2 which is filled with water. Fig. 4a illustrates the chamber 6a which is filled with water. The water inlet-outlet pipe 3 is connected to a pump 15. Water is supplied from the pump 15 which flows out into the chamber 6a through the inlet-outlet part 7. At the same time, the air inlet-outlet pipe 4 is open on the outside of the hollow element 2. Air in the hollow element 2 is emptied thus through the air inlet-outlet pipe 4 in accordance with the amount of water injected into the hollow element 2.

[0024] As water is injected into the chamber 6a, the height of the water 21 in the chamber 6a rises. After the water level in the chamber 6a reaches the inlet-outlet part 11 of the fluid channel 10, the water starts to flow into the fluid channel 10 through the inlet-outlet part 11. Water in the fluid channel 10 then flows out to chamber 6b through the inlet-outlet part 12.

[0025] Water continues to be injected into the chamber 6a until the water height reaches the inlet outlet part 11 in the fluid channel 10 located on the upper side of the chamber 6a. That is that the water starts to fill chamber 6b after almost filling chamber 6a, which causes a reduced amount of air to leave chamber 6a.

[0026] Fig. 4B illustrates chamber 6b which is filled with water. The water height in chamber 6b is raised until it reaches the inlet-outlet part 11 in chamber 6b. As in chamber 6a, water starts to fill chamber 6c after almost filling up chamber 6b. Likewise, water starts to fill chamber 6d after almost filling up chamber 6c.

[0027] Fig. 4C illustrates chamber 6d which is filled with water. As the water continues to be injected as in the situation in Fig. 4C, the height of the water 21 rises until it reaches the inlet outlet part 8 located on the upper side of chamber 6d. Therefore, chamber 6d ends up being almost filled with water.

[0028] As illustrated in Figures 4A to 4C, as water continues to be injected into the hollow element 2, air is deflated from the hollow element 2. In accordance with the amount of air deflated, the hollow element 2 loses its buoyancy. Consequently, the hollow element 2 floats on the surface of the water and sinks into the water as the water continues to be injected.

[0029] Fig. 5 is a section showing the hollow element 2 which is filled with air. Fig.5A illustrates the chamber 6d which is filled with air. The air inlet-outlet pipe 4 is open on the outside of the hollow element 2 in Fig. 4, while in Fig. 5 the air inlet-outlet pipe 4 is connected to a compressor 16. The pump 15 connected to the water inlet-outlet pipe 3 in Fig. 4 is removed in Fig. 5 until the water inlet-outlet pipe 3 is opened on the outside of the hollow element 2.

[0030] Air is supplied from the compressor 16 which flows out to the chamber 6d through the inlet-outlet part 8. With the water inlet-outlet pipe 3 open on the outside of the hollow element 2, water is emptied on the inside of the hollow element 2 through the water inlet-outlet pipe 3 in accordance with the amount of air injected into the hollow element 2.

[0031] After air is injected into the chamber 6d, the height of the water 21 in the chamber 6d drops. After the water height reaches the inlet-outlet part 12 in the fluid channel 10, the air flow starts through the inlet-outlet part 12 into the fluid channel 10. The air in the fluid channel 10 then flows out to chamber 6c through the inlet-outlet part 11.

[0032] Air continues to fill the chamber 6d until the water level reaches the inlet-outlet part 12 after which the inlet-outlet part 12 of the fluid channel 10 is located on the lower side of the chamber 6d. I.e. that air starts to fill chamber 6c after water in chamber 6d is almost emptied, which leads to a reduced amount of water having to remain in chamber 6d.

[0033] Fig. 5B illustrates the chamber 6c which is filled with air. The height of the water 21 in chamber 6c falls until it reaches the inlet-outlet part 12 in chamber 6c. As in chamber 6d, air starts to fill chamber 6b after water in chamber 6c is almost emptied. Similarly, air filling of chamber 6a starts after water in chamber 6b has almost been emptied.

[0034] Fig. 5C illustrates the chamber 6a which is filled with air. As air continues to be injected as in the situation in Fig. 5C, the height of the water 21 decreases until it reaches the inlet-outlet part 7 located on the lower side of the chamber 6a, whereby the water in the chamber 6a is almost emptied.

[0035] As shown in Fig. 5A to 5C, air continues to be injected into the hollow element 2 and the water is emptied from the hollow element 2. In accordance with the amount of water being emptied, the hollow element 2 achieves its buoyancy. Consequently, the hollow element 2 which is submerged in water will rise towards the water surface as air continues to be injected.

[0036] As explained in Fig. 4, if water continues to be injected into the hollow element 2, an adjacent next chamber is injected with water after each chamber is almost filled with water. This prevents air from remaining in the chambers and has the entire hollow element 2 filled up with water. In contrast, as explained in Fig. 5, if air continues to be injected into the hollow element 2, an adjacent next chamber will be injected with air, after which water in each chamber is almost emptied. This prevents water from remaining in the chambers and has water throughout the hollow element 2 emptied. According to the present embodiment, water and air are therefore safely supplied and emptied to achieve an efficient use of a limited space on the inside of the hollow element 2. This enables a quick and safe raising and lowering movement.

[0037] According to the present embodiment, the number of chambers filled with water increases in a stepwise manner as water is injected and is emptied in a stepwise manner as air is injected. Water tends not to flow between the chambers as each chamber is divided by the partition walls 5. In accordance with this configuration, if the frame 1 is designed with several hollow elements 2 as in figure 1, parts filled with water can be emptied to balance the weight of frame 1, which is effective for controlling the position and preventing tilting of the structure 30 in water. This is explained with reference to Fig. 6 and 7.

[0038] Fig. 6 are plan sketches illustrating frame 1 in accordance with a first example. Fig. 6 corresponds to a plan view of frame 1 in Fig. 1. Fig. 6A and 6B are the same configuration and differ with regard to the amount of water that is filled. Fig. 6A illustrates a state where chamber 6A in each of the hollow elements 2 is filled with water (shaded areas). Fig. 6B illustrates a state where the chambers 6A and 6B in each of the hollow elements 2 are filled with water (shaded areas).

[0039] Frame 1 in Fig. 6 has the same configuration as frame 1 in Fig. 1, formed of four hollow elements 2 and respectively provided with four water inlet-outlet pipes 3 and four air inlet-outlet pipes 4. In this case, the four water inlet- outlet pipe 3 and the four air inlet-outlet pipes 4 configured so that the four pipes are branched from respective single pipes. This enables water to be supplied to the four water inlet-outlet pipes 3 by means of the one pump 15 (Fig. 4) or air to be supplied to the air inlet-outlet pipes 4 by means of the one compressor 16 (Fig. 5). This can also be applied to the configuration in Fig. 7 which is explained later. However, with respect to several of the water and air inlet-outlet pipes, they are provided from several pumps or compressors depending on certain conditions.

[0040] In the configuration in Fig. 6, the water inlet-outlet pipes 3 and the air inlet-outlet pipes 4 are separated between the neighboring hollow elements 2. This leads to an equal length of the parts not being filled with water between the chambers which are filled with water in a peripheral direction in the frame 1. In Fig.6A, the length of each part not filled with water between the chambers 6A filled with water is equal to those in the three chambers.

[0041] As water continues to be injected, the chambers 6A and 6B in each hollow element 2 are filled with water as illustrated in Fig. 6B. In this state, the length of the parts not filled with water between the chamber 6A and the chamber 6B, which is filled with water, in the adjacent hollow members 2 is equal to the length of the two chambers in the peripheral direction of the frame 1.

[0042] Frame 1 sinks into the water in accordance with the amount of water that fills it. As described above, while filling frame 1 with water, the length of the parts not filled with water between the chambers filled with water is kept equal in the peripheral direction of frame 1. In addition, the water tends not to flow between the chambers as each chamber is divided by partitions 5, which prevent tilting of the frame 1 in water. This reduces twisting of the nets 20 as a result of tilting of the frame 1 in the case where the structure 30 serves as a fishpond as illustrated in Fig. 1.

[0043] Fig. 7 is a plan view illustrating frame 1 in accordance with a second example. Fig. 7A and 7B are the same configuration and differ in the amount of water that is filled. Fig. 7A illustrates a state where chamber 6A in each of the hollow elements is filled with water (shaded areas). Fig. 7B illustrates a state where the chambers 6a and 6b in each of the hollow elements 2 are filled with water (shaded areas).

[0044] In the configuration in Fig. 7, the water inlet-outlet pipes 3 are adjacent between the adjacent, hollow elements 2. This arrangement also means that an equal length of the parts is not filled with water between the chambers filled with water in the peripheral direction of the frame 1 In Fig. 7A, the length of each of the parts not filled with water between the chambers 6A filled with water is equal to the length of the six chambers.

[0045] As the water continues to be injected, each of the chambers 6a and 6b in each hollow element 2 is filled with water as shown in Fig.7B. In this state, the length of the parts not filled with water between the chambers 6b, each filled with water, is adapted to the length v of four chambers. The frame 1 with the configuration in Fig. 7 is thus prevented from tipping in the water as in the configuration in Fig. 6.

[0046] In Fig. 6 and 7, the case where frame 1 is filled with water is explained. Tilting of frame 1 in water is prevented in the same way as is also the case when air is filled into frame 1 which is full of water and submerged in water. In this case, the length of the parts not filled with air between the chambers filled with air is equal in the peripheral direction of frame 1.

[0047] Tilting of the frame 1 in water is prevented in accordance with the configuration in Fig. 6 and 7. This is because the center of gravity of the frame 1 is present in the central position of the frame 1 in the state where each of the hollow elements 2 is filled with water . Therefore, a configuration different from the examples in Fig. 6 and 7 is adapted as long as the hollow elements 2 filled with water are arranged to keep the center of gravity of the frame 1 in the central position of the frame 1.

[0048] E.g. the number of hollow elements 2 can be changed to be different from four as in Fig. 6 and 7. Also, although frame 1 is explained with an example of circular shape, this is not limited to circular shape and can have rectangular shape or polygonal shape. The adjacent hollow elements may have openings between them instead of being directly connected.

[0049] Although the above embodiment describes an example of installing the fluid channel 10 in the partition wall 5 with the hollow fluid channel 10 included in the hollow element 2 as illustrated in Fig. 2 to 5, the fluid channel is not limited to this configuration. Fig. 8 is a section illustrating another example of the fluid channel 10. In an example according to this figure, the connection is achieved between the adjacent chambers through the fluid channel 10 which runs on the outside of the hollow element 2. The fluid channel 10 can be designed in a single tube or by connection to different pipes 10a and 10b with a fluid channel element 10c, such as a pipe or hose.

[0050] Although the embodiment above describes an example whereby frame 1 has a circular shape, this is not limited to this. Fig. 9 is a perspective view illustrating another example of the structure. Frame 1a shown in Fig. 9 is configured by arranging linear hollow elements in parallel to form the frame. In the configuration in Fig. 9, the water inlet-outlet pipes 3 and the air inlet-outlet pipes 4 are arranged in the opposite way between a pair of the hollow elements 2. In this configuration, the water first fills the chambers in opposite corners (shaded areas) and then the chambers in the pairs are filled with the hollow elements 2 in opposite directions (arrow direction a and arrow direction b), which is effective in preventing tilting of frame 1a. The structure is occasionally sunken or floating with its sloping angle as well as sunken or floating where the angle is horizontal in some cases. The hollow elements can be arranged in a line to use this as a round structure.

[0051] Fig. 10 is a perspective view illustrating a structure in accordance with another embodiment of the present invention. A frame 1b in Fig. 10 has a double circular shape, while frame 1 in Fig. 1 has a single circular shape. This configuration is advantageous for achieving buoyancy.

[0052] Although an example has been explained where the structure is used as a fishpond in the embodiment above, the structure can be used for other purposes. E.g. the structure is used as a floating bridge, a floating body for an oil barrier boom, a net hauler for setting fishing nets, a drying apparatus for lichen culture, or a floating body for fixing fishing equipment on the sea surface, and these can be lowered and stored in water when they are not is in use.

[0053] In the above embodiment, a hollow element 2 is explained as an element which respectively includes a water inlet-outlet pipe 3 and an air inlet-outlet pipe 4 as in Fig. 2. However, the hollow element can be designed by combining several elements. E.g. a hollow element 2 can be formed by combining hollow elements configured by dividing the hollow element in Fig. 2 into four chambers (6a to 6d). Although the inside of the hollow element 2 in the embodiment is divided into several chambers (6a to 6d) by means of the partitions 5 as in Fig. 2, a configuration without partitions 5 and the fluid channels 10 can be adapted.

REFERENCE CHARACTER LIST

[0054]

1, 1a, 1b frame

2 hollow element

3.4 inlet-outlet pipe

5 partition wall

6a, 6b, 6c, 6d chambers

7, 8, 11, 12 inlet-outlet part

10 fluid channel

30 sink-float structure

Claims (3)

PATENT CLAIMS 1. A sinking-floating structure (30) which can be raised and lowered in relation to the water surface where the sinking-floating structure includes: a hollow element (2) divided into several chambers (6), a water inlet-outlet part (7) through which water flows into and out of the hollow element (2), an air inlet-outlet part (8) through which air flows in and out of the hollow element (2), and fluid channels (10) located between adjacent chambers that allow water and air to flow through the adjacent chambers (6), wherein, if a lower side is defined as the side located on the bottom side of the water in the case where the hollow element floats on the water surface and an upper side is defined as a side opposite to the lower side, the water inlet-outlet part (7) is on the lower side in the hollow element (2), the air inlet-outlet part (8) is on the upper side in the hollow element (2), and the fluid channels (10) located between the adjacent chambers (6) have an inlet-outlet part for water and air (11) located on the upper side of one of the chambers (6), and another inlet-outlet part for water and air (12) located on the lower side (12) in an adjacent chamber (6), where several of the hollow elements (2) form a frame (1). 2. Sink-float structure (30) according to claim 1, in which the hollow element (2) is arranged to keep the center of gravity in the frame in the central part of the frame (1) while the hollow elements (2) are filled with water or air. 3. Sink-float structure (30) according to claim 1 or 2, in which the hollow elements (2) are arranged to keep an equal distance between the chambers (6) filled with water or air in the peripheral direction of the frame (1) while the hollow elements (2) are filled with water or air.