GB1596950A

GB1596950A - Fish-breeding tank

Info

Publication number: GB1596950A
Application number: GB25101/78A
Authority: GB
Original assignee: Pirelli Furlanis Applicazioni Idrauliche Agricole Gomma SpA
Current assignee: Pirelli Furlanis Applicazioni Idrauliche Agricole Gomma SpA
Priority date: 1978-02-07
Filing date: 1978-05-31
Publication date: 1981-09-03
Also published as: IT1108848B; IT7820043A0

Description

(54) FISH-BREEDING TANK (71) We, PIRELLI FURLANIS AP PLICAZIONI IDRAULICHE AGRICOLE GOMMA SPA, an Italian Company of Centro Pirelli, Piazza Duca d'Aosta No. 3, 20100 Milan, Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention concerns a fishbreeding tank and preferably a circular shaped tank for the hatching of fish eggs and for breeding the fry of the various species, preferably salt-water fish, e.g. cunner, bass, mullet, and the like.

There are 'known' circular shaped tanks for hatching fish eggs and for breeding the fry of the various types of fish. Said 'known' tanks however, present certain drawbacks. One of these drawbacks regards the cleaning-out, and in particular the removal of the incrustations that form on the inner walls of the tanks themselves. In these 'known' tanks, the incrustations are removed by interrupting the operation of the tanks so as to empty the water contained in the tanks and subsequently cleaning them out with the aid of mechanical means. This may be done either at the end of the fry-breeding cycle, or by removing the fry themselves and later returning them to the tank when the latter has been deaned-out. Using the first method, considerable incrustations are formed in the tanks themselves because the breeding cycles are of a very long duration. The incrustations, moreover, tend to favour the spreading of infectious diseases and can also give off gases that are harmful to the fry. What is more, the said incrustations are a source of mortality to the fry themselves. Using the second method, on the other hand, since the fry have to be caught by nets in order to transfer them to other containers whilst the tank is emp:ied and cleaned out, the said fry are at risk of being damaged by these very same nets. For the above given reasons, even using the second method the mortality rate increases.

Another drawback of the 'known' tanks is in the oxygenating of the water. To keep the fry alive, it is necessary that a certain quantity of oxygen is dissolved in the water.

Said oxygenating takes place in various ways in the 'known' tanks, and in particular by means of admitting air into the tank itself through pipes at whose extremities porous stones are placed. These systems of inletting air are the cause of undissolved air-bubbles forming in the water, said bubbles being of such dimensions that, if swallowed, can give rise to great sufferance to the fry, and could probably even lead to mortality among them.

Moreover, the strong currents of water mixed with air that are created around the diffuser interfere in a negative way with the early stages of fry life by subjecting the fry to unnecessary exertions.

It must also be added that the usual method of introducing water directly into the tank in which the larvae or fry are present can bring about the introduction of oxygenated water that is oversaturated with oxygen, or nevertheless the introduction of water containing dissolved gases in an oversaturated quantity. This factor is frequently the cause of an increase in the death rate among the fry from gas disease.

Yet another drawback, is the coming into contact of the eggs or the concentration of the eggs when the tanks are utilised as hatcheries. In such cases, both if the eggs are heavier than the water itself (in the case of fresh-water fish) and if the eggs are lighter than the water itself (in the case of salt-water fish), the water has to be made to circulate in order to prevent any contact or concentration of the eggs, and also to prevent the loss of the eggs by their passing into the exhaust-pipe. Moreover, the maximum attention has to be undertaken within the tanks themselves to re-create the very characteristics which are peculiar to the natural habitat where the reproduction of the desired species normally takes place.

The aim of the present invention is to overcome the drawbacks found in 'known' fish-breeding tanks, and in particular to pro vide a fish-breeding tank that considerably reduces the mortality rate of the fry that is either due to the oxygenating of the water itself, or to the presence of contaminating elements, or to the presence of incrustations in the tank itself, which, besides spreading infectious diseases, can also give off gases that can prove harmful to the fry.

A further aim of the present invention, is to provide a tank for hatching the eggs by re-creating, as far as possible, the same habitat existing in places where the desired species of fish reproduce naturally, while preventing at the same time any contact or concentration of the eggs themselves, and also preventing the eggs from passing into the exhaust pipe.

Still another aim of the present invention is to provide a tank wherein it is possible to use water having dissolved gases perfectly wellbalanced in it, the water having already undergone all the physical, chemical and physicochemical treatments considered necessary before coming into contact with the fry.

The object of the present invention is a fishbreeding tank having preferably a circular shape, and comprising means for oxygenating the water, and means for re-cycling the water, characterised in that it comprises means suitable for continuously cleaning, as hereinafter defined, the inner surface of the walls of said tank. "Continuously cleaning" means cleaning without having to interrupt the normal operation of the tank.

The present invention will be better understood from the following detailed description by way of example only, with reference to the accompanying drawings in which: - Figure 1 shows in a perspective view, a cross-sectioned diametrical plane of a fishbreeding tank according to the present invention; Figure 2 shows a cross-sectional view along II--II of Figure 1; Figure 13 shows a perspective view of the complex hole 13/baffle 14 of Figure 1.

In the more general form of embodiment of the fish-breeding tank, according to the present invention, said tank, having preferably a circular shape, comprises (besides the per se 'known' means for re-cycling the water and for oxygenating the water) means suitable for cleaning, continuously, the inner surfaces of the said tank walls, and means for varying both the velocity, as well as the trajectory of the water particles that are in the tank.

A fish-breeding tank, and in particular a tank for hatching fish eggs and for breeding the fry, is shown in Figure 1. In said Figure 1 a fish-breeding tank 1, having a circular shape is shown in a perspective view, crosssectioned according to a diametrical plane.

Said tank 1, comprises a basin 2 that is raised from the ground by a supporting structure 3, the upper part of the said basin having a cylindrical form, and the lower part being frusto-conical in form. Said basin 2, is made from a material that is non-toxic to the fry and the eggs-e.g. a metallic material, or stainless steel in particular.

To the lower vertex of the frusto-conical portion of the basin 2, there is connected a branch 4 of an exhaust pipe 5 having the shape of a 'U', and lying in a vertical plane.

The other branch 6 of the said exhaust pipe 5 has a slidable tubular part 7 inside the branch 6. The purpose of the said exhaust pipe 5 and of the slidable tube 7 (apart from the obvious purpose of letting the water out) will be discussed further on. All around the perimeter of the upper cylindrical part of the said basin, there is present a feeding canal 8 having, for instance, a rectangular crosssection. Said feeding canal is, for preference, placed outside the basin itself. Into said feeding canal the tubes 9 discharge, (one such tube has been shown in Figure 1), through which the re-cycled water is conveyed; whereas per se 'known' means-such as for example, pumps (not shown in Figure 1) are used for recycling said water-said means being associated with the said tubes 9. Moreover, in the upper section of the said tubes there they discharge into the feeding canal 8, there is present means for oxygenating the water such means being for example, a porous stone 10 into which a conduit 11, is inserted, and through which air is admitted for oxygenating the water. Also in the feeding canal 8 there enters, through the pipe 12, the fresh water for the tank 1. Moreover, inside the feeding canal 8 may also be present per se 'known' means (not shown), for effecting all the possible physical, chemical and/or physicochemical treatments considered necessary for the water that is present in the said feeding canal 8. The feeding canal 8, communicates with the basin 2 through a series of holes 13 protected on the side turned towards the inside of the basin, by baffles 14 (the complex hole/baffle, will be examined in detail later on, when dealing with Figure 3).

A removable rigid structure is placed inside the tank. To this rigid structure there is connected a motor of a 'known' type, to allow it to rotate. Said rigid structure comprises a vertical shaft 13, connected to a base 16. The rotation of the base 16, and of the vertical shaft 15, is facilitated by per se 'known' means placed between the said base 16 and the housing 17 (at the bottom of the basin 2) where said base 16 is housed.

Said base 16 is hollow and allows the passage of water either to the exhaust pipe 5 or to the tubes 9 for re-cycling the water.

A plurality of arms 18 (two are shown in Figure 1) are joined at one of their extremities to the vertical rotating shaft 15, while the other extremity of the said arms 18 rests (through per se 'known' means) on a track 19, made on the upper rim 20 of the basin 2. Said track acts as support and guide for the arms 18 during their rotatory movement around the tank itself. Some structural members 21-shaped like a generatrix of the tank and lying in a vertical plane-are joined at one extremity to said arms 18. The other extremity is joined to the rotating shaft 15.

Said structural members 21, have a "C"shaped section (see Figure 2) with their concave side turned towards the walls of the basin 2. On the free extremities of the said "C"-shaped structural members 21, are affixed at least one substantially continuous lamina of a resilient and flexible material, which is maintained in contact with the internal walls of the basin.

In a further preferred form of the present invention the laminae are of an elastomeric material.

In the particular form of embodiment represented in Figures 1 and 2, the laminae are actually two in number: a lamina 22 disposed in a forward position with respect to the rotatory direction of the rigid structure and a second lamina 23. (The rotatory direction of the rigid structure is indicated by the arrow in Figure 2). The lamina 22 is not in actual contact with the walls of the basin but the lamina 23 is placed in contact with said walls.

This disposition permits the utilization of laminae that have a diverse resilience and flexibility, in order to carry out an improved cleaning of the walls themselves, and moreover, to increase the vorticity of the water itself in such a way as to favour the variation in the trajectory of the water particles. Actually, said structural member 21, and the said laminae 22 and 23, are particular forms of embodiment both of the means capable of continuously cleaning the inner walls of the tank (i.e. without having to interrupt the normal operation of the tank itself), as well as of the means capable of varying the velocity and trajectory of the water within the tank itself.

A filter 24, placed in a branch 4 of the exhaust pipe 5, and a filter 25, fitted into the entrance of the tubes 9 for conveying the re-cycled water, prevent the fry or the eggs from leaving the tank. The said filters can be, when necessary, changed or cleaned by suction means or by blowing with a suitable fluid once the rigid structure is raised. Besides this, the said tank 1 is also furnished with an exhaust pipe (not shown in the drawings) for preventing the outflow of the water in case the exhaust pipe 5 becomes blocked.

In Figure 3, there is shown a preferred form of embodiment of the complex hole 13/baffle 14, that allows the passage of the water from the feeding canal 8 to the basin 2. Said hole 13, is made in the separating wall present between the feeding canal 8 and the basin 2, and preferably is circular. Moreover, the hole 13 is protected on the side turned towards the inside of the said basin 2 by the baffle 14 which is closed on four sides (i.e. the upper side, the lower side, and the lateral left-hand side when looking at Figure 3); while it remains open on the right-hand side (i.e. when looking at Figure 3), in such a way that the water issuing from the hole 13, is forced to pour out only from the said right-hand side of the baffle, and consequently to assume a trajectory which is no longer radial (as would be the case if the said baffle was not present), but tangential i.e.

directed about the perimeter of basin 2. Said baffle 14 (in the form of embodiment shown) is firmly fixed to the basin wall, but in an alternative embodiment it can be oriented around the hole. Said baffle 14, helps to increase the efficiency of the slidable tubular part 7 which is present on the inside of the branch 6 of the exhaust pipe 5, when the said slid able tubular part 7 functions as a means capable of varying the trajectory and the velocity of the water in the basin. In actual fact, the modulus of the velocity of the jet of water issuing from the opening of the baffle 14, is a function according to Bernouilli's Law as applied to a hole made in the side of a container, of the distance existing between the free surface of the water in the feeding canal and the ideal barycentre (centre of gravity) of the jet of water issuing from the baffle 14 and of the acceleration due to gravity. The direction of said jet of water issuing from the opening made in the baffle 14, on the contrary, remains constant and tangential to the circumference of the basin. The direction and the modulus of the jet of water, when said jet is introduced into the water contained in the basin is, on the contrary, made to vary by raising the slidable tubular part 7.

In effect, by lowering or raising the slidable tubular part 7, through the principle of the 'communicating vessels' the level of water contained in said basin 2, is either lowered or raised. But, in doing so, the distance 'h' existing between the ideal barycentre of the jet of water issuing from the opening of baffle 14 and the free surface of water contained in the basin 2, is either increased or reduced. In fact, from the time the jet of water issues from the baffle 14, to the time it is introduced into the water contained in the basin, the modulus of the velocity and the direction of the velocity changesdepend ing upon the height 'h' (defined previously) and upon the acceleration due to gravity.

Said jet, as a matter of fact, is subject to the Law of "free falling bodies" and hence it follows a parabolic trajectory. By varying the height 'h' by shifting the said slidable tubular part 7, it can be observed how one can succeed in varying the velocity and the trajectory of the water issuing from the baffle 14, and how the said slidable tubular part 7 is actually a particular form of embodiment (according to the present invention) of means suitable for varying the trajectory and the velocity of the water entering into the basin, and hence, also the rotational velocity of the water in the basin itself.

For better clarifying the functioning of the fish-breeding tank (according to the present invention), besides what has already been stated, the flow of the water introduced into the tank can be followed step by step, when the said tank it utilised e.g.

for breeding fry. The fresh water enters from the pipe 12, and is distributed into the feeding canal 8 where it is mixed with the oxygenated water brought in by the tubes 9 for the re-cycling of the water. Inside the feeding canal 8, the water is subjected to all the chemical, physical and/or physicochemical treatments considered necessary, that are carried out by per se 'known' means e.g. de-gasification (i.e. the elimination of any air-bubbles present in the water), the elimination of gases that prove harmful te the fry and which can become dissolved in the water and the addition of certain additives to the water, and such like. The water is then admitted by the complex hole 13/baffle 14, into the interior of the basin 2 present in the said tank. Here, also owing to the rotatory motion furnished by the baffles and also by the movement of the rigid structure and in particular by the structional members 21 and the laminae 22 and 23 associated with them, the water in following a spiral course descends towards the tank bottom, taking with it oxygen and food to the fry. (Said food may be introduced directly, by means of automatic dosers, either in the basin 2 or in the feeding canal 8).

To make it easier for the fry to see and consequently get to the food, the inner walls of the said basin 2 are treated such that they will impede light e.g. are painted in a dark colour, e.g. blue. While descending to the bottom of the tank, the water conveys along with it any debris, and carries this away from the tank. By passing through base 16, the water enters the exhaust pipe 5, to exit from it by the slidable tubular part 7. A part of the said water is sent back into the tubes 9 by per se 'known' means-so as to be re-cycled into the feeding canal 8i.e. after the water has been oxygenated by 'known' means in the upper part of the tubes 9. The deaning-out, and the movement of the water inside the basin 2, is brought about by the rigid structure-and in particular by the laminae 22 and 23 associated with the structural member 21.

In fact, the lamina 22, during the rotation of the structural member 21 around the tank, eliminates the thicker incrustations; whereas the lamina that is in direct contact with the walls of the said basin, carries out the more delicate job of removing the re maining incrustations. Moreover, by varying the number of the structural members 21 and the laminae associated with them, and the rotational velocity of the rigid structure, the desired number of repeated actions can be effectuated to the said inner surface in such a way as to prevent the deposit of any substances or the formation of incrustations on the said walls. The said structural members 21, and the said laminae 22 and 23, increase the vorticity of the water by their continuous rotatory movement and because of their particular shapes. Besides this, their repeated rotatory movements help to re-create the ambient 'habitat' conditions that are necessary for the better acclimatization of the fry (or the eggs-in such cases when the tank is utilised as a hatchery), for example due to tides, or the like. Finally, the filters 24 and 25-being chosen for their best suited dimensions, can also impede the eggs from being dispersed by passing into the exhaust pipe.

WHAT WE CLAIM IS:- 1. A fish-breeding tank having means for oxygenating the water, and means for recycling the water, characterised in that it comprises means suitable for continuously cleaning, as hereinbefore defined, the inner surfaces of the walls of the said tank.

2. A fish-breeding tank according to claim 1 wherein the tank has a circular shape.

3. A fish-breeding tank according to claim 1 or 2, wherein the means suitable for con tinuously cleaning the inner surfaces of the said tank walls comprises at least one con tinuous lamina of a resilient flexible material in contact with the inner tank surface, along a generatrix of the said tank, and a structural member bearing said lamina and rotatable about the centre of the tank, shaped in such a way as to keep said lamina in con tact with the said generatrix of the tank.

4. A fish-breeding tank according to claim 1, 2 or 3 wherein the means suitable for continuously cleaning the inner surfaces of the said tank walls comprises at least one continuous lamina of a resilient, flexible material adjacent to but not in contact with the inner tank surface, along a generatrix of the said tank, and a structural member bearing said lamina and rotatable about the centre of the tank, shaped in such a way as to keep said lamina adjacent to the said generatrix of the tank.

5. A fish-breeding tank according to claim 3 or 4 wherein at least one lamina com prises an elastomeric material.

6. A fish-breeding tank according to any of the preceding claims which comprises means suitable for varying the velocity and the trajectory of the water inside the said tank.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

7 is actually a particular form of embodiment (according to the present invention) of means suitable for varying the trajectory and the velocity of the water entering into the basin, and hence, also the rotational velocity of the water in the basin itself.

For better clarifying the functioning of the fish-breeding tank (according to the present invention), besides what has already been stated, the flow of the water introduced into the tank can be followed step by step, when the said tank it utilised e.g.

for breeding fry. The fresh water enters from the pipe 12, and is distributed into the feeding canal 8 where it is mixed with the oxygenated water brought in by the tubes 9 for the re-cycling of the water. Inside the feeding canal 8, the water is subjected to all the chemical, physical and/or physicochemical treatments considered necessary, that are carried out by per se 'known' means e.g. de-gasification (i.e. the elimination of any air-bubbles present in the water), the elimination of gases that prove harmful te the fry and which can become dissolved in the water and the addition of certain additives to the water, and such like. The water is then admitted by the complex hole 13/baffle 14, into the interior of the basin 2 present in the said tank. Here, also owing to the rotatory motion furnished by the baffles and also by the movement of the rigid structure and in particular by the structional members 21 and the laminae 22 and 23 associated with them, the water in following a spiral course descends towards the tank bottom, taking with it oxygen and food to the fry. (Said food may be introduced directly, by means of automatic dosers, either in the basin 2 or in the feeding canal 8).

To make it easier for the fry to see and consequently get to the food, the inner walls of the said basin 2 are treated such that they will impede light e.g. are painted in a dark colour, e.g. blue. While descending to the bottom of the tank, the water conveys along with it any debris, and carries this away from the tank. By passing through base 16, the water enters the exhaust pipe 5, to exit from it by the slidable tubular part 7. A part of the said water is sent back into the tubes 9 by per se 'known' means-so as to be re-cycled into the feeding canal 8i.e. after the water has been oxygenated by 'known' means in the upper part of the tubes 9. The deaning-out, and the movement of the water inside the basin 2, is brought about by the rigid structure-and in particular by the laminae 22 and 23 associated with the structural member 21.

In fact, the lamina 22, during the rotation of the structural member 21 around the tank, eliminates the thicker incrustations; whereas the lamina that is in direct contact with the walls of the said basin, carries out the more delicate job of removing the re maining incrustations. Moreover, by varying the number of the structural members 21 and the laminae associated with them, and the rotational velocity of the rigid structure, the desired number of repeated actions can be effectuated to the said inner surface in such a way as to prevent the deposit of any substances or the formation of incrustations on the said walls. The said structural members 21, and the said laminae 22 and 23, increase the vorticity of the water by their continuous rotatory movement and because of their particular shapes. Besides this, their repeated rotatory movements help to re-create the ambient 'habitat' conditions that are necessary for the better acclimatization of the fry (or the eggs-in such cases when the tank is utilised as a hatchery), for example due to tides, or the like. Finally, the filters 24 and 25-being chosen for their best suited dimensions, can also impede the eggs from being dispersed by passing into the exhaust pipe.

WHAT WE CLAIM IS:- 1. A fish-breeding tank having means for oxygenating the water, and means for recycling the water, characterised in that it comprises means suitable for continuously cleaning, as hereinbefore defined, the inner surfaces of the walls of the said tank.
2. A fish-breeding tank according to claim

1 wherein the tank has a circular shape.
3. A fish-breeding tank according to claim

1 or 2, wherein the means suitable for con tinuously cleaning the inner surfaces of the said tank walls comprises at least one con tinuous lamina of a resilient flexible material in contact with the inner tank surface, along a generatrix of the said tank, and a structural member bearing said lamina and rotatable about the centre of the tank, shaped in such a way as to keep said lamina in con tact with the said generatrix of the tank.
4. A fish-breeding tank according to claim 1, 2 or 3 wherein the means suitable for continuously cleaning the inner surfaces of the said tank walls comprises at least one continuous lamina of a resilient, flexible material adjacent to but not in contact with the inner tank surface, along a generatrix of the said tank, and a structural member bearing said lamina and rotatable about the centre of the tank, shaped in such a way as to keep said lamina adjacent to the said generatrix of the tank.
5. A fish-breeding tank according to claim

3 or 4 wherein at least one lamina com prises an elastomeric material.
6. A fish-breeding tank according to any of the preceding claims which comprises means suitable for varying the velocity and the trajectory of the water inside the said tank.
7. A fish-breeding tank according to claim

6, characterised by the fact that the means for varying the velocity and the trajectory of the water inside the said tank comprises a tube open at both extremities and slidable in a fluid-tight manner, in one branch of a 'U'shaped exhaust pipe lying in a vertical plane, the other branch of the exhaust pipe being in communication with the bottom of the tank.
8. A fish-breeding tank according to claim 6 or 7, characterised by the fact that the means for varying the velocity and the trajectory of the water inside the said tank, comprises at least one continuous lamina of a resilient, flexible elastomeric material, in contact with the inner surface of the tank, along a generatrix of the said tank, and a structural member bearing said lamina rotating about the centre of the tank.
9. A fish-breeding tank according to any of the preceding claims which comprises, about the perimeter of the tank, and in communication with said tank, a feeding canal into which is sent the water from the aerating means.
10. A fish-breeding tank according to claim 9 characterised by the fact that the feeding tank comprises means for the physical, chemical and physico-chemical treatment of the water prior to the introduction of the water into the tank.
11. A fish-breeding tank according to any of the preceding claims wherein its internal walls are pretreated so that they will impede the passage of light into the tank.
12. A fish-breeding tank according to claim 11 wherein the internal walls are coated with coloured paint.
13. A fish-breeding tank substantially as herein described and shown with reference to the accompanying drawings.