The present invention relates to a feeding plant for fish breeding, in particular an apparatus for breeding young fish and fish fry. The apparatus comprises a funnel for supply of fish food to a water surface by means of a feeding device having a motor driven feeding screw.

It is previously known from e.g. Norw. Pat. No. 149.372 (O.A. Opstad et al ) that food which is filled into a funnel , by its own weight is transferred to a feeding tube where it is transported to a feeding place by means of a motor driven feeding screw. In accordance with this patent the food is added to a stream of water from a water jet so that it is distributed over a large area.

From Norw. Pat. Appl . No. 860436 (P.H. Heyerdahl ) there is known a dosage device which in particular is designed for distributing food powder, pellets, granulates and the like, to young fish. The device comprises a feeding screw which with a small clearance is arranged in a tube having an inlet opening and an outlet hole for the fish food. The drawback of the described dosage device is that the food is directed to a relatively small area where only the most active fish get enough food. Some fish will therefore get smaller amounts of food so that they grow slower and this will require more frequent sorting of the fish.

In Norw. Patent No. 157 761 (G. ulbotten) there is shown a dosage device for use with feeding apparatus for fish fry in connection with fish breeding. The device is provided with one longitudinal slot 22 which extends along the whole length of a screw chamber 12. A feeding screw 19 is provided with groves 20 which are shallow and the grove angle is very small . The food material is guided from a magazine 18 to the top of the screw along its whole length. It is transported one half revolution with the screw and falls onto the water surface. The food is continuously deposited from the full length of the longitudinal slot 22, and if the movement in the water is slow, food will be sprinkled on top of food and most of it will sink to the bottom of the water reservoir.

From the field of feeding poultry, such as exemplified in US Pat. Nos. 2 801 610 ( .E. Wallace et al ), 3 598 087 STITUTE SHEET

(F.L. Ramser) and 3 799 116 (E. Hostetler) there are known feeding plants where feeding screws are arranged in tubes having a number of feeding holes along the length of the tube. The technique and the results shown and described are not considered to be suitable for fish feeding. The food material used for young fish and fish fry, must be sprinkled carefully and cautiously over a water surface. The fish food is usually very finely divided as a powder and it must float on the water surface until it is eaten by the fish fry. To be able to transport a powder with a screw so that it does not pack within the screw, the construction of the screw and the feeding holes are very important.

In said US patents there are mentioned prior art plants with feeding holes having vertical outlets. These plants have the drawback that the food will disappear through the first hole. The US patents represents an improvement over the prior art by distributing the feeding holes along a screw line or helix. It will, however, be important when fish feeding is concerned, that the finely divided food powder do not accumulate and pack in the feeding holes. No remedies are made in the US patents for preventing food from packing in the feeding holes, simply because this is not important when feeding poultry. The poultry food is distributed to a number of containers and the important feature is that each container receives the same amount of food.

In most known feeding devices the food is not ideally distributed, from a fish breeding point of view. With known plants the food is distributed so unevenly that the fish must be sorted according to size too often, and the water reservoirs get greatly contaminated.

The object of the present invention is to provide a fish feeding apparatus where the food is supplied to the water surface as gently as possible. The main features of the invention will appear from the attached patent claims. A feature of fish feeding plants for water vessels where the water rotates is that the same amount of food should not be let out from each hole. In the mentioned poultry feeding plants the feeding holes to the six containers all have the

same area because all containers should receive the same amount of food. When the water rotates in a water reservoir it will be necessary to give out more food near the edge of the vessel than in the middle of the vessel where the water has very little rotation. In our fish feeding plant it is therefore important that the area of the feeding slots per unit length of the tube decreases from the edge of the reservoir to the middle of the vessel .

In accordance with the present invention the food is sprinkled successively onto the water surface along a straight line for each screw thread which passes the slot during the rotation of the screw. The main difference between feeding plants for poultry as mentioned above and our fish feeding plant is that the food for poultry is guided into cups, while we obtain that the food is sprinkled out through slots like drawing a line from each of the slots. It is important that food is not sprinkled onto already floating food.

In accordance with the invention the food is transferred to the water surface from at least two slots which are arranged close to the surface. The food will therefore remain floa ing on the water surface as long as possible, and it will be distributed as evenly as possible over the water surface. The food can thereby be ideally utilized by the fish.

Above mentioned and other features and objects of the present invention will clearly appear from the following detailed description of embodiments of the invention taken in conjunction with the drawings, where

- Fig. 1 schematically illustrates a feeding plant according to the invention, - Fig. 2 schematically shows an embodiment of a feeding apparatus for the plant of Fig. 1, and

- Figures 3 - 10 show details of one embodiment of the feeding tube for the plant according to Figures 1 and 2.

In Fig. 1 is schematically shown a fish feeding plant comprising a vessel 1 with water 2 as well as a feeding apparatus 3 consisting mainly of a funnel 4, a feeding tube 5 and a motor 6. The motor 6 is placed at the edge of the vessel , but it may alternatively be placed in the other, or

outer, end of the feeding tube. The feeding apparatus 3 may as indicated be arranged at the edge of the vessel 1 so that it possibly may be made to move along the edge of the vessel, and possible along the edge of a number of successively placed vessels. The vessel can be rectangular or circular or it may have any suitable form. The plant may include a lifting and lowering device at indicated at 8. The device can be provided with a float or the like (not shown) which senses the height of the feeding tube above the water surface and supplies control signals to a device (not shown) which automatically can rotate the screw device so that the apparatus is lifted or lowered to a desired level. The device can also be provided with a control arrangement which starts and stops the feeding motor in accordance with a predetermined feeding program. The feeding tube 5 is provided with at least two feeding slots 9 which are distributed over the tube and which are arranged at different levels above the water surface. The slots 5 will normally be distributed along a helix on the surface of the tube. The tube will also be provided with an emptying slot (shown in Fig. 2) in the outer end. If desired, - the emptying slot together with one other feeding slot 9 can make up the at least two feeding slots. The tube 5 may further be provided with screens (not shown) in order to prevent that water is splashed on the feeding slots. Within the tube 5 there is a feeding screw as shown in

Figure 2. When the feeding screw is rotated, the food supplied from the funnel 4 will be fed out through the slots 9. The amount of food within the tube will be gradually reduced in the longitudinal direction of the tube because the feeding slots 9 are arranged at a gradually lower level. The tube will be emptied in its outer end through the emptying slot 21, Fig. 2. The positioning of the slots 9 as well as their shape is of great importance for obtaining good results. This will be described in more detail in connection with the additional drawings. The funnel 4 is in Fig. 1 only shown as an outline, and the lower outlet of the funnel leads directly to the feeding tube 5 and the feeding screw within this tube. The opening from the funnel 4 to the tube 5 should preferably have

a longitidunal shape and be as long as at least two threads of the screw. In Fig. 1 there are indicated two stirring arms or rods 10 and 11 which are mounted within the funnel 4 and which are extended into the feeding tube 5 so that the ends of the rods will be moved with the screw when it rotates and the rods move back to the original position when the screw thread has moved far enough. These rods or arms may be designed so that they produce sufficient movement in the amount of food within the funnel 4 so that the food does not pack. In some cases it will be sufficient to use only one arm which is formed so that the necessary movement is obtained.

In Fig. 2 the tube 5 is shown in greater detail, with a screw 20 arranged within the tube. The feeding slots 9 are not shown in this drawing but the emptying slot 21 and the inlet 22 to the tube from the funnel 4 are shown. Stirring arms 10 and 11 are also indicated. When the screw 20 is rotated as shown with the arrow 23, the pin 11 will be moved to the right a certain distance until it slips over the screw thread and falls back into its original position. In a similar manner the pin 10 will be moved with the screw threads to the right a certain amount before it is released. The length of the pins 10 and 11 should be so long and shaped in such a manner that maximum movement will be obtained in the funnel for each revolution of the screw. The distance between two screw threads should preferably be 30 to 70 % of the inner diameter of the screw tube, preferably 40 to 60 % . The core diameter of the screw determines the space wherein the food is to be transported, and this diameter should be 50 to 80 % of the inner diameter of the screw tube, preferably 60 to 70 % . The practical length of the screw tube will to a certain extent depend of the dimensions of the vessel , but it is assumed that it should not be longer than 60 times the inner diameter of the screw tube. In a practical case the inner diameter of the screw tube was 30 mm while the core diameter was 20 mm and the length of the tube was 80 cm. The distance between screw threads was then 16 mm. The tube can be made from a plastic material as polyethylene, while the screw may be made from a strong plastic material as i .e. polyoxymethyl ene (POM), known

as Polyacetal , or from a polyacryl plastic material. The stirring pins 10 and 11 can be made from plastic covered steel wire, in particular on the ends.

The feeding slots of the tube, which are not shown in Fig. 2, will be arranged on the part of the tube wall which is 90 to 180° displaced from the inlet opening in the direction of rotation of the screw. The feeding slots should be distri¬ buted in accordance with requirements along the length of the tube and they should have such an area and shape that the food is distributed as evenly as possibly in the vessel. In many cases the water in such fish breeding vessels 1 is rotated. Even if the vessel has a rectangular shape there can be obtained a circulation or rotation in the water so that the food is distributed with the water over the whole surface. With reference to Fig. 1, this means that the amount of food which is let into the water at the edge of the vessel, e.g. at the motor 6, should be larger than the amount of food which is sprinkled on the water at the outer end of the tube which is positioned in the middle of the vessel. It should be mentioned that the plant illustrated in Fig. 1 does not show the desired exact relationships and dimensions. The amount of food which is sprinkled through the emptying slot 21 should be so small that this slot only makes sure that the food is not packed within the tube, in the end of the tube. The Figures 3 - 10 show an example of how the feeding tube 5 may be formed. Figures 3 and 7 show the feeding tube 5 seen from below (with reference to Fig. 2) while Figures 4-6 and 8-10 show a crossection of the tube taken through some of the slots in the tube. The food inlet 22 is indicated by broken lines in Fig. 3 and a cut IV-IV through the slot is shown in Fig. 4. Figures 5, 6, 8 and 9 show examples of four inter¬ mediate feeding slots 25, 26, 28 and 29. The feeding slot 25 is as indicated in Fig. 3 arranged 90° displaced relatively to the inlet slot 22 and has the same height or level as the longitudinal axis of the tube. The slot is longitudinal along the axis of the tube, but it could also be given a slope relatively to the axis, a slope that could correspond to a helix between the left corner of the slot and the emptying

slot 21. As shown in Fig. 5, the slot 25 has a shape so that food which is brought to the lower inner edge 30 of the slot will be sprinkled to fall vertically without being accumulated or packed on the edge. The slot may be made with a milling machine so that it gets the desired shape. The next feeding slot 26 may for instance be arranged 15° displaced relatively to the slot 25. In the examples shown in Figures 3-10 the same milling machine is used to shape the slots 25, 26, 28 and 29. It is common for all these slots that the food will be allowed to fall to the water surface as soon as it reaches the lower inner edge 30, Fig. 5 and 31, Fig. 6. As indicated the slot 26 is shorter than the slot 25. In this way it will be advantageous to let the length of the slots decrease in the longitudinal direction towards the emptying slot 21. Two other emptying slots 28 and 29 are indicated in Figures 7, 8 and 9. The outlet slots 28 and 29 may for instance be arranged 60° and 75°, respectively, displaced relatively to the outlet slot 25. The emptying slot 21 is shown arranged 90° displaced relatively to the first feeding slot 25 and 180° displaced relatively to the inlet slot 22. In connection with the embodiment shown in Figures 3-10 it is assumed that there are two feeding slots between the slots 26 and 28, but it will be obvious that the number of feeding slots and the positioning of these can be varied. With a plant as described above we have obtained that fish food can be sprinkled in a dry condition on a water surface so that it is deposited gently on the water surface and stay floating as long as possible. We have thereby obtained that very little of the food sinks to the bottom and contaminates the water and vessel . We have also obtained that all fish fry in the vessel can utilize the food simultaneously and grow at about the same rate. This has the advantage that sorting work is minimized.

The above detailed description of embodiments of this invention must be taken as examples only and should not be considered as limitations on the scope of protection.