METHOD FOR FILLETING OF FISH AND FILLETING MACHINE FOR USE IN THE METHOD

Abstract: The invention relates to a method for filleting of fish (1), wherein the fish comprises head (2), body (3) and tail (4) and a longitudinal backbone (5) with ribs (6) which extend in the fish flesh (7) in longitutinal directions along sides of the fish's body (3). At least one row of needles (8) where the intervals (9) between the needles (16) are greater than the thickness of the ribs (6) is inserted into the fish flesh (7) in a direction substantially across the ribs' (6) longitudinal direction, with the result that the ribs (6) penetrate the intervals (9) between the needles (16). By means of a relative movement between the fish (1) and at least some of the needles (16) in the row (8) the fish flesh (7) is pressed substantially in the ribs' (6) longitudinal directions, whereby the fish flesh (7) is loosened from the backbone (5) and the ribs (6), forming a fillet (17).

Description: Method for filleting of fish and filleting machine for use in the method The present invention relates to a method for filleting of fish, wherein the fish comprises head, body and tail and a longitudinal backbone with ribs which extend in the fish flesh in longitudinal directions along sides of the fish's body. The invention also relates to a filleting machine for use in the method. Filleting of fish is performed in filleting machines in fish processing plants. In known filleting machines the fillets are cut with rotating knives. With such machines there is always a risk that fish bones, particularly ribs, will be cut and left in the fillet. Alternatively, the cut may be made so far from the bones that a large part of the fish flesh sticks to the fish skeleton and thereby is not utilised. The various species of fish have different bone structure, and for some species with a great many bones, such as herring, it is virtually impossible when using known filleting machines to obtain boneless fillets along with satisfactory utilisation of the fish. In many cases the choice is made to make the cuts in such a way that some bones remain in the fillet, whereupon the bones are removed manually. The object of the invention is to provide a method for filleting of fish where few or no bones remain in the fillet after filleting, and where at the same time the utilisation of the fish will be satisfactory. The object is further to provide a filleting machine for use in the method. The object is achieved according to the invention with a method and a filleting machine of the type mentioned in the introduction which is characterized by the features which are stated in the claims. Thus the invention relates to a method for filleting of fish, where the fish comprises head, body and tail and a longitudinal backbone with ribs which extend in the fish flesh in longitudinal directions along sides of the fish's body, and according to the invention at least one row of needles where the interval between the needles is greater than the thickness of the ribs is inserted into the fish flesh in a direction substantially across the ribs' longitudinal direction, with the result that the ribs penetrate the intervals between the needles. Furthermore, a relative movement is provided between the fish and at least some of the needles in the row in a direction which results in the fish flesh being pressed substantially in the ribs' longitudinal directions, whereby the fish flesh is loosened from the backbone and the ribs, forming a fillet. The invention also relates to a filleting machine for use in the method, comprising: at least one row of needles where the interval between the needles is greater than the thickness of the ribs, holders for the rows of needles, a holding device for the fish, - movement devices adapted to generate relative movement between the fish and at least some of the needles in the row in order to produce the piercing movement of the row of needles and the movement of the row of needles where it presses the fish flesh in the ribs' directions of movement. The row or rows of needles can be inserted in the fish flesh at different points in the fish. The point where it is appropriate to insert the needles is partly dependent on the fish's bone structure, partly on the shape required for the fillets and partly on the design of the devices which are employed to implement the method according to the invention. The object of the holders for the row of needles is to hold the needles in place and connect the row of needles with the movement devices. The holders may therefore be of any suitable design, and are preferably provided in such a manner that the row of needles is replaceable for adaptation to different fish species and fish sizes. During the movement of the rows of needles the fish must be secured, and this can be done by placing the fish in a holding device which can be constructed in various ways, such as a mould corresponding to the fish's external shape. The movement devices may be designed in a number of ways, and may comprise mechanisms with rotating joints or linearly movable elements which are moved by hydraulic or pneumatic cylinders. According to the invention the row of needles should be inserted in the fish flesh in a direction substantially across the ribs' longitudinal direction. The longitudinal direction of the fish's ribs depends on the fish's bone structure, and also varies for the different ribs in the same fish, but for most types of fish is substantially slantingly backwards from the backbone. The object of inserting the row of needles is that after the insertion it should be capable of pressing the fish flesh along the ribs in their longitudinal direction by means of a laterally directed movement of the row of needles without the ribs being exposed to a pressure which breaks or detaches them. In order to achieve this, when it is located inside the fish flesh, the row of needles must at least partly be placed across the ribs' longitudinal direction, with the result that the ribs penetrate the intervals between the needles, and the laterally directed movement of the row of needles must at least partly be performed in the ribs' longitudinal direction. It should be understood, therefore, that neither the statement that the row of needles should be inserted in the fish flesh in a direction substantially across the ribs' longitudinal direction nor the statement that the fish flesh is pressed substantially in the ribs' longitudinal directions should be understood in an exact sense. Moreover, the form of the row of needles can be varied depending on the design of the filleting machine, and may be curved or straight. Furthermore, the underside of the row of needles, which is defined by the needles' length, may be adapted to the holding device for the fish. In order to achieve sufficient pressure on the fish flesh to loosen it from the ribs without tearing it to pieces, the row of needles should be designed in such a manner that the needles form a relatively close row inside the fish, thus enabling the row of needles together to exert a uniform force on the fish flesh which is sufficient to loosen the fish flesh from the backbone and the ribs and the rest of the fish. In addition to the fact that the ribs' thickness and spacing depend on the bone structure of the various fish species, these factors are also dependent on the size of the fish within the same species. The row of needles should therefore be adapted to the fish which has to be filleted, and this is done by adapting the length of the row of needles and the length of the needles to the size of the fish concerned, and by adapting the spacing and thickness of the needles to the thickness and spacing of the ribs. In order to produce two identical fillets, one on each of the sides of the fish, two rows of needles are inserted preferably symmetrically into the fish relative to the backbone. This has the additional advantage that forces on the fish from the rows of needles partly counteract each other, thus facilitating the securing of the fish. The method according to the invention relates to a principle of filleting where the rows of needles and the relative movement between the fish and the rows of needles are the crucial factors. As mentioned, both the points where the rows of needles are inserted in the fish and the needles' movement in the ribs' longitudinal directions are associated with several possibilities of variation, and it is also possible to generate these movements in various ways. Furthermore, as mentioned, the fish can also be secured in various ways. Thus it is possible to design devices which can be employed to implement the method according to the invention in a number of different ways, and it should be understood that every implementation of the method according to the invention, regardless of which devices are employed, and regardless of how the relative movement between the fish and the row of needles is produced, will be within the scope of the invention. The invention will now be explained in more detail in connection with a description of specific embodiments, and with reference to the drawings, in which: figs. 1-3 illustrate an embodiment of the method according to the invention, figs. 4-6 are elevational views of the basic components in a filleting machine according to the invention at different stages of processing, figs. 7-8 are an elevational view and an end view respectively of a filleting machine, fig. 9 illustrates a fish inside a filleting machine, fig. 10 illustrates a butterfly fillet which is produced by a filleting machine according to the invention, figs. 11-12 illustrate an alternative embodiment of the method according to the invention. The same reference numerals are employed for corresponding parts of the different figures. Fig. 1 is an elevational view of a fish 1 with head 2, body 3 and tail 4 which is placed in a holding device 15, with the top 10 of the fish facing upwards and its belly 11 facing downwards. Two holders 14, each with its row of needles 8 with needles 16, are arranged beside each other above the holding device 15. Both the holders 14 are disposed in the paper plane in fig. 1, one behind the other, only one holder 14 with its row of needles 8 being visible. Fig. 1 further illustrates how the row of needles 8 is located immediately above the top 10 of the fish. The holder 14 is movable in the direction of the fish 1 by means of not shown movement devices. Fig. 2 is an elevational view of the fish 1 after the holder 14 has been moved towards the fish 1 , and the row of needles 8 has been inserted into the fish from above, down to the fish's belly 11. Fig. 3 is a top view of the same fish 1 from above, illustrating the top 10 and a longitudinal rib 5, which is not really visible since it is located inside the fish. Fig. 3 shows additional ribs 6 which extend in longitudinal directions from the backbone 5 into the fish flesh 7 along sides of the fish's body. It illustrates how a row of needles 8 is provided on each side of and along the backbone 5. The movement of the holder 14 and the row of needles 8 is performed in a plane which is perpendicular to the paper plane in fig. 3, and thus fig. 3 is illustrative of the needles' 16 position with reference both to fig. 1 and fig. 2, i.e. before and after insertion of the row of needles 8 in the fish 1. It shows how the needles 16 are inserted into the fish flesh 7 in a direction substantially across the ribs' 6 longitudinal direction. The interval 9 between the needles 16 in the row of needles 8 is greater than the thickness of the ribs 6, with the result that after the insertion of the needles 16 the ribs 6 penetrate the intervals 9. The rows of needles 8 are then moved laterally relative to the backbone 5 by means of not shown movement devices, as illustrated by the arrows Pj in fig. 3. The rows of needles 8 thereby press the fish flesh 7 substantially in the ribs' 6 longitudinal directions, which also approximately coincide with the arrows ?\ , whereby the fish flesh 7 is loosened from the backbone 5 and the ribs 6, forming fillets, which will be explained in more detail with reference to fig. 6. Fig. 3 illustrates how the two rows of needles 8 are inserted symmetrically into the fish 1 relative to the backbone 5. Two identical fillets are thereby produced, one on each of the fish's sides. The symmetrical insertion of the rows of needles 8 has the additional advantage that forces on the fish 1 from the rows of needles 8 partly counteract each other, thus simplifying the securing of the fish. Figs. 1-3 also illustrate knives 21 in end areas of the rows of needles 8 for cutting off the fish's head 2 and tail 4. The knives are shown as stationary knives, and are to ensure that the fish's head and tail are completely cut off slightly longer than the needles 16. The knives 21 may also be movable and designed, for example, as rotating knives. Figs. 4-6 are elevational views of the basic components in a filleting machine according to the invention at different stages in the processing. Fig. 4 corresponds to fig. 1, illustrating the filleting machine in a position before the rows of needles are inserted in the fish 1. The fish 1 with the backbone 5, the ribs 6 and the fish flesh 7 are shown here in a cross section. It illustrates how the fish 1 is held by a holding device which is composed of two parts 15a and 15b. It further illustrates how the holder 14 for the rows of needles 8 is provided with two guides 27 for control of linear movement in the direction of the holding device's parts 15a and 15b along guide rods 26, in order to provide the insertion of the row of needles in the fish 1. A rotating joint 24, a hydraulic cylinder 28 and a holder 18 for some of the needles will be discussed in more detail with reference to figs. 5 and 6. Fig. 5 corresponds to fig. 2, illustrating the filleting machine in a position after the rows of needles 8 have been inserted in the fish 1 , after a downwardly directed movement of the holder 14. The downwardly directed movement is generated by the hydraulic cylinder 28, which via a piston rod 29 has pushed the holder 14 downwards along the guide rods 26. Fig. 5 further illustrates how the rows of needles 8 in this filleting machine are inserted through the fish 1 , and into not shown openings in the holding device's parts 15a, 15b. This is a difference from the embodiment which is illustrated in fig. 2, where the rows of needles are only inserted down to the fish's belly. Fig. 6 illustrates the filleting machine in a position after the needles have been moved laterally relative to the backbone 5. It illustrates how the holder 14 is composed of two relatively movable parts 14a and 14b, each of which is connected via the guide rods 26 to parts 15a, 15b of the holding device for the fish 1. The two parts 15 a, 15b of the holding device are also relatively movable, and are both rotatable about the rotating joint 24 which is provided at a distance below the point where the fish is secured during the insertion of the rows of needles 8. In fig. 6 the holding device's two parts 15a, 15b are rotated out to the side about the rotating joint 24. These rotating movements can be performed by hydraulic or pneumatic cylinders, or possibly by electric torque motors. Due to these rotating movements the rows of needles 8 undergo laterally downwardly directed circular movements away from the backbone 5, as illustrated by the arrows Pi . The needles 16 in the rows of needles 8 thereby press the fish flesh 7 substantially in the ribs' 6 longitudinal directions, which substantially coincide with the arrows Pi , whereby the fish flesh 7 is loosened from the backbone 5 and the ribs 6, forming fillets 17, which remain in the holding device's two parts 15a, 15b. If all the needles in the rows of needles 8 are moved laterally away from the backbone 5, the backbone is left unsecured when the fish flesh is pressed laterally, which can result in the backbone sticking to one of the fillets, or inadvertently falling down into the filleting machine. In order to solve this problem the filleting machine in fig. 6 comprises holders 18 which keep a remaining part 19 of the needles in the rows of needles 8 steady while at the same time some 16 of the needles in the rows of needles are moved laterally in the direction Pi away from the backbone 5, as explained above. The remaining part 19 of the needles in the row of needles 8 thereby keep the backbone 5 steady, with the result that the entire fish skeleton 20 comprising the backbone 5 and the ribs 6 is kept immobile. Figs. 7-8 are an elevational view and an end view respectively of a filleting machine which is very similar to the filleting machine illustrated in figs. 4-6. In this case, however, the hydraulic cylinder 28 is provided between the holder 14 and the holding device 15 for the fish 1, in a plane beside the fish, thus enabling the holder 14 to be pulled towards the holding device 15. Figs. 7 and 8 further illustrate a frame 25 for securing the components in the filleting machine. Fig. 9 illustrates a fish inside a filleting machine, and corresponds to fig. 3. It illustrates how the fish 1 is kept in position by the holding device's two parts 15a and 15b. In order to facilitate the production of two separate fillets the filleting machine may also comprise a stationary or movable knife (not shown) for splitting the fish's belly 1 1. This knife may, for example, be designed as a rotating knife which is movable in a longitudinal opening between the holding device's parts 15a and 15b. A second alternative is that when they are inserted into the fish the needles 16 in the row of needles 8 are not passed completely through the fish, but only inserted down to a position slightly above the fish's belly 1 1 , and that the movement devices are provided so as to permit the rows of needles to almost rotate about the needle points by means of the laterally directed movement, which can be achieved by providing the rotating joint 24 near the fish's belly 11. In this embodiment the rows of needles 8 will approximately flatten out the fish, producing a connected wide fillet, which is designated a butterfly fillet in the field. A butterfly fillet 23 of this kind is illustrated in fig. 10. In this embodiment, of course, no knife is used to split the fish's belly 11. Tests have shown that with a filleting machine for use in the method according to the invention it is possible to obtain fish fillets with few or no bones, where the utilisation of the fish is better than for known filleting machines where knives are employed. Tests with herrings have given particularly good results. After the fish has been filleted as described in the above, the fillets can be passed to a washing and hosing device, and therefrom to packing, for example vacuum packing, canning or freezing. Figs. 1 1 and 12 illustrate an alternative embodiment of the method according to the invention, and shows the holders 14 with the rows of needles 8 and a fish in an elevational view and a top view respectively. The two rows of needles 8 are each provided here in a stationary holder 14, while the fish 1 is passed tail first in its longitudinal direction P2 towards the rows of needles 8. The two rows of needles 8 are provided with the longitudinal direction substantially in the same plane as the surface of the outside 22 of the sides of the fish, and are tilted with the needle points pointing in towards the fish's backbone 5. The distance between the rows of needles is adapted so as to enable the rows of needles to be inserted in the fish at an area 13 on each side of the tail. Due to the oblique position of the row of needles 8 the movement of the fish in the direction P2 causes the needles 16 to press the fish flesh 7 at least partly in the ribs' longitudinal directions, whereby the fish flesh 7 is loosened from the backbone and the ribs, forming a fillet. In order to facilitate the filleting the needles 16 may be curved (not shown). The fish 1 can also be passed head first towards the rows of needles 8, in which case the rows of needles are adapted so as to enable the rows of needles to be inserted in the fish in an area 12 beside the gills on each side of the head. This is a more advantageous embodiment for fish types where the ribs are facing slantingly backwards, since in this embodiment the needles are located in a more perpendicular fashion on the ribs with the result that they can more easily press the fish flesh in the ribs' longitudinal directions than in the embodiment where the fish is passed tail first towards the rows of needles 8. In the embodiment illustrated in figs. 11 and 12 the holding device for the fish may be designed, for example, as two opposing belts which press the fish between them, and which move in the direction P2.

Claims: PATENT CLAIMS 1. A method for filleting of fish (1), where the fish comprises head (2), body (3) and tail (4) and a longitudinal backbone (5) with ribs (6) which extend in the fish flesh (7) in longitudinal directions along sides of the fish's body (3), characterized in that at least one row of needles (8) where the intervals (9) between the needles (16) are greater than the thickness of the ribs (6) is inserted into the fish flesh (7) in a direction substantially across the ribs' (6) longitudinal direction, with the result that the ribs (6) penetrate the intervals (9) between the needles (16), and that by means of a relative movement between the fish (1) and at least some of the needles (16) in the row (8) the fish flesh (7) is pressed substantially in the ribs' (6) longitudinal directions, whereby the fish flesh (7) is loosened from the backbone (5) and the ribs (6), forming a fillet (17). 2. A method according to claim 1 , characterized in that two rows of needles (8) are inserted into the fish (1) symmetrically relative to the backbone (5). 3. A method according to claim 1 or 2, characterized in that a row of needles (8) is inserted into the fish (1) from above along each side of the backbone (5). 4. A method according to claim 1 or 2, characterized in that the rows of needles (8) are inserted into the fish (1) from the end, from the front in an area (12) beside the gills on each side of the head, or from the back in an area (13) on each side of the tail. 5. A filleting machine for use in the above method, characterized in that it comprises: at least one row of needles (8) where intervals (9) between the needles (16) are greater than the thickness of the ribs (6), holders (14) for the rows of needles (8), - a holding device (15, 15a, 15b) for the fish, movement devices (26, 27, 28, 29) adapted to generate relative movement between the rows of needles (8) and the fish (1), where the rows of needles are inserted into the fish flesh (7) in a direction substantially across the ribs' (6) longitudinal direction, with the result that the ribs penetrate the intervals (9) between the needles (16), and further adapted to produce a relative movement (Pi ) between the fish (1) and at least some of the needles (16) in the row (8) where the fish flesh (7) is pressed substantially in the ribs' longitudinal directions (Pi), whereby the fish flesh (7) is loosened from the backbone (5) and the ribs (6), forming a fillet (17). 6. A filleting machine for fish according to claim 5, characterized in that two rows of needles (8) are each arranged in a holder (14), that the holders (14) are arranged above the holding device (15, 15a, 15b) for the fish (1), that the movement devices (26, 27, 28, 29) and the holders (14) are adapted first to insert the rows of needles (8) into the fish (1) from above along each side of the backbone (5), and then to move at least some of the needles (16) in the rows (8) laterally (P i) relative to the backbone (5), thus causing the rows of needles (8) to press the fish flesh (7) substantially in the ribs' (6) longitudinal directions (Pi). 7. A filleting machine for fish according to claim 6, characterized in that it also comprises holders (18) for a remaining part (19) of the needles in the rows (8) for keeping the remaining part (19) of the needles steady when some of the needles (16) in the rows are moved laterally (Pi) relative to the backbone (5), with the result that the remaining part (19) of the needles in the row (8) keep the backbone (5) immobile. 8. A filleting machine for fish according to one of the claims 5-7, characterized in that it comprises stationary or movable knives (21) in end areas of the rows of needles (8) for cutting off the fish's head (2) and tail (4). 9. A filleting machine for fish according to claim 5, characterized in that two rows of needles (8) are each arranged in a holder (14), and that the movement devices and the holders (14) are adapted to insert the rows of needles (8) into the fish (1) from the end, from in front in an area (12) beside the gills or from the back in an area (13) on each side of the tail. 10. A filleting machine for fish according to claim 9, characterized in that the holders (14) with the rows of needles (8) are stationary, that the longitudinal direction of the rows of needles (8) is substantially in the plane of the surface of the outside (22) of the fish's sides, that the needles (16) are slanting or curved with the needle points pointing in towards the fish's backbone (5), and that the holding devices for the fish (1) are arranged to move the fish in its longitudinal direction (P2) towards the rows of needles (8). 1 1. A filleting machine for fish according to one of the claims 5-10, characterized in that it comprises a stationary or movable knife for splitting the fish's belly (11).

Inventors: NORDSTRAND ARNE K, NORDSTRAND, ARNE K.
Applicants: NORDSTRAND ARNE K, NORDSTRAND, ARNE K.
Application year: 1999
Main classification: A22C25
IPC codes: A22C25