DE2134776A1 - Fish location - for beheading using photo-electric cell to determine tail position as reference point for cutting blade - Google Patents

Abstract

Based on the principles of fish proportions, a photoelectric detection system is used to locate the position of the tail in the cutting trough, and this position gives an accurate location for the cutting blade to remove the fish head without wastage. The movement of the photoelectric cell to determine the tail position is translated into a mechanical movement either to the trough or the cutting blade, to give an accurate relative positioning between fish and blade, to ensure the head is removed at the gills, without wastage.

Description

DR. BERG DIPL.-ING. STAPF

PATENT LAWYERS 8 MUNICH 8O, MAUERKIRCHERSTR. AS 2134776

Dr. Berg Dipl.-Ing. Stopf, 8 Munich 80, Mouerkircherstro6e 45

Your reference Your letter Our reference 21 193 ^Date 1? JuH 1971

Lawyer file 21 193

Morski Instytut Rybacki, Gdynia / Poland

Method for head of fish and device for carrying out this method

The invention "relates to a method for the head of spindle-type Fish, the fish that make up the majority of food fish and usually a spine exhibit. The invention also comprises an apparatus for carrying out the method. There should be fish of various kinds both excluding and excluding with high processing power and high speed to be beheaded.

VI / My - 2 -

209808/0289

Heading devices are known in which the fish is headed by means of a transport device, which the position of the fish is fixed, guided past a circular knife or a pair of circular knives. Here the fish must be in just the right position in relation to the knife so that the head is correct, so usually just behind the gills, is cut off. It is placed on the transport device by hand or automatically by a control device of the machine.

The position of the fish in relation to the knife is determined by eye when placing it by hand in the Hegel.

When the fish is placed on the machine, it is placed in the transport device loaded, whereby it is usually pushed with its head against a stop plate. A control device then measures the machine forms a certain parameter of the fish body, which is decisive for the fish size this into a corresponding parameter of the head length. Then the fish is moved in the transport device or the head knife is moved in such a way that that the cut surface runs behind the gill covers or the attachment of the pectoral fins during the beheading operation.

The known heading methods described and their corresponding machines have various shortcomings.

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Thus, in fixing the position of the fish in relation to the cutting tools by hand, it is difficult to do both one to achieve a satisfactory throughput through the machine as well as a corresponding accuracy in processing. The throughput is at the expense of the accuracy or vice versa. This complicates the operation.

When automatically inserting the fish in relation to the | Cutting elements is a complicated control circuit provided with a mechanical lever switch, which is used for contact measurement of a certain parameter of the fish body is used and the measured parameters via a complicated arrangement of levers and cams in appropriate feed lengths the elements or the cutting instruments guiding the fish.

The maximum thickness or Jj Height of the fish measured with relatively large deviations. In the case of gutted fish, the measurement errors are inadmissible high. Therefore, the decapitation is done with insufficient accuracy. Determining the length of the fish based on the measurement the maximum thickness or height of the fish is not sufficiently accurate because the ratio of length to thickness / or. Height fluctuates relatively strongly.

The known machines are used to transport fish

209808/0289 _ ₄ _

those that are trough-like or "ribbon-like. Both types "require a relatively complex and dimensionally developed construction. In" both cases the usability for different fish species is limited. That is true both in terms of a different one Freshness of the fish to be processed with one and the same fish species as well as in relation to the size range of the fish to be processed in which the machine works properly.

With the first type of conveyor, this is due to the predetermined shape and size of the troughs, while with the second Kind of the width, number and arrangement of the conveyors encompassing the fish on both sides, the restrictions set out originate.

If the fish are in the state of "rigor mortis", Difficulties arise not only when inserting them, but especially when correctly measuring the relevant ones Size parameters by means of a contact button.

The enlargement of the perfect working area of known topping machines is made difficult by the fact that it is difficult is, mechanical control circuits based on various proportions of the size of the head to be measured directly To change parameters for different fish species, whereby

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it is also difficult to set the correct angle of the head cut depending on the species of fish. Therefore, the topping devices with mechanical ones are suitable Fish scanning in principle only for the head of a species of fish and only in a relatively narrow range Size range of fish. They are not suitable for processing gutted fish, have large dimensions and great weight, are expensive, and the work done relative to the head of the hand is unsatisfactory.

The invention provides a method and a device which avoid the disadvantages set out. This goal is according to the invention by a fundamentally new principle of fish management and the measurement and control of the EeIativlage of the fish in terms of the head knife.

The invention has established and takes advantage of the fact " that you can behead fish of different species, gutted or not, in a simple manner when the head cut in connection with the sliding of the fish transversely to its longitudinal axis between two at an angle to each other standing plates, which can be pivoted apart symmetrically against spring action, takes place, with the fish on a circular knife arranged underneath is pushed in, which is automatically adjustable in relation to the fish

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is that its cutting plane goes through, a point on the fish's body which determines the length of the head to be cut off. The relative position of the fish and the knife in relation to each other is thereby related to the previous exposure of the fish due to a non-contact measurement of the total fish length. The measured fish length is converted into a proportional ■ feed rate of circular knife and fish guide relative to one another converted. Research has shown that the length of the head is best measured by measuring the total length of the fish is determined because the ratio of head length to total length only fluctuates very little is subject.

The determination of the relative position of the fish and knife in relation to each other for the required transverse or In the case of contactless measurement, it is advantageous not to cut the fish at an angle by measuring the entire length of the fish determined, but by measuring only the differences in length of the successively decapitated Fish by means of a preferably photoelectric sensing device. Depending on the type of fish to be processed, this can be done by means of an adjustable transmission gear be connected to the adjustment device for the position of knife and fish relative to one another. That Gear ratio in this gearbox is due to the

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Ratio of fish length to head length determined. Either the movable head knife can be moved or when using an immovable knife, a movable element for adjusting the position of the fish relative to the knife.

One arm of the movable feeler, which determines the position of the end of the caudal fin, can be connected to a displaceable one Circular knife carrier be rigidly connected, or in the second case with an element that a longitudinal movement of the Forcing fish in the trough with the help of the same intermediate gear in the same proportions. In both Cases each position of the movable probe for the fish length corresponds to a specific fish position in relation to the knife, cutting off the head just behind the gill cover or possibly the base of the pectoral fin guaranteed.

Since the length of the fish is determined by the position of the end of the caudal fin, it is essential that the fish during touches a fixed stop surface with the head during measurement.

Torteilhaft carried inserting and guiding the Jieches for measuring the total length which is determined by the end of the tail fin, and the cutting head dee,

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by placing the fish in a horizontal loading bay with his back open or down and he is there can touch the stop surface with the head, whereupon the fish when opening one of the plates forming the trough in a horizontal position with the head on the stop surface in a horizontal recess below falls down. This second trough has two running down towards each other at a certain angle Plates that are normally arranged in a V-shape when viewed from the front. There is the lisch for the purpose of corresponding and simultaneous adjustment of the head knife measured. Then the fish is brought in from above by means of a Push-through device pushed through downwards. In doing so, he passes the latter two, symmetrically Plates that can be swiveled away from each other, which press it together on the sides and until it is completely cut off of the head.

The plates that form the measuring well are compressed before the fish falls and open only under the pressure of the fish being pushed through the push-through device.

The method and the device according to the invention make it possible to differentiate the fish, depending on the species of fish appropriate angles to head. Cutting off the

2Ö98ÖÖ / Ö289 - 9 _

Head cut in a cross or diagonal cut depends on the position in which the fish is pushed past the knife.

If the fish is pushed past the knife with the vertebral column running perpendicular to the knife plane, you get one Section perpendicular to the spine. If the fish is attached to the knife with its spine at an angle to the plane of the knife pushed past, the cut is made at an angle to the spine.

The position of the fish while it is being pushed through is determined by the angle of the push-through plane that can be set on the push-through element determined in terms of level.

In the method according to the invention, the fish are advantageously entered into the machine with their backs pointing downwards inserted.

The device for carrying out the method according to the invention has a head unit as well as for the invention essential loading and transport equipment for the fish in the machine and a measuring device for the fish, which is connected to a control and drive set.

The head unit has a rotating circular knife that advantageously runs in a vertical plane and on one

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axially displaceable shaft is seated. This can be done using a on the shaft in turn axially displaceable drive wheel, for example a belt pulley, driven will.

Two troughs, which are deflectable, are used to insert the fish into the machine and to transport the fish into the machine Have plates which run in the closed position so that they run in a V-shape in section. the both iröge are arranged one above the other.

The upper trough, which is used to insert the fish, is referred to below as the loading trough, while the lower trough, in which the fish lies during the measurement of its length and which guides the fish during the head is shown below referred to as a measuring trough.

Both troughs have a common front or face plate on which the fish is placed head first. This plate forms a fixed reference plane for measuring the length of the fish lying in the measuring trough.

The profiled tabs, which are inclined on the inner surfaces of the plates of the measuring trough in the front part of which can be attached. Both troughs are connected by means of an inclined sliding plate, which

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the correct dropping of fish from the loading trough in the measuring trough facilitated. To facilitate this purpose, a shower is advantageous for the purpose of sprinkling it Plate attached.

To push through the fish located in the measuring trough downwards and to guide them in relation to the one below Circular knife, which has been set in the correct position beforehand, is advantageously used as a push-through element in the form of a curved arm with an adjustable stop plate at one end and an adjustable stop plate at the other end is pivotably mounted in the machine frame.

The push-through element, which can be actuated by a rotating control shaft by means of a cam, leads as a function from this actuation its pendulum movements advantageous in a vertical plane about an axis supporting it the end.

The stop plate exercises as the fish moves downwards constant pressure from above on the fish in the measuring trough. This puts the fish between them against each other Spring effect-opening plates moved downwards. The measuring trough opens with the movement of the push-through element coupled.

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To counteract harmful twisting of the fish during braiding, which could be caused by the frictional forces of the knife on the fish body is a spring plate provided, which extends one of the walls of the measuring trough downwards. It provides a lateral stop surface for the body and / or head of the fish to be cut off.

In the plates of the measuring trough cutouts are provided which allow the stop plate of the push-through element to pass through without opening the plate even if there is no fish in the measuring trough.

In order to ensure full operational safety when placing the fish in the loading trough, a of the two plates forming it opened cyclically, so that the fish from the loading trough into the one below Messtr'og can fall. This plate is advantageously connected to a lever that deflects it via a spring shock absorber.

be-The measuring arrangement of the device according to the invention / advantageously consists of a movably mounted photoelectric Sensor which has a light source and a photoelectric element mounted on a common arm are.

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The optical axis of this arrangement can be horizontal or inclined. It is directed across the measuring trough, TJm To enable the measurement of the length of the fish in the measuring trough, the two have the side surfaces this trough forming plates longitudinal braids through which the optical axis of the cooling arrangement extends. Another possibility is that the plates of the trough are made of a transparent material.

The arm of the feeler is advantageously coupled to the drive mechanism for the knife. He's in one of those Movable level so that the optical axis can be shifted over the entire length of the column of the measuring trough, whereby fish of different lengths can be measured, when the optical axis passes the end of the caudal fin in the trough.

An essential detail of the device according to the invention is the coupling of the feeler arm to the carrier of the Circular knife, whereby the feeler arm and the circular knife are proportionally moved horizontally.

The transmission ratio between the movements of the carrier of the circular knife and the movements of the photoelectric Feeler-bearing arm is dependent on

209800/0289 -H-

the fish to be processed. This allows the ratio of the feed of the optical axis of the Sensor in the gap of the measuring trough for the size of the knife advance the proportion of the total fish length to the length of the Mixing head for the type of fish to be processed to adjust.

According to the invention, the measuring trough or the element pushing the fish through can also be movable instead of the knife be arranged. Permanent under-lighting of the movable photoelectric sensor can also be used.

To ensure that the To achieve the device, the movement of the element pushing the fish through, the opening of the plate of the loading tray and the start-up of the knife sensor can be synchronized. This is advantageously done with the help of a common control shaft, which carries out or controls the corresponding actuations with corresponding cams or triggers.

The control of the mechanism driving the arm of the probe as well as the mechanism coupled with it for the horizontal advance of the circular knife is advantageous by means of a contactless electronic circuit via electromagnetic clutches and brakes that

2098Ö8 / O2Ö9 - 15 -

are arranged on the shaft of the mechanism driving the circular knife feed.

The invention, which has just been explained in general, makes it possible to decapitate different species of fish both exempted and unexcepted. Das.wird achieved that the type of fish guidance an adaptation of the element transporting the fish during processing to i

makes concrete changeable forms of the fish superfluous.

The contactless measurement of the fish length according to the invention and the control of the corresponding feed caused by this of the circular knife makes it possible to determine the ratio of fish length and fish head length depending on the species of the fish to be processed. This measuring method also ensures a high level of accuracy.

The advantages set forth differ, the method of the invention overall * measured from the known Köpfverfahren.

The device according to the invention is characterized by a simple design, small external dimensions and a large length range of the fish to be processed, a high throughput rate and absolute operational reliability.

The surface of the fish pushing through the fish

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Elements is easy to adjust. This enables “linen” in relation to the longitudinal symmetry axis of the fish vertical head cut, but depending on the desired Section the direction of the spine of the fish can be perpendicular or oblique to the cutting plane.

The method and the device according to the invention are explained in more detail below. In the drawing are those for the function of the invention less essential elements omitted for the sake of clarity.

The device has a loading trough into which the fish to be beheaded can be placed by hand. This consists of an immovable plate 1 and one that can be swiveled out about an axis running horizontally in the exemplary embodiment Plate 2. A lever 4 is used to deflect the plate 2, which is connected to the plate 2 via a telescopic spring arm 5 is resiliently connected. The lever 4 is pivotably mounted on an axis 5. He can by means of a hoe 6 can be pivoted, which sits on a driven control shaft.

As an extension of the plate 1, underneath it is a second plate 9 which can be swiveled out about a horizontal axis provided, which can also be swiveled out about a horizontal axis together with one arranged opposite it

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Plate 10 forms the measuring trough. Both plates are against spring action can be swiveled out. Should the plates 9 and 10 be pivoted apart with their lower edges to open the measuring trough the force of the springs (not shown) holding the measuring trough must be overcome for this purpose. Furthermore, the tension member 17 acting on the plate 10 in the manner shown in the drawing must be released, which is connected to an arm 15 for pushing through of the fish. The synchronous and symmetrical deflection of the plates 9 and 10 is known per se Ensured symmetrizing device, which is not shown for the sake of clarity.

Above the lower edges of the plates 9 and 10 extend in this in the same way as the lower edges Edges horizontally extending slots 11 · At the Profiled tabs 12 are attached to the inner surfaces.

Furthermore, the plates have cutouts that allow the stop surface 16 of the arm 15 to be pushed through of the fish.

At the lower edge of the plate 10, a further plate 13 is articulated in a hinge-like manner, which is connected to the curved arm 15. is resiliently connected by a telescopic spring tension member 8. A gate extending in a yertical plane

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Plate 14 forms a common front end of the plates mentioned above.

The curved arm 15 is used to push the fish through, which is pivotably mounted on a shaft 7a attached to the housing. The free end of the arm 15 carries the stop surface 16, which is adjustable in relation to the I level. The arm 15 is also connected to the machine frame connected by a spring, which has a lifting sequence Jump of the arm 15 always in contact with a cam 18 the control shaft holds. In this way the sock regulates the movement of the arm 15.

For measuring the length of the fish in the measuring trough is a photoelectric element 19 and a light source 20 is provided, both of one in one Arm 21 pivotable about a vertical axis in the horizontal plane be worn. The optical axis of the system 19-20 runs through the column 11 in the plates 9 and 10 in their closed location. This can be done by pivoting of the arm 21 is the length of that located in the measuring trough Fish to be scanned. If desired, the arm 21 can also be arranged pivotably in an inclined plane will. The machine must then be designed accordingly.

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The arm 21 is connected to an arm 23 of a bearing 24 of the shaft 25 of a circular knife 26 by means of a link 22 tied together. The circular knife sits firmly on the shaft 25. The bearing 24 guides the shaft 25 both axially and radial. The drive of the shaft 25, which is axially displaceable relative to the machine frame, takes place, for example by means of a belt drive which transmits the torque to the shaft 25 via a pulley which is axially displaceable sits on the shaft 25, for example by means of a splined profile. The bearing 24 is parallel to one another to the lower edges of the plates 9 and 10 and parallel to the shaft 25 extending rack 27 is rigidly supported. This rack is driven by a gear 28 periodically reciprocated so that the rotating circular knife also reciprocates in the axial direction of its axis of rotation will. With this to-and-fro movement, the one carrying the photoelectric system is pivoted at the same time Arm 21 with the help of the handlebar 22.

Two electromagnetic ones are used to drive the shaft 29 of the gearwheel 28 Couplings 30, which can drive the shaft 29 in opposite directions of rotation. Further sits on the shaft 29 an electromagnetic brake 31, which enables a rapid shutdown of the shaft and thus the axial movement of the circular knife 26.

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The control shaft 7, which also carries the cams 6 and 18 mentioned, is used to control the device. The steering shaft 7 actuates a microswitch as it rotates by means of a cam (not shown) and moves it cyclically on. This triggers the drive of the rack 27. The drive direction of the rack 27 depends on it from which of the two clutches 30 is engaged. The engagement of the clutches 30 again takes place as a function from the photoelectric sensor.

To stop the rack 27, the clutch 30, which has just been engaged, reacts to a signal from the photoelectric Element 19 disengaged when the latter detects the end of the caudal fin of the fish in the measuring trough. At the same time, the electromagnetic brake 31, which is synchronized with the clutches 30, is actuated. As a result, the shaft 29 is braked quickly.

The device works as follows.

First, the fish is - for example by hand - in the Laying trough formed by the plates 1, 2 is inserted. The insertion is done in such a way that the fish heads to the Front plate 14 rests. Controlled by the cam 6 seated on the control shaft 7, the plate 2 is periodically deflected. This opens the loading trough and the fish

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tet on the moistened surface of the plate 1 down into the measuring trough below, while his head remains in contact with the gate plate 14. During this time, the arm 21 of the measuring sensor begins in a correspondingly synchronized manner, triggered by a cyclical electrical signal from a cam of the control shaft 7 actuated microswitch, its pivoting movement in horizontal sighting (the measuring sensor does not necessarily have to be pivoted, a corresponding mounting is also possible in which it performs a translational movement parallel to the movement of the circular knife easily corresponding gear ratios, the motion relationships are possible.)

As soon as there is a change in the illumination of the piezoelectric element, when the optical axis of the itihlers passes the end of the tail fin of the fish in the trough, the drive shaft 29 », the gearwheel 28 and the rack 27» which advance the knife 26, by means of a corresponding electrical signals of the photoelectric Hellen te 19 shut down, loads * the engaged clutch 50 is disengaged and the brake 31 is switched on. Simultaneously with this, via the coupling elements 22 and 23 with the toothed bang 27 synchronously moved jffühlinrichtung is stopped.

209808/0288

When the rack 27 comes to a standstill, the axial advance of the circular knife 26 is also terminated, specifically in a position of the circular knife which is favorable for cutting off the head of the fish whose length was measured. When the axial movement of the circular knife 26 stops, the cam 18 of the control shaft 7 pivots the arm 15 against the action of the spring acting on it. The stop surface 16 carried by the arm 15 thus presses the fish down between the plates 9 and 10, which are released by the tension member 17 with the movement of the arm 15. Under the pressure of the stop plate 16, the plates 9 and 10 can yield outwards and the fish, which is still held by these when passing between the plates 9 and 10, moves down past the previously set circular knife 26. The sliding movement becomes continued until the fish's head is completely cut off. While äes cutting, the spring-loaded plate 13 prevents * ln otherwise may "öglichee twisting äes fischet, iaa tenet could erfeigen by the Schalttwiderttand de · Hester.

After the head has been cut off, the eder guides the arm 15 back into its starting position. The arm 15 also moves the plates 9 and 10 back into their starting positions via the tension member 17. Then the next cycle of fish processing can take place.

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Claims (12)

Patent claims: Method for head of fish, thereby marked-Eet, that the gutted or gutted fish is yielding transversely to its longitudinal axis between two by springs compressed plates is pushed through, the 'in a symmetrical movement from each other by two preferably parallel axes can be pivoted apart, so that the fish here against a arranged in its path of movement Head knife is performed, which is automatically adjustable in relation to the fish that its cutting plane runs through a point on the fish body, which determines the length of the head to be cut, that this is the Relative position of the fish and the head knife to one another by a previous pushing through of the fish Measurement of the total length of the fish is determined, and that the measured variable corresponding to the fish length in one of her proportional feed of the head knife or the fish guide is reshaped. 2. The method according to claim 1, characterized in that the determination of the relative position of the fish and head knife for head in cross or bevel cut by contactless measurement of the sizes of the differences in length of the successively beheaded fish is determined by means of a movable sensor, which by means of a 209808/0289 - 24 - the ratio of total fish length to head length adjustable Transmission gear with a movable head knife or, in the case of an immovable knife, with a movable one Element for adjusting the position of the fish in relation to it is connected. 3. The method according to claim 1 or 2, characterized in that the fish with the back up or down is placed in a horizontal trough in such a way that its head is preferably vertical, transversely to the longitudinal direction of the fish extending stop plane is applied that the fish then out of the trough by opening two of these forming Plates falls down, where he remains with the head in contact with the stop plane that the fish here in the under the horizontal trough, also horizontal measuring trough falls, in which the length of the fish is contactless is measured to adjust the position of the knife in relation to the fish, that afterwards by means of a from top to bottom moving the fish down on the preferably as a circular knife trained head knife is pushed between two swing-out plates of the measuring trough, and that the two Swing-out plates of the measuring trough here compress the fish from the sides and up to the complete Cutting off the head lead. - 25 209808/0289 4. The method according to any one of claims 1 "to 3, characterized characterized in that the fish so moves during the beheading is that its plane of symmetry is perpendicular to the cutting plane of the knife, while corresponding Adjustment of the stop surface of the push-through element to the normal plane running through the fish's longitudinal axis The plane of symmetry of the fish is perpendicular to the cutting plane of the knife or at a certain angle to the latter can run. 5. Device for carrying out the method according to one of claims 1 to 4 with a circular head knife, characterized by a horizontal loading trough (1,2), a also horizontal measuring trough (9,10) arranged below the loading trough, a measuring sensor which has a light source (20) and a photoelectric sensing element (19), an element for pushing the fish through the measuring trough, which has an arm (15) which can be pivoted about an axis (7a) and which has a stop surface (16) at its end, which in their angular position is adjustable, and an electro-mechanical system for controlling the links to adjust the relative position of the fish and circular knife (26) to one another, 6. Apparatus according to claim 5 »characterized in that that the Ladefcrog has two plates (1,2) which are inclined 209808/0 ^ 89 - 26 - converge to the vertical downwards that at least one of these plates around its upper, preferably horizontal, Edge pivotably mounted on the frame of the machine and by means of a telescopic spring tension member (3) with a pivotable lever (4) is connected, which can be pivoted out by means of a cam carried by a control shaft (7) and is arranged under the measuring trough that the measuring trough has two plates (9, 10) which can be swiveled out symmetrically to one another has, which rest in the closed position of the trough with their lower edges against one another, while their upper Edges are rotatably mounted on the frame of the machine, and that the plates (9 »10) of the measuring trough have longitudinal slots (11) exhibit. 7. Apparatus according to claim 5 or 6, characterized in that the photoelectric sensor of an arm (21) is carried, which is movably mounted on the machine housing in such a way that during its inevitably guided movement the optical axis between a light source (20) and a photoelectric element (19) of the photoelectric The sensor runs through the slots (11) in the plates (9,10) of the measuring trough. 8. Modification of the device according to one of claims 5 to 7 »characterized in that the light source is immobile is arranged and illuminates the entire measuring zone 20980d / 0289 - 27 - and / or that instead of gaps (11) in the plates (9, 10) inserts made of transparent material are provided. 9. Device according to one of claims 5 "to 8, characterized characterized in that the movable arm (21) of the photoelectric sensor via a lever system with a Depending on the type of fish to be processed, the transmission or reduction ratio can be regulated with a j Bearing (24) is connected to the knife shaft, which determines the position of the circular knife relative to the fish. 10. Device according to one of claims 5 to 9 »characterized in that the pushing through of the Fischea serving arm (15) is coupled to a plate (10) of the measuring trough via a tension member (17) which connects the plates (9, 10) swings together when the arm (15) moves upwards - and releases the plates to pivot apart, when the arm moves down. ^ 11. Device according to one of claims 5 to 10, characterized in that at the lower edge of the one plate (1O) of the measuring trough in the front part of which a plate (13) is pivotably articulated, which by means of a spring-loaded, telescopic tension member (8) is connected to the arm (15) for pushing through the fish, and that on the plates (9,10) of the measuring trough, which at the points 209808/0289 -28- of the passage of the stop surface (16) of the push-through arm (15) have cutouts, attached profiled tabs are. 12. Device according to one of claims 5 Ms 11, characterized in that the means for determining the relative position of the knife in relation to the fish drive elements (30) for driving the shaft (29) for the axial feed of the knife has that these drive elements are electromagnetic clutches that are dependent from a signal of the photoelectric element (19) of the sensor via an electronic circuit contactless elements is controlled. 209808/0789