CA1330477C - Cutting of swim bladder - Google Patents

Abstract

ABSTRACT
The invention is a method and a machine for cutting a swim-bladder from a spine of a fish after the spine has been removed from the fish or the fish has been flitched. The method includes laying the spine upon a guiding wedge, which perforates the swim-bladder and cuts it open, moving the spine forward toward a motor driven knife, which cuts the swim-bladder free from the spine. The machine includes a cantilever beam which guides the spine toward a horizontal motor driven knife. The guiding wedge is fastened into the frame of the machine. Its lower part is elastic in order to be able to cut different sizes of swim-bladders.
The forward motion is powered by a conveying wheel, belt or arm, above the guiding wedge.
A single conveying wheel has a rift for the crest of the spine.
Two conveying wheels are spaced for the crest. The conveying wheel has spikes for grasping the spine and increasing the friction against it, thereby increasing the conveying force. The guiding wedge has a tip, to perforate the swim-bladder, and a cutting edge for cutting or tearing a hole into the backmost and foremost ends thereof. To prevent accidents, the conveying wheel and knife are both surrounded by a screen.

Description

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Field of the Invention The invention relates to a method and an apparatus for cutting a swim-bladder from the spine of a fish after the spine has been removed from the fish or after the fish has been flitched.

Background The fish is a vertebrate having a spine. Opposite the abdominal cavity of the fish, each vertebra of the spine has sports three projections: a central dorsal crest on the 1 10 upper side and two banks of ribs, one at each side.
Extending therefrom are outer walls of bones.
When a fish has been caught, its throat is cut to ¦ remove the blood. It is then dressed, disembowelled, the I abdomen is cut open and the intestines removed. For curing in salt, large fish are selected. In this case, the head is cut free from the fish and the spine opposite the abdomen is removed. When a fish is flitched, the flitches are cut from the bones in flitching machines.
Below the spine and the banks of ribs inside and along the abdominal cavity is a white thick membrane called swim-bladder. The swim-bladder demarcates against the spine an airtight bladder, which the fish can fill with air for increasing its volume and thereby modifying its specific weight in the seawater. At the perimeter of the swim-bladder, where it is fastened to the walls of ribs, it formsbubbles. Adjacent to the swim-bladder and adjacent to the abdominal cavity is a black membrane, which is referred to as the swim-bladder membrane.
When the spine of the fish is removed, the swim-bladder remains adjacent the spine. A large cod (6-7 kg) typically has a spine of 350g including a swim-bladder of 50g. Thus the swim-bladder is 1/7 part of the spine by weight and 1/120 - 1/140 part by weight of the fish.
Formerly, when the swim-bladder was destined for human consumption, the swim-bladder was removed from the spine manually and cured in a labour intensive process. First, the swim-bladder must be cut loose manually from the spine by means of a knife. Then the black membrane adjacent to the swim-bladder is scraped or brushed loose and the swim-kb:ycc -1-1~3~ .77 bladder cured in salt. Curing results in a 25% reduction in weight. After curing, the price is 500kr/kg (10.9OC$/kg).
After that the swim-bladder is pickled, dried, smoked, cooked or fried, and is an expensive and delicious food.
Disembowelled fish with heads are sold for approximately 40kr/kg (0.87C$/kg), and the spine as a raw material for fishmeal is sold for 0.40kr/kg (0.0087C$/kg).
Thus, the raw material for the curing of the swim-bladder costs 0.40kr/kg (0.0087C$/kg~ and the salted swim-bladder is sold for 500kr/kg (10.9OC$/kg). Thus there is much increase in price for the curing of the swim-bladder.
Curing of the swim-bladder includes cutting the swim-bladder loose from the spine, removing the black membrane and further curing the swim-bladder in salt. The ¦15 increase in value of 460kr (lOC$) does not pay the labour for removal of 20 swim-bladders or 23kr/piece (0.5C$/piece).
Thus one cured swim-bladder weighs approximately 40g and is equivalent to 0.5kg of fish or has 12 times the value/weight of disembowelled fish. In spite of this value, the curing has not been valued to pay, and it has been thrown away with the bones (spines) or has been processed for fish meal.
Recently there has been developed a method for removing the black membrane chemically by means of enzymes which saves much labour. However, the only known method of cutting the swim-bladder loose is by a knife and that is by hand. That method claims much labour and is expensive. The purpose of this invention is to improve that process by providing a method and a machine for cutting loose the swim-bladder from the spine mechanically.

~ummary of the Invention The inventidn present invention automates this process by providing a method and an apparatus for removing the swim-bladder from the spine of a fish. The method comprises the steps of:
penetrating the cavity of the swim-bladder at its ~I front end by means of a diverging guiding wedge such that ~ the wedge intercedes the spine and the swim-bladder;
J ~ moving the spine along a path, defined in part by the guiding wedge, towards a conveying means, so that the kb:ycc -2-:L3~ 7 7 conveying means grasps the spine and drives it forwards and downwards against the guiding wedge so as to generally flatten the ribs outwardly in a plane;
driving the spine together with the swim-bladder along the diverging guiding wedge, towards a cutting knife, thus opening the swim-bladder and separating it from the spine to form a clearance for the cutting knife;
further driving the spine on the guiding wedge 50 that the guiding wedge penetrates the rear end of the swim-bladder; and driving the swim-bladder past the cutting knife and at the same time laterally cutting the swim-bladder below or at said plane and as near as po~sible to the ribs so that the swim-bladder is cut away from the spine.
The apparatus for removing a swim-bladder from a spine of a fish comprises in general: -a path along which the spine of the fish is moved generally longitudinally, the path comprising a cantilevered guiding wedge having a leading free end for penetrating the swim-bladder at its foremost end;
conveying means for pressing the spine of the fish against the guiding wedge and along the path so that the ribs are generally flattened thereagainst;
cutting means disposed substantially horizontally along the path, downstream of the leading free end of the guiding wedge and below the flattened ribs of the spine for cutting away the swim-bladder from the ribs as the spine is moved along the path.

Brief Description of the Drawings Fig. 1 shows one embodiment of a swim-bladder machine as seen from above.
Fig. 2 shows the embodiment of Fig. 1 seen from Gne side while processing a fish spine.
Fig. 3 shows a section through the centre of the horizontal cutting knife and the mid-line of the guiding wedge.
Fig. 4 shows a section of the spine during the swim-bladder removal process.
Figs. 5 and 6 show alternate conveying means, in kb:ycc -3-~ A

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particular, a spike conveyor chain as seen from one side and from above, respectively.
Fig. 7 illustrates an alternate embodiment showing in plan the relative position of the guiding wedge and two i 5 knives, which are powdered by separate motors, as well as a ~ partial side view of the guiding wedge.
¦ Fig. 8 is showing section A in Fig. 7.

De aile~ Description of the I~vention Turning now to Figs. 1 and 2, motor 14 drives the conveying wheel 13, which moves the spine 7 (Fig. 2) in the moving direction 15 towards the circular knife 1. Below the spine 7 is the guiding wedge 6. The conveying wheel 13 is covered by a saftey screen, not shown in the figure. The screen is only open where the spine 7 enters into the conveying wheel 13. Above the knife l there is a screen, which could be a table-top on the frame 4. It is not shown in the figure. The screen and the table-top are security screens for preventing accidents.
The circular knife l has a vertical driving axle 2 which, at its lower end, is connected to a motor 3 mounted on the frame 4. Above or to one side of the knife 1 there is the guiding wedge 6. The front end of the spine 7 is `
laid upon the guiding wedge 6, so that the guiding wedge 6 intercedes the spine 7 and the swim-bladder 8. The lower part of the guiding wedge 6 is elastic or comprises an elastic rod 9, which pulls the swim-bladder 8 down from the spine 7 and in that way moves the swim-bladder 8 down below the knife l. The knife l cuts the swim-bladder 8 from the spine, when the spine 7 is move towards the knife 1, and the swim-bladder falls down into a container for swim-bladders, whereas the spine 7 moves on towards a container for spines.
The motion of the spine is provided by the conveyor wheel 13~ which in turn is driven by a motor 14 fixed to the frame 4. The motor 14 is mounted onto a plate 12, which at the front end is connected to the frame by means of elastic springs 11, but has hinges 10 at the rear end~ By this means, the conveying wheel 13 can elastically move away from an obstacle or roughness in the spine 7 and also conform to spines of different sizes. The motor 3 is surrounded by a kb:ycc -4-~ A
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cover 5, which only is open, where the swimming-bladder 8 enters towards the knife 1.
Fig~ 3 shows a section through the centre of a knife 1 and the mid-line of the guiding wedge 6. The beam 18 is seen from the side and the table-top 16 in section 24 illustrates that point of the knife where the swim-bladder is being cut.
Fig. 4 shows a section of the spine 7 with the crest 21 and the wall 22 of bones, the conveyor wheel 13, the swim-bladder 8, the lower part 9 of the guiding wedge 6, the upper part 6 of the guiding wedge 6, the beam 18 and the bubbles 20 of the swim-bladder 8. The cutting line of the `~
knife 1 is marked by 23. The conveyor wheel 13 presses the spine 7 down upon the guiding wedge 6 and the beam 18.
Thereby the spine becomes flatter at the lower side and I forms a direct cutting line, at the upper limits of the swim-bladder, for the knife 1, which is not shown, so that the knife 1 is able to cut all the swim-bladder loose from the spine 7, without cutting any bones from the wall 22 of bones. The section is placed in front of the knife 1 and the cutting line 23 is at the upper limits of the guiding wedge 6 according to the arrangement shown in Fig. 3. If the guiding wedge 6 is above the knife 1, as shown in Fig.

2, the cutting line 23 is at the lower edge of the guiding wedge 6 or a little lower than that. In that case the ends of the bones are more apt to be cut with the swim-bladder 8, or the whole of the swim-bladder may not be cut loose.
Figs. 5 and 6 illustrate alternate conveying means materialised as a spike conveyor chain 28 seen from one side and from above, respectfully. The motor 14 drives the gearbox 25 and, hence, the axle and the pulley 26, driving the fixed axle 27, which is joined to the frame 4 through the bearings 32. In bearings on the axle 27 is the supporting element 29, which in the same way is connected to the axle 31 of the other chain-wheel. The supporting element 29 is by an arm connected to a spring 30, where the other end is fixed to the frame 4. The spring 30 pulls the conveyor-chain down to the guiding wedge 6 and presses the spikes down towards the spine 7.
As an alternative, Fig. 7 shows the relative kb:ycc -5-~' ~330~77 position of the guiding wedge 6 and two knives 1, which are powered by separate motors 3. The knives 1 turn against the direction of motion 15. There may be a screen 35 covering the knives, but they can as well be in the same plane as the table-top 16. Between the knives 1 is the path 36 continuing from the guiding wedge 6. The foremost part of the guiding wedge 6 is directed upwards and its tip 34 is directed downwards.
The walls 22 of bones of the spine 7 rest on the sides 37 of the guiding wedge 6, whereas in the middle there is the dip 38 for the core 39 of the spine 7. Against the guiding wedge 6 the knives l lie with their cutting edges in the same plane as the upper edge of the guiding wedge 6 and the lower edge of the walls 22 of bones, whereas the core 39 moves along the dip 38.
The swim-bladders are of different sizes according to the size of the respective fish, of different length and of different width. The guiding wedge 6 must be smaller than the smaller swim-bladder to be cut. It is advantageous to cut 3-4 cm nearest the mid line of the swim-bladder 8 by means of a knife behind or at the tip of the guiding wedge 6, in order to make a hole for the guiding wedge 6, which can be of the same width at these holes. These cuts will become end cuts in the swim-bladders 8. The sidecuts are then cut by means of circular knives 1.
The method includes driving the spine through the machine along a path by conveying means. On the way the tip perforates and the tip-knife cuts a hole into the front end and the rear end of the swim-bladder 8, and the knife 1 cuts the sidecuts. Whether the knife has begun cutting the front -end before the tip makes the hole at the rear end depends upon the length of thei guiding wedge. Increased control around a vertical axis is achieved by means of a long ~ guiding wedge 6, which makes a hole at the rear end before - 35 the knife 1 has cut the front end. Thus, the method is - characterized by the knife being preceded by a tip, whichmakes a hole at the front end of the swim-bladder 8, and farther back comes a guiding wedge 6, 9, which opens the swim bladder 8 wide apart from the spine 7 and forms a clearance for the knife 1. As the guiding wedge 6 has a kb:ycc -6-. .

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~ 33Q~77 fixed width to which the tip must cut, the tip must be followed by a tip-knife, which cuts or tears that width.
Thereby the ord~r of tools becomes: Tip, tip-knife, wedge, knife.
As the cavity of the swim-bladder has two ends, the tip must leave the rear end of the cavity in the same way as it entered the front end. When the tip has left the rear end, the knife 1 has still left to cut the rearmost part of the side cuts.
The conveying means 13 may consist of one or more wheels 13, of one or more conveyor belts 13 or of one or more arms 13 or similar means. The conveying force should grasp the spine 7 in such a way as to move it directly forwards without rotation. This requires a kind of a control. This control is obtained by means of a rift in the conveying wheel 13 and grasping means at each side of the crest 21 of the spine, or two coaxial conveying wheels 13.
It is advantageous to outfit the conveying wheel 13 with spikes or similar means for increasing the friction and the grip. A spiked chain or belt is suitable conveying means, which grasps the spine 7 in front of the knife 1 and continues the grip over the knife 1. Opposite the direct part of the chain a supporting element 29 is suitable for supporting the chain against the spine.
The tip has the task of penetrating the swim-bladder 8 and the tip-knife has the task of cutting or tearing a hole into it at the front and at the rear, in order to enable the guiding wedge 6 to enter the cavity and to exit it, in order to open the swim-bladder 8 wide apart from the spine 7 and, thereby, to form a clearance for the knife 1, which cuts the side-cuts and cuts the swim-bladder loose from the spine.
The guiding wedge 6 has the task of guiding the swim-bladder 8 towards the knife 1. The guiding wedge may lie in a plane above the knife 1 as shown if Figs. 1 and 2.
The guiding wedge 6 may also lie in the same plane as the knife 1, as shown if Figs. 3 and 4. In that case the upper edge of the guiding wedge 6 is in the same plane as the upper edge of the knife 1. When moved in the direction 15, the guiding wedge 6 ends, where the knife 1 begins, having ' kb:ycc -7-1~3~77 only a small clearance in between, and the knife 1 can cut close up to the spine 7. The guiding wedge is then fixed onto one or more cantilever beans 18, lying under the knife 1, and cantilevered into the frame 4.
When there are two knives, the guiding wedge 6 may lie between them and in that case the knives 1 will cut from the side up towards the sides of the guiding wedge 6, as shown if Fig. 8. In that case the width of the top-knife 33 must be at least equal to the distance between the knives 1.
The knife-motor 3 is shown below the knife 1. It must be protected against water an offal. Therefore it is not out of the question to actuate the knife 1 by means of a chain or a belt and to mount the axle 2 in bearings and locate the motor away from the knife. The same is true regarding the motor 14 which actuates the conveying wheel 13. There an absent drive is possible, chain drive, belt drive, pneumatic drive or hydraulic drive.
The specific relationship referred to herein regarding horizontal knife 1 and the spine 7 on top is only for simplifying the discussion of the invention. The main point is the relative position of the conveying wheel 13, the spine 7, the guiding wedge 6 and the knife 1.
At the front part of the abdominal cavity of the fish, where the core of the spine reaches down from the walls of bones or ribs, it is suitable to use two knives, one at each side of the guiding wedge 6 tsee Fig. 8), so that each knife cuts along the lower limits of the wall of bones, up to the core of the spine. In that embodiment, the guiding wedge 6 with unchanged section can continue past the knives as a path for the spine after the cut. Furthermore, the table-top 16 could be in the same plane as the knives.
The output of the swim-bladder machine is approximately 25-30 pieces/min, corresponding to 1 kg of swim-bladders per minute. Thus, the swim-bladder machine is cutting the swim bladder from 1500 cods in an hour, each cod weighting approximately 6-7kg, totalling to approximately 10 tons of big cods. The output is enormous. The weight of the swim-bladders is 60kg, corresponding to 40kg after curing, present sales value being lO.90C$/kg or 870C$,after bathing in enzymes for a sufficient time and curing in salt.
kb:ycc -8-~3~77 By increasing supply the prices will become lower and the market will become bigger.
In the year 1987, there were in Iceland cured in salt 130,000 tons of cod (disembowelled and with heads), roughly 2n million pieces, representing a loss of 800 tons of swim-bladder, which after curing would have been 500 tons and would have been sold at present prices for 250 million kr. (5.43 million CS~.

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Claims (16)

1. An apparatus for removing a swim-bladder from a spine of a fish, said swim-bladder being disposed generally below the spine and between the ribs, the apparatus comprising:
a path along which the spine of the fish is moved generally longitudinally, said path comprising a cantilevered guiding wedge having a leading free end for penetrating the swim-bladder at its foremost end;
conveying means for pressing the spine of the fish against the guiding wedge and along the path so that the ribs are generally flattened thereagainst;
cutting means disposed substantially horizontally along the path, downstream of the leading free end of the guiding wedge and below the flattened ribs of the spine for cutting away the swim-bladder from the ribs as the spine is moved along the path.

2. The apparatus of claim 1, wherein the width of the guiding wedge is less than the width of the smallest swim-bladder to be removed but sufficiently broad to prevent rotation of the spine as it moves therealong.

3. The apparatus of claim 2, wherein the guiding wedge tapers outwardly from its leading end in the direction of travel of the spine and wherein the guiding wedge has a lower part which diverges vertically in the direction of travel, whereby as the spine is moved along the path, the swim-bladder is wedged apart from the spine.

4. The apparatus of claim 3, wherein the lower part of the guiding wedge comprises one or more resilient rods for providing an opening force proportional to the size of the swim-bladder to be removed.

5. The apparatus of claim 3, wherein the leading end of the guiding wedge is directed obliquely upwardly in the upstream direction and then downwardly to form a tip, and wherein a cutting edge is provided at the tip for cutting a hole into the swim-bladder at its foremost and rearmost ends as the spine moves along the path.

6. The apparatus of claim 1, wherein the guiding wedge is provided with a depression along its centreline for guiding the spine and, off the centreline, gliding surfaces for the ribs.

7. The apparatus of claim 1, wherein the guiding wedge is cantilevered onto a frame by means of a cantilever beam.

8. The apparatus of claim 1, wherein the cutting means comprises a circular knife disposed slightly beyond the cantilevered end of the guiding wedge in the direction of travel of the spine, said path intersecting generally diametrically said circular knife.

9. The apparatus of claim 1, wherein the cutting means comprises a pair of spaced-apart, circular knives disposed horizontally opposite one another across the path, having a clearance therebetween which is less than the width of the guiding wedge.

10. The apparatus of claim 8 or claim 9, wherein the circular knife or knives have cutting edges in the same plane as the surface of the guiding wedge against which the ribs are flattened.

11. The apparatus of claim 8 or claim 9, wherein the knife or knives lie in a plane which is slightly below the surface of the guiding wedge against which the ribs are flattened.

12. The apparatus of claim 1, further comprising a table-top disposed below the leading edge of the guiding wedge for supporting the ribs as the spine is being pushed in the direction of travel.

13. The apparatus of claim 1, wherein the conveying means is located above the path and comprises a conveying wheel or belt having an axis transverse to the path and having a circumferential rift for accommodating a dorsal crest on the spine.

14. The apparatus of claim 1, wherein the conveying means is located above the path and comprises coaxial conveying wheels or belts having axes transverse to the path and being axially spaced for accommodating a dorsal crest on the spine.

15. The apparatus of claim 13 or claim 14, wherein spikes are provided on the conveying means for increasing the friction between the conveying means and the spine and thereby increasing the conveying force in the direction of travel.

16. A method of mechanically separating a swim-bladder from the spine of a fish, said swim-bladder being disposed generally below the spine and between the ribs defining a cavity therein and having a front end and a rear end, comprising the steps of:
penetrating the cavity of the swim-bladder at its front end by means of a diverging guiding wedge such that the wedge intercedes the spine and the swim-bladder;
moving the spine along a path, defined in part by the guiding wedge, towards a conveying means, so that the conveying means grasps the spine and drives it forwards and downwards against the guiding wedge so as to generally flatten the ribs outwardly in a plane;
driving the spine together with the swim-bladder along the diverging guiding wedge, towards a cutting knife, thus opening the swim-bladder and separating it from the spine to form a clearance for the cutting knife;
further driving the spine on the guiding wedge so that the guiding wedge penetrates the rear end of the swim-bladder; and driving the swim-bladder past the cutting knife and at the same time laterally cutting the swim-bladder below or at said plane and as near as possible to the ribs so that the swim-bladder is cut away from the spine.