Note: Descriptions are shown in the official language in which they were submitted.
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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-
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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
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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
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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
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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
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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
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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
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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.
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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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