Note: Descriptions are shown in the official language in which they were submitted.
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Net cage installation for fish farming
The present invention relates to a net cage installation arranged for
replacement of the
net while fish can remain in the net cage, said net cage installation
comprises a net, a
floating frame construction circumferentially placed around the net and a
number of net
suspensions placed internally of and circumferentially on the frame
construction.
The invention also relates to a method for carrying out the replacement of a
net.
The net cage installation is particularly developed for use with an
installation where a
floating frame construction having a wall~way is assembled of several floating
elements
that are articulately connected to each other and that individually follow the
movements
of the sea. However, it must be understood that the net cage installation also
can be used
with installations having a rigid frame construction.
The traditional replacement of a net on fish farming installations is a time
consuming
process requiring much manpower. The net replacement takes place in that a
fish
farming net is prepared for deployment in a net cage, i.e. that the net is
properly
prepared and arranged, and is usually delivered on a pallet to ensure simple
transportation and storage. The net is delivered with a top net, i.e. a
jumping net that
prevents the fish from jumping over the edge of the net, lying on top. When
the net is to
be moved from a boat to a net cage, the fish farming net is simultaneously
turned so that
the bottom of the net is lying uppermost on another pallet.
The pallet with the fish farming net is placed on the opposite side to where
the net that
is to be replaced is drawn up from the sea. Before the net replacement can
begin, the net
must be released from weights or other appliances that are secured to the net
to keep it
down. The net, i.e. the jumping net, must first be released from the edge of
the net
cage/railing.
After the net is in position at the middle of one side of the net cage, the
fish farming net
is put out with the bottom first. Almost the entire net is put into the sea
between the
walkway and the net that is to be replaced. When about four metres of the net
remains
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on the walkway, the net is temporarily secured so that one can find the net
corners.
When all four corners have been found, they are drawn to the side, and the
fish farming
net is now ready to be pulled out.
One side of the new net is drawn out by hand and hooked onto the railing. This
side is
to be sewn together with a corresponding side of the net that is to be
replaced. The
opposite side of the net is drawn in the same way and secured to the railings.
The two
other sides of the net are drawn out to each side of the net cage and sewn
together on the
wallcway. When both nets are sewn together, those sewn parts are ready to be
lowered
into the sea.
The net is now ready to be drawn towards the outer edge of the net cage
installation. On
the two sides where the new net is sewn together, it can be released, and one
can start to
pull both the new net and the net that is to be replaced forward. This is very
time
consuming and heavy work since one must carry the weight of both nets as they
are
pulled forward. During the entire replacement process, it is very important
that the net
does not go below the surface of the water so that fish can escape. Just at
this stage there
is a great risk for fish to escape. When the entire net that is to be replaced
has been
drawn forward a few meters, there will be an "excess" of net at the outer side
where the
fish farming boat will be laying. It is now ready for the crane on the boat to
pull the
surplus net onboard.
The net is pulled onboard by the crane with the help of straps that are
temporarily
fastened to the net. In this way, by continuously fastening straps to the net
and then
pulling, the net will gradually be drawn onboard. The fence on both nets that
are in the
net cage is moved forwards to the outer edges of the net cage, where the boat
is located.
This must be done by hand. After the net that is to be replaced has come all
the way to
the outer side, the new net will finally have taken over the place in the net
cage. The
seam is released and the remaining portions of the net that is to be replaced
are taken
onboard the boat. The net is then threaded with a rope through the top of the
net, i.e. the
jump net, thereafter to be tied in a bundle at the top. The tying together is
secured or
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knotted, and will thus ensure that the net does not get tangled up during
washing/transportation. The net is now ready to be taken away and washed.
Replacing a dirty fish farming net as described above will require 4 to 5
persons to
obtain efficiency. The time consumption will be about 6 hours including the
time to
remove weights/attachments from the dirty net and securing the same to a clean
net
after the net is in place. The transportation of the nets to and from the fish
farm
installation comes in addition.
More recently, a new installation that uses drums to coil up/uncoil the nets
has entered
the market. Such an installation is described in Norwegian Patent 308 761.
However,
this installation is intended for rigid frame constructions and cannot be used
in a net
cage installation having an articulated frame construction.
In accordance with the present invention a net cage installation of the
introductorily
described type is provided, which is characterised in that a rail system is
internally
arranged to the frame construction, said rail system is utilised during
replacement of the
net and comprises an inner rail to which the net that is to be replaced can be
connected
via a number of suspension means that are displaceable along the rail, and a
dual rail
nearest to the frame construction to which the new net can be connected via a
number of
suspension means that are displaceable along the dual rail, said new net,
prior to the net
replacement itself, is connectable to a respective rail of the dual rail so
that the net is
hanging twofold down into the water, and external of the net that is to be
replaced, and
that the dual rail comprises either respective turning means that turn the
suspension
means around and thus turns the inside out of portions of the new net to be
the outside
when the net passes the turning means, or alternatively that the suspension
means are
turned manually.
Preferably, the net is supplied in the form of a closely packed magazine
supplied on a
shorter dual rail from which the net hangs twofold down via said suspension
means.
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In one embodiment each suspension means can be a hanger having a roller
designed to
run along a rail, and also fixing means for the net.
In a preferred embodiment intended for an articulated frame construction, the
rail
system comprises a number of flexible points (joints) that are arranged near
articulated
locations of a frame construction/wall~way of the articulated type.
In one embodiment each turning means constitutes part of the rail system,
where the
outer rail of the dual rail is continuous, the inner rail in the dual rail is
discontinuous and
makes a jump down at the turning means and continues in a same first
direction, in the
opposite direction the inner rail forms an arch that terminates at one end
which points
more than 90° baclc in the first direction, said end makes a jump to an
underlying rail
which constitutes the extension of the inner rail of the rail system in said
opposite
direction.
Additional and further objects, features and advantages will appear from the
following
description of one presently preferred embodiment of the invention, which is
given for
the purposes of description, without thereby being limiting, and given in
connection
with the appended drawings, in which:
Fig. 1A shows a net cage installation according to the invention seen from
above.
Fig. 1B shows in more detail a section of the lower left corner of fig. lA.
Fig. 2 shows in perspective view a turning means for a net cage installation
according to
the invention, at a first stage of a net replacement.
Fig. 3 shows in perspective view the turning means according to fig. 2 at a
second stage
of a net replacement.
Fig. 4 shows in perspective view the turning means according to fig. 2 at a
third stage of
a net replacement.
Fig. 5 shows an outline of a suspension in the form of a davit that supports
the rail
system.
Fig. 6 shows an outline corresponding to that shown in fig. 5 as the nets hang
before a
net replacement begins.
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Fig. 7 shows a magazine for storing, transportation, washing and placing of a
net.
Fig. 8 shows a simpler embodiment of the invention shown in fig. lA, but which
requires somewhat more manual labour.
Fig. 9 shows a variant of the simpler embodiment of the invention shown in
fig. 8, and
Fig. 10 shows how the rail system according to the invention is arranged for
use on a
fish farming net cage of substantially circular type.
Reference is first made to fig. lA that generally illustrates a fish farming
net cage 10. A
fish farming installation can have more net cages, normally arranged in pairs
in a longer
row. The net cage 10 comprises an encircling frame construction with walkway
15 for
personnel. Larger installations can also have a centrally located track
intended for
vehicle access. In a common installation the frame construction is often
assembled of
floating sections 16 which are articulately connected to each other to cope
with and
adapt to the wave motions of the sea. A number of such articulated connections
are
shown in figure 1 with reference number 17.
A rail system 5 is arranged along the inner circumference of the frame
construction
around the net cage 10. The rail system 5 comes into use during a net
replacement and
is otherwise not used. The rail system 5 stands at a predetermined height
above the sea
level, for example, about 1.5 - 2 metres. The rail system 5 is connected to
the frame
construction by means of a number of suspension means 20 in the form of davit-
lilee
constructions. In each corner of the net cage 10 the individual rails 5a, Sb,
Sc of the rail
system 5 form an arch which turns each rail 90°. At, or adjacent to
each articulated
connection 17 of the frame construction/walkway 15, the individual rails Sa,
Sb, Sc are
connected to each other in an articulated way so that they flex when the
floating
sections 16 follow the motions of the waves. This is shown in further detail
in fig 1B,
where the joints are marked with the reference number 12. For a fish farming
installation of the rigid type (without articulated connections), the rails do
not need to
have flexible points, i.e. do not need to be linked.
In more detail, the rail system 5 comprises an inner rail Sa that runs along a
first, second
and third side l, 2, 3 of the net cage 10 and with an opening 7 for pulling up
of a net
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(not shown in fig. lA) on the fourth side 4. The fourth side 4 with the
opening 7 may
face the open sea for possible access for crane or winch vessels. The rail
system 5
further comprises a dual rail Sb, 5c that lies between the inner rail Sa and
the walkway
15. The dual rail Sb, Sc extends from one corner at the one end of the fourth
side 4,
along the entire first side l, the entire second side 2 and halfway down the
third side 3.
Which corner at the end of the fourth side 4 one starts from is optional.
Approximately in the middle of the first and third sides 1,3 the rail system 5
has turning
mechanisms 8a, 8b respectively, which are only shown schematically in fig. 1.
Their
construction and shape will now be explained further with reference to fig. 2.
Fig. 2 also
shows a net 6a that is suspended from the inner rail Sa with the help of a
number of
suspension means 9 which are displaceable along the rail Sa. The net 6a is the
old net
that has been in the sea for some time and is to be replaced. How the net
replacing
occurs will be described later in connection with figs. 3 and 4.
Each turning mechanism 8a, 8b constitute a part of the rail system 5. The
outer rail Sc of
the dual rail is continuous. The inner rail Sb of the dual rail is
discontinuous and at the
turning mechanism makes a jump dl down and continues in the same first
direction R1.
In the opposite direction R2, the inner rail Sb forms an arch Sbl that
terminates at an end
Sb2 which points more than 90° baclc in the first direction Rl. This
end Sba malces a
jump d2 down to an underlying rail Sal which constitutes the extension of the
inner rail
Sa of the rail system 5 in the mentioned opposite direction R2. Furthermore,
the inner
rail Sa is discontinuous and makes a jump d3 down in the mentioned opposite
direction
R2 at the turning mechanism. The turning mechanisms 8a, 8b, on the respective
sides of
the net cage 10, are basically alike, but inverted, and with the difference
that on the one
side the outer rail Sc of the dual rail terminates here.
Fig. 5 shows a typical suspension means in the form of a davit 20. The davit
20 is
rigidly fastened to the frame construction/wall~way 15. A number of fastening
means 21
are arranged on the davits 20 to secure the horizontal beams that together
with the davits
20 form a railing on the wall~way 15. From a cantilever 22 of the davit is a
structure 23
that supports the rail system 5 suspended. The supporting structure 23 is
suspended in
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chains 24 with associated shackles 25. As illustrated, the supporting
structure 23 fixes
the inner rail 5a and the two rails 5b and 5c of the dual rail.
In the shown embodiment the rails 5a, 5b, 5c are in the form of circular pipe
profiles.
Each suspension means 9 constitutes a hanger 9a, a lower eye 9b and an upper
roller 9c.
The lower eye 9b is intended for suspension of a net. In longitudinal section,
the roller
9c is twin concave and with a radius of curvature that is adapted to the
diameter of the
pipe profiles of the rails. This results in the desired property that when the
roller 9c rolls
along a rail, it is guided sideways at the same time as the hanger 9a can
pivot or
oscillate about the longitudinal axis of the rail.
As mentioned previously, the rail system 5 is used at net replacement.
Normally the net
hangs in hooks 28 arranged on each support structure 23 at the same time as
the net is
drawn out to the side and hooked onto lower hooks 27 on the davit 20. Then the
suspension means 9 hangs freely down along the net in its eye 9b. That portion
of the
net, which is above the water level and hangs from the hooks 28 and via the
hooks 27,
foiins a jumping net for the net cage so that the fish cannot jump out.
Further hooks 26
are arranged on the cantilever 22 and are intended for securing a bird net
thereto, which
will extend as a "roof' over the entire net cage.
How a net replacement is carried out will now be described. At first, the net
6a that is to
be replaced is hanged on the inner rail 5a by means of the suspension means 9
such that
each roller 9c on the hanger 9a is hooked onto the pipe-formed rail 5a. The
net 6a will
then hang down into the water as shown in fig 5. It is to be understood that
the entire net
6a is still hanging down into the water as a net bag that surrounds the live
fish that
might be there. Then the new net 6b is hanged via the suspension means 9 onto
the dual
rail 5b, 5c for one half of the net cage 10. With reference to fig 1A, the new
net 6b will
then hang down into the water as a "twofold curtain" from the dual rail 5b,
Sc, but in a
limited extent from each turning mechanism 8a, 8b, and along the other side 2
which is
opposite to the fourth side 4 with the opening 7. In this half of the net cage
10, the new
net 6b will hang externally to the net 6a that is to be replaced, as shown in
fig. 6.
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Note that the space, which after the net replacement is to constitute the net
bag, is in fig.
6 defined between the downwardly hanging net sections of the net 6b. This
means that
when the net bag shall be developed to become the new net bag, the inner net
section
that hangs from the rail 5b must "en route" be turned inside out. This means
that the side
of the mentioned inner net section that faces the net 6a will be on the
outside of the net
bag after the net replacement.
The further net replacement continues, in that, along the entire side 2 and
somewhat
around the arch in each corner, the top of the net 6a is sewn together with
the top of the
nearest placed net section of the net 6b. Thereafter, the suspension means 9
are lifted,
over the same length extension as the nets 6a, 6b are sewn together, off from
respective
rails 5a, 5b, and lowered into the water together with the sewn together
section of the
nets. Then, the sewn together section of the nets 6a, 6b hangs in an arch down
into the
water, perhaps 3-4 metres at the deepest. This form an escape opening between
the nets
6a, 6b that the fish gradually will use as the net replacement proceeds.
The next step will be to get hold of the net 6a at the opening 7 and start to
pull the net
6a at this place. The suspension means 9 will then be displaced, i.e. in the
case
illustrated, roll along the inner rail 5a. The suspension means 9 will roll,
one by one, on
the inner rail 5a and move towards the opening 7 where they jump off and
follow the
net 6a up from the net cage 10. Reference is now made to figs. 2-4 that
illustrate how
the new net 6b is turned or turned "inside out". As mentioned, it is only one
half of the
net 6b that is turned, in particular the part that hangs from the rail 5b
nearest the net 6a
that is to be replaced. In the first stage of the pulling in, the suspension
means 9 roll on
the inner rail 5a as shown in fig. 2. Because the nets 6a, 6b are sewn
together, the part of
the net 6b that hangs down from the rail 5b is drawn along the rail 5b via the
rollers 9c.
At the same time, the part of the sewn together section of the nets 6a, 6b
that hang down
into the water will be drawn along. Some fish will now be able to swim over
into the
new net 6b.
When the sewn together section of the nets 6a, 6b approaches the turning
mechanisms
8a, 8b, a situation arise as illustrated in fig. 3. What initially was the
outer part of the net
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6b, will all the time hang approximately stationary down into the water from
the rail Sc,
via respective suspension means 9, here illustrated with the one suspension
means 9'.
The inner part of the net 6b will, because of the sewing together, be drawn
along "from
behind" and will collect accordion-like near the turning mechanism.
By further pulling of the net 6a, the foremost roller on the rail Sb will
after a while make
a jump d2 down onto the extension Sal of the inner rail Sa and roll towards
the end of
the rail. The suspension means 9 is now turned approximately 180°, see
fig 4.
Thereafter, the other suspension means 9 follow in turn and make the jump d2
down
onto the extension Sal. When all suspension means 9 have passed the jump d2
down to
the extension Sal, their order is reversed and all have turned approximately
180°. Thus
the new net 6b is also turned or turned "inside out" when it passes. At the
same time,
the jump dl-d3 is made as small as possible, i.e. so that a roller can pass
between them.
When the last suspension means 9 has passed the jump d2, this will be the
first that is
drawn along the rail Sa when pulling-in continues. The others follow in turn,
at the same
time as more fish swim over into the new net bag that is being formed. When
the entire
net 6a that is to be replaced has reached the opening 7, the sewing together
of the net
bags is released and the rest of the net 6a is removed. The new net 6b is now
in place
and hooked onto the suspension hooks 28 on the support structures 23 and the
hooks 27
at the same time as the suspension means 9 are unhooked from the rail Sa.
In addition, in order to simplify the work with the net replacement, a
magazine that
stores the new net 6b in a compact way has been developed. The magazine stores
the
net 6b via the same suspension means 9 on a short dual rail with the same
distance
between the rails as the dual rail of the rail system 5. This magazine is
indicated
schematically in fig. lA with the reference number 11, and an exemplified
embodiment
of the magazine I 1 is shown in fig. 7. Two parallel rails 13a, 13b are
secured to the
magazine housing 14 by brackets. The distance between the rails 13a, 13b,
corresponds
to the distance between the individual rails of the dual rail 5b, Sc. In
addition, two
parallel rails 15a, 15b are arranged over the rails 13a, 13b and at such a
distance
between them that a roller 9c can freely pass between them, but still not jump
off. The
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magazine housing 14 can be closed in one end. The other end can advantageously
be
closed with a cover (not shown). The cover can have openings through which the
rails
13a, 13b project. The magazine 11 can be connected directly to the dual rail
Sb, Sc, the
cover is removed and the suspension means 9 can be pulled continuously and in
parallel
5 onto the dual rail Sb, Sc, and further all the way round to one end reaches
the second
turning mechanism 8b and the other end reaches the first turning mechanism 8a.
Fig. 8 shows a simpler embodiment of a net cage 10a than the net cage 10 shown
in fig.
lA, in that the turning mechanisms are omitted. This means that the individual
rails Sa,
10 Sb, Sc are continuous and lie in a straight line also where the turning
mechanisms are
located. However, this solution will require somewhat more manual labour. With
such a
solution, the new net is pulled out from the magazine 11 in the same way as
before.
After the nets are sewn together, the sections of the new net that go forward
on each
side 1, 3 can be drawn to their own corner at the ends of the side 2. When one
starts to
pull in the net that is to be replaced, the suspension means 9 that hang on
the middle rail
Sb must be manually lifted from the rail, turned 180° and be hooked
onto the inner rail
Sa. One starts with the suspension means 9 on the middle rail Sb that is
nearest the
corner and continues with the next suspension means 9 etc until the middle
rail Sb is
emptied. When the middle rail Sb is emptied, one continues to pull the net
that is to be
replaced and the suspension means 9 on the outer rail Sc that is furthest from
the corner
moves first and the remaining suspension means 9 follow in turn. Note that one
does not
need to turn or lift these suspension means 9 over onto the inner rail Sa, but
can let them
roll along the outer rail Sc. When the suspension means 9 on each side that
initially are
located furthest from the corner, reach the middle of the sides 1 and 3, the
new net is
substantially pulled out and in place. The net can now be hung onto the
respective
hooks 27 and 28.
Alternatively, a procedure more like the one described first can be used, i.e.
let the new
net hang all the way round from approximately the middle of each side 1 and 3.
This
means again that the suspension means 9 on the middle rail Sb must manually be
lifted
from the rail, turned around 180° and hooked onto the inner rail Sa.
This can occur
either when the sewn together part passes the suspension means 9 on the middle
rail Sb,
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or near the middle of the sides 1, 3 after the new net, still on the middle
rail Sb, has
aggregated at the mentioned place. Still with the suspension means 9 that is
nearest the
corner first. When the rail Sb is emptied, the new net will substantially have
been pulled
out and in place. The net can now be hung onto the respective hooks 27 and 28.
Fig. 9 shows yet another embodiment of a net cage l Ob that still is somewhat
simpler
that the embodiment l0a shown in fig. 8. However, this requires more manual
labour.
As before, one has the inner rail Sa nearly all the way round. The dual rail
Sb, Sc is now
only at the side 2 which is opposite to the side 4 with the opening 7. The
magazine 11
can normally be placed in one of the corners at the ends of the side 2. The
new net is
pulled out on the dual rail and hangs twofold into the water. One fords the
middle of the
net on the middle rail Sb and pulls the suspension means 9 out towards each
corner and
thereby tightens the net on the middle rail Sb so that this section of the net
can be seyvn
together with the corresponding section of the net that is to be replaced.
Thereafter, the
sewn together section is let into the sea so that it hangs in an arch down
into the water.
As the net that is to be replaced is drawn in, the suspension means 9 on the
middle rail
Sb must be lifted from the rail manually, turned round 90° and hooked
onto the inner
rail Sa. Firstly, the rail Sb is emptied and thereafter one continues to lift
a number of
suspension means 9 onto the outer rail Sc until the new net is drawn out along
the side 2
simultaneously with it being stretched out along the sides 1 and 3. The net
can now be
hung onto the respective hooks 27 and 28.
Fig. 10 shows yet another net cage 30 that illustrates how the rail system
according to
the invention is adapted for use on a fish farming net cage of a substantially
circular
type. As before, the inner rail Sa runs nearly all the way round and ends at
an opening 7.
The dual rail Sb, Sc only run .about halfway round the net cage and at the
part that is
opposite to the opening 7. The magazine 11 cari optionally be placed at one of
the ends
of the dual rail Sb, Sc. As before, the new net is pulled out onto the dual
rail Sb, Sc and
hangs twofold down into the water. The new and the old net are sewn together
over a
sufficient length, possibly along the entire length in the longitudinal
direction of the
dual rail Sb, Sc and thereafter lowered into the water. The suspension means 9
on the
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middle rail Sb is either lifted manually over onto the inner rail Sa, or one
can use turning
mechanisms as described previously for a more automated net replacement.
Furthermore, it is to be understood that a rail system can be used without
being
suspended from davits. The rails can be fastened to brackets, which in turn
are secured
directly to existing railings, or the rails are fastened to brackets directly
secured to
davits. To make this possible, the rails must have flexible joints to take up
motions in
the fish farming installation. This can be attained by use of rubber joints,
hinged joints,
rails of plastic or the like. It is also possible to use rails that are not
made of circular
section pipes. Alternatives are rails of square sectioned pipes, angled
profiles, U-shapes,
etc and partly closed profiles where pulleys or rollers run inside the closed
profile, in
which a bottom slit is provided in the longitudinal direction of the rail.
Furthermore, the rails can be placed down along the edge of the net cage. By
doing it in
this way, the rails will be less exposed to the movements of the fish farming
installation.
Then plastic pipes or the like can be used along the railings to keep the
jumping net of
the net standing.
