Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR STRIPPING ~LESH FROM FISH
FRAMES
Hithert~o ~flesh was strlpped from fish ~rames
by a cutting action, ~either: manually ~ or mechanically~
Both methods are not~feasible for treating~s;mall~fishes.
Accordingly, s~mall fi~she~s were;previously comminuted~and
; 5 pressed through sleve~mean~s, thereby removing the bones
but yielding an off-colour mince. The invention~provides~
a method and;~apparatus~for~reme~dylng~this~
The invention provlde~s a~ me;thod for sbripping~
- ~ 10 flesh from ~he frame ~and skin: of a :fish port,ion,~ in which
proeess a decapi;tated and gutted~fish portion2~whleh~ls~
; unsXinned and still contàins~the~backbone, is~p~assed tail-
first between~a~pair~;of contra-rota~ing~paralle~ squeeze
rollers, the~nip between whi~eh~has~su~ch a width;~that;~the~
~ail and the~skin ~o~ said~fish~portion is~gri~pped~su-f;~
ciently tightly for~the~skin and~ackbone of the fish~-to
be drawn betwe~en~the rollers~wlthout being significantly
damaged, and~while~the fish portion is being drawn between
the squeeze rolle~rs flesh is~expressed from the head end
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The inventicn also provides an apparatus in which the
above process can be conducted~ comprising a housing,
feeding means for fish portions, treating rneans and dis-
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charging means, which apparatus is characterised inthat the treating means comprise at least two pairs of
contra-rotatably~drivable parallel rollers having
upright axes, the first pair of rollers, viewed in the
direction of transport~ being at a greater distance
than the second pair of rollers, at least the second
pair being coated with a resllient material having a
profiled surface.
Although not absolutely necessary, it is highly
desirable to have a second pair of rollers situated
immediately in front of the squeeze rollers and rotated
in a similar contrary manner relative to each other such
that these rollers firstly guide the fish into the nip
between the squeeze rollers and secondly apply a light
pre-squeezing action to the fish which loosens the bond
between the flesh and the frame. This pre-squeezing fa-
cilitates the action of the squeeze rollers in express-
ing the flesh from the fish as already described. This
second pair of rollers will hereafter be referred to as
the "pre-squeezing rollers".
Although not essential, it is also desirable to
have a further pair of rollers situated immediately
behind the squeeze rollers and rotated in a similar
contrary manner relative to each other, such that these
rollers grip the tail of a fish emerging from between
the squeeze rollers and assist in the passage of the
skin and frame of the fish through the apparatus.
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~ his further pairof rollers will hereinafter
be referred to as the "discbarge rollers "~
An apparatus according to the invention can
be provided with squeeze rollers plus pre-squeeze
rollers, or with squee~ze rollers plus discharge~rollers
or with a combination of all three types of rollers ?
as desired~
Although the~squeeze rollers can be mounted in
any orientation, it is~nevertheless highly desirable~ ;
that the nip between the squee~ze rollers sh;ould~ e~
in a vertical, or~at lèast~su~stantially ve~r-tical,plane.
; This feature is beneficial in assisting the recovery
of the flesh expressed from the fish because the ~'lesh
will tend to drop away from the~rollers rather than~
; 15 being caught between~bhem. ;
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A further~des~irable f'eature is a means for
applying water eithqr continuousl~ or in-termittently~
to the various~palrs of rollers.
~; Application~of the water can be, for~example,
b~ means of a j~et;o~r~spray. ~he~wat~er assists~in
keeping the~rollers~clean~and~there~fore~maintaining~
their gripping~qualit~les. ~;It~is generally desirable ~ ~ -
to ensure that excessive~ amounts o~ water do not
become mixe~d :with -th~e Xlesh expressed from the ~ish~
and therefore the provislon of means for collecting
and removing the water falling ~rom the rollers is
advantageous~
~ he s~ueeze rollers must have a degree of
resilience~suff~icient to accommodate the naturally- ;
varying cross-section of a typical fish and -to
accommodate the~variations in~size ~rom one fish to
another. We have found that in general the squeeze
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rollers should be made of a material having a hardness
in -the range 20 to 40 on the ~hore scale. With this
consideration in mind, the squeeze rollers are best made
from natural or synthetic rubber having a hardness in
this range.
~ he surface texture of the squeeze rollers must
be such that sufficient fric-tion can be generated bet-
ween the roller surfaces and the skin of a fish to
draw the fish between the rollers, while not causing
~ny significant damage to the skin. A surface fea-t-
uring a multitude of small closely-spaced inden-ta-tions
or projections is very suitable. Alternatively, a
multitude of grooves or ribs, arranged for example
parallel to the cylindrical axis of the roller, can
be used. ~hese surface fea-tures can be moulded into
the ma-terial from which the bulk of the roller is
constructed, or can be imparted -to the roller by means
of a surface covering.
~he pre-squeeze discharge rollers can be
constructed of similar materials wi-th similar surface
properties. We have found, however, that a relatively
more frictional surface on the discharge rollers is
beneficial.
~he physical size of the squeeze rollers may
be varied deperlding upon the physical size of the fish
to be processed using -the invention. ~he process of
-the invention can be readily adapted for small,
intermediate or large fish. Clearly fac-tors such as
the ph~sical size of the rollers, their positioning
relative to one another, and the speed with which a
fish passes between the rollers may need adjustmen-t
according to the particular fish being handled.
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In general, we have found that the squeeze
rollers should have a diameter in the range 30 to 90 mm
and a length in the range 60 -to 250 ~m.
~ he pre-squeeze rollers ~hould ideally have a
length the same as that of the squeeze rollers. ~he
dia~eter of the pre-squeeze rollers is preferably
substantiall~ greater -than that of the squeeze rollers,
thus promoting maximum fish-roller contact. In general
we have found that the pre-squeeze rollers should have
diameters in the range 70 to 120 mm.
.
~ he discharge rollers should ideally have a
length -the same as that of the squeeze rollers~ ~he
- diameter of the discharge rollers, however, is
preferabl~ substantiall~ less than that of -the squeeze
rollers so that close proximity between the two pairs
of rollers can be obtained. In general we have found
that the discharge rollers should have diameters in
the range 30 to 60 mm.
Ideally the apparatus of the invention should
be constructed such that the distance between the
cylindrical axes of the squeeze rollers can be adjusted
readily, thus making the apparatus better able to be
used in -the processing of a wide range of fish sizes~
Preferably, the pre-squeeze rollers and the discharge
rollers are similarly adaustable.
Preferabl~, -the squeeze rollers should be in con
tact with each other With roLlers of hardness 20-40 and
preferably 30-35 on the "A" ~hore scale, and a diameter of
50 to 90 mm, the cylindrical axes can be set so that
the rollers are just touching, the resilience of the
s~05~
rollers then providing for passage of a fish between
them~ The more resilient the rollers, the closer
can be the cylindrical axes to produce an effective
pressure on a fish passing between the rollers~
Preferably, there is a gap between the pre-squeeze
rollers, thus ensuring that their action on a fish passing
between them is merely a mild squeeze and does not cause
any significant expression of flesh from the fish in the
manner intended during subsequent passage between the
~ squeeze rollers. In genaral, this gap will be from
about 2 to about 30 mm. ~he gap between the pre-s~ueeze
rollers~ when small fish such as blue whiting are being
processed, will generally be about 4 to about 14 mm. ~or
substantiall~ larger fish, such as haddock, -this gap will
generally be about 16 to about 26 mm.
~he discharge rollers should ideally be in contact
with one ano-ther, to ensure that they grip adequately
the tail of a fish emerging from between the squeeze
rollers, thus drawing the spent skin and skeleton of
the fish onwards through the apparatus.
~he speed with which a fish passes between the
various pairs of rollers should be constant, or prefer-
ably increasing slightly as the fish progresses through
the apparatus. ~he speed of rotation of the rollers
should be set accordingly. A typical throughput for
small fish, such as blue whiting, fed continuously into
the apparatus, can be up to about 100 fish per minute, but
a throughput of 25 to 50 fish per minute would be more
normal.
~ ~he extent to which relatively bone-free and skin-
free flesh can be recovered from a fish by means of the
invention depends to a considerable extent on the ~uality
of the fish used and the manner in which the fish has been
treated and prepared prior to rolling. It is obviously
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essential that the head and gut regions of the fish
should be removed prior to rolling. It is also use~ul if
the dorsal fins of the fish are cut off7 as we have found
that thiS can res~l~ in ~ smoother passage of the fish
between the rollers and a lower incidence of back-
bone breakage. It can also be advantageous if the
belly flaps o:~ the fish are removed prior to rolling.
In the case of small fish such as blue whiting,
small haddock, whiting and codling, the whole fish
(minus head and guts) can be processed as a single unit.
Due to their small size, such fish are difficul-t -to
process economically by conventional filleting operations
conducted either mechanically or by hand9 In the
case of larger fish, for example cod, it can be
advantageous to "halve" the fish into "top" (head)
and "tail" por-tions. ~he top portion can be pro-
cessed using conventional techni.~ues to yield high
quality fillet material. ~he intact tail por-tion
can be processed usin~ the invention~
~he invention will now be more particularly
described with reference to the accompanying drawings,
of which:
~igs 1, 2, and 3 i.llustrate diagramatically
the passage of a fish carcass between a pair of
contra-rotating rollers;
~ig 4 represents a general plan view of a fish
processing apparatus in accordance with the invention;
and
~ig 5 represents a ~ertical cross-section of
3o the apparatus depicted in ~ig 4 taken on the line
AA shown in ~ig 4.
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Figs 1 to 3 show a pair of parallel contra-
rotating squeeze rollers 101 and 102, preceded by a pair
of contra-rotating pre-squeeze rollers 106,107, set at a
wider nip distanGe, and illustrate the passage of a head-
ed and gutted fish carcass 103 between the rollers. Tail104 of fish 103 is presented to the pre-squeeze rollers,
and on being gripped between the rollers and thereby
slightly pressed passes through in the direction indicated
between the squeeze rollers 101,102. As the bulk of fish
103 contacts the squeeze rollers it is squeezed between
them and the flesh 105 within the fish is expressed there-
from tFig 2).
Fig 3 shows the final stage of the rolling proce-
dure, with fish 103 (now comprising essentially merelythe skin and backbone structure) having passed completely
between the rollers and the flesh 105 remaining in front
of the rollers.
Fig 4 is a plan view showing the general lay-out
of a fish processing apparatus according to the invention.
The apparatus comprises a rectangular chamber 201, of which
side walls 202 and 203 can be seen in section. Ends 204
and 205 of chamber 201 are open. A horizontal floor 206
spans the entire width of chamber 201, and extends slight-
ly over half' the length of the chamber from forward end
204.From the rear edge 207 of floor 206, a sloping chute
208 leads downwardly and outwardly from chamber 201.
Chute 208 also spans the entire width of chamber 201.
The apparatus is provided with a pair of parallel
pre-squeeze rollers 209 and 210 mounted with their longi
tudinal axes vertical, the pair of rollers being adjacent
the forward end 204 of chamber 201, and being symmetrical-
ly arranged on either side of the centre line AA runningthrough chamber 201. A narrow gap 211 exists between the
pair of pre-squeeze rollers.
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Immediately behind pre-squeeze rollers 209
and 210 are a pair of squeeze rollers 212 an~ 213,
again mounted with their longitudinal axes vertical
a~d similarly symmetrically axr~nged on either
side of centre line AL Squee~e rollers 212 and
213 contact one another. ~he diameter of squeeze
rollers 212 and 213 is less than that of the pre-
squeeze rollers 209 and 210. Behind squeeze
rollers 212 and 21~ are mounted a pair of discharge
rollers 214 and 2159 again with t-heir longitudinal
axes vertical and also symmetrically arranged on
either side of centre line AA. Rollers 214 and
215 are also in contact with one another, and their
diameters are less than those of squeeze rollers
212 and 213. Each roller is rotatable about its
longitudinal axes in a contrary manner relative
to its par-tner, and in such a manner that an object
presented from forward end 204 of chamber 1 between
the pre-squeeze rollers 209 and 210 will be drawn
i~to chamber 201 and progressed in turn between
the three pairs of rollers towards rear end 205~
A pair of water pipes 216 and 217 each termin-
ating in a verticall~-aligned ~-jet spray head, lead
into chamber 201 ~nd are directed respectively against
pre-squeeze rollers 209 and 210 such that water from
the jets will impinge on the rear of each roller
(relative to forward end 204 of chamber 201).
further palr of water pipes 218 and 219 lead into
the apparatus and are directed via similar ver-tically-
~ ali~ned V-jet spray heads against -the rear of squeeze
rollers 212 and 213. A third pair of water pipes
220 and 221 are similarly directed via similar spray
heads against the rear of discharge rollers 214 and
215.
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A rectangular aperture 222 exists in floor
206~ and lies symmetrically benea-th the pre~squeeze
rollers 209 and 210, and the s~ueeze rollers 212
and 213 such that anything falling between the two
pairs of rollers will drop below floor 206. ~eading
edge 223 o~ floor 206 is provided with an up-turned
lip 224 which runs the entire width of the shelf.
~nother up-turned lip 225 runs round the entire edge
of aperture 222. Side edges 226 and 227 of chute
208 are also provided with up-turned lips 228 and
229 respectively.
Below floor 206 is a second chute 230 which
leads dow~wardl~ and outwardly from the fron~ end 204
of chamber 201, commencing from the rear of aperture
222 such that an~thing falling through aperture 222
will land on chute 230 and be directed towards the
front of the apparatus. Chute 230 is also provided
with up-turned lips 231 and 232 along its side edges
233 and 234 respectively.
~he apparatus is also provided with a ~eeder
mechanism 235 comprising an upper continuous belt
2~6 and a lower continuous belt 227 arranged in
parallel one above the other along centre line AA
at the forward end 204 o~ chamber 201~ ~ower
belt 236 extends further from the chamber than
does the upper belt.
Referring to ~ig 5, which illus-tra-tes a vertical
cross-section of the apparatus taken on centre line
AA shown in ~ig 4~ rollers 209, 212 and 214 can be
seen within chamber 201. Each roller is mounted
on a ver-tical shaft 237, 238 and 239 respectivley,
running through bearings 240, 241 and 242 respec-tively,
situated in the roof 243 of chamber 201. ~he shaf-ts
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are connected to a motor means (not shown) capable
of causing rotation of each roller in the manner
already described in relation to ~ig 4. Water jet
220 playing onto the back of rollers 214 can also
be seen.
~loor 2Q5 with aperture 222 and rim 225 can
be seen, as also can the two sloping c~utes 208 and
230. ~he sloping chutes are depicted as leading
down to trays 244 and 245 respectively, capable
of catching any material sliding down each chute.
~he two continuous belts 235 and 2~6 comprising the
feeder mechanism can also be seenO ~elt 235 runs
round a pair of horizontally moun-ted rollers 246
and 247. ~el-t 236 runs round a similar pair of
horizontally mounted rollers 248 and 249~
~he belts lead upwards into the open end 204
of chamber 201 adjacent the gap 211 between the
pair of pre-squeeze rolle~ 209 and 210~ A narrow
gap 250 exis-ts between the two belts along their
entire adjacent length. The belts 235 and 236 can
be driven via their respective rollers by a motor
~eans (not shown), such that they run in a contrary
manner and any material placed between the belts
will be drawn between them upwards into the apparatus.
~he whole apparatus is depicted as s-tanding on
grou~d 251 by means of legs mounted one at each
corner, only the farther two of which legs (252
and 253) can be seen in this cross-section.
In operation, the three pairs of rollers within
the apparatus are set in rota-tional mo-tion and -the
belts are also set running. Water is fed via -the
inlet pipes to the jets and played onto the rear
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of each rollerO Headed and gutted but otherwlse
who-e fish carcasses are fed -tail first between
the two belts~ which con~ey the carcasses upwards
into the gap 211 between the pre~squeeze rollers
209 and 210, which apply rela-tively gentle pressure
to each fish carcass and soften up the muscle
s-tructure. ~he continuous ro-tation of the pre-
squeeze rollers progresses the fish carcass towards
the pair of squeeze rollers 212 and 213 which tigh-tl~
grip the tail of the fish and draw the fish between
them. A~ the tail of ths fish emerges from between
-the squeeze rollers it is engaged between the discharge
rollers 214 and 215 which actively con-tinue the progress
of the carcass through the apparatus~ As the fish
carcass passes between the squeeze rollers it is
subject to considerable pressure, and the flesh
within -the carcass is separated from the skin and
bone stl~c-ture and is extruded from the head end of
the carcass. ~he extruded flesh falls through
aperture 222 onto forwardly sloping chu-te 230, and
slides down into the waiting -tray 245, ~he spent
skin and bone structure of -the carcass is discharged
from the apparatus after passing between the discharge
rollers by sliding down rea~wardly sloping ch~te
208 into the o-ther waiting tra~ 244. ~he continuous
jets of water pla~ed onto the rollers help in keeping
each roller clean of fish flesh and slime from the
fish skin, and thereby ensuring tha-t the rollers
maintain an adequate grip on each carcass and tha-t
the ~aluable fish flesh collected in tray 2'~5 is
not unduly co~ltaminated with unwanted low-grade
material. ~he water from each jet cascades down
each roller onto floor 206 and then down rear chu-te
208. ~`he up-turned lips 22l~ and 225 around the
:Leading edge 22~ of floor 206 and around aperture 222
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help to prevent undue amounts of water becoming
mixed with the valuable fish flesh.
An additional or alternati~e means of ensuring
that the fish flesh collected does no-t ha~e an
excessive water content, is to use a foraminous
material, such as an expanded metal screen, as the
floor of the chute 230. Water can fall -throu~h the
holes while the fish flesh slides down the chute into
the waitin~ tray 2450
~ n apparatus according to the invention and
basically as just described with reference to Fi~s
4 ~nd 5, was used to recov0r flesh from blue whiting~
The apparatus had the following technical
specification~
The pre-squeeze rollers ~ere constructed of
rubber having a hardness of 30 on the Shore scale,
moulded onto 20 mm stainless steel shafts. Each
roller had a length of 150 mm and a diameter of
90 mm. A textured surface, comprising a non-
slip vinyl sheet ma-terial recommended for use as
a deck covering for yachts, was bonded to each roller.
A gap of 5 mm existed between the pre-squeeze rollers.
~he squeeze rollers were of identical construction
to the pre-squeeze rollers, except -that they had a
diame-ter of 70 mm, and were just in contact with one
another.
~ he discharge rollers were constI~Icted of rubber
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having a hardness of 35 on the ~hore scale, moulded
o~to 15 mm diameter stainless steel shafts. ~ach
roller had a length of 150 mm and a diameter of 40 mm.
~he~ were covered with the same non-slip material
and were just in contact with one another.
Gutted frozen-at-sea b~ue whiting were thawed,~
and headed manually. 200 kilos of fish were pro-
cessed in the apparatus in ~ hour 45 minu~es,~and~
70 kilos o~ acceptable flesh reco~ered, giving a~
yield of 35%.
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