Method and apparatus for cutting slices from fish fillets with the skin still on

The invention relates to longitudinal cutting of fish fillet pieces substantially parallel with the skin side (S) of the original fillet. This cutting in layers or slices takes place in that the fish fillet (F, F1) is brought into contact with a rotating cooled freezing drum (7, 7') which freezes the fillet (F2) at the skin side (S) and conveys it in retained position against the operative cutting edge of a driven, endless band knife (18). During the rotation of the drum (7, 7'), the operative cutting edge of the band knife (18) is displaced stepwise in relation to the drum circumference between two successive revolutions of the drum (7, 7'), in order to cut a fish meat slice (FS) successively for each drum revolution.

BACKGROUND OF THE INVENTION 
The present invention relates to a method for cutting slices from fish 
fillers with the skin still on, wherein the fillet is fed toward a 
freezing drum causing freezing and anchoring of the fillet at the skin 
side, whereby the longitudinal direction of the fillet preferably is 
orientated in the circumferential direction of the drum, and wherein a 
cutting tool, preferably in the form of a driven endless band knife, is 
positioned with the operative cutting edge thereof at a (radial) distance 
from the drum mantle surface, and wherein, from the fillet adhering to the 
drum through freezing, a fish meat slice is cut, the cutting plane 
extending substantially parallel with the drum circumference. 
It is previously known methods and machines adapted to cut the skin from 
the fillet, wherein is utilized a rotating freezing drum, i.e. a drum 
being frozen down to beneath the freezing point. When wet fillets with the 
skin side thereof come into contact with the rotating freezing drum, they 
become frozen to the circumferential surface of the drum, where they are 
kept securely in place while being conducted toward a cutting device in 
the form of a band knife which cuts the fillet free from the skin, and 
wherein the skin is scraped off from the drum by means of a scraper means 
following the band knife and permanently contacting the drum surface. This 
known method and machine are well suited for skinning (flaying) fish 
fillets, but they are not suitable for cutting a toneless fillet slice at 
the skinless fillet side, and the stationary scraper means renders it 
impossible to divide a fillet into several parallel slices, each extending 
substantially parallel with the skin side. 
Norwegian patent specification No. 54 801 discloses methods and devices for 
anchoring fish fillets upon the removal of the skin or other treatment. 
According to this patent specification, it is likewise used a retaining 
surface operating through freezing and which, thus, freezes the fillet 
during the skin removal or other treatment, whereafter the freezing of the 
fish fillet is neutralized through thawing. In rational fillet treatment, 
thawing is a too slow process. 
Norwegian patent specification No. 109 486 discloses an apparatus for 
treating fish, comprising a conveyor movable along a closed path and 
having the form of a freezing surface retaining the fish through freezing 
during the treatment, the fish in frozen position being conveyed past a 
stationarily placed treating tool. The movable freezing conveyor consists 
of a freezing drum assigned a scraper means permanently attacking on the 
external mantle face of the drum, serving to scrape off those pieces of 
the fish which have become frozen to the drum as well as to scrape off any 
hoar and ice formations. This known apparatus is especially well suited 
for the skinning of herring; it does not allow to divide a fish fillet 
"into layers" parallel with the skin side. 
With filleting, processing and further cutting of fine kinds of fish such 
as salmon and trout, it has been found that dividing the fillet into 
several slices substantially parallel with the two main faces of the 
fillet may result in substantial advantages in various connections. Such a 
division of salmon and trout will i.a. result in a quicker smoking of such 
slices, resulting in a better quality product, simultaneously as the 
wastage is reduced. 
Thus, each fillet is cut into two or more such slices, parallel with the 
main faces of the fillet. 
SUMMARY OF THE INVENTION 
The object of the present invention has been to provide a method and a 
machine well suited to accomplish the dividing operations just mentioned, 
the slicing-up representing a new way of dividing fillets. 
In accordance with the invention, said object is realized through 
proceeding as set forth in the independent method claim, said method 
appropriately being carried out by means of a machine as defined in the 
independent apparatus claim. Subordinate, advantageous features are made 
the subject matter of dependent claims. 
A machine according to the invention includes a freezing drum known per se 
and adapted to retain the fish fillet or several fish fillets through 
freezing and to convey them past a stationarily placed cutting tool (which 
may have a self-motion) set at such a distance in relation to the mantle 
face of the drum that said tool upon passage of the fillets may cut a 
slice having a predetermined thickness, parallel with the skin side, the 
drum being assigned at least one movable scraper means. Upstream, the drum 
is assigned a movable flap adapted to open and close the admission to the 
drum and to be controlled such that the flap--in case one intends to cut 
two or more parallel slices from one or more fillets--will let past itself 
a "length" corresponding to one or more fillets which together do not 
cover the entire drum in the circumferential direction. The cutting 
device, preferably constituted by a band knife, is assigned a programmed 
controller serving to position the operative cutting edge of the band 
knife at the desired distance from the drum circumference, for cutting the 
first slice. During the slicing or slice cutting, the one or more movable 
scraper means are displaced to The inoperative position thereof, in which 
they do not interfere with the cutting process. 
When cutting the first slice, the programmed controller may have positioned 
the operative cutting edge of the band knife at a distance of e.g. 15 mm 
from the circumferential face of the drum, whereby the band knife effects 
cutting-off of the outermost slice front the fillets, said cut off slices 
being conducted out of the machine as finished fresh goods, or they may be 
treated further, e.g. smoked. Subsequent to this first slicing or slice 
cutting, the controller makes provision for--while the portion of the drum 
circumference not covered by fillets passes the band knife--to displace 
the bank knife to a new programmed position, in which the cutting edge is 
e.g. 2 mm closer to the drum's circumferential face than at the first 
programmed position. When the fillets for the second time pass the band 
knife, the latter will cut a new slice, parallel with the skin side, 2 mm 
thick, said thin slices during second time's cutting being taken out of 
the machine, while the remaining fillet pieces which still adhere to the 
skin, are retained on the drum through freezing and rotate together with 
the drum. This procedure is repeated until one has cut off the number of 
slices desired and which is consistent with the original fillet thickness. 
Thereafter, the programmed controller transmits a signal to the movable 
scraper means which, thereby, are brought into contact with the drum 
surface, while the drum portion not covered by fillet passes; the drum 
continues its rotation and becomes scraped clean and made ready for a new 
positioning and freezing of one or more fillets. Thereafter, the 
controller transmits a signal to said movable flap which opens the 
admission to the drum for one or more new fillets, as soon as the movable 
scraper means have been brought into inoperative positions withdrawn from 
the area that will be passed by the fillets. 
With small amounts to be treated/processed, i.e. small amounts of fish 
fillet to be divided into parallel slices this manner, the process may be 
operated manually, i.e. without controller. It represents no technical 
problems achieving individual fish slice thickness. With individual slice 
thickness as well as with equal thickness, the band knife is adapted to be 
displaced step by step in the direction toward the drum's circumferential 
surface.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In the drawings, reference numeral 1 denotes the machine frame, at the 
insertion end thereof a supply chute 2 for fish fillet F to an endless 
belt conveyor 3 is mounted. The conveying belt extends in the longitudinal 
direction/the fillet feeding direction 4 and is laid around a turning 
roller 5 at the upstream side of the machine and a drive roller 6 at the 
downstream side of the machine. The material of the conveying belt 3 and 
the suspension thereof are such that the belt has a limited elastic 
resilience laterally. The lower portion of the conveying belt 3 is denoted 
at 3'. 
In the machine frame 1, an in per se known freezing drum 7 has been 
supported, the freezing aggregate thereof being denoted at reference 
numeral 8. 
A gear motor 9 mounted on the machine frame 1, serves to operate both the 
freezing drum 7 and the conveying belt 3. A first chain 10 is laid around 
a sprocket 11 on the gear motor's 9 shaft and a sprocket 12 on the 
freezing drum 7, while a second chain 13 is laid partly around a sprocket 
14 on the drive roller 6 of the conveying belt 3, partly around a freely 
rotatably supported sprocket 15 driven by first chain 10, reference 
numeral 16 denoting a tension sprocket. 
The rotational direction 17 of the freezing drum 7 is counterclockwise. 
The fish fillets F to be processed in the machine have the skin thereon, 
and they are laid into the supply chute 2 skin side up. Thus, one or more 
fillets F are conveyed toward the freezing drum 7, laying on the conveying 
belt 3 skin side up. The skin side of the fillet F is, thus, that fish 
portion first to come into contact with the mantle face 7' of the freezing 
drum 7. This is illustrated by a fillet F1 just entered into contact with 
the mantle face 7' of the drum 7, the skin side of the fillet being 
denoted with the letter S. 
The freezing drum 7 operates according to a principle known per se with 
fish processing in general, namely that the wet fillet freezes to the 
circumferential surface 7' of the drum, where it is securely anchored 
while being displaced toward and past a cutting tool, e.g. a driven 
endless band knife 18 of a design known per se. 
At a predetermined distance upstream the freezing drum 7, a movable flap 19 
has been arranged. In FIG. 1, the flap has been shown in open, swung-up 
position, in which it allows admission for fillets F, F1 to the drum 7. In 
FIG. 2, the flap is shown in swung-down closure position, in which it 
blocks fillet admission to the drum 7. 
This movable flap 19 is controlled, preferably electronically and 
automatically. In case one intends to cut several parallel slices from one 
or each of a plurality of fish fillets F, F1, F2, parallel with the main 
faces thereof, i.e. parallel with the skin side S, the flap 19 is 
controlled such that it only will let a "length" of fish fillets pass past 
it, comprising one or more fillets which together will not cover the 
entire drum circumference when the fillet or the fillets are frozen to the 
mantle face of the drum and extend with the longitudinal direction thereof 
in the circumferential direction of the drum. 
Reference numerals 20 and 21 denote displaceable scraper means movable 
between an operative position, FIG. 2, wherein they scrape the mantle face 
of the drum free from frozen skin, etc., and an inoperative position, FIG. 
1, wherein they are withdrawn, not only from scraping contact with the 
mantle face of the drum, but so far away from the same that the fillets 
F2, FIG. 1, adhering through freezing action, may pass the scraper means 
20, 21 unimpededly upon the rotation of the drum 7. 
As previously mentioned, the conveying belt 3,3' has, partly due to 
inherent material properties, partly due to the suspension thereof, a 
certain elastic resilience laterally. The resiliency of the conveying belt 
3,3' is shown in the area of the freezing drum 7, beneath the same, where 
the upper portion of the conveying belt 3,3' at any time passes through a 
deflected portion 3" between an upstream support roller 22 and a 
downstream support roller 23, the deflected portion 3" of said upper 
portion, in an intermediate area between the support rollers 22, 23, 
following a course substantially corresponding to the radius of the drum 
7. Such an arrangement has be found to favour the delivery of fish fillet 
F1 from conveying belt 3 to freezing drum 7 such that the freezing of the 
skin side S of the fillet F1 to the drum mantle is secured and effected at 
an appropriate stage of the transport. 
When one or more fish fillets F2, adhering with the skin side S to the 
circumferential face of the drum 7, are conducted past the band knife's 18 
cutting edge, which is set at a predetermined (radial) distance from the 
drum surface 7' smaller than the thickness of the fillet F2, said cutting 
edge effects the cutting of a slice from the skinfree side of the fillet, 
which during the cutting-off extends substantially parallel with the drum 
circumference, i.e. parallel with the two main faces of the fillet, 
consequently the skin side and the skinfree fillet side. This first slice 
will be free of socalled "thick-fish-bones" (fish bones extending 
approximately perpendicular to the skin side) and represents a novel 
product of optimum quality. With small thin fillets, it might be assumed 
that the skin thereafter does not contain sufficient fish meat to allow 
the cutting of a second or a plurality of further slices parallel with the 
first one. However, with larger thicker fillets, one may utilize the 
invention optimally and effect a displacement of the band knife in 
relation to the fillets F2 on the drum that secures dividing of one or 
each fillet into two or more such large slices, the division planes 
extending substantially parallel with the skin side. 
To this end, for the displaceable suspension of the band knife 18, a 
bracket 24 has been mounted on the machine frame 1, and the frame 25 of 
the band knife 18 is pivotally suspended in The bracket 24 by means of a 
horizontal rotary shaft or pivot 26. An arm 27 of the band knife frame 25 
engages a drive device 28 for stepwise rotation of the frame 25 and, 
consequently, the cutting edge of the band knife 18 in relation to the 
freezing drum. This drive device 28 can be operated from a wheel 29 for 
manual fish slice thickness adjustment, og it can be controlled 
electronically by means of a programmed control unit. The drive device 28 
may be constituted by any suitable mechanism and can e.g. comprise a 
motion screw adapted for stepwise rotation and with which the arm 27 of 
the bank knife frame 25 cooperates. 
Thus, when said first fish meat slice is separated from the rest of the 
fillet F2 still adhering to the drum 7, the drive device 28 (either 
through the hand wheel 29 or through electronics) makes provision for 
setting the cutting edge of the band knife 18 e.g. 2 mm closer to the 
circumference 7' of the drum 7. When the fillet or fillets F2 pass the 
band knife the next time, the knife will cut a second slice parallel with 
the first one, but now with an exact thickness of said 2 mm. One may 
continue in this way dependent on the thickness of the original fish 
fillet, such that the band knife is displaced in relation to the drum 
between each rotation thereof, in order to cut third, fourth slice and so 
forth parallel with the preceding slice. 
Such a finish cut fillet slice on its way out of the machine is indicated 
at FS. 
Reference numeral 30 denotes an outlet chute for scrap 31, FIG. 2, e.g. 
skin scraped off from the drum mantle face 7' by means of the scraper 
means 20, 21.