Apparatus for deboning fish fillets

In accordance with this invention, there is provided apparatus for removing pin bones from fish fillets, the apparatus having a rotatable bone pulling cylinder and a puller plate defining a pin bone receiving space between the bone pulling cylinder and puller plate. The bone pulling cylinder has a cylindrical surface which is adapted to snag pin bones extending from a fish fillet disposed adjacent to the bone pulling cylinder and puller plate, and the puller plate has a forward portion profiled to have a radius of curvature which is commensurate with the radius of curvature of the cylindrical surface of the bone pulling cylinder. The puller plate is slidably mounted to a body and adapted to be slid toward the bone pulling cylinder to bring the leading edge to mate with the bone pulling cylinder, the relative position of the puller plate to the bone pulling cylinder being maintained by mounting openings provided in the puller plate and the body, and by fasteners received in the mounting openings which couple the puller plate to the body. The fasteners are adapted to apply a minimum predetermined tension to the leading edge of the puller plate over a selected arc length of the bone pulling cylinder so that any pin bones received between the puller plate and the bone pulling cylinder are squeezed, and continued rotation of the bone pulling cylinder withdraws the pin bones from the fish fillet.

FIELD OF THE INVENTION 
This invention relates to the food processing industry in general and, in 
particular, relates to processing fresh and salt water fish species for 
human consumption. More particularly, this invention relates to the 
removal of bones from fish fillets. 
BACKGROUND OF THE INVENTION 
Fresh and salt water fish species are well-known as foods for human 
consumption. Fish processing operations typically involve a number of 
steps including gutting the fish, removing the head and tail, removing 
scales, separating the fish fillets from the backbone, and washing and 
packaging the separated fillets. Many of these steps are automated, and 
are performed in large capacity machines. Although different fish species 
are processed in different manners, this invention is of particular 
interest for processing fish fillets. 
One of the drawbacks of fish fillets is the presence in the fillets of thin 
or fine fish bones, which are commonly referred to as pin bones. These 
bones are all that remain of the fish skeleton, the bulk of which has been 
removed during typical fish meat processing as described above. However, 
pin bones may be secured firmly in the fish fillet flesh, and thus, when 
the backbone is separated from the fish fillet, remain in the flesh 
instead of being removed with the remainder of the backbone. The presence 
of theses pin bones in the fish fillet makes the fillet more difficult and 
awkward to eat. During cooking, the flesh becomes easily separable from 
the pin bones. However, the pin bones are typically very fine and may not 
be easily noticed by the person eating the fish. Thus, there is a tendency 
for the pin bones to be taken into the mouth, and swallowed. This can lead 
to choking, or other discomfort in the event that the sharp pin bone is 
not removed prior to eating the fish. 
In the past, attempts have been made to remove pin bones by various 
mechanisms. For example, U.S. Pat. No. 2,771,511 relates to a tool and a 
method for deboning fish. The tool, in essence, comprises a pair of 
tweezers for gripping and pulling a large number of pin bones from the 
fish fillet simultaneously. However, the tool is manually operated and 
awkward to use. An attempt to automate the process was provided in U.S. 
Pat. No. 4,945,607 which relates to a gripping device which automatically 
extends, opens and closes the jaws for the purpose of gripping the ends of 
the pin bones to remove them from the fish fillet. However, each of these 
devices require a precise positioning of the gripping jaws in order to 
have the desired effect of removing pin bones. 
A departure from the "tweezer" approach is embodied in the inventions 
described in WO 94/10848 and WO 92/12641 where the pin bones are removed 
by being nipped or snagged between a rotating cylinder and a 
counter-pressure device. 
In both of these inventions, the counter-pressure devices are pivotally 
mounted in order to accommodate the pin bones as they pass between the 
counter-pressure device and the cylinder. During such pivoting, the 
counter-pressure devices move away from the rotating cylinder, thereby 
defining a gap. This gap is dynamic in that its magnitude will vary during 
operation of the devices according to the number, size and position of any 
snagged bones. The counter-pressure devices are biased to return to a 
start position corresponding to minimum predetermined gap by a resilient 
member comprising a coil spring, in WO 92/12641 and pin-mounted O-rings in 
WO 94/10848. 
These devices fail to apply and maintain a minimum pressure and tension to 
snagged pin bones during their withdrawal from the fish fillet, with the 
result that the bones are often broken and repeated passes of the devices 
on the fish fillet are required to fully withdraw the pin bones. Such 
repeated handling inevitably results in bruising of the flesh and scraping 
of flesh which must be discarded. This diminishes the value of the fillet 
and also wastes time. 
An object of this invention is to address the above-described problems and 
to maximize the value of a fish fillet by withdrawing pin bones from the 
fillet with minimal flesh being scrapped and with virtually no bruising of 
the fillet. 
SUMMARY OF THE INVENTION 
In accordance with this invention, there is provided apparatus for removing 
pin bones from fish fillets, the apparatus having a rotatable bone pulling 
cylinder and a puller plate defining a pin bone receiving space between 
the bone pulling cylinder and puller plate. The bone pulling cylinder has 
a cylindrical surface which is adapted to snag pin bones extending from a 
fish fillet disposed adjacent to the bone pulling cylinder and puller 
plate, and the puller plate has a forward portion profiled to have a 
radius of curvature which is commensurate with the radius of curvature of 
the cylindrical surface of the bone pulling cylinder. The puller plate is 
slidably mounted to a body and adapted to be slid toward the bone pulling 
cylinder to bring the leading edge to mate with the bone pulling cylinder, 
the relative position of the puller plate to the bone pulling cylinder 
being maintained by mounting openings provided in the puller plate and the 
body, and by fasteners received in the mounting openings which couple the 
puller plate to the body. The fasteners are adapted to apply a minimum 
predetermined tension to the leading edge of the puller plate over a 
selected arc length of the bone pulling cylinder so that any pin bones 
received between the puller plate and the bone pulling cylinder are 
squeezed, and continued rotation of the bone pulling cylinder withdraws 
the pin bones from the fish fillet.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
According to the present invention, there is provided a device for deboning 
fish fillets which is indicated generally in FIG. 1 by reference numeral 
10. The fish fillet deboner 10 has a body 12 which includes an upper 
surface 14, a chain guard 16, a motor control 18, and on/off reverse 
switch 19 and a collection tray 20. In the most preferred form of the 
invention, the upper surface 14 is sloped, and is higher at the back. The 
collection tray 20 has a drain 21 and is formed around the perimeter of 
the base of the device. Also shown are a vacuum attachment 22 and 
electrical connections 24. 
The upper surface 14 of the fish fillet deboning device 10 includes first 
and second top plates 26 and 28 respectively, into which are set a puller 
plate 32 and a guide plate 30, each having a length of twelve inches. Each 
of the plates 26, 28, 30 and 32 include a plurality of countersunk 
mounting openings 34, for fasteners 37. In the embodiment shown, there are 
five such openings distributed over the entire length of the puller and 
guide plates. Such mounting openings 34 in the puller plate 32 preferably 
include elongated slots 34a, as explained below. The fasteners attach the 
plates to the main body 12. 
The guide plate 30 is preferably formed from food grade polyethylene, and 
machined to have a radius along a forward portion. The puller plate 32 is 
preferably formed from food grade material machined to have a double 
radius along a forward portion as described below. The preferred material 
is Ertalyte.RTM. which is very strong and which can be accurately machined 
using custom tooling. It is also characterized by negligible water 
absorption and is durable, both of which are very desirable features in 
this application. 
The plates 30 and 32 are adjacent, but have a gap therebetween, identified 
as 36. This may be referred to as the fillet registering opening. 
Additionally, there is shown a bone pulling cylinder in the form of a 
perforated cylinder 38, which is at least partially exposed through the 
fillet registering opening 36. The bone pulling cylinder 38 is described 
in more detail below. 
An electric motor 40 shown in FIG. 2 is conveniently mounted within the 
body 12 of the fish fillet deboner 10. The electric motor 40 includes a 
drive sprocket 42 which drives a toothed chain or drive belt 44. Good 
results have been obtained through use of a rubber drive belt 44. Drive 
belt 44 also goes around a slave sprocket 46 which is mounted on an axle 
48. The bone pulling cylinder 38 is also mounted on the axle 48 and the 
electric motor drives the drive sprocket 42 which, in turn, drives the 
drive chain 44 which, in turn, drives the slave sprocket 46. The axle 48 
is caused to rotate, thereby rotating bone pulling cylinder 38. The drive 
belt 44 is, in turn, covered by a guard 16 (shown in FIG. 1). As a 
majority of people are right-handed, it is preferred to mount the drive 
belt 44 and the chain guard 16 on the left of the device 10. However, it 
will be appreciated by those skilled in the art that these could also be 
placed on the right-hand side, if preferred. 
The electric motor 40 is controlled by a pair of switches 18, 19 on the 
front of the device 10 (FIG. 1). Toggle switch 19 permits the motor to be 
run in a forward, stopped, or reverse mode, in the event that anything 
gets caught. Dial 18 permits the speed of rotation of the motor 40 to be 
finely varied. The preferred motor is a low voltage direct current geared 
head motor, capable of withstanding a high torque at low revolutions. 
A vacuum manifold 50, shown in FIG. 3, ensures that the vacuum applied 
through vacuum connection 22 is placed across bone pulling cylinder 38. 
The resulting air flow in the manifold 50 is indicated by arrows 52. 
Also shown in FIG. 3 is a fish fillet 60 resting skin side up on the upper 
surface 14. The fish fillet 60 includes skin 62, a fleshy body 63 and a 
plurality of pin bones, one of which is illustrated at 64. 
The bone pulling cylinder 38 is most preferably in the form of a 
cylindrical drum which is caused to rotate by said electrical motor 40 in 
a clockwise direction (as drawn) indicated by arrows 54 in FIG. 3. The 
outer surface of the bone pulling cylinder 38 has a plurality of holes 
formed in it as shown in FIG. 3a. These holes are referred to as bone 
registering openings 70. Most preferably, the bone registering openings 70 
have a larger diameter at the outer perimeter, and a smaller diameter at 
the inner perimeter (when the bone pulling cylinder 38 is viewed in 
cross-section) as shown in FIG. 3. Although satisfactory results have been 
achieved with a bell-shaped shoulder, as shown at 72 in FIG. 4, other 
shaped shoulders may also be appropriate. Preferably, the bone registering 
openings are between 1/16 and 1/2 inches in diameter and, most preferably, 
the bone registering openings 70 at the outer perimeter are about 3/16 
inches in diameter. The most preferred size of the bone registering 
openings 70 will vary depending upon the type of fish fillet being 
deboned. For fish fillets having larger pin bones, slightly larger bone 
registering openings 70 are preferred. Conversely, for smaller fish 
fillets having smaller pin bones, smaller bone registering openings 70 are 
preferred. For fresh water trout, the 3/16 inch diameter holes yield 
satisfactory results. 
It will be noted that the bone registering openings 70 are formed with 
sharp edges 71 in cross-section, i.e., approximately 90 degree edges. 
These sharp edges are important for snagging the pin bones to drag the pin 
bones out of the fish fillet 60 as described in more detail below. The 
most preferred material for the bone pulling cylinder 38 is stainless 
steel, although other food grade non-corroding materials may also be used. 
It is preferred, for ease of operation of the device 10, to have the bone 
registering openings 70 sweep over all of the exposed surface of the fish 
fillet from which bones are to be removed. Therefore, it is most preferred 
to have the bone registering openings 70 in a staggered pattern across the 
entire surface of bone pulling cylinder 38. 
As the bone pulling cylinder 38 is rotated, the sharp edges 71 formed on 
the bone registering openings 70, act to snag the ends of any protruding 
pin bones. In some species the bones may have thicker ends, but they do 
not typically have enlarged heads. Once snagged in a bone registering 
opening 70, the continued rotation of the bone pulling cylinder 38 will 
create an axial force or pull on the pin bone 64. Because the pull is 
generally aligned with the axis of the pin bone 64, it has been found that 
the pin bone 64 easily and without any separation of flesh, pulls out of 
the fish fillet 62. With this method of bone removal, there is very little 
flesh loss, in the order of less than 1% which may vary according to flesh 
consistency). 
An important feature of the invention is the configuration of the puller 
plate 32. The puller plate 32 has a leading edge adjacent the fillet 
registering opening 36 which is made relatively thin (in the order of 
0.010-0.015 in.) as possible over a predetermined width thereof to 
maximize the resiliency and flexibility required to accommodate pin bones 
64 received between the bone pulling cylinder 38 and the puller plate 32, 
and to engage pin bones 64 which may protrude only a small distance from 
the fleshy body 63 of a fillet 60. 
The profile of a forward portion of the puller plate 32 as shown in 
cross-section in the accompanying drawings is designed to be concentric 
with the surface of the bone pulling cylinder 38 over a selected arc 
length of the bone pulling cylinder. Before emerging into the vacuum 
manifold 50, snagged pin bones 64 are released from the bone pulling 
cylinder 38 and the puller plate 32 into a gap 80 defined by a trailing 
portion 33 of the puller plate 32 which is profiled to have a radius of 
curvature that exceeds the radius of curvature of the bone pulling 
cylinder 38. 
The relative position of the puller plate 32 to the bone pulling cylinder 
38 must be maintained to ensure conformity between the outer cylindrical 
surface of the bone pulling cylinder 38 and the profiled forward portion 
of the puller plate 32. Such conformity allows a minimum pressure and 
tension to be applied to a snagged pin bone 64 so as to permit the entire 
pin bone 64 to be withdrawn. Otherwise, if the pressure is released, a 
snagged pin bone may snap and break away or slip and remain in the flesh 
of the fish fillet. In Applicant's apparatus, many pin bones emerging from 
the fish fillet deboner 10 are actually flattened. 
Conformity between the outer surface of the bone pulling cylinder 38 and 
the profiled forward portion of the puller plate 32 is achieved by sliding 
the puller plate 32, as required, toward the bone pulling cylinder 38 
which is fixed on the mounting axle 48, such adjustment being permitted by 
the elongated slots 34a that receive threaded fasteners 37. The relative 
position of the puller plate 32 to the bone pulling cylinder 38 is 
maintained by bolting the fasteners 37 to the surface 14 of the underlying 
body 12. Tightening the fasteners 37 also pulls the puller plate 32 down 
onto the surface of the bone pulling cylinder 38. 
The tension applied to the leading edge of the puller plate 32 is 
controlled by a compressions slot 34b formed in the puller plate beneath 
the upper surface thereof and extending from the forward portion of the 
puller plate adjacent to the bone pulling cylinder 38 through the mounting 
openings 34 provided in the puller plate 32. By varying the penetration of 
the fasteners 37 in the body 12, the tension applied to the leading edge 
of the puller plate may be adjusted, as required. It will be noted that 
the puller plate 32 is fixed relative to the bone pulling cylinder 38 so 
that the pin bone receiving space between the puller plate 32 and the bone 
pulling cylinder 38 does not increase to accommodate any snagged bones. 
The inherent resiliency of the thin leading edge of the puller plate 32 
and the magnitude of the tension applied through the fasteners 37 to 
pre-stress the forward portion of the puller plate 32 will define the size 
of the pin bone which will be admitted into the pin bone receiving space. 
Thus, while the thin leading edge of the puller plate may flex, the 
remainder of the puller plate is fixed. 
A compression slot 34c similar to compression slot 34b may be defined in 
guide plate 30 for adjusting the position of guide plate 30 relative to 
bone pulling cylinder 38. 
Turning now to FIG. 4, it can be seen how the fillet 60 with the pin bone 
64 is to be positioned. In FIG. 5, the pin bone 64 is engaged in a 
particular bone registering opening 100 and is snagged by sharp corner 102 
just past a head 104 of the pin bone 64. It can also be seen that the 
axial path of the pin bone 64" as the bone pulling cylinder rotates in 
accordance with arrow 54 causes it to be drawn out of the fish fillet 60. 
Turning again to FIG. 4, it can be seen that the pin bone 64 has moved 
along and is indicated by the numeral 64". As the bone pulling cylinder 70 
continues to rotate in the direction of arrow 54, the pin bone 64" is 
dragged along past the puller plate 32, and is eventually freed beyond the 
end of the trailing edge 33 which is indicated at 35. At this point, the 
pin bone 64" will either fall away as shown in FIG. 6 or remain loosely 
attached to the bone pulling cylinder 38. Attachment may occur because of 
moisture, wetness or other substances causing the pin bon 64" to remain 
stuck to the surface of the bone pulling cylinder 38 (shown as 64'" in 
FIG. 5). Therefore, according to the present invention, there is also 
preferably provided a scraper blade 110 which is used to scrape any such 
bones which remain attached to the bone registering openings 70 of the 
bone pulling cylinder 38 prior to the bone pulling cylinder 38 making a 
full rotation. Although the scraper blade 110 is shown separated from 
plate 30, it is also capable of being positioned flush against the 
underside of plate 30. This may be preferred, in some cases, the prevent 
the blade 110 from riding up and over caught bones. The pin bones are 
drawn away from the bone pulling cylinder 38 by means of a vacuum or 
suction 52 facilitated by the vacuum manifold 50. 
Of course, due to the nature of the application, all of the material from 
which the device 10 is made should be made of food grade quality. This 
applies to the upper plates 26, 30, 32 and 28, as well as to the body 12 
with the tray 20. The bone pulling cylinder 38 is formed preferably from 
stainless steel or other high quality metal which will not corrode. In 
addition, the fiberglass body, stainless steel and nickel components 
should be easy to assemble and disassemble in order to adjust their 
relative spacing for different fish species and to make it easy to clean 
after, for example, a shift change or the like. 
The drive through the electric motor is preferably through a DC motor which 
is wired to an AC/DC convertor. This allows the drive to be infinitely 
variable in terms of speed through speed control knob 18. The speed of 
rotation of the bone pulling cylinder 38 will be selected according to the 
nature of the fish and the degree of rigor mortis. It has been found that 
the preferred operating speed is usually from about 40 to 50 r.p.m. for 
fresh water fish such as trout. 
To utilize the equipment, the operator places the fillet meat side down and 
skin side up on the body 12. Then the fillet should be placed to cause the 
pin bones to be aligned with the bone fillet registering opening 36, 
allowing them to contact the bone pulling cylinder 38. In this position, 
the fillet should have the belly edge towards the operator so that the pin 
bones will be removed on an angle approaching the natural disposition of 
the pin bones in the flesh in order to minimize meat loss, as indicated 
above. The operator may apply gentle finger pressure on the skin side of 
the fish fillet (FIG. 5) to cause the bones to protrude slightly from the 
flesh. Once snagged by the pin bones, the fillet tends to self-align with 
the fillet registering opening 36 and typically all of the bones will be 
removed in a single pass. If any of the bones tend to be snapped off, it 
is necessary to lower the speed of rotation of the bone pulling cylinder 
to allow for a more gentle gripping and removal of the pin bones. 
It will be appreciated that the upper surface 14 of the body 12 is sloped 
to improve the ergonomics of the device, to assist the operator. Such a 
sloped upper surface is preferred but not essential, as other 
configurations may also be used to assist operators. It will also be 
appreciated that, unlike prior art devices, the device according to the 
invention is self-supporting and does not have to be held by the operator. 
This greatly relieves fatigue in the operator and the operation of the 
device produces more consistent results. 
It is preferable to have a water supply nearby to clean the working surface 
and the bone pulling cylinder periodically. Water and other wastes are 
then caught in the drip tray 20 which is preferably molded right into the 
body 12. Then the drain 21 can be used to ensure that an overflow does not 
occur. 
It is also preferred to provide an on/off/reverse switch which should be 
located on the front of the device so that the operator may shut down the 
machine or reverse the bone pulling cylinder 38 in case of a sudden 
jamming. 
An alternative embodiment of the invention is drawn in FIG. 7 in which the 
bone pulling cylinder is generally indicated by numeral 72, and the 
associated guide plate and puller plate are indicated by numerals 74, 76 
respectively. A fillet registering opening 78 is defined by a gap between 
the guide plate and puller plate 74, 76 and is vertically aligned with the 
axis of rotation of the bone pulling cylinder 72. A compression slot 80 is 
formed in the puller plate 76 beneath an upper surface thereof and extends 
from a forward portion of the puller plate adjacent to the bone pulling 
cylinder 72. The forward portion of the puller plate 76 adjacent to the 
bone pulling cylinder is profiled to have a radius of curvature which is 
commensurate with the radius of curvature of the cylindrical surface of 
the bone pulling cylinder over a selected arc length corresponding to the 
angle a shown in the drawings. The arc length is selected to be of 
sufficient length to apply .alpha. tension to a snagged pin bone which 
will exceed the force of retension of the bone in the fish fillet. 
The puller plate 76 is slid in the direction indicated by arrow 82 relative 
to a fixed body 84 so as to bring the profiled forward portion of the 
puller plate to an operative position where the forward portion mates with 
the bone pulling cylinder 72 over the above-referenced selected arc 
length. To maintain the operative position, coupling means in the form of 
a bolt 86 are provided to couple the puller plate 76 to the body 84. The 
body 84 has a slotted opening 88 to accommodate movement of the bolt 86 in 
the direction indicated by arrow 82. A corresponding mounting opening 90 
is formed in the puller plate 76 and is lined with a Helicoil.TM. insert 
92 which is threaded to receive the bolt 86. 
It will be noted that the bolt 86 and the mounting opening 90 for the bolt 
are disposed across the compression slot 80 and terminate in a blind hole 
94 spaced beneath the upper surface of the puller plate 76. In this way, 
tensioning of the bolt 86 will operate to narrow the gap defined by the 
compression slot 80 and pre-stress the leading edge 95 of the puller plate 
76, as indicated by directional arrow 96. 
It will be appreciated that the compression slot 80 will extend throughout 
the length of the puller plate 76 and be commensurate with the length of 
the associated bone pulling cylinder 72. In order to maintain a minimum 
pre-determined tension to the leading edge 94 of the puller plate 76, a 
plurality of bolts 86 will be used to apply the required tension and these 
will be placed at pre-determined intervals along the length of the 
compression slot 80. 
In the embodiment shown in FIG. 7, the compression slot 80 extends from the 
forward portion of the puller plate 76 adjacent to the bone pulling 
cylinder 72 through the mounting openings 90. It is preferable that the 
bolt used to apply tension to the leading edge to be discrete from the 
bolt used to adjust the relative position of the puller plate to the bone 
pulling cylinder. 
Accordingly, in FIG. 8, there is illustrated yet another embodiment of the 
invention in which discrete fasteners are provided to perform these two 
functions. For convenience, like parts in FIGS. 7 and 8 are identified by 
like numerals. 
Here it will be seen that the mounting opening 90 for receiving the 
coupling bolt 86 is remote from the bone pulling cylinder 72 and traverses 
the entire height of the puller plate 76. The slotted opening 88 whereby 
the fore and aft position of the puller plate 76 may be adjusted relative 
to the body 84 so as to bring the forward portion of the puller plate into 
its operative position on the bone pulling cylinder 72 is accessible from 
the top surface of the puller plate 76. In this embodiment, a blind hole 
94 is formed in the body 84 and lined with insert 92 which is threaded to 
engage the bolt 86. 
An adjustable tension member in the form of a bolt 98 is received in a 
respective opening 112 lined with an insert 114 and aligned with a 
corresponding blind hole 116 formed in the puller plate 76 on the opposite 
side of the compression slot 80. The tension applied to the bolt 98 may 
thus be used to perform fine adjustments indicated by directional arrow 
118 whereby the tension applied to the leading edge 95 may be 
independently controlled. 
It will be understood that the bolt-receiving openings 112, 90 formed in 
the puller plate 76 are preferably spaced from the upper surface of the 
plate and accessible from the bottom of the plate (as shown in FIG. 7) in 
order to provide a smooth working surface for laying down the fish. Other 
variations may be made to the above-described embodiments of the invention 
within the scope of the appended claims. It will be understood that 
snagged bones emerging from the bone pulling cylinder may simply fall by 
gravity and that a vacuum manifold is an attractive but unnecessary 
feature. Similarly, providing a scraper plate to dislodge snagged bones 
which remain caught in the bone pulling cylinder may be supplanted by the 
use of a plurality of water-spray nozzles. Inevitably, the working 
environment will be wet and therefore the drain tray and overflow may be 
optional. 
Thus, it will be appreciated by those skilled in the art that, while the 
foregoing makes reference to certain specific embodiments of the 
invention, many variations and adaptations are possible within the broad 
scope of the invention. Some of these have been discussed above and others 
will be apparent to those skilled in the art. However, the scope of the 
invention is to be considered as defined by the appended claims.