Note: Descriptions are shown in the official language in which they were submitted.
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Humane Crustacean Processor
Field of Invention
The present invention relates to an apparatus and a method for applying an
electric current to a crustacean such that the crustacean is, anaesthetised or
killed. The
invention extends to apparatus and methods for the bulk treatment of
crustacea.
Background to the invention
The cooking of fresh shellfish or crustaceans has always presented some people
with
an ethical dilemma. The flesh of a crustacean decays very quickly after death
which
significantly affects the flavour of the meat. Lobsters and other crustaceans
do spoil
rapidly after death, which is why many buyers insist on receiving them alive.
If the lobster is "headed" before or soon after death, the body meat will keep
fresh
longer. This is because the head area contains the thorax which is the site of
most of
the viscera and gills which spoil much more rapidly than the claw or tail
meat.
Freezing slows deterioration and harmful chemical reactions that follow death.
Neither of these solutions are totally effective as they either involve
removing parts of
the animal or the possibility of damaging the delicate flesh through freezing.
The most
desirable method of cooking crustaceans is when they are at their optimum
freshness
i.e. alive. However many people have an ethical objection to the concept of
cooking a
live animal.
It is accordingly an object of the present invention to provide an apparatus
for
applying an electric current to a crustacean such that the crustacean is
anaesthetised or
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killed and which overcomes or at least mitigates one or more of the problems
noted
above.
SummarSr of the Invention
According to the present invention there is provided an apparatus for applying
an
electric current to a crustacean comprising:
(i) a plurality of electrodes arranged such that the crustacean can be placed
between
the electrodes; and
(ii) means for creating an electrical potential across the electrodes such
that in use
current flows between the electrodes and through the crustacean such that the
crustacean is anaesthetised or killed.
A corresponding method of applying an electric current to a crustacean
comprises the steps of:-
(i) placing the crustacean between at least two electrodes; and
(ii) creating an electrical potential across the electrodes such that in use
current flows
between the electrodes and through the crustacean such that the crustacean is
anaesthetised or killed.
This provides the advantage that a crustacean such as a lobster can be quickly
and simply killed or anaesthetised prior to cooking. The crustacean does not
have to be
cut or decapitated or cooked whilst still alive.
Preferably the apparatus further comprises a tank adapted to contain the
crustacean. This provides the advantage that the crustacean can be held in the
tank
prior to processing and is prevented from moving away. Also, the user is
protected from
the crustacean whilst it is held within the tank and is also protected from
any other
contents of the tank.
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Preferably the tank is adapted to hold an electrically conductive fluid. For
example a saline solution can be used. Using a fluid in this way gives the
advantage
that the crustacean itself does not need to come into contact with the
electrodes and the
risk of burning or other damage from the electrodes themselves is reduced.
Preferably the tank further comprises a heat source such that it is possible
to
retain the crustacean in the fluid filled tank for cooking, after the
crustacean has been
anaesthetised cr killed.
According to one embodiment of the invention the electrodes are substantially
rigid. These electrodes are simple to manufacture and install.
According to another embodiment of the invention the electrodes are deformable
and are adapted to be placed against the crustacean such that in use the
electrodes
conform to fit the shape of the crustacean. This has the advantage that a good
electrical contact between the electrodes and the crustacean can be readily
achieved.
The area of contact between the electrodes and the crustacean is increased by
allowing
the electrodes to conform to the shape of a crustacean which can be irregular
and
varied in shape.
In a further embodiment of the invention each electrode comprises a plurality
of
curved fingers. This has the advantage that a crustacean can be held in place
between
the electrodes and also a good electrical contact between the electrodes and
the
crustacean is achieved.
In another embodiment each electrode comprises a resilient mesh. In this way
one or more crustacea can be held between the electrodes and a good electrical
contact achieved. The resilient mesh is deformable and conforms to fit against
the
crustacean.
In another embodiment each electrode comprises a plurality of resiliently
biased
probes arranged to protrude from the periphery of the tank towards the centre.
A
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crustacean can be placed between the probes, which then conform to fit the
shape of
the crustacean and maintain a good electrical contact with it. By increasing
the number
of points of contact of the electrodes with the crustacean the delivery of an
effective
dose of electricity is more readily achieved.
Preferably, at least one electrode comprises a grille within the tank such
that in
use a crustacean's body can be supported on the grille but the crustacean is
substantially unable to stand on the grille. This enables electrical contact
to be made
with the lower part of the main body shell of the crustacean and helps to
prevent the
crustacean from rising onto the ends of its legs during the application of the
electrical
stun. If the crustacean rises onto its legs, the electrical resistance is
increased and the
risk of damage to the crustacean and of the crustacean shedding its legs is
increased.
In one embodiment at least one electrode comprises a flexible mesh mounted
over a resiliently deformable body. The resiliently deformable body acts to
bias the
mesh against the body of a crustacean and enables a good electrical contact to
be
achieved between the mesh and the crustacean.
In another embodiment at least two electrodes are arranged to form at least
part
of the sides of a funnel such that in use a crustacean may be dropped into the
funnel
and lodge between the sides of the funnel, forming contact with the
electrodes. An
apparatus that is inexpensive and simple to manufacture is thus provided.
Also, a batch
of crustaceans can quickly and easily be processed using this apparatus by
simply
dropping the crustaceans, one at a time, into the funnel.
Preferably, an upper part of said funnel is electrically isolated. This
improves the
safety of the apparatus and reduces the risk of human operators contacting
electrically
charged areas of the apparatus.
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Advantageously, the funnel is openable, such that in use when a crustacean is
lodged in the funnel the funnel may be opened to remove the crustacean. This
provides
a simple and effective method of removing the crustacean from the funnel.
Preferably, at least one of said electrodes forms at least part of a moving
platform adapted to support the crustacean; and at least one other electrode
forms at
least part of a rotating brush, positioned above the moving platform. This has
the
advantage that the motion of the platform and the rotating brush can be used
to draw a
crustacean through the apparatus in order that several crustacea can be
processed
consecutively.
Advantageously the apparatus comprises a pair of moving carrier surfaces
adapted to move in the same direction, said carrier surfaces being positioned
so that
they are facing each other such that in use a crustacean can be supported
between the
surfaces. This has the advantage that the motion of the platforms can be used
to draw
a crustacean through the apparatus in order that several crustacea can be
processed
consecutively. The crustacea can be held between the two carrier surfaces and
prevented from moving about or falling off the apparatus. Also, at least two
of said
electrodes may each comprise a rotating brush, said brushes being positioned
substantially opposite each other on either side of the moving carrier
surfaces and
wherein for each brush at least some bristles of the brush are arranged to
extend
through one of the moving surfaces such that ih use, when a crustacean is
supported
between the carrier surfaces, the crustacean contacts at least some of the
bristles of
each brush at the same time. This enables electrical contact to be made with
the
crustacea held between the moving carrier surfaces.
In a further example, said electrodes comprise a bed of rotating rollers
adapted
to support at least one crustacean. This provides the advantage that motion of
the
rollers can be used to draw crustacea through the apparatus thus allowing
several
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crustacea to be processed quickly. The apparatus may further comprises a frame
for
supporting the bed of rotating rollers wherein the frame is inclined towards
its base. By
inclining the bed of rollers using the frame the crustacea slide down the bed
of rollers
and are drawn through the apparatus.
In another embodiment the apparatus comprises a chute adapted such that in
use a crustacean may be slid down the chute and wherein at least two
electrodes are
located in side walls of the chute such that in use, when a crustacean is slid
down the
chute it contacts the electrodes. This provides a simple and effective
apparatus for
processing several crustacea which is inexpensive to produce and operate.
In another example, one of said electrodes comprises the screw of an auger and
at least one other electrode comprises a casing of the auger. This allows
several
crustacea to be drawn through the auger because of the motion of the screw.
Advantageously, the apparatus comprises an apparatus for determining the
electrical resistance between the electrodes and for adjusting the voltage
applied across
the electrodes on the basis of the determined resistance. This enables the
correct
current to be applied to the crustacean and prevents undue suffering of the
crustacean.
In another example at least two of the electrodes comprise fine piercing
elements adapted to pierce the shell of a crustacean. This allows direct
electrical
contact with the soft body tissues of the crustacean and allows the crustacean
to be
anaesthetised or killed using lower -voltages -and currents. By using fine
piercing
elements the risk of excessive damage to the shall is reduced.
In another example, at least two of the electrodes form part of a pair of
tongs,
said pair of tongs being adapted to grip a crustacean in use. This enables the
crustacean to be restrained, held and moved during application of a stun.
Also, the
tongs can be used to apply a stun either across the body of the crustacean or
across
the head or other specified body part of the crustacean.
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In another example the apparatus comprises a nozzle arranged such that in use,
an electrically conducting liquid may be passed through the nozzle to form a
jet of liquid
and wherein at least one of said electrodes is arranged in use to apply an
electrical
potential to said jet of liquid. The liquid forms a good contact with the
crustacean and is
simple to apply.
Preferably, said means for creating an electrical potential across the
electrodes
comprises means for creating a pulsed or alternating potential across the
electrodes.
This enables a pulsed or alternating current to be applied to the crustacean
which has
been found to be effective for killing or anaesthetising crustacea.
Preferably the tank further comprises a sealable lid and the apparatus further
comprises a safety device adapted to prevent opening of the lid whilst
electric current
flows between the electrodes. This prevents the cook from electrocuting him or
herself
accidentally.
It is also preferred that the apparatus further comprises at least one
detector,
adapted to detect the presence of the crustacean between the electrodes. This
enables
the flow of electric current to be prevented except when a crustacean is
present in the
apparatus.
Preferably, said method of applying an electric current to a crustacean
further
comprises at least one of said electrodes being arranged to extend along
substantially
the full body length of the crustacean.- This provides the advantage that good
electrical
contact is obtained between the electrode and the crustacean in order that the
crustacean may be effectively anaesthetised or killed.
Preferably, said method of applying an electric current to a crustacean
further
comprises the step of applying an electrically conductive gel or liquid to at
least one of
the electrodes. This enables the electrical contact between the electrode and
the
crustacean to be improved.
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Description of the drawings
The invention will be further described, by way of example, with reference to
the
accompanying drawings in which:
Figure 1 shows an alternating voltage.
Figure 2 shows a pulsed voltage.
Figure 3 is a schematic diagram of the electronic components of an apparatus
for
applying an electric current to a crustacean.
Figure 4 is a perspective view of the apparatus.
Figure 5 is a perspective view of a fixed electrode version of the apparatus.
Figure 6 is a perspective view of a wire mesh version of the apparatus.
Figure 7 is a perspective view of a spring contact electrode version of the
apparatus.
Figure 8 is a side view of two finger electrodes in an open configuration.
Figure 9 is a side view of two finger electrodes in a closed configuration.
Figure 10 is a perspective view of two finger electrodes.
Figure 11 is a side view of a vertical feed system version of the apparatus.
Figure 12 is a side view of a horizontal feed system version of the apparatus.
Figure 13a illustrates a crustacean in a shallow bath electrode.
Figure 13b illustrates a crustacean on an array of rods or wires.
Figure 13c illustrates a crustacean on an array of rollers.
Figure 13d illustrates a crustacean in contact with a conductive net with
additional
pressure and conductive fluid being provided by a sponge.
Figure 14 shows the electrodes of a stunning funnel without the necessary
protective
insulated housing.
Figure 15 shows crustaceans on a conveyer belt passing under rotating drums
which
have conductive bristles or fingers.
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Figure 16 shows a crustacean passing between two vertical brush or finger
drums.
Figure 17 shows a crustacean trapped between slotted belts and passing between
rotating brush drums. Bristles pass through the belt to make electrical
contact with the
crustacean.
Figure 18 shows two crustaceans on a series of rotating, electrified rollers.
Figure 19 shows a crustacean sliding down a chute, each wall of the chute
being at a
different electrical potential.
Figure 20 shows an inclined bed of contra-rotating rollers at different
electrical
potentials.
Figure 21 shows a side view of a humane crustacean processing apparatus which
has a
tray for carrying crustacea.
Description of preferred embodiments
Embodiments of the present invention are described below by way of example
only. These examples represent the best ways of putting the invention into
practice that
are currently known to the Applicant although they are not the only ways in
which this
could be achieved.
Theory of Operation
This section will describe the method of humanely anaesthetising or killing of
the
crustacean used by the apparatus. The practical implementation of these
methods will
be discussed later in this document.
The basis of operation is that an animals' neurology can be disturbed by the
application of external electric currents. The application of an electric
current may
render an animal unconscious or even kill it if the disturbance to the
neurological
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structure is sufficiently great. The response that an externally applied
current has on an
animal depends on the level of current applied, the type of current and its
duration.
The crustacean is placed in a dry or liquid-filled vessel containing two or
more
electrodes which may be in contact with the crustacean. A voltage potential is
created
across the electrodes using either direct, pulsed or alternating current. The
term
electrode is used to refer to any conductor by which a current enters or
leaves the
region around the crustacean. For example, an electrode could be a metal plate
as
shown in figure 5 or a wire mesh as shown in figure 6. An electrode can also
be a
plurality of spring loaded contact probes as shown in figure 7 or a bar with a
plurality of
curved fingers extending from it as shown in figure 10. Another possibility is
for the
electrode to be a conductive mesh conveyor belt as shown in figures 11 and 12,
a tank
of saline solution, a series of rollers or brushes that may be inclined or the
side walls of
a chute. Examples of these are shown in the figures. Another example is for
one
electrode to comprise a stream or jet of electrically charged saline solution.
In this case
a nozzle is provided and saline or other electrically conducting liquid is
passed through
the nozzle to form a jet of liquid. The nozzle is arranged so that the jet of
liquid is
projected towards the crustacea. One electrode is arranged to apply an
electric charge
to the jet of liquid.
Direct current flows from the negative electrode (cathode) to the positive
electrode (anode). In the case of alternating current the electrodes alternate
between
being cathode and anode continuously as the alternating voltage reverses its
polarity
and the direction of flow of the current. Alternating current is generally
based on a
sinusoidal signal producing a wave form similar to that shown in the graph in
figure 1. In
figure 1 the y axis 1 represents volts and the x axis 2 represents time.
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Direct current produces a unidirectional current. However, this current can be
switched
on and off to produce a pulsed wave-form as shown in figure 2. As for figure
1, the y
axis 1 represents volts and the x axis 2 represents time.
The frequency and duty cycle of direct current pulses or the frequency of the
alternating
current can have a variety of effects on animals varying from involuntary
muscle
contraction to paralysis, unconsciousness and death. The effect that frequency
has
varies from species to species, but the most effective frequency of operation
tends to be
in the region of 10 to 120 hertz.
The level of voltage and current required depends on the conductivity of the
water or
saline solution, if present. The reason for immersing the crustacean in a
liquid is to
reduce the possibility of localised burning at the electrode contact point and
to allow the
possibility of current flow into parts of the crustacean which are not in
direct contact with
the electrodes.
The conductivity of these fluids will normally lie in the range of 50 to 2,000
microsiemens. A fluid with a low conductivity will require a greater potential
voltage to
sustain the required current than a fluid with a high conductivity. This
implies that the
voltage source required may range from 100 to 1,000 volts depending on the
conductivity of the fluid.
The magnitude of current necessary will depend on the size and nature of the
crustacean and the conductivity of any liquid present. The person skilled in
the art can
determine the preferred current flow by experiment. The means for creating an
electrical potential may also include a means for varying the current.
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The electrical voltage to be used for stunning can be constant (DC) voltage or
may vary
periodically in time with a range of wave forms and frequencies. The voltage
may also
be varied in response to the impedance of the crustacean being stunned.
In one example, the electrical resistance between the electrodes is measured
and if it is
within a range that indicates that a good electrical stun can be achieved, a
voltage is
applied for a short, measured period of time to put the crustacean into a
state of
insensibility to pain. The period during which the crustacean remains
insensible after
the electrical current is ceased is dependant on both the current which passed
through
the crustacean and the time period for which it was passed. If enough current
is passed
for sufficient time and the crustacean is cooked shortly after the end of the
stunning
current then the crustacean remains insensible until it is killed by the
cooking process.
The electrical stun may be achieved either with a single application of
electrical current
or with an initial application of current under the controlled conditions
described above
to render the crustacean insensible, followed by a reinforcing stun of longer
duration
under less controlled conditions to ensure the period of insensibility lasts
until the death
of the crustacean. Several stuns of increasing duration or strength may be
used in this
way to render the crustacean insensible, anaesthetise the crustacean and
eventually kill
it.
The electrical current flowing through the crustacean may be determined by the
resistance of the crustacean and the voltage applied across the electrodes.
Any
conventional method or apparatus may be used to determine the resistance in
this way.
It is also possible to use an automatic system to rapidly identify the
resistance of each
crustacean and monitor this resistance during the period of a stun. The
applied voltage
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can then advantageously be adapted, taking into account the resistance, so as
to
achieve the required current levels during a stun.
Apparatus and Systems
In this section we will look at the methods of implementing the above concept.
The
design of apparatus can be split into single use and continuous use systems. A
single
use system is primarily for the consumer market and allows for one crustacean
or a
batch of crustaceans to be killed in a single cycle. The continuous use system
is for
large domestic, commercial or industrial applications where crustaceans can be
placed
on a conveyor or other continuous flow processing lines. Both of these systems
will use
similar electronics which will be explained later.
Single Use/Consumer Version
This version of the crustacean processor is designed for use in catering
establishments
or the home. An example is shown in figure 4. The crustacean processor
apparatus 41
has the outward appearance of a box 44 with a sealed lid on it 42. On one side
of the
box there is a control panel/display 43 and a lid or door release mechanism.
The lid 42
is provided with a hinge 45 that has a safety interlock switch. The crustacean
processor
box 44 comprises a processing tank which contains electrodes and may also be
filled
with liquid of suitable salinity. The user opens the apparatus, places the
crustacean or
crustaceans inside the tank or box 44 and shuts the lid 42. The user then
selects the
type/quantity of crustacean on the control panel 43 which then starts the
humane
electrocution process. The user may also have the ability to cook the
crustacean by
use of an electrical heating element within the crustacean processor which can
rapidly
boil the water. Alternatively the user can remove the now anaesthetised/dead
crustacean from the processor and cook in a conventional manner with the
knowledge
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that any suffering of the animal has been kept to a minimum. Internally the
crustacean
processing apparatus may be one of several designs.
Figure 5 shows a simple design of apparatus which consists of fixed electrodes
51
positioned at diametrically opposite sides or ends of a tank 52. This design
necessitates that the crustaceans must be immersed in a fluid 53 of suitable
salinity for
electrical current to flow. The electrodes in this version can be of any
conventional
design. An electronics module 54 is provided to control and power the
electrodes 51.
Figure 6 shows a direct contact version where the bottom and top of the tank
61 have a
conductive woven wire mesh 62, 64 supported by springs 63 or a large soft
elastomer.
The crustacean is placed on the lower electrode 62 and as the lid is closed
the upper
and lower mesh elastomeric surfaces 62, 64 will conform to the contours of the
crustacean providing a reliable electrical contact. This method does not rely
on fluid for
electrical conductivity although fluid could still be used to improve contact
resistance.
This embodiment is intended to encompass any form of resiliently deformable or
resiliently mounted electrode. The object is to increase the
electrode/crustacean
contact.
Another method of implementing the flexible electrode method is shown in
figure 7. In
this design the elastomer mesh support is replaced by a matrix or array of
spring loaded
contact probes 71 which conform to the shape of the crustacean on closing the
lid 72.
The spring loaded contact probes extend from the base of the tank 73 as well
as from
the lid 72 of the tank.
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The fourth version is shown in figures 8, 9 and 10. It consists of two sets of
curved
electrodes 81 mounted in inter-digitated format on two independent shafts 82
which also
form electrical bus bars. The two shafts can rotate and the electrodes are
mounted
offset on the two opposing shafts producing an effect similar to interlocking
fingers of
two human hands. When the lid of the processor is opened as shown in figures 8
and
the two sets of "fingers" move apart to allow the crustacean to be placed
between
them. On closing the lid the two sets of fingers move back together to hold
the
crustacean as shown in figure 9 and provide good electrical contact. This
method may
be used with or without fluid 83.
All four designs have common attributes such as safety interlocks on the lid
to make it
physically impossible for the lid to open whilst there is electric current
flowing between
the electrodes. The designs also share the same electronics and are all
"double
insulated" i.e. there are no external metal parts connected to earth.
Another example of a single use/consumer version is shown in figure 13. Figure
13a
shows a crustacean 130 placed in an electrically insulated container 131 on a
lower
electrode that is integrated into the container 131. An electrically
conductive liquid such
as salt water is placed into the bottom of the container 131 to form a shallow
bath 132.
The liquid in the bath 132 is deep enough to contact the lower part of the
main body
shell of the crustacean 130 as shown in figure 13a. This allows good
electrical contact
with the main body of the crustacean 130 over a wide area. The second
electrode may
be mounted on the lid of the container as shown in figure 13d. However, any
type of
second electrode can be used.
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Instead or in addition to the shallow bath 132, an array of rods, wires or
freely rotating
cylinders 133 can be used as the lower electrode. These rods, wires or
cylinders form a
grille within the container 131. This provides the advantage that the
crustacean 130 is
unable to stand on the rods, wires or cylinders 133 and rests its body on them
so that
electrical contact is made with the lower part of the crustacean's main body
shell (as
shown in figures 13b, 13c and 13d). In instances where the crustacean is able
to stand
on the electrode (such as when it is a flat sheet of metal) the crustacean
tends to rise
onto the ends of its legs during the application of the electrical stun and
this increases
its electrical resistance and increases the risk of damaging or shedding the
legs of the
crustacean during the stun. This is a significant disadvantage because it
makes the
stun more difficult to apply effectively and also impairs the appearance of
the
crustacean.
Figure 13d shows one example of the upper electrode. The upper electrode is
mounted
on the lid of the container 134 and, comprises a fine, flexible, conductive
net 135 such
as chain mail. This is used to provide a conformable and robust method of
making
electrical contact over a wide area of the upper part of the body shell of the
crustacean
130. The net 135 is suspended from a few points above the crustacean with
enough
slack to enable it to conform to the shape of the top part of the crustacean's
shell as
shown in figure 13d. However, the net 135 is not so slack as to enable it to
contact the
other electrode 133 in the absence of a crustacean 130. Additional pressure to
ensure
good electrical contact can be applied with an elastic body such as a sponge
136,
mounted behind and protected by, the net 135 as shown in figure 13d. The net
135 can
be coated with an electrically conductive gel or liquid to improve electrical
contact with
the shell of the crustacean 130. This coating can be achieved by immersing the
net 135
in saline solution immediately prior to use, by spraying the net 135 while it
is in contact
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with the crustacean shell, or by mounting a sponge 136 behind the net 135 so
that by
pressing down on the sponge 136, as for example, when closing the lid 134, the
liquid
or gel in the sponge is forced out and wets the net 135 and the shell.
Once the lid 134 is closed, the electronic stunning circuit (not shown in
figure 13)
checks the electrical resistance presented by the crustacean, and if it is
within a suitable
range applies the electrical stun for a pre-determined time period.
An alternative method of making electrical contact with the crustacean is to
pierce the shell with one or two fine electrodes. This allows direct
electrical contact with
the soft body tissues of the crustacean. It is necessary to drive these
electrodes with
sufficient force to rapidly pierce the shell and to apply the electrical
current immediately
to avoid increased suffering. Small diameter electrodes are used to avoid
excessive
damage to the shell. It may be necessary to leave the shell penetrating part
of the
electrodes in place during cooking to avoid excessive loss of body fluids. In
this case
the electrodes must be disconnected from the electrical supply after stunning.
Crustaceans can also be stunned by application of electrical stunning tongs.
These can be used to apply a stun either across the body of the crustacean or
across
the head or other body part. These tongs may be designed with multiple contact
points
enabling the crustacean to be restrained, held, or moved during application of
the stun.
Such tongs can be used to apply an initial controlled stun. Crustaceans can,
for
example, be unloaded from a crate picking therii up with a pair of tongs which
applies
the initial stun. They may then be placed on a chute or auger, as described
below
which passes further electrical current through the crustacean to extend the
period of
insensibility while moving them to the point of cooking. This is described
further below
in the section headed "continuous use/ commercial application".
Figure 14 shows an example in which crustaceans are stunned by dropping
them into a stunning device 140 that comprises a pair of converging electrodes
141 in
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the form of a funnel. The crustacean dropped down this will lodge and make
electrical
contact where the funnel is too narrow for the crustacean to fall further. The
upper part
of the funnel may be electrically isolated for operator safety (not shown).
The funnel
electrodes 141 can be continuously wetted by a fine spray of film of a
conducting liquid.
This improves the electrical contact made with the crustacean. To remove the
crustacean the funnel is opened or some other in-built retrieval device is
used.
Figure 10 illustrates a humane crustacean processing apparatus that is
particularly suited for stunning single crustaceans such as lobsters and
crabs. This
apparatus can be arranged to provide a stun to the crustacean in order to
render the
crustacean insensible for approximately 2 minutes. The stunned crustacean can
then
be immersed in boiling water in which it dies after approximately 1 minute
from
immersion. In this way the crustacean is killed before it regains
consciousness.
However, it is not essential for the crustacean to only be stunned using this
apparatus.
It is also possible to increase the strength and duration of the current
applied in order
that the crustacean is killed in the apparatus.
The apparatus comprises a tank or housing 1000 that is similar to the housing
of
a conventional microwave oven. That is, the housing 1000 is based on a
modified
microwave oven carcass, from which all the electronics have been removed. This
gives
a neat and pleasing exterior that blends well with the other equipment in a
kitchen
environment. The housing 1000 has a door as for a conventional microwave oven.
The
electronic apparatus required for the crustacean processor are not shown in
figure 10.
These may be housed separately or alternatively are incorporated into the
housing 1000
in any suitable way.
The apparatus has two electrodes one of which (not shown) is positioned on the
base 1002 of the shell or housing 1000 and the other 1001 which is placed on
the top of
the housing. The electrical shock is thus delivered from the top to the bottom
of the
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crustacean. Safety interlocks are provided in the housing 1000 which ensure
that the
electrodes can never be powered with the door of the housing open. An
additional
safety interlock may also be provided which ensures that the electrodes can
only be
powered when the upper electrode 1001 is in contact with a crustacean.
The upper or top electrode 1001 comprises a foam pad that is covered with
stainless steel chain mesh. Thus the electrode 1001 is deformable and when
pressed
against the top of a crustacean the electrode 1001 conforms to fit the upper
surface of
the crustacean. Any suitable type of foam or other deformable material can be
used.
Similarly, the stainless steel chain mesh can be replaced with any suitable
conducting
material that is deformable. One advantage of using foam material is that
electrolyte
solution can be absorbed into the foam so that when the foam is pressed
against the
crustacean electrolyte is released and runs over the crustacean to form a good
electrical contact. A container of electrolyte can be positioned in the
housing and
arranged to feed the foam or other deformable electrode with electrolyte as
required.
The bottom or lower electrode comprises a stainless steel or other conducting
plate which is arranged to contact the underside of the crustacean. In order
to facilitate
loading of a crustacean into the apparatus this stainless steel plate is
mounted into the
base of a drawer or tray 1005. The drawer or tray 1005 can be mounted on
runners or
slides within the housing 1000 that enable the drawer 1005 to be drawn out of
the
housing 1000 as shown in Figure 10. When the drawer is pulled out a crustacean
1003
can be placed into or removed from the housing easily. The drawer 1005 may
contain a
shallow bath of electrolyte 1004 such as saline solution. This acts to improve
electrical
contact between the crustacean 1003 and the lower electrode.
A lever (not shown) or other suitable mechanism is provided for lowering the
upper electrode 1001 down into contact with a crustacean 1003 that is placed
in the
drawer 1005 inside the housing 1000.
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The housing 1000 and drawer 1005 are preferably made from a corrosion
resistant material that is easy to clean such as stainless steel.
The housing is sized and shaped to deal with crustaceans up to about 275mm in
length and between 50mm and 75mm thick. The apparatus is also designed to cope
with crustacea of a live weight of about 500 grams. Also, the lever or other
mechanism
for lowering the upper electrode is able to clamp the crustacean using a force
of up to
about 20 N.
Details of the electronic apparatus for the crustacean processor in this
example
are given below as an example only:
~ An isolated electrical supply of up to 110V, 50Hz AC is provided that is
capable of
supplying up to 3.5 Amps.
~ A timer is provided to allow the length of the stun to be controlled for a
period of
between 0 to 5 seconds in 1 second intervals. The control has a manual
override so
that longer stuns can be applied if required or the stun can be stopped if
required.
The timer can be integral with the mechanical unit.
~ Safety interlocks are provided as described above to ensure that the unit is
operated
safely. These are integral with the mechanical unit.
~ An electronic power unit is also provided. This may be housed separately
from the
mechanical unit or may be integrated with the housing 1000 as required.
The operation of the crustacean processor illustrated in Figure 10 is now
described.
The door of the housing (not shown) is first opened and the drawer 1005 pulled
out as
illustrated in Figure 10. A crustacean 1003 is then placed into the drawer
1005 which
may contain a shallow bath of electrolyte. In this way the crustacean 1003 is
placed so
that its underside is in contact with the steel plate that forms part of the
lower electrode.
The drawer 1005 is then pushed back into the housing 1000 and the door of the
housing closed. The lever or other mechanism is then operated to bring the
upper
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electrode 1001 into contact with the crustacean 1003. As the upper electrode
1001 is
pressed against the crustacean it conforms to fit the upper surface or shell
of the
crustacean in order that a good electrical contact is formed. Also, the
crustacean 1003
is gently pressed down against the steel plate in the bottom of the drawer
1005 which
forms part of the lower electrode.
The timer is then set to the required stunning time and the stun initiated by
pressing
a "start" button or other activation mechanism. Once the stun has been
completed the
lever is released and the upper electrode 1001 drawn up to its rest position
away from
the crustacean as shown in Figure 10. The drawer 1005 is then pulled out in
order that
the stunned crustacean can be removed.
By using a drawer 1005 to hold the crustacean 1003 the process of placing the
crustacean into and removing the crustacean from the apparatus is made easier.
The
user does not have to remove a lid from the tank and reach over the sides of
the tank of
housing 1000 in order to insert the crustacean. By using a drawer 1005 in this
way the
upper electrode 1001 is effectively shielded from the user and this improves
the safety
of the apparatus. Use of the drawer 1005 permits side entry of the crustacean
1003 to
the apparatus which avoids the user needing to reach past one of the
electrodes.
The mechanism for lowering and raising the upper deformable electrode is
particularly advantageous. This allows the crustacean to be clamped in place
during
application of the stun which helps to-prevent damage to the crustacean and
prevents
the crustacean from moving about within the drawer. Also the clamping action
acts to
improve the electrical contact with the crustacean which enables the stun to
be
efficiently and effectively applied. A further advantage of the mechanism for
lowering
and raising the upper deformable electrode is that this electrode is raised to
a shielded
position during insertion and removal of the crustacean and this improves the
safety of
the apparatus.
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Continuous Use/Commercial Application
This version of the processor is for use in large domestic, commercial or
industrial
operations where a large number of crustaceans need to be processed quickly
and
humanely. Two versions are described:- a hopper style version shown in figure
11 and
a conveyor style processor shown in figure 12.
The hopper processor shown in figure 11 consists of two vertically running
belts
110. The belts comprise conductive woven wire mesh or are of non-conducting
material
coated with a conductive layer or have a conductive wire mesh sewn into them.
Each
belt is connected to one of the electrodes via a slip ring. The belts are
gently sprung
loaded 111 so that they approach close together but do not actually contact
each other.
The belts are driven by an electric motor so that they are continuously moving
down and
towards themselves in the middle section as shown by the arrows in figure 11.
The
method of operation is that the crustaceans are fed into the hopper at the top
112 of the
processors. As the crustaceans reach the middle part of the processor the
spring
mounted belts 110 move apart and adjust themselves to the width of the
crustacean.
After the crustacean contacts both belts it is exposed to the electric current
which
anaesthetises/kills it. The presence of a crustacean at the anaesthetising
position is
sensed by a detector 113 which signals the electronics to activate the
electrodes. The
crustacean then drops out of the bottom of the processor for further
processing such as
cooking in boiling water 114.
The horizontal processor shown in figure 12 works on the same principle as the
hopper processors. Two conveyor belts which approach but do not touch each
other
are used. The important point to notice is that the conveyor part of the
processing unit
is either electrically isolated from the rest of the conveyor system for
safety reasons, or
has the exposed conveyor electrode at ground potential 120. The crustacean is
contained between the two belts 121 and then lowered into a saline solution
122. When
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the presence of a crustacean is sensed 123 at the central point the electrodes
are
activated.
Once again both methods use the same electrical discharge techniques
described in this document to anaesthetise and or kill the crustacean.
Further examples suitable for continuous use and commercial application are
now described. For example, the crustaceans can be electrically stunned as
they slide
down a chute, are driven along on or between belts, or driven on a bed of
rollers directly
to the place they are to be killed by cooking.
Figure 15 shows how crustaceans 150 may be placed, spaced apart on an
electrically conducting conveyor belt 151 which moves them under a series of
rotating
brushes 152. The conveyor belt 151 forms one electrode and the brushes 152
another
electrode. As the crustaceans 150 pass under the rotating brushes 152
electrical
contact is made between the brushes and the crustaceans and, once continuous
electrical contact has been established, electrical power is applied to stun
the
crustacean 150. The stun can be reinforced, to ensure the period of
insensibility fasts
long enough by applying an electrical current as the crustacean passes under a
second
or third rotating brush (as shown in figure 15). The crustaceans are spaced on
the
conveyor belt 151 so that the rotating brush or drum 152 can contact no more
than one
crustacean at a time. An alternative configuration of this is shown in figure
16. The
crustacean 160 is placed on a non-coriducting belt 161 or slide between pairs
of vertical
brush 162 or finger drums. The pairs of drums or brushes 162 make contact on
each
side of the crustacean 160 as it passes through and deliver the electrical
stun. Another
example is shown in figure 17. If the crustaceans 170 need to be restrained or
moved
more positively then they can be held between non-conducting slotted belts
171. In this
case the bristles of the drums 172 are able to penetrate slots in the belt 171
in order to
make contact with the crustacean 170. For example, the belt may be made from
mesh
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WO 99/55166 PCT/GB99/01309
type material or may be perforated. Any suitable material can be used to form
the belt.
The bristles of the drums 172 are resiliently deformable. As the crustacean is
drawn
into the nip between the drums 172 the bristles penetrate the belt 171 and
touch the
crustacean. This causes the bristles to deform resiliently and this improves
the
electrical contact with the crustacean.
Figure 18 shows a situation in which movement and stunning of a crustacean
180 can be achieved using a series of rotating rollers 181. The rollers 181
are held at
different electrical potentials as shown in figure 18 so that electrical
current is passed
through the crustaceans as they are moved. This is because the crustaceans are
large
enough to occupy an area over the bed of rollers 181 which include area of
dififerent
electrical potential. Current then flows through the body of the crustacean
180. The
rollers are spaced apart so that current does not flow between then in the
absence of a
crustacean 180. Electrical contact between the crustacean 180 and the rollers
181 is
enhanced where the rollers 181 have a slightly compliant surface. Lack of
positive
contact between the electrodes 181 and the crustacean 180 makes this method
suitable
for the application of a reinforcing stun rather than an initial stun.
Figure 19 shows an example where movement and stunning of a crustacean
190 is achieved by sliding the crustacean down a chute 191. The walls 192, 193
of the
chute 191 form the two electrodes and deliver the electric current to the
crustacean 190.
Lack of positive contact between the electrodes -181 and the crustacean 180
makes this
method suitable for the application of a reinforcing stun rather than an
initial stun.
Figure 20 shows an example where movement and stunning of the crustaceans
200 is achieved by placing the crustaceans on an inclined bed of counter-
rotating rollers
201, 202. The rollers are held at different electrical potentials as shown in
figure 20. As
the crustaceans 200 slowly slide down the bed they make contact with an
adjacent pair
of rollers and so receive an electrical stun.
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In another example, the movement of crustaceans is achieved by use of an
auger. A screw of the auger is held at a different electrical potential to a
casing of the
auger and so crustaceans contacting both as they are moved along the auger
receive
an electric stun.
Examples of stunning multiple crustaceans in a batch are now described.
Crustaceans can be batch stunned in large plastic crates such as those in
which
they might be delivered to the processing facility. This can be achieved by
applying an
electrical potential across the whole crate. The electrodes can include a
shallow pool of
conducting liquid in which the crate stands, conducting brushes or fingers
which can be
applied through the perforations at the top and bottom of the crate, or
conducting grids
built into or inserted in the ends of the crate. Where this is not possible,
the
crustaceans can be transferred from the delivery crates into a purpose built
stunning
crate. When using the batch stunning method measurements are made to determine
the electrical potential which must be applied to achieve a suitable
electrical current
through each crustacean. This can either be done for each batch or an
predetermined
value used. The target electrical current is slightly higher then that used
when stunning
single crustaceans to allow for differences in the current received by
different
crustaceans.
Generic Electronics
The key parts of the electronics are shown in Figure 3. The purpose of the
electronics
is to provide a controlled current to the electrodes which are in contact with
the
crustacean. As already discussed the frequency, duty cycle and duration of the
current
pulse need to be controlled. The purpose of each principle part of the
electrical circuit
will now be defined. Figure 3 shows the electronics in the context of the
single use
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system and any differences between the electronics for the single use and
continuous
use system is described where necessary.
Mains Isolator 31
The use of mains electricity in the proposed environment can be potentially
hazardous.
The proposed design must have a mains isolation transformer 31 between the
mains
electricity supply and the device. This is essential in a consumer product but
may not
be necessary in a commercial environment. EC wide EMC and LVD requirements are
met by suitable protection components.
Power Supply Unit 32
The apparatus requires a stabilised low voltage DC supply for a voltage
generator 33
and to power auxiliary components such as a microcontroller 34 and amplifier
circuits
35. The voltage levels required for a commercial system may vary from those
required
for a consumer system.
Voltage Generator 33
This module produces the high voltages required to effectively kill a
crustacean. The
voltage generated will need to be in the range of 100 to 1,000 volts depending
on the
crustacean and the existing conductivity within the vessel. The discharge
power level
and duration are controlled by the microcontroller 34. The high voltages that
are
required may be generated by a step-up transformer circuit or by capacitive
discharge.
A capacitive discharge power supply would not be suitable for a continuous use
system
unless the throughput was adjusted to match the capacitor re-charge time, but
would be
ideal for a single use consumer system. This module also contains circuitry
for limiting
the maximum voltage discharge and controlling the duration of the discharge.
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Pulse Shaper 36
This is one of the most important modules of the electronics system. As
previously
described the type of current wave form applied to the crustacean is very
important.
The pulse shaper 36 contains circuitry that can produce alternating, pulsed or
direct
current output from the voltage generator 33. It will also be able to produce
different
frequencies and alter the duty cycle of the output wave form. These variables
can be
adjusted via the micro-controller 34 to pre-determined values or by manual
adjustment.
Micro-controller 34
The micro-controller 34 controls the overall operation of the apparatus. The
micro-
controller is responsible for determining the correct voltage level, current
type,
frequency, duty cycle and duration which has to be applied to the crustacean.
The
values that it selects for these attributes are dependant on the type of
crustacean and
the existing electrical conductivity across the electrodes 37. The controller
is also
responsible for informing the user of what is happening and enabling the user
to select
the type and quantity of crustacean. In the continuous use system it also has
to monitor
and control the throughput rate. In both single use consumer product or
industrial
applications the micro-controller also has to monitor various safety aspects.
Safety Interlock
This is an essential part of the single use consumer product, where the
electrodes 37
might be accessible to the user during loading/unloading of crustaceans. The
safety
interlock provides the dual purpose of making it electrically impossible for
any current to
flow to the electrodes when the user could touch them. It is also used to
inform the
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micro-controller 34 whether the lid of the device is open or closed.
Continuous use
systems will have a safety interlock on their protective guards so that
current cannot
flow to electrodes when the guards are removed for maintenance.
Electrodes/Conductivity Detectors 37, 38
The electrode 37 is the part of the circuit which delivers the electrical
charge and
detects the conductivity. The electrodes 37 and the detectors 38 may be
separate
devices or may be integrated into the same device for the single use system,
but would
have to be separate contacts in the continuous use system.
Conductivity Amplifier 35
This module simply monitors the conductivity across the conductivity detectors
38 and
converts this into a suitable analogue voltage for use by the microcontroller
34. It
ensures that there is sufficient high conductivity to ensure full electrical
discharge to
humanely kill or anaesthetise the crustacean and avoids malfunction of the
apparatus.
Keypad/Display 39
The user will need to be able to input parameters into the device such as type
and
quantity of crustacean, cooking time, etc. This is effected using the keypad /
display 39.
The keypad / display 39 can also be used to give visual feedback to the user
as to the
current status of the device. Indicators will signal the status of the safety
circuits. A
control panel which is part of the key pad/display may include the door
release and its
safety interlock.
A number of general points are now described.
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It is advantageous in many cases to rinse the crustaceans in fresh water prior
to
stunning. Salt water is a good conductor of electricity and if the crustaceans
are wet
with saline solution then any electrical current applied to the crustacean is
likely to flow
through the film of salt water across the surface of the crustacean rather
than through
the body of the crustacean. This reduces the effectiveness of the electric
stun on the
crustacean. Removal of the salt water by, for example replacing it with fresh
water
which has a higher electrical resistance, will reduce the conductivity of this
path and so
increase the proportion of the electric current which passes through the body
of the
crustacean.
It is also possible to place the crustacean in a container prior to stunning
in order to
facilitate its transfer to a cooking device and subsequent removal from that
cooking
device. The container may take the form of a basket such as a conventional
potato chip
basket and may include one or both electrodes. The container may then be
driven
through a long vat of boiling water, or a steam bath in order to cook the
crustacean. In
this way an accurate cooking time can be ensured without the need to
accumulate a
batch of stunned crustaceans for batch cooking.
29
