WO2012039634A1

WO2012039634A1 - Automated shellfish opening system

Info

Publication number: WO2012039634A1
Application number: PCT/NZ2011/000198
Authority: WO
Inventors: Kenneth Barry Davison
Original assignee: Stl Limited
Priority date: 2010-09-23
Filing date: 2011-09-23
Publication date: 2012-03-29
Also published as: AU2011306534A1; NZ588154A

Abstract

The invention provides a shell removal device for removing a top shell of a partially opened shellfish. The shell removal device comprises asymmetric leading edge adapted to enter the front of the partially open shellfish conveyed towards the device, slidably engaging the top shell towards one side of the shellfish. Said engagement causes pivoting and twisting of the hinge ligament between top and bottom shells of the shellfish, weakening the hinge ligament. Subsequent engagement of the shellfish with an engaging member removes the top shell entirely. Also disclosed is a shellfish opening system incorporating the shell removal device, and a shell removal system comprising a plasma torch to partially open the shellfish.

Description

AUTOMATED SHELLFISH OPENING SYSTEM

Field

This invention relates to automation of the opening of shellfish. More particularly, the invention provides a system and method for removing half of the shell of a bivalve mollusc.

Background

Shellfish, in particular bivalve molluscs such as mussels, are commonly processed for sale in a number of forms, including mussel meat (i.e. shelled) and half-shell forms, which both require the removal of at least half of the shell. New Zealand green-lipped mussels (Perna canaliculus), for example, are mostly processed and sold frozen in a half-shell for export. The shellfish meat may be sold raw or cooked. A shellfish processing method is therefore required for removing half of the shell without cooking the shellfish or unduly damaging the remaining half-shell.

Traditionally, a shellfish would be opened and the shell or half-shell removed manually using a shucking knife, for example, although a number of apparatuses have been developed to automate this task.

International Patent Publication No. WO 03037091A1 discloses a machine in which partially opened mussels are opened by engagement of the respective half-shells with cleats provided on opposing main and inclined conveyors. A cleat on the inclined conveyor engages the top half-shell and "flips, the shellfish open", allowing the shellfish to pass beneath the upper conveyor. The top shell is broken off by sandwiching the opened mussel between a press conveyor and the main conveyor and passing the shellfish around a roller, bending the half-shells past 180° and breaking the joint.

United States Patent No. 4,143,444 to James P. Cox discloses an oyster processing apparatus including a conveyor belt which carries an oyster towards a concussion bridge barrier which forcibly strikes the upper shell of the oyster just above the joint/hinge, thereby arresting forward movement of the upper shell as the lower shell is driven forward by the conveyor. The concussion bridge barrier thus separates the top and bottom shells by way of a concussive shearing force. United States Patent No. 3,988,805 to Roger C. Martin describes a method for shucking shellfish, in particular scallops, including exposing the shellfish to steam to clean the shells, then conveying the still-closed shellfish to a sheller comprising a striker plate and a belt which are arranged to provide a narrowing aperture through which the shellfish are forced by the belt. The striker plate is held at a predetermined angle with respect to the belt such that respective half-shells of the shellfish engage major faces of the striker plate and the belt, respectively, subjecting the partially- opened shellfish to a shearing force which separates the shell halves. United States Patent No. 3,594,860 to Richard W. Nelson et al. discloses an apparatus for removing the edible flesh from the shells and viscera of bivalve molluscs, in particular scallops. The apparatus heats an upper shell of the scallop using a high- temperature oxy-acetylene burner flame to partially open the shellfish. The partially opened shellfish is then driven against and past a shucking bracket which engages the top shell, breaking it off by bending the top shell backwards about the hinge.

Disadvantages of these and other prior art systems and methods include one or more of a requirement for cooking the shellfish to partially open it, unsuitability for presenting the shellfish in a half-shell, excessive force requirements, unnecessary complexity, unreliability, throughput limitations, undesirable damage to the shell, energy consumption, gas exhaust requirements, and/or cost, for example.

Object of the Invention

It is therefore an object of the invention to provide a system and/or method which overcomes or at least ameliorates one or more disadvantages of the prior art, or alternatively to at least provide the public with a useful choice.

Further objects of the invention will become apparent from the following description. Summary of Invention

According to a first aspect the invention may broadly be said to consist in a shell removal device for removing a top shell of a partially opened shellfish by way of relative movement between the shellfish and the shell removal device, the shell removal device having a body comprising:

an asymmetric leading edge adapted to enter the front of the partially open shellfish and slidably engage the top shell substantially toward a first side of the shellfish, to pivot and twist a hinge ligament between top and bottom shells of the shellfish about substantially orthogonal axes; and

an engaging member adapted to engage the shellfish at or substantially adjacent the hinge ligament between the top shell and a bottom shell of the shellfish, to remove the top shell from the shellfish.

Preferably the engaging member is positioned rearwardly with respect to the leading edge such that the engaging member engages the shellfish after the leading edge pivots and twists the hinge ligament.

Preferably the engaging member removes the top shell from the bottom shell by way of a substantially shearing force.

Preferably the engaging member comprises a projection projecting downwardly with respect to the body.

Preferably the leading edge comprises a rolled or rounded edge to prevent damage to the shellfish meat. Preferably a lower surface of the body is adapted to slidably engage the lower shell to brace the lower shell against the engagement of the leading edge and the engagement member with the top shell.

Preferably the relative movement of the shell removal device and the shellfish creates tension, torsion, and shear forces on the hinge ligament, thereby weakening and breaking the hinge to remove the top shell.

According to a second aspect, the invention may broadly be said to consist in a shellfish opening system comprising:

conveying means for conveying the shellfish;

direct heating means adapted to heat a top shell of the shellfish substantially adjacent abductor muscles of the shellfish as they are conveyed past the heating means by the conveying means, said heating causing the shellfish to release the top shell to partially opening the shellfish; and

a shell removal device for removing the top shell of the partially-open shellfish as it is conveyed past the shell removal device, the shell removal device comprising a leading edge adapted to enter the front of the partially open shellfish, slidably engage the top shell substantially toward a first side of the shellfish, and pivot and twist a hinge ligament of the shellfish, the shell removal device further comprising an engaging member adapted to engage the shellfish at or substantially adjacent the hinge ligament to remove the top shell from the shellfish.

Preferably the conveying means is adapted to convey the shellfish past the heating means and the shell removal means in a forward direction, whereby the heating means and the shell removal device are fixed in position relative to the direction of movement.

Preferably the conveying means is adapted to convey the shellfish individually on one or more receptacles such that the shellfish are substantially forward-facing, the receptacles being curved upwardly towards the rear to brace the shellfish against the shell removal device.

Preferably the direct heating means comprises at least one plasma torch.

Alternatively, or additionally, the direct heating means may comprise one or more gas burners, lasers, or infrared heaters.

Preferably the system further comprises a first sensing and control means to sense whether a shellfish has opened and to control the direct heating means accordingly.

Preferably the shell removal device includes adjustment means to adjust the height of the shell removal device to accommodate various sizes and/or species of shellfish.

Preferably the adjustment means comprises an actuator. The actuator is preferably pneumatically-operated. Preferably the system further comprises sensing and control means to sense the size of the shellfish and control the actuator to automatically adjust the height of the shell removal device accordingly.

Preferably the engaging member is positioned rearwardly with respect to the leading edge and the direction of conveyance of the shellfish, whereby the engaging means engages the shellfish once the shellfish has substantially passed the leading edge. According to a third aspect, the invention may broadly be said to consist in a shellfish opening system comprising:

conveying means for conveying the shellfish;

heating means adapted to heat the top shell of the shellfish substantially adjacent abductor muscles of the shellfish as they are conveyed by the conveying means, causing the shellfish to release the top shell and thereby partially opening the shellfish; and

a shell removal device adapted to remove the top shell of the shellfish by insertion into the partially opened shellfish and engagement with the top shell; and sensing and control means adapted to sense the size of the shellfish conveyed towards the shell removal device, and adjust the height of the shell removal device accordingly. Preferably the sensing and control means is further adapted to sense whether the heating means has caused the shellfish to partially open, and to control the application of heat accordingly.

Preferably the sensing and control means is further adapted to discard any shellfish which are not partially opened by the heating means once the shellfish has been conveyed past the heating means.

According to a fourth aspect, the invention may broadly be said to consist in a shellfish opening system comprising:

conveying means for conveying the shellfish;

a plasma torch adapted to heat the top shell of the shellfish substantially adjacent an abductor muscle of the shellfish as they are conveyed by the conveying means, causing the shellfish to release the top shell and thereby partially opening the shellfish; and

shell removal means adapted to mechanically remove the top shell.

Preferably the plasma torch is adapted to rapidly expel an inert gas from a nozzle directed towards the approximate area of the shellfish abductor muscle, and to selectively create an electrical arc through the expelled gas adjacent the nozzle to turn at least some of the gas to plasma. Preferably the shellfish opening system further comprises a semi-cylindrical mounting frame comprising at least one arcuate slot within which said plasma torch is adjustably mounted. Preferably the shellfish opening system comprises a plurality of plasma torches.

Further aspects of the invention, which should be considered in all its novel aspects, will become apparent from the following description. Drawing Description

A number of embodiments of the invention will now be described by way of example with reference to the drawings in which:

Figure 1 is a partial diagram of a first embodiment of an automated shellfish opening system according to the present invention;

Figure 2 is a rear view of a shellfish receptacle suitable for use with an automated shellfish opening system according to the present invention;

Figure 3 is a diagram of a second embodiment of a shell removing device according to the present invention;

Figure 4 is a front view of the shell removing device of Figure 3;

Figures 5(a) - 5(c) show the removal of the top shell as a mussel is conveyed past the shell removal device according to the present invention;

Figure 6 is a diagram of a second embodiment of an automated shellfish opening system according to the present invention;

Figure 7 is plan view of the system of Figure 6;

Figure 8 is an isometric view of semi-cylindrical mounting frame for mounting plasma torches to a shellfish opening system; and

Figure 9 is a front view of the mounting frame of Figure 8.

Detailed Description of the Drawings

The present invention will be described herein below with reference to the drawings, in which various embodiments of the invention are shown by way of non-limiting example for illustrative purposes. Throughout the description like reference numerals will be used to refer to like features in different embodiments. The present invention provides a system for removing at least half of the shell of shellfish, in particular bivalve molluscs including, but not limited to, mussels, scallops, clams, oysters, cockles, pipis, and/or tuatuas. For illustrative purposes only, the invention will be described herein largely with reference to particular examples of the invention adapted for removing half of the shell of New Zealand green-lipped mussels. Referring first to Figure 1 there is shown a diagram of a first embodiment of an automated shellfish opening system according to the present invention. The system comprises a conveying means for conveying shellfish past a heating means and a shell removal device. The heating means directly heats the shellfish substantially adjacent the abductor and/or connector muscles as it passes on the conveying means, causing the shellfish to release the top shell and thereby gaping or partially opening the shellfish, without cooking the shellfish. The shell removal device enters the front of the shellfish and removes the top shell by bending it backwards and twisting it to one side, weakening the hinge ligament at the rear of the shellfish before the top shell is removed entirely by an engaging member which engages the shellfish substantially adjacent the hinge. In other words, the leading edge of the removal device causes the shell to both pivot and twist about the hinge ligament, while the engaging means tears the top shell from the bottom shell. The top shell is thus removed by weakening and breaking the hinge through a combination of torsion, tension, and shear forces, the shell removal device gradually peeling off the top shell due to the relative movement as the shellfish is conveyed forwards by the conveying means.

In the illustrated embodiment, the conveying means comprises a chain 10, driven by a sprocket and motor (not shown), upon which is mounted a plurality of shellfish receptacles 11. As shown in further detail from the rear in Figure 2, the receptacles are preferably shaped to accommodate and brace the shellfish 15 (in this case, a mussel) with an up-turned rear end 20 shaped to correspond substantially with the hinged end of the shell fish. The receptacle thus preferably holds or cups the shellfish in a stable position with one half-shell 15a facing upwards and the other half-shell 15b facing downwards into the receptacle, as shown in Figure 1. The upturned rear end braces the shellfish so that the conveying means can propel the shellfish forwards, against a substantially opposing obstructive force from the shell removal device (described in further detail below). The front edge 21 of the receptacle may taper out to a relatively low and open or flat surface, as shown. A shellfish 15 may be placed on the shellfish receptacle 11 manually, or mechanically using any standard or known apparatus (such as a singulation and orientation conveyor) capable of reliably placing one shellfish on each receptacle in a forward- facing direction (i.e. the hinge of the shellfish towards the rear end 20 of the receptacle 1 1), preferably with one half-shell facing substantially upwards and the other facing substantially downwards. Although reference is made herein to a "top" half-shell 15a and/or "bottom" half-shell 15b, or simply top and bottom shells, it is to be appreciated that such terms are merely used to distinguish the two half-shells for illustrative purposes according to the preferred embodiments of the invention, and are not intended to be limiting in any way. The system may be modified to operate in any alignment, for example, without departing from the scope of the invention.

Once correctly placed, the conveying means conveys each receptacle and shellfish past the heating means. Referring again to the example of Figure 1 , the heating means is shown comprising a plurality of gas burners 12 positioned to directly apply heat in the general area of the shellfish abductor muscle as the shellfish passes, without cooking the shellfish. The heat causes the shellfish abductor muscle to release the top shell, "gaping" or partially opening the shell (due to the shell being urged open by the hinge ligament joining the two half shells), typically to a width of approximately 3 to 10 millimetres. According to the preferred embodiment of the invention, the system includes a sensing and control means to sense or detect whether a shellfish has opened, and to control the application of further heat from a secondary burner or group of burners. If the shell has opened after passing the primary burner or group of burners, it is not necessary to heat the shell further. Alternatively, if the shell has not opened, further heat is required and may be applied by the second or subsequent burner or group of burners, as appropriate. In the case of the gas burners 12, for example, the burners may be controlled through the use of a solenoid valve in the gas burner torch assembly.

If the shell has not opened after passing the heating means, the shellfish may be dead and should be discarded, using an ejection arm which is preferably mechanically or pneumatically operated. The sensing and control means is preferably also adapted to effect this by sensing whether the shellfish is open and actuating the ejection arm as appropriate. All open shellfish are conveyed towards the shell removal device for removal of the top shell. As described above, the shell removal device is adapted to remove the top shell by a combination of torsion, tension, and shear forces due to the relevant movement of the shell removal device with respect to the conveying means. The shell removal device is preferably fixed in position relative to the direction of movement of the conveying means (e.g. chain 10).

One possible embodiment of a shell removal device 13 is shown in Figure 1 , and a preferred embodiment is shown in further detail in Figures 3 and 4. Referring in particular to the preferred embodiment of Figures 3 and 4, the shell removal device 13 preferably comprises a leading edge 30 adapted to enter the front of the shellfish 15 between the top and bottom shells (15a and 15b, respectively). The leading edge 30 preferably comprises a rounded surface devoid of any sharp edges, such as a rolled edge, to avoid damaging the shellfish meat.

The leading edge 30 is preferably adapted to slidably engage an inner surface and/or outer peripheral edge of the top shell substantially toward a first side of the shellfish, and is therefore substantially asymmetric with respect to a substantially vertical plane passing through the major or longitudinal axis 22 of the shellfish receptacle 11 , and therefore the shellfish which it is adapted to engage. In the preferred embodiment, the leading edge 30 is preferably provided substantially adjacent one side of the body of the shell removal device. This is more clearly shown in the front view of the preferred shell removal device 13 in Figure 4, in which the leading edge 30 can be seen as being provided substantially towards the right hand side (when viewed from the front, i.e. in the direction of movement of the conveying means).

This asymmetric sliding engagement causes the top shell to both bend backwards about a substantially horizontal axis passing through the hinge ligament of the shellfish, and to twist about an axis substantially orthogonal to the horizontal axis, thereby applying tensile/compressive (on the dorsal/ventral ligaments, respectively) and torsional forces on the hinge ligaments. Alternatively, or additionally, the body may further comprise an angled member 17 on its top surface to guide the top shell to one side, as shown in Figure 1. The leading edge 30 is provided at a front end 31 a of a body 31 of the shell removal device. According to the preferred embodiment, the front end 31 a of the body is angled or curved upwardly with respect to the substantially planar body 31 , which is preferably substantially parallel with the conveying means above which the shell removal device 13 is provided in use. The curved or angled front portion 31a ensures that the lower surface of the shell removal device 13 slidably engages a peripheral edge of the bottom shell 15b. The bottom shell 15b of the shellfish is thus braced against and between the lower surface of the body 31 of the shell removal device and the shellfish receptacle 11 , such that the bottom shell 15b of the shellfish (including the shellfish meat) is continued to be conveyed forward by the conveying means as the leading edge 30 engages and removes the top shell 15a.

The body 31 of the shell removal device 13 preferably further includes an engaging member adapted to engage the shellfish at or substantially adjacent the hinge ligament to remove the top shell 15a from the bottom shell 15b by way of a substantially shearing force. According to the preferred embodiment, the engagement member comprises a downwards projection 32 provided on a side of the body 31. The projection 32 is preferably provided on the side of the body towards which the top shell 15a is twisted or pivoted by the leading edge 30, and is thus on the side of the body 31 opposing that to which the leading edge 30 is substantially adjacent. The downward projection 32 is preferably positioned rearwardly with respect to the leading edge 30 and the front end 31a of the body such that it engages the shellfish after the top shell 15a has been substantially opened and twisted by engagement with the leading edge 30.

Operation of the shell removal device is illustrated in detail in the series of drawings in Figures 5(a) to 5(c), which show a detailed rear isometric view of the shell removal device and a shellfish receptacle 11 upon which a mussel is provided and conveyed by the chain 10. The mussel is partially open when it reaches the shell removal device as shown in Figure 5(a), and asymmetric engagement of the leading edge 30 with the mussel between the top and bottom shells causes the top shell 15a to pivot backwards while simultaneously twisting about the hinge ligament as shown in Figure 5(b), until the top shell lays open (i.e. at approximately 180° about a horizontal axis, such as the hinge ligament) but substantially orthogonal (i.e. at an angle of between approximately 45° and 135° about a substantially vertical axis) with respect to the bottom shell 15b, as shown in Figure 5(c). The bottom shell 15b is braced between the receptacle 11 and a lower surface of the shell removal device as it is propelled forward until the top shell 15a engages the downward projection 32 to tear or shear the top shell away from the bottom shell. The receptacle 11 , in particular the upturned rear end thereof, is preferably shaped to prevent the top shell 15a merely twisting to pass beneath the shell removal device.

The top shell, once separated from the bottom shell, is preferably directed via a chute system to a waste conveyor. To ensure that the leading edge 30 enters the partially-open shellfish and the bottom shell 15b may pass beneath the shell removal device 13, the shell removal device preferably further includes adjustment means to automatically adjust the height of the shell removal device with respect to the conveying means. The system therefore automatically adapts to accommodate various sizes and/or species of shellfish with no need for manually adjusting the system or pre-sorting/grading the shellfish to ensure reliable operation.

According to the preferred embodiment as illustrated in Figure 3, the adjustment means comprises a servomechanism including a pneumatic actuator 33 operated by the aforementioned sensing and control means to automatically adjust the height of the shell removal device 13 based on the size of the next shellfish. It is to be appreciated, however, that any suitable sensing means, control means, and/or actuator may be used without departing from the scope of the invention. In particular, the adjustment means may use a separate sensing and control means, and alternative actuators may include hydraulic actuators and/or electric motors or servomotors.

According to the preferred embodiment, the sensing and control means used to control either or both of the heating means or the shell removal device comprises an optical sensor 16. Preferably the sensing means comprises a plurality of pairs of substantially collimated light sources and light sensors at various heights, whereby passage of a shellfish may interrupt the passage of light between each light source and sensor pair. With knowledge of the height of the light source/sensor pairs, the approximate size of the shellfish may be determined by monitoring the interruption of light as the shellfish is conveyed past the sensors. Preferably the light sources each comprise an infrared light emitting diode (LED), and the light sensors each comprise an infrared detector. In alternative embodiments, however, the sensing means may be communicatively coupled with any suitable means for sensing the approximate size or height of a shellfish, and may include other non- contact or contacting sensors such as visible light optical sensors, laser distance sensor, machine vision, ultrasonic range sensors, and/or micro-switches, for example.

The control means may comprise any suitable means for controlling the system, in particular the actuation of the heating means and/or adjustment of the height of the shell removal device, such as a programmable logic controller (PLC) or microcontroller, for example. Implementation of such a control means is considered to be within the ambit of skills of a person familiar with the technology in view of the description of the invention, and is thus not described in detail herein. Referring to Figures 6 and 7, a preferred embodiment of an automated shellfish opening system according to the present invention is shown.

In this embodiment, the conveying means comprises two chains 10 between which are provided bars 60 on each of which are mounted three receptacles 1 1 , thus forming three processing lines or rows. The two chains 10 mesh with drive sprockets 61 mounted to an axle driven by an electric motor and gearbox 63. The conveyor chains 10 and receptacles 1 1 thus all move continuously at the same speed. In other embodiments, each processing line or row of receptacles may be mounted to an independent chain 10 which may convey the shellfish at the same or different speeds, the system may comprise any number of processing lines or rows, the movement of the receptacles may be indexed (i.e. intermittent, staged movement), and/or the conveying means may comprise a belt or screw conveyor, for example, without departing from the scope of the invention. In this embodiment of the invention, the heating means are shown as a fixed gas burner or torch assembly 12. Only one torch assembly 12 (comprising two burners/torches) is shown in these figures for clarity, but there are preferably between 4 and 8 such heat source assemblies provided for each conveyor line. Alternatively, a single movable heat source may be provided to track the movement of each shellfish and thus provide a continuous source of heat for a required period. In use, the gas burners would be coupled to a gas supply to fuel the burner. However, the supply lines are not shown for clarity reasons. A skilled person could readily select and couple an appropriate source of the required gas to the gas burners. In other embodiments, the heating means may be a laser, an infrared heater, or any other suitable source of heat sufficient to gape or partially open the shellfish. In a preferred alternative embodiment, for example, the heating means comprises a plasma torch or brush, as described in further detail below. The shellfish, partially opened by the heating means, are conveyed towards the shell removal devices 13 which remove the top shells of each shellfish. The conveying means and/or receptacle 1 1 may or may not be adapted to yield slightly as the shellfish passes beneath a lower surface of the shell removal device 13. The bottom shell 15b and shellfish meat attached thereto may then be transferred to another conveyor such as a conveyor belt and taken away for further processing, such as cleaning, grading, cooking, freezing, and/or packing, for example. Alternatively, or additionally, such processing may take place prior to the shellfish being processed by the automated shellfish opening system of the present invention. The system may also be modified or adapted for further processing to take place between the opening and shell removal steps, such as debearding (i.e. removal of the byssal threads) for example.

According to another aspect, the invention may be said to consist in an automated shellfish opening system including a plasma torch or "brush" adapted to heat the shell of a shellfish substantially adjacent the abductor muscle, causing the abductor and/or connector muscles to release from the heated shell, thereby partially opening the shellfish. The shellfish may then be processed further by removing the shell or a half- shell, eviscerating the shellfish, and/or extracting the shellfish meat from the shell, by any known process. The plasma torch may be used, for example, in an automated shellfish opening system or with a shell removal device as described above, but is in no way limited to use with such systems/devices.

A plurality of plasma torches 80, supplied by Applied Plasma Technologies of McLean, Virginia, are shown mounted to a semi-cylindrical mounting frame 81 in Figures 8 and 9. Arcuate slots 82 in the mounting frame 81 enable the position and angle of the plasma torches 80 to be adjusted. In use, the mounting frame 81 would be provided parallel with, and above, a chain or other conveyor carrying the shellfish the so that heat generated by the torches is directed, in use, towards the shellfish as they are conveyed substantially along the length of the mounting frame. For example, the plasma torches 80 and mounting frame 81 may be substituted for the gas burners 12 in the system of Figures 6 and 7.

To heat the shell using a plasma torch 81 , an inert gas or fuel-air mixture is expelled from a nozzle 90 of the plasma torch at high speed towards the approximate area of the shellfish abductor and/or connector muscle. The inert gas is preferably air, although a small amount of liquid petroleum gas (LPG) may be added if a higher temperature is required.

An electrical arc is selectively formed through the expelled gas adjacent the nozzle to turn at least some of the gas to plasma (ionized gas). The plasma torch 81 can thus be controlled electronically, and has significant advantages over other heat sources by way of improved control, high temperatures, and obviating the need for ventilation and exhaust means necessary for gas torches, for example. In use, the plasma torches would be coupled to a gas supply, pump, or compressor (not shown), and an electrical power supply (also not shown). The requirements, and thus selection and coupling, of appropriate gas and power supplies would be apparent to a skilled person. The system may also include sensing and control means to control the application of heat until the shellfish opens or it becomes apparent that the shellfish will not open, as described above with respect to the first aspect of the invention which utilises gas burners. Compared to other potential heating means, the plasma torches have further advantages in terms of one or more of lower running costs, production of sterilizing ozone, and durability. The plasma torches may also offer additional advantages over gas burners including, but not limited to, improved ignition reliability, improved combustion efficiency, improved flame stability, and reduced emissions. The present invention may also broadly be said to consist in the methods for opening a shellfish and/or removing at least a half-shell of the shellfish as performed by the above-described systems and devices. From the foregoing it will be seen that the present invention provides a shell removal device, a system including the shell removal device, and a shellfish opening system including a plasma torch, each of which overcome or ameliorate one or more disadvantages of the prior art. In particular, the shell removal device has been found to be effective and reliable in automatically and consistently removing the top shell of a bivalve mollusc which has been partially opened, by using a combination of forces to weaken and break the hinge ligament of the shellfish. A system including at least one such shell removal device also offers improved reliability, adaptability and scalability, leading to increased throughputs, less downtime, and/or higher recovery rates (i.e. proportion of shellfish from which the top shell is successfully removed). Trials of a prototype three-conveyor or processing line system according to the invention have resulted in throughput of over 150 mussels per minute, with a 95% recovery rate. The plasma torch effectively heats the shellfish causing it to partially open, and provides advantages in terms of improved control and high temperature without the need for ventilation and exhaust systems.

Unless the context clearly requires otherwise, throughout the description, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including, but not limited to".

Although this invention has been described by way of example and with reference to possible embodiments thereof, it is to be understood that modifications or improvements may be made thereto without departing from the scope of the invention. The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features. Furthermore, where reference has been made to specific components or integers of the invention having known equivalents, then such equivalents are herein incorporated as if individually set forth. Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

Claims

1. A shell removal device for removing a top shell of a partially opened shellfish by way of relative movement between the shellfish and the shell removal device, the shell removal device having a body comprising:

asymmetric leading edge adapted to enter the front of the partially open shellfish and slidably engage the top shell substantially toward a first side of the shellfish, to pivot and twist a hinge ligament between top and bottom shells of the shellfish about substantially orthogonal axes; and

2. The shell removal device of claim 1 , wherein the engaging member is positioned rearwardly with respect to the leading edge such that the engaging member engages the shellfish after the leading edge pivots and twists the hinge ligament.

3. The shell removal device of claim 1 or claim 2, wherein the engaging member removes the top shell from the bottom shell by way of a substantially shearing force.

4. The shell removal device of any one of claims 1 to 3, wherein the engaging member comprises a projection projecting downwardly with respect to the body.

5. The shell removal device of any one of claims 1 to 4, wherein the leading edge comprises a rolled edge.

6. The shell removal device of any one of claims 1 to 5, wherein a lower surface of the body is adapted to slidably engage the lower shell to brace the lower shell against the engagement of the leading edge and the engagement member with the top shell.

7. The shell removal device of any one of claims 1 to 6, wherein the relative movement of the shell removal device and the shellfish creates tension, torsion, and shear forces on the hinge ligament, thereby weakening and breaking the hinge to remove the top shell.

8. A shellfish opening system comprising: 2012/039634 PCT/NZ2011/000198 conveying means for conveying the shellfish;

9. The shell opening system of claim 8, wherein the conveying means is adapted to convey the shellfish past the heating means and the shell removal means in a forward direction, whereby the heating means and the shell removal device are fixed in position relative to the direction of movement.

10. The shell opening system of claim 8 or claim 9, wherein the conveying means is adapted to convey the shellfish individually on one or more receptacles such that the shellfish are substantially forward-facing, the receptacles being curved upwardly towards the rear to brace the shellfish against the shell removal device.

11. The shell opening system of any one of claims 8 to 10, wherein the direct heating means comprises at least one plasma torch or gas burner.

12. The shell opening system of any one of claims 8 to 11 , wherein the system further comprises a first sensing and control means to sense whether a shellfish has opened and to control the direct heating means accordingly.

13. The shell opening system of any one of claims 8 to 12, wherein the shell removal device comprises adjustment means to adjust the height of the shell removal device to accommodate various sizes and/or species of shellfish.

14. The shell opening system of claim 13, wherein the adjustment means comprises a pneumatic actuator. 2012/039634 PCT/NZ2011/000198

15. The shell opening system of claim 13 or claim 14, wherein the system further comprises a second sensing and control means to sense the size of the shellfish and control the actuator to automatically adjust the height of the shell removal device accordingly.

16. The shell opening system of any one of claims 8 to 15, wherein the engaging member is positioned rearwardly with respect to the leading edge and the direction of conveyance of the shellfish, whereby the engaging means engages the shellfish once the shellfish has substantially passed the leading edge.

17. A shellfish opening system comprising:

conveying means for conveying the shellfish;

a shell removal device adapted to remove the top shell of the shellfish by insertion into the partially opened shellfish and engagement with the top shell; and

sensing and control means adapted to sense the size of the shellfish conveyed towards the shell removal device, and adjust the height of the shell removal device accordingly.

18. The shellfish opening system of claim 17, wherein the sensing and control means is further adapted to sense whether the heating means has caused the shellfish to partially open, and to control the application of heat accordingly.

19. The shellfish opening system of claim 17 of claim 18, wherein the sensing and control means is further adapted to discard any shellfish which are not partially opened by the heating means once the shellfish has been conveyed past the heating means.

20. A shellfish opening system comprising:

conveying means for conveying the shellfish;

a plasma torch adapted to heat the top shell of the shellfish substantially adjacent an abductor muscle of the shellfish as they are conveyed by the conveying means, causing the shellfish to release a top shell and thereby partially opening the shellfish; and

shell removal means adapted to mechanically remove the top shell.

21. The shellfish opening system of claim 20, wherein the plasma torch is adapted to rapidly expel an inert gas from a nozzle directed towards the approximate area of the shellfish abductor or connector muscle, and to selectively create an electrical arc through the expelled gas adjacent the nozzle to turn at least some of the gas to plasma.

22. The shellfish opening system of claim 20 or claim 21 , further comprising a semi- cylindrical mounting frame comprising at least one arcuate slot within which said plasma torch is adjustably mounted.