Introduction The present invention relates to a fishing dredge suitable for catching molluscs and in particular for catching scallops.

Background to the Invention Dredging is used for harvesting bivalve molluscs such as oysters, clams and scallops. A traditional scallop dredge is a framed basket attached to a set of connected iron rings or wire netting called a belly or chain belly. The lower edge of the frame has a raking bar, with or without teeth or swords depending upon the species of mollusc that is being caught. In use, the catch is lifted off the seabed or out of the sea by the raking bar or teeth and passes back into a basket or bag known as a belly. Depending on the size of the boat and the depth of water fished the number of dredges may vary from a single dredge towed behind the vessel to from 5 to 20 or more dredges per side. Dredges are generally attached to a towing bar and one is operated from each side of the vessel simultaneously.

Dredging for molluscs will now be described in more detail with reference to figures 1 to 3. Figure 1 shows a trawler 1 which has a tether or trawl warp 3 connected between the winch of the boat and a dredge 5 which is pulled along the sea bed 9. Figure 2 shows the features of a typical dredge set up. The dredges 11 are connected to the trawler via the trawl warp 3 which connects to a towing triangle 13. Four chain bridles 15 extend from the towing triangle 13 and are connected to a tow bar which has a pair of bobbin wheels 17. The tow bar couples the chain bridles 15 to dredges 2 .

The dredges 21 are shown in more detail in figure 3.ln this figure, dredge 23 comprises a frame 25 and a net bag 26. The frame is typically made from steel and has a plurality of teeth or swords 31 which extend downwards from the frame. Eyebolt 27, H-plate 29, spring 32 and paw 33 provide the mechanism by which the sword 31 engages with the sea bed in order to disturb the molluscs. In use, the molluscs are dug out from the sea bed by the sword 31 , they gather along the front surface of the frame 34 and then they pass through the frame into the net 26.

The teeth 31 mounted on the tooth bar are fixed in position and are connected to the frame at a pivot point towards the top of the frame. The tooth bar is also attached to a compression spring 32. In normal use the teeth 31 are retained in the downward position in which they dig into the seabed to uncover molluscs. However when a tooth encounters a hard object such as a stone, the tooth bar moves about the pivot point to raise the tooth bar and move over the object. This prevents the tooth bar from getting stuck on the sea bed. However, raising the tooth bar also means that the molluscs that have accumulated on the front of the tooth bar escape under the raised toothbar. Dredging in general is viewed as having a significant environmental impact because it agitates the sea bed and in the process causes significant damage. In addition, the act of dragging the dredges along the sea bed requires the trawler to use significant amounts of fuel to power its engines. International patent application WO 2010/020775 describes improvements relating to a fishing dredge. This prior art describes the use of teeth or swords which are resiliently mounted such that they can be displaced upwards to move over an obstacle on the sea bed such as a stone. ! Figure 4 is a side view which shows a frame 41 having an open side 42 which is supported by a diagonal frame member. The frame has a ground engaging rail 45 which is in contact with the seabed and which slides along the seabed in use. Support beam 47 extends across the frame and supports the sword or tooth 49 which is attached to the support beam 47 by means of a helical winding 51 with which it is integrally formed and is an extension of the spring as shown in figure 5. An abutment 53 is positioned above the helical winding and acts to retain the tooth 49, helical winding 51 and support beam 47 in position. The tooth 49 extends outwards from the frame such that it can scrape the seabed in order to uncover molluscs.

In use, the frame 41 is dragged along the seabed using rails 45 and the tooth 49 digs into the seabed in order to uncover molluscs. The frame 41 has eight teeth which are independently resiliently mounted on the support beam 47 such that when one of the teeth encounters a hard object such as a stone it will move backwards under tension in order to move over of the stone. As the teeth are all independently resiliently mounted the movement of one tooth over a stone does not affect the ability of the other teeth to continue the operation of digging into the seabed. Therefore even when one tooth encounters an object such as a stone and has to move, the remaining teeth can continue to collect molluscs.

However, there is a desire to improve the fuel efficiency of dredging, further reduce environmental impact of the dredging process and increase the catch.

Summary of the Invention

It is an object of the present invention to provide a more efficient fishing dredge.

In accordance with a first aspect of the invention there is provided a fishing dredge for making a catch of molluscs such as scallops, the fishing dredge comprising:

a dredge frame with a first and a second rotatable sea bed engaging members arranged on respective first and second sides of the dredge frame along the length of said sides; a catch tray for collecting an unearthed catch, the catch tray being positioned in the dredge frame between the first and a second rotatable sea bed engaging members a plurality of sea bed engaging teeth mounted on the dredge frame, the teeth being positioned at or near the front of the dredge frame for unearthing objects buried in the sea bed; the dredge frame further comprising a sorting mechanism positioned between the sea bed engaging teeth and the catch tray for separating the catch from other unearthed objects and for moving the catch into the catch tray. Preferably, the rotatable sea bed engaging member comprises a continuous track operatively connected to two or more wheels.

Optionally, the rotatable sea bed engaging member comprises one or more wheel arranged on each side of the dredge frame.

Preferably, the rotatable sea bed engaging member rotates as it crosses the sea bed in response to motion provided when the dredge is pulled along the sea bed.

Optionally, the rotatable sea bed engaging portion is powered.

The power source may be an electric motor, a hydraulic motor or other suitable system.

Preferably, the sorting mechanism comprises a rotatably mounted brush, mounted on an axis of rotation which extends across the front of the dredge frame behind the seabed engaging teeth, the rotation of which causes the catch to be moved into catch tray.

Preferably, the brush comprises a plurality of axially arranged bristles having a predetermined stiffness which allows unearthed objects which are denser, heavier or larger than the catch to pass through the bristles.

Optionally, the sorting mechanism comprises a brush fixed in position across the front of the dredge frame and having a plurality of bristles having a predetermined stiffness which allows unearthed objects which are denser, heavier or larger than the catch to pass through the bristles. Preferably the sorting mechanism extends through the catch tray.

Optionally, the sorting mechanism comprises a grating positioned above the catch tray. Preferably, the grating extends fully across the catch tray.

Preferably, the grating comprises a plurality of substantially parallel bars which extend from the front to the back of the dredge frame. Preferably, the grating comprises first and second alternate bars, the first bars being a distance D1 from the catch tray and the second bars being a distance D2 from the bars where D1≠ D2.

Optionally D1 is greater than D2. Optionally D2 is greater than D1.

Preferably the difference between D1 and D2 is 60mm.

Preferably, the catch tray comprises an enclosed box made wherein at least one surface of the box is made from an open mesh.

Preferably, at least the lower surface of the catch tray is made from an open mesh. Advantageously, most if not all of the surfaces of the catch tray are made from an open mesh, the mesh being sized to retain the catch in the catch tray. The use of an open mesh also allows water to move easily through the catch tray and for small debris objects such as sand and gravel to be easily removed from the catch tray.

Preferably, the bottom surface of the catch tray comprises a mesh situated towards the rear of the catch tray and an open section positioned substantially below the position of the sorting mechanism, Preferably, the dredge further comprises a base positioned below the catch tray and onto which debris which has passed through the sorting mechanism falls.

Preferably, the dredge further comprises a height adjuster which allows the height of the catch tray above the sea bed to be controlled.

Preferably, the dredge further comprises a height adjuster which controls the extent to which the teeth extend below the dredge. Optionally, the catch tray is removeably attached to the dredge frame such that it may be removed from the dredge frame to be emptied.

In accordance with a second aspect of the invention there is provided a dredge frame as defined in the first aspect of the invention.

In accordance with a third aspect of the invention there is provided a catch frame as defined in the first aspect of the invention.

Brief Description of the Drawings

The present invention will now be described with reference to the accompanying drawings in which:

Figure 1 is illustrates the process of dredge fishing;

Figure 2 illustrates a known type of fishing dredge;

Figure 3 is a side view of a known type of fishing dredge frame and belly; Figure 4 is a side view of another known type of dredge frame; Figure 5 is a rear perspective view and shows a dredge in accordance with the present invention;

Figure 6 is an exploded view from the front of the dredge shown in figure 5;

Figure 7 is a front view of the dredge shown in figure 5; Figure 8 is a side view of the dredge shown in figure 5; Figure 9 is a cutaway view from the side as shown in figure 8; Figure 10 is a plan view of the dredge shown in figure 5; and

Figure 11 A is a plan view of the sorting mechanism and figure 11 B is a side view of the sorting mechanism showing its position relative to a catch tray.

Detailed Description of the Drawings

Embodiments of the present invention provide an improved fishing dredge which:

1. moves across a sea bed on continuous tracks which are rotatably mounted on the side of the dredge; and

2. has a sorting mechanism which separates the catch from debris such as stones, sand and gravel which has been removed from the sea bed in the dredging process.

Figure 5 is a rear perspective view and shows an embodiment of a dredge 101 in accordance with the present invention which comprises a catch tray 103 located inside a dredge frame 104. The catch tray 103 has an open mesh-type structure which is designed to allow water and small debris to pass through the mesh but to retain the catch, typically scallops, inside the tray. As seen in figure 5, the dredges frame 104 comprises a track assembly 105 and a base 149 which connects together the two sides 105 of the track assembly. The towing frame 113 is connected to the front end of the dredge frame 104 and is connectable to a trawler or other means for pulling the apparatus along the sea bed.

Figure 6 is an exploded view of the dredge of figure 5 shown from the front of the apparatus. Figure 6 shows the dredge 101 , the catch tray 103 and the dredge frame 104. The catch tray 103 comprises a pair of side walls 115, a rear wall 117, a top wall 119 and a floor 121. In this embodiment of the present invention, the side walls 115 and the rear wall 117 all comprise a circular mesh which is sized to allow water and debris to pass through the mesh but to retain the catch within the catch tray 03. The top wall 119 is a square mesh; because debris and water will readily exit through the rear and floor of the catch tray, a smaller square mesh may be used for the roof to improve the strength of the catch tray. The floor 121 of the catch tray 109 comprises a circular mesh which, in this example of the present invention extends along the length of the catch tray but short of its full length. This leaves an open section 123 through which the brush 128 of the sorting brush assembly 127 extends. The floor 121 of the catch tray 103 has a leading edge 125 which comprises a set of circular mesh elements which extend diagonally downwards and forwards towards the tow bar 113 from the front end of the catch tray floor 121. Spacers 131 are provided between the tray floor 121 and the inner side surface of the track assembly 105 in order to correctly position the catch tray in the track assembly 105. The catch tray connector 133 connects together the side walls 115 to the floor 121 of the catch tray.

The dredge frame 104 comprises the track assembly 05, the towing frame 113, and the elements of the frame which are associated with digging up the molluscs and removing debris such as stones from the catch. The track assembly 105 comprises elements which are positioned on each side of the dredge frame and which are substantially identical. The track assembly comprises a support plate 106 upon which is mounted a plurality of rotatable wheels. In this example of the present invention four large wheels 109 are positioned at the lower part of the support plate 106 four smaller wheels 111 are positioned at the upper part of the support plate. The wheels 109, 111 are free to rotate and the track 107 is operatively connected to the wheels such that the track is connected to all of the wheels and is free to move when in connection with the rotatable wheels 109, 111.

The sorting brush assembly 127 is mounted at a position towards the front of the dredge frame 104. The brush 128 is axially mounted for rotation upon assembly 127 such that the bristles of the brush extend to and/or through the forward open section 123 of the catch tray floor 121. The presence of the open section 123 prevents damage to the brush which could occur as a result of frictional contact with the catch tray floor, it also allows for use of a brush with longer bristles than might otherwise be possible

The locking bar guide 135 and the height adjustment bolt 137 allow a user to set the position of the catch tray 03 with respect to the seabed engaging surface of the track 08. This ability to adjust this height is important for at least two reasons.

1. In use, the spring tines 141 will reduce in length as a result of the wear and tear.

It is therefore, important to be able to adjust the height of the tines to ensure proper operative contact with the sea bed.

2. The dredge may be used in different types of sea bed where the amount of sand and rock encountered by the dredge can differ. Adjustment of the height may improve the functioning and efficiency depending on the sea bed conditions.. The spring tines 141 are mounted upon a support bar/tube 139. The spring tines 141 extend downwards from the support bar/tube 139 beyond the seabed engaging section 108 of the track 107.

The stone pass base 149 comprises a pair of support beams 150 which extend towards the rear of the dredge frame 104. A mesh section 152 extends between the support beams 150 to be substantially in alignment with the open section 123 of the catch tray floor 121.

The above described features of this embodiment of the present invention are shown in figures 7 to 10. It is notable in figure 7 that the distance by which the tines 141 extend below the seabed engaging surface of the track 108. It is also notable that the leading edge 125 of the catch tray floor 121 acts as a barrier to prevent the catch from failing to enter the catch tray 103 by passing through the gap between the catch tray and the seabed engaging surface of the track 108.

In use, the dredge is pulled along the seabed by a trawler or other means. The force exerted by the trawler on the towing frame causes the track 107 to turn, thereby easing the passage of the dredge 101 across the seabed. As the dredge 101 is being pulled along, the tines 141 dig into the seabed in order to dig up molluscs (typically scallops). This process causes other debris such as sand and stones to be removed from the seabed.

It should be noted that large stones or other objects which are embedded are not moved and the spring loaded tine passes over such objects and returns to its original digging position. In addition, water moves through the dredge as part of this process. Water may assist with the removal of small debris because it can carry such debris out through the sides of the frame.

In the case of stones and other debris which has been dug up by the tines along with the molluscs, ail this material is pushed upwards into the frame 104 along the direction of the tines 141 and the catch tray floor leading edge 125. The material then comes into contact with the sorting brush assembly 127. The assembly brushes 128 are axial ly mounted and rotate so as to move the molluscs up and into the catch tray 103. Larger, heavier and denser objects such as stones pass through the brushes and onto the stone pass base 149 where they fall out of the bottom of the frame. Other small debris may be removed by the flow of water through the frame. In this embodiment of the present invention, the catch tray 103 is fixed to the dredge frame 104. In other embodiments of the present invention the catch tray may be removably attached to the dredge frame such that the dredge frame may be provided separately from the catch tray. In some circumstances easy removal of the catch tray allows for fast and efficient removal of the catch from the dredge because the catch tray is significantly lighter than the combined catch tray and dredge frame.

Figures 11 A and 11 B shows a further feature of the sorting mechanism in accordance with the present invention.

Figure 11 A is a plan view of the sorting mechanism and figure 11 B is a side view of the sorting mechanism showing its position relative to a catch tray such as that shown in figure 6. Figure 11A shows a grating 161 which comprises an outer substantially rectangular frame 163 and a number of bars arranged over the breadth of the frame. Bars R, 165 and Bars R2 167 are spaced at distances D, 169 and D2 171 from the catch tray 173 as shown in figure 11 B. The offset position of adjacent grating bars 165,167 and the distance between adjacent bars across 175 the breadth of the frame 163 is designed to assist with sorting scallops from other objects such as stones. In this embodiment, the adjacent bars are approximately 60mm apart with a height difference of about 60mm. It will be appreciated that the configuration of the grating will allow flatter items such as scallops to pass through the gaps between the bars in the grating and larger and/or rounder objects such as stones will be caught between bars in the grating and will not fall into the catch tray. Once a stone or similar object is caught on the grating 161 the flow of water through the dredge will move the stone to the rear of the grating where it will exit out of the back of the grating.

Improvements and modifications may be incorporated herein without deviating from the scope of the invention.