GB2456518A

GB2456518A - A shellfish dredge comprising teeth welded to a bar

Info

Publication number: GB2456518A
Application number: GB0800687A
Authority: GB
Inventors: Andrew Fraser Barr; Thomas Iain Nicholson
Original assignee: BARRNON Ltd; TN TRAWLERS Ltd
Current assignee: BARRNON Ltd; TN TRAWLERS Ltd
Priority date: 2008-01-16
Filing date: 2008-01-16
Publication date: 2009-07-22
Also published as: GB0800687D0

Abstract

A shellfish dredge comprises a bar 6 of substantially rectangular cross-section onto which teeth 8 have been welded. Each tooth has a first face 14 which contacts to a first face of the bar 6 and a projection 16 defining a second face 18 which contacts a second face of the bar 6. The tooth 8 and bar 6 are welded together along contacting faces.

Description

2456518

TITLE

Teeth for shellfish dredges

DESCRIPTION Technical Field

The present invention relates to the teeth that are fixed to a bar forming part of a shellfish dredge.

Background Art

Dredges are commonly used to fish for scallops and other shellfish. An example of a conventional shellfish dredge is shown in Figure 1 and includes a frame 22 that enables the dredge to be connected to a towing warp 24, a bar 26 carrying spaced teeth 28, and an enclosure or net 30 having an open mouth 32. The teeth 28 are normally made of strip-milled steel and are welded directly to a face of the bar 26.

The bar 26 may be pivotally mounted with respect to the frame 22 and spring-loaded so that the teeth 28 are urged into a vertical position for raking the sea bed but are allowed to pivot or yield when they come into contact with obstructions during use.

In use, the shellfish dredge is dragged along the sea bed behind a marine vessel such as a trawler TR. Shellfish, which often lie recessed in the fine gravel and sand on the sea bed, are raked out by the teeth 28 and swept into the enclosure or net 30.

Contact with obstructions on the sea bed may cause the teeth to shear leaving just an upper part of the tooth still welded to the bar. Teeth may also become completely detached from the bar as a result of weld fatigue.

Summary of the Invention

The present invention provides a tooth for a shellfish dredge, wherein the tooth has a first edge for contacting a first face of a bar and a projection defining a second edge for contacting a second face of the bar.

The addition of the projection strengthens the tooth and increases the effective area that is available for welding, thereby making the tooth less susceptible to damage and shearing and reducing the risk of weld fatigue.

The angle between the first and second edges will depend on the cross-section of the bar to which the teeth are to be fixed. More particularly, the shape and/or contour of the first and second edges may correspond to the shape and/or contour of the first and second faces of the bar.

The present invention further provides a bar for a shellfish dredge, wherein the bar has a first face and a second face and at least one tooth as described above fixed to the bar. In practice, the bar will normally carry a plurality of identical teeth (typically no more than nine) spaced apart along its length.

The at least one tooth is preferably welded to the bar. In this case, the weld preferably extends substantially along the first and second edges of the at least one tooth. The at least one tooth is preferably welded to the first and second faces of the bar.

The present invention further provides a shellfish dredge comprising a bar as described above. The shellfish dredge will preferably further comprise a frame that enables the dredge to be connected to a towing warp (optionally by means of a tow bar) and an enclosure or net having an open mouth. The bar will preferably be pivotally mounted with respect to the frame and spring-loaded.

The overall dimensions, weight and construction of the shellfish dredge and its various component parts (including the teeth and the bar) may be constrained to be within certain legal limits.

Drawings

Figure 1 is a perspective view of a conventional shellfish dredge;

Figure 2 is a perspective view of a bar carrying spaced teeth according to the present invention;

-3 -

Figure 3 is a side view of the bar of Figure 2;

Figure 4 is a front view of the bar of Figure 2; and

Figure 5 is a side view of a tooth according to the present invention.

5 A bar 2 for a shellfish dredge will now be described with reference to Figures 2 to 5.

The bar 2 is made of steel and is mounted to a steel frame (not shown) of a shellfish dredge in a suitable way.

10 The bar 2 has a rectangular cross section and includes a bottom face 4 and a side face 6.

Nine identical teeth 8 are welded to the bar 2 along its length. A single tooth 8 is shown in more detail in Figure 5 and includes a pointed (lower) part 10 that is in 15 contact with the sea bed when the shellfish dredge is used and which rakes out the shellfish. An opposite (upper) part 12 includes a first edge 14. A substantially triangular-shaped projection 16 defines a second edge 18 that is at right angles to the first edge 14.

20 To fabricate the bar 2, each tooth 8 is positioned with its first edge 14 in contact with the side face 6 of the bar and its second edge 18 in contact with the bottom surface 4 of the bar. The addition of the projection 16 therefore helps to position the tooth 8 correctly relative to the bar 2 during the fabrication process. The tooth 8 is then welded to the bar 2 to fix it in place. As shown in Figures 3 and 4, the weld 20 runs 25 along both the first and second edges 14, 18 of the tooth on both sides of the tooth. In other words, the tooth 8 is welded to both the side and bottom faces 6, 4 of the bar. The projection 16 provides a greater surface area for welding adjacent the bar 2 and the weld 20 is therefore less likely to suffer from weld fatigue. The projection 16 also strengthens the tooth by providing additional support and helps to prevent unwanted 30 shearing.

Claims

1. A tooth for a shellfish dredge, wherein the tooth has a first edge for contacting a first face of a bar and a projection defining a second edge for contacting a second face of the bar.

2. A tooth according to claim 1, wherein the first and second edges are substantially at right angles to each other.

3 A bar for a shellfish dredge, wherein the bar has a first face and a second face and at least one tooth according to claim 1 or claim 2 fixed to the bar.

4. A bar according to claim 3, having a substantially rectangular cross section.

5. A bar according to claim 3 or claim 4, wherein the at least one tooth is welded to the bar.

6. A bar according to claim 5, wherein the weld extends substantially along the first and second edges of the at least one tooth.

7. A bar according to claim 5 or claim 6, wherein the at least one tooth is welded to the first and second faces of the bar.

8. A shellfish dredge comprising a bar according to any of claims 3 to 7.

9. A tooth for a shellfish dredge substantially as herein described and with reference to the drawings.

10. A bar for a shellfish dredge substantially as herein described and with reference to the drawings.