GB2178778A - Trawl device - Google Patents

Abstract

A trawl device, suitable for collecting worms, shellfish and other such products from beneath a sand surface, comprises at least one elongated skid or skid assembly (5, 6), a grid member (4) fixed at a level below the surface of the skid or skid assembly and inclined upwardly in the direction of the length of the skid or skid assembly, and a collector bag (13) to receive material from the upper end of the grid member. <IMAGE>

Description

SPECIFICATION Trawl device The present invention is a trawl device, suitable for collecting worms, shellfish and other such products from beneath a sand surface.

There is a large demand from sea anglers for bait such as lugworm, clams andthe like. However, bait of this type is usually located below the surface of the sand and has to be retrieved by digging from a beach when tidal conditions permit. Recovery of bait in this way is hard and tedious work and therefore the supp ly of such bait to anglers is scarcely a viable proposi- tion. The demand from anglers is therefore usually greaterthan the supply and the price ofthe bait is accordingly high.

There is a clear need for a more economical and physically less strenuous method of recovering bait for commercial supply. An object of the present invention is to provide a device which is designed to meetthat need.

According to the present invention, a trawl device suitableforcollecting under-sand organismscomprises at least one elongated skid or skid assembly, a grid member, fixed at a level below the surface of said skid or skid assembly and inclined upwardly in the direction of length of said skid orskid assembly, and a collector bag, disposed to receive material from the upper end of said grid member.

The trawl device is, as its name indicates, dragged along over the sand surface with the lower end of the grid memberforwards. The grid member digs below the sand surface at a level determined by its distance below the skid level and thereby establishes a flow of sand and its contents upwards overthe grid. By virtue ofthe inclination ofthe grid and its movementforward, sand is caused to fall through the grid, while the organisms desired for bait remain on the grid surface and move upwardly and rearwardly into the collector bag, from where they are subsequently removed.

The device is supported, as stated, upon at least one elongated skid or skid assembly. While it is possi bletoobtainsatisfactoryresultswith asingleelon- gated skid of suitable design, it is much preferred that the device should have a plurality of skids, which may or may not themselves be individually elongated, in an elongated skid assembly. Preferably at least two skids are spaced apart athwart the length of the device and at least two skids are spaced apart down the length ofthe device. Thus the particularly preferred arrangement is an elongated assembly comprising three or more, especiallyfour, skids,thereby imparting a high degree of stability to the trawl device in use.

Advantageouslythe skids are pivotally mounted upon the trawl device, to lessen the stresses caused by movement ofthe device over irregular surfaces and also to assist in maintaining the device level over such surfaces.

The grid member is fixed at a level belowthe skid or skid assembly in an inclined position. The depth at which the grid member is fixed may be adjustable, for example by varying the position of a bolt associated with one relatively adjustable member in an elongated slot associated with the other or by varying the orientation of a skid or skids located forwardly of the grid member. Thusthe depth ofthegrid membermay be adjusted to accommodate different depths of sand over bedrock orto collect different desired baits located at different depths. The angle of inclination of the grid member may also be adjustable if desired but in general angularadjustmentofthe grid member independent of depth adjustment is unnecessary.

It is preferred that the angle of inclination of the grid member be between 5 degrees and 40 degrees below the horizontal, preferably between 10 degrees and 30 degrees. A particularly preferred angle of inclination is between 10 degrees and 20 degrees.

The grid member has to take a major part ofthe force imposed upon the trawl device and is therefore preferably very solid and rigid in its design. This result is very conveniently achieved by forming the grid memberofa numberofaligned bars, especially round bars, at the desired spacing. The forward end of the grid member is particularly exposed to potential damage and therefore preferably is in the form of a horizontal or inclined flat metal plate. The plate then functionsto lead the grid memberintothe sand and to direct the sand and its contents on to the grid member.

The trawl device ofthe present invention cuts a shallow channel in the sand and then redeposits the sand inthatchannel. However, especially when the device is working under water, the sides of the channel maytend to collapse intothe channel andthereby impede redepositing ofthefiltered sand and in turn adversely affectthe operation ofthetrawl. It is there- fore highlydesirableto dispose a pair of platesgener ally vertically atthe sides ofthe grid member and below its surface, in order to retain the integrity of the channel until the filtered sand has been redeposited.

The collector bag is disposed at the rear of the grid memberto receive material filtered out by the latter.

The bag is preferably easily removable to gain access to its contents and to permit itto be exchanged or replaced. Collector bags of different mesh size may be used, in order to varythe nature or size ofthe bait retained.

A ballast tank may be mounted upon thetrawl device, either simply to add weight to the trawl for normal use orto perm it the loading to be adapted to different operating conditions, for example the depth of water when the device is used underwater and the firmness of the sand being trawled.

The trawl device of the present invention isparticu- larly suited fortowing by a boat in relatively shallow depths of water. However it may also be used on exposed sand bytowing behind atractororother vehicle.

The device is ofparticularvalueforcollecting fishing bait and has been described accordingly. It may, however, be used forothersimilar purposes such as for collecting cockles or other products buried in sand.

The present invention will now be further described with reference to the accompanying drawings, which illustrate by way of example a preferred embodiment of the trawl device according to the invention. In the drawings Figure lisa side elevation ofthe device; Figure2 is a corresponding plan view; and Figure 3 is a vertical sectional view of a part ofthe device described below.

The trawl device illustrated in the drawings essen tiallycomprises a filter grid 4 mounted upon four skids, namely a pairofforward skids Sand a pairof rearward skids 6. Each of the skids is pivotally mounted to permitthe skid to adjust to irregularities in the ground surface but the freedom to pivot is restricted to a limited angle by stops (not shown). A cross-bar7 upon which the forward skids 5 are mounted is carried by side-arms 8 which are themselves adjustably pivotted at 9 to the frame of the trawl. Thus by releasing locking nuts which fix the pivotal angle at9 between the side arms 8 and the trawl frame, the vertical height of the skids 5 above the level ofthe front of the grid 4 may be changed.

To the front end of the grid 4 is welded a lifter plate 10, smoothly curved at its corners into vertical sandretaining side plates 11. Above the grid 4, the frame of the trawl supports ballast tank 12. Atthe upper (rear) end ofthe grid 4 a collector bag 13 offlexible net is removably secured.

In use,the illustrated trawl device is towed along the underwater sand surface 14, in the direction of the arrow, by a boat. The trawl is supported on the sand surface by the skids 5 and 6 and the lifter plate 10 cuts a channel inthesand. Sandfrom the channel passes overthe lifter plate 10 on tothefiltergrid 4, which removes solid articles such as clams and lugworms from the sand and allows the filtered sand to fall back into the channel. The side plates 11 keep the walls of the channel supported until the trawl has passed.

Material removed by the grid 4 passes on into the collector bag 13, wherein it remains, washed over by sea water, until it is subsequently removed with the bag.

Claims (13)

1. Atrawl device for collecting under-sand organisms, comprising at least one elongated skid or skid assembly, a grid member, fixed at a level below the surface of said skid or skid assembly and inclined upwardly in the direction of length of said skid or skid assembly, and a collector bag, disposed to receive material from the upper end of said grid member.

2. Atrawl device as claimed in claim 1, incorporating a skid assembly comprising at least two skids spaced apart athwart the length ofthe device and at least two skids spaced apart down the length ofthe device.

3. Atrawl device as claimed in claim 2, wherein the skid assembly comprises four said skids.

4. Atrawl device as claimed in any ofthe preced ing claims, wherein said skids are pivotally mounted for limited pivotting about a horizontal axis.

5. Atrawl device as claimed in any of the preced ing claims, wherein the working depth ofthe grid member is adjustable.

6. Atrawl device as claimed in any ofthe preced ing claims, wherein the angle of inclination ofthe grid member is between 5 degrees and 40 degrees below the horizontal.

7. Atrawl device as claimed in claim 6, wherein said angle of inclination is between 10 degrees and 20 degrees below the horizontal.

8. Atrawl device as claimed in any ofthe preceding claims, wherein the grid member comprises a numberofaligned, round bars.

9. Atrawl device as claimed in any of the preceding claims, wherein the forward end of the grid member is a flat metal plate.

10. Atrawl device as claimed in any of the preceding claims, having a pair of generally vertical plates at the sides of the grid member and below its surface.

11. Atrawl device as claimed in any of the preceding claims, wherein the collector bag is of open mesh and is mounted so as to permit its easy removal.

12. Atrawl device as claimed in any ofthe preceding claims, comprising also a ballast tank.

13. Atrawl device for collecting under-sand organisms, said device being substantially as hereinbefore described with reference to, and as illus- trated in, the accompanying drawings.