GB1573922A

GB1573922A - Shellfish traps

Info

Publication number: GB1573922A
Application number: GB755476A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-02-23
Filing date: 1977-02-23
Publication date: 1980-08-28

Description

(54) IMPROVEMENTS IN OR RELATING TO SHELLFISH TRAPS (71) We, NICHOLAS JOHN ASH WORTH and EILEEN FLORENCE ASH WORTH, both British subjects, and both of Stoverlake, Ashford, Aveton Gifford, Kingsbridge, Devon TQ7 4NL, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and bv the following statement:- The present invention relates to a shellfish trap, and particularly to a trap of the type comprising a body which is normally, but not always, of frusto conical shape having an entrance throat in the form of a tube-like passage projecting into the interior of the body.

Such shellfish traps are widely used for catching crabs and lobsters and as such are generally known as "crab pots" or "lobster pots": they are traditionally made of woven basketware and, in use, are placed on the sea bed with a piece of bait fixed to the rim of the throat where it projects into the interior of the body. If a shellfish such as a crab or lobster enters the pot through the throat in an attempt to reach the bait, it is led along the throat into the interior of the pot and having entered the pot is unable to leave since the exit, formed by the interior rim of the throat, is located near the centre of the space enclosed by the body of the pot whereas a shellfish can only crawl around the walls of the body. Even if it should happen to climb onto the throat itself, it cannot manoeuvre itself around the rim of the throat to enter the passageway defined thereby and so escape from the pot.

Sea water is extremely corrosive and basket work lobster pots therefore have only a very limited life before they are weakened to such an extent that they are no longer usable. This short life is further shortened by the abrasive action of the rocks and stones on the sea bed and on the sea shore against which the pots frequently collide both in use and when being handled ashore.

Modern materials have been tried as an alternative to the basketwork construction of conventionai pots, and various alternatives, for example utilising a welded mesh of tubular plastic or of plastics coated steel rod have been tried. These constructions have not proved entirely satisfactory, however, because of the cost of the materials and the manufacturing process, and because of the difficulty of joining the members to form the mesh securely in the rather complex shape required: in fact, because of the unusual shape, manufacture has usually been undertaken by hand, and this is obviously expensive at a time when labour is no longer cheap.

The present invention seeks, therefore, to provide a shellfish trap in which the disadvantages of fragility, high cost, limited availability, and the susceptibility to corrosion are largely overcome.

According to the present invention there is provided a shellfish trap of the type comprising a body having an entrance throat in the form of a tube-like passage opening into one face thereof and projecting towards the interior of the body, in which the body and throat are formed as separate members, the body member comprising a unitary moulded open frame structure of a mesh size greater than the claw span of a shellfish which could enter the trap through the throat, the trap further comprises an open mesh structure formed openings in the body member. The body may be of any convenient shape and is not necessarily restricted to the traditional "inkwell" shape conventionally associated with lobster pots and crab pots. For example, the body may be rectangular or cylindrical and the throat may open into one end or into one of the major faces (if rectangular) or the curved face (if cylindrical).

By forming the body member as a unitary moulded open frame structure its strength can be ensured, and by selecting a suitable material, for example a plastics such as polypropylene from which the pots can be moulded, the resistance to corrosion can also be ensured. In a preferred embodiment of the invention the body is of the traditional "inkwell" shape. It may be integrally formed with a base over the wider end thereof, but preferably the body is formed in this shape separately from Lhe base and is attachable thereto at the wider end of the body. The base also preferably comprises an open mesh structure formed as a unitary moulding.

Making the mesh size of the body such that any shellfish which can enter the pot through the throat will not have a sufficiently wide pincer grip to be able to span the mesh of the body, ensures that the shellfish cannot obtain sufficient purchase to crush the body.

In conventional lobster pots the base is attached to the body by winding a resilient strip around the adjacent frame elements effectively to tie the base and the body member together. Embodiments of the present invention may be made in such a way that this method of attachment can be used or the base may be snap-engageable onto the rim at the wider end of the body.

This conventional method of attachment has certain advantages since the resilient strip can then act as a buffer to resist abrasion.

By forming the body member in the "inkwell" shape, with the base as a separate member, transport and storage is facilitated since the two components can readily be stacked with like components, whereas the assembled trap takes up a considerable amount of space.

The throat member is preferably a solid plastics tubular member having flared ends, and is preferably snap-engageable into an opening in the narrower end of the body member. For this purpose the throat member may have an upstanding ridge, triangular in cross section, extending around it, the ridge serving to snap-engage in the rim of the opening in the body member. The flared ends of the throat facilitate handling since the easiest way to move the pots about in a boat is to insert the arm into the throat and grasp its lower rim.

There may further be provided at least one spacer element fitted between the base and body member when the trap is assembled, the spacer element serving to provide an escape route for small fry which may enter the trap through the throat.

The trap includes a net which covers at least the openings in the body member. The net may be a plain panel sewn into a tubular form, secured to the ends of the body member by tying, or may be specifically shaped to fit and have a draw-string or resilient band around the neck by means of which it can be fitted onto the body member. If a plain tubular net is tied onto the body member, the tying element may also be used to tie together the body member and the base.

In order to resist degradation by sea water, the net would preferably be made of a plastics material which has a long or indefinite life in sea water. However, this may mean that any traps lost or misplaced, by the fisherman could become almost permanent traps for shellfish, the decomposing remains of each trapped fish serving to lure in further shellfish. In order to avoid this, it is preferable that any plastics material netting used to cover the shellfish trap of the present invention includes a biodegradable panel which would decompose after a predetermined time to form an opening sufficiently large for shellfish entering the trap through the throat to escape unharmed.

In embodiments of the invention in which the base is snap engageable in the wider end of the body, the body member and/or the base member may be provided with a replaceable resilient buffer element, or with means for receiving such a buffer element.

Such a buffer element would be sacrificial in that it would be shaped to project from the trap to receive any knocks or abrasions to which the trap may be subject in use. For this reason such buffer elements should be readily removable for replacement.

The body member is preferably constituted by a plurality of circumferential frame elements extending parallel to the ends of the body member, and a plurality of generally axial frame elements extending from end to end of the body member, the axial frame elements varying from a T-shape cross section to a cruciform cross section along their length. Likewise, it is preferred that the circumferential frame elements have.

a channel section and the axial frame elements are stepped at each junction with a circumferential frame element. This construction ensures adequate strength while economising on the material used in order to obtain maximum economy of manufacture.

The base member may be provided with a plurality of locating studs or projections.

shaped to engage in the openings or an adjacent base to assist in stacking thereof.

Similarly, projecting studs may be provided to assist in locating the base member into the body member which, in this case, is preferably provided with cooperating recesses for receiving the studs.

One embodiment of the present invention will now be more particularly described. by way of example, with reference to the accompanying drawings, in which: Figure 1 is an exploded perspective view of the embodiment; Figure 2 is a perspective view of the assembled trap; and Figure 3 is a central vertical cross section of the embodiment.

Referring now to the drawings there is shown a shellfish trap generally indicated 11 which is formed to represent the traditional "inkwell" shape lobster pot. The trap 11 comprises a body member 12a, a base member 12b and a throat member 12c.

The body member 12a is generally frusto ellipsoidal, and has a plurality of circular circumferential members 13 spaced apart bv "axial" members 14 which extend from the wider end of the body 12a, formed by the largest of the circumferential members 13a. to the narrower end of the body 12a, formed by the smallest of the members 13d which is in the form of a perforated annulus. The remaining circumferential members 13a, 13b. and 1 3c are all plain rings having a channel shape cross section. The "axial" frame elements 14 are in the form of a flat web the plane of which is parallel to a radial plane, the web 14a extending the full length of the "axial" frame element; the web 14a is reinforced between each circumferential frame element by a flat strip 14b, 14c, 14d each of which lies in a plane perpendicular to the plane containing the web 14a and extends, along its length from a position adjacent the radially inner edge of the web 14a at the bottom of the associated section, to a position adjacent the radially outer edge of the web 14a at the top of the associated section. The "axial" frame elements thus vary from a T-shape cross section through a cruciform cross section to an inverted T-shape cross section along their length, and are stepped at the junction with each circumferential frame element 13.

This shape ensures adequate rigidity of the elements while economising on the amount of material used. The body is integrally moulded from a plastics material, and for this purpose a suitable thermoplastics material such as polypropylene or medium density polythene may be used. It is an advantage if the frame is slightly resilient and so a suitable balance must be struck between resilience, stiffness and strength when selecting the material for the body.

Into the opening in the perforated annulus 13d forming the narrower end of the body member is inserted a throat member 12e which is a tapering plastics tube having a flared entrance 15a and a flared exit 15b which is generally similar to the entrance I 5a. Around the outside of the throat member 12c, adjacent the entrance 15a, is a ridge 16. triangular in cross section, which serves to snap-engage the throat into the rim of the opening in the narrow end of the body member 12a. At the other end of the throat member 1 2c there are a plurality of further ridges 17, again of triangular cross section, which serve to locate a resilient band (not shown) which is used to hold in place strips of fish or other bait when the pot is assembled. It has been found in practice that a motor car inner tube cut into rings, of appropriate size forms a suitable resilient band for this purpose. The diameter of the throat is important in determining the maximum size shellfish which can enter the pot. For most uses a minimum diameter, at the lower end of the throat, of 8" is used, although for special purposes a throat having a minimum inside diameter of 6" can be provided.

The diameter of the throat is related to the mesh size of the base member 1 2b which is a unitary moulded structure having a lattice work of flat ribs 18, 19 extending perpendicularly to one another. The separation between adjacent ribs is in the region of 143", this being sufficiently great to prevent any shellfish which can enter through an 8" throat from obtaining sufficient purchase with their claws to crush the ribs 18, 19 and thereby escape. In order to economise on manufacturing costs the walls of the grid all meet at right angles without the customary radiusing; this economises in the production of the mould tool.

In use of the trap the three main elements are attached together, the throat member 1 2c being snap-engaged into the opening in the annular member 13d which defines the narrower end of the body member 12a, and the base member 12b being secured to the rim of the wider end of the body member 12a. For this purpose, the base member 12b may be tied on by wrapping around it a resilient strip of material which also encircles the wider circumferential frame element 13a. This is particularly convenient if a plain panel net is to be used over the pot since the end of the net and the base 12b can be attached to the wider rim of the body member 12a at the same time. Alternatively, the base 12b may be snap engageable into the circumferential frame element 13a. In this case a net specially shaped to fit over the shellfish trap may be provided, such a net having a generally frusto-conical form the narrow end of which is narrower than the outer diameter of the annular end element 13d, and the wider end thereof being formed with a draw string or being elasticated whereby it can simply be snapped into position.

Between the base 12b and the circumferential frame element 13a there may be provided a plurality of distance pieces 20, one of which is shown in the drawing. Such elements are of the order of U thick and if used, provide an exit for small fry which may have entered the pot through the throat 12c. If such distance pieces are used, the net covering the body 12a must be attached to the circumferential frame element 13a and not to the base 12b to ensure that such exit is not obstructed.

WHAT WE CLAIM IS:- 1. A shellfish trap of the type comprising .

body having an entrance throat in the form of a tube-like passage opening into one face thereof and projecting towards the interior of the body, in which the body and throat are formed as separate members, the body member comprising a unitary moulded open frame structure of a mesh size greater than the claw span of a shellfish which could enter the trap through the throat, the trap further comprising a net covering at least the openings in the body member.

2. A shellfish trap as claimed in Claim 1, in which the body member is generally frusto-ellipsoidal in shape.

3. A shellfish trap as claimed in Claim 2, in which there is further provided a base separate from the body and attachable thereto at the wider end thereof, the base comprising an open mesh structure formed as a unitary moulding.

4. A shellfish trap as claimed in Claim 3, in which the base is snap engageable onto the rim at the wider end of the body.

5. A shellfish trap as claimed in any of Claims 2 to 4, in which the throat member is snap engageable in the narrow end of the body member.

6. A shellfish trap as claimed in Claim 5, in which the throat member has an upstanding ridge of triangular cross section extending around it, the ridge serving to snap engage in the rim of an opening in the narrow end of the body member.

7. A shellfish trap as claimed in any of Claims 3 to 5, in which there is further provided at least one spacer element separating the base and the body member, when these two are attached together. to provide an escape route for small fry which may enter the trap through the throat.

8. A shellfish trap as claimed in any preceding claim, in which the said net is made of a plastics material and has at least one bio-degradable panel set into it.

9. A shellfish trap as claimed in any preceding Claim, in which the body member, and/or the base member, is or are provided with a replaceable resilient buffer element.

10. A shellfish trap as claimed in any preceding claim, in which the body member is constituted by a plurality of circumferential frame elements extending substantially parallel to the ends of the body member, and a plurality of longitudinal frame elements extending from one end to the other of the body member.

11. A shellfish trap as claimed in Claim 10, in which the circumferential frame elements have a channel section, and the longitudinal frame elements are stepped at each junction with a circumferential element.

12. A shellfish trap as claimed in any of Claims 3 to 11, in which the base member is provided with a plurality of locating studs or projections shaped to engage in cooperating openings in the body member to assist in locating the base in position on the body member.

13. A shellfish trap substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. fry which may have entered the pot through the throat 12c. If such distance pieces are used, the net covering the body 12a must be attached to the circumferential frame element 13a and not to the base 12b to ensure that such exit is not obstructed. WHAT WE CLAIM IS:-

1. A shellfish trap of the type comprising .