Patent Application
20210321596
Trawl doors, also known as otter boards, deflectors, paravanes and vanes, hereinafter collectively referred to as “spreading devices”, are used at opposite sides of a fishing trawl or opposite sides of seismic system to keep the fishing trawl open or a line of seismic guns and streamers in their correct use position.
Trawl doors are used to open a system of fishing gear. They are set from the vessel into the sea with its fishing gear connected between them. The doors spread out to each side from the vessel and generate a distance so that the gear, namely the fishing trawl, wires and cables herein after referred to as a “system”, are in optimal fishing conditions.
A trawl door is connected to a steel wire cable or a synthetic rope leading from the vessel, and the fishing net is connected to the trawl door in the opposite direction with another set of steel wire cables or synthetic ropes.
Trawl doors are generally used in pairs where the trawl door on the right side is called “starboard door” and the trawl door on the left side is called “port door”.
Deflectors, paravanes or vanes are used to spread a system of streamers for a seismic survey. They are also used in pairs and are set from the vessel in a similar manner to trawl doors in order to pull the streamers to each side of the vessel.
Paravanes are almost without exception, connected to synthetic ropes leading from the vessel and the seismic system, between the streamers and other components are also connected with synthetic ropes.
In essence, trawl doors and paravanes have the same purpose, to spread and hold the components in position therebetween.
Overall in the industry, the method to change the positioning of a trawl door or paravane, its angle of attack or pitch or roll, is both a complex and time consuming process as it is necessary to pull the spreading device to the surface to the vessel or onboard the vessel. Connecting units, shackles, connector or hooks leading to and from the spreading devices are disconnected and re-connected in different positions and the system is set out again into the sea.
It is known to construct a trawl door in such a way that the lateral force which it exerts is adjustable. Our European Patent No EP 2734039 B1, it is described and claimed: “A spreading device (10) for trawl fishing and seismic survey operations, the device comprising:-
The object of the present invention is to provide a manually adjustable spreading device.
According to the invention there is provided a spreading device for trawl fishing and seismic survey operations, the device comprising:
Normally one or more upper panels and one or more lower panels are fixed, preferably the aftermost panels in the device, with the other panels being adjustable. There may be only single forward panels or two or more forward panels. In the preferred embodiment there are two forward panels. One only of these may be adjustable, but preferably they both are.
The adjustable panels could be pivoted at trailing edges or intermediate axes between the respective frames. However, in the preferred embodiments they are pivoted substantially at their leading edges.
The manual adjustment means is conveniently provided by sets of apertures aligned at different angles and able to receive pins to set the adjustment. The apertures can be arrayed in the direction of adjustment, i.e. circumferentially with respect to the local direction of adjustment. However, they are preferably arrayed obliquely, whereby finer adjustment is achievable.
It is envisaged that the manual adjustment means can be provided at one or all of the frames, though they are preferably at the intermediate frame. The adjustment means can be provided on the top side of the intermediate frame, preferably however, they can be provided on both the top and bottom side of the intermediate frame.
To provide interconnection of the frames at the leading edges of adjustable panels, fixed members can be provided close to the leading edges. Preferably these are hydrodynamically shaped in cross-section to divide flow past them to respective sides of the panels.
To help understanding of the invention, a specific embodiment thereof will now be described by way of example and with reference to the accompanying drawings, in which:
Referring to the drawings,
The spreading device 100 of
The spreading device 100 of the invention has an upper frame 111 and a lower frame 112, separated by an intermediate frame 113. Between the upper and intermediate frame, there are three panels. The first two panels or hydrofoils 22, 23 are adjustable and have fixed leading edges 25, 26. These extend structurally between the frames, that is the leading edges 25, 26 welded to the upper frame 111 and the intermediate frame 113 and the intermediate frame 113 and the lower frame 110.
Third, after panels 24 fixedly interconnect the upper & intermediate and intermediate & lower frames respectively.
Both the upper and lower first and second fixed leading edges, 25, 26, are supportingly welded to each other by horizontal bars 21, with the second leading edge 26, being welded to the fixed third panel 24. These bars extend at both the front and rear faces of the spreading device 100 to act as a protection for the hydrofoil bodies.
The first and second hydrofoils 22, 23, have pivot round bar handles 35 extending between sockets (not shown) in the respective frames. The first and second hydrofoils have inner and outer panel plates 40, 41, which are curved to provide the panels with hydrodynamically induced lateral force.
For pivotal adjustment of the hydrofoils 22, 23, as shown
By adjusting the position of the first and second hydrofoils, 22, 23, the volume of water passing through the spreading device 100 is controlled, and as a result, so is the force exerted on the hydrofoils. This allows the device's position in the water to be altered, either vertically or horizontally.
A lug 7 is attached to the base of first and second upper hydrofoils by a bolt 4 that extends through it, passing through the chosen aperture in the intermediate frame 13 to hold the lug in place. A pin 6 passes through the head of the bolt 4 and subsequently through an aperture 5 in the side of the lug, thus restricting rotation of the bolt. A carabiner 30 passes through a slot in the end of the pin 6 to hold it in place.
The spreading device 100 has a slight inward facing curvature wherein the upper and lower frames extend in opposite directions from the intermediate frame 113.
There are a pair of apertured wings 37 extending inwards from the upper and lower faces of the intermediate frame 113. A threaded screw 40 extends through the apertures on both of the wings 37, to be secured in place by a nut 38 on the underside of the bottom wing. The screw 40 passes through four ears 36 on a plate 29, the plate itself having four separate apertures 31 onto which the towing cables will attach. The to ears 36 and the intermediate frame 113 being separably supported by individual hollow tubes 22. The plate can be rotated about the screw to adjust its radial position, thus altering the attachment position of the towing cables.
The outer face of the spreading device 100 is shown in
The upper first and second hydrofoil bodies, 22 and 23 respectively, have a handle 35 each in order to aid the user to physically adjust the position of the hydrofoils.
The invention is not intended to be restricted to the details of the above described embodiment. Alternatively, the bolts 4 could be held in place using an alternative locking mechanism such as a linchpin or split pin that is directly attached to the bolt, rather than through a pin 6.
Furthermore, the bolts 4 could have a threaded end such that upon passing through the aperture, they can be locked in place with a nut.
It can be envisaged that any other suitable locking mechanism could be used instead of a bolt, pin and R-clip.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1811369.6 | Jul 2018 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2019/055793 | 7/8/2019 | WO | 00 |
