Patent Description:
Apparatus are known for burying cables in the seabed, and consist of a plough having a plough share which forms a trench in the seabed into which the cable is inserted by the plough. However, such ploughs involve loading the cable into the plough by means of a crane manipulator having a cable grab, and a tipping cable trough for manipulating the cable into the plough. Such arrangements suffer from the drawback that in the case of delicate cables, such as lead-lined cables, there is a risk of damage to the cable.

<CIT> published after the present application filing date, describes an underwater plough able to pivot the top section if its body.

<CIT> describes an underwater plough comprising a drawbar with a two-stage pivot arrangement.

<CIT> discloses a subsea plough with a pivotable guide member.

Preferred embodiments of the present disclosure seek to overcome one or more of the above disadvantages.

The invention is a claimed in the claims.

According to an aspect of the present disclosure, there is provided an apparatus for inserting an elongate object into a trench in a floor in a body of water, the apparatus comprising:-.

By providing attachment means moveable relative to the trench-forming means between the second position and a third position, to enable at least part of the elongate object to be received in the receiving means from a side of the apparatus remote from the trench-forming means, this provides the advantage of reducing the risk of damage to the elongate object, by avoiding the need to manipulate the elongate object with cable grabs, and reducing the time taken to load the elongate object into the apparatus, since the elongate object can be loaded into the apparatus from above.

The attachment means may be adapted to be attached to each of a plurality of tensile members at a respective location, and the position of at least one said location may be adjustable relative to the trench-forming means.

This provides the advantage of enabling an effective hitch point of the apparatus to be adjusted, as a result of which the apparatus can be steered by means of a single cable attached to a plurality of said tensile members.

The attachment means may be pivotable between the first and second positions. This provides the advantage of enabling easy movement of the attachment means between the first and second positions by means of actuators.

The attachment means may be pivotable between the second and third positions.

The apparatus may further comprise urging means for urging the elongate object into the trench formed by the trench-forming means.

The urging means may be moveable between a fourth position in which the urging means is adapted to urge the elongate object into the trench formed by the trench-forming means, and a fifth position to enable at least part of the elongate object to be received in the receiving means from a side of the apparatus remote from the trench-forming means.

Movement of the attachments means from the second position to the third position may cause movement of the urging means from the fourth position to the fifth position.

This provides the advantage of simplifying the construction of the apparatus.

The apparatus may further comprise guide means for guiding the elongate object into the receiving means.

This provides the advantage of reducing the risk of damage to the elongate object.

The trench-forming means may further comprise a plurality of nozzles for emitting water jets.

A plurality of said nozzles may be selectively operable.

This provides the advantage of improving efficiency of operation of jetting.

The apparatus may further comprise floor engaging means for engaging the floor of the body of water.

The floor engaging means may comprise a plurality of first floor engaging members for engaging the floor of the body of water forwards of the trench-forming means.

The floor-engaging means may further comprise second floor engaging members for engaging the floor of the body of water rearwardly of the first floor engaging means.

This provides the advantage of enabling sinking of the trench-forming means into a soft floor of the body of water to be controlled, and stability in deployment and recovery of the apparatus from the floor of a body of water to be improved.

The position of the floor engaging means relative to the trench-forming means may be adjustable.

The apparatus may further comprise bend limiting means for limiting bending of the elongate object at an inlet to the receiving means.

This provides the advantage of further reducing the risk of damage to the elongate object by preventing bending of the elongate object around a bend radius less than a predetermined value.

The height of an inlet to the bend limiting means may be adjustable relative to the trench-forming means.

This provides the advantage of enabling greater trench depths, because the entry height of the elongate object to the bend limiting means can be minimised during shallow trenching or when transitioning to and from full depth.

The apparatus may further comprise retaining means mounted to the body forwards of the trench forming means and having a released condition, enabling insertion of an elongate object into the retaining means from a side of the body remote from the trench forming means, and a retaining condition, for retaining an elongate object in the retaining means.

The retaining means may be adapted to prevent the attachment means from coming into contact with an elongate object retained in said retaining means in a retaining condition thereof.

The retaining means may comprise at least one retaining member mounted to the body and moveable between released and retaining conditions thereof.

At least one said retaining member may be pivotably moveable between released and retaining conditions thereof.

According to another aspect of the present disclosure, there is provided an apparatus for inserting an elongate object into a trench in a floor in a body of water, the apparatus comprising:-.

By providing retaining means mounted to the body forwards of the trench forming means and having a released condition, enabling insertion of an elongate object into the retaining means from a side of the body remote from the trench forming means, and a retaining condition, for retaining an elongate object in the retaining means, this provides the advantage of minimising the risk of damage to the elongate object, for example when moving an attachment means relative to the trench-forming means between its second position and its third position.

The apparatus may further comprise attachment means for enabling attachment of at least one tensile member to the apparatus, wherein the attachment means is moveable relative to the trench-forming means between a first position, in which the apparatus is adapted to be towed by at least one said tensile member to move the trench-forming means relative to the floor of the body of water to form a trench therein, and a second position, in which the apparatus is adapted to be supported by at least one said tensile member to enable the apparatus to be deployed to the floor of the body of water; and.

The attachment means may be adapted to be attached to each of a plurality of tensile members at a respective location, and the position of at least one said location is adjustable relative to the trench-forming means.

The attachment means may be pivotable between the first and second positions.

A height of an inlet to the bend limiting means may be adjustable relative to the trench-forming means.

Preferred embodiments of the disclosure will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which:-.

Referring to <FIG>, an apparatus in the form a plough <NUM> for inserting an elongate object in the form of a cable <NUM> (<FIG>) into a trench <NUM> (<FIG>) in the seabed <NUM> has a body <NUM> which supports trench-forming means in the form a plough share <NUM> for forming the trench <NUM> in the seabed <NUM>. The plough <NUM> has attachment means in the form of a drawbar <NUM> having an attachment part <NUM>, including a pair of attachment locations <NUM> for respective tensile members <NUM> forming part of a towing cable <NUM> for towing the plough <NUM> (<FIG> and <FIG>), and a support member <NUM> pivotably attached to the attachment part <NUM> at one end and to the body <NUM> at the other end. The attachment locations <NUM> are pivotable relative to the support member <NUM>, as a result of which the effective hitch point of the towing cable <NUM> is adjustable by pivoting one or both of the attachment locations <NUM> about their respective pivot axes.

Receiving means in the form of a cable path <NUM> is provided in an upper part of the body <NUM> on an opposite side of the body <NUM> to the plough share <NUM>, and guide means in the form of curved cable guides <NUM> is provided at the inlet to the cable path <NUM>, to assist in guiding the cable <NUM> into the cable path <NUM> and to minimise the risk of damage to the cable <NUM>. Bend limiting means in the form of a bellmouth <NUM> is provided at an inlet to the cable path <NUM>, to prevent bending of the cable <NUM> around a bend radius smaller than a predetermined value.

Urging means in the form of a depressor <NUM> is provided rearwardly of and above the cable path <NUM> and is pivotably mounted to a lower part of the support member <NUM> so that the depressor <NUM> is pivotable relative to the body <NUM> to urge the cable <NUM> into a trench <NUM> formed in the seabed <NUM> by the plough share <NUM>. The depressor <NUM> is also pivotable between a fourth position, in which it is located above and rearwardly of the cable path <NUM> to urge the cable <NUM> into the trench <NUM>, and a fifth position, in which it is moved out of the way of the cable path <NUM> to enable the cable <NUM> to be located in the cable path <NUM> from above the plough <NUM>.

Floor engaging means in the form of front skids <NUM> and rear skids <NUM> is pivotably mounted to the body <NUM> at a forward part of the body <NUM>. The height of the plough share <NUM> can be adjusted by pivoting the front skids <NUM> relative to the body <NUM>, and the rear skids <NUM> provide stability while deploying the plough <NUM> to and recovering the plough <NUM> from the seabed <NUM>.

A row of jetting nozzles <NUM> is provided at a forward edge of the plough share <NUM>, for emitting water jets to assist in breaking soil when the trench <NUM> is formed by the plough share <NUM>. Water can be selectively jetted from some or all of the nozzles <NUM>, therefore increasing the efficiency of operation of the jetting nozzles <NUM>.

The drawbar <NUM> is pivotable relative to the body <NUM> about a first axis between a first position, in which the plough <NUM> is in its ploughing mode (<FIG> and <FIG>) and in which the plough <NUM> can be towed by the towing cable <NUM> to cause the plough share <NUM> to form a trench <NUM> in the seabed <NUM> into which the cable <NUM> is inserted by means of the depressor <NUM>, and a second position (<FIG>) in which the plough <NUM> is in its lifting mode and can be deployed to or recovered from the seabed <NUM> by means of the towing cable <NUM>. This enables a single towing cable <NUM> to be used for deploying and recovery of the plough <NUM> to the seabed <NUM> and for towing the plough <NUM> to enable a cable <NUM> to be buried in the seabed <NUM>.

The drawbar <NUM> is also pivotable relative to the body <NUM> about a second axis, generally perpendicular to the first axis, between the second position and a third position (<FIG>), in which the cable <NUM> to be buried can be inserted into the cable path <NUM> from above the plough <NUM>.

The operation of the plough <NUM> of <FIG> will now be described.

Referring to <FIG>, the plough <NUM> is initially deployed from a surface vessel (not shown) to the seabed <NUM> by means of the towing cable <NUM> supporting the plough <NUM>, the plough <NUM> being in its lifting mode in which the drawbar <NUM> is located in its second position. The plough <NUM> is located on the seabed <NUM>, and the front <NUM> and rear <NUM> skids support the plough <NUM> so that the plough share <NUM> does not sink into the seabed <NUM>.

The drawbar <NUM> is then pivoted from the second position to the third position ( <FIG>), and because the depressor <NUM> is mounted to the drawbar <NUM>, pivoting of the drawbar <NUM> from the second position to the third position causes pivoting of the depressor <NUM> from the fourth position to the fifth position to enable access the rear part of the cable path <NUM>. The cable <NUM> is then introduced into the cable path <NUM> from above (<FIG>), and the cable guides <NUM> assist in guiding the cable <NUM> into the cable path <NUM>. Once the cable <NUM> is located in the cable path <NUM>, the drawbar <NUM> is pivoted from the third position back to the second position which in turn causes the depressor <NUM> to be pivoted from the fifth position back to the fourth position, so that the drawbar <NUM> and depressor <NUM> are located above the cable path <NUM>. The drawbar <NUM> is then pivoted relative to the body <NUM> into its first position, and the depth of ploughing by the plough share <NUM> is then selected by means of suitable selection of the orientation of the rear <NUM> and front <NUM> skids relative to the body <NUM>.

The plough <NUM> is then towed by means of the towing cable <NUM>, to cause the plough share <NUM> to form a trench <NUM> in the seabed <NUM>, and the cable <NUM> passes from the cable path <NUM> into the trench <NUM> and is urged into the trench <NUM> by the depressor <NUM>. Formation of the trench <NUM> is assisted by water jets from jetting nozzles <NUM> on the forward edge of the plough share <NUM>, and the efficiency of jetting can be improved by suitable selection of predetermined jetting nozzles <NUM>.

Referring to <FIG>, a plough <NUM> of a second embodiment is shown, in which parts common to the embodiment of <FIG> are denoted by like reference numerals but increased by <NUM>. In the plough <NUM> of <FIG>, the attachment part <NUM> of the drawbar <NUM> is pivotable relative to the support member <NUM> between the second position (<FIG>) and the third position (<FIG>) to provide access to the cable path <NUM> from above to enable the cable <NUM> to loaded into the cable path <NUM>.

In addition, the plough body <NUM> is pivotable relative to the plough share <NUM> about pivot axis <NUM>, which enables the height of the bellmouth <NUM> to be adjusted. This enables the bellmouth entry height to be minimised during shallow trenching or in transitioning to and from full depth, as a result of which the trench depth can be greater.

Referring to <FIG>, a plough <NUM> of a third embodiment is shown, in which parts common to the embodiment of <FIG> are denoted by like reference numerals but increased by <NUM>. The plough <NUM> of <FIG> is provided with retaining means in the form of an opening bellmouth assembly <NUM> mounted to the body <NUM> of the plough <NUM> forward of the plough share <NUM>. The bellmouth assembly <NUM> includes a pair of retaining members <NUM> mounted to the body <NUM> such that the retaining members <NUM> are pivotable between a released condition, in which the cable <NUM> can be inserted into the bellmouth assembly <NUM> from above the plough <NUM>, and a retaining condition, in which the retaining members <NUM> retain the cable <NUM> in the bellmouth assembly <NUM> to prevent the cable <NUM> from being damaged by coming into contact with the drawbar <NUM> as the drawbar <NUM> is moved from its second position to its first position. In the released condition, the retaining members <NUM> also assist in guiding the cable <NUM> into the cable path <NUM> of the plough <NUM>.

Referring to <FIG>, a plough <NUM> of a fourth embodiment is shown, in which parts common to the embodiment of <FIG> are denoted by like reference numerals but increased by <NUM>. The plough <NUM> of <FIG> is provided with retaining means in the form of an opening bellmouth assembly <NUM>, which operates in a similar manner to the bellmouth assembly <NUM> of <FIG>.

Claim 1:
An apparatus (<NUM>) for inserting an elongate object (<NUM>) into a trench (<NUM>) in a floor (<NUM>) in a body of water, the apparatus (<NUM>) comprising:-
trench-forming means (<NUM>) for forming a trench (<NUM>) in a floor (<NUM>) of a body of water;
attachment means in the form of a drawbar (<NUM>) and support member (<NUM>), the drawbar (<NUM>) having an attachment part (<NUM>) including a pair of attachment locations (<NUM>), for enabling attachment of at least one tensile member (<NUM>) to the apparatus, wherein the drawbar (<NUM>) is moveable relative to the trench-forming means (<NUM>) between a first position, in which the apparatus (<NUM>) is adapted to be towed by at least one said tensile member (<NUM>) to move the trench-forming means (<NUM>) relative to the floor (<NUM>) of the body of water to form a trench (<NUM>) therein, and a second position, in which the apparatus is adapted to be supported by at least one said tensile member (<NUM>) to enable the apparatus (<NUM>) to be deployed to the floor (<NUM>) of the body of water, wherein the drawbar (<NUM>) is pivotable relative to the body (<NUM>) about a first axis when moving between the first position and the second position; and
receiving means for receiving at least part of an elongate object (<NUM>) to be inserted into the trench (<NUM>);
wherein the drawbar (<NUM>) is moveable relative to the trench-forming means (<NUM>) between the second position and a third position, to enable at least part of the elongate object (<NUM>) to be received in the receiving means from a side of the apparatus (<NUM>) remote from the trench-forming means (<NUM>), wherein the drawbar (<NUM>) is also pivotable relative to the body about a second axis, which is generally perpendicular to the first axis; wherein the support member (<NUM>) is pivotably attached to the attachment part (<NUM>) of the drawbar (<NUM>) at one end and to the body (<NUM>) at the other end, to allow pivoting of the support member (<NUM>) around the second axis extending in a towing direction.