Patent Description:
A device according to the present invention may be referred to as an underwater "blower" or as a "water blade" or "water rake".

The invention pertains to excavation, and in particular, though not exclusively, to underwater or subsea excavation and/or to an underwater or subsea excavator.

There is often a desire or need to move underwater material. For example, if a trench has been formed on a floor of a body of water, such as a sea bed, there may be a desire to backfill the trench. This may be the case after laying a cable, pipeline or the like in the trench. This may also be the case if or when reburying a cable, pipeline or the like which has been deburied.

When a trench is formed, a ridge or ridges (also known as a berm or berms) of spoil may be formed on either or both sides of the trench. The trench may, therefore, be back-filled or refilled from such ridge(s) or berm(s).

<CIT> discloses improvements in and relating to underwater excavation apparatus, the content of which is incorporated herein by reference. The apparatus comprises at least one rotor and an arrangement for dampening reactive torque on the excavation apparatus caused by rotation of the rotor, in use, wherein the excavation apparatus further comprises at least one stator comprising stator blades, the torque dampening arrangement comprising the stator blades, the stator blades comprising a plurality of primary stator blades and a plurality of secondary or splitter blades provided between adjacent pairs of primary stator blades.

The apparatus of <CIT> further comprises a housing comprising an inlet and an outlet, a rotor having a rotor rotation axis, the rotor comprising a first body and a plurality of impeller blades provided within the housing, such that, in use, flow of fluid passed or across the rotor is at a first angle from the axis of rotation.

The apparatus of <CIT> further comprises the housing comprising an inlet and an outlet; at least one rotor comprising an impeller provided within the housing; at least one stator provided within the housing; and an arrangement for producing at least one vortex in a flow of fluid; wherein, the or each at least one vortex producing arrangement comprises a planar member provided adjacent the outlet of the housing, an edge of the planar member being attached to the housing or to a body within the housing.

The device/apparatus of the present invention hereinafter described may incorporate one or more features of the apparatus disclosed in <CIT>.

Mass Flow Excavation (MFE) is a means of creating cavities in the seabed with relatively low pressure(s) (Kilopascals, KPa), e.g. in sand and/or pre-loosened or disturbed material. Mass flow excavators typically comprise a hollow body housing and at least one impeller or rotor provided within the housing which draws fluid into the housing and directs the fluid out of the housing towards the seabed.

Known mass flow excavators comprise impellers designed to draw in large volumes of fluid and to discharge the fluid at relatively low speed and low pressure - typically less than <NUM>/s and less than <NUM> KPa. Due to the relatively low pressure and low fluid flow speed of mass flow excavation, many passes may be required to effectively excavate an area, as with each pass only a limited penetration of the seabed may be achieved. It is a further characteristic of mass flow excavation that trenches created in the seabed may be wide but shallow. This is because the mass flow excavator may first move looser material on the surface due to pressure limitations before penetrating firmer material underneath, creating a wide and ill-defined or uncontrolled excavation profile.

Further, mass flow excavation apparatus are primarily suitable for excavation by directing fluid at the seabed, but due to the low pressure nature of the apparatus, such are of limited use in the collection and removal of seabed material by suction. Thus, after the mass flow device has disturbed the seabed material, a separate tool - such as a centrifugal pump - may require to be deployed to suck-up and remove the material.

To distinguish from "mass flow" or "Mass Flow Excavators" (MFE) the terms "controlled flow" or "Controlled Flow Excavator" (CFE) are hereinafter used in connection with use of the present invention which may be configured to produce and/or direct a flow of fluid (water) at a pressure of typically around <NUM> to <NUM> KPa and volume flow of typically around <NUM><NUM>/s to <NUM><NUM>/s.

It is an object of at least one embodiment of at least one aspect of the present invention to obviate or mitigate one or more problems and/or disadvantages in the prior art.

<CIT> describes an underwater excavation apparatus comprising mass flow excavation means and jet flow excavation means. The mass flow excavation means causes a mass flow at a pressure less than that of a jet flow of the jet flow excavation means. The mass flow excavation means causes a mass flow at a volume flow rate greater than that of a jet flow volume rate of the jet flow excavation means. An outlet of the jet flow means is provided within an outlet of the mass flow means.

<CIT> describes an excavation apparatus, such as an underwater excavation apparatus, having means for producing, in use, at least one vortex, spiral or turbulent flow in a laminar flow of fluid, e.g. water. The excavation apparatus comprises a rotor having a rotor rotation axis, wherein, in use, flow of fluid passed or across the rotor is at a first angle from the axis of rotation. The excavation apparatus comprises the rotor and means or an arrangement for dampening reactive torque on the apparatus caused by rotation of the rotor, in use. The turbulent flow is provided within, such as within a (transverse) cross-section, of the laminar flow.

<CIT> describes a vessel having means at its bow to direct a water flow ahead of the vessel downwardly towards the seabed in front of and to either side of the path of the vessel to displace material from the seabed including any weapon system or obstacles on or buried in the seabed away from the path of the vessel. The means may comprise a duct of rectangular cross-section having an upright portion with a water inlet at its upper end, an arcuate portion sweeping forwardly of the vessel and an outlet facing forwardly and downwardly from the vessel. Impeller means may be provided in the inlet of the duct to draw water into the duct. The duct means may be mounted on a boom which extends forwardly of the vessel and may be lowered or raised by a hoist on the bow of the vessel.

<CIT> describes a dredging apparatus comprising a body mounting thrust means to direct, in use, a wash of water downwards towards an area of sea bed or the like, connection means to connect said dredging apparatus to a support means above the sea bed, said connection means including attitude adjusting means to selectively adjust the attitude of the dredging apparatus in a side to side (roll) orientation.

According to a first aspect of the present invention there is provided an underwater material moving device according to claim <NUM>.

The device of the present invention may be referred to as a "blower", "water blade" or "water rake".

The inlet may be substantially circular.

The inlet and outlet may be aligned substantially parallel to or with one another.

In one implementation the elongate shape or slot may comprise at least one, and preferably two, full radiussed end(s). The end(s) of the slot may be at least part circular, e.g. beneficially semi-circular.

In another implementation the elongate slot may comprise at least one, and preferably two, ends which may be linear and/or may be substantially parallel to one another.

First and second sides of the slot may be substantially parallel to one another. First and second sides of the slot may be linear.

In said one implementation first and second sides of the slot may extend, for example, tangentially extend, from ends of the slot.

In said another implementation first and second sides of the slot may extend, for example, substantially perpendicularly, from ends of the slot.

The outlet of the device is provided on an outlet portion, for example, an outlet portion of the body or of a nozzle. The outlet portion or nozzle may be detachably attached to the body. The outlet portion or nozzle may comprise a fluid passageway extending linearly between the inlet end and the outlet end. The inlet end of the nozzle may be substantially circular.

The inlet end and the outlet end/outlet may be aligned substantially parallel to or with one another.

Beneficially a length of the outlet end/outlet may increase, flare and/or taper outwards in a direction from the inlet end to the outlet end/outlet.

Beneficially the inlet end may be circular and/or the outlet end/outlet maybe of an elongate (slot) shape.

Beneficially a width of the outlet end/outlet may be less than a width/diameter of the inlet end.

Advantageously a ratio of outlet end/width to inlet end width/diameter maybe in the range of <NUM> to <NUM>, for example, <NUM>.

Beneficially a length of the outlet end/outlet may be greater than a width/diameter of the inlet end. Advantageously a ratio of outlet end/outlet length to inlet end width/diameter may be in the range of <NUM> to <NUM>, for example, <NUM>.

The device comprises one or more guide blades or vanes, for example, beneficially at or adjacent the outlet portion/outlet. The blade(s) or vane(s) are arranged so as to provide a substantially even fluid flow (distribution) across and/or along the outlet portion or nozzle.

A width (or length) of each blade or vane may taper, decrease or narrow in a direction towards the outlet. Such arrangement may act to facilitate or encourage an improved or even fluid (water) flow distribution.

The one or more blades or vanes comprise one or more primary or guide blades or vanes.

The one or more blades or vanes may comprise one or more secondary or splitter blades or vanes. The secondary or splitter blades or vanes may be provided between adjacent primary or guide vanes. The one or more blades or vanes may be substantially symmetrically dispersed around a centre of the device.

One or more of the one or more blades or vanes are curved in cross- section.

The one or more blades or vanes may extend to the outlet.

The primary or guide blades or vanes may be longer (e.g. in a direction extending between the inlet and the outlet) than the secondary or splitter blades or vanes.

The/each primary or guide blade(s) or vane(s) comprise a first curved portion and a second curved portion.

For each primary or guide blade or vane, the first curved portion is curved or bent in an opposite disposition or direction to the second curved portion.

The first curved portion of the/each primary or guide blade or vane may be provided proximal the inlet. The second curved portion of the/each primary or guide blade or vane may be provided proximal outlet.

The/each secondary or splitter blade(s) or vane(s) may comprise a first curved portion.

The first curved portion of the/each primary or guide blade or vane may be provided proximal the inlet end. The second curved portion of the/each primary or guide blade or vane may be provided proximal the outlet end outlet.

The first curved portion of a/each secondary or splitter blade may be provided between and/or be disposed in a same orientation as the second curved portions of adjacent primary or guide blades or vanes.

The primary or guide blades or vanes may be "s" shaped. The secondary or splitter blades or vanes may be "r" shaped.

The outlet portion or nozzle comprises a first dimension, a second dimension and third dimension.

The first dimension comprises a width or breadth dimension or direction. The second dimension comprises a length dimension or direction. The third dimension comprises a height dimension or direction. The third dimension may extend between the/an inlet end and the/an outlet end of the outlet portion or nozzle.

The first dimension decreases or tapers along at least a portion of the third dimension, e.g. in a direction towards the outlet end.

The second dimension may increase or flare along at least a portion of the third dimension e.g. in a direction towards the outlet end.

According to a second aspect of the present invention there is provided an underwater material moving apparatus comprising at least one underwater material moving device according to the first aspect of the present invention.

The apparatus may comprise a pair of devices according to the first aspect of the present invention.

According to a third aspect of the present invention there is provided a method of moving underwater material according to claim <NUM>.

Moving said underwater material may comprise filling or back-filling an underwater trench, for example, with material comprising spoil or berm.

According to the present invention there is provided an outlet portion or nozzle for use in or with an underwater material moving device according to a first aspect of the present invention.

The outlet portion or nozzle may be termed a "tool" or "attachment".

Also described is an (underwater) material moving apparatus or excavator comprising first and second or at least one pair of underwater material moving devices (or excavators).

Beneficially said devices may be symmetrically disposed on a yoke or frame.

Beneficially each device may be substantially the same or identical.

Each device may comprise a blower or "controlled flow" device as hereinbefore described and/or defined.

The/each device may be referred to as a "blower", "water blade" or "water rake". Each device may comprise a device according to the first aspect of the present invention.

Each device comprises an outlet. The outlet comprises an elongate shape or slot.

The/each device comprises a body. The outlet is provided on or at an end of the body or on an outlet portion or nozzle or tool or attachment connected or (releasably) connectable to the body. The body comprises a body outlet, which may be circular. The outlet portion/nozzle/tool/attachment comprises a inlet end which may be circular. The device comprises an inlet. The inlet may be substantially circular. The inlet may be provided on or at another (e.g. opposite) end of the body.

The body comprises a through-passage, for example, extending from inlet to body outlet. The inlet/body inlet and the outlet/body outlet are disposed substantially along an axis of the body. The inlet/body inlet and outlet/body outlet are aligned substantially parallel to or with one another.

In one implementation the elongate shape or slot may comprise at least one, and preferably two, full radiussed end(s). The end(s) of the slot may be at least part circular e.g. beneficially semi-circular.

The outlet of the device may be provided on an outlet portion of the body or on a nozzle. The outlet portion or nozzle may be detachably attached to the body. The outlet portion or nozzle may comprise an inlet end. The outlet portion or nozzle may comprise a fluid passageway extending linearly between the inlet and the outlet. The inlet end of the nozzle may be substantially circular.

The/each device comprises one or more guide blades or vanes, for example, beneficially at or adjacent the outlet.

One or more of the one or more blades or vanes may be curved in cross-section.

The first curved portion of the/each primary or guide blade or vane may be provided proximal the inlet end. The second curved portion of the/each primary or guide blade or vane may be provided proximal the outlet end/outlet.

The/each secondary or splinter blade(s) or vane(s) may comprise a first curved portion.

The first curved portion of a/each secondary or splitter blade may be provided between and/or be dispersed in a same orientation as the second curved portions of adjacent primary or guide blades or vanes.

The outlet portion or nozzle comprises a first dimension, a second dimension and a third dimension.

The first dimension being a width or breadth dimension of the outlet portion.

The second dimension being a length dimension of the outlet portion. The third dimension being a height dimension of the outlet portion which extends between the inlet end and the outlet end of the outlet portion of the nozzle.

Beneficially the outlet of the/each device may face or may be angled at least partially away (outwardly away) from the frame or yoke and/or from the other device, for example, at an angle of between <NUM>° and <NUM>°, for example, <NUM>°.

The frame or yoke may comprise an arrangement for retaining or supporting each device, for example, for pivotally retaining each device. The frame or yoke may have a centre or central axis. The devices may be disposed symmetrically about the centre or central axis of the frame or yoke. This may provide for balance of force on the apparatus, in use, for example, if the devices are used simultaneously, and are driven at the same flow rates and/or pressure.

The outlets of the devices may be angled away from a centre of the frame or yoke, e.g. so as to face partially downwardly, in use.

An angle between a body of the/each device and the frame or yoke may be around between <NUM>° and <NUM>°, and beneficially around <NUM>°.

Beneficially, the flared out nature of the devices of the present invention allows for provision of a relatively short/small frame/yoke.

Also described is a method of moving underwater material comprising:.

Back-filling said trench may bury or rebury a cable, conduit or the like.

Embodiments of the present invention will now be described by way of example only, and with reference to the accompanying drawings, which are:.

Referring to <FIG>, there is shown an underwater material moving apparatus or excavator, generally designated <NUM>, according to an embodiment of the present invention. The apparatus <NUM> comprises first and second underwater material moving devices or excavators 10a, 10b.

The/each device 10a, 10b comprises a controlled flow underwater excavation (CFE) apparatus as disclosed in <CIT>, the content of which is incorporated herein by reference, and is not repeated herein merely for reasons of brevity.

Each device comprises an outlet <NUM>, wherein the outlet <NUM> comprises an elongate shape or slot <NUM>. The device 10a, 10b can be referred to as a "blower" or as a "water blade".

The device 10a, 10b comprises a body <NUM>. The outlet <NUM> is provided on or at an end of the body <NUM>. The device 10a, 10b comprises an inlet <NUM>. The inlet <NUM> is substantially circular. The inlet <NUM> is provided on or at another (opposite) end of the body <NUM>.

The body <NUM> comprises a through-passage <NUM>. The inlet <NUM> and the outlet <NUM> are substantially disposed along an axis A of the body <NUM>. The inlet <NUM> and outlet <NUM> are aligned substantially parallel with one another. The elongate shape or slot <NUM> comprises at least one, and in this embodiment two, full radiussed end(s) <NUM>, <NUM>, i.e. the end(s) of the slot <NUM> are at least part circular, i.e. are semi-circular.

First and second sides <NUM>, <NUM> of the slot <NUM> are substantially parallel to one another. The first and second sides <NUM>, <NUM> of the slot <NUM> are linear. First and second sides <NUM>, <NUM> of the slot <NUM> extend, i.e. tangentially extend, from ends <NUM>, <NUM> of the slot <NUM>.

The outlet <NUM> of the device 10a, 10b is provided on a nozzle <NUM>. The nozzle <NUM> is detachably attached to the body <NUM>. The nozzle <NUM> comprises an inlet end <NUM>. The nozzle <NUM> comprises an outlet end. The outlet end of the nozzle comprises the outlet <NUM> of the device 10a, 10b. The nozzle <NUM> comprises a fluid passageway <NUM> extending linearly between inlet end <NUM> and the outlet <NUM>/outlet end. The inlet end <NUM> of the nozzle <NUM> is substantially circular.

The present invention further provides the underwater material moving apparatus <NUM> comprising at least one underwater material moving 10a, 10b. The apparatus <NUM> comprises a pair of devices 10a, 10b.

According to the present invention there is provided a method of moving underwater material comprising:.

Moving said underwater material <NUM> can comprise filling or back-filling an underwater trench <NUM>, for example, with material <NUM> comprising spoil or berm.

The present invention provides an underwater material moving apparatus (or excavator) <NUM> comprising first and second underwater material moving devices (or excavators) 10a, 10b.

Said devices 10a, 10b are symmetrically disposed on a yoke or frame <NUM>. Each device 10a, 10b is substantially the same or identical. Each device 10a, 10b comprises a blower or controlled flow device as hereinbefore described and/or defined. Each device 10a, 10b comprises outlet <NUM>, the outlet <NUM> comprising elongate shape or slot <NUM>.

The/each device 10a, 10b of the present invention can be referred to as a "blower" or "water blade".

The/each device 10a, 10b comprises body <NUM>. The outlet <NUM> is provided on or at an end of the body <NUM>. The device 10a, 10b comprises inlet <NUM>. The inlet <NUM> is substantially circular. The inlet <NUM> is provided on or at said another (opposite) end of the body <NUM>.

The body <NUM> comprises through-passage <NUM>. The inlet <NUM> and the outlet <NUM> are substantially disposed along axis A of the body. The inlet <NUM> and outlet <NUM> are aligned substantially parallel with one another.

The elongate shape or slot <NUM> comprises at least two ends <NUM>, <NUM>, which in this embodiment comprises at least two full radiussed end(s) <NUM>, <NUM>. The end(s) <NUM>, <NUM> of the slot <NUM> are at least part circular, and beneficially semi-circular.

Beneficially the outlet <NUM> of the/each device 10a, 10b face or is angled at least partially away (outwardly away) from the frame or yoke <NUM> and/or from the other device 10a, 10b.

The frame or yoke <NUM> comprises an arrangement for retaining or supporting each device 10a, 10b, for example, for adjustably pivotally retaining each device 10a, 10b. The frame or yoke <NUM> has a centre or central axis C. The devices 10a, 10b are disposed symmetrically about the centre C of the frame or yoke <NUM>. This provides for balance of force on the apparatus <NUM>, in use, for example, if the devices 10a, 10b are used simultaneously, and are driven at the same flow rates and/or pressure.

The outlets <NUM> of the devices 10a, 10b are angled away from centre C of the frame or yoke <NUM>, e.g. so as to face partially downwardly, in use.

An angle α between a body <NUM> of the/each device 10a, 10b and the frame or yoke <NUM> is around between <NUM>° and <NUM>° and beneficially around <NUM>°.

Beneficially, the flared out nature of the devices 10a, 10b of the present invention allows for provision of a relatively short/small frame/yoke <NUM>.

The present invention provides a method of moving underwater material comprising:.

Moving said underwater material <NUM> can comprise filling or back-filling underwater trench <NUM>, for example, with material comprising spoil or berm. Beneficially said trench <NUM> is used to bury or rebury a cable, conduit or the like (not shown).

Referring now to <FIG>, there is shown an underwater moving apparatus or excavator, generally designated <NUM>, according to a second embodiment of the present invention. The apparatus <NUM> is similar to the apparatus <NUM> of <FIG>, like parts being denoted by like numerals, but incremented by "<NUM>".

The device 110a, 110b comprises guide vanes or blades <NUM> within the nozzle <NUM>. The outlet guide vanes or blades <NUM> can act to reduce fluid swirl and/or provide a more coherent output fluid flow or jet. In particular, the guide vanes or blades <NUM> can be arranged so as to provide a substantially even fluid flow (distribution) across and/or along the outlet portion or nozzle. The vanes or blade <NUM> can extend into the nozzle <NUM> as far as a quarter or a half of the length of the nozzle <NUM> from the outlet <NUM>, with none or one blade <NUM> in the middle of a long axis of theoutlet <NUM> and either two (as shown) or three vanes or blades <NUM> across a short axis of the outlet <NUM>.

Referring now to <FIG>, there is shown an underwater material moving apparatus, generally designated <NUM>, according to a third embodiment of the present invention. The apparatus <NUM> is similar to the apparatus <NUM> of <FIG>, like parts denoted by like numerals, but incremented by "<NUM>".

As can be seen from <FIG> in the apparatus <NUM>, the devices 210a, 210b are angled inwards so that the berms <NUM> on either side of thread <NUM> are blown simultaneously.

Referring now to <FIG>, there is shown an underwater moving apparatus, generally designated <NUM>, according to a fourth embodiment of the present invention. The apparatus <NUM> is similar to the apparatus of <FIG>, like parts denoted by like numerals, but incremented by "<NUM>".

The inlet end <NUM> and the outlet end/outlet <NUM> are aligned substantially parallel to or with one another. A width of the outlet end/outlet <NUM> decreases, narrows and/or tapers inwardly in a direction from the inlet end <NUM> to the outlet end/outlet <NUM>.

A length of the outlet end/outlet <NUM> increases, flares and/or tapers outwardly in a direction from the inlet end <NUM> to the outlet end/outlet <NUM>.

The inlet end <NUM> is circular and/or the outlet end/outlet <NUM> is of an elongate (slot) shape.

A width of the outlet end/outlet <NUM> is less than a width/diameter of the inlet end <NUM>.

A ratio of outlet end <NUM> width to inlet end <NUM> width/diameter is beneficially in the range of <NUM> to <NUM>, for example, <NUM>.

A length of the outlet end/outlet <NUM> is greater than a width/diameter of the inlet end <NUM>. A ratio of outlet end/outlet <NUM> length to inlet end <NUM> width/diameter is beneficially in the range of <NUM> to <NUM>, for example, <NUM>.

A width (or length) W of each blade or vane 375a, 375b tapers, decreases or narrows in a direction towards the outlet <NUM>. Such arrangement acts to facilitate or encourage an improved or even fluid (water) flow distribution (see <FIG> and <FIG>).

Similar to the apparatus <NUM> of <FIG>, the apparatus <NUM> comprises guide vanes or blades 375a, b.

The one or more blades or vanes 375a, b may comprise one or more primary or guide blades or vanes 375a. The one or more blades or vanes 375a, b comprise one or more secondary or splitter blades or vanes 375b. The secondary or splitter blades or vanes 375b are provided between adjacent primary or guide vanes 375a. The one or more blades or vanes <NUM> are substantially symmetrically dispersed around a longitudinal axis A of the device 310a, 310b.

All but one of the one or more blades or vanes 375a, b are curved in cross-section. A central blade or vane <NUM> disposed at the longitudinal axis A is straight. The one or more blades 375a, b extend to the outlet <NUM>.

The primary or guide blades or vanes 375a are longer (e.g. in a direction extending between the inlet <NUM> and the outlet <NUM>) than the secondary or splitter blades or vanes 375b.

The/each primary or guide blade(s) or vane(s) 375a comprises a first curved portion and/or a second curved portion.

For each primary or guide blade or vane 375a, the first curved portion is curved or bent in an opposite disposition or direction to the section curved portion.

The first curved portion of the/each primary or guide blade 375a or vane is provided (more) proximal the inlet <NUM>. The second curved portion of the/each primary or guide blade or vane 375a is provided (more) proximal outlet <NUM>.

The/each secondary or splinter blade(s) or vane(s) 375b comprise a first curved portion.

The first curved portion of a/each secondary or splitter blade 375b is provided between and/or is dispersed in a same orientation as the second curved portions of adjacent primary or guide blades or vanes 375a.

The primary or guide blades or vanes 375a can be said to be "s" shaped. The secondary or splitter blades or vanes 375b can be said to be "r" shaped.

The outlet portion or nozzle <NUM> comprises a first dimension, and/or a second dimension, and/or a third dimension.

The first dimension comprises a width or breadth dimension or direction W. The second dimension comprises a length dimension or direction L. The third dimension comprises a height dimension or direction H. The third dimension H extends between an inlet end <NUM> and an outlet end <NUM> of the outlet portion or nozzle <NUM>.

Beneficially the first dimension W decreases or tapers along at least a portion of the third dimension H in a direction towards the outlet end <NUM>.

Beneficially also the second dimension L increases or flares along at least a portion of the third dimension H in a direction towards the outlet end <NUM>.

Referring now to <FIG>, there is shown an underwater material moving apparatus, generally designated <NUM>, according to a fifth embodiment of the present invention. The apparatus <NUM> is similar to the apparatus <NUM> of <FIG>, like parts denoted by like numerals, but incremented by "<NUM>". In particular the apparatus <NUM> is the same as the apparatus <NUM> in respect of the blades or vanes 475a, b, i.e. the primary or guide blades or vanes 475a and the secondary or splitter blades or vanes 475b.

The apparatus <NUM> provides a plate member or baffle (or further blade or vane) <NUM> which spans between the first and second ends <NUM>, <NUM>, is parallel to the first and second sides <NUM>, <NUM>, and divides each blade or vane 475a, b into first and second blade or vane portions 475a , 475b.

In this embodiment there is provided a tool or attachment or nozzle, generally designated <NUM>, comprising a water rake which is a water-jet nozzle attachment for a subsea mass-flow excavator (MFE) or controlled-flow excavator (CFE). The rake is designed to create a flatter, smoother seabed profile than conventional MFE or CFE nozzles. Generally, MFE and CFE nozzles have simple circular outlets and are designed primarily to produce excavations which are as deep and narrow as possible, for example for the burial or de-burial of subsea cables or pipes. The water rake is used where the seabed is to be levelled out, producing a more or less flat seabed profile. This is useful, for example, in preparing the seabed for the placing of mattresses, jack-up rig spud-cans, or other structures, and for clearing a path through sand-waves for tracked vehicles. Achieving such a flat seabed profile with circular MFE or CFE nozzles is challenging.

The water rake achieves this by producing a substantially linear water jet with a substantially uniform jet speed along the exit rather than the more usual circular water jet typical of MFE and CFE devices. The inlet of the water rake attaches to a circular outlet of a conventional CFE tool. The circular jet at the water rake inlet <NUM> is converted into a substantially linear jet at the water rake outlet <NUM>. Operational constraints require a CFE device to be as short as practical, for stability while stored on the deck of a moving vessel, for safety during launch and recovery, and to allow it to operate in as shallow water as possible. The water rake, therefore, employs a series of internal guide blades or vanes 475a, b to direct the flow through the tool or nozzle <NUM>, allowing the jet to be converted from circular to linear in a relatively short distance. The rake tapers, reduces in width, from inlet <NUM> to outlet <NUM> and increases in length from inlet <NUM> to outlet <NUM>. In the embodiment shown the outlet <NUM> is rectangular for ease of manufacture, but could also incorporate semi-circular ends.

The spacing of the vanes 475a, b accounts for two phenomena. Firstly, the tendency of fluid flow to take the shortest, easiest route between inlet <NUM> and outlet <NUM>, in particular the tendency for flow to concentrate near the centre of the outlet <NUM>. This provides motivation to make the inner passages narrower than the outer passages to encourage more flow to the extremities of the tool <NUM>.

Secondly, flow exiting a CFE device <NUM> generally has higher energy towards an outer diameter of the device, with a lower energy region towards the centre. This mitigates the first phenomenon, as the outer passages are proportionally more exposed to higher energy flow regions of an incoming jet, whereas the inner passages have greater exposure to a low energy central region.

In a preferred implementation, the ratio of passage widths (not areas) at the inlet <NUM>, symmetrically from inner passage to outer passage is <NUM>:<NUM>:<NUM>:<NUM> (a:b:c:d) (see <FIG>). An alternative implementation has passage width ratios of <NUM>:<NUM>:<NUM>:<NUM>.

Splitter guide vanes 475b are used to seek to improve fluid flow towards the outlet <NUM> of the tool <NUM>. As a fluid passage expands linearly from inlet <NUM> to outlet <NUM>, the splitter guide vanes 475b help to evenly distribute flow across the outlet <NUM>. Splitter guide vanes 475b are used as another set of full-length guide vanes 475a would result in increased energy loss due to skin friction and too much restriction in the narrow passages towards the inlet <NUM>.

At the outlet <NUM>, the guide vanes 475a, b are uniformly spaced. A central guide vane or baffle <NUM> extends longitudinally through the device <NUM> from inlet <NUM> to outlet <NUM>, to reduce secondary circulating flows and to increase the structural rigidity of the guide vanes 475a and splitter guide vanes 475b.

The water rake can be used individually, or can be deployed with two excavators side by side, e.g. to increase (double) a length of the rake. In this case, the rakes/excavators can be mechanically connected, e.g. bolted together using brackets on an end of each.

Claim 1:
An underwater material moving device (10a, 10b; 110a, 110b; 210a, 210b; 310a, 310b; 410a, 410b) comprising:
a body (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>);
an inlet (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>) provided on or at an end of the body (<NUM>;<NUM>;<NUM>; <NUM>;<NUM>); and
an outlet (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>) provided on or at another, opposite, end of the body to the inlet, wherein
the body comprises a through-passage (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>) extending from the inlet to the outlet,
wherein the outlet is provided on an outlet portion comprising an inlet end (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>) and an outlet end, the outlet end comprising the outlet of the device, the outlet portion comprising a first dimension (W), a second dimension (L) and a third dimension (H), the first dimension (W) being a width or breadth dimension of the outlet portion, the second dimension (L) being a length dimension of the outlet portion, and the third dimension (H) being a height dimension of the outlet portion which extends along a direction of a longitudinally extending axis (A) of the body,
the first dimension of the outlet portion decreases or tapers along at least a portion of the third dimension in a direction from the inlet end towards the outlet end of the outlet portion, and
the outlet comprises an elongate shape or slot (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>), the inlet and the outlet are substantially disposed along the longitudinally extending axis (A) of the body such that the inlet and outlet are aligned with one another, characterized in that the device further comprises one or more primary or guide blades or vanes (375a; 475a), and each primary or guide blade or vane comprises a first curved portion and a second curved portion, the first curved portion being curved or bent in an opposite disposition or direction to the second curved portion.