GB2536119A

GB2536119A - Bristle propelled tool

Info

Publication number: GB2536119A
Application number: GB1601387.2A
Authority: GB
Inventors: William Stutchbury Neil
Original assignee: Reece Innovation Centre Ltd
Current assignee: Reece Innovation Centre Ltd
Priority date: 2015-01-26
Filing date: 2016-01-26
Publication date: 2016-09-07
Also published as: GB201501229D0; GB201601387D0

Abstract

A bi-directional tractor unit that can be used for traversing, cleaning, and/or inspecting external surfaces, such as mooring chain links, comprises a bristle drive system for providing bi-directional propulsion. The bristle drive system comprises bristles which engage with the exterior of a surface and can be utilized for tractive effort to traverse external surfaces and for cleaning the external surfaces. The unit can traverse using a push-me pull-you action utilizing a combination of a grip mode and shuffle mode between brush modules. The deflection of the bristles can be controlled by anti-splay means, and can be changed via moving a linear main drive actuator. The bristles can be provided on interchangeable bristle plates, which can be bolted so that different bristle properties can be provided on the same tractor. The unit may additional comprise a sensor module and an inspection module, which can include CCTV recording functionality.

Description

BRISTLE PROPELLED TOOL

The present invention relates generally to a tool and particularly to a tool for traversing and/or cleaning and/or inspecting surfaces.

A number of bristle propelled pigs or tractors exist. Typically, these tractors are used for traversing the inside bore of a pipe. Bristle traction is very useful in this environment as the bristles are highly compliant with their surroundings, as such, if there were a partial blockage in the pipe then the bristles and therefore, the tractor, would deflect and successfully ride over/around it. Bristle traction is able to impart high grip forces equating to high tractive effort. Bristle traction is based on the 'push me -pull you' system.

The present invention seeks to provide improvements in or relating to units for traversing and/or cleaning and/or inspecting surfaces.

According to an aspect of the present invention there is provided a bi-directional tractor unit for traversing and/or cleaning and/or inspecting external surfaces, the unit comprising a bristle drive system for providing bi-directional propulsion, in which the bristle drive system comprises bristles which engage the exterior of a surface whereby the bristle drive system can be utilised for tractive effort to traverse external surfaces and also for cleaning external surfaces.

According to a further aspect of the present invention there is provided a tractor unit utilising bristles both for tractive effort and cleaning.

A further aspect provides a cleaning unit comprising a bristle drive system. i

A further aspect provides a bi-directional tractor unit for traversing and/or cleaning and/or inspecting surfaces.

A further aspect provides a tractor unit that utilises bristle traction, biased towards traversing external, irregularly shaped surfaces.

A further aspect provides a bristle traction unit comprising anti-splay means for controlling deflection (for example transverse deflection) of bristles.

In some aspects and embodiments the present invention provides a bi-directional tractor able to traverse, clean and/or inspect the mooring/anchor chains that are used to secure FPSO's and the like to the ocean bed. In other aspects and embodiments the tractor unit may be adapted to clean/inspect/traverse a riser or umbilical (for example such structures used in the oil and gas industry), a chain or other elongate member. An external bristle drive traction system formed in accordance with the present invention could also be adapted to traverse any regular or irregularly shaped, longitudinal profile, subsea or otherwise. A traction system formed in accordance with the present invention could also be used to transport equipment along a longitudinal member such as a chain -a type of lift.

A simple example of a typical, in-pipe, bristle traction system is as follows: a tractor may consist of two radially bristled brushes inter-connected by a reciprocating actuator. The radially bristled brushes have head diameters slightly greater than the diameter of the pipe into which they are to be inserted. During insertion, the bristles on the leading brush become swept rearwards as do the bristles on the trailing brush. Being a circular brush in a circular conduit -the bristles deflect rearwards with respect to the brush core but remain urged radially outwards with respect to the pipe wall, that is, the bristle tips naturally extend to the furthest radial point on the internal bore of the pipe. Operation is simple: the actuator is extended, the bristles on the trailing brush act as individual struts and point contact allows them to 'grip' the pipe wall, as such, the leading brush slides forward along the pipe as the actuator extends. The actuator is then retracted, the reverse occurs, that is, the bristles on the leading brush 'grip' the pipe wall and the trailing brush slides forward. The differential between grip and slide (slip) is nominally 3:1 with a 'standard' radial bristled brush. Brush design can be engineered to produce higher grip to slip ratios. Bristle material can be any suitable material.

The present invention utilises the above principle, however, it utilises the compliant nature of the bristles to adhere to the complex external geometry of, for example, a multi-link anchor/mooring chain. Further, it must be noted that bristles used to impart drive to an external surface as opposed to an internal concave surface are inclined to splay, that is, they naturally attempt to straighten due to the spring effect caused by their imposed deflection. In doing so they have a tendency to move off-plane, that is, if they are positioned on a convex surface, for example, a chain link, they have a tendency to slide down the sides, path of least resistance, as they attempt to straighten. Once bristles have splayed, as described above, and they are no longer axially presented to the intended tractive surface, they lose a proportion of their ability to impart useful tractive effort. Further, they buckle and therefore fail, structurally, much faster. This patent intends to address that issue and that of the issue of tractor reversibility. To make the tractor bidirectional a means must be provided to retract the inclined bristles away from the tractive surface and re-present them to the same surface whilst re-orientating the direction of their inclination.

Aspects of the present invention may be provided with one or more features as described herein.

A unit may comprise two or more brush modules which can be moved (for example shuffled) independently. Each module could have a natural inclination to grip or a natural inclination to slip. Each module may have a grip mode and a slip (for example a shuffle mode) mode.

A unit may include brush modules which are inter-connected by one or more actuators (such as a double acting actuator) suitable for achieving "push-me pull-you" traction and/or the movement of a payload.

A unit may comprise three or more brush modules interconnected by double acting actuators, in which two or more modules can be placed in a grip mode whilst one or more further modules are pulled along with any payload.

In some embodiments a minimum of two brush modules may be inter-connected by one or more double acting actuators to achieve "push-me pull-you" traction. Where higher payload capacity is required additional brush modules can be incorporated with each brush being shuffled in turn -here, two or more brushes will be in grip mode whilst pulling the trailing brush and the tractor's payload. Where additional brush modules are added, one or more additional double-acting actuators may be required.

A unit may be bi-directionally moveable by combining transverse movement of bristles whilst simultaneously changing the inclination of the bristles such that the direction of travel of the tractor unit can be altered.

A tractor unit may be bi-directional by combining the transverse movement of the bristle plates whilst simultaneously moving the linear main drive actuators it is possible to change the inclination of the bristles, thus, the direction of travel of the tractor can be altered.

The inclination of bristles may be changeable by moving a linear main drive actuator, in conjunction with radial/transverse movement of a bristle plate.

The unit may be capable of arranging bristle plates in any configuration to suit a tractive surface.

Bristles may be mounted on generally L-shape plates to produce longitudinal quadrants of bristles. Alternatively or additionally bristles may be mounted on planar plates or curved, concave or convex plates.

Bristles may be provided on interchangeable bristle plates. Bolt-on bristle plates may be provided so that different bristle properties can be obtained on the same tractor.

Within a bristle array bristles with different properties can be provided. For example: offset or staggered bristle ferrule holes between bristle plates, bristle diameter, bristle length, number of bristles, bristle stiffness, bristle material, pre-angled bristles, X-ply bristles, bristle section, composite bristles, for example, bristles specifically designed to clean and/or abrade -polymeric bristles impregnated with Silicon Carbide or Aluminium Oxide.

A unit may further comprise guide means for maintaining tractor stability and/or maintaining a pre-defined bristle stand-off distance.

The guide means may comprise one or more sets of guide wheels and/or guide rollers. The wheels and/or rollers may be affixed to the front and/or rear brush modules.

A tractor unit may incorporate one or more sets of guide wheels or guide rollers that are affixed to the front and/or rear brush modules to maintain tractor stability and pre-defined bristle stand-off distances. The use of such wheels ensure bristles yield optimum tractive effort and are not able to straighten nor collapse resulting in the tractor stalling.

Bristles may be provided on bristle plates that incorporate bristle anti-splay plates to control and therefore limit the amount of side displacement of bristles ensuring optimum tractive effort is maintained.

The bristle anti-splay plates may be of a fixed height The bristle anti-splay plates may be adjustable (for example infinitely adjustable).

The bristle anti-splay plates may be rigid or semi-flexible or progressively stiff to allow the bristles to be controlled with respect to degree of sideways latitude permitted.

The unit may comprise a means and/or a method of controlling the deflection angle and/or plane of the bristles Sprung plates with holes for bristles to pass through may be provided.

A unit may utilise short stiff bristle clusters extended normal from the tractor or tractor's bristle plates to the tractive surface, but not touching the tractive surface to provide appropriate guidance and stability. This type of arrangement may be used in conjunction with, or as an alternative to, guide means (e.g. wheels, rollers or other rolling support means).

A unit may comprise a chassis with two distinct halves that are pivoted such that the chassis can open and close in a clamshell arrangement to allow it to attach to a structure.

A unit may be able to move bristles towards and away from the tractive surface to allow the tractor to load and to reverse.

A unit may have a means and/or a method of rapid hydraulic pressure modulation to vibrate bristle plates free and allow them to return to an open position.

A unit may comprise bristle plate guide rods and bearings to separate the lateral forces created when the bristles deflect away from the hydraulic actuators and also to prevent the bristle plate carriers from canting and seizing.

A unit may comprise two or more bristle modules in which separate modules can rotate with respect to one another. The unit may comprises a clamshell chassis and in which the modules are rotatable whilst still allowing the clamshell arrangement to remain operational.

A unit may comprise tapered guides at the extremities of each brush module to allow each module to passively orientate itself to align with a misaligned chain link. The tapered guides may comprise wide-mouth collectors.

A unit may comprise thrusters to rotationally adjust its position sub-sea and/or free swim.

A unit may comprise buoyancy means.

A unit may comprise high pressure water jetting manifolds.

A unit may comprise high pressure water jetting manifolds that can utilise offset, staggered or overlapping jet nozzles to achieve full surface coverage when cleaning. One more trepanning nozzles may be provided to trepan the chain link profile.

A unit may comprise rotating cleaning brushes.

A unit may comprise a plough or scraper.

A unit may comprise brush module locking actuators to provide a locking force to allow the tractor to load, reverse, step or lock. The locking actuators form part of a fail-safe function.

A unit may further comprise proximity sensors and control algorithms to determine which of the module locking actuators to deploy to ensure adequate clamping forces can be obtained.

Module locking actuators may be used on a chain to lock onto the flats on a chain link.

A unit may comprise a sensor for giving its rotational position, either absolute, or relative to a datum such as a ship, chain, structural elongate member.

A unit may comprise a control system that is used to automatically adjust the clockwise or anticlockwise bias to maintain a desired rotational position or path.

The control system may control: release of all bristle plates; utilising thrusters to rotate to true; and then re-loading crawler.

The control system may be a programmable logic controller (PLC).

A unit may further comprise an on-board electrically driven (hydraulic power unit) HPU, where electrical power is provided via an umbilical or cable from a power supply remote to the vehicle.

The on-board HPU may be used to supply hydraulic fluid to motors, cylinders and/or additional on-board systems.

A unit may further comprise a module for cleaning a tractive surface.

The cleaning module may clean by: scraping, ploughing, abrading, rotating and/or oscillating brushes, ultrasound or water jetting.

A unit may further comprise inspection means. The inspection means may comprise chain link inspection technology. The inspection means may comprise a CCTV recording facility. The inspection means comprises one or more of: ultrasound, eddy current, MFL, physical chain link measurement via dial gauges, Vernier and/or Micrometer, corrosion detection, surface corrosion detection or any other non-destructive testing/measurement.

A tractor unit may incorporate a sampling scoop, arm or grab, scraper or any other device deemed necessary to recover marine growth or rust particulate for sampling and/or to adjust the mechanics of the chain.

A unit may further comprise means for: recovery of marine growth or rust particulate; sampling; or adjusting the mechanics of a chain. A unit may comprise: a sampling scoop, arm or grab, or scraper.

A unit may further comprise a chain link counter.

A unit may further comprise a sensor module.

A unit may further comprise an inspection module.

A unit may comprise a flapper wheel, rotating flapper, flailing arm system or the like, for example to remove marine growth. Two or more "lobes" or the like may be provided.

Sensor and for inspection modules may be positioned at a location on, before or after the tractor.

In some units the position of centre of gravity and centre of buoyancy may be in or near to the same position.

The present invention also provides a unit as shown and described herein.

The present invention also provides a method of traversing and/or inspecting and/or cleaning a surface as shown and described herein.

Different aspects of the present invention may be used separately or together.

Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. Features of the independent and dependent claims may be combined with the features of the other independent and dependent claims as appropriate, and in combination other than those explicitly set out in the claims.

The present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure I. A schematic of a simple external bristle traction system.

Figure 2. A chassis member demonstrating the clamshell ability.

Figure 2a. A schematic of the external bristle traction system orientating its bristles (vehicle loading) to begin traversing the surface/chain.

Figure 3. A schematic detailing the method of altering the inclination direction of the bristles.

Figure 4. Embodiment A -Overview: bristle driven chain cleaning/inspection tractor.

Figure 5. Bristle driven chain tractor -end view.

Figure 6. Bristle carrier and bristle plates with suspension wheels; showing some bristle clusters and bristle anti-splay guides.

Figure 7. Tractor; bristle plates orientated ready for drive.

Figure 8. Embodiment B -Overview: bristle driven chain cleaning/inspection tractor Figure 9. Bristle driven chain tractor -rear end view.

Figure 10. Bristle plate -anti-splay guides, individual bristle clusters and central aperture for guide wheel assembly is shown.

Figure I I. Detail showing opposing bristle directions on front and rear modules of Embodiment B. Figure 12. Front of tractor showing four over-lapping high pressure jetting manifolds.

Figure 13. High pressure jetting manifold.

Figure 14. Bristle anti-splay and directional deflection control plate Figure 15. A method of altering bristle properties without changing bristle plates.

Figures 16 to 18. Front perspective, side and rear perspective view of a flapper wheel formed in accordance with the present invention.

Example embodiments are described below in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein.

Accordingly, while embodiments can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate.

The terminology used herein to describe embodiments is not intended to limit the scope. The articles "a," "an," and "the" are singular in that they have a single referent, however the use of the singular form in the present document should not preclude the presence of more than one referent. In other words, elements referred to in the singular can number one or more, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and/or "including," when used herein, specify the presence of stated features, items, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, items, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealized or overly formal sense unless expressly so defined herein.

Figure I shows the basic principle of the 'push me -pull you' external bristle drive traction system -this is a very simplistic model: * Drawing A; Tractor is stationary -in this state the tractor has been loaded (loading will be discussed and detailed separately) onto a thin, planar surface represented by the chain dotted line. All bristle plates, on both sides of the actuator, are extended and the bristles are correctly inclined and in contact with the tractive surface.

* Drawing B; Main drive actuator is extended -bristles on the left-hand bristle plates grip the planar surface as they become axially loaded due to the reaction force they experience counter-acting the static and sliding friction of the right-hand bristle plates sliding forward -the result being the right-hand bristle plates are free to slide.

* Drawing C; Main drive actuator closes -bristles on the right-hand bristle plates grip the planar surface as they become axially loaded due to the reaction force they experience counter-acting the static and sliding friction of the left-hand bristle plates sliding forward -the result being the left-hand bristle plates are free to slide. The tractor in drawing C is in the same position as it were in Drawing A, however, at this point the tractor, in its entirety, has moved forward equivalent to the stroke length of its main drive actuator.

* Drawing D; Tractor drive sequence repeats: Drawings D through G show the tractor moving the equivalent of two additional main drive actuator stroke lengths. Movement is not continuous -it is stop/start in nature.

When the tractor is initially loaded onto a chain its bristles are in the fully retracted position. To begin the drive process, as detailed by the simple schematic in Figure I, it is necessary to orientate all bristles to a forward or rearward swept position depending upon the vehicle's intended direction of travel. This requires the vehicle to go through a load procedure. The load procedure is illustrated in Figure 2 and 2a.

* Drawing A; Tractor's clamshell chassis is opened (Figure 2 shows a chassis member in the open position) and positioned around the chain via a clamping arrangement Bristles are retracted and thus not in contact with the tractive surface at this stage.

* Drawing B; Locking actuators are closed on the left-hand bristle module.

* Drawing C; Locking actuators remain closed on the left-hand bristle module. The main drive actuator extends whilst the right-hand bristle carriers are urged towards the tractive surface. These combined actions result in the right-hand bristles being correctly orientated for travel.

* Drawing D; Locking actuators on the right-hand bristle module are closed. Locking actuators on the left-hand bristle module are opened.

* Drawing E; Locking actuators remain closed on the right-hand bristle module. The main drive actuator closes whilst the left-hand bristle carriers are urged towards the tractive surface. These combined actions result in the left-hand bristles being correctly orientated, such that they are orientated in the same direction as the bristles on the right-hand module.

* Drawing F; Locking actuators on right-hand bristle module are released. The bristles on both sides of the main drive actuator are now correctly loaded and inclined. The vehicle is now correctly loaded and ready to begin traversing the surface from the left to the right This present invention also intends to describe an external bristle drive tractor that is fully bi-directional. The tractor achieves this by employing a mechanism that allows the controlled retraction of the bristle carriers fully away from the chain, that is, the bristles have neither inclination nor contact This occurs sequentially; acting upon each side of the main drive actuator in turn. During this operation the other half of the tractor is mechanically clamped to the chain to provide a suitable reaction force for the next step; as the bristle carriers are urged back towards the chain their direction can be changed by combining their transverse movement with the axial movement of the main actuator(s). By changing the inclination of both sets of bristles via this method the direction of the tractor can be altered. Of note is the fact that tractor's direction can be altered infinitely. The change of direction procedure is illustrated in Figure 3.

* Drawing A; Tractor direction of travel is left to right A change of direction is required.

* Drawing B; Locking actuators on the left-hand bristle modules are locked. The bristle modules on the right-hand brush are released. The bristles retract from the tractive surface -it should be noted that an additional extension and retraction of the main drive actuator may be required here to fully release the bristle plates or a rapid switching (modulation to induce vibration/shock) of the main actuator hydraulics would give the same result.

* Drawing C; Left-hand locking actuators remain locked. Right-hand bristle modules remain in their retracted position. Main drive actuator is opened.

* Drawing D; Left-hand locking actuators remain locked. Main drive actuator is closed, simultaneously, the right-hand bristle modules are urged towards the tractive surface. The result is the right-hand bristles change their direction of inclination.

* Drawing E; Locking actuators on the left-hand bristle modules are released.

* Drawing F; Locking actuators on the right-hand bristle modules are locked. The bristle modules on the left-hand brush modules are released -the bristles retract from the tractive surface.

* Drawing G; Locking actuators on the right-hand bristle modules remain locked. Main drive actuator is opened, simultaneously, the left-hand bristle modules are urged towards the tractive surface. The result is the left-hand bristles change their direction of inclination.

* Drawing H; Tractor direction of travel is now right to left.

EMBODIMENT A: A marine biased, bi-directional, bristle driven tractor that is able to traverse, clean and inspect irregularly shaped external profiles, for example, an anchor or FPSO mooring chain. The tool can operate in sea, air and/or through the splash-zone. The tool can ascend and descend whether in water or air. Further, the tractor could be used as a cargo lift to transport equipment to the ocean floor or from the ocean floor to the surface. The tractor is controlled and operated by a topside operative via a power and/or control umbilical. The tractor may carry an HPU or it may be remotely located. The tractor has the ability carry high pressure water jetting manifolds and nozzles positioned such that they encompass a chain or other structure to yield successful cleaning. The tractor has the ability to incorporate small thrusters -sufficient to rotate the tractor around the chain or other structure when the bristles are retracted -the tractor utilises buoyancy to maintain buoyancy, adjustable depending upon requirements. Combined, these features allow the tractor's umbilical to unwind from the traversed chain/structure assuming the tractor rotates during its traverse. Without this feature the tractor's umbilical may become helically wound around the chain/structure -this would result in the tractor stalling due to the capstan effect of the umbilical winding around the chain. The bristle drive system also provides a cleaning function as the bristles abrade over the surface of the chain. The tractor and therefore the bristles are able to cope with some irregularities on the mooring chain/structure as the bristles are able to deflect rearwards away from the obstacle. Further, as the tractor utilises bristle module locking clamps as well as axial drive actuators it has an ability to step over obstacles. Small thrusters allow the tractor to swim over obstacles when the bristles are retracted.

The tractor in Figure 4 comprises front and rear modules. The modules are interconnected by one or more double acting hydraulic (main drive) actuators -linear actuators are typically used in the "push me-pull you" method of traction. Each module is made up of two distinct hinged halves -in the style of a clamshell (see Figure 2) -this enables the tool to open and close around the chain. The halves of each module are moved towards and away from one another by one or more double acting hydraulic (clamshell) actuators. When the two halves are closed and the bristle plates are in their retracted positions the tool has clearance around the chain.

The front and rear modules of the tool each have four longitudinal bristle plates -each is an 1' shape in section. Each bristle plate has four guide/stabiliser wheels attached to each plate. The guide/stabiliser wheels act to maintain the bristles at a pre-determined distance from the chain links. Without the wheels, the bristles would have to perform two functions -guidance and drive; bristles on one side of the tractor may collapse and the bristles on the other side would begin to straighten due to inherent instability. The bristles must be maintained within a window of angular deflection as well as transverse splay to yield optimum tractive effort -bristles collapsing or straightening would result in poor tractive effort. Each plate can be moved towards and away from the chain or tractive surface by means of two or more double acting hydraulic actuators. Each bristle plate is also guided by bristle plate guide rods and bearings -these act to remove lateral loads from the bristle plate actuator(s) nose bearings, nose seals and the piston/seal(s) -they also prevent the plates from seizing/locking in a canted position due to the forces imposed by the deflected bristles along the plate's length. Combined traction and cleaning bristles are attached to each bristle plate -some bristles are normal to the faces of each plate -these are the main drive/cleaning bristles and are designed to contact the sides of the chain link(s). Some bristles protrude from additional bristle plates mounted normal across the apex area of each plate -these are designed to reach into the corners of overlapping chain links with respect to cleaning but also provide some tractive effort. The main drive/cleaning bristles are prevented from moving/splaying sideways with respect to the axis of the chain by bristle anti-splay guides.

Each module, front and rear, has eight module locking actuators. Only four of the actuators, on each module, are used at a given time to lock the front or rear module during loading and reversal operations. To lock, it is necessary for the tractor to use opposing actuators. The four that are chosen depend on the position the tractor stops at with respect to the position of each chain link -a chain link may be vertically or horizontally orientated with respect to the tractor. A proximity sensor is included on each actuator mount plate -these provide feedback with respect to which four actuators should be activated to provide suitable clamping force. These four actuators clamp on the sides of the chain link, two sets of two, with each actuator opposing and providing a suitable reaction force for the other.

As each link of the chain is able to partially rotate independent of its inter-connected neighbour, provision must be made on the tractor to allow rotational compliance. A small amount of rotational compliance is provided by the ability of the bristles to deflect a limited distance -up to the limits of the anti-splay guides. In addition, independent module rotation, can be included by the addition of slew ring segments at one end or the other of the main drive actuators. A segmented slew ring will still enable the clamshell tractor chassis to be opened and closed whilst still allowing good angular displacement, for example, tens of degrees (slew ring segmented mechanism is not shown to maintain clarity).

Figure 5 shows an end view of the tool. Here, the tool is shown clamped around a 180mm diameter mooring chain and about to orientate its bristles ready to begin driving. The two halves of the tool are shown in their closed position. The 1' shaped bristle plates are clearly shown as are the two different types of bristle carriers and bristles -the bristles normal to the chain sides and the bristles extending from the bristle plate apex -these extend into the corners of the inter-connected chain links.

Figure 6 shows a single bristle plate. Guide and suspension wheels are clearly shown. The individual bristle carriers can be seen. Only a few bristle clusters are represented in the interests of clarity. The bristle anti-splay guide plates can be seen -again only a small amount are shown -these plates would be positioned across the surface of the bristle carriers to prevent excessive transverse bristle splay and therefore loss of tractive effort. Note: the drilled holes to receive the bristle ferrules on the two end bristle carrier plates are offset with respect to the central bristle carrier plate. This is to ensure full cleaning capability and optimum tractive effort Two smaller bristle plates are shown positioned on the apex of the bristle plate.

Figure 7 shows the tool correctly loaded onto the chain. The tool can now undertake its intended operation, whether that be cleaning, inspection or transportation. Small plates carrying cleaning bristles can be added (not shown) to clean the radii of the chain links in the positions where no bristles coverage is shown. (Note: for clarity, no cleaning tools, inspection tools, transportation securing devices, umbilical, buoyancy, thrusters or HPU are shown in these Figures).

EMBODIMENT B: The tractor in Figure 8 comprises front and rear modules. The modules are interconnected by one or more double acting hydraulic drive actuators -actuators are used in the "push me-pull you" method of traction. Each module is made up of two distinct hinged halves -in the style of a clamshell -this enables the tool to open and close around the chain. The halves of each module are moved towards and away from one another by one or more double acting hydraulic actuators. When the two halves are closed and the bristle plates are in their retracted positions the tool has clearance around the chain.

The front and rear modules of the tool each have four longitudinal bristle carrier channels -onto each carrier channel is mounted 6 bristle plates, each has its own guidance wheel -the front module has four vertically orientated bristle carrier channels and bristle plates (bristles are arranged vertically). The rear module has four horizontally orientated bristle carrier channels and bristle plates (bristles are arranged horizontally). The bristle carrier channels and bristle plates are arranged in two sets of two on each module and are orientated such that each bristle channel and associated bristle plates oppose one another. Such an arrangement allows all facets of the chain link to be cleaned and to provide suitable and full tractive surfaces. The front module has two longitudinal, horizontally orientated guide roller plates and the rear module has two longitudinal, vertically orientated guide roller plates. The purpose of each is to help centralise the tractor on the chain and to prevent off-axis movement of the tractor. The front pair work in conjunction with the rear pair to maintain overall tractor stability.

Each bristle plate has its own guide/stabiliser wheel. The guide/stabiliser wheels act to maintain the bristles at a pre-determined distance from the chain links. Without the wheels, the bristles would have to perform two functions -suspension and drive; bristles on one side of the tractor would collapse and the bristles on the other side would begin to straighten due to inherent instability. The bristles must be maintained within a specific window of angular deflection to yield optimum tractive effort -bristles collapsing or straightening would result in poor tractive effort. Each bristle carrier channel and associated bristle plates (unit) can be moved towards and away from the chain or tractive surface by means of two or more double acting hydraulic actuators. Each bristle unit may be guided by bristle plate guide rods and bearings (not shown in this embodiment) -these act to remove lateral loads from the actuator nose bearing, nose seal and piston/seal(s). The main drive/cleaning bristles are prevented from moving/splaying sideways with respect to the axis of the chain by bristle anti-splay guides.

Figure 9 shows the rear view of the tractor. The rear module bristle carrier channels, bristle plates and individual bristle clusters are shown -bristle clusters are in a transverse orientation. The guide rollers shown at the top and the bottom control the rear module -these work in conjunction with the wheels mounted onto each bristle plate. Note: upper right and lower left bristle plate guide wheels are not shown for clarity reasons. The front module guide roller and front module bristles are also visible.

Figure 12 illustrates an arrangement of four high pressure jetting manifolds. Each manifold has a number of high pressure jets fitted. Each manifold is attached to one of the bristle carrier channels. As the bristle carrier channels and thus, the bristle plates and bristle clusters are urged towards the chain, simultaneously, the high pressure jetting manifolds are also brought closer to the chain. As such, when the tractor is loaded or it reverses, then the high pressure jetting manifolds are correctly retracted and subsequently repositioned. Ready to continue cleaning operations.

Figure 13 shows the detail of the manifold design. The design is such that it provides a means of overlapping and off-setting the nozzles and therefore the coverage of the high pressure jetting fluid such that the full perimeter of each chain link can be pressure jetted/cleaned with the minimum amount of manifolds whilst still allowing the manifolds to retract to allow tractor loading and reversal.

An alternative to bristle anti-splay guides is the use of bristle anti-splay and direction control plates on each bristle plate, as shown in Figure 14. The bristle control plates control the plane that the bristles are able to deflect through. In the example in Figure 14, the bristles are controlled such that they are able to freely deflect in/along the direction of the bristle plate's longest side due to the springs on both ends of the bristle plate being able to deflect in that plane. However, the bristle clusters are unable to deflect in the direction/plane of the bristle plate's short side, as such, the springs are fully constrained in that plane. By placing the springs along the long-side of the bristle plate these properties, deflect and constrain, would be reversed. The bristle control plates can also act to control bristle splay, increase or decrease bristle cluster effective stiffness, forcing bristles to act as one or forcing some bristles to act as one and others to act as specific longitudinal groups. For example, instead of holes, a proportion of the holes could be replaced with slots (not shown) -this would give similar results to that of bristle anti-splay guides, that is, that line of bristles would be free to substantially move without having to overcome the forces of the end springs and/or the other (controlled by constraint) bristle clusters. Such plates allow the bristles to be controlled or, designed, to operate with respect to a specific tractive surface condition(s).

Figure 15 shows a method of providing some control with respect to anti-splay, however, its main role is to alter, typically, stiffen when added or loosen when removed, bristles/bristle clusters of a specific length on an existing bristle plate. In this example, a machined or moulded block can be inserted over existing bristle clusters to effectively shorten the bristle clusters. By doing this the stiffness of the individual bristle cluster increases, as its root position effectively alters. Different thickness blocks can be added or subtracted depending upon properties desired. Thus, bristle plates with bristle clusters of a certain length can be used on different tractive surfaces without the need to change complete bristle plates.

Figure 16 to 18 show a flapper wheel system. In this embodiment a wheel with five sets of three resilient, stacked flailing arms are provided for cleaning marine growth in use.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment shown and that various changes and modifications can be affected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Claims

CLAIMS1) A bi-directional tractor unit for traversing and/or cleaning and/or inspecting external surfaces, the unit comprising a bristle drive system for providing bidirectional propulsion, in which the bristle drive system comprises bristles which engage the exterior of a surface whereby the bristle drive system can be utilised for tractive effort to traverse external surfaces and also for cleaning external surfaces.
2) A unit as claimed in claim I for traversing external, irregularly shaped surfaces.
3) A unit as claimed in claim I or claim 2, comprising anti-splay means for controlling deflection of bristles.
4) A unit as claimed in any preceding claim, comprising two or more brush modules which can be shuffled independently.
5) A unit as claimed in claim 4, in which each module has a grip mode and a shuffle mode.
6) A unit as claimed in claim 4 or claim 5, in which the brush modules are interconnected by one or more double acting actuators suitable for achieving "push-me pull-you" traction and/or a payload.
7) A unit as claimed in any preceding claim, comprising three or more brush modules interconnected by double acting actuators, in which two or more modules can be placed in a grip mode whilst one or more further modules pull the trailing module/s.
8) A unit as claimed in any preceding claim, in which the unit is bi-directionally moveable by combining transverse movement of bristles whilst simultaneously changing the inclination of the bristles such that the direction of travel of the tractor unit can be altered.
9) A unit as claimed in claim 8, in which the inclination of the bristle is changed by moving a linear main drive actuator.
10)A unit as claimed in any preceding claim, in which the unit can arrange the bristle plates in any configuration to suit a tractive surface.
11)A unit as claimed in claim 10, in which bristles are mounted on generally L-shape plates to produce longitudinal quadrants of bristles.
12) A unit as claimed in claim 10, in which bristle are mounted on planar plates or curved, concave or convex plates.
13) A unit as claimed in any preceding claim, in which bristles are provided on interchangeable bristle plates.
14) A unit as claimed in claim 13, in which bolt-on bristle plates are provided so that different bristle properties can be obtained on the same tractor.
15)A unit as claimed in any preceding claim, in which bristles with different properties can be provided.
16) A unit as claimed in claim 15, in which the different properties include: offset bristle ferrule hole diameter, bristle diameter, bristle length, number of bristles, bristle stiffness, bristle material, pre-angled bristles, X-ply bristles, bristle section, composite bristles, for example, bristles specifically designed to clean and/or abrade -polymeric bristles impregnated with Silicon Carbide or Aluminium Oxide.
17) A unit as claimed in any preceding claim, and further comprising guide means for maintaining tractor stability and/or maintaining a pre-defined stand-off distance.
18)A unit as claimed in claim 17, in which the guide means comprise one or more sets of guide wheels and/or guide rollers.
19) A unit as claimed in claim 18, in which the wheels and/or rollers are affixed to front and rear brush modules.
20)A unit as claimed in any preceding claim, in which bristle are provided on bristle plates that incorporate bristle anti-splay plates to control and therefore limit the amount of side displacement of bristles ensuring optimum tractive effort is maintained.
21)A unit as claimed in claim 20, in which the bristle anti-splay plates are of a fixed height.
22)A unit as claimed in claim 20, in which the bristle anti-splay plates are infinitely adjustable.
23) A unit as claimed in any of claims 20 to 22, in which the bristle anti-splay plates are rigid or semi-flexible or progressively stiff to allow the bristles to be controlled with respect to degree of sideways latitude permitted.

24)A unit as claimed in any preceding claim, comprising a method of controlling the deflection angle and/or plane of the bristles 25)A unit as claimed in claim 24, in which sprung plates with holes for bristles to pass through are provided.26)A unit as claimed in any preceding claim and utilising short stiff bristle clusters extended normal from the tractor or tractor's bristle plates to the tractive surface, but not touching the tractive surface to provide appropriate guidance and stability.27)A unit as claimed in any preceding claim, comprising a chassis with two distinct halves that are pivoted such that the chassis can open and close in a clamshell arrangement to allow it to attach to a structure.28)A unit as claimed in any preceding claim, in which the unit is able to move bristles towards and away from the tractive surface to allow the tractor to load and to reverse.29)A unit as claimed in any preceding claim and having a method of rapid hydraulic pressure modulation to vibrate bristle plates free and allow them to return to an open position.30)A unit as claimed in any preceding claim, comprising bristle plate guide rods and bearings to separate the lateral forces created when the bristles deflect away from the hydraulic actuators and also to prevent the bristle plate carriers from canting and seizing.31) A unit as claimed in any preceding claim, comprising two or more bristle modules in which separate modules can rotate with respect to one another 32) A unit as claimed in claim 31, in which the unit comprises a clamshell chassis and in which the modules are rotatable whilst still allowing the clamshell arrangement to remain operational.33) A unit as claimed in any preceding claim, comprising tapered guides at the extremities of each brush module to allow each module to passively orientate itself to align with a misaligned chain link.34)A unit as claimed in claim 33, in which the tapered guides comprise wide-mouth collectors.35)A unit as claimed in any preceding claim, comprising thrusters to rotationally adjust its position sub-sea and/or free swim.36)A unit as claimed in ay preceding claim and comprising buoyancy means.37)A unit as claimed in any preceding claim, comprising high pressure water jetting manifolds.38)A unit as claimed in any preceding claim, comprising high pressure water jetting manifolds that can utilise offset, staggered or overlapping jet nozzles to achieve full surface coverage when cleaning.39) A unit as claimed in any preceding claim, further comprising rotating cleaning brushes.40)A unit as claimed in any preceding claim, further comprising a plough or scraper.41) A unit as claimed in any preceding claim, further comprising brush module locking actuators to provide a locking force to allow the tractor to load, reverse, step or lock.42)A unit as claimed in claim 41, in which the locking actuators form part of a fail-safe function.43)A unit as claimed in claim 41 or claim 42, further comprising proximity sensors and control algorithms to determine which of the module locking actuators to deploy to ensure adequate clamping forces can be obtained.44)A unit as claimed in claim 43, in which module locking actuators used on a chain lock onto the flats on a chain link.45)A unit as claimed in any preceding claim, further comprising a sensor for giving its rotational position, either absolute, or relative to a datum such as a ship, chain, structural elongate member.46)A unit as claimed in any preceding claim, in which a control system is used to automatically adjust the clockwise or anticlockwise bias to maintain a desired rotational position or path.47)A unit as claimed in claim 46, in which the control system controls: release of all bristle plates; utilising thrusters to rotate to true; and then re-loading crawler.48)A unit as claimed in claim 46 or claim 47, in which the control system is a PLC.49)A unit as claimed any preceding claim, further comprising an on-board electrically driven HPU, where electrical power is provided via an umbilical or cable from a power supply remote to the vehicle.50) A unit as claimed in claim 49, in which the on-board HPU is used to supply hydraulic fluid to motors, cylinders and/or additional on-board systems.51)A unit as claimed in any preceding claim, further comprising a module for cleaning a tractive surface.52)A unit as claimed in claim 51, in which the cleaning module cleans by: scraping, ploughing, abrading, rotating and/or oscillating brushes, ultrasound or water jetting.53)A unit as claimed in any preceding claim, further comprising inspection means.54)A unit as claimed in claim 52, in which the inspection means comprises chain link inspection technology.55)A unit as claimed in claim 53 or claim 54, in which the inspection means comprises a CCTV recording facility.56)A unit as claimed in any of claimed 53 to 55, in which the inspection comprises one or more of: ultrasound, eddy current, MFL, physical chain link measurement via dial gauges, Vernier and/or Micrometer, corrosion detection, surface corrosion detection, or any other non-destructive testing/measurement.57)A unit as claimed in any preceding claim, further comprising means for recovery of marine growth or rust particulate; sampling; or adjusting the mechanics of a chain.58) A unit as claimed in claim 57, comprising: a sampling scoop, arm or grab, or scraper.59)A unit as claimed in any preceding claim, further comprising a chain link counter.60)A unit as claimed in any preceding claim, further comprising a sensor module.61)A unit as claimed in any preceding claim, further comprising an inspection module.62)A unit as claimed in any preceding claim, further comprising a cleaning module.63)A unit as claimed in claim 60 or claim 61, in which the module is positioned at a location on, before or after the tractor.64)A unit as claimed in any preceding claim, further comprising a flapper wheel, flailing arm system or the like.65)A unit as claimed in any preceding claim, in which the position of centre of gravity and centre of buoyancy are in or near to the same position.66)A unit substantially as hereinbefore described with reference to and as shown in, the accompanying drawings.67) An FPSO chain cleaning tool comprising a unit as claimed in any preceding claim.68) A method of traversing a surface substantially as hereinbefore described with reference to and as shown in, the accompanying drawings.69) A method of cleaning a surface substantially as hereinbefore described with reference to and as shown in, the accompanying drawings.70) A method of inspecting a surface substantially as hereinbefore described with reference to and as shown in, the accompanying drawings.