Floating dock

A floating dock is provided for efficiently cleaning ship hulls and for reducing pollution problems associated with the cleaning of ship hulls. A method for cleaning ship hulls with a floating dock also is provided. The floating dock is ballasted and independently manoeuvrable. The floating dock has a ship hull receiving section which can be submerged at least partly so that a base part of the ship hull receiving section may be positioned beneath a ship hull. Cleaners are provided on at least one inner side of the ship hull receiving section to contact a side of the ship hull, and a debris collector may be provided to collect debris removed from the cleaning operation for later processing or dumping at a remote site. The floating dock can be self propelled forward and backward to reach the ship and can be self propelled laterally to clean the ship.

TECHNICAL FIELD 
This invention relates to a method and apparatus for cleaning a ship hull, 
and in particular to a manoeuvrable floating dock. 
BACKGROUND ART 
Barnacles and marine growth on the hulls of ships, below the water line, 
are a significant factor in reducing the efficiency of marine shipping. 
There are two methods by which this problem has been addressed. The first 
has been the development of various anti-fouling paints. In general these 
paints include the composition tributyltin (TBT). For example, the most 
commonly used anti-fouling paint systems currently in use are the 
TBT-self-polishing copolymer (SPC) systems. TBT is toxic to marine life 
and also to humans. TBT can enter the environment in significant 
concentrations where ships sit in shallow relatively stationary water, and 
also as a result of ship hull cleaning. Thus, the use of TBT-containing 
paints is on the decline. Indeed, a number of countries have now banned 
the use of paints including TBT, or are in the process of passing 
legislation to prohibit its use. Alternative, non-TBT containing 
antifouling paints are being developed and tested but these tend to be 
effective for a shorter period and/or may be effective only against marine 
growth of selected types. 
The second option for dealing with barnacles and marine growth is to 
conduct regular cleaning of ship hulls. Traditionally, ship hulls have 
been cleaned by divers operating small submarine machinery with steel 
brushes to brush off the barnacles and marine growth. However, this is a 
very time consuming process, the efficiency of the cleaning is 
questionable and the debris, which generally includes some possibly toxic 
paint, is discarded on the seabed at the mooring site of the ship (usually 
in a port). 
Thus, it is an object of the present invention to provide a method and 
apparatus for cleaning the hull of a ship which reduces or overcomes the 
abovementioned problems, or which at least provides the public with a 
useful alternative. 
Other objects of the invention may become apparent from the following 
description which is given by way of example only. 
DISCLOSURE OF INVENTION 
According to one aspect of the present invention there is provided a 
floating dock comprising a ship hull receiving means adapted to 
accommodate the beam of a ship, buoyancy means to control buoyancy of the 
receiving means, lateral cleaning means adapted to contact and clean at 
least a part of a side of a ship hull, adjustment means adapted to adjust 
the position of the lateral cleaning means to accommodate ships of 
different beam and self propulsion means adapted to manoeuvre the 
receiving means both to and from moored ships and along the length of a 
moored ship hull, and wherein said adjustment means and self propulsion 
means operate independently of a ship to be cleaned. 
In a further preferred form the floating dock of the present invention may 
further comprise support means adapted to support a base of the receiving 
means, when in use, beneath the ship hull. 
The receiving means of a floating dock of the present invention may 
preferably comprise a substantially U-shaped hull, said hull having a base 
part and lateral towers. Preferably, the buoyancy means may provide 
buoyancy to at least the base, and preferably also to each of the lateral 
towers. 
In one preferred form of the floating dock of the present invention there 
may be lateral cleaning means associated with each lateral tower and 
bottom cleaning means. Each cleaning means may comprise a plurality of 
brushes in rotatable disc form. 
In one preferred form of the invention the plurality of brushes forming a 
lateral cleaning means may be adjustable collectively on one or more 
lateral panels. Preferably the adjustment means enable lateral movement, 
as well as tilt and/or rotation of the lateral panels about a vertical 
axis. 
Alternatively, the or each lateral cleaning means may comprise a plurality 
of separate cleaning panels, each cleaning panel being separately 
adjustable and having a plurality of brushes. 
In a preferred form of the invention the adjustment means may comprise 
hydraulically controlled telescopic arms, a plurality of which may control 
the adjustment of the or each lateral panel, or each one of which may 
control the adjustment of a single cleaning panel. 
In a further preferred form, the floating dock of the present invention may 
further comprise a collection means adapted to collect debris cleaned off 
a ship hull by the floating dock. Preferably, the collection means may 
comprise a collection chamber and dumping or removal means for dumping 
collected debris at a remote site or removing collected debris internally 
to the floating dock for subsequent processing or dumping. 
According to an alternative aspect of the present invention there is 
provided a method of cleaning a ship hull when in substantially open 
water, said method comprising: 
manoeuvring a floating dock to a moored ship by self-propulsion means; 
submerging at least a part of a ship hull receiving means of the floating 
dock adapted to clean ship hulls and accommodate the beam of a ship, 
beneath the ship hull; 
contacting cleaning means of the floating dock with a part of at least one 
side of the ship hull; 
operating the cleaning means, and 
manoeuvring the floating dock by the self-propulsion means substantially 
the length of the ship hull to clean at least one side thereof. 
In a preferred form of this aspect of the present invention cleaning means 
may be contacted on both sides of the ship hull to enable cleaning of each 
side simultaneously. 
In one preferred form, the method of the invention may further comprise 
adjusting the or each cleaning means substantially to follow the contour 
of the ship hull. 
In a further preferred form of the invention cleaning means may also 
contact the bottom of the ship hull. 
In another preferred form, the method of the invention may further comprise 
collecting material cleaned off the ship hull for subsequent processing 
and/or dumping remote from the site of cleaning. 
According to a further aspect of the present invention there is provided a 
cleaning panel adapted for cleaning the hull of a ship, said panel 
comprising a plurality of brushes in the form of rotatable discs, said 
brushes configured in at least two rows, one row offset in relation to an 
adjacent row, and at least one brush connected by hinging means to the 
rest of the panel, said one or more hinging means biased to maintain its 
associated brush in the plane of the panel at rest. 
Further aspects of the present invention will become apparent from the 
following description which is given by way of example only, and with 
reference to the accompanying drawings, in which:

MODES FOR CARRYING OUT THE INVENTION 
The floating dock 1 of the present invention may comprise a hull or 
superstructure 2, adjustable lateral arms 3, cleaning means 4a, 4b and one 
or more drive means 5a, 5b, 5c for propelling the dock. 
The hull 2 may comprise a base part 6 and lateral towers 7a, 7b. In the 
embodiment shown in FIG. 1 one lateral tower 7a is more substantial than 
the other 7b since the drive means, hydraulic controls and bridge of the 
floating dock are accommodated in or on this lateral tower 7a in this 
embodiment. However, it will be appreciated that the specific 
configurations of the lateral towers 7a, 7b are not essential to the 
invention, and in other embodiments the lateral towers 7a, 7b may be 
symmetrical, each housing functional equipment. 
At least a part of the hull 2 may provide buoyancy to the floating dock 1. 
This buoyancy may be provided in the base 6, lateral towers 7a, 7b and/or 
a combination of these. There may be means for controlling the degree of 
buoyancy to enable the floating dock 1 to be floated or substantially 
submerged for operation. 
The floating dock 1 is manoeuvrable by virtue of having its own drive 
means. In the embodiment shown in FIG. 1 there may be propellers 5c to 
move the floating dock 1 forwards and backwards, and additional propellers 
5a to move the dock 1 laterally. In embodiments of the invention having 
large lateral towers it is envisaged that additional lateral propulsion 
means 5b will be required to ensure stability of the floating dock when in 
use. Whilst in the embodiments shown in the drawings propulsion of the 
floating dock 1 is provided by propellers, it will be appreciated that 
other means of self-propulsion are anticipated and included within the 
scope of this invention. In the embodiment of the invention shown in FIGS. 
13 and 14 propulsion is provided by rotatable motors 40 (e.g. AZIPOD 
motors), positioned at either end of the floating dock, with an 
additional, reversible, central propulsion means 41. 
Whilst the embodiments shown in the drawings include drive means to enable 
independent manoeuvrability of the floating dock it will be appreciated 
that the cleaning operation performed by the dock could equally be 
achieved by mooring the dock and driving or towing ships through the dock 
when partially submerged. In that case a dock of the present invention 
would not require separate drive means. 
In one preferred form of the invention, and as shown for example in FIGS. 
2, 3 and 13-15, there may be a means for collecting debris removed by the 
cleaning means 4a, 4b. There may be one or more collection means 8 
positioned in a central upper part of the base 6. When in operation the 
design of the floating dock 1 may be adapted to direct removed debris into 
the collection means 8. At a lower part 9 of the collection means 8 there 
may be dump doors 10 through which collected debris may be discarded, as 
shown in FIGS. 2 and 3. 
In the alternative embodiment of FIGS. 13 to 15, and also with reference to 
FIG. 18, the collection means 8 may collect debris internally for 
subsequent processing and/or disposal. Referring to FIG. 18, such a 
collection means 8 may comprise a receiving means 47 comprising a 
plurality of cylindrical containers 42, rotatable in cylindrical housings 
43. The containers 42 may be rotatable between a collecting position in 
which an open part 44 of the container faces upwards to receive debris, 
and a dumping position in which the open part 44 faces downwards for 
dumping the debris through corresponding openings 45 in the cylindrical 
housings 43 on to conveyor 46. It will be appreciated that this type of 
dumping system requires appropriate sealing between the cylindrical 
containers 42 and their housings 43 to enable operation of the collection 
means whilst the lower part of the floating dock 1 is submerged when in 
operation. 
Debris and any contaminated water would be transferred by the conveyor to 
appropriate means for transporting the material from the vessel at a later 
time. 
In one embodiment, as shown in FIGS. 1 to 9, the lateral arms 3 may 
comprise a substantially vertically disposed panel 37, cleaning means 4a 
interconnected to a front surface 38 of the panel 37, and fenders 39 
adjacent longitudinal edges 40 of the front surface 38. The lateral arms 3 
may be connected by hydraulic rams 11 to their corresponding lateral 
towers 7a, 7b. In the embodiment shown in FIGS. 1 to 9 there may be upper 
and lower pairs of hydraulic rams 11. These hydraulic rams 11 are adapted 
to move the lateral arms 3 inwards and outwards along rails 12, as shown 
in FIG. 3. Thus, the base part of each lateral arm 3 may be supported on 
support means 13 adapted to interconnect with rails 12. 
In one form of the invention, as shown in FIG. 10, the rail 12 may be in 
the form of a girder with cogs 14 on an upper surface 15. Wheel cog(s) 16 
at an upper inner part 17 of the support means 13 may be adapted to 
intermesh with the cogs 14 of the rail 12. At a lower part 18 of the 
support means 13 there may be wheels 19 adapted to travel in the recesses 
20 of the rail 12. In the embodiment shown in FIGS. 6 to 9 the support 
means 13 may interconnect with their lateral arm 3 via interconnection 
means 21 which enable the lateral arm 3 to tilt and swivel in relation to 
the support means 13. 
In the embodiment shown in FIG. 6 the rails 12 initially run parallel to 
one another towards each end of the floating dock 1 but curve inwards 
towards a mid-part 21. With this configuration a lateral arm 3 can be made 
to swivel or rotate by extending the hydraulic rams 11 on one side of the 
lateral arm 3 to a greater extent than on the other side when the lateral 
arm reaches the curve of the rail. This pivoting action enables the 
lateral arms 3 to follow the contour of the hull of a ship, for example 
towards the bow and stern of the ship. 
The lateral arms 3 may also be caused to tilt about the connections means 
21 through separate control of the upper and lower pairs of hydraulic arms 
11. 
In the embodiment of the floating dock 1 of the present invention shown in 
FIGS. 3 to 5 an alternative means is employed to enable the apparatus to 
adapt to the contour of a ship's hull. In this embodiment the cleaning 
means 4a rather than the lateral arms 3 are adapted to tilt and swivel. 
Thus, the rails 12 may be parallel and there is no requirement for the 
lateral arms 3 to swivel in relation to the support means 13. The cleaning 
means 4a may be positioned on a series of panels 22, as shown in FIGS. 4 
and 5. Each panel 22 may be connected via a universal joint 23 to a 
hydraulic arm 24 extending from the lateral arm 3. Thus, each panel 22 is 
adjustable towards or away from the lateral arm 3 by its hydraulic arm 24. 
Further, when pressure is applied between the cleaning means 4a and the 
side of a ship hull the universal joint 23 enables the plane of the panel 
22 to conform substantially to the contour of the ship hull. 
A third alternative embodiment of the configuration of lateral arms 3 is 
shown in FIGS. 13 to 17. In this embodiment there are four sets of lateral 
arms on each side of the floating dock. It will be appreciated that the 
number of sets of lateral arms is not an essential feature of the 
invention, the minimum number being one set, and the maximum dependent on 
cost and practicality. In this embodiment the cleaning means 4a are in 
cleaning panels 48 each of five brushes. Each panel 48 has its own 
hydraulically controlled telescopic arm 49, and its lateral position is 
therefore independently adjustable. In this embodiment, lateral fenders 50 
are provided on inner sides of the floating dock 1 adjacent the lateral 
arms 3. FIG. 16 shows details of a telescopic arm 49. The arm 49 
incorporates hydraulic pipe 51 for controlling movement of the telescopic 
arm 49, and separate retractable hydraulic pipes 52 for providing power to 
each of the five cleaning means 4a. A panel 48 is attached to the outer 
end 54 of the telescopic arm 49 via a universal joint 55. 
FIG. 17 shows a configuration of a preferred panel 48 of this embodiment of 
the invention. Referring to FIG. 17A, there is a central brush 56, two 
outer, hinged brushes 57 positioned in line with this central brush 56, 
and two further, hinged, displaced brushes 58. The displaced brushes 58 
are so positioned as to cover the gaps between the other three in-line 
brushes 56, 57. The hinges 59 are biased to maintain brushes 57, 58 in a 
substantially flat plane, at rest. When uneven pressure is applied to the 
panel 48, for example when being forced against a bow or stern part of a 
ship hull, the hinges 59 enable the position of the brushes 57, 58 to 
adapt to the hull contour. This adaptation is further facilitated by 
adjacent panels 48 on a lateral arm 3 being inverted, as shown in FIG. 15. 
Rollers or wheels 60 may be positioned between brushes on a panel 48, as 
shown in FIG. 17A, controlling the distance between a panel 48 and a ship 
hull, and facilitating lateral movement of a panel along a ship hull. 
A hydraulic pressure supply line 61 is provided to each brush, and a low 
pressure return line 62 (see FIG. 17B). 
Additional cleaning means 4b may be positioned on an inner surface 25 of 
the base 6 of the hull or superstructure 2. In most cases there is minimal 
marine growth beneath the bottom of a ship's hull, primarily because of 
the absence of light. Thus, it is not essential that there be cleaning 
means to clean the bottom of a ship hull, in which case the bottom 
cleaning means 4b can be replaced with some other form of support means, 
for example rollers or interspersed wheels, which when the floating dock 
is in use allow the base 6 of the dock 1 to be supported on and run along 
the bottom of the ship. 
It will be appreciated that a floating dock 1 of the present invention 
could operate effectively without any support between the base 6 and the 
bottom of the ship, for example by appropriate control of the depth of 
submersion of the floating dock 1 by the buoyancy control means. 
In the embodiments of FIGS. 3 and 6 bottom cleaning means 4b are shown 
towards outer parts of the inner surface 25 of the base 6 leaving the 
central part free for the rails 12 and collection means 8. A fender 28 may 
be located outwardly of each bottom cleaning means 4b on each side of the 
inner surface 25 of the base 6. These fenders 28 serve two purposes, the 
first being to control the distance between the base 6 and the bottom of 
the hull of a ship during operation of the dock 1, and the second being to 
contain material cleaned off the ship hull within the confines of the 
floating dock 1, avoiding contamination of the local environment. 
An alternative configuration of bottom cleaning means 4b and fenders 64 is 
shown in the embodiment of FIGS. 13 to 15. In this case the bottom 
cleaning means 4b are positioned in sets corresponding with the sets of 
lateral arms. The sets of bottom cleaning means 4b do not need to be 
formed into the panel-type grouping of the lateral cleaning means 4a, 
since most do not need to pivot or tilt. However, individual cleaning 
means 4b towards the outer parts 65 of each set may have separate control 
means adapted to raise and/or adjust the angle of the cleaning means 4b to 
facilitate cleaning of the angled part of a hull between the bottom and 
sides of a ship. 
The bottom fenders 64 in this embodiment may comprise rollers adapted to 
facilitate movement of the floating dock 1 along the bottom of the hull of 
a ship. 
Essentially, the cleaning means 4a, 4b may comprise rotatable brushes 29, 
examples of which are shown in FIGS. 11A and B. It will be appreciated 
that the invention is not restricted to any particular pattern or 
configuration of cleaning means 4a, 4b. Preferably, however there will be 
more than one row of brushes, with one offset in relation to the next to 
provide optional removal of marine growth. Nor is the invention restricted 
to cleaning means in the form of brushes. Other forms of pads or abrasive 
means are also envisaged, which may rotate, vibrate, oscillate or the like 
to effect cleaning. 
Each brush 29 has an outer surface of bristles 30, preferably of steel or 
nylon reinforced with, for example, graphite. Each brush 29 also has a 
drive means 27 for rotating the brush. This may be a hydraulic drive 
means. In addition, there may be means provided to enable each brush 29 or 
a panel of brushes to apply pressure to the side of a ship's hull. This 
means may be by independent hydraulic controls 31 for each brush 29 (see 
for example FIGS. 7 and 8), by hydraulic arms controlling panels of 
brushes (as in FIGS. 4 and 5 or 16), and/or by impelling means 32 (see 
FIG. 11B). In the latter situation each brush 29 may be interconnected 
with a small propeller 33 by an elongate shaft 34. The shaft 34 may be 
adapted to slidingly engage with the drive shaft 35 (as, for example shown 
in FIG. 11C) such that when the drive means 27 causes the brush 29 to 
rotate, the propeller 33 also rotates impelling the bristles 30 of the 
brush forwards either until they contact the ship hull or until the bush 
29 abuts a stop means 36 at the end of the drive shaft 35. 
It is envisaged that under different circumstances different types of brush 
29 may be required with the floating dock 1 of the present invention. 
Thus, the panels 22, 48 and/or each individual cleaning means or brush may 
be interchangeable. For example, a ship hull heavily encrusted with 
barnacles will require cleaning with steel wire brushes. In contrast, 
ships previously painted with potentially toxic anti-fouling paints, and 
with mild marine growth, would preferably be cleaned with nylon brushes to 
avoid paint damage. 
Where there are a plurality of sets of lateral arms 3, each set may carry 
cleaning means 4a adapted to deal with fouling of a different type or 
intensity, for example a first set might have coarse cleaning means, a 
second medium cleaning means and a third fine cleaning means. 
Use of a floating dock 1 of the present invention will now be described. 
In a buoyant condition (see FIG. 2) the floating dock 1 can be manoeuvred 
as a conventional ship to the site of mooring of a ship requiring 
cleaning. The floating dock 1 can then be submerged to the required depth 
to enable the base part 6 to be supported beneath one end of the hull of a 
ship. The position of the lateral cleaning means 4a are then adjusted to 
contact the sides of the ship by movement of the lateral arms and/or 
separate control of individual or panels of cleaning means. In this 
position the floating dock 1 is in contact with the ship hull via lateral 
and bottom fenders or rollers. 
Buoyancy/ballasting of the floating dock 1 may be adjusted to ensure 
substantially even pressure at the contact points between the ship and the 
floating dock 1. 
The cleaning means 4a, 4b, in the form of brushes or the like are then 
caused to operate in their cleaning action. At the same time the 
propulsion means 5a, 5b, are used to direct the movement of the floating 
dock 1 along the length of the ship hull. In the embodiment of FIGS. 1 to 
9 the hydraulic rams 11 control the position of the lateral arms 3 to 
ensure that their gross position follows substantially the contour of the 
ship hull, whilst individual control of the brushes 29 by independent 
hydraulic controls 31 and/or impelling means 32, or of panels 22 of 
brushes by hydraulic arms 24, ensures that appropriate pressure is applied 
between the brushes and the hull at all times. In the embodiment of FIGS. 
13 to 15 the required degree of control is provided through the separate 
control of each cleaning panel 48. 
As well as controlling contact between the ship and the floating dock, the 
fenders 28, 39, 64 also ensure that debris removed from the ship hull by 
the cleaning means 4a, 4b is confined to the central inner part of the 
floating dock 1, so that it settles into the collection means 8. Rotation 
of the brushes 29 may also assist in directing the debris into the 
collection means 8. 
Once the floating dock 1 has passed from one end to the other of a ship, 
cleaning substantially the full length, it may be refloated and manoeuvred 
to the next waiting ship. Once the collection means is full, or the 
containers receiving debris from the conveyor in the embodiment of FIGS. 
13 to 18 are full, the floating dock 1 may proceed to a preferred site for 
dumping or unloading of collected debris. 
It is envisaged that the floating dock of the present invention will be 
able to clean the hull of most medium to large ships, and will be able to 
clean at least 90 percent of the hull of such ships. 
The invention has been described by way of example, and with particular 
reference to preferred embodiments. Variations and modifications are 
anticipated. For example, it is envisaged that a lower part of each 
lateral arm 3 may include a plurality of water jets for cleaning the 
transition area between the sides and bottom of a ship hull. It is also 
envisaged that video equipment may be employed to monitor the positioning 
and progress of the cleaning means. 
A further anticipated modification of the embodiment of FIGS. 1 to 9 
involves replacement of the lower pair of hydraulic rams 11 connecting the 
lateral arms 3 with the lateral towers 7a, 7b with a drive means acting 
directly on the wheel cogs 16 of the support means 13. 
It will also be appreciated that pressure sensors may be employed to 
control movement of the lateral arms 3 and positioning of the cleaning 
means 4a, 4b. Such sensors may be located in the fenders 28, 39, to enable 
manual or automatic control of ballasting and buoyancy of the floating 
dock 1 and positioning of the cleaning means 4a, 4b, and/or on individual 
panels of cleaning means. Alternatively the distance between the cleaning 
means and the side of a ship may be sensed employing sonar. 
Where in the foregoing description reference has been made to specific 
components and integers of the invention having known equivalents then 
such equivalents are herein incorporated as if individually set forth. 
Although the invention has been described by way of example, and with 
particular reference to the preferred embodiments shown in the 
accompanying drawings, it should be appreciated that variations and 
modifications may be made thereto, without departing from the scope of the 
invention as defined in the following claims.