Abstract:
A sacrificial anode holder for use by a water borne vessel, the holder comprising a first member comprising at least one of (i) a cartridge to hold an elongate anode and (ii) an elongate anode, and a housing forming part of or being adapted to fit to the vessel to house the first member, the housing including a first aperture to expose the anode through the hull of the vessel to the water and a closable second aperture via which the first member can be removed from the housing and inserted into the housing, from the interior of the vessel.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a sacrificial anode holder and related anodes.  
       BACKGROUND  
       [0002]     Sacrificial anodes have been used in boats and oil rigs for many years. The use of sacrificial anodes is considered to be an essential element to prevent metallic corrosion of such structures. Corrosive activity arises when two different metals are electrically connected and/or come into contact with water. Such a process is known as galvanic corrosion and can rapidly decay metal.  
         [0003]     An effective method of reducing galvanic corrosion is to introduce a sacrificial anode. This is usually of zinc.  
         [0004]     It is important that such sacrificial anodes are regularly checked and if depleted, be replaced.  
         [0005]     Most boat owners operate a preventative maintenance programme to check the state of all items that may be subject to a degree of wear and tear or deterioration. Normally, the checking of under water items occurs when the boat is out of the water, such as for re-painting of anti-fouling. Sacrificial anodes of a marine craft may only be fitted or replaced once the boat has been lifted out of the water. Lifting is costly and for commercial marine craft may also be expensive because of the down time.  
         [0006]     With recent advances in maritime anti-foul technology, the need to reapply anti-fouling normally arises once every three to five years. The frequency of boat lifting is hence usually reduced. This time interval may be longer than that typically required for checking the status of sacrificial anodes.  
         [0007]     It is therefore an object of the present invention to provide a sacrificial anode holder that will go at least some way towards addressing the above desiderata, or at least provide the public with a useful choice.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0008]     In a first aspect the present invention consists in a sacrificial anode holder for use by a water borne vessel, said holder comprising  
         [0009]     a first member comprising at least one of (i) a cartridge to hold an elongate anode and (ii) an elongate anode, and  
         [0010]     a housing forming part of or being adapted to fit to the vessel to house said first member, said housing including a first aperture to expose said anode through the hull of said vessel to said water and a closable second aperture via which said first member can be removed from said housing and inserted into said housing, from the interior of the vessel.  
         [0011]     Preferably intermediate of said first aperture and second aperture, said housing carries a moveable valve to close passage of water through said housing from said first aperture to said second aperture.  
         [0012]     Preferably the valve includes a one way valve flap movable between a closed position to extend across the passage between the first and second aperture and an open position and that is held in the open position by said first member when housed by said housing and can move to the closed position when the anode has been removed from housing.  
         [0013]     Preferably the valve includes a valve seat defined by a lip contiguous part of an inner wall surface of the housing and projecting and presented therefrom to receive an edge of the valve flap when in the closed position.  
         [0014]     Preferably when in the open position the valve flap in contiguous part of the inner wall surface of the housing.  
         [0015]     In a further aspect the present invention consists in a sacrificial anode holder as hereinbefore described further including;  
         [0016]     a thin walled rigid valve seat defined at an inner wall of said housing between said first and second apertures said valve seat being a ledge,  
         [0017]     a valve flap hingeably mounted at the inner wall to move between an open condition and a closed condition,  
         [0018]     wherein said valve flap has a first major side that is of a shape commensurate the shape of part of the inner wall so that in the open condition it sits flush against said the inner wall, and  
         [0019]     wherein said valve flap has a perimeter of a shape in part complimentary the valve seat so that when in said closed condition said flap valve extends across the passage between said first and second aperture and places its perimeter contiguous that of the valve seat.  
         [0020]     Preferably the valve flap is of a constant wall thickness.  
         [0021]     Preferably said flap valve is engaged to said duct or has its hinge axis fixed relative to said duct via a live hinge.  
         [0022]     Preferably said hinge axis of said valve flap is at the inner wall.  
         [0023]     Preferably said valve seat is defined by a bush, insertable into a duct, said bush being of an exterior surface shape when viewed in its longitudinal direction that is commensurate with the interior surface of said housing.  
         [0024]     Preferably said valve seat presents at least one planar surface with which a planar surface of said valve flap can seat.  
         [0025]     Preferably the perimeter of said valve seat presents two planar edge surfaces with which two corresponding planar surfaces of the perimeter of said valve flap can seat.  
         [0026]     Preferably each of the planar surfaces of said valve seat and valve flap are non parallel when in the open position and are parallel when in the closed position.  
         [0027]     Preferably said valve flap is of constant curvature along its length. It is preferably of a section of a tube.  
         [0028]     Preferably said flap valve is defined from a section of a tube.  
         [0029]     Preferably said valve seat where it is defined as a bush, is of constant curvature along its length.  
         [0030]     In a further aspect the present invention consists in a sacrificial anode holder as hereinbefore described wherein the housing holds said first member in close proximity at least at longitudinally extending contiguous regions.  
         [0031]     In a further aspect the present invention consists in a sacrificial anode holder as hereinbefore described wherein said housing includes an elongate sleeve section into an out of which said first member can slidingly move through said second aperture.  
         [0032]     Preferably said housing has an inboard more end and outboard more end and defines said first aperture at said outboard more end of said sleeve and said second aperture at said inboard more end of said sleeve.  
         [0033]     Preferably a flange extends radially outwardly from said sleeve at said outboard more end to sit outboard and against the hull of said vessel, and wherein said sleeve includes a threaded outer surface to receive a nut to clamp said housing to said hull between said nut and said flange.  
         [0034]     In a further aspect the present invention consists in a sacrificial anode holder as hereinbefore described wherein said first member is a cartridge holding said anode.  
         [0035]     Preferably said cartridge includes a sleeve (herein after “second sleeve”) provided about the elongate direction extending surfaces of the anode and includes an opening through which said anode is exposed, said opening positioned in use, proximate said first aperture.  
         [0036]     Preferably the second sleeve is insertable into the first mentioned sleeve from the inboard more end of the first mentioned sleeve.  
         [0037]     In a further aspect the present invention consists in a sacrificial anode holder as hereinbefore described wherein said anode is held in use to be movable relative said housing in its elongate direction and is biased in an outboard direction of said vessel from said holder.  
         [0038]     Preferably said bias is affected by gravity by mounting of said holder to said vessel in an orientation such that said elongate direction of said anode is vertically extending.  
         [0039]     Preferably said bias is affected by a spring acting between said anode and the inboard end of said housing.  
         [0040]     In a further aspect the present invention consists in a sacrificial anode holder as hereinbefore described wherein at least one anode stopper is presented against which an outboard most end of said anode is biased in use, said stopper preventing the anode from passing entirely out of said housing through said first aperture.  5  Preferably said at least one stopper extends partially across the first aperture.  
         [0041]     Preferably the at least one stopper is provided by at least one of the first member and housing.  
         [0042]     Preferably the at least one stopper comprises of a washer presented at the outboard end of the anode and held by a connection rod extending through a bore of said anode from the inboard more end thereof, said bore being of a size smaller than said washer and said connection rod coupled to said housing to hold said anode.  
         [0043]     Preferably wherein the at least one stopper is defined by said housing, a castellation formed at the outboard end of the first member (preferably the second sleeve thereof) can locate therewith to lock rotation of the first member with said housing.  
         [0044]     Preferably the outboard more end is at or proximate which the anode is presented for outboard positioned more contact with the surrounding water and the inboard more end includes said second aperture that is a generally closed or capped.  
         [0045]     Preferably the stopper is provided outboard of the hull of said vessel allowing said anode to extend proud of the hull.  
         [0046]     Preferably said stopper includes a bar that extends across said first aperture and against which said anode is pressed by a biasing means.  
         [0047]     Preferably said anode has a plurality of parallel slots that extend in the longitudinal direction from the outboard most end of said anode.  
         [0048]     Preferably said stopper is at least one bar that extends parallel to said slots and is positioned for an outboard most portion of said anode to press against.  
         [0049]     Preferably one of said housing and cartridge includes a grill extending across said first aperture, said grill positioned in the slots of said anode.  
         [0050]     Preferably the housing and cartridge could be any particular shape in cross section, for example circular, square, hexagonal, crescent, pentagonal or indeed may even incorporate straight and curved areas. Shapes other than circular can have the advantage of locking relative movement of the housing and cartridge together about an axis or axes parallel to their longitudinal direction. The castellations provided at the end of the cartridge may also perform the same function when engaged with the stoppers for the housing.  
         [0051]     Preferably the first member and the housing are generally tubular in cross section and when assembled, are concentric each other.  
         [0052]     Preferably said sleeves are fixable in their elongate directions relative each other at different dispositions to allow adjustment in the placement of the anode to be made.  
         [0053]     Preferably the first mentioned sleeve defines said second aperture as an inboard more opening of a size and shape through which said second sleeve of said first member can pass.  
         [0054]     Preferably the cartridge includes a biasing means acting between the anode and the cartridge to bias the anode toward the outboard more end of the cartridge.  
         [0055]     Preferably the housing has been adapted to span a pre-formed aperture within the hull of a vessel and be able to be locked into a fluid tight position about the hull adjacent the aperture.  
         [0056]     Preferably the cartridge includes a flange to seat onto the second aperture of said housing members and thereby close said second aperture and locate the cartridge with said housing.  
         [0057]     Preferably the cartridge includes a plug to push into the second aperture of said housing members and thereby close said second aperture and locate the cartridge with said housing.  
         [0058]     Preferably said housing includes an external thread at the inboard more end thereof to receive a threaded clamp to secure and press said flange against said seat.  
         [0059]     Preferably said clamp is an overcap to close said second aperture.  
         [0060]     Preferably said clamp can be locked to at least one both of said housing and cartridge.  
         [0061]     Preferably said locking of said overcap is by slit-pin, locating pin, snap-lock mechanism or similar.  
         [0062]     Preferably this will ensure on a repeated basis that the cooperating members are correctly positioned when connected, thus ensuring that the optimum operative connection between the cooperating members has been.  
         [0063]     Preferably the cartridge and housing include cooperating locked features that lock the two together (such as the castellations mentioned above or alternatives mentioned below).  
         [0064]     In a further aspect the present invention consists in a sacrificial anode as hereinbefore described wherein the anode includes a longitudinal key way located in a longitudinally sliding manner with a key of one of said housing and cartridge.  
         [0065]     Although the sacrificial anode has been described as being made from zinc it will be appreciated by those skilled in the art that other metals or even possible metal alloys may be used.  
         [0066]     In a further aspect the present invention consists in a sacrificial anode as hereinbefore described wherein the anode is engaged by an electrical connector passing through said housing and into said vessel.  
         [0067]     In a further aspect the present invention consists in a water submerged or partially submerged vessel or structure that has affixed to its hull, a sacrificial anode holder as hereinbefore described wherein the first aperture is positioned below the waterline to present the outboard more end of the anode to the surrounding water and wherein the second aperture is positioned inboard of the hull to allow the removal of the anode from the housing via the second aperture from within the vessel or structure.  
         [0068]     Preferably the sacrificial anode holder holds an anode within its housing.  
         [0069]     Preferably the sacrificial anode holder holds an anode within its housing said anode sitting proud of the exterior surface of the hull of said vessel.  
         [0070]     Preferably said anode is slidingly housed within said housing and a spring is located to act between said housing and anode to press the outboard most end of said anode in an outboard direction against at least one anode stopper fixed relative said housing.  
         [0071]     In a further aspect the present invention consists in a waterborne vessel that has affixed to its hull a sacrificial anode holder as hereinbefore described wherein the first aperture is positioned below the waterline of the vessel, said housing and first member are positioned to the interior of the hull of the vessel and wherein said stopper is affixed on the exterior to the hull of said vessel.  
         [0072]     In a further aspect the present invention consists in a sacrificial anode holder for a water submerged or partially submerged vessel or structure, said holder comprising:  
         [0073]     a housing to hold an elongate sacrificial anode that includes an inboard and outboard distal end, said housing including a sleeve section into which said sacrificial anode can be inserted through a closeable opening of said housing that is positioned inboard of said vessel, said housing including an outboard opening to expose said anode to the surrounding water, and wherein the holder includes an anode stopper acting on the outboard end of said anode at where, in use, galvanic erosion reducing the end to end length of said anode predominantly occurs, wherein in use said anode is biased for movement within the housing to be pressed against the stopper to ensure a constant positioning of the eroding end of the anode relative said housing.  
         [0074]     In a further aspect the present invention consists in a sacrificial anode holder for a water submerged or partially submerged vessel or structure comprising:  
         [0075]     a housing to retain a straight elongate anode, that includes an inboard and outboard distal end, in an elongate direction sliding manner, said housing engaged inboard of said vessel and including an outboard proximal opening to allow exposure of the anode to the surrounding water,  
         [0076]     wherein said anode is of a non-circular cross sectional perimeter and said housing and said anode are in a close fitting relationship to thereby prevent relative rotation in a direction parallel to the elongate direction.  
         [0077]     Preferably said housing includes a stopper to capture said anode from sliding out of said outboard opening and against which, in use, said anode is pressed.  
         [0078]     Preferably the housing includes a key to locate into a keyway extending in the elongate direction at the non-circular cross sectional perimeter of said anode.  
         [0079]     In a further aspect the present invention consists in an elongate sacrificial anode that includes a keyway formed at an elongate direction extending surface of said anode.  
         [0080]     In a further aspect the present invention consist in an elongate and straight sacrificial anode that has a first and second distal end and that includes a keyway extending from said first distal end at an elongate direction extending surface of said anode.  
         [0081]     In a further aspect the present invention consists in an elongate and straight sacrificial anode that has a first and second distal end and that is of a non circular cross sectional perimeter.  
         [0082]     Preferably the first aperture is positioned below the waterline of the vessel to present the outboard more end of the anode to the surrounding water and wherein the second aperture is positioned inboard of the hull of the vessel to allow the removal of the anode from the housing via the second aperture from within the vessel.  
         [0083]     In a further aspect the present invention consists in a water submerged or partially submerged vessel or structure as hereinbefore described wherein the sacrificial anode holder holds an anode within its housing.  
         [0084]     Preferably the sacrificial anode holder holds an anode within its housing said anode sitting proud of the exterior surface of the hull of said vessel.  
         [0085]     Preferably said anode is slidingly housed within said housing and a spring is located to act between said housing and anode to press the outboard most end of said anode in an outboard direction against at least one anode stopper fixed relative said housing.  
         [0086]     As used herein the term “and/or” means “and” or “or”, or both.  
         [0087]     As used herein “(s)” following a noun means the plural and/or singular forms of the noun.  
         [0088]     The term “comprising” as used in this specification means “consisting at least in part of”. When interpreting statements in this specification which include that term, the features, prefaced by that term in each statement, all need to be present but other features can also be present. Related terms such as “comprise” and “comprised” are to be interpreted in the same manner. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0089]     The preferred embodiment of the present invention will be more particularly described by way of example only, with reference to the accompanying drawings in which  
         [0090]      FIG. 1   a  illustrates a cutaway elevation view of one embodiment of the present invention,  
         [0091]      FIG. 1   b  illustrates a cutaway elevation view of another embodiment of the present invention,  
         [0092]      FIG. 1   c  is a sectional view through a housing and anode and illustrates a variation to the stopper arrangement that may be utilised,  
         [0093]      FIG. 2   a  shows a plan view of the embodiment as illustrated in  FIG. 1   a,    
         [0094]      FIG. 2   b  shows a plan view of the embodiment as illustrated in  FIG. 1   b,    
         [0095]      FIG. 3  is a perspective view of part of the cartridge or housing illustrating a location key and stopper or stoppers at the outboard end,  
         [0096]      FIG. 4  is a plan view of an anode adapted to be received by the cartridge or housing of  FIG. 3 ,  
         [0097]      FIG. 5  is a sectional view through part of a hull of a vessel and showing an anode retained by a stopper that is positioned outside of the hull of the vessel,  
         [0098]      FIG. 6   a  illustrates a cutaway elevation view of another embodiment of the present invention where the housing includes a flange against the outside of the hull,  
         [0099]      FIG. 6   b  incorporates a cutaway elevation view of the embodiment shown in  FIG. 6   a  but incorporating the stopper features of the embodiment shown in  FIG. 1   b,    
         [0100]      FIG. 7  shows a cutaway partially exploded elevation view of another embodiment of the present invention whereby a biasing means is employed to encourage the anode toward the outside of the hull,  
         [0101]      FIG. 8  illustrates an exploded cutaway view as shown in  FIG. 7 ,  
         [0102]      FIG. 9  shows a cutaway elevation view of an outward extension allowing the zinc anode to extend beyond the hull surface,  
         [0103]      FIG. 10   a  shows a perspective view of the internal valve component,  
         [0104]      FIG. 10   b  shows an elevation view of the valve component shown in  FIG. 10   a  as viewed from the direction A as indicated in  FIG. 10   a,    
         [0105]      FIG. 10   c  shows a section view of the hinge component as identified by region X 1  in  FIG. 10   b,    
         [0106]      FIG. 11   a  shows a perspective view of the internal valve component inherent within the present invention,  
         [0107]      FIG. 11   b  shows an elevation view of the valve component shown in  FIG. 11   a  as viewed from the direction A of  FIG. 11   a,    
         [0108]      FIG. 11   c  shows a section view of the hinge component as identified by region Y 1  in  FIG. 11   b,    
         [0109]      FIG. 12  shows a perspective view of the valve component as shown in  FIGS. 10-11  with the valve components upside down showing the seat at which the hinge flat portion rest against for secure closure,  
         [0110]      FIG. 13  shows a perspective cutaway view of the valve component shown in  FIGS. 10-12  as positioned in an open condition within the housing,  
         [0111]      FIG. 14  shows a perspective cutaway view of the valve component shown in  FIGS. 10-13  as positioned in a closed condition within the housing,  
         [0112]      FIG. 15  is a perspective view of an anode showing it containing a spline or slot,  
         [0113]      FIG. 16  is an end view of the cylinder as part of the invention of the present invention showing anode stoppers protruding into the opening through which the anode could otherwise project, and  
         [0114]      FIG. 17  is a perspective view of the housing showing castellations for registering with the stoppers as shown in  FIG. 16 ,  
         [0115]      FIG. 18  shows a perspective view of an alternative embodiment of the zinc anode,  
         [0116]      FIG. 19  shows a perspective view of part of the housing for the anode of  FIG. 18 ,  
         [0117]      FIG. 20A  shows a section view of the outboard end of the housing,  
         [0118]      FIG. 20B  shows a section view of  FIG. 20A  but showing the anode erosion,  
         [0119]      FIG. 21A  shows a perspective view of part of the housing including anode stoppers,  
         [0120]      FIG. 21B  shows the perspective view of  FIG. 21A  and including an anode,  
         [0121]      FIG. 22  is a front elevation view of zinc anode holder assembly showing the spacer elements applied to the current assembly to vary the exposure of the zinc anode into the water, and  
         [0122]      FIG. 23  shows a vessel that includes an anode holder as herein after described. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0123]      FIG. 1  shows a cutaway sectional view of one embodiment of the present invention. The holder ( 700 ) may generally include the housing ( 12 ) for locating a zinc sacrificial anode ( 1 ) to be substantially enclosed and preferably captured substantially within a “well” of an elongate housing ( 12 ).  
         [0124]     The anode ( 1 ) is preferably elongate in nature and substantially straight and constant in cross section (taken transverse to the elongate direction). It is preferably substantially circular in cross sectional perimeter shape (taken transverse the elongate direction). It is preferable that the housing ( 12 ) spans a length to accommodate a majority if not all of the anode ( 1 ). The housing has a distal or inboard more end ( 177 ) that is generally closed but has an openable opening positioned or to be positioned inboard of a vessel. The housing also has a proximal or outboard more end ( 178 ) that includes an opening ( 179 ) to expose the anode to the surrounding water in which the vessel is floating.  
         [0125]     A metal stud or terminal ( 3 ), preferably passing in to the body of the housing ( 12 ), may be electrically connected to the anode ( 1 ) thus ensuring the appropriate connectivity between the two components. The stud may be threaded or cast into the anode. Alternatively a flexible wire may be cast into the anode to connect the stud and anode. The portion of the stud ( 3 ), preferably projecting from the distal end ( 117 ) of the housing ( 12 ) and in its normal mode of operation, is configured so as to be able to connect to wires ( 4 ) that are intended to facilitate further electrical connections for the purposes of reducing galvanic corrosion.  
         [0126]     The diameter of the anode is slightly smaller than the internal diameter of the anode housing ( 12 ). A circumferential gap ( 10 ) may exist about the anode ( 1 ). Within the housing ( 12 ), this gap ( 10 ) may allow for water to ingress and make contact substantially with all of the anode ( 1 ). However such water in the gap ( 10 ) will have low circulation thereby resulting in low erosion of the anode ( 1 ) at such regions.  
         [0127]     The housing ( 12 ), may include a mounting flange ( 13 ) at its proximal end ( 178 ) and may be provided with a male screw thread, that may span the entire length of the exterior surface of the housing ( 12 ) up to the flange ( 13 ). A nut ( 7 ) containing a complementary female screw thread to that of the male screw thread located on the housing ( 12 ) may engage therewith. A nut ( 9 ) that also contains a cap member may provide the same.  
         [0128]     In use, an exterior surface of the vessel hull ( 5 ) receives the flange ( 13 ) of the housing ( 12 ). The flange is preferably substantially flush with the exterior surface of the hull ( 5 ) as shown in  FIG. 1   a  or may sit proud as shown in  FIG. 6   a.    
         [0129]     A nut ( 7 ) may be used to clamp the flange ( 13 ) to it tightens onto the interior surface of the hull ( 5 ) forming a watertight seal between the hull ( 5 ).  
         [0130]     In one mode the anode ( 1 ) may be removably located directly into the housing. In another mode, the anode ( 1 ) may be retained by a cartridge ( 2 ) removably located inside the housing ( 12 ).  
         [0131]     In the preferred form where the cartridge is utilised, the cartridge may enclose a substantial part or only a small part of the electrode.  
         [0132]     In the example shown in  FIG. 1   a  the cartridge ( 2 ) has side walls that extend substantially the entire length of the anode ( 1 ). The cartridge is preferably a sleeve or cylinder with an open end outboard most. However such side walls need not project such a distance and may alternatively be significantly shorter in length extending from the proximal end. Indeed the cartridge may merely consist of the end flange ( 11 ) or base and means for retention of the anode ( 1 ) therewith.  
         [0133]     The interior diameter or size and shape of the housing ( 12 ) is complimentary to the exterior diameter or size and shape of the cartridge ( 2 ) to allow a snug sliding engagement to be established therebetween.  
         [0134]     A tight fit between the outside of the cartridge and inside surface of the housing is desired to prevent marine organisms growing between the cartridge ( 2 ) and the housing ( 12 ). An “O” ring seal ( 6 ) may facilitate this.  
         [0135]     Towards the distal or inboard end of the cartridge ( 2 ) is a flange with shoulder ( 11 ) projecting beyond the exterior surface of the cartridge ( 2 ). It may contain a male screw thread.  
         [0136]     The cartridge ( 2 ) may slide into the housing ( 12 ) from the inboard side until the shoulder ( 11 ) abuts the proximal top face or seat ( 236 ) of the housing ( 12 ). A nut ( 9 ), may be passed over the ends of the housing ( 12 ) and cartridge ( 2 ) locking these together. Nut ( 9 ) tightening will create a water tight seal, enclosing the housing save for at the opening ( 179 ).  
         [0137]     With reference to  FIG. 16  there is shown an end view of the housing ( 12 ) wherein the stoppers ( 40 ) are shown to be projecting radially inwardly from the fairing or flange. With reference to  FIG. 17 , a perspective view of the cartridge ( 2 ) is shown. It can be seen that the cartridge ( 2 ) may at its end ( 113 ), include castellations ( 114 ) which are of a shape and location so as to be able to sit onto the stoppers ( 40 ) of the housing ( 12 ) as shown in  FIG. 16 . This allows for the cartridge ( 2 ), to register with the housing ( 12 ). Such registration will lock relative rotation between the housing ( 12 ) and the cartridge ( 2 ). This has the advantage that when the nuts or fasteners at the other end of the cartridge ( 2 ) are being tightened, the cartridge ( 2 ) will not rotate relative to the housing ( 12 ) due to the forces being applied to the fasteners.  
         [0138]     The proximal end ( 180 ) of the anode, adjacent or at the proximal end ( 178 ) of the housing ( 12 ) is presented to water. It is at this end that consumption or erosion of the anode ( 1 ) will predominantly occur. Exposure of the end ( 180 ) of the anode to the exterior body of water to the hull of the vessel will ensure that the highest degree of circulation of water occurs at this end ( 180 ) rather than along other surfaces of the anode towards the opposite end of the anode.  
         [0139]     Whilst water may penetrate into the gap ( 10 ) between the anode ( 1 ) and the housing ( 12 ), such water will be relatively stagnant or non-circulating thereby reducing the electrolysis activities in such regions.  
         [0140]     The majority of consumption or erosion of the electrode will occur at parts of the electrode where non-stagnant or highly circulating water is in contact with the anode, namely at the end ( 180 ).  
         [0141]     In other embodiments of the present invention, the anode ( 1 ) may be retained by the housing ( 12 ) without also being retained within or by the cartridge ( 2 ).  
         [0142]     Erosion of the anode at the distal end ( 180 ) will result in a progressive shortening of the anode in its longitudinal direction. It is desirable to keep this eroding end at a constant position. This may occur either by gravity, manually by a displacement mechanism to move the anode ( 1 ) relative to the housing ( 12 ) or by other mechanisms such as a spring which will hereinafter be described.  
         [0143]     The height of the housing ( 12 ) may be greater than the level of water that surrounds the vessel (denoted by the dashed line ( 8 ) in  FIG. 1 ) when the vessel is in the water. Access and subsequent periodic inspection of the state of the sacrificial anode ( 1 ) can take place without the possibility of flooding the vessel.  
         [0144]     Anode inspection and/or replacement takes place by removing nut ( 9 ) and subsequently removing the anode ( 1 ) plus cartridge ( 2 ) if present, from on board the vessel.  
         [0145]     Reference is now made to  FIGS. 10-14  where a housing sealing valve is described.  
         [0146]     The sealing valve ( 53 ) is located inside the housing between the opening ( 179 ) and the closable opening at end ( 177 ). As seen in perspective view in  FIG. 10   a  the valve ( 53 ) includes a valve flap ( 15 ) which is hingeably engaged at X 1 , to a sleeve portion ( 52 ). Preferably a live hinge ( 14 ) is used.  
         [0147]      FIG. 10   b  shows a front elevation view of the sealing valve ( 53 ) as indicated from the direction “A” indicated in  FIG. 10   a.  The valve flap ( 15 ) in a closed position restricts the access or ingress of water toward the end ( 54 ) of the valve ( 53 ) by articulating at the hinge ( 14 ) to rotate point D to D 1  as indicated on  FIG. 10   b.  This effectively closes the valve. Points D and D 1  lie at a distal end of the valve component ( 53 ).  
         [0148]     The hinge ( 14 ), which facilitates articulation of the valve flap ( 15 ) with respect to the sleeve ( 52 ), may be defined in a number of ways. Preferably it is provided for articulation that will not restrict entry of the anode ( 1 ) into the housing. Preferably it sits flush against the inside wall of the housing ( 12 ).  
         [0149]     The operation of the valve ( 53 ) is shown in  FIG. 11 .  FIG. 11   a  shows the same perspective view as shown in  FIG. 10   a,  however the valve flap ( 15 ) is now illustrated in a closed condition. This is illustrated in  FIG. 11   b  which shows a front elevation view as indicated by direction B and  FIG. 11   a.  The hinge ( 14 ) is shown in a sectional view in  FIG. 11   c.    
         [0150]      FIG. 12  shows a valve ( 53 ) in an open condition. The valve ( 53 ) is preferably insertable into the housing ( 12 ). When the valve flap ( 15 ) moves to the closed condition, its outer surface having previously been sitting against the inside surface of the housing, moves away from the surface of the housing.  
         [0151]     The surface or edge ( 109 ) of the valve flap ( 15 ) is of the same profile as the edge or seat ( 56 ) of the sleeve portion ( 52 ). As well as being of the same profile the edge shape is preferably flat or complimentary and preferably sits parallel with the flat or complimentary surface of the edge ( 109 ) when in the closed condition. Water pressure of the surrounding body of water will press and hold the valve flap shut. As can be seen the surface ( 110 ) of the edge ( 56 ) is presented to allow for it to sit flush with the surface (not shown) of the edge ( 109 ) as shown in  FIG. 12 . The valve flap ( 15 ) articulates to rest against the edge or seat ( 56 ) of the sleeve ( 52 ). The meeting of these two complementary edges allows an effective seal to be established.  
         [0152]     The edges ( 56 ) and ( 109 ) may be lined with appropriate sealing materials or substances that enhance the sealing properties of the valve ( 53 ).  
         [0153]     As can be seen with reference to  FIG. 12 , both the valve flap ( 15 ) and the sleeve ( 52 ) are of a substantially part cylindrical and constant cross section. Accordingly when in the open condition, both the valve flap ( 15 ) and the sleeve ( 52 ) present little or no obstruction to the well of the housing.  
         [0154]      FIG. 13  shows a perspective cutaway view of the valve ( 53 ) sitting internal to the hollow plastic housing ( 12 ) of the kind as described. The valve ( 53 ) is shown in its opened condition whereby a cartridge and/or zinc anode may be captive within the assembly for normal operation.  
         [0155]      FIG. 14  shows the same perspective cutaway view of the valve ( 53 ) in a closed condition showing the situation whereby a zinc anode has been removed enabling the valve flap ( 15 ) to close and thus prevent water entry or ingress.  
         [0156]      FIG. 1   b  illustrates a further embodiment of that shown in  FIG. 1   a,  wherein axial movement stoppers ( 40 ) extend inward to the opening ( 179 ). One or Preferably several regularly spaced stoppers ( 40 ) may extend from the housing ( 12 ) at or near the flange ( 13 ) or from the cartridge ( 2 ). They are of a size and shape so that the anode ( 1 ) is retained within the housing ( 12 ) and cannot completely pass out through the opening ( 179 ) unless perhaps when completely depleted. The stopper presents interference to such passage.  
         [0157]     Such stopper(s) ( 40 ) may be established by the use or inclusion of a constricting opening ( 179 ) defined by a circumferential lip. However, it is preferable that the sacrificial anode ( 1 ) is exposed to the water (sea or fresh as the case may be) as much as possible hence the stoppers are preferably discrete lips extending partially across the opening ( 179 ) or a bar or bars extending completely across the opening.  
         [0158]     As the anode erodes at its end ( 180 ) the anode can be displaced in the outboard direction. Continual erosion will mean that the stoppers are in contact with newly exposed anode, as erosion takes place. The use of a lip or lips or narrow bar(s), having small surface contact with the anode, can also facilitate the refreshing of anode surface contact by the lips. At the interface between the lips and the anode reduced erosion will take place due to reduced circulation of water at such interface. Being lip or narrow in form will result in a small castellation being generated of the anode. Such a castellation will be relatively fragile and may fracture thereby refreshing the contact between the anode and the lip or lips and displacement of the anode in an outboard direction.  
         [0159]     In the example shown in  FIG. 1   b,  the stoppers ( 40 ) are shown to be projecting into the opening ( 179 ) and are formed integrally with the housing ( 12 ). Alternatively such stoppers may be provided by the cartridge ( 2 ).  
         [0160]     With reference to  FIG. 1   c,  a variation to the stopper ( 40 ) is shown wherein the stopper ( 40 ) consists of a washer or hook or lip or the like that is held by a connection rod ( 185 ) engaged directly or indirectly to the housing ( 12 ). The anode ( 1 ) shown in cross section may include a bore ( 186 ) to receive a connection rod ( 185 ) to hold the washer and thereby act as a stopper to prevent the anode from passing entirely through the opening ( 179 ) of the housing ( 12 ). The washer sits on the distal end erosion surface of the anode and thereby allows the anode to maintain constant distal end exposure to water.  
         [0161]     The example shown in  FIG. 1   c  is absent of the use of a cartridge but may include one.  
         [0162]     To facilitate manual periodic outboard anode displacement in one mode a screw thread portion projecting within the distal end ( 191 ) of the sacrificial anode ( 1 ) may be used. The screw thread may extend through the housing ( 12 ) and into an aperture of the anode incorporating a complementary internal thread. The screw thread portion may terminate with a handle or similar, hence allowing a user to manually wind it to displace the zinc anode at regular intervals to ensure the proximal or outboard more surface ( 180 ) has good water exposure.  
         [0163]     With the use of the stoppers as herein described a mechanical device that can control the axial positioning of the anode ( 1 ) relative the housing ( 12 ) need not be utilised.  
         [0164]     In the example shown with reference to  FIG. 1   b,  gravity may bias the sacrificial anode ( 1 ) towards the proximal end ( 178 ), the stopper or stoppers ( 40 ) preventing a dropping of the entire anode ( 1 ) out through the opening ( 179 ) in a normal mode of use.  
         [0165]     A flexible wire ( 49 ) may make the electrical connection between the stud ( 3 ) and the anode ( 1 ). This flexible wire can accommodate the travel of the anode ( 1 ) within the housing ( 12 ).  
         [0166]     In another mode of encouraging displacement the holder of the present invention may incorporate a biasing means ( 41 ) between the inner distal end ( 106 ) of the cartridge ( 2 ) and the zinc anode ( 1 ). The biasing means ( 41 ) (such as a coil spring or the like) exists to encourage the zinc anode ( 1 ) in an outboard direction such as towards the proximal end ( 178 ) of the housing ( 12 ).  
         [0167]     The presence of the biasing means ( 41 ) allows continual bias and displacement of the eroding zinc anode ( 1 ) toward the proximal end. It will be appreciated that this will maintain the exposure of the zinc anode ( 1 ) at any given time to the sea water as the anode is eroded.  
         [0168]     The stopper such as the stopper ( 40 ) is used in conjunction with a biasing means ( 41 ).  
         [0169]     Electrical connection may be maintained by use of a wire fastened or cast within the sacrificial anode ( 1 ). In a similar regard, the electrical connection may be achieved by way of the spring ( 41 ) being in contact with the zinc anode ( 1 ). Where no cartridge is present the spring may be positioned between the anode ( 1 ) and the housing ( 12 ) to bias the spring in an outboard direction.  
         [0170]      FIG. 9  represents an additional mode of increasing the exposure of the zinc anode ( 1 ) to the sea water environment. This involves a protruding structure ( 50 ) having stoppers ( 40 ) (performing the function as has previously been described herein) allowing the zinc anode ( 1 ) to project outside the hull extremity.  
         [0171]     The structure may be grommet shaped or may be a radially extending flange with gaps or slots in between. Such a structure ( 50 ) may be more preferable for use in recreational or cruising yachts however it may also be adapted for use within race or performance yachts.  
         [0172]     Fairing may be employed to form a fairing portion that is aligned with the general axis of the hull (or the forward direction of movement) whereby allowing the transverse or side portions to be omitted thus allowing such sides of the zinc anode to be exposed completely to the marine sea water environment yet being retained in place by the stoppers ( 40 ).  
         [0173]     Within this embodiment, the stoppers ( 40 ) may only be one or two inwardly projecting protrusions of enough material and sufficient strength to retain the zinc anode in the appropriate position.  FIG. 5  illustrates a sectional view through a hull ( 5 ) wherein the anode ( 1 ) held by the housing (not shown) is presented proud of the exterior surface ( 500 ) of the hull ( 5 ) of the vessel. The anode ( 1 ) is located against a stopper ( 600 ) that sits proud of the surface ( 500 ) of the hull. The stopper may form part of the housing and/or part of the cartridge or may alternatively be affixed at the exterior of the hull.  
         [0174]      FIG. 18  shows an example where the surface area of the zinc is increased to improve the efficiency of the sacrificial anode. The portion of the anode ( 1 ).that is to be exposed to the sea water incorporates a series of fins ( 120 ). The fins ( 120 ) may be of any shape or form to increase the surface area of the anode. Each fin is preferably uniform in thickness and in depth. The length of the fins may be to any depth of the anode ( 1 ). The fins ( 120 ) may adopt other shapes that may be used to increase the surface area offered to the water when in use.  
         [0175]      FIG. 19  shows the flange portion ( 13 ) of the anode assembly of the present invention adapted to allow the fins ( 120 ) to be positioned further outward into the sea water. The flange portion ( 13 ) incorporates apertures ( 122 ) that remain complimentary to the geometry of the fins ( 120 ) so that the apertures ( 122 ) allow the fins to protrude further into the sea water as is shown in  FIG. 20A and 20B .  FIG. 20A  shows a cross section view of the assembly of the anode ( 1 ) within the anode cartridge ( 2 ) and housing ( 12 ) at the portion that is exposed to the water. The fins ( 120 ) can be seen to protrude through apertures ( 122 ) within the flange portion ( 13 ). It may also be seen from  FIG. 20A  that each fin ( 120 ) is captured by a stopper ( 121 ) corresponding to at least one and preferably each fin ( 120 ).  
         [0176]     The stopper ( 121 ) stops the anode ( 1 ) from falling out. They are preferably one or a plurality of raised elements or bars that may be part of the anode cartridge ( 2 ) or housing ( 12 ) and that engage the ends of respective fins ( 120 ) of the anode ( 1 ) when assembled and in operation. It may be appreciated that at least one stopper ( 121 ) may be used to adequately capture and retain the anode ( 1 ) in the desired position.  
         [0177]     This embodiment may work in conjunction with the biasing means or gravity to encourage the anode toward the stopper(s) ( 121 ) and thus ensuring that the stopper ( 121 ) always engage the outer most surface of the fins ( 120 ) of the anode ( 1 ).  FIG. 20B  shows the erosion of the fins ( 120 ) of the anode ( 1 ) over time whereby the original form of the fins ( 120 ) is shown as a broken line and indicated as XX′. The eroded form is identified as YY′ with the most severe erosion occurring towards or at the region of the tip. As the ongoing erosion occurs, the tip will subsequently wear thus reducing the overall length of the anode. The capture elements may be aligned to be parallel with the longitudinal direction of the boat and thus aligned with the flow of the water over the hull surface. The capture elements may be aerodynamically shaped by providing a faired shape to reduce drag.  
         [0178]      FIG. 22  shows the anode cartridge ( 2 ) and the fins ( 120 ) of the anode ( 1 ) that by adding spacer elements ( 132 ) to fit between the anode cartridge ( 2 ) and housing ( 12 ) allows positions A, B and C to be achieved. This can increase the distance between the anode cartridge ( 2 ) and the housing ( 12 ) in order to reduce the protrusion of the fins ( 120 ) through the flange portion ( 13 ) accordingly. Any number of spacer elements ( 132 ) may be used to generate the required exposure.  
         [0179]     A key way or similar recesses may be incorporated within the anode ( 1 ) to coincide with complimentary features within the anode cartridge ( 2 ) or housing ( 12 ) to locate the orientation of the anode ( 1 ) when in place. Such means for location of the anode may be achieved in any of a number of ways.  
         [0180]     Relative rotation may be prevented between the cartridge ( 2 ) (or housing ( 12 )) and the anode ( 1 ), as shown with reference to  FIG. 15  by a slot or key way or spline ( 116 ) or similar. The slot ( 116 ) preferably extends longitudinally and preferably linearly along the anode ( 1 ). A key lug or pin or similar may be provided to the interior surface of the cartridge ( 2 ) (or housing). The key can locate within the slot ( 116 ) to prevent relative rotation of the anode to the cartridge ( 2 ) and/or housing. This may be desired for the purposes of keeping the anode aligned in a desired direction. Alternatively to a key way, the anode may be of a non circular perimeter cross section to snugly locate inside of a complementary shaped housing or cartridge to thereby prevent relative rotation about an axis parallel the elongate direction. The anode may be polygonal in cross sectional shape such as triangular or square to facilitate such an objective.  
         [0181]      FIG. 3  shows a perspective view of the outboard end of the cartridge or housing ( 2 / 12 ). At the opening ( 179 ) or proximate thereto, may be provided the stoppers ( 361 ). One or both of the stoppers ( 361 ) are positioned flanking a key ( 362 ). The key ( 362 ) is to be received in a key way ( 363 ) of an anode ( 1 ) as shown in plan view in  FIG. 4 . The anode in  FIG. 4  is substantially constant in perimeter cross section and includes a longitudinally extending key way ( 363 ) and preferably extends the entire length of the anode. It at least extends in from the outboard end of the anode towards its inboard end. The key way is of a size to accommodate the key ( 362 ) therein. The key ( 362 ) will ensure that the anode ( 1 ) remains rotationally fixed relative the cartridge ( 2 ) and/or housing ( 12 ). This will also ensure that the stopper or stoppers ( 361 ) are consistently in contact with the anode ( 1 ) adjacent the same perimeter region. Whilst in the preferred form the stoppers ( 361 ) are shown flanking the key ( 362 ), alternatively the stoppers may be provided at other locations to engage the erosion surface end of the anode ( 1 ) adjacent the perimeter of the anode ( 1 ). In an alternative form of the present invention the key ( 362 ) may be provided by the cartridge  2  and the stoppers ( 361 ) provided by the housing ( 12 ) or may be separately provided to the exterior of the hull from the housing. The key may also be of or engaged to the housing rather than the cartridge.