Patent Publication Number: US-2006016379-A1

Title: Aquatic vessel hull

Description:
TECHNICAL FIELD  
      This invention relates to devices and applications of generating electromagnetic fields within a body of water to repel aquatic creatures such as sharks.  
     BACKGROUND TO THE INVENTION  
      Numerous devices are known for the purpose of repelling aquatic creatures. The majority of these devices are designed to generate an electromagnetic field in close proximity of a diver or to form a barrier or boundary in the nearby water.  
      Most studies are conducted on the aquatic creature sub-group of elasmobranchii, otherwise known as sharks. Most shark repelling apparatus use electromagnetic pulses, delivered into the water by submerged antennae or electrodes, to create an appropriate electromagnetic field in the vicinity of a swimmer, diver or general water recreationist.  
      Various types of pulse signal generators are used, the characteristics of which include a specification of signal duration, repetition rate, amplitude and pulse rise time. The value or ranges of each characteristic are carefully selected so as to create the electromagnetic field deemed most effective.  
      In the past, such signal generators have been disposed on the body of the swimmer or as a separate unit to be used in an area that is desired to be shark-free.  
      Not only are individuals at risk from being attacked by sharks, sometimes small aquatic vessels such as surfboards, kayaks, rafts and small boats can be disturbed by sharks.  
      It is an object of the present invention to provide a means by which shark-repelling electromagnetic fields can be generated about an aquatic vessel to reduce the risk of the vessel being disturbed by sharks.  
     SUMMARY OF THE INVENTION  
      According to a first aspect of the present invention, there is provided an aquatic vessel hull adapted to support at least two electrodes connectable to an electromagnetic field signal generator, in use, the electrodes generating an electromagnetic field in a volume of water about the vessel, the electromagnetic field acting to repel selected aquatic creatures.  
      Preferably, the aquatic vessel hull includes at least two recesses for receiving one each of the at least two electrodes, such that the at least two electrodes do not protrude substantially beyond the upper surface of the hull.  
      Preferably, the aquatic vessel hull further includes a channel connecting said recesses, said channel adapted to accommodate an electrode cord terminating at each end being one of said at least two electrodes.  
      Preferably, the recesses are formed so as to allow maximum efficiency of distribution of the electromagnetic field generated by said electrodes when in use.  
      According to a second aspect of the present invention, there is provided an aquatic vessel hull incorporating at least two electrodes, connectable to an electromagnetic field signal generator, in use, the said electrodes generating an electromagnetic field in a volume of water about the aquatic vessel, said field acting to repel selected aquatic creatures.  
      Preferably, the electrodes do not substantially protrude beyond the surface of said hull.  
      Preferably, the electrodes are received in corresponding recesses in said hull.  
      Preferably, the electrodes constitute respective ends of a cord, which is received in a channel in said hull connecting said recesses.  
      Alternatively, the electrodes consist of respective conductive plates.  
      Preferably, the recesses are formed so as to allow maximum efficiency of distribution of the electromagnetic field generated by said electrodes when in use. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a side elevation of an aquatic vessel hull according to a preferred embodiment of the present invention;  
       FIG. 2  shows a plan view of the top of the aquatic vessel hull of  FIG. 1 ;  
       FIG. 3  shows a plan view of the bottom of an aquatic vessel hull of  FIG. 1 ;  
       FIG. 4  shows the hull of  FIG. 3  with the electrode cord inserted;  
       FIG. 5  shows a detail of the recess for receiving the electric field signal generator;  
       FIG. 6  shows a cross-sectional view of the recess along the lines A-A′ of  FIG. 3 .  
       FIG. 7  shows an alternative arrangement of the hull of  FIG. 1 .  
       FIG. 8  shows the hull of  FIG. 1  in use, generating an electromagnetic field. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      It will be understood that the phrase “aquatic vessel” refers to any suitable vessel including surfboard, surf rescue board, kayak, sailboat, rowboat, ship and water skis to be worn on the feet of a user.  
      A typical aquatic vessel hull  10  is shown in side elevation in  FIG. 1 . Provided in hull  10  is channel  11  for accommodating a cord (not shown) having electrodes at either end of the cord. The type of electrode cord that will be suitable for this application is the subject of a co-pending PCT Patent Application No PCT/AU02/01297, the contents of which are hereby incorporated by reference. It will be appreciated however, that any other suitable electrode arrangement may be used.  
      Hollowed recesses  12  and  13  accommodate the electrodes (not shown) of the electrode cord which in use, is slid through channel  11  until both electrodes are in place in respective recesses  12  and  13  and then secured in place by any appropriate means.  
       FIGS. 2 and 3  show these features in a top plan view and a bottom plan view respectively.  
       FIG. 4  show the view of  FIG. 3  (bottom view), but with an electrode cord  23  inserted in channel  11 . Electrodes  24  and  25 , being the ends of cord  23  are received in recesses  12  and  13  respectively.  
      Channel  11  may accommodate a fibre glass tube  11   a  (see  FIG. 6 ) through which the electrode cord may be slid. Channel  11  is then covered or filled such that the contour of the exterior surface of hull  10  is maintained.  
      Recesses  12  and  13  are shaped such that exposed electrodes are able to radiate effectively from their position within the hull. As can be seen  FIG. 6 , a preferred range of angles for recesses  12  and  13  is 100°-110°.  
      Hull  10  also includes a recess or cavity  14  which is sealable with lid  15 . Recess  14  is adapted to receive and store an electric field signal generator. Such signal generators are well known and one such suitable generator is described in Australian Patent No 669806. Any suitable electric field signal generator however, may be used.  
      Channel  14   a  provides a means by which the signal generator can be connected to the electrodes (see  FIG. 5 ).  
      It is also within the concept of the present invention to provide a hull having incorporated therein electrodes which are connectable to a suitable signal generator. The electrodes may consist of metal plates or a conductor of any other suitable configuration, which may be attached to, or form an integral portion of the hull. For example, a portion of the front end of the hull may be made from or include a metal or other conductive plate providing a first electrode, while a portion of the back end of the hull may be made from a metal or other conductive plate, forming a second electrode. Such an arrangement is shown in  FIG. 7 , in which electrode plates  20 ,  21  are shown incorporated within hull  10 . Upon connection to a suitable signal generator, these plates may radiate the required electromagnetic field to produce a shark-deterring region within the water about the hull.  
       FIG. 8  shows the hull of  FIG. 1  incorporating the cord with electrodes housed in channels  12  and  13  (not shown), in use in a body of water  30 .  
      When activated the signal generator (not shown) causes the electrodes (not shown) to generate electromagnetic field  40  about hull  10 , forming a shark-repelling region about the vessel. This reduces the risk of a shark attacking the vessel, or a person who is in the water, and near the vessel, such as a person who has fallen off or out of the vessel.  
      While the above has been described with reference to a preferred embodiment, it will be understood that further modifications and alterations may be made within the scope of the present invention.