Float and a floatable structure

#The present invention relates to a float, such as a float for suspending an article submersed in water, or a float of the type used as a navigational buoy or for carrying instrumentation, such as weather monitoring instrumentation, although the invention is not limited to such floats. The invention is also directed towards a floatable structure of the type suitable for use as a navigational buoy or for carrying instrumentation, and the invention also relates to a method for damping buoyant movement of a float in water, as well as to a method for growing marine molluscs.

#Floats for suspending articles submersed in water, for example, in the sea, lakes, rivers and the like are well known. Such floats, are commonly used in the commercial mussel growing industry for suspending ropes impregnated with mussel spawn in the sea, and mussels which grow on the ropes are harvested by withdrawing the ropes from the water. Such ropes are commonly referred to as crop ropes. In general, a plurality of such floats are secured between a pair of spaced apart tethering ropes, at spaced apart intervals along the tethering ropes, and the crop ropes are secured to and suspended from the tethering ropes at spaced apart intervals along the tethering ropes between the floats, so that the crop ropes depend downwardly into the sea. Respective opposite ends of the tethering ropes are secured to suitable moorings. Such arrangements of floats will be well known to those skilled in the art. In general, the floats are of cylindrical construction terminating in opposite domed ends. Coupling members extend axially from the domed ends, and the spaced apart tethering ropes are secured to the coupling members, so that the floats extend between the tethering ropes with their respective central axes extending perpendicularly to the tethering ropes.

#Typically, the floats are of plastic material, and may be foam filled, or air filled. Such floats known heretofore suffer from a serious disadvantage. In general, such floats are suitable for use in sheltered waters only; they are unsuitable for use in open unprotected waters. When subjected to waves in open unprotected water, and in particular, when subjected to relatively large waves which occur in stormy conditions, and which can be up to ten metres in height and greater, the floats become submerged, and can be submerged to depths of up to twenty metres and greater. This is particularly so as the mussels grow on the crop ropes and the crop ropes become increasingly heavier. When submerged to such depths there is a danger of the floats collapsing, and where such floats do not collapse, the buoyant upward force on the floats tend to propel the floats out of the water to heights above the water which can be up to four metres. This is totally undesirable, since the rapid propulsion of the floats out of the water and their sudden return tends to shake the mussels from the crop ropes, and the larger the mussels, the greater is the danger of the mussels being shaken from the crop ropes.

#The invention will be more clearly understood from the following description of some preferred embodiments thereof which are given by way of example only with reference to the accompanying drawings in which:

#FIG. 1 is a top perspective view of a float according to the invention,

#FIG. 2 is a partly cutaway underneath perspective view of the float of FIG. 1,

#Referring to the drawings and initially to FIGS. 1 to 9 there is illustrated a float according to the invention indicated generally by the reference numeral 1, which in this embodiment of the invention is suitable for use in the growing of marine molluscs, and in particular for use in commercial mussel growing, for locating and coupling between a pair of longitudinally extending spaced apart parallel tethering ropes 2 and for suspending crop ropes 3 impregnated with mussel spawn submersed in seawater on which mussels are grown, see FIGS. 8 and 9. The float 1 in this embodiment of the invention is of plastics material, and may be of low-density polyethylene or high-density polyethylene material and is formed by rotational moulding, although the float may be formed by blow moulding or by other suitable plastics materials forming processes. The float 1 comprises a hollow ovoid shell 5 which defines an airtight hollow interior region 6, and the shell 5 is of strength sufficient to withstand the hollow interior region 6 being pressurised by compressed air to a pressure of approximately two atmospheres. The shell 5 defines first and second major central planes 8 and 9 which are perpendicular to each other, the first major central plane 8 extending horizontally, in use, and coinciding with a plane, which in use extends longitudinally through the float 1 at its maximum horizontal longitudinal cross-sectional area, and the second major central plane 9 extending vertically, in use, and coinciding with a plane which in use extends longitudinally through the float 1 at its maximum vertical longitudinal cross-sectional area. The normal waterline of the float 1 defines a third horizontal plane, in use, which in this embodiment of the invention coincides with the first major central plane. A fourth plane, which in this embodiment of the invention is a minor central plane 10 defined by the shell 5 coinciding with a plane extending transversely through the float 1 at its maximum vertical transverse cross-sectional area in use, extends perpendicularly to both the first and second major central planes 8 and 9.

#A damping means for damping upward and downward vertical movement of the float 1 comprises a damping plate 12 extending laterally outwardly from and around the shell 5. The damping plate 12 defines a first plane 14 which extends parallel to the first major central plane 8 and is spaced apart below the first major central plane 8. Thus in this embodiment of the invention the damping plate 12 extends from a lower portion 15 of the surface 16 of the shell 5, which in use, in general, is below the normal waterline of the float and is submersed. Accordingly, the damping plate 12 is in normal use located within the water for damping upward buoyant movement of the float 1 in the water. However, prior to commencement of growing of the crop and during the early stages of crop growth, when the weight of the crop ropes is less than their weight as the crop develops, the damping plate may not be submerged in calm water.

#A longitudinally extending keel 18 extends radially outwardly and downwardly from the shell 5 from a front end 19 to a rear end 20 of the shell 5 for minimising rolling of the float 1 in water. The keel 18 defines a keel plane which coincides with the second major central plane 9, and accordingly, the keel plane defined by the keel 18 is perpendicular to the first plane 14 defined by the damping plate 12.