Abstract:
The invention concerns a fender for absorbing shocks and preventing wear of a first object in relative movement with respect to a second object, comprising a main protective element with axial symmetry and circular cross-section rotating freely about a geometrical axis fixed relative to a support secured to one or the other of the first and second objects and having a hardness index less than that of said first object, and two secondary protective cone-shaped elements with axial symmetry and circular cross-section arranged at each end of the main protective element, independent thereof, and also freely rotating about the same geometrical axis.

Description:
TECHNICAL FIELD 
     The present invention relates generally to devices aimed at absorbing shocks from an object moving against a fixed object such as a boat at anchor in a port, and relates more particularly to a fender device aimed at preventing wear on boat hulls due to shock and friction against quaysides. 
     BACKGROUND ART 
     It is well-known to use fenders which are elastomeric bodies hanging from ropes along the hull of a boat and which are inserted between the boat and the quayside when the boat comes alongside, thus protecting the hull against shock and wear. Unfortunately, as the fenders are hung vertically, there is very little protection against roll, which causes the boat to move along the vertical axis. In addition, when the boat comes alongside an articulated pontoon, fenders have the unfortunate disadvantage of bouncing off the pontoon when a person jumps onto the latter. 
     Fenders also exist, which are attached to pontoons or to quays. But because the latter are fixed, they do not protect the hull against wear when the boat is subjected to rolling. 
     The best system consists therefore of installing moving rollers around a fixed axis, either on the boat, or to the pontoon. A device of this kind is described in U.S. Pat. No. 3,145,685. It includes an axis on which a plurality of rubber rollers are mounted for absorbing the energy of shocks when the boat is subjected to vertical movements. Unfortunately, boat movements produced by turbulence in the water are not only vertical, and a boat is almost always subjected to horizontal movements which result in the boat rotating in one direction or another. In this case, unless rollers are fitted all along the boat or all along the pontoon, which would be exorbitant in cost terms, the boat is no longer protected by a roller at either end and its hull then strikes along the protruding axis, typically made of metal, at either end of the rollers, as in the patent referred to above. 
     SUMMARY OF THE INVENTION 
     This is why the main object of the invention is to provide an improved fender device for absorbing shocks and thus avoiding the wear to a moving object in contact with a fixed object regardless of the movements the moving object is subjected to. 
     The invention relates therefore to a fender device for absorbing shocks and thus preventing wear of a first object in relative movement with respect to a second object, in particular when the first object is a boat hull in contact with a pontoon, comprising a main protective element with axial symmetry and a circular section, freely rotating around a support integral with one or other of the objects, and having a hardness which is less than that of the first object, and two cone-shaped secondary protective elements, with axial symmetry and circular section, arranged at either end of the fender element and freely rotating around the same geometric axis. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects and features of the invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which: 
     FIG. 1 shows a longitudinal section of a first embodiment of the device according to the present invention, mounted on its support, and 
     FIG. 2 shows a longitudinal section of a second embodiment of the device according to the present invention, mounted on its support. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The fender device illustrated in FIG. 1 is made up of a cylinder-shaped main protective element  10  and two cone-shaped secondary protective elements  12  and  14 . The protecting elements  10 ,  12  and  14  freely rotate around a geometric axis  16  which is fixed to a support comprising a support plate  18  and two flanges  20  and  22  meant for supporting the fender device. The support plate  18  is fixed by screws  28  to a floating pontoon or to a mooring berth  29 . 
     The two flanges  20  and  22  include two circular roll bearings  24  and  26  in which a high strength metal axle  30  freely rotates around the geometric axis  16 . 
     The main protective element  10  is mounted onto the metal axle  30  and may or may not be integral with the latter. If it must be integral with the metal axle  30 , element  10  may be mounted by casting and made integral with the metal axle  30  by means of washers  32  and  34  fixed onto the axle  30  or by any other fixing process, including gluing. But it is also possible to allow element  10  to move freely around axle  30 . However, transverse fixings will have to be provided for in order to avoid translation movement in the element in relation to the axle  30 . These fixings could be carried out using clips set in grooves provided in the axle  30 . 
     The two elements  12  and  14 , like the main element  10 , have an axial symmetry around the geometric axis  16 , and they have a circular section. They are cone-shaped, that is to say the longitudinal section illustrated in FIG. 1 is a mainly triangularly curvilinear shaped curve, but could also be any other curvilinear form, and especially a semi-circle. 
     In the same way as the main protective element  10 , the two elements  12  and  14  are supported by the metal axle  30  and can be made integral with the latter by washers  36  and  38  mounted on the axle and onto which the elements are cast, or by using any other fixing means, including gluing. If it is desired that the two elements  12  and  14  are not integral with axle  30  but simply rotate around the latter, means have to be allowed for holding the elements in position onto the axle so that they can freely rotate around it, such as clipping means in grooves in the axle. 
     In the preferred embodiment, the protective elements  10 ,  12  and  14  are made from elastomeric material such as polyvinyl chloride (PVC), polyethylene, polyurethane or any other equivalent material. In a variant, element  10  and/or elements  12  and  14  may be hollow and filled with air, water or partly filled with an air and an aqueous solution. When filled with air, valves may be incorporated to allow air filling and suitable internal pressure to be maintained. 
     It should be noted that it is advisable to allow for soft bosses  40  and  46  on the two elements  12  and  14  and  42  and  44  at either end of element  10  in such a way as to strengthen the portions of those elements which are to be subjected to heavy compression. 
     The device according to the invention can have a length which varies depending on the needs, a length ranging from 20 cm to 2 m being preferred. It may be attached to a mooring berth or to a floating pontoon. Fixing is carried out in such a way that the metal axle is horizontal so that a boat hull coming alongside and subjected to roll movements caused by water turbulence may drive the elements into rotation, and thereby cause a rolling without friction, thus protecting hull against wear. 
     As mentioned above, a boat is almost never parallel to the mooring berth and carries out small rotary motions. In this case, the hull of the boat moves away from the main element  10  and strikes either of the elements  12  and  14 . If the boat is, as mentioned above, additionally subjected to roll due to turbulence in the water or to wind pressure on the hull, contact by the latter causes the rotation of the secondary element  12  or  14 . It should be noted that this rotation is not quite a friction-free rolling because of the variation in the rotation radius in element  12  and  14  along the axle, but it will avoid wear to the boat hull which would inevitably occur if the fender device only included a main element and the boat hull were to strike and rub against the metal axle. 
     It should also be noted that the secondary elements  12  and  14  are almost always engaged and fully justify their existence to the extent to which a boat coming alongside rarely comes parallel to the quayside and inevitably strikes one of the secondary elements  12  or  14 . 
     A second embodiment that is especially suited to the angular movements of boat hulls in relation to axle  30  is illustrated in FIG.  2 . In this embodiment, the main protective element  10  is no longer cylindrical but presents a curvilinear longitudinal section whose profile is approximately an extension of the profile of the longitudinal section of elements  12  and  14 . In this way, the main element  10  will be engaged at the same time as one of the elements  12  and  14  each time the boat makes a slight rotary motion. This arrangement therefore allows loading to be shared over two out of the three elements most of the time, that is to say over the main element and one of the two secondary elements instead of a single element. 
     Even though the fender device according to the invention is mounted with its axis horizontal in the above mentioned embodiments, it is possible to use it with its axis set vertically. This may be the case to ensure protection to hulls of boats that navigate river waters, and especially when the boat is in narrow waters between two quays in a channel or in a lock. The two cone-shaped elements are useful in this case too in protecting the hull of the boat subjected to roll due to water turbulence whilst it moves alongside the quaysides. 
     Variants of above embodiments may be used without departing from the frame of the invention. In this way, the device could be mounted to a boat hull using a support that is suitable for the hull, rather than fixing it to the quay or pontoon. In addition, the device according to the invention may include several main elements set within the bearings, and especially in the first embodiment where these are cylindrical.