Abstract:
An improved floating boat lift incorporates a passive hydraulic pivoting lift mechanism, onto which a boat can be driven and positioned ready for storage using only the motive power of the boat itself. The passive hydraulic pivoting lift mechanism provides mechanical advantage in the pivoting action of the apparatus by way of passive hydraulic action, while at the same time dampening pivoting of the apparatus. Embodiments further provide means for adjusting the elevation of the pivot point relative to the surface of the body of water by way of adjusting the buoyancy of the pivoting lift mechanism.

Description:
[0001]     This application is a continuation of U.S. patent application Ser. No. 11/324,010, filed 31 Dec. 2005, which application is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to an improvement in floating boat lift apparatus.  
       BACKGROUND OF INVENTION  
       [0003]     Various apparatus have been devised for dry-docking boats. Pleasure boats of the kind to which the present invention is particularly adapted are thought of, for purpose of the present description, as being generally within the range of about fifteen feet to twenty-four feet in length and within the range of about 800 pounds to 6000 pounds in weight. Apparatus for docking pleasure boats has been associated with both non-floating as well as floating docks. The use of such apparatus is intended to facilitate removal of a boat from the water, maintaining the boat in a stored position elevated above the water, and for launching of the boat into the water.  
         [0004]     Among the many methods known and used for lifting boats for dry docking, floating lifts (such as set forth in U.S. Pat. No. 7,021,861, issued Apr. 4, 2006 to the inventor of the present invention) are known to have particular advantages. Secured or anchored in some fashion, such lifts can provide dry docking for boats in areas which were formerly open water. Floating upon the body of water, such lifts provide convenient dry docking at a constant level above the surface, in contrast with fixed lifts whose use may at times be rendered difficult or impractical due to varying seasonal depth of the body of water. Floating lifts can provide dry docking in bodies of water in which securing a fixed boat lift is difficult, as in deep muddy or sandy bottoms. Floating lifts may also be relocated with considerably greater ease than fixed boat lifts.  
         [0005]     An improved form of floating boat lift apparatus is illustrated in U.S. Pat. No. 6,602,022 to Wilkins, incorporated herein by reference, in which a tilting apparatus, installed in a floating boat well, receives a boat driven by its operator. The apparatus is then tilted about a pivot point, thereby elevating the boat in dry dock. In some embodiments, the lift mechanism, responsive to the change in weight distribution on the apparatus caused by the receipt of the boat, pivots on its own and elevates the boat. In other embodiments, after the boat has been received by the apparatus, it is necessary to use a winch or other mechanical assist to tilt the mechanism to elevate the boat.  
         [0006]     Advantageously over the prior art, Wilkins provides an apparatus that incorporates a single pivotal frame onto which a boat can be driven and positioned ready for storage using only the motive power of the boat itself and which can be pivoted so as to either elevate the boat above the water for storage or discharge the boat into the water for further use.  
         [0007]     However, the operation of Wilkins boat lift is subject to several shortcomings. First, the elevation of the pivot point relative to the boat well (and therefore its elevation relative to the surface of the water) is fixed in Wilkins lift. It is desirable to allow adjustment of the elevation of the pivot point relative to the surface of the water in order both to optimize the tilting operation of the lift and to provide adequate clearance of the boat from the water for dry dock purposes when the lift is in the elevated position.  
         [0008]     Second, no additional mechanical advantage is employed by Wilkins to augment the leverage provided by the change in weight distribution caused by receipt of the boat. Indeed, in embodiments elevating the boat above a relatively low height above the water (approximately six inches) or when elevating heavier boats, the Wilkins lift does not tilt on its own, instead requiring the use of the aforesaid winch or other mechanical means to effect tilting of the mechanism to elevate the boat. It is desirable to provide augmentation of the leverage provided by the weight of the boat, in order to allow the lift to be pivoted to the elevated position with greater ease and to provide for embodiments in which boats may be elevated above relatively low heights by operation of the apparatus on its own without the need for additional mechanical means to effect tilting.  
         [0009]     Third, Wilkins does not provide a damping functionality for his tilting apparatus: in embodiments relying on change in weight distribution to effect tilting, as the apparatus is tilted to elevate the boat and the center of gravity of the mechanism passes over-center of the pivot point, the lift apparatus settles to the elevated position in an abrupt fashion which can be jarring for the boat operator and tends to cause wear and fatigue of the lift mechanism.  
         [0010]     What is needed is an improved floating boat lift, having a pivoting lift mechanism onto which a boat can be driven and positioned ready for storage using only the motive power of the boat itself, but which also further provides mechanical advantage to augment the leverage provided by the change in weight distribution caused by receipt of the boat while providing a damping functionality to mitigate abrupt pivoting of the apparatus. What is needed further is such a floating boat lift that affords a means of adjusting the elevation of the lifting pivot point relative to the body of water.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention is an improved floating boat lift incorporating a passive hydraulic pivoting lift mechanism, onto which a boat can be driven and positioned ready for storage using only the motive power of the boat itself. The passive hydraulic pivoting lift mechanism provides mechanical advantage in the pivoting action of the apparatus by way of passive hydraulic action, while at the same time dampening pivoting of the apparatus. Some embodiments further provide means for adjusting the elevation of the pivot point relative to the surface of the body of water by way of adjusting the buoyancy of the pivoting lift mechanism.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     Other objects, advantages, features and characteristics of the present invention, as well as methods, operation and function of related elements of structure, and the combination of parts and economies of deployment, will become apparent upon consideration of the following description and claims with reference to the accompanying drawings, all of which form a part of this specification, wherein:  
         [0013]      FIG. 1  is a side elevation section view of the present invention illustrating the lift positioned for receipt of a boat;  
         [0014]      FIG. 2  is a side elevation section view of the present invention after the boat has been driven onto the frame under its own motive power;  
         [0015]      FIG. 3  is a side elevation showing the lift after it has pivoted, thereby lifting the boat;  
         [0016]      FIGS. 4   a ,  4   b  and  4   c  are cross-sectional views showing operation of the passive hydraulic mechanism in an embodiment of the present invention;  
         [0017]      FIGS. 5   a  and  5   b  are cross-sectional views of an embodiment of the present invention permitting adjustment of the elevation of the pivot point relative to the body of water; and  
         [0018]      FIGS. 6   a ,  6   b  and  6   c  depict cross-sectional views of an alternative embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     Turning to  FIG. 1 , illustrated is a floating boat lift  102 , positioned for receipt of a boat, comprised of a frame  104 , pivoting about a pivot point  106  which is buoyantly suspended by floating means  108  floating upon the surface  110  of a body of water. As is known to those in the art, floating means  108  may comprise a well formed by conjoined floating dock segments. Alternatively, floating means  108  my comprise pontoons specifically fashioned for the purpose of providing flotation for the lift. In any case, as will become clear from examination of the subsequent drawings, the lifting functionality of such floating boat lifts derives from the ability of the frame to pivot about a buoyantly suspended pivot point. Improving upon the prior art, the present invention further provides a passive hydraulic contrivance  112 , affixed to and pivoting with the frame.  
         [0020]     Turning now to  FIG.2 , illustrated is the lift immediately after a boat  202  has been driven onto it under its own motive power. Receipt of boat  202  by frame  204  results in distribution of weight on frame  204  forward of pivot point  206 , causing frame  204  to pivot upon pivot point  206 . As will be explained further in reference to subsequent drawings, hydraulic contrivance  212  both provides mechanical advantage to the pivoting action and also dampens the speed with which pivoting occurs.  
         [0021]     In  FIG. 3 , frame  304  has fully pivoted on pivot point  306 , coming to rest upon restraining bar  314 . Resting on frame  304 , boat  302  is buoyantly suspended by floating means  308  above the surface  310  of the body of water. The operation of passive hydraulic contrivance  312  is explained in reference to the cross-sectional views presented in  FIG. 4 .  
         [0022]      FIG. 4   a  illustrates the passive hydraulic contrivance  402  in a position prior to pivoting of the frame about pivot point  404 , in particular as when the lift is positioned for receipt of a boat ( FIG. 1 ). As illustrated, contrivance  402  is comprised of two communicating chambers,  406  and  408 , and in this position chamber  408  is lower than chamber  406 . Contrivance  402  is partially filled with ballast water  410 , which fills lower chamber  408 , while upper chamber  406  is empty.  
         [0023]     In  FIG. 4   b , the frame (not illustrated) and the contrivance  402  have begun to pivot, as is the case when the frame, receiving a boat driven onto the frame under the boat&#39;s own motive power, pivots about pivot point  404  because of the forward change in weight distribution ( FIG. 2 ). Ballast water  410  flows from chamber  408  to chamber  406 , further distributing weight forward of pivot point  404 , thereby providing mechanical advantage to the pivoting action. However, because the flow of water  410  from chamber  408  into chamber  406  is not instantaneous, at the same time contrivance  402  resists rapid pivoting about pivot point  404  by virtue of the weight of ballast water  410  remaining in chamber  408  and, in some embodiments, the buoyancy of the portion of chamber  406  that remains yet unfilled.  
         [0024]     In  FIG. 4   c , the frame has fully pivoted, coming to rest against its restraint ( 314  in  FIG. 3 ), and the level of ballast water  410  is equalized between chamber  406  and chamber  408 .  
         [0025]     While one embodiment is depicted, it will be appreciated by those of skill in the art that embodiments of the present invention may employ a wide variety of passive hydraulic contrivances that provide the mechanical advantage and dampening action taught herein. For example, the contrivance may comprise more than two chambers. Furthermore, the shape and size of the chambers may vary widely. Yet further, the amount of ballast within the contrivance may be varied, and ballast need not be limited to water. All that is required for such a contrivance is that it pivot with or in response to the pivoting of the frame of the lift, and that, with such pivoting, ballast flows gradually to augment the force provided by the weight distribution about the pivot point.  
         [0026]      FIG. 5  illustrates a further advantage some embodiments of the invention may derive from the hydraulic contrivance. In such embodiments, pivot point  502  is releasably secured at height selected by the user within a vertical channel  504  disposed within floating means  506 . The height of pivot point  502  above the surface  508  of the body of water may be adjusted by the user by releasing pivot point  502  within channel  504  and varying the amount of ballast  510  within contrivance  512 . More ballast will cause pivot point  502  to be lower in relation to the surface  508  of the body of water, as in  FIG. 5   a , while, with less ballast, the contrivance provides buoyancy to raise pivot point  502  higher above the surface  508  of the body of water, as in  FIG. 5   b . When, by varying ballast  510  in contrivance  512 , the user has established a desired height for the pivot point, and hence of the frame for receiving the boat ( FIG. 1 ) and of the boat when the lift has pivoted ( FIG. 3 ), the user then again releasably secures pivot point  502  at such height within channel  504 .  
         [0027]     An alternative embodiment of the present invention is depicted in cross section in  FIG. 6 . In this embodiment, the contrivance itself functions both as the frame and the floating means for the pivoting lift. In  FIG. 6   a , lift  602  is a hollow vessel, partially filled with ballast  604 , tilted upward for receipt of a boat, and anchored at a pivot point  606  via chain  608  to the floor of the body of water upon whose surface  610  the lift floats.  
         [0028]     In  FIG. 6   b , lift  602  has received a boat  612  driven onto the lift under the boat&#39;s own motive power. The change in weight distribution resulting from receipt of boat  612  causes lift  602  to pivot about the pivot point  606 , causing ballast  604  to flow toward the front of the lift, further distributing weight forward of the pivot point and thereby providing mechanical advantage to the pivoting of lift  602 .  
         [0029]      FIG. 6   c  depicts lift  602  after completion of pivoting, whereby ballast  604  has flowed within the lift so that weight is balanced on either side of pivot point  606 , thereby leveling and raising boat  612  above the surface  610  of the body of water.  
         [0030]     As taught in the foregoing discussion, the present invention, employing a passive hydraulic contrivance, improves upon the prior art floating boat lift by providing both mechanical advantage and damping action to the pivoting functionality of such a lift. Further, embodiments of the present invention facilitate user adjustment of the elevation of the lift pivot point in relation to the surface of the body of water.  
         [0031]     Although the detailed descriptions above contain many specifics, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Various other embodiments and ramifications are possible within its scope, a number of which are discussed in general terms above.  
         [0032]     While the invention has been described with a certain degree of particularity, it should be recognized that elements thereof may be altered by persons skilled in the art without departing from the spirit and scope of the invention. Accordingly, the present invention is not intended to be limited to the specific forms set forth herein, but on the contrary, it is intended to cover such alternatives, modifications and equivalents as can be reasonably included within the scope of the invention. The invention is limited only by the following claims and their equivalents.