Abstract:
A floating low profile watercraft lifting apparatus comprises a buoyant support apparatus and a watercraft lift attached to the buoyant support apparatus. Embodiments of the lift have first and second cantilever arms pivotally mounted to a base at offset pivot points for use in shallow water. The lift includes an actuator connected to the first and second cantilever arms and operable to move the first and second cantilever arms between a collapsed configuration and an extended configuration with uniform application of force and a minimum amount of travel of actuator components. The support apparatus comprises inflatable pontoons within a frame attached to the lift and providing buoyant support for the lifting apparatus.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a continuation-in-part of U.S. application Ser. No. 10/816,992, filed Apr. 2, 2004, which is a continuation of PCT Application No. PCT/US01/46253, filed Oct. 23, 2001, which is a continuation-in-part of U.S. application Ser. No. 09/316,928, filed May 21, 1999, and claims priority from U.S. provisional application No. 60/086,428, filed May 22, 1998, entitled LOW PROFILE LIFT FOR WATERCRAFT. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to lifting devices, specifically to improvements in such devices that are employed to lift watercraft, for example boats and seaplanes.  
         [0004]     2. Description of the Related Art  
         [0005]     Users of watercraft have need to lift their watercraft from the water, for example for maintenance or in preparation for land transportation of the watercraft. Equally, watercraft users have need to lower their watercraft into the water, for example for launching or simply for flotation at dock. Users have heretofore employed a number of devices for such lifting and lowering.  
         [0006]     Exemplary of such devices is U.S. Pat. No. 5,184,914, issued to the inventor of the present invention which is incorporated herein by reference and discloses a watercraft lifting device having a rectangular stationary base formed of two longitudinal parallel beams and two transverse beams, generally described as front and rear transverse, beams. The rectangular base is submersible under water. Pivoting booms connect each of the four corners of the rectangular base to swingable mounting arms positioned parallel to and coplanar with each of the longitudinal beams to form two pairs of pivoting booms, generally described as front and rear pivoting booms. The two pair of pivoting booms form with the mounting arms collapsing parallelograms on which watercraft supports extended a predetermined distance above the mounting arms hold the craft during lifting. A double-acting hydraulic cylinder is pivotally connected to the rear transverse beam and its piston rod is pivotally connected to the two front pivoting booms such that expansion of the double-acting cylinder extends the piston rod and swings front pair of pivoting booms upward from a collapsed configuration. The parallelogram linkage forces the mounting arms and rear pair of pivoting booms to follow the front pair of pivoting booms. Thus, expansion of the double-acting hydraulic cylinder raises the front pair of pivoting booms and lifts the rear pair of pivoting booms, the mounting arms and the watercraft supports attached to the mounting arms upward to lift a watercraft out of the water. Upward movement continues until the pivoting booms pass through a vertical orientation into an over-center orientation whereby the watercraft is supported above the surface of the water.  
         [0007]     Retraction of the piston rod into the piston jacket of the double-acting hydraulic cylinder reverses the motion of the pivoting booms. Thus, retraction of the double-acting hydraulic cylinder first raises the pivoting booms and lifts the mounting arms and watercraft supports attached to the mounting arms upward. Upward movement causes the pivoting booms to pass back through vertical orientation. Continued retraction of the piston rod into the double-acting hydraulic cylinder combined with the weight of the latching apparatus and the watercraft collapses the parallelograms whereby the watercraft is lowered into the water. The piston rod continues to retract into the double-acting hydraulic cylinder collapsing the parallelograms, including the mounting arms and watercraft supports attached to the mounting arms, until contact between the watercraft supports and the watercraft is broken and the watercraft can float free.  
         [0008]     Although the apparatus of the prior art operates effectively in many practical applications, a need exists for a floating watercraft lifting apparatus that operates effectively in shallow water applications where the typical water depth is minimal and the apparatus of the prior art cannot collapse sufficiently to break contact between the watercraft supports and the watercraft and release the watercraft to float free, and where the depth of the water varies due to tides, seasonal fluctuations, and the like. Such an apparatus is specified and claimed in currently pending U.S. application Ser. No. 10/816,992 by the inventor of the present invention, incorporated herein by reference.  
         [0009]     The invention claimed in application &#39;992 comprises a boyant support apparatus and a watercraft lift attached to the boyant support apparatus. Embodiments of the boyant support apparatus disclosed in &#39;992 are rigid pontoons, preferably comprised of sectional airtight flotation chambers having a hollow interior. While floating watercraft lifts are advantageous generally for reasons set forth above, rigid pontoons for such an apparatus present several limitations.  
         [0010]     First, the required dimensions for boat lift pontoons presents significant manufacturing costs if rigid pontoons are employed. A floating boat lift, such as the Floatlift™ model FL 6012 from Sunstream Corporation must have pontoons providing roughly 8,300 pounds of buoyancy, requiring displacing roughly 1000 gallons of water. Even if boat lift pontoons are manufactured sectionally, as described in application number &#39;992, manufacturing rigid pontoons of such large displacement entails considerable difficulty and cost. Second, shipment of such large rigid pontoons to the site where the boat lift is to be assembled and deployed entails additional difficulty and cost. Third, disassembly of a floating lift, whether for maintenance or relocation, is more complicated when large rigid pontoons are involved.  
         [0011]     What is needed is a floating boat lift that offers the advantages of such lifts generally but that does not have the disadvantages associated with large rigid pontoons.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0012]     The present invention improves upon prior art floating watercraft lifts by providing a buoyant support apparatus comprised of inflatable pontoons. The pontoons comprise inflatable tubular chambers, typically fabricated of polymer coated fabric sheet material. The inflatable buoyant support apparatus attaches to the watercraft lift via rigid attachment means. Advantageously, the pontoons may be shipped deflated to the boat lift location and, in situ, both inflated for deployment and deflated for maintenance or relocation.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The foregoing objects, as well as further objects, advantages, features and characteristics of the present invention, in addition to methods of operation, function of related elements of structure, and the combination of parts and economies of manufacture, 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 like reference numerals designate corresponding parts in the various figures, and wherein:  
         [0014]      FIG. 1  is a perspective view of a floating watercraft lift in the raised, over-center position, according to the present invention.  
         [0015]      FIG. 2  is a front elevational view of a floating watercraft lift in the raised position, according to the present invention.  
         [0016]      FIG. 3  is a side elevational view of a pontoon affixed to support apparatus according to the present invention.  
         [0017]      FIG. 4  is a detail of a pontoon affixed to support apparatus in a preferred embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]     Referring to  FIG. 1  and  FIG. 2 , floating lift  100  comprises a watercraft lift apparatus  102  affixed to a buoyant support frame  104 . In the depicted embodiment, the support frame  104  includes two adjustable transverse beams  106 ,  108  that are attached to lift  102  by connectors  110  located on each end  112  of parallel longitudinal beams  114   a ,  114   b  on lift  102 . Attachment to connectors  110  may be accomplished by welding, fasteners, or other known methods. Transverse beams  106 ,  108  are formed of tubular metal having a substantially square cross-sectional shape that defines a hollow longitudinal interior  116  that opens at each end  118 . Lift  102  holds transverse beams  106 ,  108  in spaced parallel relationship.  
         [0019]     In use, the floating lift  100  is positioned in a body of water with the support frame  104  attached to the floor of the body of water. The support frame stands upon support stands  120 , resting upon base plates  122 , suitably secured in a conventional manner that will not be described in detail herein. Stands  120  connect to catwalks  124  via arcuate bands  126 , which encompass inflatable pontoons  128 . Pontoons  128  may be inflated with air or other gas to provide buoyancy. In the depicted embodiment, catwalks  124  rest upon floating inflatable pontoons  128  and thereby support buoyant support frame  104 . While the preferred embodiment is depicted, other arrangements for the inflatable pontoons  128  to provide buoyancy to frame  104  are within the scope of the present invention. For example, both the catwalks  124  and the pontoons  128  may be directly connected to frame  104 .  
         [0020]     In this embodiment, stands  120  are laterally positioned by sliding the lateral beams  130  with respect to front and rear transverse beams  106 ,  108  and affixing them with suitable fasteners. Once base plates  122  are anchored, buoyant support frame  104  is adjusted vertically along adjustment post  129 , thus keeping lift  102  at the right height with respect to the surface of the water.  
         [0021]     As depicted, pontoons  128  are each comprised of pairs of tubes of polymer coated fabric material, made airtight and fitted with valves for inflation and deflation in the manner of inflatable rafts of rubberized fabric, well known to those in the art. As will be appreciated by those of skill in the art, a wide variety of other configurations of inflatable pontoons are possible in keeping with the teachings of the present invention. It is preferred that each pontoon  128  comprise a plurality of inflatable members, so that in the event of a rupture, the pontoon will still retain partial buoyancy.  
         [0022]     As will be further appreciated by those of skill in the art, other embodiments of the present invention are possible wherein inflatable pontoons are fabricated of materials other than polymer coated fabric, such as sheet elastomer or heavy gauge sheet mylar®. It is to be understood that pontoons comprised of any material are within the scope of the present invention, so long as such pontoons may be inflated with air for flotation and are substantially reduced in volume when deflated.  
         [0023]     In the presently depicted embodiment, pontoons  128  are secured to catwalks  124  by nautical ropes  130  which are threaded through handles  132  that are affixed to pontoons  128 . The depicted handles  132  are comprised of a rigid material, such as solid polymer, affixed to pontoon  128  by bonding to a rigid or semi-rigid reinforcing sole within pontoon  128 , and made airtight with pontoon  128  by polymeric seal with the material comprising pontoon  114 , in a manner well-known to those in the art. As will be appreciated by those of skill in the art, various other conventional means may be employed to secure inflatable pontoons  128  to catwalks  124 . By way of example, such means may include nylon straps instead of nautical ropes. By way of further example, pontoon  128  may be secured to catwalk  124  by a connecting means such as a clamp attached to catwalk  124  which directly engages an attachment such as handles  132  in the pontoon  128 . By way of yet further example, catwalk  124  may be integral to pontoon  128 , comprising a rigid or semi-rigid element disposed within and/or bonded to the polymer coated fabric or other material comprising pontoon  128 .  
         [0024]     Watercraft lift apparatus  102  may be of any design whose dimensions and extensions in operation are accommodated by buoyant support frame  104 . An exemplary lift apparatus is that described in U.S. Pat. No. 5,184,914, issued to the inventor of the present invention and incorporated herein by reference. In the depicted embodiment, lift  102  comprises a base made up of front and rear beams  134 ,  136  and transverse beams  114   a ,  114   b . Two pair of upwardly extending booms  138 ,  140  are each pivotally connected at their lower end to the base at its corners. The members of each pair of booms are rigidly connected to each other in parallel by cross supports  142 ,  144 . Two substantially horizontal arms  146  are each pivotally connected to one member of each pair of booms  138 ,  140  at the upper end of the boom, so that each arm pivotally connects to one member of one pair of booms  138  at one end of the arm and to one member of the other pair of booms  140  at the other end of the arm. Two connected, collapsible parallelograms are thereby formed, one on each side of the base formed by  114   a ,  114   b ,  134  and  136 , the corners of each parallelogram comprising the upper and lower pivot points of the front and rear booms  138 ,  140  on one side of the base. The pivotally connected arms lie in a plane, which is lowered as the parallelograms are collapsed and is raised when the parallelograms are expanded. A watercraft supported by support means connected to the arms in that plane may thereby be lowered and raised as the parallelograms are respectively collapsed and expanded. An expanding and contracting actuator,  146 , such as a hydraulic cylinder, supplies the motive force for expanding the parallelogram for lifting watercraft.  
         [0025]     In preferred embodiments of watercraft lifts, such as claimed in &#39;914, the parallelogram expands over-center, so that initially obtuse angles of the parallelogram become acute and initially acute angles become obtuse, providing an advantageous, gravity-based locking for raised lifts. Such a lift requires that the actuator be double-acting, providing expanding actuation for raising, but also providing contracting actuation for moving the lift back over center for lowering, as provided preferably by a double-acting hydraulic cylinder. As will be appreciated by those of skill in the art, however, the present invention will accommodate a wide range of embodiments of watercraft lift  102 , not limited to those expressly described herein.  
       CONCLUSIONS, RAMIFICATIONS, AND SCOPE  
       [0026]     Accordingly, it can be seen that the invention described herein provides an improved floating watercraft lift apparatus wherein the buoyancy of the lift is supplied by inflatable pontoons. Because the pontoons are inflatable and deflatable, the pontoons may be shipped deflated to the boat lift location and, in situ, both inflated for deployment and deflated for maintenance or relocation.  
         [0027]     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.  
         [0028]     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.