Abstract:
A boat-lift system adapted to move a smaller boat relative to a larger boat. The boat-lift system comprises a structural support, a lift structure, a pivot system, and an actuator assembly. The structural support is adapted to be rigidly connected to a transom of the larger boat. The lift structure defines a second pivot portion, an actuator portion, an extension portion, and first and second boat-engaging portions. The pivot system connects the first and second pivot portions to allow rotation of the lift structure between first and second lift positions relative to the structural support. Actuation of the actuator assembly causes the lift structure to move between the first and second lift positions. When the smaller boat is in a docking position adjacent to the lift structure, operation of the actuator assembly moves the lift structure to lift the smaller boat from the docking position to a first storage position.

Description:
FIELD OF THE INVENTION 
     The present invention relates to boat-lift systems and methods and, more particularly, to boat-lift systems and methods adapted to lift a small boat out of the water for stowage on a larger boat. 
     BACKGROUND OF THE INVENTION 
     Operators of relatively large boats (i.e., over twenty-five feet long) often use smaller, more mobile boats for certain activities or to reach locations not accessible to the larger boats. When not in use, these smaller boats are often stowed aboard the larger boat. 
     A number of systems are known for lifting a smaller boat out of the water and into a storage position on a larger boat. One such system will be referred to herein as a davit system. A davit system comprises two uprights that are swung out over the side of the larger boat to raise and lower the smaller boat. With the smaller boat in the raised position, the uprights are typically swung back to place the smaller boat in a stowed position. Davit systems occupy a substantial amount of deck area on the larger boat and are relatively complex and expensive. 
     A swim step is typically mounted to the transom of larger boats. The swim step comprises a flat step surface supported just above the water line. An operator can stand on the step surface when accessing, entering, or exiting the water. Some boat-lift systems make use of the swim step as support for the lift system and/or as a storage location for the smaller boat. For example, a winch may be mounted at the stern of the larger boat. The winch is connected to cables that extend around the smaller boat, and operation of the winch displaces the cables to lift the smaller boat onto the swim step. Swim steps are not necessarily designed to accommodate the weight of the smaller boat, and the winches and cables can interfere with use of the stern and swim step of the larger boat. 
     RELATED ART 
     The following references were turned up in a professional patentability search conducted on behalf of the Applicant. 
     U.S. Pat. No. 5,937,783 to Costa, U.S. Pat. No. 5,483,912 to Thomas, U.S. Pat. No. 5,193,479 to Bielefeld, U.S. Pat. No. 5,133,275 to Maurizio, and U.S. Pat. No. 4,864,951 to Koepp, Jr. all teach davit systems for hoisting small boats onto a swim platform of a larger boat. In each of these patents, a member or assembly is rotatably attached to the end of the swim platform distal from the larger boat. All of these systems use cables to pull either the boat or the rotatable member or assembly from a loading position to a storage position. 
     U.S. Pat. No. 3,647,089 to Christiansen patent describes a system that it is pivotably supported by a swim step mounted on the transom of a larger boat. However, the device disclosed in the Christiansen patent employs bumpers that engage the side of the smaller craft and a frame that extends over the top of the smaller craft. The smaller craft is lifted from above rather than from below. The Christiansen device also employs winches and cables, is supported by the swim step, and obstructs access to the swim step. 
     U.S. Pat. No. 4,627,377 to Zooens, U.S. Pat. No. 6,327,992 to Martin, U.S. Pat. No. 5,636,587 to Klimowicz, and U.S. Pat. No. 4,763,593 to Lasko disclose davit systems that are pivotably connected at a pivot point at or near the transom of a larger boat. The systems disclosed in these patents rotate between loading and stored positions in a manner that would inhibit the use of a conventional swim platform. 
     The Applicant is further aware of a boat-lift product sold under the tradename FreedomLift. The FreedomLift product employs a pivot point adjacent to the transom of the larger boat. A lift structure extends from the pivot point and is moved between upper and lower positions to raise and lower the smaller boat to the rear of the swim step. 
     SUMMARY OF THE INVENTION 
     The present invention may be embodied as a boat-lift system adapted to move a smaller boat relative to a larger boat. Typically, a swim step is secured to the stern of the larger boat, and the swim step defines an aft edge and a swim step surface. The boat-lift system comprises a structural support, a lift structure, a pivot system, and an actuator assembly. 
     The structural support defines a first pivot portion and is adapted to be rigidly connected to the transom of the larger boat. So connected, the first pivot portion is arranged below the swim step surface and forward of the aft edge of the swim step. The lift structure defines a second pivot portion, an actuator portion, an extension portion, and first and second boat-engaging portions extending from the extension portion. The pivot system connects the first and second pivot portions to allow rotation of the lift structure between first and second lift positions relative to the structural support. The actuator assembly is secured at a first end relative to the structural support and at a second end to the actuator portion of the lift structure. Actuation of the actuator assembly in a first mode causes the lift structure to move from the second lift position to the first lift position. 
     When the lift structure is in the first lift position, the first boat-engaging portion extends over the swim step surface and the second boat-engaging portion extends rearwardly beyond the aft edge of the swim step. When the lift structure is in the second lift position, the first boat-engaging portion is spaced rearwardly of the aft edge of the swim step surface and the second boat-engaging portion extends below the first boat-engaging portion. 
     Accordingly, when the smaller boat is in a docking position adjacent to the lift structure and the actuator assembly is operated in the first mode, the lift structure moves the smaller boat from the docking position to a first storage position relative to the larger boat. 
     The lift structure may further be an assembly comprising a pivot member and a lift member. The pivot member defines the pivot portion, the actuator portion, and a socket portion. The lift member defines the extension portion and the first and second boat-engaging portions. The lift member is detachably attached to the pivot member to allow the lift member to be removed and stored when the boat-lift system is not in use. 
     The present invention may be embodied as a method comprising the steps of providing a structural support, a lift structure, a pivot system, and an actuator assembly and connecting and operating these structural elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a larger boat employing a boat-lift system of the present invention to support a smaller boat in a first stowage position; 
     FIG. 2 is a side elevation view depicting the boat-lift system of FIG. 1 in a first configuration relative to the larger boat; 
     FIG. 3 is a side elevation view depicting portions of a lift structure of the boat-lift system depicted in FIG. 1; 
     FIG. 4 is a side elevation view depicting the boat-lift system of FIG. 1 in a second configuration relative to the larger boat; 
     FIG. 5 is a side elevation view depicting the boat-lift system of FIG. 1 in an intermediate configuration between the first and second configurations; and 
     FIG. 6 is a side elevation view depicting the boat-lift system of FIG. 1 in the first configuration relative to the larger boat, with the smaller boat being supported in a second stowage position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 depicts a boat-lift system  20  constructed in accordance with, and embodying, the principles of the present invention. The boat-lift system  20  is used to stow a smaller boat  22  on a larger boat  24 . 
     FIG. 1 depicts the boat-lift system  20  mounted to a stern  30  of the larger boat  24 . More specifically, the larger boat  24  defines a transom  32  to which the boat-lift system  20  is attached. As is conventional, the larger boat  24  comprises a swim step  34  that is also mounted to the transom  32  and which extends rearwardly from the stern  30 . The swim step  34  defines a swim step surface  36  that is, under normal conditions, substantially parallel to the surface of the water. The swim step  34  further defines an aft edge  38  distal from the transom  32 . The swim step  34  is not required to implement the present invention and is described herein only to the extent necessary for a complete understanding thereof. 
     The smaller boat  22  is or may be conventional. The exemplary smaller boat  22  comprises a V-shaped hull  40  and port and starboard pontoons  42  and  44  and a keel  46 . The use of the exemplary smaller boat  22  is typical, but boats of roughly the same size and employing other construction techniques and hull shapes can also be accommodated by the boat-lift system  20 . 
     The boat lift system  20  comprises a structural support assembly  50 , a lift structure  52 , a pivot system  54 , and an actuator assembly  56 . The pivot system  54  pivotably mounts the lift structure  52  to the structural assembly  50 . The actuator assembly  56  is connected between a fixed location such as the structural support assembly  50  and the lift structure  52 . Operation of the actuator assembly  56  causes the lift structure  52  to rotate relative to the structural support assembly  50  between a first lift position (FIGS. 1,  2 ,  3 , and  6 ) and a second lift position (FIG.  4 ). FIG. 5 depicts the lift structure  52  in an intermediate position between the first and second lift positions. 
     To lift the smaller boat  22  out of the water, the lift structure  52  is first placed in the second lift position. The smaller boat  22  is then arranged in a docking position adjacent to the lift structure  52  as shown in FIG.  4 . The lift structure  52  is then moved into the first position, engaging the smaller boat  22  and lifting it out of the water as shown in FIG.  5  and into a first storage position as shown in FIG.  6 . The smaller boat  22  may then be pulled by hand into a second storage position as shown in FIGS. 1 and 2. The smaller boat will typically be secured with lines in the first and second storage positions. 
     To place the smaller boat  22  into the water, the lift structure  52  is moved from the first lift position into the second lift position. The smaller boat  22  will slide under control out of either of the first or second storage positions into the water; the smaller boat  22  will be in the docking position when it enters the water. 
     The details of construction and operation of the boat-lift system  20  will now be described in detail with reference to FIGS. 2 and 3. 
     The exemplary structural support assembly  50  comprises first and second support members  60  and  62 . The size, shape, and materials of the support members  60  and  62  are not critical to a particular implementation of the present invention. The support members  60  and  62  are capable of bearing the loads associated with the lift system  20  and the smaller boat  22 . In some configurations, the support members  60  and  62  may also be engineered to support the swim platform  34 ; in most configurations, the swim platform  34  will have its own support system separate from that of the boat-lift system  20 . 
     In the exemplary boat-lift system  20 , the support members  60  and  62  are preferably identical, but these members need not be identical. Only the port support member  60  will be described herein in detail, with the understanding that the following discussion also applies to the support member  62 . 
     The support members  60  and  62  are made of metal bent into the shape of an inverted “U” to define a first side wall  60   a , second side wall  60   b , and upper wall  60   c . A slot  62  is formed below the upper wall  60   c  and between the side walls  60   a  and  60   b . One end of the support members  60  is adapted to be bolted, adhered, and/or otherwise securely affixed to, the transom  32  of the larger boat  24 . The exact means for securing the support members  60  to the transom  32  are not important as long as the support members  60  are capable of bearing the loads of the boat-lift system  20  constructed in accordance with the principles of the present invention. 
     The exemplary lift structure  52  comprises two pivot members  70  and two lift members  72 . Each lift member  72  is detachably attached to one of the pivot members  70  by a lock pin  74 . 
     As seen in FIGS. 1,  2 , and  4 - 6 , The lift member  72  is the only portion of the boat-lift system  20  that is not under the swim step  34 . By removing the lock pin  74 , the lift member  72  can be detached from the pivot member  70  and stowed away. When the lift member  72  is stowed away, no portion of the boat-lift system  20  is visible during normal use of the larger boat  24 , and the larger boat  24  and swim step  34  may be used as if no boat-lift system  20  is installed thereon. 
     Although preferred, the use of a two-piece lift structure  52  is optional. The present invention may be implemented with a lift structure made of a unitary member or, alternatively, a lift structure of more than two pieces that can be broken down or disassembled for compact storage and shipping. The preferred two-piece lift structure  52  represents a good compromise of rigidity, simplicity, and ease of storage when not in use. 
     The two pivot members  70  are preferably the same as each other. The exemplary lift members  72  are also the same as each other. The pivot members  70  and lift members  72  can, however, be different in other embodiments of the present invention. 
     The exemplary pivot members  70  are generally L-shaped tubular metal members each defining a pivot portion  70   a , an actuator portion  70   b , and a socket portion  70   c . The pivot portion  70   a  is formed by the corner of the pivot member  70 . The actuator portion  70   b  is formed by one leg and the socket portion  70   c  is formed by the other leg of the member  70 . The pivot members  70  are sized and dimensioned to be received within the slot  63  defined by either of the support members  60  and  62 . 
     The lift members  72  are tubular metal members each defining a first to extension segment  72   a , a second extension segment  72   b , a first boat-engaging segment  72   c , a second boat-engaging segment  72   d , and a tip segment  72   e.    
     The first extension portion  72   a  is adapted to be received by the socket portion  70   c  of the pivot member  70  to prevent movement of the lift member  72  relative to the pivot member  70  except along a lock axis. The lock pin  74  extends through first and second socket openings  76  formed in opposite side walls of the socket portion  70   c  and first and second extension openings  78  formed in opposite side walls of the first extension portion  72   a  of the lift member  72 . 
     With the first extension portion  72   a  within the socket portion  70   b  and the holes  76  and  78  aligned, the lock pin  74  is inserted through the openings  76  and  78 . The lock pin  74  thus prevents relative movement of the lift member  72  along the lock axis relative to the pivot member  70 . However, removing the lock pin  74  from the openings  76  and  78  allows the first extension  72   a  to be removed from the socket portion  70   b  along the lock axis and thus allows the lift structure  52  to be disassembled as described above. 
     The pivot system  54  is formed by a pivot pin  80 , first and second support openings  82  formed in the support member  60 , and first and second lift openings  84  formed in the pivot portion  70   a  of the pivot member  70 . With the support openings  82  aligned with the lift openings  84 , the pivot pin  80  is inserted through these openings  82  and  84 . The pivot pin  80  defines a pivot axis A about which the pivot member  70  rotates relative to the support member  60 . 
     More specifically, with the pivot member  70  received within the slot  63  defined by the support member  60  and the pivot pin  80  inserted through the openings  82  and  84 , the pivot member  70  is allowed to rotate within a limited arc relative to the support member  60 . In the preferred embodiment, this limited arc is approximately  90  degrees. A first boundary of the arc corresponds to the first lift position and a second boundary corresponds to the second lift position. 
     The actuator assemblies  56  form a part of a hydraulic system  90 . Each actuator assembly  56  comprises a cylinder  92  and a rod  94 . The hydraulic system  90  is configured such that operation of a first button (not shown) causes the rods  94  to extend from the cylinders  92  and operation of a second button (not shown) causes the rods  94  to retract into the cylinders  92 . Such hydraulic systems and actuator assemblies are well-known in the art, and the actuator assemblies  56  and hydraulic system  90  will not be described herein in further detail. 
     The cylinder  92  is connected to the support member  60  by a cylinder pin  96 ; the pin  96  allows the cylinder  92  to rotate about a cylinder axis B relative to the support member  60 . Similarly, the rod  94  is connected to the actuator portion  70   b  of the pivot member  70  by a rod pin  98 . The rod pin  98  allows the rod  94  to rotate about a rod pin axis C relative to the pivot member  70 . The actuator assembly  56 , support member  60 , and actuator portion  70   b  thus generally define three sides of an actuator triangle, and extension and retraction of the rod  94  changes the interior angles of the actuator triangle. 
     The operation of the boat-lift system  20  might be better understood with reference to various axes defined by the components of this system  20 , in addition to the axes A, B, and C defined by the pivot pin  80 , cylinder pin  96 , and rod pin  98 , respectively. In particular, the first extension portion  72   a  defines a first extension axis D, and the second extension portion  72   b  defines a second extension axis E. The first boat engaging portion  72   c  defines a first boat extension axis F, while the second boat engaging portion  72   d  defines a second boat extension axis G. The lift member tip portion  72   e  defines a tip axis H. Finally, an actuator axis I is defined by the actuator assembly  56 , and a displacement axis J intersects the pivot axis A and the rod pin axis C. 
     The actuator triangle is more specifically defined by the first extension axis D, the actuator axis I, and the displacement axis J. Extension and retraction of the actuator assembly  56  causes a displacement angle α between the first extension axis D and the displacement axis J to change. In the preferred embodiment, this displacement angle α is approximately 110 degrees when the lift structure  52  is in the first lift position and approximately 20 degrees when the lift structure  52  is in the second lift position. 
     The displacement angle thus allows the pivot member  70  to rotate through an angle of approximately 90 degrees. The pivot member  70  can be made to rotate through an angle in a first preferred range of approximately 80 to 100 degrees and in any event should rotate through an angle in a second preferred range of approximately 60 to 180 degrees. 
     The first and second extension axes D and E, first and second boat-engaging axes F and G, and tip axis H are all fixed relative to each other. The following Table A sets forth the preferred approximate angular relationships between certain of these axes and first and second preferred approximate ranges of these angular relationships. All angles are in degrees. 
     
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
               
               
                   
                   
                 First 
                 Second 
               
               
                   
                 Preferred 
                 Preferred 
                 Preferred 
               
               
                 Definition of Angular Relationship 
                 Angle 
                 Range 
                 Range 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 between axes D and E 
                 90 
                 60-120 
                 40-140 
               
               
                 between axes E and F 
                 75 
                 70-80 
                 50-90 
               
               
                 between axes E and G 
                 75 
                 70-80 
                 50-90 
               
               
                 between axes G and H 
                 40 
                 30-50 
                  0-90 
               
               
                 between axis D and horizontal 
                 0 
                  0 ± 10 
                  0 ± 20 
               
               
                   
               
             
          
         
       
     
     The lift structure  52  is thus supported by the pivot system  54  from the structural support assembly  50  and rotated by the actuator assembly  56  to lift the smaller boat  22  out of the water  58  or to place the smaller boat  22  into the water  58 . When the lift structure  52  is in the first lift position, the shape of the lift structure  52  allows the smaller boat  22  to be stowed above the swim step  34  adjacent to the stern  30  of the larger boat  24 . But when the lift structure  52  is in the second lift position, the upper surface  36  of the swim step  34  is essentially unobstructed. In addition, in the second lift position, the lift members  72  are mostly underwater and do not form a substantial obstruction at the aft edge  38  of the swim step  38 . To the contrary, ladder rungs may be formed on the lift member  72  so that the lift member  72  can be used as a swim ladder for swimmers entering or exiting the water  58 . 
     It will be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not intended to be limited to the details given herein.