Abstract:
A floating low profile watercraft lifting apparatus comprises a buoyant support apparatus and a watercraft lift attached to the buoyant support apparatus. Depending from the apparatus are support posts terminating in support shoes. When immersed in a body of water of sufficient depth to provide buoyancy, the apparatus operationally floats upon the body of water. When the body of water is too shallow to provide buoyancy, the apparatus remains operational, suspended by the support posts on the support shoes resting on the floor of the body of water.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a divisional 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, now U.S. Pat. No. 6,318,929, 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. Technical Field  
         [0003]     The invention relates to lifting devices, and in particular to floating devices for lifting watercraft, for example, boats and sea planes.  
         [0004]     2. Description of the Related Art  
         [0005]     Known 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 comers 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 expansive energization of the double-acting hydraulic 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, expansive energization 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.  
         [0006]     Retractive energization of the double-acting hydraulic cylinder retracts the piston rod into the piston jacket of the double-acting hydraulic cylinder and reverses the motion of the pivoting booms. Thus, retractive energization 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&#39; 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.  
         [0007]     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.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     The present invention resolves limitations of the prior art by providing a floating low profile watercraft lifting apparatus. In one embodiment, a floating watercraft lifting apparatus is provided that includes a pair of floats, a support frame with support stands, and a lift having a generally rectangular base adapted to be submerged under water. The base is formed of two longitudinal beams joined by two transverse beams generally described as front and rear transverse beams. Pivoting booms connect each of the four comers of the rectangular base to swingable mounting arms positioned generally parallel with the longitudinal beams to form two pairs of pivoting booms, generally described as a front pair of pivoting booms and a rear pair of pivoting booms. The pivoting booms form with the mounting arms collapsing mock parallelograms on which watercraft supports hold the craft during lifting.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     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:  
         [0010]      FIG. 1  is an isometric view of the low profile watercraft lifting apparatus according to one embodiment of the present invention shown in an extended configuration;  
         [0011]      FIG. 2  is an isometric view of the low profile watercraft lifting apparatus of  FIG. 1  shown in a collapsed configuration;  
         [0012]      FIG. 3  is a detail view of the double-acting hydraulic cylinder pivotal connection to the rear pivoting booms of the embodiment shown in  FIG. 1 ;  
         [0013]      FIG. 4  is an operational side elevation view of the watercraft apparatus of  FIG. 1 ;  
         [0014]      FIG. 5  is an isometric projection of another embodiment of a low profile lift for watercraft in accordance with the invention;  
         [0015]      FIG. 6  is a side plan view of the lift of  FIG. 5  in an extended configuration;  
         [0016]      FIG. 7  is a side plan view of the lift of  FIG. 5  in a retracted configuration;  
         [0017]      FIG. 8  is an isometric projection of the lift of  FIG. 5  showing optional attachments;  
         [0018]      FIG. 9  is an isometric projection of a first attachment bracket in accordance with the invention;  
         [0019]      FIG. 10  is an isometric projection of a second attachment bracket in accordance with the invention;  
         [0020]      FIG. 11  is a partial top plan view of the accessories of  FIG. 8  mounted on the lift with the brackets of  FIGS. 9 and 10 ;  
         [0021]      FIG. 12  is a partial front plan view of the accessory mounting of  FIG. 11 ;  
         [0022]      FIG. 13  is an isometric projection of a floating lift formed in accordance with the present invention;  
         [0023]      FIG. 14  is a front elevation view of the floating lift of  FIG. 13 ;  
         [0024]      FIG. 15  is a side elevational view of the floating lift of  FIG. 13 ; and  
         [0025]      FIG. 16  is an enlarged isometric projection from a bottom view of the pontoon attached to the lift.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]      FIGS. 1 and 2  show isometric views of the low profile watercraft lifting apparatus according to one embodiment of the present invention in an upright or extended configuration and a collapsed attitude, respectively. In  FIGS. 1 and 2  the watercraft lifting apparatus  10  includes an essentially rectangular base  12  including a front transverse beam  14  and a rear transverse beam  16  connected to opposite ends of spaced-apart longitudinal beams  18   a ,  18   b . In one embodiment, longitudinal beams  18   a ,  18   b  are essentially equal in length and parallel with one another and transverse beams  114 ,  116  extend beyond the connection points with longitudinal beams  18   a ,  18   b  to form “I”-shaped base  12 . In a preferred embodiment, base  12  further includes four sleeves  20 . One sleeve  20  is connected to each end of transverse beams  14 ,  16 . Each sleeve  20  receives a support post  22  which is independently adjustable for positioning and leveling base  12  at a desired depth submerged under water. Support posts  22  include shoes  24  which rest on the river or lake bed.  
         [0027]     Four pivoting booms  26   a ,  26   b ,  26   c ,  26   d  are attached to rectangular base  12 , one pivoting boom  26  adjacent each of the four comers of rectangular base  12 , with the lower ends of each front boom  26   a ,  26   b  pivotally joined to base  12  adjacent front ends of each longitudinal beam  18   a ,  18   b  and the lower ends of each rear boom  26   c ,  26   d  pivotally joined to base  12  adjacent rear ends of each longitudinal beam  18   a ,  18   b . In a preferred embodiment, longitudinal beams  18   a ,  18   b  are fitted with brackets  28  which include a pivot point  30  extended an off-set distance  32  above the centerline  34  of longitudinal beams  18   a ,  18   b . Brackets  28  pivotally join rear booms  26   c ,  26   d  to longitudinal beams  18   a ,  18   b  such that rear booms  26   c ,  26   d  pivot about pivot point  30  relative to longitudinal beams  18   a ,  18   b . In one preferred embodiment, pivot point  30  is several inches. above centerline  34 . Brackets  28  position rear booms  26   c ,  26   d  either between longitudinal beams  18   a , I 8   b  (shown) or astride longitudinal beams  18   a ,  18   b  (not shown) such that in a fully collapsed attitude, rear pivoting booms  26   c ,  26   d  are positioned in a side-by-side orientation with longitudinal beams  18   a ,  18   b.    
         [0028]     One or more cross supports or cross braces  36  provide structural integrity to front pair of pivoting booms  26   a ,  26   b . Those of skill in the art will recognize that alternative cross support configurations may provide structural integrity to front pair of pivoting booms  26   a ,  26   b . The cross supports or cross braces  38   a ,  38   b ,  38   c ,  38   d  provide structural integrity to rear pivoting booms  26   c ,  26   d . The cross braces  38  may be formed in a hull-clearing convex or channel shape. In one preferred embodiment, the cross support  38   a  is a “V”-shaped member extending between rear pivoting booms  26   c ,  26   d  which points generally rearward when watercraft lifting apparatus  10  is in an extended configuration as shown in Figure I and point generally downward when watercraft lifting apparatus  10  is in a collapsed configuration as shown in  FIG. 2 . The hull-clearing “V” shape of cross support  38   a  provides increased clearance for watercraft having generally “V”-shaped hulls as compared with the lifting apparatus of the prior art. Lower cross support  38   b  is a “V”-shaped member which extends between rear pivoting booms  26   c ,  26   d  adjacent pivot point. In one embodiment, cross supports  38   c ,  38   d  extend between the outer ends of intermediate cross support  38   a  and the approximate center of lower cross support  38   b . Those of skill in the art will recognize that other configurations of cross supports may be employed, for example, intermediate and lower cross supports  38   a ,  38   b  may be formed as a straight beam or in a “U” shape or a “C” shape, and the cross supports  38   c ,  38   d  extending between cross supports  38   a ,  38   b  may be positioned parallel with the rear booms  26   c ,  26   d  or at any other suitable orientation whereby the cross supports  38   a ,  38   b  provide a shape suitable for clearing the bottoms of boats having shaped hulls.  
         [0029]     Two mounting arms  40   a ,  40   b  are pivotally mounted adjacent the upper ends of pivoting booms  26  to rotate about pivot points  42   a ,  42   b  and swing with pivoting booms  26  as a mock parallelogram. The invention provides an essentially parallel relationship between mounting arms  40  and longitudinal beams]  8  when lifting apparatus  10  is in a fully extended or upright orientation. The essentially parallel relationships between mounting arms  40   a ,  40   b  and longitudinal beams]  8   a , ]  8   b , respectively, are provided by varying the lengths of front pair of pivoting booms  26   a ,  26   b  relative to the lengths of rear pair of pivoting booms  26   c ,  26   d . When front pivoting booms  26   a ,  26   b  are adapted to pivot about a pivot axis passing through centerlines  34  of both longitudinal beams  18   a ,  18   b , the lengths “A” of front pivoting booms  26   a ,  26   b  are essentially equal to the lengths “B” of rear pivoting booms  26   c ,  26   d  plus dimension “C” defined as an off-set distance  32  between rear boom pivot point  30  and centerline  34  of longitudinal beams  18   a ,  18   b . Thus, the relationship between the lengths of front pivoting booms  26   a ,  26   b  and rear pivoting booms  26   c ,  26   d  is given by: 
 
 A=B+C    (Eq. 1) 
 
 where: 
    A=lengths of rear pivoting booms  26   a ,  26   b  defined as the distance between pivot point  42   a  and a pivot axis passing through centerlines  34  of both longitudinal beams  18   a ,  18   b,       B=lengths of rear pivoting booms  26   c ,  26   d  defined as the distance between pivot point  42   b  and pivot point  30 , and     C=off-set distance  32  as defined by the vertical distance between rear pivot point  30  and centerline  34 .    
 
         [0033]     When lifting apparatus  10  is retracted to a collapsed orientation as shown in  FIG. 2 , mounting arms  40   a ,  40   b  are oriented at an angle relative to longitudinal beams  18   a ,  18   b . Mounting arms  40   a ,  40   b  angle downward toward the rear portion of lifting apparatus  10  to provide a self-guiding aspect whereby the bow of a boat is guided into the center of lift apparatus  10  midway between mounting arms  40  by the rising angle of mounting arms  40  leading toward FRONT of lifting apparatus  10 . The downward and backward sloping angle of mounting arms  40  is provided in part by the position of pivot point  30  relative to the pivot points of front booms  26   a ,  26   b  about an axis passing through centerline  34  and in part by the shorter lengths of rear pivoting booms  26   c ,  26   d  relative to the lengths of front pivoting booms  26   a ,  26   b . In one preferred embodiment, watercraft supports (not shown) attached to mounting arms  40  brace the watercraft during lifting.  
         [0034]     In one embodiment of the present invention, a suitable actuator, for example a double-acting hydraulic cylinder  44 , extends diagonally across the mock parallelogram. Double-acting hydraulic cylinder  44  comprises a piston rod  46  extending from and retracting into a piston jacket  48 . In a preferred embodiment, upper end  50  of piston rod  46  is connected to cross rod  52  and cross rod  52  is rotatably fitted in flanges  54  which are attached to front pivoting booms  26   a ,  26   b  adjacent the upper ends of booms  26   a ,  26   b . Alternatively, upper end  50  of piston rod  46  is connected to a collar (not shown) rotatable on cross rod  52  as disclosed in prior U.S. Pat. No. 5,184,914. Lowering and raising of mounting arms  40  and watercraft supports (not shown) is achieved by extension and retraction of piston rod  46  of double-acting hydraulic cylinder  44 . Those of skill in the art will recognize that the present invention may be practiced using alternative raising and lowering means or actuator, for example, pneumatic cylinders, opposing single-acting hydraulic cylinders, electrically driven push/pull rods, or other suitable actuator including chain, cable, or rope pulley drives.  
         [0035]      FIG. 3  shows a detail view of the pivotal connection between double-acting hydraulic cylinder  44  and rear pivoting booms  26   c ,  26   d  according to one embodiment of the present invention. A boom extension  56  projects from rear pivoting booms  26   c ,  26   d  opposite pivot point  30  whereby a lever is formed. The lever includes a first lever arm defined by rear pivoting booms  26   c ,  26   d ; a second lever arm defined by boom extension  56 ; and a fulcrum defined by pivot point  30  positioned between the first and second lever arms. In one preferred embodiment, boom extension  56  projects downward from the approximate center of lower cross support  38   b  and provides a pivot point  58 . The lower end  60  of hydraulic cylinder piston jacket  48  is adapted to pivotally connect to boom extension  56  at pivot point  58 . According to one preferred embodiment, pivot point  58  is located at a distance  62  from rear boom pivot point  30 . Distance  62  provides the lever arm over which the force exerted by hydraulic cylinder  44  acts to rotate rear pair of pivoting booms  26   c ,  26   d  about pivot point  30 . In one preferred embodiment of the present invention, pivot point  58  is located at a distance  62  from rear boom pivot point  30  selected to provide an adequate force movement.  
         [0036]      FIG. 4  shows an operational side elevation view of the watercraft apparatus according to one embodiment of the present invention. To lift a watercraft from the water, watercraft lifting apparatus  10  is positioned in a first retracted or collapsed configuration (shown in solid) with the craft to be lifted (not shown) floating above mounting arms  40  and watercraft supports, if so equipped. Piston rod  46  of double-acting hydraulic cylinder  44  is extended by introduction of water under pressure into the lower end  60  of piston jacket  48  as disclosed in prior U.S. Pat. No. 5,184,914. A piston (not shown) inside piston jacket  48  extends piston rod  46 , forcing cross rod  52  and hence front pivoting booms  26   a ,  26   b  to swing upwardly and forwardly from their collapsed configurations to their raised configuration (shown in phantom). Simultaneously, lower end  60  of piston jacket  48  exerts an equal and opposite force on pivot point  58  of boom extension  56  acting over lever arm distance  62  forcing cross supports  38  and hence rear pivoting booms  26   c ,  26   d  to swing upwardly and forwardly about pivot point  30  from their collapsed configuration to their raised configuration above the water surface (shown in phantom). Pivotally attached mounting arms  40  follow as the mock parallelogram is deployed. Thus, a craft is lifted out of the water on mounting arms  40  or watercraft supports, if so equipped. In a preferred embodiment of the present invention, full extension of watercraft lifting apparatus  10  is achieved when the piston (not shown) inside piston jacket  48  extends piston rod  46  to its fully extended configuration.  
         [0037]     Prior U.S. Pat. No. 5,184,914 discloses various alternative means of defining full extension of watercraft lifting apparatus  10  which are fully applicable to the present invention. For example, each longitudinal beam  18   a ,  18   b  may be equipped with boom stops (not shown) located adjacent rear transverse beam  16  and/or adjacent front transverse beam  14  engaging sides of pivoting booms  26  adjacent their lower pivoting ends to brace pivoting booms  26  and mounting arms  40  in their fully extended configuration. Alternatively, full extension of hydraulic cylinder  44  may swing booms  26  from a collapsed or retracted attitude through a vertical attitude into an over-center position. When the hydraulic cylinder reaches its full extension, it prevents further travel of the booms and holds the watercraft lifting apparatus  10  in a fully extended configuration. Another alternative combines both boom stops and an over-center locking position.  
         [0038]     According to one embodiment, the present invention provides an over-center locking position including booms stops. The present invention provides brackets  66  connected between the ends of each pivoting boom  26  and the ends of each mounting arm  40 . Each bracket  66  provides pivot point  42  such that one mounting arm  40   a  is oriented in a plane defined by front pivoting boom  26   a  and rear pivoting boom  26   c  and the other mounting arm  40   b  is oriented in a plane defined by front pivoting boom  26   b  and rear pivoting boom  26   d . Brackets  66  are configured to position pivot points  42  such that a portion of mounting arm  40  contacts the end of each pivoting boom  26  when lifting apparatus  10  is in a fully extended upright and over-center configuration. Brackets  66  are further configured such that, when lifting apparatus  10  is oriented in any configuration other than a fully extended upright and over-center configuration, clearance is provided between the ends of each pivoting boom  26  and each mounting arm  40 .  
         [0039]     Retraction of watercraft lifting apparatus  10  is accomplished by positive retractive energization of double-acting hydraulic cylinder  44  which retracts piston rod  46  into piston jacket  48 . Retraction of piston rod  46  causes upper piston rod end  50  to pull front pivoting booms  26   a ,  26   b  from their raised configuration back over-center if an over-center lock is used. Simultaneously, the force exerted by retraction of piston rod  46  acts over lever arm  62  causes lower piston jacket end  60  to pull boom extension  56  upwardly which rotates pivoting booms  26   c ,  26   d  about pivot points  30  from their raised configuration back over-center. After booms  26  pass through their vertical over-center configuration, the weight of booms  26 , mounting arms  40  and the supported craft lower watercraft lifting apparatus  10  into its collapsed or retracted configuration.  
         [0040]     According to one embodiment of the present invention, longitudinal beams  18   a ,  18   b  are fitted with brackets  70  which include a pivot point  72  extended a distance “0” defined as off-set distance  74  below centerline  34  of longitudinal beams  18   a ,  18   b . Brackets  70  pivotally join front booms  26   a ,  26   b  to longitudinal beams  18   a ,  18   b  such that front booms  26   a ,  26   b  pivot relative to longitudinal beams  18   a ,  18   b  at pivot point  72 . Brackets  70  position front booms  26   a ,  26   b  either between longitudinal beams  18   a ,  18   b  (shown) or astride longitudinal beams  18   a ,  18   b  (not shown) such that in a fully collapsed configuration, front pivoting booms  26   a ,  26   b  are positioned in a side-by-side orientation with longitudinal beams  18   a ,  18   b . Positioning of pivot points  72  at offset distance  74  below centerline  34  of longitudinal beams  18   a ,  18   b  accentuates the self-guiding watercraft entry configuration of the invention by accentuating the downwardly and rearwardly sloping angle of mounting arms  40  when lifting apparatus  10  is collapsed. Thus, front boom pivot points  72  are off-set a total vertical off-set distance “E” defined as vertical off-set distance  76  from rear boom pivot points  30  which accentuates the downwardly and rearwardly sloping angle of mounting arms  40  when lifting apparatus  10  is in a collapsed configuration. Off-set distances  32 ,  74  in combination with the differing lengths of front pivoting booms  26   a ,  26   b  relative to the lengths of rear pivoting booms  26   c ,  26   d  reduces the downwardly sloping angle of mounting arms  40  when booms  26  are fully extended such that mounting arms  40   a ,  40   b  are essentially parallel with longitudinal beams  18   a ,  18   b  when lifting apparatus  10  is in an upright or extended configuration.  
         [0041]     According to this embodiment, the essentially parallel relationship between mounting arms  40   a ,  40   b  and longitudinal beams  18   a ,  18   b  when lifting apparatus  10  is in an upright or extended configuration is provided by varying the lengths “A” of front pair of pivoting booms  26   a ,  26   b  relative to the lengths “B” of rear pair of pivoting booms  26   c ,  26   d . The lengths “A” of front pivoting booms  26   a ,  26   b  minus off-set distance  74  are essentially equal to the lengths “B” of rear pivoting booms  26   c ,  26   d  plus off-set distance  32 . Thus, the relationship between the lengths of front pivoting booms  26   a ,  26   b  and rear pivoting booms  26   c ,  26   d  is given by: 
 
 A′−D≈B+C    (Eq. 2) 
 
 where: 
    A′=lengths of rear pivoting booms  26   a ,  26   b  defined as the distance between pivot point  42   a  and pivot point  72 ,     B=lengths of rear pivoting booms  26   c ,  26   d  defined as the distance between pivot point  42   b  and pivot point  30 ,     C=off-set distance  32  as defined by the distance between pivot point  30  and centerline  34 , and     D=off-set distance  74  as defined by the distance between centerline  34  and pivot point  72 . 
 
 In one preferred embodiment, pivot point  72  is several inches below centerline  34 . 
   
 
         [0046]     Stated differently, the lengths “B” of rear pivoting booms  26   c ,  26   d  plus vertical off-set distance  76  between rear boom pivot points  30  and front boom pivot points  72  are essentially equal to the lengths “A” of front pivoting booms  26   a ,  26   b . Thus, the relationship between the lengths of front pivoting booms  26   a ,  26   b  and rear pivoting booms  26   c ,  26   d  is alternatively given by: 
 
 A′≈B+E    (Eq. 3) 
 
 where: 
    A′=lengths of rear pivoting booms  26   a ,  26   b  defined as the distance between pivot point  42   a  and pivot point  72 ,     B=lengths of rear pivoting booms  26   c ,  26   d  defined as the distance between pivot point  42   b  and pivot point  30 , and     E=off-set distance  76  as defined by the vertical distance between rear pivot point  30  and front pivot point  72 .    
 
         [0050]     Referring next to  FIGS. 5-7 , another embodiment of a lift  100  formed in accordance with the invention is shown. The lift  100  includes a rectangular base  112  formed from front and rear transverse beams  114 ,  116 , respectively, that are each connected to parallel longitudinal beams  118   a ,  118   b . A sleeve  120  is connected to each of the transverse beams  114 ,  116 . Each sleeve  120  is sized and shaped to receive a support post  122 . A plurality of openings  123  in each sleeve  120  and each support post  122  enables independent adjustment of the base  12  relative to support shoes  124 , which can rest on a river bed or lake bed.  
         [0051]     Four pivoting booms  126   a ,  126   b ,  126   c ,  126   d , are pivotally attached to the rectangular base  112  at each of the four corners  127 . Ideally, brackets  128  are connected to the rear booms  126   c ,  126   d  and the longitudinal beams  118   a - b  such that the rear booms  126   c ,  126   d  pivot about a pivot point  130 . The pivot point  130  is a distance  132  that is several inches above a longitudinal axis  134  of the longitudinal beams  118   a ,  118   b . In one embodiment the pivot point is in the range of five (5) to twelve (12) inches above the axis  134 . In the embodiment shown, the brackets  128  position the rear booms  126   c ,  126   d  inside the longitudinal beams  118   a - b , although the brackets  128  can be mounted astride the longitudinal beams  118   a - b  such that when in a fully collapsed configuration, the rear pivoting booms  126   c ,  126   d  are positioned in a side-by-side orientation with the longitudinal beams  118   a - b . A first pair of cross braces  136  provides structural integrity to the front pair of pivoting booms  126   a ,  126   b . A second pair of cross braces  138  provides structural integrity to the rear pivoting booms  126   c ,  126   d . In the depicted embodiment, the cross braces  138  are formed to have a v-shape, with the vertex  139  pointing downward when the lift  100  is in a collapsed configuration, as shown in  FIG. 7 . This v-shape of the cross support  138  provides increased clearance for a watercraft having generally v-shaped hulls. Other configurations of the cross brace  138  may also be used as desired.  
         [0052]     Mounted to the top of pivoting booms  126   a  and  126   c  is a support rail  140   a ; and similarly mounted to pivoting booms  126   b ,  126   d  is a support rail. Mounting brackets  142  are fixedly attached to pivoting booms  126   a - d  and provide a pivot attachment point  143  for attachment of the support rails  140   a - b.    
         [0053]     The length and function of the pivoting booms  126   a - d  is the same as described above with respect to the pivoting booms  26   a - d  in  FIG. 1 , and will not be described in detail herein. As shown in  FIG. 6 , the support rails  140   a - b  are essentially parallel to the longitudinal beams  118   a - b  when the lift  100  is in the extended configuration.  
         [0054]     An actuator  144 , similar to the double-acting hydraulic cylinder  44  described above with respect to Figure I, is connected to the pivoting booms  126   a - d  by means of a front T-bar  152  connected to forward pivoting booms  126   a ,  126   b  and a rear T-bar  154  connected to rear pivoting booms  126   c ,  126   d . The front T-bar  152  is rotatably mounted to support brackets  156 , each attached to a respective pivoting boom  126   a ,  126   b . The rear T-bar  154  is similarly pivotally attached to support brackets  158  that are each attached to pivoting booms  126 ,  126   d . The actuator  144  is attached to the rear T-bar  154  with a sleeve  160  and to the front T-bar  152  by a yolk  162 . Ideally, the T-bars  152 ,  154  can be easily replaced to facilitate interchangeability of high-pressure and low-pressure activators.  
         [0055]     In a preferred embodiment, a bunk  164   a,b  is pivotally mounted to each support rail  166   a,b . The bunks  164   a,b  can pivot about a longitudinal axis that is parallel to the axis  134  of the longitudinal beams  1 I 8   a - b . The bunks I  64   a,b  can either freely pivot or be attached to a fixed orientation, thus accommodating hulls of a particular configuration.  
         [0056]     Referring again to  FIGS. 6 and 7 , the relationship between the actuator  144  and the pivoting booms  126   a - d  is illustrated. In  FIG. 6 , the lift  100 , working in a cantelever arm arrangement, is in an extended configuration wherein the actuator  144  is fully extended. In  FIG. 7 , the lift  100  is in a collapsed configuration wherein the actuator  144  is retracted.  
         [0057]     In a preferred embodiment, the front pivoting booms  126   a,b  have a pivot point  129  that is lower than the pivot point  130  of the rear pivoting booms  126   c,d . The relative distance between the pivot points  129 ,  130  ranges from four inches to ten inches, and in the configuration shown in  FIG. 6 , is eight inches. In other words, the rear pivot point  130  is approximately 8 inches higher than the front pivot point  129 . It is to be understood that these distances can vary according to the size of the lift  100 .  
         [0058]     The actuator  144  provides a linkage through the front and rear T-bars  152 ,  154  with the pivoting booms  126   a - d . When mounted as shown, the actuator  144  provides a pushing force on the forward and rear booms  126   a - d . The pushing action of the actuator  144 , in combination with the moving mounting points of the actuator  144  on the pivoting booms  126   a - d , enables lifting of loads with nearly uniform force throughout the travel of the pivoting booms  126   a - d.    
         [0059]     In addition, as shown in  FIG. 7 , when the lift  100  is in a retracted or collapsed configuration, the bunks  164   a,b  are angled downward towards the rear of the lift  100 . This facilitates in loading of watercraft, especially in very shallow water.  
         [0060]     Referring next to  FIGS. 8-12 , shown therein is the lift  100  of  FIG. 5  having optional accessories attached thereto. More particularly, four guide-ons  802  are attached near the free ends of the pivoting booms  126   a - d . In addition, a stern stop  804  is connected to the upper ends of the pivoting booms  126   c,d.    
         [0061]     Each of the guide-ons  802  are formed from tubular members  806  having a 90° bend to create first and second legs  808 ,  810 , respectively. The first leg  808  is attached to the lift  100  by an attachment bracket  812 , which is shown more clearly in  FIG. 10 .  
         [0062]     Referring to  FIG. 10 , the attachment bracket  812  comprises a mounting plate  814  having a pair of mounting holes  816  formed therein. Attached to the plate  814  adjacent the holes  816  is a sleeve  818  sized and shaped to slidably receive the first leg  808  of the guide-on  802 . A pair of set screws  820  are threadably engaged with the sleeve  818  such that as the screws  820  are threaded into the sleeve  818 , they project into the internal bore  822  of the sleeve  818  and will bear against the guide-on  802 . Alternatively, holes may be formed in the guide-on  802  to accept the screws  820 .  
         [0063]     The stem stop  804  is of tubular construction having a U-shaped configuration with two legs  824  joined at a 90° bend by a cross member  826 . The stern stop  804  is attached to the bunk support rails  166   a,b  with attachment brackets  828 , shown in greater detail in  FIG. 9 . As shown therein, each attachment bracket  828  includes a mounting plate  830  with openings  832  formed therein, that is attached to or integrally formed with a sleeve  834 . The sleeve  834  has a longitudinal axial bore  836  with a circular cross-sectional configuration. The mounting plate  830  is attached at a right angle to the sleeve  834  and reinforced with a gusset  838 . A pair of set screws  840  (only one shown in  5   FIG. 9 ) are threadably received in the sleeve  834  such that when tightened, they project into the axial bore  836  and will bear against the stem stop  804  or be received in preformed holes in the stem stop  804 , as shown in  FIG. 11 .  
         [0064]      FIGS. 11 and 12  show the attachment of the guide-on  802  and stem stop  804  to the bunk support rail  166   b  on the pivoting boom  126   d . To facilitate mounting of the brackets  812 ,  828  and the bunk  166   b  to the support rail  164   b , a universal plate  842  is provided. As shown more clearly in  FIG. 12 , the universal plate  842  has a substantially rectangular configuration with one of its planar sides attached to the support rail  166   b ˜preferably by welding, although other attachment means known in the art may be used. Mounting holes  844  centrally located on the universal plate  842  are used for attachment of the brackets  812 ,  828 . Additional holes  846  are provided near the top of the universal plate  842  for attachment of the bunk  164   b . As shown here, a bunk attachment plate  848  connects the bunk  164   b  to the universal plate  842 .  
         [0065]     As shown in  FIG. 12 , the bunk attachment plate  848  is connected to the universal plate  842  through one opening  846  (on the right side) to permit rotation of the bunk  164   b  about an axis that is parallel with the axis  134  of the longitudinal beam  118   b . This permits orienting the bunk  164   b  to accommodate different hull shapes. The bunk  164   b  can be attached to the bunk support rail  166   b  in a fixed orientation, or it can be freely rotatable, as desired.  
         [0066]     To enable the bunk  164   b  to rotate without interference from the universal plate  842 , the top comers  850  of the plate  842  are angled downward as shown. However, the top edge  852  between the comers  850  remains straight to provide a bearing surface for the bottom surface  854  of the bunk bracket  848 . This prevents the bunk  164   b  from inadvertently rotating counterclockwise (from the orientation shown in  FIG. 12 ) and causing damage to a boat hull.  
         [0067]     As shown more clearly in  FIG. 11 , the guide-on  802  mounting bracket  812  is first attached to the universal plate  842  followed by the stem stop bracket  828  through the openings  844  with suitable fasteners (not shown). The guide-ons  802  and stem stop  804  are inserted into their respected sleeves  818 ,  834  where they are slidably received for adjustable positioning to accommodate the watercraft. The guide-ons  802  aid in centering the watercraft on the lift  100 , while the stem stop  804  is contacted by the stem drive or outboard drive to position the boat longitudinally on the lift  100 .  
         [0068]     Suitable materials for use in a marine environments, as known to those skilled in the art, can be used to construct the components of the lift  100 , including the accessories described above, i.e., the guide-ons  802 , stem stop  804 , and associated brackets  812 ,  828 , and universal plate  842 , and fasteners. The guide-ons  802 , as well as the stem stop  804 , can be formed from sturdy plastic that will help prevent damage to the exterior of the boat hull and the stern drive or outboard drive components  
         [0069]     Another embodiment of the invention is shown in  FIGS. 13-16 . A floating lift  200  is provided that includes a watercraft lift  202  attached to a support frame  204  having first and second pontoons  206 ,  208  attached thereto. The lift  202  is adapted from the design of the lift  100  described above. It is to be understood, however, that this embodiment of the invention can be used with other lifts as well as those described herein.  
         [0070]     The support frame  204  includes two adjustable transverse beams  210 ,  212  that are attached to the lift  202  by connectors  214  located on each end  216  of the parallel longitudinal beams  218   a ,  218   b  on the lift  202 . Attachment to the connectors  214  may be accomplished by welding, fasteners, or other known methods. The transverse beams  210 ,  212  is formed of tubular metal having a substantially square cross-sectional shape that defines a hollow longitudinal interior  220  that opens at each end  222 . The lift  202  holds the transverse beams  210 ,  212  in spaced parallel relationship.  
         [0071]     The support frame  204  further includes four support stands  224  located at each end  222  of the transverse beams  210 ,  212 . In the illustrated embodiment, each support stand  224  includes a base plate  226  having an upright support member  228  slidably mounted to an attachment post  242  of the base plate  226  attached to a top surface  230  to project at substantially a right angle from the base plate  226 . Extending laterally from the upright support member  228  is a lateral beam  232  sized and shaped to be slidably received within the transverse beams  210 ,  212 . Fasteners  234  at each end  216  of the transverse beams  210 ,  212  secure the lateral beams  232  to the transverse beams  210 ,  212 , and permit telescopic adjustment in the position thereof. The lateral beam  232  is fixedly attached to the upright support  228 .  
         [0072]     A base support  236  is attached to the base plate  226  and the attachment post  242  is sized and shaped to be slidably received within the base support  236  and held in place by a fastener  240 . Thus, as shown in  FIG. 13 , the position of the upright support member  228  can be adjusted by sliding the upright support  238  along the attachment post  242 . In the embodiment shown in  FIG. 13 , the upright support member  228  at the end  216  of the first transverse beam  210  slides upward on the adjustment post projecting from the base support  236  to accommodate the pontoons moving up and down with changing water levels.  
         [0073]     Each pontoon  206 ,  208  is supported on the four support stands  224  by an attachment bracket  244  and adjustment strap  246 . The attachment bracket  244 , as shown more clearly in  FIG. 16 , is comprised of a first arcuate bracket member  247  and a second accurate bracket member  248  extending from a channel bracket  250  attached to the upright support  238 . At one end of the first bracket member  247  is a yolk  252  comprising a pair of ears  254  projecting in parallel at approximately a 90° angle from the central member  248 . Openings  256  in each ear  254  are provided for attaching the adjustment strap  246 . An angle bracket  258  is attached to the second bracket member  248  and includes two openings  260  in a leg  262  of the bracket  258  for attachment to another end of the adjustment strap  246 . The attachment straps  246  in one embodiment comprise a nylon strap that over the angle iron and the deck piece  276 , and has a loop in each end. A bolt passes through the loop in one end to attach to the two ears  254 , and a V-bolt is used with the other end to attach to the angle bracket  258  via the openings  260 .  
         [0074]     Each pontoon  206 ,  208  is comprised of a center section  264  attached between a first end section  266  and a second end section  268 . A first end cap  270  is attached to the exposed end of the first end section  266  and a second end cap  272  is attached to the exposed end of the second end section  268  on each of the pontoons  206 ,  208 . Each of the sections  264 ,  266 ,  268  comprises an airtight flotation chamber having a hollow interior formed in a conventional manner known to those skilled in the art and, hence, will not be described in detail herein. Further, each of the sections  264 ,  266 ,  268  are slidably attached in a conventional manner that will not be described in detail. Each pontoon  206 ,  208  is held together by angle irons  274  that extend across the central section  264  and substantially across both the first and second end sections  266 ,  268 . A deck piece  276  is formed on each of the pontoon sections  264 ,  266 ,  268  to form a longitudinal deck surface  278  that is substantially flat along the entire length of each pontoon  206 ,  208  with the exception of the first and second end caps  270 ,  272 . The angle irons  274  are attached along the two exposed comers  280  of the deck pieces  276  with suitable fasteners (not shown). Preferably, the angle irons  274  are bolted to the pontoons  206 ,  208  with bolts that thread into holes having brass or stainless steel inserts molded into the deck pieces  276 .  
         [0075]     In one embodiment, the deck pieces  276  are molded, such as roto molding or blow molding, during the formation of the center and end section tanks  264 ,  266 ,  268 . Each tank has one end that is convex and another end that is concave to facilitate interlocking with other tanks to form the pontoons  206 ,  208 . The end sections  266 ,  268  were integrally formed therewith.  
         [0076]     On an opposing side of each pontoon  206 ,  208  from the deck piece  276  is formed a raised longitudinal rail  282 . In one embodiment, the rail is integrally formed with each of the pontoon sections  264 ,  266 ,  268 . The channel bracket  250  at the top of each support stand  224  is sized and shaped to receive the rail  282  therein. In other words, the channel bracket  250  has a substantially V-shaped cross-sectional configuration to from a channel  284  that receives the rail  282  having a similar cross-sectional configuration. The attachment bracket  244  is integrally formed with the channel bracket  250  so that the adjustment strap  246  holds the pontoons  206 ,  208  to the support stand  224 .  
         [0077]     In use, the floating lift  200  is positioned in a body of water with the support frame  204  attached to the floor of the body of water. Each base plate  226  is suitably secured in a conventional manner that will not be described in detail herein. The support stands  224  are laterally positioned by sliding the lateral beams  232  with respect to the front and rear transverse beams  210 ,  212  and affixing them with suitable fasteners. Once the support stands  224  are anchored, the pontoons  206 ,  208  are permitted to move vertically along the adjustment post  242 , thus keeping the lift  202  at the right height with respect to the surface of the water. The size and shape of the fenders  206 ,  208  is such that they will resist pitching under the dock and getting stuck.  
         [0078]     Ideally, each pontoon section  264 ,  266 ,  268  is constructed of a pliable material, such as fendering material, so that the pontoons  206 ,  208  act as fenders. As such, they can bump off an adjacent dock, and they provide centering for a boat with respect to the bunks  286  on the lift  202 . The deck pieces  276  provide a deck upon which users can walk. The angle brackets  258  also provide attachment points in the openings  260  for cleats and other accessories.  
         [0079]     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.  
         [0080]     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.