Abstract:
The pontoon boat lift system comprises a plurality of lifts mounted to an underside of a deck of the pontoon boat. Each lift comprises a leg that pivotally mounted to the underside of the deck and is moveable between a raised position and a lowered position. A free end of each leg includes its own support pad that contacts, for example, a lake bottom when the legs are in the lowered position. The operation of the lifts is coordinated to raise the pontoon boat above the surface of the water at desired shoreline locations.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This is a continuation of application Ser. No. 11/216,691, filed Aug. 31, 2005, now U.S. Pat. No. 7,051,665 which is a continuation of application Ser. No. 11/130,458, filed May 16, 2005, now U.S. Pat. No. 6,983,707, which is a divisional of application Ser. No. 10/792,942, filed Mar. 4, 2004, now U.S. Pat. No. 6,907,835. 

   BACKGROUND OF THE INVENTION 
   The present invention generally relates to a lift system for watercraft. In particular, the present invention relates to a portable lift system for a pontoon boat that is carried beneath a deck of the pontoon boat. 
   It is desirable to lift pontoon boats out of the water when not in use so that the pontoons are not continually exposed to the water and to avoid disruption to the boat or its occupants as a result of waves or wakes from other passing watercraft. Conventional pontoon boat lifts are well known, but are stationary, i.e. typically adjacent to a dock, and include a platform which is submersible under the water below the pontoon boat. With the pontoon boat positioned above the platform, the platform is raised to elevate the pontoon boat above the water. To avoid damage during sub-freezing weather, docks and conventional lifts must be removed from the water before it freezes, usually well before the end of a normal boating season. Also, the effectiveness of conventional lifts can be impacted by fluctuations in the water level of a lake. 
   Thus, there is a need in the art for a portable lift system for pontoon boats that allows a pontoon boat to be lifted and securely held out of the water at any desired location. 
   BRIEF SUMMARY OF THE INVENTION 
   A pontoon lift system for a pontoon boat having a deck comprises a plurality of independently movable legs. A first leg of the system is pivotally mounted to an underside of the deck and has a first support pad on a free end thereof. A second leg of the system is spaced from the first leg and is pivotally mounted to the underside of the deck. The second leg has a second pad, separate from the first pad, on a free end thereof. A third leg of the system is spaced from the first and second legs and is pivotally mounted to the underside of the deck. The third leg has a third pad, separate from the first and second pads, on a free end thereof. A fourth leg of the system is spaced from the first, second and third legs and is pivotally mounted to the underside of the deck. The fourth leg has a fourth pad, separate from the first, second and third pads, on a free end thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a pontoon boat in phantom showing the lift system of the present invention. 
       FIG. 2  is an enlarged perspective view of a lift of the present invention. 
       FIG. 3  is an enlarged cross-sectional view of the lift of  FIG. 2  taken along line  3 — 3 . 
       FIG. 4  is an exploded perspective view of a threaded follower of the lift of the present invention. 
       FIG. 5  is an exploded side view of a thrust bearing and housing for a screw of the lift of the present invention. 
       FIG. 6  is a perspective view of an electric motor mounting plate of the lift of the present invention. 
       FIG. 7  is an exploded perspective view of one embodiment of the electric motor mounting plate of the lift of the present invention. 
       FIG. 8  is a side partially sectioned view of a screw/keyed motor shaft connection for the lift of the present invention. 
       FIG. 8A  is an enlarged perspective view of a coupler for connecting together the screw and the keyed motor shaft of  FIG. 8 . 
       FIG. 9  is an enlarged perspective view of leg members connected to a second end of the pair of channels of the lift of the present invention. 
       FIG. 9A  is an exploded top view of the connection of one leg member to a wing of the electric motor mounting plate. 
       FIG. 10  is an enlarged rear perspective view of the connection of fulcrum arm members to leg members of the lift of the present invention. 
       FIG. 11  is a partially sectioned side view of the lift of the present invention. 
       FIG. 12  is an exploded view of a pad of the lift of the present invention. 
       FIG. 13  is an enlarged partial perspective view of one embodiment of the lift of the present invention with stop sensors. 
   

   While the above-identified drawing figures set forth preferred embodiments of the invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the present invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of this invention. It should be specifically noted that the figures have not been drawn to scale, as it has been necessary to enlarge certain portions for clarity. 
   DETAILED DESCRIPTION 
     FIG. 1  is a perspective view of lift system  10  of the present invention mounted to a pontoon boat  12  (shown in phantom). Pontoon boat  12  generally comprises a pair of pontoons  14  placed parallel to one another and extending from a forward end  16  to a rearward end  18  of pontoon boat  12 . A deck  20  is supported above pair of pontoons  14  by a plurality of spaced deck support members  22  that extend between pair of pontoons  14 . Lift system  10  comprises four identical lifts  24  that are connectable to deck support members  22  of pontoon boat  12 . Two lifts  24  are connected to deck support members  22  between pontoons  14  near forward end  16  of pontoon boat  12  and two lifts  24  are connected to deck support members  22  between pontoons  14  near rearward end  18  of pontoon boat  12 . Each set of lifts  24  are oriented generally parallel to pontoons  14  and to each other. 
   Each lift  24  generally comprises a channel  26 , a motor  28 , a screw  30 , a leg  32 , and a fulcrum arm  34 . Channel  26  comprises a pair of spaced channel members  26 A,  26 B. Each channel member  26 A,  26 B includes a flange  36  for mounting channel  26  to support members  22 . A motor mounting plate  38  is welded to channel  26  at a first end  40 . Motor  28  is mounted to motor mounting plate  38  and is connected to a first end  29  of screw  30 . A second end  31  of screw  30  is supported by a bearing  42  secured to a bearing plate  44  welded to a second end  46  of channel  26 . A leg  32  is pivotally connected to wings  48  of motor mounting plate  38 . Leg  32  is pivoted by a fulcrum arm  34 , which has one end connected to leg  32 , and a second end connected to a threaded follower  50  that is threaded onto screw  30 . Threaded follower moves along screw  30  when motor  28  turns screw  30 . When screw  30  is turned in a first direction, leg  32  is extended by virtue of the fulcrum arm connection such that leg  32  is radially spaced from screw  30 . When screw  30  is turned in a second direction, leg  32  is retracted by virtue of the fulcrum arm connection such that leg  32  is proximate to screw  30 . 
     FIG. 2  is an enlarged perspective view of one of lifts  24  of lift system  10  shown in  FIG. 1 . Channel  26  serves to attach lift  24  to deck support members  22 . Channel  26  is connectable to deck support members  22  by either pre-formed holes in flanges  36  of each channel member  26 A,  26 B or by drilling holes in flanges  36 . Connection of lift  24  to pontoon boat  12  is accomplished by drilling complimentary holes in deck support members  22  and securing flanges  36  to deck support members  22  with bolts. Channel members  26 A,  26 B are located to define a space to house screw  30 . Each channel member  26 A,  26 B serves as a track to assist in a smooth movement of threaded follower  50  along screw  30 . Channel  26  has a length that spans several deck support members  22 . Each channel member  26 A,  26 B has a length approximating leg  32 , which in one embodiment is about 56.75 inches. The preferable material for channel members  26 A,  26 B is aluminum. 
   Motor  28  is operatively connected to screw  30  and turns screw  30  to raise and lower leg  32 . Motor  28  is mounted to motor mounting plate  38 , which is welded to first end  40  of channel  26 . In one embodiment, motor  28  is a reversible electric motor. In a preferred embodiment, motor  28  is a one-half horsepower motor manufactured by Bodine Electric Company capable of providing 400 lb-in. of torque. Motor  28  is preferably coated by waterproofing material. 
   Screw  30  is housed between channel members  26 A,  26 B. First end  29  of screw  30  is operatively connected to motor  28  by a drive coupling  52 . Second end  31  of screw  30  extends to second end  46  of channel  26  and is supported by bearing  42 . In one embodiment, screw  30  has a length of about 54.78 inches and is a threaded 1–4 2 Start Acme screw having an outside diameter of approximately one inch. 
   Threaded follower  50  is located between first and second ends  29  and  31  of screw  30  and is threaded onto screw  30 . Screw  30  guides threaded follower  50  along the length of channel  26  when screw  30  is turned by motor  28 . 
   Leg  32  comprises a pair of leg members  32 A,  32 B which are pivotally connected to wings  48  of motor plate  38  at a first end of leg  32 . A brace plate  54  is welded to leg members  32 A,  32 B adjacent the first end of leg  32  and serves to provide support and stability to leg members  32 A,  32 B as leg members  32 A,  32 B pivot about first end  40  of channel  26 . Leg brackets  56  are connected to leg members  32 A,  32 B below brace plate  54  and support a pivot tube  58  for connection of fulcrum arm  34 . Leg  32  has a length sufficient to raise pontoon boat  12  above the surface of the water when leg  32  is fully extended relative to channel  26 . When leg  32  is extended, lift  24  is supported on the bottom of the body of water by a pad  60  pivotally connected to a second end of leg members  32 A,  32 B by a pad pivot tube  62  and pad brackets  64 . In one embodiment, the length of leg members  32 A,  32 B is about 65.56 inches. The preferable material for leg members  32 A,  32 B is aluminum. 
   Fulcrum arm  34  serves to raise and lower leg  32  as threaded follower  50  travels along screw  30 . First end  66  of fulcrum arm  34  is pivotally connected to threaded follower  50  and second end  68  of fulcrum arm  34  is pivotally connected to pivot tube  58 . In one embodiment, fulcrum arm  34  comprises a pair of fulcrum arm members  34 A,  34 B. Each fulcrum arm member  34 A,  34 B includes a plurality of holes  35  equally spaced along the length of fulcrum arm member  34 A,  34 B for weight reduction. A cross-piece may optionally be welded between fulcrum arm members  34 A,  34 B to maintain fulcrum arm members  34 A,  34 B at a constant distance from each other when fulcrum arm members  34 A,  34 B are extending and retracting leg  32 . Each fulcrum arm member  34 A,  34 B has a length sufficient to extend leg  32  such that leg  32  is generally normal to channel  26  when fully extended. In one embodiment, fulcrum arm members  34 A,  34 B have a length of about 30.64 inches and structure holes  35  have a diameter of 1.5 inches. Fulcrum arm members  34 A,  34 B are preferably formed from aluminum. 
     FIG. 3  is an enlarged cross-sectional view of channel  26  of  FIG. 2  taken along line  3 — 3 . Each channel member  26 A,  26 B is comprised of flange  36  and a C-shaped track  70  defined by a top wall  72 , a bottom wall  74 , and a vertical wall  76  that is normal to top wall  72  and bottom wall  74 . Flange  36  and walls  72 ,  74 , and  76  are integrally connected and formed by extruding aluminum. In one embodiment, flange  36  and walls  72 ,  74 , and  76  have a wall thickness of about 0.1875 inches. Channel members  26 A,  26 B are spaced and oriented such that C-shaped track  70  of channel members  26 A,  26 B are oriented toward screw  30 . 
   Slider blocks  78  are housed in C-shaped track  70  of channel members  26 A,  26 B and are dimensioned to slide along C-shaped tracks  70  as threaded follower  50  moves along screw  30  to assist in smooth travel of threaded follower  50  along screw  30 . In one embodiment, slider blocks  78  are made of a polymer material, preferably plastic. In an alternative embodiment, slider blocks  78  can be replaced with wheels, bearings, or any other known structure that functions to provide a smooth travel of threaded follower  50  along screw  30 . 
   Threaded follower  50  is threaded onto screw  30  between channel members  26 A,  26 B. Threaded follower  50  generally comprises a drive block  80 , drive screw  82 , and anchor pin  84 . Drive block  80  and drive screw  82  are located on screw  30 . Anchor pin  84  fixes drive screw  82  relative to drive block  80  to prevent drive screw  82  from rotating relative to drive block  80  when screw  30  is rotated. Drive block  80  includes posts  86  (shown in phantom) which extend from opposite sides of drive block  80  toward C-shaped tracks  70 . Each post  86  serves to pivotally connect fulcrum arm members  34 A,  34 B to threaded follower  50 , and to connect threaded follower  50  to slider blocks  78 . 
     FIG. 4  is an exploded perspective view of threaded follower  50 . As shown in  FIG. 4 , drive block  80  is an aluminum block with posts  86  extending from opposite sides oriented toward slider blocks  78 . Each post  86  has a length sufficient to pass through fulcrum arm members  34 A,  34 B and connect drive block  80  to slider blocks  78 . Drive block  80  also includes a smooth bore  88  that is axially aligned with screw  30 . Bore  88  has a diameter that is larger than the outer diameter of screw  30 . Drive block  80  further comprises a lock pin hole  90  located at side  92  of drive block  80  adjacent bore  88 . Lock pin hole  90  has a depth and diameter sufficient to securely maintain a portion of anchor pin  84 . Anchor pin  84  is sized such that anchor pin  84  is frictionally held in lock pin hole  90 . 
   Drive screw  82  is comprised of a head  94 , a tubular body  96 , and a bore  98  extending therethrough. Head  94  has an outer diameter larger than that of tubular body  96  and includes a notch  100  at a circumferential edge of head  94 . Body  96  of drive screw  82  has an outer diameter sized to fit within bore  88  of drive block  80  and a length sufficient to extend through bore  88  of drive block  80 . Body  96  has external threads that mate with a drive nut  102  when body  96  extends through bore  88  to secure drive screw  82  relative to drive block  80 . Bore  98  of drive screw  82  is provided with internal threads that mate with the external threads of screw  30 . 
   Each fulcrum arm member  34 A,  34 B has an opening  104  which receives a brass bushing  106  that is dimensioned to fit onto posts  86  of drive block  80 . Each slider block  78  is provided with a hole  108  to receive an end portion of posts  86 . 
   To assemble threaded follower  50  on screw  30 , channel members  26 A,  26 B are secured to deck support members  22  of pontoon boat  12  with screw  30  supported at one end by bearing  42 . Before motor mounting plate  38  is welded to channel  26  and screw  30  is secured to coupler  52 , drive nut  102  is slid onto first end  29  of screw  30 . Fulcrum arm members  34 A,  34 B are then connected to drive block  80  by positioning brass bushings  106  over posts  86  and slider blocks  78  are positioned to allow posts  86  to extend within hole  108  of slider blocks  78 . Next, slider blocks  78  are positioned within C-shaped tracks  70  of channel members  26 A,  26 B while bore  88  of drive block  80  is passed over first end  29  of the screw  30 . 
   Drive screw  82  is then threaded onto first end  29  of the screw  30 . Once drive screw  82  is at the desired location on screw  30 , bore  88  of drive block  80  is positioned over body  96  of drive screw  82 . Drive screw  82  is rotated until notch  100  of drive screw  82  is aligned with lock pin hole  90  of drive block  80  and anchor pin  84  is press fit into lock pin hole  90  with a portion extending to engage notch  100 . Drive nut  102  is then threaded onto the end portion of body  96  of drive screw  82  that extends from bore  88  of drive block  80  to prevent axial movement of drive screw  82  relative to drive block  80 . 
     FIG. 5  is an exploded side view of bearing assembly  110  for supporting second end  31  of screw  30  relative to bearing mounting plate  44 . As shown in  FIG. 5 , second end  31  of screw  30  is machined to define an end portion  112  of reduced diameter for mounting a pair of bearings  42 . Each bearing  42  is housed in a bearing race  114  and is retained on the end portion  112  of screw  30  by a washer  116  and nut  118  that mates with a threaded end  119  of end portion  112 . Bearing assembly  110  and second end  31  are covered by a bearing housing  120  consisting of facing cups  120 A,  120 B. Cups  120 A,  120 B are provided with a plurality of bores  121  that correspond to holes  122  in mounting plate  44 . Bores  121  in cup  120 A include internal threads which allow bearing housing  120  and bearing assembly  110  to be secured to mounting plate  44  by bolts  124 . 
     FIG. 6  is a perspective view of first end  40  of channel  26  showing motor  28  mounted to motor mounting plate  38 . As shown in  FIG. 6 , motor mounting plate  38  has a width W which is greater than the spacing of channel members  26 A,  26 B. As such, wings  48  are spaced from channel members  26 A,  26 B to create a gap G for mounting leg members  32 A,  32 B. 
   As shown in  FIG. 7 , in one embodiment wings  48  are welded to ends  125  of motor mounting plate  38 . Alternatively, wings  48  may be integral to motor mounting plate  38  and are formed by bending end portions of motor mounting plate  38 . As further shown in  FIG. 7 , motor mounting plate  38  is provided with motor mounting holes  126  which align with bolt holes in motor casing  128  ( FIG. 6 ) for connecting motor  28  to motor mounting plate  38  with bolts. Motor mounting plate  38  also is provided with an opening  130  to permit a drive shaft of motor  28  to connect to screw  30 . 
     FIG. 8  is a partial cutaway side view of first end  40  of channel  26  showing screw  30  connected to motor  28 . As shown in  FIG. 8 , first end  29  of screw  30  is machined to define an end portion  132  of reduced diameter. End portion  132  is positioned within bore  134  of drive coupling  52  and is secured by welding. Second end  136  of drive coupling  52  is positioned over drive shaft  138  of motor  28 . As shown in  FIG. 8A , bore  134  of drive coupling  52  is configured with a key-slot  140  that extends along the inner circumference of drive coupling  52  along the length of bore  134 . Referring to  FIG. 8 , drive shaft  138  of motor  28  is keyed to permit a portion of drive shaft  138  to extend into key-slot  140  at second end  136  of drive coupling  52  to allow motor  28  to rotate screw  30 . 
     FIG. 9  is an enlarged perspective view of first end  40  of channel  26 . A portion of flange  36  is cut away to show a first end  142  of leg members  32 A,  32 B connected to wings  48  of motor mounting plate  38 . As shown in  FIG. 9 , first end  142  of leg members  32 A,  32 B are mounted to wings  48  within gap G beneath flanges  36  of channel members  26 A,  26 B. First end  142  of leg members  32 A,  32 B are mounted to wings  48  by bolts to provide pivotal movement of leg members  32 A,  32 B relative to channel  26 . 
     FIG. 9A  is an exploded top view of first end  142  of leg member  32 A between wing  48 A and channel member  26 A. As shown in  FIG. 9A , first end  142  of leg member  32 A has a hole  144 , which receives a brass bushing  146 . First end  142  of leg member  32 A is axially aligned with pre-drilled holes  148  in wing  48 A and in vertical wall  76  of channel member  26 A. Washers  150  are aligned with holes  148  on either side of leg member  32 A and leg member  32 A is connected by bolt  152  and nut  154 . First end  142  of leg member  32 B connects to wing  48 B and channel member  26 B in an identical manner. 
   With leg members  32 A,  32 B mounted to wings  48  of motor mounting plate  38  and channel members  26 A,  26 B, second end  68  of fulcrum arm members  34 A,  34 B are pivotally connected to leg members  32 A,  32 B. 
     FIG. 10  is an enlarged rear perspective view of second end  68  of fulcrum arm members  34 A,  34 B connected to leg members  32 A,  32 B. Second end  68  of each fulcrum arm member  34 A,  34 B has an opening (not shown) that receives pivot tube  58 . Spacing S of fulcrum arm members  34 A,  34 B along pivot tube  58  is chosen to locate each fulcrum arm member  34 A,  34 B generally equidistant from a respective leg member  32 A,  32 B and to space fulcrum arm members  34 A,  34 B generally equal to the spacing of first end  66  of fulcrum arm members  34 A,  34 B. Once fulcrum arm members  34 A,  34 B are properly spaced along pivot tube  58 , pivot tube  58  is welded to fulcrum arm members  34 A,  34 B. Pivot tube  58  has a length less than the distance between leg brackets  56  secured to leg members  32 A,  32 B to permit positioning of brass bushings  156  (not shown) at each end of pivot tube  58 . 
     FIG. 11  is a partially sectioned side view of one of lifts  24  showing first and second ends  66  and  68  of fulcrum arm  34  connected to threaded follower  50  and leg  32 , respectively. As motor  28  turns screw  30  in a first direction, threaded follower  50  carries first end  66  of fulcrum arm  34  along screw  30  in the direction of arrow A causing leg  32  to move in the direction of arrow B to a retracted position and stow leg  32  against channel  26 . When leg members  32 A,  32 B are fully retracted, leg members  32 A,  32 B extend along the exterior side of vertical wall  76  of channel members  26 A,  26 B and pad  60  extends beyond second end  46  of channel  26 . 
   To lower leg  32 , motor  28  turns screw  30  in a second opposite direction and threaded follower  50  carries first end  66  of fulcrum arm  34  along screw  30  opposite the direction of arrow A to lower leg  32 . Leg  32  is lowered until pad  60  contacts the bottom of the body of water. Operated in concert with a plurality of lifts  24 , as shown in  FIG. 1 , as legs  32  of lifts  24  are further lowered, pontoon boat  12  is elevated above the surface of the body of water. 
     FIG. 12  is an exploded perspective view of one embodiment of pad  60 . As shown in  FIG. 12 , end portion  176  of second end  178  of leg members  32 A,  32 B is curved to mate with pad pivot tube  62 . End portion  176  of leg members  32 A,  32 B are spaced at opposite ends of pad pivot tube  62  and are secured by welding. 
   Pad  60  is pivotally connected to pad pivot tube  62  by a pair of U-shaped pad brackets  64  sized to fit over pad pivot tube  62 . Pad brackets  64  are placed over pad pivot tube  62  adjacent to an inner side of leg members  32 A,  32 B. Holes  180  of pad brackets  64  align with corresponding holes  182  provided in pad  60  to pivotally connect pad  60  to pad brackets  64  with bolts  184  and nuts  186 . 
   In one embodiment, pad  60  is formed of an aluminum plate and may include one or more support braces  188  welded to a bottom of pad  60 . Support braces  188  shown in  FIG. 12  comprise V-shaped aluminum pieces sized to fit bottom contours of pad  60 . 
     FIG. 13  is an enlarged partial perspective view of one of lifts  24  representing a control for synchronized operation of lift system  10 . As shown in  FIG. 13 , in one embodiment of lift system  10 , each lift  24  is equipped with a pair of spaced stop sensors  200  and  202 , which aid in preventing motor  28  from being over-operated when leg  32  is in the complete up position or the complete extended position. Stop sensor  200  is connected to bearing mounting plate  44  and extends within channel  26  with an end oriented toward one of slider blocks  78 . Stop sensor  202  is located on a plate  204 , which is mounted within channel  26  between channel members  26 A,  26 B, such as by welding. Plate  204  is provided with a hole  206  that is sized to permit screw  30  to pass therethrough. Stop sensor  202  also has an end oriented to an opposite side of slider block  78 . 
   In one embodiment, the leading and trailing faces of slider block  78  are provided with a magnet  208 . As previously discussed, as threaded follower  50  travels along screw  30  toward bearing mounting plate  44 , leg  32  is raised to a stowed position. When leg  32  reaches the raised, stowed position, magnet  208  on the leading face of slider block  78  is adjacent stop sensor  200 . Stop sensor  200  senses the presence of the magnetic field and sends a representative signal via electrical connection  210  to a switch in control box  212 , which opens an electrical connection  213  of motor  28  to battery  214 . In alternative embodiments, stop sensor  200  may be positioned to correspond with a portion of leg  32  when leg  32  is in a raised, stowed position, with a magnet mounted on the corresponding portion of leg  32 . 
   Likewise, as threaded follower  50  travels in an opposite direction along screw  30 , leg  32  is lowered to engage a bottom of the body of water. In one embodiment, plate  204  with stop sensor  202  are located within channel  26  to ensure that leg  32  is not over-rotated and motor  28  is not over-operated. When threaded follower  50  is near plate  204  and magnet  208  on the trailing face of slider block  78  is adjacent stop sensor  202  a signal is transmitted via electrical connection  216  to a switch in control box  212  to open the electrical connection  213  of motor  28  to battery  214 . In alternative embodiments, magnet  208  may be positioned on head  94  of drive screw  82  with corresponding stop sensor  202  positioned on plate  204  accordingly. 
   The remaining lifts  24  of lift system  10  are similarly electrically configured to control box  212 . Control box  212  also receives inputs from a user and synchronizes operation of motors  28  of each lift  24  to raise and lower pontoon boat  12  relative to the surface of the water. Additionally, each motor  28  can be individually operated such as for leveling pontoon boat  12 . 
   Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.