Patent Publication Number: US-8539896-B2

Title: Lift mechanism for added stability for a swim platform of a boat

Description:
FIELD 
     This invention relates to boats and more particularly to a lift mechanism for lifting a swim platform of a boat. 
     BACKGROUND 
     Some boats have what is known as a swim platform extending outwardly from the rear of the boat (stern). For many uses, the swim platform is stationary and provides added space and safety features. The added space is very useful when swimming from the back of the boat, providing a clear area for the swimmer to board the boat when finished swimming. For inboard/outboard boats, the swim platform provides additional safety by extending outward, over the propeller and the outdrive. This helps keep swimmers and divers away from the features, such as propellers, that sometimes come into contact with the swimmer/diver, causing injuries. 
     Another popular use for the swim platform is for transportation of a personal watercraft such as a dingy. For some light weight personal watercraft, such as canoes and kayaks, it is relatively easy for the user to slide the personal watercraft off the swim platform into the water and, somewhat easy for the user to get the personal watercraft back onto the swim platform after use. This is not the case for a heavier personal watercraft such as a jet ski, an inflatable boat with an outboard engine, a larger dingy for a yacht, etc. With such heavier watercraft, it is difficult or impossible for a user to manually deploy such watercraft and even harder to lift these heavy watercraft back onto the swim platform. 
     There are several known solutions for deploying such heavy watercraft. The first, often used on larger boats or yachts, is the use of a crane. The crane is used to lift the watercraft then swing the watercraft around for placement into the water adjacent to the boat. When finished with the watercraft, the crane is used to lift the watercraft for replacing it onto the swim platform of the boat. Cranes are well known and are useful for swim platform storage as well as storage of the personal watercraft at other locations on the boat. 
     Another solution for deploying the watercraft is to mechanically lower and lift the swim platform. The swim platform is lowered below the water surface so that the personal watercraft floats and is easily moved away from the boat. Likewise, to return the watercraft to the swim platform, the swim platform is again lowered beneath the surface of the water, the watercraft is positioned over the submerged swim platform, and then the swim platform is raised to a position where it is level with a deck of the boat. Such mechanical systems are usually hydraulic lift systems. 
     There are several problems with prior swim platforms that have mechanical systems to lower the watercraft (dingy, jet ski, etc.) into the water. First, the weight of the mechanical systems for lowering, the weight of the swim platform itself, and the weight of the watercraft greatly affect the center of gravity of the boat. This additional weight is especially disadvantageous for many boats that must get up “on plane” during cruising speeds, requiring more fuel and time to get on plane, and increasing the speed required to remain on plane. This results in a vast reduction in fuel economy. 
     Many prior swim platforms are fixed in place and well supported by the transom of the boat. The brackets that hold such swim platforms in place provide a very sturdy platform that does not bend when one steps onto the platform. It is very disconcerting for a boater to step on a swim platform that bends or oscillates up and down. Swim platforms that have mechanical systems to lower the watercraft often do not have this stiff, sturdy feel. When one steps onto a mechanically lowered/raised swim platform of the prior art, the swim platform bends or bounces, yielding an uneasy feeling. This is often due to the mechanical design of the system. Most conventional lifts leave their arms in a position where they perform as bending beams and are therefore susceptible to noticeable deflection. 
     What is needed is a mechanism that will raise and lower the swim platform of the boat and provide enhanced stability to the swim platform when the swim platform is in the raised position. 
     SUMMARY OF THE INVENTION 
     The swim platform lift mechanism mounts between the transom of a boat and a bottom surface of a swim platform, providing for lifting/lowering of the swim platform from a retracted position that is level with the deck of the boat to a deployed position where the swim platform is below the surface of the water surrounding the boat. In the deployed position, easy deployment of a dingy or other watercraft that is stored on the swim platform is made possible. The swim platform lift mechanism has an adjustable stop and a rest area that provides a third support lever to stiffen the swim platform when the swim platform is in the retracted position, reducing up/down movement and oscillation. 
     In one embodiment, a platform lifting mechanism for a boat is disclosed. The lifting mechanism has a mechanism for raising and lowering the platform of the boat to/from a first position that is level with a deck of the boat to/from a second position that is at least lower than the deck of the boat. The mechanism for raising and lowering a platform of the boat has a transom bracket affixed to a transom of the boat and a platform bracket affixed to the platform. The mechanism has a plurality of upper arms, a plurality of lower arms and at least one hydraulic ram. The upper arms are hingedly interfaced at one end to an upper area of the transom bracket and at a distal end to the platform bracket. The lower arms are hingedly interfaced at one end to a lower area of the transom bracket and at a distal end to the platform bracket. The hydraulic ram(s) interfaced between an upper area of the transom bracket and the lower arms. A stop is interfaced to a lower surface of the platform bracket and rest areas are included at the distal end of the lower arms, whereas, the stop engages with the rest areas in the first position, thereby providing structural support to the platform bracket 
     In another embodiment, a swim platform lifting mechanism for a boat is disclosed. The boat is floating in a liquid. The lifting mechanism includes a mechanism for raising and lowering a platform of the boat to/from a first position that is level with a deck of the boat to/from a second position that is at least lower than the deck of the boat. The mechanism has a transom bracket affixed to a transom of the boat and a platform bracket affixed to the platform. A first end of the two side-by-side upper arms are hingedly interfaced to an upper area of the transom bracket and a distal end of each of the two side-by-side upper arms is hingedly interfaced to the platform bracket. The mechanism has a strut with a first end and a distal second end, the first end interfaced to the platform bracket. The mechanism has two side-by-side intermediate arms, the first ends hingedly interfaced to the platform bracket. The mechanism has two side-by-side lower arms, a first end of each is hingedly interfaced to a lower area of the transom bracket and a distal end of each is hingedly interfaced to both the second end of the side-by-side intermediate arms and to the distal second end of the strut. The mechanism has a hydraulic ram, a first end interfaced to an upper area of the transom bracket and a second end interfaced to a cross member connected between the two side-by-side lower arms. An adjustable stop is located on a lower surface of the platform bracket and rest areas are located at the distal end of each of the lower arms, whereas, the adjustable stop engages with the rest areas in the first position, thereby providing structural support between the platform bracket and the transom bracket. 
     In another embodiment, a method of lifting a swim platform for a boat is disclosed. The boat is floating in a liquid. The method includes connecting the swim platform to a transom of the boat with a deployment lift mechanism. The deployment lift mechanism includes a transom bracket affixed to the transom of the boat and a platform bracket affixed to the swim platform. The deployment lift mechanism has upper arms hingedly interfaced at one end to an upper area of the transom bracket and at a distal end to the platform bracket and lower arms hingedly interfaced at one end to a lower area of the transom bracket and at a distal end to the platform bracket. The deployment lift mechanism has a hydraulic ram interfaced between an upper area of the transom bracket and the lower arms. A stop is positioned on a lower surface of the platform bracket and rest areas is positioned at the distal end of the lower arms whereas the stop engages with the rest areas in the first position, thereby providing structural support to the platform bracket. The method continues with lowering the swim platform using the deployment lift mechanism until the swim platform is below a surface of the liquid, positioning a water craft upon the swim platform and raising the swim platform using the deployment lift mechanism until the swim platform is substantially level with a deck of the boat, whereas the rest areas are supported by the stop, thereby providing rigidity to the swim platform. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which: 
         FIG. 1  illustrates a swim platform and mechanism for deploying a watercraft that is held by the swim platform in a lowered position. 
         FIG. 2  illustrates a swim platform and mechanism for deploying a watercraft that is held by the swim platform in a raised position. 
         FIG. 3  illustrates the mechanism for deploying a watercraft transitioning between a lowered position to a raised position. 
         FIG. 4A  illustrates a first view of a swim platform holding a watercraft, the mechanism for deploying a watercraft and a mechanism for raising the water craft up and over the boat deck, the swim platform being in the up-and-over position. 
         FIG. 4B  illustrates a second view of a swim platform holding a watercraft, the mechanism for deploying a watercraft and a mechanism for raising the water craft up and over the boat deck, the swim platform being even with the deck of the boat. 
         FIG. 4C  illustrates a third view of a swim platform holding a watercraft, the mechanism for deploying a watercraft and a mechanism for raising the water craft up and over the boat deck, the swim platform being lowered into the water. 
         FIG. 5  illustrates a detail view of a swim platform, the mechanism for deploying a watercraft and a mechanism for raising the water craft up and over the boat deck, moving from a deployed position (in the water) to the swim platform even with the deck of the boat. 
         FIG. 6  illustrates a detail view of a swim platform, the mechanism for deploying a watercraft and a mechanism for raising the water craft up and over the boat deck, with the swim platform in an extended position (up and over the deck of the boat). 
         FIGS. 7A-7D  illustrate a detail view of the mechanism for raising the water craft up and over the boat deck transitioning from a retracted position (level with the boat deck) to an extended position (up-and-over the deck). 
         FIG. 8  illustrates a perspective view of the mechanism for raising the water craft up and over the boat deck in the extended position (up-and-over the deck). 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Throughout the following detailed description, the same reference numerals refer to the same elements in all figures. Throughout this description, the term “boat” refers to any aquatic vehicle of any size or type including, but not limited to, boats, yachts, pleasure craft, etc. The term “dingy” refers to any secondary aquatic vehicle that is carried or towed by the boat including, but not limited to, jet skis, kayaks, canoes, a dingy, rafts, pontoon boats, etc. Throughout this description, the term “retracted position” refers to a condition in which the swim platform is substantially level with a deck of the boat and “deployed position” refers to a condition in which the swim platform is at a level lower than the deck of the boat, preferably below the surface of a body of water in which the boat is floating. 
     Referring to  FIGS. 1 ,  2  and  3 , a swim platform  11  and mechanism for deploying  10  a dingy  7  (see  FIG. 4 ) that is held on the swim platform  11  will be described. In  FIG. 1 , the swim platform  11  is in the lowered position, preferably situated far enough below the surface of the surrounding body of water as to let the dingy  7  float, allowing the dingy  7  to be deployed from and/or returned to the swim platform  11 . Note, in some embodiments, the dingy  7  is held in place on the swim platform  11  by chocks or a frame  14  (see  FIG. 4 ). 
     In  FIG. 2 , the swim platform  11  is in the raised position, preferably situated level with the deck  4  of the boat  5  (see  FIG. 4 ). 
     The mechanism for deploying  10  the dingy  7  includes two hinged arms  24 / 26  that keep the swim platform  11  in line with the deck  4  of the boat  5 . This is to say that, when the swim platform  11  abuts the deck  4  of the boat  5 , both are in substantially the same plane, and when the swim platform  11  is lowered the plane of the swim platform  11  is substantially parallel to the plane of the deck  4 . A first end of a lower hinged arm  26  is hingedly attached to a lower section of a transom bracket  22  and a distal end of the lower hinged arm  26  is hingedly attached to a lower attach point of a swim platform interface bracket  12 . Similarly, a first end of an upper hinged arm  26  is hingedly attached to a mid-section of a transom bracket  22  and a distal end of the upper hinged arm  26  is hingedly attached to an upper attach point of a swim platform interface bracket  12 . The transom bracket  22  is affixed to the transom  3  of the boat  5  (see  FIG. 4 ) and the swim platform interface bracket  12  is affixed to the swim platform  11  as known in the industry. 
     Although a single mechanism for deploying the dingy  7  is shown, any number of mechanisms  10  are anticipated, working side-by-side in parallel. For many boats, at least two mechanisms  10  are used, providing structural strength to support the swim platform  11  and increase side-to-side stability. 
     The swim platform  11  is deployed and retrieved by one or more hydraulic rams  28 , as known in the industry. The hydraulic rams  28  are supplied with a controlled source of hydraulic pressure to extend or retract. One end of the hydraulic ram(s)  28  is affixed to the swim platform interface bracket  12  and the other end of the hydraulic ram(s)  28  is affixed to the transom bracket  22 . 
     For completeness, a hydraulic locking mechanism is shown. The hydraulic locking mechanism includes a catch  32  that engages with a peg  30  when the swim platform  11  is in the retracted position (as shown in  FIG. 2 ). Just before deploying the swim platform  11 , the cylinder  34  is pressurized to pull (or push) the catch  32  away from the peg  30  to release the swim platform  11 . The catch  32  is biased towards the peg  30  by a spring  36  and the force of the spring  36  is overcome by the cylinder  34  to release the catch  32 . The catch  32  maintains the retracted position of the swim platform  11 , especially during boating wherein the constant motion of the boat  5  over waves would otherwise constantly apply back pressure against the hydraulic ram and either requires constant fluid pressure or near-perfect seals to maintain the retracted position. Any type of locking mechanism is anticipated, including, but not limited to hydraulic locking mechanisms, solenoid locking systems, and manually released locking mechanisms. 
     Once the swim platform  11  reaches the retracted position as shown in  FIG. 2 , it is desired that the swim platform  11  feel sturdy and secure as it is often stood on by boaters when boarding, swimming, etc. Due to the manner in which the forces act on the dual-point arm system  24 / 26 , when stepping onto or off of the swim platform  11 , the weight of the boater results in up/down movement of the swim platform  11 . This is often disconcerting to the boater who is used to a sturdy deck and swim platform surface because boats of the prior art had fixed swim platforms  11 . To provide the desired sturdiness, the lower arm  26  has a rest area  40 . As the swim platform is retracted, rest area  40  contacts an adjustable stop  42 , providing a sturdy resting point at a greater distance from the transom  3  of the boat  5 . The adjustable stop  42  is threaded so that turning of the adjustable stop  42  moves the adjustable stop inwardly (outwardly) with respect to the swim platform interface bracket  12 . By turning the adjustable stop  42 , the retracted position of the swim platform  11  is adjusted slightly to adjust the retracted position of the swim platform  11  with respect to the deck  4  of the boat  5 . 
     When in a retracted position, as in  FIG. 2 , the weight of the swim platform  11 , swimmer and or dingy  7  wants to push the platform  11  down and toward the water. Without the rest area  40  and adjustable stop  42 , the resulting force had to be withstood by the hydraulic ram  28 , and or the catch  32 . Due to those constraints the force acts through the strut  27  which connects between to the top portion of the lower arm  26  and the swim platform interface bracket  12 , in conjunction with a third-point arm  29 . With the lower arm  26  loaded and restrained in this fashion it represents a classical overhanging beam with two simple supports and a load at its end. Deflection of this type of beam is significantly related to the overhung length, in this case the distance between where the strut  27  and ram  28  connect to the lower arm  26 . This deflection is directly related to the deflection of the swim platform  11 . 
     The design shown improves on the prior art with the addition of the rest area  40  and the adjustable stop  42 . The contact between the rest area  40  and adjustable stop  42  changes the load path due to the weight of the swim platform  11 , swimmer and or dingy  7 . The reaction through the strut  27  is now negligible due to the reaction taking place on the rest area  40  by the adjustable stop  42 . The lower arm  26  is now loaded in a manner which reflects a classical axial loaded column. This type of structure has minimal deflection compared to an overhung beam with geometry held constant. The minimal deflection of the lower arm  26  due to the contact between the rest area  40  and adjustable stop  42  allows for nominal movement in the swim platform  11  providing the desired sturdy feel. 
     In  FIG. 3 , the mechanism  10  for deploying a watercraft transitioning the swim platform  11  between a deployed position to a retracted position is shown. As the hydraulic ram  28  is pressurized to contract, the swim platform interface bracket  12  is lifted until the rest area  40  of the lower arm  26  contacts the adjustable stop  42 , at which point the swim platform interface bracket  12  is in the retracted position and is locked in place by the catch  32 . This three-point structure provides improved stiffness to a swim platform  11  that is attached to the swim platform interface bracket  12  while also enabling minor adjustments to the retracted position of the swim platform  11  to eliminated potential tripping issues caused by an edge of the swim platform  11  not being flush with an upper edge of the deck  4  of the boat  5 .  FIG. 4B  shows the edge of the swim platform  11  flush with the upper edge of the deck  4  of the boat  5  as obtained by proper adjustment of the adjustable stop  42 . 
     Referring to  FIGS. 4A through 4C , transitional views of an up-and-over swim platform  11  holding a watercraft, the mechanism  10  for deploying a watercraft  7  and a mechanism for raising  9  the dingy  7  over the boat deck will be described. As shown in  FIG. 4A , the dingy  7  is positioned up (higher than the deck  4  of the boat  5 ) and over (moved towards the bow of the boat  5 , thereby overlapping the back section of the deck  4 ). There are several advantages to positioning the swim platform  11  and dingy  7  in this position. First, especially in rough seas, the dingy  7  is further removed from the water surrounding the boat  5  and, therefore, has less of a chance of dragging in the water. Second, because the dingy  7  and swim platform are lifted and moved forward (towards the bow), the center of gravity of the boat  5  is less affected by the weight of the swim platform  11  and of the dingy  7 . This is especially important in boats  5  that need to come up on plane in order to achieve better fuel efficiency, more comfortable rides and higher speeds. Many pleasure craft operate at a certain angle with respect to the water when at very low speeds and at cruising speed or higher. Operating at a speed between the two speeds is often uncomfortable because of the angle of the boat&#39;s  5  deck  4 , and results in the inefficient consumption of fuel because the propeller is busy pushing the hull of the boat  5  into the water instead of sliding the hull across the top of the water. When additional weight is added to the stern area of the boat  5 , even higher speeds are required to achieve plane because the center of gravity moves farther towards the stern of the boat  5 . Since the shift in the center of gravity is related to the weight of the dingy  7  times the distance of the dingy from the bow of the boat  5 , the closer the weight of the dingy  7  is to the bow, the less effect the weight of the dingy  7  will have on the center of gravity. 
     Therefore, the up-and-over mechanism  9  continues the upward movement of the mechanism  10  for deploying a watercraft  7  while also moving the swim platform  11  and hence the dingy  7  towards the bow of the boat  5 , thereby moving the center of gravity of the boat  5  closer to the bow of the boat  5 . Throughout the travel of the swim platform  11 , the swim platform preferably remains substantially within parallel planes to the plane of the deck  4 . As shown in  FIG. 4B , the up-and-over mechanism  9  is retracted and the swim platform  11  is level with the deck  4  of the boat  5 . 
     Following through with  FIG. 4C , the mechanism  10  for deploying a watercraft  7  is fully deployed and the dingy  7  is lowered into the water surrounding the boat  5 . 
     Referring to  FIGS. 5 and 6 , a detail view of a swim platform  11 , the mechanism  10  for deploying the dingy  7  and a mechanism  9  for raising the water craft up and over the boat deck  4  is shown. In  FIG. 5 , the swim platform  11  is shown moving from a deployed position (in the water) to where the swim platform is even with the deck  4  of the boat  5 . In  FIG. 6  the swim platform  11  continues to move up and over the deck  4 . The operation of the mechanism  10  for deploying the dingy  7  is as described with  FIGS. 1-3 , except that the mechanism  9  for raising the water craft up and over the deck  4  is interfaced to the mechanism  10  for deploying the dingy  7  instead of the swim platform  11  and, consequently, the swim platform  11  is interfaced to the mechanism  9  for raising the water craft up and over the boat deck  4 . 
     In this example, there are two frames  12 A/ 13  interfacing to the swim platform which is part of the mechanism  9  for raising the water craft up and over the boat deck  4 . A first, upper frame  13  interfaces to and attaches to the swim platform  11 . A second, lower frame  12   a  interfaces and hingedly attaches to the arms  24 / 26  of the mechanism for deploying the dingy  7 . The lower frame  12   a  is connected to the upper frame  13  by two or more arms  14 / 16  and a second hydraulic ram (see  FIGS. 6 and 8 ). The Ram extends the upper frame  13  from a first position even with the boat deck  4  to a position that is up and over the boat deck  4 . One end of the ram  18  is interfaced to the upper frame  13  by a cross member  19  as known in the industry while the distal end of the ram  18  is interfaced to either the lower frame  12   a  (not shown) or a cross member  21  connected to arms  16 . In  FIG. 5 , up-and-over mechanism  9  is retracted and the swim platform  11  is level with the deck  4 . In  FIG. 6 , the swim platform  11  is lifted up and over the edge of the deck  4  to move the center of gravity forward towards the bow of the boat  5 . The hydraulic ram  18  pushes the upper frame  13  up and over the lower frame  12   a  as will be described with  FIGS. 7A-7D . The arms  14 / 16  force the connection points on the upper frame  13  to move in an arc having a radius centered on the connection points of the lower frame  12   a . Since the arc is biased in its travel, the beginning of travel from the lowered position (even with the deck  4 ) to the up and over position (above and forward of the deck  4 ), the initial direction of movement is upward and optionally rearward before the later direction of movement is upward and forward, thereby the forward edge of the swim platform  11  clears the rear edge of the deck  4 . Without this arced movement, the edges would interfere with each other, preventing the forward movement of the swim platform  11 . Although two arms  14 / 16  are shown, any number of arms  14 / 16  is anticipated. It is preferred to have at least two arms  14 / 16  to provide rigidity and to maintain parallel planes between the top surface of the deck  4  and the top surface of the swim platform  11 . 
     In some embodiments, the strut  27  is provided to adjust the angle of the swim platform  11  to a position such that the plane in which the upper surface of the swim platform  11  resides is the same as or parallel to the plane in which the deck of the boat resides. Adjustments are made as known in the industry using, for example, threaded fasteners, etc. 
     Referring to  FIGS. 7A-7D , detail views of the mechanism  9  for raising the water craft up and over the boat deck  4  transitioning from a retracted position (level with the boat deck) to an extended position (up-and-over the deck) will be described. In  FIG. 7A , the upper frame  13  is in the retracted position (e.g. the swim platform is level with the boat deck). In this position, the back edge of the deck  4  aligns with the boat-side edge of the swim platform  11  as shown in  FIG. 5 . Because the edges are at approximate right angles to the surfaces of the deck  4  and swim platform  11  and because the edges are desired to be very close to each other, the swim platform must be first lifted so that the boat-side edge of the swim platform  11  clears the back edge of the deck  4  without rubbing. To provide the lift-first, move forward second motion, the arc members  14 / 16  are positioned such that the upper frame  13  moves on an arc with respect to the lower frame  12   a , moving first in a slightly stern direction but predominately upward direction until the back edge of the deck  4  clears the boat-side edge of the swim platform  11  as in  FIG. 7B , then, after the back edge of the deck  4  clears the boat-side edge of the swim platform  11 , movement continues upward as in  FIG. 7C  and finally upward and forward as in  FIG. 7D   
     Referring to  FIG. 8 , a perspective view of the mechanism  9  for raising the dingy  7  up and over the boat deck  4  (up-and-over the deck) will be described. In this view, the base of the hydraulic ram  18  is visible and attached to a cross member  21  that is connected to the rear arc members  16 . The front of the hydraulic ram  18  is connected to a forward mounted cross member  19  (partially hidden) that is connected to the upper frame  13 . 
     Equivalent elements can be substituted for the ones set forth above such that they perform in substantially the same manner in substantially the same way for achieving substantially the same result. 
     It is believed that the system and method of the present invention and many of its attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely exemplary and explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.