Abstract:
A hydraulic lift device for in-water boat hoists. A hydraulic cylinder is utilized to extend and retract a cylindrical rod with a vertical cross member at its end. Lift cables are attached to the cross member on opposite sides and extend rearwardly toward the hydraulic cylinder. One cable is horizontally reversed, 180° by a pulley, with both cables then directed 90° downward over respective pulleys and affixed to opposite ends of the cradle of the hoist, equalizing end to end lift. Side to side lift may be equalized by a second parallel device or by levelings cables. Primary components are contained within an attached enclosure, above water level. Remote operation and solar power may be provided.

Description:
THIS APPLICATION CLAIMS BENEFIT OF U.S. PROVISIONAL APPLICATION SERIAL NO. 60/355,734 FILED FEB. 2, 2002. 
    
    
     BACKGROUND OF INVENTION 
     This invention relates to boat hoists, generally, and, more specifically, to a hydraulic lift device for a boat hoist, in which the structure to which the principal components thereof are attached also provides a protective enclosure for those components. 
     A variety of prior art applications are known related to the function of vertically moving a suspended boat cradle by various means including some hydraulic applications. Such hoists are used in residential, recreational and light commercial settings, to lift a boat out of the water when not in use. In northern locales, these hoists must also be seasonably removable to prevent ice damage of hoist components at or below the water surface. 
     Prior art applications in the field have included variations of cantilever-style hoists. Many of these employ hydraulic cylinders below the water surface. Some hoists of this type have utilized large winches forward of the hoist to pull the hoist&#39;s bed or cradle over its pivot point. There has been limited success, as well, with vertical lifts which utilize hydraulics or large cable winches. 
     Existing vertical winch lifts, typically may be outfitted with two or more winches, particulary for heavier weight applications, and these multiple winches may run at varying speeds, which may be disadvantageous. 
     Hydraulic vertical lifts of the existing art often use one cable to lift one corner of the lifting bed or cradle, using multiple leveling cable to equalize lift on all other corners. Existing hydraulic applications, as well, utilize the “pull” of the hydraulic cylinder, rather than the “push”. Because of these factors most existing hydraulic lifting devices have significant load limitations. 
     Hydraulic cantilever lifts require substantial structure support because of compounded force at bottom of the lifting cycle. Significantly more power is required in the initial portion of the cycle than in the latter. It is also typical of the prior art that the hydraulics are beneath the water surface when the hoist is operated. This creates a number of disadvantages. 
     Below surface hydraulics are not only difficult to service, but are exposed to harsh elements, including sand, salt (in salt water applications), zebra muscles and barnacles. Below lift mechanical components will also require deeper water, which is a luxury not always available, because the lift bed may not be able to be placed as proximate to the bottom as is optimally desired. Because of their method of operation, and upper configuration, hydraulic cantilever hoists may also be difficult to accessorize with such important additions as canopies and motor and bow stops. 
     Winch cantilever hoists address some concerns, but present their own problems. Structure size and weight, to address strength requirements, limit mobility of the entire hoist assembly. They are also generally powered by 220 volt electricity which is potentially hazardous in a marine environment. 
     Representative of the prior art are U.S. Pat. No. 5,934,826 to Mansfield disclosing a combination boat lift apparatus and piling; U.S. Pat. No. 5,522, 671, to Keesling, disclosing a pair of hydraulic cylinders vertically mounted in conjunction with reinforced concrete pilings; U.S. Pat. No. 5,090,841, to Pench, Jr. et al, disclosing a hydraulic pump and cylinder on a manual boat lift; U.S. Pat. No. 4,773,346 to Blanding et al., disclosing vertically mounted hydraulic cylinders, at each corner of a boat hoist; and U.S. Pat. No. 4,641,596 to Reprogle et al., which discloses a combination of vertical hydraulic cylinders and moveable pulley blocks; 
     Accordingly, a need exists for a boat hoist hydraulic lift device which may be used in conjunction with an easily portable boat hoist to maximize mobility; which allows the lift bed of the hoist to rest as proximate to the bottom of the body of water as possible; which utilizes the “push” as opposed to the “pull” of the hydraulic cylinder unit; which does not require 220 volt electrical power from an external source; which provides equal vertical “lift” directly to both ends of the lift bed; and which is constructed so that the primary mechanical and power components are located above the surface of the water and are otherwise shielded from the elements. 
     The present invention is so directed. 
     SUMMARY OF THE INVENTION 
     The present invention has been designed to the overcome the shortcomings in the prior art as noted above. It is directed to the provision of a significantly improved lifting device for utilization with in-water boat hoists. 
     More specifically, this invention is directed to a boat hoist hydraulic lift device which may be used in conjunction with currently existing boat hoist frames to provide a portable boat hoist which maximizes mobility. 
     An additional object of the invention is to provide a boat hoist hydraulic lift device which allows the lift bed of the hoist to rest as approximate as possible to the bottom of the body of water and, further is constructed so that the primary mechanical components are located above the surface of the water, and are shielded from other elements as well. 
     An additional object of the invention is to provide a hydraulic lift device which maximizes lifting power by utilizing the “push” of a hydraulic cylinder, as opposed to the “pull” thereof. Further, the device is directed to provision of a hydraulic lifting function in an in-water boat hoist application which does not require 220 volt electrical power from an external source and which provides equal vertical lift directly to both ends of the lift bed. 
     The boat hoist lift device which is a primary object of the invention is utilized in conjunction with in-water boat hoists having a base frame, which is normally adjustable, to rest substantially horizontally on the bottom of a body of water. Such hoists are normally substantially rectangular in shape, with a lower rectangular base, and supporting shoes or skids, which have an adjustment means to level the lower portion of the hoist. The hoist itself has a plurality of stanchions which extend vertically, normally at the corners thereof, and along the sides. Stanchions are not normally provided along the ends of the hoist, as that is where the boat, or other load to be lifted, normally enters and exits. 
     In conjunction with the type of hoist described, the present invention, in an important feature, may utilize either one hydraulic lift device or a pair of such devices mounted in parallel, on opposite sides of the boat hoist. 
     According to a further important feature of the invention, each individual hydraulic lift device unit initially includes a support and enclosure unit, extending between upright stanchions of the boat hoist assembly itself, on one side of the boat hoist. This rigid unit provides the dual function of supporting the hydraulic lift device and its primary components, and further, enclosing those components and shielding them from the elements. This rigid support member is essentially a rigid, longitudinal box member, extending between upright boat hoist stanchions and includes joined and enclosed bottom, back, top, and end units. A front cover unit, which is removable, is also provided, for access to the components for service and maintenance. 
     According to a further feature of the invention, within the support structure enclosure, a hydraulic cylinder, which includes a cylinder body and extendable piston, is secured, in horizontal relationship. The cylinder body itself is located more closely to one end of the enclosure, and the piston rod is extended by hydraulic pressure, outwardly, toward the other end of the enclosure. 
     A further feature of the invention includes a vertical yoke member which is centered on and attached, by clevis, or other means, to the end of the piston rod. Two separate lift cables extend rearwardly, substantially in parallel, from the yoke at the end of the piston rod, towards the end of the enclosure where the cylinder body is located. One of the lift cables continues such horizontal extension to a point closely approximate to the end of the support enclosure member, where it is directed downwardly, at approximately a 90° angle, over a fixed pulley. The other lift cable extends in the same initial direction, until it reaches a pulley affixed within the enclosure at, or beyond the point where the piston rod enters and exits the cylinder body. The cable is reversed on the pulley, and extends, in substantially a 180° reversal, to another pulley located approximate to the opposing end of the support enclosure member. At that point it is directed downward approximately 90° over another fixed pulley. Both cables extend through openings provided in the base of the support enclosure member substantially vertically downward and are connected, respectively, at opposite ends, thereof, to the lift bed. 
     It is a further feature of the invention that the extension of the piston rod from the hydraulic cylinder, for a specified distance, occasions a rise in the lift bed of the boat hoist of an equivalent distance. 
     Another important feature of the invention limits rotational movement of the yoke at the end of the piston rod, and limits upward or downward movement, as well, thus minimizing wear on the hydraulic cylinder, at the point where the rod enters and exits. It is a feature of the invention, that this is accomplished by utilization of two tracks, which may be extruded ridges, a separate “C-channel” member in parallel with the piston rod, or other upper and lower track means, which contact the yoke at the end of the piston rod in a manner which allows it to slide back and forth horizontally, but which do not allow rotational, or vertical movement. 
     It is another feature of the invention, that, when a single hydraulic lift device is utilized on one side of a boat hoist assembly, with lift cables affixed to each end of the lift bed, of the hoist assembly, that the lift bed may be maintained in a substantially horizontal position, by utilization of one or more leveling cables. Each leveling cable is affixed to the upper end of a vertical stanchion, on the side of the boat lift opposite the location of the support enclosure member and primary components. The leveling cable runs substantially vertically down to the lift bed, where it contacts a pulley and is guided, directionally, approximately horizontally, along one end of the lift bed to the opposite side thereof, where it contacts another pulley and is thereby directed approximately 90° downwardly, where the cable is affixed to the base of the boat hoist either on the end of vertical stanchion or approximate thereto. The leveling cables may be used on either or both ends of the hoist assembly, and are optimally used on both. When one hydraulic lift device is utilized, with leveling cables at both ends, each leveling cable commences by attachment at the top of the end stanchion on the opposite side of the lift from the device, and runs, as stated, to the lower corner of the hoist assembly on the side where the hydraulic device is located. 
     According to a further feature of the invention, when a pair of hydraulic lift devices are utilized in parallel on opposite sides of the boat hoist assembly, the leveling cable at one end of the boat lift will commence affixed to the top of an end stanchion on one side of the boat lift, and the other end leveling cable will commence at the top of a stanchion on the opposing side of the hoist. 
     The leveling cables are installed and maintained under static tension. 
     It is a further feature of the invention that a power source for operating one or both hydraulic cylinders is self contained within the enclosure member and the hydraulic cylinder, either singly, or in parallel when two are provided, and may be activated by means of a self-contained on/off switch and, in some applications such on/off switch or function may be accomplished by utilization of radio frequency receiver unit located adjacent one of the cylinder bodies, within the enclosure member and a remote radio frequency sender unit. 
     A further feature of the invention, is that the self-contained power source may be a 12 volt battery affixed within the support enclosure member and, as a further feature of the invention the power source may be replenished by means of a rigid solar panel connected thereto, and outwardly affixed on the exterior of the hoist assembly. It is a further feature of the invention that where a pair of hydraulic lift devices are utilized in parallel, a single power source and common means of activating the hydraulic cylinders may be utilized. 
    
    
     The above and additional features of the invention may be considered and will become apparent upon review of the drawings in particular and the detailed description which follows. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following detailed description is best understood by reference to the following drawings, in which: 
     FIG. 1 is a side perspective view of a boat hoist having a pair of parallel mounted lift devices with the cover of the forward device removed. 
     FIG. 2 is a side view of the device as shown in FIG. 1, showing extension of the piston rod and the raised position of the lift bed coincident to such extension. 
     FIG. 3 is a side perspective view of a boat hoist having a single lift device, with the cover panel removed to expase the components thereof, and further demonstrating the inclusion of leveling cables. 
     FIG. 4 is a side view of the device shown in FIG. 3, showing extension of the piston rod from the hydraulic cylinder and the corresponding elevation of the lift bed coincident thereto. 
     FIG. 5 is a cross-sectional view of a forward or first end of a boat hoist having one hydraulic device, showing the relative relationship of the device, the lift bed, and a leveling cable. 
     FIG. 6 is a perspective view a boat hoist employing two hydraulic lift devices in parallel, with a rigid solar panel. 
     FIG. 7 is a cross-sectional view of a corner of a boat hoist showing a portion of the base, a corner stanchion, and configuration of a lift bed corner relative to the corner stanchion. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention boat hoist hydraulic lift device, broadly considered, includes a boat hoist assembly  10  and a rigid support enclosure  20 , which as stated below, may be provided singly as shown in FIGS. 3,  4  and  5 , or in tandem as shown in FIGS. 1,  2  and  6 , and in either case, permanently fastened to the hoist assembly  10 . A lift bed or deck  30  is also provided. 
     The hoist assembly  10  includes a generally rectangular rigid base frame  11 . In the preferred embodiment four vertical stanchions  12   a ,  12   b ,  12   c  and  12   d , extend upwardly from the four corners  13   a ,  13   b ,  13   c  and  13   d  of base frame  11 . The base frame  11  is supported by skids  14  located below corners  12   a ,  12   b ,  12   c  and  12   d . Struts  15  may be provided at angles between the base frame  11  and one or more of stanchions  12   a ,  12   b ,  12   c  and  12   d  to provide additional support. 
     In the preferred embodiment the rigid support enclosure  20  is a rigid box having a first end  20   a  and a second end  20   b . Enclosure  20  has a horizontal flat base panel  21  and a corresponding parallel flat top panel  22 . Base panel  21  has a first end edge  21   a , a corresponding with first end  20   a , a second end edge  21   b  corresponding with second end  20   b , a forward edge  21   c  and rearward edge  21   d . Top panel  22  has a corresponding first end edge  22   a , second end edge  22   b , forward edge  22   c  and rearward edge  22   d.    
     Base panel  21  has two openings  23 , located near first end  20   a , and  24 , located near second end  20   b.    
     A back panel  25  is also provided running between and connecting rearward edge  21   d  of base panel  21  and rearward edge  22   d  of top panel  22 , between first edges  21   a  and  22   a  and second edges  21   b  and  22   b , forming a unitary first end edge  26  and a unitary second end edge  27 . There is a first end panel  28  and second end panel  29  extending across and affixed, respectively, to first end edge  26  and second end edge  27 . The joining of base panel  21 , top panel  22 , back panel  25 , first end panel  28 , and second end panel  29  forms rigid support enclosure member  20 . 
     Rigid support enclosure  20  is rigidly affixed between the upper portions  16  of stanchions  12   a  and  12   b.    
     In the preferred embodiment of the invention, a front panel or cover  40  is provided. Front panel  40  opposes back panel member  25 . Panel  40  contacts the forward  40  edges  21   c  and  22   c  of base panel  21  and top panel  22  respectively and is removably held in place by a plurality of fasteners  41 , which in the preferred embodiment may be threaded screws or bolts. 
     When the front panel or cover  40  is in place the interior of support enclosure member  20  is effectively sealed from the elements. 
     Lift bed or platform  30  is generally rectangular as demonstrated in FIGS. 1,  3  and  6 . Platform  30  has a forward or first end  31  and rearward entry or second end  32 . Platform  30  is moveably held in a substantial horizontal plane between lowered position AA and raised position BB, as shown in FIGS. 2 and 4. Platform  30  in the preferred embodiment is also rectangular and may also be described as a frame  30  constructed of a first end beam or member  31 , a second end beam or member  32 , a forward side beam or member  33  and an opposing side beam or member  34 . Said members  31 ,  32 ,  33 , and  34  are joined at their adjacent ends to form the rectangular lift platform  30 . For purpose of this detailed description first end  31  is synonymous with first end beam or member  31  and rearward entry or second end  32  is synonymous with second end beam or member  32 . 
     In the preferred embodiment members  31 ,  32 ,  33  and  34  are hollow along their length for weight purposes and, as shown below, containment of moving elements therein. 
     The lift platform  30 , in the preferred embodiment includes boat skids  35  affixed by support members  36  attached to end members  31  and  32 . The lifting power of the device is provided by a hydraulic cylinder assembly as most clearly demonstrated in FIGS. 2 and 4. FIG. 2 depicts a hydraulic cylinder assembly  50  to be operated in parallel with a second assembly  50  on the opposite side of the hoist assembly  10 . FIG. 4 depicts the components of an assembly  50  which is utilized alone. Assembly  50  includes a hydraulic cylinder  51  which has a cylinder body  52  fixed within enclosure  20  with a closed end  53  aligned toward the first end  20   a  of the support enclosure member  20  and aligned lengthwise, substantially in horizontal parallel with such enclosure  20 . Opposite the closed end  53  a piston rod  54  is extendable from the cylinder body  52 , substantially horizontally toward the second end of enclosure support member  20 . A yoke member  55  is affixed to outer end  56  of the piston rod  54 , vertically centered and perpendicular to piston rod  54 . 
     In the preferred embodiment an upper guide track  57   a  and lower guide track  57   b  are fixed horizontally within the support enclosure structure  20  in parallel with piston rod  54  from the hydraulic cylinder body  52  to a position  58  proximate the second end  20   b  of the support enclosure structure  20 . Tracks  57   a  and  57   b  are located on opposite sides of piston rod  54  and are conformed to retain the yoke member  55  slidably between them with upper end  55   a  of yoke member  55  contacting track  57   a  and lower end  55   b  of yoke member  55  contacting lower track  57   b . The conformation of tracks  57   a  and  57   b  to yoke  55  prevents rotational and vertical movement of the yoke  55  and piston rod  54 , thus minimizing wear on cylinder body  52 . 
     In the preferred embodiment of the invention tracks  57   a  and  57   b  are formed by provision of a “C-channel” fitting. Other possible applications include extruded ridges on back panel  25  and separate track elements separately attached to said back panel  25 . 
     A first lift cable  60  is affixed to yoke  55  at its upper end  55   a . Lift cable  60  extends substantially horizontally to and over a first pulley  61  fixed within support enclosure member  20  proximate its first end  20   a . Cable  60  is directed over pulley  61  downward approximately 90° and continues to extend vertically downward through opening  23  until it reaches and is affixed to lift platform  30  at its first end  31 . In a preferred embodiment this at a fixed point  65 . 
     A second lift cable  62  is affixed to yoke  55  at its lower end  55   b . Lift cable  62  extends substantially horizontally parallel to lift cable  60  until it reaches center pulley  63 . Cable  60  is reversed approximately 180° over pulley  63  and further extends substantially horizontally to and over third pulley  64  fixed within support member  20  proximate its second end  20   b . Cable  62  is directed over pulley  63  downward approximately 90° and continues to extend vertically downward through opening  24  until it reaches and is affixed to lift platform  30  at its second end  32 , at fixed point  66 . 
     As shown in FIG. 2, extension of piston rod  54  to move yoke  55  from position CC to position DD (distance CD) moves lift platform  30  upward from position AA to position BB (distance AB). Distance AB is approximately equal to distance CD. 
     In the preferred embodiment of the invention stabilization of the horizontal inclination of the lift platform  30  when traversing between points AA and BB is maximized by the use of one or more leveling cables  70 . Two leveling cables  70   a  and  70   b  are partially shown in FIG.  3  and FIG. 4. A complete leveling cable  70  assembly is shown in FIG. 5, as cable  70   a.    
     Leveling cable  70   a  is affixed to the upper portion  16  of stanchion  12   c . It extends generally vertically downward to and under a first platform pulley  71  affixed to and horizontally aligned on the first end member  31  of lift platform  30  approximately 90° laterally and further extends along the length of first end member  31  to and over a second platform pulley  72  approximately 90° vertically downward where it is affixed at a point  73  on the base frame  11  on or proximate to stanchion  12   a.    
     In the preferred embodiment of the invention first end member  31  is hollow and the interior thereof provides an enclosure  74  which houses pulleys  71  and  72  and the traverse of leveling cable  70   a  between them. 
     In boat hoist  10  utilizing a single hydraulic cylinder  51  a second leveling cable using corresponding pulleys  71  and  72  is utilized with said cable affixed to the upper portion  16  of stanchion  12   d  traversing downward then along second end member  32  and downward to a corresponding point on the base frame  11  on or proximate to stanchion  12   b.    
     In boat hoist applications where two hydraulic cylinders  51  are used on opposite sides of the hoist assembly  11 , if leveling cables  70  are used, in the preferred embodiment the leveling cable  70  which corresponds with the second end  32  of the lift platform  30  would be initially affixed to the upper portion of stanchion  12   b , extend downward and under pulley  72 , along end member  32  and over pulley  71  and downward to a point  75  on base frame  11 , on or proximate to stanchion  12   d.    
     FIG. 7 shows a portion of a corner of base  11  including a cross section of a stanchion  12  and corresponding portion of lift platform  30  with alignment guide members  80  and  81  to maintain the position of platform  30  in relationship the base  11  and stanchions  12   a ,  12   b ,  12   c  and  12   d.    
     A battery  90 , which in the preferred embodiment is a 12 volt battery is included as a self contained power source for operation of the hydraulic cylinder  52 . In the preferred embodiment of the invention, as shown in FIG. 6, a rigid solar panel  91  is provided, to regenerate the power source  90 . An on/off switch mechanism  92  is provided to activate the horizontal cylinder. In the preferred embodiment the switch  92  is a radio frequency receiver, which may be activated by a remote sender unit. 
     Whereas, the preferred embodiment of the invention has been illustrated and described in detail, it will be apparent that various changes may be made in the disclosed embodiment without departing from the spirit of the invention.