Abstract:
A boat lifting assembly includes a cradle for carrying a boat mounted between three pilings on each cradle side. A pair of support housings is affixed to the pilings on each cradle side. A pair of hydraulic lifts are housed in the housings and connected to the cradle for moving same vertically. Each lift includes a horizontally extensible piston carrying a piston pulley block and a stationary hydraulic cylinder. Three cables have one end portion threaded between the pulleys of the block and the cradle. Transition pulleys are supported by the housing and direct the cable vertically for moving the cradle when the block is moved. Additional pulleys and various anchor points may be employed to provide for vertical lifts of 1.5, 2.0 and 3.0 times the distance of movement of the piston. The housings are in the same plane as the cradle deck and/or dock.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is related to U.S. application Ser. No. 10/659,516, entitled BOAT LIFT, filed Sep. 11, 2003 by the present applicant. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not Applicable.  
       REFERENCE TO A MICROFICHE APPENDIX  
       [0003]     Not Applicable.  
       BACKGROUND OF THE INVENTION  
       [0004]     1. Field of the Invention  
         [0005]     This invention relates to a boat lift and, more particularly, to a hydraulically operated boat lift including a plurality of pulleys for raising and lowering a boat along two pilings.  
         [0006]     2. Related Art  
         [0007]     A multiplicity of boat lifts have been employed by prior art for docking vessels or lifting them out of the water for servicing. One type of such boatlifts is hydraulically operated by a plurality of pulleys and cables. However, conventional hydraulic boat lifts employing such pulleys and cables typically require unsightly overhead steel construction and are free standing, i.e. not secured to a dock, as illustrated in  FIG. 1  of published U.S. Patent Application No. 2002/0150427 and U.S. Pat. No. Re. 32,118 both to Godbersen, for example.  
         [0008]     As a result, such boat lifts must be supported by four pilings and require a large amount of space for allowing a boat to maneuver therebetween. In addition, such boatlifts typically position their mechanical/electrical components at heights well above an operator&#39;s reach thereby making access to such components difficult. None of the prior art lifts are desired.  
         [0009]     In view of the foregoing background, it is therefore an object of the present invention to provide a hydraulically operated boat lift supportable by only two pilings with readily accessible components.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010]     In one aspect of the present invention there is provided an assembly for lifting a boat including a cradle for carrying a boat, a plurality of spaced vertically disposed pilings on each side of the cradle, each piling having a lower portion mounted into a floor of a body of water and an upper portion extending thereabove; a pair of support housings affixed to upper portions of the plurality of pilings on each side of the cradle. A pair of lifting means are housed in and mounted on the support housing and connected to the cradle for moving the cradle vertically, each lifting means including a horizontally extensible piston carrying a piston pulley block at its forward end, a stationary hydraulic cylinder mounted to the housing, and cable means having one end portion threaded around the pulley block and another end portion connected to the cradle. Transition pulley means are supported by the housing and carry a portion of the cable means to direct another end portion of the cable means vertically for moving the cradle when the piston pulley block is moved horizontally by the piston, and hydraulic control means for operating each hydraulic cylinder. The cradle includes three spaced structural members having opposite end portions and extending laterally of the cylinder and piston, the cable means includes three cables, each cable having a first end attached to an end portion of the member and another end portion threaded around the piston pulley block and affixed to the housing. One member is disposed adjacent and below a stern of a boat carried by the cradle, a second member is disposed adjacent and below amidships of a boat carried by the cradle, and a third member is disposed adjacent and below a bow of a boat carried by the cradle. Each transition pulley means includes a down bow pulley, a down amidships pulley, and a down stern pulley, each down pulley being disposed vertically to dispose an axis of rotation of each down pulley horizontally. Each housing includes a lower wall, each lower wall of the housing has spaced slots, each down pulley being mounted with its axis horizontal and extending partially through the slot with its axis in the housing. Each piston pulley block includes three piston pulleys, each piston pulley being mounted horizontally to dispose an axis of rotation of the piston pulley vertically.  
         [0011]     In another aspect of the present invention there is provided motion-sensing means for determining the distance of rotation of one down pulley of each lifting means and providing an output signal indicative of such measured distance of rotation. The control circuit means receives the output signals for operating the hydraulic control means in response to the difference between the control signals.  
         [0012]     In a further aspect of the present invention there is provided an assembly for lifting a boat comprising a cradle for carrying a boat, three vertically disposed pilings on each side of the cradle and the pair of support housings are each affixed to the upper portion of each respective piling. Each cable is threaded around the pulley block and connected to the cradle to provide that the cradle end of each cable moves vertically twice the distance of the movement of the pulley block by said piston. Also included are three redirect pulleys mounted in a fixed position on each housing, each cable having one end portion affixed to the cradle and another end portion affixed to the pulley block, each cable being threaded around the pulleys of the pulley block and a redirect pulley to provide that the cradle moves three times the distance of movement of the pulley block by the hydraulic means. Alternately, three redirect pulleys are mounted in a fixed position on each housing, each cable having one end portion affixed with respect to the housing and another end portion affixed to the pulley block, three cradle pulleys mounted on each side of the cradle, each cable being threaded around the pulleys of the pulley block and a respective redirect pulley and respective cradle pulley to provide that the cradle moves one and one half times the distance of movement of the pulley block by the hydraulic means.  
         [0013]     In a further aspect of the invention there is provided an assembly for lifting a boat comprising a cradle for carrying a boat, a plurality of spaced vertically disposed pilings on each side of the cradle, each piling having upper and lower end portions with the upper end portions being located above water at a predetermined height, a pair of elongated support housings being affixed to respective the upper portion of the plurality of the pilings on each side of the cradle, a pair of hydraulic lifting means disposed in respective housing for moving the cradle upwardly and downwardly, each hydraulic lifting means including a cylinder affixed to the housing and a movable piston, a plurality of pulleys and a plurality of cables, the cylinder and piston moving in a substantially horizontal direction, the cradle including a deck part substantially horizontally aligned with a dock, and the housings having an upper wall substantially parallel to and parallel with the deck part of said cradle. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0014]     The novel features believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:  
         [0015]      FIG. 1  is a perspective view of the boat lift according to the present invention;  
         [0016]      FIG. 2  is a perspective view of the various components of the boat lift of  FIG. 1  with sides and covers not shown;  
         [0017]      FIG. 3  is a motion diagram of the configuration of a first cable in accord with the present invention;  
         [0018]      FIG. 4  is a motion diagram of the configuration of a second cable in accord with the present invention;  
         [0019]      FIG. 5  is a motion diagram of the configuration of a third cable in accord with the present invention;  
         [0020]      FIG. 6  is a top diagrammatic view of the cable connections and pulleys of  FIGS. 3-5 ;  
         [0021]      FIG. 7  is a perspective view of the mounting of the aft end of the port CHU;  
         [0022]      FIG. 8  is a perspective view of the amidships portion of the port CHU;  
         [0023]      FIG. 9  is a perspective view of the forward down transition pulley of the port CHU;  
         [0024]      FIG. 10  is a motion diagram of the configuration of a first cable in accord with another embodiment of the invention;  
         [0025]      FIG. 11  is a motion diagram of the configuration of a second cable in accord with the embodiment of  FIG. 10 ;  
         [0026]      FIG. 12  is a motion diagram of the configuration of a third cable in accord with the embodiment of  FIGS. 10 and 11 ;  
         [0027]      FIG. 13  is a top diagrammatic view of the cable connections and pulleys of  FIGS. 10-12 ;  
         [0028]      FIG. 14  is a detail of one embodiment of cable termination in accord with the present invention;  
         [0029]      FIG. 15  is a detail of an alternate cable termination in accord with the present invention;  
         [0030]      FIG. 16  is a perspective view of the pulley motion sensing apparatus in accord with the present invention;  
         [0031]      FIG. 17  is a block diagram of the feedback system that receives information from the apparatus of  FIG. 16 ;  
         [0032]      FIG. 18  illustrates an alternate routing of the cables in accord with the present invention;  
         [0033]      FIG. 19  is pictorial end view illustrating the relationship between the cable-handling units, boat platform and pilings in accord with the present invention; and  
         [0034]      FIG. 20  is a detail of  FIG. 19 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]     The boat lift  10  design ( FIG. 1 ) is based on a hydraulically operated Cable-Handling Unit or “CHU” that “shortens” the lifting cables as opposed to “winding” the cable on a rotating drum or pipe.  
         [0036]     The use of a hydraulic cylinder ensures that the maximum amount of cable “gathered” or “released” is determined by the physical length of the cylinder rod stroke. This relationship never changes. Maximum lift travel is therefore not dependent on the use of a mechanical limit switch or similar devices.  
         [0037]     This feature is what a lift  10  is dependent on. Because the possibility of crashing, or “two-blocking” the moving apparatus against the non-moving machinery is impossible, the typical safety margin of 16 to 18 inches between these two elements can be reduced to less than 1 inch.  
         [0038]     The lift  10  is comprised of a starboard and port CHU shown generally at  15 ,  14 . A moving deck or cradle structure of members  20  disposed athwartships below a boat, hydraulic power supplies  21  and  22  and six support pilings. Depending on the configuration, two or three cables are used on each CHU.  FIG. 2  illustrates the CHU&#39;s  18 ,  19  of lift  17  in more detail. To facilitate explanation, only the starboard CHU  18  as configured for the “double pass” three-cable platform lift will be discussed.  
         [0000]     Cable Routing  
         [0039]     Cable routing for the CHU is shown in  FIGS. 3-9 . There are eight pulleys and three cables employed. Cable  24 , the Stern Lift Cable ( FIG. 3 ) uses two pulleys: one 180 degree wrap pulley  27  in the cylinder rod-end pulley block assembly and one 90 degree wrap “down transition” pulley  29 , part of the main pulley block assembly.  
         [0040]     Cable  32 , the Amidships Lift cable ( FIG. 4 ) utilizes three pulleys: One 180 degree wrap pulley  37  in the cylinder rod pulley block assembly, one 180 degree wrap pulley  35 , part of the main pulley block assembly and one 90 degree wrap “down transition” pulley  38 .  
         [0041]     Cable  41 , the Forward Lift Cable ( FIG. 5 ), utilizes three pulleys: One 180 degree wrap pulley  44  in the cylinder rod-end pulley block assembly  42 ,  43 , one 180 degree wrap pulley  46  in the main pulley block assembly, and one 90 degree wrap “down transition” pulley  47 .  
         [0042]     All cable stationary or “bitter-ends” are attached to the CHU cable anchor block  55  ( FIG. 6 ) at points  28 ,  36 ,  45 . Preferably, a single cylinder rod-end pulley  53 ,  54  is used to move platform  13  up and down.  
         [0043]     The “free-ends” of cables  24 ,  32 , and  41  are attached to the moving platform cross members  20 .  
         [0044]     In the “double-pass” configuration, the total platform travel is equal to 2× cylinder rod travel. A  6 ′ cylinder rod stroke yields  12 ′ of platform travel.  
         [0045]     Observation of safe working limits on wire rope are the primary limitations of the hydraulic operated boat hoist. The easiest way to increase the lifting capacity of the lift is to run the free end of the lifting cable through an additional pulley installed on the platform cross-member. Attaching the free end to new purchase point  93  ( FIG. 15 ) effectively reduces the load on the lifting cable by 50%. Although increases in lifting capacity are realized immediately, the length of cable gathered by the respective CHU  14 ,  15  is immediately reduced by 50%.  
         [0046]     There are two ways to overcome the disadvantage of the cross-member mounted pulley.  
         [0047]     1) Increase the length of the hydraulic cylinder.  
         [0048]     2) Increase the number of pulleys in the CHU.  
         [0049]     Increasing the length of the hydraulic cylinder rod by  1 ′ increases the overall length of the extended cylinder and rod by  2 ′. To obtain 12′ of travel as desired, a cylinder of  12 ′ would be required. The disadvantages are obvious.  
         [0050]     Increasing the number of pulleys within the CHU is a more feasible solution. A triple pass, 11-pulley CHU is shown in  FIGS. 10-13 . The primary difference is adding another set of redirect pulleys and moving the cable anchor from its stationary position, to the modified rod-end pulley block assembly. The triple pass, 11-pulley configuration provides an advantage of 3:1 (cable gathered: cylinder length).  
         [0051]      FIGS. 10-12  illustrate the triple pass configuration. In  FIG. 10 , first cable  60  is wound around pulleys  63 ,  59  and redirect pulley  62  and is operated by cylinder/piston  57 ,  58 . The rod end pulley  59  is carried by anchor point  61 . Lift portion of cable  60  terminates in attachment bracket. Second cable  68  is wound around pulleys  70 ,  71 ,  72  and redirect pulley  73  and is anchored at  69 . Cylinder  66  operates rod  67  to control cable lift portion  74  terminating in attachment bracket  75 . In  FIG. 12  the third cable  78  is wound around pulleys  80 ,  81  and redirect pulleys  84 ,  85  and is anchored at  79 . Cylinder/piston  76 ,  77  operates lift portion  82  of cable  78  having attached bracket  83 .  
         [0052]     Preferably, as shown in  FIG. 13 , cable anchor  88  is the point of attachment ( 61 ,  69 ,  79 ) and is moved by a single cylinder/piston  86 ,  87  and pulley block  89  which carries pulleys  59 ,  70 ,  80 . Fixed pulley block  90  carries pulleys  62 ,  73 ,  85  and fixed pulley block  91  carries pulleys  72 ,  73 . Pulley  63  is mounted via block  92 .  
         [0053]     The primary disadvantage to this configuration is the increased load exerted on the main pulley block assembly  88  and the hydraulic cylinder  86 ,  87 . On the double pass configuration, the cylinder must lift 2×0.5 total load. The triple pass configuration, the cylinder must lift 3×0.5 total load. When using the additional pulley on the lifting beam, the triple pass configuration cylinder load calculation can be expressed: 3×0.25 total load. Therefore, it becomes advantageous to utilize the triple pass configuration only when also utilizing the additional pulley cradle  94  installed on the platform cross-member ( FIG. 15 ) via clamp  95  and post  93  which now becomes a 1.5:1 advantage.  
         [0054]      FIG. 18  illustrates an alternate routing of the cables otherwise shown in  FIG. 13 . Cylinder  105  operates piston rod  106  to which rod end pulley block  107  which is narrower than the block  89  of  FIG. 13 . Pulley stack  108  is carried by block  107  and also includes cable anchor point  109 .  
         [0055]     Redirect pulley blocks  110  and  111  are substantially the same as blocks  90 ,  91  of  FIG. 13 . Pulleys  108  are preferably approximately 50% larger than the pulleys  62 ,  73 ,  85  and  72 ,  84  carried by blocks  91  and  90  respectively to allow for proper cable clearance with the narrower pulley block  107 . In addition, the width of the CHU&#39;s  14 A and  15 A in this embodiment of the invention is less than CHU&#39;s  14 ,  15  discussed hereinabove.  
         [0056]      FIGS. 19 and 20  illustrate the platform  13  including upper surface deck  112  with members  113  and associated connectors as understood in the art. Area  114  is shown enlarged in  FIG. 20 . Vertical motion upwardly and downwardly is indicated at arrow  115 . All construction materials and methods are chosen to be appropriate in the marine environment in which the lift is to be built and operated.  
         [0000]     Closed Loop Feedback System  
         [0057]     When utilizing two independent hydraulic drive mechanisms including pump  101 , bypass valve  103  and control valve  102 , a means of keeping the platform or cradle “level” from port to starboard as it travels from “stop to stop” can be done without interference (fully automatic) from the lift operator. The hydraulic lift automatic leveling system consists of four main parts:  
         [0058]     1. Target Wheel: A ferrous metal sprocket  96  with 120 teeth or grooves around the 5.5″ diameter periphery. The wheel is coupled to the side of the FORWARD WIRE down transition sheave via conventional bolts or other appropriate means (One each is mounted within the port/starboard CHU).  
         [0059]     2. Proximity Sensor: “hall effect”  97  A device is mounted by bracket  99  ( FIG. 16 ) used to read or “count” the “high spots” or teeth on the ferrous metal target wheel. As the rope sheave/target wheel rotates,  120  “couples pulses” are generated every complete revolution. This yields one pulse per 0.125″ (1/8 th .″) of rope travel.  
         [0060]     3. Programmable Relay: An electronic device (micro controller PLC  100 ) is known to the art and is used to count pulses generated from each Cable Handling Unit (port/starboard target wheel  96 ). An uneven count (disparity) greater than five pulses between port and starboard target wheel represents an “out of tolerance” condition that is rectified in the form of “interruption” of CHU&#39;s drive solenoid. Simply, the side (port or starboard) that “leads is forced to stop briefly to “null” the error signal.  
         [0061]     4. Directional Valves: Port and starboard directional valves  104  are the final component of the feedback subsystem. Whether traveling up or down, when an “out of tolerance” condition is detected, the directional valve  104  for the leading cylinder is forced by the PLC  100  to “center” (bypass fluid) for predetermined short intervals of a duration sufficient to “null” (reduce to zero), pulse disparity.  
         [0062]     While the lift platform  13  is moving up or down, the “closed loop” feedback subsystem continuously monitors, compares and when necessary, corrects out of tolerance conditions instantaneously. In the event of “Auto Level Control” equipment failure, a means is provided to level the lift “manually” utilizing a push-button on the electronics cabinet. Note: An optical encoder can be used in place of the target wheel and proximity sensor.  
         [0063]     The target wheel  96 , proximity sensor  97  and directional valve  102  are contained within the respective CHU assembly. (Port/starboard) The PLC device  100  is contained within the electronic cabinet mounted on the dock structure.  
         [0064]     In all embodiments, platform deck  112  is preferably flush with the surface of CHU&#39;s  14  and  15  and with the surface of dock  16 . Pilings  23 , units  14  and  15 , cradle members  20  and the ultimate vertical movement of the apparatus are all of predetermined height and dimension for the location and intended use including the length and weight of the boat  11  to be lifted.  
         [0065]     While the invention has been described with respect to certain specific embodiments, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended, therefore, by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.