Patent Publication Number: US-7594781-B1

Title: Lift boat leg

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Priority of U.S. Provisional Patent Application Ser. No. 60/941,429, filed Jun. 1, 2007, incorporated herein by reference, is hereby claimed. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable 
   REFERENCE TO A “MICROFICHE APPENDIX” 
   Not applicable 
   BACKGROUND 
   The present invention relates to lift boats or jack-up boats that feature a hull having a plurality of legs, each leg having an associated jacking mechanism that enables the hull to be elevated or lowered relative to the legs and wherein each leg has a load bearing pad that engages the seabed during use. More particularly, the present invention relates to an improved lift boat having an improved leg configuration that contributes buoyance by providing a specially shaped and watertight leg that has one or more racks that engage pinion gear(s) of a drive or jacking unit. 
   Lift boats are well known in the art. These devices are also referred to as jack up barges or jack up boats. Such vessels include a floating hull that allows the vessel to travel on a body of water. When the vessel reaches a selected locale, jacking units lower the legs and then elevate the barge or hull above the water surface so that the hull is not affected by substantial wave action. 
   Patents have issued for lift boats or jack up vessels. Possibly relevant examples (each incorporated herein by reference) can be found in the following table. 
   
     
       
         
             
             
             
           
             
                 
             
             
               U.S. 
                 
                 
             
             
               Pat. No. 
               Title 
               Issue Date 
             
             
                 
             
           
          
             
               2,308,743 
               Barge 
               Sep. 16, 1939 
             
             
               3,183,676 
               Mobile Sea Platform 
               Oct. 20, 1960 
             
             
               3,290,007 
               Jack Arrangement For A 
               Jun. 28, 1965 
             
             
                 
               Platform Structure 
             
             
               3,367,119 
               Flotation Device for Offshore 
               Jan. 20, 1966 
             
             
                 
               Platform Assembly 
             
             
               3,606,251 
               Leg Supported Offshore Structure 
               Nov. 14, 1969 
             
             
                 
               With Jacking Apparatus 
             
             
               3,750,210 
               Apparatus For The Construction 
               Aug. 7, 1973 
             
             
                 
               Of Bridges 
             
             
               3,945,450 
               Apparatus and Method For 
               Mar. 23, 1976 
             
             
                 
               Rendering An Offshore Drilling 
             
             
                 
               Platform Mobile 
             
             
               3,967,457 
               Self-elevating Offshore Drilling Unit Legs 
               Jul. 6, 1976 
             
             
               4,417,664 
               Method and Apparatus For 
               Nov. 29, 1983 
             
             
                 
               Mounting Lift Crane On Offshore Structures 
             
             
               4,456,404 
               Method and Apparatus For 
               Jun. 26, 1984 
             
             
                 
               Positioning A Working Barge Above 
             
             
                 
               A Sea Surface 
             
             
               4,482,272 
               Load Transfer And Monitoring 
               Nov. 13, 1984 
             
             
                 
               System For Use With Jackup Barges 
             
             
               4,505,616 
               Self-locking Chock System 
               Mar. 19, 1985 
             
             
                 
               For A Jack-up Rig Unit 
             
             
               4,589,799 
               Device For Locking Platform Of 
               May 20, 1986 
             
             
                 
               Offshore Structure 
             
             
               4,627,768 
               Locking Device For Oil Platforms 
               Dec. 9, 1986 
             
             
               4,678,165 
               Mode Of Construction Of Lifting 
               Jul. 7, 1987 
             
             
                 
               Mechanisms For Jack-up Platform And 
             
             
                 
               Lifting Mechanism For a Jack-up Platform 
             
             
               4,722,640 
               Slant Leg Offshore Platform 
               Feb. 2, 1988 
             
             
                 
               And Method Of Operating Same 
             
             
               4,813,814 
               Leg-holding Device For Offshore 
               Mar. 21, 1989 
             
             
                 
               Platform 
             
             
               5,139,366 
               Offshore Jackup Rig Locking 
               Aug. 18, 1992 
             
             
                 
               Apparatus And Method 
             
             
               5,580,189 
               Jack-up Rig Crane 
               Dec. 3, 1996 
             
             
               5,797,703 
               Elevating Unit For Use With 
               Aug. 25, 1998 
             
             
                 
               Jack-up Rig 
             
             
                 
             
          
         
       
     
   
   Some of these patented rigs/vessels employ an open truss or lattice type leg. For example, see U.S. Pat. No. 3,183,676 issued to R. G. Letourneau which shows an open truss or lattice type leg structure for a jack-up or lift boat. 
   BRIEF SUMMARY OF THE PRESENT INVENTION 
   In one embodiment, the present invention provides an improved jack up vessel that includes a hull, a plurality of legs (preferably three), a plurality of pads, one pad attached to each leg, and a jacking mechanism for moving each leg upward and downward. Each leg is a triangular, non open truss leg having a generally continuous outer wall or walls that envelop an interior buoyant cavity. Each such buoyant cavity contributes buoyancy to the vessel. 
   There are multiple advantages of this triangular non open truss leg arrangement. Vortex shedding is eliminated or minimized. Harmonic Rhythmic movement is eliminated or minimized. Provides a transitional leg design between a traditional columnar lift boat leg design and a triangular/lattice legs, i.e., leg lengths of about 260′ and greater. Provides buoyancy to reduce bottom bearing pressure unlike truss/lattice legs that provide no buoyancy. Such truss/lattice legs increase bottom bearing pressure due to their weight. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     For a further understanding of the nature, objects, and advantages of the present invention, reference should be made to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein: 
       FIG. 1  is a perspective view of one preferred embodiment of the apparatus of the present invention; 
       FIG. 2  is a top plan view of one preferred embodiment of the apparatus of the present invention; 
       FIG. 3  is a fragmentary view taken along lines  3 - 3  of  FIG. 1 , illustrating the preferred embodiment of the apparatus of the present invention; 
       FIG. 4  is a fragmentary view of an alternative embodiment of the apparatus of the present invention; 
       FIG. 5  is a fragmentary view of another alternative embodiment of the apparatus of the present invention; 
       FIG. 6  is a fragmentary view of another alternative embodiment of the apparatus of the present invention; 
       FIG. 7  is a partial sectional elevation view of the preferred embodiment of the apparatus of the present invention; 
       FIG. 8  is a sectional view taken along lines  8 - 8  of  FIG. 7 ; 
       FIG. 9  is a sectional view taken along lines  9 - 9  of  FIG. 7 ; and 
       FIG. 10  is a sectional view taken along lines  10 - 10  of  FIG. 7 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows the preferred embodiment of the apparatus of the present invention, designated generally by the numeral  10 . Lift boat or jack up vessel  10  has a hull  11  and a plurality of legs (e.g., three legs  12 ,  13 , and  14 ). Leg  12  can include pad or foot  15 . Leg  13  can include pad or foot  16 . Leg  14  can include pad or foot  15 . Each leg  12 ,  13 ,  14  is preferably a closed wall, watertight member. Each leg  12 ,  12 ,  14  preferably has a generally triangular transverse cross section, such as those shown in  FIGS. 3-10 . Further, each leg  12 ,  13 ,  14  is preferably of a closed wall, non-lattice or non-truss construction. Each leg  12 ,  13 ,  14  can be of welded steel construction, for example. 
   In one embodiment a cross section comprises three sides which can be triangular in shape. In one embodiment at least one lifting portion is included which includes a lifting rack. In one embodiment a plurality of lifting portions are included, each including a lifting rack. In one embodiment each lifting rack includes a plurality of lifting threads. 
     FIG. 3  shows one example of a closed wall construction (i.e. non-lattice or non open truss) for legs  12 ,  13 ,  14  with cross section  20 , It comprises side  31 , side  32 , and side  33 . In  FIG. 3 , lifting portion  35  can include a lifting rack  34  that is substantially parallel to side  31 . Such a rack  34  is engaged by a lifting unit or jacking unit  100  that provides one or more pinion gears  66 . 
     FIG. 4  shows another example of a non-truss construction for a leg having cross section  21 . It comprises side  41 , side  42 , and side  43 . Lifting portion  45  can include a lifting rack  44  that is substantially parallel to side  41 . Lifting portion  46  can include a lifting rack  44  that is substantially parallel to side  42 . Lifting portion  47  can include a lifting rack  44  that is substantially parallel to side  43 . 
     FIG. 5  shows another example of a non-truss construction for a leg having cross section  22 . It comprises side  51 , side  52 , and side  53 . Angles  23 ,  24 , and  25  are shown. Lifting portion  55  can include a lifting rack  54  and intersect the angle made by sides  51  and  53  (angle  23 ). Preferably, it substantially bisects the angle created by sides  51  and  53 . Lifting portion  56  can include a lifting rack  54  and intersect the angle  24  made by sides  51  and  52 . Preferably, it substantially bisects the angle created by sides  51  and  52  (angle  24 ). Lifting portion  57  can include a lifting rack  54  and intersect the angle made by sides  52  and  53  (angle  25 ). Preferably, it substantially bisects the angle created by sides  52  and  53  (angle  25 ). 
     FIG. 6  shows another example of a non-truss construction for a leg having cross section  26 . It comprises side  61 , side  62 , and side  63 . Lifting portion  65  can include a lifting rack  64  and be substantially perpendicular to any side, such as side  63  and substantially bisect such side (e.g.  63 ) as shown. 
   Legs  12 ,  13 , and  14  protrude through hull  11 . Each leg  12 ,  13 ,  14  interfaces with a jacking portion  100  to facilitate the upward or downward movement of hull  11  upon the legs  12 ,  13 ,  14 . Each leg  12 ,  13 , and  14  can have one or more jacking portions  100 . Upward and downward movement is schematically indicated by arrows  19  in  FIG. 1 . 
   For example, jacking mechanism  100  moves hull  11  along leg  13  in either an upward or downward motion as is required. Jacking portion  100  moves along the length  18  of lifting portion  35  by virtue of a lifting rack  34  which includes a plurality of teeth that engage the teeth of a pinion gear  66  of mechanism  100 . 
   As a result of the leg cross sectional shapes  20 ,  21 ,  22 ,  26  and closed wall construction ( FIGS. 3-6 ), the problem of vortex shedding is minimized and possibly eliminated. Further, the problem of harmonic rhythmic movement is minimized and possibly eliminated. 
   In one embodiment each leg  12 ,  13 ,  14  can provide a buoyancy of about 5, 10, 15, 20, 25, 30, and 35 percent of the overall weight of the vessel. In other embodiments the buoyancy provided by each leg  12 ,  13 ,  14  can range between any to of the above specified percentages (5-35%). 
   In one embodiment each leg  12 ,  13 ,  14  can be 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 125, 150, 175, 200, 250, 300, 350, 400 feet or longer. In other embodiments the length of each leg  12 ,  13 ,  14  can range between any two of the above specified lengths. 
   In one embodiment each leg can have a cross section of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 175, 200, 225, or 250 square feet or larger. In other embodiments the cross sectional area of each leg can range between any two of the above specified areas. 
   Each of the legs  12 ,  13 ,  14  shown in  FIGS. 1-6  is a closed wall buoyant structure. The sidewalls such as the walls  31 ,  32 ,  33  in  FIG. 3  provide a closed wall buoyant structure in combination with an upper or top wall  27  and a welded, sealed arrangement that connects the bottom of each leg  12 ,  13 ,  14  to its foot or pad  15 ,  16 ,  17 . Each of the legs shown in  FIGS. 4 ,  5 ,  6  would likewise provide an upper or top wall  27  and a sealed connection of its foot to the lower end portion of the leg  12 ,  13 ,  14  as shown in  FIG. 2 . 
     FIGS. 7-10  show that each leg  12 ,  13 ,  14  can have a shape or cross section  28  defined by walls  38 ,  39 ,  40  to provide a closed wall buoyant chamber  37 . As with the embodiment of  FIGS. 1-6 , the legs  12 ,  13 ,  14  shown in  FIGS. 7-10  can provide a lifting portion and a lifting rack. In  FIG. 8 , the lifting portion  48  provides lifting rack  49  that forms an angle with each of the sides  38 ,  39 , preferably an obtuse angle. The side  40  is co-linear with two lifting portions  48 , each having its own lifting rack  49  as shown. 
     FIG. 8  illustrates that internal bracing can be employed for the leg  12 ,  13 ,  14  such as the internal brace  29  that extends perpendicularly from and which bisects the leg  40 . In  FIG. 9 , internal brace  30  is a diagonally extending brace that bisects the side  38  and that extends perpendicularly therefrom. The internal brace  36  in  FIG. 10  bisects the side  39  and extends perpendicularly therefrom. Such braces  29 ,  30 ,  26  can be of welded steel construction, for example. 
   The following is a list of suitable parts and materials for the various elements of the preferred embodiment of the present invention: 
   
     
       
         
             
          
             
                 
             
             
               PARTS LIST 
             
          
         
         
             
             
          
             
               Reference Numeral 
               Description 
             
             
                 
             
          
         
         
             
             
          
             
               10 
               jack up vessel 
             
             
               11 
               hull 
             
             
               12 
               leg 
             
             
               13 
               leg 
             
             
               14 
               leg 
             
             
               15 
               pad or foot 
             
             
               16 
               pad or foot 
             
             
               17 
               pad or foot 
             
             
               18 
               lifting portion 
             
             
               19 
               arrow 
             
             
               20 
               cross section 
             
             
               21 
               cross section 
             
             
               22 
               cross section 
             
             
               23 
               angle 
             
             
               24 
               angle 
             
             
               25 
               angle 
             
             
               26 
               cross section 
             
             
               27 
               top wall 
             
             
               28 
               cross section 
             
             
               29 
               brace 
             
             
               30 
               brace 
             
             
               31 
               side 
             
             
               32 
               side 
             
             
               33 
               side 
             
             
               34 
               lifting rack 
             
             
               35 
               lifting portion 
             
             
               36 
               brace 
             
             
               37 
               buoyant chamber 
             
             
               38 
               side 
             
             
               39 
               side 
             
             
               40 
               side 
             
             
               41 
               side 
             
             
               42 
               side 
             
             
               43 
               side 
             
             
               44 
               lifting rack 
             
             
               45 
               lifting portion 
             
             
               46 
               lifting portion 
             
             
               47 
               lifting portion 
             
             
               48 
               lifting portion 
             
             
               49 
               rack 
             
             
               51 
               side 
             
             
               52 
               side 
             
             
               53 
               side 
             
             
               54 
               lifting rack 
             
             
               55 
               lifting portion 
             
             
               56 
               lifting portion 
             
             
               57 
               lifting portion 
             
             
               61 
               side 
             
             
               42 
               side 
             
             
               63 
               side 
             
             
               64 
               lifting rack 
             
             
               65 
               lifting portion 
             
             
               66 
               pinion gear 
             
             
               100 
               jacking unit 
             
             
                 
             
          
         
       
     
   
   All measurements disclosed herein are at standard temperature and pressure, at sea level on Earth, unless indicated otherwise. 
   The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.