Abstract:
A vertical translation mechanism for reconfiguring the hull form of a reconfigurable vessel having independently movably side hulls and a center hull is disclosed. The vertical translation mechanism includes a hydraulic-force actuator and a nonmetallic bearing. The hydraulic force actuator comprises a rod that is disposed within a hydraulic cylinder. Responsive to changes in hydraulic pressure in the cylinder, the rod is extended or retracted therefrom. Movement of the rod controls the vertical translation of the center hull and its rotational attitude relative to the side hulls.

Description:
STATEMENT OF RELATED CASES  
       [0001]     This case claims priority of U.S. provisional patent application 60/710,171, which was filed on Aug. 22, 2005 and is incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to sea-faring vessels. More particularly, the present invention relates to a vessel having a multiple, reconfigurable hulls and a variable draft.  
       BACKGROUND OF THE INVENTION  
       [0003]     Vessel hulls have traditionally been optimized for use in either shallow water or in deep water. For example, to navigate shallow waters, a relatively flat hull is used to maximize displacement and minimize draft. On the other hand, vessels that operate in deep waters frequently have v-shaped hulls that provide deep draft for good seakeeping.  
         [0004]     If a vessel is designed for use in shallow waters, its performance in deep waters will be compromised, and vice-versa. This has spurred the development of variable-draft vessels, which are designed to operate well in both shallow and deep waters.  
         [0005]     As the name implies, a variable-draft vessel is capable of varying its draft to accommodate changes in water depth or mission requirements. A variable-draft vessel that is disclosed in U.S. Pat. No. 6,877,450 B2 is capable of reconfiguring its hull form to change draft. The vessel includes a flat, center hull that is coupled to two side or outer hulls. The center hull is vertically movable relative to the side hulls to vary draft.  
         [0006]     According to the patent, the center hull can be moved above or below the waterline. When the center hull is above the waterline, all buoyancy is provided by the side hulls, and the vessel takes maximum draft. As the center hull dips below the waterline, it contributes to the buoyancy provided by the side hulls. As a consequence, vessel draft is reduced.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention provides a vertical translation mechanism for reconfiguring the hull form of a reconfigurable, variable-draft vessel. Such a vessel includes a center hull that is flanked by two side hulls. The side hulls typically contain the propulsion mechanism(s) for the vessel. The center hull contains the pilot house, passengers, and vehicle storage.  
         [0008]     In accordance with the illustrative embodiment of the present invention, the vertical translation mechanism includes a hydraulic force actuator and a nonmetallic bearing.  
         [0009]     The hydraulic force actuator comprises a rod that is disposed within a hydraulic cylinder. Powered by hydraulic force, the rod is extended or retracted from the hydraulic cylinder. Movement of the rod controls the vertical translation of the center hull and its rotational attitude relative to the side hulls.  
         [0010]     A nonmetallic bearing, which is (indirectly) coupled at one end to one of the side hulls, slides along a guide post that is anchored to the center hull. The coupling to the side hull provides a structural connection to transmit lateral plane forces to the side hulls.  
         [0011]     In the illustrative embodiment, four vertical translation mechanisms are positioned at four corners of the center hull. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  depicts a reconfigurable, variable-draft vessel in accordance with the illustrative embodiment of the present invention.  
         [0013]      FIG. 2  depicts the vessel of  FIG. 1  in a deep-draft mode configuration.  
         [0014]      FIG. 3  depicts the vessel of  FIG. 1  in a shallow-draft mode configuration.  
         [0015]      FIG. 4  depicts a top view of vessel of  FIG. 1 , showing four vertical translation mechanisms.  
         [0016]      FIG. 5  depicts a top of the vertical translation mechanism.  
         [0017]      FIG. 6  depicts a side view of the vertical translation mechanism when the vessel is in a deep-draft mode configuration.  
         [0018]      FIG. 7  depicts a side view of the vertical translation mechanism when the vessel is in a shallow-draft mode configuration. 
     
    
     DETAILED DESCRIPTION  
       [0019]      FIG. 1  depicts re-configurable, variable-draft vessel  100  in accordance with the illustrative embodiment of the present invention. Vessel  100  includes side hulls  102 , struts  104 , sponson  106 , and deck house  108 . The deck house, which is also referred to as the center hull, incorporates a pilot house, and, internally, a (lower) deck for vehicles and an (upper) deck for passengers.  
         [0020]     Vessel  100  is capable of reconfiguring between deep-draft modes (i.e., catamaran and SWATH) and shallow-draft modes (i.e., barge and wet-deck). To do so, vessel  100  incorporates vertical translation mechanism  110  for moving the center hull  108  relative to side hulls  102 . For vessel  100 , four vertical translation mechanisms  110  are used, wherein two mechanisms are disposed on each side of center hull  102 , one located aft and one located toward the stern.  
         [0021]      FIG. 2  depicts vessel  100  in a typical deep-draft mode, wherein bottom  212  of center hull  108  is disposed well above side hulls  102  and above the waterline WL. Since center hull  108  does not typically contact the water when vessel  100  is configured in a deep-draft mode, vessel  100  can travel at higher speeds or with improved sea keeping relative to a shallow-draft mode.  
         [0022]      FIG. 3  depicts vessel  100  in a typical shallow-draft mode, wherein the bottom of side hulls  102  and bottom  212  of center hull  108  are substantially co-planar. In the shallow-draft mode configuration that is depicted in  FIG. 3 , a portion of side hulls  102  and center hull  108  are submerged. In the shallow-draft mode, vessel  100  can approach a shoreline to launch or recover vehicles and personnel (e.g., via ramp  314 , etc.).  
         [0023]     Referring generally to  FIGS. 2-7 , each vertical translation mechanism  110  includes bearing  214 , guide rod  216 , two hydraulic cylinders  218 , two rods  220  which are coupled to the hydraulic cylinders, and support plate  416 . Vertical translation mechanism  110  is driven by a pump, which is not shown. Those skilled in the art, after reading the present disclosure, will know how to size and operate a pump to power hydraulic vertical translation mechanism  110 .  
         [0024]     Guide rod  216  and rods  220  are fixed to a surface of center hull  108  near a marginal region thereof. Guide rod  216  is received by support plate  416  and bearing  214 . Support plate  416  is attached to sponson  106 . Hydraulic cylinders  218  are supported by support plate  416 . Since side hulls  102  are attached, via struts  104 , to sponson  106 , support plate  416  is considered to be “coupled” to the side hulls. Furthermore, center hull  102  is considered to be “movably coupled” to side hulls  102  due to this structural relationship.  
         [0025]     Under hydraulic pressure that builds in hydraulic cylinders  218 , rods  220  are pushed downward from the hydraulic cylinders. As rods  220  are extended, center hull  108  is pushed downward. Conversely, as rods  220  are retracted in hydraulic cylinders  218 , center hull  108  is pulled upward. The guide rod freely slides through bearing  214 , which is formed of an elastomeric material.  
         [0026]     In this fashion, hydraulic cylinders  218  and rods  220  perform vertical translation of center hull  108 . The use of multiple (e.g., four, etc.) vertical translation mechanisms  110  (e.g., see  FIG. 4 , showing four mechanisms  110 , etc.) enables control of the attitude of center hull  108  via differential actuation. This enables, for example, increased draft of side hulls  102  at the stern for increased propulsion efficiency or decreased draft at the bow for beach landings.  
         [0027]     Support plate  416 , in conjunction with bearing  214  and guide rod  216  resist horizontal plane forces. The bearing, since it is a non-metallic, such as molded rubber or plastic, enables non-binding movement and provides a way to control position and attitude between center hull  108  and sponson  106 /side hulls  102 . Importantly, non-metallic bearings  214  provide a means for holding center hull  108  while permitting the inevitable structural deflections, which are prevalent in lightweight, aluminum ship structures.  
         [0028]     Returning now to a discussion of  FIG. 2 , which depicts vessel  100  in the deep-draft mode, vertical translation mechanism  110  is in a retracted state. That is, rods  220  are substantially retracted within hydraulic cylinders  218 . This retracted state is also depicted in  FIG. 6 . Since rods  220  are fixed to center hull  108 , this places the center hull at a maximum vertical position relative to side hulls  102 .  
         [0029]     Returning now to a discussion of  FIG. 3 , which depicts vessel  100  in the shallow-draft mode, vertical translation mechanism  110  is in an extended state. In particular, rods  220  are substantially extended from hydraulic cylinders. This extended state is also depicted in  FIG. 7 . The extended rods  220  force center hull  108  to a minimum vertical position relative to side hulls  102 .  
         [0030]     An exemplary design for vertical translation mechanism  110  is provided below. The design is based on using four mechanisms  110  and the following assumptions: 
        weight of center hull  108 , loaded: 149.3 LT     weight of center hull  108 , unloaded: 99.6 LT     displacement of center hull  108  at 3.874 Ft of draft (unloaded condition): 391.7 LT        
 
         [0034]     Based on the foregoing assumptions, each mechanism  110  includes two pin-ended cylinders having a twenty-two foot stroke. The hydraulic pressure of the cylinders is 2800 psi operating pressure and 3000 psi max pressure. Each cylinder must be capable of pushing 163,576 pounds and must be capable of lifting 83,608 pounds. The bore of the cylinder is ten inches and the rod is eight inches. Outside diameter of the cylinder is 11.5 inches.  
         [0035]     Each cylinder, when filled with hydraulic fluid, weighs 6,596 pounds. The fluid in the cylinder weights 242.3 pounds. To actuate the system in within two minutes will require 133 horsepower.  
         [0036]     It is to be understood that the above-described embodiments are merely illustrative of the present invention and that many variations of the above-described embodiments can be devised by those skilled in the art without departing from the scope of the invention. For example, in this Specification, numerous specific details are provided in order to provide a thorough description and understanding of the illustrative embodiments of the present invention. Those skilled in the art will recognize, however, that the invention can be practiced without one or more of those details, or with other methods, materials, components, etc.  
         [0037]     Furthermore, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the illustrative embodiments. It is understood that the various embodiments shown in the Figures are illustrative, and are not necessarily drawn to scale. Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that a particular feature, structure, material, or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the present invention, but not necessarily all embodiments. Consequently, the appearances of the phrase “in one embodiment,” “in an embodiment,” or “in some embodiments” in various places throughout the Specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.