Patent Publication Number: US-7213528-B1

Title: Bulkhead door for a vessel

Description:
RELATIONSHIP TO OTHER APPLICATIONS AND PATENTS 
   The present application draws priority from a pending U.S. Provisional Patent Application Ser. No. 60/607,020, filed Sep. 3, 2004. 

   TECHNICAL FIELD 
   The present invention relates to doors for bulkheads on vessels; more particularly, to bulkhead doors which can be sealed against passage of water and gas; and most particularly, to an improved bulkhead door formed of multi-material composites and having universal hinge and handle features and superior capture and retention of a sealing gasket without adhesives. 
   BACKGROUND OF THE INVENTION 
   Bulkhead doors are well known on naval vessels. As used herein, “bulkhead door” should be taken to mean a sealable door installed in a vertical surface (bulkhead door), horizontal surface (“hatch cover”), or a door-within-a-door (“scuttle”). A typical prior art bulkhead door includes a resilient gasket that mates with an edge of a collar surrounding a bulkhead opening and extending from the bulkhead outer surface. In sealing use of a bulkhead door, a plurality of pivotable latches, known in the art as “dogs”, are mounted on the bulkhead and may be pivoted into position against the outer surface of the door where they progressively engage wedged elements, known in the art as “strikers”. Such progressive engagement causes the gasket to be compressed against the collar edge, sealing the bulkhead opening against water and/or gas transmission. 
   Prior art bulkhead doors have several disadvantages. Such doors typically are formed of sheet steel and are relatively heavy, for example, about 125 pounds. Navy regulations require that a door or hatch cover may require no more than a maximum of 50 pounds of force to open; thus, many doors and hatches require helper springs to partially offset the weight of a steel door. 
   Being formed of steel, prior art doors are vulnerable to rust, especially under saltwater exposure, requiring that the lower door edges and gasket channels be reconstructed relatively often, requiring welding and grinding. Prior art inventoried doors also tend to be inconsistent in their manufacture. Thus each door must be custom-fitted to its respective bulkhead opening to assure watertight and gastight sealing performance, which fitting typically requires grinding and/or welding (“hot work”) and is a generally “dirty” operation. When hot work or an open flame is required during maintenance of a vessel, naval regulations require a large force of fire security personnel to be present not only on the deck on which the work is conducted but also on the decks immediately above and below the work. The Navy estimates that 1000 manhours are required for maintenance of a single door during the service life of a vessel. 
   Prior art doors typically are formed by stamping from sheet metal and include a stamped relief pattern to enhance flexural rigidity. It has been found that such a pattern is highly undesirable, for two reasons: first, the pattern greatly increases radar reflection from the door, thus aiding an enemy; and second, the pattern is difficult to wash down easily and thoroughly as may be required for washdown of a chemical spill or biochemical attack. For these considerations, a smooth surface is preferred. 
   Typically, many of the bulkhead openings in a ship are identical in height, width, and shape. However, a ship typically is outfitted with a mixture of left-hinge and right-hinge bulkhead openings, requiring doors having corresponding right- and left-oriented hinge blades and door handles. Further, the openings may vary between 2 and 10 in the number of dogs provided for engaging a bulkhead door, requiring an equivalent number and placement of strikers on the door. Thus, in the prior art, although bulkhead openings may be identical, the required doors are not. Therefore, a naval vessel carries an extensive, expensive, and heavy inventory of spare doors to cover all possible replacement contingencies. 
   This cumbersome inventory is made worse by the need on many ships to cover a variety of naval door opening sizes, for example, 26×66 inches and 26×63 inches, both left and right hinged, each with possibly 3, 6, 8, or 10 dogs; and 18×36 inches, both left and right hinged (a scuttle door), having 2, 4, or 6 dogs. 
   Further, in prior art bulkhead doors, the resilient gasket is not well-captured by the door and require adhesives for retention in a gasket channel. Further, the gasket is exposed to attack by fire, which can result in sealing failure of the door. Further, replacement of a deteriorated gasket requires laborious and time-consuming scraping off of the old gasket and adhesives and re-preparation of the door surface for receiving the new gasket and adhesive. 
   What is needed in the art is a universal bulkhead door that eliminates exposed metal dogs on the exterior of the door, has a smooth surface on both the interior and exterior of the door, provides consistent lockdown pressure across the door, shields the door gasket from attack by fire, is readily and cleanly washed down, may be opened easily without helper springs in a hatch mode, provides for simple replacement of a door gasket, and may itself be easily replaced without requiring hot work. 
   It is a principal object of the present invention to reduce the inventory of spare bulkhead doors which must be carried on a naval vessel. 
   It is a further object of the invention to reduce the weight of a bulkhead door. 
   It is a still further object of the invention to protect a bulkhead door gasket from exposure to fire. 
   It is a still further object of the invention to simplify replacement of a bulkhead door gasket. 
   SUMMARY OF THE INVENTION 
   Briefly described, an improved bulkhead door in accordance with the invention comprises an outer shell and an inner shell formed as by molding of a strong, durable material such as a multi-material composite that may include carbon fiber and organic polymers as well as inorganic materials. The molded shells are bonded together along their peripheries to form a core chamber therebetween and a continuous cove channel along the margin of the door for receiving, retaining without adhesive, and protecting a resilient gasket. The molded cove channel also increases the flexural rigidity of the door. Either or both of the shells may be ribbed within the core chamber which may be filled with another material such as a rigid foam for additional strength and increased rigidity of the door. 
   The outer shell is provided with a molded handle and with hinge blades spaced apart by a standard distance, the handle and each blade being spaced by equal distances from an end of the door. Thus each door may be used for either a right-hand or left-hand bulkhead hinge pin orientation. The handle may be centered in the door, such that all door, either left or right opening, have their handles in the same place. However, for use as hatch covers, the handle may be laterally offset from the hinges although still equidistant from the door ends. Metal strikers are bonded to the outer surface of the door for engaging closure dogs in use. A door may be provided with the maximum number of strikers in use on a door on a particular vessel, or alternatively, a door may be provided without any strikers, and the strikers then bonded to the door at appropriate locations during installation of a door to a specific bulkhead opening location. 
   A bulkhead door in accordance with the invention improves on the prior art by reducing the number and variety of spare doors required on a naval vessel; reducing required door maintenance over the working lifetime of a bulkhead door; eliminating rust; eliminating time-consuming and dirty fitting of a new door to an existing bulkhead opening; increasing hinge life, striker life, and bushing life through reduced swing weight; improving personnel egress when the bulkhead opening and door comprise a deck hatch; providing increased chemical resistance; providing smooth exterior and interior surfaces for enhanced chemical and biochemical washdown; and providing an easily removable emergency flotation device. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
       FIG. 1  is an elevational exterior view of a prior art watertight bulkhead door system, showing a plurality of pivotable dogs (eight) for securing the door against a collar surrounding a bulkhead opening; 
       FIG. 2  is an elevational view of a bulkhead door in accordance with the invention; 
       FIG. 3  is an exploded cross-sectional view of the bulkhead door shown in  FIG. 2 , showing outer and inner door shells; 
       FIG. 4  is an assembled cross-sectional view of the bulkhead door shown in  FIGS. 2 and 3 , showing capture of a sealing gasket in a cove channel thereof; and 
       FIG. 5  is a cross-sectional view taken along line 5—5 in  FIG. 2 , showing an integral hinge blade. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , a prior art watertight bulkhead door system  10  comprises a bulkhead door  12  provided with a handle  14 , hinges  16 , and hinge pins  17  mounted to a collar  18  attached to an exterior surface of a bulkhead  20  and surrounding a bulkhead opening  22 . Prior art door  12  includes a pattern of stampings  23  to increase flexural rigidity and continuous peripheral gasket  24  disposed on a reverse side of door  12  for sealingly mating with a collar  18  extending away from the exterior bulkhead surface. System  10  is shown in door closed and locked position. 
   The peripheral surface of door  12  is provided with a plurality of strikers  26  tapered in a direction generally parallel with the sides of door  12 . An equal number of dogs  28  are pivotably disposed, one for each striker, outboard of door  12  in collar  18 . Dogs  28  are mounted on spindles  30  extending through collar  18  and bulkhead  20 , the spindles being synchronously rotatable by an articulated mechanism (not visible in  FIG. 1 ) surrounding opening  22  on the interior of bulkhead  20 . The mechanism comprises a linkage of spindles, connecting rods, and bellcranks, manually actuable by a master lever  32  mounted on a pivotable spindle  34  extending through collar  18  and bulkhead  20  as a component of the articulated mechanism. Lever  32  has a counterpart (not visible) on the interior of bulkhead  20 . 
   Prior art door  12  is typically formed from sheet steel as by stamping from sheet stock and may weigh typically about 125 pounds. 
   In operation of prior art system  10 , starting in an open position, rotation of lever  32  in a first direction causes dogs  28  to be rotated on their individual spindles  30  into overlapping relationship with strikers  26  whereby each dog  28  engages the wedged surface of its respective striker  26 . Continued rotation of dogs  28  on the striker wedged surfaces urges door  12  toward bulkhead  20 , causing the gasket to be compressed against the collar flange. Opening of system  10  is the reverse of closing. 
   Referring to  FIGS. 2 through 5 , an improved watertight bulkhead door  112  has the same height  150 , width  152 , and shape as prior art door  12  such that improved door  112  can directly replace prior art door  12  without requiring any custom fitting or hot work. Door  112  is formed of an outer door shell  154  and an inner door shell  156  ( FIG. 3 ) which are independently molded and then are joined and sealed along a peripheral interface  158  ( FIG. 4 ) creating a cove channel  160  extending along the entire periphery of door  112 . A continuous resilient gasket  162  is compressed and inserted into channel  160  for sealing against the bulkhead collar flange as in the prior art. Gasket  162  is captured and retained in channel  160  by the shape of the channel itself and thus requires no adhesives to maintain position. Further, gasket  162  is easily and readily removed and replaced manually without resort to special tools or solvents as in prior art gasket replacement. 
   Shells  154 , 156  of improved door  112  are preferably laid up as composite laminates in female molds (as is well known in the prior molding art), which provides a smooth outer surface to each shell. Color may be cast into the surface coat as is known in the molding arts. Useful laminates may include various organic polymers such as, for example, polyesters, epoxies, polyamides, and the like, as well as glass fiber, carbon fiber, and the like. 
   As used herein, the term “composite” should be taken to mean a three-dimensional combination of at least two materials differing in form or composition with a distinct interface separating the components; composite materials are usually man-made and created to obtain properties that cannot be achieved by the components acting alone. Consistent with this definition of component materials comprehended by the invention are all solid materials that may be, at least, metallic, organic, ceramic, inorganic, organometallic, and the like. 
   Door shells in accordance with the invention may also be formed of materials, which may be homogeneous or not, by methods other than laminating, for example, by stamping from sheet stock or by injection molding. 
   Outer door shell  154  is provided with a grab handle  164 , which may be raised above the surface of shell  154  or recessed therein. Grab handle  164  preferably is located in the center of the door with respect  165  to ends of the door, as shown, to permit universal use of the door. As noted above, for doors, the handle is preferably equidistant from the door sides, although for hatch covers, the handle preferably is offset from the hinge side to increase opening leverage. The relative lightness of an installed door makes feasible a universal central door handle. Shell  154  is further provided with first and second preformed hinge blades  166 , 168  having root regions  170  preferably comprising a plurality of laminae that are interleaved with shell laminae as the door is laid up, thereby maximizing the strength of hinge blade attachment to the door. 
   It is an important feature of the invention that hinge blades  166 , 168  are spaced apart by a precise distance  170  equal to the distance between the prior art bulkhead hinge pins, and further, that each hinge blade is positioned at a single, predetermined distance  172  from the nearer end  174  of door  112 . Precisely positioning the hinge blades at these locations permits door  112  to be used interchangeably in any right-hinged or left-hinged bulkhead opening by simply lowering the hinge blade openings  176 , 178  over the corresponding bulkhead hinge pins  17  and applying retainers thereto as is known in the prior art. Precision uniformity of hinge blade placement is an inherent and highly-desirable consequence of forming the outer door shell in a mold containing the preformed hinge blades. 
   When outer and inner shells  154 , 156  are bonded together, a hermetically sealed chamber  180  is created therebetween such that door  112  is positively buoyant and thus may be used as an emergency flotation device. During the assembly process, chamber  180  may be partially or wholly filled with any desired core filler  182 , for example, polystyrene foam or polyurethane foam, to increase door stiffness, strength, and/or fire resistance. 
   A fully-formed door  112  in accordance with the invention may weigh about 42 pounds, depending upon the materials of construction, whereas a comparable prior art steel door may weigh about 125 pounds. The reduction in weight can increase the working lifetimes of hinge pins, bushings, and thrust washers, as well as making the door easier to open and close. Further, in comparative tests to leakage failure, improved door  112  exceeds the performance of a 10-dog prior art door  12 . 
   When carried aboard ship in an inventory of spare doors, improved door  112  may be stocked without any strikers (not shown) attached, as door  112  may be substituted for any door currently in service, which may require striker patterns for 2, 3, 6, 8, or 10 bulkhead dogs. Metal strikers may be readily bonded by adhesive at the appropriate surface locations when a door is placed into service. Further, seats (not shown) for strikers at all possible striker positions may be cast readily into the surface of outer shell  154  during molding thereof. Of course, door  112  may be provided as manufactured with any predetermined pattern of strikers overmolded in place, as may be desired. 
   While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.