Patent Publication Number: US-7210421-B1

Title: Latch system for a watertight bulkhead door

Description:
The present application draws priority from a pending U.S. Provisional Patent Application Ser. No. 60/607,019, filed Sep. 3, 2004. 

   TECHNICAL FIELD 
   The present invention relates to doors for naval bulkheads; more particularly, to latching mechanisms for watertight sealing of doors in naval bulkheads; and most particularly, to a novel latching mechanism for a bulkhead door that provides consistent lockdown tension, improves fire resistance for a sealing gasket, and eliminates the use of exposed metal latching dogs, thus improving radar cross-section. 
   BACKGROUND OF THE INVENTION 
   Watertight 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), a 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. 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 areas, known in the art as “strikers”. Such progressive rotational engagement causes the gasket to be compressed against the collar, sealing the bulkhead opening against water and/or gas transmission. 
   In some prior art embodiments, the dog spindles extend pivotably through the bulkhead and are mechanically linked around the interior of the bulkhead opening such that actuation of a master handle, extending pivotably through the bulkhead and actuable from either side thereof, causes all the dogs to be engaged or disengaged synchronously. 
   Prior art bulkhead door systems employing exposed metal dogs create an undesirably enhanced radar cross-section, to the benefit of an enemy combatant in naval warfare. 
   Further, 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; 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. 
   The gasket of a prior art door system is relatively exposed to damage by fire on the exterior of the bulkhead, resulting in failure of the watertight and gastight seal. 
   Use of a plurality of spaced-apart dogs results in inconsistent lockdown pressure across the door such that under extreme pressure conditions the door may become distorted and leakage may occur between adjacent dog positions, especially when the door is formed of a non-metal polymeric composite. 
   What is needed in the art is an improved latching system for a bulkhead door that eliminates exposed metal dogs on the exterior of the door, provides consistent lockdown pressure across the door, permits easy and thorough washdown from a chemical spill or biological attack, and shields the door gasket from attack by fire. 
   It is a principal object of the present invention to provide a uniform lockdown pressure at all points of a bulkhead door gasket. 
   It is a further object of the invention to reduce the radar cross-section of a bulkhead door assembly. 
   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 facilitate easy, rapid, and thorough cleanup of a chemical spill or a biological attack. 
   It is a still further object of the invention to utilize existing bulkhead openings and door actuation mechanisms. 
   SUMMARY OF THE INVENTION 
   Briefly described, a latch system for a watertight bulkhead door for closing a bulkhead opening comprises a plurality of shield elements that may be translated by an articulated mechanism into and out of locking engagement with the bulkhead door. The door is provided with a first elongate continuous wedged striker surface along the periphery of the outer door surface, and the shield elements are provided with second elongate wedged surfaces for mating with the first wedged surface when the shield elements are translated into locking relationship with the door. Such wedged mating causes a resilient gasket mounted in a flange of the door to be compressed against an edge of a collar surrounding the bulkhead opening. The exterior shield elements abut each other in closed position, forming a continuous frame around and over the periphery of the door, thereby shielding the gasket from ready attack by fire and providing a small radar cross-section. Preferably, the exterior shield elements are mounted to a modified prior art articulated mechanism disposed on the interior of the bulkhead and surrounding the bulkhead opening. Preferably, a plurality of translatable inner bulkhead shields is also provided to cover the articulated mechanism during actuation thereof for reasons of personnel safety. 

   
     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, showing a plurality of pivotable dogs for securing the door against a collar surrounding a bulkhead opening; 
       FIG. 2  is an elevational exterior view of a watertight bulkhead door having a latch system in accordance with the invention, showing the latch system in locked position; 
       FIG. 3  is a view like that shown in  FIG. 2 , showing the latch system in open position; 
       FIG. 4  is a view like that shown in  FIG. 2 , having the exterior shields removed for clarity to show the latching wedges in locked position; 
       FIG. 5  is a view like that shown in  FIG. 4 , showing the latching wedges in open position; 
       FIG. 6  is an elevational interior view of the door and latch system shown in  FIG. 2 , having the interior shields removed for clarity to show the articulated mechanism in locked position; 
       FIG. 7  is a view like that shown in  FIG. 6 , showing the articulated mechanism in open position; 
       FIG. 8  is a cross-sectional view of a portion of a latch system in accordance with the invention, showing the system in open position; and 
       FIG. 9  is a view like that shown in  FIG. 8 , showing the system in locked position. 
   

   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  and hinges  16  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 a 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 . 
   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 and 3 , a watertight bulkhead door latching system  110  in accordance with the invention for a vessel  111  comprises a bulkhead door  112  provided with a handle  114  and hinges  116  mounted to a collar  118  attached to an exterior surface of a bulkhead  120  and surrounding a bulkhead opening  122 . Door  112  includes a continuous peripheral gasket (not visible in  FIGS. 2 and 3  but described fully below) disposed on a reverse side of door  112  for sealingly mating with a collar flange extending away from the exterior bulkhead surface. 
   The peripheral surface of door  112  is provided with an elongate striker  126 , preferably continuous around the periphery of door  112  and having a surface  127  tapered in a direction generally orthogonal to the sides of door  112 . A translatable exterior shield assembly  128  comprising a plurality of individually translatable shield elements, preferably numbering four  130   a , 130   b , 130   c , 130   d , is disposed on an articulated mechanism (not visible in  FIGS. 2 and 3  but described fully below in respect of  FIGS. 4 through 9 ) outboard of door  112  in collar  118 . The mechanism comprises a linkage of spindles, connecting rods, and bellcranks, and is manually actuable by a master actuating lever  132  mounted on a pivotable spindle  134  extending through collar  118  and bulkhead  120  as a component of the articulated mechanism. Lever  132  has a counterpart (not visible) on the interior of bulkhead  120 , as discussed below. 
   In locked position, as shown in  FIGS. 2 and 9 , exterior shield elements  130  including locking wedge elements  142  have been translated into an overlapped relationship with wedged striker surface  127  as described below to urge door  112  toward bulkhead  120 , thus compressing the gasket against the collar flange to seal the bulkhead door over the bulkhead opening. Further, exterior shield elements  130  closely abut each other at junctures  138  to form a substantially continuous exterior frame  139  around the periphery of door  112 . 
   In open position ( FIG. 3 ), exterior shield elements  130  are retracted from overlap with door  112  in respective directions  140  away from door  112 , permitting the door to be opened outwards on its hinges  116 . 
   In a currently preferred embodiment, bulkhead door  112  comprises outer and inner shells  113 , 115  formed of material composites and bonded together. 
   Referring to  FIGS. 2–5 ,  8 , and  9 , exterior shield assembly  128  comprises each exterior shield element  130   a , 130   b , 130   c , 130   d  and a corresponding locking wedge element  142   a , 142   b , 142   c , 142   d  attached thereto and extending generally parallel to the edge of door  112  and the adjacent striker  126 . Upper and lower locking wedge elements  142   a , 142   c  are pivotably mounted on curved lock lever arms  144   a , 144   c  respectively. Arms  144   a , 144   c  in turn are fixedly mounted on respective spindles  146   a , 146   c  which are pivotably extended through collar  118  and bulkhead  120  such that rotation of spindles  146   a , 146   c  causes wedge elements  142   a , 142   c  to be urged into or out of overlapping relationship with door striker  126 . The wedge elements are sized such that an interference exists between wedge elements  142   a , 142   c  and striker surface  127  which is relieved by compression of gasket  148  against collar flange  150 . 
   Similarly, left and right locking wedge elements  142   b , 142   d  are pivotably mounted on lock lever arms  144   b , 144   d  respectively. Arms  144   b , 144   d  in turn are fixedly mounted on respective spindles  146   b , 146   d  which are pivotably extended through collar  118  and bulkhead  120  such that rotation of spindles  146   b , 146   d  causes wedge elements  142   b , 142   d  to be urged into or out of overlapping relationship with door striker  126 , causing compression of gasket  148  against collar flange  150 . 
   Referring still to  FIGS. 8 and 9 , bulkhead  120  is reinforced in the regions of passage of each of spindles  146  therethrough by a frame stiffener  152  supportive of a spindle bushing  154  and sleeve  156 . Spindle  146  is entered into sleeve  156  from the interior of bulkhead  120 . A boss  158  on lock lever arm  144  is captured by a compression nut  160  and lock nut  162 . Exterior shield element  130  is attached to locking wedge element  142  by screws  164  and is formed to cover the spindle assembly and to have a surface  166  tapered toward striker  126 . Preferably, striker  126  is also provided with a tapered outer surface  168  which abuts surface  166  ( FIG. 9 ) when system  110  is in locked position to provide a continuous radar-diverting surface having a low radar cross-section. 
   Referring to  FIGS. 6 through 9 , a bulkhead-interior mechanism  170  and operations thereof will now be discussed. Each side spindle  146   b , 146   d  is fixedly connected to a respective actuating lever arm  172   b , 172   d . Actuating lever arms  172   b , 172   d  are connected by first and second connecting rods  174   b , 174   d  respectively. The upper ends of connecting rods  174   b , 174   d  are themselves linked by connecting rods  176   b - 1 , 176   d - 1  to upper bellcranks  178 - 1 , 178 - 2 . Bellcrank  178 - 1  is pivotably mounted on a blind spindle  180 . Bellcrank  178 - 2  is fixedly mounted on spindle  146   a - 2 . Bellcranks  178 - 1 , 178 - 2  are connected by connecting rod  176   a . First upper curved lever arm  182 - 1  is mounted on spindle  146   a - 1  for actuation by a linkage  184  connected to bellcrank  178 - 1 . Second upper curved lever arm  182 - 2  is fixedly attached to bellcrank  178 - 2  for rotation therewith. 
   Similarly, the lower ends of connecting rods  174   b , 174   d  are themselves linked by connecting rods  176   b - 2 , 176   d - 2  to lower bellcranks  178 - 3 , 178 - 4 . Bellcrank  178 - 3  is pivotably mounted on a blind spindle  180 . Bellcrank  178 - 4  is fixedly mounted on spindle  146   c - 2 . First lower curved lever arm  182 - 3  is mounted on spindle  146   c - 1  for actuation by a linkage  184  connected to bellcrank  178 - 3 . Second lower curved lever arm  182 - 4  is fixedly attached to bellcrank  178 - 4  for rotation therewith. 
   A master interior actuating lever  184  is fixedly mounted on pivotable spindle  134  extending through the bulkhead and collar to a master exterior actuating lever  132  as described above. Master interior actuating lever  184  is attached to actuating lever  172   d  such that rotation of either of levers  132 , 184  and spindle  134  serves to move mechanism  170 , and consequently exterior shield system  128 , into or out of locked position. 
   Preferably, system  110  further comprises an interior shield system  188  analogous to exterior shield system  128 . Interior shield system  188  comprises a plurality of individually translatable interior shield elements  190  analogous to exterior shield elements  130   a , 130   b , 130   c , 130  and disposed on lever arms  172 , 182  of articulated mechanism  170  such that the linkages in mechanism  170  are shielded during actuation thereof to prevent injury to personnel. 
   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.