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The present invention relates generally to sealing closures such as those associated with hangar doors and hatches onboard marine vessels. 
     BACKGROUND OF THE INVENTION 
     Hatches and door openings on board ships sometimes require watertight sealage to meet high performance standards, as well as other design requirements such as non-flammability, corrosion, fuel and chemical resistances and prolonged impact resistance. Current closure sealing systems do not accommodate many of such closure sealing requirements. 
     Presently available advancements in the fabrication of superelastic metals, allow for manufacture of such metals directly into sheet form, with the required strength, dimensions and configurations for closure sealing applications. It is therefore an important object of the present invention to provide a closure sealing system utilizing the superelastic properties of such sheet metals for watertight sealing purposes or the like with improved high standards to meet a wide variety of current design requirements. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, the composition of a shape memory sheet metal material is selected to provide superelastic properties for improved closure sealing purposes without externally imposed control. Such selected metal involves Nitinol alloying by undergoing thermo-mechanical treatments already known in the art resulting in load elongation characteristic accommodating the establishment of closure systems providing the desired sealage conditions such as watertightness onboard ships as well as to deal with other associated environmental hazards. Such closure systems involve positioning of the selected sheet metal by direct attachment onto the edge surfaces of rigid structural parts of a closure arrangement, as seal elements to be deformed by engagement in response to closure displacement. 
    
    
     BRIEF DESCRIPTION OF DRAWING 
     A more complete appreciation of the invention and many of its attendant advantages will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein: 
     FIG. 1 is a graphical representation of the superelastic phenomenon associated with shape memory metallic alloys selected for use in accordance with the present invention; 
     FIGS. 2 and 2A are partial section views illustrating a closure sealing arrangement in accordance with one embodiment of the present invention; 
     FIGS. 3 and 3A are partial section views illustrating a second embodiment; 
     FIG. 4 is a partial section view illustrating a modification of the embodiment shown in FIGS. 3 and 3A; 
     FIG. 5 is a partial section view taken substantially through a plane indicated by section line  5 — 5  in FIG. 4; 
     FIG. 6 is a partial section view illustrating a third embodiment; and 
     FIGS. 7 and 7A are partial section views illustrating a fourth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawing in detail, FIG. 1 graphically diagrams physical properties of a superelastic shape memory material selected for use pursuant to the present invention. Such superelastic material, as generally known in the art, is formed from a Nitinol metal which had thermo-mechanical treatments so as to exhibit 6% elasticity via a change of atomic structure during deformation. Such superelasticity phenomena as depicted in FIG. 1, for a Nitinol metal which undergoes an 8% change in strain as represented along the abscissa, during change in stress applied thereto as represented along the ordinate of the graph. A graphical curve  10  in FIG. 1 for a particular composition with Austenite finish of about 0° C. thus depicts a 5% change in strain during deformation under a stress of approximately 400 MPa imposed at a temperature of 10° C., while the graphical curve  12  depicts a 5% change in strain during a deformation stress of approximately 700 MPa imposed at a temperature of 50° C. The selected sheet material is furthermore non-flammable, corrosion resistant, fuel and chemical resistant and long-lived deformation resistant. 
     FIGS. 2 and 2A illustrate use of the selected superelastic sheet material for door hatch purposes in the form of matching seal strip elements  14  and  16  of cross-sectionally arcuate shape respectively positioned on confronting edges of a stationary, rigid door frame section  18  and a rigid door panel  20  pivotally mounted on the frame  18  by conventional hinges  22 . In an open position of the door panel  20  as shown in FIG. 2, the seal strips  14  and  16  are in closely spaced angular relationship to each other. When the door panel  20  is pivotally displaced to its closed position as shown in FIG. 2A, the seal strip elements  14  and  16  are in contact with each other under deformation in the direction of compressive strain corresponding to watertight sealing engagement between the closely spaced confronting edges of the hingedly connected door frame section  18  and door panel  20 . 
     As also shown in FIG. 2, the edge of the door panel  20  opposite the edge at which the hinges  22  are located, is also provided with a seal strip element  16  matching seal strip element  14  also positioned on the edge of the door frame section  18 ′ in alignment with the hinge mounting door frame section  18 , so as to form a door opening  24  therewith. Such door opening is substantially closed by the door panel  20  when pivotally displaced to the closed position shown in FIG. 2A, bringing the other pair of matching seal strip elements  14  and  16  into the same watertight sealing engagement condition as hereinbefore described with respect to FIG. 2A. A watertight sealed closure is thereby established between the door panel  20  and the door frame sections  18  and  18 ′. 
     FIG. 3 illustrates by way of example a pair of movable rigid door panel sections  26  and  28  having confronting edges  30  and  32  on which a pair of matching compression seal elements  34  are mounted. Each seal element  34  is cross-sectionally profiled so as to include at one end an edge portion  36  fixedly attached to its door section  26  or  28 . The seal element  34  also includes compressible loop portion  38  at its other end interconnected by an intermediate gutter portion  40  to the portion  36  attached to the door panel section. With the door panel sections  26  and  28  displaced toward each other from the positions shown in FIG. 3 to a closure position, the loop portions  38  of the seal elements  34  are in deformed contact engagement with each other as shown in FIG. 3A to establish the watertight sealing condition. In addition to establishment of such watertight sealing condition, the profiling of the matching pair of compression seal elements  34  by including the gutter portions  40 , may collect and accommodate water run off. 
     The compression seal elements  34  as shown in FIGS. 3 and 3A are of a length perpendicular to their profiled cross-sections corresponding to the length of the edges of the door panel sections  26  and  28  on which they are mounted. In order to accommodate longer edged door panel sections  26 ′, overlapping profiled seal elements  34 ′ and  34 ″ may be attached by spot if welding thereto as shown in FIGS. 4 and 5. In such case, a drain  42  would be positioned at one end of the underlying seal element  34 ″ beyond the edge of the door panel section  26 ′ in order to receive run-off drainage flow from the gutter portions  40 ′ and  40 ″. 
     FIG. 6 illustrates yet another sealing hatch type of closure arrangement between relatively movable rigid door panels and/or door frames such as the door panel  44  having an edge  46  to which is attached a compression seal element  48  made of the selected superelastic sheet material. The seal element  48  is of an oval shape in cross-section, with a slit  50  at one end through which it is attached by suitable means such as continuous molding ( 5 ) to the door panel edge  46 . At the other cross-sectional end  52  of the seal element  48  it is engageable by a matching seal element for watertight sealing purposes as hereinbefore described. 
     Finally, yet another embodiment is illustrated in FIGS. 7 and 7A, for establishing a watertight sealing condition between a rigid frame section  54  and a relatively displaceable hatch panel  56 . Secured to the edge surface of the frame section  54  by means of an attachment bolt  58  is a flat end portion  60  of a lip seal element  62  connected by a loop portion  63  to a curved end portion  64  in sliding contact with another lip seal element  66  in close spaced relation to its curved end portion  68 . The other flat end portion  70  of the lip seal element  66 , connected to a loop portion  73  of the element  66 , is secured by an attachment bolt  72  to the abutting edge surface  74  of the hatch panel  56 . When the hatch panel  56  is displaced to a hatch sealing position, the curved end portion  68  of its lip seal element  66  is in sealing contact with the curved end portion  64  of the lip element  62  as shown in FIG. 7A so as to establish the watertight sealing condition. 
     In each of the foregoing described embodiments, two metal sheet seal elements act against each other for watertight sealing of openings associated with hanger doors and hatches on board ships under conditions and with advantages made possible by the superelastic properties of the selected Nitinol alloyed metallic composition of such seal elements which are lighter than steel while having comparable design strength. In view of their metallic composition, the sheet seal elements are also capable of sealing out electromagnetic interference. The concepts embodied in the described embodiments are also potentially applicable to other closure devices, such as sliding and turnstile doors, water canal doors, radiation chamber closures and non-magnetic signature doors. Further, an elastomer coating may be applied to the superelastic metallic sheet seal elements to accommodate other environments which include for example dusts, fumes, gasses and small particles of debris. 
     Obviously, other modifications and variations of the present invention may be possible in light of the foregoing teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

Summary:
A closure system including a rigid structural part has an edge surface along which sealage is established in response to deformation of a superelastic sheet metal element positioned thereon, such sheet metal element being endowed with a shape memory characteristic by formation as a Nitinol alloy to meet high sealage standards and other environmental requirements.