Pressure-resistant housing
BACKGROUND OF THE INVENTION 
     The present invention pertains generally to the field or art of fabricating a housing which is transparent to light of selected wavelength. More specifically, the invention pertains to the fabrication of a housing for selected electro-optical equipment which requires the joining of a selectively shaped window of glass or other brittle material with a mounting of metallic material. Even more specifically, the invention pertains to the fabrication of a housing which includes a hyperhemispherical-shaped window and which may be employed to house a periscope or other device for a submarine. 
     The importance of a periscopic viewing device for the operation of submarines for military or other purposes is quite well known. Presently used periscopes generally comprise a system of lenses and mirrors enclosed in a tubular housing, which penetrates the hull of any submarine with which it is used in order to provide a path for received optical images. As is well known in the field of naval architecture, physical penetration weakens a submarine hull and reduces the resistance thereof to hydrostatic pressure. 
     In addition, certain presently used periscopes include a housing which is of circular cross-section so as to be rotatable about the longitudinal axis of the housing. Such rotation is necessary to enable view of a 360° azimuth. However, a housing of circular cross section is not hydrodynamically streamlined, and increases wake and resistance to travel through water. Also, the wear on a mechanically rotatable housing may be substantial. 
     It has been recognized that the above disadvantages may be overcome by providing a periscope housing which includes a window of selected shape or configuration constructed from material which is transparent to light. The window could be joined to a mounting to enclose electro-optical viewing equipment, along with electromechanical equipment to maneuver the viewing equipment through a selected azimuth and angle of elevation. All movement required to view an object would thereby take place within the housing. Required power and control signals to the equipment and information therefrom could be coupled through electric cable, whereby very minimal penetration of a submarine hull would be required. 
     However, in fabricating a housing of the above type, it would most likely be necessary to sealably join a window of glass or similar brittle material with a mounting of metal, such as steel or titanium. Since the respective thermal coefficients of such joined materials are very different, their respective rates of flexure differ substantially as the joint therebetween is subjected to increasing pressure, leading to possible failure of the brittle material. 
     SUMMARY OF THE INVENTION 
     The present invention provides a housing which is transmissive to radiation of selected frequencies and includes a window which is shaped or configured in the form of a segment of a sphere, the window being provided with a seating surface. The invention further includes a mounting means for supporting the window, the mounting means having a bearing surface in abutting relationship with the seating surface of the window, and a compressible retaining means adjacent to the window and to the mounting means for retaining the window in immovable relationship with the mounting means. 
     In a useful embodiment of the invention, the window comprises a material which is transparent to light of selected wavelength, the mounting means comprises a metallic material and the retaining means includes first resilient means for resisting external pressure upon the window, and second resilient means for resisting internal pressure therewithin. The first and second resilient means is adapted to retain the window by means of friction force applied upon internal and external surfaces, respectively, of the window. By being compressible, the retaining means provides compensation for different flexure rates of the window and mounting means along a joint therebetween, as the joint is subjected to varying pressure. 
     Preferably, the window comprises a hollow hyperhemisphere, or spherical segment which is greater than a hemisphere and less than an entire sphere. The hyperhemispherical window is of selected outside and inside diameter, and an access opening thereinto is surrounded by the aforementioned seating surface, the seating surface lying upon a spherical angle which has its apex at the center of the hyperhemispherical window. 
     An embodiment of the invention may be usefully employed in a periscopic viewing device for a submarine, electro-optical viewing apparatus being contained therein. The viewing apparatus is maneuvered to view an object at a selected azimuth and elevation angle by electro-mechanical means, which are also contained within the housing as aforementioned. Consequently, the housing may be immovably attached to a submarine, for example, by means of a mast positioned between the submarine and the mounting means, and the mounting means may be provided with a hydrodynamically streamlined shape. The viewing apparatus may, for example, be capable of viewing light in the visible region, the window being of material such as glass or acrylic, or may be capable of viewing light in the infrared region, the window being of material such as germanium. It will be readily apparent that, in addition to housing radiation sensing equipment, an embodiment of the invention may be employed to house radiation transmitting equipment, for example, to provide a light beacon. 
     While it is believed that the present invention may be usefully embodied or employed as above stated, it is not intended to limit the invention thereto. 
     OBJECTS OF THE INVENTION 
     An object of the invention is to provide an improved housing which comprises a window joined to a mounting, the window being transmissive to radiation of selected frequencies, and the joint between the window and the mounting being sealed to resist extreme external pressures thereupon. 
     Another object is to provide an improved means for sealably joining a hyperhemispherical window and a mounting therefor, wherein the materials respectively used to form the window and mounting have very different thermal coefficients, and the joint therebetween is subjected to extreme external pressures. 
     Another object is to provide an improved housing which comprises a hyperhemispherical window of glass, germanium, or other brittle material and a mounting of metallic material, wherein means used to join the window and the mounting must be capable of resisting a selected pressure contained within the housing, and extreme hydrostatic pressures external thereto. 
     Another object is to provide an improved periscope or other viewing device for a submarine, which requires minimum penetration of the submarine hull. 
     Another object is to provide an improved periscope or other viewing device for a submarine, which may view an object through a selected azimuth and elevation angle, while the periscope housing remains stationary with respect to the submarine. 
     Another object is to provide an improved periscope or other viewing device for a submarine which includes a hyperhemispherical-shaped window and a mounting of hydrodynamically streamlined shape. 
     These and other objects of the invention will become more readily apparent from the ensuing specification when taken together with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing an embodiment of the invention employed by a submersible vehicle in a marine environment. 
     FIG. 2 is a plan view of the embodiment of FIG. 1 taken on line 2--2 of FIG. 1. 
     FIG. 3 is a sectional view of the embodiment of FIG. 1 taken on line 3--3 of FIG. 2. 
     FIG. 4 is a sectional view of the embodiment of FIG. 1 taken along line 4--4 of FIG. 3. 
     FIG. 5 is an enlargement of a portion of FIG. 3. 
     FIG. 6 is an exploded isometric view of the embodiment of FIG. 1, a portion thereof being broken away. 
     FIG. 7 is an isometric view showing an holding ring employed in a modification of the embodiment of FIG. 1. 
     FIG. 8 is a plan view showing a fastening means for the external ring of FIG. 7. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, there is shown a submarine or other submersible vehicle 10 in a marine environment 12, a mounting 14 being immovably joined thereto by means of a mast 16 which does not penetrate the hull of submarine 10. Mounting 14 is formed from a metal such as aluminum or titanium, and is provided with a hydrodynamically streamlined shape, the external contours of mounting 14 being designed to minimize resistance to travel through water. Equipment 18, which is employed by submarine 10, is enclosed in a housing formed by immovably joining a window 20, comprising a hollow hyperhemisphere, to mounting 14, by means hereinafter described. Window 20 is formed from material which is transparent or highly transmissive to light or other radiation over a selected range of wavelength or frequency, and equipment 18 includes one or more devices for sensing and/or transmitting radiation over the selected range. 
     Referring further to FIG. 1, there are shown cables 22, such as electric or fiber optic cables, coupled between submarine 10 and equipment 18 to provide communication therebetween. It may be noted that the penetration of the hull of submarine 10 required for cables 22 is very minimal. 
     Referring to FIG. 2, there is shown mounting 14 having side surfaces 14a and 14b which are curved to hydrodynamically streamline mounting 14 as aforementioned, minimizing drag and wake thereof when mounting 14 moves through environment 12. 
     Referring to FIGS. 3 and 4, there is shown window 20 comprising a hollow hyperhemisphere which has its center at C, an outside diameter of d 1 , and an inside diameter of d 2 , where d 1  is approximately 10 inches and d 2  is approximately 8.5 inches. An access opening into window 20 is defined by a spherical angle α having its apex at C, where α usefully is 90° to 96°, and the portion of window 20 which lies on spherical angle α comprises an annular seating surface 24 which surrounds the access opening. Mounting 14 is provided with an annular groove, one side of which comprises a flat bearing surface 26 to match seating surface 24 of window 20, and window 20 is supported by mounting 14, seating surface 24 being in abutting relationship with bearing surface 26. 
     Referring further to FIGS. 3 and 4, there is shown a compressible retaining means, described hereinafter in greater detail, which comprises a first resilient means 28, second resilient means 30 and holding means 32. FIGS. 3 and 4 also show equipment 18 including an element 34 which may comprise a viewing device which has a lens 36 and which is mechanically coupled by means of a linkage 38 to an electromechanical drive 40. Drive 40 comprises an electric motor or the like, and receives power and control signals from submarine 10 through cables 22 to maneuver lens 36 through a 360° azimuth and an elevation angle in excess of 90°, enabling device 34 to view or sense radiation from a selected object. 
     Device 34 may comprise, for example, a conventional electro-optic device for viewing light images having wavelengths in the visible range, 0.4-0.7 microns, the device converting viewed images into electrical information which is coupled to submarine 10 through a cable 22. For such application, window 20 would be formed from material such as glass or acrylic. 
     Alternatively, viewing device 34 could comprise a conventional electro-optic device for viewing or sensing images having wavelengths in the infrared range, 1.8-23 microns. For such application, window 18 would be formed from material such as germanium. 
     Consistent with the principles of the present invention, element 34 could comprise a device for radiating or transmitting radiation of selected frequency or wavelength, window 20 being formed of material transmissive thereto. For example, the housing formed by window 20 and mounting 14 could be employed to enclose a light beacon or communication equipment. 
     Referring to FIG. 5, there are shown resilient means 28 and 30 comprising respectively, external and internal O-rings of compliant material, and holding means 32 comprising a ring which is joined to mounting 14 by means of a plurality of bolts 42. Ring 32 has an outer edge 44 which is shaped and dimensioned to match the inside curvature and dimensions of window 20 in proximity to seating surface 24. 
     Referring further to FIG. 5, there is shown the aforementioned annular groove of mounting 14 configured to provide an annular channel 46, for receiving external O-ring 28. Similarly, ring 32 is configured to provide an annular channel 48 for receiving internal O-ring 30. The dimensions of channels 46 and 48 are respectively selected with respect to O-rings 28 and 30 so that O-ring 28 is compressed between mounting 14 and the external surface of window 20, and O-ring 30 is compressed between mounting 14, the internal surface of window 20, and ring 32, when bolts 32 are tightened. Compressed O-ring 28 is capable of sealing window 20 against hydrostatic pressure thereupon in excess of 1000 psi, and compressed O-ring 30 is capable of resisting internal pressure within window 20 which is normally 5 psi. In addition, compressed O-rings 28 and 30 retain window 20 in immovable relationship with mounting 14 by applying friction force upon adjacent portions of the external and internal surfaces, respectively, of window 20. 
     FIG. 5 also shows a gasket 50 positioned between seating surface 24 and bearing surface 26 for resisting wear therebetween. 
     Referring to FIG. 6 there is shown ring 32 comprising a split ring of two segments 32a and 32b, and there is further shown mounting 14 having an opening 52 therethrough. The several components of the present embodiment may be assembled by first positioning external O-ring 28 in channel 46 and seating surface 24 of window 20 upon bearing surface 26 of mounting 14. Gasket 50 being positioned therebetween. Then, by reaching through opening 52 internal O-ring 28 and split ring 32 are positioned, and bolts 42 are tightened to compress O-rings 28 and 30. 
     Referring to FIG. 7, there is shown a modification of the invention, wherein annular channel 48, which receives external O-ring 28 as aforementioned is partially formed by an edge of a ring 56, comprising a plurality of segments which is variably tightened around the external surface of window 20 in proximity to sealing surface 24. By providing segmented ring 56, respective tolerances required to mate window 20 and mounting 14 become greater, whereby manufacturing costs may be reduced. 
     Referring to FIG. 8, there are shown segments 56a and 56b of ring 56, which are joined by means of adjustable screw 58 passing through matching threaded holes in segments 56a and 56b. 
     Obviously, many modifications and variations of the present invention are possible in the light of the above teachings, and, it is therefore understood that within the scope of the disclosed inventive concept, the invention may be practiced otherwise than as specifically described.