Patent Publication Number: US-2009229507-A1

Title: Submersible Vessels

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention relates to submersible vessels such as (without prejudice to the generality) submarines. 
     BACKGROUND 
     It has long been known that hollow submersible bodies of spherical shape are capable of withstanding approximately twice the external pressure of a substantially cylindrical body of comparable diameter and wall thickness. Submersible vessels having pressure hulls formed from a number of interconnected sections in the form of truncated spheres are already known, as disclosed for example in GB 279 483, GB 2 223 716 A and U.S. Pat. No. 5,477,798. 
     In submersible vessels, windows or viewports may also be formed with a part-spherical shape for strength. A common material used in the manufacture of such viewports is acrylic plastics, since this has a refractive index close to that of seawater and therefore minimises visual distortion. However, the viewport mounting must be capable of maintaining an effective seal over a wide range of external pressures and operating temperatures. 
     In a known form of mounting for part-spherical viewports, a radial face of the viewport surrounding a circular opening is seated against a part-conical surface with provision of suitable seals. The viewport is held in position by a clamping ring which holds a peripheral edge of the viewport against the part-conical seat. Such arrangements may be used to effectively secure viewports of substantial size. 
     In general, increasing the angle of the opening reduces the range of hydrostatic pressures which the mounting can handle. On the other hand, reducing the angle of the opening restricts the internal space. In pressure hulls which include a viewing area formed from a number of adjoining part-spherical transparent sections this would place a restriction on the size of the internal compartment. 
     The present invention seeks to provide a new and inventive form of submersible vessel having a number of adjacent part-spherical transparent sections in which the size of the internal compartment is maximised whilst maintaining an effective seal throughout a wide range of external pressures. 
     SUMMARY OF THE INVENTION 
     The present invention provides a submersible vessel having a pressure hull which includes:
         a body section,   a substantially transparent part-spherical end section having a single opening, and   at least one substantially transparent part-spherical intermediate section having a pair of openings and being disposed between the end section and the body section such that the said sections provide a common internal compartment;   characterised by   a cage partially surrounding the end section;   and   a plurality of tension elements connecting the cage to the body section, disposed externally of the intermediate section or sections.       

     The cage preferably comprises a tension ring and a plurality of anchoring members projecting from the tension ring and each connected with a respective tension element. 
     In a preferred arrangement a thrust member is interposed between adjacent transparent sections, and the tension elements pass slidably through the thrust member. The thrust member may thus locate the tension elements whilst balancing the sealing pressures on opposite sides of the thrust member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings: 
         FIG. 1  is an external side view of a submarine in accordance with the invention; 
         FIG. 2  is a plan view of the submarine; 
         FIG. 3  is an end view of the submarine as seen from the bow end; 
         FIG. 4  is a side view of an internal pressure hull of the submarine; 
         FIG. 5  is a plan view of the pressure hull which comprises a body section and two transparent sections; 
         FIG. 6  is an end view of the pressure hull as seen from the bow end; 
         FIG. 7  is a transverse section through the pressure hull, the right hand side of the drawing showing the section A-A of  FIG. 4  and the left hand side showing the section B-B; 
         FIG. 8  is a section through the area of the thrust ring which separates the two transparent sections, including an inset detail; and 
         FIG. 9  is a section through the area where the transparent sections join the body section. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIGS. 1 to 3  show a vessel which is commonly referred to as a submarine. The vessel is capable of both surface and sub-surface use. The vessel has an external hull  10  which is shaped for surface cruising, having a leading bow end  11  and an aft end  12  with a propeller  15 . During surface use the propeller  15  may be driven by an internal diesel engine to provide economical use over a considerable distance, but during dives the propeller may be driven by an internal electric motor powered by a rechargeable battery. The external hull is surmounted by a deck area  16 , which is surrounded by an upstanding safety wall  17 . The bow end  11  is provided with a transparent window  18  which extends on both sides of the vessel. 
     The external hull  10  contains an internal pressure hull  20 , shown in  FIGS. 4 to 7 , which is designed to withstand the high external pressures encountered during sub-surface dives. Starting at the bow end, the pressure hull includes a bow section  21 , an intermediate section  22 , a mid section  23 , and an aft section  24 . The bow and intermediate sections  21  and  22  are both formed of transparent acrylic plastics (other suitable transparent materials could be used, of course) whereas the mid and aft sections  23  and  24  form a metal body section, both being generally of cylindrical shape with circumferential, axially-spaced reinforcing rings  25 . The aft section  24  is closed by a part-spherical end  26  and is joined to the mid section  23  by conventional flange seals  27 . Referring back to  FIG. 1 , the transparent sections  21  and  22  form part of an internal passenger compartment  30  within the pressure hull, which extends into the mid and aft sections. The passenger compartment is accessed through a cylindrical access hatch  32  which passes through the top of the mid section  23  into the deck area  16  and is closed during dives by a pressure cover  33 . The remainder of the body section  23 ,  24  outside the passenger compartment contains service equipment such as the drive motors, batteries, air supply equipment etc. 
     A space is formed between the body section  23 ,  24  of the pressure hull and the external hull  10 , containing one or more enclosed ballast tanks which are part-flooded to control the diving depth. The transparent sections  21  and  22  of the pressure hull are disposed behind the bow window  18  so that the external environment is clearly visible to people in the passenger compartment. The intervening space between the sections  21 ,  22  and the window  18  may be flooded to reduce pressure forces on the window  18  during dives. 
     Returning to  FIGS. 4 to 7 , the bow section  21  is formed as a truncated sphere with a single opening subtending an angle C at the centre of the sphere of about 120°. The intermediate section  22  is similarly formed as a truncated sphere of the same radius, but this section has two opposing openings each subtending the same angle (about 120 degrees) from the centre of the sphere. A metal thrust ring  38  is interposed between the transparent sections  21  and  22  whereas the mid section  23  is provided with a ring-shaped seat  39  against which the intermediate section  22  is held. A cage  40  is shaped to partially surround the bow section  21 , in contact with its external surface. The cage includes a tension ring  41  and a number of anchoring members  42  which project aft from the tension ring, each terminating, adjacent to the thrust ring  38 , in a pair of spaced pivot plates  43 . A respective tension rod  44  is pivotally connected with each of the anchoring members by means of a pivot pin inserted through the plates  43 . The tension rods  44  extend externally of the intermediate section  22  substantially parallel to the fore-aft axis of the pressure hull, each terminating in a clevis  45 . Each of the tension rods  44  is pivotally secured to the mid section  23  by means of a respective external anchorage plate  46 . The two uppermost tension rods are secured to circumferential anchorage plates on the access hatch  32  whereas the remaining plates  46  project radially from the mid section. The anchorage plates  46  are all located within the ballast tanks, but the tie rods pass slidably through low pressure seals at the point of entry  47  into the ballast tanks. 
     The cage  40  and tension rods  44  clamp the transparent sections  21  and  22  to the mid section  23 . Eight tension rods are provided in the present embodiment. However four of the rods are disposed at the upper region of the transparent sections  21  and  22  and four are disposed at the lower region. The rods  44  do not therefore impede the side view from the passenger compartment but the balanced arrangement enables the cage  40  to apply even clamping pressure to the transparent sections. It will also be noted that a base platform  48  projects forwardly from the mid section  23  below the transparent sections  21  and  22 , which supports the transparent sections during assembly and maintenance of the pressure hull. 
     The thrust ring  38  is provided with outwardly-projecting flanges  49  through which the tension rods  44  are slidably inserted to ensure accurate circumferential and radial location of the rods.  FIG. 8  shows how the thrust ring  38  is interposed between the two transparent sections  21  and  22  whilst  FIG. 9  shows how the intermediate section  22  is held against the seat  39  of the mid section  23 . The adjacent opening of each section is surrounded by a radially-extending face  50  which is supported against a respective part-conical seat  51 . The outer circumferential limit of each seat is formed by an abutment face  53  which projects substantially perpendicularly from the seat  51 . (See inset detail of  FIG. 8 .) The adjacent corner of the transparent section, between the radially-extending face  50  and the external face  54 , is formed with a short inclined face  55 . An O-ring seal  56  is enclosed between the seat  51 , the abutment face  53  and the inclined face  55  so that, when the rods  44  are correctly tensioned, the O-rings are sealingly compressed between these three faces. 
     During a dive the hydrostatic pressures on the external faces of the transparent sections are resisted by the cage  40  and tension rods  44  so that the radial faces  50  are held against the part-conical seats  51 . Since the thrust ring  38  is slidably located on the tension rods  44  the compression forces are equally divided between the three seats  51 . As the external pressure increases the faces  50  may eventually slide radially inwards on the seats  51  but as long as the O-rings remain compressed an effective pressure seal is maintained. 
     In larger vessels which are intended to accommodate a larger number of passengers the pressure hull may include two or more intermediate sections  22  with a similar thrust ring  38  interposed between each adjacent pair of sections. 
     With the arrangement described the size of the passenger compartment is maximised whilst maintaining effective seals over a wider range of external hydrostatic pressures. The high pressures to which the seals may be subjected during a dive remain substantially balanced throughout the intended operating range. 
     It will be appreciated that the features disclosed herein may be present in any feasible combination. Whilst the above description lays emphasis on those areas which, in combination, are believed to be new, protection is claimed for any inventive combination of the features disclosed herein.