Patent Abstract:
The present invention permits the positioning and support of a fuel tank in a stable state while preventing unnecessary stresses from being generated in the fuel tank. A tapered, single projecting portion for positioning is formed on either the bottom portion of an inner wall of a hull or the bottom of the fuel tank. A tapered, single depressed portion for positioning is fitted on the projecting portion, and is formed on the opposing bottom portion of the fuel tank or the inner wall of the hull, respectively. A space is formed between a peripheral wall of the fuel tank and the inner wall of the hull that permits contraction and expansion of the fuel tank.

Full Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
         [0001]    This nonprovisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2000-301721, filed in Japan on Oct. 2, 2000, the entirety of which is herein incorporated by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a fuel tank fixing structure for a small-size boat or craft, and more particularly to a fuel tank fixing structure for a saddle-type, small-sized boat or small craft.  
           [0004]    2. Description of the Background Art  
           [0005]    As shown in FIG. 8( a ), a first exemplary fuel tank fixing structure for a small-size boat is known in the background art in which a pair of tank supporting portions  3 ,  3  are provided on the bottom portion of an inner wall  2  of a hull  1 . A fuel tank (hereinafter simply referred to as a tank)  4  is mounted on the tank supporting portions  3 ,  3 , in a position in which the bottom portion of the tank  4  is sandwiched between the pair of tank supporting portions  3 ,  3 . The tank  4  is fixed to the hull I by a belt  5 . The belt  5  is fixed to one side of the hull and looped over the top surface of the tank  4  to the other side of the hull (see Japanese Unexamined Patent Publication No. 4-201797).  
           [0006]    Further, as shown in FIG. 9, a second exemplary fuel tank fixing structure is known in the background art in which a tank  6  is formed in a shape adapted to the bottom portion of the inner wall  7  of a hull and is sandwiched, positioned and fixed by inner wall side surfaces  8 ,  8  opposing other (see Japanese Unexamined Patent Publication No. 5-16882).  
           [0007]    The above-mentioned fuel tank fixing structures suffer from the following problems and drawbacks. First, the fuel tank is not always positioned and fixed in a stable state, as described hereinafter. Typically, a fuel tank does not always have a high dimensional accuracy after manufacture. For instance, where a fuel tank is manufactured from blow molding of synthetic resin, the dimensional accuracy inevitably becomes very low.  
           [0008]    Under such conditions, for example, as shown in FIG. 8( a )-( b ), in the structure in which the pair of tank supporting portions  3 ,  3  sandwich the tank  4 , in the case a gap C is produced between the smaller tank  4 ′ and the supporting portions  3 ,  3  where the tank  4  is smaller than a predetermined size. As seen in FIG. 8( b ), the tank  4 ′ cannot be accurately positioned and fixed in a stable state.  
           [0009]    In contrast, as shown in FIG. 8( c ), in the case where the tank  4  is larger than a predetermined size, the larger tank  4 ″ is pressed by the supporting portions  3  by forces F producing undesirable stresses.  
           [0010]    These problems are similarly presented in the structure shown in FIG. 9. In the case where the tank  6  is smaller than a predetermined size, a gap is produced between the small tank and the inner wall surfaces  8 ,  8 . Accordingly, the tank cannot be positioned and fixed in a stable state. In contrast, in the-case where the tank  6  is larger than a predetermined size, the larger tank  6  is pressed by the inner wall side surfaces  8  by forces producing undesirable stresses.  
         SUMMARY OF THE INVENTION  
         [0011]    The present invention overcomes the shortcomings associated with the background art and achieves other advantages not realized by the background art.  
           [0012]    An object of the present invention is to provide a fuel tank structure that permits stable attachment of a fuel tank to a small craft of vessel.  
           [0013]    A further object of the present invention is to provide a fuel tank structure that permits stable attachment of the a fuel tank without incurring undesirable stresses in the surface of the fuel tank and surrounding structure.  
           [0014]    These and other objects are accomplished by a fuel tank support structure for a small-size boat, the fuel tank support structure comprising a boat hull; a fuel tank mounted on a bottom portion of the hull; a tapered, single projecting portion for positioning formed on either an inner wall of the bottom portion of the hull or on a bottom portion of the fuel tank; a tapered, depressed portion for positioning fitted on the projecting portion and formed on either the bottom portion of the fuel tank or the inner wall of the bottom portion of the hull, the tapered, single projecting portion and the tapered, depressed portion matingly engaging in order to position the fuel tank with respect to the hull; and a space formed between a peripheral wall of the fuel tank and the inner wall of the hull.  
           [0015]    Therefore, even if the fuel tank does not have a high dimensional accuracy, the tapered surface of the depressed portion or the projecting portion of the fuel tank is fitted on the tapered surface of the projecting portion or the depressed portion of the hull. The depressed portion or the projecting portion of the fuel tank is then positioned with respect to the projecting portion or the depressed portion of the hull in a stable state.  
           [0016]    That is, even if the fuel tank is a little smaller or larger than a predetermined size, the fuel tank is positioned without experiencing undesirable play and unnecessary stresses in the fuel tank. Further, since the space is formed between the peripheral wall of the fuel tank and the inner wall of the hull, even if the fuel tank is a little larger than a predetermined size, no unnecessary stresses are generated in the fuel tank.  
           [0017]    As described above, according to the fuel tank support structure for a small-size boat described hereinabove, the fuel tank can be positioned and fixed in a stable state and unnecessary stress are not generated in the fuel tank. Further, even if the fuel is put into the fuel tank to expand the fuel tank, it is possible to keep the fuel tank in a stable, reliably positioned state and to prevent any unnecessary stresses from being generated in the fuel tank.  
           [0018]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    The present invention will become more fully understood from the detailed description given hereinafter and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:  
         [0020]    [0020]FIG. 1 is a partial side view of an exemplary small craft with a fuel tank fixing structure according to an embodiment of the present invention;  
         [0021]    [0021]FIG. 2 is a plan view an exemplary small craft with a fuel tank fixing structure according to an embodiment of the present invention;  
         [0022]    [0022]FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1;  
         [0023]    [0023]FIG. 4 is a partial cross-sectional view taken along line IV-IV in FIG. 1;  
         [0024]    [0024]FIG. 5 is a perspective view of a portion of an inner wall of a hull where a fuel tank is mounted according to an embodiment of the present invention;  
         [0025]    [0025]FIG. 6 is a bottom view of a fuel tank according to an embodiment of the present invention;  
         [0026]    [0026]FIG. 7( a ) and FIG. 7( b ) are enlarged end views showing portions of the embodiments shown in FIG. 3;  
         [0027]    [0027]FIG. 8( a ), FIG. 8( b ) and FIG. 8( c ) are end views of portions of a fuel tank support structure in a small boat hull according to the background art; and  
         [0028]    [0028]FIG. 9 is an end view showing an alternative fuel tank structure according to the background art. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]    The present invention will hereinafter be described with reference to the accompanying drawings. FIG. 1 is a partial side view of an exemplary small craft with a fuel tank fixing structure according to an embodiment of the present invention. FIG. 2 is a plan view an exemplary small craft with a fuel tank fixing structure according to an embodiment of the present invention. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. FIG. 4 is a partial cross-sectional view taken along line IV-IV in FIG. 1. FIG. 5 is a perspective view of a portion of an inner wall of a hull where a fuel tank is mounted according to an embodiment of the present invention. FIG. 6 is a bottom view of a fuel tank according to an embodiment of the present invention. FIG. 7( a ) and FIG. 7( b ) are enlarged end views showing portions of the embodiments shown in FIG. 3.  
         [0030]    As shown in these figures, a small-size boat  10  in a preferred embodiment is a saddle-type boat where the rider sits on a seat  12  mounted to a hull  11 . The rider can drive the boat by gripping a steering handlebar  13  having a throttle lever  13   a . One will appreciate that the present invention can be applied to a wide variety of boats, small craft and vessels well known in the related art, all collectively referred to hereinafter as a small-size boat  10 .  
         [0031]    The hull  11  has a floating structure in which a lower hull panel  14  is bonded to an upper hull panel  15  to form a space  16  therein. In the space  16 , an engine  20  is mounted on the lower hull panel  14  and a jet pump  30  as a propelling unit driven by the engine  20  is provided at a rear portion of the lower hull panel  14 .  
         [0032]    The jet pump  30  has a flow passage  32  extending from a water intake port  17  made in the bottom of the boat to a jet nozzle  31  provided at the rear end of the hull. An impeller (not shown) is disposed in the flow passage  32  and a shaft  33  of the impeller is connected to the output shaft  21  of the engine  20 . Accordingly, when the impeller is rotated by the engine  20 , water taken from the water intake port  17  is jetted out from the nozzle  31  whereby the hull  11  is propelled.  
         [0033]    The number of revolutions of the engine  20 , which translates to a propelling force produced by the jet pump  30 , is operatively controlled by turning the throttle lever  13   a  (see FIG. 2) of the operating handlebar  13 . The nozzle  31  is connected to the operating handlebar  13  by an operating wire (not shown) and is turned by the operation of the handlebar  13  to change the direction of the boat.  
         [0034]    A fuel tank  40  for supplying fuel to the engine  20  is mounted forward of the engine  20  on the bottom portion of an inner wall of the hull  11 . The lower hull panel  14 , as shown in FIG. 3 and FIG. 4, has a double hull structure, including an outer hull  14   a  and an inner hull  14   b , at least at the portion where the fuel tank  40  is mounted. The fuel tank  40  is mounted on the inner hull  14   b , e.g. on the bottom portion of the inner wall of the hull  11 . In this area, the space between the outer hull  14   a  and the inner hull  14   b  is filled with a foaming material  14   c  to form a floating body.  
         [0035]    As shown in FIG. 3 to FIG. 5, the inner hull  14   b  is provided with a single projecting portion for positioning  18  and four projecting supporting portions  19 . The projecting portion  18  includes a base portion  18   a  integrally formed with the inner hull  14   b  and a cap  18   b  made of an elastic material (for example, rubber). The cap  18   b  is fixed to the base portion  18   a  so that it covers the base portion  18   a . Similarly, the supporting portion  19  includes a base portion  19   a  integrally formed with the inner hull  14   b  and a cap  19   b  made of an elastic material (for example, rubber). The cap  19   b  is fixed to the base portion  19   a  so that it covers the base portion  19   a.    
         [0036]    The outer peripheral surface of the projecting portion for positioning  18  is formed with a tapered surface (circular truncated cone)  18   c . On the other hand, as shown in FIG. 3 and FIG. 6, the bottom portion of the fuel tank  40  is formed with a single depressed portion for positioning  41 , which is fitted on the projecting portion for positioning  18  of the hull side of the boat  10 .  
         [0037]    The inner peripheral surface of the depressed portion  41  is formed with a tapered surface (circular truncated cone)  41   c  which is formed in the same direction as the tapered surface  18   c  of the projecting portion for positioning  18  of the hull side. The fuel tank  40  is molded by blow molding synthetic resin (for example, polyethylene or the like). Portions  42 ,  42  of both the sides of the depressed portion for positioning  41  on the bottom surface are formed with slanting surfaces  42  nearly parallel to the slanting portion of the inner wall surface of the bottom portion of the hull (in the present preferred embodiment, top surface  19   c  of the cap  19   b  of the supporting portion  19 ). These slanting surfaces  42 ,  42  are supported movably in the direction of arrow (a) along the slanting surface  42  (as seen in FIG. 7( a )- 7 ( b )) by the four projecting supporting portions  19  formed on the inner wall surface of the bottom portion of the hull  14 .  
         [0038]    The fuel tank  40  formed in the above manner, as shown mainly in FIG. 3 and FIG. 4, is mounted on the bottom portion of the hull  14  so that the depressed portion for positioning  41  is fitted on the projecting portion for positioning  18  on the hull side of the boat  10 . In this mounting state, the depressed portion for positioning  41  is fitted on and positioned by the projecting portion for positioning  18 , and the slanting surfaces  42 ,  42  of both sides are supported by the four supporting portions  19  of the hull side.  
         [0039]    Further, as shown in FIG. 3 to FIG. 5, the fuel tank  40  is fixed to the hull  11  by an elastic belt ( 50 ,  50 ′) looped from one side  11   a  of the hull  11  to the other side  11   b  of the hull  11  along the top surface  40   a  of the fuel tank  40 . In FIG. 3, two elastic belts are used and designated by symbols  50 ,  50 ′, but the number of the belts may be suitably selected and varied as desired. The number of the belts incorporated may be one, two or even three or more.  
         [0040]    As shown in FIG. 4, a supporting portion  45  for supporting a fuel supply hose  43  communicating with the fuel tank  40 , and a fuel return hose  44 , is integrally formed on the top surface  40   a  of the fuel tank  40 . The fuel supply hose  43  and the fuel return hose  44  are fixed to the fuel tank  40  by the supporting portion  45  and the elastic belt  50 .  
         [0041]    A space S is formed, in the plan view, between the peripheral wall  46  of the fuel tank  40  mounted in this manner and the inner wall  11   c  of the hull  11  (see FIG. 3 and FIG. 4). The fuel tank fixing structure described above can produce the following operations and effects.  
         [0042]    The single projecting portion for positioning  18  with the taper  18   c  is formed on the bottom portion of the inner wall of the hull  11 . The single depressed portion for positioning  41 , which is fitted on the projecting portion  18  and has the taper  41   c  in the same direction as the projecting portion  18 , is formed on the bottom of the fuel tank  40  mounted on the bottom portion. The space S is formed between the peripheral wall  46  of the fuel tank  40  and the inner wall  11   c  of the hull  11 . Therefore, when the fuel tank  40  is mounted on the bottom portion of the inner wall of the hull  11 , the single depressed portion for positioning  41  formed on the bottom portion of the fuel tank  40  is fitted on the single projecting portion  18 , whereby the fuel tank  40  is positioned on the bottom portion of the inner wall of the hull  11 .  
         [0043]    Since the tapers  18   c ,  41   c  are formed in the same direction on the projecting portion  18  of the bottom portion side of the hull  11  and on the depressed portion  41  of the fuel tank  40 , the depressed portion  41  is fitted on the projecting portion for positioning  18  by putting the tapered surface  18   c  into contact with the tapered surface  41   c.    
         [0044]    Therefore, even if the fuel tank  40  does not have a high dimensional accuracy, the tapered surface  41   c  of the fuel tank  40  is fitted on the tapered surface  18   c  of the projecting portion  18  of the hull  11 , whereby the depressed portion  41  of the fuel tank  40  is stably fitted on and positioned with respect to the projecting portion  18  of the hull  11 .  
         [0045]    That is, even if the fuel tank  40  is a little smaller than a predetermined size (shown by a solid line  40 ), as shown by a single dot and dash line  40 ′ in FIG. 7( a ), or a little larger than the predetermined size, as shown by a double dots and dash line  40 ″ in FIG. 7( b ), the fuel tank  40  is fitted without demonstrating any play at the positioning portion. Accordingly, no unnecessary stresses are generated therein.  
         [0046]    Further, since the space S is formed, even if the fuel tank  40  is a little larger than a predetermined size, as shown by a double dots and dash line  40 ″ in FIG. 7( b ), the outer peripheral wall of the fuel tank  40  can deflect toward the space S and upward. Therefore, unnecessary stresses are not generated in the fuel tank  40 .  
         [0047]    Further, even if the fuel tank  40  is mounted on the hull  11  and then fuel is put into the fuel tank  40  to expand the fuel tank  40 , the tapered depressed portion  41  is fitted on the tapered projecting portion  18  and hence the tank is kept in the stable positioning state and no unnecessary stress is generated in the fuel tank  40 .  
         [0048]    At least one part ( 42 ) of both sides of the depressed portion  41  on the bottom surface of the fuel tank  40  is formed with slanting surfaces  42 ,  42  slanting nearly parallel to the slanting portion  19   c  of the inner wall of the bottom portion of the hull. These slanting surfaces  42 ,  42  are supported movably in the direction along the arrow (a) in FIG. 7 by the projecting supporting portion  19  formed on the inner wall of the bottom portion of the hull  11 .  
         [0049]    For this reason, even if the fuel tank  40  is a little smaller or larger than a predetermined size, as shown in FIG. 7( a ), ( b ), the slanting surfaces  42 ,  42  are fitted on the supporting portion  19 , which can position and fix the fuel tank  40  in the more stable state and further surely prevent unnecessary stresses from being generated in the fuel tank  40 .  
         [0050]    Still further, even if the fuel tank  40  is mounted on the hull  11 , and fuel is put into the fuel tank  40  to expand the fuel tank  40 , the slanting surfaces  42 ,  42  formed nearly parallel to the slanting portion  19   c  of the inner wall of the bottom portion of the hull can be moved in the direction along the slanting surface  42  in the direction of arrow (a) in FIG. 7. Therefore, this can further prevent unnecessary stresses from being generated in the fuel tank  40 .  
         [0051]    Since the fuel tank  40  is molded by blowing synthetic resin, the fuel tank  40  can be formed more easily. Although the fuel tank molded by blowing synthetic resin has a low dimensional accuracy, the fuel tank  40  of the present invention can be positioned and fixed in the stable state and no unnecessary stresses are generated in the fuel tank  40 . Further, even if the fuel tank  40  is mounted on the hull  11  and then fuel is put into the fuel tank  40  to expand the fuel tank  40 , it is possible to keep the fuel tank  40  in a stable and fixed position, and to prevent unnecessary stresses from being generated in the fuel tank  40 . That is, the fuel tank fixing structure like the present preferred embodiment is particularly effective in the case where the fuel tank  40  is blow molded with synthetic resin.  
         [0052]    The fuel tank  40  is fixed to the hull  11  by the elastic belts  50 ,  50 ′ looped from one side  11   a  of the hull  11  to the other side  11   b  of the hull  11  over the top surface  40   a  of the fuel tank  40 . Therefore, even if the fuel tank  40  is a little smaller or larger than the predetermined size, it is possible to position and fix the fuel tank  40  in the more stable state and to prevent unnecessary stresses from being generated in the fuel tank  40  by the operations and effects described in the aforementioned paragraphs and by the elastic action of the elastic belts.  
         [0053]    The supporting portion  45  for the fuel supply hose  43  and the fuel return hose  44 , both of which communicate with the fuel tank  40 , are provided on the top surface of the fuel tank  40 . The fuel supply hose  43  and the fuel return hose  44  are fixed to the top surface of the fuel tank  40  by the supporting portion  45  and the elastic belt  50 . Therefore, it is possible to position and fix the fuel supply hose  43  and the fuel return hose  44  with the fuel tank  40  in the stable state.  
         [0054]    It will be obvious that the aforementioned embodiments can be varied in many ways. For example, although the projecting portion for positioning  18  is formed on the bottom portion of the inner wall of the hull  11 , and the depressed portion for positioning  41  is formed on the bottom portion of the fuel tank  40  in the above preferred embodiment, the depressed portion for positioning  41  may be formed on the bottom portion of the inner wall of the hull  11  and the projecting portion for positioning  18  maybe formed on the bottom portion of the fuel tank  40 .  
         [0055]    The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Technology Classification (CPC): 1