Abstract:
A toilet closure apparatus mounts on a toilet having a base assembly defining a bowl and a bowl ledge, a tank assembly, a toilet lid and a toilet seat. A tank mounting bolt has a tank mounting bolt bore extending axially therethrough. A cable housing is sealedly affixed within the tank mounting bore and disposed to allow a cable to move axially through the tank mounting bore. A hinge assembly includes a frame defining a downwardly extending cable run and an internal cavity including a cylindrical bearing surface having a horizontally extending axis. A hinge member is supported by the bearing surface for rotation about the axis. A hinge pin extends outwardly of the frame, and is fixedly engaged with the toilet seat to effect toilet seat rotation in common with rotation of the hinge member about the axis, the hinge member having at least one camming surface.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to the automatic closure of toilet seats and lids specifically through mechanical unpowered means. 
       BACKGROUND OF THE INVENTION 
       [0002]    There has been a long-felt need for a device which automatically, or semi-automatically, lowers a toilet seat, a toilet lid, or a toilet seat and lid assembly after use. Naturally enough, the toilet has presented a household hazard when users neglect to fully close a toilet lid after use. For example, children and pets have been known to play in the water the toilet bowl contains even to the point of drinking from the toilet bowl or, in the extreme, falling into the toilet bowl. By closing the toilet bowl, users prevent these hazards, by making the bowl less accessible to both children and pets. 
         [0003]    The use of a toilet by multiple members of a household also presents some hazards. For example, male users tend to leave the seat and lid assembly in an open position after urination. When open, however, an inattentive and subsequent user might sit on the actual toilet bowl instead of the toilet seat, by acting on an assumption that the toilet is in a seat down lid up position. While never pleasant, in the case of an elderly user, such an episode might cause injury, or at least discomfort in the actual sitting and recovery. Thus, in addition to being more aesthetically pleasing, a consistently closed lid and seat, can prevent the spread of germs, possible injury, and, possibly, embarrassment to members of the household. 
         [0004]    The number of alternate means various inventors have proposed of achieving the result of a uniformly closed toilet when not in use has borne witness to the desirability of such consistent practice of toilet lid closure upon completion of use. But, a number of these solutions have, themselves, presented users with contraptions that have been unwieldy, bulky, and visually unacceptable in an activity that is, out of necessity, both private and necessary. Users tend to avoid solutions that intrude too much upon their expectations of a simple and sanitary toilet. Large cylindrical dampers and smaller but extremely complex clockworks that can perform the simple task of closing a toilet lid and seat are available but have never gained much of a market share over the simple hinged toilet seats. Whether true or not, these large installation toilets are considered as complex and intrusive, and in practice the intrusive and complex nature outweighs any benefit achieved by their presence. 
         [0005]    In addition, such devices are difficult to install, complex in design, and therefore often expensive. For example, devices employing sensors of various types and electric switches to close the lid and seat are believed to be considerably complex and costly. The more complex, the more perceived opportunities to foster the growth of bacteria and molds in nooks and crannies defined by the complexity of the devices. For these reasons, even if unearned, these devices are tagged with a reputation for being unclean. 
         [0006]    Finally, toilets are one province wherein thrifty homeowners have felt confident enough to repair and even upgrade the conventional toilet. For example, Fluidmaster™, a maker and supplier of higher end internal mechanical parts for toilets has about $150 million in annual sales and 350 employees located in San Juan Capistrano in California according to a 2011 issue of Orange County Business Journal. Do-It-Yourselfers (“DIYers”) take pride and are willing to spend money on the toilet care products Fluidmaster™ sells annually including more toilet tank replacement valves than any other manufacturer in the world. But the success of Fluidmaster™ has been due to the extremely simple nature of the hardware they have sold and the simple installation of a superior product which affords DIYers a feeling of success beyond that obtained in a simple repair. Perceived as an upgrade, the installation of Fluidmaster™ parts has, for fifty years, been driven by the DIY market. 
         [0007]    For that reason, however, nearly every of the solutions proposed by inventors has required breaking into toilet&#39;s supply line or tank requiring additional professional plumbing work placing such innovations solely in the hands of the manufacturers as complete toilets rather than as DIY upgrades and, in that market, manufacturers are not willing to adopt changes on systems that they do not view as being “broke.” Unless flush requirements had been imposed upon the manufacturers, there seemed little movement among manufacturers to adopt water thrifty mechanisms. Likewise, any innovation relating to seat installation will not likely gain market acceptance unless it is either legislated or forced by the DIY market acceptance. 
         [0008]    The vast numbers of proposed solutions belie the need for a successful implementation that can be readily adopted by the DIY market. Robert Anderson, in U.S. Pat. No. 7,398,564, dated Jul. 15, 2008 taught a closure apparatus including a mounting bolt having an opening therethrough and a rod disposed within the opening. A spring biases the rod and a lever movable with respect to the mounting bolt. A latch release mechanism causes the latch point of the lever to move with respect to the mounting bolt to close the lid. To accomplish this, however, Anderson teaches an unwieldy lever drawn against the bolt with a substantial lever arm that may be subject to racking within the bolt. 
         [0009]    A nonexhaustive list of other such devices include U.S. Pat. No. 6,230,336 which disclosed use of a direct mechanical connection to the toilet&#39;s flush arm as the actuating means. However, this direct mechanical connection is relied upon only to, through use of a line or cord, activate an electrical switch in an obtrusive electro-mechanical device atop the toilet bowl&#39;s ledge that suffers from the complexity decried above. Another device as set forth in U.S. Pat. Nos. 6,230,336 and 6,185,754 discloses use of the mounting opening as a water conduit to an obtrusive mechanism mounted atop the toilet bowl&#39;s ledge which, in practice is subject to leaking and requires extensive modification of the workings. U.S. Pat. No. 5,867,843 discloses use of the mounting opening for an air tube to an obtrusive mechanism mounted atop the toilet bowl&#39;s ledge. U.S. Pat. Nos. 5,410,766 and 4,951,323 disclose use of the mounting opening as a pathway for a flexible cable to raise, rather than automatically lower, a seat or lid; while U.S. Pat. No. 4,975,988 discloses use of the mounting opening as a pathway for a flexible cable connected to a foot pedal to lower as well as raise the seat. 
         [0010]    In none of the above nor anywhere in the art, has a tank mounting bolt having an axial bore been sealed to a housing of a cable so as to provide a nonleaking passage for a housed cable to pass from the inside of the toilet tank to a latch at the seat and lid hinge to allow the seat and lid to close in response to axial movement of the cable within the housing. There exists, therefore, within the art, an unmet need for an automatic lid and seat closer based upon such a tank mounting bolt and cable housing. 
       SUMMARY OF THE INVENTION 
       [0011]    A toilet closure apparatus mounts on a toilet having a base assembly defining a bowl and a bowl ledge, a tank assembly, a toilet lid and a toilet seat. A tank mounting bolt has a tank mounting bolt bore extending axially therethrough. A cable housing is sealedly affixed within the tank mounting bore and disposed to allow a cable to move axially through the tank mounting bore. A hinge assembly includes a frame defining a downwardly extending cable run and an internal cavity including a cylindrical bearing surface having a horizontally extending axis. A hinge member is supported by the bearing surface for rotation about the axis. A hinge pin extends outwardly of the frame, and is fixedly engaged with the toilet seat to effect toilet seat rotation in common with rotation of the hinge member about the axis, the hinge member having at least one camming surface. 
         [0012]    Embodiments of the invention include at least one pawl. Each pawl is configured to engage each of the at least one camming surface corresponding to the pawl, such that when in a first pawl position, each pawl will detain the hinge member in the open position and when in a second pawl position will allow the hinge member to rotate through the range of motion to a closed position. A bellcrank is mechanically connected to the at least one pawl such that in movement from a first bellcrank position to a second bellcrank position. The bellcrank draws the at least one pawl from the first pawl position to the second pawl position. 
         [0013]    The cable extends from the bellcrank through the cable run such that drawing the cable through the cable housing moves the bellcrank from the first bellcrank position to the second bellcrank position, thereby allowing the hinge member to rotate from the open position to the closed position. Once the at least one pawl is drawn into the second position, the lid will fall under the influence of gravity to a closed position in response to activating the flush lever. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Preferred and alternative examples of the present invention are described in detail below with reference to the following drawings: 
           [0015]      FIG. 1  is a perspective view of a conventional toilet including a cutaway to depict one embodiment of the inventive toilet closure device; 
           [0016]      FIG. 2A  depicts a flush lever and flush lever arm in a rest position showing the inventive cable attached to flush lever arm; 
           [0017]      FIG. 2B  depicts the flush lever arm in a flush position showing the inventive cable attached to flush lever arm; 
           [0018]      FIG. 3A  depicts an exploded view of a cable attachment hook configured to draw the cable axially through the cable housing; 
           [0019]      FIG. 3B  depicts a perspective view of the cable attachment hook configured to draw the cable axially through the cable housing; 
           [0020]      FIG. 4  depicts in orthogonal view a float lever in a second position and the float lever in a first position shown in phantom; 
           [0021]      FIG. 5  shows an inventive cable assembly in cutaway perspective view; 
           [0022]      FIG. 6  shows an off-axis perspective view of a hinge assembly; and 
           [0023]      FIG. 7  shows an orthogonal view of the hinge assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0024]      FIG. 1  is a perspective view of a conventional toilet  10  including a cutaway to depict one embodiment of the inventive toilet closure device. An overview of the toilet  10  provides a roadmap to understand the instant invention. A toilet  10  includes two principle subassemblies: a tank assembly  13  and a base assembly  15  defining a bowl  17  and a bowl ledge  151 . The bowl ledge  151  provides an upper surface for landing a hinge assembly  18  having a hinge assembly cover  19  to cover principal working of the hinge assembly. A cable assembly  11  mechanically links a mechanism within the tank assembly  13  to the hinge assembly  18  and effects the release of the hinge assembly to allow the toilet lid  12  and seat  14  to fall to their closed position in response to mechanical action within the tank assembly  13  drawing a cable through the housing assembly  11 . A flush lever  133  is shown as located on a front face of the tank  131 ; as the flush lever  133  is used to initiate the flushing sequence that culminates in the closing of the toilet lid  12  and seat  14 . The hinge assembly  18  is covered by a hinge assembly cover  19 . 
         [0025]      FIG. 2A  depicts a flush lever  133  in a rest position showing the inventive cable  111  attached to flush lever arm  135  and  FIG. 2B  depicts the flush lever  133  in a flush position. Importantly, in the first preferred embodiment, the flush lever arm  135  as it progresses from the rest position to the flush position the flush lever arm  135  draws a cable  111  axially from a cable housing  113 . The axial movement of the cable  111  within the cable housing  113  is the principal movement that enables timing of operation of the hinge assembly  18 . 
         [0026]    In a presently preferred embodiment, a cable attachment hook assembly  132  includes a cable attachment hook  134  for connecting the cable  111  to the flush lever arm  135  is depicted in  FIG. 3A  in exploded view and in  FIG. 3B  a perspective view of the hook. While connection between the cable  111  can be accomplished within the spirit of the invention by any of a number of conventional means, such as a swivel, a shackle, a stirrup fastened to the flush lever arm  135  with a pin or even a swaged end. Nonetheless, the presently preferred embodiment includes the cable attachment hook  134  as it allows the DIYer to attach the cable  111  to an otherwise unprepared flush lever arm  135 . 
         [0027]    The cable attachment hook  134  is generally S-shaped in profile to enable it to engage the flush lever arm  135  on opposite sides. Affixation is achieved by rotation of a set screw  136  within a threaded hole  137  to mechanically engage the flush lever arm  135  fixing a radius between the rotational axis of both the flush lever  133  and the flush lever arm  135  and an attachment point to hold the cable  111 . By keeping the radius constant, the cable hook assembly  134  causes the flush lever arm  135  to draw a predictable and repeatable length of the cable  111  axially through the cable housing  113  on each full range deflection of the flush lever  133 . The cable hook assembly  134  engages the cable  111  by means of a cylindrical cable stop  139  cooperating with a cable stop screw  138 . The cable stop  139  and cable stop screw  138  fixedly engages the cable  111  and provides an orthogonally disposed rod to rest in tines formed in the cable hook  134 . Because the tines engage the cable stop  139  while still allowing the cable stop  139  to rotate within the tines to orient the cable stop  139  to most efficiently draw the cable even should the orientation change throughout the movement of flush lever arm  135 . Once again, other connection means will serve the ends of the invention, however, the cable hook assembly  134  is the presently preferred embodiment. 
         [0028]    To achieve the same axial movement of the cable  111  through the cable housing  113 , a second presently preferred embodiment as shown in  FIG. 4  exploits a float  141   a, b  on a float arm  142   a, b  to draw the cable  111  from the cable housing  113 . As opposed to the first embodiment, there are both advantages and disadvantages to this second embodiment. Among the advantages is the lack of tactile feedback through the flush lever  133  betraying the mechanical connection between the flush lever arm  135  and the hinge assembly  18 . Nonetheless, the presence of the cable  111  on the flush lever arm  135 , if improperly placed, might impede the functional operation of the float  141   a, b . Nonetheless, this second embodiment allows installation in any tank in that it is based upon the presence of water, even if the flushing is achieved by unconventional flush triggering means such as a flush button rather than a flush lever  133 . By triggering on a water level within a tank, the cable  111  is not mechanically connected to the flush lever  133  in any fashion but rather simply triggers based upon the flushing event which empties the tank. In some conventional toilets a float mechanism resides as part of the flushing capability of the toilet. The float embodiment may either exploit the existing float or may comprise a second, independent float to draw the cable  111  through the housing  113 . 
         [0029]      FIG. 4  depicts in orthogonal view a float lever in a second position and the float lever in a first position shown in phantom. As is apparent in  FIG. 4 , as the water level in the tank, and correspondingly as the tank float  141   a  and float arm  142   a  (shown in phantom in the full tank position or rest position) drops to a lower level (float  141   b  and float arm  142   b ) correspondingly moves a float lever arm  143  to draw the cable  111  axially out of the housing  113  just as the first embodiment likewise draws the cable  111  out of the housing  113 . Because of the leverage the lever arm  143  affords, the weight of the float need not be great in order to draw the cable  111  axially from the cable housing  113 . As such, buoyancy of the float  141   a, b  need not be significantly adversely affected to provide sufficient torque about a float pivot  144  on a float tower  145  in order draw the cable  111  axially out of the housing  113 . 
         [0030]    Other embodiments are also possible. One of the simplest is not illustrate but is easy to understand. Consider, for example a distinct button on a lid of a toilet tank assembly  13 . Configured to draw the cable  111  axially from the cable housing  113  upon depression, such a button could easily operate the hinge assembly in the same manner as is described in either of the first two preferred embodiments. As such, the invention is not limited to either a flush lever arm  135  embodiment nor a float lever arm  143  embodiment but rather can be practiced with any practical means of drawing the cable axially from the cable housing  113 . Indeed, a bicycle brake lever could perform the task and the inventor envisions the use of a tool comprising such a lever for diagnostic troubleshooting of the inventive automatic toilet lid closure apparatus, the tool being useful for isolating linkage problems as might exist in an installation by independently operating the hinge assembly without requiring the use of either of the first or second preferred embodiments to do so. Axial movement of the cable  111  within the cable housing  113  however effected is sufficient to practice the essence of the invention and to do so is not limited to the specific manner in which the movement is effected. 
         [0031]    Naturally, then, the cable assembly  11  stands at the heart of the invention.  FIG. 5  shows the inventive cable assembly  11  in cutaway perspective view in order to demonstrate its features in the automatic toilet lid closure device on a toilet  10 . The affects of relative axial movement between the cable  111  and the cable housing  113  have been discussed above and cannot be overstated, but without the ability to traverse between the water-filled environment of the tank assembly  13  to the necessarily dry environs outside of the tank assembly  13  the cable would be of little use. 
         [0032]    A two piece toilet  10  ( FIG. 1 ) has a set of bolts  121  that secure the tank  131  to the base  15  at a base ledge  151 . These bolts  121  go through a hole the tank  131  defines located at the bottom of the tank  131  and through matching holes in the bowl ledge  151 . Typically rubber washers  124  fit between the bolt  121  head and the inside of the tank  131 . A gasket  152  fits between the tank  131  and the bowl ledge  151  and finally a rubber, plastic or metal washer (not shown for clarity of illustration as it is optional but mentioned here as it is known in the art) fits onto the bolt  121  between the bowl ledge  151  and the nut  123  that secures it in place. 
         [0033]    The bolt  121  is distinct from those known in the art. The bolt  121  defines a bolt bore  122  axially through the bolt  121 . Within the defined bore  122  the cable housing  113  is sealingly bedded into the bore  122  thus, with the bolt  121  providing an integral unit such that proper installation of the toilet bowl bolt  121  effects proper placement of the cable housing  113  at the interface between the water within the tank  131  and the dry environs surrounding the toilet  10 . For this reason, the cable housing will either be sealed at its upper end within the tank or will merely extend beyond and above the upper surface of the water within the tank  131  such that the housing  113  itself does not become a syphon to empty the tank. 
         [0034]    Advantageously, neither plumbers nor most DIYers will need distinct instructions as to installation or to troubleshooting the bolt  121  with the cable housing  113  potted within it because the bolt  121  acts just as a conventional toilet tank bolt would. It is the intent of the inventor that the bedding or potting of the cable housing  113  within the bore  121  is so completely watertight, that the introduction of the inventive bolt  121  to the toilet  10  will not add a new failure mode to the resulting toilet  10 . This is a reasonable expectation as the bolt  121  supports the cable housing  113  throughout the length of the bore  122  thereby eliminating undue flexure of the housing  113 . Thus, any bedding sealant used will not be unduly stressed after curing. With a suitably selected sealant and housing  113 , the use of the bolt  121  and potted cable housing  113  will not adversely affect the life span of the toilet  10 . 
         [0035]    In one embodiment, a toilet hinge bolt  125  is inserted into a frame  181  of the hinge assembly  18  to hold the frame  181  in engagement with the bowl ledge  151  providing registry and secure footing for the hinge assembly  18  and is then secured by a hinge nut  127 . In some other embodiments of the invention, the toilet hinge bolt  125  is not a distinct structure but may be an integral part of the frame  181 . Nonetheless, in either embodiment, a lower stud portion will exist and is inserted into holes the bowl ledge  151  defines a hinge bolt bore  126  similar to that the toilet bowl bolt  121  defines. (For convenience of illustration, the application will continue to refer to the toilet hinge bolt  125  as though it were a distinct structure though the invention is practiced in either embodiment.) The toilet hinge bolt  125  cooperates with the toilet hinge nut  127  or the stud extension of the frame  181  to hold the frame  181  in place. In a conventional manner the toilet hinge nut  127  is threaded onto the toilet hinge bolt  125  and tightening conventionally. The barrel adjuster  128  is then threaded onto the toilet hinge bolt  125  to a state of being “hand tight”. 
         [0036]    As stated above, either of the toilet hinge bolt  125  (or the stud extension) defines the toilet hinge bolt bore  126  just as if the toilet hinge bolt  125  had been a distinct and separable structure. Once the cable housing  113  and toilet bowl bolt  121  have been suitably installed by sufficient and appropriate tightening of the toilet bowl nut  123  and toilet hinge nut  127  respectively, the DIYer will insert the cable housing  113  extending out of the bottom of the toilet bowl bolt  121  into a recess in a barrel adjuster  128  threadedly residing on the toilet hinge bolt  125 . (At the toilet hinge bolt  125 , there is no need for a watertight engagement between the cable housing  113  and the hinge bolt bore  126 .) When fully assembled, the cable  111  extends from the interior of the tank  131 , through cable housing  113  as it, in turn, extends through the toilet bowl bolt  121  out of the cable housing  113  and through barrel adjuster  128  and into the toilet hinge bolt bore  126  on to connect to the hinge assembly  18 . 
         [0037]    Within the hinge assembly  18 , the cable  111  extends through bellcrank (not shown) and as well through the frame  181  and hinge bolt  125  into the housing  113  and through the housing  113  axially and thus through the toilet bowl bolt  121  and into the interior of the tank  131 . Once the cable is connected within the tank  131 , the barrel adjuster  128  is rotated to lengthen and shorten the path of the cable to assure proper operation of the hinge assembly  18  in response to axial movement of the cable within the housing  113 . This sort of adjustment is known in conventional art in the context of use of barrel adjusters to adjust cable brakes or shifters on bicycles. 
         [0038]    Also shown in  FIG. 5  is a bendable sleeve  129 . In a preferred embodiment, the sleeve has a smooth sleeve made of any of the thermoplastics known as PE, PVC, PA, PP, or of HDPE sized to slidingly enclose the cable housing  113 . The sleeve is, in the nonlimiting preferred embodiment, overwrapped with jacketed metallic wire to allow the resulting bendable sleeve to be bent into distinct shapes thereby providing the housing with the ability to snake around mechanical pieces within the tank  131  without interfering with their operation. The sleeve is not necessary for the operation of the invention but is provided in a preferred embodiment of the invention to assure appropriate support for the cable housing in even the most tightly configured tank  131  environs. 
         [0039]    Moving on to the operation of the hinge assembly  18  when suitably affixed to the bowl ledge  151 ,  FIG. 6  shows an off-axis perspective view of a hinge assembly  18 . To the left of  FIG. 6  the cable  111  emerges from the toilet hinge bolt  125  to pass through an arm on the bellcrank  182  to then terminate in a means to fixedly engage the cable  111   a  swaged end  111   e  in a nonlimiting embodiment. A knob is permanently affixed to the end of the cable  111  by a method known as swaging, a forging process in which the dimensions of the knob are compressed using a die or dies to assure a permanent fixture of the knob allowing it to impart an axial tension on the cable  111  without parting. Thus, axial movement of the cable  111  imparts a rotational movement of the bellcrank  182 . 
         [0040]    A bellcrank  182  is a type of crank that changes motion through an angle. The angle can be any angle from 0 to 360 degrees, although 90 degrees and 180 degrees are common. The name comes from its first use, changing the vertical pull on a rope to a horizontal pull on the striker of a bell, used for calling staff in large houses or commercial establishments. In the preferred embodiment, the bellcrank  182  is of a typical 90 degree bellcrank  182  configuration and consists of an “L” shaped crank pivoted where the two arms of the L meet. As explained above, the cable  111  is attached to one of the two arms of the bellcrank  182 . A moving rod  183  is attached to the end of the other L arm. When the cable  111  is pulled to move axially into the toilet hinge bolt bore  126 , the L rotates around the pivot point, pulling on the other arm, thereby moving the rod  183 . 
         [0041]    Changing the length of the arms changes the mechanical advantage of the system. Selection of suitably lengths is an engineering issue and not treated here. There is a tradeoff between range of motion, linearity of motion, and size. The greater the angle traversed by the crank, the more non-linear the motion becomes (the more the motion ratio changes). In this nonlimiting embodiment, the lengths are selected to impart a relatively short linear movement to the rod  183  and therefore issues of nonlinearity are not dominating in the solution of the optimal bellcrank  182 . 
         [0042]    As is evident, the frame  181  governs the spatial relations of components within the hinge assembly  18  (shown here without the cover  19  to reveal the inner workings.) Hinge bases  181   b  are affixed to the frame  181  and then bolted to the bowl ledge  151  with, alternately, the toilet hinge bolt  125  and the standard bolt  120 . These two bolts  120 ,  125  securely hold the hinge assembly  18  to the bowl ledge  151  and, in conjunction with the frame  181  prevent relative movement between the hinge bases  181   b , the seat hinges  114   h , and the lid hinges  112   h  with the attached camming surfaces  112   c  which rotate with the lid hinges  112   h , at least in the closing direction such that preventing the camming surface  112   c  from rotating prevents the hinge  112   h  likewise preventing the lid  112  from closing whenever the camming surfaces  112   c  are prevented from rotating. Rotation of the seat hinge  114  on an extending hinge pin (not shown) is not prevented in the preferred embodiment. Both of the seat hinge  114   h  and the lid hinge  112   h  ride on the hinge pin. The hinge pin rotates within a circular bearing surface to allow opening and closing of either of the seat  114  and the lid  112 . 
         [0043]    Returning now to the linear motion of the rod  183  moving in response to axial movement of the cable  111  relative to the housing  113  and the toilet hinge bolt  125 . Linear movement of the rod  183  translates the stirrup  184  and its attendant pivot  185  biased by a tensioning spring  189  urging the stirrup  184  in a direction pulling the cable  111  out of the toilet hinge bolt  125  opposing actuating movement into the cable housing  113 . A lever arm  186  pivots on a pivot pin  187  rotating in a releasing direction in response to the axial movement of the cable  111  into the toilet hinge bolt  125  rotating the bellcrank  182  as described above. 
         [0044]    In one embodiment of the invention, there exist two pawls  112   p  that selectively engage two camming surfaces  112   c  to selectively prevent and allow rotational motion of the lid hinge  112   h . Nothing requires that there be exactly two pawls  112   p  engaging two camming surfaces  112   c . Either a single pawl  112   p /camming surface  112   c  pair or multiple pawl  112   p /camming surface  112   c  pairs can selectively prevent rotation of the lid hinges  112   h  in practice of the invention. For that reason, within the application the terms at least one pawl will be used to correspond with at least one camming surface do not dictate a specifically limiting structure to only a single configuration. Removing one of the two single pawl  112   p /camming surface  112   c  pairs will not, for example, impair the normal use of the hinge assembly  18 . 
         [0045]    As the lever arm  186  rotates, the pawls  112   p  pivotally connected to the lever arm  186  at pins  188  withdraw from engagement with the camming surfaces  112   c  to free the lid hinges  112   h  to rotate relative to the hinge base  181   h . Additionally, in order to allow for vagaries in the rotation of the lever arm  186 , the stirrup  184  is slidingly mounted on the rod  183  to allow relative linear motion of the stirrup  184  on the rod  183  though that movement is limited in order to transfer actuating movement of the bellcrank  182  to the lever arm  186 . 
         [0046]    Additional optional governing mechanisms are desirable but not required for the operation of the hinge assembly  18  in light of the designed movement of the seat hinges  114   h  and the lid hinges  112   h  relative to the base hinges  181   b .  FIG. 7  shows an orthogonal view of the hinge assembly  18  depicting, at least, a torsional spring  114   s  that serves two purposes. In operation, the torsional spring urges the lid  112  and with it the lid hinge  112   h  into a closed position. Thus, once the at least one pawls  112   p  withdraws from engagement with the corresponding camming surface  112   c  allowing rotation, the torsional spring  114   s  rotates the lid driving the center of gravity horizontally away from the tank  131  past the hinge pin toward a closed position. After passing the hinge, the position of the center of gravity tends to urge the lid into a closed position, at some point overtaking any contribution from the torsion spring  114   s . At this point, the torsion spring  114   s  actually becomes overly deformed and retards the rotational speed of the lid as it rotates to the closed position. Properly selected for its exerting forces, the torsional spring  114   s  can assure a “soft closure” by the lid even after urging it into a closed positon. 
         [0047]    Along with the torsional spring  114   s , a conventional damper (not shown) can be used to slow rotational movement of the hinges  114   h ,  112   h  relative to the hinge base  181   h  without applying an accelerating force to the lid. These dampers are available in various configurations which will augment the operation of the inventive closure apparatus to assure that closure will not produce jarring noises or undue wear on either the lid or the seat. These are not, by themselves, claimed as a basis for novelty though when used in conjunction with the hinge assembly  18  the resulting configuration when viewed as a whole is novel and useful. 
         [0048]    While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.