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BACKGROUND TO THE INVENTION  
         [0001]    THIS invention relates to a toilet cistern dual flush valve which is capable of discharging different volumes of water from the cistern at the election of the operator.  
           [0002]    Toilet cisterns generally have a fixed volume of water, the full content of which is discharged to the toilet bowl when flushing is initiated. In many instances, a full discharge is not required and effective flushing of the toilet bowl could be achieved by discharging a smaller volume from the cistern. In this way wastage of water could be minimised resulting in reduced water consumption and associated costs to the consumer.  
           [0003]    A number of dual flush toilet cistern valves have been devised with a view to providing the user of the toilet with a choice between a full flush in which the full content of the cistern is discharged into the toilet bow), and a partial flush in which only part of the cistern content is discharged. Many of the known dual flush valves are either complicated and expensive to manufacture or are unreliable in operation. Another problem with some known dual flush valves is their use of two separate floats each at the end of a relatively long, transverse float arm to achieve selective locking of a valve stem carrying the valve closure which controls the discharge of water from the cistern to the bowl. The long float arms make such valves unsuitable for use in the compact cisterns which are currently in favour. The present invention seeks to provide a compact, simple and relatively inexpensive dual flush valve.  
         SUMMARY OF THE INVENTION  
         [0004]    According to the invention there is provided a toilet cistern dual flush valve operable selectively in a full flush mode in which a relatively large volume of water is discharged from the cistern or a partial flush mode in which a relatively small volume of water is discharged from the cistern, the valve comprising;  
           [0005]    a valve stem carrying a valve closure seatable on an outlet from the cistern and movable between a raised, open position in which the closure is spaced from the outlet and a lowered, closed position in which the closure seats on the outlet,  
           [0006]    means operable in both full and partial flush modes to raise the stem,  
           [0007]    operatively buoyant means attached to the stern which in the full flush mode maintains the stem in the open position until the relatively large volume of water has been discharged and the buoyant means loses buoyancy whereafter the stem descends under gravity to the closed position, and  
           [0008]    means which operates in the partial flush mode to add sufficient further mass to the stem when the relatively small volume of water has been discharged, to cause the stem to descend to the closed position.  
           [0009]    A preferred embodiment of the invention includes actuators which are selectively, manually operable to initiate the full or partial flush mode, an upper float unit, upper and lower collars on the stem, and linkages extending between the actuators and the upper float unit such that operation of either actuator raises the upper float unit into abutment with an upper collar on the stem thereby raising the stem to the open position. The linkages may include a toggle attached pivotally to the upper float unit and carrying a detent, the arrangement being such that operation of the relevant actuator to initiate a partial flush causes the toggle to pivot to a position in which the detent engages the lower collar and adds the mass of the upper float unit to the stem when the water in the cistern has dropped to a level at which the upper float unit loses buoyancy. The upper float unit may include a water reservoir to accommodate a volume of water providing gravitational mass.  
           [0010]    Both the main float and the upper float unit may include inverted cup-shapes to accommodate air which renders both the main float and upper float units buoyant in water. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The invention will now be described, by way of example only, with reference to the accompanying drawings in which:  
         [0012]    [0012]FIG. 1 shows a partially exploded perspective view of a dual flush valve according to this invention;  
         [0013]    [0013]FIG. 2 shows a side view of the stem, main float and closure assembly of the dual flush valve of FIG. 1;  
         [0014]    [0014]FIG. 3 shows a side view of the secondary float unit of the dual flush valve of FIG. 1;  
         [0015]    [0015]FIG. 4 shows a side view of relevant components of the dual flush valve of FIG. 1 when a full flush is initiated;  
         [0016]    [0016]FIG. 5 shows a vertical cross-sectional view of relevant components of the dual flush valve of FIG. 1 when a partial flush is initiated;  
         [0017]    [0017]FIG. 6 shows a horizontal cross-section at the line  6 - 6  in FIG. 4;  
         [0018]    [0018]FIG. 7 shows a horizontal cross-section at the line  7 - 7  in FIG. 5;  
         [0019]    [0019]FIG. 8 shows a side view of a second embodiment of the dual flush valve according to the invention;  
         [0020]    [0020]FIG. 9 shows an exploded perspective view of components for suspending the dual flush valve of FIG. 8 in a cistern; and  
         [0021]    [0021]FIG. 10 shows a perspective view of actuating buttons of the dual flush valve of FIG. 8. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]    [0022]FIG. 1 shows a dual flush valve  10  according to this invention. The valve  10  includes an outlet structure  12  having a threaded spigot  14 , a nut  16  mateable with the spigot, a flange  18  and three legs  20  extending vertically from the flange and carrying enlargements  22  at their upper ends.  
         [0023]    The valve  10  also includes a housing  24  of generally inverted cup shape. The housing has a cylindrical skirt  25  carrying circumferentially spaced locking formations  26  and an annular upper wall  28  from which a cylindrical sleeve  30  projects vertically.  
         [0024]    When installed in a toilet cistern  31  the spigot  14  is passed downwardly through an opening in the base  33  of the cistern and the outlet structure  12  is locked in place by engaging the nut  16  with the spigot beneath the base. The housing  24  is then located over the outlet structure  12  with the enlargements  22  received through enlarged zones  32  of the locking formations  26 . The housing is then rotated relative to the outlet structure to locate the enlargements  22  over relatively narrow zones  34  of the locking formations  26 . It will accordingly be understood that the housing  24  is locked to the outlet structure  12  by what is, in effect, a bayonet action.  
         [0025]    The dual flush valve  10  also includes a vertical, hollow stem  36  carrying a closure  38  at its lower end which can seat on the rim of the outlet opening  40  through the outlet structure  12 . The stem passes slidably through the sleeve  30  of the housing  24  and carries a relatively large collar  42  and a relatively small collar  44  at spaced apart positions near to its open upper end. Beneath the upper wall  28  of the housing the stem passes through, and is fixed to, a central sleeve  46  extending downwardly from the horizontal upper wall  48  of a main float  50 . The float  50  is in the form of an inverted cup and has a cylindrical skirt  52  depending downwardly from the periphery of the upper wall  48 . The outside diameter of the float skirt  52  is somewhat less than the inside diameter of the housing skirt  25  so the float  50 , which is fixed to the stem  36 , is capable of free vertical movement within the housing.  
         [0026]    Another component of the valve  10  is a secondary or upper float unit  54  which has an upper cup-shaped reservoir section  56 , a lower float section  58  of inverted cup-shape and a horizontal wall  60  serving both as a base of the section  56  and an upper wall of the section  58 . A central, vertical sleeve  62  extends upwardly from the wall  60 . The stem  36  extends freely through this sleeve which has an internal diameter greater than the external diameter of the lower collar  44  but smaller than the external diameter of the upper collar  42 . The upper edge of the sleeve  62  is formed with a cut-out  64  shaped as shown in FIG. 3.  
         [0027]    Pivoted externally to the side of the sleeve  62 , at a pivot axis  66  located generally beneath the cut-out  64 , is a toggle  68  having the shape of a sector of a circle. The upper edge of the toggle carries a detent  70  which projects transversely into the cut-out  64  in a direction towards the stem  36 .  
         [0028]    Attached pivotally to the toggle at spaced apart points on opposite sides of the pivot axis  66  are upright arms  72  and  74 . At their upper ends, the arms  72  and  74  are pivoted to respective transverse arms  76  and  78 . The arm  76 , which is a full flush arm, extends from a collar  80  fixed on a hollow shaft (not shown) which in use extends through the front wall  81  of the cistern and to which a full flush actuating handle  82  is connected. The arm  78 , which is a partial flush arm, extends from a collar  84  fixed on a shaft  85  which extends rotatably through the hollow shaft and to which a partial flush actuating handle  86  is connected. An element  88  extends from the collar  84  and overlies the collar  80 .  
         [0029]    When the valve  10  is installed in the cistern in use, the actuating handles  82  and  86  are located externally on the front wall  81  of the cistern for selective operation by the user. When the full flush actuating handle  82  is depressed, i.e. pivoted in a clockwise direction as illustrated, the hollow shaft to which it is attached will rotate in a clockwise direction, thereby raising the arm  72  via the collar  80  and full flush arm  76 . Because of the presence of the element  88 , this action also rotates the collar  84  and hence the shaft  85  to which the partial flush actuating handle  86  is connected. As a consequence, the arm  74  is also raised via the partial flush arm  78 . The arms  72  and  74  apply balanced lifting forces to opposite sides of the toggle  68  which is itself lifted but does not rotate.  
         [0030]    When the partial flush actuating handle  86  is depressed, the shaft to which it is connected rotates accordingly. The arm  74  is therefore raised via the collar  84  and partial flush arm  78 . However in this case, there is no corresponding movement of the arm  72 . The arm  74  applies an unbalanced force to the toggle and causes it to pivot, in an anticlockwise direction as viewed in FIG. 1, on the axis  66 . The detent  70  moves to a position in which it extends directly towards the axis of the stem  36 .  
         [0031]    The operation of the dual flush valve  10  will now be explained with reference to a full flush action and a partial flush action. In both instances a flushing action will commence when the cistern is full of water, volumes of air are trapped in the main float  50  and in the float section  58  of the upper float unit  54 , the reservoir section  56  of the upper float unit is full of water, and the valve closure  38  is seated in sealing manner on the rim of the outlet opening  40 .  
         [0032]    Full Flush  
         [0033]    As just explained a full flush is initiated by depressing and then releasing the actuating handle  82 . Depression of the actuating handle has the effect of raising both arms  72  and  74 . Because the toggle  68  is attached to the upper float unit  54  at the pivot axis  66 , the upper float unit is pulled upwardly. When the upper edge of the sleeve  62  encounters the upper collar  42  on the stem  36 , the stem is also raised. This lifts the valve closure  38  off the rim of the outlet  40 , allowing water to discharge from the cistern through the spigot  14  and into the toilet bowl to perform a flushing action. During flushing the stem is kept in a raised position by the buoyancy of the main float  50 , attributable to the pocket of air trapped therein. Flushing will continue until the water level in the cistern has dropped to a level where the float  50  loses buoyancy, allowing the stem  36  and with it the closure  38  to drop. The closure reseats on the rim of the outlet opening  40 , thereby closing the valve again.  
         [0034]    The upper float unit  54  is kept in a raised position during an initial part of the full flush by the air pocket trapped in the lower float section  58 . When the water level in the cistern drops beneath the lower edge of the float section  58 , the float unit  54  will descend with the water level until it eventually comes to rest on the upper wall  28  of the housing  24 . As described previously, the stem  36  and closure  38  are kept in the raised position by the buoyancy of the main float  50  until the full flush is completed  
         [0035]    It is to be noted that because the toggle does not pivot when the full flush is initiated, the detent  70  remains in a position off-set laterally from the axis of the stem  36 , and so does not interfere with the collar  44 , as shown in FIG. 6.  
         [0036]    Partial Flush  
         [0037]    The partial flush is initiated by depressing the actuating handle  86 . As described previously, this has the effect of raising the arm  74  only. The unbalanced force on one side of the toggle causes the toggle to pivot as it is pulled upwardly by the arm  74 . As in the full flush mode of operation, the upper edge of the upper float unit  54  encounters the upper collar  42  and raises the stem  36  and closure  38 , initiating the flush. However in this case, the pivotal movement of the toggle aligns the detent  74  with the axis of the stem, with the result that the detent locates over the collar  44 , as shown in FIG. 7.  
         [0038]    As in the full flush mode the stem  36  is kept raised and the closure  38  remains in an open position because of the buoyancy of the main float  50 . The upper float unit is also kept raised by the buoyancy attributable to the air pocket trapped in the float section  58 .  
         [0039]    When a partial flush has taken place, the water in the cistern has dropped to the level of the lower edge of the float section  58 . At this point, the float unit  54  loses buoyancy and starts dropping. Because the detent  70  has located over and moves into contact with the collar  44 , the gravitational force on the float unit  54  is transferred to the stem  36 . While the unit  54  is itself relatively light, its mass is considerably increased by the volume of water in the reservoir section  56 . The combined mass of the float unit  54  and the volume of water in the reservoir section is sufficient to overcome the buoyancy of the main float  50 , so the stem is forced downwardly for the closure  38  to reseat on the rim of the opening  40  and close the valve. At this stage, only a part of the cistern contents have been discharged.  
         [0040]    As the float unit  54  drops the toggle  68  is reset to a neutral or balanced position, in which the detent is free of the collar  44 , by the upward force on the toggle applied by the arm  72 .  
         [0041]    In both the full and partial modes of operation, the cistern is refilled in the normal way via a cistern inlet valve which forms no part of the present invention and which is not shown in the drawings.  
         [0042]    The design of the valve  10  described above is suitable for use in modern, compact toilet cisterns in which internal space is at a premium. It will also be appreciated that the valve  10  is of sufficiently simple construction to enable it to be manufactured at relatively modest cost.  
         [0043]    A feature of the design is the use of the mass of water in the reservoir section  56  to apply a valve closing force in the partial flush mode. It is however within the scope of the invention for the required mass to be provided by, for instance, a weight attached to the float unit, although this would increase the overall cost of the valve.  
         [0044]    A second embodiment of a dual flush valve is depicted in FIG. 8 and indicated by the reference numeral  110 . In this instance actuating buttons  112  and  114  replace the pivoted actuating handles  82  and  86  on the front wall of the cistern as described in the first embodiment.  
         [0045]    The actuating buttons  112  and  114  are clearly illustrated in FIG. 10. It will be noted that they have flat portions at their sides allowing them to be placed juxtaposed within the flat portions facing one another.  
         [0046]    [0046]FIG. 8 shows that the actuating buttons  112  and  114  are located in a sleeve  118  and are moveable relative to each other in the sleeve  118 . It will be noted that the sleeve is a carried by a support beam  120 .  
         [0047]    The support beam  120  is suspended within the cistern by two brackets  122  and  124 . The connection between the support beam  120  and the brackets  122  and  124  is illustrated in FIG. 9. The support beam  120  has a tongue  126  locatable in a cavity  128  of the bracket  122 . Once the tongue  126  is located in the cavity  128 , it can be secured with a bolt  134 , shown in FIG.  8 , that is placed through holes  130  and  132  which are located in the tongue  126  and the bracket  122  respectively. The support beam  120  is connected to the support bracket  124  in a similar manner.  
         [0048]    Various different options are available for suspending the brackets in position. FIG. 9 illustrates one possibility in which the bracket  122  has two protruding members  136  and  138  at its ends. The protruding member  136  is slidably locatable in a slot  140  defined by a support frame  142  that is attached to the inside of the front wall (not illustrated) of the cistern with adhesive. The protruding member  138  is attached to the back wall of the cistern in a similar fashion. Placing the cistern&#39;s lid in position will prevent the protruding members being removed from their respective slots.  
         [0049]    It is envisaged that slots similar to the slot  140  can be formed in the walls of the cistern itself. However, the dual flush valve  110  should also be capable of use in existing cisterns and in such situations will require the use of frames as described above.  
         [0050]    Turning again to FIG. 8, it will be noted that the sleeve  118  has two lugs  144  and  146  connected thereto, each support frame having a pivot pin indicated by the reference numerals  148  and  150  respectively.  
         [0051]    The pivot pin  148  pivotally connects the button  112  via an arm  151  with an arm  152 , which is in turn connected to an arm  156 . A portion of the arm  151  is located in a cavity  153  shown in FIG. 10. In operation the linear movement of the button  112  in a downward direction will cause the arm  152  to pivot on the pivot pin  148  thereby moving the arm  156  in an upward direction. This movement, illustrated in broken lines in FIG. 8, will initiate a partial flush as described previously. Depressing both buttons simultaneously will lead to a full flush, also as described previously,  
         [0052]    A further feature of the second embodiment is also illustrated in FIG. 8. It is know that toilet cisterns are normally manufactured in two standard sizes, i.e. 6 I and 9 I. In different embodiments of these cisterns the height of the cistern may vary. From an economic perspective it would therefore be desirable if a single dual flush valve  110  could be installed and used in cisterns having either of these standard sizes and varying cistern heights.  
         [0053]    This objective is addressed by having arms  156  and  158  of telescopic construction. Telescopic movement is achieved in that the arms  156  and  158  include ratchets  160  and  162  as well as catches  164  and  166  respectively. Telescopic construction is well known in the art and it will suffice to say that each catch can be moved on the associated ratchet in such a manner that the effective length of the arms  156  and  158  can be either increased or decreased depending on the cistern size.  
         [0054]    In FIG. 8 both the lower float section  58  of the upper float unit  54  and the float  50  are filled with closed cell foam. It has been mentioned that the floats  50  and  54  are kept in a raised position due to the buoyancy attributable to air pockets trapped therein. Using closed cell foam manufactured air pockets trapped therein will lead to a more constant degree of buoyancy of the floats thereby enhancing the overall performance of the dual flush valve  110 .  
         [0055]    As indicated previously, the stem  36  is hollow. Its open upper end serves as a cistern overflow to allow water to escape from the cistern in the event of overfilling. In another modification, the stem could be of telescopic construction to allow its upper end to be raised or lowered to suit a particular cistern and the desired flush volume.

Summary:
The invention provides a toilet cistern dual flush valve ( 10 ) operable selectively in a full flush mode in which a relatively large volume of water is discharged from the cistern or a partial flush mode in which a relatively small volume of water is discharged from the cistern. The dual flush valve ( 10 ) comprises a stem ( 36 ) carrying a valve closure ( 38 ) seatable on an outlet from the cistern, means to raise the stem ( 70, 72,74 ), buoyant means ( 50 ) attached to the stem ( 36 ) which in the full flush mode maintains the stem ( 36 ) in the open position until the relatively large volume of water has been discharged and the buoyant means ( 50 ) loses buoyancy whereafter the stem ( 36 ) descends under gravity to the closed position, and means ( 54 ) which operates in the partial flush mode to add sufficient mass to the stem when the relatively small volume of water has been discharged causing the stem ( 36 ) to descend to the closed position.