The conservation of water is an issue that preoccupies an increasing number of people. Among all domestic appliances, toilet is an appliance that consumes an appreciable quantity of water. The present invention provides a dual flush system that allows to select the volume of water when using a toilet by choosing between two volumes of water. The dual flush system can be easily installed without tools on a toilet.

CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present Patent Application is a continuation-in-part of the U.S. patent application Ser. No. 11/531,861 filed on Sep. 14, 2006. 
   The present patent application claims the benefits of priority of commonly assigned U.S. Provisional Application No. 60/750,371 entitled “Dual flush system for toilet” filed at the USPTO on Dec. 15, 2005. The present patent application claims the benefits of priority of commonly assigned U.S. patent application Ser. No. 11/531,861, entitled “Dual Flush System for Toilet” and filed at the USPTO on Sep. 14, 2006. The present patent application claims the benefits of priority of commonly assigned Canadian Patent Application No. 2,557,956, entitled “Dual Flush System for Toilet” and filed at the CIPO on Sep. 19, 2006. 


   FIELD OF THE INVENTION 
   The present invention generally relates to toilets flush systems. 
   BACKGROUND OF THE INVENTION 
   The use of toilet flushing devices is known in the prior art. There is a growing consciousness of the need to conserve water, particularly in toilets where it is not always necessary to have a full flushing of the toilet. In order to conserve flushing water, attempts have been made at providing two flushing modes. 
   In conventional toilets, there is often provided in the water tank a tank-ball or flapper that can engage the annular seat formed by the flush pipe outlet. The tank-ball is linked by means of a lift chain to a lever pivotally mounted to the water tank inner wall. A flush actuator, usually a handle located outside the water tank controls the lever. As known in the art, upon the flush handle being pivoted from a rest position to an operative position, the lever will pull on the lift chain which in turn will raise the tank-ball from its seat to allow the water inside the water tank to flow into the toilet bowl. A water supply valve will allow water to be fed into the water tank until a float ball, connected to the supply valve, reaches a determined position in the water tank, at which point the supply valve will be closed. It is noted that the tank-ball is pivotally attached to the base of the overflow tube to pins, this simply as a matter of convenience since the overflow pipe extends closely adjacent to the flush pipe outlet. Also, the tank-ball is slightly buoyant, such that it will remain spaced from the flush pipe outlet while the water in the water tank flows out into the toilet bowl, but the combined action of the gravity and a suction effect from the flush pipe when the last water flows out through the flush pipe, will bias the tank-ball to engage its seat and seal the flush pipe outlet once the water tank is empty, to allow the water tank to be re-filled with water. 
   Indeed, toilets are conventionally made to allow a full flush to be accomplished, although this is not always necessary. Providing a selective dual flush system as contemplated by this invention would allow considerable water volumes to be saved. 
   OBJECTS OF THE INVENTION 
   Accordingly, a first object of the present invention is to provide a dual flush system for toilets allowing the user of the toilet to calibrate how much water he/she wishes to use when flushing the toilet. 
   Another object of the present invention is to provide a dual flush system which may be installed on existing toilets without modification of the latter. 
   A further object of the present invention is to provide a dual flush system which is inexpensive. 
   A still further object of the present invention is to provide a dual flush system which is easily installed without tools, and needs low maintenance. 
   Other and further objects and advantages of the present invention will be obvious upon an understanding of the illustrative embodiments about to be described or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice. 
   SUMMARY OF THE INVENTION 
   According to the present invention, there is provided a dual flush system for a toilet to allow a user to calibrate how much water he/she wishes to use when flushing the toilet. Either a partial flush if the flush handle is pivoted to its first position or a full flush if the flush handle is pivoted to its second position. Alternatively, two different flush handles could be provided, one for a partial flush and a second for a full flush. 
   In use, if the toilet flush handle is pivoted from its rest position to a first predetermined position, the lever will in turn be pivoted and will pull upwardly on lift chain to raise the tank-ball from its seated to its lifted position, spacedly over a flush pipe extension and out of its sealed engagement with the flush pipe extension. This will allow water in the toilet water tank to flow through the coextensive flush pipe extension and flush pipe into the toilet bowl. However, it is understood that the entire water tank would not be emptied into the toilet bowl if only the tank-ball is raised by lift chain, since the height of flush pipe extension would prevent this from happening. More specifically, when tank-ball is raised from its seated to its lifted position while flush pipe extension remains in its lower position, water is allowed to drain from the toilet water tank until it reaches a level within the water tank which is equal to the position of the second flush outlet, which is higher than the first flush outlet. 
   Upon the flush handle being pivoted from its rest position to a second predetermined position which is angularly beyond than its first predetermined position, the lever will in turn be pivoted further and will pull upwardly on lift chain to first raise the tank-ball from its seated to its lifted position and to further raise flush pipe extension from its lower to its upper position. More particularly, as the tank-ball is gradually lifted by lift chain, the tank-ball will first reach its lifted position and further pulling on tank-ball will raise the guiding part along overflow tube, effectively moving the flush pipe extension from its lower to its upper position. This will allow water in the toilet water tank to flow through the flush pipe into the toilet bowl. 
   Consequently, if the flush handle is only pivoted from its rest position to its first position, then the water tank will be partly drained into the toilet bowl, since the water level will only be allowed to lower until it reaches the second flush outlet. However, if the flush handle is pivoted from its rest to its second position, then the water tank will be entirely drained due to the flush pipe extension being raised to its upper position spacedly above the first flush outlet. With a double handle system, each handle is connected to one of the flush outlets. 
   It is noted that the dual flush system of the present invention can be simply retrofitted into a conventional toilet water tank. Indeed, to do so, the user simply needs to remove the existing tank-ball from a pair of pins provided at the lower extremity of overflow tube, and to which the tank-ball is conventionally releasably attached. The guiding part is then inserted along overflow tube, and the tank-ball is pivotally installed onto pins provided on the guiding part. Finally, the lift chain simply needs to be shortened to compensate for the height of the flush pipe extension. Alternately, a new tank-ball could be provided with the dual flush system, the former tank-ball being disposed of. 
   Also, it is further noted that the presence of the downwardly convergent alignment arm allows the flush pipe extension to be self-centering and auto-aligning with respect to the flush pipe due to the sliding engagement of alignment arm along the flush pipe if any positional offset of the flush pipe extension was to occur while it moves away or towards the flush pipe. The alignment arm thus ensures that the flush pipe extension bottom opening will systematically come into a sealed engagement with the first flush outlet when the flush pipe extension is in its lower position. Furthermore, the buoyant member can be undersized on one side or even absent to fit to more toilets models. Because the distance between the wall of the water tank and the flush pipe may vary, the buoyant member can be thinner on the side of the wall of the water tank fit to a majority of toilets or may even be located on only one side of the flush pipe. 
   The dual flush system of the present invention also provides for the tank-ball to return to its seated position once a partial flush is completed. The same is also provides for the tank-ball to return to its seated position and for flush pipe extension to return to its lower position once a full flush is completed. 
   Indeed, while a partial flush is under way, the buoyant tank-ball will float in the water above the second flush outlet, thus remaining in its lifted position. Once the water level in the water tank reaches the position of the second flush outlet, the tank-ball will also reach the second flush outlet under the effect of gravity. The suction effect of the water flowing down into the toilet bowl will draw the tank-ball, now not being countered by its buoyancy, into a tight, sealed engagement against the second flush outlet. 
   Likewise, while a full flush is under way, the buoyant tank-ball will remain in its lifted position until the water level reaches the position of the second flush outlet. The flush pipe extension will also remain in its raised position due to the buoyant member maintaining the flush pipe extension above the first flush outlet. While the water level first reach the level of the second flush outlet and continue to drain from the water tank between the raised flush pipe extension and the flush pipe, tank-ball will return to its seated position against the second flush outlet. Then, when the water level reaches the position of the first flush outlet, the flush pipe extension, not being countered by its own buoyancy, will engage the first flush outlet under the effect of gravity. The suction effect of the water flowing down into the toilet bowl will draw the tank-ball into a tight, sealed engagement against the second flush outlet, and with the flush pipe extension thus sealingly covered by the tank-ball, the flush pipe extension will also be drawn into a tight, sealed engagement against the first flush outlet. 
   The buoyancy of both the tank-ball and the buoyant member are just sufficient to counter the effect of gravity respectively on the tank-ball and the flush pipe extension. Thus, the tank-ball and flush pipe extension are not forced towards the water line, but will simply be maintained in a floating position when they are forced away from their respective seated and lower positions by the lift chain. The buoyancy is provided by a tight cavity enclosing air or any suitable buoyant material. 
   It is understood that the height of the flush pipe extension can be chosen according to the desired relative volume of water which is to be flushed with a partial flush. An adjustable tank ball may also be used in combination with the dual flush system of the present invention. This allows a better control of the quantity of water to evacuate when flushing. A tank ball as described in the U.S. Pat. No. 5,966,749 entitled ‘Adjustable flush valve’ may be used for this purpose. 
   The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the present invention will be described in greater detail below with reference to the following drawings, in which: 
       FIG. 1  is a perspective view of the dual flush system installed in a toilet. 
       FIG. 2  is a perspective view of the dual flush system in accordance with the present invention. 
       FIG. 3  to  FIG. 5  are side views of the dual flush system, showing the device in a closed, partially opened and completely opened condition, respectively. 
       FIG. 6  is a cross side view of the dual flush system. 
       FIG. 7  is a front view of the dual flush system. 
       FIG. 8  is a cross side view of a first embodiment of the bottom opening of the dual flush system. 
       FIG. 9  is a cross side view of a second embodiment of the bottom opening of the dual flush system. 
       FIG. 10  is a top view showing the buoyant member. 
       FIGS. 11   a ,  11   b  and  11   c  are, respectively, a rear view, a side view and a bottom view showing another way to attach the buoyant member to the flush pipe extension and another way to seal the flush pipe to the flush outlet. 
       FIGS. 12   a  and  12   b  are top views showing other embodiments for the buoyant member. 
       FIG. 13  is a top view showing a sealing member. 
   


   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 2  shows the dual flush system for a toilet installed on a conventional flush pipe  20  having a first flush outlet  22  located inside the water tank (not shown) of a conventional toilet, near the bottom wall of the water tank. Flush pipe  20  leads towards the toilet bowl (not shown), as known in the art, so as to allow water located in the water tank to selectively flow out of the tank and into the bowl through the flush pipe  20 . 
   Near flush pipe  20 , there is conventionally provided an upright overflow tube  30  having an overflow tube inlet  32 . Overflow tube  30  merges with flush pipe  20  at the bottom end of overflow tube  30  to convey water towards the toilet bowl if the water level in the water tank rises above the position of the overflow tube inlet  32 . 
   Still in  FIG. 2 , there is provided, according to the present invention, a movable guide part  50  that is more particularly mounted to and slidable along an overflow tube  30 , as detailed hereinafter. Guiding part  50  carries a cylindrical, hollow flush pipe extension  40  that is integrally attached to guiding part  50  by means of a rigid member  52 . An buoyant member  46  is carried by the flush pipe extension  40  wherein the buoyancy is provided with a tight cavity enclosing air or a buoyant material. Flush pipe extension  40  defines a second flush outlet  42  and a bottom opening  44 , respectively. The bottom opening  44  is capable of sealed engagement with the first flush outlet  22  for selectively forming therewith an extended flush pipe member within the toilet water tank. In other words, when flush pipe extension  40  operatively engages the flush pipe  20 , the two pipes become coextensive. By means of the sliding engagement of guiding part  50  along the overflow tube  30 , flush pipe extension  40  is movable between a lower position shown in  FIGS. 3 and 4 , in which its bottom opening  44  rests on and sealingly engages the first flush outlet  22 . The upper position is shown in  FIGS. 2 and 5 , in which the flush pipe extension  40  is located spacedly above flush pipe  20 , and in which the flush pipe extension  40  clears the first flush outlet  22 . 
   A tank-ball  60  is pivotally attached by means of a pair of pins  92  to guiding part  50 , near its upper end. The tank-ball  60  can move from a seated position shown in  FIG. 3 , where it sealingly engages the second flush outlet  42  of flush pipe extension  40  to selectively close the access to flush pipe extension  40 ; to a lifted position shown in  FIGS. 2 ,  4  and  5 , where it is lifted spacedly over the flush pipe extension  40  and it clears the second flush outlet  42  to allow water to flow therethrough. A lift chain  62  is attached at its bottom end to tank-ball  60  and to a lever (not shown) pivotally mounted to the water tank and controlled by a flush handle (not shown), similarly to prior art devices. The tank ball  60  may be a standard one or an adjustable tank ball allowing a more precise control of the amount of water to flush such as the one shown in U.S. Pat. No. 5,966,749. 
   A V-shaped alignment arm  48  is formed of two downwardly convergent rods attached at their spaced-apart top ends to the flush pipe extension bottom opening  44  and attached to each other at their bottom ends. Alignment arm  48  projects downwardly away from the flush pipe extension  40 . The bottom end of the alignment arm  48  is destined to extend within the flush pipe  20  in at least most positions of guiding part  50  along overflow tube  30 . 
     FIG. 8  shows a first embodiment of the bottom opening  44  having sealing function provided with an angular section. 
   In  FIG. 9 , another embodiment for the bottom opening  44  is shown, wherein the sealing function is provided by a sheet-like piece. 
     FIG. 10  shows an embodiment of the buoyant member  46  which has an elliptical shape with a center line displaced from the center line of the second flush outlet  42 . 
   In  FIGS. 11   a  to  11   b , another embodiment is shown for the buoyant member. The buoyant member  146  is attached on one side of the flush pipe extension  40 . The buoyant member  146  is connected to the flush pipe extension  40  with a pin  196  which is inserted in the hole  199  of the buoyant member  146 . The pin  196  comprises gripping means  197  helping to maintain the buoyant member  146  in place. The pin  196  is preferably leaning toward the flush pipe extension  40  to help the buoyant member  146  to stay in place when inserted. Indeed, the portion of the buoyant member  146  comprised between the pin  196  and the flush pipe extension is forced between the latter, and it is necessary to apply a force to remove the buoyant member  146 . 
   The pin  196  is fixed to the buoyant member support  194  which is fixed to the flush pipe extension  40 . 
   The  FIGS. 11   a  to  11   c  show also another embodiment to seal the flush pipe extension  40  to the first flush outlet (not shown). The sealing member  200  (shown in  FIG. 13 ) is inserted in the groove  198  which will maintain the sealing member in place. The sealing member  200  has an annular form and the groove  198  has a complementary shape to receive it. The sealing member  200  is preferably made of evazote foam but may be made from any another material suitable to seal the flush pipe extension to the first flush outlet. 
   Although preferred embodiments of the invention have been described in detail herein and illustrated in the accompanying figures, it is to be understood that the invention is not limited to these precise embodiments and that various changes and modifications may be effected therein without departing from the scope or spirit of the present invention.