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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     The present invention relates to a flush valve for toilets, and more specifically to a converter or adapter for changing a single flush valve into a dual flush valve. 
     In order to prevent the unnecessary of use of water when flushing a toilet, a number of different dual valve systems have been designed which enable the toilet to be flushed using either a large amount or a reduced amount of water as desired. 
     An early example of a dual valve system of this type is disclosed in Rath U.S. Pat. No. 1,474,288. In this construction, a pair of flapper valves are positioned at different heights on a unitary tubular valve housing. Each valve is independently operated and enables an individual to utilize either a large amount or a reduced amount of water when flushing the toilet. 
     Other examples of dual valve systems are disclosed in Eastman U.S. Pat. No. 3,795,016; Contreras U.S. Pat. No. 4,042,982; Cameron U.S. Pat. No. 4,175,295 and Bliss U.S. Pat. No. 6,178,567B1. In each of these patents, a pair of flapper valves are disposed at different heights on a valve housing. Each of the flapper valves is connected to a pivotable handle by a chain extending from the valve to an attachment point on the handle or to a lever extending from the handle. In order to control the volume of water utilized when flushing the toilet, the handle is rotated in a first direction to open the higher flapper valve to provide the desired amount of water. To open the lower flapper valve, the handle is either rotated in the opposite direction or rotated further in the first direction to open the lower valve and use an increased amount of water when flushing the toilet. 
     While each of the above-referenced patents illustrates a useful manner of controlling the amount of water utilized when flushing a toilet, in each of the above patents, the dual valve system is comprised of a single structure on which the pair of flapper valves are disposed. As a result, when incorporating one of these dual valve systems into an existing toilet, the single valve system already present within the toilet must be completely removed in order to insert the particular dual valve system. The single valve system is then discarded, resulting in a significant waste of material and money. Furthermore, should the valve housing for the dual valve system ever become damaged, the entire valve housing must be removed and replaced which increases the expense of utilizing a dual mode valve system, reducing the benefit obtained by the reduction in water consumption. 
     Therefore, it is desirable to develop a converter or adapter for a conventional single valve flush system capable of converting the single valve system into a dual valve flush system. Such a converter should be easily attachable to the flush tank for the toilet and to the existing single valve system. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an adapter for converting a single valve flush system into a dual valve flush system incorporating the conventional single valve system. 
     It is another object of the invention to provide an adapter that is easily attachable to the existing single flush system and to the flush tank for the toilet. 
     It is still another object of the invention to provide an adapter that has a simple construction and is inexpensive to manufacture. 
     It is still a further object of the present invention to provide an adapter which can be configured for mounting to either a side wall or a front wall of the flush tank to accommodate various configurations for the particular single valve system located within the tank. 
     The present invention is an adapter for a single valve flush system utilized to convert the single valve system into a dual mode valve system. The adapter includes a first tubular section having an open upper end securable to the bottom of the single valve system and a closed lower end, and a second tubular section having an open upper end and an open lower end attachable to the flush tank. The second tubular may conveniently comprise one type of existing flapper valve commonly used. The first section and second section are connected by a hollow channel extending between the lower end of the first section and the upper end of the second section such that the upper end of the second section is generally at the same height as the lower end of the first section. 
     The adapter also includes a flapper valve pivotally mounted to the first section and releasably engageable with the upper end of the second section to selectively open and close the upper end of the second section. 
     When the adapter and the single valve system are secured to one another and to the flush tank, the flapper valves are operated by a pair of handles located on the exterior of the tank and attached to a mounting assembly. The mounting assembly includes a sleeve extending through a wall of the flush tank and enclosing a pair of cylindrical arms that are rotatably contained within a pair of throughbores extending through the sleeve. Opposite the handles, the arms are connected to a pair of levers which are in turn connected to a pair of chains which lead down to the flapper valves. By moving one or the other of the handles, the selected valve can be opened in order to flush the toilet with the desired volume of water. 
    
    
     Various other features, objects and advantages of the invention will be made apparent from the following detailed description taken together with the drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following drawings illustrate the best mode currently contemplated of practicing the present invention. 
     FIG. 1 is a side elevation view of a toilet tank enclosing a single valve flush system connected to an adapter constructed according to the present invention to form a dual valve flush system; 
     FIG. 2 is an enlarged partial sectional view through the toilet tank of FIG. 1 showing the dual valve flush system. 
     FIG. 3 is a vertical sectional view of the flush system of FIG. 2 with the low volume flapper valve opened; 
     FIG. 4 is a vertical sectional view of the flush system of FIG. 2 with the high volume flapper valve opened; 
     FIG. 5 is a partial horizontal section through a toilet tank showing a mounting assembly and handles secured to a wall of the toilet tank for connection to the dual valve flush system of FIG. 2; 
     FIG. 6 is an enlarged partial sectional view of the handles and mounting assembly of FIG. 5; 
     FIG. 7 is a sectional view taken on line  7 — 7  of FIG. 6; 
     FIG. 7A is a sectional view taken on line  7 A— 7 A of FIG. 6; 
     FIG. 8 is a view similar to FIG. 5 showing the handle mounting assembly attached to the opposite side of a tank front wall; and, 
     FIG. 9 is a horizontal section through a toilet tank showing a handle mounting assembly with extended operating arms for mounting to a tank side wall. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With respect now to the drawing figures in which like reference numerals designate like parts throughout the disclosure, in FIG. 1 a flush system adapter  10  is illustrated schematically and shown connected to a single valve system  12  within a toilet flush tank  14  to provide the present invention. Referring also to FIG. 2, the tank  14  includes a bottom wall  16  which defines a discharge opening  18 , a front wall  20 , a rear wall  22  and a pair of side walls  23  joining front and rear walls  20  and  22 , respectively, to form an open top  24  that is closed by a removable cover  25 , all in a conventional manner. 
     Referring also to FIGS. 3, and  4 , the single valve system  12  can be any conventional flush system used for single flush toilets but preferably is the system made by Fluid Master, Inc. of San Juan Capastrano, calif. The system  12  includes an upper tubular section comprising an upwardly extending stand pipe  26  having an open upper end  28  and connected at a lower end  29  to an L-shaped tube  30 . The tube  30  includes a sleeve  32  into which the lower end  29  of the stand pipe  26  is inserted. The sleeve  32  is in fluid communication with an passage  34  which extends perpendicularly from the sleeve  32  to a lower tubular section including a discharge pipe  36 . The discharge pipe  36  is generally circular in shape and includes a sloped, open upper end  38 , and an open lower end  40 . The upper end  38  is connected to the passage  34  such that fluid flowing down the stand pipe  26  into the sleeve  32  will flow through the passage  34  and into the discharge pipe  36 . 
     The sleeve  32  also includes a pair of outwardly extending projections  42  spaced on opposite sides of the sleeve  32 . The projections  42  are each connected to a pair of flanges  44  extending from opposite sides of a valve support  46 . The valve support  46  is connected to a first flapper valve  48  that is capable of moving pivotally with the valve support  46 . With the pivoting movement, the valve  48  is releasably engageable with the sloped open upper end  38  of the discharge pipe  36 . This enables the discharge pipe  36  to be selectively opened and closed by the movement of the flapper valve  48 . 
     Referring now to FIGS. 5-7, a chain  50  is connected at one end to the flapper valve  48  and at the opposite end to a first lever  52 . The first lever  52  is in turn connected opposite the chain  50  to a mounting assembly  54 . The mounting assembly  54  includes a generally cylindrical sleeve  56  disposed in a wall  23  of the flush tank  14 . The sleeve  56  has a pair of parallel throughbores  58  which extend the length of the sleeve. Each throughbore  58  encloses a rotatable cylindrical arm  60  and  61 , respectively, which has its opposed ends positioned on opposite sides of the tank wall  23 . The arms  60  are connected outside of the tank  14  to a pair of handles  62  and  63  each of which terminates in a finger grip  64  opposite the arms  60  and  61 . 
     On the exterior of the flush tank wall, the end of cylindrical sleeve  56  also includes a mounting flange  66  that retains the outer ends of the rotatable arms  60  and  61  and cooperates with a mounting collar  67  threaded on the threaded OD  69  of the sleeve  56  inside the tank wall to hold the entire assembly in place. The opposite ends of the rotatable arms  60  and  61  are retained in place axially with an end cap  71  threaded over the end of the sleeve  56 . More specifically and referring also to FIG. 7A, before the end cap  71  is threaded over the end of the sleeve  56 , a retainer insert  103  is first placed over the ends of the rotatable arms  60  and  61  and against the end of the cylindrical sleeve  56 . Preferably, the retainer insert is provided with two openings  106  sized to receive the ends of the arms  60  and  61  and also includes a pair of diametrically opposite retaining tabs  105 . The retainer insert  103  is received in a shallow circular recess  104  formed in the end of the cylindrical sleeve  56 . The rim  108  defining the end recess  104  is provided with a pair of notches  107  that receive the retaining tabs  105  when the insert is positioned in the recess  104 . The end cap  71  has a central opening  109  large enough in diameter to receive both extended arms  60  and  61  so it may be threaded onto the end of the sleeve  56  to hold the insert  103  in place. 
     Looking again at FIGS. 2-4, the adapter  10  includes an upper tubular section  68  having an open upper end  70  and a closed lower end  72 . Adjacent the lower end  72 , an enclosed channel  74  extends outwardly from the first tubular section  68  and is connected to a lower tubular section  76 . The lower tubular section  76  includes a sloped open upper end  78 , to which the channel  74  is connected, and an open lower end  80 . The lower end  80  connects to the toilet stool inlet in a conventional manner. The upper section  68 , channel  74  and lower section  76  are all formed of a rigid, durable material, such as a hard plastic, preferably the same material as the upper valve system  12 , and are connected by any suitable means. Each of the lower section  68 , upper section  76  and channel  74  may be formed of PVC and secured to the remaining parts by an adhesive. 
     The adapter  10  also includes a second flapper valve  82  having a pair of extensions  84  extending outwardly from opposite sides of the second valve  82  parallel to one another. The extensions  84  are pivotally mounted to opposite sides of the upper section  68  by a pair of projections  86 . The second valve  82  further includes a chain  88  attached to the second valve  82  at one end and to a second lever  90  at the other end (see FIG.  5 ). The second lever  90  is attached to the cylindrical arm  61  adjacent the arm  60  to which the first lever  52  is attached. 
     To secure the single valve system  12  to the adapter  10 , a threaded collar  92  is threadably engaged with the lower end  40  of the discharge pipe  36 . A first  0 -ring  94  is then positioned around the lower end  40  beneath the washer  92 . The lower end  40  is then threadedly engaged within the open upper end  70  of the upper section  68  until the flush system  12  is positioned at a desired height above the adapter  10 . The collar  92  is then rotated with respect to the discharge pipe  36  until the washer  92  compresses the  0 -ring  94  into engagement with the upper end  70  of the upper tubular section  68 . In this manner, the O-ring  94  forms a water-tight barrier between the discharge pipe  36  and upper tubular section  68 . 
     Once the single valve system  12  is attached to the adapter  10 , the adapter  10  can be secured to the flush tank  14 . A sealing ring  96  is positioned around the open lower end  80  of the lower tubular section  76  and the section  76  is inserted through the discharge opening  18  in the bottom wall  16  of the flush tank  14 . A second collar  98  is then threadedly engaged with the lower end  80  beneath the bottom wall  16  of the flush tank  14 . The collar  98  is then rotated with respect to the lower section  76  in order to compress the sealing ring  96  between the bottom wall  16  of the tank  14  and the lower end  80  of the lower section  76  to form a watertight seal between the lower section  76  and the bottom wall  16  of tank  14 . 
     Referring now to FIGS. 1,  3  and  5 , once the adapter  10  and single valve system  12  are secured to one another and to the flush tank  14 , the handles  62  and  63  can be utilized to operate either the first valve  48  on the system  12  or the second valve  82  on the adapter  10  to provide the desired amount of water for flushing the toilet. As shown in FIGS. 3 and 5, when the handle  62  is pivoted with respect to the flush tank  14 , the attached cylindrical arm  60  rotates and first lever  52  moves upwardly to unseat the first valve  48  from within the open upper end  38  of the discharge pipe  36 . Movement of the first valve  48  causes the volume of water contained between the full water level at the top of the standpipe  26  for the flush tank  14  and a water level  99  at the bottommost portion of the open upper end  38  to flow through the discharge pipe  36  and provide a flushing action for the toilet. 
     Alternatively and referring also to FIG. 4, when the handle  63  is pivoted with respect to the flush tank  14 , the attached cylindrical arm  61  and second lever  90  operate to lift the second valve  82  from within the upper end  78  of the lower tubular section  76 . Unseating of the second valve  82  allows the volume of water contained between the full water level for the flush tank  14  and a water level  101  at the bottommost portion of the upper end  78  to flow through the lower section  76  and provide a flushing action for the toilet. FIG. 8 shows how the operating handle mounting assembly  54  is easily adapted for opposite mounting on the other end of the tank front wall  20  from the FIG. 5 mounting. 
     In an alternative embodiment, as best shown in FIG. 9, the handles  62  and  63  can also be mounted on a side wall  23  of the flush tank  14 . In this embodiment, each of the rotatable arms  160  and  161  extending outwardly from the throughbores  58  in the sleeve  56  has a length greater than the arms  60  and  61  utilized when the mounting assembly  54  is disposed on the front wall  20  of the tank  14 . In this embodiment, the arms  160  and  161  are supported opposite the side wall  22  by a support  100  extending across the tank  14  between the front wall  20  and rear wall  22 . The arms  160  and  161  extend through a pair of adjacent openings  102  disposed in the support  100  and in alignment with the throughbores  58  in the sleeve  56 . The openings  102  have a diameter slightly larger than the diameter of the arms  160  and  161  such that the arms may rotate easily within each of the openings  102 . Further, the arms  160  and  161  are attached to the chains  50  and  88  secured to the first and second valves  48  and  82 , respectively, on the side of the support  100  opposite the mounting assembly  54 . All of the other components of the mounting assembly are identical to the previously described embodiment. 
     The support  100  can be positioned between the front wall  20  and rear wall  22  of the tank  14  by any suitable means, such as an adhesive  104 , as shown in FIG. 9, or by other suitable means, such as by U-shaped hanger brackets, not shown, attached at opposite ends of the support  100  and engageable with the top edges of the front wall  20  and rear wall  22 . 
     Various alternatives are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.

Summary:
An adapter for attachment to an existing single flush valve system to convert the single valve system to a dual flush valve system comprises a pair of tubular sections vertically offset from one another and connected by a hollow, enclosed channel. The upper section is adapted to engage a discharge pipe of an existing single flush valve system in order to select a discharge level for a lower volume flush and direct water flowing through the discharge pipe through the adapter. The bottom section of the adapter includes a pivotable flapper valve that can be operated independently of the flapper valve disposed on the single flush system in order to provide a greater volume of water for flushing of the toilet. A mounting arrangement is also provided for attachment to the toilet tank which enables the existing and additional flapper valves to be selectively activated using a pair of handles connected to the arrangement.