You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a toilet and more particularly, to a tank ball assembly for toilet that can be adjusted to control the flushing amount of tank water for flushing urine.  
         [0003]     2. Description of the Related Art  
         [0004]      FIGS. 1A and 1B  show a prior art tank ball assembly and the use of the tank ball assembly in the tank of a toilet. As illustrated, the tank ball assembly comprises a cover stopper  1 , a tank ball  2  formed integral with the cover stopper  1 , and a gasket  3  fixedly fastened to the top wall of the cover stopper  1  around the tank ball  2 . When installed in the tank  4  of a toilet, the cover stopper  1  with the gasket  3  stop the passage of the drain port  6  of the tank  4 . When lifted the trip lever  5  of the tank  4 , the tank ball assembly is floating in tank water, and tank water runs out of the tank  4  through the drain port  6  in a rush. At the same time, the tank ball  2  is lowered with the water level till that the cover stopper  1  and the gasket  3  are stopped at the drain port  6  again. This design of tank ball assembly is functional, however it does not adjustment of flushing amount of tank water.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a tank ball assembly for toilet, which allows adjustment of flushing amount of tank water. According to one aspect of the present invention, the that tank ball assembly comprises a cover stopper mounted with a gasket for closing the drain port of the tank of a toilet, and a tank ball coupled to an upright short tubular flange of the cover stopper. The tank ball has a water inlet at the top center, and an air outlet at one lateral side. The user can rotate the tank ball on the upright short tubular flange of the cover stopper to adjust the angular position of the air outlet so as to adjust the flushing amount of tank water. According to another aspect of the present invention, an adjustment screw is threaded into a screw hole at the top side of a post at the cover stopper. The user can adjust the elevation of the adjustment screw so as to further adjust the flowing rate of tank water into the tank ball. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1A  is an exploded view of a tank ball assembly according to the prior art.  
         [0007]      FIG. 1B  is a schematic sectional view showing the use of the prior art tank ball assembly in the tank of a toilet.  
         [0008]      FIG. 2  is an exploded view of a tank ball assembly according to the present invention.  
         [0009]      FIG. 3A  is a sectional assembly view of the present invention, showing one position of the adjustment screw in the post of the cover stopper of the tank ball assembly.  
         [0010]      FIG. 3B  is similar to  FIG. 3A  but showing the position of the adjustment screw adjusted.  
         [0011]      FIG. 4A  is a schematic applied view of the present invention, showing the tank ball assembly opened from the drain port of the tank.  
         [0012]      FIG. 4B  is a schematic applied view of the present invention, showing the tank ball assembly stopped the drain port of the tank.  
         [0013]      FIG. 5A  is a schematic drawing of the present invention, showing the air outlet of the tank ball in the 90° position.  
         [0014]      FIG. 5B  is a schematic drawing of the present invention, showing the air outlet of the tank ball in the 40° position.  
         [0015]      FIG. 5C  is a schematic drawing of the present invention, showing the air outlet of the tank ball in the 0° position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     Referring to FIGS.  2 ˜ 4 , a tank ball assembly in accordance with the present invention is shown comprised of a cover stopper  10 , a gasket  15 , and a tank ball  20 . The cover stopper  10  comprises a post  12  vertically upwardly extending from the top wall at the center, and a short tubular flange  11  upwardly protruded from the top wall around the post  12 . The post  12  has a screw hole  120  at the top. An adjustment screw  13  is threaded into the screw hole  120 . The short tubular flange  11  has a first annular groove  110  and a second annular groove  111  extending around the periphery at different elevations. The gasket  15  is attached to the top wall of the cover stopper  10  around the short tubular flange  11  and secured thereto by a retaining ring  16  that is fastened to the first annular groove  110 . The tank ball  20  is capped on the short tubular flange  11  of the cover stopper  10  and pressed on the retaining ring  16  against the gasket  15 , having a bottom coupling flange  21  coupled to the second annular groove  111  of the short tubular flange  11  of the cover stopper  10 , a water inlet  22  at the center, and an air outlet  23  at one lateral side. The diameter of the water inlet  22  is greater than the air outlet  23 .  
         [0017]     After installation of the tank ball assembly in the tank  4  of a toilet as shown in  FIG. 4B , the cover stopper  10  with the gasket  15  and the tank ball  20  close the drain port  6  of the tank  4 . When biased the flush handle to turn the trip lever  5  upwards, the tank ball assembly is lifted from the drain port  6 , allowing tank water W to flush out of the tank  4  through the drain port  6  as sown in  FIG. 4A . At this time, the tank ball  20  is dipped in tank water W, and tank water W passes through the water inlet  22  into the inside of the tank ball  20  to expel air H out of the tank ball  20  through the air outlet  23 . When the tank ball  20  has been filled up with tank water W, the pressure of tank water W in the tank ball  20  forces the tank ball  20  downwards, and therefore the tank ball assembly is lowered to the drain port  6  to stop the passage again. During water filling stroke of the tank ball  20 , the tank ball  20  is floating in tank water W and the drain port  6  is opened for letting out tank water W. Within the time where tank water W is filling into the tank ball  20 , an amount of tank water W equal to the volume (height or depth) L shown in  FIG. 4B  is discharged out of the tank  4 . The volume L of tank water W is used to flush urine. When flushing stool, a relatively greater amount of flushing water is required. At this time, the user can hold the trip lever  5  in the lifted position for a relatively longer period of time, enabling tank water W to continuously run out of the tank  4  through the drain port  6  to clean the waste passage of the toilet.  
         [0018]     Further, the user can adjust the volume L of tank water W for flushing urine in either of two ways. The first way is to change the angular position of the air outlet  23  of the tank ball  20 , i.e., the tank ball  20  can be rotated on the short tubular flange  11  of the cover stopper  10  to the first position where the air outlet  23  is in the 90° position as shown in  FIG. 5A , the second position where the air outlet  23  is in the 45° position as shown in  FIG. 5B , or the third position where the air outlet  23  is in the 0° position as shown in  FIG. 5C . Subject to COS θ theory, when the air outlet  23  is in the 90° position as shown in  FIG. 5A , COS90°=0, therefore the speed of tank water W passing through the water inlet  22  into the tank ball  20  and the speed of air H passing through the air outlet  23  out of the tank ball  20  are the fastest; when the air outlet  23  is in the 45° position as shown in  FIG. 5B , COS45°=0.7, therefore it requires a relatively longer period of time than in the 90° position to have the tank ball  20  be fully filled up with tank water W; when the air outlet  23  is in the 0° position as shown in  FIG. 5C , COS0°=1, therefore it requires more longer period of time than in 90° position and in 45° position to have the tank ball  20  be fully filled up with tank water W. When in the 90° position, the air outlet  23  is at a first level L 1 . When in the 45° position, the air outlet  23  is at a second level L 2  below the first level L 1 . When in the 0° position, the air outlet  23  is in a third level L 3  below the second level L 2 . Therefore, by means of changing the angular position of the air outlet  23 , the flushing amount of tank water W is relatively adjusted.  
         [0019]     The second way to adjust the volume L of tank water W for flushing urine is to adjust the elevational position of the adjustment screw  13  in the screw hole  120  of the post  12  as shown in  FIGS. 3A and 3B . When adjusted the adjustment screw  13  to a relatively higher position as shown in  FIG. 3B , the adjustment screw  13  detains the flowing of tank water W into the tank ball  20 . On the contrary, adjusting the adjustment screw  13  to a relatively lower position as shown in  FIG. 3A , the adjustment screw  13  will not hinder the flowing of tank water W into the tank ball  20 , and therefore the tank ball  20  can be filled up with tank water W within a relatively shorter period of time.  
         [0020]     A prototype of tank ball assembly has been constructed with the features of FIGS.  2 ˜ 5 . The tank ball assembly functions smoothly to provide all the features discussed earlier.  
         [0021]     Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention, for example, the tank ball  20  and the cover stopper  10  can be made in integrity and the water inlet  22  and the air outlet  23  can be made after formation of the tank ball  20  with the cover stopper  10 . Accordingly, the invention is not to be limited except as by the appended claims.

Summary:
A tank ball assembly is disclosed to include a cover stopper mounted with a gasket for closing the drain port of the tank of a toilet, a tank ball coupled to an upright short tubular flange of the cover stopper and rotatable on the upright short tubular flange to adjust the angular position of the air outlet thereof and to further adjust the flushing amount of tank water, and an adjustment screw fastened to a post at the cover stopper and adjustable to approach to the water inlet of the tank ball and to further adjust the flowing rate of tank water into the tank ball.