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CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims priority based on U.S. provisional application 61/021,099, filed Jan. 15, 2008. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    The present invention relates to automatic dispensers used in liquid holding tanks in which the liquid level changes, and in particular to such dispensers which dispense cleaner from a container into a toilet overflow tube. 
         [0004]    A variety of dispensers exist for automatically dispensing chemicals into a water tank such as a toilet tank. Some toilet bowl cleaner dispensers use a float valve which opens and closes with changes in the toilet tank level during a flush cycle. For example, U.S. Pat. No. 5,903,930 describes a toilet cleansing agent dispenser having a cylindrical housing, a receiving body, and a float piece. The cylindrical housing is provided with a frame for mounting the dispenser in a toilet water tank. The float piece is capable of up-and-down displacement in accordance with the water level in the toilet water tank, so as to regulate the flow of the toilet cleansing agent from the receiving body into the toilet water tank. 
         [0005]    As the water level in the toilet water tank rises to a certain level after the flush, the float piece seals off the flow hole of the receiving body so as to terminate the flow of the cleansing agent into the toilet water tank. This type of dispenser can be inefficient. First, many such automatic liquid dispensers have a tendency for the product that is being dispensed to leak out of the dispenser in a somewhat uncontrolled manner which can result in overdosing of the product. Second, the objective is to keep the toilet bowl clean, not the water holding tank. Since all the cleaner is dispensed into the tank, rather than the bowl, most of the cleaner is flushed down the drain without cleaning the toilet bowl at all. 
         [0006]    It has been recognized that cleaner can be dispensed into the toilet overflow tube rather than into the toilet tank. For example, U.S. Pat. No. 3,254,797 describes a liquid chemical dispenser that is attached to the overflow pipe with a float positioned beneath the water in the toilet tank. Upon flushing, the water moves downward allowing the float to move downward to flex a diaphragm downwardly. This opens an inlet valve which allows liquid to fill the diaphragm cavity above the diaphragm. As the toilet tank refills with water, the float moves upward to flex the diaphragm upwardly to discharge liquid from the cavity above the diaphragm and into the overflow pipe. 
         [0007]    U.S. Pat. No. 6,321,392 describes another example device that dispenses cleaner into the toilet overflow tube. The device uses a solid puck of a chlorine donor. A body member receives the solid puck of cleaning agent. An inlet is in communication with the body member and is connectable to a ball cock through a refill tube, and an outlet is in communication with the body member and is connectable to the toilet overflow pipe through a connecting hose. The device delivers water and dissolved cleaner to the toilet overflow tube as the tank fills after a flush. However, the use of a solid puck results in inconsistent release of actives to the toilet bowl, particularly when the puck is near the end of its life. 
         [0008]    U.S. Pat. No. 5,353,957 describes yet another example device that dispenses cleaner into the toilet overflow tube. The device includes a container for holding a liquid cleaner, a dispensing nozzle, and a sensing tube. The dispensing nozzle is positioned on the container below the liquid level within the container. The sensing tube is immersible in the water in the toilet tank, whereby the cyclic fall and rise of the tank water results in the discharge of the liquid from the container through the dispensing nozzle. The container can be clipped to the upper open end of the toilet overflow tube such that the liquid falls from the dispensing nozzle into the toilet overflow tube. 
         [0009]    U.S. Pat. No. 5,152,015 describes still another example device that dispenses cleaner into the toilet overflow tube. The dispensing device includes an accumulator chamber having a conduit communicating with the toilet tank water. The accumulator chamber also has a product inductor conduit communicating with a product chamber. The device also includes a first product discharge conduit communicating with the accumulator chamber and a second product discharge conduit communicating with the discharge conduit and extending into the toilet tank overflow pipe. When the toilet tank water level falls during flushing, the water level in the conduit falls, causing a reduced pressure in the accumulator chamber and a rising of the product in the inductor conduit. When the toilet tank fills, the water rises in the toilet tank, compressing the air in the conduit forcing the product to be discharged from the accumulator through the first and the second product discharge conduit and into the toilet tank overflow pipe. 
         [0010]    Notwithstanding this variety of devices which dispense cleaner into a toilet overflow tube, a need still exists for improved dispensers for delivering an accurately controlled volume of liquid cleaner into a toilet overflow tube at a time when it will remain in the toilet bowl until the next flush. 
       SUMMARY OF THE INVENTION 
       [0011]    In a general aspect, the invention provides a dispenser that hangs on the outer wall of a toilet tank and utilizes the rise and fall of the toilet tank water during a flush to deliver a flowable composition from a container into the toilet overflow tube. The composition is then delivered into the toilet bowl from the toilet overflow tube after the flapper valve in the toilet tank closes which allows all of the cleaner to stay in the toilet bowl and work until the next flush. A user can hang the dispenser on the outer wall of a toilet tank and attach the composition container with little fuss. The working mechanism of the dispenser is a pumping system that does not require any moving parts but uses the rise and fall of the toilet tank water during a flush. Using the rise and fall of the tank water to pump a liquid composition from a container to the overflow tube allows a greater concentration of chemicals in the toilet bowl that stay there in between flushes to keep the toilet bowl cleaner for a longer period of time. 
         [0012]    In one aspect, the invention provides a dispenser for dispensing a composition in response to level changes in a liquid in a tank. The dispenser has a container for holding the composition, a discharge conduit in fluid communication with the container, an air inlet in fluid communication with the container, and a level sensing member mounted to the dispenser such that a lower end of the level sensing member contacts the liquid in the tank and senses its level. 
         [0013]    A rise of the liquid in the tank between a lower liquid level and a higher liquid level can cause the level sensing member to displace a volume of air from one section of the dispenser, thereby causing a concurrent displacement of product from another section of the dispenser while maintaining a constant (e.g., atmospheric) pressure throughout the dispenser during the entire cycle. 
         [0014]    In certain embodiments, the dispenser further comprises a holder structured to mount the container on a top end of an outer wall of the tank, the holder has at least one hook for mounting the container on a top end of an outer wall of the tank, there is a vent tube having an upper end opening and a lower end opening, the upper end opening of the vent tube being in fluid communication with the air inlet, and the lower end opening of the vent tube being in fluid communication with a section of an interior space of the container. In one particular non-limiting embodiment, the vent tube includes a check valve in the lower end opening. 
         [0015]    There can also be a compartment in fluid communication with the container and in fluid communication with the discharge conduit, the compartment accumulating an amount of the composition before a portion of the amount of the composition is discharged from the discharge conduit. The compartment can be in fluid communication with the container by way of a composition supply conduit having a lower orifice, the compartment includes an exit passageway having an upper inlet and a lower outlet, and the lower orifice of the composition supply conduit is positioned in the compartment below the upper inlet of the lower exit passageway of the compartment when a holder mounts a fluid control tube. The upper inlet of the lower exit passageway can be located on a top surface of an interior shoulder of the compartment, such that the lower orifice of the composition supply conduit is positioned in a well below the top surface of the interior shoulder of the compartment. 
         [0016]    In other forms, there can be an air gap hole located in a discharge passageway between the container and a discharge opening of the discharge conduit, a vent tube having an upper end opening and a lower end opening, the upper end opening of the vent tube being in fluid communication with the air inlet, and the lower end opening of the vent tube being in fluid communication with a lower section of an interior space of the container, and a supply tube having an upper end opening and a lower end opening, the upper end opening of the supply tube being in fluid communication with the discharge conduit, and the lower end opening of the supply tube being in fluid communication with the lower section of the interior space of the container. 
         [0017]    In this regard the lower end opening of the supply tube can be located above the lower end opening of the vent tube, and there can be a closure for sealing a mouth of the container as well as a vent tube attached to the closure. The vent tube has an upper end opening and a lower end opening, the upper end opening of the vent tube being in fluid communication with the air inlet, and the lower end opening of the vent tube being in fluid communication with a lower section of an interior space of the container, and there is a supply tube attached to the closure, the supply tube having an upper end opening and a lower end opening, the upper end opening of the supply tube being in fluid communication with the discharge conduit, and the lower end opening of the supply tube being in fluid communication with the lower section of the interior space of the container. A latch can be provided for holding the closure against the mouth of the container. 
         [0018]    In another aspect of the invention the dispenser further comprises a housing and a diaphragm wherein the housing has an open end that is sealed by the diaphragm thereby defining an interior space of the housing. The interior space is in fluid communication with the headspace of the container above the composition. The level sensing member can be a float, and the float can be attached to the diaphragm. As liquid falls in the tank from a higher liquid level to a lower liquid level, the diaphragm may flex in a first direction and displace air in the headspace to be vented into the headspace from the air inlet. The rise of liquid in the tank between the lower liquid level and the higher liquid level causes the diaphragm to flex in a second direction to alter air pressure in the headspace of the container above the composition and thereby cause the controlled discharge of the composition from the discharge conduit. In some embodiments, there is a constant pressure within the dispenser during the entire cycle. In one embodiment, the pressure is atmospheric. 
         [0019]    The float can be attached to a rod that is attached to the diaphragm, and the longitudinal position of the float on the rod can be adjustable so that the height of the float in the tank can be adjusted. 
         [0020]    Also, the parts can be configured and selected such that the air inlet passes through the closure, the tank is a toilet tank, and the liquid is water. 
         [0021]    In another aspect the invention provides a method for delivering a composition to a toilet bowl of a toilet having a toilet tank using a device of the above kind. One mounts the level sensor such that a lower end of the level sensor contacts water in the toilet tank, positions the discharge conduit such that a discharge opening of the discharge conduit can deliver the composition to the toilet bowl, and flushes the toilet. 
         [0022]    A fall of liquid in the tank between a higher liquid level and a lower liquid level (as the flush cycle starts) causes the level sensing member to alter air pressure in a headspace of the container above the composition and thereby causes air to be vented into the headspace from the air inlet. A subsequent rise of the liquid in the tank between a lower liquid level and a higher liquid level (as the flush cycle is ending) causes the level sensing member to alter pressure in the headspace and thereby causes a controlled discharge of the composition from the discharge conduit. 
         [0023]    In preferred forms of the method, the discharge opening of the discharge conduit is positioned in or above an overflow tube of the toilet or adjacent a rim of the toilet bowl of the toilet. Also, the container can be mounted on a top end of an outer wall of the toilet tank or on a top end of an outer wall of the toilet tank such that the container is located outside the toilet tank. 
         [0024]    In one aspect the liquid level sensor is in the form of a tube having a lower end immersed in the tank water such that water rises or falls in the tube during the flushing cycle. 
         [0025]    The foregoing and other advantages of the present invention will become apparent from the following description. In that description reference will be made to the accompanying drawings which form a part thereof, and in which there is shown by way of illustration an example embodiment of the invention. The example embodiment does not limit the full scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a perspective view of a dispenser of the present invention; 
           [0027]      FIG. 2  is another perspective view of the dispenser of  FIG. 1  with the top shroud, the fluid control tube, and the discharge conduit omitted; 
           [0028]      FIG. 3  is a cross-sectional view taken along line  3 - 3  of  FIG. 2  with the top shroud and the container omitted; 
           [0029]      FIG. 4  is a side view of the dispenser of  FIG. 1  installed on a toilet tank; 
           [0030]      FIG. 5  is a cross-sectional view of the dispenser taken along line  5 - 5  of  FIG. 4  with the container, the supply tube, the vent tube, and the holder omitted; 
           [0031]      FIG. 6  is a top, front, right perspective view of a second embodiment of a dispenser of the present invention; 
           [0032]      FIG. 7  is a front elevational view of the dispenser of  FIG. 6  with the top shroud omitted; 
           [0033]      FIG. 8  is a top plan view taken along line  8 - 8  of  FIG. 7  with the top shroud omitted; 
           [0034]      FIG. 9  is a side view of the dispenser of  FIG. 6  installed on a toilet tank, the view of the dispenser being a cross-sectional view taken along line  9 - 9  of  FIG. 7 ; 
           [0035]      FIG. 10  is a cross-sectional view of the dispenser of  FIG. 6  taken along line  10 - 10  of  FIG. 9  with the container and the holder omitted; 
           [0036]      FIG. 11  is a detailed view of the dispenser of  FIG. 6  taken along line  11 - 11  of  FIG. 9 ; and 
           [0037]      FIG. 12  is a cross-sectional view of the dispenser of  FIG. 6  taken along line  12 - 12  of  FIG. 11  with the shroud omitted. 
       
    
    
       [0038]    Like reference numerals will be used to refer to like parts from Figure to Figure in the following detailed description. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0039]    An example embodiment of the present invention is a dispenser that delivers liquid toilet cleaning composition to a toilet tank overflow tube during the flushing cycle in the toilet tank. However, it should be appreciated from the present description that the invention will be suitable for use with any liquid holding tank in which the liquid level changes, and any composition as long as the composition can flow. 
         [0040]    Turning now to  FIGS. 1 to 5 , there is shown a dispenser  10  according to an example embodiment of the invention. All of the components of the dispenser  10  may be fabricated from corrosion resistant metallic materials, or various clear or pigmented polymeric materials, such as polyethylene, polypropylene, silicone, etc. The dispenser  10  includes a holder  12  for mounting the dispenser components to a liquid holding tank. The holder  12  includes a lower generally U-shaped wall  13  that is integral with a back vertical wall  14 . The holder  12  includes a top surface  16  that can be flat or bowed slightly downward. The holder  12  includes a first mounting hook  17  having a top horizontal member  18  and a vertical member  19  that depends downwardly from the horizontal member  18 . The holder  12  also includes a second mounting hook  20  having a top horizontal member  21  and a vertical member  22  that depends downwardly from the horizontal member  21 . The hooks  17 ,  20  are used to attach the holder  12  to a tank as described below. 
         [0041]    The holder  12  also includes a central mounting beam  24  that supports a tubular first socket  25  having a hollow side port  26  that opens into an interior space of the first socket  25 . The central mounting beam  24  also supports a tubular second socket  27  having an air gap hole  28  that extends into the interior of the second socket  27 . The top surface  16  of the holder  12  also includes shroud mounting holes  29   a ,  29   b  at opposite sides of the top surface  16 . The top surface  16  of the holder  12  further includes a supply conduit passage  30 , fluid conduit passages  31   a ,  31   b  and a fluid compartment passage  32 . 
         [0042]    The dispenser  10  further includes a rigid hollow elongated fluid control tube  34  having a lower open end  35 , and also includes a flexible hollow discharge conduit  36  having a lower open end  37 . The fluid control tube  34  is attached to the first socket  25  (using, for example, an interference fit or an adhesive), and the discharge conduit  36  is attached to the second socket  27  (using, for example, an interference fit or an adhesive). 
         [0043]    The dispenser  10  further includes a fluid conduit  39  that connects the port  26  to a container closure  41 . In particular, the fluid conduit  39  is placed in fluid communication with a fluid passageway  42  in the top of the closure  41 . The fluid conduit  39  extends from the port  26  downward through the fluid conduit passage  31   b , back upward through the fluid conduit passage  31   a  and into the fluid passageway  42  in the top of the closure  41  (see  FIGS. 2 and 3 ). The fluid passageway  42  extends through the bottom surface of the closure  41 . A composition passageway  46  also extends through the closure  41  to a bottom surface of the closure  41 . A first composition supply conduit  48  with a lower orifice  49  places the composition passageway  46  and a fluid compartment  50  in fluid communication. 
         [0044]    The fluid compartment  50  is installed through the fluid compartment passage  32  in the top surface  16  of the holder  12  and is held against the back vertical wall  14  of the holder  12 . Looking at  FIGS. 2 and 5 , the generally rectangular compartment  50  includes opposed side walls  51 ,  52 , a back wall  53 , a front wall  54 , and an open upper end  55 . In the interior space of the compartment  50 , a shoulder  56  is arranged adjacent side wall  52  (see  FIG. 5 ). The shoulder  56  has a top surface  57 . A composition exit passageway  58  extends from an upper inlet  59  in the top surface  57  to a lower outlet  60 . In the interior space of the compartment  50 , a lower well  61  is also formed. The compartment  50  is dimensioned to assure that no composition overflow occurs during priming. The initial surge may occur faster than composition can drain from the compartment  50 . The volume of the compartment  50  just needs to be able to absorb the surge so the height of the compartment  50  required depends on the priming volume. 
         [0045]    A second composition supply conduit  63  places the lower outlet  60  and the second socket  27  in fluid communication. The second composition supply conduit  63  extends upward from the lower outlet  60  upward through the supply conduit passage  30  in the top surface  16  of the holder  12  and back downward to the second socket  27 . See  FIGS. 1 ,  3  and  5 . The downward slope of the second composition supply conduit  63  to the second socket  27  creates an inverted U-shape at the top of the second composition supply conduit  63  (see  FIG. 1 ). 
         [0046]    Referring now to  FIGS. 3 and 4 , the dispenser  10  includes a tubular supply tube  65  having an upper end opening  66  and a lower end opening  67 . The upper end opening  66  of the supply tube  65  is connected to the composition passageway  46  to place the upper end opening  66  of the supply tube  65  in fluid communication with the composition passageway  46 . The dispenser  10  further includes a tubular vent tube  69  having an upper end opening  70  and a lower end opening  71 . The upper end opening  70  of the vent tube  69  is connected to a vent conduit  72  having a lower end opening  73  that is positioned in the interior space of the compartment  50  as shown in  FIG. 5 . Air can flow from the interior space of the compartment  50  through the vent conduit  72 , through the vent tube  69  and out of the lower end opening  71  of the vent tube  69 . 
         [0047]    The dispenser  10  also includes a container  74 . The container  74  holds a flowable composition  75 , preferably a liquid cleaner. Headspace  76  is created in the container  74  above the composition  75 . The container  74  has an open mouth  77  that can be installed for leak-free fit in the closure  41  by way of suitable means such as an interference fit, a bayonet mounting, a pin and track mounting, a snap and socket mounting, or a hose-type coupler. The closure  41  may include a suitable sealing ring for creating a leak-free fit with the mouth  77  of the container  74 . In  FIG. 2 , it can be seen that the container  74  includes shroud mounting tabs  78   a ,  78   b . Looking at  FIG. 4 , the lower end opening  67  of the supply tube  65  opens at a location in the lower section of the interior space of the container  74 , and the lower end opening  71  of the vent tube  69  also opens at a location in the lower section of the interior space of the container  74 . As shown in  FIG. 4 , the lower end opening  67  of the supply tube  65  is located above the lower end opening  71  of the vent tube  69  in the container  74 . 
         [0048]    Referring now to  FIG. 1 , the dispenser  10  also includes a top shroud  80  to cover the container  74  and attach the container  74  to the holder  12 . The shroud  80  has a pair of holder mounting tabs  81   a ,  81   b  that may be fastened to the holder  12  by way of suitable fasteners (e.g., screws, pins, rivets, etc.) that connect the holder mounting tabs  81   a ,  81   b  to the shroud mounting holes  29   a ,  29   b  (see  FIG. 3 ) at opposite sides of the top surface  16  of the holder  12 . The shroud  80  also has a pair of container mounting tabs  83   a  (right side tab not shown in  FIG. 1 ) that may be fastened to the container  74  by way of suitable fasteners (e.g., screws, pins, rivets, etc.) that connect the shroud mounting tabs  78   a ,  78   b  of the container  74  to the container mounting tabs  83   a  (right side tab not shown) at opposite sides of the container  74  (see  FIGS. 1 and 2 ). 
         [0049]    Turning now to  FIG. 4 , the dispenser  10  is shown mounted on a toilet tank  90 . The toilet tank  90  has an outer wall  91  having a top end  92 . Water  93  is contained in the toilet tank  90 , and the toilet tank  90  includes an overflow tube  94 . The functioning of a toilet overflow tube is known in the art and therefore, will not be described further. When the dispenser  10  is mounted on the toilet tank  90 , the top horizontal member  18  of the first mounting hook  17  rests on the top end  92  of the outer wall  91  of the toilet tank  90 , and the vertical member  19  of the first mounting hook  17  resiliently engages an inner surface  95  of the outer wall  91  of the toilet tank  90 . The top horizontal member  21  of the second mounting hook  20  also rests on the top end  92  of the outer wall  91  of the toilet tank  90 , and the vertical member  22  of the second mounting hook  20  resiliently engages the inner surface  95  of the outer wall  91  of the toilet tank  90 . The central mounting beam  24  also rests on the top end  92  of the outer wall  91  of the toilet tank  90 . When the dispenser  10  is mounted on the toilet tank  90 , the lower open end  35  of the hollow fluid control tube  34  is located in a lower position in the toilet tank  90 , and the lower open end  37  of the flexible hollow discharge conduit  36  is located in the overflow tube  94 . When the tank lid is placed back on the toilet tank  90 , the user does not see the fluid control tube  34  and the hollow discharge conduit  36 . 
         [0050]    Having described the components of the dispenser  10  and the mounting of the dispenser  10  on a toilet tank  90 , fluid flow in the dispenser  10  can be explained further. Starting first with the fluid control tube  34 , when the fluid control tube  34  is placed in the water  93  contained in the toilet tank  90 , the water  93  rises to a level within the fluid control tube  34  approximately equal to the level of water  93  in the toilet tank  90 . 
         [0051]    When the toilet is flushed, the level of water  93  in the fluid control tube  34  and the level of water  93  in the toilet tank  90  move downward in direction D in  FIG. 4 . The downward movement of the water  93  in the fluid control tube  34  creates downward suction in the fluid control tube  34 . Because the fluid control tube  34  is in fluid communication with the headspace  76  of the container  74  by way of the first socket  25 , the side port  26 , the fluid conduit  39  and the fluid passageway  42  in the top of the closure  41 , a region of lower pressure is created in the headspace  76  of the container  74 . The region of lower pressure in the headspace  76  of the container  74  draws atmospheric air in through the vent conduit  72 , down through the vent tube  69 , up through the composition  75  in the container  74  (e.g., by bubbling) and into the headspace  76  of the container  74  to restore the pressure in the headspace  76 . Thus, the vent conduit  72  serves as an air inlet that allows atmospheric air to be sucked into the container  74  as the height of the tank water falls during a flush to maintain atmospheric pressure in the container  74 . 
         [0052]    When the toilet flapper valve closes during the flushing cycle in the typical manner, the level of water  93  in the fluid control tube  34  and the level of water  93  in the toilet tank  90  move back upward in direction U in  FIG. 4 . The upward movement of the water  93  in the fluid control tube  34  displaces air upward in the fluid control tube  34 . Because the fluid control tube  34  is in fluid communication with the headspace  76  of the container  74  by way of the first socket  25 , the side port  26 , the fluid conduit  39  and the fluid passageway  42  in the top of the closure  41 , a region of higher pressure is created in the headspace  76  of the container  74 . The region of higher pressure in the headspace  76  of the container  74  pushes composition  75  up through the supply tube  65 , into composition passageway  46 , down into the first composition supply conduit  48  and into the well  61  of the fluid compartment  50  to restore the pressure in the headspace  76 . Thus, the rise and fall of the water  93  in the tank  90  translates into a consistent dosage volume of composition  75 . Typically, the height difference in the rise and fall of the water  93  during a flush multiplied by the interior cross sectional area of the fluid control tube  34  equals the volume of composition  75  delivered per dose as the volume of air forces an equal volume of composition  75  from the container  74 . While the inner surface of the fluid control tube  34  in the example embodiment is circular (creating an interior cross sectional area of radius squared multiplied by pi), it should be appreciated that the fluid control tube can have different shapes and/or different interior dimensions that create different interior cross sectional areas. 
         [0053]    The composition  75  collects in the well  61  of the fluid compartment  50 . The well  61  remains filled with the composition  75  applying back pressure to keep the first composition supply conduit  48  primed. When more composition  75  is added to the well  61  of the fluid compartment  50 , the composition  75  rises above the top surface  57  of the shoulder  56  of the compartment  50 . The composition  75  then enters the composition exit passageway  58  and exits the lower outlet  60 . The composition  75  then enters the second composition supply conduit  63  and continues to the second socket  27  and the discharge conduit  36  where the composition  75  is discharged into the overflow tube  94 . The air gap hole  28  in the second socket  27  allows air into the second socket  27  to stop the siphon, preventing the entire volume of composition  75  from dosing in one shot. Because the composition  75  is discharged into the overflow tube  94 , the composition  75  enters directly into the toilet bowl without entering the water  93  in the tank  90 . As a result, the composition  75  does not get diluted with the water  93  in the tank  90  and does not merely get flushed down the drain. The composition  75  is allowed to work within the toilet bowl (e.g., by cleaning, disinfecting, fragrancing) until the next flush. 
         [0054]    Turning now to  FIGS. 6-12 , there is shown a dispenser  110  according to a second example embodiment of the invention. All of the components of the dispenser  110  may be fabricated from corrosion resistant metallic materials, or various clear or pigmented polymeric materials, such as polyethylene, polypropylene, silicone, etc. The dispenser  110  includes a holder  112  for mounting the dispenser components to a liquid holding tank. The holder  112  includes a lower generally U-shaped wall  113  that is integral with a back vertical wall  114 . The holder  112  includes a clip  117  having a top front horizontal member  118  and a front vertical member  119  that depends downwardly from the top front horizontal member  118 . The clip  117  also includes an intermediate vertical member  120  that depends downwardly from the top front horizontal member  118 , and a top rear horizontal member  121  and a rear vertical member  122  that depends downwardly from the top rear horizontal member  121 . The front vertical member  119 , the top front horizontal member  118 , and the intermediate vertical member  120  are used to attach the holder  112  to a tank as described below. 
         [0055]    The holder  112  also includes a mounting bracket  123  that is attached to the front vertical member  119 , and supports a level sensing assembly  124 . The holder  112  also includes a mounting plate  125  that is attached to the front vertical member  119 . The mounting plate  125  supports a tubular socket  127  having an air gap hole  128  that extends into the interior of the socket  127 . A flexible hollow discharge conduit  130  having a lower open end  131  is attached to the socket  127  (using, for example, an interference fit or an adhesive). A port  132  is in fluid communication with the interior of the socket  127 . 
         [0056]    Looking next at  FIGS. 8 and 9 , the level sensing assembly  124  includes a housing  182  having a top wall  183  and a circular side wall  184  that extends downwardly from the top wall  183 . The side wall  184  has a fluid port  185  with a central passageway that extends through the side wall  184 . The fluid port  185  is connected to a fluid conduit  139 . The level sensing assembly  124  also includes a rolling seal flexible diaphragm  186  that is coupled along its circumference to the side wall  184  of the housing  182 . The diaphragm  186  can be formed from an elastomeric material such as rubber. A piston  187  is attached to the bottom surface of the diaphragm  186  for flexing the diaphragm  186 . A rod  188  is connected to the piston  187 . The rod  188  includes threads  189  at its lower end. The rod  188  is supported in a vertical orientation by spaced apart collars  190   b ,  190   t  of the mounting bracket  123 . The level sensing assembly  124  also includes a float  191  having a cylindrical outer wall  192  that is attached by an annular plate  193  to a cylindrical inner wall  194 . The cylindrical inner wall  194  has an inner surface  195  with threads. The internal threads on the inner surface  195  of the cylindrical inner wall  194  of the float  191  engage the external threads  189  on the rod  188 . The position of the float  191  on the rod  188  can be adjusted by screwing and unscrewing of the float  191  on the rod  188 . 
         [0057]    The dispenser  110  includes a fluid compartment  150  that is installed to the holder  112  and is held against the back vertical wall  114  of the holder  112 . Looking at  FIGS. 7 and 10 , the generally rectangular compartment  150  includes opposed side walls  151 ,  152 , a back wall  153 , a front wall  154 , and an open upper end  155 . In the interior space of the compartment  150 , a shoulder  156  is arranged adjacent side wall  152  (see  FIG. 10 ). The shoulder  156  has a top surface  157 . A composition exit passageway  158  extends from an upper inlet  159  in the top surface  157  to a lower outlet  160 . In the interior space of the compartment  150 , a lower well  161  is also formed. The compartment  150  is dimensioned to assure that no composition overflow occurs during priming. The initial surge may occur faster than composition can drain from the compartment  150 . The volume of the compartment  150  just needs to be able to absorb the surge so the height of the compartment  150  required depends on the priming volume. A second composition supply conduit  163  places the lower outlet  160  of the compartment  150  and the socket  127  in fluid communication. The downward slope of the second composition supply conduit  163  to the socket  127  creates an inverted U-shape at the top of the second composition supply conduit  163  (see  FIG. 7 ). 
         [0058]    Looking at  FIGS. 7 and 8 , the dispenser  110  further includes a container closure  141 . The fluid conduit  139  is placed in fluid communication with a fluid passageway  142  in the top of the closure  141 . The fluid passageway  142  extends through the bottom surface of the closure  141 . A composition passageway  146  also extends through the closure  141  to a bottom surface of the closure  141 . A first composition supply conduit  148  with a lower orifice  149  places the composition passageway  146  and the fluid compartment  150  in fluid communication as shown in  FIGS. 8 and 10 . 
         [0059]    Referring to  FIGS. 8 and 12 , the dispenser  110  includes a tubular supply tube  165  having an upper end opening  166  and a lower end opening  167 . The upper end opening  166  of the supply tube  165  is connected to the composition passageway  146  to place the upper end opening  166  of the supply tube  165  in fluid communication with the composition passageway  146 . The dispenser  110  further includes a tubular vent tube  169  having an upper end opening  170  connected to a vent conduit  172  and having a lower end opening  173  that is positioned in the interior space of the compartment  150  as shown in  FIG. 10 . Air can flow from the interior space of the compartment  150  through the vent tube  169 , through the vent conduit  172 , and out of the lower end opening  173  of the vent conduit  172 . 
         [0060]    The dispenser  110  also includes a container  174 . The container  174  holds a flowable composition  175 , preferably a liquid cleaner. Headspace  176  is created in the container  174  above the composition  175 . The container  174  has an open mouth  177  that can be installed for leak-free fit in the closure  141  by way of suitable means such as an interference fit, a bayonet mounting, a pin and track mounting, a snap and socket mounting, or a hose-type coupler. The closure  141  may include a suitable sealing insert  144  (see  FIG. 11 ) for creating a leak-free fit with the mouth  177  of the container  174 . Referring now to  FIG. 6 , the dispenser  110  also includes a top shroud  180  to cover the container  174 . The shroud  180  is attached to the holder  112 . 
         [0061]    Referring to  FIGS. 11 and 12 , the mouth  177  of the container  174  includes a circular flange  178  having a lower surface  179 . When the container  174  in installed against the closure  141 , the lower surface  179  of the flange  178  is engaged by a protrusion  196  on a latch  197  that is pivotally mounted to the shroud  180  by way of pins  198   a ,  198   b . The protrusion  196  on the latch  197  may be biased toward the mouth  177  of the container  174  by a spring. The container  174  may be removed from the closure  141  by pressing the latch  197  in direction “A” in  FIG. 11  and pulling the container  174  downward away from the closure  141 . As shown in  FIG. 12 , the lower end opening  167  of the supply tube  165  opens at a location in the lower section of the interior space of the container  174 , and the lower end opening  171  of the vent tube  169  also opens at a location in the lower section of the interior space of the container  174 . 
         [0062]    Thus, the latch  197  allows consumers to secure the removable container  174  in place, and can also be used to help remove the container  174  when the container  174  is empty. Simply pushing the container  174  onto the closure  141  causes the latch  197  to click into place. This mechanical attachment adds a level of security to the friction fit between the mouth  177  of the container  174  and the sealing insert  144  of the closure  141 . The latch  197  can be used to help dislodge the mouth  177  of the container  174  from the sealing insert  144  of the closure  141 . 
         [0063]    Turning now to  FIG. 9 , the dispenser  110  is shown mounted on a toilet tank  90 . The toilet tank  90  has an outer wall  91  having a top end  92 . Water  93  is contained in the toilet tank  90 , and the toilet tank  90  includes an overflow tube  94 . The functioning of a toilet overflow tube is known in the art and therefore, will not be described further. When the dispenser  110  is mounted on the toilet tank  90 , the top front horizontal member  118  rests on the top end  92  of the outer wall  91  of the toilet tank  90 , the front vertical member  119  resiliently engages an inner surface  95  of the outer wall  91  of the toilet tank  90 , and the intermediate vertical member  120  resiliently engages an outer surface  96  of the outer wall  91  of the toilet tank  90 . When the dispenser  110  is mounted on the toilet tank  90 , the lower open end  131  of the flexible hollow discharge conduit  130  is located in the overflow tube  94 . The user can set the bottom of the float  191  to the height of the water  93  just as the tank  90  starts to fill (i.e., in the middle of a flush). 
         [0064]    Having described the components of the dispenser  110  and the mounting of the dispenser  110  on a toilet tank  90 , fluid flow in the dispenser  110  can be explained further. When the toilet is flushed, the level of water  93  in the toilet tank  90  moves downward in direction D in  FIG. 9 . As the level of water  93  falls, downward movement of the float  191  creates downward suction in the interior of the housing  182  above the diaphragm  186  because the diaphragm  186  flexes downward due to the piston  187  moving downward with the rod  188  and float  191 . Because the housing  182  is in fluid communication with the headspace  176  of the container  174  by way of the port  185 , the fluid conduit  139  and the fluid passageway  142  in the top of the closure  141 , a region of lower pressure is created in the headspace  176  of the container  174 . The region of lower pressure in the headspace  176  of the container  174  draws atmospheric air in through the vent conduit  172 , down through the vent tube  169 , up through the composition  175  in the container  174  (e.g., by bubbling) and into the headspace  176  of the container  174  to restore the pressure in the headspace  176 . Thus, the vent conduit  172  serves as an air inlet that allows atmospheric air to be sucked into the container  174  as the height of the tank water falls during a flush to maintain atmospheric pressure in the container  174 . 
         [0065]    When the toilet flapper valve closes during the flushing cycle in the typical manner, the level of water  93  in the toilet tank  90  moves back upward in direction U in  FIG. 9 . The upward movement of the water  93  and the float  191  (which rises with the water  93 ) flexes the diaphragm  186  upward due to the piston  187  moving upward with the rod  188  and float  191 . Because the interior of the housing  182  is in fluid communication with the headspace  176  of the container  174  by way of the port  185 , the fluid conduit  139  and the fluid passageway  142  in the top of the closure  141 , a region of higher pressure is created in the headspace  176  of the container  174 . The region of higher pressure in the headspace  176  of the container  174  pushes composition  175  up through the supply tube  165 , into composition passageway  146 , down into the first composition supply conduit  148  and into the well  161  of the fluid compartment  150  to restore the pressure in the headspace  176 . Thus, the rise and fall of the water  93  in the tank  90  translates into a consistent dosage volume of composition  175 . 
         [0066]    The composition  175  collects in the well  161  of the fluid compartment  150 . The well  161  remains filled with the composition  175  applying back pressure to keep the first composition supply conduit  148  primed. When more composition  175  is added to the well  161  of the fluid compartment  150 , the composition  175  rises above the top surface  157  of the shoulder  156  of the compartment  150 . The composition  175  then enters the composition exit passageway  158  and exits the lower outlet  160 . The composition  175  then enters the second composition supply conduit  163  and continues to the socket  127  and the discharge conduit  130  where the composition  175  is discharged into the overflow tube  94 . The air gap hole  128  in the socket  127  allows air into the socket  127  to stop the siphon, preventing the entire volume of composition  175  from dosing in one shot. The internal diameter of the discharge conduit  130  downstream from the air gap hole  128  can be varied such that the composition  175  is delivered as discrete drops, and the cleaner does not continuously wick down the internal surface of the discharge conduit  130 . A ¼ inch (6.35 mm.) internal diameter in the discharge conduit  130  is suitable. 
         [0067]    Because the composition  175  is discharged into the overflow tube  94 , the composition  175  enters directly into the toilet bowl without entering the water  93  in the tank  90 . As a result, the composition  175  does not get diluted with the water  93  in the tank  90  and does not merely get flushed down the drain. The composition  175  is allowed to work within the toilet bowl (e.g., by cleaning, disinfecting, fragrancing) until the next flush. 
         [0068]    The above description has been that of example embodiments of the present invention. It will occur to those that practice the art, however, that still other modifications may be made without departing from the spirit and scope of the invention. Hence, the scope of the invention should not be entirely judged by just the example embodiments. 
       INDUSTRIAL APPLICABILITY 
       [0069]    The present invention provides a dispenser that hangs on the outer wall of a toilet tank and utilizes the rise and fall of the toilet tank water during a flush to deliver a flowable cleaning composition from a container into the toilet overflow tube which then delivers the composition into the toilet bowl.

Summary:
Disclosed is a dispenser for dispensing a composition in response to level changes in a liquid in a tank. The dispenser includes a container for holding the composition, a discharge conduit in fluid communication with the container, an air inlet in fluid communication with the container, and a level sensing member mounted to the dispenser such that a lower end of the level sensing member contacts the liquid in the tank and senses its level. In use, a rise of the liquid in the tank between a lower liquid level and a higher liquid level causes the level sensing member to alter air pressure in a headspace of the container above the composition and thereby cause a controlled discharge of the composition from the discharge conduit; and a fall of the liquid in the tank between the higher liquid level and the lower liquid level causes the level sensing member to alter pressure in the headspace and thereby causing air to be vented into the headspace from the air inlet.