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CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of UK patent application GB0323135.4 filed 03 Oct. 2003. 
     BACKGROUND TO THE INVENTION 
     1. Field of the Invention 
     This invention relates to an overflow device for a bathtub. 
     2. Description of the Prior Art 
     Conventionally, bathtubs are provided with an overflow hole at a level near the top of the bathtub, and the overflow hole is connected to the waste pipe leading from the bathtub. Accordingly, once the level of water reaches the overflow hole, the excess water can drain away to reduce the risk that water will spill over the upper edge of the bathtub and cause a mess and possible damage. Nevertheless, in some cases the overflow cannot cope with the rate of flow required to prevent spillage, for example if the pressure of the water supply to the taps is very high, or if the overflow passageway has become partly or completely blocked. Furthermore, preventing a bathtub from overflowing by draining away the excess water is wasteful of water. 
     There have been various proposals to deal with these problems. For example, systems are known for automatically opening the normal plug of the bathtub when the water level reaches a predetermined level, but such systems still result in wasted water. Also, electrical systems are known for automatically turning off the supply of water to the bathtub when the water level reaches a predetermined level, but such systems require a supply of electricity and a great amount of care in design and installation to prevent any risk of electrical shock. Furthermore, mechanical systems are known for automatically turning off the supply of water to the bathtub when the water level reaches a predetermined level, but such systems suffer variously from the problems of: bulkiness (see WO099/11876); that they would be difficult to reset when applied to a bathtub (see GB2312838); that reliance is made purely on the buoyancy of a float to provide the motive force to close off the water supply valve(s) (see GB2288330); that they need to be reset by a mechanism that it may be difficult to make accessible in a bathroom scenario (see WO93/09303); or that they are mounted inside the bathtub and need to be connected to the outlet of a conventional bath tap (see JP55042982). The present invention, or at least specific embodiments of it, addresses these problems. 
     SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the present invention, there is provided an overflow device for a bathtub having a bath tap and an overflow hole, the device having: an overflow inlet arranged for mounting in the overflow hole; an overflow outlet communicating with the overflow inlet and for connection to a waste; a water inlet for connection to a water supply; a water outlet for connection to the bath tap; a valve connected between the water inlet and water outlet and having a closed state and an open state; means (such as a spring) for storing energy that can be used to change the valve from the open state to the closed state; means for detecting water that has entered the overflow inlet and for triggering the device to change, using energy stored by the energy storing means, from a set state in which the valve is open to a triggered state in which the valve is closed; and a manually operable resetting element that can be operated by a user to replenish the energy storing means with energy and to return the device to the set state. Because the device is arranged to be connected between the water supply and a conventional bath tap, it can be permanently plumbed in and the bulk of the device can be hidden from view outside the bathtub, for example behind a conventional bath panel. Because the device has an energy storing means that can be replenished with energy upon manual operation by the user, rather than relying, for example, purely on the buoyancy of a float to close a valve, the device can be of small size and yet have sufficient energy stored to close the valve reliably. 
     Preferably, the resetting element has a portion that projects, or is accessible, through the overflow inlet. Therefore there is no need to provide a hole through the bathtub or a bath panel, other than the conventional overflow hole in order to provide access to the resetting element. 
     Preferably, the water-detecting/triggering means comprises a float and a lever acting between the float and a detent arrangement for holding the resetting element in the set state, the lever having a velocity ratio of greater than unity. Such a velocity ratio enables any friction in the detent arrangement to be overcome more reliably. 
     Preferably, the device has a second such water inlet for connection to a water supply, a second such water outlet for connection to the, or another, bath tap, and a second such valve connected between the second water inlet and second water outlet and having a closed state and an open state, and the water-detecting/triggering means, energy storing means and resetting means are arranged also to operate the second valve. Accordingly, both a hot water supply and a cold water supply to the bathtub can be closed off when the bath begins to overflow. 
     Preferably, the energy storing means comprises a respective spring for each valve. This enables the stored energy to be more directly applied to each valve than if a single spring were used operating through some mechanism that divided is energy between the valves and no doubt introduced unwanted friction into the arrangement. 
     Preferably, the valves are symmetrically arranged to either side of a line of action of the resetting element. This produces a balanced arrangement and avoids sideways loading of the water-detecting/triggering means. 
     In accordance with a second aspect of the invention, there is provided a bathtub having a bath tap, an overflow hole and an overflow device of the first aspect of the invention, the overflow inlet being mounted in the overflow hole and the water outlet being connected to the bath tap. 
     Preferably, the bulk of the device is disposed outside the bathtub. For example, in a specific embodiment, all of the device is disposed outside the bathtub except the end of the overflow inlet, a nut, the end of the resetting element, a rose and a mounting plate for the rose. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 to 5  are a front view, rear view, plan view, underplan view and side view, respectively, of an overflow device; 
         FIG. 6  is a cross-sectioned side view, on a larger scale, of the device, with its top cover removed, in its set state; 
         FIG. 7  is a plan view of the device, with its top cover omitted, in the set state; and 
         FIGS. 8 &amp; 9  are similar to  FIGS. 6 and 7 , respectively, but with the device in its triggered state. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings and in particular to  FIGS. 1 to 5 , the overflow device  10  comprises a housing  12  having top and bottom covers  14 , 16  with associated gaskets  18 , 20  and attached to the housing  12  by screws. The housing  12  and covers  14 , 16  are moulded in plastics material. The housing  12  provides a cold water inlet  22  and cold water outlet  24  which communicate with each other via a cold water valve  26 . The housing  12  also provides a hot water inlet  28  and hot water outlet  30  which communicate with each other via a hot water valve  32 . In use, the inlets  22 , 28  are connected to the domestic cold and hot water supplies, and the outlets  24 , 30  are connected to conventional cold and hot taps of a bathtub  34  or to a conventional bath mixer tap. The valves  26 , 32  are ceramic disc valves each having an operating spindle that can be rotated by about a quarter of a turn to turn the valve  26 , 32  on or off. Referring also to  FIG. 6 , the housing  12  also provides an overflow inlet  36  that in use passes through a conventional overflow hole in the wall of the bathtub  34  and is held in place by a nut  38 . A sealing washer  40  is sandwiched between the wall of the bathtub  34  and a boss  42  formed on the front wall of the housing  12 . A rose fixing plate  44  is sandwiched between the wall of the bathtub  34  and the nut  38 . A rose  46  is a snap-fit on the rose fixing plate  44 , and the end of a reset plunger  48  protrudes through a hole in the rose  46 . The underside of the rose  46  has a cut-away  50  so that, when the water in the bathtub  34  reaches a sufficient level, it can flow through the cut-away  50  into the rose  46  and thence into the overflow inlet  36 . The bottom cover  16  provides an overflow outlet  52  that in use is connected to a conventional waste pipe leading from the bathtub  34 . 
     Referring now in particular to  FIGS. 6 and 7 , the housing  12  and a portion  54  of the bottom cover  16  together provide a float chamber  56  containing a float  58  and which can fill with bath water entering the device  10  through the overflow inlet  36 . The housing  12  also provides a weir  60  over which water can flow from the float chamber  56  to a passageway  62  leading to the overflow outlet  52 . A fine drain hole  64  is formed in the portion  54  of the bottom cover  16  providing the base of the float chamber  56  so that, in time, water can escape from the float chamber  56  into the overflow outlet  52  without needing to pass over the weir  60 . 
     The reset plunger  48  extends from the rose  46  almost as far as the rear of the housing  12  and is formed with a notch  66  in its underside adjacent the rear end of the plunger  48 . A trigger lever  68  with integral trunnions  70  is supported by the housing  12  for pivoting about the horizontal axis  72  of the trunnions  70 . To the rear of the axis  72 , the trigger lever  68  provides a pawl  74  releasably engageable with the notch  66  in the reset plunger  48  to provide a detent. To the front of the axis  72 , the trigger lever  68  provides a surface  76  against which a protrusion  78  on the top of the float  58  can bear. The distance between the surface  76  and the axis  72  is substantially greater than the distance between the pawl  74  and the axis  72  so that as the surface  76  moves upwardly a particular distance, the pawl  74  moves downwardly by a substantially smaller distance so as to give a velocity ratio of greater than unity from the float  58  to the pawl  74 . 
     Below and symmetrically to either side of the rear end of the trigger lever  68 , the housing  12  provides a pair of compartments (shown by dotted lines  73  in  FIG. 6 ) each containing a respective one of the valves  26 , 32 . The operating spindles  80  of the valves  32  project upwardly from the compartments. Each spindle  80  is fitted with a crank  82  having a central boss  84  and an eccentric crank pin  86 . A torsion spring  88  is wound around each boss  84  and has one arm engaging the respective crank pin  86  and the other end engaged in a notch  90  in the housing  12  to the side of the weir  60 . The springs  88  are arranged to urge the spindles  80  in the directions to close the valves  26 , 32  and are sufficiently strong to do so even if the valves  26 , 32  are furred up to some extent. The reset plunger  48  is provided adjacent its rear end with a pair of laterally-projecting, rearwardly-facing abutments  92  that engage the crank pins  86  so that when the reset plunger  48  is pressed inwardly the abutments  92  urge the crank pins  86  in a direction to open the valves  26 , 32 . The underside of the top cover  14  is formed with a portion  94  that projects downwardly into sliding engagement with the rear end of the plunger  48  between the abutments  92 , to prevent the rear end of the plunger  48  lifting upwardly so that the pawl  74  will not engage properly with the notch  66 . 
     The plumbing device  10  is normally maintained in the “set” state shown in  FIGS. 6 and 7 . In the set state, the cold and hot water valves  26 , 32  are open. Therefore, when a user wishes to run a bath, they can open the conventional hot and/or cold taps, and the bathtub  34  will fill with water flowing from the hot and/or cold supplies, via the hot and/or cold water valves  32 , 26  and the conventional hot and/or cold taps, into the bathtub  34 . If the user does not then turn off the conventional hot and/or cold taps before the bathtub  34  starts to overflow, the device  10  is triggered to the “triggered” state shown in  FIGS. 8 and 9  in which the hot and cold water valves  32 , 26  are closed so that filling of the bathtub  34  ceases even though the conventional hot and/or cold taps are still open. More specifically, as the water in the bathtub  34  rises to the level of the overflow inlet  36 , it starts to flow through the cut-away  50  in the rose  46  and through the overflow inlet  36  into the float chamber  56 , so that the float  58  rises. Gravity tends to hold the trigger lever  68  down on the float  58 , but as water level in the float chamber  56  rises and the buoyancy of the float  58  increases, it eventually overcomes the weight of the trigger lever  68  and the friction between the pawl  74  on the trigger lever  68  and the notch  66  in the reset plunger  48 , so that the trigger lever  68  pivots anticlockwise as viewed in FIG.  6  and the pawl  74  disengages from the notch  66 . The reset plunger  48  is then free to slide to the right as viewed in  FIG. 6 . Therefore the actions of the springs  88  on the crank pins  86  cause the cranks  82  to turn so that the cold and hot water valves  26 , 32  close, and the crank pins  86  bearing on the abutments  92  cause the reset plunger  48  to move to the right. The device  10  therefore attains the triggered state of  FIGS. 8 and 9 . 
     Once the user gets into the bathtub  34 , the water level will rise above the level of the weir  60 , so that the weir  60  overflows and the water can pass via the passageway  62  and the overflow outlet  52  to waste. Once such overflowing ceases, the float chamber  56  can gradually empty of water by leakage through the drain hole  64 , as a result of which the float  58  falls to the bottom of the float chamber  56  and the trigger lever  68  pivots clockwise, due to gravity, maintaining its surface  76  in contact with the protrusion  78  on top of the float  58 . The device  10  is then in a “resettable” state. 
     Once in the resettable state, for example when the user has finished their bath, or when a user is ready to run another bath, the user can reset the device  10  to its set state by depressing the end of the reset plunger  48  that projects through the rose  46 . The plunger  48  will therefore slide to the left as viewed in  FIGS. 8 and 9 . The abutments  92  on the plunger  48  bearing on the crank pins  86  will turn the cranks  82  so that the cold and hot water valves  26 , 32  open. The end of plunger  48  will ride over the pawl  74  on the trigger lever  68 , slightly tipping the lever  68  anticlockwise, until the notch  66  in the plunger  48  reaches the pawl  74 , whereupon the lever  68  will tip back and the pawl  74  will engage the notch  66 , so that the device is reset to the set state. If the user has not turned off the conventional bath taps before resetting the device  10 , that will be immediately apparent as the cold and hot water valves  26 , 32  open, thus prompting the user to turn off the conventional bath taps, unless of course they are running another bath. 
     Various modifications and developments may be made to the embodiment described above. For example, since the end, overflow-providing wall of a typical bathtub is inclined to the vertical by a few degrees, the overflow inlet  36  may be modified so that its axis, and so that the face of its boss  42 , are inclined correspondingly. Also, the arrangement of the abutments  92  on the reset plunger  48  may be modified so that the reset plunger  48  cannot be moved to the right, as viewed in  FIG. 7 , free of the pins  86 . For example, the reset plunger  48  may be provided with lateral slots in which the pins  86  are engaged. 
     It should be noted that the embodiment of the invention has been described above purely by way of example and that many modifications and developments may be made thereto within the scope of the present invention.

Summary:
An overflow device for a bathtub with an overflow inlet arranged for mounting in a conventional overflow hole of the bathtub and a valve connected between a water supply and a conventional bath tap. A spring can be used to change the valve from its open state to its closed state. A float and trigger lever can detect water that has entered the overflow inlet and trigger the device to change, using the stored spring energy, from a set state in which the valve is open to a triggered state in which the valve is closed. A manually operable resetting element can be operated by a user to replenish the spring with energy and return the device to the set state. The device can be permanently plumbed in and the bulk of the device can be hidden from view outside the bathtub.