WO2011013142A2

WO2011013142A2 - End of life system for a water filter

Info

Publication number: WO2011013142A2
Application number: PCT/IN2010/000493
Authority: WO
Inventors: Dilshad Ahmad; Ujas Prataprai Dave
Original assignee: Tata Chemicals Ltd.; Tata Consultancy Services Ltd.
Priority date: 2009-07-28
Filing date: 2010-07-27
Publication date: 2011-02-03
Also published as: WO2011013142A3; ZA201200682B; AP2012006131A0

Abstract

An auto shut off device for liquids comprising of at least one liquid inlet, at least one liquid outlet, a casing that defines an opening, and a stopper shaped to close the opening comprising of a top, bottom and side surfaces. The stopper further defines a liquid inlet aperture on the top surface, a liquid outlet aperture on the top surface; a connecting passage connecting the liquid inlet aperture to the liquid outlet aperture, a liquid inlet passage connecting the liquid inlet to the liquid inlet aperture, and a liquid outlet passage connecting the liquid outlet aperture to the liquid outlet. A water dissolvable tablet and a plunger are placed within the casing the plunger including a plug configured to block the liquid inlet aperture.

Description

END OF LIFE SYSTEM FOR A WATER FILTER

The document generally relates to a device for measuring the total amount of water that has passed through a water filter. In particular the document relates to a device for stopping the flow of water through the device once a predetermined quantity of water has passed through the water filter.

BACKGROUND

Clean potable water is a basic human requirement. However, a large portion of the world's population, especially those living in developing counties do not have access to clean potable water.

A number of water treatment devices are well known in the art. Such devices are employed directly in a water system, either in-line or at a terminal end, or in self-contained batch systems. An example of an in-line system is an under-the-counter device which filters water prior to reaching the faucet. Terminal end devices include counter top and faucet mounted filtration systems. Self-contained batch systems include devices such as carafe units.

Typical water treatment devices employ mechanical filtration or chemical treatment. Mechanical filters treat water by preventing passage of particulates and / or bio-organisms. Chemical treatment (e.g., activated carbon-based and ion exchange media) employs processes such as adsorption and ion exchange for removing undesirable chemical species and inactivation of microorganisms. A major drawback associated with chemical treatment is that the chemical media eventually becomes inactive, providing no indication that the useful life of the chemical element has been exhausted.

Various methods have been employed to indicate end of life to the user where it is not inherently provided by the behaviour of the filter media. One such means of indicating end of useful life of treatment units is through devices that use a process commonly referred to as "flow totalization". These devices totalize the liquid volume which passes through the treatment media. Both electrical and mechanical "flow totalization" devices are known in the art.

Electrical flow totalization devices employ pressure transducers. The transducers include integrated outputs to calculate total volume. After a predetermined volume has been reached, a valve is electrically actuated to stop the flow. A mechanical flow totalization device may employ a turbine interconnected with a series of gears. The gears are designed and adapted to mechanically "add up" the volume of water passed through the device.

Other mechanical flow totalization devices employ a float mechanism. The float is designed and adapted to rotate a pre-determined distance upon each fill cycle of the water treatment unit. Once that float has made a specific number of rotations and has travelled the complete distance across a support rod, the float rests in a position where it is visible through an opening in housing, indicative of the end of life of the water treatment unit.

Although these devices address the end of life problem, they have drawbacks. Electronic totalizers require batteries as a power source, which are expensive and hence the cost of the totalizing device may become comparable to the purification cartridge itself. On the other hand mechanical totalizers devices are generally complicated and often expensive and fragile. Moreover, these devices are generally in good working condition even after the purification cartridge, in which device is fitted, is exhausted, hence adding to a redundant cost within the purification cartridge.

Indian patent application number 917/MUM/2006 discloses a biocide cartridge for purification where the absence of the biocide prevents further flow of water. The device comprises of a container containing a water leachable biocide tablet resting on a base. A movable support having an external arm with a plug is stacked on the biocide tablet, such that as the water leachable biocide tablet is consumed, the movable support descends and at a predetermined end-of-life position the external arm plugs the water outlet, thereby shutting off the flow of water.

However, this device has a number of disadvantages. As the arm and plug in this device are external, this makes the device bulky. Moreover, the external arm and plug are delicate and prone to breakage. As the plug for stopping the flow of water is external, the system is open that may allow dirt and microorganisms to enter into the purified water. Moreover, the external arm and plug allows for external tampering of the device.

There is therefore a need for a device for measuring the total amount of water that has passed through a water filter. In particular the device should stop the flow of water once a predetermined quantity of water has passed through the water filter. The device should be simple and compact without any external parts such that the total system is a closed system. BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

The accompanying drawings illustrate the preferred embodiments of the invention and together with the following detailed description serves to explain the principles of the invention, where:

Figure 1 illustrates an auto shut off device for measuring the total amount of water that has passed through a water filter in accordance with an embodiment of the invention,

Figure 2 illustrates the dissasembly of the device illustrated in Figure 1,

Figure 3 illustrates a top perspective view of a stopper of the device of Figure 1,

Figure 4 illustrates a side view of the stopper in accordance with an embodiment of the invention,

Figure 5 illustrates a bottom view of the stopper in accordance with an embodiment of the invention,

Figure 6 illustrates a top view of the stopper in accordance with an embodiment of the invention,

Figure 7 illustrates a partial view along line A-A of Figure 6,

Figure 8 illustrates a pair of water dissolvable tablets wrapped in a water proof film in accordance with an embodiment of the invention,

Figure 9 individually illustrates the pair of tablets and the water proof film of Figure 8,

Figure 10 illustrates an alternate water proof film for the water dissolvable tablets in accordance with an embodiment of the invention;

SUMMARY

An auto shut off device for liquids is disclosed. The device comprises of at least one liquid inlet and at least one liquid outlet. The device further comprises of a casing that defines an opening. The device further comprises of a stopper shaped to close the opening and comprises of a top, bottom and side surfaces such that the top surface is positioned within the casing and the bottom surface is positioned outside the casing when the stopper is received in engagement in said opening. The stopper further defines a liquid inlet aperture on the top surface and a liquid outlet aperture on the top surface. The stopper further defines a connecting passage connecting the liquid inlet aperture to the liquid outlet aperture. The stopper further comprises of a liquid inlet passage connecting the liquid inlet to the liquid inlet aperture, and a liquid outlet passage connecting the liquid outlet aperture to the liquid outlet. The device further comprises of a water dissolvable tablet within the casing and configured to rest on the top surface of the stopper. The device further comprises of a plunger resting on the water dissolvable tablet, the plunger including a plug configured to block the liquid inlet aperture and a spring member above the plunger and configured to urge the plunger downwards towards the stopper such that water exiting the liquid inlet aperture impinges on the water dissolvable tablet before entering the liquid outlet aperture.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.

An auto shut off device for measuring and indicating the total amount of water that has passed through a water filter is disclosed. In particular an auto shut off device for stopping the flow of water once a predetermined quantity of water has passed through a water filter is disclosed. The description below describes the use of device for water.

Figures 1 and 2 illustrate an auto shut off device (10) for measuring and indicating the total amount of water that has passed through a water filter (not shown). The device (10) comprises of at least one water inlet (18), at least one water outlet (20) and a casing (12) that defines an opening (14). The device (10) also comprises a stopper (16) that is shaped to close the opening (14). A water soluble tablet (22) is placed in the casing (12) such that it rests on the stopper (16). A plunger (24) rests on top of the water soluble tablet (22). The casing (12) is leak proof everywhere except at the opening (14). The stopper (16) is engaged with the casing (12) at its opening (14) and together form a closed chamber housing the water dissolvable tablet (22) and the plunger (24).

Referring next to Figures 3 to 7 a stopper (16) in accordance with an embodiment of the disclosure is illustrated. The stopper defines a top surface (28), a bottom surface (34) and a side surface (36). As seen in Figure 1, the stopper (16) is so configured that when engaged in opening (14) of the casing (12) the top surface (28) is within the casing (12) while the bottom surface (34) is outside the casing (12). In the embodiment illustrated, the water inlet (18) and water outlet (20) are formed on the stopper (16). The stopper (16) also includes a liquid inlet aperture (32) and a liquid outlet aperture (42) at the top surface (28). A connecting passage (44) connects the liquid inlet aperture (32) to the liquid outlet aperture (42). In the embodiment illustrated and as best seen in Figure 4, the stopper (16) has a pair of diagonally opposite liquid inlets (18) present on the side face (36) of the stopper (16). As best seen in Figures 5 and 7, a liquid inlet passage (30) is provided in the stopper (16) that provides a fluid connection between the liquid inlets (18) and the liquid inlet aperture (32). The liquid inlet passage (30) is preferably configured such that water exits the liquid inlet aperture (32) substantially vertically and impinges on the bottom surface (60) of the water dissolvable tablets (22). A liquid outlet passage (46) provides a fluid connection between the liquid outlet aperture (42) and the liquid outlet (20). In the embodiment illustrated a plurality of liquid outlet apertures (42) is provided on the top surface (28) of the stopper (16). A liquid outlet passage (46) connects each of the liquid outlet apertures (42) to a plurality of liquid outlets (20) on the bottom surface (34) of the stopper (16). A plurality of connecting passages (44) connects the liquid inlet aperture (32) to the plurality of the liquid outlet apertures (42). The connecting passages (44) may be configured to permit liquid to contact the water dissolvable tablets (22) resting above the stopper (16). The plurality of connecting passages (44) extending away from the liquid inlet aperture (32) provides a more uniform consumption of the water dissolvable tablets (22).

As seen in Figure 4, the stopper (16) may be provided with a flange (48) on its side surface (36). The flange (48) serves as a separator between the liquid inlet (18) on the side surface (36) and the liquid outlet (20) on the bottom surface (34) such that when the device (10) is used in a water filter device (not shown), the flow of water is restricted through the auto shut off device (10).

The stopper (16) is also provided with a locking structure (50) to couple the stopper (16) to the casing (12). In the embodiment illustrated, the stopper (16) is provided with diagonally opposite columns (52) extending along the side surface (36), each column (52) defining a recess (54) that is configured to slidably receive a projection (not shown) extending from the casing (12).

The water-soluble tablet (22) is provided in the casing (12) such that the water-soluble tablet (22) rests on the stopper (16) above the liquid inlet aperture (32). Any number of water-soluble tablets (22) may be provided in the casing (12) depending on the solubility of the tablet (22) and the predetermined amount of water flow after which auto shut off is desired. In the embodiment illustrated in Figures 8 and 9 two water-soluble tablets (22) are provided in the casing (12).

In accordance with an aspect, the water soluble tablet (22) is made of a chemical having low solubility in water. The water soluble tablet (22) includes but is not limited to tablet (22) composed of CaSO₄.2H₂O, CaO or MgO. The water soluble tablet (22) may also include binders maltodextrin, lactose or PVPK30 and lubricants magnesium stearate, calcium stearate, stearic acid, polyethylene glycol, sodium benzoate or sodium stearyl fumarate.

In accordance with an embodiment, the water soluble tablet (22) is made of CaSO₄.2H₂O as a base material and with PVPK-30 as binder and magnesium stearate as lubricant. Sieved CaSO₄.2H₂O powder, preferably sieved with mesh number 60, is mixed with an appropriate amount, preferably 1.5% of the total CaSO4 taken, of sieved binder PVPK30. The CaSO₄.2H₂O and PVPK30 are mixed by adding the sieved binder PVPK30 slowly into the sieved CaSO₄.2H₂O powder in an appropriate mixer preferably a ribbon mass mixer. After about 10 seconds to- 8 hours, preferably 20 minutes of mixing of CaSO₄.2H₂O and PVPK30 in the ribbon mill, water is slowly added to the mixer to form granules and further mixed for another 10 seconds to 8 hours, preferably 20 minutes. The granules from the ribbon mill are sieved with a 10-200 mesh number sieve preferably a 16 mesh sieve. The sieved chemical granules are dried between 20 degrees centigrade and 200 degrees centigrade preferably at 80 degrees centigrade for about 5-6 hours in a suitable drier, preferably in a tray drier. The dried chemical granules are further sieved to remove under sized material with 20- 100 mesh preferably with 60 mesh. The chemical granules are made into tablets (22) in a tablet press by adding a suitable binder, preferably magnesium stearate. A suitable amount, 0.1%- 10%, preferably 1.5% of the weight of granule, of magnesium stearate is thoroughly mixed with the granules preferably in a drum mixer. In the current embodiment, one such tablet (22) is designed to dissolve completely in approximately 3000 liters of continuous/discontinuous flow of water.

In accordance with an aspect, the water soluble tablet (22) is coated with water resistant material (40). The water resistant material (40) including but not limited to poly propylene, low density poly propylene, polyethylene, Teflon, Para-film™ or any other thin elastic water resistant film preferably Para-film™. Alternatively, the surface (56) of the water soluble tablet (22) may also be treated with a suitable coating material to achieve desired water resistance. Alternatively, the surface (56) may be treated with a heat treatment or chemical treatment process to impart water resistance. In accordance with an alternate embodiment, the water soluble tablet (22) is made of CaSO₄.2H₂O by adding and mixing water to CaSO₄.2H₂O and compressing the mixture in a pressure die. Alternatively, the water soluble tablet (22) may also be made in an automated tablet making machine. In accordance with an embodiment the amount of CaSO₄.2H₂O per tablet (22) may vary from lgm to lOOgm.Specifically the amount of CaSO₄.2H₂O per water soluble tablet (22) may be lOgm. The proportion of water to CaSO₄.2H₂O may vary from O to 50% and is preferably 20%. The compression pressure may vary from 0 to 50 tons and is preferably 8 tons.

hi the embodiment illustrated, two such water soluble tablets (22) are designed to dissolve completely in approximately 3000 liters of continuous/discontinuous flow of tap water.

Still referring to Figures 8 and 9, the water soluble tablets (22) may be coated with a water resistant material (40) on a top surface (62) and a side surface (64) and may be uncoated on a bottom surface (60). The bottom surface (60) is placed above the stopper (16) such that only one surface of the tablet (22) is exposed to water entering the casing (12) from the liquid inlet aperture (32). The water resistant material (40) may include polypropylene, low density polypropylene, polyethylene, Teflon, Para-film™ and combinations thereof.

In accordance with an alternate embodiment, the water soluble tablets (22) may be wrapped with a water proof film such that one surface is exposed to water. The water soluble tablets (22) may be coated with a water resistant material (40) and may be wrapped with a water proof film (58).

The water proof film (58) used to cover the tablets (22) on the top and side surfaces is preferably a stretchable material such as parafilm. As illustrated in Figure 9, the stretchable film (58) is smaller in size than the tablets (22) to be covered by it, and is stretched to fit over the tablets (22).

In accordance with an alternate embodiment as illustrated in Figure 10, the stretchable film (58) is stretched and wrapped in a spiral manner over the tablets (22). The stretchable film (58) is configured to shrink vertically along the tablets (22) as the tablets (22) are dissolved by the water entering the casing (12). The spiral stretch wrapping functions as an extended spring that retracts as the tablets (22) are dissolved.

The plunger (24) is placed in the casing (12) such that it rests on top of the water- soluble tablets (22). The plunger (24) is in the form of a disk or plate that is sized to just fit within the casing (12) and to prevent water from passing across the plunger (24). In the embodiment illustrated the plunger (24) is a cylindrical shaped component. The plunger (24) on its lower end is provided with a plug (26) that fits in the liquid inlet aperture (32) of the liquid inlet passage (30) in the stopper (16). In accordance with an embodiment, the plunger (24) is a hollow cup shaped member that includes a plug (26) at the closed end and is configured to receive a resilient member such as spring (38) from its open end.

In accordance with an aspect, the plunger (24) may provide a continuous visual indicator of the amount of water that has passed through the water filter (not shown). The casing (12) may be completely transparent for visual inspection of the plunger (24) or may have a transparent column (not shown) along the length of the casing (12). The plunger (24) may be a brightly colored component (not shown). Alternatively, a separate indicator in the form of a bright coloring or tape may be provided on the periphery of the plunger (24). The plunger (24) or the indicator may be visually inspected to determine the level of the tablets (22) remaining in the casing (12) of the device (10). Alternatively, the casing (12) may be provided with a transparent window (not shown) for visual inspection of the plunger (24) or the indicator when the plunger (24) is at or close to the end-of-life position. In accordance with an embodiment, the casing (12) may also be provided with marking that indicates the amount of water that has passed through the water filter (not shown).

In accordance with an aspect, a spring member (38) may be provided between the plunger (24) and the closed end of the casing (12). The spring member (38) provides an additional downward force to the plunger (24) ensuring that it descends through the casing (12) as the water soluble tablets (22) are dissolved by water. In accordance with an embodiment, the spring member (38) may be coated with a water resistant material to prevent corrosion. In accordance with an aspect, the spring (38) is made of a material with good elastic properties and coated with a suitable water resistant material. The spring (38) is made of, but not limited to stainless steel preferably stainless steel grade AISI 304. The coating material may be composed of, but not limited to polyethylene, polypropylene, preferably with food grade low density polyethylene (LDPE). Alternatively, an uncoated spring (38) may be employed.

In accordance with a further embodiment, the casing (12) may be provided with guiding projections on an internal surface (not shown) to guide the travel of the spring member (38) and the plunger (24) towards and away from the stopper (16).

Again with reference to figure 1 and 2, the flow of water through the device (10) is illustrated. Water enters into the stopper (16) through the liquid inlet (18) and rises up through the liquid inlet passage (30). Once water reaches the liquid inlet aperture (32) of the liquid inlet passage (30), air in the casing (12) gets trapped within the casing (12). As the water rises up further in casing (12), the trapped air in the casing (12) starts getting compressed till the pressure of the compressed air becomes equal to the water pressure at the liquid inlet (18). This rise in pressure of the compressed air prevents water from rising further up in the casing (12). Water rises up the liquid inlet passage (30) and impinges onto the bottom surface (60) of the lowermost tablet (22). The water is diverted by the tablet (22) towards the liquid outlet (20). The water soluble tablet (22) dissolves continuously with the flow of water at its bottom surface (60). The dissolution of water soluble tablets (22) from the bottom surface (60) and top surface (62), due to rise of water in the casing (12), is prevented by coating the tablet (22) with a water resistant material. The dissolution of tablets (22) relates to the total amount of water passed through the water filter (not shown). The plunger (24) or any indicator attached to it incrementally moves down as the tablets (22) dissolve indicating the cumulative amount of water passed. After the passage of a predefined amount of water through the water filter (not shown) the water soluble tablets (22) are configured to dissolve completely. Once the water soluble tablets (22) are completely dissolved by water, the spring (38) forces the plunger (24) to enter the liquid inlet aperture (32) in the liquid inlet passage (30) in the stopper (16). This stops the flow of water through the water filter (not shown).

SPECIFIC EMBODIMENTS ARE DESCRIBED BELOW

An auto shut off device for liquids comprising at least one liquid inlet and at least one liquid outlet; a casing defining an opening; a stopper shaped to close the opening and comprising top, bottom and side surfaces such that the top surface is positioned within the casing and the bottom surface is positioned outside the casing when the stopper is received in engagement in said opening; the stopper further defining a liquid inlet aperture on the top surface, a liquid outlet aperture on the top surface, a connecting passage connecting the liquid inlet aperture to the liquid outlet aperture, a liquid inlet passage connecting the liquid inlet to the liquid inlet aperture, and a liquid outlet passage connecting the liquid outlet aperture to the liquid outlet; a water dissolvable tablet within the casing and configured to rest on the top surface of the stopper; a plunger resting on the water dissolvable tablet, the plunger including a plug configured to block the liquid inlet aperture and a spring member above the plunger and configured to urge the plunger downwards towards the stopper such that water exiting the liquid inlet aperture impinges on the water dissolvable tablet before entering the liquid outlet aperture. Such auto shut off device(s) for liquids, wherein the liquid inlet is on the side surface of the stopper and is configured to be positioned outside the casing when the stopper is received in engagement in the opening.

Such auto shut off device(s) for liquids, wherein a plurality of liquid inlets are formed on the side surface of the stopper, with the liquid inlet passage connecting each of the liquid inlets to the liquid inlet aperture.

Such auto shut off device(s) for liquids, wherein the liquid outlet is on the bottom surface of the stopper.

Such auto shut off device(s) for liquids, wherein a plurality of water dissolvable tablets is stacked over the stopper.

Such auto shut off device(s) for liquids, wherein the water dissolvable tablet is wrapped in a waterproof film such that a single surface is exposed to water.

Such auto shut off device(s) for liquids, wherein the waterproof film is stretchable and is stretch wrapped in a spiral manner on the water dissolvable tablet.

Such auto shut off device(s) for liquids, wherein the casing includes internal projections to guide the travel of the plunger and the spring member.

Such auto shut off device(s) for liquids, further comprising a locking structure to retentively couple the stopper to the casing.

Such auto shut off device(s) for liquids, further comprising a flange to separate the liquid inlet from the liquid outlet.

Such auto shut off device(s) for liquids, further comprising a plurality of liquid outlets and wherein the stopper defines a plurality of liquid outlet apertures on the top surface with a plurality of liquid outlet passages connecting the plurality of liquid outlet apertures to the plurality of liquid outlets. Such auto shut off device(s) for liquids, further comprising a plurality of connecting passages connecting the liquid inlet aperture to the plurality of liquid outlet apertures.

Such auto shut off device(s) for liquids, wherein the water dissolvable tablet is made of a material having low solubility in water.

Such auto shut off device(s) for liquids, wherein the water dissolvable tablets are coated on the top and side surfaces with a water resistant material.

Such auto shut off device(s) for liquids, wherein the plunger is configured to provide a visual indication through the casing of the amount of water that has passed through the device.

Such auto shut off device(s) for liquids, wherein the water dissolvable tablets are made from any of calcium sulphate, calcium oxide, magnesium oxide or combinations thereof.

Such auto shut off device(s) for liquids, wherein the water dissolvable tablets includes a binder comprising any of maltodextrin, lactose, PVPK30 or combinations thereof.

Such auto shut off device(s) for liquids, wherein the tablets may include a suitable lubricant comprising any of magnesium stearate, calcium stearate, stearic acid, polyethylene glycol, sodium benzoate, sodium stearyl fumarate or combinations thereof.

Such auto shut off device(s) for liquids, where the tablets are coated with a water resistant material comprising polypropylene, low density polypropylene, polyethylene, Teflon, Para-film or combinations thereof.

INDUSTRIAL APPLICABILITY

The device (10) as disclosed allows for the measurement and indication of the total amount of water that has passed through a water filter or a water treatment cartridge (not shown). Moreover, the device (10) as disclosed stops the flow of water once a predetermined amount of water has passed through the water filter.

The device (10) as disclosed is simple, closed, compact, accurate and reliable. It is inexpensive and easy to manufacture. Moreover, the device (10) can measure variable flow rate with accuracy. As the device (10) disclosed is a sealed system it does not allow any external matter such as dirt and microorganisms from entering into the water passing through the device (10). Also as the device (10) does not have any external elements it cannot be tampered with externally by a user.

In this device (10), in addition to passing through a passage, the water faces no further resistance and hence the pressure drop in the device is negligible. Therefore, the performance of the equipment to which this device (10) is attached is not adversely affected by the presence of the device (10) in the flow path.

The device (10) may also be configured to separate two chambers such that flow of water between the chambers is through the device (10).

Claims

WE CLAIM:

1. An auto shut off device for liquids comprising:

at least one liquid inlet and at least one liquid outlet;

a casing defining an opening;

a stopper shaped to close the opening and comprising top, bottom and side surfaces such that the top surface is positioned within the casing and the bottom surface is positioned outside the casing when the stopper is received in engagement in said opening; the stopper further defining:

a liquid inlet aperture on the top surface,

a liquid outlet aperture on the top surface,

a connecting passage connecting the liquid inlet aperture to the liquid outlet aperture, a liquid inlet passage connecting the liquid inlet to the liquid inlet aperture, and a liquid outlet passage connecting the liquid outlet aperture to the liquid outlet;

a water dissolvable tablet within the casing and configured to rest on the top surface of the stopper;

a plunger resting on the water dissolvable tablet, the plunger including a plug configured to block the liquid inlet aperture; and

a spring member above the plunger and configured to urge the plunger downwards towards the stopper such that water exiting the liquid inlet aperture impinges on the water dissolvable tablet before entering the liquid outlet aperture.

2. An auto shut off device for liquids as claimed in claim 1 wherein the liquid inlet is on the side surface of the stopper and is configured to be positioned outside the casing when the stopper is received in engagement in the opening.

3. An auto shut off device for liquids as claimed in claim 2 wherein a plurality of liquid inlets are formed on the side surface of the stopper, with the liquid inlet passage connecting each of the liquid inlets to the liquid inlet aperture.

4. An auto shut off device for liquids as claimed in any preceding claim wherein the liquid outlet is on the bottom surface of the stopper.

5. An auto shut off device for liquids as claimed in claim 1 wherein a plurality of water dissolvable tablets is stacked over the stopper.

6. An auto shut off device for liquids as claimed in claim 1 or 5 wherein the water dissolvable tablet is wrapped in a waterproof film such that a single surface is exposed to water.

7. An auto shut off device for liquids as claimed in claim 6 wherein the waterproof film is stretchable and is stretch wrapped in a spiral manner on the water dissolvable tablet.

8. An auto shut off device for liquids as claimed in claim 1 wherein the casing includes internal projections to guide the travel of the plunger and the spring member.

9. An auto shut off device for liquids as claimed in claim 1 further comprising a locking structure to retentively couple the stopper to the casing.

10. An auto shut off device for liquids as claimed in claim 1 further comprising a flange to separate the liquid inlet from the liquid outlet.

11. An auto shut off device for liquids as claimed in claim 1 further comprising a plurality of liquid outlets and wherein the stopper defines a plurality of liquid outlet apertures on the top surface with a plurality of liquid outlet passages connecting the plurality of liquid outlet apertures to the plurality of liquid outlets.

12. An auto shut off device as claimed in claim 11 further comprising a plurality of connecting passages connecting the liquid inlet aperture to the plurality of liquid outlet apertures.

13. An auto shut off device as claimed in claim 1 wherein the water dissolvable tablet is made of a material having low solubility in water.

14. An auto shut off device as claimed in claim 1 wherein the water dissolvable tablets are coated on the top and side surfaces with a water resistant material.

Ib. An auto shut off device as claimed in claim 1 wherein the plunger is configured to provide a visual indication through the casing of the amount of water that has passed through the device.

16. An auto shut off device as claimed in claim 1 wherein the water dissolvable tablets are made from any of calcium sulphate, calcium oxide, magnesium oxide or combinations thereof.

17. An auto shut off device .as claimed in claim 1 wherein the water dissolvable tablets includes a binder comprising any of maltodextrin, lactose, PVPK30 or combinations thereof.

18. An auto shut off device as claimed in claim 1 wherein the tablets may include a suitable lubricant comprising any of magnesium stearate, calcium stearate, stearic acid, polyethylene glycol, sodium benzoate, sodium stearyl fumarate or combinations thereof.

19. An auto shut off device as claimed in claim 1 where the tablets are coated with a water resistant material comprising polypropylene, low density polypropylene, polyethylene, Teflon, Para-film or combinations thereof.