BACKGROUND AND PRIOR ART Purification systems of the type discussed above require the fluid to be treated to traverse under gravity flow through the purification unit to effect contact of the flowing fluid with the fluid treatment media employed. There is a need for controlling the gravity flow in such systems to achieve effective treatment and purification.

US 458 4106 discloses a chlorination system for distributing chlorine as the active in a hot tub or spa. The system regulates the flow of water through a mixing chamber with a valve or stopcock to control the rate of chlorine distribution. An assembly of venturies and baffles also regulates the flow of water through the mixing chamber and controls the size of particles of chlorination tablets that will flow out-of the chlorination system.

US 5089127 discloses a chemical feeder including a cylinder for receiving a canister which holds a plurality of shaped solid sanitizing elements in the form of pellets or tablets, for example of calcium hypochlorite or of chloroisocyanurate. The bottom and the lower end of the canister sidewall are perforated and the lower end portion of the canister is located within the upper portion of an open top inlet or erosion reservoir. Water enters the lower end of the erosion reservoir through an inlet opening in the form of a jet and passes upwardly to contact the solid sanitizing elements in the lower end portion of the canister to gradually erode and dissolve the solid sanitizing elements in the lower end portion of the canister. The amount of chemical supplied to the water passing through the feeder is controlled by varying the inlet flow rate of the water which impinges upon the elements in the lower end portion of the canister. In this system an inlet control valve is mounted in the inlet conduit to control the flow of the inlet water into the sanitizing element reservoir.

US 6298871 B1 discloses a chemical feeder that produces a solution of a chemical treating agent such as sodium hypochlorite. The feeder comprises a housing defining a cavity, and an elongated vertical hollow container is centrally located within the cavity. The bottom wall of the side wall of the container is adjacent to the base and contains a plurality of perforations in the lower portion of the side wall which is spaced from the inside wall of the housing. At least one hollow canister having a plurality of perforations in its base and the lower portion of its sidewall is slidably received within the container.

Conduits are provided for delivering the liquid in which the chemical treating agent is provided to a chamber below the perforations in the canister and for removing the liquid stream containing the chemical treating agent from the feeder.

A problem with devices such as venturies and baffles is that they require regular manual intervention and do not provide uniform flow control. On the other hand, more complex control mechanisms such as electronic, electric, pneumatic or hydraulically actuated systems may be more reliable but are costly to manufacture and maintain.

OBJECT OF THE INVENTION The object of the present invention is to provide a flow regulator for controlled release of fluids under gravity flow, irrespective of the source height or volume, which is simple and cost-effective, yet does not suffer from irregular control, drastic changes in flow characteristics or turbulence, and does not involve complexities in installation and maintenance.

The flow regulator of the invention may be adapted for convenient attachment or installation to any supply or source, such as storage units supplying water under gravity.

The flow regulator of the invention provides for controlled release of fluid under gravity flow and may be adapted for use in conjunction with any conventional gravity based purification systems, especially those requiring controlled

contact or residence time of water for the purpose of purification and filtration, such as biocide discharge units. This enables control over contact with or release of purifying actives such as biocides to maintain uniform purification of the water and avoids problems of insufficient purification or excessive loading of active to the water being treated.

The flow regulator of the invention does not require complex electrical, electronic, pneumatic or hydraulically actuated flow controlled valves or stop cocks, and does not require repeated manual intervention.

The flow regulator of the invention is simple and compact for ready assembling in any gravity flow system requiring regulated flow of fluids therethrough and at the same time takes care of problems of clogging or disruption of fluid flow or complexity in maintenance.

SUMMARY OF THE INVENTION The present invention provides a flow regulator for controlled gravity flow of fluid comprising: - a flow control reservoir adapted to discharge the required volume of fluid and comprising at least one inlet for entry of the fluid into the reservoir; - at least one siphon discharge operatively connected to the flow control reservoir and adapted to control the flow rate of the fluid from the reservoir.

In the flow regulator of the invention, the rate of flow of the fluid is regulated first by way of selective dimension of the control reservoir which achieves a first stage of control of the flow rate irrespective of the flow rate or volume of the fluid source. Further flow control is achieved by way of the siphon discharge, which preferably comprises a tubular member of pre-selected dimensions to facilitate the flow rate control.

More preferably, the siphon discharge comprises an inverted tubular"U"or"V"shaped member having two arms, one end of which constitutes the inlet end while the other end constitutes the outlet end, with the inlet end positioned at a higher level and projecting into the control reservoir at the bottom thereof, and the outlet end disposed lower than the inlet end to maintain a difference in height between the inlet and outlet ends of the tubular member.

By controlling the dimensions of the inner diameter of the tubular member as well as the difference in height of its inlet and outlet ends, it is possible to regulate the flow rate of the fluid through the siphon discharge. This may be achieved by using an inverted"U"or"V"shaped tubular member with the inlet and outlet ends at the respective ends of the tubular member, the arm of the tubular member having the inlet end being shorter than the length of the arm having the outlet end.

To achieve a regulated flow of 10 to 200ml/min the dimension of the control reservoir can be selected to be 50 to 500 ml and the tubular siphon discharge can have a diameter in the

range of 0.5 to 50 mm, with a difference in height between the inlet and outlet ends of the tubular siphon discharge of 1 to 200mm.

Also, considering that the resistance offered by the tubular siphon discharge also has a relation to the flow rate, the material of the tubular siphon discharge should be selected based on the desired flow rate. Preferred materials are glass, plastic, polymer, ceramic or metal.

The flow regulator of the invention may comprise a plurality of separate control reservoirs. In this case, each reservoir is provided with an independent siphon discharge for the controlled flow rate of fluid from the respective control reservoirs.

Preferably, the or each control reservoir is provided with a vent adapted to allow the inside and outside air pressure in the reservoir to equalize after each discharge of fluid and ensure reliable operation of the siphoned regulated discharge. Suitably such venting may be provided at the opening of the reservoir's inlet for fluid entry.

The flow regulator of the invention can be incorporated in gravity feed systems such as gravity feed water purification systems where regulated flow of water through various water purification media is desired for effective purification.

Accordingly, the present invention also provides a purification system comprising ; - a source of untreated fluid;

- a flow regulator system operatively connected to the source comprising a flow control reservoir adapted to discharge the required volume of fluid, and comprising at least one inlet for entry of the fluid from the source into the reservoir, at least one siphon discharge operatively connected to the flow control reservoir and adapted to control the flow rate of the fluid from the reservoir, and at least one outlet for exit of the fluid from the siphon discharge, and - a purification unit for the fluid which is operatively connected to the outlet.

The purification unit typically contains any conventional purification agent in powder, granular, resin or tablet form. Preferred purification agents include pentaiodide resin and trichlorocyanuric acid (TCCA). It is also possible to use other conventional chlorine releasing compounds such as potassium dischloroisocyanurate, sodium dichloroisocyanurate, chlorinated trisodium phosphate, calcium hypochlorite, lithium hypochlorite, monochloramine, dichloramine, [ (monotrichloro)-tetra (monopotassium dichloro) ] pentaisocyanurate, 1,3 dichloro-5,5- dimethylidanotone, paratoluene sulfodichloroamide, thrichloromelamine, N-chloramine, N-chlorosuccinimide, N, N'- dichloroazodicarbonamide, N-chloroacetyl-urea, N, N- dichloroazodicarbonamide, N-chloroacetyl-urea, N, N- dichlorbiurile, chlorinated dicyandiamide, and mixtures thereof.

Preferably the purification unit contains a biocide delivery unit operatively connected to the outlet of the siphon discharge, so that the regulated flow of fluid comes into contact with the biocide for controlled purification.

Preferably, the purification unit also contains a mechanism for regulated discharge of the biocide treated fluid, more preferably for regulated discharge of the biocide treated fluid to a downstream dwell chamber and further through a scavenger system (for removal of residual impurities), to be finally collected in a bottom chamber as treated fluid, which may be discharged from an outlet in the bottom chamber.

The flow regulator of the invention is simple but effective in achieving control over the rate of flow of fluid. To accommodate and fix the flow regulator, it can be provided with simple fixing means, which could be integrated with any conventional purification unit. It is also possible to secure the flow regulator detachably with respect to the inside of the purification unit.

Detailed Description of the Invention The present invention is particularly suitable for the provision of control over the flow of water in water purification systems, especially gravity flow water purification devices for the purification of water for domestic consumption. Such devices usually involve various components and typically have five basic units comprising:

(a) a top chamber which is used for storage of water to be treated. This chamber usually carries a pre-filter, usually a carbon block to remove sediments, organic impurities and cysts.

(b) a biocide delivery system which usually carries chlorine tablets such as NaDCCA, TCCA, iodinated resin or other biocides. The biocide delivery system receives water from the top chamber by gravity. c) a dwell chamber or residence time chamber which provides the necessary time for pathogens and biocide to stay together to achieve the target kill of pathogens.

(d) a scavenging system (usually granular activated carbon) which receives water from the dwell chamber and removes residual impurities such as iodine, chlorine, THMS and the like.

(e) a bottom chamber which receives purified water from the scavenger for consumption.

The important factor for such gravity purification devices is the variable flow rate of input water that such systems encounter. Considering that the various components have different requirements for effective purification based on the contact time or residence time of the water passing through, it is important that the flow rate in such devices is effectively controlled to achieve the desired purification of the water. In particular, the biocide treatment in such systems has a critical relation to the flow rate of water through said the biocide delivery system, since while it is important that the water should come into contact with the biocide for the desired kill of pathogens, it is not desirable that the water passing through the

biocide delivery system contains proportions of the biocide beyond a stipulated safe limit for domestic consumption.

The flow regulator of the invention enables effective control of the flow rate of the water to bring about safer purification of the, water to be treated.

Description in relation to accompanying figures The flow regulator of the invention is hereafter explained in greater detail in the following non-limiting Examples, as illustrated by the accompanying Figures, in which Figure 1 is a sectional view of a bucket filter for purification of drinking water including a flow regulator of the present invention; Figure 2 is a sectional view illustrating the flow regulator used in the bucket filter of Fig. l.

In Figure 1, a bucket filter is comprised of a top chamber (1) for storage of the water to be treated. The top chamber also houses a pre-filter (PF) which is a carbon block used to remove sediments and organic impurities and cysts. From the pre-filter (PF), the water is allowed to flow by gravity into a further chamber (2) which houses a flow regulator (FR). The flow regulator is adapted so that irrespective of the water volume in top chamber (1) and the speed of flow of water through the pre-filter (PF), the water from the flow regulator (FR) is discharged at regulated amounts and at a controlled rate. The flow regulator (FR) comprises a control reservoir which is dimensioned to allow the

controlled volume flow of the water from the control reservoir. The flow regulator (FR) further comprises a siphon discharge member (SDM) which is an inverted"U" shaped tubular member having an inlet (IN) which is at a higher level with respect to the outlet (OT). The height difference between the inlet (IN) and the outlet (OT) can be adjusted depending upon the required flow rate desired.

The water from the flow regulator (FR) with controlled flow rate exits from outlet (OT) and passes through a biocide unit (3) which release a pre-selected dose of biocide into the water. Thereafter, the biocide treated water is allowed to flow under gravity to a bottom chamber (5) via a scavenger unit (4). The treated water collects in the bottom chamber (5) to be finally discharged as and when required from a discharge outlet (DO) in the bottom chamber (5).

Figure 2 further illustrates the flow regulator (FR). This comprises a control reservoir (CR) which stores water of a controlled volume irrespective of the volume of the source from which the reservoir is fed. A tubular siphon discharge member (SDM) provides for exit of the regulated contents of the water. The dimensions of the control reservoir (CR) and the diameter and inlet/outlet height of the tubular siphon discharge member (SDM) are chosen to achieve the desired control of the flow rate. The flow regulator (FR) can be further adapted so that the controlled flow of water from the control reservoir (CR) via the tubular siphon discharge member (SDM) takes place only when the control reservoir (CR) has filled up to a desired height.

Example: Demonstration of flow regulation: The filter shown in Figure 1 was used to demonstrate the control on flow of water irrespective of the head in top chamber (1). Various levels in the top chamber (1) ranging from 170 mm to 55 mm were taken and the flow of water through the outlet (OT) was determined (Example 1). The experiment was repeated using a filter as shown in Figure 1, except that the flow regulator (FR) was absent (Comparative Example A). The results are shown in table 1.

Table 1 Head (mm) Average Flow rate (ml/min) Example 1 Comp. Ex. A 170 81 1162 11086106 558927 The results show that in the presence of the flow regulator (FR), the water flow rate is independent of the head in the top chamber. This is not the case in Comparative Example A.

Therefore the flow regulator of the invention is effective in de-linking the upstream flow rate variation from the feed to biocide dispenser, resulting in uniform delivery of biocide.