FIELD OF THE INVENTION

This invention relates to a water filter, and more particularly, to a self-cleaning water filter.

BACKGROUND TO THE INVENTION

Water filters are well known and widely used, especially with swimming pools.

The pumps of swimming pool filters are usually not required to pump the swimming pool water through the filter for 24-hour filtration. It is more common to filter the swimming pool water for only a few hours each day. As a result, the pumps need to be switched either manually or by timing devices connected in the electrical circuits of power supplies for the pumps. When timing devices are included the pumps will be switched on and off at predetermined times, as set and determined by the timing devices.

Swimming pool filters and pump inlet strainers (leaf traps) have to be backwashed and cleaned at regular intervals to ensure that contaminants and debris are removed from the pump inlet strainer and filter material and thus from the water circulation system. Partially blocked pump inlet strainers and filters (for the material of the filter such as filter sand) are inefficient in operation and waste electricity as a blocked system puts a strain on the pump and/or requires that the pump operates for longer to clean the water properly.

Backwashing of filters wastes large quantities water and discards chemicals with the backwash water. This may damage the environment.

Servicing swimming pool filters (such as cleaning leaf traps and backwashing) may be time consuming and present a difficulty when a caretaker or a homeowner is away or unable to attend to the servicing, for extended periods.

Backwash water from most swimming pool filters is discarded into drains or into gardens. This creates a serious environmental hazard especially where salt water chlorinators are used but even when pool water is treated with powdered or compressed chlorine, acid and the like.

OBJECT OF THE INVENTION

It is an object of the invention to provide a water filter that, at least partially, alleviates the abovementioned difficulties.

SUMMARY OF THE INVENTION

In accordance with this invention there is provided a water filter comprising: a pump for pumping water from a body of water to be filtered through a filter and through a pressure vessel and backpressure means for providing backpressure against flow caused by the operation of the pump, so that air in the pressure vessel is compressed, in use.

A flow path is defined through plumbing from the body of water to be filtered, to a volute of the pump which houses an impeller, to the filter, to the pressure vessel, to the back pressure means and back to the body of water to be filtered.

The flow path includes a flap check valve.

The flap check valve is located upstream of the pump. The water filter includes a leaf trap.

The leaf trap is upstream of the pump but downstream of the flap check valve.

The flow path splits downstream of the flap valve to continue to the leaf trap but to also continue to a check backwash valve.

The backwash valve is a duckbill valve.

The backwash valve is housed in a backwash collector container. The backwash container includes a backwash filter.

The backwash filter is a filter bag. The backwash container includes an outlet opening.

The outlet opening is at an operatively lower end of the backwash container. The backpressure valve is a spring operated valve.

The back pressure valve is a narrowing of the flow path.

The back pressure valve is a disc having holes therein to provide resistance against flow.

In accordance with another aspect there is provided a water filter comprising a flow path defined through plumbing from a body of water to be filtered, through a flap valve, into a first filter container, through a filter, through a volute of a pump which houses an impeller of the pump, into a second compartment and past a backpressure means.

This invention extends to a method of filtering water including the steps of: pumping water from body of water to be filtered through a filter;

pumping the water through pressure vessel containing air; and pumping the water against a backpressure means to allow the air to be compressed.

The method including stopping pumping to allow the air to expand and water to flow back through the filter.

The method including the step of allowing backwash water to collect in a filter and for the backwash water to be returned back to the body of water after backwash filtration.

In accordance with yet another aspect there is provided a water filter comprising a hosing defining a compartment, the housing having an inlet opening, an outlet opening and a drain opening so that a flow path exist between the compartment and each of the openings; filter media in the compartment and in the flow path between the outlet opening on the one side and the inlet and drain openings on the other side; and a septum provided in the compartment to define two sub-compartments. In accordance with still another aspect of this invention there is provided a filtration system comprising a filter compartment, a pressure compartment and flow path between the filter and pressure compartment to define two sub- compartments.

In accordance with a still further aspect of this invention there is provided a filtration system comprising a filter compartment, a pressure compartment and flow path between the filter and pressure compartment and a pump for pumping water through the compartments, as well as a backwash check valve. The backwash check valve is a duckbill valve.

The backwash check valve is made of pliable material. The filter media is located in the upper sub-compartment.

There is provided for the outlet opening to lead from an operatively lower sub- compartment and for the inlet and drain openings to lead form an operatively upper compartment defined by the septum. This invention extends yet further to a method of filtering water and cleaning the filter comprising the steps of: pumping water in a first direction through container forming a filtration compartment and including filter media;

causing air to be compressed inside the lower filtration compartment; and forcing the water and trapped debris out of the filtration compartment by allowing the compressed air to expand when the pumping of the water is stopped.

The invention also extends to a method of filtration backwash comprising forcing water to be filtered through a filter;

causing air to be pressurized in a compartment;

switching off a pump means;

causing air to expand and to force water through the filter media to backwash the filter media.

The method extends to the step of directing the backwash water through a secondary or backwash filter. The backwash water may be collected in a backwash container.

The backwash container may contain the secondary filter.

The backwash container may have a drainage means.

The drainage means may be a thin pipe to drain the water back to a body of water being filtered.

These and other features of the invention are described in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention is described below, by way of example only, and with reference to the drawings in which: Figure 1 shows a schematic cross-sectional view of a water filter in accordance with a first embodiment of the invention;

Figure 2 shows a schematic cross-sectional view of a water filer in accordance with a second embodiment of the invention;

Figure 3 shows a schematic flow diagram of a water cleaning system including a water filter in accordance with a third embodiment, with the water filter during filtration operation; and

Figure 4 shows the same drawing as Figure 3 but with the water filter in backwash operation.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to figures 1 and 2, in which like features are indicated by like numerals, a water filter is generally indicated by reference numeral 1 .

The water filter 1 consist of a cylindrical housing 2 having a centrally located pipe 25, which pipe is open-ended at a top and bottom of the housing and terminates short of the top and bottom ends, inside of the housing. Filter media 21 is located around the pipe 25 above screen 27 (figure 2 only) or directly on a septum 28. The septum divides the housing into two sub- compartments. An inlet pipe 4 is located on the upper end of the upper sub- compartment. An outlet opening 8 and pipe is located on the lower compartment. Backwash opening or pipe 7 is located at an upper end of the upper compartment. A check valve 30 allows flow only out of the upper compartment through the outlet 7. The check valve can be a flap valve or a duckbill valve.

A check valve 32 in the form of a flap valve allows flow only into the upper compartment through the inlet 4.

The centrally located pipe 25 provides a flow path form a top of the housing 2 to a bottom of the housing through the septum 28. A pump motor 10 drives an impeller 1 1 inside the lower compartment of the housing 2 and has operatively upper opening 12 in a volute 31 through which water is pumped into the lower compartment. In use, water is sucked through the operation of the pump 1 through the inlet opening 4, through valve 32 into the upper compartment, through the filter media 21 and through an opening 24 of the connector pipe 25 down the connector pipe 25 into the an impeller volute 31 and out of the volute 31 through the discard opening 12 in the volute, into the lower compartment. When the pump starts, the water level in the lower compartment is low as is shown in figure 2. As the pump gets going the water level raises and compresses the volume of air 33. At some point, the water will force open back-pressure valve 9 and escape down pipe 5. The back-pressure valve 9 then maintains the pressure and keeps the air volume 33 at pressure and compressed. In this way, the water form a swimming pool is filtered through the filter media an pumped back to the swimming pool through the outlet opening 8. As stated above, the outlet opening 8 has a backpressure valve 9. The volute has a primer-opening 13, to assist with starting the pump. Pressure is built up by the pumping of water inside the lower compartment due to the rising water level against a volume of air 33 in the upper end of the lower compartment. When the pump is switched off by the timer, or manually, the pocket of air at high pressure will force some of the water in the lower compartment back through the opening 12 and through pipe 25 and out through the backwash pipe 7, past the check valve 30 thereby dislodging any debris collected in the filter media 21 so that the debris is expelled through the backwash pipe 7. As stated above, the backwash pipe 7 includes a one-way valve 30 which may be a flap valve or a duckbill valve. The operation of the embodiment of the invention shown in figure 2 is similar to that of figure 1 but for a different type of filter media. In the embodiment of Figure 2, loose filter media 21 , is supported by a filter support screen 27 around the connector pipe 25, which in this case has an opening at the lower end of the upper sub-compartment and an extension 23 to act as an air vent to the upper compartment.

With reference more specifically to figure 2, which shows an embodiment of the invention of similar operation to the embodiment described in figure 1 , the flow path of the water is a little different. An opening 24 is provided in the connector pipe 25, through which water can flow form the upper to the lower compartment. The inlet opening of the inlet pipe 4 in this case is located above the filter media so that incoming water moves through the filter media from above and into the lower compartment. The outlet opening 8 is closed off with a backpressure valve and pressure builds up in the lower compartment to a predetermined level (determined by the backpressure valve), before water forces the backpressure valve. When the pump 1 1 stops and thus allows the air pressure of the air volume 33 to force the water back through openings 12 and 13 in to the lower end of the connector pipe 25 and up through pipe 25 and back through the filter media and out through the backwash pipe 7 which, in this case, is located above the filter media 21 .

The backwash valves (30) may be a soft duckbill type valves so it will close off at the slightest amount of back pressure. With reference to figure 3 which shows filtration operation of a filtration system including a water filter, the pump motor sucks water from the swimming pool through the flap valve. The flap valve is forced open by the water. The water is sucked through the leave trap, through the motor impeller, from where it is pushed through a sand filter, by the pump.

From the filter, the water is pumped into a pressure vessel where the force of the water causes air at the top of the vessel to compress. An outlet pipe of the pressure vessel is connected to a backpressure valve which is adjusted to determine the pressure in the pressure vessel. Water flows past the backpressure valve back into the pool, once pressure has built up to force water past the backpressure valve.

Backwash operation shown in figure 4.

The pump motor is switched off, causing an initial slight pressure drop in the pressure vessel. This pressure drop causes the backpressure valve to close when the air expands. The compressed air now further expands causing the water in the pressure vessel to flow in a reverse direction through the filter (thus backwashing the filter), through the impeller, through the leave trap basket (taking with it all leaves and debris collected in the basket), down the T-pipe and out through the duckbill valve into a filter bag. Note that the water flow causes the flap valve to automatically close so that water can only go down the T-pipe and not back into the pool.

The filter bag is located in a backwash water collector. All debris that was in the leave trap basket and filtration backwash debris collects in the filter bag and the filter bag filters the finer particles from the water before the water exits the backwash water collector, under force of gravity, back to the return line and back to the pool.

From the above it is clear that the water filter backwashes every time it is switched off. The filter media and leave trap thus remains clean ensuring efficient operation of the system. A timer can be connected to the pump motor electrical supply. The timing can be changed depending on how dirty the pool is. For example, if the pool is dirty and full of leaves, short cycles, say, 2 hour cycles can be selected to remove leaves and other larger debris from the pool as well as backwash the sand filter every 2 hours. There is no need to manually clean a weir basket. All the debris collects in the washable or replaceable filter bag much like a vacuum cleaner bag. Every now and then, the filter bag may be emptied or replaced. It will be appreciated by those skilled in the art that many embodiments are possible without departing form the scope of the invention. The invention will be reinvented to use as the filter media will be cleaned every time the pump is switched off. No manual back washing would be required. Also, the backwash pressure valve may be bypassed and only engaged (brought into the flow path) only a few minutes before the whole system is switched off so that pressure builds up in the last few minutes of operation only and does not have to be maintained for the whole time during operation.