FIELD OF INVENTION

This invention relates to filters for swimming pools. BACKGROUND ART A typical swimming pool filtration system consists of a skimmer box, a skimmer box filter, a pre-pump filter, a pump and a main filter. The skimmer box is mounted on the side of the pool near the level of the completely filled pool. Water from the surface of the pool is sucked into the skimmer box carrying with it any debris floating on the water surface such as leaves. The skimmer box filter, which is usually a small plastic mesh basket, traps larger pieces of debris.

The pre-pump filter, which is located immediately before the pump, is a fine mesh filter adapted to trap smaller particles (i.e. those visible to the naked eye). The pump sucks water from the pool through the skimmer box and skimmer box filter, and through the pre-pump filter at high pressure. Pool water from the pump is delivered to the main filter which removes fine microscopic particles from water and the filtered water is then returned to the pool.

Although some of the debris floating on the surface of the pool is sucked into the skimmer box, debris not sucked into the skimmer box eventually sinks to the bottom of the pool. The debris on the bottom of the pool may be removed by manual or automatic vacuuming devices. With manual

vacuuming, a closure plate is placed over the skimmer box to restrict the flow through an aperture in the closure plate. A vacuum hose is attached to the closure plate which has, at is other end, a vacuum head adapted to be moved over the pool floor by means of a long pole. With automatic vacuuming devices, the flow of water through the vacuum hose is utilized to move the cleaning head around the pool, usually in a random fashion.

There are a number of disadvantages of present pool filtration systems not the least of which arises because of the size of known skimmer boxes.

The capacity of the prior art filters is limited so that when there is a heavy load of debris in the pool, the filters quickly reach capacity and filtering efficiency falls away. In these circumstances, if the filters are not regularly emptied, they become blocked and damage can be caused to the pump and/or the filters.

Typically, the skimmer box filter is a plastic mesh basket set into the base of the skimmer box and as such is difficult to remove and empty. Moreover, when the pump is turned off, the plastic basket can float to the surface of the water in the skimmer box allowing debris previously collected to float back into the pool. This latter drawback can be overcome by placing a weight in the filter basket but this leads to a drop in pumping efficiency. Another drawback of present filtration systems is that a relatively small load

of debris in the filters can lead to large increases in the resistance through the filters with consequent loss of filtering efficiency.

It is, therefore, an object of the present invention to provide an improved filtration system for a swimming pool which reduces the amount of debris drawn into the filters of a conventional filtering system. DISCLOSURE OF THE INVENTION

According to one aspect of the invention, there is provided a filter for a swimming pool filtration system, said filter comprising a hollow body, a water inlet through which water and debris from the pool enters the body and a water outlet through which water is delivered to the skimmer box or other part of the filtration system, and, a basket between the water inlet and outlet adapted to remove debris from the incoming water. BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings in which:-

Fig. 1 is a schematic diagram of a typical prior art swimming pool filtration system, Fig. 2 is a perspective view of a filter for a swimming pool according to one embodiment of the invention, and,

Fig. 3 is a perspective view of the filter basket of the filter shown in Fig. 2. DESCRIPTION OF PREFERRED EMBODIMENTS

The filtration system shown in Fig. 1 is arranged to treat a body of water 10 in the swimming pool 11. The normal level of the water is indicated by the dotted line 12 when the pool is full. Surface water from the pool 11 is drawn into the skimmer box 13 having a skimmer box filter 14 which removes larger pieces of debris. Water from the skimmer box 13 is drawn through a pre-pump filter 15 by the suction pump 16. The pre-pump filter 15 removes the smaller particles of debris (i.e. those visible to the naked eye). Water from the pump 16 is delivered to the main filter 17 and the filtered water is returned to the pool through return pipe 18. The filter of the invention shown in Figs. 2 and 3 consists of a body 20 having a base 21, a front wall 22 and a rear wall 23. A filter basket 24 is supported by a central wall 25 which with the front wall 22, base 21 and rear wall 23 defines the filter chamber 26. As can be seen in Fig. 2, the basket 24 has a peripheral mounting flange 27 and a V- shaped base 28.

An inlet plate 29 is hingedly mounted on the front wall 22 and generally overlies the basket 24. An inlet port 30 on the plate 29 provides a point of attachment for the hose of a mobile pool cleaner such as those sold under the Registered

Trade Mark KREEPY KRAULY. At the centre of the base 21 there

is a water outlet 31 which receives a plastic hose that is connected to the vacuum plate of the skimmer box 13. Above the base 21 there is a pair of spaced apart baffles 32, 33 which act to draw water evenly across the basket 24. The space between the baffles 32, 33 increases from the centre towards each side.

When the filter pump is off, the inlet plate 21 is vertical and when the pump is turned on, the plate assumes an angle of around 45°, the actual angle depending upon the buoyancy of the inlet plate 29. When a mobile cleaner is to be connected to the inlet plate 30, the inlet plate 29 is pushed down to a horizontal disposition and held against the peripheral flange 27 of the basket 24 by latch 34. The shape and configuration of the filter basket 24 is achieved by sewing or forming a suitable filter fabric. There is sufficient clearance beneath the bottom of the filter basket 24 and the baffle plates 32, 33 to ensure that the basket is not sucked into the space between the baffles 32 and 33. Existing pools may have the filter of the invention located in the pool immediately adjacent to the existing skimmer box. The filter could be suspended from the skimmer box inlet by locating arms. New pools under construction may have the filter installed in place of the existing skimmer box or in addition to the skimmer box. Existing pools may, of course, be altered to achieve a new pool type installation having a pre-filter according to the invention and no skimmer box.

The efficient operation of the filter is unaffected by the debris collected, which contrasts with the conventional filtration system where the debris already collected decreases the efficiency of operation by blocking the filter mesh. The efficient packing of collected debris and the constant packing action by the passage of water over the mesh provide this continuing efficiency.

As will be apparent from the foregoing description, the time of unattended operation is increased dramatically because the safe capacity of the pre-filter is much greater than the skimmer box filters of present installations. The basket 34 will need emptying less frequently so that the chance of the filter becoming filled to total capacity and thereby becoming blocked is much reduced. Various modifications may be made in details of design and construction without departing from the scope and ambit of the invention.