AU2006100736A4 - A cover for a body of water - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION INNOVATION PATENT Applicant(s): ELITE POOL COVERS PTY LTD Invention Title: A COVER FOR A BODY OF WATER The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 A COVER FOR A BODY OF WATER Field of the Invention The present invention relates to a cover for a body of water and, in particular, but not exclusively, to a swimming pool cover.

Background of the Invention The use of pool covers or solar blankets for the purposes of heating swimming pools is well known and wide-spread.

The heating is produced by a combination of mechanisms.

These include reducing heat loss through evaporation and convection; and reducing radiation losses from the water itself. In addition, when the pool cover or solar blanket is in place, it allows a significant portion of incident solar energy (and in particular UV radiation) to pass therethrough which is absorbed by the underlying water causing an increase in water temperature. However, the blanket further acts to minimise emission of heat energy absorbed by the water.

Summary of the Invention According to the present invention there is provided a cover for a body of water the cover comprising: a liquid impervious sheet of plastics material, the sheet provided with a plurality of sealed gas-containing compartments on at least one side, the sheet being substantially opaque to solar radiation.

A first side of the sheet that, in use is incident to solar radiation, may have a reflectivity to solar radiation of at least 10%. However the level of reflectivity may be increased to at least 50%. In a H:\mcamp\keep\speci\INNOV\P61941 A Cover for a Body of Water.doc 30/08/06 -3further embodiment the reflectivity may be at least 80% of incident solar radiation. The reflectivity can be controlled by selecting the colour of the first side. The first side may have a colour selected from the group of white, silver and blue. Further, the first side may be formed to have a gloss finish.

In one embodiment, the cover has an R value of at least 0.075.

In one embodiment, the sheet comprises two layers of plastics material with a first layer being substantially planar and a second layer being formed of a plurality of spaced apart receptacles; the first and second layers overlying each other and connected together in a manner so that the receptacles are sealed to an adjacent surface of the first layer to form the plurality of sealed gascontaining compartments.

According to a further aspect of the present invention there is provided a method for maintaining a body of water comprising the steps of: forming a liquid impervious sheet of plastics material with a plurality of sealed gas-containing receptacles on at least one side, the sheet further being formed to be substantially opaque to solar radiation; forming a first side of the sheet to have a reflectivity to solar radiation of at least 10%; and, laying the sheet on the body of water with the first side uppermost.

Brief Description of the Drawings An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: H:\mcamp\keep\speci\INNOV\P61941 A Cover for a Body of Waterdoc 30/08/06 4 Figure 1 is a representation in section view of an uncovered swimming pool; Figure 2 is a representation in section view of a swimming pool covered by a conventional pool cover or solar blanket; Figure 3 is representation in section view of a pool cover in accordance with an embodiment of the present invention disposed on a swimming pool; and, Figure 4 is a schematic representation in section view of the pool cover shown in Figure 3.

Detailed Description of Preferred Embodiment Figure 1 depicts a body or volume of water 10 contained within a swimming pool 12. During the day time, the body of water 10 is heated to some extent by incident solar radiation 14. However, assuming that the pool 10 is uncovered, heat contained or absorbed in the water 10 is typically lost through three different mechanisms. Some sources indicate that approximately 60% of heat in the water 10 is lost by evaporation arising from the generation of convection currents 16 produced by the wind.

Approximately 30% of heat is also lost by radiation 18 from the water 10 to the surrounding atmosphere. Finally, approximately 10% of heat is lost through conduction into the ground.

It is generally desired by owners of swimming pools to heat the water 10 within their pools to increase the length of time throughout the year in which they can use their pools 12. Known methods for heating swimming pools include the use of solar heaters, gas heaters, and pool covers or solar blankets.

H:\mcamp\keep\speci\INNOV\P61941 A Cover for a Body of Waterdoc 30/08/06 5 Figure 2 depicts the operation of a conventional pool cover or solar blanket 22 on the surface of the body of water 10. The blanket or cover 22 is typically made of a translucent material that allows solar radiation and in particular UV radiation to pass through the blanket. UV radiation is absorbed by the water 10 increasing its temperature. Radiation of heat from the body of water is minimised by the cover 22.

The net effect of the pool cover or solar blanket 22 is to increase water temperature by up to 100C in comparison with an equivalent body of water 10 without the cover 22.

In contrast to the conventional cover or blanket 22, the cover 24 in accordance with embodiments of the present invention, depicted in Figures 3 and 4, is designed to prevent or minimise absorption of heat from solar radiation in the body of water 10. The cover 24 comprises a liquid impervious sheet 26 of plastics material. The sheet 26 is provided with a plurality of sealed gascontaining bubbles or compartments 28. Typically, the gas contained within the bubbles or compartments 28 is air.

The bubbles or compartments 28 are depicted in Figure 4 as lying on one side of the sheet 24. However it is envisaged that the cover 24 may be made with similar bubbles or compartments 28 on both sides of the sheet 26.

The cover 24 is substantially opaque to solar radiation 14. Accordingly no or substantially no solar radiation and in particular no or substantially no UV radiation is able to penetrate the cover 24 to enter and thus be absorbed by the underlying water 10. In order to further insulate the water 10 from heat absorption from the solar radiation, first side 30 of the cover 24, being the side that in use is incident to solar radiation, has a reflectance to solar radiation of at least 10%. In alternative embodiments, the degree of reflectance of the H:\mcamp ,k eo\spcci'INNOV\P61941 A Cover for a Body of Water.doc 30/08/06 6 first side 30 is at least 50%, yet in further alternative embodiments of the cover 24, this reflectance may be at least 80%. The degree of reflectance may be controlled by selection of the colour of the first side 30. It is envisaged that the colour of the cover 24, and in particular the first side 30 is selected from the group of: white, blue including ice blue which comprises a mixture of a white base with 2% to 4% light blue tint, and silver.

As shown in Figure 4, the cover 24 comprises first and second layers 32 and 34. The first layer 32, which includes the first side 30, is substantially planar. The second layer 34 is shaped or profiled so as to be provided with a plurality of receptacles. The receptacles are typically in the shape of circular wells with a diameter in the order of 18mm. The layers 32 and 34 overlie each other and are joined together so that the receptacles are sealed against an inside surface 36 of the first layer 32 and thereby form the plurality of sealed bubbles or compartments 28.

In one embodiment the layer 32 is made of polyethylene with a thickness of 200 microns; while the layer 34 is made of the same material as layer 32 but with a greater thickness typically in the order of 220 microns.

The formation of the sealed gas-containing bubbles or compartments 28 aids in insulating the body of water from the environment to minimise heat transfer. The typical thermal resistance (R value) of the cover 24 is 0.075.

Embodiments of the cover 24 may be used in countries or locations where due to climatic conditions the natural heating of a body of water 10 and in particular a swimming pool would increase water temperature to a level that H: \mcamp\keep\speci\INNOV\P61941 A Cover for a Body of Water.doc 30/08/06 would scald or burn or would otherwise be uncomfortable or detract from the enjoyment of swimming or pool play.

However, it is further envisaged that in such countries and locations it would also be desirable to minimise loss of water through evaporation and convection as well as minimise use of pool chemicals that degrade when subjected to solar radiation.

Embodiments of the cover 24 facilitate a minimisation of water loss through evaporation, assist in saving chemicals, and maintaining water quality but without providing any substantive increase in temperature of the underlying body of water 10. Use of a conventional pool cover or blanket 22 in such locations typically results in water temperature exceeding 30 0 C which makes swimming uncomfortable and ineffective for the purposes of cooling oneself down.

It is envisaged that one pattern of use of the cover 24 is to apply the cover 24 in summertime during the day in order to minimise temperature increase in the water 10 and remove the cover at night time to enable loss of heat from the water 10 to the surrounding atmosphere while minimising evaporation loss; and, during winter, removing the cover 24 during the day to enable absorption of solar radiation and applying the cover at night time in order to retain heat absorbed during the day.

Modifications and variations of the invention as will be apparent to those of ordinary skill in the art are deemed to be within the scope of the present invention the nature of which is to be determined from the above description and the appended claims.

H: \mcamp\keep\speci\INNOV\P61941 A Cover for a Body of Water.doc 30/08/06

Claims (4)

1. A cover for a body of water the cover comprising: a liquid impervious sheet of plastics material, the sheet provided with a plurality of sealed gas-containing compartments on at least one side, the sheet being substantially opaque to solar radiation.

2. The cover according to claim 1 wherein a first side of the sheet, which in use is incident to solar radiation, has a reflectivity to solar radiation of at least

3. The cover according to claim 2 wherein the reflectivity of the first side is at least

4. The cover according to any one of claims 1-3 wherein the first side has a colour selected from the group of white, silver, blue and ice blue. A method for maintaining a body of water comprising the steps of: forming a liquid impervious sheet of plastics material with a plurality of sealed gas-containing receptacles on at least one side, the sheet further being formed to be substantially opaque to solar radiation; forming a first side of the sheet to have a reflectivity to solar radiation of at least 10%; and, laying the sheet on the body of water with the first side uppermost. Dated this 30th day of August 2006 ELITE POOL COVERS PTY LTD By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia H: \mcamp\keep\speci\INNOV\P61941 A Cover for a Body of Water.doc 30/08/06