U.S. patent application number 10/669011 was filed with the patent office on 2004-04-08 for heat retaining swimming pool cover.
This patent application is currently assigned to Cantar/Polyair Corporation. Invention is credited to Bartlett, Chris.
Application Number | 20040064882 10/669011 |
Document ID | / |
Family ID | 22014266 |
Filed Date | 2004-04-08 |
United States Patent
Application |
20040064882 |
Kind Code |
A1 |
Bartlett, Chris |
April 8, 2004 |
Heat retaining swimming pool cover
Abstract
A plastic film for a heat-retaining swimming pool cover. The
film is made of plastic material and has contained therein an
infrared absorbent material. The amount of infrared absorbent
material is insufficient to prevent some light from substantially
penetrating the film. The film is used as a lower film in a
floatable cover, with an I.R. pockets being formed between the
lower and upper films.
Inventors: |
Bartlett, Chris;
(Missisauga, CA) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
Cantar/Polyair Corporation
|
Family ID: |
22014266 |
Appl. No.: |
10/669011 |
Filed: |
September 24, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10669011 |
Sep 24, 2003 |
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10339489 |
Jan 10, 2003 |
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6637046 |
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10339489 |
Jan 10, 2003 |
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10058037 |
Jan 29, 2002 |
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6523190 |
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Current U.S.
Class: |
4/502 |
Current CPC
Class: |
E04H 4/103 20130101 |
Class at
Publication: |
004/502 |
International
Class: |
E04H 004/00 |
Claims
1. A film for a heat-retaining floating swimming pool cover,
comprising: a plastic film; and an infrared absorbent material
contained in said plastic film in an effective amount, but which is
insufficient to prevent atmospheric sunlight from substantially
penetrating the film.
2. The film according to claim 1, wherein the plastic film is made
of vinyl or olefin or acetate.
3. The film according to claim 2, wherein the plastic film has a
small amount of tint therein, which amount is only sufficient for
cosmetic appearance and which amount does not significantly reduce
the transmission of sunlight.
4. The film according to claim 1, wherein the I.R. absorbent is a
solid, particulate absorbent.
5. The film according to claim 4, wherein the solid, particulate
absorbent is substantially non-reflective.
6. The film according to claim 4, wherein the solid, particulate
absorbent is in or on the lower film in an amount of between 0.5 to
8% by weight of the lower film.
7. The film according to claim 4, wherein the I.R. absorbent is
talc.
8. The film according to claim 7, wherein the talc is white talc
and has an average particle size of between about 0.1 and about 10
microns.
9. The pool cover of claim 8, wherein the talc has a specific
gravity of between about 2.6 and about 2.9.
10. The film according to claim 1, wherein the amount of I.R.
absorbent is sufficient to generate substantial heat.
11. The film according to claim 10, wherein the plastic film is
sealed to a second film so as to form air pockets and wherein the
heat generated is sufficient to heat the air in the air
pockets.
12. The film according to claim 11, wherein the amount of I.R.
absorbent is sufficient to generate heat so that pool water next to
said film is substantially heated.
13. The film according to claim 12, wherein the amount of infrared
absorbent is such that sunlight passing through the film is capable
of substantially heating the pool water.
14. The film according to claim 13, wherein the amount of infrared
absorbent is sufficient to generate heat in the air of the air
pockets, and sunlight passing through the cover is capable of
substantially heating the pool water.
15. The film according to claim 1, wherein the film has a thickness
of between 1-40 mm.
Description
[0001] This application is a continuation of co-pending application
Ser. No. 10/339,489 filed Jan. 10, 2003, which is a divisional of
co-pending application Ser. No. 10/058,037 filed on Jan. 29, 2002,
which issued as U.S. Pat. No. 6,523,190 on Feb. 25, 2003, the
entire contents of which are hereby incorporated by reference and
for which priority is claimed under 35 U.S.C. .sctn. 120.
[0002] The present invention relates to a heat retaining swimming
pool cover, and especially to such a pool cover which can be
floatably disposed on pool water in a swimming pool. More
particularly, the invention relates to such swimming pool cover
which can significantly increase the temperature of pool water in
the swimming pool by absorption and retention of heat from
sunlight.
BACKGROUND OF THE INVENTION
[0003] The temperature of pool water in a swimming pool, especially
an outdoor swimming pool, can significantly change over the course
of a 24 hour period. During the day, especially on bright sunny
days, sunlight from the atmosphere enters into and is absorbed by
the pool water, which absorption generates sensible heat in the
pool water. The efficiency of absorption and retention of that heat
is not, however, very great. In one aspect, the walls of a pool are
normally light in color and that light color reflects the sunlight
back out of the pool before absorption occurs. The absorption of
the sunlight could be much improved if the pool walls were painted
a dark color, e.g. black, but this is not only unattractive, but is
illegal in some jurisdictions, since the dark color makes it
difficult to identify objects (or persons) under the pool
water.
[0004] In another aspect, heat is lost from the pool water by
re-radiation from the pool water to the atmosphere. In yet another
aspect, particularly during the dark or night hours when the
atmospheric temperature tends to drop, heat is lost by conduction
from the pool water surface to the surrounding atmosphere. In this
latter regard, it has been quite popular to provide pools with a
pool cover that floats on the pool water. This cover, essentially,
covers the entire surface of the pool water and is an insulator for
reducing the amount of heat transferred from the surface of the
pool water to the atmosphere, especially during the dark or night
hours. Since the cover is floatable on the pool water, the cover
can be easily removed during the day when required for swimming
purposes, and replaced on the pool water after swimming or in the
evenings for heat retention purposes.
[0005] These floatable pool covers, generally, have a plastic upper
layer or film for facing toward the atmosphere, a plastic lower
layer or film for facing toward the pool water, and a sufficient
number of spaced apart air pockets configured into the lower layer
or film such that the cover is floatable on the pool water. Land
areas between the air pockets are sealed, such that the upper and
lower layers or films are sealed to each other and the air pockets
are, therefore, watertight. The air pockets in the cover provide
floatibality to the cover and insulation to reduce the amount of
heat transferred by conduction from the pool water to the
atmosphere, especially during the dark or night hours. These
conventional covers are made of, generally, transparent plastic
film in which an air pocket has been configured into a lower layer
of the film by molding, embossing and the like. The air pockets may
be of any desired shape, e.g. hemispherical, square, rectangular,
triangular, etc. Usually, these conventional covers will have a
very small amount of a tint material in the plastic films forming
the cover for cosmetic purposes. Since a very light blue color is
generally associated with clean pool water, a very low intensity
blue tint is normally placed in the plastic films for that cosmetic
purpose.
[0006] However, the tints, as well as the pool cover itself, do not
essentially affect passage of sunlight through the pool cover into
the pool water during the day or radiation from the pool and pool
water to the atmosphere during the dark or night hours. As a
result, while the cover can allow the pool water to rise in
temperature during the day, by transmission of sunlight into the
pool water, substantial amounts of the heat absorbed by the pool
water are re-radiated to the atmosphere, especially during the
night or dark hours, and the temperature of the pool water
considerably drops, even though some heat retention is provided by
the insulation properties of the pool covers.
[0007] In view of the foregoing, the art has made efforts to
improve these conventional floatable pool covers, such that the
pool water, overall, retains a greater amount of heat. For example,
U.S. Pat. No. 6,286,155 B1 and U.S. Pat. No. 6,317,902 B2, disclose
such a floatable pool cover where an upper layer of the cover has a
dark color and a lower layer has a light reflective material
applied to one of the surfaces thereof. It is said that the dark
color of the upper layer acts to draw heat into the pool,
presumably by absorption and conduction, and the lower reflective
layer reflects heat radiated from the pool water back into the pool
water. The reflective material of the lower layer is a
silver-colored commercially available master batch material
containing an aluminum concentrate.
[0008] However, with this arrangement the reflective lower layer
not only reflects radiant heat from the pool water back into the
pool water, but also reflects sunlight from the atmosphere back
into the atmosphere. Thus, while absorbed heat in the pool water is
conserved by that lower layer reflectance, that lower layer
reflectance decreases the total heat absorbed by the pool water by
an amount proportional to the amount of atmospheric sunlight
reflected from that lower layer back into the atmosphere. In
addition, the dark color of the upper layer significantly decreases
the transmission of sunlight through that upper layer and into the
pool water. Thus, while the reflective lower layer of those patents
is effective in reflecting heat from the pool water back into the
pool water, hence conserving heat in the pool water, that lower
layer very undesirably also reflects sunlight from the atmosphere
back into the atmosphere, which significantly decreases the amount
of sunlight reaching the pool water for heating purposes. In other
words, something of a compromise is reached in the arrangement of
having a reflective lower layer, and the compromise entails a
decrease in the amount of sunlight passing through the pool cover
into the pool water for heating thereof. Further, in order for the
lower layer to be effective, the lower layer must be substantially
reflective. Thus, the amount of reflective material associated with
that lower layer also makes that lower layer substantially
non-transparent and can be a safety problem for the reason
mentioned above.
[0009] It would, of course, be an advantage to the art to provide a
heat retaining pool cover which does not substantially interfere
with sunlight passing through the cover and into the pool water for
heating thereof. Also, it would be an advantage to provide a pool
cover where the air pockets of the cover are specifically heated so
that heat can be transferred by conduction from the pool cover to
the pool water. With both of these means of heat transfer to the
pool water, significant amounts of heat can be generated in and
retained by the pool water both during the day and during the dark
or night hours.
SUMMARY OF THE INVENTION
[0010] The invention is based on several primary and subsidiary
discoveries.
[0011] First of all, it was recognized that the reflective lower
layer of the above-noted patents is something of a compromise, as
explained above. Thus, as a primary discovery, it was found that
the reflective layer must be eliminated, but, in addition, a
substitute therefore was required. Otherwise, just eliminating the
reflectivity of the lower layer would result, essentially, in a
conventional pool cover with a dark upper layer and such a cover
would not be significantly effective.
[0012] As a second primary discovery, it was found that instead of
providing the lower film with reflective properties, very
substantial advantages could be obtained by providing the lower
film with infrared absorbing properties. Those infrared absorbing
properties are providing by including in or on the lower film an
infrared (I.R.) absorbent.
[0013] However, as a subsidiary discovery, it was found that the
amount of the I.R. absorbent must be controlled. If the amount it
too great, then most of the heat value of the sunlight, i.e. in the
I.R. spectrum, is absorbed by the cover and does not pass directly
into the pool. This would be a disadvantage.
[0014] Therefore, as another primary discovery, it was found that
the lower film should contain an I.R. absorbent effective amount of
an I.R. absorbent, but which amount is insufficient to prevent
atmospheric sunlight from substantially penetrating the lower film
and passing into the pool water.
[0015] Such an amount of the I.R. absorbent will allow substantial
I.R. radiation to pass through the cover and into the pool water to
heat the pool water during the daytime period. However, some of the
sunlight is absorbed by the infrared absorbent and is turned into
heat in the lower film of the cover. That heat transfers from the
lower film to the pool water by way of conduction with the pool
water next to the lower film of the pool cover. Further, heat
radiated from the pool water and pool walls will be absorbed by the
I. R. absorbent in the lower film and rendered into sensible heat
which also heats the pool water next to the pool cover. In
addition, that absorption of infrared in the lower film heats the
air in the air pockets of the pool cover, as well as air trapped
between the cover and the surface of the pool water (mainly
dispersed between air pockets). The trapped air is also heated
directly by sunlight passing through the cover. That heated air,
both the air in the pockets and the trapped air, transfers heat to
the pool water, as noted above, and also forms an insulator to
prevent conduction of heat from the pool water to the
atmosphere.
[0016] Thus, as a basic principle of the invention, the lower film
of the present floatable film cover contains an I.R. absorbent in
specific amounts as described above.
[0017] Accordingly, briefly stated, the invention provides a heat
retaining pool cover for floating disposition on pool water in a
swimming pool. The cover comprises a plastic upper film for facing
toward the atmosphere, a plastic lower film for facing toward the
pool water, sufficient spaced apart air pockets configured into the
lower film for containing air such that the cover is floatable on
the pool water, sealed land area between the air pockets such that
the upper and lower films are sealed to each other, and wherein the
lower film contains an I.R. absorbent effective amount of an I.R.
absorbent, but which amount is insufficient to prevent atmospheric
sunlight from substantially penetrating the lower film and passing
into the pool water. With this arrangement, almost all of the
atmospheric sunlight, including the infrared, is either passed by
radiation into the pool water for heating thereof or absorbed by
the lower film for heating the pool water by conduction, and
essentially none of the sunlight is reflected back to the
atmosphere, as is the case in the above-described patents.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The figure is a cross-sectional view of the pool cover of
the present invention.
DESCRIPTION OF EMBODIMENTS
[0019] As can be seen from the figure, the pool cover, generally 1,
floats on pool water, generally 2, contained within a swimming
pool, generally 3. The pool cover 1 has a plastic upper film 5 for
facing toward the atmosphere, generally 6. The cover also has a
plastic lower film 8 for facing toward the pool water 2. Air
pockets 10 are sufficiently spaced apart and are configured into
lower film 8 for containing air such that the cover 1 is floatable
on the pool water 2. The cover has sealed land areas 11 between the
air pockets 10 such that the upper and lower films 5 and 8 are
sealed to each other. Lower film 8 contains an I.R. absorbent
effective amount of an I.R. absorbent, but which amount is
insufficient to prevent atmospheric sunlight, generally 14, from
passing into pool water 2.
[0020] The upper and lower films 5 and 8 are made of essentially
transparent plastic films, such as vinyl or olefin, e.g.
polyethylene and polypropylene, or acetate films. However, as noted
above and is conventional, these films will normally have a small
amount of a tint therein, but that amount is only sufficient for
cosmetic purposes and will not significantly reduce the
transmission of sunlight. The tint is generally a very light blue
tent, for the reasons explained above. This is very conventional in
the art and will not be described in more detail herein for
purposes of conciseness.
[0021] While the I.R. absorbent can be any of the conventional
liquid or solid I.R. absorbents, it is preferable that the I.R.
absorbent is a solid particulate absorbent, as indicated in the
figure by numeral 15. The drawing only shows a few particles of the
solid absorbent for illustration purposes, but in reality, the very
small particulate I.R. absorbent is widely and uniformly dispersed
in or on lower film 8. It is important that the solid particulate
I.R. absorbent is substantially non-reflective for the reasons
explained above, i.e., briefly, it is not desirable for the
sunlight 14 to be reflected back to the atmosphere 6 by reflective
material in lower film 8. The solid particulate I.R. absorbent can
be a variety of mineral-type I.R. absorbents, or even carbon or
carbon black, and the I.R. absorbent may be in a carrier which can
be useful for incorporating the I.R. absorbent into lower film 8
when that film is extruded during the manufacture. In any event,
whichever I.R. absorbent is used in lower film 8, the amount of
absorbent in lower film 8 should be, as described above,
insufficient to prevent substantial penetration of sunlight and,
generally, for solid particulate absorbents, the amount is between
about 0.5 and 8% by weight of the lower film, and more preferably
about 1 to 5%, e.g. 1.5 to 3%.
[0022] A most preferred I.R. absorbent is talc (magnesium
silicate-Mg.sub.3Si.sub.4O.sub.10(OH).sub.2). This is a
particularly good absorbent, which is somewhat dull in appearance,
substantially non-reflective, can be easily incorporated into the
usual plastics for producing pool covers of the present design, and
is sufficiently inexpensive to be commercially viable.
[0023] It is preferable that the talc is white talc, as opposed to
the available slightly green or slightly gray talc, and that the
white talc has an average particle size of between about 0.1 and 10
microns. More specifically, it is preferred that the talc have a
specific gravity of about 2.6 and 2.9.
[0024] With talc of this nature, the lower film will be
substantially non-reflective, will absorb infrared radiation
readily, but will allow passage of sunlight through the lower film
to heat the pool water during the day. Of course, the amount of
radiation passing through the cover during the day is much greater
than the radiation passing from the pool water through the cover,
especially at night. With the talc I.R. absorbent in the amounts
described above, the talc will intercept and absorb a substantial
amount of the radiation from the pool water to the pool cover,
especially at night, and conserve that energy (heat).
[0025] It is permissible to put very small amounts of I. R.
absorbent in the upper film, but it is preferred that the IR
absorbent is only in the lower film. Within the ranges described
above, the amount of I.R. absorbent is sufficient to generate
substantial heat in the air of the air pockets, i.e., the radiation
absorbed by the I. R. absorbent is converted into sensible heat
which is transferred by conduction and convection to the air in the
air pockets. Thus, the air in the air pockets becomes heated by
that absorption. If I.R. is simply passed through the air of the
air pockets by either radiation from atmospheric sunlight or by
reflection from a reflective layer, as disclosed in the above-noted
patents, very little of that radiation will be absorbed by the air
of the air pockets. In the present invention, however, the amount
of the I.R. absorbent is sufficient to generate substantial heat in
the air of the air pockets. Also, that amount is sufficient that
the heat generated in the air of the air pockets is capable of
substantially heating the pool water next the pool cover,
principally by conduction and convection. At the same time, that
amount is such that sunlight passing through the cover, since it is
not reflected by a reflective layer, is capable of substantially
heating the pool water. Accordingly, with the amount of absorbent
of the type described above, heat generated in the air of the air
pockets and sunlight passing through the cover are capable of
substantially heating the pool water.
[0026] The present invention, where some infrared is absorbed and
other infrared passes (by lack of reflection) through the lower
film, is applicable to a wide range of thicknesses of upper and
lower films. This invention can be used in connection with
thicknesses as little as 1 mm and as great as 40 mm and the same
effective function will be obtained
[0027] The covers may be made with a single upper film and a single
lower film or multiple films may form and upper layer and/or a
lower layer.
[0028] In the specification and following claims, the term
"reflectance" and variations thereof are intended to mean that at
least 30% of the intercepted radiation is reflected.
[0029] The invention will be illustrated with the following
Example, where all percents are by weight unless otherwise
indicated.
EXAMPLE
[0030] Into a blender were placed the following ingredients in the
stated percentages by weight: polyethylene, Grade # 1, 62%;
Polyethylene, Grade # 2, 19%; master batch including color (tint),
UV inhibitor and anti-block, 4.5%; white talc, 2%; and recycle
trimmings, 12.5%. After blending the ingredients, the ingredients
were transferred to a conventional cast line extruder. The extruder
melt was passed through a heated die and then passed to a
conventional embossing roll in a conventional staggered method
where a produced film is drawn into the embossing roll and another
film without talc is laminated thereto. The laminated film was
wound onto rolls and subsequently cut and finished into a pool
cover product of the invention.
[0031] The product of the invention was tested in a comparison with
an identical pool cover with the exception that the comparison
cover did not have the I. R. absorbent (talc) in either of its
layers. The test was run on identical pools on the 30.sup.th day of
September. The pool temperatures for the present cover and the
comparison cover at 8 A. M. were 55.1 and 55.2 degrees F.,
respectively. The weather was sunny with a high temperature of 72
degrees F. At 4 P. M. the pool temperatures were 68.1 and 66.7
degrees F. for the present cover and the comparison cover,
respectively, which represents an additional temperature increase
for the present cover of 2.5 degrees F. or an increase of 21%.
[0032] Thus, the present invention provides a very substantial
advance in the art and the invention extends to the breath and
spirit of the following claims.
* * * * *