Title:
RIGID, BUOYANT, INSULATING AND RAPID FOLDING SWIMMING POOL COVERS
United States Patent 3683428
Abstract:
Rigid, closed cell foam plastic sheets are joined by flexible hinges. A series of resulting strips are floated, side by side, to cover the pool. Overall dimensions are slightly smaller than the inner pool perimeter to allow for easy removal. There is attached to the outer perimeter and extending past the edge of the sheets and up the wall of the pool, a flexible lip, preferably porous, so that some pressure is exerted to keep individual sections together while sealing the open perimeter channel. This allows rain water passage to the pool below without permitting dirt to follow. Flexible or elastomeric inserts are attached at corners and at necessary breaks in the lip selected for folding or closer fitting to further keep out contamination. The alternately hinged, rigid foam sheets fold, accordion like, into a small space when not in use.
US Patent References:
Machine for unloading rows of piles of articles standing on a pallet
Dial et al. - April 1967 - 3313433
Insulated lightweight cover for pools of water
Oldshue - October 1968 - 3405410
BUOYANT SWIMMING POOL COVERS
Woycik - September 1970 - 3528110
/3555573.html
Turner - January 1971 - 3555573
Machine for unloading rows of piles of articles standing on a pallet
Dial et al. - April 1967 - 3313433
Insulated lightweight cover for pools of water
Oldshue - October 1968 - 3405410
BUOYANT SWIMMING POOL COVERS
Woycik - September 1970 - 3528110
/3555573.html
Turner - January 1971 - 3555573
Application Number:
05/041797
Publication Date:
08/15/1972
Filing Date:
06/01/1970
View Patent Images:
Export Citation:
Primary Class:
International Classes:
E04H4/08; E04H4/00; E04H3/16; E04H3/18
Field of Search:
4/172.12,172.13,172.14,172
Primary Examiner:
Matteson, Frederick L.
Assistant Examiner:
Artis, Henry K.
Claims:
I claim
1. A swimming pool cover which prevents dissipation of heat from the water of a swimming pool and prevents the water from being contaminated by substances in the atmosphere but allows easy access to the water by an individual when desired, said swimming pool cover comprising a series or rigid, or semi-rigid, water-resistant panels having a net specific gravity less than water, said panels being foldably fixed together by hinge means, said panels being of a size and shape such that the swimming pool cover has less area than the swimming pool whereby margins are left between the edge of the swimming pool and the edges of said panels which are nearest the swimming pool edge thereby leaving a space between the edge of the swimming pool and the edges of said panels, said space being insulated from the atmosphere by flexible joining means which are of a size and shape sufficient to cover said space and are porous to liquids and non-porous to solids, thereby allowing the panels to move in the swimming pool while still covering and insulating said space.
2. A swimming pool cover according to claim 1 wherein the panels are made of a closed cell polystyrene foam.
3. A swimming pool cover according to claim 1 wherein the hinge means include a longitudinally expanding flexible member folded along its longitudinal axis and secured on opposite sides to adjacent inner edges of said panels.
4. A swimming pool cover according to claim 1 wherein the edges of panels closest to the pool include a longitudinally extending flexible strip secured to the horizontal sides and extending beyond the panels.
5. A swimming pool cover according to claim 1 wherein the panels are made of honeycomb cells with facings of thin, stiff, waterproof sheets.
6. A swimming pool cover according to claim 1 wherein said panels have internally molded air cavities.
7. A swimming pool according to claim 1 wherein said panels are rigid sheets having a waffle-like pattern which thereby produces buoyancy by water displacement and entrapped air pockets.
8. A swimming pool cover according to claim 1 wherein the hinge means is provided by laminating a flexible, waterproof membrane to the entire structure, on one or both sides, said flexible membrane with appropriate slack acting as hinge means between the rigid panels.
9. A swimming pool cover according to claim 1 wherein the edges of panels closest to the pool are open cell, water resistant, compressible foams, said foams being adhesively attached and occupying the annular space between cover and pool wall.
10. A swimming pool cover according to claim 1 wherein the flexible joining means have a size greater than the space between the edge of the swimming pool and the edges of said panel.
1. A swimming pool cover which prevents dissipation of heat from the water of a swimming pool and prevents the water from being contaminated by substances in the atmosphere but allows easy access to the water by an individual when desired, said swimming pool cover comprising a series or rigid, or semi-rigid, water-resistant panels having a net specific gravity less than water, said panels being foldably fixed together by hinge means, said panels being of a size and shape such that the swimming pool cover has less area than the swimming pool whereby margins are left between the edge of the swimming pool and the edges of said panels which are nearest the swimming pool edge thereby leaving a space between the edge of the swimming pool and the edges of said panels, said space being insulated from the atmosphere by flexible joining means which are of a size and shape sufficient to cover said space and are porous to liquids and non-porous to solids, thereby allowing the panels to move in the swimming pool while still covering and insulating said space.
2. A swimming pool cover according to claim 1 wherein the panels are made of a closed cell polystyrene foam.
3. A swimming pool cover according to claim 1 wherein the hinge means include a longitudinally expanding flexible member folded along its longitudinal axis and secured on opposite sides to adjacent inner edges of said panels.
4. A swimming pool cover according to claim 1 wherein the edges of panels closest to the pool include a longitudinally extending flexible strip secured to the horizontal sides and extending beyond the panels.
5. A swimming pool cover according to claim 1 wherein the panels are made of honeycomb cells with facings of thin, stiff, waterproof sheets.
6. A swimming pool cover according to claim 1 wherein said panels have internally molded air cavities.
7. A swimming pool according to claim 1 wherein said panels are rigid sheets having a waffle-like pattern which thereby produces buoyancy by water displacement and entrapped air pockets.
8. A swimming pool cover according to claim 1 wherein the hinge means is provided by laminating a flexible, waterproof membrane to the entire structure, on one or both sides, said flexible membrane with appropriate slack acting as hinge means between the rigid panels.
9. A swimming pool cover according to claim 1 wherein the edges of panels closest to the pool are open cell, water resistant, compressible foams, said foams being adhesively attached and occupying the annular space between cover and pool wall.
10. A swimming pool cover according to claim 1 wherein the flexible joining means have a size greater than the space between the edge of the swimming pool and the edges of said panel.
Description:
This invention describes numerous combinations of rigid and semi-rigid sheets which act to insulate by floating directly on the surface, are accurately fitted to keep out contamination by use of auxiliary wiping lips, and are of light weight and quickly removable by means of flexible hinges. The thermal and economic benefits obtainable are tabulated and a typical construction is shown in detail.
Most swimming pool covers are simple sheets of plastic suspended over and sagging into the water. They are kept in place by sand bags, water bags, or mechanical fasteners. They are intended to be left in place during the winter season. Other variations include mechanically operated covers of numerous kinds using rollers, tracks, hydraulic lifts, etc. to place rigid or flexible membranes above the water. Some of the difficulties with these materials are enumerated:
1. Sheets tear easily and then admit water and dirt.
2. The water and dirt accumulates in the center of the flexible sheets as they sag and cannot be removed without spilling the debris into the water.
3. The time and energy needed to cover and uncover a plastic pool is so excessive that once in place, practical use of the pool for long periods is prevented.
4. Nearly all covers are so unattractive that pool owners will not use them.
5. The covers are so difficult to remove and replace that algae and stains may accumulate during the long dormant periods. Inspection and introduction of chemicals is tedious.
6. The air-suspended cover gives relatively poor insulation against heat losses, both because the plastic sheet is not a good insulator and a chimney effect occurs which sweeps moist warm air upward and out of the pool thru poorly sealed edges. Radiation losses are also high.
7. The thin, flexible sheets rapidly become embrittled by the sun and pool chemicals.
8. Covers designed to fit over the entire pool do not work well on pools which have raised bond beams--that is--various elevations around the pool perimeter.
9. Mechanically operated devices save time, but they are expensive, do not seal well, are quite clumsy, and often cannot be installed unless planned for in original construction.
I have found that insulating, rigid, fold in place, seals, floated in place in a manner different than any other swimming pool cover, overcomes nearly all the foregoing disadvantages of current covers, providing a low cost, attractive, and easily handled article with long life. Insulation benefits are greater than observed with any other system. The pool is instantly available for use without weather forecasting and long preheating periods. Further benefits of the self-placing buoyant covers include total prevention of water loss by evaporation, ability to refurbish by painting, ability to decorate in patterns, easy repair by removal of small damaged sections, no need of any auxiliary equipment for fastenings, and simple, rapid installation. The pre-hinged sheets, supplied in packages, can be laid in the water and cut to length. Any shape pool can be fitted if at least one strip has two straight sides. Removal is accomplished by sliding out this strip and pushing the other strips into the vacated position, if needed, to clear complex contours. I have found that it is possible to operate a swimming pool in Southern California all year around, at a fuel and chemical cost one-fifth of that required for operation during the summer alone without such a cover. Further, the cleaning and maintenance is largely eliminated by the protective cover so that pools can be left surrounded by deciduous trees and shrubs without creating undue maintenance problems.
I have found that closed cell polymeric foams made of water resistant polymers and of sufficient stiffness so that they may be placed on the surface of the water merely by pushing them away from one edge, and will lie flat and dimensionally stable are preferred materials for this purpose. Semi-flexible foams capable of being unrolled or partially cut thru for easy folding may also be suitably employed. The more rigid foams may be hinged together by such means as adhesive bonded glass fabric, flexible, bonded membranes over the entire assembly (allowing slack for alternate folds) are some means for assembly in addition to woven polyvinylidene chloride tapes, polyester tapes, etc.
The accompanying diagram labelled `Construction Details` illustrates the embodiment. FIG. 1 shows how one strip of sections rests on the pool surface. The seals in operation are also shown. If any of the edges are unjoined, these seals exert pressure to close any gaps, between strips. FIG. 2 illustrates one hinge design. Many others are useful. FIG. 3 shows the flexible seal attached to the foam periphery before insertion in the pool. FIG. 4 illustrates a method of providing corner sealing and allowing flexure in two directions.
In order to facilitate understanding and illustrate the versatility of the present invention, reference will be had to the appended drawing wherein:
FIG. 1 is a cross-sectional view of the pool cover of this invention shown in actual use covering a pool;
FIG. 2 is a diagrammatic sketch illustrating means for attaching and folding the foamed panels;
FIG. 3 is a perspective view of the edge of the pool cover;
FIG. 4 is a perspective view of a corner of the pool cover which is in contact with a corner of the pool.
The folding swimming pool covers of this invention are made of a series of panels, 10, which can be of any convenient size. For example, I have found that 4 by 6 feet panels work very well in the normal pools since they are small enough to be handled easily and yet large enough so that a great deal of them are not necessary. These panels, as aforesaid, can be made of closed cell polymeric foams of water-resistant polymers and, in the preferred exemplary embodiment are made of a closed cell polystyrene foam which is well fused (showing less than 10 percent water pick-up after 1 week immersion in water at 75° F.), 1 inch thick, and having a density of approximately 1 pound per cubic foot. In the preferred exemplary embodiment the polystyrene foam is coated with 2 mils of acrylic latex which is pigmented with titanium dioxide and phthalocyanine blue in order to give a light blue color to the panels.
The panels are held together by hinge means, indicated generally at 11, in such a manner that the panels can easily be folded together. In the preferred exemplary embodiment the hinge means are such that the panels can be folded in alternate directions, so that one fits on top of the other for easy storing. In the preferred exemplary embodiment the hinge means may include a longitudinally extending flexible member, 12, folded along its longitudinal axis, 14, and adhesively bonded on opposite sides, 20, to adjacent inner edges, 13, of said panels, 10. As best seen in FIG. 1 these hinges are alternated in direction so that, for example, the longitudinal axis, 14, of the hinges, 12, point upward and the longitudinal axis of an adjacent hinge points downward toward the body of water in the pool.
In order to insure that the panels will be securely foldably fixed together a second hinge, 15, is provided and comprises a longitudinally flexible strip, 15, of, e.g. polyvinylidene chloride, which is secured (e.g. adhesively bonded) to adjacent panels, 10, on that same horizontal side as the longitudinal axis, 14, of hinge 12 is pointed. Thus first strip 15 will be secured to the tops of panels 10 and second strip 15 will be secured to the bottom of panels 10, etc. Thus, the hinge means allow the panels to be folded flat against each other for easy removal from the pool.
The foamed panels, 10, which are alternately hinged together in the manner indicated above were floated on a swimming pool indicated generally at 16 so that approximately three-quarter-inch margins were left along the edge, 17, of the swimming pool. This margin was covered and insulated from the air by joining means 18 which is adhesively bound to the outer panel 10 of the swimming pool cover. In the preferred exemplary embodiment the joining means 18 is a flexible, woven tape which extends outward about 2 inches, as best seen in FIG. 3. This joining means is flexible to allow limited movement of the swimming pool cover which is inevitable because of the movement of the water underneath. Moreover, the joining means is a barrier to dirt, but inasmuch as it is porous to liquids, it allows water from rain or garden hose to filter through, much in the manner of a strainer.
At the corners of the pool cover, there are located corner assemblies, 19, which operate in the same manner as joining means 15 in keeping dirt and the like out of the swimming pool. Preferably corner assemblies, 19, are more flexible than joining means 15 and are attached to joining means 15 at the corners thereof by a water-resistant adhesive. Preferably these corner assemblies are made of thin sheets of chlorinated polyethylene rubber, butyl rubber, plasticized polyvinyl chloride, etc.
A 15 × 35 foot pool was covered with three series of hinged panels, each series having nine panels. One 85 pound child, standing at the edge of the pool can place the sheets into the water on edge, and they will float away with a slight push to cover the entire pool. This can be done in a matter of 3 minutes. Similarly, with the aid of a hooked pole and loops installed at alternate hinges (or with a rod equipped with a suction cup) the child may rapidly fold the sections. Alternately the first section may be dragged out of the water and folding completed on the pool deck. An average series of panels weigh about 15 pounds and since the average pool requires about three series, the entire cover only weighs 45 pounds.
The performance of the pool cover is astonishing when compared with the uncovered or the normal plastic-covered pools. In a 20,000 gallon pool with a rectangular 15 × 35 foot surface, the following table shows the observed insulating qualities:
TABLE SHOWING TEMPERATURE DROP WITH TIME OF A 20,000 GALLON POOL
(Max. Temp.-80°F, Min. Temp.-55°F, No Wind--Initial Water-85°F)
Temperature-Degrees F TIME-HOURS 24 48 72 168 336 Closed Cell Foam 84 83 82 79 73 3 Mil Polyethylene 82 79 76 67 61 Uninsulated 79 74 69 61 60
The comparison of insulation efficiency is even more remarkable when it is realized that to raise a cooled down pool to temperature requires, in an uninsulated pool, that the heater compensate for losses during the warm-up period. Thus, if the pool should be allowed to cool to 70° F. under the conditions outlined, a 250,000 BTU heater should warm the pool back to 85° F. in about 10 hours of operation, neglecting the heat capacity of the concrete and adjacent soil. However, a 40 percent loss is occurring simultaneously which requires a 0.4 factorial additional time period--or nearly 15 hours total. The insulated pool allows heating in practically the theoretical time. A surprising discovery was the low loss of heat to the ground. With the temperature and soil conditions present, it appears that the 1° daily loss of the insulated pool represents mainly heat loss to the ground.
Cleaning the pool cover requires simply hosing the debris to one corner where it is picked up. An unexpected result was the extreme case of cleaning without any hosing. It was found that the wind usually caused the debris to collect at one edge or corner where it could be swept up with a broom. Since the cover nearly completely eliminates pool contamination, very little heating and chemical treatment is required and the pump can be operated as little as 1 hour daily. The following table shows the total savings assuming one year of operation under constant conditions like those in the table showing heat loss with time.
TABLE COMPARING OPERATING costs OF INSULATED, PLASTIC COVERED, AND UNCOVERED SWIMMING POOLS
Electricity Natural Gas Organic Total Chlorine Cost ____________________________________________________________ ______________ Unit Cost $0.4/KWH 1 Mil/1000 $.13 /oz. -- BTU Uncovered Daily 12 hr 9 hr 2 oz. Cost $173 810 $85 $1068 Plastic Film Daily 8 hr 5 hr 1 oz. Cost $130 $360 $42 $532 Insulated Daily 2 hr 1 hr nil Cost $29 $90 -- $119 ____________________________________________________________ ______________
With the example given, it is seen that the simple insulative cover allows a 90 percent reduction in costs over an uncovered pool and nearly 80 percent over a plastic covered pool. Practically, it allows low cost, year around operation.
In the accompanying diagram, FIGS. 1, 2, 3, and 4, details of construction are shown which make a practical utilization of the insulating type cover, the key elements of this invention being the use of a buoyant insulating material or combination of materials having sufficient stiffness to lie uniformly in position in the surface of the water without wrinkling or folding.
The buoyant material is not limited to closed cell foams but can be composed of honeycomb structures, molded-internal large bubbles, cavities, etc.
Most swimming pool covers are simple sheets of plastic suspended over and sagging into the water. They are kept in place by sand bags, water bags, or mechanical fasteners. They are intended to be left in place during the winter season. Other variations include mechanically operated covers of numerous kinds using rollers, tracks, hydraulic lifts, etc. to place rigid or flexible membranes above the water. Some of the difficulties with these materials are enumerated:
1. Sheets tear easily and then admit water and dirt.
2. The water and dirt accumulates in the center of the flexible sheets as they sag and cannot be removed without spilling the debris into the water.
3. The time and energy needed to cover and uncover a plastic pool is so excessive that once in place, practical use of the pool for long periods is prevented.
4. Nearly all covers are so unattractive that pool owners will not use them.
5. The covers are so difficult to remove and replace that algae and stains may accumulate during the long dormant periods. Inspection and introduction of chemicals is tedious.
6. The air-suspended cover gives relatively poor insulation against heat losses, both because the plastic sheet is not a good insulator and a chimney effect occurs which sweeps moist warm air upward and out of the pool thru poorly sealed edges. Radiation losses are also high.
7. The thin, flexible sheets rapidly become embrittled by the sun and pool chemicals.
8. Covers designed to fit over the entire pool do not work well on pools which have raised bond beams--that is--various elevations around the pool perimeter.
9. Mechanically operated devices save time, but they are expensive, do not seal well, are quite clumsy, and often cannot be installed unless planned for in original construction.
I have found that insulating, rigid, fold in place, seals, floated in place in a manner different than any other swimming pool cover, overcomes nearly all the foregoing disadvantages of current covers, providing a low cost, attractive, and easily handled article with long life. Insulation benefits are greater than observed with any other system. The pool is instantly available for use without weather forecasting and long preheating periods. Further benefits of the self-placing buoyant covers include total prevention of water loss by evaporation, ability to refurbish by painting, ability to decorate in patterns, easy repair by removal of small damaged sections, no need of any auxiliary equipment for fastenings, and simple, rapid installation. The pre-hinged sheets, supplied in packages, can be laid in the water and cut to length. Any shape pool can be fitted if at least one strip has two straight sides. Removal is accomplished by sliding out this strip and pushing the other strips into the vacated position, if needed, to clear complex contours. I have found that it is possible to operate a swimming pool in Southern California all year around, at a fuel and chemical cost one-fifth of that required for operation during the summer alone without such a cover. Further, the cleaning and maintenance is largely eliminated by the protective cover so that pools can be left surrounded by deciduous trees and shrubs without creating undue maintenance problems.
I have found that closed cell polymeric foams made of water resistant polymers and of sufficient stiffness so that they may be placed on the surface of the water merely by pushing them away from one edge, and will lie flat and dimensionally stable are preferred materials for this purpose. Semi-flexible foams capable of being unrolled or partially cut thru for easy folding may also be suitably employed. The more rigid foams may be hinged together by such means as adhesive bonded glass fabric, flexible, bonded membranes over the entire assembly (allowing slack for alternate folds) are some means for assembly in addition to woven polyvinylidene chloride tapes, polyester tapes, etc.
The accompanying diagram labelled `Construction Details` illustrates the embodiment. FIG. 1 shows how one strip of sections rests on the pool surface. The seals in operation are also shown. If any of the edges are unjoined, these seals exert pressure to close any gaps, between strips. FIG. 2 illustrates one hinge design. Many others are useful. FIG. 3 shows the flexible seal attached to the foam periphery before insertion in the pool. FIG. 4 illustrates a method of providing corner sealing and allowing flexure in two directions.
In order to facilitate understanding and illustrate the versatility of the present invention, reference will be had to the appended drawing wherein:
FIG. 1 is a cross-sectional view of the pool cover of this invention shown in actual use covering a pool;
FIG. 2 is a diagrammatic sketch illustrating means for attaching and folding the foamed panels;
FIG. 3 is a perspective view of the edge of the pool cover;
FIG. 4 is a perspective view of a corner of the pool cover which is in contact with a corner of the pool.
The folding swimming pool covers of this invention are made of a series of panels, 10, which can be of any convenient size. For example, I have found that 4 by 6 feet panels work very well in the normal pools since they are small enough to be handled easily and yet large enough so that a great deal of them are not necessary. These panels, as aforesaid, can be made of closed cell polymeric foams of water-resistant polymers and, in the preferred exemplary embodiment are made of a closed cell polystyrene foam which is well fused (showing less than 10 percent water pick-up after 1 week immersion in water at 75° F.), 1 inch thick, and having a density of approximately 1 pound per cubic foot. In the preferred exemplary embodiment the polystyrene foam is coated with 2 mils of acrylic latex which is pigmented with titanium dioxide and phthalocyanine blue in order to give a light blue color to the panels.
The panels are held together by hinge means, indicated generally at 11, in such a manner that the panels can easily be folded together. In the preferred exemplary embodiment the hinge means are such that the panels can be folded in alternate directions, so that one fits on top of the other for easy storing. In the preferred exemplary embodiment the hinge means may include a longitudinally extending flexible member, 12, folded along its longitudinal axis, 14, and adhesively bonded on opposite sides, 20, to adjacent inner edges, 13, of said panels, 10. As best seen in FIG. 1 these hinges are alternated in direction so that, for example, the longitudinal axis, 14, of the hinges, 12, point upward and the longitudinal axis of an adjacent hinge points downward toward the body of water in the pool.
In order to insure that the panels will be securely foldably fixed together a second hinge, 15, is provided and comprises a longitudinally flexible strip, 15, of, e.g. polyvinylidene chloride, which is secured (e.g. adhesively bonded) to adjacent panels, 10, on that same horizontal side as the longitudinal axis, 14, of hinge 12 is pointed. Thus first strip 15 will be secured to the tops of panels 10 and second strip 15 will be secured to the bottom of panels 10, etc. Thus, the hinge means allow the panels to be folded flat against each other for easy removal from the pool.
The foamed panels, 10, which are alternately hinged together in the manner indicated above were floated on a swimming pool indicated generally at 16 so that approximately three-quarter-inch margins were left along the edge, 17, of the swimming pool. This margin was covered and insulated from the air by joining means 18 which is adhesively bound to the outer panel 10 of the swimming pool cover. In the preferred exemplary embodiment the joining means 18 is a flexible, woven tape which extends outward about 2 inches, as best seen in FIG. 3. This joining means is flexible to allow limited movement of the swimming pool cover which is inevitable because of the movement of the water underneath. Moreover, the joining means is a barrier to dirt, but inasmuch as it is porous to liquids, it allows water from rain or garden hose to filter through, much in the manner of a strainer.
At the corners of the pool cover, there are located corner assemblies, 19, which operate in the same manner as joining means 15 in keeping dirt and the like out of the swimming pool. Preferably corner assemblies, 19, are more flexible than joining means 15 and are attached to joining means 15 at the corners thereof by a water-resistant adhesive. Preferably these corner assemblies are made of thin sheets of chlorinated polyethylene rubber, butyl rubber, plasticized polyvinyl chloride, etc.
A 15 × 35 foot pool was covered with three series of hinged panels, each series having nine panels. One 85 pound child, standing at the edge of the pool can place the sheets into the water on edge, and they will float away with a slight push to cover the entire pool. This can be done in a matter of 3 minutes. Similarly, with the aid of a hooked pole and loops installed at alternate hinges (or with a rod equipped with a suction cup) the child may rapidly fold the sections. Alternately the first section may be dragged out of the water and folding completed on the pool deck. An average series of panels weigh about 15 pounds and since the average pool requires about three series, the entire cover only weighs 45 pounds.
The performance of the pool cover is astonishing when compared with the uncovered or the normal plastic-covered pools. In a 20,000 gallon pool with a rectangular 15 × 35 foot surface, the following table shows the observed insulating qualities:
TABLE SHOWING TEMPERATURE DROP WITH TIME OF A 20,000 GALLON POOL
(Max. Temp.-80°F, Min. Temp.-55°F, No Wind--Initial Water-85°F)
Temperature-Degrees F TIME-HOURS 24 48 72 168 336 Closed Cell Foam 84 83 82 79 73 3 Mil Polyethylene 82 79 76 67 61 Uninsulated 79 74 69 61 60
The comparison of insulation efficiency is even more remarkable when it is realized that to raise a cooled down pool to temperature requires, in an uninsulated pool, that the heater compensate for losses during the warm-up period. Thus, if the pool should be allowed to cool to 70° F. under the conditions outlined, a 250,000 BTU heater should warm the pool back to 85° F. in about 10 hours of operation, neglecting the heat capacity of the concrete and adjacent soil. However, a 40 percent loss is occurring simultaneously which requires a 0.4 factorial additional time period--or nearly 15 hours total. The insulated pool allows heating in practically the theoretical time. A surprising discovery was the low loss of heat to the ground. With the temperature and soil conditions present, it appears that the 1° daily loss of the insulated pool represents mainly heat loss to the ground.
Cleaning the pool cover requires simply hosing the debris to one corner where it is picked up. An unexpected result was the extreme case of cleaning without any hosing. It was found that the wind usually caused the debris to collect at one edge or corner where it could be swept up with a broom. Since the cover nearly completely eliminates pool contamination, very little heating and chemical treatment is required and the pump can be operated as little as 1 hour daily. The following table shows the total savings assuming one year of operation under constant conditions like those in the table showing heat loss with time.
TABLE COMPARING OPERATING costs OF INSULATED, PLASTIC COVERED, AND UNCOVERED SWIMMING POOLS
Electricity Natural Gas Organic Total Chlorine Cost ____________________________________________________________ ______________ Unit Cost $0.4/KWH 1 Mil/1000 $.13 /oz. -- BTU Uncovered Daily 12 hr 9 hr 2 oz. Cost $173 810 $85 $1068 Plastic Film Daily 8 hr 5 hr 1 oz. Cost $130 $360 $42 $532 Insulated Daily 2 hr 1 hr nil Cost $29 $90 -- $119 ____________________________________________________________ ______________
With the example given, it is seen that the simple insulative cover allows a 90 percent reduction in costs over an uncovered pool and nearly 80 percent over a plastic covered pool. Practically, it allows low cost, year around operation.
In the accompanying diagram, FIGS. 1, 2, 3, and 4, details of construction are shown which make a practical utilization of the insulating type cover, the key elements of this invention being the use of a buoyant insulating material or combination of materials having sufficient stiffness to lie uniformly in position in the surface of the water without wrinkling or folding.
The buoyant material is not limited to closed cell foams but can be composed of honeycomb structures, molded-internal large bubbles, cavities, etc.