US3747132A - Swimming pool cover - Google Patents

Abstract

A flexible pool cover is stored in rolled condition on a reel at one end of a swimming pool. Cables extend along the pool sides and over a reversing pulley for attachment to a trolley secured to the free cover end. The cable reels and cover reel are driven at the same rotational rate. Means are provided for maintaining the cover and the cables free of substantial slack throughout reeling and unreeling movement.

Description

United States Patent 1 Foster [451 July 24,1973

[ SWIMMING POOL COVER [76] Inventor: Elton Gordon Foster, 147 Trinidad Dr., Tiburon, Calif. 94920 [22] Filed: May 12, 1972 [211 Appl. No.: 252,580

[52] US. Cl. 4/l72.l4, 160/310 [51] Int. Cl E04h 3/16, E04h 3/18 [58] Field of Search 4/172, 172.14, 172.13,

[56] References Cited UNITED STATES PATENTS 7/1956 Karobonik et al. 4/l72.l4 X 8/1959 McGuire ll/l960 Shook et al.. 11/1961 McGuire 4/l72.14

3,019,450 2/1962 Karasiewicz 4/l72.l4 3,050,743 8/1962 Lamb 3,277,498 10/1966 Kleinbard et al. 3,426,366 2/1969 Bailey et al.

Primary Examiner-Henry K. Artis Attorney-Colton & Stone [57] ABSTRACT A flexible pool cover is stored in rolled condition on a reel at one end of a swimming pool. Cables eaitend along the pool sides and over a reversing pulley for attachment to a trolley secured to the free cover end. The cable reels and cover reel are driven at the same rotational rate. Means are provided for maintaining the cover and the cables free of substantial slack throughout reeling and unreeling movement.

10 Claims, 5 Drawing Figures PATENIEU 3, 747. 132

Sam 2 UF 3 8 mnmmm m HIIIIIIHIIHI FIG. 3

llllll llllllll lllllllllllll I SWIMMING POOL COVER BACKGROUND OF THE INVENTION Swimming pool covers which are advanced and retracted by motor operated mechanisms are well known in the prior art. One typical type swimming pool cover involves a spooled cover adjacent one end of the pool, a reversing pulley at the other end of the pool, and suitable cables passed over the reversing pulley and connected at opposite ends to the driving mechanism and the cover. Typical disclosures of this type are found in U. S. Pat. Nos. 2,754,899; 2,958,083; 3,277,498 and 3,426,366. In the typical device of this type, the cable reels and the cover reel are driven simultaneously, either by being mounted on the same shaft or by connection through single ratio gearing.

There is a substantial problem with simple drives of this type which is a result of the changing diameter of the cover reel'and the cable reels. It will be apparent to those skilled in the art that, at the beginning of cover placement, the cover reel is of larger diameter than the cable reels and the diameter of the cover reel decreases while the diameter of the cable reels increases. When beginning the placement of the swimming pool cover, one revolution of the cover reel pays out a length of cover equal to the circumference of the cover reel while the cable reels retract a length of cable equal to the circumference of the cable reels. Since the cover reel is of substantially larger diameter than the cable reels, the pool cover becomes slack and tends to wind up on the roller in the wrong direction when it should in fact be unwinding.

Accordingly, the devices of the prior art present a substantial disadvantage at the beginning of cover placement. Since the diameters of the cover and cable reels approach each other during cover placement, the amount of slack in the cover increases until the diameters of the cover reel and the cable reels are substantially equal. Since the cable reels are increasing in diameter, the amount of slack in the cover decreases in proportion to the number of revolutions made by the cover and cable reels after their diameters are substantially equal. It will be apparent that all of the slack may be taken out of the cover and, upon subsequent rotation of the cable and cover reels, the cover is placed substantially in tension. This also has its disadvantages since the cover material may be subject to stretching. It will be apparent that some care must be exercised in the design of the prior art pool covers to avoid overtensioning the cover.

It will also be apparent to those skilled in the art that, at the beginning of cover retraction, the cover reel is of smaller diameter than the cable reels and the diameter of the cover reel increases while the diameter of the cable reels decrease. At the outset of cover retraction, one revolution of the cover reel spools a length of material equal to the cover reel diameter while one revolution of the cable reels pays out a length of cable equivalent to the circumference of the cable reel. Since the cable reel is of greater diameter than the cover reel at this point in time, the cable goes slack and tends to wind up on the reel in the wrong direction when it should be unwinding. The cable continues to slacken until the diameters of the cable reel and the cover reel are the same at which time the cable begins to tighten.

The prior art has recognized this disadvantage as evi- I denced by U. S. Pat. Nos. 3,019,450 and 3,050,743. In

these disclosures, clutches are provided for the cable reels so that the cable drum is permitted to rotate freely in the unwinding direction as the cover reel is being driven. Similarly, a one-way clutch is provided for the cover reel so that the cover reel is permitted to rotate freely in the unwinding direction as the cable reel is being driven in the winding direction. While this is a satisfactory technical solution to the'problem, it will be appreciated that considerable expense is entailed in the provision of the one-way clutches both in initial cost and in maintenance.

The device of this invention allows the incorporation of an extremely simple drive mechanism for the cover and cable reels while maintaining the cover and cable free of substantial slack.

SUMMARY OF THE INVENTION It is an object of this invention to provide a motorized swimming pool cover including means for maintaining the cover free of substantial slack throughout spooling and unspooling movement thereof.

Another object of the invention is to provide a mechanized swimming pool cover in which the cover and cable reels are simultaneously driven and including resilient means operatively disposed between the driving mechanism and the cover for allowing differential travel between the cable means and the cover.

In summary, the swimming pool cover of this invention comprises a reel having a cover spooled thereon; means operatively connected to the cover for spooling and unspooling the same across a swimming pool and including a reel having thereon spoolable cable means operatively connected to the cover and means for simultaneously rotatably driving the cover and cable reels; the improvement wherein the spooling and unspooling means includes means for maintaining the cover and the cable means free of substantial slack adjacent the respective reel thereof throughout spooling and unspooling movement, the maintaining means including resilient means in driving connection between the driving means and the cover for allowing differential travel between the cable means and the cover.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of one embodiment of the invention;

FIG. 2 is an enlarged cross sectional view of the trolley which moves alongside the pool during cover placement and retraction and is taken along line 2-2 of FIG. 1 as viewed in the direction indicated by the arrows;

FIG. 3 is a cross sectonnal view through the cable reels and the cover reel illustrating another embodiment of the invention;

FIG. 4 is a partial plan view of one end of the trolley of another embodiment of the invention; and

FIG. 5 is a cross sectional view of the embodiment of FIG. 4, taken along line 5-5 thereof as viewed in the direction indicated by the arrows.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Attention is directed to FIG. 1 wherein there is illustrated aswimming pool 10 containing a quantity ofwater 12. A motorized swimming pool cover 14 constituting this invention is illustrated as substantially covering thepool 10. The swimming pool cover 14 comprises as major components a sheet orcover 16, aroller 18 constituting a reel for thesheet 16, means 20 for unspooling thesheet 16 includingcable reels 22, 24 having cable means 26, 28 spooled therearound and driving means 30 for driving theroller 18 and thecable reels 22, 24.

The sheet orcover 16 may be of any suitable material such as polyethylene and is wrapped or spooled about theroller 18. As will be apparent from FIG. 1, thesheet 16 is paid out and retracted from adjacent the top of theroller 18. It is well known that leaves and other debris collect on thesheet 16. Since thesheet 16 is reeled onto the top of theroller 18, leaves or debris on thesheet 16 pass over the top of the roll and onto the ground adjacent thereto. The pool owner is thus faced with the rather minor task of cleaning up the pool edge adjacent theroll 18. If thesheet 16 were taken up along the bottom of theroll 18, leaves and debris would be trapped in the spirallywound sheet 16 thereby tending to puncture the same.

Theroller 18 may conveniently be a piece of aluminum tubing mounted by suitable ball bearings or the like (not shown) on astationary shaft 32 mounted on opposite ends thereof bysuitable brackets 34. Thebrackets 34 are stationary and may be affixed to the walkway surrounding the pool in any suitable manner.

The unspooling means includes atrolley 36 comprised of an I-beam or otherstructural member 38 spanning thepool 10. The opposite ends of the l-beam 38 are affixed tosuitable dollies 40 havingwheels 42 thereon for traversing thepool 10. Thecables 26, 28 are disposed on opposite sides of thepool 10 and extend respectively from thereels 22, 24 undersuitable idler pulleys 44 through suitable ring guides 46 (FIG. 2) and aroundstationary reversing pulleys 48 for connection to the I-beam 38 in any suitable manner.

Thecable reels 22, 24 may be constructed in any suitable manner. Conveniently, the hub of thereels 22, 24 may comprise theroller 18 while thereel flanges 50, 52 respectively may comprise annular disks affixed to theroller 18. In order to drive theroller 18 andreels 22, 24, one of thereel flanges 52 may be grooved to receive an endless belt 54. l

The driving means 30 includes the endless belt 54 and a drivingsheave 56 operatively connected to agear box 58 which is driven by a suitableelectric motor 60 in a conventional manner. Themotor 60 is preferably a reversing motor controlled by a three-way switch 62. Theswitch 62 allows covering and uncovering of thepool 10 as well as a neutral position as will be apparent to those skilled in the art.

When themotor 60 is energized to uncover thepool 10, the diameter of the cover spool is substantially less than the diameter of thecable reels 22, 24. Accordingly, thecables 26, 28 pay off cable more rapidly than thesheet 16 is wound onto theroller 18. Thecables 26, 28 accordingly tend to wind in the wrong direction about thereels 22, 24 rather than unwind. Basically, the same problem occurs with thesheet 16 when it is in the process of being placed over thepool 10.

To overcome this disadvantage and still provide an extremely simple drive mechanism for theroller 18 andreels 22, 24, thecables 26, 28 are, in accordance with one embodiment of this invention, selected from a known group of resilient tensile force transmitting means. This group is known in the boating arts as shock cord and is normally used instead of rope to fasten boat fixtures where some elasticity is desired or required. Shock cord is commercially available through most boating supply stores and is commonly constructed of elastic rubber strands with a woven sleeve or overlay of nylon. One manufacturer of shock cord is N. A. Taylor, Inc., of Waxahachie, Texas. The diameter of the shock cord may vary widely depending on the length of the pool, the elasticity required, and the weight of thesheet 16. As might be expected, the diameter of a typical shock cord decreases significantly du ring stretching. A typical shock cord elongates approximately 30 per cent when placed under about 100 pounds tension. Substantial elasticity is required in the normal pool installation since the differential travel of thecables 26, 28 with respect to thesheet 16 is in the range of l-8 feet and typically is about 6 feet.

By utilizing a typical shock cord for thecables 26, 28, there is sufficient elasticity in the cable means to allow spooling and unspooling of thesheet 16 without creating substantial slack in either thecables 26, 28 or thesheet 16. Accordingly, the practice of this invention allows an extremely simple drive arrangement wherein thecable reels 22, 24 and theroll 18 are driven simultaneously and yet avoids the creation of substantial slack in either thesheet 16 or thecables 26, 28.

Referring to FIG. 3, there is illustrated another embodiment of the invention. FIG. 3 comprises a longitudinal cross sectional view through the cover roll and the cable reels as will be more fully apparent hereinafter. FIG. 3 illustrates a motorizedswimmlng pool cover 64 having a sheet or cover 66 spirally wound about aroller 68. Theroller 68 is mounted bysuitable ball bearings 70 for rotation about astationary shaft 72 which is supported at opposite ends thereof by suitable brackets (not shown). Axial movement of theroll 68 is precluded bysuitable thrust plates 74 which are affixed to thestationary shaft 72 in any suitable manner.

Comprising a part of a driving means similar to that illustrated in FIG. 1 is asheave 76 which is affixed to theroller 68 in any suitable fashion. As is illustrated in FIG. 3, thesheave 76 not only acts to drive theroller 68 but also bears against thethrust plate 74. It will accordingly be seen that theroller 68 is directly driven by thesheave 76 in a 1:1 ratio.

There is also provided a pair ofcable reels 78, 80 which are driven simultaneously with theroller 68 but which do not necessarily rotate at the same velocity. Thereels 78, 80 are generally S-shaped in cross section and comprise radiatingplates 82, 84, 86 and 88, 90, 92 respectively. l-lubs 94, 96 define, with thewalls 84, 86 and 88, respectively, a pair of cable receiving areas as in a conventional reel.Circumferential'plates 98, 100 define, with thewalls 82, 84 and 90, 92 respectively, a pair of spring housings incorporated in thereels 78, 80. Thereels 78, 80 are mounted for rotation about theroller 68 by housing andspool bearings 102, 104, 106, 108.Suitable thrust collars 110, 112 are affixed to theroller 68 and prevent inward movement of thereels 78, 80 respectively. Outward movement of thereel 78 is precluded by athrust collar 114 acting between thethrust plate 74 and thehousing bearing 102. Outward movement of thereel 80 is prevented by thehousing bearing 106 abutting thesheave 76.

Disposed in the spring housing of each of thereels 78, 80 is aspirally wound spring 116, 118 having one end thereof affixed to theroll 68 and the other end thereof affixed to thecircumferential plate 98, 1011 respectively.

Suitable cables 120, 122 are operatively connected to thereels 78, 80 and are connected to a suitable trolley as in the embodiment of FIG. 1 for spooling and unspooling thecover 66 across a swimming pool. It will be apparent'that the elasticity afforded by thesprings 116, 118 operates in much the same manner as the resilient cable means 26, 28 of FIG. 1 to prevent excessive slack developing in thecover 66 and thecables 128, 122 during covering and uncovering of the swimming pool.

As is apparent from the relative amount of spooledcable 120, 122 and spooledcover 66, FIG. 3 illustrates the situation where thecover 66 is placed over the swimming pool. When the sheave '76 is driven in the cover spooling direction, the length of thecable 120, 122 paid out is greater than the length ofcover 66 spooled onto theroller 68. Thus, thecable 120, 122 becomes slack and tends to wind up in the wrong direction. Thesprings 116, 188 accordingly elongate and retard rotation of thereels 78, .80 and retard payout of thecable 128, 122 to maintain the same reasonably taut. Continued spooling of thecover 66 creates addi- 6 out ofcable 120, 122.

Referring now to FIGS. 4 and 5, there is illustrated another embodiment of the invention. FIGS. 4 and 5 illustrate atrolley 124 comprising an l-beam or otherstructural member 126 spanning a swimming pool. Thetrolley 124 includes adolly 128 on each side thereof having wheels 1311 enabling thetrolley 124 to traverse the length of the pool. Affixed'to the web of the I-beam 126 is a mountingplate 132 carrying astationary stub shaft 134. A thrust plate 136 is affixed to the end of thestub shaft 134 and captivates thereon a take-upreel 138. The take-up reel is substantially identical to thereels 78, 80 and includes acable receiving area 140 and aspring housing 142 mounted together for rotation about thestub shaft 134 bybearings 144', 146. Aspiral spring 148 is positioned in thespring housing 142 and has one end affixed to thestub shaft 134 and the other end affixed to thecable housing 142. Acable 150 is spooled onto a driving reel of the type shown in FIG. 1 and passes around a reversing pulley, also as shown in FIG. 1, and is then attached to the take-upreel 138. The tension in thecable 150 is controlled by how tightly the spring 1481s wound.

To provide a comparison of the embodiments of this tional slack in thecables 120, 122, which is accommoinvention, the following table is provided:

Embodiment of- Relation of cover Result without When speed to cable speed this invention FIG. 1 FIG. 3 FIGS. 4 plus 5 Start of cover pay Cover pay out rela- Cover to slackCables 26, 28 shorten toSprings 116, 118elongate Spring 148 elongates to out. tlvely too fast. move trolley relatively to take up cable and Mid-point of cover Cover pay out rela- Coyer begins to faster.Cables 26, 28 elongate take up cable and move trolley faster.Spring 148 compresses move trolley faster.Springs 116, 118 compress pay out. tively too slow. tighten. to move trolley slower. to pay out additional to pay out additional cable and move trolley cable and move trolley slower. slower. Start of cover Cable pay out rela- Cable tooslack Cables 26, 28 shorten toSprings 116, 118elongate Spring 148 elongates to retraction. tively too fast. inotve trolley relatively to take up cable. to take up cable.

as er. Mid-point of cover Cable pay out rela- Cable begins toCables 26, 28 elongate toSprings 116, 118compress Spring 148 compresses retraction. tively too slow. tighten. move trolley slower. to bplay out additional to bplay out additional ea c. ea e. End of cover retraction.

dated by further elongation of thesprings 116, 118. As the diameter of the spooledcover 66 passes that of the reeledcable 120, 122, the length of thecover 66 spooled per revolution is greater than the length ofcable 120, 122 paid out from thereels 78, 88. Thecables 128, 122 accordingly begin to tighten and thereby compress thesprings 116, 118 to pay out additional length of thecable 128, 122.

At the start of cover pay out, the diameter of the spooledcover 66 exceeds that of the reeledcable 120, 122 causing excessively rapid cover pay out. As a result, thecover 66 becomes slack. Thesprings 116, 118 begin to expand thereby taking up additional lengths of 'cable to move the trolley (not shown) an additional incremental length and thereby take the slack out of thecover 66. Until the diameter of the spooledcover 66 equals the diameter of thereeled cable, cover pay out is relatively too fast tending to induce slack in the cover. Thesprings 116, 118 continue to expand thereby taking up additional or incremental cable lengths to move the trolley slightly faster and take the slack out of thecover 66. As thecover 66 approaches the'end of its unspooling travel, the diameter of the spooled cover is less than the diameter of the reeled cable such that cover pay out is relatively too slow. Since cover pay out is relatively too slow, the tension in thecables 120, 1122 increases thereby compressing thesprings 116, 118 effectively allowing additional pay The inspection of the foregoing summary will illustrate that the resilient components of the various embodiments of this invention undergo a cyclical lenthening and shortening. It should be apparent that, for example at the start of cover pay out with the embodiment of FIG. 1, thecables 26, 28 should be stretched to allow shortening during the initial portion of cover pay out. Similarly, thesprings 116, 118 of the embodiment of FIG. 3 should be compressed to a significant extent in order to take up cable during the initial portion of cover pay out.

Another important feature of the invention resides in the provision of a plurality of attachments 152 (FIG. 1) and 154 (FIG. 4) between the l-beams 38, 126 and the respective covers. Using FIG. 1 as exemplary, theattachments 152 comprise the force transmitting connection between the l-beam 38 and thecover 16. When the l-beam 38 is moving away from theroller 18, theattachments 152 are in tension to pull thecover 16 off theroller 18. When the I-beam 38 is moving toward theroller 18, theattachments 152 are in tension and thesheet 16 is pulling thetrolley 36.

One substantial difficulty with swimming pool covers occurs after a substantial rainfall. Since thecover 16 is desirably impermeable, rainfall accumulates thereon. Using a 20feet X 40 feet swimming pool as exemplary, a 2 inch rainfall accumulation weighs approximately 8,300 pounds. Initial retraction of thecover 16 is not a substantial problem since thecover 16 slides through the water. A substantial problem exists at the termination of cover retraction. Since thetrolley 36 and theroller 18 are above the water level, thecover 16 assumes an upwardly concave configuration when thetrolley 36 approaches theroller 18. Under this circumstance, thecover 16 would have to be vertically lifted to completely retract the same. Even if only 10 percent of the accumulated rainfall remains on thecover 16, the weight to be lifted by theroller 18 is so substantial as to prevent complete retraction of thecover 16.

To overcome this difficulty, theattachments 152 are selected of a predetermined length of flexible materials. The minimum length of the stretchedattachments 152 is the distance from the I-beam 38 where theattachments 152 are secured and thewater 12, so that thecover 16 does not assume an upwardly concave configuration when loaded with rainwater. The maximum length of theunstretched attachments 152 is the distance from the l-beam 38 where theattachments 152 are secured to a point above thewater 12 to avoid dipping the leading edge of thecover 16 into the water when thecover 16 is not loaded with rainwater. In the typical pool installation, this length of theunstretched attachments 152 is between 4-l0 inches. In a prototype constructed in accordance with the invention, the optimum length of theunstretchable attachments 152 proved to be 5 inches.

Although theattachments 152 may be made of any flexible material meeting the above criteria, they conveniently are the same material as thecables 26, 28.

I claim:

1. A swimming pool cover of the type comprising a reel having a cover spooled thereon; means operatively connected to the cover for spooling and unspooling the same across a swimming pool and including a reel having thereon spoolable cable means operatively connected to the cover and means for simultaneously rotatably driving the cover and cable reels; the improvement wherein the spooling and unspooling means includes means for maintaining the cover and the cable means free of substantial slack adjacent the respective reel thereof throughout spooling and unspooling movement, the maintaining means including resilient means in driving connection between the driving means and the cover for allowing differential travel between the cable means and the cover.

2. The swimming pool cover of claim 1 wherein the resilient means comprises the cable means.

3. The swimming pool cover of claim 1 wherein the resilient means consists essentially of the cable means.

4. The swimming pool cover of claim 1 wherein the differential travel between the cable means and the cover lies in the range of 1-8 feet.

5. The swimming pool cover of claim 1 wherein the resilient means comprises cable takeup means.

6. The swimming pool cover ofclaim 5 wherein the cable takeup means comprises a resiliently biased takeup reel between the cable means and the cover.

7. The swimming pool cover of claim 1 wherein the resilient means comprises means allowing differential rotation of the cable reel and the cover reel.

8. The swimming pool cover of claim 7 comprising means mounting the cable reel for free rotation about an axis and the resilient means comprises a spring drivably interconnecting the driving means and the cable reel.

9. The swimming pool cover of claim 8 wherein the spring comprises a spiral spring.

10. A swimming pool cover of the type comprising a reel having an impermeable cover spooled thereon; means operatively connected to the cover for spooling and unspooling the same across a swimming pool and including a trolley for traversing the pool, means for moving the trolley and attachment means connecting the trolley to the cover; the cover defining a path of movement along the surface of water in the swimming pool and then upwardly adjacent the edge of the pool, the trolley being above the water surface; the improvement comprising means for removing accumulated rainwater from the top of the cover at the completion of spooling movement of the cover, the removing means including the attachment means, the attachment means comprising flexible elements having a minimum stretched length sufficient to reach the water surface and a maximum unstretched length insufficient to reach the water surface.

i i t i UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3.747.132 DatedJulv 24, 1973 lnvent fl Elton Gordon Foster It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Change patentee's address from 147 Trinidad Drive, Tiburon, California 94920 to 2034 Dryden Road, Houston, Texas 77025. 7

Signed and sealed this 30th day of April 197R.

(SEAL) Attest:

EDWARD I-I.FLETCHER,JR. C. MARSHALL DANN Atte sting Officer Commissioner of Patents I FORM 90-1050 (10- uscoMM-oc 60376-P69 h US GOVERNMENT PRINTING OFFICE I969 O-366-3 4

Claims (10)

1. A swimming pool cover of the type comprising a reel having a cover spooled thereon; means operatively connected to the cover for spooling and unspooling the same across a swimming pool and including a reel having thereon spoolable cable means operatively connected to the cover and means for simultaneously rotatably driving the cover and cable reels; the improvement wherein the spooling and unspooling means includes means for maintaining the cover and the cable means free of substantial slack adjacent the respective reel thereof throughout spooling and unspooling movement, the maintaining means including resilient means in driving connection between the driving means and the cover for allowing differential travel between the cable means and the cover.

2. The swimming pool cover of claim 1 wherein the resilient means comprises the cable means.

3. The swimming pool cover of claim 1 wherein the resilient means consists essentially of the cable means.

4. The swimming pool cover of claim 1 wherein the differential travel between the cable means and the cover lies in the range of 1-8 feet.

5. The swimming pool cover of claim 1 wherein the resilient means comprises cable takeup means.

6. The swimming pool cover of claim 5 wherein the cable takeup means comprises a resiliently biased takeup reel between the cable means and the cover.

7. The swimming pool cover of claim 1 wherein the resilient means comprises means allowing differential rotation of the cable reel and the cover reel.

8. The swimming pool cover of claim 7 comprising means mounting the cable reel for free rotation about an axis and the resilient means comprises a spring drivably interconnecting the driving means and the cable reel.

9. The swimming pool cover of claim 8 wherein the spring comprises a spiral spring.

10. A swimming pool cover of the type comprising a reel having an impermeable cover spooled thereon; means operatively connected to the cover for spooling and unspooling the same across a swimming pool and including a trolley for traversing the pool, means for moving the trolley and attachment means connecting the trolley to the cover; the cover defining a path of movement along the surface of water in the swimming pool and then upwardly adjacent the edge of the pool, the trolley being above the water surface; the improvement comprising means for removing accumulated rainwater from the top of the cover at the completion of spooling movement of the cover, the removing means including the attachment means, the attachment means comprising flexible elements having a minimum stretched length sufficient to reach the water surface and a maximum unstretched length insufficient to reach the water surface.

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