GB2199741A

GB2199741A - Pool cover systems

Info

Publication number: GB2199741A
Application number: GB08725019A
Authority: GB
Inventors: Peter David Jeffery; Rosemary Dawn Jeffery; Ian James Scott Macmath
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-10-27
Filing date: 1987-10-26
Publication date: 1988-07-20
Anticipated expiration: 2007-10-26
Also published as: GB8725019D0; GB8625637D0; GB2199741B

Abstract

A pool cover system 10 for a swimming pool P comprises a roll-formable pool cover 11, the edges of which carry a laterally-spaced pair of male coupling elements 17a slidably cooperable with female coupling elements 19a. The female coupling elements 19a which are of a channel-like form, extend in substantially parallel array outside but adjacent to the pool surround 20. The elements 19a are substantially flush with the structure 22 forming the pool surround. <IMAGE>

Description

"Pool Cover Systems" This invention relates to pool cover systems for use with pools such, for example, as swimming pools.

BACKGROUND OF THE INVENTION Pools particularly open air pools, share the problem that they are easily and freely contaminated by debris. Whilst such debris may be of various forms, a particularly common nuisance is the deposit of leaves in the pool, during autumn notably, especially in windy conditions.

Existing known methods of protecting pools against the ingress of such debris commonly involve either the use of simple sheet-like covers which are, in use, inconvenient in that they involve an undue amount of manipulation in their installation, removal and storage, or they involve the use of large and relatively weighty rigid pool covering structures which are not only cumbersome but also present acute storage problems when not installed covering a pool.

Because of their disadvantages the known arrangements mentioned above tend to fall into disuse with the result that periodically it is necessary to engage in a major pool cleansing operation.

Another important point to be considered is that of child safety, as there are occasions when it is desired to cover an "unguarded" pool, in order to prevent a child entering the pool, either deliberately or accidentally.

OBJECTS OF THE INVENTION It is an object of this invention to provide a pool cover system which is reliable, which is easy to operate, and which, as a result, encourages its regular and frequent use thereby avoiding, or at any rate diminishing, the problems created by sloth and/or child safety.

It is a further object of the invention to provide a pool cover which can be used with pools of irregular plan form.

The invention provides a pool cover system whereby, with the simplest of action on the part of the user, the pool cover may be drawn accurately into place covering the pool from a roll and, when not required to cover the pool, is readily drawn into a roll from clear of the pool.

SUMMARIES OF THE INVENTION According to the invention, a pool cover system comprises a roll-formable pool cover, and aligned in directions perpendicular to the direction of roll-flexure of the cover, a laterally-spaced pair of first coupling elements, cooperable with a laterally-spaced pair of second coupling elements extending in substantially parallel array outside the pool surround.

The first and second coupling elements are preferably of male and female form, respectively, and the female coupling elements are preferably disposed substantially flush with the structure defining the pool surround.

The invention also comprises the pool cover per se, and further comprises the combination of the pool cover system and a pool.

The male coupling elements preferably form part of a guide of flexible construction slidable on the pool surround.

The guide preferably comprises an inner portion spaced from and joined to the said male coupling element by a flexible hinge portion.

A pair of male and female coupling elements may together define a coupling, the female coupling element comprising a channel, the male coupling element and the female element couplingly engaging by relative motion between them in the longitudinal direction of thechannel, the male and female elements being of such crosssectional form that the elements are not capable of being parted in a direction normal to the channel opening.

Preferably the pool cover has a gully disposed between and extending in the direction of alignment of the first coupling elements.

The gully may be progressively deeper from one end to the other end thereof.

Conveniently, the pool cover comprises two rectangular sheet members and, between the said rectangular members, a gusset portion which constitutes the said gully. Advantageously, a mesh extends across the mouth of the gully. Preferably, a pipe extends from the bottom of the gully.

Preferably the pool cover has, at one end thereof, an extension piece which, in use of the cover, overlies a margin of the pool surround so as to be anchored thereto.

Preferably also the pool cover has buoyancy means, attached to the underside thereof. The said buoyancy means may comprise heat insulative material.

The pool cover system may also include a pool cover take-up roller stationed at one end of a pool and to and from which the pool cover is fed for engagement of and guidance by the first and second coupling elements.

Preferably the pool cover has two laterally-spaced hitching points adjacent one end thereof; and two cables connected at one end to the said hitching points extending around individual pulleys and connected by a single cable to which a cover towing force may be applied, the resultant forces on the cover at the two said laterally-spaced hitching points being substantially equal.

The pool cover system may be provided with a capstan for winding up the said single cable.

The pool cover system may further include buoyancy bolster means disposed adjacent the leading edge of the pool cover so as to support and protect the cover against damage from contact with the pool surround, as the leading edge of the cover is drawn from the pool. Conveniently, the buoyancy bolster comprises a flotation bag.

The take-up roller adaPted to be stationed at one end of the pool may incorporate a dog clutch comprising a member movable along a shaft between two positions, movement being caused by inertia forces, the member carrying first and second dogs arranged back to back and oppositely facing, and third and fourth dors disposed at two positions whereby either the first and third dogs engage or, alternatively, the second and fourth dogs engage.

The invention also extends to a kit for a pool cover system having the features described hereinbefore or any of them, and to pool cover roll-up means per se.

BRIEF DESCRIPTION OF THR DRAWINGS An embodiment of the invention is hereinafter described, by way of example only, with reference to the aucompanying drawings, wherein : Figure 1 is a plan view of a pool cover system for a swimming pool, Figure 2 shows a section taken on the vertical plane at in in Figure 1, Figure 3 shows a section taken on the vertical plane at Y-Y in Figure 1, Figures 4a and 4b are diagrammatic plan views showing one feature, the fixed parts, of the cover system, Figure 5 is a diagram showing a cross-section through one of the said fixed parts, Figure 6 is a diagrammatic end elevation of the movable cover, Figure 7 is a diagrammatic end elevation showing the cover part engaged with the fixed part of the pool cover system, Figure 8 is a rough sketch showing in longitudinal elevation other features of the pool cover system, Figure 9 shows a cross-section through a preferred form of male coupling element, Figure 10 is an end elevation of a pool cover winding arranzement, Figure 11 is a part sectional side elevation of the winding arrangement of Figure 10, and Figure 12 is a plan view of a pool cover system for a swimming pool of rectangular form.

DErAITFn DESCRIPTION OF THE PREFERRED EMBODIFENT Referring first to Figures 1 to 5, and 9, a pool cover system 10 for a swimming pool P comprises a roll-formable pool cover 11, and aligned in directions perpendicular to the direction of roll-flexure of the cover, a laterally-spaced pair of first coupling elements 17a, 17b, (Figure 9), cooperable with a laterallyspaced pair of second coupling elements 19a, 19b (Figure 5) extending in substantially parallel array outside the pool surround 20. (Figures 4a, 4b).

The first and second coupling elements 17a, 17b and 19a, 19b are of male and female form, respectively. As shown in Figure 9, these elements together define a coupling wherein the female coupling elements 19a, 19b each comprise a channel and the male and female coupling elements couplingly engage, allowing relative motion between in the longitudinal direction of the channel. The male and female coupling elements are of such cross-sectional form that the elements are not capable of being parted in an upward direction normal to the channel opening.

The female coupling elements 19a, 19b, or more accurately, the upper surfaces thereof, are disposed substantially flush with the structure defining the pool surround 20.

With reference to Figure 1, the pool cover 11, which is of flexible sheet material, comprises a main body part 13. The male coupling elements 17a, 17b (not shown in Figure 1) are disposed along, and are attached to, opposite sides 15a, 15b of the body part 13. (See Figure 9).

The channels 19a, 19b, which are open at both ends, are set into paving at margins 21a, 21b of the pool P. (See Figures 4a, 4b). The upper surfaces 23a, 23b of the channels are substantially flush with the said paving. The channels l9a, 19b are locked firmly in the required positions and relationship by means of the adjoining paving stones. With reference to Figure 5, the channels 19a, 19b have, at intervals along their bottom walls 25a, soak-away drains 27a. The channels may serve as conduits for cables employed, as hereinafter described, in the moving of the cover 11 between pool uncovered and covered positions.

Each channel 19a (and similarly channel 19b) has, opposite the bottom wall 25a thereof, two longitudinally extending flange portions 29, 31, the edges of which are spaced apart so as to define a slot portion 33 extending the full length of the channel.

The flange portions 29, 31 define the upper surfaces 23a, 23b of the channels and the narrowness of the slots 33 are calculated not to present a hazard to a bather's feet.

The channels l9a, 19b which may, of course, be fitted in or to the margins of the surrounds of new or of existing pool installations, extend longitudinally for the full length of the pool P, plus any overlap deemed necessary. The pool P may be of regular rectangular form (Figure 4a), or of irregular form (Figure 4b).

The channels 19a, 19b may run in any direction provided that they are substantially parallel to one another and extend the full (projected) length of the pool (plus adequate overlap) in the chosen direction. The channels 19a, 19b may, for example, be perpendicular to the directions depicted in Figures 4a and 4b.

The channels 19a, 19b and the pool cover 11 might then be shorter; the cover would,. of course, be, correspondingly, of greater width.

Considering the pool cover 11 in greater detail, with reference once more to Figure 1, the main body part 13, which is of woven reinforced P.V.C. sheet material, is in three parts, comprising two equal size generally rectangular sheet members 35a, 35b respectively, and an intermediate gusset portion 37 (Figure B) which forms a gully 39 between the said sheet members. The three parts are joined together by application of heat to form welded seams between the gusset 37 and the rectangular sheet members 35a, 35b.

The gusset portion 37 is of substantially triangular form in cross-section, and is constructed so that the gully 39 is progressively deeper from its rear end 41 to its front end 43.

The main body part 13 of the pool cover 11 is maintained substantially rectangular by means of a cloth reinforced P.V.C.

mesh rectangular strip 45 secured, by heat welding, at its longitudinal edges, to the rectangular sheet members 35a, 35b, along the seams made with the gusset portion 37, The mesh strip 45 serves as a filter allowing rain water to drain into the gully 39 but preventing the passage of fallen leaves and other large debris.

As shown in Figure 2, adherent to the underside of the rectangular sheet members 35a, 35b, but not to the gusset portion 37, there are sheets 47awl 47b respectively. The sheets 47a, 47b are of heat insulative material in the form wherein air is trapped in pockets between two thin plastic skins. Typically, the insulative material may be of the kind utilised in "Jiffy" (Registered Trade Mark) mail packets. Such material allows sunlight into the pool, so as to warm the water, but reduces heat loss from the water. Such insulative material has the additional merit of being highly buoyant.

From the lowest position of the gully 39, there extends a flexible drain pipe 48 from which, as will be touched on later, water and any small solid material therein, draining into the gully from the main body part 13 of the pool cover 11 may be withdrawn.

With further reference to Figure 9, a coupling element 17a, (and similarly a coupling element 17b), forms an outer portion of a guide structure 50 of flexible, (roll-formable), construction.

The guide 50 is of extruded plastics material (P.V.C.).

The outer portion formed by the coupling element 17a is attached to an inner portion 55 of the guide 50 by a web-like flexible hinge portion 112. The element 17a and inner portion 55, (which is of strip-like form), extend in substantially parallel array, being interconnected by the hinge portion 112.

The coupling element 17, in cross-section, is anvil-shaped, having a base portion 49 of width greater than that of the slot 33 of the associated channel 19a. The upper portion 51 of the element 17a is also of greater width than the slot 33, and is connected to the base portion 49 by a stem or pedestal portion 53.

The inner portion 55 of the guide 50 has, for lightness and economy, grooves 57 and holes 59 therethrough. The inner edge 61 of the upper portion 51 is beaded.

The lower surfaces of the guide 50 are slidably supported by the flat upper surface 22 of the pool surround 20. The said lower surfaces include the bead 61.

The guides 50, (one each side of the pool cover 11), which extend for the length of the pool cover, ensure that the rolling radii at opposite ends of the cover, when it is rolled-up, are substantially equal. The guides 50 are made wide enough to allow for a degree of misalignment between superimposed portions thereof when the cover is rolled-up.

The inner portions 55, by their presence, also relieve weightloading on the guides 50 caused by the pool cover 11.

In a modification, which results in improved compensation for the differing diameters (rolling radii) of pool cover material when wound up, layer upon layer, the web-like hinge portions 112 are disPensed with so that the coupling elements 17a and inner portions 55 are joined only by pool cover material.

The main body part 13 of the cover 11 is wraF-sd at the edges around the upper portions 51 of the coupling elements 17a and is secured thereto by stitching 63. (Figure 6).

The pool cover 11 is retained at its edges by the male and female couplings, the male coupling elements, 17a, 17b, being received at corresponding open ends of the channels 19a, 19b, respectively, with the extended base portion 49 of each male coupling element 17a, 17b within the channels, the stem or pedestal portions 53 of the elements 17a, 17b extending through the slots 33 and the upper portions 51 of the male coupling elements resting with their beaded edges 61 in contact with the inwardly disposed flanges 31 of the channels, as well as with the adjacent structure.

The beaded edges 61 serve as wear-pads.

With the cover system 10 installed, the cover 11 spans the pool P, widthwise, from channel 19a to parallel channel l9b.

With reference to Figure 1, secured to the front end of the main body part 13 of the pool cover 11 there is a flap 65 of P.V.C. plastics material provided at intervals 67 therealong with preferably, for safety, hooks; and the adjacent front portion of the pool surround 20 is provided with a transversely extending removable rod or wire (not shown) to be engaged by the said hooks. An alternative would be to provide, at intervals along the flap 65, eyelets to be engaged by hooks or the like fixed to the pool surround. One or more "VELCRO" (Registered Trade Mark) fasteners may be used as alternatives.

The "VELCRO" fasteners may be fitted to the front flap 65 of the pool cover 11 and to the leading ends of the guides 50, so as to secure the flap and guides together.

The greater part of the main body part 13 of the pool cover rests on the surface of the water P, the air pocketed sheets 47a, 47b (Figure 2) contributing to its buoyancy.

The gusset portion 37, hanging dependant from the rectangular buoyant sheet members 35a, 35b, serves not only as a gully for the collection of rain water draining from the cover 11. It also constitutes a sheet anchor stabilising the cover 11 in windy conditions. It may be observed, in passing, that with many traditional pool covers, rain water may drag the cover into the pool and, where the cover is of the mesh type, dust and grit may enter the pool.

Water and small particles therein draining into the gully 39 through the mesh strip 45 may be drained from the gully through a hose (not shown) under the action of a small pump (not shown) away from the pool P, the pump being switched in and out of operation by a float switch (not shown) disposed in the gully.

Alternatively, a venturi may be connected between the said hose, and by means of a T-junction, a garden hose or the like, the contents of the gully being then evacuated by venturi suction effect. Where the outlet of the hose can be located lower than the water level in the gully 39, syphon action may be employed. Finally, with new pools, at the building of the pool a permanently installed flexible tube 48, extending from the lowest position of the gully 39, may have its outlet end connected to a drainage inlet in the pool wall at least, say, two feet below the pool waterline. The drainage inlet may lead to a soakaway; and when the cover 11 is, as hereinafter described, moved to the pool uncovered position, a flap may fall to cover the drainage inlet.

To keep the pool cover 11 out of the water present in the pool when the cover is wound out, a buoyant bolster is provided.

The bolster comprises a flotation bag 67 (Figure 2) welded-to the main body part 13 adjacent the leading edge of the pool cover.

For irregular shaped pools such, for example, as depicted in Figure 4b, the bolster/bag 67 may be replaced by a boom attached to the front ends of the guides 50 and to the leading edge of the main body part 13 of the cover 11. The boom, which will extend at least the transverse span of the pool, will have a height above water level, to enable the pool cover in its suspended state to clear the coping of the pool surround 20 and thus protect the pool cover against abrasive damage from contact with the pool surround.

Mounted on the pool surround 20 at the rear of the pool P, pool cover roll-up means (Figure 10) are provided, comprising winding gear 71. Wire cables 73 and 75 (Figure 12) disposed along the channels 19a, 19b are connected, passing around pulleys 77 and 79, to corresponding ends of the male coupling elements 17a, 17b.

The said ends provide laterally-spaced hitching points.

It is necessary that, in operation, the male coupling elements 17a, 17b move in substantially complete unison. Unequal movement between the said coupling elements could give rise to jamming.

It is for this reason that the vables 77 and 79 are joined, as shown in Figure 12, and that a cover towing force is applied, by the winding gear 71 (Figure 11) to cable 73 only. Thus the resultant forces at the two hitching points are substantially equal.

The winding gear 71 comprises a frame 80, one end member 81 only of which is depicted in Figure 11, with a mainshaft 83 supported in aligned tapered roller bearings 85, in the end members.

A D.C. motor 86 is supported on the illustrated end member 81 and on the mainshaft 83 there is a capstan 72 and a cover roller 88.

Between the two there is a double inertia dog clutch 87 movable relative to the mainshaft 83. The dog clutch 87 is connectable to the roller 88 by way of a self-aligning bearing 89.

The dog clutch 87 comprises a member carrying dogs 87a, 87b disposed back to back and oppositely facing. The dogs 87a are engagable with dogs 72a carried by the capstan 72. (Alternatively, the dogs 87b are engagable with dogs 89a carried by the bearing 89).

The clutch 87 is movable between its engaging positions, but is constrained by a peg 92 secured to and extending laterally from the mainshaft 83, the peg being located by a helical slot 90 formed in the dog clutch 87. A dwell period between disengagement of one set of dogs and engagement of the other set is provided for.

The slot 90 may be formed to suit left or right-hand rotation of the clutch.

The D.C. motor 86 may be energised from batteries housed near the motor, maintained by trickle charge. The motor 86 may be operated by switches (not shown) having normally open contacts, one to be operated when it is intended to cover the pool, and the other when the action required is to uncover the pool.

Alternatively, for fully alltomatic operation, limit switches (not depicted) may be disposed at pool fully covered and pool fully uncovered positions so as to operate the motor 86. Reed switches or relays at the open and closed cover positions may be operated by means of a magnet at the leading (front) end of the pool cover 11.

Other forms of proximity switches may be employed.

The motor 86 drives the mainshaft 83 in one sense or the other through a gear train. As shown in Figure 11, a toothed belt 91 meshes with an output gear 93 on the motor, a gear 95 is fixed to the mainshaft, a gear 97 on the mainshaft meshes with a second toothed belt 99 another gear 101 is in mesh with belt 99, a further gear 103 is rotatable with gear 101 in mesh with a third toothed belt 105 and yet another gear 107 on the mainshaft.

The motor 86 runs selectively in either sense, clockwise or counter-clockwise through the gear train. Rotating in one direction it winds the capstan 72 and the cover roller 88 is left to freewheel. When the cover roller 88 is powered, the capstan 72 freewheels. Overrunning is prevented by a band brake 100 which applies an arresting force to the capstan 72. This is necessarv because of the different rolling radii of the roller 88 and capstan 72.

By using a double inertia dog clutch 87, when the mainshaft 83 turns in one sense, the dogs 87b are caused to engage the roller 88 by inertial forces whereby the clutch 87 moves toward the roller 88, by means of the helical slot 90 moving relative to peg 92. Should the mainshaft 83 be rotated in the opposite sense, the peg 92 runs down the slot 90 forcing the clutch 87 to change over, disengaging the dogs 89a from the bearing 89 and causing the dogs 87a to engage with the dogs 72a of the capstan 72. The inertia of the dog clutch 87 is increased (and the clutching action improved) by the use of a brake band 110. The various parts are retained on the mainshaft by "Circlips" (Registered Trade Mark).

The dog clutch 87, which is inexpensive, provides a good measure of controls With the cover 11 covering the pool, when, in operation, the motor 86 causes the winding mechanism 71 to uncover the pool, the cover roller 88, in rotating, draws the male coupling elements 17a, 17b in unison along their channels 19a, 19b. As the guides 50 (Figure 9) emerge from the open rear ends of the channels 19a, 19b, with the main body part 13 therebetween, the pool cover 11 is caused by the roller 88 to wind up thereon.

In a modification, the mainshaft 83 is driven by a gearbox assembly.

It will be appreciated that the pool cover system of the invention can toe fitted to existing pools, without disturbing the pools. This advantage stems from the fact that the pool cover channels 19a, 19b are disposed outside of the pool periphery, i.e.

the pool surround.

The plate-like portions 55 of the guides 50 could be replaced by portions of "I"-like section.

Whilst the invention has been described with reference to the accompanying drawings and certain generalisations asserted as to the nature and scope of the invention, the invention also embraces or comprises any novel subject matter or any novel combination including novel subject matter as herein disclosed or contemplated.

Claims

C L A I DI S

1. A pool cover system, comprising a roll-formable pool cover, and aligned in directions perpendicular to the direction of rollflexure of the cover, a laterally-spaced pair of first coupling elements, cooperable with a laterally-spaced pair of second coupling elements extending in substantially parallel array outside the pool surround.

2. A pool cover system as claimed in Claim 1, wherein the first and second coupling elements are of male and female form, respectively.

3. A pool cover system as claimed in Claim 2, wherein a pair of male and female coupling elements together define a coupling, the female coupling element comprising a channel, the male coupling element and the female element couplingly engaging by relative motion between them in the longitudinal direction of the channel, the male and female elements being of such cross-sectional form that the elements are not capable of being parted in a direction normal to the channel opening.

4. A pool cover system as claimed in Claim 2 or 3, wherein the female coupling elements are disposed substantially flush with the structure defining the pool surround.

5. A pool cover system as claimed in Claim 2, 3 or 4, wherein each male coupling element forms part of a guide of flexible construction slidable on the pool surround.

6. A pool cover system as claimed in Claim 5, wherein the guide comprises an inner portion spaced from and joined to the said male coupling element by a flexible hinge portion.

7. A pool cover system as claimed in any preceding claim, wherein the pool cover has a gully disposed between and extending in the direction of alignment of the said first coupling elements.

8. A pool cover system as claimed in Claim 7, wherein the said gully is progressively deeper from one end of the gully to the other end thereof.

9. A pool cover system as claimed in Claim 8, wherein the pool cover comprises two tectangular sheet members and, between the said rectangular members, a gusset portion which constitutes the said gully.

10. A pool cover system as claimed in Claim 7, 8 or 9, wherein mesh extends across the mouth of the gully.

11. A pool cover system as claimed in Claim 7, 8 or 9, wherein a pipe extends from the bottom of the gully.

12. A pool cover system as claimed in any preceding claim, wherein the pool cover has, at one end thereof, an extension piece, which, in use of the cover, overlies a margin of the pool surround, so as to be anchored thereto.

13. A pool cover system as claimed in any preceding claim, wherein the pool cover is provided with buoyancy means attached to the underside thereof.

14. A pool cover system as claimed in Claim 13, wherein the said buoyancy means comprises heat insulative material.

15. A pool cover system as claimed in any one of Claims 1 to 14, provided with a pool cover take-up roller stationed at one end of the pool, and to and from which the pool cover is fed for engagement of and guidance by the male and female coupling elements.

16. A pool cover system as claimed in Claim 15, wherein the pool cover has two laterally-spaced hitching points adjacent one end thereof; and two cables connected at one end to the said hitching points extending around individual pulleys and connected by a single cable to which a cover towing force may be applied, the resultant forces on the cover at the two said laterally-spaced hitching points being substantially equal.

17. A pool cover system as claimed in Claim 16, provided with a capstan for winding up the said single cable.

18. A pool cover system as claimed in any of Claims 1 to 17, provided with buoyancy bolster means disposed adjacent the leading edge of the pool cover so as to support and to protect the cover against damage from contact with the pool surround, as the leading edge of the cover is drawn from the pool.

19. A pool cover system as claimed in any of Claims 15 to 18, wherein the take-up roller incorDorates a dog clutch comprising a member movable along a shaft between two positions, movement being caused by inertia forces, the member carrying first and second dogs arranged back to back and oppositely facing, and third and fourth dogs disposed at two positions whereby either the first and third dogs engage or, alternatively, the second and fourth dogs engage.

20. The combination of a pool and a pool cover system as claimed in any one of Claims 1 to 19.

or pool cover

21. Pool coverlroll-up means for use with a pool cover system as claimed in any one of Claims 1 to 19.

22. A pool cover system substantially as hereinbefore described with reference to Figures 1, 2, 3, 6, 7, 8 and 9 of the accompanying drawings.

23. A pool cover system substantially as hereinbefore described with reference to Figures 1, 2, 3, 4a, 4b, 5, 6, 7, 8 and 9 of the accompanying drawings.

24. A pool cover system substantially as hereinbefore described with reference to the accompanying drawings.

25. A pool cover substantially as hereinbefore described with reference t9 Figures 1, 2, 3, 6, 7, 8 and 9 of the accompanying drawings.

26. Pool cover roll-up means substantially as hereinbefore described with reference to Figures 1, 10, 11 and 12 of the accompanying drawings.

26. A pool cover substantially as hereinbefore described with reference to Figures 1, 2, 3, 4 4b, 5, 6, 7, 8 and 9 of the accompanying drawings.

27. Pool cover roll-up means substantially as hereinbefore described with reference to Figures 1, 10, 11 and 12 of the accompanying drawings.

Amendments to the claims have been filed as follows 1. A pool cover system, comprising a roll-formable pool cover, and aligned in directions perpendicular to the direction of rollflexure of the cover, a laterally-spaced pair of male coupling elements, cooperable with a laterally-spaced pair of female coupling elements extending in substantially parallel array outside the pool surround, the male and female coupling elements together defining a coupling, the female coupling element comprising an upwardly-facing channel, the male coupling element and the female element couplingly engaging by relative motion between them in the longitudinal direction of the channel, the male and female elements being of such cross-sectional form that the elements are not capable of being parted in a direction normal to the channel opening, the female coupling elements being set in the structure defining the pool surround, so that their upper surfaces are substantially flush with said structure.

2. A pool cover system as claimed in Claim 1, wherein each male coupling element forms part of a guide of flexible construction slidable on the pool surround.

3. A pool cover system as claimed in Claim 2, wherein each guide comprises an extrusion of plastics material.

4. A pool cover system as claimed in Claim 2 or 3, wherein the guide comprises an inner portion spaced from and joined to the said male coupling element by a flexible hinge portion.

5. A pool cover system as claimed in any one of Claims 1 to 4, wherein the pool cover has a gully disposed between and extending in the direction of alignment of the male coupling elements.

6. A pool cover system as claimed in Claim 5, wherein the said gully is progressively deeper from one end of the gully-to the other end thereof.

7. A pool cover system as claimed in Claim 6, wherein the pool cover comprises two rectangular sheet members and, between the said rectangular members, a gusset portion which constitutes the said gully.

8. A pool cover system as claimed in any one of Claims 5, 6 or 7, wherein mesh extends across the mouth of the gully.

9. A pool cover system as claimed in any one of Claims 5, 6 or 7, wherein a pipe extends from the bottom of the gully.

10. A pool cover system as claimed in any one of Claims 1 to 9, wherein the pool cover has, at one end thereof, an extension piece, which, in use of the cover, overlies a margin of the pool surround, so as to be anchored thereto.

11. A pool cover system as claimed in any one of Claims 1 to 10, wherein the pool cover is provided with buoyancy means attached to the underside thereof.

12. A pool cover system as claimed in Claim 11, wherein the said buoyancy means comprises heat insulative material.

13. A pool cover system as claimed in any one of Claims 1 to 12, provided with a pool cover take-up roller stationed at one end of the pool, and to and from which the pool cover is fed for engagement of and guidance by the male and female coupling elements.

14. A pool cover system as claimed in Claim 13, wherein the pool cover has two laterally-spaced hitching points adjacent one end thereof; and two cables connected at one end to the said hitching points extending around individual pulleys and connected by a single cable to which a cover towing force may be applied, the resultant forces bn the cover at the two said laterally-spaced hitching points being substantially equal.

15. A pool cover system as claimed in Claim 14, provided with a capstan for winding up the said single cable.

16. A pool cover system as claimed in any of Claims 1 to 15, provided with buoyancy bolster means disposed adjacent the leading edge of the pool cover so as to support and to protect the cover against damage from contact with the pool surround, as the leading edge of the cover is drawn from the pool.

17. A pool cover system as claimed in any of Claims 13 to 16, wherein the take-up roller incorporates a dog clutch comprising a member movable along a shaft between two positions, movement being caused by inertia forces, the member carrying first and second dogs arranged back to back and oppositely facing, and third and fourth dogs disposed at two positions whereby either the first and third dogs engage or, alternatively, the second and fourth dogs engage.

18. The combination of a pool and a pool cover system as claimed in any one of Claims 1 to 17.

19. Pool cover per se for use with a pool cover system as claimed in any one of Claims 1 to 17.

20. Pool cover roll-up means for use with a pool cover system as claimed in any one of Claims 1 to 17.

21. A pool cover system substantially as hereinbefore described with reference to Figures 1, 2, 3, 6, 7, 8 and 9 of the accompanying drawings.

22. A pool cover system substantially as hereinbefore described with reference to Figures 1, 2, 3, 4a, 4b, 5, 6, 7, 8 and 9 of the accompanying drawings.

23. A pool cover system substantially as hereinbefore described with reference to the accompanying drawings.

24. A pool cover substantially as hereinbefore described with reference to Figures 1, 2, 3, 6, 7, 8 and 9 of the accompanying drawings.

25. A pool cover substantially as hereinbefore described with reference to Figures 1, 2, 3, 4a, 4b, 5 6, 7, 8 and 9 of the accompanying drawings.