Field of the invention The invention relates to a device for covering a surface that is easy to use and better meets the requirements of the application concerned.

Technical background Covers are applied to surfaces for reasons which are dependent on the nature of these surfaces.

Hence, in the case of a basin such as a swimming pool, the cover may prevent contamination by leaves or by animals, may save energy, water and reagents, and may or needs to ensure the safety of people, especially children. In a basin for the desalination or other treatment of a fluid, a cover prevents dilution of liquid due to rainwater or excessive evaporation due to heat.

In the case of a sports ground such as a clay court or grass court outdoor tennis court, a cover protects the court against inclement weather, particularly intermittent rain.

Furthermore, a vehicle body is covered particularly to ensure the stability of the load in the face of the suction caused by the movement of the vehicle and to protect this load against inclement weather.

Covers are also used as blinds for greenhouses, conservatories or vehicle windows to prevent any overheating inside, and as protection against the sun for patio awnings.

In all these scenarios, what is generally being sought is an economical cover device that allows covering and uncovering to be done easily, dependably, repeatably and quickly, with the need for a minimum amount of human intervention .

A very basic first device used in the case of a swimming pool comprises a cover which may or may not be inflatable which is unrolled, stretched out and fixed manually to the edges of the swimming pool. This type of device is illustrated for example in documents US 6 691 334, GB 2 379 163 and FR 2 652 373. It is clear that in this instance, given the handling and storage required, only fairly small-sized swimming pools are involved.

For surfaces of larger dimensions recourse may be had to cover devices which also have a drum fixed to one of the transverse ends of the surface that is to be protected. The cover is deployed manually by pulling, being unrolled from the drum, to cover the surface. The weight and the dimensions of the cover require the intervention of a number of individuals in order to fit it correctly. The cover is removed by winding it up around the drum by rotation: the cover is thus removed from the surface by sliding along it. The rotation of the drum in order to remove the cover is performed manually or using an electric motor that is powerful enough to be able to pull the fully deployed cover. It should be emphasized that ease of deployment of the cover, particularly in the case of a swimming pool, is a contributory factor in the safety thereof, because any handling that is awkward discourages its use.

In this application, the terms "longitudinal", "transverse" and derivatives thereof refer respectively to the direction of travel of the drum and to the direction of the axis of revolution thereof.

In order to eliminate human intervention, (fully) automatic devices have been proposed; the cover is wound around a motorized drum that can be used for removing it, the drum being fixed to one of the transverse ends of the surface that is to be protected. The cover is deployed by pulling it from its visible end, using automatic pulling means of the rack or chain or hauling cable type, with or without a return pulley, the cover perhaps being guided by guideways arranged at the longitudinal ends of the surface that is to be covered; the cover then slides over the surface, covering it. Likewise, as the cover is removed, it slides over the surface that is to be covered as it winds up around the drum. This automatic cover device is illustrated notably in documents US 3 574 979, GB 2 199 741, US 2005/0097834, CA 2 115 113, US 2001/0023506, US 5 930 848, US 4 001 900 and on the website www.aquatop.be.

The cover devices mentioned hereinabove, in which the drum is fixed at one of the transverse ends of the surface that is to be protected, have the main disadvantage of making the cover slide, which cover is dragged along the surface that is to be protected as it is being deployed and as it is being removed, thus causing premature wear of this cover together with additional work due to the friction thus generated. To alleviate this disadvantage, there has been developed a new type of cover device with a drum, the motorized or manual drum now being mounted on a longitudinal-translation mechanism. This mechanism moves the drum over the surface that is to be covered, allowing the cover to be literally "laid" onto the surface, as it is deployed, by simultaneously unrolling it from the drum while it is being moved longitudinally, then allowing it to be lifted, as it is removed, while simultaneously winding it up onto the drum. The cover therefore slides over the surface neither while it is being deployed nor while it is being removed. The cover device also comprises a system for fixing the cover to a transverse end of the surface that is to be covered such that the translational and rotational movements of the drum cause the cover to be unwound or wound up above the surface that is to be covered.

Examples of automatic devices of this type are disclosed for example in documents WO2005/026473, FR 2 900 951, DE 2 257 231, FR 2 893 651, FR 2 789 425, FR 2 803 769, FR 2 743 502, EP 1 719 858, and on the website www.kimbay.fr. Moreover, a completely manual alternative form of the drum mounted for longitudinal translation is illustrated in documents WO2007/036625 and US 4 195 370.

In order repeatably to control the path of the longitudinal translational movement of the drum during deployments and removals of the cover, the longitudinal- translation mechanism generally comprises parallel rails positioned on each side of the surface that is to be covered and along which the drum travels via wheels or any other translation means. It is therefore essential to ensure alignment between the translation means and the rails, failing which the system would become jammed. This is a particularly sensitive issue in instances where the translational movement of the drum is activated by the rotation of a pinion meshing in a rack placed on or near the rails. Now, the distance between the rails and the length of the structure supporting the drum may vary considerably over time as a function of temperature, the shifting of the rails, the deformation of the structure through wear or knocks, etc.

GB2410473 proposes a system for covering a surface, notably the roof of the loading bed of a truck, comprising a segment of rack capable of moving longitudinally and driving the rotation of a pinion and of a first arm, which rotates as one with the pinion, and to the end of which there is attached a tarpaulin as depicted in the attached figure 7 (the reference numerals between parentheses correspond to the numbering used in GB2410473) . The rotation of the first arm opens the roof of the loading bed of the truck. A drum is mounted at a first end of a second arm, the second end of this arm being mounted for rotation approximately at the middle of the first arm. Said roller presses down on the tarpaulin during opening to ensure that the part of the tarpaulin that covers the section of the surface that is still covered over remains suitably taut. The drum in this system is not able to roll up a cover. For a pinion of diameter D = 30 to 50 cm (it seems somewhat improbable for the pinion to have a diameter in excess of 50 cm) , the travel of the rack, [] ^x D/2, along the rail is of the order of 0.5 to 0.8 m. Over such lengths, there can scarcely be any significant problems with loss of parallelism between the rails and GB2410473 does not describe such a problem or propose a solution for it. The problem of loss of parallelism of the rails may, however, become significant in other applications and cover systems than the one described in GB2410473.

Specifically, the surface to be covered may be large as in the case of a swimming pool or sports ground, and the drum may have a length ranging up to 10 m, or even more, and may be subjected to significant variations in temperature between day and night, in the summer and in the winter, leading to variations in the length of the structure supporting the drum which may be great. In addition, the periphery of the surface that is to be covered is not necessarily stable; for example, in the case of sports grounds or swimming pools, the rails may be laid on the ground (grass, gravel) or on a wooden edging deck, which move over time. As it is not possible to maintain the parallelism of the rails by using cross members which would run across the sports ground or the swimming pool, rail parallelism is often difficult, if not impossible, to achieve in the long term. There therefore remains a problem to be solved in order to ensure correct long-term operation of automatable systems for covering a surface comprising guide rails.

Summary of the invention

It is a particular object of the invention to afford a device for covering a surface that is easy to implement and ensures that it operates correctly irrespective of external parameters such as the thermal expansion of the elements of which it is made, the loss of parallelism of the rails, etc.

The invention is as defined in the main claims. Preferred variants are defined in the dependent claims. The present invention relates to a device for covering a surface comprising a drum mounted to rotate and able to wind up or unwind a cover, said drum being mounted on a longitudinal-translation mechanism, said longitudinal- translation mechanism comprising

(a) rails placed on either side of said surface, at least one of said rails comprising a rack; and (b) at least one pinion meshing with said rack and the rotation of which allows the longitudinal translation of the drum;

characterized in that the longitudinal-translation mechanism is such that it allows a transverse movement of the pinion and/or of the rack and/or of the rail, allowing the alignment between the pinion and the corresponding rack to be automatically adjusted.

According to a preferred embodiment, the cover device is suitable for covering a multitude of surfaces such as, for example, a basin that may or may not be filled with a liquid, such as a swimming pool, a water desalination, treatment or retention basin; a sports ground, such as a tennis court or a cricket pitch; a body of a vehicle such as a truck or a truck trailer; a glazed surface such as a greenhouse, a conservatory or a window of a vehicle (train, bus, etc.) .

In order automatically to adjust the alignment between the pinion and the rack as a function of the lateral deviations of the pinion, for example as a result of expansion of the structure supporting the drum, or of the rack, for example, through movement of the base on which the rails housing the rack are fixed, there are a number of possible solutions:

(a) The rails and the rack or racks are fixed and at least one pinion which meshes in a rack can move freely in the transverse direction over a certain distance along the axle on which it is mounted, thus correcting lateral deviations in the pinion/rack alignment;

(b) The rails and the pinion or pinions are fixed and the rack or racks themselves are mounted such that they can move on the rails in such a way as to allow them a transverse movement with respect to the rails; the rack or racks can thus follow the straight path dictated by the pinion fixed rigidly to its rotation axle; (c) The pinion is fixed on its axle and the rack or racks are fixed rigidly to the rails, which are themselves mounted such that they can move on supports fixed at the periphery of the surface so as to allow said rails a transverse movement with respect to said supports; the rails - and therefore the rack or racks - can thus follow the straight path dictated by the pinion fixed rigidly to its rotation axle; or

(d) A combination of solutions (a) to (c) listed hereinabove, in which several of the elements of the system have a degree of freedom in the direction transverse to the rails.

Once at least one of the pinions, racks or rails have a degree of freedom in the transverse direction to provide adjustment for the lateral deviations in alignment between the pinion and the rack, use is advantageously made of a centering shoe that, on the one hand, moves in longitudinal translation as one with the drum, and, on the other hand, fits into one of the rails and envelops the corresponding rack, so that it can move freely along said rail and which additionally comprises a longitudinal opening partially enveloping the pinion.

Above all, but not exclusively, in the case of large surfaces, it is advantageous for the drum to be mounted on a carriage and/or to provide a motor to effect the longitudinal translational movement of the drum. Brief description of the figures

These aspects, together with other aspects of the invention, will be clarified in the detailed description of some particular embodiments of the invention, reference being made to the figures in which:

Fig.l is a perspective overview of a surface with a moving drum and the rails extending on each side of the surface;

Fig.2 is a perspective view of a rail mounted on a support fixed to the periphery of a surface so as to allow said rail a transverse movement with respect to said support;

Fig. 3 is a perspective view of a variant of the invention, showing a pinion meshing in a rack through a centering shoe;

Fig. 4 is a perspective view of a centering shoe fitting into a rail;

Fig. 5 is a cross section through a centering shoe fitting into a rail and enveloping the rack with (a) little or no clearance between the shoe and the rail and (b) a certain amount of clearance between the shoe and the rail.

Fig. 6 is a perspective view of a carriage one of the ends of which is mounted on hinges. Fig.7 Three steps (a) to (c) , illustrating the system for opening/covering a surface as disclosed in GB2410473.

Detailed description of some particular embodiments As depicted in Fig. 1, the automatic device (1) for covering a surface (3) according to the invention comprises a cover (10) intended to protect said surface (3) . The device (1) makes it possible to cover notably surfaces defined by the contour of a basin of water such as a swimming pool, a water treatment basin, a waste water purification station, a retention basin, a desalination plant, etc. However, the invention may be used in any field that requires the covering of a surface, for example a clay court or grass court tennis court, the body of a vehicle, a glazed surface of a greenhouse, a window of a vehicle such as a train or bus, or a conservatory, etc. In general, throughout the present application, "surface" therefore means any area delineated by a perimeter.

The device (1) comprises a drum (2) which has a length at least equal to the width of the cover (10), the latter having to be sufficient in width and in length to cover the entire surface (3) that is to be protected, when it is deployed. The drum (2) is mounted on a longitudinal-translation mechanism comprising rails (6) positioned on each side of said surface (3) . The drum (2) has two directions of rotation: the first direction of rotation allows it to unwind the cover (10) to deploy it and cover the surface (3) that is to be protected, and the second direction of rotation allows it to wind the cover (10) up in order to remove it and provide access to said surface (3) . The longitudinal translation of the drum is afforded by the rotation of a pinion (9) meshing in a rack (7) positioned on or near a rail (6) . The pinion may be rotated manually using, for example, a cranking handle, or by a motor connected to the shaft of the pinion. The device (1) further comprises a fixing system (8) situated at a transverse end of the surface that is to be covered and allowing the cover to be unwound/wound above the surface (3) that is to be covered during the translat ional and rotational movement of the drum (2) . Any known type of fixing system that meets the constraint and safety criteria dependent on the application may be used for this. For example, the fixing system (8) may comprise a plurality of straps secured to the visible transverse end of the cover (10), said straps being, for example, equipped with anchoring hooks which fix onto the transverse part of the contour delimiting the surface (3) that is to be covered. Alternatively, the end of the cover that is to be fixed may be equipped with eyelets which fix onto the transverse edge of the surface via a series of eyebolts, screws, a cable or any other means. These anchoring means keep the visible transverse end of the cover (10) immobilized allowing longitudinal tension to be applied thereto and allowing it to be unwound, if necessary without a motor, when the drum (2) moves to cover the surface (3) .

The cover may be made of any material suited to the application in question: synthetic or natural textile materials, polymer films, slats made of polymer, metal or wood, etc. It may be transparent, opaque or translucent and may form a barrier to fluids or, on the other hand, be porous, or may even have mesh structures like in a net . Longitudinal tension may be applied to the cover as it is being deployed simply by ensuring that the speed at which the cover is unwound by the rotation of the drum is lower than the speed of longitudinal translation of the drum, or by using a brake or spring in the drum rotation system, or by differential motorized control of the rotational and translat ional movements of the drum. If these two speeds are synchronized, the cover will be deployed with no tension other than the tension generated by its self weight in the case of the covering of a surface comprising a cavity such as a swimming pool.

The cover may additionally be equipped with drainage means allowing any fluid that settles on its surface to be removed, thus making it easier to handle.

The device (1) that forms the subject of the invention is notable in that it allows automatic correction for any lateral deviation between the rails and the pinions which may be caused either by a variation in the span of the drum or of a carriage supporting it as a result of thermal expansion, or by a loss of parallelism of the rails brought about by a knock or by a movement of the base on which they are fixed (for example if the rails are laid on the ground or inserted in a wooden structure, two bases which are subject to potentially substantial movements over time) .

Deviations in the alignment between a pinion and the rack in which it meshes may be of the order of a few millimeters to a few centimeters depending on the application. The larger the surface that is to be covered and the more subject the base on which the rails are laid is to dimensional variations, the greater these deviations may be. For example, in the case of swimming pools, in which the drum may have a span of 10 m or more, and in which the rails, which are often laid on the ground or on a wooden floor are subject to substantial stress under the self weight of the cover which overhangs the cavity of the swimming pool, deviations in alignment of as much as 50 to 100 mm or even more are not exceptional and may be corrected for by the device that forms the subject of the present invention. For more modest surfaces, such as window blinds, they may be of the order of 5 to 10 mm, or even 20 mm for large glazed openings .

As indicated in the above summary of the invention, automatic adjustment of the alignment between the pinion and the rack is possible by providing a degree of freedom in the direction transverse to the rails to at least one of the following elements: (a) the pinion (9) (see figure 3), (b) the rack (7) (see figure 5 (b) ) , or (c) the rails (6) (see figure 2) or, of course, (d) any combination of these three options. The alignment between the pinion and the rack is advantageously adjusted using a centering shoe (20) that, on the one hand, moves in longitudinal translation as one with the drum (2) and, on the other hand, fits into one of the rails (6) and envelops the corresponding rack (7), so that it can move freely along said rail and which additionally comprises a longitudinal opening (23) partially enveloping the pinion (9) . In any event it is preferable for the shoe to have little or no clearance with respect to the pinion (9) and the rack (7) in order to best provide alignment between these two elements. What is meant by "little or no clearance" is that the tolerance between these components allows them to rotate or slide freely, but does not allow any substantial transverse movement. The clearance between the centering shoe (20) and the rail (6) into which it fits, on the other hand, depends on the variant selected from among solutions (a) to (d) listed hereinabove.

In case (a) in which the lateral deviations in pinion/rack alignment are corrected for by transverse movement of the pinion along its rotation axle, it is preferable for there to be little or no clearance (Si) between the centering shoe and the rail, thus allowing the shoe to force the pinion to follow the path of the rail and of the rack (see figure 5 (a) ) . The same will be true of case (c) in which the rails are mounted such that they can move on supports fixed to the periphery of the surface so that the shoe imposes on the rail the straight path dictated by the pinion which is fixed to its rotation axle.

In case (b) on the other hand, where the racks are mounted such that they can move on the rails so as to allow them a transverse movement with respect to the rails, it is absolutely essential to provide a lateral clearance (S2) between the centering shoe and the rail so as to allow the former to dictate the straight path of the pinion to the rack (see figure 5 (b) ) . If the shoe had little or no clearance with respect to the rail, the rack would not be able to correct lateral discrepancies in its alignment with the pinion.

Above all, but not exclusively, in the case of large surfaces, it is advantageous for the drum to be mounted on a carriage (21) . The carriage comprises a structure of metal, composite or the like beams, which supports various elements such as the drum (2), the centering shoe

(20) and the pinion (9) positioned in the longitudinal opening (23) of the shoe and, where appropriate, a motor connected to the rotation axle of the pinion. In case (a) in which the lateral deviations in the pinion/rack alignment are corrected by the transverse movement of the pinion along its rotation axle, it is important that the carriage allows this movement of the pinion. The simplest solution is for the carriage to be sized according to the extreme outermost position of the pinion or pinions. However, that has the disadvantage of making the system unnecessarily large, something which is undesirable both from the esthetic point of view in the case of a swimming pool, for example, and from a technical point of view in the case, for example, of the loading bed of trucks. An alternative solution is for the centering shoe to be fixed to an end of the carriage that is connected to the remainder of the carriage structure by a system of hinges (22) (see figure 6) and/or of telescopic tubes (not depicted) allowing the shoe to follow the transverse deviations of the rail into which it is fitted. For example, the rotation shaft of the pinion may itself be telescopic so that it never protrudes beyond the structure of the carriage and at the same time gives the pinion a degree of freedom in the direction transverse to the rails in accordance with a preferred variant of the present invention. The geometry of the rails (6) and of the racks (7) may vary with the application. Figures 2 to 6 depict a geometry considered to be particularly advantageous. The rails consist of a C-section having an opening (14) toward the outside on one of their faces and comprising flanges which partially close said opening (14) on each side, leaving enough space to accommodate the pinion (9) and, where appropriate, the shoe (20) . The rack (7) is positioned "inside" the section, facing the opening (14) to allow the pinion (9) to mesh therein. When a centering shoe (20) is used, this shoe fits into the section of the rail as depicted in figure 5, enveloping the rack (7) and the pinion (9) , thus ensuring alignment of both. The geometry of the systems depicted in figure 5 allows the drum or the carriage on which this drum is mounted to be attached to the rails thus preventing any risk of derailment. The geometry depicted in the figures has the advantage that it can be embedded in the base that forms the perimeter of the surface (3) that is to be covered, thus making it possible to have no projecting parts. If such an approach is not needed, other geometries are also possible, for example a rail (6) consisting of a substantially T-shaped section with a shoe (20) which envelops the horizontal bar of the "T" from the outside; or, more simply, a C-section as depicted in the figures, but the opening of which is partially closed by just one rather than by two flanglets. It may be seen that there are numerous possible rail geometries which impose no restriction on the present invention.

When the rack is "inside" a section piece that forms the rail, as illustrated in the figures, the cover device of the invention may comprise, for each rail, a system comprising a rail closure strip which is inserted in the rail and thus closes off its opening, as the cover is gradually wound up onto the drum. The purpose of this strip is to prevent, for example in the case of an uncovered swimming pool, a swimmer from sustaining injury from contact with the rails. In addition, the closing off of the rails by said strip when the swimming pool is uncovered keeps the rails and racks clean.

The shoe (20) may additionally be fitted with brushes at each of its ends so as to clean off any dust or debris that has become deposited on the rack (7) downstream of the pinion (9) .

Finally, whereas the longitudinal-translation mechanism may be actuated manually, according to another embodiment it comprises at least one motor so that the system can be at least partially automated, something which is particularly advantageous in the case of a cover of relatively large size. As far as swimming pools for example are concerned, safety is dependent on this because awkward handling operations would soon discourage users from deploying the cover every time they should.

When the longitudinal translational movement of the drum is not actuated by a pinion fitted into a rack, but for example using automatic pulling means of the chain or hauling cable type, with or without a return pulley, the same principle can be used to ensure the alignment between the drum guide rails and wheels or rollers that follow the rails with or without the interposition of a guide shoe.