WO2024017934A1

WO2024017934A1 - A retractable screen construction

Info

Publication number: WO2024017934A1
Application number: PCT/EP2023/069990
Authority: WO
Inventors: Michele BIZZARRO
Original assignee: Corradi S.R.L.
Priority date: 2022-07-20
Filing date: 2023-07-19
Publication date: 2024-01-25

Abstract

A retractable screen construction (1) comprising: comprising: a support; a screen guide located in the support; a retractable screen (4) having a lateral side guided in the screen guide; and a leaf spring to tension the screen. The leaf spring comprises a connection region extending between regions where the leaf spring engages the support and the screen guide. The connection region comprises first and second curved region which curves in opposite rotational direction, wherein a hypothetical cylinder tangential to either one of the curved regions extends in a direction perpendicular to the screen. By providing at least two curved regions with a different curvature direction, the amount of deformation of each curved region in order to account for the dynamic load exerted by the screen is reduced, leading to an improved durability of the leaf spring.

Description

A retractable screen construction

Technical field

The present invention is generally related to a retractable screen construction.

Background art

Retractable screen constructions are a common accessory of buildings and housing, such as awnings, canopies or terrace canopies, sunscreens, curtains, sun sails, etc. in order to delimit and protect specific areas from atmospheric agents (e.g. wind, sun, precipitation, etc.). A retractable screen may also provide an enclosed space, for example a tent, a gazebo, a porch, etc. Creating portable or non-permanent enclosures or spaces using retractable screens is particularly relevant for outdoor use where a flexible screen that can be unrolled from a roller (along a predefined direction, be it horizontal, vertical, oblique or curvilinear), is used to protect (upwardly or laterally) a predefined area and/or constitute a hindrance to access from the outside on the part of people, insects and other animals, atmospheric agents, etc. Other applications include retractable screens for protecting solar panels from rain or dust or for efficiently blocking or reducing sunlight exposure through a window.

The screen is usually manufactured from flexible material, for instance fabric (e.g. textiles) or plastics material. The screen may be transparent, partially transparent, or opaque to visible light. Particular types of screens, when closed, may block wind and rain. Usually, the materials used for these screens are light weight, which presents some problems for outdoor use. For example, wind may lift and/or bend the screen, thus interrupting the primary function of the screen. In some cases, the screen may become deformed or may even tear or otherwise break.

This problem is alleviated by including guides which hold the screen in place at the side thereof. More specifically, the lateral sides of such a screen are encased in such a screen guide in order to, for example, absorb wind loads without the screen moving, e.g. starting to flap. The lateral sides of the screen may be encased in such a screen guide by, for example, providing the lateral sides with a thickening, which is accommodated in a space provided in the screen guide. Such a thickening may be configured, for example, as half a zip fastener.

This screen guide is preferably tensioned by means of one or more springs with respect to a support, so that the screen remains smooth and loads on the screen are absorbed without this screen tearing. In this case, elastic material or springs exert a spring force on the screen guide which forces the screen guide away from the screen thus tensioning the screen. In this case, the support is typically fixed and stationary.

In classical screen constructions, elastic material is provided between the screen guide and the support in which this screen guide is fitted in order to tension the screen guide with respect to the support. However, such elastic material suffer durability issues, especially in outdoor conditions, as they undergo changes on account of the temperature and the passing of time.

Spiral springs, such as for example described in JP 2003013680 or JP 10212878, may be used as an alternative for such elastic material. However, such spiral springs are not easy to fit and screen guides using the solutions described cannot be designed as compact as those using the known elastic materials.

Several different retractable screen constructions are known in which leaf springs are used to tension the screen guide with respect to the support. Such screen devices are described, for example, in EP 3 271 540 and EP 2 157 275. These documents disclose a retractable screen construction comprising: a frame including a support extending in a longitudinal direction and a screen roller extending in a transverse direction which is substantially perpendicular to the longitudinal direction; a screen guide extending in said longitudinal direction and being located in the support; a retractable screen able to be unrolled from said screen roller and rolled up on said screen roller, the retractable screen having a lateral side which is guided in the screen guide; and a leaf spring disposed between the support and the screen guide, the leaf spring being configured to tension the screen in said transverse direction, the leaf spring comprising a first region engaging the support, a second region engaging the screen guide, and a connection region connecting the first and second region.

However, these known retractable screen constructions have drawbacks. For example, the leaf spring disclosed in EP 2 157 275 relies on multiple engagement points on the support which are on opposing sides of the screen guide and at a different height thus giving rise to torsional forces exerted on the screen. For example, the leaf spring disclosed in EP 3 271 540 has a relatively complex shape with various parts in different planes leading to manufacturing difficulties. Furthermore, both known leaf springs are also known to suffer from fatigue due to the long-term dynamic load exerted thereon which eventually leads to a decreased elasticity so that the screen is no longer properly tensioned.

Disclosure of the invention

It is an object of the present invention to provide a leaf spring for tensioning a retractable screen of a retractable screen construction having an improved durability.

This object is achieved according to the invention in that the connection region comprises a first curved region which curves in a first rotational direction and a second curved region which curves in a second rotational direction which is opposite said first rotational direction, wherein a hypothetical cylinder tangential to either one of the curved regions extends in a normal direction which is substantially perpendicular to both the longitudinal direction and the transverse direction.

The present invention is based on the realization that the known leaf springs rely on a single curved region between the engagement points. In essence, the known leaf springs are V-shaped and have a single curved region with a first leg extending therefrom to engage the screen guide and a second leg extending therefrom to engage the support. The dynamic load exerted by the screen on such leaf springs causes a frequent bending of the single curved region eventually leading to fatigue which may in turn cause fracture and/or plastic deformation.

The present inventors have found that this fatigue can be severely reduced by increasing the number of curved regions between the engagement points. More specifically, by providing at least two curved regions with a different curvature direction (i.e. one clockwise and the other counter-clockwise), the amount of deformation of each curved region in order to account for the dynamic load is reduced, which leads to less fatigue and thus an improved durability.

Furthermore, the orientation of the curved regions, i.e. with a hypothetical cylinder tangential to either one of the curved regions extending in a normal direction which is substantially perpendicular to both the longitudinal direction and the transverse direction, amounts to the leaf spring being substantially engaging the support and screen guide in a plane perpendicular to them thus leading to an optimal force transfer and stability. This further provides a compact design as the leaf spring in its longest dimension is in line with the support and screen guide.

Moreover, the use of a leaf spring is advantageous when compared to using elastic materials, such as a mousse or the like, as this is far less susceptible to environmental wear and tear.

Advantageously, in contrast to the leaf spring disclosed in EP 2 157 275, the leaf spring according to the present invention, engages the screen guide and the support on a same side of the screen. This allows placing leaf springs at different heights along the screen guide on opposing (with respect to the screen) sides thereof, thus providing flexibility towards optimal tensioning of the screen. In an embodiment of the present invention, the first curved region has a concave side and the second curved region has a concave side, the concave sides of the first curved region and the second curved region facing one another. This results in a leaf spring including a S-shaped or Z-shaped region which is particularly suited for providing the required long-term elasticity to handle the dynamic load.

In an embodiment of the present invention, the first region and/or the second region comprises a substantially flat section which preferably engages a respective one of the support and the screen guide when the leaf spring is compressed. This results in an enlarged contact area between the leaf spring and the support and/or the screen guide, improving both stability and force transfer. It is especially advantageous when the substantially flat section engages with the support and/or the screen guide when the leaf spring is most compressed, rather than in its most relaxed state, as the force exerted by the leaf spring is larger in its most compressed state.

In an embodiment of the present invention, the first curved region has a first radius of curvature and the second curved region has a second radius of curvature, wherein the first radius of curvature and/or the second radius of curvature is comprised between about 10% and 50%, with particular lower limits of about 15%, about 20% and about 25% and with particular upper limits of about 40%, about 35% and about 30%, of the distance over which the screen guide is moveable with respect to the support in the transverse direction. Such radii of curvature are a compromise between opposing constraints. On the one hand, the radii of curvature are desirably as large as possible as this reduces the bending and folding which occurs during compression and relaxation, thus reducing the fatigue risk. On the other hand, the radii of curvature are preferably as small as possible as this leads to a larger possible distance variation between the support and the screen guide.

In an embodiment of the present invention, the first curved region has a first radius of curvature and the second curved region has a second radius of curvature, wherein one or more of the radii of curvature are substantially unchanged when compressing the leaf spring. This lack of or very low change is curvature of the curved regions between the most compressed and the most relaxed state of the leaf spring reduces the fatigue risk due to long-term dynamic loading (i.e. frequent compressing and relaxing of the leaf spring). The required leaf spring dimensional compression may be in such a case achieved by other (non-curved) sections of the leaf spring which exhibit a pivoting motion with respect to the curved regions.

In an embodiment of the present invention, the leaf spring comprises an abutment, preferably formed by a free end of the leaf spring, which engages another region of the leaf spring when the leaf spring is fully compressed. The leaf spring is thus self-limiting in the sense that the abutment avoids further compressing the curved regions. As such, excessive pressures due to a too large compression are avoided.

In an embodiment of the present invention, the first region of the leaf spring is fixed to the support, wherein, preferably, the support comprises a fastening guide and the first region of the leaf spring comprises a clamping section which is clamped in the fastening guide. As the support is larger than the screen guide (i.e. the screen guide is positioned in the support), there is more space available to fasten the leaf spring, thus simplifying the leaf spring design or at least removing the amount of constraints involved when designing the leaf spring. Furthermore, the provision of a fastening guide and clamping section allow for the leaf spring to be fixed at any desired position along the length of the fastening guide which provides flexibility in the positioning.

In an embodiment of the present invention, the connection region comprises no further curved regions with the curved regions being preferably connecting by a substantially flat intermediate region. This results in S-shaped or preferably Z-shaped, leaf springs which are minimalistic in dimensions thus allowing a compact design. Brief description of the drawings

The invention will be further explained by means of the following description and the appended figures.

Figure 1 illustrates a perspective view of a retractable screen construction according to the present invention.

Figure 2A shows a transverse cross-section trough the side profile of the retractable screen construction with a first embodiment of the leaf spring in its relaxed state.

Figure 2B shows a transverse cross-section trough the side profile along plane ‘B’ indicated in figure 2A.

Figures 3A and 3B show a same view as respective ones of figures 2A and 2B with the leaf spring in its stressed state.

Figures 4A to 5B show a same view as respective ones of figures 2A to 3B for a second embodiment of the leaf spring.

Figures 6A and 6B show a side view of the leaf spring of the first embodiment in its relaxed, respectively stressed, state.

Description of the invention

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not necessarily correspond to actual reductions to practice of the invention.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. The terms are interchangeable under appropriate circumstances and the embodiments of the invention can operate in other sequences than described or illustrated herein. Moreover, the terms top, bottom, over, under and the like in the description and the claims are used for descriptive purposes. The terms so used are interchangeable under appropriate circumstances and the embodiments of the invention described herein can operate in other orientations than described or illustrated herein.

Furthermore, the various embodiments, although referred to as “preferred” are to be construed as exemplary manners in which the invention may be implemented rather than as limiting the scope of the invention.

The term "substantially" comprises variations of +/- 10% or less, preferably +/- 5% or less, more preferably +/- 1 % or less, and even more preferably +/- 0.1 % or less, of the specified state, as far as the variations are applicable to function in the present invention. It is to be understood that the term "substantially A" is intended to include "A".

The present invention generally relates to a tensioning leaf spring used in retractable screen constructions, which advantageously provide high resistance against wind while still allowing flexible, lightweight materials to be used, such as polymer, glass fiber, glass cloth, textiles and the like.

Although in some embodiments of the present invention reference is made to "rolling" and "unrolling" of "retractable screens", the present invention is not limited by the actual mechanism of retraction. The present invention may be applied to any type of deployment and retraction of retractable screens, whether the screens are actually wound or folded. The present invention may also be applied to various types of screen, whether it is a textile screen or a screen formed by (semi-)rigid strips of material connected to each other.

Figure 1 illustrates a perspective view of a retractable screen construction 1 according to the present invention. The retractable screen construction 1 comprises two side guides 2 connected by a cross beam 3 with a retractable screen 4 that is partially unrolled in figure 1. The retractable screen 4 is fixed at one end to a screen roller (not shown) and a screen slat 5 is fixed to the other end. In the illustrated embodiment, the cross beam 3 acts as a housing for the screen roller and the retractable screen 4 when in its retracted state. Although, in other embodiments, the cross beam and the screen housing may be formed by different beams. Such a housing is beneficial as this protects the screen 4 when retracted from atmospheric conditions. Furthermore, various other screen components (e.g. the screen roller, a motor, screen supports, ...) are also protected by the housing.

A motor (not shown) may be provided for actuating the screen. This motor may be placed inside the housing. A motor controller may be provided which may either be programmed to unroll the screen to a desired length. Alternatively, a detector (e.g. a torque sensor) may detect a screen limit movement. The motor may also be manually controllable by a user. Furthermore, in other embodiments, the retractable screen 4 may be fully manual (e.g. using a winch or the like).

As illustrated in figure 1 , the side guides 2 extend in a longitudinal direction 20 and the cross beam 3 extends in a transverse direction 21 which is substantially perpendicular to the longitudinal direction 20. The longitudinal direction 20 and the transverse direction 21 together define a planar surface (which particularly is parallel to a plane defined by the retractable screen 4 when unrolled) with a normal direction 22.

The various beams or guides 2, 3, 5 are typically made of a rigid material. This can be aluminium, for example. Aluminium has many advantages as a material, as it is robust and light at the same time, can withstand bad weather conditions and requires little maintenance. However, other materials are further suitable and their advantages or disadvantages are considered known by those skilled in the art. A beam or guide can be produced using various techniques depending on the material, including extrusion, milling, setting, casting, welding, etc., with extrusion being preferred. The appropriate manufacturing technique is considered known by those skilled in the art.

As shown in figure 2A, 3A, 4A and 5A, the side guide 2 comprises a fixed support 6 which provides the required rigidity to the frame of the retractable screen construction. The support 6 includes a hollow 7 (or space) in which a screen guide 8 is positioned. The screen guide 8 also comprises a hollow 9 (or space) in which a locally thickened lateral side of the retractable screen 4 is fixed. Although the screen guide 8 may be manufactured from various materials, such as metals, in particular aluminium such that the same material is used for both the support 6 and the screen guide 8, it is preferred to manufacture the screen guide 8 from a plastic material which advantageously is more elastic than a metal material. One or more leaf springs 10 are disposed between the support 6 and the screen guide 8.

The screen guide 8 is moveable with respect to the support 6 in the transverse direction 21 between a maximal tensioning state (shown in figures 2A and 4A) and a minimal tensioning state (shown in figures 3A and 5A). With “maximal tensioning state” it is meant that the screen 4 is maximally tensioned since the screen guide 8 is located at its outermost location with respect to the support 6 and with “minimal tensioning state” it is meant that the screen 4 is minimally tensioned since the screen guide 8 is located at its innermost location with respect to the support 6. In the maximal tensioning state, the leaf spring 10 is in its most relaxed state, while, in the minimal tensioning state, the leaf spring 10 is in its most compressed state. The leaf springs 10 urge the screen guide 8 to its maximal tensioning state. The screen guide 6 movement is delimited in the maximal tensioning state by stopping surfaces 15 provided in the support 6. The screen guide 6 movement is delimited in the minimal tensioning state by the leaf spring 10 design as described below. The support 6 is further provided with stopping surfaces 16 which would delimit a screen guide 8 motion in case the leaf spring(s) 10 malfunction. In the illustrated embodiment, a shortest distance between the stopping surfaces 15, 16 in the transverse direction 21 is about 16 mm. However, this distance may vary depending on the desired tensioning leeway. In general, this distance is comprised between about 5 and about 50 mm with particular lower limits of about 10 mm, about 13 mm and about 15 mm and with particular upper limits of about 40 mm, about 30 mm, about 25 mm, about 20 mm and about 17 mm.

A leaf spring 10 according to a first embodiment of the present invention is illustrated in figures 2A to 3B and 6A to 6B, while a leaf spring 10’ according to a second embodiment of the present invention is illustrated in figures 4A to 5B. The main difference between the embodiments is the way of fixing the leaf spring 10, 10’ to the side guide 2 as described below. However, the features common in both embodiments are described first.

Each leaf spring 10, 10’ comprises a first region 1 1 engaging the support 6, a second region 12 engaging the screen guide 8, and a connection region 13 connecting the first region 1 1 and the second region 12. The connection region 13 includes a first curved region 17, a second curved region 18 and an intermediate region 19 connecting the curved regions 17, 18. In the illustrated embodiment, the intermediate region 19 is substantially planar resulting in a connection region 13 with only two curved regions. However, in other embodiments, the intermediate region 19 may also include one or more curved regions or may be absent with the curved regions being contiguous with one another. The first and second curved regions 17, 18 have an opposing direction of curvature with one of them (i.e. the first one in the illustrated embodiments) curving in a clockwise direction when going form the first region 1 1 to the second region 12 and with the other one of them (i.e. the second one in the illustrated embodiments) curving in a counter-clockwise direction when going form the first region 11 to the second region 12. In other words, the connecting region 13 in both embodiments is generally Z-shaped or S-shaped to provide a desired elasticity and flexibility. Both leaf spring designs 10, 10’ allow for a substantial decrease of their length viewed in the transverse direction 21 , i.e. the shortest distance between region 30 and region 28 in leaf spring 10 (see figure 6A). In some embodiments, this distance is decreased with 40%, particularly 50% and more particularly 55% when going from the most relaxed state (shown in figures 2A, 2B, 4A and 4B) to the most compressed state (shown in figures 3A, 3B, 5A and 5B). This allows a sufficient leeway on the screen 4 to account for high wind loads to be borne without damaging the screen 4.

One of the reasons underlying this possible distance decrease is that the outer point of one curved region is able to pass a centre point of the other curved region when viewed in the transverse direction 21. More specifically, outer point 27 of curved region 18 passes centre point 35 of curved region 17 when compressing the leaf spring 10 and/or outer point 26 of curved region 17 passes centre point 36 of curved region 18 when compressing the leaf spring 10.

Another one of the reasons underlying this possible distance decrease is the relatively large radii of curvature of the curved regions 17, 18. This allows the intermediate region 19 to pivot with respect to either curved region 17, 18 without causing excessive stress on the curved regions 17, 18. In the illustrated embodiment, the radius of curvature of the curved region 17 is about 2 mm and the radius of curvature of the curved region 18 is about 2 mm. In general, the radii of curvature are comprised between about 0,2 mm and about 30 mm with particular lower limits of about 0,5 mm, about 1 mm and about 1 ,5 mm and with particular upper limits of about 20 mm, about 15 mm, about 10 mm, about 5 mm and about 3 mm.

The radii of curvature of the curved regions 17, 18 generally also depends on the thickness of the sheet of material from which the leaf spring 10, 10’ is manufactured. More specifically, a thicker sheet of material will increase the radius of curvature. For example, while a thickness of about 0,5 mm to 1 ,5 mm leads to radii of curvature of about 2 mm to 3 mm, a thickness of about 2 mm leads to radii of curvature of about 6 mm, while a thickness of about 3 mm leads to radii of curvature of about 10 mm. Which material thickness is used is, a.o., dependent on the desired tensioning force that may be generated with the leaf spring 10, 10’. In the illustrated embodiment, the thickness is about 0,5 mm and may vary in general from about 0,1 mm to 4 mm.

Furthermore, the radii of curvature of the curved regions 17, 18 remain substantially the same when compressing/relaxing the leaf spring 10, 10’. In other words, the distance decrease of the leaf spring 10, 10’ in the transverse direction 21 is rather caused by a pivoting of the intermediate region 19 and/or a pivoting of the flat region 24 and/or a pivoting of the flat region 29 rather than a folding the curved regions 17, 18 which could lead to the occurrence of folding lines leading to a decreased elasticity.

Both leaf springs 10, 10’ also have the orientation of the curved regions 17, 18 in common. More specifically, the curved regions 17, 18 are bent about an axis extending in the normal direction 22 (i.e. perpendicular to the screen 4). In other words, a hypothetical cylinder tangential to either one of the curved regions 17, 18 extends in the normal direction 22. Such hypothetical tangential cylinder are indicated in dotted lines in figure 6A with reference number 37 for the cylinder tangential to curved region 17 and with reference number 38 for the cylinder tangential to curved region 18. This allows the leaf springs 10, 10’ to extend substantially in the longitudinal direction 20 parallel to the side guide 2 thereby alleviating space constrictions for the leaf springs 10, 10’.

Another common feature in both embodiments is that the leaf spring 10, 10’ in their most compressed state abut against themselves. More specifically, the intermediate region 19 abuts against a folded-over free end 23 of the leaf spring 10, 10’. Both leaf spring designs 10, 10’ are therefore self-limiting to avoid excessive bending which could cause damage and/or a plastic deformation causing a decreased elasticity.

Yet another common feature in both embodiments is the presence of flat planar sections near or at the engaging regions 11 , 12. More specifically, flat region 24 is adjacent the contact area 30 in leaf spring 10. As shown in figure 2A, contact area 30 engages the screen guide 8 when the leaf spring 10 is relaxed. However, when compressing the leaf spring 10, also flat region 24 engages the screen guide 8. As such, the higher the force exerted by the leaf spring 10 on the screen guide (i.e. when compressed), the larger the contact area thus lowering the overall pressure and reducing the risk of damaging the screen guide 8. A similar mechanism is used in leaf spring 10’ when contacting the support 6.

In the illustrated embodiment, the opening angle a between legs 19, 24 is about 22,5° and the opening angle [3 between legs 19, 29 is about 10° in the most relaxed state of leaf spring 10 shown in figure 6A. In general, these opening angle are comprised between 2° and 70°, with particular upper limits of about 50°, about 40° and about 30 and with particular lower limits of about 5° and about 8° for the opening angle [3 and with particular lower limits of about 10°, about 15° and about 20° for the opening angle a.

The first embodiment of the leaf spring 10 is fixed to the support 6 while it is free to move with respect to the screen guide 8. In the illustrated embodiment, this is achieved by providing a fastening guide 40 in the support 6. A free end of the leaf spring 10, i.e. the part extending between point 28 and 34, is clamped in the fastening guide 40. More specifically, the part extending between point 28 and 34 includes a curved region 31 with adjacent flat regions 29, 32 extending to end regions 28 and 33. Due to this curve, the regions 28, 33 are forced away from region 31 thus clamping the leaf spring 10 in the fastening guide 40.

The bent free end 33, 34 allows for an easier placement of the leaf spring in the fastening guide 40 in particular by avoiding that end region 33 would get caught in the fastening guide 40 when sliding the leaf spring 10 therein.

As best shown in figure 2A, the curved region 18 has a local narrower width when compared to the remainder of the leaf spring 10. This enables placing a leaf spring 10 at any desired position along the length of the fastening guide 40. This would not be the case in absence of the narrower part as the fastening guide would then have to be provided with fixed location openings through which the leaf spring 10 is placed.

The second embodiment of the leaf spring 10’ is fixed to the screen guide 8 while it is free to move with respect to the support 6. In the illustrated embodiment, this is achieved by providing a hooked-part 41 in the leaf spring 10’ and corresponding grooves (not shown) in the screen guide 8. However, this does not allow to place the leaf spring 10’ at any desired location along the screen guide 8 contrary to the leaf spring 10. Furthermore, as leaf spring 10’ has a section extending between the screen guide 8 and the stopping surfaces 15, the design is also less compact when compared to leaf spring 10.

The illustrated leaf springs 10, 10’ may be made in a single piece. This may be achieved, for example, by punching a strip of material from a sheet, which may be made of, for example, spring steel, and afterwards folding the strip into the desired Z-shape or S-shape. As an alternative, such a leaf spring 10, 10’ could also be made of, for example, plastic.

The required number of leaf springs 10, 10’ per screen guide 8 may be determined on the basis of the type of screen 4 and the known loads which may act thereon. Furthermore, it may be desired to distribute the leaf springs 10, 10’ in a non-uniform manner along the length of the screen guide 8, e.g. to include a higher density near the middle of the screen 4 where wind loads are usually higher. Moreover, leaf springs 10, 10’ can be placed independent on both sides of the screen guide 8 (when viewed in the normal direction 22) thus allowing further variation to optimally balance the load across the screen guide 8.

Although aspects of the present disclosure have been described with respect to specific embodiments, it will be readily appreciated that these aspects may be implemented in other forms within the scope of the invention as defined by the claims.

Claims

1 . A retractable screen construction (1 ) comprising:

- a frame including a support (6) extending in a longitudinal direction (20) and a screen roller extending in a transverse direction (21 ) which is substantially perpendicular to the longitudinal direction;

- a screen guide (8) extending in said longitudinal direction and being located in the support;

- a retractable screen (4) able to be unrolled from said screen roller and rolled up on said screen roller, the retractable screen having a lateral side which is guided in the screen guide; and

- a leaf spring (10, 10’) disposed between the support and the screen guide, the leaf spring being configured to tension the screen in said transverse direction, the leaf spring comprising a first region (1 1 ) engaging the support, a second region (12) engaging the screen guide, and a connection region (13) connecting the first and second region, characterized in that the connection region comprises a first curved region

(17) which curves in a first rotational direction and a second curved region

(18) which curves in a second rotational direction which is opposite said first rotational direction, wherein a hypothetical cylinder (37, 38) tangential to either one of the curved regions extends in a normal direction (22) which is substantially perpendicular to both the longitudinal direction and the transverse direction.

2. The retractable screen construction according to claim 1 , characterized in that the first curved region has a concave side and the second curved region has a concave side, the concave sides of the first curved region and the second curved region facing one another.

3. The retractable screen construction according to claim 1 or 2, characterized in that the first region and/or the second region comprises a substantially flat section, the substantially flat section of the first region preferably engaging the support and/or the substantially flat section of the second region preferably engaging the screen guide when the leaf spring is compressed.

4. The retractable screen construction according to any one of the preceding claims, characterized in that the first curved region has a first radius of curvature and the second curved region has a second radius of curvature, wherein the first radius of curvature and/or the second radius of curvature is comprised between about 10% and 50% of the distance over which the screen guide is moveable with respect to the support in the transverse direction.

5. The retractable screen construction according to any one of the preceding claims, characterized in that the first curved region has a first radius of curvature and the second curved region has a second radius of curvature, wherein the radii of curvature are substantially unchanged when compressing the leaf spring.

6. The retractable screen construction according to any one of the preceding claims, characterized in that the leaf spring comprises an abutment (23), preferably formed by a free end of the leaf spring, which engages another region of the leaf spring when the leaf spring is fully compressed.

7. The retractable screen construction according to any one of the preceding claims, characterized in that the first region of the leaf spring is fixed to the support.

8. The retractable screen construction according to claim 7, characterized in that the support comprises a fastening guide (40) and the first region of the leaf spring comprises a clamping section which is clamped in the fastening guide.

9. The retractable screen construction according to any one of the preceding claims, characterized in that the connection region comprises no further curved regions.

10. The retractable screen construction according to claim 9, characterized in that the connection region comprises an intermediate region (19) connecting the first and second curved regions, the intermediate region being preferably substantially flat.