Background Art In the technical field of interior decoration products, there are known curtains, so- called"pleated curtains", which are formed by a fabric sized and folded according to a zigzag configuration, and that may be lifted and lowered by means of a system of pulleys mounted on the upper side of the window or of the French window. The various rectangular portions bounded by the folding lines formed by the pleated fabric of the curtain present various holes arranged along vertical lines and traversed by respective lifting threads.

A disadvantage of this known system lies in the fact that the user must act on the threads, by pulling or releasing them, and finally fixing them each time in the desired position. This system, although not complex, could be improved by eliminating the need of a direct action to be performed by the user on the threads. In addition, it would be advantageous to provide a system which, besides being self-locking, could also insure a reliable guiding function for the curtain during its lifting and lowering.

Other products that are similar to common curtains, specifically the mosquito curtains, also have drawbacks. Usually, mosquito curtains include a wrapping roller which is mounted on the upper part of the window, or French window, said roller receiving the net-like fabric of the mosquito curtain and rolling up-or unrolling-the

same during the lifting-or respectively the lowering-operation performed by the user on the mosquito net. A first drawback of this system consists in the fact that if a client provides inexact values for the distance between the lateral guides of the mosquito curtain, the latter may easily come out of the lateral guides after its installation, e. g. because of a wind gust or for any other reason. hi any case, the fact that the net-like cloth comes out of the lateral guides, is a common cause of complaints made by clients who buy this product.

A further disadvantage of the"wrapping-roller system"lies in the fact that it often cannot be mounted between a shutter or rolling shutter, and the window or French window, since the available space is very limited. hi fact, the wrapping roller must have a diameter not less than a prescribed value, in order to avoid its possible flexion at the middle, especially in case of particularly wide windows or French windows.

The thickness of the fabric of the mosquito net which is gradually wound around the roller when the mosquito net is being lifted, adds up to the diameter of the roller.

Consequently, this device typology does not allow to reach such dimensions as to permit, in any situation, to perform the installation of the mosquito curtain between the (rolling) shutter and the (French) window.

An object of the present invention is to realise a closing and opening device of a self-locking kind, having lateral guides, and which is characterised by a simple construction and operation, by the fact that it eliminates the previous drawbacks, and finally, by the fact that it may be employed equally well for a normal pleated curtain, for a curtain used to darken a room, and for a mosquito curtain of an innovative kind formed by a pleated net-like fabric.

Disclosure of Invention The objects of the present invention are attained by means of a self-locking opening and closing device for curtains with lateral guides as defined in claim 1.

Some specific embodiments are included in the dependent claims.

In substance, the device of the present invention provides lateral guides having thread-locking devices (at their lower ends) in order to fix these threads.

Several pulleys are provided preferably inside a slidable bar-handle, in order to guide the threads, from the thread-locking devices up to stationary fixing points of an upper box element, wherein these threads are made to pass through holes of the pleated fabric.

Therefore, the user only needs to act on the bar-handle and does not need to repeatedly lock and unlock the threads at their ends as in the prior art. Moreover, since at least two lateral threads traversing the fabric extend within the lateral guides, the curtain will not come out of these guides (for instance in consequence of a wind gust), and this is particularly important if the device of the invention is applied to an innovative mosquito curtain formed by a net-like pleated fabric.

Preferably, the device includes elastic means used to compensate for the variations in length of the threads resulting from use and sudden changes of temperature.

Moreover, the pulleys present thread-guiding means and means for changing the direction of the threads, which are advantageously formed by moulded polypropylene rollers, these rollers having at the same time the function of spacers that prevent mutual interference between threads which pass through the pulleys.

Brief Description of Drawings The present invention will now be described in more detail by means of one of its preferred embodiments, only for illustrative, but not for limitative or binding purposes, referring also to the figures annexed to the present application, wherein: FIGURE 1 is a general front view, showing the self-locking opening and closing device, used for pleated curtains, or for mosquito curtains including a pleated net- shaped fabric, according to the present invention;

FIGURE 2 shows the lower rail of the device, according to a perspective view and- respectively-a cross-sectional view; FIGURE 3 shows the inner core or inner part to be introduced inside the lower rail shown in Fig. 2, according to a perspective view and a cross section respectively; FIGURE 4 is a front, schematic view, of the external appearance of the curtain according to the present invention in the closed condition ; FIGURE 5 shows views from different directions of the lateral pulleys of the device according to the present invention, which are located at both sides of the device and inside the bar-handle; FIGURE 6 shows various views of the intermediate pulleys of the device of the present invention, which are also located inside the bar-handle, between the lateral pulleys; FIGURE 7 shows a lateral view and a plan view of a conical helical spring; FIGURE 8 shows various views of thread-locking means making part of the device of the invention, which are located inside and at the lower ends of lateral rails; FIGURE 9 shows an upper plug of the lateral guides or rails, which is used for mounting and fixing the upper rail in its final position; FIGURE 10 shows, according to a perspective view, a variant in which the bar- handle is arranged vertically instead of horizontally, and is capable of horizontally sliding between a starting upright (or opened-position upright), and a final upright (or

closed-position upright); FIGURE 11 is a front view of the variant (alternative embodiment) shown in Fig. 10, showing in particular the path of a"flexometer"or other kind of sliding means used to cover the lateral guides of the bar-handle; FIGURE 12 is a view of a detail, showing the means used for preventing the bar- handle from coming out of its guides or lateral rails, in the alternative embodiment according to Figs. 10 and 11.

Description of the preferred embodiment Fig. 1 is a schematic front view of the device according to the present invention. The device comprises two lateral guides, or lateral rails, 1, 1', substantially formed by respective"C"-channels, or section bars, made of plastics or aluminium, whose respective opening formed by the channel is directed towards the opening formed by the window, in such a way as to act as guides for a bar-handle to be described later on, and so as to receive the fixed upper rail which is also described next. The bases of the C-channels 1, 1'will be fixed in an adequate manner to the sides of the window (note that in this description the word window will be used indifferently also for indicating a French window, except in case the relative context allows a unique interpretation).

The upper rail 2 is rigidly fixed to the lateral guides 1, 1'and between these two; the upper rail includes a C-channel almost identical to that indicated by numeral 3 in Fig.

2, inside which there is introduced a core or inner part, which is identical to that indicated by numeral 4 in Fig. 3. Moreover, between the lateral guides 1, 1', a lower rail 3 may slide upwards and downwards, this rail being shown in isolation in Fig. 2 and receiving an inner part or core 4 (Fig. 3). The assembly formed by the lower rail 3 and by the core 4 will also be called"bar-handle"in the following description.

Moreover, the assembly formed by the upper (fixed) rail 2 and the core 4 will also be called-in the following description-"upper box"or"upper box-type element".

Referring to Figs. 2 and 3 we will first describe the details of the bar-handle, and next we will describe the similar upper box.

As may be seen in Fig. 2, the lower rail 3 does not form a perfect"C"or"U" ; instead, it has ribs 5 extending parallel to the base 6 of the rail. These ribs 5 have the function of retaining the core 4 when the latter is inserted into the rail 3. Note that the core 4 is introduced inside the lower rail 3 according to the orientation shown in Fig.

3, that is, with the edges of the base 7 of the core 4 abutting the ribs 5. Moreover, the core 4 presents circular holes 8 preferably realised equidistantly on its base 7.

Finally, the lower rail 3 has end notches 9 (only one of which is visible in the perspective view of Fig. 2) obtained on the base 6 at its opposite ends. The structure of the upper box-type element differs from the structure of the bar-handle only in that on the base of the upper rail 2 there are no end notches 9. Otherwise, both structures are identical to each other, and the core 4 of the upper box is introduced inside the upper rail 2 according to an orientation such that the base 7 of the inner part or core 4 abuts the ribs 5 of the upper rail 2.

However, we note the following: while the bar-handle is oriented, in the assembled condition shown in Fig. 1, with the base 7 (of the core 4) directed upwards, the upper box-type element is oriented, always with regard to the assembled state shown in Fig.

1, with its base 7 directed downwards. Obviously, note also that in order to be able to insert the two rails 2 and 3 between the two C-channels, or section bars, forming the lateral guides 1, 1', the inner width (free inner space) between these latter guides must necessarily be greater than the external width of the rails 2 and 3.

While the upper rail 2 is fixed (stationary), as has already been said, the bar-handle is vertically movable within the lateral guides 1, 1'.

In order to fix the upper box (or box-type element) between the upper ends of the guides 1,1', two upper plugs, like the one denoted by numeral 10 in Fig. 1, are used,

and these plugs are inserted from above inside the upper ends of the lateral guides 1, 1'. These upper plugs 10 engage with complementary pieces (not shown) that are integral with the upper rail 2 at its two extremities. This type of removable restraint is not described in detail, also in view of the fact that several other fixing systems for the upper rail 2 could be used in its place.

The pleated curtain 11 is located between the horizontal rails 2 and 3; it has several rectangular portions with circular holes 12 (only some of which are indicated by the numeral 12 in Fig. 1 for simplifying the drawing). The holes 12 are arranged along vertical and equidistant rows. The embodiment of the device shown in Fig. 1 includes five vertical equidistant rows of holes 12. Each rectangular portion of pleated cloth 11 consequently includes a horizontal row of five equidistant holes 12.

In the background art, pleated curtains are folded on themselves in a"squeezebox" fashion by acting on a pulley system which lifts the curtain by means of a series of threads passing through a plurality of vertical holes totally similar to the holes 12.

Obviously, these threads are fixed, independently of each other, to the lower margin of the curtain, in order to allow its lifting operation to be performed.

The system adopted by the present invention is completely different. In the present invention, the device is of a"self-locking"type ; this means that the user needs only to move the bar-handle upwards or downwards, and the latter will remain exactly in the position where the user left it, thereby avoiding the need of locking-each time- the lateral threads, in contrast with the prior art. Moreover, the inventive system consists of a device with lateral guides (1, 1') which determines a perfect verticality of the curtain and which prevents the curtain from coming out of the guides. In what follows we will describe the details of the device according to the present invention, which allow this kind of operation. Several pulleys are arranged inside the bar- handle. The pulleys are aligned with the rows of vertical holes 12. In the embodiment shown in Fig. 1 there are two lateral pulleys 13 and three intermediate pulleys 14, which are arranged in equidistant positions. Fig. 5 shows various views of a lateral

pulley 13, while Fig. 6 shows various views of an intermediate pulley 14. The mounting positions of the pulleys inside the bar-handle are highlighted by their numerals in Fig. 1. Moreover, at the lower ends of the lateral guides 1, 1' there are two respective thread-locking means 15, whose"L-configuration"is clearly shown in Fig. 8. The mounting position of these two thread-locking means 15 is also shown in Fig. 1.

Within the upper box-type element there are fixed several conical helical springs 16 (see Fig. 1). Specifically, the base of each spring 16 is fixed to the base 7 of the inner core 4 of the upper box-type element. Moreover, the axis of each conical spring 16 coincides with the straight line defined by the respective row of holes 12. In the illustrated embodiment there are five springs 16, corresponding in number to the row of holes 12 and to the total number of pulleys 13,14. The positions of the springs 16 are clearly indicated in Fig. 1.

Observe that even the circular holes 8 of the base 7 of the core 4 associated with the upper rail 2, and those of the base 7 of the core 4 associated with the lower rail 3, are all aligned with the vertical row of holes 12. In addition, note that the fabric 11 is obviously fixed to both rails 2 and 3 at its respective upper and lower sides.

The device of the present invention, to be able to operate, also includes a plurality of threads. Starting from the embodiment shown in Fig. 1 in order to understand the way it functions, note that there are six threads in total, three on one side and three on the other side of the central row of holes 12. The three threads on the right are grouped together and locked, at one end, by the right-side thread-locking means 15.

The first thread 17 of these threads 17, 17'and 17", extends vertically, starting from the thread-locking means 15, and it reaches the apex of the respective conical helical spring 16. Moreover, it is fixed to this apex of this conical helical spring 16.

Additionally, it completely extends inside the lateral guide 1'and it traverses all the holes of the row of holes 12 situated on the right side, in addition to the right hole 8 of the core 4 of the bar-handle and the right hole 8 of the core 4 associated with the

upper box.

The second thread 17'extends from the right-side thread-locking means 15, and its path is first modified (from vertical to horizontal) by the right-side lateral pulley 13, and thereafter, it is again modified (from horizontal to vertical) by the right-side intermediate pulley 14, located between the central intermediate pulley 14 and the right-side lateral pulley 13.

Similarly, the third thread 17"of the right-side group of threads, extends from the right-side thread-locking means 15, and its path is first deviated (from vertical to horizontal) by the right-side lateral pulley 13, and then (from horizontal to vertical) by the central intermediate pulley 14.

The threads 17'and 17"are also fixed-at their opposite ends-to the apex of the respective helical conical springs 16, and extend along the axis of these springs 16 (as shown in Fig. 1). Moreover, these threads also pass through two other respective rows of holes 12 provided in the fabric 11, and through the corresponding holes 8 provided in the core 4 of the bar-handle and of the upper box-type element.

Due to device symmetry, the threads 18, 18'and 18"on the left side similarly extend from the left-side thread-locking means 15 to the vertexes of corresponding conical helical springs 16, passing through the holes 12 of the three left-side rows and the corresponding holes 8.

Thus, in their horizontal path, the threads 17', 17"and 18', 18"completely extend within the bar-handle, thereby improving the outer appearance of this product.

Similarly, the thread 18, in its completely vertical path, only extends inside the lateral guide 1. Consequently, no thread remains visible from the outside. From the preceding description it also follows that the central row of holes 12 is traversed by two threads, that is, by the threads 17"and 18", whose upper ends are fixed to the vertex of the same (central) spring 16.

Note that we have used the wording"the three left-side rows of holes 12", although, obviously, one of these rows coincides with the central row of holes 12, since the

number of rows of holes 12 in this embodiment is five.

We will describe next in more detail, only for illustrative and non-limitative purposes, the exact configuration of the pulleys 13 and 14.

These pulleys have a double function. On the one hand they are used to change the direction of the path of some of the threads, while guiding the others without changing their direction (path), and on the other hand, they must maintain a'safety distance'between the various threads that pass through them, in order to avoid a mutual interference of these threads that would lead to an anomalous operation or to the disruption of the device according to the present invention. For instance, if we take the right-side intermediate pulley 14, it must deviate the path of the thread 17' (from horizontal to vertical) and simply guide the thread 17"along its horizontal path, maintaining at the same time a minimum distance between these two threads, in order to prevent them from interlacing (getting entangled). With reference to Fig. 6 and Fig. 1, the pulley 14 includes six rollers that are mounted on the axes a, b, c, d, e, f, respectively. The pulley also has an inverted"U"configuration, and an upper hole 19 for the passage of the thread 17'. Laterally, the pulley is open, to allow the passage of the threads 17'and 17". More specifically, the roller mounted on the axis b acts as a direction-changing roller, and the thread 17'passes through the couple of rollers mounted on the axes a and b. Additionally, the thread 17"continues on its straight path and passes above the couple of rollers mounted on the axes e, f and beneath the couple of rollers mounted on the axes c, d.

As concerns the left-side intermediate pulley 14, its function is identical to the function of the right-side intermediate pulley 14, being the device symmetrical with respect to the axis defined by the central row of holes 12. This pulley is used for modifying the path of the thread 18', and for letting the thread 18"pass through the thread-guiding means formed by the rollers mounted on the axes c, d, e, f, the latter acting also as spacers in order to prevent any interference between the threads 18', 18".

On the contrary, in the present embodiment, the central pulley 14 only serves the purpose of modifying the direction of both threads 17"and 18". Therefore, it could comprise only the means for redirecting the threads (rollers mounted on the axes a and b, thereby excluding the thread-guiding means (rollers related to the axes c, d, e, f. However, it is clear that a rationalisation of the production processes imposes a minimisation of the number of pulleys with different configurations.

With regard to the two lateral pulleys 13, they have on their bases a plurality of holes 22 for allowing the passage of the threads 17, 17', 17"and 18,18', 18" respectively; an upper hole 21 for the passage of the thread 17 (and respectively 18) ; and finally, two axes g, h for two corresponding rollers used to redirect the threads 17', 17" (and respectively 18', 18").

The lateral pulley 13 has a box-type structure in this embodiment.

The operation of the device according to the present invention will be described next.

When the user acts on the bar-handle in order to lift or to lower the pleated curtain, the threads slide through the various pulleys and through the holes 12 of the pleated fabric 11.

By selecting an adequate value for the weight of the bar-handle, it is clear that the inevitable frictional forces opposing the downward sliding motion of the curtain, will be able to overcome the overall weight force of the bar-handle and its pulleys. Thus, a"self-locking effect"will be achieved, that is, the curtain will remain in the position corresponding to the position at which the bar-handle is released by the user.

The function of the springs 16 is to compensate for the elongation and shortening of the threads 17,17', 17", 18,18', 18", caused by temperature variations especially between the summer and winter. Moreover, their function is to counterbalance the different elongation of the threads occurring during an extended use of the device, due to the fact that these threads are obviously subjected to stresses and have different lengths (e. g. the thread 17"is clearly longer than the thread 17'); this measure is taken in order to avoid an entangling of the threads deriving from their

possible slackening (that should be prevented).

The reason why a conical spring 16 is preferably used in place of a cylindrical helical spring is that the maximum inflexion of the spring corresponds to its height in case of a helical conical spring. This also allows to reduce the height of the upper box-type element, with obvious advantages under the aesthetic point of view, through the optimisation of the"stroke"of the spring (which equals 2 cm in this embodiment).

The present invention is obviously applicable also to curtains used to darken a room.

In this case the pleated fabric is coupled to a thin film of PVC. In the application directed to common curtains (that is not those used for darkening a room), the threads 17 to 18"are preferably formed by interlaced polypropylene filaments. In the application directed to curtains used for darkening a room, in order to avoid the penetration of light through the holes 12 of the curtain 11, the threads preferably will have a certain degree of hairiness. Moreover, both in the application of the invention related to darkening curtains, and in that related to usual curtains, it is possible to use already known small lateral brushes on the bottom (base) of the lateral guides 1, 1', this measure being taken in order to prevent: (i) the passage of light (for curtains used to darken a room); (ii) the entrance of ants or of other insects (in both cases).

The present invention may also be applied to mosquito curtains. According to the prior art, as has been said above, often a system involving a wrapping roller, used to roll up the planar net fabric of conventional mosquito curtains (mosquito nets), is too cumbersome and cannot be installed between the window and the (rolling) shutter.

Using a device according to the invention, in which the fabric 11 forms a net-like fabric which is pleated and dressed, one obtains a mosquito curtain based on an innovative concept. The dimension of this device in the direction of its depth (that is, its thickness measured in the direction orthogonal to the plane of Fig. 1) may reach minimal values without affecting at all the functionality of the device (e. g. this thickness or depth may be 16 mm). This is due to the fact that the fabric is not rolled

up on a roller, but is vertically folded on itself in a"squeezebox fashion", thereby minimising the required space.

Still another advantage of the present mosquito curtain is that in contrast to traditional mosquito curtains including a roller, in which the planar net fabric could easily come out of the lateral guides, in the present invention the threads 17 to 18" preserve the verticality of the net (preventing it from bulging due to wind gusts) and particularly, the threads 17 and 18 prevent the net from coming out of the guides.

Also in this kind of mosquito net, known lateral small brushes are preferably used in order to avoid the entry of insects.

Note that the present invention-in its specific application to mosquito nets-may be applied directly, because mosquitoes only fly but do not walk, as reported by those who study their behaviour, and for this reason it is practically impossible for them to penetrate through the tiny holes 12 of the pleated net fabric.

The present invention has been described in detail only for illustrative purposes, with reference to its preferred embodiment shown in Figs. 1-9, in order to let the average skilled person understand how the invention may be put into practice. However, it is clear that the average skilled person may easily modify the preferred embodiment shown in the drawings, without departing from the scope of the invention and from its inventive concept.

For example, the helical springs 16 could be replaced by other suitable and adequately calibrated elastic means insuring a"stroke"identical to that of the springs 16. These elastic means are preferably included in order to insure a lasting operation of the device; nonetheless, the device could function even if they were omitted, although for a much shorter period of time.

Moreover, in an alternative embodiment, the pulleys could be mounted inside the upper box-type element, and the elastic means inside the bar-handle (that is, the opposite of the preferred embodiment), by appropriately changing the paths of the threads.

The rollers used for redirecting the threads could be idly or rigidly mounted on the devices 13,14 for guiding and redirecting the threads, using-in case they are rigidly mounted-a material which guarantees a minimum friction. Preferably, all rollers that are mounted on the axes a, b, c, d, e, f, g, h are made of moulded polypropylene and are idly mounted-so as to be able to rotate-on the respective pulleys 13,14.

Turning again our attention a last time to the preferred embodiment, the following should be noted. In general, the number of threads 17 to 18"is not binding and normally will vary according to the width of the window. It is obvious that if with respect to the embodiment of Fig. 1 it is required to use a greater number of threads, then it will also be necessary to increase the number of thread-guiding means, since for instance the right-side intermediate pulley 14 must then allow the passage, through the same and along a rectilinear path, of at least a further thread (in addition to the thread 17"). All these considerations regard alternative designs that are straightforward for a skilled person. In case it is desired to avoid (see Fig. 1) that the two"central"threads 17"and 18"extend along the same path (in the last vertical portion thereof), and in order to prevent them from getting entangled, according to a further preferred embodiment (not shown) two separate pulleys for redirecting the path of the threads 17"and 18"could be provided in place of the single central intermediate pulley 14, and accordingly, two separate springs could also be provided in place of the single central spring 16. In this case too, the device of the present invention would preserve its symmetry.

We will now refer to Figs. 10,11, 12 to describe an alternative embodiment that does not modify at all the present inventive concept, but which concerns an application in which the handle-bar slides horizontally. This application mainly but not exclusively refers to a French window.

In this embodiment the handle-bar 103 is movable between two vertical uprights, or posts, 102 and 100, wherein the starting post (or opened-position post) 102 corresponds to the upper box-type element (2,4) of the previous embodiment and is

fixed at one side of the French window, while the final upright (closed-position upright or post) 100 is fixed at the opposite side of the French window (the arrow F denotes the closing direction in Figs. 10 and 11).

The bar-handle 103 slides within two lateral guides 101, 101' (whose function corresponds to that of the previous lateral guides 1,1'), which are obviously horizontal in this embodiment, and which are fixed at the upper and lower side respectively of the French window.

This variant, that seems obvious, includes two improvements, shown in Figs. 10-12, which will be described next.

To prevent the bar-handle 103 from accidentally coming out of these lateral guides 101, 101', there is provided, on both sides of the bar-handle, a system formed by a runner and a runner support, whose specific parts are clearly shown in the detail of Fig. 12.

The system formed by the runner and the runner support will only be described with reference to the lateral (lower) guide 101', since this system is perfectly "symmetrical".

The system includes two lateral runner supports, 104 and 104', which are slidable within respective grooves 105 (only one of which is visible in Fig. 12) obtained on the bar-handle 103. A locking screw (not shown) may be inserted in a slot 106 in order to lock the runner support 104, or 104', to the bar-handle 103, in a predetermined position.

Each runner support 104, 104'of the system sustains a respective runner 107,107' which is capable of easily sliding (under a low friction) along the upper edges of the guide 101'.

If the guide 101'is made of aluminium, the runners 107,107'could be made of nylon (it being understood that particular materials are not binding for the present patent application).

The runners 107, 107'are mounted on a"sprung system", consisting of elastic

suspensions, on the respective runner support 104,104', so as to be able to easily slide even when the user exerts a force on the bar-handle that is not perfectly horizontal.

Thus, the described system, which is identical to the system situated on the upper side of the bar-handle 103 (and which is associated to the guide 101), has the double function to prevent the bar-handle 103 from coming out of the lateral guides 101, 101', and to facilitate the sliding motion of the bar-handle 103 by virtue of the presence of the anti-friction means (runners) 104, 104'and of the suspensions. To prevent the bar-handle from coming out of its guides 101, 101', during assembling the system consisting of the runner and runner support is moved along the guides 105 and is locked in the desired position, this being done-obviously-after the insertion of the ends of the bar-handle 103 inside the lateral guides 101, 101'.

The flanges 108 of the runners insure at the same time a smooth and rectilinear sliding displacement of the bar-handle 103.

The system that has just been described could obviously also be provided in case of a bar-handle which slides vertically, such as in Fig. 1.

The variant shown in Figs. 10 to 12 solves another problem too.

In Fig. 12 one may note that longitudinal grooves 109, which are very narrow, have been obtained within the lower guide 101', near its upper edges 110, on both sides of this guide 101' (it should be noted that corresponding guides 109 are also provided inside the lateral guide 101, although they remain hidden in the drawing).

Looking at Fig. 11 it can be noted that two small metallic bands or webs 111 are slidable within the longitudinal grooves 109 of the guide 101 and of the guide 101' respectively, wherein these small bands 111 are fixed at one end 112 to the bar- handle 103, while their opposite ends 113 are free. Two rollers 114 for redirecting the path of the metallic webs 111 are used to deviate these webs towards an inner guide 115 obtained in the final upright 100.

The operation is as follows.

In the region 116 occupied by the pleated fabric and which is bounded by the bar- handle 103 and by the starting upright 102, the guides (or C-shaped channels) 101' and 101 remain uncovered, while in the region 117, which is not occupied by the fabric, these guides are always covered, for every position of the bar-handle 103, by the above mentioned flexible and small metallic webs 111 which slide (during the displacement of the bar handle 103) within the grooves 109 and 115.

Consequently, it is possible to prevent an accumulation of dirt or of any kind of substance in the guides 101, 101', that could possibly hinder the sliding displacement of the bar-handle.

In practice, the two small metallic bands or webs 111 are comparable to two flexometers made of hardened steel, which could hardly come out of their grooves 109 except in case of intentional tampering.

Note that, since the region 117 corresponds, for a French window, to a region used as a passage, undesired material or dirt could easily accumulate inside the guide 101'.

The present invention puts this defect right.