Field of application of the invention

The present invention refers to the field of movable blinds placed inside "double glazings", i.e. structures comprising at least two mutually parallel glass sheets supported by a frame interposed therewith.

The movable blinds housable in the double glazings are of various types, for example: with roller, pleated, with vertical strips, with panels, Venetian, etc. The present invention has application in reference to blinds comprising elements extended lengthwise, mutually parallel, and to which it is possible to impart both a translational motion parallel to the two glass sheets between which said elements are moved, and a rotary motion around a respective longitudinal axis due to which the orientation of said movable elements is modified in space. By way of example, among the blinds belonging to this category, there are the Venetian blinds and the blinds with vertical strips.

Hereinbelow in the present description: with the word "blind" it is intended to identify all the blinds belonging to the aforesaid category; with the word "slats" it is intended to identify the longitudinal elements of the blind that are translatable and rotatable with respect to the double glazing in which the blind is housed. More precisely, the invention refers to a device that allows adjusting the orientation of the slats of a blind placed inside a double glazing. The invention also refers to a blind placed inside a double glazing and equipped with said device. Review of the prior art

In blinds housed inside double glazings, the device through which the transla- tional movement of the slats is controlled between the two glass sheets generally also acts as control device for the rotary motion of the slats around the longitudinal axis thereof. In other words, with reference to a Venetian blind in which the slats translate vertically, the orientation of the slats is generally adjusted with the same device that controls the raising and lowering of the slats (and hence of the blind) within the double glazing.

This is due to the fact that a blind placed inside a double glazing generally comprises a single group for moving the slats, structured in a manner such that the translation and the rotation of the slats occur due to the rotation of a single shaft, preferably parallel to the slats. Around said shaft, at least one first support cord for the slats is wound and unwound. In addition, at least one pulley is fit to said shaft; on such pulley, a second cord for orienting the slats is partially wound, such cord integrally connected with all the slats and the translation thereof causes the rotati5on of the slats. The actuation of the movement group initially causes the rotation and simultaneous translation of the slats, and subsequently only the translation thereof. The group for moving a blind briefly described herein is of substantially known type, hence further details thereof will not be provided.

The devices for controlling the actuation of the group for moving a blind are of various types. Among these devices, there are the devices with "continuous" cord (i.e. a cord having two ends joined together so as to form a ring) and the devices with translating slider.

The continuous cord control devices comprise a cord ring placed outside the double glazing and maintained taut by a pair of coplanar pulleys, also outside the double glazing, around each of which the cord is wound for a section equal to half a circumference. One of the two pulleys is pivoted to the double glazing and is magnetically coupled to the group for moving the slats placed inside the double glazing. Hereinbelow in the present description said pulley is identified with the expression "drive pulley". The second pulley is idle and, serving to keep the cord taut, is indicated hereinbelow in the present description with the ex- pression "tensioning pulley". The drive pulley has a groove for housing the cord section wound around the pulley. The width of the groove is less than the diameter of the cord and the tension produced by the tensioning pulley is such to force the cord inside the groove in a manner such that the cord is integrally connected with the drive pulley at the section where they are in contact. This ensures that by applying a force at one of the two cord sections that join the pulleys, a torque is generated that tends to rotate the drive pulley. Such torque is transmitted to the movement group by suitable transmission means, so as to cause the rotation and the translation of the slats.

The translating slider control devices lack drive pulley and comprise at least one tensioning pulley inside the double glazing and pivoted to a slide, also situated inside the double glazing, translatable preferably vertically by means of a grip placed outside the double glazing and magnetically coupled to said slide. In the control devices of the aforesaid type, a cord of the movement group for the blind is wound around the tensioning pulley for a section equal to at least half a circumference. By making the slide translate by grasping the grip, the translation of the pulley is obtained and by means of the cord, the actuation of the blind movement group is obtained.

Incidentally, in both control device types, as in the blind movement group, as an alternative to the cord it is possible to employ another flexible member extended lengthwise, such as a chain. In such case, the pulleys and the return elements are toothed wheels. Hereinbelow in the present description, with the word "cord" it is intended to identify all the flexible members extended lengthwise of the aforesaid type.

As previously mentioned, in the current double glazings including blinds, the rotation of the drive pulley in the continuous cord control devices and the translation of the slide in the translating slider control devices initially cause the rotation and simultaneous translation of the slats, and subsequently only the translation thereof. In order to adjust the orientation of the slats, it is therefore necessary to lightly pulling the cord in the continuous cord control devices, or slightly move the slide in the control devices with translating grip. In such a manner, however, the adjustment of the orientation of the slats cannot be precisely car- ried out.

In order to remedy such drawback, a blind has been ideated that is placed inside a double glazing and equipped with two separate groups for moving the slats: a first group whose actuation causes the translation of the slats and a second group whose actuation causes the rotation of the slats. The actuation of the two movement groups is controlled by two respective devices. Each movement group comprises a shaft preferably parallel to the slats. The shaft of the translation group is connected to the support cord for the slats. The shaft of the rotation group is connected to the cord for orienting the slats.

The device for controlling the actuation of the rotation group for the slats comprises a cord ring placed inside the double glazing and maintained taut by a pair of coplanar pulleys, also situated inside the double glazing; the cord is wound around each pulley for a section equal to half a circumference. One of the two pulleys is coupled to the shaft to which the slat orientation cord is connected. The pulleys have a groove for housing the section of the cord wound around the same. The width of the groove is less than the diameter of the cord and the tension of the cord is such to force the latter inside the grooves, in a manner such that the cord is integrally connected to the pulleys at the section where they are in contact. The cord is also integrally connected to a slide inside the double glazing and translatable parallel to the cord by means of a grip placed outside the double glazing and magnetically coupled to said slide. By making the slide translate by grasping the handle, one obtains the translation of the cord and thus the rotation of the shaft to which the slat orientation cord is connected. The rotation of the shaft causes the rotation of the slats.

The presence of two devices for respectively controlling the translation group and the rotation group for the slats however implies, given the same space oc- cupiable by the double glazing, a considerable reduction of the area of the glass sheets and therefore a reduction of the opening of the double glazing (i.e. referring to a double glazing in which glass sheets and the control devices are vertically arranged, the horizontally-measured distance between the vertical edges of either glass sheet).

Objects of the invention Object of the present invention is to overcome the aforesaid drawbacks and to indicate a blind in which the presence of a device for controlling the rotation of the slats, separate from a device for controlling the translation thereof, does not further reduce the opening of the double glazing, i.e. it does not involve a reduction of the opening in addition to the reduction implied by the presence of the device for controlling the translation of the slats.

Summary of the invention

Object of the present invention is a device for controlling the actuation of a first group for moving at least one slat of a blind, the slats being placed inside a double glazing and being rotatable and translatable with respect to the double glazing, the actuation of said first movement group causing the rotation of the slats;

said blind comprising a device for controlling the actuation of a second group for moving the slats, the actuation of said second movement group causing the translation of the slats;

the device for controlling the rotation of the slats comprising:

first graspable means by a user of the blind, said first graspable means being placed outside the double glazing and being movable with respect to the double glazing by said user;

• first means for transmitting the motion of the first graspable means to the first movement group thus causing the actuation thereof, said first transmission means being placed inside the double glazing;

• first means for coupling between the first graspable means and the first transmission means;

the device for controlling the translation of the slats comprising:

• second graspable means by said user, said second graspable means being placed outside the double glazing and being translatable with respect to the double glazing by said user;

• second means for transmitting the translational motion of the second graspable means to the second movement group thus causing the actuation thereof, said second transmission means being placed inside the double glazing; • second means for coupling between the gnppable second means and the second transmission means;

wherein according to the invention:

• the first graspable means comprise a knob connected to the second grasp- able means by means of first means suitable for allowing the rotation of the knob around an axis thereof;

• the first transmission means being for transmitting the rotary motion of the knob to the first movement group;

• the first coupling means being magnetic coupling means.

Advantageously, the fact that the knob is connected to the grippable second means allows optimizing the bulk of the two devices for controlling, respectively, the rotation and the translation of the slats.

Further innovative characteristics of the present invention are described in the dependent claims.

According to one aspect of the invention:

• the second transmission means comprise a slide translatable with respect to the double glazing and coupled, by means of the second coupling means, to the second graspable means, the translation of the second graspable means causing the translation of the slide;

• the first coupling means comprise a first magnet and a second magnet which are magnetically attracted to each other, the first magnet being placed outside the double glazing and being integrally connected to the knob, the second magnet being placed inside the double glazing and being rotationally coupled to the first transmission means, the second magnet being connected to the slide by means of second means suitable for allowing the rotation of the second magnet around an axis thereof, the first and the second magnet being mutually opposite, a wall of the double glazing being interposed between the first and the second magnet, said magnetic attraction being of size such that the rotation of the knob causes the rotation of the second magnet.

The second magnet can therefore carry out a rototranslational movement: it translates together with the slide due to the application of a translating force to the second graspable means (in order to control the translation of the slats) and rotates together with the first magnet due to the application of a torque to the knob (in order to control the rotation of the slats).

Advantageously, given that the coupling between the knob and the first transmission means is magnetic, even though the knob is placed outside the double glazing and the first movement group is placed inside the double glazing, the rotation of the knob is transmitted to the first movement group without any hole being made in the walls of the double glazing.

According to another aspect of the invention, said wall of the double glazing interposed between the first and the second magnet is a glass sheet.

Advantageously, given that the glass is a diamagnetic material, it interferes only minimally with the magnetic attraction between said first and second magnet. According to another aspect of the invention:

• the first transmission means comprise a shaft connected to the double glazing by means of third means suitable for allowing the rotation of said shaft around an axis thereof, the shaft being rotationally coupled to the first movement group such that the rotation of the shaft causes the actuation of the first movement group;

• the first transmission means also comprise a first toothed wheel connected to the slide by means of fourth means suitable for allowing the rotation of the first toothed wheel around an axis thereof, the first toothed wheel being rotationally coupled, by means of the first coupling means, to the knob, the first toothed wheel also being rotationally coupled to the shaft.

The first toothed wheel can therefore complete a rototranslational movement: it translates together with the slide due to the application of a translating force to the second graspable means (in order to control the translation of the slats) and rotates together with the knob due to the application of a torque thereto (in order to control the rotation of the slats). During the translation, the first toothed wheel remains rotationally coupled to the shaft. The rotation of the knob therefore causes, by means of the first coupling means and the first toothed wheel, the rotation of the shaft and hence the actuation of the first movement group, independent of the position occupied by the slide (and thus by the grippable second means) with respect to the double glazing. According to another aspect of the invention, the rotation axis of the shaft is arranged parallel to the direction in which the translation of the slide occurs.

According to another aspect of the invention:

• the first toothed wheel is integrally connected to the second magnet, the rotation of the second magnet causing the rotation of the first toothed wheel;

• the first transmission means also comprise a second toothed wheel connected to the slide by means of fifth means suitable for allowing the rotation of the second toothed wheel around an axis thereof, the second toothed wheel having at least one through hole, the shaft traversing the second toothed wheel at said hole, the second toothed wheel being slidable on the shaft and being rotationally coupled thereto, the second toothed wheel engaging the first toothed wheel so as to be rotationally coupled to the knob.

The rotary motion of the knob is therefore transmitted, in the following order, to: the first magnet, the second magnet, the first toothed wheel, the second toothed wheel, the shaft, and the first movement group; thus causing the actuation of the latter.

According to another aspect of the invention, the fifth connection means comprise a seat for housing the second toothed wheel, said seat being obtained in the slide and being traversed by the shaft.

According to another aspect of the invention, the rotation axis of the shaft coincides with the rotation axis of the second toothed wheel.

According to another aspect of the invention, the shaft has a first cross section that does not vary along the rotation axis of the shaft, said hole of the second toothed wheel having a second cross section complementary to said first cross section, said first and second cross sections being non-circular.

Another object of the invention is a blind comprising:

• slats placed inside a double glazing, the slats being rotatable and translatable with respect to the double glazing;

• a first movement group for the slats, the actuation of said first movement group causing the rotation of the slats;

• a second movement group for the slats, the actuation of said second movement group causing the translation of the slats; • a device for controlling the actuation of the first movement group;

• a device for controlling the actuation of the second movement group;

the device for controlling the rotation of the slats comprising:

• first graspable means by a user of the blind, said first graspable means being placed outside the double glazing and being movable with respect to the double glazing by said user;

• first means for transmitting the motion of the first graspable means to the first movement group thus causing the actuation thereof, said first transmission means being placed inside the double glazing;

• first means for coupling between the first graspable means and the first transmission means;

the device for controlling translation of the slats comprising:

• second graspable means by said user, said second graspable means being placed outside the double glazing and being translatable with respect to the double glazing by said user;

• second means for transmitting the translational motion of the second graspable means to the second movement group thus causing the actuation thereof, said second transmission means being placed inside the double glazing;

• second means for coupling between the second graspable means and the second transmission means;

wherein according to the invention:

• the first graspable means comprise a knob connected to the second graspable means by means of first means suitable for allowing the rotation of the knob around an axis thereof;

• the first transmission means being for transmitting the rotary motion of the knob to the first movement group;

• the first coupling means being magnetic coupling means.

Brief description of the figures

Further objects and advantages of the present invention will be clearer from the following detailed description of an embodiment thereof and from the enclosed drawings, given as a mere non-limiting example, in which: - figure 1 is a perspective view of a Venetian blind placed inside a double glazing and provided with a device for adjusting the orientation of the slats according to the present invention;

- figure 2 is a closer view of the device of figure 1 ;

- figure 3 is a front plan view of several components of the Venetian blind and of the device of figure 1 ;

- figure 4 is a front perspective view of the device of figure 1 , partially exploded;

- figure 5 is a rear perspective view of the device of figure 1 , partially exploded.

Detailed description of several preferred embodiments of the invention

In the present description, to facilitate the description, reference is only made to a preferred embodiment of the invention in which the device for controlling the rotation of the slats is applied to a Venetian blind. It must be clear that the described device is not limited to the aforesaid embodiment but is applicable to any blind with movable elements belonging to the aforesaid category, such as a blind with vertical strips.

In the present description, a figure can also be illustrated with reference to elements not expressly indicated in that figure but in other figures. The scale and proportions of the various depicted elements do not necessarily correspond with the actual scale and proportions.

With reference to figures 1 and 2, a structure 1 is illustrated known as a "double glazing" and comprising two mutually parallel glass sheets 2 and 3 supported by a frame 4 partially interposed between them. By way of example, the glass sheets 2 and 3 are vertically arranged and the frame 4 is metallic. Incidentally, the latter can also be made of other materials, for example plastic or rubber materials. The glass sheets 2 and 3 delimit, together with the frame 4, a parallelepiped chamber within which a Venetian blind 5 is placed. The blind 5 comprises a multiplicity of slats 6 arranged, by way of example, horizontally and movable with respect to the double glazing 1. In particular, the blind 5 comprises a first movement group suitable for rotating the slats 6 around a respective longitudinal axis, and a second movement group suitable for translating the slats 6 parallel to the glass sheets 2 and 3. Incidentally, the actuation of the first movement group modifies the orientation of the slats 6 with respect to the double glazing 1 ; the actuation of the second movement group causes what is usually indicated as "lowering" or "raising" of the blind 5. Hereinbelow in the present description: the first movement group will be identified with the expression "rotation group for the slats"; the second movement group will be identified with the expression "translation group for the slats".

The rotation group for the slats 6 comprises two cords 7a and 7b arranged, by way of example, vertically; each of the cords is transversely connected to all the slats 6 at a respective longitudinal edge thereof. Hereinbelow in the present description, the cords 7a and 7b will be indicated with the expression "ladder-like cords".

The translation group for the slats 6 comprises two cords 8a and 8b arranged, by way of example, vertically, each of the cords transversely crosses all the slats 6 at a respective hole 9. The slats 6 therefore comprise two vertical sequences of holes 9, each of which traversed by one of the two cords 8a and 8b. The latter are integrally connected, at a respective end 34 and 38, to the slat that, in the group slats 6, is in the figure placed at the lowest height. This slat will hereinbelow in the present description be indicated with the reference number 13 and will be called the "bottom" slat.

With reference to figures 1 and 2, it is also possible to observe a slider 10 with nearly parallelepiped shape placed outside the double glazing 1 and translatable along a wall 11 thereof. Preferably, the wall 11 is arranged vertically and the slider 10 is vertically translatable on said wall 11. By way of example, the wall 11 is extended lengthwise to form a strip, it is parallel to the glass sheet 2, and it is adjacent to the latter at a lateral edge 12 of the sheet 2. As will be illustrated with reference to figure 3, the slider 10 acts as a device through which the actuation of the translation group for the slats 6 is controlled. In particular, a user of the blind 5, in order to control the raising or lowering of the slats 6, grasps the slider 10 and translates it on the wall 11 , respectively downward or upward.

A knob 15, preferably circular, is pivoted to the slider 10 at one face of the slider 10 not opposite the double glazing 1. In such a manner, the knob 15 can be grasped by the user of the blind 5. Preferably, the knob 15 is vertically arranged and is rotatable around an axis arranged orthogonal to the wall 11. As will be illustrated with reference to figures 4 and 5, the knob 15 acts as a device through which the actuation of the rotation group for the slats 6 is controlled. In particular, the user of the blind 5, in order to adjust the orientation of the slats 6, grasps the knob 5 and rotates it in one direction or in the other.

With reference to figure 3, a slide 20 is illustrated that is placed inside the double glazing 1 and translatable in the same direction in which the translation of the slider 10 occurs. The slide 20 is opposite the slider 10 and is coupled thereto by means of a pair of magnets 21 and 22 which attract each other. The magnet 21 is placed inside the double glazing 1 and is integrally connected to the slide 20. The magnet 22 (visible in figure 5) is placed outside the double glazing and is integrally connected to the slider 10. The magnets 21 and 22 are mutually opposite and the magnetic attraction between the same is of size such to ensure that the translation of the slider 10 set by the user of the blind 5 causes the translation of the slide 20. The wall 11 is interposed between the slider 10 and the slide 20, and hence also between the two magnets 21 and 22. The wall

11 is preferably made of diamagnetic material, such that it does not interfere with the magnetic field between the two magnets 21 and 22. By way of example, said wall 11 could be one of the two glass sheets 2 and 3.

The slide 20 is slidable on a shaft 23, preferably vertically arranged. The shaft 23 therefore acts as a guide both for the slide 20 and, due to the magnetic coupling, for the slider 10.

Two idle pulleys 24 and 25 (more visible in figure 5) are pivoted on the slide 20 at a portion 26 of the latter that is higher in the figure. Preferably, the pulleys 24 and 25 are arranged vertically, they are rotatable around an axis arranged orthogonal to the wall 11 , they are mutually opposite and they are coaxial. The cords 8a and 8b of the translation group for the slats 6 are respectively partially wound around the pulleys 24 and 25. In particular, the path of the cords 8a and 8b inside the double glazing 1 is the following.

The cord 8a is integrally connected at one end 30 thereof, to the frame 4 at a portion 31 thereof in the figure placed at a greater height than the pulleys 24 and 25 when the slide 20 is at the upper end stop. Starting from said end 30, the cord 8a descends, preferably vertically, towards the pulley 24; it passes under the pulley, partially winding around it and re-ascends, preferably vertically, towards the upper portion 31 of the frame 4. Subsequently, the cord 8a passes over a first transmission element 32 (figure 3) before proceeding, preferably nearly horizontally, towards a second transmission element 33 vertically aligned with the first sequence of holes 9 of the slats 6 (sequence placed on the right in figure 3). The cord 8a passes over the second transmission element 33 before descending, preferably vertically, towards the bottom slat 13, traversing the slats 6 at the holes 9 of said first sequence. As stated above, the cord 8a is integrally connected, at the other end 34, to the bottom slat 13.

In an entirely equivalent manner, the cord 8b is integrally connected, at one end 35 thereof, to the upper portion 31 of the frame 4. Starting from said end 35, the cord 8b descends, preferably vertically, towards the pulley 25; it passes under the pulley, partially winding around it, and re-ascends, preferably vertically, towards the upper portion 31 of the frame 4. Subsequently, the cord 8b passes above a third transmission element 36 before proceeding, preferably nearly horizontally, towards a fourth transmission element 37 vertically aligned with the second sequence of holes 9 of the slats 6 (sequence placed on the right in figure 3). The cord 8b passes above the fourth transmission element 37 before descending, preferably vertically, towards the bottom slat 13, traversing the slats 6 at the holes 9 of said second sequence. As stated above, the cord 8b is integrally connected, at the other end 38, to the bottom slat 3.

With regard to the functioning, given that the cord 8a is integrally connected to the upper portion 31 of the frame 4 at the end 30, and to the bottom slat 13 at the other end 34, the downward translation of the slide 20 (figure 4) causes the elongation of the two sections of cord 8a respectively comprised between the end 30 and the pulley 24 and between the pulley 24 and the first transmission element 32. Analogously, given that the cord 8b is integrally connected to the upper portion 31 of the frame 4 at the end 35, and to the bottom slat 13 at the other end 38, the downward translation in the figure of the slide 20 causes the elongation of the two cord sections 8b respectively comprised between the end 35 and the pulley 25 and between the pulley 25 and the third transmission element 36. The downward translation in the figure of the slide 20 thus causes an upward of the bottom slat 13. The slats 6 are progressively set on the bottom slat 13 while this translates upward in the figure, thus causing the raising of the blind 5. In an equivalent manner, an upward translation in the figure of the slide 20 causes a downward translation of the bottom slat 13. The slide 20 and the pulleys 24 and 25 therefore transmit the translational motion of the slider 10 to the cords 8a and 8b (i.e. to the translation group for the slats 6).

With reference to figures 4 and 5, it is possible to observe a toothed wheel 40, preferably helical cylindrical, placed inside the double glazing 1 and pivoted to the slide 20 at a portion 41 of the latter that is lower in the figure. Preferably, the toothed wheel 40 is arranged vertically and is rotatable around an axis arranged orthogonal to the wall 11. The toothed wheel 40 is opposite the knob 15 and is coupled thereto by means of a pair of magnets 42 and 43, preferably discoidal, which are attracted to each other. The magnet 42 is placed inside the double glazing 1, it is pivoted to the center of the slide 20, it is preferably vertically arranged, and it is rotatable around the same rotation axis of the toothed wheel 40 and is integrally connected thereto. The magnet 43 is placed outside the double glazing 1 , it is pivoted to the center of the slider 20, it is preferably vertically arranged, it is rotatable around the same rotation axis of the knob 15 and it is integrally connected thereto. The magnets 42 and 43 are mutually opposite such that the toothed wheel 40, the magnets 42 and 43, and the knob 15 are rotatable around the same rotation axis. The magnetic attraction between the magnets 42 and 43 is of size such to ensure that the rotation of the knob 15 set by the user of the blind 5 causes the rotation of the toothed wheel 40. The wall 11 is interposed between the knob 15 and the toothed wheel 40, and hence also between the two magnets 42 and 43. Analogous to that said with regard to the magnets 21 and 22 which obtain the translational coupling between the slide 20 and the slider 10, given that the wall 11 is preferably made of diamag- netic material, it does not interfere with the magnetic field between the two magnets 42 and 43. With reference to figures 4 and 5, it is also possible to observe that the toothed wheel 40 engages an involute screw 44 (i.e. a helical cylindrical toothed wheel with very large helix angle, also known as a "worm screw") arranged with its longitudinal axis preferably vertical. The involute screw 44 is housed in the slide 20 at a seat 45, and is traversed by the shaft 23 at a through hole placed along the longitudinal axis thereof. The shaft 23 is rotatable around its longitudinal axis, preferably vertically arranged. The involute screw 44 is slidable on the shaft 23 but is rotationally coupled thereto. The involute screw 44 is therefore rotatable, together with the shaft 23, around a vertical axis. The rotational coupling between the involute screw 44 and the shaft 23 is obtained, by way of example, by making the shaft 23 in a manner such that the cross section of the shaft 23 is not circular and does not vary along the vertical rotation axis thereof, and by making the involute screw 44 in a manner such that its through hole has a cross section complementary to that of the shaft 23.

By way of example, as an alternative to the toothed wheel 40 and the involute screw 44, the rotational coupling between the magnet 42 and the shaft 23 is obtainable by means of a pair of conical toothed wheels.

The rotation group for the slats 6 comprises a second shaft 50 housed at the upper portion 31 of the frame 4 and preferably arranged parallel to the slats 6. The shaft 50 is rotatable around the longitudinal symmetry axis thereof and is rotationally coupled to the shaft 23 by means of a gear 51. The ladder-like cords 7a and 7b are integrally connected to the shaft 50 at a respective end. The rotation of the shaft 50 causes the raising or the lowering of the ladder-like cords 7a and 7b and hence the rotation of the slats 6 around the respective longitudinal axis.

The toothed wheel 40, the involute screw 44 and the shaft 23 transmit the rotary motion of the knob 15 to the shaft 50 (i.e. the rotation group for the slats 6). In particular, with regard to the functioning, the rotation of the knob 15 causes, through the magnetic coupling obtained by the magnets 42 and 43, the rotation of the toothed wheel 40. The latter rotates the involute screw 44 and, with this, the shaft 23. The rotation of the shaft 23 is transmitted, by means of the gear 51 , to the shaft 50 thus causing the rotation of the slats 6. On the basis of the description provided for a preferred embodiment, it is clear that some changes can be introduced by the man skilled in the art without departing from the scope of the invention as defined in the following claims.