CA2906721A1 - Method and fastening element for installing a sunshade to a glazing part - Google Patents

Abstract

In the method a sunshade is installed to a glazing part, which comprises a transparent sheet (10) with a first end edge and second end edge and a first side edge (16) and second side edge (18). The side edges are free edges of the sheet. In the method at least one first fastening element (20) is attached close to the first end edge of the transparent sheet and at least one second fastening element is attached close to the second end edge of the transparent sheet, and the sunshade (100 is suspended on the said fastening elements. The first and second fastening elements are attached to the side edges of the transparent sheet. Typically the sunshade can comprise at least one guide wire (24), which has a first end and second end. In this case the first end of the guide wire is attached to the first fastening element and the second end of the guide wire is attached to the second fastening element. The fastening element of the sunshade used in the method has gripping means for attaching to the glazing part and a fastening body for attaching to the sunshade. The gripping means comprises a slot formed by the first flank (26), the second flank (28) and the base (30) connecting the flanks, to which slot the free edge of the transparent sheet can be fitted.

Description

Method and fastening element for installing a sunshade to a glazing part The invention relates to a method for installing a sunshade to a glazing part, the glazing part comprising a transparent sheet with a first end edge and a second end edge, and a first side edge and a second side edge, the side edges being free edges of the sheet, and in which method at least one first fastening element is at-tached close to the first end edge of the transparent sheet and at least one second fastening element is attached close to the second end edge of the transparent sheet, and the sunshade is suspended on the said fastening elements. The inven-tion further relates to a fastening element of a sunshade with gripping means for attachment to the glazing part and a fastening body for attaching to the sunshade.
Blinds are often used as sunshades in glazed balconies to prevent insolation from accessing the balcony. Sunshades are attached to the edge profiles in the upper and lower edges of the balcony glazing with fastening elements, which have grip-ping means for attaching to the sunshade and a suspension element for attaching to the edge profile.
Fastening elements used in the fastening of sunshades are usually metal parts, which encircle at least in part the edge profile of the glazing. Dust and dirt are easily accumulated to such fastening elements and especially to the gap between the fastener and edge profile, which is difficult to remove. The fastening elements are locked into place usually by means of a tight fit between the fastening element and edge profile. Due to the dimensional variances of the edge profiles and fas-tening elements and the sagging of the paint surface of the edge profiles it is often difficult to install the fastening elements dimensioned for the tight fit.
It is an object of the invention to introduce a method for attaching the sunshade to the glazing part and a fastening element, with which disadvantages and draw-backs related to the state of the art can be eliminated.
The objects of the invention are achieved with a method and fastening element, which are characterized in what is presented in the independent claims. Some ad-vantageous embodiments of the invention are disclosed in the dependent claims.
The invention relates to a method for installing a sunshade to a glazing part com-prising a transparent sheet. The transparent sheet has a first end edge and a sec-ond end edge, and a first side edge and a second side edge. The end and side . CA 02906721 2015-09-30 ,

2 edges in this presentation refer to the side surface perpendicular to the plane of the transparent sheet and the narrow edge strip parallel to the plane on both sides of the transparent sheet, which edge strip borders to the side surface. The side edges are free edges of the sheet, i.e. no edge profiles have been attached to the side edges, which would cover or embed part of the side edge. In the method at least one first fastening element is attached close to the first end edge of the transparent sheet and at least one second fastening element is attached close to the second end edge of the transparent sheet and the sunshade is suspended on the said fastening elements. In the method said first and second fastening ele-ments are attached to the side edges of the transparent sheet. The fastening ele-ments are preferably attached to both side edges of the transparent sheet so that there are two first fastening elements close to the first end edge of the transparent sheet and two second fastening elements close to the second end edge of the transparent sheet. Typically in the glazing part installed in place the first and sec-ond side edges are in a substantially vertical position.
In an advantageous embodiment of the method of the invention the said sunshade comprises at least one guide wire with a first end and a second end. In the method the first end of the guide wire is attached to the first fastening element, the second end of the guide wire is attached to the second fastening element and the guide wire is tightened to an appropriate tightness. Sunshades used in balcony glazing typically have two guide wires, the first one of which is located in the first edge of the sunshade and the other one in the second edge of the sunshade. In this case the first guide wire is attached to the fastening elements to be fastened to the first side edge of the transparent sheet and the second guide wire is attached to the fastening elements to be fastened to the second side edge of the transparent sheet. The curtain section of the sunshade providing protection against insolation is supported to the guide wires so that the sunshade can be unfolded into an open position, in which it covers the transparent sheet substantially entirely, and pressed it into a folded position, in which it covers as small a portion as possible of the area of the transparent sheet.
In a second advantageous embodiment of the invention the fastening element is arranged tightly around a section of the side edge of the transparent sheet.
The fastening element then stays in place in the edge of the transparent sheet by means of friction caused by the tight fit between the transparent sheet and fas-tening element. The friction between the transparent sheet and fastening element can be increased by arranging a friction-increasing friction element between the

3 fastening element and the transparent sheet. The friction element can be, for ex-ample, a flexible friction lamella arranged onto the surface of the fastening element settling against the transparent sheet.
In yet another advantageous embodiment of the method of the invention the sun-shade is attached to the fastening element so that the force applied from the sun-shade to the fastening element increases the force applied from the fastening el-ement to the transparent sheet. Such an attachment can be realised, for example, so that the sunshade is attached eccentrically in relation to the vertical travelling through the mass-centre of the fastening element, in which case the load generat-ed by the sunshade attempts to turn the fastening element attached to the edge of the transparent sheet. The turning movement of the fastening element makes the edge section of the fastening element surrounding the side edge of the transparent sheet to press strongly against the surface of the transparent sheet. The force ap-plied from the sunshade to the fastening element can be adjusted, for example, by tightening the guide wires of the sunshade to an appropriate tightness.
In yet another advantageous embodiment of the method of the invention the fas-tening element is attached to the side edge of the transparent sheet by glue or a stick-on label. The glue or stick-on label can extend in the side edge to the one or both surfaces parallel to the transparent sheet and/or to the side surface of the transparent sheet.
In yet another advantageous embodiment of the method of the invention the fas-tening element is pressed around a section of the side edge of the transparent sheet by spring force. The compression achieved by the spring force also increas-es the friction force keeping the fastening element in place. The fastening element can also be pressed around a section of the side edge of the transparent sheet by using a tightening screw. In this case the tightening screw is arranged to the fas-tening element so that its point is pressed against the surface of the transparent sheet. A compression sheet can be arranged between the point of the tightening screw and the surface of the transparent sheet, the surface of the compression sheet being pressed against the surface of the transparent sheet.
In yet another advantageous embodiment of the method of the invention the fas-tening elements are attached to the glazing part, in which the first end edge of the transparent sheet has a first edge profile and the first fastening element is at-tached to the first edge profile in addition to the side edge. The second end edge of the transparent sheet preferably has a second edge profile and the second fas-

4 tening element is attached to the second edge profile in addition to the side edge.
By means of the attachment to the edge profiles it is ensured that the fastening elements cannot glide towards each other in the direction of the side edge.
In the fastening element of a sunshade, which is an object of the invention, there are gripping means for attaching to the glazing part and a fastening body for fas-tening to the sunshade. Said gripping means comprise a slot formed by a first flank, a second flank, and a base connecting the flanks to which slot it is possible to fit the free side edge of the transparent sheet of the glazing part. The side edg-es in this presentation refer to the side surface perpendicular to the direction of the plane of the transparent sheet and the narrow edge strip parallel to the plane on both sides of the transparent sheet, which borders to the side surface.
Preferably said fastening body comprises a fastening projection in the second flank of the fastening element.
One advantageous embodiment of the fastening element of the invention compris-es a fastening hole or slot for attaching the guide wire of the sunshade. It is pref-erable to arrange the fastening hole or slot to the fastening projection. The pulling force of the guide wire causes a bending moment to the fastening projection, which attempts to rotate the fastening element and especially its one flank.
The rotation of the fastening element increases the compression and friction force act-ing between the flanks and the transparent sheet, which promotes the fastening element to stay in place.
One advantageous embodiment of the fastening element of the invention compris-es an interface for attaching to the edge rail of the sunshade. In this embodiment the edge rail of a sunshade, such as a blind, is attached directly to the interface of the fastening element. The interface may have a shaping, which is compatible with the shaping of the fastening surface settling against the interface of the edge rail.
In this case the edge rail can set tightly against the interface and attach to the fas-tening element by means of the tight fit between the interface and the fastening surface. It is preferable to arrange the interface to the fastening projection.
A second advantageous embodiment of the fastening element of the invention comprises further a spring element for moving the first flank and the second flank towards each other. The fastening element can further comprise a friction element to be placed against the surface of the transparent sheet.

A third advantageous embodiment of the fastening element of the invention com-prises a tightening screw, the point of which can be moved to the space between the first flank and the second flank. The fastening screw can extend through the first or second flank or base of the fastening element so that the head of the fas-

5 tening screw is visible on the outer surface of the fastening element. By rotating the fastening screw its point is pressed to the gap between the surface of the transparent sheet and the flank and presses the first or second flank of the fas-tening element tightly against the surface of the transparent sheet. Because of the tightening screw the width of the slot limited by the first and second flank can be bigger than the thickness of the transparent sheet, and the same fastening ele-ment can be attached to transparent sheets of different thicknesses. A compres-sion plate can be arranged to the space between the first and second flank, be-tween the point of the tightening screw and the transparent sheet so that the sur-face of the compression plate is pressed against the surface of the transparent sheet when rotating the tightening screw.
The fastening element of the invention can be a part formed of a thread-type piece or a part formed of a sheet-type piece. Preferably the fastening element is made of some easily formable, flexible material, such as plastic or metal. The base of the attachment element of the invention settles to the gap between the adjacent glaz-ing parts of the balcony glazing. By limiting the thickness of the base to be less than 5 mm, it is ensured, that the bases of the fastening elements do not increase the width of the gap between the glazing parts. Although the fastening element is designed to attach in place particularly to the free edge of the glazing part, the fas-tening element may also comprise a support element for attaching to the edge pro-file of the glazing part.
It is an advantage of the invention that the sunshade can be attached to the glaz-ing part fast and easily without the use of tools. The dimensional variances and sagging of paint in the edge profiles of the glazing part do not prevent or make difficult the installation of the sunshade.
It is a further advantage of the invention that in the method the attached sunshade does not cause dirtying of the edge profile of the glazing section or hinder the cleansing of the edge profile.
It is further an advantage of the invention that no visible traces remain in the glaz-ing part from the attachment of the fastener, which would deteriorate the appear-ance of the glazing part.

. CA 02906721 2015-09-30

6 The invention will next be explained in detail, referring to the enclosed drawings, in which Figure 1 is an exemplary illustration of a glazing part, to which a sunshade has been installed using the method of the invention;
Figure 2 illustrates a corner of the glazing part of Figure 1 as partial enlargement;
Figure 3 is an exemplary illustration of an advantageous embodiment of the fas-tening element of the invention;
Figures 4a and 4b illustrate a second advantageous embodiment of the fastening element of the invention;
Figure 5 illustrates a third advantageous embodiment of the fastening element of the invention; and Figures 6a and 6b illustrate a fourth advantageous embodiment of the fastening element of the invention.
In Figure 1 there is illustrated a glazing part for balcony glazing, to which a sun-shade has been installed by using the method of the invention. The glazing part comprises a rectangular transparent sheet 10 with two parallel side edges, the first side edge 16 and the second side edge 18, and two parallel end edges, the first end edge 12 and the second end edge 14. The transparent sheets used in balcony glazing are typically made of hardened glass with a thickness of 4 ¨ 6 mm, but also other materials and sheet thicknesses are possible. The first end edge of the transparent sheet has the first edge profile 13 and the second end edge has the second edge profile 15. The edge profiles are aluminium profiles, which have a groove to which the end edge of the transparent sheet 10 has been fitted. The ends of the edge profiles are provided with plastic end pieces 38. The side edges 16, 18 of the transparent sheet are free edges, in other words edges with no edge profile.
In the method of the invention fastening elements 20, 22 are attached to the glaz-ing part, the sunshade 100 being suspended on the fastening elements. The first fastening elements 20 are attached to the first and second side edge 16, 18 of the transparent sheet 10, as close to the first end edge 12 as possible. In practice the first fastening elements are attached to the side edges so that they are settled in contact with the first edge profile 13. The second fastening element 22 are at-

7 tached to the first and second side edge 16, 18 of the transparent sheet 10, as close to the second end edge 14 as possible. In practice the second fastening el-ements are installed to contact the second edge profile 15. After the fastening el-ements have been installed in place, the guide wires 24 belonging to the sunshade are attached to the first fastening element 20 from their first end and to the second fastening element 22 from their second end, and tightened. The sunshade typically has two guide wires so that the first guide wire is attached to the fastening ele-ments attached to the first side edge 16 of the transparent sheet and the second guide wire is attached to the fastening elements attached to the second side edge 18 of the transparent sheet. The curtain section of the sunshade offering protec-tion from insolation comprises an upper rail 102, a lower rail 104 and between them a curtain 106 folded into zig-zag form. The upper and lower rail can be moved on the guide wires up and down so that the area of the region covered by the curtain 106 changes.
Figure 2 illustrates in an exemplary way the upper corner of the glazing part shown in Figure 1, i.e. the corner formed by the first end edge and the first side edge 16 of the transparent sheet 10. In the Figure there is shown the attachment of the first fastening element 20 to the first side edge of the transparent sheet 10. The fas-tening element has a first flank 26, a second flank 28, and a base 30 connecting said flanks. The flanks and the base form a slot, the width of which is substantially equal to the thickness of the transparent sheet 10. In the edge of the second flank there is provided a tongue, which is folded substantially to a right angle from the plane of the second flank so that it forms a fastening projection 32. The corners of the fastening projection are bevelled, and close to its end there is the hole 40 for attaching a guide wire 24 of the sunshade 100. The fastening element has been formed by shaping a thin metal sheet into U-form and by turning the tongue formed to the flank of the second branch of U outwards as the fastening projection 32. The thickness of the metal sheet can be approximately 0.5 ¨ 1.0 mm.
The fastening element is attached in place to the transparent sheet 10 by fitting the first side edge 16 to the slot of the fastening element so that the first flank 26 of the fastening element is settled on the first side of the sheet, the second flank 28 is settled to the second side of the sheet, and the base 30 is pressed against the edge surface of the first side edge of the sheet. The width of the base 30, i.e. the distance between the first and second flank, has been selected so that it is sub-stantially equal to the thickness of the transparent sheet 10. The fastening element has been made of a metal sheet behaving in a spring-like manner into such a ,

8 shape that in the free state the flanks 26, 28 turn towards each other. Upon in-stalling the fastening element, the flanks thus have to be folded apart from each other so that spring force is stored to the fastening element. In the fastening ele-ment 20 installed in place, the spring force presses the flanks 26, 28 tightly against the surface of the transparent sheet so that friction force is generated between the flanks and the surface of the transparent sheet, preventing the movement of the fastening element.
In Figure 2 there is illustrated the attachment of one fastening element 20 to the side edge of the transparent sheet 10 as close to the first end edge of the trans-parent sheet 10 as possible. In practice this means that the edges of the flanks 26, 28 of the fastening element 20 are placed to the edge profile 13 in the first end edge of the transparent sheet. The remaining fastening elements are attached to the side edges in similar manner. After the attachment of the fastening elements, guide wires 24 of the sunshade 100 are attached to them, after which the installa-tion work of the sunshades is complete.
In Figure 3 there is shown in an exemplary manner an advantageous embodiment of the fastening element 20a used in a method of the invention, attached to the first side edge of the transparent sheet 10.The embodiment in Figure 3 is substan-tially of the same shape as in Figure 2, i.e. it has the first flank 26, the base 30, the second flank 28 and the fastening projection 32 turning from the point of the sec-ond flank to an angle. This embodiment has been prepared by casting from flexi-ble plastic material, and the material thicknesses of its parts are substantially big-ger than in Figure 2. The distance between the flanks has been chosen so that the side edge 16 of the transparent sheet 10 settles between the flanks with a tight fit.
The fastening element stays in place in the side edge due to the compression and friction forces generated by the tight fit.
Figures 4a and 4b illustrate in an exemplary manner a second advantageous em-bodiment of the fastening element 20b used in the method of the invention.
Figure 4a illustrates the embodiment as a separate part and in Figure 4b the embodiment is shown installed in place to the glazing part. The embodiment shown in the Fig-ures is substantially of a similar shape as in Figure 3, i.e. it has the first flank 26, the base 30, the second flank 28, and the fastening projection 32 turning to an an-gle from the second flank. This embodiment has been made by casting from flexi-ble plastic material, and the distance between the flanks has been chosen so that the side edge 16 of the transparent sheet 10 settles between the flanks with a tight fit. In this embodiment the base 30 extends above the plane defined the flank edg-,

9 es, and the base has two support elements 42 parallel to the flanks. The size and shape of the support elements has been chosen so that they can be fitted to the cavities 17 opening to the end surface of the first edge profile 13 in the first end edge 12 of the transparent sheet 10 (Figure 4b). The base can be made so big that it substantially covers the entire end surface of the edge profile. In this case there is no need for a separate end piece at the end of the edge profile.
In Figure 5 there is illustrated in an exemplary manner a third embodiment of the fastening element 20c used in the method of the invention, attached to the first side edge 16 of the transparent sheet 10. The embodiment in Figure 5 has the first flank 26, the base 30, the second flank 28, and the fastening projection 32 turning from the point of the second flank to an angle, i.e. it has the same functional ele-ments as the embodiments in Figures 2 and 3. This embodiment has been made by shaping a metal wire behaving in a spring-like manner into the shape shown in Figure 5. Therefore, its appearance deviates distinctly from the previously shown embodiments. The distance between the flanks formed of the metal wire has been selected so that the side edge 16 of the transparent sheet 10 settles between the flanks with a tight fit. The fastening element stays in place in the side edge be-cause of the compression and friction force generated by the tight fit.
Figures 6a and 6b illustrate in an exemplary manner an advantageous fourth em-bodiment 20d of the fastening element used in the method of the invention.
Figure 6a illustrates the fastening element as a separate part and Figure 6b illustrates the fastening element installed in place to the glazing element of the balcony glazing.
In the embodiment shown in Figures 6a and 6b there is the first flank 26, the base 30, the second flank 28 and the fastening projection 32 turning to an angle from the second flank. The embodiment of the fastening element has been made by casting from plastic material. The distance between the flanks has been chosen so that the side edge 16 of the transparent sheet 10 can be placed loosely between the flanks, i.e. the distance between the flanks is clearly bigger than the thickness of the transparent sheet (Figure 6b). The first flank 26 has a threaded through-hole 52, to which a plastic tightening screw 50 is fitted. The point of the tightening screw extends to the gap between the first and second flank, and the head of the tightening screw can be seen outside the fastening element through the hole 52.
The fastening element is fitted in place to the side edge 16 of the transparent sheet 10 so that the side edge is settled between the flanks. Attaching the fas-tening element in place is effected by tightening the tightening screw so that the point of the tightening screw is pressed against the surface of the transparent sheet. The fastening element stays in place in the side edge due to the compres-sion and friction force generated by the fastening screw between the second flank 28 and the transparent sheet 10.
An elongated neck 54 is shaped to the second surface of the fastening projection 5 32, the cross-sectional shape of which is substantially similar to that of the groove in the edge rail 110 of the sunshade 100 to be attached to the fastening element.
The edge rail of the sunshade can thus be attached to the fastening element simp-ly by fitting the necks of the fastening elements to the groove in the edge rail in the way illustrated in Figure 6b. The surface of the fastening element facing the neck

10 thus forms an interface, to which the sunshade can be attached without separate fastening bodies. The sunshade can be, for example, a blind comprising several laths 112 hanging on wires from the edge rail 110.
The embodiment illustrated in Figures 6a and 6b comprises both the tightening screw 50 for attaching the fastening element to the transparent sheet 10 and the interface for attaching the edge rail of the sunshade. It is evident that these fea-tures are not dependent from each other, i.e. embodiments comprising only one of the above-mentioned features can be made of the fastening element 20d.
The fastening elements illustrated in Figures 2 ¨ 6 can be provided with one or several friction elements, which in the fastening element installed in place settle against the surface of the transparent sheet. Natural places for the friction ele-ments are the surfaces of the first and second flank and base settling against the surface of the transparent sheet. The friction element can, for example, comprise friction lamellas or bulges, which prevent the friction element from gliding along the surface of the transparent sheet. Further, to ensure the attachment of the fas-tening element, glue or self-adhesive stickers can be used on the contact surface between the fastening element and the transparent sheet. Figures 2 ¨ 6 only de-scribe the first fastening elements and their structure. The second fastening ele-ments have a similar or corresponding structure as the first fastening elements.
Some advantageous embodiments of the method and fastening element of the invention have been described above. The invention is not restricted to the solu-tions described above, but the inventional idea can be applied in different ways within the scope defined by the patent claims.

Claims (15)

Claims

1. Method for installing a sunshade (100) to a glazing part comprising a trans-parent sheet (10) with a first end edge (12) and a second end edge (14) and a first side edge (16) and second side edge (18), which side edges are free edges of the sheet, and in which method at least one first fastening element (20, 20a, 20b, 20c, 20d) is attached close to the first end edge (12) of the transparent sheet and at least one second fastening element (22) is attached close to the second end edge (14) of the transparent sheet and the sunshade (100) is suspended on the said fastening elements, characterized in that, the said first and second fastening el-ements (20, 20a, 20b, 20c, 20d, 22) are attached to the side edges (16, 18) of the transparent sheet (10).

2. Method according to claim 1, characterized in that said sunshade (100) comprises at least one guide wire (24) with a first end and second end, and in the method the first end of the guide wire (24) is attached to the first fastening element (20, 20a, 20b, 20c, 20d), the second end of the guide wire (24) is attached to the second fastening element (22) and the guide wire (24) is tightened to an appropri-ate tightness.

3. Method according to claim 1 or 2, characterized in that the fastening ele-ment (20, 20a, 20b, 20c, 20d, 22) is arranged tightly around a section of the side edge (16, 18) of the transparent sheet (10).

4. Method according to any of the claims 1-3, characterized in that a friction-increasing friction element is arranged between the fastening element (20, 20a, 20b, 20c, 20d, 22) and the transparent sheet (10).

5. Method according to any of the claims 1-4, characterized in that the sun-shade (100) is attached to the fastening element (20, 20a, 20b, 20c, 20d, 22) so that the force applied from the sunshade (100) to the fastening element (20, 20a, 20b, 20c, 20d, 22) increases the force applied from the fastening element (20, 20a, 20b, 20c, 20d, 22) to the transparent sheet (10).

6. Method according to any of the claims 1-5, characterized in that the fas-tening element (20, 20a, 20b, 20c, 20d, 22) is attached to the side edge (16, 18) of the transparent sheet (10) with glue.

7. Method according to any of the claims 1-6, characterized in that the fas-tening element (20, 20a, 20b, 20c, 20d, 22) is pressed around a section of the side edge (16, 18) of the transparent sheet (10) with spring force or with a tightening screw (50).

8. Method according to any of the claims 1-7, characterized in that the fas-tening elements (20, 20a, 20b, 20c, 20d, 22) are attached to the glazing part, in which the first end edge (12) of the transparent sheet (10) has a first edge profile (13) and the second end edge (14) of the transparent sheet (10) has a second edge profile (15) and the first fastening element (20, 20a, 20b, 20c, 20d) is at-tached also to the first edge profile (13) in addition to the side edge (16, 18) and the second fastening element (22) is also attached to the second edge profile (15) in addition to the side edge (16, 18).

9. Fastening element (20, 20a, 20b, 20c, 20d, 22) of a sunshade (100), which has gripping means for attaching to a glazing part and a fastening body for attach-ing to the sunshade (100), characterized in that the said gripping means compris-es a slot formed by a first flank (26), a second flank (28) and a base (30) connect-ing the flanks, to which slot a free side edge (16) of a transparent sheet (10) of the glazing part can be fitted.

10. Fastening element (20, 20a, 20b, 20c, 20d, 22) according to claim 9, charac-terized in that said fastening body comprises a fastening projection (32) in the second flank (28).

11. Fastening element (20, 20a, 20b, 20c, 20d, 22) according to claim 9 or 10, characterized in that said fastening body comprises a fastening hole (40) or slot for attaching a guide wire (24) of the sunshade (100).

12. Fastening element (20, 20a, 20b, 20c, 20d, 22) according to any of the claims 9-11, characterized in that said fastening body comprises an interface for attaching to an edge rail (110) of the sunshade (100).

13. Fastening element (20, 20a, 20b, 20c, 20d, 22) according to any of the claims 9-12, characterized in that it comprises a spring element for moving the first flank (26) and the second flank (28) towards each other.

14. Fastening element (20, 20a, 20b, 20c, 20d, 22) according to any of the claims 9-13, characterized in that it comprises a friction element to be placed against a surface of the transparent sheet (10).

15. Fastening element (20, 20a, 20b, 20c, 20d, 22) according to any of the claims 9-14, characterized in that it comprises a tightening screw (50), the point of which is movable to the space between the first flank (26) and second flank (28).