EP0801201B1 - System for fixing a toughened glass sheet and accordingly equipped glass sheet - Google Patents

Abstract

The connection between a toughened glass sheet (1) having a reamed hole and another glass sheet or metal structure comprises two parts. One part (7), which fits the hole conical surface (3), has a force perpendicular to the hole axis exerted on it. The other (14) is supported on the side (6) of the sheet opposite the reamed holed and supports the reaction force. The force is sufficient to establish on the glass sheet a system of minimum localised compression restraints at a distance from the hole edge greater than 1% of the hole maximum diameter. The metal connecting piece part fitting the reamed hole conical surface has a cone opening angle greater than that of the hole. An aluminium sleeve (23) is interposed between the connecting piece and the hole to avoid excessive local constraints.

Description

The present invention relates to an assembly system between a sheet of glass, in particular glass having undergone a reinforcement treatment especially thermal or chemical surface, comprising at least one countersunk hole and either another sheet of glass or a structural element in particular metal, as well as a sheet of glass equipped with such a system and the application of such a sheet to the production of a prefabricated assembly.

In document EP-A-0 655 543, the applicant has described a system assembly between a glazed element comprising a countersunk hole and a structure carrier, this system comprising a connecting part between two parts of which one, frustoconical, conforms to the conical surface of the countersunk hole, the other of which, forming part of reaction, rests on the surface of the sheet opposite to milling the hole. A screw connection between these two parts allows the workpiece to be clamped connecting in the hole.

The present invention aims to provide a solution to this problem.

To obtain this result, the invention provides a method of assembly between a sheet of glass having a countersunk hole on at least one side and either another sheet of glass, i.e. a structural element, notably metallic, the system comprising a connecting piece, the particularity of this system being that the piece of connection comprises two parts, one of which follows the conical surface of the hole milled on which a force is exerted substantially parallel to the axis of the hole and whose the other rests on the side of the sheet opposite the milling of the hole to withstand the reaction to said force, and that this force is sufficient to establish the surface of the glass sheet at rest, a system of constraints of compression with a minimum located at a distance from the edge of the countersunk hole greater than 1% of the maximum diameter of this hole.

The method of the invention makes it possible to avoid that extension constraints, likely to cause cracking on the walls of the hole and therefore the rupture of the glass sheet, do not appear under the effect of the forces transmitted by the other sheet of glass or structural element. The value of 1% indicated results experiments carried out on a very wide range of sheet thicknesses and hole diameters.

Preferably, the part of the connecting piece which hugs the surface taper of the countersunk hole has a larger cone opening angle than the cone of the countersunk hole, the half angles at the top of the cones differing advantageously from 0.5 ° to 5 °.

In this way, the contact between the countersunk hole and the conical part of the part support is located as close as possible to the surface which carries the milled part of the hole, which is favorable to a compression of the area surrounding the hole.

Preferably, the part of the connecting piece which follows the conical surface of the countersunk hole is metallic and a sleeve is interposed between it and the countersunk hole of a malleable material such as aluminum.

Preferably also the countersunk hole is truncated and ends on the surface of the sheet opposite by a coaxial cylindrical part and, advantageously, in this case no element of the connecting part is in contact with the cylindrical part of the countersunk hole.

According to an interesting embodiment, the connecting piece is a screw-nut system.

According to another embodiment, the two parts of the connecting piece are crimped on top of each other. This embodiment is less expensive but does not allows no adjustment.

The invention also provides a method for a tempered glass sheet with a thickness of at least minus 6 mm, having at least one countersunk hole on one of its surfaces, and which has for the particularities that it has inside the countersunk hole a conical part and on the opposite surface a reaction piece, that a force directed substantially along the axis of the hole is exerted between the conical part and the reaction part, and that this force is such that if the glass sheet is stressed planned in advance, the result in the glass sheet is a system of surface compressive stresses which have a minimum located at a distance from the edge of the countersunk hole greater than 1% of the maximum diameter of this hole.

According to an interesting embodiment, this glass sheet has a hole doubly milled with a conical part opening out on both sides and a cylindrical middle part which has substantially the same axis as the parts conical, it includes inside each conical part a conical part, a force directed along the axis of the hole is exerted between the two conical parts and this force is such that if the glass sheet is stressed planned in advance, the result in the glass sheet is a system of surface compressive stresses which have a minimum located at a distance from the edge of the countersunk hole greater than 1% of the maximum diameter of this hole.

Preferably the conical part or parts have an opening angle of the cone greater than that of the cone of the corresponding countersunk hole.

Advantageously the conical part or parts and possibly the part on the opposite surface are equipped with gripping means such as holes, bosses, etc. to transmit forces directed substantially in the plane of the glass sheet either to a structural element or to another sheet of glass.

An interesting application of such a method consists in carrying out assemblies made of prefabricated elements assembled in particular on site.

• figure 1 : un système d'assemblage entre une plaque en verre trempé et une structure,
• figure 2 : un système d'assemblage entre une plaque faite de deux verres trempés feuilletés et une structure,
• figure 3 : un système d'assemblage avec articulation (entre plaque trempée et structure),
• figure 4 : un système d'assemblage entre deux plaques en verre trempé, et
• figure 5 : une plaque trempée équipée d'une pièce lui permettant de supporter des efforts importants dans son plan, et
• figure 6 : une variante de la figure 5,
• figure 7 : un assemblage de deux plaques de verre feuilleté avec deux systèmes selon l'invention.

The present invention will now be explained in more detail using practical examples illustrated with the drawings which are cross-sections of systems obtained using the invention and which respectively represent:

• FIG. 1: an assembly system between a tempered glass plate and a structure,
• FIG. 2: an assembly system between a plate made of two laminated toughened glasses and a structure,
• FIG. 3: an assembly system with articulation (between hardened plate and structure),
• FIG. 4: an assembly system between two tempered glass plates, and
• FIG. 5: a hardened plate fitted with a part allowing it to withstand significant forces in its plane, and
• FIG. 6: a variant of FIG. 5,
• Figure 7 : an assembly of two laminated glass plates with two systems according to the invention.

FIG. 1 shows an assembly system between a toughened glass plate 1 and a structure S which may be, as the case may be, a load-bearing structure or a supported structure, or else a connecting element or another toughened glass plate or no.

The plate 1 is pierced with a countersunk hole 2, which has a conical part 3, which opens onto a face 4 of the plate 1 opposite the structure S and a cylindrical part 5 which opens onto the opposite face 6 of the plate. The system assembly comprises a first part 7, which has a conical surface 8 which follows the shape of the conical part 3 of the hole 2 and a part cylindrical 9, which penetrates into the cylindrical part 5 of the hole 2, without reaching the opposite face 6. This cylindrical part 9 is of smaller diameter than that of the cylindrical part 10. The part 7 is traversed by a bore 10, in two parts of different diameter, separated by a shoulder 11. The larger part diameter corresponds substantially to the conical part 8, while the part of smaller diameter passes through the cylindrical part 9. A screw 12 is housed in the bore 10, its head resting on the shoulder 11. The threaded part 13 of the screw 12 is screwed into a nut 14 which constitutes the reaction part of the system, and comes to bear against the face 6 of the glass plate 1, by means of a polyethylene plastic washer 15. The end of the screw 12 is screwed still in a bore 16 of the structure S and is blocked by a lock nut 17.

It will be observed that, in a view parallel to the axis of the hole, the surface of contact of the nut 14 is superimposed on that of the part 7, which avoids any risk appearance of shear stresses inside the glass plate soaked 1.

Figure 1 explains the idea which is the basis of the invention.

The tightening of the nut 14 on the screw 12 generates, between the conical surface 3 of the countersunk hole 2 on the opposite side 6 of the plate, a force substantially parallel to the axis of the hole, and which at rest tends to create a compression stress in the matter surrounding the hole. Mathematical calculations, for example by the method of the tensorial calculation or that of the calculation by finite elements, allow to determine the relationship between the clamping force and the extent of the area surrounding the hole which is thus subject to a compressive stress, if we know the geometric and mechanical characteristics of the plate and the hole.

The application to the assembly system of an external constraint, transmitted here from the structure S to the screw 12, modifies the distribution of the stresses inside the material. The minimum dimension of 1 mm for the area in compression around the hole at rest has been determined experimentally as avoiding the appearance of dangerous stress conditions in the wall of the hole when the plate is subjected to external stresses that it can bear elsewhere.

In each concrete case, the determination of the force to be applied for achieving the conditions of the invention will be done with the methods of analysis of usual constraints, in particular optical methods. It is about observing the displacement of the area where the minimum surface stress of compression. The stronger the clamping force, the more this area moves away from the edge of the countersunk hole. Observation in polarized light, or finer measurements derived for example from the EPIBIASCOPE, make it possible to determine which is the force required to move the area in question to the desired distance from the edge of the countersunk hole, for example 1 mm.

So, for example, in the case of a 12 mm toughened glass normal chemical (surface compressive stress of around 90 MPa) with a 54 mm large diameter countersunk hole, conical to 8 mm and terminated by a 38 mm diameter cylinder with a screw-nut system as in the figure 1, a tightening torque of 100 Nm made it possible to obtain an axial force of 35 kN, sufficient for the minimum stress of 7 MPa to be carried over to 1.5 mm from the periphery of the hole.

On samples of the previous type, tests were then carried out traction, the force being applied to the screw, perpendicular to its axis, in the plane of the glass kept mobile. Systematic efforts of 30 kN have been applied while the samples were subjected to 23 thermal cycles of -15 ° C to + 56 ° C with a duration of 6 hours each. No break in samples tested only appeared when the clamping force was only 3.5 kN (tightening torque 10 Nm) breakage occurs as soon as the charge.

Figure 2 describes a structure quite similar to that of Figure 1, suitable for the case where, instead of a single glass plate, we are in the presence of a laminated plate formed by two glass sheets 1A, 1B. In this case, the nut 14 comes to bear on only one of the glass sheets for example, here, that which is furthest from the structure S. For this, the nut 14 is housed in a hole 18 in the plate glass 1B. In addition, the structure S has been shown as coming directly to bear on the glass plate 1B, with however the interposition of a plastic washer 19.

The arrangement of Figure 3 differs in only a few points from that of Figure 1: the part 7 does not have a through bore 10 and the screw 12 is deleted. In contrast, the cylindrical part 9 extends beyond the face 6 of the glass plate 1. It is provided with a thread 20 and cooperates directly with the nut 14. The part 7 has a blind cavity 21, which opens out on the side of the nut 14. In this cavity is housed a rod 22 for connection to the structure S, not shown. The rod 22 is mounted so as to be able to present slight oscillations, in a manner which is described in detail in the document EP-A-0 655 543 mentioned above.

Figure 3 being on a larger scale, allows a better view of the nature of the contact between the frustoconical parts of hole 2 and part 7.

Note first that Figure 3 is a section made before tightening the device.

The half-angle at the top of the frustoconical part 3 of the hole 2 is 45 °. The frustoconical surface 8 of the part 7 has a half-angle at the top slightly higher, by 46 °. This angular difference, combined with the choice of diameters means that part 7 comes into contact with hole 2 only at the place where it opens onto face 4 of the glass slide. Exhibit 2 being in "304 stainless steel", between part 7 and the conical part of the hole, a tapered washer 23 made of aluminum intended to avoid local excess of constraint. The two faces of the frustoconical washer 23 each have a half angle at the top of 46 °, like part 7. Aluminum is preferred here to a plastic material because of its greater stability over time.

For reasons of clarity, the exact values of angles and thicknesses relative have not been shown in the figure.

It will be noted that, for aesthetic considerations, the dimensions of the parts and hole have been calculated so that part 7 comes exactly in flush with the surface 4 of the glass plate 1, after tightening the device.

Figure 4 shows an embodiment according to the invention, for the assembly of two tempered glass plates. Two plates 1A, 1B have countersunk holes 2A, 2B in opposite directions, in which parts 7A, 7B are engaged identical to those of FIG. 1. The screw 12 is unique, it penetrates into the bore 10A of part 7A , and in the bore 10B of the part 7B, and is screwed into a nut 30, which abuts on a shoulder 11B of the hole 10B. Plastic (polyethylene) rings 31, 30A, 30B are interposed between the two glass sheets.

FIG. 5 schematically shows a variant in which the part 7 and the nut 14 are identical parts, placed symmetrically in the hole 2. The part 7 and the nut 14 have frustoconical parts having an apex angle of 46 °, while the hole has two opposite frustoconical parts 3A, 3B placed symmetrically and having an apex angle of 45 ° and separated by a cylindrical part 5.

The tightening is ensured by a threaded rod 40, which crosses parts 7 and 14 and two nuts 41, 42 which are screwed onto the rod 40. An extension 43 of the rod 40 is used for fixing the assembly to a support structure, not shown.

Figure 6 shows an embodiment with a double milling hole. The first part 7, which comes to marry a first frustoconical part 3A of the hole is connected to the reaction part 14, which marries the other frustoconical part 3B, by a connecting part 44, which has the shape of a head screw , whose threaded rod 45 is screwed into the reaction part 14n and the head 46 is housed with clearance in a cavity 47 of the part 7 by bearing on a shoulder 48 at the bottom of the cavity. The play makes it possible to compensate for a possible deviation between the axes of the frustoconical parts 3A, 3B. A central bore 49 passes through the connecting piece 45. It is intended to receive a structural element forming a fixing means, not shown.

FIG. 7 represents an assembly of two laminated plates 50, 51, each formed from two sheets of tempered glass 50A, 50B and 51A, 51B.

In the plate 50, an "internal" sheet 50A goes less far than the sheet outer 50B and, similarly, the inner sheet 51A goes less far than the sheet external 51B.

The sheet 50A comes to bear on the sheet 51B and the sheet 51A comes in press on sheet 50B.

Assemblies 52, 53 similar to those of FIG. 4 connect the sheets 50A, 51B and 51A, 50B. The sheets 50B and 51B have holes 54, 55 which are opposite the respective assemblies to allow the establishment and tightening.

The arrangement of the assemblies 52, 53 and the holes 54, 55 is calculated for avoid embrittlement of the whole. In particular, we will avoid putting them on the same vertical, a short distance from each other.

Of course, the invention applies not only to glass, but to all fragile materials.

Claims (17)

1. Method for assembling a glass sheet (1) having a countersunk hole at least on one side (2) with either another glass sheet or a structural element (S), in particular a metallic one, in which there is disposed in the countersunk hole (2) a connecting piece having two parts, one (7) of which fits the conical surface (3) of the countersunk hole, on which there is exerted a force substantially parallel to the axis of the hole, and the other (14) of which rests on the side (6) of the sheet opposite to the countersinking of the hole in order to support there the reaction of said force, characterised in that the two parts of the connecting piece are tightened with a tightening force which sets up, at the surface of the glass sheet at rest, a system of compressive stresses with a minimum located at a distance from the edge of the countersunk hole greater than 1% of the maximum diameter of this hole.
2. Method according to Claim 1, characterised in that the part (7) of the connecting piece which fits the conical surface (3) of the countersunk hole (2) has an angle of taper of the cone greater than that of the cone of the countersunk hole.
3. Method according to Claim 2, characterised in that the half angles at the top of the cones differ by 0.5° to 5°.
4. Method according to one of the preceding claims, characterised in that the part (7) of the connecting piece which fits the conical surface of the countersunk hole is metallic, and in that a sleeve of a malleable material such as aluminium is interposed between it and the countersunk hole.
5. Method according to one of the preceding claims, characterised in that the countersunk hole (3) is truncated and ends on the surface of the opposite sheet with a coaxial cylindrical part (5).
6. Method according to Claim 5, characterised in that no element (7, 9) of the connecting piece is in contact with the cylindrical part (5) of the countersunk hole (2).
7. Method according to one of the preceding claims, characterised in that the connecting piece is a nut-and-bolt system.
8. Method according to one of Claims 1 to 6, characterised in that the two parts of the connecting piece are crimped onto one another.
9. Method according to one of Claims 1 to 8, characterised in that the glass sheet is made of heat-treated glass with a thickness of at least 6 mm, and in that the two parts of the connecting piece are tightened with a tightening force such that, if the glass sheet is subjected to an external stress provided for in advance, said force sets up in this glass sheet a resulting system of compressive surface stresses which has a minimum situated at a distance from the edge of the countersunk hole greater than 1% of the maximum diameter of this hole.
10. Method according to Claim 9, characterised in that the heat-treated glass sheet has a doubly countersunk hole with a conical part (3A, 3B) opening out on either side and a cylindrical central part (5) which has substantially the same axis as the conical parts, in that it has a conical piece (7, 14) inside each conical part, in that a force directed along the axis of the hole is exerted between the two conical pieces, and in that the two conical pieces are tightened with a force such that, if the glass sheet is subjected to an external stress provided for in advance, there is set up in this glass sheet a resulting system of compressive surface stresses which has a minimum situated at a distance from the edge of the countersunk hole greater than 1% of the maximum diameter of this hole.
11. Method according to Claim 9 or 10, characterised in that the conical piece or pieces (7, 14) have an angle of taper of the cone greater than that of the cone of the corresponding countersunk hole.
12. Method according to one of Claims 9 to 11, characterised in that the conical piece or pieces (7) and possibly the reaction piece on the opposite surface are equipped with gripping means (12, 21, 22, 43) such as holes or projections, in order to transmit loads directed substantially in the plane of the glass sheet either to a structural element (S), or to another glass sheet.
13. Application of the method according to one of Claims 9 to 12 to the implementation of assemblies formed from prefabricated elements assembled on the worksite.
14. Prefabricated assembly comprising a heat-treated glass sheet with a thickness of at least 6 mm, provided with at least one countersunk hole (2) on one of its surfaces, and equipped with at least one connecting piece having a conical piece (7) inside the countersunk hole and a reaction piece (14) on the opposite surface, and where a force directed substantially along the axis of the hole is exerted between the conical piece and the reaction piece, characterised in that the two parts of the connecting piece are tightened with a force such that, if the glass sheet is subjected to an external stress provided for in advance, said force sets up in this glass sheet a resulting system of compressive surface stresses which has a minimum situated at a distance from the edge of the countersunk hole greater than 1% of the maximum diameter of this hole.
15. Prefabricated assembly according to Claim 14, characterised in that the heat-treated glass sheet has a doubly countersunk hole with a conical part (3A, 3B) opening out on either side and a cylindrical central part (5) which has substantially the same axis as the conical parts, in that it has a conical piece (7, 14) inside each conical part, in that a force directed along the axis of the hole is exerted between the two conical pieces, and in that the two conical pieces are tightened with a force such that, if the glass sheet is subjected to an external stress provided for in advance, there is set up in this glass sheet a resulting system of compressive surface stresses which has a minimum situated at a distance from the edge of the countersunk hole greater than 1% of the maximum diameter of this hole.
16. Prefabricated assembly according to Claim 14 or 15, characterised in that the conical piece or pieces (7, 14) have an angle of taper of the cone greater than that of the cone of the corresponding countersunk hole.
17. Prefabricated assembly according to one of Claims 14 to 16, characterised in that the conical piece or pieces (7) and possibly the reaction piece on the opposite surface are equipped with gripping means (12, 21, 22, 43) such as holes or projections, in order to transmit loads directed substantially in the plane of the glass sheet either to a structural element (S), or to another glass sheet.

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