How to break a glass plate

Abstract

The method comprises: a step of using a cutting tool (6) to draw a cutting line (2) on the surface of the glass; a step of positioning a flat supporting device (20), the flat supporting device (20) being arranged to generate pressure on the cutting line; and a step of breaking using a local supporting device (10), the local supporting device (10) being applied to a surface (4B) opposite to and facing the cutting line (2), the local supporting device (10) being moved on the opposite surface (4B) and supporting along the cutting line (2).

Description

[0001] This application is a divisional application of the PCT patent application "Method for breaking glass sheets" (national application number: 201880001835.5, applicant: Saint-Gobain Glass Factory, France), which entered the Chinese national phase on October 31, 2018. Technical Field

[0002] The present invention relates to the field of breaking glass sheets. Background Art

[0003] To perform such a break, two operations occur in sequence:

[0004] - a preliminary operation of scoring one or more surface flaws on the surface of the glass, for example with a glass engraving wheel or a laser; these flaws form lines on the contour of the shape; this operation is called a "cutting" operation;

[0005] - The operation of propagating an initial surface crack through the thickness of the glass sheet; this operation is called "breaking" and allows the shape to be cut to be separated from the initial glass sample called blank.

[0006] Currently, there are two techniques for breaking glass, based on the complexity of the volume to be cut out:

[0007] For simple shapes with straight edges that do not penetrate into the shape (no concavity in the shape), a straight reverse breaking technique can be used. This involves making a straight crosscut, that is, cutting from one edge to the other, and then using a rod or one or more point contacts to extend the entire crack by lifting the glass sheet over the entire length of the crack.

[0008] However, this method does not allow for the cutting of complex shapes. For shapes with non-rectilinear contours, the operation begins with a sheet of glass that is larger than the shape to be cut. This sheet is called a blank and is usually trapezoidal in shape.

[0009] The starting point is a blank with a square, rectangular or trapezoidal shape.

[0010] The outline of the shape to be cut is scored, for example, using a glass engraving wheel. Supplementary cuts on the shape with straight or curved sections are located on the periphery of the shape to be cut. These sections are called additional lines and allow for the correct breaking of the blank portion that lies outside the shape to be cut.

[0011] The breaking apart of the portion of the blank that is outside the shape to be cut in several steps results in the formation of distinct pieces called "offcuts" surrounding the complex shape to be cut.

[0012] The shapes to be cut are then separated from the offcuts of the blank.

[0013] When cutting the complex shapes described here, the breaking occurs by a technique of locally bending the initial crack by supporting or clamping the edge on the edge. The crack is bent by a lever arm mechanism by supporting the glass sheet outside the shape and at a limited number of points on a hard or soft cover.

[0014] By subjecting the portion outside the shape to be cut to bending, the glass sheet can be broken by subjecting an initial crack of a complex shape to bending.

[0015] The breaking apart can be done on a flexible mat. Force is applied to the scrap by bearing against it until it breaks and separates.

[0016] Breaking can also be done on a hard pad. The glass sheet is placed in an overhanging position so that a force is applied to the edge by supporting or clamping the glass sheet, causing it to deform until it breaks.

[0017] However, these techniques have several disadvantages.

[0018] In the case of breaking on a hard pad, there is a loss of sacrificial glass surface required to place the glass in an overhanging position during breaking.

[0019] There may also be problems with the cutting quality of complex shapes, because when a bearing force is applied to the edge material, it is often impossible to generate bending stresses at all points along the cutting line. This is especially true for reentrant shapes (where there is a concave shape on the shape to be cut). In this case, the glass can be bent at the entrance of the concave portion, but once a small crack has already propagated and before the tool applying the bearing force can be withdrawn, the stress field at the crack head is altered by the geometry of the cutting line. The pure bending applied at the beginning of the concave portion is quickly converted into shear stress and leads to spalling. In the case of shapes with small radii, cracks can propagate outside the initial cutting line and lead to losses.

[0020] Furthermore, this leads to restrictions on the complex shapes that can be realized, in particular in the case of geometries with small concave radii of curvature (deep inwardly curved areas), where it is difficult to position the bearing points in a suitable manner.

[0021] These difficulties make cracking concave shapes particularly complex. If the radius of curvature is very small, the location of the bearing points and the adjustment of the forces at these points become long and complex. In production, cracking of these geometries is often sensitive to the slightest changes in operating parameters, resulting in considerable waste. In addition, as the thickness of the glass increases, the tendency of the stress field at the end of the crack to change from a pure bending mode to a shear mode is exacerbated. Therefore, concave corner shapes are considered very difficult to produce for glass with a thickness of 3.85 or 5 mm. Summary of the Invention

[0022] It is an object of the present invention to provide a method for breaking a glass sheet with improved cutting quality.

[0023] To this end, the present invention provides a method for breaking a glass plate, comprising:

[0024] - a step of using a cutting tool to draw a cutting line on the surface of the glass;

[0025] - a step of positioning a flat supporting abutment means arranged to generate a pressing force on or around the cutting line and the area to be broken open;

[0026] - a step of breaking open using local bearing means applied to the face opposite to and facing the cutting line, said local bearing means being moved along the cutting line and bearing on said face opposite.

[0027] The supporting bearing means may be a flat surface provided with a covering whose rigidity enables the deformation zone of the glass to be controlled and limited when a local bearing force is applied on said face opposite the cutting line.

[0028] This bearing surface can be flat as described below, but it can also be more point-shaped (see diagram). The purpose remains the same, namely to control the deformation of the glass during the breaking operation.

[0029] The means for containing and controlling the deformation zone relative to the local bearing force applied to the face opposite the cutting line can also be obtained by using a vacuum to hold the face where the local bearing force is applied.

[0030] The local bearing force applied to the face opposite the cutting line can be generated by pressure or position.

[0031] This method has the advantage of enabling better control of the breaking quality by applying a holding force on the glass sheet in order to limit the propagation of the crack. The deformation of the glass is controlled by placing the glass sheet between the local breaking abutment means and the holding abutment means, so that the bending of the glass sheet during the breaking step can be controlled and limited, so as to locally control the crack propagation zone and thus prevent the occurrence of kinetic stresses / shear stresses that could lead to spalling.

[0032] According to one example, the bearing means is a flat surface. This surface is pressed against the glass (on the side on which the cutting line is formed) during the breaking operation. The force of this pressing is controlled. The hardness of this surface is selected to allow the above-mentioned control.

[0033] According to one example, the supporting device includes at least a pair of bodies acting as weights, the bodies being arranged on both sides of the cutting line on a surface where the cutting line is formed.

[0034] According to one example, each body is a profile.

[0035] According to one example, each body is a plot.

[0036] According to one example, a pair of cast blocks are placed so that the line is equidistant from the cast blocks.

[0037] According to one example, each cast block is positioned so as to form a straight line assembly with an adjacent pair of cast blocks.

[0038] According to one example, the flat bearing means comprise at least one pair of suction elements arranged on either side of the cutting line on a face opposite to the face on which the cutting line is formed.

[0039] According to one example, the getter element is a getter zone comprised in a getter station.

[0040] According to one example, the getter element is a getter cup.

[0041] According to one example, a pair of getter cups are positioned so that the line is equidistant from the getter cups.

[0042] According to one example, each of a pair of suction cups is positioned so as to form a straight line assembly with an adjacent pair of suction cups.

[0043] According to one example, the flat bearing means comprises a pair of casting blocks or suction cups, and said breaking step also comprises moving the flat bearing means, said movement of the flat bearing means being identical and simultaneous with the movement of the local bearing means. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The invention will be more readily understood by reading the following description, which is provided purely as a non-limiting example, with reference to the following drawings:

[0045] - Figure 1a and 1b is a schematic view in vertical section of the different steps of the method according to a particular embodiment of the invention;

[0046] - Figures 2 to 7 is a schematic view of a first embodiment of the present invention and its application mode;

[0047] - Figures 8 to 11 is a schematic view of a second embodiment of the present invention and its application mode;

[0048] - Figure 12 Various embodiment variations are shown. DETAILED DESCRIPTION

[0049] The method according to a particular embodiment of the invention first comprises a step of marking a cutting line 2 (or "line"), that is, a step of producing a crack on a first face 4A of the glass sheet 4, followed by a step of turning the glass sheet over in order to carry out a subsequent step of locally bearing against the crack on a face 4B opposite the first face. The marking of the cutting line corresponds, for example, to the contour of the complex shape to be cut, without any additional lines.

[0050] It should be noted that throughout this document, by "complex shape" is meant a curved line, or a series of lines, some of which are not straight lines, or straight lines with a change of direction forming at least one concave portion. The method according to the invention thus allows the cutting of simple (straight) or complex shapes from a glass sheet.

[0051] The expression "two interlocking shapes" is used to mean that a convex portion extends into another concave portion; that is, the outlines of the two shapes cannot be separated by a straight line.

[0052] The expression "two tangent shapes" is used to mean that they have a portion in common to their contours.

[0053] Also make sure the glass sheet you are cutting is flat.

[0054] The cutting line is drawn, for example, using a glass engraving wheel 6 or any other suitable cutting device, such as a laser. The cutting line 2 is intended to allow for a crack along this line during the breaking step. This is therefore a partial cut, meaning that it only cuts through a portion of the thickness of the glass sheet. This is used throughout the text to mean the "cutting line."

[0055] As described above, with this method, some or all of the additional lines according to prior art methods may be eliminated. In fact, the additional lines may only be needed to open the contour to extract the shape, rather than to facilitate breaking apart complex shapes.

[0056] The first face 4A of the glass sheet 4, on which the cutting line 2 has been formed, rests on a flat supporting surface 8. This can be, for example, a flexible pad. The deformation of the flat supporting surface 8 is selected so as to control the stress field applied by the local supporting means. By controlling the stress field, the crack propagation length can be controlled. Depending on the shape to be cut, the aim is for the crack to propagate to a predetermined length. The length selected for the crack will decrease as the local radius of curvature is reduced. If the crack propagates too quickly, a less deformable surface or a lower supporting pressure must be selected. If the crack propagates too slowly, a more deformable surface or a higher supporting pressure must be selected.

[0057] For a standard soda-lime-silica glass pane of the Planilux type with a thickness of 3.15 mm, the parameters are as follows:

[0058] Cutting parameters:

[0059] Grinding wheel: angle 150°, width = 1mm, diameter: 5 mm

[0060] Grinding wheel speed: 100 m / min

[0061] Force applied to the glass = 50 N

[0062] Grinding wheel penetration into glass: 4 / 100 mm

[0063] Glass thickness: 3.15 mm

[0064] Reverse breaking parameters:

[0065] Breaking tool: wheel type, diameter: 5 mm, width: 1 mm

[0066] Tool movement speed: 30 m / min

[0067] Force applied to the glass = 70 N

[0068] Hardness of the covering of the flat support device: Felt pad, hardness: 45-52 Shore

[0069] The local bearing device 10 is, for example, a ball of any suitable type, or another local bearing device of any suitable type, such as a scoring wheel, preferably a ring-shaped scoring wheel. The ball has, for example, a diameter of 1 mm. In a variant, any suitable diameter can be selected, in particular up to 10 or even 20 mm.

[0070] The selected local bearing means 10 is preferably rigid, for example made of steel or a suitable plastic.

[0071] The local bearing means 10 are moved along the cutting line, preferably simultaneously applying a continuous bearing force along the entire length of the cutting line, e.g. Figure 1a and 1b . However, in one variant, the bearing is continuous but with variable intensity, the intensity being chosen, for example, based on the radius of the local curvature of the shape to be cut, and supplemented, for example, with a periodic variation of intensity, that is to say an oscillating bearing. In another variant, the bearing on the glass sheet is implemented in a discontinuous manner.

[0072] The local bearing means is moved relative to the glass sheet. However, it should be noted that in a variant it is the glass sheet or both elements that are moved. As a general principle, there is a relative movement of the local bearing means 10 relative to the glass sheet 4.

[0073] The flat bearing surface 8 is formed, for example, by a table and is therefore formed by a continuous flat surface. However, in a variant, the flat bearing surface 8 can be discontinuous. It can, for example, comprise a plurality of flat bearing surfaces, for example obtained from a plurality of parts of a table. It is important to provide a flat bearing surface 8 facing the partial bearing device 10, that is, a bearing that is at least twice as wide as the bearing applied by the partial bearing device, in order to achieve a clean break.

[0074] It should also be noted that the turning step is optional. For example, the glass sheet 4 can be raised using a suction table, and thus the local bearing means 10 can be applied from below, against which the first face 4A of the glass sheet rests.

[0075] According to the invention, the breaking method also comprises a step of positioning flat abutment means 20. These flat abutment means 20 can take various forms.

[0076] These flat bearing means 20 are arranged to generate pressure on the face of the glass on which the cutting line 2 is arranged. This pressure is applied to the glass at the location of the cutting line.

[0077] These bearing devices 20 have the function of applying compressive stress / pressure to the glass sheet 4 in order to control the propagation of the cut. This stress / force applied to the sheet at the cut line allows for controlled crack propagation. In practice, this pressure is applied so that the glass sheet 4 is positioned between the localized bearing devices 10 and the flat bearing devices 20. This arrangement limits or even eliminates bending of the glass sheet 4 during the breaking step, preventing the occurrence of shear stresses that could cause delamination.

[0078] This control of the breaking apart is provided by the compressive stress of the flat bearing means 20 .

[0079] exist Figure 2 In the first embodiment shown in FIG, a flat supporting device 20 comprises at least two weights 21. These weights 21 are simple bodies made of metal, mineral, or other materials. These bodies are positioned on the first face 4A of the glass sheet 4 on which the cutting line 2 has been formed. This arrangement enables the bodies to exert a force on the glass sheet 4.

[0080] exist Figure 3 In the first application mode shown in FIG, a flat supporting device 20 comprises two bodies 21 acting as weights. These bodies are arranged in the form of strips or profiles 22a. These profiles 22a are then positioned on either side of a portion of the cutting line. According to a first example, the profiles 22a are rectilinear.

[0081] If this part Figure 3 As can be seen in the figure, the straight-line profile 22a is positioned parallel to the portion.

[0082] If the section is curved, the rectilinear profile 22a is positioned parallel to a tangent to the section.

[0083] If this part Figure 4 The straight profile 22a is located parallel to the guide axis of the section, which is considered to be the axis passing through the mean value.

[0084] according to Figure 5 In a second example, visible in FIG, the profile 22 a has a shape similar to the cutting line, so that if this line is curved, the profile 22 a will be curved with the same curvature, and if the line is sinusoidal, the profile 22 a will be sinusoidal with the same sinusoidal form. Advantageously, this second example allows the profile 22 a to be placed at the same distance from the line presenting a non-straight portion, so as not to unbalance the opening.

[0085] exist Figure 6 In the second application mode, which can be seen in FIG, the flat support device 20 comprises a plurality of pairs of bodies 21 acting as weights. These bodies are made, for example, in the form of cast blocks 22b or cylindrical parts. These cast blocks 22b are then positioned on both sides of a portion of the cutting line 2.

[0086] If the portion is rectilinear, the cast blocks 22b are positioned in pairs so that the line 2 is equidistant from the two cast blocks 22b of the same pair. The cast blocks 22b of the pair are then regularly distributed along the portion.

[0087] If the portion is not straight, the cast blocks 22b are advantageously positioned in pairs so that the line 2 is equidistant from the two cast blocks 22b of the same pair, e.g. Figure 6 These sprues 22b are then regularly distributed along the portion. However, in the case of a sinusoidal curve, the sprues 22b may be positioned so that all sprues 22b on each side of the sinusoidal line are aligned in a straight line, as shown in FIG. Figure 7 This arrangement is possible because this distribution based on a sinusoidal line enables a uniform stress to be applied along the breaking line 2 .

[0088] In the second embodiment, the flat supporting device 20 includes suction elements 23. These suction elements 23 are devices or apparatuses comprising at least one pump and a suction nozzle. These suction elements 23 are positioned on the face 4B opposite the first face of the glass sheet 4. This arrangement enables the suction elements 23 to exert tension on the glass sheet 4.

[0089] exist Figure 8In the first application mode, visible in FIG, the suction element 23 comprises a suction table. This table comprises a cutting table, that is, a table that allows relative movement of the partial support device 10 relative to the glass sheet 4. Its suction element 23 is in the form of at least two suction zones 25, each of which is a plate having at least one opening, preferably a plurality of openings. These plates are connected to a pump via lines connecting the pump to the openings in the plate, in order to generate the suction effect. The two suction zones 25 are arranged so as to allow the partial support device 10 to circulate between them. Thus, the suction zones 25 are able to draw suction from the glass sheet on both sides of the breaking line.

[0090] exist Figure 9 In the second application mode, which can be seen in FIG, the suction element 23 comprises a plurality of suction cups 24. These suction cups 24, which are preferably arranged in pairs, are manufactured, for example, in the form of a cast block or a cylindrical part. These suction cups 24 are then positioned on both sides of a portion of the cutting line. Each suction cup 24 is connected to a suction system, which can be dedicated to each cup or common to all suction cups 24, to allow suction.

[0091] If the portion is straight, the suction cups 24 are positioned in pairs so that the line is equidistant from the same pair of two pouring blocks, e.g. Figure 10 These pairs of suction cups 24 are regularly distributed along the portion.

[0092] If the portion is not straight, the suction cups 24 are advantageously positioned in pairs so that the line is equidistant from the two suction cups 24 of the same pair, e.g. Figure 3 As shown in . These pairs of suction cups 24 are then regularly distributed along the portion. However, in the case of a sine curve, the suction cups 24 may be positioned so that all suction cups 24 on each side of the sine line are aligned in a straight line, as shown in . Figure 11 This arrangement is possible because this distribution based on the sinusoidal lines 2 enables a uniform stress to be applied along the breaking line.

[0093] In a variant of the various embodiments, a movable flat support device 20 can be provided. To this end, the flat support device comprises two suction cups 24 or two bodies 21 acting as weights. The two suction cups 24 or bodies 21 acting as weights are arranged so as to be motion-fixed. This means that a movement of one of the bodies or cups acting as weights automatically causes the same movement of the other body or cup acting as weight, e.g. Figure 12 Visible in.

[0094] The breaking step can thus take place with simultaneous movement of the partial support means 10 and the flat support means. This breaking step therefore first comprises placing the partial support means 10 and the flat support means facing each other relative to the glass sheet. In the case of the suction cup 24, suction is then started.

[0095] Then, pressure is applied to the partial bearing means so that the partial bearing means presses the glass sheet at the location of the breaking line and the glass sheet can be broken.

[0096] Third, the partial bearing means and the flat bearing means move simultaneously in the same manner. It is understood that the movement of the partial bearing means and the flat bearing means is achieved in such a way that the partial bearing means and the flat bearing means continuously face each other. This simultaneous movement advantageously allows pressure to be applied only at the locations where rupture is desired.

[0097] It is obvious that the invention is not limited to the illustrated examples but can be varied and modified in different ways obvious to a person skilled in the art.

Claims

1. A method for breaking a glass plate (4), comprising: - a step of scoring a cutting line (2) on the surface of the glass using a cutting tool (6), said cutting line being the outline of a complex shape, said complex shape being a curved line or a series of lines, some of which are at least not straight lines, or being straight lines with a change of direction forming at least one concave portion; - a step of positioning a flat abutment (20) arranged to generate pressure on the face of the glass on which the cutting line is arranged; and - a step of breaking open using a local bearing device (10), said local bearing device (10) being applied to a surface (4B) opposite and facing said cutting line (2), said local bearing device (10) being moved on said opposite surface (4B) and bearing along said cutting line (2); The breaking step also includes moving the flat supporting device, and the movement of the flat supporting device is the same as and simultaneous with the movement of the partial supporting device.

2. The breaking method according to claim 1, wherein the flat supporting device (20) includes at least a pair of bodies (21) acting as weights, which are arranged on both sides of the cutting line on the surface on which the line is formed.

3. The breaking method according to claim 2, wherein each main body (21) is a profile (22a).

4. The breaking method according to claim 2, wherein each main body (21) is a cast block (22b). 5 . The breaking method according to claim 4 , wherein a pair of the casting blocks are placed so that the cutting line is equidistant from the casting blocks.

6. The breaking method of claim 4, wherein each of a pair of cast blocks is positioned so as to form a straight assembly with an adjacent pair of cast blocks.

7. The breaking method according to claim 1, wherein the flat supporting device (20) comprises at least one pair of suction elements (23) arranged on both sides of the cutting line (2) on opposite sides of the surface on which the line is formed.

8. The breaking method according to claim 7, wherein the suction element (23) is a suction area (25) included in a suction table.

9. The breaking method according to claim 7, wherein the suction element (24) is a suction cup (24).

10. The breaking method according to claim 9, wherein a pair of the suction cups (24) are placed so that the cutting line is equidistant from the suction cups.

11. The breaking method according to claim 9, wherein each of a pair of suction cups (24) is positioned so as to form a straight assembly with the suction cups of an adjacent pair.

12. The breaking method according to claim 4 or 9, wherein the flat supporting device (20) comprises a pair of casting blocks (22b) or suction cups (24).

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