JPS5921534A - Heater for bending glass plate - Google Patents

Abstract

PURPOSE:To obtain bent parts having superior appearance and quality by placing spirally wound heaters such having a flat cross-section above a glass plate along the bending lines for relatively sharp bending while leaving a prescribed interval. CONSTITUTION:When a glass plate 1 is bent with a bending die 4 composed of the body 11 for bending the middle part of the plate 1 and bending sections 13 attached to both sides of the body 11 so that the sections 13 can be freely bent through supporting shafts 12, the parts of the plate 1 along the bending lines are heated with heaters 5a, 5b suspended from supporting rods and placed above the surface of the plate 1 at a prescribed interval. Each of the heaters 5a, 5c is formed by spirally winding a linear or ribbonlike heater filament and by making the cross-section flat. Electric currents are supplied to the heaters 5a, 5b through feeders 7 to heat the heaters 5a, 5b, thereby partially heating the parts of the plate 1 along the bending lines, and the plate 1 is sharply bent by its empty weight along the bending lines.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a glass plate heating device for bending a glass plate to a relatively sharp angle.

Recently, in response to the diversification of automobile designs, glass plates that are relatively sharply bent into a V-shape or an L-shape as shown in FIG. 1 have begun to be used. As a method of forming this type of glass plate, ribbon heaters for local heating of the glass plate are placed under tension at a predetermined interval along the bending line of the glass plate, and the heaters are electrically heated. A method has been proposed in which the curved portion of the glass sheet is heated to a higher temperature than the other portions and bent sharply. However, this method is suitable for bending to a sharp angle of 30R or less, but it is suitable for bending into a curve of about 30R to 150R, or when bending into a curved line as shown in Figures 2 and 3. When bending sharply along a bending line, heating of the sharply bent portion becomes inadequate, and the desired curvature is
Alternatively, it was found that it is difficult to bend with a desired curved shape with a good appearance, and that the heater tends to stretch easily due to the tension, and the lifespan is short.

The present invention has improved on these points, and relates to a heating device for bending a glass plate that can easily obtain a desired heating state and can be easily installed. That is, the gist of the present invention is to arrange a heater at a predetermined distance from the surface of the glass plate on the bending line where the glass plate is to be bent relatively sharply, and to heat the heater with electricity to bend the curved portion of the glass plate. In a heating device for bending a glass plate relatively sharply along the bending line by heating the glass plate to a temperature higher than its softening point, the heater winds a wire or ribbon-shaped heater filament in a helical shape, The present invention relates to a heating device for bending a glass plate, characterized in that the heater is flat and is supported by a support member at a predetermined distance from the surface of the glass plate.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

1 to 3 show front views of a glass plate for a rear window of an automobile manufactured according to the invention, in which the glass plate 1 is sharply bent along a bending line 2. FIG.

FIG. 4 shows an oblique front perspective view of a glass plate bending and heating apparatus according to a specific example of the present invention, in which 3 is a frame, 4 is a bending mold, and 5a and 5b are heaters (hereinafter referred to as 5). omitted)
, 6a, 6b, 6c, and 6d (hereinafter abbreviated as 6), and 7 indicate power supply lines that supply electric power to heat the heater.

In this heating device for glass plate bending, the frame 3 supports the bending die 4, and the energized vertical support member 8
It is composed of a horizontal support member 9 and a bending mold mounting member 10. This frame body 3 is conveyed within the glass plate heating furnace by, for example, rollers, chains, or other various conveyance means.

The bending mold 4 is a skeleton type that is composed of a main body 11 that takes charge of bending the middle part of the glass plate 1, and bending parts 13 that are attached to both sides of the main body 11 so as to be bendable about a support shaft 12. The main body part 11 and the bent part 1
The upper surface of 3 serves as a forming curved surface and is formed into substantially the same shape as the final bent shape of the glass sheet 1 at the end of the bending operation.

A counterweight 14 for applying a moment to bend the bending part 13 around the support shaft 12 is attached to the bending part 13 on a mounting arm 15 whose end is fixed to the bending part 13. The bending action of the bending portion 13 helps the plate 1 to bend under its own weight.

The heater 5 serves as a heating means for locally heating the bending line portion of the glass plate 1 where the glass plate 1 is to be bent sharply, and for sharply bending the glass plate 1 to, for example, 15R to 150R by its own weight along the bending line portion. 1 along a desired bending line and at a predetermined distance from the glass plate surface.

Usually, the heater 5 is arranged between the main body part 11 and the bending part 13 of the bending die 4, that is, on a line connecting the opposing support shafts 12 of the bending die 4, or in the vicinity of the line. . Particularly in the case of molding a concavely curved glass plate, it is preferable that the heater 5 is placed slightly closer to the center of the glass plate than the above-mentioned bending line connecting the opposing support shafts 12. because,
When the central part of the glass plate is bent into a concave shape by its own weight, the glass plate moves downward, causing the heater 5 to shift from the desired bending line of the glass plate 1 toward the side of the glass plate, causing the heater 5 and the bending line to become disconnected. The above-mentioned arrangement is particularly preferable, since the bending along the desired line will not be possible due to misalignment.

When the heater 5 is placed on the bending line 2 of the glass plate 1,
It is preferable that the distance between the glass plate 1 and the heater 5 be 2 mm to 50 mm, particularly preferably 5 mm to 15 mm. For example, if this gap is smaller than 2 mm, there is a risk that the heater will come into contact with the glass plate surface during the bending process, leaving traces of the heater, or that the heater may weld to the glass plate. When a colored band is provided at the bent portion, there is a risk of welding to the colored band, which is not preferable. Moreover, if it is larger than 50 mm, even if the electric power is increased, it is not possible to locally heat the curved portion of the glass plate, and it becomes difficult to bend the glass plate relatively sharply to a curvature of, for example, 15R to 150R.

The distance between the glass plate and the heater should be within the above range, depending on the angle of bending, curvature, heating temperature of the heater,
Change as appropriate depending on the width of the heater, etc.

The heater may be arranged on the side of the glass plate that is sharply bent, or on the opposite side, that is, below the forming surface of the bending mold 2, or on both sides.

The width of the effective radiation surface that effectively locally heats the curved line portion of the glass plate of such a heater is 15R to 15R.
3mm to 50mm so that it can be bent with a curvature of 0R
, particularly preferably from 5 mm to 20 mm.

Note that a lead wire for power supply is connected to the end of the heater, so that it is heated by electricity.

The bending method of the heating device for glass plate bending shown in Fig. 4 is to heat the glass plate and locally heat the bent line part of the glass plate using a heater, and then use the glass plate's own weight to bend the glass plate into the bent line. This method describes a method of sharply bending a glass sheet along a curved line, but the invention is not limited to this method. Similarly, after locally heating the curved portion of a glass sheet, the heated glass sheet is placed between the press molds of a press-forming device. A method in which a glass plate is press-formed and sharply bent along a curved line portion with or without removing the heater is also applicable to the present invention.

In the present invention, as a heater, a linear or ribbon-shaped heater filament is wound in a helical shape, and the cross section thereof is flattened. A heater consisting of a heater wire is used. Such ribbon-shaped heater wires include ribbon-shaped nichrome, platinum alloy, stainless steel, and tantalum having a thickness of about 0.05 to 1 mm, a width of about 2 mm to 20 mm, and an electrical resistance of about 0.1 Ω/m to 20 Ω/m. Typical examples include molybdenum, platinum, tantalum alloys, and molybdenum alloys.

Typical linear heater wires include nichrome, platinum alloy, and stainless steel with a diameter of about 0.5 to 5 mm and an electrical resistance of about 0.1 Ω/m to 20 Ω/m. .

By winding such a linear or ribbon-shaped heater filament in a spiral shape and flattening its cross section, it is possible to apply more than twice the electric power per unit length compared to a conventional ribbon heater. It is easy to generate heat using electricity, and since the heater is not under tension, burnout can be prevented, and appropriate rigidity can be provided. , or
A curved heater can be easily obtained, and a heater that is also lightweight and easy to handle can be obtained. Therefore,
When the heater is placed along the curved line of the glass plate, there is no need for tension, and the heater can be easily installed. In addition, when winding a linear or ribbon-shaped heater filament in a spiral shape, it is preferable that there is no core material.

A typical heater and its specific installation in the case where heaters made of such flat cross-section spiral-wound heater wires are arranged at predetermined intervals along a desired curved line of a glass plate will be described below. The structure shown in FIG. 5 consists of a plurality of thin metal wires on the surface opposite to the glass plate of the flat cross-section spiral-wound heater 20, which is formed by winding heater wires in a spiral shape and making the cross section flat. A part of the metal ring 21 is welded, this metal ring 21 is locked with a support body 22 made of a heat-resistant insulating material, and the support body 22 is attached to a part of a bending mold or frame body to form a glass plate. They are arranged at predetermined intervals along a desired bending line.

Such a flat cross-section spiral-wound heater 20 is suspended from above a glass plate placed on a bending mold, so that the heating surface 23 of the heater 20 faces the curved line portion of the upper surface of the glass plate, and heats the glass plate. Alternatively, the glass plate placed on a bending mold may be supported from below so that the heating surface 23 of the heater 20 faces the bent line portion of the lower surface of the glass plate and heated. You may also do so.

The example shown in Fig. 5 has a width of 6.5 mm, a thickness of 0.3 mm,
A glass plate of a flat cross-section spiral-wound heater 20 (without core) in which a ribbon-shaped nichrome heater wire with a resistance value of 0.597 Ω/m is wound in a spiral shape without any gaps and is flattened to have a flat cross section of 2 mm and a width of 5 mm. A metal ring 21 made of 0.5φ SUS304 metal wire is spot welded and attached at a predetermined interval on the opposite side of the surface facing the It is designed to be supported by a support body 22. In this case, since the support body 22 is tubular, it can be easily supported by a bending mold or a frame by inserting support member attachment members 24 into both ends of the support body. Further, in the example shown in FIG. 6, metal strips made of SUS metal wires of 0.5φ are placed at a predetermined interval on the opposite surface of the flat cross-section spiral-wound heater 20 that faces the glass, similar to that shown in FIG. The ring 21 is attached by spot welding, and using this metal ring 21, it is supported by a plurality of supports 22 made of φ3 alumina insulating tubes, and also via an insulating support 25 made of alumina etc. The heater 20 supported by the support body 22 is supported by the second support body 26.

In the example shown in FIGS. 5 and 6, the glass plate is supported vertically by the pressing method, whether the heater 20 is placed on the upper surface of the curved portion of the glass plate or on the lower surface. It can also be preferably applied when it is arranged on one or both sides of. In addition, since the heater 20 is supported using a support rather than directly supported by means such as directly tensioning it, it is possible to suppress the heater from sagging, and also to support the heater 20 along the curved line of the glass plate. The heaters can be accurately supported at predetermined intervals, desired heating can be performed, and bending can be performed along a predetermined curvature and a predetermined bending line. In particular, the heater and its mounting structure shown in Figures 5 and 6 are optimal when sharply bending a glass plate along a curved curved line that requires heating with high precision and desired distribution. It is.

Next, a method for sharply bending a glass plate using the apparatus according to the embodiment of the present invention shown in FIG. 4 will be described.

A soda lime glass plate for a rear window of a passenger car with dimensions of 1425 mm x 615 mm x 4 mm was placed on a skeleton type bending mold 4 having a molding surface on the top as shown in Fig. 2.
Next, a curved bending line (curvature of 14,000R) 2 of the glass plate 1 is used to bend the glass plate 1, that is, a bending die 4
A heater like the one shown in FIG. 5 is installed as shown in FIG. 5 at an interval of 5 to 30 mm on a curved line connecting the opposing support shafts, and a power supply line 7 is connected to both ends of the heater for heating. connected. The bending mold with this glass plate placed thereon is placed in a heating furnace, and the entire glass plate is heated to 640°C to 670°C. When the glass plate reaches this temperature, turn on the heater.
A power of 36 V x 50 A (1,800 W) is supplied, the heater is electrically heated to a temperature of 1100°C to 1300°C, and the curved line portion of the glass plate 1 near the heater 5 is locally heated to 690°C Heat to a temperature of 730°C.

14, due to the load of the counterweight 14 of the bending mold 4 when the bending line portion of the glass plate reaches 650°C or higher.
The glass plate was sharply bent to a curvature of about 20R along a curved bend line with a curvature of 000R. Then, the wind cooling is strengthened,
Made of tempered glass.

As described above, according to the device of the present invention, especially 15R to 15
With a curvature of 0R, the glass plate can be sharply bent into a straight or curved shape, and the appearance of the bent part is
Particularly excellent quality can be obtained. The heating device for bending a glass plate of the present invention heats the bending line portion of the glass plate, and then bends the glass plate under its own weight or press-forms it to 15R to 150mm.
It is best suited for bending into a straight or curved shape with a curvature of It can also be applied when bending sharply.

[Brief explanation of drawings]

Figure 1 is a perspective view of a glass plate sharply bent along a straight curved line, Figures 2 and 3 are perspective views of a glass plate sharply bent along a curved curved line, and Figure 4. 1 is a front perspective view of a heating device for bending a glass plate according to an embodiment of the present invention, and FIGS. 5 and 6 are explanatory views showing a heater and a mounting portion of the heater. 1: glass plate, 2: bending line, 5: frame, 4: bending mold, 5, 20: heater, 6: heater support, 7: power supply line, 21: metal ring, 22: support, 23 :Heating surface of heater

Claims (6)

[Claims] (1) A heater is arranged at a predetermined distance from the curve of the glass plate on the bending line where the glass plate is to be bent relatively sharply, and the heater is energized and heated to bend the curved part of the glass plate above the softening point of the glass plate. In the heating device for bending a glass plate relatively sharply along the bending line by heating the glass plate to a temperature of 1. A heating device for bending a glass plate, characterized in that the heater is supported by a support member at a predetermined distance from the surface of the glass plate. (2) The heating device for bending a glass plate according to claim 1, wherein the heater is supported by a plurality of insulated supports at a predetermined distance from the glass plate surface. (3) A thin metal wire is welded to the surface opposite to the glass plate of the heater, which is wound in a helical shape and has a flat cross section, and the metal wire is locked to an insulated support body to achieve the above-mentioned 2. A heating device for bending a glass plate according to claim 1, wherein the heater is supported at a predetermined distance from the surface of the glass plate. (4) Claims characterized in that a heater wound in a spiral shape and having a flat cross section is supported by a support made of a heat-resistant insulating material that is thinner on the side opposite to the surface of the heater that faces the glass plate. 2. The heating device for bending a glass plate according to item 1. (5) The heating device for bending a glass plate according to claim 1, wherein the heater is linear. (6) The heating device for bending a glass plate according to claim 1, wherein the heater has a curved shape.