GB2357756A

GB2357756A - Forming belt for shaping glass

Info

Publication number: GB2357756A
Application number: GB9930651A
Authority: GB
Inventors: Christopher David Willia Lomas; Philip George Reeves
Original assignee: Pilkington PLC
Current assignee: Pilkington Group Ltd
Priority date: 1999-12-24
Filing date: 1999-12-24
Publication date: 2001-07-04
Anticipated expiration: 2019-12-24
Also published as: GB9930651D0; GB2357756B

Abstract

A forming belt for use in shaping glass comprising a flexible, continuous belt (1) with a seam (18) and a heat resistant web piece (12) positioned on a surface of the belt to cover the seam, at least partially, so as to provide a substantially even forming surface. Preferably, the belt comprises a laminate having a durable layer (8) and a soft layer (6), with the exposed surface of the soft layer comprising the forming surface (20) of the belt, and the heat resistant web piece comprises an elongate flap (12), integral with the soft layer, which is laid across the seam in the belt. The invention also relates to apparatus for and a method of shaping glass using a forming belt by heating the glass sheet to be shaped and bringing the glass sheet into contact with the forming surface of the forming belt.

Description

2357756 FORMING BELT The present invention relates to a forming belt,

which is a belt used to modify the shape of, or impart a specific shape to, work pieces brought into contact with it. In particular the present invention relates to a forming belt for use in shaping glass sheets.

It is known to shape glass sheets for use in glazings in buildings and especially in vehicles. It is important that shaped glass sheets are free of optical defects for reasons of safety and aesthetics.

There are several methods known for shaping glass sheets. The methods involve heating the glass sheet to its softening temperature, shaping the sheet and, often, quenching the hot glass sheet in order to toughen it. The shaping step may involve pressing the hot glass sheet between opposed moulds. Alternatively, the hot glass sheet may be supported on a frame and allowed to sag under its own weight. Methods are also known for shaping glass sheets using a forming belt.

WO 99124373 discloses a method and apparatus for bending a glass sheet using a forming belt, especially a continuous belt. The method disclosed involves pressing the hot glass sheet with at least one belt against a bending member.

European patent EP 0 374 691 B 1 discloses a method of shaping a glass sheet using an advancing flexible belt to transfer a hot glass sheet and to position it relative to an upper shaping surface of a press mould. When so positioned the belt is stopped and the belt and shaping surface are moved together in order to shape the glass sheet. In this document, it is preferred that the belt should not be continuous so as to avoid the presence of a seam, which could adversely mark the glass. Instead, the belt reciprocates, returning to its initial position between glass sheets.

However, this has the disadvantage that a certain length of time is needed for the belt to return to its initial position. In order to allow the very high throughputs required of modem continuous shaping processes, it is desirable to use a continuous (i.e. endless) forming belt, and so a suitable technique for joining the belt is required. The joint should be of high strength to withstand tension in the belt, and yet it is important that a smooth surface is maintained over the joint so that the glass sheet is not marked.

The present invention accordingly provides a forming belt comprising a flexible, continuous belt having a seam therein, wherein a surface of the belt comprises a heat resistant 2 web piece Positioned so as to cover, at least partially, the seam in the belt, thereby providing substantially even forming surface.

This is advantageous because a substantially even forming surface reduce; the likelihood of marking when the forniing belt is used in e.g. shaping glass sheets.

The seam in the belt may have an orientation extending generally traversely across the belt i.e. in a direction lying in the plane of the belt and generally perpendicular to its edge.

The heat resistant web piece will usually be firmly fixed to the surface of the belt by at, least one of its edges. The method used to fix the or an edge of the heat resistant web)iece. will depend on the materials from which the web piece and the belt are made. It is pref -,rred;, if the method used to fix the or an edge of the web piece to the belt does not itself fcrm a seam in the fornuing surface of the belt. Suitable methods include needle punching and' sewing.

In a preferred embodiment of the invention the heat resistant web piece is firmly: '1xed to the surface of the belt by only one or some of its edges leaving at least one end free. Mius,; preferably the beat resistant web piece comprises a flap, the free end of which is laid at east: partially over the seam in the belt. If the seam is only partially covered by the flap, it is,: preferred if another web piece is positioned so as to cover the remaining part of the scam. The other web piece may be a second flap, the free end of which is positioned in abuting', relationship to the first flap so that together they cover the seam. However, more prefer, Lbly, the heat resistant web piece comprises an elongate flap, the free end of which is laid agoss the seam in the belt. Usually, the free end of the flap or the elongate flap will be li adhered to the forming surface over or across the seam. Possibly, there may be one or ore narrow flaps which together make up the width of the belt. These flaps may be laid a oss the seam in the same, opposed or alternating directions.

The material of the heat resistant web piece may be any suitable heat resistant fabric and is preferably relatively soft, so as to reduce the marking of glass when the forming bt It is used to shape glass. Preferably the heat resistant web piece comprises a heat resistant itonwoven fabric, for example, a heat resistant twill or felt. Most preferably the heat resi tant web piece comprises a non-woven needle punched stainless steel fabric (for example as wId as BekinoXTM fabric by Bekintex NV, Wetteren, Belgium).

3 The material of the belt may be any suitable heat resistant fabric and is preferably mechanically durable with an even or relatively soft surface comprising the forming surface of the belt. A particularly suitable material is of a multi-layer or laminate construction having a mechanically durable layer (for strength) and a soft layer (to reduce marldng of the glass). Thus, preferably, the belt comprises a laminate having a mechanically durable layer (preferably a woven layer) and a soft layer (preferably a non-woven, needle-punched layer), and wherein the exposed surface of said soft layer comprises the forming surface of the belt. The laminate is preferably joined through the mechanically durable layer to form the continuous belt.

Preferably, the soft layer of the laminate comprises a heat resistant nonwoven fabric, for example a heat resistant twill or felt, more preferably a non-woven, needle-punched stainless steel fabric. The mechanically durable layer of the laminate may be a woven material, especially woven stainless steel. The soft layer may be fixed to the mechanically durable layer by any suitable method, preferably by needle-punching or sewing. A suitable material for the laminate is Bekitherin Wm stainless steel fabric (obtainable from Bekintex NV, Wetteren, Belgium).

If the belt comprises such a laminate it is preferred that the heat resistant web piece comprises an elongate flap integral (i.e. forming a whole) with the soft layer, the free end of said elongate flap being laid across the seam in the belt. This is advantageous because an integral elongate flap is simple to make and avoids the problem of a separate heat resistant web piece having to be fixed to the surface of the belt and thereby possibly introducing unevenness at the fixing point on the surface of the belt.

The elongate flap integral with the soft layer is preferably adhered to the soft layer across the seam. This may be achieved by thinning the fabric of the elongate flap and of the soft layer and then by intimately contacting the elongate flap with the soft layer by, for example, brushing or combing. Thus preferably, the free end of the elongate flap is adhered to the soft layer across the seam by brushing or combing said elongate flap on to the soft layer so that the constituent fibres of the fabrics become entangled. Surprisingly, this simple method of attachment has been found to withstand extended use without the flap detaching from the soft layer.

4 The forming belt of the present invention usually comprises at least one flexible s rip of material joined at its ends to define the belt; the seam occurTing at the join. The ends of the, strip may be joined by overlapping or by abutting the ends. A reinforcing piece oF heg resistant fabric may be fixed across the join so as to strengthen it. Usually, the strip will b joined at its ends by welding, spot-welding or sewing. Preferably, the strip is joined b. i spot welding with overlapping spot welds to improve the strength of the weld and to redu c the likelihood of ridges of belt material rising up between spot welds.

In a preferred embodiment, the present invention provides a forming belt for x se in shaping glass comprising at least one flexible strip of material joined at its ends to delne a flexible, continuous belt having a transverse seam therein, wherein the belt compr ses 11 laminate having a mechanically durable layer and a soft layer, the exposed surface of sai I sof layer comprising the forming surface of the belt, and wherein said soft layer comprises an elongate flap integral with the soft layer, the free end of said elongate flap being laid across' the seam in the belt, thereby providing a substantially even fom-iing surface.

In a second aspect, the present invention provides apparatus for shaping glass, heets comprising a furnace for heating a glass sheet, a shaping station for shaping the sheet and C5 conveying means for advancing the glass sheet through the furnace and shaping station, the shaping station comprising a forming belt which serves as a surface contacting the glass heet,: and driving means for rotating the forming belt, wherein said forming belt comprises a, flexible, continuous belt having a seam therein, and wherein a surface of the belt comprises heat resistant web piece positioned so as to cover, at least partially, the seam in the belt,: thereby providing a substantially even forming surface.

Preferably, the heat resistant web piece of the forming belt comprises an elongate flap: laid across the seam in the belt in a direction opposite to that in which the driving means: rotates the forming belt. This is advantageous because the flap will be continuously pr-.ssed down during shaping and is less likely to be detached or ride up during operation cf the: apparatus.

The forming belt in the apparatus may press the heated glass sheet on to a former or other suitable forming means so that the glass sheet is shaped in a desired manner. Ho-Wever,: preferably, the glass sheet is pressed by two forming belts counter-rotating around respective; formers and pressing the glass sheet on each surface as the glass sheet passes thro gh a passage between the two belts, resulting in the glass sheet being shaped according to the configuration of the formers.

In a further aspect, the present invention provides a method of shaping glass sheets using a forming belt, comprising providing a glass sheet, heating the glass sheet, and bringing the glass sheet into contact with the forming surface of the forming belt to shape the glass sheet, wherein said forming belt comprises a flexible, continuous belt having a seam therein, and wherein a surface of the belt comprises a heat resistant web piece positioned so as to cover, at least partially, the seam in the belt, thereby providing a substantially even forming surface.

By way of example, specific embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

Figures 1 and 2 are perspective views of two embodiments of the invention, Figure 3 is a schematic section illustrating apparatus for shaping glass using a forming belt according to the invention.

Referring to Figure 1, a flexible, continuous forming belt 1 for use in shaping glass comprises a strip of a 3-layer laminate 2 (BekitherffiTm NP fabric, obtained from Bekintex NV, Wetteren, Belgium) formed into an endless loop by joining the two end portions of the strip. The inner layer 4 and outer layer 6 of the laminate comprise needle-punched layers of stainless steel fibres. The middle layer 8 of the laminate comprises a mechanically durable woven stainless steel fabric. To make the belt, the first end portion 11 of the belt is delaminated by pulling the outer layer 6 away from the middle layer 8, thus forming the outer layer 6 of the laminate into an elongate flap 12 at one end of the belt. Because the elongate flap 12 is formed from belt material, it is integral with the belt. A short length of the middle layer 8 and a longer length of the inner layer 4 are cut so that the end 14 of the middle layer is exposed and overlapped by the elongate flap 12.

At the second end portion 16 of the belt, short lengths of the outer layer 6 and inner layer 4 are cut away, exposing the middle layer 8. The exposed end of the middle layer 8 of the second end-portion is placed over the exposed end of that of the first end-portion and spot welded at a plurality of points 17 across the width of the belt. The plurality of spot-welding points 17 form a seam 18 extending transversely across the belt, i.e. in a direction lying in the plane of the belt and generally perpendicular to its edges.

6 The elongate flap 12 is laid across the seam 18 so as to cover it. To improve the evenness of the forming surface 20 the end of the elongate flap 12 and the end regior 22 of the outer layer 6 near the join are thinned to a taper by brushing away strands. The elongato flap 12 is brushed down on to the forming surface 20 in order to entangle the cons ituerl,t fibres of the fabrics and so to lightly adhere the elongate flap 12 to the forming surface '4 0.

Referring to Figure 2, in a second embodiment, a flexible continuous forming belt 24 comprises a similar Mayer laminate 25 having an inner layer 26 and an outer layer 28 both of needle-punched stainless steel fibres and a middle layer 30 of woven stainless steel lbric, The outer layers 28 at each end are delaminated from the middle layer 30 in such a way that one end has a long flap 32 and the other a short flap 34. At each end the inner layer 26 is cut away, thus exposing the middle layer. The continuous belt is made by overlapping th exposed ends of the middle layers at the ends to form an overlap 36 and spot-welding the ends, of the middle layers together at a plurality of points 38 across the width of the belt thus forming a seam 40 in the same way as before. To cover the seam 40, the long flap 32 i; laid, partially across the seam so as to closely abut the short flap 34, so that together they cover the:

seam. The lengths of the flaps 32, 34 may be varied.

Referring to Figure 3, apparatus for shaping glass comprises a furnace 44 for heating, pre-cut glass sheets for shaping, and rollers 46 in the furnace for conveying the heat-sof,ened' glass sheets to the shaping station 48. The shaping station comprises a top forming device 50: and a bottom forn-dng device 52. The forming devices comprise driver rollers 54, 56 to kive, counter-rotating forming belts 58,60 respectively around a top former 62 and a bottom fcrmer 64. The forming belts are arranged to rotate in the opposite direction to the lie of the eloligate:, flaps covering the seams of the forming belts so that the flaps do not ride up during operation: of the apparatus. The forming devices also comprise idler rollers 66, 68, 70 and tensic ning units 72,74. Each hot glass sheet is transfer-red from the furnace 44 and moved between the: top forming unit 50 and the bottom forming unit 52 through a passage 80 of suitable height in:; which it is brought into contact with the forming belts. The counter rotating forming befts 58: and 60 make contact with upper and lower faces of the glass sheet respectively, and so a the;, glass sheet passes through the passage it is shaped according to the configuration of the top, former 62 and bottom former 64. After shaping, the glass sheet is moved over rollers 76 along a curved path by nip rollers 78 and then to a cooling unit (not shown) for quenching 7

Claims

1. A forming belt comprising a flexible, continuous belt having a seam therein, wherein a surface of the belt comprises a heat resistant web piece positioned so as to cover, at least partially, the seam in the belt, thereby providing a substantially even forming surface.

2. A forming belt as claimed in claim 1 wherein the heat resistant web piece comprises an elongate flap, the free end of which is laid across the seam in the belt.

3. A forn-fing belt as claimed in either claim 1 or claim 2 wherein the belt comprises a laminate having a mechanically durable layer and a soft layer, and wherein the exposed surface of said soft layer comprises the forming surface of the belt.

4. A forming belt as claimed in claim 3, wherein the heat resistant web picce.comprises an elongate flap integral with the soft layer, the free end of said elongate flap being laid across the seam in the belt.

5. A forming belt as claimed in claim 4 wherein the free end of the elongate flap is adhered to the soft layer across the seam by brushing or combing said elongate flap on to the soft layer.

6. A forming belt as claimed in any one of claims 3 to 5 wherein the soft layer comprises a heat resistant non-woven fabric.

7. A forming belt as claimed in any one of the preceding claims wherein the forming belt comprises at least one flexible strip of material joined at its ends by welding, spotwelding or sewing.

8 8. A forming belt for use in shaping glass sheets comprising at least one flexible strip of material joined at its ends to define a flexible, continuous belt having a transverse seam therein, wherein the belt comprises a laminate having a mechanically durable layer and a soft layer, the exposed surface of said soft layer comprising the forming surface of the ' belt, and wherein said soft layer comprises an elongate flap integral with the soft layer the free end of said elongate flap being laid across the seam in the belt, threby providing a substantially even forming surface.

9. Apparatus for shaping glass sheets comprising a furnace for heating a glass sheet, a shaping station for shaping the sheet and conveying means for advancing the glass sheet through the furnace and shaping station, the shaping station comprising a forn-iin belt which serves as a surface contacting the glass sheet, and driving means for rotatin 3, the; forming belt, wherein said forming belt comprises a flexible, continuous belt hav rig a: seam therein, and wherein a surface of the belt comprises a heat resistant web iece positioned so as to cover, at least partially, the seam in the belt, thereby provid ng a: substantially even forMling surface.

10. Apparatus as claimed in claim 9 wherein the heat resistant web piece of the forming belt comprises an elongate flap laid across the seam in the belt in a direction opposite tc that in which the driving means rotates the forming belt.

11. A method of shaping glass sheets using a forming belt, comprising providing a glass' sheet, heating the glass sheet, and bringing the glass sheet into contact with the fonning: surface of the forming belt to shape the glass sheet, wherein said forming belt compnses, a flexible, continuous belt having a seam therein, and wherein a surface of the belt': comprises a heat resistant web piece positioned so as to cover, at least partially the seam in the belt, thereby providing a substantially even forming surface.

12. A forming belt substantially as herein described with particular reference to the drawings, Figures 1 to 3.