AU603958B2 - Improved glass bending method - Google Patents

Description

fin ~I fit

AUSTRALIA

PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE Application Number: Lodged: This do-um,- contains the anizidments made under Section 49 and is correct for printing.

Complete Specification Lodged: Accepted: c C I It Priority: Related Art: Published: f c S TO BE COMPLETED BY APPLICANT Name of Applicant c"'s Name of Applicant: Address of Applicant: a 0 ".Actual Inventor: Address for Service: ao0 Complete Specification for BENDING METHOD.

O'BRIEN GLASS INDUSTRIES

LIMITED

43-53 Davies Road, Padstow, New South Wales, 2211, Australia Brian Herdey ARTHUR S. CAVE CO.

Patent Trade Mark Attorneys Level Barrack Street SYDNEY N.S.W. 2000

AUSTRALIA

the invention entitled IMPROVED GLASS The following statement is a full description of this invention including the best method of performing it known to me:- 1 ASC 49 0 1 Z019/89^~~ 0431J/PP -4L_ The present invention relates to an improved bending mould for shaping heat softenable material, sheet glass.

In particular, the invention is directed to an improved peripheral mould for bending heat softenable material using gravity.

Prior art glass bending moulds fall into three general categories 'ring' moulds, 'wing' moulds and full face moulds. In each case, a flat sheet of glass is cut into shape and placed on a mould which is heated in a furnace. In the manufacture of laminated glass windscreens, two sheets of glass oooo are separated by a fine layer of separating material, e.g., oooo ooo: diatomaceous earth or the like and placed together on the 0o o 0000 mould. The purpose of the separating layer is to prevent the two glass sheets rrom coalescing during the shaping stage, thus allowing the two sheets to be separated and an intermediate layer to be introduced.

Conventional 'ring' moulds consist of a peripheral t support member which fully conforms to the desired final shape of the glass. As the glass is heated to its softening point, gravity makes the sheet sag to conform to the shape of the cre mould. This type of mould is used for achieving fairly gentle curvatures and is suitable only for shapes w:,th no or very little cross-curvature. Differential heating, heat sinks and reflectors may be used to produce variations in temperature throughout the glass sheets, with the glass being heated to higher temperatures in the positions where a smaller radius of curvature is required. However these methods are of limited assistance where, for example, the desired shape has a 2 1685c 1(1 il_ substantially flat portion in the centre and a relatively small radius of curvature at one or both ends. In that case, even 'ith differential heating, the centre portion will tend to fall through the conventional peripheral 'ring' mould before the end portions can be moulded to the desired curvature.

Conventional peripheral 'wing' moulds consist of a stationary peripheral support member for supporting a portion of the glass and at least one pivotable peripheral support I member for supporting the remainder of the glass. The pivotable member is pivotally connected to the stationary j support member. When the 'wing' mould is not supporting a i soo.:. sheet of glass the pivotable support member is urged to its jI uppermost position by a resilient force such as a spring or Ji counterweights and the 'wing' mould conforms to the desired shape of the glass. When a sheet of glass is placed on the 'wing' mould, the weight of the glass causes the pivotable It support member to move downwardly against the resilient force.

JI t As the glass is heated and begins to soften, the resilient force causes the pivotable member to move gradually upwardly ii until the pivotable section reaches its uppermost position, thus assisting the bending of the glass. The 'wing' moulds have proven to be superior to the conventional 'ring' moulds in many applications but are limited in the degree of cross-curvature achievable and are unable to produce glass sheets having a substantially flat portion in the centre and a small radius of curvature at one or both ends.

Full face moulds may be used in applications where prior art peripheral moulds have been unsuccessful. In particular, -3- 1685c the use of full face moulds allows glass sheets to be moulded to shapes having a low degree of cross-curvature or having a combination of substantially flat portions and portions with a small radius of curvature. However, the use of full face moulds has substantial disadvantages and such moulds have typically been used only as a last resort. Due to the heat capacity of the full face moulds, glass moulding using full face moulds requires an extended heating period of approximately three to four times that required for peripheral moulds, with resultant increases in plant utilisation and at r energy costs. Furthermore, full face moulds are very expensive to manufacture and are prone to producing imperfections in the surface of the moulded glass, resulting in a high proportion of rejects.

The present invention seeks to obviate the disadvantages of the prior art moulds and according to one aspect resides in a peripheral mould for moulding a sheet of heat softenable material, glass, comprising a fixed peripheral support 4 t member capable of supporting a glass sheet over substantially the entire periphery thereof, and at least one pivotable support member pivotally connected to said fixed member, said pivotable support member being urged by a resilient force toward an uppermost position in which said pivotable member and a portion of said fixed member together form a substantially continuous peripheral support corresponding to the desired final shape of the moulded glass sheet. Preferably the heat softenable material is glass.

The resilient force is preferably applied by means of 4 1685c counterweights, and reflectors and/or heat sinks may be attached to the mould to produce temperature variations in the glass as previously described.

The invention from a further aspect comprises a peripheral mould for moulding a sheet of heat softenable material comprising a fixed peripheral support member capable of supporting a sheet of heat softenable material over substantially the entire periphery thereof and at least one pivotal support member pivotaliy connected to said fixed member, said pivotal support member being urged by a resilient force toward an uppermost position in which the pivotal support member and a portion of the fixed member together form a o00000 o.oo substantially continuous peripheral support corresponding to the desired final shape of the moulded sheet.

Preferred embodiments of the present invention shall now be described with reference to the accompanying drawings, in

I

C C which: Figure 1 is an elevation of a preferred mould according to the present invention when supporting a sheet of glass, prior to the moulding process; :I 'Figure 2 and 3 are elevations of the mould of Figure 1 at intermediate stages of the moulding process; and Figure 4 is an elevation of the mould of Figures 1, 2 and 3 at the completion of the moulding process.

As illustrated by Figures 1 to 4, the mould comprises a fixed peripheral support member and at least one pivotable support member which pivots about the pivot points The pivotable support members are urged upwardly 5 1685c I_ by the force applied due to the counterweights The shape of the mould will vary according to the desired shape of the moulded glass sheet.

In use, at least one sheet of glass is placed on the mould, and the mould and glass are heated in a furnace. In the moulding of laminated glass windscreens, two sheets of glass separated by a fine layer of separating material are placed on the mould. As shown in Figure i, the glass is initially supported by the fixed peripheral member and the pivotable Smember is forced downwardly against the resilient force by the weight of the glass. As the glass begins to soften (Figure 2), the centre portion of the glass begins to sag under gravity until the glass is supported over substantially its entire 44t0 periphery by the fixed member. As the glass softens further (Figure the pivotable member is gradually urged upwardly by the resilient force and lifts the glass away from a part of the C' fixed support member. When the pivotable member reaches its uppermost position (Figure the glass conforms to the continuous peripheral support formed by the pivotable member and a part of the fixed member. The mould and the moulded glass sheet may then be removed from the furnace.

The preferred embodiment of Figures 1 to 4 shows the pivotable member as being positioned outside the fixed member However, the pivotable member may be positioned inside the fixed member. Other configurations are possible, such as a multi-staged pivotable member or the use of two or more pivotable members, and such configurations are embraced by the invention.

-6- 1685c

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By providing a fixed peripheral support member capable of giving full peripheral support to a glass sheet, the present inventijn has substantial and unexpected advantages over the prior art 'wing' moulds. The fixed support member allows the desired degree of cross-curvature to be imparted to the glass sheet at the stage represented in Figure 2 and gives greater support to the glass sheet during the moulding process. The peripheral moulds of the present invention are useful for moulding glass sheets to shapes which previously required full face moulds.

The present invention has been herein described with reference to certain preferred embodiments however, it should be understood that numerous variations and modifications can be made to the peripheral moulds as herein described without departing from the overall spirit and scope of the invention as broadly described herein.

a 00 6a 1 o6 o g C C iC 6 €j t 0 0 C 6 C Cr r c 7 1685c i

Claims (9)

1. A peripheral mould for moulding a sheet of heat softenable material comprising a fixed peripheral support member capable of supporting a sheet of heat softenable material over substantially the entire periphery thereof and at least one pivotal support member pivotally connected to said fixed member, said pivotal support member being urged by a resilient force toward an uppermost position in which the pivotal support member and a portion of the fixed member j together form a substantially continuous peripheral support corresponding to the desired final shape of the moulded sheet. i

2. A peripheral mould as claimed in claim 1 wherein the resilient force is applied by counterweights fixed to one end of said pivotal support member.

3. A peripheral mould as claimed in claim 1 or 2 wherein the I1 *t fixed pivotal support member has a flat heat softenable |j c material supporting surface. ii

4. A peripheral mould as claimed in any one of claims 1 to 3 wherein reflectors and/or heat sinks are attached to the mould to produce temperature variations in the facilitate moulding of the heat softenable material.

A peripheral mould as claimed in any one of claims 1 to 4 wherein the heat softenable material is glass.

6. A method of moulding a sheet of heat softenable material residing in positioning a sheet of heat softenable material on a fixed peripheral support member which supports said sheet over substantially the entire periphery thereof, heating said sheet to bending temperatures, at least one pivotal support 8 I member pivotally connected to said fixed support member and movable as a result of the heating of said heat softenable material toward an uppermost position in which the pivotal support member and a portion of the fixed member together form a substantially continuous peripheral support corresponding to the desired final shape of the moulded sheet.

7. A method as claimed in claim 6 wherein said heat softenable material is glass.

8. A peripheral mould for moulding heat softenable material substantially as hereinbefore described with reference to the accompanying drawings.

9. A method of moulding a sheet of heat softenable material substantially as hereinbefore described with reference to the accompanying drawings. DATED this 31st day of August, 1989. c rte O'BRIEN GLASS INDUSTRIES LTD. c' sBy Its Patent Attorneys, ARTHUR S. CAVE CO. -9 1685c