WO2014018322A1

WO2014018322A1 - Apparatuses and methods for heating sheets of glass

Info

Publication number: WO2014018322A1
Application number: PCT/US2013/050787
Authority: WO
Inventors: John Harold Brennan; Juergen Tinz
Original assignee: Corning Incorporated
Priority date: 2012-07-23
Filing date: 2013-07-17
Publication date: 2014-01-30
Also published as: TW201406678A

Abstract

A method of heating sheets of glass includes a step of arranging a plurality of sheets vertically in a juxtaposed manner inside a predetermined space defmed by an outer boundary. The method further includes a step of surrounding the predetermined space with heating elements such that the heating elements extend across substantially all of the outer boundary. The method further includes a step of moving the predetermined space with the plurality of sheets therein through a plurality of thermal zones. The method further includes a step of, for each thermal zone, maintaining a heating intensity of the heating elements to be substantially the same as one another within that the thermal zone. The method further includes a step of changing the intensity of the heating elements in at least one of the thermal zones. Moreover, there is provided an apparatus for heating sheets of glass comprising a furnace (14) an a plurality of vehicles (22) or accomodating each a plurality of glass sheets (12), each vehicle (22) comprising heating elements (62, 64). Furthermore an assembly with a frame and a clamp (52) for transporting a sheet of glass is provided.

Description

APPARATUSES AND METHODS FOR HEATING SHEETS OF GLASS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Serial No. 61/674519 filed on July 23, 2012 the content of which is relied upon and incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates to an apparatus and a method for heating sheets of glass and, more particularly, an apparatus and a method for heating sheets of glass so that efficient use of manufacturing space is made and defects on the sheets are reduced.

BACKGROUND

[0003] Glass used in display devices typically undergoes thermal processing after being rendered in a sheet form. In order to prepare the sheets of glass for downstream processes, the sheets sometimes undergo thermal processing, for example a time-temperature cycle, in order to density the glass and lower the Active temperature of the glass.

SUMMARY

[0004] In one example aspect, a method of heating sheets of glass is provided and includes a step of arranging a plurality of sheets vertically in a juxtaposed manner inside a predetermined space defined by an outer boundary. The method further includes a step of surrounding the predetermined space with heating elements such that the heating elements extend across substantially all of the outer boundary. The method further includes a step of moving the predetermined space with the plurality of sheets therein through a plurality of thermal zones. The method further includes a step of, for each thermal zone, maintaining a heating intensity of the heating elements to be substantially the same as one another within that thermal zone. The method further includes a step of changing the intensity of the heating elements in at least one of the thermal zones.

[0005] In another example aspect, an apparatus for heating sheets of glass is provided. The apparatus includes a furnace and a plurality of vehicles. The furnace includes an entrance, an exit and a passageway therebetween. The passageway is enclosed by a ceiling and opposing side walls. The ceiling includes a top heating element that extends substantially across the ceiling. The opposing side walls include side heating elements that extend substantially across the opposing side walls. The plurality of vehicles is configured to be moved through the passageway. Each of the vehicles is configured to accommodate a plurality of sheets of glass. Each of the vehicles includes a base above which the plurality of sheets is vertically arranged in a juxtaposed manner. The base includes a base heating element that extends substantially across a top surface of the base. The base further includes an intermediate heating element that is mounted vertically at a first end of each of the vehicles and is juxtaposed about one of the plurality of sheets. The intermediate heating element extends substantially across a surface of the one of the plurality sheets. The plurality of vehicles is lined up inside the passageway such that the intermediate heating element is adjacent a second end of an adjoining vehicle, and the plurality of sheets on each of the vehicles is configured to be surrounded by the top heating element, the side heating elements, the base heating element, the intermediate heating element at the first end of one of the vehicles and the intermediate heating element at the first end of an adjoining one of the vehicles.

[0006] In yet another example aspect, an assembly for transporting a sheet of glass is provided. The assembly includes a frame and a clamp. The frame includes a transversely extending member. The clamp is coupled to the transversely extending member. The clamp includes a pair of proximal members and a pair of distal members. Each of the proximal members includes a first proximal section and a first distal section. Each first proximal section is pivotally coupled to the transversely extending member. Each of the distal members includes an intermediate section about which the distal members are pivotally coupled to one another. Each of the distal members further includes a second proximal section. Each second proximal section is pivotally coupled to a corresponding one of the first distal sections. Each of the distal members further includes an inwardly bent second distal section terminating in a pad. The pads are configured to pinch a sheet of glass therebetween in a closed position of the clamp and to release a sheet of glass in an open position of the clamp.

[0007] The accompanying drawings are included to provide a further understanding of principles of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the description serve to explain, by way of example, principles and operation of the invention. It is to be understood that various features disclosed in this specification and in the drawings can be used in any and all combinations. By way of non-limiting example the various features may be combined with one another as set forth in the following aspects: [0008] According to a first aspect, there is provided a method of heating sheets of glass including steps of:

arranging a plurality of sheets vertically in a juxtaposed manner inside a predetermined space defined by an outer boundary;

surrounding the predetermined space with heating elements such that the heating elements extend across substantially all of the outer boundary;

moving the predetermined space with the plurality of sheets therein through a plurality of thermal zones;

for each thermal zone, maintaining a heating intensity of the heating elements to be substantially the same as one another within that thermal zone; and

changing the intensity of the heating elements in at least one of the thermal zones as compared to another one of the thermal zones.

[0009] According to a second aspect, there is provided the method of aspect 1, further including steps of forming a plurality of predetermined spaces each of which is occupied by a plurality of sheets arranged vertically in a juxtaposed manner, and moving the predetermined spaces simultaneously and horizontally through the thermal zones.

[0010] According to a third aspect, there is provided the method of aspect 1 or aspect 2, wherein the heating elements are configured to transfer heat to the plurality of sheets of glass by way of radiation.

[0011] According to a fourth aspect, there is provided the method of any one of aspects 1-3, wherein at least one of the plurality of sheets is touched only along one edge during the step of arranging the sheets.

[0012] According to a fifth aspect, there is provided the method of any one of aspects 1-4, further including a step of pulling down on a bottom edge of at least one of the plurality of sheets to reduce warping of the at least one of the plurality of sheets.

[0013] According to a sixth aspect, there is provided the method of any one of aspects 1-5, wherein the step of moving involves movement at constant speed.

[0014] According to a seventh aspect, there is provided the method of any one of aspects 1-6, wherein the predetermined space is substantially box-shaped.

[0015] According to an eighth aspect, there is provided the method of any one of aspects 1-7, wherein the step of arranging involves holding at least one of the plurality of sheets with a clamp made of material having a coefficient of thermal expansion similar to a coefficient of thermal expansion of the at least one of the plurality of sheets.

[0016] According to a ninth aspect, there is provided an apparatus for heating sheets of glass, the apparatus including:

a furnace including an entrance, an exit and a passageway therebetween, the passageway enclosed by a ceiling and opposing side walls, the ceiling including a top heating element that extends substantially across the ceiling, the opposing side walls including side heating elements that extend substantially across the opposing side walls; and

a plurality of vehicles configured to be moved through the passageway, each of the vehicles configured to accommodate a plurality of sheets of glass, each of the vehicles including a base above which the plurality of sheets is vertically arranged in a juxtaposed manner, the base including a base heating element that extends substantially across a top surface of the base, the base further including an intermediate heating element that is mounted vertically at a first end of each of the vehicles and is juxtaposed about one of the plurality of sheets, the intermediate heating element extending substantially across a surface of the one of the plurality of sheets,

wherein the plurality of vehicles is lined up inside the passageway such that the intermediate heating element is adjacent a second end of an adjoining vehicle, and the plurality of sheets on each of the vehicles is configured to be surrounded by the top heating element, the side heating elements, the base heating element, the intermediate heating element at the first end of one of the vehicles and the intermediate heating element at the first end of an adjoining one of the vehicles.

[0017] According to a tenth aspect, there is provided the apparatus of aspect 9, the furnace being divided lengthwise into a number of thermal zones, each of the thermal zones having a length to accommodate one of the vehicles, the top heating element being divided into a number of segmented top heating elements and the side heating element being divided into a number of segmented side heating elements such that each of the thermal zones is surrounded by one of the segmented top heating elements and one of the segmented side heating elements, the base heating element, the intermediate heating element at the first end of one of the vehicles and the intermediate heating element at the first end of an adjoining one of the vehicles. [0018] According to an eleventh aspect, there is provided the apparatus of aspect 9 or aspect 10, each of the vehicles including a thermocouple, and wherein the base heating element and the intermediate heating element are configured so that a power of the base heating element is independently adjustable from a power of the intermediate heating element.

[0019] According to a twelfth aspect, there is provided an assembly for transporting a sheet of glass, the assembly including:

a frame including a transversely extending member; and

a clamp coupled to the transversely extending member, the clamp including: a pair of proximal members, each of the proximal members including a first proximal section and a first distal section, each first proximal section pivotally coupled to the transversely extending member; and

a pair of distal members, each of the distal members including an intermediate section about which the distal member are pivotally coupled to one another, each of the distal members further including a second proximal section, each second proximal section pivotally coupled to a corresponding one of the first distal sections, each of the distal members further including an inwardly bent second distal section terminating in a pad, the pads being configured to pinch a sheet of glass therebetween in a closed position of the clamp and to release a sheet of glass in an open position of the clamp.

[0020] According to a thirteenth aspect, there is provided the assembly of aspect 12, the pads including an inner portion configured to contact a sheet of glass.

[0021] According to a fourteenth aspect, there is provided the assembly of aspect 13, the inner portion including a recessed area.

[0022] According to a fifteenth aspect, there is provided the assembly of aspect 13 or aspect 14, the inner portion made of deformable material.

[0023] According to a sixteenth aspect, there is provided the assembly of any one of aspects 13-15, the inner portion being readily removable from the remainder of the pad or from the second distal section.

[0024] According to a seventeenth aspect, there is provided the assembly of any one of aspects 13-16, in combination with a sheet of glass, at least the inner portion and the transversely extending member having a coefficient of thermal expansion similar to a coefficient of thermal expansion of the sheet of glass.

[0025] According to an eighteenth aspect, there is provided the assembly of any one of aspects 12-17, including a pair of the clamps, each of the clamps configured to pinch a part of an edge of a sheet of glass in the closed position.

[0026] According to a nineteenth aspect, there is provided the assembly of any one of aspects 12-18, in combination with a sheet of glass, furthering including a weight clamp attached to an edge of the sheet of glass opposite an edge pinched by the clamp.

[0027] According to a twentieth aspect, there is provided the assembly of any one of aspects 12-19, the frame and the clamp made of material resistant to temperatures of about 750 °C.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] These and other aspects are better understood when the following detailed description is read with reference to the accompanying drawings, in which:

[0029] FIG. 1 is a perspective view of an example embodiment of an apparatus for heating sheets of glass in which a furnace and a set of tracks are shown;

[0030] FIG. 2 is a top schematic view of an apparatus and the tracks along which vehicles are transported;

[0031] FIG. 3 is a cutaway view of an example embodiment of the furnace including heating elements therein and one of the vehicles entering a double-door structure provided at an entrance of the furnace;

[0032] FIG. 4 is a close-up view of an example embodiment of the vehicles including a base and a frame about which sheets of glass are secured;

[0033] FIG. 5 is an isolated view of an example embodiment of an assembly including a rod and a pair of clamps for pinching a sheet of glass; and

[0034] FIG. 6 is a cross-sectional view of pads and inner portions of the clamps pinching a sheet of glass.

DETAILED DESCRIPTION

[0035] Examples will now be described more fully hereinafter with reference to the accompanying drawings in which example embodiments are shown. Whenever possible, the same reference numerals are used throughout the drawings to refer to the same or like parts. However, aspects may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0036] Referring now to FIGS. 1-2, an example of embodiment of an apparatus 10 for heating sheets of glass 12 is illustrated. The apparatus 10 may include a horizontally oriented furnace 14 with an entrance 16, an exit 18 and a passageway 20 therebetween. The apparatus 10 may further include a plurality of vehicles 22 and a transportation structure 24 that moves the vehicles 22 through the furnace 14 and from the exit 18 to the entrance 16 of the furnace 14.

[0037] The transportation structure 24 may include a set of tracks 26 by way of which the vehicles 22 can travel horizontally and which intersect one another such that the vehicles 22 can be moved from one track 26 to another. In the embodiment of FIGS. 1-2, the tracks 26 include a furnace track 26a, a return track 26b, a first transfer track 26c and a second transfer track 26d. The furnace track 26a routes the vehicles 22 through the furnace 14. The first transfer track 26c routes the vehicles 22 from the furnace track 26a to the return track 26b while the second transfer track 26d routes the vehicles 22 from the return track 26b to the furnace track 26a. The return track 26b routes the vehicles 22 from the first transfer track 26c to the second transfer track 26d and towards the entrance 16 of the furnace 14. The transfer car 30 may move back and forth on the first transfer track 26c and the second transfer track 26d between the furnace track 26a and the return track 26b. Each track 26 may be configured to operate with a mechanism that powers the vehicles 22 along the tracks and that operates by way of a set of gears, a motor or the like. For example, the mechanism may be a pusher device. The transfer tracks 26c, 26d may include transfer cars 30 onto which the vehicles 22 from either the furnace track 26a or the return track 26b can be loaded and moved and which may include a turntable mechanism to change the orientation of the vehicles 22. Alternatively, the transportation structure 24 may include a single track 26 that routes the vehicles 22 directly through the furnace 14 and from the exit 18 to the entrance 16 of the furnace 14. The vehicles 22 may include wheels for movement along the tracks 26 and may be moved at a constant speed by the transportation structure 24.

[0038] The passageway 20 inside the furnace 14 provides a heated environment to which the sheets of glass 12 are exposed as the vehicles 22 are moved through the furnace track 26a in order to perform compaction, annealing, strain relief or the like on the sheets 12. The sheets of glass 12 may be moved through the furnace 14 after being formed into a sheet 12 by any of a variety of processes known in the art, for example by a fusion down draw method. Means, for example robotic arms, may be used to move the sheets 12 about a factory floor (e.g., from the manufacturing site to the furnace 14) and place the sheets 12 on the vehicles 22. In case the fusion down draw method is used for making the sheets of glass 12, the apparatus 10 may be located near the bottom of the draw in order to reduce the time for transportation of the sheets 12.

[0039] As shown in FIG. 3, in order to reduce the likelihood of contaminants entering the passageway 20, the entrance 16 and the exit 18 of the passageway 20 may be provided with a vestibule 28 that includes an outer door 28a and an inner door 28b. The operation of the vestibule 28 at the entrance 16 may be such that the outer door 28a is opened to allow a vehicle 22 to completely enter the vestibule 28 only if the inner door 28b is closed while the inner door 28b is opened to allow the vehicle to enter the passageway 20 only if the outer door 28a is closed. The operation of the vestibule 28 at the exit 18 may be such that the inner door 28b is opened to allow a vehicle 22 to completely enter the vestibule 28 only if the outer door 28a is closed while the outer door 28a is opened to allow the vehicle 22 to enter the passageway 20 only if the inner door 28b is closed. Such a process may be repeated for every vehicle 22 that enters and exits the passageway 20. Other features, for example an air curtain, may be provided with or separately from the vestibule 28 to reduce contamination.

[0040] In this embodiment, the passageway 20 is substantially box-shaped and is partially enclosed by a ceiling 32 and opposing side walls 34. The heated environment is created by a top heating element 36 that extends substantially across the ceiling 32 and side heating elements 38 that extend substantially across each of the side walls 34. The heating elements 36, 38 may be embodied as resistive coils or wires that can transfer heat by way of radiation although other manners of heat transfer (e.g., convection) can also be contemplated. The temperature inside the passageway 20 may be adjusted by changing the power of the heating elements 36, 38. The ceiling 32 and the side walls 34 of the furnace 14 may include insulation to reduce leakage of heat from the passageway 20 in upward and lateral directions.

[0041] As shown in FIGS. 3-4, the vehicle 22 may be configured to transport one or more sheets of glass 12 and may include a base 40 and a frame 42 mounted on the base 40. The base 40 may include wheels allowing the vehicle 22 to move along the tracks 26.

[0042] FIG. 4 shows an example embodiment of an assembly 48 used to place the sheets of glass 12 inside a predetermined space 46 of the vehicle 22. It must be noted that certain features of the assembly 48 are omitted for purposes of illustration. The frame 42 may be formed of bars 45 that are arranged to form an outer boundary defining the predetermined space 46 in which the sheets of glass 12 are placed. The frame 42 may be made of temperature resistant materials, for example silicon carbide. The predetermined space 46 may be shaped like a box, a cube, a polyhedron or the like with the bars 45 defining the edges of such a shape although the predetermined space 46 need not be defined by straight lines. The top of the frame 42 includes two horizontally oriented, parallel bars 45 and a rod member 50 is placed to extend transversely between the two bars 45. While the rod 50 (or the transversely extending member) is shown to have a circular cross-section, the rod 50 may have a rectangular cross-section to reduce movement about the two bars 45 or may be immobilized about the frame 42 by features that keep the ends of the rod 50 still, for example cavities in which the ends of the rod 50 can fit.

[0043] As shown in FIGS. 5-6, the rod 50 may be coupled to a clamp 52 that secures a sheet of glass 12. While a single clamp 52 may be used to suspend the sheet of glass 12 from the rod 50, a pair of clamps 52 is used in the present embodiment. The clamp 52 may be a linkage that operates similarly to an ice tong and includes a plurality of pivotally coupled members allowing the clamp 52 to assume an open position and a closed position. In this embodiment, the clamp 52 includes a pair of proximal members 54 and a pair of distal members 56. Each of the proximal members 54 includes a first proximal section 54a and a first distal section 54b while each of the distal members 56 includes a second proximal section 56a, an intermediate section 56b and a second distal section 56c. Each of the first proximal sections 54a of the proximal members 54 is pivotally coupled to the rod 50. The distal members 56 are pivotally coupled to one another at the intermediate sections 56b so as to be movable in a scissor-like fashion. Each second proximal section 56a of the distal members 56 is pivotally coupled to a corresponding one of the first distal sections 54b of the proximal members 54. Each of the second distal section 56c of the distal members 56 terminates in a pad 58 and is inwardly bent such that an edge 12a of a sheet of glass 12 can be pinched between the pads 58 when the clamp 52 assumes a closed position and can be released from the pads 58 when the clamp 52 assumes an open position.

[0044] As shown in FIG. 6, the pads 58 may include an inner portion 60 that is configured to contact the sheet of glass 12. A number of mechanisms may be contemplated to secure the sheet of glass 12 to the clamp 52. A factional force between the inner portion 60 and a surface of the sheet of glass 12 engaged by the inner portion 60 may be sufficient to keep the clamp 52 in the closed position. In an alternative embodiment, the surface of the sheet of glass 12 may include a feature (e.g., a bead) that can mate or be engaged by a corresponding feature (e.g., a recessed area) in the inner portion 60. For example, the inner portion 60 may include alternating recessed areas and protruding areas, and the bead may be contoured to fit within the recessed area. In another alternative embodiment, the inner portion 60 may be formed of material that is deformable but provides sufficient rigidity so as to pinch and secure the sheet of glass 12 between the pads 58. Moreover, the inner portion 60 may be a part of the pad 58 that gradually becomes worn so as to require replacement and the inner portion 60 may be configured to be attached to and detached from the pad 58 so as to be replaceable.

[0045] Sheets of glass 12 made by the fusion down draw method are drawn in a downward direction by a set of rollers that engage the lateral edges of a ribbon of glass. The engagement by the rollers leaves beads along the lateral edges of the sheets 12 cut from the ribbon and the beads may act as the protruding feature that is engaged by the inner portion 60. When the sheets 12 are initially placed inside the predetermined space 46, the sheets 12 may be pinched by and suspended by the beaded edge after the sheets 12 are rotated 90 degrees from the orientation out of the draw. When the sheets 12 are removed from the vehicles 22, the sheets 12 may be rotated again to orient the beaded edges vertically, rather than horizontally at the top and bottom. Moreover, the beaded edges may be removed or cut off from the sheets 12 once the sheets have moved through the furnace 14.

[0046] The assembly of the frame 42 and the clamp 52 allows the sheets of glass 12 to be suspended from the rod in a vertically oriented fashion. By providing a plurality of rods 50 coupled to a pair of clamps 52 at the top of the frame 42 in a parallel manner, it is possible to arrange a plurality of sheets 12 vertically in a juxtaposed manner inside the predetermined space 46. Additionally, as shown in FIG. 5, a bottom edge 12b of the sheet of glass 12 may be pinched by a second pair of clamps 52 such that warping is reduced by gravity and the sheet of glass 12 is made straighter. Attaching the second pair of clamps 52 to the bottom edge 12b may also reduce the likelihood of the sheets of glass 12 swinging back and forth about the frame 42. In case of the sheets of glass 12 engaged by rollers in the fusion down draw method, the bottom edge 12b of the sheet of glass 12 would also include the beads formed from engagement by the rollers. [0047] All of the parts that move through the furnace 14, for example the vehicle 22, the frame 42 and the clamp 52, need to be made of materials that can withstand operating temperatures, for example from 450 to 800 °C. Moreover, certain parts of the frame 42 and the clamp 52 may be made of materials with a coefficient of thermal expansion similar to the glass materials so that thermal expansion of the clamp 52 and the frame 42 inside the furnace 14 do not create undesired stresses or strains exerted on the sheets of glass 12. For example, the rod 50 and the inner portion 60 may be made of such materials. In particular, a clamp 52 made of high nickel stainless steel may be used with an inner portion 60 made of woven stainless mesh while a clamp 52 made of quartz may be used with an inner portion 60 made of quartz wool felt that is frit sealed to the quartz pad.

[0048] Each of the vehicles 22 may include a base heating element 62 that extends substantially across a top surface of the base 40. The base heating element 62 can thus emit heat toward the sheets of glass 12 arranged above the base 40. Moreover, the frame 42 may include an intermediate heating element 64 that is arranged to be juxtaposed about one of the sheets of glass 12 and is located at least at a first end 22a (FIG. 4) of the vehicle 22 which may be the front end or the rear end. In this embodiment, the intermediate heating element 64 is located at the rear end of the vehicle 22 or the rear edge of the rectangular base 40. In alternative embodiments, the intermediate heating element 64 may be located at the front end of the vehicle 22, or at both the front and rear end of the vehicle 22. The intermediate heating element 64 is thus arranged to extend substantially across the surface of an adjacent sheet of glass 12. The base 40 may include insulation below the base heating element 62 in order to protect the components of the vehicle 22 from high temperatures of the furnace 14.

[0049] Based on the aforementioned configuration, each vehicle 22 may transport or move the predetermined space 46 in which a unit of sheets of glass 12 is located through the passageway 20 of the furnace 14. While a unit of sheets of glass 12 inside the predetermined space 46 is shown to include six sheets 12 in the present embodiment, the number of sheets 12 may of course vary. By arranging a plurality of vehicles 22 to continuously and horizontally move through the passageway 20, the apparatus 10 is capable of subjecting a large number of sheets of glass 12 to a high temperature environment while efficiently using space available in the furnace 14 or the manufacturing facility. [0050] The vehicles 22 may be lined up along the furnace track 26a in proximity with one another such that the intermediate heating element 64 on the first end 22a of a vehicle is adjacent a second end 22b of an adjoining vehicle. The open, second end 22b may provide a loading side to load the sheets of glass onto the vehicle 22. The open, second end 22b may be provided opposite the end where the intermediate heating element 64 is located. The pusher device pushes the vehicles 22 along the furnace track 26a. For example, the vehicles 22 may be sufficiently close to one another that pushing one of the vehicles 22 results in simultaneous forward movement for all of the vehicles 22. By keeping the vehicles 22 in proximity with one another, each unit of sheets of glass 12 is configured to be surrounded by the top heating element 36, the side heating elements 38, the base heating element 62, the intermediate heating element 64 on the first end 22a of a vehicle 22 and the intermediate heating element on the first end 22a of an adjoining vehicle 22. The power or intensity of each heating element 36, 38, 62 and 64 may be independently adjustable from one another.

[0051] The furnace 14 may be divided lengthwise into a number of thermal zones 66 (FIGS. 2-3) and a discrete set of heating elements 36, 38 may be provided for each of the thermal zones 66. Specifically, the top heating element 36 and the side heating elements 38 may be divided into a set of top segmented heating elements 36a and a set of side segmented heating elements 38a respectively such that each thermal zone 66 is surrounded at least in part by a corresponding top segmented heating element 36a and corresponding side segmented heating elements 38a. Moreover, each thermal zone 66 may be of a length to accommodate only one vehicle 22 at a time and each of the top segmented heating elements 36a and each of the side segmented heating elements 38a may be dimensioned to extend along a single thermal zone 66. For example, the passageway 20 may be 35 meters long dividable into 35 thermal zones 66 and the vehicle 22 may be about 1 meter long. The apparatus 10 may be configured to transport a vehicle 22 through the passageway 20 at a speed that is consistent with the manufacturing capacity of the method used to make the sheets 12 (e.g., 90 minutes). The power or heating intensity of each segmented heating element 36a, 38a may be independently adjustable from one another.

[0052] In such a configuration of the heating elements 36a, 38a, each unit of sheets of glass 12 in a thermal zone 66 is configured to be surrounded by a top segmented heating element 36a, two side segmented heating elements 38a, a base heating element 62, an intermediate heating element 64 on the first end 22a of a vehicle 22 and another intermediate heating element 64 on the first end 22a of an adjoining vehicle 22. As a result, the heating elements 36a, 38a surround the predetermined space 46 so as to extend across substantially all of the outer boundary defining the predetermined space 46. In this embodiment, all six faces of the box-shaped predetermined space 46 are substantially covered by the heating elements 36a, 38a, 62 and 64. The furnace 14 may be configured to allow access to the heating elements 36, 38 from outside the furnace 14 for maintenance, replacement or to reduce contamination of the passageway 20.

[0053] Each thermal zone 66 in the passageway 20 may be configured to create an atmosphere providing a given temperature or temperature range and it is possible to configure the sheets of glass 12 to undergo a variety of temperature ranges as the vehicle 22 moves through the passageway 20. Specifically, each top segmented heating element 36a and each side segmented heating element 38a may be configured to operate at the same or substantially the same intensity or power with one another in a given thermal zone 66. Moreover, the base heating element 62 and the intermediate heating element 64 of the vehicle 22 may be adjusted to operate at the same or substantially the same intensity or power with one another as the vehicle 22 passes through the thermal zone 66. Specifically, each vehicle 22 may include one or more thermocouple 68 (FIG. 4) that can sense a temperature of the thermal zone 66 that the vehicle 22 is passing through and the intensity of the base heating element 62 and the intermediate heating element 64 may be adjusted based on the temperature sensed by the thermocouple 68. For example, each of the base heating element 62 and the intermediate heating element 64 may operate with a corresponding thermocouple 68. An interior of the passageway 20 for each of the thermal zones 66 may include a first contact element configured to engage a second contact element of the vehicle 22 where engagement of the two contact elements causes the thermocouple 68 to gauge the temperature of the atmosphere that the vehicle 22 is passing through (i.e., the thermal zone 66). The first contact element and the second contact element may be embodied as switches or strips formed on the interior of the furnace 14 and on the exterior of the vehicle 22 respectively and such that temperature sensing by the thermocouple 68 occurs at intervals and at the same point within a thermal zone 66. For example, the first contact element may be part of the furnace track 26a and the second contact element may be provided underneath the vehicle 22. Thus, between the moment the front end (i.e., the second end 22b) of the vehicle 22 enters the thermal zone 66 and the moment the rear end (i.e., the first end 22a) of the vehicle 22 enters the thermal zone 66, there is a point where the first contact element and the second contact element engages one another and the intensities of the base heating element 62 and the intermediate heating element 64 are adjusted to be the same or substantially the same as the top segmented heating element 36a and the side segmented heating elements 38a. As a result, all of the heating elements 36a, 38a, 62 and 64 surrounding the predetermined space 46 can be maintained to operate at substantially the same intensity within each thermal zone 66. Also, by setting the top segmented heating element 36a and the side segmented heating elements 38a to operate at higher or lower intensity in at least one of the thermal zones 66, the sheets of glass can be exposed to thermal zones 66 that vary in temperature. Moreover, the likelihood of a heat gradient inside the predetermined space 46 is reduced because the heating elements 36a, 38a, 62 and 64 surrounding a unit of sheets 12 operate at substantially the same intensity. Therefore, as the vehicles 22 move through the passageway 20, the sheets of glass 12 undergo a time-temperature cycle that may provide an effect of compaction, annealing, strain relief or the like.

[0054] Each of the top segmented heating element 36a, the side segmented heating element 38a, the base heating element 62 and the intermediate heating element 64 may be formed of an array of heating components, for example a 2 x 1 array, a 3 x 3 array, etc., that may be rectangular shaped. It may be possible to differentiate the heating intensity among the heating components in order to achieve better thermal uniformity inside the predetermined space 46. For example, since heat tends to rise, the heating intensity of the heating components may be configured to gradually decrease toward the top of the predetermined space 46.

[0055] An example series of processing conducted on the sheets of glass 12 may occur as described in the following. A vehicle 22 is returned to the entrance 14 of the furnace 14 via the return track 26b and is placed on the transfer car 30 on the second transfer track 26d. The transfer car 30 moves the vehicle 22 from the return track 26b to the furnace track 26a. One or more sheets of glass 12 made by a fusion down draw method are cut off from a drawn ribbon and are rotated 90 degrees from the orientation out of the ribbon for pinching by one set of clamps 52 along the top, beaded edge 12a by a robot which also manipulates opening and closing of the clamps 52. The robots may carry the sheets of glass 12 through the use of vacuum cups or grippers. Another set of clamps 52 may also pinch the bottom, beaded edge 12b for reduction of warping. The rod 50 to which the clamps 52 are pivotally coupled is thereafter placed on the bars 45 of the frame 42 of the vehicle 22 through the second end 22b. The turntable mechanism of the transfer car 30 then rotates the vehicle 22 (e.g., by 180 degrees) such that the vehicle 22 is ready to be routed through the furnace 14 via the furnace track 26a. The vehicle 22 enters the passageway 20 of the furnace 14 through the double-door vestibule 28 and proceeds through each thermal zone 66. This process is repeated for each of the empty vehicles 22 that return toward the entrance 16 of the passageway 20 via the return track 26b such that a continuous line of vehicles 22 is pushed through the passageway 20. At each thermal zone 66, the top segmented heating element 36a and the side segmented heating elements 38a operate at a given intensity. Once a vehicle 22 proceeds up to a given point within a thermal zone 66, temperature sensing by the thermocouple 68 is actuated by the engagement between contact elements and the intensities of the base heating element 62 and the intermediate heating element 64 are adjusted to be substantially similar to intensities of the top segmented heating element 36a and the side segmented heating element 36b such that substantially all of the boundary of the predetermined space 46 provides substantially the same degree of radiative heating. The intermediate heating element 64 located at the first end 22a of a vehicle provides heating for the predetermined space 46 of the corresponding vehicle and the predetermined space 46 of an adjoining vehicle 22. Such adjustment occurs at every interval which may equal the length of a vehicle 22 (i.e., 1 meter). The thermal zones 66 (for example the thirty- five thermal zones shown in the figures) in the passageway 20 may be configured such that the time -temperature cycle increases the temperature of the predetermined space 46 from about room temperature at the entrance 16, to about 600-750 °C at some point between the entrance 16 and the exit 18, and then lowers the temperature to about 300-400 °C approaching the exit 18. Once the vehicle 22 has moved through the passageway 20, the vehicle 22 moves through the vestibule 28 located at the exit 18 and exits the furnace 14. The vehicle 22 is thereafter loaded onto a transfer car 30 on the first transfer track 26c. The sheets of glass 12 are unloaded from the vehicle 22 by way of a robot that releases the sheets of glass 12 from the clamps 52. The sheets of glass 12 can be re-oriented and transported to a scoring machine that cuts off the beaded edges 12a, 12b of the sheets of glass 12. The empty vehicle 22 is placed on the return track 26b and can be accelerated to the entrance 16 of the furnace.

[0056] The aforementioned apparatus 10 allows a large number of sheets of glass to undergo thermal processing while touching the sheets of glass 12 along the edges and keeping most of the glass surfaces untouched. Moreover, by placing the sheets of glass 12 in the predetermined space 46 the outer boundary of which is substantially surrounded by the heating elements 36a, 38a, 62 and 64, the sheets of glass 12 can be heated more evenly in an environment in which heat gradients are less likely to exist. The apparatus 10 can also be used to thermally process glass sheets 12 of various sizes since the vehicles 22 can accommodate glass sheets 12 with dimensions up to the width and height of the predetermined space 46.

[0057] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the claimed invention.

[0058] For example, although the heating elements are shown and described as being single units, any given heating element may be composed of multiple sections that may be powered together or powered separately.

Claims

CLAIMS What is claimed is:

1. A method of heating sheets of glass including steps of:

2. The method of claim 1, further including steps of forming a plurality of predetermined spaces each of which is occupied by a plurality of sheets arranged vertically in a juxtaposed manner, and moving the predetermined spaces simultaneously and horizontally through the thermal zones.

3. The method of claim 1, wherein the heating elements are configured to transfer heat to the plurality of sheets of glass by way of radiation.

4. The method of claim 1, wherein at least one of the plurality of sheets is touched only along one edge during the step of arranging the sheets.

5. The method of claim 1, further including a step of pulling down on a bottom edge of at least one of the plurality of sheets to reduce warping of the at least one of the plurality of sheets.

6. The method of claim 1, wherein the step of moving involves movement at constant speed.

7. The method of claim 1, wherein the predetermined space is substantially box-shaped.

8. The method of claim 1, wherein the step of arranging involves holding at least one of the plurality of sheets with a clamp made of material having a coefficient of thermal expansion similar to a coefficient of thermal expansion of the at least one of the plurality of sheets.

9. An apparatus for heating sheets of glass, the apparatus including:

1" a furnace including an entrance, an exit and a passageway therebetween, the passageway enclosed by a ceiling and opposing side walls, the ceiling including a top heating element that extends substantially across the ceiling, the opposing side walls including side heating elements that extend substantially across the opposing side walls; and

10. The apparatus of claim 9, the furnace being divided lengthwise into a number of thermal zones, each of the thermal zones having a length to accommodate one of the vehicles, the top heating element being divided into a number of segmented top heating elements and the side heating element being divided into a number of segmented side heating elements such that each of the thermal zones is surrounded by one of the segmented top heating elements and one of the segmented side heating elements, the base heating element, the intermediate heating element at the first end of one of the vehicles and the intermediate heating element at the first end of an adjoining one of the vehicles.

11. The apparatus of claim 9, each of the vehicles including a thermocouple, and wherein the base heating element and the intermediate heating element are configured so that a power of the base heating element is independently adjustable from a power of the intermediate heating element.

12. An assembly for transporting a sheet of glass, the assembly including:

a frame including a transversely extending member; and

13. The assembly of claim 12, the pads including an inner portion configured to contact a sheet of glass.

14. The assembly of claim 13, the inner portion including a recessed area.

15. The assembly of claim 13, the inner portion made of deformable material.

16. The assembly of claim 13, the inner portion being readily removable from the remainder of the pad or from the second distal section.

17. The assembly of claim 13, in combination with a sheet of glass, at least the inner portion and the transversely extending member having a coefficient of thermal expansion similar to a coefficient of thermal expansion of the sheet of glass.

18. The assembly of claim 12, including a pair of the clamps, each of the clamps configured to pinch a part of an edge of a sheet of glass in the closed position.

19. The assembly of claim 12, in combination with a sheet of glass, furthering including a weight clamp attached to an edge of the sheet of glass opposite an edge pinched by the clamp.

20. The assembly of claim 12, the frame and the clamp made of material resistant to temperatures of about 750 °C.