WO2019046767A1 - Apparatus for actuation of glass in thermal tempering - Google Patents

Abstract

An apparatus for thermal strengthening of glass sheets comprises first and second gas bearings having first and second gas bearing surfaces facing each other across a gap and a carriage positioned beside and outside of the gap, the carriage structured and/or mounted for motion in a direction beside and along the gap. A frame positioned within or positionable within the gap is mounted to the carriage. The frame is sufficiently thin to pass within the gap on the air bearings without contacting the surfaces of the air bearings.

Description

APPARATUS FOR ACTUATION OF GLASS IN THERMAL TEMPERING

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U. S.C. § 119 of U. S. Provisional Application No. 62/552,627, filed August 31, 2017, the content of which is incorporated herein by reference in its entirety.

FIELD

[0002] The present disclosure relates to apparatus for producing thermally strengthened glass and more specifically to systems and apparatus for actuating glass in thermal tempering processes and apparatuses.

SUMMARY

[0003] The following presents a simplified summary of the disclosure in order to provide a basic understanding of some exemplary embodiments described in the detailed description.

[0004] In embodiments, an apparatus for thermal strengthening of glass sheets comprises first and second gas bearings having first and second gas bearing surfaces facing each other across a gap and two wires strung in tension through the gap between the gas bearing surfaces. At least two carrier members, each carrier member extending at least from one wire to the other, and being positioned or positionable within the gap.

[0005] In embodiments, an apparatus for thermal strengthening of glass sheets comprises first and second gas bearings having first and second gas bearing surfaces facing each other across a gap and a carriage positioned beside and outside of the gap structured and/or mounted for motion in a direction beside and along the gap. A frame positioned within or positionable within the gap is mounted to the carriage. The frame is sufficiently thin to travel within the gap contacting the surfaces of the air bearings. The frame can be attached to or formed integrally together with a carrier, which carrier is mounted to the carriage. The apparatus can comprise two carriages, one on each side of the gas bearings.

[0006] Embodiments of the apparatus further comprise a race track drive and a plurality of carriages supported on the race track drive. In embodiments, the carriages supported on the race track drive, or subsets of the carriages supported on the race track drive, are independently actuated.

[0007] In embodiments, the frame comprises a clamping region and a glass cavity joined to the clamping region by a plurality of flexure fingers.

[0008] The above embodiments are exemplary and can be provided alone or in any combination with any one or more embodiments provided herein without departing from the scope of the disclosure. Moreover, it is to be understood that both the foregoing general description and the following detailed description present embodiments of the present disclosure, and are intended to provide an overview or framework for understanding the nature and character of the embodiments as they are described and claimed. The accompanying drawings are included to provide a further understanding of the embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure, and together with the description, serve to explain the principles and operations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other features, embodiments, and advantages of the present disclosure can be further understood when read with reference to the accompanying drawings:

[0010] FIG. 1 shows an isometric view of an embodiment of the present disclosure;

[0011] FIG. 2 shows an isometric view of the system shown in FIG. 1;

[0012] FIG. 3 shows a close up isometric view of the embodiment shown in FIGS. 1 and 2;

[0013] FIG. 4 shows a close-up end view of one alternative embodiment of particular features of the embodiment shown in FIGS. 1-3;

[0014] FIG. 5 shows an isometric view of an actuation system according to additional embodiments of the present disclosure;

[0015] FIG. 6 shows an isometric view of the disclosure shown in FIG. 5 in which the top bearings and plenums have been removed for clarity;

[0016] FIG. 7 shows a close-up isometric view of the frame system of shown in FIG.

6; [0017] FIG. 8 shows a diagrammatic plan view of a system according to embodiments of the present disclosure in which a glass conveyance system includes actuators that travel in a continuous oval or "race track" path;

[0018] FIG. 9 shows a plan / perspective view of an embodiment of a frame of the present disclosure; and

[0019] FIG. 10 shows a plan view of another embodiment of a frame of the present disclosure.

[0020] FIG. 11 shows a plan view of another embodiment of a frame of the present disclosure, together with associated carriages and carriage rails.

DETAILED DESCRIPTION

[0021] Methods and apparatus will now be described more fully hereinafter with reference to the accompanying drawings in which exemplary embodiments of the disclosure are shown. Whenever possible, the same reference numerals are used throughout the drawings to refer to the same or like parts. However, this disclosure can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[0022] The present disclosure comprises a glass article actuation apparatus and method or actuation system 100 which may be and preferably is integrated into the design of thermal tempering equipment. One embodiment as seen in FIGS. 1 and 2, uses two wires 12 that are strung in tension through a gas bearing system of the tempering equipment. Each ends of the wires are mounted on two carriages 14 whose motion in the actuation direction can be precisely controlled. The wires 12 are positioned such that their spacing is slightly larger than the width of a glass article 16 to be conveyed, thereby constraining the glass along its two longitudinal edges. Carrier members in the form of a frame 18 are attached to the wires 12 such that they constrain the remaining two edges of the glass article 16. The motion of the two carriages 14 is synchronized for actuation with a prescribed acceleration, velocity, and position such that the glass article 16 is moved from the hot zone (the hot bearing or hot gas bearing 20) to the cold zone (the cold bearing ro cold gas bearing 22) with minimal forces, thereby minimizing the amount of distortion in the glass, which may be somewhat softened in the hot zone prior to quenching.

[0023] In an additional embodiment of the present disclosure, shown in additional figures and described below, the carrier is a thin frame that is mounted to a carriage that is outboard and parallel to the bearing system. Two carriages and carriers may also be used, one on each side of the bearing system. The carriages may be mounted on a "race track" drive and are desirably independently actuated, or if pairs are used, independently actuated in pairs.

[0024] Compared to methods in which the glass article is actuated from the hot zone to the cold zone using either (a) a contact pusher from one side of the glass, (b) gravity actuation by tilting the gas floatation bearing system, (c) gas pressure actuation by reducing or increasing the gas escaping the two ends of the gas floatation bearing system, or (d) side driven rollers which contact the glass which is tilted into gravitational contact with the drive rollers (a method which is utilized by the two leading manufacturers of thermal tempering systems for commercial glass production), the methods and apparatuses described herein:

[0025] (1) Capture the glass on both its leading and trailing ends such that the acceleration, velocity, and position of the glass can be controlled throughout its journey. This feature enables the start and stop forces imparted on the softened glass to be controlled minimized and applied to specific contact positions to minimize the distortion of the glass part.

[0026] (2) Capture the glass on both its lateral sides with a constraining member (two wires or two sides of a frame) that move along at the same speed as the glass such there is essentially no relative motion between the constraining members and the glass sides. This feature essentially eliminates (or at least minimizes) frictive contact damage to the edges of the glass that might occur during the thermal tempering process.

[0027] (3) Since the glass is fully constrained and does not rely on the aspect ratio of the part to aid in its guidance, the methods and apparatuses described herein enable the part to be actuated through the thermal tempering process such that its shortest dimension is in the direction of actuation, if desired. This feature enables the glass article to be actuated from the hot zone into the full submersion of the cold zone as quickly as possible. Shortening the time with which the part can be fully submerged in the cold zone may lead to higher temper levels (larger tempering stresses), improved temper uniformity, and reduced edge stresses that the part experiencing as its leading region begins to contract (due to inherent material thermal- dimensional behavior) before the trailing region does.

[0028] (4) In embodiments having the ability to independently actuate multiple glass articles within a thermal tempering machine, the dwell time spent in each zone of the thermal tempering system can be independent and variable. This is important for process control and optimization; for example, one conveyance frame can be independently stationed in the hot zone of the tempering machine to allow the part to come up to full temperature (usually the rate-limiting step of a thermal tempering system), while a second conveyance frame is actuated independently first to the quench zone and then to the unload station to allow an operator or an unload robot to pick up the unload the glass. This independence between each actuator (or pair of actuators, if paired) enables parts to be processed at a higher rate and with a higher level of control that can be tailored to each individual part.

[0029] FIG. 1 shows an isometric view of an embodiment of the present disclosure in which two wires are strung in tension through a thermal tempering system such as that described in US Pat. No. 9,296,638, incorporated herein in its entirety by reference. FIG. 2 shows an isometric view of the system shown in FIG. 1 wherein the top bearings and top plenums have been removed for clarity.

[0030] With reference to FIGS. 1 & 2, a glass article 16 is constrained vertically between surfaces of opposing gas hot and cold gas bearings 20, 22 such that the glass article makes no mechanical contact with the surfaces of the bearings. Wires 12 are positioned such that they are largely centralized vertically between the opposing surfaces of bearings 20, 22 and such that their lateral spacing is slightly larger than the width of the glass article 16. The wires 12 are attached to two carriages 14 which are optionally attached to precision slide systems which may be built or purchased. The wire lengths, and the stroke lengths of the slide systems, if present, are chosen such that the glass article 16 can be conveyed from a load gas bearing 24 through the hot and cold gas bearings 20, 22 to the unload gas bearing 26. Separate Plenums 30 assist in supplying the gas to the various bearings. FIG. 2 shows the view of FIG. 1 with the upper ones of the plenums 30 and the top halves of the hot and cold bearings removed for clarity, and with the carriages 14 moved to position the glass article 16 on the unload gas bearing 26.

[0031] FIG. 3 shows a close-up isometric view of the embodiment shown in FIGS. 1 and 2. Two frames 18 are mounted to the wires 12 such that there is a small clearance between their edges and the leading and trailing edges of the glass article 16.

[0032] FIG. 4 shows a close-up end view of one alternative embodiment of particular features of the embodiment shown in FIGS. 1-3. In this embodiment, the two frames 18 have recesses 19 built into their ends that engage with the wire 12 and keep the frames 18 vertically centered to the centerlines of the wires 12. Tension on the wires 12 is utilized to provide a contact preload between the wire sides and the frame ends and the frames 18 are constrained in the conveying direction (as indicated by the arrows in FIGS. 1 and 2) by the friction between their contacting surfaces.

[0033] Since hot zone bearings in the glass thermal tempering system may typically reach temperatures greater than 620° C and up to as high as 890° C or more, the wires 12 and the frames 18 are made from materials that will withstand these temperatures. They are also made from material able to withstand the rather large thermal shock that they experience as they are actuated from the hot to the cold zones. For this reason, both the wires and the frames are preferably made from metals which remain relatively stiff and resist oxidation at temperatures within this range. Exemplary materials are various stainless-steel alloys, Inconel alloys, Hasteloy alloys, Waspaloy, and so forth.

[0034] In additional embodiments of the present disclosure, alternative methods to attach the frames to the wires could include welding, brazing, and so forth. In embodiments, small step recesses could be machined into the wires such that the frames lock into the shoulders of the recesses.

[0035] FIG. 5 shows an isometric view of an actuation system 100 according to additional embodiments of the present disclosure, in which the motion of the glass article 16 to be conveyed and tempered is controlled by a frame 18 connected to an outboard carriage 14. FIG. 6 shows an isometric view of the system 100 shown in FIG. 5 in which the top halves of the two-sided hot and cold bearings and plenums have been removed for clarity. FIG. 7 shows a close-up isometric view of the frame 18 shown in FIG. 6.

[0036] With reference to FIGS. 5-7, the glass article 16 is constrained vertically between sets of gas bearings 20, 22 such that it makes no mechanical contact with the bearing surfaces. The frame is thin and the resulting bending stiffness is low, such that, in this embodiment, the gas bearings act to centralize the frame vl8 ertically. The frame surrounding the other edges of the glass is constrained such that it is largely centralized vertically between the upper and lower bearings, and such that the lateral spacing of the interior of the frame 18 is slightly larger than the width of the glass article to be conveyed. The frame is attached to an outboard carriage 14 which may desirably be carried by or part of a precision slide system which can be custom built or sourced commercially.

[0037] FIG. 8 shows a diagrammatic plan view of a system according to embodiments of the present disclosure in which a glass conveyance system 100 includes actuators that travel around a continuous oval or "race track" drive 110 such that continuous, relatively high-speed operation is possible. With reference to FIG. 8, in currently preferred embodiments of this system, the actuators or carriages 14, or subsets of the total number of actuators, move independently of each other around the "race track" drive 110. In such embodiments, for example, the conveyance system may have carriages which are each actuated independently by means of a linear electric motor as one example of independent actuation. The ability to independently actuate each carriage, or each set of carriages, enables the dwell time spent in each zone of the thermal tempering system to be independent and variable. This is desirable for process control and optimization; for example, one conveyance frame 18 can be independently stationed in the hot zone of a tempering machine to allow the part to come up to full temperature (usually the rate-limiting step of a thermal tempering system), while a second conveyance frame is actuated independently first to the quench zone and then to the unload station to allow an unloader (such as a robot or human operator) to pick up the glass. This independence between each conveyor actuator or between each set of actuators enables parts to be processed at a higher rate and with a higher level of control that can be tailored to each individual part.

[0038] In embodiments, the system shown in FIG. 8 may also be a simple belt drive in a continuous oval shape with each carriage rigidly connected to the belt, however, the actuated motion of such a belt would deliver each carriage with dependence on each other and would not enable the same level of part rate optimization and control sophistication.

[0039] According to embodiments as further represented in FIG. 8, two tempering machines 10 and 10a may be combined with a single conveyance system 100. This dual system would enable the glass parts to be processed at a higher rate of speed and the capital cost of the equipment (using only one conveyance system) 100 would be better optimized to maximize profits.

[0040] FIG. 9 shows an embodiment of a frame 18 of the present disclosure, surrounding a glass cavity 17, in which a clamping region 40 (at which the frame is held by an associated actuator or actuation system) and the frame region (the region wahich surrounds the glass) have been separated with thin-walled flexure fingers 42 which allow the frame to grow and contract with minimal stresses on the framed portion of the design. An added benefit of this design is that the fingers would act as a "mechanical fuse"; in the event that the glass became stuck within the machine during a high-speed actuation, the fingers would rip off from the frame and prevent large forces from being induced into the various machine members. [0041] The fingers 42 of the frame design shown in FIG. 9 can be designed by those skilled in the art of solid mechanics. The displacements due to thermal differences can be estimated simply by multiplying the coefficient of thermal expansion (CTE) of the metal by the distance from the midpoint of the frame to its edge by the temperature rise. In this case it is approximately 0.092". This is the displacement that the finger at the edge of the part will experience. The finger can be modeled as a simple cantilevered beam in order to compute its stresses, such as by use of Roark's Formulas for Stress and Strain by Warren C. Young, 6th edition or similar formulas.

[0042] A computed finite element analysis of the frame shown in FIG. 9, subjected to a thermal condition whereby the frame region reaches 700° C while the clamped side region is at 25° C, was performed, including temperature distribution, displacement, and stress. The resulting stresses were nearly entirely limited to the fingered regions and were of sufficiently small magnitude (approximately 27ksi) to stay below the yield strength of most common stainless steels in sheet form (approximately 34ksi).

[0043] FIG. 10 shows another embodiment of frame 18 useful the context of the embodiments of the present disclosure, in which frame 18 the clamping region 40 and the frame of the glass cavity 17 have been separated with thin-walled flexure fingers 42 which allow the frame to grow and contract with minimal stresses on the glass cavity 17 frame portion of the design. In this design, the flexure fingers 42 have thickness which varies from thickest in a central region 42a at and nearest a central plane to thinnest when furthest from the central plane at an end region 42b. An advantage of this design is that the robustness (ability of the frame to withstand various forces) would be maximized while keeping the stress in each individual finger about the same. The formulas previously disclosed were implemented into a table with computations for the 20 fingers shown in FIG. 10. The largest finger has a height of 0.295" and the smallest has a height of 0.038". The computed maximum stress in each case is approximately 18ksi.

[0044] FIG. 11 shows a plan view of another embodiment of a frame of the present disclosure, comprising frame members 18a, 18b together with associated carriages 14a, 14b and carriage rails 15a, 15b. Frame members 18a, 18b are stretched under tension between the two carriages, such as by springs S with opposing fixed mounts F, with the moveable end of the frames contained in a sliding guide M. The frame members 18a, 18b, also desirably comprise one or more weakened breakaway areas BW so as to allow the frame to break in the event of a glass sheet becoming jammed during conveyance thereof. A small clearance may be provided at the edges of the glass 16 such that the glass is contacted only at the corners thereof, as shown in the figure. This can result in less overall distortion of the glass as a result of the conveyance forces.

[0045] It will be appreciated that the various disclosed embodiments can involve particular features, elements or steps that are described in connection with that particular embodiment. It will also be appreciated that a particular feature, element or step, although described in relation to one particular embodiment, can be interchanged or combined with alternate embodiments in various non-illustrated combinations or permutations.

[0046] It is to be understood that, as used herein the terms "the," "a," or "an," mean "at least one," and should not be limited to "only one" unless explicitly indicated to the contrary. Thus, for example, reference to "a component" includes embodiments having two or more such components unless the context clearly indicates otherwise.

[0047] Ranges can be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, embodiments include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0048] Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that any particular order be inferred.

[0049] While various features, elements or steps of particular embodiments can be disclosed using the transitional phrase "comprising," it is to be understood that alternative embodiments, including those that can be described using the transitional phrases "consisting" or "consisting essentially of," are implied. Thus, for example, implied alternative embodiments to an apparatus that comprises A+B+C include embodiments where an apparatus consists of A+B+C and embodiments where an apparatus consists essentially of A+B+C. [0050] It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the spirit and scope of the disclosure. Thus, it is intended that the present disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.

Claims

CLAIMS What is claimed is:

1. An apparatus for thermal strengthening of glass sheets, the apparatus comprising: first and second gas bearings having first and second gas bearing surfaces facing each other across a gap;

two wires that are strung in tension through the gap between the gas bearing surfaces; and

at least two frame members, each frame member extending at least from one wire to the other, each frame member being positionable within the gap.

2. An apparatus for thermal strengthening of glass sheets, the apparatus comprising: first and second gas bearings having first and second gas bearing surfaces facing each other across a gap;

a carriage positioned beside and outside of the gap structured and/or mounted for motion in a direction beside and along the gap;

a frame positioned within the gap and mounted to the carriage, the frame being sufficiently thin to pass between the surfaces of the air bearings within the gap without contacting the surfaces of the air bearings.

3. The apparatus of claim 2 wherein the frame is attached to or integral with a carrier which carrier is mounted to the carriage.

4. The apparatus of either of claims 2 and 3 wherein the apparatus comprises two carriages one on each side of the gas bearings.

5. The apparatus of either of claims 2 and 3 wherein the apparatus comprises a race track drive supporting a plurality of carriages.

6. The apparatus of claim 5 wherein the plurality of carriages are independently actuated.

7. The apparatus of any of claims 2-6 wherein the frame comprises a clamping region and a glass cavity joined to the clamping region by a plurality of flexure fingers.

8. The apparatus of any of claims 4-6 wherein the frame comprises first and second frame members stretched under tension between the two carriages.

9. The apparatus of claim 8 wherein the first and second frame members comprise one or more weakened breakaway areas so as to allow the frame to break in the event of a glass sheet becoming jammed during conveyance thereof.