CA1199794A - Arrangement of apertures for vacuum holders for shaping glass sheets - Google Patents
Arrangement of apertures for vacuum holders for shaping glass sheetsInfo
- Publication number
- CA1199794A CA1199794A CA000429893A CA429893A CA1199794A CA 1199794 A CA1199794 A CA 1199794A CA 000429893 A CA000429893 A CA 000429893A CA 429893 A CA429893 A CA 429893A CA 1199794 A CA1199794 A CA 1199794A
- Authority
- CA
- Canada
- Prior art keywords
- vacuum
- sheet
- holder
- glass
- deformable
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B23/00—Re-forming shaped glass
- C03B23/02—Re-forming glass sheets
- C03B23/023—Re-forming glass sheets by bending
- C03B23/035—Re-forming glass sheets by bending using a gas cushion or by changing gas pressure, e.g. by applying vacuum or blowing for supporting the glass while bending
- C03B23/0352—Re-forming glass sheets by bending using a gas cushion or by changing gas pressure, e.g. by applying vacuum or blowing for supporting the glass while bending by suction or blowing out for providing the deformation force to bend the glass sheet
- C03B23/0357—Re-forming glass sheets by bending using a gas cushion or by changing gas pressure, e.g. by applying vacuum or blowing for supporting the glass while bending by suction or blowing out for providing the deformation force to bend the glass sheet by suction without blowing, e.g. with vacuum or by venturi effect
Abstract
ABSTRACT
When sheets of glass or other deformable material are shaped by a method that comprises the use of a vacuum holder having a lower sheet wall provided with an array of apertures through which air is drawn by vacuum to engage a sheet to be shaped by vacuum, the array must be larger than each dimension of the sheet to be shaped so that when the sheet arrives at a shaping station in proper alignment for engagement by the vacuum holder, there is a continuous line of apertures beyond each side of the sheet to be engaged by suction. Otherwise, when the sheet is engaged by suction, it is displaced an uncontrolled amount transversely and/or longitudinally en route to engagement by the apertured lower wall. Since the amount of displacement cannot be controlled under such circumstances, the sheet becomes misaligned relative to its desired position of engagement against the vacuum holder. By providing apertures at approximately equal distances around the periphery of the sheet, this tendency for displacement is minimized.
When sheets of glass or other deformable material are shaped by a method that comprises the use of a vacuum holder having a lower sheet wall provided with an array of apertures through which air is drawn by vacuum to engage a sheet to be shaped by vacuum, the array must be larger than each dimension of the sheet to be shaped so that when the sheet arrives at a shaping station in proper alignment for engagement by the vacuum holder, there is a continuous line of apertures beyond each side of the sheet to be engaged by suction. Otherwise, when the sheet is engaged by suction, it is displaced an uncontrolled amount transversely and/or longitudinally en route to engagement by the apertured lower wall. Since the amount of displacement cannot be controlled under such circumstances, the sheet becomes misaligned relative to its desired position of engagement against the vacuum holder. By providing apertures at approximately equal distances around the periphery of the sheet, this tendency for displacement is minimized.
Description
97~
ARRANOEMENT OF APERTUBES FOR VACUI~I }IOLDERS
FOR SHAPING GLASS S~EETS
RELATIO~ TO OTHER CASES
-A preferred embodiment of the present invention may also con-tain other inventions described and claimed in the following copending applications, all of which are filed on the same date,i.e. June 7, 1983.
D~formable Vacuum Holder Used to Shape Glass Sheets, disclosed and claimed in Can. patent application Serial No. 429,895_, of John D.
Kellar ~nd Gordon F. Pereman.
Vacuum Holder with Anti-Bulging Means for Shaping Glass Sheets, disclosed and claimed in ~ an. patent application Serial No. 429,892 , of John D. Kellar and Gordon F . Pereman.
Deformable Vacuum Holder with Helical Coil Springs for Shaping Glass Sheets, disclosed and claimed in Can. patent application Serial No.
429,896, of John D. Rellar and Gordon F. Pereman.
Cooling Vacuum Holder by Suction, disclosed and claimed in ~an.
patent application Serisl No. 429,891, of John D. Kellar and Gordon F~
Pereman.
Multiple Chamber Vacuum Holder Used to Shape Glass Sheets with Means to Isolate Adjacent Vacuum Chambers, disclosed and claimed in Can.
patent application Serial No. 429,890, of Robert Ç. Frank aDd John J.
~wing.
~ackground of the Invention 1. Field of the Invention This invention relatea to shaping sheets of defonmable materials, such as glass sheets, and particularly relates to the high speed produ~tion ~,~
~979~
of bent glass sheets that are toughened by air quenching, and most par-ticularly, for shaping and heat treating relatively thin glass sheets, particularly those having a nominal thicknes~ of 1/8 inch (3.2 mm) or less. Thinner glass sheets sag more readily than thicker glass sheets at any given elevated temperature above the glass deformation temperature.
Hence, it is more difficult to control the shape imparted to thinner glass sheets.
Shaped and tempered glass sheets are widely used as side windows or rear windows in vehicles such as automobiles or the like and, to be suitable for such application, flat glass sheets must be shaped to pre-cisely defined curvatures dictated by the shape and outline of the frames defining the window openings into which the glass side or rear windows are installed. It is also important that the side or rear windows meet strin-gent optical requirements and that the windows be free of optical defects that would tend to interfere with the clear viewing therethrough in their vlew~ng areas.
During fabrication, glass sheets intended for use as shaped windows in vehicles are subject to thermal treatment to temper the glass for strengthening the glass and increasing the resistance of the shaped window to damage resulting from impact. In addition to increasing the resistance of a glass sheet to breakage, tempering also causes a glass sheet to fracture into relatively small, relatively smoothly surfaced fragments that are less injurious than the relatively large, jagged fragments that result from the more frequent breakage of untempered glass.
The commercial production of shaped glass sheets for such pur-poses commonly includes heating flat sheets to the softening point of the glass, shaping the heated sheets to a desired curvature and then cooling the bent sheets in a controlled manner to a temperature below the annealing range of the glass. During such treatment, a glass sheet is conveyed along a substantially horizontal path that extends through a tunnel-type furnace where the glass sheet is one of a series of sheets that are heated to the deformation temperature of glass and along an extension of said path into a shaping station (located either within the furnace or immediately beyond the furnace~ where each glass sheet in turn is transferred onto a vacuum holder. The vacuum holder holds the heat-softened glass sheet thereagainst by suction. At about the same time, a transfer and tempering ring having an outline shape conforming to that desired for the glass sheet slightly inboard of its perimeter moves upstream into a position below the vacuum holder. Release of the vacuum deposits the glass sheet onto the tempering ring. The tempering ring supports the peripheral portion of the glass sheet while it conveys the glass sheet into a cooling station for rapid cooling.
In prior art apparatus, the vacuum mold was either provided with a lower, rigidly curved shaping surface that shaped the heat-softened glass sheet incrementally by suction thereagainst or had a smoothly surfaced flat shaping surface that lifted the flat glass sheet by suction thereagainst and depended on a release of the vacuum within the mold to permit the hot glass sheet to drop by gravity or by replacing the vacuum with positive pressure to drop the glass sheet by a combination of gravity and an addi-tional force onto the tempering ring to develop the shape dictated by the outline configuration of the tempering ring. The latter process has been called drop forming.
~ 9~3~t;,~4 When a rigid, curved surface is adjacent a heat-softened flat glass sheet during the application of suction through said surface, much power is needed to obtain the suction necessary to lit and shape a hot glass sheet simultaneously by suction at a rate su~ficiently rapid to provide a high speed mass production operation for shaping and tempering glass sheets. The glass sheet bending art has developed distortable vacuum holders that normally have a smooth, flat, lower perforated surface and engage the upper surface of one or more flat glass sheets by suction and distort the engaged heat-softened glass sheeets to a desired shape as they lift the engaged glass sheets. A ring-like member having both an outline shape and elevational configuration desired for the glass sheet shuttles to a position below the vacuum holder. When vacuum is either stopped or replaced by a positive downward pressure, the glass sheet drops onto the ring-like member for conveyance thereon to a cooling station where the hot bent glass sheet is cooled sufficiently rapidly to impart a temper to the sheet.
A problem exists using a vacuum holder to help shape flat glass sheets when the outline of the area encompassed by the evacuating apertures of the lower sheet wall of the vacuum holder occupies a smaller area than the sheet outline or is offset with respect to tne sheet outline so that the apertures do not form a continuous line of exposed apertures outside of the outline of the glass sheet to be shaped. When the lower apertured sheet wall has no exposed apertures outside one side but not the other side and/or outside one end but not the other end of the glass sheet supported nearby for vacuum engagement, the glass sheet will translate in position relative to the array of apertures either in a transverse direction or in a longitudinal direction away from said side or end devoid of exposed aper-9~9~
tures when vacuum is applied through the array of apertures. Under theseconditions, the glass sheet may engage the vacuum holder in a position of misalignment with a position the flat glass must occupy in order to insure proper alignment of the shaped glass sheet with the deformed Yacuum holder.
ARRANOEMENT OF APERTUBES FOR VACUI~I }IOLDERS
FOR SHAPING GLASS S~EETS
RELATIO~ TO OTHER CASES
-A preferred embodiment of the present invention may also con-tain other inventions described and claimed in the following copending applications, all of which are filed on the same date,i.e. June 7, 1983.
D~formable Vacuum Holder Used to Shape Glass Sheets, disclosed and claimed in Can. patent application Serial No. 429,895_, of John D.
Kellar ~nd Gordon F. Pereman.
Vacuum Holder with Anti-Bulging Means for Shaping Glass Sheets, disclosed and claimed in ~ an. patent application Serial No. 429,892 , of John D. Kellar and Gordon F . Pereman.
Deformable Vacuum Holder with Helical Coil Springs for Shaping Glass Sheets, disclosed and claimed in Can. patent application Serial No.
429,896, of John D. Rellar and Gordon F. Pereman.
Cooling Vacuum Holder by Suction, disclosed and claimed in ~an.
patent application Serisl No. 429,891, of John D. Kellar and Gordon F~
Pereman.
Multiple Chamber Vacuum Holder Used to Shape Glass Sheets with Means to Isolate Adjacent Vacuum Chambers, disclosed and claimed in Can.
patent application Serial No. 429,890, of Robert Ç. Frank aDd John J.
~wing.
~ackground of the Invention 1. Field of the Invention This invention relatea to shaping sheets of defonmable materials, such as glass sheets, and particularly relates to the high speed produ~tion ~,~
~979~
of bent glass sheets that are toughened by air quenching, and most par-ticularly, for shaping and heat treating relatively thin glass sheets, particularly those having a nominal thicknes~ of 1/8 inch (3.2 mm) or less. Thinner glass sheets sag more readily than thicker glass sheets at any given elevated temperature above the glass deformation temperature.
Hence, it is more difficult to control the shape imparted to thinner glass sheets.
Shaped and tempered glass sheets are widely used as side windows or rear windows in vehicles such as automobiles or the like and, to be suitable for such application, flat glass sheets must be shaped to pre-cisely defined curvatures dictated by the shape and outline of the frames defining the window openings into which the glass side or rear windows are installed. It is also important that the side or rear windows meet strin-gent optical requirements and that the windows be free of optical defects that would tend to interfere with the clear viewing therethrough in their vlew~ng areas.
During fabrication, glass sheets intended for use as shaped windows in vehicles are subject to thermal treatment to temper the glass for strengthening the glass and increasing the resistance of the shaped window to damage resulting from impact. In addition to increasing the resistance of a glass sheet to breakage, tempering also causes a glass sheet to fracture into relatively small, relatively smoothly surfaced fragments that are less injurious than the relatively large, jagged fragments that result from the more frequent breakage of untempered glass.
The commercial production of shaped glass sheets for such pur-poses commonly includes heating flat sheets to the softening point of the glass, shaping the heated sheets to a desired curvature and then cooling the bent sheets in a controlled manner to a temperature below the annealing range of the glass. During such treatment, a glass sheet is conveyed along a substantially horizontal path that extends through a tunnel-type furnace where the glass sheet is one of a series of sheets that are heated to the deformation temperature of glass and along an extension of said path into a shaping station (located either within the furnace or immediately beyond the furnace~ where each glass sheet in turn is transferred onto a vacuum holder. The vacuum holder holds the heat-softened glass sheet thereagainst by suction. At about the same time, a transfer and tempering ring having an outline shape conforming to that desired for the glass sheet slightly inboard of its perimeter moves upstream into a position below the vacuum holder. Release of the vacuum deposits the glass sheet onto the tempering ring. The tempering ring supports the peripheral portion of the glass sheet while it conveys the glass sheet into a cooling station for rapid cooling.
In prior art apparatus, the vacuum mold was either provided with a lower, rigidly curved shaping surface that shaped the heat-softened glass sheet incrementally by suction thereagainst or had a smoothly surfaced flat shaping surface that lifted the flat glass sheet by suction thereagainst and depended on a release of the vacuum within the mold to permit the hot glass sheet to drop by gravity or by replacing the vacuum with positive pressure to drop the glass sheet by a combination of gravity and an addi-tional force onto the tempering ring to develop the shape dictated by the outline configuration of the tempering ring. The latter process has been called drop forming.
~ 9~3~t;,~4 When a rigid, curved surface is adjacent a heat-softened flat glass sheet during the application of suction through said surface, much power is needed to obtain the suction necessary to lit and shape a hot glass sheet simultaneously by suction at a rate su~ficiently rapid to provide a high speed mass production operation for shaping and tempering glass sheets. The glass sheet bending art has developed distortable vacuum holders that normally have a smooth, flat, lower perforated surface and engage the upper surface of one or more flat glass sheets by suction and distort the engaged heat-softened glass sheeets to a desired shape as they lift the engaged glass sheets. A ring-like member having both an outline shape and elevational configuration desired for the glass sheet shuttles to a position below the vacuum holder. When vacuum is either stopped or replaced by a positive downward pressure, the glass sheet drops onto the ring-like member for conveyance thereon to a cooling station where the hot bent glass sheet is cooled sufficiently rapidly to impart a temper to the sheet.
A problem exists using a vacuum holder to help shape flat glass sheets when the outline of the area encompassed by the evacuating apertures of the lower sheet wall of the vacuum holder occupies a smaller area than the sheet outline or is offset with respect to tne sheet outline so that the apertures do not form a continuous line of exposed apertures outside of the outline of the glass sheet to be shaped. When the lower apertured sheet wall has no exposed apertures outside one side but not the other side and/or outside one end but not the other end of the glass sheet supported nearby for vacuum engagement, the glass sheet will translate in position relative to the array of apertures either in a transverse direction or in a longitudinal direction away from said side or end devoid of exposed aper-9~9~
tures when vacuum is applied through the array of apertures. Under theseconditions, the glass sheet may engage the vacuum holder in a position of misalignment with a position the flat glass must occupy in order to insure proper alignment of the shaped glass sheet with the deformed Yacuum holder.
2. Description of Patents of Interest U.S. Patent No. 4,277,276 to John D. Kellar and Gordon F. Pereman discloses glass sheet shaping and tempering apparatus that comprises a deformable vacuum holder having a glass engaging surface as smooth as that of flat vacuum molds o the prior art, and that also shapes the glass sheet to a shape approximately its final desired shape adjacent a heating furnace before releasing the glass sheet onto a shaping and tempering ring to make it possible to increase the speed of a mass production operation for shap-ing and tempering glass sheets, particularly those thinner than 3.2 mm nominal thickness.
U.S. Patent No. 4,282,026 to Harold A. McMaster, Norman C.
Nitschke and John S. Nitschke discloses bonding a board of fibrous material to a rigid vacuum holder of ceramic composition in glass sheet bending apparatus that uses a vacuum holder in the glass shaping process. The adhesive bond is not durable enough to adhere a board of fibrous material to a defol~mable metal sheet surface at elevated temperature cycles required to shape glass sheets against a deformable vacuum holder.
Whenever thin glass sheets are shaped within a heating furnace by sandwiching between pressing molds of complementary shape, such a process saves energy because it avoids the need to overheat the glass, which is necessary to overcome the rapid cooling of the glass sheet that takes place en route to a shaping station located outside the furnace~
However, it is difficult to control the shape and temperature of vacuum molds permanently installed within a furnace. It is also difficult to obtain access to repair or to provide maintenance for a mold that is permanently installed within a furnace.
U.S. Patent No. 4,297,118 to John D. Kellar and Gordon F. Pereman provides a glass sheet shaping method using apparatus that comprises an upper vacuum holder that first engages and lifts a heat-softened glass sheet by suction, and that provides clearance for a shaping and tempering ring to enter the shaping station. The glass sheet shaping station of this patent is located within the heating furnace. The vacuum mold that is used to engage and lift a heat-softened glass sheet by suction is moved outside the furnace between successive bending operations. Such movement cools the vacuum mold intermittently. Such intermittent cooling helps to control the temperature rise somewhat and consequently the shape of the vacuum mold departs only a limited amount from its desired shape during a mass produc-tion campaign that uses this patented invention.
U.S. Patent No. 4,349,375 to John D. Kellar and Gordon F. Pereman discloses other apparatus that comprises a more durable, deformable vacuum holder capable of assuming a flat configuration suitable for engaging a flat glass sheet by suction and deforming into a curved configuration.
Despite the utility of apparatus of this type that has been demonstrated in commercial operations, room exists for further improvement in results obtained using vacuum holders, such as providing vacuum holders that require less frequent maintenance during elevated cyclic temperature conditions associated with glass sheet shaping, reducing bulging of the vacuum holders to limits acceptable to the customer, providing even more uniform, repetitive deformation of the vacuum holder than before, avoiding 7~
collapse of the vscuum holder, providing more efficient cooling of the holder between shaping cycles, avoiding misalignment of glass sheets with the distorted shape of the vacuum holder and helping maintain different lev-els of vacuum in adjacent vacuum chambers of multiple chamber vacuum holders.
Summary of the Present Invention The present invention relates to a vacuum holder used to shape a glass sheet either within a furnace or immediately beyond a furnace through which glass sheets are conveyed into alignment below said holder for vacuum engagement. Release of vacuum or replacement of vacuum with positive downward pressure transfers the glass sheet onto a ring or ring-like member for transfer to a cooling station. In the latter location, the glass sheet is cooled rapidly enough to develop at least a partial temper in each glass sheet supported in turn on the ring-like member.
The present invention provides improvement in glass sheet bending using a deformable vacuum holder having upper and lower sheet walls separated by spacer means as will be better understood in the light of a description of a preferred illustrative embodiment and variations thereof that follows.
When deformable vacuum holders are used, the vacuum engagement continues as the vacuum holder and its engaged glass sheet become distorted in unison.
In this inventive feature, the bottom sheet wall contains an arra~ of apertures that surrounds the entire outline of the position that the glass sheet to be bent should occupy when vacuum is applied. Unless this precaution is taken, the glass sheet is liable to translate to a posi-tion out of alignment with the position it should occupy relative to the array of apertures. Unless the sheet is properly aligned with the array of apereures, it becomes difficult9 if not impossible, to install the bent 794~`
glass sheet in a bent vehicle frame defining a bent opening to be occupied by said bent glass sheet.
The preferred embodiment of the present invention may incorporate several other inventions. For example, vacuum holders with flexible metal walls having scratched surfaces mar a heat-softened glass sheet when they engage the glass sheets with vacuum. Covers of fibrous material having a smooth glass facing surface have been bonded by adhesive to the lower wall of nonmetallic vacuum holders. However, adhesive used prior to this inven-tion has not been able to retain its adhesive properties to deforming metal vacuum holders at varying elevated temperatures for sufficient time to be suitable for mass production because of the need for frequent replacement of the adhesive when the latter is exposed to elevated temperatures required for glass sheet shaping.
The preferred embodiment of the present invention insures that the upper surface of the glass sheet retains its smoothness by mechanically supporting, rather than by adhering, a smoothly surfaced insulator sheet against the lower flexible metal sheet wall of a vacuum holder to control the temperature increase of the lower flexible wall of the deformable vacuum holder during mass production. Supporting the smoothly surfaced insulator sheet wall to the lower flexible wall of the vacuum holder keeps the latte-- from separating when an adhesive bond breaks in response to a temperature change. The support encompasses the edge of the smoothly surfaced insulator sheet within the periphery of the lower flexible sheet wall and clamps the smoothly surfaced insulator sheet to the lower flexible sheet wall beyond the outline of a vacuum supported glass sheet.
Another problem that exists with vacuu~ holders used to shape glass sheets is that, during an extended campaign of shaping glass sheets on a mass production basis, the lower flexible sheet wall tends to develop _ ~ _ 7~9}
a bulge in the dimension transverse to its lengthO
The lower flexible sheet wall of the vacuum holder is slit longitudinally outward of an unslit central portion to form longitudinally extending strips of limited width thae are free to expand transversely of their length from an unslit central region. Thus, any t~ansverse bulge across the width of the lower sheet wall does not exceed the slight bulge of each strip, which is limited to an amount that does not cause distortion beyond acceptable tolerances. Longitudinal bulging is controlled to within acceptable tolerances by connecting side central portions of the upper and lower flexible sheet walls of the vacuum holder with bolts extending through a pair of aligned~ round, centrally disposed holes flanked by bolts e~tending through longitudinally extending sloes in at least one of the flexible sheet walls that increase in length according to their distance from said centrally disposed holes.
Another problem that exists with vacuum holders that are defo~mable is the problem of maintainin~ the vacuum holdes pliable over a wide tempera-ture range 50 that it readily changes shape between a flat configuration snd one confonming to a desired complicated shape. At the ssme time, the vacuum holder must be strong enough to avoid collapse in its thickness dimension when vacuum is applied thereto. Another invention included in the preferred embodiment solves these problems by enclosing e~sentially parallel, longitudinal helical coil springs h~ving a diameter approximstely equal to the space between the flexible sheet walls within the vacuum holder, so that the springs serve as spacers between the flexible upper and lower sheet walls of the deformable holder, proYide clesranre passages for _ g _ 7~
the evacuation of air from the vacuum chamber and flex with the vacuum holder to help distort the latter into a curved shape defined by rigid end forming members that the deformable vacuum holder engages when distorted.
Another problem that exists with a vacuum holder is that it becomes heated to a high temperature due to repetitive engagement ~ith a hot glass sheet during every bending cycle. Removing the holder to a holder retraction station outside the furnace between shaping steps reduces the rate at which the holder becomes heated and thermally expanded to a shape too large for the desired shaping pattern, unless the mass production rate is decelerated to a slow output level by increasing the time spent to cool the holder between shaping steps. Once mass production is kept at an increased rate, a more efficient holder cooling operation becomes necessary.
Cooling the vacuum holder by drawing vacuum by suction through the bottom apertured flexible sheet wall when the holder is outside the furnace has been found to be more efficient than merely keeping the glass sheet vacuum support outside the furnace between shaping cycles or merely blowing hot ambient furnace air within the holder through the apertures of the bottom flexible sheet wall when the holder is outside the furnace between shaping cycles, according to another invention incorporated in the preferred embodiment and claimed in another copending patent application.
Another problem exists when using a vacuum holder having a plurality of vacuum chambers, each of which requires a different level of vacuum to support a glass sheet of complicated shape. This problem arises from the fact that the glass sheet facing surface of the vacuum holder is covered by a porous fiber glass cloth cover that insulates the bottom wall of the holder from direct contact with the heat-softened glass sheet. ~hen diferent levels of vacuum are applied simultaneously to adjacent vacuum chambers of a vacuum holder covered by a single porous fiber glass cover, tends to equalize the level of vacuum in adjacent vacuum chambers when the engaged sheet seals the sheet covered portions of the chambers. This tendency to equalize the vacuum level sometimes causes a glass sheet to drop from its position of engagement with the vacuum holder prematurely because the overall level of vacuum that results from this bleeding lowers the overall vacuum level to a level below the level of vacuum needed to maintain the entire glass sheet in vacuum engagement against the holder.
More specifically, when glass sheets are shaped to complicated shapes involving a gently bent main portion and one or more end portions more sharply bent, the level of vacuum needed for a vacuum chamber facing the main portion to support the gently bent portion is much less than that needed for an end vacuum chamber facing an end portion to be sharply bent.
W~len bleeding of vacuum level occurs, the vacuum chamber facing the main portion of the glass sheet develops a level of vacuum greater than is needed to support the glass sheet while the end vacuum chamber loses vacuum. Consequently, the gently bent main portion develops markings replicating the pattern of the fiber glass cover and the sharply bent end portion does not develop the sharpness of bend required.
The last described invention solves the problems just explained by isolating adjacent vacuum chambers of the vacuum holder from one another by including a narrow elongated space vented to the atmosphere bet~een each pair of adjacent vacuum chambers. As a result, ehe level of vacuum in each individual vacuum chamber can be controlled independently of the control exercised for each other chamber.
The following description of a preferred embodiment of the present invention is made to clarify the present invention, and includes the accompanying drawings wherein like reference numbers refer to like structural elements.
~9799~
Brief Description of the Drawings In the drawings forming part of the description that follows, FlG. 1 is a fragmentary, perspective view of apparatus for shaping ~nd tempering glass sheets incorporating a preferred embodiment of the present invention comprising a shaping station located within a roller hearth furnace, with certain parts omitted for clari~y;
FIG. 2 i6 a fragmentary plan view of elements of a vacuum holder incl~ded in the apparat~s of FIG. 1 with parts omitted to show as ~any details of the structure of the deformable vacuum shaping holder as possible;
FIG. 3 is a fragmentary bottom plan view looking upward at the vacuum holder of FIG. 2 with certain part6 omitted or broken away to show other parts of the apparatus more clearly;
FIG. 4 is a fragmentsry, elevational view, partly in section, of the deformable vacuum holder taken along the line IV-IY of FIG. 2, ~ith parts broken away to show as ~any other parts as possible;
FIG. 5 i6 an enlarged ele~ational view partly in section of a portion of the deformable vacuum holder of FIG. 4, showing its deformable shaping surface in its flst configurstion to lift and shape a flst glass sheet and with certain parts omi~ted to show certain interior structural elements;
FIG. 6 is another enlarged sectional view of a smaller portion of the vacuum holder taken along the line VI~VI of FIG. 2 ;
FIG. 7 is still another se~tional view of the ~acuu~ holder taken along the li~e VII-VII fo FIG. ~; -FIG. 8 is a sectional view across ~n end portion of the vacuu~
holder along the line VIII~YIII of FIG. 2; and ~97~
FlG. 9 is a sectional view across a side portion of the vacuum holder taken along the line IX-IX nf FIG. 2.
Description of the Preferred Embodiments Referring now to FIG. 1 of the drawings, an apparatus for heating and 6haping sheets of heat-softened materialJ such AS glass, includes conveyor means 41 extending through a heating means compri6ing a tunnel-type furnace 42 (the exit end of which is shown). The furnace includes a shaping station 43 to which sheets of glass are conveyed along the conveyor means 41 from a loading station (not shown) while bein~ heated to the glass deformation temperatu~e. A cooling station generally indi-cated at 44 for cooling the curved sheets of glass and an unlosding station Inot shown) beyond the cooling station 44 are located in end-to-end relation along a transverse path to one side of the shaping station 43. A holder retraction station 45 is located at the other side of the shaping ctation 43, which is the side opposite the cooling station 44. A sheet transfer means 47 shown beside the shaping station 43 transfers glass sheets between the shaping fitation 43 and the cooling station 44.
~ eat may be supplied in the furnace 42 by hot gases from gas burners or by electrical radiant heaters or by a c~mbination nf both, which heat supply ~eans ~re well known in the art. Bearing housings (not shown) adjacent the furnace side walls support bearings for longitudinally spaced, tran~vercely extending conveyor rolls 48 that tefine a path of trsvel for conveyor meanc 41 which extends the length of furnace 42. Some of ~he conveyor rolls 48 &re locaeed at the shaping station 43 to for~ a continua-tion of the path of t~vel ~i~hin the furnace 42. The rolls of the conveyor means 41 ~re arran~ed in sections and their ~otational speed controlled by clutches ~not shown) ~o that ehe ~peed of the diffesent conveyor RPctions ~ay be controlled ~nd synchronized in a ~anner well kno~n in the ~rt.
'7~'~
One or more glass sensing elements (not shown) are located a short distance upstream of the shaping station 43 to initiate a cycle of opera-tion of this ~pparatus in a manner well known in the art. Limit cwitche6 or electronic counter circuits may be provided to synchronize the operation of various elements of the apparatus according to a predetermined sequence.
Since their arrangement and manner of operation are not part of this invention, they will not be described in detail herein.
The shaping station 43 comprises a deformable upper vacuum holder 50 in the form of a deformable metal box. The latter is divided into a central chEmber 51 flanked by end chambers 52. A blanket 53 of flexible, porous refractory material, such as fiber glass, is tightly clamped for biasing against the bottom of the vacuum holder 50 in a manner well known in the art.
The deformable metal box comprises a flexible, apertured, lower me~al sheet wall 54 having perforations 55 distributed throughout and an upper metal sheet wall 56 that is also flexible but has apertures there-through at critical locations only, as will be explained later. The metal sheet walls 54 and 56 form flexible lower and upper sheet walls of the deformable vacuum holder 50. Upper and lower flexible sheet walls 54 and 56 are of half hard tempered sheet steel, and are of essentially polygonal outlines and 6ufficiently larger than the glass sheets to be shaped to provide a fr~me-like area beyond the glass sheet outline. The latter is illustrated in dashed lines in FIG. 3.
~ suitable ~rray of perforations 55 is a checkerboard pattern arr~nged on ~ne inch (2.5 centi~eter~) centers, except for two transversely extendirlg areas. A suitable diameter for each perforation ic 0.172 inch~s ~4.635 millimeters~.
7~
The longit~dinal ~ide edges of the flexible metal cheet walls 54 and 56 are separated al~ng their length by a pair of l~minated springs 58 (see FIG. 9). The latter are constructed of thin flexible layers of strip metal to form flexible laminated spacer6 3/4 inch (19 millime~ers) thick. The laminaeed springs 58 extend inside and adjacent the longitudinal side edges of the holder 50 and have a symmeerical arrangement of longitudinal lots 59 of increasing length with increasing distance from the longitudinal center of the holder 50 along the length of the laminated springs 58. The longitudinal slots 59 coincide with elongated slotted apertures 62 extend-ing vertically through the longitudinal side portions of the upper flexible metal sheet wall 56. The lower flexible metal sheet wall 54 has ro~nd apertures 66 spaced adjacent the opposite longitudinal sides thereof in alignment with the corresponding longitudinal slots 59 and slotted aper-tures 62 to receive attachment bolts 68. The latter exeend through ~pacer sleeves 69. The latter are 3/4 inch (19 millimeters) high to maintain the longitudinal edges of sheet walls 54 and 56 ~eparated while interconected.
Along each of the oblique ~ides at each end of the vacuum holder 50, the lower flexible ~heet wall 54 has a ~eries of spaced holes 70, each coinciding with ~ corresponding elongated, longitudinally slQtted opening 72 of maximum length in the upper flexible metal plate. A rubber spacer 74 for each oblique ~ide (FIG. 8) defines the gap between the corresponding oblique ends of the flexible metal sheet walls 54 and 56. In ~ddieion~
rigid end bar6 76, special rigid end bars 78, and rigid side bars 80 help ~ecure the flexible ~etal sheet walls 54 snd 56 together. Each l$~inated spri~g 58 h~s a centering hole 81 at its longitudinal ceneer to f x the longitudi~al center lines of ~heet ~alls 54 and 56 in alig~ment ~t their geo-me~ric cen~ers. A pla~e 82 i~ fixed to each end of each 6pecial end b~r 78.
91-~99~
A clamp 83 is pivotally attached to each plate 82. An apertured sheet 84 6imilar in outline to, but slightly smaller than flexible metal sheet walls 54 and 56, is composed of insulator material to provide thermal insulation between the lower flexible metal sheet wall 54 and a hot glass ~heet engaged thereto by vacuum.
The rigid bars 76, 78 and 80 cooperate with frame members 77 tsee FIGS. 8 and 9) secured to lower flexible sheet wall by self tapping screws 79 to help support the apertured sheet 84 of impregnated fibrous, flexible material, such as a random fiber glass mat impregnated with a cured polyester resin (which is more rigid than metal sheet wall 54), below the flexible metal sheet wall with the outline of said apertured sheet 84 within the marginal portion of the vacuum holder 50 and aligned with a frame defined by the laminated springs 58 and the rubber spacers 74. The apertured sheet 84 has apertures 85 corresponding to and aligned with the apertures 55 in flexible lower metal sheet 54.
The array of apertures 55, 85 encompasses a larger area than that of the glass sheet undergoing shaping and tempering. It i6 important that the boundary portion of the array of apertures surrounding the outline of the glass sheet form at least one row of essentially uniformly spaced aper-tures exposed to the atmosphere. Uhless this feature is included, ~hen vacuum is applied to holder 50 to engage a flat glass sheet, the latter will translate sidewise and/or lengthwise ineo a position where its outline may be arranged out of &lignment with respect to its desired position against the holder. Unless the apertures 55 and 85 are provided ~ver an area large enough to insure that apertures exposed to the at~osphere s~r-round the entire pesiphery of the flat glass shee~ initially, a chance exists that the misaligned glass sheet will be shaped to an undesired configurntion becau6e of this uncontrolled translation, and will not fit properly in an auto fr~me.
7~?4 A heat-reflecting coating 86 of aluminum paint or other heat-reflecting material is applied to the bottom surface of the apertured sheet 84. The heat reflecting properties of the coating 86 and the thermal insulation properties of the apertured sheet 84 moderate the temperature changes in vacuum holder 50 during repeated cycles of temperature experi-enced during mass production of bent, tempered glass sheets.
Transverse grooves 88 extend across the width of critical portions of the apertured sheet 84 along its upper surface to promote additional flexibility in those portions. The bottom surface of apertured sheet 84 is smooth and resists local deformation to a greater extent than the flexible lower metal sheet wall 54. Hence, the glass sheets are less likel~ to develop optical distortion in their upper surfaces when apertured sheet 84 is interposed between the glass sheet and flexible metal sheet wall 54 then when the apertured shPet 84 is omitted.
Holes corresponding to the centering holes 81 are located in corresponding positions adjacent the longitudinal sides of apertured sheet 84, and extend through the lower flexible sheet wall 54, and the upper flexible sheet wall 56 and the laminated springs 58. A pair of connecting bolts extend through these corresponding holes to secure the sheets and springs to one another on a pair of transversely spaced points along the longitudinal center line o~ the vacuum holder ~0. This enables the ~acuum holder to expand thermally in each longitudinal direction from its longitu-dinal center line equal distances so as to minimize the chance of ~arpage of the lower sheet 54 which faces the glass sheets to be shsped.
C-shaped clips 89 (FIG. 2 and 4) slide over spaced portions of the margin of the flexible holder 50 ~ith their lips overlapping the outer surfaces of flexible sheets 54 and 56. Self-tapping screws are threaded a7~
through the bottom lips to engage the lower sheet 54 only beyond the outer edges of laminated springs 58 and rubber spacers 74. The apertured sheet 84 is dimensioned to have its outer peripheral edge abut the inner edges of laminated springs 58 and rubber spacers 74. Additional bolts 68 extend through spacer sleeves 69 of fixed height (3/4 inch-l9 millimeters) to interconnect the ~arginal portions of sheets 54 and 56 between clips 89.
The lower flexible sheet wall 54 has longitudinal cuts 90 extend-ing to each longitudinal end from an uncut central portion. These longitu-dinal cuts form flexible strips 91 of limited width, for example, about 5 inches (12.7 centimeters) maximum width, that li~it transverse distortion of the lower, thin, flexible, metal sheet wall 54 when the vacuum holder 50 is heated from a room temperature configuration at which the holder is assembled to a higher temperature range that is developed during an extended mass production campaign. The presence of the smoothly surfaced apertured sheet ~4 coated on its glass facing surface with a thin heat-reflecting film 86 and the porous fiber glass covers 53 thereagainst lessens the temperature range established in the vacuum holder 50 during an extended campaign. In addition, the sheet 84, being of a composition less likely to develop surface distortion at elevated temperatures than the flexible metal sheet wall ~4, protects the heat softened glass sheets from replicating any surface marks in the flexible metal sheet ~all 54 due to scratches and other flaws.
The upper flexible sheet wall 56 has central ~pertures 92 commu-nicating the central vacuum chamber 51 with a central vacuum duct 94, and end chamber aperLures 96, one for each end chamber 52. m e latter aper-tures 96 communicate with flexible end vacuum ducts 98. The vacuum ducts 94 and 98 communicate with a vacuum source (not shown) through a co~mon 7~
plenum 99. ~ach vacuu~ duct 94 and 98 is provided with a cont~ol valve 100. Thi~ arrangement enables individual control for vacuum applied tD
chambers Sl and 52. If desired, the common plenum 99 may be adapted for ~elective connection to a vacuum source or a pressure source. The latter may be used to help separate a shaped glass sheee of more complica~ed shape from the flexible holder 50 after the sheet has been sucked by vacuum to conform to the shape of the lower flexible sheet wall 54.
A linkage system 101 is associated with each plate 82 to help distort the vacuum holder 5Q at each of four corner portions thereof. Each plate 82 carries a pivot member 102 (FIG. 5) on which is pivotally mounted the lower end of a first link 104 of adjustable length. The latter is pivotally mounted at it~ upper end to an apertured arm 106. The latter has several spaced holes to adjust its pivotal connection to the first link 104. A Eecond link 108 of adjustable length is pivotally connected ~t its lower end to apertured arm 106. A cam arm 110 is pivotally connected to the upper end of second link lOB. Cam arm 110 is fixed ~o a drive shaft 112 of a motor (not shown). The latter together with a plur~lity of rigid end forming ~ember6 113 and 114 (see FIG. 2) are 6upported from overhead ~upport structure 115. The end forming member~ have lower, curved ~rfaces defining a ~hape desired for sharply bent end portions of the bent glass sheets.
Rotation of the drive ~hafts 112 causes the linkage ~ystem jU6t described to ~pply force on the respective plate6 82 ~o raise the lat~er and c2~Be ehe longitudinal end portions of thP holders 50 ~o di~tort upwardly to develop a ~oncave elevational configuration &t each end ch~mber 52 that conform~ to the ahape of the end forming ~ember~ 113 ~nd 114, or to lower the pl~tes 82 ~o red~ce the 6everi~y o bend impar~ed to the hslder 50 until the bo~tom ~rface of the ~pertuFed sheet 84 is fl~t.
The fiber glass cover 53 is biased against the heat reflecting aluminum coating 86 applied to the bottom surface of apertured shee~ 84 and the latter is mechanically secured to the flexible metal sheet 54 near its periphery 60 that the cover 53 sssumes whatever shape is imparted to the bottom surfare of lower flexible metal sheet 54. To conerol a more c~mplex shape impareed to the holder 50, a pair of end forming members 113 and 114 of different configurations is ~upported from support structure 115 above each end of the holder 50. Each forming member 113 and 114 has a lower surface of desired shape for the side end portion of a shaped glass sheet that engages the upper surface of the upper flexible metal sheet 56 when the latter is lifted.
Since the lo~er flexible metal sheet wall 54 and plate 84 have aligned perforations, and cover 53 is porous, when suction is applied through the common plenum to the deformable vacuum holder 50, a flat glass sheet G having arrived on the conveyor solls 48 to a shaping position below the deformable vacuum holder 50 is sucked by vacuum into engagement against the porous fiber glass cover 53 backed by the flexible apertured sheet 84 and the lower flexible metal sheet wall 54. When the drive shaft~ 112 are 6i~ultaneously rotated to deorm ~he vacuum holder 50 upwardly st its ends, the upper flexible metal sheet wall 56 bears upward against the curved lower surfaces of the rigid end forming members 113 and 114, the~eby distorting the deformable vacuum holder 50 to conform to the shape of thei~
curved lower surfaces. The glass sheet, being heat softened, ~nd bei~g sucked into engagement against the lower flexible ~etal she~t wall 54, a6sume3 the defo~med ~hape of the lower flexible sheet ~all.
~ hen the end portions of the ~acu~ holder defined by the end chanbera 52 are curved ~harply ~nd the central portion defi~ed by the 7~
central chamber 51 is essentially flat, it is necessary to apply a relatively high v~cuu~ to the end p~rtions of the glass sheet and a relatively low vacuum to it~ central portion. The control valves 100 for each chEmber are individually and independently adjusted to provide a ~eak vacuum in chamber 51 and st~onger ~acuums in end chambers 52.
To insure against the sheets 54 and 56 collapsing toward one another when suction is applie~ to the vacuum holder 50 even when the vacuum holder is distorted in shape, a plurality of longitudinally extend-ing helical 20il springs 120 are provided. The springs 120 extend in side by side relation along the length of the vacuum holder. Preferably, the outer diameter of the springs 120 approximates the vertical ~pace between the upper and lower flexible sheet walls 56 and 54.
Whenever the ch~mbers 51 and 52 are subjected to different lPvels of vacuum, the porous fiber glass cover 53 provides a conduit tending to equalize the level of YaCuum in adjacent chambers. To avoid this lea~age, the chambers are isol~ted from one another in a manner to be described.
A pair of channel shAped ~embers 122 extend across essentially the entire width of sheet6 5C~ and 56 to define the outer ends of the central vacuum ch~mber 51 and another pair of similar channel chaped member~ 124 defines the inner ends of each end vacuum chamber 52. Channel shaped members 122 and 124 sre arranged in spaced ~irror-image pairs to provide narrow transversely extending spaces 126 that i~olaee the ~entr~1 ~acuum ch$mber 51 from the end vacuum chæmbers 52.
~ pscer tabs 1~8 are fixed ~o the upper su~face ~f the bottom flexibl~ ~heet 54 to help separat~ the helical coil ~prings 1~0 frv~ one anothPrO I~ addition, the helical eoil spri~gs extend through hole6, drilled through the bases of ~he channel shaped members 122 ~nd 124 and lster filled a~er the coil ~pri~gs 120 8re ~hre~ded therethssugh~
79t~
Vent hole~ 130 are provided across ~he upper flexible sheet wall 56 over each trans~erse space 126. These vent holes are especially important ~hen the deformable vacuum holder 50 is deformed to a shape that requires a different level of vacuum in ~djacent vacuum chambers 51 and 52. Venting the spaces 126 to atmosphere under such circumstances isolates adjacent vacuum chambers 51 and 52 from one another to avoid a loss iD vacuum differential be~ween end chambers 52 and central chæmber 51. Thi6 enables the holder 50 to have a different cycle of level of vacuum for the central vacuum chamber 51 than those imparted to the end vacuum chambers 52, which is very important during the shaping of glass sheets having sharply bent end portions.
The common plenum 99 is connected to a carriage 140 (see FIG. 1) which is fixed for vertical movement with the deformable vacuum holder 50 in whatever shape it is forced to assume by the arrang~ment of the linkage system 101. In order to provide the vertical adjustment feature for positioning the defonmable vacuum holder 50, the carriage has a front ~upport be~m 141, a rear fiupport beam 142, a pair of slide bars 143, and a pair of slide bar housings 144 supported on each support be~m.
~ ach rear support beam 142 is supported on a pair of vertical posts 145. The posts 145 ~upport rear ~ertical pi6tons 146, which act in unison ~ith a pair of front vertical pistons 147 ~ounted on the roof 3f the furnace 42 at ~haping staeion 43 ~o raise or lower the frQnt snd ~ear support beams 141 and 142 and their supported slide bar housings 144. Such actua~ion raises or lowers the defDrmable Yacuum holter 50 in the shaping st~tioD 43.
~ ho~izontal piston 148 i5 eonnected through a pi8ton rod 150 to a lug 154 iixed to front 6upport be~m 141. A~tuation of ~he hori~ontal piston 148 mo~es ~he deformable Yacuum holder 50 between the haping s~ation 43 and the m~ld retractio~ station 45.
The sheet trsnsfer means 47 comprises a ring-like member 159 conforming in elevation and plan outline to the shape desired immediately inward of the peripheral edge of ~ glass sheet to be ~haped At the shaping station 43. The ring-like member 159 is surrounded by ~ pipe type reinforce-ment 161. The ring-like member has an upper edge surface that is not~hed or serrated to minimize contact wi~h the glass and preferably is constructed in the manner of U.S. Patent No. 3,973,943 to Samuel L. Seymour. ~onnectors 162 are provided around the periphery to interoonnec* the ring-like member 159 and the around the periphery to interconnect the ring-like member 159 and the reinforcement 161. Extension arms 163 e~tend outward from the opposite longit~ldinal ends of the outline formed by the sheet transfer me~ns 47 and terminate in connections to cantilevered rods 167 which are actuated or movement in unison by motor drive means (not shown) to move the ring-like member 159 from shaping station 43 through cooling station 44 to an unload-ing station (not shown) and a return to the shaping station 43.
The cooling station 44 comprises an upper plen~ 170 connected to an air supply duct 171 which delivers air under pressure from a source of tempering medi~ (not shown) to said upper plenum 170 for delivery through downwardly directed pipe nozzles 172 toward the upper surface of a glass sheee supported on said ring-like member 159. Additional te~pering medium supply means cDmmunicates with a lower plenum 174 which is provided with upwardly directed noz~les 176 for supplying the tempering medium ~uch as pressurized air against the lower surface of a glass sheet ~upported on said sing-like member 159.
Cycle of Operation A plurality of ~lass sheets ~re conveyed through the furnace 42 while supported on rotating furnace co~veyo~ rDll~ 48. ~he~ a glass ~heet - ~3 -~,...
7~4 is sensed to be in proper position, the apparatus is ready to begin a shaping cycle.
The glass sheet travels rapidly along the conveyor rolls 48 into the shaping station as the hori~ontal piston rod 150 extends to move the vacuum holder 50 into vertical alignment over a glass sheet shaping posieion at the shapi~g station 43. The deformable holder 50 is in its flat confi~uration and vacuum is started to lift the hot, flat glass sheet into engagement against the deformable vacuum holder 50 when the latter is flat and supported in a lowered position by extension of vertical pistons 146 and 147.
As soon as the flat glass sheet engages the vacuum holder S0, pistons 146 and 147 retract upward in unison to cause the vacuum holder 50 to lift the glass sheet. At the same time, vacuu~ i9 increased in the end chambers 52. The drive shafts 112 rotate to cause the vacuum holder 50 to deform upwardly st its longitudinal end portions. Vacuum continues to be applied to ehe deformed vacuum holder 50 so thqt the ~lass ~heet continues to engage said vacuum holder a6 the latter is lifted and 6haped to conform to the bottom surfaces of the end forming members 113 and 114.
The sheet transfer means 47 including said ring-like member 159 enters the shaping station 43 immediately after the vacuum holdes 50 lift6 and shapes the glass sheet. Entry of the sheet transfer means 47 ic corre-lated with ehe glass sheet being raised sufficienely to provide clearance for its entry.
The pistons 146 and 147 continue to lift the vacuum holder 50 and the drive shafts 112 continue to rotate until the ring-like member 159 reaches ~ po~ition in the 6haping station 43 under the vacuu~ holder 50.
At that ~oment, Yacuu~ i3 released or replaced by ~ down~ard pozit * e pres6ure to drop the ~lass sheet on~o the ring-like ~e~ber.
7~4L
The e~pty vacuum holder 50 is removed in one direction toward the mold retraction station 45 by retraction of piston rod 150 while the drive shafts 112 rotate to cause the deformable holder 50 to resume its flat configuration as the sheet transfer means 47 moves in a direction opposite said one direction with the glass sheet supported on its ring-like ~ember 159 for transfer into cooling station 44.
~ hile the transer means 47 c}ears the shaping station 43, the deformable metal holder 50 and its assocated reinforcing structure 115 move to holder retraction station 45 ~here the holder is cooled. In order to improve the efficiency of holder cooling, it is preferred to apply 6uc~ion through the apertures 55 and 85 of the holder 50 at the holde~ retraction station 45. This suction introduces cooler air of the atmosphere outside the furnace into the holder 50 between each successive shaping cycle. As a result, the holder is cooled more efficiently than i~ it is merely exposed to the outside atmosphere or cooled by positi~Te air pressure forcing relatively hot air from within the furnace to pass from ehe holder 50 through the apertures 55 and 85.
At the eooling station 44, the ring-like ~ember 15~ supports the glass sheee between upper and lo~er plenum chambers 170 and 174 thst provide cold air under pressure to the sets of nozzles 172 and 1~6 in the cooling station until the fiheet is cooled 6u~ficiently to impart ~ desired degree of temper. Then, the ring-like member 159 is unloaded and returned toward the shaping ~tation as the latter ~waits the arrival of a succeeding glass ~heet that i6 conveyed ehrough ehe furnace toward said glass sens ng seaeiO~. ~he unlosded glass sheee is inspected prior ~o fur~her handling which may i~clude packaging. The retracted horizontal pisto~ rod 150 i~
ready to be extended ~nd the apparatus is ready for another cycle Df operat iD~ .
o 2~ -~9~
Various alternati~e embodi~ents may be used in the practice ofthe present invention. For example, any available energy source such as electricity; gs6, oil, coal, etc., may be used to heat the glass sheet6 within he furnace. Any type of conveyor, such as a gas hearth type of conveyor or a conveyor ehat uses rolls in conjunction with a fluid that compensates for part of the mass of glass rotatably supported on the rolls of a roller conveyor may be substieuted for the roller conveyor 6ystem for delivering glass shee~s to the shaping station. Furthermore, the deforma-ble vacuum mold of the illustrated embodiment that moves vertically may be replaced by a deformable vacuum mold that maineains a fixed position rela-tive to vertically movable conveyor rolls and the ring-like member may be made of spaced rail sections to provide clearance to lower 6aid rolis and drop a glass 6heet from the de~ormable vacu~m box onto the ring-like member and provide clearance for the ring like member to transfer the gls6s 6heet t~ the cooling station and ~o return empty to the shaping station before ~he vertically movable rolls rise to their glass sheet receiving position in time for the arrival of the next glass sheet to be shaped.
In snother embodiment contemplated, the deformable vacuum mold may move horizontally instead of vertically from a first mold position above the additional conveyor rolls to a second mold position above ~he rail-like ~ember and change its con~iguration during its horizontal movement.
The cooling station may use li~uids or other fluids instead oi air as the cooling ~edium and m~y use slot type nozzles or bar type noz~les inSteAt of Dr in combinaticn with the pipe-type nozzles shDwn.
Xn ~ typical coDmercial installation u6ing a ~acuum holder 6ectionalized to cGmprise three vacuum ch~mbers, the central ~acuu~ ch~mber 9979~
only has been used as a vacuum support for making tempered glass sheet6 bent to relatively gently bent curvatures, and the two end vacuu~ chambers have been used to ~ake a pair of bent, tempered glass sheets, such ~6 automobile aide windows3 fiimultaneously.
It is also understood that while the embodiments described previ-ously relate to shaping and tempering glass sheets, the present invention can be used to shape glass sheets that are to be annealed subsequently.
In such a case, the cooling station 44 is replaced by an annealing lehr 6ection wherein the bent glsss is cooled at a conerolled rate after its shaping.
The form of the invention shown and described in this disclosure represents an il`1ustrative preferred embodiment and certain modifications thereof. It is understood that various additional changes may be made wiehout departing from the gist of the invention as defined in the claimed subject matter which follows.
U.S. Patent No. 4,282,026 to Harold A. McMaster, Norman C.
Nitschke and John S. Nitschke discloses bonding a board of fibrous material to a rigid vacuum holder of ceramic composition in glass sheet bending apparatus that uses a vacuum holder in the glass shaping process. The adhesive bond is not durable enough to adhere a board of fibrous material to a defol~mable metal sheet surface at elevated temperature cycles required to shape glass sheets against a deformable vacuum holder.
Whenever thin glass sheets are shaped within a heating furnace by sandwiching between pressing molds of complementary shape, such a process saves energy because it avoids the need to overheat the glass, which is necessary to overcome the rapid cooling of the glass sheet that takes place en route to a shaping station located outside the furnace~
However, it is difficult to control the shape and temperature of vacuum molds permanently installed within a furnace. It is also difficult to obtain access to repair or to provide maintenance for a mold that is permanently installed within a furnace.
U.S. Patent No. 4,297,118 to John D. Kellar and Gordon F. Pereman provides a glass sheet shaping method using apparatus that comprises an upper vacuum holder that first engages and lifts a heat-softened glass sheet by suction, and that provides clearance for a shaping and tempering ring to enter the shaping station. The glass sheet shaping station of this patent is located within the heating furnace. The vacuum mold that is used to engage and lift a heat-softened glass sheet by suction is moved outside the furnace between successive bending operations. Such movement cools the vacuum mold intermittently. Such intermittent cooling helps to control the temperature rise somewhat and consequently the shape of the vacuum mold departs only a limited amount from its desired shape during a mass produc-tion campaign that uses this patented invention.
U.S. Patent No. 4,349,375 to John D. Kellar and Gordon F. Pereman discloses other apparatus that comprises a more durable, deformable vacuum holder capable of assuming a flat configuration suitable for engaging a flat glass sheet by suction and deforming into a curved configuration.
Despite the utility of apparatus of this type that has been demonstrated in commercial operations, room exists for further improvement in results obtained using vacuum holders, such as providing vacuum holders that require less frequent maintenance during elevated cyclic temperature conditions associated with glass sheet shaping, reducing bulging of the vacuum holders to limits acceptable to the customer, providing even more uniform, repetitive deformation of the vacuum holder than before, avoiding 7~
collapse of the vscuum holder, providing more efficient cooling of the holder between shaping cycles, avoiding misalignment of glass sheets with the distorted shape of the vacuum holder and helping maintain different lev-els of vacuum in adjacent vacuum chambers of multiple chamber vacuum holders.
Summary of the Present Invention The present invention relates to a vacuum holder used to shape a glass sheet either within a furnace or immediately beyond a furnace through which glass sheets are conveyed into alignment below said holder for vacuum engagement. Release of vacuum or replacement of vacuum with positive downward pressure transfers the glass sheet onto a ring or ring-like member for transfer to a cooling station. In the latter location, the glass sheet is cooled rapidly enough to develop at least a partial temper in each glass sheet supported in turn on the ring-like member.
The present invention provides improvement in glass sheet bending using a deformable vacuum holder having upper and lower sheet walls separated by spacer means as will be better understood in the light of a description of a preferred illustrative embodiment and variations thereof that follows.
When deformable vacuum holders are used, the vacuum engagement continues as the vacuum holder and its engaged glass sheet become distorted in unison.
In this inventive feature, the bottom sheet wall contains an arra~ of apertures that surrounds the entire outline of the position that the glass sheet to be bent should occupy when vacuum is applied. Unless this precaution is taken, the glass sheet is liable to translate to a posi-tion out of alignment with the position it should occupy relative to the array of apertures. Unless the sheet is properly aligned with the array of apereures, it becomes difficult9 if not impossible, to install the bent 794~`
glass sheet in a bent vehicle frame defining a bent opening to be occupied by said bent glass sheet.
The preferred embodiment of the present invention may incorporate several other inventions. For example, vacuum holders with flexible metal walls having scratched surfaces mar a heat-softened glass sheet when they engage the glass sheets with vacuum. Covers of fibrous material having a smooth glass facing surface have been bonded by adhesive to the lower wall of nonmetallic vacuum holders. However, adhesive used prior to this inven-tion has not been able to retain its adhesive properties to deforming metal vacuum holders at varying elevated temperatures for sufficient time to be suitable for mass production because of the need for frequent replacement of the adhesive when the latter is exposed to elevated temperatures required for glass sheet shaping.
The preferred embodiment of the present invention insures that the upper surface of the glass sheet retains its smoothness by mechanically supporting, rather than by adhering, a smoothly surfaced insulator sheet against the lower flexible metal sheet wall of a vacuum holder to control the temperature increase of the lower flexible wall of the deformable vacuum holder during mass production. Supporting the smoothly surfaced insulator sheet wall to the lower flexible wall of the vacuum holder keeps the latte-- from separating when an adhesive bond breaks in response to a temperature change. The support encompasses the edge of the smoothly surfaced insulator sheet within the periphery of the lower flexible sheet wall and clamps the smoothly surfaced insulator sheet to the lower flexible sheet wall beyond the outline of a vacuum supported glass sheet.
Another problem that exists with vacuu~ holders used to shape glass sheets is that, during an extended campaign of shaping glass sheets on a mass production basis, the lower flexible sheet wall tends to develop _ ~ _ 7~9}
a bulge in the dimension transverse to its lengthO
The lower flexible sheet wall of the vacuum holder is slit longitudinally outward of an unslit central portion to form longitudinally extending strips of limited width thae are free to expand transversely of their length from an unslit central region. Thus, any t~ansverse bulge across the width of the lower sheet wall does not exceed the slight bulge of each strip, which is limited to an amount that does not cause distortion beyond acceptable tolerances. Longitudinal bulging is controlled to within acceptable tolerances by connecting side central portions of the upper and lower flexible sheet walls of the vacuum holder with bolts extending through a pair of aligned~ round, centrally disposed holes flanked by bolts e~tending through longitudinally extending sloes in at least one of the flexible sheet walls that increase in length according to their distance from said centrally disposed holes.
Another problem that exists with vacuum holders that are defo~mable is the problem of maintainin~ the vacuum holdes pliable over a wide tempera-ture range 50 that it readily changes shape between a flat configuration snd one confonming to a desired complicated shape. At the ssme time, the vacuum holder must be strong enough to avoid collapse in its thickness dimension when vacuum is applied thereto. Another invention included in the preferred embodiment solves these problems by enclosing e~sentially parallel, longitudinal helical coil springs h~ving a diameter approximstely equal to the space between the flexible sheet walls within the vacuum holder, so that the springs serve as spacers between the flexible upper and lower sheet walls of the deformable holder, proYide clesranre passages for _ g _ 7~
the evacuation of air from the vacuum chamber and flex with the vacuum holder to help distort the latter into a curved shape defined by rigid end forming members that the deformable vacuum holder engages when distorted.
Another problem that exists with a vacuum holder is that it becomes heated to a high temperature due to repetitive engagement ~ith a hot glass sheet during every bending cycle. Removing the holder to a holder retraction station outside the furnace between shaping steps reduces the rate at which the holder becomes heated and thermally expanded to a shape too large for the desired shaping pattern, unless the mass production rate is decelerated to a slow output level by increasing the time spent to cool the holder between shaping steps. Once mass production is kept at an increased rate, a more efficient holder cooling operation becomes necessary.
Cooling the vacuum holder by drawing vacuum by suction through the bottom apertured flexible sheet wall when the holder is outside the furnace has been found to be more efficient than merely keeping the glass sheet vacuum support outside the furnace between shaping cycles or merely blowing hot ambient furnace air within the holder through the apertures of the bottom flexible sheet wall when the holder is outside the furnace between shaping cycles, according to another invention incorporated in the preferred embodiment and claimed in another copending patent application.
Another problem exists when using a vacuum holder having a plurality of vacuum chambers, each of which requires a different level of vacuum to support a glass sheet of complicated shape. This problem arises from the fact that the glass sheet facing surface of the vacuum holder is covered by a porous fiber glass cloth cover that insulates the bottom wall of the holder from direct contact with the heat-softened glass sheet. ~hen diferent levels of vacuum are applied simultaneously to adjacent vacuum chambers of a vacuum holder covered by a single porous fiber glass cover, tends to equalize the level of vacuum in adjacent vacuum chambers when the engaged sheet seals the sheet covered portions of the chambers. This tendency to equalize the vacuum level sometimes causes a glass sheet to drop from its position of engagement with the vacuum holder prematurely because the overall level of vacuum that results from this bleeding lowers the overall vacuum level to a level below the level of vacuum needed to maintain the entire glass sheet in vacuum engagement against the holder.
More specifically, when glass sheets are shaped to complicated shapes involving a gently bent main portion and one or more end portions more sharply bent, the level of vacuum needed for a vacuum chamber facing the main portion to support the gently bent portion is much less than that needed for an end vacuum chamber facing an end portion to be sharply bent.
W~len bleeding of vacuum level occurs, the vacuum chamber facing the main portion of the glass sheet develops a level of vacuum greater than is needed to support the glass sheet while the end vacuum chamber loses vacuum. Consequently, the gently bent main portion develops markings replicating the pattern of the fiber glass cover and the sharply bent end portion does not develop the sharpness of bend required.
The last described invention solves the problems just explained by isolating adjacent vacuum chambers of the vacuum holder from one another by including a narrow elongated space vented to the atmosphere bet~een each pair of adjacent vacuum chambers. As a result, ehe level of vacuum in each individual vacuum chamber can be controlled independently of the control exercised for each other chamber.
The following description of a preferred embodiment of the present invention is made to clarify the present invention, and includes the accompanying drawings wherein like reference numbers refer to like structural elements.
~9799~
Brief Description of the Drawings In the drawings forming part of the description that follows, FlG. 1 is a fragmentary, perspective view of apparatus for shaping ~nd tempering glass sheets incorporating a preferred embodiment of the present invention comprising a shaping station located within a roller hearth furnace, with certain parts omitted for clari~y;
FIG. 2 i6 a fragmentary plan view of elements of a vacuum holder incl~ded in the apparat~s of FIG. 1 with parts omitted to show as ~any details of the structure of the deformable vacuum shaping holder as possible;
FIG. 3 is a fragmentary bottom plan view looking upward at the vacuum holder of FIG. 2 with certain part6 omitted or broken away to show other parts of the apparatus more clearly;
FIG. 4 is a fragmentsry, elevational view, partly in section, of the deformable vacuum holder taken along the line IV-IY of FIG. 2, ~ith parts broken away to show as ~any other parts as possible;
FIG. 5 i6 an enlarged ele~ational view partly in section of a portion of the deformable vacuum holder of FIG. 4, showing its deformable shaping surface in its flst configurstion to lift and shape a flst glass sheet and with certain parts omi~ted to show certain interior structural elements;
FIG. 6 is another enlarged sectional view of a smaller portion of the vacuum holder taken along the line VI~VI of FIG. 2 ;
FIG. 7 is still another se~tional view of the ~acuu~ holder taken along the li~e VII-VII fo FIG. ~; -FIG. 8 is a sectional view across ~n end portion of the vacuu~
holder along the line VIII~YIII of FIG. 2; and ~97~
FlG. 9 is a sectional view across a side portion of the vacuum holder taken along the line IX-IX nf FIG. 2.
Description of the Preferred Embodiments Referring now to FIG. 1 of the drawings, an apparatus for heating and 6haping sheets of heat-softened materialJ such AS glass, includes conveyor means 41 extending through a heating means compri6ing a tunnel-type furnace 42 (the exit end of which is shown). The furnace includes a shaping station 43 to which sheets of glass are conveyed along the conveyor means 41 from a loading station (not shown) while bein~ heated to the glass deformation temperatu~e. A cooling station generally indi-cated at 44 for cooling the curved sheets of glass and an unlosding station Inot shown) beyond the cooling station 44 are located in end-to-end relation along a transverse path to one side of the shaping station 43. A holder retraction station 45 is located at the other side of the shaping ctation 43, which is the side opposite the cooling station 44. A sheet transfer means 47 shown beside the shaping station 43 transfers glass sheets between the shaping fitation 43 and the cooling station 44.
~ eat may be supplied in the furnace 42 by hot gases from gas burners or by electrical radiant heaters or by a c~mbination nf both, which heat supply ~eans ~re well known in the art. Bearing housings (not shown) adjacent the furnace side walls support bearings for longitudinally spaced, tran~vercely extending conveyor rolls 48 that tefine a path of trsvel for conveyor meanc 41 which extends the length of furnace 42. Some of ~he conveyor rolls 48 &re locaeed at the shaping station 43 to for~ a continua-tion of the path of t~vel ~i~hin the furnace 42. The rolls of the conveyor means 41 ~re arran~ed in sections and their ~otational speed controlled by clutches ~not shown) ~o that ehe ~peed of the diffesent conveyor RPctions ~ay be controlled ~nd synchronized in a ~anner well kno~n in the ~rt.
'7~'~
One or more glass sensing elements (not shown) are located a short distance upstream of the shaping station 43 to initiate a cycle of opera-tion of this ~pparatus in a manner well known in the art. Limit cwitche6 or electronic counter circuits may be provided to synchronize the operation of various elements of the apparatus according to a predetermined sequence.
Since their arrangement and manner of operation are not part of this invention, they will not be described in detail herein.
The shaping station 43 comprises a deformable upper vacuum holder 50 in the form of a deformable metal box. The latter is divided into a central chEmber 51 flanked by end chambers 52. A blanket 53 of flexible, porous refractory material, such as fiber glass, is tightly clamped for biasing against the bottom of the vacuum holder 50 in a manner well known in the art.
The deformable metal box comprises a flexible, apertured, lower me~al sheet wall 54 having perforations 55 distributed throughout and an upper metal sheet wall 56 that is also flexible but has apertures there-through at critical locations only, as will be explained later. The metal sheet walls 54 and 56 form flexible lower and upper sheet walls of the deformable vacuum holder 50. Upper and lower flexible sheet walls 54 and 56 are of half hard tempered sheet steel, and are of essentially polygonal outlines and 6ufficiently larger than the glass sheets to be shaped to provide a fr~me-like area beyond the glass sheet outline. The latter is illustrated in dashed lines in FIG. 3.
~ suitable ~rray of perforations 55 is a checkerboard pattern arr~nged on ~ne inch (2.5 centi~eter~) centers, except for two transversely extendirlg areas. A suitable diameter for each perforation ic 0.172 inch~s ~4.635 millimeters~.
7~
The longit~dinal ~ide edges of the flexible metal cheet walls 54 and 56 are separated al~ng their length by a pair of l~minated springs 58 (see FIG. 9). The latter are constructed of thin flexible layers of strip metal to form flexible laminated spacer6 3/4 inch (19 millime~ers) thick. The laminaeed springs 58 extend inside and adjacent the longitudinal side edges of the holder 50 and have a symmeerical arrangement of longitudinal lots 59 of increasing length with increasing distance from the longitudinal center of the holder 50 along the length of the laminated springs 58. The longitudinal slots 59 coincide with elongated slotted apertures 62 extend-ing vertically through the longitudinal side portions of the upper flexible metal sheet wall 56. The lower flexible metal sheet wall 54 has ro~nd apertures 66 spaced adjacent the opposite longitudinal sides thereof in alignment with the corresponding longitudinal slots 59 and slotted aper-tures 62 to receive attachment bolts 68. The latter exeend through ~pacer sleeves 69. The latter are 3/4 inch (19 millimeters) high to maintain the longitudinal edges of sheet walls 54 and 56 ~eparated while interconected.
Along each of the oblique ~ides at each end of the vacuum holder 50, the lower flexible ~heet wall 54 has a ~eries of spaced holes 70, each coinciding with ~ corresponding elongated, longitudinally slQtted opening 72 of maximum length in the upper flexible metal plate. A rubber spacer 74 for each oblique ~ide (FIG. 8) defines the gap between the corresponding oblique ends of the flexible metal sheet walls 54 and 56. In ~ddieion~
rigid end bar6 76, special rigid end bars 78, and rigid side bars 80 help ~ecure the flexible ~etal sheet walls 54 snd 56 together. Each l$~inated spri~g 58 h~s a centering hole 81 at its longitudinal ceneer to f x the longitudi~al center lines of ~heet ~alls 54 and 56 in alig~ment ~t their geo-me~ric cen~ers. A pla~e 82 i~ fixed to each end of each 6pecial end b~r 78.
91-~99~
A clamp 83 is pivotally attached to each plate 82. An apertured sheet 84 6imilar in outline to, but slightly smaller than flexible metal sheet walls 54 and 56, is composed of insulator material to provide thermal insulation between the lower flexible metal sheet wall 54 and a hot glass ~heet engaged thereto by vacuum.
The rigid bars 76, 78 and 80 cooperate with frame members 77 tsee FIGS. 8 and 9) secured to lower flexible sheet wall by self tapping screws 79 to help support the apertured sheet 84 of impregnated fibrous, flexible material, such as a random fiber glass mat impregnated with a cured polyester resin (which is more rigid than metal sheet wall 54), below the flexible metal sheet wall with the outline of said apertured sheet 84 within the marginal portion of the vacuum holder 50 and aligned with a frame defined by the laminated springs 58 and the rubber spacers 74. The apertured sheet 84 has apertures 85 corresponding to and aligned with the apertures 55 in flexible lower metal sheet 54.
The array of apertures 55, 85 encompasses a larger area than that of the glass sheet undergoing shaping and tempering. It i6 important that the boundary portion of the array of apertures surrounding the outline of the glass sheet form at least one row of essentially uniformly spaced aper-tures exposed to the atmosphere. Uhless this feature is included, ~hen vacuum is applied to holder 50 to engage a flat glass sheet, the latter will translate sidewise and/or lengthwise ineo a position where its outline may be arranged out of &lignment with respect to its desired position against the holder. Unless the apertures 55 and 85 are provided ~ver an area large enough to insure that apertures exposed to the at~osphere s~r-round the entire pesiphery of the flat glass shee~ initially, a chance exists that the misaligned glass sheet will be shaped to an undesired configurntion becau6e of this uncontrolled translation, and will not fit properly in an auto fr~me.
7~?4 A heat-reflecting coating 86 of aluminum paint or other heat-reflecting material is applied to the bottom surface of the apertured sheet 84. The heat reflecting properties of the coating 86 and the thermal insulation properties of the apertured sheet 84 moderate the temperature changes in vacuum holder 50 during repeated cycles of temperature experi-enced during mass production of bent, tempered glass sheets.
Transverse grooves 88 extend across the width of critical portions of the apertured sheet 84 along its upper surface to promote additional flexibility in those portions. The bottom surface of apertured sheet 84 is smooth and resists local deformation to a greater extent than the flexible lower metal sheet wall 54. Hence, the glass sheets are less likel~ to develop optical distortion in their upper surfaces when apertured sheet 84 is interposed between the glass sheet and flexible metal sheet wall 54 then when the apertured shPet 84 is omitted.
Holes corresponding to the centering holes 81 are located in corresponding positions adjacent the longitudinal sides of apertured sheet 84, and extend through the lower flexible sheet wall 54, and the upper flexible sheet wall 56 and the laminated springs 58. A pair of connecting bolts extend through these corresponding holes to secure the sheets and springs to one another on a pair of transversely spaced points along the longitudinal center line o~ the vacuum holder ~0. This enables the ~acuum holder to expand thermally in each longitudinal direction from its longitu-dinal center line equal distances so as to minimize the chance of ~arpage of the lower sheet 54 which faces the glass sheets to be shsped.
C-shaped clips 89 (FIG. 2 and 4) slide over spaced portions of the margin of the flexible holder 50 ~ith their lips overlapping the outer surfaces of flexible sheets 54 and 56. Self-tapping screws are threaded a7~
through the bottom lips to engage the lower sheet 54 only beyond the outer edges of laminated springs 58 and rubber spacers 74. The apertured sheet 84 is dimensioned to have its outer peripheral edge abut the inner edges of laminated springs 58 and rubber spacers 74. Additional bolts 68 extend through spacer sleeves 69 of fixed height (3/4 inch-l9 millimeters) to interconnect the ~arginal portions of sheets 54 and 56 between clips 89.
The lower flexible sheet wall 54 has longitudinal cuts 90 extend-ing to each longitudinal end from an uncut central portion. These longitu-dinal cuts form flexible strips 91 of limited width, for example, about 5 inches (12.7 centimeters) maximum width, that li~it transverse distortion of the lower, thin, flexible, metal sheet wall 54 when the vacuum holder 50 is heated from a room temperature configuration at which the holder is assembled to a higher temperature range that is developed during an extended mass production campaign. The presence of the smoothly surfaced apertured sheet ~4 coated on its glass facing surface with a thin heat-reflecting film 86 and the porous fiber glass covers 53 thereagainst lessens the temperature range established in the vacuum holder 50 during an extended campaign. In addition, the sheet 84, being of a composition less likely to develop surface distortion at elevated temperatures than the flexible metal sheet wall ~4, protects the heat softened glass sheets from replicating any surface marks in the flexible metal sheet ~all 54 due to scratches and other flaws.
The upper flexible sheet wall 56 has central ~pertures 92 commu-nicating the central vacuum chamber 51 with a central vacuum duct 94, and end chamber aperLures 96, one for each end chamber 52. m e latter aper-tures 96 communicate with flexible end vacuum ducts 98. The vacuum ducts 94 and 98 communicate with a vacuum source (not shown) through a co~mon 7~
plenum 99. ~ach vacuu~ duct 94 and 98 is provided with a cont~ol valve 100. Thi~ arrangement enables individual control for vacuum applied tD
chambers Sl and 52. If desired, the common plenum 99 may be adapted for ~elective connection to a vacuum source or a pressure source. The latter may be used to help separate a shaped glass sheee of more complica~ed shape from the flexible holder 50 after the sheet has been sucked by vacuum to conform to the shape of the lower flexible sheet wall 54.
A linkage system 101 is associated with each plate 82 to help distort the vacuum holder 5Q at each of four corner portions thereof. Each plate 82 carries a pivot member 102 (FIG. 5) on which is pivotally mounted the lower end of a first link 104 of adjustable length. The latter is pivotally mounted at it~ upper end to an apertured arm 106. The latter has several spaced holes to adjust its pivotal connection to the first link 104. A Eecond link 108 of adjustable length is pivotally connected ~t its lower end to apertured arm 106. A cam arm 110 is pivotally connected to the upper end of second link lOB. Cam arm 110 is fixed ~o a drive shaft 112 of a motor (not shown). The latter together with a plur~lity of rigid end forming ~ember6 113 and 114 (see FIG. 2) are 6upported from overhead ~upport structure 115. The end forming member~ have lower, curved ~rfaces defining a ~hape desired for sharply bent end portions of the bent glass sheets.
Rotation of the drive ~hafts 112 causes the linkage ~ystem jU6t described to ~pply force on the respective plate6 82 ~o raise the lat~er and c2~Be ehe longitudinal end portions of thP holders 50 ~o di~tort upwardly to develop a ~oncave elevational configuration &t each end ch~mber 52 that conform~ to the ahape of the end forming ~ember~ 113 ~nd 114, or to lower the pl~tes 82 ~o red~ce the 6everi~y o bend impar~ed to the hslder 50 until the bo~tom ~rface of the ~pertuFed sheet 84 is fl~t.
The fiber glass cover 53 is biased against the heat reflecting aluminum coating 86 applied to the bottom surface of apertured shee~ 84 and the latter is mechanically secured to the flexible metal sheet 54 near its periphery 60 that the cover 53 sssumes whatever shape is imparted to the bottom surfare of lower flexible metal sheet 54. To conerol a more c~mplex shape impareed to the holder 50, a pair of end forming members 113 and 114 of different configurations is ~upported from support structure 115 above each end of the holder 50. Each forming member 113 and 114 has a lower surface of desired shape for the side end portion of a shaped glass sheet that engages the upper surface of the upper flexible metal sheet 56 when the latter is lifted.
Since the lo~er flexible metal sheet wall 54 and plate 84 have aligned perforations, and cover 53 is porous, when suction is applied through the common plenum to the deformable vacuum holder 50, a flat glass sheet G having arrived on the conveyor solls 48 to a shaping position below the deformable vacuum holder 50 is sucked by vacuum into engagement against the porous fiber glass cover 53 backed by the flexible apertured sheet 84 and the lower flexible metal sheet wall 54. When the drive shaft~ 112 are 6i~ultaneously rotated to deorm ~he vacuum holder 50 upwardly st its ends, the upper flexible metal sheet wall 56 bears upward against the curved lower surfaces of the rigid end forming members 113 and 114, the~eby distorting the deformable vacuum holder 50 to conform to the shape of thei~
curved lower surfaces. The glass sheet, being heat softened, ~nd bei~g sucked into engagement against the lower flexible ~etal she~t wall 54, a6sume3 the defo~med ~hape of the lower flexible sheet ~all.
~ hen the end portions of the ~acu~ holder defined by the end chanbera 52 are curved ~harply ~nd the central portion defi~ed by the 7~
central chamber 51 is essentially flat, it is necessary to apply a relatively high v~cuu~ to the end p~rtions of the glass sheet and a relatively low vacuum to it~ central portion. The control valves 100 for each chEmber are individually and independently adjusted to provide a ~eak vacuum in chamber 51 and st~onger ~acuums in end chambers 52.
To insure against the sheets 54 and 56 collapsing toward one another when suction is applie~ to the vacuum holder 50 even when the vacuum holder is distorted in shape, a plurality of longitudinally extend-ing helical 20il springs 120 are provided. The springs 120 extend in side by side relation along the length of the vacuum holder. Preferably, the outer diameter of the springs 120 approximates the vertical ~pace between the upper and lower flexible sheet walls 56 and 54.
Whenever the ch~mbers 51 and 52 are subjected to different lPvels of vacuum, the porous fiber glass cover 53 provides a conduit tending to equalize the level of YaCuum in adjacent chambers. To avoid this lea~age, the chambers are isol~ted from one another in a manner to be described.
A pair of channel shAped ~embers 122 extend across essentially the entire width of sheet6 5C~ and 56 to define the outer ends of the central vacuum ch~mber 51 and another pair of similar channel chaped member~ 124 defines the inner ends of each end vacuum chamber 52. Channel shaped members 122 and 124 sre arranged in spaced ~irror-image pairs to provide narrow transversely extending spaces 126 that i~olaee the ~entr~1 ~acuum ch$mber 51 from the end vacuum chæmbers 52.
~ pscer tabs 1~8 are fixed ~o the upper su~face ~f the bottom flexibl~ ~heet 54 to help separat~ the helical coil ~prings 1~0 frv~ one anothPrO I~ addition, the helical eoil spri~gs extend through hole6, drilled through the bases of ~he channel shaped members 122 ~nd 124 and lster filled a~er the coil ~pri~gs 120 8re ~hre~ded therethssugh~
79t~
Vent hole~ 130 are provided across ~he upper flexible sheet wall 56 over each trans~erse space 126. These vent holes are especially important ~hen the deformable vacuum holder 50 is deformed to a shape that requires a different level of vacuum in ~djacent vacuum chambers 51 and 52. Venting the spaces 126 to atmosphere under such circumstances isolates adjacent vacuum chambers 51 and 52 from one another to avoid a loss iD vacuum differential be~ween end chambers 52 and central chæmber 51. Thi6 enables the holder 50 to have a different cycle of level of vacuum for the central vacuum chamber 51 than those imparted to the end vacuum chambers 52, which is very important during the shaping of glass sheets having sharply bent end portions.
The common plenum 99 is connected to a carriage 140 (see FIG. 1) which is fixed for vertical movement with the deformable vacuum holder 50 in whatever shape it is forced to assume by the arrang~ment of the linkage system 101. In order to provide the vertical adjustment feature for positioning the defonmable vacuum holder 50, the carriage has a front ~upport be~m 141, a rear fiupport beam 142, a pair of slide bars 143, and a pair of slide bar housings 144 supported on each support be~m.
~ ach rear support beam 142 is supported on a pair of vertical posts 145. The posts 145 ~upport rear ~ertical pi6tons 146, which act in unison ~ith a pair of front vertical pistons 147 ~ounted on the roof 3f the furnace 42 at ~haping staeion 43 ~o raise or lower the frQnt snd ~ear support beams 141 and 142 and their supported slide bar housings 144. Such actua~ion raises or lowers the defDrmable Yacuum holter 50 in the shaping st~tioD 43.
~ ho~izontal piston 148 i5 eonnected through a pi8ton rod 150 to a lug 154 iixed to front 6upport be~m 141. A~tuation of ~he hori~ontal piston 148 mo~es ~he deformable Yacuum holder 50 between the haping s~ation 43 and the m~ld retractio~ station 45.
The sheet trsnsfer means 47 comprises a ring-like member 159 conforming in elevation and plan outline to the shape desired immediately inward of the peripheral edge of ~ glass sheet to be ~haped At the shaping station 43. The ring-like member 159 is surrounded by ~ pipe type reinforce-ment 161. The ring-like member has an upper edge surface that is not~hed or serrated to minimize contact wi~h the glass and preferably is constructed in the manner of U.S. Patent No. 3,973,943 to Samuel L. Seymour. ~onnectors 162 are provided around the periphery to interoonnec* the ring-like member 159 and the around the periphery to interconnect the ring-like member 159 and the reinforcement 161. Extension arms 163 e~tend outward from the opposite longit~ldinal ends of the outline formed by the sheet transfer me~ns 47 and terminate in connections to cantilevered rods 167 which are actuated or movement in unison by motor drive means (not shown) to move the ring-like member 159 from shaping station 43 through cooling station 44 to an unload-ing station (not shown) and a return to the shaping station 43.
The cooling station 44 comprises an upper plen~ 170 connected to an air supply duct 171 which delivers air under pressure from a source of tempering medi~ (not shown) to said upper plenum 170 for delivery through downwardly directed pipe nozzles 172 toward the upper surface of a glass sheee supported on said ring-like member 159. Additional te~pering medium supply means cDmmunicates with a lower plenum 174 which is provided with upwardly directed noz~les 176 for supplying the tempering medium ~uch as pressurized air against the lower surface of a glass sheet ~upported on said sing-like member 159.
Cycle of Operation A plurality of ~lass sheets ~re conveyed through the furnace 42 while supported on rotating furnace co~veyo~ rDll~ 48. ~he~ a glass ~heet - ~3 -~,...
7~4 is sensed to be in proper position, the apparatus is ready to begin a shaping cycle.
The glass sheet travels rapidly along the conveyor rolls 48 into the shaping station as the hori~ontal piston rod 150 extends to move the vacuum holder 50 into vertical alignment over a glass sheet shaping posieion at the shapi~g station 43. The deformable holder 50 is in its flat confi~uration and vacuum is started to lift the hot, flat glass sheet into engagement against the deformable vacuum holder 50 when the latter is flat and supported in a lowered position by extension of vertical pistons 146 and 147.
As soon as the flat glass sheet engages the vacuum holder S0, pistons 146 and 147 retract upward in unison to cause the vacuum holder 50 to lift the glass sheet. At the same time, vacuu~ i9 increased in the end chambers 52. The drive shafts 112 rotate to cause the vacuum holder 50 to deform upwardly st its longitudinal end portions. Vacuum continues to be applied to ehe deformed vacuum holder 50 so thqt the ~lass ~heet continues to engage said vacuum holder a6 the latter is lifted and 6haped to conform to the bottom surfaces of the end forming members 113 and 114.
The sheet transfer means 47 including said ring-like member 159 enters the shaping station 43 immediately after the vacuum holdes 50 lift6 and shapes the glass sheet. Entry of the sheet transfer means 47 ic corre-lated with ehe glass sheet being raised sufficienely to provide clearance for its entry.
The pistons 146 and 147 continue to lift the vacuum holder 50 and the drive shafts 112 continue to rotate until the ring-like member 159 reaches ~ po~ition in the 6haping station 43 under the vacuu~ holder 50.
At that ~oment, Yacuu~ i3 released or replaced by ~ down~ard pozit * e pres6ure to drop the ~lass sheet on~o the ring-like ~e~ber.
7~4L
The e~pty vacuum holder 50 is removed in one direction toward the mold retraction station 45 by retraction of piston rod 150 while the drive shafts 112 rotate to cause the deformable holder 50 to resume its flat configuration as the sheet transfer means 47 moves in a direction opposite said one direction with the glass sheet supported on its ring-like ~ember 159 for transfer into cooling station 44.
~ hile the transer means 47 c}ears the shaping station 43, the deformable metal holder 50 and its assocated reinforcing structure 115 move to holder retraction station 45 ~here the holder is cooled. In order to improve the efficiency of holder cooling, it is preferred to apply 6uc~ion through the apertures 55 and 85 of the holder 50 at the holde~ retraction station 45. This suction introduces cooler air of the atmosphere outside the furnace into the holder 50 between each successive shaping cycle. As a result, the holder is cooled more efficiently than i~ it is merely exposed to the outside atmosphere or cooled by positi~Te air pressure forcing relatively hot air from within the furnace to pass from ehe holder 50 through the apertures 55 and 85.
At the eooling station 44, the ring-like ~ember 15~ supports the glass sheee between upper and lo~er plenum chambers 170 and 174 thst provide cold air under pressure to the sets of nozzles 172 and 1~6 in the cooling station until the fiheet is cooled 6u~ficiently to impart ~ desired degree of temper. Then, the ring-like member 159 is unloaded and returned toward the shaping ~tation as the latter ~waits the arrival of a succeeding glass ~heet that i6 conveyed ehrough ehe furnace toward said glass sens ng seaeiO~. ~he unlosded glass sheee is inspected prior ~o fur~her handling which may i~clude packaging. The retracted horizontal pisto~ rod 150 i~
ready to be extended ~nd the apparatus is ready for another cycle Df operat iD~ .
o 2~ -~9~
Various alternati~e embodi~ents may be used in the practice ofthe present invention. For example, any available energy source such as electricity; gs6, oil, coal, etc., may be used to heat the glass sheet6 within he furnace. Any type of conveyor, such as a gas hearth type of conveyor or a conveyor ehat uses rolls in conjunction with a fluid that compensates for part of the mass of glass rotatably supported on the rolls of a roller conveyor may be substieuted for the roller conveyor 6ystem for delivering glass shee~s to the shaping station. Furthermore, the deforma-ble vacuum mold of the illustrated embodiment that moves vertically may be replaced by a deformable vacuum mold that maineains a fixed position rela-tive to vertically movable conveyor rolls and the ring-like member may be made of spaced rail sections to provide clearance to lower 6aid rolis and drop a glass 6heet from the de~ormable vacu~m box onto the ring-like member and provide clearance for the ring like member to transfer the gls6s 6heet t~ the cooling station and ~o return empty to the shaping station before ~he vertically movable rolls rise to their glass sheet receiving position in time for the arrival of the next glass sheet to be shaped.
In snother embodiment contemplated, the deformable vacuum mold may move horizontally instead of vertically from a first mold position above the additional conveyor rolls to a second mold position above ~he rail-like ~ember and change its con~iguration during its horizontal movement.
The cooling station may use li~uids or other fluids instead oi air as the cooling ~edium and m~y use slot type nozzles or bar type noz~les inSteAt of Dr in combinaticn with the pipe-type nozzles shDwn.
Xn ~ typical coDmercial installation u6ing a ~acuum holder 6ectionalized to cGmprise three vacuum ch~mbers, the central ~acuu~ ch~mber 9979~
only has been used as a vacuum support for making tempered glass sheet6 bent to relatively gently bent curvatures, and the two end vacuu~ chambers have been used to ~ake a pair of bent, tempered glass sheets, such ~6 automobile aide windows3 fiimultaneously.
It is also understood that while the embodiments described previ-ously relate to shaping and tempering glass sheets, the present invention can be used to shape glass sheets that are to be annealed subsequently.
In such a case, the cooling station 44 is replaced by an annealing lehr 6ection wherein the bent glsss is cooled at a conerolled rate after its shaping.
The form of the invention shown and described in this disclosure represents an il`1ustrative preferred embodiment and certain modifications thereof. It is understood that various additional changes may be made wiehout departing from the gist of the invention as defined in the claimed subject matter which follows.
Claims (7)
1. A deformable vacuum holder for shaping glass sheets comprising an upper flexible sheet wall, a lower apertured flexible sheet wall, spacer means spacing said walls from one another to enclose a deformable enclosed chamber having a desired thickness between said flexible sheet walls, means adapted to couple said chamber to a source of vacuum for re-ducing the pressure within said chamber to a subatmospheric level to draw a heat softened glass sheet thereagainst, means connected to said holder adapted to distort the shape of said holder and end forming means engageable by said upper flexible sheet wall to define the distorted shape of said deformable vacuum holder, characterized by a plurality of essentially parallel helical coil springs extending longitudinally lengthwise of said vacuum holder between said flexible sheet walls, said helical coil springs extending along a straight line when free from external force and distortable into a curved shape when said vacuum holder is distorted.
2. A vacuum holder as in claim 1, wherein said helical coil springs extend longitudinally substantially the entire length of said deformable vacuum holder in substantially parallel relation to one another.
3. A vacuum holder as in claim 2, wherein said chamber is subdivided into a plurality of separate vacuum chambers, transverse wall members separate said vacuum chambers from one another and said helical coil springs extend through the thick-ness of said transverse wall members.
4. A vacuum holder as in claim 2, further including spacer tabs fixed in position along spaced rows along said lower, apertured, flexible sheet wall to provide longitudinally extend-ing spacer means between adjacent of said helical coil springs to retain each of said helical coil springs in transversely spaced relation to said helical coil springs adjacent thereto.
5. A deformable vacuum holder as in claim 1, wherein said helical coil springs have a diameter approximately equal to said desired thickness.
6. In the art of shaping a deformable sheet of heat-softened glass or other deformable material while engaging said sheet at its deformation temperature by vacuum against a deformable vacuum holder of desired thickness while said holder is distorted so that the sheet facing surface distorts from a flat to a curved configuration, the improvement comprising supporting helical coil springs within said vacuum holder in position to distort with said deformable vacuum holder when the latter is distorted to a shape desired for said sheet and to help the deformable vacuum holder resist a tendency to collapse in response to the application of vacuum thereto.
7. The improvement as in claim 6, comprising supporting helical coil springs having an outer diameter approximating said desired thickness of said vacuum holder during said engagement by vacuum.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US49622683A | 1983-05-24 | 1983-05-24 | |
| US496,226 | 1983-05-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1199794A true CA1199794A (en) | 1986-01-28 |
Family
ID=23971753
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000429893A Expired CA1199794A (en) | 1983-05-24 | 1983-06-07 | Arrangement of apertures for vacuum holders for shaping glass sheets |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA1199794A (en) |
| FR (1) | FR2546507B1 (en) |
| IT (1) | IT1179934B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3527558A1 (en) * | 1985-08-01 | 1987-02-05 | Ver Glaswerke Gmbh | METHOD AND DEVICES FOR BENDING A GLASS DISC |
| JPH06256030A (en) * | 1993-03-02 | 1994-09-13 | Nippon Sheet Glass Co Ltd | Bending of sheet glass |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2085464B1 (en) * | 1970-04-23 | 1974-08-09 | Saint Gobain Pont A Mousson | |
| CA1120725A (en) * | 1978-01-25 | 1982-03-30 | Norman C. Nitschke | Apparatus for bending and tempering glass |
| US4277276A (en) * | 1980-03-17 | 1981-07-07 | Ppg Industries, Inc. | Method and apparatus for shaping glass sheets using deformable vacuum mold |
-
1983
- 1983-06-07 CA CA000429893A patent/CA1199794A/en not_active Expired
-
1984
- 1984-05-21 FR FR848407869A patent/FR2546507B1/en not_active Expired - Lifetime
- 1984-05-23 IT IT67525/84A patent/IT1179934B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| IT8467525A1 (en) | 1985-11-23 |
| FR2546507B1 (en) | 1991-10-11 |
| IT8467525A0 (en) | 1984-05-23 |
| IT1179934B (en) | 1987-09-16 |
| FR2546507A1 (en) | 1984-11-30 |
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| MKEX | Expiry |