Note: Descriptions are shown in the official language in which they were submitted.
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
-- 1 --
~,~
~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
-- 2 --
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.
-- 3 --
~ 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~
-- 5 --
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
-- 6 --
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,
-- 10 --
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
- 12 -
~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.
13 -
'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~.
- 14 -
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.
- 15 -
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.
- 16 -
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
- 18 -
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.
-- 19 --
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
- 20
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~
- 21
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.
22 -
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
- 26 -
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.
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