Note: Descriptions are shown in the official language in which they were submitted.
Background of the Invention
1~ Field of the Invention
The present invention relates to shaping glass sheets
into complicated shapes incorporating one or more sharp lines o~
bending extending completely across a dimension, i.e., the length
or the width, of the bent glass sheet. Such lines of bending
provide continuations of lines of sharp bending in the automobile
body in which the bent glass is installed. Such bends satisfy
the desires of automobile stylists to incorporate shaped glass
sheets whose shapes conform to the shape of the automobile body
in which the glass is mounted. Such bends are useful
as windshields, back windows, side windows and roof windows of auto-
mobiles and other vehicles and may also be used in shaped windows in
buildings and for other articles such as showcases, shaped instrument
covers and thc~
2. Description of the Prior Art
In recent years, several patents have lssued relating to the
bending of glass sheets to sharp curvatures. V.S. Patent No. 3,762,903
to Harold E. Hamilton discloses the application of an elongated line of
electroconductive frit of ceramic silver or other suitable electrocon-
ductive material in one or more layers along a line desired for sharp
bending to one or more surfaces of one or more glass sheets to be shaped
on an outline bending mold defining a V-shaped configuration desired for
the bent glass. The glass sheet i5 initially heated to a temperature
slightly below the glass softening point that is sufficient to fuse the
frit along the line of sharp bending. Electrodes are held against the
opposite ends of the electroconductive frit and voltage is impressed
between the electrodes. The impressed voltage passes current through
the frit, thereby heating the frit electrically. The electrically induced
heat raises the glass temperature locally along the line desired for sharp
bending. The glass sags rapidly along the line of sharp bending until
it conforms to the shaping surface of the V-shaped outline mold. The
frit remains as an opaque line extending across a dimension of the ultimate
product because it is very difficult to remove a fused ceramic frit.
V.S. Patent No. 3,762,904 to Harold E. Hamilton, Robert E. Bamford
and Paul Pastorek discloses forming a groove in a glass surface along a
line of sharp bending, applying a line of electroconductive frit that is
fusible onto the glass either in the groove or aligned with the groove
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along the surface of the glass opposite the grooved surface. The
electroconductive frit fuses to the glass to provide an opaque line
in the finished product. Furthermore, while grooves accentuate the
rate at which the glass sheet sags along the line of sharp bending,
grooving weakens the glass and also enhances optical distortion.
Therefore, grooving preferably should be avoided.
U.S. Patent No. 3,879,184 to Harold E. Hamilton and
Ivan L. Soreghy discloses a process for altering the residual stain
remaining along the relatively sharp bend of a glass sheet resulting
from the passage of an electric current through an elongated line of
electroconductive material previously applied to a glass surface by
interposing a strip of coloring agent between the glass sheet surface
and the line of electroconductive material along a line lengthwise of
the line of electroconductive material before applying the voltage that
causes electrical heating of the glass along the line desired for sharp
bending.
In each of the three patents enumerated thus far, the applica-
tion of electrodes to the ends of the lines of electroconductive material
causes problems in maintaining the sharp bend at the ends of the line of
sharp bending. U.S. Patent No. 3,865,680 to Thomas J. Reese and
Harry S. Koontz discloses a technique where transverse extensions of the
line of electroconductive frit are applied to extend in offset relation
from the ends of the line of sharp bending to provide relatively large
areas for electroconductive contact with the electrodes through which
electrical power is applied. While this invention improves the sharpness
of bend, particularly at the edges of the bent glass sheet, this technique
also leaves the problem of removing frit from the bent glass sheet.
U.S. Patent No. 3,795,501 to Robert A. Jansson and
Thomas J. Reese; U.S. Patent No. 3,795,570 to Robert A. Jansson and
Dean L. Thomas and U.S. Patent No. 3,847,586 to Thomas J. Reese,
George R. Claassen and Melvin W. Tobin relate to method and apparatus
for bending glass sheets :into curvatures including a sharp bend using
one or more narrow, elongated ribbons of electroconductive material
which may be removed from the line of sharp bending after the glass
is shaped. In each of the latter three patents, it is necessary to
complicate the loading and unloading of the glass relative to the mold
because of the need to apply and remove the narrow, elongated ribbon
of electroconductive material relative to the glass in conjunction with
loading or unloading the glass relative to the mold.
U.S. Patent No. 2,111,392 to Henry J. Galey; U.S. Patent No.
2,176,999 to Robert A. Miller; U.S. Patent No. 2,215,228 to James G. Oliver
and U.S. Patent No. 3,248,195 to James S. Golightly and Harold ~. McKelvey
disclose the use of radiant heaters in glass sheet bending apparatus
that apply sharp localized bends to a glass sheet along an elongated axis
thereof. However, these patents show apparatus that support the heaters
in such positions that it is difficult to load or unload a glass sheet
from the mold.
U.S. Patent No. 2,950,573 to William P. Bamford, Frank J. Carson
and Leslie H. Laine and U.S. Patents Nos. 3,160,491 and 3,227,538 to
Carl F. Binkert and Leslie H. Laine show apparatus comprising a single
carriage that supports a pair of molds for bending pairs of glass sheets
to mirror images of one another simultaneously. These apparatus do not
include elongated heating elements, such as electroconductive ribbons,
supported on the mold.
U.S. Patent No, 2,999,338 to Ronald L. Richardson
discloses a mold for bending glass sheets to compound curvatures.
In this patented apparatus~ electrical heating elements are
carried by a pivotable overhead member which must be pivoted out
of the way to load and unload a glass sheet relative to the mold.
In addition, localized heaters are permanently installed within
the outline end sections of a sectionalized mold. These localized
electrical heaters are permanently mounted below the glass surface
in the open or spread-apart position of the end mold sections of
the sectionalized mold and the glass moves upward away from the
localized electrical heaters as the glass is lifted while it is
shaped.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to
provide a sectionalized mold for bending glass sheets by the
gravity sag method that incorporates one or more elongated,
flexible, electroconductive metal ribbons that are located below
the mold shaping surface in the area subtended by the shaping
rails that comprise the mold and guiding means to prevent the
heating elements from contacting the hot glass surface, and a
method of bending glass sheets by the gravity sag method to a
shape including one or more sharp bends while the glass is
supported over such a mold.
The present invention provides a method and
apparatus for shaping a glass sheet to a complicated shape in-
cluding one or more sharply curved, crease-like bends extending
across an entire dimension, namely, the length or the width of
the sheet.
Thus, according to the invention in one aspect
there is provided apparatus for shaping a glass sheet to a shape
that includes a sharp bend extending across a dimension of said
sheet by the gravity sag method comprising a plurality of rigid,
elongated, metal shaping rails disposed in end-to-end relation to
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i
define an outllne shaping mold having an upper shaping surface
conforming to the shape desired slightly inward of the margin of
a glass sheet to be shaped thereon, each of said shaping rails
having an upper edge surface providing a different portion of said
upper shaping surface and including an end shaping rail defining
an end section of said mold and a pair of longitudinally extend-
ing, transversely spaced shaping rails defining a main section
of said mold, means supporting said end shaping rail for pivoting
relative to said main mold section between an open mold position
wherein said end section is spaced from said main section and a
closed mold position where said end section is closer to said main
section, a mold support, an elongated, flexible, electroconductive
ribbon extending along the space. between said end section and said
main section entirely below said upper shaping surface, guiding
means located laterally outside each of said elongated shaping
rails and having a surface engaging said ribbon to control the
vertical position of said flexible electroconductive ribbon to
one below said shaping surface, a pair of electrodes comprising an
electrode laterally outside each of said guiding means for
electrical connection with the ends of said ribbon and means
carried in electrically insulated relation to said mold and its
support adapted to couple said pair of electrodes with a source
of electrical energy, said apparatus being free of any structural
element above the area enclosed by said rigid metal shaping rails
to facilitate loading and unloading of a glass sheet relative to
said mold.
Apparatus for performing the method according to a
specific embodi:ment of the present invention comprises a mold
support carriage supporting an outline metal mold of the skeleton
: 30
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type including a main mold section comprising a pair of longitudinally
extending shaping rails fixed to the carriage to form longitudinal side
portions of an outline shaping surface of the mold and an end shaping
rail pivotally connected relative to the main mold section for pivoting
between a spread position where its inner ends are longitudinally spaced
from the adjacent longitudinal ends of the fixed shaping rails for
receiving flat glass sheets for bending and a closed mold position where
the inner ends are closely spaced from the longitudinal ends of the
longitudinally extending shaping rails to define a longitudinal end
portion of a discontinuous outline shaping surface for the mold that con- -
forms in elevation and plan outline to the shape desired for shaped glass
sheets.
In another specific embodiment, the main mold section is flanked
at each end with a pivotable end shaping rai]. Localized heating means
is provided by one or more flexible metal ribbons, each supported in
insulated relation to the shaping rails below the mold shaping surface in
non-contacting relation to -the supported glass between electrodes disposed
beyond the mold outline along a line that is closely adjacent to a pair
of transversely spaced longitudinal ends of the longitudinally extending
shaping rails. The apparatus may include means to insulate the ribbon
from the metal shaping rails. Guiding means engage each ribbon and
cooperate with ribbon tensioning means to hold the ribbon in a vertical
position below the outline shaping surface and out of contact with the
glass supported on the mold for bending.
When the glass sheet is to be bent sharply only along one line
of sharp bending near one end, the other ends of the shaping rails of the
main mold section are connected together at one end thereof a~d only one
end shaping rail is pivoted relative to the laterally opposite pair of
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ends of the shaping rails of the main mold section longitudinally opposite
from the interconnected ends. A single ribbon is supported beneath the
mold shaping surface and extends across the mold along a line adjacent
and below a line connecting the transversely opposite ends of the main
mold section shaping rails that are ad~acent to the pivoting end shaping
rail in a closed mold position.
If the size oE the glass sheets to be shaped permits, a pair
of mirror image duplicates can be fabricated in unison by mounting a
pair of molds in mirror image relation to one another on a single mold
support carriage for simultaneous processing. Each mold of the aforesaid
pair comprises a pivotable end shaping rail that pivots relative to a
main mold section and a single ribbon supported beneath the mold shaping
surface and extending along a line aligned with the space between the
adjacent ends of the main mold section and the inner end of the pivotable
shaping rail. Each mold supports a glass pattern that is the mirror
image of the pattern supported by the other mold of the mold pair.
In a preferred embodiment for producing especially severely bent
shapes, when the ribbon is positioned very close to the glass surface to
maximize the heating obtained along a line of sharp bending, means is
provided to bias the ribbon downward in response to the pivoting of an
adjacent end shaping rail to a closed mold position. This downward bias
feature may be omitted in case the sharpness of bend is not so intense so
that the ribbons can be supported permanently on the mold at sufficient
distance below the glass greater than the maximum amount the glass sheet
sags during a shaping operation.
In any oE these embodiments, any electroconductive ribbons used
to impart localized intense heat to produce the sharp bend is permanently
mounted on the mold below the shaping surface in the area defined by the
shaping rails so that when the mold is open to support a glass
sheet, the ribbon is below the position occupied by the flat glass-
sheet when the latter is mounted on the mold for shaping and
remains below said glass sheet occupying position throughout the
bending operation when the glass sheet is mounted on the mold.
This feature of the present invention prevents the ribbons from
contacting the glass and marring the latter, yet the ribbons are
kept sufficiently close to the glass along the lines to be bent
sharply to insure a thin line of intense heat.
According to a further inventive aspect there is
provided a method of bending a glass sheet to a sharp bend by the
gravity sag technique on an outline sectionalized mold comprising
supporting a flat glass sheet intermediate its ends on a pair of
transversely spaced ends of elongated shaping rails forming a main
section of said mold and at one longitudinal end portion thereof
on a longitudinally outer portion of an end shaping rail pivotally
movable between a spread mold position where its inner ends are
spaced from the ends of said main section shaping rails and a
closed mold position wherein said ends of said shaping rails are
adjacent to one another so that a main portion of said glass sheet
is superimposed over said main section of the mold and an end
portion of said glass sheet is superimposed over said end shaping
rail of the mold, supporting an electroconductive ribbon below
and in approximate alignment with a line of support provided by
said pair of ends of said main section shaping rails, heating the
glass sheet in an enclosed hot atmosphere to an elevated tempera-
ture, applying electric current to said electroconductive ribbon
whereby the latter radiates heat upward toward the bottom surface
of said supported glass shee., pivoting said end shaping rail
upward to fold the end portion of said glass sheet supported
thereon relative to the main portion of said glass sheet along a
line aligned with the length of said ribbon.
8 --
According to a specific embodiment of the method
of the present invention, a glass sheet to be bent ls mounted
for support intermediate its longitudinal extremities on the ends
of the upward facing surface of a pair of main section shaping
rails adjacent the inner ends of a pivotable end shaping rail of
an outline mold of concave elevation, with a ribbon of electro
conductive heating material supported below the mold shaping
surface in closely spaced relation to the lower surface of the
sheet along each line parallel to the lines formed across the
width of the mold between transversely spaced support locations
at the ends of the main mold section shaping rails. The mold and
its supported glass sheet are heated by overall furnace heat to
a temperature near the deformation temperature of the glass with
the ribbon spaced below the glass sheet a distance dependent
upon the sharpness of bend desired. At an appropriate time in the
heating cycle, the elongated ribbons of electroconductive heating
material are energized by applying voltage thereto accGrding to
a desired time cycle of voltage application. The voltage causes
the ribbons to radiate more intensive heat locally into the glass
sheet along the lines of sharp bending. This localized intensive
heat accelerates the shaping of the glass sheet about the lines
of sharp bending. Each flexible electroconductive ribbon is
either maintained in tension at a fixed distance below one or
the other
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.,
line of support provided by the two pairs oE support locations or is
lowered relative to the glass sheet as the portion of the glass sheet to
be bent sharply forms a crease-like bend. Just before or at approximately
the same time as the glass sheet conforms to the shaping surface of the
mold, the voltage to the ribbon is stopped, the bend is completed by
overall heating and the mold is removed from the heating area and trans-
ferred to a cooling area where the shaped glass is cooled at a rate
sufficient to impart a desired degree of temper or anneal.
The outline mold of the skeleton type according to a specific
embodiment of the present invention comprises an elongated array of metal
shaping rails disposed edgewise to form a sectionalized bending mold of
concave elevation and comprises a pair of pivoted end mold rails forming
end mold sections, each pivoted to a pair of hinges or bearing housings
to rotate relative to a pair of longitudinally extending rails transversely
spaced from one another and disposed along the length of the opposite sides
of the mold to form a main section of the mold. The upper edges of the
rails form a shaping surface conforming substantially to the shape desired
a short distance inside of the outline of the glass sheet after bending
when the end mold rails are piyoted inwardly. The end mold rails pivot
outwardly to a flat glass supporting position in which the ends of the
pair of longitudinal shaping rails provide two pairs of support locations
for the flat glass along lines extending across the mold between the
transversely opposite ends of the longitudinally extending rails.
The elongated ribbons of electroconductive material are each
supported between a pair of ribbon guiding means. In a specific embodiment
of this invention, -the guiding means comprises a first grooved spool
located laterally outside one end of one longitudinally extending shaping
rail and a second grooved spool located laterally outside of the laterally
opposite end of the other longitudinally extending shaping rail and along
a transverse line of alignment with the first grooved spool. Each ribbon
is tensioned to provide a straight line between the bottoms of the grooved
portions of the spools. The transverse lines of alignment between the
grooved spools lie in transverse lines that are below and adjacent to
the transversely extending llnes between the corresponding transversely
opposite ends of the longitudinally extending shaping rails of the main
mold section. In the alternative, the grooved spools may have their top
portions engage the bottom surface of the ribbon provided the ribbon is
tensioned at an elevation below the ribbon engaging surface of the spools
and the grooved surface of the spools is below the line of support for
the flat glass sheet.
In order to prevent electrical energization of the mold in case
the current in the ribbon is not discontinued in time, means is provided
to insulate the ends of the shaping rails from the ribbons. To accomplish
this object, each end of the longitudinally extending shaping rails and
each inner end of the end shaping rails is covered ~ith an insulator
material to avoid direct contact bet~een the metal of the mold and the
ribbons. The insulator material is preferably a cover sheet of dielectric
material attached to a cut-away end portion of each longitudinally extending
rail portion. Thus, the energized ribbon of electroconductive material is
maintained in electrical insulation from the metal mold rail throughout
the bending operation and in closely spaced relation to the glass sheet
area to be bent sharply throughout the portion of the bending cycle during
which said area is exposed to intensive localized heating.
These and other features of the present invention will become
obvious in the light of a description of an embodiment of glass sheet bending
mold used to bend glass sheets to a double V-shape according to the present
-- 10 --
~9~l~6
invention which follows. It is understood that the present in~ention
is equally applicable to the shaping of a glass sheet to a bend that
includes a single line of sharp bending. In such a case, the elongated
shaping rails of the main mold section are connected together by a cross
rail at one end distant from a pivoted end shaping rail and only one
ribbon is supported below the mold shaping surface along a line below
and adjacent a line formed between the ends of the elongated shaping
rail that are adjacent to the inner ends of the single p:ivoted end shaping
rail.
~ Brief Description of the Drawings
In the drawings which form part of the description of a specific
embodiment of this invention and where like reference numbers refer to
like structural elements:
FIG. 1 is a perspective view of a glass sheet bending mold
conforming to the present invention in the open mold position preparatory
to mounting a flat glass sheet thereon for bending;
FIG. 2 is a vie~ similar to FIG. 1 showing the mold in its closed
position that it assumes supporting the glass sheet after the latter has
been shaped to a desired shape;
FIG. 3 is a fragmentary, enlarged, cross-sectional view of the
mold of FIGS. 1 and 2, showing the relation of a flat glass sheet to
various structural mold elements including a transversely opposite pair of
ends of longitudinally extending shaping rails forming one of said pair of
transverse lines o:E support, a flexible, electroconductive ribbon, a pair
of electrodes and ribbon guiding means 9 when a flat glass sheet is mounted
on the mold at the beginning of a bending cycle;
99~
FIG. 4 is a fragmentary, enlarged, cross-sectional view similar
to FIG. 3, illustrating the relative positions assumed by the elements
shown in FIG. 3 during an intermediate portion of a bending cycle;
FIG. 5 is a fragmentary, enlarged, cross-sectional view similar
to FIGS. 3 and 4, illustrating the relative positions assumed by the
elements depicted in FIGS. 3 and 4 at the end of a bending cycle;
FIG. 6 is an enlarged, fragmentary view showing the portion of
the mold where an electroconductive ribbon crosses between the adjacent
diverging ends of a main section shaping rail and an end shaping rail and
depicting their relative positions that make it unnecessary to mount and
remove the ribbon for loading and unloading a glass sheet;
FIG. 7 is an enlarged, fragmentary view of an electrical
connection portion of an electrical circuit included in the specific
embodiment of the present invention;
FIG. 8 is an enlarged, fragmentary view taken along the lines
8-8 of FIG. 3, showing how electrodes are connected and supported;
FIG. 9 is an enlarged, fragmentary view taken along the ].ines
9-9 of FIG. 3, showing how ribbon guiding means is adjustably mounted in
ins.ulating relation to the mold;
FIG. 10 is a perspective view of an alternate embodiment of
this invention comprising a pair of molds molmted on a single carriage
for simultaneous processing of glass sheets into patterns that are the
mirror images of one another; and
FIG. 11 is a perspective view showing how the glass sheet pair
processed by the apparatus of FIG. 10 is mounted in the roof of an auto
shown in phantom.
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Description of the Preferred Embodimen-t
Referring to the drawings, FIGS. 1 to 9 show a sectionalized,
outline, bending mold of the gravity sag type comprising a main mold
section and a pair of end mold sections. The main mold section comprises
a pair of longitudinally extending shaping rails 10 and 11 of stainless
steel that are shaped in elevation and outline to conform to the longi-
tudinal side edges of the mold. The rails 10 and 11 are transversely
spaced from one another. Each of the longitudinally extending shaping
rails 10 and 11 is disposed with its width extending vertically transverse
to its length and its thickness extending horizontally transversely to
its length.
Each shaping rail 10 and 11 is reinforced by outrigger bracing
members 14 which are connected to the laterally outward facing surfaces
of each of the longitudinally extending shaping rails 10 and 11 by
horizontally extending, spaced connecting members 16. The outrigger
bracing members 14 also rigidly support four laterally outward extending
arms 18 which serve as stop members. The outrigger bracing members 14
support additional laterally outward, horizontally extending arms 20 on
the laterally outer ends of which are supported one of four bearing
housings 21. The outrigger bracing members 14 are connected to horizontally
and transversely outward extending connecting members 22 to longitudinally
extending members 24 of a cradle-like mold supporting carriage. The
carriage includes, in addition to the longitudinally extending members 24,
obliquely upward extending connecting members 25 and horizontal extension
members 26 which are interconnected through end connecting brackets 28 at
each longitudinal end of each of the horizontal extension members 26. The
end connecting brackets 28 include a pair of transversely extending runners
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29 adapted to ride over stub rolls 30 in a heating furnace
provided with the usual complement of heating elements which
may be of the electric or gas burning type.
An elongated lever arm 32 that is counterweighted
on its longitudinally inner end is mounted for pivoting about
each of the bearing housings 21. Each lever arm 32 extends
longitu~inally outward to a connection with an end section
Outrigger 34. The outriggers 34 are arranged in pairs and
provide a rigid pair of connections between a pair of lever
arms disposed at each longitudinal end of the mold and an out-
rigger bracing member 36, that interconnects the outrigger 34
of each pair. Each of the latter is arranged in outward encom-
passing relation about an associated end shaping rail 38 or 39
and is attached to the latter through spaced connectors 40.
Each end section rail 38 and 39 forms an end section of the
mold and is oriented in a similar fashion to shaping rails 10
and 11 with its length curved to form a longitudinal end o~ the
outline shaping surface. The outrigger bracing members 36 are
shaped in plan similar to the shapes of the corresponding end
section rails 38 or 39. In this manner, the lever arms and
outriggers cooperate with the bearing housings to provide
means for pivotally supporting each end shaping rail relative
to the main mold section.
The upper edge surface of the shaping rails 10, 11,
38 and 39 are serrated to allow air blasts to move between the
bent glass sheet and the supporting mold when the glass-laden
mold is in a cooling station that it occupies after bending.
The connectors 40 and connecting members 16 extend in directions
parallel to the tangent to the portion of the shaping surface
defined by the upper edge surface of the attached shaping rail.
The lever arms 32 are so weighted relative to the
bearing housings 21 and the mass of the end section outriggers
34 and outrigger bracing members 36 and end shaping rails 38 and
tr~ 14
~9~
39 to tend to pivot the end shaping rails 38 and 39 about an
associated pair of transversely spaced bearing housings 21
into a closed mold position depicted in FIG. 2 in the absence
-14a-
of any outside force. Shaping rails 10 and 11 are provided with longi-
tudinal ends 41 whereas the end shaping rails 38 and 39 are curved to
form the ends of the outline shaping surface and extend longitudinally
inward to form inner ends 42 at the longitudinal inner extremities thereof.
The inner ends 42 are spaced from the longitudinal ends 41 in the spread
mold position of FIG. 1 and are closely adjacent thereto in the closed
mold position of FIG. 2.
What has been described thus far represents a typical prior art
glass sheet bending and tempering mold wherein the cradle-like supporting
carriage occupies approximately the same plane and is spaced outwardly
from the side edges of the sectionalized mold it supports when the end
shaping rails 38 and 39 are pivoted into the closed mold position depicted
in FIG. 2 to permit a shaped glass sheet and its supporting mold and mold
carriage structure to pass through a curved space between shaped upper
and lower arrays of nozzle openings extending toward one another from
plenum chambers through which air is blasted against the opposite surfaces
of bent glass sheets in a manner well known in the art of bending and
tempering glass sheets.
The dimension occupied by each cross-sectional thickness of the
mold and its supporting structure in prior art tempering molds is a
maximum of about 3 inches (76 millimeters) normal to the localized tangent
to the shaping surface to permit this clearance. In the present invention,
the additional elements provided for the mold structure to produce the one
or more sharp bends desired are contained within the dimensions required
by prior art tempering molds and their support structures.
Each end 41 of the shaping rails 10 and 11 and each end 42 of
the end shaping rails 38 and 39 is cut obliquely downward from its serrated
upper edge surface at a relatively sharp angl~ of divergence from its
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~L~9~
associated end 41 or 42 and a thin sheet 44 of electrical insulator
material is attached against a surface of the end of the respective
shaping rails. The sheets 44 of insulator material are shaped to form
outer edges that extend obliquely downward at lesser angles of divergence
than the shaping rails to which -they are attached to provide means to
insulate the ends of the shaping rails electrically from electroconductive
heating elements that extend across the mold below its shaping surface
and between the downwardly diverging edges of each adjacent pair of ends
41 and 42 according to the present invention for a purpose to be described.
According to a specific embodiment of FIGS. 1 to 9 inclusive
for providing double V-bends, each mold is provided with a pair of
electroconductive heating elements in the form of flat, flexible ribbons
that are permanently disposed below the mold shaping surface and extend
across the mold in lines that traverse the downwardly obliquely diverging
ends of adjacent shaping rails. The ribbons form part of an electrical
circuit adapted for electrical engagement with a sburce of potential to
provide current to said electroconductive heating ribbons when said
circuit is coupled to said source of potential and are located in positions
where they do not interfere with loading or unloading of the mold but in
positions where the electroconductive heating ribbons can radiate additional
localized heat toward closely spaced glass sheet portions that extend along
the lines desired for sharp bending when the circuit is energized. The
lines along which the ribbons extend are closely adjacent to the lines of
support for the flat glass formed by the transversely opposed ends 41 of
shaping rails 10 and 11.
Flat ribbons are preferred over rods or wires as the electro-
conductive heating means carried by the mold below the mold shaping surface
in closely spaced relation to the glass, particularly when the flat upper
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surface of the ribbon is disposed parallel to the exposed ]ower surface
of the supported glass sheet. Flat ribbons radiate a larger proportion
of the heat developed by electrical energy in a direction normal to their
flat surface, whereas wires radiate heat radially in all directions, thus
providing a smaller amount of the electrically generated heat along the
line of sharp bending unless used in conjunction with heat reflectors
which complicate the heat generating system of the furnace. Secondly,
a ribbon of given electroconductivity is lighter than a rigid, round
rod and cools more rapidly when the bent glass is quenched in cold air _
blasts after shaping than round rods. Hence, thin ribbons provide less
of a heat sink that would tend to disrupt the uniformity of cooling
pattern desired in the glass than a round rod providing the same electro-
conductivity. Furthermore, a round wire having equivalent current carrying
capacity to that of a flat ribbon is more rigid and tends to kink and
remains permanently kinked if engaged locally by a guiding means to lower
the heating element away from close proximity to the glass as is sometimes
required. This kinking cannot be removed readily from round wire for a
subsequent bending cycle under circumstances in ~hich tension applied to
a ribbon removes such a kink.
In a specific embodiment of this invention, the electroconduc- -
tive circuit adapted for coupllng to a source of voltage comprises a
pivoted electrode 50 pivotally mounted on a hinge 51 supported on an
insulating support member 52 of an electrically insulating material carried
by each of the transversely extending runners 29. The pivoted electrode
50 is attached on the side opposite the hinge 51 to a counterweighted
lever arm 53. (See FIG. 7).
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A flexible lead wire 54 is connected at one end to the bottom
surface of each pivoted electrode 50 and a power lead wire 55 is connected
to the other end of each flexible lead wire 54. Wires 54 and 55 are
enclosed in electrical insulator material to insulate them electrically
from the metal of the mold and its support structure. Each power lead
wire extends in insulated relation along one or the other of the trans-
versely extending runners 29 of the end connecting brackets 28, the
horizontal extension members 26, the obliquely extending connecting members
25 and the longitudinally extending members 24 of the mold supporting
carriage and is supported relative to these members by spaced insulator
supports 56. Each of the power lead wires 55 is connected to an electrode
60 that terminates in a hook 62 through an angularly shaped threaded rod
63 and a flexible connection wire 61 (FIG 8). The electrode is fixed to
a metal bearing housing rotor 66 rotatably supported about the angularly
shaped threaded rod 63 so that each electrode 60 pivots with rotor 66
relative to the rod 63 and is connected to an elbow type structure provided
with an outer weighted lever arm 64 having a weight 65 on its distal end,
which weight biases the pivoting of the elbow type structure to cause
hook 62 to rotate upwardly and laterally outwardly about an axis generally
parallel to the length of shaping rails 10 and 11. Wire 61 bypasses the
rotatable connection between rotor 66 and rod 63 to avoid arcing.
The shaping rail reinforcement structure also supports two
apertured platforms 67. An externally threaded angular shaft 68 has a
vertical leg adjustably fixed relative to each apertured platform 67 by
lock nuts. The horizontal legs of angular shafts 68 adjustably
support spools 70 and 72 of four circumferentially grooved spools
70, 71, 72 and 73. The spools form pairs of transversely spaced, circum-
ferentially grooved spools 70 and 71 near one longitudinal end of
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the shaping rails 10 and 11 and an additional pair of circum-
ferentially grooved spools 72 and 73 near the other end of the
shaping rails 10 and 11. The spools are disposed laterally
Outward of the ends of the shaping rails 10 and 11, in position
to slidably engage a pair of flexible, electroconductive ribbons
in a manner to be described later. The lowermost portions of
the grooved circumferences of the spools 70 and 71 are adjusted
to be located in adjustably fixed position slightly below a line
intersecting the upper edges of the ends of shaping rails 10 and
11. The spools are composed of a non-electroconductive material
such as a machinable or moldable ceramic, for example, a glass
ceramic composition sold under the trademark MACOR. Details of
the means to adjust the position of a spool (which serves as
means to guide the vertical position of the ribbon it engages)
are shown in FIG. 9.
The electrical heating circuit also comprises additional
electrodes 75 and 76, each rigidly supported in vertically and
horizontally adjustably position transversely outward of spools
71 and 73 laterally outward of the ends of shaping rail 10.
Electrodes 75 and 76 are interconnected by a power lead wire 77
carried in electrically insulated relationship to the metal of
the mold and its supporting carriage by insulator supports 78
similar to insulator supports 56. Spools 71 and 73 are pivotally
connected to the inner ends of curved arms 80 that extend trans~
versely outward from the spools 71 and 73 along lengths that are
curved both horizontally and vertically. The arms 80 are pivotally
mounted around pivots 81 that are carried on short, longitudinally
extending legs of angular, externally threaded rods 8~. The latter,
in turn, are adjustably mounted on apertured mounting plates 83
secured to a convenient portion of the support carriage structure.
The pivots 81 form pivot axes extending approximately longitudinally
of the mold. The outer end of each curved arm 80 is slidably sup-
-19-
9~6
ported in bearing relation on the upper surface of one or the
other of the elongated lever arms 32 longitudinally
. ~
.~ -19a-
~9~
outward of its associated bearing housing 21. Each curved arm 80 is
constructed and arranged with its center of gravity laterally outside
the pivot 81 so that its outer end plvots downward to rest on its
associated lever arm 32.
A thin, elongated electroconductive ribbon 84 has an end loop
85 connected to the hook 62 of one of the electrodes 60 and its other
end clamped to additional electrode 75 while another electroconductive
ribbon 86 has its end loop 85 connected to the hook 62 of the other
electrode 60 and its other end clamped to the additional electrode 76.
Each of the ribbons 84 and 86 extends from its electrical connection to
the hook 62 of each electrode 60 beneath the grooved portions of spools
70 and 72 in the case of ribbon 84 and beneath the grooved portions of
spools 71 and 73 in the case of ribbon 86 and below and between the down-
wardly diverging ends 41 and 42 of adjacent shaping rails to the respective
connections of ribbon 84 with additional electrode 75 and of ribbon 85
to additional electrode 76.
The ribbons in the illustrative embodiment are preferably double
thicknesses of ribbon spot welded together approximately every 2 inches
(5 centimeters) of length. The ribbons are composed of nichrome and are
3 mils (.08 millimeter) thick and 1/8 inch (3 millimeters) wide.
It is thus seen that spools 70 and 72 are fixed in their adjusted
positions while spools 71 and 73 are capable of lowering when lever arms
32 rotate in conjunction with the pivoting of the end shaping rails 38
and 39 to the closed mold position. Thus, ribbons 84 and 86 are lowered
when the end shaping rails closç with the spools 70 to 73 serving as
ribbon guiding means that establish the vertical position, orientation
and direction of the ribbons that extend between laterally opposite ends
of the shaping rai:Ls of the main mold section.
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The distance the ribbon is separated below the support provided
for the glass sheet depends upon the severity of bend desired along the
line of sharp bending. For less severe bends, all four spools 70 to 73
may be adjustably positioned in Eixed positions so that the ribbons extend
at a fixed minimum distance oE about 1/4 inch (6 millimeters) below the
lines connecting the laterally opposing ends of the shaping rails 10 and 11.
The need to lower the ribbons as the glass sags is not important in such
an instance because the fixed spools can be positioned in such vertical
dispositions relative to the ends of the shaping rails 10 and 11 that
support the glass sheet that when the glass sheet mounted on the mold is
heated, it sags transversely of the mold between its supports on the ends
41 of shaping rails 10 and 11 a distance too small to contact the ribbons.
For sharper bends, the ribbons are initially supported about l/8 inch
(3 millimeters) and less from the glass. In such cases, it is necessary
to lower the ribbons as the glass sags to conform to the mold shaping
surface. Pivoting of the end shaping rail or rails occurs when the glass
sags and initiates the lowering of the ribbon when the latter is necessary
to avoid ribbon to glass contact.
~r~
The apparatus of FIG. 10 is similar to that of FIG. ~ except
for the fact that a mold support carriage 91 supports a pair of molds 93
and 94 in mirror image relation to one another. ~old 93 is shown in the
closed position after shaping a glass sheet supported thereon, while mold
94 is shown in the open position for receiving a flat glass sheet thereon
for illustrative purposes only. It is understood that initially both molds
are pivoted to the position depicted by mold 94 for loading a pair of glass
sheets thereon for shaping the sheets in unison and that after bending is
completed, both molds 93 and 94 are in the position depicted in FIG. lO
by mold 93.
- 21 -
Mold 93 comprises a main mold section 95 and a pivotable end
mold section 96. In FIG. 11, a pair of rooE panels 97L and 97R is shown.
These have been bent on molds 93 and 94 with panel 97L having been bent
on mold 93 with its main portion 98 supported on main mold section 95
and its end portion 99 supported on end mold section 96 to form the sharp
line of bending along the portion of panel 97L that was superimposed over
ribbon 84.
The circuit elements and the structural elements of the carriage
91 of FIG. 10 correspond to those of the FIGS. 1 to 9 embodiment. The same
reference numbers are applied to FIG. 10 for several of these elements of
FIGS. 1 to 9 to illustrate this correspondence of electrical and structural
elements.
According to the method of the present invention, a flat glass
sheet is mounted on a mold with its end shaping rails 38 and 39 rotated
into a spread position depicted in FIG. 1. The flat glass sheet mounted
on the mold is initially supported on the outer longitudinal extremities
of the end shaping rails 38 and 39 curved in plan and the ends 41 of the
longitudinally extending shaping rails 10 and 11 with the ribbons 84 and
86 disposed slightly below the diverging spaces between the insulator
sheets 44 covering the ends 41 of the longitudinally extending shaping
rails 10 and 11 and the inner ends 42 of the end shaping rails 38 and 39.
The ends of the shaping rails are angled downward and inward at a given
angle and the insulator sheets 44 of non-conductlve material bonded to
the ends 41 and 42 of the rails at a lesser angle to extend into the
space between the ends to provide means to prevent contact o~ the ribbons
84 and 86 with the shaping rails~ thereby electrically insulating the
ribbons from the shaping rails.
- 22 -
The glass-laden mold enters a bending furnace which has a pair
of bus bars 90 mounted along the opposite side walls of said furnace for
sliding engagement of their undersurfaces by the top surfaces of the
pivoted electrodes 50. Leads ~2 connect the bus bars 90 to a power supply.
It is noted that the bus bars 90 are located in spaced relation above the
stub rolls 30 of the furnace to provide clearance for moving the trans-
versely extending runners 29 over the stub rolls 30 as the glass is heated
within the heating furnace.
When the glass is heated sufficiently for softening, the end
shaping rails 38 and 39 pivot upward to lift the longitudinal end portions
of the supported glass sheet upward about lines parallel to and above
the ribbons 84 and 86. These lines are approximately aligned with lines
extending between transversely opposite ends 41 of the shaping rails 10 and 11.
FIG. 3 shows how one of the ribbons is initially supported in
tension by its end loop 85 engaging the counterweighted electrode hook 62
so that the ribbon extends across the mold a short distance below the
bottom surface of the flat glass sheet at the beginning of a bending cycle.
As electric current is passed through the ribbons 84 and 86, the ribbons
become heated and tend to elongate because of thermal expansion and would
droop away from close proximity to the glass were it not for the fact that
the weighted lever arms 64 hold the respective ribbons 84 and 86 in
tension along the lines of support provided by the bottoms of the circum-
ferential grooves in spools 70, 71, 72 and 73.
FIG. 4 shows how the lever arms 64 rotate to hold the ribbons
in tension in clasely spaced relation below the supported glass during
an intermediate portion of the bending cycle when the ribbons have expanded
somewhat, but have not radiated sufficient heat to develop lines of sharp
bending in the glass. By the time the glass is heated sufficiently to
- 23 -
enable the end shaping rails 38 and 39 to pivot upward to help form the
sharp bends along the lines facing the ribbons, the glass also tends to
sag transversely as shown in FIG. 5. The parts of lever arms 32 at the
one slde of the mold below the curved arms 80 lift as the end shaping
rails pivot upward, thereby forcing the laterally outer ends of the
curved arms 80 laterally outside the pivots 81 to also lift, thereby
pivoting the spools 71 and 73 downward to lower one end portion of each
of the ribbons 84 and 86 to a position sufficient to maintain clearance
with the center of the glass sheets G intermediate the shaping rails 10
and 11 that sags the most as a result of the bending operation.
Thus, it is seen that when it is necessary to hold the ribbons
84 and 86 close to the glass initially (as little as 1/8 inch or 3
millimeters) so as to impress very sharp bends (less than 1/2 inch or 12
centimeters radius) on the glass, it becomes necessary to lower the ribbons
as the glass sags. However, when the ribbons are initially supported a
distance greater than the amount the glass sheet sags between transversely
spaced supports at ends 41 (usually at least 1/4 inch or 6 centimeters
or more), each of the guiding means or spools of each transversely spaced
pair of spools may he rigidly supported on both sides of th~ mold at a
suitable vertical position with the ribbons extending between the bottoms
of transversely aligned grooved portions of the transversely spaced spool
pairs in positions below the glass sheet across its entire width. Having
the spools disposed with their grooves guiding the ribbons adjacent and
below the lines of support defined by the transversely spaced ends 41 of
the elongated, longitudinally extending shaping rails 10 and ll of the
main mold section develops a sharp line of bending in the glass portion
facing each ribbon that has a reduced amount of sag compared to cross sag
normally obtained along other lines extending across the mold. In other
- 24 -
words, the combination of the specific position for the flat glass
supports at the ends of the main mold section shaping rails and the
ribbons extending adjacent lines defined by the ends of the main section
shaping rails causes an improved definition of the line of sharp bending.
Example
A typical cycle to produce a double V-bend and temper in glass
sheets using bending and tempering apparatus comprislng a two~stage
furnace each provided with a separate pair of bus bars and an adjustable
voltage source and a cooling station is as follows.
Furnace ambient temperature in the first stage averages about
1200F. (649C.) and in the second stage averages approximately 1430F.
(777C.). A glass sheet is mounted on a mold after the latter returns
from a heating and cooling cycle and the glass-laden mold enters the
furnace with no power on the bus bars. Ten seconds after mold entry,
power is applied to supply 5 amperes of electrical current to each ribbon.
This current is increased in steps of 5 amperes every 10 seconds until
current reaches 25 amperes after 1 minute in the furnace and is kept at
this level. The mold moves to the second stage of the furnace after 3
minutes and 35 seconds when the glass sheet starts to bend. The bus bars
in the second stage are spaced from the bus bars in the first stage by a
short distance traversed by the pivoted electrodes in less than 1 second
so that there is virtually no interruption in current so that current is
applied almost continuously to the ribbons through the pivoted electrodes
from the onset of the application of current to the ribbons.
At a time of 4 minutes and 35 seconds from its entry into the
first stage of the furnace, current to the second stage bus bars is turned
- 25 -
off and the bend is completed by exposure to ambient heat. At 4 minutes
and 55 seconds, the mold enters a quenching station disposed beyond the
exit of the furnace. Cool air jets applied through elongated, curved,
slot-type nozzles impinge against the opposite major surfaces of the bent
glass sheet to temper the latter in a manner well known in the art.
A typical quenching station has a pair of opposite nozzle sets
disposed to provide a 6 inch (15 centimeter) space between sets. Each
set comprises elongated nozzles 1/4 inch (6 millimeters) wide spaced about
4 inches (10 centimeters) apart center-to-center spacing reciprocating at
a 5 inch (12.7 centimeter) displacement 30 cycles per minute. Air is
supplied through these nozzles at a pressure of 9 to 12 ounces per square
inch (.04 to .05 atmospheres) depending on the glass thickness, which may
be 5 millimeters to 6 millimeters, to impart a temper that develops a break
pattern when the tempered glass is fractured that meets U.S. Government
specifications (4.25 grams maximum particle size). Fifteen to twenty
seconds of cooling under these conditions provide sufficient cooling to
obtain adequate temper. ~or insurance, cooling continues for thirty seconds.
Separation between bus bars in the multiple stage furnace enables
different glass sheets to occupy positions in the various stages. The
duration of stay in the various stages of a multi stage bending furnace
is a maximum in the first stage and no more than the maximum for each
successive stage in case of furnaces having two or more stages. In this
way, each stage can be cleared for a new mold when a prior mold finishes
its heating step and leaves said stage.
The present invention is also susceptible of use with furnaces
having a continuous movement of glass sheets through the heating furnace
- 26 -
where the pivoted electrodes contact closely spaced electrodes in
succession as the molds move through the Eurnace in a continuous mass
production operation.
In cases where glass sheets are to be bent to a single sharp
curvature about one axis, two molds may be conveyed side-by-side, size
permitting,~with a pivoted end shaping rail of each mold disposed toward
each side wall of the furnace. The ribbons for each mold may be operated
simultaneously as they can be connected in series or in parallel between
the bus bars carried by the laterally opposite walls of the furnace. If
the sheets are too long to be conveyed in side-by-side relation, only one
ribbon is in the circuit between the bus bars.
If glass sheets are to be bent sharply along a single axis
extending in the direction of their length, the main mold section of the
outline mold that supports the glass sheet for such shaping is provided
with a pair of shaping rails that are relatively short in length and that
are interconnected at one end by a relatively long connecting end rail,
and the pivoted end mold section of the outline mold is also modified
to conform with the outline of the end portion of the glass sheet to be
shaped. The heating ribbon and its guiding means are otherwise constructed
in a manner consistent with the other embodiments already described.
The form of the invention shown and described in this specification
represents an illustrative preferred embodiment and certain modifications
thereof. It is understood that various changes may be made without
departing from the gist of the invention as defined by the claimed subject
matter that follows.
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