Note: Descriptions are shown in the official language in which they were submitted.
- ~2~37s~
~ETHOD AND APPARATUS FOR SHAPIN~ GLASS SHE~TS BY DROP FOR~ING
'
.
- Background of the Invention
.~ .
This invention relates to the benting of sheets of thermoplastic
material, especially glass. Many techniques for bending glass sheets are
- known. Perhaps the simplest technique i9 to heat a glass sheet while
supported o~ a contoured mold and to permit the glass sheet to sag into
- conformity with the mold. However, it is often desirable to speed ehe
process by applying a mechanical bending force such as by pressing the
.
glass betwee~ a pair of contoured molds. A particularly advantageous press
. bending process is shown in U.S. Patent No. 3,846,104 to S. L. Seymour
`; - wherein a horizontally oriented glass sheet is heated and lifted by a lower
bending mold into contact with an upper bending mold where it is retained
` ~ by vacuum while the lowe`r bending mold retracts. Then a tempering ring
2 receives the bent glass sheet and conveys it from the bending station into
i` a tempering staeion. That arrangement is especially advantageous in thac
it provides contoured support Eor the bent gLass sheet during the tempering
step and frees the bending staeion for initiating the next bending cycle
while tempering of the first glass sheet is being carried out. A dr~wbac~
! - ~o such an arrangement is that ehree major components of the apparatus, ;~
the upper and lower forming molds and the tempering ring, must all be
custom fabricated for each differenc shape produced on such a bending and
tempe-ing line. I; would be desirable not only to reduce the cost of
,
_ I _
, : .
. ., '.~; 'g~ ~
~L~28~SS
fabricating these elements wiCh each shape change, but also to reduce the
down time of the bending and tempering line necessitate~ by the instaLla-
tion vf these elements with each product change.
In U.S. Patent No. 3,713,799 to H. A. McMaster, a similar
arrangement is disclosed, but in which the lower shaping mald serves to
carry the bent glass sheet into the tempering station, thus delaying
the commencement of the next bending cycle until the lower bending ring
deposits the glass sheet in the tempering station and returns to the
bending station. Likewise, in this arrangement a product change re-
quires a major retooling of the bending station since the upper and
lower forming molds as well as the gas support block into which the
lower forming mold recesses, all must conform to the shape of the glass
sheets being processed. A similar arrangement in U.S. Patent No. 3,573,889
to H. A. McMaster et al. has the same drawback.
U.S. Patent Nos. 39507,639 to S. L. Sey~our and 3,676,098 to
H. R. Hall both show horizontal press bending arrangements wherein only
two elements, the upper and lower bending molds, need to be custom fabri-
cated for each glass shape being produced. It would be desirable to reduce
the number of custom made parts even further. Furthermore, in both of
these arrangements the edges of the bent glass sheets are not supported as
they are conveyed from the bending station into the tempering station.
U.S. Patent No. 3,476,540 to Ritter et al. discloses a gLass
bending arrangement whereby the inertia of a single vertically rising
lower bending mold effects the bending. Disadvantageously~ the bent
glass sheets must pass without edge support along a roller conveyor
into the tempering æone.
U.S. Patent No. 3,oOO,150 to Rougeux shows a glass bending
arrangement wherein a heat-softened glass sheet is slipped from a roller
~L~2~3~5~
conveyor onto a flexible hammock and thereafter press bent between
upper and lower forming molds. The purpose of the flexible hammock i9
to support the glass sheet initially out o~ contact with the rigid shaping
mold aurfaces. It is apparent that a major reconstruction of the apparatus
would be required when a change in the glass shape is desired.
Summary of the Invention
In the present invention a single shaping mold conforming to
the outline and contour of the bent glass sheet is employed, onto which
a heat-softened glass sheet is dropped to impart the bending force to
the glass. Immediately after each glass sheet leaves a heating furnace,
it is elevated by means of a flat vacuum platen which is brought into
contact with the upper side of the glass sheet. ~hen the vacuum platen
and the glass sheet are raised to an elevated position, the shaping
mo-ld is conveyed into a position beneath the glass sheet, the vacuum
is released, and the glass sheet drops onto the shaping mold to effect the
bending. The shaping mold is then retracted from beneath the vacuum platen
and passed into a tempering station where blasts of air are directed onto
the opposite surfaces of the glass sheet to temper the glass. This arrange-
ment greatly simplifies change-over from one shape to another since the
single bending mold is the only major element which must be reconstructed.
Another important feature of the present invention is that the arrangement
may be readily adapted to bending and tempering a pluralfty o~ glass sheets
simultaneously, thereby greatly increasing the productivity of the instal-
lation.
The Drawings
Figure 1 is a side view of a spècific preferred embodiment of a
glass sheet bending and tempering installa~ion incorporating the drop
forming process and flat vacuum pick-up of the present invention.
-- 3 --
i
5~
Figure 2 is a perspective view of the drop forming section of
the bending and tempering apparatus of Figure 1.
Figure 3 i9 a cross-sectional view through the gas support
block in the forming zone taken along line 3-3 in Figure 2.
Figures 4 through 8 illustrate se4uential steps in a cycle
of operation of the apparatus of Figure 1.
Figure 9 is an end view of the bending mold and support structure
taken along line 9-9 in Figure 1.
Figure 10 is a perspective view oE the gas support bed in the
shaping station showing a quadruple aligning frame and an alternate
mounting arrangement for the aligning frame,
Figure 11 is a perspective view oE another alternate mounting
arrangement for the aligning frame in the shaping station.
Figure 12 is a side view of an alternate embodîment for
drop forming glass sheets using a 1at lifting ring.
Detailed Description
In Figure 1 there is shown a bending and tempering line in-
cluding a furnace 10 (only the exit end of which is shown), a bending
station 11, a tempering station 12, and an unloading station 13. l'he
furnace, tempering station, and unloading station form no part of the
present invention, and the description of a specific embodiment herein
is for the purpose of illustration only. Any arrangement known in the
art for heating and tempering a series of horiæontally disposed glass
sheets may be employed in connection with the bending process of the
present invention. Accordingly, only a brief description of the fur- -
nace, tempering station and unloading station will be set forth here.
-- 4 --
. - ,: .
,~ ,: ; . , :~
2875~
Additional details regarding these aspects of the overall bending and
tempering line may be obtained from U.S. Patent No. 3,846,104 (Seymour),
Furnace 10 is preferably of the gas support type wherein the
sheets of glass are supported on a layer of hot gases as they are heated
and conveyed through the furnace. Examples of gas support furnaces for
heating glass sheets may be found in U.S. Patent No. 3,223,501 to Fredley
et al. and in U.S. Patant No. 3,332,759 to McMaster et al. In the cut-away
portion of the furnace in Figure 1 it can be seen that the gas support bed
is defined by a hearth block 21 through which a large number of vertical
bores extend, some of which communicate ehe upper surface of the hearth
block with bot, pressurized gases from a plenum chamber 22 and others of
which communicate the top surface of the hearth block with cross-bored
exhaust passages 23. ~he same hearth block construction continues beyond
the furnace exit to an extension 24 and a support block 25 in the bending
zone. Greater detail of the hearth biock construction may be found in
the cross-sectional view of support block 25 in Figure 3. There, it can be
seen that vertical bores 26 extend completely throu~h che block and that
bores 27 extend from the surface to the horizontally extending exhaust
passages 23-
Referring again now to Figure 1~ there is shown one typicalarrangement for propelling the glass sheets through the Eurnace as they are
supported on a film of hot gases. The conveying mechanism there comprises
a pair of parallel, endless chains 30 flanking the path of the glass sheets
inside the furnace and joined by a plurality of pusher bars 31. At the
exit of the furnace, each glass sheet may be released from the chain
conveying means and driven at an accelerated speed across the extension
~'12~75~i
block 24 and into the bending station by means of a take-out roll 32 and alt
aligning rollt~3. Passage of the glass sheets rom the urnace rnay be
aided by providing the hearth blocks 21, 24, and 25 with a sli~ht downward
slope (e.g., l'degree to 2 degrees). Typically, sufficien~ gas pressure is
maintained between the hearth blocks and the glass sheets so as to float
the glass sheetts about 1/16 inch tl 6 millimeters) above the upper surface
of the hearth blocks. Take-out roll 32 and aligning roll 33 project above
the upper surface of the hearth blocks just enough to make contact with the
undersides~of the glass sheets.
.When a glass sheet has arrived in the bending station, its
forward progress is stopped by a locator frame 35 resting on hearth block :.
25. The locator rame defines at least one open-ended "pocket" within
which the forward portion of a glass sheet may be received. As shown in
Figure 2, the locator frame 35 includes two such~pockets for receiving
glass sheets G..and G'. Each of the glass shèet receiving pockets is
contoured to.correspond approximately to the outline of the leading portion
of each glass-~heet so thàt the glass sheet, when urged into engagement
with the locator frame, will become seated firmly within the pocket with
little or no.freedom of movement. The locator frame 35 is spaced from
aligning roll 33 a precisely determined distance so that the trailing
edge of a properly aligned glass sheet is approximately directly over the
center of the aligning roll 33 as shown in Figure 3. The aLigning roll 33
continues rotating so as to urge ehe glass sheet into the pocket of the
aligning frame as the glass sheet floats on the layer of hot gases. The
frictional forc~ between the aligning roll 33 and the glass sheet is
minimized and restricted to the trail;ng edge of the glass sheet in :'
order to avoid scuffing the glass, but is sufficient to drive the
- 6 -
ZtF3~755
floating glass sheet into an equilibrium position in align~ent with the
pocket of the locator frame and to retain the glass sheet therein. Such an
aligning arrangement readily lends itse~ to processing a pLurality o
glass sheets side by side. For example, the locacor frame in Figure 2 is
constructed to receive two glass sheets and in Figure 10 a loc~tor frame is
sho~n for receiving four glass sheets. It shoult be appasent that a
loca~or frame coult be adapted to accommodate any nu~ber of glass sheets
which will fit side-by-side on the hearth block 25. The locator frame 35
~ay be held in place by means of rods 36 which, as shown in Fi~ure ~, may
exeend laterally toward support means on each side of the hearth block 25.
The rods 36 are preferably supportet at their ends with some provision for
,
adjustability, such as by clamping between a pair of plates 37 as shown.
Oeher arrangements for mounting the locator frame will be described later
in connection with Figures 10 and 11. The loca~or frame arrangement itself
is the subject matter of U.S. Patent 4,204,853 by S.L.
Seymour and entitled "Glass Sheet Alignment Means and Method".
While the use of a locator frame and an aligning roll as described
above is the preferred arrangement for repetitively establishing a precisely
predeter~inet location for each glass sheet as it enters the bending
station, other arrangements may serve ehe same purpose. For example, the
use of vertically recractable pins as shown in U.S. Patent ~os. 3,573,889
and 3,676,098 may be resorted to. It may also be noted that in the even~
that a roller conveyor were to be used instead of a gas support bed, the
need to precisely align the glass sheets within the bending station may be
less critical. This is because glass sheets are more prone to drift out of
alignment when floating freely on gas support. When a roller conveyor is
- 7 -
l~Z~75~;
used to convey the glass sheets into the bending station, final orientation
of the glass sheets may be carried upstream from the bending station as
shown in U.S. Patent No. 3,701l643 to R. G. Frank, for example.
Directly overlying the locator frame 35 is vacuum platen 40.
The vacuum platen is comprised of a hollow chamber having a flat bottom
plate 41 through which a large number of perforations 42 extend. In
order to protect the surface of the hot glass sheets, the underside of
the vacuum platen may be covered with a protective coves 43, which may
be a stretchable knit fiber glass fabric ~s disclosed in U.S. Patent
No. 3,148,968 to J. H. Cy?her et al. The cover 43 may be held in place by
a plurality of clamps 44. The hollow interior of the vacuum platen communi-
cates with a source of vacuum by means of a flexible conduit 45. The area
of the vacuum platen should exceed the total area of the largest glass
sheet or sheets to be received at one time in the locator frame 35. For
the greatest versatility the vacuum platen may cover substantially the
entire area of hearth block 25.
The flatness and rigidity of the bottom plate 41 of the vacuum
platen are important factors for the successful practice of the present
invention. Any significant deviation from flatness can result in distortion
being imparted to the glass sheets. Thus, the bottom plate 41 should be
fabricated with careful attention to providing a flat bottom surface and
should be sufficiently rigid to avoid any bending or warping during use.
Preferably, the bottom plate is a relatively thick, single piece of heat-
resistant metal, such as stainless steel, although in some cases it may be
possible to use thinner stock material with reinforcement members welded to
the interior surface. As an example of the preferred one-piece construction,
a stainless steel thickness of at least one-half inch (13 millimeters),
.
- ~
1~2~SS
preferably at least 5/8 inch (16 milLimeters), has been found suitable
for a plate 32 inches by 78 inches (81 centimeters by 2 meters). In
that example, the interior of the vacuum platen was 3 inches (7.5 centi-
meters) tall.
The vacuum platen is provided witb means for vertical reciprocation,
such as hydraulic cylinders 50 and guide rods 51, as shown in Figure 1.
The guide rods 51 may slide in fixed, annular sleeves 52. The cylinders 50
reciprocate the vacuum platen between a raised position, as shown in Figure
l, and a lowered position in which the platen is brought closely adjacent
to, or in contact with, the locator frame 35 and the glass sheet or sheets
held by the locator frame. When the vacuum platen is in the lowered
position, sufficient vacuum is applied to draw the glass sheets into
contact with the platen and to be lifted `by the vacuum platen as the vacuum
platen is raised. The platen need not come into contact with the glass
sheets in order to pick them up. Merely approaching within 1/32 inch (0.8
millimeter) to about l/16 inch (1.6 millimeters) has been found sufficient
to lift the glass sheets, although this may vary depending upon the amount
of vacuum applied and the weight of the glass. Additionally, the amount of
vacuum required, the number of perforations 42 in the vacuum platen, and
the diameter of the perforations are interdependent. It is desirable to
keep the perforations 42 small in number and diameter so as to minimize the
power requirement for maintaining a vacuum in the vacuum platen, but there
should be enough pesforations so that a relatively uniform distribution of
the perforations will overlie each portion of the smallest piece of glass
to be processed. A spacing of about one perforation per square inch (6.5
square centimeters) has been Eound to be suitable for most purposes.
Perforation diameters larger than 0.075 inch (1.9 millimeters), for example
~ ~, ` , .
l~LZ!37SS
about 0.090 inch (2.3 ~illimeters), have been found satisfactory with a
vacuum of 4 inches tlO centimeters) water (gauge). These data pertain to
the processing Oe 3 millimeter thick sheets of soda-lime-silica floa~ glas~
of standard co~mercial composition.
With the glass sheet or sheets drawn against its underqide by
vacuum, the platen 40 is raised to the elevated position as shown in Figure
1 so as to leave sufficient clearance to insert an outline shaping mold 60
between the hearth bloc~ 25 ant the platen. The shaping mold conforms to
the outline and contour desired for the bent glass sheets and is preferably
constructed in accordance with the disclosure of U.S. Patent No. 3,973,943
to S.L. Seymour. The shaping mold is preferably
of the outllne ring type, light in weight
and notched along its upper edge in order to provide minimal interference
with the flow of air during tempering. The shaping mold is carried on a
shuttle 61 by which the shaping mold is translated horizontally through the
bending, tempering and unloading zones. In the specific embodiment illus-
trated, the shuttle consists of a pair of cantilevered beams 62 supported
at one end by vertical braces 63, ehe upper ends of which are adapted to
slide along a pair of horizontal guide rods 64. The means for driving the
shuttle 61 along the horizontal path may be provided by way of aa electric
motor (not shown) driving a continuous chain 65 to which the upper ends of
braces 53 are affixed. Cross-braces 66 may support the shaping mold or
molds on the shuttle. An end view of the shuttle may be seen in Figure 9
wherein two shaping molds 60 and 60' are included for simultaneously
receiving sheets G and G' in Figure 2.
When the vacuum platen 40 has been raised to a height above
the elevation of the shaping mold 60, the shuttle is driven to Che left as
- 10 -
75~
viewed in Figure l so as to bring the bending mold into direct alignment
beneath the sheet o glass elevated on the vacuum platen. Typically, the
distance between ~he vacuum platen and the hearth block 25 a~ this point
may be about 6 to 8 inches (15 to 20 centimeters). This distance wilL have
an effect on the rate at which the glass sheet loses heat, since a higher
elevation raises the glass sheet into a cooler environment. This effect
may be used to "fine tune" the temperature (and thus the viscosity) at the
moment the glass sheet is dropped onto the shaping mold. The uppermost
extent of the shaping mold when in position directly beneath the glass
sheet is spaced from the glass sheet a distance greater than the minimum
required to clear the glass sheet, so that when the glass sheet is released
from the vacuum platen it will fall a distance onto the shaping mold
sufficient to generate a substantial bending force on the glass upon
impact. In the typical case where the contour of the shaping mold includes
points of maximum elevation, the falling glass sheet first contacts
these high points~ and a bending moment about these points is generated
which forces the remainder of the glass sheet to bend downwardly until
substantially complete contact is made with the shaping mold. A suitable
distance between the vacuum platen and the high points of the shaping mold
has been found to be about I to 2 inches (2.S to 5 centimeters), and about 2
to 6 inches (5 to 15 centimeters) at the low points of the mold. The
precise distance through which the glass falls will depend upon the weight
and temperature of the glass, the degree of curvature to be imparted to the
glass, and the geometry of the particular shape, and in unusual cases may
vary beyond the distance ranges given above.
Release;of the glass sheet from the vacuum platen i9 carr;ed out
by reducing the vacuum to an amount insufficient to support the glass sheet.
~287S~
This may be accomplished conveniently by opening a valve to bring the
interior of the vacuum platen into communicat;on with atmospheric pressure.
Or in some cases, it may be desirable to e~pedite the release o~ the glass
from the platen by following a rapid decay o the vacuum ~ith a rapid
buildup to a positive pressure. Another optional Eeature is to provide the
vacu-m platen with a pLurality of separately controllable vacuum zones so
that the vacuum may be released nonuniformly. For example, it may be
beneficial in some cases to release the edge portions and the center
portion of a glass sheet at different times. By delaying the release of
the center portions a slight reverse bend may be imparted to the glass,
~hich may be helpful in avoiding excessive center sag when the glass sheet
is dropped onto a concavely contoured outline shaping mold. Conversely,
differential vacuum release may be utilized to accentuate a relatively deep
bend which may be otherwise difficult to attain by impact force alone.
The momentum imparted to the glass sheet by its free fall onto
the shaping mold preferably provides essentialLy the sole bending force
for conforming the glass sheet to the contour of the shaping mold. Although
some minor amount of sagging due to the force of gravity may take place
after the glass sheet has come to rest on the shaping mold, its magnitude
is insignificant relative to the bending produced by the momentum-generated
force in the preferred mode of operation. Sagging is a relatively slow
process, and in the present invention, tempering is preferably initiated
in the minimum amount of time, thereby providing insufficient time for a
significant amount of gravity-induced sagging to take place. On the other
hand, for some di~ficult bends it may be desirable to delay the start of
tempering so as to permit a significant amount of additional sagging to
take place after the glass sheet has dropped onto the mold. Although
- 12 -
~Z~'755
slower than the preferred mode, such a technique would be considerably
faster than gravity sagging alone since the initial dropping of the glass
onto the mold would accomplish a substantial part of the bending very
quickly.
Upon receiving the glass sheet, the shaping mold is immediately
transferred out of the bending station into the tempering station 12.
The tempering station includes upper and lower blast heads 70 and 71 which
direct blasts of tempering medium (usually air) onto opposite sides of the
glass sheet so as to rapidly cool surface portions of each glass sheet,
thereby imparting a temper to the glass sheet. In the type of tempering
station shown in Figure 1, each blast head includes a plurality of pipe
modules 72 in fluid communication at their ends with a manifold 73 or 74.
Each manifold, in turn, is supplied with pressurized tempering fluid
through ducts 75 and 76. Each oE the pipe modules 72 has a plurality of
small orifices oriented so as to direct jets of tempering fluid toward the
position occupied by gIass sheets conveyed into the space between the upper
and lower blast heads 70 and 71. The pipe modules 72 may be provided with
adjustability in the vertical direction with respect to the ~anifolds 73
and 74 so that more uniform spacing between the glass surfaces and the pipe
modules may be provided. The lower blast head 71 may be provided with
hinged support 81 at one end and cylinder means 81 at the opposite end so
as-to permit the lower quench module-to be tilted when the need arises to
clear glass fragments from the blast head. While blasts of tempe}ing
medium are being directed onto the glass sheets in the tempering station,
it is preferred to provide relative motion between the blast heads and the
glass sheets. This may be carried out by horizontally reciprocating the
shuttle means ~1 on which the shaping mold and glass sheets are carried.
~2~37SS
When tempering has been completed, the shuttle means 61 advances
to the Eull right-hand position as shown in Figure L to brin~ the glass
sheet or sheets into the unloading station 13. There, the glass sheets
may be removed from the shaping mold by hand or by suitable mechanical
means.
Figures 4 through 8 illustrate one cycle of operation in the
method of bending glass sheets in accordance with the present invention. In
Figure 4j a sheet of glass G is emerging from the furnace 10. At the same
time, an already bent and tempered sheet of glass G' is about to be unloaded
from the shuttle 61. In Figure 5, the sheet of glass G has entered
the bending station 11 and its front end has engaged the locator frame 35
while being driven at its trailing edge by aligning roll 33. At the same
time, vacuum platen 40 is being lowered to engage the glass sheet. The
previous glass sheet has been unloaded from the shuttle 61 and the shuttle
has begun to move toward the bending zone. In Figure 6, the sheet of glass
has been lifted from the gas support bed 25 by the vacuum platen 40 and
shuttle 61 has co~e to rest, with the shaping mold 60 directly beneath the
glass sheet. In Figure 7, the vacuum has been released Erom the vacuum
platen and the sheet of glass has falLen onto the shaping mold 60 and has
thereby become bent to the desired curvature. The shuttle immediately
carries the glass sheet out of the bending station and into the tempering
station 12 where it is rapidly cooled by blasts of air as shown in ~igure 8.
Thereafter, the shuttle carries the glass sheet into the unloading station 13.
The following operating parameters are an example of a successful
operation of the above-described preferred embodiment of the invention with
glass sheets 3 millimeters thick. Under different conditions the data will
vary. The furnace atmosphere was maintained at a temperature of about
1~ 7S~
1300F. (700C. ). The gas issuing from the hearth block 25 in the bending
zone may be about 1100 to 1350F. (600C. to 725C. ), typically about
1250F. (675C. ) . The vacuum platen ~0 attained a tempera~ure oE àbout
500 to 750F. (260 to 400C.) after a period of operation due to its
proximity to the hot gases from hearth block 25. The glass was typically
at about 1210F. (650C. ) when picked up by the vacuum platen. A total of
about 6 seconds elapsed from the time of glass pick-up until the initiation
of tempering, at which time the glass had cooled to about 1190F. (640C.).
About 3 seconds elapsed from the time the glass was dropped onto the
shaping mold until tempering was initiated. Altogether about lO seconds
was required for the glass to pass from the furnace exit, undergo bending,
and enter the tempering station. These rapid bending rates not only
indicate a high rate of throughput, but are also advantageous for the sake
of attaining high degrees of temper since the rapidity of the bending
process permits tempering to begin before the glass sheets have lost an
appreciable amount of heat.
Figure 10 shows an alternate arrangement Eor mount;ng a locator
frame onto the hearth block 25 in the bending station. In order to illus-
trate the versatility of the locator frame arrangement, a locator frame 85
is depicted in Figure lO which is provided with four pockets ~7 permitting
the simultaneous alignment and bending of four sheets of glass. For
retaining the locator frame in place, two or more pins 86 are welded to the
front edge of the locator frame and may be inserted into holes bored into
the hearth block 25. The holes may be those already present in the hearth
block for the passage of gases, or special holes may be drilled for the
purpose of receiving the pins 86.
Figure 11 depicts yet another variation on the mounting arrange- -
ment ~or the locator frame. In this case, the locator frame is provided
~2~7.~5i
with pivoting support so that the locator frame may be readily raised above
the surface o~ the hearth block 25 if it sho~ld become necessary to remove
glass fragments from the hearth block. A pair of rods 91 telescope into
the ends of a tubular hinge bracket 92 for lateral adjustability. The
hinge bracket 92 pivots through a sleeve 93 which is affixed with vertical
adjustability to a support arm 94. The outer end of hinge bracket 92 may
be engaged by mechanical actuating means such as a hydraulic cylinder 95 so
as to provide remote control of the locator frame lifting mechanism. In
the embodimene of Figure 11, it is preferred that the locator frame consist
oE two halves, with each half being lifted by its own respective hinge
means.
Figure 12 shows an alternate arrangement which incorporates
some, but not all, of the features and advantages of the preferred embodi-
ment of the present invention. In Figure 12, like nurnerals refer to
elements which may be identical to those which have been described in
connection with the preferred embodiment of Figure 1. In particular~ the
furnace 10, tempering station 12, and unloading station 13 are identical to
those of Figure 1 and need not be described here. However, in the bending
station 100 in Figure 12, the vacuum platen 40 is not vertically recipro-
cated but is rigidly suspended by beams 101. Like the preferred embodiment,
the vacuum platen is flat and need not be modified when changing glass
shapes. ~ut instead of being picked up by the vacuum platen, the glass
sheets in this embodiment are lifted into contact with the underside of the
vacuum platen by a lifting ring 102. ~ifting ring 102 is vertically
reciprocated by means of a hydraulic cylinder 104 which is connected to the
ring by means of a laterally extending tab 103. The ring 102 may fit
around a gas support hearth block 125 which may be of essentially the same
- 16 -
37~5
construction as that of previously described hearth block 25, but of
reduced size. Alternatively, the ring 102 may Eit iato grooves cut into
the top of a larger size hearth block. The upper side of the lifting ring
defines a flat plane of support for a gLass sheet along either a continuous
or discontinuous line of contact with marginal edge portions of a glass
sheet. Glass sheets are aligned on hearth block 125 by a locator frarne 35
and aligning roll 33 in the same manner as previously described. After
each gIass sheet is lifted by the ring 102 and retained on the underside of
the vacuum platen 40, the ring is retracted to its lower pOsieion, a
shaping mold 60 is brought into alignment beneath a each glass sheet, and
the glass sheet is dropped onto the shaping mold to impart the desired
curvature to the glass sheet. This arrangement is advantageous relative to
prior art vacuum assisted bending arrangements in that the vacuum platen is
flat and need not be reconstructed when a product change is made, and in
that it can be readily adapted to the simultaneous processing of a plurality
of glass sheets. However, the Figure 12 arrangement is not as advantageous
as that of the preferred embodiment because the hearth block 125 and the
lifting ring 102 must be replaced for each change in the shape or number of
glass sheets to be processed.
Other variations on the Figure 1 embodiment which are contemplated
by the present invention may involve the use of a roller conveyor instead
of the gas support means for supporting and conveying the gLass sheets. A
roller conveyor may be used in place of all of the gas`support bed sections
in the furnace and bending station, or it may be advantageous to substitute
a roller conveyor for the gas support bed in the furnac2 only and to
utili~e a gas support hearth block such as 25 in the bending station.
~287S5i
It should also be apparent that the step oE aligning the shaping
mold with the glass sheet prior to dropping the glass sheet ~ay aptio~all~
entail translating the platen rather than the shaping mold.
Another alternative within the scope of the invention is to heat
the glass sheets as they are being supported in a generally vertical
orientation. For example, the glass sheets may be conveyed through a
furnace while resting on their lower edges and being held upright by
currents of heated gases, as disclosed in U.S. Patent No. 3,341,312 to R.
W. Wheeler. The vacuum platen may swivel to receive each glass sheet in a
vertical orientation and then rotate to a horizontal orientation for
dropping the glass sheet onto a shaping mold.
Descriptions of specific embodiments have been set forth herein
for the sake of illustrating the best mode and other illuserative examples
fQr practicing applicant's invention, but it should be understood that
other variations and modifications as are known to those of skill in the
art may be resorted to without departing from the spirit and scope of the
invention as set forth in the claims which follow.
- 18 -
" " ~ ~
