Method and apparatus for forming a glass sheet

This invention is directed to a method and apparatus for forming a glass sheet with differential gas pressure over opposite surfaces thereof. The glass sheet is formed by the action of differential gas pressure over a forming area located on a curved exterior surface of a rotatable glass former. The forming area moves on an arcuate path about an axis of rotation of the glass former. The glass sheet forming operation is carried out in an incremental manner by rotational contact of the forming area of the glass former and the glass sheet being formed. Full dimensional control can be achieved, whereby glass sheets may be produced which are substantially identical copies of one another.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method and apparatus for forming a glass sheet 
and, more particularly, to a method and apparatus wherein forming occurs 
while the glass sheet is being transported on a rotating forming surface. 
2. Description of the Related Art 
In the art of forming glass sheets into finished products of complex shape, 
there are few known methods of transporting the glass sheet to and through 
a forming or shaping operation after it has been heated to the softening 
point, i.e., to a temperature sufficiently high that it may be formed. 
A first known manner of transporting a heated glass sheet is by gripping an 
upper edge thereof with tongs. This method leaves marks in the upper edge 
of the glass sheet and generally does not work well on a relatively thin 
glass sheet. 
A second method of transporting a heated glass sheet is on a metal ring 
which engages the periphery of the glass sheet. This transportation method 
tends to leave marks along the edges of the glass sheet. There is also no 
full, direct surface dimensional control of the shape of the formed glass 
sheet if the glass sheet remains supported by the metal ring during a 
shaping operation, because the ring contacts only the periphery of the 
glass. 
A third method of transporting a heated glass sheet during a shaping 
operation is on a cushion of gas, such as in the well known "Gas Hearth" 
process, which is used typically only for bending a glass sheet into a 
cylindrical form. For other than cylindrical forms, the glass sheet is 
picked up from the air cushion and moved against a suitable shaping mold. 
A fourth method of transporting a heated glass sheet is on ceramic rolls. 
Once again, some device must be used to pick the glass sheet up from the 
ceramic rolls and bring it into contact with a suitable forming die in 
order to form it into a product having a complex shape. Transportation of 
glass sheet on ceramic rolls generally is acceptable for a glass product 
which is to be used as a side lite for an automobile, for example. This 
method is not known to work satisfactorily, however, for the production of 
a windshield quality glass product or for a relatively thin glass product. 
In all except the second method mentioned above to be known in the art for 
transporting a heated glass sheet in a glass shaping operation, the glass 
sheet is stopped in its transportation path and thereafter moved into 
engagement with some type of forming equipment. Thus, there is an 
interruption in the glass forming process which adds time, complexity and 
cost to the forming process. One complexity added by stopping the glass 
sheet is the need to determine or at least estimate the degree of cooling 
of the glass during the stop and to compensate for such cooling in the 
heating of the glass sheet. 
It is an object of this invention to provide a method and apparatus for 
forming a glass sheet in which the sheet can be formed while continuously 
in motion from a heating operation through the forming operation. It is 
another object of this invention that forming of a glass sheet be carried 
out concurrently with the transportation of that glass sheet toward the 
end of a glass processing line. It is a further object of this invention, 
according to certain preferred embodiments, to provide a method and 
apparatus for forming a glass sheet with dimensional control over the 
entire surface area thereof. 
These and other objects and features of the invention will be better 
understood in the light of the following disclosure and discussion 
thereof. 
SUMMARY OF THE INVENTION 
According to a first aspect of the invention, a method is provided for 
forming a glass sheet from a first condition into a second condition, the 
glass sheet having a selected thickness with first and second suffaces and 
having a selected peripheral configuration defining a peripheral edge. The 
forming method of the invention comprises the steps of: 
heating the glass sheet to a temperature at which it is formable from the 
first condition into the second condition; 
conveying the heated glass sheet by conveying means at a selected velocity 
along a path of travel to a forming station comprising a rotatable glass 
former including means defining an outer peripheral forming surface having 
at least a portion thereof with a defined shape substantially 
corresponding to the second condition of the glass sheet, the outer 
peripheral forming surface being in communication with a source of reduced 
pressure, wherein a leading edge of the glass sheet is brought into 
registered contact with a leading portion of the peripheral forming 
surface while the peripheral forming surface is being rotated by rotating 
means about an axis substantially transverse to the path of travel at a 
peripheral velocity substantially equivalent to the aforesaid selected 
velocity of travel of the glass sheet; and 
Progressively moving the first surface into close proximity with the 
defined shape portion of the outer peripheral forming surface by 
cooperation of the conveying means, the rotating means and the reduced 
pressure source, the glass sheet there being transformed into the second 
condition at least in part by external flid pressure acting against the 
second surface of the glass sheet while reduced pressure acts against the 
first surface and while the peripheral forming surface continues rotating. 
According to a second aspect of the invention an apparatus is provided for 
forming a glass sheet, as above, from a first condition into a second 
condition. The apparatus comprises, in combination, means for conveying 
the glass sheet at a selected velocity along a path of travel from a first 
position to a second position, the peripheral edge on the glass sheet 
having a leading edge portion while moving along the path of travel, means 
for treating the glass sheet, while being conveyed, so as to be formable 
while at the second position, means at the second position for forming the 
glass sheet into the second condition, such forming means including means 
defining an outer peripheral surface having at least a portion thereof 
with a defined shape substantially equivalent to the second condition of 
the glass sheet, means for rotating the outer peripheral surface about an 
axis transverse to the path of travel and at a peripheral velocity 
substantially equivalent to the selected velocity of the conveying means, 
the peripheral surface having a leading position during rotation, the 
conveying means conveying the leading edge portion of the glass sheet into 
registered contact with such leading position of the peripheral surface, 
the forming means including means communicating with a reduced pressure 
source and with the defined shape portion of the peripheral surface for 
causing the glass sheet to transfer along its first surface from the 
conveying means to the defined shape portion as a result of external 
pressure acting against the second surface while the aforesaid reduced 
fluid pressure acts against the first surface, the conveying means, 
rotating means and reduced pressure source cooperating for progressively 
moving the first surface of the glass sheet into close proximity with the 
defined shape portion of the outer peripheral surface of the forming 
means, the glass sheet being formed into the second condition while on the 
defined shape portion and while the forming means continues rotation.

DESCRIPTION OF PREFERRED EMBODIMENTS 
To aid understanding of the invention, a brief overview is first set forth, 
followed by a more detailed discussion of the preferred embodiments. It 
should be understood in the following discussion that reference to a sheet 
of glass is intended to be a generic reference to a slab or template of 
glass prior to, during or after being processed in accordance with the 
present invention. 
In accordance with the invention, a glass sheet is heated to a temperature 
at which it is formable by application of different gas pressures on 
opposite surfaces thereof. The heated glass sheet is conveyed on a path 
toward a forming area over which the heated glass sheet will be formed. 
While any suitable method and means may be used to heat the glass sheet 
and to transport it to the forming area, such as ceramic rolls, the 
preferred embodiments disclosed below employ gas hearth means to perform 
these functions in view of the better glass surface and optical qualities 
achieved thereby. Certain preliminary, simple glass forming can be 
performed by the heating and transport means according to known 
techniques. 
The heated glass sheet is transported to a forming station comprising a 
glass former having a forming area located on a modified conical surface, 
specifically, a portion of an exterior surface of a rotatable drum or 
mandrel or the like. The forming area is moved on an arcuate path about an 
axis of rotation of the glass former. The term "glass former" will be used 
herein to refer both specifically to the rotating forming drum or mandrel 
or surface thereof and, more generally, to the glass forming station or 
process step. The portion of the glass former defining the forming area is 
sufficiently porous that a differential pressure may be established 
thereacross when a reduced pressure is applied, e. g., from the interior 
of the glass former. The differential pressure is established across the 
forming area. 
A leading edge of the first surface of the heated glass sheet and a leading 
portion of the forming area are brought into registered contact with one 
another while both the aforementioned leading edge and the aforementioned 
leading portion are moving at the same velocity. Attachment of the glass 
sheet to the forming area is initiated because of the differential in 
pressure which is established between a portion of the forming area which 
engages the first surface of the glass sheet and the gas pressure, 
typically atmospheric or higher pressure, acting on the second surface of 
the glass sheet. 
Concurrent movement of the forming area and the glass sheet is continued so 
that the entire length of the glass sheet is incrementally moved from its 
path of conveyance into attachment with the forming area. Different gas 
pressures are at that point still acting on the first and second surfaces 
of the glass sheet. In this manner, the glass sheet can be formed 
progressively with full dimensional control on the forming area of the 
glass former often, and preferably, by the use of differential gas 
pressure only. In an embodiment of the invention directed to making formed 
glass sheets for a motor vehicle windshield manufacturing operation, such 
as in preferred embodiments described below, a formed glass sheet is made 
having variable height and size, and any of various simple or complex 
geometric shapes for example that shape commonly called a "flattened cone" 
shape, an S-shape, a saddle shape, etc. 
In accordance with preferred embodiments of the invention, rotation of the 
glass former is interrupted only briefly when the glass sheet has been 
completely formed on the forming area thereof by action of the 
differential gas pressure. The formed glass sheet is removed at that point 
from the glass former. 
Describing preferred embodiments now in greater detail and referring first 
to FIG. 1, a plurality of elongate glass sheets 10, 10 are conveyed 
sequentially through a heating lehr, or furnace, generally designated by 
the numeral 16. Each glass sheet has a first surface 12 and a second 
surface 14. In the case of this preferred embodiment, the first surface is 
an upper surface of the glass sheet and the second surface is a lower 
surface of the glass sheet. The glass sheets are conveyed through the 
heating lehr by a gas float mechanism in which gas flowing through a 
porous surface 18 supports the glass sheets above that surface. The glass 
sheets are moved along the porous surface by means of an edge roller drive 
(not shown) engaging an edge of the glass sheet. Although other means, 
such as ceramic rolls, could be used within the scope of the invention to 
heat and convey the glass sheets, the gas float is much preferred since it 
reduces glass surface contact with other solid surfaces which could damage 
the optical quality of the glass sheet. The heating lehr also has a 
sliding roof portion 20, the purpose of which will be described 
hereinbelow. Such glass conveying and heating means are conventional in 
the art. 
In the heating lehr 16, the glass sheet 10 is heated to a temperature at 
which the glass sheet is formable by application of different gas 
pressures on the first surface 12 and the second surface 14 thereof. The 
sheet typically is heated to a temperature in a range from 600.degree. C. 
to 640.degree. C. depending on the thickness of the glass sheet. When the 
glass is heated to a temperature in this range, the application of 
different pressures on the different surfaces thereof, the differential 
being in a range from 10 mm to 100 mm of water gauge, depending on 
thickness, usually will be sufficient to form the glass sheet into a 
desired configuration. Of course, it is apparent that the higher the 
temperature, the lower the differential in glass pressure required to form 
a heat softened glass sheet. 
The individual glass sheets 10 are conveyed toward a glass former, 
generally designated by the numeral 22. The glass former, which will be 
described in greater detail hereinbelow, and as may best be seen in FIG. 
2, is mounted for rotation by means of a pair of shafts 24 and 26. The 
shaft 26 is hollow so that a vacuum line 28 may be attached thereto for a 
purpose to be described hereinbelow. The shafts are connected to trunnions 
30 and 32, respectively, with the trunnion 32 also being hollow. The 
shafts 24 and 26 are mounted in sliding bearings 34 and 36, respectively, 
for both rotative and oscillating movement. Sliding bearings 34 and 36 are 
mounted for vertical up and down movement in paired guide posts 38--38 and 
40--40, respectively. 
As seen in FIG. 1, the glass former 22 is rotated by means of a pulley 42 
mounted on the end of the shaft 24. The pulley in turn is rotated by a 
belt 44 driven by a suitable electric motor (not shown). The direction of 
rotation of the glass former in the preferred embodiment is in one 
direction only, that being in the direction of arrow A of FIG. 1. During 
this rotation, as different portions of the surface of the glass former 
are moved down toward the porous surface 18 of the heating lehr 16, the 
sliding bearings 34 and 36 will move vertically downward or upward as 
required in their associated guide posts 38--38 and 40--40 to accomplish 
the glass bending action which will be described below. 
The configuration of the glass former 22 is best understood by reference to 
FIGS. 3 and 5. Basically, the glass former defines a forming area 50 over 
which a glass sheet will be formed. As shown in outline form in FIG. 2, 
glass sheets of substantially different sizes but of similarly curved 
forms can be formed on the same glass former. One such shape is generally 
identified by the letter X and another such shape is generally identified 
by the letter Y. Glass sheets of these two shapes are shown also in FIG. 4 
being conveyed on the porous surface 18 of the heating lehr in a direction 
toward the glass former. Thus, the glass former may be used to shape 
different configurations of glass, that is, larger and smaller 
configurations, so long as the desired radius of curvature for each formed 
glass sheet is the same. If different radii of curvature are required, a 
different modified conical drum would be used as the glass former. The 
conical drum of the glass former is designed and constructed as a separate 
and easily interchangeable unit so that it can be easily moved in and out 
of position. This interchangeability permits rapid tool change, a very 
significant advantage of the invention. 
As best seen in FIG. 5, the forming area 50 of the glass former 22 is 
porous. Thus, a differential pressure may be applied across the forming 
area 50 by the establishment of a vacuum, i.e., a sub-atmosphereic 
pressure, in the interior of the glass former 22. The vacuum is 
established by drawing a vacuum on vacuum line 28 which in turn results in 
a vacuum being drawn on hollow shaft 26, the hollow trunnion 32, and the 
interior of a slide valve 52 shown in FIGS. 5 through 11. The slide valve 
consists of a stationary shutter 54 which comprises open shutter areas 
56--56 and a closed shutter area 58. The interior of the glass former 22 
then acts as a rotating slide valve 60 which has open valve areas 62--62 
and a closed valve area 64. 
With reference to FIG. 5, it is seen that there are six open valve areas 
62--62 associated with the forming area 50 of the glass former 22. The six 
open valve areas define six independent vacuum chambers 66--66 which are 
separated from one another by partitiqn walls 68--68 and walls 70--70 
connected to a wall segment with constant radius 72 which defines the 
nonforming area of the glass former. Although in FIG. 5 is shown six 
separate vacuum chambers, the interior of the glass former can similarly 
be divided, depending on need, into any number of independently activated 
or controlled vacuum chambers. 
As shown in FIG. 5, with the glass former 22 rotating in the direction of 
arrow A of that FIG., a first open valve area 62 of a first vacuum chamber 
66 has moved beyond the closed shutter area 58, thereby connecting the 
first vacuum chamber 66 to the source of vacuum. As additional rotation of 
the glass former takes place, additional open valve areas 62 are also 
moved beyond the closed shutter area 58 so that they also will be 
connected to the source of vacuum. The open arc of valve area 56 of the 
stationary slide valve member 54 is sufficient so that all of the open 
valve areas 62--62 may pass beyond the closed shutter area 58 of the 
stationary slide valve member 54 and thereby have all of the vacuum 
chambers 66--66 connected to the forming area 50 also connected to the 
vacuum source. 
In operation, as may best be understood by reference to FIGS. 5 to 9, a 
heated glass sheet 10 is conveyed over the porous surface 18 of the 
heating lehr 16 on a path toward the forming area 50 of the gass former 22 
over which the heated glass sheet will be formed. As has been described 
above, the forming area 50 is located on a modified conical surface formed 
on an exterior surface of the rotatable glass former 22. Consistent with 
an explanation given above in this regard, it should be understood that 
the term "glass former" is used herein both specifically in reference to 
the conical drum component and, more generally, in reference to that 
component in association with support means, vacuum and valve means, 
rotating means and like associated components, such as those described 
herein. When the conical drum of the glass former is rotated, the forming 
area moves on an arcuate path about the axis of rotation of the glass 
former. It can be seen that the axis of rotation is substantially 
transverse to the direction of travel of the glass sheet along surface 18 
of the heating lehr. 
Reference is now made to FIG. 5. In accordance with the teachings of the 
method of our invention, a leading edge 80 of the glass sheet 10 is 
brought into registered contact with a leading portion 82 of the forming 
area 50 of the glass former 22. The location on the surface of the conical 
drum at which the leading edge 80 of the glass sheet makes contact will 
effect the orientation and location of the entire glass sheet thereon. 
Thus, by registered contact is meant, generally, that the angular position 
of the glass former and the glass sheet are such that the glass sheet will 
be taken up into a preselected location on the conical drum. Typically, 
the center of the glass sheet will wind up in the center of the glass 
former during the glass forming operation. Different lengths of glass, of 
course, will cover different lengths of the forming area of the glass 
former. The shorter the glass sheet, the less forming area will be used, 
but the glass sheet still will be located centrally of that forming area. 
The exact registered contact may be assured by controlling the rate of 
rotation of the glass former as well as the rate of advancement of the 
glass sheet. Commercially available means for coordinated actuation and 
advancement of different components of forming and processing lines have 
long been well known to the skilled of the art and their application in 
and to the present invention will be readily apparent in view of the 
present disclosure. 
Again, with reference to FIG. 5, the leading edge 80 of the upper surface 
12 of the glass sheet 10 is brought into registered contact with the 
leading portion 82 of the forming area 50 of the glass former. The forming 
surface should be rotating at the time of contact with the glass and the 
leading edge and the leading portion should be moving at the same, i. e. 
equivalent, velocity to avoid shearing or other damage to the glass. As 
seen in FIGS. 5 and 6, the first open valve area 62 is exposed, causing 
the first vacuum chamber 66 to be evacuated, thereby resulting in the 
attachment of the glass sheet 10 to the forming area. This attachment 
occurs because a differential pressure is established between the interior 
of the first vacuum chamber 66 which applies a vacuum to the first or 
upper surface 12 of the glass sheet and the second or lower surface 14 of 
the glass sheet which is subjected to at least atmospheric pressure and, 
typically, to the increased pressure of a positive flow of air through the 
porous surface 18. Thus, as shown in FIGS. 6 and 7, initial attachment of 
the glass sheet to the glass former is achieved. 
During the rotation of the glass former 22, as shown in FIGS. 5 to 11, the 
sliding roof portion 20, and similarly constructed side seals (not shown), 
of the lehr 16 are kept in close proximity to the surface of the glass 
former in order to keep the heat in the lehr. This action may be 
accomplished by counterweighting the sliding roof and side seals in a 
manner known in the art so that they are biased slightly to positions in 
close proximity to the surface of the glass former. 
FIG. 7 shows vacuum now applied to two of the vacuum chambers 66--66 of the 
glass former 22 because of the aforementioned operation of the slide valve 
52. In such a manner, concurrent movement of the forming area 50 and the 
glass sheet 10 is continued so that the entire length of the glass sheet 
is incrementally moved from its path of conveyance and is attached to and 
moves with incremental sections defining the forming area 50. This action 
occurs because of the establishment of a differential gas pressure acting 
between the forming area engaging the first surface 12 of the glass sheet 
and the second surface 14 of the glass sheet. The positive pressure of the 
gas flow through the porous surface 18 of the glass hearth can assist the 
pickup of the glass sheet by vacuum at the rotating forming surface. This 
advantage is another reason a gas hearth heating means is preferred. 
As shown in FIGS. 8 and 9, continued rotation of the glass former 22 causes 
additional vacuum chambers 66--66 to be connected to the vacuum source so 
that the glass sheet 10 is picked up and formed by a bending action onto 
the forming area 50 in a progressive, incremental manner with the forming 
on the surface being accomplished solely by the application of gas 
pressure. Since no solid force applying tools are used in the glass 
forming process according to the illustrated preferred embodiment, the 
formed glass sheet will not have any tool marks thereon. It will be 
recognized by the skilled in the art in view of the present disclosure 
that alternative, less preferred embodiments of the invention may employ 
glass forming means in adition to such differential fluid pressure. Thus, 
for example, the glass former may comprise peripheral rings, frames, 
rollers, clamps, or the like acting simultaneous with or subsequent to the 
fluid pressure differential to form the glass sheet. In addition, it may 
be desirable to employ means to control the temperature of the glass sheet 
such as, for example, cooling bars or heating means, after it has been 
picked up by the glass former. 
As stated above, a differential pressure of between about 10 mm and 100 mm 
of water gauge is usually sufficient to form the glass on the forming area 
50 of the glass former 22. The glass is formable at these pressures when 
it has been heated to a temperature generally in a range from 600.degree. 
C. to 640.degree. C. This applies, usually, for glass having a thickness 
in a range of 3 millimeters or less. Thicker glass sheets typically 
require more pressure or more bending time, or need to be heated to a 
higher temperature in order to soften them to a greater extent. The 
heating and bending schedules and the pressures required to obtain the 
required forming can be determined or at least closely approximated 
mathematically by the skilled of the art using generally known 
heating/cooling rates, conveying speeds, etc. Also, they can be worked out 
easily by empirical methods such as simply carrying out a few test 
operations on individual glass sheets to achieve the best forming 
conditions. The forming condition variables include the differential 
pressure placed on the glass sheet, the bending or forming time required, 
and the temperature to which the glass sheet is heated. 
In the preferred embodiment of the invention described above the glass 
sheet is formed with full dimensional control on the forming area of the 
glass former by the action of differential gas pressure alone. This means 
that glass sheets will be repeatedly formed to the same accurate 
dimensional tolerances. This control is achieved because the forming area 
50 of the glass former is rigid and remains in the same position time 
after time of use. 
The removing of a formed glass sheet 10 from the forming area 50 of the 
glass former 22 will best be understood by reference to FIGS. 1, lA, 10 
and 11. In FIGS. 1 and lA, a glass pickup device, generally designated by 
the numeral 86, is shown. This device includes a vacuum pickup head 88 
having a vacuum line 90 connected thereto so that a vacuum may be drawn on 
the interior portion of the vacuum pickup head. The face of the vacuum 
pickup head coming in contact with the glass sheet is porous so that a 
pressure differential may be applied to pick up a glass sheet. A pair of 
support arms 92--92 (only one being shown in the drawings) is provided to 
support and move the vacuum pickup head 88. An upper portion of each of 
the support arms is pinned at shaft 94 to the vacuum pickup head while a 
lower portion of each of the support arms is pinned at shaft 96 to a base 
member 98 for pivotal movement with respect thereto. 
The operation of the glass pickup device 86 is as follows. When the forming 
area 50 of the glass former 22 has formed the glass sheet as desired, the 
glass former is rotated to the position depicted in FIG. 10 and stopped. 
It should be noted here that the glass forming process carried out by 
fluid pressure differential at the rotating surface of the glass former is 
carried out while the glass is moving and there is no stoppage involved. 
Thus, an advantage of the present invention occurs in that less time is 
required in that forming process. 
At the point shown in FIG. 10, the pickup device 86 is moved into its glass 
pickup position. At this point, vacuum is applied to the vacuum pickup 
head 88 and concurrently the vacuum is released and slight pressure is 
supplied to the interior of the glass former 22. Thus, the glass sheet 10 
is transferred in its bent condition from the glass former 22 to.the glass 
pickup device 86. The size and configuration of the gap between the glass 
former and the pickup head should correspond generally to the size and 
shape of the formed glass sheet. To preserve surface and optical quality, 
however, the gap should not be such that the glass is compressed between 
those fixtures. 
A pulley 100 is driven by a pulley belt 102 whereby the support arms 92--92 
of the glass pickup device are pivoted to the dotted position shown in 
FIG. 1A. The vacuum pickup head 88, of course, carries the glass sheet 10. 
A drive chain conveyor, generally designated by the numeral 104 in FIG. 1, 
is used to carry the formed glass sheet 10 away from the forming 
operation. This is accomplished by pivoting the glass pickup device 86 to 
the dotted position shown in FIG. 1. Once in that position, the vacuum is 
released in the vacuum pickup head 88. The released glass sheet drops a 
short distance by gravity to rest on the drive chain conveyor. The drive 
chain conveyor transports the glass sheet to other work stations where 
additional operations may be carried out thereon. For example, if it is 
desired to temper the formed glass sheet, the drive chain conveyor may 
convey the glass sheet 10 directly to a tempering station where the 
temperature of the glass sheet is reduced at a rapid rate in order to 
temper the same. The drive chain conveyor may also be a conveyor for 
transporting the glass sheet through an annealing process in which the 
glass sheet is slowly cooled under controlled conditions to form an 
annealed glass product. The vacuum pickup head may be synchronized to the 
glass former by any of various means known to the skilled of the art. 
Thus, electrical controls may be used or, more preferably, the components 
may be mechanically interlocked. 
It is a feature and an advantage of this and like preferred embodiments of 
the invention that a glass sheet is formed and a glass product is produced 
thereby with dimensional control over its entire surface area without any 
intermittent or reciprocating motion applied to the glass sheet during its 
forming process. It is another advantage that a glass sheet can be formed 
and a glass product produced thereby with dimensional control over its 
entire surface area without the glass sheet being contacted by peripheral 
rings or frames during the forming or transportation of the glass sheet. 
The invention may be practiced to produce a wide variety of glass products. 
These products may be either tempered or annealed glass products through 
the use of peripheral equipment in accordance with additional (separate or 
integrated) processing steps known to and uunderstood by the skilled of 
the art. 
The invention has particular utility in forming thin glass windshields. 
Thin glass windshields typically are formed of two sheets of glass, each 
sheet having a thickness less than about 3 millimeters. As is known by 
those skilled in the art, two glass ply laminated windshields are formed 
by bending together an inner glass sheet and an outer glass sheet. Prior 
to the present invention, the two glass sheets would be uniquely matched 
to each other, since the bending operation would be carried out on paired 
glass sheets and would result in a unique shape for each pair of bent 
glass sheets. Therefore, if one of the pair of bent glass sheets were 
damaged or broken, the other would be discarded as well. 
In accordance with the present invention, however, a glass sheet can be 
formed with dimensional control over its entire surface area so that glass 
sheets of identical curvature may be formed one after the other. Thus, the 
method may be used to first produce the outer glass sheet for a 
laminated-type windshield, and then subsequently used to produce an inner 
glass sheet for the laminated-type windshield construction. Because of the 
dimensional control, any inner glass sheet may be matched with any outer 
glass sheet in order to form a laminating pair to form a laminated 
windshield. 
Additionally, the invention may be used to form a complex curved thin glass 
sheet into a particular shape. The thin glass sheet may subsequently be 
laminated to another glass sheet or be chemically tempered, or be 
subjected to combinations of those additional processing steps, in order 
to produce various types of glass products. Thus, precision bent complex 
glass sheets may be produced for use in automotive, architectural, and 
industrial applications. 
According to alternative preferred embodiments of the invention, a glass 
sheet is formed having a complex geometric shape commonly called a "saddle 
shape" or the surface known as a hyperbolic paraboloid with variable 
dimensions. According to such embodiments, the forming area of the glass 
former has at least one zone wherein the surface is offset from the curved 
plane defining the main surface area. Such zone can define either a 
convexity or, more typically, a concavity. A concavity here means a zone 
depressed inwardly toward the axis of rotation of the glass former and a 
convexity is the reverse. The dislocation can be neither so abrupt or 
sharp nor so large in any direction as to interfere overly with the fluid 
pressure differential attachment of the glass sheet to the glass former. 
It will be understood also, in view of this disclosure, that the face of 
the vacuum pickup head 88 in FIG. 1A must accommodate any convexity 
present in the glass forming surface of the glass forming (and 
correspondingly present in the glass sheet). If the glass former 22 in 
FIG. 1 has a concave zone, the face of the vacuum pickup head should 
present a corresponding convexity so as to preserve the configuration 
imparted to the glass sheet by such concave zone. This would be a concern, 
however, generally only if the glass is still at a forming temperature 
when transferred to the vacuum pickup head. If the glass temperature is 
suitable, it may be possible to preserve the glass configuration without 
the aforesaid corresponding convexity in the face of the pickup head by 
having the face non-porous in that area, so as not to create a vacuum in 
that area. Generally, however, it is preferred that the pickup head 
provide a convexity corresponding to each glass former concavity to 
achieve better uniformity in the formed glass sheets. 
As best seen in FIGS. 12-15, the forming area 250 of the glass former 222 
has associated therewith a zone 251 which is depressed inwardly toward the 
axis of rotation of the glass former. In the preferred embodiment shown, 
the zone is a single continuous zone of substantial size located generally 
centrally within the forming area. The number and location of such zone(s) 
is controlled by the shape one desires in the finished glass product. The 
proper placement of such zone(s) produces a glass sheet with a desired 
complex geometry. 
As shown in FIG. 14, a portion of the glass sheet 210 is formed into the 
zone 251 of the forming area 250 by the differential gas pressure 
discussed above. Formation of the the glass sheet in this zone gives a 
complex geometric shape to the glass sheet. A formed glass sheet 284, 
formed in accordance with the teachings of this preferred embodiment of 
this invention, is shown in FIG. 16. The formed glass sheet 284 is used, 
as shown in FIG. 17, as a windshield for a motor vehicle 285. The formed 
glass sheet 284 has a "saddle shape" form as viewed from the exterior of 
the motor vehicle. The concave curvature of this shape runs generally from 
the top to the bottom of the formed glass sheet. As has been discussed 
above, the desired shape of the glass product can be altered by the 
number, size and location of the zone or zones 251 placed in the forming 
area 250 of the glass former 222. The glass sheet 210 is transferred in 
its bent condition from the glass former 222 to the glass pickup device 
286. This transfer action is shown in FIG. 15. This figure shows that the 
pickup device is formed to the shape of the surface of the glass sheet 
being picked up. 
According to yet other preferred embodiments of the invention, secondary 
forming of the glass sheet is performed by a pickup and forming surface of 
a secondary glass former brought into contact with the glass sheet after 
it has been formed on the (primary) glass former. Of course, the glass 
must be still, or must be brought again to, a forming temperature. The 
pickup and forming surface of the secondary glass former is sufficiently 
porous that a differential pressure may be established thereacross when a 
pressure below atmospheric pressure is applied from an interior surface of 
the secondary glass former. The pickup and forming surface of the 
secondary glass former also has at least one concave region, i.e., at 
least one zone thereon which is depressed inwardly toward the interior 
thereof. Typically, the secondary glass former can be a modified version 
of the vacuum pickup head disclosed and described above. Thus, following 
the principles set forth above regarding operation of the vacuum pickup 
head, a differential pressure is established across the pickup and forming 
surface of the secondary glass former. The differential pressure is 
released across the forming area of the primary glass former 
(corresponding to glass formers 22 and 222 above), whereby the glass sheet 
is transferred from the forming area of the primary glass former to the 
pickup and forming surface of the secondary glass former. The glass sheet 
can be formed in this way with full dimensional control on the pickup and 
forming surface of the secondary glass former by the use of differential 
gas pressure to produce a formed glass sheet having a complex three 
dimensional bent shape. 
In accordance with a preferred embodiment, the secondary glass former then 
can be moved to a drop off station. At the drop off station, the 
differential pressure across the pickup and forming surface of the 
secondary glass former is released so that the completely formed glass 
sheet is delivered to the drop off station. 
An embodiment of the invention, wherein a formed glass sheet is removed 
from the forming area of the glass former and further formed, is now 
discussed with reference to FIGS. 18 to 21. In the embodiments discussed 
above with reference to FIGS. 1 and 1A, glass removal device 86 includes a 
vacuum pickup head 88 having a vacuum line 90 connected thereto so that a 
vacuum may be drawn on the interior portion of the vacuum pickup head. In 
the embodiment of FIGS. 18-20, a secondary glass former 386 corresponds to 
pickup device 86 discussed above. It differs in that vacuum pickup head 
388 has a pickup and forming surface 391, best seen in FIGS. 19 and 20. 
The vacuum pickup head coming in contact with a glass sheet 310 is porous 
so that a pressure differential may be applied to pick up and form the 
glass sheet. 
The operation of the secondary glass former 386 is as follows. When the 
forming area 50 of the primary glass former 22 has formed the glass sheet 
as desired, the primary glass former is rotated to the position depicted 
in FIG. 10 and briefly stopped. It should be noted here that the glass 
forming process carried out on the primary glass former can be (and 
preferably is) carried out while the glass is moving with no stoppage 
involved, as discussed above. Thus, this embodiment shares the above noted 
advantage that less time is required in the forming process carried out on 
the primary glass former. 
At the point shown in FIG. 10, the secondary glass former 386 is moved into 
its glass pickup position. At this time, vacuum is applied to the vacuum 
pickup head 388 and concurrently the vacuum is released and slight 
pressure is supplied to the interior of the primary glass former 22. Thus, 
the glass sheet 310 is transferred from the primary glass former 22 to the 
secondary glass former 386. This transfer action is shown best in FIGS. 18 
to 20. 
FIG. 20 shows that the pickup and forming surface 391 of the secondary 
glass former 386 has at least one zone 393 thereon which is depressed 
inwardly toward the interior surface thereof. In the preferred embodiment 
illustrated, the zone is a single continuous zone of substantial size 
located generally centrally in the pickup and forming surface. The number, 
size and location of such zone(s) is controlled by the shape one desires 
in the finished glass product. The placement of such zone(s) permits 
production of a three dimensional formed glass sheet with complex 
geometry. 
When the secondary glass former 386 is in the position shown in FIG. 19, a 
differential pressure is established across the pickup and forming surface 
391 of the secondary glass former. The differential pressure is 
established by drawing a vacuum in the vacuum pickup head 388. At this 
time the differential pressure is released across the forming area 50 of 
the primary glass former 22, whereby the glass sheet 310 is transferred 
from the forming area of the primary glass former 22 to the pickup and 
forming surface of the secondary glass former 386. The glass sheet can be 
formed in this way with full dimensional control on the pickup and forming 
surface of the secondary glass former and by the use of differential gas 
pressure only to produce a formed glass sheet having a three dimensional 
bent shape with complex geometry. 
As shown in FIG. 20, a portion of the glass sheet is formed into the zone 
393 of the pickup and forming surface 391 of the secondary glass former 
386 by the differential gas pressure discussed above. Formation of the 
glass sheet in this zone gives a complex three dimensional form to the 
glass sheet. 
A formed glass sheet with complex geometry, generally identified by the 
numeral 395 in FIG. 21, formed in accordance with the teachings of the 
preferred embodiment of FIGS. 18-21, is used as a back lite for a motor 
vehicle 397. The formed glass sheet has a convex form as viewed from the 
exterior of the motor vehicle. The convex form runs generally from the top 
to the bottom of the formed glass sheet. As has been discussed above, the 
desired shape of the glass product can be altered by the number, size and 
location of the zone or zones 393 placed in the pickup and forming surface 
391 of the secondary glass former 386. 
It should be noted that vacuum pickup head 388 has hinge means 399 at its 
center. It will be apparent to the skilled of the art in view of the 
present disclosure that the vacuum pickup heads 86 and 286 of above 
described embodiments also may have such feature. Hinge means 399 allows 
opening of the pickup head, whereby scuffing of the glass during transfer 
from the primary glass former by contact with the face of the pickup head 
can be reduced or entirely avoided. 
According to yet other preferred embodiments of the invention, a glass 
sheet can be formed to have a complex geometric shape commonly referred to 
as "a complex shape with an S shaped vertical centerline" or the surface 
known as "a complex three dimensional shape containing the foci of 
variable curvature on opposite sides of the surface." A preferred such 
embodiment is described below with reference to FIGS. 22-29. As 
illustrated therein, glass former 422 defines a forming area 450 over 
which a glass sheet 410 will be formed into glass sheet product 484. As 
shown in outline form in FIGS. 22 and 23, glass sheets of substantially 
different sizes but of similarly curved forms can be formed on the same 
primary glass former. One such glass shape is generally identified by the 
letter X and another such glass shape is generally identified by the 
letter Y. Thus, the glass former may be used to shape different 
configurations of glass, that is, larger and smaller configurations, so 
long as the radii of curvature for each glass sheet are the same. If 
different radii of curvature are required, a different, modified conical 
drum generally will be required. The primary glass former 422 is designed 
and constructed as a separate and easily interchangeable unit so that it 
can be moved easily in and out of position, as were the embodiments 
described above. 
As best seen in FIGS. 23, 24 and 25, the forming area 450 of the primary 
glass former 422 has associated therewith a small, elongated zone 451 
which is depressed inwardly toward the axis of rotation of the primary 
glass former. As in embodiments described above, the surface zone 451 also 
could be a convexity, rather than a concavity, so long as it did not 
extend radially outwardly so abruptly or so far that it interfered with 
the vacuum attachment of the glass sheet to the forming surface. In the 
preferred embodiment, the zone 451 is a single, elongated concave zone 
which is narrow in width and located near one of the edges of the forming 
area. The number, size and location of such zone(s) is controlled by the 
shape one desires in the finished glass product. The placement of such 
zone(s) produces a complex geometric shape in a formed glass sheet. 
The forming area 450 of the glass former 422 is porous. In this manner, a 
differential pressure may be applied across the forming area 450 by the 
establishment of a vacuum in the interior of the primary glass former 422. 
The vacuum is established by drawing a vacuum on vacuum line 28 which in 
turn results in a vacuum being drawn on hollow shaft 26, the hollow 
trunnion 32, and the interior of a slide valve 52, which corresponds to 
those elements of the embodiment shown in FIGS. 5 through 11. The slide 
valve operates in accordance with principles described above. As shown in 
FIGS. 24 and 25, a small portion of the glass sheet 410 is formed into the 
zone 451 of the forming area 450 by the differential as pressure. 
Formation of the glass sheet in this zone means that the formed glass 
sheet will have a first area of three dimensional shape bent in a first 
direction. This is the first bend made to achieve a finished product 
having an "S" shape profile along some sections. 
The further forming and removing of a formed glass sheet 410 from the 
forming area 450 of the primary glass former 422 will best be understood 
by reference to FIGS. 26 and 27. In the embodiment of FIGS. 26 and 27 (as 
in the embodiment of FIGS. 18-20) a secondary glass former 486 corresponds 
to pickup device 86 of FIGS. 1 and lA. Vacuum pickup head 480 has a vacuum 
line 490 connected thereto so that a vacuum may be drawn on the interior 
portion of the vacuum pickup head. A pickup and forming surface 491 of the 
vacuum pickup head comes in contact with the glass sheet 410 and is porous 
so that a pressure differential may be applied to pick up and form the 
glass sheet. 
The operation of the secondary glass former 486 is as follows. When the 
forming area 450 of the primary glass former 422 has formed the glass 
sheet as desired, the primary glass former is rotated to a position 
corresponding to that depicted in FIG. 10 and stopped for a brief period 
of time. It should be noted here that the glass forming process can be 
carried out on the primary glass former while the glass is moving without 
stopping involved. Thus, this embodiment shares the aforesaid advantage 
that less time is required in the forming process carried out on the 
primary glass former. 
At the point corresponding to that of FIG. 10, the secondary glass former 
486 is moved into its glass pick up position. At this time, vacuum is 
applied to the vacuum pickup head 488 and concurrently the vacuum is 
released and slight pressure can be supplied to the interior of the 
primary glass former 422. Thus, the glass sheet 410 is transferred from 
the primary glass former 422 to the secondary glass former 486. 
FIG. 26 shows that the pickup and forming surface 491 of the secondary 
glass former 486 has at least one zone 493 thereon which is depressed 
inwardly toward the interior surface thereof. As described above, the 
surface 491 may comprise of a convexity in addition to or in lieu of 
concavity 493. Any such convexity(ies) should not extend outwardly from 
surface 491 so far or so abruptly as to interfere with the vacuum pick up 
and forming of glass sheet 410. Also, the surface 450 of the primary glass 
former would have to provide a corresponding concavity to receive the 
convexity of surface 491. In that case, of course, the surface of such 
concavity in the primary glass former preferably would be in communication 
with the aforesaid source of reduced pressure, whereby the desired glass 
formation in that zone already would have been achieved by the time vacuum 
pickup head 488 took the glass sheet from the primary glass former. 
In the preferred embodiment of FIGS. 26 and 27, the zone 493 is a single 
continuous zone of substantial size located generally centrally in the 
pickup and forming surface. The number, size and location of such zone(s) 
is controlled by the shape one desires in the finished glass product. The 
proper placement of such zone(s) can produce a formed glass sheet having 
an "S" shaped cross-section. 
When the secondary glass former 486 is in the position shown in FIG. 10, a 
differential pressure is established across the pickup and forming surface 
491 of the secondary glass former. The differential pressure is 
established by drawing a vacuum on the vacuum pickup head 488. At this 
time the differential prssure is released across the forming area 450 of 
the primary glass former 422, whereby the glass sheet 410 is transferred 
from the forming area of the primary glass former to the pickup and 
forming surface of the secondary glass former. The glass sheet is thereby 
formed with full dimensional control on the pickup and forming surface of 
the secondary glass former by the use of differential gas pressure only to 
produce a completely formed glass sheet having a second area of three 
dimensional bent shape thereon in a direction away from the aforesaid 
first direction, so that the formed glass sheet has an "S" shaped profile 
along some sections. 
As shown in FIG. 27, the edges of the glass sheet 410 are not necessarily 
formed into a convex or concave zone. Thus, the edges of the formed glass 
sheet 484 may or may not have an "S" shaped vertical cross section in the 
preferred embodiment. 
A formed glass sheet 484, formed in accordance with preferred embodiment of 
FIGS. 22-27 is shown in FIGS. 28 and 29. The formed glass sheet 484 is 
used, as shown in FIG. 29, as a windshield for a motor vehicle 485. The 
formed glass sheet has an "S" shaped cross section through its vertical 
centerline. As viewed from the exterior of the vehicle, the top part of 
the windsheld is convex while the bottom part of the windshield is 
concave. As has been discussed above, the desired shape of the glass 
product can be altered by the number, size and location of the deflection 
zone or zones placed in the forming area of the primary glass former and 
the number, size and location of the deflection zone or zones of the 
forming surface of the secondary glass former. 
While particular embodiments of the invention have been illustrated and 
described, it will be obvious to those skilled in the art that various 
changes and modifications may be made without departing from the 
invention, and it is intended to cover in the appended claims all such 
modifications and equivalents as fall within the true spirit and scope of 
this invention.