Method of producing curved laminated glass panels

The method of manufacturing curved laminated glass panels comprises overlaying at least two sheets of flat strengthened glass. Adjacent edges of the at least two sheets are sealed along a predetermined extent thereon to form a closed space between these two sheets. An opening is formed into the closed space along one edge of the glass sheets and glass laminating material is poured into the opening to fill the space between the two sheets. The opening is then closed and the at least two sheets are compressed in a preselected curvature form until the sheets assume the curvature of the form. Finally, the two sheets are held in the preselected curvature until the glass laminating material substantially cures.

BACKGROUND OF THE INVENTION 
The present invention relates to laminated glass panels and, more 
particularly, to a method of manufacturing curved laminated glass panels 
from flat sheets of heat strengthened or tempered glass. 
Generally, methods for forming curved laminated glass panels such as, for 
example, glass panels for use as windshields, require that the glass 
sheets used in forming the panels be curved prior to the lamination 
process. These processes for forming pre-curved glass sheets are generally 
expensive. In addition, it is difficult to strengthen or temper preformed 
glass prior to lamination. For this reason, most curved glass laminating 
methods use annealed glass for the laminating process. However, curved 
laminated glass products made of annealed glass are subject to breakage 
upon small impacts or twisting. Accordingly, systems requiring tempered or 
strengthened pre-curved glass for laminating require very expensive curve 
glass tempering or strengthening apparatus. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a method for forming 
curved laminated glass panels which overcomes the disadvantages of prior 
art methods. 
It is another object of the present invention to provide a method for 
forming curved laminated glass panels from tempered or strengthened flat 
glass sheets. 
In a preferred form of the invention, a curved laminated glass panel is 
formed from flat sheets of tempered or strengthened glass. The method 
includes the step of placing at least two sheets of flat strengthened 
glass in an overlaying position with adjacent edges of the glass spaced 
apart by preselected dimensions. This spacing may be achieved by using 
double sided tape along the edges of the glass to separate the glass and 
to hold them together during the forming process. The glass sheets are 
sealed around the majority of the edges of the sheets to form a closed 
space between the at least two sheets. An opening is maintained along at 
least one edge of the sheets through which a laminating material is 
poured. The laminating material is allowed to flow into the space between 
the two sheets and to completely fill the space. After the laminating 
material has filled the space between the two sheets, the final opening is 
closed and the two sheets are placed in a pre-curved forming apparatus. 
The forming apparatus includes a pair of mating curved surfaces for 
compressing the glass panels. The form is closed on the glass panel to 
force the pair of flat sheets to conform to the shape of the form and the 
form is maintained in a closed position compressing the panels until the 
laminating material is substantially cured. After the laminating media is 
cured, the form is removed and the resultant curved laminated glass panel 
is lifted from the form. 
Applicant has found that this method results in a laminated glass panel 
which maintains substantially the shape of the form. While the panels have 
some predetermined amount of spring back towards a flat shape upon removal 
of compression, this amount of spring back can be compensated by adjusting 
the shape of the form. Thus, a predetermined degree of curvature of a pair 
of flat glass sheets can be achieved in a laminated glass product.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring first to FIG. 1A, there is shown a laminated glass panel 8 
comprising a pair of flat glass sheets 10 and 12 spaced apart by a 
laminating media or lamination resin 14. FIG. 1B illustrates the same type 
of laminated glass construction but with the upper and lower glass sheets 
10 and 12 being curved to a preselected radius to form a curved laminated 
glass panel. From the drawings in FIGS. 1A and 1B, it will be apparent 
that the construction of flat laminated glass is the same as the 
construction of the curved laminated glass except for the shape of the 
resultant panel. In the illustrative form of the invention, the curved 
glass panel of FIG. 1B is formed by placing the flat glass panel of FIG. 
1A into a forming apparatus substantially as shown in FIG. 2. The forming 
apparatus includes a male or upper form portion 16 and a female or lower 
form portion 18. The glass panel 10 is placed in the form and the upper 
portion 16 is closed on a lower portion 18 to compress the glass panel as 
illustrated by FIG. 3. 
The curved shape of the laminated glass panel is achieved by placing the 
flat glass panel into the form prior to the laminating media 14 being 
cured. When the stacked glass structure 8 is compressed between the form 
portions 16 and 18 and held in that position until the laminating media is 
substantially cured, it has been found that the resultant laminated 
product will maintain the curved shape. Typically, the pressure required 
to compress the tempered or strengthened glass sheets 10 and 12 has been 
found to be from ten to fifteen pounds per square inch. The assembled 
glass panel 8 is maintained in the forming apparatus until the laminating 
media 14 is between 85-90% cured. At that point, the glass panel may be 
removed from the mold and will maintain substantially the same shape as 
the form. As mentioned previously, there is a predetermined amount of 
spring back when the form is released but that amount of spring back is 
compensated for by having a slightly overcurved set of forms 16 and 18. 
The process of forming a curved laminated glass panel as described above 
generally includes additional detailed steps in preparing the glass and in 
inserting the laminating media between the spaced sheets of flat glass. 
For example, the flat glass sheets used for forming the curved glass panel 
are normally inspected to eliminate those sheets having scratches, cords, 
stones, spots, or distortion and being of improper size. The glass panels 
are then washed and cleaned using appropriate cleaners to make sure that 
all dust and grease or other contaminants are removed from the glass. 
Commercial glass washer and alcohol may be used in the cleaning process. 
After cleaning, a spacer tape 20 is placed along the edge of the lower 
glass sheet 12 as is shown in FIG. 4. The spacer tape is preferably a 
double-sided tape which allows the upper and lower glass sheets 10 and 12 
to be bonded together along their edges. The tape is placed along the edge 
all around the lower glass sheet 12 but leaving a small air escape vent 21 
at corners of the glass sheet. Typically, the air escape vent may be a 
break in the tape of approximately 1/8 inch wide. 
After the spacer tape 20 has been placed along the edges of the lower sheet 
12, the upper sheet 10 is aligned with and placed on top of the lower 
sheet. To facilitate the aligning of the edges of the upper and lower 
glass sheets, the backing paper 23 on the upper side of the double sided 
spacer tape 20 may be left in place so that the upper glass sheet 10 may 
be moved with respect to lower glass sheet 12. Once the two glass sheets 
are aligned, the paper backing 23 on the upper side of the double sided 
spacer tape may be pulled off without disturbing the positioning of the 
upper glass sheet 10. The upper glass sheet 10 can then be compressed down 
onto the lower glass sheet to bond the two sheets together along their 
edges. A further sealing process can be implemented by using another tape 
layer overlapping the edges of the upper and lower glass sheets 10 and 12. 
Referring to FIG. 5, there is shown a partial cross-sectional view of the 
upper and lower glass sheets 10 and 12, respectively, with the spacer tape 
20 between the glass sheets and an outer sealing tape 22 overlapping the 
edges of the glass sheets. It will be noted that in the disclosed method, 
at least the spacer tape 20 along at least one adjoining edge of the 
opposed glass sheets 10 and 12 does not have the paper backing 23 removed 
so that that edge is not adhesively bonded. 
Referring now to FIG. 6, the pair of glass sheets 10 and 12, joined along 
at least three edges, are placed in the lower form 18 with a flat 
supporting board 24 supporting the glass sheets above the form. In 
addition, a brace 26 is placed beneath one end of the glass sheets to 
raise that end of the glass sheets above the opposite end. As will become 
apparent, the laminating material is poured into the spacing between the 
panels using gravity for flow control and the angle of the glass sheets is 
required to distribute the laminating media. Typically, the front end of 
the glass sheet is raised about four inches higher than the back end of 
the glass sheets. 
Referring to FIG. 7, the front end of the glass sheets, along the unsealed 
edge, are pried apart using small plastic pry bars 28 to form a spacing or 
gap 30 of about 1/4 inch between the upper glass sheet 10 and the surface 
of the spacer tape 20. A pouring funnel 32 is inserted into the gap to 
allow the laminating material to be poured into the space between the two 
sheets. The laminating material may be any of a known type of glass 
laminating materials such as, for example, polyester resin mixed with 
curing catalysts. The mixed laminating material is poured into the spacing 
between the upper and lower glass sheets 10 and 12 through the funnel 32. 
When the laminating material gets to the opposite corners of the two glass 
sheets where the preformed vents 21 have been left, the vents are blocked 
with a glazing compound and secured by tape. The pouring funnel 32 is 
removed and the spacer tape's paper backing 23 at the open end is pealed 
away to allow the last edge of the upper and lower glass sheets to be 
bonded together. A masking tape is then placed over this last edge to 
complete the sealing process. The brace 26 is then removed from under the 
laminated glass sheets and the sheets are allowed to lie flat on the board 
24 in the form 18. Pressure is then applied to the top of the assembled 
glass panel 8 to spread the laminating media 14 throughout the space 
between the upper and lower glass sheets 10 and 12. Pressure may be 
applied by positioning a second flat board (not shown) on top of the upper 
glass sheet and placing a preselected weight on top of the board. The 
laminating mixture can then spread throughout the space between the glass 
sheets. When the laminating mixture begins dripping through the vent holes 
21, the holes can be plugged with glazing compound and secured with 
masking tape. Any air bubbles in the laminating material can be removed by 
use of a syringe and needle. 
After the laminating material has been throughly spread throughout the 
space between the upper and lower glass sheets 10 and 12, the flat boards 
can be removed from above and below the glass sheets and the glass sheets 
placed in the desired position within the form portion 18. The form 
portion 16 is then brought down into postion over the glass sheet and 
allowed to compress the glass between the upper and lower form portions 16 
and 18. After a suitable curing time, the form can be released and the 
curved laminated glass removed from the form. 
It will be noted that various types of glass laminating materials may be 
utilized to bond the upper and lower glass sheets together. If desired, an 
ultraviolet light cured laminating material can be used by covering one or 
both of the upper and lower form portions 16 and 18 with a light 
transmissive material such as a clear acrylic material so that ultraviolet 
light can be transmitted to the laminating media. Furthermore, the forming 
apparatus can be constructed with heating equipment to provide heat to the 
glass assembly if the laminating media requires additional heat for 
curing. 
What has been described is a method for forming a curved laminated glass 
panel which allows the curved laminated glass panel to be formed in situ 
and without preformed or pre-curved glass. While the invention has been 
described in what is presently considered to be a preferred embodiment, 
other variations, modifications, and arrangements will become apparent to 
those having ordinary skill in the art. For example, it has been found 
that the curved, laminated glass panels can be removed from the form prior 
to curing of the laminating material and the curved shaped held until 
curing by a wire or cord stringer extending from edge-to-edge of the 
panel, similar to a bow string. It is intended, therefore, that the 
invention not be limited to the disclosed embodiment but to be interpreted 
within the full spirit and scope of the appended claims.