Method and apparatus for forming a glass article possessing an aperture

The present invention is directed to an apparatus and method for forming glass article from sheet glass. More specifically the apparatus comprises a mold, a plunger being cooperative alignment with the mold, wherein the mold and the plunger form a cavity exhibiting the shaped of the glass article, an outer trimmer for separating the glass article from the surrounding excess sheet glass, and an inner trimmer for forming the aperture in the glass article, and the method involves forming the aperture during the hot-forming process, therefore eliminating a post-formation step.

BACKGROUND OF THE INVENTION 
1. Technical Field 
The present invention relates generally to glass forming, and particularly 
to a method and apparatus for forming articles possessing an aperture from 
sheet glass. 
2. Description of Related Art 
In the glass industry diamond tooling, i.e., diamond drill, is ordinarily 
employed in the cutting of holes or apertures in glass articles, usually 
in a post-formation or secondary process. Alternatively, after the glass 
article is formed it is reheated and a desired shaped hole is punched, 
again in a secondary process. These processes, however, are labor 
intensive and time consuming in addition to being costly, all which 
translate into increased costs with the end user. 
Automated cutting or trimming techniques for glass, however, are known in 
the industry. U.S. Pat. Nos. 3,193,367 (Giffen), 3,528,791 (Giffen), 
4,361,429 (Anderson et al.), and U.S. Pat. No. 4,605,429 (Rajnik) disclose 
trimming of articles formed from sheet glass during a hot-forming 
operation. The trimming methods disclosed therein are directed at 
separating a formed article from the excess hot glass cullet which 
surrounds the periphery of an article-forming mold. U.S. Pat. Nos. 
3,193,367 (Giffen), 3,528,791 (Giffen) and U.S. Pat. No. 4,361,429 
(Anderson et al.) disclose trimming the formed article by applying a 
shearing load to sever the surrounding glass. Whereas, U.S. Pat. No. 
4,605,429 (Rajnik) discloses trimming the glass cullet by pressing a thin 
spot in the glass between a blunt edge trimmer and a flat surface in the 
mold. 
None of these disclosures, however, teach the forming of regular and 
irregular holes or apertures in a newly formed glass article during the 
hot-forming process. Therefore, there exists the need for a simple, 
cost-effective apparatus and method for cutting or trimming glass to form 
regular and irregular shaped apertures in a newly formed glass article 
during conventional hot-glass molding and pressing process. 
It is an object of the present invention to provide an apparatus and method 
for forming apertures in glass articles during the molding and pressing 
process and not in a post-formation operation. 
It is also an object of the present invention to provide an apparatus and 
method for trimming regular and irregular apertures in glass articles that 
provides reliable trimming and pristine trimmed edges. 
SUMMARY OF THE INVENTION 
Briefly, the present invention provides for an apparatus for forming a 
glass article possessing an aperture formed from sheet glass, comprising a 
mold, a plunger being in cooperative alignment with the mold, wherein the 
mold and the plunger form a cavity exhibiting the shape of the desired 
glass article, an outer trimmer for separating the glass article from the 
surrounding excess sheet glass, and an inner trimmer for forming the 
aperture in the glass article. 
Also provided herein is a method for forming a glass article possessing an 
aperture from molten glass sheet. In one embodiment, a single sheet of 
molten glass is delivered and deposited to the surface of a mold assembly 
having a mold groove formed therewithin so as to overlie the mold groove 
and the surrounding surface of the mold assembly. The sheet of molten 
glass is initially permitted to substantially conform to the contour of 
the mold groove, then the molded glass sheet is pressed within the mold 
groove into an article of desired upper and lower surface configuration. 
An aperture is formed in the article while the glass is still in a 
semi-molten condition and the glass within the mold groove is trimmed from 
the surface portions of the mold assembly, and the completed article is 
removed from the mold cavity. 
In another embodiment a second sheet of molten glass is delivered and 
deposited on the contoured sheet prior to the pressing operation, wherein 
the second sheet of glass bridges but does not sag into contact with the 
contoured surface of the molded glass sheet. The second glass sheet 
hermetically seals to the first sheet wherever contact is made. 
Thereafter, the two sheets of glass are pressed into an article of desired 
upper and lower surface configuration. An aperture is formed in the 
article while the glass is still in a semi-molten condition, the article 
is then trimmed within the mold groove from the surface portions of the 
mold assembly, and the article is completely removed from the mold cavity. 
The inventive apparatus and method eliminate a post-formation cutting or 
trimming operation, resulting in a simpler, more cost-efficient process.

The accompanying drawings are included to provide a further understanding 
of the invention and are incorporated in and constitute a part of this 
specification, illustrate one embodiment of the invention and together 
with the description serve to explain the principles of the invention. In 
the drawings, like reference characters denote similar elements throughout 
the several views. It is to be understood that various elements of the 
drawings are not intended to be drawn to scale, but instead are sometimes 
purposely distorted for the purposes of illustrating the invention. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the present invention in one embodiment, a single sheet of molten glass 
is delivered and deposited to the surface of a mold assembly having a 
groove formed therewithin so as to overlie the mold groove and the 
surrounding surface of the mold assembly. The sheet of molten glass is 
initially permitted to substantially conform to the contour of the mold 
groove, then the molded glass sheet is pressed within the mold groove into 
an article of desired upper and lower surface configuration. Thereafter, 
an aperture is formed in the article while the glass is still in a 
semi-molten condition and the glass within the mold groove is trimmed from 
the surface portions of the mold assembly. The completed article is 
removed from the mold cavity. It should be noted that pressing is not 
always necessary, only when altering the thickness or shape of the sheet 
glass. 
In most preferred embodiment a second sheet of molten glass is delivered 
and deposited on a contoured first glass sheet as described in U.S. Pat. 
No. 5,858,046 (Allen et al.), co-assigned to the instant assignee, and 
herein incorporated in its entirety. 
FIG. 1 illustrates the present inventive apparatus for forming glass 
articles possessing an aperture from two sheets of molten glass. It should 
be noted, however, that the apparatus of FIG. 1 may be adapted to receive 
and form glass articles possessing an aperture from a single sheet of 
glass. 
Specifically the apparatus comprises plunger 2, outer trimmer 4 and inner 
trimmer 6 in cooperative alignment with mold 8 for forming glass articles. 
The term "outer trimmer" as used herein refers to that component of the 
inventive apparatus which is engaged to separate the newly formed glass 
article from the surrounding excess glass sheet. The term "inner trimmer" 
as used herein refers to that component of the inventive apparatus which 
is engaged to form an aperture in the glass article. 
Therefore, in the present inventive process there are in effect two 
trimming operations. To differentiate between these two trimming 
operations, the terms "inner trimming" and "outer trimming" will be 
employed. The term "inner trimming" as used herein refers to forming of 
regular and irregular apertures in a newly formed glass article during the 
hot-forming process. The term "outer trimming" as used herein refers to 
trimming of the newly formed glass article from the excess hot-glass 
cullet after the molding and pressing operations. 
Plunger 2 has an upper portion 10 and a lower portion 12. Plunger lower 
portion 12 has a glass contacting surface 14. Outer trimmer 4 and inner 
trimmer 6 are connected to each other through mounting surface 16. Plunger 
2 is adapted to receive inner trimmer 6 through plunger upper portion 10 
at cavity 18. 
Shown at 20 is inner trimmer guide. It is desirable for the inner trimmer 
to be relatively small in size to reduce machining costs. Inner trimmer 
guide 20 functions as a means of attachment to connect inner trimmer 6 to 
mounting surface 16, and as an alignment and guiding component which 
positions inner trimmer 6 relative to plunger 2 and mold 8. In the 
preferred embodiment inner trimmer guide 20 is made of cast iron and 
plunger 2 is made stainless steel. The use of different materials in the 
two components is employed to prevent "galling"; an art-known term which 
means chafing or abrasion resulting from two materials, especially similar 
ones, when rubbing against one another under high loads. Galling is more 
significant at elevated temperatures because of localized heating of the 
materials due to friction. 
Shown at 22 is a fastener which functions as a means to locate and attach 
inner trimmer 6 to guide 20. 
Outer trimmer 4 and inner trimmer 6 are connected to each other through 
mounting surface 16, and are mechanically independent of plunger 2. The 
outer and inner trimmers may be adjusted to sustain different heights via 
shims (not shown) or other art-known height adjusting mechanism at the 
attachment sites on mounting surface 16. In addition horizontal movement 
is allowed for in the trimming members tooling to accommodate differential 
thermal growth during the glass-article hot-forming process. Outer and 
inner trimmers 4 and 6 are beveled at 24 and 26 respectively, to form 
outer trimmer and inner trimmer cutting edges 28 and 30, respectively. 
During the forming process when sheet glass is loaded in the inventive 
apparatus, outer trimmer cutting edges 28 and inner trimmer cutting edges 
30 operate to apply a load to the glass via a shearing action to sever the 
glass at the points of contact, as disclosed in U.S. Pat. No. 4,361,429 
(Anderson et al.); 
the teachings of which patent are herein incorporated by reference in their 
entirety. More specifically, outer trimmer cutting edges 28 are moved 
downwardly in cooperation with outer mold edges 32, and inner trimmer 
cutting edges 30 are moved downwardly in cooperation with inner mold edges 
34. The glass is severed at the point where the load is applied. 
Mold 8 possesses glass contacting surface 36. In FIG. 1 plunger 2, outer 
trimmer 4 and inner trimmer 6 are shown in position for forming a glass 
article in cooperation with mold 8, i.e., plunger glass contacting surface 
14 and mold glass contacting surface 36 form a cavity 40 exhibiting the 
shape of the desired glass article. 
Mold 8 further possesses cavity 42. After the aperture is formed by inner 
trimmer 6, the residual glass is cut-away from the article and pressed 
into cavity 42. 
The shape of the aperture, may be regular, i.e., rectangular, round, or 
irregular; notwithstanding, the desired shaped aperture is determined by 
the configuration of inner trimmer 6 and corresponding mold shape. 
As shown in FIG. 2, an incline or chamfer is machined in mold 8 at 44 to 
maintain the glass hot for effective trimming . As the sheet glass lays 
over the mold and sags slightly, the glass will not make intimate contact 
with the mold due to the mold surface being angled downward at the 
chamfer. This is well known in the art. Additionally, a "draw ring", i.e., 
a raised metal lip, may also be machined on the periphery of the mold to 
also prevent intimate contact of the glass with the mold surface. 
A key feature of the present invention is that outer trimmer 4 and inner 
trimmer 6 are completely divorced mechanically and in process from plunger 
2. It is contemplated, however, that inner trimmer 6 may be attached to 
plunger 2. In such an embodiment the forming of regular and irregular 
apertures in a glass article is linked to and defined by the movement and 
parameters of plunger 2. More specifically, the inner trimming operation 
occurs at the same time as the pressing operation. Whereas, in the 
preferred embodiment herein above described, the inner trimming operation 
occurs subsequent to the pressing operation and concurrently to the outer 
trimming operation. 
Perfection of the trimming process is driven to a great degree by the 
dimensional tolerances between the cutting edges on the mold and cutting 
edges on the trimming members. These tolerances are refined empirically 
via tooling dimensions, mechanical mounting height and temperature 
control. Physical attachment of the inner trimming members to the plunger 
tooling not only precludes a separate process cycle, but also hinders the 
ability to alter vertical mounting height and temperature control during 
the trimming operation. Therefore, it was found that even though apertures 
can be formed in a glass article when the inner trimming members are 
attached to the plunger tooling, only marginal results are obtained, i.e., 
the process capability and product quality are reduced. 
Therefore, in the preferred embodiment of the present inventive apparatus 
where inner trimming members are attached to outer trimming members, 
differential height adjustment and thermal control are more easily 
accomplished due to lack of contact with the plunger. Other advantages 
include reduced glass checking, better release of the glass, i.e., the 
glass shrinks less due to a shorter contact time with the inner trimming 
members, reduced trimming force and a more pristine internal trim edge and 
less bulging of the glass produced via lateral glass flow during trimming. 
EXAMPLE 
The following nonlimiting example is presented to better illustrate the 
present invention. 15 The apparatus and method described above have been 
successfully utilized to produce a glass article of the shape as depicted 
in FIG. 3; a glass envelope 50 for a light emitting device. Glass envelope 
50 possesses aperture 52 which is centrally located in the glass article. 
Glass envelope 50 is symmetrically shaped and exhibits dimension of 
14".times.5". Aperture 52 exhibits dimensions of 10".times.1". 
A glass consisting essentially of, expressed in weight percent on the oxide 
basis, 77.4 wt. % SiO.sub.2, 5.3 wt. % Na.sub.2 O, 15.4 wt. % B.sub.2 
O.sub.3, 1.9 wt. % Al.sub.2 O.sub.3, 0.48 wt. % Cl was delivered and 
deposited as a first sheet of glass 54 to a mold 8 as depicted in FIG. 4. 
First sheet of glass 54 was made to conform to the mold groove 36 by 
drawing a vacuum. A second sheet of glass 56, possessing the same glass 
composition as given above, was deposited and delivered over the contoured 
first sheet of glass prior to the pressing operation. The second sheet 56 
is delivered at a viscosity preferably in the range of 5,000-6,000 poises 
such that it hermetically sealed the first sheet 54 wherever contact 58 
was made between the two sheets, but the second sheet 56 did not sag into 
the contours of first glass sheet 54. 
Referring now to FIG. 5, plunger 2 is brought into contact with second 
sheet 56, to press the two sheets of glass at contact points 58 to ensure 
a good glass-to-glass seal. Plunger 2 also applies a profile to second 
sheet 56. Second sheet 56 is made to substantially conform to the contour 
of plunger glass contacting surface 14 by way of conventional vacuum, 
whereby an article of desired upper and lower surface configuration is 
formed. Alternatively to vacuum, positive air may be blown into the glass 
envelope through open sites formed in the first sheet (not shown), to 
assist the second sheet to better conform to the groove of the plunger. 
The air is preferably introduced via an air line orifice which is 
connected to machined slots in the mold (not shown) in the mold and is in 
communication with open sites (not shown) in the first sheet. 
The plunger is pressed into the molten glass under hydraulic force in the 
range of 50 to 250 psi per unit area of glass, and dwell times in the 
range of 1 to 4 seconds are preferred. 15 After the molding operation, the 
inner and outer trimming operations are activated. Outer trimmer cutting 
edges 28 are moved downwardly into cooperation with outer mold edges 32, 
as shown in FIG. 6 by the arrows. The glass is severed away at the points 
of contact, such that the newly formed symmetrically shaped glass article 
is separated from the surrounding excess hot glass. Concurrently, inner 
trimmer cutting edges 30 are moved downwardly into cooperation with inner 
mold edges 34 to form aperture 52. The excess glass trimmed away from 
glass article 50 to form aperture 52 is pressed away into cavity 42. 
Reasons for forming aperture 52 are numerous and including for mounting the 
glass envelope as a lamp to a fixture, and for aesthetic reasons. 
Glass envelope 50 is employable as a light emitting device when electrodes 
(not shown) are attached thereto and the envelope is filled with an 
ionizable gas, such as neon. The glass envelope may also be used for 
fluorescent applications. 
Although there is herein shown and described only one specific form of 
apparatus embodying the invention, it will be understood by one skilled in 
the art that such is not to be considered in any way limiting but that 
various changes or modifications may be made therein within the purview of 
the appended claims without departing from the spirit and scope thereof.