Glass manufacturing – Product or parison centering means – or mold and/or core...
Reexamination Certificate
2000-10-31
2004-11-09
Colaianni, Michael (Department: 1731)
Glass manufacturing
Product or parison centering means, or mold and/or core...
C065S305000, C065S307000, C065S315000, C065S317000, C065S322000, C425S352000
Reexamination Certificate
active
06813906
ABSTRACT:
This application claims priority under 35 U.S.C. §§ 119 and/or 365 to 311458/1999 filed in Japan on Nov. 1, 1999; the entire content of which is hereby incorporated by reference.
1. Technical Field
The present invention relates to forming molds that are suited to the manufacture of molded glass articles such as high-precision lenses and do not require cutting or polishing following press molding. The present invention also relates to methods of molding glass articles employing these forming molds. The present invention further relates to methods of assembling formed glass article manufacturing devices suited to the manufacture of formed glass articles such as high-precision lenses.
2. Background Art
A great number of techniques for producing molded glass articles such as high-precision lenses by forming in mold presses have been developed in recent years. These molding techniques can be divided into roughly two categories. In the first method, the glass material to be molded is placed in the forming mold at room temperature outside the molding device. Next, the forming mold into which the glass material to be molded has been placed is placed in the device, a number of sections within the device are moved to conduct heated pressing and cooling, the forming mold is removed from the device, and the molded glass article is removed from the forming mold outside the device.
By contrast, in the second method, a forming mold is employed in which an upper mold and a lower mold are mounted in advance on vertical press shafts within the device. In this method, the glass material to be molded is supplied at room temperature onto the forming surface of the lower mold, and in that state, the forming mold is heated to heat the glass material to be molded. The glass material is pressed, cooled, and removed from the device upon reaching room temperature. However, in the preferred method, the glass material to be molded is heated separately from the forming mold, transferred to the forming mold, pressed (sometimes heated and pressed), and released from the mold once it has been cooled to below the transition point of the glass. The molded glass article is then immediately removed from the mold. Since this method does not require that the forming mold be brought down to room temperature, an extremely short molding cycle and efficient production are possible.
A number of conditions must be satisfied to produce a formed glass article such as a high-precision lens by heating the forming mold to a temperature corresponding to a glass viscosity of 10
8
-10
12
poise, heating the glass material being molded to a temperature equal to or greater than that of the forming mold, press forming the glass material being molded with the forming mold, cooling the glass material being molded to below the transition temperature of the glass, releasing the mold, and removing the molded glass article from the forming mold.
The forming surface of the forming mold must be machined to a high surface precision and a fine surface roughness, and must not fuse with the glass as a result of press forming. To perform as a lens, specifications such as thickness, outer diameter, surface precision, eccentricity precision (axial shift, tilt), and outer appearance must be met. Although the formed glass article is released immediately from the mold once cooled to below the transition point of the glass, it is extremely important to achieving stable, continuous production that the upper mold not adhere to the formed glass article during that process and that the formed glass article come out smoothly. During mold release, cooling to below the glass transition point is required to achieve surface precision. Additionally, shrinkage tends to occur when the mold is released at a temperature exceeding the glass transition point. Such problems do not occur at below the glass transition point so long as the glass consolidates.
Further, rapid heating and cooling of the forming mold are desirable from the perspective of improving production efficiency by shortening the molding cycle time to the extent possible.
The present inventors have developed and proposed a forming mold (Japanese Patent Application Publication No. Hei 11-49523) that can be employed in methods satisfying the above-stated requirements. The structure of this forming mold is shown in
FIG. 9
, and a schematic of the forming method employing this forming mold is given in FIG.
10
. However, it has become clear that the following problems tend to occur due to the mold structure in the molding method employing this forming mold.
The molding device for formed glass articles shown in
FIG. 9
is equipped with a forming mold
110
; a drive mechanism comprised of a cylinder and the like for vertically displacing forming mold upper member
114
in a manner described further below; a heater for heating prescribed members comprising forming mold
110
, such as upper mold
120
and lower mold
130
; and a high-frequency coil.
Forming mold
110
is roughly cylindrical in shape and comprises a forming mold upper member
112
secured at prescribed positions and a forming mold lower member
114
capable of being moved vertically by a cylinder (not shown). Forming mold upper member
112
is provided with a roughly cylindrical first upper matrix
116
, a hollow cylindrical second upper matrix
118
positioned beneath upper matrix
116
and secured to upper matrix
116
, and an upper mold
120
inserted into second upper matrix
118
and disposed with a matching center shaft. An upper mold descent stop ring
122
[sic:
127
] concentric with, and positioned radially between, second upper matrix
118
and upper mold
120
; a sleeve
124
, positioned concentrically with upper matrix
118
and upper mold
120
and positioned further to the forming surface side of upper mold
120
than upper mold descent stop ring
122
; and a spring
125
pushing against sleeve
124
between upper mold descent stop ring
122
and sleeve
124
are also provided.
Additionally, forming mold lower member
114
is provided with a [first] lower matrix
126
, secured on its lower surface to a cylinder (not shown); a hollow cylindrical second lower matrix
128
secured to [first] lower matrix
126
, and a lower mold
130
, positioned concentrically with [second] lower matrix
128
and configured so as to permit the placing of a glass material onto the forming surface, or upper surface, thereof. [Second] lower matrix
128
is positioned by means of a protrusion
148
.
Prior to insertion of lower mold
130
into sleeve
124
(as shown in FIG.
10
(
b
)), the center shaft of the upper mold and the center shaft of the lower mold are not necessarily perfectly aligned. Even once the lower mold has been inserted into the sleeve (as shown in FIG.
10
(
c
)), the sleeve dangles loosely in a vertical direction from the spring. Further, the clearance between sleeve
124
and upper mold
120
on the one hand, and upper matrix
180
, on the other, may result in radial shifting. A protrusion for contacting and scraping away the formed article that has adhered to the forming surface of the upper mold is provided on the inner surface of sleeve
124
. The clearance between sleeve
124
and the inside of upper mold
120
is adjusted so that when sleeve
124
slides vertically, the protrusion on its inner surface contacts the outermost rim portion of the molded article. Thus, while the clearance in a common forming mold is about 2-10 &mgr;m between the drum and the forming mold, in the mold shown in
FIG. 10
, for the above-stated reasons, the spacing between sleeve
124
and the inside of upper mold
120
ranges from about 0.1 to 5 mm.
Thus, sleeve
124
is kept in a dangling state by the spring and has considerable clearance with the upper mold. There is also a prescribed clearance between lower mold
130
and sleeve
124
. Thus, in this state, sleeve
124
sometimes tilts within the above-stated prescribed clearance. When sleeve
124
tilts, a tilt develops between lower mold
130
Hirota Shin-ichiro
Sugawara Kishio
Colaianni Michael
Hoya Corporation
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