Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
1998-03-31
2001-06-26
Ostranger, Allen (Department: 3725)
Abrading
Abrading process
Glass or stone abrading
C451S277000, C451S450000
Reexamination Certificate
active
06250992
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a grinding method using the fine-particle electrophoresis phenomenon, and to a glass lens worked by the grinding method.
A grinding method using the electrophoresis phenomenon is known from, for example, document “Research Concerning Grinding Method Using Electrophoresis Phenomenon of Ultra-fine Particles” published in a 1996 spring convention of The Japan Society for Precision Engineering.
The document describes a grinding device for grinding an object or workpiece
25
so that its surface becomes flat, which comprises, as is shown in
FIG. 17
, a cup-shaped grinding stone
20
rotatable about its axis of rotation, mounted on an air spindle
30
which is movable along the axis of rotation of the grinding stone, and having a cylindrical portion and a disk-shaped portion; an electrode
21
provided with a predetermined distance from a ring-shaped working end surface of the cylindrical portion of the grinding stone
20
; a DC power
22
connected to the electrode
21
and the air spindle
30
such that the electrode and the grinding stone serve as a cathode and an anode, respectively; means
23
for supplying, between the electrode and the stone, a grinding solution with silica fine particles (colloidal silica)
24
dispersed therein; and a sample table
26
opposed to the ring-shaped working end surface and disposed to mount the object
25
thereon.
While in the above grinding device, the grinding solution is supplied between the electrode
21
and the grinding stone
20
, negative and positive voltages are applied to the electrode
21
and the grinding stone
20
from the DC power
22
, respectively, thereby electrically attaching, to the surface of the grinding stone, silica fine particles which have been charged with negative electricity. Thus, a silica fine-particle layer is formed on the grinding stone surface, as a result of the electrophoresis phenomenon. In this state, the grinding stone
20
is gradually moved along the axis of rotation, and the silica fine-particle layer is brought into contact with the to-be-worked surface of the object. At the same time, the grinding stone
20
is rotated about the rotation axis to thereby make silica fine particles serve as a grinding blade for grinding the object. As a result, the object surface is polished into a mirror surface with little damage.
The above-described grinding method is effective in a case where the to-be-worked surface of the object has beforehand a certain shape (which is not a final surface shape or a surface of a mirror state), and is polished into a mirror surface by slightly removing material therefrom using silica fine particles. For example, the method is effective where only a very thin or small portion of a material has to be ground as in the case of a semiconductor wafer, and it is necessary to minimize the degree of deformation inside the worked material.
However, since in the above-described prior case, the electrical force for holding silica fine particles on the grinding stone is much smaller than the force for grinding the material, the fine particles will fall from the grinding stone if deep cuts are formed in the grinding stone to create a great working force.
In light of this, it is necessary to set the depth of cuts in the grinding stone at an extremely low value of several microns or less, in order to prevent falling of silica fine particles from the stone and to effectively use them as grinding particles.
Therefore, grinders having cuts with a depth of several microns or less are not effective in deeply grinding a workpiece, for example, to generate an optical element such as a lens from a glass blank (an optical glass workpiece). Since the cutting amount of the grinders is extremely small, efficient grinding cannot be performed, and hence an extremely long cutting time is required. This being so, it is necessary in the prior technique to beforehand prepare a material which has its to-be-worked surface ground into as close a shape as possible to the final shape, using another polishing or grinding device. Thus, lots of time is necessary for preparation of such a half product or for generation of a mirror surface from the workpiece or material.
BRIEF SUMMARY OF THE INVENTION
It is the object of the invention to provide a grinding method for simultaneously performing shape generation and mirror surface grinding of an optical glass material, and a glass lens worked by the grinding method.
Additional object and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The object and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
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patent: 3823515 (1974-07-01), Coes, Jr.
patent: 3877177 (1975-04-01), Taniguchi
patent: 3881661 (1975-05-01), Powers et al.
patent: 4907376 (1990-03-01), Bouchard et al.
patent: 4908995 (1990-03-01), Dougherty et al.
patent: 4910924 (1990-03-01), Holden et al.
patent: 4928435 (1990-05-01), Masaki et al.
patent: 4974368 (1990-12-01), Miyamoto et al.
patent: 5085007 (1992-02-01), Tusinski
patent: 6113464 (2000-09-01), Ohmori et al.
patent: 7-39074 (1995-05-01), None
patent: 7-164286 (1995-06-01), None
patent: 9-253938 (1997-09-01), None
“Research Concerning Grinding Method Using Electrophoreis Phenomenon of Ultra-Fine Particles” published in 1996 Spring Meeting of The Japan Society for Precision Engineering; pp. 106-107.
“Study of grinding technology which utilizes electrophoresis phenomenon of ultrafine abrasives” Feb. 2, 1993, Society of Grinding Engineers by Shaobu Gai, Yasuhiro Tani and Junichi Ikeno.
Ikeno Junichi
Kishida Takayuki
Saeki Masaru
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Hong William
Olympus Optical Co,. Ltd.
Ostranger Allen
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