Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
1998-05-21
2001-01-30
Scherbel, David A. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S059000, C451S299000, C451S042000, C451S057000, C451S305000
Reexamination Certificate
active
06179689
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and device for processing into a convex spherical mirror form the end face of an optical fiber connector, a cylindrical material, or a block-shaped end face made of glass, ceramic, or plastic, and particularly to a method and device that can carry out processing with improved efficiency and accuracy.
2. Description of the Related Art
FIG. 1
is a schematic view showing the connection portion of the two end faces
8
of ferrule
21
of an optical connector
22
that has undergone a mirror grinding process to produce a convex spherical form. When two optical fibers
23
are connected and optical signals are propagated, every effort must be made to suppress the optical loss and reflection that occur at the gap between the end faces of the optical fibers. Currently, PC (Physical Contact) optical connectors
22
are widely employed as a method of realizing connections with low optical loss. In these PC optical connectors
22
, end faces
8
of ferrules
21
provided at the ends of optical fibers
23
are formed with convex spherical mirror surfaces and the end faces of optical fibers
23
are brought into close contact.
When fabricating PC optical connector
22
, surplus adhesive or surplus length of optical fiber may remain at the tip from the process of inserting and securing optical fiber
23
in ferrule
21
. When mirror grinding end face
8
to a convex spherical form in a processing device of the prior art, this surplus adhesive or surplus optical fiber is first removed by coarse grinding, and then, as shown in
FIG. 2
, abrasive tape
2
is disposed over stage
3
having a surface for which the section is a concave arc, the end face of workpiece
1
is placed in contact with abrasive tape
2
and pressure applied, abrasive tape
2
is put in motion while confined to the upper surface of stage
3
in concave form, workpiece
1
is given a rotating and back-and-forth motion to transfer the concave surface shape of stage
3
to workpiece
1
by the grinding action of the abrasive tape and finish a smooth, convex spherical form (Refer to, for example, Japanese Patent Laid-open No. 029599/97).
The above-described ferrule end-surface spherical processing method of the prior art has the disadvantage of low processing efficiency because grinding fluid is not employed, and in cases in which grinding fluid is supplied as in normal grinding methods, there is the disadvantage that the amount of grinding fluid supplied becomes excessive, or that an appropriate amount of grinding fluid cannot be supplied in the processing of the spherical surface of the end face of the ferrule.
SUMMARY OF THE INVENTION
The object of the present invention is to solve the above-described problems of the prior art by providing a spherical processing device and processing method that can process, not only an optical fiber connector, but the end face of a block or cylindrical material made of, for example, glass or ceramic, into a mirror surface of convex spherical shape with high efficiency and high accuracy.
In the present invention, processing efficiency can be improved and a workpiece that has a highly accurate mirror surface can be obtained by running an abrasive tape over a stage that has an upper surface for which the section is a concave arc; pressing the end face of the workpiece into contact with the tape and rotating, and in addition, giving a reciprocating movement to the workpiece; and supplying a thin film of grinding fluid to the surface of the abrasive tape.
In addition, the vertical load applied to the workpiece is reduced during initial processing in which the edge portions of the end face are ground, and then increased upon completion of processing of the edge portions, whereby the movement of the abrasive tape does not become unstable and processing can be carried out with high efficiency.
Further, the exchange of abrasive tape is simplified by providing the abrasive tape in cassette form.
Finally, processing of the workpiece continues without interruption because the time of reversal of the rotation of the workpiece does not coincide with the time of reversal of the reciprocating movement, thereby both improving processing efficiency and realizing stable processing without sudden loads being placed on the workpiece.
According to first spherical mirror surface processing method of the present invention, in a spherical processing method that processes the end face of the workpiece by means of the grinding action of an abrasive tape, wherein the abrasive tape is arranged on a stage having an upper surface For which a section taken at a right angle to the longitudinal direction describes a concave arc, the end face of a workpiece is placed in contact with the abrasive tape and pressure is applied, the abrasive tape is put in motion, and the workpiece is given a rotating and reciprocating movement; an amount of 10 cc/m
2
to 50 cc/m
2
of grinding fluid is supplied to the surface of the abrasive tape to generate a thin and uniform layer of grinding fluid. The processing efficiency is thus improved by supplying a uniform and consistent amount of grinding fluid to the working surfaces of the abrasive tape.
According to the second spherical mirror surface processing method of the present invention, in the first spherical mirror surface processing method of the present invention described hereinabove, the processing pressure applied against the end face of the workpiece is reduced in initial processing in which the edge portions of the end face of the workpiece are processed, and the processing pressure is increased upon completion of processing of the edge portions. In other words, the processing load focuses on the edge portions during initial processing because the flat end face of the workpiece presents a pointed edge portion. A low processing load is therefore applied until processing of the edge portions is completed. In this way, the application of excessive load is avoided as necessary so that the edge portions do not cause instability in the movement of the abrasive tape, thereby ensuring stable initial processing. The processing pressure is then increased upon completion of processing of the edge portions to allow more efficient processing.
The first spherical mirror surface processing device of the present invention is provided with a water-holding material that contains a grinding fluid for generating a thin and uniform grinding fluid film on the surface of the abrasive tape in an end face processing device that includes: a stage having an upper surface for which a section taken at a right angle to the longitudinal direction describes a concave arc; an abrasive tape arranged on the stage perpendicular to the longitudinal direction; a mechanism for driving the abrasive tape; a mechanism for placing the end face of the workpiece in contact with the abrasive tape and applying pressure such that the axis of rotation of a rod-shaped workpiece coincides with the center of the radius of curvature of the section of the stage; and a mechanism for moving the rod-shaped workpiece back and forth on the concave surface of the stage in the longitudinal direction while rotating the rod-shaped workpiece. The water-holding material enables a uniform and consistent supply of the necessary amount of grinding fluid to the working surface of the abrasive tape, thereby enabling an improvement in processing efficiency. The water-holding material may employ, for example, fiber or sponge of porous substance made from, for example, polyurethane foam.
According to the second spherical mirror surface processing device of the present invention, in the first spherical mirror surface processing device of the present invention described above, a load varying device is provided that reduces the processing pressure for a certain fixed interval of time until the edge portion is processed during initial processing of the end face of the workpiece, and subsequently increases the processing pressure. In other words, during initi
Mitsuhashi Masashige
Ohno Kenichi
NEC Corporation
Scherbel David A.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Wilson Lee
LandOfFree
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