Turning – Radially moving rotating tool inside bore – Tool simultaneously moving axially
Reexamination Certificate
2001-03-27
2003-10-28
Tsai, Henry W. H. (Department: 3722)
Turning
Radially moving rotating tool inside bore
Tool simultaneously moving axially
C082S161000, C082S173000, C082S904000
Reexamination Certificate
active
06637303
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvements of an elliptical vibration cutting method and an elliptical vibration cutting apparatus which elliptically vibrates a cutting tool relative to a workpiece such as a steel product.
2. Description of the Prior Art
In general, a workpiece such as a steel product is cut by a conventional cutting method for providing the workpiece with a required shape.
Conventionally, a cutting tool is advanced relative to the workpiece in a constant direction, thereby cutting the workpiece by a prescribed chip removal.
Conventional cutting encounters the problem of frictional resistance or cutting resistance by the workpiece relative to the tool. This cutting resistance has a tendency to increase as the tool advances, thereby increasing the chip thickness which results in an inferior machinability.
When a ferrous material such as a steel product is cut with a diamond tool for ultraprecision working, the diamond tool is constantly in contact with the ferrous material, whereby frictional heat is generated in the contact area between the tool and the workpiece resulting in high-temperature, high-pressure working conditions. Further, carbon is dispersed in the ferrous material of the workpiece due to the chemical affinity between the diamond tool that is a form of carbon and the ferrous material. Thus, the diamond tool is subject to wear which prevents working the ferrous material with ultraprecise cutting with a diamond tool.
Elliptical vibration cutting with an elliptical vibration cutting apparatus
51
as shown in
FIGS. 8
,
9
and
10
is also known.
The cutting apparatus
51
performs an intermittent cutting for reducing the resistance thereby also reducing the heat conduction to the cutting tool. The intermittent cutting provides a cooling time for the cutting tool, thereby enabling an ultraprecise cutting of a ferrous material with a diamond tool.
The apparatus
51
shown in
FIGS. 8 and 9
includes a cutting tool
53
cutting a workpiece
52
such as a steel product, an elliptical vibrator
54
elliptically vibrating the cutting tool
53
, support members
55
A and
55
B supporting the elliptical vibrator
54
, and a base
56
for mounting the support members
55
a
and
55
b
. The elliptical vibrator
54
includes a prismatic vibrator support body
57
forming a central portion of the elliptical vibrator
54
. The body
57
has an axial projection
58
at one end and an axial projection
58
A at the opposite end. Compared to the vertical dimension of the body
57
, the projections
58
and
58
A have reduced vertical dimensions to provide a stepped configuration. One of the projections
58
has a mounting surface
64
for mounting the cutting tool
53
.
The apparatus
51
further includes piezoelectric elements
61
and
62
for generating elliptical or so-called flexible vibrations in the elliptical vibrator
54
and a control mechanism
63
individually applying prescribed sinusoidal voltages to the piezoelectric elements
61
and
62
for driving the vibrator body
57
. Horizontal surfaces
59
and vertical surfaces
60
on the side surfaces of the prismatic body
57
define plane mounting surfaces for the piezoelectric elements
61
and
62
.
The control mechanism
63
individually applies sinusoidal voltages of the same frequency which are 90 degrees out of phase, for example to the piezoelectric elements
61
mounted on the horizontal surfaces
59
and to the piezoelectric elements
62
mounted on the vertical surfaces
60
for energizing the piezoelectric elements, thereby generating flexible vibrations in the elliptical vibrator
54
in two perpendicular directions (vertical and horizontal directions in FIG.
9
). The support members
55
A and
55
B form supporting points for the vibration of the body
57
. The elliptical vibrator
54
is elliptically vibrated by energizing the piezoelectric elements which generate an elliptical vibration of the elliptical vibrator
54
, whereby the cutting edge of the cutting tool
53
mounted on the mounting surface
64
moves along an elliptical path or “locus”.
Thus, the apparatus
51
can perform an elliptical vibration cutting operation on the workpiece
52
with the cutting tool
53
. In other words, the apparatus
51
converts electrical energy to mechanical energy when a sinusoidal voltage is applied to the piezoelectric elements to generate a flexible elliptical vibration through the elliptical vibrator
54
.
Referring to
FIG. 8
, there are three loops of vibration in the spacing M between the support members
55
A and
55
B.
When performing an elliptical vibration cutting on the aforementioned ferrous material with a diamond tool the cutting resistance and the heat conduction to the cutting tool are reduced due to the intermittent cutting operation which provides a cooling time for the cutting tool between periods when the ferrous material is engaged by the tool and ultraprecise working with the diamond tool becomes possible.
When the elliptical vibrator
54
is flexibly elliptically vibrated, however, corner portions of the prismatic body
57
remarkably impede or hinder the two-directional flexible vibration, whereby the elliptical tool path is distorted. The impeding of the vibrations results in a respective energy loss in the elliptical vibrator
54
which makes it difficult to obtain a desired locus or tool path caused by the elliptical vibration.
With the elliptical vibrator
54
having the prismatic vibrator support body
57
, therefore, the elliptical vibration path of the cutting tool
53
cannot be enlarged, disadvantageously leading to an inferior machinability of the workpiece
52
cut with the cutting tool
53
.
In other words, electrical energy cannot be efficiently converted to mechanical energy with the elliptical vibrator
54
having a prismatic vibrator support body
57
. In
FIG. 8
the body
57
has a square cross-section.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention in a vibration cutting apparatus having an elliptical vibrator, to enlarge a locus or path of elliptical vibration of a cutting tool that is elliptically vibrated by the elliptical vibrator to thereby improve the machinability of a workpiece cut with the cutting tool.
Another object of the present invention is to provide an elliptical vibration cutting apparatus capable of efficiently converting electrical energy to mechanical energy and to efficiently perform elliptical vibration cutting operations on a workpiece with an increased tool vibration amplitude.
Another object of the invention is to construct the vibrator, more specifically a cylindrical body portion of a tool support body forming the vibrator, in such a way that the geometric moment of inertia of the cylindrical body portion is constant or at least substantially constant for 360° around a central longitudinal axis of the cylindrical body portion carrying at least two piezoelectric drive elements. A constant or substantially constant moment of inertia is achieved according to the invention by providing the cylindrical body portion with a circular cross-section or with a substantially cylindrical cross-section.
The term “substantially constant” as used in this context to qualify the geometric moment of inertia is intended to cover any geometric moment of inertia that is distinguished from a moment of inertia of a conventional tool carrier body having an octagonal cross-section. A curve tracing the size of a conventional geometric moment of inertia of a tool carrier body with an octagonal cross-section in a polar coordinate system is also octagonal, because the moment of inertia is largest in a corner of the octagon and smallest centrally between two corners. This pattern is repeated around the octagon. Contrary thereto, the respective curve of the geometric moment of inertia of the cylindrical body portion with a substantially circular cross-section according to the invention, is also substantially circular and hence substantially constant.
The cylindrical body
Matsuo Makoto
Moriwaki Toshimichi
Shamoto Eiji
Fasse W. F.
Fasse W. G.
Tsai Henry W. H.
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