Electric heating – Metal heating – Cutting or disintegrating
Reexamination Certificate
2002-09-05
2004-06-08
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
Cutting or disintegrating
Reexamination Certificate
active
06747236
ABSTRACT:
TECHNICAL FIELD
The present invention relates to improvements in a wire electrical discharge machine for machining a workpiece by electric discharge energy by supplying machining electric power between a wire electrode and the workpiece.
BACKGROUND ART
FIG. 8
is a schematic diagram illustrating a conventional wire electrical discharge machine, in which reference numeral
1
denotes a wire electrode;
2
, a workpiece,
3
, a wire bobbin;
4
, a main tension pulley for imparting tension to the wire electrode
1
; and
5
, a braking motor for causing the main tension pulley to produce torque. Numerals
6
a
and
6
b
denote wire guides respectively provided above and below the workpiece
2
;
7
a
and
7
b
, working fluid nozzles respectively provided above and below the workpiece
2
, and
8
a
and
8
b
, feeders for supplying machining electric power to the wire electrode
1
. Numeral
9
denotes a power supply unit for machining;
10
, a wire-electrode-traveling roller;
11
, a wire-electrode-traveling motor;
12
, a wire-electrode collection box; and
13
, a braking motor for pretensioning for causing the wire bobbin to generate torque. Numerals
14
a
,
14
b
, and
14
c
denote guide pulleys. In addition, arrow A in the drawing indicates the traveling direction of the wire electrode
1
.
In such a conventional wire electrical discharge machine, as the wire-electrode-traveling roller
10
is driven-by the wire-electrode-traveling motor
11
, the wire electrode
1
is pulled out from the wire bobbin
3
. In the main tension pulley
4
and the wire bobbin
3
, predetermined tensions are applied to the wire electrode
1
by the braking motors
5
and
13
. In the state in which these predetermined tensions are applied, the wire electrode
1
travels in the direction of arrow A in the drawing while maintaining a predetermined speed. The wire bobbin
3
rotates about a wire bobbin shaft as the wire electrode
1
travels. The wire electrode
1
is wound around the wire bobbin
3
, and is continuously pulled out from the wire bobbin
3
. In conjunction with the traveling of the wire electrode
1
, machining electric power is supplied to the gap between the wire electrode
1
and the workpiece
2
from the machining power supply unit
9
through the feeders
8
a
and
8
b
, and a working fluid is supplied to the gap through the working fluid nozzles
7
a
and
7
b
, with the result that electric discharge occurs. As the wire electrode
1
and the workpiece
2
are relatively moved in a predetermined machining direction by an unillustrated drive mechanism, the machining of the workpiece
2
progresses.
In such wire electrical discharge machining, a substantial portion of the wire electrode
1
facing the machining direction is worn due to the discharge. Accordingly, since the frequency of disconnection of the wire electrode
1
increases, there has been a problem in that the machining rate declines appreciably.
In addition, the wear of the wire electrode
1
has a large effect on the machining accuracy as well. Namely, since the wear of the wire electrode
1
progresses while the wire electrode
1
is traveling from an upper portion to a lower portion of the workpiece
2
, there has been a problem in that taper-like errors occur on the machined surface of the workpiece
2
with respect to the traveling direction of the wire electrode
1
. Such taper-like errors become noticeable particularly in cases where the thickness of the workpiece
2
is large.
FIG. 9
is a partial cross-sectional view illustrating a wire-electrode loading mechanism in a wire electrical discharge machine disclosed in JP-A-63-2630 for the purpose of resolving the problems of the above-described conventional art. In the drawing, reference numeral
1
denotes the wire electrode;
3
, a wire bobbin; and
14
a
, a guide pulley. Numerals
15
a
and
15
b
denote bearings, and numeral
16
denotes a rotating jig;
17
, a bearing;
18
, a rotating motor;
18
a
, an output shaft of the rotating motor
18
; and
19
, a fixing base. The wire bobbin
3
is supported by the rotating jig
16
by means of the bearings
15
a
and
15
b
so as to be rotatable about a &bgr; axis in the drawing. Further, the rotating jig
16
is connected to the output shaft
18
a
of the rotating motor
18
.
The overall construction of the wire electrical discharge machine having the wire-electrode loading mechanism having the arrangement shown in
FIG. 9
is similar to that shown in
FIG. 8
, and corresponds to an arrangement in which the wire bobbin
3
, the braking motor
13
, and the like in
FIG. 8
are replaced by FIG.
9
. It should be noted, however, that a motor corresponding to the braking motor
13
shown in
FIG. 8
is not present in FIG.
9
. Accordingly, in order to be provided with functions utterly identical to those of the overall construction shown in
FIG. 8
, it is necessary to add the braking motor
13
to, for example, the &bgr; axis shown in
FIG. 9
In
FIG. 9
, if the wire electrode
1
travels (in the direction of arrow A in the drawing), the wire bobbin
3
rotates about the &bgr; axis (in the direction of arrow B in the drawing), and the wire electrode
1
wound around the wire bobbin
3
is pulled out from the wire bobbin
3
. In conjunction with the traveling of this wire electrode
1
, the wire bobbin
3
is rotated about an &agr; axis (in the direction of arrow C in the drawing) by the rotating motor
18
to impart rotation to the wire electrode
1
, thereby making it possible to disperse the wear of the wire electrode
1
at the time of wire electrical discharge machining. Therefore, there is an advantage, among others, in that the machining accuracy of the workpiece can be improved.
In the arrangement of the wire-electrode loading mechanism such as the one shown in
FIG. 9
, the rotating motor
18
used exclusively for imparting rotation to the wire electrode
1
is required in addition to the braking motor (e.g.,
13
in
FIG. 8
) for applying tension to the wire electrode
1
. In addition, since there is a need to rotate the entire wire bobbin
3
about the &agr; axis, the load inertia of the rotating motor
18
is large, so that the rated output of the rotating motor
18
and the capacity of the allowable rated load and the like of machine elements such as the bearing
17
are required to be large. Hence, there has been a problem in that an increase in cost is large, and this arrangement is not practical.
DISCLOSURE OF THE INVENTION
The present invention has been devised to overcome the above-described problems, and its object is to obtain a wire electrical discharge machine which makes it possible to disperse the wear of the wire electrode and improve the machining rate and machining accuracy.
Another object is to obtain a wire electrical discharge machine which makes it possible to suppress an increase in cost without requiring the provision of a new motor for imparting rotation to the wire electrode, and which is highly reliable and is practical.
The wire electrical discharge machine in accordance with the invention is a wire electrical discharge machine for machining a workpiece by electric discharge energy by causing discharge to occur between a traveling wire electrode and the workpiece, comprising: a wire bobbin with the wire electrode wound therearound; fixing means for fixing the wire bobbin so that the wire bobbin does not rotate; guiding means for supporting the wire electrode; wire-electrode rotating means for supporting the guiding means and for pulling out the wire electrode from the wire bobbin and rotating the wire electrode about the wire bobbin; and driving means for driving the wire-electrode rotating means.
In addition, in the wire electrical discharge machine in accordance with the invention, the driving means is a braking motor for imparting predetermined tension to the wire electrode.
In addition, in the wire electrical discharge machine in accordance with the invention comprises: sliding means for supporting the guiding means slidably with respect to the wire-electrode rotating means,
Magara Takuji
Yamada Hisashi
Evans Geoffrey S.
Mitsubishi Denki & Kabushiki Kaisha
Sughrue & Mion, PLLC
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