Wire electrical discharge machine

Details Wire electrical discharge machine Wire electrical discharge machine

2000-06-22

2001-09-18

Evans, Geoffrey S. (Department: 1725)

Electric heating

Metal heating

Cutting or disintegrating

Reexamination Certificate

active

06291789

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvements in a wire electrical discharge machine, and more particularly to a wire electrical discharge machine which prevents a fluid from coming into contact with a capstan roller and a pinch roller, and in which a wire electrode is difficult to become intangled with the rollers.
2. Description of the Related Art
A conventional wire electrical discharge machine will be described with reference to
FIGS. 6
to
7
disclosed in JP-A-4-105822. In
FIGS. 6 and 7
, the wire electrical discharge machine is a machine tool wherein a phenomenon of electric discharge is caused to take place between a wire electrode
1
and a workpiece
3
to perform cutting-out processing with respect to the workpiece
3
such as a superalloy. At the time of starting discharge machining, the wire electrode
1
must be inserted in advance in a start hole formed in the workpiece
3
, and the wire electrode
1
must always be fed during wire electrical discharge machining.
The wire electrical discharge machine comprises a mounting surface plate
5
for mounting the workpiece
3
thereon; a processing tank
7
for keeping the workpiece
3
and the mounting surface plate
5
immersed in a working fluid
60
a;
a guide means
8
for guiding the wire electrode
1
; a lower idler
20
for converting the direction of the wire electrode
1
being fed from a lower portion of the workpiece
3
into a horizontal direction; a wire conveying means
22
for conveying the wire electrode
1
and having a pipe-shaped portion; a wire taking-up means
30
for taking up the wire electrode
1
; a cylinder
50
for moving the wire taking-up means
30
in the horizontal direction; a working-fluid supplying section
60
for supplying the working fluid
60
a
to the wire conveying means
22
; and a collecting section
75
including a shielding plate
72
and a collecting box
74
.
The wire conveying means
22
comprises a hollow cylindrical inlet portion
22
a
into which the wire electrode
1
is inserted and the working fluid
60
a
is allowed to flow from a side surface thereof; a hollow cylindrical guide member
23
connected to this inlet portion
22
a;
and a nozzle member
25
which envelops the guide member
23
and is formed slidably around an outer peripheral surface of the guide member
23
and which is larger than the guide member
23
. As a rod
50
a
of the cylinder
50
is extended or retracted, the wire conveying means
22
moves the overall wire taking-up means
30
in the horizontal direction, and is adapted to allow the nozzle member
25
to be movable in synchronism therewith.
The wire taking-up means
30
includes a capstan roller
34
serving as a first roller for nipping and taking up the wire electrode
1
, a lever-type pinch roller
36
serving as a second roller, and a motor
32
for rotating the capstan roller
34
.
The working-fluid supplying section
60
includes a storage tank in which the working fluid
60
a
is stored, a first pump
64
for pumping up the working fluid
60
a
from the storage tank
62
and supplying it to the processing tank
7
, and a second pump
66
for supplying the working fluid
60
a
to the wire conveying means
22
in a similar manner.
Referring to
FIGS. 6 and 7
, a description will be given of the operation of the wire electrical discharge machine constructed as described above. First, the wire electrode
1
is passed through a machining portion
3
a
of the workpiece
3
, undergoes a change in its direction by the lower idler
20
, and is inserted in the inlet portion
22
a
of the wire conveying means
22
.
Next, the second pump
66
is started, and the working fluid
60
a
pumped up from the storage tank
62
passes through the interior of the wire conveying means
22
. A conveying force is hence imparted to the wire electrode
1
by the flow of the working fluid
60
a
as shown in
FIG. 6
, so that the wire electrode
1
is automatically fed to the wire taking-up means
30
and automatically drops into the collecting box
74
. This drop is detected by an unillustrated detector to stop the second pump
66
.
Next, the cylinder
50
is driven to move the wire taking-up means
30
to a position above the collecting box
74
and stops as shown in
FIG. 7
, and electrical discharge machining is effected. At this time, the wire electrode
1
which is continuously fed to the machining portion
3
a
of the workpiece
3
is collected in the collecting box
74
.
However, there has been a problem in that when, during electrical discharge machining, the working fluid
60
a
flows from the processing tank
7
to the capstan roller
34
through the lower idler
20
and the wire conveying means
22
, and the working fluid
60
a
is attached to the capstan roller
34
, the wire electrode
1
becomes liable to be entangled with the roller
34
due to the surface tension of the working fluid
60
a.
SUMMARY OF THE INVENTION
The present invention has been devised to overcome the above-described problem, and its object is to provide an electrical discharge machine in which the working fluid is difficult to be transmitted to the rollers during machining.
To attain this object, in accordance with a first aspect, there is provided a wire electrical discharge machine characterized by comprising: a wire electrode for causing electrical discharge to take place between the same and a workpiece; a first roller and a second roller for feeding the wire electrode while nipping the same; wire conveying means for inserting the wire electrode into a nip between the first roller and the second roller by causing a fluid to flow to opposing portions of the first roller and the second roller; and driving means for moving a distal end of the wire conveying means to a vicinity of the opposing portions, and for moving the distal end of the wire conveying means away from the opposing portions a predetermined distance upon completion of the insertion of the wire electrode into the nip between the first roller and the second roller.
In accordance with a second aspect, the wire electrical discharge machine is characterized in that the wire conveying means is provided with a hole formed therein.
In accordance with a third aspect, there is provided a wire electrical discharge machine characterized by comprising: a wire electrode for causing electrical discharge to take place between the same and a workpiece; a first roller and a second roller for feeding the wire electrode while nipping the same; and wire conveying means for inserting the wire electrode into a nip between the first roller and the second roller by causing a fluid to flow to opposing portions of the first roller and the second roller, wherein the wire conveying means includes a guide member for guiding the wire electrode by allowing the wire electrode to be inserted in a hollow portion of a main body thereof, a nozzle member engaging on an outer peripheral surface of the guide member in such a manner as to be slidably movable thereon, and fluid driving means for moving a tip of the nozzle member to a vicinity of the opposing portions by the hydraulic pressure of the fluid, and for moving the tip of the nozzle member away from the opposing portions when the influx of the fluid substantially stops.
In accordance with a fourth aspect, there is provided a wire electrical discharge machine characterized by comprising: a wire electrode for causing electrical discharge to take place between the same and a workpiece; a first roller and a second roller for feeding the wire electrode while nipping the same; and wire conveying means for inserting the wire electrode into a nip between the first roller and the second roller by causing a fluid to flow to opposing portions of the first roller and the second roller, wherein the wire conveying means includes: a guide member for guiding the wire electrode by allowing the wire electrode to be inserted in a hollow portion of a main body thereof, the guide member having a branch portion from which the fluid is separated; a nozzle

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