Wire electrical discharge machine

Details Wire electrical discharge machine Wire electrical discharge machine

2000-05-25

2001-11-20

Evans, Geoffrey S. (Department: 1725)

Electric heating

Metal heating

Cutting or disintegrating

Reexamination Certificate

active

06320152

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 mechanism for feeding and collecting a wire electrode.
2. Description of the Related Art
A conventional wire electrical discharge machine disclosed in Japanese Patent Unexamined Publication No. Hei. 7-276146 will be described with reference to
FIGS. 4
to
6
. In
FIGS. 4
to
6
, the wire electrical discharge machine is a machine tool wherein a phenomenon of electric discharge is caused to take place between a wire electrode land a workpiece
2
to perform cutting-out processing with respect to the workpiece
2
such as a superalloy. When discharge machining is started, the wire electrode
1
must be inserted in advance in a start hole formed in the workpiece
2
, and the wire electrode
1
must always be fed during wire electrical discharge machining.
In terms of its main elements, the wire electrical discharge machine is comprised of a mechanism for feeding the wire electrode
1
and a mechanism for collecting it; a driving section for rotating a capstan roller
32
of this mechanism; a pressing section for imparting a pressing force to a pinch roller
52
; and a processing tank
9
placed on a surface plate
4
to keep the workpiece
2
immersed in a working fluid
7
.
The mechanism for feeding the wire electrode
1
is adapted to feed the wire electrode
1
, which is wound around a feed bobbin
10
, by means of a pulley
11
and a lower roller
12
, and is arranged such that the fluid flowing out from a pump
13
serving as a liquid supplying means, together with the wire electrode
1
, is passed through a pipe
14
incorporated in a lower arm
6
, and is fed into a gap between the capstan roller
32
and the pinch roller
52
.
The mechanism for collecting the wire electrode
1
is arranged such that the wire electrode
1
fed from the lower roller
12
is passed through the pipe
14
, and while the wire electrode
1
is being nipped by a nipping section formed by the capstan roller
32
and the pinch roller
52
, the two rollers
32
and
52
rotate to take up the wire electrode
1
and accommodate it in a collection box
60
.
As shown in
FIG. 5
, the driving section for the capstan roller
32
is arranged such that a shaft of a drive motor
20
is coupled to one end of a shaft
24
by means of a coupling
22
, the other end of the shaft
24
is fixed to the capstan roller
32
by a bolt
36
, and the shaft
24
is supported by bearings
28
and
29
engaged and fixed in a groove portion of a housing
30
, and is engaged in a seal
26
provided on the outer end of the groove portion of the housing
30
.
A pressing portion for the pinch roller
52
is rotatably supported by a shaft
47
by means of a pair of bearings
58
incorporated in the pinch roller
52
, and a lever
21
is fixed to a periphery of the shaft
47
and has one end supported rotatably and the other end fixed to a distal end of a spring
58
so as to impart a pressing force to the pinch roller
52
and nip the wire electrode
1
at its surface of contact with the capstan roller
32
. It should be noted that the other end of the spring
58
is fixed to a projecting portion
61
formed on an unillustrated casing.
A first gear
34
and a second gear
54
are respectively fixed to the capstan roller
32
and the pinch rollers
52
. Here, the reason for disposing the gears
34
and
54
in the vicinities of the two rollers
32
and
52
is that the maintenance is facilitated.
Referring to
FIGS. 4
to
6
, a description will be given of the operation of the wire electrical discharge machine constructed as described above. After the wire electrode
1
is inserted in advance in the start hole formed in the workpiece
2
, and the lever
21
is raised by an unillustrated cylinder, the wire electrode
1
, together with the liquid flowing out from the pump
13
through the lower roller
12
, is passed through the pipe
14
, and a liquid column in which the wire electrode
1
is entrained is pressed and inserted into the gap between the two rollers
32
and
52
. By means of this insertion, the pinch roller
32
undergoes rotating operation by the lever
21
so as to enlarge the gap between the two rollers
32
and
52
and allow the wire electrode
1
to be inserted therethrough. Incidentally, after this insertion is finished, the supply of the liquid is stopped.
Next, while the phenomenon of electric discharge is caused to take place, between the wire electrode
1
and the workpiece
2
, the workpiece
2
is subjected to cutting-out processing, and the drive motor
20
is rotated, which in turn causes the first gear
34
fixed to the shaft
24
to rotate and the second gear
54
to rotate simultaneously. Consequently, the capstan roller
32
and the pinch roller
52
rotate while nipping the wire electrode
1
, the wire electrode
1
is fed from the wire bobbin
10
through the pulley
11
, and the used wire electrode
1
is accommodated in the collection box
60
.
However, curling of the wire electrode
1
can sometimes occur, so that there has been a problem in that the wire electrode
1
becomes entangled with the first gear
34
and/or the second gear
54
, or the wire electrode
1
in the collection box
60
assumes a bulky state.
The reason for this is that, in the first place, since the pinch roller
52
is rotated about the fulcrum of rotation of the lever
21
, the pinch roller
52
is moved perpendicularly to the capstan roller
32
, so that the pinch roller
52
is deformed as shown in
FIG. 7
due to the pressing force applied between the two rollers
32
and
52
.
Secondly, since the seal
26
is present between the bearing
29
and the capstan roller
32
, a large distance is produced between the bearing
29
and the pinch roller
52
, and due to the external force applied to the pinch roller
52
flexural distortion is produced and skew occurs in the contact surfaces of the two rollers
32
and
52
.
SUMMARY OF THE INVENTION
The present invention has been made to overcome the above-described problems, and its object is to provide a wire electrical discharge machine in which the curl in the wire electrode is difficult to occur, and trouble is unlikely to occur even if the curl occurs.
To attain this object, according to the invention, there is provided a wire electrical discharge machine 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; perpendicularly moving means for moving the second roller in a perpendicular direction with respect to the first roller; and liquid supplying means for guiding the wire electrode into a gap between the first roller and the second roller by means of a liquid.


REFERENCES:
patent: 4027815 (1977-06-01), Young
patent: 4866970 (1989-09-01), Castiglioni
patent: 5073691 (1991-12-01), Magara et al.
patent: 5495086 (1996-02-01), Onandia
patent: 59-14428 (1984-01-01), None
patent: 63-312025 (1988-12-01), None
patent: 64-20929 (1989-01-01), None
patent: 1-150676 (1989-06-01), None
patent: 7-276146 (1995-10-01), None
patent: 1-92029 (1989-04-01), None
International Search Report

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