Electric heating – Metal heating – Cutting or disintegrating
Reexamination Certificate
2002-12-09
2004-12-14
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
Cutting or disintegrating
C219S069140
Reexamination Certificate
active
06831245
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an electric discharge machining apparatus using a wire electrode as a tool for supplying electric discharge energy between the wire electrode and an electrically conductive subject to be machined to machine the subject into a desired shape. Particularly the invention relates to improvement in a sealing unit, which suppresses outflow of a machining solution from a machining tank when the subject is machined while immersed in the machining solution.
BACKGROUND ART
FIG. 8
is a schematic side view showing a conventional wire electric discharge machining apparatus. In the drawing, the reference numeral
1
designates a machining tank disposed on an X-Y cross table of an apparatus body not shown. A table
3
is disposed in the inside of the machining tank
1
. The machining tank
1
is set in a state in which a subject
6
to be machined is immersed in a machining solution
7
. Reference numeral
10
designates an upper wire guide device. A wire guide, which supports a wire electrode
11
so that the wire electrode
11
can slide freely, is provided in the inside of the upper wire guide device
10
. The upper wire guide device
10
is retained above the subject
6
by a Z axis
13
which moves up and down in the drawing. Reference numeral
15
designates a lower wire guide device. A wire guide, which supports the wire electrode
11
so that the wire electrode
11
can slide freely, is provided in the inside of the lower wire guide device
15
. The lower wire guide device
15
is retained in a position below the subject
6
and opposite to the upper wire guide device
10
by a lower arm
17
. Reference numeral
20
designates a long hole which is provided in a side surface of the machining tank
1
and which is long in a front-and-rear direction of the paper plane of the drawing. The lower arm
17
passes through the long hole
20
. The long hole
20
has an opening size which allows the X-Y cross table to move. Reference numeral
24
designates a sealing unit, which is disposed so as to cover the long hole
20
formed in the machining tank
1
. The sealing unit
24
has: a base
23
fixed to the machining tank
1
and having a long hole
23
h like the long hole
20
of the machining tank
1
; a sealing plate
25
defining hole
25
h
allowing the lower arm
17
to pass therethrough and having a length sufficient to cover the machining tank
1
and the long hole
23
h
of the base
23
; and a first packing
26
attached to the base
23
in order to minimize leakage of the machining solution
7
from between the base
23
and the sealing plate
25
. Reference numeral
27
designates a roller retaining mechanism. The roller retaining mechanism
27
has a shaft
28
, and a bearing
29
. The roller retaining mechanism
27
is formed so that the bearing
29
can rotate freely relative to the shaft
28
. The roller retaining mechanism
27
is fixed to the base
23
so that the sealing plate
25
is retained so as to be movable in a front-and-rear direction of the paper plane of the drawing. Reference numeral
30
designates a second packing which is fixed to the sealing plate
25
in order to prevent the machining solution
7
from leaking from a gap between an outer circumferential portion of the lower arm
17
and the through-hole
25
h
of the sealing plate
25
.
An operation of the conventional apparatus configured as described above will be described below. At the time of machining, while a voltage supplied from a power supply not shown is applied between the wire electrode
11
and the subject
6
to generate electric discharge therebetween, the subject
6
is moved with respect to the wire electrode
11
by the X-Y cross table not shown to machine the subject
6
. On this occasion, the subject
6
is entirely immersed in the machining solution
7
an upper surface thereof, stability of electric discharge is obtained so that the wire electrode
11
becomes hard to break. Therefore, the machining solution
7
is stored in the machining tank
1
. In this case, leakage of the machining solution
7
from the long holes
20
and
23
h
, which are formed in the machining tank
1
and the base
23
, respectively and are pierced by the lower arm
17
is suppressed by entirely covering with the sealing plate
25
. That is, when the X-Y cross table moves, the three of the machining tank
1
, the base
23
and the first packing
26
move relative to the sealing plate
25
. When the machining tank
1
moves in a horizontal direction (in the front-and-rear direction of the paper plane of
FIG. 8
) with respect to the lower arm
17
, the distance between the sealing plate
25
and the base
23
is kept constant by the roller retaining mechanism
27
so that the sealing plate
25
and the base
23
are retained in positions where they always come into contact with the first packing
26
. In this state, while the sealing plate
25
and the first packing
26
slide on each other, the machining tank
1
moves in the horizontal direction. On the other hand, when the machining tank
1
moves in an axial direction (in a left-and-right direction of the paper plane of
FIG. 8
) of the lower arm
17
, the machining tank
1
moves while the lower arm
17
and the second packing
30
slide on each other. Hence, leakage of the machining solution
7
from the gap between the base
23
and the sealing plate
25
is suppressed by the first packing
26
. Further, leakage of the machining solution
7
from the gap between the outer circumferential portion of the lower arm
17
and the through-hole
25
h of the sealing plate
25
is suppressed by the second packing
30
.
Since the conventional sealing unit in the electric discharge machining apparatus is configured as described above, the machining solution
7
in the machining tank
1
is contaminated with foreign matter such as sludge at the time of machining. If such a state continues for a long time, the foreign matter is stuck and deposited on the machining tank
1
side surface of the sealing plate
25
. For this reason, the coefficient of friction between the first packing
26
and the sealing plate
25
increases, and the resistance to sliding of the sealing plate
25
also increases. When the resistance to sliding of the sealing plate
25
increases, load imposed on the lower arm
17
increases. As a result, the lower arm
17
is deformed to reduce machining accuracy as shown in
FIG. 9
, which is a plan typical view slightly exaggerated.
Moreover, when the foreign matter such as sludge increases, a gap is produced between the first packing
26
and the sealing plate
25
. As a result, the quantity of leakage of the machining solution
7
increases. Hence, there may arise a problem that the machining solution
7
cannot be stored in the machining tank
1
.
DISCLOSURE OF THE INVENTION
The present invention is designed to solve the aforementioned problems in the background art and an object of the invention is to provide a wire electric discharge machining apparatus in which foreign matter such as sludge produced at a time of machining is not deposited on a surface of a sealing plate and the foreign matter can be removed even if the foreign matter is deposed on the surface of the sealing plate.
In the wire electric discharge machining apparatus according to the invention, a sealing unit is constituted by a sealing plate and a packing, the sealing plate for blocking long hole of a machining tank, a groove is formed along an outer periphery of the long hole, and nozzles are provided for jetting the machining solution into the groove, and a machining solution jetting unit is provided for jetting the machining solution from the nozzles into a small gap formed between a peripheral portion of the long hole and the sealing plate. Further, in the wire electric discharge machining apparatus according to the invention, a plurality of the nozzles are provided and apertures of low-pressure nozzles are made larger than those of high-pressure nozzles. Further, the wire electric discharge machining apparatus according to th
Adachi Akihito
Koba Ryogo
Tanaka Makoto
Evans Geoffrey S.
Mitsubishi Denki & Kabushiki Kaisha
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