Metal deforming – With means to drive tool – Including pneumatic- or fluid-actuated tool support
Reexamination Certificate
2000-11-08
2003-09-30
Ostrager, Allen (Department: 3725)
Metal deforming
With means to drive tool
Including pneumatic- or fluid-actuated tool support
C100S035000, C100S270000, C100S269140
Reexamination Certificate
active
06626023
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a hydraulic pressure compensating method and device for a pressure-equalizing apparatus for pressure pins of a pressing machine.
BACKGROUND ART
A pressing machine is a machine for forming a work piece such as a metal plate, which is carried in, between a vertically movable upper die and a lower die placed to face the upper die. An outline of a pressing machine equipped with a conventional pressure-equalizing apparatus for pressure pins (for example, Japanese Patent No. 2705393) will be explained with reference to
FIGS. 6 and 7
.
FIG. 7
is an enlarged view of a pressure-equalizing apparatus illustrated in FIG.
6
.
An upper die
1
is attached on an underside surface of a slide
2
movable up and down by means of a slide driving mechanism (not illustrated). A press carrier
5
is movably placed on a bed
50
of the pressing machine, and a bolster
4
is placed on a top portion of the press carrier
5
. The bed
50
is equipped with a die cushion device
9
, a cushion cylinder
9
b
fixed to a cushion rod
9
j
inside the die cushion device
9
is movable up and down. A cushion pad
10
is placed on the cushion cylinder
9
b
so as to be in contact therewith and separate therefrom, and a pressure-equalizing plate
26
is attached on the cushion pad
10
. A plurality of pressure-equalizing cylinders
8
are attached on the top surface of the pressure-equalizing plate
26
, and a pressure-equalizing piston
8
b
is slidably inserted in each of the pressure-equalizing cylinders
8
. A lower end portion of a pressure pin
7
abuts to the pressure-equalizing piston
8
b
, and an upper end surface of each pressure pin
7
supports a lower die
3
.
An oil chamber
8
d
of each of the pressure-equalizing cylinders
8
communicates with a pressure-equalizing circuit
42
formed inside the pressure-equalizing plate
26
, and the pressure-equalizing circuit
42
is connected with a hydraulic pump
25
via a pipe line
15
. The applied pressure, which is applied when the descending upper die
1
forms a work piece
18
, is transmitted to the oil chambers
8
d
of a plurality of the pressure-equalizing cylinders
8
via a plurality of the pressure pins
7
and the pistons
8
b
, and the applied pressure is equalized by a plurality of the pressure-equalizing cylinders
8
communicated with one another.
An air chamber
52
defined by a cushion piston
9
a
and the cushion cylinder
9
b
is supplied with air of predetermined air pressure from an air source
9
f
via a regulator
9
g
and an air tank
9
h
. The cushion rod
9
j
penetrating in an axial direction is placed at a center portion of the cushion cylinder
9
b
, and an upper end of the cushion rod
9
j
is fixed to the cushion cylinder
9
b.
In the pressing machine equipped with the pressure-equalizing apparatus for the pressure pins having the configuration as above, a hydraulic control of the oil chamber
8
d
of each pressure-equalizing cylinder
8
to equalize the applied pressure is carried out in accordance with a method shown in FIG.
8
.
The oil chamber
8
d
of each pressure-equalizing cylinder
8
communicates with one another via the pressure-equalizing circuit
42
of the pressure-equalizing plate
26
. An electromagnetic valve
20
is placed at an inlet side of a hydraulic port at one end of the pressure-equalizing circuit
42
, and an electromagnetic valve
21
is placed at an outlet side of the hydraulic port at the other end. The oil of an oil tank
29
is fed to the pressure-equalizing circuit
42
via the electromagnetic valve
20
at the inlet side by means of the hydraulic pump
25
, and the pressure oil from the electromagnetic valve
21
at the outlet side is returned to the oil tank
29
. The electromagnetic valve
20
at the inlet side and the electromagnetic valve
21
at the outlet side have two positions: an electromagnetic valve open position
27
and an electromagnetic valve closed position
28
. The electromagnetic valve operates in the electromagnetic valve closed position
28
when an off signal is inputted, and it operates in the electromagnetic valve open position
27
when an on signal is inputted.
A hydraulic pressure signal detected by a hydraulic pressure detector
22
for detecting the hydraulic pressure at the hydraulic port at the other end of the pressure-equalizing plate
26
, and a positional signal from a position detector
24
for detecting the position of the slide
2
are inputted into a controller
23
. On/off signals to the electromagnetic valve
20
at the inlet side and the electromagnetic valve
21
at the outlet side are outputted from the controller
23
respectively.
When the slide
2
with the upper die
1
being attached thereto descends to form the work piece
18
, the electromagnetic valve
20
at the inlet side and the electromagnetic valve
21
at the outlet side remain in the electromagnetic valve closed position
28
. When the position detector
24
detects that the slide
2
, which has completed forming, ascends and reaches approximately the upper dead center, the on/off signals are outputted to the electromagnetic valve
20
at the inlet side and the electromagnetic valve
21
at the outlet side. In this situation, when the on signal is outputted to the electromagnetic valve
20
at the inlet side, the OFF signal is outputted to the electromagnetic valve
21
at the outlet side, and the ON/OFF signals are alternately and repeatedly outputted in this manner so that the control is carried out to make the hydraulic value detected by the hydraulic pressure detector
22
approach a predetermined hydraulic value.
When the hydraulic value detected by the hydraulic pressure detector
22
is sufficiently close to the predetermined hydraulic value, both the electromagnetic valve
20
at the inlet side and the electromagnetic valve
21
at the outlet side are in the closed position
28
, and the hydraulic pressures of the oil chambers
8
d
of all the pressure-equalizing cylinders
8
are maintained at the predetermined hydraulic value.
In the above art, however, the following disadvantage arises.
The electromagnetic valve
20
at the inlet side and the electromagnetic valve
21
at the outlet side are mounted near the pressure-equalizing plate
26
to make it easy to control the hydraulic pressures of the pressure-equalizing cylinders
8
at predetermined hydraulic pressure. Since the pressure-equalizing plate
26
is placed on a cushion pad
10
, which is always subjected to vigorous vibrations and impacts, the electromagnetic valve
20
at the inlet side and the electromagnetic valve
21
at the outlet side are always subjected to the vigorous vibrations and impacts. Iron powders and oil splashes come into and scatter at the top portions of the pressure-equalizing cylinders
8
placed under the bolster
4
from holes in the bolster
4
in which the pressure pins
7
ascend and descend. Hence, the electromagnetic valve
20
at the inlet side and the electromagnetic valve
21
at the outlet side are always exposed to an atmosphere with iron powders and oil splashes. As a result, oil enters the electromagnetic valve
20
at the inlet side and the electromagnetic valve
21
at the outlet side to frequently produce trouble, thus causing the disadvantage of reducing availability of the pressing machine.
SUMMARY OF THE INVENTION
The present invention is made in view of the aforementioned disadvantage, and its object is to provide a pressing machine with fewer breakdowns in a hydraulic pressure compensating device for a pressure equalizing apparatus.
In order to attain the above object, a hydraulic pressure compensating method for a pressure-equalizing apparatus for pressure pins according to the present invention is a hydraulic pressure compensating method for a pressure-equalizing apparatus for pressure pins, for compensating a hydraulic pressure value of a pressure-equalizing circuit by connecting oil feeding means to a pressure-equalizing circuit, which is provided between a lower die and a die cushion device of a pressing machin
Armstrong Westerman & Hattori, LLP.
Komatsu Artec Ltd.
Ostrager Allen
Self Shelley
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