Metal deforming – By use of closed-die and coacting work-forcer – Cup or shell drawing
Reexamination Certificate
2002-06-26
2004-10-19
Ostrager, Allen (Department: 3725)
Metal deforming
By use of closed-die and coacting work-forcer
Cup or shell drawing
C072S453130
Reexamination Certificate
active
06804983
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a die cushion apparatus for a press machine. In particular, the invention relates to a feature in the operating mechanism of a die cushion apparatus.
2. Description of the Related Art
Conventionally, with a single-acting press, when a cylindrical container, for instance, is pressed, the blank is prevented from being wrinkled at the periphery thereof. That is, the press is provided with a die, and a punch is arranged in the lower mold. The punch is fixed to the bolster. A blank holder is provided outside the punch to support the periphery of the blank. This blank holder is supported by cushion pins attached to a die cushion apparatus.
The lower structure of a conventional press machine is described referring to drawings.
FIG. 1
is a sectional side view of the lower structure of a press machine incorporating a conventional die cushion apparatus.
The lower structure
1
of the press machine is provided with a die cushion apparatus
300
, a blank holder
10
, a die
20
, a punch
30
, a bolster
40
, a press bed
50
and a slide
60
.
The press bed
50
is the lower structure of the press frame, and is connected to the upper structure by means of an upright member, and supports the weight of the whole press. The bolster
40
, the lower surface of which is resting on the press bed
50
is a base that supports the punch
30
. The punch
30
is a lower die, the lower surface of which is supported by the bolster
40
. The die
20
is an upper mold, the upper surface of which is attached to a slide
60
. The slide
60
holds the die
20
, is supported on the press frame in a manner such that it is free to move up and down, and is driven up and down by a drive mechanism. The blank holder
10
is a device that sandwiches the periphery of the blank between the upper surface
11
of the blank holder
10
and the lower surface
21
of the die
20
when the machine presses the blank between the die
20
and the punch
30
. The blank holder
10
is also a device that supports the blank after the pressing process is finished and transfers it to an unloading device, and the lower surface of the holder is supported by the die cushion apparatus
300
. The die cushion apparatus
300
is a device for supporting the blank holder
10
, and is attached to the press bed
50
.
Here, the functions that the die cushion apparatus
300
must provide are described. The primary function is the requirement to reduce the noise and vibration produced by the die
20
and the punch
30
during the pressing process (this is called the cushion function). In addition, another function of the apparatus is to clamp the outer periphery of the blank between the lower surface
21
of the die
20
and the upper surface
11
of the blank holder
20
to prevent the outer periphery of the blank from being creased when the die
20
presses the blank (this is called the crease-pressing function). Also, to protect the outer periphery of the blank from being damaged when the die
20
passes bottom dead center and starts to rise, the blank holder
10
that supports the blank is locked so that it does not travel past the bottom dead center position (this is called the locking function). Furthermore, this locking function is preferably also capable of lowering the blank holder
10
with the blank resting on it from the bottom dead center position by a predetermined distance (for example, about 3 mm). Moreover, when the die
20
passes bottom dead center and travels to the top dead center, the blank must be quickly transferred to an unloading device. For this purpose, another function is required that is to lift the blank holder
10
that supports the blank by a predetermined distance (for example, about 35 mm) and then stop the holder (this is called the secondary lifting function).
Next, the construction of a conventional die cushion apparatus is described. The die cushion apparatus is composed of pusher pins
310
, a pusher pad
320
, pneumatic cylinders
330
, a hydraulic servo cylinder
340
, a hydraulic servo valve
350
, a cushion stroke sensor
360
, a hydraulic unit
370
and a hydraulic servo controller
380
, to provide the aforementioned functions.
The pusher pins
310
are rod-shaped structures that support the blank holder
10
. The pusher pins
310
penetrate the bolster
40
, support the lower surface of the blank holder
10
at the top end thereof, and are supported by the pusher pad
320
at the bottom end thereof.
The pusher pad
320
is a structural body that supports the pusher pins
310
, and is disposed below the bolster
40
in a manner such that it is free to move in the up/down direction.
The pneumatic cylinders
330
are air-type RAM cylinders that support the pusher pad
320
from below, and are installed on the press bed
50
. The cylinder members of the pneumatic cylinders
330
are fixed to the lower surface of the pusher pad
320
, and the lower ends of the RAM piston members are supported by the press bed
50
. The cylinder members engage with the RAM piston members in such a manner that they are free to move up and down. The pneumatic cylinders
330
are connected through air piping to an air source (not illustrated).
The hydraulic servo cylinder
340
is a dual-rod-type hydraulic servo cylinder which is attached to the press bed so that the rods of which can move freely in the up/down direction. The upper rod
341
is connected to the pusher pad
320
.
The hydraulic servo valve
350
is a servo control valve for the hydraulic servo cylinder
340
, that drives the upper rod
341
of the hydraulic servo cylinder
340
with a preferred stroke, operating force and speed under the control of the hydraulic servo controller
380
.
The cushion stroke sensor
360
is a sensor for measuring the travel of the pusher pad
320
, the output of which is transmitted to the hydraulic servo controller
380
.
The hydraulic unit
370
is a hydraulic unit dedicated to the hydraulic servo cylinder
340
, and supplies the hydraulic servo cylinder
340
with an operating fluid through the hydraulic servo valve
350
.
The hydraulic servo controller
380
is a control device that actuates the hydraulic servo valve
350
, and outputs control signals to the hydraulic servo valve
350
based on positional information sent from the cushion stroke sensor
360
.
Next, the procedure by which the die cushion apparatus performs the required functions is described.
FIG. 2
shows the movement of the die passing through points
2
,
4
,
3
and
5
and the movement of the blank holder passing through points
6
,
7
,
8
and
9
. The movements of the lower surface of the die moving up and down and the upper surface of the blank holder moving up and down are shown with elapsed time on the abscissa.
The movement curve of the die is similar to that of a sine wave, although it may differ depending on the mechanism of the press machine. The top and bottom of the movement curve are called top dead center point
2
and bottom dead center point
3
, respectively.
When the die is located at the top dead center point
2
, the blank holder
10
remains stationary at an intermediate predetermined point
6
between the top dead center point
2
and the bottom dead center point
3
.
The die
20
moves down from the top dead center point
2
along the movement curve
4
, and reaches the bottom dead center point
3
while pressing the blank against the punch
30
. The blank holder
10
is pushed down by the die
20
and moves to the bottom dead center point
3
. Meanwhile, the outer periphery of the blank is clamped between the upper surface
11
of the blank holder
10
and the lower surface
21
of the die
20
, and is pressed with a predetermined force produced by the pneumatic cylinders
330
. The force prevents the outer periphery of the blank from being creased. Also, since the die cushion apparatus
1
presses the die
20
upwards with a predetermined clamping force created by the pneumatic cylinders
330
, the noise and vibration that would othe
Mori Yoshio
Nagami Shinkichi
Griffin & Szipl, P.C.
Ishikawajima-Harima Heavy Industries Co. Ltd.
Nguyen Jimmy
Ostrager Allen
LandOfFree
Die cushion apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Die cushion apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Die cushion apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3291365