Metal deforming – By use of closed-die and coacting work-forcer – Cup or shell drawing
Reexamination Certificate
2001-10-09
2003-05-20
Larson, Lowell A. (Department: 3725)
Metal deforming
By use of closed-die and coacting work-forcer
Cup or shell drawing
Reexamination Certificate
active
06564609
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to an equalizing cushioning apparatus for a pressing machine, and more particularly to an equalizing fluid-operated apparatus which includes a plurality of fluid-operated cylinders and applies substantially equal wrinkling-preventing loads to a workpiece via respective piston rods of the cylinders that are positioned at their neutral positions by a working fluid.
2. Related Art Statement
There is known a pressing machine employing an equalizing cushioning apparatus which includes (a) a cushion pad to which a prescribed movement resistance is applied by a wrinkling-preventing-load applying device, (b) a plurality of fluid-operated cylinders which are provided on the cushion pad and whose pressure chambers are communicated with each other, and (c) a plurality of cushion pins which are interposed between respective piston rods of the fluid-operated, cylinders and a wrinkling-preventing die, and which applies, when the wrinkling-preventing die and an upper movable die cooperate with each other to press a workpiece while preventing wrinkling of the workpiece owing to the above-indicated movement resistance, substantially equal wrinkling-preventing loads to the workpiece via the respective piston rods of the cylinders that are positioned at their neutral positions by a working fluid. In a state in which the wrinkling-preventing die and the upper movable die cooperate with each other to press the workpiece, those two dies are moved with the cushion pad, in a pressing direction relative to a lower fixed die in the form of a punch, against the above-indicated movement resistance, so that the workpiece is worked (i.e., drawn) by a working surface of the punch. This pressing machine is disclosed in, e.g., Japanese Utility Model Document No. 1(1989)-60721, and a pressing machine
8
shown in
FIG. 10
is an example of this machine. Even if respective lengths of the cushion pins of the pressing machine may more or less differ from each other, or the cushion pad thereof may be more or less inclined relative to a horizontal plane, the pressing machine can apply substantially equal wrinkling-preventing loads to the respective cushion pins via the respective piston rods of the fluid-operated cylinders that are positioned-at their neutral positions by the working fluid. Therefore, the pressing machine can provide a desirable wrinkling-preventing-load distribution corresponding to a cushion-pin distribution.
More specifically described by reference to the pressing machine
8
shown in
FIG. 10
, a punch
10
is fixed to a bolster
12
which in turn is supported by a base
16
via a press carrier
14
. A movable die
18
is fixed to a press slide
20
which is movable upward and downward by a drive mechanism, not shown. The bolster
12
has, at respective lattice points, respective through-holes
24
through which respective cushion pins
22
extend. A cushion pad
26
which supports the cushion pins
22
is provided below the bolster
12
, such that the cushion pad
26
extends in a substantially horizontal plane. The cushion pins
22
cooperate with one another to support a wrinkling-preventing die
28
(i.e., a wrinkling-preventing ring) which is provided in the vicinity of the punch
10
. An arbitrary number of cushion pins
22
are provided at respective prescribed positions, depending upon a specific shape of the wrinkling-preventing die
28
. The punch
10
has a plurality of through-holes corresponding to the through-holes
24
of the bolster
12
. The cushion pad
26
has a plurality of hydraulic cylinders
30
corresponding to the through-holes
24
. Respective lower ends of the cushion pins
22
are supported by respective piston rods of the hydraulic cylinders
30
. The punch
10
functions as a lower pressing die, the movable die
18
functions as an upper pressing die, and the hydraulic cylinders
30
function as the fluid-operated cylinders.
The cushion pad
26
is provided in the press carrier
14
, such that the pad
26
is movable upward and downward, and is normally biased upward by an air-operated cylinder
32
. A pressure chamber of the air-operated cylinder
32
is communicated with an air tank
34
which in turn is supplied with pressurized air from a pressurized-air supply
36
via an air-pressure control circuit
38
. The air tank
34
is connected to a shut-off valve
37
and to an air-pressure sensor
39
, so that an air pressure Pa in the air tank
34
or the air-operated cylinder
32
is controlled depending upon a desired wrinkling-preventing load. More specifically described, when the movable die
18
is moved downward with the press slide
20
, the movable die
18
cooperates with the wrinkling-preventing die
28
to sandwich an outer peripheral portion of a workpiece
40
, while preventing wrinkling of the workpiece
40
owing to a biasing force resulting from the air pressure Pa in the air-operated cylinder
32
. When the movable die
18
and the wrinkling-preventing die
28
are further moved downward with the cushion pad
26
, against the biasing force of the air cylinder
32
, the workpiece
40
is drawn by a working surface of the punch
10
. In the present pressing machine, the air-operated cylinder
32
, the air tank
34
, the pressurized-air supply
36
, and the air-pressure control circuit
38
cooperate with one another to provide a wrinkling-preventing-load applying device
42
; and the biasing force of the air-operated cylinder
32
, i.e., the air pressure Pa provides a movement resistance applied to the cushion pad
26
. In addition, the air-operated cylinder
32
provides a gas-operated cylinder, or a fluid-operated cylinder that utilizes a pressurized fluid.
Respective hydraulic chambers (i.e., pressure chambers) of the hydraulic cylinders
30
are communicated via an fluid passage
46
with one another, and the fluid passage
46
is connected via a flexible tube
48
to a piping
50
. A working fluid which is pumped up from a tank
54
by an air-driven hydraulic pump
52
, is supplied via a check valve
56
to the piping
50
. The piping
50
is connected to a hydraulic-pressure control circuit
58
including a relief valve, etc. The hydraulic-pressure control circuit
58
cooperates with the hydraulic pump
52
to control a hydraulic pressure Ps of the working fluid present in the piping
50
and the hydraulic cylinders
30
, to a value which assures that the respective piston rods of all the hydraulic cylinders
30
that are involved in preventing wrinkling during drawing, i.e., the cylinders
30
that support the cushion pins
22
, are kept at their neutral positions. Thus, the cushion pins
22
transmit equal wrinkling-preventing loads to the wrinkling-preventing die
28
. The hydraulic pressure Pa is detected by a hydraulic-pressure sensor
60
which is connected to the fluid passage
46
. In the present pressing machine, the cushion pins
22
, the cushion pad
26
, the hydraulic cylinders
30
, and the wrinkling-preventing-load applying device
42
cooperate with one another to provide an equalizing cushioning apparatus
44
.
The hydraulic pressure Ps and the air pressure Pa are controlled by a control device, not shown. Before a pressing operation is started, e.g., when the current pair of pressing dies are exchanged with another pair of pressing dies, the hydraulic pressure Ps and the air pressure Pa are controlled or adjusted to respective appropriate pressure values Ps
0
, Pa
0
. The hydraulic pressure Ps
0
is determined in a “trial” pressing operation or according to a mathematical expression, so that the respective piston rods of the hydraulic cylinders
30
may be positioned at their neutral positions during the pressing operation. In the latter case, the hydraulic pressure Ps
0
is so determined as to satisfy the following expression (1):
Xav
=(
Fs−n·As·Ps
0
)
V
2
·As
2
·K
(1)
where
Xav is an average forced-movement distance of the piston rod of each hydraulic cylinder
30
;
As is a pressure-receiving area of eac
Amano Masayoshi
Kawamura Shinji
Kirii Kazunari
Kirii Sigehiro
Kyoho Machine Works, Ltd.
Larson Lowell A.
LandOfFree
Equalizing fluid-operated apparatus and method of assembling... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Equalizing fluid-operated apparatus and method of assembling..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Equalizing fluid-operated apparatus and method of assembling... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3064112