Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting – Positioning of a mold part to form a cavity or controlling...
Reexamination Certificate
1999-09-14
2002-01-08
Heitbrink, Jill L. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
Positioning of a mold part to form a cavity or controlling...
C264S297800, C318S625000, C425S167000, C425S233000, C425S344000, C425S346000
Reexamination Certificate
active
06337042
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a press machine and a method of manufacturing pressed products, and particularly to an improvement for reducing mutual interference between a plurality of sets of molds to enhance the processing accuracy.
2. Description of the Background Art
FIG. 6
is an explanation diagram showing the structure of a conventional press machine as a background of the invention. This machine
151
has a bottom base
71
installed on the floor, a pair of supports
75
a
and
75
b
uprightly provided on the bottom base
71
, and a top base
72
supported on the supports
75
a
and
75
b
. The bottom base
71
, supports
75
a
and
75
b
, and top base
72
fixedly coupled to each other form a frame stand
86
. A pair of fixed molds
73
a
and
73
b
are fixed on the bottom base
71
. Fixed on the top base
72
are a pair of a (first) servo motor
76
a
and a (second) servo motor
76
b.
The servo motors
76
a
and
76
b
are respectively in mesh with ball threads
77
a
and
77
b
, which rotate to individually drive the ball threads
77
a
and
77
b
in the vertical direction. Moving molds
74
a
and
74
b
are fixed at the lower ends of the ball threads
77
a
and
77
b
, respectively.
The moving molds
74
a
and
74
b
are located right above the fixed molds
73
a
and
73
b
to face the fixed molds
73
a
and
73
b
, respectively. The servo motors
76
a
and
76
b
rotate in the normal rotation and reverse rotation directions to move the moving molds
74
a
and
74
b
in the mold-closing direction (i.e. downward) and in the mold-opening direction (i.e. upward).
The servo motors
76
a
and
76
b
are supplied with current (i.e., electric current) from a (first) servo amplifier
78
a
and a (second) servo amplifier
78
b
, respectively. The servo amplifiers
78
a
and
78
b
are individually controlled by an amplifier controlling unit
85
, so that the magnitudes of currents supplied to the servo motors
76
a
and
76
b
are controlled individually. The amplifier controlling unit
85
includes a CPU
80
and a pulse generator
79
.
FIG. 7
is a block diagram showing the inside structure of the servo amplifier
78
a
, which is representative of the servo amplifiers
78
a
and
78
b
. The servo amplifier
78
a
is supplied with a directing value X
0
related to the operating position of the servo motor
76
a
(i.e. the rotating position of the rotor) from the pulse generator
79
and a measured value X related to the operating position of the servo motor
76
a
from an encoder
90
.
As shown in the timing chart of
FIG. 8
, the directing value X
0
is represented by the number of pulses along the time series. A normal rotation directing signal CW is outputted in pulse form when directing that the servo motor
76
a
should operate in the normal rotation direction, and a reverse rotation directing signal CCW is outputted in pulse form when directing that it should operate in the reverse rotation direction. The cumulative value of the difference between the number of pulses of the normal rotation directing signal CW and the number of pulses of the reverse rotation directing signal CCW corresponds to the directing value X
0
related to the operating position of the servo motor
76
a.
The rate of change of the directing value X
0
corresponds to the target value of the operating speed of the servo motor
76
a
(i.e. its rotating speed), which is proportional to the pulse frequency as shown in FIG.
8
. The encoder
90
outputs pulses of the same form in correspondence with the amount of operation of the servo motor
76
a
(i.e. the amount of rotation of the rotor).
Referring to
FIG. 7
again, the subtracter
91
calculates the difference between the directing value X
0
and the measured value X and outputs the calculated value as a positional deviation &Dgr;X. The amplifier
92
amplifiers the positional deviation &Dgr;X. The subtracter
91
and the amplifier
92
form a position controlling unit. The F/V converter
97
converts the rate of time change in the measured value X, i.e., the frequency of the pulses representing the measured value X to a voltage signal. The subtracter
93
calculates the difference between the output signal from the amplifier
92
and the output signal from the F/V converter
97
and outputs the calculated value as a speed deviation &Dgr;S. The amplifier
94
amplifies the speed deviation &Dgr;S. The subtracter
93
, amplifier
94
and F/V converter
97
form a speed controlling unit.
The output signal from the amplifier
94
is inputted to a current amplifier
96
. The current amplifier
96
amplifies the input signal and supplies a current I proportional in magnitude to the input signal to the servo motor
76
a
. Thus the current I is controlled so that the measured value X follows the directing value X
0
at speed proportional to the difference between the measured value X and the directing value X
0
. The CPU
80
shown in
FIG. 6
executes arithmetic processing and the directing value X
0
is outputted through the pulse generator
79
on the basis of the value calculated in the arithmetic processing. The operation of the servo motor
76
a
is thus controlled.
FIG. 9
is a flowchart showing the procedure of the arithmetic processing performed by the CPU
80
. When the arithmetic processing is started, first, the processings in steps S
51
and S
52
are simultaneously executed. Specifically, the servo motors
76
a
and
76
b
are driven to return to the origin (the initial position). This processing is continued until they have returned to the origin (step S
53
), and the process moves to steps S
54
and S
55
after it is finished. When they have returned to the origin, the moving molds
74
a
and
74
b
are positioned at the standby position separated above the fixed molds
73
a
and
73
b.
In the following steps S
54
and S
55
, the servo motors
76
a
and
76
b
are driven to perform weighting operation. Then the moving molds
74
a
and
74
b
move in the mold-closing direction to respectively hit on the fixed molds
73
a
and
73
b
, and they are further pressurized for the press work. Steps S
54
and S
55
are simultaneously executed. These processes are executed until the press work is completed (step S
56
). When the press work has been finished, the process moves to steps S
57
and S
58
.
In steps S
57
and S
58
, the servo motors
76
a
and
76
b
are driven to perform withdrawing operation. Then the moving molds
74
a
and
74
b
move in the mold-opening direction to return to the standby position. The steps S
57
and S
58
are carried out at the same time. These processes are continued until they return to the standby position (step S
59
). When they have returned, the process moves to steps S
54
and S
55
again. The above-described processes are repeated to repeatedly carry out the press work.
FIG. 10
is a flowchart showing the internal flow in step S
54
, which is representative of steps S
54
and S
55
. Similarly,
FIG. 11
shows a flowchart showing the internal flow in step S
57
, which is representative of steps S
57
and S
58
.
FIG. 12
is a timing chart showing variations in the target value of the operating speed (i.e. the changing rate of the directing value X
0
), the positional deviation &Dgr;X, and the torque of the servo motor
76
a
that are caused in the weighting operation of step S
54
and the withdrawing operation of step S
57
. Now, referring to
FIGS. 10
to
12
, the weighting operation and withdrawing operation of the machine
151
will be described.
When the weighting operation based on the processing in step S
54
is started, first, the moving mold
74
a
is driven to move in the mold-closing direction at high speed (step S
61
). At this time, the target value of the operating speed first increases from zero, stays at a high value when the directing value X
0
reaches a given reference value, and then decreases when the directing value X
0
reaches another reference value. Subsequently, the target value of the operating speed is maintained at a
Aoki Hideji
Kawano Yasuo
Nakashima Suekazu
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