Presses – Reciprocating press construction – Fluid pressure actuation
Reexamination Certificate
2002-11-01
2004-04-20
Ostrager, Allen (Department: 3725)
Presses
Reciprocating press construction
Fluid pressure actuation
C072S453180, C060S476000, C060S413000
Reexamination Certificate
active
06722270
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hydraulic press and particularly relates to a hydraulic press suited for sheet metal formation.
2. Description of the Related Art
To manufacture the door, food, trunk lid or the like of a vehicle, hem-press for peening an inner component and an outer component at their edges is conducted. To this end, a hydraulic press is employed. According to a conventional hydraulic press, a hydraulic pump is constantly driven by an induction motor. If no oil is supplied to a hydraulic cylinder, pressure oil is returned to a tank by an unload valve. This causes the temperature rise of the oil, requires a water-cooling cooler or the like which water-cools the hydraulic oil and consumes lots of energy (power).
The conventional hydraulic press has the following disadvantage. If a single hydraulic cylinder is employed, pressure oil in large quantities and much time are required to elevate dies, with the result that productivity deteriorates. To solve this disadvantage, there is proposed in JP-A-2000-254799 (to be referred to as “Reference 1” hereinafter) that a screw sliding driver
15
and a hydraulic cylinder sliding driver
22
are disposed in parallel, the screw sliding driver
15
is employed for fast elevation and the hydraulic cylinder sliding driver
22
is employed only to pressurize a workpiece. In addition, there is proposed in JP-A-10-263888 (to be referred to as “Reference 2” hereinafter) that a high speed cylinder
36
for elevation and a pressure cylinder
37
for pressurizing a workpiece are employed. Further, there is proposed in JP-A-10-180499 (to be referred to as “Reference 3” hereinafter) that a first cylinder
24
for pressurizing a workpiece, a second cylinder
25
for descending the workpiece and a third cylinder
26
for ascending the workpiece are provided and a hydraulic pump
17
is driven by an alternating current servo motor
18
, thereby accurately controlling a ram
6
.
Nevertheless, according to Reference 1, since the screw sliding driver
15
and the hydraulic cylinder sliding driver
22
are provided, the structure of this hydraulic press and control over the hydraulic press are disadvantageously complicated. According to Reference 2, since the two cylinders
36
and
37
are connected in series and have large heights, the hydraulic press becomes disadvantageously large in size. Further, according to Reference 2, since a servo valve
52
is employed to adjust the pressure and quantity of oil, the hydraulic press has disadvantageously heavy energy loss. According to Reference 3, although the alternating current servo motor
18
is employed, the hydraulic pump
17
connected to the motor
18
discharges oil in one direction but cannot discharge oil in a counter direction. Due to this, the alternating current servo motor
18
controls only the number of revolutions and torque of the pump
17
and not control the pump
17
to make a counter rotation. As a result, return oil from the respective cylinders
24
,
25
and
26
is returned to the tank
16
, in which tank energy loss and the temperature rise of the oil disadvantageously occur.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a hydraulic press which has the smaller temperature rise of hydraulic oil, which can dispense with a water-cooling cooler or the like, which can be made compact in size and which can realize energy saving.
In order to achieve the above mentioned object, a hydraulic press according to the present invention as shown in
FIG. 2
is characterized by comprising:
a multi-cylinder including a first cylinder chamber
51
having a small pressure receiving area and used for reciprocation, a second cylinder chamber
52
having an equal pressure receiving area to the pressure receiving area of the first cylinder chamber
51
, a third cylinder chamber
53
having a large pressure receiving area and used for reciprocation, and an integral piston member
54
partitioning the respective cylinder chambers
50
;
a constant volume, reversible hydraulic pump
7
, and a servo motor
6
, driving the hydraulic pump
7
to rotate in positive and counter directions;
a closed hydraulic circuit
31
and
34
connecting said first cylinder chamber
51
to said second cylinder chamber
52
through said hydraulic pump
7
;
an automatic supply hydraulic circuit
32
connecting said third cylinder chamber
53
to an oil tank
1
through said automatic supply valve
23
;
a pressurization hydraulic circuit
35
connecting one of discharge ports of said hydraulic pump
7
to the third cylinder chamber
53
through a check valve
27
;
a pressure sensor
28
detecting oil pressure of said third cylinder chamber
53
; and
a controller
80
controlling said servo motor
6
based on a signal from said pressure sensor
28
.
According to the present invention, a first cylinder chamber
51
is employed as a quick feed and pressurization cylinder, a second cylinder chamber
52
is employed as a quick return cylinder and a third cylinder chamber
53
is employed as a pressurization cylinder. During quick feed, a closed hydraulic circuit which ranges from the second cylinder chamber
52
to the first cylinder chamber
51
through a hydraulic circuit
31
, a hydraulic pump
7
and a hydraulic circuit
34
is formed. Since the pressure receiving area of the first cylinder chamber
51
is set equal to that of the second cylinder chamber
52
, the quantity of hydraulic oil discharged from the second cylinder chamber
52
is equal to that supplied to the first cylinder chamber
51
. Due to this, the hydraulic oil discharged from the hydraulic pump
7
is only passed through the closed hydraulic circuit comprising the second cylinder chamber
52
, the hydraulic circuit
31
, the hydraulic pump
7
, the hydraulic circuit
34
and the first cylinder
51
and not returned to an oil tank
1
. Accordingly, no energy loss and no temperature rise of the hydraulic oil occur. It is noted that the hydraulic oil of the oil tank
1
is sucked to the pressurization third cylinder chamber
53
through an automatic supply hydraulic circuit
32
and an automatic supply valve
23
by negative pressure.
Likewise, during quick return, a closed hydraulic circuit which ranges from the first cylinder chamber
51
to the second cylinder chamber
52
through the hydraulic circuit
34
, the hydraulic pump
7
and the hydraulic circuit
31
is formed. By driving the hydraulic pump
7
to rotate in a counter direction, the hydraulic oil is fed from the first cylinder chamber
51
to the second cylinder chamber
52
to thereby regress a piston member
54
. As in the case of the quick feed, no energy loss and no temperature rise of the hydraulic oil occur. It is noted that the hydraulic oil of the third cylinder chamber
53
is relieved to the oil tank
1
through the automatic supply valve
23
and the automatic supply hydraulic circuit
32
. In this way, during the quick feed and quick return, the hydraulic oil is automatically sucked and discharged to and from the third cylinder chamber
53
, thereby decreasing the discharge quantity of the hydraulic pump
7
and making the hydraulic pump
7
small in size.
When pressure is applied, the automatic supply valve
23
is closed. In addition, the hydraulic circuit
34
which communicates with the hydraulic pump
7
is connected to the pressurization hydraulic circuit
35
which communicates with the third cylinder chamber
53
. By driving the hydraulic pump
7
to rotate in a positive direction, the hydraulic oil is fed to the third cylinder chamber
53
and the first cylinder chamber
51
and the piston member
54
is pressed out with pressure received by a pressure receiving area which is a combination of the pressure receiving area of the third cylinder chamber
53
and that of the first cylinder chamber
51
. At this moment, the oil pressure of the third cylinder chamber
53
is detected by a pressure sensor
28
and the number of revolutions of the servo motor
6
is controlled so
Muserlian Lucas and Mercanti
Nguyen Jimmy
Nippo Industry Co., Ltd.
Ostrager Allen
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