Pumps – Condition responsive control of pump drive motor – By control of electric or magnetic drive motor
Reexamination Certificate
1999-09-29
2001-06-12
Thorpe, Timothy S. (Department: 3746)
Pumps
Condition responsive control of pump drive motor
By control of electric or magnetic drive motor
C417S045000
Reexamination Certificate
active
06244825
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a pump-protecting device, a pump-protecting method and a pumping apparatus having such a device.
BACKGROUND OF THE INVENTION
Conventionally, a vacuum pumping apparatus making use of a vacuum pump has been used to evacuate a predetermined container. The conventionally used vacuum pumping apparatus
1
disclosed in Japanese Laid-Open Patent Publication No. 8-42487 is shown in FIG.
12
. The vacuum pumping apparatus
1
comprises a vacuum pump (pump)
4
for evacuating a vacuum container
2
by discharging the air through a valve
3
, a motor
5
for driving the vacuum pump
4
, an inverter
7
for adjusting power transmission from a power source
6
to the motor
5
, and a controller
8
for controlling the inverter
7
. The above-described apparatus
1
is equipped with a mode for operating the pump at a low speed of revolution, in order to prevent condensed or sublimated gas from adhering onto the inner wall of the pump.
However, if the motor
5
becomes overloaded for some reason, the above-described pumping apparatus
1
does not take any effective countermeasure. Therefore, if the motor
5
becomes overloaded, rotary drive of the motor
5
has to be discontinued to protect the motor
5
. In consequence, the above-described pumping apparatus
1
can not keep the vacuum condition any longer. Accordingly, products being processed in the vacuum container become defective, contributing to various problems including increased costs.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an apparatus and a method for protecting a vacuum pump while maintaining the vacuum condition even when the motor becomes overloaded.
A characteristic of the pump-protecting device, the pump-protecting method and the pumping apparatus according to the present invention is to protect the vacuum pump from being overloaded or to decrease power consumption by changing a driving amount of a drive means in accordance-with a load value received by the drive means of the vacuum pump. Specifically, a characteristic of the pump-protecting device, the pump-protecting method and the pumping apparatus according to the present invention is to detect power consumption of the drive means or necessary torque by using the load detector, and to decrease, to increase, or to variously change the driving amount of the drive means when the load or the rising rate of the load is equal to or greater than a predetermined value. It should be understood that the term, “driving amount”, described in this specification means the speed of revolution, the driving speed, and the rate of acceleration. For example, if a motor is used as a drive means and a load or a rising rate of a load is equal to or greater than the predetermined value respectively, the speed of revolution of the motor is increased, decreased or variously changed.
An essential part of the pump-protecting device and the pump-protecting method of the present invention is to protect the pump and motor from being overloaded while maintaining the vacuum condition by decreasing the speed of revolution of the motor to the predetermined lowest speed by the use of the controller and by maintaining the motor operation at almost the same speed as the predetermined lowest speed when a motor is used as a drive means and if the load value detected by a load-detecting means is equal to or greater than the predetermined value.
Another essential part of the present invention is to maintain the vacuum condition by detecting the overloaded condition of the motor, decreasing the load by decreasing the speed of revolution of the motor again by recognizing that the overloaded condition is transitory by the control means after the load is left under the predetermined period o time.
REFERENCES:
patent: 4242625 (1980-12-01), Hedges
patent: 4511312 (1985-04-01), Hartwig
patent: 4820317 (1989-04-01), Fahey
patent: 4864287 (1989-09-01), Kierstead
patent: 5209110 (1993-05-01), Sano et al.
patent: 5226800 (1993-07-01), Morino
patent: 5582017 (1996-12-01), Noji et al.
patent: 5646499 (1997-07-01), Doyama et al.
Imai Akihiko
Sasaki Tatsuya
Yuzuhara Naoki
Anderson Jay H.
Gray Michael K.
International Business Machines - Corporation
Thorpe Timothy S.
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