Pumps – Condition responsive control of pump drive motor – Responsive to pump or pump fluid temperature
Reexamination Certificate
2001-06-08
2003-04-22
Tyler, Cheryl J. (Department: 3746)
Pumps
Condition responsive control of pump drive motor
Responsive to pump or pump fluid temperature
C417S044100, C318S471000, C318S478000, C361S023000, C361S078000
Reexamination Certificate
active
06551065
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a fan protection device, more particularly to a protection device to protect a fan from overpowering and overheating.
2. Description of the Related Art
Conventional fan protection devices are activated to allow the fans to be shut down when blockage or stalling of the fan is caused by obstacles or less obvious reasons. Fatigue in fan-shafts is unavoidable due to constant use, added to the increase in friction, resulting in heat generation and larger driving current. Thus fans may constantly overheat or overload with large current. Either case will increase the likelihood of fans igniting. This not only damages the fans, but also imposes a greater danger on the systems cooled by the fans. Moreover, when fans are obstructed by obstacles, they may not come to a complete halt, and the continued rotation requires increased current to sustain. When there is no device in conventional fan protection devices to detect such a situation, this kind of damage occurs easily, shortening the life span of the fan and posing great danger to its environment.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a fan protection device as shown in
FIG. 1
, comprising: a temperature detector
10
, a current detector
12
and an alarm unit
14
. The temperature detector
10
is used to detect overheating of the fan. The temperature detector
10
comprises a temperature-voltage transformer
10
a
and an overheating-judgment device
10
b.
The temperature-voltage transformer
10
a
is located at the thermo-generating source of the fan, to transform the thermo-energy thereof into a corresponding voltage signal Vt; and the overheating-judgment device
10
b
is used to determine whether the fan temperature exceeds a predetermined temperature according to an output voltage signal Vt from the temperature-voltage transformer
10
a
and then deciding whether the fan is overheated.
The current detector
12
is used for detecting overload of driving current of the fan. The current detector
12
comprises a current-voltage transformer
12
a
and an overload-judgment device
12
b
. The current-voltage transformer
12
a
is located on the path of the current flow of the fan, for transforming the current of the fan into a corresponding voltage signal Vi; and the overload-judgment device
12
b
is used to determine whether the current of the fan surpasses a predetermined current according to the current-voltage transformer
12
a
and deciding whether the fan is overloaded.
The alarm unit
14
may function as a lockup device. When the fan is operating normally, the lockup device sends a signal V
0
of a first state to keep the switch SW conductive, and allows the fan to maintain normal operations. If one of the overheating and overload of the fan is detected, the lockup device outputs a signal of a second state to cut off the power supply to the fan to stop the fan from operating, until the lockup device is reset.
REFERENCES:
patent: 5168415 (1992-12-01), Osuga
patent: 5534854 (1996-07-01), Bradbury et al.
patent: 5539601 (1996-07-01), Farag
patent: 5831405 (1998-11-01), Massie
patent: 6023402 (2000-02-01), Kaminski
patent: 6040668 (2000-03-01), Huynh et al.
patent: 6122153 (2000-09-01), Becker
patent: 6135718 (2000-10-01), Yang
Intellectual Property Solutions Incorporated
Liu Han L.
Mitac International Corporation
Tyler Cheryl J.
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