Pumps – Condition responsive control of pump drive motor – By control of electric or magnetic drive motor
Patent
1994-01-27
1996-08-13
Berisch, Richard A.
Pumps
Condition responsive control of pump drive motor
By control of electric or magnetic drive motor
417 12, 417 441, 417 45, 4174233, 318484, F04B 4906
Patent
active
055450121
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
This invention relates to a soft-start pump control system for a pump motor which operates much more quietly and without the need for a float switch or other level sensing device.
BACKGROUND OF INVENTION
Bilge pumps, sump pumps and similar DC or AC electric powered pumps used to pump out accumulated water traditionally use a float switch for the pump power circuit in which the water level raises and lowers the float sufficiently to close and open the associated switch. Such float switch devices require a number of moving parts which wear or bind and eventually fail; and the wearing and binding is often accelerated by the damp, corrosive and dirty environment in which these float switches are used. Failure of the switch can have catastrophic effects since when the pump does not operate the water accumulates and can flood the area. In the case of bilge pumps, the flooding can sink the vessel.
One attempt to eliminate the need for such float switches includes means to periodically, automatically, e.g. every five minutes, turn the pump on whether or not there is water or liquid buildup. The pump current is then monitored, and, if it is low, a no-load condition is detected and the pump is shut off. If the current is normal, a load condition is detected and the pump is permitted to keep pumping until the water is drained and the low current condition reoccurs. See U.S. Pat. No. 5,076,763, "Pump Control Responsive to Timer, Delay Circuit and Motor Current", by the present inventors. While this solves the float switch problems, it adds another. Namely, in some installations the noise of the pump turning on every five minutes or for a similar time interval annoys owners and crew. For, even if no water is present the pump still relentlessly makes noise every five minutes.
SUMMARY OF INVENTION
It is therefore an object of this invention to provide an improved pump controller system.
It is a further object of this invention to provide such a pump controller system which is simple and reliable, even in dirty, contaminated, hostile environments.
It is a further object of this invention to provide such a pump controller system which operates periodically, automatically to eliminate the need for a float switch but which is quieter in operation.
It is a further object of this invention to provide such a pump controller system combined with a pump to make a smaller, more compact, easy to install unit.
This invention results from the realization that a truly effective pump motor for periodically yet quietly operating a pump can be effected by automatically energizing the pump motor at regular intervals but at reduced power by reducing the duty cycle while sensing the motor current and then stepping up the power if the motor current amplitude indicates that there is liquid to be pumped. The invention can be effectively applied to AC motor applications. In the same manner as DC motors, AC motors also exhibit higher levels of current draw when pumping liquids.
This invention features a soft-start pump controller system for controlling a pump motor, which includes switching mean for supplying power to the pump motor and a periodic duty cycle generator for periodically actuating the switching means at a fraction of the full duty cycle to operate the pump at a reduced, quieter level. There are sensor means for sensing the current drawn by the pump motor, a reference circuit, and a liquid detector for detecting the presence of the liquid to be pumped and responsive to the sensor means in the reference circuit for overriding the periodic duty cycle generator and actuating the switching mean to operate the pump motor continuously at full power when the motor current exceeds a predetermined level indicating liquid is present.
In a preferred embodiment the periodic duty cycle generator may include a duty cycle generator for providing a fractional duty cycle to the switching means and a cycle timer for periodically operating the duty cycle generator. The duty cycle generator may provide a 30% duty cycle. The li
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Anastos William N.
Boyd Stephen B.
Berisch Richard A.
Rule Industries Inc.
Thai Xuan M.
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