| 摘要 |
A sump pump includes a submersible electric motor for driving an impeller which discharges water radially outward into a volute oriented in a horizontal plane at the bottom of the device. An optical sensor located at a predetermined pump-operating level utilizes the light reflecting and refracting properties of the sensor-chamber interface to sense the presence or absence of water at such level. In a first embodiment, the pump includes a supplementary water level-sensing chamber which has a first leg ascending from an inlet near its lower end to an overflow point at the top of a vertical barrier separating the first leg from a second leg which descends to the low pressure area of the impeller. The optical sensor is located at the overflow point such that the sensor will detect water and therefore activate the motor and the pump when the static water level is at least as high as the overflow point and will continue to detect water as the level subsequently drops because the pump will siphon water over the overflow point until the siphon is broken when the water level in the sump drops below the inlet of the first leg of the sensing chamber. When that occurs, the optical sensor will respond to the air drawn into the chamber by the pump and the control circuit will shut off the pump motor. In the preferred embodiment a single optical sensor is selectively positioned within the sump chamber to establish the pump-activating level. When the optical sensor senses water at this level, the pump motor is started, and once the water level falls below the pump-activating level, a signal for stopping the motor is generated. However, a delay circuit operates to delay the stopping of the motor for a predetermined time interval equal to the time required to pump a predetermined volume of water from the sump chamber. After this delay, the motor is stopped and will remain so until the liquid has again risen in the sump to the pump-activating level. In both embodiments, a single optical sensor functions to detect both the upper and lower levels which are predetermined to be the pump-starting and the pump-stopping control levels.
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