Abstract: A silencing device for a vacuum cleaner includes dampers for absorbing operational vibration of a suction motor. The operational noises of the suction motor are intercepted and suppressed by a middle case, a lower case, a bottom case and a top case. The exhaust noises caused by exhaust air flow are repeatedly absorbed and suppressed by a plurality of exhaust ports. The exhaust air flow is also dispersed so as to suppress the exhaust noises. In the primary embodiment, the noises generated by both the suction motor and the exhaust air flow are effectively suppressed to desired low levels. In a second embodiment, the silencing device comprises a noise absorber for absorbing and suppressing both suction noises caused by suction air flow and operational noises of the suction motor. The silencing device also has a cover for covering and supporting the front surface of the noise absorber. The back of the noise absorber is supported by a rear supporter.

Abstract: An ultrasonic scanning device includes an ultrasonic sensor mounted for rotation. The sensor can be automatically oriented in a predetermined reference position from a random position. During a scanning operation the sensor is rotated by incremental angles. The length of the angles is changed after a predetermined time elapse following the initiation of a scanning operation.

Abstract: A self moving robot cleaner capable of moving to an automatic charging unit to charge its battery when a charging voltage of the battery is decreased to below a predetermined level during a cleaning operation and then again carrying out the cleaning operation. The robot cleaner has a cleaner body, a suction unit provided in the cleaner body for sucking dirt on a floor, a navigation sensor positioned at an upper portion of the cleaner body for sensing a distance to and a direction of an obstacle and for outputting a distance sensing signal and a direction sensing signal, a driving unit positioned at a lower portion of the cleaner body for moving the cleaner body in a moving direction, and a control unit for determining a cleaning area and a moving direction in response to the distance sensing signal and the direction sensing signal from the navigation sensor and outputting a control signal to move the cleaner body and a control signal to drive the suction unit.

Abstract: An ultrasonic scanning device includes an ultrasonic sensor mounted for rotation. The sensor can be automatically oriented in a predetermined reference position from a random position. During a scanning operation the sensor is rotated by incremental angles. The length of the angles is changed after a predetermined time elapse following the initiation of a scanning operation.