Alarm system for constructional machine

Abstract

An excavator includes an upper structure swingably supported by a lower structure. A worker position sensor consists of a plurality of radio frequency transceivers provided in the excavator and a radio frequency transceiver carried by each of the excavation workers working within the working range of the excavator. A signal processing unit determines whether the relative distance between each worker and the excavator is either of short distance, slightly long distance or long distance and identifies the position of each worker for each of the predetermined identifying areas. A determining signal from the signal processing unit is supplied to a control unit. The control unit is connected to a drive unit which includes electro-hydraulic proportional valves for energizing actuators for positioning, swing, and traveling of the excavator. This control unit is also connected to a machine sensor which includes a swing angle sensor, a traveling level sensor, and a swing operation lever sensor. The control unit determines whether the machine is moved to approach the workers. The control unit controls the machine so that the lower structure stops or travels slowly or the upper structure swings slowly when the machine is approaching the workers and, so that the movement of the machine remains unchanged when it is moved away from the workers.

Dependencies are inferred from the claim text.