Matsushita Electric Works, Ltd.

Koji Soshin

Yoji Minami

Shinichi Okamoto

Hirotada Higashihama

Toshiaki Saito

Hisashi Usui

An electrical leak detecting apparatus for detecting electrical leak of a power supply device includes two voltage division elements which have an identical impedance value and are connected to each other in series between input terminals or output terminals of a DC/AC conversion circuit of the power supply device, a detection element which has one end connected to a junction of the voltage division elements, a capacitor which is inserted between the other end of the detection element and ground and a decision member which receives a voltage drop across the detection element as a detection signal and processes the detection signal so as to judge occurrence of the electrical leak.

Electrical leak detecting apparatus

A power tool includes a DC motor for tightening a fastener through three consecutive stages. In the first stage, the motor is rotated at a high speed to tighten the fastener to a pre-seated condition which is acknowledged by the tool. Then, the motor is temporarily stopped and restarted at a low speed for tightening the fastener to its seated condition to complete the second stage. At the third stage, a control is made to gradually increase a field current in a feedback manner by constantly monitoring the field current flowing through the motor up to a predetermined current limit determined as directly related to an intended tightening torque at which the fastener is tightened past the seat condition. After the field current reaches the current limit, the motor is stopped to complete the tightening cycle. By monitoring the field current during the third stage to control the field current in the feedback manner, it is possible to accurately determine the final tightening torque which is related substantially directly to the field current, assuring to tighten the fastener accurately to a desired final torque. The tool is also capable of increasing the field current at differing rates up to the current limits of different values within a constant period of time so as to complete the tightening of the fastener within substantially the same perod of time irrespective of the differing requirements for the final tightening torque.

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Toyonaka, Japan

Koji Soshin