Abstract: A charging system includes an electric power tool (2) and a charger (1) having internal rechargeable batteries (6) and a controller (9) for monitoring the charge/discharge level of the batteries (6). The electric power tool (2) additionally includes a pair of charge terminals (13a, 14a) for carrying current to charge the batteries (6), a temperature terminal (15a) for outputting to the charger (1) data on the temperature of the batteries, and a data terminal (16a) for outputting to the charger data on the battery charge/discharge level from the controller (9). The charger (1) includes a pair of charge terminals (13b, 14b), a temperature terminal (15b), and a data terminal (16b) that are electrically connected to the corresponding tool terminals when the tool (2) is set on the charger for a charge.

Abstract: A belt drift control device (20) is mounted in the side wall (2a) of belt sander (1) comprises a shoulder bolt (22) threaded through a nut 21 in the side wall (2a). A generally conical, tapered roller (23) is rotatably engaged with the free end of the shoulder bolt (22). The tapered roller (23) comprises a taper portion (24) and a flange (24a). The axial movement of the tapered roller (23) is restricted by a washer (26) and a stop ring (27). A control knob (29) is fitted around the head of the shoulder bolt (22) and pressed outwardly by a compression spring (28) surrounding the shoulder bolt (22). Rotation of the control knob (29) axially feeds the shoulder bolt (22) to permit adjustment of the position of the tapered roller (23) relative to an abrasive belt (10). The tapered roller (23) is preferably positioned such that the top end of the taper portion (24) is in contact with the left edge (10a) of the abrasive belt (10) when the belt (10) is a normal position.

Abstract: A battery charger includes a microcomputer operable to receive an input value corresponding to a value of charging current. A thyristor has the gate connected to an output port of the microcomputer. The microcomputer operable to adjust the firing angle of the thyristor for controlling the value of the charging current through a phase control of the charging current in response to the input value. A capacitor has a first electrode connected to the gate of the thyristor. A transistor has the collector connected to a second electrode of the capacitor, the base connected to the output port of the microcomputer, and the emitter connected to a power source voltage for the microcomputer.

Abstract: A battery charger includes a battery voltage detecting circuit for detecting a voltage of a battery during a charging operation. The battery voltage detecting circuit includes a pair of a first and a second voltage-dividing resistor. A transistor is interposed between the first and second voltage-dividing resistors. A predetermined voltage is applied to the base of the transistor, so that the battery voltage is detected based on the voltage divided by the first and second voltage-dividing resistors.

Abstract: A speed control device for a DC motor controls the rotational speed of the DC motor through adjustment of a duty cycle of a semiconductor switching element. The rotational speed to be obtained is determined by an amount of operation of an operation member. A second contact switch is arranged to bypass the semiconductor switching element and is turned on to eliminate influence of the internal resistance of the semiconductor switching element. A power source contact switch is provided between a power source and the DC motor and is turned on and off through operation of the operation member.

Abstract: A tightening tool includes a hammer for impacting on an anvil which drives a nut etc. A microphone is provided for converting impact sounds of the hammer on the anvil into an electric signal. A counting device counts the number of pulses of the electric signal. A setting device is provided for setting a set number of impacts to be obtained. A switch device compares the counted number of pulses with the set number and stops a motor for driving the hammer when the number of pulses coincides with the set number.

Abstract: A tightening tool includes a hammer for impacting on an anvil which drives a nut etc. A microphone is provided for converting impact sounds of the hammer on the anvil into an electric signal. A counting device counts the number of pulses of the electric signal. A setting device is provided for setting a set number of impacts to be obtained. A switch device compares the counted number of pulses with the set number and stops a motor for driving the hammer when the number of pulses coincides with the set number.

Abstract: A speed control device for a DC motor includes a voltage maintaining circuit connected between the DC motor and a comparator circuit for maintaining the voltage corresponding to an electromotive force when a pulse wave outputted from a pulse-width extension circuit is at a level for off-operation of a switch element. Additionally, an average voltage maintaining circuit is connected between the DC motor and the comparator circuit and maintains in average the voltage corresponding to the back electromotive force produced in the DC motor during the time when the control pulse signal outputted from the control pulse signal output circuit is not at a level for on-operation of the switch element.