초록 ▼

The instant invention relates to a power screwdriver with torque limiter, with a drive unit and a secondary transmission, with an output shaft for the attachment of a keyed bit. According to the invention the drive unit is a pneumatic motor (2) with a compressed-air intake (13) and a compressed-air

The instant invention relates to a power screwdriver with torque limiter, with a drive unit and a secondary transmission, with an output shaft for the attachment of a keyed bit. According to the invention the drive unit is a pneumatic motor (2) with a compressed-air intake (13) and a compressed-air outlet (14), whereby the differential pressure between the compressed-air intake (13) and the compressed-air outlet (14) (measuring circuits 19 and 20) is taken as the measure of the torque produced by the power screwdriver (1). The differential pressure is measured in a differential pressure measuring device (21) and the measure signal is transmitted to a control unit (23). The control unit (23) contains a comparator unit which compares the measured differential pressure signal with a set value of differential pressure (adjusting potentiometer 24) and transmits a switching signal to a switch unit (solenoid valve 19) to switch off the power screwdriver when the compared values become equal. In this manner a simple calculation of torque is achieved by means of a differential pressure measurement in combination with a simple switch-off possibility. In further embodiments the rotational speed of the pneumatic motor is usedr additionally in the determination of torque.

대표청구항 ▼

A power screwdriver having a torque limiter, a drive unit, and a secondary transmission coupled to said driving unit having an output shaft for the attachment of a keyed bit, characterized in that said drive unit includes a pneumatic motor having a compressed-air intake and a compressed-air outlet;

A power screwdriver having a torque limiter, a drive unit, and a secondary transmission coupled to said driving unit having an output shaft for the attachment of a keyed bit, characterized in that said drive unit includes a pneumatic motor having a compressed-air intake and a compressed-air outlet; a differential pressure measuring unit for measuring the pressure difference between said compressed-air intake and said compressed-air outlet as an indication of the torque produced by the power screwdriver; a comparator unit for comparing said measured pressure difference in the form of an actual pressure value with a preset pressure difference in the form of a set pressure value representing a preset torque value, said comparator unit having a switch output signal; and a switch unit for switching said power screwdriver off when said set value of differential pressure has been reached in response to said switch output signal.