method for the determination of the installed torque in a skruvförband at impulsåtdragning, method for control of a åtdragningsprocess,method for quality supervision and momentimpulsverktyg for tighte

摘要

A basic method for determining the installed torque in a screw joint which is being tightened by a series of repeated torque impulses, wherein the rotational movement of the screw joint is detected during each impulse, the point in which the screw joint ceases to rotate is detected, and the actually applied torque is indicated the very instance the screw joint ceases to rotate. In a tightening process control application of the above described basic method, the per impulse increasing value of the installed torque is compared to a predetermined target value in a way known per so, and the tightening process is interrupted as the target value is reached. In a tightening process quality check application of the above described basic method, the accomplished angular displacements of the joint at repeated impulses are indicated and added, and high and low limit values for the final installed torque and the total angle of rotation are provided and compared to the actually obtained values. A torque impulse delivering power tool comprising an impulse generator (12) with an output shaft (13) having a torque transducer (23) and a rotation detecting device (24) both connected to a process control unit (33) in which a device is arranged to provide a torque target value and a comparating circuit is provided to compare the actual value of the installed torque with the target value and to initiate shut-off of the power supply to the power tool as the target value is reached. IMAGE