Patent ID: 6581472
Filing Date: 2003-06-24
Classification: B25B,G01N

Abstract:
A method for monitoring a screwing process in creating a screw connection with a screw, comprising:(a) before starting a tightening process of said screw, coupling at least one first ultrasonic pulse into said screw using a pulse-echo method, starting from a head of said screw, and measuring propagation time of said at least one first ultrasonic pulse for traversal of length of said screw; calculating at least one value of a change in propagation time of said at least one first ultrasonic pulse as a function of a predetermined tension of said screw, the calculating being of material specific characteristic values of said screw and said propagation time; and storing the at least one value for the change in propagation time as a function of said predetermined tension to provide stored values; (b) during said tightening process, repeatedly coupling second ultrasonic pulses into said screw using a pulse-echo method, starting from the head of said screw, and measuring propagation times of said second ultrasonic pulses for traversal of the length of said screw; determining at least once a first value of a relationship between a change in propagation time and a change in a screw parameter influencing said predetermined tension of said screw from the propagation times measured of said second ultrasonic pulses; determining at least one second value of the relationship between a change in propagation time and a change in said predetermined tension of said screw from said stored values; and comparing said at least one first value with said at least one second value.