Patent ID: 7588098
Filing Date: 2009-09-15
Classification: B25B,H02P

Abstract:
1. A controller for use with a screwdriver having a drive shaft and an electric motor activated to tighten a screw, the controller being configured to determine whether or not a correct tightening operation has been carried out, by comparing a time taken to complete the tightening operation and a reference time, the controller comprising: a torque monitor configured to monitor whether or not a load torque exerted by the screwdriver for the tightening operation has reached at a tightening completion torque; a timer configured to measure a tightening operation time which starts at a beginning of the tightening operation and ends when the tightening torque has reached at the tightening completion torque; a reference time setter configured to determine the reference time for use in subsequent tightening operations, based on a plurality of tightening operation times measured by the timer; an expected time setter configured to initially define an expected time to complete the tightening operation; a comparator configured to compare a tightening operation time against the expected time, every time the timer measures the tightening operation time taken to complete a respective tightening operation; and an expected time renewer configured to define the measured tightening operation time as a new expected time, each time the comparator determines that the measured tightening operation time is not longer than the expected time, wherein the reference time is defined with the expected time calculated from the tightening operation times taken to complete a plurality of the tightening operations performed.