Patent ID: 8129635

Claim:
A method for weighing a moving article, comprising: receiving an incoming article having a first velocity; gripping the incoming article between a pinch roller and a capstan roller; synchronizing rotation of the pinch roller and the capstan roller to each other to avoid slippage of the article gripped between them; providing a capstan servo motor having a shaft operatively coupled to the capstan roller so that the motor shaft and the capstan roller rotate in unison; providing a servo amplifier coupled to the capstan servo motor so as to form a closed-loop servo system for driving the motor and for monitoring actual torque applied by the motor; in the servo amplifier, prior to said gripping the article, commanding the servo motor to a predetermined, constant command speed that is different from the first velocity of the incoming article; beginning after the article is gripped between the pinch roller and the capstan roller, acquiring a series of capstan servo motor torque sample data as the mail piece moves through pinch roller and capstan roller, so that the captured torque data reflects the torque applied by the capstan servo motor to change the article speed from the first velocity to the command speed; and processing the acquired torque data to determine a weight of the article without regard to actual speed of the article.