Patent ID: 8020468

Claim:
A robot arm comprising: an arm member of a specific length; pulleys disposed on the arm member and spaced apart from each other; an endless belt mounted on the pulleys; a belt tension sensor mounted on the arm member and facing the belt at a first location in the robot arm and operative to generate a signal representative of the tension of the belt; at least one tension adjustor mounted to the arm member and including a roller disposed in contact with a run of the belt at a respective location, spaced along the belt from the first location, the roller for pressing the belt to tension the belt, and a drive mechanism operatively connected to the roller so as to move the roller in a direction inclined with respect to the longitudinal direction of said run of the belt to thereby change the tension of the belt; and a controller operatively connected to the sensor and to the drive mechanism of the tension adjustor so as to receive the signal generated by the sensor as a measure of the tension of the belt, and control the drive mechanism of the tension adjustor responsive to the measured tension, wherein the arm member has a slot therein elongated in said direction inclined with respect to the longitudinal direction of said run of the belt, and wherein the drive mechanism of the tension adjustor includes a guide having a rotary shaft and received in the slot in said arm member such that the guide is slidable back and forth in the inclined direction relative to said run of the belt, wherein the roller is supported by the rotary shaft so as to be rotatable, wherein the robot arm includes a drive motor connected to one of the pulleys so as to rotate said one of the pulleys and thereby drive the belt, and wherein the drive motor is operative to output a signal indicative of a running speed at which the belt is driven by the drive motor, the tension adjustor also includes a rotary motor connected to the roller so as to rotate the roller, the controller is operatively connected to the drive motor so as to receive the signal output by the drive motor, and the controller is operatively connected to the rotary motor so as to control the rotary motor to rotate the roller at a rate based on the running speed.