Arm position control device for use in an industrial robot

An arm position control device for use in an industrial robot including a cylindrical support body with a longitudinal axis and a rotary arm mounted on the support body for rotation within a permissible angular extent, the rotary arm having a rotational axis in alignment with the longitudinal axis of the support body, which comprises:

• a home position sensor fixedly secured to the support body at a position of first radius from the longitudinal axis to detect a home position and direction of deviation from the home position of the rotary arm;
• a limit sensor affixed to the support body at a position of second radius from the longitudinal axis in a diametrically opposing relationship with the home position sensor to detect undue rotation of the rotary arm beyond the permissible angular extent;
• a sensor activator disk coaxially attached to the rotary arm for selectively interrupting and releasing the home position sensor and the limit sensor, the sensor activator disk having first and second radial flanks oppositely located along a diameter of the disk, a first sector extending from the first radial flank up to the second radial flank with a diameter enough to interrupt the home position sensor, a second sector provided at an opposite side of the first sector with a smaller diameter than the first sector to release the home position sensor, and an arcuate cutout provided radially inwardly of the first radial flank in an overlapping relationship with the first and second sectors to release the limit sensor as the rotary arm is caused to turn beyond the permissible angular extend;
• and
• an arm actuator means operatively associated with the home position sensor and the limit sensor for causing the rotary arm to stop as the limit sensor is released and turn toward the home position in a first direction if the home position sensor remains interrupted with the limit sensor released and to turn toward the home position in a second direction if the home position sensor and the limit sensor are released.