Patent ID: 8649900
Filing Date: 2014-02-11
Classification: H01L

Abstract:
1. A stocker system, comprising: a stocker comprising a shelf on which a product is loaded; a rack master to move toward or away from the stocker and comprising a body part and an arm part connected to the body part to carry the product; a sensor unit disposed on the arm part and comprising a facing surface that is not in contact with the arm part; and a control unit to determine whether the shelf is level, wherein: the facing surface faces the shelf when the arm part is above or below the shelf, and the sensor unit further includes displacement sensors respectively disposed on a plurality of positions of the facing surface to measure relative positions between the sensor unit and the shelf at the plurality of positions when the arm part is above or below the shelf, the displacement sensors include a plurality of first displacement sensors arranged in a first direction and a plurality of second displacement sensors arranged in the first direction, the first sensors spaced from and aligned with respective ones of the second sensors in a second direction crossing the first direction, the sensor unit includes a wireless communication unit to transmit the measured relative positions to the control unit, and the control unit determines that the shelf is level in the first direction when the relative positions between the sensor unit and the shelf measured by the first displacement sensors arranged in the first direction are substantially equal, when the relative positions between the sensor unit and shelf measured by the second displacement sensors arranged in the first direction are substantially equal, and when the relative positions between the sensor unit and shelf measured by the first and second displacement sensors respectively aligned in the second direction, when compared, are determined to be substantially equal.