Automatic lifting/lowering black-board

The utility model discloses an automatic up and down blackboard, it aims to solve the shortcoming of the present blackboard that the height can not be adjusted. It comprises a black board, an framework used to mount the blackboard, the framework is a rectangular frame fixed on the wall behind the blackboard which consists of bottom beam, top beam left and right side beams; a coattail through slot which is perpendicular to bottom beam which is made in front of the left and right beams; guide rails are fixed on the back of the blackboard at the position in correspondence with the said coattail slots , the guide rails are perpendicular to the bottom beam and its section matches the coattail slot shape, the two guide rails are mounted in the coattail slot respectively; there is a set of transmission device mounted on the top beam, the transmission device comprises a micro-motor which can rotate and reverse is mounted on the middle place of the top beam, the motor has left and right two output axles, a roller drum is mounted on each output respectively, wire rope winds around the roller drum, one end of the wire rope is fixed on the top surface of the blackboard, the other end is fixed on the balance weight.