Circulating self-cleaning blackboard capable of utilizing synchronous belt to drive planet belt wheel

The utility model relates to a self-locking circulating self-cleaning blackboard, in particular to a blackboard device which is capable of realizing the self-locking circulating translational movement of two blackboard surfaces by utilizing a synchronous belt to drive a planet belt wheel and has a function of automatically cleaning the blackboard-writing. The blackboard adopts the synchronous belt for driving, and a hand-operated wheel drive transmission system is operated to transmit the power into the double-sided synchronous belt, so that speed difference is generated between the double-sided synchronous belt and a fixed internal-tooth one-side synchronous belt arranged at equal interval together with the double-sided synchronous belt, and the planet synchronous belt wheel connected with a blackboard surface frame can run in a gap between the double-sided synchronous belt and the fixed internal-tooth one-side synchronous belt when being meshed with the double-sided synchronous belt and the fixed internal-t