Motor operated chalk board mounting

Claim 1

THE COMBINATION WITH AN ELONGATED CHALK BOARD AND APPARATUS FOR MOVING THE SAME UP AND DOWN, OF THE IMPROVEMENT FOR REDUCING THE DANGER OF UNEQUAL TOTAL ELONGATION IN FLEXIBLE TENSION MEMBERS CONNECTING SAID BOARD WITH SAID APPARATUS, SAID IMPROVEMENT INCLUDING A MOTOR, A ROTATABLE THREADED SHAFT DRIVEN BY SAID MOTOR, A NUT IN THREADED ENGAGEMENT WITH SAID SHAFT, A ROLLER TYPE CHAIN SECURED TO EACH SIDE END PORTION OF SAID BOARD AND OF A TYPE TO SUSTAIN ITS PORTION OF THE WEIGHT OF SAID BOARD WITH SUBSTANTIALLY NO ELONGATION, A SUPPORT PULLEY OVER EACH END PORTION OF SAID BOARD AND OVER WHICH ONE CHAIN IS PASSED, A FORCE APPLYING PULLEY ON EACH OF OPPOSITE SIDES OF SAID NUT, A SUPPORT FOR SAID MOTOR AND FOR SAID SUPPORT PULLEYS, A CHAIN FROM ONE SIDE BEING PASSED FROM ITS END PULLEY AND THENCE OVER A NUT SUPPORTED PULLEY AND SECURED TO SAID SUPPORT, A CHAIN FROM AN OPPOSITE SIDE OF SAID BOARD BEING PASSED FROM ITS END PULLEY THENCE OVER A PULLEY FOR CHANGING THE DIRECTION OF CHAIR MOVEMENT AND FINALLY OVER THE NUT SUPPORTED PULLEY AND SECURED TO SAID SUPPORT WHEREBY ON TRANSLATION OF SAID NUT BY ROTATION OF SAID SHAFT SAID BOARD IS MOVED SUBSTANTIALLY VERTICALLY.