Automatic erasing device for erasing chalk marks on a writing board by water

An automatic erasing device for erasing chalk marks on a writing board, the writing board having left and right end portions that extends in a longitudinally axis thereof and an intermediate portion between the left and right end portions, said automatic erasing device comprising:

• an erasing mechanism including an elongated housing adapted to be disposed frontwardly of and slidable relative to the writing board, said elongated housing extending in a transverse axis relative to the longitudinal axis, and having an upper portion, a lower portion formed with a water tank that is adapted to receive water, and a rear wall formed with an elongated rear opening to confront the writing board and extending from said upper portion to said lower portion;
• an eraser unit disposed in said elongated housing, and biased to protrude outwardly and rearwardly of said rear wall via said elongated rear opening, and adapted to abut against the writing board, said eraser unit being connected to said water tank in such a manner that water flows from said water tank into said eraser unit so as to soak said eraser unit while said eraser unit is adapted to move on the writing board;
• and
• means for driving said elongated housing to move reciprocally in the longitudinal axis between the left and right end portions of the writing board;
• said erasing mechanism further includes:
• upper and lower axles journalled in said elongated housing proximate to said upper and lower portions, respectively, each of said upper and lower axles extending parallel to the longitudinal axis;
• a transmitting belt trained on said upper and lower axles under tension so as to be rotated upon rotation of said upper and lower axles, said transmitting belt being movable along a rear route proximate to and in alignment with said elongated rear opening, and a front route parallel to said rear route and distal to said elongated rear opening;
• said eraser unit including a plurality of eraser members disposed detachably on, and spaced apart from one another along a circumferential outer surface of said transmitting belt, each of said eraser members, when moving along said rear route, protruding outwardly and rearwardly of said rear wall via said elongated rear opening and being adapted to abut against the writing board, said eraser members being connected to said water tank in such a manner that water flows from said water tank into said eraser members, while said eraser members leave said rear route, so as to be entrained on said eraser members when said eraser members are adapted to move on the writing board;
• and
• a driving motor disposed to drive either one of said upper and lower axles so as to move said eraser members along said front and rear routes.