A conveyor assembly for a continuous belt conveyor. The conveyor assembly includes a drive assembly and a belt tensioner that are both mounted to one end of the conveyor assembly. The belt tensioner includes a housing that surrounds a catenary sag portion of an endless conveyor belt. A weighted tension roller is positioned in contact with the conveyor belt in the catenary sag portion to exert tension onto the conveyor belt due to gravity. The tension roller includes a main body and a pair of weight plates that increase the overall weight of the tension roller. The housing of the belt tensioner includes a pair of guide slots that guide the vertical movement of the tension roller. A stationary ratchet plate and a movable ratchet member restrict the direction of vertical movement of the tension roller in the pair of guide slots.