Abstract: An air filtering mechanism for use on crop harvesting machinery having a generally cylindrical, rotary, perforate filter element, a fan operable to draw air therethrough, drive means operable rotatably to drive the filter element, and blanking off means mounted within the filter element for blanking off the perforations thereof over a predetermined region, is disclosed wherein a duct having an open portion is provided exteriorly of the filter element opposite to the blanking off means, A pressurized flow of air from the fan is directed through the duct in the form of a cleaning air blast in a direction parallel to the external surface of the filter element to clean foreign matter collected on the filter element in the region of the blanking off means by virtue of the filter element being exposed to the pressurized air in the duct along the open portion thereof.

Abstract: A tensioning apparatus for a power transfer mechanism utilizing an endless flexible member having a normally slack run and a normally taut run is disclosed wherein the tensioning apparatus is operable to take up the slack in the endless member under both normal operating conditions and reverse power conditions during which the normally slack run becomes taut and vice-versa. The tensioning apparatus varies the amount of tensioning force applied to each run of the endless member in response to the amount of tension within the respective run. A constant biasing force is applied to a pair of tensioning idlers through an elongated rod which positionally changes relative to the tensioning idler pivots to vary the amount of tensioning force applied by the tensioning idlers.