Many agricultural harvesting heads use drum conveyors that employ the retractable fingers extending to the wall of the drum to engage cut crop material and pull it underneath the drum. These drums may also be equipped with helical flutes to assist crop flow in a lateral direction.
Drum conveyors (sometimes called “feed drums”, or “feed rollers”) are driven in rotation at 200-300 RPM. Elongate fingers are rotatably mounted to a stationary shaft disposed inside the drum. These fingers extend through holes in the wall of the drum and are driven in rotation about the stationary shaft by the drum itself.
The fingers have one end that extends outside the drum and engages the crop, and a second end that is coupled to a bushing that wraps around the stationary shaft. As the drum is driven in rotation, the drum pushes on the side of the finger and causes it (and its bushing) to rotate around the shaft.
In recent years these bushings to which the fingers are attached have been made of thermoplastics such as nylon 66 or high molecular weight polyethylene (HMWPE). These plastic materials are less expensive to manufacture than metal bushings.
In US2011/0061354, for example, plastic is molded to form a plastic finger (1) with a metal core (9) with an integral a plastic bushing (7). Fourteen of these fingers are mounted for rotation on a stationary shaft (2). They rotate about this stationary shaft (2) at the same speed as the drum (not shown) through which they extend. The stationary shaft is rigidly clamped at its outer ends to two stub axles that are concentric with the drum itself. The stationary shaft is fixed in a position that is slightly offset from the rotational axis of the drum and of the two stub axles.
US2006/0252472 shows a similar arrangement in which a finger is pinned to a plastic bushing, (shown here as a hinged collar) that likewise rotates around an offset stationary shaft (38) that is clamped to stub axles at both ends.
Since the fingers are supported on the stationary shaft and extend through holes in the drum, every time the drum rotates, the bushings also rotate about the stationary shaft.
One problem with this arrangement is plastic bushing wear. This wear could be reduced by providing a ball or roller bearing instead of a bushing, but the cost would be prohibitive, given that drum conveyors on agricultural harvesting heads can have more than fifteen of these fingers.
What is needed therefore is a drum conveyor for an agricultural harvesting head with decreased finger wear. It is an object of this invention to provide such a drum conveyor.