Adjustable shear bar for a harvester cutterhead

In a forage harvester having a mobile frame, a cutterhead housing mounted on the frame and having opposite side walls and an inlet opening, a rotary cutterhead mounted in the housing and having a plurality of knives with cutting edges at the cutterhead periphery generating a cylinder as the cutterhead rotates and a generally horizontal transverse shear bar extending between the opposite side walls adjacent the cutterhead periphery parallel to the cutterhead axis so that crop material moving through the inlet opening moves past the shear bar into the cutterhead, the combination therewith of improved means for adjustably mounting the shear bar on the housing to adjust the clearance between the shear bar and the cutterhead and comprising:

• a support structure including a pair of support members respectively rigidly connected to the opposite side walls and including a pivot means;
• a pair of lever elements respectively pivotally mounted on the pivot means and having first portion swingable in a generally fore and aft arc in response to rocking of the lever elements on their pivots;
• a pair of generally fore and aft link members respectively connecting the first portions of the lever elements to the opposite ends of the shear bar so that rocking of the lever elements shifts the opposite ends of the shear bar in a generally fore and aft direction toward or away from the cutterhead periphery;
• a pair of clamping means respectively operatively associated with the opposite ends of the shear bar for generally vertically clamping the opposite ends of the shear bar against the support structure so that the shear bar is shiftable in said fore and aft direction only upon exertion of a sufficient force through the link members to overcome the generally vertical clamping force exerted by the clamping means;
• and
• a pair of force multiplying means respectively connected to the respective lever elements and including input elements, each force multiplying means being operative to rock the lever member about its pivots upon exertion of an input force on the input elements sufficient to overcome the clamping force exerted by the clamping means, said clamping force being substantially greater than the input force, whereby exertion of said input force on an input element in one direction shifts the end of a shear bar toward the cutterhead periphery and exertion of said input force in the opposite direction shifts the end of the shear bar away from the cutterhead periphery.