US Patent 6874965 Drywall finishing head with tensioner assembly

A drywall finishing head is provided for applying mastic material over a tape joint between adjacent wallboard surfaces. The finishing head includes a coater connected to a pneumatic applicator for delivering the mastic material. A wiper blade extends across the length of the coater with a cover underlying the wiper blade and a backer bar overlying the wiper blade. A cam assembly is rotatably mounted on a tensioning portion of the coater. Adjustment of the cam assembly is constructed and arranged to change the force of the backer boar so that a proper crown or profile of mastic material can be delivered to the tape joint through a gap between the cover and the wiper blade.