HOESTMASKINE

A pull-type forage harvester has a feed roll transmission shiftable between forward, reverse and neutral modes by means of a pair of identical single-acting hydraulic cylinders connected symmetrically to the rockshaft of a shifting fork and controlled through a solenoid-operated valve controlled electrically from the operator's station of the pulling tractor. Hydraulic connections are such that after completion of shifting from one transmission output mode to another, both hydraulic cylinders are open to a common hydraulic return line. However, inadvertent change of pressure in the return line will not cause shifting of the feed roll transmission as, due to the equal size of the hydraulic cylinders and the symmetrical arrangement of the cylinders with relation to the transmission shifter rockshaft, the shifting effort applied to the rockshaft by the respective cylinders would be equal but opposite, resulting in zero net shifting effort.