Semi-automatic hydraulic chain adjuster

Claim 1

An adjusting mechanism for a machine having an idler wheel and a drive wheel, an endless belt entrained over said wheels, said mechanism comprising: a pressure fluid source, control valve means for selectively communicating said fluid source with opposite ends of a double acting hydraulic cylinder, said double acting cylinder having a movable piston therein and a rod extending therefrom, and being movable into and out of said double acting cylinder, hydraulic cylinder means, said hydraulic cylinder means motivating the idler wheel with respect to the drive wheel so as to adjust the tension of the endless belt, first relief valve means for limiting the magnitude of fluid pressure communicated to said hydraulic cylinder means, second relief valve means for protecting said hydraulic cylinder means from pressure surges caused by external forces transmitted thereto from said idler wheel means, and further including check valve means intermediate said control valve means and said hydraulic cylinder means, said check valve means preventing fluid flow to said control valve means from said hydraulic cylinder means, when said rod has moved out of said double acting cylinder to thereby keep said endless belt in tension while permitting fluid flow from said control valve means to said hydraulic cylinder means, whereby said endless belt will be tensioned upon each occurence of said rod moving substantially completely out of said double acting cylinder, and before commencing its return movement.