Patent ID: 7344097

Claim:
A jaw rock crusher comprising: a first jaw; a pitman; an eccentric shaft coupled to said pitman; a toggle plate disposed adjacent said pitman on an opposite side from said first jaw; a means for adjusting a location of said pitman so as to control a maximum size of material which is permitted to pass between said fixed jaw and said pitman; a spring tension rod comprising a spring and a rod coupled to said pitman and configured to create a force which is biased toward increasing contact between said pitman and said toggle plate; said spring tension rod having a hydraulic piston coupled thereto for pre-loading said spring, so that said force may be maintained at a predetermined level irrespective of a setting location of said pitman as determined by said means for adjusting; said hydraulic piston having coupled thereto a path of hydraulic fluid to a source of hydraulic fluid at an adjustable pressure; and a pressure sensor configured to measure a fluid pressure characteristic which is indicative of a pressure in said path of hydraulic fluid.