MATHEMATICAL MODEL OF CRANK-TYPE JOINT CLEARANCE OVERTRAVEL ASSESSMENT IN OSCILLATING CRANK DRIVE OF JAW CRUSHER

The magnitude decrease of the dynamic loads that arise during  the operation of machines in general and metallurgical ones in particular, is one of the main tasks of general problem of increasing their  reliability and durability. The analysis of work of lever mechanisms  of jaw crusher with internal degrees of freedom conditioned by presence of clearances in hinges, was made. It has shown that presence of  unstable forces of locomotive masses inertia during work of oscillating  crank drive results in breakage of pin surfaces in joint of piston-rod  with a crank, and in subsequent change of working surfaces of this  kinematics pair, followed by hitting of the masses of movable links  and in generation of considerable dynamic load, providing the reason  of breakages of details of executive mechanism and the source of resilient vibration (vibrations) and harmful acoustic vibration generation.  With the purpose of removal of influence of clearances in hinges on the  origin of additional dynamic forces it is necessary to reveal regularities of impulse loads appearance. Regularities of such loads appearance in crank-type mechanisms with clearances in joints of kinematics  pairs, caused by contact fault as a result of change in working surfaces contact, can be determined by kinetic static analysis. Analysis  of work of crank-type hinge with clearance of oscillating crank drive  of jaw crusher was conducted. Based on the analysis results it was  determined, that contact fault in joint of crank-piston-rod kinema tics  pair elements is conditioned by change of sign of reaction force. Clearance overtravel in a crank-type hinge takes place when both links are  on one line. Determination of mechanism links positions, at which  there is interconnection of crank-type hinge contact surfaces, allows  to use mechanisms rationally for selection of clearances with resilient  elements that during all work cycle of oscillating crank drive choose  clearance in crank-type joint and prevent additional dynamic load occurrence. That promotes reliability of jaw crusher operation in whole.