Use of Non-Circular Gears in Pressing Machine Driving Systems

The paper describes a new approach in non-circular gears design, based on the mathematical description of the meshing progress. The teeth profiles are generated by numerical integration of a differential equation, which describes the contact point displacement, along the line of action, as a function of the pitch lines shape and of the pressure angle. In the typical arrangement, a pair of non-circular gears is used to drive a slider-crank mechanism, whose cursor follows a prescribed law of motion, thus working as a function generator. A procedure of inverse kinematics is illustrated, to determine the variable transmission ratio and then the pitch curves, once given the geometry of the slider-crank mechanism and the distance between the gears centres of rotation. An application of the method is described, where the ram of a mechanical press is driven according to a cinematically optimized law of motion. First step is the pitch lines synthesis, starting from the prescribed output curve. The teeth profiles are then generated on the primitives previously determined. A virtual analysis is performed to validate the method. Key-Words: Non-Circular Gears, Pitch Line Synthesis, Function Generator, Mechanical Presses, Virtual Prototyping