Synthesis of concave helical compression springs

Helical compression springs are used to resist compressive forces or store energy in push mode. They are found in many applications that include automotive, aerospace and medical devices. The common configuration of helical compression springs is straight cylindrical shape that has constant coil diameter, constant pitch and constant spring rate. Unlike, cylindrical helical compression springs, concave and a smaller diameter in the middle of the spring. The variable coil diameter enables them to produce nonlinear load deflection characteristics, reduce solid height, buckling and surging, and keep them centered on a large diameter hole. The unique feature of concave helical compression springs also arise their synthesis challenges. In this research a method is introduced to synthesize concave shaped helical compression springs. The variable coil diameter of a concave helical compression is describe by a spline curve. A cylinder with variable diameter is generated by revolving the spline curve on spring axis. The concave helical compression spring is then modeled by wrapping a spring wire on the variable diameter cylinder. The synthesis of a concave helical compression spring is systemized as the optimization of the geometric control parameters of its wrapped spring wire. A synthesis example is presented in the research to verify the effectiveness and demonstrate the procedure of the introduced method