US Patent 9040851 Keycap assembly with an interactive spring mechanism

A touchsurface assembly comprises a base, a pressable touchsurface, and a deflectable spring. The pressable touchsurface is configured to move between an unpressed position and a pressed position relative to the base. The deflectable spring comprises a fixed portion and a contact portion. The contact portion is configured to contact a spring guiding profile. As the touchsurface moves from the unpressed position to the pressed position, the contact portion physically interacts with different sections of the spring guiding profile. This interaction causes different deflections of the deflectable spring and produces reaction forces that resist keycap motion toward the pressed position and bias the keycap toward the unpressed position.