US Patent 7234988 Enhanced expressive feature mechanism for animated characters and devices

A mechanism effectively mimics human facial expressions for use in animated characters. On the front surface of the mechanism, four gears, meshed in pairs, provide rotational surfaces for a series of cranks and pins. As the gears rotate, the cranks and pins engage a loop of elastomeric material. As pin distance from each other, the loop stretches. As pins approach each other, the loop contracts. Other pins located on the cranks or gears cause an inflection or deflection of the loop as the gears rotate. The resulting stretch or bending of the loop more accurately and efficiently mimics facial expressions.