Infallible, according to Webster's Seventh Edition, refers to accuracy and absense of error, not uniqueness, perfection of design, size, color, you name it. A design for a mechanical device that never malfunctions can be changed, cheapened, made lighter, made redder or greener, smaller or larger, and still not malfunction. It will have always been "infallible" regardless of new patents and design changes. However, your point is well taken.