It is the time it takes for a child born when Mary Kenner’s patent was granted to grow from a newborn to someone old enough to vote.

During those eighteen years — between the 1956 grant of her sanitary belt patent and the eventual manufacture of the product — Mary Kenner got up every morning and went to the flower shop.

She ordered flowers and arranged them and served customers and managed the operational demands of a small retail business.

She probably thought about her invention.

She may have continued to try to find a manufacturing partner, or she may have accepted for a time that the market was closed to her.

She filed additional patents in this period — her 1966 patents for the back washer and the walker attachment were both filed and granted during the eighteen-year window.