Chalmers likely began working on her menstrual cup design in the 1930s, driven by a desire to create a more hygienic and comfortable alternative to existing menstrual products. She sought to improve upon earlier, less successful cup designs.

Leona Chalmers filed for a patent for her menstrual cup design. This marked a significant step in officially recognizing her invention and securing her intellectual property rights.

The U.S. Patent Office granted Chalmers U.S. Patent 2,089,113 for her menstrual cup. The patent described a cup made of vulcanized rubber designed to be inserted into the vagina to collect menstrual flow. This patent represents the foundation of the modern menstrual cup.

Chalmers began manufacturing and marketing her menstrual cup, initially under the name 'Daintette'. The cup was promoted as a reusable, more sanitary, and comfortable alternative to disposable pads and tampons. However, she faced challenges in gaining widespread acceptance due to societal taboos surrounding menstruation and the relative novelty of the product. Her company sold the product under multiple names including Tass-ette and Tassaway.

Leona Chalmers sold Tassette Inc to Beverly Kenner. The product would struggle to gain widespread popularity and ceased production. The early cups suffered setbacks from quality and comfort issues.