Anti-Eating Facemask

U.S. Patent No. 4,344,424 (.pdf)

And now... for the macabre. Here's one that, if anything, must have been designed by a very bitter restaurant owner: an owner with a big problem revolving around the kitchen workers eating too much of the food they prepare. According to the description, this is a large problem for every kitchen. Don't despair, chefs! Thanks to this gruesome invention, you can keep your workers from eating anything at all. Padlock a mask to your worker's mouth, and no food will go missing. (Good luck finding any workers who will put up with wearing one of these things every day, though.)