Unexpectedly Intriguing!
09 June 2023

It's a summer time ritual. You want to get friends and family together for a big outdoor gathering, which includes serving a meal featuring lots of food.

While you may have thought your biggest problem would be the weather, you will almost certainly have another problem. Hundreds, if not thousands, of uninvited guests who will come to dine on your food. They'll come for the barbecue. The potato salad. The cornbread. And if they do get to your food, none of your invited guests will want to have any of it.

We are, of course, talking about insects. Probably ants, if there's any truth to the stereotypes. And short of encasing every dish with its own cover or lid that will have to be repeatedly lifted and replaced as your invited guests serve themselves, there's nothing you can do about it.

Or at least there wasn't until Richard Mahan invented the Electrified Table Cloth, for which he was awarded U.S. Patent 5,107,620. He gets straight to business describing his innovation in the patent's abstract (the IIE team has added the paragraph breaks to make it easier to read):

An electrified table cloth for preventing crawling insects from gaining access to the consumer's food or drink comprises a cloth formed of electrically insulated material which has at least one pair of parallel electrically conductive strips secured to the edge or border of the cloth to completely encircle the cloth and which are connected to a low voltage DC battery also secured to the cloth.

The strips of electrical conductive material are spaced apart sufficiently to normally prevent completion of a circuit across the strips and for completion of a circuit across said strips through an insert's body as the insect attempts to traverse the strips when crawling acorss the edge of the cloth. The current passing through the insect's body is sufficient to produce a sensation which will discourage further travel across the edge of the cloth.

A consumer who may come into contact with the strips will usually not feel the current and, even if the consumer is wet, the current will produce only a slight tingling sensation. The electrical apparatus may also be provided in kit form to be installed on table cloths by the consumer.

Those last two sentences are important because they directly address the second biggest obstacle to the success of the invention in the marketplace: product liability! Because nothing will ruin the memory of your outdoor gathering faster than the multiple lawsuits from the guests who were either shocked or burned from coming into contact with the electrified portion of your tablecloth that's intended to zap bugs to keep them away from your food. So it's a good thing that Mahan's innovation addresses it as a key feature within the patent.

Figure 1 from the patent illustrates Mahan's concept for how those electrical elements would be incorporated into a tablecloth.

U.S. Patent 5,107,620 Figure 1

While product liability risks were the second biggest obstacle to the success of electrified table cloths, which Mahan addressed, what he couldn't address was the biggest obstacle: customer demand for the innovation. The IIE team was unable to identify any electrified tablecloths to prevent crawling insects from reaching the food on it anywhere on the internet. The only search result is Mahan's 1992 patent and a handful of articles from intellectual property law firms referencing it as a "wacky patent".

That may be because there are many other ways to deter ants from your outdoor food spread that are less costly than a special purpose tablecloth. Which is to say it was outcompeted by other innovations.

From the Inventions in Everything Archives

We scanned the archives and found only one other invention involving insect control:


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