This article will be the first in a series on the technology and innovations that came about or were first majorly used during World War II. We will cover a number of incredible inventions, so make sure to check back in the coming weeks for more articles.

In 1921, as engineers and scientists were trying to develop a magnetically controlled relay or amplifier that they could use instead of the patented triode, they created the first “magnetron.”[i]

The cavity magnetron was individually devised across the globe throughout the early to mid-20^th century but found one of its most popular forms in England in 1939.[ii] This version, which was used during WWII, was invented by researchers looking for a way to improve British radar systems. The goal was to create a smaller, lighter magnetron with better image resolution. To accomplish this, designers developed a new cavity magnetron with the following qualities:

• Operate in the microwave range.
• Have a wavelength of 10cm or less.
• Have a peak power of 1KW.

These attributes allowed for radar equipment that could be installed in aircraft and were less susceptible to interference from ground echoes. Unfortunately for the British, they were in the middle of a war and did not have the resources or available workforce to begin mass-producing their cavity magnetrons with the speed needed to keep up with demand.

A Modern Cavity Magnetron

In 1940, a British envoy traveled to the United States and Canada to share the results of British military research and development, including the cavity magnetron. The American and Canadian scientists welcoming the envoy were so amazed by the cavity magnetron that they convinced their respective governments to further research and, luckily for the British, to manufacture and deliver the devices back to England. MIT created the Radiation Laboratory or “Rad Lab” to further research the cavity magnetron.[iii]

The Rad Lab eventually produced 150 distinct radar systems, ranging from compact, lightweight units for aircraft all the way up to huge ground-based early-warning systems that each had to be transported in five trucks!

A Radar Antenna Today

After WWII, research on the cavity magnetron continued for intellectual and commercial purposes. While conducting such an experiment, an engineer named Percy Spencer at Raytheon Laboratories in Massachusetts found that a chocolate bar in his pocket had melted entirely. He soon realized the chocolate melted due to the microwaves produced by the cavity magnetron.[iv]

When he began throwing other foods into the area of the cavity magnetron, such as popcorn kernels, he found that these microwaves could heat all sorts of different foods. He later developed a box to contain the microwaves and direct them toward food items. Thus, the microwave oven was born![v]

The design of the microwave oven evolved from Percy's original prototype into the more modern appliance we use today, as shown below.

How a Microwave Oven Nukes Your Pizza

Have you ever wondered why we use the term “nuke” when heating food in the microwave? It is actually because of the cavity magnetron and its use of microwave radiation! People at the time thought radiation, whether it be nuclear or microwave, was all the same. So, they began using “nuke” to describe both types of radiation and this has stuck in the public vernacular ever since.

The patent for the first microwave oven was filed in 1945, with the first commercial microwave ovens hitting the market a year later.[vi]

These first microwave ovens were mainly sold to larger businesses as they were roughly 750 pounds, almost 6 feet tall, and cost close to $5,000 (over $78,000 when adjusted for inflation).

A Pair of Early Version Microwave Ovens

There are several takeaways from the story of the cavity magnetron.

First, different people can invent the same thing in different places. New inventors often see this as a problem that cannot be overcome. However, as of March 16, 2013, the United States patent system works on a first-to-file basis. This means that even if you are not the first to invent something, as long as you do not know about the other invention and are the first to file a patent application, you have the right to try to patent your version.

Second, inventions do not have to be intentional. Your invention can be a complete accident, but that does not mean you do not deserve to try to get a patent.

Finally, you can patent new uses of existing technology, so long as they are not obvious to a person having ordinary skill in the art. Because reheating food in a microwave oven was not an obvious result of the cavity magnetron, a wartime device, the microwave oven was deemed patentable.

How Gallium Law Can Help

Unlike the chocolate bar in an engineer's pocket, you do not have to melt away at the thought of navigating the patent system. We are here to help you, whether you are someone who thinks they might have accidentally invented something or someone who has spent years developing your creation. To get in touch with us, please fill out this online form or call us at 651-256-9480 to schedule a free and confidential consultation.

*The information in this article is not legal advice and should not be relied on. The content of this article is for informational purposes only and is meant as a starting point in your search for answers to your legal questions.

[i] https://www.radartutorial.eu/04.history/hi80.en.html

[ii] https://www.armms.org/media/uploads/06_armms_nov12_rburman.pdf

[iii] https://spectrum.ieee.org/magnetron

[iv] https://www.technologyreview.com/1999/01/01/236818/melted-chocolate-to-microwave/

[v] https://www.whirlpool.com/blog/kitchen/history-of-microwave.html

[vi] https://spectrum.ieee.org/a-brief-history-of-the-microwave-oven