Percy LeBaron Spencer Invented the microwave oven (1946)

The Microwave Oven Cooks Food Quickly
by Microwave Radiation

PERCY SPENCER 24jan1950

Patent Name: Method of Treating Foodstuffs
Patent Number: 2,495,429
Patent Date: 24 January 1950
Inventor: Percy L. Spencer, of West Newton, Massachusetts
What It Does: Cooks food quickly by microwave radiation.


Background: In 1946, Percy Spencer, a self-taught electronics wizard who never graduated grammar school, received U.S. patent 2,408,235 for the development of a high-efficiency magnetron. Magnetron tubes employ heated cathodes to generate electrons that are affected by electro-magnetic energy and reduced microwave radiation. Microwave radiation is used both in radar and in the "method of treating foodstuffs" that Spencer invented and patented four years later.
While working for the Raytheon Manufacturing Company, Spencer was running tests on one of the new magnetron tubes when he noticed the candy bar in his pocket began to melt. In playing his natural inventor instincts, he decided to play some uncooked popcorn in front of the magnetron tube. To his delight, the Colonels began popping. (This is still a favorite application of microwave technology.)
Engineers at Raytheon went to work on Spencer's discovery. The first commercial microwave oven was introduced in 1947. It was 750 pounds and 5 1/2 feet tall. Twenty years in many modifications later, the first countertop, domestic microwave oven hit the market. By 1975, microwaves were selling faster than conventional gas range ovens.

1. Electron-discharging cathodes (14) housed within oscillators are joined by conductors (20, 21).
2. These conductors are interned connected by another conductor (22), a center tap on a winding (17) of the transformer (18).
3. Coaxial transmission lines (24, 25) alternately deliver hyper-frequency energy to a wave guide (23).
4. The wave guide is directed at a piece of food on the speed-adjustable conveyor (28).