How Percy Spencer Invented the Microwave Oven
This 1945 patent describes the process of using concentrated microwave energy to cook food, the fundamental technology behind the modern microwave oven.
Original patent title: “Method of treating foodstuffs”
This 1945 patent describes the process of using concentrated microwave energy to cook food, the fundamental technology behind the modern microwave oven. Granted to Raytheon Manufacturing Co in 1950 with 2 claims and 20 forward citations, and it is now in the public domain.
Coverage
What does this patent actually cover?
The patent outlines a method for cooking food by generating electromagnetic waves specifically in the microwave range. It requires guiding and concentrating these waves into a restricted, enclosed space where the food is placed. By exposing the food to this concentrated energy for a specific duration, the internal temperature of the food rises, effectively cooking it.
The gap
What does this patent NOT cover?
- Does not cover the specific electronic circuitry or magnetron design used to generate the waves.
- Does not cover methods of cooking that use infrared radiation or traditional convection heat.
- Does not cover the use of microwave energy for non-food applications like telecommunications or radar.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The invention recognized that high-frequency electromagnetic waves could be trapped and directed to excite water molecules in food, causing rapid heating through dielectric loss rather than external heat transfer.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Amana Radarange
Modern household microwave ovens
Industrial microwave food processing equipment
Why it matters
The bigger picture
This patent is the origin of the microwave oven, a device that transformed domestic life and the food industry. It turned radar technology, developed for military use during World War II, into a common household appliance.
Filed
October 8, 1945
Granted
January 24, 1950
Market context
Who's building on this
Companies in this space
Raytheon, the original assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →, pioneered the first commercial units. Today, major appliance manufacturers like Samsung, LG, and Whirlpool continue to refine the efficiency and control systems of microwave cooking technology.
Market impact
This patent enabled the creation of an entirely new category of kitchen appliance. It shifted consumer expectations for meal preparation speed and became a standard fixture in global kitchens, fundamentally altering how frozen and processed foods are marketed and consumed.
Claim 1 — Plain English
What this patent covers
The patent outlines a method for cooking food by generating electromagnetic waves specifically in the microwave range. It requires guiding and concentrating these waves into a restricted, enclosed space where the food is placed. By exposing the food to this concentrated energy for a specific duration, the internal temperature of the food rises, effectively cooking it.
The clever bit
The invention recognized that high-frequency electromagnetic waves could be trapped and directed to excite water molecules in food, causing rapid heating through dielectric loss rather than external heat transfer.
What it does not cover
- Does not cover the specific electronic circuitry or magnetron design used to generate the waves.
- Does not cover methods of cooking that use infrared radiation or traditional convection heat.
- Does not cover the use of microwave energy for non-food applications like telecommunications or radar.
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
This patent is in the public domain
See the Freedom to Build guide — what is free to use, what is not, and how to cite this patent.
PatentBrief Score
Impact Score
Early stage
Citation count
26/40
Moderately cited
Claim breadth
1/20
Narrow claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$24K – $76K
Midpoint $48K · expired or expiring · industry ×2.2
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Patent Claims
1 independent claim · 0 dependent
Claims are the legal boundaries of the patent. An independent claim stands alone. A dependent claim adds limitations to its parent, narrowing — but not broadening — the scope.
The original legal language
Original claims
2 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Spencer, P. L. (1950). How Percy Spencer Invented the Microwave Oven (U.S. Patent No. 2,495,429). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/2495429/microwave-oven-cooking
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How Percy Spencer Invented the Microwave Oven cover?
This 1945 patent describes the process of using concentrated microwave energy to cook food, the fundamental technology behind the modern microwave oven.
Who owns patent US 2495429?
Raytheon Manufacturing Co owns this patent, granted in 1950.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 2495429 cited by?
This patent has been cited by 20 later patents that build on its ideas.
What problem does this patent solve?
This patent is the origin of the microwave oven, a device that transformed domestic life and the food industry. It turned radar technology, developed for military use during World War II, into a common household appliance.
What does this patent NOT cover?
Does not cover the specific electronic circuitry or magnetron design used to generate the waves.
Patent monitoring