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Archaic Legal Glossary & Citations

“Letters Patent”14th–20th Century
19th-C Meaning:

Open public letters from a monarch or government (literae patentes) granting monopoly rights.

Modern Engineering Decoded:Issued USPTO utility or design patent publication.
Historical note: Contrasted with 'letters close' (private sealed royal correspondence).
“In testimony whereof”19th Century
19th-C Meaning:

Formal concluding legal formula affirming under oath the execution of the instrument.

Modern Engineering Decoded:Inventor and witness digital/physical signatures.
Historical note: Required two witness attestations in 19th-century USPTO filing procedure.
“Aeroplane”Early 20th Century (Wright era)
19th-C Meaning:

A flat or cambered lifting aerofoil surface supported dynamically by air pressure.

Modern Engineering Decoded:Wing / Airfoil lifting surface (later evolved to mean the entire motorized aircraft).
Historical note: The Wrights used 'aeroplane' to denote the individual fabric-covered wings.
“Undulating Current”19th Century (Bell era)
19th-C Meaning:

An electric current whose magnitude varies continuously and periodically without interruption.

Modern Engineering Decoded:Continuous analog AC or audio-frequency electrical waveform.
Historical note: Bell's central legal weapon against telegraph companies who relied on pulsed DC make-and-break circuits.
“Subdivision of the Electric Light”1870s–1880s (Edison era)
19th-C Meaning:

The problem of operating numerous small domestic lamps off a single electrical generator.

Modern Engineering Decoded:Parallel circuit wiring of high-resistance incandescent electrical loads.
Historical note: Pundits claimed it was physically impossible until Edison increased filament resistance to 100 ohms.
“Optically Anisotropic Solution”1960s (Kwolek era)
19th-C Meaning:

A liquid solution that exhibits direction-dependent refractive indices due to molecular alignment.

Modern Engineering Decoded:Liquid crystalline nematic phase polymer dope.
Historical note: Technicians initially tried to throw out Kwolek's cloudy solution thinking it was contaminated.
“Unitary Body of Semiconductor Material”1950s–1960s (Noyce era)
19th-C Meaning:

A single continuous crystal structure of silicon or germanium.

Modern Engineering Decoded:Monolithic single-crystal silicon die / integrated circuit wafer.
Historical note: Differentiated Noyce's monolithic planar circuit from Jack Kilby's hybrid flying-wire prototype.
“Peculiar and Novel Construction”19th Century
19th-C Meaning:

A distinctive, patentable structural arrangement not found in prior art.

Modern Engineering Decoded:Novel and non-obvious mechanical embodiment under 35 U.S.C. § 103.
Historical note: Standard 19th-century legal terminology establishing novelty.

Museum Broadside & Archival Print Edition

Authentic archival layout formatted for framing, study, and high-resolution printing

Paper:
Theme:
The United States Patent & Trademark Archive

Historical Specification & Engineering Broadside

Curated, Verified & Restored by Classic Patents (classic-patents.com)
METHOD OF TREATING FOODSTUFFSPaired magnetrons, a common wave guide, and conveyor exposure at microwave wavelengths
US 2,495,429Class: H05B 6/64 (Dielectric heating / Microwave ovens)
Inventor(s):Percy L. Spencer
Origin / Location:West Newton, Massachusetts
Grant & Filing:Filed October 8, 1945 · Granted January 24, 1950

I. Historical Context & Grant Summary

US 2,495,429 claims methods for cooking food with microwave electromagnetic energy concentrated and guided in a restricted region. Spencer's illustrated apparatus uses two magnetron-type electron-discharge devices in push-pull, a common hollow wave guide, and a conveyor that carries food through the energy region. Claims 1–3 specify microwave-region energy; claims 4–6 state a wavelength of substantially ten centimetres.

II. Core Mechanism & Scientific Principles

The source starts from Spencer's complaint that earlier food-heating experiments at frequencies no higher than 50 megacycles required too much energy. His proposed method uses microwave wavelengths, with ten centimetres or less as the example, and brings food into a restricted region where that energy is concentrated and guided. The illustrated system is a conveyor process, not a description of a later countertop oven.

Physical Operation:Transformer 18 supplies two magnetron-type electron-discharge devices 10 and 11. Their resonant cavities are proportioned for electrical oscillations whose wavelength is comparable to the food's average dimension. In push-pull operation the two devices alternately feed high-frequency energy through coaxial lines 24 and 25 into common hollow wave guide 23. Conveyor 28 moves food through the energy region at a speed chosen for the food and the desired cooking time. The source states that relationship; it does not assign a universal frequency, a power rating, or a particular enclosure.
Governing Formulation:
Wavelength and resonant-cavity scale:f ≈ c / λ
Electromagnetic energy exposure:P_v = 2 pi f epsilon_0 epsilon'' |E|^2

III. The Granted Legal Monopoly (Key Claims)

Claim 1 (Independent)microwave-region energy

Claim 1 requires a method that generates microwave-region electromagnetic energy, concentrates and guides that energy within a restricted region, and exposes food there until it is cooked to a predetermined degree. Each of those three method steps is an express limitation.

Claim 2 (Independent)microwave-region energy

Claim 2 uses microwave-region energy in a restricted guided region and adds transport: the food is conveyed through that region at a speed that gives it the stated cooking interval. The conveyor rate and time condition distinguish it from stationary exposure.

Claim 3 (Independent)electromagnetic field

Claim 3 requires the guided energy to establish an electromagnetic field in the restricted region, then requires food exposure and movement of the food relative to that field while exposure continues. It is a relative-motion method claim, not a claim to one named mechanical drive mechanism.

IV. Mechanical Organ Breakdown

Paired magnetron oscillatorsTerm: “electron-discharge device” → vacuum electronic oscillator

Two evacuated, conductive envelopes with radial anode vanes supply the illustrated high-frequency energy.

Transformer and push-pull feedTerm: “raw A.-C.” → mains alternating current

A centre-tapped transformer circuit drives the two illustrated devices on opposite halves of the alternating supply.

Common wave guide and conveyorTerm: “wave guide” → hollow electromagnetic waveguide

Coaxial lines and loop couplers send energy to a common hollow guide, while a transverse conveyor sets exposure time.

CLASSIC PATENTS DIGITAL ARCHIVE • PERMANENT EXHIBIT ID: us-2495429-spencer-microwave
classic-patents.com/patents/us-2495429-spencer-microwave
Original USPTO PDF
Classic Patents/US 2,495,429
Electronic Era (1920–1960)Microwave Engineering

Spencer's Microwave Food Treatment

US 2,495,429

Paired magnetrons, a common wave guide, and conveyor exposure at microwave wavelengths

Inventor(s)Percy L. Spencer
Grant DateJanuary 24, 1950
Filing DateOctober 8, 1945
LocationWest Newton, Massachusetts
US 2,495,429 claims methods for cooking food with microwave electromagnetic energy concentrated and guided in a restricted region. Spencer's illustrated apparatus uses two magnetron-type electron-discharge devices in push-pull, a common hollow wave guide, and a conveyor that carries food through the energy region. Claims 1–3 specify microwave-region energy; claims 4–6 state a wavelength of substantially ten centimetres.
USPTO PDF
Audio Engineering Breakdown~2 min listen

Listen to the narrated mechanical breakdown and civilizational context

Engineering Analysis & Physical Principles

How It Works: Step-by-Step Mechanical & Physical Breakdown

The source starts from Spencer's complaint that earlier food-heating experiments at frequencies no higher than 50 megacycles required too much energy. His proposed method uses microwave wavelengths, with ten centimetres or less as the example, and brings food into a restricted region where that energy is concentrated and guided. The illustrated system is a conveyor process, not a description of a later countertop oven.
The Core Breakthrough Mechanism

Transformer 18 supplies two magnetron-type electron-discharge devices 10 and 11. Their resonant cavities are proportioned for electrical oscillations whose wavelength is comparable to the food's average dimension. In push-pull operation the two devices alternately feed high-frequency energy through coaxial lines 24 and 25 into common hollow wave guide 23. Conveyor 28 moves food through the energy region at a speed chosen for the food and the desired cooking time. The source states that relationship; it does not assign a universal frequency, a power rating, or a particular enclosure.

Interactive Real-Time Physical Simulation

Drag to rotate · Pinch to zoom · Shared controls update the displayed model
INITIALIZING THREE.JS WEBGL SIMULATION...
Dual-Magnetron Guided Food-Treatment Apparatus.
Host-Model Telemetry/Computed Readout
Dual-Magnetron Guided Food-Treatment Apparatus
Energy Path
Reader Scenario
active[1]
Wavelength Region
Source
about 10 cm or lesssource text[1]
Vacuum f at 10 cm
Source-Derived
2.998GHz[1]
Printed Path
Source
10/11 → 24/25 → 23 → 28source numerals[1]
Tube & Cooking SI
Source Refusal
refusedmissing source card[1]
oscillators 10 and 11 → common wave guide 23 and conveyor region 28
1 on/off
ts-fallback
Waveguide Energy-Path Display
∂q_{path} / ∂u_{reader} (host sensitivity)
1 display fraction / reader-control fraction
Source-Path Highlight1 on/off
Coupled Transfer Dynamics · fs-couple
ts-fallback
oscillators 10 and 11common wave guide 23 and conveyor region 28
+1on/off
Interval ghosts
Source path1.0 on/off · [0, 1]
Coupled channels
magnetron anode → dielectric food heat780 W
Plume refused
US 2,495,429 does not quantify a plume, steam rate, food temperature, or thermal-output field, so no cosmetic plume is drawn.
Dated scenarios

Detailed Component Architecture

1Paired magnetron oscillators
Two evacuated, conductive envelopes with radial anode vanes supply the illustrated high-frequency energy.

Each adjacent pair of anode vanes and the intervening envelope wall form a cavity resonator. Spencer asks that the generated electrical wavelength be comparable to the average food dimension and gives about ten centimetres or less as an example. Heated cathodes provide thermionic emission; magnetic means establish a transverse field between cathode and anode.

19th-C. Term: electron-discharge deviceModern: vacuum electronic oscillator
2Transformer and push-pull feed
A centre-tapped transformer circuit drives the two illustrated devices on opposite halves of the alternating supply.

Conductors 15 and 16 connect the envelopes to opposite secondary terminals 17. Conductors 20 and 21 tie the cathodes together and conductor 22 takes them to the centre tap. The source calls the resulting arrangement push-pull and says the devices alternately deliver hyper-frequency energy.

19th-C. Term: raw A.-C.Modern: mains alternating current
3Common wave guide and conveyor
Coaxial lines and loop couplers send energy to a common hollow guide, while a transverse conveyor sets exposure time.

Lines 24 and 25 are coupled to the oscillators by loops 26 and 27 and feed common hollow wave guide 23. Conveyor 28 carries food into its outlet region. The conveyor speed is expressly selected for the nature of the food and the required cooking time, a limitation retained in claims 2 and 5.

19th-C. Term: wave guideModern: hollow electromagnetic waveguide
Engineering Principles & Equations

Governing Equations & Engineering Principles

Authored explanation paired with its stated mathematical relation

Source-Stated Microwave Wavelength Region

Applied ElectromagneticsClaim 1
Mathematical Governing Law
Terms:
Plain English DecoderHover or tap any highlighted phrase
Spencer specifies , giving wavelengths of about ten centimetres or less as the example. The usual wave relation connects that wavelength to and , but the grant does not assign one exact operating frequency to the illustrated apparatus.
λ\lambda
Microwave-region wavelength
The source's example is a wavelength of the order of ten centimetres or less.
centimetres

This preserves Spencer's printed wavelength boundary without silently converting it into a fixed modern appliance frequency.

Physical Principle & Engineering Insight

The legal teaching is the generated-and-guided microwave-region treatment path. This card refuses the later 2.45-GHz appliance, dielectric-loss, turntable, Hull-cutoff, and commercial-magnetron parameters that the grant does not print.

Historical Context: Claim 1 covers generating microwave-region energy, concentrating and guiding it within a restricted region, and exposing food there long enough to cook it to a predetermined degree.

Wavelength and resonant-cavity scaleAuthored Principle 1
Stated relationf≈c/λf ≈ c / λ
For an electromagnetic wave in free space, frequency and wavelength are inversely related. Spencer does not give a calculated frequency; he directs the reader to size each resonant cavity so the generated wavelength is comparable to the average food dimension, using about ten centimetres or less as the stated example.
Electromagnetic energy exposureAuthored Principle 2
Stated relationPv=2pifepsilon0epsilon′′∣E∣2P_v = 2 pi f epsilon_0 epsilon'' |E|^2
The claims require generation, concentration, and guidance of microwave energy in a restricted region, followed by food exposure long enough to reach a predetermined degree of cooking. Modern absorbed-power patterns depend on the field geometry and food properties; the patent itself confines its legal method to those listed operations rather than a universal heating equation.

Interactive Schematic Sheet (Sole figure)

The source drawing shows magnetrons 10 and 11, transformer 18, common wave guide 23, coaxial lines 24 and 25, loops 26 and 27, and conveyor 28. Source PDF p. 1.

1.00x
US 2,495,429 · SOLE FIGUREMAGNETRON 10MAGNETRON 11TRANSFORMER 18LINES 19WAVE GUIDE 2324 / 25CONVEYOR282627SOURCE: λ OF ORDER 10 cm OR LESS · TUBE / FIELD / COOKING SI REFUSED
Tap any numbered pin3 Curated Callouts
Callout Pin Inspector

Select Any Numbered Pin

Click pins on the schematic or select from the list below to inspect historical specifications.

Why It Still Matters

The document preserves an early method claim for microwave food treatment and an industrial-style apparatus: a paired oscillator feed, common guide, and moving conveyor. Its lasting technical interest lies in joining cavity-generated microwave energy to controlled exposure of food, while keeping the source's own wavelength, conveyor, and duration conditions visible.

Legal Claims Decoder (6 Numbered Claims)

Compare dense legalistic claims directly with decoded plain-English functional specifications.
Claim #1Independent Master Claim
1/6
Verbatim Historical Legal Text
“In the method of treating foodstuffs, those steps which include: generating electromagnetic wave energy of a wavelength falling in the microwave region of the electromagnetic spectrum; concentrating and guiding said wave energy within a restricted region of space and exposing the foodstuff to be treated to the energy so generated for a period of time sufficient to cook the same to a predetermined degree.”
Plain English Engineering Translation
Claim 1 requires a method that generates microwave-region electromagnetic energy, concentrates and guides that energy within a restricted region, and exposes food there until it is cooked to a predetermined degree. Each of those three method steps is an express limitation.
Key Protected Innovations:
microwave-region energyrestricted guided regionpredetermined cooking degree

The Historical Bottleneck

Spencer identifies a practical-energy problem: earlier food treatment using frequencies no higher than 50 megacycles demanded too much energy to make the process practical. The source's solution is to use microwave wavelengths and direct that energy to a food-treatment region.

Why Prior Art Failed

  • •The specification says prior food-treatment energy was used at relatively low frequencies, for example not over 50 megacycles.
  • •At that order of frequency, Spencer says the energy needed to generate enough heat for satisfactory cooking was too high for practical use.
The Breakthrough Insight
“The patent combines a wavelength-scale condition with guided exposure: use microwave energy of about ten centimetres or less, concentrate and guide it in a restricted region, and control the food's time there. The illustrated magnetron and conveyor arrangement makes that method concrete.”

Patent Wars & Legal Litigations

Vs. Tappan Stove Company & Amana RefrigerationInfringement Challenge
Rival Claim & Defense:
Appliance manufacturers attempted to engineer RF cavity heating ovens using continuous-wave magnetrons without paying Raytheon royalties.
Litigation Conflict:
Raytheon held Spencer's foundational patent on enclosing food within an electromagnetic cavity fed by a magnetron with a conductive mode stirrer. Raytheon licensed the patents to Tappan (1955) and acquired Amana (1965).
Final Resolution & Judicial Outcome:
Raytheon launched the 'Amana Radarange' in 1967 at $495, utilizing Spencer's exact cavity waveguide feed and safety interlocks.
Civilizational Impact
US 2,495,429 documents a transition from low-frequency food-heating experiments to a microwave method with defined wavelength, guided-region, duration, and movement conditions. The paired-magnetron and conveyor drawing also records the industrial process framing of this early food-treatment system.
Further Context
  • The grant prints source examples of 2 kilowatt-seconds for a hard-boiled egg against 36 kilowatt-seconds conventionally, and about 240 kilowatt-seconds for a potato against 72,000 kilowatt-seconds in an electric oven. The specification calls the examples illustrative.
  • The printed references-cited table contains nine United States patents, from Goucher's US 1,181,219 of May 2, 1916 to Supplee et al.'s US 2,382,033 of August 14, 1945.