CLASSIC PATENTS
Historical Technical Museum
Classic Patents/US 223,898
Electrification & Early Modern (1870–1920)Illumination & Materials Science

Edison High-Resistance Incandescent Lamp

US 223,898

High-Resistance Carbonized Filament in a High-Vacuum Sealed Glass Globe

Inventor(s)Thomas A. Edison
Grant Date1880-01-27
Filing Date1879-11-04
LocationMenlo Park, New Jersey
Edison's 1879 lamp is a high-resistance carbon filament ($R \approx 100\,\Omega$) in a Sprengel vacuum, with platinum leads sealed through the glass. The resistance is the point: thousands of lamps can hang in parallel on modest copper instead of each needing a feeder the size of a gas main.
USPTO PDF
Engineering Analysis & Physical Principles

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

Before Edison, dozens of inventors (including Joseph Swan, Humphry Davy, and Warren de la Rue) had demonstrated incandescent light, but their lamps burned out within minutes or hours and used thick, low-resistance carbon or platinum rods (1–4 Ω). To run thousands of low-resistance lamps in parallel, a power grid would require massive, solid copper cables as thick as tree trunks ($I = V / R$). Edison solved both the physics and the economics: by making the filament a micro-thin, high-resistance carbonized thread (100–200 Ω) inside a millionth-of-an-atmosphere vacuum, he reduced the required current by 95% ($P = V^2 / R$), making thin copper home wiring financially feasible for the first time.

The Core Breakthrough Mechanism

An electric current is passed through a micro-thin carbonized bamboo filament (R≈100 ΩR \approx 100\,\Omega). Due to Joule heating (P=I2RP = I^2 R), the filament reaches 2,200 Kelvin and radiates brilliant blackbody incandescence. Because the glass bulb is evacuated to a high vacuum (10−6 Torr10^{-6}\text{ Torr}), there are no oxygen molecules to burn the carbon, and no gas convection to cool the wire, allowing the filament to glow continuously for over 1,200 hours.

Interactive Real-Time 3D Physics Simulation

Initializing 3D WebGL Physics Engine

Calibrating studio lighting, shaders & telemetry...

Detailed Component Architecture

1High-Resistance Carbonized Filament

A micro-thin thread of carbonized organic fiber (cotton, paper, Japanese bamboo).

Offers an electrical resistance of 100–200 Ω at operational temperature. High resistance allows hundreds of lamps to be connected in parallel (1/Rtotal=∑1/Ri1/R_{total} = \sum 1/R_i) across a constant 110V supply without drawing destructive branch currents.

19th-C. Term: Carbon wire or filament of high resistanceModern: High-resistance incandescent emitter
2Hermetically Sealed High-Vacuum Glass Envelope

An all-glass globe evacuated using Sprengel mercury vacuum pumps.

Evacuation to 10−6 Torr10^{-6}\text{ Torr} eliminates oxygen (stopping oxidation combustion) and increases the mean free path of residual gas molecules, stopping molecular 'air washing' of carbon atoms and thermal conduction losses.

19th-C. Term: Receiver exhausted to one-millionth of an atmosphereModern: High-vacuum glass envelope
3Fused Platinum Leading-in Wires

Platinum wire leads passing through the glass stem.

Platinum has nearly the identical coefficient of thermal expansion as soda-lime glass (α≈9×10−6/K\alpha \approx 9 \times 10^{-6}/\text{K}). As the lamp heats and cools, the glass and platinum expand together, preventing microscopic air leaks along the seal.

19th-C. Term: Platinum leading-in wires sealed by fusionModern: Hermetic glass-to-metal matched seals

Governing Physical Equations & Principles

Joule Heating & High-Resistance Sub-Division
P=V2R=I2R,I=VRP = \frac{V^2}{R} = I^2 R, \quad I = \frac{V}{R}
By increasing filament resistance R from 1 Ω to 100 Ω, the current I required for identical radiant power drops by 90%, reducing power transmission losses in copper supply cables by 99% (P_{loss} = I^2 R_{wire}).
Planck Blackbody Radiation & Color Temperature
u(λ,T)=8πhcλ51ehcλkBT−1u(\lambda, T) = \frac{8\pi h c}{\lambda^5} \frac{1}{e^{\frac{hc}{\lambda k_B T}} - 1}
Heating the carbon filament to 2,200 K shifts its spectral emission curve into the visible spectrum, producing warm 2700K incandescent light.
High-Vacuum Mean Free Path & Kinetic Gas Theory
λmfp=kBT2πd2P\lambda_{mfp} = \frac{k_B T}{\sqrt{2} \pi d^2 P}
At 10⁻⁶ Torr, the molecular mean free path exceeds the dimensions of the glass bulb, preventing gas convection cooling and chemical degradation of the incandescent carbon.

Why It Still Matters

The socket, the parallel feeder, the meter, and the fuse box are the lamp's companions. LEDs changed the burner; they still hang on the distribution geometry this patent forced Edison to invent.

Legal Claims Decoder (4 Numbered Claims)

Compare dense legalistic claims directly with decoded plain-English functional specifications.
Claim #1Independent Master Claim
Verbatim Historical Legal Text
“An electric lamp for giving light by incandescence, consisting of a filament of carbon of high resistance, made as described, and secured to metallic wires, as set forth.”
Plain English Engineering Translation
The master apparatus claim covering any electric incandescent lamp using a high-resistance carbon filament connected to metal lead wires.
Key Protected Innovations:
High-resistance carbon filamentIncandescent filament geometryMechanical lead-in wire clamping

The Historical Bottleneck

Brush and Jablochkoff arc lamps were street tools: thousands of candlepower, a hiss, and nitric fumes. They could not sit on a desk. Earlier incandescent rods (Starr, Sawyer, Swan) were a few ohms. Feeding a city of them in parallel would have required copper on the scale of a gasworks. The lamp and the feeder were one design problem.

Why Prior Art Failed

  • •Low-resistance carbon rods (1–4 Ω) demanded uneconomic copper sections.
  • •Poor vacuums oxidized the carbon and blackened the bulb in minutes.
  • •Platinum-to-glass seals cracked when the expansion coefficients missed.
  • •Series arc circuits put every lamp on one failure chain.
The Breakthrough Insight

“Raise each lamp to about 100 Ω. Then $I = V/R$ per lamp is small, $I^2R$ in the street mains stays tolerable, and you can hang lamps in parallel the way gas jets hang on a pipe. The Sprengel pump and the carbonized sewing-thread (later bamboo) filament were how he hit that resistance and kept it from burning.”

Patent Wars & Legal Litigations

Vs. Joseph Swan, Sawyer–Man, and Heinrich Goebel claimantsInfringement Challenge
Rival Claim & Defense:

Swan had British carbon-lamp patents and a working demonstration. Sawyer–Man claimed broad US rights in carbonized paper. Later litigants waved Goebel's 1850s bottles.

Litigation Conflict:

In Britain, Edison and Swan merged into Ediswan rather than litigate to death. In the United States the Sawyer–Man interest fought through to the Supreme Court.

Final Resolution & Judicial Outcome:

The Incandescent Lamp Patent, 159 U.S. 465 (1895), held Sawyer–Man's claim to any 'fibrous or textile material' invalid as too broad. Edison's specific high-resistance carbon filament in high vacuum survived.

After the Grant

Edison General Electric merged into GE in 1892. The carbon lamp lasted commercially into the tungsten era (Coolidge, 1910). The parallel-feeder idea outlived every filament chemistry.

Civilizational Impact

Pearl Street (1882) sold light by the hour. Once the feeder math worked, generating stations had a load that paid for the copper. Gas mantles did not vanish overnight; they lost the indoor evening.

Historical Fact

The Menlo Park notebooks list thousands of carbonized candidates: woods, flax, horsehair, fishing line, and at least one assistant's beard. The 1,200-hour lamp that went on sale used Japanese bamboo, chosen after a worldwide fiber hunt, not after a single lucky night.

Further Context
  • Francis Upton, a Princeton mathematician, did much of the Ohm's-law arithmetic that convinced Edison the high-resistance path was the only path that could be sold.
  • The first public Menlo Park demonstration was 31 December 1879. The US patent issued 27 January 1880. Pearl Street did not open until 4 September 1882.
  • Swan's British lamps were real. Treating Edison as the sole inventor of incandescence is American courtroom history, not laboratory history. His contribution is the high-R, high-vacuum, parallel-grid package.