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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)
ELECTRO-MAGNETIC MOTORProgressive magnetic fields from independently timed alternating currents
US 381,968Class: Electro-Magnetic Motor (title printed on the grant)
Inventor(s):Nikola Tesla
Origin / Location:New York, New York
Grant & Filing:Filed October 12, 1887 · Granted May 1, 1888

I. Historical Context & Grant Summary

Granted on May 1, 1888, this specification describes motors with two or more independently connected circuits fed by a suitable alternating-current generator. Tesla uses the changing strengths and directions of those currents to shift the motor's magnetic poles progressively around a ring, then gives several motor-generator arrangements that turn a disk or armature without a motor commutator.

II. Core Mechanism & Scientific Principles

Tesla's stated problem is a practical transmission-and-conversion system: a motor should hold a substantially uniform speed through normal loads, use simpler and more reliable apparatus, and reduce the danger associated with high-tension transmission. This grant answers with two or more motor circuits that receive alternating currents at proper intervals. Their changing magnetic effects shift the places of greatest attraction around the motor, and a disk or armature follows that shift. The document gives several arrangements, including directly connected motor and generator circuits; it does not specify every later alternating-current motor construction.

Physical Operation:For the two-circuit arrangement, one generator coil can be near zero while the other is at a maximum; an eighth turn later both contribute, and the resultant motor-pole direction lies between the two coil axes. In modern vector notation, the teaching shorthand is B_net = B_B + B_B′. Tesla traces that resultant through eight generator positions and says that one generator revolution shifts the motor's poles around the ring once. The free magnetic disk follows the moving position of greatest attraction. Other illustrated arrangements use three circuits, fixed coils, or windings on both field and armature, but retain the same causal chain: timed currents, progressive pole shift, then mechanical rotation.
Governing Formulation:
Superposition of the magnetic effects:\mathbf{B}_{\mathrm{net}} = \mathbf{B}_{B} + \mathbf{B}_{B'}
Synchronous relation in the Figure 9 form:\Delta\theta_{\mathrm{poles}} = 2\pi \quad \text{per generator revolution in Fig. 9}
Relative movement of two magnetic patterns:\Delta\theta_{\mathrm{relative}} = \Delta\theta_{\mathrm{field}} - \Delta\theta_{\mathrm{armature}}

III. The Granted Legal Monopoly (Key Claims)

Claim 1 (Independent)Paired motor-generator polyphase circuits

This claim covers the combination of a motor with separate or independent circuits on its armature, field-magnet, or both, and an alternating-current generator whose induced circuits connect independently to matching motor circuits. The legal result required is that generator rotation progressively shifts the motor poles.

Claim 2 (Independent)Independent alternating-current transmission system

This system claim narrows the first combination to a motor with two or more independent magnetizing coils, a generator with corresponding induced coils, and direct circuit connections in the order that passes the generator currents through their corresponding motor coils to move the motor poles progressively.

Claim 3 (Independent)Annular ring stator geometry

This claim selects a particular motor geometry: an annular field magnet and a cylindrical or equivalent armature, with independent coils on the field, armature, or both. It pairs that motor with a generator having corresponding independent coils and requires the circuit arrangement to shift the motor poles progressively.

IV. Mechanical Organ Breakdown

Independent motor circuitsTerm: “independent circuits” → separately connected phase paths; not necessarily electrically isolated

Two or more separately connected coil paths receive alternating currents at properly chosen intervals.

Ring and free armatureTerm: “armature” → the motor's rotating magnetic element

A magnetic disk or a wound armature turns within a ring or field structure as the field's attractive region moves.

Generator-to-motor correspondenceTerm: “induced circuits” → generator windings that develop the alternating currents sent to the motor

The generator's independently connected coils feed matching motor circuits in the order that produces the progressive shift.

CLASSIC PATENTS DIGITAL ARCHIVE • PERMANENT EXHIBIT ID: us-381968-tesla-motor
classic-patents.com/patents/us-381968-tesla-motor
Original USPTO PDF
Classic Patents/US 381,968
Electrification & Early Modern (1870–1920)Electromagnetism & Power Generation

Tesla Progressive Alternating-Current Motor

US 381,968

Progressive magnetic fields from independently timed alternating currents

Inventor(s)Nikola Tesla
Grant DateMay 1, 1888
Filing DateOctober 12, 1887
LocationNew York, New York
Granted on May 1, 1888, this specification describes motors with two or more independently connected circuits fed by a suitable alternating-current generator. Tesla uses the changing strengths and directions of those currents to shift the motor's magnetic poles progressively around a ring, then gives several motor-generator arrangements that turn a disk or armature without a motor commutator.
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

Tesla's stated problem is a practical transmission-and-conversion system: a motor should hold a substantially uniform speed through normal loads, use simpler and more reliable apparatus, and reduce the danger associated with high-tension transmission. This grant answers with two or more motor circuits that receive alternating currents at proper intervals. Their changing magnetic effects shift the places of greatest attraction around the motor, and a disk or armature follows that shift. The document gives several arrangements, including directly connected motor and generator circuits; it does not specify every later alternating-current motor construction.
The Core Breakthrough Mechanism

For the two-circuit arrangement, one generator coil can be near zero while the other is at a maximum; an eighth turn later both contribute, and the resultant motor-pole direction lies between the two coil axes. In modern vector notation, the teaching shorthand is B_net = B_B + B_B′. Tesla traces that resultant through eight generator positions and says that one generator revolution shifts the motor's poles around the ring once. The free magnetic disk follows the moving position of greatest attraction. Other illustrated arrangements use three circuits, fixed coils, or windings on both field and armature, but retain the same causal chain: timed currents, progressive pole shift, then mechanical rotation.

Interactive Real-Time Physical Simulation

Drag to rotate · Pinch to zoom · Shared controls update the displayed model
INITIALIZING THREE.JS WEBGL SIMULATION...
Progressive Magnetic Poles in Tesla's Fig. 9 Apparatus.
Host-Model Telemetry/Computed Readout
Progressive Magnetic Poles in Tesla's Fig. 9 Apparatus
Generator rotation
3,600RPM[1/T]
Pole shift around ring
3,600RPM[1/T]
Fig. 9 disk relation
3,600RPM[1/T]
generator G → progressive pole shift
60 rpm / Hz
ts-fallback
progressive pole shift → disk D
1 rpm / rpm
ts-fallback
Generator Rotation
∂n_G / ∂f (host sensitivity)
60 RPM / Hz
Generator phase-cycle rate (teaching model)60 Hz
Live AC Hum Audio0 on/off
Energy · electromagnetics_flux
Polyphase AC Stator Input
1,500 W
Rotating Field Rotor Torque Work
1,290 W
Stator Resistance & Magnetic Hysteresis
210 W
Coupled Transfer Dynamics · fs-couple
ts-fallback
generator Gprogressive pole shift
+60rpm / Hz
progressive pole shiftdisk D
+1rpm / rpm
Interval ghosts
Disk3600.0 rpm · [1200, 7200]
B1.0 · [0.3, 1]
Fidelity / MMS residual
Fig. 9 disk vs generator
model3600 rpm
reference3600 rpm
residual0 rpm
Coupled channels
polyphase stator → rotor torque1290 W
Dated scenarios

Detailed Component Architecture

1Independent motor circuits
Two or more separately connected coil paths receive alternating currents at properly chosen intervals.

In the Figure 9 system, four coils C C C′ C′ surround the ring. Diametrically opposite coils cooperate in pairs; their four free ends go to T T T′ T′. The generator's two coils B B′ supply corresponding motor paths through wires L and L′. The source shows the resultant magnetic direction advancing in eighth-turn steps as those two generator currents change.

19th-C. Term: independent circuitsModern: separately connected phase paths; not necessarily electrically isolated
2Ring and free armature
A magnetic disk or a wound armature turns within a ring or field structure as the field's attractive region moves.

Figure 9 places magnetic disk D inside annular ring R. Tesla says the disk takes the position embracing the greatest possible number of magnetic lines and therefore follows the moving points of greatest attraction. Later figures instead use a wound drum armature, a disk between stationary coils, or a field and armature both supplied with coils. The grant does not specify a single universal rotor construction.

19th-C. Term: armatureModern: the motor's rotating magnetic element
3Generator-to-motor correspondence
The generator's independently connected coils feed matching motor circuits in the order that produces the progressive shift.

Claims 1 through 4 require a relationship, not merely a motor shape: independently connected induced generator circuits correspond to the motor circuits, and their order makes a generator revolution progressively shift the motor poles. Figure 9 uses collector rings and brushes on the generator. Tesla's stated avoidance is the motor commutator and the usual commutating appliances, not every sliding contact in every illustrated embodiment.

19th-C. Term: induced circuitsModern: generator windings that develop the alternating currents sent to the motor
Engineering Principles & Equations

Governing Equations & Engineering Principles

Authored explanation paired with its stated mathematical relation

Figure 9 Progressive Pole Shift

Electromagnetics & KinematicsClaim 1
Mathematical Governing Law
Terms:
Plain English DecoderHover or tap any highlighted phrase
Tesla's carries the attractive region once around ring R for one generator revolution in the Figure 9 teaching model.
Δθpoles\Delta\theta_{\mathrm{poles}}
Progressive Pole Shift
The source-stated once-around shift of the motor's attractive region for one Figure 9 generator revolution.
revolutions per generator revolution

Tesla describes this relation for the illustrated generator and motor. It is not a general speed, slip, torque, current, power, or material-performance formula.

Live Physical Value:
60.00 revolutions per generator revolution
Physical Principle & Engineering Insight

The card keeps the equation tied to Tesla's Figure 9 statement: corresponding generator circuits progressively shift the ring poles, and disk D follows the moving points of greatest attraction.

Historical Context: This is the source-specific correspondence between generator rotation and progressive motion of the motor's poles. The separate Figure 13 three-coil arrangement is described in the edition but is not silently merged into Figure 9.

Superposition of the magnetic effectsAuthored Principle 1
Stated relationBnet=BB+BB′\mathbf{B}_{\mathrm{net}} = \mathbf{B}_{B} + \mathbf{B}_{B'}
Tesla's sequence diagrams combine the magnetic effects from separate coil pairs. As the relative strengths and directions change, the resultant pole position advances around the ring. The source illustrates positions rather than supplying a modern sinusoidal field equation.
Synchronous relation in the Figure 9 formAuthored Principle 2
Stated relationΔθpoles=2πper generator revolution in Fig. 9\Delta\theta_{\mathrm{poles}} = 2\pi \quad \text{per generator revolution in Fig. 9}
Tesla says that one generator-armature revolution moves the attractive region around the ring once. In that construction he reports that the disk motion is synchronous with the generator armature, subject to the arrangement and normal working conditions he describes.
Relative movement of two magnetic patternsAuthored Principle 3
Stated relationΔθrelative=Δθfield−Δθarmature\Delta\theta_{\mathrm{relative}} = \Delta\theta_{\mathrm{field}} - \Delta\theta_{\mathrm{armature}}
For Figures 17 and 19, the wiring shifts the field-magnet's high-attraction regions opposite to those on the armature. Tesla states that this arrangement increases the speed of rotation. The grant does not provide a modern torque characteristic.

Interactive Schematic Sheet (Fig. 1)

The left diagram shows generator armature coil B B′ between field-magnets N S. The adjoining diagram, Fig. 1a, shows the corresponding motor-ring position with ring R and coil pairs C C C′ C′.

1.00x
US 381,968 · FIG. 1
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 patent makes a visitor inspect the engineering move that matters across later polyphase machinery: use multiple timed electrical paths to move a magnetic condition through space, then arrange a rotor or armature to follow it. The source also preserves an important boundary: this particular grant claims motor-generator combinations and expressly says that the method of operating motors was the subject of a separate application.

Legal Claims Decoder (4 Numbered Claims)

Compare dense legalistic claims directly with decoded plain-English functional specifications.
Claim #1Independent Master Claim
1/4
Verbatim Historical Legal Text
“The combination, with a motor containing separate or independent circuits on the armature or field-magnet, or both, of an alternating-current generator containing induced circuits connected independently to corresponding circuits in the motor, whereby a rotation of the generator produces a progressive shifting of the poles of the motor, as herein described.”
Plain English Engineering Translation
This claim covers the combination of a motor with separate or independent circuits on its armature, field-magnet, or both, and an alternating-current generator whose induced circuits connect independently to matching motor circuits. The legal result required is that generator rotation progressively shifts the motor poles.
Key Protected Innovations:
Paired motor-generator polyphase circuitsIndependent magnetic phase windingsProgressive pole shifting from generator rotation
Historical Legal Impact:
This is the broadest claim to the specified motor-generator combination; it requires corresponding independent circuits and the progressive pole shift, rather than claiming every later alternating-current motor.

The Historical Bottleneck

Tesla says the apparatus then available could not jointly provide uniform motor speed through normal loads, economical conversion, simple reliable construction, easy management, and reduced danger when high-tension currents are used for economical transmission.

Why Prior Art Failed

  • •The specification says earlier apparatus and systems had not fulfilled the stated transmission-and-conversion requirements.
  • •Tesla treats mechanical commutation and reversal of a considerable direct current as difficult and expensive, especially where many energizing circuits would otherwise be needed.
  • •The Figure 9 discussion retains collector rings and brushes on the generator while seeking to avoid a motor commutator and the usual commutating appliances in the system.
The Breakthrough Insight
“The patent's stated move is to send alternating currents through two or more independent circuits at proper intervals so that the motor's magnetism, or “lines of force,” shifts progressively. The movable disk or armature follows the resulting moving points of greatest attraction.”
After the Grant
The document itself limits this application to apparatus and system combinations and says that the method of operating motors was the subject of a separate application. That distinction matters when relating this 1888 source to later alternating-current motor practice.
Civilizational Impact
This grant gives a carefully illustrated historical account of coordinated independent current paths moving a magnetic condition through space. It records two-circuit, three-circuit, stationary-induced-element, and doubly wound variants rather than collapsing them into one generic later motor.
Historical Fact
The grant has four drawing sheets and nineteen numbered figures, including paired diagrams 1 through 8 and 1a through 8a that trace successive magnetic positions.
Further Context
  • The filing notice printed on the grant is October 12, 1887, Serial No. 252,132, and carries the parenthetical “No model.”
  • The patent explicitly defines “independent” as not necessarily electrically isolated, because connections may regulate or modify motor action without producing a new or different action.
Technological Lineage & Descent

The Polyphase Electric Grid

From Direct-Current Motors to Resonant Alternating Power Systems

The electrical revolution that replaced localized chemical galvanic cells and direct current with universal polyphase induction motors and high-voltage transmission.

1837First Rotary Electric Motor
US 132

Davenport Contact-Plate Electric Motor

Commutator-switched electromagnets creating continuous rotary motive torque.

1871Continuous DC Dynamo
US 120,057

Gramme and d’Ivernois Endless-Bobbin Dynamo

Closed-ring continuous toroidal armature eliminating pulsating current ripple.

1880High-Resistance Parallel Grid
US 223,898

Edison's High-Resistance Carbon Lamp

High-resistance carbon filament in high vacuum enabling parallel circuit distribution.

1888Rotating Magnetic FieldThis Patent
US 381,968

Tesla Progressive Alternating-Current Motor

Independent out-of-phase AC currents inducing rotor torque without brushes or sparks.

1897Resonant High-Frequency Transformer
US 593,138

Tesla's High-Potential Transformer

Air-core loosely coupled resonant LC circuits generating high-potential oscillations.