US 3,187,206 is Thomas Townsend Brown's later patent with the same title as US 2,949,550, "Electrokinetic apparatus". It was filed on 9 May 1958 as application US734342A, assigned to Electrokinetics Inc, and granted on 1 June 1965; a Swedish counterpart, SE210000C1, was filed in 1962 and published on 27 December 1966. The patent record lists it as expired. It matters to this dossier less for any single device than for what it shows about how Brown's account of his effect had shifted since the wire-and-plate patent he filed the year before.
What the patent claims
The patent opens by describing an electrical device that produces thrust "by the direct operation of electrical fields". Its central idea is the shaped field. If the electric field between two electrodes is made strongly non-uniform, Brown asserts, the device that does the shaping experiences a force, and it moves steadily one way while the surrounding masses move the other.
Much of the work of shaping is given to the insulating piece that holds the electrodes apart. The patent says it can be tapered, or made so that its electrical (and even magnetic) properties change gradually from one end to the other, either way making the field change unevenly across the gap. Mismatched electrode shapes and the charge carried by neighbouring objects are offered as other routes to the same end, and any of these may be combined.
From a medium to the walls of a vacuum chamber
The earlier patent, described in US 2,949,550: Thomas Townsend Brown's Electrokinetic Apparatus Patent (Wire-and-Plate Thrusters, Discs and a Torpedo Body), explained thrust as a reaction against charged particles of the surrounding medium. This one widens that account considerably. The reaction, it says, shows up in the medium but also on every solid body in the environment, and it names the walls of a vacuum chamber as an example. It then goes further: according to the patent, some propelling force remains even after everything in the surroundings has been taken out of the field's reach.
That is a much stronger claim than a push against air, because an ion wind needs gas to push against. Martin Tajmar's 2004 review cites this patent for the assertion that thrust persisted at pressures down to 10^-6 Torr, and treats it as the key claim to test (The Biefeld-Brown Effect as a Misread Corona Wind: Martin Tajmar's Sealed-Box Pendulum Test and Its 10 µN Limit). In the patent, the vacuum-chamber and removed-bodies statements are made as assertions; the document itself does not establish that they hold.
Four ways to make the field lopsided
Across its eight figures the patent relies on four broad strategies for making the field uneven.
- A curved, focusing electrode. The basic design pairs a curved electrode at one end of an insulating rod with an oppositely charged electrode at the other, placed where the curve concentrates the field. The curve can be continuous metal or a mesh of tightly spaced wires. Brown reports good results when the far electrode is a sphere wider than the rod, and says the curved electrode charged on its own still gives some thrust, though less than the pair.
- A graded insulator. Instead of a uniform spacer, the rod can taper or vary in conductivity or dielectric constant along its length; one figure is simply a graph of the uneven flux density this is meant to produce. A cone-shaped variant seeds the insulator with semi-conducting granules near a disc at its tip and allows alternating voltage, alone or on top of direct voltage, at a frequency where the disc spans half a wavelength.
- Loaded wedges. Insulating wedges carry electrodes on opposite faces. The taper is said to add thrust, and dense embedded particles such as lead oxide, packed towards the narrow edge, to add more. Wedges can be banked so their thrusts sum, or two banks wired in series, though the patent concedes the shared middle electrode would seem to be pulled towards the outer ones.
- An off-centre ring. A ring with a small electrode at its exact centre gives no thrust, according to the patent. Moving the electrode off-centre along the ring's axis is said to produce thrust: downward with either polarity in Figure 8B, and upward in Figure 8C, where the electrode sits beneath the ring's centre. The patent gives these arrow directions without stating a general rule.
The patent describes cyclically varying potentials as one advantageous way to energise the devices, and its claims cover the curved stitched-wire surface, electrodes of unequal area joined by a dielectric, a conductivity gradient produced by semi-conducting particles, and the annular electrode.
What the document does and does not show
As the wiki's note on Patent as Evidence explains, a granted patent shows that an application was examined and issued, not that the devices work. The embodiments are described in comparative terms: thrust is said to be produced, augmented or made greater.
Two details are worth comparing with later tests. First, the claim that the off-centre ring thrusts with either polarity matches what the Army Research Laboratory reported for wire-and-foil lifters in 2003; that report linked polarity independence to force terms that depend on the square of the field (Force on an Asymmetric Capacitor: The 2003 Army Research Laboratory Lifter Tests and Why Their Ion-Wind Estimate Fell Short (Bahder & Fazi)). Second, the lead-oxide loading echoes the idea, reported in Tajmar's review, that Brown thought a heavier dielectric strengthened the effect. In this patent, though, the stated reason for the particles is the steeper voltage gradient they are said to create.
The direction of motion also changes. In the 1957 patent, the device moves small electrode first. Here the pair is said to move in the direction of the larger, field-shaping electrode, and a curved electrode charged on its own towards its apex.
Connections in the patent record
The patent cites two earlier documents. One is Brown's own "Electrostatic motor" (US1974483A, 1930 priority, published 1934). The other is French patent FR1003484A, "Reaction propulsion process and devices for very high speed mobiles" (1947 priority, published 1952). Among its classifications is F03H1/00, which covers using plasma to produce a reactive propulsive thrust; it is also classified under C08L93/00, compositions of natural resins. These are administrative labels, not findings. Later patents citing it include Gravitec Inc's "Propulsion device and method employing electric fields for producing thrust", PST Associates' "Field converter" family, and a run of electric-field propulsion filings by Richard Banduric and James Wayne Purvis. Being cited by later patents shows that the document has influenced later filings, not that its effect has been confirmed.
Source notes & attribution
- https://patents.google.com/patent/US3187206A/en