US Patent 3,791,349 (1974): The Schaefer/Sonaqua Steam Generator and Its Water-Hammer Rotor

US Patent 3,791,349, titled simply "Steam generator", is the primary technical document behind the Schaeffer Steam Generator. It was filed on 1973-01-29 as application US00327430A, granted on 1974-02-12, and is now listed as expired. The patent record names the inventor as "C Schaefer" and the original assignee as SONAQUA Inc. The patent number and grant date match those the dossier attributes to Schaeffer (steam generator inventor); the record's spelling and initial differ from the "Karl Schaeffer" used elsewhere in the dossier, and the patent itself does not resolve that difference.

This page describes what the patent says the machine is and how it is supposed to work. It is a statement of a claimed invention, not a test report.

What the patent claims

The two independent claims (1 and 13, out of fifteen) describe the same core arrangement:

• a stationary housing with a rotor mounted to turn inside it;
• a water-filled space between and within the two, which the patent calls a "distended" chamber, meaning one broken up into many narrow passageways running in different directions rather than a single open cavity;
• at least one passageway with a closed end, and at least one with a radial component;
• a means of turning the rotor, a water supply, and an outlet for steam.

The claims assert that spinning the rotor sets up shock waves in the water, raising its temperature and pressure until part of it becomes steam. Dependent claims add a cone-shaped rotor, nested cone-shaped passageways joined by radial holes, a central vertical passage in the rotor, and two alternative locations for the closed-end passageway.

How it is said to work

The specification's explanation rests on water hammer, which it defines as the dynamic pressure produced when moving water is stopped abruptly and its kinetic energy becomes pressure energy.

According to the patent, two opposing effects are set against each other. Radial passageways in the spinning rotor fling water outward by centrifugal action, and this draws water out of the closed-end passageway, leaving a vacuum there. The vacuum then pulls the water column back. The patent describes the water as being pulled one way and then snapping back the other, with its motion "suddenly extinguished" at the dead end. Each such stop is treated as a shock.

The inventor's argument for heating is cumulative. Citing page 172 of J. N. Bradley's Shockwaves in Chemistry and Physics, the specification accepts that a single shock in a liquid produces only a small temperature rise alongside a very large pressure change. It then asserts that because the shocks repeat continuously, the pressure dissipates through the water while the heat accumulates, and that steam appears "almost instantaneously". The one number offered is a force of approximately 63.4 pounds per square inch for every foot of extinguished velocity, stated without a derivation or a measurement.

Two embodiments

FIG. 1 (preferred). A cone-shaped rotor (16) sits on a vertical motor-driven shaft (12) inside a bolted housing (11). Water enters through an inlet (17) in the under cap. Above the housing stands a superstructure of three concentric pipes. The closed-end passageway, which in this version is part of the stationary structure, is the series of chambers 49 to 52: a lower chamber (49) inside the fitting at the base of the superstructure, an annular chamber (50) between the outer and intermediate pipes, and finally two thin, concentric annular chambers (51 and 52), joined to each other over the top of the intermediate pipe. Steam is said to rise through the central bore (54) of the inner pipe to an adjustable valve (40), while water that has not converted is drawn back down and cycled again. Fresh water is admitted continuously to replace what leaves as steam. The specification notes that rotation is started before the system is completely full.

FIG. 5 (modified). Here the closed-bottom channels (98) are a ring of vertical holes drilled in the rotor itself. Small radial relief holes (102), set above the channel bottoms, let steam escape inward to a central rotor passage (100, 103). The patent says conversion to steam begins near the closed bottoms of these channels.

The patent presents the second design mainly to show that the chamber shape is not critical, so long as it has a closed-end channel and a passage where centrifugal action can occur.

Where the patent places itself

The specification distinguishes the device from U.S. Pat. No. 3,141,296 (Jacobs, Jr., et al.), which it describes as using shock waves from an electric discharge in liquid to drive a pump. The six patents cited in the record point elsewhere, to mechanical and rotary heaters:

The record also lists US3198191A (Kinetic Heating Corp, "Heat generator") as a family citation, and classifies the patent under F22B3/06: steam generation by transformation of mechanical, e.g. kinetic, energy into heat energy. That classification treats the machine as one that turns shaft work into heat, which is a conventional category and implies no energy gain.

Sonaqua pursued protection abroad as well: the record lists family members in Canada, Britain, Japan, Australia, the Netherlands, Israel, France, Sweden, Italy, Brazil, Switzerland and Germany. Later rotary fluid-heater patents cite it, including several assigned to Hydro Dynamics, Inc. and US5419306A, "Apparatus for heating liquids", in the name of Michael T. Huffman.

What the patent does and does not establish

The patent establishes that this design was disclosed in 1973, who held the rights, and what mechanism the applicant proposed. It does not establish that the mechanism is the correct account of whatever heating occurs. A rotor churning water in narrow passages will heat it by ordinary fluid friction, and the document offers no measurement separating that from shock heating.

The operating description gives no rotor speed beyond "relatively high", and no motor power, dimensions, steam output, temperature or pressure reading. Neither independent claim recites an efficiency or a ratio of heat out to work in. The efficiency figures discussed in Schaeffer Steam Generator Claims vs. Evidence: An Archive Dossier Without Test Data, including the readings above 100%, therefore come from the dossier's press and test material, not from this patent. A granted patent records a disclosure; it is not evidence that the device performs as described.

Further reading

• Schaeffer Steam Generator — the device as presented in the dossier.
• Steam Generator Claim — the general class of claim.
• Steam Generation — the conventional engineering background.
• Schaeffer's Steam Generator: A source Dossier — the archive dossier that reproduces the patent alongside press coverage.
• Cavitation Heat Generators for Building Heating: The 2017 Ved, Nikolsky, Oliynyk and Lipeev Study of Series Operation and Vibration-Based Control — a later, openly published study of cavitation heat generators for building heating, which explains heating through bubble collapse and pressure impulses and monitors the process by vibration.