The Orbital Engine was invented by John Patrick Ettridge from South Australia in 1969. His Provisional patent No.22884/70 has a priority date of 3rd December 1969 and Australian patent number 474336. This patent covered the use of two crankshafts geared to rotate together, or three crankshafts placed at 90 degrees apart, which imparted the orbital motion in the rotor, and covered the vanes being in the rotor, or the stator.

Many inventors had tried various engine, compressor and pump designs, trying to achieve the orbital motion, mainly by using the vanes to limit the spinning motion of the rotor. John Patrick Ettridge was the first to realize that the rotor motion had to be controlled first, independent of the vanes.

In a newspaper clipping from the Advertiser, Saturday, February 1973, it showed a picture of John Patrick Ettridge holding the Ettridge Orbital Engine, and had a heading "SA man claims orbital engine 'I have the patents to prove it." It goes on to say, "A 27 year old Adelaide man claims he invented an orbital engine almost identical to the WA developed Sarich engine. Mr.Ettridge said he started developing an orbital engine in 1968, soon after he completed his National Service. He said that, while he held patents to practically every feature in the Sarich engine, lack of money had stopped him from continuing with his invention. The Sarich orbital engine uses the least preferred configuration, that is with the vanes in the stator, while Mr.Ettridge prefers the vanes to be in the rotor, with the tips of the vanes contacting the inner edge of the stator. The vanes do not recipricate, it is the rotor moving up and down the vanes.

The Orbital motion has many uses yet to be realized, its unique charateristics make it desirable for use in pumps, compressors, internal compustion engines, steam engines and many uses yet to be developed. The rotary motion of the rotor make it ideal where high speed revolutions and positive displacement torque are required.

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