Hundreds of patents have been filed in Europe and America to protect inventions or improvements in hot air engines.
This section will present most of them.
Few patent have been filed before 1850. In the first half of the 19th century, just a few air engine had been invented. None of them has been a lasting technology, not even the famous Stirling air engine of Dundee which did last less than three years.
After 1850, and especially after 1860 came the hot air engine industrial age. Quite a few well-working hot air engines were built, amongst them the engines of Laubereau, Shaw, Brown, Lehman, Ericsson, Heinrici, Hock, Woodbury, Rider, Stenberg, Wilcox, Robinson, Wenham, to name just a few. All these air engines were built on an industrial scale.
To find old patents is sometimes arduous. For this reason some inventors, although their engines were successful, could not be listed here below because their patents could not be found.
Nonetheless, the reader will find information on them in The Inventors section.
Hot air engines can be classified in three groups:
The air engines patents being numerous, they will be presented in the order of the mentionned groups.
However, regarding the first group, it is necessary to bear in mind the fact that some inventors first brought up some non working engines or hardly working engines, before being successful. Woodbury, Ericsson are in this case. They are part of this group because they finally achieved to built a reliable air engine.
The second group of patents is about inventors that built air engines that worked for a period of time, but could not be built on a industrial scale because they could not last technically. For instance the Stirling engine never came up as a completed air engine, and therefore could not be built on a large scale.
The third and last group is about non working air engines patents. It is also the most populated group: what an amount of effort and energy was spent to meet failure!
Nonetheless the patents are utmost interesting as failure is an excellent way to learn.
When browsing through the patents, depending on the inventors, one will see a fair amount of reissued patents. Those patents are usually very interesting as their purpose is to correct, improve or simplify the original patent.
Each time whenever possible, for better reading, the reissued patent will be linked to the original patent.
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