A very nasty type of patent, where the patent owner hides the fact that he has a patent on something obvious, waits for the idea to become commonly used, then starts asking for royalties and fees.

The canonical example of a submarine patent is Unisys' patent on LZW (Lempel-Ziv-Welch) compression. They had it since the early 1980's. Compuserve then used LZW in its graphics format (which just happened to become the popular GIF format). GIFs then became popular on the Web; all the time Unisys hiding this patent. Then recently, Unisys comes out of the woodwork, says that the GIF format uses patented LZW technology and demands every Web site pay it a US$5000 licensing fee.

British Telecom recently claimed that they had a patent on hyperlinking (i.e. you click on underlined text and it takes you somewhere else). They want to charge licensing fees ... this would also be a submarine patent.

In some states and countries, they've introduced laws to prevent submarine patents, which means that if you want to maintain a patent, you have to enforce patents from the beginning of your patent being granted until it expires. This has a nasty side effect though, as it sometimes gets in the way, for example, of open source projects, since the companies with the patents can't just give the patents away or they would be risking losing the patent.

The Fraunhofer Institute (see mp3) has done the same thing, asking the writers of such freeware encoders as BladeEnc to cease-and-desist. Of course, all this means is you have to compile your own copy of LAME, or use a better format, like Ogg Vorbis.

I first heard this term in regard to a now disallowed practice with regard to patenting, with a far different usage than that detailed above.

The way patent law used to work, you could come up with a patentable idea, have it all sealed and notarized, and then not patent it. Years later, once your "ideas" are in use, you then were able to get a patent and sue the companies using them.

This practice was banned, but not before someone, one Jerome Lemelson, managed to get overly-broad patents on just about all modern technology, which he then used to shakedown big companies like Ford, Intel, Johnson & Johnson, etc. After his death, he passed the patents to a "charitable organization" which used them in the same way but claimed some unspecified amount would go to give scholarships to those pursuing innovative patent law as a career. However, because the United States Constitution prohibits ex post facto law, they are still able to sue with these patents.

Unfortunately, I no longer have the patent in hand, but I recall part of the one that was being used to beat a company over the head went like this (I know this isn't the exact specificaiton):

  1. It is possible to encode numerical data as electric signals and then manipulated.
  2. It is possible to take light, translate it to electric signals and then analyze said image.
Unfortunately, the courts repeatedly allow these patents to stand up, despite their overly-broad specifications. Patents on One-Click shopping and LZW pale in comparison to these patents.
Thanks to the Uruguay round of the General Agreement on Tariffs and Trade ("GATT"), the submarine patent is no longer.

According to provisions set out by GATT, which are now codified in US law, patent protection extends 20 years from the filing date of the application, rather than from its issue date as before. This means that Jerry Lemelson cannot wait until his invention has been invented, marketed, and made profitable.
