Do you gents really want to know? I am a USA patent attorney, with >30 years experience. There is no exemption from infringement for personal use unless it is for pursuit of "philosophical" interests as contrasted with commercial exploitation. A tinkerer (no reference to FOG's famous W. Tinker intended) who experiments with another's patented invention is exempted from liability, as long as his efforts are merely that -- pursuit of his curiosity or use for education. Infringement of a patent does not require exact copying, it only requires making, using, selling, offering to sell or importing whatever is the patented subject matter, e.g. a structure such as a table extension having all the elements of that structure as stated in the granted patent claims. It is those numbered statements at the end of a patent that define what is the patented subject matter, not what is shown in the drawings, and not necessarily what appears in the products of the patent holder. It may be that some of the embodiments in the drawings are not covered by the granted patent claims, and it may be that a product that doesn't look much at all like the product of the patent holder does infringe. Yes, this is legalese. It isn't simple, although a particular invention may be. Infringement and liability for damages to the patent holder are not exactly the same. Damages for infringement do not accrue under US law until the accused infringer is notified of the infringement. In earlier days, that requirement could be met by affixing the patent number(s) on the product or the packaging it came in if the nature of the product made marking the product itself impractical (e.g. a carbon brake disk for an aircraft) Today, it seems USA courts want a more specific direct notice to be given, one that rises to the level that enables the accused party to file a declaratory judgment action against the patent holder if he so chooses to pull the trigger first. The cost of enforcing patent rights is usually quite substantial (a "cheap" lawsuit is in the order of $1M cost, most patent fights between corporations cost much more) and can take many years. The inventor of the interval windshield wiper (Kearns) fought Ford and other automotive companies for many, many years before being paid for his patent [http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=4&f=G&l=50&co1=AND&d=PTXT&s1=kearns.INNM.&s2=wiper&OS=IN/kearns+AND+wiper&RS=IN/kearns+AND+wiper]. Thus, many minor violations are often not pursued by the patent owner.
Patents are territorial in nature. A patent in Germany cannot be used to stop infringement in USA and
vice versa. The claims of corresponding patents in USA and Germany are likely to be somewhat different in language and legal scope, as are the laws that govern them.
Copyright and trademarks are separate and distinct categories of intellectual properties, and the legal rules governing each of them are different from those that apply to patents. Patents have a much shorter life than copyrights and trademarks, 20 years from the date of patent application in most countries including USA. Copyright lasts longer than the life of the author, hence Elvis' estate is still making a fortune on his recordings. Trademarks can be renewed and thus last indefinitely if properly used and protected by the owner. Anyone interested can obtain a lot of information at the
http://www.uspto.gov/. I recommend honoring any contract that you enter.
Dave R.
---- patents are confusing by design I suppose.