Patents are long (getting longer each year), pretty poorly written from a scientific communication viewpoint, and full of obscure phrases from lawyers, but making an initial decision on what a patent covers is easy - skip to the very back and read the claims, and if you really are into the TL;DR part of life (TL;DR = too long; didn't read) only read the first claim. Don't read the title of the patent, the abstract, the introduction or anything else written. The claims and only the claims define what is patented. The rest of that stuff was written when the initial application was written. Once the patent office got a hold of the application, they most likely cut the claims down in scope, but it was only the claims that were edited, not the body of the patent application - that other stuff will still remain there for all eternity even as the claims are withered down to nothing. Again, pay attention only to the claims and nothing else.
Let me give you a specific example. Here's a patent that issued last week, US 8,182,888.[*] Claim 1 states
"A packaging article, comprising: a layer of an oxygen-scavenging composition including: an oxygen-scavenging polymer that includes: a condensation backbone, and an unsaturated side chain attached to the backbone, wherein the side chain includes at least one acyclic carbon-carbon double bond that does not involve the first carbon atom of the side chain; and an oxidation catalyst; wherein the packaging article is suitable for use in packaging food or beverage products to preserve the freshness of the food or beverage products.
If that is tough to read, it should be as it violates all the good writing habits we've learned. However, it is legally necessary to write it in a style like this as all claims must be written as single sentences - hence the difficulty. If we can use multiple sentences, its much easier to get the point across. Let me show you.
The patent claims packaging materials with oxygen scavengers in them. The scavengers are made from polymers formed from a condensation reaction and they have an unsaturated side chain. The unsaturated side chain has at least one acyclic double bond, and that double bond isn't associated with the first carbon in the side chain. There is also an oxidation catalyst, and that is required since it doesn't claim that the catalyst is optional. And that's it. Nothing more, nothing less.
But lets look at the rest of the writing that's in the patent particularly what's on the first two pages. Start with the title: "Oxygen Scavenging Polymer" Does that mean it covers ALL oxygen scavenging polymers? No, having read the claims, we know better. Look at the abstract (it's right there on page 1 and it's really short and so easy to read!):
"A polymer with a backbone and an unsaturated side chain attached to the backbone. The polymer may optionally be combined with an oxidation catalyst and/or other ingredients."Now that is very misleading, isn't it? The abstract discusses a polymer backbone, but doesn't mention that the claims limit it to a condensation backbone. The abstract also states that the catalyst is optional, even though the claims, what is actually protected by the patent, do in fact require the catalyst to be present.
Turning to page 2, the Technical Field is described as
"This invention relates to an oxygen scavenging polymer. The polymer may be applied to a package, or made into package, wrapping, and storage articles to preserve the freshness of, for example, foods and beverages."Here is says the polymer may be made into a package, yet we know from the claims, it has to be made into one.
This post came about as a result of a remark made a colleague here - that a new invention is already covered by other patents. If you look at the body of the patents, you may be lead to believe that that is the case, but only when you look at the claims do you see that there is no overlap at all. Claims can be difficult to read because of the one-sentence requirement, but parse them just like you did sentences back in high school so you can understand them. Then you will see what is protected and what isn't and you won't be part of the telephone chain.
[*] I just picked this patent at random. I'm not working on oxygen scavengers, and I certainly am not holding this patent up as an example of a "bad" patent. It is representative of many patents where the claims can be quite different from the rest of the patent. My point here is to show clearly that the claims are what matters and that they can conflict with the balance of the publication rather badly at times.