Reading a Patent Specification

I spent some time this morning advising on a patent and what it prevented competitors from doing.

It was a great long affair drafted in the USA, and it was not necessary to read much of it, because patent specifications all follow a standard format.  The most important part is the set of “Claims” at the end.  These are the legal definitions of the invention protected by the patent.

The first claim is the most important and the broadest.  It is a list of technical features that go to make up the invention.  If you want to place a competitive producton the market, which has all the features of the main claim, then you will infringe the patent (all other things being equal, such as the patent being still in force and being a patent in respect of the country where you want to operate).

So, if the claim is to a car with four wheels, an engine, a gearbox and a specially balanced prop-shaft to the rear, driving axle, there is no way that you can infringe this claim with a car that has two unbalanced solid drive shafts driving the front wheels.  The reason is that there is no prop-shaft, never mind how it is balanced.  If you have a rear wheel drive car or a four wheel drive car with a conventionally balanced prop-shaft, you won’t infringe because you don’t have the special balancing feature.  This illustrates a very important feature of patent law – if you use something that was on the market before a later patent, then you cannot infringe the later patent, because the later patent is not valid if it covers what was done before.  Patents only protect new inventions.

You infringe only if the have all the features of the claim, namely the car with the four wheels, the engine, the gearbox and the specially balanced prop-shaft to the rear, driving axle.

A couple of other points.  Firstly, there are usually a fair number of claims.  The first is the broadest and the others are narrower.  The analogy I gave this morning was that claim 1 was the whole farm, claim 2 the fields around the farmhouse, and claim 3 the front meadow.

Why, the if the claims are the important part, is there so much more to a patent specification?  There are two reasons: (1) terms used in the claims often need a bit of explanation and (2) there is an obligation to describe the invention sufficiently fully so that someone coming along after the patent has expired can read the instructions and make the invention, which is no longer patented.

Patent specifications then have a description of something that works and a definition – the claims – of what it is that the judge will say you should not be doing if you are sued for infringing the patent.