It’s not really possible to offer a definition of a strong patent as such – it’s often easier to illustrate a weak one – but there are some characteristics we can consider. Let’s start by saying that there are at least two types of strength we might consider: technical strength and commercial strength.

A technically strong patent is strong because it has been well written, taking into account all relevant prior art. It is likely to stand up to scrutiny if the patent owner needed to go to court to enforce the patent.

A commercially strong patent is one that will achieve its owners’ commercial objectives, whether those are to exploit the patent themselves or to licence it to others.

Technically strong patents will make claims for the invention that are as broad as possible, so that a competitor can’t just make small changes to avoid infringing the patent. Imagine, for example, you’ve designed a new vacuum cleaner. Your patent application states the sizes of its key new components very precisely. If a competitor is able to vary those sizes and still achieve the same technical effect as you did, then your patent may be ineffective.

All patents must be novel and have an inventive step, but some have a higher “inventive step”, than others. The more distinctive an invention is, the easier it is to define its inventive step, and the stronger the patent may be. The less the inventive step, the more skill will be needed to make the most of what novelty there is.

Commercially, a patent may be strong for very different reasons. Even a very small inventive step, well defined, may be worth millions if it adds significant value to a product which already exists. It may do so because it gives a company that’s exploiting its own IP another twenty years’ ownership of the market-leading product. Or, it may stop a competitor from further enhancing their product without paying you licence fees.

A patent’s commercial effectiveness will be all the greater if it’s not possible to create a substitute product that will achieve a similar commercial effect in a different way. In the 1970s, for example, Xerox had a seemingly impregnable suite of patents on plain paper copiers. What they hadn’t realised, however, was that there was another way of going about the process, and Canon’s engineers saw that opportunity and filed a series of patents to control that new paper copying process. Often, however, it will be difficult to anticipate substitutes.

You will probably agree with us that a truly strong patent will be both technically and commercially strong. It will protect an invention with clear commercial potential in the best way possible considering the “state of the art” and its novelty and inventive step. As we’ve said elsewhere, if you see commercial potential in your invention, you need to submit the most appropriate application you can. So if you’re based in the UK, why not get some advice from a UK Patent Attorney?