As a general rule, mathematical methods are excluded from patentability, although practical applications involving mathematics may still be patentable (advances in cryptography, for example). However, mathematical terms themselves aren’t excluded and some of those have made their way into the lexicon of patents. Here are five common aspects of patent law involving relatives of words you might expect to find in a maths textbook.
1) Added subject matter, by addition (+)
A patent application is a snapshot of the invention at a particular point in time once it has been finalised to a large extent. Of course, you may continue improving your invention after a patent application has been filed – this happens all the time. However, you are not allowed to add any new information to your patent application to describe those improvements. If you need to make changes to the application, you can only do so using the information that was in the application at the time it was filed.
If the improvements to the invention are valuable in their own right, then you would need to file a new patent application to protect them. Of course, the original application may still cover your invention (unless there have been major changes), but protecting incremental improvements as well can allow you to prolong patent protection for your products beyond the 20-year patent term, and may allow you to take advantage of Patent Box tax relief over a longer period of time.
2) Added subject matter, by subtraction (–)
This is the other side of the coin to the situation above. Claim 1 of your patent application might claim “a widget comprising a first widget part, a second widget part and a third widget part”. All of these features are in the independent claim (claim 1), so they are considered to be essential to how your invention works. But what if you find that the third widget part isn’t actually essential, and keeping it in claim 1 would make for an easy workaround? Can you delete it from claim 1?
The answer is maybe. It depends if there is another part of the patent specification that indicates the third part is non-essential. Taking out the third part would constitute “claim broadening” (a kind of claim amendment), which is allowed before the patent grants, but not after grant. Of course, removing a feature from claim 1 could also mean that there is more prior art standing in the way of patentability, so it may be necessary to add other features in to compensate for that.
There is also the chance that you might need to disclaim (i.e. exclude) a particular feature or scenario to get around an objection based on prior art. Disclaimers can be based on something said in the patent application (a “disclosed disclaimer”, e.g. my widget does not include a handle), or occasionally based on something that is not said (an “undisclosed disclaimer”). This second type of disclaimer could be argued to add matter, but is essentially restricted for use in a situation where the prior art is completely unrelated, e.g. your invention is a dog toy, and the prior art involves helicopters.
3) Multiple embodiments (×)
It is often the case that an invention can be put into practice in more than one way. If you have found two or more ways to solve the same technical problem, then there are potentially multiple embodiments to describe when preparing a patent application. For example, a lever-type door handle solves the same problem as a rotatable doorknob – but one of these is only useful if you need to keep a bear in the next room.
Sometimes a patent examiner may decide that two or more embodiments are claimed in different enough ways that they will not perform a patent search for all of the embodiments, even if they are related to each other. There is usually the option to request a further search for the unsearched embodiments, but to obtain patent protection for those other embodiments may require a divisional application (see below).
4) Divisional applications (÷)
A patent is limited to a single invention. If your patent application includes multiple inventions, e.g. the lever and rotating door handles example mentioned above, then you may need to file a second patent application which is divided out from the first. A divisional application would be searched and examined separately and, if granted, renewable separately to the first patent.
A divisional application can only be filed whilst the original application is still pending (European patent applications) or usually no later than three months before the compliance deadline (UK patent applications). This is one reason why it can be beneficial not to get a patent granted as fast as humanly possible – keeping an application pending retains the option to file a divisional, which can be useful if there is infringement.
5) Infringement by equivalence (=)
An infringing product does not need to copy every single feature of a claim in a granted patent for there to be infringement. Sometimes, it is enough that an equivalent feature is provided. That is to say, patent protection isn’t limited to the literal wording of the claims – it is the claims as construed in light of the specification as a whole, and taking account of equivalent features, that determines the scope of protection and whether a variant infringes.
For example, in 1990, the Improver v Remington case found that a slitted rubber rod was equivalent to a helical spring, mainly because the epilator obviously worked in the same way. This was taken further in Actavis v Eli Lilly which went all the way to the UK Supreme Court, with the result that potassium was considered to be equivalent to sodium, for the purposes of interpreting the scope of the patent claims at issue.
For UK patents, if the variant works in the same way and achieves the same result as the invention, and strict compliance with the claim wording is not essential to the invention, then it should be found to infringe. This is assessed on a case-by-case basis though.
Summing up
The take-home messages here are that you can’t add new information to a patent application after filing, you might need to split your patent application in two (or three, or four…) to protect multiple versions of your invention, and assessing patent infringement isn’t always as straightforward as it might seem – there are a lot of factors to consider.
For advice on your patents or other intellectual property, please give us a call and have an initial chat with one of our attorneys.
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