Reading patents for fun

As usual, everyone on the Internet can be grouped into two categories:

  1. Those for whom the patent system is a bit of a mystery, a seeming free-for-all where anything can be claimed and it’s lawyers at 50 paces.
  2. Those who have to navigate the patent system as part of doing their job, either in creating new patents or understanding a body of patents to avoid infringement.

If you’re in the second category, then this article isn’t for you. You probably already know more about patents than you really want to, and you have access to the required legal knowledge to navigate the patent system.

If you’re still with me, then I’m going to give you a high-level overview of how patents work, and how you can read them and get the important and interesting stuff from them. I’m not going to tell you how to legally interpret patent issues, because I am  unqualified to do so.

Why read a patent?

It seems like every week you read on Slashdot or Hacker News about some major company that has been granted a patent for some generic-sounding invention. Cue the great hoard of critics stating that the invention that is completely obvious, and was done years ago by such-and-such a product.

Are they right? You can bet they didn’t read the patent properly and distill out the actual invention. Wouldn’t it be nice if you could do that?

So, what exactly is a patent?

Basically, a patent is a contract between an inventor and the government where the government grants the inventor exclusive, time-limited rights to implement (and presumably sell) an invention in exchange for the inventor telling the world what they invented. When the patent expires, everyone is free to use the invention. The goal is to foster invention by encouraging people to disseminate their creative results to the world while still protecting their investment. Typically the rights to the invention are limited by country and for a fixed period, usually 20 years.

A patent is a form of intellectual property (IP). Other types of intellectual property include:

Trademarks are symbols, designs or text that identifies some form of product or service. The main purpose of a trademark is to protect the association of a product with the company that makes it. Interestingly, trademarks need to be defended by their owner, because if they become used in a generic sense by people, they can lapse. For example, kleenex, aspirin, hoover and thermos all lost their trademark status because they became used generically.

Copyright is the ownership rights of the an original, creative work (e.g. a song, novel, photograph or software program). These days it is automatically assigned to the author upon the creation of a work. Copyright does not protect ideas or algorithms, so if someone re-implements a copyrighted work, it often will not infringe. For example, you cannot copy a telephone book but you can re-type the numbers into your own version and publish that. Work protected by copyright can be protected for an astonishingly long time.

Trade secrets are knowledge that a company does not publish or release in any way. Of course, nothing stops someone from independently discovering the same knowledge. Even worse, nothing stops someone else discovering and patenting your trade secrets, thus preventing you from using them in the future!

You will also hear about something called a “design patent”. These are rights granted to the appearance or ornamental design of a product. A design patent can help protect a product from imitators. Famously, Apple was granted a design patent that covered the rounded corners of their iPad.

Of course, you can’t just patent anything. There are 4 broad requirements that must be met before a patent can be granted:

  1. The invention must be patentable. This can be a legally fluid area, but broadly the patent cannot be an abstract concept, a law of nature, a literary work or similar. Also, if you want to patent a free energy device or perpetual motion machine, the patent office will insist on seeing a prototype first 🙂
  2. The invention must be useful in some way. A patent that doesn’t provide any benefit is unlikely to be granted. I could invent a device for rotating a pencil on a desk, but it is unlikely to be patentable because it has no purpose.
  3. The invention must be novel. This basically means that it has not been published by anyone else in public before you. It doesn’t really matter where it was published, and obviously you cannot check everywhere, so you need to have some familiarity with the “prior art” before you can safely say that something hasn’t been published previously. Note that trade secrets do not count as prior publication!
  4. The invention must be inventive. That is, there should be a a notable creative step above and beyond what was known before.  If the patent office thinks that anyone could have created your invention if they needed to, then the patent will not be granted.

Finally, a patent does not grant you the right to practise your invention, just the right to prevent others from doing so. A patent can satisfy all the requirements described above, but some part of it could be covered by someone else’s patent. If you want to practise your invention, you would then need to license the other party’s invention first.

Why do companies file patents?

Apart from the cost to a company of drafting a patent application, the process of getting it granted by a patent office can be very expensive. So, a company needs some good reasons to go down this path. They can include:

  • The company has a new invention that they want to develop into a product. It’s really cool, so they want to make sure that no-one else can just copy them.
  • Sometimes companies will file defensive patents, where they patent improvements or developments to ensure that competitors don’t get in and file their own patents and therefore prevent them from using them.
  • Large companies like to build up portfolios of patents for licensing or cross-licensing purposes.
  • Occasionally, a patent is granted, and the invention freely made available for anyone to use. Bell Labs patented the “setuid” access right concept and then put it in the public domain, because they thought it was the best outcome for the industry. This doesn’t happen as often as it could…

So… how do I read a patent?

Firstly, we’re just going to consider patents that are granted in the US. While many countries have their own patent offices and jurisdictions, for most companies the USPTO (US Patent Office) is the one that matters. Rather than navigating through to find a patent, I find that the simplest way is to use Google’s patent search at

Let’s look at a rather infamous patent from recent times, the Amazon “1-click” patent. We will read the original version on the PDF link. The text at the web page is usually extracted via OCR and can have typos, especially for older patents. On the other hand, the Google patents page shows the post-granting history of the patent down at the bottom of the page; this can be interesting to read.

Front page

The front page contains some important administrative information, including:

  • The inventor’s names – to be celebrated or damned for all time. You can see that Jeff Bezos was one of the 1-click inventors.
  • The entity that owns the patent (usually the employee’s company).
  • The filing and granting dates. Generally speaking, the patent will be valid for 20 years after the patent’s grant date. So this patent will probably expire in 2019 (unless Amazon stops paying the renewal fees).
  • Relevant prior art (but which obviously does not describe the invention!).
  • The abstract, which may give you a clue about what the patent is about.
  • A representative diagram.


Next we have a bunch of diagrams. They may describe the invention, or they may cover relevant information.  All will be revealed in the later text. Do note that all diagrams have a Figure number and most will have lots of numbers on them; these will all be referenced in the main text.

Background of the invention

Often there will be a background section, which describes the setting for the invention. It can describe a problem that needs to be solved, and related inventions and functionality. One thing you don’t put in the background is any details about your invention – otherwise you’re telling the patent office that it has already been done!

Summary of the invention

Sometimes this is a good background to the invention, other times it is just useless boilerplate.

Detailed description of the invention

This is half of the contract the inventor has with the government. Here, the invention must be described for the benefit of the public. There are some rules about the content here:

  • You must describe your invention in such a way that a competent person can follow and reproduce your invention. You can’t hide or obfuscate anything.
  • You can describe multiple ways of implementing the invention (these are known as “embodiments”). If you provide multiple embodiments, they may have different advantages. You must include the best embodiment that you know (but you don’t have to indicate which one it is).
  • Whatever you describe here is not protected by the patent. Or to put in another way, you can’t infringe on a patent’s description.

For the purposes of reading a patent, the detailed description will help you understand exactly what the inventor has created.

In this case, the patent talks about online shopping, and how terribly onerous it is for the purchaser to perform multiple mouse clicks in order to complete the purchase.


The claims are the other half of the contract. If a patent is granted (and is still in force), then no-one (in the patent’s jurisdiction) can implement the invention without a licence. The claims are expressed in fairly precise language. If there is a dispute about potential infringement of a patent, the claims are what will be examined in a court.

There are two types of claims:

  • Independent claims are stand-alone, and describe the features that make up the invention. If someone else implements something that uses all the features, then they are infringing on the claim (it doesn’t matter if they do extra things).
  • Dependent claims are derived from independent claims. They create a more specific derivation of the independent claim. Once again, you must not infringe on a dependent claim. Dependent claims are easy to spot, they start with text like, “The method of claim 1 wherein…”

Several things to note about claim language. The bit at the beginning of each claim is called the preamble, and it isn’t really part of the claim proper. The rest of the features in the claim are known as the integers. You don’t have to do them in the same order to infringe. Also, you’ll note that each claim is a single sentence. The use of colons, commas and semi-colons is very precise! Also, you can always tell an engineer who has spent too much time looking at patents, when they start using words like “plurality”, “comprising” and “apparatus” in other contexts…

Assessing whether a claim is infringed is a difficult thing to do. You need to map the legalese language into features in a product. Sometimes you need to interpret words broadly to understand how the claim can be fully appreciated. At the end of the day, only a court can decide for sure.

One thing to note that you can’t claim something that is not described in the main description (there’s that contract again!). So, the description can help you understand the scope of the claims – but… the scope of the claims are not limited by just what is in the description.

When you file a patent application, there is often some correspondence back-and-forth between the inventor and the patent office. Usually this is where the patent office cites other patents that they claim describes your invention, and the inventor has to show why this is not so. Sometimes you win these battles, and sometimes you don’t. One thing you can do during this process is amend your claims. Maybe you can narrow the scope or reword it so that it steers away from known prior art. What you can’t do is change the description. So you can’t migrate your invention across to something completely different, as the claims will no longer match the description.

For the Amazon claim, you can follow Claim 1 and see what features make up the invention, without too much effort.

But wait, there’s more!

This patent is quite unusual in that the patent office was forced to re-examine the patent’s validity in 2010 (after a fairly wide outcry).

So, after the claims you can see a Reexamination Certificate. This contains some updates to the patent. In particular, there is an absolute ton of additional cited prior art. At the end, you can see that Amazon were forced to modify Claims 1 and 11 to avoid some of the newly-cited prior art. Normally these kinds of amendments happen during the initial patent examination process, before the patent is granted.

Next time a patent argument comes along…

So next time some rabid discussion about the next “stupid patent of the week” comes along, why not have a look at the actual patent?  Have a look at the claims, and see if you can understand what they are really trying to protect.

Also, bear in mind that just because a company patents something, it doesn’t mean that it will ever see the light of day.


If you’re looking at patents as part of your job, I [deliberately] haven’t tried to provide enough information to make a sensible decision. You need to talk to people with proper patent legal training. For example, I haven’t covered things like:

  • calculating the expiry date of a patent,
  • how to find related patents in the same family,
  • understanding the cited prior art,
  • how to decide if you infringe on a claim, or
  • how to determine if prior art would really invalidate a patent.

You need to know this (and more) to avoid potentially very costly litigation.

Some interesting patents to read

So, now you have some idea about how to interpret a patent, here are a few interesting ones to look at.

  • US2415012 (A helical spring toy, also knows as a Slinky)
  • US3005282 (Another children’s toy, Lego)
  • US5255452 (Michael Jackson’s anti-gravity shoes, as seen in the “Smooth Criminal” video)
  • US1867377 (What’s better than sliced bread, but a bread slicer?)
  • US6368227 (What happens when a patent attorney wants do demonstrate how the system works…)
  • US6285999 (Larry Page’s patent of Google’s page-rank algorithm)
  • US2292387 (Secret communications using frequency hopping, by actress Hedy Lamarr)
  • US2717437 (Velcro!)

Finally, the USPTO maintains a list of perpetual motion applications and granted patents 🙂