Patent Articles

The articles in this section are transcripts from my “Patenting for Inventors” podcast. You can read articles covering more 80 topics related to how to patent your invention. Alternatively, you can listen to the podcast by clicking the podcast link or image below.

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Claim Drafting Part 4 - Independent and Dependent Claims. Episode 12

These articles are near verbatim transcripts of my “Patenting for Inventors” podcast. Click here, or the podcast image to get to the podcast feed.

Claim Drafting Part 4 - Independent and Dependent Claims. Episode 12

So far I’ve talked about several important things to know about claim drafting. In the first part I talked about figuring out what your invention is. In the second part I talked about how to draft device or apparatus claims.  In the last part I talked about how to draft method claims.  In this episode I’m going to go through independent and dependent claims.

If you’ve looked at any of the patents I’ve gone through before, and go to the claims section, you’ll see that that it’s common for patents to have around 20 claims. This is because the Patent Office charges more money if you put in more than 20 claims.  The Patent Office also charges more money if you have more than 3 independent claims, so a general practice, people draft 3 independent claims and 17 dependent claims, but its not a hard and fast rule.

What is an independent claim and a dependent claim? An independent claim doesn’t make reference to any other claim and is what you believe is the broadest aspect of your invention that you think you should get protection for.  A dependent claim references that that broad independent claim and narrows it to something less broad.

Dependent claims act as backups in case your independent claim isn’t found to be patentable.  It’s easier to go through some examples.  Let’s say that you invented a flying bicycle that could fly by pedal power, but for some reason, you thought that you actually invented the regular bicycle.

You start thinking of all the parts. There’s a frame, there are wheels, there are handle bars, there are pedals, there’s a chain connecting the pedal to the wheels, there are wings attached to the frame, and a rudder.  Because you thought you invented the bicycle and you want to get patent protection for all bicycles, you start writing your claims.  You might write something like this:

1.      I claim a device for transporting a person, the device comprising:
a frame;
a plurality of wheels attached to the frame member’
at least one pedal’
a chain connecting the pedal to the plurality of wheels so that when the pedal rotates the chain causes the plurality of wheels to rotate; and,
a handle bar connected to the frame to steer the device.

This is a really simplified way to write the claim and isn’t exactly how it would be written, but this is just to show some major elements of bicycles that might be in a claim if you were trying to patent a generic bicycle.

You didn’t mention anything in your claims about wings because you didn’t want to limit yourself to just a flying bicycle. You wanted to get a patent for all bicycles. Now let’s say the patent examiner looks at your claim and for whatever reason also had never seen a bicycle, and issues your patent.  You’re excited that you have a patent for the bicycle.

Then you find out that a company is making flying bicycles and you decide to sue them because they’re making a device that has all the limitations of your claim. The flying bicycle has a frame, wheels, pedals, a chain and handle bar. You take them to court and the bicycle maker says, “bicycles have existed for a hundred years, so what you claimed, you never should have gotten a patent for.”  They provide evidence of basic bicycles and the judge invalidates your patent.  You now have nothing because you never claimed wings.  You didn’t claim wings because you thought that your invention was broader.  So what could you have done?

This is where dependent claims come in.  Dependent claims act as backups in case your original claim is found invalid because it wasn’t novel or non-obvious. What you should have done was made an extra claim besides the really broad one that said:

I claim a device for transporting a person, the device comprising:
a frame,
a plurality of wheels attached to the frame
at least one pedal
a chain connecting the pedal to the plurality of wheels so that when the pedal rotates the chain causes the plurality of wheels to rotate;
a handle bar connected to the frame to steer the device; and,
wings attached to the frame.

If you had had that claim, then even if your broad claim was found invalid, the judge might say, even thought that claim for a basic bicycle is invalid, your claim for a bicycle with wings is novel and non-obvious, and the flying bicycle manufacturer infringed your patent.  That’s why you want to have more than one claim in your patent.

It’s not required, but its generally a good idea to have dependent claims because you never know if your broad claims will be found invalid and you’ll have to rely on some narrower interpretation of your invention in order to sue someone for patent infringement.

What is the dependent claim in this example? One way to write the claim is to copy all the same elements as as your broad claim and then start adding new features. But there’s a shortcut, and what what a dependent claim is.  Instead of writing out the entire claim with all the limitations again, you can write, “Claim 2. The device of Claim 1, further comprising wings attached to the frame.” 

What this allows you to do is not not have to write everything out again, but just say that you’re adding a feature to Claim 1.  Why is this better that writing everything out again?  Cost is a big reason. As I mentioned before, you are only allowed 3 independent claims in a patent application before you have to start paying more fees, but you can have 20 claims total, so what you do is make your independent claim broad, and then have a lot of dependent claims that cover specific features that might be patentable if your broad claim is found invalid or unpatentable.

You can also made dependent claims that depend from other dependent claims. So for example, let’s say that you also have a rudder on the back of your bike. You can write a claim that says, “The device of Claim 2, further comprising a rudder attached to the frame member.”  There are all sorts of strategies for drafting independent claim and dependent claims so that you get a good mix of broad claim and narrow claims in case your broad claim is found invalid or not patentable.

You can also have dependent method claims.  In the last episode I talked about a method for making guacamole. If you go back to that patent, and you can find it using a google patent search for u.s. patent 5871794, and go to Claim 10 you can see the broad method claim.  The method involved removing the skin and pit from the avocado, removing the husk and seeds from a tomatillo to get tomatillo pulp, mixing the avocado and tomatillo pulp together and heating the mixture to about 85 degree for about 10 minutes.  That’s the broad independent method claim.  But if you look just below that you’ll see claim 11, which says, “The process of claim claim 10 further comprising the steps of washing, scalding and pressing the tomatillo pulp prior to removing the seeds and outer skin. “

The purpose of this is just in case claim 10 is found invalid, but the judge thinks that adding the steps of washing, scalding and pressing the pulp prior to removing the seeks and skin is valid, then you still have protection in that narrower method.  What if claim 11 is also found invalid? Well you can keep adding steps to make it narrower and narrower until there are some claims that is found valid. 

At some point your claim is so narrow and requires so many steps to be infringed that it is easy for someone to just omit one of those steps to design around your patent. This is why it’s important to have a good mix of broad and narrow claims in your patent, because you never know what claims might be found invalid and when you’ll have to rely on your backup dependent claims. 

The main reason of the dependent claims are legal backups but there are other reason to include them. It easier to amend the claims in your patent application if the examiner rejects your broad independent claim because you already have something narrow written down that the examiner can review at the time of the application, instead of later on when a judge might determine whether your claims are valid. 

You can describe specific features in your dependent claim to help others understand what different embodiments are. Dependent claims having lots of details are easier for a jury to understand, and there are lots of other reasons why you might have them, but the main reason to have them is to serve as a backup in case your broad claims are found invalid.

There probably could be a hundred episodes on claim drafting techniques, but at some point you’re going to have to start drafting the rest of your application, so the next episode will be the last episode geared specifically for claim drafting and it will just be a “Top 10 Tips” for claim drafting that will cover a whole bunch of little things to think about when you draft claims.  I’ll also cover some other details of claim drafting when I get to the episodes on responding to patent application rejections because of claim rejections.

If you want help with drafting your patent application and claims I do offer those services through my practice at Diament Patent Law.