How should I structure my claims and embodiments in regards to a patent for an invention to be implemented by a text editor?

Question

In US patent law, how are claims that are dependent on an earlier claim affec the interpretation of the earlier claim. Is the prior claim's interpretation based on each dependent claim, or is the scope only interpreted in relation to the dependent claim itself?

Explained: I have claim 1 that makes a point, and claim 2 which is dependent on claim 1 along with some content refining the meaning of claim 1. If I wanted to use claim 3 which is dependent on claim 1, would the method of claim 1, in view of claim 3, be limited by claim 2? If so, how should I avoid this in claim 1, and avoid making excessive independent claims.

Answer 1

Is the meaning of a first claim modified by having a second claim dependent on it?

Yes. Or at least, it can do, in some circumstances.

In the US, the doctrine of claim differentiation provides basically that a dependent claim must be interpreted to be different in scope from an independent claim. More formally, "the presence of a dependent claim that adds a particular limitation gives rise to a presumption that the limitation in question is not present in the independent claim" (Phillips v. AWH Corp., 415 F.3d 1303 (Fed. Cir. 2005)).

This doctrine is also present in European and UK patent law, though it is commonly called the "repercussive effect".

To help explain, let's look at two claim sets for a knife.

Example 1

Let's assume you have a single independent claim, with no dependent claims.

1. A knife comprising a blade and a handle.

Based on this (and the description, drawings, file wrapper and the like), you might interpret "blade" to implicitly have a cutting edge. Perhaps because otherwise the knife wouldn't really work.

Example 2

However, consider if there was a dependent claim:

1. A knife comprising a blade and a handle.
2. The knife of claim 1, wherein the blade comprises a cutting edge.

The doctrine of claim differentiation provides that claim 2 must be different in scope from claim 1. However, if "blade" in claim 1 already had a cutting edge, then claim 2 would not be adding anything. So, by the doctrine, "blade" in claim 1 must be broader than that, and therefore need not necessarily have a cutting edge.

In both examples, the meaning of "blade" claim 1 comes out differently, based solely on the presence or absence of a dependent claim.

In practice

Claim interpretation is a very tricky area. Until a patent goes through the courts, it is impossible to say with certainty how it will be interpreted. Moreover, although the doctrine of claim differentiation provides a good presumption, it can be rebutted in a given case.

What can you do?

You cannot reliably know how a given term will be interpreted by the courts. So the best you can do is to be mindful of whether a given dependent claim is actually limiting the scope of the independent claim. If it is not, it would probably be better not to include it.

How do you allow a claim to have different definitions based on each of its dependent claims?

A single claim can only have one interpretation. By the doctrine of claim differentiation, claim 1 will be interpreted in view of all its dependent claims.

However, the doctrine is not that strong. All that is required is for the independent claim to be a little bit broader, in some way.

So given a set of claims:

1. A knife comprising a blade and a handle.
2. The knife of claim 1, wherein the blade comprises a cutting edge.
3. The knife of claim 2, wherein the blade comprises two cutting edges on opposite sides of the blade.
4. The knife of claim 1, wherein the blade is formed of metal.

The knife of claim 1 need not have a cutting edge (since it must be broader than claim 2) and need not be metal (since it must be broader than claim 4). All this means is that the cutting edge and being metal are not essential features. Assuming this is true, this is not a bad position to be in.

Answer 2

Having only a very broad independent claim runs the risk of the patent not being granted. In the above instance if the sole claim was "1.A knife comprising a blade and a handle." , it would in all probabilities be never granted as being indefinite. One way of looking at dependent claims is that, instead of being limitations, they actually broaden the independent claim and ensure that the limitations of the dependent claim are read into the independent claim.

For instance dependent claim 4 above expands the definition of a blade to include blades made of metal.

If there was a dependent claim No 5 which said "5. A knife of claim 1 whose blade is made of amber." then the blade in claim 1 could be either of metal or of amber and its meaning is broadened.

BTW having more than one independent clause causes the cost of issuing the patent to go up substantially. Ashok