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All Questions in Patent Drafting >> Positive limitation Vs. Negative limitation

Positive limitation Vs. Negative limitation

Posted by Anonymous . updated on 2/26/2009
Student at PIT. came across couple of terms in this forum.
Positive limitation and Negative limitation, Anyone care to explaim the terms and their difference.

Thanks in advance
Answers (6)
Using a negative limitation means specifying the absense of something in a patent claim.   One might attempt to describe an invention in this way if the point of the invention is to accomplish something without some element that was previously thought to be essential.   For example if the prior art consisted of bicycles and tricylces and you invented a unicycle, you might want to describe your invention in terms of the absense of extra wheels.  

Is it inherently more difficult to have patent examiners OK the negative limiation than a positive limitation??
I don't think so.  It all comes down to whether the claim as a whole is novel and non-obvious.  In the very rare cases that I've used negative limitations (or something sort of close to that), I've never had an examiner give me a hard time about it.  

I think the bigger issue with negative limitations is that it's often fairly easy for a competitor to get around it.  Take's "1-click" as an example.  Other e-tailers had to just add an "Are you sure?" second click.  If the practitioner(s) who filed and prosecuted that application captured as much of the invention as possible, then the entire value of that patent comes down to how much the consuming public cares to avoid the "Are you sure?" second click.  

I haven't read the patent with as much care as I would if I wear responding to a rejection or otherwise handling prosecution of the case and I haven't read the file history at all.  But it would be interesting to see if there wasn't a better way to capture the true value of that innovation that wasn't so easily avoided.  I'm betting the practitioner(s) focused on what the engineer was excited about -- the end result of 1 click.  It's often better to step back and look at what novel feature enables that result and to focus on that in the claims.  Then, maybe an "Are you sure?" second click would still infringe and other e-tailers would have to ask for at least one piece of delivery or payment information.

To be fair, there is at least one claim in that patent that doesn't rely on "1-click".  So, maybe they did exactly what I suggest.  However, I might have made the underlying technology the primary focus rather than the simplistic cool result.  It's really hard to second-guess someone without knowing all the facts, but I've seen that mistake before and it wouldn't surprise me if it turned out to be a mistake for too.

There is not always a clear black / white distinction between a negative and a positive limitation; as Jim implied "... I've used negative limitations (or something sort of close to that) ..."

If a prior art product comprised four materials, and I write a claim for a similar product that consists of three of those materials - is that a positive or negative limitation?  It sure looks like a positive limitation:

- A product consisting of A, B & C.

But relative to the prior art it is essentially a negative limitation, i.e. the prior art product, but without element D.
Was the element D thought to be essential?  
Was the element D thought to be essential? ?

I'm not sure that's exactly the question to answer since we really aren't asking whether A,B,C is distinguishable over the prior art, but rather we are asking what meaning is to be given to  "consisting of A,B,C" .  

What's important is whether D is an element which the inventor intends the claim to omit.  The content of the prior art is important only when we can see that the inventor means to write a claim avoiding the prior art.

For example "A,B,C" in one case might be interpretted not to exclude a D that is an inactive material or an insignificant impurity amount.  In a different case however, the point of the invention might be that A,B,C are to be applied in a pure state omitting an inactive diluting material used in the prior art.   D might even be a previously undetected material that has been found by the inventor to have an interferring effect.

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