I just read in a very old post here that "when you get into the business of claiming numerical ranges, you're asking for trouble". Is this true? If you can file without getting into numbers, should you?
One of the first questions my counsel asked me was "do you have any rough numbers?"
It can be tough to base an argument of non-obviousness on a range that is outside the disclosure of cited prior art. E.g., Say you claim a composite comprising components A and B, where A is present in an amount ranging from 20-40 weight %, and B is present in an amount ranging from 60-80 weight %. During prosecution, the Examiner cites art disclosing a composite comprising A and B in a 50/50 ratio (i.e., 50 weight % each). The claimed invention would be novel over that prior art, but the examiner would likely argue that the optimization of the amounts of A and B would be within the skill of one of ordinary skill in the art (for innumerable reasons), and reject the claimed invention under 103(a) as being obvious.
There are many, many arguments as to why the position taken by the examiner is improper. But the trend I have observed over the years is the success or failure of those arguments turns on whether the applicant can present data showing something beyond a mere optimization of ranges. E.g., synergy (A+ B in the claimed amounts produces a significant jump in properties that would not be suggested by the prior art); unexpected results (A&B in the claimed amounts exhibits properties contrary to those suggested by the 50/50 composition) etc.
It is also important to claim numerical ranges in the right way. There is quite a bit of caselaw out there construing claim terms that define ranges, so it is important to be precise when drafting claims. E.g., "between 5 and 7" does not mean the same thing as "ranging from 5 to about 7," which does not mean the same thing as "from greater than 5 to about 7."
A final note is that numerical ranges have been frequently construed as putting concrete limitations on the scope of a claim. This is particularly true if the range is relied upon by the applicant during prosecution in an argument favoring patentability. This means that if you claim "about 5 to about 7" of component A, and your competitor makes a composition comprising 4 or A, chances are good that if you sue your competitor for infringement of the claim, you will lose unless you have very good evidence (e.g., a statement in the specification) indicating that the term "about" means +/- 1)