Added Matter (7) – Ranges

A particular type of amendment concerns claim limitations based on numerical ranges. This occurs most commonly in chemistry-related cases but is applicable in nearly every technical area to some extent.

As should be no surprise the usual rule of "direct and ambiguous" basis applies to amendments to add or modify a range in a claim, but there are some specific points about how this is applied.  In the general sense it is a simple case that the claimed range needs to be disclosed and that any change in span or values of the range must have direct and unambiguous basis.

Ranges are typically defined by a pair of end points with the claim requiring (or excluding) values of the relevant parameter between those end points.  Disclosure of the end points is therefore key. It is not possible to amend a range to a new end point that is not directly and unambiguously disclosed, even if the newly created range is narrower and all values within it were covered by an old broader range.

Therefore, one basic, but important, point is how the end points are defined; are they included in, or excluded from, the range?  A disclosure of "x is in the range 10 to 20" is different to "10 < x < 20" - the first includes 10 and 20, the latter excludes them.  It would be a rare set of circumstances where this difference would prevent you claiming what you wanted to, but this distinction does happen by mistake where an amendment is not made carefully. This can be fatal for a patent as an accidental amendment to "10 < x < 20" could not be fixed after grant to "x is 10 to 20" because that would expand the claim and you would be stuck in the inescapable trap discussed previously.

A related issue concerns the accuracy of values and rounding.  When dealing with ranges the accuracy of the values affects the size of the range - "50 to 60" runs from 49.5 to 60.4, whereas 50.0 to 60.0 runs from 49.95 to 60.04.  An amendment which varies the accuracy of the end points may therefore not find basis as there is no direct and unambiguous basis for the precise scope of the claim.  The EPO may allow amendments which combine disclosed end points of different ranges. For example, if there is disclosure of "x is in the range 10 to 50, and preferably 20 to 30", it may well be possible to claim the range "20 to 50" which takes the bottom end of the preferred range and the top end of the general range.  Although such an amendment is usually permissible, if there are too many possible ranges, or reasons why the claimed range would not be considered, the amendment may be refused.

The previous example covers the situation where the claimed range includes the preferred range, but it may sometimes be possible to claim only the end part(s) of the general range without the preferred range - that is for the previous example "10 to 20" or "30 to 50". However, this can cause difficulties because an end point that was previously disclosed as an upper limit is now being used as a lower limit, or vice versa.  Although this is not covered by the generally allowable case where the preferred range is included, such a claim may still be possible. The facts of the specific disclosure will need to be considered and it needs to be argued that the reader would seriously contemplate working in the claimed non-preferred range. 

It may also be possible to define the end point of the range based on disclosure of a single point value from an example that falls within the range. For example, a range of "10 to 50" and a point value of 25 might give basis for the range 10 to 25, or 25 to 50.  However, this relies on the reader deriving the point value as a general disclosure and not linked inextricably to specific other features of the example. If the reader would conclude the point value was only applicable to the specific situation of the example, generalising to the range would not be permissible.

The law in this area contains both examples of extremely strict rules (50.0 does not disclose 50) and a more generous approach in the ability to combine disclosed end points of ranges.  There are both traps for the unwary and rewards for specialist knowledge. 

This article is a part of our EPO Practice and Peculiarities series. Click here to explore.