Practice Pointer: When is “When”?

By: Jonathan P. Osha

It is common to see the word “when” used in U.S. patent claims.  However, it is also common to see a disconnect between the meaning intended by the applicant and the meaning given by the examiner at the USPTO (and perhaps by a court during litigation).  This Practice Pointer will attempt to clarify the meaning and proper usage of this common English word.

Initially, it is important to understand that the word “when” is ambiguous as to time.  In one sense, it can mean at the same time.  For example, “when I strike the bell I hear a sound.”  In this example, the “when” is immediate.  In another sense, it can mean “sometime after.”  For example, “when I get a headache, I take a pill.”  In this example, “when” implies that taking the pill occurs sometime after getting the headache, but is not specific as how soon or how long after.  In another sense, “when” can mean “soon after.”   For example, “when the phone rings, I answer it.”  Here, the timing is not simultaneous, but it is understood that “answering” closely follows the “ringing” in time.  In yet another sense, “when” can mean “during.”  For example, “when I am in Paris, I visit the Louvre.”  In this example, the visit to the Louvre could occur once, or many times, and the “in Paris” could be short, or a period of many years.   In yet another sense, “when” can simply indicate cause and effect.  For example, “when I don’t sleep well, I find it hard to concentrate at work.”  In this example, “when” indicates lack of sleep causes loss of concentration, but does not imply any specific timing.

In Renishaw v. Marposs[1] the Court of Appeals for the Federal Circuit considered the meaning of the claim limitation, “the probe generat[es] a trigger signal when said sensing tip contacts an object.”  At issue in the case was whether the trigger signal was generated immediately upon contact between the sensing tip and the object, or sometime thereafter.  The court of first instance (the District Court) had interpreted “when” narrowly to mean “as soon as contact is made.”  On appeal, Appellant argued “when” should be given one of its broader dictionary meanings: “at or after the time that,” “in the event that,” or “on condition that,” thereby covering a situation of a timing delay between contact and generation of the trigger signal.  The Federal Circuit considered these arguments but ultimately looked to how the word “when” was used in the embodiments described in the detailed description.  Because all disclosed embodiments evidenced a desire to signal as soon as possible after contact, the Federal Circuit interpreted the limitation to mean “probes which signal within a non-appreciable period of time after contact such that the delay in signaling is insignificant when compared to the sensitivity and accuracy of the probe.”  Hence, in this case, “when” meant “very, very soon after.”

There is nothing inherently wrong with using “when” in a patent claim so long as its potential ambiguity is understood.  A U.S. patent examiner will give the broadest reasonable interpretation to this word, and thus will often interpret the word more broadly or in a different sense than was intended by the Applicant.  This is particularly true of patent applications that are filed as translations of non-English language priority applications, where the nuance of this word may have been lost.  It is advisable, therefore, that if a particular sense of the word “when” is intended, additional language be included to clarify this intent.  Optionally, other words can be used when appropriate, such as “upon,” “after,” “in response to,” “if…then” and the like.  The most important situation to avoid is one where the word “when” is given a broad interpretation by the examiner (based on broadest reasonable interpretation) during examination and a narrow interpretation by a court (based on usage in the embodiments in the detailed description) during litigation.

“When” becomes additionally complex if combined with “and” in a claim.  Consider the phrase, “I drink coffee when I eat breakfast and I read the newspaper.” This phrase has a clear meaning: both the conditions of eating breakfast and reading the newspaper must occur at the same time to drink coffee.  This phrase can be reorganized into typical claim-type language without altering its meaning: “when breakfast is eaten and a newspaper is read, coffee is drunk.”

A slight change however – and one often seen in patent claims – has the potential to significantly change the meanings of this phrase.  Specifically, this involves the difference of whether the “and” separates only the two conditions, or separates different “when” clauses.  One might express this as when (A and B) ≠ when(A) and when (B). Consider a modified version of the example phrase: “I drink coffee when I eat breakfast and when I read the newspaper.” In this case, the phrase no longer means that the two conditions must occur at the same time, or even that both occur at all.  The two “when” clauses are now independent such that even if I never read the newspaper, but I do eat breakfast, I drink coffee and the limitation is satisfied.  Because these subtle differences can result in significant differences in meaning, careful attention to the construction of these types of phrases in claims is essential.

We hope, when you have read this Practice Pointer, you will know when to use “when,” and when not.

[1] Renishaw PLC v. Marposs Societa’per Azioni, 158 F.3d 1243(Fed. Cir. 1998).