patent enforcement when patent lapses

Patent infringement suit can be instituted for in-force period of a patent i.e. for a period from date of issue to date of lapse or to date of end of lifetime.

35 U.S. Code § 286 limits infringement claim period to most recent six years counted back from date of infringement claim and does not specifically mentions about end of lifetime cases. That is to say, this limitation should be equally applicable to lapsed patent cases too.

First paragraph read with the second, leads us to a period when there is overlapping of 'patent in force period' and 'infringement claim limitation period'. Owner of patent can sue for infringement and have relief for said period for lapsed patent as well as for end of lifetime case.

There is an interesting scenario related to maintenance fee and patent right.

For lapse of patent right due to non payment of maintenance fee cases, a grace period of six months is allowed after due date for payment of maintenance fee 35 U.S.C. § 41(b)(2).

Issue 1. If maintenance fee is paid by expiry of grace period, 'patent in force period' is considered to have continued without break.

Issue 2. If maintenance fee is paid after grace period and the same is accepted, then if there is any instance of substantial activity for manufacture, sale, use, import in the intervening period by any third party, court may allow continuation of such activity by said third party even if patent right is restored. 35 U.S.C. § 41(c)(2).