In reference to patent US 6,797,357, "Three dimensional structures useful as cleaning sheets", when will it expire?
The patent was filed on June 14, 2001, which normally means (because it was filed after June 8, 1995), that the patent is enforceable to 20 years from the filing date, which is June 14, 2021.
However, in the Cross References section you will find the following note:
This application is a divisional of US. application Ser. No. 09/082,396, filed May 20, 1998, Which claims the benefit of US. Provisional Application Ser. No. 60/055,330, filed Aug. 12, 1997 and US. Provisional Application Ser. No. 60/047,619, filed May 23, 1997.
Now we need to go back to the earliest filing date of these patent applications, which is May 20, 1998. Adding 20 years to that filing date, we now have an expiration of May 20, 2018. The provisional filing dates are not included in the calculation, because those are never disclosed to the public. For reference US 09/082,396 is PCT/US1998/010362 application, which is the same as WO1998052458 A1.
Next, in the patent grant, you will find the following notice:
Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.
Which in this case (0 days) has no effect on the expiration of the patent.
Finally, the last thing you need to look at are the Legal Events:
Feb 21, 2008 FPAY Fee payment Year of fee payment: 4 Feb 24, 2012 FPAY Fee payment Year of fee payment: 8
The maintenance fees have been paid, and the next one isn't due until September 28, 2016. This means that the patent is certainly enforceable until then. After that, you will need to check the Legal Events to see if they paid the next fee. Failure to pay maintenance fees will be noted in the Legal Events and results in a non-enforceable patent.
The cost of maintenance fees increases with each payment, and the company may ultimately decide that paying the final maintenance fee on this patent in order to get an additional 2 years, 8 months of coverage is not worth it. Since they are tending to pay in February, check the legal status in March 2016 to see if they paid the maintenance fee.
Incidentally, they are highly likely to pay the maintenance fee to extend their coverage until May 20, 2018 because they are still pursuing new patents based on WO1998052458 and WO1998052459, which were both filed on May 20, 1998.
Specifically, refer to US 9,040,146 which was filed January 17, 2014 and issued May 26, 2015. This patent will only be valid for less than three years. Procter & Gamble have a lot of money invested in this series of patents (over 40 publications with worldwide coverage), and on May 21, 2018 they will no longer be enforceable.