U.S. Patent No. 8,067,381 is based on a chain of eight US applications – the patent at issue is from the eighth application (page 2). The cross-reference in the CIP fifth application was amended to delete reference to the first through fourth applications, resulting in claiming priority to just a provisional application filed after the fourth application (page 3). This amendment to priority for the fifth application occurred after filing the sixth application, which claimed priority to the fifth application and then to the first through fourth through the fifth (pages 2-3). The sixth through the eighth applications claimed priority to the first application and the provisional through the fifth application (pages 3-4). Amending an earlier filed application may affect the priority of child applications (pages 7-9). Since the eighth application claimed benefit of the first application by way of the fifth application and the fifth application was amended to remove the priority, the requirements for claiming priority were not met even where the requirements were met at the time of filing the sixth application (page 10). While the MPEP directs waiver of a benefit claim to the “instant application,” this does not exclude the waiver occurring for the children applications (pages 10-11). Like CIP claims, the priority is a trade off with term (pages 12-14).
Hindsight: If playing with priority, it may be best to have later applications claim benefit through separate chains to any pending applications. In this case, two applications could have been filed to replace the fifth application, one with priority to just the provisional and another with priority to the pending application with chain back to the first application. The later applications (6th-8th) could then claim priority through the extra application with the never amended priority chain.