US 9403550

US Patent 9403550, titled "Seat attachment for a stroller," was issued on August 2, 2016, to its current assignee, Baby Jogger II LLC. The patent was invented by Mark Zehfuss and filed on January 15, 2015, under application number US14/597,420.

The abstract describes the invention as a seat attachment for strollers, including single and double strollers, designed to convert a single stroller into a double stroller. It features left and right seat attachment portions, each with a connector capable of removably connecting to a stroller frame. A seat support element allows a second seat to be connected in either a forward or backward position. The attachment can support various types of child seats, such as a stroller seat, baby seat, bassinet, pram, car seat, or baby carrier.

A plain-language overview of the independent claims is as follows:

Independent Claim 1:
This claim describes a stroller system. It includes a stroller frame with multiple front and back wheels, and a first seat positioned closer to the stroller's handle at a higher vertical position, designed to hold a first child. Additionally, there is a second seat attachment located at a lower vertical position, closer to the front wheels. This second attachment comprises a left seat support element with a connector that can be easily attached and detached from the stroller frame near the left front wheel, and a left seat connector for a second child's seat. Similarly, a right seat support element includes a connector releasably attached to the frame near the right front wheel, and a right seat connector for the second seat. The second seat itself is designed to be easily attached and detached to both the left and right seat connectors, and can be faced either forward or backward, holding a second child while the first child occupies the first seat.

Independent Claim 7:
Similar to Claim 1, this claim also describes a stroller system with a frame and multiple front and back wheels. It features a first seat attached to the stroller frame at a first vertical position, near the handle, for holding a first child. A second seat attachment is coupled to the stroller frame closer to the front wheels. This second attachment includes a left seat support element with a releasably connected first connector portion near the left front wheel and a left seat connector for a second seat (which can face forward or backward). It also includes a right seat support element with a releasably connected second connector portion near the right front wheel and a right seat connector for the second seat. The second seat is releasably connected to both the left and right seat connectors and is positioned at a second vertical position, substantially below the first seat, to hold a second child while the first child is in the first seat.

As of April 26, 2026, a search of the CAFC 2026 dockets for patent number 9403550 did not directly return any specific scheduled cases or filings. While the patent itself indicates previous litigation (PTAB case IPR2025-01106, and US District Court cases in Delaware and Massachusetts filed in 2024), these are not CAFC cases or confirmed CAFC dockets for 2026.