US Patent 7571841 Interchangeable adapter for in-can and on-can fuel cells

An adapter configured for use in combination with a cap on a fuel cell having a closure formation, the cap having at least one leg portion and a corresponding foot extending from the leg, including a ring portion configured for engagement upon the closure formation of the fuel cell and including a top edge, a bottom edge, and a sidewall therebetween having an inner sidewall and an outer sidewall, a grooved portion defined by the inner sidewall, a convex gripping formation on the outer sidewall complementary to the closure formation, and at least one recessed formation adjacent the grooved portion for receiving the foot.