Inner tube assembly for run-flat tires

An inner tube assembly for a pneumatic tire, said assembly comprising an annular primary tube means, primary valve means connected to and communicating with the interior of said primary tube means, secondary tube means surrounding said primary tube means, and secondary valve means interconnecting and communicating with the interiors of said primary and secondary tube means, said secondary valve means remaining open and intercommunicating the interiors of said primary and secondary tube means for as long as there remains an equilibrium of pressure therebetween, said secondary valve means including closure means for pneumatically isolating the interiors of said primary and secondary tube means from one another when there occurs a pressure drop in said secondary tube means relative to said primary tube means, said secondary valve means including a housing having a pair of coaxially open ends, an elongate rod supported for endwise movement in said housing and defining with the interior of said housing an annular space, said rod including a pair of enlarged heads coaxially spaced from one another over a distance that is greater than the spacing between said opposite open ends of said housing, spring means surrounding said rod between said heads, one of the ends of said spring means being engageable with one of said heads of said rod, the other end of said spring means being engageable with the interior of said housing adjacent to one of said open ends of said housing, said spring means urging said rod into a position at which one of said heads of said rod engages one of said open ends of said housing, the latter said head being diametrically larger than the latter said open end and including groove means for intercommunicating the exterior of said housing with the interior thereof when the latter said head is engaged with the latter said open end, the opposite one of said heads also being diametrically larger than its corresponding one of said open ends of said housing and held remote from the latter by said spring means when the other head engages its corresponding one of said open ends of said housing, said head which is held remote from its corresponding open end of said housing by said spring means confronting the interior of said primary tube means and being movable in response to pneumatic pressure thereagainst into engagement with its corresponding open end of said housing to close the latter said open end and pneumatically isolate the interiors of said primary and secondary tube means from one another.