Structure for confining a valve knob

A valve assembly comprising:

• a valve body having an interior passageway with a ball valve disposed rotatably therein, said ball valve having a channel formed there through, said valve body having a tubular projection extending upwardly therefrom, said valve body having a link rod extending upwardly from said ball valve through said tubular projection;
• an arresting block extending outwardly of said tubular projection;
• a valve knob having a fastening portion extending from an underside thereof, said fastening portion being of a generally tubular shape, said fastening portion being engaged with said link rod of said ball valve, said valve knob movable between a first position in which, said channel of said ball valve is axially aligned with said interior passageway and a second position in which said channel of said ball valve is transverse to said interior passageway, said fastening portion having a first confinement slot and a second confinement slot symmetrical to said first confinement slot, said first confinement slot having a radian of 90 degrees, said radian of said first confinement slot being defined by an inner surface of a first stop wall and an inner surface of a second stop wall, said inner surface of said first stop wall contacting said arresting block when said valve knob is in said first position, said inner surface of said second stop wall contacting said arresting block when said valve knob is in said second position, said second confinement slot having a radian of 90 degrees, said radian of said second confinement slot being defined by an inner surface of a third stop wall and a inner surface of a fourth stop wall, an outer surface of said first stop wall and an outer surface of said third stop wall defining a radian of less than 90 degrees therebetween, an outer surface of said second stop wall and an outer surface of said fourth stop wall defining a radian of less than 90 degrees therebetween.