Gas and oil sealing in a rotary valve

A rotary valve assembly for an internal combustion engine comprising an axial flow rotary valve having a cylindrical portion, and an inlet port and an exhaust port terminating as openings in said cylindrical portion, a cylinder head having a bore in which said valve rotates about an axis with a predetermined small clearance between said cylindrical portion and said bore, a window in said bore communicating with a combustion chamber, said window being substantially rectangular in shape and said openings periodically communicating with said window as said valve rotates, bearing means journaling said valve in said bore, an array of floating seals surrounding said window, and a bias means preloading said array of floating seals against said cylindrical portion, said array of floating seals comprising at least two spaced apart elongate axial seals adjacent opposite sides of said window and at least two spaced apart arcuate circumferential seals adjacent opposite ends of said window, each said axial seal being housed in a respective axially extending axial slot formed in said bore, and each said circumferential seal being housed in a respective circumferentially extending circumferential slot formed in said bore, characterised in that said circumferential seals are axially disposed between the ends of said axial seals.