Gas sealing system for rotary valves

A rotary valve assembly for an internal combustion engine comprising a hollow cylindrical valve, said valve having one or more ports terminating as openings in its periphery, a cylinder head having a bore in which said valve rotates in a predetermined small clearance fit, a window in said cylinder head bore communicating with a combustion chamber, said openings successively aligning with said window by virtue of said rotation, bearing means at least one axially on each side of the window for journalling said valve in said cylinder head bore, said bearing means serving to maintain said predetermined small clearance fit, axial sealing elements housed within said cylinder head bore extending inwardly of said bore an amount equal to said predetermined clearance fit and being preloaded against the periphery of the valve, said axial sealing elements being housed within axially extending grooves formed in said cylinder head bore, said grooves being positioned at least one on each side circumferentially of said window, two inner circumferential sealing elements positioned along the axis of said valve and housed in circumferentially extending grooves formed either in said periphery of said valve or in said cylinder head bore and radially preloaded against the surface of the other, each said inner circumferential sealing element being positioned at either axial extremity of said axial sealing elements and immediately adjacent thereto, a first seal pressurizing cavity existing by virtue of said predetermined small clearance fit and formed circumferentially between said axial sealing elements on either side of said window, and bounded axially by the planes of the inner faces of said inner circumferential sealing elements, whereby high pressure combustion gas pressurizes said first seal pressurizing cavity during combustion by virtue of said communication between said window and said combustion chamber thereby loading said axial sealing elements radially inwardly against said periphery of said valve in a direction so as to augment said preload, and circumferentially outwardly against the sides of said axially extending grooves, characterised in that, at least two outer circumferential sealing elements are also positioned along the axis of said valve, at least one axially outwardly of each said inner circumferential sealing element, thereby defining two second seal pressurizing cavities, each lying between adjacent inner and outer circumferential sealing elements, axially on either side of said window, and passage means permitting said high pressure combustion gas to pass from said first seal pressurizing cavity to said two second seal pressurizing cavities, whereby, during combustion, said outer circumferential sealing elements are caused to seal said second seal pressurizing cavities to prevent axially outward movement of gas and said inner circumferential sealing elements are caused to be loaded axially inwardly to seal against the axially innermost sides of said circumferentially extending grooves, and loaded radially to seal against the surface against which they are preloaded.