Patent ID: 8869823

Claim:
A non-return valve mechanism comprising a tubular member ( 1 ) having an external periphery with a substantially constant external diameter whereby the tubular member can be inserted into a pipe ( 5 ) from an open end thereof, a pivotable closure member ( 9 ) provided at one end of the tubular member for closing the one end of the tubular member the closure member being adapted to be positioned externally of the pipe, at least one first seal ( 3 ) extending around the external periphery of the tubular member for sealing with an internal surface of the pipe into which the tubular member is inserted, and an annular second seal ( 11 ) mounted on the closure member ( 9 ) such that the closure member ( 9 ) bears against an end of the tubular member ( 1 ) by way of the annular second seal ( 11 ), the annular second seal ( 11 ) being substantially S-shaped in cross-section whereby the second seal envelopes a peripheral region of the closure member ( 9 ) and includes a radially outwardly extending flange portion for sealing against the end of the tubular member ( 1 ).