Abstract: The invention relates to a valve (11) for defining a one way flow, having one pair of lips (12) that are arranged in a converging relationship. Each lip has a lip base end (12B) and a lip outer end (12A), wherein the lip base ends form part of an open valve base end and the lip outer ends are disposed adjacent each other to define one slit (13). The valve further comprises a flange (15) extending outwardly at the valve base end. Each lip base end runs along one or more substantially straight lines (12B) and each lip (12) is provided with one or more folding lines (12F) running over the surface of the lip from the lip base end towards the slit.

Abstract: The invention relates to a valve assembly comprising a valve (1), having a pair of lips (2) that are arranged in a converging relationship to define a slit (3) and a flange (5), and a valve housing comprising a first housing part (110) and a second housing part (120) to cooperate to enclose the valve (1), wherein the first housing part comprises a pair of first walls (112) that are arranged in a converging relationship and a first collar part (115). Each lip base end runs along straight lines and each first wall base end (112B) runs along straight lines, the flange (5) comprises two opposing straight lines and the second housing part (120) comprises a second collar part (125) that comprises an open space for accommodating the flange (5) of the valve (1), wherein the circumferential edge (122B) of the open space comprises two opposing straight lines.