A closure device for closing an opening (11; 31) in a structure (10; 30), such as an opening in a wall or floor, said closure device having a sealing assembly (13; 33; 53; 63; 73; 83; 93) comprising: - a first clamping body (15; 35; 55; 95) having a first clamping surface (18; 38; 48; 98) and a second clamping body (16; 36; 76) having a second clamping surface (19; 39; 79), said first and second clamping body being oppositely spaced, - a deformable member (17; 37; 47; 77; 87) of sealing material, placed between said first and second clamping surface of said oppositely spaced first and second clamping body, and arranged for circumferentially engaging an inner surface (12; 32) of said opening (11; 31), and - clamping means (25, 26; 56, 26) arranged for moving said first and second clamping body in a direction (z) relative to each other, for exerting a compression force on said deformable member by said first and second clamping surface when said first and second clamping body are moved towards each other, thereby expanding said deformable member in a direction transverse (r) to said moving direction (z) of said first and second clamping body for engaging said inner surface of said opening, characterized in that said deformable member (17; 37; 47; 77; 87) is disc-shaped, said first (18; 38; 48; 98) and second clamping surface (19; 39; 79) of said first (15; 35; 55; 95) and second clamping body (16; 36; 76) and said deformable member are shaped providing an increased distance between said first clamping surface (18; 38; 48; 98) and an opposite first surface (20; 43; 49) of said deformable member in inward radial direction thereof, and providing an increased distance between said second clamping surface (19; 39; 79) and an opposite second surface (21; 44; 74) of said deformable member in outward radial direction thereof, for deflecting said deformable member along said moving direction (z) of said first and second clamping body when exerting said compression force on said deformable member. - a first clamping body (15; 35; 55; 95) having a first clamping surface (18; 38; 48; 98) and a second clamping body (16; 36; 76) having a second clamping surface (19; 39; 79), said first and second clamping body being oppositely spaced, - a deformable member (17; 37; 47; 77; 87) of sealing material, placed between said first and second clamping surface of said oppositely spaced first and second clamping body, and arranged for circumferentially engaging an inner surface (12; 32) of said opening (11; 31), and - clamping means (25, 26; 56, 26) arranged for moving said first and second clamping body in a direction (z) relative to each other, for exerting a compression force on said deformable member by said first and second clamping surface when said first and second clamping body are moved towards each other, thereby expanding said deformable member in a direction transverse (r) to said moving direction (z) of said first and second clamping body for engaging said inner surface of said opening, characterized in that said deformable member (17; 37; 47; 77; 87) is disc-shaped, said first (18; 38; 48; 98) and second clamping surface (19; 39; 79) of said first (15; 35; 55; 95) and second clamping body (16; 36; 76) and said deformable member are shaped providing an increased distance between said first clamping surface (18; 38; 48; 98) and an opposite first surface (20; 43; 49) of said deformable member in inward radial direction thereof, and providing an increased distance between said second clamping surface (19; 39; 79) and an opposite second surface (21; 44; 74) of said deformable member in outward radial direction thereof, for deflecting said deformable member along said moving direction (z) of said first and second clamping body when exerting said compression force on said deformable member.