Patent ID: 7000899

Claim:
A shut-off device for shutting-off and opening flow through a conduit comprising a housing ( 10 ) provided with a passage ( 11 ), a device ( 13 ) movable in said housing ( 10 ), said device ( 13 ) having an opening portion which registers with said passage ( 11 ) in a first position and a closing portion which registers with said passage ( 11 ) in a second position, an opening ( 14 ) in said opening portion, an annular sealing body ( 28 ) arranged around the passage ( 11 ) on each side of the device ( 13 ), each annular sealing body ( 28 ) having a contact surface ( 34 ) which contacts a contact surface ( 38 , 39 ) on each side of the device ( 13 ) at the respective opening and closing portions thereof in the first and second positions, the device contact surfaces ( 38 , 39 ) being a hard material layer which is harder than the material of the device ( 13 ) and has a surface roughness of less than 10 μm, said device contact surfaces ( 38 , 39 ) are each of a substantially annular configuration, one of said annular device contact surfaces ( 38 ) at each side of said device ( 13 ) at said opening portion substantially surrounds said opening ( 14 ) in said first position, and another of said annular device contact surfaces ( 39 ) at each side of said device ( 13 ) at said closing portion seals against said annular sealing body contact surfaces ( 34 ) in said second position.