Rotary valve with pressure urged sealing member

A valve comprising a housing (1) provided with a flow-through passage (4), and a closing member having the shape of a rotational body and provided with an aperture (6), and turnably disposed in said flow-through passage, a sealing member (3) disposed between the closing member and the housing (1), and between the sealing member (3) and the housing (1) a space being provided in which, when the valve is in closed position, prevails a pressure urging the sealing member against the closing member (2) and from which space at least one passage is provided which leads to a point close to the sealing face (7) of said sealing member (3) and intermediate said sealing face (7) and said flow-through passage (4), the improvement comprising said rotational body being turnable from a first position wherein said rotational body closes said flow-through passage and a second position wherein said flow-through passage is opened, such that said aperture (6) is cut off from said flow-through passage when said rotational body is in said first position and communication between said aperture (6) and said flow-through passage is established as said rotational body is moved from said first position to said second position, said passage of said sealing member leading to that portion of the sealing member (3) adjacent to which open communication between said aperature (6) and the flow-through passage is first established when the valve is being opened, whereby on opening the valve a flow is produced at the site of said passage of said sealing member, this flow causing suction at the mout of the passage of said sealing member and reducing the pressure in said space so as to be lower than the pressure acting on the sealing surface (7);

• said space being exposed to fluid pressure only through said passage.