Patent ID: 6508268
Filing Date: 2003-01-21
Classification: F16K,Y10S,Y10T

Abstract:
A vacuum pressure control apparatus for controlling vacuum pressure in a vacuum vessel from which gas is sucked by means of a vacuum pump, the apparatus including:a vacuum proportional opening and closing valve which is disposed between the vacuum pump and the vacuum vessel and changes its opening for controlling the vacuum pressure in the vacuum vessel, the vacuum proportional opening and closing valve including a valve seat having a continuous peripheral seating surface and a central flow passage through which the gas is sucked from the vacuum vessel to the vacuum pump, and a valve member that is movable to come into contact with the seating surface of the valve seat and to separate from the same, the valve member being provided with an elastic sealing member on a surface that comes into contact with the valve seat after progressive elastic deformation of the elastic sealing member from a minimum value at which gas leakage occurs between the elastic sealing member and the seating surface of the valve seat, through intermediate values at which the gas leakage is progressively reduced, to a maximum value at which no gas leakage occurs between the seating surface of the valve seat, a pressure sensor for measuring the pressure in the vaccum vessel, and a vacuum pressure control system for controlling a change in an elastic deformation amount of the elastic sealing member in contact with the valve seat to regulate the quantity of gas leakage between the elastic sealing member and the valve seat, the control system having previously stored, with respect to plural levels of vacuum pressure in the vacuum vessel, data representing the relation between the quantity of gas leakage and the deformation amount of the elastic sealing member at each level of the vacuum pressure, selecting a pressure level corresponding to a measured value detected by the pressure sensor from among the plural levels, and controlling the deformation amount of the elastic sealing member based on the relation between the leakage amount and the deformation amount at the selected vacuum pressure level.