Patent ID: 6041814
Filing Date: 2000-03-28
Classification: F16K,G05D,Y10T

Abstract:
A vacuum pressure control system comprising a vacuum vessel, a vacuum pump for sucking gas in said vacuum vessel, a vacuum proportional opening and closing valve disposed on a pipe connecting the vacuum vessel and the vacuum pump, the vacuum proportional opening and closing valve changing its opening to change the vacuum pressure in the vacuum vessel, a pressure sensor to measure the vacuum pressure in the vacuum vessel and a vacuum pressure control device to control the opening of the vacuum proportional opening and closing valve based on the output of the pressure sensor, whereinsaid vacuum proportional opening and closing valve includes a valve seat having a central flow passage and a valve member having a peripheral portion that is inserted in the central flow passage and having an upper part, a substantially vertical surface formed on the upper part of the peripheral portion and a tapered surface formed on the peripheral portion below the vertical surface, and a substantially horizontal surface portion extending outwardly from the vertical surface and having a seal disposed thereon, and a pilot valve connected to move the valve member in the central flow passage, the substantially vertical surface fitting the central flow passage so that when the substantially vertical surface is in the central flow passage, gas leaks past the valve member until the seal engages the valve seat; andsaid vacuum pressure control device controlling a servo valve to change the air pressure to be supplied to said pilot valve based on the output of said pressure sensor.