Programmable pressure regulator for titanium superplastic forming apparatus

An apparatus for controlling gas pressure in a metal forming chamber comprising:

• a source of pressurized gas;
• first electrically responsive valve means interposed between said source of pressurized gas and said forming chamber and operable in response to an electrical signal to admit gas from said pressurized source to said forming chamber;
• second electrically responsive valve means coupled to said forming chamber for bleeding gas from said forming chamber, said second valve means being operable in response to an electrical signal to bleed gas from said forming chamber;
• third electrically responsive dump valve means coupled to said forming chamber for exhausting gas relatively rapidly from said forming chamber and thereby reducing the pressure of said gas in said forming chamber to ambient atmospheric pressure;
• pressure-sensing means coupled to said forming chamber, said sensing means being operable to produce a signal representative of the pressure of said gas in said chamber;
• a profile generator operable to produce time varying high and low set point signals representative of preselected upper and lower pressure limits;
• comparator means for comparing said electrical signal from said pressure-sensing means with each of said high and low set point signals, said comparator means operating to apply an electrical signal to said first electrically responsive valve means in the event the difference between said electrical signal from said pressure-sensing means and said low set point signal represents a pressure in said forming chamber less than said lower pressure limit, said comparator means further operating to provide an electrical signal to said first electrically responsive valve means in the event the difference between said upper set point signal and said signal from said pressure-sensing means represents a gas pressure in said chamber greater than said upper pressure limit.