Gas compressor unloading means

A rotary gas compressor having a plurality of compression chambers, rotary means confined in each of said chambers for displacing and compressing gas in said chambers, spaced-apart gas inlet and outlet port means for each of said chambers, and unloading means for the compressor, comprising:

• unloading port means, for each of said compression chambers, each of said unloading port means opening both into its respective compression chamber and externally thereof;
• and
• valving means coupled to said unloading port means operative for independently opening and closing selective ones of said unloading port means;
• wherein
• said rotary means comprises rotors;
• each of said rotors having a first radial sector which defines a hub, a second innermost radial sector which defines a groove, and a third outermost radial sector which defines a tooth;
• said outlet port means of a given one of said chambers is cyclically sealed off from said given one chamber, sequentially, by two of said sectors of one of said rotors;
• said unloading port means of a given one of said chambers is cyclically sealed off therefrom by only one of said sectors of one of said rotors;
• said compression chambers each being defined by an enveloping, arcuate side wall, with which said teeth of said rotors effect a rotary interface, and an end wall joined to said side wall;
• said rotors are arranged for rotation within said chambers on axes lying normal to said end wall;
• each said gas inlet port means opening onto its respective chamber at a first location;
• each said gas outlet port means opening through said end wall onto its respective chamber at a second location, relative to one of said rotation axes, which is spaced apart from said first location a given rotary or angular distance;
• each said unloading port means opens onto said end wall at a location which, relative to at least one of said rotation axes, is intermediate said rotary or angular distance;
• each said unloading port means comprises a port, a walled cylinder external to or outboard of said chambers, said port being formed in an end of said cylinder, said cylinder having venting means opening through the wall thereof for venting gas therethrough, and said cylinder slidably supporting a port-closure plunger, and said plunger having means cooperative with said port for metering an opening and closing of said port to effect, and to prohibit, a communication of said port with said venting means;
• and
• means interactive with said cylinder for moving said plunger to effect closure and opening of said port.