Vane compressor with means for obtaining sufficient back pressure upon vanes at the start of compressor

A vane compressor comprising:

• a pump housing having an endless inner peripheral camming surface, said pump housing including a front side block and a rear side block disposed at opposite ends thereof, said front and rear side blocks each having a through hole axially formed therein;
• a rotor rotatably fitted within said pump housing, said rotor having an outer peripheral surface formed therein with a plurality of slits, and defining therein a back pressure chamber communicating with said slits;
• a plurality of vanes slidably fitted in said slits of said rotor for sliding contact with said endless inner peripheral camming surface of said pump housing;
• a front head secured to said front side block and cooperating therewith to define a shaft-seal chamber therebetween;
• a rotary shaft having a portion thereof disposed within said pump housing and drivingly supporting said rotor fitted thereon, said rotary shaft extending through said shaft-seal chamber and being fitted in said through holes of said front and rear side blocks;
• a compressor casing accommodating said pump housing and cooperating therewith to define a discharge pressure chamber therebetween;
• a pair of radial roller bearings arranged in respective ones of said through holes of said front and rear side blocks and rotatably supporting said rotary shaft fitted in said through holes;
• partition means cooperating with one end face of said rear side block remote from said rotor to define a sealing chamber therebetween, one of said through holes formed in said rear side block opening into said sealing chamber, and the other of said through holes formed in said front side block opening into said shaft-seal chamber;
• communication means communicating said through holes with said back pressure chamber in said rotor;
• passage means formed in said pump housing and communicating said discharge pressure chamber with said sealing chamber;
• and valve means arranged in said passage means and operable to open at a value of the difference in pressure between said discharge pressure chamber and said back pressure chamber below a predetermined value to establish communication between said discharge pressure chamber and said sealing chamber, and to close at a value of the difference in pressure above said predetermined value to interrupt the communication between said discharge pressure chamber and said sealing chamber.