Two stage vacuum pump

CAFC
  • US 4,523,897 A
  • Filed: 07/16/1984
  • Issued: 06/18/1985
  • Est. Priority Date: 06/11/1982
  • Status: Expired due to Term
First Claim
Patent Images

1. A two stage rotary vacuum pump including a pump module having first and second pumping chambers defined therein each having a cylindrical circumference, a rotor shaft rotatably mounted within the module extending through the chambers and eccentrically related thereto, an electric motor drivingly connected to the rotor shaft, first and second rotors each having an axis, lateral sides, and fixed to the shaft located within the first and second chambers, respectively, at least one non-radial vane movably mounted in each rotor extending from the periphery thereof having an outer end engaging the associated chamber circumference and translatable between extended and rectracted positions, the vane being in a gas compression exhausting position at its retracted position and the outer end having trailing and leading edges with respect to the direction of rotor rotation, a valve plate located intermediate the rotors having a port defined therein establishing communication between the chambers at predetermined rotational positions of the rotors, an exhaust plate disposed adjacent the second rotor having an exhaust port defined therein selectively communicating with the second chamber at a predetermined rotational position of the second rotor, the improvement comprising, each of the rotors including a cylindrical circumference and lateral sides radially perpendicular to the rotor shaft, the lateral side of the first rotor adjacent the valve plate and both lateral sides of the second rotor being recessed intermediate the associated rotor circumference and the rotor shaft, an annular hub defined upon the recessed lateral sides of the rotors adjacent the rotor shaft, the rotor recesses being of an annular configuration and located intermediate the associated rotor circumference and hub, a slot defined in each rotor intersecting the associated rotor lateral side recesses, the rotor vane being slidably mounted within said slot, the port within the valve plate communicating with said rotors'"'"' recesses whereby fluid pressure within the second chamber biases the vanes toward the chambers'"'"' circumferences and hydraulic axial forces upon the second rotor are substantially balanced, the vanes'"'"' outer ends comprising a cylindrical segment surface having a radius substantially equal to the radius of the associated chamber circumference and having a center coinciding with the axis of the associated chamber at the vanes'"'"' retracted position whereby the entire outer ends of the vanes engage the chamber circumference at the termination of the compression cycle at the vanes'"'"' retracted position to produce optimum compression and reduce the likelihood of gas re-expansion, the valve intermediate the rotors comprising a relatively thin plate and including first and second parallel sides, said first side defining a portion of the first chamber and said second side defining a portion of the second chamber, said valve plate port comprising a first recess defined in said valve plate intersecting said first side, a second recess defined in said valve plate intersecting said second side and an axial passage defined in said valve plate directly intersecting said valve plate sides and communicating with said recesses, said recesses being elongated in the direction of rotor rotation and offset with respect to each other in the direction of rotor rotation, said passage being located centrally with respect to said recesses in the direction of rotor rotation.

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