Pump rotor adjustment mechanism

Claim 1

In a rotary pump of the fixed-clearance type, including housing means having a pair of spaced head plates and a ringlike cylinder disposed between and fixedly connected to said head plates, said cylinder having an inner annular guide surface, said cylinder and said head plates defining a pumping chamber therebetween, a rotatable pumping rotor disposed within said chamber and mounted for rotation about an axis which is fixed relative to said head plates, said rotor having a plurality of vanes thereon disposed for slidable engagement with an inner annular guide surface formed on said cylinder, and means defining inlet and outlet openings communicating with said pumping chamber, the improvement comprising: connecting means coacting between said cylinder and said head plates for permitting said cylinder to be positioned in a selected one of two predetermined positions relative to said head plates only during assembly of said pump housing means, the preselection of one of said two positions during assembly of the pump housing enabling the pump to be provided with a preselected one of two different minimum clearances between the rotor and the surrounding cylinder; said connecting means comprising eccentric pin means coacting between each of said head plates and said cylinder for fixedly connecting and positioning said cylinder relative to saId head plates in a selected one of said two predetermined positions, said eccentric pin means including at least two eccentric pin members fixedly connected between each said head plate and an adjacent axial end of said cylinder; each said eccentric pin member including first and second cylindrical portions axially spaced but fixedly connected together, said first and second cylindrical portions respectively having first and second longitudinally extending axes which are substantially parallel but laterally spaced from one another by a predetermined distance; at least one axial end face of said eccentric pin members being provided with indicia means thereon for indicating the orientation of said eccentric pin members relative to the longitudinally extending axis thereof, said indicia means permitting selective orientation of said pin members relative to said cylinder during assembly of said pump so as to permit said cylinder to be fixed relative to said head plates in a selected one of said two predetermined positions to permit preselection of the minimum clearance between the cylinder and the pump rotor; each said head plate having at least two cylindrical recesses formed therein for snugly receiving therein one of the cylindrical portions of said eccentric pin members, and each axial end of said cylinder also having at least two cylindrical recesses formed therein for snugly receiving therein the other cylindrical portions of said eccentric pin members, the cylindrical portions of the eccentric pin members being pressfitted into their respective cylindrical recesses as formed in said head plates and said cylinder for fixedly and rigidly connecting together said head plates, said cylinder and said eccentric pins, thereby providing said assembled pump with a non-adjustable fixed minimum clearance.