Self-centering gear pump

Abstract

The invention relates to a self-centering gear pump, in particular for conveying and metering free-flowing paste and liquids, but operating within various temperature ranges during the conveying process by means of a drive gear mounted axially an a central smooth motor shaft without a positive-fit connection and an eccentrically located hollow gear that meshes on its interior face and rotates within a cylindrical housing. Said housing is closed on both sides by lateral walls.

What is claimed is:  
     
         1 . A self-centering gear pump with the following features: 
 a) a drive gear ( 4 ) which is made of plastic and can be mounted axially with the gear hub ( 7 ) is held in a cylindrical housing ( 1 ) by a smooth, circular, rotatably held drive shaft ( 3 );    b) the drive gear ( 4 ) is rigidly connected in a non-detachable way by means of a non-positive connection to the gear hub ( 7 );    c) by driving the drive shaft ( 3 ) about the stationary center point ( 5 ) an arising torque abruptly produces the non-positive connection between drive shaft ( 3 ) and gear hub ( 7 ) by means of a roller free-wheel ( 6 ), with the rollers of the roller free-wheel ( 6 ) clamping over the entire circumference on the smooth surface of the drive shaft ( 3 ), but detaching again upon standstill of the drive shaft ( 3 );    d) through continual gear meshing ( 9 ) the hollow gear ( 8 ) which has one tooth more is made to perform a relative rotary movement towards the driving drive gear in a manner sliding along the inner-wall semi-circle ( 10 ) within the housing ( 1 );    e) the cylindrical housing ( 1 ) has a circular inner space of the housing which is slightly arranged as an oblong hole and in which the inner wall is arranged as a short straight line between the central axes ( 17 ) and  18 );    f) in the case of operationally induced heating of the material, any radial heat expansions of the elastic hollow gear ( 8 ) or drive gear ( 4 ) are displaced into and compensated in the available free space ( 16 );    g) when using the roller free-wheel ( 6 ) and in the case of an axial thermal elongation of the drive shaft ( 3 ), said roller free-wheel is used for compensating the thermal elongation through the axial displacement possibility of the drive gear ( 4 ) on the smooth drive shaft ( 3 ).    
     
     
         2 . A self-centering gear pump with the following features: 
 a) a drive gear ( 4 ) which is made of plastic and can be mounted axially with the gear hub ( 7 ) is held in a cylindrical housing ( 1 ) by a smooth, circular, rotatably held drive shaft ( 3 );    b) the drive gear ( 4 ) is rigidly connected in a non-detachable way by means of a non-positive connection to the gear hub ( 7 );    c) by driving the drive shaft ( 3 ) about the stationary center point ( 5 ) in the direction of the arrow an arising torque abruptly produces the non-positive connection between drive shaft ( 3 ) and gear hub ( 7 ) by means of a roller free-wheel ( 6 ), with the rollers of the roller free-wheel ( 6 ) clamping over the entire circumference on the smooth surface of the drive shaft ( 3 ), but detaching again upon standstill of the drive shaft ( 3 );    d) through continual gear meshing ( 9 ) the elastic hollow gear ( 8 ) which has one tooth more is made to perform a relative rotary movement towards the driving drive gear ( 4 ) in a manner sliding along the inner-wall semi-circle ( 10 ) within the housing ( 1 );    e) the drive gear ( 4 ) has a difference in teeth of  1  with respect to the hollow gear ( 8 ), with the semi-circular tooth geometry of the drive gear ( 4 ) being arranged as a positive shape and that of the hollow gear ( 8 ) as a negative shape;    f) the cylindrical housing ( 1 ) has a circular inner space of the housing which is slightly arranged as an oblong hole and in which the inner wall is arranged as a short straight line between the central axes ( 17 ) and  18 );    g) in the case of operationally induced heating of the material, any radial heat expansions of the elastic hollow gear ( 8 ) or drive gear ( 4 ) are displaced into and compensated in the available free space ( 16 );    h) when using the roller free-wheel ( 6 ) and in the case of an axial thermal elongation of the drive shaft ( 3 ), said roller free-wheel is used for compensating the thermal elongation through the axial displacement possibility of the drive gear ( 4 ) on the smooth drive shaft ( 3 );    i) the relative movement between drive gear ( 4 ) and hollow wheel ( 8 ) forms hollow spaces ( 11 ) which extend their volumes on the suction side from zero to the largest expansion and decrease the volume again back to zero on the pressure side;    j) the enlargement of the hollow spaces ( 11 ) on the suction side ensures that the liquid to be conveyed is sucked in through the pump input ( 12 ) via the overflow channel ( 13 ) into the interior of the pump;    k) the reduction of the hollow spaces ( 11 ) on the pressure side ensures that the liquid to be conveyed is displaced again via the pressure-side overflow channel ( 14 ) through the pump output ( 15 ).    
     
     
         3 . A self-centering gear pump as claimed in  claim 1  or  claim 2 , characterized in that the rotating gear parts of drive gear ( 4 ) and hollow gear ( 8 ) have the same coefficients of expansion with respect to their material as the housing ( 1 ).