Rotary Pump And Multiple Rotary Pump Employed Thereof

Abstract

A rotary pump is provided in which a drive motor is provided such that an output shaft of the drive motor is placed at an offset position, so that a rotational speed of the pump can be changed to a high or low speed. Furthermore, rigid balls or needle roller bearings are used in each rotor unit such that each eccentric rotary body is in rolling contact with a circumferential inner surface of each cylindrical housing, thus reducing friction between them, thereby ensuring smooth rotation of the rotor units. In addition, a space, which is defined between each cylindrical housing and each eccentric rotary body, prevents a cross-plate from being damaged due to torsional stress and tensile force, thereby ensuring superior durability of the pump.

1 . A rotary pump comprising:
 a drive motor;   upper and lower chambers;   a pair of rotor units respectively provided in the upper and lower chambers such that the pair of rotor units are configured to be driven by the drive motor and moving along inner surfaces of the chambers;   a cross-plate integrally connecting the pair of rotor units to each other,   wherein each of the rotor units includes:   a cylindrical housing;   an eccentric rotary body installed and eccentrically rotatable in the cylindrical housing; and   means for reducing friction between the eccentric rotary body and the cylindrical housing when the eccentric rotary body rotates within the cylindrical housing.   
   
   
       2 . The rotary pump as claimed in  claim 1 , wherein the cylindrical housing includes a cylindrical shape with a diameter smaller than an inner diameter of each chamber, with a plurality of bearing seats formed in a circumferential inner surface of the cylindrical housing, and a space defined in the cylindrical housing, the eccentric rotary body having a diameter smaller than the inner diameter of the cylindrical housing and eccentrically fitted over a rotatable shaft, and the means for reducing friction includes a plurality of bearing members respectively seated into the plurality of bearing seats of the cylindrical housing. 
   
   
       3 . The rotary pump as claimed in  claim 2 , wherein the bearing seats each have a depth, respective magnitudes of the depths sequentially decreasing from a 12 o'clock position to a 3 o'clock position, being substantially constant from the 3 o'clock position to a 9 o'clock position, and sequentially increasing from the 9 o'clock position to the 12 o'clock position, the clock positions being positioned with respect to the circumferential inner surface of the cylindrical housing. 
   
   
       4 . The rotary pump as claimed in  claim 3 , wherein when the cylindrical housing is sectioned into a center side half-circle portion which is adjacent the cross-plate and a remaining outside half-circle portion, the bearing seats formed in the center side half-circle portion of the cylindrical housing have a most shallow depth with respect to the other bearing seats, the center side half-circle portion extending from the 3 o'clock position to the 9 o'clock position. 
   
   
       5 . The rotary pump as claimed in  claim 2 , wherein the bearing seats each have a diameter, respective magnitudes of the diameters sequentially increasing from a 12 o'clock position to a 3 o'clock position, being substantially constant from the 3 o'clock position to a 9 o'clock position, and sequentially decreasing from the 9 o'clock position to the 12 o'clock position, the clock positions being positioned with respect to the circumferential inner surface of the cylindrical housing. 
   
   
       6 . The rotary pump as claimed in  claim 5 , wherein when the cylindrical housing is sectioned into a center side half-circle portion which is adjacent the cross-plate and a remaining outside half-circle portion, the bearing seats formed in the center side half-circle portion of the cylindrical housing have a most largest diameter with respect to the other bearing seats, the center side half-circle portion extending from the 3 o'clock position to the 9 o'clock position. 
   
   
       7 . The rotary pump as claimed in  claim 1 , wherein the cylindrical housing includes a cylindrical shape with a diameter smaller than an inner diameter of each chamber, with a space defined in the cylindrical housing, the eccentric rotary body having a diameter smaller than the inner diameter of the cylindrical housing and eccentrically fitted over a rotatable shaft, with a plurality of bearing seats formed in a circumferential outer surface of the eccentric rotary body, and the means for reducing friction includes a plurality of bearing members respectively seated into the plurality of bearing seats of the eccentric rotary body. 
   
   
       8 . The rotary pump as claimed in  claim 7 , wherein the bearing seats each have a depth, respective magnitudes of the depths sequentially increasing from a 12 o'clock position to a 3 o'clock position, sequentially decreasing from the 3 o'clock position to a 6 o'clock position, sequentially increasing from the 6 o'clock position to a 9 o'clock position, and sequentially decreasing from the 9 o'clock position to the 12 o'clock position, the clock positions being positioned with respect to the circumferential outer surface of the eccentric rotary body. 
   
   
       9 . The rotary pump as claimed in  claim 8 , wherein when the cylindrical housing is sectioned into a left side half-circle portion and a right side half-circle portion by a line which is extended along a longitudinal direction of the cross-plate, the left side half-circle portion and the right side half-circle portion are symmetrically formed along the circumferential outer surface of the eccentric rotary body. 
   
   
       10 . The rotary pump as claimed in  claim 8 , wherein the bearing seats each have a diameter, respective magnitudes of the diameters sequentially decreasing from a 12 o'clock position to a 3 o'clock position, sequentially increasing from the 3 o'clock position to a 6 o'clock position, sequentially decreasing from the 6 o'clock position to a 9 o'clock position, and sequentially increasing from the 9 o'clock position to the 12 o'clock position, the clock positions being positioned with respect to the circumferential outer surface of the eccentric rotary body. 
   
   
       11 . The rotary pump as claimed in  claim 10 , wherein when the cylindrical housing is sectioned into a left side half-circle portion and a right side half-circle portion by a line which is extended along a longitudinal direction of the cross-plate, the left side half-circle portion and the right side half-circle portion are symmetrically formed along the circumferential outer surface of the eccentric rotary body. 
   
   
       12 . The rotary pump to as claimed in  claim 1 , wherein the means for reducing friction includes ball bearings or needle roller bearings positioned between the cylindrical housing and the eccentric rotary body. 
   
   
       13 . The rotary pump as claimed in  claim 1 , wherein the rotary pump further comprises an overload prevention unit provided on an output shaft of the drive motor in order to prevent the drive motor from overloading. 
   
   
       14 . The rotary pump as claimed in  claim 13 , wherein the overload prevention unit comprises:
 a plurality of ball seats formed in a circumferential outer surface of an end of the output shaft of the drive motor;   a coupler having a receiving space in which the output shaft is inserted and a plurality of ball insertion holes formed along a sidewall of the coupler at positions corresponding to the ball seats; and   a cover ring fitted over a circumferential outer surface of the coupler to prevent balls from being undesirably removed, wherein   the balls are inserted into the ball insertion holes and seated into the ball seats, and the cover ring surrounds the balls, so that, when an overload is applied to the clutch unit, the balls push outwards and deform the cover ring thus interrupting power transmission.   
   
   
       15 . The rotary pump as claimed in  claim 4 , wherein a motor gear is formed on a circumferential outer surface of the coupler, wherein the motor gear is a helical gear. 
   
   
       16 . The rotary pump as claimed in  claim 1 , wherein the rotary pump further comprises a power transmitting, unit in order to transmit power from the drive motor to the rotor units, wherein a rotational speed of the drive motor is changed by the power transmitting unit. 
   
   
       17 . The rotary pump as claimed in  claim 16 , wherein the power transmitting unit comprises:
 a pair of rotatable shafts which are parallel to each other;   a drive gear rotatable engaging with a motor gear formed on an end of an output shaft of the drive motor, and fitted on either one of the rotatable shafts;   a first main gear fitted on either one of the rotatable shafts which is rotatable together with the drive gear; and   a second main gear engaging with the first main gear and fitted on the other rotatable shaft wherein   the first main gear and the second main gear are rotatable in an opposite direction to each other.   
   
   
       18 . The rotary pump as claimed in  claim 16 , wherein the power transmitting unit comprises:
 a pair of rotatable shafts which are parallel to each other;   a first transmitting gear engaging with a motor gear formed on an end of an output shaft of the drive motor and idly inserted on either one of the rotatable shafts, the first transmitting gear being integrally formed with a subsidiary transmitting gear which has a diameter smaller than the diameter of the first transmitting gear;   a second transmitting gear fitted on either one of the rotatable shafts or the other of the rotatable shafts;   a first main gear fitted on the rotatable shaft which is rotatable together with the drive gear;   a second main gear engaging with the first main gear and fitted on the rotatable shaft on which the first main gear is not fitted; and   a plurality of driven gears arranging between the subsidiary transmitting gear and the second transmitting gear and transmitting power from the subsidiary transmitting gear to the second transmitting gear, the driven gears being integrally formed with respective subsidiary driven gears which have a diameter smaller than the diameter of the driven gears, wherein   each of the driven gears is idly inserted on the rotatable shafts such that a downstream driven gear is rotatably engaged with an upstream subsidiary driven gear, and the first main gear and the second main gear are rotatable in an opposite direction to each other.   
   
   
       19 . The rotary pump as claimed in  claim 16 , wherein the power transmitting unit comprises:
 a pair of the rotatable shafts which are parallel to each other;   a first transmitting gear engaging with a motor gear formed on an end of an output shaft of the drive motor and idly inserted on either one of the rotatable shafts, the first transmitting gear being integrally formed with a subsidiary transmitting gear which has a diameter larger than the diameter of the first transmitting gear;   a second transmitting gear fitted on either one of the rotatable shafts or the other of the rotatable shafts;   a first main gear fitted on the rotatable shafts which is rotatable together with the drive gear;   a second main gear engaging with the first main gear and fitted on the rotatable shaft on which the first main gear is not fitted; and   a plurality of driven gears arranging between the subsidiary transmitting gear and the second transmitting gear and transmitting power from the subsidiary transmitting gear to the second transmitting gear, the driven gears being integrally formed with respective subsidiary driven gears which have a diameter larger than the diameter of the driven gears, wherein   each of the driven gears is idly inserted on the rotatable shafts such that a downstream driven gear is rotatably engaged with an upstream subsidiary driven gear, and the first main gear and the second main gear are rotatable in an opposite direction to each other.   
   
   
       20 . A rotary pump comprising:
 a drive motor;   a plurality of upper and lower chambers which are laterally arranged to each other;   a plurality of pairs of rotor units respectively provided in the respective upper and lower chambers such that the pairs of rotor units are configured to be driven by the drive motor and moving along inner surfaces of the chambers; and   a cross-plate integrally connecting the pairs of rotor units to each other,   wherein each of the rotor units includes:   a cylindrical housing;   an eccentric rotary body installed and eccentrically rotatable in the cylindrical housing; and   means for reducing friction between the eccentric rotary body and the cylindrical housing when the eccentric rotary body rotates within the cylindrical housing.