Drain pump assembly for a dishwasher appliance

Abstract

A dishwasher appliance is provided having a sump for collecting wash fluid and a drain pump assembly for discharging wash fluid. The sump defines a drain basin and a drain cover is positioned over the drain basin to define a drain volute. A drain pump impeller is positioned within the drain volute on a drive shaft driven by a motor in a first direction during a wash cycle and in an opposite second direction during a drain cycle. During the wash cycle, soil enters the drain volute through a suction inlet defined by the drain cover where it is urged radially outward and trapped within the drain basin. When the motor operation is reversed, the drain pump impeller discharges the soiled wash fluid from the drain volute through a discharge conduit.

What is claimed is: 
     
         1 . A drain pump assembly for a dishwasher appliance, the drain pump assembly comprising:
 a sump for collecting wash fluid, the sump defining a drain basin proximate a bottom of the sump;   a drain cover positioned over the drain basin to define a drain volute, the drain cover defining a suction inlet to the drain volute;   a drive shaft defining an axial direction and a radial direction perpendicular to the axial direction, the drive shaft extending through the suction inlet into the drain volute;   a motor operable to rotate the drive shaft in a first direction during a wash cycle and in a second direction during a drain cycle, the second direction being opposite the first direction; and   a drain pump impeller positioned within the drain volute and coupled to the drive shaft.   
     
     
         2 . The drain pump assembly of  claim 1 , further comprising a discharge conduit in fluid communication with the drain volute. 
     
     
         3 . The drain pump assembly of  claim 2 , wherein the discharge conduit extends from the drain basin substantially perpendicular to the radial direction. 
     
     
         4 . The drain pump assembly of  claim 1 , wherein a radial gap is defined between the drain pump impeller and the drain basin along the radial direction. 
     
     
         5 . The drain pump assembly of  claim 4 , wherein the drain volute defines a first diameter and the drain pump impeller defines a second diameter, the first diameter being about ten to fifty percent larger than the second diameter. 
     
     
         6 . The drain pump assembly of  claim 1 , wherein the drain pump impeller is coupled to the drive shaft using a one-way clutch. 
     
     
         7 . The drain pump assembly of  claim 1 , wherein the motor is a variable speed motor. 
     
     
         8 . The drain pump assembly of  claim 7 , wherein the variable speed motor is configured for rotating drive shaft at a first speed when rotating in the first direction and a second speed when rotating in the second direction, the second speed being slower than the first speed. 
     
     
         9 . The drain pump assembly of  claim 1 , wherein a vertical gap is defined between a top of the drain pump impeller and the drain cover. 
     
     
         10 . The drain pump assembly of  claim 1 , wherein the sump and the drain cover define a frustum of a cone above the drain basin. 
     
     
         11 . The drain pump assembly of  claim 1 , wherein the motor is vertically oriented within a sump area of the dishwasher appliance, such that the drive shaft is vertically oriented relative to the dishwasher appliance. 
     
     
         12 . A dishwasher appliance defining a vertical direction, the dishwasher appliance comprising:
 a wash tub that defines a wash chamber;   a sump for collecting wash fluid;   a drive shaft defining an axial direction and a radial direction perpendicular to the axial direction;   a motor operable to rotate the drive shaft in a first direction during a wash cycle and in a second direction during a drain cycle, the second direction being opposite the first direction;   a wash pump impeller coupled to the drive shaft for providing a flow of wash fluid for cleaning articles placed within the wash chamber when the motor rotates in the first direction; and   a drain pump assembly comprising:   a drain basin positioned proximate a bottom of the sump;   a drain cover positioned over the drain basin to define a drain volute, the drain cover defining a suction inlet to the drain volute; and   a drain pump impeller positioned within the drain volute and coupled to the drive shaft for discharging wash fluid when the motor rotates in the second direction.   
     
     
         13 . The dishwasher appliance of  claim 12 , further comprising a discharge conduit in fluid communication with the drain volute. 
     
     
         14 . The dishwasher appliance of  claim 13 , wherein the discharge conduit extends from the drain basin substantially perpendicular to the radial direction. 
     
     
         15 . The dishwasher appliance of  claim 12 , wherein a radial gap is defined between the drain pump impeller and the drain basin along the radial direction. 
     
     
         16 . The dishwasher appliance of  claim 15 , wherein the drain volute defines a first diameter and the drain pump impeller defines a second diameter, the first diameter being about ten percent larger than the second diameter. 
     
     
         17 . The dishwasher appliance of  claim 12 , wherein the drain pump impeller is coupled to the drive shaft using a one-way clutch. 
     
     
         18 . The dishwasher appliance of  claim 12 , wherein the motor is a variable speed motor. 
     
     
         19 . The dishwasher appliance of  claim 12 , wherein a vertical gap is defined between a top of the drain pump impeller and the drain cover. 
     
     
         20 . The dishwasher appliance of  claim 12 , wherein the sump and the drain cover define a frustum of a cone above the drain basin.