Pumps for transferring fluids intended for human consumption

Abstract

Pumps are provided for transferring fluids between tanks and other types of vessels. The pumps include a rotating impeller that pumps the fluid, and an electric motor that imparts rotation to the impeller. The impeller is mounted for rotation on a shaft by way of a bushing. The bushing is made of a material suitable for contact with food products intended for human consumption. Also, the material can withstand the elevated temperatures that arise in the bushing when the pump is run in a dry condition, i.e., without any fluid passing through the pump.

We claim: 
     
         1 . A pump for transferring fluids, comprising:
 an electric motor comprising a rotatable output shaft;   a pump housing having an inlet and an outlet;   a shaft mounted on the pump housing; and   an impeller assembly comprising: a bushing mounted for rotation on the shaft and comprising a resin-impregnated, carbon-graphite material; and an impeller comprising a body and a plurality of blades attached to the body, wherein: the impeller is mounted on the bushing, the impeller is magnetically coupled the output shaft of the electric motor so that the output shaft is operable to impart rotation to the impeller when the output shaft rotates; and the impeller is configured to pump the fluids between the inlet and the outlet of the housing as the impeller rotates.   
     
     
         2 . The pump of  claim 1 , wherein the impeller is magnetically coupled to the output shaft of the electric motor. 
     
     
         3 . The pump of  claim 2 , further comprising a magnet mechanically coupled to the output shaft of the electric motor so that the electric motor is operable to rotate the magnet; wherein the impeller assembly further comprises a magnetic sleeve mounted on the impeller and positioned within a magnetic field of the magnet so that the magnet is operable to impart rotation to the impeller assembly. 
     
     
         4 . The pump of  claim 1 , wherein the impeller comprises a plastic material. 
     
     
         5 . The pump of  claim 1 , wherein the bushing is substantially cylindrical. 
     
     
         6 . The pump of  claim 5 , wherein the bushing has a chamfered surface positioned between a side surface and a forward end of the bushing. 
     
     
         7 . The pump of  claim 5 , wherein the bushing has a substantially cylindrical internal passage extending between a forward and a rearward end of the bushing, and the passage is configured to receive the shaft. 
     
     
         8 . The pump of  claim 7 , wherein the bushing has two slots formed therein at diametrically-opposed locations on the forward end of the slot. 
     
     
         9 . The pump of  claim 1 , wherein the resin-impregnated, carbon-graphite material is a food grade material. 
     
     
         10 . The pump of  claim 1 , wherein the resin-impregnated, carbon-graphite material has a maximum operating temperature of at least about 500° F. 
     
     
         11 . The pump of clam  5 , wherein the bushing has a substantially cylindrical exterior side surface, and the impeller encapsulates at least a portion of the exterior side surface. 
     
     
         12 . The pump of clam  11 , wherein the impeller encapsulates a substantial entirety of the exterior side surface. 
     
     
         13 . The pump of  claim 1 , wherein the impeller is separated from the shaft by the bushing. 
     
     
         14 . A pump for transferring a fluids, comprising:
 an electric motor comprising a rotatable output shaft;   a pump housing having an inlet and an outlet;   a shaft mounted on the pump housing; and   an impeller assembly comprising: a bushing mounted for rotation on the shaft and comprising a food-grade material having a maximum operating temperature of at least about 500° F.; and an impeller comprising a body and a plurality of blades attached to the body, wherein: the impeller is mounted on the bushing, the impeller is coupled the output shaft of the electric motor so that the output shaft is operable to impart rotation to the impeller when the output shaft rotates; and the impeller is configured to pump the fluids between the inlet and the outlet of the housing as the impeller rotates.   
     
     
         15 . The pump of clam  14 , wherein the bushing material is resin-impregnated carbon-graphite. 
     
     
         16 . A process for producing an impeller assembly for a pump for transferring fluids, comprising:
 forming a bushing from a resin-impregnated, carbon-graphite material; and molding an impeller over the bushing.   
     
     
         17 . The process of  claim 16 , further comprising immersing the impeller and the bushing in an ice bath having an initial temperature of about 50° F. or below, for a time period of about 60 seconds. 
     
     
         18 . The process of  claim 16 , wherein forming a bushing from a resin-impregnated, carbon-graphite material comprises milling a blank of the resin-impregnated, carbon-graphite material. 
     
     
         19 . The process of  claim 16 , wherein molding an impeller over the bushing comprises placing the bushing in a mold and injecting molten resin into the mold. 
     
     
         20 . The process of  claim 16 , wherein the resin-impregnated, carbon-graphite material is a food-grade material having a maximum operating temperature of at least about 500° F.