Magnetically coupled fan blade and motor for a food cabinet

Abstract

A food cabinet includes a container holding a refrigerated food product, and the cabinet further includes a cooling device to refrigerate the food product. A fan for the cooling device includes an impeller mounted to a stationary shaft and a motor with a rotor. The impeller is exposed to fluids, but the motor and rotor are opposite a sealed surface and not exposed to the fluids. The impeller is coupled to the rotor by means of complementary sets of magnets mounted on each, such that rotation of the rotor similarly rotates the impeller.

1 . A food product refrigeration system, comprising:
 a container for holding a refrigerated food product;   a cooling frame substantially around and below the container, the cooling frame including openings designed for allowing the passage of air therethrough;   a ventilation chamber defined by the cooling frame and an insulated wall substantially around and below the cooling frame, the ventilation chamber containing a fan impeller and an evaporator coil; and   a motor controlling a rotor, the rotor magnetically coupled to the impeller such that rotation of the rotor by the motor results in operation of the impeller, the motor and rotor separated from the ventilation chamber by a sealed surface;   wherein the impeller operates to draw air into the ventilation chamber, past the evaporator coil, and out of the ventilation chamber into contact with the container.   
   
   
       2 . The refrigeration system of  claim 1 , wherein
 the ventilation chamber is an outer ventilation chamber;   an inner ventilation chamber is formed between the container and the cooling frame;   the cooling frame includes an outlet that opens into the inner ventilation chamber and an outlet that opens into the air above the container; and wherein   the fan impeller operates to draw air from the inner ventilation chamber into the outer ventilation chamber, past the evaporator coil, and through the outlets of the outer ventilation chamber into both the inner ventilation chamber and the air above the container.   
   
   
       3 . The refrigeration system of  claim 1 , wherein the rotor contains a set of magnets spaced therein, and wherein the impeller contains a set of magnets spaced such that the magnets of the impeller and the magnets of the rotor form individual pairs for magnetic coupling of the rotor and impeller. 
   
   
       4 . The refrigeration system of  claim 3 , wherein each individual pair of coupled magnets is positioned such that the magnets are proximate the sealed surface and on opposite sides of the sealed surface, such that the magnets communicate magnetically across the sealed surface. 
   
   
       5 . The refrigeration system of  claim 3 , wherein the set of impeller magnets are spaced evenly and at a common distance from the center of the impeller, and wherein each magnet is oriented such that its polarity is opposite from the polarity of both of the two magnets adjacent to it. 
   
   
       6 . The refrigeration system of  claim 1 , wherein the container is a condiment pan. 
   
   
       7 . The refrigeration system of  claim 1 , wherein the sealed surface is made of a nonmagnetic material. 
   
   
       8 . The refrigeration system of  claim 7 , wherein the nonmagnetic material is stainless steel. 
   
   
       9 . The refrigeration system of  claim 1  wherein the impeller is mounted on a stationary shaft that extends upward through the sealed surface, the stationary shaft having an associated stationary seal member. 
   
   
       10 . A food cooling system, comprising:
 a food holding area;   a fan impeller mounted for rotation below the food holding area;   a motor including a rotor magnetically coupled to drive the fan impeller without mechanical contact between the rotor and the fan impeller; and   a sealed surface separating the motor from the impeller.   
   
   
       11 . The food cooling system of  claim 10 , wherein the rotor contains a set of magnets spaced therein, and wherein the impeller contains a set of magnets spaced such that the magnets of the impeller and the magnets of the rotor form individual pairs for magnetic coupling of the rotor and impeller. 
   
   
       12 . The refrigeration system of  claim 1 , wherein the set of impeller magnets are spaced evenly and at a common distance from the center of the impeller, and wherein each magnet is oriented such that its polarity is opposite from the polarity of both of the two magnets adjacent to it. 
   
   
       13 . The food cooling system of  claim 10 , wherein the sealed surface is made of a nonmagnetic material. 
   
   
       14 . The food cooling system of  claim 13 , wherein the nonmagnetic material is stainless steel. 
   
   
       15 . The food cooling system of  claim 10  wherein the impeller is mounted on a stationary shaft that extends upward through the sealed surface, the stationary shaft having an associated stationary seal member. 
   
   
       16 . A food preparation cabinet including the food cooling system of  claim 10 , wherein:
 the food holding area includes a condiment pan holding a condiment;   the fan impeller located below the condiment pan and exposed to potential contact with condiment that falls from the condiment pan;   the sealed surface preventing the motor from being contacted by condiment.   
   
   
       17 . A food presentation station including the food cooling system of  claim 10 , wherein:
 the food holding area includes a display area with a removable food tray displaying food product;   the fan impeller located below the food tray and within the display area;   the sealed surface preventing the motor from being contacted by wash liquid during cleaning of the display area.