Powder feed hopper

A powder feed hopper, comprising:

• a housing having a wall which defines a hollow interior;
• a fluidizing plate mounted to said wall within said hollow interior of said housing, said fluidizing plate having a top surface adapted to support particulate powder material and a bottom surface, said fluidizing plate defining a fluidized bed within said housing above said top surface thereof and a plenum within said housing beneath said bottom surface thereof;
• means for introducing pressurized air into said plenum at a location beneath said bottom surface of said fluidizing plate, the pressurized air flowing upwardly toward said fluidizing plate;
• a baffle plate having an outer periphery, said baffle plate being mounted within said plenum in the path of said pressurized air flowing toward said fluidizing plate so that said baffle plate is spaced a predetermined distance from said bottom surface of said fluidizing plate and so that said outer periphery of said baffle plate is spaced a predetermined distance from said outer wall of said housing forming a space therebetween, said baffle plate being effective to direct said pressurized air introduced into said plenum through said space between said outer wall of said housing and said outer periphery of said baffle plate prior to passage of said pressurized air through said fluidizing plate;
• and
• stirrer means located above said top surface of said fluidizing plate for creating turbulence within the particulate powder material supported atop said fluidizing plate.

A powder feed hopper, comprising:

• a housing having an outer wall which defines a hollow interior;
• a fluidizing plate mounted to said wall within said hollow interior of said housing, said fluidizing plate having a top surface adapted to support particulate powder material and a bottom surface, said fluidizing plate defining a fluidized bed within said housing above said top surface thereof and a plenum within said housing beneath said bottom surface thereof;
• air supply means for supplying pressurized air;
• nozzle means mounted within said plenum and connected to said air supply means for directing pressurized air toward said bottom surface of said fluidizing plate;
• a baffle plate having an outer periphery, said baffle plate being mounted within said plenum in the path of said pressurized air directed by said nozzle means toward said fluidizing plate so that said baffle plate is spaced a predetermined distance from said bottom surface of said fluidizing plate and so that said outer periphery of said baffle plate is spaced a predetermined distance from said outer wall of said housing, said baffle plate being effective to direct said pressurized air introduced into said plenum through said space between said outer wall of said housing and said outer periphery of said baffle plate prior to passage of said pressurized air through said fluidizing plate, whereby a flow of pressurized air is created above said upper surface of said fluidizing plate in which the air velocity is greatest at said wall of the housing and substantially uniformly decreases toward the center of said fluidizing plate, said flow of pressurized air forming a circulating flow of air-entrained particulate powder material within said fluidized bed wherein the air-entrained particulate powder material circulates in a direction from said wall of said housing toward the center thereof.

The method of forming a fluidized bed of air-entrained particulate powder material within the interior of a powder feed hopper having a substantially uniform density and even particle distribution, comprising:

• directing a stream of pressurized air toward the bottom surface of a fluidizing plate mounted within the interior of the powder feed hopper;
• deflecting said stream of pressurized air toward the wall of the powder feed hopper prior to contact with said fluidizing plate, said stream of pressurized air having a higher air flow volume and thus a higher velocity at the periphery of said fluidizing plate than toward the center portion thereof so as to form a fluidized bed above said fluidizing plate in which air-entrained powder material has a lower density at said periphery of said fluidizing plate and a higher density at said center portion thereof;
• creating a circulating flow of air-entrained particulate powder material within said fluidized bed above said fluidizing plate as a result of the difference in density of said air-entrained powder material at said periphery compared to said center of said fluidizing plate, wherein said air-entrained particulate powder material flows upwardly along said wall of said powder feed hopper and then downwardly along said center portion thereof within said fluidized bed;
• and
• rotating at least one stirrer blade with respect to the top surface of said fluidizing plate to create turbulence thereat.