Common field magnetic susceptors

1. An apparatus for heating and dispensing particulate material, comprising:

a housing having an outlet portion having an axis and a central orifice on the axis;

an outer susceptor mounted within the housing in coaxial alignment with the orifice, the outer susceptor having a perforated side wall, the side wall of the outer susceptor and the housing defining between them an annular outer bin having an inlet for receiving a portion of the particulate material prior to melting;

an inner susceptor mounted within the outer susceptor in coaxial alignment with the orifice and being non rotatable relative to the outer susceptor, the inner susceptor having a perforated side wall, the side wall of the inner susceptor and the side wall of the outer susceptor defining between them an annular heating chamber that is open to the orifice, the side wall of the inner susceptor defining an inner bin having an inlet for receiving a portion of the particulate material prior to melting;

an induction coil disposed within the heating chamber to cause the inner and outer susceptors to apply heat to the particulate material in the inner and outer bins and to cause the particulate material to melt and flow through perforations of the inner and outer susceptors into the heating chamber and from the heating chamber into the outlet portion and out the orifice; and wherein

the outer bin and the inner bin having ends opposite the inlets that are closed so as to prevent the particulate material within the outer and inner bins from flowing directly to the orifice rather than through the perforations.

2. The apparatus according to claim 1 , wherein:

the end of the inner bin comprises a baffle having inclined portions for directing the particulate material in the inner bin toward the inner susceptor.

3. The apparatus according to claim 2 , wherein the baffle is of a nonmetallic material and has a conical shape with an apex extending away from the orifice.

4. The apparatus according to claim 1 , wherein the end of the outer bin opposite the inlet of the outer bin is inclined so as to direct the particulate material within the outer bin toward the outer susceptor.

5. The apparatus according to claim 1 , wherein:

a diameter of the inner susceptor at the inlet of the inner bin equals a diameter of the inner susceptor at the end of the inner bin; and

a diameter of the outer susceptor at the inlet of the outer bin equals a diameter of the outer susceptor at the end of the outer bin.

6. The apparatus according to claim 1 , wherein the side walls of the inner and outer susceptors comprise a plurality of folds extending from the inlets of each of the inner and outer bins to ends of the inner and outer bins opposite the inlets.

7. The apparatus according to claim 6 , wherein the folds of the side wall of the inner susceptor comprise an inboard fold and an outboard fold, the inboard folds joining each other at an inboard angle, and the outboard folds joining each other at an outboard angle that differs from the inboard angle.

8. The apparatus according to claim 7 , wherein the inboard angle is greater than the outboard angle.

9. The apparatus according to claim 7 , wherein the folds of the side wall of the outer susceptor comprise an inboard fold and an outboard fold, the inboard folds joining each other at an inboard angle and the outboard folds joining each other at an outboard angle that differs from the inboard angle.

10. The apparatus according to claim 9 , wherein the inboard angle is greater than the outboard angle.

11. The apparatus according to claim 1 , further comprising:

an inboard fold and an outboard fold in the side wall of the inner susceptor, the inboard folds joining each other at an inboard angle, and the outboard folds joining each other at an outboard angle; and

an inboard fold and an outboard fold in the side wall of the outer susceptor, the inboard folds of the outer susceptor joining each other at an inboard angle and the outboard folds of the outer susceptor joining each other at an outboard angle.

12. The apparatus according to claim 11 , wherein the inboard angle of the folds of the inner susceptor is equal to the outboard angle of the folds of the outer susceptor.

13. The apparatus according to claim 11 , wherein a surface area of the inner susceptor is equal to a surface area of the outer susceptor.

14. The apparatus according to claim 1 , wherein the housing has a common bin that is open to the inlets of the outer and inner bins and contains particulate material so as to allow the particulate material contained in the common bin to flow into the inlets of both the outer and inner bins.

15. The apparatus according to claim 1 , wherein the inlets of the outer and inner bins are isolated from each other to allow different types of the particulate material to be simultaneously contained in the inner and outer bins.

16. An apparatus for heating and dispensing particulate material, comprising:

a housing having a conical outlet portion having an axis and a central orifice on the axis;

a metallic outer susceptor mounted within the housing in coaxial alignment with the orifice, the outer susceptor having a perforated side wall extending around the axis, the side wall of the outer susceptor and the housing defining between them an annular outer bin having an inlet end for receiving a portion of the particulate material prior to melting and a closed end opposite the inlet end;

an inner susceptor mounted within the outer susceptor in coaxial alignment with the orifice, the inner susceptor having a perforated side wall extending around the axis, the side wall of the inner susceptor and the side wall of the outer susceptor defining between them an annular heating chamber that is open to the orifice, the side wall of the inner susceptor defining an inner bin having an inlet end for receiving a portion of the particulate material prior to melting and a closed end opposite the inlet end of the inner bin; and

an induction coil disposed within the heating chamber to cause the inner and outer susceptors to apply heat to the particulate material in the inner and outer bins and cause the particulate material to melt and flow through perforations of the inner and outer susceptors into the heating chamber and from the heating chamber into the outlet portion and out the orifice.

17. The apparatus according to claim 16 , wherein:

a diameter of the inner susceptor at the inlet end of the inner bin equals a diameter of the inner susceptor at the closed end of the inner bin; and

a diameter of the outer susceptor at the inlet end of the outer bin equals a diameter of the outer susceptor at the closed end of the outer bin.

18. The apparatus according to claim 16 , wherein the closed end of the inner bin comprises a nonmetallic baffle that has a conical shape with an apex extending away from the orifice, the baffle blocking all flow of the particulate contained in the inner bin from flowing directly into the outlet portion of the housing.

19. The apparatus according to claim 16 , further comprising:

inboard folds and outboard folds in the side wall of the inner susceptor, the inboard folds joining each other at an inboard angle, and the outboard folds joining each other at an outboard angle;

inboard folds and outboard folds in the side wall of the outer susceptor, the inboard folds of the outer susceptor joining each other at an inboard angle and the outboard folds of the outer susceptor joining each other at an outboard angle; and

wherein the inboard and outboard angles of the inner and outer susceptors are selected to provide a surface area of the inner susceptor equal to a surface area of the outer susceptor.

20. A method for melting particulate material, comprising:

mounting inner and outer susceptors concentrically within a housing, each of the inner and outer susceptors having a perforated side wall, defining an annular outer bin between the outer susceptor and the housing, an inner bin within the inner susceptor, and an annular heating chamber between the inner and outer susceptors that contains an induction coil;

dispensing the particulate material within the inner bin and the outer bin; and

applying electrical energy to the coil, thereby heating the particulate material in the inner and outer bins and to cause the particulate material to melt and flow through perforations of the inner and outer susceptors into the heating chamber and from the heating chamber out an outlet of the housing.