Humidifier and layered heating element

1. A humidifier for humidifying a pressurized flow of breathable gas for respiratory therapy for a patient, comprising:

a gas inlet configured to receive gas from a flow generator;

a tub adapted to hold a liquid, the tub including sidewalls and a bottom;

a gas outlet adapted to be connectable to a tube to provide humidified gas to a patient interface; and

a heating apparatus including:

a heating element which converts electrical power to heat energy;

a thermally conductive hot plate having a first surface and a second surface, the first surface of the hot plate being arranged to receive the heat energy from the heating element, the second surface of the hot plate being configured and arranged to heat the liquid in the tub; and

a protective coating overmolded over the hot plate to provide a sealed protective layer across the second surface of the hot plate.

2. The humidifier of claim 1 , said heating apparatus further comprising a dielectric laminate layer between the heating element and the first surface of the hot plate, wherein the dielectric laminate layer is thermally conductive to transfer heat energy from the heating element to the hot plate.

3. The humidifier of claim 2 , wherein the dielectric laminate layer is a thin layer comprising at least one of polytetrafluoroethylene, polyimides, boron nitride, alumina, beryllium oxide, aluminum nitride, boron nitride, epoxy composite, and reinforced fiberglass.

4. The humidifier of claim 1 , wherein the heating element is in direct contact with the first surface of the hot plate.

5. The humidifier of claim 1 , wherein the protective coating provides a water and/or vapor sealed protective layer across the second surface of the hot plate.

6. The humidifier of claim 1 , wherein the protective coating is thermally conductive so as to effectively transfer heat from the hot plate to the liquid in the tub.

7. The humidifier of claim 1 , wherein the protective coating is formed of a biocompatible material.

8. The humidifier of claim 7 , wherein the protective coating is formed of silicone or a UV cured polymer.

9. The humidifier of claim 1 , wherein the bottom of the tub includes a bottom external wall of the tub that is spaced upwardly from lower ends of the sidewalls such that the tub has an open bottom.

10. The humidifier of claim 9 , wherein the heating apparatus forms the bottom external wall of the tub.

11. The humidifier of claim 1 , wherein the bottom of the tub includes a bottom external wall below the heating apparatus that connects with lower ends of the sidewalls.

12. The humidifier of claim 1 , wherein the sidewalls are overmolded onto the heating apparatus.

13. The humidifier of claim 1 , wherein the sidewalls are formed of plastic.

14. The humidifier of claim 1 , wherein the hot plate is a metallic plate.

15. The humidifier of claim 14 , wherein the hot plate comprises aluminum, stainless steel, or copper.

16. The humidifier of claim 1 , wherein the hot plate is a non-metal material.

17. The humidifier of claim 16 , wherein the hot plate comprises a ceramic material or a thermally conductive plastic material.

18. The humidifier of claim 1 , wherein the heating element comprises heating tracks.

19. The humidifier of claim 18 , wherein the heating element is a metallic printed circuit board (PCB) and the heating tracks are conductive metallic foils arranged on the PCB.

20. The humidifier of claim 19 , wherein a substrate is provided to an end portion of the heating element to form a connector section, and wherein the end portion of the heating element forms an electrical contact to receive electrical power.