Aerosol generating device with improved temperature distribution
There is provided an aerosol generating device configured to receive an aerosol-forming substrate and configured to heat the aerosol-forming substrate using both an internal heater, positioned within the substrate, and an external heater positioned outside of the substrate. The use of both an internal and an external heater allows each heater to operate at a lower temperature than would be required when using either an internal or external heater alone. By operating the external heater at a lower temperature than the internal heater, the substrate can be heated to have a relatively uniform temperature distribution while the external temperature of the device can be kept to an acceptably low level.
1. An aerosol generating device, comprising:
a substrate receiving cavity configured to receive an aerosol-forming substrate;
an internal heater positioned within the substrate receiving cavity;
an external heater positioned on a perimeter of the substrate receiving cavity;
and a controller configured to control a supply of power to the internal heater or to the external heater, or to both the internal heater and the external heater, so that the external heater is operated at a lower temperature than the internal heater;
wherein the external heater is provided on a sleeve that is slidable relative to a housing of the device.
2. The aerosol generating device according to claim 1 , wherein the external heater is shaped or controlled to provide, in conjunction with the internal heater, a substantially uniform temperature distribution around a perimeter of the cavity.
3. The aerosol generating device according to claim 1 , wherein the controller is configured to control the external heater to have a temperature between 100 and 200 degrees centigrade.
4. The aerosol generating device according to claim 1 , wherein the controller is configured to control the internal heater to have a temperature between 320 and 420 degrees centigrade.
5. The aerosol generating device according to claim 1 , wherein the external heater is disposed substantially symmetrically around a perimeter of the substrate receiving cavity.
6. The aerosol generating device according to claim 1 , wherein the external heater comprises a plurality of external heater elements.
7. The aerosol generating device according to claim 6 , wherein the external heater comprises two heater elements each extending partially around the perimeter of the cavity.
8. The aerosol generating device according to claim 1 , configured such that, in use, the external heater has a temperature lower than the aerosol-forming substrate but higher than ambient temperature.
9. The aerosol generating device according to claim 1 , further comprising a support structure around the external heater, the support structure comprising an internal surface having one or more ribs or projections, the ribs or projections contacting the external heater.
10. The aerosol generating device according to claim 1 , wherein the external heater is positioned on or forms an inner surface of the cavity so that, in use, the external heater contacts the aerosol-forming substrate.
11. The aerosol generating device according to claim 1 , wherein the device is an electrically heated smoking device.
12. A method of heating an aerosol-forming substrate, comprising:
providing a first heater configured to contact an internal region of the aerosol forming substrate in a device;
providing a second heater configured to contact an exterior surface of the substrate; and
providing a controller configured to control the temperature of the first heater and the second heater so that the second heater is operated at a lower temperature than the first heater;
wherein the second heater is provided on a sleeve that is slidable relative to a housing of the device.
13. The method according to claim 12 , wherein the second heater is controlled to have a temperature between 100 and 200 degrees centigrade.
14. The method according to claim 12 , wherein the first heater is controlled to have a temperature between 320 and 420 degrees centigrade.