# US 2018/0020733 A1 · Feedback controlled rtd adjustment for an aerosol-generating device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0020733 A1 - Document ID: US20180020733A1 - Status: Published application - Kind: A1 - Application number: 15/551,223 - Filed: 2016-02-25 - Published: 2018-01-25 - Earliest claimed: 2015-02-27 - Assignees: Philip Morris Products S.A. - Applicants: Philip Morris Products S.A. - Inventors: Evan JOCHNOWITZ - Web page: https://patentgrep.com/patent/US20180020733A1 ## CPC - A24F 40/485: Valves; Apertures - A24F 40/50: Control or monitoring - F22B 1/284: {with water in reservoirs} - G01F 1/00: Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow (measuring a proportion of the volume flow G01F5/00) - H05B 3/44: heating conductor arranged within rods or tubes of insulating material - A24F: SMOKERS' REQUISITES; MATCH BOXES; SIMULATED SMOKING DEVICES (inhaling appliances for medical purposes, shaped like cigars, cigarettes or pipes A61M15/06) - F22B: METHODS OF STEAM GENERATION; STEAM BOILERS - G01F: MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL ## Abstract An electrically heated aerosol-generating device and ststem are provided, the device including an outer housing having a cavity configured to receive an aerosol-generating substrate; an electrical heater including at least one heating element configured to heat the aerosol-generating substrate in the cavity to generate an aerosol; at least one air inlet, at least one air outlet; an airflow pathway extending from the at least one air inlet, through the cavity, to the at least one air outlet; means for determining the resistance-to-draw of the airflow pathway; and means for adjusting the resistance-to-draw of the airflow pathway in dependence on the determined resistance-to-draw. The system comprises an electrically heated aerosol-generating device and an aerosol-forming substrate comprising tobacco. ## Claims ### Claim at position 1 -15. (canceled) ### Claim 16 An electrically heated aerosol-generating device, comprising: an outer housing having a cavity configured to receive an aerosol-generating substrate: an electrical heater comprising at least one heating element configured to heat the aerosol-generating substrate in the cavity to generate an aerosol; at least one air inlet; at least one air outlet; an airflow pathway extending from the at least one air inlet, through the cavity, to the at least one air outlet; means for determining the resistance-to-draw of the airflow pathway; and means for automatically adjusting the resistance-to-draw of the airflow pathway in dependence, on the determined resistance-to-draw. ### Claim 17 (depends on 16) The electrically heated aerosol-generating device according to claim 16, wherein the means for automatically adjusting is configured to maintain the resistance-to-draw of the airflow pathway within a predetermined range. ### Claim 18 (depends on 17) The electrically heated aerosol-generating device according to claim 17, wherein the predetel mined range of the resistance-to-draw is between about 80 mm WG and about 100 mm WG. ### Claim 19 (depends on 16) The electrically heated aerosol-generating device according to claim 16, wherein the means for automatically adjusting comprises an adjustable orifice. ### Claim 20 (depends on 19) The electrically heated aerosol-generating device according to claim 19, wherein the adjustable orifice is an iris diaphragm. ### Claim 21 An electrically heated aerosol-generating system, comprising: an electrically heated aerosol-generating device, comprising: an outer housing having a cavity configured to receive an aerosol-generating substrate, an electrical heater comprising at least one heating element configured to heat the aerosol-generating substrate in the cavity to generate an aerosol, at least one air inlet, at least one air outlet, an airflow pathway extending from the at least one air inlet, through the cavity, to the at least one air outlet, means for determining the resistance-to-draw of the airflow pathway, and means for automatically adjusting the resistance-to-draw of the airflow pathway in dependence on the determined resistance-to-draw; a power supply configured to supply power to the electrical heater: electrical hardware connected to the power supply and the electrical heater; and a controller configured to control the supply of electrical power from the power supply to the electrical hea ### Claim 22 (depends on 21) The electrically heated aerosol-generating systemaccording to claim 21, whe ein the means for determining the resistance-to-draw includes a press ### Claim 23 (depends on 22) The electrically heated ae sol-generating system according claim 22, wherein the resistance-to-draw is determined by correlating a pressure sensor output to a resistance-to-draw using a look-up table, or by evaluating a polynomial formula dependent the pressure sensor output. ### Claim 24 (depends on 21) The electrically heated aerosol-generating system according to claim 21, wherein the controller is further configured to control the rrtcans for automatically adjusting, the means for automatically adjusting being electrically operated. ### Claim 25 (depends on 24) The electrically heated aerosol-generating system according to claim 24, wherein the controller is configured to determine the resistance-to-draw during a first puff, and to automatically control the means for automatically adjusting between the first puff and a second puff to adjust the resistance-to-draw for the second puff in dependence on the determined resistance-to-draw of the first puff. ### Claim 26 (depends on 16) The electrically heated aerosol-generating device according to claim 16, further comprising a rnechanically operated pressure compensated flow valve configured to maintain an air flow rate through the valve it dependence on a pressure difference across the valve. ### Claim 27 (depends on 26) The electrically heated aerosol-generating device according to claim 26, wherein the mechanically operated pressure compensated flow valve comprises a spring having a spring coefficient to set the pressure difference across the valve. ### Claim 28 (depends on 16) The electrically heated aerosol-generating device according to claim 16, wherein the electrical heater is provided adjacent at least one wall of the cavity. ### Claim 29 An electrically heated aerosol-generating system, comprising: an electrically heated aerosol-generating device, comprising: an outer housing having a cavity configured to receive an aerosol-generating substrate, an electrical heater comprising at least one heating element configured to heat the aerosol-generating substrate in the cavity to generate an aerosol, at least one air inlet, at least one air outlet, an airflow pathway extending from the at least one air inlet, through the cavity, to the at least one air outlet, means for determining the resistance-to-draw of the airflow pathway, and means for automatically adjusting the resistance-to-draw of the airflow pathway in dependence on the determined resistance-to-draw, wherein the aerosol-generating substrate comprises tobacco. ### Claim 30 (depends on 29) The electrically heated aerosol-generating system according claim 29, wherein the tobacco is at, least one of: pipe tobacco, cut filler, reconstituted tobacco, and homogenized tobacco.