Method and apparatus for cleaning a heating element of aerosol generating device

Abstract

A method of using an aerosol-generating device is provided, including bringing a heating element of the aerosol-generating device into contact with an aerosol-forming substrate, raising a temperature of the heating element to a first temperature to heat the aerosol-forming substrate sufficiently to form an aerosol, removing the heating element from contact with the aerosol-forming substrate and heating the heating element to a second temperature, higher than the first temperature, to thermally liberate organic materials adhered to or deposited on the heating element. An aerosol-generating device is also provided, including a heating element coupled to a controller configured to heat the heating element to the first temperature and to the second temperature.

Claims

1. A method of using an aerosol-generating device having a reusable heating element, comprising: bringing the heating element into direct contact with an aerosol-forming substrate by inserting the heating element into a smoking article comprising the aerosol-forming substrate; raising a temperature of the heating element to a first temperature to heat the aerosol-forming substrate sufficiently for an aerosol to be formed; removing the heating element from the direct contact with the aerosol-forming substrate; and raising the temperature of the heating element to a second temperature, higher than the first temperature, to thermally liberate organic materials adhered to or deposited on the heating element.

2. The method of using an aerosol-generating device according to claim 1, in which the organic materials deposited on the heating element are thermally liberated by raising the temperature of the heating element to the second temperature of greater than about 430 degrees cenfigrade.

3. The method of using an aerosol-generating device according to claim 1, in which the heating element is held at the second temperature for a period of between 5 seconds and 60 seconds.

4. The method of using an aerosol-generating device according to claim 1, in which the aerosol-forming substrate comprises tobacco.

5. The method of using an aerosol-generating device according to claim 1, in which an aerosol is formed as a result of heating the heating element to an average first temperature of between 80 degrees centigrade and 375 degrees centigrade with a nmaximum localized temperature limit of 420 degrees centigrade while in contact with the aerosol-forming substrate.

6. The method of using an aerosol-generating device according to claim 1, in which the step of raising the temperature of the heating element to a first temperature to heat the aerosol-fonning substrate sufficiently to fonii an aerosol is performed two or more times prior to the step of raising the temperature of the heating element to a second temperature, higher than the first temperature, to thermally liberate organic materials adhered to or deposited on the heating element.

7. The method of using an aerosol-generating device according to claim 1, in which the step of raising the temperature of the heating element to a second temperature, higher thanthe first temperature, to thermally liberate organic materials adhered to or deposited on the heating element, occurs in response to a trigger actuated by a user.

8. The method of using an aerosol-generating device according to claim 1, in which the aerosol-generating device is coupleable to a docking station, in which the step of raising the temperature of the heating element to a second temperature, higher than the first temperature, to thermally liberate organic materials adhered to or deposited on the heating element occurs when the aerosol-generating device is coupled to the docking station.

9. The method of using an aerosol-generating device according to claim 1, further comprising a step of cooling the heating element a temperature below the first temperature before the step of removing the heating element from the direct contact with the aerosol-forming substrate.

Description

Exemplary Embodiments

(1) Exemplary embodiments will now be described with reference to the figures, in which;

(2) FIG. 1 is a schematic cross-sectional diagram of a first embodiment of an aerosol-generating device engaged with a smoking article;

(3) FIG. 2 is a schematic diagram illustrating a heating element of the first embodiment of an aerosol-generating device;

(4) FIG. 3A is an illustration showing a heating element of the first embodiment of an aerosol-generating device with a surface that has been soiled with organic components;

(5) FIG. 3B is an illustration showing the heating element of FIG. 3A after the organic components have been thermally liberated;

(6) FIG. 4 is a flow diagram illustrating a first embodiment of a method;

(7) FIG. 5 is a block diagram illustrating the configuration of an aerosol-generating device; and

(8) FIG. 6 is a flow diagram illustrating a second embodiment of a method.

(9) FIG. 1 illustrates a portion of an aerosol-generating device 10 according to a first embodiment. The aerosol-generating device 10 is engaged with a smoking article 20 for consumption of the smoking article 20 by a user.

(10) The smoking article 20 comprises four elements, an aerosol-forming substrate 30, a hollow tube 40, a transfer section 50, and a mouthpiece filter 60. These four elements are arranged sequentially and in coaxial alignment and are assembled by a cigarette paper 70 to form a rod 21. The rod has a mouth-end 22, which a user inserts into his or her mouth during use, and a distal end 23 located at the opposite end of the rod to the mouth end 22. Elements located between the mouth-end 22 and the distal end 23 can be described as being upstream of the mouth-end or, alternatively, downstream of the distal end.

(11) When assembled, the rod 21 is 45 millimetres long and has a diameter of 7.2 millimetres.

(12) The aerosol-forming substrate 30 is located upstream of the hollow tube 40 and extends to the distal end 23 of the rod 21. The aerosol-forming substrate comprises a bundle of crimped cast-leaf tobacco wrapped in a filter paper (not shown) to form a plug. The cast-leaf tobacco includes additives, including glycerine as an aerosol-forming additive.

(13) The hollow tube 40 is located immediately downstream of the aerosol-forming substrate 30 and is formed from a tube of cellulose acetate. The tube 40 defines an aperture having a diameter of 3 millimetre. One function of the hollow tube 40 is to locate the aerosol-forming substrate 30 towards the distal end 23 of the rod 21 so that it can be contacted with a heating element. The hollow tube 40 acts to prevent the aerosol-forming substrate 30 from being forced along the rod towards the mouth-end 22 when a heating element is inserted into the aerosol-forming substrate 30.

(14) The transfer section 50 comprises a thin-walled tube of 18 millimetres in length. The transfer section 50 allows volatile substances released from the aerosol-forming substrate 30 to pass along the rod 21 towards the mouth end 22. The volatile substances may cool within the transfer section to form an aerosol.

(15) The mouthpiece filter 60 is a conventional mouthpiece filter formed from cellulose acetate, and having a length of 7.5 millimetres.

(16) The four elements identified above are assembled by being tightly wrapped within a cigarette paper 70. The paper in this specific embodiment is a standard cigarette paper having standard properties or classification. The paper in this specific embodiment is a conventional cigarette paper. For example, the paper may be a porous material with a non-isotropic structure comprising cellulose fibers (crisscross s of fibers, interlinked by H-bonds), fillers and combustion agents. The filler agent may be CaCO3 and the burning agents can be one or more of the following: K/Na citrate, Na acetate, MAP (mono-ammonium phosphate), DSP (di-sodium phosphate). The final composition per squared meter may be approximately 25 g fiber+10 g Calcium carbonate, +0.2 g burning additive. The porosity of the paper may be between 0 to 120 coresta. The interface between the paper and each of the elements locates the elements and defines the rod 15 of the smoking article 1.

(17) The interface between the paper and each of the elements locates the elements and defines the rod 21 of the smoking article 20. Although the specific embodiment described above and illustrated in FIG. 1 has five elements assembled in a cigarette paper, it will now be clear to one of ordinary skill in the art that a smoking article according to the embodiments discussed here may have additional elements and these elements may be assembled in an alternative cigarette wrapper or equivalent. Likewise, a smoking article according to the invention may have fewer elements. Moreover, if will now be apparent to one of ordinary skill in the art that various dimensions for the elements discussed in relation to the various embodiments discussed here are merely exemplary, and that suitable, alternative dimensions for the various elements may be chosen without deviating from the spirit of the embodiments discussed herein.

(18) The aerosol-generating device 10 comprises a sheath 12 for receiving the smoking article 20 for consumption. A heating element 90 is located within the sheath 12 and positioned to engage with the distal end 23 of the smoking article. The heating element 90 is shaped in the form of a blade terminating in a point 91.

(19) As the smoking article 20 is pushed into the sheath 12 the point 91 of the heating element 90 engages with the aerosol-forming substrate 30. By applying a force to the smoking article, the heating element 90 penetrates into the aerosol-forming substrate 30. Once properly located, further penetration is prevented as the distal end 23 of the smoking article 20 abuts an end wall 17 of the sheath 12, which acts as a stop.

(20) When the smoking article 20 is properly engaged with the aerosol-generating device 10, the heating element 90 has been inserted into the aerosol-forming substrate 30.

(21) FIG. 2 illustrates a heating element 90 as comprised in the aerosol-generating device 10 of FIG. 1 in greater detail. The heating element 90 is substantially blade-shaped. That is, the heating element has a length that in use extends along the longitudinal axis of a smoking article engaged with the heating element, a width and a thickness. The width is greater than the thickness. The heating element 90 terminates in a point or spike 91 for penetrating a smoking article 20. The heating element comprises an electrically insulating substrate 92, which defines the shape of the heating element 90. The electrically insulating material may be, for example, alumina (Al.sub.2O.sub.3), stabilized zirconia (ZrO.sub.2). It will now be apparent to one of ordinary skill in the art that the electrically insulating material may be any suitable electrically insulating material and that many ceramic materials are suitable for use as the electrically insulating substrate.

(22) Tracks 93 of an electrically conductive material are plated on a surface of the insulating substrate 92. The tracks 93 are formed from a thin layer of platinum. Any suitable conductive material may be used for the tracks, and the list of suitable materials includes many metals, including gold, that are well known to the skilled person. One end of the tracks 93 is coupled to a power supply by a first contact 94, and the other end of the tracks 93 is coupled to a power supply by a second contact 95. When a current is passed through the tracks 93, resistive heating occurs. This heats the entire heating element 90 and the surrounding environment. When a current passing through the tracks 93 of the heating element 90 is switched off, there is no resistive heating and the temperature of the heating element 90 is swiftly lowered.

(23) Heater element 90 also includes collar 96. The collar 96 may be formed of a suitable material that allows for conduction of electricity, so long as the design of the collar 96 is also selected to minimize resistive heating. In one embodiment, when the tracks 93 are formed of platinum or a platinum alloy, the collar 96 may be formed of gold or silver, or an alloy including either. Because of the difference in the electrical resistivity of the collar 96 material, less heat is generated over the collar area and the collar 96 sees a lower average temperature than the portion of heater element 90 including tracks 96. In another embodiment, the collar 96 may be formed of an insulating material, such as a ceramic or other appropriate insulator.

(24) Collar 96 provides a cold zone as compared to the average surface temperature of the portion of heater element 90 that includes tracks 93. For example, the average temperature of the cold zone may be greater than 50 degrees centigrade cooler than the average surface temperature of the portion of heater element 90 including the tracks 93 during operation. Including the collar 96 may provide a number of benefits including that it reduces the temperature seen by any on-board electronics. In addition, collar 96 protects against the melting or degradation of various portions of device 10, when materials such as plastic are used in the device. The collar also reduces condensation at the distal end of the device because such aerosol is cooled as it passes over the collar 96. This reduction of condensation seen by electronics (not show) and contacts 94 and 95 included in the device 10 helps protect such elements.

(25) The aerosol-generating device 10 comprises a power supply and electronics (not shown) that allow the heating element 90 to be actuated. Such actuation may be manually operated or may occur automatically in response to a user drawing on the smoking article. When the heating element is actuated, the aerosol-forming substrate is warmed and volatile substances are generated or evolved. As a user draws on the mouth end of the smoking article 20, air is drawn into the smoking article and the volatile substances condense to form an inhalable aerosol. This aerosol passes through the mouth-end 22 of the smoking article and into the user's mouth.

(26) In a specific embodiment (schematically illustrated in FIG. 5) an aerosol-generating device comprises a processor or controller 19 coupled to a heating element 90 to control heating of the heating element. The controller 19 is programmed to actuate the heating element through a first thermal cycle in which the temperature of the heating element is raised to a first temperature of 375 degrees centigrade. This allows the formation of an aerosol from an aerosol-forming substrate disposed in proximity to the heating element. The controller is further programmed to actuate the heating element through a second thermal cycle in which the temperature of the heating element is raised to a second temperature of 550 degrees centigrade for a period of 30 seconds. This allows organic material deposited on the heating element to decompose or pyrolyse.

(27) A specific embodiment of a method of using an aerosol-generating device will now be described with reference to FIGS. 1 and 4. FIG. 4 is a flow diagram setting out the steps carried out in an embodiment of the inventive method.

(28) Step 1(Reference numeral 100 in FIG. 4): A heating element 90 of an aerosol-generating device 10 is brought into contact with an aerosol-forming substrate 30 contained within a smoking article 20. In order to achieve this, the smoking article 20 is inserted into a sheath 12 of the aerosol-generating device 10. A heating element 90 is located within the sheath 12, and projects from a bottom surface 17 of the sheath 12 such that it may be inserted into any smoking article that is received in the sheath. As the smoking article 20 is slid into the sheath 12, a tip or point 91 of the heating element 90 contacts a distal end 23 of the smoking article. Further movement of the smoking article towards the bottom end 17 of the sheath causes the heating element 90 to penetrate into an aerosol-forming substrate located at the distal end 23 of the smoking article 20. Once the smoking article has been fully inserted into the sheath, the distal end 23 of the smoking article abuts the bottom surface 17 of the sheath 12 and the heating element has reached maximum penetration.

(29) Step 2: (Reference numeral 200) As the user draws or puffs on a mouth end 22 of the smoking article 20, sensors in the aerosol-generating device 10 may detect this event. In the event of detecting a user puffing or drawing, a controller 19 sends instructions that activate the heating element to heat to a first temperature. A current is passed through conductive tracks 93 disposed on the heating element, which results in resistive heating of the heating element. The first temperature is 375 degrees centigrade, which is sufficient to liberate volatile compounds from the aerosol-forming substrate 20. These volatile compounds condense to form an inhalable aerosol, which is drawn through the smoking article and into a user's mouth. Alternatively, a continuous heating may be used during operation of device 10 and detection of a user puffing or drawing may be used to trigger heating to compensate for any temperature drop of heater element 90 during the user puffing or drawing.

(30) Step 3: (Reference numeral 300) When the user stops drawing or ends his puff on the mouth end 22 of the smoking article 20, sensors in the aerosol-generating device detect this event. The controller 19 sends instructions to switch off the current passing through the heating element 90. This stops the resistive heating of the tracks 93, and the temperature of the heating element is swiftly lowered. As the temperature is lowered, aerosol stops being generated. Alternatively, during the continuous heating discussed above, the controller 19 may instead simply reduce the amount of energy seen during the user puffing or drawing, based on a desired set point temperature.

(31) If the aerosol-forming substrate 30 still contains volatile compounds, the user may take another puff on the smoking article 20 and repeat step 2 (indicated by arrow 350 in FIG. 4). Steps 2 and 3 may be repeated as often as necessary to consume the smoking article.

(32) Step 4: (Reference numeral 400) When the user has finished with the smoking article 20, for example when no more aerosol is generated on heating the aerosol-forming substrate 30, the smoking article 20 is removed from the sheath 12 of the aerosol-generating apparatus 10. This means that the heating element 90 is removed from contact with the aerosol-forming substrate 30. Almost inevitably, the heating element 90 will have become soiled with some deposits or residues derived from the aerosol-forming substrate 30. Such deposits may impair performance of the heating element. For example, deposits on the heating element may inhibit thermal transfer between the heating element and the aerosol-forming substrate. Deposits on a heating element may also inhibit temperature sensing when the heating element is utilized to sense temperature. Deposits on a heating element may also generate bitter compounds on repeated heating, which may impair the flavour of aerosols generated when consuming subsequent smoking articles.

(33) If a user feels that the deposits on the heating element are at a sufficiently low level, he may decide to consume a further smoking article. In this case, steps 1 to 4 may be repeated. This is indicated by the arrow 450 in FIG. 4.

(34) Step 5: (Reference numeral 500) If a user believes that the heating element is in need of cleaning, he then presses a button (not shown) on the aerosol-generating device 10 that causes the controller to activate a cleaning cycle. During the heating cycle, current is passed through the tracks 93 of the heating element 90 to raise the temperature of the heating element to a second temperature. This second temperature is 550 degrees centigrade, a temperature at which deposits on the heating element can thermally degrade or pyrolyse. The heating element 90 is held at a temperature of 550 degrees centigrade for a period of 30 seconds to thermally liberate the organic compounds deposited on the heating element 90.

(35) FIG. 3A illustrates a portion of an aerosol-generating device. This figure illustrates a heating element 90 after use of the device to consume a smoking article. That is, FIG. 3A illustrates a heating element 90 of an aerosol-generating device after step 4 of the method described above. It can be seen that the heating element 90 is coated in organic deposits, which appear to be black in FIG. 3A.

(36) FIG. 3B illustrates the same heating element as illustrated in FIG. 3A after the performance of a cleaning cycle as described by step 5 above. That is, the heating element 90 of FIG. 3A has been heated to a temperature of 550 degrees centigrade and held at that temperature for a period of 30 seconds. It can be seen that the black deposits visible in FIG. 3A have been removed and the heating element has been cleaned. In FIG. 3B, the heating element now has a shiny appearance where the organic deposits have been removed.

(37) After cleaning, the aerosol-generating device is ready for use. Steps 1 to 5 may be repeated. This is indicated by the arrow 550 in FIG. 4.

(38) In the embodiment of a method described above, the step of heating the heating element to a first temperature to produce an aerosol occurred when the device detected a user taking a puff. In other embodiments, a user may manually activate the heating element to produce an aerosol.

(39) In the embodiment of a method described above, the step of initiating a cleaning cycle was manually activated. In other embodiments, a cleaning cycle may be automatically triggered every time a smoking article is removed from the aerosol-generating device.

(40) The aerosol-generating device 10 may be used in conjunction with a docking station (not illustrated). A docking station may be used, for example, to recharge batteries used to power the aerosol-generating device. FIG. 6 illustrates an embodiment of a method that may be used when the aerosol-generating device coupled to a docking station.

(41) Steps 1 to 4 are the same as described above in relation to FIG. 4. FIG. 6 uses the same reference numerals for steps that are the same as previously described.

(42) Step 5: (Reference numeral 600) The aerosol-generating device 10 is coupled to a docking station (not shown) for receiving the device.

(43) Step 6: (Reference numeral 700) When the aerosol-generating device 10 is detected, a controller activates a cleaning cycle. During the heating cycle, current is passed through tracks 93 of the heating element 90 to raise the temperature of the heating element to a second temperature. This second temperature is 550 degrees centigrade, a temperature at which deposits on the heating element can thermally degrade or pyrolyse. The heating element 90 is held at a temperature of 550 degrees centigrade for a period of 30 seconds to thermally liberate the organic compounds deposited on the heating element 90. In one embodiment, the controller may be triggered from a signal from the docking station indicating that the device has not been cleaned after a predetermined number of uses, e.g., the user has contacted the heating element 90 with 10 or more times without performing a cleaning cycle. The controller 19 may then force the user to perform a cleaning cycle. For example, the user may be prohibited from activating heater element 90 unless a cleaning cycle is first performed. Controller 19 itself may contain instructions for locking the device 10 or the docking station may maintain information regarding use and provide the locking and unlocking instructions to the controller 19.

(44) Step 7: (Reference numeral 800) The aerosol-generating device is removed from the docking station. The aerosol-generating device is ready for use. Steps 1 to 7 may be repeated. This is indicated by the arrow 850 in FIG. 6.

(45) The exemplary embodiments described above illustrate but do not limit the invention. In view of the above discussed exemplary embodiments, other embodiments consistent with the above exemplary embodiments will now be apparent to one of ordinary skill in the art.