Abstract
An aerosol-generating system is provided, including a liquid storage portion including a container configured to hold a liquid aerosol-generating substrate and defining an opening; a heater assembly extending across the opening along a plane transverse to the opening and including at least one electrically operated heating element; and a first channel defining a first flow route, a portion of the first channel being arranged with respect to the plane transverse to the opening such that at least a portion of the first channel is configured to direct air originating from outside the system to impinge against and across a surface portion of the at least one electrically operated heating element. A method for guiding an airflow in an electrically operated aerosol-generating system is also provided.
Claims
1.-14. (canceled)
15. An aerosol-generating system, comprising: a liquid storage portion comprising a container configured to hold a liquid aerosol-generating substrate and defining an opening; a heater assembly extending across the opening along a plane transverse to the opening and comprising at least one electrically operated heating element; and a first channel defining a first flow route, a portion of the first channel being arranged with respect to the plane transverse to the opening such that at least a portion of the first channel is configured to direct air originating from outside the system to impinge against and across a surface portion of the at least one electrically operated heating element.
16. The aerosol-generating system according to claim 15, further comprising a second channel defining a second flow route, wherein the first flow route and the second flow route merge prior to or along said portion of the first channel.
17. The aerosol-generating system according to claim 15, wherein said portion of the first channel is orthogonal to the plane transverse to the opening.
18. The aerosol-generating system according to claim 15, the heater assembly further comprising a plurality of heating elements through which a common plane passes.
19. The aerosol-generating system according to claim 15, further comprising a capillary medium aligned with the opening and in contact with the heating assembly, wherein the liquid aerosol-generating substrate is drawn via the capillary medium to the at least one electrically operated heating element.
20. The aerosol-generating system according to claim 19, wherein the at least one electrically operated heating element comprises a plurality of electrically conductive filaments.
21. The aerosol-generating system according to claim 15, further comprising a main housing and a cartridge that is removably coupled to the main housing, wherein the liquid storage portion and the heater assembly are disposed in the cartridge and the main housing comprises a power supply.
22. The aerosol-generating system according to claim 21, wherein the main housing further comprises at least one inlet configured to draw ambient air from outside the system and at least a first portion of the first channel corresponding to a flow path relative to the heater assembly.
23. The aerosol-generating system according to claim 21, wherein the cartridge further defines at least one inlet configured to draw ambient air from outside the system and at least a first portion of the first channel corresponding to a flow path relative to the heater assembly.
24. The aerosol-generating system according to claim 23, wherein the cartridge further defines a second portion of the first channel in fluid communication with the first portion.
25. The aerosol-generating system according to claim 22, wherein the main housing defines a second portion of the first channel in fluid communication with the first portion.
26. The aerosol-generating system according to claim 15, wherein a portion of the first channel is dimensioned and configured so as to transport air away from the heater assembly along an elongate channel between the liquid storage portion and an interior surface portion of the cartridge.
27. The aerosol-generating system according to claim 15, wherein a portion of the first channel is dimensioned and configured so as to transport air away from the heater assembly along a bend.
28. A method for guiding an airflow in an electrically operated aerosol-generating system, the method comprising: supplying an aerosol-generating substrate; directing air originating from outside the system against and along a heating element aligned with an opening in a container containing the aerosol generating substrate; and conveying a generated aerosol to a downstream end of the system.
Description
[0027] The invention is further described with regard to embodiments, which are illustrated by means of the following drawings, wherein:
[0028] FIG. 1 shows an aerosol-generating system employing a flow of air according to embodiments consistent with the present disclosure;
[0029] FIG. 2 shows an aerosol-generating system employing a flow of ambient air and vapor-entrained air according to other embodiments consistent with the present disclosure
[0030] FIG. 3A shows the assembled form, in cross section, of an aerosol-generating system employing a flow of ambient air and vapor-entrained air according to another embodiment consistent with the present disclosure;
[0031] FIG. 3B shows a broken apart or unassembled form, in cross section, of the embodiment of FIG. 3A;
[0032] FIG. 4 shows the cooling effect of different airflows on different heating element;
[0033] FIG. 5 shows a temperature curve based on an exemplary flow impingement pattern and substantially planar arrangement of powered heating filaments forming a mesh heater;
[0034] FIG. 6 shows temperature curves at the outlet of the mouthpiece;
[0035] FIG. 7 shows average vapor saturation curves at the outlet of the mouthpiece;
[0036] FIG. 8 shows the ratio of droplet diameters at the outlet of the mouthpiece for the air airflow geometries of FIGS. 1 and 2 with the same heater configuration and applied power;
[0037] FIG. 9a, 9b show heating elements as may be used in the smoking system according to the invention.
[0038] In FIG. 1 a cartridge 4 and mouthpiece 1 embodiment for an aerosol generating smoking system is shown. An elongate main housing 5 accommodates a cartridge with a tubular shaped container 4 containing an aerosol-forming substrate, for example a liquid containing capillary material 41. The container 4 has an open proximal end 42. A heater 30, is arranged to cover the open proximal end of the container 4. In some embodiments, the heater 30 is a fluid permeable heater having a substantially flat profile. In an embodiment, the heater 30 is a substantially flat mesh arrangement of electrically heated filaments. The filaments or other heating element(s) of heater 30 may or may not be in direct physical contact with the aerosol-forming substrate 41. A mouthpiece 1 having a substantially tubular shaped elongate body 15 is aligned with the main housing, the container 4 and the heater 30. The elongate body 15 has an open distal end facing the heater 30.
[0039] The embodiment shown in FIG. 1 comprises a first channel 10 which defines a first flow route in the mouthpiece 1. Incoming ambient air 20 enters the first flow route via inlet 100 and follows the flow path defined by first channel 10. This flow path brings the ambient air into impingement against the center of heater 30. Preferably, the impingement occurs at the geometric center of the heater and at angle at or close to ninety degrees (i.e., the flow is substantially orthogonal to a plane containing heated surface(s) of heater 30. The vaporized liquid produced by heater 30 is entrained as an aerosol by the air flow 20, and from there the air is delivered to outlets 12 at a proximal end or mouth end of the mouthpiece 1, to be inhaled when a consumer puffs. In some embodiments, a single channel as first channel 10 may be alone sufficient for drawing a desired amount of ambient air with each puff. In other embodiments, it may be desirable to include two or more inlets and associated channels. For example, a second channel (not shown) may be provided to draw in additional air such that the ambient air flows are combined before impinging upon heater 30.
[0040] In the embodiment of FIG. 1, inlet 100 into the first flow route is an opening or bore hole in the mouthpiece 1 located at a distal half of the elongate body 15 of the mouthpiece 1. The first flow route in an upstream second channel portion 101 runs in the elongate body parallel to the circumference of the elongate body to the proximal end of the mouthpiece. In a radially inwardly directing portion 102 of the first channel 10, the first airflow 20 is directed to the center of the elongate body and in a centrally arranged portion 103 of the first channel the first airflow 20 is directed to the heater 30 to impinge to the center 31 of the heater 30. The first airflow 20 passes over the heater 30 and spreads radially outwardly to several longitudinal end portions 104 of the first channel 10. The longitudinal end portions 104 are regularly arranged along the circumference within the elongate body.
[0041] In this embodiment the flow route and corresponding channel is arranged entirely within the mouthpiece 1 of the aerosol generating system. One or more additional flow routes defined, for example, by symmetrically arranged channels, may be defined in the mouthpiece such that the flows merge by the time the ambient air reaches the centrally arranged portion 103.
[0042] In FIG. 2 an embodiment of a cartridge 4 with heater 30 arranged at the bottom of the cartridge covering an open distal end 43 of the container 41 is illustrated. In this embodiment, first inlet 100A is arranged in the main housing 5 and the ambient air 20A is directly led in a radially inwardly directing portion 102A of the first channel to the center of the main housing. In addition, a second inlet 100B is arranged in the main housing 5 and the ambient air 20B is directly led in a radially inwardly directing second channel 102B to the center of the main housing 5. The first and second channels merge to form a single flow within centrally arranged portion 103 of the first channel, and the merged air flow is directed to impinge perpendicularly onto the heater 30. The air then passes the heater 30, entrains aerosol caused by heating the liquid in the aerosol-forming substrate 41 through the heater 30. The aerosol containing air is led to the proximal end of the cartridge 4 after entering a ninety degree bend into one of several elongated, longitudinal portions 105 of first channel 10 arranged between and along cartridge 4 and an interior surface of main housing 5.
[0043] There, the aerosol containing airflow is guided to and out of a single centrally arranged opening 52 in the main housing 5. A mouthpiece (not shown) may be arranged adjacent to and aligned with the main housing. Preferably, the mouthpiece then also has a centrally arranged opening and end portion 104 of first channel 10 to receive the aerosol containing airflow and guide it to a single outlet opening 12 in the proximal end of the mouthpiece 1.
[0044] FIGS. 3A and 3B depict an additional embodiment of a system 8 that includes a cartridge 4 with heater 30 arranged at the bottom of the cartridge covering an open distal end 43 of the cartridge housing 41 is illustrated. In this embodiment, first inlet 100A is arranged in the main housing 5 and the ambient air 20A is directly led in a radially inwardly directing portion 102A of the first channel to the center of the main housing. In addition, a second inlet 100B is arranged in the main housing 5 and the ambient air 20B is directly led in a radially inwardly directing second channel 102B to the center of the main housing 5. The first and second channels merge to form a single flow within centrally arranged portion 103 of the first channel, and the merged air flow is directed to impinge perpendicularly onto the heater 30. Conductive contacts 60, which are electrically coupled to a power source (not shown) located within main housing 5 are in electrical contact with corresponding contacts of heater 30, and supply the heater with the electrical current.
[0045] The air arriving via first channel portion 103 passes the heater 30 and entrains vapor and condensed droplets caused by heating the liquid in the aerosol-forming substrate 41 through the heater 30. The aerosol so generated is led to the proximal end of the cartridge 4 after entering a ninety degree bend 45a, 45b into one of several elongate longitudinal portions 105 of first channel 10 arranged between and along cartridge 4. Thereafter, the aerosol guided to and out of a centrally arranged outlet opening 12 in the proximal end of the mouthpiece 1.
[0046] FIG. 3B is broken apart to show the system 8 in greater detail. It can be seen that the cartridge housing 4, comprising sections 4A and 4B, receives a liquid containing high retention material or high release material (HRM) 41 which serves as a liquid reservoir and to direct liquid towards the heater 30 for evaporation at the heater. A capillary disc 44, for example a fiber disc, is arranged between HRM 41 and heater 30. The material of the capillary disc 44 may be more heat resistant than the HRM 41 due to its closeness to the heater 30 in order to provide thermal isolation and protect the HRM itself from decomposition. The capillary disc 44 is kept wet with the aerosol-forming liquid of the HRM to secure provision of liquid for vaporization if the heater is activated.
[0047] The data shown in FIG. 4 demonstrate the relationship between air flow rate and cooling of the mesh heater. Cooling rates were measured using different mesh heaters: Reking (45 micrometers/180 per inch), Haver (25 micrometers/200 per inch) and 3 strips Warrington (25 micrometers/250 per inch). Measurement data for the Reking heater are indicated by crosses, measurement data for the Haver heater are indicated by circles and measurement data for the 3 strips Warrington heater are indicated by triangles. All heaters were operated at three Watt. Temperature was measured with a thermocouple coupled to the heaters. Increasing the flow rate as indicated on the x-axis in liter per minute [L/min] results in a lower measured temperature on the mesh heater. Typical sizes of airflows in aerosol-generating systems can be approximated by standard smoking regimes, for example the Health Canada smoking regime, which leads to significant cooling of the heater. Exemplary smoking regimes such as Health Canada draw 55 ml of a mix of air and vapour over 2 seconds. An alternative regime is 55 ml over 3 seconds. Neither exemplary smoking regime mimics behaviour precisely but instead act as a proxy to what an average user would draw. To compensate for the higher cooling rate associated with a high rate of air flow and perpendicular impingement of air onto the surface(s) of heater 30, it may be necessary to supply increases levels of current to the heating element(s) thereof.
[0048] In the graph of FIG. 5, average temperatures at the heater versus time during one puff is shown. Curve 60 represents reference temperature data for the heater, where the total airflow is directed to the heater. For the reference data the heater had been heated with 5 Watt.
[0049] FIG. 6 shows the effect, on the temperature of the aerosol carrying airflow at the outlet of the mouthpiece during one puff, of directing the vapor-entrained airflow along the portion of the cartridge housing 4 containing the liquid storage portion 41. The data refers to embodiments where ambient airflow is brought in through outlets in a main housing, perpendicularly impinged against the surface of a substantially planar heater arranged in a transverse plane across a cartridge opening distal to the inhalation end of the mouthpiece, and bent around a downstream flow channel to carry the airflow toward the inhalation end of the mouthpiece, as shown in FIGS. 2 and 3A. Temperature curve 61 represents outlet air temperatures for a heater powered with 5 Watt with the total airflow impinging on the heater and exiting according to the arrangement shown in FIG. 1. Temperature curve 71 represents outlet air temperatures for a heater also powered with 5 Watts, but where the airflow is passed in close proximity to the liquid storage portion to promote cooling as shown in FIGS. 2 and 3A. There are significant lower temperatures of the aerosol carrying airflow at the proximal outlet of the main housing 5 and mouthpiece 1 in the arrangements of FIGS. 2 and 3A due to the transfer of heat to the zone of the cartridge housing proximate the liquid storage portion. Typically ‘fresh’ air mixed into the aerosol carrying airflow is at room temperature.
[0050] Significant difference may also be seen in the ratio of vapour pressure to the saturation pressure (Pvapor/Psaturation) of a glycerol solution at the outlet of the mouthpiece during one puff. This ratio is shown in FIG. 7. Curve 72 refers to pressure data at the outlet for the heater powered with 5 Watt, with the total airflow directed to the heater according to the arrangements of FIGS. 2 and 3A. Curve 62 refers to pressure data at the outlet for the heater powered with 5 Watt with the total airflow impinging on the heater according to the arrangement of FIG. 1. This represents a larger degree of super saturation of the glycerol solution, which favours aerosolization with smaller droplets. Simulation clearly predicts smaller droplet sizes for the cooler vapour of the split airflow embodiment compared to vapour of non-split or total airflow embodiments. These simulation data 67 are shown in FIG. 8 for one puff at the outlet of the mouthpiece. Y-Axis represents the ratio of droplet diameters for split airflow to total airflow systems. The ratios are calculated and shown as d_split/d_ref=T*Ln(S) ref/T*Ln(s) split versus time (in seconds) during one puff on the aerosol-generating system where T is the temperature expressed in degrees Kelvin and S is the saturation ratio which is a function of Pv and P(T).
[0051] FIG. 9a is an illustration of a first heater 30. The heater 30 is a fluid permeable assembly of heating elements and comprises a mesh 36 formed from 304L stainless steel, with a mesh size of about 400 Mesh US (about 400 filaments per inch). The filaments have a diameter of around 16 micrometer. The mesh is connected to electrical contacts 32 that are separated from each other by a gap 33 and are formed from a copper or tin foil having a thickness of around 30 micrometer. The electrical contacts 32 are provided on a polyimide substrate 34 having a thickness of about 120 micrometer. The filaments forming the mesh define interstices between the filaments. The interstices in this example have a width of around 37 micrometer, although larger or smaller interstices may be used. Using a mesh of these approximate dimensions allows a meniscus of aerosol-forming substrate to be formed in the interstices, and for the mesh of the heating element to draw aerosol-forming substrate by capillary action. The open area of the mesh, that is, the ratio of the area of interstices to the total area of the mesh is advantageously between 25 percent and 56 percent. The total resistance of the heating element is around 1 Ohm. The mesh provides the vast majority of this resistance so that the majority of the heat is produced by the mesh. In this example the mesh has an electrical resistance more than 100 times higher than the electrical contacts 32.
[0052] The substrate 34 is electrically insulating and, in this example, is formed from a polyimide sheet having a thickness of about 120 micrometer. The substrate is circular and has a diameter of 8 millimeter. The mesh is rectangular and has side lengths of 5 millimeter and 2 millimeter. These dimensions allow for a complete system having a size and shape similar to a convention cigarette or cigar to be made. Another example of dimensions that have been found to be effective is a circular substrate of diameter 5 millimeter and a rectangular mesh of 1 millimeter times 4 millimeter.
[0053] FIG. 9b is an illustration of an alternative heater assembly. In the heating element of FIG. 8b, the electrically conductive, heat-producing filaments 37 are bonded directly to substrate 34 and the contacts 32 are then bonded onto the filaments. The contacts 32 are separated from each other by insulating gap 33 as before, and are formed from copper foil of a thickness of around 30 micrometer. The same arrangement of substrate filaments and contacts can be used for a mesh type heater as shown in FIG. 8a. Having the contacts as an outermost layer can be beneficial for providing reliable electrical contact with a power supply.
[0054] Returning to FIGS. 1 to 3B, capillary material 41 is advantageously oriented in the housing 4 to convey liquid to the heater 30. When the cartridge is assembled, the heater filaments 36, 37, 38 may be in contact with the capillary material 41 and the aerosol-forming substrate can be conveyed directly to the mesh heater.
[0055] In use the heating elements operate by resistive heating. Current is passed through the filaments 36,37,38, under the control of control electronics (not shown), to heat the filaments to within a desired temperature range. The mesh or array of filaments has a significantly higher electrical resistance than the electrical contacts 32,35 and electrical connectors (not shown) so that the high temperatures are localised to the filaments. The system may be configured to generate heat by providing electrical current to the heating element in response to a user puff or may be configured to generate heat continuously while the device is in an “on” state.
[0056] Different materials for the filaments may be suitable for different systems. For example, in a continuously heated system, graphite filaments are suitable as they have a relatively low specific heat capacity and are compatible with low current heating. In a puff actuated system, in which heat is generated in short bursts using high current pulses, stainless steel filaments, having a high specific heat capacity may be more suitable.
[0057] In the above cartridge systems as described in FIGS. 1 to FIG. 3B, the cartridge housing 4 may also be a separate cartridge container in addition to the cartridge housing as described for example in FIG. 1. Especially, a liquid containing cartridge is a pre-manufactured product, which may be inserted into a cartridge housing provided in the aerosol generating system for receiving the pre-manufactured cartridge.
