GB2588113A

GB2588113A - Apparatus for testing a tobacco heating product

Info

Publication number: GB2588113A
Application number: GB1914459.1A
Authority: GB
Inventors: Cole Akinwande; Tindall Ian
Original assignee: MPRD Ltd
Current assignee: MPRD Ltd
Priority date: 2019-10-07
Filing date: 2019-10-07
Publication date: 2021-04-21
Anticipated expiration: 2039-10-07
Also published as: GB201914459D0; GB2588113B

Abstract

An apparatus 24 (i.e. analytical smoking or vaping machine) for testing a tobacco heating product (THP) 1, comprising: means 32 for puffing the product 1; means 40 for sensing a temperature of a gas downstream of the product 1; and means 38 for generating a status signal indicating a heating status of the product 1 in dependence on the sensed temperature. The apparatus 24 may also remove particles from the aerosol drawn from the product 24, and/or capture particles for further analysis. The means 40 (i.e. thermocouple sensor, thermistor, resistance thermometer, silicon bandgap/optical/solid-state temperature sensor) may produce a temperature signal depending on the difference between the temperature of the gas stream and ambient temperature, wherein said temperature signal is compared to a threshold value. The control unit 36 may cease or modify puffing the product 1, and/or may output an alarm, in dependence on the status signal. The product 1 may comprise a tobacco heated stick 3 heated by an external electrical heating system, an internal electrical heating system, a sustainably self-heating tip (i.e. carbon tip), or by means of a chemical reaction.

Description

APPARATUS FOR TESTING A TOBACCO HEATING PRODUCT

The present invention relates to an apparatus for testing a tobacco heating product, and in particular a testing apparatus which can detect a heating status of the product. The present invention has particular but not exclusive application in detecting when the tobacco heating product has reached end of life and/or fails to heat correctly.

Tobacco heating products (THPs) are devices that heat tobacco without combustion or smouldering to release an aerosol which the user inhales. THPs come in various forms, including devices which heat the tobacco by electronic means, or products in which heat is provided by a carbon tip that is separated from the tobacco.

With tobacco heating products appearing in the marketplace, there is an increasing need to analyse the emissions produced by such products for public health, regulatory and quality control purposes. Analytical testing machines have therefore been developed for such analysis. Such machines typically puff one or more THPs in order to produce an aerosol which can then be analysed.

When testing the emissions of THPs on analytical testing machines, gases or compounds in the aerosol are analysed and the yield (amount of material) is typically expressed as mass per unit volume puffed. However, if the product is puffed after the generation of these compounds ceases at the end of a smoking session, then the concentration per unit volume of puffs may be erroneously under reported. When carrying out such tests, it is therefore important to know when the product has reached the end of its life. In the case of devices that use electronic heating, this could be software defined number of puffs or "session duration'. In the case of carbon tipped products it is when the carbon ceases to heat. Typically, an estimate of the end of life of the product is made based on the number of puffs expected from the product. However, in both types of product, there may be some uncertainty as to exactly when the session of smoking is complete.

Another problem which may arise in analysing some electronic tobacco heating products is that the device may require a button to be pressed for each puff or to initiate a puffing cycle. Machines are available for analytical smoking that incorporate button pressing mechanisms. However, any failure in the mechanism or its interface with the button could lead to the button not being depressed or being incompletely depressed. This could lead to puffs being taken when the product is not producing aerosol, in which case any calculation of yield of material per unit volume would be flawed.

A further problem which may arise in analysing tobacco heating products is that the product may fail to adequately heat the tobacco due to a fault in the product. For example, in the case of an electronic tobacco heating product, the heater may fail to make proper contact with the tobacco. In the case of a carbon tipped product, a crack may develop in the carbon tip which may compromise the thermal connection to the tobacco column. In either case, the calculation of yield from the product may be flawed.

It would therefore be desirable to provide a technique for determining the status of a tobacco heating product, and in particular for determining when the tobacco heating product ceases to heat the tobacco and/or fails to heat the tobacco correctly.

According to a first aspect of the present invention there is provided apparatus for testing a tobacco heating product, the apparatus comprising: means for puffing the tobacco heating product; means for sensing a temperature of a gas stream drawn from the tobacco heating product; and means for generating a status signal indicating a heating status of the tobacco heating product in dependence on the sensed temperature.

The present invention may provide the advantage that, by sensing a temperature of a gas stream drawn from the tobacco heating product and generating a signal indicating a heating status of the tobacco heating product in dependence on thereon, it may be possible to determine when the tobacco heating product ceases to heat or fails to heat the tobacco. This may allow a more accurate calculation of yield of material per unit volume when analysing emissions from the product.

The emissions produced by a tobacco heating product typically comprise an aerosol, that is, a suspension of solid and/or liquid particles in air or another gas.

The process of forming the aerosol in the product requires heated air to form aerosol droplets. Thus, the aerosol, including gases from the air (nitrogen, oxygen, carbon monoxide etc.), leaves the tobacco heating product at an elevated temperature with respect to its surroundings.

Embodiments of the present invention are based on the realisation that the gas stream forming part of the aerosol leaving the tobacco heating product has a temperature which is elevated above ambient temperature in order to form the aerosol. Thus, the temperature of the gas stream drawn from the tobacco heating product can provide an indication of the heating status of the product.

In principle, it would be possible to detect the temperature of the aerosol as it leaves the tobacco heating product. However, this may increase the path length from the tobacco heating product to a collector of aerosol particles, reducing the collection efficiency and potentially resulting in an underestimate of the aerosol yield produced. Furthermore, condensation of aerosol particles on the temperature sensor may reduce its reliability. Thus, the temperature sensing means is preferably situated in the gas stream remotely from the tobacco heating product, preferably after removal of the majority of the particulate matter.

Preferably the tobacco heating product is of a type which produces an aerosol. The apparatus may be arranged to remove at least some particles from an aerosol drawn from the tobacco heating product to yield the gas stream. Thus, the apparatus may be arranged to sense the temperature of the gas stream with at least some particles in the aerosol removed. For example, at least some solid particles and/or liquid droplets in the aerosol may be removed.

Preferably the apparatus comprises means for capturing at least some particles in an aerosol drawn from the tobacco heating product for further analysis. In this 35 case, the temperature sensing means may be located downstream of the capturing means. For example, at least part of the temperature sensing means may be located in a gas transfer tube for transferring gas from the capturing means to the puffing means.

The capturing means may be, for example, means for holding a particulate filter.

In this case, the temperature sensing means may be located downstream of the particulate filter. The particulate filter may be, for example, a filter pad, and may be arranged to capture solid and/or liquid particles for example above a predetermined diameter.

The above arrangements may help to improve the efficiency of capture and/or reduce the likelihood of aerosol particles affecting the temperature sensor.

The apparatus preferably comprises means for holding the tobacco heating product. The holding means is preferably arranged to create a seal around the product to enable a puff to be drawn through the product. For example, the holding means may be in the form of a lip seal, or any other appropriate means for creating a seal. The holding means may for example be arranged to hold a tobacco stick containing tobacco to be heated. The holding means may be, for example, connected to or part of a filter holder, or may be separate therefrom.

The means for sensing the temperature of the gas stream may comprise any suitable temperature sensor, such as a thermocouple sensor, a thermistor, a resistance thermometer, a silicon bandgap temperature sensor, an optical temperature sensor, a solid-state temperature sensor, or any other type of temperature sensor.

The means for generating a status signal may be arranged to compare the sensed temperature with a threshold value, and to output the status signal in dependence on a result of the comparison. For example, the temperature sensing means may be arranged to produce a temperature signal, and the means for generating a status signal may be arranged to compare the temperature signal with a threshold value and to output the status signal when the temperature signal exceeds the threshold value. The threshold value may be fixed, or may be varied depending on for example the type of tobacco heating product, the type of puff, time elapsed since the start of the smoking session, the number of puffs taken, historic testing results, or any other appropriate parameter. Furthermore, a number of different threshold values may be provided. In this case, the sensed temperature may be compared with each threshold value, and the status signal may depend on the result of each comparison.

If desired, it would be possible to compare an absolute value of the gas stream temperature with a threshold value. However, it has been found that, when testing a tobacco heating product, the temperature of the heated aerosol may not be uniform throughout the testing process. As a consequence, comparing the absolute value of the gas stream temperature with a threshold value may not always produce accurate results.

In a preferred embodiment, the temperature sensing means is arranged to sense a difference between the temperature of the gas stream and ambient temperature. Thus, the sensed temperature may be the temperature of the gas stream above ambient temperature.

For example, the temperature sensing means may be arranged to produce a temperature signal which depends on a difference between the temperature of the gas stream and ambient temperature, and the means for generating a status signal may be arranged to compare this temperature signal with a threshold value to output the status signal when the temperature signal exceeds the threshold value. In this case, the threshold value may correspond to a predetermined value of temperature above ambient temperature. This may help to produce more accurate results, particularly where the ambient temperature may vary.

In one embodiment, the temperature sensing means comprises a thermocouple sensor, and the thermocouple sensor comprises a sensing junction located in the gas stream and a reference junction located outside of the gas stream (for example, at ambient temperature). In this case, a differencing amplifier may amplify a voltage at the reference junction. Alternatively, the temperature sensing means may comprise a first temperature sensor in the gas stream and a second temperature sensor outside of the gas stream, and a differencing amplifier may amplify the difference in the signals produced by the two temperature sensors.

The signal indicating a heating status preferably indicates whether or not the tobacco heating product is heating the tobacco. Thus, the status signal may provide an indication of when the tobacco heating product ceases to heat the tobacco and/or fails to heat the tobacco.

In order to provide an accurate indication of heating status, the means for generating a status signal is preferably synchronised with the puffing means. For example, the means for generating a status signal may be arranged to output the status signal only during time periods corresponding to periods when the puffing means is drawing a puff. This can help to ensure that only the temperature during puffs is taken into account when determining the heating status.

The apparatus may further comprise a control unit for controlling the puffing means. The control unit may be arranged to control puffing parameters such as puff intervals, volumes, durations and shapes. Such parameters may be user defined and/or part of a routine programmed into the control unit.

The control unit may be arranged to produce a control signal for controlling the puffing means. In this case, the means for generating a status signal may be arranged to receive the control signal and to output the status signal in dependence on the control signal. For example, the means for generating a status signal may be arranged to output the status signal only during time periods corresponding to periods when the control signal has a value which causes the puffing means to draw a puff.

In practice, it has been found that there may be a delay between the control unit producing a signal which causes the puffing means to draw a puff, and a resulting rise in the sensed temperature of the gas stream. This delay may be caused by, amongst other things, the time taken for the gas stream to travel through the apparatus, and any time lag of the temperature sensing means.

In a preferred embodiment of the invention, the apparatus further comprises delay means for delaying a control signal from the control unit, and the means for generating a status signal is arranged to output the status signal in dependence on the delayed control signal. For example, the means for generating a status signal may be arranged to output the status signal only when the delayed control signal has a value which would cause a puff to be drawn. This can help to ensure that only the temperature during puffs is taken into account when determining the heating status.

The amount of delay may correspond to the time between the control unit issuing a control signal to cause the puffing means to draw a puff, and a resulting rise in the sensed temperature. The amount of time delay may be fixed, or may be varied depending on, for example, the type of tobacco heating product that is being tested, the type of puff being taken, historic testing results, the type of equipment being used, or any other appropriate parameter.

Preferably the control unit is arranged to cease or modify puffing of the tobacco heating product in dependence on the status signal. For example, puffing may be ceased when the status signal indicates that the tobacco heating product has ceased and/or failed to heat the tobacco. This may help to ensure that further puffs are not taken when the tobacco heating product is at end of life and/or faulty. This may help to avoid the yield from the tobacco heating product from being under reported. Alternatively, or in addition, the puffing conditions could be automatically modified to control the heating of the tobacco heating product (for example, to restore the heating efficiency of a carbon tipped tobacco heating product).

As well as or in addition to any of the above, the control unit may be arranged to output an alarm signal in dependence on the status signal. The alarm signal may indicate that the tobacco heating product has cease to heat the tobacco and/or failed to heat the tobacco correctly. The alarm signal may be used to provide, for example, a visual or audible alarm to a human operator who may then take appropriate action.

The tobacco heating product may be any type of product in which tobacco is heated to release an aerosol. For example, the tobacco heating product may comprise at least one of: a tobacco heated stick heated by means of an external electrical heating system; a tobacco heated stick heated by means of an internal electrical heating system; a tobacco heated stick heated by means of a tip that is sustainably self-heating such as a carbon tip; and a tobacco heating stick heated by means of a chemical reaction.

The apparatus is preferably an analytical smoking or vaping machine.

According to another aspect of the invention there is provided a method of testing a tobacco heating product in a testing apparatus, the method comprising: puffing the tobacco heating product; sensing a temperature of a gas stream drawn from the tobacco heating product; and generating a status signal indicating a heating status of the tobacco heating product in dependence on the sensed temperature.

Features of one aspect of the invention may be provided with any other aspect. Apparatus features may be provided with method aspects and vice versa.

Preferred features of the present invention will now be described, purely by way of example, with reference to the accompanying drawings, in which: Figures 1 and 2 show a typical tobacco heating product with an electrical heat source; Figure 3 shows a tobacco heating product employing a carbon tip; Figure 4 shows results of experiments to measure the temperature of a gas stream from a tobacco heating product; Figure 5 shows parts of an apparatus for testing a tobacco heating product in embodiment of the present invention; Figure 6 shows parts of a temperature sensor; and Figure 7 shows in more detail parts of the status determination unit.

Novel tobacco heating products (THPs) have recently started to appear on the marketplace. These products are characterised by the ability to heat a tobacco column without combustion or smouldering to release an aerosol containing nicotine and flavours. THPs come in various forms including systems where the tobacco is heated by electronic means initiated usually by pressing a button, or where heat is provided by igniting a carbon tip that is separated from the tobacco column by a metal foil that transfers heat to the tobacco without combusting the same. For example, EP 2 327 318, the subject matter of which is incorporated herein by reference, discloses an electronically heated smoking system with internal or external heater. WO 2009/022232, the subject matter of which is incorporated herein by reference, discloses a smoking article which comprises a combustible heat source, an aerosol-generating substrate downstream of the combustible heat source, and a heat-conducting element around and in contact with a rear portion of the combustible heat source and an adjacent front portion of the aerosol-generating substrate.

Figure 1 shows a schematic of a typical THP with an electrical heat source.

Referring to Figure 1, the THP comprises an electrical heating device 1 with a button 2 for initiating a use session. The device 1 receives a tobacco stick 3 which contains tobacco to be heated.

Figure 2 is a sectional drawing schematic of the tobacco heating product. The tobacco stick 3 is inserted into the electrical heating device 1, where a heating blade 8 is inserted into the tobacco column 7. Alternatively, the THP may comprise a heater which surrounds the tobacco column. A use session is initiated by pressing the button 2 for a set amount of time. This allows the heating blade 8 to reach the required temperature before puffing can commence.

This usually starts a timer for the session duration or a puff counter. The electrical heating blade 8 is controlled, as is the duration of the use session, by a control board 4 which includes a microprocessor. Power is provided by a rechargeable battery 9.

In this example, the tobacco stick 3 itself consists of a tobacco column 7 made from reformed tobacco sheet high in glycerine and other humectants, a cooling zone 6 which allows aerosol to form and a particulate filter 5 which may be formed from multiple filter elements.

Figure 3 shows a schematic of a THP 14 employing a carbon tip to provide a heat source for the tobacco. This alternative THP resembles the electrically heated product in that there are particulate filters 5, a tobacco column 7 and possibly a cooling and aerosol formation zone 6. Features specific to this type of construction are a carbon block tip 12, a metal foil barrier 11 which transfers heat from the carbon tip while preventing the tobacco from burning, an air inlet source to the carbon tip 13, and ventilation holes 10 allowing air to enter the tobacco column and transport heat to the whole column by means of heated air.

When testing the emissions of these products on analytical smoking machines it is necessary to know when the rod has reached the end of its life and that heating has ceased. In the case of the systems that use electronic heating this could be software predefined number of puffs or "session duration'. In the case of the carbon tipped products it is when the carbon is consumed. Typically an estimate of the end of life of the product is made, based for example on the number of puffs expected from the product. However, there remains some uncertainty as to when exactly the session of smoking is complete.

It is known to provide a system that detects the aerosol formed by vaping products through the detection and measurement of scattered light. This technique relies upon the aerosol forming droplets that scatter light. This has limitations where the vaping device has a formulation that produces an aerosol without the distinctive clouds of white vapour -achieved by adjusting the balance between propylene glycol and glycerol as a carrier for the nicotine. Further limitations exist as this requires the use of a transmitter and receiver, often based on a laser diode and photoreceptor that needs to be in very close proximity to the butt of the e-cigarette.

Furthermore, an analytical smoking or vaping machine normally has a capture pad close coupled to the butt of the test article which filters out aerosol so the optical detection system must be between this pad and the e-cigarette. This increases the path length to the pad allowing condensation of aerosol on the optical surfaces of the detection device reducing its efficiency as well as adversely impacting the collection efficiency of the capture pad. This is a more acute effect in the case of THPs where an increase in path length of a few millimetres can reduce pad collection significantly. Moreover the aerosol produced by THPs tends to be much finer (smaller droplets) than for an e-cigarette and so the light scattering properties of the aerosol are much reduced making this a less sensitive technique for determining if aerosol is being formed or has ceased being formed at the end of life.

An alternative would be to use an optical sensor that identified if a button had been pressed if the button were to incorporate an LED. This method would be limited only to those electronic devices with an LED and would suffer from problems with positioning of the LED -many locations on an electronic device would be possible -it cannot be assumed that the LED is on the button. An additional limitation would be that this is only relevant for some devices for initiating the THP smoking session as the button is pressed at the start of a session and then the session is timed. Failure of heating source, battery or other fault would not be detected. Finally such a system is not suitable for carbon tipped devices.

It would be possible for carbon tipped devices to use a thermally sensitive camera or infra-red sensor to determine if the carbon tip is still generating heat.

This solution suffers from the cost of such devices and also the intrusiveness of the same. It would be necessary to have the sensors relatively close to the tip. This is a problem in an analytical smoking machine where the airflow over the device under test is carefully controlled as any obstruction in the path of the air flow will create turbulence and impact yields of potentially harmful toxins. This is not a desirable solution.

A further problem exists if a crack develops in the carbon tip and, although alight, the thermal connection to the tobacco column is flawed and ceases to produce aerosol. The detector will see this as actively heating although aerosol is not being formed.

It would therefore be desirable to provide a technique for detecting when a tobacco heating product ceases to heat or fails to heat the tobacco. Such a technique would ideally be suitable for THPs using an electrical heating system and a carbon tip heating system. Furthermore, a technique which is not intrusive and which neither disturbs the air flow over the THP nor interferes with the collection efficiency of aerosol formed would be desirable.

The principle employed in embodiments of the present invention uses the knowledge that aerosol leaving the end of a THP is elevated above room temperature in order to form the aerosol. Heated air is a component of the process of forming aerosol from the THP and cooling sections within the THP are used to form aerosol droplets but not to over cool the aerosol so that all condenses before leaving the THP. Consequently the aerosol including gases from the air (Nitrogen, Oxygen, Carbon Monoxide etc.) leaves the THP at an elevated temperature with respect to its surroundings.

If the aerosol particles are filtered out by means of a pad such as a Cambridge filter pad specified in 1S03308, the air and other gases that pass through the collection pad are still at this elevated temperature. This can be monitored and detected by means of a temperature sensor held in line with the gas stream (aerosol particles removed) and the change in gas stream temperature will be indicative of the progress of the heating process.

Figure 4 shows results of experiments to measure the temperature of the gas stream from a tobacco heating product during a session of product usage. In this example the test piece was an electronically heated product. The puff duration PD was set to 3 seconds, the puff interval set to 30 seconds, the puff volume PV to 55m1 and the number of puffs expected from the device due to software control was set to 12 puffs.

It can be seen from Figure 4 that the air flowing through the system during a puff is at a greater temperature when compared to the air temperature between puffs. This can provide a clear indication of a puff successfully taking place. In embodiments of the invention, the temperature is synchronised analytically to the puffing engine control and a comparison is made to establish if the piece under test is still being heated. Of note is that the air temperature as heated is not uniform throughout the process. As a consequence, a comparison of the measured temperature against ambient may be necessary with a threshold for ceasing puffing set at an appropriate level above ambient. Appropriate timing lags may also need to be taken into consideration when testing the temperature rise.

Figure 5 shows schematically parts of an apparatus for testing a tobacco heating product in embodiment of the present invention. Referring to Figures, the apparatus comprises a Cambridge filter pad holder 20 which is plugged into a mechanical interface 22 of a smoking machine 24. The Cambridge filter pad holder 20 comprises a port 26 for holding a tobacco heating product. In this example, the tobacco heating product is an electrical heating device 1 with a tobacco stick 3, and the port 26 incorporates means for holding the tobacco stick (for example, a lip seal). The Cambridge filter pad holder 20 is arranged to hold a particulate capture filter 28. The filter pad may be, for instance, a glass fibre pad and may be capable of capturing particles having a diameter of, for example, 0.2 microns or above.

The smoking machine 24 comprises a gas transfer tube 30, a puff engine 32, an outlet tube 34, a control unit 36, and a user interface 38. The control unit 36 is operable to control the puff engine 32 to draw a series of puffs through the tobacco heating product 1, 3 via the port 26, filter pad holder 20 and transfer tube 30. The gas drawn in by the puff engine 32 is expelled through the outlet tube 34, and optionally may be collected for further analysis or for safe disposal. The user interface 38 is used to program the control unit 36 to perform an appropriate puffing routine. This allows the programming of parameters such as puff intervals, volumes, durations and shapes. The user interface may comprise input means such as a keyboard, mouse and/or touch screen, and/or output means such as a display, speaker, lights and/or audible alarm. The control unit may be in the form of hardware or a software module comprising computer code running on a processor.

The puff engine 32 can be likened to an automated syringe with a piston moving inside a cylinder. Movement of the piston away from the tip draws fluid in, and movement towards the tip exhausts fluid. A three-way valve couples the syringe to an inlet tube during the inlet stroke and to an outlet tube during the exhaust stroke. The puff engine 32 may be, for example, as described in co-pending UK patent application number GB 1805946.9, the subject matter of which is incorporated herein by reference, although any other suitable means for drawing puffs could be used instead.

Although only a single port 26 is shown in Figure 5, a plurality of ports could be provided for smoking a plurality of tobacco heating products. In this case, a suitable mechanism may be provided for connecting the puff engine 32 to each smoking port in turn.

In the arrangement of Figure 5, a temperature sensor 40 is located in the gas transfer tube 30 between the Cambridge filter pad holder 20 and the puff engine 32. The temperature sensor 40 can be remote from the filter pad holder 20, but in practice moderately close proximity will usually produce the best results. The output of the temperature sensor 40 is fed to a status determination unit 44 via an amplifier 42. The status determination unit 44 is arranged to determine the status of the tobacco heating product based on the sensed temperature. The output of the status determination unit 44 is fed to the control unit 36.

In operation, the puff engine 32 is used to draw a series of puffs through the tobacco heating product 1. An aerosol comprising heated air and gas and particles from the product enter into the Cambridge filter pad holder 20. The particulate capture filter 28 captures particles in the aerosol stream. At this point aerosol particles have been substantially removed and hot gas phase passes through the transfer tube 30 to the puff engine 32. The temperature sensor 40 senses the temperature of the gas in the transfer tube 30 between the filter pad holder 20 and puff engine 32. The output of the sensor 40 is amplified by amplifier 42 and fed to the status determination unit 44. The status determination unit 44 determines the status of the tobacco heating product, and outputs a status signal to the control unit 36.

Figure 6 shows in more detail parts of the temperature sensor 40 in one embodiment. In this embodiment, the temperature sensor is a thermocouple sensor. Referring to Figure 6, the thermocouple sensor comprises two wires of dissimilar metals joined together at a sensing junction 46. The sensing junction 46 is located inside the gas transfer tube 30. The two wires are each connected to the amplifier 42 via reference junction 48. The reference junction 48 is located outside of the tube at ambient temperature. The voltage produced at the reference junction depends on the difference in temperature between the sensing junction 46 and the reference junction 48. The amplifier 42 amplifies the voltage at the reference junction to produce a temperature signal T. The temperature signal T is fed to the status determination unit 44. Thermocouple sensor circuits are known in the art, and accordingly not described further.

Figure 7 shows in more detail parts of the status determination unit 44 in one embodiment. The status determination unit may be in the form of hardware or a software module comprising computer code running on a processor. Referring to Figure 7, the status determination unit 44 comprises delay module 50, comparator 52 and reference generator 54. The delay module 50 receives a puff control signal C from the control unit 36. The output of the delay module 50 is used to control the comparator 52. The comparator receives the output of the thermocouple amplifier 42 at one input, and the output of the reference generator 54 at the other input. The output of the comparator is a status signal S which is fed to the control unit 32.

In operation, the thermocouple amplifier 42 produces a temperature signal T which depends on the difference between the temperature inside of the transfer tube 30 and ambient temperature outside of the tube. The reference generator 54 generates a threshold signal TH corresponding to a predetermined threshold for the temperature difference. The comparator 52 compares the temperature signal T to the threshold signal TH and outputs a status signal S in dependence on the result of the comparison.

The delay module 50 receives a puff control signal C from the control unit 36. The puff control signal is a signal which causes the puff engine 32 to produce a puff. The delay unit 50 produces a time delayed version C' of the puff control signal. The time delay is used to compensate for delays in the system caused by, amongst other things, the time lag between the control unit issuing the puff control signal to the puff engine and the gas from the tobacco heating product 1 appearing in the transfer tube 30, and the time constant of the thermocouple sensor 40. The output of the delay module 50 used to control the comparator 52 in such a way that the comparator 52 only outputs the status signal S when the delayed puff control signal C' is positive (i.e. corresponds to the drawing of a puff).

Thus, the comparator 52 outputs the status signal S when the difference between the temperature in the transfer tube 30 and ambient temperature is above the threshold set by the reference generator 54, but only when the output of the temperature sensor 40 corresponds to periods in which the puff engine 32 is drawing puffs through the tobacco heating product 1, 3. The status signal S is therefore a signal indicating whether there is an elevated temperature in the transfer tube (compared to ambient) as a puff is being drawn through the tobacco heating product. The status signal threshold may be dependent on the puffing conditions selected and this threshold can be modified as a result of this selection. This signal is therefore an indication of whether or not the tobacco heating product is heating the tobacco during a puff. Continuing puffing is determined by comparison with a pre-defined threshold as some residual heating may be present even when the session of smoking no longer generates nicotine and other components of the aerosol.

The status signal S output by the status determination unit 44 is fed to the control unit 36. The control unit uses the status signal to control puffing frequency and other parameters of the puff engine 32. In particular, when the status signal indicates that the tobacco heating product is not heating the tobacco, the control unit ceases the puffing routine. Alternatively or in addition, the status signal can be fed to the user interface to provide a visual and/or audible warning that the tobacco is not being heated.

In addition, or as an alternative to any of the above, the puffing conditions could be automatically modified to restore the heating efficiency of a carbon tipped THP. If desired, a plurality of different thresholds could be set, and a different action taken in dependence on which threshold or thresholds had been exceeded.

The amount of delay provided by the delay unit 50 may be determined empirically by observing the time delay between the issuance of a puff control signal and the corresponding change in voltage at the output of the amplifier 42. This time delay may be predetermined or set as part of a calibration procedure. The amount of time delay may be fixed, or varied depending on, for example, the type of tobacco heating product that is being tested, the type of puff being taken, historic testing results, the type of equipment being used, or any other appropriate parameter.

The threshold signal TH is set to a value which is sufficiently low to detect all likely differences between the temperature in the transfer tube 30 and ambient temperature when the tobacco heating product is heating the tobacco, and sufficiently high to avoid false positives. In practice a suitable value for the threshold signal has been found to be a value corresponding to approximately 3°C, although of course other values could be used instead. The value of the threshold signal may be fixed, or may be varied in dependence on, for example, the type of tobacco heating product that is being tested, the type of puff being taken, time elapsed since the start of the smoking session, number of puffs taken, historic testing results, or any other appropriate parameter.

The techniques described above can help to ensure that no further puffs are taken when the tobacco heating product ceases to heat or fails to heat the tobacco. This can help to ensure that the concentration of material yielded from the tobacco heating product is not under reported.

The tobacco heating product may be tobacco based or made of other herbal material. The tobacco heating product may comprise a plurality of components including built in heating source or an external electronically controlled heating source.

In the above description, preferred features of the invention have been described with reference to various embodiments. However, it will be appreciated that the invention is not limited to these embodiments, and variations in detail may be made within the scope of the appended claims. For example, rather than using a thermocouple sensor, any suitable form of temperature sensor, such as a thermistor, a resistance thermometer, a silicon bandgap temperature sensor, optical temperature sensor, or any other type of temperature sensor could be used instead or as well. Other modifications will be apparent to the skilled person.

Claims

CLAIMS1. Apparatus for testing a tobacco heating product, the apparatus comprising: means for puffing the tobacco heating product; means for sensing a temperature of a gas stream drawn from the tobacco heating product; and means for generating a status signal indicating a heating status of the tobacco heating product in dependence on the sensed temperature.
2. Apparatus according to claim 1, wherein the temperature sensing means is situated in the gas stream remotely from the tobacco heating product.
3. Apparatus according to claim 1 or 2, wherein the apparatus is arranged to remove at least some particles from an aerosol drawn from the tobacco heating product to yield the gas stream.
4. Apparatus according to any of the preceding claims, further comprising means for capturing at least some particles in an aerosol drawn from the tobacco heating product for further analysis.
5. Apparatus according to claim 4, wherein the temperature sensing means is located downstream of the capturing means.
6. Apparatus according to claim 4 or 5, wherein at least part of the temperature sensing means is located in a gas transfer tube for transferring gas from the capturing means to the puffing means.
7. Apparatus according to any of the preceding claims, further comprising means for holding the tobacco heating product.
8. Apparatus according to any of the preceding claims, wherein the means for sensing the temperature of the gas stream comprises at least one of a thermocouple sensor, a thermistor, a resistance thermometer, a silicon bandgap temperature sensor, an optical temperature sensor and a solid-state temperature sensor.
9. Apparatus according to any of the preceding claims, wherein the means for generating a status signal is arranged to compare the sensed temperature with a threshold value, and to output the status signal in dependence on a result of the comparison.
10. Apparatus according to any of the preceding claims, wherein the temperature sensing means is arranged to sense the temperature of the gas stream above ambient temperature.
11. Apparatus according to any of the preceding claims, wherein the temperature sensing means is arranged to produce a temperature signal which depends on a difference between the temperature of the gas stream and ambient temperature, and the means for generating a status signal is arranged to compare the temperature signal with a threshold value.
12. Apparatus according to claim 11, wherein the threshold value corresponds to a value of temperature above ambient temperature.
13. Apparatus according to any of the preceding claims, wherein the temperature sensing means comprises a thermocouple sensor, and the thermocouple sensor comprises a sensing junction located in the gas stream and a reference junction located outside of the gas stream.
14. Apparatus according to any of the preceding claims, wherein the status signal is a signal indicating whether or not the tobacco heating product is heating the tobacco.
15. Apparatus according to any of the preceding claims, wherein the means for generating a status signal is synchronised with the puffing means.
16. Apparatus according to any of the preceding claims, wherein the means for generating a status signal is arranged to output the status signal only during time periods corresponding to periods when the puffing means is drawing a puff.
17. Apparatus according to any of the preceding claims, further comprising a control unit for controlling the puffing means.
18. Apparatus according to claim 17, wherein the control unit is arranged to produce a control signal for controlling the puffing means, and the means for generating a status signal is arranged to receive the control signal and to output the status signal in dependence on the control signal.
19. Apparatus according to claim 18, wherein the means for generating a status signal is arranged to output the status signal only during time periods corresponding to periods when the control signal has a value which causes the puffing means to draw a puff.
20. Apparatus according to any of claims 17 to 19, further comprising delay means for delaying a control signal from the control unit, wherein the means for generating a status signal is arranged to output the status signal in dependence on the delayed control signal.
21. Apparatus according to any of claims 17 to 20, wherein the control unit is arranged to cease or modify puffing of the tobacco heating product in dependence on the status signal.
22. Apparatus according to any of claims 17 to 21, wherein the control unit is arranged to output an alarm signal in dependence on the status signal.
23. Apparatus according to any of the preceding claims, wherein the tobacco heating product comprises at least one of: a tobacco heated stick heated by means of an external electrical heating system; a tobacco heated stick heated by means of an internal electrical heating 35 system; a tobacco heated stick heated by means of a tip that is sustainably self-heating such as a carbon tip; and a tobacco heating stick heated by means of a chemical reaction.
24. Apparatus according to any of the preceding claims, wherein the apparatus is an analytical smoking or vaping machine.
25. A method of testing a tobacco heating product, the method comprising: puffing the tobacco heating product; sensing a temperature of a gas stream drawn from the tobacco heating product; and generating a status signal indicating a heating status of the tobacco heating product in dependence on the sensed temperature.