Aerosol Generating Devices

Abstract

An aerosol generating device includes sensing means for detecting when an aerosol generating article is inserted into or withdrawn from a heating chamber of the device. A roller is mounted for rotation about a roller axis such that an article moving along a pre-defined insertion path engages a surface of the roller and causes it to rotate. The sensing means determines a direction of rotation of the roller. The sensing means may be responsive to a property of the roller, such as its radius or a magnetic field. The property may vary with angle about the roller axis to define one or more indexes that can be detected by one or more sensors disposed adjacent to the roller.

Description

TECHNICAL FIELD

The present disclosure relates generally to an aerosol generating device for heating an aerosol generating substrate to generate an aerosol for inhalation by a user of the aerosol generating device. The present disclosure is particularly applicable to a portable (hand-held) aerosol generating device. Such devices heat, rather than burn, an aerosol generating substrate, e.g., tobacco or other suitable materials, by conduction, convection, and/or radiation to generate an aerosol for inhalation by a user.

TECHNICAL BACKGROUND

The popularity and use of reduced-risk or modified-risk devices (also known as aerosol generating devices or vapour generating devices) has grown rapidly in recent years as an alternative to the use of traditional tobacco products. Various devices and systems are available that heat or warm aerosol generating substances to generate an aerosol for inhalation by a user.

A commonly available reduced-risk or modified-risk device is the heated substrate aerosol generating device, or so-called heat-not-burn device. Devices of this type generate an aerosol or vapour by heating an aerosol generating substrate to a temperature typically in the range 150° C. to 300° C. Heating the aerosol generating substrate to a temperature within this range, without burning or combusting the aerosol generating substrate, generates a vapour which typically cools and condenses to form an aerosol for inhalation by a user of the device.

In general terms, a vapour is a substance in the gas phase at a temperature lower than its critical temperature, which means that the vapour can be condensed to a liquid by increasing its pressure without reducing the temperature, whereas an aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas. It should, however, be noted that the terms ‘aerosol’ and ‘vapour’ may be used interchangeably in this specification, particularly with regard to the form of the inhalable medium that is generated for inhalation by a user.

Currently available aerosol generating devices can use one of a number of different approaches to provide heat to the aerosol generating substrate. One such approach is to employ an induction heating system. In such a device, an induction coil is provided in the device and an inductively heatable susceptor is provided to heat the aerosol generating substrate. Electrical energy is supplied to the induction coil when a user activates the device which in turn generates an alternating electromagnetic field. The susceptor couples with the electromagnetic field and generates heat which is transferred, for example by conduction, to the aerosol generating substrate and an aerosol is generated as the aerosol generating substrate is heated. Another approach is to employ a resistive heating system, in which current is supplied directly to a heating element. The heating element generates heat, which is transferred, for example by conduction, to the aerosol generating substrate. The susceptor or heating element may surround the aerosol generating substrate and transfer heat to an outer surface of the aerosol generating substrate. Alternatively, the susceptor or heating element may be in the form of a blade that becomes embedded in the aerosol generating substrate when the aerosol generating substrate is inserted into the aerosol generating device.

The aerosol generating substrate forms part of a consumable article that is removably received in the aerosol generating device. Typically, a distal end of the consumable article, which comprises the aerosol generating substrate, is received in a heating chamber of the aerosol generating device, while a proximal end of the consumable article projects from the aerosol generating device in order that it can be engaged by the mouth of a user. It is beneficial for the aerosol generating device to be able to detect when a consumable article is inserted into the device or withdrawn from the device, in order that certain functions of the device may be activated or de-activated in an appropriate manner.

SUMMARY OF THE INVENTION

The invention provides an aerosol generating device comprising:

• • a heating chamber for receiving an elongate aerosol generating article that may be inserted into the heating chamber along a pre-defined insertion path or withdrawn from the heating chamber along the same insertion path:
  • a roller mounted for rotation about a roller axis that is generally perpendicular to the insertion path such that an aerosol generating article moving along the insertion path engages a surface of the roller, thereby causing the roller to rotate: and
  • sensing means for determining a direction of rotation of the roller.

The use of a roller provides a convenient and mechanically simple way of converting the linear movement of the consumable article, when it is being inserted or removed, into rotational movement, which can be detected using a number of alternative methods. The rotational movement of the roller takes place within a compact space, which enables the sensing means to be deployed within the restricted volume of a hand-held aerosol generating device. By detecting the direction of rotation of the roller, the device can determine whether a consumable article is being inserted or removed, which is important for controlling the device in an appropriate manner. If the movement were to be detected without determining its direction, then insertion could only be distinguished from removal if the previous state of the consumable article was known. In other words, if the consumable article was previously known to be present, then movement must indicate that it is now being removed: and if the consumable article was previously known to be absent, then movement must indicate that it is now being inserted. With the present invention, it is not necessary to store a memory of the state of the consumable article or, alternatively, to employ a separate sensor to detect the presence or absence of the consumable article.

Preferably, the roller comprises a property that varies with angle about the roller axis and the sensing means comprises at least one sensor capable of measuring the variation in the property as the roller rotates past the sensor to determine the direction of rotation of the roller. The property may be any physical characteristic that can be measured by a sensor. The measurement need not be of a continuous value: it includes detection of a property that may be present or absent to give a two-state (ON/OFF) output signal from the sensor. The property may be internal to the roller, e.g. a magnetic property: a surface property such as brightness or colour: or an external property such as its radius.

Preferably, the variation in the property of the roller with angle about the roller axis defines an index at an index angular position on the roller: the sensing means comprises a first sensor capable of detecting movement of the index past a first sensor angular position about the roller axis and a second sensor capable of detecting movement of the index past a second sensor angular position about the roller axis; and the angle between the first and second sensor angular positions is less than 180°. The index is any feature of that property that can be measured by the sensor and used to identify an angular position on the roller as it rotates past the sensor. The index may be well defined only in relation to the sensor or other aspects of the sensing means. An index does not necessarily need to identify an angular position that is unique around the entire circumference of the roller: the index may still be useful for determining the direction of rotation of the roller if it forms part of an identifiable pattern (including a repeating pattern) around the circumference. By disposing the first and second sensors at an angular spacing less than 180°, the order in which the two sensors detect the passing of the index will change, depending on the direction of rotation of the roller, thus enabling the direction to be determined.

In some embodiments of the invention, the sensing means further comprises a timer and a comparator. As the roller rotates, the timer measures a first time interval from when the first sensor detects movement of the index past the first sensor angular position to when the second sensor detects movement of the index past the second sensor angular position, and a second time interval from when the second sensor detects movement of the index past the second sensor angular position to when the first sensor detects movement of the index past the first sensor angular position. The comparator then compares the first interval with the second interval to determine the direction of rotation of the roller.

In other embodiments of the invention, the sensing means further comprises a timer, a comparator and a third sensor capable of detecting movement of the index past a third sensor angular position about the roller axis. As the roller rotates, the timer measures a first time when the first sensor detects movement of the index past the first sensor angular position; a second time when the second sensor detects movement of the index past the second sensor angular position; and a third time when the third sensor detects movement of the index past the third sensor angular position. The comparator can then determine the direction of rotation of the roller from the order in which the first time, the second time and the third time occur. In this embodiment the determination does not depend on measuring and comparing time intervals so, at the expense of an additional sensor, it is less sensitive to possible changes in the speed of rotation of the roller.

In some embodiments of the invention, the measured property of the roller preferably varies with angle about the roller axis in a pattern that is not mirror-symmetric. This has the advantage that it may be possible to determine the direction of rotation of the roller using only a single sensor, or a simpler arrangement of sensors.

In some embodiments of the invention, the asymmetric variation of the property of the roller with angle about the roller axis defines first and second indexes on the roller, which the sensor is capable of distinguishing between, the angular positions of the first and second indexes being spaced less than 180° apart. Accordingly, the order in which the sensor detects the passing of the respective indexes will change depending on the direction of rotation of the roller, thus enabling the direction to be determined.

In other embodiments of the invention, the asymmetric variation of the property of the roller with angle about the roller axis defines first, second and third indexes respectively at first, second and third index angular positions on the roller, the angles between the first, second and third index angular positions all being different. If the roller rotates at a roughly constant rate, the different angular spacings of the respective indexes will give rise to a pattern of different time intervals between detections of a passing index by the sensor. The sensing means can therefore determine the direction of rotation of the roller from the order in which the different time intervals occur. This embodiment has the advantage that the sensor does not need to be able to distinguish between different types of index. For example, it may determine only the presence or absence of an index.

In some embodiments of the invention, the property that varies with angle about the roller axis is a magnetic property: and the or each sensor is capable of detecting changes in a magnetic field as the roller rotates past the sensor. A magnetic field sensor requires no moving mechanical parts and integrates easily into a microelectronic circuit, which permits a simple design and manufacture of the aerosol generating device. The magnetic field sensor may, for example, be a Hall effect sensor. The roller may comprise one or more permanent magnets arranged to create the magnetic property that varies with angle about the roller axis.

In other embodiments of the invention, the property that varies with angle about the roller axis is a radius of the roller; and the or each sensor is capable of detecting changes in the radius of the roller as the roller rotates past the sensor. A roller of varying radius is simple to manufacture and avoids complications that can arise from, for example, the use of permanent magnets in a manufacturing environment because of their tendency to attract or repel one another and to attract metallic particles to them.

The varying radius of the roller can be measured in various ways, with or without contacting the surface of the roller. For example, the or each sensor may comprise a sensor element that engages the surface of the roller and moves towards and away from the roller axis in response to changes in the radius of the roller as the roller rotates. Such a sensor may measure changes in the radius as a continuous variable or it may further comprise an electrical switch, which is toggled between ON and OFF conditions as the sensor element moves towards and away from the roller axis. Accordingly, a measurement signal output by the sensor may be essentially analogue or digital.

The aerosol generating device may further comprise a heater for heating an aerosol generating article received in the heating chamber; a counter for counting revolutions of the roller; and a controller for activating the heater when the counter has counted a predetermined number of revolutions. By counting the revolutions of the roller when an aerosol generating article is inserted along the pre-defined insertion path, the device can measure the distance travelled by the article and thus determine when the article has been fully inserted into the heating chamber. This avoids the need for a further sensor at the distal end of the heating chamber, which may be subject to high temperatures.

The invention further provides a method of determining when an aerosol generating article is inserted into or withdrawn from a heating chamber of an aerosol generating device, the method comprising:

• • moving an aerosol generating article along a pre-defined insertion path to or from the heating chamber;
  • engaging the aerosol generating article with a surface of a roller that is mounted for rotation about a roller axis that is generally perpendicular to the insertion path, thereby causing the roller to rotate; and
  • using sensing means to determine a direction of rotation of the roller.

DRAWINGS

FIG. 1 is a schematic elevation of an aerosol generating device in accordance with the invention.

FIG. 2 is a schematic plan view on line A-A of FIG. 1.

FIGS. 3 to 6 schematically illustrate different types of roller properties and sensors that may be used to measure them in accordance with the invention.

FIGS. 7 to 12 illustrate some examples of possible arrangements of indexes and sensors in accordance with the invention, and the ways they may be used to derive the direction of rotation of the roller. Each numbered Figure comprises a Figure A, which schematically illustrates the arrangement of indexes and sensors in relation to the roller, and a Figure B, which shows the signals output by the sensors, plotted against time.

FIG. 1 shows a handheld aerosol generating device 1 that is assembled within a housing 2. The housing 2 contains a battery 4 and a control circuit 6, which are not illustrated in detail. The battery 4 may be conventional and serves as a power source for the device 1. The control circuit 6 receives power from the battery 4 and controls the operation of the device 1, including the supply of power from the battery 4 to a heater 8 for heating a consumable article 10. The control circuit 6 may vary the operation of the device 1 in response to signals that it receives from one or more sensors, examples of which are described below. The device 1 may also comprise a user interface (not shown), which is used to convey information to a user, for example via lights, sounds or a display screen, and to receive instructions from a user, for example via buttons or a touch screen. The device may further comprise a transmitter/receiver (not shown) for sending information to and/or receiving information from a remote device. The transmitter/receiver may use any suitable communication technology, preferably a wireless technology such as Bluetooth® or WiFi. The remote device may be a smart phone of the user, which can be used to provide information to the user, receive instructions from the user or carry out data processing for the control circuit 6. The remote device may alternatively be a central computer, e.g. operated by the manufacturer of the device 1, which can be used to collect and store data about the usage of the device 1, to carry out data processing for the control circuit 6 of the device 1 or to provide data to the device 1, for example software upgrades.

The housing 2 contains a heating chamber 12, which is blind at one end. At the other end, the heating chamber 12 is open to the exterior of the device via an aperture 14 in the housing 2. There may be provided a sliding cover 16, which can be moved across the aperture 14 to close it when the device 1 is not in use. The heating chamber 12 is sized and shaped to receive the distal end 18 of a consumable article 10 such that the proximal end 19 of the consumable article 10 projects from the device 1 through the aperture 14 and can be received in the mouth of the user during a smoking session. For example, the heating chamber 12 may have a generally circular cross section to receive a typical consumable article 10 of cylindrical shape. Other shapes of consumable article 10 are known, for example a flattened card-like shape, in which case the heating chamber 12 may be in the form of a slot with a generally rectangular cross-section. The internal dimensions of the heating chamber 12 may be slightly larger than the external dimensions of the consumable article 10 in order that, when the user draws on the proximal end 19 of the consumable article 10, there is space around its exterior for air to flow from the aperture 14 and be drawn into the distal end 18.

The consumable article 10 is inserted into the heating chamber 12 through the aperture 14 and along a pre-defined insertion path 20, as indicated by an arrow 21, to reach its desired position when fully inserted in the heating chamber 12. The cross-section of the aperture 14 may be somewhat larger than that of the heating chamber 12 to make it easier for the user to insert a consumable article 10 into the aperture 14. A throat portion 22 may be provided between the aperture 14 and the heating chamber 12, the cross-section of the throat portion 22 tapering inwards from the aperture 14 to guide the consumable article 10 along the insertion path 20 towards the desired position. The throat portion 22 may be formed integrally with the walls of the heating chamber 12 (as illustrated) or it may be a separate component formed from a material that does not need to withstand the high temperature inside the heating chamber 12. The throat portion 22 may provide the rotary mounting for the roller 26. Projections 23 may be provided inside the heating chamber 12 to support the consumable article 10 in the desired position. It will be understood that the consumable article 10 may subsequently be withdrawn from the heating chamber 12 in the opposite direction along the same insertion path 20.

The consumable article 10 contains an aerosol generating substrate 24 at or near its distal end 18. When the temperature of the aerosol generating substrate 24 is increased, it evolves a vapour or aerosol that can be drawn into the mouth and lungs of the user via the proximal end 19 of the consumable article. The aerosol may contain active components such as nicotine and additional components such as flavourings. The space between the aerosol generating substrate 24 and the proximal end 19 allows an opportunity for the aerosol to cool to a suitable temperature before it is inhaled. The space may also comprise a filter (not shown).

The heater 8 is configured to apply heat to the interior of the heating chamber 12 and raise the temperature of the aerosol generating substrate 24 of a consumable article 10 received in the heating chamber 12. For example, the heater 8 may comprise an induction coil surrounding the heating chamber 12, which can be activated to induce heat in a susceptor (not shown) within the heating chamber 12. In other embodiments, the heater 8 may use resistive heating. The heater 8 may comprise a blade or other element (not shown) that directly contacts the consumable article 10 to conduct heat into it. Additionally or alternatively, the heater 8 may be designed to pre-heat the air before it flows into the distal end 18 of the consumable article 10. In order to save energy and to prevent the temperature of the aerosol generating substance from increasing excessively, the device I may comprise pressure or flow sensors (not shown) that can detect the movement of air through the heating chamber 12, whereby the control circuit 6 only activates the heater 8 when it determines that the user is drawing on the consumable article 10.

In accordance with the invention, a roller 26 is mounted in the aerosol generating device 1 for rotation about an axis 28 that is generally perpendicular to the line of the insertion path 20 (as seen in FIG. 2). A circumferential surface 30 of the roller 26 extends slightly into the interior of the heating chamber 12 or the throat portion 22 in order to contact the surface of a consumable article 10 that lies in the insertion path 20. As the consumable article 10 is inserted into the heating chamber along the insertion path 20 (indicated by the arrow 21), friction between the surface of the consumable article 10 and the roller 26 causes the roller 26 to rotate in one direction (anti-clockwise as viewed in FIG. 1, indicated by an arrow 32). When the consumable article 10 is withdrawn from the heating chamber in the opposite direction along the insertion path 20, friction between the surface of the consumable article 10 and the roller 26 causes the roller 26 to rotate in the opposite direction (clockwise as viewed in FIG. 1).

Frictional contact between the surface 30 of the roller 26 and the surface of the consumable article 10 may be enhanced by texturing the roller surface 30 or by forming it from a resilient or high-friction material such as rubber. The roller 26 is preferably mounted relatively close to the aperture 14 in order that the insertion of a consumable article 10 can be detected soon after it enters the aperture 14. The diameter and position of the roller 26 should preferably be such that as the consumable article 10 moves from initial contact with the roller 26 to being fully inserted in the heating chamber 12, it drives the roller 26 to complete at least one full revolution.

Not all properties of the roller 26 have perfect circular symmetry about the roller axis 28: there is at least one property (discussed below) that varies with angle about the axis 28. Located adjacent to the roller 26 are one or more sensors 34, which can measure variations in the property as the roller 26 rotates. The one or more sensors 34, alone or in combination with logic provided by the control circuit 6, form a sensing means that detects the direction of rotation of the roller 26. From the direction of rotation, the control circuit 6 knows when a consumable article 10 is inserted or withdrawn and can respond by operating the aerosol generating device 1 in a suitable manner. For example, when a consumable article 10 is inserted, it may activate the device 1 or, prior to activation, it may carry out steps to authenticate the consumable article 10 as being suitable for use with the device 1 and/or to authenticate the user as an authorized user of the device 1. When a consumable article 10 is withdrawn, the control circuit 6 may de-activate the device 1 and it may take other steps such as recording or transmitting details of the smoking session that has just ended.

Because the sensor(s) 34 can measure a property of the roller 26 that varies with angle about the roller axis 28, the measurements repeat in a cyclical manner with each revolution of the roller 26. Therefore it is easy for the sensing means to count the number of revolutions and, from the known circumference of the roller 26, to determine how far the consumable article 10 has been inserted into the device (or withdrawn from the device). In particular, this enables the control circuit 6 to prevent activation of the aerosol generating device 1 if the consumable article 10 has not been fully inserted into the heating chamber 12, such that the aerosol generating substrate 24 is not in the optimum position to be heated by the heater 8. In this situation, the control circuit 6 preferably issues a warning to the user that the consumable article 10 is not correctly inserted.

FIG. 2 is a schematic plan view on line A-A of FIG. 1. It shows the roller 26 mounted for rotation about the roller axis 28, which is generally perpendicular to the axis of a cylindrical consumable article 10. Preferably, the ends of the roller 26 are mounted in bearings (not shown) but alternatively the roller could rotate about an axle that passes through a bore in the roller. FIG. 2 illustrates how the sensor 34 may be offset in the axial direction of the roller from the surface 30 that contacts the consumable article 10. This allows an index portion 36 of the roller 26, which is detected by the sensor 34, to be separated from the contact surface 30. In particular, if the varying property of the roller 26 that is measured by the sensor 34 is the radius of the roller 26, then the radius of the index portion 36 may be freely varied while the radius of the contact surface 30 remains uniform to maintain good contact with the consumable article 10. Alternatively, contact surface 30 may be designed to provide high-friction engagement with the consumable article 10 while the sensor 34 may be designed to make sliding contact with the index portion 36.

FIG. 2 shows the contact surface 30 of the roller 26 having a slightly greater radius than the remainder of the consumable article. The extra radius may be occupied by shallow teeth (not illustrated) that can indent a paper wrapper of the consumable article 10 or by a sleeve of a resilient material such as rubber that can deform and grip the surface of the consumable article 10 is it moves past the roller 26. In other embodiments, the contact surface 30 and the index portion 36 of the roller 26 may be axially aligned with one another, the one or more sensors 34 being similarly aligned at angular positions about the roller axis 28 where they will not interfere with the passage of the consumable article 10. In still other embodiments the measurable property of the roller 26 may be present along the whole axial extent of the roller 26, such that there is no distinct index portion 36.

In this specification, the term “index” is used, in relation to the property of the roller 26 that varies with angle about the roller axis 28, to mean any feature of that property that can be measured by a sensor 34 and used to identify an angular position on the roller 26 as it rotates past the sensor 34. An index may be well defined only in relation to the sensing means used: for example, it may be an angular position where the measured value of a continuously varying property exceeds a predetermined threshold. With this in mind, whether the sensing means detects an index may also depend on the direction of rotation of the roller 26: if, in a given embodiment of the invention, an index is detected when the measured value of the property rises above a threshold then, when the roller 26 is rotating in the opposite direction, at the same angular position of the roller 26 the value is instead likely to fall below the threshold. Moreover, an index does not necessarily need to identify an angular position that is unique around the entire circumference of the roller 26: the index may still be useful if it forms part of an identifiable pattern (including a repeating pattern) around the circumference.

FIGS. 3 to 6 schematically illustrate different types of property of the index portion 36 of the roller 26 and the ways that sensors 34 may be used to measure them.

In FIG. 3, the varying property is a magnetic field. A permanent magnet 38 is mounted centrally in the roller 26, with the north-south axis of the magnet 38 being generally perpendicular to the roller axis 28 so that the north pole of the magnet 38 is in one half-cylinder of the roller 26 and the south pole of the magnet 38 is the other half-cylinder. The sensor 34 is a magnetic field sensor 40 such as a Hall effect sensor, disposed close to the surface of the index portion 36 of the roller 26, which can detect changes in the magnetic field caused by the permanent magnet 38 as the roller 26 rotates. An index may be defined, for example, as the angular position of the roller 26 where the measured magnetic field changes from negative to positive (or south to north). It is not essential for the permanent magnet 38 to be mounted centrally in the roller 26. A single magnet could be mounted off-centre, with a suitable counter-weight to prevent the roller 26 becoming unbalanced, or a plurality of magnets could be disposed about the circumference of the roller 26, each defining an index as it rotates past the sensor 34.

Other methods of detecting the direction of rotation using magnets can easily be envisaged. For example, a rotating magnetic field, e.g. provided by a permanent magnet like that illustrated in FIG. 3, can act as a dynamo to induce an electrical current in a coil. Such a current can be detected and its direction may indicate the direction of rotation of the roller 26.

In FIG. 4, the varying property is again a magnetic field and the sensor 34 is again a magnetic field sensor 40 such as a Hall effect sensor. However, in this case the magnetic field is provided by a fixed magnet 41 outside the roller 26, which may be a permanent magnet or may be an electromagnet operated only when the aerosol generating device 1 is in use. In this case the property of the roller 26 that varies with angle about the roller axis 28 is magnetic susceptibility or magnetizability. FIG. 4 shows one cylindrical half-cylinder 42 of the roller 26 being formed from a relatively highly susceptible material, such as iron, while the other half-cylinder of the roller 26 is formed from a material of relatively lower susceptibility. As the roller 26 rotates, field lines from the fixed magnet 41 will be diverted through the material of the roller 26 to a varying degree and the magnetic field sensor 40 will measure a different magnetic field strength at its fixed location, from which one or more indexes can be determined to identify the angular position of the roller 26.

It is not essential for the roller 26 to be divided exactly in half between the materials of relatively high and low susceptibility. For example, a single insert or a plurality of inserts of highly susceptible material could be embedded in an otherwise uniform roller material to form one or more indexes at positions disposed about the circumference of the roller 26.

FIG. 5 shows a roller 26, in which the property that varies with angle about the roller axis 28 is the radius of the roller. In this example, the index portion 36 of the roller has a substantially uniform radius around the majority of its circumference. However, over a short range of angles, the radius is increased to form a radial projection 44. A sensor 34 that can measure the radius of the roller 26 is shown schematically as a pin 45 that slides over the surface of the roller 26 as it rotates. The pin 45 is maintained in contact with the roller surface by the force of a spring 46 that urges the pin 45 radially inwards. The pin 45 is formed with a rounded tip, at least in a plane perpendicular to the roller axis 28, in order that when the radial projection 44 moves past the sensor 34, the pin 45 can ride over it, causing the pin 45 to be displaced radially outwards, against the force of the spring 46. Means (not shown) respond to the radial movement of the pin 45 to generate a signal that represents the varying radius of the roller 26. The radial movement of the pin 45 may simply operate a switch (not shown) to generate a signal that is either ON or OFF, whereby it can be understood that a plurality of such projections 44 arranged around the circumference of the roller 26 could be used to generate a digital code in the signal.

Instead of a radial projection 44, an index position around the roller axis 28 could be defined by a radial recess 48, as shown in dashed lines in FIG. 5. When such a recess 48 rotates past the angular position of the sensor 34, the pin 45 moves radially inwards instead of outwards. The recess 48 is shown extending over a greater angle than the projection 44 because it must at least be wide enough to accommodate the width of the pin 45. The use of projections 44 and recesses 48 in combination is not excluded, which will result the sensor generating a signal that has three possible states, e.g. zero, positive or negative.

The projection 44 and recess 48 illustrated in FIG. 5 are essentially “square”, i.e. they are formed by a substantially uniform increase or decrease in radius respectively, over their angular extent. This leads to a relatively rapid movement of the pin 45 at the start or end of the feature 44,48 as it rotates past the sensor. (The signal generated by the sensor 34 will not have exactly the same square profile as the projection 44 or recess 48 because of the rounded tip of the pin 45, which ensure smooth rotation of the roller 26.) Such a shape of projection 44 or recess 48 is well suited when a two-state (ON/OFF) output signal is desired. FIG. 6 illustrates an alternative possibility with a radial projection 50 that changes radius with angle more gradually. This may offer less resistance to the rotation of the roller 26 and it may be more suitable if the sensor 34 measures the position of the pin 45 as a continuous variable rather than as an ON or OFF signal. Although the radial projection 50 in FIG. 6 is still shown as a discrete projection from an otherwise uniform radius, it will be understood that the radius could vary smoothly around the entire circumference of the roller 26 such that it is not possible to identify a “default” radius at all.

Types of sensor other than those illustrated can be employed in devices according to the invention. For example, radial projections 44 such as that shown in FIG. 5 may be detected by interrupting a light beam that is shone parallel to the roller axis 28. In that case, the radial projection 44 could be formed as part of a thin disc, without any great extent in the axial direction, which would be an advantage in the confined space of a handheld aerosol generating device 1. Other examples of properties that can vary with angle about the roller axis 28 and other examples of sensors for measuring them will be apparent to the reader.

It is noted that in some of the foregoing examples, the positions of the indexes and the sensors could in principle be exchanged, whereby one or more sensors rotate with the roller and detect indexes that are disposed at fixed angular positions around the roller as the sensors move past them. In practice, it is more difficult to make electrical connections to sensors that are mounted in a rotating roller, in order that they can form part of an electrical circuit by which power can be provided to the sensors and measurement signals can be received from them.

FIGS. 7 to 12 illustrate some examples of possible arrangements of indexes and sensors in accordance with the invention, and the ways they may be used to derive the direction of rotation of the roller 26. In each case there is a pair of Figures, of which Figure A schematically illustrates the arrangement of indexes and sensors and Figure B shows the signals output by the sensors, plotted against time. It will be seen that in each case, Figure B is not mirror-symmetric with respect to time, which means that the illustrated pattern of signals can be used to determine the direction of rotation of the roller 26.

FIG. 7A shows a roller 26 similar to that of FIG. 3, in which a permanent magnet (not shown in FIG. 7A) is mounted in the roller 26 such that its two halves serve as the north and south poles of a magnetic field. Two magnetic field sensors 34, labelled s₁ and s₂, are disposed at fixed angular positions adjacent to the roller 26. The sensors 34 are angularly spaced at less than 180°. In this example, they are angularly spaced at approximately 90°. Although the roller 26 is illustrated as being divided into two distinct poles, in practice the magnetic field measured by each sensor 34 will vary smoothly as the roller 26 rotates past them. As the roller 26 rotates, each sensor 34 may measure a magnetic field that varies approximately as a sine wave, as illustrated by the respective output signals 61,62 in FIG. 7B. Because the sensors s₁, S₂ are at different angular positions, the two waves 61,62 are out of phase: in this example, the signal 61 from sensor s₁ leads the signal 62 from sensor s₂ by approximately 90°.

An index of the roller 26 may be identified by a consistent and identifiable index point 65 on the cyclical curve of each signal 61,62, for example the point 65 where the signal transitions from a negative to a positive value. This may correspond in practice to the angular position on the circumference of the roller 26 where it transitions from a south to a north pole but the physical interpretation of the index is not important, provided it can be consistently identified by the two sensors 34. The sensing means, which may be embodied as part of the control circuit 6 or in its own a dedicated circuit (not illustrated), compares the timing of the indexes 65 in the respective signals to determine the direction of rotation of the roller 26.

The sensing means determines a first time interval Δt₁₂ from when the first sensor s₁ detects movement of the index past its angular position to when the second sensor s₂ detects movement of the index past its angular position. The sensing means also determines a second time interval Δt₂₁ from when the second sensor s₂ detects movement of the index past its angular position to when the first sensor s₁ again detects movement of the index past its angular position. Because the initial position of the roller 26 is not known, the two time intervals may occur in either order: the first time interval Δt₁₂ is not necessarily the first to be detected. It can be seen in FIG. 7B that the first time interval Δt₁₂ is shorter than the second time interval Δt₂₁, which indicates in this case that the roller 26 is rotating in a clockwise direction. If the phase of the signal 61 from sensor s₁ lagged the signal 62 from sensor s₂ instead of leading it, then the first time interval Δt₁₂ would be longer than the second time interval Δt₂₁, which would indicate that the roller 26 was moving in an anti-clockwise direction. From this is may be understood why the angle between the positions of the first and second sensors s₁, s₁ cannot be 180°. If that were the case, the two waves would be 180° of phase and the pattern would be mirror-symmetric with respect to time. In other words, it would appear identical if the roller 26 were rotating in the opposite direction and the arrangement could not be used to determine the direction of rotation of the roller 26.

Because the embodiment illustrated in FIGS. 7A and 7B depends on comparing the two time intervals Δt₁₂ and Δt₂₁ while the roller 26 completes a full revolution, it depends on the roller 26 being rotated at approximately a constant rate while those two time intervals are measured, i.e. on the consumable article 10 being inserted or withdrawn at approximately a constant speed. If the angular spacing of the sensors s₁ and s₁ is not too close to 180° then this is a reasonable assumption. For example, in the illustrated embodiment of FIG. 7B, when the roller 26 is rotated at constant speed the second time interval Δt₂₁ is three times longer than the first time interval Δt₁₂. It follows that the user would need to vary speed of movement of the consumable article 10 quite radically during the course of a single revolution of the roller 26 in order to make the two time intervals equal in duration and result in a false detection of the direction of rotation. Any variation in the speed of insertion or withdrawal is most likely to occur near the start or end of the movement so if this is a concern the sensing means could be configured to make allowance for that, e.g. by ignoring the first detected revolution of the roller 26 before making a determination of the rotation direction.

FIG. 8A illustrates a roller 26, in which the measured property of the roller 26, shown schematically by an elongated triangle 52, varies with angle about the roller axis in a pattern that is not mirror-symmetric. For example, if the measured property is the radius of the roller 26, then over at least a range of angles, the radius may gradually increase to form a smooth ramp, which ends in a steep step to return to its initial value. Because the property varies in a pattern that is not symmetrical, it is possible to determine the direction of rotation of the roller 26 by measuring changes in the property as the roller rotates past a single sensor 34, labelled s₁.

FIG. 8B shows an example of a signal 61 from a sensor 34 that measures the radius of a roller 26, which varies in the pattern just described. The ramp-shaped pattern in which the radius varies about the circumference of the roller 26 is reflected in the ramp-shaped triangular wave pattern of the signal 61. (In this example, it is necessary that the sensor 34 should be able to measure a range of values of the property and not just two states ON or OFF.) An index may be identified with the points 65 on the curve at the end of the “ramp” where the signal drops rapidly from a high value back to its original value. If the roller 26 was rotating in the opposite direction, there would be no such sudden drop; at the same angular position of the roller 26 there would be a sudden jump in the value. Thus the sensing means can use the signal 61 to determine the direction of rotation of the roller 26.

It will be understood that any pattern of variation of the property that is not mirror-symmetric about the roller axis 28 can be used in this way to determine the direction of rotation. It does not need to be ramp-like. The pattern may extend fully around the circumference of the roller 26 or only partially around the circumference, as seen in FIG. 8A. The pattern may be repeated around the circumference in order that the direction of rotation can be determined before the roller 26 has completed a full revolution.

In FIGS. 9A to 12A, the index positions on the roller 26 are indicated schematically using triangles and the principles described do not depend on the way in which those indexes are physically implemented, for example on the property of the roller 26 that varies with angle about its axis of rotation 28. In these Figures only the arrangements of the indexes and the sensors 34 are important.

In FIGS. 9B to 12B, the signals 61,62,63 measured by the sensors 34 show the detection of an index schematically as a point 65,66 on a timeline. The principles described do not depend on the particular way the index is manifested in the signal output by the sensor but examples include a rising edge, a falling edge, a crossing (in either direction) of zero or another threshold value, a peak or a trough, etc. In these

Figures only the relative timings of the indexes 65,66 detected in the signals 61,62,63 are important.

FIG. 9A shows an arrangement similar to that in FIG. 7A, except that the index 54 is shown as a discrete angular position on the roller 26. This may correspond, for example, to the transition between the north and south poles of the magnet in FIG. 7A or to any other identifiable feature in the angularly varying property of the roller 26. Again, two sensors 34, labelled s₁ and s₂, are disposed at fixed angular positions adjacent to the roller 26. (It is understood that for the measurement of some angularly varying properties of the roller 26, such as its radius, the sensors 34 may be in contact with the surface of the roller 26.) The sensors 34 are angularly spaced at less than 180°, for example at approximately 90° apart.

FIG. 9B shows two signals 61,62 that respectively represent the timing of the indexes detected in the measurements from the first sensor s₁ and the second sensor s₂ as the roller 26 rotates. If the roller 26 rotates at constant speed then the positions of the indexes along the respective timelines 61,62 correspond to the angular positions of the two sensors 34 about the roller axis 28 (relative to an arbitrary zero position). As in FIG. 7B, the sensing means determines a first time interval Δt₁₂ from when the first sensor s₁ detects movement of the index past its angular position to when the second sensor s₂ detects movement of the index past its angular position. The sensing means also determines a second time interval Δt₂₁ from when the second sensor s₂ detects movement of the index past its angular position to when the first sensor s₁ again detects movement of the index past its angular position. In FIG. 9B the first time interval Δt₁₂ is shorter than the second time interval Δt₂₁ , which indicates in this case that the roller 26 is rotating in a clockwise direction. If the first time interval Δt₁₂ was longer than the second time interval Δt₂₁ , that would indicate that the roller 26 was moving in an anti-clockwise direction.

FIG. 10A schematically illustrates an embodiment of the invention that has three sensors 34, labelled s₁, s₂, s₃, disposed adjacent to the roller 26 at different angular positions about the roller axis 28. They are shown at approximately equal angular intervals of 120° but that is not essential.

FIG. 10B shows three signals 61,62,63 that respectively represent the timing of the indexes 65 detected in the measurements from the first, second and third sensors s₁, s₂ and s₃; as the roller 26 rotates. In this case it is not the timings of the indexes 65 as such but the order in which they occur. In the illustrated example, indexes 65 are detected cyclically in the order s₁, s₂, s₃ (any of which may come first), which indicates in this case that the roller 26 is rotating in a clockwise direction. If the indexes 65 were detected cyclically in the reverse order s₁, s₂, s₃, that would indicate that the roller 26 was moving in an anti-clockwise direction. The order in which the indexes 65 are detected by the three sensors 34 will remain the same even if the speed of rotation of the roller varies radically (provided the direction does not reverse during the measurement), therefore this arrangement with three sensors 34 is more robust if uneven insertion or withdrawal of the consumable article 10 is anticipated.

FIG. 11A schematically illustrates an embodiment of the invention, in which a single sensor 34, labelled s₁, is disposed at an angular position adjacent to the roller 26. The roller 26 comprises two indexes 54,55, which the sensor 34 is able to distinguish. For example, the indexes 54,55 could respectively represent the radial projection 44 and recess 48 of FIG. 5; or the start and end of the ramp-like projection described in relation to FIG. 8A: or a signal representing a magnetic field when it crosses a threshold level in a rising and a falling direction. The indexes 54,55 are located on the roller 26 at angular positions about the roller axis 28 that are less than 180° apart. It is noted that a sensor 34 having only two measurement states (e.g. a switch with ON and OFF positions) is unlikely to be able to distinguish between two types of index 54,55.

FIG. 11B shows a signal 61 that represents the timings of detections 65 of the first index 54 and detections 66 of the second index 55 in the measurement signal from the sensor s₁ as the roller 26 rotates. The sensing means determines a first time interval Δt₁₂ from when the sensor s₁ detects movement of the first index 54 past its angular position to when the sensor s₁ detects movement of the second index 55 past its angular position. The sensing means also determines a second time interval Δt₂₁ from when the sensor s₁ detects movement of the second index 55 past its angular position to when the sensor s₁ gain detects movement of the first index 54 past its angular position. In FIG. 11B the first time interval Δt₁₂ is shorter than the second time interval Δt₂₁, which indicates in this case that the roller 26 is rotating in a clockwise direction. If the first time interval Δt₁₂ was longer than the second time interval Δt₂₁, that would indicate that the roller 26 was moving in an anti-clockwise direction.

FIG. 12A schematically illustrates another embodiment of the invention, in which a single sensor 34, labelled s₁, is disposed at an angular position adjacent to the roller 26. In this embodiment the roller 26 comprises three indexes 54, which may be identical in the sense that the sensor 34 cannot distinguish between them (so a simple ON/OFF sensor could be used). The indexes 54 are disposed on the roller 26 at angular positions distributed about the roller axis 28 such that the three angles between adjacent pairs of indexes are all different. In the illustrated embodiment, the respective angles between adjacent pairs of indexes are approximately in the ratio 1:2:4 but this is not essential.

FIG. 12B shows a signal 61 that represents the timings of detections 65 of indexes in the measurement signal from the sensor s₁ as the rotation of the roller 26 carries the indexes 54 past the angular position of the sensor 34. Each individual detection 65 could represent any one of the indexes 54 but it is known that they must be detected cyclically (assuming that the direction of rotation of the roller 26 is not reversed during the measurement). The sensing means determines three time intervals Δt₁, Δt₂, Δt₃ between four consecutive detections 65 of an index by the sensor s₁. It then compares the durations of the sequence of time intervals to determine the direction of rotation of the roller 26. In FIG. 12B the time intervals Δt₁, Δt₂, Δt₃ occur cyclically in order of increasing duration (although any of them may occur first in the cycle), which indicates in this case that the roller 26 is rotating in a clockwise direction. If the time intervals Δt₁, Δt₂, Δt₃ were to occur cyclically in order of decreasing duration, that would indicate that the roller 26 was moving in an anti-clockwise direction.

It is noted that in the embodiments that depend on comparing time intervals between the detections of indexes in the sensors signals as the roller rotates, different choices could be made of which time intervals to compare. For example, with reference to FIG. 7B, instead of comparing the time intervals Δt₁₂ and Δt₂₁ with one another, either of them could be compared with the total time interval ΔT that is measured for a complete revolution of the roller. Similar alternatives are available for the embodiments of FIGS. 9B, 11B and 12B and are intended to fall within the scope of the present invention.

The illustrated embodiments of the invention disclose the use of a single index 54 on the roller 26 in combination with multiple sensors 34 distributed around the roller axis 28; or the use of a multiple indexes 54,55 distributed around the roller 26 in combination with a single sensor 34 disposed at a fixed angular position adjacent to the roller 26. It is possible to combine multiple sensors 34 with multiple indexes 54,55 but care needs to be taken that this does not give rise to ambiguity in the signals that are generated. For example, in relation to FIG. 9A, it can easily be imagined that providing a second index on the roller 26 at an angular position 180° from the illustrated index 54 will provide the benefit that the direction of rotation of the roller 26 can be determined when it has completed only half a revolution instead of a full revolution. That is true but only if the angular spacing between the sensors s₁, s₂ is reduced to less than 90°.With a 90° sensor spacing and a 180° index spacing, the respective sensors s₁, s₂ would alternately detect an index passing with every 90° rotation of the roller 26, in either direction, so the pattern would be symmetrical and the direction of rotation could not be determined.

Claims

1. An aerosol generating device comprising: a heating chamber configured for receiving an aerosol generating article that may be inserted into the heating chamber along a pre-defined insertion path or withdrawn from the heating chamber along the same insertion path;a roller mounted for rotation about a roller axis that is generally-substantially perpendicular to the insertion path, wherein when an aerosol generating article moves along the insertion path, the aerosol generating article engages a surface of the roller, thereby causing the roller to rotate; andsensing means for determining a direction of rotation of the roller.

2. The aerosol generating device according to claim 1, wherein: the roller comprises a property that varies with angle about the roller axis; andthe sensing means comprises at least one sensor configured to measure a variation in the property as the roller rotates past the at least one sensor to determine the direction of rotation of the roller.

3. The aerosol generating device according to claim 2, wherein: the variation in the property of the roller with angle about the roller axis defines an index at an index angular position on the roller;the at least one sensor comprises a first sensor capable of configured to detecting movement of the index past a first sensor angular position about the roller axis and a second sensor configured to detecting movement of the index past a second sensor angular position about the roller axis; andan angle between the first and second sensor angular positions is less than 180°.

4. The aerosol generating device according to claim 3, wherein the sensing means further comprises: a timer for measuring, as the roller rotates,a first time interval from when the first sensor detects movement of the index past the first sensor angular position to when the second sensor detects movement of the index past the second sensor angular position, anda second time interval from when the second sensor detects movement of the index past the second sensor angular position to when the first sensor detects movement of the index past the first sensor angular position; anda comparator for comparing the first interval with the second interval to determine the direction of rotation of the roller.

5. The aerosol generating device according to claim 3, wherein the sensing means further comprises: a third sensor configured to detecting movement of the index past a third sensor angular position about the roller axis; anda timer for measuring, as the roller rotates, a first time when the first sensor detects movement of the index past the first sensor angular position,a second time when the second sensor detects movement of the index past the second sensor angular position, anda third time when the third sensor detects movement of the index past the third sensor angular position; anda comparator for determining the direction of rotation of the roller from the order in which the first time, the second time and the third time occur.

6. The aerosol generating device according to claim 2, wherein: the property of the roller varies with angle about the roller axis in a pattern that is not mirror-symmetric.

7. The aerosol generating device according to claim 6, wherein: the variation of the property of the roller with angle about the roller axis defines a first index at a first index angular position on the roller and a second index at a second index angular position on the roller;the at least one sensor is configured to distinguish between the first and second indexes; andan angle between the first and second index angular positions is less than 180°.

8. The aerosol generating device according to claim 6, wherein: the variation of the property of the roller with angle about the roller axis defines first, second and third indexes respectively at first, second and third index angular positions on the roller; andangles between the first, second and third index angular positions are all different.

9. he aerosol generating device according to claim 2, wherein: the property that varies with angle about the roller axis is a magnetic property; andthe at least one sensor is capable of configured to detecting changes in a magnetic field as the roller rotates past the at least one sensor.

10. The aerosol generating device according to claim 9, wherein the roller comprises one or more permanent magnets arranged to create the magnetic property that varies with angle about the roller axis.

11. The aerosol generating device according to claim 2, wherein the property that varies with angle about the roller axis is a radius of the roller; and wherein the at least one sensor is configured to detecting changes in the radius of the roller as the roller rotates past the at least one sensor.

12. The aerosol generating device according to claim 11, wherein the at least one sensor comprises a sensor element that engages the surface of the roller and moves towards and away from the roller axis in response to changes in the radius of the roller as the roller rotates.

13. The aerosol generating device according to claim 12, wherein the at least one sensor further comprises an electrical switch, which is toggled between ON and OFF conditions as the sensor element moves towards and away from the roller axis.

14. The aerosol generating device according to claim 1, further comprising: a heater for heating an aerosol generating article received in the heating chamber;a counter for counting revolutions of the roller; anda controller for activating the heater when the counter has counted a predetermined number of revolutions.

15. A method of determining when an aerosol generating article is inserted into or withdrawn from a heating chamber of an aerosol generating device, the method comprising: moving an aerosol generating article along a pre-defined insertion path to or from the heating chamber;engaging the aerosol generating article with a surface of a roller that is mounted for rotation about a roller axis that is substantially perpendicular to the insertion path, thereby causing the roller to rotate; andusing sensing means to determine a direction of rotation of the roller.

16. The method according to claim 15, wherein the sensing means comprises at least one sensor.

17. An aerosol generating device comprising: a heating chamber configured for receiving an aerosol generating article inserted into the heating chamber along a pre-defined insertion path or withdrawn from the heating chamber along the same insertion path;a roller mounted for rotation about a roller axis that is substantially perpendicular to the insertion path, wherein when an aerosol generating article moves along the insertion path, the aerosol generating article engages a surface of the roller, thereby causing the roller to rotate; andat least one sensor for determining a direction of rotation of the roller.