GB2061519A

GB2061519A - Improvements relating to the Measurement of the Ventilation of Smoking Articles

Info

Publication number: GB2061519A
Application number: GB8032102A
Authority: GB
Original assignee: British American Tobacco Co Ltd
Current assignee: British American Tobacco Investments Ltd
Priority date: 1979-10-09
Filing date: 1980-10-06
Publication date: 1981-05-13
Also published as: GB2061519B

Abstract

Apparatus and method for measuring a quantity of air entering a cigarette 2 utilise a housing 1 bounding a sealed annular space around the cigarette or a part thereof, a duct 6, communicating with the said space, through which air can pass thereto and a heat-effect anemometer, for example of thermistor type, including a probe disposed within the duct. For measuring the quantity of ventilation air entering the cigarette, the annular space, surrounding the rod except for the burning coal, may be formed by an outer sleeve member displaceable axially over an inner member. For measuring also the quantity of air entering a filter tip of the cigarette, another sealed space, surrounding a length of the tip, may be formed in the inner member. For measuring also the air supplied to the burning coal, the housing may bound a further sealed annular space, which encloses the coal. <IMAGE>

Description

SPECIFICATION Improvements Relating to the Measurement of the Ventilation of Smoking Articles This invention relates to an apparatus and method for measuring the quantity of air entering smoking articles, cigarettes for example.

In designing smoking articles such as cigarettes, it is valuable to be able to establish the percentage ventilation of a part or the whole of the article when lit, i.e. during smoking, especially on a puff-by-puff basis.

A known method of measuring the ventilation of lit cigarettes involves the inclusion of a bubblevolume indicator in a ventilation-air duct. The use of such an indicator, however, presents a number of problems. The impedance to air flow of the indicator detracts from the accuracy obtainable by the known method, the impedance being dependent inter alia upon the dampness of the column of the indicator, the number of bubbles present therein and the concentration of the detergent used. In a dynamic situation such as that existing during a puff, it is not easy to determine the volume indicated by the position of the bubble. Moreover it occasionally happens that the bubble bursts and thus the result is lost.If a determination of delivered-smoke constituents is to be made simultaneously with the ventilation measurement, errors may be occasioned by the presence in the smoke of substances derived from the detergent.

With the presently increasing use of ventilated cigarettes, there is a demand for an accurate, simple and easy-to-use apparatus for the determination of ventilation during smoking. It is an object of the present invention to provide apparatus capable of fulfilling these requirements.

The invention provides apparatus, for measuring a quantity of air entering a smoking article, comprising housing means adapted for bounding a sealed annular space around the article or a part thereof, duct means communicating with the said space, through which air can pass thereto, and a heat-effect anemometer including a probe disposed within the said duct means.

The invention further provides a method of measuring a quantity of air entering a smoking article, in which the article is disposed within housing means bounding a sealed annular space around the article or a part thereof, air is induced, during a puff, to flow through duct means to said smoking article via said annular space and the airflow is determined by a probe of a heat-effect anemometer disposed within said duct means.

The heat-effect anemometer may advantageousiy be of the thermistor or of the hot wire type.

With the aforesaid apparatus and method, it is possible to satisfy the essential requirement that the duct means and probe have no more than a negligible air-flow impedance effect.

Preferably the apparatus further includes an integrator operable to integrate the air-flow/time signal from the anemometer.

In order that the invention may be clearly understood and readily carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which: Figure 1 shows a lit-cigarette ventilation apparatus; Figures 2a and 2b show, respectively, front and side elevations of an alternative form of a part of the apparatus of Figure 1; Figure 3 shows, in axial section, a housing which may be used in an apparatus similar to that of Figure 1, and Figure 4 is a section, similar to Fig. 3, showing a supplementary housing which can be used in conjunction with that of Fig. 3.

Referring to Figure 1, the ventilation apparatus there shown and constituting a ventilation meter comprises a housing 1 of annular form adapted to receive a longitudinal portion of the filter tip 2' of a ventilated-tip cigarette designated 2. A mouthend portion of the tip 2' is held in a socket portion of a holder 3 which is constructed to receive a Cambridge filter pad. The holder 3 is connected to, or mounted on, a smoking machine (not shown) with which it communicates by way of duct 3'. The machine may be programmed to operate in the standard smoking mode, i.e. a puff of 35 c.c. volume and 2 seconds duration every minute, or in other smoking modes as required.

The housing 1 is provided with sealing means in the form of an air-pervious sleeve 4 of dentaldam sheet material, which is held between end caps 1 ' of the housing 1 sealed to the body of the latter by 'O'-rings 5, the end caps 1' and dental dam serving to provide spaced apart seals about the periphery of the tip 2' of the cigarette. There is thereby defined within the housing 1 an annular space 1" surrounding a portion of the tip 2'. An air-supply tube 6 communicates with the interior of the housing 1 and, at the end remote from the housing, with an anemometer head 7 through which extends a bore 8 in communication with the bore of the tube 6. Mounted in the head 7, so as to protrude into the bore 8, is a thermistor bead 9.Mounted on the head 7, at the side remote from the tube 6, is a flow-smoothing tube 10, for example 10 cm. in length, which is open to atmosphere at its free end.

The head 7 is electrically connected to a unit 11 which is operable to provide an output signal indicative of the velocity of ventilation air flowing through the ventilation duct of negligible impedance formed by the smoothing tube 10, the bore 8 in the head 7, and the tube 6. The anemometer used may be an instrument supplied by Airflow Developments under model designation TA 3000, which monitors the amount of electrical energy required to maintain the bead 9 at a constant temperature of 1 500 C. This instrument is provided with a temperature compensation circuit, including a second, unheated, bead (not shown), so that the output signal is independent of air temperature.The output signal from the instrument 11 is of logarithmic form and is passed to an interface logarithmic-to-linear convertor 12, whose output signal is passed to an integrator unit 13, which operates to provide an integration function related to the linearised air-flow velocity/time curve signal of the instrument 11 and thus to give a measure of the ventilation-air volume during a puff, which volume may be expressed as a percentage of the total volume of smoke and air passing through the puff from the cigarette 2 to the smoking machine. The integrated data from the unit 13 may, if required, be displayed in the form of a curve representative of the puff profile, using for example an ultra-violet recorder 14.

In place of the tube 6, which serves to conduct the ventilation air to one entry location only of the housing 1, there may be employed a ring-form tube 16 (Figures 2a and 2b) which communicates between a straight air-supply tube 17 and two, diametrically opposed, locations of the housing 1, so providing for an improved distribution of ventilation air to the filter tip (2') through a dental-dam sleeve. The bores of the tubes 16 and 17 are such that the tubes are of negligible airflow impedance.

The bead 9 of the anemometer head 7 is of negligible dimensions compared to the cross section of the bore 8, so that its presence results in no more than negligible air-flow impedance.

The purpose of the smoothing tube 10 is to ensure laminar-flow conditions in the region of the bead 9 and to prevent stray air-flow effects being registered by the bead 9, caused for example by movement of an operator in the vicinity of the apparatus or even by a nearby door being opened or closed.

In that a standard puff is of only 2 seconds duration, the velocity-detection instrumentation must possess a fast response. This is especially the case if the smoking machine is operated in simulation of a smoker's puff profile, which profile, rather than being smooth, is typically of highly irregular wave form. This requirement can be met by the use of the thermistor anemometer.

However, other forms of heat-effect anemometers having the requisite response time, hot-wire instruments for example, could be used.

The ventilation meter described above is adapted for measuring the ventilation of the tip of a cigarette. It may, however, be required to measure the ventilation with respect to the rod of smoking material, i.e. the ventilation through the cigarette paper, as an alternative to or together with the measurement of the tip ventilation. With this object, a housing shown in Figure 3 is designed to receive the total length of a cigarette except the portion accounted for by the burning coal.

The housing of Figure 3 comprises a generally cylindrical block 20 and a sleeve 21 which extends around and can be moved axially with respect to the block 20. '0'-rings 22 provide a seal between the block 20 and the sleeve 21.

Received in a screw-threaded axial bore 23 of the block 20 is a holder 24 comprising at its outer end (to the right in Figure 3) a recess 25 dimensioned to receive a 9 mm. length of the filter tip 26' of a cigarette 26. The holder 24 has an open-ended axial bore 27 in communication with a bore 23' in the block 20. An elastomeric seal 28 is mounted, at the outer end of the holder 24, by means of a ring 29 screwed on to the holder 24, and is in sealing contact with the filter tip 26'. A second elastomeric seal 28' spaced a short distance from the seal 28 is mounted in a ring 30 screwed on to the block 20, the seal 28' also being in sealing contact with the tip 26'. A sealed ventilation space 31 is thus provided surrounding a predeterminable length of the filter tip of the cigarette 26.Two further bores, 32 and 33, extend through the block 20 and communicate with the ventilation space 31. A second ventilation space 34, surrounding the tobacco rod of the cigarette 26, is sealed at the rightward end thereof by means of an elastomeric seal 35 mounted in an end-closure disc 36 screwed on to the sleeve 21. Two ports 37, 38 extend through spigots on the wall of the sleeve 21 at diametrically opposed positions.

In use of the housing of Figure 3, the bore 23' communicates with a smoking machine, the bores 32, 33 are both connected to the head 7 of a thermistor anemometer and units 11-14 (not shown, but provided as in Figure 1) and the ports 37, 38 are in communication with the head 7 of a second, similar, thermistor anemometer associated with units 1 (not shown). As the burning coal progresses along the tobacco rod, the sleeve 21, and hence the seal 35, is moved in a leftward direction in relation to the cigarette 26, the unburnt residual portion of the tobacco rod remaining within the space 24 for continuing measurement of the ventilation of the said rod, while the filter tip 26' remains within the space 31 for continuing measurement of the ventilation of the said tip.The leftward movement of the sleeve 21 may be imparted manually by an operator or automatically by means responsive to the progress of the hot coal.

All of the air-flow bores of the housing of Figure 3 are of adequate cross section to ensure that they present no more than negligible air-flow impedance.

The apparatus of Fig. 4 constitutes a modification or supplement to that of Figure 3 which makes it possible to measure the flow of air to the burning coal 26n of a cigarette as well as the air flows to the wrapped tobacco rod and filter-tip section of the cigarette.

For this purpose the disc 36 is removed from the end of the sleeve 21 shown in Fig. 3 and an extension piece generally indicated at 39 is screwed onto the said end. The extension piece comprises a generally cylindrical wall 40, a removable end wall 41 provided with an o-ring seal 42 and a partition wall 43 beyond which the coal 26n projects into the sealed chamber 39' formed by the walls 40, 41, 43. An elastomeric seal 44 surrounding the cigarette 26 is held in position by a screw-in member 45. Bores 46, 47 are in communication with the head 7 of a third thermistor anemometer associated with integration and display apparatus (not shown).

The bores 46, 47 and connections thereto are of cross-sections presenting no more than negligible air-flow impedance.

In order to provide for an adequate supply of air to the cigarette during the inter-puff periods, holes 48 are provided in the wall 40. Suitably, these holes may be approximately 1 5 mm in diameter and disposed in two diametrically opposed groups of three. A rotatable collar 49 arranged around the wall 40 is provided with holes 50 of similar size and disposition. By turning the collar 49, the holes 50 can be displaced between positions of partial or complete coincidence with respective holes 48, permitting ingress of air during each inter-puff period and positions of partial or complete non-coincidence in which the holes 48 are covered, normally completely, during each puff period, so that air can enter the chamber 39' only through the bores 46,47.

In use of the apparatus comprising the housing of Fig. 3 fitted with housing of Fig. 4, the latter is moved together with the sleeve 21 of the former in relation to the block 20 with similar effect except that the coal 26 remains within the space 39'. To permit observation of the progress of the coal, the extension piece 39 may be made of, for example, Perspex (Registered Trade Mark) and the collar 49 of polyethylene material.

Instead of the member 39 being a screw fit onto the sleeve 21 (Fig. 3), a bayonet fitting may be provided which utilises the spigots of the ports 37, 38 as the connection pins.

Claims

1. Apparatus for measuring a quantity of air entering a smoking article comprising housing means adapted for bounding a sealed annular space around the article or a part thereof, duct means, communicating with the said space, through which air can pass thereto and a heateffect anemometer including a probe disposed within the said duct means.

2. Apparatus according to claim 1, wherein the anemometer is of the thermistor type.

3. Apparatus according to claim 1 or 2 and comprising an integrator connected to the anemometer for integrating an air flow/time signal from the anemometer.

4. Apparatus according to any one of claims 1 to 3 for measuring the quantity of ventilation air entering a filter tip of the smoking article, wherein the sealed annular space, in use of the apparatus, surrounds a length of the said tip from which it is separated by an air pervious sleeve.

5. Apparatus according to any one of claims 1 to 3 for measuring the quantity of ventilation air entering the rod of smoking material of the smoking article, wherein the housing means comprises an outer sleeve member disposed over an inner member and bounding therewith the said sealed annular space, which, in use of the apparatus, surrounds the smoking-material rod except for the burning coal thereof, said outer member being displaceable axially over said inner member as the burning coal progresses along the said rod.

6. Apparatus according to claim 5 for measuring also the quantity of ventilation air entering a filter tip of the smoking article wherein another said sealed space is formed within the inner member, which space, in use of the apparatus, surrounds a length of the said filter tip.

7. Apparatus according to claim 5 or 6 for measuring also the quantity of air supplied to the burning coal of the article, wherein the housing means bounds a said sealed annular space which in, use of the apparatus, encloses the said burning coal.

8. Apparatus for measuring a quantity or quantities of air entering a smoking article substantially as hereinbefore described with reference to Fig. 1, Figs. 2a and 2b or Fig. 3 of the accompanying drawings.

9. Apparatus for measuring a quantity or quantities of air entering a smoking article substantially as hereinbefore described with reference to Figure 4 of the accompanying drawings.

10. A method of measuring a quantity of ventilation air entering a smoking article, wherein the article is disposed within housing means bounding a sealed annular space around the article or a part thereof, air is induced, during a puff, to flow through duct means to said smoking article via said annular space and the air-flow is determined by a probe of a heat-effect anemometer disposed within said duct means.

11. A method of measuring a quantity of ventilation air entering a smoking article substantially as hereinbefore described with reference to Fig. 1, Figs. 2a and 2b or Fig. 3 of the accompanying drawings.

12. A method of measuring a quantity of ventilation air entering a smoking article substantially as hereinbefore described with reference to Fig. 4 of the accompanying drawings.