GB1597510A

GB1597510A - Testing ventilated cigarettes

Info

Publication number: GB1597510A
Application number: GB5365277A
Authority: GB
Original assignee: Molins Ltd
Current assignee: Mpac Group PLC
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-09-09

Description

(54) TESTING VENTILATED CIGARETTES (71) We. MOLINS LIMITED, a British Company. of 2. Evelyn Street, Deptford, London SE8 5DH, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:: This invention relates to the testing of rodlike articles. for example cigarettes, having an air pervious filling and an open-ended wrapping. and is particularly concerned with methods and apparatus for performing an air test on rod-like articles which are designed to have a predetermined air-leak through their wrappings such as "ventilated" cigarettes, to ensure that the wrappings pass an amount of air which is neither too great (indicating excessive leakage) nor too small (indicating insufficient ventilation). Normally such cigå- rettes are provided with perforations in or near the filter.

A method of testing a ventilated cigarette of the type in which air inlets are provided in the wrapper at or near the filter ends according to the invention comprises the steps of forming an enclosed chamber around the cigarette, terminated at or near the ends of the cigarette by seal portions arranged to restrict communication between the chamber and the exterior regions of the cigarette which are adjacent the open ends of the cigarette except via the cigarette wrapping, applying suction to the said chamber, measuring the suction at each end of the cigarette. and processing the suction signals to determine the "dilution" i.e. the expected air flow. in use, into the cigarette through the wrapper.

Instead of applying suction to a chamber around the cigarette it is also possible to apply pressure air to chambers connected to the ends of the cigarette so that air is forced out through the wrapper, and measure the back pressure in each of the chambers.

The invention also extends to apparatus for testing a ventilated cigarette the apparatus comprising means for forming an enclosed chamber around the cigarette, terminated at or near the ends of the cigarette by seal portions arranged to restrict communication between the chamber and the exterior regions of the cigarette which are adjacent the open ends of the cigarette except via the cigarette wrapping, means for applying suction to the said chamber, a space at each end of the cigarette communicating with the inside of the cigarette and with a respective suction transducer, and electrical circuit means arranged to process the outputs of one or both of the transducers to produce a signal indicative of the degree of ventilation of the cigarette. Such apparatus may comprise a modified inspection device of the type shown in U.S.Patent 3,608,380, or a modified version of the Molins CID 4 or CID 4N.

Preferably the transducers are of the balanced transformer type exhibiting a varying phase of output voltage as the amount of suction varies. Preferably the electrical circuitry for processing the outputs from the transducers also include means for averaging the dilution readings of successive cigarettes to provide an indication of their mean dilution. Circuit means may also be provided for generating a reject signal in the event of the detection of a cigarette having an incorrect level of dilution, so as to cause that cigarette to be rejected.

Preferably the circuit can be preset so that a cigarette may be rejected either on the basis of one or both of the pressure signals, or on the basis of the computed dilution signal.

Preferably also the circuitry includes upper and/or lower threshold detection means so that cigarettes can be rejected if the pressure signal or the dilution signal do not fall within a predetermined range, or if they exceed one particular threshold in either direction.

A preferred form of cigarette tester in accordance with the invention comprises a rotary carrier drum which has circumferentially spaced axial flutes and which carries the cigarettes, one in each flute, from an input conveyor, and including seal portions at the ends of the flutes to restrict communication between the interior and exterior of the cigarettes via the open ends of the cigarette wrappings during testing, characterised in that the cigarettes are carried by the carrier drum past a co-operating closure drum which rotates adjacent ta the carrier drum, about an axis parallel to that of the carrier drum and at the same peripheral speed, and has circumferentially spaced closure parts which register with the flutes on the carrier drum and are so shaped that each closure part of the closure drum co-operates with a flute of the carrier drum to define momentarily a chamber around the cigarettes, terminated at or near the ends of the cigarette by seal portions defined partly by the carrier drum and partly by the closure drum to restrict communication between the interior and exterior of the cigarette wrapping via open ends of the cigarette wrapping, each of the said ends being arranged to communicate with a suction transducer, which transducers are connected to processing means for producing a signal indicative of the degree of ventilation of the cigarette.

The carrier drum and closure drum preferably both have circumferentially spaced axially-extending flutes, so that at the moment of testing of a particular cigarette, the cigarette lies partly in the flute in the carrier drum and partly in the flute in the closure drum.

In a preferred tester according to the invention the closure drum is carried by a housing pivoted about an axis parallel to the carrier drum and closure drum axes to enable the closure drum to be swung away from the carrier drum, about the housing pivot axis, for inspection or for any other reason; the closure drum axis is preferably at a higher level than the carrier drum axis, and the housing pivot axis is so positioned that the closure drum is held against the carrier drum by gravity during testing. Preferably the bearing mounting the closure in the pivoted housing allows the closure drum a slight freedom to swivel about an axis parallel to the common tangent to the closure drum and carrier drum to ensure that both ends of the closure drum are in rolling contact with the carrier drum.

There may be a single rotary drive input to the tester, this being transmitted to the carrier drum, while the closure drum is driven by virtue of carrying a gear wheel meshing with a gear wheel on the carrier drum. Preferably the number of teeth on each gear wheel equals the number of flutes on the corresponding drum, so that the gear wheel can be brought into mesh in any position and will automatically cause the flutes on the two drums to register with one another.

One embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure I is an elevation of a testing machine: Figure 2 is a section on the line Il-Il of Figure 1; Figure 3 is a view similar to Figure 2 on the line Ill-Ill in Figure 1; Figure 4 is an enlarged fragmentary view of the test area of the testing machine of Figure 1: Figure 5 is a block diagram of a dilution measuring circuit for use with the machine of Figures 1 and 2; Figure 6 is a more detailed diagram of one type of dilution measuring circuit; and Figure 7 is a diagrammatic drawing of an alternative testing system.

The machine shown in Figures 1 to 4 comprises a carrier drum 1 and a closure drum 2 both of which are fluted to accommodate cigarettes and are mounted for rotation in synchronism with one another so that successive flutes of one register with those of the other to define at a testing point a succession of test chambers for the cigarettes.

Suction for testing is applied from a suction chamber in the drum 2, being supplied through a hollow shaft 3 which communicates with a fan. The closure drum 2 and the supply duct are carried in a single housing 4 which is pivoted about the axis of the shaft 3 so that it can be swung upwards away from the carrier drum 1 to provide access between the drums. A clamp (not shown) can be operated to lock the housing in its "up" position.

A continuous stream of cigarettes is fed on to the carrier drum 1 from a belt conveyor 7 by means of a fluted suction-pickup drum 8 and is set down on the conveyor 7 by means of a fluted suction-return drum 9. The cigarettes are retained in position in their flutes on the drum 1 between the testing point and the points of pick-up and return by pairs of guide rails 10 and 11 respectively.

The closure drum 2 has a series of radial passages 12 opening at one end into flutes 13 and communicating at the other end with an internal suction chamber 14 through a fixed chamber 15 which is provided with an aperture 49 registering with the suction supply duct 3 to provide communication to the chamber 14, and with a port 50 to provide communication from the chamber 14 to each of the flutes 13 in turn at the testing point by way of the radial passages 12.

The construction of the flutes of each of the two drums is shown in Figure 2. In each drum there are two axially spaced sealing ribs at each end of each flute. In the drum 1 the ribs, indicated by the reference 16. are defined by the escalloped edges of four discs 17, 18, 19 and 20. Between the discs 17 and 18, and between the discs 19 and 20 there are air spaces 21, 22 which communicate with the middle of the carrier drum 1 which is open to atmosphere. Between the discs 18 and 19, in the neighbourhood of the ciga rettes, there is a centre portion 23 of the drum which is formed in its outer periphery with grooves shaped to conform with the cigarettes but with clearance so as to define an approximately half-annular space with each cigarette.

The closure drum 2 is formed with flutes which complete the suction chamber around each cigarette at the testing point. In this case there are semi-circular sealing ribs 26 which are defined by the escalloped edges of rings 27 and 28 each of which has a circumferential groove. 29 and 30 respectively, between the ribs 26. In the testing position these grooves 29 and 30 communicate with the air spaces 21 and 22 respectively to define around the end of each cigarette an air ring at atmospheric pressure. Between the rings 27 and 28 the closure drum has a centre portion 31 which is formed with the radial passages 12 and in its outer periphery with the flutes 13 into which the passages 12 open.

End pieces 32 and 33, which form part of the closure drum, roll on the rings 24 and 25 of the carrier drum 1. The closure drum is kept in rolling contact with the carrier drum by gravity. Alternatively the closure drum may be held just out of contact with the carrier drum by means of a stop (preferably adjustable) limiting clockwise movement of the housing 4 about its pivot axis.

The cigarette-facing periphery 34 of each rib 16 or 26 is semi-circular (see Figure 4) and they are all of the same size which is chosen according to the size of the cigarettes which varies within a tolerance range. The peripheral faces 35 of the discs 17 to 20 and rings 27 and 28 in the regions between the flutes are curved about the centres of the respective drums so as to be in rolling contact or just clear of rolling contact. The radius of the peripheries 34 of the ribs 16 and 26 is chosen so as to leave a gap around the largest possible cigarettes of certain normal size, having regard to the tolerance on the diameter of the cigarettes. In an example, for cigarettes having a diameter of 7.88 mm.

within a tolerance of + 0.1 mm., the diameter of the peripheries 34 is about 8.04 mm. with a tolerance of + 0.02 mm. For tipped cigarettes, which are larger at the tipped end, the peripheries 34 are larger at one end than the other.

Thus, in the testing position, there is a pair of sealing ribs 16. 26 encircling each end of the cigarette. Between the ribs there are annular spaces 21, 22, 29 or 30 which are substantially at atmospheric pressure and which isolate the annular suction chamber around the cigarette from the spaces at the ends of the cigarette, so as to prevent a direct leak of suction. except through the cigarette wrapping.

Means are provided at the testing position to communicate between each end of a cigarette and a respective stationary test device. These means comprise a sliding valve block 36 which is urged by a spring 37 into engagement with a manifold ring 38 on the end face of the carrier drum 1 and which has a flow passage 39 connected by a pipe 40a to a testing device in the form of a suction transducer 40 which generates an electrical signal related to the pressure at the end of a cigarette. The sliding valve block 36 is supported from a shaft 41 (Figure 1), on which the drum 1 rotates, by a bracket 42.

The manifold 38 is formed with transverse passages 43, one for each end of the cigarette, to provide communication successively between the suction transducer and the ends of the successive cigarettes via passageways 45 and 46 (see Figure 2). Between the passageways 43 there are passageways 44 (see Figure 1): these communicate with the air space 21 and 22 via 47 in the discs 17, and 20, respectively as shown in Figure 3, which is a radial section slight offset from Figure 2 so as to pass through a passageway 44. By this means, as the carrier drum 1 rotates, the suction transducer is alternately connected with a cigarette subjected to suction in the testing position, and then with atmosphere.

The suction transducer may for example be of the type incorporated in the Molins CID 4, comprising a pair of stainless steel diaphragms each forming part of a chamber to which a pipe is connected at each end of the transducer. The diaphragms are joined at their centres by a light rod which carries at its centre a core of magnetic material. A differential transformer carrying a primary winding and two oppositely-connected secondary windings, surrounds the core. The primary winding is driven with an alternating voltage at 10 KHz and with the diaphragms at rest the core provides equal magnetic coupling to each secondary winding. Thus each secondary winding has the same voltage induced in it, and the differences of these voltages is zero.Diaphragm deflection, due to applied positive or negative pressure, moves the core and increases the coupling to one secondary while reducing that to the other so that an a.c. output results either in phase or out of phase with the energising voltage and with an amplitude proportional to diaphragm deflection.

The leading end 48 of the guide II extends up into the groove 29 in the ring 27 of the closure drum 2 to ensure that none of the cigarettes sticks in the flutes 13 after testing.

The closure drum 2 is driven to rotate in synchronism with the carrier drum I by a gear 51 on the closure drum which meshes with a gear 51a on the carrier drum. On each drum the number of gear teeth equals the number of flutes, so that the gears can be brought into mesh in any position and will automatically cause the flutes on the two drums to register. Alternatively there may for example be twice as many gear teeth as there are flutes, though some care is then required to ensure that the flutes register.

An ejector is provided to remove from the stream of tested cigarettes any that are regarded as being unsatisfactory. The ejector may comprise an air jet positioned, for example. adjacent to the end of one of the flutes of the drum 9, to blow cigarettes endwise out of the stream, and operated by a valve controlled from the signal produced by the suction transducer.

The machine is positioned at the output from a cigarette-making machine, which may include plug-assembler apparatus for making filter tip cigarettes, and operates continuously to separate unsatisfactory cigarettes from the stream produced by the cigarette-making machine in the manner which will now be described.

The cigarettes on the conveyor 7 are picked up by suction on to the drum 8 and carried around to the carrier drum 1, at which point suction to the flutes of the drum 8 is cut off and they are held in the flutes in the carrier drum I by the guide rails 10.

Rotation of the drum I carries each cigarette in succession under the guide 10 into the testing position, and as it approaches this position it is gradually covered by one of the flutes 13 of the closure drum 2. At the same time the passage 12 in the closure drum comes into register with the port 50, thereby connecting the flute 13 with suction. In the testing position, as can be seen in Figure 2, suction is applied to the zone around the middle of the cigarette between the formers 27 and 28 and between the discs 18 and 19.

Some air flows into this zone from atmosphere in the air rings around the cigarettes under the ribs 16 and 26, but since the free flow under these ribs is not possible and since the suction source is large, the pressure in this zone is reduced below atmosphere. As a result of this reduced pressure some air may flow from the interior of the cigarette through the wrapper.

If, as is the usual case with cigarettes. the wrapper is somewhat air-pervious then there is always some air flow through the wrapper in addition to the ventilation flow through the perforations of the filter. even with cigarettes that are regarded as being satisfactory. However. if the wrapping of the cigarettes is leaky owing, for example, to holes in the wrapping or owing to an excessively porous wrapping or owing to a poor joint, then this air flow is increased. The effect of this increased air flow through the wrapper is to reduce the pressure inside the cigarette.

The filling of a cigarette has a relatively low resistance to air flow and thus the pressure at the ends of the cigarette in the regions of the end rings 24 and 25 and the end pieces 32 and 33 is reduced. This reduction of pressure at the end is sensed by the transducers 40, which causes the leaky cigarette to be ejected.

Continuous rotation of the carrier drum 1 exhausts the suction transducer to the air space 22 through the passages 44 and 47. in readiness for the next cigarette. and carries the cigarette under the guide 11 to the return drum 9 which returns the cigarette', to the conveyor 7.

Figure 5 shows a block diagram of a circuit for processing the signals obtained from the transducers 40 of Figure 1. The transducers are of the balanced-transformer type and are driven from a common oscillator 102. The output of each transducer is fed to a respective signal circuit 104 which is arranged to provide a variable degree of amplification to the signal. A sensitivity control 106 connected to the signal circuits allows the operator to set the sensitivity to the required level. The outputs from the signal circuits are connected to a "dilution computer" 108 which is arranged to process the two signals in accordance with a formula which provides a measure of the dilution, and to average dilution measurements of a number of successive cigarettes to produce a mean percentage dilution readout.

The formula for dilution may (for example) be of the general form D = K, P1 + K2 P2, where P,=suction pressure measured at the filter end of the cigarette, P2 = suction pressure at the tobacco end of the cigarette, K1, K = constants.

The exact formula used will depend on the characteristics of the cigarettes under test.

For example in some cases K, will be equal to K2 reducing the formula to D = K (P, + P2).

Generally speaking the constants must be determined empirically.

A fault detection circuit 110 may also be provided to monitor the pressure signal from one or other of the transducers directly to determine if it is too high or too low, and thus provide a signal to a "fault memory" 112 which operates a rejector device 114 after a suitable delay so as to reject a faulty cigarette from a predetermined position on a conveyor beyond the inspection device.

Referring to Figure 6, which illustrates a more practical form of the generalised circuit of Figure 5, it will be seen that a pair of transducers 116 and 118 are used which respectively monitor the suction pressure at the filter end and the tobacco end of the cigarette under test. These transducers are driven by a ten kilohertz signal from an oscillator 120 and their output signals (P, and P2 respectively) are amplified and demodulated in respective amplifiers 122 and 124.

An operational amplifier 126 has its input connected directly to a line 130 which carries the P, signal, and also, via switch 128, to line 132 which carries the P2 signal. Thus by opening the switch amplifier 126 can be supplied with an input signal representing only P, whereas by closing the switch a signal representing (P1 + P2) can be supplied. The amplifier is arranged to multiply the input signal by a factor K which is variable from 0.5 to 5. and the output is supplied. via an averaging circuit 134 which has a time constant of 2 seconds, to a dilution readout meter 136.

The output of amplifier 126 is also connected to a pair of comparator amplifiers 138 and 140 which are arranged to give outputs if the dilution of a cigarette exceeds an upper threshold (amplifier 138) or falls below a lower threshold (amplifier 140). The lower threshold may be inactivated, if not required, by opening switch 142 which normally sets the threshold level. The signals from the two threshold detecting amplifiers are fed to an "OR" gate 144 which can be connected to supply a signal for rejecting individual cigarettes on the basis of the dilution signal (i.e. if the dilution exceeds one of the thresholds) by selecting the upper position of switch 146.

In this position a signal is supplied from the "OR" gate, in the case of a defective cigarette, to an "AND" gate 148 which also receives an enabling pulse at its other input from line 150 whenever a cigarette is actually present in the test position, as will be explained below. The output from "AND" gate 148 is passed. via the "reject" position of a "sample" switch 152, to a shift register 154 which is used td introduce a set delay in the signal path, before passing the signal via an OR gate 156 and monostable 158 to a rejector drive 160, thus ensuring that the reject signal reaches the rejector at the same time as the defective cigarette. A push-button 162 can also be used to connect the "OR" gate to the positive supply so as to reject all cigarettes, if required for testing purposes.

Alternatively if it is wished to sample the "good" cigarettes. switch 152 can be switched over so as to receive an inverted output from gate 148 via gate 153.

Rejection may also be accomplished on the basis of either of the pressure signals, P, or P2 rather than the computed "dilution" signal, by changing over switch 146 from the position shown to the alternative position, so as to disconnect the output of "OR" gate 144.

and to connect the rejector circuit to an alternative threshold detecting circuit which works as follows: A switch 162 is arranged to connect line 164 selectively to either the P, signal line (upper position) or the P. signal line (lower position). A pair of comparator amplifiers 168 and 170 have their inputs connected to line 164 via trimmer potentiometer 166 and operate to provide upper or lower threshold signals, via an "OR" gate 174, the lower threshold being switchable on and off via switch 172 so as to provide a reject signal in exactly the same way as described above with reference to the circuit comprising elements 138-144, but on the basis of the pressure signal P, or P2.

Line 164 is also permanently connected to an electronic switching device 176 which is close whenever cigarettes are present to be tested. The "cigarette present" signal, which is also supplied to line 150 as mentioned above, is generated by an optical detector device 178 whose output is connected via an inverting gate 180, to a shift register 182.

When a cigarette is detected a "low" level appears at the output of detector 178 which is transformed to a "high" output by the gate 180 and applied to shift register 182. A timing pulse generator 183 drives the shift register 182 so that the gate signal appears after a preset time interval, at the output of the shift register and closes switch 176, and thus switch 176 is maintained closed so long as cigarettes are detected by the optical detector 178, so that the pressure signal (P, or P2) is passed to an averaging circuit comprising a capacitor 184 and voltage follower amplifier 186 driving an average cigatette signal meter 188.

For testing purposes it may be required to run the apparatus without cigarettes, to check for correct operation. To enable this to be done a line 190 is connected to a potentiometer 192 which supplies an attenuated signal representing the average of the two suction pressures appearing at the ends of the cigarette test position. Another electronic switch, 194, in this line is normally kept open, in the presence of cigarettes by the "low" output from an inverting gate 196 connected to the output of shift register 182.

When the optical detector 178 gives a "high" output, indicating the absence of cigarettes, a "low" output appears at the output of shift register 182 (after a preset delay) so that switch 176 is opened, blocking the path of the P, or P. signal, and switch 194 is closed supplying the averaged suction pressure signal to the averaging circuit 181 188 instead.

As an alternative to the system described above in which suction is applied around the cigarette wrapper and the consequent suction pressure at the ends is measured, another arrangement which may be utilised to provide two signals which can be processed in the same way, is one as shown in Figure 7 in which the wrapper of the cigarette is not surrounded by a suction chamber but is open to atmosphere, whereas each end 202 (or 204) of the cigarette is connected to a source of air pressure 206 by means of an air tight seal 208 (or 210). The air pressure is applied to the end via a restrictor 212 (or 214) and a pressure transducer 216 (or 218) is connected to the air conduit between the end 202 (or 204) and the restrictor 212 (or 214). The two signals thus obtained can be processed in the same way as before. for example by a circuit such as that shown in Figure 6.

WHAT WE CLAIM IS: 1. A method of testing ventilated cigarettes of the type in which air inlets are provided in the wrapper at or near the filter or mouth end, comprising the steps of forming an enclosed chamber around the cigarette. terminated at or near the ends of the cigarette by seal portions arranged to restrict communication between the chamber and the exterior regions of the cigarette which are adjacent the open ends of the cigarette except via the cigarette wrapping, creating an air pressure difference between the chamber and the ends of the cigarette so as to cause an air flow through the wrapper, measuring the resulting pressure at each end of the cigarette and processing the pressure signals to determine the dilution, i.e. the expected air flow. in use, into the cigarette through the wrapper.

2. A method as claimed in claim 1 in which the pressure difference is created by applying suction to the said chamber, and the resulting pressure is measured by monitoring the suction at each end of the cigarette.

3. A method as claimed in claim I in which the pressure difference is created by applying pressure air to chambers connected to the ends of the cigarette so that air is forced out through the wrapper, and the resulting pressure is measured by measuring the back pressure in each of the chambers.

4. Apparatus for testing a ventilated cigarette the apparatus comprising means for forming an enclosed chamber around the cigarette. terminated at or near the ends of the cigarette by seal portions arranged to restrict communication between the chamber and exterior regions of the cigarette which are adjacent the open ends of the cigarette except via the cigarette wrapping, means for applying suction to the said chamber, a space at each end of the cigarette communicating with the inside of the cigarette and with a respective suction transducer. and electrical circuit means arranged to process the outputs of one or both of the transducers to produce a signal indicative of the degree of ventilation of the cigarette.

5. Apparatus as claimed in claim 4 in which the transducers are of the balanced transformer type exhibiting a varying phase of output oltage as the amount of suction '-aries.

6. Apparatus as claimed in claim 4 or claim 5 further comprising an electrical circuit for processing the outputs from the transducers which includes means for averaging the dilution readings of successive cigarettes to provide an indication of their mean dilution level.

7. Apparatus as claimed in any of claims 4 to 6 further comprising an electrical circuit adapted to generate a reject signal in the event of the detection of a cigarette having an incorrect dilution characteristic.

8. Apparatus as claimed in claim 7 in which the cigarette is rejected on the basis of one or both of the measured pressure signals.

9. Apparatus as claimed in claim 7 in which the cigarette is rejected on the basis of a dilution signal computed from one or both of the pressure signals.

10. Apparatus as claimed in any of claims 4 to 9 further comprising electrical circuitry includes upper and/or lower threshold detection means so that cigarettes can be rejected if the measured or computed signals fall outside a predetermined range.

I I. Cigarette testing apparatus comprising a rotary carrier drum which has circumferentially spaced axial flutes and which carries the cigarettes, one in each flute, from an input conveyor, and including seal portions at the ends of the flutes to restrict communication between the interior and exterior of the cigarette wrappings via the open ends of the cigarette wrappings during testing, characterised in that the cigarettes are carried by the carrier drum past a cooperating closure drum which rotates adjacent to the carrier drum, about an axis parallel to that of the carrier drum and at the same peripheral speed. and has circumferentially spaced closure parts which register with the flutes on the carrier drum and are so shaped that each closure part of the closure drum co-operates with a flute of the carrier drum to define momentarily a chamber around the cigarettes, terminated at or near the ends of the cigarette by seal portions defined partly by the carrier drum and partly by the closure drum to restrict communication between the interior and exterior of the cigarette via the open ends of the cigarette wrapping, each of the said ends being arranged to communicate with a suction transducer, which transducers are connected to processing means for producing a signal indicative of the degree of ventilation of the cigarette.

12. Apparatus as claimed in claim 11 in which the carrier drum and closure drum have circumferentially-spaced axially-extending flutes, so that at the moment of testing of a particular cigarette, it lies partly in the flute in the carrier drum and partly in the flute in the closure drum.

13. Apparatus as claimed in claim 11 or claim 12 in which the closure drum is carried by a housing pivoted about an axis parallel to the carrier drum and closure drum axes to enable the closure drum to be swung away from the carrier drum about the housing pivot axis.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

204) and the restrictor 212 (or 214). The two signals thus obtained can be processed in the same way as before. for example by a circuit such as that shown in Figure 6.

WHAT WE CLAIM IS: 1. A method of testing ventilated cigarettes of the type in which air inlets are provided in the wrapper at or near the filter or mouth end, comprising the steps of forming an enclosed chamber around the cigarette. terminated at or near the ends of the cigarette by seal portions arranged to restrict communication between the chamber and the exterior regions of the cigarette which are adjacent the open ends of the cigarette except via the cigarette wrapping, creating an air pressure difference between the chamber and the ends of the cigarette so as to cause an air flow through the wrapper, measuring the resulting pressure at each end of the cigarette and processing the pressure signals to determine the dilution, i.e. the expected air flow. in use, into the cigarette through the wrapper.
2. A method as claimed in claim 1 in which the pressure difference is created by applying suction to the said chamber, and the resulting pressure is measured by monitoring the suction at each end of the cigarette.
3. A method as claimed in claim I in which the pressure difference is created by applying pressure air to chambers connected to the ends of the cigarette so that air is forced out through the wrapper, and the resulting pressure is measured by measuring the back pressure in each of the chambers.
4. Apparatus for testing a ventilated cigarette the apparatus comprising means for forming an enclosed chamber around the cigarette. terminated at or near the ends of the cigarette by seal portions arranged to restrict communication between the chamber and exterior regions of the cigarette which are adjacent the open ends of the cigarette except via the cigarette wrapping, means for applying suction to the said chamber, a space at each end of the cigarette communicating with the inside of the cigarette and with a respective suction transducer. and electrical circuit means arranged to process the outputs of one or both of the transducers to produce a signal indicative of the degree of ventilation of the cigarette.
5. Apparatus as claimed in claim 4 in which the transducers are of the balanced transformer type exhibiting a varying phase of output oltage as the amount of suction '-aries.
6. Apparatus as claimed in claim 4 or claim 5 further comprising an electrical circuit for processing the outputs from the transducers which includes means for averaging the dilution readings of successive cigarettes to provide an indication of their mean dilution level.
7. Apparatus as claimed in any of claims 4 to 6 further comprising an electrical circuit adapted to generate a reject signal in the event of the detection of a cigarette having an incorrect dilution characteristic.
8. Apparatus as claimed in claim 7 in which the cigarette is rejected on the basis of one or both of the measured pressure signals.
9. Apparatus as claimed in claim 7 in which the cigarette is rejected on the basis of a dilution signal computed from one or both of the pressure signals.
10. Apparatus as claimed in any of claims 4 to 9 further comprising electrical circuitry includes upper and/or lower threshold detection means so that cigarettes can be rejected if the measured or computed signals fall outside a predetermined range.
I I. Cigarette testing apparatus comprising a rotary carrier drum which has circumferentially spaced axial flutes and which carries the cigarettes, one in each flute, from an input conveyor, and including seal portions at the ends of the flutes to restrict communication between the interior and exterior of the cigarette wrappings via the open ends of the cigarette wrappings during testing, characterised in that the cigarettes are carried by the carrier drum past a cooperating closure drum which rotates adjacent to the carrier drum, about an axis parallel to that of the carrier drum and at the same peripheral speed. and has circumferentially spaced closure parts which register with the flutes on the carrier drum and are so shaped that each closure part of the closure drum co-operates with a flute of the carrier drum to define momentarily a chamber around the cigarettes, terminated at or near the ends of the cigarette by seal portions defined partly by the carrier drum and partly by the closure drum to restrict communication between the interior and exterior of the cigarette via the open ends of the cigarette wrapping, each of the said ends being arranged to communicate with a suction transducer, which transducers are connected to processing means for producing a signal indicative of the degree of ventilation of the cigarette.
12. Apparatus as claimed in claim 11 in which the carrier drum and closure drum have circumferentially-spaced axially-extending flutes, so that at the moment of testing of a particular cigarette, it lies partly in the flute in the carrier drum and partly in the flute in the closure drum.
13. Apparatus as claimed in claim 11 or claim 12 in which the closure drum is carried by a housing pivoted about an axis parallel to the carrier drum and closure drum axes to enable the closure drum to be swung away from the carrier drum about the housing pivot axis.
14. Apparatus as claimed in claiin 13 in

which the closure drum axis is at a higher level than the carrier drum axis so that the closure drum is held against the carrier drum by gravity during testing.
15. Apparatus as claimed in any of claims Il to 14 including a single rotary input drive to the carrier drum, the closure drum being driven by virtue of carrying a gear wheel meshing with a gear wheel on the carrier drum.
16. Apparatus as claimed in claim 15 in which the number of teeth on each gear wheel equals the number of flutes on the corresponding drum, so that the gear wheel can be brought into mesh in any position and will automatically cause the flutes on the two drums to register with one another.
17. A method of testing ventilated cigarettes substantially as herein described.
18. Apparatus for testing ventilated cigarettes substantially as herein described with reference to the accompanying drawings.