WO1997029654A1

WO1997029654A1 - Cigarette manufacture

Info

Publication number: WO1997029654A1
Application number: PCT/GB1997/000442
Authority: WO
Inventors: John Dawson; Eric Bryden
Original assignee: Molins Plc
Priority date: 1996-02-15
Filing date: 1997-02-17
Publication date: 1997-08-21
Also published as: AU1803997A; GB9603193D0

Abstract

A cigarette rod scanning device for a cigarette making machine comprises an X-ray beam emitter (20) arranged to emit an X-ray beam of which a portion will pass through the cigarette rod (18) and towards a first detector (22), and to direct a second portion of the beam to a second detector (26), the output from the second detector being fed to a control circuit (30) whereby the X-ray emitter is controlled so as to maintain the output from the second detector substantially constant, and the output from the first detector being used to produce a signal indicative of the density of the cigarette rod.

Description

Cigarette Manufacture

2

3 This invention relates to the control of cigarette rod weight, during

« manufacture, by means of an X-ray scanner. In this connection attention

₅ is directed to our patent publication No. WO 95/31908. e According to one aspect of the present invention, a scanning

7 device for a cigarette making machine comprises an X-ray beam emitter a arranged to emit an X-ray beam of which a portion will pass through the

9 cigarette rod and towards a first detector, and to direct a second portion ιo of the beam to a second detector, the output from the second detector ii being fed to a control circuit whereby the X-ray emitter is controlled so as ι₂ to maintain the output from the second detector substantially constant, i3 and the output from the first detector being used to produce a signal

IA indicative of the density of the cigarette rod. The control circuit is preferably controls the output of the X-ray emitter by controlling the ie applied voltage or by controlling the anode current. i7 The two detectors are preferably maintained at the same is temperature. For example, they may be mounted on a common heat i9 sink. The level of the temperature may be controlled by heating or

∑o cooling devices so as to lie permanently within a predetermined range.

₂ι In one preferred construction according to this invention, the

22 portion of the X-ray beam that is directed towards the second detector

23 also passes through a reference member which preferably has X-ray

₂4 energy absoφtion characteristics similar to a cigarette rod. For example, ₂s the reference member may include tobacco, possibly in the form of ∑e parallel sheets of reconstituted tobacco bonded together by an

27 appropriate material having similar X-ray absoφtion characteristics, or

₂8 characteristics similar to those of windows in a guide tube for the

29 cigarette rod through which the X-ray beam scanning the rod must pass.

30 The X-ray emitter is preferably positioned in relation to the 3i cigarette rod and reference member so as to pass substantially identical

32 radiation beams through both and towards their respective detectors; the

33 two detectors may, for example, be symmetrically disposed on

3 diametrically opposite sides of the axis of the X-ray beam. The

35 difference between the outputs from the two detectors is indicative of

36 deviation of the cigarette rod weight from what can be regarded as a

37 normal value. That difference may be used to control the position of a

38 cigarette filler stream trimmer or other device for controlling the rod 1 weight or density. If a different nominal rod weight is required, this may

2 be achieved by replacing the reference member with a member which

3 absorbs more or less of the X-ray radiation, or by changing the amplified signal from the second detector before it is applied to a comparator

5 receiving also a constantly amplified signal from the first detector.

6 Alternatively, the nominal cigarette weight may be altered by

7 adjusting the gain of an amplifier in the control device controlling the β beam emitter, and the trimmer or other means for controlling the amount 9 of tobacco going into the cigarette rod may be controlled by the ιo difference between the outputs from the two detectors so as to maintain ii that difference as close as possible to zero. i2 The output from the first detector (or the difference between the is outputs from the two detectors) is preferably amplified by a log amplifier i (or log ratio amplifier) before being applied to the device for controlling is the amount of tobacco going into the cigarette rod. By this means, the i output obtained from the amplifier can be arranged to be substantially i7 proportional (or inversely proportional) to the density of the cigarette rod. ie The amplifier may be type 4127 made by Burr Brown, of International i9 Airport Industrial Park, Tucson A2 85734, USA.

20 The X-ray emitter is preferably powered by an accelerating voltage

2i of approximately 10kV or less. An accelerating voltage of approximately

22 10kV provides optimal sensitivity to variations in the density of the

23 cigarette rod since an average cigarette rod absorbs about 50% of the

2 X-rays from an emitter powered at 10kV. The X-ray emitter may be of a

25 concentric ceramic type. The current may be approximately 3mA or less,

26 for example as low as 1mA. For this purpose the X-ray emitter may have

27 a copper or silver target in place of the more usual tungsten target to

28 enhance the energy in the relevant energy band.

29 In the case of a twin-track cigarette making machine, a single

30 X-ray emitter may be used to direct identical beams towards and through 3i the two rods and through a common reference member, as described in

32 our above-mentioned patent application. However, it is preferable to use

33 two X-ray emitters for scanning the respective cigarette rods, each with

34 an associated reference member and corresponding second detector.

35 A scanning device according to this invention may include a third

36 detector which receives a portion of the beam emitted by the X-ray

37 emitter and of which the output is compared continuously with that of the

38 first detector to produce a signal indicative of the density of the cigarette 1 rod, the portions of the beam directed towards the second and third

2 detectors being preferably arranged to pass through the same reference

3 member or through similar reference members. Alternatively, the function of the third detector just described may be performed by the

5 second detector, and the third detector may be omitted.

6 Example of scanning devices and systems according to this

7 invention are shown diagrammatically in the accompanying drawings. In β the drawings: Figure 1 is a schematic illustration of one system according to this ιo invention; a Figure 2 further illustrates diagrammatically the relationship of the i2 rod scanning components of a system such as that shown in figure 1 ; i3 Figure 3 is a sectional view of the slightly modified arrangement; i4 and is Figure 4 is a circuit diagram illustrating one form of system ie according to this invention. i7 As shown in Figure 1 , a tobacco stream 10 carried by a suction is band 12 is trimmed by a trimming device 14 before entering a rod i9 forming device 16 in which the tobacco stream is enclosed in a paper

20 wrapper to form a continuous cigarette rod 18. The rod is scanned by a

2i device comprising an X-ray emitter 20 which passes a beam of X-ray

22 radiation through the rod 20 and towards a first detector 22, and also

23 through a reference member 24 (what may be termed a "dummy

24 cigarette") and towards an identical second detector 26. The rod 18 and

25 reference member 24 are symmetrically positioned with respect to the

26 X-ray beam (as illustrated in Figure 2 or Figure 3) so that the total X-ray

27 energy reaching each of them is the same.

2β The outputs from both detectors 22 and 26 are fed to a control

2 unit 27 (which may include a log ratio amplifier) whereby a difference

30 signal (the difference between the signals from the two detectors) is 3i amplified and fed through a line 28 to control the position of the trimmer

32 14. The signal fed by the line 28 is substantially proportional to the

33 density of the cigarette rod at the scanner.

34 The output from the second detector 26 is also fed to a control

35 circuit 30 which controls the X-ray energy of the emitter 20 so as to

36 maintain the output from the detector 26 substantially constant. For

37 example, the control circuit 30 may vary the current which passes 3β through a heater for the X-ray filament; an alternative is that the X-ray 1 emitter may comprise an X-ray tube including a grid for controlling the

₂ anode current, an example of a tube suitable for use in that way being

3 available from Hamamatsu Photomics UK, Lough Point, 2 Gladbeck Way, Windmill Hill, Endfield, Middlesex, UK (e.g. their type No. M1335). s In the region of the scanner the cigarette may be guided by being

6 passed through a thin-walled tube which is preferably of a suitable

7 plastics material such as polycarbonate or PEEK. The dummy cigarette a (reference member 24) may comprise a rod formed from tobacco 9 particles impregnated and encapsulated in a resin such that the X-ray absorption of the tobacco particles in the path of the X-ray beam is substantially the same as the tobacco in a cigarette rod of the desired nominal density, and the resin absorbs X-rays to substantially the same i3 extent as the part of the cigarette guiding tube which is in the path of the i4 X-rays directed towards the detector 22. Alternatively the member 24 is may comprise sheets of reconstituted tobacco bonded together by ie layers of a resin to form a composite sheet through which the X-ray i7 beam portion directed towards the second detector is arranged to pass. ie The target weight of the cigarettes may be changed by altering a i9 reference signal with which the signal from the line 28 is compared

20 before controlling the trimmer. Another possibility is that the reference

2i member may be replaced by one having a different X-ray absorption

22 characteristic, or may be an elongated wedge shape so that axial

23 movement of the reference member changes the part of the reference

24 member which is in the path of the X-ray beam, and hence changes the

25 X-ray absorption. Another possibility is that the beam directed towards

₂6 the second detector may pass through a window or past a shutter

₂7 adjustable to vary the proportion of the beam that can reach the second ∑β detector; in this case it may be possible to omit the reference member.

29 Figure 2 shows diagrammatically more details of a cigarette rod

30 scanning device according to this invention. The device includes an 3i X-ray beam emitter 32 comprising an outer case 34 carrying at opposite

32 ends an anode 36 and a cathode 38. The cathode 38 comprises a coil

33 or filament which is heated by means of a power supply 40. An

34 accelerating voltage is applied between the cathode and the anode by

35 means of a power supply 42 and produces an X-ray beam 44 which

36 emanates from the centre of an inclined surface 36A of the anode. The

3 anode may be of copper, and the "target" from which the X-ray beam is 3β emitted may be of tungsten. 1 The X-ray beam 44 passes out of the casing 32 via a window 46

₂ which may be of beryllium. Identical portions of the X-ray beam pass

3 respectively through a cigarette rod 48 and a reference member 50 which is shown as having the form of a dummy cigarette; for this

5 purpose the cigarette rod and reference member are symmetrically e disposed on opposite sides of the centreline of the X-ray beam.

7 Similar proportions of the X-ray beam portions directed towards s the cigarette rod and reference member are absorbed respectively by those members, and the remainder of each beam portion passes ιo towards a corresponding first detector 52 and second detector 54. ii Figure 2 shows diagrammatically also a mask 56 with apertures through i2 which the X-ray beam portions pass and by which their boundaries are i3 determined, though the actual arrangement (as shown in Figure 3) may i be different. is Figure 2 also shows a heat sink member 58 for carrying the two i6 detectors and for maintaining them at the same temperature. In Figure i7 2, the planes of the detectors 52 and 54 are shown to be inclined so that is each is normal to the central axis of the portion of the X-ray beam i directed towards it; in practice, however, the detectors may lie in a

₂o common plane, as shown in Figure 3.

2i The outputs from the detectors 52 and 54 pass respectively to

22 amplifiers 60 and 62, and the outputs from these amplifiers may be fed

23 to a differential amplifier as shown in Figure 4. The output from the

24 amplifier 62 may also be used to control the accelerating voltage applied

₂5 to the emitter 32 by the power supply 42 in accordance with this

26 invention.

27 Figure 3 shows a more precise form of cigarette rod scanning 2β device according to this invention. In particular it shows an X-ray beam

2 emitter 64 (which may be like that shown in Figure 2) mounted in a 0 casing 66 including a window 68 to allow the passage of two X-ray beam 3i portions 70 and 72. These two portions of the X-ray beam are directed

32 respectively to first and second detectors mounted on a heat sink

33 member 74, the detectors being in a common plane for convenience.

34 The cigarette rod is guided, in the region of the X-ray beam scanner, by 5 a guide tube 76 having front and back windows (transparent to X-rays)

36 defining the cross-section of the portion of the X-ray beam that passes

37 through the cigarette and towards the corresponding detector. A similar

38 tubular member 78 in this arrangement is arranged to hold a dummy 1 cigarette serving as a reference member, and this may have windows

₂ similar to those in the guide tube for the cigarette rod. The casing 66 may be filled with oil for cooling purposes.

4 Vertical sheets of material transparent to X-rays (e.g. Mylar) may

5 be placed on each side of the tubes 76 and 78 to isolate the X-ray beam

6 emitter and the detectors from tobacco in the cigarette rod. In that case

7 the windows in the tube 76 can, for convenience be true openings. a Figure 4 shows more fully a form of control circuit which may be associated with a cigarette rod scanning device according to this

10 invention. As in Figure 2, it shows an X-ray beam emitter 80 comprising

11 an anode 82 and a cathode 84. A constant accelerating voltage of

12 approximately 10kV or slightly less is applied between the anode and the i3 cathode by a voltage source 85. Control of the X-ray beam energy is i4 achieved by controlling the voltage applied to the filament which is comprises the cathode 84, this control being described below. i6 As an alternative, or in addition, the anode current in the emitter i7 80 may be controlled by means of a grid 87 to which a controllable is voltage is applied in a manner not shown. An X-ray beam emitter in this i9 form (minus the grid) is available from Lohmann, of

20 Hardenbergstrasse-1 , Leverkusen, Germany.

2i Identical portions of the X-ray beam are directed towards and

22 through a cigarette rod 86 and a reference member 88. In this Figure

23 the detectors are represented respectively by diodes 90 and 92 which

₂4 are connected to respective identical current-to-voltage converters 94

₂5 producing outputs at points 96 and 98 which are applied to a differential

26 amplifier 100. The output from the amplifier 100 is fed to an error

27 amplifier 102 to which an input is also applied from a potentiometer 104.

28 Adjustment of the potentiometer 104 adjusts the output from the

29 amplifier 102 and hence the average position of the trimming device

30 (item 14 in Figure 1 ) which determines the weight per unit length or 3i density of the cigarette rod. In other words, if the target weight of the

32 cigarette rod is to be increased then the potentiometer is adjusted in one

33 way, and conversely if the target weight is to be decreased.

3 The voltage applied to the filament 84, and hence the anode

35 current and the intensity of the X-ray beam, is determined by an amplifier

36 106 of which the output is determined firstly by the output at point 108

37 from the reference detector 92, and secondly by the settling of a

₃₈ potentiometer 110. As a result, the voltage applied to the cathode 1 filament 84 is continuously controlled so as to maintain the X-ray beam

2 energy at a desired level determined by the setting of the potentiometer

3 110. Thus the intensity of the X-ray beam directed through the cigarette

4 rod is maintained at a desired level.

5 The circuit shown in Figure 4 does not include a log ratio

6 amplifier. If such an amplifier is to be used, the currents passed by the

7 diodes 90 and 92 are fed through the log ratio amplifier to produce an s output representing the log of the ratio of those currents. That output

9 may be fed to a summing amplifier which also receives an adjustable

10 input from a further amplifier such that the output from the summing ii amplifier is zero when the cigarette rod is at the desired density, and is i2 positive or negative at other times so as to drive the trimming device 14 i3 (Figure 1) upwards or downwards, as the case may be, to achieve the i desired cigarette density. The control of the X-ray emitter may be is effected by means of a third detector (as described above) which ie preferably receives a proportion of the X-ray beam identical to those i7 received by the first and second detectors.

18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38

Claims

Claims:

3 1. A cigarette rod scanning device for a cigarette making

4 machine, comprising an X-ray beam emitter (20; 32; 64; 80) arranged to s emit an X-ray beam of which a portion will pass through the cigarette rod 6 (18; 48; 86) and towards a first detector (22; 52; 90), and to direct a

7 second portion of the beam to a second detector (26; 54; 92), the output β from the second detector being fed to a control circuit (30; 40; 106, 110)

9 whereby the X-ray emitter is controlled so as to maintain the output from ιo the second detector substantially constant, and the output from the first ii detector being used to produce a signal indicative of the density of the i2 cigarette rod.

13 i4 2. A scanning device according to claim 1 , in which the is control circuit (30; 40) controls the output of the X-ray emitter by ie controlling the voltage applied to the X-ray emitter.

17 is 3. A scanning device according to claim 1 , in which the i9 control circuit (30; 106,110) controls the output of the X-ray emitter by

20 controlling the anode current thereof.

21

22 4. A scanning device according to claim 3, in which the anode

23 current is controlled by controlling the filament current which determines

24 the temperature of the cathode (84) of the X-ray emitter, or is controlled

25 by controlling the voltage applied to a grid (86) lying between the

26 cathode and the anode.

27

28 5. A scanning device according to any one of claims 1 to 4, in

29 which the second detector (26; 54) is associated with a reference

30 member (24; 50) through which the portion of the X-ray beam directed 3i towards the second detector passes.

32

33 6. A scanning device according to claim 5, including a circuit

3 for comparing the outputs of the two detectors and for producing

35 therefrom a signal indicative of the density of the cigarette rod.

36

37 7. A scanning device according to any one of claims 1 to 5,

38 including a third detector which receives a portion of the beam emitted 1 by the X-ray emitter and of which the output is compared continuously

2 with that of the first detector to produce a signal indicative of the density

3 of the cigarette rod.

4

5 8. A scanning device according to claim 7, in which the

6 portions of the X-ray beam directed towards the second and third

7 detectors we both arranged to pass through a common or similar a reference member.

9 lo 9. A scanning device according to any one of claims 5, 6 and ii 8, in which the reference member (or members) is formed partly from i2 tobacco.

13 i 10. A scanning device according to any one of claims 1 to 5, in is which the portions of the X-ray beam directed towards the first and ie second detectors are identical, the two detectors being equidistant from i7 the centre-line of the whole X-ray beam and at equal distances from the is source of the X-ray beam.

19

20 11. A scanning device according to any one of claims 1 to 10,

2i in which the X-ray energy absorption characteristics of the reference

22 member are identical or similar to those of a cigaretter rod.

23

2 12. A scanning device according to any one of claims 1 to 11 ,

25 in which the reference member comprises sheets of reconstituted

26 tobacco bonded together.

27

28 13. A scanning device according to any one of claims 1 to 12,

29 in which the two detectors are both connected to a log ratio amplifier

30 whereby an output linearly proportional (or inversely proportional) to the 3i cigarette rod density is produced.

32 33 34 35 36 37 38