Cigarette manufacture

Details Cigarette manufacture Cigarette manufacture

1996-11-18

1998-08-25

Millin, Vincent

Tobacco

Cigar or cigarette making

Molding or forming

131 842, 131 844, 131281, A24C 514

Patent

active

057974063

DESCRIPTION:

BRIEF SUMMARY
In the manufacture of cigarettes it is common to use a nucleonic device for scanning the finishing cigarette rod, usually before it is cut into individual rod lengths, to enable cigarette weights to be controlled by means of a trimming device which removes a variable proportion of the tobacco stream forming the cigarette filler. The rod weight signal can also be used to enable underweight cigarettes or cigarettes with pronounced voids to be ejected further downstream, usually in the filter attachment machine. The use of nucleonic scanning devices for these purposes has been common in the cigarette industry for many years.
This invention is based partly on an appreciation that a low-energy X-ray beam of the type described (which for convenience will be referred to as an X-ray beam) can be used safely in the environment of a cigarette making machine and produces a satisfactory weight signal when used in combination with a photodiode detector with a height approximately equal to the diameter of a cigarette rod. Low-energy X-ray sources have become available as proprietary items. Previously available higher-energy sources were not suitable for cigarette scanning, mainly because the predominately higher frequencies penetrated too readily to give a useful rod weight signal. A low energy X-ray source, on the other hand, can be used in combination with a photodiode by which a beam about the same height as, or slightly less than, the diameter of the cigarette rod can be received and monitored to provide a signal averaging the rod density across its diameter; the reference here to the height of the beam is based on the assumption that the beam is directed horizontally through the rod, though the beam may alternatively, for example, be vertical.
The use of an X-ray beam system for scanning a cigarette rod is disclosed in British patent specification No. 2133965. That specification discusses the possibility of scanning, by means of an X-ray beam, either the completed cigarette rod or the cigarette filler stream before it is enclosed in a wrapper web to form a rod. For both purposes the patent applicant assumes that the strength of the X-ray beam can be maintained precisely. However, we have discovered that, for precise control of the weights of cigarettes, it would be very difficult and very expensive to maintain the voltage applied to the X-ray beam emitter with sufficient accuracy to achieve a satisfactory result. Moreover, we have found that temperature variations of the X-ray beam detector can have a significant effect on the output signal of the detector, and we have found it important to provide a second or reference detector to compensate for temperature variations of the main detector.
According to the present invention, a scanning device for a cigarette making machine comprises a low energy X-ray beam emitter for passing an X-ray beam through the cigarette rod and towards a photodiode or other plate-like X-ray detector which produces an output signal responsive to the strength of the X-ray beam reaching the detector, which signal is fed to a control circuit for the cigarette making machine, characterised in that the scanning device includes a reference detector of similar type to the first-mentioned detector, that both detectors are mounted on a heat-conducting member whereby they are maintained at substantially the same temperature, and that outputs from both detectors are fed to the control circuit, which is arranged to compensate for temperature-induced variations in the output from the first detector by reference to the output from the second detector.
The second (reference) detector is preferably substantially identical to the first detector, and the two detectors are mounted symmetrically with respect to the axis of the X-ray beam so that equal beam strengths are directed towards the two detectors. Thus the output from the second detector can compensate not only for variations in the temperature of both detectors, but also for variations which inevitably occur in the beam strength of the X-ray emitter a

REFERENCES:
patent: 4785830 (1988-11-01), Moller et al.
patent: 4865052 (1989-09-01), Hartmann et al.

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