Paper perforation monitor - Patent Review GB19830022842 19830825

Description

SPECIFICATION

Perforation monitor

This invention relates to an optical device for monitoring perforated cigarette tipping.

In the cigarette manufacturig industry a "tip" or "tipping" is the term used to describe the paper wrapper which is provided around a cigarette filter and which extends a little way over the adjacent paper around the tobacco thereby securing the filter to the rest of the cigarette. In recent years it has become the practice to perforate the tip with small or microperforations that are barely visible.

When such a cigarette is smoked air is drawn in through the perforations which dilutes the tobacco smoke that is inhaled by the smoker.

The effect, therefore, of the perforations is to reduce the tar rating of a cigarette.

It is, of course, essential that the amount of perforation in a tip be very carefully controlled. If the tip is excessively perforated then the dilution of the cigarette smoke will be too great. On the other hand if the tip is inadequately perforated there will be insufficient dilution. In either case the cigarette performance may differ from the tar rating indicated on the package.

The present method of checking perforations in the tip is to remove a length of tipping during manufacture thereof, that is to say from the perforating machine, and test it mechanically in a laboratory by measuring the air flow therethrough. The disadvantage with this method is that the perforating machine must be stopped while the peforations are being checked. There is, therefore, a need for an in-line perforation testing device and the invention has been made with that in mind.

According to the invention there is provided a device for examining perforations in sheet material comprising a light source, means for stabilising said light source, means for directing radiation from said source onto one side of material to be examined, transducer means for receiving radiation passing through said material and producing a signal indicative of the said received radiation, which signal is representative of the amount of perforation in said sheet material.

The invention provides, therefore, a device which does not contract the material to be tested and which can be conveniently installed in a plant producing perforated tipping for continuously checking the tipping during manufacture thereof. If desired the output from the device of the invention can be used to regulate the operation of the perforating plant in response to any detected variation from a predetermined level of perforation.

The device of the invention can also be used by a cigarette manufacturer to monitor the perforating in tipping as it is drawn off a bobbin prior to making up into cigarettes.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing which shows a part sectional, part diagrammatic illustration of a device for examining perforations.

Referring to the drawings the device comprises a collimator1 2 having a lamp 10 mounted at one end thereof. A condenser lens1 4 is located in the collimator which directs the light from the lamp through a heat filter1 6 and an optical glass diffuser1 8 also mounted in the tube collimator.

A partition 20 extends across the collimator with a pin hole 22 formed therein. Light from the pin hole is directed as a parallel beam by collimator lens 24 from the other end of the collimator onto material 26 such as paper which is adopted to pass across the said other end of the collimator. The major plane of the material 26 is normal to the light radiation emitted from the collimator.

Light radiation passing through any perforations in the material 26 is received by lens 30 of a detector 32 which directs the light onto a fibre optic detector 28. As illustrated diagram matically the positions of the lamp, the collimator lens 24 and the detector lens 30 can be adjusted so that the light can be properly focussed. The space between the collimator 12 and detector 32 is as small as possible so as to reduce the amount of stray light that might be reflected off the material into the detector. A spacing of from 3 to 5 mm is preferred.

The light received by the detector represents the porosity of the material. The difference in detected light radiation between perforated and unperforated material is a measure of the total area of perforations in the area of the parallel beam. This information can be displayed by suitable means 34 as shown in the drawing by processing the detected light signal. In addition the information can be recorded as indicated at 36.

For reliable operation it is important that the intensity of light from the collimator should be constant. To that end a fibre optic detector 40 is positioned in the collimator near the pin hole to provide a feedback signal that is used to control the lamp power supply 42.

In the production of perforated tipping it is usual to perforate a plurality of reels of tipping paper simultaneously on one machine. The device of the invention is sufficiently small that a number of them can be mounted on the perforating machine, one for each reel of paper if desired. The signals from each device can be displayed separately or fed together to a display arrangement which will display the scan from each device successively for a predetermined period. If the measured porosity exceeds a pre set level then an audio and/or visual alarm may be triggered.

The signals from the detector can also be used to control the perforation of the tipping.

For example the signals can be compared with a pre set level and any deviation used as a feedback to the apparatus performing the perforation. When perforation is effected by spark erosion control can be achieved by using the feedback to vary the discharge chopping frequency thereby varying the density of perforation.