Cigarette ends testing

A cigarette ends tester includes a conveyor for conveying cigarettes sideways past a source of light arranged to direct light substantially axially into the ends of successive cigarettes in such a way that the paper wrapper around the end of each cigarette is illuminated if there is insufficient tobacco in the end, and a detecting device for monitoring the consequent external illumination of the end of the cigarette. The test signal for each cigarette is evaluated against a reference signal derived from satisfactory cigarettes tested previously during a predetermined time interval, thus compensating for variable factors affecting the test signal, such as ageing or dirt on the light emitting or detecting devices.

This invention is concerned with a device for testing the ends of 
cigarettes to detect cigarette ends which are inadequately filled with 
tobacco. Such cigarettes may be rejected automatically. An earlier 
proposal using a source of light and a light detector is described in our 
British patent specification No. 1335662. 
According to the present invention, a device for testing the ends of 
cigarettes comprises means for conveying cigarettes sideways past a source 
of light arranged to direct light substantially axially into the ends of 
successive cigarettes in such a way that the paper wrapper around the end 
of each cigarette is illuminated if there is insufficient tobacco in the 
end, and means for monitoring the consequent external illumination of the 
end of the cigarette. 
The source of light is preferably mounted in a member which is contacted by 
each cigarette to prevent direct transmission of light (i.e. between the 
member and the cigarette) towards the light detector. The source of light 
may be unfocussed so as to emit a wide-angle diverging beam capable of 
illuminating the entire wrapper around an inadequately filled cigarette 
end. 
Preferably there are a number of detectors focussed onto circumferentially 
spaced areas of the wrapper. For example, there may be two pairs of 
detectors between which the cigarettes are arranged to pass during 
testing. 
The test signal for each cigarette is preferably evaluated against a 
reference signal derived from satisfactory cigarettes tested previously 
during a predetermined time interval.

FIG. 1 shows one cigarette 10 at a testing station in which it is axially 
aligned with a light-emitting diode 12 mounted in a member 14 so as to be 
recessed from the surface of the member 14 adjacent to the end of the 
cigarette. As seen in FIGS. 1 and 2, an annular insert 15 in the member 14 
serves as a shield preventing or minimizing the direct transmission of 
light from the source 12 to a number of light detectors in the form of 
photo-transistors 16 arranged to detect light emanating from the wrapper 
in the region of the cigarette end. 
Light from the source 12 enters the cigarette via a thin transparent window 
18 which seals the aperture containing the source 12 and forms a smooth 
continuation of the surface 15A of the member 15 adjacent to the cigarette 
end and having a light transmitting bore 15B of diameter equal to that of 
the cigarette (or slightly less). In practice, each cigarette end is 
intended to contact the member 15 immediately before and after testing, 
and to contact the window 18 during testing. 
The source 12 emits a beam diverging by about 80 degrees so as to 
illuminate the cigarette wrapper to an extent dependent upon the amount of 
tobacco in the cigarette end. Each of the photo-transistors 16 is able to 
detect illumination of the wrapper to an angle of approximately 34 degrees 
with a reduction of sensitivity at the extremities of not more than 50%. 
Accordingly, as also apparent from FIG. 2, the four detectors 16 cover 
substantially the entire circumference of the cigarette. 
By way of example, the source 12 may be a G.E. F5E1 device capable of being 
pulsed at 1 amp for 100 microseconds. The detectors 16 are Optron OP603 or 
OP643 phototransistors. 
FIG. 3 shows two sources 12 for testing the ends of two rows of cigarettes 
simultaneously. The remainder of FIG. 3 shows the circuit for one test 
arrangement and is duplicated if two rows are to be tested. 
Each test occurs during a period of 100 microseconds timed by a strobe 
pulse which is transmitted via a monostable device 20 to a transistor pair 
TR to strobe the two light sources 12. As a result of two solid-state 
switches B1 and B2, which are controlled by the monostable device 20, the 
combined signal received from the four detectors via amplifier A1 is 
applied to amplifier A2 and effectively inverted (see the A2 input wave 
form in FIG. 4), to produce a negative-going signal and the amplitude of 
each pulse at the output of amplifier A2 is averaged by a capacitor 22 to 
establish a reference level. The capacitor 22 with a 10 second time 
constant stores a potential corresponding to this reference level. A 
digital attenuator 24 controlled by a hexadecimal switch 26 reduces, by a 
set proportion, the signal level of the pulses received from each 
individual cigarette, and the result is fed via amplifier A3 to a 
comparator C2 in which each signal is compared with the reference 
potential provided by capacitor 22. A signal from any given cigarette 
which exceeds the reference potential by a set amount (e.g. 1.33 times) 
will result in a fault signal being emitted by the comparator C2 and 
stored in a latch L1 under control of a monostable circuit 23. A faulty 
cigarette may be automatically rejected by any well known ejector means in 
response to the fault signal. 
The arrangement enables cigarette ends to be tested reliably without undue 
sensitivity to temperature, ambient light, or ageing or misalignment of 
the light emitting and detecting devices. 
It should be noted that missing cigarettes are detected and that signals 
from them are not transmitted to the reference capacitor. For this purpose 
amplifier C1, on receiving a signal of less than 1 V, causes the A2 output 
to go positive so as not to change the reference capacitor voltage.