Patent Application
20070079840
The present invention relates to a packing machine and to a method and device for controlling cigarette tips.
On cigarette packing machines, the tips of cigarettes in a group are analyzed to ensure they are filled.
More specifically, this is done by light scattering analysis of the cigarette tips. Devices employing this type of analysis comprise a source for emitting a light beam substantially parallel to the axis of a cigarette for analysis; and sensors positioned crosswise to the cigarette to detect scattered light. As described in U.S. Pat. No. 4,907,607, to perform this type of analysis correctly on groups of cigarettes, the individual cigarettes must be offset with respect to the groups, so that the sensors are positioned correctly about the cigarettes. This complicates the packing machine (devices must be provided to offset and re-position the cigarettes) and increases the risk of damaging the cigarettes.
To check filling of cigarette tips, back scattering analysis has also been proposed, and which comprises directing a light beam, parallel to the cigarette axis, onto the tip of the cigarette, and determining the light scattered in the direction of the beam. Back scattering has the disadvantage that, in the event the cigarette tip is filled on the surface but with a void at the back, the light is still detected and the cigarette tip therefore considered properly filled.
Another important point to note is that both scattering and back scattering analysis also have the drawback of the detected data depending on the colour of the tobacco. Which means a change in tobacco colour involves recalibrating the sensors, thus increasing running cost and downtime.
It is an object of the present invention to provide a packing machine and a method and device for controlling the fill of cigarette tips, designed to eliminate the aforementioned drawbacks, and which, in particular, are cheap and easy to implement.
According to the present invention, there is provided a device and a method for controlling the fill of cigarette tips and a packing machine, as claimed in the attached Claims.
A number of non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which:
Number 1 in
Conveyor 6 comprises a belt 10; and a number of seats 11, each for housing a respective group 7 of cigarettes 4 comprising three superimposed rows 12 of cigarettes 4.
Control unit 9 comprises a number of—in particular, three—microwave sensors 13 arranged one on top of another, so that, as group 7 of cigarettes 4 travels through control station 8, each sensor 13 detects the density of the tips of cigarettes 4 in a respective row 12.
In the
Each sensor 13 comprises a body 15 made of conducting material (e.g. aluminium) and having a substantially circular groove 16 defining a flat member 17 coated externally with two layers 17′ and 18 of dielectric material (e.g. alumina or plastic), and a further layer 19 of conducting material. Layer 17′ directly contacts flat member 17, and is located on the opposite side of layer 19 to layer 18. Flat member 17 is typically about 8 mm in diameter.
Each sensor 13 also comprises two electrodes 20 for connecting layer 17′ of dielectric material to a generator 21 and to a detector (not shown) of a computer 22 respectively.
In actual use, as a group 7 of cigarettes 4 travels through control station 8, each sensor 13 emits a detection signal for each cigarette 4 whose tip 3 travels through the respective microwave field 14. At this point, computer 22 compares the detection signal with a reference data item. More specifically, computer 22 determines a detection data item as a function of the detection signal, and compares the detection data item with the reference data item. If the difference between the detection signal and the reference data item exceeds a given threshold value, an error signal indicating a faulty cigarette 4 is emitted. In which case, the reject unit (not shown) downstream from device 1 and connected to computer 22 eliminates the faulty cigarette 4 or (in other embodiments) the group 7 containing the faulty cigarette 4.
Operation of sensor 13 and computer 22 will now be explained in more detail with particular reference to
In actual use, to determine the fill of tip 3 of cigarette 4, computer 22 receives the detection signal, and determines peak detected frequency Ai and detected amplitude Bi, which are then processed to permit a comparison between the detection signal and the reference data item.
Computer 22 preferably determines a first deviation AΔ between peak detected frequency Ai and reference frequency AR, and a second deviation BΔ between detected amplitude Bi and reference amplitude BR. At this point, a detected humidity of tip 3 of cigarette 4 is determined, in particular by means of the following equation:
where φ is directly proportional to detected humidity. In this connection, it should be pointed out that, in a test graph showing first deviation AΔ along the x axis, and second deviation BΔ along the y axis (as in
Given the detected humidity, computer 22 determines a detected density of tip 3 of cigarette 4 as a function of detected humidity and of first deviation AΔ or second deviation BΔ. More specifically, density is calculated using curves (in particular, straight lines) T determined beforehand experimentally (and shown in
At this point, the detected density (i.e. the detected data item) is compared with a reference density (i.e. the reference data item); and, if the difference between the detected density and the reference density exceeds the threshold value, the error signal is emitted.
In a further embodiment shown in
In a further embodiment shown in
Device 1 has the following advantages:
| Number | Date | Country | Kind |
|---|---|---|---|
| BO2005A000602 | Oct 2005 | IT | national |
