Method and means for the identification of a roll

A method for the identification of rolls, in particular big paper rolls, by means of a code attached to or marked on the end surface of the roll. The code comprises several characters located side by side and is read by a combined signal optical beam transmitter-receiver, preferably a laser device, scanning a restricted angle in a plane (8). The scanning is adjusted to extend slightly over the end limits of the code at its both ends and the scanning plane is turned until at least one scanning over the enire code (4) is obtained.

BACKGROUND OF THE INVENTION 
The invention relates to a method, and to an arrangement for the 
application of the method, for the identification of rolls, in particular, 
big paper rolls, by means of a code attached to or marked on the end 
surface of the roll, which code comprises several code characters located 
side by side. 
Big paper rolls are produced in a paper mill for different deliveries 
comprising rolls of different axial length, different diameter and/or 
different weight. Rolls being similar with respect to the properties just 
mentioned may comprise different paper grades having different density 
and/or composition. Also the package requirement may vary, for instance, 
shipping of rolls to overseas customers requires a much more durable 
package than rolls delivered to nearby customers. In order to avoid 
delivery delays it is also important to be able to reproduce a roll of a 
specific character quickly, if the original roll winding has failed or if 
the roll has been damaged. 
In an automatized paper roll production and packaging line, for instance, 
the roll weight and diameter are measured and the measured values are 
transferred to the governing and data processing unit of the line. A 
labelling unit produces an identification label for each roll and attaches 
it to the end surface of the roll. The label indicates the measured values 
and possibly also other recorded data identifying the customer and the 
paper grade of the roll. All data are expressed in the form of a code 
modified to suit an automatic reader device. 
It is suitable to use a so-called bar code formed by a series of stripes. 
The code is read across the stripes by sensing the value of the code 
stripes one after another. In order to facilitate the code reading, the 
label is usually attached to the center of the roll. Nevertheless, there 
will be variations in the vertical position of the label, because the roll 
diameters may vary considerably. Another problem is that the scanning 
plane of the reader has no connection with the random orientation of the 
label. It is known to eliminate this problem by rotating the roll during 
code reading by means of scanning all over the roll end surface by means 
of a narrow, collimated optical beam. Thus, the scanning motion of the 
beam has to cover the entire end surface of the roll. This is cumbersome, 
time-consuming and uneconomical. Moreover, roll rotation requires rotation 
means, which increases the expenses. Rotation of a roll weighing several 
tons is slow, and slows down the entire roll handling process. 
OBJECT AND SUMMARY OF THE INVENTION 
The object of the invention is to provide a roll identification method 
suitable for an automatized roll handling line and means for the 
application of the method, by means of which roll identification can be 
made rapidly, accurately and economically. 
The object of the invention is realized by using a combined optical beam 
transmitter-receiver known per se, preferably a laser device, which scans 
over a restricted angle in a plane. By means of the linear motion of the 
optical beam, a good alignment of the beam at the label code is 
obtainable. All the elements of the code are read by arranging the 
scanning to extend slightly over the code area at both its ends. The time 
spent in scanning is used economically, since mainly only the area 
including information is scanned. By turning the scanning plane, so that 
it crosses the total code, all elements of the code can easily be read. 
In a preferred embodiment of the invention, the center of the scanning 
angle is adjusted to fall between the first and last characters of the 
code. Then the scanning plane will all the time sweep the code, at least 
partly. By adjusting the magnitude of the scanning angle so that it 
corresponds to about twice the width of the code, the scanning will with 
certainty extend all over the code without being unnecessary wide. 
In order to adjust the scanning of a label centrally attached to a roll 
end, the transmitter-receiver is moved in a vertical direction according 
to the measured value of the roll diameter, until the midpoint of the 
scanning is close to the roll axis. A favourable way to carry out this 
positioning is to combine, in any manner known per se, the vertical 
movements of the transmitter-receiver and the roll diameter measuring 
device so that the transmitter-receiver movement is about half the 
movement of the measuring device. The roll diameter measuring device may 
also comprise correction means taking into account the influence on the 
roll center position caused by the horizontal distance between the roll 
supporting members. In an automatized roll handling plant, the correction 
can be taken into account by computing and be transmitted to the 
operational center of the arrangement for exact positioning of the 
transmitter-receiver. 
By turning the scanning plane at an angular speed considerably lower than 
the angular speed of the scanning, the code reading precision will be 
unaffected by the scanning plane rotation. The ratio between the scanning 
angular speed and the rotation speed of the scanning plane should 
preferably exceed 10:1. This will ensure that several scannings include 
the total code. The scanning can be terminated after the receiver has 
received a signal group including the first character as well as the last 
character of the code. This indicates that necessary information has been 
received. There might be several readings to confirm the information. 
By continuously turning the scanning plane at the most through 180.degree., 
a momentary orientation of the plane relative to the code will be such, 
that all the characters of the code are scanned at least once. 
The invention also relates to an arrangement for the application of the 
described method.

DISCLOSURE OF BEST MODE 
In the drawing, reference numeral 1 refers to a big paper roll, at the end 
2 of which an identification label 3 is attached. Label 3 includes for 
roll identification a bar code 4 formed by parallel stripes 5. For 
identifying the fore and tail end of the code, it comprises a first stripe 
5a and a last stripe 5b of special character. For reading code 4, there is 
an optical transmitter-receiver 6, for instance, a laser device 
transmitting a narrow, collimated beam 7. Beam 7 scans rapidly over a 
restricted scanning angle a in a plane 8. The contact point 9 of beam 7 on 
roll 1 moves along a line 10 at the roll end surface 2. 
Transmitter-receiver 6 is rotatably supported on a carrier 16, so that 
scanning plane 8 can be turned around an axis 11 lying in said plane. The 
angular speed of the scanning beam movement continuously to and fro is 
considerably higher than the turning speed of plane 8 around axis 11. A 
device 13 for measuring roll diameter is schematically illustrated, as 
well as means 15 for vertical movement 15a of device 13. The diameter 
measuring device may, for instance, be a mechanical slide gauge, the rigid 
jaw of which is the pair of roll supporting drums 12. The distance between 
the rigid jaw and the movable jaw setting onto the top of the roll mantle 
is registered electrically and the measured value is transferred to a 
computer unit governing the process. Transmitter-receiver 6 is adjusted in 
a vertical direction according to the diameter data of roll 1, so that the 
center 10a of the scanning angle will come close to the longitudinal axis 
of roll 1. For vertical movement of measuring device 13 and 
transmitter-receiver 6 there are displacement means 15 and 14, for 
instance, chain or belt drives. They can be interconnected, so that 
movement 14a is about one half of movement 15a. The interconnection 
members are not shown in the drawing. Conventional means can be used for 
this purpose. 
As a result of the turning of scanning plane 8, scanning line 10 turns 
around a point 10a, as shown by arrows 18 in FIG. 2. Since the to and fro 
scanning speed of beam 7 is considerably higher than the turning speed of 
plane 8, several readings of the code are made. Thereby, at least one 
reading is carried out so, that code 4 is read in a proper order beginning 
from the first stripe 5a, then reading data stripes 5, and finally last 
stripe 5b. The example illustrated in FIG. 2 corresponds mainly to a 
perpendicular setting of beam 7 against label 3. This is not compulsory 
for carrying out a reading. If label 3, which is carried by a header 17 
attached to the roll core, includes stripe material with a retroreflecting 
property, that is, giving reflection in the direction of the incoming 
beam, beam 7 does not have to hit label 3 perpendicularly. 
The invention is not limited to the embodiments shown, but several 
modifications thereof are feasible within the scope of the attached 
claims. The turning of scanning plane 8 around axis 11, for instance, may 
also be carried out by varying the optics of transmitter-receiver 6.