[0001] The invention relates to a method for inspecting an elongated element, in particular
a rod-shaped elongated element made of fibrous material for determining the quality
of a capsule of non-fibrous material inserted into the elongated element.
[0002] In particular, by the term "fibrous raw material" fibres of filtering material are
intended (for example cellulose acetate) intended for forming a continuous rod of
filter in a machine, either single or double line, for producing smoking articles
such as cigarette filters, and alternatively the tobacco fibres intended for forming
a rod of tobacco in a machine, either single or double line, for producing smoking
articles such as cigarettes. The rod-shaped elongated element, can therefore be a
continuous filter rod, or a portion of rod-shaped filter, or a portion of filter in
a smoking article, or a continuous rod of tobacco, or a portion of a rod of tobacco
in a cigarette.
[0003] A cigarette is one of the products of the tobacco industry, comprising a part of
tobacco wound by paper joined to a portion of filter, which is able to retain the
substances generated by the combustion of the tobacco.
[0004] For a long time already, it has been known to propose the production of portions
of filter incorporating additive substances into the filtering material, which are
in particular immersed therein. Such aromatising additive substances, which are supplied,
for example, in liquid form as in the case of menthol, are contained in capsules.
Such capsules can be of spherical or elongated shape and can contain one or more aromatising
additive substances. In this latter case, each of the different aromatising substances
is received in a separate compartment of the capsule.
[0005] The capsules can be breakable by mechanical action, and i.e. crushing, by a user
immediately before consumption of the smoking article. The user is thus able to decide
whether to consume a cigarette or not, the filter of which is aromatised.
[0006] Proposing making portions of rods of tobacco is also known in which capsules containing
aromatising additive substances are mixed with tobacco fibres. Also in this case the
aromatising additive substances are provided in liquid form and are contained in microcapsules
but the microcapsules comprise in this case a heat-sensitive shell. During consumption
of the smoking article, the action of the heat generated by the combustion of the
tobacco fibres weakens the shell of the capsule that, upon breaking, releases the
aromatising substance that is suitable for soaking the tobacco fibres. The user can
thus take advantage of an aromatised smoking article in which the aroma is dispersed
only at the moment of consumption.
[0007] In order to improve even further the quality of an elongated element made of fibrous
material containing internally a capsule made of non-fibrous material, over time increasingly
refined inspection methods for the elongated element have therefore been proposed.
In particular, inspection methods have been proposed for checking that the position
of the capsule or of the capsules, that is or are inserted into the fibrous raw material
conforms to the required quality standards. The inspection can occur on-line, i.e.
during production by control of all the elongated elements produced, or off-line,
at the end of the production process only on certain selected elongated elements,
if more precise but also slow measuring instruments than those used on-line are needed.
[0008] We observe first of all that the capsules containing aromatising substances have
to be inserted inside each elongated element at reference positions established a
priori, both longitudinally and radially with respect to a longitudinal axis of the
element. If ideal reference positions established
a priori for each capsule are considered, an acceptability interval is supplied that is defined
between a minimum acceptability position and a maximum acceptability position, inside
which a capsule is considered to be present and of acceptable quality. If the capsule
is present but outside the acceptability interval, the elongated element is to be
rejected in because it does not conform to quality requisites. The presence and correct
positioning of each capsule are thus controlled by sensors that are able to detect
a characteristic property of the elongated element with which the sensor interacts,
when the capsule enters the measuring field of the sensor, the characteristic property
being detected as a variation of the output signal of the sensor. Such variations
are obtained by "scanning" in several point the elongated element and typically equidistant
acquisitions are made over the entire length of an elongated element, for example
every mm. This also applies in the case of a continuous rod or of portions of filter
rod, or in the case of a continuous rod of tobacco or of portions of tobacco rod,
or in the case of a multiportion element, in which several elongated elements are
joined together. In fact, it is always possible to define the start and finish of
each elongated element, even if joined to others, during production.
[0009] Several different types of sensors are indicated for identifying the presence of
a capsule in an elongated element made of fibrous material, such as, for example,
an optical capacitive sensor, or laser, also used together in combination. For this
purpose, also microwave resonators have been successfully proposed that are usable
as density and humidity sensors, which have already been used for many years during
production for measuring the weight of the continuous rod of tobacco.
[0010] The profile obtained by reconstructing a density of an elongated element such as
a filter rod from equidistant samples acquired from a microwave resonator, shows that
at the position of each capsule present in the filter rod, a maximum peak of detected
density is present. It follows that it is possible to identify the presence/absence
or percentage of movement with respect to the ideal position of each capsule by merely
comparing the maximum density position with the corresponding acceptability interval.
[0011] Nevertheless, the presence/movement of the capsule with respect to the ideal position
is not the only parameter that determines the quality of the smoking article, inasmuch
as the presence of a non-intact capsule in the fibrous raw material compromises the
quality of the smoking article much more.
[0012] If in fact a capsule that is breakable by crushing releases the aromatising substance
early with respect to the moment of consumption, by breaking of the capsule during
or after the process of production of the filtering material incorporating the capsule,
the user may no longer be able to choose whether to consume or not an aromatised smoking
article, inasmuch as the filtering material presents itself to the user already aromatised
at the moment of consumption. Similarly, if a heat-sensitive capsule mixed with the
tobacco fibres breaks before or after the production process of the smoking article,
the user will have at the moment of consumption of a smoking article the tobacco of
which is devoid of the required aromatic qualities. As the aromatising substances
are in fact very volatile, the smoking article will present itself to the user already
aromatised, but only weakly.
[0013] In order to detect the intactness of a capsule inserted into an elongated element,
it has been requested to detect the humidity thereof, in addition to the density thereof,
and to check the humidity variations compared with a reference. If in fact a capsule
releases the liquid contained therein into the fibrous raw material, the liquid spreads
in the fibrous raw material, determining a variation in humidity in a volume of fibrous
raw material surrounding the capsule and also consequently a variation in density.
[0014] The obtained profile reconstructing a humidity curve of an elongated element such
as a filter rod shows that at the position of each capsule a peak of maximum of the
detected humidity is present, if the capsules are intact, which increases if a non-intact
capsule is present.
[0015] Also the density profile is modified in the presence of a broken capsule, as is clearly
shown by the experimental tests shown in Figures 1 and in Figures 2, that respectively
show a density profile and a humidity profile of a first and a second elongated element,
and i.e. a filter rod, containing 4 capsules.
[0016] With 1 the reference density profile is indicated of a first elongated element in
which the capsules are intact, with 2 the density profile is indicated that is detected
in the presence of a second elongated element in which capsules two and four are broken.
[0017] With 3 the humidity profile of the first elongated element is shown with intact capsules,
with 4 the detected humidity profile of the second elongated element is indicated,
with broken capsules two and four.
[0018] It follows that it is possible to identify the intactness of each capsule, by comparing
the maximum density or humidity peak at the position in which each capsule is present,
with respect to a corresponding reference profile, for example defined as a threshold
profile or as a predefined width threshold band, within which the detected profile
has to be comprised.
[0019] Experimentally, it has nevertheless been noted that a not insignificant variability
exists linked to the weight and to the dimension of the capsules and a not insignificant
variability in the detectable features of the fibrous raw material. For example, depending
on the production batch, the filtering material can contain variable quantities of
acetate or triacetin.
[0020] Owing to this variability, the density profiles of intact capsules inside filters
can also be rather different from one another and all this implies that determining
the threshold profile or the width of the tolerance band is complex, inasmuch as a
threshold profile defined for one production batch could be too strict (and thus impose
the rejection of good quality elongated elements) or too loose (and thus consider
elongated elements to be rejected to be of good quality) even for a similar production
batch.
[0021] In order to overcome the problems of inspecting correctly filters despite the variability
of the capsules and/or of the fibrous raw material, from
WO 2011/083406 is known setting up a plurality of different types of optical, laser, capacitive,
inductive or microwave sensors, that interact on line or off-line with a continuous
rod or portions of filter and is able to detect components inside the filtering material.
The configuring parameters of this plurality of sensors are stored in a library of
the control system of the machine PLC, associated with each production batch or with
each brand and such configuring parameters can be varied during operation of the system
to improve the sensitivity of the system, in response to statistics on the number
of filtering elements considered to be of acceptable quality or else rejected.
[0022] It should be observed that the variation of the configuring parameters, especially
if complex sensors are considered that need calibrating procedures and involve several
configurable parameters of the sensor and possibly need the intervention of a machine
operator, it is not often always possible during production in an automatic machine
but may require a machine stop and thus lower machine production in an unrequested
manner. Further, although in a production batch wherein the features of the filtering
material and of the capsules are known a priori, the variation of the configuring
parameters of the sensors might not, however, be suitable for determining non-intact
capsules in the filtering material, given the extreme variability of the features
of both the filtering material and of the capsules.
[0023] A further problem of the known methods of inspection is that it is not possible to
define correctly elongated elements with non-intact capsules, if the inspection is
conducted after some time has elapsed after the breakage of the capsule. This occurs
above all with off-line inspections, in which the elongated elements selected for
inspection are also inspectable after some time has elapsed since production.
[0024] Experimentally, it has in fact been established that the result of the inspection
depends on the moment at which the inspection is conducted, in the sense that if the
inspection of the same elongated element is repeated time spaced the density and humidity
profiles are not repeated. This is due to the highly volatile nature of the additive
substances. In Figures 7 and 8 the density and humidity profiles of the elongated
elements of Figures 1 and 2 recorded after 10 days are shown. In particular the breakage
of capsules two and four in a filter rod was provoked and the result of the inspection
within two hours of the breakage is shown in Figures 1 and 2, after 10 days in Figures
7 and 8.
[0025] It can be observed experimentally that if the elongated element is inspected after
a short lapse of time from the breakage of the capsule (Figures 1 and 2), the liquid
impregnating the fibrous raw material is easily detectable but this is not so if on
the other hand the elongated element is inspected after a long lapse of time from
the breakage of the capsule. The density profile 2 of Figures 7, at positions two
and four in which the capsules are broken, shows a maximum density value peak that
is much less than the value detected in Figures 1. In Figures 8, the humidity profile
4 is indeed almost superimposed on the reference profile 3.
[0026] By changing over time the properties of the elongated element, modifying the configuring
parameters of the sensors used in the measurement does not enable non-intact capsules
in an elongated element to be identified.
[0027] The object of the present invention is to devise a method for inspecting elongated
elements made of fibrous raw material that is able to identify the presence and intactness
of capsules made of non fibrous material that are inserted into the fibrous raw material,
which is free of the problems disclosed above and at the same time is easy and cost-effective
to develop. In particular, the object of the present invention is to provide a method
for inspecting that maintains the same configuration of the measuring sensors during
operation of the inspection system over time.
[0028] A further object is to provide a method for inspecting that enables non-intact capsules
to be determined both immediately after breakage of the capsules and a long time after
breakage and which is independent of the moment in which the inspection is conducted.
[0029] These objects and still others are all achieved by a method for inspecting an elongated
element made of non-fibrous material for identifying the presence and the intactness
of a capsule made of non-fibrous material inserted into the fibrous raw material,
as established by claim 1 and the further claims set out below.
[0030] The invention can be better understood and implemented with reference to the attached
drawings that illustrate embodiments thereof by way of non-limiting example, in which:
- Figure 1 shows density profiles of a first and of a second elongated element, such
as a multi-portion filter rod containing 4 capsules, in which the first elongated
element has intact capsules whereas the second elongated element has broken capsules
two and four;
- Figure 2 shows respective humidity profiles, detected simultaneously on the density
profiles of Figure 1, of the same first and second elongated element inspected in
Figure 1;
- Figure 3 shows the density profiles obtained by the inspection method according to
the invention, considering a sample of 100 filter rods;
- Figure 4 shows the humidity profiles detected simultaneously on the density profiles
of Figure 3, considering the same sample of 100 filter rods;
- Figure 5 shows the density profiles of Figure 1, in association with a minimum density
limit profile and with a maximum density limit profile calculated according to the
method of the invention;
- Figure 6 shows the humidity profiles of Figure 2, in association with a minimum humidity
limit profile and with a maximum humidity limit profile calculated according to the
method of the invention;
- Figure 7 shows density profiles of the same first and second elongated element inspected
in Figure 1, the inspection being conducted 10 days after the inspection of Figure
1;
- Figure 8 shows humidity profiles of the same first and second elongated element inspected
in Figure 7, the inspection being conducted simultaneously as the inspection of Figure
7;
- Figure 9 shows the density profiles of Figure 1, in association with a minimum density
limit profile and with a maximum density limit profile calculated according to one
embodiment of the method of the invention, which provides for moving the acquired
profiles;
- Figure 10 shows the humidity profiles of Figure 2, in association with a minimum humidity
limit profile and with a maximum humidity limit profile calculated according to one
embodiment of the method of the invention, which provides for moving the acquired
profiles;
- Figure 11 shows the density profiles of Figure 7, in association with a minimum density
limit profile and with a maximum density limit profile calculated without moving the
profiles.
- Figure 12 shows the humidity profiles of Figure 8, in association with a minimum humidity
limit profile and with a maximum humidity limit profile, calculated without moving
the profiles.
- Figure 13 shows the density profiles of Figure 7, in association with a minimum density
limit profile and with a maximum density limit profile calculated according to the
method of the invention which provides for moving the acquired profiles.
- Figure 14 shows the humidity profiles of Figure 8, in association with a minimum humidity
limit profile and with a maximum humidity limit profile calculated according to the
method of the invention which provides for moving the acquired profiles.
[0031] An inspection unit (not illustrated) of an elongated element (not illustrated) for
smoking articles comprises one or more sensors that are able to interact with the
elongated element to detect at least a first and a second measurable physical quantity.
The elongated element is rod-shaped and is made of a first "fibrous raw material",
as defined previously.
[0032] The inspection unit comprises a control device that receives the signal/s detected
by the sensor or by the plurality of sensors and is able to process the signals to
determine the presence of at least one capsule made of non-fibrous material inserted
inside the fibrous element. The capsule is spherical or elongated and contains one
or more aromatising additives, like menthol, as defined previously.
[0033] In particular, a first and a second profile are processable that are obtainable respectively
by the first and second measurable physical quantity.
[0034] A microwave resonator (not illustrated) is a device which has a determined geometry,
makes a resonant microwave field by means of an emitting antenna and enables the properties
of the material inserted into this field to be measured by an analysis of the variations
of the frequency received from a receiving antenna. By varying the frequency at which
the microwave field is emitted, by measuring the power received at each emitted frequency
and processing the peak value and the band width of the response curve at half the
peak height, it is possible to determine a first measurable physical quantity such
as the density, and i.e. the mass, and a second measurable physical quantity such
as humidity of the material subjected to inspection. A microwave resonator can be
considered to be a measuring unit provided with two virtual sensors that are able
to measure two characteristic parameters simultaneously.
[0035] The cylindrical microwave resonators have an axial hole for receiving the material
to be subjected to inspection and they are particularly used for measuring the density
and humidity of a continuous filter rod or of portions thereof, in a single or double-line
machine for producing cigarette filters or the density and humidity of a rod of tobacco
or portions thereof, in a single or double line machine for producing tobacco rods.
The continuous rod or the portion is supplied through the hole and pass through the
microwave resonator for the inspection. The cylindrical resonators can also be advantageously
used in off-line apparatuses comprising the inspection unit, typically designed for
thorough statistical or quality analyses of samples, of portions of filters or of
rods of tobacco taken from the machines during production. Resonators with different
geometries, for example planar geometries, can on the other hand be advantageously
positioned in machine zones, for example drums for transferring elongated elements,
in which the cylindrical resonators would be too bulky.
[0036] Without loss of generality, the following discussion refers to a method for inspecting
that provides density to be obtained as a first measurable physical quantity and humidity
to be obtained as a second measurable physical quantity, from a microwave resonator.
Nevertheless, other types of density and humidity sensors could be used, other than
a microwave resonator, because more suitable for detecting variations of a specific
fibrous raw material or more suitable because of small dimensions, or also sensors
for detecting measurable parameters that are different from density or humidity, for
example NIR-type optical sensors.
[0037] Despite the profile, for example the humidity profile, that is obtainable from a
microwave resonator during inspection of an elongated element, shown in the attached
figures, is shaped differently from the profile that is obtainable by an optical sensor
during inspection of the elongated element (for example the presence of a capsule
could be defined by a minimum in the profile and not by a maximum), it is pointed
out that the method of the present invention is invariant compared with the type of
sensor and the type of measured parameter considered.
[0038] The inspection unit uses the method of the present invention for inspecting an elongated
element in a fibrous raw material and determining the capsule quality features of
non fibrous material inserted into the elongated element. Without loss of generality,
the following discussion refers to a method for inspecting that can be used on line
or off-line. A programme is provided in association with the inspection unit, which
comprises a code for implementing the inspection method according to the invention
when this programme is run in the inspection unit itself. The programme can be for
example performed by the control device of the inspection unit when stored in the
inspection unit.
[0039] In use, during an operating step of the operation of the inspection unit, if the
capsule is present inside the fibrous raw material, a quality feature of the capsule
such as intactness is evaluated by comparing the first or the second profile with
a respective first and second threshold reference, which are established dynamically.
The first threshold reference is established by statistical processing of the first
profile, the second threshold reference is established by statistical processing of
the second profile, the first and the second statistical processing being performed
on profiles obtained in the preceding inspection cycle defined by a predetermined
number of previously inspected elements.
[0040] Each statistical processing is thus performed upon conclusion of each inspection
cycle, is based on profiles obtained from the predetermined number of inspected elongated
elements of the inspection cycle, the results of which are provided for the elongated
elements inspected in the subsequent inspection cycle.
[0041] During the switch-on transient of the inspection unit in which the statistical processing
of the first and of the second profile are not yet available, it is possible to provide
a first and a second reference that are stored in the inspection unit, deriving from
previous statistical analyses or profiles preset a priori to define the first and
second reference threshold.
[0042] In order to identify the presence of the capsule, in known manner, the first or the
second profile is processed to identify a maximum value, the corresponding position
of which is that of the capsule in the elongated element.
[0043] The capsule is present if the position of the capsule is a research zone defined
by an interval between a minimum reference position and a maximum reference position
comprising an ideal reference position in such a manner that:
[0044] The search zone of the elongated element is thus that in which the first or the second
profile are processed in order to define the position of the capsule.
[0045] The capsule is present and in a correct position if, on the other hand, the position
of the capsule is present and is arranged inside an acceptability zone, in which,
according to specifications established a priori, the capsule has to be positioned
in order to be able to meet predefined quality criteria.
[0046] This acceptability zone is thus an interval of the elongated element comprised inside
or coinciding with the interval that defines the research zone. If a capsule is outside
the corresponding envisaged acceptability zone, the elongated element containing the
capsule must be rejected, if the inspection unit is connected to the control system
of the automatic machine, and runs an online control, during production of the machine.
[0047] Nevertheless, if the capsule is present in the research zone, even if it is outside
the acceptability zone, this capsule can also be further analysed to evaluate the
intactness thereof, as we shall see below. It is understood that if the research zone
coincides with the acceptability zone, the intactness analysis is conducted only on
capsules present and positioned according to predefined quality criteria.
[0048] It should be noted that the density and humidity profiles shown at least in Figures
1 to 4 show four positions along the elongated element in which the density or humidity
value is maximum, which define corresponding capsules.
[0049] The capsule could also be moved radially with respect to the longitudinal axis of
the capsule. For the sake of simplicity, the radial movement is not considered here.
[0050] In order to determine the presence of a capsule in the elongated element, it is possible
to consider indifferently both the density profile and the humidity profile, i.e.
the first or the second profile. Without loss of generality, it is considered that
the determination of the presence of the capsule is achieved by processing only the
density profile.
[0051] Elongated elements have been experimentally inspected that are called FILTER 24 that
are 108 mm in length, comprising a plurality of portions of a predetermined length
joined together, each comprising a respective capsule made of non fibrous material
with which a corresponding ideal reference position is associated. Determining the
intactness of a capsule inserted into an elongated element comprising a plurality
of portions has to be repeated for each capsule, or for the corresponding research
zones or acceptability zones along the elongated element in which the capsules are
provided.
[0052] If the capsule is present and is analysed further, the inspection unit associates
with each capsule quality features thereof, such as intactness, and places the quality
features at the disposal of the control unit of the machine, if the inspection unit
is in line, in such a manner that the control unit of the machine can reject the elongated
element with the defective capsule, if necessary.
[0053] We have said that the first and the second profile are compared with a respective
first and second threshold reference, established dynamically. To establish the first
threshold reference by statistical processing of the first profile an average reference
profile of the first profile is established and with this average reference profile
a first tolerance reference band is associated in which the average reference profile
is comprised, bounded by a minimum limit profile and by a maximum limit profile, which
are a function of the average reference profile.
[0054] In particular, the minimum and maximum limit profile of the first tolerance reference
band are a function of both the average reference profile of the first profile and
of the standard deviation of the first profile, calculated from this predetermined
number of elongated elements inspected previously, according to the following formulas:
[0055] What has been said about the first density profile, applies in the same manner to
the second humidity profile, which can be processed simultaneously or separately with
respect to the density profile. The second threshold reference is established by a
statistic of the second profile, calculating an average reference profile of the second
profile obtained from this predetermined number of filtering elements inspected previously.
A second tolerance reference band, bounded by a minimum limit profile and by a maximum
limit profile according to the average reference profile, is associated and comprises
the average reference profile of the second profile.
[0056] Also the minimum limit profile and minimum limit profile of the second band are a
function of both the average reference profile of the second profile and of the standard
deviation of the second profile obtained from this predetermined number of filtering
elements inspected previously according to the following formulas:
[0057] The capsule, as will be explained better below, is intact only if the first profile
is inside the first tolerance reference band and the second profile is inside the
second tolerance reference band.
[0058] In Figures 3 and 4, the predetermined number of elongated elements inspected for
the statistical determination of the first and second reference, respectively for
the first profile and for the second profile, is 100. An inspection cycle comprises
inspecting the profiles of the predetermined number of elongated elements, and i.e.
100, and at the end of each inspection cycle the threshold profiles calculated by
statistical processing replace those calculated in the previous cycle.
[0059] In Figure 3 reference is made to density measurements and thus to the first profile.
With 5 the average reference profile is indicated of the first profile. With 6 there
is indicated the maximum limit profile, obtained as an average profile + 3 * standard
deviation. With 7 the minimum limit profile is indicated, obtained as an average reference
profile of the first profile - 3 * standard deviation. With 8 the profile of the maximums
is indicated, as will be illustrated further on. With 9 there is indicated the profile
of the minimums, as will be illustrated further on.
[0060] In Figure 4 reference is made to humidity measurements and thus to the second profile.
With 10 there is indicated the average reference profile of the second profile. With
11 there is indicated the maximum limit profile, obtained as an average profile +
3 * standard deviation. With 12 there is indicated the minimum limit profile, obtained
as an average reference profile of the second profile - 3 * standard deviation. With
13 there is indicated the profile of the maximums. With 14 there is indicated the
profile of the minimums.
[0061] The first profile is obtained by sampling a signal that expresses the first measurable
physical quantity and i.e. the density. A set plurality of samples are thus acquired,
interpolated along the longitudinal extent of the elongated element, that enable the
first density profile to be reconstructed. What has been said applies equally to the
reconstruction of the second profile that is obtainable by the second measurable physical
quantity and i.e. by the humidity.
[0062] Sampling of the signal of the first and/or the second measurable physical quantity
is conducted in equidistant positions, each mm in the represented figures, of the
longitudinal extent of the elongated element and along the entire elongated element
and each ith sample of the first and/or of the second profile corresponds to a corresponding
longitudinal ith position of the elongated element. For example, if the inspection
is conducted in line during production and the elongated element advances with respect
to the measuring sensor, an acquisition can be made at each machine revolution or
at different intervals of time, provided sampling is carried out in equidistant positions.
The control unit of the inspection unit or the control unit of the automatic machine
that is able to supply the sampling command performs suitable processing on the machine
speed and on the sampling instant to respect this constraint.
[0063] All the acquired samples of a number of inspected elements of an inspection cycle
are stored in the inspection unit, both for the first and for the second profile.
In particular, for each kth element inspected, each acquired ith sample of the first
and/or second profile is stored associated with the corresponding ith position of
the elongated element. A two-dimensional table of stored samples is thus stored, ordered
by each inspected element "k" and by the position "i" of the sample in the element.
[0064] After inspecting the hundred elongated elements of the inspection cycle, the stored
samples are processed and the average reference profile of the first and/or the second
profile can thus be calculated. In each ith position an average ith sample is calculated
that is obtained from "i" samples of all the inspected elements of the first profile
and/or of the second profile stored in the ith position, and the average reference
profile is reconstructed by interpolating this plurality of average ith samples. In
Figure 3 and in Figure 4, we have said that respectively with 5 there is indicated
the average reference density profile, whereas with 10 there is indicated the average
reference humidity profile.
[0065] Standard deviation of the first profile and/or of the second profile is like what
has been said above, calculated at the end of the inspection cycle. In each ith position
an ith standard deviation is calculated obtained from ith samples of all the inspected
elements of the first profile stored in the ith position, and standard deviation is
obtained by interpolating said plurality of standard ith deviations. At the end of
each inspection cycle, each average ith sample and standard ith deviation replace
the deviations calculated in the previous cycle. The minimum limit profile and maximum
limit density profile and humidity profile of Figures 3 and 4, respectively indicated
by 7 and 6 and by 12 and 11, obtained by using Formulas 3 to 6 for each ith position,
in which the average ith sample and the standard ith deviation are calculated.
[0066] In Figures 3 and 4 there are also dedicated the respective profiles of the density
minimums and maximums (indicated with 9 and 8) and of the humidity minimums and maximums
(indicated with 14 and 13), obtained by considering in each ith position respectively
the minimum ith value and the maximum ith value recorded in all the acquired samples.
Considerations related with the profile of the minimums and with the profile of the
maximums are supplied below.
[0067] As said before, the profiles of Figures 3 and 4 refer to elongated elements containing
four capsules but the processing of the profiles for each capsule can also be made
only in the zone of the elongated element in which, according to specifications established
a priori, the capsule has to be present and/or in an acceptable position, ie. in the
research zone and/or acceptability zone.
[0068] It is advantage to reconstruct the profiles from values that are sampled only in
some portions of the longitudinal extent of the elongated element, inasmuch as it
increases the processing speed of the inspection method. For this reason, in the Figures
that we shall take into consideration, density and humidity profiles are shown only
at the research zones along the entire extent of the elongated element.
[0069] Figures 5 and 6 shown the density profile 2 and the humidity profile 4 of the elongated
element with broken capsules two and four, superimposed on the tolerance limits calculated
according to the method of the present invention, in particular the average density
profile 5 and humidity profile 10, the maximum limit density profile 6 and humidity
profile 11 and the minimum limit density profile 7 and humidity profile 12 are superimposed
on the density profiles 2 and humidity profiles 4.
[0070] It should be noted in Figure 5, that the elongated element would have capsules two
and four intact, inasmuch as the density profile 2 is inside the reference band identified
by the minimum limit profile 7 and by the maximum limit profile 6. Otherwise, the
humidity profile of Figure 6 correctly identifies capsules two and four as capsules
that are not intact, inasmuch as the humidity profile is not inside the corresponding
tolerance reference band, but is outside at least in some portions of the research
zone. In other words, in order to be able to be intact after the capsule is inspected,
the first and also the second profile have to be entirely comprised in the tolerance
reference band.
[0071] It is observed that, even if only the first or the second profile can be analysed
to identify the presence of a capsule, both the first and the second profile have
to be examined for the purposes of determining intactness. In fact, by analysing just
one measurable parameter, i.e. the density, the capsules would have erroneously been
considered to be intact. On the other hand, the humidity analysis correctly identifies
the non intactness of a capsule. From what has been said so far, it is noted that
the statistical processing of the first and of the second profile enables capsules
that are not intact to be identified very simply in an elongated element. In fact,
the first threshold profile and the second threshold profile, associated with a reference
band calculated dynamically by statistical processing, are always able to adapt to
the type of elongated elements considered and to great variability in the weight of
the elongated element and/or of the capsule. It is therefore not necessary, during
on-line production, to perform demanding operations of reconfiguring of the detection
sensors or of the parameters of these sensors, inasmuch as the inspection unit is
able to adapt itself to the properties of the samples that are fed to the inspection
unit and are to be inspected, except for a configuration transient during a first
acquisition cycle of the predetermined number of elongated elements.
[0072] As the maximum and minimum reference profile of the tolerance band are established
dynamically and are a function of the average profile of the profiles, which is also
established dynamically, the inspection of the elongated elements is able to adapt
to properties of each elongated element that are not foreseeable a priori, for example
a change of production batch. Further, the more similar the specifications of a production
batch are to the specifications of the next production batch, the more the inspection
method will be able to adapt swiftly to the new batch.
[0073] For inspections performed on line, the importance has been seen experimentally of
always processing two different measurable parameters, inasmuch as the analysis of
only a first or second profile could erroneously determine capsules as being intact
that are not intact.
[0074] In order to make the inspection method of the present invention even more effective,
the first profile and the second profile are moved to the ideal reference position
of the capsule along the elongated element. Similarly to what has been said previously,
the first threshold reference is established by statistical processing of the first
profile 2 and the second threshold reference is established by statistical processing
of the second profile 4, but the statistical processing of the first profile 2 and
of the second profile 4 is performed on moved profiles of the previous inspection
cycle.
[0075] If we then go back to considering Figures 3 and 4, it is noted that near the maximums
of the average density profile of Figure 3, the profile of the maximums 8 is spaced
away from the profile 6, constructed as a function of the average profile and of the
standard deviation according to Formula 4. Similarly, near the changes of slope that
are different from those that identify the maximums, the profile of the minimums 9
is far from the profile 7 constructed as a function of the average profile and of
the standard deviation according to the Formula 3. In the other zones on the other
hand, the profile of the maximums 8 is near the profile 6 and the profile of the minimums
9 is near the profile 7.
[0076] If the humidity profile of Figure 6 is now observed, also the profile of the maximums
13 is spaced away from the profile 11, and the profile of the minimums 12 is fairly
spaced away from the profile 14.
[0077] An even more precise definition of the limits of the tolerance band is obtained if
the disturbance is eliminated that is due to the identified position of the capsule
along the elongated element, which influences the form of the density and/or humidity
profile acquired. In order to eliminate this disturbance, the first profile 2 and
the second profile 4 are moved by superimposing the identified position of the capsule
to the ideal reference position in which the capsule should have been located according
to reference specifications.
[0078] The movement is performed for each profile acquired that is stored moved and the
calculation of the average profile and of standard deviation is based on moved profiles
and not on profiles as originally obtained. Possible disturbance is thus eliminated
in statistical processing that is due to movement of the profile from the ideal position.
In other words, the calculation of the average profile and of standard deviation is
performed at the conclusion of the inspection cycle on profiles obtained during the
inspection cycle itself, each moved profile realigned on an ideal position and then
stored for statistical processing performed at the end of the acquisition cycle.
[0079] The first profile and the second profile obtained from the first physical quantity
and from the second physical quantity are on the other hand used, just as acquired,
to identify the position of the capsule in the elongated element but are moved, for
the comparison respectively with the first threshold reference and the second threshold
reference, established according to the statistical processing of the moved profiles,
stored during the previous acquisition cycle.
[0080] In detail, for each inspected elongated element of an inspection cycle a first and
a second profile is reconstructed by the ith samples acquired, as has already been
illustrated previously with reference to non-moved profiles. By means of the thus
reconstructed first or second profile the position of the capsule in the elongated
element is identified.
[0081] The ith samples are, however, moved so as to make the ideal position of the capsule
coincide with the identified position. The first and the second profile reconstructed
from moved ith samples is used for comparing with the first threshold reference and
the second threshold reference, obtained from moved profiles of the previous inspection
cycle.
[0082] The ith samples are further stored. In this manner the average ith profile and the
ith standard deviation are calculated according to Formulas 3 to 6 on moved "i" start
samples. In fact, the two-dimensional table of the samples ordered for each inspected
"k" element and for the "i" position of the sample in the element, stores the moved
ith samples.
[0083] Similarly to what has been said before, only the research zone or acceptability zone
is processed in which the presence of the capsule is expected.
[0084] If Figures 9 and 10 are now considered, wherein the reference profiles are calculated
after the profiles have been moved, it is noted that the tolerance band constructed
with the average profile 15, the maximum limit profile 16 and the minimum limit profile
17, using the average values and the standard deviations, is narrower, as it noted
for the density profile of Figure 9 compared with the density profile of Figure 5.
The profile of the maximums and the profile of the minimums are not shown as they
are substantially superimposed on the maximum limit profile 16 and on the minimum
limit profile 17. In Figure 10, similarly, the average profile 20 and the maximum
humidity limit profile 21 and minimum humidity limit profile 22 are more suitable,
inasmuch as they substantially coincide respectively with the profiles of the minimums
and of the maximums.
[0085] In Figure 9, it is seen that the density profile 2 is outside the reference band
identified by the maximum limit profile 16 and minimum limit profile 17, for positions
of capsules two and four. Specifically, the density profile 2 of capsule four is superimposed
on the maximum limit profile.
[0086] Capsules two and four are therefore not intact even by means of a density measurement
whereas, as said before, with reference to Figures 5 and 6, they would be found to
be non intact owing only to the humidity measurement.
[0087] The first threshold reference in association with the density shown in Figure 9 now
expresses, after movement of the profiles, a stricter but more precise limit. The
second threshold reference in association with the humidity shown in Figure 10, which
already without moving the profiles, according to what was said in reference to Figure
6, was able to identify correctly a non intact capsule, all the more so, indicate
the lack of intactness in capsules two and four.
[0088] Nevertheless, it is observed that the method of the present invention is even more
advantageous if an elongated element is considered with capsules that are not intact,
analysed a long time after the breakage of the capsules.
[0089] Figures 11 and 12 show the density profile 2 and the humidity profile 4 of the elongated
element with broken capsules two and four analysed 10 days after the breakage in the
capsule, superimposed on the maximum limit profile (6 for the density profile and
11 for the humidity profile) and minimum limit profile (7 for the density profile
and 12 for the humidity profile) calculated according to Formulas 3 to 6 but without
the step of moving the profiles for statistical processing. It is noted that the capsules
would all have been considered to be intact, both using the density profile 2 and
the humidity profile 4 with respect to the corresponding tolerance bands. The comparison
between the density profile and the corresponding reference profile, the humidity
profile and the corresponding reference profile would not have highlighted differences
with respect to the reference profile.
[0090] The non intactness of capsules two and four would not have been detected. On the
other hand, by applying the movement of the profiles, i.e. moving the first and the
second profile in an ideal reference position, by calculating the average profile
and the standard deviation from moved profiles, it is possible to identify the broken
capsules two and four, even if the elongated element is analysed 10 days after breakage
of the capsules. What has been said has been established by experiment, as shown in
Figures 13 and 14. In fact it is noted that the density profile at the capsules in
positions two and four falls outside the limits whereas the humidity profile never
falls outside the limits. The elongated element is considered after inspection to
contain non-intact capsules, as indicated by the analysis of the density profile.
[0091] Owing to the present invention, which establishes the first threshold reference and
the second threshold reference by statistical processing and the movement of the profiles,
and comparing the first moved profile and the second moved profile respectively with
the first threshold reference and with the second threshold reference, it is thus
possible to provide a very sensitive inspection method that not only enables the problem
to be solved of making the inspection method invariant in relation to the type of
elongated element inspected, but also with respect to the moment in which the inspection
is conducted. For this reason, the inspection method according to the invention is
advantageously usable not only in an on-line inspection unit but also and above all
in an off-line inspection unit to which elongated elements to be inspected can be
supplied even some time after production.
[0092] This ensures great reliability in the very simple and cheap inspection method in
as much as it does not require modifications to the configuration of the parameters
of the sensors and the inspection unit does not need to be instructed in the physical
properties of the production batches but it above all enables a reference profile
to be obtained that is always appropriate, even over the long term.
1. Method for inspecting an elongated element for smoking articles, wherein the element
is rod-shaped and is made of a fibrous raw material, comprising the steps of
- obtaining at least a first profile (2) of a first measurable physical quantity,
for example density, and a second profile (4) of a second measurable physical quantity,
for example humidity, by means of at least one sensor interacting with the elongated
element along the same elongated element;
- processing at least one of the first profile (2) and the second profile (4) to determine
the presence of at least one capsule made of non-fibrous material, for example an
aromatising additive inserted inside the elongated element;
- if the capsule is present, evaluating the intactness of the capsule, comparing the
first (2) and the second profile (4) respectively with a first (16, 17) and second
threshold reference (21, 22); characterised in that said method further comprises:
- moving the first profile (2) and/or the second profile (4) to an ideal reference
position of the capsule along the elongated element;
- establishing, during the operational functioning, the first threshold reference
(16, 17) by statistical processing of the first profile (2) and establishing the second
threshold reference (21, 22) by statistical processing of the second profile (4);
- the first and second statistical processing being performed respectively on moved
profiles of a preceding inspection cycle, defined by a predetermined number of inspected
elements.
2. Method according to claim 1, wherein the step of establishing the first threshold
reference (16, 17) by statistical processing of the first profile (2) comprises the
steps of calculating an average reference profile (15) of the first profile (2) in
the preceding inspection cycle and associating with said average reference profile
(15) a first tolerance reference band (16, 17) in which said average reference profile
(15) is comprised, bounded by a minimum limit profile (17) and by a maximum limit
profile (16) as a function of said average reference profile (15) of the first profile
(2); and wherein moreover/optionally the step of establishing the second threshold
reference (21, 22) by statistical processing of the second profile (4) comprises the
further steps of calculating an average reference profile (20) of the second profile
(4) in the preceding inspection cycle and associating with said average reference
profile (20) a second tolerance reference band (21, 22) in which said average reference
profile (20) is comprised, bounded by a minimum limit profile (22) and by a maximum
limit profile (21) as a function of the average reference profile (20) of the second
profile (4).
3. Method according to claim 2, wherein the step of evaluating the intactness of the
capsule comprises comparing the first profile (2) with the first tolerance reference
band (16, 17) and the second profile (4) with the second tolerance reference band
(21, 22), the capsule being intact if the first profile (2) is inside this first tolerance
reference band (16, 17) and the second profile is inside this second tolerance reference
band (21, 22).
4. Method according to claim 2 or 3, wherein the minimum limit profile (17) and maximum
limit profile (16) of said first band (16, 17) are a function of average reference
profile (15) of the first profile (2) and of the standard deviation of the first profile
(2) in the preceding inspection cycle, according to the following formulas:
5. Method according to claim 2 or 3, wherein the minimum limit profile (22) and maximum
limit profile (21) of the second band (21, 22) are a function of average reference
profile (20) of the second profile (4) and of the standard deviation of the second
profile (4) in the preceding inspection cycle, according to the following formulas:
6. Method according to any preceding claim, wherein processing the first profile (2),
or the second profile (4), for determining the presence of at least one capsule comprises
the steps of: identifying the position of the capsule in the elongated element, and
in particular wherein said identifying the position of the capsule comprises identifying
a maximum value of the first profile (2), or respectively of the second profile (4)
in said elongated element, the corresponding position of the maximum value in the
elongated element corresponding to the position of the capsule, comparing said position
identified with a minimum reference position and a maximum reference position comprising
an ideal reference position, the capsule being present if the identified position
is comprised in a research zone between the minimum reference position and the maximum
reference position.
7. Method according to claim 6, wherein moving the first profile (2) and/or the second
profile (4) to an ideal reference position comprises superimposing the identified
position of the capsule on the ideal reference position, and wherein performing the
statistical processing of the first profile (2) and of the second profile (4) on moved
profiles comprises for each inspected elongated element of the preceding inspection
cycle the steps of moving each first profile (2) and/or each second profile (4) in
such a manner as to superimpose the identified position of the capsule on the ideal
reference position, performing the statistical processing of the first profile and
of the second profile on the basis of said moved profiles.
8. Method according to claim 7, as appended to claim 2, or as appended to claim 4 or
5, and comprising the further steps of storing each first profile moved and second
profile moved and calculating said average reference profile (15; 20) of the first
profile (2) and/or of the second profile (4) and/or said standard deviation of the
first profile (2) and/or of the second profile (4) from the stored moved profiles.
9. Method according to any preceding claim, wherein obtaining a first profile (2) and/or
a second profile (4) comprises acquiring a preset plurality of samples respectively
of a first signal obtainable of the first measurable physical quantity and of a second
signal obtainable of the second measurable physical quantity, and reconstructing the
first profile (2) and/or the second profile (4) by interpolating this preset plurality
of sampled values.
10. Method according to claim 9, and comprising performing this sampling in a preset plurality
of equidistant positions along the longitudinal extent of the elongated element, each
i-th sample of the first (2) and/or of the second profile (4) corresponding to a corresponding
i-th longitudinal position of the elongated element.
11. Method according to claim 9 or 10, and further comprising the steps of: identifying
a position of the capsule in the elongated element, moving the first profile (2) and/or
the second reconstructed profile (4) by superimposing the identified position of the
capsule on the ideal position; the method further comprising the step of storing,
for each k-th inspected element of an inspection cycle, each acquired and moved i-th
sample of the first (2) and/or of the second profile (4) associated with the corresponding
i-th position of the elongated element.
12. Method according to claim 11, as appended to claim 2, wherein calculating an average
reference profile (15) of the first profile (2) and/or an average reference profile
(20) of the second profile (4) in the preceding inspection cycle comprises, in each
i-th position, calculating an average i-th sample of the first profile (2) or of the
second profile (4) obtained from i-th moved samples of the first profile (2) or of
the second profile (4) that are stored in the i-th position, and reconstructing the
average reference profile (15, 20) by interpolating this plurality of average i-th
samples obtained from i-th samples of the first profile (2) or of the second profile
(4) moved in the preceding inspection cycle.
13. Method according to claim 11, as appended to claim 4, or to claim 5, wherein calculating
standard deviation of the first profile (2) and/or of the second profile (4) comprises,
in each i-th position calculating a standard deviation i-th of the first profile and/or
of the second profile obtained from i-th moved samples that are stored in the ith
position of the first profile (2) and/or of the second profile (4), and reconstructing
the standard deviation of the first profile and/or of the second profile by interpolating
this plurality of i-th samples of standard deviation of the first profile (2) and/or
of the second profile (4) moved in the preceding inspection cycle.
14. Inspection unit of an elongated element for smoking articles, wherein the element
is rod-shaped and is made of a fibrous raw material, comprising one or more of detection
sensors of a first measurable physical quantity and of a second measurable physical
quantity from which a first profile and a second profile are respectively obtainable,
which can be processed by a control device of the inspection unit for determining
the presence of at least one capsule of non fibrous material, for example an aromatising
additive, inserted inside the fibrous element using an inspection method according
to any one of claims 1 to 13.