Cigarette checking apparatus

A cigarette checking apparatus having a selector mechanism for selectively withdrawing cigarettes from a first transportation roller, transporting the cigarettes to a conveyor; and a second conveyor for transporting the selected cigarettes to a number of checking devices, each checking device checking a specific characteristic of the selected cigarette; the checking devices having independent inlets facing the second conveyor, and at least one of the checking devices having an outlet opening towards the first conveyor.

BACKGROUND OF THE INVENTION 
The present invention relates to a cigarette checking apparatus, 
particularly suited for location at the output of a filter assembly 
machine 
The cigarettes coming off a filter assembly machine are usually supplied to 
a packing machine on a conveyor belt on which they are stacked in a 
substantially uniform layer crosswise in relation to the traveling 
direction. 
At the output of the filter assembly machine, the cigarettes are subjected 
to a series of checks to determine given geometrical and physical 
characteristics, such as length, diameter, ventilation, weight, firmness, 
etc. Should the results of said checks fail to conform with given 
reference data, they are interpreted by the operator for making 
appropriate adjustments, for example, to the cutters on the manufacturing 
and filter assembly machines, to the printing means, to the number of 
holes formed by the filter perforating means, etc. Correct interpretation 
of the data supplied by the checking devices naturally depends on correct 
interpretation of the faults detected during inspection. The problem of 
interpreting inspection data relative to cigarettes produced on single 
and, particularly, dual rod cigarette manufacturing machines, is solved by 
the cigarette sampling unit described in Italian Patent Application 
N.3386A/88 of Mar. 21, 1988 filed by the present Applicant and the content 
of which is included herein purely by way of reference as required. Said 
unit provides for selectively withdrawing cigarettes from a given location 
on the filter assembly machine, so that the exact origin of the sampled 
cigarette and the positions occupied by the same between the filter 
assembly machine and the input of the checking device are known. 
A known checking device consists of a series of units arranged one on top 
of the other. Inside said device, each sample cigarette is fed downwards 
from one unit to the next, each of which provides for checking a given 
characteristic. 
The time taken to check each cigarette therefore equals the total operating 
time of the various units, which is fairly lengthy. Moreover, no provision 
is made on said device for repeat checking a given characteristic to the 
exclusion of the others. A further point to note is that, should said 
device comprise a firmness testing unit, the cigarettes are usually 
subjected to destructive testing and consequently rejected. 
SUMMARY OF THE INVENTION 
The aim of the present invention is to provide a cigarette checking 
apparatus designed to overcome the aforementioned drawbacks, and which may 
be controlled automatically and selectively. 
With this aim in view, according to the present invention, there is 
provided a cigarette checking apparatus, characterized by the fact that it 
comprises means for selectively withdrawing said cigarettes from first 
transportation means transporting said cigarettes to first conveying means 
to a subsequent operating machine; and second transportation means for 
transporting said selected cigarettes to a number of checking devices, 
said devices presenting independent inlets facing said second 
transportation means.

DETAILED DESCRIPTION OF THE INVENTION 
Number 101 in FIG. 1 indicates the checking apparatus according to the 
present invention, said apparatus being located parallel to the traveling 
direction between the output of a known filter assembly machine 102 and 
the input of a follow-up packing machine 103. As shown in FIG. 2, filter 
assembly machine 102 is supplied by a cigarette manufacturing line 
comprising a dual rod cigarette manufacturing machine 2, i.e. having two 
parallel lines 3 and 4 for producing respective rods 5 and 6. Filter 
assembly machine 102 is thus supplied with cigarette portions 8 and 9 
twice as long as those required for producing a filter cigarette. On said 
machine 102, portion 8 is cut in known manner into halves 10 and 11, and 
portion 9 into halves 12 and 13. Said two halves of each two portions 8 
and 9 are then parted so as to define a space in which to accommodate a 
double filter, which is first connected to said two halves by means of a 
strip, and then cut in half to produce a succession of single cigarettes 
16 which are fed to a roller 104 (FIG. 1). Said filter assembly machine 
102 presents an output portion having a supply roller 14 designed to 
successively receive cigarettes 16, inside a number of equally-spaced 
peripheral seats 15, from a tangent feed roller 17 in turn supplied by 
roller 104. Cigarettes 16 on roller 14 are then fed in known manner to a 
supply unit 18 by which they are fed on to a conveyor belt 135. On said 
conveyor belt 135, cigarettes 16 are arranged transversely in relation to 
the traveling direction of the conveyor, and stacked in a layer 136 of 
substantially uniform thickness, which is fed to packing machine 103. In 
FIG. 1, cigarettes 16 are numbered 16A, 16B, 16C and 16D depending on 
whether they consist of a half 10, 11, 12 or 13 of portions 8 and 9 (FIG. 
2). To enable the type of cigarette 16 to be determined at all times, 
seats 15 and those formed on all the rollers (not shown) on machine 102 
upstream from roller 17 are in multiples of 4, so that each seat 15 is 
always assigned the same type of cigarette 16. 
Roller 14 is assigned a withdrawal unit 19 comprising a withdrawal roller 
20 tangent to roller 14 and turning about its axis at the same speed as 
the same. Roller 20 presents a number of peripheral axial grooves, four of 
which, appropriately spaced about roller 20, constitute seats 21A, 21B, 
21C and 21D for withdrawing respective cigarettes 16A, 16B, 16C and 16D, 
whereas the others constitute counterseats 22 enabling safe passage of 
cigarettes 16 between rollers 14 and 20. In this case also, the number of 
counterseats 22 between each pair of adjacent seats 21A, 21B, 21C and 21D 
is such that each of said seats 21A, 21B, 21C and 21D is always engaged by 
the same type of cigarette 16A, 16B, 16C, 16D. 
As shown in FIG. 3, roller 14 comprises a rotary outer ring 23 having seats 
15 and turned anticlockwise by a central shaft 24 supporting two fixed 
cylindrical distributors 25 and 26, the first 25 of which is located 
inside the second 26 and communicates via a central passage 27 with a 
suction device (not shown). Distributor 25 presents two through radial 
slots 28 and 29 communicating, on one side, with central passage 27 and, 
on the other, with two respective radial passages 30 and 31 on distributor 
26, in turn communicating with respective outer chambers 32 and 33 defined 
between the outer edge of distributor 26 and the inner edge of ring 23. 
Chambers 32 and 33 communicate with seats 15 via radial channels 34 formed 
through ring 23, and are separated by a partition 35 over the outer edge 
of which the inner surface of ring 23 slides in substantially contacting 
manner. Partition 35 is located at the point of tangency between rollers 
14 and 20, so as to successively cut off communication between each seat 
15 and central passage 27 as seat 15 moves through the point of tangency 
between rollers 14 and 20. 
A further partition 36 similar to 35 separates chamber 32 from a further 
chamber 37, which is completely isolated from central passage 27 and 
located at the point of connection between roller 14 and supply unit 18, 
so as to enable removal of the vacuum inside channels 34. 
As shown in FIG. 3, roller 20 comprises a rotary outer ring 38 having seats 
21A, 21B, 21C, 21D and counterseats 22, and turned clockwise by a central 
shaft 39 supporting two fixed cylindrical distributors 40 and 41, the 
first 40 of which is located inside the second 41 and communicates, via a 
central passage 42, with a suction device (not shown). Distributor 40 
presents a through radial slot 43 communicating, on one side, with central 
passage 42 and, on the other, with a respective radial passage 45 in turn 
communicating with an outer chamber 47 defined between the outer edge of 
distributor 41 and the inner edge of ring 38. Chamber 47 communicates with 
seats 21A, 21B, 21C and 21D via suction means consisting of radial 
channels 49 formed through ring 38, and is defined on one side by a 
portion 50 over the outer edge of which the inner surface of ring 38 
slides in substantially contacting manner. Said portion 50 is located at 
the point of tangency between roller 20 and a transfer roller 51, which, 
as regards the innermost portion and the main peripheral chamber, is 
substantially similar to roller 14. The function of said portion 50 is to 
successively cut off communication between each seat 21A, 21B, 21C, 21D 
and central passage 42 as each said seat moves through the point of 
tangency between rollers 20 and 51. 
A partition 55 on the other side of chamber 47 separates this from a 
further chamber 56, which is completely isolated from central passage 42 
and located at the point of tangency between rollers 20 and 14. Via an 
axial duct 57 formed through distributor 41 and an electrovalve 58 (for 
enabling selective withdrawal as described in more detail later on), 
chamber 56 communicates with a suction duct 59 communicating with a 
suction device (not shown). 
As shown in FIG. 1, each seat 21A, 21B, 21C and 21D on roller 20 is 
assigned a respective, e.g. inductive, sensor 60A, 60B, 60C and 60D 
integral with ring 38 and moving with the same about a circular route, one 
portion of which, at the point of tangency between rollers 14 and 20, is 
governed by signal emitting means comprising a fixed block 61 consisting, 
for example, of a metal element. 
Roller 51 also comprises a rotary outer ring 123 having peripheral seats 
115 for cigarettes 16 and turned anticlockwise by a central shaft 124 
supporting two fixed cylindrical distributors 125 and 126, the first 125 
of which is located inside the second 126 and communicates, via a central 
passage 127, with a suction device (not shown). Distributor 125 presents a 
through radial slot 143 communicating, on one side, with central passage 
127 and, on the other, with a respective radial passage 145 in turn 
communicating with an outer chamber 147 defined between the outer edge of 
distributor 126 and the inner edge of ring 123. Chamber 147 communicates 
with seats 115 via suction means consisting of radial channels 149 formed 
through ring 123, and is defined on one side by a portion 150 over the 
outer edge of which the inner surface of ring 123 slides in substantially 
contacting manner. Said portion 150 is located immediately upstream (in 
relation to the rotation direction) from the point of tangency between 
rollers 51 and 20, wherein roller 20 presents portion 50, and therefore 
provides for automatically transferring cigarettes 16 by means of suction 
from roller 20 to roller 51. Said chamber 147 is defined on the other side 
by a similar portion 151 located at the point of tangency between roller 
51 and a conveyor belt 211. The function of said portion 151 is to 
successively cut off communication between each seat 115 and central 
passage 127 as seat 115 moves through the point of tangency between roller 
51 and conveyor 211, thus enabling automatic transfer of cigarettes 16. 
Said conveyor 211 presents a belt 212, the surface of which presents 
transverse seats 216 for housing cigarettes 16. Said belt 212 is located 
between two rollers 213 (one of which is powered) and runs over a 
supporting structure 214 in which is formed a longitudinal suction duct 
215 with which seats 216 housing cigarettes 16 communicate via suction 
means consisting of central perpendicular channels 217 formed through belt 
212. 
As shown in FIG. 1, between top conveyor 211 and bottom conveyor 135, 
provision is made for three vertically parallel known units 230, 231 and 
232, designed to perform individual checks of the physical and geometrical 
characteristics of cigarettes 16 (weight, diameter, ventilation, firmness, 
etc.). Said units 230, 231 and 232 present a respective top inlet located 
beneath respective sequential portions of the route of belt 212, and a 
respective bottom outlet located over layer 136 of cigarettes 16 on 
conveyor 135. At said outlets, each unit 230, 231, 232 presents a 
respective sensor 233, 234, 235, e.g. a photoelectric cell, designed to 
detect the passage of a cigarette 16 at the end of a respective inspection 
cycle. At the inlets of units 230, 231, 232, on the bottom branch of 
conveyor 211, provision is made for respective devices 219, 220, 221 for 
selectively picking cigarettes 16 off belt 212. As shown also in FIGS. 4 
and 5, said devices 219, 220, 221 comprise a respective electrovalve 
connected to a compressed air source and communicating with two vertical 
through ducts 240 formed in structure 214. As belt 212 moves forward, said 
ducts 240 are so located as to match up with vertical holes 242 formed in 
belt 212 on either side of central channel 217, and to correspond at all 
times with seats 216 housing cigarettes 16. 
Checking apparatus 101 is controlled by an electronic control system 250 
comprising a central processing unit 251 (FIG. 6). Said control system 250 
receives information output signals from respective sensors 60A, 60B, 60C, 
60D as they move past element 61, and, depending on the operating mode 
(described in more detail later on) whereby cigarettes 16 are selectively 
withdrawn from roller 14, enables the control input of electrovalve device 
58. Said elements combine to form a selective withdrawal control circuit 
62. 
Control system 250 also controls electrovalve devices 219, 220 and 221 for 
selectively supplying cigarettes 16 to checking units 230, 231 and 232; 
receives information signals from sensors 233, 234 and 235; and exchanges 
control and information signals with checking units 230, 231, 232, and 
with a block 249 controlling means for activating the various cigarette 
supply units, in particular rollers 14, 20 and 51 and conveyor belt 211, 
so as to supply control system 250 with a machine cycle count. 
Control system 250 may also be connected to a computer 290 for controlling 
the entire cigarette manufacturing line. 
Operation of the checking apparatus according to the present invention will 
be described with reference to the operating block diagram of processing 
unit 251 in FIG. 7. 
In actual use, cigarettes 16 are fed successively by roller 14 to transfer 
unit 18, on to which they are normally unloaded unless selective 
withdrawal device 62 is activated by control system 250. On moving past 
partition 35, the suction through each seat 15 is reduced substantially to 
zero in preparation for withdrawal of cigarette 16 by roller 20, which is 
obviously only possible when one of seats 15 corresponds with one of seats 
21A, 21B, 21C or 21D. 
With reference to FIG. 7, the first step in the unit 251 program is block 
260, which detects and the checking sequence and the type of check to be 
performed on each cigarette in the sequence, as set, for example, by the 
operator. The set checking sequence indicates which of cigarettes 16A, 
16B, 16C or 16D is to be checked: one from half 10, 11, 12 or 13 (FIG. 2); 
a combination, e.g. of halves 10 and 11 or 12 and 13; or all four halves 
10, 11, 12 and 13, etc. The set check type, on the other hand, indicates 
by which of units 230, 231 or 232 each type of cigarette is to be checked. 
As rollers 14 and 20 turn, control system 250 is supplied by control 
circuit 62 with a series of signals emitted by sensors 60A, 60B, 60C and 
60D as respective seats 21A, 21B, 21C and 21D travel over an arc extending 
through the point of tangency between rollers 14 and 20. With reference to 
FIG. 7, block 260 goes to block 261, which determines whether a signal has 
been received from sensor 60A, 60B, 60C or 60D. In the event of a negative 
response, it switches back to the wait cycle; whereas, in the event of a 
positive response, it goes on to block 262, which determines whether the 
incoming signal is from the sensor assigned to the type of cigarette 16A, 
16B, 16C, 16D to be checked. In the event of a positive response, block 
262 goes on to block 263, which determines whether said type of cigarette 
is to be checked by first unit 230 (setting A=1). In the event of a 
positive response, block 263 goes on to block 264, which determines 
whether said unit 230 is free, i.e. is not already engaged in checking a 
previously sampled cigarette 16. This may be determined, for example, by 
examining the status of a digital signal AL indicating engagement or not 
of said unit 230. In the event of a positive response (unit 230 free, 
AL=1), block 264 goes on to block 265; whereas, in the event of a negative 
response, block 264, as also block 263, goes on to block 266. 
As shown in FIG. 8, block 265 comprises: 
a block 270 establishing a value AL=0 for said digital signal indicating 
engagement of checking unit 230; 
a block 271 for determining the enabling signal of electrovalve 58; 
a block 272, which provides for enabling electrovalve 219 of unit 230 with 
a delay equal to a given number of machine cycles and commencing from when 
electrovalve 58 is enabled 
A single machine cycle is known to correspond to a given angular excursion 
of a machine shaft (drive shaft) to which the means activating rollers 20 
and 51 and roller 213 of belt 212 are connected. 
Said electrovalve 58 controls transfer of cigarette 16 (in the set sequence 
type) on to roller 20 (FIG. 3). Thereafter, by virtue of the described 
internal suction system on rollers 20 and 51 and belt 212, whereby suction 
is cut off from one seat and applied in the mating seat on the tangent 
element, cigarette 16 is fed automatically from roller 20 to roller 51 and 
on to belt 212 by which it is fed, by virtue of the suction in central 
channel 217, to electrovalve 219. As the means activating rollers 20 and 
51 and roller 213 of belt 212 are connected to said drive shaft, the 
machine cycle count for cigarette 16 to reach electrovalve 219 is known. 
Consequently, when said count (enabled by block 272) is reached, 
electrovalve 219 is activated by control system 250 and feeds compressed 
air through ducts 240 to lateral holes 242 of seats 216, thus releasing 
and dropping cigarette 16 into checking unit 230. This provides for 
performing a specific check of cigarette 16; exchanges phase and test 
finding signals with central processing unit 250; and, depending on the 
results of the check, either rejects cigarette 16 or feeds it through the 
outlet on to layer 136 on conveyor 135 by which it is fed to follow-up 
machine 103. As cigarette 16 drops through the outlet of unit 230, this is 
detected by sensor 23 and digital signal AL on control system 250 is set 
to 1, i.e. indicating that unit 230 is again free. The same applies even 
in the event of cigarette 16 being rejected. Block 266 (FIG. 17) 
determines whether the type of cigarette at the point of tangency between 
rollers 14 and 20 is to be checked in second unit 231 (setting B=1). In 
the event of a positive response, block 266 goes on to block 275, which 
determines whether unit 231 is free by examining the status of a digital 
signal BL indicating engagement of unit 231. In the event of a positive 
response (unit 231 free, BL=1), block 275 goes on to block 265' similar to 
block 265. In the event of a negative response, block 275, as also block 
266, goes on to block 276. 
Block 265' also comprises: 
a block establishing value BL=0 for said digital signal indicating 
engagement of unit 231; 
a block for determining the enabling signal of electrovalve 58; 
a block which provides for enabling electrovalve 220 of unit 231 with a 
delay equal to a given number of machine cycles (obviously different from 
that of block 272) commencing from when electrovalve 58 is enabled. Block 
276 determines whether the type of cigarette at the point of tangency 
between rollers 14 and 20 is to be checked in third unit 232 (setting 
C=1). In the event of a positive response, block 276 goes on to block 277, 
which determines whether said unit 232 is free by examining the status of 
a digital signal CL indicating engagement of unit 232. In the event of a 
positive response (unit 232 free, CL=1), block 277 goes on to block 265" 
similar to block 265. In the event of a negative response, block 277, as 
also block 276, goes on to block 280. 
Block 265" also comprises: 
a block establishing a value CL=0 for said digital signal indicating 
engagement of unit 232; 
a block for determining the enabling signal of electrovalve 58; 
a block which provides for enabling electrovalve 221 of unit 232 with a 
delay equal to a given number of machine cycles and commencing from when 
electrovalve 58 is enabled. 
As regards the exchange of phase and test finding signals with central 
processing unit 250 and the definition of signals BL and CL from sensors 
234 and 235 or units 231 and 232, units 231 and 232 operate in the same 
way as unit 230 already described. 
As soon as the delay count commences for enabling electrovalve 219, 220 or 
221, blocks 265, 265' and 265" (as well as block 262 in the event of a 
negative response) all go to block 280, which determines whether any 
change has been made to the set type of cigarette 16 to be checked. In the 
event of a positive, response, block 280 goes to block 260 for memorizing 
the new setting; whereas, in the event of a negative response, block 280 
goes on to block 261 for detecting incoming signals from sensor 60A, 60B, 
60C or 60D and so repeating the cycle described above 
Via electronic control system 250 and central processing unit 251, the 
checking apparatus according to the present invention therefore provides 
for automatically: 
detecting the passage of a cigarette 16 through the point of tangency 
between rollers 14 and 20, i.e. in a suitable position for selective 
withdrawal for checking; 
determining whether said cigarette 16 is of the type specified for 
checking; 
determining the type of check to be performed and whether the unit designed 
to perform the same is free; in the event of a positive response, the 
apparatus according to the present invention also provides for 
automatically: 
withdrawing cigarette 16 via electrovalve 58 and feeding it on to conveyor 
belt 211; 
timing activation of one of electrovalves 219, 220 and 221 for selectively 
feeding cigarette 16 off conveyor belt 211 and into the selected unit 230, 
231 or 232; 
indicating engagement of the selected unit 230, 231 or 232 until cigarette 
16 has been checked. 
The advantages of the present invention will be clear from the foregoing 
description. In particular, routine flow of cigarettes 16 to follow-up 
machine 103 is substantially unaffected: only cigarettes 16 of the 
selected type/s are withdrawn, and only if the relative unit for 
performing the required check is free. Moreover, by virtue of said units 
230, 231 and 232 being arranged vertically parallel between conveyors 211 
and 135, parallel checks may be performed on several cigarettes, each of 
which is subjected solely to the type of check provided for by the 
selected unit, thus enabling a considerable reduction in checking time. 
Finally, any cigarettes not damaged during inspection are fed back on to 
layer 136 and to follow-up machine 103. 
The cigarette and check type settings for block 260 may be entered by the 
operator, or automatically by processing unit 251, e.g. as a function of 
the test findings received from checking units 230, 231 and 232, or via 
computer 290. By means of computer 290, processing unit 251, given the 
origin of each sampled cigarette 16 and the difference between the test 
findings and required theoretical values, may provide for automatically 
correcting the appropriate production parameters for eliminating the 
faults detected by units 230, 231 and 232 and relative to cigarettes 
formed from halves 10, 11, 12 and 13. The data supplied to processing unit 
251 for performing the above function is unquestionably valid by virtue of 
deriving from statistical analyses of a large number of samples, and by 
virtue of the accuracy of each check which is performed statically. 
FIG. 9 shows a variation of the checking apparatus according to the present 
invention. The only difference as compared with the FIG. 1 apparatus lies 
in the configuration of the means for selectively feeding cigarettes 16 
off conveyor belt 211 to checking unit 230, 231 or 232. In the FIG. 9 
embodiment, electrovalves 219, 220 and 221 are dispensed with and, between 
the top inlets of units 230, 231 and 232 and conveyor belt 211, provision 
is made for respective selective withdrawal rollers 326, 327 and 328 
having an internal structure similar to that of roller 20. As shown in 
FIG. 10, each of said rollers 326, 327, 328 comprises a rotary outer ring 
338 having peripheral cigarette seats 321 and turned anticlockwise by a 
central shaft 339 supporting two fixed cylindrical distributors 340 and 
341. Distributor 340 is located inside 341 and communicates via a central 
passage 342 with a suction device (not shown) Distributor 340 presents a 
through radial slot 343 communicating, on one side, with central passage 
342 and, on the other, with a respective radial passage 345 in turn 
communicating with an external chamber 347 defined between the outer edge 
of distributor 341 and the inner edge of ring 338. Chamber 347 
communicates with seats 321 via suction means consisting of radial 
channels 349 formed through ring 338, and is defined, on one side, by a 
portion 350 over the outer edge of which the inner surface of ring 338 
slides in substantially contacting manner. Said portion 350 is located at 
the bottom of roller 326, 327, 328, over the inlet of respective unit 230, 
231, 232, and therefore provides for successively cutting off 
communication between each seat 321 and central passage 342 as seat 321 
moves over the inlet of respective unit 230, 231, 232. A partition 355 on 
the other side of chamber 347 separates this from a further chamber 356, 
which is completely isolated from central passage 342 and located at the 
point of tangency between rollers 326, 327, 328 and belt 212. Via an axial 
duct 357 formed through distributor 341 and a respective electrovalve 358, 
359, 360 (for each of rollers 326, 327, 328) for enabling selective 
withdrawal as described in more detail later on, chamber 356 communicates 
with a suction duct communicating with a suction device (not shown). As 
shown by the dotted lines in the top right-hand corner of the operating 
block diagram in FIG. 6, control system 250 therefore controls 
electrovalves 358, 359 and 360 as opposed to electrovalves 219, 220 and 
221. The FIG. 9 apparatus operates in exactly the same way as that of FIG. 
1 as regards the manner in which cigarettes 16 are selectively withdrawn 
by roller 20 and fed on to conveyor belt 211, and also as regards timed 
transfer of cigarette 16 from belt 212 into respective unit 230, 231 or 
232 on the basis of a given number of machine cycles wherein cigarette 16 
is fed from portion 35 of roller 14 to the respective portion of belt 212 
tangent to respective roller 326, 327 or 328. Upon cigarette 16 reaching 
said point of tangency, control system 250 activates respective 
electrovalve 358, 359 or 360, so as to suck cigarette 16 out of seat 216 
on belt 212 and into the adjacent seat 321 on ring 338 of respective 
roller 326, 327 or 328. Similarly, upon said seat 321 on 
anticlockwise-rotating ring 338 reaching said portion 350, the suction 
through said seat is cut off, thus causing cigarette 16 to drop down into 
unit 230, 231 or 232 underneath. 
To those skilled in the art, it will be clear that changes may be made to 
the embodiments described and illustrated herein without, however, 
departing from the scope of the present invention. For example, changes 
may be made to the system whereby cigarettes 16 are selectively withdrawn 
from roller 14; to the system whereby cigarettes 16 are selectively fed to 
checking units 230, 231 and 232; to the number of said units; or to the 
operation of central processing unit 251. Also, instead of depending on 
unit 251 determining non-engagement of a respective checking unit, a 
predetermined type of cigarette 16 may be withdrawn periodically by roller 
20, e.g. via a timing block allowing a sufficiently long interval to 
ensure inspection of any previously sampled cigarettes 16 has been 
completed.