CIGARETTE MANUFACTURING APPARATUS

Abstract: When cigarettes are continuously manufactured by continuously wrapping shredded tobacco, which is continuously supplied with a supply amount thereof controlled by a lengthy rolled paper to form a tobacco rod and cutting the tobacco rod to a predetermined length, charging quantities (charging densities) in various portions of the tobacco rod in a longitudinal direction are successively measured interlocking with continuous wrapping of the tobacco rod. The charging quantities (instantaneous values) in various portions of the tobacco rod are compared with a preset threshold to detect local excess shredded tobacco charging portions and/or shredded tobacco undercharging portions. The detected result is output in synchronism with a conveying timing of cigarettes of a predetermined length continuously cut from the tobacco rod, so that cigarrettes containing local excess shredded tobacco charging portions (hard spots) and local shredded tobacco undercharging portions (soft spots) can be surely eliminated.

Description: TECHNICAL FIELD The invention relates to a cigarette manufacturing apparatus for continuously manufacturing cigarettes according to the preamble of claim 1 and as disclosed in JP 6 277030 A. The present invention relates to a cigarette manufacturing apparatus for manufacturing cigarettes by continuously supplying tobacco shreds obtained by finely cutting tobacco leaves, continuously wrapping the continuously supplied tobacco shreds with an elongated cigarette paper to form a tobacco rod, and then cutting the tobacco rod to predetermined lengths. More particularly, the invention relates to a cigarette manufacturing apparatus having a function of detecting local excess and deficiency of filling amount of tobacco shreds in a tobacco rod to reject a cigarette which is cut from the tobacco rod, including local excess filling portion or deficient filling portion of tobacco shreds. BACKGROUND ART FIG. 1 shows a schematic configuration of a cigarette manufacturing apparatus. This cigarette manufacturing apparatus continuously supplies tobacco shreds 2a fed into a hopper 1 to a wrapping unit 4 by sucking them to the lower surface of a conveyor belt (tobacco band) provided in a suction unit 3. The suction amount (supply amount) of tobacco shreds 2a sucked to the lower surface of the conveyor belt 3a is controlled by a trimming disk 5. The wrapping unit 4 continuously wraps the tobacco shreds with an elongated cigarette paper 6 supplied continuously from a roll R to form a long tobacco rod 2b. This tobacco rod 2b is cut to predetermined lengths in a cutting section 7. For example, the tobacco rod 2b is cut into cigarette rods 2c of a double unit length, which corresponds to a length of substantially two final cigarettes, and the cigarette rods 2c are supplied to a filter attachment unit 8. The wrapping unit 4 is provided with a garniture tape 4b drivingly run by a main shaft 4a. As shown in FIG. 2, the garniture tape 4b rolls both sides of the cigarette paper 6 inside and upward while conveying the cigarette paper 6 supplied from the roll R, and continuously wraps the tobacco shreds 2a supplied onto the cigarette paper 6 in cooperation with a tongue 4c disposed opposingly above the garniture tape 4b. By this wrapping operation, the long tobacco rod 2b, in which the tobacco shreds 2a are wrapped with the cigarette paper 6, is continuously formed. The running speed of the conveyor belt 3a, which determines the supply speed of tobacco shreds 2a to the wrapping unit 4, is determined in synchronization with the rotation of the main shaft 4a, that is, depending on the running speed of the garniture tape 4b. The trimming disk 5 is rotated in synchronization with the rotation of the main shaft 4a (running speed of the garniture tape 4b). The trimming disk 5 regulates the thickness of tobacco shreds 2 sucked to the lower surface of the conveyor belt 3a, and controls the suction amount (supply amount) of tobacco shreds 2a conveyed to the wrapping unit 4 by scraping away the excess shreds. By the control of the supply amount of tobacco shreds 2a using the trimming disk 5, the amount of tobacco shreds 2a wrapped with the cigarette paper 6, that is, the amount (filling amount) of tobacco shreds 2a in the tobacco rod 2b is controlled. The trimming disk 5 is provided with pockets 5a for partially increasing the filling amount of tobacco shreds 2a in the tobacco rod 2b. The presence of these pockets partially increases the suction amount (supply amount) of tobacco shreds 2a conveyed to the wrapping unit 4, for example, each time the disk makes a half turn. As a result, the filling amount (filling density) of tobacco shreds 2a in the tobacco rod 2b is increased partially at every predetermined portion in the lengthwise direction. The hardened portion where the filling density of tobacco shreds 2a is increased is the cut portion where the aforesaid cigarette rods 2c are cut off, and further each cigarette is cut off. As a result, the tobacco shreds 2 are prevented from dropping off the cigarette dense end. The filling density of tobacco shreds 2a in the tobacco rod 2b is detected continuously by using, for example, a radiation density detector. By integrating the filling density of tobacco shreds 2a, which is continuously detected at every portion in the lengthwise direction of tobacco rod 2b in sequence, over a predetermined length in the lengthwise direction of tobacco rod 2b, for example, the total filling amount and average filling amount, and further the standard deviation of filling amount, and the like per one cigarette are determined. In the prior art disclosed in Japanese Patent application No. 6-277030, the amount of tobacco shreds contained in each of a predetermined number of sections, in to which a cigarette is divided, is obtained. In accordance with this detection result, the supply amount of tobacco shreds 2a is variably controlled, for example, by the trimming disk 5, so that the filling amount (filling density) of tobacco shreds 2a in the tobacco rod 2b is controlled. If it is judged from the aforementioned detection result that the total filling amount or average filling amount of tobacco shreds 2a per one cigarette is short, the cigarette rod 2c or cigarette cut from the tobacco rod 2b, which includes the portion where the filling amount is short, is rejected. The tobacco shreds 2a sometimes drop off the cigarette dense end due to the deficiency of filling amount (filling density) of tobacco shreds 2a. Therefore, the state of the cigarette dense end is checked by using, for example, a photosensor or capacitance proximity sensor. If the dropping-off of tobacco shreds 2a is found, that cigarette (cigarette rod 2c) is also rejected. As described above, even if the whole filling amount of tobacco shreds 2a in the tobacco rod 2b is controlled, some variations in filling density are naturally caused. In particular, as the cigarette manufacturing speed, specifically the wrapping speed of tobacco rod 2b, increases, the variations in the filling density in the lengthwise direction of tobacco rod 2b increases. For example, due to the slip of the cigarette paper 6 with respect to the garniture tape 4b, or the reaction of the tobacco shreds 2a when the tobacco shreds 2a is sucked to the conveyor belt (tobacco band), the filling density of tobacco shreds 2a in the tobacco rod 2b is increased (hard spot) or decreased (soft spot) locally. The excess filling portion (hard spot) of tobacco shreds 2a hinders the air flow in the cigarette, exerting an influence upon the cigarette quality. Meanwhile, the deficient filling portion (soft spot) of tobacco shreds 2a causes variations in burning state, for example, during smoking. Further, the deficient filling portion (soft spot) of tobacco shreds 2a hinders uniform smoking, and has an influence upon the change in burning velocity, the yielding amount of tar and nicotine, and in turn the smoking taste. Conventionally, however, the filling state of tobacco shreds 2a in the tobacco rod 2b is monitored merely, for example, as an average amount of tobacco shreds contained in a cigarette, an average of respective amounts of tobacco shreds in a predetermined number of sections, in to which is secret is divided, or the like, as described above. Also, the dropping-off state of tobacco shreds 2a at the cut end of cigarette is merely monitored. The present invention was made in view of the above situation, and accordingly an object thereof is to detect a local excess filling portion (hard spot) and deficient filling portion (soft spot) of tobacco shreds in a tobacco rod efficiently and reliably, and to surely reject a cigarette rod or cigarette cut from the tobacco rod, which includes the local excess filling portion (hard spot) or deficient filling portion (soft spot) of tobacco shreds. Another object of the present invention is to improve the production quality of cigarette by reliably rejecting a cigarette including the local excess filling portion (hard spot) or deficient filling portion (soft spot) of tobacco shreds in consideration of the fact that these defective portions are liable to be produced as the cigarette manufacturing speed increases. The present invention provides a cigarette manufacturing apparatus capable of achieving these objects. DISCLOSURE OF THE INVENTION To achieve the above objects, the present invention provides a cigarette manufacturing apparatus for continuously manufacturing cigarettes according to the preamble of the claim which comprises the characterizing features of this claim. Accordingly the filling amount of tobacco shreds at every portion in the lengthwise direction of the tobacco rod is detected by the measuring means, and the momentary value of filling amount detected by the measuring means is compared with predetermined threshold values, by which local excess and deficiency of the filling amount of tobacco shreds at every portion in the lengthwise direction of the tobacco rod are judged. The judgment result is output in synchronization with the conveying timing (cut timing) of cigarette cut from the tobacco rod including the detected portion, by which a cigarette including a local excess filling portion (hard spot) or deficient filling portion (soft spot) of tobacco shreds can be rejected surely. The total filling amount of tobacco shreds per one cigarette cut from the tobacco rod is determined by integrating the filling amount detected by the measuring means, the supply amount of tobacco shreds supplied for the wrapping operation is controlled in accordance with the total filling amount of tobacco shreds, and a cigarette in which the filling amount of tobacco shreds is short is detected by judging the total filling amount of tobacco shreds. The control of supply amount of the tobacco shreds is carried out so that the filling amount of tobacco shreds at the cut portion of tobacco rod continuously wrapped with the cigarette paper is larger than the filling amount of tobacco shreds at portions other than the cut portion, a first threshold value being set to be higher than the target filling density of tobacco shreds at the cut portion and a second threshold value being set to be lower than the target filling density of tobacco shreds at portions other than the cut portion are used. When the filling density of tobacco shreds at every portion in the lengthwise direction of the tobacco rod is higher than the first threshold value, the tobacco rod portion where that filling density is detected is judged to be an excess filling portion, and when the filling density is lower than the second threshold value, the tobacco rod portion where that filling density is detected is judged to be a deficient filling portion. That is to say, the filling amount of tobacco shreds in the tobacco rod is controlled so that the filling amount is partially increased at the cut portion. Apart from the change in filling amount (filling density) at every portion in the lengthwise direction, the first threshold value for judging the local excess filling of tobacco shreds is set to be larger than the target filling density of tobacco shreds at the cut portion of tobacco rod, and the second threshold value for judging the local deficient filling of tobacco shreds is set to be lower than the target filling density of the tobacco shreds at portions other than the cut portion. Thereupon, the local excess filling portion (hard spot) and/or deficient filling portion (soft spot) of tobacco shreds, which pose a production quality problem, can be detected easily and surely. Further, the detection result of the excess filling portion or deficient filling portion is output in synchronization with the conveying timing of cigarette cut from the tobacco rod, by which instructions to reject a cigarette including a defective portion are given surely. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a general schematic view of a cigarette manufacturing apparatus; FIG. 2 is a view schematically showing the state of tobacco shreds continuously wrapped with a cigarette paper; FIG. 3 is a block diagram showing a configuration of a tobacco shreds filling amount monitoring system in a cigarette manufacturing apparatus in accordance with one embodiment of the present invention; FIG. 4 is a diagram schematically showing the relationship between the tobacco rod state, the cut timing signal, the signal mode at each position such as analog filling amount signal, and the sampling timing for these signals, for illustrating one embodiment of the present invention; FIG. 5 is a block diagram showing another example of configuration of a spot detecting section showing another embodiment of the present invention; FIG. 6 is a block diagram showing still another example of configuration of a spot detecting section showing another embodiment of the present invention; and FIG. 7 is a diagram showing the relationship between the first and second threshold values S + and S - set in the spot detecting section shown in FIG. 6 and the analog filling amount signal. BEST MODE OF CARRYING OUT THE INVENTION To explain the present invention in more detail, one embodiment of a cigarette manufacturing apparatus in accordance with the present invention will be described with reference to the accompanying drawings. The cigarette manufacturing apparatus in accordance with this embodiment is basically configured as shown in FIGS. 1 and 2, and the filling amount monitoring system for tobacco shreds 2a which fulfills the characteristic features of the present invention is schematically configured as shown in FIG. 3. This filling amount monitoring system has a function of continuously detecting the filling density of tobacco shreds 2a at every portion in the lengthwise direction of the tobacco rod 2b, monitoring the total filling amount (average filling amount) of tobacco shreds 2a per one cigarette in accordance with the filling density, and determining whether the whole filling amount of cigarette is surplus or short. Further, the filling amount monitoring system has a function of detecting the local excess filling portion (hard spot) and deficient filling portion (soft spot) of tobacco shreds 2a at every portion in the lengthwise direction of the tobacco rod 2b in accordance with the filling density. More specifically, as shown in FIG. 3, the filling amount monitoring system has a scanning head (sensor) 11 for continuously detecting the filling density of tobacco shreds 2a at every portion in the lengthwise direction of the tobacco rod 2b continuously wrapped in the wrapping unit 4. The scanning head 11, which consists mainly of a radiation density detector and is arranged close to the conveying path of tobacco rod 2b, continuously detects the filling density of tobacco shreds 2a at every portion in the lengthwise direction of the tobacco rod 2b passing through the sensing portion. Specifically, the scanning head has, for example, a pair of β ray sources 12, 12 and two ion chambers receiving the β rays radiated from the β ray source 12, 12. One β ray radiation path is used as the sensing portion through which the tobacco rod 2b passes and the other β ray radiation path as a reference system. The tobacco rod 2b passing through the sensing portion attenuates the β rays reaching the ion chamber 13 depending on the filling density of tobacco shreds 2a. Therefore, by measuring the amount of β rays received by one ion chamber 13, the filling density of tobacco shreds 2a is determined from the attenuation amount of β rays. In particular, by determining a difference between the β ray amount attenuated depending on the filling density of tobacco shreds 2a and the β ray amount determined by the ion chamber 13 of the reference system by using a subtractor 14, the time-related attenuation of the β ray sources 12, 12 is compensated, and the filling density (filling amount) of tobacco shreds 2a in the tobacco rod 2b is detected with high accuracy. the information on the filling density (filling amount) of tobacco shreds 2a at every portion in the lengthwise direction of the tobacco rod 2b, detected continuously in such a manner, is output as an analog filling amount signal via an amplifier 15. The filling amount judging section plays a role in determining the filling amount of tobacco shreds 2a per one cigarette in the tobacco rod 2b in accordance with the filling amount signal generated from the scanning head 11, outputting it as a filling amount control signal, and judging whether the filling amount is surplus or short. Specifically, the filling amount judging section 21 includes an integrator 22, a sample-and-hold circuit 23, and two comparators 24 and 25. The integrator 22, which is reset by a timing signal T generated by a timing circuit 51 in synchronization with the rotation of the main shaft 4a, integrates the filling amount signal over one period of timing signal T. By this integration of filling amount signal, the filling amount of tobacco shreds 2a per one cigarette is determined. The sample-and-hold circuit 23, which is operated in accordance with the timing signal T, samples and holds the total filling amount (integral value of filling amount signal) of tobacco shreds 2a per one cigarette determined by the integrator 22. The timing signal T consists of a timing pulse signal indicative of the cut position of tobacco rod 2b. For example, the sample-and-hold circuit 23 is driven at the leading edge of the timing signal T, and the integrator 22 is reset at the trailing edge thereof. The two comparators 24 and 25 compare the integral value (total filling amount of tobacco shreds 2a per one cigarette) held by the sample-and-hold circuit 23 with filling amount threshold values V + and V - set in advance in accordance with the target filling amount by a reference circuit 61, respectively, to judge whether the filling amount of tobacco shreds 2a per one cigarette is surplus or short. Specifically, when the total filling amount (integral value) of tobacco shreds 2a exceeds the reference value (filling amount threshold value V + ), the comparator 24 judges that the filling amount is surplus. In synchronization with the cutting of the cigarette portion judged to have an excess filling amount from the tobacco rod 2b, the comparator 24 generates a removal signal giving instructions to reject this cigarette. When the total filling amount of tobacco shreds 2a is smaller than the reference value (filling amount threshold value V - ), the comparator 25 judges that the filling amount is short. In synchronization with the cutting of the cigarette portion judged to have a deficient filling amount from the tobacco rod 2b, the comparator 24 generates a removal signal giving instructions to reject this cigarette. Besides, the filling amount judging section 21 plays a role in determining the average filling amount of tobacco shreds 2a in the tobacco rod 2b and the standard deviation of the filling amount from the total filling amount per one cigarette detected successively as described above, and controlling the filling amount of tobacco shreds 2a (average filling amount control). In accordance with this control information, for example, the control of the suction amount of tobacco shreds 2a to the conveyor belt 3a in the suction unit 3 (control of negative pressure) and the height adjustment of the trimming disk 5 (control of thickness) are carried out. On the other hand, a spot detecting section 31 plays a role in detecting the local excess filling portion (hard spot) and local deficient filling portion (soft spot) of tobacco shreds 2a at every portion in the lengthwise direction of the tobacco rod 2b. This spot detecting section 31 has two comparators 32 and 33 and two delay circuits 34 and 35. The comparators 32 and 33 receive the filling amount signal, and continuously judge the local filling amount (filling density) by comparing the momentary value indicating the filling amount of tobacco shreds 2a at every portion in the lengthwise direction of tobacco rod 2b with first and second threshold values S + and S - . The first threshold value S + is set to a value 15 to 25% higher than a reference, the reference being, for example, the target filling amount (filling density) at the cut portion where the filling amount of tobacco shreds 2a in the tobacco rod 2b is partially increased. The second threshold value S - is set to a value 15 to 25% lower than the target filling amount (filling density) of tobacco shreds 2a at the main portion excluding the cut portion of the tobacco rod 2b. When the local filling density of tobacco shreds 2a at every portion in the lengthwise direction of the tobacco rod 2b, which is indicated as the momentary value of the filling amount signal, exceeds the first threshold value S + , the comparator 32 judges that the portion is the excess filling portion (hard spot). When the local filling density of tobacco shreds 2a, which is indicated as the momentary value of the filling amount signal, is lower than the second threshold value S + , the comparator 33 judges that the portion is the deficient filling portion (soft spot). Conventionally, the filling amount of tobacco shreds 2a has merely been monitored as a whole as the total filling amount of tobacco shreds 2a per one cigarette in the tobacco rod 2b or as the filling amount (filling density) of tobacco shreds 2a at the dense end portion by the aforementioned filling amount judging section 21. Additionally, in the present invention, the momentary value of filling amount signal, which varies every moment, is compared continuously with the first and second threshold values S + and S - and judgment is made by the two comparators 32 and 33 in the spot detecting section 31, by which the local excess and deficiency of the filling amount (filling density) of tobacco shreds 2a at every portion in the lengthwise direction of the tobacco rod 2b are detected continuously. The judgment result of these comparators 32 and 33 is output as a removal signal giving instructions to reject a cigarette, cut from the tobacco rod 2b, including the excess filling portion (hard spot) or deficient filling portion (soft spot) of tobacco shreds 2a. In particular, the removal signal is timing regulated via the delay circuits 34 and 35, which are driven by receiving the timing signal T, and generated in synchronization with the cutting of cigarette from the tobacco rod 2b. In the filling amount judging section 21, after the analog filling amount signal is integrated over one cigarette, the total filling amount of tobacco shreds 2a is judged from the integral value. Meanwhile, in the spot detecting section 31, the analog filling amount signal is judged in real time. For this reason, a time shift corresponding to one cigarette occurs in the judgment timing. To absorb this time shift, the delay circuits 34 and 35 delays the judgment result (removal signal) of the comparators 32 and 33 for a time corresponding to one cigarette, by which the judgment result of the comparators 32 and 33 is synchronized with the output timing of the judgment result (removal signal) from the filling amount judging section 21. The outputs (removal signals) from the filling amount judging section 21 and the spot detecting section 31 are input to shift registers 43 and 44 for removal control through OR circuits 41 and 42. The removal signals are further timing regulated by the shift registers 43 and 44, and given to the removal control section (not shown) of a filter attachment unit 8. As a result, the cigarette rod 2c including the excess filling portion (hard spot) or deficient filling portion (soft spot) is cut from the tobacco rod 2b in the cutting section 7, and the removal signal is given to the removal control section (not shown) of the filer attachment unit 8 in synchronization with the timing at which the cigarette rod 2c is sent to the filter attachment unit 8. FIG. 4 schematically shows the relationship between the state of tobacco rod 2b continuously wrapped in the wrapping unit, the cut positions of the tobacco rod 2b, the cut timing signal giving instructions to cut the tobacco rod 2b, the filling amount signal determined continuously from the tobacco rod 2b, the signal mode at each position determined from the filling amount signal, and the timing for these signals. The functions and operation of the spot detecting section 31 will now be described in more detail with reference to FIG. 4. In the wrapping unit 4, one tobacco rod 2b wrapped into a long rod has portions where the filling amount of tobacco shreds 2a is partially increased at intervals of one cigarette by the action of the pocket 5a of the trimming disk 5 rotated in synchronization with the timing signal T. The portion where the filling amount of tobacco shreds 2a is partially increased is the cut portion of tobacco rod 2b as indicated by hatching. The timing signal T is generated at each of predetermined timing by counting a reference clock generated by an encoder (not shown) connected to the main shaft 4a. Assuming that for example, when the main shaft 4a makes one turn, the encoder generates a reference clock of 1200 pulses corresponding to the length of four cigarette rods 2c, the timing signal T is generated as a signal for defining the first cut timing at the time when 81 pulses of reference clock are counted from the reference position (0 pulse position), and subsequently, it is generated each time 150 pulses of reference clock are counted. Therefore, the timing signal T is generated with a period corresponding to the length of one cigarette. The trimmer disk 5 is rotated in synchronization with the timing signal T, and the pocket 5a thereof is positioned at a portion facing the lower surface of the conveyor belt for a time period of 20 pulses before and after the timing signal T (a total of 40 pulses) as indicated as a gate signal G. By the rotation control of the trimmer disk 5, the filling amount of tobacco shreds 2a in the lengthwise direction of the tobacco rod 2b is partially increased with a period of the length of one cigarette. The tobacco rod 2b is cut to a unit of the cigarette rod 2c corresponding to the length of two cigarettes in accordance with the timing signal T in the cutting section 7, and then the cigarette rods 2c are sequentially supplied to the filter attachment unit 8, where they are cut to a length of one cigarette. The cutting of the tobacco rod 2b in the cutting section 7 is done in synchronization with the odd-numbered timing (black arrow C1) of the timing signal T (control of tobacco rod cut position). The even-numbered timing (white arrow C2) of the timing signal T is used as a timing for regulating the position where the cigarette rod 2c is cut in half when a filter chip is mounted to the cigarette rod 2c in the filter attachment unit 8 (control of final cut position). On the other hand, the tobacco shreds 2b wrapped continuously is introduced to the scanning head 11 in connection with the wrapping, and the filling amount of every portion in the lengthwise direction is continuously inspected. The scanning head 11 continuously detects the filling amount (filling density) of tobacco shreds 2a at every portion in the lengthwise direction of tobacco rod 2b as shown as an analog filling amount signal D in FIG. 4. The aforementioned filling amount judging section 21 integrates the thus detected analog filling amount signal D over the period corresponding to one cigarette in accordance with the timing signal T, for example, as shown as an integration output signal I in FIG. 4, and thereby determines the total filling amount of tobacco shreds 2a filling per one cigarette. The sample held integral value I in the sample-and-hold circuit 23, that is, the total filling amount of tobacco shreds 2a per one cigarette is compared with the filling amount threshold values V + and V - , which have been set in advance, at a timing defined by the timing signal T as shown in FIG. 4. This comparison of the integral value I with the filling amount threshold values V + and V - determines whether the filling amount per one cigarette is larger than the target filling amount and whether it is smaller than the target filling amount. In other words, it determines whether the cigarette is an excessively filled cigarette and whether the cigarette is a deficiently filled cigarette. The average filling amount of tobacco shred 2a filling per one cigarette is calculated by averaging the total filling amounts I sequentially determined for each cigarette over a plurality of periods. The standard deviation of filling amount is calculated by determining the distribution of the filling amounts I. Although the processing circuit is not especially shown herein, the filling amount judging section 21 partially integrates the filling amount signal D at the cut portion, as shown as a partial integration signal B in FIG. 4, for example, in accordance with the timing signal T shown in FIG. 4 and the gate signal G showing the cut portion. This partial integration of the filling amount signal D determines the filling amount (filling density) of tobacco shreds 2a at the dense end of cigarette where the filling amount of tobacco shreds 2a is partially increased. By judging the filling amount (partial integral value B) at each timing defined by the timing signal T, the possibility for the tobacco shreds 2a to come off from the cut end of cigarette is judged. In contrast, the spot detecting section 31 continuously compares the filling density itself of tobacco shreds 2a at every portion in the lengthwise direction of tobacco rod 2b shown by the filling amount signal D with the first and second threshold values S + and S - as shown in FIG. 4. In this case, continuous comparison of the filling amount signal D with the first and second threshold values S + and S - is made regardless of the timing signal T. When the magnitude (momentary value) of the filling amount signal D exceeds the first threshold value S + or falls below the second threshold value S - , it is judged that the filling amount (filling density) of tobacco shreds 2a at the detection portion of the filling amount of tobacco rod 2b shown by the detection timing is locally surplus or locally short. That is, it is judged that the detection portion is an excess filling portion (hard spot) or a deficient filling portion (soft spot), which poses a quality problem. Thus, according to the apparatus configured as described above, in the process in which the tobacco rod 2b is manufactured by continuously wrapping the tobacco shreds 2a, not only whether or not the total filling amount of tobacco shreds 2a per one cigarette is proper is sequentially judged but also whether or not a local excess filling portion (hard spot) and/or deficient filling portion (soft spot) is present in the cigarette can be inspected efficiently. As the wrapping speed increases, the filling density of tobacco shreds 2a in the lengthwise direction of tobacco rod 2b is liable to be nonuniform, which causes a local excess filling portion (hard spot) and deficient filling portion (soft spot) of tobacco shreds 2a. This apparatus can detect these defective portions surely and in real time in connection with the manufacture (wrapping). Also, the excess filling portion (hard spot) and deficient filling portion (soft spot) can be detected easily by using the output of the scanning head 11 used for inspecting the filling amount of tobacco rod 2b, that is, the analog filling amount signal D. Further, the detection result (removal signal) of the excess filling portion (hard spot) and deficient filling portion (soft spot) is output in synchronization with the judgment signal (removal signal) for the total filling amount, so that defective cigarettes can be rejected easily and surely in the subsequent filter attachment unit 8 etc. In the above-described embodiment, the first and second threshold values S + and S - are set fixedly, and the local filling amount of tobacco rod 2b is judged uniformly in the lengthwise direction. However, for example, as shown in FIG. 5, a gate circuit 36 may be provided at the front stage of the comparators 32 and 33 in the spot detecting section 31 to judge only the local excess and deficiency of filling amount at the cut portion where the filling amount of tobacco shreds 2a is increased in the tobacco rod 2b. In this case, the first and second threshold values S +1 and S -1 may be set to be 15 to 25% higher and lower than the reference, respectively, the reference being the target filling amount of tobacco shreds 2a at the cut portion. When the filling amount exceeds the first threshold value S +1 , which is set to be 15 to 25% higher than the target filling amount, the detected portion may be judged to be an excess filling portion (hard spot), and when the filling amount falls below the second threshold value S -1 , which is set to be 15 to 25% lower than the target filling amount, that portion may be judged to be a deficient filling portion (soft spot). Likewise, only the filling amount signal at the main portion excluding the cut portion where the filling amount of tobacco shreds 2a is increased is extracted via the gate circuit 31, and the filling amount at that portion is compared with the first and second threshold values S +2 and S -2 , which are 15 to 25% higher and lower than the target filling amount of tobacco shreds 2a at that portion, respectively, by which an excess filling portion (hard spot) and deficient filling portion (soft spot) at the main portion may be detected. Further, in order to separately detect an excess filling portion (hard spot) and deficient filling portion (soft spot) at the main portion of tobacco rod 2b and the cut portion where the filling amount of tobacco shreds 2a is increased, for example, as shown in FIG. 6, selectors 37 and 38 for selectively setting the first and second threshold values S +1 , S +2 , S -1 , and S -2 is provided, by which comparison reference threshold values S + and S - given to the comparator 32 and 33 may be variably set in accordance with the general level change of the filling amount signal D as shown in FIG. 7. In this case, for example, the first and second threshold values S + and S - , which are set in advance, may be changed by a level α corresponding to the increased amount of tobacco shreds 2a at the cut portion of tobacco rod 2b. Specifically, the apparatus can be so configured that the level α is added to or subtracted from the first and second threshold values S + and S - by using an adder (not shown) in place of the selectors 37 and 38. According to the configuration in which the threshold values S + and S - for detecting the excess filling portion (hard spot) and deficient filling portion (soft spot) are variably set in accordance with the change in filling amount of tobacco rod 2b such that the filling amount of tobacco shreds 2a is increased at the cut portion, the excess filling portion (hard spot) and deficient filling portion (soft spot) with respect to the target filling amount of tobacco shreds 2a at every portion in the lengthwise direction of the tobacco rod 2b can be detected. By rejecting the cigarette having these defective portions, the cigarette production quality can be enhanced. The present invention is not limited to the above-described embodiment. For example, the present invention can be applied similarly to the apparatus using infrared rays or ultrasonic waves instead of β rays as the scanning head 11. Also, as the delay circuits 34 and 35 for timing adjustment, shift registers driven by receiving, for example, the timing signal T may be used. Needless to say, in addition to the sensors for detecting the filling amount of one cigarette, special purpose sensors for detecting an excess filling portion (hard spot) and deficient filling portion (soft spot) may be provided. INDUSTRIAL APPLICABILITY As described above, according to the present invention, a local excess filling portion or deficient filling portion at every portion in the lengthwise direction of the tobacco rod is detected by comparing the momentary value of the filling amount signal indicative of the filling amount (filling density) of tobacco shreds at every portion in the lengthwise direction of the tobacco rod with the threshold values set in advance, and the detection result is output in synchronization with the conveying timing of the cigarette rod of a predetermined length cut from the tobacco rod or the cigarette. Therefore, in addition to the removal of cigarette in which the total filling amount is short, which has been effected conventionally, the cigarette including a local excess filling portion (hard spot) and/or deficient filling portion (soft spot) of tobacco shreds can be rejected surely. As a result, the production quality can be enhanced even if the cigarette manufacturing speed is increased. Moreover, since the aforesaid excess filling portion or deficient filling portion is detected under the threshold values set in accordance with the filling amount of each portion in which the filling portion is controlled, a local excess filling portion (hard spot) and local deficient filling portion (soft spot), which pose a quality problem, can be detected easily and surely. Therefore, an effect can be achieved that defective cigarettes can be rejected based on the inspection result of the total filling amount of cigarette, and also a cigarette including the defective portions can be rejected surely.

Claims: A cigarette manufacturing apparatus for continuously manufacturing cigarettes by continuously wrapping continuously-supplied tobacco shreds (2a) with an elongated strip of cigarette paper to form a tobacco rod (2b) and cutting said tobacco rod (2b) into cigarettes of predetermined length, wherein the amount of supplied tobacco shreds (2a) is controlled so that each of regions where said tobacco rod (2b) is to be cut may contain a larger amount of tobacco shreds per unit volume than the other regions of said tobacco rod, said cigarette manufacturing apparatus comprising measuring means (11, 21) for continuously measuring an amount of tobacco shreds (2a) at every portion in the lengthwise direction of said tobacco rod (2b), in connection with the continuous wrapping operation of said tobacco rod (2b), and calculating a total amount of tobacco shreds (2a) contained in each of the cigarettes to be cut from said tobacco rod (2b) by integrating the amount of tobacco shreds measured at the every portion by said measuring means (21), comparing means (24, 25) for comparing the integrated amount of tobacco shreds (2a) in each of the to-be-cut cigarettes with an upper reference value above which a cigarette containing surplus tobacco shreds is observed and with a lower reference value below which a cigarette being short in tobacco shreds is observed, and control means (5) for controlling the amount of tobacco shreds (2a) supplied for the wrapping operation based on the integrated amount of tobacco shreds (2a) in each of the to-be-cut cigarettes determined by said comparing means (24, 25) so that the total amount of tobacco shreds (2a) contained in each of the cigarettes is maintained within a required range, characterized in that : said cigarette manufacturing apparatus further comprises detecting means (31) for detecting at least one of a local excess filling portion and a local deficient filling portion of said tobacco rod at every portion in the lengthwise direction of said tobacco rod by comparing the filling amount of tobacco shreds (2a) at every portion in the lengthwise direction of said tobacco rod (2b) acquired by said measuring means (11) with an allowable upper threshold value (S+), set in advance, above which the local excess filling portion is observed and with an allowable lower threshold value (S-), set in advance, below which the local deficient filling portion is observed and locating a defective cigarette having said local excess filling portion or deficient filling portion, and output means (43, 44) for outputting a rejection signal in synchronism with the conveying timing of the defective cigarette. The cigarette manufacturing apparatus according to claim 1, characterized in that : the allowable upper threshold value has first and second upper values for inspecting the cut regions and the other regions of tobacco rod (2b), respectively, and the allowable lower threshold value has first and second lower values for inspecting the cut regions and the other regions of tobacco rod (2b), respectively. The cigarette manufacturing apparatus according to claim 1 or 2, characterized in that : said measuring means measures the amount of tobacco shreds by means of a β ray and has a compensation means for compensating the time-related fluctuation of the β ray.

Inventors: KIDA SHINZO, KIDA, SHINZO
Applicants: JAPAN TOBACCO INC, JAPAN TOBACCO INC.
Application year: 1997
Main classification: A24C5
IPC codes: A24C5