US2925818A - Machines for manipulating cut tobacco - Google Patents

Description

Feb. 23, 1960 D. w. MOLINS ETAL MACHINES FOR MANIPULATING CUT TOBACCO 2 Sheets-Sheet 1 Filed March 1, 1956 a L mmfl wuw y a ww 35 m D F Feb. 23, 1960 w, MQLINS ETAL MACHINES FOR MANIPULATING CUT TOBACCO Filed March 1, 1956 2 Sheets-Sheet 2 I 2,925,818 MACHINES FOR MANIPULATING CUT TOBACCO Desmond Walter Molins and Gordon Francis Wellington Powell, Deptford, London, England, assignors to Molins -Machine Company Limited, London, England, a British company Application March 1, 1956, Serial No. 568,738 Claims priority, application Great Britain March 8, 1955 12 Claims. (Cl. 13121) This invention concerns improvements in or relating to machines for manipulating cut tobacco, for example cigarette-making machines. In tobacco manipulating machines, cut tobacco is fed and may subsequently issue from the machine in separated portions, e.g. as cigarettes in a cigarette-making machine, or as packages in a tobacco packaging machine.

In such tobacco manipulating machines cut tobacco is removed from a mass and spread in some way on a conveyor which carries it as a continuous stream or filler through or towards devices which manipulate it to form it into a continuous tobacco rod which may eventually be enclosed in a continuous paper wrapper. The bestknown example of such a machine is the continuous rod cigarette-making machine.

Cigarette-making machines of the continuous rod type are provided with tobacco-feeding apparatus in which a mass of cut tobacco is placed in a hopper and subjected to various brushing and combing operations and finally showered onto a conveyor, where it forms a loose tobacco filler, and by means of which, or of a succeeding conveyor, it is formed into a tobacco rod or core which is afterwards wrapped in paper.

The aforesaid loose filler and the resulting rod are not as uniform in consistency as is desirable, and many attempts have been made to improve the uniformity of distribution of the tobacco in the final rod and the present invention is directed towards this end.

As will appear later the carrying of the invention into eifect requires a detector responsive to changes in mass of a passing tobacco stream and two kinds of detector are available for this purpose. One is what is termed an electrostatic, or high-frequency, detector where the tobacco passes between a pair of plates of electrically conductive material and becomes the dielectric of a condenser formed by the plates and the tobacco. This arrangement is responsive mainly to the moisture content of the tobacco, but if this remains constant, variations in the detector readings will indicate variations in the mass of the tobacco.

The other kind of detector employs a source of penetrative radiation, such as a beta-ray source, and a rayresponsive device whereby changes in the mass of the passing tobacco cause minute changes of current in the apparatus. 1

According to the present invention there is provided a machine of the kind. referred to comprising means to feed tobacco as a stream (e.g. a conveyor on which tobacco is carried as a stream), a second means comprising a conveyor to which the tobacco is delivered by the first conveyor and conveyed as a stream, means for varying the speed of the conveyor of said second means, a detector associated with the first said means and responsive to changes in the mass of the passing tobacco stream and adapted to cause the speed of the conveyor of said second means to be altered when the passing mass varies from a desired value, said detector being so located that the time taken by tobacco moving from the detector posinited Stats Patent ICC tion to reach the conveyor in the said second means is equal to the time required for the speed of the last said conveyor to be altered in response to a detector signal; The time factor will depend on the type of detector and the nature of the driving devices for the conveyor in the said second means as well as the amplifying or like apparatus necessary between the detector and the driving devices. Further the transfer of tobacco from one conveyor to the other (where two such conveyors are used) may require special apparatus in some constructions. It will be appreciated that each of these pieces of apparatus will have a certain amount of timelag and thus a signal from the detector will not be translated into a speed change of the second conveyor until a certian time has elapsed. The detector must therefore be located at some distance from the beginning of the second conveyor so that the time taken for detected tobacco to reach the second conveyor is equal to the time elapsing between a detector signal and the resulting speed change. Since in general it will be desired to keep at least thefirst conveyor, where one is used, fairly short, an electrostatic detector is preferable as it responds very rapidly to a change of mass and though the detector action is mainly due to the moisture content of the tobacco the mass is proportional to this so long as the moisture content remains constant.

In apparatus of the kind under consideration it is generally desirable to employ the detector to react to a variation in the average value of a passing stream, as measured over a short length, that is, the detector gives a signal after the lapse of a short time during which the stream is passing. The detection apparatus therefore preferably embodies devices of known kind for this purpose, the results of a short series of responses being smoothed out to give an average signal. This method of measuring permits an easier and more reliable control of the machine for it is neither easy nor desirable to alter the conveyor speed every instant a difference in the passing mass appears.

In some cases there may be a difference in the nominal speeds of the two conveyors according to their position in the machine and their functions. Sometimes the first conveyor may travel considerably faster than the second conveyor, while in a different construction of the machine the first conveyor will be considerably slower than the second. Examples of various arrangements are given later.

It should be understood that the term equal used in the foregoing statements of invention means equal so far as the apparatus available will permit, that is, the timelags are carefully calculated or measured and the detector position is fixed so that the time taken for the tobacco to reach the second conveyor is as near as possible to the average time taken for the correction to be made in a given arrangement.

The invention will be more fully explained with reference to some examples shown in the accompanying drawings which are of a diagrammatic nature showing only the fundamentals of the apparatus.

In the drawings:

. Figure 1 shows two conveyors and a detector and the speed changing devices of the second conveyor;

Figure 2 is similar to Figure 1 but the first conveyor is a shower receiving conveyor;

Figure 3 shows the invention applied to a cigarettemaking machine of the kind where tobacco is compacted by a delivery of a fast moving stream on to a slower moving conveyor; and

Figure 4 shows another type of machine where the first conveyor is a shower collecting conveyor moving at a slower speed than is usual for shower collection.

Referring to Figure 1, a first conveyor 1 is shown feeding tobacco to a second conveyor 2. Between the neighbouring ends of the conveyors is a narrow bridge 3. An electrostatic detector hasits plates 4 positioned as shown, though in practice the plates might be put at the sides of the tobacco, which is in the form of a stream on both conveyors.

The plates 4 are connected to high-frequency amplifying and other known devices, whereby a change in capacity of the condenser formed by the plates 4 and the tobacco stream can be caused to operate a relay or the like. This apparatus is indicated by a block 5. The relay causes a motor 6 to be set into motion in either direction according to the nature of the detector signal. The motor alters a V pulley variable speed gear 7 from which the conveyor 2 is driven.

When the tobacco at any instant between the plates ,4 is above or below the desired mass the change in capacity of the condensercan be used as a signal. As previously remarked averaging over a short time is desirable so said signal, or an average signal, is used to cause operation of all the detector apparatus and the relay. This detection and relay operation takes only some extremely short time. In addition to the time taken so far, the relay has to start the motor 6 which again takes a small time; the motor has then to alter the gear ratio in the gear 7 and finally the conveyor 2 has to take up the new speed. In all :there is an appreciable delay between the occurrence of the signal and the occurrence of the speed change, totalling said A to /2 second, according to circumstances. The distance A must therefore be such that the streamtraverses it in the appropriate period of time. If it is supposeduthat the .conveyors are traveling at rod speed of 1,200 cigarettes .per mintue, the distance A would be equal to the total length of five cigarettes for atime-lagof A ofa second. It will be understood that the figures given are merely by way'of exampleand that in :practice the various time-lags of the various pieces of apparatus are accurately determined and the conveyor speeds and distance A are arranged to suit'the total lag. If the conveyor speeds are such that the first conveyor is not long enough to give the necessary distance then the time-lags must be shortened by using more suitable detector-speed-change apparatus.

The arrangement shown in Figure 2 is in all respects similar to that of Figure 1 but the conveyor 1 is shown acting as a shower receiving conveyor passing beneath a tobacco feeder 8. The conveyor 2 may be the rodforming conveyor .in which case it -will be arranged similar to the conveyor 12 described later with reference to Figure '3.

Referring-to Figure '3, the first conveyor 11 is arranged to receive the shower froma tobacco feeder 13 and the resulting stream is fed down a smooth passage 14, as described in United States Patent No. 2,671,452, issued March 9, 1954.

The stream is discharged on to the second conveyor 12 which carries a paper web 15 in which the tobacco is eventually wrapped to form a continuous cigarette rod.

The conveyor'12is drivenby a tape drum 16 and the speed .of the drum is varied in the same way as the speed of conveyor 2 in the former examples. In this case there is a distinct difference between the normal speeds of the first and second conveyors, the former travelling faster 'ina ratioof, say, 1402100. As the first conveyor speed is constant, any change in the speed of the second conveyor makes-a slight difference in this ratiobut that does not-matter, the speed difference being to effect -a certain compacting action in the smooth passage as described in the aforesaid specification. The changes due to detection are fairly small and transient and do not injuriously affect the compacting action.

Referring to Figure 4, tobacco is showered down from a tobacco feeder '20 and falls on-a slow conveyor 21. The conveyor 21in thjs-example may -be about 4'' wide whereas the width of the stream formed on the hopper tape of an ordinary cigarette machine is say 1"-1 A" wide, assuming that a flat stream is being formed. This means that the conveyor 21 can run at about A to /2 of the speed of a normal hopper tape and carry three to four times the tobacco per inch of length. The showered tobacco then forms a 4" wide carpet on the belt. However, the conveyor 21 may be narrower than in the specific example given and will then be a wide deep stream and of course go proportionately faster.

The right-hand end of the conveyor 21 is' near a toothed or pin-roller 23 and to the left of this is a pickerroller 24. Tobacco is pressed into the pin-roller by a smooth roller 25. The pins of the roller 24 are canted backwards as considered in the direction of rotation and this helps the roller to pick up the tobacco from the pin-roller without appreciable breakage. The peripheral speed of the pin-roller is slightly less. than the linear speed of the conveyor 21 so that there is a certain amount of packing action in the transfer of tobacco from belt to pin-roller. A concave 26 surrounds the right-hand side of the pin-roller and tobacco is picked at the edge 27 of the concave in the usual way. The picked tobacco is thrown down a chute 28 on to a second conveyor 22. This conveyor is 1%" wide so its speed will be 3.2 times that of the belt 21. Because it is narrow relatively to the belt 21, the chute 28 has converging side walls.

The conveyor 22 is shown sloping upwards in the direction of its movement but this .is merely incidental to the particular machine shown, as the conveyor has to raise the tobacco to a position where it can pass into a smooth passage 29, of the kind described in the abovementioned specification. At the bottom of-the passage is a paper web 30 which carries the filler through the rod forming, sealing, and cutting devices.

The carpet or wide deep stream, as the case may be, carried onthe conveyor 21 passes between detector plates 4 as in the-previous case andthe driving control arrangements for conveyor 22 are as before. In this case the distance A shown on the. preceding figures is the length of a rather tortuous path from plates ,4 around the pin roller '23 ,and tom the picking point to conveyor 22.

The purpose of the high-frequency detector is, in the main, to cure local or short-term variations in the mass, but it is generally desirable also toprovide a control which is responsive .to the average of a series of suc' ceeding local masses that is to cover rlong-terrn variations in .thestream mass. As illustrated Lat 31, there may be a radio-active detector arranged -to control the speed of the paper web 30 in the manner set-forth in the United States Patent No. 2,815,759, issued December 10, 1957.

In :the above example, described with reference to Figure.4, the conveyor 22--has its speed altered in ac cordance with the change in mass at the detector 4.

In an alternative arrangement if the passing tobacco varies sufiiciently in mass the detector response is such that the speed of the conveyor 22 will be altered by a predetermined amount. However, the control mechanism is such that the speed change will not take place for avcertain,time, which isthe time necessary for the detected tobacco to reach the surface of the conveyor 22. Thus for a deficiencybeyond a given tolerance in the. detected mass the conveyor222 will have its speed reducedby a fixed-amount, and vconversely supposing that in a particular case-thecigarettes tobe produced by the machine must ,not be morethan plus or minus ten percent from a given weight and assuming that the detector .4 detects thatthe quantity of'tobacco passing at a given time is outside the tolerance given, say, it is twelve percent above the desired=figure (then the conveyor 22 is .given a correction to move by a fixed amount,

faster or slower, tocompensate for this excess variation.

The fixed amountat which.it .will. go faster andslower will; be:the.same percentage of its normal,,sp,eed .asthe percentage tolerance within which cigarettes are to be produced, normally plus or minus ten percent. Accordingly assume that the portion of tobacco passing the detector 4 is twelve percent too heavy then if the conveyor 22 is accelerated ten percent at the time that that measured quantity of.tobacco reaches the conveyor 22 the tobacco on the conveyor 22 will be within the tolerance shown; in other words it will be at two percent above the desired weight. Likewise if a portion measured by the detector 4 is found to be, say, minus fifteen percent from the given weight then in this case, the conveyor 22 is slowed by its fixed amount, normally ten per cent, thus bringing the weight of tobacco on to the conveyor 22 to minus five percent from the given weight. In this case therefore by causing the conveyor 22 to either go faster or slower by a fixed amount, it will ensure that variations outside the tolerance amount are brought within the desired tolerance. The device is so arranged that as far as practicable the time taken for the tobacco leaving the detector 4 to reach the conveyor 22 is equal to the time lag of the correcting device. Thus if the portion of tobacco passing the detector is found to be outside the given tolerance the ten percent correction is applied immediately to the control and driving devices for the conveyor 22 and by the time the detected tobacco reaches the conveyor 22, the correction is simultaneously taking place on that tape, thus the desired correction is made so far as that section of tobacco is concerned as the latter reaches the conveyor 22.

The driving arrangements for the conveyor 22 can be similar to those already described as it is only necessary for a detector signal to cause the motor to run for a fixed time whereafter it switches itself off and will stay still until a contrary impulse sets it going in the opposite direction, each time shifting the gear 7 an equal amount. Supposing the gear is first moved from the mean position to the high speed position, the next signal will move it back to the mean position. If then the tobacco supply continues to be low the next movement will shift the gear to the low speed position.

What we claim as our invention and desire to secure by Letters Patent is:

1. A machine of the kind referred to comprising means to feed tobacco as a stream, a second means compris ing a conveyor to which the tobacco is delivered by the first said means and conveyed as a stream, means for varying the speed of the conveyor of said second means, a. detector associated with the first said means and responsive to changes in the mass of the passing tobacco stream and adapted to cause the speed of the conveyor of said second means to be altered when the passing mass varies from a desired value, said detector being so located that the time taken by tobacco moving from the detector position to reach the conveyor in the said second means is equal to the time required for the speed of the last said conveyor to be altered in response to a detector signal.

2. A machine as claimed in claim 1 wherein the detector is an electrostatic detector.

3. A machine as claimed in claim 2 wherein the electrostatic detector has associated therewith devices for smoothing out a series of responses from said detector to give an average signal after the lapse of a short time during which time the stream is passing the detector.

4. A machine as claimed in claim 1 wherein the first said means is a conveyor on which tobacco is carried as a stream, and wherein the speeds of the two conveyors are of a difierent order.

5. A machine as claimed in claim 4 wherein the first said conveyor travels considerably faster than the second conveyor and the tobacco on the first conveyor is compacted during or before delivery to the second conveyor by reason of said considerable difference in speed.

6. A machine as claimed in claim 4 wherein the first said conveyor travels considerably slower than the second conveyor and carries a wider stream, and means is provided for transferring the tobacco from the first conveyor to the second and contracting the width of said stream during the transfer.

7. A machine as claimed in claim 1 comprising a tobacco feeding mechanism and means for showering tobacco therefrom on to the first said conveyor.

8. A machine as claimed in claim 1 wherein the second conveyor carries a paper web on which the tobacco stream is supported, whereby said stream may eventually be wrapped in said web to form a continuous wrapped rod of tobacco.

9. A machine as claimed in claim 6 comprising a carded roller at the end of the first said conveyor into which tobacco carried by said conveyor is fed, a picker roller associated with said carded roller and adapted to pick tobacco therefrom and shower it on to the second said conveyor, and converging guides to control and narrow the shower to the width of the second conveyor.

10. A machine as claimed in claim 8 comprising a radioactive detector associated with the second conveyor whereby the speed of the paper web may be controlled to cover long term variations in the mass of the stream.

11. A machine as claimed in claim 7 wherein the second conveyor delivers tobacco to a third conveyor carrying a paper web on which the tobacco stream is supported and comprising a radioactive detector associated with the third conveyor whereby the speed of the paper web may be controlled to cover long term variations in the mass of the stream.

12. Apparatus as claimed in claim 1 comprising means whereby the speed of the second conveyor is altered by a fixed amount and the detector is provided with means to give a signal to efiect such speed change when variations in the mass from a predetermined value exceed a certain amount, that is, while the stream differs only from said value within a given tolerance no speed change is efiected but when the variation is outside the tolerance the second conveyor has its speed altered by a fixed amount.

No references cited.

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