US2938520A - Machines for manipulating cut tobacco - Google Patents

Description

May 31, 1960 e. F. w. POWELL mcumss FOR MANIPULATING CUT TOBACCO 2 Sheets-Sheet 1 Filed May 15, 1957 NECHT/VE SUPPLY H. c. HIIWPLIFIER a/vo Pms SENSITIVE REC T/F/ER lNVENTo'R M3211}. PM

g M/ r3125? ATTORNEYS May 31, 1960 e. F. w. POWELL 2,938,520

MACHINES FOR MANIPULATING CUT TOBACCO Filed May 15, 1957 2 Sheets-Sheet 2 225 '25 224 A I 2; I Y

INVENTOR bo'ww 7 United States Patent MACHINES FOR MANIPULATING CUT TOBACCO Gordon Francis Wellington Powell, Deptford, London,

England, assignor to Molins Machine Company Limited, Deptford, London, England, a British company This invention concerns improvements in or relating to machines for manipulating cut tobacco (which term includes shredded tobacco material capable of being substituted for out tobacco and generally referred to hereafter as tobacco), that is machines in which cut tobacco is fed from a hopper to form a moving filler on a conveyor system, for example, cigarette-making machines, and wherein the mass of a length of moving tobacco filler is measured by subjecting the length to rays from a radio-active source of penetrative radiation, for example beta-rays, the ionization powers of which are absorbed by the material in known proportion to its mass, and determining changes in the absorption with variations in the tobacco mass by an ionization chamber, and applying the current due to the ionization to regulate at some stage in the machine the rate at which tobacco is being fed at that stage for the formation of the final product. Such machines are now Well known and a machine of this kind will be termed hereafter a machine of the kind referred to. a

In such machines arrangements have been provided whereby the measurement may be made of either a loose filler or a wrapped rod but in the present case in the preferred arrangement and specifically described later the measurement is made on the loose filler because this can take place at an earlier stage than when a wrapped rod is measured and consequently correction to the tobacco feeding devices can be made more nearly to the time when deviation occurs.

According to the invention there is provided a machine of the kind referred to having measuring apparatus comprising a radio-active scanning unit for the filler and a cooperating balancing unit, from which a current due to variations in the mass of the filler is fed to an input resistor of an amplifier, and means for checking the functioning of the apparatus, to which end the scanning unit is cleared of filler, said means comprising switching devices for injecting a voltage into the circuit of the apparatus to ofiset the abnormal ionization current in the scanning unit due to the absence of tobacco filler therefrom.

The said switching devices may comprise a manual switch which when closed causes current to be fed to a relay having a contact which moves to connect one end of said input resistor to a source of negative voltage to oppose voltage generated in said resistor by the said abnormal current.

In this kind of apparatus it is usual to have feedback arrangements from the amplifier to the input and said relay may therefore comprise a further contact adapted to alter a resistance in the feedback circuit to increase feedback.

The output from the measuring apparatus may be fed to two relays, one controlling speed control mechanism adapted to alter the speed of the tobacco feeding apparatus and the other operating signal lights which indicate what is happening in the apparatus, that is, it shows "ice how the speed controlling mechanism is operating, if at all.

The first said relay is preferably a moving coil relay and it is used to operate other relays which directly control the speed control mechanism and to save wear on the moving coil relay contacts the relay is coupled to said other relays through transistors.

A machine according to the invention and its control apparatus will now be described by way of example with reference to the accompanying drawings in which:

Figure l is an elevation of part of a continuous rod cigarette making machine showing the disposition of certain elements of the control apparatus; I

Figure 2 is a circuit diagram of the basic electrical elements of the measuring apparatus and relays controlled thereby; and

Figure 3 is a further circuit diagram of electrical indicating and controlling elements of the apparatus which are controlled by the relays of Figure 2.

Referring first to Figure 1, 1 is the tobacco hopper of the machine in which tobacco is showered and falls on a hopper tape 2. A paper web 3 is drawn from a reel 4 and the filler accumulated on the tape 2 is discharged on to the paper web 3 at the position where the latter passes over a guide roller 5. The paper web then runs over the top of an ionization chamber 6 of cylindrical form constructed as described in the copending application of Gordon F. W. Powell, Serial No. 659,325, filed concurrently herewith, and above the loaded paper web is a radio-active source 7. These devices 6 and 7 constitute the scanning unit. The radio-active source used in the present construction may be strontium embedded in a solid silver strip and because the distance between the ionization chamber and the radio-active source may be considerably reduced with the devices and arrangements described later, the source strength compared with that previously employed may also be'reduced, a suitable strength being 7 /2 millicuries. Thereafter the paper web runs on to a'tape 8, the garniture tape, whereby it is drawn into the rod forming devices of the machine all the rest of which is of conventional construction. Another ionization chamber having a similar radio-active source, not visible in the drawing, is shown at 9, this constituting the balancing unit of the equipment and this is constructed as described in the copending application of Gordon F. W. Powell, Serial No. 659,348 filed concurrently herewith.

As will be described in more detail later, variations in the mass of the filler will, through the operation of the measuring apparatus, cause a variable speed gear device indicated at 10 to alter the speed of the tobacco feeding devices when the variation is suflicient to warrant this. The variable speed device is constructed as described in the copending application, Serial No. 659,349, of Gordon F. W. Powell, filed concurrently herewith, and the mainshaft 11 of the cigarette making machine has a pulley 12 fixed thereon which drives the variable speed gear all as described the last mentioned specification.

Referring now to Figure 2 the ionization chambers 6 and 9 are connected as shown so that any current from one opposes that from the other and the difference shows variations in the mass of the tobacco filler because the output from chamber 9 is nominally constant. Thus differences between the scanning unit and balancing unit ionization currents develop a D.C. voltage across an input resistor 20, which voltage is converted to A.C. by a dynamic condenser 21. The AC. voltage is amplified and converted back to D.C. by an amplifier and 'a phase-sensitive rectifier, indicated by a block diagram 22 and fed along line 224 through an output meter 23, control relay 24, and limit relay 25 and along line 225' to feedback resistors 26 and 27 in which the output current develops a voltage which is fed back to the lower end of the dynamic condenser 21 to oppose the voltage produced by the input current. In this manner by varying the position of a slider on resistor 26 the sensitivity of the equipment to input current can be varied as required. Resistr'27 ensures that at all times at least a minimum of feedback is present. An A.C. drive for the dynamic condenser is indicated at 28.

It has, in previous specifications been proposed, where measurement is made on a cigarette rod, to substitute a metallic absorber for the tobacco in the scanning unit for checking purposes, either if the cigarette rod is present by shifting the unit to scan said absorber, or if the rod is broken, by shifting the absorber into the rod path, but it is desired in the present case to check the apparatus without either tobacco 'or an equivalent absorber at the r scanning position. This method is termed herein check zero, and is brought into operation by a manual switch 29; a press button switch. For this purpose conditions must be arranged so that the extra ionization current in the scanning unit due to the absence of the tobacco is offset'injthe circuit so that the input to the amplifier at' 22 and the output meter 23 can be brought to zero.-

. In the circuit shown, with the extra scanning unit current, the upper end of the input resistor becomes positive relative to the earth line. push button 29 is pressed, a switch contact 30 associated with'a relay 31 connects the lower end of resistor 20 to a source of negative voltage formed by the resistor network 32, 33, and 34 and a source of stabilized negative supply 35. With a slideron resistor 33 suitably adjusted the upper end of resistor 20 can now be brought down to earth potential even though extra scanning unit current is flowing in resistor 20. Thus ifthe balance unit hasbeen'adjusted to give correct weight with the machine running normally, then if the tobacco is removed and the switch button 29 pressed andthe slider on resistor 33 adjusted to give zero on the output meter'23, hence fo'rth' pressing the check zero button with the tobacco removed will provide a means of checking that the scanning and balance unit ionization currents are unchanged and that theelectronic equipment is in a satisfactory state. If preferred adjustment may be made so that the output meter when checking is being done comes to,

When the check zero say, one division. This is more certain than working on a null indication. v

It should be noted that since at check zero the scanning unit ionization current is much larger than when the tobaccois being scanned it is desirable to reduce the sensitivity of the indicating circuits while checking zero. This is eflfected by a switch contact 36 also controlled by relay 31, which operates to cut out the short circuit on the resistor 37 and increases the feedback and thus reduces the overall sensitivity.

In normal operation the decay of the scanning unit source is balanced by the decay of the balancing unit relays 40 and 41, as explained later, it has been. found in service that thewear. .on the switch contacts: is sufii cient to impair their performance; To overcome this the circuit incorporates transistors 38 and 39 whichfare connected betweenthe said further relays40 and 41 and the moving coil relay. When a pair of contacts of the moving coil relay close, a transistor is brought into "circuit and operates one of said. further relays and in this way the load on the switch contacts is reduced to a very small value indeed, depending on the amplification available from the transistor.

Closure of one of said further relay contacts causes current to be fed to a small reversible motor 42, which shifts one way or the other) the regulator of the variable speed gear 10in Figure l. n

The relay '40 has contacts '43 for the control of said motor while the relay41' has contacts 44 for the same purpose. In addition relay 40 has other contacts 45 which cause a coloured lamp 46 to light when the motor control contacts are .closed. Similarly relay 41 has other contacts 47 which cause a different coloured lamp 48 to lightwhen the motor control contacts of relay 41 are closed. The contacts of relay 25 are connected to another relay 49 which has contacts50 which close to light a further lamp 51 which gives a flashing signal through the device 52. This signal occurs whendeviation in the filler mass exceeds'predetermined limits and further contacts 53 of said relay 49 break the supply to the motor and prevent any alteration to the speed of the tobacco feeding mechanism. This is to avoid excessive regulation which is generally undesirable but a manual 'switch 54 is provided so that even if contacts 53 have stopped the motor 42 it can, at the discretion of the operator,- be restarted by pressing the switch 54. A further switch 55 is provided and operated by the starting devices of the cigarette machine, for example, a starting handle. 'This switch brings all the control apparatus into operation and shuts it ofl when the machine is stopped. If the machine is being started at the commencement of a shift there will be no appreciable filler at the scanning position and the check zero switch could be pressed until an approximately correct filler is passing because excess ionization current tends to paraly's'e the apparatus. 3 3 v For checking, the scanning device source is moved away for safety and the voltage to its'chamber switched OE and the trough is then carefully cleared of tobacco, after which the source is returned to the operative position and the chamber voltage switched on. Checkingis based on the fact that the ratio of scanning unit current with tobacco present to current without tobacco, constant. Thus by applying sufiicient voltage to bring the device to balance when no tobacco is present, the voltage value will show up any changes in performance.

During operation of the machine conditions in th apparatus are shown by the meter 23 whose needle swings left or right as the filler gets lighter or heavier thanthe desired weight. g g The twocoloured lights show respectively decreases or increases below and above the desired mass of-such amount that the control apparatus is operating to alter the hopper feed rate.

Movements of the meter needle show lesser changes in mass, that is, changes insufficient to bring the control apparatus into operation.

The flashing light flashes when the mass is diflereu from the desired mass by an excessive amount; an amount of such value that it is undesirable for the controls to operate. For instance, when the machine is first started on the days work, the trough is empty, so the scanneris hopelessly out of accord with the balancer and if under these conditions the controls operated, the hopperfeed rate would be' altered to an undesirably higher rate. Therefore when the flashing light is showing the circuit connections are such that the controls are 013?. If for anyreason the light flashes when the machine is apparently under normal operation the controls can be brought into operation by the push button 54.

The description so far has dealt entirely with the, scanning of a loose filler but if it is desired to scan a cigarette rod it will be apparent that at starting there is nothing in thescanning position, so to meet this condition the check zero control is operated by the starting arrangements of the machine, usually a starting lever. Then if the machine is stopped and there is no rod the measuring apparatus is not adversely affected and the meter will read zero or any other value chosen for check zero condition.

What I claim as my invention and desire to secure by Letters Patent is:

1. In a cigarette making machine comprising a conveyor and feeding apparatus delivering cut tobacco to said conveyor to form thereon a moving filler, said machine having measuring apparatus comprising a radio-active scanning unit, a balancing unit, and an amplifier having an input resistor to which current from said units representing variations in the mass of said filler is fed, means for checking the functioning of the measuring apparatus after the scanning unit is cleared of filler whereupon the ionization current in the scanning unit increases greatly, said means comprising a source of stabilized voltage and switching devices for injecting a voltage from said source into the circuit of the measuring apparatus to ofiset the abnormal ionization current in the scanning unit due to the absence of tobacco filler therefrom.

2. A machine as claimed in claim 1 wherein said switching devices comprise a relay and a manual switch which when closed causes current to be fed to the relay, the relay having a contact which moves to connect one end of said input resistor to said source of stabilized voltage to oppose voltage generated in said resistor by the abnormal ionization current in the scanning unit.

3. A machine as claimed in claim 2 and wherein a feedback circuit from the amplifier output to the amplifier input is provided, comprising a resistance and a further contact on said relay adapted to switch said resistance into the feedback circuit to increase feedback.

4. A machine as claimed in claim 1, comprising a relay to which the output from the amplifier is fed, said relay being operatively connected to said tobacco feeding apparatus to alter the speed of said feeding apparatus, and signal means operable by said relay to indicate the direction of alteration of speed of said feeding apparatus.

References Cited in the file of this patent UNITED STATES PATENTS 2,704,079 Molins et a1 Mar. 15, 1955 2,800,131 Molins et a1. July 23, 1957

Images