GB1601551A - Tobacco cutter and a method of controlling same - Google Patents

Description

(54) A TOBACCO CUTTER AND A METHOD OF CONTROLLING SAME (71) We, HAUNI-WERKE KRBER & CO KG., a German Company of Kampchaussee 12-22, 2050 Hamburg 8Q Germany (Fed. Rep.) do hereby declare the invention for wihch we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:: The invention relates to a method of controlling a tobacco cutter which is supplied with tobacco for the purpose of forming an accumulated stock, wherein different heights of the accumulated stock are supervised with which specific cutting speeds of the tobacco cutter are associated, and tobacco is removed from the accumulated stock for the purpose of forming a compressed tobacco cake from which narrow strips of tobacco fibres are cut off.

Moreover, the invention relates to a tobacco cutter having an accumulation shaft for forming a tobacco stock which is provided at different levels with monitoring means for supervising the level of the stock, as well as with a feeder preceding the accumulation shaft, a removal presser conveyor following the accumulation shaft, and a cutting drum arranged therebeyond, wherein the cutting drum and the presser conveyor comprise a common drive from which the presser conveyor may be disconnected.

Tobacco cutters of the kind referred to above are usually arranged ahead of further manipulation machines, e.g. driers, which must be supplied with a stream of a tobacco quantity which is as uniform as possible in respect of weight and which is delivered by the tobacco cutter; such tobacco cutters are frequently not in a position to satisfy this demand with sufficient certainty. Inter alia a fluctuating supply of tobacco to the tobacco cutter is to blame for this. It has been attempted to compensate such fluctuation by means of a so-called overflow control, wherein an accumulated stock of the tobacco cutter is monitored and the tobacco supply is interrupted when this accumulated stock threatens to overflow, and the excess tobacco quantity is guided back.Such a volume control of the tobacco stream involves the risk that the excess tobacco guided back dries out too much or is cooled too much because of the longer conveyance paths and times, the latter if it is to be cut in a warm state. It becomes brittle and breaks and the cutting quality suffers.

According to Offenlegungsschrift 2 504 902, a solution which fulfils more nearly the demand for a constant weight output of the tobacco cutter consists in that the tobacco cutter is coninuously supplied with a constant tobacco quantity; this may be effected for example by means of a metering belt weighing device or from a tobacco silo from which a defined tobacco quantity is discharged in a certain unit of time. Fluctuations of volume which occur in spite of the constant weight stream in consequence of properties specific for tobacco, such as temperature, moisture and particle size, are monitored in the accumulated stock and are compensated by changing the rotary speed of the cutting drum.A further difficulty occurs in practice because in spite of the constant or continuous tobacco supply in the long term, the charging of the tobacco cutter occurs in a batch-like manner in the short term, e.g. it may be interrupted for a short period of time or there may be occasional surges. This is caused for example by irregular delivery from a metal detector device employed immediately upstream of the tobacco cutter. These unpredictable variations in the feed cause severe fluctuations in the level of the accumulated stock, which can be absorbed only with difficulty by the control mentioned above. In this case a level which has dropped too low is not so very serious. It is compensated by a corresponding speed reduction of the cutter and finally stoppage of the removal chains.More serious, however, is a sudden rise of the level which cannot be compensated so quickly by an increase in the speed of the cutter.

A strongly fluctuating storage level has negative effects upon the cutting quality in respect of fluctuating cutting differences which result from different packing densities depending upon the storage level of the accumulated stock.

When the level has dropped too far, the longer fall path of the incoming tobacco particles and the greater kinetic energy attained thereby may enable the required packing density to be attained to a large extent. In contrast, when the tobacco level has risen too much, the precompression is insufficient. For this reason it is endeavoured to maintain the level of the accumulated stock largely constant as far as possible in the middle region.

An object of the present invention is to provide a tobacco cutter and a method of controlling same whereby fluctuations in the level of the tobacco in the store are evened out.

According to first aspect of the present invention there is provided a method of controlling a tobacco cutter which is fed with tobacco for the purpose of forming a tobacco supply store, comprising removing tobacco from the store in order to form a compressed tobacco cake from which narrow strips of tobacco fibres are cut by a cutter, monitoring different levels of the supply store, reducing or increasing the cutter speed and the removal speed as the storage level falls or rises, generating a signal when a lower storage level is reached for interrupting the removal of tobacco from the supply store and for increasing the speed of the cutter to a value above that obtaining at the time of interruption of removal, and when the storage level rises to an upper level resuming removal of the tobacco at said increased cutter speed.

Preferably, when the storage level falls below the upper level, the cutting and removal speed is reduced in steps dependently upon a time factor.

Preferably, the feed of tobacco to the supply store is started when the storage level falls below said upper level. In normal operation the tobacco cutter is adjusted to a preselected output lying below the maximum output.

In order to cater for the situation in which a desired mean tobacco level cannot be maintained at this normal output, it is proposed according to a further advantageos feature of the invention that when the store reaches a third level lying above said upper level, the cutting and removal speed is increased to a higher value lying above the value corresponding to said upper level.

In case this feature does not suffice to lower the storage level, the invention preferably provides that feed of tobacco to the supply store is terminated when the store reaches a fourth level above the third level.

According tc. a second aspect of the present invention there is provided a tobacco cutter comprising means for containing a tobacco store, tobacco feed means arranged upstream of said containing means for feeding tobacco to the tobacco store, a presser conveyor arranged downstream of said containing means for removing and compressing tobacco from the store, and a cutter drum arranged downstream of the conveyor for cutting the tobacco, the cutter drum and the presser conveyor having a common drive from which the presser conveyor may be disconnected, monitoring means for monitoring the storage level of the tobacco store and control means for controlling the speed of the cutter drum and the presser conveyor, wherein first monitoring means defining a lower storage level is connected to disconnecting means for disconnecting the presser conveyor from the common drive and to speed adjustment means for increasing the speed of the cutter drum to a preselected value lying above that obtaining at the time of disconnection of the presser conveyor, and second monitoring means defining an upper storage level is in operative connection with reconnecting means for reconnecting the presser conveyor to the common drive, Preferably, the tobacco cutter operates in the region of a mean storage level. In order to rapidly counteract a fall in level the invention preferably provides that the second monitoring means is in operative connection with the common drive for effecting time-dependent reduction of the speed of the cutter drum and the presser conveyor.

As an additional measure, the second monitoring means is preferably in operative connection with the feed means to render the same operative. The two operative connections are activated whenever the storage level drops below the second monitoring means.

In normal operation the tobacco cutter operates at a preselected output below the maximum output, i.e. reserve output is available for dealing with peaks in the tobacco supply.

Preferably, the invention provides a third monitoring means which is located above the second monitoring means and which is in operative connection with the common drive for effecting an increase of the speed of the drive.

The invention may provide for a second output reserve and according to this preferred feature a fourth monitoring means is provided which is located above the third monitoring means and which is in operative connection with the feed means for bringing the same to a stand-still.

Preferably, all the monitoring means are photoelectric devices.

The invention is explained below in detail with reference to a constructional example in the drawing. There are shown in: Fig. 1 a diagrammatically illustrated tobacco cutter with monitoring means associated with an accumulation shaft, and Fig. 2 diagrammatically a control arrangement according to the invention for the tobacco cutter.

The tobacco cutter illustrated in Fig. 1 comprises a substantially vertical accumulation shaft 1 in which an accumulated stock 2 is formed from tobacco in the form of leaf material. In the region of its rear wall, the lower portion of the accumulation shaft 1 has arranged therein a rake 3 which is rhythmically reciprocable in the direction of the arrow and which feeds the tobacco in steady succession to a pressing device 7 which consists of two presser chains 4 and 6. The presser chains 4 and 6 converge towards each other in the feed direction (arrow 8); they are drivable by a drive in the form of a hydraulic motor 9, engage the leaf material and convey it to a mouthpiece 14 which consists of an upper member 12 and a lower member 13, while pressing and condensing it to form a cake 11.

A pressure generator 16 acts upon the presser chain 4. The lower member 13 forms the counter-cutter for cutter blades 17 in a cutting drum which is likewise drivable by a hydraulic motor 18, so that during rotation the cutter blades 17 cut narrow strips of tobacco fibres off the tobacco cake 11. A grinding disc 21 which is dressed by a diamond 22 serves for grinding the cutter blades 17. The hydraulic motor 9 for the presser chains 4 and 6 as well as the hydraulic motor 18 for the cutting drum 19 are both actuated by a hydro-static driving unit 23, this being indicated by the two dashdotted operating lines 24 and 26, respectively.

Furthermore, the tobacco cutter is associated with a supply feeder 28 which is driven by a motor 27 and which, in a manner not illustrated, e.g. removes a certain quantity of tobacco from a tobacco silo in a certain unit of time and conveys it to the accumulation shaft 1. Alternatively the supply feeder 28 may even be associated with a metering belt weighing device which ensures a tobacco quantity stream of constant weight.

A monitoring device for different accumulation heights of the tobacco is provided within the accumulation shaft 2 of the tobacco cutter and is in the form of four photo-electric devices 29, 31, 32 and 33 forming monitoring means which are disposed one above the other.

According to Fig. 2, the monitoring means 29, 31, 32 and 33 are linked with the drives for the individual aggregates of the tobacco cutter to form a control circuit in the following manner: The setting input a of a store 34 is connected to the photo-electric device 31 by way of a NOT-gate 38.

The photo-electric device 29 is connected to the cancel input b of the store 34 the output c of which is connected through an amplifier 36 to a swltching means in the form of a valve 37 which is capable of separating the hydraulic motor 9 for the presser chains 4 and 6 from the hydrostatic driving unit 23 or of connecting them thereto.

Furthermore, the photo-electric device 31 is connected through a NOT-gate 39 and an ORgate 41 to the set input a of a store 42 the output c of which is connected to the hydror static driving unit 23 by way of a rotary speed adjuster member 43 for a normal operating speed as well as an amplifier 44. A further input of the OR-gate 41 is connected to the photo-electric device 29. The cancel input b of the store 42 is in connection with the photoelectric device 32 by way of an OR-gate 46 and a NOT-gate 47 and by way of the OR-gate 46 with the photo-electric device 31. The same connection from the photo-electric device 32 via the NOT-gate 47 is led to the set input a of a further store 48 as well as to the OR-gate 41 of the store 42 in the form of a branch in front of the NOT-gate 47.The output c of the store 48 is connected to the hydro-static driving unit 23 by way of a rotary speed adjuster member 49 for a maximum rotary speed and an amplifier 44. The cancel input b of the store 48 is in indirect connection with the photoelectric device 32. The set input a of a further store 51 is connected to the photo electric device 31, whereas its output c is in connection with the hydro-static driving unit 23 by way of a rotary speed adjuster member 52 for a slow rotary speed by way of the amplifier 44.

The cancel input b of the store 51 may be supplied via an OR-gate 53 either with a signal from the photo-electric device 29 or via the NOT-gate 39 with a signal from the photoelectric device 31. The set input a of an additional store 54 is connected to the photoelectric device 31, whereas its output c is connected to the motor 27 by way of an amplifier 56. Its cancel input b may be supplied with a signal from the photo-electric device 33 via a NOT-gate 57.

The manner of working of the control arrangement is as follows: Let it be assumed that the feeder 28 charges the accumulation shaft 1 continuously with tobacco, the accumulated stock 2 being located at a level at which the photo-electric device 31 is just covered. All photo-electric devices are so connected that they deliver a signal when they become uncovered. When the tobacco level is in the region of the photo-electric device 31, the hydraulic motors 9 and 18 for the presser chains 4 and 6, or the cutting drum 19, respectively, are driven by the hydro-static drive 23 at a pre-selected rotary operating speed which lies below the maximum rotary speed (preferably 850/o of the maximum output).

If for any reason, for example because of the ejection of tobacco quantities which contain metal parts, the charging of the tobacco cutter is interrupted, the tobacco level drops below the photo-electric device 31, so that the latter becomes free and delivers a signal to the set input a of the store 51 as well as simultaneously a cancel signal to the cancel input b of the store 42 by way of the OR-gate 46. Thereby the rotary speed adjuster member 43 for the preselected normal rotary operating speed is de-energised and the rotary speed adjuster member 52 for the adjustment of a reduced rotary speed is energised by the signal which appears at the output c of the store 51, the output signal of which adjusts the hydro-static.

driving unit 23 in accordance with a reduced rotary speed, by way of the amplifier 44. The rotary speed adjuster member 52 is so constructed that an initial adjustment ensures an increased reduction of the rotary speed, the rotary speed adjustment member 52 comprising furthermore a time-dependent switching mechanism which further reduces the rotary speed in a step-wise manner (in the con structional example down to 33% of the maximum output) in certain defined intervals of time in which the photoelectric device 31 is still not covered again.

If in spite of this reduction of the rotary speed or the cutting output, respectively, the tobacco level continues to drop because of falling or insufficient charging and thereby falls below the lowest photo-electric device 29, the latter delivers a signal via the OR-gate 53 to the cancel input b of the store 51 so that the output signal thereof disappears and the rotary speed adjuster member 52 is de-activated. At the same time the photo-electric device 29 delivers a cancel signal to the store 34 whereby the output signal thereof disappears and the electro-magnetically actuated valve 37 changes over, so that the hydraulic motor 9 for the presser chains 4 and 6 is disconnected from the hydro-static drive 23.Additionally, in a manner not illustrated, the hydraulic motor 9 is caused to retum the presser chains 4 and 6 for a short distance and then to stop them again, in order to attain that the mouthpiece 14 of the tobacco cutter is relieved of the tobacco cake 11 and that tobacco fibres are prevented from being cut off by the cutter drum which continues to rotate, because of the imminent risk of fire. The signal issued by the photo-electric device 29 is furthermore delivered by way of the OR-gate 41 to the set input a of the store 42 the output signal of which activates the rotary speed adjuster member 43 in such a manner that the output signal of the latter, by way of the amplifier 44, controls the hvdro-static driving unit 23 upwards to a pre-selected rotary operating speed (85 % of the maximum output).As soon as the accumulation shaft 1 is being charged again and the tobacco level has risen to such an extent that the photo-electric device 31 is covered, the output signal of the latter disappears, whereby in consequence of the negation thereof by the NOT-gate 38, a set signal is supplied to the store 34. The output signal of the latter reverse again the valve 37 by way of the amplifier 36, whereby the hydraulic motor 9 is reconnected again to the hydrostatic drive 23. Thus, when the tobacco level at the height of the photo-electric device 31 is attained again, the normal rotary operating speed associated with this level and controlled upwards during the stand-still of the cutter, is immediately available again.Consequently the presser chains 4 and 6 can remove corresponding tobacco quantities from the accumulated stock 2 even when the charging is continued to the full extent, and compress them, and also the cutting drum 19 can sever corresponding quantities from the tobacco cake 11.

If, for any reasons whatsoever, the tobacco level rises so far that the photo-electric device 32 is covered, the signal thereof disappears; this sets the store 48 because of negation by the NOT-gate 47 and cancels the store 42 by way of the OR-gate 46. Thereby the rotary speed adjuster member 43 for the normal rotary operating speed is rendered inoperative and the rotary speed adjuster member 49 for a maximum rotary speed of the tobacco cutter is activated, so that the hydro-static driving unit 43 is correspondingly adjusted by way of the amplifier 44, i.e. in the present constructional example the output reserve of 15 % is activated.

If this measure is sufficient for processing the increased tobacco quantities, the photo-electric device 32 which is being uncovered delivers a signal for cancelling the store 48 and a set signal via the OR-gate 41 to the store 42 for activating the rotary speed adjuster member 43 which again controls the hydrostatic driving unit 23 down to the normal rotary operating speed.

If, in consequence of extraordinary charging peaks, the tobacco level in the accumulating shaft 1 should rise so far that even the photoelectric device 33 is covered, the signal of the latter disappears; in consequence of negation by the NOT-gate 57, the store 54 is cancelled thereby, its output signal disappears and stops the motor 27 of the supply feeder 28, so that the feed is interrupted. The supply feeder 28 is not taken into operation again until the tobacco level falls below the photo-electric device 31, so that the signal of the latter re-sets the store 54 again and the output signal thereof re-activates again by way of the amplifier 56 the motor 27 of the supply feeder 28.

The advantage obtained by means of the invention resides in the fact that after the cutter output has been controlled down as far as stoppage of the tobacco cutter in consequence of a falling tobacco level, the rotary speed of the cutting drum is so guided or increased independently of the momentary operational state of the cutter that upon rise of the stock level occurring afer the stoppage of the tobacco cutter drive, the normal cutter output corresponding to this level is immediately available when the drive is switched on again, so that the mean stock level which is preferred to be maintained, remains largely stable. Thereby strong fluctuations of the stock level are successfully counteracted, which in turn has a positive effect on the cutting quality of the cut tobacco fibres.

Claims (13)

WHAT WE CLAIM IS:-

1. A method of controlling a tobacco cutter which is fed with tobacco for the purpose of forming a tobacco supply store, comprising removing tobacco from the store in order to form a compressed tobacco cake from which narrow strips of tobacco fibres are cut by a cutter, monitoring different levels of the supply store, reducing or increasing the cutter speed and the removal speed as the storage level falls or rises, generating a signal when a lower storage level is reached for interrupting the removal of tobacco from the supply store and for increasing the speed of the cutter to a value above that obtaining at the time of interruption of removal, and when the storage level rises to an upper level resuming removal of the tobacco at said increased cutter speed.

2. A method as claimed in claim 1, wherein, when the storage level falls below the upper level, the cutting and removal speed is reduced in steps dependently upon a time factor.

3. A method as claimed in claim 1 or 2, wherein feed of tobacco to the supply store is started when the stolage level falls below said upper level.

4. A method as claimed in any one of claims 1 to 3, wherein, when the store reaches a third level lying above said upper level, the cutting and removal speed is increased to a higher value lying above the value corresponding to said upper level.

5. A method as claimed in claim 4, wherein feed of tobacco to the supply store is terminated when the store reaches a fourth level above the third level.

6. A tobacco cutter comprising means for containing a tobacco store, tobacco feed means arranged upstream of said containing means for feeding tobacco to the tobacco store, a presser conveyor arranged downstream of said containing means for removing and compressing tobacco from the store, and a cutter drum arranged downstream of the conveyor for cutting the tobacco, the cutter drum and the presser conveyor having a common drive from which the presser conveyor may be disconnected, monitoring means for monitoring the storage level of the tobacco store and control means for controlling the speed of the cutter drum and the presser conveyor, wherein first monitoring means defining a lower storage level is connected to disconnecting means for disconnecting the presser conveyor from the common drive and to speed adjustment means for increasing the speed of the cutter drum to a preselected value lying above that obtaining at the time of disconnection of the presser con veyor, and second monitoring means defining an upper storage level is in operative connection with reconnecting means for reconnecting the presser conveyor to the common drive.

7. A tobacco cutter as claimed in claim 6, wherein the second monitoring means is in operative connection with the common drive for effecting time-dependent reduction of the speed of the cutter drum and the presser conveyor.

8. A tobacco cutter as claimed in claim 6 or 7, wherein the second monitoring means is in operative connection with the feed means to render the same operative.

9. A tobacco cutter as claimed in any one of claims 6 to 8, wherein a third monitoring means is provided which is located above the second monitoring means and which is in operative connection with the common drive for effecting an increase of the speed of the drive.

10. A tobacco cutter as claimed in claim 9, wherein a fourth monitoring means is provided which is located above the third monitoring means and which is in operative connection with the feed means for bringing the same to a stand-still.

11. A tobacco cutter as claimed in any one claims 6 to 10, wherein the monitoring means are photo-electric devices.

12. A method of controlling a tobacco cutter with a tobacco supply store, substantially as herein described with reference to the accompanying drawings.

13. A tobacco cutter, substantially as herein described with reference to and as illustrated in the accompanying drawings.