GB2265296A - Method of and machine for making filters for tobacco smoke - Google Patents

Description

22652,96 -IMETHOD OF AND MACHINE FOR MAKING FILTERS FOR TOBACCO SMOKE The

invention relates to improvements in methods of and in apparatus for making filters for tobacco smoke. More particularly, the invention relates to improvements in methods of and in apparatus for making rod- shaped filters of the type wherein a wrapper of cigarette paper, imitation cork or other suitable sheet material surrounds a rod-like filler consisting of or containing a fibrous filter material. Still more particularly, the invention relates to improvements in methods of and in apparatus for processing so-called tows of fibrous filter material into rod-shaped fillers.

As used herein, the terms "fiber" and "fibrous -material" are intended to denote elongated filaments, shorter flexible strands and all other threadlike or hairlike materials which can be utilized in filter mouthpieces to filter tobacco smoke passing from the lighted end of a filter cigarette, cigar or cigarillo into a smoker's mouth. Fibers which are to be processed in accordance with the present invention can be supplied in the form of separated or substantially separated strands and/or in the form of intermingled, interlaced and/or otherwise interconnected or coherent strands of fibrous masses including those known in the tobacco processing industry as bales and presently used for the making of fillers in filter rod making machines.

A filter rod making machine of presently known design normally comprises a conveyor system which draws a continuous tow of fibers from a bale and subjects the tow to spreading and stretching treatments prior to contacting the thus treated tow with at least one additive normally in the form of finely atomized liquid plasticizer, for example, triacetin. such plasticizer is frequently utilized when the tow consists of or contains cellulose acetate fibers, and its purpose is to soften portions of fibers so that they can be bonded to each other in order to establish a maze of paths for the f low of tobacco smoke through the mouthpiece of a f ilter cigarette, cigar or cigarillo. The next step of conventional processing involves conversion of the spread-out, stretched and plasticizer-treated tow into a rod-like f iller which is draped into a web of wrapping material, and the resulting filter rod is thereupon cut up into filter rod sections of unit length or multiple unit length. The filter rod sections can be transported into storage or directly into a tipping machine which is constructed to turn out filter cigarettes, cigars or cigarillos. Draping of the f iller into a continuous strip or web of wrapping material involves the application of adhesive (f or example, hot melt) to one marginal portion of the strip and subsequent treatment of the axially parallel seam (which develops as a result of overlapping the other marginal portion of the web by the one (adhesive- coated) marginal portion) to ensure reliable setting of adhesive prior to subdivision of the f ilter rod into sections of selected length. Spreading of the tow normally includes treatment with one or more air discharging nozzles (called banding devices) which effect at least some separation of interlaced fibers prior to stretching between two pairs of rollers which are driven at different peripheral speeds. The application of atomized plasticizer follows the stretching step because this ensures that the fibers are at least substantially singularized at the time they are contacted by plasticizer, i.e., the distribution of plasticizer is more uniform than if the plasticizer were to be applied to an untreated tow of cellulose acetate fibers or the like. In fact, proper distribution of plasticizer on the spread-out and stretched filaments of a running tow is one of the most important stages of processing the tow because it greatly affects the tobacco smoke filtering quality of mouthpieces. The plasticizer can be atomized to form one or more streams or droplets or a fine spray or mist of extremely small liquid particles.

one feature of the present invention resides in the provision of a method of treating a f ibrous filter material. The method comprises the steps of advancing at least one tow of interlaced fibers in a predetermined direction along a predetermined path, and applying to the at least one tow electric charges having a polarity such that the applied electric charges singularize the interlaced fibers, i.e., that the charges effect at least some separation of interlaced fibers from one another.

The applying step can include establishing a source of voltage (preferably a source of high potential) and effecting a spray discharge from the source upon the at least one tow in the path. The step of effecting a spray discharge can include discharging sparks between electrodes which are located at opposite sides of the path and at least one of which is preferably a pointed metallic electrode.

The method can further comprise the step of maintaining the charges at least close to a predetermined constant value.

The applying step can comprise maintaining the at least one advancing tow in frictional engagement with at least one electrical insulator to thus generate electric charges having first and second polarities, and separating charges of first polarity from the at least one tow. The charges of second polarity are effective to separate the interlaced fibers from each other.

If the electric charges which are applied to the at least one tow have a first polarity and the applying step is carried out in a first portion of the predetermined path, the method can further comprise the steps of atomizing a f lowable plasticizer (such as triacetin), applying to the atomized plasticizer electric charges having a second polarity opposite the first polarity, and spraying the charged and atomized plasticizer onto the charged at least one tow in a second portion of the path downstream of the first portion. Such method can further comprise the step of converting the at least one tow into a substantially rod-shaped filler in a third portion of the path between the first and second portions, and the spraying step of such method can include directing the charged and atomized plasticizer against the exterior of the filler. Such spraying step can include dividing the charged and atomized plasticizer into a plurality of streams, and the directing step then includes directing the streams against spaced apart portions of the filler. such portions can be spaced apart in the circumferential and/or longitudinal direction of the substantially rod- shaped filler.

If the method comprises the step of converting the at least one charged tow into a tubular filler, the spraying step can include directing at least some of the charged and atomized plasticizer against the internal surface of the filler, against the exterior of the filler, or against the internal surface as well as against the exterior of the filler.

The plasticizer can be metered prior to the step of applying thereto charges of second polarity; the metering step can be carried out prior to the atomizing step.

The advancing step can include advancing a plurality of tows in the predetermined direction along neighboring paths, and the applying step then includes applying electric charges to each tow of such plurality of tows to singularize or separate the respective interlaced fibers. Such method can further comprise the step of maintaining the electric charges for each tow of the plurality of tows at a substantially constant value. Still further, the method can comprise the steps of monitoring at least one characteristic of charges which are applied to the respective tows and regulating the applying step as a function of deviations of monitored characteristics of the charges from predetermined characteristics. If the tows of the plurality of tows consist of different fibrous materials, the regulating step can include regulating the application of electric charges to each tow of the plurality of tows as a function of deviations of monitored characteristics of the charges from a different predetermined characteristic, i.e., from a particular predetermined characteristic for each tow of the plurality of tows which consist of different fibrous filter materials.

Another feature of the invention resides in the provision of a method which also serves to treat fibrous filter material and comprises the steps of advancing at least one tow of fibers in a predetermined direction along a predetermined path, applying to the advancing tow electric charges having a first polarity, atomizing a f lowable plasticizer (such as triacetin), applying to the atomized plasticizer electric charges having a second polarity opposite the first polarity, and spraying the thus charged and atomized plasticizer onto the charged tow which advances along its path.

An additional feature of the invention resides in the provision of a machine for treating a fibrous filter material (such as acetate fibers). The improved machine comprises means for advancing at least one tow of interlaced fibers in a predetermined direction along a predetermined path, and means for applying to the at least one advancing tow electric charges having a polarity such that the charges effect a singularization or separation of interlaced fibers.

The applying means can include a source of electrical energy and at least one charge-applying electrode which is connected to the energy source. The source can include a source of high voltage.

The machine can further comprise means for maintaining the electric charges at least close to a predetermined at least substantially constant value.

In accordance with another presently preferred embodiment, the improved machine is provided with applying means including at least one electrical insulator which is adjacent the predetermined path and is in frictional engagement with the at least one tow to thus generate electric charges having first and second polarities, and means for conducting charges of one polarity away from the at least one insulator and from the at least one tow.

The machine can include means for applying to the at least one tow electric charges having a first polarity, and such machine can further comprise a source of flowable plasticizer (such as triacetin), means for atomizing the plasticizer, means for applying to atomized plasticizer electric charges having a second polarity opposite the first polarity, and means for spraying the thus charged and atomized plasticizer onto the charged at least one tow in t he predetermined path. The means for applying electric charges to the at least one tow can be installed adjacent a first portion of the predetermined path, and the means for spraying atomized plasticizer can be installed adjacent a second portion of the path downstream of the first portion. Such machine can further comprise means (e.g., a so-called gathering horn) for converting the at least one tow into a substantially rod-shaped filler in a third portion of the predetermined path between the first and second portions. The spraying means of such machine can include means for directing charged and atomized plasticizer against the exterior of the rod-shaped filler. If the converting means is designed to convert the at least one charged tow into an elongated tubular filler, the spraying means can comprise means for spraying charged and atomized plasticizer against the internal surf ace of the filler, means for spraying charged and atomized plasticizer -against the exterior of the filler, or means for spraying charged and atomized plasticizer against the internal surface as well as against the exterior of the filler.

The just described machine can further comprise means for supplying metered quantities of plasticizer from the source of plasticizer to the atomizing means.

The advancing means can comprise means for advancing a plurality of tows along neighboring paths, and the applying means then comprises means for applying electric charges to each tow of such plurality of tows. Such machine can further comprise means for maintaining the electric charges for each tow of the plurality of tows at a substantially constant value. If the tows of a plurality of advanced tows consist of different fibrous materials, the applying means can include means for applying electric charges to each tow of the plurality of tows and the machine can further comprise means f or maintaining the electric charges for each of the tows at a different value.

Still another f eature of the invention resides in the provision of a machine which is designed to treat a fibrous filter material and comprises means for advancing at least one tow of f ibers in a predetermined direction along a predetermined path, means f or applying to the advancing tow electric charges having a first polarity, a source of flowable plasticizer, means for atomizing the plasticizer, means for appying to the atomized plasticizer electric charges having a second polarity opposite the first polarity, and means for spraying the charged and atomized plasticizer onto the at least one advancing charged tow in the predetermined path.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved machine itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.

FIG. 1 is a schematic elevational view of a f ilter rod making machine which embodies one form of the invention and wherein the fibers of a tow are electrically charged as a result of frictional engagement with electrical insulators; FIG. 2 is a fragmentary schematic elevational view of a detail in a modified filter rod making machine wherein an electric charge is sprayed upon the fibers of a running tow of filter material FIG. 3 is a fragmentary schematic elevational view of a third filter rod making machine wherein atomized plasticizer is applied to electrically charged fibers of a tow which is being converted into a rod-like filler; FIG. 4 is an enlarged sectional view substantially as seen in the direction of arrows from the line IV-IV in FIG. 3.

FIG. 5 is a sectional view similar to that of FIG. 4 but showing the details of a modified unit for the application of atomized plasticizer to a rod-like filler of fibrous filter material; FIG. 6 is a fragmentary elevational view of a further filter rod making machine which is designed for simultaneous processing of several tows of fibrous filter material; FIG. 7 is a plan view of the structure which is shown in FIG. 6; and FIG. 8 is a fragmentary elevational view of a machine which constitutes a modification of the machine shown in FIGS. 6 and 7.

Referring f irst to FIG. 1 there is shown a f ilter rod making machine which is designed to process one tow 4 and one web 21 of wrapping material into a continuous f ilter rod 24. The tow 4 contains separable f ibers of cellulose acetate or any other natural or synthetic material which does not conduct electric current. The machine comprises two main units or apparatus, namely an apparatus 1 which processes the tow 4 bef ore the thus processed tow reaches the web 21, and an apparatus 2 which converts the processed tow 4 and the web 21 into a rod 24 and preferably further contains means for subdividing the rod 24 into filter rod sections 28 of desired length.

The apparatus 1 comprises a pair of driven rollers 3 which draw the tow 4 from a source 6a including a bale 6 of compacted and normally crimped fibrous filter material. The tow 4 is advanced in the direction of arrow Pf along a predetermined path which is defined in part by a deflecting roller 5 upstream of the rollers 3, a second pair of rollers 9 downstream of the rollers 3, and a third pair of rollers 11 downstream of the rollers 9. The 'means for spreading and loosening the tow 4 on its way toward the nip of the rollers 11 includes two air-discharging nozzles 7 and 8, called banding devices and described, f or example, in commonly owned U.S. Pat. No. 4,259,769 granted April 7, 1981. The devices 7 and 8 effect at least some singularization of f ibers, f irst upstream and thereupon downstream of the deflecting roller 5.

An applicator 12 of atomized liquid or liquefied plasticizer (such as triacetin) is adjacent the path of the tow 4 between the rollers 9 and 11 to apply droplets or even smaller bodies of flowable plasticizer to separated (singularized) fibers of the advancing tow. The peripheral speed of the rollers 3 is less than that of the rollers 9 so that the fibers of the tow 4 are stretched between these pairs of rollers and are further singularized or separated f rom one another on their way toward the applicator 12. one roller of each of the pairs of rollers 9 and 11 is preferably provided with a circumferentially grooved peripheral surface and the other roller of each of these pairs of rollers is preferably provided with a smooth peripheral surface surrounding a layer of elastomeric material.

At least one roller of each of the three pairs of rollers 3, 9 and 11 is driven by a main prime mover 13 (e.g., a variable-speed electric motor) through belt transmissions 13a, 13b and 13c. The transmission 13b derives motion directly from the output element of the main prime mover 13 and drives the lower roller 9, the transmission 13c also derives motion directly from the output element of the main prime mover 13 and drives the lower roller 11, and the transmission 13a derives motion from the lower roller 9 and drives the input element of a variable-speed transmission 14 (e.g., a gear trans-mission) for the lower roller 3. The ratio of the transmission 14 can be varied by a motor 16 (either by hand or by remote control) to thus select the stretching action upon the fibers of the tow 4 between the pairs of rollers 3 and 9.

The illustrated means for driving the pairs of rollers 3, 9 and 11 can be replaced by a set of discrete prime movers, one for each pair of rollers or one for one of these pairs of rollers and the other for the other pairs of rollers.

The rollers 3 act not unlike a brake which cooperates with the rollers 9 to ensure that the fibers of the running tow 4 are stretched to a desired extent. The transmissions 13a and 14 and the motor 16 can be omitted if the rollers 3 are not driven, i.e., if they merely define a nip wherein the fibers of the tow 4 are braked on their way toward the nip of the rollers 9 as a result of more or less pronounced (preferably regulatable) frictional engagement with the peripheral surfaces of the rollers 3 or equivalent braking devices.

In accordance with one important feature of the invention, the apparatus 1 of the filter rod making machine of FIG. 1 further comprises a unit 15 which is installed adjacent the path of the tow 4 between the rollers 9 and the applicator 12 and serves as a means for applying to the partially separated and stretched fibers electric charges upstream of the path portion where the fibers are contacted by atomized plasticizer. The illustrated unit 15 comprises two roller-shaped elements 42, 43 of nonconductive material which are located at opposite sides of the path for the tow 4 and are driven to rotate in directions indicated by arrows. The peripheral speed of the elements 42, 43 (hereinafter called insulators) departs from the speed of the tow 4 so that the resulting friction entails the generation of positive and negative electric charges. The peripheral surfaces of the insulators 42, 43 (which can receive motion from the main prime mover 13, from the lower roller 9 or from one of the other rollers 3 and 9) are respectively contacted by wipers 44, 46, which, in turn, are connected to the ground, as at 47 and 48. If the tow 4 consists of or contains -cellulose acetate fibers, negative charges are retained by the fibers advancing toward the applicator 12, and the positive charges are separated by the wipers 44, 46 and conveyed to the ground. Coulomb repulsion forces which develop between the fibers of the tow 4 at the station for the charge applying unit 15 repel and thus separate neighboring fibers of the tow from each other to further enhance the singularizing action upon the tow before the fibers are contacted by atomized plasticizer which is sprayed by one or more nozzles, brushes or analogous components 53 of the applicator 12.

In accordance with another important feature of ---14- the invention, the negative charges which are applied to the f ibers of the tow 4 at the station for the unit 15 further serve to effect a more reliable application and -retention of atomized plasticizer in the path portion between the unit 15 and the rollers 11. This is achieved in that the applicator 12 is provided with means for applying to atomized plasticizer a positive charge so that the negatively charged fibers of the running tow 4 attract the positively charged atomized particles and thus establish the circumstances for the making of a superior f iller 10 which is ready to be draped into the web 21 of wrapping material. This novel feature (of attracting atomized plasticizer to the oppositely charged fibers of a running tow) can be resorted to with equal advantage if the plasticizer is not triacetin (e.g., because the fibers of the tow 4 are not made of cellulose acetate) but another solvent which can sof ten the contacted portions of the fibers and enables or causes the thus softened portions to adhere to each other f or the af oredescribed purpose of establishing a maze of paths for the flow of tobacco smoke in the rod-like f illers of a f ilter rod section. As already 'mentioned above, highly unif orm and predictable application of atomized plasticizer is desirable because it is an important factor which determines the tobacco smoke filtering ability of the ultimate product.

The applicator 12 includes the aforementioned combined atomizing and spraying device 53 as well as a metering device 51 (e.g., a suitable variable-delivery pump) which draws metered quantities of plasticizer per unit of time from a suitable source of supply 52, e.g., a vessel which contains a body of atomizable plasticizer. The atomizing and spraying device 53 is or includes an electrode which is connected with one pole of a source 54 of electrical energy, preferably a source of high potential. If the unit 15 is designed to apply to the are Publication No f ibers of the tow 4 a negative charge, the device or electrode 53 is connected with the positive pole of the source 54 so that the atomized plasticizer receives a charge which is opposite to that of the fibers in the tow 4. This ensures that the positively charged particles of atomized plasticizer are attracted by the negatively charged f ibers of the running tow 4 to thus guarantee predictable (uniform) distribution of atomized plasticizer and the formation of a superior f iller 10. The exact details of an electrostatic applicator which can be utilized in the filter rod making machine of the present invention disclosed, for example, in Defensive 665476 on page 860/3 of the Official Gazette of the United States Patent and Trademark Office dated March 18, 1969. The disclosures of this Defensive

Publication as well as of U.S. Pat. No. 4,259,769 are incorporated herein by reference.

The tow 4 advances beyond the applicator 12 through the nip of the rollers 11 and is converted from a flat strip-shaped body into a rod-like filler 10 on its way toward and through a so called gathering horn 17 of the apparatus 2. Successive increments of the filler 10 reach the upper side of the continuously advancing web 21 of wrapping material which is drawn off a bobbin 18 and one marginal portion of which is coated with a suitable adhesive (e.g., a hot melt) during advancement along a paster 19. The means for advancing the web 21 and the filler 10 through a wrapping mechanism 23 of the apparatus 1 includes an endless belt 22 (known as garniture) driven by the main prime mover 13. The mechanism 23 drapes the web 21 around the filler 10 to form a continuous filter rod 24 wherein the adhesive-coated marginal portion of the web 21 adheres to the other marginal portion to form therewith an elongated seam extending in parallelism with the axis of the rod 24. Such seam is cooled during advancement past a so-called sealer 26 having means for cooling the adhesive so that the seam can withstand the action of the knife or knives forming part of a cutoff 27 which divides the running filter rod 24 into filter rod sections 28 of unit length or multiple unit length. Successive sections 28 are engaged by a rotary accelerator 29 which propels them axially into successive flutes in the peripheral surface of a rotary drum-shaped conveyor 31. The latter moves the sections 28 sideways and transfers them onto the upper reach of an endless belt conveyor 32 which delivers the sections into storage or into the magazine of a f ilter tipping machine, e.g., a machine known a MAX which is distributed by the assignee of the present application.

An important advantage of the improved f ilter rod making machine is that electric charges which are applied at 15 ensure highly satisfactory separation (untangling) of fibers in the tow 4 before the thus separated fibers reach the applicator 12.

Another important advantage of the improved machine is that the application of an electric charge at 15 not only promotes and improves the separation of interlaced fibers of the running tow 4 but that such charging can also serve the additional purpose of enhancing the application of atomized plasticizer at 12, i.e., between the locus of completion of the spreading and stretching operations and the locus of converting the f lat strip-shaped tow into a rod-like filler 10. All that is necessary is to apply to the atomized plasticizer a charge of opposite polarity so that the oncoming f ibers of the tow 4 attract the particles of plasticizer and thus enhance the predictability of distribution of plasticizer on the fibers of the tow prior to draping of the tow into the web 21 of cigarette paper, imitation cork or other suitable wrapping material.

FIG. 2 illustrates a modified unit 15 which can be used to apply a negative charge to fibers of cellulose acetate forming part of or constituting a tow 4 advancing in direction indicated by the arrows Pf. The unit 15 of FIG. 2 is designed to ef f ect a so-called spray discharge between a pointed metallic electrode 57 at one side and a complementary electrode or counter electrode 58 at the other side of the path for the tow 4. The pointed electrode 57 is connected with one pole of an energy source 56 (e.g., a source of high voltage) the other pole of which is grounded at 59. The counterelectrode 58 is also grounded at 59. The pointed electrode 57 applies to the fibers of the tow 4 a positive or a negative charge, e.g., a negative charge if the tow consists of or contains cellulose acetate fibers.

The charge applying unit 15 of FIG. 1 or 2 can be installed at the locus of the unit 15 in FIG. 1 or at any one of a number of different locations of the apparatus 1. Three additional locations are indicated in FIG. 1 by the arrows A, B and C. Thus, the fibers of the tow 4 can be electrically charged ahead of the deflecting roller 5 (as at B), between the deflecting roller 5 and the rollers 3 (as at A) or between the rollers 3 and 9 (as at C).

The apparatus I of the improved f ilter rod making machine can be further provided with a measuring instrument 50 (shown in FIG. 2) which is designed to monitor the magnitude of electric charges (electric field) which are being applied to the f ibers of the running tow 4 and to generate signals which are used to control the speed of the insulators 42, 43 and/or to adjust the source 56 in a sense to ensure that the strength of the applied electric field remains at least substantially constant and at least approximates an optimum value.

Referring to FIGS. 3 and 4, there is shown a portion of a filter rod making machine wherein the apparatus 1 differs from the apparatus 1 of FIG. 1 in that the applicator 62 of atomized plasticizer and the means 61for applying electric charges to the f ibers of the tow 4 are located downstream of the rollers 11, namely in the region where the gathering horn 17 is effective to convert the flat strip-shaped tow 4 into a rodlike filler 10. Thus, atomized plasticizer is applied to the cylindrical or substantially cylindrical external surface of the filler 10 (see particularly FIG. 4). The applicator 62 comprises a metering pump 63 which draws predetermined quantities of liquid or liquefied plasticizer from a suitable source 63a and delivers three streams of plasticizer through conduits 64, 66, 67 to discrete nozzles 68, 69, 71, respectively. These nozzles are installed in a tubular or ring-shaped carrier 72 and are equidistant from each other in the circumferential direction of the rod-shaped filler 10 which is caused to advance through the interior of and preferably centrally of the carrier 72. The sprays 74, 76 and 77 of plasticizer issuing from the nozzles 68, 69 and 71, respectively, are preferably configurated and distributed in such a way that the entire exterior of the filler 10 is provided with a uniformly distributed coat of atomized plasticizer. The carrier 72 preferably constitutes an electrode which is connected to the positive po le of a source 73 of electrical energy. This ensures that the droplets of plasticizer which are discharged by the orifices of the nozzles 68, 69, 71 are positively charged and are attracted to the negatively charged fibers of the filler 10.

It is clear that the number of nozzles can be reduced to less than three or increased to four or more without departing from the spirit of the invention. Irrespective of their exact number, the nozzles 68, 69, 71 are preferably configurated, dimensioned and distributed in such a way that they discharge mists or sprays which uniformly contact the fibers of the running tow 4 at the center of the space within the electrode 72.

The arrow D indicates in FIG. 3 that the unit 61 which charges the fibers of the tow 4 is located downstream of the rollers 11, in a region where the tow is being converted into the filler 10.

FIG. 5 shows a portion of an apparatus 1 which constitutes a modification of the apparatus 1 shown in FIGS. 3 and 4. The main difference is that the filler 10 constitutes an elongated tubular body having an internal surface which is contacted by an annular spray 79 of atomized plasticizer issuing the radially extending orifices of a nozzle 78. In addition, the electrode 72 carries nozzles 68, 69, 71 which simultaneously apply sprays or mists 74, 76, 77 of atomized plasticizer to the external surface of the hollow tubular filler 10. This even further enhances the uniformity of distribution of atomized plasticizer on the fibers of the filler 10, i. e., on the fibers of the converted tow. The nozzle 78 can constitute a perforated pipe which discharges the annular mist or spray 79 of finely atomized plasticizer against the entire internal surface of the running filler 10. The electrode 72 applies a positive charge to the sprays 74, 76, 77 which issue from the nozzles 68, 69 and 71, and the nozzle 78 also constitutes an electrode which applies a positive charge to the mist or spray 79. It is assumed here that the fibers of the tubular filler 10 are made of cellulose acetate and carry a negative charge on their way within the electrode 72 and around the nozzle (electrode) 78 of FIG. 5.

The number of nozzles which are carried by the ring-shaped electrode 72 can be increased to four or-more, and the single electrode or nozzle 78 can be replaced with two or more nozzles in order to ensure uniform distribution of atomized plasticizer on the internal and external surfaces of the running tubular filler 10. The manner of making a tubular filler is known in the art and need not be described here. The f ibers of the tubular f iller 10 of FIG. 5 can be electrically charged in a manner as described in connection with FIG. I or FIG. 2.

In accordance with a further important and advantageous feature of the present invention, the improved f ilter rod making machine can be designed to simultaneously process a plurality of tows of fibrous f ilter material. FIGS. 6 and 7 illustrate a portion of a machine which is designed to simultaneously process two discrete tows 4a, 4b advancing next to each other along two parallel paths. The width of each of the tows 4a, 4b can be less than a presently preferred standard width because the fibers of such tows are separated from each other under the action of electric charges in a highly efficient manner so that it is not necessary to start with relatively wide tows and to increase the width of the tows on their way from a common bale or from discrete bales toward the applicator or applicators of atomized plasticizer. This also applies for the tow 4 which is treated in the machine of FIG. 1, in the machine including the apparatus of FIG. 2, in the machine including the apparatus of FIGS. 3-4 and/or in the machine including the apparatus of FIG. 5.

The machine which embodies the apparatus of FIGS. 6 and 7 includes two devices 81a and 81b which serve to apply (e.g., negative) electric charges to the fibers of the respective tows 4a and 4b. Each of the devices 81a, 81b can constitute a rod-shaped corona discharge device of the type known as ALSA 030-500 distributed by Haug GmbH & Co. KG, Echterdingen, Federal Republic Germany. The counterelectrode can be constituted by the lower roller 9 which is then grounded as shown in FIG. 6. However, it is equally possible to employ a discrete counterelectrode in lieu of one of the rollers 9. The means for electrically charging the devices 81a, 81b are shown at 82a and 82b, respectively. Such charging means can be of the type known as AG-3/7612 (distributed by Haug). FIGS. 6 and 7 further show monitoring means 83a and 83b which are constructed, assembled and installed to ascertain the magnitude of electric charges applied to the fibers of the tows 4a and 4b and to generate corresponding signals which are used to effect appropriate adjustments of the charging means 82a and 82b. The monitoring means 83a and 83b can be of the type known as Stato 11/7209 (distributed by Haug). The signals at the outputs of the monitoring means 83a, 83b are respectively transmitted to signal comparing stages 84a, 84b which further receive reference signals from suitable sources 86a, 86b, respectively.

The illustrated circuitry ensures that the electric charges (e.g., negative charges) which are being applied to the fibers of the tows 4a and 4b can be regulated and maintained at a selected optimum value to thus ensure satisfactory separation of fibers in each of the tows. The intensity of reference signals furnished by the source 86a can depart from the intensity of reference signals furnished by the source 86b if the maker of filter rods desires to produce two filter rods having different characteristics. This is or can be desirable if the material of the tow 4a is dif f erent f rom that of the tow 4b or if the manufacturer desires to turn out two sets of filter rod sections which exhibit at least slightly different characteristics. Such making of a plurality of dif f erent f ilter rods in one and the same machine is desirable and advantageous for several reasons. For example, the tows 4 can be advanced by one and the same pair of rollers 3 and/or by one and the same pair of rollers 9 because the spreading and stretching actions of these rollers are no longer as critical as in conventional machines wherein the fibers of a tow are not separated from each other in response to the application of an appropriate electric charge in a manner as already described with reference to FIG. 1 or FIG. 2.

An important advantage of a machine which embodies the structure of FIGS. 6 and 7 and which is designed to simultaneously treat a plurality of tows is that the space requirements of such machine are but a fraction of the space requirements of two or more conventional f ilter rod making machines each of which is designed to process a single filter tow. Additional savings are achieved because at least certain treatments (such as advancing and/or the application of plasticizer) can be carried out by equipment which is common to two or more tows. still further, certain conventional constituents of heretofore known filter rod making machines can be omitted altogether because the application of electric charges to a single tow or to two or more tows can be readily selected and regulated in such a way that the electric charge or charges effect at least the major part of the fiber spreading and separating action.

Numerous details of a machine which is designed for the simultaneous making of a plurality of filter rods are disclosed in commonly owned copending patent application serial No. filed March I 19 9 3 by Chehab et al. for "Method of and machine for making filter rods for rod-shaped smokers' products."

FIG. 8 illustrates a portion of af ilter rod making machine which is also designed to simultaneously process a plurality of filter tows (e.g., two filter tows 4a and 4b). In contrast to the machine of FIGS. 6 and 7 (wherein the tows 4a, 4b are at least substantially coplanar and advance next to each other, i.e., side-by side), the tows 4a and 4b of FIG. 8 are advanced along two paths which are disposed one above the other. Reference may be had again to the aforementioned copending patent application serial No. of Chehab et al. The charge applying means 15 in the machine embodying the -23 structure of FIG. 8 comprises a discrete f irst electrode 81a, 81b for each of the tows 4a, 4b and a common counter e 1 ectrode 87 between those portions of the paths for the tows 4a, 4b which are respectively adjacent the electrodes 81a and 81b.

The electrodes 81a, 81b need not be installed close to each other, i.e., they can be installed in different portions of the apparatus 1. This depends on the nature and the location of the applicator or applicators of atomized plasticizer. For example, a 'machine embodying the structure of FIGS. 6-7 or the structure of FIG. 8 can be provided with a discrete applicator of atomized plasticizer for each of the tows 4a, 4b or with a common adhesive applicator, depending on the nature of the selected applicator.

The improved filter rod making machine is susceptible of numerous additional modifications without departing from the spirit of the invention. For example, the features of the machines embodying the structures of FIGS. 1, 2, 3-4, 5, 6-7 and 8 can be combined or interchanged or further modified, depending on the nature of the tow or tows and/or on the desired filtering action of the ultimate products. The speed of the machine which embodies the structure of FIGS. 6-7 or FIG. 8 can be reduced below the speed of a standard machine to thus subject the fibers to gentler treatment; such expedient will be resorted to if the quality of ultimate products is more important than the output of the machine. on the other hand, if the output is of utmost importance or of greater importance, a machine embodying the structure of FIGS. 6-7 or FIG. 8 can turn out twice as many filter rod sections than a conventional machine which is designed to process a single filter tow.

In the preceding description of the illustrated machines, the charge applying units 15 or 61 were designed to apply to the fibers a negative charge. However, it is equally possible to apply to fibers of cellulose acetate a positive charge; it is then necessary to modify the -applicator 12 or 62 so that the particles of atomized plasticizer will be negatively charged.

An important advantage of the improved method and machine is that the fibers of a tow can be singularized or separated in a simple and accurately adjustable manner. Thus, the charges which are applied to the f ibers can be selected with a view to ensure that neighboring f ibers repel each other with a desired force. Moreover, the treatment of f ibers during separation with electric charges is gentler than heretofore known purely mechanical treatments with stretching rollers, braking rollers, deflectors, banding devices and like components so that the fibers are less likely to break. Moreover, the application of positive or negative charges to the fibers of a running tow renders it possible to improve the next treatment which involves the application of atomized plasticizer. Thus, all that is necessary is to apply to atomized plasticizer a charge of opposite polarity so that the particles of plasticizer are actually attracted to the fibers of a properly charged tow with attendant more predictable and more uniform distribution of atomized plasticizer on the separated fibers of the tow or tows advancing toward the rod forming apparatus of the improved machine. It has been found that the homogeneousness of distribution of atomized plasticizer on the running tow or tows, filler or fillers is much more satisfactory than in conventional filter rod making machines.

A further important advantage of the improved method and machine is that they render it possible to simultaneously process a plurality of tows. This can raise the output of the machine and/or improve the quality of the ultimate products. Furthermore, it is possible to simultaneously turn out a plurality of products which exhibit different characteristics, to achieve savings in energy because the number of prime movers can be reduced by utilizing common prime movers for certain mobile parts which treat two or more running tows or fillers. still further, the space requirements of a number of improved filter rod making machines in a filter cigarette making plant or in a plant for the production of filter cigarillos or filter cigars can be greatly reduced, not only because a single machine can simultaneously process a plurality of tows but also because the width of the untreated and partially treated tows is or can be less than that of the tows which are being processed in presently available machines. Still further, it is possible to achieve savings in plasticizer because the machine can be designed to deliver to each applicator 12 or 62 only that quantity of plasticizer which is necessary to ensure optimal distribution of atomized plasticizer on the separated fibers of one or more tows or fillers.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it f or various applications without omitting features that, from the standpoint of prior art, f airly constitute essential characteristics of the generic and specific aspects of our contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the appended claims.

Claims (32)

CLAIMS:

1. A method of treating a fibrous filter material, comprising the steps of advancing at least one tow of interlaced fibers in a predetermined direction along a predetermined path; and applying to the at least one tow electric charges to singularize the interlaced fibers.

2. The method of claim 1, wherein said applying step comprises establishing a source of voltage and effecting a spray discharge from the source upon the at least one tow in the path.

3. The method of claim 2, wherein said step of effecting a spray discharge includes discharging sparks between electrodes which are located at opposite sides of said path and at least one of which is a pointed metallic electrode

4. The method of claim 1, further comprising the step of maintaining said charges at least close to a predetermined value.

5. The method of claim 1, wherein said applying step comprises maintaining the at least one advancing tow in frictional engagement with at least one electrical insulator to thus generate electric charges having first and second polarities and separating charges of first polarity from the at least one tow, the charges of second polarity being effective to separate the interlaced fibers from each other.

6. The method of claim 1, wherein said electric charges have a first polarity and said applying step is carried out in a first portion of said path, and further comprising the steps of atomizing a flowable plasticizer, applying to the atomized plasticizer electric charges having a second polarity opposite said first polarity, and spraying the thus charged atomized plasticizer onto the at least one tow in a second portion of said path downstream of said first portion.

7. The method of claim 6, wherein the plasticizer contains triacetin.

8. The method of claim 6, further comprising the step of converting the at least one tow into a substantially rod-shaped filler in a third portion of said path, said spraying step including directing the charged atomized plasticizer against the exterior of the filler.

9. The method of claim 8, wherein said spraying step includes dividing the atomized plasticizer into a plurality of streams and said directing step comprises directing said streams against spaced apart portions of the filler.

10. The method of claim 6.. further comprising the step of converting the at least one tow into a tubular filler having an internal surface and said converting step is carried out in a third portion of said path, said spraying step including directing at least some of the charged atomized plasticizer against the internal surface of the filler.

11. The method of claim 10. wherein said spraying step further includes directing additional charged atomized plasticizer against the exterior of the filler.

12. The method of claim 6, further comprising the step of metering the plasticizer prior to said step of applying charges of second polarity.

13. The method of claim 1, wherein said advancing step includes advancing a plurality of tows in said direction along neighboring paths and said applying step includes applying electric charges to each of said plurality of tows to singularize the respective interlaced fibers.

14. The method of claim 13, further comprising the step of maintaining the electric charges f or each of the tows at a substantially constant value.

15. The method of claim 13, further comprising the steps of monitoring at least one characteristic of charges which are applied to the respective tows and regulating the applying step as a function of deviations of monitored characteristics of said charges from predetermined characteristics.

16. The -method of claim 15 of treating a plurality of tows which consist of different fibrous filter materials, wherein said regulating step includes regulating the application of electric charges to each of said plurality of tows as a function of deviations of monitored characteristics of said charges from a different predetermined characteristic.

17. A method of treating a fibrous filter material, comprising the steps of advancing at least one tow of fibers in a predetermined direction along a predetermined path; applying to the advancing tow electric charges having a first polarity; atomizing a flowable plasticizer; applying to the atomized plasticizer electric charges having a second polarity opposite said first polarity; and spraying the thus charged atomized plasticizer onto the charged advancing tow.

18. A machine f or treating a f ibrous f ilter material, comprising means for advancing at least one tow of interlaced fibers in a predetermined direction along a predetermined path; and means f or applying to the at least one tow electric charges to singularize the interlaced fibers.

19. The machine of claim 18, wherein said applying means includes a source of electrical energy and at least one charcSe-app lying electrode connected to said energy source.

20. The machine of claim 19, wherein said source includes a source of high voltage.

21. The machine of claim 18, further comprising means for maintaining said electric charges at least close to a predetermined value.

22. The machine of claim 21, wherein said applying -means comprises at least one insulator adjacent said path and in frictional engagement with the at least one tow to generate electric charges having first and second polarities, and means for conducting charges of one of said polarities away from said at least one insulator.

23. The machine of claim 18. wherein said applying means includes means for applying to the at least one tow electric charges having a first polarity and further comprising a source of flowable plasticizer, means for atomizing the plasticizer, means for applying to atomized plasticizer electric charges having a second polarity opposite said first polarity, and means for spraying charged and atomized plasticizer onto the charged at least one tow in said path.

24. The machine of claim 23, wherein the means f or applying electric charges to the at least one tow is adjacent a first portion of said path and said means for spraying is adjacent a second portion of said path downstream of said first portion, and further comprising means for converting the at least one tow into a substantially rod-shaped filler in a third portion of said path, said spraying means including means for directing charged and atomized plasticizer against the exterior of the filler.

25. The machine of claim 24, wherein said converting means includes means for converting the at least one tow into a hollow f iller having an. internal surface, said spraying means further comprising means for directing charged atomized plasticizer against the internal surface of the filler.

26. The machine of claim 23, further comprising means for supplying metered quantities of plasticizer from said source to said atomizing means.

27. The machine of claim 23, wherein the means f or applying electric charges to the at least one tow is adjacent a first portion of said path and said means for spraying is- adjacent a second portion of said path downstream of said first portion, and further comprising means for converting the at least one tow into a tubular filler having an internal surface, said converting means being disposed in a third portion of said path and said spraying means including means for spraying charged and atomized plasticizer against the internal surface of the filler.

28. The machine of claim 18, wherein said advancing means comprises means for advancing a plurality of tows along neighboring paths and said applying means includes means for applying electric charges to each of said plurality of tows, and further comprising means for maintaining the electric charges for each of the tows at a substantially constant value.

29. The machine of claim 18, wherein said advancing means comprises means for advancing a plurality of tows consisting of different fibrous materials along neighboring paths and said applying means includes means for applying electric charges to each of said plurality of tows, and further comprising means for maintaining the electric charges for each of the tows at a different value.

30. A machine for treating fibrous filter material, comprising means for advancing at least one tow of fibers in a predetermined direction along a predetermined path; means for applying to the advancing tow electric charges having a first polarity; a source of a flowable plasticizer; means for atomizing the plasticizer; means for applying to atomized plasticizer electric charges having a second polarity opposite said first polarity; and means for spraying the charged and atomized plasticizer onto the at least one advancing charged tow.

31. A method of treating a fibrous filter material, substantially as herein described with reference to the accompanying drawings.

32. A machine for treating a fibrous filter material, substantially as herein described with reference to the accompanying drawings.