Abstract:
The conveyor which converts an ascending shower of tobacco particles into a rod-shaped filler ready to be draped into a running web of cigarette paper in a cigarette rod making machine employs an endless permeable belt having a lower reach disposed beneath a suction chamber and at a level above a channel for advancement of the filler toward the wrapping mechanism. The channel and the marginal portions of the lower reach of the belt are flanked by walls which consist, at least in part, of a wear-resistant ceramic material capable of standing long periods of use due to a minimal wear as a result of sliding contact with tobacco particles, even if the belt is driven at an elevated speed to advance tobacco particles past a trimming device and thereupon into the wrapping mechanism of the cigarette rod making machine.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The invention relates to the making of rod-shaped products which contain flowable particulate material, such as fragments of tobacco leaves, artificial tobacco and/or reconstituted tobacco. More particularly, the invention relates to improvements in apparatus for advancing and simultaneously influencing (such as reshaping, condensing, changing the speed of and/or changing the direction of advancement of) streams or flows of particles of smokable material.  
           [0002]    A modern cigarette making machine (e.g., the machine known as PROTOS which is distributed by the assignee of the present appication) comprises a conveyor which gathers particles of tobacco leaves and/or other combustive tobacco smoke producing material (such particles will be referred to as tobacco particles) into at least one rod-like filler ready to be trimmed and thereupon draped into a running web of cigarette paper or other suitable wrapping material. To this end, the conveyor includes a duct defining an elongated path arranged to receive a continuous shower of tobacco particles. The shower is converted into an elongated stream by an elongated stretch or reach of an endless foraminous belt. One side of such reach is adjacent a suction chamber and the particles are attracted to the other side of the reach to advance along the aforementioned path toward a trimming or equalizing station where the surplus of smokable material is removed by a system of knives so that the stream is converted into a rod-like filler ready to be draped into the web of cigarette paper or the like. Reference may be had, for example, to commonly owned U.S. Pat. No. 5,072,742 granted Dec. 17, 1991 to Heitmann for “METHOD OF AND APPARATUS FOR MAKING A FILLER OF SMOKABLE MATERIAL”.  
           [0003]    As a rule, or at least in many instances, the shower of tobacco particles is caused to rise into the duct to form a stream at the underside of the lower reach of the foraminous belt. Thus, the lower reach of such belt constitutes one wall of the duct, and the duct includes stationary additional walls serving to flank the sides of the path beneath the lower reach of the belt and being in continuous contact with the moving tobacco particles.  
           [0004]    A modified conveyor for advancement and conversion of a shower of tobacco particles into a tobacco stream is disclosed in commonly owned published German patent application Serial No. 197 33 443 A1.  
           [0005]    A drawback which is common to presently known conveyors of the above outlined character is that the stationary walls which come in contact with tobacco particles are subject to extensive wear due to continuous pronounced uninterrupted frictional engagement with the advancing stream of comminuted tobacco. This affects the useful life of the conveyor. Moreover, such pronounced frictional engagement can exert adverse influence upon the the consistency and/or configuration of the growing tobacco stream in the duct.  
           [0006]    Attempts to ensure that the stationary walls of the duct of the conveyor will offer relatively low resistance to sliding movement of tobacco particles therealong include the coating of such walls with linings of tungsten carbide. This material exhibits a satisfactory resistace to wear; however, its coefficient of friction is very high so that it can affect the quality of cigarettes, e.g., in that the weights of numerous cigarettes depart considerably from an optimum or acceptable weight, and the quality of the tobacco-containing ends of the ultimate products is less than satisfactory.  
           [0007]    The aforementioned published German patent application Serial No. 197 33 443 A1 proposes to provide the duct which receives the shower of tobacco particles with ceramic tracks serving to guide the continuously moving endless belt and holding it in an optimum position relative to those stationary walls of the duct which are in continuus contact with the sides of the growing and advancing tobacco stream. The published German patent application does not disclose or suggest the making of such stationary walls of a ceramic material, i.e., to employ a ceramic substance as the material of stationary walls which are in continuous and extensive contact with comminuted smokable material.  
         OBJECTS OF THE INVENTION  
         [0008]    An object of the present invention is to provide a conveyor which is constructed and assembled in such a way that all stationary parts which come into extensive contact with moving tobacco particles exhibit several desirable properties, especially a pronounced resistance to wear and a low resistance to sliding of tobacco particles therealong.  
           [0009]    Another object of the instant invention is to provide a conveyor wherein the stationary walls which come in direct contact with the conveyed tobacco particles and/or with the moving belt are subject to less pronounced wear than in conventional conveyors.  
           [0010]    A further object of the invention is to increase the area of contact between the moving belt and the tracks which guide the belt for movement along a desired path in a cigarette rod making machine.  
           [0011]    An additional object of the present invention is to provides a novel and improved method of prolonging the useful life of the belt and/or of other parts in a conveyor of the above outlined character.  
           [0012]    Still another object of this invention is to provide a cigarette making machine which employs one or more conveyors exhibiting the above-enumerated desirable characteristics.  
           [0013]    A further object of our invention is to provide a conveyor which can be utilized with advantage in modern high-speed cigarette rod making machines which are designed to turn out huge quantities of cigarettes or analogous rod-shaped smokers&#39; products per unit of time.  
           [0014]    Another object of the invention is to provide a conveyor which can be utilized in machines designed to turn out a single continuous cigarette rod as well as in machines which can turn out simultaneously a plurality of continuous cigarette rods.  
         SUMMARY OF THE INVENTION  
         [0015]    The invention resides in the provision of a conveyor for flowable particulate material of the tobacco processing indsutry, wherein a duct defines a path for the flowable material and has walls bounding the path, i.e., being in direct contact with moving particulate material. In accordance with a feature of the invention, at least one of the walls consists at least in part of a ceramic material, i.e., such ceramic material comes in direct contact with the moving particulate material.  
           [0016]    The at least one wall is or can be stationary, and such at least one wall can constitute a lining having a surface adjacent the path and consisting of ceramic material. The duct of such conveyor can comprise a back support for the lining; the lining is affixed to the back support in such a way that it is disposed between the back support and the path for moving particulate material. For example, the lining can be bonded (such as by a suitable adhesive) to its back support and the thickness of such lining can be between about 0.05 mm and 0.5 mm. Instead of being bonded to the back support, the lining can be applied to the back support in molten state, and such molten material can be poured or sprayed onto the back support.  
           [0017]    That surface of the at least one wall of the duct which is adjacent the path for and is contacted by the moving particulate material can have a consistency or configuration resembling that of an orange peel or rind.  
           [0018]    Another wall of the duct can constitute a portion (e.g., an elongated lower reach or stretch) of a conveyor belt which is arranged to advance particulate material along the path. A third wall of such duct can be installed to confront the at least one wall and is preferably disposed at that side of the belt portion which faces the at least one wall. The third wall consists, or can consist, at least in part of a ceramic material, e.g., of a material identical with that of the at least one wall. Two additional walls of such duct can be disposed at the other side of the aforementioned portion of the belt and are or can be designed to provide (i.e., establish or constitute) tracks or guideways for the aforementioned portion of the belt. At least one of the additional walls can be provided with one or more projections (e.g., with substantially trapeziform arms or the like) which abut the other side of the elongated portion of the belt. The additional walls can be provided with surfaces each of which is adjacent and extends lengthwise of a different one of the two elongated marginal portions (edge faces) of the elongated portion of the belt. The latter is or can be located at a level above the path, i.e., at a level above the at least one wall and the third wall of the duct. The duct can form part of a cigarette rod making machine.  
           [0019]    The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved conveyor itself, however, both as to its construction and the modes of assembling and utilizing the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 is a transverse sectional view of a conveyor which embodies one form of the present invention and employs a total of four walls made at least in part of a wear-resistant ceramic or ceramic-containing material;  
         [0021]    [0021]FIG. 2 is an enlarged view of a detail in the structure of FIG. 1; and  
         [0022]    [0022]FIG. 3 is a plan view of certain parts in a modified conveyor.  
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0023]    [0023]FIG. 1 shows a portion of a conveyor  2  which embodies one form of the present invention and includes an elongated channel or duct defining an elongated path  1  for reception and advancement of successive increments of a continuous ascending shower of tobacco particles forming a stream at the underside of the lower reach or stretch  20  of an endless foraminous belt being driven in a manner not shown in the drawings to advance tobacco particles in a direction at right angles to the plane of FIG. 1. Reference may be had, for example, to FIG. 3 of the aforementioned U.S. Pat. No. 5,072,742 to Heitmann which shows a conventional conveyor having an endless foraminous belt  61  including a lower reach located below the perforated bottom wall  59  of a suction chamber  61  and above the open upper end of a tubular guide  52  for an ascending shower of tobacco particles. The ascending shower of tobacco particles gathers into a continuous stream which is advanced along an at last substantially horizontal path and past a surplus removing or equalizing device. The resulting rod-like filler  78   c  is draped (at  89 ) into a web  91  of cigarette paper to form therewith a continuous cigarette rod ready for repeated severing of its leader to yield a succession of discrete plain cigarettes of unit length or multiple unit length. The structure shown in FIGS. 1 and 2 of the present application is a cross-sectional view of the novel conveyor  2  taken at right angles to the plane in FIG. 3 of the patent to Heitmann.  
         [0024]    Referring again to FIGS. 1 and 2 of the present application, the lower reach  20  of the endless belt is located at a level below two confronting sidewalls or cheeks  8 ,  10  mounted in a housing  4 . The sidewalls  8 ,  10  are connected to each other and form part of a holder  6  which is bolted, screwed or otherwise affixed to the two halves of the housing  4 . These sidewalls are respectively provided with elongated grooves  12 ,  14  for discrete inserts or walls  16 ,  18  respectively adjacent the lateral marginal portions or edge faces  30 ,  32  of the lower reach  20  of the belt. The inserts  16 ,  18  are respectively provided with guide surfaces  22 ,  24  for the respective edge faces  30 ,  32 . The configurations of the surfaces  22 ,  24  bounding the grooves or cutouts  12 ,  14  are such that the lower reach  20  of the endless belt is compelled to advance in an accurately defined plane extending at least substantially at right angles to the plane of FIG. 1 or  2 .  
         [0025]    The suction chamber  48  in the interior of the housing  4  above the lower reach  20  of the endless belt attracts the fragments of tobacco particles in a manner to form a stream which is entrained by the lower reach  8 . The upper side of this lower reach is propped by the surfaces  25  of several rollers  28  rotatably mounted in the suction chamber  48  on horizontal shafts  26 . The shafts  26  are installed in the cheeks  8  and  10 .  
         [0026]    The inserts or walls  16 ,  18  are further provided with parallel surfaces  34 ,  36  which are adjacent the edge faces  30 ,  32  of the lower reach  20 .  
         [0027]    The duct of the conveyor  2  further includes parallel walls  44 ,  46  which flank the channel or path  1  and are respectively borne by back supports  38 ,  40  secured to and depending from the respective portions of the housing  4 . Each of the walls  44 ,  46  is bonded (such as glued) to the respective back support  38 ,  40 . Those surfaces of the back supports  38 ,  40  which are adjacent the walls  44 ,  46  are provided with pairs of shallow recesses  42  which can receive the adhesive. This adhesive can be of the type known as Delo Automix 1895 distributed by the Firm Delo in Landsberg am Lech, Federal Republic Germany. Each of the walls or linings  44 ,  46  can consist of a series of successive panels or plates which are placed next to each other to jointly form composite linings extending beneath the lower reach  20  of the endless belt in a direction at right angles to the plane of FIG. 1 or  2 .  
         [0028]    It will be seen that the path  1  is bounded by a total of three walls which actually contact, guide and entrain the tobacco particles rising into the duct, namely by the lower reach  20  of the endless belt, by the wall constituted by the composite lining  44 , and by the wall including the composite lining  46 . In accordance with a feature of the present invention, at least the wall  44  but preferably also the wall  46 , and most preferably also the walls or inserts  16 ,  18  is or are made of a ceramic material.  
         [0029]    The friction coefficient of the ceramic material of the linings  44  and  46  is low or very low, i.e., the exposed surfaces of these linings offer only a relatively small or negligible resistance to sliding movement of tobacco particles therealong. This ensures that the quality of cigarettes which have rod-like fillers built up in a machine embodying the structure shown in FIGS. 1 and 2 is not unduly affected by the walls  44 ,  46  because these walls do not unduly interfere with the distribution (in the duct  1 ) of tobacco particles in a manner as determined by the means for propelling tobacco particles into the duct from below, by suction in the chamber  48  and/or by the speed of forward movement of the lower reach  20  of the belt.  
         [0030]    The making of the inserts or walls  16 ,  18  of a ceramic material (such as Al 2 O 3 ) is desirable and advantageous but optional. On the other hand, the making of the walls  44 ,  46  from a ceramic material (at least in part) is highly desirable and constitutes an unexpectedly advantageous feature of the present invention. The ceramic material of portions of or of the entire walls  44 ,  46  is or can be the same as that of the portions of or of entire inserts or walls  16  and  18 . The utilization of a ceramic material for the walls  44 ,  46  has been found to contribute significantly to the useful life of the conveyor  2  and is attributable to the unexpected discovery that the coefficient of friction between ceramic walls and a shower and/or stream and/or other flow of tobacco particles is surprisingly low so that, once installed, such panels or walls  44 ,  46  as well as the walls or inserts  16 ,  18  can stand long periods of continuous use in a tobacco processing machine. This holds true regardless of whether the belt including the reach or stretch  20  is driven slowly (e.g., during starting) or while the vehicle embodying the structure shown in FIGS. 1 and 2 is driven at a relatively high speed.  
         [0031]    The neighboring panels of a composite ceramic lining (such as  44  or  46 ) can be properly (such as form-lockingly) interfitted with each other by mechanical means, e.g., by providing neighboring edge faces of such panels with mating teeth or with otherwise configurated overlapping parts (such as ledges or the like).  
         [0032]    In lieu of employing prefabricated ceramic or partly ceramic walls, it is also possible to employ a flowable ceramic material which is poured or sprayed onto selected surfaces of the back supports  38  and  40 . The same holds true for the inserts or walls  16  and  18 . The substances which are to be sprayed onto the confronting surfaces of the cheeks  38 ,  40  can be made of a ceramic material or they can contain a certain percentage of or inlays made from a suitable ceramic material.  
         [0033]    An additional important advantage of ceramic or partly ceramic linings  44 ,  46  is that such linings can be applied to the back supports in presently known or utilized panels of metal or the like. Thus, all that is necessary to significantly improve a conventional conveyor is to replace standard linings with novel linings of the type shown, e.g., in FIGS. 1 and 2. Such undertaking can significantly lengthen the useful lives of existing standard conveyors.  
         [0034]    The utilization of walls or linings  44 ,  46  having tobacco-contacting surfaces of a configuration similar to that of an orange rind has been found to contribute to longer useful life of the conveyors which embody the present invention.  
         [0035]    The spacing between the surfaces  34 ,  36  of the inserts or walls  16 ,  18  is such that the surfaces  34 ,  36  need not come into contact with the lower reach  20  of the endless belt; this greatly reduces the likelihood of excessive wear upon the edge faces of the foraminous belt including the lower reach  20 .  
         [0036]    A cigarette making machine which can employ a conveyor with two paths (or two discrete conveyors each defining a path  1 ) is disclosed, for example, in commonly owned U.S. Pat. No. 4,893,640 granted Jan. 16, 1990 to Heitmann et al. for “MULTIPLE-ROD CIGARETTE MAKING MACHINE”.  
         [0037]    [0037]FIG. 2 shows, drawn to a larger scale, those portions of the conveyor  2  which surround the lower reach  20  of the endless belt that surrounds the suction chamber  48 .  
         [0038]    [0038]FIG. 3 is a plan view of a portion of a conveyor  2   a  which constitutes a modification of the conveyor  2  shown in FIG. 1. All such parts of the conveyor  2   a  which are identical with or plainly analogous to those of the conveyor  2  are denoted by similar reference characters each followed by the letter “a”.  
         [0039]    The cheeks  8   a ,  10   a  on the holder  6   a  in the conveyor  2   a  flank a suction chamber  48   a  and respectively carry rows of ceramic or partly ceramic sections  16   a ,  18   a  replacing the one-piece walls or inserts  16 ,  18  shown in FIGS. 1 and 2. The sections  16   a ,  18   a  respectively include substantially trapeziform extensions or projections  51 ,  52  which overlie relatively small portions of the upper side of the lower reach  20  of the endless belt (not shown in FIG. 3) to prop the lower reach of this conveyor from above but to still permit the suction chamber  48   a  to draw tobacco particles into the path  1   a  and against the underside of the continuously advancing lower reach of the endless belt. The projections  51  alternate with the projections  52 , as seen in the longitudinal direction of the path  1   a , and at least some of their exposed surfaces have configurations corresponding to those on the exposed surface of the rind of an orange, lemon or an annalogous fruit. This is indicated in FIG. by the dots  50  on the projections  51 ,  52  and on the major parts of the inserts or walls  16   a ,  18   a . Such configuration of surfaces contacting the running endless belt and the advancing stream of tobacco particles in the path  1   a  greatly reduces the likelihood of extensive and/or rapid wear upon the surfaces of the walls  16   a ,  18   a  and their respective projections  51 ,  52  (if any).  
         [0040]    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 for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and specific aspects of the above outlined contribution to the art of apparatus for advancing streams of particulate smokable material and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the appended claims.