Method and apparatus for delivering particles of tobacco to shredding machines
BACKGROUND OF THE INVENTION 
     The present invention relates to a method and apparatus for delivering particles of tobacco to a tobacco cutting machine, particularly to the system which transports a cake of tobacco particles into the range of one or more knives in a tobacco shredding machine. 
     Presently known tobacco shredding machines comprise convergent upper and lower chain conveyors which deliver a cake of condensed tobacco particles into the range of orbiting knives on a rotary carrier whereby the knives cut across the leader of the cake and convert the particles into smaller fragments or shreds which are delivered to a conditioning unit prior to transport into the magazine of a cigarette maker. The rear end of the lower chain conveyor extends beyond the rear end of the upper chain conveyor and receives a shower of tobacco particles from a duct. A rake or an analogous device is provided to push the descending particles into the space between the two chain conveyors whereby the conveyors convert the stream into the aforementioned cake whose density increases on the way toward the cutting station. The just described cutting machines are used for comminution of tobacco leaf laminae and/or tobacco ribs. 
     A drawback of presently known systems which deliver tobacco particles to the chain conveyors of a shredding machine is that the particles which form the cake are oriented in random fashion. This affects the homogeneousness of the cake and often results in extraction (rather than severing) of relatively large particles from the front end of the cake. Large fragments of ribs are likely to affect the quality of the filler of a cigarette rod and/or to puncture the wrapping material (cigarette paper) which is used to convert the filler into a rod ready to be subdivided into discrete cigarettes or analogous smokers&#39; products. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     An object of the invention is to provide a novel and improved method of delivering particles of tobacco to the transporting and compacting or condensing unit of a tobacco cutting machine in such a way that the resulting cake is more homogeneous than the cakes which are formed in heretofore known cutting machines. 
     Another object of the invention is to provide a method which insures predictable orientation of all or nearly all particles of tobacco on their way toward and in the compacting or condensing zone. 
     A further object of the invention is to provide a method which insures that the cutting machine can produce a large number of elongated tobacco shreds which are best suited for conversion into the filler of a cigarette rod or the like. 
     An additional object of the invention is to provide a novel and improved apparatus which can be combined with or incorporated in tobacco cutting machines to insure the formation of a homogenous cake consisting of compacted tobacco ribs and/or tobacco leaf laminae. 
     Another object of the invention is to provide a relatively simple apparatus which contributes to compactness of the cutting machine and which can be installed in existing cutting machines as a superior substitute for conventional tobacco delivering systems. 
     A further object of the invention is to provide novel and improved conveyor means for use in the above outlined delivering apparatus. 
     An ancillary object of the invention is to provide a tobacco delivering apparatus which can advance particles of tobacco at a predictable rate and which insures optimum orientation of tobacco particles prior to and during conversion of such particles into a cake. 
     One feature of the invention resides in the provision of a method of comminuting particles of tobacco, such as tobacco ribs or tobacco leaf laminae wherein a stream of tobacco particles is built up at a location remote from a cutting station and is transported lengthwise toward the cutting station, and wherein the stream is condensed during transport toward the cutting station. In accordance with the invention, the improvement comprises the steps of conveying particles of tobacco toward the aforementioned location (which can be called a stream building zone) substantially in the longitudinal direction of the stream, and agitating the particles in the course of the conveying step. The stream is preferably transported along a substantially horizontal path whose cross-sectional area decreases in a direction from the stream building zone toward the cutting station, and the conveying step then comprises advancing the particles of tobacco along at least one second substantially horizontal path whose discharge end or outlet is disposed at the stream building zone. 
     The agitating step may comprise vibrating the particles in the second path or paths to thereby orient the particles in the second path or paths in such a way that at least the majority of particles which reach the stream building zone are substantially horizontal and extend substantially transversely of the stream. 
     The improvement preferably further comprises the steps of feeding particles of tobacco into each second path at a variable rate, monitoring the quantity of tobacco particles in at least one second path, and varying the rate at which the particles are supplied when the monitored quantity deviates from a predetermined range of quantities. For example, the monitoring step may include the utilization of one or more level detectors which scan the height of the mass of tobacco particles in a predetermined portion of a second path and a control system which regulates the rate of feed when the monitored height is outside of an optimum range of heights. 
     If the conveying step includes advancing the particles of tobacco along a plurality of second paths, such second paths are preferably substantially parallel to and may be disposed above each other. At least one second path may include a plurality of successive sections, and each preceding section of such second path is preferably disposed at a level above the next-following section so that the particles descend during transfer from a preceding section into the next-following section of such second path. 
     The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus 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 specific embodiments with reference to the accompanying drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic side elevational view of a tobacco shredding machine and a schematic partly longitudinal sectional view of a tobacco delivering apparatus which embodies one form of the invention and comprises a single conveyor constituting a vibrating trough for tobacco particles; 
     FIG. 2 is a fragmentary elevational view of the shredding machine and partly elevational and partly longitudinal sectional view of a second apparatus wherein the conveyor means for tobacco particles comprises two vibratory troughs disposed at different levels; 
     FIG. 3 is a view similar to that of FIG. 2 but showing a third apparatus whose vibratory trough is pivotable in the region of its discharge end; and 
     FIG. 4 is a view similar to that of FIG. 2 or 3 but showing a vibratory trough whose bottom wall is formed with several steps. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a tobacco cutting or shredding machine which comprises a frame or support F for a transporting unit 3 including an upper endless chain conveyor 4 and a lower endless chain conveyor 6. The lower reach of the conveyor 4 slopes forwardly and downwardly, and the upper reach of the conveyor 6 slopes upwardly and forwardly so that such reaches define a substantially horizontal elongated path A wherein particles of tobacco (e.g., tobacco ribs 2) are transported in a direction to the left, i.e., in the longitudinal direction of the stream of tobacco particles which are converted into a cake CK prior to reaching a cutting or severing station 19. The leader of the cake CK advances into the range of orbiting knives or cutters 21 which are mounted at the periphery of a cylindrical carrier 22 mounted in the frame F and driven by a discrete prime mover 23 here shown as an electric motor whose output element transmits torque to the shaft 22a of the carrier 22 by way of a chain or belt transmission 23a. 
     The sprocket wheels 6a and 6b of the lower chain conveyor 6 are mounted on shafts which are journalled in the frame F. The front sprocket wheel 6a is rotated by a variable-speed prime mover 7 (e.g., an electric motor) through the medium of a chain or belt drive 16. The shaft 8 for the rear sprocket wheel 4b of the upper chain conveyor 4 is also journalled in the frame F; however, the front sprocket wheel 9 of the upper chain conveyor 4 is movable up and down and is biased downwardly, as viewed in FIG. 1, by a fluid-operated cylinder and piston unit 11 or by analogous yieldable biasing means. The front sprocket wheel 9 is driven by a gear train 12, 13, 14 which derives motion from the sprocket wheel 6a of the lower chain conveyor 6. 
     The cutting edges of the knives 21 are sharpened by a grinding wheel 24 which is driven by a motor 24a. The active surface of the grinding wheel 24 is treated by a dressing tool 26. 
     The outlet of the path A between the chain conveyors 4 and 6 is defined by a mouthpiece including an upper portion 17 which shares the (up and down) movements of the front sprocket wheel 9 and a lower portion 18 which is fixedly secured to the frame F and constitutes a counterknife for the orbiting knives 21. The shreds which are formed in response to severing of successive increments of the cake CK are caused to descend into the inlet of a pneumatic conveyor PC which transports the shreds to the next processing station, e.g., to the drier of a conditioning unit which changes the moisture content of the shreds. 
     The rear portion of the lower chain conveyor 6 extends rearwardly beyond the rear portion of the upper chain conveyor 4 and is disposed at a level below a location 1 (hereinafter called stream building zone) which receives tobacco particles 2 from an apparatus embodying one form of the invention. The apparatus comprises conveyor means including a trough-shaped vibratory conveyor 27 which defines an elongated path B substantially or exactly in line with the elongated path A between the chain conveyors 4 and 6. The outlet of the path B is located at the stream building zone 1. The means for agitating the particles 2 of tobacco in the trough 27 comprises an eccentric 27a which is driven by a motor, not shown. The trough 27 is mounted on leaf springs 28 which are secured to the frame F. When the eccentric 27a rotates, the trough 27 performs recurrent movements which cause the particles 2 to advance toward the stream building zone 1. 
     The means for feeding tobacco particles 2 into the trough 27 comprises a chute 33 which can deliver particles of tobacco at a variable rate. Such rate can be varied by a monitoring means including photocells 32 which are adjacent to the path B and serve to monitor the upper level of the mass of particles in the trough 27. When the height of such mass is too low, one of the photocells 32 transmits a signal to a control circuit 32a which increases the rate of delivery of particles via chute 33. If the height of the mass in the trough 27 is excessive, the other photocell 32 transmits a signal which causes the control circuit 32a to reduce the rate of tobacco feed. Thus, the photocells 32 cooperate with the control circuit 32a to insure that the quantity of tobacco particles in the trough 27 is always within a desired range. The manner in which the photocells 32 cooperate with the control circuit 32a to insure that the upper level of the mass of tobacco particles 2 in the trough 27 remains within the optimum range for the formation of an acceptable cake CK is preferably the same as or similar to that described in commonly owned U.S. Pat. No. 4,172,515 granted Oct. 30, 1979 to Waldemar Wochnowski except that the photocells 32 transmit signals which regulate the rate of supply of tobacco particles 2 via chute 33 rather than or in addition to regulating the speed of the motor 7. For example, the control circuit 32a can transmit signals to a variable-speed motor which drives a conveyor serving to draw tobacco particles from a hopper and to deliver the withdrawn particles into the chute 33. 
     The bottom wall 29 of the trough 27 is stepped, i.e., it comprises an upper section upstream and a lower section downstream of a transversely extending step 31 along which the particles 2 descend on their way toward the stream building zone 1. The bottom wall 29 slopes slightly downwardly and forwardly, i.e., toward the zone 1; however, it is also possible to employ a horizontal bottom wall. The step 31, which extends transversely of the path B, contributes to densification of the stream of particles 2 in the trough 27 even before such particles reach the stream building zone 1. 
     It is also within the purview of the invention to use the photocells 32 and the control circuit 32a solely for regulation of the speed of the motor 7, i.e., for regulation of the speed of the chain conveyors 4, 6 of the transporting unit 3 in response to variations of the height of the mass of particles 2 in the trough 27 downstream of the discharge end of the chute 33. 
     It has been found that the conveyor means including the trough 27 contributes to predictable orientation of particles 2 on their way toward the stream building zone 1. This, in turn, insures that the homogeneousness of the cake CK is constant or nearly constant and also that the particles 2 (particularly ribs) assume such positions that, even though they cannot be readily extracted by the knives 21, the particles are converted into relatively long shreds which are best suited for the making of a satisfactory tobacco filler stream. As a rule, the particles 2 are substantially horizontal and extend transversely of the direction of transport along the path A not later than when they reach the stream building zone 1. 
     The vibrating trough 27 insures a preliminary compacting or condensation of material on the bottom wall 29. If the particles 2 are ribs, they are converted into a substantially homogeneous stream of interlaced particles even before they descend onto the upper reach of the lower chain conveyor 6. Agitation of particles 2 in the trough 27 insures that the majority of particles assume a horizontal position not later than on arrival at the outlet of the second path B. Some of the particles will make an acute angle with the direction of transport along the path B; however, the majority of particles will extend at right angles to such direction. This insures the formation of a homogeneous or nearly homogeneous cake. Moreover, and as already mentioned above, the knives 21 convert successive increments of the cake CK into elongated shreds which are more desirable than short tobacco. 
     Another important advantage of the improved apparatus is that its height is a fraction of the height of apparatus which are presently in use for delivery of tobacco particles to the compacting and transporting unit of a tobacco cutting or shredding machine. Presently known apparatus invariably employ an elongated vertical duch which accumulates a stack of tobacco particles at a level above the rear portion of the lower chain conveyor, and a rake or analogous means for intermittently advancing tobacco particles from the lower end of such duct into the space between the upper and lower chain conveyors of the transporting unit. 
     FIG. 2 shows a portion of a modified apparatus wherein all such parts which are identical with or clearly analogous to corresponding parts of the structure of FIG. 1 are denoted by similar reference characters plus 100. The conveyor of the tobacco delivering apparatus of FIG. 2 comprises several troughs 127 which are disposed at different levels (one above the other) and receive particles 102 of tobacco from discrete feeding ducts 133. The bottom walls 129 of the troughs 127 are configurated in the same way as the bottom wall 29 of the trough 27, i.e., each bottom wall 129 comprises a first or preceding section at a higher level, a second or next-following section at a lower level and a transversely extending step 131 between such sections. The outlets of the paths B which are defined by the troughs 127 terminate at the stream building zone 101, i.e., at a level above the rear portion of the upper reach of the chain of the lower chain conveyor 106. The paths which are defined by the troughs 127 are at least substantially parallel to the path A along which the cake CK moves between the chain conveyors 104, 106 of the transporting unit 103 and on toward the cutting station. 
     The paths B which are defined by the troughs 127 may but need not be exactly parallel to each other. For example, the lower path B may be horizontal and the upper path B may slope slightly forwardly and downwardly toward the stream building zone 101. The apparatus of FIG. 2 can be used with advantage when the cutting machine is designed to produce a large quantity of shreds per unit of time. The level of the masses of particles 102 in the troughs 127 can be monitored in the same way as described in connection with FIG. 1, and the signals which are generated by the transducer or transducers of the monitoring means can be used to regulate the rate of delivery of particles 102 via respective chutes or ducts 133 and/or the speed of the motor which drives the chain conveyors 104 and 106. 
     FIG. 3 shows a third apparatus wherein all such parts which are identical with or clearly analogous to corresponding parts of the apparatus of FIG. 1 are denoted by similar reference characters plus 200. The front end portion of the trough 227 (in the region of the outlet of the path indicated by the arrow B) is pivotable about a horizontal axis which is defined by a roller 235. The directions in which the trough 227 is pivotable are indicated by arrows 235a, 235b. Such adjustability of the trough 227 is desirable in order to insure that the rate of delivery of tobacco particles 202 to the cutting station matches or closely approximates the selected output of the cutting machine. It is clear that the pivot means 235 can be installed at the rear end of the trough 227, i.e., the trough can pivot about its rear end to move the outlet of the path B nearer to or further away from the upper reach of the chain conveyor 206. The rate of delivery of particles 202 to the zone 201 is increased by increasing the inclination of the trough 227. 
     FIG. 4 shows a further apparatus with a modified trough-shaped conveyor 327. All such parts of this apparatus which are identical with or clearly analogous to corresponding parts of the apparatus of FIG. 1 are denoted by similar reference characters plus 300. The bottom wall 329 of the trough 327 comprises several transverse steps 331 which are disposed at different levels so that the particles 302 repeatedly descend by gravity on their way toward the stream building zone 301. The apparatus of FIG. 4 has been found to be particularly suited for the advancement of tobacco leaf laminae toward the upper reach of the lower chain conveyor 306. Repeated showering of laminae on their way toward the zone 301 insures a highly satisfactory preliminary homogenization before the particles are converted into a cake. The number of steps 331 can be reduced to two or increased to four or more. The elasticity of laminae exceeds the elasticity of tobacco ribs so that a mass which consists of laminae can undergo a highly satisfactory preliminary compacting and homogenization upstream of the transporting unit 303 including the chain conveyors 304 and 306. 
     The improved tobacco delivering apparatus is susceptible of many additional modifications. For example, the means for agitating the particles in the conveyor means can include means for regulating the amplitude and/or frequency of vibrations of the trough or troughs. Such adjustments will be carried out in order to insure that the rate of delivery of particles to the stream building zone matches or closely approximates the output of the cutting machine. The frequency and/or amplitude of vibrations can be changed when particles of a first type are followed by particles of a second type, when the speed of the chain conveyor is changed and/or for certain other reasons. Furthermore, the monitoring means may be used to regulate the frequency and/or amplitude of vibrations of the trough or troughs to thereby insure an optimum rate of delivery of tobacco particles to the stream building zone. All such modifications will be readily understood by persons having the required skill in this art without additional illustrations. 
     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 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 claims.