Abstract:
An air accelerator dosing tube for a form/fill/seal machine used to package fine cut tobacco material includes an axially-adjustable annular venturi communicating with the particulate material passage. A lining of polyether ether ketone optionally covers surfaces exposed to the particulate material. A metering assembly for delivering predetermined quanitites of particulate material at predetermined time intervals may also be fabricated from polyether ether ketone. Each dosing tube is adapted for calibration by adjustment of the annular venturi to produce a predetermined force at a predetermined stand-off distance. In operation, consistent simultaneous operation of multiple dosing tubes, each of which has been calibrated, gives substantially uniform deposit of particulate material in pouch-type packages. The particulate material may include finely cut tobacco in addition to humectants, flavorants, and other tacky substances.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/506,465, filed on Jul. 11, 2011, the entire content of which is incorporated herein by reference thereto. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    This disclosure generally pertains to apparatus for metering material that includes particles. More specifically, this disclosure concerns apparatus having a compressed air acceleration. 
       OVERVIEW 
       [0003]    This disclosure has particular application to pouching machines used for forming and assembling pouches of particulate material, such as by way of example fine cut smokeless tobacco. Typical pouching machines simultaneously form and assemble, for example, ten pouches from a substantially continuous strip or web of pouch material and metered charges of prepared smokeless tobacco. To effect the simultaneous pouch assembly, pouching machines typically include a bank of generally vertical tobacco feed tubes. Typical pouching machines also include arrangements for drawing and directing a strip or ribbon of pouch web to each feed tube, and wrapping the strip around the corresponding feed tube to form a tubular formation, as well as arrangements to repetitively close and seal that tubular formation so as to form a lower transverse seam at a lower end portion of the tubular web formation just prior to charging each tubular formation with predetermined amount of smokeless tobacco. The pouching machine further includes arrangements for repetitively feeding individual charges of tobacco down corresponding feed tubes and into corresponding tubular formations. After each tobacco charge, the pouching machines close and seal the tubular formation at a second location above the tobacco charge to form an individual loaded and sealed pouch, which is then severed from the tubular formation. 
         [0004]    Typically, smokeless tobacco material has a low moisture content, for example, about 30 to about 40% moisture level, and optionally includes flavorants, humectants and/or other tacky substances. Accordingly, smokeless tobacco has a tendency to stick to machine surfaces. Such smokeless tobacco is difficult to feed through pouch forming machines that rely merely on gravity feed techniques. Some pouching machinery incorporates pressurized air in the tobacco feed tubes to augment gravitational delivery of the smokeless tobacco charges. Because drier tobaccos are lighter than wetter tobaccos, the drier tobaccos have a greater tendency to scatter if subjected to jets of pressurized air during feeding, and that scatter can adversely affect the top seal on the associated pouch. 
         [0005]    Prior pouching machines include a tobacco feed mechanism for repetitively discharging a predetermined amount of tobacco from a hopper or the like into a funnel at the upper end portion of a tobacco feed tube. Generally, if gravity is the only active force to move the tobacco down the feed tube, a charge of tobacco released into the tube forms into a column of tobacco traveling down the feed tube such that it is constrained along a significant path length that may be too long for proper filling operations. More particularly, not all of the entrained tobacco may have time to enter the confines of a partially closed pouch before the machine closes and seals the pouch along its upper transverse seam. 
         [0006]    One solution has been to establish a Venturi arrangement at the base of the funnel. In this arrangement, pressurized air is introduced into the feed tube from a manifold through four to six or so small channels. Those small channels are fixed in size and may vary from tube to tube depending on machine tolerances and the like. Any clogging of one or more of the small channels tends to affect tobacco delivery for that feed tube in such a way that the bank of feed tubes performs inconsistently from one feed tube to another. 
         [0007]    Another disadvantage of the foregoing arrangement that the small channels may impart a horizontal or transverse velocity component to the air being introduced through the small channels, with the result that some tobacco flow back may be caused. 
         [0008]    It is desired to have the feed tubes of the bank of tobacco feed tubes operate consistently amongst one another so that filling operations across the entire bank are consistent with one another. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The many innovative features and aspects of the present disclosure will be apparent to those skilled in the art when this specification is read in conjunction with the attached drawings wherein like reference numerals are applied to like elements and wherein: 
           [0010]      FIG. 1  is a schematic view in partial cross section of tobacco dosing apparatus; 
           [0011]      FIG. 1A  is a partial cross-sectional view of the feed apparatus of  FIG. 1 ; 
           [0012]      FIG. 2  is an enlarged, partial cross-sectional view taken through the dose delivery apparatus of  FIG. 1 ; 
           [0013]      FIG. 3  is a detail view of the venturi discharge for the air accelerator unit of the dose delivery apparatus; and 
           [0014]      FIG. 4  is a schematic illustration of a calibration set-up. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    In the production of pouched products, including for example and without limitation, smokeless tobacco products, continuous-motion packaging machinery is often used, and is commonly known as form/fill/seal equipment. Such machinery receives packaging material is substantially continuous strips, receives material to be pouched as a substantially continuous supply from a supply chamber, meters substantially uniform quantities of the material, partially forms a pouch, fills the metered material into the pouch, and finally seals the pouch such that the pouch surrounds that material. While various companies make such equipment, one such company is known as Ropak. 
         [0016]    Typical form/fill/seal equipment produces pouched products in a plurality of parallel streams of packaging material and product. For example, 5, 10, or more parallel lanes may be provided. Operating speeds on the order of 100 cycles per minute are known for each of the parallel lanes. As may be expected, that actual manufacturing speed depends on, for example, product flow characteristics, packaging materials used, and temperature at which filling occurs. 
         [0017]    In accord with this disclosure, a form/fill/seal apparatus  10  typically includes a plurality of suitable dose delivery apparatuses  20  (see  FIG. 1 ) to deliver particulate material in predetermined quantities. Typically, the form/fill/seal apparatus  10  receives a quantity of material to be parsed into predetermined quantities of doses of that material, and then delivers each predetermined quantity of material to a dose delivery apparatus  20 . The dose delivery apparatus  20  moves the predetermined quantity of material to a portion of the form/fill/seal apparatus where a pair of continuous webs  22 ,  24  have been joined with a transverse seal  26  and longitudinal edge seals  26 ,  26 ′ so as to define a pocket or pouch  29 . That pocket or pouch  29  is typically formed around the end  30  of a discharge tube of the dose delivery tube of a corresponding dose delivery apparatus  20 . Alternatively, a single web may be folded into a tubular form about the dose delivery tube and sealed along a single longitudinal edge, whereupon transverse seals applied to the tubular structure define a pouch  29 . Since the dose delivery apparatuses  20  are essentially identical, it will suffice to describe one in detail, with it being understood that the others are substantially the same. The principal difference from one dose apparatus  20  to another resides in its connection with the supply conduit. 
         [0018]    Each dosing apparatus  20  may include a supply conduit  24  connected at one end to the form/fill/seal apparatus  10  and connected at the other end to metering apparatus  12 . The metering apparatus  12  is operable to receive particulate material from the apparatus  10 , parse the particulate material into predetermined portions, doses, or quantities, and then deliver those predetermined portions, doses, or quantities of particulate material to the upper end of the dose delivery apparatus  20  at predetermined time intervals. The predetermined time intervals are selected so that a dose is delivered to the dose delivery apparatus  20  as each partial pouch is ready to be filled. 
         [0019]    While the metering apparatus  12  may take a variety of physical forms and arrangements, a presently preferred arrangement is depicted in  FIG. 1 . More specifically, the metering apparatus  12  preferably includes a pair of generally parallel feed screws  14   a,    14   b  that are arranged so as to be generally perpendicular to the axis of the dose delivery apparatus  20 . A suitable conventional drive mechanism is connected to at least one of the feed screws  14   a,    14   b  such that the two feed screws rotate in the same direction about their respective axes. The drive mechanism is controlled, in a conventional manner, such that the feed screws intermittently rotate, with the time interval of the intermittent rotation being operable to define the predetermined dose of particulate tobacco material delivered to the dose delivery apparatus  20 . 
         [0020]    The feed screws  14   a,    14   b  are preferably designed such that the flight of one screw cleans the flight of the adjacent screw as the two screws rotate. This characteristic of the feed screws  14   a,    14   b  helps assure consistent weight and volume for the predetermined doses being delivered to the dose delivery apparatus  20 . Furthermore, the feed screws  14   a,    14   b  are preferably fabricated from polyether ether ketone (PEEK). 
         [0021]    The metering apparatus  12  also includes a housing  16  (see  FIG. 1A ) within which the feed screws  14   a,    14   b  are positioned and within which those feed screws are mounted for rotation. The discharge end of the housing  16  is positioned above the inlet to the dose delivery apparatus  20 , and may be offset from both the center and the edge as depicted so that particulate tobacco material of a given dose can drop directly in to dose delivery apparatus  20 . The housing  16  closely conforms to the peripheral edge of the flight of each feed screw  14   a,    14   b  so that particulate material does not spill over the edge of the flight and dosing quantity is thus controlled. Preferably, the housing  16  is also fabricated from PEEK. 
         [0022]    The discharge end of the housing  16  is connected to a snout  18  which encloses the end of the housing and couples the housing  16  to the upper end of the funnel  32  of the dose delivery apparatus  20 . The snout  18  assures that particulate tobacco material delivered to the dose delivery apparatus  20  by the feed screws  14   a,    14   b  does not escape and falls into the dose delivery apparatus  20 . In addition, the snout  18  is effective to avoid any external contamination of the particulate tobacco material passing therethrough. The snout  18  is also preferably fabricated from PEEK. 
         [0023]    The use of PEEK as a preferred material for fabrication of the feed screws  14   a,    14   b,  the housing  16 , and the snout  18  has several advantageous and desirable attributes. PEEK functions as a thermal insulator. Thus, use of PEEK between the delivery apparatus  10  and the dose delivery apparatus  20  functions to substantially thermally insulated those apparatuses from one another. Moreover, PEEK substantially reduces and effectively avoids sticking of the particulate tobacco material to the surfaces of the housing, the feed screws, and the snout. Especially where the apparatus must be disassembled and cleaned on a regular basis (e.g., daily), this attribute is highly advantageous because it can reduce the cleaning time and thus add more processing time to the apparatus. 
         [0024]    For purposes of this disclosure, the particulate material may be particulate tobacco that has optionally been blended with other components including, for example, flavorants, humectants, and/or other substances, some or all of which may be tacky or may add tackiness to the particulate tobacco. The particulate tobacco material may include fine cut tobacco that has been comminuted at about 70 cuts per inch. Preferred particulate tobacco material may include up to about 39% oven volatiles. 
         [0025]    The snout  18  of the metering apparatus  12  attaches to a supply funnel  32  (see  FIG. 1 ) at the inlet of the dose delivery assembly  20 . Preferably, the supply funnel  32  is circularly symmetric about an axis passing therethrough. At the bottom end of the supply funnel  32 , and in communication with the interior of the supply funnel, an air accelerator assembly  34  is provided. This air accelerator assembly  34  is operable to provide continuous or pulsed flow of particulate tobacco material. To that end, the air accelerator assembly  34  connects with an air supply conduit  38 , which in turn receives pressurized air from an air supply  40 . The air supply  40  may be a pump, air compressor, plenum chamber, or the like, as may be desired or appropriate for a particular application. A valve  42  may be in fluid communication with the air supply  40  and the air accelerator assembly  34 . As desired, the valve  42  may be operable to interrupt air flow to the air accelerator assembly  34  so as to start, stop, and/or pulse air delivered to the air accelerator assembly  34 . Typically, air at ambient temperature and pressure in the range of 4-18 psig has been found to be suitable for use with an air accelerator assembly  34  of the type described herein. 
         [0026]    At the bottom end, the air accelerator assembly  34  attaches to a dosing tube  36 . That dosing tube  36  preferably terminates in a position where the pouch has been partially formed and can receive particulate material from the discharge end of the dosing tube  36 . 
         [0027]    The air accelerator assembly  34  includes a body  50 , and an internal member  52  which is axially adjustable with respect to the body  50  along an axis  54 . Preferably, the funnel member  32  is rotationally symmetric about the axis  54 . Internal surfaces of the body  50  that are exposed to air flow, as well as surfaces of the internal member  52  that are exposed to air flow or to product flow are also rotationally symmetric with respect to the axis  54 . 
         [0028]    The narrow or lower end of the funnel member  32  preferably includes a radially extending flange  56  having a periphery that corresponds to the outer peripheral surface of the body  50 . In addition, the flange  56  of the funnel member  32  includes a radially extending annular face  64  which is configured to mate with a corresponding radially extending annular face  66  at the upper end of the body  50 . The flange  56  preferably also includes a projecting land  68  which is received in a threaded bore  70  of the body  50 . Cooperation between the projecting land  68  and the associated bore  70  assures that the body  50  and the funnel member  32  are coaxial when joined together. To that end, a plurality of axially extending bolts, or threaded fasteners  58 , may be used to attach the flange  56  and the body  50 . Suitable gasket material may be provided between the abutting surfaces  64 ,  66  of the flange  56  and the body  50 , respectively, if desired. 
         [0029]    Extending longitudinally through the body  50 , along the axis  54 , is a body cavity that includes a threaded, generally cylindrical portion adjacent the funnel member  32 , a frustoconical portion  72  extending downstream from the threaded portion, and a discharge tube connection portion at the lower or bottom end of the body  50 . The frustoconical portion  72  essentially matches the diameter of the threaded portion at it upstream end. In addition, the downstream or lower end of the frustoconical portion  72  is preferably sized to have a diameter corresponding to the inside diameter of the discharge tube  36 . The discharge tube  36  is preferably attached to the downstream end of the body  50  using a suitable conventional attachment. For example, any of a threaded connection, a welded connection, or an adhesively bonded and sealed connection would be satisfactory. 
         [0030]    Turning to the longitudinally movable or adjustable member  52  of the air accelerator assembly  34 , the adjustable member  52  includes a generally cylindrical longitudinal bore  80  extending from the upstream end to the downstream end of the adjustable member  52 . The longitudinal bore  80  preferably has a diameter corresponding to the opening at the discharge end of the funnel member  32  so that particulate material can move downwardly through the funnel member  32  and into the longitudinal bore  80  substantially free of impediment. 
         [0031]    The upper or upstream end of the adjustable member  52  includes a flange portion  84  preferably having a peripherally threaded portion that mates with the threaded portion of the cavity in the body  50 . Cooperation between the externally threaded flange  84  and the internally threaded portion of the body cavity not only secures the adjustable member  52  in the body  50 , but also allows the adjustable member  52  to have its spatial relationship with the body  50  controlled in the longitudinal direction along the axis  54 . 
         [0032]    Preferably, the exterior surface of the adjustable member  52  also includes a frustoconical surface  82  extending from the flange  84  to the distal end  88  at the downstream end of the adjustable member  52 . Preferably, the frustoconical surface  82  meets the longitudinal bore  80  at the distal end  88  of the adjustable member  52  so that an acute sharp angle is defined in the material of the adjustable member  52 . Both the frustoconical surface  82  of the adjustable member  52  and the frustoconical portion of the cavity in the body  50  are preferably polished. Because the facing frustoconical surfaces define a chamber for pressurized air, and because it is desirable to accurately control the flow rate of pressurized air through that chamber, it is believed to be important that those facing frustoconical surfaces be as smooth as possible so as to avoid creating inconsistent resistance to air flow from one air accelerator assembly  34  to another. Accordingly, these facing frustoconical surfaces may be honed and/or polished so that the surface roughness is about 100 microinches or less, and preferably about 30 microinches of less. 
         [0033]    As noted, the cavity of the body  50  and the frustoconical surface  82  of the adjustable member  52  cooperate to define a chamber  90  for pressurized air. That chamber  90  has fluid communication with the conduit  38 , and thus the pump  40  and associated control valve  42  (see  FIG. 1 ). The frustoconical surface  82  (see  FIG. 3 ) of the adjustable member defines an angle a with the axis  54  of its central bore  80 . The frustoconical surface portion  72  of the cavity in the body  50  has an angle b with the axis  54 . The distal end  88  of the adjustable member  52  cooperates with the frustoconical surface portion  72  of the cavity in the body  50  to define a throat or minimum flow area at the downstream end of the chamber  90 . To assure that the flow area through the chamber  90  decreases as air moves downstream toward the throat, the angle a must be less than the angle b. Thus, the chamber  90  (see  FIG. 3 ) effectively comprises a venturi through which pressurized air in the chamber  90  passes as it moves toward and through the reduced area throat  100 . With the longitudinal adjustability of the member  52  in the direction of the arrow  102 , the throat  100  can be adjusted as described more fully below to calibrate and adjust the various air acceleration assemblies of a form/fill/seal machine. 
         [0034]    Since it is also important that air supplied to the chamber  90  (see  FIG. 2 ) through the conduit  38  be constrained to pass out of the chamber  90  only through the throat  100 , a suitable conventional gasket  86  may be provided at the upper end of the chamber  90  between the flange  84  of the adjustable member  52  and the cavity of the body  50 . 
         [0035]    In a preferred embodiment, the body  50  and the adjustable member  52  are constructed from air-hardened tool steel. 
         [0036]    As noted above, the particulate tobacco material processed through the doping tube assembly described above may exhibit tackiness. Accordingly, one or more of the interior surface of the funnel member  32 , the cylindrical channel  80  of the adjustable member  52 , and the interior of the discharge tube  36  may also be coated with polyether ether ketone (PEEK). More preferably, the adjustable member  52  may be constructed entirely from PEEK. Such a coating can improve mechanical and chemical resistance to the particulate material as that material moves through the doping tube assembly. 
         [0037]    It will now be understood by those skilled in the art that the tapered angle a of the adjustable member  52  (see  FIG. 2 ) is greater than the corresponding taper angle b of the frustoconical channel of the body  50  such that as the member  52  is threaded into the body  50  a tapered convergent chamber  80  is defined around a portion of the adjustable member  52  in the space provided between the body  50  and the member  52 . As the member  52  is threaded further and further into the body  50 , the annular discharge orifice or throat  100  at the distal end  88  of the member  52 , and near the base of the body  50 , becomes smaller and smaller. 
         [0038]    Conventional set screws may be provided as a locking means to fix or otherwise lock the relative positions of the member  52  and the body  50 . 
         [0039]    To prepare an air acceleration assembly  34  for use, the assembly  34  and its discharge tube  36  are removed from the tobacco feed system. Then the assembly  34  is calibrated by adjusting the throat of the variable venturi such that a predetermined force is obtained from the associated discharge tube. To that end, the assembly  34  with its discharge tube  36  is positioned in a fixture such that the end  36  at the base of the discharge tube  36  is proximately positioned relative to a suitable conventional a precision scale  112 . The discharge tube  36  is held at a predetermined stand-off distance d above the surface of the precision scale  112 . Preferably that predetermined stand-off distance d between the end of the discharge tube  36  and the precision scale  112  is about 1 mm. 
         [0040]    The feed tube is connected to the source  40  of pressurized air through the conduit  38  (see  FIG. 1 ) and the pressure regulator  42 . The pressure regulator is adjusted to a desired operating pressure for the tobacco pouching machine, for example eighteen psig. Then the longitudinally adjustable member  52  is rotated so that it can be adjusted either up or down relative to the body  50  until the discharge of air through the discharge tube onto the precision scale registers a reading of a predetermined force, preferably in the range of about 20 to about 30 g. For example, the predetermined force or target scale reading might be 25 g. Once body  50  and member  52  have been adjusted so that the desired force reading is obtained, the member  52  is locked in place relative to the body  50  by a set screw or other suitable mechanism to fix the relative position of the body  50  and the member  52 . While a mechanical locking arrangement such as a set screw may be used, the relative positions of the member  52  and the body  50  are most preferably permanently attached to one another, as by welding, so that the calibration is fixed. Otherwise, when the feed tube is cleaned (typically a daily occurrence), recalibration is required. The foregoing steps are repeated for each remaining air acceleration assembly  34  until all assemblies  34  have been calibrated to provide the same predetermined force. 
         [0041]    After each air acceleration assembly  34  has been calibrated and returned to the tobacco feed mechanism, the pouching machine, i.e., the form/fill/seal machine, is ready for operation. Typically, a machine operator adjusts the air regulator  42  ( FIG. 1 ) of the pouching machine to achieve desired pouch loading operation across the bank of feed tubes. 
         [0042]    At one extreme, the air pressure may be too high, in which case the tobacco is driven into the pouch with such force that the pouch tends to open or cause tobacco to enter the first lower transverse seal of the pouch being formed. In another case, the pressure may be too low such that the upper transfer seam is closed and sealing initiated before all the tobacco has fully arrived into the body portion of the pouch. For this latter condition, the operator typically increases the operating pressure. Once the filling sequence has been optimized, the operator is assured uniform filling across the bank of feed tubes, because each air acceleration assembly has been calibrated the same way. 
         [0043]    Preferably, the operating pressure of all feed lanes (or delivery apparatuses  20 ) is adjustable from a single, common regulator  42 . Such arrangement contributes uniform tobacco feeding characteristics across the entire bank of feed lanes to enhance machine operation and performance. The arrangement assures that downstream timing requirements are uniformly met. For example the cutting knives for severing fully formed pouches operate uniformly at a fixed rate across the entire bank of feed lanes. The feed system as taught herein, with its locking down each air delivery system to a common, uniform calibration and uniform adjustment of operating pressure from a common regulator assures that tobacco is delivered at the right time and at the right speed across the bank of feed lanes. During operations, should delivery speed of the feed lanes drift, the operator may return the entire bank of feed lanes back into desired delivery speed by observing a single feed lane while adjusting the common regulator. 
         [0044]    In this description, the word “substantially” is used as an adjective to show that the modified term need not be used literally, but is intended to include equivalent terms which do not materially depart from the spirit and scope of the term. When the word “substantially” is used in connection with a geometric term, it is intended that the geometric term not be interpreted rigidly with respect to geometric definitions. 
         [0045]    To similar effect, the word “about” is used in this description in connection with numerical terms to demonstrate that mathematical precision is not required and that a tolerance of ±10% around that numerical term is intended. 
         [0046]    It will now be apparent to those skilled in the art that this specification provides a novel and unobvious improvement to a metering device for particulate material, particularly where pressurized fluid functions to assist movement of the particulate material through the apparatus. Furthermore, it will be apparent to those skilled in the art that numerous modifications, variations, substitutions, and legal equivalents exist for features of the invention described herein. Accordingly, it is expressly intended that all such modifications, variations, substitution, and legal equivalents that fall within the spirit and scope of the appended claims be embraced thereby.