Abstract:
The present invention is an air conveyor system which has a blower in communication with a plenum. The blower provides air to the plenum to move the objects within the plenum. The present invention includes a plurality of dampers disposed at predetermined locations along the plenum with the dampers being normally open. A sensor device senses the location where the objects have accumulated within the plenum. Furthermore, the present invention includes a closing device for closing the damper which is at the location where the objects have accumulated within the plenum. The closing of the damper is based upon the sensed accumulated location. The system includes a variable speed blower for providing air to move objects within the plenum. The objects are either in an accumulated or unaccumulated state within the plenum. A velocity measuring device measures the velocity of the objects, and an adjustment device which is connected to the velocity measuring device adjusts the speed of the blower to a predetermined speed based upon the velocity of the unaccumulated objects.

Description:
This is a continuation of United States patent application Ser. No. 08/826,157, filed Mar. 27, 1997. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to air conveyor systems and more particularly to flow control in air conveyor systems. 
     2. Description of the Related Art 
     In general, air conveyance systems are accumulators where the conveyor fills with product and then empties out. Common applications of air conveyor systems include handling two piece aluminum cans and blow molded plastic bottles. 
     An air conveyance system provides motive force to the product being conveyed through momentum transfer from an air jet to the product. When the system is full of product, the air pressure must be set high enough to clear out the entire weight of all the product present. When the system is empty and single items are moving through the system, there is a tendency for the single objects to move too fast and either become damaged or jammed. The difference between accumulated and unaccumulated flow may be analogized to the difference between bumper-to-bumper rush hour traffic and single cars moving at the speed they choose. 
     A conventional two pressure design is shown in FIG.  1 . In this design, a blower  50  pressurizes a plenum  54  which supplies air  56  to the jets  58  which impart momentum to the product. When the sensor tells the control system that the subject fan zone has become accumulated (i.e., backed up), then the automatic damper  62  opens, supplying more air  56  into the plenum  54 . Inlet dampers, outlet dampers, and variable speed drives which change the motor&#39;s revolutions per minute (RPM) have been-used as methods for changing plenum pressure. 
     A second conventional two pressure design is shown in FIG.  2 . In this design the plenum is split by a divider  68 . A blower  70  pressurizes the primary plenum  74 , and multiple dampers  78  in parallel regulate the flow of air  80  into the secondary plenum  82 . Louvers which form the air jets  86  that drive the product are connected to the secondary plenum  82 . U.S. Pat. No. 5,222,840 is representative of this type of conventional design. 
     A disadvantage with the first approach is that the length of the control zone is the same as the blower zone. Once the control zone becomes too long then the advantage of the two pressure system is lost. The sensor which switches the zone to high pressure must be located so far from the upstream end of the zone that the product has a chance to gain terminal speed before hitting the back end of the accumulated pack—thereby causing damage to the product and to the pack. 
     Moreover, the use of smaller blowers and a shorter blower zone in order to shorten the control zone increases both the cost of the equipment and the cost to install it. Lastly, a disadvantage with the second approach is the sheet metal fabrication cost to divide the two plenums. 
     SUMMARY OF THE INVENTION 
     The present invention is an air conveyor system which has a blower in communication with a plenum. The blower provides air to the plenum to move the objects within the plenum. The present invention includes a plurality of dampers disposed at predetermined locations along the plenum with the dampers being normally open. A sensor device senses the location where the objects have accumulated within the plenum. Furthermore, the present invention includes a closing device for closing the damper which is at the location where the objects have accumulated within the plenum. The closing of the damper is based upon the sensed accumulated location. 
     The present invention also includes a system for moving objects within a plenum that includes a variable speed blower for providing air to move objects within the plenum. The objects are either in an accumulated or unaccumulated state within the plenum. A velocity measuring device measures the velocity of the objects, and an adjustment device which is connected to the velocity measuring device adjusts the speed of the blower to a predetermined speed based upon the velocity of the unaccumulated objects. A velocity measuring device uses the two pressure system with short control zones. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a schematic showing a first conventional air conveyor system; 
     FIG. 2 is a schematic showing a second conventional air conveyor system wherein the plenum is split; 
     FIG. 3 is an entity relationship diagram showing the interrelationships regarding the control of the dampers; 
     FIG. 4 is an entity relationship diagram showing the interrelationships of the control for the speed of a blower; 
     FIG. 5A is an entity relationship diagram showing the interrelationships of the damper control and the blower control systems; 
     FIG. 5B is a schematic view showing the zone sensor arrangement for the air conveyor system; 
     FIG. 6 is a schematic view of an air conveyor which handles cans; 
     FIG. 7 is a cross-sectional view of the air conveyor of FIG. 6 taken through  7 — 7 ; 
     FIG. 8 is a schematic view showing the blower and plenum opening with respect to the blower; 
     FIG. 9 is a cross-sectional view of the air conveyor system of FIG. 8 taken through  9 — 9 ; 
     FIG. 10 is a schematic view showing a sequencing damper within the air conveyor system; 
     FIG. 11 is a schematic view showing the can-flow area within the air conveyor system; 
     FIG. 12 is a schematic view showing the accumulation/unaccumulated measurement device within the air conveyor system; 
     FIG. 13 is a cross-sectional view of the air conveyor system of FIG. 12 taken through  13 — 13 ; 
     FIG. 14 is a schematic view showing the top cover for the direct measurement device of the air conveyor system; 
     FIG. 15 is a cross-sectional view of the air conveyor system of FIG. 14 taken through  15 — 15 ; 
     FIG. 16 is a schematic view showing the plenum of the air conveyor system for handling plastic bottles; 
     FIG. 17 is a schematic view of the bottle air conveyor system showing the blower and plenum opening; 
     FIG. 18 is a schematic view showing the sequencing damper for the bottle air conveyor system; 
     FIG. 19 is a schematic view showing the bottle flow area for the bottle air conveyor system; 
     FIG. 20 is a schematic view showing the accumulation/unaccumulated measurement device for the bottle air conveyor system; 
     FIG. 21 is a cross-sectional view of the bottle air conveyor system of FIG. 20 taken through  21 — 21 ; 
     FIG. 22 is a schematic view showing the direct measurement device for the bottle air conveyor system; and 
     FIG. 23 is a cross-sectional view of the bottle air conveyor system of FIG. 22 taken through  23 — 23 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 3, the present invention includes a blower  100  which provides pressure within a plenum  104  to move objects  108 . The blower  100  has a discharge  112  at the downstream end  116  of the plenum  104 . The objects  108  have a point  120  where the objects have accumulated on the plenum  104 . The point  120  is sensed by an accumulator sensor  124  which provides accumulation point data to a controller  128 . Controller  128  issues open and close commands to dampers  132  which are situated within plenum  104 . The controller  128  issues commands based upon the accumulation point data. FIGS. 5B and 10, which are discussed below, show the physical structure of FIG.  3 . 
     Referring to FIG. 4, the RPM  150  of blower  100  is controlled based upon the unaccumulated single product velocity  154  (i.e., while objects are in the unaccumulated state  156  within the plenum). If this velocity drops too low, then the objects  108  “bunch up” and “stall out.” If this velocity is too high, then damage to the objects  108  and increased jamming occurs. In the accumulated state  158 , when the objects  108  are backed up within the plenum, the pressure settings are typically much less critical. 
     The present invention measures the unaccumulated single product velocity  154  through a Velocity Measurement Device (VMD  162 ) and adjusts the RPM  150  of the blower  100  to control the unaccumulated single product velocity  154  at the desired level. The economics of the VMD  162  and the blower Variable Speed Drive usually require a long blower zone and fewer number of blowers to make the system cost effective. In addition, a two pressure system assists to control the unaccumulated single product velocity  154  without a serious concern for recovery from accumulation. 
     The following equations illustrate the relationship between the unaccumulated single product velocity and accumulation efficiency. For a single lane system, the relationship is as follows:            12   ″       ContainerDiameter        (   inches   )         =   ContainersPerFootAccumulated             Rate     Single                 Container                 Speed       =   ContainersPerFtUnaccumulated                          
     where Rate is expressed as Containers Per Minute and Single Container Speed is expressed as Feet Per Minute.        Efficiency   =               Containers                 Per               Ft                 Accumulated           -           Containers                 Per               Ft                 Unaccumulated               Containers                 Per                 Ft                 Accumulated                              
     With respect to mass flow, the following equations apply:            [       12   ″       ContainerDiameter        (   inches   )         ]          [       12   ″       ContainerDiameter        (   inches   )         ]       =   ContainersPerSquareFootAccumulated             Rate     Single                 Container                 Speed       =   ContainersPerFtUnaccumulated             Efficiency   =               Containers                 Per               Ft                 Accumulated           -           Containers                 Per               Ft                 Unaccumulated               Containers                 Per                 Ft                 Accumulated                                           
     For the preferred embodiment, the VMD  162  operates by placing two sensors at a known distance from each other and measuring the time delay between the product reaching the first sensor  166  and the second sensor  170 . Once this value is measured, the control system  174  checks that the system is, in fact, unaccumulated. If the system is unaccumulated, then this velocity value is sent to the control system which for the preferred embodiment is a central processor  180 . This velocity value is typically imprecise because of the nature of air conveyors in general. 
     For this reason, the central processor  180  stores the measured velocities over a period of time in data store  184  and performs a series of statistical functions including ignoring certain data that is invalid and finding a central tendency such as a mean or median. In the preferred embodiment since the conditions vary over a period of hours and the measurement can be done at a rate of hundreds of points per minute, large samples are taken before any adjustment of the output is required. With large samples, the power of statistical manipulation provides highly precise measurements of the actual conditions on the conveyor. 
     For the preferred embodiment, the statistical processing by the central processor  180  includes: calculating the mean; disregarding all points which are outside of two standard deviations from the mean; recalculating the mean; subjecting the mean value to a null hypothesis where the mean is the same value as the previous calculations. If there is a ninety percent probability that they are different, then the difference is calculated. The difference is multiplied by an RPM factor (which is empirically determined) in order to get the RPM difference. The blower RPM is changed by this calculated value. Depending on the application, sample sizes vary, but typically they can be rather large in the order of 1,000. 
     Additionally, for the RPM changes, the following equation is also used in the preferred embodiment: 
     
       
         
           Q=K{square root over (P)} 
         
       
     
     Where Q is flow in cubic feet per minute; P is pressure in inches water column and K is a constant which converts units and accounts for open area and takes into account the flow coefficient for the orifice itself;          P   2     =       (       P   1          (       RPM   2       RPM   1       )       )     2               Q   2     =       Q   1          (       RPM   2       RPM   1       )                 HP   2     =       (       HP   1          (       RPM   2       RPM   1       )       )     3                            
     Which follows since HP α P×Q          Q   1     =       K          P   1                     and                   Q   2       =     K          P   2                     Q   2     =     K              P   1          (       RPM   2       RPM   1       )       2                   Q   2     =     K        P          (       RPM   2       RPM   1       )                              
     FIG. 5A shows the operational interrelationship between the control of the dampers  132  and the blower  100 . The objects  108  which move on the plenum  104  have their accumulation point within the plenum  104  sensed by an accumulator sensor  124 . A controller  200  receives the accumulation point data from the accumulator sensor  124  and controls the dampers  132  based upon the accumulation point data. Furthermore, the controller  200  adjusts the RPM of blower  100  based upon the unaccumulated single product velocity as supplied by the VMD  162 . 
     Referring to FIG. 5B which is a sideview of the preferred embodiment of the present invention, the inlet  202  of the blower  100  for the plenum  104  is at the downstream end of the blower zone. Top cover  422  lies above can  280  which is on deck  284 . FIG. 5B shows eight accumulator sensors ( 211 ,  212 ,  213 ,  214 ,  215 ,  216 ,  217 ,  218 ). Seven dampers correspond to the first seven accumulator sensors. The seven dampers are D1  221 , D2  222 , D3  223 , D4  224 , D5  225 , D6  226 , and D7  227 . Also, a VMD  162  and turning vanes  240  are shown on FIG.  5 B. For the preferred embodiment for the arrangement shown in FIG. 5B, blower  100  is a 20 horse power variable speed blower and has no outlet damper. 
     While FIG. 5B shows an eighty foot blower zone and a four foot wide conveyor arrangement, it is to be understood that the present invention is not limited to these dimensions nor to the number of sensors or dampers shown. Also, while FIG. 5B shows a ten foot distance between successive dampers and an eight foot distance between a sensor and its corresponding damper, it is to be understood that the present invention is not limited to these dimensional arrangements. For example, more dampers, and hence, correspondingly more sensors could be used within this blower zone or even less dampers and less sensors. 
     The inlet  202  at the discharge end of the blower zone allows multiple dampers in the plenum  104  to open and close, thus dividing the plenum  104  into two zones, one high pressure, and one low pressure with the dividing line between the two matching the point to which the product has accumulated. With respect to the damper and sensor arrangement of 
     FIG. 5B, the following table is used in the preferred embodiment to control the dampers based upon sensor readings of where the product has accumulated: 
     
       
         
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 D1 
                 D2 
                 D3 
                 D4 
                 D5 
                 D6 
                 D7 
                 Fan RPM 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 S1 Covered 
                 O 
                 O 
                 O 
                 O 
                 O 
                 O 
                 O 
                 High 
               
               
                 S2 Covered 
                 C 
                 O 
                 O 
                 O 
                 O 
                 O 
                 O 
                 High 
               
               
                 S3 Covered 
                 O 
                 C 
                 O 
                 O 
                 O 
                 O 
                 O 
                 High 
               
               
                 S4 Covered 
                 O 
                 O 
                 C 
                 O 
                 O 
                 O 
                 O 
                 High 
               
               
                 S5 Covered 
                 O 
                 O 
                 O 
                 C 
                 O 
                 O 
                 O 
                 High 
               
               
                 S6 Covered 
                 O 
                 O 
                 O 
                 O 
                 C 
                 O 
                 O 
                 High 
               
               
                 S7 Covered 
                 O 
                 O 
                 O 
                 O 
                 O 
                 C 
                 O 
                 High 
               
               
                 S8 Covered 
                 O 
                 O 
                 O 
                 O 
                 O 
                 O 
                 C 
                 High 
               
               
                 S8 Uncovered 
                 O 
                 O 
                 O 
                 O 
                 O 
                 O 
                 O 
                 Low 
               
               
                   
               
             
          
         
       
     
     The letter “O” denotes that the damper is open and “C” denotes that the damper is closed. 
     The present invention provides for: long blower zones with short control zones with no need to split the plenum; the ability to set control zones at whatever length is required for the particular application; unidirectional turning vanes at blower to plenum connection which are correctly designed for the application for lower pressure loss; and the ability to compensate for high plenum velocities, where low pressures would normally be observed nearest the blower, by adjusting the sequencing dampers to a partially closed position when open. 
     FIG. 6 shows the preferred embodiment for an air conveyor system which conveys cans. Cans (for example, can  280 ) are conveyed upon deck  284 . Plenum  104  is also shown for reference. 
     Referring to FIG. 7, can  280  is conveyed upon deck  284 . At location  288 , zeebar  292  is spot welded to deck  284 . For the preferred embodiment, the deck  284  is a 33% perforated plate. At location  296 , zeebar  292  is fastened onto a sheet  300  via a stud which is “shot onto” zeebar  292  with a stud gun. Sheet  300  is perforated and provides additional structural support for deck  284 . 
     FIG. 8 shows the blower and plenum opening arrangement for the preferred embodiment. Blower  310  is a direct drive vane axial blower. Box  314  is lined with sound absorbing material and additionally has sound absorbing material at location  318 . 
     Elbow  322  directs the air flow  326  towards a “bolt in” turning vane assembly  330 . Plenum  104  and deck  284  are also shown in FIG.  8 . Moreover, the preferred embodiment uses filters  338  through which air flows into the plenum  104 . 
     FIG. 9 is a sideview of the present invention and it shows air flow and also how sound is abated in the preferred embodiment. Air flow  350  passes through air filter  354 . A sheet metal tube  358  is bolted onto a tube-shaped blower  362  via bolt  366 . Sheet metal box  370  is lined with sound absorbing foam  374 . 
     FIG. 10 shows the configuration of a sequencing damper for the preferred embodiment. Can  280  travels upon deck  284  which is supported by zeebar  292 . Deck  284  is perforated and includes louvers. Zeebar  292  is fastened upon perforated sheet  300 . 
     A damper plate which possibly could be perforated, is shown in its closed position at location  396   a.  The damper, when it is partially open, is shown at location  396   b.  The damper is welded onto a round shaft  400 . The bottom of the plenum is shown at location  404 . 
     FIG. 11 shows the can flow area. Can  280  is conveyed upon deck  284  which lies above plenum  104 . Above the can  280  is a top cover perforated stainless sheet (top cover  422 ) which is supported by a top cover support angle  426 . Also, the preferred embodiment includes a side rail bracket  430  and side guards  434 . 
     FIG. 12 illustrates the use of the accumulation/unaccumulated measurement device for the preferred embodiment. Can  280  is conveyed upon deck  284  which lies below top cover  422 . Side guards  434  are provided for can  280 . For the preferred embodiment, sensor  456  is a proximity induction sensor block. Such sensors are available from Allen-Bradley. 
     Referring to FIG. 13, sensor  456  lies between side guards  434  and is greater than one can diameter for the preferred embodiment. For reference, deck  284  is shown. 
     FIGS. 14 and 15 illustrate the direct measurement aspect to the present invention. FIG. 14 shows top cover  422 . Referring to FIG. 15, the preferred embodiment uses a plastic top cover insert  489 . Six tube proximity sensors ( 491 ,  492 ,  493 ,  494 ,  495 , and  496 ) are shown with each being for the preferred embodiment one-half the diameter of the can. The dimensional arrangement for the preferred embodiment includes having tube proximity sensor  491  being two diameters of the can away from tube proximity sensor  494  and being three quarters of the diameter of the can away from tube proximity sensor  493 . 
     If tube proximity sensor  492  is broken (i.e., activated) before tube proximity sensors  491  and  493 , and tube proximity sensor  495  is broken before tube proximity sensors  494  and  496 , and tube proximity sensor  492  is not broken by another can before tube proximity  495  is broken, then a measurement is taken. 
     FIG. 16 illustrates the preferred embodiment for an air conveyor system which conveys plastic bottles, such as PET bottles. A plenum is shown at location  500 . A drive slot  504  is used within the preferred embodiment to direct air toward the open end of the bottle. An aluminum channel  508  is fastened to deck  512  via a through bolt  516  and weld nut  520 . Deck  512  is fastened to the structure  524  which forms the plenum  500  via a sheet metal screw  528 . For the preferred embodiment, the aluminum channel is 1.5 inches by 1.5 inches and is fastened to a neck guide  532  via a through bolt  536  and weld nut  540 . The neck guide  532  for the preferred embodiment is made of stainless steel and is used to guide bottle  544 . 
     FIG. 17 shows the preferred embodiment for the blower and plenum opening for an air conveyor system which conveys plastic bottles. Blower  550  is mounted directly to plenum  554  in the preferred embodiment and includes a blower direct drive (e.g., a 3.5 or 12.25 inch Chicago SQAD). Within plenum  554  are “bolt on” turning vanes  558  which direct air flow to transport bottle  544 . 
     FIG. 18 shows the configuration for the preferred embodiment for a sequencing damper for a bottle air conveyor system. A plenum flange  566  is used in the preferred embodiment to attach adjacent conveyor sections. Upon deck  570  is a deck diffuser perforated plate  574 . Upon a round shaft  578  is welded a damper  582 . 
     FIG. 19 shows the configuration for the bottle flow area. Plenum  590  and drive slot  594  lie above deck  598 . The neck guide  602  is connected to deck  598  through channel  606 . The neck guide  602  guides bottle  610 . Also, side guard  614  guides bottle  610  and is connected to side rail bracket  618 . 
     FIG. 20 shows the preferred embodiment for performing the accumulation/unaccumulated measurements. Neck guide  626  is connected to deck  630  via channel  634 . Channel  634  has an opening as indicated at location  638 . The openings at location  638  allow a photoeye sensor  642  to be able to have a line of sight with respect to reflector  646 . The photoeye sensor  642  is available from such companies as Allen-Bradley. Referring to FIG. 21, photoeye sensor  642  shines a beam  644  upon reflector  646 . The photoeye sensor  642  detects the threaded portion  650  of bottle  654  via beam  644 . 
     FIG. 22 shows the preferred embodiment with respect to the direct measurement device. Drive slot  660  is situated above deck  664 . Neck guide  668  is connected to deck  664  via channel  672 . Channel  672  has an opening as indicated at location  676 . A photoeye sensor  680  is able to shine a beam to reflector  684  with this type of arrangement. Photoeye sensor  680  is available from such companies as Allen-Bradley. 
     Referring to FIG. 23, a first sensor  700  shines a beam upon a first reflector  704 . At a distance of two diameters of bottle  716  away from the first sensor  700  is positioned a second sensor  708  in the preferred embodiment. Second sensor  708  shines a beam upon a second reflector  712 . If the light beam from the second sensor  708  is broken before the light beam from the first sensor  700  is broken for a second time, then the measurement is taken for calculating the velocity of the product flow. 
     The embodiment which has been set forth above was for the purpose of illustration and was not intended to limit the invention. It will be appreciated by those skilled in the art that various changes and modifications may be made to the embodiment described in this specification without departing from the spirit and scope of the invention as defined by the appended claims.