Abstract:
A vibratory conveyor for transporting an object includes a spiral deck enclosed in a housing having passageways for allowing air flow between adjacent deck tier segments. In addition, the conveyor may include two concentric spiral decks operably coupled to one another, wherein a vibratory force is capable of simultaneously advancing objects both up the first spiral deck and down the second spiral deck.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     The present application is a divisional of U.S. application Ser. No. 11/153,677, filed on Jun. 15, 2005, which claims the benefit of U.S. Provisional Application No. 60/604,227, filed on Aug. 25, 2004, both of which are hereby incorporated by reference in their entirety in the present application. 
     
    
     FIELD OF THE DISCLOSURE  
       [0002]     The present disclosure generally relates to vibratory process equipment and, more particularly, to vibratory spiral conveyors for transporting work pieces.  
       BACKGROUND OF THE DISCLOSURE  
       [0003]     Vibratory spiral conveyors are generally known in the art. Such apparatus typically includes a spiral deck, formed in the shape of a helix, and a source of vibration operatively coupled to the deck. The spiral conveyor may be a brute force system, such as that disclosed in U.S. Pat. No. 2,927,683 to Carrier, or a two-mass system, as disclosed in U.S. Pat. No. 5,024,320 to Musschoot.  
         [0004]     Spiral conveyors are often used to heat or cool work pieces or granular material. With foundry castings, for example, red hot castings (which may have a temperature of approximately 1000 degrees F. or more) are fed into the spiral conveyor. Cool air is directed over the castings as the castings travel up the spiral, thereby to reduce the temperature of the castings. Conventional spiral conveyors direct air from a center axis of the conveyor outwardly, with or without nozzles for directing the air toward the castings. The air is exhausted out an exterior of the spiral conveyor.  
         [0005]     In one conventional design, air is generally directed radially across the spiral conveyor from the center core inlets to the outer periphery outlets. As a result, the inner facing side of the castings (or the inner row, should more than one row of castings be fed into the conveyor) will receive a lower temperature air than the outer facing side (or outer row).  
         [0006]     In another conventional design, both the air inlet and air outlet are positioned at the outer periphery of the spiral conveyor. As the air enters the spiral conveyor area, it passes about the center core in at least two separate sub-streams. The air then exhausts from the spiral conveyor through a common outlet.  
         [0007]     In addition, the deck used in conventional spiral conveyors is typically constructed of plate steel. As a result, when viewed in cross-section, the conveying surface defined by the deck is typically “flat” across the width of the deck. Stated alternatively, the conveying surface is substantially linear across its width.  
         [0008]     While a flat deck is satisfactory for many applications, it may cause unintended and undesirable results when used to convey certain objects. For example, when conveying generally cylindrical objects such as cam shafts along a flat deck, the objects may roll transversely across the width of the deck, and therefore are not located on the deck with any degree of certainty. In addition, the cylindrical objects may become oriented transversely across the deck, and therefore more easily roll into and possibly damage other objects on the deck.  
         [0009]     Flat decks are also difficult to employ for certain path configurations. In a spiral conveyor, for example, it is preferable to form the deck in a helicoid shape. To approximate the helicoid shape with flat plate steel, several bends such as cross crimps are typically formed in the deck. Such cross crimps, however, create abrupt changes in the pitch of the deck and cause the conveying surface to be non-linear across its width. Consequently, the cross-crimps create localized high wear area and non-uniform stresses in the deck. These problems are exacerbated during thermal expansion and contraction, which can be significant when the spiral conveyor is used for heating or cooling of the objects being conveyed. In addition, the need for cross crimps or other bends in the deck increases manufacturing costs and makes assembly more difficult, especially for conveyors that are constructed as multiple sub-assemblies that are mated together, such as for large conveyor sizes. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a side elevation view of a vibratory spiral conveyor;  
         [0011]      FIG. 2  is an enlarged sectional side view of the conveyor of  FIG. 1 ;  
         [0012]      FIG. 3  is an enlarged cross-sectional view taken along line  3 - 3  of  FIG. 1 ;  
         [0013]      FIG. 4  is a side elevation view of a vibratory spiral conveyor;  
         [0014]      FIG. 5  is an enlarged, partially schematic, sectional side view of the conveyor of  FIG. 4 ;  
         [0015]      FIG. 6  is a plan view of the conveyor of  FIG. 4 ;  
         [0016]      FIG. 7  is an enlarged sectional side view of a portion of the conveyor deck before the bending force is applied to the deck;  
         [0017]      FIG. 8  is an enlarged sectional side view of a portion of the conveyor deck with a bending force applied to the deck;  
         [0018]      FIG. 9  is a plan view of a section of the deck;  
         [0019]      FIG. 10  is a plan view of a section of a spiral conveyor having air flow passages around the deck;  
         [0020]      FIG. 11  is a side elevational view of the spiral conveyor portion illustrated in  FIG. 10 ;  
         [0021]      FIG. 12  is side elevational view, in cross-section, of a spiral conveyor having two spiral decks; and  
         [0022]      FIG. 13  is a plan view of the spiral conveyor of  FIG. 12 . 
     
    
     DETAILED DESCRIPTION  
       [0023]     Referring to  FIGS. 1 and 2 , a spiral conveyor  10  is shown having a frame  12  supporting a spiral deck  16 . As used herein, the word spiral includes helix and helicoid shapes. The frame  12  is resiliently supported above the ground or mounting surface by isolation means, such as springs  18 . An exciter mass  20  and vibration generators  22  are resiliently coupled to the trough frame  12 , such as by springs  25  ( FIG. 2 ). Any generally known vibration generators may be used, such as motors having rotating shafts carrying eccentric weights.  
         [0024]     A housing  15  is provided for enclosing the spiral deck  16  and defining a conveyor chamber  17 . As best shown with reference to  FIG. 3 , the spiral deck includes an inner edge  19  and an outer edge  21 . The housing  15  has a cylindrical inner wall  38  coupled to the spiral deck inner edge  19  and a cylindrical outer wall  50  coupled to the spiral deck outer edge  21 . The housing  15  may also include a top wall  23  ( FIG. 2 ), so that the housing  15  completely encloses the spiral deck  16  but for a housing inlet  24  and outlet  26 . Accordingly, the housing  15  and spiral deck  16  define the conveyor chamber  17 , which has a spiral configuration in the illustrated embodiment. A plurality of access doors  52  ( FIG. 1 ) may be formed in the housing outer wall  50  for accessing the conveyor chamber  17  and deck  16 .  
         [0025]     In the illustrated embodiment, the spiral deck  16  is oriented to vertically elevate work pieces, such as hot castings, from the inlet  24  to the outlet  26 . The work pieces may be transferred from an origination point, such as a molding line, to the inlet  24  by any conveying means, such as by a linear vibratory or other type of conveyor (not shown). The spiral deck  16  is formed in a helical pattern so that, as the work pieces move circumferentially around the deck, they are also elevated in the vertical direction. At the outlet  26 , the work piece may be deposited onto an outlet transport (not shown), which may also be a conveyor. While the conveyor  10  is described herein as conveying the work pieces vertically upward, the inlet and outlet may be reversed so that the work pieces are conveyed vertically downward along the spiral deck  16 .  
         [0026]     When viewed in elevational cross-section, as shown in  FIG. 2 , the spiral deck  16  defines a plurality of stacked tier segments  14 . The tier segments  14  are vertically aligned so that adjacent tier segments  14  define upper and lower boundaries of a cross-sectional area of the conveyor chamber  17 .  
         [0027]     The vibration generators  22  may be controlled in any known fashion to produce the desired vibrational motion of the trough frame  12  and coupled spiral deck  16  to advance the work pieces along the deck  16 . For example, the motors may be rotated in opposite directions (i.e., counter-rotated) and controlled to maintain a desired phase angle between the eccentric weights. While the illustrated embodiment is a two mass system, it will be appreciated that the conveyor  10  may be provided as a single mass or brute force system.  
         [0028]     An air distribution system is provided for directing air over the work pieces as they travel along the spiral deck  16 . As best shown in  FIG. 2 , a plenum housing  29  defines an inlet air plenum  30  formed near a top of the spiral deck  16  and within a central chamber  56  defined by the housing inner wall  38 . A pair of air inlet ducts  32  is connected to the plenum housing  29  by flexible joints  34 . Alternatively, a single inlet duct  32  or more than two inlet ducts  32  may communicate with the inlet air plenum  30 . Extending downwardly from the inlet air plenum  30  is a plurality of vertical air conduits  36 . As best shown in  FIG. 3 , the housing inner wall  38  forms outer portions of each conduit  36 , while concave chamber walls  40  form a remainder of each conduit  36 . Air flow may be generated by a positive air pressure source in fluid communication with the inlet air plenum  30  or a negative air pressure source in fluid communication with the central chamber  56 .  
         [0029]     A plurality of air distribution chambers  42  is attached to a bottom side of the spiral deck  16  and communicates with each vertical air conduit  36 . The air distribution chambers may be oriented to extend generally horizontally and, as best shown in  FIG. 3 , may be aligned generally radially between the housing inner wall  38  and housing outer wall  50 . In the illustrated embodiment, a pair of air distribution chambers  42  on each spiral deck tier portion  14  fluidly communicates with a respective vertical air conduit  36 . Alternatively, each air conduit  36  may fluidly communicate with a single air distribution chamber  42  or more than two air distribution chambers  42  on each spiral deck tier portion  14 . While  FIG. 3  illustrates a single tier portion  14  of the spiral deck  16 , it will be appreciated that similar sets of air distribution chambers  42  may be constructed on each of the spiral deck tier segments  14 , so that each conduit  36  may communicate with multiple vertical levels of air distribution chambers  42 .  
         [0030]     Each air distribution chamber  42  includes a plurality of spaced nozzles  44  oriented to direct air flow downwardly toward the next lower tier. The nozzles  44  may be apertures formed in a bottom of the air distribution chambers  42 . The apertures are arranged across at least a portion of a lateral width “W” of the spiral deck  16  to form an air distribution pattern. In the illustrated embodiment, the apertures are generally equally spaced across the entire lateral width “W” of the spiral deck  16 .  
         [0031]     The vertical air conduits  36  and horizontal air chambers  42  may be formed of structural steel members, such as channels and angles, to provide structural support to the spiral conveyor  10 . In this case, the conduits  36  and chambers  42  provide the dual functions of air distribution and structural support.  
         [0032]     The vibratory conveyor  10  further provides for exhaust of air out of the conveyor chamber. As best shown in  FIG. 3 , a plurality of outlet openings  54  are formed in the housing inner wall  38 , each opening  54  being positioned between adjacent vertical air conduits  36 . The outlet openings  54  fluidly communicate with the central chamber  56  defined by the housing inner wall. An air exhaust outlet  58  fluidly communicates with the central chamber  56  and is coupled, such as by flexible joint  60 , to exhaust duct  62 . The exhaust duct  62  may communicate with an air vacuum source  63  (schematically illustrated in  FIG. 2 ), such as an exhaust fan, to create air flow through the air distribution system. In the illustrated embodiment, the plenum housing  29  has a generally annular shape, so that an inner edge  31  of the plenum housing  29  defines the exhaust outlet  58 .  
         [0033]     In operation, the air vacuum source pulls air through the inlet ducts  32  to the inlet air plenum  30 . The air stream flows from the plenum through the air conduits  36  and air distribution chambers  42  for discharge through the nozzles  44 , which evenly distribute air across the entire lateral width “W” of the spiral deck  16 . The air vacuum source is preferably sized so that the air stream discharged from each nozzle  44  has a velocity sufficiently high to create non-laminar flow around the work pieces. By creating a non-laminar air flow, the heat transfer coefficient for the system is increased, thereby increasing heat transfer, which is beneficial for both heating and cooling applications. The air exits the conveyor chamber  17  through the outlet openings  54  and into the central chamber  56 , where it is discharged through the exhaust outlet  58 .  
         [0034]     The conveyor  10  may include a fines collection system for collecting any fines entrained in the air stream passing through the conveyor chamber  17 . The objects or work pieces loaded into the conveyor  10  may include unwanted debris, such as sand, sprue, or other fines material. To remove this debris from the air stream, the fines collection system may include a catch floor  70  extending across a bottom of the central chamber  56  and coupled to the housing  15  below the lowest outlet opening  54 . In the illustrated embodiment, the catch floor includes a conical center portion  72  attached to a frusto-conical outer portion  74 . A fines discharge opening  76  is formed at an outer periphery of the outer portion  74  and communicates with a fines discharge chute  78  ( FIG. 1 ). The discharge opening communicates with atmosphere via the chute  78 , and therefore the negative pressure in the central chamber  56  creates a pressure differential that tends to hold the fines within the chamber  56 . As schematically illustrated in  FIG. 1 , an air lock  80  may be provided in the chute  78  to allow and control discharge of fines through the chute.  
         [0035]     In operation, air is discharged from the nozzles  44  at a relatively high velocity, so that fines may become dislodged from the work pieces and entrained in the air stream. The air stream then passes through the outlet openings  54 , which causes a pressure drop and associated reduction in velocity of the air stream as it enters the central chamber  56 . The reduced velocity causes the fines entrained in the air stream to drop to the catch floor  70 . The vibratory motion of the spiral deck  16  and attached catch floor  70  moves the particles toward an outer periphery of the catch floor outer portion  74 . The circular component of the vibratory motion conveys the particles circumferentially about the floor periphery until the particles reach the discharge opening  76 , at which point they travel down the discharge chute  78  and into the air lock  80 . The air lock  80  may be operated to periodically interrupt fluid communication between the chute  78  and the central chamber  56 , thereby to allow a batch of fines to be discharged from the chute  78  for collection.  
         [0036]     The fines collection system utilizes the existing internal structure of the spiral conveyor to collect and discharge particles entrained in the air stream. As a result, separate filter houses are not required and the space required for spiral conveyor apparatus is reduced.  
         [0037]      FIGS. 4-9  illustrate an alternative embodiment of a conveyor deck having a conveying surface and a back surface. A rib is attached to the back surface and a “force assembly” is coupled to the rib. By applying a force to the rib with the force assembly, the deck may be bowed either concavely or convexly. If formed with a concave bend, the conveying surface of the deck, when viewed in cross-section, will have a localized low point adjacent the rib that defines a deck along which objects are conveyed. The concave shape also tends to orient cylindrical objects longitudinally on the deck, defined herein as parallel to the direction of travel. Additionally, when used in a spiral conveyor, the bowed cross-sectional shape allows the deck to be formed more nearly to a pure helicoid, where the pitch of the deck is consistent along the entire conveyor path and each radial cross section of the deck will have linear opposing deck edges, regardless of whether the deck is curved concavely or convexly. While the disclosed embodiment is a spiral conveyor, it will be appreciated that the bowed deck shape provides advantages for other conveyor path configurations, including linear, curved, and inclined paths.  
         [0038]     Referring to  FIGS. 4 and 5 , a spiral conveyor  110  is shown having a frame  112  supporting a spiral deck  116 . The frame  112  is resiliently supported above the ground or mounting surface by isolation means, such as springs  118 . An exciter mass  120  and vibration generators  122  are resiliently coupled to the frame  112 , such as by springs  125  ( FIG. 5 ). Any generally known vibration generators may be used, such as motors having rotating shafts carrying eccentric weights.  
         [0039]     The spiral deck  116  is oriented to vertically elevate work pieces, such as hot castings, from an inlet  124  to an outlet  126 . The deck  116  defines a conveying surface  116   a  for receiving the work pieces and a back surface  116   b  ( FIGS. 7 &amp; 8 ). The work pieces may be transferred from an origination point, such as a molding line, to the inlet  124  by any conveying means, such as by a linear vibratory or other type of conveyor (not shown). The spiral deck  116  is formed in a helical pattern so that, as the work pieces move circumferentially around the deck, they are also elevated in the vertical direction. When the conveyor  110  is viewed in elevational cross-section, as schematically shown in  FIG. 5 , the spiral deck  116  defines a plurality of stacked tier segments  114 . At the outlet  126 , the work piece may be deposited onto an outlet transport (not shown), which may also be a conveyor. While the conveyor  110  is described herein as conveying the work pieces vertically upward, the inlet and outlet may be reversed so that the work pieces are conveyed vertically downward along the spiral deck  116 .  
         [0040]     The vibration generators  122  may be controlled in any known fashion to produce the desired vibrational motion of the frame  112  and coupled spiral deck  116 , thereby to advance the work pieces along the deck  116 . For example, the motors may be rotated in opposite directions (i.e., counter-rotated) and controlled to maintain a desired phase angle between the eccentric weights. While the illustrated embodiment is a two mass system, it will be appreciated that the conveyor  110  may be provided as a single mass or brute force system.  
         [0041]     As best shown with reference to  FIGS. 7-9 , the spiral deck  116  includes an inner edge  119  and an outer edge  121 . An inner housing wall  130  is coupled to the spiral deck inner edge  119  and an outer housing wall  132  is coupled to the spiral deck outer edge  121 . More specifically, the deck inner edge  119  is secured to the inner housing wall  130  by a first or inner wall support assembly  134 , which may clamp the deck inner edge  119  between a bottom flange  136  and a top retainer  138  ( FIG. 8 ). Similarly, the deck outer edge  121  may be secured to the outer housing wall  132  by a second or outer wall support assembly  140 , which may clamp the deck outer edge  121  between a bottom flange  142  and a top retainer  144 . A plurality of access doors  146  ( FIG. 4 ) may be formed in the housing outer wall  132  for accessing the different tier portions  114  of the deck  116 , should the outer housing wall  132  completely enclose the deck  116 .  
         [0042]     A rib assembly  150  is attached to the deck back surface  116   b  between the inner and outer deck edges  119 ,  121  ( FIGS. 7-9 ). The rib assembly may  150  may extend continuously along the deck  116  in the longitudinal direction, so that, in the illustrated embodiment, the rib assembly has a spiral shape. The rib assembly  150  may include a pair of ribs  152  having aligned transverse apertures.  
         [0043]     A force assembly  160  coupled to the rib assembly  150  to create a force that bends the deck  116  into an arcuate shape when viewed in cross-section. The exemplary force assembly  160  includes a pin  162  mechanically coupled to the rib assembly  150 , such as by insertion through the transverse apertures formed in the ribs  152 . A cross support  164  is spaced from the deck  116  and supported by the inner and outer housing walls  130 ,  132 . As shown, the cross support  64  is provided as a tubular steel member, and has apertures  65  formed in the upper and lower support surfaces  164   a ,  164   b . A link  166  is inserted through the apertures in the cross support  164  and defines a first end  168  coupled to the pin  162  and a second end  170 . The link  166  also includes a threaded portion  172  for receiving a nut  174 .  
         [0044]     The nut  174  may be adjusted on the link threaded portion  172  to generate a force in the link  166  that is transferred by the rib assembly  150  to the deck  116 , thereby to bend the deck  116  in an arcuate shape. As shown in  FIGS. 7 &amp; 8 , the nut  174  may be located below the cross support  164 . In  FIG. 7 , the deck  116  is shown in a relaxed state, where the force assembly  160  applies no force to the deck  116 . The nut  174  may be adjusted upwardly along the threaded portion  172  so that the nut engages the lower surface of the cross support  164 , thereby to create tension in the link  166 . The tension in the link  166  is transferred by the pin  162  as a downwardly directed force acting against the rib assembly  150  and attached deck  116 . The nut  174  may be adjusted along the threaded portion  172  to create a tension force in the link  166  sufficient to bend the deck  116  into an arcuate shape, as shown in  FIG. 8 .  
         [0045]     In an alternative embodiment, the pin  162  may be provided as a bar coupled to the ribs  152  and formed with a threaded aperture. The link  166  may be a bolt or threaded rod with the first end  168  threadably engaging the bar threaded aperture. The second end  170  of the bolt is a bolt head, which takes the place of the nut  174 . Accordingly, bolt may be threaded into the bar threaded aperture to create the tension force.  
         [0046]     The ribs  152  may project sufficiently past the pin  162  to define stop ends  176  that are engageable with the top surface  164   a  of the cross support, thereby to limit the amount of deflection of the deck  116 . As shown in  FIG. 7 , when the deck  116  is in the relaxed state, the rib stop ends  176  are spaced from the top surface of the cross support by a known distance “D”. As the nut  174  is tightened to deflect the deck  116 , the stop ends  176  are drawn toward and eventually engage the cross support top surface  164   a , thereby limiting the amount of deflection of the deck  116 .  
         [0047]     While the illustrated embodiment shows the deck conveying surface  116   a  bent into a concave arcuate shape, the conveying surface may also be formed with a convex arcuate shape. To do so, the force assembly  160  may be modified so that the link threaded portion  172  is adjacent an upper surface of the cross support  164 , and the nut  174  may be adjusted downwardly along the threaded portion to engage the upper surface  164   a  of the cross support. Consequently, a compression force is generated in the link  166  that is transferred by the pin  162  as an upwardly directed force against the rib assembly  160  and attached deck  116 .  
         [0048]     To create the compression force in the alternative embodiment described above, a nut may simply be provided on the bolt above the cross support upper surface  164   a , and the nut may be adjusted downwardly along the bolt to engage the upper surface  164   a.    
         [0049]     While only a single force assembly  160  is shown coupled to the rib assembly  160  in  FIGS. 7 &amp; 8 , it will be appreciated that a plurality of force assemblies may be coupled to the rib assembly  160  at points spaced along the longitudinal length of the rib assembly  150 . In the segment of the deck  116  shown in  FIG. 9 , a total of three force assemblies  160  are shown coupled to the rib assembly  150 .  FIG. 9  also illustrates the ribs  162  extending along the longitudinal length of the deck  116 . Furthermore, while a single deck segment is shown in  FIG. 9 , it will be appreciated that multiple deck segments may be fabricated independently and assembled to create the complete conveyor deck. The improved fit of the arcuate shaped deck allows the ends of the deck segments to be more reliably located, thereby facilitating assembly of mating deck segments.  
         [0050]     While a spiral conveyor path has been described and illustrated, the present disclosure is applicable to other conveyor path configurations requiring different deck shapes, such as linear, inclined, or curved decks, while still providing some or all of the benefits described herein. Still further, multiple concentric (in the case of curved or spiral path configurations) or parallel (in the case of linear path configurations) rib assemblies may be attached to the deck  116  or adjacent sub-decks, each of which having force assemblies coupled thereto, so that the deck is bent with multiple arcs defining multiple lanes for transporting a column of objects.  
         [0051]     Another alternative spiral conveyor  200  is illustrated in  FIGS. 10 &amp; 11  having a deck assembly  202  that allows air to flow around the deck, thereby to increase the dwell time of the air within the conveyor  200 . The deck  202  is coupled to a vibration generator, such as motors having rotating shafts carrying eccentric weights as disclosed above, which creates a vibratory force for advancing objects in the desired direction along the deck assembly  202 .  
         [0052]     The deck assembly  202  includes a deck  204  supported by cross supports  206 . The illustrated deck  204  has a helical shape defining a plurality of vertically stacked tier segments  205 . The deck  204  includes inner and outer edges  208 ,  210  that are spaced from an inner housing  212  and an outer housing  214 , respectively, to define inner and outer gaps  216 ,  218  therebetween. The inner and outer housings  212 ,  214  enclose the deck  204  to define a conveyor chamber.  
         [0053]     As with previous embodiments, the cross supports  206  may include apertures (not shown) for distributing air over objects conveyed along the deck. In this embodiment, the inner housing  212  may be imperforate, so that air from the apertures that is directed toward the deck  204  passes through the inner and outer gaps  216 ,  218  to an adjacent tier of the deck. A single outlet may be located at the bottom tier to direct exhaust air toward atmosphere. Accordingly, the average dwell time of the air provided to the conveyor  200  is increased, and construction of the conveyor is simplified by requiring only a single exhaust outlet.  
         [0054]     The deck assembly  202  may further include inner and outer guide rails  230 ,  232 . The guide rails may be used to at least partially support the objects transported by the conveyor  200 , and/or to prevent objects and debris from falling through the inner and outer gaps  216 ,  218 . Each of the inner and outer guide rails  230 ,  232  may include a vertical support  234 , which, for example, may be formed of bar stock, and contact surface  236 , which, for example, may be formed of tube stock. As best illustrated in  FIG. 10 , the inner and outer rails  230 ,  232  are secured to the deck  204  with guide rail supports  238 .  
         [0055]      FIGS. 12 and 13  illustrate yet another embodiment of a spiral conveyor  300  having inner and outer spiral decks connected in series to increase the dwell time of objects transported through the conveyor  300  while minimizing additional space requirements. The objects may be castings  301 , such as drums or rotors that require cooling. The spiral conveyor  300  includes a first spiral deck  302  defining a conveying surface, and includes a plurality of tier segments  302   a . A second spiral deck  304  is operatively coupled to the first spiral deck  302  and defines a conveying surface, the second spiral deck  304  also having a plurality of tier segments  304   a . Adjacent ends of the first and second spiral decks  302 ,  304  may simply be connected together to form a single, continuous conveying path that traverses both decks.  
         [0056]     An exciter mass assembly  306  is coupled to the first and second decks  302 ,  304 , and includes a vibration generator adapted to generate a vibratory force. The vibratory force advances objects, such as castings  301 , along the first and second spiral decks  302 ,  304  simultaneously in different vertical directions. For example, objects may be transported vertically downward along the first spiral deck  302  and vertically upward along the second spiral deck  304 . Accordingly, the first and second spiral decks  302 ,  304  may be arranged to emulate a “double helix” pattern.  
         [0057]     As best shown with reference to  FIG. 13 , the first and second spiral decks  302 ,  304  are substantially concentric about a common axis  310 . Accordingly, the first spiral deck is disposed substantially at a first radius while the second spiral deck is disposed at a second radius greater than the first radius, so that the first spiral deck is disposed inside or “nested” within the second spiral deck.  
         [0058]     A housing  312  is provided for enclosing the first and second decks  302 ,  304  and for assisting in directing cooling air to the decks. The housing includes a first chamber  314  for enclosing the first spiral deck  302  and a second chamber  316  for enclosing the second spiral deck  304 . The first and second chambers  314 ,  316  define a conveyor chamber extending along the conveyor path defined by the two decks  302 ,  304 . In the illustrated embodiment, the first chamber  314  defines an inlet for receiving the objects to be conveyed and the second chamber  316  defines an outlet for discharging the conveyed objects.  
         [0059]     An inlet air plenum  318 , which may include three inlets  320 , is formed by the housing and is adapted to direct cooling air, provided by an air source, into the conveyor chamber. The inlet air plenum  318  includes a roughly cylindrical inlet portion  322  and a generally annular distribution portion  324  disposed between the first and second housing chambers  314 ,  316 .  
         [0060]     Air distribution chambers  326  extending generally radially across the first and second housing chambers  314 ,  316  communicate with the inlet plenum distribution portion  324  and include apertures  327  for directing air downwardly toward the first and second spiral decks  302 ,  304 . In the illustrated embodiment, the air distribution chambers  326  also support the first and second spiral decks  302 ,  304 , which are connected to upper sides of the chambers  326 . The distribution portion  324  may include divider walls  328  for directing air toward the distribution chambers  326 . Accordingly, a single inlet air plenum  318  directs cooling air to both the first and second housing chambers  314 ,  316 .  
         [0061]     The conveyor  300  includes air flow passages communicating between adjacent tier segments of the first and second spiral decks  302 ,  304 . The first spiral deck  302  has inner and outer edges  330 ,  332  that are spaced from inner and outer walls  334 ,  336  of the housing first chamber  314 . The space between the inner edge  330  and inner wall  334  defines a first deck inner gap  338 , while the space between the outer edge  332  and outer wall  336  defines a first deck outer gap  340 . Air provided from the air distribution chambers  326  may therefore flow toward the nearest tier segment  302   a  and through the first deck inner and outer gaps  338 ,  340  to an adjacent tier segment  302   a.    
         [0062]     Similarly, the second spiral deck  304  has inner and outer edges  342 ,  344  that are spaced from inner and outer walls  346 ,  348  of the second housing chamber  316 . The space between the inner edge  342  and inner wall  346  defines a second deck inner gap  350 , while the space between the outer edge  344  and outer wall  348  defines a second deck outer gap  352 . Air provided from the air distribution chambers  326  may therefore flow toward the nearest tier segment  304   a  and through the second deck inner and outer gaps  350 ,  352  to an adjacent tier segment  304   a.    
         [0063]     The first and second decks  302 ,  304  may further include guide rails for supporting objects to be conveyed, for retaining objects on the decks, or for directing debris removed from the objects to a collection area. In the illustrated embodiment, the first spiral deck  302  includes inner and outer guide rails  360 ,  362  and the second spiral deck  304  includes inner and outer guide rails  364 ,  366 . The guide rails  360 ,  362 ,  364 , and  366  may be located on their respective decks and constructed similar to those described above with reference to the embodiment of  FIGS. 10 &amp; 11 .  
         [0064]     The housing  312  may also include an outlet plenum  370  for receiving cooling air from the conveyor chamber and directing it to atmosphere. In the illustrated embodiment, the outlet plenum  370  includes a hood section  372  positioned directly above the top deck tier segment  302   a  of the first spiral deck  302  and an outlet  374  adapted for connection to ductwork or the like for discharging air to atmosphere. Thus, a single outlet point (i.e., above the first deck tier segment) is provided for discharging air from the conveyor chamber. Accordingly, air provided to other tier segments will pass through the inner and outer gaps  338 ,  340 ,  350 , and  352  and ultimately to the outlet plenum  370 , thereby increasing the period during which this air is resident in the conveyor chamber.  
         [0065]     Sand or other fines capable of being carried by the air flow through the conveyor chamber may be removed at any convenient location. For example, where the first spiral deck  302  transitions to the second spiral deck  304 , which is near the bottom of the housing  312 , the reversal of air flow direction provides one possible location for collecting and removing fines.  
         [0066]     Although certain apparatus constructed in accordance with the teachings of the disclosure have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all embodiments of the teachings of the disclosure fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.