Patent Publication Number: US-2011061997-A1

Title: Side-flexing Conveyor Chain with Pivoting Slats and Related Methods

Description:
This application is a continuation of U.S. patent application Ser. No. 12/302,080, which is the national stage of PCT/US2007/069644, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/802,898, filed May 24, 2006, the disclosure of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to the conveyor art and, more particularly, to a side-flexing conveyor chain incorporating pivoting elongated slats and related methods. 
     BACKGROUND OF THE INVENTION 
     Conveyor systems form an integral part of modern production facilities. Such systems are especially beneficial in the food processing and article packaging industries, where it is often desirable to move articles to and from different areas of the production facility to undergo various manufacturing/packaging operations. For example, many food manufactures require transportation of food items from a baking area to a position for final packaging. However, many of these items, such as breads and other baked goods require cooling prior to packaging. Additionally, these food products are often soft and fragile, thereby requiring special care during transportation through the production facility to avoid damage. 
     In this regard, conveyor chains with rows of laterally repeating modular links forming the conveying surface are perhaps the most popular on the market today. Such a conveying surface does not, however, maximize the amount of thermal transfer to the underside of the articles being conveyed. This can be deleterious for cooling items during conveyance, such as baked goods or frozen foods being packaged at a downstream location. Soft goods also tend to conform to the conveying surface, if interrupted, which can lead to unwanted vestiges. 
     Another limitation with prior art chains with laterally repeating links is the creation of multiple crevasses and recesses in which debris and residue can become lodged. Despite the existence of various types of belt or chain “washers,” it remains difficult to ensure that the cleaning is as thorough as possible in view of the large number of open spaces in the conveying surface of a typical modular link chain. Such thorough cleaning may be crucial in certain situations (such as food processing), but may also contribute substantially to the operating expense. 
     Additionally, many production facilities also have limited floor space, thereby making efficient use of the space available imperative. Thus, manufacturers are increasingly desirous of conveyor systems occupying as small an area as possible. To do so, the conveyor chain must have the capability to move product smoothly around curves (including along a helical or spiral path), as well as along extended runs. 
     In the past, others have proposed linear conveyors incorporating slats, such as for use in applications involving the freezing of products. An early example is found in U.S. Pat. No. 3,447,668 to Jernigan, which discloses an endless conveyor formed of a plurality of thermally conductive (metal) elements designed to form a substantially planar conveying surface along the forward run. Along the return run, the elements pivot to a generally vertical position. This allows the thermal media (cold air) to reach the underside of the elements of the forward run and facilitate cooling of the articles being conveyed via the conductive element. 
     While this approach is advantageous in certain respects, it is not without significant limitations. For one, the conveyor is incapable of side flexing and, thus, can only assume a linear condition. This greatly limits its usefulness (including in connection with spiral-type freeze conveyors). Another limitation is that the elements are in direct contact along the forward run, and are thus subject to frictional wear. The free, uncontrolled pivoting of the elements may also render them susceptible to reaching undesirable positions and becoming “caught up” with adjacent elements. 
     Accordingly, a need is identified for a conveyor chain with a conveying surface capable of providing full, even support for any articles being conveyed, including smaller ones that might normally pass through or become caught within an open conveying surface. The conveyor chain would also be easy to clean and capable of negotiating turns or bends, thus potentially creating a savings in the amount of floor space occupied in the production facility. Overall, a substantial improvement in terms of efficiency and operator satisfaction would result, especially when used in conveying food products or other articles to be cooled during conveyance. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the invention, a modular link conveyor chain with at least one elongated slat is capable of assuming a compressed and an expanded condition as the result of side-flexing, and moving along a forward run and a return run in an endless path (which may be partially spiral). The chain comprises a plurality of links arranged in rows spaced apart in a conveying direction. The links in at least a first row include first aligned apertures and the links in at least a second row including second, oversized apertures for aligning with the aligned first apertures of the links in the first row. A first connector associated with the first and second apertures interconnects the first and second rows of links. The at least one elongated slat is mounted to the connector for movement between a first position forming at least part of a conveying surface along the forward run and a second position along the return run. 
     In one embodiment, a connector is associated with each of a plurality of rows of adjacent links, and a slat associates with two or more of the connectors (such as every other one). Preferably, in such configuration, the slats are capable of nesting at least partially within each other in the compressed condition of the chain. In any case, the plurality of slats maintain the substantially continuous conveying surface, including when the chain undergoes side-flexing. However, to avoid frictional contact among the slats during side-flexing, it is preferable to maintain a gap between adjacent slats, including along the return run. A spacer may be provided to help maintain this desirable gap. 
     In one particularly preferred embodiment, each row of links includes at least two side links. Each side link is characterized by the inclusion of a depending arm. The depending arm carries an inwardly projecting tab, which may be used for engaging a guide rail or like structure for guiding and supporting the chain as it traverses the endless path. 
     In accordance with another aspect of the invention, a modular link conveyor chain with slats is capable assuming a compressed and an expanded condition and moving along a forward run and a return run in an endless path. The chain comprises a plurality of links arranged in rows spaced apart in a conveying direction. The links include first apertures and second oversized apertures for aligning with the first apertures of adjacent links. A plurality of connectors associate with the first and second apertures. A slat is pivotally mounted to the connector, such that adjacent slats overlap at least along the forward run when the chain is in the compressed condition. 
     Preferably, a spacer is provided for preventing adjacent slats from directly contacting each other when the chain is in the compressed condition. This is done to avoid direct frictional contact among and reduce wear on the slats. Most preferably, the spacer comprises a receiver for receiving a first side of the slat. One of the connectors may carry the receiver and, ideally, a first receiver is supported by a first connector and a second, adjacent receiver is supported by a second connector. In use, the first receiver engages the second receiver when the chain is at least partially in the compressed condition. 
     In accordance with yet another aspect of the invention, a modular link conveyor chain capable of side flexing and moving along a forward run and a return run in an endless path incorporates slats. The chain comprises a plurality of links arranged in rows spaced apart in a conveying direction, the links in at least a first row including first apertures and the links in at least a second row including second, oversized apertures for aligning with the first apertures when interdigitated with the links in the first row. A connector associates with each of the first and second apertures in the first and second rows of links. A slat is mounted to each connector so as to be capable of at least partially nesting with the next-adjacent slat when the chain side-flexes or undergoes longitudinal compression. Preferably, the chain further includes a spacer for preventing adjacent slats from directly contacting each other in the compressed condition in order to avoid direct frictional contact among and reduce wear on the slats. 
     According to still a further aspect of the invention, a method of manufacturing a conveyor belt is disclosed. The method comprises interconnecting a plurality of links arranged in rows spaced apart in the conveying direction so as to form a side flexing chain. The method further comprises mounting at least one elongated slat to the links for pivoting movement between a first position and forming at least part of a conveying surface along the forward run, and a second position along the return run. 
     Yet a further aspect of the invention is a method of operating a conveyor chain including a plurality of pivoting slats. The method comprises moving the conveyor chain along a forward run with each slat spaced from and at least partially overlapping with an adjacent slat to form a substantially continuous conveying surface. 
     In one particular embodiment, the method further comprises moving the conveyor chain to an expanded condition. The method may further include the step of contacting one slat with an adjacent slat in the expanded condition. The moving step along the forward run may comprise driving the conveyor chain along a curve such that the slats overlap to a greater extent along the inside of the curve than the outside of the curve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a side flexing conveyor chain with slats forming one aspect of the invention; 
         FIG. 2  is a schematic side view of a slat or possible use with the conveyor chain of  FIG. 1 ; 
         FIG. 3  is a schematic side view of a plurality of slats for possible use with the conveyor chain of  FIG. 1 , and illustrates when the chain is in a non-compressed or extended condition; 
         FIG. 3   a  is a view similar to  FIG. 3 , but illustrates what happens when the corresponding chain is compressed; 
         FIGS. 4 and 5  are side schematic views showing one possible manner in which the slats may pivot as the conveyor chain traverses an endless path including a forward and a return run; 
         FIGS. 6 and 6   a  are views similar to  FIGS. 3 and 3   a , but in which the slats have a different cross-sectional shape or profile; 
         FIGS. 7   a ,  7   b , and  7   c  illustrate another embodiment of a side flexing conveyor chain with slats forming another aspect of the invention; 
         FIGS. 8   a ,  8   b  and  8   c  show the chain of  FIGS. 7   a - 7   c  in a non-compressed condition along a forward or non-inverted run; 
         FIGS. 9   a ,  9   b ,  9   c ,  9   d  and  9   e  show the chain of  FIGS. 7   a - 7   c  in a compressed condition along a forward or non-inverted run; 
         FIGS. 10   a ,  10   b , and  10   c  show the chain of  FIGS. 7   a - 7   c  in a non-compressed condition along a return or inverted run; 
         FIG. 11  is a schematic view illustrating the possible effects of uncontrolled pivoting of the slats; and 
         FIG. 12  is a spiral conveyor incorporating a side flexing conveyor chain with slats. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference is now made to  FIG. 1 , which depicts a conveyor belt or chain  10  including a conveying surface  11  for engaging and supporting articles. In this particular embodiment, the chain  10  comprises modular links in the form of side guide links  12  arranged in spaced apart rows R 1  . . . R n , which thus partially create the conveying surface  11 . As should be appreciated, the chain  10  may form part of an overall conveyor system, which may include guide rails for guiding the chain as well as a drive system incorporating a sprocket or roller for driving the chain. In such a system, the chain  10  may be driven along an endless path between a forward run F and a return run N, which may be vertically offset or otherwise. 
     Adjacent rows R 1 , R 2  of the side links  12  interconnect via transversely extending connectors  14 , which are also referred to in the vernacular as “cross rods,” “hinge pins,” etc. Specifically, as shown in  FIGS. 1 ,  7   a , and  7   b , each side link  12  includes a plurality of laterally repeating sections, each having an apex portion  17 . A pair of leg portions  18  extend or project from each apex portion  17 , preferably in an outwardly diverging relationship. Consequently, a single laterally repeating section of the link  12  in this embodiment is substantially V-shaped in plan view, which of course means that a pair of the sections are substantially W-shaped. As should be appreciated, the upper surfaces of the apex portion  17  and leg portions  18  are adapted for engaging and supporting articles for conveyance. 
     Each leg portion  18  is also associated with a foot portion  20 . The foot portion  20  is typically barrel shaped, and may include an upper surface defining a surface capable of engaging and conveying articles. In the usual arrangement, and although a chain  10  formed of links  12  of this type is fully reversible, the apex portions  17  define the leading end of the link  12  and the foot portions  20  define the trailing end. In other words, the chain  10  may be normally driven in either direction along an endless path in the course of conveying articles in the desired manner. 
     Each apex portion  17  provided in the link  12  includes a first opening or aperture oversized relative to the connector  14 , which may be in the form of an elongated slot  28 . Furthermore, the foot portion  20  of each leg portion  18  includes a second opening or aperture, such as a hole  30 . The holes  30  of adjacent foot portions  20  are thus coaxial, as are the slots  28  when multiple apex portions  17  are provided. 
     As is shown in  FIGS. 7   a  and  7   b , when two links  12  spaced in the conveying direction along each side of the chain  10  are interdigitated, the connector  14  passes through the slot  28  in each apex portion  17  and the hole  30  in each foot portion  20 . Consequently, the links  12  in adjacent rows R 1 , R 2  are interconnected with each other, but capable of relative movement. As discussed further below, the longitudinal freedom of the connector  14  in the slot  28  is desirable, since it allows relative movement among the rows R 1 , R 2  of links  12  to take place and permits the chain to side flex as well as to expand and compress. 
     To hold the first connector  11  in this position, it is retained in the outer side portion of each link  12 . In one embodiment, as shown in  FIG. 7   b , this is accomplished by providing the outermost foot portion, or side portion  24 , of each link  12  with a depending arm portion  32  having a hole  35  co-axial with the hole  30  of each foot portion  20 . The hole  35  receives the first connector  14 , and an integral locking tab  36  is inserted within a slot  38  formed in the link  12 . The locking tab  36  may include prongs  39  to engage a corresponding circumferential notch  40  provided at each end of the first connector  14 . In the preferred embodiment, the locking tab  36  is fabricated from a resilient or flexible material, such as nylon. This construction allows the prongs  39  of the tab  36  to snap lock in the notch  40  for secure engagement and further allows the locking tab  36  to be easily installed and removed. 
     The locking tab  36  also includes an offset release button  42  seated in an open-ended portion of the slot  38 . The button  42  assists in the installation and removal of the locking tab  36  from the side when, for example, maintenance and repair is required. More specifically, a blade tool, such as a screwdriver, is tapped against the button to initiate plying action. Once sufficient movement is initiated, the screwdriver then provides increased leverage to facilitate removal of the tab  36 . The inherent resiliency of the tab  36  allows the prongs  39  to disengage from the notch  40 . To reinsert the tab  36 , the prongs  39  are directed into the slot  38 . It can be appreciated that the resiliency of the tab  36  allows the prongs  39  to snap around the notch  40 . Thus, secure retention of the connector  14  results. 
     In accordance with one aspect of the invention, an elongated slat  16  may be pivotally mounted to each transverse connector  14 . Preferably, each slat  16  is formed from a single piece of material (such as by extrusion) and includes a channel, bore or opening  16   a  extending in a direction transverse to the conveying direction for receiving the connector  14 . This opening  16   a  is preferably slightly oversized relative to the outer diameter of the connector  14 . As a result, the opening  16   a  slidably receives the connector  14  while it retains the capability of undergoing free pivoting movement about a transverse axis. 
     As perhaps best shown in  FIGS. 2 and 3 , each slat  16  is preferably provided with a taper along each side so as to form a first, generally narrow end  16   b  and a second, generally wider end  16   c  (note the height dimension H). The taper may be mutual, thus giving the slat  16  general symmetry about a longitudinal axis A and the appearance of a teardrop when viewed in profile or cross-section. The slats  16  are also provided with a length L in the longitudinal direction (see  FIG. 2 ) such that at least along the forward run F, the narrow end  16   b  each preceding slat  16  overlies the second end  16   c  of the succeeding slat. Stated another way, the maximum pitch P of adjacent transverse connectors  14  is preferably equal to or less than the length L of each slat  16  (see  FIG. 3 ). 
     Turning to  FIG. 3 , each slat  16  in use thus includes a conveying face  16   d  for partially defining a corresponding interior portion  11   a  of the conveying surface  11 . The spacing Q from a generally horizontal plane extending through the opening  16   a  in the slat  16  along the second end  16   c  for receiving the connector  14  (which thus defines a bi-directional pivot point) to the conveying face  16   d  in the “home” or generally horizontal position is such that the entire interior portion  11   a  of the conveying surface  11  is generally planar. In other words, there is no or negligible “skew” among adjacent slats  16  when overlapped in the normal or “home” position, which of course helps to provide full, reliable article support during conveyance. 
     As a result of this arrangement, and as perhaps best shown in  FIG. 3 , the slats  16  together form the substantially continuous interior portion  11   a  of the conveying surface  11 . The overlapping nature of the slats  16  means that this portion  11   a  of the conveying surface  11  is substantially continuous and free of gaps or openings, and is thus well-suited for providing full, even support, including for the smallest of articles. Moreover, the slats  16  both individually and collectively provide a large surface area for improved thermal transfer to or from the articles being conveyed. 
     In contrast, when the slats  16  transition to the return run N, such as at the ends of the conveying path, the free pivoting movement allows the slats  16  to pivot and assume a generally vertical orientation (note action arrow V). As should be appreciated from  FIG. 4 , the slats  16  in this orientation are not overlapping or otherwise in contact. When spaced apart in this fashion, the conveying surfaces  16   d  of the slats  16  are thus more easily cleaned, as is the exposed underside of the slats along the forward run F. The return run N with the slats  16  in this non-overlapping or spaced apart condition thus defines a cleaning “zone” Z. 
     Cleaning may be effected in any manner desired, with a preference for the more efficient automatic sprayer for spraying a cleaning fluid (air, water, etc., with or without sanitizing agents) over the now fully exposed surfaces of the slat  16 . Alternatively, a cleaner in the form of a fluid bath into which the slats  16  are introduced may be provided. In any case, cleaning most preferably occurs along the return run N (note block C in  FIG. 4 ) and within the cleaning zone Z. 
     The substantially uninterrupted, continuous nature of the slat  16  further serves as a significant advantage in terms of cleaning, as compared to prior art approaches with interdigitated rows formed solely of individual links. Indeed, it may be the case that cleaning is not required as frequently as a result of this type of arrangement in view of the lack of crevasses or recesses in at least the interior portion  11   a  of the conveying surface  11 . 
     As a result of the free pivoting movement, it should also be appreciated that the slats  16  automatically return to the overlapping condition during the transition from the return run N to the forward run F. The substantially continuous interior portion  11   a  of the conveying surface  11  is thus automatically re-established, ready for receiving any articles to be conveyed as the chain  10  moves along the forward run F. As should be appreciated, this cycle automatically repeats itself as the chain  10  moves along the endless conveying path between the forward run F and the return run N. 
     The chain  10  as described above includes side-flexing capability, as well as the ability to compress and expand in the longitudinal direction. Aside from eliminating the deleterious catenary approach prevalent in prior art conveying systems, when used in connection with the slats  16 , this allows the chain  10  to negotiate curves. Specifically, in moving along a curve or compressing longitudinally, the slats  16  in view of their overlapping nature along the forward run F tend to either partially or fully pivot away from the plane of the conveying surface  11 . The connectors  14  thus assume a reduced pitch P′ while the slats  16  have a greater center-to-tip spacing Q′, or “skew,” at least along the corresponding side or face  16   d  (see  FIG. 3   a ). Moreover, this may form a relatively large “skew” angle α (approx. 25° in the illustrated embodiment) between a generally horizontal plane aligned with the opening  16   a  in the slat  16  and the plane of the conveying face  16   d . As a result, the slats  16  become “bunched up,” but may still form a generally continuous portion  11   b  of the conveying surface  11 . As should be appreciated, when negotiating curves, the slats  16  assume the position shown in  FIG. 3   a  along the inside edge of the curve, but may remain spaced as shown in  FIG. 3  along the outside of the curve. 
     In the illustrated embodiment, the difference between the center-to-tip distance Q in the vertical direction when the slats  16  are collapsed as shown in  FIG. 3  (skew approximately zero) and the augmented distance Q′ shown in  FIG. 3   b  (non-zero skew) can be significant. To reduce the skew resulting from side-flexing, and as perhaps best understood with reference to  FIGS. 5 ,  6 , and  6   a , it is possible to provide each slat  16  with a generally thin, flat first end  16   b  (note dimension T in  FIG. 6 , and compare with dimension H in  FIG. 2 ). This thin, flat end  16   b  also defines a recess  16   e  in the underside of each slat  16 , and gives each slat an asymmetrical, “whistle”-shaped profile or cross-section. 
     Consequently, adjacent slats  16  may nest together and collapse in an orderly fashion while overlapping during longitudinal compression or side flexing of the chain  10 . As can be appreciated from comparing  FIGS. 6 and 6   a , there is much less difference between the center-to-surface spacing (Q vs. Q′) or skew, and the corresponding angle (α vs. β) with such slats  16 . However, the operation of the chain  10  when transitioning between the forward and return runs F, N is not compromised in any way, as shown in  FIG. 5 . 
     Yet another aspect of the invention is described with reference to  FIGS. 7-9 . Specifically, the illustrated embodiment of the chain  10  incorporates a spacer designed to maintain a space between the adjacent slats  16  while simultaneously controlling the relative position thereof. In the illustrated embodiment, with reference to  FIGS. 7   a  and  7   b , the spacer takes the form of a receiver  50  for associating with every other connector  14  along each side of the chain  10  and adapted for receiving one end of each slat  16 . It should be further appreciated that one slat  16  is associated with every other connector  14  in the conveying direction (which further means that the connectors  14  not associated with slats  16  need not extend the full transverse width of the chain  10 , but instead may extend from the outer side to the inner side of the side link  12  without in any way compromising performance). 
     In the illustrated embodiment, each receiver  50  includes a first end with an aperture  52  for receiving a first one of the connectors  14   a . The opposite end of the receiver  50  forms a yoke  54  for receiving a second, adjacent one of the connectors  14   b . An arm  56  connects the ends of the receiver  50 . 
     With reference to  FIGS. 7   a ,  7   b  and  7   c , it can be seen that the yoke  54  comprises generally elongated, spaced fingers  58  forming a U-shaped recess. One of the fingers  58  (the upper one in the illustration) supports a projecting plate-like portion  60  having an upper surface generally parallel to the upper surface of each slat  16 . A projecting sidewall  62  with a generally planar, linearly sloping surface  63  is provided adjacent the arm  56 . Together, the sloping surface  63  of the sidewall  62  and the underside of the plate-like portion  60  form a channel  64  for receiving and capturing one side of the slat  16 , with the side face thereof generally in abutment with the matching side face of the arm  56 . 
     With reference now to  FIGS. 8   a ,  8   b , and  8   c , the operation of the chain  10  of this embodiment can be better understood. Along the forward run F when the slats  16  are in a non-compressed or non-side flexing state, the receivers  50  are generally spaced apart from each other or otherwise not in intimate contact. Consequently, the adjacent slats  16  make only limited contact along a front end and a rear portion, respectively. The desirable substantially planar conveying surface  11   a  is thus maintained. 
     In contrast, and with reference to  FIGS. 9   a - 9   e , adjacent receivers  50  interdigitate when the chain  10  compresses, such as during side flexing or longitudinal compression ( FIGS. 9   a  and  9   b ). The manner in which one receiver  50   a  may receive the adjacent receiver  50   b  is shown in  FIGS. 9   d  and  9   e . Along the forward run F, this results in the underside of the portion of the first (or upper) finger  58  of a first receiver  50   a  adjacent the planar surface  60  engaging the corresponding rearward portion of a second, adjacent receiver  50   b . As a result of this reception, the slats  16  are skewed slightly in the vertical direction. This results in a small space S or gap being established and maintained between the adjacent slats  16  (see  FIG. 9   b ). As should be appreciated, engagement between opposite portions of the receivers  50   a ,  50   b  creates a similar result (i.e., a gap or space S between the slats  16 ) along the return run N (see, e.g.,  FIGS. 10   a - 10   c ) when the receivers  50   a ,  50   b  are in contact. 
     Even if slight, the ability to maintain this space S or gap between adjacent slats  16  during relative movement in an automatic and reliable fashion is advantageous for several reasons. Primarily, this keeps the slats  16  from frictionally engaging each other when the chain  10  compresses, such as during side flexing. Aside from being generally of benefit from a wear standpoint, this lack of contact also helps to maintain the integrity of any low friction or like protective coating applied to the surface of the slats  16 . A secondary benefit is that the control afforded by the receivers  50   a ,  50   b  prevents adjacent slats  16  from freely pivoting and assuming undesirable positions in which the slats become inter-engaged. This is especially beneficial along the transition from the forward run F to the return run N, where adjacent slats  16  can interact in an undesirable fashion and possibly become “tented” in a manner that prevents further movement (see  FIG. 11 ). 
     As a result, the natural pivoting movement of the slats  16  is ensured as the transition from the forward to the return run is made. In order to prevent debris from entering the opening  16   a  in each slat  16 , it may be sealed. For example, as shown in  FIGS. 7   a  and  7   b , a bushing  66  may be provided on each connector  14 . As shown in  FIG. 7   c , a corresponding seating recess  68  may also be provided in each receiver  50  for receiving the bushing  66 . The bushing  66  in this position may thus not only help to seal the openings in the receiver  50  and slat  16  against the entry of dirt and debris (thereby resulting in a more sanitary and easier to clean arrangement), but also helps to reduce relative friction between the elements. 
     The arrangements of a side-flexing slat conveyor chain  10  described above are believed to have particular utility with spiral conveyor systems of the type in which the chain is driven in a generally spiral or helical path, at least along the forward run. Specifically, in the case of a spiral “freeze”  100  as shown in  FIG. 12 , the slats incorporated in the chain  10  may be cooled from an external source in order to lower the temperature of the articles being conveyed. Even in the absence of such active cooling, the slats when used in a spiral conveyor  100  would help to effect the desired thermal transfer for cooling the articles in a more efficient fashion and without occupying a significant amount of floorspace. 
     To improve thermal transfer to the articles, it may be desirable to fabricate the slats  16  of a material having a high degree of thermal conductivity, such as various metals including aluminum. However, it is also possible to make the slats out of polymer materials, which are not only lighter, but generally less susceptible to corrosion and oxidation than metal. Ceramics and composite materials are, of course, also viable options. Coatings and surface treatments may also be used as desired to prevent articles from adhering during conveyance. 
     The foregoing descriptions of various embodiments of the invention are provided for purposes of illustration, and are not intended to be exhaustive or limiting. Modifications or variations are also possible in light of the above teachings. For example, while shown as being operated such that the slats  16  are driven in a particular direction, with the second end  16   c  leading, it should be appreciated that the chain  10  can be driven bi-directionally. Also, it may be possible to maintain the desired spacing of the slats  16  during compression using only one receiver  50  along one side of the chain. The embodiments described above were chosen to provide the best application to thereby enable one of ordinary skill in the art to utilize the disclosed inventions in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention.