Abstract:
A modular plastic conveyor belt has upright support members at ends of each row and, in some cases, at intermediate positions, to support a conveyor tier above such that the belt is self-supporting in a helical stack in a spiral conveyor system. Modular rows can be made up of one or more modules, and the modules can be in various different configurations. The support members or spacer frames are either integral or securely connected to heavier link ends in end members of the modules. Preferably there are teeth and notches in the support frames and the bottom of the end member of the tier above, to hold the tiers of the helical stack in registry, preventing sliding and misalignment.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention relates generally to a conveyor belt and system of the type that follows a helical path and in conventional practice is driven by a driving tower or cage, with the belt exiting one axial end of the helical path and being fed to the other axial end. The conveyor is usually known as a “spiral” conveyor system. The invention particularly concerns a modular plastic conveyor belt which articulates to accommodate straight and radius travel as applied to a helical conveyor belt, and to such a belt system wherein the belt is self-supporting and eliminates the need for a helical platform to support the stacked helically extending tiers of the belt, and also eliminates the driving tower. The invention also concerns side guards or side plates which can support successive tiers in such a spiral conveyor belt and which can be used in other helical plastic belts that are not self-supporting. 
     U.S. Pat. No. 3,938,651 discloses a self-supporting spiral conveyor belt system of a type which has been known, the conveyor belt being formed of metal links or rows which were capable of articulation to travel around the curving path of the helical conveyor belt system, as well as to travel in straight paths from the exit at one axial end of the helical conveyor to be fed back into the other axial end where the belt resumes helical travel. The belt was self-supporting in that it had metal spacers extending up from each side of each belt row, with upper portions of the spacers positioned to bear against the bottom of a link or row above, so that an overlying tier of the belt is supported by the immediately underlying tier. Thus, the metal belt of the referenced patent was arranged in a self-supporting helical stack without need for a support platform or wear strip under each tier and also without the need for a driving tower which normally would engage against inner edges of the belt rows or links to drive the belt up the helical path. 
     The helical conveyor belt of the ′651 patent was not made up of integral modules but rather of rods and various metal components assembled together, with each spacer device being secured to several of the rods to retain it in position. 
     In the present invention a modular plastic conveyor belt is configured so as to be self-supporting, to be arranged in stacked helical tiers in a spiral conveyor belt system. The modules are integral and formed of injection molded plastic. Each module row may be one integral module or may be several integral modules assembled side by side on a common connecting rod. End members, at least at the edges of each row, preferably are larger as compared to inner ones of the series of interdigited projections of the belt modules, and these end members support plastic frames or side plates which extend upwardly from the end members and which include a generally horizontal bar providing a support surface for a generally similar end member immediately above in a succeeding tier of the belt. 
     The plastic frames preferably are generally shaped in an inverted “U” shape, and in a preferred embodiment the frames extend in an orientation which is somewhat close to parallel to the path of travel, but canted slightly. Alternate rows of modules, in one embodiment, have these frames at alternating positions and canted orientations, in an arrangement whereby the frames can be in overlapped juxtaposed position from module to module, whether at the collapsed inner edge of the helical belt travel or at the expanded outer edge of such a curving path. Further, the preferred belt construction includes a notch and tooth coactive between the top of each frame and the bottom of a belt end member immediately above, for engaging the two tiers together and retaining the belt in stacked relation both as to prevention of side-to-side sliding movement and advancing or retarding movement between tiers. 
     There are several important advantages of the integral plastic modular conveyor belt of the invention as a stacked tier, self-supporting helical conveyor. One important consideration is that the all-plastic belt eliminates metal contamination which is particularly important in food handling applications, a primary use of helical conveyors. Another advantage is the superior release characteristics of plastics, which improve throughput and reduce product damage and loss. Moreover, the lighter weight of plastic as opposed to a metal belt reduces installation time and helps in the support of the stacked helical tiers by considerably reducing the total weight of the helical stack. 
     In addition, the lower friction and higher fatigue resistance characteristics of plastic materials can improve belt life in the sometimes stressful travel path of a spiral conveyor. In the case of module rows each formed with a single module, the one-piece integral rows increase stiffness over assembled belts, thus better supporting a load in the absence of a supporting platform. 
     Still further, the injection molding of the modules allows for very intricate shapes and surface configurations to meet a variety of needs. Also, the modular plastic design allows the support members or frames to be placed at multiple locations across the width of the spiral belt, in order to provide adequate support in wider belt widths. Thus, if each row is made up of several modules, one or more of the interior module ends can include a support frame, to interact with a module end above, providing intermediate support between the edges of the belt. 
     The modular plastic spiral conveyor system in the self-supporting arrangement is also advantageous over metal in that it can be maintained with hand tools, and in the event of a catastrophic system jam in the spiral conveyor, a higher percentage of the plastic belt is salvageable. 
     The plastic frames also comprise side guards or side plates that retain products on the belt, and these form an important feature. They are open, allowing air circulation, and can be used effectively on non-self-supporting helical conveyor belts. 
     It is thus among the objects of the invention to provide for smooth and efficient belt movement in a helical or spiral conveyor belt system, with the belt formed of integral plastic modules with means for self-supporting the belt, with the tiers along the helical path being supported by the tier below. These and other objects, advantages and features of the invention will be apparent from the following description of a preferred embodiment, considered along with the accompanying drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view showing a spiral or helical conveyor belt system in accordance with the invention. 
     FIG. 2 is a plan view showing a portion of a plastic conveyor belt formed of integral modules and including the features of the invention. 
     FIG. 3 is a plan view of a section of a different conveyor belt showing the belt section on a curve as in the helical conveyor, and with each conveyor row made up of several modules side by side. 
     FIG. 4 is a view similar to FIG. 3 but showing a different style of plastic conveyor belt. 
     FIG. 5 is a perspective view showing several module rows of a conveyor belt, traveling in a radius path, with features of the invention. 
     FIG. 6 is a side or edge view showing two stacked module rows of a conveyor belt according to the invention. 
     FIG. 7 is a perspective view showing stacked module rows according to the embodiment of FIG.  6 . 
     FIG. 8 is a perspective view showing the belt of FIG.  2 . 
     FIGS. 9 and 10 are perspective views showing another embodiment of a stacking spiral conveyor belt, with solid stacking side plates. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 is a perspective view showing a helical or spiral conveyor belt system  10  which includes a conveyor belt  12  arranged in a stacked, helical configuration, with various tiers  14 ,  16 ,  18 , etc. stacked serially and directly on one another, without the need for an intervening helically-shaped platform as is typical with conventional spiral conveyor belt systems. Thus, there is no need for a driving tower or cage which would ordinarily be within the center space  20  of the coiled conveyor belt stack  22 . 
     As in other spiral conveyor belts, the belt  12  is normally fed into the helical, coiled stack  22  from the bottom, and makes its way through the various tiers and is fed out of the stack at the top, as indicated at  24  (although this could be reversed). There, the belt is fed around various rollers or drums  26 ,  27 ,  28 ,  29  and  30 , one or more of which can have sprockets effective to drive the belt. Vertically extending, low-friction guides  32  can be included to retain the helically stacked belt in the helical arrangement as shown. 
     This arrangement is generally as shown in U.S. Pat. No. 3,938,651, describing a metal self-supporting spiral conveyor belt. 
     Also as in U.S. Pat. No. 3,938,651, a supporting base  36  comprising a separate conveyor belt having an inclined helical pattern with a step at  38  to accommodate the entry (or exit) of the conveyor belt from the stack preferably is provided. The helical stack  22  requires some form of rotation-allowing support at the bottom of the stack, which can be as in the ′651 patent, incorporated herein by reference. 
     It should be understood that the rotation of the belt  12  in the helical stack  22  can be in either direction, clockwise or counterclockwise as seen from the top of the stack in FIG.  1 . 
     FIGS. 2,  3  and  4  show several different types of conveyor belt modules in multiple-row sections of belts, of types that can be used with the invention. In FIG.  2  and also FIG. 8, each module row  40  comprises a single, integral module  42 . (A module row can be made up of a single module, several side-by-side modules, or a mix of multi-projection modules and single links, or all single links serving as modules. Single links can have one projection each direction, or tow in one direction and one in the other.) Each module  42  has a set of first projections or projecting link ends  44  and a second, oppositely-directed set of projecting link ends  46 . These are interdigited in the normal way and connected together by connecting rods (not visible in FIGS. 2 and 8) which pass through apertures in the sets of link ends. One of the sets of projections is slotted, to accommodate curving belt travel. At left and right ends of the modules  42 , the link ends are heavier, as at  44   a,  a somewhat heavier link end, and  44   b,  also a wider link end, and this situation occurs at both edges of the belt. Similarly, a much wider link end preferably occurs at the edges in the second group of projections  46 , at  46   a.    
     From these much wider link ends  46   a  extend a support member  48  or side plate at each edge of the belt. The support member  48  in a preferred embodiment is a generally U-shaped frame which is founded on the wide link end protection  46   a  and also on the edge link end  44   b  of the other set of projections of a module. These support members or spacer frames preferably are integrally molded with the conveyor belt modules, although they can be secured by a snap-in connection or screws or other fasteners, if it is desired to have them removable to provide a more versatile module or conveyor belt. 
     In the belt section of FIGS. 2 and 8, the modules  42  (module rows  40 ) are arranged for straight travel, thus completely aligned and with the rods pulled to the back of the slotted projection holes (not shown). The support members or frames  48  are positioned at a canted, angular arrangement at the edges of the conveyor. This not only accommodates the staggered positioning of the module projections  46   a  and  44   b,  but also is necessary to allow the side plates or spacer frames  48  to slip alongside each other in overlapping relationship, to varying degrees. On a curve, the modules will collapse inwardly toward one another and nest closely at the inner edge of the belt. In this position, the spacer frames or support members  48  will become much more greatly overlapped, e.g. about 50%, than what is shown in the straight, aligned configuration in FIG.  2 . 
     Each support member or spacer frame  48  preferably has a generally horizontal top bar  50  which, as will be shown below, serves to support the conveyor belt tier immediately above, engaging it against the bottom of similar module portions of the belt section above. The open frame allows all flow laterally through the belt tier. 
     FIGS. 3 and 4 show short belt sections  52  and  54  made up of somewhat different modules  56 ,  56   a  and  58 ,  58   a.  Both types of modules exhibit limited product contact, and maximize airflow through the belt. These belt modules have heavier end members, identified generally as  60 . Again, these end members preferably are integrally molded with the remainder of each module, the modules including the first sets of projections  62  and second sets of projections  64 , as shown. The second sets of projections have slotted openings, allowing the module rows to collapse together at the inside of a curve, shown at the left in both FIGS. 3 and 4. 
     The end members  60  each have thick second projections  64   a  as shown, and a similarly thick outer first projection  62   a  and also a heavy inner second projection  62   b,  the two second projections  62   a  and  62   b  forming a yoke shape with the fat first projection  64   a  as shown. As the drawings illustrate, the end members  60  on opposite sides of the module rows preferably are opposite-hand in configuration. 
     Each of the end members  60  has a support member  70 , preferably extending integrally upwardly by common molding with the end member as a single piece of material but which can be connected by snap-in fasteners, etc., or which could be permanently secured by adhesion or sonic bonding. The side plates or spacer frames  70  are generally similar to the support frames  48  seen in FIG. 2, and in this embodiment, alternate rows of these support members  70  are canted in the same direction, as FIGS. 3 and 4 show. In the embodiment shown, the other alternate module rows, such as the row  72  in FIG. 3, have a substantially similar support frame or side plate  70   a  which is canted in the opposite direction. This provides support for the belt tier above at alternate locations from row to row, adding greater support with the staggered and spaced arrangement, while also affording more space between the spacer frames  70  in the collapsed configuration shown on the left in FIG.  3 . In this configuration the frames are generally about 50% overlapped, as illustrated; if all frames were canted in the same direction, this back flexing could be hindered. The advantage of the FIG. 2 arrangement is in providing greater product support area than FIGS. 3 and 4. 
     Each of the support members or spacer frames  70 ,  70   a  has a top bar  74 ,  74   a  which is generally horizontal, i.e. parallel to the approximate plane of the belt in the surrounding area. 
     FIGS. 3 and 4 show two modules making up each module row. The dividing line between modules is seen at  76 . In this case, the connecting rods  80  between rows are sufficiently strong to support the module row across the span between the end members  60 , since the module rows are freely suspended between these ends, as supported on the horizontal bars  74  of the spacer members  70 ,  70   a.  Metal rods can be used if needed. Also, alternate module rows can comprise a single module, this alternating with the split rows and adding strength. However, it should be understood that another heavy member such as the end member  60  can be positioned at or adjacent to the split line  76  between the modules in a row. Such an end member can form a second end of one of the modules, and the end member will then have support member or spacer frame so as to support the tier above from such an approximate midpoint, shortening the unsupported span of belt. 
     The FIG. 4 belt is similar functionally to the FIG. 3 belt, but with V-shaped or A-shaped link end structures. Thus, the set of first link ends in the modules  58 ,  58   a  in FIG. 4 are identified as  82 ,  82   a,  and the second set of link ends are identified as  84 ,  84   a.  These types of link ends are well known in plastic belts. 
     FIG. 5 shows a section of a belt  90  which may be similar to that of FIG. 4, with the nearer belt edge shown collapsed as on the inside of a curve. The belt  90  has module end members  60  similar to those shown in FIGS. 3 and 4, preferably integral with module structure including link end projections  82 ,  84  as in FIG.  4 . The link ends  82  and  84  may be in a single module extending from end member  60  to end member  60 , or these can comprise parts of several modules assembled together side by side on the connecting rods  80 . FIG. 5 illustrates the arrangement of the support members or spacer frames  70 ,  70   a  in this type of stackable spiral conveyor belt. The spacer frames  70 ,  70   a  are shown as having vertical legs  94  which are triangular-shaped in cross section, and the top bars  74 ,  74   a  may also be formed in this same cross section. This shape helps maximize air flow while providing the needed strength, but other cross sections can be used if desired. As also shown in FIG. 5, the top bars  74  have upwardly protruding nipples or teeth  96  (also seen in FIGS.  3  and  4 ), which may be triangularly shaped as shown, preferably aligned in an orientation perpendicular to the direction of travel, for engaging in notches  98 ,  98   a  in the bottoms of the projections  64   a  on the end members  60  supported on these frames  70  directly above. The notches  98  provide a forward/back locating function and also a lateral locating function by engagement with the nipples or teeth  96 . The width of these notches is limited to the width of the projections  64   a,  and in the assembled conveyor belt the teeth cannot move laterally beyond the width of the projection  64   a  because of the immediately adjacent projections  62   a  and  62   b  of the end member of the assembled adjacent module row. The reason two notches  98 ,  98   a  are provided, at tandem locations as shown, is to facilitate easier placement on the belt&#39;s support platform and engagement between tiers; each tooth  96  will engage with one or the other of the two notches above. 
     FIG. 6 shows two stacked modules  100  of a slightly modified form of the invention. The groove or notch  102  is in the first set of projections, engageable with a nipple or tooth  104  or a spacer frame  105  of a module below as shown. FIG. 7 shows this embodiment in perspective, schematically indicating module rows  106  from two successive tiers of the belt. The illustrated spacer frames  105  are shown somewhat heavier than the frames  70  in other embodiments, formed as complete rectangles including a bottom beam  108 . Again, these can be integrally molded with the modules or they can be arranged to snap in or can be secured by adhesive, solvent bonding or fasteners. 
     FIG. 8 is a perspective view from above, showing the conveyor belt of FIG.  2 . 
     FIGS. 9 and 10 show another embodiment of a radius type conveyor belt, which may be used on spiral conveyors, with module rows  110  each including module end members  112  having solid stacking side plates  114  that can be assembled into the modules. In this embodiment, each solid side plate  114  is generally S-shaped as shown, and with at least one tab  116  insertable into a slot  118  included in a wide projection  120  in the module end member  112 . This is preferably a tight snap-in connection, and the side plate  116  can have a rubbery foot piece  122  (connected to the end member by comolding, mechanical connection or adhesion), to help assure a close and stable fit. The bottoms of the end members  112  can have appropriate structure for seating the top edges  124  of these stacking side plates, to assure lateral stability of the stacked spiral conveyor belt. This type spacer frame, in addition to its removability, has the added advantage of providing an essentially solid barrier at the edge of the belt to retain small products on the belt, acting as a side guard or side plate (the side plates need not be totally solid, but can have openings). 
     The earlier-described frames also act as side guards, and are open for air circulation. Not limited to self-supporting spiral belts, these side guards are effective on non-self-supporting spiral belts (riding on a helical platform), wherein air circulation from the sides of the helical belt is important. The open frames can have additional product-retaining structure for smaller products if needed, partially closing the rectangular opening shown while still allowing adequate air circulation. 
     The open side guards can also be used on non-spiral radius type conveyor belts that articulate to travel around curves. 
     Broadly, the belt of the invention can be formed of modules connected by rods or otherwise, as by interconnected projections from module to module. Also, the support members or side plates can extend upwardly or downwardly or, if desired they could extend both upwardly and downwardly and engage one another between tiers. Still further, the location of the supports, through preferably on end members of modules as shown in the drawings, could be inboard somewhat and can include intermediate supports between the ends, so long as stable support is provided between tiers. 
     The conveyor belt of the invention may be injection molded from any of several different plastic materials: for example, polyethylene, polypropylene and actual. Actual tends to be best for freezer conveyors. 
     The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to this preferred embodiment will be apparent to those skilled in the art and may be made without departing from the spirit and scope of the invention as defined in the following claims.