Abstract:
A plastic modular conveyor belt of the type which is capable of traversing lateral curves, with module rows collapsing together at inner sides of curves, has a solid deck over a central portion, but leaving terminal ends of interdigited projections not covered by the deck structure. The solid decks on each module are above the level of the interdigited projections, such that upon traversing curves the projections toward the inside of the curve can slide under the deck of the adjacent module, and the dimensions of the solid decks allow the inner edges of the module rows to collapse substantially fully without limitation by the edges of the decks, which do not lap over one another. The gap between module rows in straight belt travel is mostly closed by the interdigited terminal portions of the projections. In some embodiments the edges of the decks include interdigiting finger structure to provide a more continuous load-supporting surface.

Description:
BACKGROUND OF THE INVENTION 
     The invention concerns conveyor belts assembled from plastic modules to produce a belt in virtually any length and width. In particular the invention relates to a conveyor belt capable of following a path including both straight and curved sections, and such a belt which has a substantially continuous solid top supporting surface. 
     Modular plastic conveyor belts, and the modules of which they are constructed, are very well known and the subject of a large number of patents. See, for example, U.S. Pat. Nos. 5,181,601 and 4,742,907, owned by the assignee of the present invention. The belts of both those patents are capable of straight and curving travel, due to the provision of slotted holes in link ends on one side of each module, and elongated interdigited link ends, rendering the ability of module rows to collapse together at the inside of a curve. 
     Belts having solid, substantially closed conveying surfaces are also very well known. For an example of a modular plastic conveyor belt with a solid conveying surface, see U.S. Pat. No. 5,706,934, also owned by the assignee of the present invention. 
     Conveyor belts for some specific purposes have included solid conveying surfaces which remain closed when the conveyor traverses a curve. To achieve this, such solid top belts have generally included plates which lap over one another, or lap more deeply over one another on curves, to achieve the required contraction at the inner side of a curve. Examples are the metal conveyors found in baggage handling equipment at airports. An example of such a lap-over structure in a modular conveyor belt is found in patent publication WO93/14010. The components of that belt were disclosed as being either of metal or plastic; the belt modules did not include a multiplicity of interdigited link ends or projections as in the above-referenced patents and as in the present invention described below. 
     In many applications there is a need for a conveyor belt, having the versatility and practical advantages of modular construction as in the &#39;601 patent referenced above, and at the same time having a substantially solid or continuous conveying surface without the sometimes objectionable feature of one plate sliding over another which can result in wear and moving edges that can catch or snag conveyed articles. 
     SUMMARY OF THE INVENTION 
     According to this invention, a plastic modular conveyor belt, of the type described in U.S. Pat. No. 5,181,601, achieves the above stated goals. Such a belt, of the type which is capable of traversing lateral curves, with module rows collapsing together at inner sides of curves, has a solid deck over a central portion, but leaving terminal ends of interdigited projections not covered by the deck structure. The solid decks on each module are above the level of the interdigited projections, such that upon traversing curves the projections toward the inside of the curve can slide under the deck of the adjacent module, and the dimensions of the solid decks are such as to allow the inner sides of the module rows to collapse substantially fully without interference by the edges of the decks, which do not lap over one another. 
     While traveling through a straight section, the conveyor belt has a gap between succeeding module rows, but this is substantially closed by the interdigited terminal portions of the projections, so that only relatively small objects would be capable of falling through, and such small objects are not carried on the belt. 
     In some embodiments the edges of the deck structures include longitudinally extending fingers for providing a more continuous load-supporting surface, the fingers becoming more deeply enmeshed in corresponding slots of a succeeding module when the module rows come together at the inside of a curve. 
     A further embodiment of the invention is for conveyor situations where all curves are in the same direction. In that embodiment, the solid deck or decks making up a module row define a wedge shape, generally trapezoidal, so that on the curves, are all generally of a prescribed radius, the solid deck portions form a truly continuous conveying surface. In straight sections of such a conveyor, the module rows form generally triangular shaped gaps between them, but these are substantially filled by the terminal ends of the interdigited projections at a slightly lower level. Again, interdigited finger structure can be included to provide a more continuous conveying surface in these gaps. 
     It is thus among the objects of the invention to improve on conveyors capable of traversing straight and curving sections while presenting a substantially closed or continuous conveying surface, by combining the features of interdigited molded plastic conveyor modules with solid deck surfaces covering most of the modules, without the need for plates lapping over one another, therefore providing belts having a substantially continuous top, not completely impervious but sufficiently so for the type of articles to be carried. 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 plan view showing a portion of a conveyor belt of the invention, comprised of several modules, with the belt section shown traversing a curve. 
     FIG. 2 is a view similar to FIG. 1, but showing the belt portion in a straight section. 
     FIG. 3 is a plan view showing a module. 
     FIG. 4 is a bottom plan view of the module FIG.  3 . 
     FIG. 5 is an end elevation view showing a module and indicating a portion of a second module interlinked with the first. 
     FIG. 6 is a plan view showing several modules side by side, in another embodiment. 
     FIG. 7 is a partial view in longitudinal elevation of a module of FIG.  6 . 
     FIG. 8 is a plan view similar to FIG. 1, showing another embodiment. 
     FIG. 8A is a side elevation view indicating modules as in FIG.  8 . 
     FIG. 8B is a view similar to FIG. 8, showing the modules as nested together on a curve. 
     FIGS. 9A and 9B are plan views schematically indicating another embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a portion  10  of a conveyor belt formed of a series of module rows  12 ,  13 ,  14 , etc. as shown. Although each belt row can comprise a single module, as further illustrated below, the belt in wider implementations will normally have two or more individual modules, as at  16  and  17  in the module row  12  and as at  19 ,  21  and  22  in the module row  13 . The modules are thus staggered in position, with joints  24  between side-by-side modules not forming a single line through the conveyor but being offset in position as shown. Thus, the module  14  is similar to the module  12 , with the row being made up of a pair of modules  16  and  17  between which is a central joint  24 . 
     Each module is comprised of a central bar or intermediate section  25  from which extend rows of first projections or link ends  26  in one longitudinal direction and second projections or link ends  27  in the opposite longitudinal direction. These projections become interdigited in the assembled belt as shown, connected by a connecting rod  30  which passes through openings in the projections, as shown in U.S. Pat. No. 5,181,601, incorporated herein by reference. Projection openings  32  on the second projections  27 , i.e. those extending in one direction from each module, are slotted, as is well known from the referenced U.S. Pat. No. 5,181,601 and other patents showing plastic modular conveyor belts capable of curving travel. Those openings  32  allow the inner edge of the belt, on the left in FIG. 1, to collapse together as shown in FIG.  1 . 
     Also as shown in &#39;601 patent, the modules at the ends of each belt module in this particular embodiment have integral sideplates, or special link ends  26   a  and  27   a  to withstand the high tension in the outside of a curve in a conveyor made up of such modules. 
     The central feature of this invention is the provision of solid decks  34  on the modules. These solid decks are positioned in the modules so as to extend essentially entirely from left to right in each module row (although lesser width is possible), and to extend in longitudinal directions as far as possible without causing interference with the collapse of the modules together at the inside of a curve. 
     As seen in FIG. 1, one or both of the confronting deck slabs  34 , at the extreme ends of the module rows, can have an angled edge  36  to enable the two decks to nest together more closely, or, stated another way, to enable the generally triangular gap  38  between decks in the module rows to be smaller, simply by truncating a small portion of one or both decks near the edge of the row. This assumes the degree of collapsing together of the two rows at the inside edge of the curve is limited only by the configurations of the link ends or projections  26  as nesting between projections  27  from the adjacent module row. The object is not to interfere with that nesting together capability, which would limit the radius of turn available, while still making the gap  38  as small as possible. 
     The solid decks  34  are at a level higher than the projections  26 ,  27  and the intermediate bars  25  of the modules. Preferably the decks are integrally molded with the modules, with the bottoms of the decks being substantially at the level of the tops of the projections, so that the projections of one module row can slide under the deck slabs of the adjacent module row, as illustrated in FIG.  1 . 
     FIG. 2 shows the belt section  10  of FIG. 1, but in a straight section of conveyor. This view illustrates the gaps  38  at their maximum, when there is no angular shifting of module rows and the chain of rows is in tension, separating the decks to the maximum extent. 
     FIG. 3 shows a single module  40  in top plan view, in a particular embodiment and configuration. In this the module  40  is shown as having a width which will become the full width of the conveyor belt, the module having edge structure  42  which is similar at both edges and which serves to accept tension of the belt at the outside of a curve, as described in U.S. Pat. No. 5,181,601. The module  40  may be similar in most respects to the modules disclosed in U.S. Pat. No. 5,181,601, except in having a solid top deck  34  as shown in FIGS. 1 and 2. The link ends or projections  26  and  27 , the latter having slotted openings  32 , are seen with their terminal ends  26   a,    27   a  extending out longitudinally from under the deck structure  34 , which is at a level above the tops of the projections  26 ,  27 . FIG. 5 shows the module  40  in edge view, in elevation, revealing the slotted openings  32 , cylindrical openings  33  of the other projections  26 , the transverse central bar or intermediate section  25  (dashed lines) of the module, and the solid deck  34  on top of the projections. A second module  40   a  is partially shown at the right side of FIG. 5, indicating its deck slab  34  and the gap  38  between the decks of the two modules when the belt is in a straight configuration rather than on a curve. FIG. 5 also shows the angled edge  36  which may be included near the extremities of deck structures which will be at the edges of the belt, as one means for nesting the slabs closer together on curves. From FIG. 5 it can be seen that when the belt enters a curve, an edge such as shown in FIG. 5 will encounter convergence or collapsing of the two modules together, thus moving the terminal end  26   a  of the link end  26  to the left and underneath the deck slab  34  of the module  40 , until the connecting rod  30  is substantially at the left extremity of the projection slot  32 , at which the deck slabs  34  will be substantially abutted, or very nearly so, with the inter-deck gap  38  substantially closed at that edge of the belt. 
     FIG. 4 shows the bottom side of a module such as the module  40  shown in FIGS. 3 and 5. The figure reveals the heavier edge projections  42  or integral sideplates of this type of radius belt, as in the &#39;601 patent referenced above, as well as the guide members with hold down tabs  44  extending downwardly and inwardly as in the &#39;601 patent. The bottom side of the solid deck  34  is visible, as is the solid transverse bar  25  forming a central intermediate spine of this type of belt module. In an integrally molded construction, which is preferred, the configuration of the link ends and the connecting spine  25  can be different, since the link ends are integrally retained in position by the solid top deck structure  34 . Thus, the intermediate solid bar  25  can be eliminated if desired, although in some high tension conveyor belt applications it may be needed for higher tensile strength. The elimination of the cross bar or transverse intermediate section  25 , when possible, can increase the degree of collapse possible at the inner edges of the belt on a curve, i.e. decrease the radius of curve. 
     FIG. 6 shows another embodiment of a module row  45  for a radius type conveyor belt, the module row  45  including modules  46  and  47 . The modules  46  and  47  are both edge modules, the module  47  being considerably wider in order it place a joint  48  at an off-center position for staggering of modules, as discussed above. A succeeding module row (not shown) would have the joint  48  in an off-set location, such as by reversing the sizes of the left and right modules. Additional modules, with half-width link ends  50  such as shown, but at both left and right edges, can be placed between the modules  46  and  47  for increased width. 
     FIG. 6 shows the modules  46 ,  47  in plan view, with much of the structure of the link ends  52  and  54  and the structure of the solid intermediate bar  56  hidden and shown in dashed lines. The solid deck  58  is shown covering all but terminal ends  52   a,    54   a  of the projections or link ends. 
     FIG. 7 shows a portion of this same type of belt module in elevation view, with the right edge shown as having a horizontal slot  60  formed between upper and lower horizontal flanges  62  and  64 . The slot  60  is positioned to engage with an inwardly extending horizontal rail connected to the supporting wearstrip (not shown) of stationary structure on which the conveyor belt glides. This structure is an alternative to the guide/hold down structure  44  shown in FIG.  4 . 
     FIG. 8 shows in a plan schematic view another embodiment of the invention wherein a series of fingers  66  are included on each module, for engaging within corresponding slots  68  on the opposing adjacent module. The modules are provided with these extending fingers in this embodiment in order to provide a more continuous platform at the level of the top of the solid decks  34   a,  thus reducing the maximum width of the gap  38   a,  where the deck surface dips to the level of the tops of the terminal link ends as in the embodiment shown in FIGS. 1-5. Although the fingers  66  could be independent of the link ends, for reasons of strength and integrity it is preferred that these fingers simply comprise integrally molded bosses or tops on the link ends, with the notches  68  being located between link ends on the opposing module. FIG. 8B shows the modules  70  of FIGS. 8 and 8A in the angled, collapsed inner side configuration of a curve. 
     FIGS. 9A and 9B show another embodiment of a conveyor belt and modules of the invention, wherein the belt is intended for straight and curved travel, but with all curves being in the same direction. FIG. 9A schematically indicates three modules or module rows  72 , each having a solid deck slab  74  which is essentially trapezoidal in shape leaving triangular gaps  76  between the module rows as indicated. These gaps can be partially lessened by the finger and notch structures  66 ,  68  shown in FIGS. 8-18B. 
     FIG. 9B shows the modules  72  collapsed at an inner side  78 , traveling around a left curve. In this curving configuration, of a prescribed radius, the deck slabs  74  provide a continuous upper conveying surface. 
     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.