LIGHTWEIGHT MODULAR CONVEYOR BELT

Abstract: A conveyor belt composed of interconnected identical modules of integral plastic molded construction. Each of the modules includes a multiplicity of elongated parallel spaced link elements having first and second pluralities of link ends and an intermediate section of a grid-­ like structure between the link ends. The link ends each include a portion projecting from one side of each of the link elements along the pivotal axis of the module. The portions extend from the same facing side for each group of link ends, such that when adjacent modules are linked together the projecting portions of adjacent link ends are rotated 180° with respect to each other, in that the projecting portions of the link ends of each adjoining module extend in opposite directions. Thus, the flat sides of the linked ends of mated modules are in engage­ ment to provide only a very small offset in the line of pull through the adjacent link elements to minimize bending forces in the links and link ends.

Description: FIELD OF THE INVENTION This invention relates to conveyor belts and modules for the construction thereof, and more particularly to a modular conveyor belt comprising inter­ connected modules of the same integral construction. BACKGROUND OF THE INVENTION Modular conveyor belts are known which comprise modules pivotally connected to one another, each module being molded as a single unit, preferably of a plastic material. Such conveyor belts are shown, for example, in U.S. patents 3,870,141 and 4,051,949 of the same inventor and assignee as herein. Each module includes a number of parallel spaced links having end sections with aligned holes for accommodation of pivot rods, and intermediate sections joined by integral cross members to form a rigid supporting grid. The upper portions of the links and intermediate sections define a conveyor surface on which a product is carried. Alternatively, the link elements can extend upwardly to a plane which is above the plane of the upper portions of the intermediate sections to provide raised link elements or raised ribs which define parallel longitudinal channels between adjacent links, and in which channels a conveyor comb can be disposed for transfer to a product to and from the conveyor belt, as shown in the aforesaid patent 4,051,949. In co-pending application Serial No. 179,523 filed August 19, 1980, (LAIT-59) a conveyor module is shown which includes sprocket recesses located midway between the pivot axes and which are adapted to mate with corresponding sprocket teeth of an associated sprocket wheel. the sprocket recesses are provided by angled surfaces of the intermediate sections. These intermediate sprocket recesses provide the benefit of minimizing chordial action and scrubbing between the mating surfaces of the module and sprocket. SUMMARY OF THE INVENTION The present invention provides a conveyor belt and module which is similar to, and an improvement over the aforesaid structures. The conveyor belt is composed of a plurality of interconnected modules, each of identical construction and each including a multiplicity of elongated spaced link elements terminating in first and second pluralities of link ends. An intermediate section between the pluralities of link ends is of a grid-like structure providing a box beam across the width of the module for structural strength. This intermediate section also includes angled surfaces which define sprocket recesses located midway between the pivot axes and which are adapted to mate with corresponding sprocket teeth of an associated sprocket wheel. The link ends each include a projecting portion that extends from one side of each of the link elements along the transverse or pivotal axis of the module. The portions extend in the same direction and from the same facing side of each plurality of link ends. The opposite side of the link ends are substantially flat and have only minimal, if any, outward projection. The link ends and extending portions contain openings which are aligned on respective pivotal axes of the module for accommodation of pivot rods by which interconnected modules are retained in linking engagement. In one embodiment, the portions are constituted as cylin­ drical projections. In a further embodiment, raised ribs integral with the link elements are dimensioned to define the portions. The modules in both embodiments are linked together such that the extending or projecting portions of the link ends of each module are rotated 180° with respect to the link ends of an adjacent mated module such that that the extending portions of each adjacent module extend in opposite directions. The flat sides of the linked ends of mated modules are in engagement to provide a very small offset in line of pull through the adjacent link elements. As a result, the line of pull through the pivot rod is substantially in a shear condition, since the shear point is near the tensile members, thereby minimizing bending forces on the linked ends. DESCRIPTION OF THE DRAWINGS The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying draw­ ings, in which: Figure 1 is a pictorial view of a conveyor module embodying the invention; Figure 2 is a side view of the module of Figure 1; Figure 3 is a cutaway top view of the module of Figure 1; Figure 4 is a pictorial view of interconnected modules of Figure 1; Figure 5 is a top view of interconnected modules of Figure 1; Figure 6 is a pictorial view of an alternative embodiment of the module of Figure 1; Figure 7 is a side view of the module of Figure 6; Figure 8 is a cutaway top view of the module of Figures 6 and 7; Figure 9 is an elevation view of a modular conveyor belt embodying the module of Figure 6 with a sprocket wheel and conveyor comb; Figure 10 is a top view of interconnected modules of Figure 6 and cooperative with a conveyor comb; Figure 11 is a cutaway top view of interconnected modules including side guards; Figure 12 is an elevation view of interconnected modules including side guards and cooperative with a sprocket wheel; Figures 13, 14, and 15 are pictorial, side, and end views, respectively, of side guards useful with the conveyor belt of the invention; Figure 16 is a partial perspective view of a sprocket wheel useful in the invention; Figure 17 is a bottom plan view of another embodiment of interconnected conveyor modules embodying the invention; Figure 18 is a top plan view thereof; Figure 19 is a sectional view along the lines 19-19 of Figure 18; Figure 20 is a sectional view along the lines 20-20 of Figure 19; and Figure 21 is a sectional view along the lines 21-21 of Figure 19. DETAILED DESCRIPTION OF THE INVENTION A conveyor belt module in accordance with the invention is shown in Figures 1-3 and is integrally formed of a plastic material by a plastic molding process. The module includes a plurality of linear link elements 10, each terminating in respective link ends 12 and 14 arranged in parallel relationship across the width of the module. The link elements 10 are spaced and joined by first and second transverse members 16 and 18 which have upper and lower edges which are coplanar with the respective upper and lower edges of the link elements 10. The transverse member 16 has sloping surfaces 17 which downwardly and outwardly extend toward link ends 12, while the transverse member 18 has sloping surfaces 19 which downwardly and outwardly extend toward link ends 14, the confronting sloping surfaces 21 defining sprocket recesses between the pivot axes and which are colinear with the spacing between adjacent link elements 10. The link elements 10 and transverse members 16 and 18 are preferably of uniform thickness to facilitate molding and preferably provide uniform thermal expansion and contraction in response to ambient temperature conditions. The open grid construction prevents any significant bending of the module about its longitudinal or transverse axes. The link ends 12 and 14 each include a generally cylindrical projection 20 which extends from one side of each of the link elements along the transverse or pivotal axis of the module. The projections 20 extend from the same facing side of each link element, the opposite side of the link elements being substantially flat and with minimal, if any, outward projection. The link ends and projections 20 contain openings 22 which are aligned on respective pivotal axes of the module. The transverse members 16 and 18 include portions 16a and 18a which extend from the outer sides of the outer link elements 10 by an amount equal to the outward extent of the projections 20. The portions 16a and 18a serve to abut like portions of laterally adjacent modules to provide lateral support therefor. In the illustrated embodiment, the link ends include flattened sections 23 which serve as wear surfaces for riding on conveyor wear strips or support surfaces. The sloped surfaces 25 are for ease of mold construction. The surfaces 23 and 25 are not necessary but are convenient features. The modules are linked together with like modules as shown in Figures 4 and 5. Each module is rotated 180° with respect to the mated modules such that the projections 20 of each adjacent module extend in opposite directions. A pivot rod or pin 27 is inserted in the aligned openings 22 of interconnected modules and retains the modules for pivotal movement with respect to each other. The pivot rods are typically formed of the same or compatible plastic material as the modules themselves, and are typically retained in the modules by headed ends 29 formed on the pivot rods. The flat sides 31 of the link ends of one module are in engagement with the flat sides 33 of the link ends of a mated module, as best seen in Figure 5, to provide a very small offset in the line of pull through the adjacent link elements. As a result, the line of pull through the pivot rod is nearly in a pure shear condition, since the shear point is near the tensile members 10, thereby minimizing bending forces in the links 10 and in the link ends. The projections 20 have a thickness slightly less than the spacing between adjacent link ends such that the link ends fit within the corresponding spacings of adjacent modules and are pivotable with respect thereto. The projections provide sufficient bearing surface with the pivot rod to accommodate the tensile forces on the belt during its driven operation. An alternative module embodiment is shown in Figures 6-8 wherein the link elements 30 each extend upwardly to a plane which is above the plane at which the upper surfaces of the transverse members 16 and 18 terminate. These raised link elements, or raised ribs, define parallel longitudinal channels 32 between adjacent link elements. A conveyor comb 34 has its tines 36 disposed within the channels 32 in the manner shown in Figures 9 and 10, the upper surfaces of the tines being substantially at or slightly below the conveying surface and by which a product is removed from the conveyor belt as the conveyor traverses a downwardly curved path, as shown in Figure 9. A module having raised ribs and usable with a conveyor comb is shown in U.S. patent 4,051,949 of the same inventor as herein and is also shown in co-pending application Serial No.179,523. The inclined portions 17 and 19 of the transverse members 16 and 18 have confronting inner surfaces 21 which define sprocket recesses centrally disposed between the pivot axes of the module. The sprocket recesses are adapted to mate with corresponding sprocket teeth 38 of an associated sprocket wheel 40, as shown in Figure 9. The sprocket wheel has teeth 38 with parallel side surfaces, and inclined front and back surfaces 42 configured to engage the corresponding surfaces 21 of the sprocket recesses. The teeth 38 are laterally offset to accommodate the offset recesses of the mated modules, as seen in Figure 16. In the illustrated embodiment, the sprocket wheel 40 has a hub 44 adapted to be secured to a square shaft, and a plurality of sprocket wheels are employed across the width of the module to provide intended support and driving force. The centrally driven sprocket recesses provide the benefits of minimizing chordal action and scrubbing between the mating surfaces of the module and the sprocket wheel. A centrally disposed sprocket recess employed in a different module is shown in co-pending application Serial No. 179,523 of the same inventor as herein, and can be considered the inverse of the center sprocket tooth shown in co-pending application Serial No. 228,154 of the same inventor. The placement of the sprocket recesses midway between the pivot axes and driving the modules at this mid-position, rather than driving the modules at the position of the pivot axes, proivdes substantially constant speed drive of the conveyor belt, substantially eliminates sprocket-to-belt wear, and provides a belt capable of faster running speeds than conventional belts by reason of the minimized chordal action and scrubbing. The inclined surfaces also serve to present greater surface area to water and/or steam jets which can be located above and below the modules for cleaning of the belt. The inclined surfaces also facilitate visual inspection of the belt. The modules are preferably made in widths which are multiples of the smallest module width so that they can be arranged in brick-laid fashion to provide a conveyor belt of intended overall width. The modules are staggered laterally such that a module straddles laterally adjacent modules to achieve a belt which resists bending across the width of the belt. The modules are preferably fabricated as an integral unitary structure by injection molding of a plastic material such as polyethylene and polypropylene. The particular plastic material is determined in accordance with the character­ istics desired to suit a particular operating environment. The pivot rods are typically of the same or compatible plastic material. Selected link ends of the modules can have their lateral projections removed, as shown at link ends 12a and 14a in Figure 3. The projections can be eliminated during fabrication of the module or can be removed after such fabrication, such as by machining the intended projections from the associated link ends. The increased spacing provided by the absence of projections provides room for belt attachments such as the side guards 50 illustrated in Figures 11-15. The side guard is of molded plastic having a relatively thin plate-like body with inwardly sloped edges 52 and 54, and a downwardly extending pair of flanges 56, each having an opening 58 therethrough. The flanges 56 and openings 58 are sized to be of the same pitch length as the associated module, and to fit into the projection-less link ends and to be retained therein by the pivot rod 22, in the manner illustrated in Figure 11. A rib 60 protrudes from each side and downwardly of the guard 50 to provide for strengthening and stiffening thereof and is adapted to fit into the upper openings of the modules. The side guards are assembled with the ends overlapping, as seen in Figure 12. As the connected modules are conveyed around a sprocket wheel, the adjacent guards slidably move but remain in overlapping engagement to provide an effectively continuous side barrier for the belt. Typically, side guards are employed near the side edges of the connected modules to contain a product within a channel between the pair of guards. Alternatively, guards can be provided along the center of the conveyor belt to separate the belt into left and right halves, as is desirable for some conveying purposes. A further conveyor module embodiment is shown in Figures 17-21. Each of the modules includes a plurality of stepped-link elements 10', each terminating in respective link ends 12' and 14' and arranged in laterally spaced relationship across the width of the module. The boundary of a conveyor formed by such stepped modules thereby defines a generally rectangular configuration, not specifically illustrated. The link elements 10' are spaced and joined by first and second transverse members 16' and 18' which have upper and lower edges which are coplanar with the respective upper and lower edges of the link elements 10' as can best be seen in Figures 19 through 21. The transverse member 16' has sloping surfaces 17' which downwardly and outwardly extend toward link ends 12', while the transverse member 18' has sloping surfaces 19' which downwardly and outwardly extend toward link ends 16', the confronting sloping surfaces 21' (Figure 19) defining sprocket recesses centrally disposed between the pivot axes. The link elements 10' and transverse members 16' and 18' define an open grid construction that prevents any significant bending of the module about its longitudinal or transverse axes. The cross members 16', 18' have upper and lower surfaces 50, 52 (Figure 19), coplanar with respective upper and lower surfaces 55, 56 (Figure 19) of the link elements. Stepped-ribs 58 (Figure 18) are integrally formed with the upper surfaces of the links and extend from link end to link end. As can best be seen in Figures 18, 20, 21, the dimensions of the ribs 58 are selected to be less than the corresponding dimensions of said link ends defining a transversely extending portion 60 projecting toward a confronting link end and terminating short of the confronting link by an amount to accommodate the link end of a mated module. The portions 60 have a body configuration that defines central openings 62 therethrough which are aligned on respectively pivotal axes of the modules. A pivot rod or pin 27' is inserted in aligned openings 62 of interconnected modules and retains the modules for pivotal movement with respect to each other. The portions 60 have a body configuration that wholly surrounds the pivot rods. The flat sides of the link ends of one module are in engagement with the flat sides of the link ends of a mated module, as can best be seen in Figure 17 and 18, to provide a very small offset in the line of pull through the adjacent link elements. As a result, the line of pull through the pivot rod is nearly in a pure shear condition, since the shear point is near the tensile members 10' thereby minimizing bending forces in the links 10' and in the link ends. The thickness of the portions 60 is slightly less than the spacing between adjacent link ends such as the link ends fit within the corresponding spacings of adjacent modules and provide sufficient bearing surface with a pivot rod to accommodate the tensile forces on the belt during its driven operation. A conveyor comb 34 having the tines 36 may be disposed between the innerspace defined between adjacent stepped ribs 58 to receive and remove elements onto and off the conveyor module as described above in connection with the description of Figures 9 and 10. Many modifications of the present invention will be apparent to those skilled in the art without departing from the scope of the appended claims.

Claims: 1. A conveyor belt composed of a plurality of linked modules each of substantially identical pitch dimension, and each of integral plastic molded construction, each module comprising: a plurality of spaced link elements, the length of the module being equal to the length of the link elements, and the width of the module being determined by the number of link elements; the link elements terminating in first and second pluralities of link ends, each link end being formed to circumscribe a pivot hole; a grid structure integral with the link elements and disposed between the link ends and having longitudinal members integral with the link elements and extending along the length of the modules and having two cross members integral with the link elements extending across the width of the module which separate and join longitudinal members and link elements; the cross members being spaced along the length of the module and angularly disposed to provide sprocket recess intermediately positioned between the pivot axes and adapted to mate with corresponding sprocket teeth of the sprocket wheel; the cross members having upper and lower surfaces coplanar with respective upper and lower surfaces of the link elements; substantially all of said link elements each defining a transversely extending portion projecting toward a confronting link end and termina­ ting short of the confronting link end by an amount to accommodate the link end of a mated module, each of said projecting portions associated with one of said first and second pluralities being on the same facing side, and the side opposite said extending portion being substantially flat and not defining any transversely extending portions, each of the transversely extending portions having an opening therethrough in alignment with the pivot hole of the associated link ends; the modules being linked together by pivot rods such that the projecting portion of each link end of each module are rotated 180° with respect to mated link ends of adjacent modules such that the trans­ versely extending portions of each adjacent module extend in opposite directions, with the flat sides of link ends of one module being in engagement with the flat sides of the link ends of mated modules to provide a line of pull through the pivot rod near the link elements; each of the transversely extending portions defining a preselected body configuration selected to wholly surround the pivot rods. 2. The invention of claim 1, wherein said transversely extending portions include cylindrical projections integrally formed with said link elements and on the same side for each of the link ends of one of said first and second pluralities. 3. The intention of claim 1, further including ribs integrally formed with the upper surfaces of the link elements and extending from link end to link end, and wherein the dimensions of said ribs are selected to be less than the corresponding dimensions of said link ends defining said transversely extending portions. 4. The invention of claim 3, wherein each of said link elements has a step provided therealong, that are arranged in laterally spaced relation across the width of the belt. 5. The invention of claim 4, wherein each of said ribs has a step provided therealong that substantially conforms to said step of the link element, and define said extending portions.

Inventors: LAPEYRE, JAMES M.
Applicants: THE LAITRAM CORPORATION
Application year: 1986
Main classification: B65G17
IPC codes: B65G17