Sideflexing conveyor chain

Abstract: A conveyor includes a track (16) having at least one arcuate section, and a conveyor chain (10). The track comprises a pair of spaced apart track portions (18,19), each including a generally vertical guide surface (20,21). A first one (20) of the guide surfaces defines the inside of an arcuate path and the other one (21) of the guide surfaces defines the outside of the path. The conveyor chain (10) is constructed and arranged for traversing the path and comprises a plurality of links (12), each of which has a first pivot eye (25) at one end thereof and a pair of pivot eyes (26) at the other end thereof and complementary to the first pivot eye (25). Pins (14) couple the pivot eyes (25,26) of pairs of adjacent links (12) for pivotally connecting the same. Each link (12) engages the first one (20) of the surfaces as the chain traverses the path to generate reaction forces (Fr) acting on each link and having an average line of action (CLs) intersecting the first one of the surfaces (20). The pins (14) are oriented transversely to the path defined by the surfaces (20,21) and the axis (CLp) of each pin (14) is located below the average line of action (CLs) of the reaction forces (Fr).

Description: This invention relates to conveyor chains and more particularly to side-flexing chains designed to convey material along a track having arcuate sections. Side-flexing conveyor chains are commonly used for transporting articles along a track having at least one arcuate or curved section. Under certain conditions, such as high speed and loading, these side-flexing chains have a tendency to "climb" or lift out of the curved sections of the track. This is a significant safety problem, in addition to causing poor product handling. As a result, there have been many prior art attempts to maintain conveyor chains within such curved track sections. These have included mechanical retainers such as tabs, as disclosed in US-A-4,096,943; US-A-4,436,200; DE-A-3 046 568 and EP-A-0 355 080, and beveled surfaces on the track wear sections and the chain links, such as are disclosed in DE-A-3 046 568; FR-A-2 558 808; US-A-3 804 232 and US-A-3,262,550. While such mechanical retainers did prevent the chain from pulling out of the curved track sections, they also prevented the chain from being lifted from the straight sections of the track. As a result, the track sections had to be removed for maintenance and cleaning, thereby complicating these procedures. Furthermore, chains with mechanical retainers still experienced some lift or tilting within the permitted tolerances between the chain and the track sections. In order to avoid the maintenance and cleaning problems associated with mechanical retainers, an alternative method has been to magnetically maintain the conveyor chain in the curved track sections. Such magnetic retainers generally include permanent magnets positioned in or between the rails for applying a magnetic hold-down force on ferromagnetic portions of the chain links or coupling hinge pins. The magnetic approach has the advantage of allowing the chain to be easily pulled upwardly away from the corner sections of the track, since no mechanical retainer is employed. Examples of magnetic chain conveyors are disclosed in U.S. patents 3,581,873; 4,236,632; 4,643,298; 4,742,906; and 4,805,764; and U.K. patent application no. 8608993, filed 14 April 1986; GB 2182296A; and GB 2037690A. While magnetic retainers permit the chain to be lifted without removing track sections, the magnetic approach has several disadvantages. For example, the additional force exerted by the magnets consumes some of the chain's capacity by increasing turn factors, thereby limiting performance. In addition, the use of magnets is costly in that the corner track sections are complicated and require expensive components. Additionally, magnetic chain conveyors present a safety hazard because they provide no fail-safe mechanism to prevent the chain from leaving the corner sections other than the magnetic attraction. Another disadvantage of magnetic retainers is that at least a portion of the conveyor chain must be formed of a magnetic material. For example, the magnetic chain conveyor disclosed in U.S. patent 4,805,764 comprises plastic chain links interconnected by hinge pins formed of a ferromagnetic material, while in U.S. patent 4,742,906, the links themselves are ferromagnetic. Such magnetic conveyor chains cannot be totally formed of plastic or Austenitic stainless steel, which possesses certain advantages over ferritic stainless and carbon steels, such as corrosion resistance and work hardening capability. It is an object of the invention to provide a new and improved chain conveyor for transporting products through a curved track section wherein the conveyor is safe to operate and the chain can readily be removed from the track for cleaning and servicing. A further object of the invention is to provide a chain conveyor for transporting articles through a curved track section which does not rely on mechanical retainers or expensive magnetic components to retain the conveyor chain within the track, and which enables all of the chain components to be formed of non-magnetic materials if desired. Accordingly, the invention provides a conveyor chain for traversing a track having at least one arcuate section comprising a pair of spaced apart track portions having respective surfaces which define an arcuate path therebetween, a first one of the surfaces defining the inside of the arcuate path and the other one of said surfaces defining the outside of the arcuate path, said conveyor chain comprising a plurality of links each having a first pivotal connection means at one end thereof and a second pivotal connection means at the other end thereof and complementary to the first pivotal connection means, and pin means pivotally coupling the first and second pivotal connection means of pairs of adjacent links, said pin means being oriented tranversely to the path traversed by said chain, each of said links being engageable with said first one of the path defining surfaces as said chain traverses said path to generate a reaction force acting on said link and having an average line of action, characterised in that the axis of each pin means is located below said average line of action to create a couple on said links acting to retain said links within the arcuate section of the track, this being the sole means for retaining the links within the arcuate section. Preferably each link includes a generally planar top portion for being supported on a carrying surface, the first pivotal connection means of the link comprising first eye means extending downwardly from one end of the link and at substantially the center of said one end, the second pivotal connection means of the link comprising a pair of eye means extending downwardly from the opposite end of the link and spaced apart from the center thereof for engaging the first eye means on an adjacent link, and said pin means extends through the second eye means on one link and the first eye means on the adjacent link for pivotally connecting the same. A preferred embodiment of a conveyor in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a perspective view of a portion of the conveyor; Figure 2 is an underneath plan view of a portion of the conveyor chain illustrated in Figure 1; Figure 3 is a side view of the conveyor chain portion shown in Figure 2; Figure 4 is a cross-section taken along line 4-4 of Figure 2; Figure 5 is a diagram illustrating the operation of the conveyor shown in Figure 1; Figure 6 is an underneath view of a portion of the conveyor shown in Figure 1; and Figures 7,8 and 9 are views similar to Figure 5, illustrating details of the construction of the preferred conveyor. FIGURE 1 shows the conveyor chain 10 in accordance with the preferred embodiment of the invention to comprise a plurality of links 12 which are interconnected by hinge pins 14 (FIGURE 2). The chain 10 traverses a guide track 16 which is formed by a pair of spaced apart wear strips or rails 18 and 19. The strips 18 and 19 are mounted atop a suitable, generally horizontal support structure and each respectively has a generally vertically oriented guide surface 20 and 21 and generally horizontally oriented carrying surfaces 22 and 23, which are equispaced apart along their entire lengths. It will be appreciated that the chain 10 is endless and that only a segment is shown in FIGURE 1 to be located in a curved or corner section of the track 16 which may also include one or more straight and/or curved section, depending on the application. The chain 10 is driven by a drive sprocket (not shown) and may also engage one or more idler sprockets. The links 12 each include a generally planar top plate 24 having a center hinge eye 25 at its trailing end and a pair of complementary hinge eyes 26 at its leading end. The trailing edges 27 of the links are preferably beveled and extend at a slight angle rearwardly, as seen in FIGURES 1 and 2, to permit relative pivotal movement of the links 12 in the horizontal direction. The hinge eye 25 extends outwardly and downwardly from the trailing edge of top plate 24 and has a bore 28 extending therethrough from end to end and having an axis parallel to the plane defining the upper carrying surface 29 of top plate 24. As seen particularly in FIGURES 2 and 4, the bore 28 is conical from its center to each end which also facilitates relative horizontal pivotal movement of the links 12. The eyes 26 extend downwardly from the leading edge of top plate 24 and are spaced apart on the opposite sides of the center line for receiving the eye 25 therebetween. In addition, each of the eyes 26 has a bore 31 aligned with the other for receiving the hinge pin 14, which also passes through the bore 28 of the eye 25 of the next adjacent identical link 12. In order to permit relative pivotal movement of the links 12 in the vertical direction, a gap 32 is formed in the top plate 24 between the eyes 26. The links 12 according to the illustrated embodiment also include a pair of ribs 33 extending downwardly from the undersurface 34 of the top plate 24. At one end of the link, the outer surfaces 35 and 36 of the ribs 33, respectively, are spaced apart a distance equal to that between the outer ends of the eyes 26 and extend forwardly therefrom in general parallelism to inwardly curved sections which terminate in third sections spaced apart a distance defining gap 32 substantially equal to the width of the eye 25. The links 12, the pins 14, and the wear strips 18 and 19 may be formed from a variety of materials depending upon the application. For example, steel or stainless steel is preferred for applications where abrasives, such as broken glass, are present, and in rugged industrial applications. Stainless steel is preferably employed where corrosive materials are present, while thermoplastic materials may be used to provide low friction chain or conveyor materials and to provide smooth product conveyance where little or no abrasion is present. As seen in FIGURE 5, the outer surfaces 35 and 36 of the ribs 33 of each link 12 are disposed in proximity to the guide surfaces 20 and 21 of the wear strips 18 and 19. As the chain traverses a curved section of the wear strips as seen in FIGURE 1, the tensile forces F t within the chain tend to force the link surfaces 35 at the inside of the curve against the corresponding guide surface 20 of the wear strip 18, which is also at the inside curve. These tensile forces F t cause the surface 35 of each link 12 to ride on the surface 20 at the inside of the curve so that surface 35 thus becomes the thrust surface. This results in a reaction force F r from the guide surface 20 on the thrust surface 35. As seen in FIGURE 5, the tensile forces F t act along the centerline or axis CL p of the pin 14. The reaction forces, on the other hand, act across the entire contacting surface 35 so that the average reaction force F r acts along an average line of action, which in the illustrated embodiment is the centerline CL s of the reaction surface 35. The forces F t and F r thus provide a moment on link 12 acting in the clockwise direction, as viewed in FIGURE 5, so that the side 40 of the link 12 on the outside of the curve is forced downwardly against the surface 23, thereby holding the chain within the track. In this manner, the outside portions of chain links 12 are held within the curved portion of the track 16 without the necessity for tabs, inclined surfaces or magnetic retainers. This permits the chain to be lifted from the track for maintenance and cleaning. Furthermore, there is no necessity for fabricating any portion of the chain from ferromagnetic materials. As a result, plastic or stainless steel components may be used as may be desirable under the particular operating conditions. In prior art conveyor chains, the pins connecting the chain links were normally located in close proximity to the upper surface of the chain to reduce kick-up of the carrying surface as the chain passed about the drive sprocket, thereby producing smoother transfer of product. As a result, the center line of the pin, through which the tensile forces acted, was located above the geometric center of the guide surface at the inside of the curve. This created a moment acting about the thrust surface centerline, tending to elevate the link on the outside of the curve from within the track, causing the link to pivot about an axis lying along the center of the thrust surface and tangent thereto. For these reasons, prior art chains employed tabs, beveled surfaces or magnets for holding the chain within the track. It has also been found that when the pin is located at the centerline of the thrust surface, no moment is created but that the chain lifts vertically upward without pivoting. It will be appreciated that the couple produced on the chain links 12 by the tensile force F t and the reaction force F r and which tends to force the end 40 of the link 12 downwardly against the surface 23 at the outside of the curve will also tend to rotate the end 41 at the inside of the curve upwardly. The chain links 112 and the rails 118 and 119 according to the preferred embodiment of the invention illustrated in FIGURES 7, 8 and 9 are configured to compensate for this tendency. In particular, the outer surfaces 135 and 136 of the link ribs 133 are beveled outwardly at a small angle of about 2°-8° from their upper to their lower ends. In addition, the guide surface 120 at the inside of the curve is generally parallel to the link surface 135, that is, it is also beveled at the same or a slightly greater angle. For example, a link having a surface angle of about 3° would be preferably matched with a rail surface of about 3°-4°. A slightly greater rail surface angle provides a compensating factor for wear. The surface 121 at the outside of the curve may be perpendicular to the upper surface 123. In order to permit the chain to be elevated out of the track, the distance between the lower edges of the link surfaces 135 and 136 is less than the narrowest space between the guide surfaces 120 and 121. As seen in FIGURE 8, as the chain traverses a curved track section under load, the tensile forces F t will force the chain surface 135 against the guide surface 120. The reaction force F r is normal to the surface 135 of the link 112, which is at an angle relative to a plane perpendicular to the pin axis. As a result, the reaction force F r has a horizontal component F rx and a vertically downward component F ry , both acting on the surface 135. The small component F ry acts to counter the reverse moment tending to lift the chain out of the track at the inside of the turn. Thus, the angled surfaces 120 and 135 at the inside of the curve act both to guide the chain in the conveyor and to lock the chain in the curved section of the track. FIGURE 9 shows the link 112 in a straight section of the track 16. Here, the guide surfaces 120 and 121 are shown to be perpendicular to the axis of the pin. In order to provide a guide for the chain link 112 in these straight track sections, a thin, perpendicular surface 150 is formed at the upper end of each of the inclined surfaces 135 and 136. In order to accommodate this vertical surface, a complementary surface 152 is formed at the upper edge of the guide surface 120 on the inside of the curved section. The surfaces 150 and 152 also provide an additional wear surface in this section of the track.

Claims: A conveyor chain (10) for traversing a track (16) having at least one arcuate section comprising a pair of spaced apart track portions (18, 19) having respective surfaces (20, 21) which define an arcuate path therebetween, a first one (20) of the surfaces defining the inside of the arcuate path and the other one (21) of said surfaces defining the outside of the arcuate path, said conveyor chain (10) comprising a plurality of links (12) each having a first pivotal connection means (25) at one end thereof and a second pivotal connection means (26) at the other end thereof and complementary to the first pivotal connection means, and pin means (14) pivotally coupling the first and second pivotal connection means (25, 26) of pairs of adjacent links (12), said pin means (14) being oriented tranversely to the path traversed by said chain (10), each of said links (12) being engageable with said first one (20) of the path defining surfaces as said chain traverses said path to generate a reaction force (Fr) acting on said link and having an average line of action (CLs), characterised in that the axis (CLp) of each pin means (14) is located below said average line of action (CLs) to create a couple on said links (12) acting to retain said links within the arcuate section of the track, this being the sole means for retaining the links within the arcuate section. A conveyor chain as claimed in Claim 1 wherein each link (12) includes a generally planar top portion (24) for being supported on a carrying surface (22, 23), the first pivotal connection means of the link comprising first eye means (25) extending downwardly from one end of the link and at substantially the center of said one end, the second pivotal connection means of the link comprising a pair of eye means (26) extending downwardly from the opposite end of the link and spaced apart from the center thereof for engaging the first eye means (25) on an adjacent link (12), and said pin means (14) extends through the second eye means (26) on one link and the first eye means (25) on the adjacent link for pivotally connecting the same. A conveyor chain as claimed in Claim 2 wherein said first eye means comprises at least one eye (25) and the second eye means comprises at least two spaced apart eyes (26) for receiving said at least one eye (25) of an adjacent link, said pin means (14) extending through aligned openings (28, 31) in said eyes for hingedly connecting adjacent links (12). A conveyor chain as claimed in any one of the preceding claims wherein each link (12) has a reaction surface (35) which engages the one (20) of said surfaces defining the inside of said arcuate path and on which said reaction force (Fr) acts, the tensile forces (Ft) in said chain (10) acting along the axis (CLp) of each of said pin means (14) to create a couple which urges that portion (40) of the link on the outside of said track (16) into engagement with the track portion (19) on the outside of said arcuate path, said reaction surface (35) and said one surface (20) each forming a small angle relative to a plane perpendicular to the axis (CLp) of said pin means (14) and being inclined outwardly relative to said path. A conveyor chain as claimed in Claim 4 wherein said angle is from 2°-8°.

Inventors: BIGONESS ROBERT H, COUNTER LOUIS F, ENSCH PETER J, BIGONESS, ROBERT H., COUNTER, LOUIS F., ENSCH, PETER J.
Applicants: REXNORD CORP, REXNORD CORPORATION
Application year: 1992
Main classification: B65G17
IPC codes: B65G17