Shuttle plugs for retaining headless pivot rods in conveyor belts

Abstract: A modular link of a conveyor belt is provided with belt edge structure for retaining in the belt so that it may not escape from a belt edge (23) a headless pivot rod (75) journalled in apertures in interdigitated link ends interconnecting adjacent links. The retention structure provides a shuttling plug (41) movable into two bistable positions within a mating shuttle cavity (35) having an open end and a blind end. The cavity (35) extends transversely in the link residing between two link end pivot rod journalling apertures to intersect only one journalling aperture. The two bistable states for the shuttle plug (41) respectively (1) lock the headless pivot rod (75) in place in a stable pivot rod occluding position extending into said journalling aperture, and (2) permits the headless pivot rod (75) to enter or leave the journalled position by movement of the shuttle plug out of the occluding position into a second stable position. The belt edge structure provides an adjoining link with a cavity closure surface which confines the open end of the mating shuttle cavity to occlude movement of the plug out of the mating shuttle cavity when the conveyor belt is operating. A detent (45) locks the shuttle plug (41) into the occluding position. The flexible arm (43) bending about thinner region (60) permits a screwdriver, or like tool, to enter the pivot rod cavity and dislodge the shuttle plug (41) from its occluding state to move toward cavity (35) so that the pivot rod (75) can be removed.

Description: TECHNICAL FIELD: This invention relates to the retention of headless pivot rods in conveyor belts, and more particularly it relates to conveyor belts using removable plugs or stops for retaining the pivot rods in place during operation of the conveyor belts, such as defined in the head clause of claim 1. BACKGROUND ART: Typical art disclosing modular link belts with removable plugs or clips that occlude headless pivot rods journalled in module link end apertures comprise the following U. S. Patents: 4,709,807 to N. J. Poerink, Dec. 1, 1987; 5,024,321 to J. M. Lapeyre, June 18, 1991; 5,096,053 to W. G. Hodlewsky, March 17, 1992; 5,217,110 to M. L. Spangler, et al., June 8, 1993; 5,247,789 to G. Abbestam, et al., Sept. 28, 1993; 5,293,989 to C. Garbagnati, March 15, 1994; 5,305,869 to P. E. Damkjaer, April 26, 1994; 5,335,768 to T. J. Schladweiler, Aug. 9, 1994; and 5,435,435 to H. Chiba, et al., July 25, 1995. All of these have the common problem and deficiency in that the plugs, clips and the like, which hold the pivot rods in place when under working conditions encountered in the operation of a conveyor belt can work themselves loose. This catastrophically results in contamination of carried products or fouling of the equipment. This problem is particularly evident in plastic belts with modular links that have some resiliency and which inherently have slick surfaces. Conditions that lead to such failures are particularly apt to be encountered in operation conditions, such as: regions of vibration, changing load weight pattens, regions of heavy or rapidly varying belt tension, and possible physical interfering items that may extend into the path of the belt, particularly at the belt edges. It is the objective of this invention to solve that problem and to introduce improved novel structure for more reliably retaining headless pivot rods in place during the working life of conveyor belts with little likelihood of catastrophic failure or loss of plugs during normal belt working conditions. DISCLOSURE OF THE INVENTION: This invention therefore provides in a conveyor belt of the type as defined hereinabove a solution of the aforementioned problem, consisting in a construction according to the characterizing clause of claim 1. Other objects, features and advantages of the invention will be found throughout the following description, claims and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS: In the accompanying drawings, where like reference characters represent similar features throughout the various views to facilitate comparison: Figure 1 is an exploded rear elevation view of two adjacent modular links of a conveyor belt embodying the link edge structure of this invention, Figure 2 is an elevation view of the modular link, looking into the right of Figure 1 at the end of the shuttle plug, Figure 3 is a front elevation view of one of the modular links of Figure 1, Figure 4 is a bottom view of the modular link of Figure 3, Figure 5 is a fragmental view, partly in section along the section lines A-A of Figure 4, looking at the link edge portion of the modular link, Figure 6 is a fragmental view, partly in section, looking along lines B-B of Figure 3 into the link edge portion of the modular link, Figure 7 is a bottom view, partly in section, looking into the lines C-C of Figure 3, Figure 8 is a perspective view of one shuttle plug embodiment of this invention, Figure 9 is a side elevation view of the shuttle plug of Figure 8, Figure 10 is a plan view looking into the bottom of Figure 9, Figure 11 is an end view looking into Figure 10 from the left, Figure 12 is an end view looking into Figure 10 from the right, Figures 13, 14 and 15 are respectively plan, side elevation and right end views of a further shuttle plug embodiment of the invention, Figure 16 is a fragmental elevation view of a modular link showing in phantom lines the internal shuttle plug disposed in one bistable position for inserting or removing pivot rods, Figure 17 is a bottom view of the modular link of Figure 16 showing in dotted lines the internal shuttle plug, Figure 18 is a fragmental elevation view of the modular link of Figure 16 showing in dotted lines the internal shuttle plug disposed in its other bistable position for occluding pivot rods, Figure 19 is a bottom view of Figure 18, Figure 20 is a fragmental end view of Figure 19 looking in at the belt edge fragment from the right. Figure 21 is a perspective cut away view showing the shuttle plug in the bistable position occluding a pivot rod, and Figure 22 is a perspective cut away view showing the shuttle plug in it bistable position opermitting insertion of a pivot rod. THE PREFERRED EMBODIMENTS: As seen in Figure 1, two adjacent modular links 21, 22 of a conveyor belt are shown in side-by-side relationship. The belt edge structure 23, 24 shown at the bottom of the respective links has an internal lateral cavity in which the shuttle plug 25 slides. This shuttle plug 25 laterally slides within the internal cavity into two bistable positions. Thus in one position a headless pivot rod (not shown) journalled in apertures of interdigitated link ends 26 is retained in the belt in one bistable position of the shuttle plug 25 so that the pivot rod cannot work its way Out of the belt edge under normal operating conditions. In the other stable position, the pivot rod may be inserted or removed from the journalling apertures through the edge 27 of the belt without obstruction by the plug 15. It is noted that the shuttle plug mating internal cavity of the link end structure has an open access end on the right and an internal blind closed end on the left. To resolve the problem of losing a plug that can cause rods to migrate axially and to contaminate goods carried by the conveyor belt or foul the machinery, the rounded ends of the link ends or fingers 23, 24, when the modules 21, 22 are interconnected by a pivot rod serve to abut the open access end of the internal cavity to block the shuttle plugs 25 from escaping from the blind open ended internal cavity. That cavity runs transversely within the modular link edge structure 23, 24 from one extremity overlapping the pivot rod journalling apertures on the left hand side of the links 21, 22 and terminating at the right hand edges 28, etc. of the link end structure, which is confronted by the left nose ends 26', etc. of the link ends 23, 24. The slot 32 of Figure 4 extending through the edge of the belt into the shuttle cavity permits entry of a tool, such as a screw driver for forcing the shuttle plug toward a detented pivot rod retaining locked-in position. The slot 29 through the outer shell extending into the internal mating cavity in which the shuttle plugs 25 slide, will also admit a tool, such as a screw driver or a blade, that could be used to remove a shuttle plug from an elastically biased and locked-in position within the internal cavity. The flanges 30 on the modules 21, 22 abut the rounded noses 26 of the link ends 31, serving to form a substantially uninterrupted flat planar load bearing surface as seen in Figure 3. There is a tapered conveying surface edge 33 terminating at the belt edge 27. In Figure 5, the section view shows the internal layout of the shuttle cavity 35 transversely disposed between the link end apertures 36, 37 in which the pivot rods are journalled. The shuttle cavity 35 has a blind inner end 34 that extends into the pivot rod journalling aperture 37. The cross section shape of the cavity 35 is substantially rectangular (Fig. 6) with a keyway 39 outwardly extending for receiving in mating plug body sliding contact the plug profile 44 with key 40 (Fig. 11). Two other grooves 62 and 72 outwardly extending from the cavity 35 provide clearance for other appendages of the plug 25. The groove 72 opposite the keyway 39 terminates just before the pivot rod aperture 37. A short portion of a cavity wall surface 48 is disposed between the groove 72 and the aperture 37. One embodiment 41 of the shuttle plug, which mates into and slides within the shuttle cavity is shown in Figures 8 to 12 in an enlarged scale. A detent 45 carrying flexible arm 43 integrally extends through a thinner intermediate region 60 from the body portion 44 of the shuttle plug 41, as provided from the hard but flexible plastic material from which the plug is molded. The substantially rectangular body portion 44 snugly fits within the mating shuttle cavity (35, Fig. 6) to shuttle back and forth therein between the two bistable working positions of plug 41. In the pivot rod occluding stable position the detent 45 enters and locks into a pivot rod journalling aperture (37, Fig. 7) to retain the detent therein as an occluding plug in a locked-in stable resident position. The sloped or tapered survace 47 on detent plug 45 expedites the movement of the detent plug 45 into and out of its occlusion position, as the flexible arm 43 is flexed by engagement with the cavity wall surface 48 between the groove 72 and the aperture 37 and opposite to the keyway 39 (Fig. 6) in which the shuttle plug key 49 moves. The cylindrical-like wall 50 about the detent plug 45 serves to lock the detent plug into its mating pivot rod journalling nest in pivot rod aperture 37 (Fig. 7) by means of the resilient bias of the flexible arm 43. The detent 45 may be overcome and removed from its locked-in position when the shuttle plug is to be moved into its other stable position to remove a pivot rod. Thus, the flexible arm 43 is flexed by an instrument, such as a screw driver, entering the pivot rod journalling aperture (37) from the edge of the belt to force the occluding plug out of its detent position. Typically a screw driver tip engages the detent 45 at the ridge formed at the intersection of tab 46 and the flat face of the detent plug 45 so that the shuttle plug may be forced laterally back into the exit cavity simultaneously as it is flexed out of its detented state by way of the screwdriver tip. The body portion of the shuttle plug is apertured at 53, 54 to provide resiliency for compressing one of the extending adjacent detent stops 55, 56 when it enters the mating shuttle cavity 38 of a modular link 21, 22 and frictionally contacts the cavity wall 57. The entry surface 58 of the detent stops 55, 56 are tapered and the stop surfaces 59 rises normally from the shuttle body surface. This detent stop rides in the slot 29 (Fig. 5) and abuts the stop surface 59 to prevent removal of the shuttle plug from the mating shuttle cavity 38. The slot 29 further provides an entry point for inserting a screw driver tip, a blade, or the like, thereinto to pare down or remove the detent stop 56 so that the shuttle plug 41 can be removed from the shuttle cavity 38. The plug 41 can be removed from a resident postion in the modular link 21 or 22 only when disassembling the belt because of the presence of an adjacent link end 26' in the manner aforesaid. Only one of the detent stops 55, 56 is used and its opposite mate rides in the keyway-like channel 62 extending along the shuttle cavity 38 as shown in FIg. 6. Thus the plugs are reversible for universal use in either right or left hand versions of the modular links. Groove 72 provides clearance for the detent plug 45 when it is in the non-occluding position. This allows edge modules to be stored, such as in stock, with plugs 41 installed in the ready-to-assemble non-occluding postiion without subjecting the arms 43 to a continuous bending force for an extended period. As shown in Figure 13 to 15, a second shuttle plug embodiment 65 has provision for a single similar flexibly movable detent stop member 66. This shuttle plug functions in a similar way, and has corresponding features including the occlusion detent member 45 riding upon the flexible arm 43 integrally affixed to the body portion 44'. The mating detent key ridge 40' however is off center to balance the spring slot 67 that renders flexibility and biasing action to overcome a locked-in stop 66. Figures 16 to 20 show in phantom the internal plug 65 in its bistable working positions within cavity 35' of the corresponding link end structure of a retaining modular conveyor belt link. These working positions are similar to those of the before described plug-shuttle cavity embodiment 41, 35. Thus Figs. 16 and 17 show the internal plug in its stable position with the pivot rod journalling aperture open to insert or remove a pivot rod. Figs. 18 and 19 show the shuttle plug in its occlusion state stable position for retaining the pivot rod within the conveyor belt. In the shuttle plug side view of Figure 16 therefore, the flexible arm 43 is flexed by contact of the detent 45 with the edge 70 of the journalling aperture 36 as the shuttle plug moves toward the right out of the pivot rod occlusion position blocking the pivot rod journalling aperture 36. From the shuttle plug plan view of Figure 17 it is seen that the stop member 66 reaches the end of slot 29 and retains the shuttle plug in place so that it cannot escape from the open right hand end of the shuttle cavity 35', that is also occluded by the position of an ajacent module link end as aforesaid. As seen from the view of the shuttle plug in Figures 18 and 21, the resiliency of the flexible arm 43 seats and locks the detent stop 45 into the pivot pin journalling aperture 36 where it occludes the removal of the headless pivot pin 72 (downwardly) from the edge of the belt 27. Any axial motion toward the shuttle plug 41 or growth in length of the pivot rod cannot push the locked in plug out of the journalling aperture 36. In both the plan view of the shuttle plug in Figure 19, and the end view of the shuttle plug in Figure 20, the slot 32 in the edge of the belt (also shown in Figure 4) permits the tip of a screwdriver to be inserted to force the shuttle plug into the occlusion position. Similarly the slot 29 may be used to push against the body portion of the shuttle plug. As seen from Figure 21, the shuttle plug 41 is in its bistable pivot rod (25) occluding position inside the shuttle cavity 35 within link end 23 with the detent 45 lodged in the pivot rod aperture 37. Thus the shuttle plug 41 cannot move outwardly (to the left), and serves to occlude the pivot rod 75. The other stable position of Figure 22 permits the pivot rod to be entered or removed in the pivot rod aperture 37. The shuttle plug 41 is held in this stable position with the rear end detent stop (not shown) abutting the left end of slot 29 (Fig. 21). It is to be recognized that other modular link configurations such as those laid in bricklaid patterns with edgeless internal modules may be constructed without departing from the invention. Having therefore introduced new and improved apparatus and methods for preventing the inadvertent removal of a pivot rod from a belt edge or the inadvertent removal of the retaining shuttle plug member from its pivot rod occluding position as a conveyor belt operates under its usual working conditions, the features of this invention are defined with particularity in the following claims.

Claims: A conveyor belt employing a plurality of conveyor belt modules having interdigitated link ends on the modules being interconnected pivotably by headless pivot rods journalled in apertures through said link ends and retained by a removable shuttle plug, characterized in that a module (21, 22) near a belt edge thereof contains a shuttle path cavity (35) disposed in longitudinal direction of the belt in the module in a position between two journalling apertures (36, 37), said cavity (35) having two opposite ends, one of them being a blind end (34) intercepting one of said journalling apertures (37) and the other being an open end so that a shuttle plug (41) may be inserted in the cavity (35) or removed therefrom in the longitudinal direction of the belt, said cavity (35) being dimensioned for receiving a slidable shuttle plug (41) movable in said longitudinal direction in the cavity (35) for retention within the cavity when adjacent modules of the conveyor belt are interconnected by journalled pivot rods (75), said shuttle path cavity (35) defining a pathway in said longitudinal direction providing alternative resident plug positions that respectively retain a pivot rod in place or permit removal of the pivot rod, a movable shuttle plug (41) mating within said shuttle path cavity (35) to move between said alternative positions, and selectively positionable detent means (45) on the shuttle plug (41) for retaining the shuttle plug (41) stably in a locked occlusion position for retaining journalled pivot rods in place without leaving said edge of the conveyor belt. The conveyor belt of Claim 1 further characterized by a plastic shuttle plug (41) with a secondary body portion (43) elastically and integrally extending from the main body portion of the plug (41), said detent means comprising an integral member (45) on said secondary body portion for entering a pivot rod journalling hole (37) at a location between an edge of the belt and a journalled pivot rod to retain the plug (41) in its bistable locked occlusion position for unlocking by elastic deflection of the secondary body portion (43). The conveyor belt of Claim 1 wherein the shuttle path cavity (35) is further characterized by a blind inner end (34) and an opposite open end, and detented stop means (56) resiliently biassed (54) for preventing exit of the shuttle plug (41) from the shuttle path cavity open end. The conveyor belt of Claim 3 further characterized by: adjacent belt modules (21, 22) that individually encompass on opposite ends a set of interdigitatable link ends (23, 26) forming pivot rod journalling apertures (36, 37), and belt edge structure (23) wherein said cavity and the module are so constructed that the shuttle (41) in a belt of interconnected modules is retained within the shuttle path cavity (35) by link end structure (31) adjacent the belt edge on an interconnected module postioned to abut the open end of said shuttle path cavity (35) to prevent exit of the shuttle plug (41) therefrom. The conveyor belt of Claim 2 further characterized in that said integral member (45) on the elastically extended secondary body portion (43) of shuttle plug (41) further comprises a tapered surface (47) adapted upon movement of the plug (41) to permit movement into and out of its pivot rod occlusion bistable position by sliding over a retaining wall of the shuttle plug cavity (35) in the region of a blind cavity end (34) when the elastically extended secondary body portion (43) is flexed in a direction facilitating removal and entry of the shuttle plug (41) from its bistable pivot rod exclusion position in the the journalling shuttle plug cavity (35). The conveyor belt of Claim 2 further characterized in that the detent means (45) and elasticallly extended secondary body portion (43) define a tool receiving surface exposed from an edge (23) of the belt through a journalling aperture (37) for overcoming the detenting bias and directing the shuttle plug to move into an alternative bistable position in the mating shuttle cavity (35) which permits removal of a pivot rod (75). The conveyor belt defined in Claim 1 further characterized in that the modules (21, 22) have an access aperture (29) extending into the shuttle cavity (35) adapted to receive a tool entering the access aperture (29) for moving the shuttle plug (41) in the mating shuttle cavity (35) from its bistable position for removing the pivot rod to its alternative bistable occlusion position for preventing removal of the pivot rod, in that the shuttle plug (41) has an extended body portion (55) for engaging the tool. The conveyor belt of Claim 1 further characterized by a shuttle plug (41) comprising: a main body portion (44) adapted to slide within said journalling cavity (35), and a flexible detent arm (43) integrally affixed to the main body portion carrying a detenting plug portion (45) arranged to elastically flex into a removable locked-in-place bistable position for occluding a pivot rod (75). The conveyor belt defined in Claim 8 further characterized by an interlocking keying ridge (55, 56) on the main body portion (44) for mating into a corresponding keyway slot (29) defined in a wall of the mating plug journalling cavity (35). The conveyor belt defined in Claim 1 further characterized by detent retaining means provided by a wall of the journalling cavity (35) and accompanying resiliently biased detent structure (55, 56, 45) integrally affixed on the main body portion (44) comprising detenting stops defining two bistable detented plug (41) positions within the shuttle cavity (35), the biased detent structure permitting forceful removal of the shuttle plug from each of the bistable positions. The conveyor belt of Claim 1 further characterized in that said shuttle cavity (35) has one blind end (34) and one open end positioned in a location between two pivot rod journalling apertures (36, 37) passing through one of the modules (21, 22) near a belt edge structure (23) and intersecting with a link end aperture (37) at said blind end. The conveyor belt defined in Claim 11 further characterized by belt edge structure on an adjacent module (21, 22) comprising link end structure movable between one position to block the open end of the shuttle cavity (35) in a normal belt operational position and a further position attained by pivoting the modules (21, 22) about a pivot rod (75) that permits access of the open end of the shuttle cavity (35) permitting the shuttle plug (41) to be removed out of the cavity (35) without removoval of the pivot rod (75) from the conveyor belt.

Inventors: GUNDLACH JAMES O, VERDIGETS CHRISTROPHER J, GUNDLACH, JAMES O., VERDIGETS, CHRISTROPHER J.
Applicants: LAITRAM CORP, THE LAITRAM CORPORATION
Application year: 1997
Main classification: B65G17
IPC codes: B65G17