Belt conveyor with a modular intermediate drive belt

An intermediate drive system for driving a conveyor belt with one or more intermediate drive belts. The intermediate drive belt includes lateral rows of pivotable teeth spaced apart along the length of the intermediate drive belt. The teeth extend into the conveyor belt along a portion of the carryway to drive the conveyor belt in a conveying direction. The only component external to the intermediate drive belt that the teeth contact is the intermediate drive belt. Engagement and disengagement of the teeth with the conveyor belt is effected without the use of cams against the teeth.

BACKGROUND

The invention relates generally to power-driven conveyors and more particularly to conveyor belts driven by one or more intermediate drive belts.

Intermediate drive belts are often used to drive conveyor belts on long or winding conveyor paths. These intermediate drive belts are short belts with drive teeth that engage the conveyor belt at strategic locations along the conveying path. In this way, part of the load is transferred from the main drive sprockets, which are typically located at the end of the conveyor carryway or in the return, to the intermediate drive belt. Because the maximum tension in a conveyor belt with intermediate drives is lower than in a conveyor belt without, a less expensive conveyor belt with a lower belt-pull rating can be used or the conveyor belt can be used for longer runs.

Some of the problems associated with conventional intermediate drive belts include: excessive wear caused by rubbing between the intermediate-drive teeth and cam surfaces acted on by the teeth; tenting of the intermediate drive belt where it engages the conveyor belt; and the need for hold downs to counteract the tendency of the intermediate drive to push the conveyor belt upward. And many intermediate drive belts and chains have pivotable teeth with cam followers that slide or roll on cam surfaces as the teeth drive the conveyor belt. Sliding cam followers are especially susceptible to wear, and rolling cam followers require more complicated roller assemblies.

SUMMARY

These shortcomings are overcome by a conveyor embodying features of the invention including a conveyor belt driven by an intermediate drive belt along a carryway. The conveyor belt has a top conveying side and an opposite bottom side and static drive-receiving surfaces accessible from the bottom side. The intermediate drive belt advances along the carryway in a conveying direction and includes a bottom surface and an opposite top surface underlying the bottom side of the conveyor belt along a portion of the carryway. Teeth are mounted at laterally spaced apart locations across the width of the intermediate drive belt and rotate about lateral pivot axes through a range of rotation. Each of the teeth includes a drive face above the top surface of the intermediate drive belt and an arm having a reaction surface on the opposite side of the pivot axis from the drive face. The arm resides entirely between the top and bottom surfaces of the intermediate drive belt throughout the range of rotation of the tooth. In this way, the arm does not rub against any conveyor components outside the intermediate drive belt.

In another aspect of the invention, an intermediate drive belt comprises a top surface and a parallel bottom surface defining its thickness. Teeth are mounted at laterally spaced apart locations across the width of the intermediate drive belt to rotate through a range of rotation about lateral pivot axes, which are disposed between the top and bottom surfaces of the belt. Each of the teeth has a drive face above the top surface of the intermediate drive belt and an arm having a reaction surface on the opposite side of the pivot axis from the drive face. Stops disposed between the top and bottom surfaces engage corresponding reaction surfaces at an extreme of the range of rotation of the teeth.

Another aspect of the invention provides a belt module having a top surface and an opposite bottom surface defining the module's thickness. Teeth are mounted at laterally spaced apart locations across the width of the belt module to rotate about a lateral pivot axis through a range of rotation. Each of the teeth includes a drive face above the top surface of the belt module and an arm having a reaction surface on the opposite side of the pivot axis from the drive face. The arm resides entirely within the thickness of the belt module throughout the range of rotation of the tooth.

In yet another aspect of the invention, a belt module comprises a top surface and an opposite bottom surface. Teeth are mounted at laterally spaced apart locations across the width of the belt module to rotate about a lateral pivot axis. Each of the teeth includes a driving arm having a drive face above the top surface of the belt module and a reaction arm having a reaction surface on the opposite side of the pivot axis from the driving arm. The drive face and the reaction surface define an angle of less than 180°.

DETAILED DESCRIPTION

A base module for an intermediate drive belt embodying features of the invention is shown inFIGS. 1A-1E. The base module10, which is preferably injection molded out of a thermoplastic polymer, such as polyethylene, polypropylene, acetal, and composite polymers, has a top surface12and an opposite bottom surface13through its thickness T. Long links14, laterally spaced apart across the width W of the base module, extend forward from an intermediate portion16of the base module. Shorter links15extend rearward from the intermediate portion. The shorter links15are laterally offset from the long links14. Both sets of links14,15form hinge elements having hinge structure18,19including lateral holes20,21.

Stops22are formed at distal ends of projections24extending from the intermediate portion16of the module and forming a portion of the top surface12of the module. Each projection has a semicircular recess26continuous with the top half of the lateral hole21through an abutting shorter link15. A gap28between the side of each projection24and the next consecutive shorter link15is sized to receive the long link14of an adjacent interconnected belt module10. Similarly, wider gaps29between consecutive long links14are sized to receive the conjoined pairs of shorter links15and projections24. The projections terminate in the stops22, which have laterally elongated curved surfaces30at their distal ends.

An overhanging ledge32extends forward from the distal end of each long link14. An undercut flat surface34forms the bottom of each ledge. A seat36is formed on the proximal end of each long link14in the intermediate portion16of the module inward of the module's rearward end. A lateral hole38is formed in each long link14between the seat36and the ledge32. Bosses40reinforcing the sides of the long links14at their proximal ends form continuations of the second holes38.

As shown inFIG. 2, teeth44are mounted at the rear of the gaps29between the long links14. Bores46through the teeth44align with the second holes38in the long links to form a lateral passageway across the width of the base module10. A pivot rod48is received in the passageway and retains all the teeth pivotably to the module. Both ends of the pivot rod have heads50that hold the rod in place. But headless rods with retention structure to capture the rods may be used as well.

A similar hinge rod52is used to interconnect adjacent belt modules10together at hinge joints54as shown inFIG. 3. The long links14along a forward end of a row56of one or more belt modules10interleave with the shorter links15and the joined projections24on the trailing end of a leading row. The lateral holes20,21of the interleaved hinge structure18,19are aligned on forward and rear lateral hinge axes58,59and receive the hinge rods52, which connect the modules together at the hinge joints54into an intermediate drive belt60that can articulate about the hinge axes. Drive faces62on the forward side of the teeth44are above the top surfaces12of the belt.

The operation of the intermediate drive belt60is shown inFIGS. 4-7with regard to a conveying system. The conveying system64includes a conveyor belt66, shown running in a conveying direction68along a portion of an upper carryway. Remotely located drive components, such as sprockets or drums (not shown) serve as the main drives of the conveyor belt. Intermediate drive components, such as the intermediate drive belt60shown inFIG. 4, engage the conveyor belt66at one or more locations along the carryway. The intermediate drive belt66is supported and rides in the conveying direction68on an intermediate drive carryway, or support platform70, mounted to the conveyor frame (not shown for clarity) with bolts through holes71formed in vertical beams73. The support platform70has an inclined ramp72leading to a horizontal support surface74. The front end76of the support platform is rounded to guide the intermediate drive belt60smoothly from the lower return path onto the ramp. The rear end78of the support platform70is concave to provide clearance for one or more drive sprockets80having bores82for receiving a drive shaft (not shown) rotatably supported in the conveyor frame and driven by a motor (not shown). Sprocket teeth84on the peripheries of the sprockets80engage the rounded drive faces42formed on the distal ends of the shorter links15(FIG. 1B) to drive the intermediate drive belt60in the conveying direction. The intermediate-drive belt66, the support platform70, the sprockets80, the drive shaft and other associated intermediated-drive components may be packaged as a drop-in module that can be installed on existing conveyor systems.

As best shown in the partly cutaway view ofFIG. 4, the intermediate drive belt's teeth44extend up into the conveyor belt66. The drive faces62on the teeth push on outer drive-receiving surfaces86formed on trailing link ends88of each row90of conveyor belt modules. In this example, the pitch, i.e., the distance between consecutive hinge axes, of the intermediate drive belt60is roughly the same as, although preferably slightly greater than, that of the collapsible conveyor belt66in its fully-tensioned expanded state. Because each row of the intermediate drive belt60has a row of teeth44, the tooth pitch, i.e., the distance between consecutive rows of teeth along the length of the intermediate drive belt, is the same as the pitch of the intermediate drive belt to provide a high density of engaging teeth along the length and across the width of the conveyor belt. Because of this high density of engagement points, the pressure and, consequently, the wear at each engagement point are reduced. This makes the use of plastic, rather than metal, teeth feasible. Of course, the tooth pitch can be increased by making the pitch of the intermediate drive belt roughly an integral multiple of the conveyor belt's pitch or by installing teeth only in every second, third, or fourth intermediate drive belt row.

The initial engagement of the intermediate drive belt60with the conveyor belt66is illustrated best inFIG. 6. As both belts advance in the conveying direction68, the intermediate drive belt rides up the ramp72. The teeth44enter into gaps92between the conveyor belt rows just aft of the trailing link ends88. As the intermediate drive belt rides up the ramp, the teeth advance deeper and deeper into the gaps until they contact the static drive-receiving surfaces86on the trailing link ends88. The drive faces62of the teeth are preferably shaped to mate with the drive-receiving surfaces86to maximize the contact area. The drive-receiving surfaces86of the conveyor belt and the drive faces62of the teeth44are generally perpendicular to the conveying direction68. Thus, the conveyor belt is not pushed upward, and hold downs are not required. A hook,89at the top end of the tooth adds surface area to the drive face and provides any minor hold down force needed.

Along the horizontal support surface74, the intermediate drive belt60is sandwiched between the conveyor belt66and the support platform70as shown inFIGS. 4 and 5. The undercut flat surfaces34of the overhanging ledges32at the forward end of each row of the intermediate drive belt60sit on the seats36of a leading row to form an interlocking engagement of the intermediate drive belt's rollers as they advance along the horizontal support surface74. The interlocking structure forms backbend limiting means that, together with the horizontal support surface74, restricts the backbending of the intermediate drive belt in the vicinity of those belt rows whose teeth are driving the conveyor belt. The reaction force of the conveyor belt on the drive faces62of the teeth tends to lift the leading end of the driving row and lower the trailing end. The backbend limiter limits backbending in the face of that tendency.

As shown inFIG. 3, the pivot rod48defines the lateral pivot axis94about which the teeth44rotate. The pivot axis94in each row is preferably coplanar with the lateral hinge axes58,59. But the range of rotation is limited by structure in the intermediate drive belt as shown inFIG. 7. Each tooth is effectively a lever with a reaction arm96on the opposite side of the pivot axis94from the arm containing the drive face62. The reaction arm96preferably extends generally perpendicular to the drive face62with an angle α between the arm96and the drive face62of less than 180° (FIG. 2). The arm96includes a concave reaction surface98that pushes against the laterally elongated convexly curved surface30on the stop22of a leading row when the tooth is driving the conveyor belt66. A hook99at a distal end of the arm helps keep the reaction-arm end of the tooth engaged with the stop. The reaction force of the conveyor belt on the drive face of the tooth is transmitted to the stop22through the reaction surface98by lever action. Because the reaction arm96is forward of the pivot access, it lifts away from the bottom of the intermediate drive belt and into the stop as the tooth drives the conveyor belt. The reaction arm96is also shaped to reside within the intermediate drive belt's thickness between the top and bottom surfaces12,13through the tooth's entire range of rotation. Thus, the only component external to the intermediate drive belt that the teeth contact is the intermediate drive belt. In this way, the arm of a driving tooth does not dig into the horizontal support surface74as it slides along. Rather, the reaction force is borne by the stop statically with no sliding friction. Consequently, contact and friction between the tooth and the support platform are eliminated.

The intermediate-drives teeth44disengage easily from the conveyor belt66as shown inFIG. 7. As the intermediate drive belt60articulates about its sprockets80, a leading belt row56′ pivots clockwise relative to a trailing row56″ about their shared hinge axis100. This lifts the leading row's stop22cleanly away from the trailing row's reaction surface98. In the meantime, the tooth44is freely rotatable on its pivot axis94with its reaction arm unencumbered. In this way, the opposite arm that includes the tooth's drive face62cannot exert any significant force against the conveyor belt as the tooth exits the gap92between rows. The pivotable tooth is just pushed out of the way without resistance. Furthermore, no external cams are needed to guide the teeth into or out of engagement with the conveyor belt.

Thus, the invention provides features and advantages such as an intermediate drive system with a high density of drive surfaces for distributed, low drive pressures, nearly vertical tooth—conveyor contact to eliminate the need for hold downs, and no cam followers on the tooth or external cams. These features allow long conveyor belts to be operated even at high speeds.

Although the invention has been described with reference to a preferred version, other versions are possible. For example, the intermediate drive belt and all its components have been described to admit of all-plastic construction, but one or more of the belt's components could be made of metal. As another example, the details of the shape of the tooth represent only one exemplary tooth for use with the conveyor belt having the characteristic shown, i.e., that of an INTRALOX® Series 2200 or 2400 conveyor belt, manufactured and sold by Intralox, L.L.C. of Harahan, La., U.S.A. And intermediate drive belts of this kind may be used with straight-running belts as well as collapsible radius or spiral belts and with chains as well as belts. So, as these few examples suggest, the scope of the claims is not meant to be limited to the details of the preferred version.