WO2008070444A2

WO2008070444A2 - Intermediate-drive conveyor and method

Info

Publication number: WO2008070444A2
Application number: PCT/US2007/085178
Authority: WO
Inventors: Andrew A. Corley
Original assignee: Laitram, L.L.C.
Priority date: 2006-12-06
Filing date: 2007-11-20
Publication date: 2008-06-12
Also published as: WO2008070444A3

Abstract

A conveyor and a method for operating a conveyor having a conveyor belt driven by one or more intermediate drive belts positioned along a conveying path. The drive belts have driving surfaces formed on teeth that are received in recesses in the conveyor belt's interior. The recesses are bounded at their forward ends by drive-receiving surfaces. The teeth and the corresponding drive-receiving surfaces have profiles with low pressure angles. To facilitate disengagement of the drive belt's teeth from the recesses without scrubbing on the conveyor belt, the drive belt's drive is slightly less than an integral multiple of the conveyor belt's drive pitch.

Description

INTERMEDIATE-DRIVE CONVEYOR AND METHOD

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 that drive the conveyor belt at strategic locations along the conveying path. In this way, the load is transferred to the intermediate drive belts and the main drive sprockets, which are typically located at the end of the conveyor carryway or in the return. Because the maximum tension in the conveyor belt is lower than in a conveyor belt without an intermediate drive, a less-expensive conveyor belt with a lower belt-pull rating can be used or the conveyor belt can be used for longer runs between the main drive sprockets.

The pressure angle at the contact of the intermediate drive belt's driving surfaces with the conveyor belt's drive -receiving surfaces affects the quality of the driving engagement. Small pressure angles direct more of the drive energy into driving the conveyor belt in its intended direction. But disengagement of a drive belt from a conveyor belt without scrubbing for small pressure angles is difficult. Greater pressure angles can reduce or eliminate scrubbing on disengagement, but result in driving the conveyor belt less efficiently and in pushing the conveyor belt upward, which may necessitate the use of conveyor belt hold downs.

SUMMARY

An intermediate-drive conveyor embodying features of the invention may be used to overcome some of these shortcomings or to solve other problems. One version of such a conveyor comprises a conveyor belt advancing along a conveying path in the direction of belt travel and a drive belt underlying the conveyor belt along a portion of the conveying path. The conveyor belt has drive-receiving surfaces disposed on regular intervals in the direction of belt travel. The regular intervals define the conveyor belt's drive pitch. The drive belt has driving surfaces disposed on other regular intervals, which define the drive belt's drive pitch. The driving surfaces of the drive belt advancing in the direction of belt travel apply a driving force to the drive-receiving surfaces along a line of action generally in the direction of belt travel to drive the conveyor belt along the conveying path. The drive belt's drive pitch is slightly less than the conveyor belt's drive pitch or an integral multiple of the conveyor belt's drive pitch.

In another aspect of the invention, a method of operating a conveyor comprises: a) arranging a conveyor belt having drive-receiving surfaces spaced apart along the length of the belt on regular intervals, which define the conveyor belt's drive pitch along the conveying path; and b) advancing a drive belt underlying the conveyor belt along a portion of the conveying path and having driving surfaces defining a pressure angle of less than about 5° engaging the drive-receiving surfaces of the conveyor belt to drive the conveyor belt along the conveying path. The driving surfaces are spaced apart on regular intervals, which define the drive belt's drive pitch. The drive belt's drive pitch is slightly less than the conveyor belt's drive pitch or an integral multiple of the conveyor belt's drive pitch.

BRIEF DESCRIPTION OF THE DRAWINGS

These features and aspects of the invention, as well as its advantages, are better understood by referring to the following description, appended claims, and accompanying drawings, in which:

FIG.l is a side elevation cross-sectional view of a portion of a conveyor showing the engagement of a drive belt with a conveyor belt;

FIG. 2 is a side elevation cross section of a portion of another conveyor embodying features of the invention including an alternative drive-belt hooked tooth structure; and

FIGS. 3A and 3B are enlarged views of portions of FIG. 2 showing in more detail the drive belt engaging and disengaging the conveyor belt.

DETAILED DESCRIPTION A portion of a conveyor embodying features of the invention is shown in FIG. 1. The conveyor 10 comprises a conveyor belt 12 advancing in a direction of belt travel 14 along an upper run defining the article-carrying portion of the conveyor belt's conveying path. The conveyor belt has a top article-conveying side 16 on the upper run and an opposite bottom side 17. The upper run is typically long and generally planar and may include a number of turns, left or right or both. One or more drive belts 18 underlie the conveyor belt along portions of the conveying path. The drive belts serve as intermediate drives for the long conveyor belt, transferring the load from the conveyor belt to the intermediate drive belts, preferably located at strategic locations, such as just before or after a turn. Although either or both belts could be flat belts, they are preferably modular plastic conveyor belts made of a series of rows of belt modules 20, 21 joined by hinge pins 22 confined in lateral passageways formed through interleaved hinge eyes at the leading and trailing ends of consecutive rows. The hinge joints allow the modular belt to articulate about drive and idle sprockets.

The drive belt is driven by one or more drive wheels 24 mounted on a motor-driven drive shaft 26. The drive belt loops around the drive wheels at one end and idle wheels 25 and an idle shaft 27 at the opposite end. The central portion of the drive belt rides on a support surface 28 positioned slightly above the level of the drive and idle wheels. The drive belt has outwardly extending teeth 29 that are regularly spaced in the direction of belt travel. The drive belt has other teeth across its lateral width inward of the teeth shown from the side in FIG. 1. The spacing 30 between the driving surfaces of consecutive teeth defines the drive belt's drive pitch P_d. The drive teeth are formed with a generally vertical leading driving surface 32 forming a pressure angle of substantially 0°. The drive belt's teeth are received in recesses 34 formed in the interior of the conveyor belt along the upper run. The recesses 34, which open onto the bottom side of the conveyor belt, are bounded at their forward ends by generally vertical surfaces 36. The drive belt's driving surfaces push against the vertical surfaces of the conveyor belt to advance the conveyor belt in the direction of belt travel. Because of the 0° pressure angle, the line of action 37 of the force applied by the drive belt to the conveyor belt is generally in the direction of belt travel. In this way, the generally vertical surfaces serve as drive-receiving surfaces against which the driving force applied by the drive belt's driving surfaces act.

Like the driving surfaces, the conveyor belt's drive-receiving surfaces are spaced apart on regular intervals 38 that define the conveyor belt's drive pitch P_c. To allow the drive belt to disengage the conveyor belt without the teeth of the drive belt scrubbing the drive- receiving surfaces of the conveyor belt, the drive belt's drive pitch Pd is preferably slightly less than the conveyor belt's drive pitch P_c. In this way, all the drive belt's driving surfaces forward of a rearmost driving surface 32' fully engaging the corresponding drive-receiving surface of the conveyor belt are spaced farther and farther back from their corresponding drive-receiving surfaces as the pitch difference accumulates in the direction of belt travel. Another version of a conveyor with an intermediate drive belt is shown in FIGS. 2 and 3. The conveyor belt 42 is similar to the conveyor belt of FIG. 1, except that the drive- receiving surfaces 44 have a lower face 46 extending generally vertically into the interior of the belt from its bottom side 48. The lower face transitions to a forwardly angled face 47 at the distal end of the drive -receiving surface. The teeth 50 on the drive belt 52 are similar to those on the drive belt 18 in FIG. 1, except that they have a different profile, in which the leading driving faces 54 are hook-shaped with a small-pressure-angle root portion 56 extending outward of the drive belt to a negative pressure-angle portion 58 terminating at a land 60. The composite pressure angle 62 of the teeth is close to 0°, preferably less than about 5°, or even slightly negative to prevent the conveyor belt from being pushed upward away from the drive belt during engagement. Thus, the hook-shaped teeth effectively hold the conveyor belt down without the need for special hold down belt or conveyor components. As already mentioned, the drive pitch Pd of the drive belt is preferably less than the drive pitch P_c of the conveyor belt. This means that, as shown in FIG. 3 A, when a rearmost tooth 50' of the drive belt fully engages a corresponding drive -receiving surface 44', all the teeth forward of that position are spaced farther and farther behind their corresponding drive- receiving surfaces. Thus, the rearmost driving surface may provide more of the driving force than all of the forward driving surfaces together. Of course, the load may be shared among a few consecutive teeth as the load transitions from the rearmost tooth to the following tooth moving into engagement or because of slop caused by belt tolerances or wear.

It is also possible to use an intermediate drive belt with a longer nominal pitch than that of the conveyor belt. If, for example, every other tooth is removed, the pitch of the drive belt would be about twice that of the conveyor belt. If two of every three drive teeth are removed, the drive belt's pitch would be about three times the conveyor belt's. As a general rule, the preferred relation of the conveyor belt's pitch to the drive belt's pitch may be given generally by nP_c = Pd + nαPd, where nG {1, 2, 3, . . .} and 0 < α < 0.1. This means that the drive belt's drive pitch Pd must be: a) slightly less than the conveyor belt's drive pitch P_c, for n = 1 (both pitches about the same); or b) slightly less than an integral multiple (nP_c) of the conveyor belt's drive pitch, for n > 1 (the drive belt pitch about double, triple, quadruple the conveyor belt's pitch). The term nαPd represents the pitch difference, where α is preferably no greater than about 0.1, or 10%.

The pitch difference causes the driving surfaces of the drive belt to separate gradually from the corresponding drive -receiving surfaces on the conveyor belt as it advances along the upper run. At the end of the drive belt's run, as shown in FIG. 3B, the separation 64 is enough to allow the tooth to exit the conveyor belt recess 66 without contact between the forward end of the tooth's land 60 and the conveyor belt's drive-receiving surface 44. In this way, the pitch difference enables teeth with small pressure angles to be used in an efficient intermediate belt drive arrangement.

The versions of conveyors used to describe the invention in detail are by way of example only. The scope of the claims is not meant to be limited to the preferred versions.

What is claimed is:

Claims

1. A conveyor comprising: a conveyor belt arranged to advance along a conveying path in a direction of belt travel and having drive-receiving surfaces disposed on first regular intervals in the direction of belt travel defining the conveyor belt's drive pitch; a drive belt underlying the conveyor belt along a portion of the conveying path and advancing in the direction of belt travel and having driving surfaces disposed on second regular intervals in the direction of belt travel defining the drive belt's drive pitch, the driving surfaces applying a driving force to the drive -receiving surfaces along a line of action generally in the direction of belt travel to drive the conveyor belt along the conveying path; wherein the drive belt's drive pitch is slightly less than the conveyor belt's drive pitch or slightly less than an integral multiple of the conveyor belt's drive pitch.

2. A conveyor as in claim 1 wherein the driving surfaces of the drive belt define a pressure angle of less than about 5 ° .

3. A conveyor as in claim 1 or 2 wherein the drive -receiving surfaces have a first portion generally perpendicular to the direction of belt travel and a second portion extending forward in the direction of belt travel away from the first portion and wherein the driving surfaces of the drive belt are formed on hook-shaped teeth defining the driving surfaces for mating with the drive -receiving surfaces of the conveyor belt to drive the conveyor belt and hold the conveyor belt in contact with the drive belt.

4. A conveyor comprising: a conveyor belt arranged to advance forward along a conveying path in a direction of belt travel and having a top side and an opposite bottom side and a plurality of recesses regularly spaced in the direction of belt travel and opening onto the bottom side, wherein the recesses are bounded by drive-receiving surfaces defining forward ends of the recesses in the direction of belt travel; a drive belt arranged to advance in the direction of belt travel along a portion of the conveying path adjacent the bottom side of the conveyor belt, wherein the drive belt has a plurality of outwardly extending teeth regularly spaced in the direction of belt travel and received in the recesses of the conveyor belt; wherein the teeth have driving surfaces defining a pressure angle of less than about 5° for drivingly engaging the drive-receiving surfaces of the conveyor belt to push the conveyor belt along the conveying path in the direction of belt travel; wherein the spacing between consecutive drive-receiving surfaces differs slightly from the spacing between consecutive driving surfaces so that the driving surfaces on all the teeth received in the recesses forward of a rearmost tooth whose driving surface is drivingly engaged with the corresponding drive-receiving surface are out of engagement with drive-receiving surfaces.

5. A conveyor comprising: a conveyor belt arranged to advance forward along a conveying path in a direction of belt travel and having drive-receiving surfaces generally perpendicular to the direction of belt travel disposed at regularly spaced positions in the direction of belt travel defining the conveyor belt's drive pitch; a drive belt underlying the conveyor belt along a portion of the conveying path and advancing in the direction of belt travel and having driving surfaces generally perpendicular to the direction of belt travel disposed at regularly spaced positions in the direction of belt travel defining the drive belt's drive pitch to apply a driving force to the drive-receiving surfaces and drive the conveyor belt along the conveying path; wherein the drive belt's drive pitch is less than the conveyor belt's drive pitch or less than an integral multiple of the conveyor belt's drive pitch by an amount sufficient to ensure that all driving surfaces forward of a rearmost driving surface drivingly engaged with a drive-receiving surface together provide less of the driving force than the rearmost driving surface provides.

6. A conveyor comprising: a conveyor belt arranged to advance along a conveying path in a direction of belt travel and having drive-receiving surfaces generally perpendicular to the direction of belt travel disposed at regularly spaced positions in the direction of belt travel defining the conveyor belt's drive pitch P_c; a drive belt underlying the conveyor belt along a portion of the conveying path and advancing in the direction of belt travel and having driving surfaces generally perpendicular to the direction of belt travel disposed at regularly spaced positions in the direction of belt travel defining the drive belt's drive pitch Pd to engage the drive- receiving surfaces and drive the conveyor belt along the conveying path; wherein nP_c = P_d + nαP_d, where n e { 1, 2, 3, 4} and 0 < α ≤ 0.1.

7. A conveyor comprising: a conveyor belt arranged to advance forward along a conveying path in a direction of belt travel and having a top side and an opposite bottom side and a plurality of drive - receiving surfaces having a first portion generally perpendicular to the direction of belt travel extending from the bottom side toward the top side and a second portion extending forward from the first portion toward the top side of the conveyor belt; a drive belt arranged to advance in the direction of belt travel along a portion of the conveying path adjacent the bottom side of the conveyor belt, wherein the drive belt has a plurality of outwardly extending teeth regularly spaced in the direction of belt travel; wherein the teeth have hook-shaped driving surfaces for mating with the drive-receiving surfaces of the conveyor belt to drive the conveyor belt and hold the conveyor belt in contact with the drive belt; wherein the spacing between consecutive driving surfaces is less than the spacing between consecutive drive -receiving surfaces or less than an integral multiple of the spacing between consecutive drive -receiving surfaces by an amount sufficient to ensure that all driving surfaces forward of a rearmost driving surface drivingly engaged with a drive-receiving surface are out of driving engagement with a drive- receiving surface.

8. A method of operating a conveyor, the method comprising: arranging a conveyor belt having drive-receiving surfaces spaced apart along the length of the conveyor belt on regular intervals defining the conveyor belt's drive pitch along a conveying path; advancing a drive belt underlying the conveyor belt along a portion of the conveying path and having driving surfaces defining a pressure angle of less than about 5° and spaced apart on regular intervals defining the drive belt's drive pitch for engaging the drive- receiving surfaces of the conveyor belt to drive the conveyor belt along the conveying path, wherein the drive belt's drive pitch is slightly less than the conveyor belt's drive pitch or slightly less than an integral multiple of the conveyor belt's drive pitch.