US-12623853-B2 - System and method for detecting belt-pulley disengagement

US12623853B2US 12623853 B2US12623853 B2US 12623853B2US-12623853-B2

Abstract

A system and method for detecting disengagement of a modular articulating conveyor belt from a toothed pulley with a laser beam. A laser transmitter and a laser detector are positioned at opposite sides of the modular conveyor belt wrapped around a toothed pulley. The laser beam is directed from the laser transmitter to the laser detector along a line that is intermittently intersected by radially outer structure on the belt as it advances fully engaged with the pulley. When the belt stretches with wear or when debris is trapped between the belt and the pulley, the belt starts to ride higher on the pulley in position to block the laser beam for longer time periods indicating disengagement of the belt from the pulley.

Inventors

Yorrick Mulder
Sven-Erik Haitjema-Burrough

Assignees

LAITRAM, L.L.C.

Dates

Publication Date: 20260512
Application Date: 20230118

Claims (16)

1 . A method for detecting disengagement of a modular conveyor belt from a toothed pulley, the method comprising: operating a modular conveyor belt constructed of articulated rows of belt modules wrapped around a portion of the periphery of and engaged by teeth on a pulley having an axis of rotation; aiming a laser beam across the width of the modular conveyor belt from one side along a beam line parallel to the axis of rotation at a radial distance from the axis of rotation so that the laser beam is blocked only by radially outer belt structure on the belt modules articulating around the wrapped portion of the periphery of the pulley when the modular conveyor belt is fully engaged with the pulley; maintaining the laser beam along the beam line at that radial distance; detecting the laser beam at the other side of the modular conveyor belt and producing a detection signal with a first level indicating that the laser beam is unblocked by belt structure and a second level indicating that the laser beam is blocked by belt structure; determining disengagement of the modular conveyor belt from the pulley when the detection signal persists at the second level for a predetermined time.
2 . The method as claimed in claim 1 wherein the predetermined time is greater than or equal to the time it takes the pulley to advance one pulley pitch.
3 . The method as claimed in claim 1 comprising producing an alarm indication when disengagement of the modular conveyor belt from the pulley is detected.
4 . The method as claimed in claim 1 wherein the radially outer belt structure includes structure at hinges at which the rows articulate.
5 . The method as claimed in claim 1 wherein the radially outer belt structure includes leading and trailing ends of belt rollers proximate hinges at which the rows articulate.
6 . The method as claimed in claim 1 wherein the modular conveyor belt has a belt pitch and wherein the detection signal exhibits a pulse pattern that corresponds to the belt structure and alternates between the first and second levels and repeats at a repetition period corresponding to the belt pitch.
7 . The method as claimed in claim 6 comprising estimating the speed of the modular conveyor belt by dividing the belt pitch by the repetition period.
8 . A system for detecting disengagement of a modular conveyor belt from a toothed pulley, the system comprising: a laser transmitter for transmitting a laser beam along a beam line; a laser detector spaced apart from the laser transmitter along the beam line to detect the laser beam; a conveyor frame; a pulley rotatably mounted to the conveyor frame to rotate about an axis of rotation and having teeth engaged with a modular conveyor belt wrapped around a portion of the pulley; wherein the laser transmitter and the laser detector are positioned in the conveyor frame so that the beam line is parallel to the axis of rotation at a radial distance from the axis of rotation so that the laser beam is blocked only by radially outer belt structure on the modular conveyor belt articulating around the wrapped portion of the pulley when the modular conveyor belt is fully engaged with the pulley; wherein the laser detector produces a detection signal with a first level indicating that the laser beam in unblocked by belt structure and a second level indicating that the laser beam is blocked by belt structure; and wherein the detection signal indicates disengagement of the modular conveyor belt from the pulley when the detection signal persists at the second level for a predetermined time.
9 . The system as claimed in claim 8 wherein the predetermined time is greater than or equal to the time it takes the pulley to advance one pulley pitch.
10 . The system as claimed in claim 8 comprising a programmable processor executing program instructions to receive the detection signal from the laser detector and to determine from the detection signal whether the modular conveyor belt has disengaged from the pulley.
11 . The system as claimed in claim 10 comprising an alarm indicator and wherein the programmable processor executes program instructions to send an alarm signal to the alarm indicator when the programmable processor determines that the modular conveyor belt has disengaged from the pulley.
12 . The system as claimed in claim 10 wherein the modular conveyor belt has a belt pitch and wherein the detection signal exhibits a pulse pattern that corresponds to the belt structure and alternates between the first and second levels and repeats at a repetition period corresponding to the belt pitch, and wherein the programmable processor estimates the speed of the modular conveyor belt by dividing the belt pitch by the repetition period.
13 . The system as claimed in claim 8 wherein the radially outer belt structure includes structure at hinges at which the rows articulate.
14 . The system as claimed in claim 8 wherein the radially outer belt structure includes leading and trailing ends of belt rollers proximate hinges at which the rows articulate.
15 . A method for detecting disengagement of a modular conveyor belt from a toothed pulley, the method comprising: operating a modular conveyor belt constructed of articulated rows of belt modules wrapped around a portion of the periphery of and engaged by teeth on a pulley having an axis of rotation, wherein the modular conveyor belt has a nominal belt pitch and the pulley has a nominal pulley pitch; aiming a laser beam across the width of the modular conveyor belt from one side along a beam line parallel to the axis of rotation at a radial distance from the axis of rotation so that the laser beam is blocked only by radially outer belt structure on the belt modules articulating around the wrapped portion of the periphery of the pulley when the difference between the belt pitch and the pulley pitch is less than a predetermined maximum distance; maintaining the laser beam along the beam line at that radial distance; detecting the laser beam at the other side of the modular conveyor belt and producing a detection signal with a first level indicating that the laser beam is unblocked by belt structure and a second level indicating that the laser beam is blocked by belt structure; determining disengagement of the modular conveyor belt from the pulley due to belt elongation when the detection signal persists at the second level for a predetermined time.
16 . The method as claimed in claim 15 wherein the predetermined maximum distance is 3% greater than the nominal belt pitch.

Description

BACKGROUND The invention relates generally to power-driven belt conveyors and, more particularly, to systems and methods using a laser to detect belt-pulley disengagement. Modular conveyor belts are constructed of a series of rows of one or more rigid belt modules joined by hinge rods at hinge joints. The belts are trained around drive and idle sprockets, drums, or pulleys. Teeth on the peripheries of the sprockets, drums, or pulleys positively engage drive structure in the belts. As a modular conveyor belt advances around a sprocket, drum, or pulley, it articulates at the hinge joints and assumes a polygonal shape. Each engaged row forms a side of a partial polygon. A new conveyor belt has a nominal belt pitch defined by the distance between consecutive hinge joints. A new sprocket, drum, or pulley with a circular periphery has a nominal pulley pitch defined by the arc length between consecutive teeth. In new conveyors the belt pitch and the pulley pitch are equal or nearly equal. As the new belt wraps around the toothed pulley, it hugs the periphery in positive engagement. As the conveyor belt wears, it tends to stretch, or elongate, due to deformation of the hinge rod or wallowing of hinge eyes at the hinge joints. Belt elongation inevitably occurs in modular plastic conveyor belts. As the belt stretches, the belt pitch exceeds the pulley pitch. When the difference in pitches is great enough, the elongated conveyor belt starts to ride up on the pulley teeth. Eventually the belt rides up high enough that it disengages from and skips a pulley tooth, which results in jerky belt motion. Debris trapped between a belt and a pulley is another common cause of belt-pulley disengagement. The trapped debris prevents the belt from tightly hugging the pulley and causes the belt to ride higher on the pulley teeth and eventually to disengage and skip a tooth. Belt-pulley disengagement has been detected using a laser system. A laser transmitter is positioned along one side of the conveyor belt to shoot a laser beam along a beam line radially outward of the belt where it is wrapped around the pulley. A laser detector is positioned at the other side of the conveyor belt along the laser beam's line. When the belt and toothed pulley are fully engaged, the laser beam is unblocked. But when the belt disengages, it blocks the laser beam, which indicates the disengagement. One problem with that detection scheme is that the proper positioning of the laser transmitter and detector requires that the belt be disengaged, which can damage the belt. Another problem is that detecting a single, non-recurring event and distinguishing that event from noise can be difficult. SUMMARY A method for detecting disengagement of a modular conveyor belt from a toothed pulley comprises: (a) operating a modular conveyor belt constructed of articulated rows of belt modules wrapped around a portion of the periphery of and engaged by teeth on a pulley having an axis of rotation; (b) aiming a laser beam across the width of the modular conveyor belt from one side along a beam line parallel to the axis of rotation at a radial distance from the axis of rotation so that the laser beam is blocked only by radially outer belt structure on the belt modules articulating around the wrapped portion of the periphery of the pulley when the modular conveyor belt is fully engaged with the pulley; (c) maintaining the laser beam along the beam line at that radial distance; (d) detecting the laser beam at the other side of the modular conveyor belt and producing a detection signal with a first level indicating that the laser beam is unblocked by belt structure and a second level indicating that the laser beam is blocked by belt structure; and (e) determining disengagement of the modular conveyor belt from the pulley when the detection signal persists at the second level for a predetermined time. A system for detecting disengagement of a modular conveyor belt from a toothed pulley comprises a laser transmitter for transmitting a laser beam along a beam line and a laser detector spaced apart from the laser transmitter along the beam line to detect the laser beam. A pulley rotatably mounted to a conveyor frame rotates about an axis of rotation and has teeth engaged with a modular conveyor belt wrapped around a portion of the pulley. The laser transmitter and the laser detector are positioned in the conveyor frame so that the beam line is parallel to the axis of rotation at a radial distance from the axis of rotation so that the laser beam is blocked only by radially outer belt structure on the modular conveyor belt articulating around the wrapped portion of the pulley when the modular conveyor belt is fully engaged with the pulley. The laser detector produces a detection signal with a first level indicating that the laser beam in unblocked by belt structure and a second level indicating that the laser beam is blocked by belt structure. The detection signal indicates disenga