WO1997005047A1

WO1997005047A1 - System for monitoring conveyor belt integrity

Info

Publication number: WO1997005047A1
Application number: PCT/GB1996/001790
Authority: WO
Inventors: Anthony Michael May
Original assignee: Btr Plc
Priority date: 1995-08-01
Filing date: 1996-07-26
Publication date: 1997-02-13
Also published as: GB2303834A8; GB9515734D0; GB2303834A; AU6620896A

Abstract

For the early detection of rip damage in a conveyor belt (2) a magnetic field is generated in a transverse rip detection element (17) embedded in the belt. Sensor means (10) is provided close to the belt continuously to monitor the flux leakage pattern of detection element(s) (17) passing thereover and the sensor means (10) is monitored to enable belt movement to be arrested if the flux leakage pattern changes to an extent associated with breakage of an element.

Description

SYSTEM FOR MONITORING CONVEYOR BELT INTEGRITY

The invention relates to a conveyor belt, a conveyor belt system and a method of monitoring a conveyor belt of a type provided with means to assist prevention of extensive rip damage to the belt.

Rip damage readily arises in a conveyor belt, particularly a steel cord reinforced belt, when the belt is penetrated by an object which has become jammed so that it does not move with the belt.

As the belt is driven forcibly against an object which penetrates the belt, rapidly a long length and eventually all of the belt may develop a longitudinal rip. It ceases then to be suitable for transporting material. It must be taken out of service so that either the whole belt can be replaced or a damaged section repaired. In consequence there is the cost of belt repair or replacement in addition to the inconvenience and associated financial loss of suspending manufacturing or other operations which rely on continual operation of the conveyor.

Extensive attempts have been made to provide a rip detector system which can promptly stop operation of a conveyor belt if a rip has occurred. But up to the time of making this invention there has not been available any system which is cost effective and is reliable especially in some dust laden environments in which belts are often used.

In one of its aspects the present invention provides a method of monitoring for the occurrence or potential initiation of a rip in a conveyor belt comprising providing the conveyor belt with at least one transversely extending element of a material of low magnetic reluctance, providing generating means for generating a magnetic field in the transversely extending element, providing sensing means and arranging said sensing means for detection of a leakage of magnetic flux from said transversely extending element to indicate a break in said element, providing monitoring means to monitor the sensing means for a signal indicative of a leakage of magnetic flux and employing said monitoring means to provide a signal in response to which continued movement of the belt may be arrested.

The at least one transversely extending element may lie at right angles to the length of the belt but preferably use is made of a belt in which said element extends obliquely. A suitable angle is between 30 degrees and 80 degrees relative to the length of the belt, preferably between 35 degrees and 70 degrees and more preferably between 40 degrees and 50 degrees.

The magnetic field generating means and sensing means may be operated continuously at least when the belt is moving. The generating means thereby is operative continually to generate a magnetic field in the or each transversely extending element as it passes the generating means.

The conveyor belt may be a conventional long length type which has main, longitudinally extending reinforcing cords of metal of a low magnetic reluctance. These cords also will be subject to the magnetic field generating means. The sensing means may be operated to sense a leakage of flux arising upon a break in at least one of said longitudinally extending cords.

The signal from the monitoring means may be used to stop the belt automatically.

Preferably use is made of sensing means able to distinguish between magnetic flux leakage due to a break in a transversely extending rip detection element and that leakage due to a break in a longitudinally extending cord.

More preferably the method comprises the step of distinguishing between a break in a main, longitudinally extending cord and a transversely extending rip detection element and of causing movement of the belt to be arrested substantially immediately only if a break is indicated in a transverse element or more than a preselected number of longitudinally extending cords. Hence it can be ensured that the belt is not stopped unnecessarily upon damage of a number of longitudinally extending cords insufficient to present a hazard to at least short term continued operation of the belt.

The method may comprise using the sensing means to monitor a magnetic flux leaking pattern of a belt, ie. the magnetic flux signature, during one complete cycle of belt circulation. That pattern or signature may then be stored electronically or otherwise utilized for comparison with the flux leakage pattern arising during subsequent cycles of the belt. The method may further comprise arranging that movement of the belt is arrested if a change of the flux signature exceeds a preselected margin of detection error.

Another aspect of the invention provides a conveyor system having a conveyor belt which comprises at least one transversely extending element of material of low magnetic reluctance, drive means for movement of the belt, generating means for generating a magnetic field in the transversely extending element, sensing means arranged to detect a leakage of magnetic flux indicative of a break in said transversely extending element and to generate a signal at least when said break is indicated and means responsive to said signal to arrest movement of the belt.

Preferably a sensing means is positioned underneath or slightly downstream a position at which material normally is loaded on to the belt. Additional sensing means may be provided at other positions.

The conveyor system additionally may comprise means of a type for performing the method aspects of the invention.

The invention further provides a conveyor belt, particularly suitable for use in the monitoring method and conveyor system of the invention, having longitudinally spaced position sensor element zones each comprising at least one element of low magnetic reluctance which extends transversely in an oblique manner relative to the length of the belt.

A suitable oblique angle is in the range 30 to 80 degrees, preferably 35 to 70 degrees, more preferably 40 to 50 degrees.

Preferably the or each transversely extending element lies between the working, load-carrying surface of the belt and the longitudinal reinforcement of the belt. Altematively the element(s) may lie the other side of the longitudinal reinforcement, ie. between the longitudinal reinforcement and non-working side of the belt, especially when the longitudinal reinforcement comprises closely spaced metal cords.

The or each transversely extending element may be a high elongation cord (eg: at least 0.35 percent at working load).

A plurality of transverse, obliquely extending elements may be provided in each sensor element zone. The elements may be at touch pitch and embedded in the material of the belt. The plurality of elements may be assembled as a pre-formed strip in which the elements are embedded in rubber or other flexible material, the strip then being built into the belt during belt manufacture and arranged to extend obliquely as aforedescribed. Two or more, typically four, such strips each typically of a width in the order of 100 mm may be provided and laid side by side in the or each sensor element zone.

Each transversely extending element may have cut ends preferably adjacent respective belt edges, in contrast to being of closed loop form.

The sensor means may be of a segmental type comprising a series of detectors positioned in line across the width of the belt. In normal use an obliquely extending transverse element will be detected by the respective detectors either at the same moment in time or in succession depending whether the line of detectors is at the same oblique angle or a different angle. This allows differention over steel transverse cords lying at a splice region and extending at right angles to the longitudinal direction of the belt. They will therefore be sensed by the respective detectors at different relative moments in time.

An embodiment of the invention is now described, by way of example, referring to the drawings in which:-

Figure 1 is a side view of a conveyor system;

Figure 2 is a plan view of part of a belt with part of the belt cover layer cut away, and

Figure 3 is a section on the line 3-3 shown in Figure 2.

A conveyor system 1 has a reinforced conveyor belt 2 which extends around two end drums 3,4. One of the two drums is powered by a motor to drive the belt.

The belt passes under a loading hopper 5 and material from the hopper 5 is transported by the load-carrying, working surface 6 of the belt in a direction to the left in Figure 1 . At the turn-around drum 3 the material falls into a second, collection hopper 7. At a position just upstream of the loading hopper 5 and facing the underside 8 of the belt a magnetic field generator 9 is provided. The generator 9 may be a permanent magnet or an electro-magnet. This extends across the width of the belt. Just downstream of the hopper 5 sensing means 10 to detect leakage of magnetic flux extends across the width of the belt. This also faces the underside 8 of the belt.

Another pair of magnetic generator and sensing means 9', 10' is provided at the beginning of the belt return section, near the unloading drum 3.

The conveyor belt 2 has upper and lower rubber cover layers 1 1 , 12 between which there is a conventional longitudinal reinforcement layer 13 of steel cords 14 embedded in rubber.

Between the upper cover layer 1 1 and the reinforcement layer 13 the belt is provided with sensor element zones 15 at longitudinally spaced intervals.

Each zone 15 comprises four 100 mm wide strips 16 of cord reinforced rubber laid to extend transversely in an oblique direction at 45 degrees to the belt longitudinal direction. Each strip 16 is formed from steel cords 17 of 0.35 percent elongation at working load and diameter 2.1 mm laid almost at touch pitch and embedded in rubber. The cords 17 lie parallel with the strip 16 and each cord has a pair of cut ends which lie close to the respective edges of the belt.

Each zone 15 is spaced from the next zone 15' by at least five times its total longitudinal length.

The sensing means 10,10' for sensing leakage from the cords 17 of magnetic flux generated therein by the flux generators 9,9' extend obliquely also at 40 degrees so as to be parallel with the cords 17.

In use of the conveyor system monitor and comparator means (not shown) is used to record the flux leakage pattern detected by the sensing means 10,10' during a first cycle of the belt around the drums 3,4. During subsequent cycles the flux leakage pattern is compared with the original pattern. The occurrence of any significant changes indicative of a break in transverse cord 17, and/or a potentially dangerous number of longitudinal cords 14 is arranged to stop the driven drum 3,4.

Claims

CLAIMS:

1. Method of monitoring for the occurrence or potential initiation of a rip in a conveyor belt comprising providing the conveyor belt with at least one transversely extending element of a material of low magnetic reluctance, providing generating means for generating a magnetic field in the transversely extending element, providing sensing means and arranging said sensing means for detection of a leakage of magnetic flux from said transversely extending element to indicate a break in said element, providing monitoring means to monitor the sensing means for a signal indicative of a leakage of magnetic flux and employing said monitoring means to provide a signal in response to which continued movement of the belt may be arrested.

2. Method of claim 1 wherein use is made of a belt in which the transversely extending element extends obliquely relative to the length of the belt.

3. Method of claim 2 wherein the element extends at an oblique angle in the range 30 to 80 degrees.

4. Method of claim 3 wherein said angle is in the range 35 to 70 degrees, preferably 40 to 50 degrees.

5. Method of any one of the preceding claims wherein the magnetic field generating means and the sensing means are operated continuously whilst the belt is moving.

6. Method of any one of the preceding claims wherein use is made of a belt having longitudinally extending metal reinforcing elements of low magnetic reluctance and the sensing means is operable to sense a break in at least one of said longitudinally extending elements.

7. Method of claim 6 wherein the sensing means is operated to distinguish between a break in a transversely extending rip detection element and a longitudinally extending reinforcing element.

8. Method of claim 7 wherein movement of the belt is arrested only if a break is detected in at least one of a transversely extending element and more than a preselected number of longitudinally extending reinforcing elements.

9. Method of any one of the preceding claims wherein the sensing means is used to monitor the magnetic flux leakage pattern of the belt during a datum cycle of belt circulation and then storing or otherwise utilizing that pattern for comparison with the pattern detected by the sensing means during subsequent cycles of the belt.

10. Method of claim 9 wherein movement of the belt is arrested if the change of flux pattern exceeds a preselected margin of detection error.

1 1 . Method of monitoring for the occurrence or potential initiation of a rip in a conveyor belt substantially as described herein with reference to the drawings.

12. A conveyor system having a conveyor belt which comprises at least one transversely extending element of material of low magnetic reluctance, drive means for movement of the belt, generating means for generating a magnetic field in the transversely extending element, sensing means arranged to detect a leakage of magnetic flux indicative of a break in said transversely extending element and to generate a signal at least when said break is indicated and means responsive to said signal to arrest movement of the belt.

13. The conveyor system of claim 12 wherein sensing means is provided underneath or at a downstream position close to a position at which material is touched on to the belt.

14. The conveyor system of claim 12 or claim 13 and comprising means for performing a method of monitoring of any one of claims 1 to 1 1.

15. The conveyor system of any one of claims 12 to 14 wherein the transversely extending element lies between the load-carrying surface and the longitudinal reinforcement of the belt.

16. The conveyor system of any one of claims 12 to 15 wherein a sensor means is of a segmented type comprising a series of detectors positioned in line across the width of the belt.

17. The conveyor system of claim 16 wherein the series of detectors lie in a straight line inclined to the length of the belt at the same angle as the transversely extending element of the belt.

18. A conveyor system substantially as described herein and as illustrated in the accompanying drawings.

19. A conveyor belt for use in the monitoring method or system of any one of the preceding claims, said conveyor belt having at longitudinally spaced positions sensor element zones each comprising at least one element of low magnetic reluctance which extends transversely in an oblique manner relative to the length of the belt.

20. The conveyor belt of claim 19 wherein said element extends obliquely at an angle in the range 30 to 80 degrees relative to the length of the belt.

21. The conveyor belt of claim 20 wherein said angle is in the range 35 to 70 degrees, preferable 40 to 50 degrees.

22. The conveyor belt of any one of claims 19 to 21 wherein the transversely extending element is a high elongation cord.

23. The conveyor belt of claim 22 wherein the cord has an elongation of at least 0.35 percent at working load.

24. The conveyor belt of any of claims 19 to 23 wherein each sensor element zone comprises a plurality of transverse, obliquely extending elements.

25. The conveyor belt of claim 24 wherein a sensor element zone comprises at least one transverse, obliquely extending pre-formed strip in which the plurality of elements extend side by side in the direction of the strip and are embedded in flexible material.

26. The conveyor belt of any one of claims 19 to 25 wherein the or each transversely extending element has cut ends.

27. A conveyor belt substantially as described herein and as illustrated in the accompanying drawings.