WO2002072452A2

WO2002072452A2 - Conveyer belts

Info

Publication number: WO2002072452A2
Application number: PCT/IB2002/000714
Authority: WO
Inventors: Hendrik Lodewyk Van Eeden; Theunis Johannes Botha
Original assignee: Ip And Innovation Company Holdings (Proprietary) Limited
Priority date: 2001-03-14
Filing date: 2002-03-12
Publication date: 2002-09-19
Also published as: WO2002072452A3; AU2002236151A1

Abstract

The invention provides a method of detecting the occurrence of an undesired conveyer belt condition. The method includes modifying the response to an interrogation signal of at least one passive radio frequency identification (RFID) transponder or tag (12), moving with the conveyer belt (16), by means of a passive conveyer belt condition sensor (14) in response to the occurrence of an undesired conveyer belt condition, and monitoring the response, if any, of the at least one passive RFID transponder (12) to the interrogation signal, thereby determining if the undesired conveyer belt condition has occurred.

Description

CONVEYER BELTS

THIS INVENTION relates to conveyer belts. More particularly this invention relates to a method of monitoring a conveyer belt and to a conveyer belt system.

During the course of operation, conveyer belts are subjected to wear and tear. Such wear and tear may in some situations lead to a fault in the belt which, if not arrested, may propagate down the length of the belt, thereby damaging a substantial portion of the belt. This is obviously a problem.

It is an object of the present invention to provide means and a method which the Inventors believe will at least alleviate this problem.

According to one aspect of the invention, there is provided a method of detecting the occurrence of an undesired conveyer belt condition, the method including modifying the response to an interrogation signal of at least one passive radio frequency identification (RFID) transponder or tag, moving with the conveyer belt, by means of a passive conveyer belt condition sensor in response to the occurrence of an undesired conveyer belt condition; and monitoring the response, if any, of the at least one passive RFID transponder to the interrogation signal, thereby determining if the undesired conveyer belt condition has occurred.

Modifying the response of the at least one passive RFID transponder to an interrogation signal may include modifying electrical properties of the RFID transponder, and/or physical properties of the RFID transponder, thereby to modify the response of the transponder. Modifying the response of the at least one passive RFID transponder to an interrogation signal may include disabling the transponder by means of the passive conveyer belt condition sensor. Thus, in this case, if the passive RFID transponder is interrogated by the interrogation signal, its altered response would be one of no response.

Instead, modifying the response of the at least one passive RFID transponder may include altering the response of the RFID transponder to the interrogation signal, without disabling the transponder.

In one embodiment of the invention, modifying the response of the at least one passive RFID transponder includes changing an identification code included in the RFID transponder and employed by the transponder to identify the transponder, by means of the passive conveyer belt condition sensor.

Typically, the method includes monitoring the response to an interrogation signal of a plurality of passive RFID transponders spaced along a length of the conveyer belt and moving with the conveyer belt.

The method may include triggering an alarm when the undesired condition has occurred and/or stopping the conveyer belt.

The method may include measuring the elapsed time since receiving a transponder response, the occurrence of an undesired conveyer belt condition being indicated by a time lapse in excess of a preselected or precalculated time lapse.

Instead, or in addition, the method may include noting the sequence of responses from the plurality of passive RFID transponders moving with the conveyer belt, the occurrence of an undesired conveyer belt condition being indicated by an incorrect or altered sequence, e.g. when an expected transponder response in the sequence of responses is missing, or an altered transponder response is received. The method may include modifying the response to an interrogation signal of one RFID transponder of a pair of associated passive RFID transponders by means of the passive conveyer belt condition sensor in response to the occurrence of an undesired conveyor belt condition, and monitoring the response, if any, of both the passive RFID transponders to the interrogation signal, the occurrence of the undesired conveyer belt condition being indicated by a response from only one of the passive RFID transponders or an altered response from one of the passive RFID transponders.

According to another aspect of the invention, there is provided a conveyer belt system which includes, a conveyer belt; at least one passive RFID transponder or tag and at least one associated passive conveyer belt condition sensor arranged to move together with the conveyer belt, the passive conveyer belt condition sensor being arranged to modify the response of its associated RFID transponder to an interrogation signal in response to the occurrence of an undesired conveyer belt condition; and a radio frequency interrogator for interrogating any passive RFID transponders moving with the conveyer belt.

Typically, the conveyer belt system includes a plurality of passive RFID transponders and a plurality of passive conveyer belt condition sensors, each passive RFID transponder and its associated passive conveyer belt condition sensor or sensors being arranged to move together with the conveyer belt and the passive RFID transponders being longitudinally spaced along the conveyer belt.

The or each conveyer belt condition sensor may be in the form of a tripwire, arranged so that a rip in the conveyer belt in the vicinity of the tripwire brakes the tripwire. Typically, the tripwire is arranged transversely to the conveyer belt. The tripwire may be imbedded in the conveyer belt.

Each passive conveyer belt condition sensor may be arranged to disable its associated passive RFID transponder when an undesired conveyer belt condition has occurred. Instead, each passive conveyer belt condition sensor may be arranged to alter a response signal of the RFID transponder to an interrogation signal transmitted by the radio frequency interrogator when an undesired conveyer belt condition has occurred, without disabling the RFID transponder.

Typically, the or each RFID transponder comprises a chip and an antenna.

In one embodiment of the invention, the tripwire is connected in series between the chip and the antenna. Accordingly, a break in the tripwire may disable the transponder.

The or each transponder may include a chip which stores a unique identification code, the chip modulating the response signal, thereby to identify the particular transponder. The tripwire may be arranged to modify the identification code of the transponder in response to a break in the tripwire. For example, a bit may be set in the transponder which modifies the transponder response signal, thereby indicating a break in the tripwire.

Each transponder may have a unique identification code. The interrogation unit may be configured to learn the sequence of transponders along the length of the belt, via each transponder's unique identification code, to store a record of the expected arrival sequence of transponders, and to take action, e.g. trigger the alarm, if the sequence is broken.

Alternatively, or in addition, the interrogation unit may be configured to learn and record the expected arrival times of consecutive transponders, or expected time intervals between consecutive transponders, and to take action, e.g. trigger the alarm, if this arrival time or time interval alters.

In a further embodiment of the invention, a pair of transponders is provided for each tripwire, and the interrogation unit is configured to detect the pair of transponders, the tripwire being arranged so that a break in the tripwire alters the response of only one of the transponders in the pair. Each transponder in the pair may include a separate antenna, and the tripwire may be connected to one of the transponders, in series between the chip and the transponder antenna. Thus, a break in the tripwire may disable the transponder connected to the tripwire. Instead, the pair of transponders may share a single antenna, and the tripwire may be arranged to modify only one transponder when the tripwire is broken.

According to a further aspect of the invention, there is provided a conveyer belt which includes a plurality of spaced passive RFID transponders arranged to move with the belt.

At least some of the transponders may be connected to an associated tripwire which is arranged transverse to the direction of motion of the belt.

The tripwires may be embedded within the belt.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings.

In the drawings,

Figure 1 shows a schematic diagram of a conveyer belt system, in accordance with the invention; and

Figure 2 shows a schematic circuit block diagram of a passive radio frequency identification (RFID) transponder and its associated tripwire.

Referring to the drawings, reference numeral 1 0 generally indicates a conveyer belt system, in accordance with the invention. The conveyer belt system 1 0 includes a plurality of passive RFID transponders 1 2, each having an associated passive conveyer belt condition sensor, in the form of a tripwire 1 4. The passive RFID transponders 1 2 are arranged to move together with a conveyer belt 1 6, with the tripwires 1 4 arranged transversely to a direction of conveyance 1 7. The tripwires 1 4 may be mounted to the surface of the conveyer belt 1 6, such that a rip or tear in the conveyer belt 1 6, will sever a tripwire 1 4. Alternatively, the tripwires 1 4 may be embedded within the conveyer belt 1 6.

The conveyer belt system 1 0 further includes a radio frequency interrogator 1 8, which includes a radio transmitter and receiver (not shown), as well as a processor, and associated memory. The interrogator 1 8 is linked to an alarm system 20.

As shown schematically in Figure 2 of the drawings, each passive RFID transponder 1 2 includes an RFID chip 22, which includes circuitry for operating the RFID transponder. The chip 22 is connected to a transponder antenna 24, and to the tripwire 1 4. As shown in Figure 2, the tripwire 1 4 is connected in series between the chip 22 and the antenna 24. The chip 22 also includes a unique identification code, stored within memory circuitry of the chip 22, for identifying the RFID transponder 1 2.

In use, as the conveyer belt 1 6 advances past the radio frequency interrogator 1 8, each RFID transponder 1 2, mounted to the surface of the conveyer belt 1 6, is successively interrogated by an interrogation signal transmitted by the interrogator 1 8. The interrogation signal activates the RFID transponder, and causes the RFID transponder to transmit a response signal. Thus, the passive RFID transponder 1 2 does not have an external power source, like a battery for example, and, instead, the interrogation signal acts as an energy beam, which activates the RFID transponder 1 2. This activation causes a small percentage of the energy originally transmitted by the interrogator 1 2 to be reflected back, in the form of the RFID response signal. This is known as the "back-scatter" technique. The circuitry of the RFID transponder 1 2 is also configured to modulate the response signal with the identification code stored within the memory circuitry of the RFID transponder 1 2, thus the interrogator 1 8 is able to distinguish between different RFID transponders 1 2.

It is also possible, in an alternative embodiment of the invention, for the interrogator 1 8 to interrogate multiple RFID transponders 1 2 simultaneously and read response signals from multiple RFID transponders 1 2 simultaneously, in which case the RFID transponders 1 2 employ an anti-collision protocol, which facilitates the reception and interpretation of multiple RFID transponder response signals, by the receiver of the interrogator 1 8 simultaneously.

Upon initialisation or start-up of the conveyer belt system 1 0, the transmitter of the interrogator 1 8 transmits an interrogation signal to each RFID transponder 1 2. As each RFID transponder 1 2 passes the interrogator 1 8, it is activated and transmits a response signal to the receiver of the interrogator 1 8. The response signal of each RFID transponder in turn is therefore received by the receiver and the processor measures the time intervals between the arrival of consecutive RFID transponders 1 2, and records these time intervals, or distances between consecutive

RFID transponders 1 2.

In the event of the propagation of a rip or tear along the conveyei belt 1 6, a tripwire 1 4 of an associated RFID transponder will be severed. The break in the tripwire 1 4 then disables the RFID transponder 1 2, as described above, with reference to Figure 2 of the drawings. Thus the processor will detect an increase in the time interval between the arrival of consecutive RFID transponders 1 2, which indicates a break in the conveyer belt 1 6. The processor then triggers the alarm system 20, which may activate an audible siren, or may automatically initiate certain precautionary measures to prevent further damage to the belt, for example, the conveyer belt 1 6 and conveyer belt system 1 0 may be stopped.

In an alternative embodiment of the invention, upon start-up, the circuitry of each RFID transponder 1 2 senses the presence of the tripwire 1 4 and, in the event of a break in the tripwire 1 4, the identification code is changed, for example, by setting a bit. Thus, the response signal which is modified by the identification code, will be different. In this case, as each RFID transponder passes the interrogator 1 8, the interrogator 1 8 records the sequence of RFID transponders 1 2 mounted to the conveyer belt 1 6, via their identification codes. Thus, after a single pass of the conveyer belt 1 6, the processor of the interrogator 1 2 will have a record of the expected sequence of RFID transponders 1 2 mounted to the belt. Thus, when a break occurs in the tripwire 14, the RFID transponder 1 2 transmits a different response signal and the receiver of the interrogator 1 8 will receive an unexpected signal, which will not correspond to the expected response signal stored in the processor's memory. This is then interpreted by the processor as a tear or rip in the conveyer belt 1 6, and similarly triggers the interrogator 1 8 to activate the alarm system 20.

It is possible, for each tripwire 1 4, to have a pair of associated RFID transponders 1 2, in which case the receiver of the interrogator 1 8 is configured to receive a pair of response signals from each of the pair of RFID transponders 1 2. In this case, if a break should occur in the conveyer belt 1 6, one of the transponders may be disabled, as described above, or the response signal of one of the transponders could be changed, thereby indicating a break in the tripwire. In this configuration, it is possible for the pair of transponders to share a single antenna 24, or for each RFID transponder in the pair to have an independent antenna 22.

The Inventors believe that the invention as illustrated provides an efficient means and method for monitoring the condition of a conveyer belt, via the conveyer belt system 1 0, as described above. The conveyer belt system 1 0 includes a conveyer belt 1 6, having a plurality of spaced passive RFID transponders 1 2, each including an associated tripwire 1 4. The conveyer system 1 0 further includes an interrogator 1 8 which activates each RFID transponder 1 2 in turn, and receives and records the arrival intervals of each RFID transponder 1 2, or arrival sequence, based on the unique identification codes stored in each RFID transponder 1 2. In the event of the propagation of a tear or rip along the length of the conveyer belt 1 6, one or more of the tripwires 1 4 will be severed thus disabling an associated RFID transponder 1 2, or altering its response signal. This will alter the expected arrival times or sequence of response signals expected by the interrogator, which indicates a break in the conveyer belt 1 6, which enables the belt to be stopped and repaired, thereby preventing extensive damage. The conveyer system 10 is also easily maintainable, as the interrogator does not have to be pre-programmed with the specific identification codes of each RFID transponder 1 2, or the sequence or expected times of arrival, as the interrogator 1 8 is able to learn this during the course of operation.

Claims

CLAIMS:

1 . A method of detecting the occurrence of an undesired conveyer belt condition, the method including modifying the response to an interrogation signal of at least one passive radio frequency identification (RFID) transponder or tag, moving with the conveyer belt, by means of a passive conveyer belt condition sensor in response to the occurrence of an undesired conveyer belt condition; and monitoring the response, if any, of the at least one passive RFID transponder to the interrogation signal, thereby determining if the undesired conveyer belt condition has occurred.

2. A method as claimed in claim 1 , in which modifying the response of the at least one passive RFID transponder to an interrogation signal includes modifying electrical properties of the RFID transponder, and/or physical properties of the RFID transponder.

3. A method as claimed in claim 1 or claim 2, in which modifying the response of the at least one passive RFID transponder to an interrogation signal includes disabling the transponder by means of the passive conveyer belt condition sensor.

4. A method as claimed in claim 1 or claim 2, in which modifying the response of the at least one passive RFID transponder includes altering the response of the RFID transponder to the interrogation signal, without disabling the transponder.

5. A method as claimed in claim 4, in which modifying the response of the at least one passive RFID transponder includes changing an identification code included in the RFID transponder and employed by the transponder to identify the transponder, by means of the passive conveyer belt condition sensor.

6. A method as claimed in any one of the preceding claims, which includes monitoring the response to an interrogation signal of a plurality of passive RFID transponders spaced along a length of the conveyer belt and moving with the conveyer belt.

7. A method as claimed in any one of the preceding claims, which includes measuring the elapsed time since receiving a transponder response, the occurrence of an undesired conveyer belt condition being indicated by a time lapse in excess of a preselected or precalculated time lapse.

8. A method as claimed in claim 6, which includes noting the sequence of responses from the plurality of passive RFID transponders moving with the conveyer belt, the occurrence of an undesired conveyer belt condition being indicated by an incorrect or altered sequence.

9. A method as claimed in any one of claims 1 to 5 inclusive, which includes modifying the response to an interrogation signal of one RFID transponder of a pair of associated passive RFID transponders by means of the passive conveyer belt condition sensor in response to the occurrence of an undesired conveyor belt condition, and monitoring the response, if any, of both the passive RFID transponders to the interrogation signal, the occurrence of the undesired conveyer belt condition being indicated by a response from only one of the passive RFID transponders or an altered response from one of the passive RFID transponders.

10. A conveyer belt system which includes, a conveyer belt; at least one passive RFID transponder or tag and at least one associated passive conveyer belt condition sensor arranged to move together with the conveyer belt, the passive conveyer belt condition sensor being arranged to modify the response of its associated RFID transponder to an interrogation signal in response to the occurrence of an undesired conveyer belt condition; and a radio frequency interrogator for interrogating any passive RFID transponders moving with the conveyer belt.

1 1 . A conveyer belt system as claimed in claim 1 0, which includes a plurality of passive RFID transponders and a plurality of passive conveyer belt condition sensors, each passive RFID transponder and its associated passive conveyer belt condition sensor or sensors being arranged to move together with the conveyer belt and the passive RFID transponders being longitudinally spaced along the conveyer belt.

1 2. A conveyer belt system as claimed in claim 1 0 or claim 1 1 , in which the or each conveyer belt condition sensor is in the form of a tripwire, arranged so that a rip in the conveyer belt in the vicinity of the tripwire brakes the tripwire.

1 3. A conveyer belt system as claimed in any one of claims 1 0 to 1 2 inclusive, in which each passive conveyer belt condition sensor is arranged to disable its associated passive RFID transponder when an undesired conveyer belt condition has occurred.

1 4. A conveyer belt system as claimed in any one of claims 1 0 to 1 2 inclusive, in which each passive conveyer belt condition sensor is arranged to alter a response signal of the RFID transponder to an interrogation signal transmitted by the radio frequency interrogator when an undesired conveyer belt condition has occurred, without disabling the RFID transponder.

1 5. A conveyer belt system as claimed in claim 1 2, in which the RFID transponder comprises a chip and an antenna, the tripwire being connected in series between the chip and the antenna.

1 6. A conveyer belt system as claimed in claim 1 2, in which the or each transponder includes a chip which stores a unique identification code, the chip modulating the response signal, thereby to identify the particular transponder, the tripwire being arranged to modify the identification code of the transponder in response to a break in the tripwire.

1 7. A conveyer belt system as claimed in any one of claims 1 0 to 1 5 inclusive, in which each transponder has a unique identification code, the interrogation unit being configured to learn the sequence of transponders along the length of the belt, via each transponder's unique identification code, to store a record of the expected arrival sequence of transponders, and to take action if the sequence is broken.

1 8. A conveyer belt system as claimed in any one of claims 10 to 1 7 inclusive, in which the interrogation unit is configured to learn and record the expected arrival times of consecutive transponders, or expected time intervals between consecutive transponders, and to take action if this arrival time or time interval alters.

1 9. A conveyer belt system as claimed in claim 1 2, in which a pair of transponders is provided for each tripwire, and the interrogation unit is configured to detect the pair of transponders, the tripwire being arranged so that a break in the tripwire alters the response of only one of the transponders in the pair.

20. A conveyer belt which includes a plurality of spaced passive RFID transponders arranged to move with the belt.

21 . A conveyer belt as claimed in claim 20, in which at least some of the transponders are connected to an associated tripwire which is arranged transverse to the direction of motion of the belt.

22. A method of detecting the occurrence of an undesired conveyer belt condition as claimed in claim 1 , substantially as herein described and illustrated.

23. A conveyer belt system as claimed in claim 1 0, substantially as herein described and illustrated.

24. A conveyer belt as claimed in claim 20, substantially as herein described and illustrated.

25. A new method of detecting the occurrence of an undesired conveyer belt condition, a new conveyer belt system, or a new conveyer belt, substantially as herein described.