AU2007100726A4 - Power Line Detection - Google Patents

Description

2007 08/01 23:31 FAX +61 3 9543 2711 MORCOM PERNAT Q006/022 0 1

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION INNOVATION PATENT "Power Line Detection" The following statement is a full description of this invention, including the best method of performing it known to me: COMS ID No: ARCS-155331 Received by IP Australia: Time 23:41 Date 2007-08-01 2007 08/01 23:31 FAX +61 3 9543 2711 MRO ENTLJO/2 MORCOM PERNAT IA007/022 2 ci POWER LINE DETECTION Field of the Invention This invention concerns the detection of overhead power lines during the operation of machinery which may accidentally come into contact wit the power lines.

o Background to the Invention o 1 Over recent years there has been a disturbing increase in the number of people killed 0 or badly injured while operating heavy machinery which has come into contact with overhead power lines. Extensive advertising and education campaigns have been implemented by various power supply authorities and safety-focussed agencies in an attempt to reduce the incidence of such accidents. Commonly such accidents are due to a worker operating a mobile piece of machinery such as tip truck, mobile crane, forklift, or elevated work platform such as boom lift or scissor lift, and not noticing that the movement of equipment is bringing them dangerously close to live power lines.

An aim of the present invention is to provide a method and apparatus which addresses these difficulties.

Summary of the Invention in one aspect the invention provides a method of warning an operator of a machine that a moveable part of the machine is approaching a live electric power transmission line, said method comprising: -providing a detector device on said moveable part of the machine, -detecting, by means of said detector device, an electromagnetic field produced by said transmission line when carrying an alternating current, determining from the nature of said detected electromagnetic field whether said detector device is within a preset distance of said transmission line, and COMS ID No: ARCS-i 55331 Received by IP Australia: Time 23:41 Date 2007-08-01 2007 08/01 23:32 FAX +61 3 9543 2711 MRO ENTIJ0/2 MORCOM PERNAT Q008/022 3 c1 activating a warning device, and/or restricting movement of said moveable part in response to said determination indicating that said detector device is within said preset distance of said transmission line.

In another aspect the invention provides safety system for a machine having a INO moveable part which in use may approach or touch a live electric power transmission Cl line, said safety system comprising: o detection means, on said moveable part of the machine, for detecting an 0 electromagnetic field produced by said transmission line when carrying an o 10 alternating current o evaluation means for determining from the nature of said detected electromagnetic field whether said detection means is within a preset distance of said transmission line, and -means for activating a warning device, and/or restricting movement of said moveable part in response to said evaluation indicating that said detection means is within said preset distance of said transmission line.

The machine may be a tip-truck, a mobile crane, a fork lift, an elevated work platform such as a boom lift or scissor lift, or any other type of mobile machinery having elevating components.

There may be a plurality of detectors, spaced appropriately, on any such machine.

Preferably each such detector is connected to a common warning device or to a conmnon means for deactivating the machine or restricting movement of said moveable part- The present invention envisages the fitting of one or more detectors to strategic points on heavy lifting vehicles where the sensors are designed to enable the detection of alternating current electromagnetic fields that would be present adjacent live overhead power cables. Typically the detectors are calibrated to signal when they are in a range of 6 metres plus or minus 1 metre from the power line.

COMS ID No: ARCS-155331 Received by IP Australia: Time 23:41 Date 2007-08-01 2007 08/01 23:32 FAX +61 3 9543 2711 MRO ENTEj0/2 MORCON PERNAT Q009/022 4 ci Brief Description of the Drawings in order that the invention may be more filly understood there will now be described, by way of example only, preferred embodiments and other elements of the invention with reference to the accompanying drawings where: INC Figure 1 shows a semi-trailer tip truck incorporating a detection system in accordance with one embodiment of the invention; o Figure 2 is a general circuit layout for the detection system on the truck in Fiue1; Figure 3 is a circuit diagram for portion of the layout in Figure 2; 0 Figure 4 shows a front panel of a control box for the detection system in Figures 1 to and Figure 5 shows a circuit layout illustrating another embodiment of the invention.

Description of the Preferred Embodiment and Other Examples of the Invention Referring to Figures 1 and 2, the semi-trailer tip truck 10 comprises a prime mover 12, and a trailer 14. The trailer has a fray 15 with a pair of side walls 16 and 17, and a front wall 18. The front wall 18 has a top edge 20. The tray also has a rear flap 19 which opens to allow the contents of the tray to slide out when the front of the tray is elevated by a hydraulic lifting mechanism (hydraulic run, not shown) activated from a power take-off (PTO) on the prime mover.

Typically such a semi-trailer tip truck would have a total length of around 18 metres and a trailer length of about I11 metres. The top edge 20 is about 4.5 metres from ground level when the tray is down, but typically reaches a maximum height of about 11 to 12 metres above ground at maximum extension of the hydraulic ramn. Mounted on the top edge 20 of the front wall 18 are two sensors 21 and 22 spaced apart by about 314 the width of the tray.

It is well known that a power cable carrying an alternating current (AC) produces round the cable an electromagnetic field which oscillates at the same frequency as COMS ID No: ARCS-155331 Received by IP Australia: Time 23:41 Date 2007-08-01 2007 08/01 23:33 FAX +61 3 9543 2711 MORCOM PERNAT @010/022 the AC and whose strength is dependent on the voltage at which the cable is operating. It is therefore possible to create a detection system which includes electrical circuitry which can provide an indication if and only if a detector component is exposed to an electromagnetic field which is both oscillating within a narrow frequency range and emanates from a cable operating within one or more narrow voltage ranges.

In Australia, all generally distributed AC electrical power is generated at a frequency of 50 Hz. Embodiments of the present invention used in Australia take advantage of this by using a sensing probe (in the form of an electromagnetic signal antenna) tuned to operate only within a narrow frequency range, such as 50 5% Hz, and more preferably 50 2% Hz. For embodiments of the invention used in other countries which have an AC transmission frequency of 60Hz or any other value, the sensing probe would be tuned to the relevant local frequency.

In Australia, all generally distributed AC electrical power is also generally distributed at nominal transmission voltages of 415V, 6.6kV, llkV or 22kV, although there is also some local power lines operating at 240V. Embodiments of the present invention used in Australia take advantage of this limited number of transmission voltages by filtering the field strength measurements in order to signal danger only when a field strength is exceeded which corresponds to being closer than a preset distance from any of the transmission voltages likely to be encountered. Substantially greater sensitivity and accuracy can be achieved by limiting the sensing of the invention to fields emanating from only the transmission voltages which may be encountered.

Each sensor 21 and 22 comprises an antenna adapted for collecting electromagnetic signals at around 50 Hz and which passes the signal it receives to an electromagnetic field strength meter 23 (EMFSM). The meter has associated electrical components which filter out substantially all of the signal received from the antenna except for that signal in the range 49-51 Hz (ie. 50 Hz The field strength meter 23 then produces a signal indicative of the maximum field strength detected by the sensors 21 COMS ID No: ARCS-155331 Received by IP Australia: Time 23:41 Date 2007-08-01 2007 08/01 23:33 FAX +61 3 9543 2711 MORCOM PERNAT [011/022 6 and 22 within the desired narrow range of frequencies. The meter 23 is housed within a control box 24 which is mounted in the cabin of the prime mover.

The meter 23 provides its output to an electronic relay which is set as desired to activate at a predetermined field strength chosen to represent the distance from the sensor to the field source (active power cable).

If the EMFSM 23 determines there is only a weak field strength (ie. there are no power cables in the near vicinity) the control relay is not activated and the "safe" indicator lamp 46 glows.

If while the tray 15 is lifted to tip its load, the sensors come within a pre-chosen distance, such as 6 metres, of a live overhead power cable, the relay in the control box is activated and will immediately perform three tasks: 1. It activates a solenoid valve 26 which instantly stops the flow of hydraulic fluid to the lifting ram of the truck, thus stopping all upwards travel of the tray.

2. It activates a kill switch 28 which causes the engine of the prime mover to stop.

3. It activates a visual alarm 48 and an audible alarm 32 to alert the operator that the tray has risen to an unsafe distance from the active power cable.

The truck operator then must lower the tray 15, thus moving it out of the danger zone.

This moves the sensors 21 and 22 out of the activation zone and the truck motor can again be started and the truck moved to a position where the load may be safely tipped.

The sensor equipment is only activated when the lifting ram is activated. Thus, while the truck is driving along a road, the sensors are disabled and cannot interfere with normal operation.

In Figures 3 and 4 the inputs from the sensors 21 and 22 are connected across terminals Sl+ and S1- and across terminals S2+ and S2- respectively.

COMS ID No: ARCS-155331 Received by IP Australia: Time 23:41 Date 2007-08-01 2007 08/01 23:33 FAX ±61 3 9543 2711 MRO ENTIj1/2 MORCON PERNAT Q012/022 7 Oil) In relation to Figure 4, the front 40 of the control box 24 has a flat central face 42 which is set forward from a surrounding face 44. The central face 42 carries three indicator lights 46, 48 and 50. Light 46 is illuminated when the detector system is turned on and detecting safe operating conditions. Light 48 is illuminated when a dangerous situation is detected. Light 50 is illuminated when an audible alarm is Cl activated as a result of the dangerous situation being detected.

The surrounding face 44 carries four terminals (marked Sl+, SI-, S2+ and S2respectively on Figure 4) along its upper portion 52 and ten terminals (marked TI to 0 TlO respectively on Figure 4) along its bottom portion 54. These correspond to terminals TI to T1O shown in Figure 3.

A Rather embodiment will now be described with reference to Figure 5. In this embodiment, when an electric field sensor on the top front edge of a truck's tipping tray detects an electric field, an associated control box sends a signal by radio communication to a second control box in the cabin of the vehicle, and that second control box activates a relay to cut the ignition to the vehicle's motor, thus cutting power to the lift mechanism.

When an operator of a truck for example needs to operate the lift mechanism of the tray of the truck, he engages the PTO unit and this in turn activates a Sky3 (trade mark) detection system (manufactured by MADE S.A. of France) whose electric field detectors are fitted to the top front edge of the tray. The Sky3 equipment then proceeds through its normal start-up routine of checking its functions. That routine lasts approximately 50 seconds, and includes a test of the radio transmitted signal which in the course of later operation of the invention would indicate a fault and trigger the cut-out sequence of the vehicle's ignition circuit. But cuffing the ignition circuit is not appropriate during the check function, so a time delay is built in to the detection apparatus of the embodiment so as to ignore the test transmission of the detection signal.

COMS ID No: ARCS-i155331 Received by IP Australia: lime 23:41 Date 2007-08-01 2007 08/01 23:34 FAX +61 3 9543 2711 MRO ENTIj1/2 MORCOM PERNAT [a 013/022 8 0 Starting the PTO unit closes the isolator I shown in Figure 5. This powers up the 12 volt timer T which is associated with a 2-pole change over relay incorporating a first timer relay TI-i and a second timer relay Tl-2. When the timer T has measured that a period of about 80 seconds has elapsed, it switches the two timer relays Ti-I and TI-2 from their "normnally open" state to a closed position. Relay Ti-i is in series with a control relay CRI1, which is normally closed, and with an air solenoid Ci S, so the air solenoid is activated which in turn activates a hydraulic ram which raises o the tray of the truck.

o 10 If' the second control box receives a radio signal indicating that a power line is 0 unacceptably close to a sensor, the signal causes the activation relay AR to close from its normally open position. But the signal from the SKY3 equipment causes the relay AR to close for only about half a second, and then for another half second one or two seconds later, whereas it is desired to turn the ignition off continuously. The remainder of the circuit achieves that goal.

When the activation relay AR closes the timer relay Ti-2 has already been closed, so the circuit to the control relay CR is completed. Control relay CR is associated with another 2-pole change over relay, this one incorporating the first control relay CR1-i mentioned above, a second control relay CRl-2 and a third control relay CRI-3.

When the circuit to the control relay CR is completed, relay CR1-i is caused to open, relay CR1 -2 is caused to close, and relay CR1 -3 is caused to open.

The opening of relay CR1 breakcs the circuit to the air solenoid S so causing the solenoid S to deactivate and thus stop the ranm. The opening of relay CR1-3 disconnects the ignition circuit for the vehicle so stopping the vehicle's motor. The closing of relay CR1-2 connects an alternative power supply circuit to the control relay CR which alternative power supply circuit bypasses the activation relay AR and the timer relay T1-2- This means that the ignition circuit remains broken by the relay CRl-3 even after the activation relay AR returns to its normally open position. The tray may be lowered to safety by the operator without starting the engine.

COMS ID No: ARCS-155331 Received by IP Australia: lime 23:41 Date 2007-08-01 2007 08/01 23:34 FAX ±61 3 9543 2711 MORCOM PERNAT Z0J14/022 09 0 Whilst the above description includes the preferred embodiments of the invention, it Oil) is to be understood that many variations, alterations, modifications and/or additions ;Z may be introduced into the constructions and arrangements of parts previously described without departing from the essential features or the spinit or ambit of the invention.

Cl It will be also understood that where the word "comprise", and variations such as "comprises" and "comprising", are used in this specification, unless the context requires otherwise such use is intended to imply the inclusion of a stated feature or o o features but is not to be taken as excluding the presence of other feature or features.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that such prior art forms part of the conmmon general knowledge in Australia.

COMS ID No: ARCS-155331 Received by IP Australia: Time 23:41 Date 2007-08-01

Claims (6)

1. A system for warning an operator of a machine that a moveable part of the machine is approaching a live electric power transmission line, said system INO comprising: -providing a detector device on said moveable part of the machine, o detecting, by means of said detector device, an electromagnetic field produced by said transmission line when carrying an alternating current, o1i determining from the nature of said detected electromagnetic field whether 0 said detector device is within a preset distance of said transmission line, and preventing movement of said moveable part in response to said determination indicating that said detector device is within said preset distance of said transmission line.

2. A method according to claim 1 wherein the prevention of movement of said moveable part includes disconnecting the ignition circuit of an internal combustion engine powering said machine.

3. A method according to claim 1 or 2 wherein said indication of being within a preset distance is by means of a signal transmitted by radio for a set limited period but said prevention of movement continues after cessation of said signal.

4. A safety system for a machine having a moveable part which in use may approach or touch a live electric power transmission line, said safety system comprising: detection means, on said moveable part of the machine, for detecting an electromagnetic field produced by said transmission line when carrying an alternating current, evaluation means for determining from the nature of said detected electromagnetic field whether said detection means is within a preset distance of said transmission line, and COMS ID No: ARCS-155331 Received by IP Australia: Time 23:41 Date 2007-08-01 2007 08/01 23:35 FAX ±61 3 9543 2711 MORCOM PERNAT Q1016/022 0 means for restricting movement of said moveable part in response to said evaluation indicating that said detection means is within said preset distance of said transnmssion, ;Z line.

5. A system according to claimn 1 or 2 wherein the machine is a tip-truck, a mobile crane, a fork lift, an elevated work platform such as a boom lift or scissor lift, ci or any other type of mobile machinery having elevating components. o6. A system according to any one of the previous claims wherein there are a plurality of detectors spaced apart on said moveable part of the machine.

7. A system according to claim 4 wherein each said detector is connected to a common warning device or to a common means for deactivating the machine or restricting movement of said moveable part. Dated this 1 st day of August 2007 Peter Anthony Wilson and Kenneth John Wilson by their patent attorneys Morcomn Pemnat COMS ID No: ARCS-155331 Received by IP Australia: Time 23:41 Date 2007-08-01