GB2310728A - Voltage detection and alarm device - Google Patents

Abstract

An alarm device comprises an earth connection 30, a power source 20 and at least one means of activating an alarm 10 when an object, which is normally substantially at ground potential, becomes energised to a voltage level substantially above that of ground potential. The earth connection 30 may be formed by a conductive rod or prod inserted or otherwise arranged to make contact with the ground. The alarm 10 may be an audible siren or a visible flashing light. The means for activating the alarm may comprise switch means 40 which may involve a bi-metallic strip and / or a relay, an inductive current sensor and / or a discharge protective cup. The relay may activate different alarms depending on the voltage level detected or the longevity of the voltage presence. The alarm 10 may also be activated if the device is not earthed. The power source 20 may be independent or dependant on a power source within the object being monitored.

Description

ALARM APPARATUS The present invention relates to an alarm apparatus. In particular, the present invention relates to an alarm apparatus which is associated, in use, with an object, such as a machine, plant, tool, vehicle or the like and is activated in the event that said object becomes energised or live with voltages typical of electrical supply networks.

Persons working in close proximity to power cables, for example, pylons and underground cables, run the risk of being electrocuted, since the vehicle in which they are located, or the machines or tools with which they are working, which are capable of conducting electricity, may become energised by the discharge of electricity from said power cables. Consequently, any resultant casual contact with such energised vehicles, tools or machines may result in injury or even death.

Accidents of this type sometimes occur in the tree maintenance industry, particularly those persons involved in live-line clearing, i.e. the removal or pruning of trees in the vicinity of power cables which are energised using access platforms.

In order to reduce such associated injuries and fatalities, attempts have been made to insulate said objects or parts of said objects which are likely to be energised by said power cables, for example, mobile access platforms associated with a vehicle utilised for live-line clearing. However, due to the nature of the work, the insulation may become damaged or breached, thereby exposing parts of the vehicle or machine which are capable of becoming energised to or close to ground level.

Therefore, although the insulation described above may reduce the occurrence of such electrocution, the risk of such associated injuries and fatalities are still unacceptably high and represent a hazard to anybody who could come into casual contact with a passively energised object.

It is the aim of the present invention to provide an alarm apparatus which is adapted to alert any person working in close proximity to power cables or other electricity carrying means that the vehicle in which they are located, or the tool or machine with which they are about to come into contact, has become energised. Thus the alarm apparatus of the present invention warns the worker of the unseen danger of energisation and hence, enables the worker to take all the necessary steps in order to avoid contact with and observe proximity zone guidelines to safely resolve the hazard.

According to the present invention there is provided an alarm apparatus suitable for use with an object, which apparatus is activated upon energisation of the object, wherein the alarm apparatus comprises earthing means, a power source, at least one alarm means and actuating means which actuates the alarm means in the event of the energisation of the object.

In a preferred embodiment, the earthing means comprises a prod made of electrically conducting material which, in use, is insertable into or otherwise makes contact with the ground.

In one preferred embodiment of the present invention, the actuating means comprises switch means.

Preferably the switch means comprises a spring loaded switch, a clamp constructed of a ceramic material which is thermo-stable, non-conductive and non-weldable, and a bi-metallic strip. In another preferred embodiment of the present invention the actuating means comprises relay means. Further preferably, the actuating means of the present invention is capable of distinguishing between low and high voltage flows.

In a still further preferred embodiment, the alarm means comprises an audible alarm means, for example, a siren and/or a visual alarm means, for example, a flashing light or a vehicles existing hazard warning mechanism i.e. a vehicles hazard lights. It is to be understood that the alarm apparatus of the present may comprise a plurality of alarm means.

In a further preferred embodiment the power source may be independent, however, in the case of a vehicle, the power source may be the same as the vehicle's power supply i.e. the vehicle's battery.

Preferred embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a block diagram illustrating the integers of the alarm apparatus of a first embodiment of the present invention; Fig. 2 illustrates a preferred switch means of said first embodiment of the present invention; Fig. 3 schematically illustrates a second embodiment of the alarm apparatus of the present invention; Fig. 4 is schematic diagram of an alternative embodiment of an alarm apparatus of the present invention; and Fig. 5 illustrates an embodiment of the alarm apparatus of Fig. 4.

With reference to Fig. 1, the alarm apparatus comprises first and second circuits which are isolated from one another, as well as being antagonistic to one another.

The first circuit comprises a prod 30, a switch means 40 and a conducting wire 50, connected in series.

The second circuit comprises a power supply 20, the switch means 40 and alarm means 10, connected in series.

With reference to Fig. 2, the switch means 40 comprises a ceramic U-shaped clamp 41 which, in use, is attached to the object. Said switch means 40 comprises a bi-metallic strip 42 which acts as a bridge between the conducting wire 50 on one side of the switch means 40 and the prod 30 connected to the other side of the switch means 40. Said switch means 40 also comprises a spring loaded switch 44 movably located therein.

The bi-metallic strip 42 of the switch means 40 is fastened at end 45 by fixing means 43 and is in contact with conducting wire 50 which is attached to a part of the object "X" which is capable of becoming energised. The opposite end 46 of the bi-metallic strip 42 is in contact with the prod 30.

Whilst the alarm apparatus of the present invention is inactive, i.e. the object to which it is attached or associated has not become energised, the first circuit is complete and the end 46 of the bi-metallic strip depresses the spring loaded switch 44.

Consequently, the second circuit is incomplete or broken, i.e. the power source 20 is not connected to the alarm means 10.

On energisation of the object, the resultant flow of electricity to earth causes side 46 of the bi-metallic strip 42 to lift, thereby releasing said spring loaded switch 44. Consequently, the second circuit is now complete and the alarm means 10 are activated, i.e. the power source 20 and the alarm means 10 are now connected.

When a vehicle (not illustrated), equipped with the alarm apparatus of the present invention, comes to a standstill in the vicinity of power cables, the prod 30 is inserted into the ground thereby completing the first circuit.

In the event that the vehicle becomes energised, an electric discharge will surge through the first circuit, i.e. to earth. Depending on the design parameters of the bi-metallic strip 42, if the voltage driving the electric discharge is of sufficient strength, end 46 of the bi-metallic strip 42 will lift or completely burn out, thereby resulting in the release of the spring-loaded switch 44. The subsequent release of the spring-loaded switch 44 results in the completion of the second circuit and hence, the activation of the alarm means 10. Thus in the event of energisation, a person in the vicinity of the vehicle can take all the necessary steps in order to avoid contact with and observe proximity zone guidelines to safely resolve the hazard.

With reference to Fig. 3, the earthing means 61 comprises a conducting member which is attached at one end 62 to an area of the object which is capable of becoming energised, for example, the chassis of a vehicle.

An inductance coil 63 is attached to said earth means 61 and may be designed so that said inductance coil 63 detects electrical discharge of designated strength.

Said inductance coil 63 is connected to a relay 64 which is connected to three separate alarm means 65, 66, 67.

Alarm means 65, 66, 67 are each connected to a power source 68.

In the event of energisation, said inductance coil 63 induces a current in said relay 64 and, depending on the design parameters of the alarm apparatus, thereby results in the activation of the alarm means 65, 66 and/or 67.

In the event of energisation, alarm means 65 is activated by said relay 64, i.e. the circuit between the alarm means 65 and power source 68 is completed. In the event that energisation ceases, said relay 64 automatically disconnects said circuit and thus alarm means 65 is subsequently inactivated.

In the event of energisation, alarm means 66 is activated by said relay 64, i.e. the circuit between the alarm means 66 and the power source 68 is completed. In the event that energisation ceases, alarm means 66 still remains activated and can only be inactivated manually.

In the event of energisation, alarm means 67 is only activated by said relay 64 in the event that the energisation persists over a prolonged period of time.

In this connection, the alarm means 67 is connected to a timer and is only activated by the relay 64 in the event that the time of energisation exceeds that which has been preset. Once activated, the alarm means 67 can only be inactivated manually.

When a vehicle (not illustrated), equipped with the second embodiment of the alarm apparatus of the present invention, comes to a standstill in the vicinity of power cables or other electricity carrying means, the earthing means 61 is inserted into or makes contact with the ground.

In the event of energisation, alarm means 65 and 66, which comprises a visual alarm means situated in the cab of said vehicle, are activated. If the energisation is temporary, alarm means 65 is deactivated, whereas alarm means 66 remain activated so that in the event that the driver has left the vehicle, on his return, he is aware that energisation has occurred. Once activated alarm means 66 can only be deactivated manually.

In the event that energisation persists for a prolonged period of time, alarm means 67 is also activated. Said alarm means 67 comprises a visual and audible alarm means thereby warning the operator or driver and anyone else in the vicinity of the vehicle that same is energised. In this connection, said alarm means 67 may activate the vehicle's horn or hooter, as well as the vehicle's hazard lights. Once activated, the alarm means 67 can only be deactivated manually.

Fig. 4 schematically illustrates an alternative embodiment of an alarm apparatus of the present invention which is able to detect different strengths of voltage.

With reference to Fig. 5, an alarm apparatus 90 is housed within an insulating box 74 and is connected to alarm means and power means (not illustrated).

Preferably, the insulating box 74 is made of a ceramic or thermo-stable impact resistant plastic. The alarm apparatus 90 is connected through the insulated box 14 at 10 to the chassis of a vehicle (not illustrated) . The alarm apparatus 90 further comprises a current limiting resistor 72, a current sensor 73, an ionic discharge spike and protective cup 75, an alarm activating relay 76, an induction coil sensor 79 to sense flows, for instance, between 50/60 HZ 100V-5000V AC and a fuse wire with isolating rod 78 connected to a micro switch 77.

The alarm apparatus 90 is connected to the earth via a spike or lightning conductor type discharger 80 which is insulated from the chassis of the vehicle. The alarm apparatus 90 is covered by a cover 81 provided with an aperture 82 through which the ionic discharge spike and protective cup 75 are visible.

The skilled person would realise that the sensitivity of the induction coil sensor 79 could be tuned to a particular range depending on the electricity supply network with which the vehicle is likely to come into contact. For example, the induction coil sensor could be tuned to a range of 150-800V, protecting the circuit with a fuse set to blow at 500V, although this is subjective to the local electricity supply network where low voltage (LV) transmission would be by single phase 240V or three phase 450V and high voltage (HV) transmission at 9, 11 or 33 KVA (all alternating current AC). Other supply networks operate at different voltages (both LV and HV) all of which could be sensed by the fine tuning of the three different sensors to the requirements of that operating environment.

In operation it is intended that the various sensing means be active in overlapping sensory ranges and modes, for instance, the ionic discharge spike could provide sensing means, at least for HV discharges, if the connection to earth through the fuse and induction coil is not made effectively.

Additionally, it is to be understood that the sensitivity of the ionic discharge spike could be tuned to provide back up to the low voltage induction coil sensor to adequately ensure against failure of the alarm due to poor earthing.

In another embodiment of the present invention, the alarm means could be supplemented by a series of light emitting diodes (LEDs). Such LEDs being prominently displayed within or on a vehicle so that same are visible to a person in or within the vicinity of the vehicle. Preferably, there would be four LEDs. The first LED would light up when energisation occurs and would remain on until the alarm is reset, i.e. the first LED would alert a person that an energisation event has occurred. The second LED would light up in the event that energisation caused by a low voltage occurs. The third LED would light up in the event that energisation caused by a medium voltage occurs and the fourth LED would light up in the event that energisation caused by a high voltage occurs. The second, third and fourth LEDs, unlike the first LEDs, will turn off as soon as energisation ceases.

Although the present invention has been described in relation to an alarm apparatus which is associated with a vehicle and is capable of detecting the energisation of said vehicle, it is to be understood that the alarm apparatus of the present invention can be adapted for use with any other object, such as a machine or tool which may become energised.

Claims (15)

1. An alarm apparatus suitable for use with an object, which apparatus is activated upon energisation of the object, wherein the alarm apparatus comprises earthing means, a power source, at least one alarm means and actuating means which actuate the alarm means in the event of the energisation of the object.

2. An alarm apparatus as claimed in claim 1, wherein the earthing means comprises a prod made of electrically conducting material, such that, in use, the prod is insertable into or otherwise makes contact with the ground.

3. An alarm apparatus as claimed in claim l or 2, wherein the alarm means are audible and/or visual alarm means.

4. An alarm apparatus as claimed in claim 3, wherein the audible alarm means comprise a siren.

5. An alarm apparatus as claimed in claim 2 or 3, wherein the visual alarm means comprises at least one flashing light.

6. An alarm apparatus as claimed in any preceding claim, wherein the actuating means comprises a switch means.

7. An alarm apparatus as claimed in claim 6, wherein the switch means comprises a spring loaded switch, a clamp constructed of a ceramic material which is thermostable, non-conductive and non-weldable, and a bimetallic strip.

8. An alarm apparatus as claimed in any one of claims 1 to 5, wherein the actuating means comprises relay means, such that, in use, the relay means are capable of actuating different alarm means depending on the longevity of the energisation event.

9. An alarm apparatus as claimed in any one of claims 1 to 5, wherein the actuating means include a plurality of sensors which are capable of sensing different strengths of voltage.

10. An alarm apparatus as claimed in claim 9, wherein said sensors have overlapping ranges of sensing.

11. An alarm apparatus as claimed in claim 9 or 10, wherein at least one of the sensors can actuate the alarm means in the event that the alarm apparatus is not earthed.

12. An alarm apparatus as claimed in any preceding claim, wherein the power source is independent of the power source of the object.

13. An alarm apparatus as claimed in any one of claims 1 to 11, wherein the power source is the same as the power source of the object.

14. An alarm apparatus substantially as hereinbefore described with reference to the accompanying drawings.

15. An object when fitted with an alarm apparatus as claimed in any one of claims 1 to 14.