Abstract:
The present invention provides an alarm apparatus suitable for use with an object or person, which apparatus is activated upon energisation of the object or person, wherein said alarm apparatus comprises a power source, at least one alarm means, actuating means associated with an unearthed sensor which actuates said alarm means in the event of the energisation of said object or person.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an alarm apparatus. In particular, the present invention relates to an alarm apparatus which, in use, is associated with an object, such as a machine, plant, tool, vehicle or the like, or a person, and is activated in the event that said object or person comes into contact with, or has a dangerous voltage potential induced from an electrical supply network and hence, becomes energised or live with voltages typical of such electrical supply networks. 
     2. The Prior Art 
     Persons working in the vicinity of 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 power-line tree 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, breached or by-passed 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. 
     With a view to overcoming the above problem, there has been provided alarm apparatus which are 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 have come into contact, has become energised to a dangerous voltage, i.e. such alarm apparatus warns such persons of the unseen danger of energisation, thereby enabling such person to take all the necessary steps in order to avoid contact with such energised object and hence, observe proximity zone guidelines to safely resolve the hazard by not touching the machinery and not allowing anybody else to do so. An example of an alarm apparatus of this type is disclosed by European Patent Application No. 87304611.4 (Flowmole Corporation). 
     Generally, and with reference to FIG. 1, known alarm apparatus of this type comprise 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. 
     As shown in FIG. 2 a suitable switch means  40  for such an alarm apparatus, developed by us, 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 bimetallic 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 such known alarm apparatus is inactive, i.e. the object to which it is attached or associated with 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 . As a result thereof, the second circuit is now complete and the alarm means  10  are activated, that is, as a result of the power source  20  and the alarm means  10  being connected. 
     When a vehicle (not illustrated), equipped with such an alarm apparatus, 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 such energised object and hence, observe proximity zone guidelines to safely resolve the hazard. 
     The problem associated with known alarm apparatus of this type is that in order to work, they are required, in use, to be earthed. Failure to do so will result in the alarm apparatus not being activated such that a person utilising such an alarm apparatus will not be made aware of any pending danger of coming into contact with an object which may have become energised. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided an alarm apparatus which, in use, is connected to an object or person, and which is activated upon energisation of said object or person, comprising: 
     at least one earthed sensor; 
     a power source; 
     at least one alarm means; 
     actuating means associated with said earthed sensor which actuates said alarm means in the event of the energisation of said object or person; characterised in that said alarm apparatus further comprises an unearthed sensor associated with said actuating means which can actuate the alarm means in the event that the earthed sensor is not earthed. 
     In a further aspect of the present invention there is provided an alarm apparatus which, in use, is connected to an object or person, and which is activated upon energisation of said object or person, comprising: 
     a power source; 
     at least one alarm means; 
     actuating means associated with an unearthed sensor which actuates said alarm means in the event of the energisation of said object or person. 
     It is an object of the present invention to provide an alarm apparatus which is believed to address the problems associated with the known alarm apparatus outlined above. More particularly, it is an object of the present invention to provide an alarm apparatus which, in use, is associated with an object, such as a machine, plant, tool, vehicle or the like, or a person, and which can activate in the event that same is not earthed properly, or can activate without the need to provide a connection to earth. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred, non-limiting, embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: 
     FIG. 1 shows a schematic view of a known alarm apparatus of the prior art; 
     FIG. 2 shows a side cross-sectional view of the prior art alarm apparatus of FIG. 1; 
     FIG. 3 is schematic diagram of one embodiment of an alarm apparatus in accordance with the present invention; 
     FIG. 4 illustrates an embodiment of an alarm apparatus in accordance with FIG. 3; and 
     FIG. 5 is a schematic diagram of an alarm apparatus in accordance with a further aspect of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As illustrated in FIG. 4, an alarm apparatus in accordance with the present invention comprises a conductive element which is associated with an object or person connected to a low voltage sensor, a medium voltage fuse and an unearthed voltage sensor. Such unearthed voltage sensor, low voltage sensor and medium voltage fuse all being connected to a relay, which in turn is connected to alarm means. As illustrated, the conductive element, medium voltage fuse and low voltage sensor are connectable to earth. An alarm apparatus of the present invention is able to detect different strengths of voltages and, unlike known alarm apparatus, can still actuate in the event that the alarm apparatus is not earthed correctly. 
     In use, when the alarm apparatus of the present invention and the object with which it is associated comes into contact with, or has a current induced from an electrical supply network and hence, becomes energised, then, and depending on the strength of the voltage detected and the settings of the sensors, the alarm means will be activated. For example, the low voltage sensor will actuate the alarm means via the relay on the detection of a low voltage. The medium voltage fuse, will actuate the alarm means via the relay on the detection of a medium voltage. The skilled person will realise that such medium voltage fuse acts to protect the low voltage sensor circuitry from damage during an energisation event, the strength of which could damage such circuitry. The unearthed voltage sensor will actuate the alarm means via the relay on the detection of an unearthed, potential voltage. Actuation of the alarm apparatus, enables a person to take the necessary action to avoid being electrocuted, i.e. by taking the necessary action to avoid acting as an earth for the voltage source. 
     With reference to FIG. 4, one embodiment of an alarm apparatus  90  in accordance with the present invention, is housed within an insulating box  74  and is connected to alarm means and power means (not illustrated). 
     Preferably, 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 another unillustrated 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 an unearthed voltage occurs. The second, third and fourth LEDs, unlike the first LEDs, will turn off as soon as energisation ceases. 
     Further preferably, the power source may be independent, however, in the case of a vehicle, the power source may be the same as the vehicle&#39;s power supply i.e. the vehicle&#39;s battery. 
     As such alarm means, including the above-mentioned LEDs, and power means are well known, the makings of same will not be further described herein. 
     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  74  at  71  to a conductive element of the object with which it is to be associated, for example, 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 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. 
     In use, and when the alarm apparatus  90  is connected to the chassis of a vehicle, the earth connection is effected by inserting prod  80  into the ground. In the event that the vehicle comes into contact with, or has a dangerous voltage induced from an electricity supply network and hence, becomes energised then the alarm will actuate. In this connection, it is submitted that the skilled person will 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 electricity supply networks operate at different voltages (both LV and HV) all of which could be sensed by the fine tuning of the different sensors to the requirements of that operating environment. 
     In operation, it is intended that the various sensors or sensing means be active in overlapping sensory ranges and modes, for example, 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. In this connection, it will be realised by the skilled person that the alarm apparatus of the present invention will activate in the event that the earth connection is not effected properly. That is, 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. 
     Additionally, and in light of the above, it is also to be understood that the alarm apparatus of the present invention, in use, and unlike known alarm apparatus, does not require to be connected to earth, that is, by tuning the sensitivity of the ionic discharge spike in light of the requirements of the operating environment, the earthing circuitry can be dispensed with. That is, and with reference to FIG. 5, an alarm apparatus in accordance with a further aspect of the present invention can be provided which does not require prod  80 , induction coil sensor  79  and the fuse wire with isolating rod  78  connected to switch  77 . Such an alarm apparatus thus being provided with sensing means which senses the potential above earth of a surface to which it is attached and hence, dispenses with the need for a connection to earth, to allow the alarm means to be activated. 
     As illustrated in FIG. 5, an alarm apparatus in accordance with a further aspect of the present invention comprises a conductive element, a sensor, a current limiting resistor and an ionic discharge spike in series, such that, and depending on the sensitivity of the sensor, when the potential or the conductive element rises to a potential above earth which is believed to be dangerous, the sensor via relay means will actuate the alarm means, that is, by completing the circuit between a known power source and the alarm means. 
     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, or person, which may become energised. Furthermore, and while certain preferred embodiments of the present invention have been disclosed in detail, it is to be understood that various modifications may be adopted without departing from the spirit of the invention, or the scope of the following claims.