Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
1998-09-02
2001-05-08
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S649000, C340S650000
Reexamination Certificate
active
06229446
ABSTRACT:
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.
REFERENCES:
patent: 3699432 (1972-10-01), Brown
patent: 3784842 (1974-01-01), Kremer
patent: 3823342 (1974-07-01), Burr et al.
patent: 4558309 (1985-12-01), Antonevich
patent: 4710751 (1987-12-01), Webster
patent: 4755805 (1988-07-01), Chau
patent: 5408186 (1995-04-01), Bakhoum
patent: 5469063 (1995-11-01), Winter
patent: 5519384 (1996
Link Roger Vernon Rufus
Lloyd-Jones David
Collard & Roe P.C.
Hofsass Jeffery
La Anh
Lloyd-Jones David
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