The invention is suitable to be used particularly, but not exclusively, in electricity supply lines in order to signal the presence of pylons and electric conductors to low-flying aircraft.

BACKGROUND OF THE INVENTION The state of the art includes devices used in electricity supply lines, especially in those situated in areas affected by air traffic, to signal the presence of the pylons and high tension cables to the aircraft.

Among these, there are signalling devices consisting of balls, usually white and red, which are associated to the guard wire of the electric line. These devices, obviously, are only efficient during the day and in good visibility.

The state of the art also includes a luminous device comprising a special neon lamp which is directly fed with current from the electricity line.

The neon lamp is the high tension, low current type and is fed by means of connection rods of a capacitive type which are hung, by means of ceramic insulators, parallel to the conductors of the high tension line.

These devices have problems in installation and are very expensive.

Moreover, the length of the rods and the whole device, and also the number of insulators and neon lamps, is inversely proportionate to the value of the voltage of the line.

This is a problem since the section of the conductors used

in the electricity supply lines is directly proportionate to the value of electric energy transported.

As a result, the devices used in lines with conductors with a smaller section are heavier than the devices used in lines with conductors with a larger section.

The present Applicant has devised and embodied this invention to overcome these shortcomings and to obtain further advantages as explained hereafter.

SUMMARY OF THE INVENTION The invention is set forth and characterised in the main claims, while the dependent claims describe other innovative characteristics of the main embodiment.

The purpose of the invention is to provide a device, simple to produce and in function, economical, robust, reliable and suitable to be installed, particularly in electric power lines, easily and quickly.

Another purpose of the invention is to provide a device with very low energy consumption.

A further purpose is to provide a device with a high level of autonomy even without any maintenance at all.

A further purpose is to provide a device with a compact structure, suitable to resist atmospheric agents, high temperature differences and mechanical stresses.

One purpose of the invention is to use extremely efficient sources of light which are easily visible even from a great distance.

The signalling system according to the invention provides to feed at least a source of light with a current induced taken from the heads of at least an electric coil coupled inductively with the electric conductor provided in the obstacle to be signalled.

The device which embodies this system comprises at least a core on which the electric coil is wound.

The alternating electric current circulating in the electric conductor generates a variable magnetic field whose lines of force affect the coil and give rise to an induced current.

In the preferential embodiment of the invention, the induced current is straightened and stabilized before feeding the source of light.

According to one characteristic of the invention, the induced current can also be used to feed other defined appliances.

According to another characteristic of the invention, at least the source of light can be remotely activated or automatically according to the light conditions of the environment or by a timer.

BRIEF DESCRIPTION OF THE DRAWINGS These and other characteristics of the invention will become clear from the following description of a preferred form of embodiment, given as a non-restrictive example, with reference to the attached drawings wherein: Fig. 1 is a schematic view of a segment of an electricity supply line using the signalling system according to the invention; Fig. 2 is a side view, partly sectioned, of a signalling device according to the invention; Fig. 3 is a prospective view of the device shown in Fig. 2; and Fig. 4 shows an enlarged detail of the device shown in Fig.

3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT With reference to Fig. 1, a plurality of signalling devices 10 according to the invention are associated with the electric conductors 11, located higher up, of an electricity supply line 12.

Each device 10, which is shown in Fig. 2 during the step when it is coupled with a conductor 11, comprises an annular-shaped upper shell 13 suitable to couple with the electric conductor 11 and a cylindrical-shaped lower shell 14.

The shells, upper 13 and lower 14, are associated by means of a tubular element 16.

The upper shell 13 comprises two semi-shells, respectively 13a and 13b, which can be opened; in Fig. 3 they are shown in the open position, constrained together at a first end by means of a pin 17 and at the other end by means of a clamping element 18.

The upper shell 13 is suitable to contain a toroidal core 19 made in two parts, respectively 19a and 19b, each associated with a respective semi-shell 13a and 13b.

The shell 13 is provided with two lateral expansions 26 which can be opened; with the help of internal locking elements, they cooperate with the conductor 11 to prevent the device 10 from sliding along the conductor 11 and thus prevent the latter from being damaged.

Around the lower half 19b (Fig. 4) of the toroidal core 19 a conductor 20 is wound in spirals, thus achieving a coil, the ends 120 of which are taken into the lower shell 14 through the tubular element 16.

The lower shell 14 comprises a cover 14a coupled with a cap 14b made of a transparent material such as for example polycarbonate.

The cover 14a and the cap 14b, just as all the other components of the device 10, are made of materials which are resistant to atmospheric agents, great differences in temperature, ageing and mechanical stresses; they can be the conventional color of white and red or other colors which can be identified at a considerable distance, or they can be

colored so as to be camouflaged, thus minimizing their optical impact on the surrounding environment during the day time.

The cover 14a and the cap 14b internally define a seating suitable to contain a source of light 15, of the type with reduced consumption and long life, electrically connected to the conductor 20 as will be described in more detail hereafter.

In this case, the source of light comprises a plurality of light emitting diodes, or LED, 21, for example red and of the ultra-luminous type, mounted on the circumference of a plurality of printed circuits 22; in the embodiment shown here there are eight, disk-shaped and stacked one on top of the other and anchored to the tubular element 16.

According to one characteristic of the invention, the electric energy needed to feed the source of light 15 is produced by induction.

To be more exact, the device 10 according to the invention functions as follows: The alternating electric current circulating in the conductor 11 generates a variable magnetic field whose lines of force affect the conductor 20 wound on the toroidal core 19 and give rise to an induced current which can be picked up at the heads 120 of the conductor 20.

The induced electric current is fed to a stabilized straightener circuit 23 made on cards associated with the tubular element 16 near the cover 14a.

By means of a cable 25, the electric current output from the straightener circuit feeds the printed circuits 22 to light up the diodes 21.

In a first embodiment of the invention, the source of light 15 is switched on and off by remote control, by means of a radio frequency transmitter device of a conventional

type connected to a receiver device 24 housed below the source of light 15.

According to a variant, the transmitter device is mounted on board the aircraft so as to automatically activate the devices 10 when the aircraft are at a defined distance from the electricity supply line 12.

In another embodiment, instead of the radio frequency receiver 24, a light-sensitive switch is provided on the device 10.

It is obvious that, given the limited consumption and long life of the source of light 15, it is also possible to keep it always switched on.

According to a variant of the invention, moreover, the electric current induced in the conductor 20 is also used to feed a de-icing heating device which can be activated automatically by a specific sensor, particularly when the source of light 15 is switched off.

According to another variant which is not shown here, the device 10 is equipped with a supplementary source of light suitable to be automatically activated in the event of breakdowns or malfunctions of the main source of light 15.

According to a further variant which is not shown here, the device 10 is equipped with a system to radio transmit a signal to give warning of a malfunction in the device itself, or to give warning that the intensity of light is insufficient, with a pre-set threshold at which it is activated.

According to a further variant, the device 10 is equipped with a buffer battery suitable to automatically feed the source of light 15 every time the electric energy in the conductors 11 accidentally fails, or when the electric current in the conductors 11 goes below a pre-set lower limit.

It is obvious that modifications or additions may be made to this invention, but these shall remain within the field and scope thereof.