BACKGROUND OF THE INVENTION

a) Field of the Invention

The present invention relates to an improved deicing device, and more particularly to an automatic deicing device for cable.

b) Brief Description of the Related Art

Known in the art is U.S. Patent No. 4,690,353 (Haslim et al) , which describes an electro-expulsive separation system for removing any solid body of a surface. This system consists of one or more overlapped conductors, folded back on themselves, embedded in an elastomeric material and installed on a surface. The system also comprises power storage units from which large current pulses are generated. The pulses travel in the conductors and create a repulsive force between the folded sections of each conductor. The repulsive force separates the folded sections and distends the elastomeric material, which tends to remove any solid body on the surface of the elastomeric material.

In U.S. Patent No. 5,143,325 (Zieve et al.), there is described an electromagnetic repulsion system for removing contaminants such as ice from the surface of an aircraft or any other objects. The repulsion system consists of a plurality of relatively thin and flat coils positioned between the aircraft surface and an outer sheet. Applying a rising current through the coils creates a repulsion between the coils and the aircraft surface, which causes ice to be removed from the outer sheet.

In U.S. Patent No. 3,835,269 (Levin et al.), there is described a deicing device for deicing the surface of a wire. This device consists of an appliance for generating electromagnetic field pulses, installed in close proximity

to the wire, which creates a repulsive force between the wire and the device. The appliance is fixed to a support that is secured to a movable transport vehicle for carrying the device along the wire to be deiced. Also known in the art is U.S. Patent No. 4,190,137 (Shimada et al.), which describes an apparatus for deicing trolley wires. This apparatus consists of a throughtype current transformer connected to the trolley wires. The current transformer generates a Joule heat along the trolley wires, that melts the ice.

Further known in the art is U.S. Patent No. 4,212,378 (Hrovat) which describes a device for deicing power cables. This device consists of a wheeled dolly mounted for rolling along the cable. The dolly has unequal weights for creating a rocking movement with the wind, and applying torsion to the cable to loosen ice formed on the cable.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a deicing device for cable which is easy to install and easy to handle, and which can be made fully automatic.

In accordance with the present invention, this object is achieved with a deicing device for cable. The deicing device comprises: at least one pair of conductive wires connected to and helically wound along the cable, the wires of each pair being electrically insulated from each other and connected together at one end; and pulsing means connected to each pair of conductive wires for generating an electromagnetic pulse within the wires; whereby, when the electromagnetic pulse is generated and travels in the wires, a repulsive force is created between the wires of each pair, which shakes the wires and

shatters the ice that may be attached to the cable.

Preferably, the conductive wires of each pair are adjacent. Moreover, the deicing device may also comprise detecting means for detecting ice on the cable and emitting a warning signal when ice is detected, and activating means for activating said pulsing means when the warning signal is emitted.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to impart full understanding of the manner in which this object and others are attained in accordance with the present invention, preferred embodiments thereof will be described hereinafter with reference to the accompanying drawings wherein:

Figure 1 is a side elevation of a deicing device according to a first embodiment of the invention, installed on a cable;

Figure 2 is a cross-sectional view along line II-II of Figure 1;

Figure 3 is a side elevation view of a deicing device according to a second preferred embodiment of the invention; and

Figure 4 is a cross-sectional view taken along line IV- IV of Figure 3.

In the following description and the drawings, the same reference numerals will refer to the same structural elements.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to Figure 1, there is shown a deicing device

1 according to a first embodiment of the present invention, installed on a cable 3. The deicing device 1 can be installed on any cable, but is preferably installed on an electric cable such as, for example, a coaxial cable, a

stranded cable, a wire cable, a power cable, a sheathed cable or a strengthened cable.

At least one pair of conductive wires 5 is helically wound along the electrical cable 3, in such a manner that the two conductive wires 5 of each pair are adjacent, as shown in Figure 2. Each pair of wires 5 is preferably symmetrically disposed around the cable 3. The conductive wires 5 may consist, for example, of copper or aluminium wires. To keep the conductive wires 5 properly wound on the cable 3, insulated rings (not shown) or any similar means may be used.

Each of the conductive wires 5 of a pair is connected at one end to a pulsing means 7, and connected together at their free end, so as to form a closed circuit with a pulsing means 7.

To avoid interference between the cable 3 and the conductive wires 5, the latter are preferably electrically insulated from the cable. Such an insulation may be achieved by sheathing the conductive wires 5 with an insulating material. Figure 2 shows an insulator sheathing 15 covering the conductive wires 5.

The pulsing means 7 may generate a single electrical impulsion or a train of electrical impulsions, whichever is desired. The electrical impulsions are characterized by three parameters which are a voltage, a current and a duration. It is possible to change the value of each of these three parameters by adjusting the pulsing means 7.

To get better results, the pulsing means 7 has an internal impedance that is similar to the one created by the conductive wires 5. The pulsing means 7 is preferably an electromagnetic pulse generator.

The electrical impulsions travel in one conductive wire 5 of each pair. Upon the passage of an electrical impulsion in the wire 5, a repulsive force is created between the conductive wires 5 of each pair. The repulsive force gives a shaking motion to the wires 5 that shatters the ice

covering the cable 3.

For example, for deicing a cable of 1 meter, covered by

3 millimeters of ice, the pulsing means 7 may generate one electrical impulsion having a voltage of 60 volts, a current of 3000 amperes and a duration of less than 100 mseconds, which correspond to an energy of 100 Joules.

Detecting means 9 can be used to detect the presence of ice on the cable 3. The detecting means 9 may be an ice indicator, but preferably is an automatic ice detector such as a "Rosemount Ice Detector" built by Rosemount Inc. Upon detection of ice, the detecting means 9 emits a warning signal.

The warning signal emitted by the detecting means 9 is received by an activating means 11. The activating means 11 may be physically connected to the detecting means 9, or nay consist of a remote actuator. Upon receipt of the warning signal, the activating means 11 activates the pulsing ncanβ

7 for generating the electrical impulsions.

It is also possible to use the deicing device 1 in manual mode by activating, whenever desired, the pulsing means 7 manually.

In the second embodiment of the invention shown in

Figures 3 and 4, the deicing device 1 is installed on a stranded cable 3. In this embodiment, each pair of conductive wires 5 is substituted for at least two strands of the cable 3, as shown on Figure 4. Each of the conductive wires 5 is covered by an insulator means, which is preferably an insulator sheathing 15, to avoid any interference between the conductive wires 5 and the cable 3. Whatever be the embodiment, the cable 3 and the wound conductive wires 5 may further be covered by a protective sheathing 13, as shown in Figure 4.

The deicing device is easy to install, completely automatic and reduces the usual manipulations required to perform deicing of a cable. Moreover, the deicing device does not affect in any way the transmissions performed in

the cable.

Although the present invention has been explained hereinabove by way of preferred embodiments thereof, it should be pointed out that any modifications to these preferred embodiments, within the scope of the appended claims, are not deemed to change or alter the nature and scope of the present invention.