BACKGROUND Wind blowing across a suspended conductor of a transmission line is a very well known source of damage. It induces vibrations which, under resonant conditions, build up to large amplitudes resulting in destructive forces on the conductor. To alleviate this problem, there is known to install a damping device on the conductor, which absorbs the vibration energy. For example, torsional dampers are devices comprising two ball-shaped weights rigidly connected together and fixed on the side of the conductor. When a vertical vibration is induced in the conductor, it is transferred to the weight which rotates in a plan perpendicular to the conductor, inducing therein a torsional movement which is attenuated much more quickly than the vibrational movement. In dampers of the type known as Stockbridge, two weights are suspended on each side of a length of cable called "messenger". When the conductor vibrates, it excites the weights generating a flexion in the messenger. The strands in the messenger rub against each other, dissipating the energy. The above described dampers are efficient in reducing wind vibrations, but lack endurance and need to be replaced often, especially in harsh climats.

Also known in the art is U. S. patent no. 4,167,646 (MATHIEU).

Mathieu discloses a vibration damper for overhead conductors, having two weight each connected to a rigid arm, each arm being themselves connected through an elastomer ball to a clamp attached to the conductor.

The use of an elastomer joint allows a more solid connection compared to the traditional messenger. However, ball-shaped elastomer joints are relatively difficult and therefore expensive to manufacture and install.

Other related art includes U. S. patents nos. 2,094,899 (D. MacINTYRE); 2,688,047 (D. MacINTYRE); 3,314,503 (V. H. NEUBERT); 3,662,08 (SMREKAR); 3,692,919 (ROSTOKER); 3,711,624 (DULHUNTY); 3,773,967 (STURM): 3,780,207 (CROSBY et al.); 3,904,811 (OTSUKI et al.); (BOUCHE); 4,113,979 (TORR et al.); 4,140,868 (TUTTLE); 4,159,393 (DULHUNTY); 4,167,646 (MATHIEU); 4,223,176 (HAWKINS); 4,259,541 (BOUCHE); 4,278,833 (HAWKINS); 4,523,053 (RAWLINS); 4,525,596 (DIANA); 4,527,009 (HAWKINS); 4,533,785 (RIGANTI); 4,554,402 (HAWKINS); 4,554,403 (HEARNSHAW); 4,620,059 (SHERMAN); 4,620,060 (PERINETTI); 4,680,424 (HAWKINS); 4,714,799 (HAWKINS); 4,777,327 (RICHARDSON, Jr.); (BUCKNER et al.); and 5,801,329 (SCHMIDT). None of these patents disclose a resistant damper for overhead conductors which is relatively easy and inexpensive to manufacture.

OBJECT AND SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a damper for an overhead cable that is resistant, even in harsh climats.

It is another object of the invention to provide such a damper that is relatively easy and inexpensive to manufacture.

Accordingly, the present invention provide a damper for an overhead cable, comprising: a support member having a first end provided with a connecting means for connecting said support member to the overhead cable, and a second end having a support axis extending substantially horizontally when the damper hangs from the overhead cable, the support member further including an axial member mounted along the support axis and rigidly

connected to the second end, the axial member being provided with at least one pair of stops; a first dampening member having an arm and a weight connected thereto, the arm having an end pivotally connectable to the support axis, the end of the arm being provided with at least one pair of stops corresponding to and cooperating with the at least one pair of stops of the axial member for limiting a pivotal movement of the first dampening member in both directions; resilient means located between the pairs of stops of the axial member and the corresponding pairs of stops of the arm for limiting in a resilient manner the pivotal movement of the first dampening member around the support axis; and restraining means for restraining a movement of the end of the arm of the first dampening member along the support axis.

Other features and advantages of the present invention will be better understood upon reading the following non-restrictive description of embodiments thereof with reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1A and 1B are perspective views of dampers installed on an overhead cable in accordance with two embodiments of the invention.

Figure 2 is an exploded view of the damper of figure 1 A.

Figure 3 is a front view of the end of the arm of the first dampening member of the damper of figure 1 A.

Figure 4 is a cross-sectional view along lines IV-IV of figure 3.

Figure 5 is a cross-sectional view along lines V-V of figure 3.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Referring to figures 1A, 1B and 2 to 5, there is shown a damper (10) for an overhead cable (12) according to embodiments of the present invention.

The damper (10) first includes a support member (14), which has a first end (16) and a second end (18). The first end (16) is connected to the overhead cable (12), here by a clamp (20). Any other appropriate connecting means may of course be used without departing from the scope of the present invention. A support axis (22) is provided at the second end (18), extending substantially horizontal when the damper (10) hangs from the overhead cable (12). The support member (14) further includes an axial member (24) mounted along the support axis (22), and a connecting mechanism for rigidly connecting the axial member to the second end (18).

The connecting mechanism comprises recesses (51) formed in the second end (18) of the support member (14) and projections (53) of the axial member (24) that cooperate with the recesses (51).

The axial member (24) is provided with at least one pair of stops. In the embodiment illustrated in figure 2, the axial member (24) is cross- shaped and has four radial legs (26a, 26b, 26c and 26d), defining four V- shaped inner corners (28a, 28b, 28c and 28d). Four first pairs of stops are therefore provided on the axial member (24) in this embodiment, defined by the branches of inner corners (28a, 28b, 28c and 28d).

In the embodiment of figure 1 A and 2, the axial member (24) is supported by two parallel arms (52,54) rigidly fixed to the clamp (20) of the support member (14) and projecting downwardly therefrom. The support axis (22) extends from one arm (52) to the other (54). The axial member (24) is pivotally connected to the support axis (22), and is held in a fixed position with respect to the arms (52,54) by means of recesses (51) which cooperate with projections (53) of the axial member (24). Referring

now to figure 1 B, the arm (54) may also be omitted and simply replaced by a closing plate (56), to limit manufacturing costs.

Referring again to figures 1A, 1B and 2 to 5, the damper (10) also includes a first dampening member (30), having an arm (32) to which is connected a weight (34). The arm (32) has an end (36) mounted around the axial member (24), the end (36) being provided with at least one pair of stops, corresponding to and cooperating with the at least one pair of stops of the axial member (24) for limiting a pivotal movement of the first dampening member (30) in both directions with respect to the axial member (24). Preferably, the end (36) of the arm (32) comprises an inner cylindrical wall (38) having four arc-shaped cavities (40a, 40b, 40c and 40d) regularly distributed along its circumference, defining four pairs of stops of the end (36) of the arm (32) which cooperate with the four first pairs of stop of the axial member (24).

The damper (10) according to the present invention may include any number of dampening members similar to the first dampening member (30) as may be convenient. Preferably, two dampening members are provided, extending on each side of the axial member (24). The second dampening member (42) includes the same components as the first dampening member (30), that is an arm (32) having a weight (34) connected thereto and having an end (36) mounted around the axial member (24). Advantageously, the weights (34) of the dampening members may be different, that is one heavier than the other, to provide different resonance frequencies for the vibration of each dampening member.

The end (36) of the arm (32) of the second dampening member (42) is also preferably provided with an inner cylindrical wall (38) having four arc-shaped cavities (40a, 40b, 40c and 40d) regularly distributed along its circumference, defining four pairs of stops of the end (36) of the arm (32).

In this embodiment the axial member (24) has four second pairs of stops provided by the branches of inner corners (28a, 28b, 28c and 28d) to

cooperate with the four pairs of stops provided by the four arc-shaped cavities (40a, 40b, 40c and 40d) of the second dampening member (42).

The axial member (24) includes four radial separating shoulders (44a, 44b, 44c and 44d) extending respectively in the V-shaped inner corners (28a, 28b, 28c and 28d). The V-shaped inner corners (28a, 28b, 28c and 28d) in this manner embody on one side of the shoulders (44a, 44b, 44c and 44d) the four first pairs of stops and on the other side of the shoulders the four second pairs of stops.

The damper (10) further includes resilient means located between the pairs of stops of the axial member (24) and the corresponding pairs of stops of each arm (32), for limiting in a resilient manner the pivotal movement of the corresponding dampening member around the support axis (22). The resilient means preferably include four cylindrical-shaped elastomer bodies (46a, 46b, 46c and 46d) per dampening member, partially located in the corresponding arc-shaped cavities (40a, 40b, 40c and 40d) and in the V- shaped inner corners (28a, 28b, 28c and 28d). The cylindrical-shaped elastomer bodies (46a, 46b, 46c and 46d) extend along axes parallel to the support axis (22). One end of each cylinder-shaped elastomer bodies (46a, 46b, 46c and 46d) abut on the shoulders (44a, 44b, 44c and 44d), and the opposed end abuts on the second end (18) of the support member. In this manner, an axial displacement of cylinder-shaped elastomer bodies (46a, 46b, 46c and 46d) along the support axis (22) is prevented.

The damper (10) according to the present invention also includes restraining means for restraining a movement of the end of the arm (36) of each dampening member (30,42) along the support axis (22). For each dampening member, these restraining means include the corresponding cylinder-shaped elastomer bodies (46a, 46b, 46c and 46d) and face walls extending along each face of the end of the arm (36). The first face walls (59) partially close two of the arch-shaped cavities (40b, 40d) along the first face (55) of the end of the arm (36). Similarly, the second face walls

(61) close the remaining two arc-shaped cavities (40a, 40c) along the second face (57) of the end of the arm (36). These walls cooperate with the cylinder-shaped elastomer bodies (46a, 46b, 46c and 46d), each of which abuts on one of the wall at one of its ends. This prevents an axial movement of the end of the arm (36) with respect to the cylinder-shaped elastomer bodies (46a, 46b, 46c and 46d). Since these elastomer bodies are themselves prevented from an axial displacement with respect to the support axis (22), the result is that the axial movement of end of the arm (36) with respect to the support axis (22) is resiliently restrained by the restraining means.

Preferably, the end (36) of the arm (32) of the first dampening member (30) comprises an outward stop (48) projecting toward the second dampening member (42). Similarly, the end (36) of the arm (32) of the second dampening member (42) comprises an outward stop (50) projecting toward the first dampening member (30). The outward stops (48,50) cooperate together to prevent the pivotal movement of the dampening members past a predetermined pivoting angle. In the preferred embodiment, two outward stops (48,50) are provided on each dampening member (30, 42).

Of course, numerus modifications could be made to the preferred embodiments disclosed hereinabove without departing from the scope of the invention as defined in the appended claims.