GB2218777A - A mechanical joint for damping vibration - Google Patents

Abstract

A mechanical joint for interconnecting e.g. the arm and body of a vibration damping coupling for cables comprises a housing formed in the body in which is received the end (3b) of the arm (3), and a plurality of rubber spheres (2) located between the arm and the housing. The arm is retained within the housing by a pin (6) which passes through a biconcave hole (7) in the arm to permit pivotal movement of the arm about three orthogonal axes. Rotation of the arm about any axis causes compression of at least two spheres. The spheres are not subject to shear forces. <IMAGE>

Description

A MECHANICAL JOINT FOR DAMPING VIBRATION The present invention relates to a mechanicaljoint for damping vibration.

Mechanical joints comprising a body, at least one arm provided with two ends, a pivot axle for each arm, and damping elements, the body being provided with a housing for each arm, inside which the pivot axle can be housed for pivotally fixing one of the ends of the respective arm are know. Such joints in which each of the housings are provided with space to receive the damping elements ts damp the pivoting movements of the arms, the other end of the arms being provided with means to fix a cable or the like, are used in overground transmission lines with a plurality of parallel conductors, for the purpose of imparting a greater stability on the conductors by interconnecting them through a semi-rigid structure that limits relative movement of these conductors. Such joints are also used for interconnecting several lift cables in suspension bridges.

In order to avoid impetuous shocks, joints have already been proposed in which damping elements are provided, e.g. of rubber, that act near the pivotable end of the arms of the joint so as to damp the limited pivoting movements carried out by the arms with respect of the body of the joint. These movements may occur both in a plane perpendicular to the pivoting axis and in a plane parallel thereto.

A known solution, schematically illustrated in Figures A and B of the drawings, consists in that damping elements a are shaped as rubber cylinders arranged parallel to the pivoting axis E1 of the arm c inside a housing defined by the central body b. If a displacement of the arm c about the pivoting axis E1 occurs, i.e., in a plane perpendicular to said axis, then there will be a pure compression of two damping elements a.

As can be seen from Figure B, the bore of the arm c has a biconical shape, in order to allow for a certain rotation about axes E2, E3 perpendicular to the pivoting axis E1. Therefore, if rotation about the perpendicular axis E2 occurs, as represented schematically in dashed lines in Figure B (which is a sectional view on the plane E1-E3, of Figure A), there will be a combination of compressive strain and shearing strain on the damping elements a.

In this known joint, the fact that the damping elements are occasionally subject to shearing forces is an inconvenience since the rubber, as well as flexible materials in general, does not show a good shearing resistance and can be easily damaged when subjected to such forces.

Therefore the objective of the present invention is to provide a joint of the type described above, in which the damping elements are not subject to disadvantageous shearing forces, so that the useful life of these elements will be prolonged.

According to the present invention there is provided a mechanical joint for damping vibration comprising a body; at least one arm provided with two ends; a housing provided by the body for each arm; a pivot axle for each arm, each pivot axle being located in a said housing for pivotally fixing one of the ends of the respective arm, the other end of the arm being provided with means to fix a cable or the like; and damping elements to damp the pivoting movements of the arms, the damping elements being located in spaces in the housing and being generally spherical.

The possibility of the damping elements undergoing damages due to the application of shearing forces is substantially eliminated since a sphere, due to its own geometrical form, can only be subject to compression forces, because, upon incidence of shearing forces in any direction, the sphere tends to roll, without offering resistance.

The invention will be better understood from the following description of an embodiment thereof, given by way of example only, reference being had to the accompanying drawings, wherein; Figure 1 is an exploded view of an embodiment of the invention; Figure 2 is a plan view, in partial section, of a detail of the embodiment of Figure 1; Figure 3 is a sectional view along the line A-A of Figure 2; Figure 4 is a perspective view of two half-shells before they are fitted together; and Figure 5 is a schematical representation of the embodiment of the joint of Figure 1-4 in the mounted state.

In Figure 1 the individual components of a joint for four parallel conductors or cables are represented. In this example, the body is formed by four elements 1, each consisting of a central portion 1a interconnecting two end portions in the form of a half-shell ib, from which a fixing eyelet 1c extends. Each half-shell la houses four spherical damping elements 2, eight spheres being therefore provided for each arm 3, i.e., four on each side of a disk-shaped central part 9 of the fixing portion 3b of the arm. Each arm 3 has, at one end a bed 3a in which a rubber trough 4 lies, which receives the conductor and, at the opposite end, a fixing portion 3b, with the help of which the arm 3 is pivotally fixed on the body by means of a screw 6 or the like, which passes through the biconical opening 7.

As can be seen more clearly from Figures 2 and 3, the fixing portion 3b of the arm 3 is provided with four recesses 8 and with a disk-shaped central part 9 and fits into the inside of the half-shells 1b of the elements 1, so that, upon movement of the arm in any direction the latter will press some of the spheres 2, thus damping the movement and creating a force that drives the arm back to its starting position. It can be seen that the fixing portion - 3b, in this embodiment, is shaped wider on the side nearer the central part of the arm 3, i.e., dimension L is larger than dimension 1, since on this side there is a greater mechanical stress, and there is even the possibility of a contact with the edges 10.

Referring again to Figure A, it can be seen that the arrangement of the damping elements a is more unfavourable as regards the formation of elastic forces when the arm c undergoes a rotation about the transverse axis E3, as compared with the solution proposed now. This is because the present joint makes possible a better utilization of the elastic forces generated by the spheres 2 through the provision of the disk-shaped central part 9 at the fixing portion 3b. These disks-shaped parts act in such a manner that if a rotation of the arm 3 about any axis transverse to its pivoting axis 5 occurs (for instance, about the axes E2 or E3 of Figure A), there will be a compression of a few spheres 2.Thus, it follows that the proposed solution not only increases the useful life of the damping elements by preserving them from the harmful shearing forces, but also improves the damping effect by making it more efficient and homogeneous in all directions.

In Figure 4 two half-shells 1b are represented, which are fittable into each other and have identical shapes that complement each other, their geometrical form in the mounted state being that represented schematically in Figure 5.

In the illustrated examples, the pivoting axis 6 of the arm 3 acts simultaneously as a fixing screw between the two half-shells 1b of adjacent elements 1. However, since screws 7 (Figure 3) are already provided for uniting elements 1 to each other, it is possible to make a dead hole inside each half-shell and, instead of a through bolt, to use a pin that will be entirely located inside the halfshells and act only as a pivot axle.

The invention can undergo numberless variations, including as regards the number of conductors, cables or the like, for which the proposed joint is designed. It is possible, for instance, to fix the body of the joint on a fixed base and provide a single arm fixing correspondingly to a single cable. The protection scope is only limited by the accompanying claims.

Claims (5)

1. A mechanical joint for damping vibration comprising a body; at least one arm provided with two ends; a housing provided by the body for each arm; a pivot axle for each arm, each pivot axle being located in a said housing for pivotally fixing one of the ends of the respective arm, the other end of the arm being provided with means to fix a cable or the like; and damping elements to damp the pivoting movements of the arms, the damping elements being located in spaces in the housing and being generally spherical.

2. A mechanical joint according to claim 1, in which the end of the arm that is pivotally fixed inside the housing is provided with a biconical opening, with recesses that partially receive the damping elements, and with a disk-shaped central part.

3. A mechanical joint according to claim 1 or 2, in which the body comprises a plurality of elements each comprising of a central portion interconnecting two end portions in the form of half-shells from which a fixing eyelet extends, said housing being formed by interconnecting two half-shells of two adjacent elements.

4. A mechanical joint according to claim 3, in which four spherical damping elements are provided on each side of the disk-shaped central part of each arm.

5. A mechanical joint substantially as herein described with reference to the accompanying drawings.