US1842809A - Method of and means for supporting transmission line conductors - Google Patents

Description

T. VARNEY Jam. 26, 11932.

METHOD OF AND MEANS FOR SUPPORTING TRANSMISSION LINE CONDUCTORS Filed Feb. 25, 1927 INVENTOR Patented Jan. 26, 1932 units!) STATES PATENT OFFICE THEODQBE VARNEY, SEWIGKLEY, PENNSYLVANIA, ASSIGNOR TO ALUMINUM COM- PANY OF AMERICA, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENN- SYLVANIA WTHUD OF AND MEANS FOR SUPPORTING TRANSMISSION LINE CONDUCTORS Application filed February 25, 1927. 7 Serial No. 170,929.

My invention relates to a new and improved method of and means for supporting transmission line cables at their points of support in the transmission line. The methods heretofore usually followed in supporting transmission line cables from string insulators suspended from transmission line towers have been unsatisfactory, due to a number of causes; for example, fixedly and tightly clamping the cable at its point of support, and the absence of means for properly taking care of the vibrations to which the cable is subjected.

In the usual practice, the entire weight of the span is carried by the supporting device, and, as cables frequently weigh one or more pounds per foot and may be from 1000 to 2000 feet long, this means that the cable at its point of support is subjected to a transverse or crushing pressure of 1000 to 2000 pounds or more. If the cable is tightly clamped to the supporting device, as is usually the case, the cable is subjected to at least double the pressure stated. In addition to this pressure, the cable in the usual suspension clamp has to carry the normal tension in the cable as well as the stresses produced by vibrations.

Among the objects of the present invena tion are, to provide a new and improved method of supporting the cables of transmission lines, to provide new and improved cable supporting means for transmission lines; to provide simple and efiicient means to damp out the vibrations to which the cables are subjected before the vibrations reach the cable supporting means; and to provide means .for relieving the cable of clamping pressure at its point of support.

In the accompanying drawings, which illustrate an application of my invention:

Fig. 1 is a diagrammatic View showing a span of an electric transmission line cable and its points of support; also the loops produced in the cable by vibrations and changes in the sag of the cable due to variations in temperature;

Fig. 2, a side elevational view of cable supporting means embodying my invention;

Fig. 3, a top plan view; v Fig. 4, a detail longitudinal sectional view of a portion of the supporting means constituting my invention;

Fig. 5, a vertical sectional view taken on line V V of Fig. 2; and

Fig. 6, a view similar to Fig. 5, taken on line VIVI of Fig. 4.

Referring to the drawings, 5 designates an electric transmission line cable designed to be supported from string insulators 6, the latter being suspended from the transmission line towers, not shown, in the usual or any preferred manner.

As illustrated and as preferred, the main cable supporting device is designated generally by the numeral 7, and, as shown, it includes a main or upper member having an elongated slightly curved portion 8 formed at its central portion with upstanding spaced members 9, the latter being adapted to receive therebetween the lower member 10 of the string insulator support 6. Member 10 is adapted to be entered between the membars 9, and the device 7 is pivotally supported on the string insulator by means of a bolt 13. Portion 8 is formed on one face thereof, with a groove 14 designed to receive the line cable 5. Cable 5, at its point of support in the said groove is not clamped therein or otherwise fixedly secured to the main support ing means 7, said cable being movable relatively thereto or free to move on said supporting means.

An opposite face of the elongated member or portion 8 is formed with two additional parallel grooves or channels 15, respectively adapted to receive one of two auxiliary wires, cables, or flexible-members l6 entering into the cable supporting means constituting my invention.

As illustrated, the auxiliary members 16 are securely clamped to portion 8 by a clamp member 17, the latter being attached to portion 8 by a plurality of bolts 18 passed through registering openings'formed in the said parts or members 8 and 17. The auxiliiary members are arranged to project or extend out on each side of the main suspension means for a short distance (i. e., approximately eight inches or more, depending on the size of the cable and the length of the span) and have their outer ends secured in clamp members 19 spaced from the main suspension means.

Clamp members 19, in addition to clamping the ends of the auxiliary cables or members 16, are designed to also clamp the transmission line cable 5, and, for this purpose, are provided with a cable receiving groove 20 in addition to grooves 21 for the cables 16. Each of the clamps 19 includes a divided structure, secured together by bolts 22, and each has a cylindrical or tubular portion 23 designed to encircle the cable 5. The cylindrical portion of each clamp surrounding the cable is approximately eight inches in length, and is preferably tapered with a pitch 0 3 2' of an inch in the eight inches. The end of the cylindrical portion, away from the clamp proper, is provided with a rapidly flaring bell mouth 24.

As the result of careful measurements and observations on a great variety of spans, it has been notedthat the transverse vibrations which are set up in the cables by reason of the wind vary in length of loop and in amplitude of vibration. It has been found, however, that the ratio of the amplitude to the length of the loop never exceeds the tangent of such an angle that, at a distance of approximately eight inches from the vertical axis of the supporting member, the longitudinal axis of the wire deviates only slightly more than of an inch, or very closely thereto from its original position. Therefore, in the present design, the taper in each of the clamps 19 is made approximately of an inch in the eight inches. This construction provides means for damping out the vibrations and for preventing the harmful bending of the cable by the vibrations set up in the spans.

Another feature of this clamp construction or arrangement is to enable the bell mouth clamp described to always adjust itself to the cable, no matter what temperature may exist.

- In other words, as the temperature changes,

the angle of the cable where it rests in the suspension clamp changes, and, unless some adjustable feature is provided, the accurate,

adjustment of the bell mouth clamp could not be maintained for all temperatures.

By means of I the construction described, the cable is supported 'on the cable suspension or supporting means without subjecting it to the usual clamp pressure at its point of support, the clamp pressure being placed at spaced apart points from the point where the pressure due to the weight of the span occurs. By clamping the cable, as shown and described, at points other than at the weight supporting point and by the employment of the auxiliary cables arranged as shown, a highly efficient damping result is accomplished. The auxiliary cables should combine a suflicient amount of flexibility with a suflicient amount of resistance to bending in order to produce the best damping effects.

My invention contemplates employing it in connection with pin type insulator supports, as well as the string type insulator supports as shown.

In order to damp the vibrations in the manner described, it is necessary to maintain a constant relation between the gradually tapering portion or bell mouth of the clamp and the quiescent cable. This is accomplished by incorporating the said tapering bell mouth in a clamp, which is separate from the main suspension or supporting clamp, and bolting the clamp 19 directly to the cable in the manner particularly shown by Fig. 4:. By this construction, the clamp 19 having the tapered portion moves up and down with the cable as a whole, as the latter responds to the effects of temperature.

Obviously, this feature cannot be incorporated into the suspension clamp itself. The result of this construction is, that the vibration waves which. are set up in the cable by the wind or any other cause approach the clamp having the tapered bell mouth and are gradually suppressed, for the reason that the angle between the quiescent cable and the tapering bell mouth of the clamp is at all times constant, no matter what the angle of the quiescent cable may be with the horizontal.

In the process of ironing out or damping the vibrations in the cable as they enter the gradually tapering bell mouth clamp, this clamp may be given a slight u and down motion as a whole. In order to a sorb and damp this up and down motion before it reaches the main suspension clamp 7, the auxiliary cables 16 are effective. These cables consist of wires stranded together and are usually of the same size and material as the main cable. It is obvious that the three parallel cables thus provided by this arrangement are stiffer than one and will absorb the motions of clamp 19 more effectively than the'cable could do by itself without the assistance of the outside cables 16. While these auxiliary cables 16 should add stifl'ness to the complete arrangement be tween clamp 19 and clamp 7, they must not be entirely rigid, because, if they were, the vibrations arriving at the clamp 19 would be completely reflected and might result in damage to the cable where it enters the clamp 19.

What I claim is: f

1. Supporting means for transmission line cables including a main supporting member on which the line cable is freely supported, a clamp member spaced from the supporting member, a flexible member connecting the said clamp member and the main supporting member, said clamp member having means for clamping both the flexible member and the line cable and an interiorly tubular portion encircling and spaced from the line cable to damp out vibrations therein.

2. Supporting'means for transmission line cables including a main supporting member on which the line cable is freely supported, a clamp member spaced from the supporting member, a flexible member connecting the said clamp member and the main supporting member, said clamp member havin means for clamping both the flexible mem er and the line cable and a tubular portion encircling and spaced from the line cable, said tubular portion having an interior taper whose smaller end is closer than its larger end to the main supporting member and adapted to damp out vibrations therein. v

3. Supporting means for transmission line cables including a main supporting member on which the line cable is freely supported, a pair of clamp members spaced from the main member on opposite sides thereof, and a pair of auxiliary cables extending from the clamp members and passing through the main supporting member effective to damp vibrations set up between the clamp members and the main supporting member, said clamp members each having means for clamping the main and auxiliary cables and a projecting interiorly tubular portion having a smaller so end closer than its larger end to the main supporting member encircling and spaced from the line cable to damp out vibrations therein.

at. Supporting means for a transmission line cable, the same comprising a main supporting member having a groove in its upper face for loosely receiving and supporting the line cable, said groove being adapted to receive a supporting member in spaced relation above the cable, an auxiliary cable member, means to clamp the latter rigidly to the under surface of the main supporting member in laterally oflset relation to said groove, and means to attach the auxiliary cable member 5 rigidly to a line cable at a distance from the apposite ends of the main supporting mem- 5. Supporting means for transmission line stranded cables including a main supporting member on which the line cable is supported,

a clamp member spaced from the supporting member, a flexible member connecting the said clamp member and the main supporting member, said clamp member having means for clamping both the flexible member and the line cable, an interiorly tubular portion and a bell-mouth of long radius encircling and spaced from the line cable, whereby when the cable is bent by vibrations in it the cable will m be restricted by a curved surface whose radius is so great that the unit stress in the outer strands of the cable will not exceed a safe value.

In testimony whereof I afix my signature. G3 THEODORE VARNEY.

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