Metal Pole

Abstract

A tubular steel power transmission line pole having a high bending strength/cost ratio and aesthetic appearance, comprising a pair of side bars and web members having side flanges lapping the side margins of the side bars on the inside of the latter, with the side bars and web members secured together by welds along the side edges of the side bars. The pole has a special base mounting structure for receiving bolts extending upward from a concrete footing, adapted to provide for secure attachment of the pole to the footing without requiring an excessive amount of steel in the structure. It also has internal bracing at points where line-supporting arms extend outward, the arms being secured to extensions of this bracing.

Description

BACKGROUND OF THE INVENTION

This invention relates to tubular metal poles, particularly for use for supporting transmission lines of an electric power transmission system, and suitable for other purposes, such as for supporting banks of lamps for illuminating athletic fields, etc.

Tubular metal poles have recently begun to come into use to replace the lattice towers conventionally used for supporting power transmission lines, for purposes of aesthetic appearance in comparison with the lattice towers and for purposes of right-of-way and foundation economy, noting that the metal pole does not require nearly as large a concrete base as a lattice tower. An example of such a tubular metal pole is the pole shown in U.S. Pat. No. 3,217,459, issued Nov. 16, 1965. However, problems have been encountered as regards use of such poles instead of lattice towers, including development of a pole which is aesthetic in appearance and attains maximum utilization of metal (steel) for strength, both as to the pole per se and as to its mounting on a concrete base, and development of suitable mountings for line-supporting arms on such poles.

SUMMARY OF THE INVENTION

Accordingly, among the several objects of this invention may be noted the provision of an improved tubular metal pole which has a relatively high bending strength/cost ratio, attaining increased utilization of metal for strength, and at the same time being of aesthetic appearance; the provision of such a pole which, while effecting savings in the amount of metal used for a given bending strength, is also economical to fabricate; the provision of a base mounting structure for such a pole which provides for secure attachment of the pole to a base (e.g., a concrete base) without requiring use of a heavy steel base plate in the mounting structure; the provision of an arm mounting structure for such a pole which enables precision location of the arms (as may be required due to the necessity for accuracy in positioning the transmission lines) without requiring precision fabrication to any extensive degree; and the provision of an arm mounting structure adapted to maintain an arm from snapping off a pole under severe abnormal conditions as may occur, such as unequal icing of stretches of line extending in opposite directions from the arm.

In general, a metal pole of this invention is tubular and tapered from its lower to its upper end and, at any transverse section thereof, has a cross section substantially symmetrical about a first axis constituting a major axis and also substantially symmetrical about a second axis at right angles to the first axis constituting a minor axis, the length of the major axis being greater than the length of the minor axis. The pole comprises a pair of side bars at the ends of the major axis extending transversely of the major axis and web members of arched shape in cross section extending between the side margins of the side bars. The web members are of convex form on their exterior and have side flanges lapping the side margins of the side bars and secured to the latter. The side bars are thicker than the web members. Means is provided at the lower end of the pole for mounting it on a base. Other objects and features will be in part apparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in elevation of a pole constructed in accordance with this invention, viewed at right angles to the arms on the pole;

FIG. 1A is a side elevation of FIG. 1 (i.e., a view in elevation from one end of the arms);

FIG. 2 is a composite view comprising seven enlarged horizontal sections on lines A-A to G-G of FIG. 1;

FIG. 3 is an enlarged horizontal section on line 3-3 of FIG. 1A, showing the base mounting structure for the pole;

FIG. 4 is a vertical section on line 4-4 of FIG. 3;

FIG. 5 is a vertical section on line 5-5 of FIG. 3;

FIG. 5A (sheet 8) is a perspective of the base mounting structure;

FIG. 6 is an enlarged vertical section on line 6-6 of FIG. 1A showing a first type of arm mounting structure;

FIG. 7 is a horizontal section on line 7-7 of FIG. 6;

FIG. 8 is a vertical section on line 8-8 of FIG. 6;

FIG. 9 is an enlarged vertical section on line 9-9 of FIG. 1A showing a second type of arm mounting structure;

FIG. 10 is a horizontal section on line 10-10 of FIG. 9;

FIG. 11 is a vertical section on line 11-11 of FIG. 9;

FIG. 12 is an enlarged vertical section on line 12-12 of FIG. 1A showing a third type of arm mounting structure;

FIG. 13 is a horizontal section on line 13-13 of FIG. 12;

FIG. 14 is a vertical section on line 14-14 of FIG. 12;

FIG. 15 is a vertical section similar to FIGS. 6, 9 and 12 showing a fourth type of arm mounting structure;

FIG. 16 is a horizontal section on line 16-16 of FIG. 15;

FIG. 17 is a vertical section on line 17-17 of FIG. 15;

FIG. 18 is a vertical section similar to FIG. 15 showing a fifth type of arm mounting structure;

FIG. 19 is a section on line 19-19 of FIG. 18;

FIG. 20 is a section on line 20-20 of FIG. 18;

FIG. 21 is a vertical section similar to FIG. 18 showing a sixth type of arm mounting structure;

FIG 22 is a section on line 22-22 of FIG. 21;

FIG. 23 is a section on line 23-23 of FIG. 21;

FIG. 24 is a plot showing the relation of the cross section of the pole to a certain closed curve; and

FIG. 25 is a view showing a modified pole cross section and its relation to certain curves.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, first more particularly to FIGS. 1 and 1A a tubular metal (steel) power transmission line pole constructed in accordance with this invention is designated in its entirety by the reference character P. As shown, the pole is tapered from its lower to its upper end, and has means generally designated 1 at its lower end for mounting it on a concrete base. It is comprised of a plurality of elongate tubular members of section arranged end-to-end with the lower end of each of these members above the lowermost of said members having a cross section corresponding substantially to the cross section of the upper end of the member immediately therebelow, and welded to the latter. As shown herein, there are six such elongate tubular members welded together end-to-end to form the pole, these six members being designated P1--P6 in order from the uppermost to the lowermost. Each is tapered from its lower to its upper end, the taper being the same as to each member so that the pole 1 is uniformly tapered from its lower to its upper end. Also as shown herein, there are four pairs of arms extending outward from the pole for supporting power transmission lines, the arms of the upper pair being designated 3, the arms of the second pair down being designated 5, the arms of the third pair down being designated 7, and the arms of the lowermost pair being designated 9. The arms of each pair extend laterally outward on opposite sides of the pole.

Each of the elongate tubular members P1--P6 is tubular and at any transverse (horizontal) section thereof, such as the transverse sections indicated by lines A-A to G-G in FIG. 1, has a cross section which is substantially symmetrical about a first axis a constituting a major axis and also substantially symmetrical about a second axis b at right angles to the first constituting a minor axis (see FIGS. 2 and 3). As to each such transverse section, the length of the major axis a is greater than the length of the minor axis b.

Each of the elongate tubular members P1--P6 comprises a pair of side bars at the ends of the major axis of its cross section extending transversely of the major axis, and a pair of web members of arched shape in cross section extending between the side margins of the side bars. As a result, the pole P in its entirety comprises a pair of such side bars B and a pair of such web members W. The side bars B are inclined toward one another from the lower to the upper end of the pole (see FIG. 1). The individual segments of bars B in the members P1--P6 are respectively designated B1--B6, and the individual segments of web members W in the members P1--P6 are respectively designated W1--W6. Each of web members W1--W6 has side flanges 11 lapping the side margins of the respective side bars and secured by welding to the latter. The portions of the web members between the side flanges 11 are inclined toward one another from the lower to the upper end of the pole. The opposed edges of the side flanges 11 are spaced apart and inclined toward one another from the lower to the upper end of the pole. As to each of tubular members P1--P6, the side bars are thicker than the web members.

The web members W1--W6 are of corresponding arched shape in cross section convex on the exterior thereof, and of tapered form to provide the taper for the pole, each being of increasing width and depth from its upper to its lower end. Thus, the lower end of web member W1 has the same cross section as the upper end of web member W2, the lower end of W2 has the same cross section as the upper end of W3, etc. Each of the web members is constituted by an elongate metal plate bent to arched shape on lines extending in the direction from its lower to its upper end and converging in this direction so that the member is of the stated tapered arched conformation. As herein shown, each web member is bent on the longitudinal centerline 13 of the plate from which it is formed, and on pairs of lines 15, 17 and 19 lying on opposite sides of line 13 so that it is of six-sided form with flanges 11 extending from its two outer sides parallel to one another and parallel to the central longitudinal plane of the web member. The two sides or panels of each web member on opposite sides of line 13 are each designated 21, the next two sides or panels are designated 23, and the two outer sides or panels are each designated 25. The flanges 11 extend from the outer edges of sides or panels 25.

Each of the side bars B1--B6 is a planar form (i.e., it is a flat bar), and the side edges 27 of each of these bars converge toward one another in the direction from the lower to the upper end of the respective web member so that it is of tapered form with its taper corresponding to the desired taper for the pole as viewed from the outside face of the bars. It will be observed from FIG. 2 that the side bars (which are planar) are disposed in planes which intersect any transverse section of the pole (e.g., A-A, B-B, etc.) in lines generally at right angles to the major axis of that transverse section. The side flanges 11 of the web members at each side of the pole are disposed in a plane parallel to the inclined plane of the respective side bar. The side bars and the web members are of decreased thickness toward the upper end of the pole. Thus, for example, in the case of a pole made in accordance with this invention which is 71 feet 2 inches long, wherein member P1 is 17 feet 6 inches long, each of members P2--P5 is 10 feet long, and member P6 is 13 feet 8 inches long, bar B6 is made of 7/8 -inch plate, bar B5 is made of 3/4 -inch plate, bars B4 and B3 are made of 5/8 -inch plate, bar B2 is made of 3/8 -inch plate, and bar B1 is made of 1/4 -inch plate; web members W6--W4 are made of 1/4 -inch plate, and web W3--W1 are made of 3/16 -inch plate.

As to each of the tubular members P1--P6, the web members have their side flanges 11 lapped with the side bars on the inside of the side bars so that the side bars are on the outside of the flanges 11, and side bars and web members are secured together by welds 29 along the side edges 27 of the side bars, these welds forming fillets in the corners defined by the side edges 27 and the outside faces of the flanges 11. Successive members P1--P6 are butted together end-to-end and welded together at the points indicated at 31 in FIGS. 1 and 1A to form the pole P.

As shown in FIGS. 2 and 24, the web members W1--W6 are so shaped and the side bars B1--B6 are so dimensioned that the cross section of the pole, at any transverse section thereof, approximates the special closed curve expressed by the formula

wherein x is the ordinate and y the abscissa of the curve, a is the length of the major axis of the curve and b is the length of the minor axis of the curve. The length of the minor axis b is preferably approximately 0.7 times the length of the major axis. While this curve resembles an ellipse, it is not a true ellipse, the formula for a true ellipse being

and is uniquely distinguished from a true ellipse in that it provides for a substantially higher moment and section modulus for the pole cross section than would a true ellipse. FIG. 24 shows a plot of the above-described special curve, which is designated Y, with a transverse pole section superimposed thereon to illustrate how the pole section approximates the curve.

Referring to FIGS. 3--5, the mounting means 1 at the lower end of the pole P is shown to comprise a pair of lower coplanar horizontal flange members 33 extending laterally outward from each of the side bars B6 of the lowermost tubular pole member P6 at its lower end and a pair of upper coplanar horizontal flange members 35 extending laterally outward from each of the side bars B6 above the flange members 33. The side bars B6 have widened portions 37 toward their lower ends to which these horizontal flanges 33 and 35 are welded. The flanges have bolt holes 39 for receiving mounting bolts 41 embedded in and extending upward from a concrete base 43. Vertical stiffening plates 45 extend between the upper and lower flanges, being welded at their inner edges to the side bars as indicated at 47, also being welded at top and bottom to the flanges as indicated at 49. These vertical stiffening plates are located alongside the bolt holes, and, in effect, box in the bolts 41. The lower flanges 33 bear on nuts 51 threaded on the bolts, these nuts being backed from below by locknuts 53. Nuts 55 are threaded down on bolts 41 into engagement with the upper flanges 35 and backed by locknuts 57. The lower end of member B6 is closed by a plate 59, and the space between this plate and the base, also the space between the lower flanges 33 and the base, is filled with grout as indicated at 61. A plate 62 (see FIG. 1) maybe welded to the upper end of the pole as a closure therefor.

I FIGS. 6--8 show a first arm mounting structure, illustrated as the mounting structure for the lowermost arms 9, including bracing means generally designated 63 extending internally of the pole crosswise of the side bars B at the location of the arms on the pole and having extension projecting laterally outward of the side bars B, the arms mounted on these extensions. More particularly, the bracing means 63 comprises a pair of vertical plates each designated 65 extending through openings constituted by elongated vertical slots 67 in the side flanges 11 of the web members W immediately outward of the side edges of the side bars B, these vertical plates being welded as indicated at 69 to the side bars and as indicated at 70 to the web members. The extensions of these plates 65 which project laterally outward of the side bars B are designated 65a. Each arm 9 has a vertical end plate 71 at its inner end formed with integral side vertical flanges 73 which flare laterally outward in the direction away from the inner end of the arm. Vertical flanges 75 extend endwise from plate 71 in the direction away from the inner end of the arm at right angles to the plate, these flanges 75 being spaced inward from the flared outside flanges 73. These flanges are cross-braced as indicated at 77. The outer side faces of flanges 75 are spaced a distance slightly less than the spacing of the inside faces of extensions 65a of plates 65. The flanges 75 are inserted between the extensions 65a, lapping the latter on the inside thereof, and upper and lower bolts 79 and 81 are applied extending through bolt holes adjacent the top and bottom of flanges 75 and extensions 65a to bolt the arm to the extensions. The flared flanges 73 have openings 83 larger than the nuts 85 on the bolts.

FIGS. 9--11 show a second arm mounting structure, illustrated as the mounting structure for the arms 7, including braces means 63 the same as above-described in respect to FIGS. 6--8, but with rectangular vertical face plates 87 extending transversely with respect to extensions 65a of plates 65 across the outer ends of the extensions and welded thereto. Arms 7 have rectangular vertical face plates 89 at the inner ends applied facewise to the face plates 87 and bolted thereto at the four corners of the face plate as indicated at 91.

FIGS. 12--14 show a third arm mounting structure, illustrated as the mounting structure for the arms 3, including the same bracing means 63, with horizontal top and bottom plates 93 and 95 spanning the extensions 65a of plates 65 and welded thereto. Each arm 3 has a vertical end plate 97 at its inner end provided with upper and lower horizontal flanges 99 and 101 extending from plate 97 in the direction away from the inner end of the arm. The inside faces of flanges 99 and 101 are spaced a distance slightly greater than the spacing of the outside faces of plates 93 and 95. In the assembly, the flanges 99 and 101 lap plates 93 and 95 on the outside of the latter, and are bolted thereto by a pair of bolts 103 extending through bolt holes in flanges 99 and 101 and the plates 93 and 95. The end plate 97 of arm 7 is also shown as having flared vertical side flanges 105 enclosing the sides of extensions 65a. These may be omitted in some instances.

FIGS. 15--17 show a further type of arm mounting structure that may be used in conjunction with arms which are of rectangular cross section, including the same bracing means 63 comprising plates 65 with extensions 65a. In the FIGS. 15--17 structure, each rectangular cross section arm, designated 107, has a pair of side plates 109 welded thereto at its inner end and extending beyond its inner end. These side plates straddle extensions 65a and are bolted thereto by upper and lower bolts 11 and 113. Braces 115 extend between extensions 65a, being inclined in downward and outward direction from the side bars B, and boxing in the bolts.

FIGS. 18--20 show a further type of arm mounting structure adapted to maintain the arm from snapping off the pole under severe abnormal conditions as may occur, such as unequal icing of stretches of line extending in opposite directions from the arm. This involves bracing means 63 comprising plates 65 as described, but shown as having upwardly angled extensions 65b instead of the straight extensions 65a, with top and bottom plates 117 and 119 spanning the angled extensions at the top and bottom thereof and welded thereto. In FIGS. 18--20, the arm, designated 120, is shown as being a T-section arm, provided at its inner end with upper and lower plates 121 and 123 extending beyond the inner end of the arm. The lower plate 123 is longer than the upper plate 121. These plates or flanges 121 and 123 straddle the top and bottom plates 117 and 119, lapping plates 117 and 119 on the outside of the latter, and are bolted thereto by a pivot bolt 125 extending through lower flange 123, the bottom plate 119, the top plate 117 and the upper flange 121, and by a short shear bolt 127 inward of the pivot bolt extending through the lower flange 123 and the bottom plate 119. The arrangement is such that in the event of an abnormally severe load imposed on the arm tending to swing it in one direction or the other about the axis of pivot bolt 125, bolt 127 will shear and permit the arm to swing about bolt 125 to prevent the arm from snapping off the pole.

FIGS. 21--23 show an arm mounting structure similar to that shown in FIGS. 18--20 but without the shear bolt feature, and employing two side-by-side bolts 129 extending through the lower flange 123, bottom plate 119, top plate 117 and upper flange 121. In this modification, flanges 121 and 123 are of equal extension from the inner end of the arm.

With the cross-sectional configuration as above-described, the pole P has a relatively high efficiency ratio, i.e., the ratio of its bending strength to cost (the latter involving material costs). The pole cross section has a relatively high moment of inertia/cost ratio, representing relative pole rigidity per unit cost, and a relatively high section modulus/cost ratio, representing pole bending strength per unit cost. In this regard, it will be observed that with the concentration of metal in the side bars B (which are relatively thick), at a substantial distance from the minor axis b, the pole cross section has a relatively high moment of inertia and hence a relatively high section modulus about the minor axis, as is desirable in view of the fact that the bending of the pole in the plane of the major axis is potentially the most severe type of strain to which the pole may be subjected, as, for example, due to winds of hurricane force blowing transversely to the power transmission lines. At the same time, the cross section of the pole is such that it has an aesthetic appearance, which may be enhanced by an ornamental treatment involving painting the side bars B a different (usually darker) color than the web members W. Also, poles of this invention have relatively low deflection under load, and thus are adapted, without any additional strengthening, for use in substations to support heavy substation switching equipment, and to maintain such equipment in the necessary close alignment on account of their low deflection characteristic.

The base mounting structure 1 of this invention is of considerable importance in that it provides for efficient transfer of load (i.e., bending load) from the pole P to the anchor bolts 39 without requiring a massive steel base plate such as heretofore used for mounting steel poles. In the mounting structure 1 of this invention the load is transferred from the pole through the vertical welds 47 to the vertical stiffening plates 45 and thence to the flanges 35 (and 33) for transmission to the nuts on the anchor bolts. These welds are of extensive length, and the unit stress transferred therethrough is well within acceptable limits. The plate 59 is not involved in stress transfer, and hence may be relatively thin. This is sharply distinguished from the usual prior type of pole base mounting involving a horizontal plate welded to the lower end of the pole with the anchor bolts extending through bolt holes in the plate, and wherein the transfer of stress form the pole to the plate is concentrated in a limited area of the weld, and the plate, which functions as a cantilever, must be made quite thick to withstand the stress transfer to the anchor bolts. It will be understood, however, that flanges 33 may be provided as integral portions of plate 59 for simplifying the fabrication of the base mounting structure (plate 59 then extending underneath the bottom edges of the side bars B6 and projecting underneath the bottom edges of the side bars B6 and projecting therebeyond), and, under these circumstances, plate 33 may be somewhat thicker than otherwise. It will also be understood that while two flanges 33 and two flanges 35 spaced apart side-by-side are shown on each side bar B6, there could be one continuous flange at 33 and one continuous flange at 35 on each side bar.

Common to all the arm mounting structures above-described is the feature of the bracing means 63 constituted by plates 65 extending internally of the pole crosswise of the side bars B at the location of the arms and having the extensions 65a or 65 b, as the case may be, projecting laterally outward of the side bars, the arms being mounted on these extensions. This arrangement enables precise location of each pair of arms, as distinguished, for example, from prior arm mounting structures involving cantilevering each pair of arms from a collar slipped on a tapered pole, relying on the taper for the heightwise location of the pole, and thus making the heightwise location subject to tolerances in the manufacture of the pole and the collar and ambient temperature conditions not only at the time of assembly but also in the field. The bracing means 63 constituted by plates 65 also serves the important function of preventing the side bars B from being squeezed toward one another (which would undesirably reduce the moment of inertia of the pole cross section). In this regard, it is to be noted that the side bars B and plates 65 are welded together at 69.

FIG. 25 illustrates a modification in the type of pole cross section, which has certain advantages over the type of pole cross section illustrated in FIG. 2 in that it simplifies the fabrication of members W1--W6, though it may somewhat reduce, but only to a minor extent, the efficiency ratio of the pole cross section. It will be observed that, as to the pole cross sections shown in FIG. 2, the sides or panels 21, 23 and 25 of each web member W intersect at different angles. Thus, the included angle K between panels 21 where they intersect at line 13 is slightly less than 180.degree. , the included angle L between panels 21 and 23 where they intersect at line 15 is less than K, and the included angle M between panels 23 and 25 where they intersect at line 17 is less than L. In FIG. 25, the panels which are designated 21a, 23a and 25a are shown as approximating an arc of a circle 125 drawn on a center at 127 in line with the minor axis b, with a radius considerably greater than the length of the minor axis. The panels 21a, 23a and 25a are flat, being equal chords of the arc of the circle 125, and intersecting at equal angles N at lines 13, 15 and 17.

While the pole of this invention is described above as a power transmission line pole, with arms for supporting transmission lines, it will be understood that it may have other uses, such as for supporting banks of lamps for illuminating athletic fields, or in a substation for supporting switchgear. As to the latter, for example, extensions 65a of plates 65 of two poles may be used for connection thereto of a load-bearing member (e.g., a beam) tying the two poles together and supporting switchgear.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

We claim:

1. A metal pole for supporting electric power transmission lines or other loads, said pole being tubular and tapered from its lower to its upper end and having, at any transverse section thereof, a cross section substantially symmetrical about a first axis constituting a major axis and also substantially symmetrical about a second axis at right angles to the first constituting a minor axis, the length of the major axis being greater than the length of the minor axis, said pole comprising a pair of side bars at the ends of the major axis extending transversely of the major axis and inclined toward one another from the lower toward the upper end of the pole, and web members of arched shape in cross section extending between the side margins of the side bars, said web members being of convex form on the exterior thereof and having side flanges lapping the side bars and secured to the latter, the portions of said web members between said side flanges being inclined toward one another from the lower toward the upper end of the pole, the side bars being thicker than said web members, and means at the lower end of the pole for mounting it on a base.

2. A metal pole as set forth in claim 1 wherein the opposed edges of the side flanges of the web members are spaced apart and inclined toward one another from the lower toward the upper end of the pole, said side flanges lapping the side margins of the side bars.

3. A metal pole as set forth in claim 1 wherein each side bar is of planar form and the side flanges of the web members lap the side bars on the inside of the side bars so that the side bars are on the outside of said flanges, the side bars and web members being secured together by welds along the side edges of the side bars.

4. A metal pole as set forth in claim 3 wherein each of the web members is constituted by an elongate metal plate bent to arched shape on lines extending in the direction from the lower to the upper end of the pole and converging in said direction so that each web member is of tapered arched conformation.

5. A metal pole as set forth in claim 4 wherein the side edges of each side bar converge toward one another in said direction.

6. A metal pole as set forth in claim 5 wherein the side bars are of decreased thickness toward the upper end of the pole.

7. A metal pole as set forth in claim 6 wherein the web members are of decreased thickness toward the upper end of the pole.

8. A metal pole as set forth in claim 1 wherein the side bars have integral widened portions at the lower end of the pole and the mounting means comprises vertically spaced horizontal flanges welded to and extending laterally outward from said widened portions of the side bars at the lower end of the pole provided with bolt holes for receiving mounting bolts extending upward from a base, and vertical stiffeners extending between said horizontal flanges welded to said widened portions of the side bars.

9. A metal pole as set forth in claim 1 wherein the cross section of the pole at any transverse section thereof approximates the closed curve expressed by the formula

wherein x is the ordinate, y the abscissa, a the length of the major axis, and b the length of the minor axis.

10. A metal pole as set forth in claim 11 wherein the length of the minor axis is approximately 0.7 times the length of the major axis.

11. A metal pole as set forth in claim 1 wherein the cross section of each web member, from one side flange to the other, and at any transverse section thereof, approximates an arc of a circle.

12. A metal pole as set forth in claim 11 wherein each web member is constituted by an elongate metal plate bent to arched shape on lines extending in the direction from the lower to the upper end of the pole, each web member having flat panels between said lines, said flat panels, at any transverse section of the web member, being equal chords of an arc of a circle, and said chords intersecting at equal angles at said lines.

13. A metal pole as set forth in claim 1 having load transferring means extending outward from the side bars, and bracing means extending internally of the pole crosswise of the side bars at the location of the load transferring means and having extensions projecting laterally outward of the side bars, the load transferring means being mounted on said extensions.

14. A metal pole as set forth in claim 13 1 having arms for supporting transmission lines extending outward from the side bars, and bracing means extending internally of the pole crosswise of the side bars at the location of the arms and having extensions projecting laterally outward of the side bars, the arms being mounted on said extensions.

15. A metal pole as set forth in claim 16 wherein said bracing means comprises a pair of vertical plates extending through openings in the side flanges of the web members immediately outward of the side edges of the side bars, said vertical plates being welded to said side bars.

16. A metal pole as set forth in claim 1 comprised of a plurality of elongate tubular members each tapered from its lower to its upper end, said tapered tubular members being arranged end-to-end with the lower end of each of said members above the lowermost of said members having a cross section corresponding substantially to the cross section of the upper end of the member therebelow and welded to the latter.

17. A metal pole as set forth in claim 16 wherein each side bar of each of said elongate tubular members is of planar form and the side flanges of the web members of each of said elongate tubular members lap the respective side bars on the inside thereof so that the side bars are on the outside of said flanges, the side bars and web members of each of said elongate tubular members being secured together by welds along the side edges of the side bars.

18. A metal pole as set forth in claim 17 wherein each of the web members of each of said elongate tubular members is constituted by an elongate metal plate bent to arched shape on lines extending in the direction from the lower to the upper end of the pole and converging in said direction so that each web member is of tapered arched conformation.

19. A metal pole as set forth in claim 18 wherein the side edges of each side bar of each of said elongate tubular members converge toward one another in said direction.

20. A metal pole as set forth in claim 19 wherein the side bars of upper ones of said elongate tubular members are of lesser thickness than the side bars of lower ones of said elongate tubular members, the internal faces of the side bars of said elongate tubular members at each end of said major axis being substantially coplanar.

21. A metal pole as set forth in claim 20 wherein the web members of upper ones of said elongate tubular members are of lesser thickness than the web members of lower ones of said elongate tubular members.

22. A metal pole as set forth in claim 16 wherein the cross section of each of said elongate tubular members at any transverse section thereof approximates the closed curve expressed by the formula

wherein x is the ordinate, y the abscissa, a the length of the major axis, and b the length of the minor axis.

23. A metal pole as set forth in claim 22 wherein the length of the minor axis is approximately 0.7 times the length of the major axis.

24. A metal pole as set forth in claim 16 wherein the cross section of each web member, from one side flange to the other, and at any transverse section thereof, approximates an arc of a circle.

25. A metal pole as set forth in claim 24 wherein each web member is constituted by an elongate metal plate bent to arched shape on lines extending in the direction from the lower to the upper end of the pole, each web member having flat panels between said lines, said flat panels, at any transverse section of the web member, being equal chords of an arc of a circle, and said chords intersecting at equal angles at said lines.

26. A metal pole as set forth in claim 16 having load transferring means extending outward from the side bars of upper ones of said elongate tubular members at points spaced from the ends of the latter, and bracing means extending internally of said upper ones of said elongate tubular members crosswise of the respective side bars st said points and having extensions projecting laterally outward of the side bars, the arms being mounted on said extensions.

27. A metal pole as set forth in claim 18 having arms for supporting transmission lines extending outward from the side bars of upper ones of said elongate tubular members at points spaced from the ends of the latter, and bracing means extending internally of said upper ones of said elongate tubular members crosswise of the respective side bars at said points and having extensions projecting laterally outward of the side bars, the arms being mounted on said extensions.

28. A metal pole as set forth in claim 27 wherein said bracing means comprises a pair of vertical plates extending through openings in the side flanges of the web members immediately outward of the side edges of the side bars, said vertical plates being welded to said side bars.

29. A tubular metal power transmission line pole comprising a pair of side bars extending longitudinally of the pole and web members extending between the side margins of the side bars, the side bars being thicker than the web members, arms for supporting transmission lines extending outward from the side bars, and bracing means extending internally of the pole crosswise of the side bars at the locations of the arms and having extensions projecting laterally outward of the side bars, the arms being mounted on said extensions, said web members being of arched cross section of convex form on the exterior thereof and having side flanges lapping the side margins of the side bars and secured thereto, said bracing means comprising a pair of vertical plates extending through openings in the side flanges of the web members immediately outward of the side edges of the side bars, said vertical plates being welded to said side bars.

30. A tubular metal power transmission line pole as set forth in claim 29 wherein said vertical plates have face plates welded on their outer ends, the arms having face plates at their inner ends bolted to the face plates on said vertical plates.

31. A tubular metal power transmission line pole as set forth in claim 29 wherein the arms have vertical flanges at their inner ends lapping said extensions and bolted thereto.

32. A tubular metal power transmission line pole as set forth in claim 29 wherein said vertical plates have top and bottom plates welded on their outer ends and the arms have upper and lower flanges lapping and bolted to said top and bottom plates.

33. A tubular metal power transmission line pole as set forth in claim 32 wherein the flanges at the inner end of the arm lap the top and bottom plates on the outside of the latter and are bolted thereto by a pivot bolt extending through the lower flange, the bottom plate, the top plate and the upper flange, and by a shear bolt extending through the lower flange and bottom plate only.

34. A tubular metal power line transmission pole having arms for supporting transmission lines extending outward from opposite sides thereof, said pole having bracing means extending crosswise internally thereof and having extensions projecting laterally outward from the pole at opposite sides thereof at the location of the arms, the arms being mounted on said extensions, said bracing means comprising a pair of vertical plates extending through openings in opposite sides of the pole and welded to opposite sides of the pole, said vertical plates having face plates welded on their outer ends, the arms having face plates at their inner ends bolted to the face plates on said vertical plates.

35. A tubular metal power line transmission pole having arms for supporting transmission lines extending outward from opposite sides thereof, said pole having bracing means extending crosswise internally thereof and having extensions projecting laterally outward from the pole at opposite sides thereof at the location of the arms, the arms being mounted on said extensions, said bracing means comprising a pair of vertical plates extending through openings in opposite sides of the pole and welded to opposite sides of the pole, the arms having vertical flanges at their inner ends lapping said extensions and bolted thereto.

36. A tubular metal power line transmission pole having arms for supporting transmission lines extending outward from opposite sides thereof, said pole having bracing means extending crosswise internally thereof and having extensions projecting laterally outward from the pole at opposite sides thereof at the location of the arms, the arms being mounted on said extensions, said bracing means comprising a pair of vertical plates extending through openings in opposite sides of the pole and welded to opposite side of the pole, said vertical plates having top and bottom plates welded on their outer ends and the arms having upper and lower flanges lapping and bolted to said top and bottom plates.

37. A tubular metal power line transmission pole as set forth in claim 36 wherein said bracing means comprises a pair of vertical plates extending through openings in opposite sides of the pole and welded to opposite sides of the pole.

38. A metal pole as set forth in claim 1 wherein the side bars are planar and disposed in planes which intersect any transverse section of the pole in lines generally at right angles to the major axis of that transverse section, the side flanges of said web members at each side of the pole being disposed in a plane parallel to the inclined plane of the respective side bar.