US2906379A

US2906379A - Wood cross arm brace

Info

Publication number: US2906379A
Application number: US715060A
Authority: US
Inventors: Burton M Smalley
Original assignee: Joslyn Manufacturing and Supply Co
Current assignee: Joslyn Manufacturing and Supply Co
Priority date: 1958-02-13
Filing date: 1958-02-13
Publication date: 1959-09-29
Anticipated expiration: 1976-09-29

Description

P 1959 B. SMALLEY 2,906,379

WOOD CROSS ARM BRACE Original Filed May 24, 1954 c I 32 i riff 77 INVENTOR. I j 15 ,Bg/ZMWZ jmaZZ Q/ United States Patent 2,906,379 Patented Sept. 29, 1959 ice WOOD CROSS ARM BRACE 1954. This application February 13, 1958, Serial No. 715,060

3 Claims. (Cl. 189-33) The present invention relates to wood cross arm braces, or, more broadly, to wood braces employed in connection with over head distribution circuits.

The present application is a continuation of the copending Burton M. Smalley application, Serial No. 431,801, filed on May 24, 1954 and assigned to the same assignee as the present application and now abandoned.

It has been customary to support cross arms which are secured to wood poles by suitable braces, usually two braces, one on either side of the pole. The ends of the braces are usually secured to the pole beneath the cross arm and the opposite ends thereof are secured to the cross arm, one brace end being secured on either side of the pole, thereby to provide the desired rigidity and strength. In certain applications light metal braces have been employed. It is preferable, however, to use wood braces, since they introduce a substantial length of insulation, and therefore, eliminate the conducting path for lightning or other high voltage surges which fre quently initiate power arcs between the conductors being supported by the cross arm.

Braces are usually secured to the pole beneath the cross arms so that they will not be in too close proximity to the conductors. Flat steel braces of a useable size are not stifli enough to act as compression members. Consequently the forces acting vertically on the cross arms by reason of icing conditions on the conductor are only counteracted by the brace in tension on the opposite side of the pole and these forces are multiplied by the long lever arm, i.e., the distance from the conductor support to the fulcrum which is the bolted attachment to the pole. Wood braces of this type, on the other hand, are excellent compression members because of the resistance offered by the wood to compression forces which would buckle the ordinary steel brace. Such Wood cross arm braces where employed have been employed to increase the flashover distance as far as the transmis sion line support is concerned. It will be appreciated that in transmission line supports involving Wooden poles and wooden cross arms the insulators for supporting the transmission lines are commonly supported on metal pins, and the proximity of the metal pins to the braces, if the braces were made of metal, would substantially reduce the insulating value of the Wood cross arms and flashover could readily occur from the metal pins to the cross arms and thence to the poles. This becomes particularly important in the case of metal cross arm braces if separate phase wires are supported on the cross arm, since flashover between the brace and the metal pin on each side could result in a short circuit through the braces between the two phases of the power line. For this reason, wood cross arm braces have been extensively employed for many years in connection with high voltage transmission lines. In fact, Stroup Patent No. 1,815,598, granted July 21, 1931, broadly claims a transmission line support comprising a wooden pole, a wooden cross arm, and diagonal braces for the cross arm.

For the purpose of securing such a wood cross arm brace to both the pole and the cross arm, it has been customary heretofore to provide metal fittings which are secured to the brace and subsequently to the pole or the cross arm, as the case may be. A problem is, of course, presented in providing a proper connection between the metal fittings and the brace which will provide long life under the various weather conditions to which such brace would be subjected in any locality, and to insure that a rigid and permanent connection is provided between the wood portion of the brace and the metal end fittings. Such braces must, of course, be capable of being employed in all climates. In very dry climates, as one would have in Arizona or New Mexico, there is a problem of drying out and shrinking of the wood, with the subsequent loosening of the metal fittings. It would be desirable to provide a construction that would insure a permanent and rigid connection between the metal fittings and the main body portion of the wood brace. It would, furthermore, be desirable to provide a brace formed from an improved material which has greater strength and is capable of being subjected to a wood treatment for preservation purposes, so as to present a brace superior to prior art arrangements.

Accordingly, it is an object of the present invention to provide a new and improved wood brace particularly useful in connection with supporting cross arms from poles of transmission line supports, although having other applications as well.

It is another object of the present invention to provide an improved wood cross arm brace with improved means for securing metal end fittings to the respective ends of the wooden brace.

Further objects and advantages of the present invention will become apparent as the following description proceeds, and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the present invention, reference may be had to the accompanying drawings in which:

Fig. 1 is a fragmentary view of a transmission line support showing a portion of a wooden pole and a portion of a cross arm secured thereto, together with the cross arm braces of the present invention shown in supporting position with respect to the cross arm and the pole;

Fig. 2 is a view illustrating in somewhat enlarged form the Wood cross arm brace of the present invention shown in Fig. 1 of the drawings;

Fig. 3 is a side elevational view of Fig. 2;

Fig. 4 is an enlarged sectional view taken on line 44 of Fig. 3;

Fig. 5 is an enlarged vieW of the fastening means employed in securing the metal ends to the wood cross arm brace;

Fig. 6 is a greatly enlarged section through the portion of the wood brace insertable into the metal fittings; and

Fig. 7 is an enlarged plan view of one of the end fittings employed with the wood brace of the present invention.

The wood cross arm brace of the present invention comprises essentially an elongated piece of wood, preferably apitong, with the ends thereof to be secured to the metal fittings having tapered sides so that a press fit can be provided between this end portion of the brace and a channel-shaped portion on the end fitting. By such a press fit arrangement a very secure connection is provided, so that even if the wood brace is used in a climate which is extremely dry there will never be enough shrinkage of the wood to cause any looseness between the interconnected parts. Improved fastening means,

which will prevent radio interference, are also employed to further secure the elements together.

Referring now to the drawings, there is illustrated in Fig. l a wooden pole of the type conventionally employed for supporting transmission lines or the like. Secured to the upper end of the wooden pole in a conventional manner is a wooden cross arm 11. The fastening means for securing the cross arm 11 to the pole 10 are unimportant as far as the present invention is concerned, and are schematically illustrated as comprising a suitable bolt 12 and bearing plate or washerlike members 13. The bolt 12 is preferably a through bolt extending through the cross arm and pole. conventionally, the pole can be provided with a notch or kerf upon which the cross arm 11 rests. Suitable insulators, not shown, will be supported from the ends of the cross arm, and perhaps also from the pole 10, which insulators will, of course, support the conventional transmission lines or the like.

In order to provide the desired rigidity between the cross arm 11 and the pole 10, there are provided, in accordance with the present invention, a pair of wood cross arm braces, generally indicated at 13 and 14-. These braces are identical and in the ensuing description only the brace 13 will be described in detail. As illustrated, the lower ends of the

braces

13 and 14 are superimposed, and a single fastening means in the form of a lag screw 15 secures the two braces to the pole at a suitable position below the cross arm. The upper or outer ends of the

braces

13 and 14 are bolted to the cross arm by suitable bolts 16. Although the

braces

13 and 14 are indicated as two separate braces, it will be appreciated that the lower metal fittings of the

braces

13 and 14 might be combined into a single fitting, so that a unitary V-shaped brace would be provided. By means of two

separate braces

13 and 14, however, greater flexibility is permitted.

Considering Figs. 2, 3, 4, 5, 6 and 7 in detail, the brace 13 primarily comprises a wood section 18 of rectangular configuration. Preferably the wood section is formed of apitong, which is obtainable from several places in the world, among them the Philippine Islands. It has been found to be much stronger than Douglas fir, which is the common wood used for wood cross arm braces, and it has a different cellular construction, so that it may be treated with a Wood preservative very successfully. Preferably the wood section 18 is treated with pentachlorophenol under suitable pressure, thereby greatly extending the life of the wood brace when subjected to the elements. Such apitong wood has been found to have very high shear strength parallel to the grain, and tests have indicated it to be substantially superior for wood cross arm braces.

The upper end of the brace 13 preferably terminates in a somewhat V-shaped or pointed configuration, as indicated at 20. The reason for this configuration will become apparent from an examination of Fig. 1, since it permits the end of the wood section 18 of the

braces

13 or 14 to more nearly conform with the adjacent edge of the cross arm 11 and eliminate the need for right and left hand members which would be necessary except for the V-shaped configuration. Actually, for a particular size cross arm the angularly disposed surface forming the V-portion 20 of the wood section may rest against the cross arm 11, but for other sizes this may not be the case.

In order to secure the wood section 18 to suitable end fittings in a simple manner, there are provided for each of the

braces

13 and 14 end fittings, generally designated as 22 and 23. These end fittings are essentially similar except that the end fittings 22 have a longer flat extension to accommodate different size cross arms. The

end fittings

22 and 23 can otherwise be considered substantially identical except that the end fitting 23 may have a somewhat larger opening 24, to accommodate the lag screw 15, than the end fitting 22, which may have a somewhat smaller opening 25 to accommodate a through bolt 16. Considering specifically the end fitting 22, it comprises a section 22a in the form of a channel, with an elongated section 22b, which is relatively flat except for some parallel disposed depressions 220 which extend into the channel section 22a. It will be apparent that the channel-shaped section is adapted to receive therein the associated end of the wood section 18 of the brace such as 13. The sides of the channel-shaped section 22a, designated in Figs. 4 and 7 of the drawings by the

reference numerals

27 and 28, respectively, are disposed in spaced parallel relationship with the upper ends thereof curved outwardly slightly, as indicated at 29 in Fig. 4 of the drawings.

The wood section 18, at least adjacent the point where it is to be connected to the end fitting 22, is provided with tapered side walls, thus to provide a somewhat wedge-shaped configuration, best shown in the enlarged view of Fig. 6 of the drawings. For a particular embodiment constructed in accordance with the present invention, the wood section 18 had a thickness of the order of inch, and was 1% inches wide. At the ends however, the wood was slightly oversized so that its narrowest dimension was 1% inches, and its widest dimension was 1 inches. The flanges or

sides

27 and 28 for the metal fitting, on the other hand, were spaced apart a distance of 1% inches. The tapered sides of the wood brace, as shown in Fig. 6, are readily received within the channel-shaped section 22a by virtue of the rounded ends 29 of

walls

27 and 28.

In accordance with the present invention, the wood section 18 is inserted within the channel portion 22a by a press fit, thereby compressing the wood fibers of the brace by at least a sixteenth of an inch at the upper end thereof, and thus insuring a very tight fit so that even when used in a very dry climate the shrinkage that occurs is not sufficient to cause any looseness. For the purpose of further securing the end fitting 22 with the wood section 18 of the wood brace 13, a suitable bolt 31 is provided, which extends through an opening drilled in the associated end of the wood section 18 and is threadedly engaged with tapped openings defined in the fitting 22. Asuitable lock nut 32, as shown in the drawings, is further included to insure that the fastening means will not become loose during use and with time. To further eliminate any possibility of radio interference due to loose metallic parts, the bolt 31 preferably is provided with a washer 31a integrally formed with the bolt 31. Itwill be apparent that by threading the bolt 31 into a tapped opening in the brace all metal parts are in good electrical contact, so that there is eliminated the problem of charging currents sparking from one metallic part to another.

The end fitting 23 insofar as its connection to the other end of the wood section 18 of the brace 13 is concerned is identical with that already described in connection with the end fitting 22. The bevelled wood section fitting into the spaced parallel side walls of the channel section insures for a tight press fit. It will be appreciated that the end fittings such as 22 and 23 are preferably formed of suitable metal such as steel or the like, which are preferably galvanized or otherwise treated for long life.

In view of the detailed description included above, the construction and operation of the present invention will readily be understood by those skilled in the art. There has been provided a very effective wood brace much stronger than prior types of wood braces by virtue of the material employed for the wood section. Furthermore, the improved connection between the wood and metal parts thereof is simple and inexpensive, and gives complete assurance that it will remain rigid under all conditions. Moreover, the problem of radio interference is completely gnlved, as is also the problem of eliminat ing charging currents sparking from one metallic part to another.

While there has been illustrated and described what is at present believed to be a preferred embodiment of the present invention, it will readily be understood that numerous changes and modifications may be made which will readily occur to those skilled in the art. It is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An insulated cross arm brace comprising a unitary metallic end fitting having a channel section and a substantially flat, generally rectangular section adjacent an end of said channel section, said channel section having a generally flat web portion interconnecting a pair of spaced parallel flanges right angularly related to said web, said flat section having a portion generally coextensive with the web portion of the channel section, an elongated section made from a compressible wood including an end portion having a pair of opposite generally bevelled sides in respective flush and frictional engagement with said walls, the portion of said end of said section adjacent to said walls being slightly compressed to provide a press-fitted connection between said elongated section and said channel section, one end of said elongated section being V-shaped with its apex lying on the longitudinal axis of the flat section and extending beyond the channel section onto the fiat section to provide a pair of cross arm engaging surfaces either of which is adapted to be placed in an abutting relation with said cross arm, and bolt means extending through said end portion of said elongated section and said web portion of said channel section fixedly securing said end fitting and said elongated section together.

2. An insulated cross arm brace for a cross arm on a pole comprising a unitary metallic end fitting having a channel section and a substantially fiat, generally rectangular section, said channel section having a pair of spaced flanges substantially right angularly related to an interconnecting web portion which is substantially coplanar with said rectangular section, an elongated wooden section provided with an end portion having a pair of opposite converging sides, said end portion of said wooden section being press-fitted into said channel section during initial assembly of said brace, and means including bolt means extending through said wooden section and said web portion of said channel section for fixedly securing said end fitting to an end of said wooden section, said end portion of said wooden section being V-shaped and having its apex disposed at the longitudinal axis of said wooden section and on said rectangular section thereby to provide a pair of cross arm engaging surfaces either of which may be placed in engagement with said cross arm.

3. An insulated cross arm brace comprising a metallic end fitting having a channel section and a substantially fiat section adjacent an end of said channel section, said channel section having a generally fiat web portion interconnecting a pair of spaced flanges, said flat section having a portion generally co-extensive with the web portion of the channel section to form a continuation of the Web of the channel section, an elongated section made from wood including an end portion embraced by said channel section, one end of said elongated section being V-shaped with its apex extending beyond the channel section and lying on the fiat section along its longitudinal axis to provide a pair of cross arm engaging surfaces either of which is adapted to be placed in an abutting relation with said cross arm, and bolt means extending through said end portion of said elongated section and said web portion of said channel section fixedly securing said end fitting and said elongated section together.

References Cited in the file of this patent UNITED STATES PATENTS 568,948 Hill Oct. 6, 1896 609,441 Kurrie Aug. 23, 1898 860,864 Harrison July 23, 1907 1,031,660 Olsen July 2, 1912 1,815,598 Stroup July 21, 1931 2,283,943 Myer May 26, 1942 2,374,623 Sale Apr. 24, 1945