US1828306A - Clamp for cables or the like - Google Patents

Description

A. O. AUSTIN Oct. 20, 1931.

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D D D HJ n. r [Il IHIIIIIIIIIIIHHHHHIHVUNHWHHHHIHHNUWI n l f a mwx @E C i INVENIOR Oct. 20, 1931. A. o. AUSTIN CLAMP FOR CABLES OR THE LIKE Filed Feb. l2, 1929 2 Sheets-Sheet 2 Il Ill L. n

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A TT ORNE Y Patented Oct. 20, 1931 UNITED STATES PATENT @FICE ARTHUR O. AUSTIN, OF NEAR BARBERTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE OHIO BRASS COMPANY, OF MANSFIELD, OHIO, A CORPORATION OF NEW JERSEY CLAMP FOR CABLES OR THE LIKE Application led February 12, 1929. Serial No. 339,305.

'l' his invention relates to clamps for holding the conductor of electrical transmission lines or other cables subjected to relatively high mechanical tension and has for one object the provision of a clamp of the class named in which the cable will be held partially by a snubbing action, the shape of the cable seat being regulated to prevent undue pressure at any point along the cable.

A further object of the invention is to provide a cable clamp which Will hold the cable in such-a manner as to prevent relative movenient of the inner and outer portions of the cable'. Other objects and advantages will appear fromthe following description.

The invention is exemplified in the combination and arrangement of parts shown in the accompanying drawings and described in the following specification, and it is more particularly pointed out in the appended claims.

In the drawings:

Fig. 1 is a side elevation of a cable clamp embodying one form of the present invention.

Fig. 2 is a top plan View of the clamp shown in Fig. 1.

Figs.3 and 4 are views similar to Figs. 1 and 2 respectively showing a modified form of the invention.

Fig. 5 is 4a. fragmentary elevation of a modified detail.

In the gripping or holding of high tension conductors where the ultimate stress in the conductors or the working tensions are high, it is somewhat difficult to grip the conductors in a manner that will distribute the load throughout the various strands so that approximately the ultimate strength of the conductor will be utilized. This is particularly difficult in conductors having high strength cores or reinforcing strands or Where a hollow core, either with or Without a spacer is used. In the case of steel reinforced aluminum conductors, a large part of the strength may "depend upon the steel conductor in the center so that it is necessary to grip this core by friction set up between the outer layer and the inner conductor or by removing the conductor entirely from the outer layer and gripping it independently. It is a decided disadvantage to remove the steel inner core or conductor for this member may be subjected to weathering which will shorten its life. Furthermore, if the steel core can be gripped without removing it or disturbing it in its location in the center of the outer layer of aluminum or softer material, the danger of breaking the weather protection such as galvanizing will be very much less, insuring maximum life. Once the steel core is destroyed, it is necessary to remove the conductor, as the tensions are so high that the outer layer will fail under the working loads should the inner core break. It is also a disadvantage to remove the inner steel core as the outer strands have to be removed and usually another piece of cable attached for carrying the current.

Vhere an efficient gripping means can be provided without removing the core, it is possible to dead-end a high tension conductor, allowing the umper to go direct to connected apparatus or to pass over to a clamp on the opposite side of the dead-end or strain structure.

If the conductor is brought into the groove of a clamp which has a curved seat so that tension in the conductor will cause bearing between the conductor and the clamp, the gripping friction will be developed by the tension in the conductor. This friction will be directly proportioned to the coefficient of friction between the conductor and the clamp. Where a conductor is curved or snubbed, a tension in any of the strands or layers throughout the conductor will always produce a bearing and friction between the various layers. Where the friction developed by this pressure which is set up by a tension in the conductor is considerable, it is evident that any clamping means which will grip the various inner layers can be reduced materially. The snubbing friction increases very materially with the angle of deflection. If T2 is taken as the tension in the conductor as it enters the snubbing groove or seat of the clamp, and TvL the tension at any other point along the seat of the clamp, the hyperbolic log of T1 in which equation n is the angle of snub in degrees divided by 360 and f is the effective coefficient of friction. The pressure between the conductor and clamp or between different layers of the conductor will be directly proportioned to the tension and inversely proportioned to the radius.

Since it is possible to control the pressure by regulating the radius of the seat, it is possible to prevent an inner core carrying a very high tension from exerting too much pressure on the outer layer. On the other hand, this pressure can be controlled so that maximum gripping` eliiciency will be obtained without' damaging the conductor. Since the angle of snub included is a determining factor in snubbing grip, it is important'. that the angle of snub be increased as rapidly as possible for a given length of seat in order to decrease the size, weight, and cost of the clamp.

lVhere the conductor enters the seat of the clamp, the radius of necessity will be comparatively large and will be decreased as the tension in the conductor is reduced by the distributed grip along the seat of the clamp. It is evident that a conductor may be wound around a shive or drum having a groove, but this tends to produce a clamp having a rather concentrated mass and requires a much more difficult construction than in the present involition.

In the present invention, as shown in the drawings, the entering conductor 10 passes into a U-shaped groove in a clamp member 11. The radius of longitudinal curvature of the seat where the conductor comes in Contact with the seat of the clamp is usually from 5 to 10 times the diameter of the conductor. In conductors where the outer layers are very soft and the tensions are high in the center layer, it is usually necessary to increase the radius so that pressure between the inner and outer layer will not damage the conductor. As the conductor traverses the seat in the clamp the load on the cable will be overcome bv the friction and the tension in the conductor gradually reduced so that the radius of curvature in the plane of the conductor may be correspondingly reduced without increasing the pressure of the cable against its seat. It may be shown by computation from the formula given above and from the equation of the logarithmic spiral that in order to increase the angle of snub as rapidly as possible without exceeding the allowable pressure of the cable against the seat, the clamping' seat will take the form of a logarithmic spiral in which the constant appearing in the equation of the logarithmic spiral is equal to the coeiiicient of friction between the cable and the cable seat. In order, however, to keep the conductor in approximate straight line and still maintain a snubbing friction, the direction of curvature is reversed where the conductor enters the second clamp member 12 having a gripping groove. The radius of curvature, however, in this member is decreased in the same way that the radius of curvature was decreased in the first member 11. The length of groove in the various meinbers can be varied materially as well as the number of members producing the groove in the clamp. The snubbing angle is the total of that included by all of the various members.

The conductor is tangent to the seats in passing from one member to the other. After traversing the member 12, the conductor enters the groove in the member 13, the curve being in a reverse direction. The arc or angle through which the aXis of the conductor moves increases the snubbing angle still further. Since the snubbing angles are accun'iulative, it is seen that a very large effective snubbing angle may be obtained without de fleeting the conductor very far from a straight line until it is desired to deflect the conductor so as to form a goed angle for the jumper 14. If the slack end of the conductor is not continued beyond the clamp to form a jumper or for other purposes, it will not be necessary to shape the seat so as to direct the slack end of the conductor but the scat may be terminated at the aXis of the clamp or in any other suitable manner. Clamping members 15 and 1G are used for gripping the cable, pressure being exerted by the bolts 17.

In a clamp of the above type. the total grip of the clamp will be increased from that produced by the gripping members to from 11/2 to 5 times that amount. depending upon the amount of grip desired in the snubbing portion. It is, of course, possible to reduce this ratio or to increase it if desired.

In the drawings the clamp is shown provided with a clevis having an eye 19 for attachment to an insulator string or other support. In the design shown, the clamp is made up of separable sections having interlocking ends so that it is not necessary to thread the conductor through the grooves of the seat. A tension member 20 in the form of a long U-bolt passing through ears 21 in the mem- 'L ber 11, allows an open seat into which the conductor 10 mav be placed. The conductor is then deflected or the member 2() raised and the curved member 12 having perforated ears 22 and 23 is slipped over the member 20.

The conductor is then raised above the tension members 2O and the final portion of the clamp 13having perforated ears 24 and 25 is slipped over the tension members 20. The conductor is then placed in t-he gripping portion' of the member 13 and the clamping pieces 15 and 16 are tightened. The terminal picce .is then slipped over the ends of the U shaped member 2() after which the nuts 27 may-'be tightened up. The various clamping members 12 and 13 slide along t-he tension members 2O until the ends interlock at the points 28 and 29. This interlocking may be dispensed with if desired in which case there v will be a bending moment or shear set up in the tension members 20. If, however, the interlock is properly formed, the tendency to deflect thetension member 2O will be negligible. It, of course, is possible to allow the ;(,\L=tension member to bend or to give at an angle between the various parts so as to regulate the amount of deflection from th-e axis of the clamp.

It will be seen that by the above arranger tfm'ent it is possibleto produce a clamp having-'a very small, mass at the point of entry and .also clamp members may be made rather small and easily formed. In order to develop high snubbing friction, all that is necessary '1; is to increase'the arc or snubbing angle in tiie various members or to increase the number of members. For maximum economy the radius will, of course, be reduced as rapidly as possible without producing too high a "pressure between. the conductor and the clamp. rvmembers or between the various layers., It should also be noted that the portion of the seat next adjacent the taut end of the cable extends through only a small are so that thecable is passed to the next adjacent portion Without being greatly diverted from its general direction and the seats are all less than-90 so that'at' no portion of the clamp is the cable bent'v back upon itself. This not only facilitatesinstallation of the cla-mp but permits the clamp to exert an effective snubbingracticn over a seat having a long radius ofcuret-'ature and yet to extend a minimum distance at eitherside of the axis of the main `portion-of the cable. The seats are all open crease the grip in a clamp by simply insertving more members. The effective coefficient may, of course, be increased by allowing Y conductor to wedge slightly in the seat. Most of the clamping members being simple, it is possible to make them out of soft terial. In fact', some of these clamps may be made of forged or cast aluminum or in bronze, copper, or other material if so desired. lVhere extreme lightness is desired, some of the light alloys may be used such as dur-aluminum. These light members may be used Where the conductor enters the clamp and heavier or stronger material used at the rear end of the clamp. This has the advantage of producing a minimum amount of mass at the point of entry of the conductor so that the danger of crystallization is reduced to a minimum. The various sections of the clamp, if made of aluminum, will usually require no liner in order to protect the strands of aluminum, but if desired, a liner 30 may be attached to the inner surface, acting as a cushion between the conductor and the seat of the clamp or, if desired, the clamp or the conductor may be wound with a protecting ribbon, as is done 1n many cases,

In a clamp similar to that disclosed in this invention, it is possible to so reduce the gripping means that there will be little or no danger of damaging the strands so that a conductor may be relocated to change .the tension or adjust the sag or for any other purpose. Should crystallization tend to dcvelop in a conductor at some point, it will' be possible to shift they conductor very read-A ily where a clamp of this type is. used. The clamp has the further advantage that direct gripping means are not applied until the tension has been materially reduced;

In place of the tension members `or rods shown in Fig. l, the various portions of the clamp or curved seats 11, 12 and13 may be secured together by ears 31, and 32 connected by bolts 33. rThe ears 31 attached to the sides of the seat' pieces pass outside of the ears 32 extending from bottom portions at the ends of the seat pieces allowing the bolts 33 to pass through the corresponding openings in the ears. to use either a single bolt or a pair of bolts or pins for holding the various endmembers together.

In Figs. 3 and 4 the boltsor pins 33ers placed in shear. lugs 35 may be placed on the sides of the seat pieces as shown in Fig. 5 and bolts 36 used in tension for holding the several parts together to form the complete clamp.

It, of course, is possible It is evident, however, that l In'order to provide rigidity in the seats,

and prevent bending moment under the longitudinal stress, the various sections may be provided with reinforcing ribs 37 and 38. For very heavy grips it is not only possible to grade the curvature of-the seat, decreasing the radius of curvature as the tension is taken up by the clamp, but it is also possible to grade other portions lof the mechanical strength of the clamp to suit the conditions. In general, as the stress is reduced in the conductor, this stress must be taken up by the clamp members, hence, they must be strengthened accordingly. Since the stress carried by the clamp is a minimum at the point of entry of the conductor, it is possible to make this portion of the clamp very light which is a material advantage in eliminating the possibility of a hard spot.

lVhere only one pin or bolt is used to join the various sections, it is possible to permit considerable movement, allowing the. clamp to assume a position determined by the resultant forces.

I claim:

l. A cable clamp having a cable seat extended in the general direction ot the axis of said cable, diferent portions ot' said seat being reversely curved relative to each other, the portion of said seat adjacent the taut end of the cable extending through an arc of less than 90O and passing the cable to the next adjacent portion with the cable continuing in the same general direction as that in which it enters the clamping seat and means for fixing said cable relative to said clamp at one end of said seat.

2. A cable clamp having a sini ng seat extended in the general direction of the length of said cable, successive portions of said seat being reversely curved and having adjacent ends relatively otl'set so as to lie at opposite sides of the cable passing from one et said portions to the other, the adjacent extremities of adjacent portions extending in substantially parallel directions.

3. A cable clamp comprising a plurality ot" separate sections arranged to engage opposite sides of a cable, said secti ns having abutting ends forming separabl nints between said sectionsand meansi'ior holding said sections in assembled relation in engagement with said cable.

4. A cable clamp comprising a plurality ot' oppositely curved separate sections arranged to engage opposite sides of a cable, said sections having abutting ends forming separable joints between said sections and means for holding said sections in assembled relation in engagement with said cable.

5. A cable clamp comprising a plurality et oppositely curved separate sections, alternate sections being arranged to engage opposite sides of a cable, the radius oi curvature ol said sections being progressively decreased 'from one end of said clamp toward the other end thereof, and means for holding said sections in assembled relation in contact With said cable.

6. A cable clamp comprising a plurality et oppositely curved separate sections, alternate sections being arranged to engage opposite sides of a cable, said sections having adjacent ends thereof arranged to interlock, and a tie-rod overlapping the successive sec tions and secured thereto for holding said sections in assembled relation.

7. A cable clamp comprising a plurality ft' reversely curved seat portions, alternate seat portions being disposed at opposite sides oi' the cable and having their outer or convex sides open, the radius of curvature of the seat portions decreasing from the portion et said clamp adjacent the taut end of the cable, means for securing said cable to said clamp adjacent the slack end thereof, the seat portions being separable to permit installation of the clamp and each comprising an arc ot less than 90.

8. A cable clamp having an elongated snubbing seat extending in the general direction of the axis of the taut portion of the cable held by said clamp, said seat comprising a plurality of seat portions distributed along said axis, alternate seat portions being curved outwardly in opposite directions and disposed at opposite sides of said cable and each forming an are of less than 90o so that the portion of the cable engaging the seat continues in the same general direction as the taut end thereof, the several seat portions bd arranged end to end and forming an ended curved snubbing seat disposed close to the position the cable would occupy if it extended in a straight line, each seat portion being trough shaped in cross section and having its bottom at the inside of the curve 'formed by said seat portion and being open at the outer side of the curve.

9. A cable clamp comprisin a plurality oi" seat portions, each portion icing trough shaped in cross section and curved through an are of less than 90, the open side of the trough being disposed at the convex side of the are, said seat portions being disposed end to end, alternate seat portions being curved in opposite directions and disposed at opposite sides of the cable held by said clamp, thus forming a snubbing seat made up of a plurality of seat portions extending along the clamp in the general direction of the taut end of the cable and forming an elongated snubbing seat for said cable, all portions of which are disposed close to said axis.

In testimony whereof I have signed my name to this specification this 9th day of February, A. D. 1929.

ARTHUR O. AUSTIN.

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