US3010700A

US3010700A - Open side stringing sheave

Info

Publication number: US3010700A
Application number: US786430A
Authority: US
Inventors: Gerald A Petersen
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-01-12
Filing date: 1959-01-12
Publication date: 1961-11-28
Anticipated expiration: 1978-11-28

Description

Nov. 2 8, 1961 G. A. PETERSEN OPEN SIDE STRINGING SHEAVE Filed Jan. 12, 1959 INVENTOR. Gerald A. Petersen United States Patent f 3,010,700 p l OPEN SIDE STRINGING SHEAVE I Gerald A. Petersen, Saratoga, Calif. Petersen Engineering CoL, 461 Kifer Road, Santa Clara, Calif.)

Filed Jan. 12, 1959,"Ser. No. 786,430 4 Claims. (Cl. 254*1343) pending from towers and, accordingly, a sheave is in stalledat eachcf the towers spaced along the line. To facilitate the stringingoperations, in the first'instance, a steel cable is passed through the sheaves and connected to the aluminum or copper conductor. The cable is pulled under tension and tends to'rot'ate as it is pulled in. To reduce rotation of the steel pulling line, swivels are frequently installed adjacent each end of the pulling line and sometimes swivels are installed along the'length of the line. Visual observation of the swivels as the stringing operation proceeds shows that one-half of the swivel spins rapidly when tensions are heavy. Since the sheave is made of a lightweight material, such'as' aluminum or magnesium, the rotating steel pulling line'tends to chew up the bottom of the groove in the sheave and thus to damage the sheave. Scoring of the groove re sults in consequential damage to the conductor when it.

follows the steel pulling line through the sheave because the rough surfaces produced by the steel pulling line on the sheave marthe conductor, and this isaserious prob- .lem in the construction of transmission lines.

In accordance with the present invention, the groove in the sheave is partly lined with a resilient substance such as neoprene which will not scuff up by action'of the steel pulling line and, hence, will not subsequently damage the conductor. The resilient insert wears much longer than aluminum or magnesium;

Insertion of rubber in the entire groove of the sheave creates a problem after the bottom of the groove is worn because the cost of revulcanization is prohibitive.

Forming the liner merely in the bottomof the groove is unsatisfactory because rotation of the pulling line under heavy tension causes it to climb up the side of the sheave groove and, if it climbs higher than the limit of the lining, it damages the sheave itself. Accordingly, the present-invention employs a-resilient' insert which extends partway up the side of the'groo've so that the steel pulling line will not damage the groove of the sheave and yet the width of the insert is not so great to make revulcanization of a new insert in the sheave 'unduly expensive. The extent of the insert up the side of the groove is about equal tothe elevation of the center of the largest size conductor used in the sheave and'about twice the diameter of the pulling line employed;

3,010,700 Patented Nov. 28', 1961 invention reduces the likelihood of flattening the conductor, because of the fact that the conductor is pulled over a resilient surface. I

Another feature of the invention is the employment of a conductive material in the resilient liner of the sheave so that the accumulation of staticelectricity is eliminated.

Other objects of the present invention will become apparent upon reading the following specification, and'referring to the accompanying drawings in which similar charactersof reference represent" corresponding parts in each of the several views.

In the drawings:

FIG. 1 is a side elevation of the sheave.

FIG. 2 is ariend elevation.

FIG. 3 is a vertical sectional view taken substantially along line 3-3 of FIG. 1.

FIG. 4 is an enlarged fragmentary sectionalview of the groove of the sheave and liner showing in dotted lines the steel pulling cable and the conductor.

FIG. 5 is afragmentary enlarged sectional view of a portionof the conductor retainer.

The stringing sheave, which is the subjectof this invention, employs pulley 11 preferably of a lightweight material such as aluminum or magnesium rotatably mounted on the lower end of bracket 13. The upper end of bracket 13 isprovided with an attachment device 14 hereinafter described in detail, which may be attached to the lower end of an insulator 17 or other means employed to'suspend a cable from a power pole cross arm.. The sheave may be grounded by wire 16 attached tobracket 13 and by a clip 15 to the cross arm, or the sheave may be directly connected to the cross arm instead of the insulator.

When the sheave is installed in position, a steel caole 21 or pulling line of relatively small diameter is first suspended by the sheave and, after having been suspended, is pulled through the sheave. The end of cable 21 is connected by means forming no part of this invention to one end of the conductor 22, which is ordinarily copper or aluminum and is of considerably greater diameter than steel cable 21. After conductor 22 has been installed in position, it is connected to insulator 17 and the stringing sheave is removed. Accordingly, pulley 11 is formed with a peripheral U-shaped groove 23 having a rounded arcuate bottom 24 and sides 26. The distance between sides 26 and the radius of curvature of bottom 24 must be sufiicient to accommodate the largest diameter conductor 22 to be usedwith the sheave.

By reason of the fact that pulley 11 is formed of a relatively soft materiahsuch as aluminum or magnesium and the pulling cable 21 of a hard material, such as steel, bottom 24 of groove 23 tends to wear rapidly, requi'ring replacement of pulley 21. A lubricant may be used to reduce the wear, but this is not satis'factory'be cause of the severe action of cable 21'. The present in A further feature of the invention is the fact that the When a vention has as one of its principal features the provision of an annular liner 27 inserted in a recess 28 in the bottom 24' of groove 23L The exterior surface 29 of liner 27 has a curvature similar to the curvature of bottom 24, but is raised above bottom 24 so as to cover corner edges 31 of recess 28 and hence protect the relatively soft power cable 22 from abrasion. Recess 28 is shallow and has a width approximately twice the diameter of the largest size stringing cable 21 which is intended to be employed with the'sheave.

A preferred material for the fabrication of liner 271s electrically conductive neoprene (synthetic rubber), which is a resilientmaterial which withstands the abrasion of pulling cable 21 and yet will conduct electricity to the pulley 11 and thence to ground, thereby preventing the building up of static electricity. When such conducis substantially continuous.

tive neoprene is employed, then the use of a conductive lubricant is obviated. As the stringing cable 21 is drawn through the sheave, it rides upon the exterior surface 29 of insert 27. Insert 27 is more resistant to abrasion than are sides 26 and bottom 24 of pulley 1.1, and hence wear is reduced. Further, liner 27 may be replaced and a new liner vulcanized in place when required.

Bracket 13 comprises an enlongated, thin vertical web 36 formed with a plurality of

apertures

37, 38, 39 to facilitate handling of the sheave to reduce weight and further, when desired, to receive the rope used to hoist the sheave into place. For similar usage, a plurality of ears 41 formed with apertures 42, similar in shape to teacup handles, are attached to the web 36 inwardly of the

apertures

37, 38 thereof and approximately at the level of the top of the pulley 11. When a rope is slung through the apertures 42 in one or both of the ears, the raising of the sheave with cable 21 installed therein is facilitated and the tendency of the cable to twist out of alignment is to a large extent eliminated.

The lower end of the web 26 is formed with a circular abutment 46 having a stepped outwardly extending boss 47. The face of hub 48 of pulley 11 adjacent abutment 46 is formed with a recess 49 having a shoulder 51 at its innermost end. Double ball bearing 54 fits within recess 49 and is held in place against shoulder 51 by snap ring retainer 52. The inner race of the bearing 54 fits over boss 47 and is held in place by snap ring retainer 53. Cover plate 56 covers over the open end of recess 49 and is secured in place on hub 48 by screws 57, the heads of which are countersunk into the face of plate 56 and the shanks of which are received in tapped holes 58 in hub 48. It will be noted that this method of mounting the pulley on the bracket insures that there are no exposed bolt heads or nuts which may snag. This feature of construction is of considerable advantage in the use of the sheave.

To prevent the cable 21 or conductor 22 from binding between the bracket and the pulley, a curved shoulder 61 is formed on the'inner surface of web 36 at the upper end of the pulley 11, the curvature of the shoulder 61 merging with the rim edge 62 of the pulley.

To facilitate installation of the conductor in the sheave, a large opening 63 is provided in the bracket 13 above the pulley. This feature is of particular advantage, in that it enables a conductor splice to pass over the pulley and through the bracket. To retain the conductor in place, a keeper 66 is provided. The keeper 66 comprises a. closure member 67 having a pair of upstanding ears 68. The bracket is cut away, as indicated by

reference numerals

69, 69 on either side thereof to receive the cars 63, so that the width of the bracket, with the ears installed, A pin 71 is inserted through the ears 6S and through the tongue 72 in the bracket between the recesses 69 to provide a pivot for the keeper. A short length of coil spring 73 is wrapped around pivot pin 71 and fixed to one of the cars 68 and to the tongue 72 and functions to bias the keeper to closed position. Here again, it will be noted that there is no exposed nut or bolt which may snag. The keeper below pivot 71 is formed concavo-convex in end elevation. The convex external surface 76 of the keeper merges with the upper edge of the outer rim 62 of the pulley 11 and, hence, when a conductor is brought to bear against said surface 76, the keeper is pivoted inwardly to permit the conductor to move into the opening 63 and thence into the groove 23 in the pulley 11. The concave inner surface 77 of the keeper 66 merges with the curvature of the groove 23 in the pulley, and it further will be observed that the lower tip 77 of the keeper is in close proximity to the rim 62 of the pulley.

The upper end of the hanger is cut away as indicated by numeral 81 and formed with a pair of spaced upwardly extending lugs 82 parallel to web 36 and reinforced with gussets 83 merging into the cut-away surface 81. A flat horizontal shoulder 84 is provided on the upper edge of the lugs 82. A sockeye fitting 14 having a downwardly projecting tongue 86 fits between the lugs 82 and is secured in place by bolt and nut 87-88 passing through aligned apertures in the lugs 82 and tongue 86. The sockeye fitting 14 has a shoulder which fits against shoulder 84 on the top of the lugs 82 to prevent pivoting of the sockeye fitting from its proper position. The construction of the sockeye fitting 14 is well understood in this art and comprises a member having a recess 91 extending horizontally inwardly from one surface thereof, the recess merging with a vertically extending recess 92 of lesser depth, which vertical recess 92 extends upwardly to the top edge of the fitting. It will be understood that other fittings may be employed.

In use, sheaves are hoisted by a rope passed through handle 41 or

aperture

37, 38 or 39' in web 36 to the cross arms of each tower along the line. A pulling line 21 may be inserted through keeper 66 into groove 23 either before or after the sheaves are hoisted. The sheave may be attached to insulator 17 by means of fitting 14 or other convenient means and may be grounded by cable 16. The pulling line is attached to conductor 22 and wound in, the conductor being pulled through each sheave along the line. As the pulling line 21 is wound in it tends to rotate, but abrasion of the sheave is resisted by insert 27. Accumulation of static electricity is prevented by reason of the conductive resilient material of which insert 27 is constructed. After the conductor has been strung, it is removed through keeper 66 and attached to insulator 17, the sheave being lowered to the ground. Whenever liner 27 is worn out, a new liner may be vulcanized in recess 28.

Although the foregoing invention has been described in some detail, by way of illustration and example for purposes of clarity of understanding, it is understood that certain changes and modifications may be practiced Within the spirit of the invention and scope of the appended claims.

I claim:

1. A stringing sheave comprising a pulley formed with a relatively deep peripheral groove, and means for rotatably mounting said pulley, said pulley being formed with a shallow circumferential arcuate recess around the bottom of said groove and partially up the sides of said groove, and an insert formed of an electrically conductive resilient material in said recess and extending around the bottom of said groove.

2. A stringing sheave comprising a pulley formed with a relatively deep peripheral groove, and means for rotatably mounting said pulley, said pulley being formed with a shallow circumferential recess around the bottom of said groove, the upper marginal edges of said groove 1 being relatively sharp, and an insert formed of an electrically conductive resilient material in said recess and extending around the bottom of said groove and partially up the sides of said groove, the upper surface of said insert along its side edges being raised above the bottom of said groove to protect said edge of said groove adjacent said recess fromcontact with a cable strung by said sheave.

3. A stringing sheave comprising a pulley having a hub and formed with a relatively deep peripheral groove, and a hanger for said pulley, said hanger having an attachment device above the axis of said pulley, a web depending from said attachment device displaced laterally from said pulley to one side of said pulley, a boss on said web extending through and concentric with the axis of said pulley, bearing means mounting said hub on said boss positioned directly below said attachment device, said pulley being formed with a shallow circumferential arcu ate recess extending around the bottom of said groove and partially up the sides of said groove, and an insert formed of an electrically conductive resilient material in said recess and extending around the bottom of said groove.

4. A stringing sheave comprising a pulley having a hub and formed with a relatively deep peripheral groove, and a hanger for said pulley, said hanger having an attachment device above the axis of said pulley, a web depending from said attachment device displaced laterally from said pulley to one side of said pulley, a boss on said web extending through and concentric with the axis of said pulley, bearing means mounting said hub on said boss positioned directly below said attachment device, said hanger being formed with an enlarged, substantially arenate, opening below said attachment device and above said pulley, the portion of said hanger defining said opening adjacent said pulley overhanging the rim of said pulley adjacent said web, a keeper depending from said hanger and extending to a point adjacent the top edge of said pulley opposite said web, said keeperbeing convex on the outside and concave on the inside, the inside surface of said keeper merging with the walls of said opening and the lower end of said keeper extending to overhang the rim of said pulley adjacent said keeper, means mounting 20 said keeper for pivotal movement inwardly into said enlarged opening, a pair of ears in the shape of teacup handles projecting out from said web parallel to said sheave and above said pulley, said pulley being formed with a shallow circumferential recess around the bottom of said groove, the upper marginal edges of said groove being relatively sharp, and an insert formed of an electrically conductive resilient material in said recessand extending around the bottom of said groove and partially up the sides of said groove, the upper surface of said insert along its side edges being raised above the bottom of said groove to protect said edge of said groove adjacent said recess from contact with a cable strung by said sheave.

References Cited in the file of this patent UNITED STATES PATENTS D. 184,880 Lindsey Apr. 14, 1959 1,780,627 Muller Nov. 4, 1930 1,944,426 Greening Jan. 23, 1934 2,197,698 Lamberth Apr. 16, 1940 2,524,509 Barney Oct. 3, 1950 2,649,282 Fate Aug. 18, 1953 2,879,452 Page Mar. 24, 1959 FOREIGN PATENTS Great Britain Dec. 1, 1921