Bundle Conductor Stringing Block With Rotary Threading Gate

This invention relates to bundle conductor stringing blocks, and more particularly to an improved block construction provided with a rotary threading gate powered by a spring and held cocked in its open position by a latch released by entry of the line into the gate slot whereupon the spring rotates the gate to transfer the hauling line into the block throat.

The installation of bundle type power conductors along a power line involves simultaneously pulling each of two or more power conductors along the power line at a level convenient for connecting these conductors to the power line insulators. Owing to the size and weight of bundle conductors, large, heavy stringing blocks are suspended from or adjacent the lower ends of the power line insulators. The hauling line for the conductors must then be threaded through the throat of successive ones of the stringing blocks. Initially, this threading operation was performed by hand but, in recent years, techniques have been developed for threading the hauling line through the stringing blocks as the line is dispensed from an aircraft, such as a helicopter flying along one side of the power line.

One proposal for performing this by aircraft operation is disclosed in the copending application for U.S. Pat. Ser. No. 515,005, filed Oct. 4, 1974 by Keith E. Lindsey and L. E. Lindsey. Another and related stringing block threadable by aircraft is disclosed in U.S. Pat. No. 3,868,089 granted Feb. 25, 1975 to the same applicants as the aforesaid copending application. In each of these prior constructions, a load transfer gate is pivotally supported crosswise of the threading passage for the conductor hauling line. When this gate is closed and the block is under load, the gate cooperates with a detent to transfer load stresses crosswise of the threading passage. However, during the threading operation, the gate is open and in consequence free of contact with the detent. Accordingly, each of these prior constructions must have a frame and a sheavesupporting shaft of sufficient strength to be supported rigidly by one side frame until the hauling line has been threaded into the block throat. Typically, stringing blocks of the character dealt with weigh several hundred pounds. Accordingly, the frames and sheave shafts of blocks threadable by aircraft must be very strong.

The foregoing and other disadvantages of prior stringing blocks threadably by aircraft are avoided by the present invention by utilizing a rotary threading gate mounted intermediate the opposite ends of one side frame and so constructed that it is continuously effective to transfer load stresses between the opposite ends of its supporting side frame. Accordingly, both of the block side frames share the block load at all times and during the hauling line threading operation. Bending moment stresses on the sheave shaft are held to a minimum by locating the axis of the threading gate inside the outer face of the adjacent outer sheave. This design criteria not only minimizes bending stresses imposed on the block shaft but contributes materially to weight reduction without sacrifice of strength. The block also includes provision for confining the hauling line to portions of the block throat such that it cannot become jammed in or cause damage to the principal components of the block. Such means include a guard preventing entry of the hauling line into the gate slot as well as spring-biased, pivotally supported guards preventing the hauling line from shifting to other than the central one of the block sheaves. Also provided is a guide horn for piloting the hauling line into the gate slot during the threading operation. This horn normally extends upwardly and outwardly from the lower side of the slot but is foldable to a collapsed position along one side of the block when not in use.

In one preferred species, the two hauling line guard members are detachably supported on a respective one of the block side frames for swinging movement in a generally horizontal plane between their stable operating and non-operating positions. In a second embodiment, the guard members are supported in vertical planes to either side of the hauling line supporting sheave and include a toggle linkage permitting the guards to swing upwardly to a retracted position along one or the other side of the plane of the throat. This permits the runningboard to pass in either direction through the throat without need for detaching or making any change in the hauling line guard units.

Accordingly, it is a primary object of the invention to provide a bundle conductor stringing block one side frame of which is provided with a rotary hauling line threading gate having various unique features.

Another object of the invention is the provision of a conductor stringing block having a rotary threading gate the axis of which overlies the outermost one of the block sheaves and inwardly of the outer face of this sheave.

Another object of the invention is the provision of a conductor stringing block having a rotary threading gate provided with a hauling line receiving slot and equipped with spring means for rotating the gate to transfer the hauling line from the exterior of the block into the block throat.

Another object of the invention is the provision of a conductor stringing block having a rotary threading gate and provided with guard means to protect parts of the block by confining the hauling line after delivery into the throat to certain areas of the throat.

Another object of the invention is the provision of a conductor stringing block having a rotary threading gate operable to transfer the conductor hauling line into the block throat through a path overlying the gate axis.

Another object of the invention is the provision of a stringing block having a rotary threading gate having guard means operable to prevent escape of the hauling line after being dropped thereinto and including guard means to prevent re-entry of the hauling line into the gate slot after the hauling line has been transferred into the block throat.

These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawing to which they relate.

Referring now to the drawing in which a preferred embodiment of the invention is illustrated:

FIG. 1 is a transverse elevational view of one preferred embodiment of a bundle conductor stringing block with a portion of the guide horn broken away and indicating in dot and dash line the collapsed position of the guide horn;

FIG. 2 is a fragmentary side elevational view of FIG. 2 as viewed from the left-hand side of FIG. 1;

FIG. 3 is a fragmentary cross-sectional view on an enlarged scale taken along line 3--3 on FIG. 1;

FIG. 4 is a fragmentary view of the threading gate subassembly showing the gate rotated clockwise to a position for discharging the hauling line into the block throat;

FIG. 5 is a fragmentary transverse cross-sectional view taken along 5--5 on FIG. 1;

FIG. 6 is a fragmentary transverse elevational view similar to FIG. 1 through the throat portion of a second preferred species of the invention; and

FIG. 7 is a cross-sectional view on an enlarged scale taken along broken line 7--7 on FIG. 6 but showing the hauling line guard member pivoted to one of its two stable inoperative positions.

Referring initially to FIG. 1, there is shown a first preferred embodiment of the invention stringing block, designated generally 10, equipped with four conductor supporting sheaves 11 supported by shaft 14 on the opposite sides of a central hauling line sheave 12. The opposite ends of shaft 14 are rigidly secured to side frames 15 and 16 by bolts 17. As here shown, the lower ends of side frames 15, 16 are rigidly interconnected by a cross-frame member 18.

The stringing block side frames 15 and 16 extend upwardly a very substantial distance above the top peripheries of sheaves 11, 12, their upper ends being suspended by clevices 19, 19 from the lower corners of a yoke plate 20. This yoke plate may be of any suitable construction such as that designated 16 in Lance U.S. Pat. No. 3,076,866 granted Feb. 5, 1963.

Portions of frames 15 and 16 overlying the upper peripheries of the sheaves are constructed somewhat differently from one another in that side frame 15 includes the rotary threading gate 22 which lies generally in the same vertical plane as the axis of shaft 14. Gate 22 is fixed by pins 23 (FIG. 3) to a pin 24 having a wrench-engaging head 25. Pin 24 journalled in ball bearing assemblies 26, 26 secured to a respective one of a pair of plates 27, 27 clamped to the opposite sides of the upper end of frame 15 by bolts 28 and spacer block 29 (FIG. 2). Plates 27 extend along the opposite sides of the gate 22. As is best shown in FIG. 3, this gate comprises a wheel having an axial flange 30 projecting from its opposite sides for a distance somewhat less than the spacing between its supporting plates 27, 27. Gate 22 is suitably secured to the axial pin 24 and is urged to rotate clockwise as viewed in FIG. 1 by a strong torsion spring 32 having one end bearing against an anchor pin 33 secured to pin 24 and its other end 34 inserted in a hole in plate 27.

Referring to FIG. 4, it will be understood that the uppermost end of side frame 15 is formed by a pair of combination shroud and suspension plates 36, 36 lying in the same plane as plates 27, 27 and held spaced apart by bolts and spacer sleeves 37, 37, the suspension clevis 19 being supported by the uppermost one of bolts 37. The sole means holding the plates 36, 36 assembled astride the upper portion of gate 22 comprises two pairs of load-bearing rollers 40 and 41. These rollers are journalled on shouldered bolts 40', 41', respectively rigidly clamped to plate 36. The two pairs of rollers are staggered or circumferentially offset from one another along the upper portion of flange 30 and serve as a heavy duty load transfer means between the plates 36, 36 and gate 22.

The upper edges 27' of plates 27 and the lower edges 36' of plates 36 are vertically spaced from one another to provide a continuous threading gap crosswise of the upper end portion of side frame 15 through which the conductor hauling line passes while being transferred from the exterior side of side frame 15 and into the throat of the stringing block. It will be understood that this throat lies in a vertical slant between the upper ends of side frames 15, 16 and overlying the upper peripheries of sheaves 11, 12.

In order to accomplish the transfer of the hauling line through this threading gap, gate 22 is provided with a deep, non-radial slot 48 extending inwardly through flange 30 to a point close to but offset from the axis of the gate as is best shown in FIG. 4. In this position of the gate, the gate is rotated to its hauling line discharge position and the hauling line indicated at 50 is positioned to fall by gravity out of the inlet end of the slot and past the normally closed guard gate 51. This gate is supported between plates 36, 36 on a pin 52 and is normally urged to the closed position shown in full lines by a torsion spring 53 encircling pivot pin 52. The weight and tension forces of the hauling line 50 bearing against gate 51 to serve to open the gate and permit the passage of the line therepast for gravitation onto the center sheave 12.

When gate 22 is cocked in its open position, slot 48 is in registry with the upper outwardly directed end of the threading gap as is shown in FIG. 1 and is latched in this cocked position by the latching unit designated generally 54 (FIGS. 1 and 4). This latching unit comprises a pair of plates 55, 55 pivotally supported along the exterior sides of plates 27 on a pivot pin 56. Plates 55 are fixed to this pivot pin and to a detent 57 urged to bear against the periphery of flange 30 by a torsion spring 58 encircling pin 56. Detent 57 seats in a notch 60 when in the rim of gate 22 when this gate is rotated counterclockwise one-half revolution from the position shown in FIG. 4 with slot 48 in registry with the upper end of the gap between plates 27 and 36. The forward ends of plates 55 then extend across slot 48 and lie in the path of the hauling line 50 as it falls downwardly toward the inner end of the slot.

When gate 22 is in its open position as shown in FIG. 1, roller 60 is spring pressed by spring 63 into a depression 66 (FIG. 4) extending crosswise of the outer periphery of gate 22. Roller 60 is loosely supported in vertical slots formed through plates 36. The left-hand ends of springs 63 embrace a bolt 64 extending between plates 36 whereas a midportion of spring 63 passes beneath a bolt 65 likewise extending between plates 36. When gate 22 is cocked in opened position, roller 60 seats in the recess 66.

The upper end of the stringing block side frame 16 does not require a rotary gate 22 and is connected to yoke 20 and clevis 19 by a pair of side plates 70, a pair of links 71 interconnected by a pivot pin 72. It will be understood that plates 70 correspond to plates 27, 27 and are connected to the upper end of side frame 16 by bolts 73 and the spacer bar 29.

To assure that hauling line 50 will be guided onto the top of central sheave 12, the stringing block is provided with a pair of guard members 75, 75 pivoted by vertical axis pivot pins 76 to bracket plates 77. The bracket plates 77 are preferably shaped to embrace the outer vertical edge of plates 70 in the manner best shown in FIG. 5 and are detachably secured thereto by quickly detachable assembly pins 78.

The guard members 75, 75 have two stable positions, one being that shown in FIGS. 1 and 5 wherein the guard members lie generally in the plane of the stringing block throat and crosswise of the upper peripheries of sheaves 11 and 12 and the other stable position being the open, inoperative position in which the guard members are held pivoted outwardly approximately 90.degree. from the position shown in FIGS. 1 and 5 thereby leaving the throat of the stringing block clear and unobstructed. The guard members are held in these two stable positions by a toggle spring 80 having one end connected to the guard members as indicated at 81 in FIG. 5 and the other end connected to the bracket 82 when closed, the center line of spring 80 lies slightly above the axis of pivot pin 76 as viewed in FIG. 5 when the guard members 75 are in their closed position whereas when the center line of this spring is below the axis of pins 76, it is effective to hold the guard members in their open position.

To guide or pilot the hauling line 50 into slot 48 of gate 22 as the line is dropped from an aircraft, stringing block 10 is provided with a guide horn 85 extending upwardly and outwardly from the upper end of the side frame plates 27, 27 by a bolt 86 and a withdrawable pin 87. So long as pin 87 extends through the guide horn, the horn is rigidly secured in the position shown in FIG. 1. However, when pin 87 is withdrawn, the guide horn is free to pivot about bolt 86 to the collapsed or retracted dotted line position shown in FIG. 1.

The operation of the first embodiment shown in FIGS. 1-5 will be readily apparent from the foregoing detailed description of the block components and their relationship to one another. Stringing block 10 is suspended from the lower end of the yoke 20 by the clevices 19. Initially the threading gate 22 will be in the closed position shown in FIG. 4 wherein the entrance or outer end of the threading slot 48 is approximately the four 0'clock position as shown in FIG. 4. To position the gate in its open, hauling line receiving position, the workman places a wrench on the hexagonal head 25 of the gate pivot pin 24 and rotates the gate counterclockwise (FIG. 4) one half turn so that notch 60 (FIG. 4) will be engageable with detent 57 of latch 54. Spring 58 will then pivot detent 57 into notch 60 and lock the gate cocked in open position with slot 48 positioned to receive a hauling line dropped onto horn 85. Roller 60 (FIG. 1) will also be seated in recess 66 (FIG. 4) of gate 22.

The operator also makes certain that the guide horn 85 is in its operating position as shown in full lines in FIGS. 1 and 2. Additionally the guard members 55 are pivoted inwardly to extend crosswise of the throat with the lower edges overlying and resting against or close to the upper edges of central sheave 11 as shown in FIG. 1. They are held firmly in this position by toggle springs 80 the center lines of which will then lie slightly inwardly of the axis of their pivot pins 76.

As the aircraft flies past the stringing block, line 50 is dropped onto the guide horn along which it gravitates into the outer or inlet end of slot 48 of the threading gate 22. As the hauling line slides downwardly into slot 48, it will engage the free ends of latch 55 and pivot the latter clockwise about its pivot pin 56 thereby releasing the latch detent 57 from notch 66 thereby permitting the hauling line to pass into the innermost end of slot 48. The disengagement of detent 57 from notch 66 allows the stressed spring 32 to rotate the gate clockwise as viewed in FIG. 1. The gate rotates one half revolution as the hauling line is passed along the threading gap between the adjacent edges of plates 27 and 36 to the position shown in FIG. 4. As the hauling line reaches the exit end of slot 48, it will engage and open the guard gate 51 and gravitate downwardly between the adjacent edges of guard members 75, 75 onto the top of center sheave 12.

Along straight sections of the power line the hauling line will remain resting on the central sheave, but along curved sections of the power line, the tension in the line often tends to shift it laterally past one or the other edge of the central sheave. However, the line cannot migrate onto any other sheave owing to the presence across the throat of the guard members 75, 75.

If portions of the power line are located in valleys between higher portions of the lower line, the hauling line may be raised into upper portions of the stringing block throat. In these circumstances, the line is prevented from entry into slot 48 because gate 51 will be closed. Nor can the line come in contact with gate 22 while being pulled lengthwise of the power line because of gate 51 and the fact that plates 36, 36 extend radially beyond the rim of the gate, thereby protecting the gate from rubbing contact with the hauling line which could result in serious wear and damage to the gate.

Referring now to FIGS. 6 and 7, there is disclosed a modified embodiment of the invention which differs from that just described in two principal respects in that the guard units 75', 75' preventing movement of the hauling line onto the sheaves to either side of the center sheave are movable about horizontal axes rather than about vertical axes and are shiftable in either direction to either of two stable open positions from their normally closed operating position. The same or similar components of the second species are identified by the same reference characters as the first described species but are distinguished therefrom by the addition of a prime.

Guard members 75' are mounted in vertical planes closely beside the opposite lateral edges of central sheave 12' and are of the same type disclosed in the aforementioned Lindsey et al. U.S. Pat. No. 3,868,089. Guard members 75' have a slotted connection with a pivot pin 90 projecting from the opposite sides of the bracket 91 secured to plates 27', 70' by bolts 92. The opposite ends of the T-head of a T-bolt 94 are pivotally supported in the lower end of bracket 91. The stem of this bolt extends downwardly through the guard members 75' and is encircled by a compression spring 95 having its lower end bearing against the lower end of members 75'. Accordingly, this spring is effective to hold the arcuate lower end 96 (FIG. 7) of guard member 75' seated against the underlying one of sheaves 11'. When so supported, the guard members 75' are firmly secured in their stable, operating position and are highly effective in preventing the hauling line from migrating or shifting from the center sheave 12' onto sheaves 11'.

The alternate embodiment operates in the same manner described above in connection with FIGS. 1 to 5. When the hauling line has advanced the conductors to stringing block 10', the runningboard customarily interconnecting the trailing end of the hauling line to the advance end of the conductors will contact the guard members 75' and pivot these guard members about pivot pins 90 and away from their seating position on sheaves 11', 11'. As this occurs, the toggle springs 95 are effective to continue the pivotal movement of the guard member 75' until the same are firmly supported in a second stable position in a horizontal plane opposite pivot pin 90. Springs 95 are then effective to support the guard members in this stable position until they are forcibly reset to their original position.

While the particular bundle conductor stringing block with rotary threading gate herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiment of the invention and that no limitations are intended to the detail of construction or design herein shown other than as defined in the appended claims.