Apparatus and method of threading a closed framed opening by helicopters

An apparatus and method of automatically threading successive closed framed openings by helicopter towing a line equipped with a separable coupling. The invention utilizes a short cable loop pre-threaded through each closed frame such as the throat of a stringing block which cable loop is provided at its ends with coupling halves releasably supported at the opposite ends of a trough overlying the framed opening to be threaded. A helicopter is manoeuvred to drop the towing line coupling into a trough where its halves are automatically separated and thereafter recoupled to a respective end of the cable loop. Subsequently, the forward coupling can be similarly separated for insertion of a second cable loop in the towing line at the next threading apparatus in the helicopter's path of travel.

THE THREADING DEVICE GENERALLY 
Referring initially more particularly to FIGS. 1 to 3 and 12, the invention 
threading apparatus, designated generally 10, is shown clamped 
transversely of the cross frame 11 of a power line tower. The midlength of 
cross frame 11 typically supports the central conductor on the lower end 
of an insulator 12. A multi-sheave bundle stringing block 13 customarily 
employed in stringing bundle type power conductors is suspended by its 
frame 14 from the lower end of insulator 12 while the bundle conductor is 
being towed into position for connection to the insulator in lieu of 
stringing block 13. It will therefore be recognized that insulator 12 is 
suspended from the mid-section of the cross frame 11 interconnecting the 
inner and outer legs of the tower, not shown. Since the cross frame and 
the tower legs form a framed opening, a helicopter commonly employed for 
dropping a lightweight towing line for the main conductor hauling line 
cannot drop the tow line into the throat of a stringing block frame in 
accordance with the practise known to the prior art and shown, for 
example, in the U.S. Pat. No. 4,129,287 granted to Lindsey et al, Dec. 12, 
1978. To circumvent this obstacle this invention utilizes a short length 
of flexible cabling, herein called a cable loop 15, having a female 
coupling attached to its trailing end and a rounded male coupling 17 
attached to its leading end. These coupling halves are temporarily and 
releasably supported at the opposite ends of a trough 18 extending 
transversely of the tower cross frame 11. Trough 18 is rigidly clamped 
temporarily to the cross frame by clamps 19 which will be described in 
greater detail presently. 
The remaining principal components of the threading apparatus comprise a 
separable tow line coupling 20 separably interconnecting the leading and 
trailing sections 21, 22 of the tow line. The leading end 21 is connected 
to helicopter 23 and the trailing end 22 leads to a supply reel not shown. 
Before proceeding to describe structural details of the threading device it 
will be understood that the helicopter advances the hauling line from 
tower to tower. Initially it approaches a given tower in the highest 
position indicated in dot and dash lines in FIG. 1 until coupling 20 
directly overlies the mid portion of trough 18. The helicopter then 
settles so as to deposit coupling 20 into the midlength of trough 18 and 
then moves a short distance to the left as indicated by arrow B allowing 
the tension in the hauling line to draw coupling 20 to the left hand end 
of the trough 18 where it is automatically uncoupled allowing its male 
component on the trailing end 22 of the line to become coupled to the 
female coupling 16 on the trailing end of cable loop 15. The helicopter 
then shifts forwardly, as indicated by arrow C, thereby trailing the 
female half of coupling 20 to the right and into coupling engagement with 
the right hand end of cable loop 15. The helicopter continues to move 
rightward as indicated by arrow D and, in so doing, carries the re-engaged 
coupling 20 forwardly toward the next tower with cable loop 15 now forming 
a section of the tow line. 
DETAILED DESCRIPTION OF THE COMPONENTS 
Referring to FIG. 2, 3 and 12, it will be seen that the main body of 
apparatus 10 comprises an open ended trough 18 all except the opposite 
ends of which flare upwardly at an obtuse angle best illustrated in FIG. 
12. Each end is generally cylindrical in shape slotted lengthwise of the 
top thereof by a slot 30 sized to freely pass the tow line and the tongue 
like arm 31 rigidly attached to the periphery of the forward end of the 
female half 32 of coupling 20. The right hand end of trough 18 is provided 
with an upwardly opening socket 33 (FIG. 2). The bottom of this socket has 
an elongated slot 34 (FIG. 2) to receive the leading end of cable loop 15. 
Referring more particularly to FIGS. 3, 10 and 11, it will be noted that 
male coupling half 17 of the cable loop 15 is supported on the upper edges 
of a forwardly facing U-shaped positioning plate 36 protruding through and 
welded to the edges of slot 34. As clearly appears from FIGS. 10 and 11, 
the upper edge 37 of U-plate 36 is positioned to support coupling 17 with 
its center in axial alignment with the right hand cylindrical portion of 
trough 18. A tang 38 projects upwardly from the outer end of member 36 to 
safeguard against the coupling half becoming accidentally and prematurely 
dislodged from its seat. Additionally, a pair of spring biased ball 
detents 39 are pressed towards one another in aligned housings carried by 
the legs of U-shaped member 36 to hold cable loop 15 and coupling half 17 
in proper position for coupling engagement with the cylindrical male half 
32 of the tow line coupling 20. Cable loop 15 is manually pressed past 
balls 39 and cooperates with the bight portion at the inner end of the 
U-shaped member 36 in holding the cable loop and sphere 17 captive 
preparatory to coupling engagement with coupling member 32. 
Before leaving FIG. 12, it will be noted that a channel shaped guide rail 
40 with flaring sidewalls is welded to the bottom of trough 18. A pair of 
identical clamping assemblies 19 is slidable lengthwise of rail 40 and 
includes a pair of brackets 41 the upper ends 42 of which converge to 
loosely engage the sidewalls of rail 40. Ends 42 can be forced into snug 
clamping relation with rail 40 by tightening clamping bolts 43. Welded to 
the lower ends of brackets 41 is a V-shaped jaw 44 for receiving the 
horizontal flange of the tower cross frame 11. 
Referring to FIGS. 2-6, it will be observed that the outwardly flaring 
sidewalls of trough 18 converge and merge with a cylindrical section 49. 
The uppermost portion of these converging and cylindrical walls have a 
slot 30 accommodating both the tow line and tongue 31 of the female 
coupling 32 of the tow line. Accordingly, slot 30 permits tongue 31 to 
advance rearwardly until the two halves of coupling 20 are disengaged by 
means to be described presently. 
Cupped over and welded to the rear end of member 49 is an end cap 50 having 
two important principal functions, namely, uncoupling the halves of 
coupling 20 and releasably supporting the female coupling half 16 on the 
trailing end of cable loop 15. End cap 50 has a deep vertical slot 51 
through which the trailing section 22 of the hauling line drops when the 
helicopter manoeuvres coupling 20 between the positions associated with 
arrows A, B and C in FIG. 1. Extending upwardly and outwardly from the 
opposite sides of the aligned slots 30 and 51 are V-shaped guide horns 53, 
53 (FIGS. 2 and 3) supported by brace rods 54. These guide horns 
supplement the flaring sidewalls of trough 18 in guiding tow line 22 into 
trough 18 and assuring that the line enters slots 30 and 51 at the rear 
end thereof. 
The female coupling 16 of the cable loop, best shown in FIGS. 4, 5, 8 and 
9, has an elongated main body provided with an egg shaped socket 55 
opening through one lateral edge of its mid-length, as clearly appears 
from FIG. 8. One end of coupling 16 is secured to the trailing end of 
cable loop 15 and its opposite end is slotted at 56 from end to end of 
socket 55 thereby to freely pass the trailing end 22 of the tow line. The 
male coupling half 57 fixed to the forward end of hauling line 22 is 
admitted into socket 55 upon release from coupling 20 and is locked 
coupled thereto by a locking pawl 58 (FIG. 8). Pawl 58 is pivotally 
supported on a pin 59 extending crosswise of a passage 60 in the body of 
coupling member 16. A torsion spring 61 encircles pin 59 and urges pawl 58 
clockwise against a stop but permits the pawl to pivot counter-clockwise 
to admit sphere 57 into socket 55. 
The outer end of cap 50 is provided with a generally rectangular pocket 60 
loosely seating coupling 16 with the inlet of its socket 55 aligned with 
the axis of trough 18. As is best shown in FIGS. 5 and 9, coupling 16 is 
held releasably seated in socket 60 by spring biased ball detents seating 
in depressions 64 formed in the outer faces of coupling 16. 
The hauling line coupling 20 and its release mechanism will now be 
described by reference to FIGS. 4, 5, 8 and 9. This coupling comprises a 
cylindrical main body or female half 32 and a sperical male half 57. Half 
32 is tubular and formed from end-to-end with a keyhole passage including 
a bulbous central passage 68 sized to freely pass sphere 57 and with a 
slot 69 sized to freely pass cable loop 15. Slot 69 is diametrically 
opposite the hauling tongue 31 of coupling half 32 and permits the forward 
end of the cable loop to enter the forward end of slot 69 and to exit from 
its rear end. 
The means releasably retaining halves 32 and 57 coupled together comprises 
a pair of ball detents 70 held captively assembled in aligned radial 
passages 71 in the main body of coupling half 32 (FIG. 5). Normally detent 
balls 70 are held locked in their inwardly extended position shown in FIG. 
5 by a pair of locking pins 72 reciprocably supported lengthwise of half 
32 and spring biased outwardly by a spring 73. Assembly screws 74 project 
into elongated notches 75 in pins 72 and limit their reciprocal movement. 
Each pin is provided with a semi-spherical socket 77 positioned to receive 
detents 70 when the pins are shifted to the right as viewed in FIG. 5. A 
split bumper ring is fixed to the outer ends of pins 72 and are located in 
a shallow axial well 79 at the trailing end of coupling half 32. This well 
provides adequate room for the operation of pins 72 and bumper ring 78 and 
safeguards against the accidental and unintended movement of the bumper. 
The means for depressing bumper 78 and releasing female coupling member 57 
from coupling half 32 comprises a tubular member 81 forming an integral 
part of end cap 50 and in axial alignment with the central passage 68 of 
coupling 20 and the inlet of socket 55 of coupling member 16 attached to 
the cable loop. The forwardly projecting larger diameter end of tubular 
member 81 is positioned to engage bumper 78 as the coupling moves 
rearwardly and to cooperate therewith in guiding the coupling sphere 57 
through tube 81 and into the socket of coupling 16. 
OPERATION 
The operation of the automatic framed-opening threading device 10 will be 
readily apparent from the foregoing description of its components. Each 
stringing block or window frame to be threaded is equipped exteriorly and 
crosswise thereof with one of the threading devices 10 such as to the 
cross bar 11 of a power line tower. A cable loop 15 is installed at the 
opposite ends of the trough 18 with its male coupling member 17 installed 
at the leading end of the trough and its female coupling 16 gripped in 
pocket 60 at the trailing end of the trough as shown in FIG. 1. An aerial 
transport, such as helicopter 23, having tow line sections 21, 22 
connected by the separable coupling 20 in clear viewing range of the pilot 
is then advanced toward the framed opening to be threaded. When the 
helicopter has approached to the uppermost position shown in FIG. 1 with 
coupling 20 directly overlying the mid-portion of the trough, the pilot 
lowers the aircraft to deposit coupling 20 into the mid-portion of the 
trough. Guide horns 53, 53, channel line 22 into slots 30 and 51. At this 
point, the pilot manoeuvres the aircraft slowly rearward as indicated by 
arrow B allowing the tension in the tow line to carry coupling 20 
rearwardly in the trough, coupling 20 being guided by the converging rear 
end of the trough into tubular member 49. As the coupling approaches the 
tubular stop 81, bumper 78 engages the stop thereby depressing pins 72 
thereby permitting the male coupling half 57 of the tow line to expand the 
detent balls 70 outwardly into recesses 77 (FIG. 9). Coupling half 57 then 
passes rearwardly through the tubular stop 81 into the pocket 55 of the 
cable loop coupling 16. As the coupling 57 enters the pocket it rocks pawl 
58 (FIG. 8) counterclockwise whereupon string 61 immediately returns the 
pawl to its normal extended position to safeguard against separation of 
coupling halves 16 and 57. The weight and tension acting in the trailing 
end 22 of the tow line promptly releases coupling 16 from its retaining 
ball detents 63 (FIG. 5) and tensions the cable loop 15 the leading end of 
which continues to be held firmly captive in the leading end of trough 18. 
The pilot then reverses the helicopter as indicated by arrows C, C and 
shifts the craft horizontally forward thereby shifting female half 32 of 
the coupling forwardly. The converging sidewalls of trough 18 (FIG. 2) 
engage tongue 31 of coupling half 32 and guide it into slot 30 in an 
upright position thereby assuring that the keyhole passage 68, 69 is 
properly oriented to receive cable loop 15 and its male coupling half 17. 
Coupling 17 is held captive near the rear end of keyhole passage 68, 69 by 
detent balls 70 which are locked against retraction by pins 72 and springs 
73 (FIG. 5). Cable loop 15 is now fully inserted and locked assembled 
between tow line sections 21 and 22. This having been accomplished the 
pilot manoeuvres craft 23 forwardly in the direction indicated by arrow D 
thereby lifting coupling 20 upwardly out of the forward end of trough 18 
and releasing the cable loop 15 from the ball detents 39, 39 (FIGS. 10, 
11). 
The pilot now moves forwardly to the next closed frame or window equipped 
with one of the threading devices 10 thereby advancing the tow line 
through the throat of the first stringing block 13. The manoeuvring 
operations described above are then repeated to insert the cable loop 
preassembled to the next threading device whereupon the second cable loop 
is inserted between the female half 32 of coupling 20 and the leading end 
of the previous cable loop. 
While the particular apparatus and method of threading a closed framed 
opening by helicopters 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.