Patent Publication Number: US-2022239076-A1

Title: Electrically insulated boom mountable temporary conductor guard structure

Description:
TECHNICAL FIELD 
     The present disclosure relates to an electrically insulated, boom mountable temporary conductor guard structure for keeping sagging conductors from contacting anything below the conductors, such as personnel, vehicles, the ground, roads, other electrical circuits as they are strung between support structures, and to increase safety to personnel and equipment by electrically insulating or isolating the boom mountable temporary conductor guard structure. 
     BACKGROUND 
     High voltage transmission and distribution lines or circuits are typically strung between a series of spaced apart support structures which could be poles or towers. Other lines which are also strung between support structures include overhead shield, or static/ground wires and overhead fiber optic cables or optical ground wires (OPGW). In an energized environment, all of these lines are treated as being energized during reconductoring and re-stringing, and thus all of these lines are collectively referred to herein as conductors throughout the present disclosure. 
     The process of stringing conductors requires safeguards to protect personnel, vehicles, roads, railroads, paths, existing circuits, telephone, cable crossings, as well as existing infrastructure from conductors sagging down while stringing is in progress. Temporary guard structures are often used to provide such protection between the support structures at these areas or crossings. Temporary guard structures may be in the form of two or three vertical poles with a horizontal member between each pole, as illustrated in  FIG. 1A , generally used when stringing transmission conductors on an H-frame or similar support structure. 
     Alternatively, temporary guard structures can comprise a single pole with crossarms as illustrated in  FIG. 1B , generally used when stringing conductors on single pole support structures, usually in cases of lower voltage transmission or distribution circuits. 
     Often, onsite construction or erection of guard structures proves physically difficult or impractical due to location. In such cases, a crane or boom truck with a stringing traveler suspended from the winch line or a temporary support mounted to the end of the boom is employed. The stringing traveler holds the conductor being strung up in position not allowing it to sag below the stringing traveler.  FIG. 1C  illustrates an example of stringing travelers suspended from a crane or boom truck winch line, which are also used to protect roadways and distribution circuits below the stringing of a transmission line. The disadvantage of such arrangements is the stringing traveler tends to swing back and forth with the conductor in movement. 
     A boom mounted temporary conductor guard structure can also be used to catch and support the moving conductor if the tension in the conductor drops during stringing, preventing the conductor from contacting the ground or the existing infrastructure below the conductors being strung. 
     Stringing of a conductor that occurs in proximity or adjacent to energized lines requires treating the conductor being strung as energized due to the risk of induced voltage and current (induction). Induction in conductors in an energized zone can be significant and dangerous, if not fatal. In many cases, the voltage has been measured to be over 20,000 volts. 
     A failure in any of the payout tensioning equipment or breakage of the conductor, pulling line, or the like can result in the conductor losing the horizontal tension and sagging or falling to the ground. Typical guard structures and crane or boom truck mounted conductor guard structures protect objects and the area below from the electrical, physical, or mechanical dangers of the falling or sagging conductors. However, conductors can also become energized if they fall or contact under-built or electrical circuits below. This in turn can energize conductor guard structures or boom mounted conductor guard structures exposing personnel and equipment to dangerous voltage and current. 
     When stringing conductors in energized zones or if the conductor being strung contacts an energized circuit below, this may expose personnel and equipment to dangerous voltage and current. This danger can be fatal to personnel and damaging to equipment. 
     In the prior art applicant owns U.S. Pat. No. 9,038,989, entitled “Boom Mountable Robotic Arm” which teaches a boom mounted robotic arm for temporarily supporting conductors with a beam adapted for mounting onto the upper end of the boom and at least one electrically insulated support post mounted to the beam, where each post temporarily supports a conductor. 
     It is desirable that crane or boom truck mounted structures be at least somewhat collapsible, stowable, or removable for transportation. 
     SUMMARY 
     An electrically insulated boom-mountable temporary conductor guard structure is provided that is adapted to mount onto a distal end of a crane or truck boom. In one embodiment the electrically insulated boom mountable temporary conductor guard structure is mounted on the end of a crane or truck boom. The electrically insulated boom mountable temporary conductor guard structure includes a rigid U-shaped frame, wherein the U-shape is comprised of an elongate horizontal beam, generally horizontal when in an operative position, having a pair of upstanding stub arms, preferably of substantially equal length, extending upwardly and outwardly from the opposite ends of the horizontal beam. In one embodiment the length of the beam may be at least twice as long as the length of each of the stub arms so that the frame, when in use, is adapted to have a long laterally extending spread to catch and support sagging or dropped conductors which extend in a longitudinal direction perpendicular to the orientation of the beam. By way of example, the beam length may be six feet, or eight feet, or twelve feet long. An included angle between the stub arms and the elongate beam is in one embodiment at least 90 degrees, and in other embodiments may preferably be in the range of approximately 100 140 degrees. 
     Elongate, rigid, electrically conductive rollers are rotatably mounted to each of the stub arms and to the horizontal beam so as to form a continuous or substantially continuous rolling surface along the entire length of the inside or interior perimeter of the U-shaped frame for rotationally supporting the conductors supported thereon. The stub arms and their rollers lie in a first plane, and in one embodiment are offset and alongside so as to overlap the ends of the horizontal beam and its corresponding roller so that the first plane is adjacent and parallel to a second plane containing the horizontal beam and its roller. In a further embodiment, the rollers on the stub arms are in-line with the roller on the horizontal beam so that all three rollers and the U-shaped frame lie in a common plane. 
     The frame mounts onto the upper end of a substantially vertically disposed electrical insulator or plurality of electrical insulators. The lower end of the insulators mount onto the free end of the crane or truck boom, for example onto an adjustable base mounted onto the free end of the boom by a boom adaptor. 
     In a preferred embodiment the frame is mounted on a swivel plate mid-way along the underside of the beam. In on embodiment the swivel plate enables the horizontal beam to be rotated so that it is perpendicular to the conductors being strung. In another embodiment the swivel also allows the frame to be rotated and folded down onto the insulators for transport. The swivel plate is parallel to the frame&#39;s beam so that a first plane in which the swivel plate lies is parallel to a second plane containing the beam. 
     In a further preferred embodiment the frame is mounted in a support bracket or channel, collectively referred to as a mounting bracket, mounted on the swivel plate, and may be disconnected and removed from the swivel plate by removing bracket pins from the support bracket or channel, or may be mounted on the swivel by other quick-connect systems so that the frame can be removed. Once removed, the frame may be stored for transport rather than folded down along the insulators, and the frame may be removed and a frame of different length substituted. Removing the frame from the swivel plate allows for frames having different length beams to be used based on, for example, lateral support length requirements and configuration of the circuits being strung. Removing the frame from the swivel plate further allows for swapping out the frame and substituting other accessories such as a stringing traveller mounted on a support so as to be directly above and adjacent to the swivel plate. 
     A method is further provided for temporarily protecting a conductor as it is strung between one or more support structures. The method comprises the steps of:
         a. mounting the above described frame of an electrically insulated boom mountable temporary conductor guard structure on top of electrical insulators, and positioning the electrically insulated boom mountable temporary conductor guard structure below the location of a conductor to be, or being, strung;   b. rotating the frame on the swivel as necessary so that the frame is perpendicular to the conductor;   c. as necessary, supporting a sagging or dropped conductor on the rigid, electrically conductive rollers on the frame as the conductor is strung so as to electrically insulate the sagging or dropped conductor from at least the crane or truck boom and the ground or personnel.       

     A method is also provided of deploying and stowing the fold-for-storage embodiment of the electrically insulated boom mountable temporary conductor guard structure described above between its elevated in-use position and its storage and transport position on the crane or boom truck. The method includes the steps of:
         a. with the electrically insulated boom mountable temporary conductor guard structure in its elevated in-use position, stowing the electrically insulated boom mountable temporary conductor guard structure by lowering the boom to lower the electrically insulated boom mountable temporary conductor guard structure until it is adjacent the crane or truck boom;   b. pivoting the U-shaped frame and the swivel plate on which the frame is mounted to align the surface of swivel plate opposite the frame flush along the insulators; and   c. rotating the frame on its swivel plate until the beam of the frame is parallel to the longitudinal axis of the insulators.       

     It is to be understood that other aspects of the present disclosure will become readily apparent to those skilled in the art from the following detailed description, wherein various embodiments of the disclosure are shown and described by way of illustration. As will be realized, the disclosure is capable of other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present disclosure. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A further, detailed, description of the disclosure, briefly described above, will follow by reference to the following drawings of specific embodiments of the disclosure. The drawings depict only typical embodiments of the disclosure and are therefore not to be considered limiting of its scope. In the drawings: 
         FIG. 1A  and  FIG. 1B  are elevation views of prior art temporary guard structures; 
         FIG. 1C  is an elevation view of a stringing traveler suspended from a crane or truck boom winch line holding the conductor up; 
         FIG. 2A  is, in side elevation view, enlarged from  FIG. 3 , a first embodiment of an electrically insulated boom mountable temporary conductor guard structure wherein the conductor guard structure frame is removable from the swivel plate for storage; 
         FIG. 2B  is, in front elevation view, the first embodiment of  FIG. 2A ; 
         FIG. 2C  is, in side elevation view, a second embodiment of an electrically insulated boom mountable temporary conductor guard structure wherein the guard structure is mounted to the swivel plate; 
         FIG. 2D  is, in rear perspective view, the second embodiment of  FIG. 2C ; 
         FIG. 3  is an elevation view of a stringing arrangement including the electrically insulated boom mountable temporary conductor guard structure of  FIG. 2A ; 
         FIG. 4  perspective view of the electrically insulated boom mountable temporary conductor guard structure of  FIG. 2C  in a storage and transport position mounted on a crane or truck boom; 
         FIG. 5  is a side elevation view of  FIG. 4 ; 
         FIG. 6  is a bottom perspective view of the electrically insulated boom mountable temporary conductor guard structure of  FIG. 2C ; 
         FIG. 7  is perspective view of the electrically insulated boom mountable temporary conductor guard structure of  FIG. 2C , in a storage and transport position; 
         FIG. 8  is a front perspective view of the second embodiment of an electrically insulated boom mountable temporary conductor guard structure of  FIG. 2A ; 
         FIG. 9  is a partially exploded perspective view of the electrically insulated boom mountable temporary conductor guard structure of  FIG. 8  showing the frame removed from the swivel plate; 
         FIG. 10  is a partially cut-away enlarged bottom perspective view of the swivel plate and mounting bracket of the electrically insulated boom mountable temporary conductor guard structure of  FIG. 8 ; 
         FIG. 11A  is a side elevation view of the swivel plate and mounting bracket of the electrically insulated boom mountable temporary conductor guard structure of  FIG. 8 ; 
         FIG. 11B  is a top plan view of the swivel plate and mounting bracket of the electrically insulated boom mountable temporary conductor guard structure of  FIG. 8 ; 
         FIG. 11C  is an end elevation view of the swivel plate and mounting bracket of the electrically insulated boom mountable temporary conductor guard structure of  FIG. 8 ; 
         FIG. 12  is a perspective view of the electrically insulated boom mountable temporary conductor guard structure of  FIG. 8  with the frame having been removed from the swivel plate and substituted with a removable stringing traveler on an adaptor support. 
         FIG. 13  is, in elevation view, a partially cutaway, enlarged view of a portion of the embodiment of the electrically insulated boom mountable temporary conductor guard structure of  FIG. 14A . 
         FIG. 14  is, in perspective view, a partially cutaway end portion of one end of the U-shaped frame and rollers of a further embodiment of the electrically insulated boom mountable temporary conductor guard structure wherein the electrically conductive rollers are mounted in-line on both ends of the U-shaped frame. 
         FIG. 14A  is, in elevation view, the embodiment of  FIG. 14 . 
         FIG. 14B  is, in plan view, the embodiment of  FIG. 14 . 
         FIG. 15  is, in perspective view, a further embodiment having a non-hydraulic angularly adjustable adapter for mounting the electrically insulated boom mountable temporary conductor guard structure and insulators onto the end of a crane or truck boom. 
         FIG. 15A  is, in elevation view, the embodiment of  FIG. 15 . 
         FIG. 16  is, in perspective view, the adapter base of  FIG. 15 . 
         FIG. 17  is, in perspective view, the insulator adapter of  FIG. 15 . 
         FIG. 17A  is, in elevation view, the adapter base coupled to the insulator adapter so as to maintain the insulators vertical when the crane or truck boom is at a 20 degree angle. 
         FIG. 17B  is, in elevation view, the adapter base coupled to the insulator adapter so as to maintain the insulators vertical when the crane or truck boom is at a 45 degree angle. 
         FIG. 17C  is, in elevation view, the adapter base coupled to the insulator adapter so as to maintain the insulators vertical when the crane or truck boom is at a 80 degree angle. 
         FIG. 17D  is, in side elevation view, the adapter base oriented with the orientation locking apertures uppermost. 
         FIG. 17E  is, in side elevation view, the adapter base oriented with the orientation locking apertures lowermost. 
     
    
    
     The drawings are not necessarily to scale and in some instances, proportions may have been exaggerated in order to more clearly depict certain features. 
     DETAILED DESCRIPTION 
     The description that follows and the embodiments described therein are provided by way of illustration of examples of particular embodiments of the principles of various aspects of the present disclosure. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the disclosure in its various aspects. 
     Prior art conductor guard structures are illustrated in  FIG. 1A  and  FIG. 1B  wherein sagging conductors are caught and supported on rigid horizontal elevated members. Prior art stringing travellers suspended from a winch line while elevated and supported on a crane or truck boom are seen illustrated in  FIG. 1C . 
     The present disclosure relates to embodiments by way of example of improved conductor guard structures and in particular to electrically insulated boom mountable temporary conductor guard structures for catching and supporting sagging or dropped conductors during stringing operations. The structure is referred to herein as a conductor guard structure or conductor guard. As seen in  FIG. 2  and  FIG. 3 , the electrically insulated boom mountable temporary conductor guard structure is mountable to a crane-or truck boom so that, with the conductor guard structure elevated on the end of the crane or truck boom and with the conductor guard structure in its operative position and orientation as better described below, the conductor guard structure provides support to one or more sagging conductors as they are being strung onto and between support structures such as poles or towers. The electrically insulated boom mountable temporary conductor guard structure also provides for support to a dropped conductor, for example which fails or otherwise loses its tension and falls between its support structures. 
     As better seen in  FIG. 2 , the electrically insulated boom mountable temporary conductor guard structure includes a rigid somewhat U-shaped frame, wherein the U-shaped frame is comprised of an elongate horizontal beam having uprights at its ends. The horizontal beam, when in its operative position, is substantially horizontal and square or perpendicular to the conductor under which the conductor guard structure is positioned. The pair of uprights at the ends of the horizontal beam are preferably of substantially equal lengths, and preferably angled upwardly and outwardly relative to the ends of the horizontal beam. The uprights may be stub arms such as illustrated. The uprights are, with out intending to be limiting, collectively referred to herein as stub arms extending upwardly and outwardly from the ends of the horizontal beam. Advantageously the pair of stub arms lie in a common plane, preferably vertical, containing only the stub arms or containing the stub arms and the horizontal beam. In the illustrated embodiment of  FIG. 2A  to  FIG. 12 , only the stub arms are contained in the common plane. In that embodiment the common plane containing the pair of stub arms is adjacent to a vertical plane containing the horizontal beam. In the embodiment of  FIG. 13 , the pair of stub arms and horizontal beam lie in the same plane. 
     The length of the horizontal beam may be at least twice as long, and advantageously longer, than the length of each of the stub arms so that, collectively, the frame, when in use, is adapted to have a long lateral spread to catch and support longitudinally extending sagging conductors. For example, and without intending to be limiting, the horizontal beam may be six, eight or twelve feet long. 
     Elongate, rigid, electrically conductive rollers are rotatably mounted to each of the stub arms and to the horizontal beam so as to form a continuous electrically conductive rolling surface along the inside perimeter of the U-shape of the frame for rotationally supporting the sagging or dropped conductors supported thereon. Thus as the conductors supported on the rollers moves longitudinally relative to the U-shaped frame, the rollers rotate so as to maintain contact with the conductor or conductors without the conductors longitudinally sliding over the rollers. The rollers are advantageously tubular, electrically conductive, and may be metallic, for example made of aluminum, or externally coated in aluminum. 
     The U-shaped frame mounts onto the upper end of a generally vertically disposed electrical insulator or plurality of electrical insulators such as the pair of insulators illustrated. The lower end of the insulators mount onto the free end of the crane or truck boom, for example onto a base, such as illustrated, mounted onto the free end of the crane or truck boom by a boom adaptor. The base may be pivotally mounted onto the boom adaptor and have a selectively actuable actuator, such as the hydraulic cylinder illustrated, cooperating between the base and boom adaptor for selectively adjusting the angle of the vertical insulators relative to vertical or relative to the boom. Alternatively, the insulators can be mounted to an insulator adapter connected to an adapter base and adjusted by lining up holes to maintain the insulators in vertical position and inserting the locking pin as shown in  FIG. 15  and  FIG. 15A . 
     An example of the electrically insulated boom mountable temporary conductor guard structure of  FIG. 2A  in use is seen in  FIG. 3 . Thus a roadway running under the conductor or conductors under which the conductor guard structure is positioned is protected from contact with the conductors if they sag or drop. 
     As seen in  FIG. 4  and  FIG. 5 , the electrically insulated boom mountable temporary conductor guard structure  2  is mountable to a crane or truck boom  4  of a crane or boom truck  6  so as to, in one embodiment, be folded down alongside the insulators for storage during travel of the truck. In a preferred embodiment of a system incorporating electrically insulated boom mountable temporary conductor guard structure  2 , the conductor guard structure  2  is mounted to base  8 , which in turn is mounted on the crane or truck boom  4 . Examples of a suitable base  8  can be seen in Applicant&#39;s U.S. Pat. No. 6,837,671, incorporated herein by reference, although other forms of the base or like structures will work as would be known by one skilled in the art. Base  8  may include an elongate platform  8   a  having a leveling mechanism  10 , such as the hydraulic cylinder actuator illustrated, pivotally mounted on the upper end of a boom adaptor, to selectively orient the platform  8   a  to the horizontal in order to position the pair of insulators  24  vertically so as to best support heavy loading in compression. Other levelling mechanisms  10  can include, without intending to be limiting, a scissor linkage such as seen in Applicant&#39;s U.S. Pat. No. 8,226,069, also incorporated herein by reference, or an adjustable non-hydraulic adapter as shown in  FIG. 15  and  FIG. 15A . 
     In the embodiments of  FIG. 2A  to  FIG. 2D , U-shaped support frame  14  includes elongate horizontal beam  16  and a pair of, upstanding and outwardly extending stub arms  18  mounted at either end thereof and off-set therefrom so as to be alongside beam  16 , for catching and supporting the conductors  100  if they drop or as they sag down for example while they are being strung. The length of the stub arms  18  and their included angle (angle A as illustrated) relative to the beam  16  can vary depending on nature of the stringing operation. Stub arms  18  may extend laterally outwardly from the ends of beam  16 , or may be vertically oriented. 
     Although various lengths of beam  16  may be employed, applicant has found that it is advantageous for the beam to be long enough to ensure that a conductor being strung is supported in the event of dropping or excessive sagging of the conductor when the conductor guard structure  2  is positioned below the conductor being strung. For example, and without intending to be limiting, the length of the beam  16  may be from four to fourteen feet, and in some instances preferably six, eight or twelve feet long. 
     As illustrated, in one embodiment not intended to be limiting, stub arms  18  may be approximately 36 inches or less in length. Stub arms  18  may be rigidly or removably affixed to the ends of beam  16  so as to extend for example vertically upward, or for example so as to extend by approximately zero to 30 degrees off vertical, outwardly oriented relative to one another to extend the lateral reach of the conductor support. The role of the stub arms  18  is to guide and maintain the conductors  100  such as seen in  FIG. 3  within the U-shaped frame  14 . Thus the stub arms  18  may be longer or shorter than depicted, and inclined at greater or lesser angular inclinations and not affect the use of the stub arms  18  to assist in the capture of conductors  100  and the maintenance of the conductors  100  within frame  14 . 
     In a further alternative embodiment, the two included angles A between the pair of stub arms  18  and the elongate beam  16  are each selectively adjustable at the intersections or elbows  28  between the stub arms  18  and the beam  16  by for example pivoting, hinged, bolted or pinned connections (not shown) or other rotatable connection having a locking mechanism to maintain the desired angular orientation between the stub arms  18  and the elongate beam  16 . Further optionally, the length of the stub arms  18  can be adjusted by the provision of telescoping stub arms  18  (not shown) or modular stub arms  18  (not shown) that can be connected to one another lengthwise to achieve a desired length. 
     The elongate beam  16  and each of the stub arms  18  rotatably support corresponding elongate rollers  20   a  and  20   b  respectively along their lengths. The three rollers; roller  20   a  along beam  16  and rollers  20   b  along the stub arms  18 , extend adjacent and parallel to beam  16 , and to the two stub arms  18  respectively so as to form a continuous or substantially continuous electrically conductive roller surface around the inside perimeter of the U-shaped frame  14 . The inside perimeter extends along and has a length illustrated by way of example in  FIG. 9 . The ends of rollers  20   a  and  20   b  may be mounted in bearings such as illustrated in the embodiment of  FIG. 2A  so that the rollers roll about their axes of rotation with movement of the conductor  100  being pulled over the rollers as the conductor  100  is strung between support structures  102 . Rollers  20   a  and  20   b  reduce damage and wear on the conductor as the conductor  100  travels over the U-shaped frame  14 . 
     The rollers  20   a  and  20   b  are electrically conductive, in contrast to rollers found in the prior art having surfaces of rubber or metal impregnated rubber material, as applicant has found that such prior art rollers tend to heat up and may burn or melt due to charging current when supporting an energized conductor. The rollers according to the present disclosure are rigid and are made from electrically conductive material such as metals including aluminum or steel, or from conductive composites such as Kevlar™ having metal threading woven or otherwise embedded into it. The electrically conductive rollers  20   a  and  20   b  serve to conduct charging current flowing to the U-shaped frame  14 . Applicant has found that this significantly reduces or eliminates the buzzing and burning that applicant has observed tends to occur when dielectric rollers are used. 
     In embodiments where the angle of the stub arms  18  is adjustable relative to the elongate beam  16 , the rollers  20   b  of each stub arm  18 , because they are mounted on their respective stub arms  18 , move simultaneously with the angular adjustment of their respective stub arms  18  to selectively adjust included angle A. 
     In embodiments where the length of the stub arms  18  is adjustable by means of telescoping or modular design (not shown), then the rollers  20   b  associated with each stub arm  18  are also advantageously either telescopic or part of each modular stub arm  18 . 
     Alternatively, as illustrated in  FIG. 2A , the lower ends of rollers  20   b  may be offset from and overlap with the ends of roller  20   a  to prevent any gaps between the ends of the rollers at intersections  28 . These arrangements ensure that the conductor  100  is always supported on the rollers  20   a  and  20   b  and is prevented from falling in between the ends of rollers  20   a  and  20   b , which would possibly damage the conductor and/or the frame. 
     The elongate beam  16  of the U-shaped support frame  14  may preferably be mounted to or on a rotatable swivel  22  which swivels to allow the opening of the U-shaped frame  14 , which extends between stub arms  18  along the length of beam  16 , to be oriented to be perpendicular relative to the conductors so as to squarely face, receive and support the conductors  100  when the conductor guard structure  2  is required and positioned for use. The U-shaped frame  14  is selectively rotatable on the swivel so as to be perpendicular to the conductor  100 , to provide the best protection in case a conductor sags or drops, and so that the crane or boom truck may be parked in a convenient location and position relative to the conductor  100  so long as the boom can be positioned under the conductor. 
     In a fold-away-for-storage embodiment such as seen in  FIG. 4 , swivel  22  optionally also rotates to position the conductor guard structure  2  in a more compact orientation for storage and transport when the boom  4  is lowered. 
     With reference to  FIG. 10 , in one embodiment the swivel  22  comprises an upper and lower swivel plate  22   a  and  22   b  sandwiching a bushing  22   c . The bushing can be made of Nylatron, which applicant believes is a commercially available material made of a molybdenum disulphide-filled Nylon™, wherein Nylon™ refers to a family of synthetic polymers, based on aliphatic or semi-aromatic polyamides. Other materials or roller bearings may also be used for the bushing as would be known to one skilled in the art. 
     In a preferred embodiment, the conductor guard structure  2  has at least one, and preferably at least two station class electrical insulators  24  mounted to, so as to extend vertically between, the U-shaped frame  14  and platform  8   a  on base  8 . Base  8  is mounted on the free or distal end of crane or truck boom  4 , for example by means of a boom adaptor. More particularly, insulators  24  are, at their lower ends, mounted on platform  8   a  or insulator base  36  and at their upper ends mounted to swivel  22 . Swivel  22  is mounted under and to beam  16 , centered between the stub arms  18 . Swivel  22  may be releasably or fixedly mounted under beam  16 . Insulators  24  electrically isolate electrically insulated boom mountable temporary conductor guard structure  2  from crane or truck boom  4 . Since rollers  20   a  and  20   b  are electrically conductive, the insulators  24  provide the sole electrical isolation between conductor guard structure  2  and crane or truck boom  4 . In the energized stringing environment, the insulators  24  serve to eliminate the formation of a second ground point should the payout tensioning or pulling equipment fail causing the conductors to drop, or the conductors  100  otherwise sag down too low. This in turn eliminates the risk of creating a circulating current. 
     The use of electrical insulators between the electrically insulated boom mountable temporary conductor guard structure  2  and the crane or truck boom  4  electrically insulates and isolates the crane or boom truck from the conductor. The U-shaped frame  14  is thus electrically insulated from the crane or boom truck  6  which is critical when stringing conductors  100  in energized conditions and inhibiting the dangerous hazard of electrical current traveling down the crane or truck boom  4 . This provides increased safety to personnel, public and equipment. 
     With reference to  FIG. 2A  through  FIG. 2D, and 4 through 7 , in one embodiment the electrically insulated boom mountable temporary conductor guard structure  2  may, as mentioned above, advantageously fold against the insulators  24  for storage and transport. A pivot connection  26  may thus be provided between the insulators  24  and the swivel  22  to allow pivoting of the U-shaped frame  14  and swivel  22  relative a longitudinal axis of the insulators  24  from an in use position as illustrated in  FIG. 2A  to  FIG. 2D  and  FIG. 6  to a storage and transport position as illustrated in  FIG. 4 ,  FIG. 5  and  FIG. 7 . In this way, the swivel  22  and U-shaped frame  14  can be pivoted such that swivel  22  is relatively flush so as to be substantially parallel to and along a longitudinal axis of the insulators  24 . The swivel  22  can also be rotated to rotate frame  14  such that beam  16  is also parallel to a longitudinal axis of the insulators  24 . 
     In a further embodiment, as illustrated in  FIG. 2A ,  FIG. 2B , and  FIG. 8  to  FIG. 11 , the U-shaped frame  14  is removably mounted to the swivel  22  by means of a channel-shaped mounting bracket  30 . As seen in  FIG. 9 , elongate beam  16  is removably affixable to the mounting bracket  30 , for example by the pins illustrated, such that the U-shaped frame  14  can be removed from the rest of the conductor guard structure  2  for transport, storage or for replacement of the U-shaped frame  14  with another U-shaped frame  14  of different dimensions, as may be required based on conductor stringing conditions. 
     In the embodiment of  FIG. 9 , beam  16  may have one or more holes  16   a  formed therein through which one or more bolts, rods, bracket pins or other elongate members  30   a  of the mounting bracket  30  can pass to releasably mount the U-shaped frame  14  to the mounting bracket  30 , and hence to the swivel  22 . 
     In a further embodiment, the stub arms  18  can be rotated about their hinged or pinned connections (not shown) at elbows  28  such that the stub arms  18  are flush along beam  16  for storage and transportation. 
     In a further embodiment seen in  FIG. 12 , elongate beam  16  may be removed from the mounting bracket  30  and an adapter  32  supporting a stringing traveler  34  may be substituted if required to keep the conductor  100  up at a fixed position and height as is sometimes required in stringing situations in tight spaces. Another advantage of using a stringing traveler  34  on an adaptor  32  so as to position the stringing traveler  34  closely adjacent, and closely under the cantilevered arm  32   a  suspending the stringing traveler approximately centered over the swivel  22  is to reduce swinging of the stringing traveler as compared for example to when the stringing traveler is suspended on a winch line from a crane or truck boom such as seen in  FIG. 1C . Adaptor  32  mounts into mounting bracket  30  by the snug fit therein of base member  32   b.    
     The use of mounting bracket  30  also provides for ease of removing a first U-shaped frame  14  of a conductor guard structure from mounting bracket  30  so as to replace it with a second U-shaped frame of a conductor guard structure having a beam  16  of a different length. In this fashion, the length of beams  16  may be changed to accommodate different stringing situations. 
     Returning now to the embodiment of  FIG. 4  to  FIG. 7 ; to shift the electrically insulated boom mountable temporary conductor guard structure  2  from an in-use position to a storage position for transportation, the boom  4  is first lowered to lower the conductor guard structure  2  to the crane or boom truck  6 . The swivel  22  and U-shaped frame  14  are pivoted about pivot connection  26  to align the swivel  22  parallel with the longitudinal axes of the insulators  24 , and the swivel  22  is rotated until beam  16  is parallel to the longitudinal axes of the insulators  24 . Optionally, in embodiments which accommodate it, the stub arms  18  are rotated about their hinged connections at elbows  28  until the stub arms  18  are flush along beam  16 . The reverse order of these steps are taken to erect the conductor guard structure  2  from its storage position to its in-use position. 
     In the case of the embodiment of  FIG. 8  to  FIG. 11 , for travel or storage the U-shaped frame  14  is removed from swivel  22  by removal of the one or more bracket pins  30   a  to release beam  16  from the mounting bracket  30 . This allows the U-shaped frame  14  to be stored for example on the crane or boom truck  6 . 
     Conductor guard structure  2  is thus positionable and operative to capture and support dropped or sagging conductors  100  during stringing operations and provides ease of storage for transportation on the crane or boom truck  6 . 
     In an alternative embodiment, not intended to be limiting, and as illustrated in  FIG. 13  and  FIG. 14 , the lower ends of rollers  20   b  and the ends of roller  20   a  may be very closely adjacent having for example a small gap  28   a  between their adjacent ends in elbows  28 . In the embodiment of  FIG. 13 , rollers  20   b  and stub arms  18  are coplanar with roller  20   a  and beam  16 , so as to effectively seamlessly extend the inside perimeter roller surfaces around, and in-line, so as to protect the conductor within the interior perimeter of U-shaped frame  14 . 
       FIG. 15  illustrates a further embodiment of an adjustable adapter for supporting the insulators and temporary guard structure according to the present disclosure. Instead of using the illustrated base  8   a  pivotally mounted on adapter  8  and angularly adjustable by hydraulic cylinder  10  as illustrated for example in  FIG. 2D , a manually selectively and releasably lockable, angularly adjustable adapter is provided for mounting the insulators and electrically insulated boom mountable temporary conductor guard structures according to the present disclosure onto the end of a crane or truck boom. U-shaped frame  14  is mounted on insulators  24 , which are mounted on insulator adapter  36 , which is mounted on adapter base  38 , which is mounted on crane boom adapter  40  (by pins  44 ), which is mounted on the end of the crane or truck boom (not shown in  FIG. 15 ). 
     In particular, insulators  24  are mounted on base plate  36   a  of insulator adapter  36 . Base plate  36   a  is mounted on a pair of parallel, spaced apart generally identical pivot plates  36   b  mounted orthogonally under base plate  36   a  as better seen in  FIG. 17 . Bolt holes  36   c  are provided in base plate  36   a  for mounting insulators  24 . Pivot apertures  36   d  are positioned identically on both pivot plates  36   b  for supporting a pivot pin  42   a  journaled therethrough. Adapter base  38  has corresponding pivot apertures  38   c  in side plates  38   a  also for having pivot pin  42   a  journaled therethrough. Side plates  38   a  are parallel and held rigidly spaced apart by perpendicular plates  38   b . Pivot pin  42   a  provides a rotation point for coupling insulator adapter  36  to adapter base  38  and a hinge constraining insulators  24  and U-shaped frame  14  to pivot about axis C. Axis C is parallel to and under plate  36   a  and perpendicular to the longitudinal axis of the crane or truck boom (not shown in  FIG. 15 ) so that rotation of insulators  24  and U-shaped frame  14  about axis C is in a vertical plane containing the longitudinal axis of the crane or truck boom. 
     The angular orientation of plate  36   a  relative to adapter base  38  is selected and releasably locked into the desired orientation by pivoting insulator adapter  36  about pivot pin  42   a  so as to align a pair of orientation locking apertures  36   e  on pivot plates  36   b  on insulator adapter  36  with a pair of orientation locking apertures  38   d  on side plates  38   a  on adapter base  38 , and sliding a locking pin  42   b  through aligned apertures  36   e  and  38   d . To re-orient insulator adapter  36  relative to adapter base  38 , locking pin  42   b  is removed, then insulator adapter  36  pivoted about pivot pin  42   a  until the desired re-oriented locking apertures  36   e  are aligned with the re-oriented locking apertures  38   d , and locking pin  42   b  then reinserted through the locking apertures. Thus, in the examples illustrated in  FIG. 17A  to  FIG. 17C , which are not intended to be limiting, insulator adapter  36  is shown pivoted relative to adapter base  38  to form crane or truck boom angles of 20 degrees, 45 degrees, and 80 degrees respectively as measured from horizontal. 
     The range of angular orientations for a crane or truck boom from a low boom angle of 20 degrees to a high boom angle of 80 degrees in 5 degree increments is afforded by the orienting of locking apertures  36   e  with locking apertures  38   d , and then fixing that orientation by insertion of locking pin  42   b , may be extended by turning adapter base  38  over so that, to extend the range of the crane or truck boom angles while keeping the insulators vertical, and as seen in  FIG. 17D , adapter base is oriented with the locking apertures  38   d  uppermost, and so that, to extend the range downwardly to decrease the crane or truck boom angle to its limits, and as seen in  FIG. 17E , adapter base  38  is oriented with locking apertures  38   d  lowermost. 
     The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article “a” or “an” is not intended to mean “one and only one” unless specifically so stated, but rather “one or more”. All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.