US2541788A - Safety grounding device - Google Patents

Description

1951 A. .s. STQVER fi fi SAFETY GROUNDING DEVICE Filed March 27, 1946 INVENTOR AT TORPIEX Patented Feb. 13, 1951 UNITED STATES PATENT OFFICE SAFETY GROUNDING DEVICE Albert J. Stover, Attalla, Ala.

Application March 27, 1946, Serial No. 657,411 6 Claims. (01. imp-1c) This invention relates to improvements in safety grounding devices, sometimes known as live line sticks, being designed to protect linemen while working on energized conductors, either single phase or three-phase.

In connection with electrical circuits, and especially with systems operating under high tension conditions, it is always dangerous for linemen in making repairs, etc., since it is the general practice to have one or two members of the crew work at the top of the supporting pole and a considerable distance from the ground; should such linemen come in contact with a live or hot" wire, the effect is extremely serious. In early days, the practice had been to throw a metallic line or chain across the wires for the purpose of short-circuiting the system to permit other members of the crew to reach the top of the pole in an effort to resuscitate the affected linemanthe short-circuiting of the lines of the particular zone made it safe for the crew members to provide the resuscitation at the top of the pole. In providing the protective short-circuit, a reaction result was to burn out one or more of the lines.

Later, devices were developed for the purpose of providing the short-circuiting operation more rapidly to enable the afiected lineman to be reached earlier, thus enabling the crew to provide an earlier administration of the pole top resuscitation. A number of different forms of such devices, commonly known as live line sticks have been developed, but these have generally been of such type that the arcing, which generall takes place at the instant of short-circuit, does so in the open, and since it is in the vicinity of the lines, liability of damaging or'burning out one or more of the lines is present as in the earlier practice.

The present invention belongs to such type of devices and has for its objects not only the provision of a structure which will operate rapidly when required, but in which any arcing that may take place will be within a practically closed compartment remote from the line wires, and in' such way that the crew members--as well as the linesmay not be affected thereby. In addition, the invention aims to produce these results with an assemblage of comparatively simple form and In the accompanying drawings, similar reference characters parts in each of the Views- Figure 1 is a schematic perspective view of the invention installed on a transmission line pole;

Figure 2 is a vertical longitudinal sectional view of the invention with the parts in inactive position;

Figure 3 in which indicate similar is a similar view with the parts in the short-circuiting position;

Figure 4 is a section on line 4--4 of Fig. 2;

Figure 5 is a cross-sectional View taken on line 55 of Fig. 2; and

. Figure 6, is a detail cross-sectional view on an enlarged scale of one form of supporting rod for a movable Contact.

Figure 7 is a vertical sectional view, partly broken away, of a support for the movable contacts wherein the bod is of insulating material, and

Figure 8 is a View similar to Figure '7 wherein the support is of a suitable metal being provided with an insulated liner.

Where the tranmission or power lines are of the high tension type, and especially where they are of multi-phase type such as three-phase installations, the individual lines must be so arranged as to prevent leakage from one line to another, clue to the fact that there is a potential diiierence between the lines owing to the phase characteristic. Transmission lines are generally in open country, and carried by poles, the leakage between lines being prevented by so spacing the lines relative to each other as to provide an air gap sufficiently great as to constitute the gap as air insulation for preventing the leakage; the higher the voltage value of the line, the greater becomes this distance. Possibly this condition may have formed the basis for the use of apparatus in which the short-circuiting arc will take place in the open; since these devices are set up each time the crew is active at the top of the pole and may remain entirely inactive during the crew operations, the air gap insulation spacing needs to be maintained, and if provided within a closed structure, the latter would assuredly be of such dimensions as to be more or less prohibitive for the service.

The present invention is designed to provide an enclosed zone within which any arcing that may occur is confined. In practice this portion of the apparatus is in the form of a tubular member of suitable cross sectionpreferably cylindrical-and formed of suitable insulating 3 material, the member having a length of approximately six Ieet with a diameter or approximately three inches, both ends or the tube being closed, these dimensions being those for the apparatus which is used where the line spacing is that generaily employed; where the apparatus is designed for use with a transmission system of considerably higher tensioned values, the dimensions of the tube are necessarily increased, since the tube, interiorly, has contacts which are opei-atively connected with the several lines, and inasmuch as these contacts are subject to the same conditions as are present in the overland lines, provision must be made to p1'ov1de for a corresponding air gap condition, so that the length and mameter OI the tube will depend somewhat upon the particular service 101 which it is designed. The tube is indicated at in and has u per and lower ends Ii and I2, respectively, these ends also being of insulating material.

Since the apparatus is usable with either single phase or three-phase operations, the upper end zone or the tube is provided with three contacts I'd, i4 and I5, these being secured to the tube walls, contact Ia being located centrally or the end wall II and having its sharia promoting through such wall to permit or securing thereto or a conductor which is uusiguefl to lead to one or the transmission lines; Bills contact being lUCameRl at the end or the tube, has the race which rorins the au'tlve contacting lace extending preieraoly on a plane parallel with the end wall and thus lacing; the length or the interior of the tube.

Contacts I4 and is are generally similar to contact is, but being secured to the side wall of the tube, have their stems extending laterally instead or longitudinally, the race forming the active contact race being formed to also face downwardly 111 the tube. Contacts It and la are located at opposite sides or the tube, with the locations such as to present the desired distance of the air gap represented by the length dimension of the tube; in the form shown, this distance is approximately ten inches in the length of the tube, this distance representing the distance between the contact face of contact I3 and that of contact IA. The distance between contacts I4 and i5 is substantially the same as that indicated, these distances conforming somewhat to the length of the gaps between lines of the overland lines.

The three contacts referred to are connected with what are known as the live lines of the overland system, each contact having an individual conductor, indicated at It, which is designed to be brought into intimate contact with the live line with which it is to be used. While it would be poisible to utilize a special line-engaging structure at the free end of each of the connections Iii-and such use is contemplated within the invention-such structure is less essential with the present invention, due to the fact that the arcing, when present, takes place remote from the point at which the connection is secured to the live line. Hence, the connection may be by simply making an ordinary splicing connection between the end of connection It and the live line, the opposite end of each connection being secured to the external portion of the stem of the internal contacts referred to. Since the contacts I3, I I, I5 are themselves spaced by the air gap conditions, it is apparent that the connection I6 may be secured to the respective live lines without disturbing the operation of the overland system, since the contact ends are so related as to be entirely inactive under these conditions, becoming active only when the contacts are closed, as presently described.

Mounted within the tube is a member I! which may be of inverted cup-form to provide for an extended surface such as will tend to prevent canting; member I! is designed to carry three contacts I8, I9 and 20 which are mounted at the upper ends of rod members 2|, the lower ends of which are secured to member I1 and rise from the upper surface thereof. The length of the rods 2I differs in connection with the three contacts and will depend upon the length of the throw designed for the movable member of the apparatus, the length of throw being the same in connection with each rod, the difference in length conforming to the distances between the contacts I3, I4 and I5. The rod of contact I8 is of the greatest length and is located central of member ll; this contact cooperates with contact I3. Contact I9 is in alinement with contact I4--with which it is to cooperate-while contact 20 is alined with contact I5 with which it is to cooperate. As indicated, the distances which represent the spec-- ing of contacts lengthwise of the tube will conform to those of contacts I3, I l and I5, and would be the ten inches referred to in connection with the latter contacts. In the particular form indicated, the length of throw referred to would approximate thirty inches, a distance which places contact I8 an equal distance (approximately ten inches) below contact I 5 which is the lowermost of the fixed contacts, thus preserving the gap characteristic which serves as insulation.

The contacts I8, I9 and 26 are raised into direct and complete contact with the fixed contacts I3, I 4 and I5 by means of a spring 22 mounted below member I1. The spring is of extended length and is of sufficient length and power to rapidly move the cup the distance required to shift the movable contacts from inactive to active positions. The lower end of the spring rests upon the lower end of the casing, and in its inactive position is necessarily under high compression, due to the length of the throw which it must provide. The upper end of the spring lies within the cup of member II. If the cup is metallic, the cup will have suitable insulation therein to prevent contact of the upper end of the spring with the metallic walls of the cup.

In view of the fact that the casing is of comparatively small diameter with respect to its length and to the distance between the fixed contacts, the rod members 2i may be formed of insulating material and provided with an axial opening for the passage of a conductor which leads from the contact borne by the rod to member I'I. Such arrangement will prevent possible difficulty during the movement of the movable contacts fromiinactive to active positions; this will be understood from the following:

During the movement of contact I8 from its inactive to its active position, it must successively pass the fixed contacts I5 and I4, with contact I8 moving axially of th casing. Since contacts I3, I4 and I5 are connected with the live lines of the transmission system, it is apparent that if rod 2| were itself metallic, such rod could, especially when opposite both contacts I4 and I5, provide an inductive path by which it would be possible to connect, inductively, the lines which are connected with contacts I4 and I5; since these contacts vary in phase, there is a difference in potential between these contacts, and with the short distance radially of the casing between con- 5. tad-ts :4 a d 15, the length of such rod could readily provide'i'or setting up a sh'ort-circuiting action prior to the time when the short-circuit is designed to be produced. By making th rods 2| of insulating material and limiting the conductive path therethrough to the axis, there is less likelihood of the production of such path during themovement or the movable contacts to their active posi-tions.'- 'Where-the rod formation is of this type, it is poss ibl that member-I lmat beformed-also-ofinsulating material; in such case, the lower ends .of .the. conduct r pa n through theserods are" then coupled together through acomr'non connectionbetweenthem and carried by the member 11, thus producing the short-circuiting-formation that would be provided by member 51 if the latter Were metallic. If the member ll be metallic, the conductors from contacts I8, it and 20 world then be secured directly to the member, with the latter then forming the common connection between such conductors. i

The member I! is held in its inactive position by a suitable trigger means. Mounted on a suitable strap support 23 carried by the casing, is an angularimember 2 one endof which is pivotally mounted, as at 25, to the strap, while the cpposite"end extends outward and is formed to carry a depending flexible element, such as a rope 26 of suitable length. The intermed ate portion of member 24 is formed with an eye 21 which is connected with the outer end of a pin 28 that is insertable through the adjacent wall portion of the casing and having a length suflicient to extend through the opposite wall of such casing, the position of the pin being such as to be above member I! and thus capable of retaining the movable contacts in their inactive position, with the spring compressed. The rope 26 extends downward a distance which would enable a crew member on the ground to grasp it and draw downward upon it, this action causing member 24 to instantly withdraw the pin from the casing and permit the spring to shift the movable contacts. With the pin in position, the assembly is practically cocked, ready for instant release by the crew member drawing downward on rope 26.

Member H, or the common connection carried thereby, is connected with the ground through a conductor 29 which extends downward from the cup through an opening in the bottom of the easing and has a length exposed below the casing sufficient to permit of the positioning of its end zone within the ground, as by a metallic member about which the end is secured with the member itself thrust into the ground; the conductor is preferably flexible and has a length sufficient to permit the cup to move the length of its throw without affecting the conductor and its contact with the ground. This conductor may and preferably does also have a connection 30 which leads from the conductor to the neutral conductor of the transmission line. Hence, when the movable contacts engage the fixed contacts and set up the short-circuiting action through the connection provided by the common connection carried by the cup, it concurrently provides a circuit connection from the common connection to the ground and also to such neutral conductor.

To permit re-setting of the device, the casing is provided with an elongated slot 31 through which a pin 32, carried by member ll, extends to provide a projecting end to which a flexible depending element 33 is secured. Pin 32 and element 33 travel with th member I! during movements or said member. between active and inactive positions. Hence, when the member is released by pin 28 and travels to its upper position to complete the contact activity, pin 32 also travels with. the member. Obviously, if element 33 is drawn downward, it will carry with it memher I! and compress the spring, this movement continuing. until member H reaches its inactive position, in which pin 28 is again made active to maintain such inactive condition. 1. While I have herein shown and described a preferred embodiment of the invention with one or: more ways in which 'it may be carried into effect, it is apparent that changes or modifications therein may be found essential'or desirable in meeting the exigencies of use and service; I therefore reserve the right to make any and all such changes or modifications as may be found desirable or essential insofar as the same may fall within the spirit and scope of the invention as expressed in the accompanying claims, when broadly construed.

' I claim:

1. In safety grounding devices for use with hightension transmission systems, wherein an instrumentality is temporarily installed in potential short-circuiting relation to the transmission system with the instrumentality normally inactive and adapted tobe-rendered active at will, said instrumentality comprising a casing of insulating material having closed upper and lower ends adapted to be temporarily mounted on a transmission line supporting pole, a live wire contact in the closed upper end, a second live wire contact in one wall of the casing, a third live wire contact in the opposite wall of the casing in spaced relationship to said first and second named contacts, each of said contacts having a potentially-active face internally of the casing and a stem exposed externally of the casing, a conductor line connected to each of said stems adapted to be operatively secured to a live wire of the transmission system, a support mounted within the casing for longitudinal sliding movement, three insulated posts of different lengths secured to the support in spaced relation and extending upwardly from the support, a contact carried by the free end of each post, said movable contacts having a potentially-active common electrical connection within the support zone with the connection rendered active by contact engagement of the support-borne contacts with said fixed contacts to thereby provide short-circuiting activity of the transmission lines of the system, an actuating spring within the casing located between the support and the closed lower end to shift the support from its inactive position to a position of contact engagement, a grounding conductor leading from said common connection and adapted to be grounded, and a trigger means for normally retaining the support in its inactive position and movable at will to release the support for spring-impelled support movement to complete the contact engagement, whereby short-circuit arcing activity will be substantially confined to the interior of the casing.

2. An instrumentality as in claim 1 characterized in that the insulated posts are of such lengths as to cause concurrent contact engagement of fixed and movable contacts by the springimpelled movement of the support.

3. An instrumentality as in claim 1 characterized in that the support is of inverted cup-shape to present an extended length to the support to assure freedom in support movement, the side Wall of the support extending into the spring zone, the support being of insulating material with the common connection carried thereby.

4. An instrumentality as in claim 1 characterized in that the support is of inverted cup-shape to present an extended length to the support to assure freedom in support movement, the side wall of the support extending into the spring zone, the support being metallic and potentially active as the common connection, means being provided to insulate the spring therefrom.

5. An instrumentality as in claim 1 characterized in that the trigger means includes a pin adapted to extend laterally through the interior of the casing above the support during normal inactivity of the instrumentality to maintain such inactivity, said pin having an externally projected end, and a pivotally mounted actuating member carried by the casing and operatively connected to said projected end, said member having an arm carrying a flexible depending element positioned to be grasped by a ground attendant and drawn downward to thereby rock the member and withdraw the pin to release the support.

6. An instrumentality as in claim 1 characterized in that the casing is slotted longitudinally, with the support having a pin extending through 8 the slot to provide a projected end having a depending flexible element, the pin and its depending element being movable with the support during the spring-impelled movement of the support, the element permitting manual resetting of the instrumentality at will to thereby break the short-circuiting conditions at the close of the specific service activity of the instrumentality which necessitated such instrumentality service activity.

ALBERT J. STOVE-R.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 376,072 Cole Jan. 10, 1888 708,006 Ball Sept, 2, 1902 1,370,189 Cohen Mar. 1, 1921 1,878,090 Alcoriza Sept. 20, 1932 1,961,004 Lemaitre May 29, 1934 2,432,581 Miller Dec. 16, 1947 FOREIGN PATENTS Number Country Date 463,694 Germany Aug. 4, 1926

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