US3189710A - Terminal connector - Google Patents

Description

June 15, 1965 R. J. LAWRENCE ETAL 3,189,710 I TERMINAL CONNECTOR Filed March-22, 1962 I I I 1 F|g.l. I/// Z Fig. 2. wnusssss: W INVENTOR S Robert J. Lawrence and mmik Charles Corothers.

United States Patent 3,189,710 TERMINAL CONNECTOR Robert J. Lawrence, Bean Blossom Township, Monroe County, and Charles H. Carothers, Bioornington Township, Monroe County, Ind, assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar. 22, 1962, Ser. No. 181,686 4 Claims. (Cl. 200-115) The present invention relates to a stud terminal construction, and more particularly, to an improved hand wheel connector for lightning arrester stud terminals.

In the usual construction of lightning arresters, particularly the 3, 6 kv. and 9 kv. ratings, stud connectors are employed at the top and bottom terminals. Conductor cables are connected to the stud terminals by a conventional hex nut or other suitable clamping device of conducting material. These stud connectors present difiicult design problems because excessive torque applied to the nut during connection of the conductor to the terminal tends to break the seal where the metal stud goes through the porcelain or other insulating housing. This allows water and other contaminants to enter the arrester. Five or six foot pounds of torque applied to a properly designed clamp is sufiicient to adequately secure the conductor to the terminal. However, it is diflicult for a lineman to judge how much torque is being applied and when the danger point is being reached. It is usual for a lineman to carry a 10-inch crescent wrench for service of this kind. A lineman tightening the usual type of connector used on a terminal stud can apply 40 to 50 foot pounds of torque quite easily. This would be sufficient to loosen the terminal and to break the seal. This is a problem at both the line and ground terminals of a lightning arrester.

But the problem is even greater at the ground terminal of an arrester where a frangible or fracturable dropout device is often used to disconnect the ground terminal from the arrester under certain abnormal conditions. In order to provide a dependable dropout feature, the weakened or frangible portion of the dropout should be quite thin in order to obtain dependable operation. The dropout portion includes a terminal stud projecting from its lower end for connecting a ground conductor. Here, again, a lineman employing the wrench with which he is equipped may inadvertently fracture the frangible portion during connection of the ground conductor to the ground terminal by application of excessive torque.

An insulating cap or cover over the terminal stud is, in most instances, required for shielding the uninsulated terminals against inadvertent contact by personnel and to protect the terminal against inclement weather and animals (birds or squirrels). Separate caps are usually provided for this purpose.

The principal object of the present invention is to provide an improved terminal connector construction for electrical equipment which reduces the possibility of damage to the terminals, seals, and insulating members during installation due to excessive application of torque.

Another object of the invention is to provide an improved terminal connector construction for electrical equipment which obviates the necessity of separate insulating caps.

A further object of the invention is to provide an improved terminal construction for electrical equipment which protect lineman from line power while working at or near the equipment.

Other objects and advantages of the invention will be apparent from the following detailed description, taken in connection with the accompanying drawing, in which:

FIGURE 1 is a side elevational view of a lightning 3,189,710 Patented June 15, 1965 arrester employing this invention, partly in section; and

FIG. 2 is a transverse sectional view showing the hand Wheel connector of this invention.

Briefly, the invention as illustrated, is embodied in a valve type lightning arrester having terminals projecting from each end. The terminals are adapted to receive a line conductor at the top and a ground conductor at the lower end. Hand wheel terminal connectors are employed on each of the terminals to secure the line and ground conductors to their respective terminal studs. The hand wheels are made from insulating material having high tensile and compressive strength and which is hard and has high resistivity. The hand wheels have a central boss with a metallic insert molded therein. The metallic insert has a threaded recess which is received on the terminal stud. There are flat radially extending surfaces disposed in opposition on the terminal stud and the metallic insert, respectively, which engage to clamp the conductor therebetween. The radially extending surface has a series of sharp concentric grooves formed thereon.

The invention as illustrated in the drawing is applied to a lightning arrester of the type shown and described in copending application Serial No. 181,687, by C. H. Carothers, filed March 22, 1962, now Patent Number 3,153,128, patented Oct. 13, 1964, and assigned to the Westinghouse Electric Corporation. Reference is made to the above-mentioned application for a detailed description of the construction and operation of the lightning arrester. It is sufiicient here to point out that such an arrester comprises a tubular casing 10 of porcelain or other suitable insulating material. The housing 10 is closed at its upper end by a porcelain cap 16 which is secured thereto in sealing engagement. At its lower end it has an enlarged inside diameter which forms a downwardly facing shoulder 18, as seen in FIG. 1, and a skirt 20. An annular recess 22 is formed on the skirt adjacent the shoulder 18. The lower end of the arrester is closed and sealed by a dropout device 24 which has projecting therefrom radial spring fingers 25 which engage the recess 22 to secure the dropout device to the housing 10. Intermediate the shoulder and the upper end of the dropout device 24 is a gasket 26 to provide good sealing engagement. The recess is filled with a sealing material 28 which may be a resin or other suitable sealing compound. One or more non-linear resistance blocks or valve blocks 30 are disposed within the housing 10 and are supported upon projections 31 formed on the upper surface of drop out device 24. A contact spring 32 is disposed centrally of the upper end of dropout housing 24 and the lower end of the bottom resistance block 30. The spring 32 is disposed in compression. At the upper end of the stack of non-linear resistance elements is a compression spring 34 which engages the upper surface of a metal contact plate 38 that is in contact with the resistance block 30.

The arrester housing 10 has its interior divided into two compartments 36 and 39 by a compartmentizer ring 40 of cork-neoprene having a central opening. The outer periphery of the compartmentizer bears against the inner wall surface of the arrester housing 10. A plate 41 of conducting material underlies the compartmentizer and has a central projection (not shown) extending upwardly through the central opening of the compartmentizer 40. The compression spring 34 engages the plate 41 to make good electrical contact.

The upper compartment 36 contains a spark gap assembly 44 which may include one or more spark gaps serially connected. The spark gaps are each formed by a pair of disc shaped electrodes 46 spaced apart by centrally disposed insulating cylinders (not shown) which may be of rutile or other suitable insulating material. Cylindrical arc barriers 48 are interposed between each pair of electrodes at the outer periphery.

The gap assembly is held together on an insulating center post 43. The electrodes 4%, central cylindrical insulating spacers, the compartmentizer and conducting plate 41 receive the center post 43 through their central openings. A U-shaped nut 47 is secured to each end of the center post 43 to secure the gap assembly parts on the post 43. The free ends of the nut 47 extend outwardly from the gap assembly forming spacers and electrical contacts with adjacent parts.

An upper terminal stud 49 is provided which extends through the upper cap lid. The stud 4% is an elongated cylindrical threaded member which passes longitudinally through the closure 16 in an axial direction and has intermediate'its end a radially extending fiange St). A boss 52 is formed on the outer side of the upper cap 16. The flange 50 engages the boss 52 and is sealed thereto by a gasket 54 and sealing resin or other suitable sealing material.' A stud nut 58 secures the stud to the closure to within the housing. This resultsin clamping engagement between the flange 5t and the stud nut 53.

The upper U-shaped nut 47 spaces the gap assembly and makes contact with the upper terminal 49 through stud nut 58. The/nut 47 engages and is secured to the center insulating post 43 and upper electrode 46 of the gap structure and is held in good electrical contact with the stud nut 58 of the terminal assembly by compression spring 34. The compression spring 34 is provided to maintain the internal parts of the arrester in good electrical contact and to provide low. resistance contact be tween the parts. A plurality of upstanding projections 51*? are provided on the flange 5% and face upwardly from the arrester as seen in FIG. 1. The projections 59 form slots 60 between them which are in alignment with a plurality of circumferentially spaced slots 62 formed in the upper surface or outer surface of the closure 16. Slots 6t and 62 are provided to receive conductors therein for connection to the terminal 49. The portion of the stud projecting outwardly from the flange Edi-is threaded and receives thereon the hand wheel connector 54.

In the usual construction of a lightning arrester, or other electrical equipment having this type of terminal stud, a conventional hexagonal nut is provided to secure the conductor to the terminal. However, the aforementioned problems of excessive torque and provision of an insulating cover over the terminal are solved by the use of the hand wheel connector of this invention. The hand wheel connector, as seen more clearly in FIG. 2, includes a molded insulating 'disc as which may be of wood flour-filled phenolic resin or any other suitable insulating material which is hard, has relatively high tensile and compressive strength, and is moldable. An example of such other resin would be melamine plastic. Although the resin is described as being wood flour-filled, other suitable fillers may be employed or an unfilled resin may be employed in accordance with the broader aspects of the invention. The disc 66 has a peripheral flange es and a central boss 70 which extend toward the arrester when the connector 64 is positioned thereon. There is a central recess 72 formed in the central boss 79 on the disc 66 which opens toward the arrester when in position. Positioned within the recess 72 and molded therein is a metal conducting insert 74 which has a central threaded recess '76 to receive the free end of the threaded stud 49. The insert 74 has an enlarged radial flange 78 which engages the face of the boss. The stem portion 80 of the insert 74 may have a coarse diamond-knurled or other means on the outer surface to better retain it within the recess and secure it against movement or displacement. The insert 74 is molded in the disc 66. Concentric grooves 81 may be formed on the opposed surfaces of the insert 74 and the terminal flange St] to improve the clamping engagement of the conductor.

The details of construction and the operation of the dropout device 24 are described in detail in the abovementioned application, SerialNo. 181,687. For the purposes of this invention, it is only necessary to state that the housing which contains the internal parts of the dropout device includes a weakened frangible portion 82 adapted to fracture upon operation of the dropout device. It is desirable to have this portion fracture as a result of as little force as possible to make the dropout device more sensitive to small fault current. The frangibility or weakness of this portion is limited largely by its resistance to fracturing as a result of the torque applied to the stud when the ground conductor is being attached to the ground terminal stud. A terminal stud 49 similar to terminal stud 49 is provided and extends through the bottom wall of the dropout device 24. Stud 49' is similar in construction to the stud 49 and has an elongated threaded portion and a flange SiVintermediate its ends which engages the outside of the bottom wall of the dropout device 24. A gasket 54' is disposed between the upper side of the flange Stl and the lower wall of the dropout device 24. This provides good sealing engagement. The stud 49 has a head 58 which corresponds to the stud nut 58 of the upper terminal 49 and engages the interior of the bottom wall of the dropout device 24. The hand wheel connector 64 is received on the free end of the stud 4'? to secure a groundconductor to the terminal stud 4?. The construction of the lower or ground end hand wheel connector 64' is identical to the construction of the hand wheel connector 64 at the line terminal end of the arrester and need not be further'described herein.

It is apparent that a construction has been described which makes it possible to have a much more sensitive dropout device than has heretofore been possible since the fracturable portion 82 can be weakened considerably. The hand wheel connector 64 is not adapted to receive the standard wrench which a lineman carries and therefore must be tightened by hand. By hand tightening a maximum of five or six foot pounds torque can be applied whereas a 10 inch wrench applied to the usual'hex nut would permit application of 40 to 50 pounds torque. to the terminal stud and to the weakened frangible portion $2 of the dropout device.

The number of threads per inch on the terminal studs 49 and 49 may be increased to enable sutficient force to be applied to the conductor and to'make the clamp more vibration resistant. Thus, the studs may have twenty-four threads per inch, for example, instead of the usual thirteen threads per inch. The hand wheel connectors 64 and 64' provide suitable insulating covers to prevent accidental contact and to prevent contamination and corrosion of the studs as a result of inclement weather. The insulated hand wheel assembly also prevents workman working at or near the terminals of the arrester from touching a live uninsulated terminal, inadvertently. This reduces the hazard of working on the lines considerably.

Although a specific embodiment of the invention has been shown and described for the purpose of illustration, it will be apparent that various other embodiments are possible within the scope of the invention.

We claim as our invention:

1. In a lightning arrester having a terminal stud for securing an electrical conductor thereto; a hand wheel connector for securing a conductor to said stud, said hand wheel connector including an insulating disc having a peripheral flange extending axially, a central boss extending axially in the same direction as said flange and a threaded recess in said boss for securing a conductor to said stud, whereby the terminal is protected from contamination by said hand wheel connector and whereby the terminal is protected from application of excessive torque thereto.

2. The combination of claim 1, wherein said central boss includes a metallic insert having a threaded recess for receiving said terminal stud.

3. In a lightning arrester having threaded terminal studs for securing electrical conductors thereto; the combination comprising a threaded terminal stud sealed to and projecting from an insulated housing, a hand wheel connector for securing a conductor to said stud, said hand wheel connector including a disc of insulating material having a threaded recess for receiving said stud, said disc having a diameter of a size effective to apply sufficient torque by hand to securely retain said conductor but of a size ineffective to apply sufiicient torque by hand to break said seal between the terminal stud and the arrester housing.

4. In a lightning arrester having a terminal stud for securing an electrical conductor thereto; the combination comprising a threaded terminal stud projecting from as insulated housing, said housing having a weakened annular portion adapted to break away from the housing to separate the terminal stud from the arrester under certain abnormal conditions, a hand wheel connector for securing a conductor to said stud, said hand wheel connector including a disc of insulating material having a threaded recess for receiving said stud, said disc having a diameter of a size effective to apply sufficient torque by hand to securely retain said conductor but of a size insuflicient to apply sutficient torque by hand to fracture said annular weakened portion.

References Cited by the Examiner UNITED STATES PATENTS 1,947,076 2/34 Beckett et al 200-115 2,311,852 2/43 McFarlin 339-201 2,937,361 5/60 Broverrnan 339202 SAMUEL BERNSTEIN, Primary Examiner.

Claims (1)

1. IN A LIGHTING ARRESTER HAVING A TERMINAL STUD FOR SECURING AN ELECTRICAL CONDUCTOR THERETO; THE COMBINATION COMPRISING A THREADED TERMINAL STUD PROJECTING FROM AN INSULATED HOUSING, SAID HOUSING HAVING A WEAKENED ANNULAR PORTION ADAPTED TO BREAK AWAY FROM THE HOUSING TO SEPARATE THE TERMINAL STUD FROM THE ARRESTER UNDER CERTAIN ABNORMAL CONDITIONS, A HAND WHEEL CONNECTOR FOR SECURING A CONDUCTOR TO SAID STUD, SAID HAND WHEEL CONNECTOR INCLUDING A DISC OF INSULATING MATERIAL HAVING A THREADED RECESS FOR RECEIVING SAID STUD, SAID DISC HAVING A DIAMETER OF A SIZE EFFECTIVE TO APPLY SUFFICIENT TORQUE BY HAND TO SECURELY RETAIN SAID CONDUCTOR BUT OF A SIZE INSUFFICIENT TO APPLY SUFFICIENT TORQUE BY HAND TO FRACTURE SAID ANNULAR WEAKENED PORTION.

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