US3369091A - Explosive disconnector with belleville washer interposed between a closure wall and an annular resistance means - Google Patents

Description

D. O. MISARE LLEVILLE WASHER INTERPOSED Filed June 20, 1966 N ?un (M N\ NVENTORs DONALD O. MSRE BY v 42,& AT

Feb. 13, 1968 EXPLOSIVE DISCONNECTOR WITH BB BETWBEN A CLOSURE WALL AND AN ANNULAR RESISTANCE MEANS United States Parent O ice i 3,369,091 EXPLOSIVE DISCONNECTOR WITH BELLEVILLE WASHER INTERPOSED BETWEEN A CLOSURE WALL AND AN ANNULAR RESISTANCE MEANS Donald 0. Misare, Riversde, Ill., assigno' to Joslyn Mfg. and Supply Co., Chicago, Ill., a Corporation ofIllinois Filed `lume 20, 1966, Ser. No. 558,675 2 Claims. (CI. 200-115) ABSTRACT OF THE DISCLOSURE An explosive disconnector of the type wherein an explosive member forms one point of a spark gap and is provided with a bleeder resistance across the spark gap. A Belleville type Washer spring loads the confronting surfaces of the explosive member and resistance in order to maintain good electrical contact and to eliminate internal corona discharge or other disturbing effects.

The present invention relates to disconnectors adapted for use in conjunction with lightning arresters for the protection of electric power transmission lines or other electrical Components used therewith.

It has been the practice to provide a disconnector for use in conjunction with a lightning arrester for the purpose of permanently opening a circuit between the arrester and ground when the arrester has failed or is not functioning. It is desirable to disconnect the arrester from the circuit after such failure or malfunction in order to prevent an abnormal flow of follow current through the failed arrester to ground, which current, unless interrupted, results in the opening of fuses or circuit breakers on the line and, hence, causes outage of the circuit until the faulty arrester can be located and replaced. On long transmisson lines it is sometimes ditficult to find and replace a faulty arrester and it is desirable to provide a disconnector which will visually indicate to a repairman driving in a vehicle on the ground along a power line, upon casual inspection, that the arrester is faulty. A common type of disconnector in present use is one which employs an explosive charge to break or rupture the outer housing of the disconnector and thus disconnect the failed arrester from the power line and also provide an easily discerna-ble visual indication of arrester failure. One such disconnector is shown in U.S. Patent No. 3,100-,246, and the present invention compn'ses an improvement thereon.

Generally, these types of disconnector-s employ an internal spark gap in which the heat generated by an arc across the gap ignites an explosive charge to sever the housing and expel the terminals, thus disconnecting the arrester from the circuit. During a sudden surge of voltage across the spark gap for a short duration of time, which might be caused by lightning or other disturbance on the line, the heat generated by the arc is not suicient to ignite the explosive. However, if, after the surge has passed, an abnormally high follow current is present because of an arrester shorted to ground, the heating caused by the prolonged duration of the arc across the spark gap ignites the explosive charge in the disconnector and disconnects the arrester from the line before fuses or circuit breakers on the line are opened. Also, in order to prevent the build'up of a high potential difference across the spark gap in the disconnector, which buildup causes radio and TV interference because of sparkover or corona efiect resulting therefrom, the electrodes forming the spark gap are shunted by a resistor or other impedance, thereby discharging any electrical charge potential which may accumulate .across the spaced electrodes forming the' spark gap.

" 336939 1 Patented Feb. 13, 1968 It is an object of the present invention to provide a new and improved disconnector of the general character described having improved electrical and mechanical characteristics.

Another object of the present invention is to provide a new and improved disconnector .having an explosive charge or gas-forming material therein which is positively sealed against the entrance of moisture or other foreign matter so that the disconnector is always relable in operation.

Still another object of the present invention is the provision of a new and improved disconnector having improved resistance connecting means between the terminals forming a spark gap therein for eliminating radio and TV interference caused 'by corona discharge across the spark gap.

Another object of the present invention is the provision of a new and improved disconnector of the character described above wherein a portion of the spark gap forming terminals is formed 'by the sealing means for enclosing the gas-forming or explosive material.

Another object of the present invention is the provision of .a new and improved arrester having improved characteristics whereby the metallic materials forming the spark gap terminals do not decompose or spatter when normal voltages and currents are present across the spark gap terminals of the arrester, a condition which eventually would decrease the spark gap spacing or short the spark gap terminals.

Another object of the present invention is the provision of a new and improved disconnector of the character described having means therein for accommodating thermal expanson and contraction of the disconnector Components without afecting appreciably the spacing across the spark gap.

Another object of the present invention is the provision of the disconnector of the character described which is simple in Construction, easy to manufacture, and relatively low in cost.

According to the present invention, the foregoing and other objects are accomplished by the provision of a new and improved disconnector adapted for use with the lightning arrester and comprising a tubular insulatng housing or shell and ta pair of conducting end terminals extended into said housing from the opposite ends thereof. One of the end terminals is adapted for connection to a lightning arrester or other protective device and the opposite end terminal may be adapted to be connected to a ground lead, power line, or other electrical device which is to be protected. An annular high resistance member having an axial bore is mounted in said housing and is interposed between inner end portions of the end terminals. Spark gap forming means including a tubular conductive member extending through and in contact with the axial bore of said resistance member is electrically connected at one end with one of said end terminals and has an opposite end portion spaced from the other of said end terminals to form a spark gap therewith. Heat responsive explosive or gas-forming means is sealed within the tubular member, and when sufiicient temperature has been generated by an arc across the spark gap for a prolonged period of time, the explosive means ignites and expels one of the end terminals from the housing to positively break the connection and provide a visual indication that disconnection has occurred. The invention, both as to its Construction and manner of operation, together with further objects and advantages will best the understood by reference to the following detailed description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a longitudinal sectional View of a disconnector `characterized by the features of the present invention; and

FIG. 2 is an exploded perspective view of the disconnector of FIG. l illustrating the various parts and components used to m'ake up the disconnector.

Referring now, more particularly, to the drawing, therein is illustrated a disconnector constructed in accordance with the present invention adapted for use with a lightning arrester and the like and generally referred to by the reference numeral 10. The disconnector includes a tubular housing 12 of porcelain or other insulating material and a pair of conducting terminal mernbers 14 and 16 axially extending into the housing from opposite ends thereof. The upper end of the insulating housing is formed with an enlarged diameter portion 12a having a threaded internal bore for receivirg the upper end terminal 14 which comprises a pluglike, generally cylindrical member having external threads and a central threaded bore 14a adapted to be connected with a terminal stud on a lightning arrester or other electric component. The terminal 14 includes a radially disposed, circular inner end face 18 and, after the terminal is threaded into the bore of the enlarged portion 12a of the housing, an epoxy resin filling or gasket '20 is poured or compressed into a shouldered recess 22 in the large end of the insulating housing to seal around the terminal and close the upper end of the housing against the entrance of dirt or moisture. To aid in threading the terminal 14 into the housing 12, the outer face thereof is provided with a pair of 'diametrically opposed blind bores 24 on either side of the central threaded bore 14a and which are adapted to receive a specially constructed wrench or tool.

The lower end of terminal 16 includes a cylindrical, plug-shaped inner portion 26 formed with an annular recess 26a on the outer surface thereof and preferably integrally molded into the lower end of the housing 12 to form an effective seal at the lower end thereof. The terminal 16 also includes an 'outwardly projecting threaded stud 28 on which a clamping member 30 and nut 32 are provided to connect the terminal with a ground lead or other electrical Component. The internal end of the lower terminal 16 is formed with ar annular radial end face 34 and an axial blind bore 36 which is one conducting surface area forming a spark gap within the disconnector housing. In Construction of the disconnector, the lower terminal 16 is held in place in a jig, or the like, and the housing 12 of porcelain, or the like, is integrally `cast around the portion 26 of the terminal to fill the recess 26a therein and eifect an airtight seal at the lower end of the disconnector housing.

In accordance with the present invention, an internal spark gap is formed within the insulating housing 12 between the surface of the bore 36 in the terminal 16 and an outer end portion of a conductive tubular rivetlike member 38 having a hollow stern 38a disposed in axial alignment with the longitudinal axis of the housing 12 and extending partially into the bore 36. The conductive rivetlike member 38 includes an enlarged head at one end which closes the upper end of the tubular stern 3811 and includes an outer convex surface which bears against the inner face 18 of the upper terminal 14 and makes electrical connection therewith. The stern 38a is filled with an explosive or gas-forming material 40 which is sealed within the bore of the stern by a small dab of sealing material 42, such as an epoxy resin, or the like, at the outer end of the stern'. In addition to the epoxy sealing material 142, the outer end of the stern 380 is provided with a cuplike, conductive, metallic sealing cap 44 which is formed of Copper or copper alloys. The Copper sealing cap 44 is inserted onto the lower end portion of the stern 38a and clinched in place thereon, and when in place forms part of the conductive surface forming one side of the spark gap.

The conductive rivet member 38 is held in centered position within the central bore of the insulating housing 12 by means of an annular resistance member 46 having a central bore 46a and a pair of annular, opposite end faces 46b and 460. The lower end face 460 of the resistor 46 bears directly against and in electrical contact with the annular end face 34 of .the lower terminal 16, while the upper end face 46b of the resistor 46 is in electrical contact with an annular undersurface on the enlarged head portion 38b of the conducting rivet member 38, as shown in FIG. 1.

In actual practice, the resistance element 46 has a resistance value of about 100,()00 ohms plus or minus 20 percent and serves to electrically interconnect the upper and lower terminals 14 and 16 of the disconnector, thereby shunting the spark gap and thus preventing or reducing the possibility of sparkover or corona discharge across the gap which causesradio and TV interference. Because of the relatively high value of the resistance 46, the current flow or normal drain therethrough is inconsequential. In order to accommodate thermal expansion and contraction of the internal `Components in the disconnector 10 caused by changes in ambient temperature in the field, an annular Belleville-type Washer 50 of conducting material is interposed between the 'upper face 461) of the resistor element 46 and the annular undersurface of the enlarged head 38b of the conducting rivet. The Washer 50 insures good electrical connection between the upper face 461) of the resistor 46 and the head portion of the rivet member 38. In addition, the Washer 50 continually urges the rivet member 38 upwardly against the surface 18 of the upper terminal 14 and urges the resistance member 46 downwardly to provide good contact between the lower surface 460 thereof and the annular face 34 on the lower terminal member `16.

Preferably, the resistance element 46 is constructed of sintered carbon, or the like, and has good mechanical strength characteristics. The tubular stern 38a of the conductive rivet member 38 projects downwardly through the central bore 46a of the resistance member and is thereby held in axial alignment with the longitudinal axis of the housing 12 and the spark gap forming surface of the bore 36 in the lower terminal 16. A relatively large portion of the surface of the stern 38a is in electrical contact with the internal surface of the bore 46a in the resistance member 46 and a lower end portion of the tubular stern projects downwardly from the lower end 460 of the resistor into the bore 36 of the lower terminal 16 in annular spaced relation with the surface thereof to form the spark gap therewith. The copper metallic cap 44 on the lower end of the stern 38a covers the lower tip of the stern 3841 and also forms a portion of the spark gap with the internal surface of the bore 36 on the lower end terminal 16.

In assembling the disconnector 10, an internal subassembly comprising the resistor 46-, Belleville Washer 50, and rivet member 38, is inserted into the housing from the upper end and the upper terminal 14 is then threaded into the housing until the inner end 18 thereof bears against the rounded surface of the enlarged head 3817 and slightly compresses the normally frustoconical Washer 50'. The resilient action of the Belleville Washer 50, maintains the lower end face 460 of the resistance member 46 tightly against the end face 34 of the lower terminal 16 and forces the head portion 38a against the surface 18 of the upper terminal 14. In hot weather, when all of the members making'up the connector begin to expand, the Belleville Washer 50 is flattened out somewhat because of the increased pressure thereon by the expanding parts in the subassembly, and in cold weather, when the parts contract slightly, the Belleville Washer continually maintains good contact between the annular resistance member 46 and the lower terminal 16 and between the rivet head 38a and the upper terminal 14. The hollow rivet stern 3841 which contains the explosive or gas forming material 40 of the device is in electrical contact with the internal bore 46a of the resistance member 46, and thus the upper terminal 14, rivet member 38, and upper end face 46b and surface of the bore 46a in the resistance member 46 are maintained at the same electrical potential. Under normal conditions, very little current flows through the resistance 46 and, accordingly, is distributed almost uniformly throughout the annular cross section of the resistor between the upper and lower faces 46b and 46c. When abnormally large current flow occurs through the resistor 46, the uniform distribution of current flow through the annular cross section of the resistor changes somewhat and a larger current flow occurs toward the central portion of the resistor between the annular bore 46a and lower surface 46c. This increased current density .is attributed to the shorter resistance path between the lower portion of the resistor bore surface and lower face thereof. Hence, in etfect, the annular resistance member 46 acts as a variable resistor with the overall resistance of the member decreasing upon heavier current flow because of nonuniform distribution of current. This feature is of considerable advantage in that it eliminates the necessity of using negative resistance material for the resistance member 46.

In previous disconnectors of the same general type, problems were present because during normaloperating currents the material of the rivet stern 38a tended to decompose to some extent and splatter over onto the facing surface of the bore 36 and thereby gradually decrease the effective distance of the spark gap. It has been found in the present invention that by using a cap member 44 of copper material covering the lower end or tip of the stern 38a, difficulty of stern erosion is eliminated or greatly reduced.

As illustrated in FIG. 1, the spark gap distance of the annular spark gap formed between a portion of the outer annular surface of the lower end portion of the tubular stern 38a and a facing annular surface of the bore 36 of the lower terminal 16, as well as between the 'outer surface of the cap 44 and the bore surface 36, is selected to accommodate a normal Operating or rated voltage for the disconnector, and for higher voltage installations, this distance is increased. Because of the slightly decreased gap distance in the vicinity of cap member 44, most of the current flow or arcing across the gap that occurs, takes place between the outer annular surface of the cap member 44 and adjacent facing portons in the bore 36, and the cap member serves as a heat sink to absorb much of the heat generated by the arc which would otherwise be absorbed by the stern 38a. Accordingly, caps 44 of different thickness can be used to provide changes in the time duration of an arc necessary to ignite the material 40 and effect a disconnection. Moreover, by utilizing copper or a copper alloy for constructing the cap member 44, the problem of electrode erosion is decreased, giving the disconnector increased life and reliability of operation.

When an abnormal current condition appears on the line, caused by a lighting strike or other disturbance, and the arrester is failed thereby, an arc is generated across the spark gap. If the arc then remains for a prolonged interval, the heat caused thereby is absorbed by the cap member 44 and the stem 38a. When the stern temperature rises to a high enough value, the explosve material 40 contained therein is ignited and the expending gas pressure within the housing explosive expels the end terminals from the housing to break the connection. Upon expulson of the terminal or terminals and rupture of the housing, a repairman or lineman can readily visually determine that arrester-disconnector failure has occurred and replacement is required. The annular resistor member 46 acts as a variable resistance to accommodate small variations in current flow between the terminals 14 and 16 to prevent radio and TV interference, caused by corona discharge or sparkover. The explosive material 40 is well sealed in the tubular stem 38a against moisture or other mpurties by means of the epoxy scaling compound 42 and the metallic cap 44 resulting in increased reliability of operation and longer field life for the disconnector 10. Also, caps 44 of different wall thicknesses can be used to provide the desired time characteristcs for operation of the disconnector. The Belleville washer 50` provides for expansion and contraction of the internal parts of the connector during ambient temperature changes and insures that good electrical connection .is always maintained between the internal Components as previously described.

Although the present invention has been described by reference to a single embodiment thereof, it will be apparent that numerous other modications and embodiments will be devised by those sklled in the art which will fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be Secured by Letters Patent of the United States is:

1. A disconnector adapted for use with lightning arresters and the like, comprsing a tubular insulating housing, a pair of end terminals extending into said housing from opposite ends thereof, an annular high resistance means in said housing having an aXial bore and interposed between inner end portions of said end terminals, spark gap forming means including a tubular conductve member extending through and in contact with said aXial bore of said annular resistance means and having one end electrically connected with one of said end terminals and an opposite end portion spaced from the other of said end terminals to form a spark gap therewith, said tubular conducting member including a closure wall at one end thereof in contact with said one end terminal, heat responsive gas-forming means contained in said tubular member for expelling one of .said end terminals from said housing in response to a prolonged rise in temperature of said tubular conductve member, and Belleville washer means interposed between an annular surface of said closure wall and a facing annular end surface of said annular resistance means.

2. A disconnector adapted for use with lighting arresters and the like, co-mprising an insu-lating housing, a pair of end terminals extending into said housing from opposite ends thereof, an annular high resistance means in said housing having an aXial bore and interposed between inner end portions of said end terminals, spark gap forming means including a conductve member extending through and in contact with said aXial bore of said annular resistance means and having one end electrcally connected with one of said end terminals and an opposite end portion spaced from the other of said end terminals to form a spark 'gap therewith, said conducting member including a closure wall at one end thereof in contact with said one end terminal, heat responsive gas-forming means contained in .said conducting member for expelling one of said end terminals from said housing in response to a prolonged rise in temperature of said conductve member, and Belleville washer spring loading the surface of said closure wall and a conf'onting surface to maintain compressive load on said resistance means and said conductive member.

References Cited UNITED STATES PATENTS 2,548,l12 4/1951 Kaminky 200- 2,559,024 7/1951 McFarlin 200-115 XR 3,017,539 1/1962 Robinson 200-115 XR 3,100,246 8/1963 Riley 200 115 3,239,631 3/1966 Snell 200-115 BERNARD A, GILI-IEANY, Pr' nary Exwn'e'. H. A. LEWITTER, Assistant Exam' 'ne'.

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