US3471669A - Encapsulated switch assembly for underground electric distribution service - Google Patents

Description

Oct. 7,1969 n T E C ENCAPSULATED SWITH .ASSEMBLY FOR UNDERGROUND ELECTRIC DISTRIBUTION SERVICE Filed Jan. 16, 1968 URTIS 2 Sheets-Sheet l 'ORNEY Oct. 7, 1969 T. E. cu ls 3,471,669

ENCAPSULATED RSIWCI ASSE Y UND ROUND ELECT TRIBUTION VIC Filed Jan. 16, 1968 2 Sheets-Sheet 2 `ig "II'IIII'I'II II'IIII..

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INVEroR l Thomas f. @wr/5 United States Patent() Int. Cl. H01h 9/ 04, 21/08 U.S. Cl. 200-168 B. of

12 Claims ABSTRACT OF THE DISCLOSURE A vacuum interrupter unit is axed to a housing which contains a toggle assembly for opening and closing the contacts of the interrupter unit. The composite assembly and line connectors therefor are encapsulated by a waterproof, elastic jacket of high dielectric strength but having an electrically conductive outer surface to distribute the electrical stress. The toggle assembly employs an operating shaft of insulating material which extends through the encapsulation and has a crank at its outer end adapted for operation from a remote location by a linemans hook stick. Moisture seals are provided at the shaft and the connectors to provide a switch assembly suitable for underground installation and operable when immersed in soil contaminated Water.

Until recently the majority of the switching apparatus for underground residential distribution systems has been mounted aboveground in cabinets into which the connecting cables are brought from underground. Often these same cabinets contain the distribution transformers and necessary protective fuses of the system. However, with the present emphasis on further improving the appearance of residential areas by the complete burial of all electric distribution facilities, the need has arisen for switching equipment which may be located underground in a vault type installation.

Such a switch for use in underground electric distribution or transmission must be capable of interrupting the load currents and any cable charging currents to be anticipated on the circuit, and must be capable of making any transformer inrush currents or interrupting any transttor-mer magnetizing currents that may be anticipated. Additionally, the switch must withstand closure against the highest anticipated short circuit current and still remain operative, must withstand the dielectric stresses induced by the operating voltage and the impulse voltages to which it may be subjected even when completely submerged in soil-contaminated water, and must be designed such that, when mounted in an underground vault, the switch can be safely operated by one man with an insulated hook stick.

It is, therefore, the primary object of this invention to provide switching apparatus for underground electric service which meets the criteria set -forth above.

More particularly, it is an important object of the instant invention to provide switching apparatus as aforesaid which is completely encapsulated to adapt the same for 4underground installation even in the presence of contaminated water.

As a corollary to the last mentioned object, it is an important aim of the invention to provide an encapsulation for the switching apparatus which has high dielectric strength, is elastic in nature to provide the necessary moisture seals and preclude fracture thereof by expansion and contraction of the components therewithin or by a physical blow, and is capable of distributing the electrical stress to preclude buildup of stresses which would 3,471,669 Patented Oct.v 7, 1969 exceed the safe dielectric value of the encapsulation.

Furthermore, with respect to switching applications in general whether above or lbelow ground involving the use of apparatus which may or may not .be encapsulated depending on the requirements of the installation, it is an important object of this invention to provide an improved toggle-type operating mechanism for single or multiple load interrupter units which is capable of effecting rapid contact separation and yet normally holds the interrupter contacts closed under suicient force to reduce the tendency of the contacts to jump apart under a fault condition.

Additionally, it is an important object of this invention to provide switching apparatus Ifor underground electric service employing a toggle mechanism as aforesaid which is remotely operable from a location outside of the vault that houses the apparatus.

Still another important object of the invention is to provide a toggle mechanism as aforesaid having a toggle spring which applies maximum force to the interrupter contacts when holding the latter closed against one another in order to thereby reduce the above mentioned tendency of the contacts to jump apart.

Yet another important object is to provide a toggle mechanism as aforesaid in which the driving parts thereof `for closing the interrupter contacts are freely movable in a direction to close the contacts and are restricted in such movement only by the ultimate engagement of the contacts so that a good electrical connection is assured regardless of any contact erosion that may be present.

In the drawings:

FIG. 1 is a top plan view of the encapsulated switch assembly showing the same mounted in an underground vault, the operating arm thereof being shown in the open position;

FIG. 2 is an enlarged, side elevational view of the encapsulated switch assembly of FIG. l, the operating arm being shown in the closed position;

FIG. 3 is an enlarged, vertical sectional view taken along line 3-3 of FIG. l showing the interrupter contacts closed and illustrating one of the male cable connectors;

FIG. 4 is a plan view of the structure shown in FIG. 3 with the top of the toggle mechanism housing and a portion of the encapsulation being broken away to reveal the interior construction;

FIG. 5 is a view similar to FIG. 3 but showing the interrupter contacts open and the components of the toggle mechanism correspondingly shifted; and

FIG. `6 is a plan detail view of the two cranks of the tlggle mechanism and the inner end of the operating s aft.

A toggle mechanism 10 is mounted within a box-like metal housing 12 to which avacuum interrupter unit 14 is aiixed. The mechanism 10 includes a rotatable operating member orshaft 16 of insulating material extending from housing 12 and having its inner end portion journalled in the wall of housing 12 by a bearing 1S. Acrank 20 is rigidly secured to the inner end ofshaft 16 within housing 12 and asecond crank 22 is rotatably mounted on the inner end ofshaft 16 as is particularly clear in FIG. 6. Thecrank 22 is shorter in effective length than thecrank 20 and is of generally T-shaped configuration, the stem of the T being the radial leg portion of thecrank 22. The top of the T terminates in a pivot pin 24 at one end thereof, the opposite end being grooved at 26 to receive one end of atoggle spring 28. The opposite end ofspring 28 is received within asimilar groove 30 in the outer end of thelonger crank 20.

Anelongated link 32 has one end thereof slipped over pin 24 to form a pivotal connection with theshorter crank 22, the opposite end oflink 32 being bifurcated and pivotally connected by apin 34 toextension member 36 connected to and aligned with the longitudinal axis of an elongated, reciprocable operating element orrod 38 extending into housing 12 frominterrupter unit 14. A pair ofspaced stops 40 and 42 are integrally formed with housing 12 and define the limits of swinging movement of thelonger crank 20. An adjustable, threaded stud 44 provides a stop for limiting movement of theshorter crank 22 during breaking of the circuit throughinterrupter unit 14.

Theoperating rod 38 is electrically conductive and terminates withinunit 14 in acontact 46 which is movable toward and away from astationary contact 48.Unit 14 has a cylindrical, ceramic envelope 50 which is evacuated, a sealing bellows 52 being employed withrod 38 to permit reciprocal movement thereof without destroying the vacuum condition within envelope 50. Thestationary contact 48 is formed at the end of an electricallyconductive shank 54, the latter androd 38 being longitudinally aligned and coaxially disposed with respect to envelope 50. Acopper gas lshield 56 of cylindrical, openended configuration is supported in the space betweencontacts 46, 48 and envelope 50 and is utilized to condense volatile metal that may escape from the contacts during load break operation ofunit 14.

Theshank 54 is supported by a conductive end plate orcap 58 to which a terminal member 60 is bolted. The opposite end ofunit 14 is closed by a conductive plate or cap l62 which is bolted to the wall of housing 12. Theoperating rod 38, being integral with themovable contact 46, presents the other terminal ofunit 14, aexible shunt lead 64 being connected torod 38 and housing 12 to provide a low resistance connection between housing 12 androd 38 and yet permit reciprocal movement of the latter. Threestrain rods 74 of insulating material extend from housing 12 adjacent cap y62 to the terminal member 60 to add structural strength to the assembly.

A female connector 66 s formed from solid rod stock and has its inner end threaded to permit mounting ofconnector 66 directly to the top of housing 12. The threaded end ofconnector 66 projecting into housing 12 also provides a convenient means of physically and electrically connectinglead 64 to housing 12, as is clear in FIGS. 3 and 5.

A secondfemale connector 68 is similar in construction toconnector 66 and is shown in longitudinal section in FIG. 3, the lower end ofconnector 68 being received in a tapped opening (not shown) in terminal member 60 to both mechanically and electrically joinconnector 68 with terminal 60. Amating male connector 70 forfemale connector 68 is also illustrated in FIG. 3 and is electrically and mechanically joined to the end of an insulated cable 72.

The housing 12,unit 14, andconnectors 66 and 68 are encapsulated by a waterproof,elastic jacket 76 of molded plastic material. The encapsulating material has a high dielectric strength and preferably comprises a suitable synthetic resin substance such as one of the elastomers, silicon rubber, or epoxy rubber. A degree of elasticity is important to provide moisture seals at theconnectors 66 and 68 and theoperating shaft 16; additionally, utilization of an elastic material reduces the danger of fracture thereof by expansion and contraction of the metallic components of the assembly or by a physical blow.

It should be noted that theinsulating shaft 16 projects laterally from housing 12 and is encased in a laterally projectingportion 78 of the encapsulation integral with themain jacket portion 76 thereof, the outer end ofshaft 16 projecting from ythe termination ofencapsulation portion 78 and being provided with anoperating arm 80 formed with aring 82 at its outer end. A pair of O-rings 84surround shaft 16 adjacent the end of theprojecting encapsulation portion 78 and, prior to molding,shaft 16 is coated with a parting agent. Thus, theshaft 16 is freely rotatable within the encapsulation but the ingress of moisture thereinto is precluded.

Referring to FIG. 1, the encapsulated switch assembly is shown in an underground installation disposed within avault 85 and attached to a suitable mounting means 87 extending inwardly from the sidewall ofvault 85. The assembly is oriented with theconnectors 66 and 68 projecting upwardly and with the axis of theoperating shaft 16 ofcrank arm 80 horizontally disposed.

Acontinuous covering 86 extends over the outer surface of both themain body portion 76 and the laterally projectingportion 78 of the encapsulating jacket and is electrically conductive in nature for the purpose of containing electric fields within the jacket and controlling the electrical stresses within the insulating material. The covering 86 may be in the form of a conductive coating such as a layer of the same substance as the main encapsulation with suitable conductive material added thereto. Alternatively, a metallic netting or a complete metal sheathing may be utilized to provide the continuousconductive covering 86. It may be appreciated that electric fields will be produced within the switch assembly under load conditions; therefore, control of the distribution of electrical stress is important in order to assure that the stresses do not exceed the safe dielectric value of the encapsulation.

Referring to FIG. 3, it may be seen that themale connector 70 there illustrated in association withfemale connectors 68 is enveloped by aninsulating shroud 88 of cylindrical configuration which complementally receives the frusto-conical sheath 90 formed around thefemale connector 68 by the encapsulating jacket. Theshroud 88 may be of the same material as the encapsulation and is provided with a radially inwardly extending,annular lip 92 at its outer end which is received within a corresponding annular recess 94 in the base ofsheath 90. A suitable conductive covering 96 extends over the outer surface ofshroud 88 and is in contact with theconductive covering 86 of the encapsulating jacket to form a continuous, electrically conductive outer surface over the connectors l68 and 70 whenlip 92 is snapped in place within recess 94. An identical male connector (not shown) is provided on the end of a second connecting cable and mates with thefemale connector 66 as the shroud thereof complementally receives the frusto-conical sheath 98 surroundingfemale connector 66.

In use, theconnectors 66 and 68 provide a means of electrically coupling thecontacts 46 and 48 ofinterrupter unit 14 in series with a curent carrying line, the circuit therethrough extending alongshunt lead 64, along the operatingrod 38 and through thecontacts 46 and 48 to the terminal 60. Thecontacts 46 and 48 are shown closed in FIG. 3 and open in FIG. 5, separation thereof being effected by rotation of arm 80l through an angle of 90 to, in turn, rotateshaft 16 in a clockwise direction as viewed in FIGS. 3 and 5.

Noting FIG. 3, it may be seen that thetoggle spring 28 is in tension between the outer ends of the twocranks 20 and 22 and biases the same toward each other. In rotating the longer crank 20 in a clockwise direction to the position thereof shown in FIG. 5, thecrank 20` is shifted from aposition abutting stop 42 to a position in engagement withstop 40. During such travel crank 20 moves over center to causespring 28 to reverse the effective direction of the force applied thereby to crank 22; this, in turn, drives crank 22 in a counterclockwise direction aboutshaft 16 to elfect a rapid separation of thecontacts 46 and 48. It should be understood that the operating speed of themovable contact 46 is independent of the operating speed of crank 20, thecontact 46 remaining in engagement with thestationary contact 48 until such time that crank 20 moves over center or past its toggle position.

The stud 44 serves as an adjustable stop to set the spacing ofcontacts 46 and 48 in order to prevent overstressing of the bellows 52. However, when it is desired to reclose. thecontacts 46 and 48, movement of the shorter crank 22 in a clockwise direction is unrestricted and is limited only by the ultimate re-engagement of the`contacts 46 and 48. Thus, if contact erosion should occur, it is assured that thetoggle spring 28 will forcibly holdcontact 46 in engagement withcontact 48.

Furthermore, with reference to FIG. 3, it may be seen that thetoggle spring 28 and the shorter crank 22 are positioned such that the moment arm about the axis ofshaft 16 is at a maximum for the operating cycle when thecontacts 46 and 48 are fully closed. Therefore, maximum force is transmitted to operatingrod 38 bylink 32 andextension 36 when thespring 28 is holding themovable contact 46 against thestationary contact 48. This reduces the tendency of the contacts to jump apart if a fault should occur upon closure thereof or at any time when the contacts are closed.

Movement of operatingarm 80 between the positions thereof illustrated corresponding to the open and closed positions of the interrupter contacts may be readily accomplished by one man utilizing a linemans hook stick inserted through thering 82 at the outerend ofA arm 80. Thus, the apparatus may be readily operated in its installed position within thevault 85 from a remote location at ground level or above. Furthermore, the male andfemale connectors 70 and 68 and the identical male counterpart and thefemale connector 66 may be readily coupled and uncoupled at ground level by one man utilizing an insulated tool as a safety precaution. Full seating of the telescoping male and female connectors is assured by the snap action of theannular lip 92 and the corresponding recess 94 which also, in cooperation with the mating surfaces of thesheath 90 and theshroud 88, provide an effective moisture seal.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A switch assembly for underground electric service comprising:

a housing;

an interrupter unit affixed to said housing and having a pair of contacts, one of the latter being movable between an open position spaced from the other contact and a closed position in engagement with said other contact, and an operating element coupled with the movable contact for shifting the latter between said positions and extending into said housing;

a remotely operable toggle mechanism disposed in said housing and including a rotatable operating member, a iirst crank rigid with said member, a second crank rotatable about the axis of rotation of said member and coupled with said element, and yieldable means interconnecting said cranks and biasing the latter toward each other to normally forcibly hold the movable contact against said other contact and to rotate said second crank in a direction to shift the movable contact to its open position under the bias of said yieldable means as said lirst crank is rotated over center, whereby the contacts rapidly separate;

a waterproof, elastic jacket of high dielectric strength encapsulating said housing and said unit,

said member extending from said housing through said jacket and being provided with means spaced from said housing adapted for actuation from a remote location to rotate the member and thereby operate said mechanism; and

connector means electrically coupled with said contacts for connecting the latter to a current-carrying line.

2. The invention of claim 1, there being means rotatably mounting said second crank for free movement in the opposite direction restricted only by the engagement of said contacts, whereby to assure that a good electrical connection is established by the contacts regardless of erosion thereof.

3. The invention of claim 2, said yieldable means being disposed to apply maximum force to said element when holding the movable contact against said other contact, whereby to reduce the tendency of the contacts t0 jump apart under a fault condition.

4. The invention of claim 2, there being a pair of spaced stops in said housing engageable by said first crank and defining the limits of its path of travel.

5. The invention of claim 4,

said second crank being rotatably mounted on said member,

said mechanism including a link pivotally connected with said element and pivotally joined to said second crank at a point radially spaced from said axis of the member.

6. The invention of claim 1,

said unit being of the vacuum interrupter type and including an evacuated envelope secured to said housing and having said contacts disposed therewithin,

said element being elongated, longitudinally reciprocable, and having an inner end within said envelope presenting said movable contact,

said yieldable means comprising a toggle spring in tension between said cranks and connected to said first crank at a point in greater spaced relationship to said axis of the member than the point of connection of the spring to said second crank,

said mechanism further including a drive connection between said second crank and the outer end of said element for imparting rectilinear motion to the latter as said second crank is rotated in said direction or the opposite direction by said spring.

7. A switch assembly for underground electric service comprising:

an electrically conductive housing;

an interrupter unit affixed to said housing and having a pair of terminals, a movable contact for establishing or breaking an electrical circuit between said terminals, and an operating element coupled with said contact for shifting the latter between positions respectively opening and closing said circuit,

said element extending into said housing and presenting one of said terminals of the unit;

means electrically interconnecting said element and said housing;

a remotely operable actuating mechanism disposed in said housing and coupled with said element for shiftthe latter to, in turn, open and close said circuit;

a first connector mounted on said housing and electrically connected to the latter;

a second connector mounted o nsaid unit and electrically connected to the other of said terminals thereof;

a waterproof, elastic jacket of high dielectric strength encapsulating said housing, said unit, and said connectors,

said mechanism including a shiftable operating member of insulating material extending from said housing through said jacket, said member being provided with means spaced from said housing adapted for actuation from a remote location to shift the member and thereby operate said mechanism; and

a moisture seal between said member and the surrounding jacket.

8. The invention of claim 7, said jacket having an outer surface provided with electrically conductive means extending thereover to present a continuous outer covering for containing electric fields within the jacket and controlling electrical stress therewithin.

9. The invention of claim 7,

said first and second connectors projecting outwardly from said housing and said unit respectively,

said jacket being configured to define a sheath extending over each connector respectively,

there being a mating connector for each of said first and second connectors respectively provided with a waterproof, elastic, insulating shroud complemental to and cooperable with the corresponding sheath to form a moisture seal at each pair of connectors when the latter are mated.

10. A switch assembly comprising:

a load interrupter having a pair of contacts, one of the latter being movable between an open position spaced from the other contact and a closed position in engagement with said other contact, and an operating element coupled with the movable contact for shifting the latter between said positions;

a toggle mechanism including a rotatable operating member, a iirst crank rigid with said member, a second crank rotatable about the axis of rotation of said member and coupled with said element, and yieldable means interconnecting said cranks and biasing the latter toward each other to normally forcibly hold the movable contact against said other contact and to rotate said second crank in a direction to shift the movable contact to its open position under the bias of said yieldable means as said rst crank is rotated over center, whereby the contacts rapidly separate,

said member being providedl with means adapted for actuation to rotate the member and thereby operate said mechanism; and.

connector means electricallyy coupled with said conts for connecting the latter to a current-carrying 11. The invention of claim 10,

there being means rotatably mounting said second crank for free movement in thel opposite direction restricted only by the engagement of said contacts, whereby to assure that a good electrical connection is established by the contacts regardless of erosion thereof,

said yieldable means being disposed to apply maximum force to said element when holding the movable contact against said other Contact, whereby to reduce the tendency of the contacts to jump apart under a fault condition.

12. The invention of claim 11,

said second crank being rotatably mounted on said member,

said mechanism including a link pivotally connected with said element and pivotally joined to said second crank at a point radially spaced from said axis of the member.

References Cited UNITED STATES PATENTS H. O. JONES, Primary Examiner U.S. Cl. X.R.

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