CA1133555A - Dual blade-type continuous high current disconnect switch - Google Patents

Abstract

DUAL BLADE-TYPE CONTINUOUS
HIGH CURRENT DISCONNECT SWITCH

Abstract of the Disclosure An improved, high voltage, electrical blade-type single-pole disconnect switch is provided which has an especially designed clip or jaw end for maintaining proper electrical contact between the switch blade and adjacent switch terminal even under very high momentary loads. The switch blade is formed of a pair of elongated, laterally spaced, deflectable metallic blade halves which engage, and are deflected laterally by, the terminal contact when the switch is closed; proper blade-terminal contact pressure is maintained by a tension bolt and sleeve spacer arrangement located adjacent the free end of the blade. The releas-able latch for the blade is pivoted thereto at a point closer to the marginal end of the blade than the engagement between the latch and stationary latching clip, such that the latch is pivoted closed (i.e., into firmer engagement with the clip) under the influence of normal electromag-netic forces which tend to pivot the blade to its open position.

(Docket No. 16521)

Description

- ~133S55 CONTINUOUS HIGH CURRENT ELECTRICAL SWITCH ~--Background of the Invention ~
.
1. Field of-the Invention The present invention is broadly concerned with high voltage single pole electrical disconnect switches of the type used in electrical transmission and distribution systems.
More particularly, it is concerned with such switches which ~-employ a number of specialized features which improve the ` `~
performance thereof, particularly with respect to maintaining proper and continuing electrical contact between the pivotal switch blade and adjacent terminal contact during all modes ~`
of operation, even during very high electrical transitory ~`
loads. ~ .-

2. Description of the Prior Art Heavy duty single pole disconnect switches have long been used in electrical transmission and distribution `
systems in order to provide necessary switching capabilitie Such switches`normally include a pair of spaced electrical ~ ~
terminals, and a pivotally shiftable, conductive switch blade ~ `
20 having a pivoted end and a free end for alternately opening `
and closing the switch as desired. Latching and disconnect structure is normally provided adjacent the free end of the switch blade for latching the latter in a closed position, and permitting selective opening of the switch through the use of a hot stick tool or the like when needed.
In order to be truly effective, such a disconnect switch must be provided with electrical contact and latching structure -which ensures that a proper electrical contact is maintained at all ~ ~335~

times to thus eliminate undesirable switch openings or other failures.
To this end, switches of the prior art have employed a number of expedients such as auxiliary contacts or helical compression springs in an attempt to ensure the integrity of operation of the switches. In addition to the added costs of such items, their presence inevitably tends to complicate and clutter the latching mechanism. Accordingly, there is a need for a simplified switch construction having a minimum number of parts and which completely eliminates use of extra-- neous springs or contacts, while nevertheless meeting all other dictates of proper switch performance.
Summary of the Invention In general terms, the present invention provides a switch comprising: a pàir of spaced apart electric terminals;
an elongated conductive switch blade of length to span said terminals; means proximal to one of said terminals pivotally supporting one end of said blade for selective movement of ;
the blade between a closed position where the other end of the blade is electrically connected to said other terminal, and an open position where said other end of the blade is electrically disconnected from said other terminal; latching means including first and second latching components having corresponding first and second surfaces which are interengaged when said blade is in the closed position thereof, said first and second components being respectively mounted on said first blade and adjacent said other terminal, one of said first and second components being pivotally mounted and the other of said components being stationary; said latching means including structure for imposing torque on said one pivotally mounted latching component which moves the surface thereof into tighter and firmer engagement with the surface of said stationary `
latching component, under the influence of the normal loop component of electromagnetic force which tends to rotate said switch blade to the open position thereof.
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3 -Preferably, the said one latching component is pivotably mounted.to said blade. The switch of-the present invention preferably includes manually operable latch-releasing structure.

Brief Description of the Drawings Figure 1 is an elevational view of an underhung switch in accordance with the invention, with certain components of the jaw end of the switch being illustrated :~
in phantom;
Figure 2 is a bottom view of the switch illustrated in Figure l;
Figure 3 is an end elevational view illustrating the jaw end of the switch;

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1 Fig. 4 is an enlarged, fragmentary bottom view illustrating in de-tail the jaw end of the switch;
~ig. 5 is a side elevational view of S another switch in accordance with the invention using a single, elongated ins~Llator;
Fig. 6 is an enlarged, fragmentary view illustrating the jaw end of the switch as well as the opening operation thereof in phantom; and Fig. 7 is a sectional view taken along line 7-7 of Fig. 6.

Description of the Preferred ~mbodiments Referring first to Figs. 1-4, a switch lS 10 is illustrated which broadly includes a pair of -spaced, conductive electrical terminals 12 and 14, and a conductive, bifurcated switch blade 16 having a pivoted end 18, and a free or jaw end 20. -, The terminals 12 and 14 are in spaced relationship as illustrated, and blade 16 is of length to normally bridge the contacts and complete a cur-` rent path through the switch 10. Latching means 22 is provided adjacent free end 20, along with ~ -disconnect apparatus 24 allowing the switch to be opened or closed as desired.
In more detail, it will be seen that -switch 10 includes an elongated, plate-like sup-port member 26 having a pair of connection devices ~ -~
28 secured thereto for allowing switch 10 to be supported in an underhung or vertical fashion on , overhead structural apparatus or the like. A pair `
of spaced, skirted insulators 30, 32 are secured to member 26 and depend therefrom as illustrated.
Terminal 12 is secured to the underside of insulator 30 by conventional bolts and includes ~. .
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,~ - 5 -``1 an elongated, apertured tab portion 3~, and an integral, upwardly and angularly extending mount-ing arm 36. l`he apertures in tab 34 faciLitate connection of an electrical conductor to the terminal 12, while mounting arm 36 supports, at its outermost end, a metallic annulus 38 for pivotal mounting of blade 16 as will be described.
Terminal 14 is likewise secured to the underside of insulator 32 and includes an elon-gated, apertured tab 42 for mounting of a second conductor, as well as a down~ardly extending, integral, generally triangular segment 44. An elongated, depending terminal contact 46 is inte-gral with segment 4hj is located at the approxi-mate center thereof, and is of substantially greater thickness than the main body of the seg-ment 44 (see Figs. 3 and 4). Insulator 32 also - supports, on i-ts underside, a pair of laterally spaced, metallic, curved and outwardly diverging ; 20 loadbreak hooks 48, 50 of conventional design.
Switch blade 16 includes a pair of elongated, rectangular, laterally spaced, side-by-side blade halves 52, 54 formed of hard drawn, , .
yieldable and deflectable copper material. The .
blade halves 52, 54 are coupled together adjacent pivoted end 18 by means of a rigid, transversely -:
extending connector 58. Also, as best seen in Fig. 2, a pivot bolt arrangement 60 extends through the respective blade halves 52, 54, as well as annulus 38, in order to pivotally secure the blade 16 to the innermost end of terminal 12. .
Stop pin 56 is optionally provided in blade halves 52 and 54 between bolt 60 and connector 58 to restrain pivotal movement of the switch blade 16 :~
to an arc oP about 90. However, iE desired by -;.
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:~3355~;i (i 1 the user, pin 56 may be removed to allow blade 16 to swing thro~lgh an arc of about 150.
The free or jaw end 20 of blade 16 is provided with an elongated, transversely extend-ing, rigid coupler 62 similar to coupler 58. A
specialized connection structure 64 (see Fig. 4) is provided closer to the outermost margin of free end 20 than coupler 62. This structure 64 includes an elongated, transversely extending headed bolt 66 which extends through blade halves 52, 54 and ;~
has a nut 68 secured to the outermost end thereof.
An elongated, tubular spacer sleeve 70 is carried `
by the bolt 66 between the respective blade halves, and is of a width to be engaged by the respective blade halves when switch 10 is in its open position ~herein free end 20 is disengaged from terminal 14. The structure 64 includes a pair of conventional spring-type belleville washers 72 and 74 which are respectively disposed -between the head of bolt 66 and the outer face of blade half 54, and nut 68 and the outer face of blade half 52.
Latching means 22 includes (see Fig. 6) a pivotally mounted, irregularly shaped latch 76 2j which has an upwardly extending portion 78 termi- i nating in a hook 80 presenting a latching surface 82 on the underside thereof. In addition, the innermost clip portion 84 of segment 44 presents a ~-i corresponding latching surface 86 which is im- ~
portant for purposes to be described. Latch 76 is ;
pivotal about the outside diameter of the sleeve 70, and the sleeve 70 is pivotal about the axis defined by bolt 66 Disconnect apparatus 24 includes a pivotally mounted disconnect member 88 having an ',''~,' .
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`1 O-ring 90, and an outwardly e~tending, latch-engaging leg 9~. The member 88 is journaled on coupler 62 between the blade halves 52, 54, for pivotal movement. Also, a return spring 94 is connected between member 88 and latch 76 as best illustrated in ~ig. 6.
Considering first the operation and orientation of switch 10 in the switch closed position thereof, attention is directed to Figs. 4 and 7. As can be seen, when the blade 16 is in the switch closed position, the respective blade halves 52, 54 engage the opposite sides of contact 46, and the latter is dimensioned to fit between the blades and laterally deflect and separate the blade halves apart a distance greater than the ~;
normal lateral spacing thereof. As seen in Fig.

4, this lateral deflection is illustrated in phantom and serves to create gaps 95 between the opposed ends of the sleeve 70 and the adjacent `
~0 blade faces. ~lso, the connection structure 64 serves to facilitate maintenance of high contact ~ pressures bet~een the blade halves and the ter-minal contact. That is to say, provision of the laterally deflect~able blade halves, in conjunction '5 ~ith the spring-biased belleville washer and bolt combination, effectively maintain contact pres-sures during all operations encountered in prac-tice. In the switch closed position, it will be seen that bolt 66 is placed in tension for ade-3~ quate maintenance of contact pressures. Further-more, in the switch closed position, high momen-tary currents cause the blade halves to be mutu- ~;~
ally attracted together to thereby press against - the terminal contact 46; and this attractive "
movement is made possible because of the gaps 95 ..

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1 as described. ~s a resul~, contact pressure will be more than double at 40,000 amperes of fault current. I
As a further means for ensuring the integrity of tlle latching assembly, latch 76 has been especially designed. Specifically, the pivot axis thereof (i.e., that defined by bolt 66) is disposed closer to the outer margin of the free end of the switch blade than the areas of mutual engagement between the latching surfaces 82, 86 (see Fig. 6). Thus, under the influence of the normal loop component of electromagnetic force ~hich tends to rotate the switch blade 16 to the ~;
switch open position thereof (wherein the free end 20 is disengaged from terminal 14), a torque is imposed on the latch which moves the surface 82 into tighter and firmer engagement with the sur-face 86. Hence, by virtue of this special con-struction, the electrical forces normally tending -to blow open the switch blade (especially during transitory overloads) actually serve to increase ~`
~ latching power.
I~hen it is desired to open switch 10, it ~-is only necessary to pivot the member 88 through 2~ the use of a hot stick tool, for example, such that leg 92 comes into engagement with the proxi- `
mal surface of latch 76. This serves to rotate the latch 76 in a counterclockwise direction as viewed in Fig. 6, in order to disengage the re~
3~ spective latching surfaces 82, 86. If the switch ~ ;
contacts are frozen in a latched position though, exertion of greater force on the member 88 causes the lower end of latch 76 to contact inclined face 45 of segment 44 (Fig. 6) in a manner to create a prying action which assists in breaking open the ;;:`

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- ` g 1 sticking s~7itch contacts. As can also be seen from Fig. 6 of the drawings, continued pulling movement on the member 88 !- and thus blade 16, serves to open the blade and break the current path throu~h s~itch 10. Over extension and damage t;o spring 94 is avoided when force is applied to ring 90 of member 88 by virtue of the fact that leg portion 92 of the member 88 engages portion 78 of latch 76 to prevent such effect.
Furthermore, when the blade is fully free of terminal 14, return spring 94 serves to shift the latch 76 and member 88 back to their normal rest positions after the hot stick tool is removed. Another feature of the latching mecha-nism is the fact that during closing of the blade 16, the pressure of the hook stick tool on member 88 is transferred to blade 16 through stop 89 as is best seen from Fig. 7 as well as pin 62 as shown in Fig. 6, thereby leaving latch 76 free to pivot as required to slide up the ramp 45 of member 46 and thus positively latch. As switch 10 is closed, pivoting movement of the switch blade 16 back to the switch closed position first causes hook 80 to engage the innermost marginal edge 84 .5 of portion 44. This surface serves as a ramp ~r --entry surface and pivots the latch 76 as necessary to clear the outermost end of the clip portion 84.
At this point the return spring 94 serves to pivot the latch 76 to its normal latching position, -`
whereupon the surfaces 82, 86 come into latching `;
engagement. As can best be seen in Fig. 4, the sides of terminal contact 46 which engage blade 16 are curved in order to present a line engagement between the flat blade and the curved surface thus serving to create a high contact pressure, com-.
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1.0 -1 pensate for misalignmen-t, if any, between blade and contact, reduce the surface area which must be broken when ice is present and provide self clean-ing of contacts when the switch blade is opened or closed.
~ ~ig. 5 illustrates another embodiment of the invention. In this case a normal, elongated, skirted insulator 96 is employed for maintaining the contacts 12 and 14 in a proper spaced rela- ~-tionship. The insulator 96 is of the type nor-- mally employed for mounting electrical cutout apparatus, and includes a central, transversely extending mounting bracket 98, and end-mounted, laterally extending connection structure 100, 102 for mounting of the-switch terminals on the insu-lator body. Insulator 96 preferably has a series of integral, circular, radially extending, longi-tudinally spaced skirts for increasing the flash-over resistance of the insulator body. In all other respects, the embodiment illustrated in Fi~.

5 is identical with switch 10, and therefore need `not be described in further detail. ;-In practice with the switches of the ' invention contact force in the order of 140 lbs. `
is provided between the terminal contact 46 and blade halves 52, 54 when an assembly torque of 10 inch/pounds is employed. This is achieved through the use of the yieldable blade halves and the speciali~ed structure 64 which limits the possible extent of deflection of the blade halves and creates the gaps 95 discussed above.

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Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A switch comprising:
a pair of spaced apart electrical terminals;
an elongated conductive switch blade of length to span said terminals;
means proximal to one of said terminals pivotally supporting one end of said blade for selective movement of the blade between a closed position where the other end of the blade is electrically connected to said other terminal, and an open position where said other end of the blade is electrically disconnected from said other terminal;
latching means including first and second latching components having corresponding first and second surfaces which are interengaged when said blade is in the closed position thereof, said first and second components being respectively mounted on said blade and adjacent said other terminal, one of said first and second components being pivotally mounted and the other of said components being stationary;
said latching means including pivot means of said one pivotally mounted latching component, said pivot means being so disposed relative to the surface of the latching component, that the said surface moves into tighter and firmer engagement with the surface of said stationary latching component, under the influence of the normal loop component of electromagnetic force which tends to rotate said switch blade to the open position thereof.

2. The switch as set forth in claim 1, said one latching component being pivotally mounted to said blade.

3. The switch as set forth in claim 1, including manually operable latch-releasing structure.