GB2043350A - Continuous high current electrical switch - Google Patents

Abstract

A high voltage, electrical blade-type single-pole disconnect switch is provided which has an especially designed clip or jaw end for maintaining electrical contact between a bifurcated switch blade (16) and adjacent switch terminal (14) even under very high momentary loads. The switch blade is formed of a pair of elongated, laterally spaced, deflectable metallic blade halves (52, 54) which engage, and are deflected laterally by, the terminal contact (14) when the switch is closed; proper blade-terminal contact pressure is maintained by a tension bolt, sleeve spacer and belleville washer arrangement (66, 68, 70, 72, 74) located adjacent the free end of the blade. The releasable latch (76) for the blade is pivoted thereto at a point closer to the marginal end of the blade (16) than the engagement between the latch and a stationary latching clip (84), such that the latch is pivoted closed into firmer engagement with the clip under the influence of normal electromagnetic forces which tend to pivot the blade to its open position. <IMAGE>

Description

SPECIFICATION Continuous high current electrical switch This invention relates to an electrical switch and specifically to a high voltage single pole electrical disconnect switch of the type used in electrical transmission and distribution systems. More particularly, the present invention is concerned with such switches which employ a number of specialized features which improve the performance thereof, par ticularlywith respect to maintaining proper and continuing electrical contact between the pivotal switch blade and adjacentterminal contact during all modes of operation, even during very high electrical transitory loads.

Heavy duty single pole disconnect switches have long been used in electrical transmission and distribution systems in order to provide necessary switching capabilities. Such switches normally include a pair of spaced electrical terminals, and a pivotally shiftable, conductive switch blade 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 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, the object of the present invention is to provide a simplified switch construction having a minimum number of parts and which completely eliminates use of extraneous springs or contacts, while nevertheless meeting all other dictates of proper switch performance.

The present invention provides an electrical switch comprising a pair of spaced electrical terminals each including structure for attachment of an electrical conductor thereto; an elongated, conductive switch blade of length to bridge said terminals and close said switch to complete a current path therethrough, said switch blade including a pair of laterally spaced, conductive, blade halves; means for electrically connecting one end of said switch blade to one of said terminals, and for pivotally mounting said switch blade for movement thereof between a switch closed position wherein said switch blade is in bridging relationship to said terminals with the free end of said switch blade in electrical contact with said other terminal, and a switch open position wherein said free end of said switch blade is in spaced relationship to said other terminal to break the current path through said switch; terminal contact means for ensuring proper electrical contact between said free end of said switch blade is in said switch closed position, including:-aterminal contact electrically connected to said other terminal and disposed to fit between and engage said blade halves when said switch blade is in said blade closed position, said contact being dimensioned for laterally deflecting and separating said blade halves apart a distance greater than the normal lateral spacing thereof; and means for maintaining high contact pressure between said blade halves and said terminal contact including an elongated, tubular spacer sleeve disposed transversely between said blade halves, a bolt disposed within said sleeve and extending through both of said blade halves, the head of said bolt being proximal to the face of one of said blade halves remote from said sleeve, a nut threaded onto said bolt and proximal to the face of the other of said bla halves remote from said sleeve, and a pair of belleville washers respectively disposed between said head and the adjacent blade half face, and said nut and the adjacent blade half face, said bolt head and nut, and the corresponding belleville washers, being spaced apart a distance for allowing said blade halves to deflect outwardly only to a limited degree when said switch blade is in said switch closed position.

The present invention also provides an electrical switch comprising a pair of spaced electrical terminals, and a pivotally shiftable, conductive switch blade having a pivoted end and a free end for alternatively opening and closing said switch as desired, and latching means for latching said switch blade in the switch closed position thereof, said latching means including stationary clip structure adjacent the free end of said switch blade when the latter is in said switch closed position and presenting a first latching surface thereon; and a latch pivoted to said switch blade proximal to the outer margin of said free end thereof and presenting a second latching surface configured for engaging said first surface when said switch blade is in said switch closed position thereof and holding the switch blade in such position, the pivot axis of said latch being disposed closer to said outer margin than the areas of mutual engagement between said first and second latching surfaces for creating, under the influence of the normal loop component of electromagnetic force which tends to rotate said switch blade to the switch opening position thereof, a torque on said latch for moving said second surface into tighter engagement with said first surface, to thereby increase the latching power of said latching means.

In preferred forms, the latching clip is mounted on the transversely extending spacer sleeve of the switch blade in orderto minimize the number of parts. Also, latch disconnect means in the form of a pivotal member mounted on the switch blade is provided for opening of the switch through the use of a hot stick tool as the need arises.

In 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; Fig. 2 is a bottom view of the switch illustrated in Fig. 1; Fig. 3 is an end elevational view illustrating the jaw end of the switch; Fig. 4 is an enlarged, fragmentary bottom view illustrating in detail the jaw end of the switch; Fig. 5 is a side elevational view of another switch in accordance with the invention using a single, elongated insulator; 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.

Referring first to Figs. 14, a switch 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 current 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 support 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 insulator30 by conventional bolts and includes an elongated, apertured tab portion 34, and an integral and angularly extending mounting arm 36. The 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 elongated, apertured tab 42 for mounting of a second conductor, as well as a downwardly extending, integral, generally triangular segment 44. An elongated, depending terminal contact 46 is integral with segment44, is located at the approximate center thereof, and is of substantially greater thickness than the main body of the segment 44 (see Figs. 3 and 4). Insulator 32 also supports, on its underside, a pair of laterally spaced, metallic, curved and outwardly diverging loadbreak hooks 48, 50 of conventional design.

Switch blade 16 includes a pair of elongate, 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 of about 90 . However, if desired by the user, pin 56 may be removed to allow blade 16 to swing through an arc of about 150 .

The free or jaw end 20 of blade 16 is provided with an elongated, transversely extending, rigid coupler 62 similar two coupler 58. A 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 wherein 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 which has an upwardly extending portion 78 terminating 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 corresponding latching surface 86 which is important 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 a ring 90, and an outwardly extending, latch-engaging leg 92.

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 Fig. 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 blade faces. Also, the connection structure 64 serves to facilitate maintenance of high contact pressures between the blade halves and the terminal contact. That is to say, provision of the laterally deflectable blade halves, in conjunction with the spring-biased belleville washer and bolt combination, effectively maintain contact pressures during all operations encountered in practice. In the switch closed position, it will be seen that bolt 66 is placed in tension for adequate maintenance of contact pressures. Furthermore, in the switch closed position, high momentary currents cause the blade halves to be mutually attracted together to thereby press against the terminal con tact46; and this attractive movement is made poss ible because of the gaps 95 as described. As a result, contact pressure will be more than double at 40,000 amperes of fault current.

As a further means for ensuring the integrity of the 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 which 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 surface 86.Hence, by virtue of this special construction, the electrical forces normally tending to blow open the switch blade (especially during transitory overloads) actually serve to increase latching power.

When it is desired to open switch 10, it is only necessary to pivot the member 88 through the use of a hot stick tool, for example, such that leg 92 comes into engagement with the proximal 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 respective 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 mannerto create a prying action which assists in breaking open the sticking switch 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 through switch 10. Over extension and damage to 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 mechanism 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 of portion 44. This surface serves as a ramp or 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, compensate for misalignment, if any, between blade and contact, reduce the surface area which must be broken when ice is present and provide self cleaning of contacts when the switch blade is opened or closed.

Fig. 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 relationship. The insulator 96 is of the type normally 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 insulator body. Insulator 96 preferably has a series of integral, circular, radially extending, longitudinally spaced skirts for increasing the flashover resistance of the insulator body. In all other respect, the embodiment illustrated in Fig. 5 is identical with switch 10, and therefore need not be described in further detail.

In the practice with the switches of the invention contact force in the order of 140 Ibs. 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 specialized structure 64 which limits the possible extent of deflection of the blade halves and creates the gaps 95 discussed above.

Claims (12)

1. An electrical switch comprising a pair of spaced electrical terminals each including structure for attachment of an electrical conductor thereto; an elongated, conductive switch blade of length to bridge said terminals and close said switch to complete a current path therethrough, said switch blade including a pair of laterally spaced, conductive, blade halves; means for electrically connecting one end of said switch blade to one of said terminals, and for pivotally mounting said switch blade for movement thereof between a switch closed position wherein said switch blade is in bridging relationship to said terminals with the free end of said switch blade in electrical contact with said otherterminal, and a switch open position wherein said free end of said switch blade is in spaced relationship to said other terminal to break the current path through said switch; terminal contact means for ensuring proper electrical contact between said free end of said switch blade and said other terminal when said switch blade is in said switch closed position, including:- a terminal contact electrically connected to said other terminal and disposed to fit between and engage said blade halves when said switch blade is in said blade closed position, said contact being dimensioned for laterally deflecting and separating said blade halves apart a distance greater than the normal lateral spacing thereof; and means for maintaining high contact pressure between said blade halves and said terminal contact including an elongated, tubular spacer sleeve disposed transversely between said blade halves, a bolt disposed within said sleeve and extending through both of said blade halves, the head of said bolt being proximal to the face of one of said blade halves remote from said sleeve, a nut threaded onto said bolt and proximal to the face of the other of said blade halves remote from said sleeve, and a pair of belleville washers respectively disposed between said head and the adjacent blade half face, and said nut and the adjacent blade half face, said bolt head and nut, and the corresponding belleville washers, being spaced apart a distance for allowing said blade halves to deflect outwardly only to a limited degree when said switch blade is in said switch closed position.

2. An electrical switch according to Claim 1, wherein there is provided support means for said terminals comprising an elongated insulator, means mounting said terminals on said insulator in spaced relationship along the length thereof, and means on said insulator for securing the latter to a supporting base.

3. An electrical switch according to Claim 2, wherein said means for mounting the terminals on the insulator are constructed and arranged to cause the insulator to be in generally parallel relationship to the blade when the latter is in the closed position thereof.

4. An electrical switch according to Claim 3 wherein said means for securing the insulator to a supporting base comprises a single mount located intermediate the ends of the insulator substantially midway between the terminals and extending away from the axis of the insulator in a direction opposite that of the terminals.

5. An electrical switch according to Claim 2, wherein said insulator comprises an elongated body having a series of circular, integral, outwardly projecting, longitudinally spaced, coaxial skirts along the length thereof for increasing the flashover resistance of the body.

6. An electrical switch according to any of Claims 1 to 5, wherein said contact pressure-maintaining means is disposed in spaced relationship to the outer margin of said free end of said switch blade, with the areas of engagement of said blade halves with said terminal contact being located between said contact pressure-maintaining means and said outer margin.

7. An electrical switch according to Claim 6 including a transversely extending, rigid reinforcing member extending between and rigidifying said blade halves, said reinforcing member being spaced from said contact pressure-maintaining means in a direction away from said outer margin.

8. An electrical switch according to any of claims 1 to 7, including means for latching said switch blade in the switch closed position thereof, said latching means comprising stationary clip structure adjacent the free end of said switch blade when the latter is in said switch closed position and presenting a first latching surface thereon; and a latch pivoted to said switch blade proximal to the outer margin of said free end thereof and presenting a second latching surface configured for engaging said first surface when said switch blade is in said switch closed position thereof and holding the switch blade in such position, the pivot axis of said latch being disposed closer to said outer margin than the areas of mutual engagement between said first and second latching surfaces for creating, under the influence of the normal loop component of electromagnetic force which tends to rotate said switch blade to the switch open position thereof, a torque on said latch for moving said second surface into tighter engagement with said first surface, to thereby increase the latching power of said latching means.

9. An electrical switch according to Claim 8, wherein said latch rotates about said sleeve for pivoting movement about the axis thereof.

10. An electrical switch according to Claim 8 or 9 including latch disconnect means for selectively pivoting said latch out of latching engagement with said clip to thereby permit shifting of said switch blade to the switch open position thereof.

11. An electrical switch comprising a pair of spaced electrical terminals, and a pivotally shiftable, conductive switch blade having a pivoted end and a free end for alternately opening and closing said switch as desired, and latching means for latching said switch blade in the switch closed position thereof, said latching means including stationary clip structure adjacent the free end of said switch blade when the latter is in said switch closed position and presenting a first latching surface thereon; and a latch pivoted to said switch blade proximal to the outer margin of said free end thereof and presenting a second latching surface configured for engaging said first surface when said switch blade is in said switch closed position thereof and holding the switch blade in such position, the pivot axis of said latch being disposed closer to said outer margin than the areas of mutual engagement between said first and second latching surfaces for creating, under the influence of the normal loop component of electromagnetic force which tends to rotate said switch blade to the switch open position thereof, a torque on said latch for moving said second surface into tighter engagement with said first surface, to thereby increase the latching power of said latching means.

12. An electrical switch substantially as herein described with reference to the embodiment of Figures 1,2,3,4,6 and 7 or the embodiment of Figure 5 in the accompanying drawings.