US3691335A

US3691335A - Knife blade contact assembly with improved contact engagement position retaining means

Info

Publication number: US3691335A
Application number: US119557A
Authority: US
Inventors: Charles M Cleaveland; Stanislaw A Milianowicz
Original assignee: Westinghouse Electric Corp
Current assignee: Westinghouse Electric Corp
Priority date: 1971-03-01
Filing date: 1971-03-01
Publication date: 1972-09-12
Anticipated expiration: 1989-09-12
Also published as: JPS4663U; JPS5620901Y2; CA926903A

Abstract

An electrical switch comprising a pair of generally parallel spaced blades pivotally mounted on a hinge contact member and rotatably movable to engage a break contact member or jaw which is spaced away from the hinge contact member. A biasing means is mounted on the blades adjacent to the break contact member to bias the blades toward one another.

Description

United States Patent Cleaveland et al. [451 Sept. 12, 1972 KNIFE BLADE CONTACT ASSEMBLY [56] References Cited WITH IMPROVED CONTACT UNITED STATES PATENTS ENGAGEMENT POSITION RETAINING MEANS 3,356,815 12/1967 S1vly ..200/162 3,240,411 3/1966 Siviy ..200/162 [721 Charles Clmelwd; 2,200,509 5/1940 Lindae ..200/15 x Milimowicl, both of Monroevllle, 2,546,366 3/1951 Lindae ..200/162 2,907,856 10/1959 Ballou ..200/170 A [73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, p Primary Examiner-J. R. Scott Attorney-A. T. Stratton and Clement L. McHale [22] Filed: March 1, 1971 211 Appl. No.2 119,557 [57] ABSTRACT An electrical switch comprising a pair of generally 521 1.8. Ci. ..200/162, 200/15, 200/170 A Parallel spaced blades Pivotally mounted a hinge 511 1111.01. ..110111 1/50, HOlh 21/54 contact member and rotatably mvable engage a [58] Field 0 searchuzoolls, 48 KB, 166 BB, 170 A break contact member or jaw which is spaced away 200,162 from the hinge contact member. Abiasing means is mounted on the blades adjacent to the break contact member to bias the blades toward one another.

10 Claims, 12 Drawing Figures 26 1' E O"\ 1 0 I o o PATENTEDSEP 12 1912 3.691. 335

SHEET 1 0F 4 1 36 o \O C S 3 22 V 13 0 FIG. I

FIG. 2

1 l i 1 l 1 248 FIG. 3

INVENTORS WITNESSES Charles M. Cleovelond 0nd Stanislaw A. Milionowicz '7 V/ ATTORNEY PATENTEDSEP 12 I972 SHEET 3 OF 4 KNIFE BLADE CONTACT ASSEMBLY WITH IMPROVED CONTACT ENGAGEMENT POSITION RETAINING MEANS This application is a continuation in part of copending application, Ser. No. 27,724 which was. filed Apr. 1 3, 1970 (now abandoned) and which is assigned to the same assignee as the present application.

BACKGROUND OF THE INVENTION This invention relates to electrical switches and more particularly to contact structures which form part of such switches.

In the construction of electrical switches of the knifeblade type which are intended to carry relatively large electrical currents, it is necessary that adequate contact pressure be maintained between the contact portions of the blades and the associated hinge and break contact members of such switches. Various means have been proposed to insure the required contact pressures in such switches, such as disclosed in U.S. Pats. Nos. 2,546,366 which issued Mar. 27, 1951 to Lindae; 2,907.856 which issued Oct. 6, 1959 to Ballou; and 3,240,911 which issued Mar. IS, 1966 to Siviy and which is assigned to the same assignee as the present application. Certain problems arise in the operation of such switches, particularly those of the polyphase or three-phase type, when such switches are called upon to carry relatively high momentary currents, such as 50,000 amperes or higher currents which may result during certain operating conditions, such as during short circuit conditions. This is because of the relatively high magnetic forces which result during such operating conditions which may cause the blades of the different poles of a three-phase switch to oscillate and despite the usual means provided to maintain contact pressure, the blades of each pole unit will periodically disengage from the associated break contact member and arcing will result between the blades and the break contact member. This problem is also aggravated by the cyclic or periodic forces of attraction between the pair of blades which form part of each pole unit of such a switch due to the parallel current paths in said blades. To assist in overcoming the above problems, are resistant contact surfaces may be provided on the switch parts.

If the contact pressures between the blades and the associated break contact member of each pole unit of such a three-phase switch are increased to overcome the above problem, other problems will result such as the galling of relatively soft silver-plated contact portions on the switch parts or the operating speed of the switch may not be sufficient to facilitate the interruption of current during an opening operation where the application of the switch requires the switch to have a current interrupting capability. It is therefore desirable to provide an improved switch of the type described which will overcome the problems described above without unduly increasing the contact pressures between the relatively movable switch parts or without the useof expensive are resistant materials.

SUMMARY OF THE INVENTION In accordance with the invention, an electric switch includes a pair of generally parallel, spaced, elongated switch blades or contact arms which are pivotally mounted on 'a hinge contact member which may be disposed between said blades. The switch also includes a break contact member or jaw which is spaced away from the hinge contact and which also may be disposed between the pair of blades when the switch is closed. Each of the blades includes one or more contact portions which are disposed along only a single line which is generally transverse or perpendicular to the length of said blade and which are disposed to engage the associated break contact member along only said single line when the switch is closed. In order to maintain sufficient contact pressures between the contact portions of said blades and the break contact member, a biasing means is mounted on said blades adjacent to the break contact member and extends between said blades to bias said blades laterally toward one another. In a preferred embodiment of the invention, the biasing means includes spring means mounted on the associated blades away from the associated hinge contact member beyond the associated break contact member or between the contact portions of said blades and the ends of said blades away from the hinge contact member. In addition, in the preferred embodiment of the invention the contact portions of the blades which engage the break contact member when the switch is closed are generally curved or arcuate in configuration to permit the blades to rock or oscillate with respect to the associated break contact member during certain operating conditions while remaining engaged with or in contact with the break contact member during such operating conditions.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, reference may be had to the exemplary embodiment shown in the accompanying drawings in which:

FIG. 1 is a side elevational view, with certain parts omitted, of an electrical switch structure embodying the principal features of the invention;

FIG. 2 is an enlarged top plan view of a break contact member which forms part of the switch structure shown in FIG. 1;

FIG. 3 is an enlarged view, in side elevation, of the break contact member shown in FIG. 2;

FIG. 4 is an enlarged view, in side elevation, of one of the blades which forms part of the switch structure shown in FIG. I;

FIG. 5 is an enlarged top plan view of the blade shown in FIG. 4;

FIG. 6 is an enlarged view, in end elevation, of the blade shown in F IGS. 4 and 5;

FIG. 7 is an enlarged top plan view of the switch structure shown in FIG. 1 with certain parts omitted for clarity;

FIG. 8 is an enlarged view, in side elevation, of the switch structure shown in FIG. 7;

FIG. 9 is an enlarged view, in side elevation, of a portion of a modified blade structure which may be employed in certain applications instead of the blade structures shown in FIGS. 4 through 6;

FIG. 10 is an enlarged view, in end elevation, of the blade structure shown in FIG. 9;

FIG. 11 is a plan view of an alternate construction embodying the invention; and

FIG. 12 is a side elevational view of the alternate construction of the invention shown in FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings and FIGS. 1, 7 and 8 in particular, there is shown a disconnecting switch assembly 10 which normally forms one pole unit of a polyphase or three-phase electrical switch structure which includes a plurality of like disconnecting switch assemblies which may be supported on a common supporting structure and each of which has the construction of the disconnecting switch assembly 10. In such a polyphase switch structure, a plurality of pole units such as the disconnecting switch assembly 10 is mounted in side-by-side relation upon a common supporting structure.

More specifically, the disconnecting switch 10 shown in FIGS. 1, 7 and 8 comprises a hinge contact member 22, a break contact member 24 spaced from the hinge member 22 and a pair of spaced, generally parallel, elongated blades 26 which are pivotally mounted on the hinge member 22 and which engage the break member 24 when the switch 10 is closed. The hinge member 22 may be supported on and secured to the top of a suitable electrical insulator 32 by suitable means, such as a plurality of bolts (not shown). In order to make electrical connections to the hinge member 22, a terminal plate or pad 25 may be also mounted at the top of the insulator 32 or formed integrally with the hinge member 22. Similarly, the break member 24 may be supported on and secured to the top of a suitable electrical insulator 34 by suitable means, such as a plurality of bolts (not shown), and a terminal plate or pad 27 may be also mounted on top of the insulator 34 to facilitate the making of electrical connectionsto the break contact member 24. The

insulators

32 and 34 may, in turn, be secured to and supported on a common supporting member or plate 29 as shown in FIG. 1. The blades 26 may be actuated between open and closed positions in a manner well known in the art, such as by means of an operating lever 23 which is operatively connected to the blades, as indicated in FIG. 1. If desired, a latch member 38 which is of a type also well known in the art, may be pivotally mounted on the break member 24 and disposed to engage a cross pin 39 which is mounted on the blades 26 in order to retain the blades in the closed position. The latch member 38 may be operated by means of a hookstick (not shown) which is inserted into a hookeye or operating ring 36 which is also known in the art.

Referring to FIGS. 7 and 8, the hinge contact member 22 includes an upright portion 22A which is disposed between the blades 26 and a base portion 22B which, as illustrated, is secured to the insulator 32. The hinge member 22 also includes a pair of generally circular, raised contact portions 22C and 22D which are disposed on the opposite sides of the upright portion 22A and against which the associated blades 26 bear. The hinge member 22 is formed from a suitable electrically conducting material, such as copper, by casting the hinge member 22 as a unitary member or by forming the hinge member 22 as a generally L-shaped stamping or punching which is secured by suitable means, such as bolts, to the insulator 32. The blades 26 are pivotally attached to the upright portion 22A by a hinge bolt 42 which passes through substantially aligned openings provided in said upright portion and the blades 26, as indicated at 110 in FIG. 4 for the blades 26, and which is retained in its assembled position by a lock nut 44 which is disposed on the bolt 42. In order to establish sufficient contact pressure between the blades 26 and the contact portions 22C and 22D of the hinge member 22, a pair of spring or Belleville

washers

52 and 54 is disposed on the bolt 42. Each of the

spring washers

52 and 54 includes a plurality of spaced radially extending recesses or slots as best shown in FIG. 8. The spring washer 52 is disposed between the head of the bolt 42 and the outer surface of the adjacent blade 26 while the other spring washer 54 is disposed between the lock nut 44 and the outer surface of the other adjacent blade 26. The contact pressure between the blades 26 and the contact portions of the hinge member 22 may be adjusted within a predetermined range by either tightening or loosening the lock nut 44 on the bolt 42.

As best shown in FIGS. 4 through 6, each of the blades 26 is generally rectangular in configuration as illustrated and is formed from a suitable electrically conducting material, such as copper. The electrically conducting material from which the blades 26 are formed may be a generally flat, elongated, strap-type material. Where the switch assembly 10 is required to have fault closing capabilities, an arc button 82 may be mounted on each of the blades 26 and secured thereto by suitable means, such as the rivets 84, to limit the erosion of the blades 26 in those portions of the blades 26 which first approach the break contact member 24 during the closing of the switch assembly 10. Each of the are buttons 82 where provided may be formed from an are resistant material such as tungsten or a copper-tungsten alloy. For reasons which will be explained hereinafter, each of the blades 26 includes one or more contact portions which are disposed along a line which is generally transverse or perpendicular to the longitudinal dimension of said blade and which are disposed to engage the break contact member 24 along said line when the switch assembly 10 is closed. More specifically as illustrated, each ofthe switch blades 26 includes a pair of

contact portions

26A and 26B which are disposed generally along a line which is transverse or perpendicular to the longitudinal dimension of the blade 26 and which are spaced from one another across the width of the blade 26 or in a vertical sense, as viewed in FIG. 4. Each of the

contact portions

26A and 26B is generally curved or arcuate in shape to permit certain rocking or rolling movements of the blades 26, as will be explained hereinafter. It is important to note that the arc buttons 82 project laterally outwardly from the blades 26 to a greater degree than the

contact portions

26A and 26B to prevent contact between said contact portions and the break member 24 during the closing of the switch 10 until said arc buttons move into the recess 102 in said break member.

Referring now to FIGS. 2 and 3 the break contact member 24 includes an upright portion 24A and a base portion 243. In order to prevent engagement of the arcing buttons 82 on the blades 26 with the break contact member 24 after the switch assembly 10 is closed, the upright portion 24A of the break member 24 may include a generally rectangular recess as indicated at 102 in FIG. 3. This is done so that the continuous current is carried through the

contact portions

26A and 26B which have lower electrical resistance. Similarly to the hinge member 22, the break contact member 24 is formed from a suitable electrically conducting material, such as copper, and may be formed by casting the break member 24 as a unitary member or by employing a generally L-shaped stamping or punching which is then secured by suitable means, such as bolts, to the insulator 34. In order to limit rotational movement of the blades 26 during a closing operation of the switch assembly 10, the break member 24 may also include a stop surface or portion, as indicated at 24D in FIGS. 2 and 3, which is disposed to engage a cross pin 66 which is mounted on the blades 26 as shown in FIG. 1. The upright portion 24A may be formed or machined to be generally curved or arcuate at the top thereof, as indicated at 24C, to facilitate the engagement of the blades 26 with the break contact member 24 during a closing operation of the switch assembly 10. The portion 24E of the break member 24 is preferably beveled at the opposite sides thereof to facilitate sliding movements ofthe arc buttons 82 over the break member 24 during the opening of the switch 10.

As previously mentioned, the blades 26 are assembled on the hinge contact member 22 in generally parallel spaced relation and with the blades 26 disposed in mutually flatwise face-to-face relation as best shown in FIG. 7. With the

contact portions

26A and 26B of the respective blades 26 projecting laterally toward one another on opposite sides of the break contact member 24 when the switch assembly is closed. It is to be noted that a predetermined spacing between the blades 26 at the hinge ends of said blades is established by the width of the upright portion 22A of the hinge member 22 and the dimensions of the associated contact portions 22C and 22D of the hinge member 22. g

In order to establish sufficient contact pressure between the

contact portions

26A and 26B of the blades 26 and the upright portion 24A of the break contact member 24 at least during certain operating conditions, the bolt 62 is disposed to extend between and pass through substantially aligned openings provided in the blades 26, as indicated at 112 in FIG. 4. In order to establish substantially the same predetermined spacing between the blades 26 at the break ends thereof as at the hinge ends of said blades, a generally tubular spacer member 66 is disposed between the blades 26 on the intermediate portion of the bolt 62 and is of a relatively larger size than the adjacent openings 112 in the blades 26 through which the bolt 62 passes. A pair. of spring or

Belleville washers

72 and 74 is disposed on the bolt 62 to bear against the outer surfaces of the blades 26 at locations between the

contact portions

26A and 26B and the ends of said blades away from the hinge member 22. The spring washers 72 and 74 include a plurality of radially extending recesses or slots as indicated at 72A for the spring washer 72 which are spaced around the periphery of said spring washers. A lock nut 64 is disposed on a threaded end of the bolt 62 to retain the

spring washers

72 and 74, the blades 26 and the spacer member 66 in assembled relation, as best shown in FIG. 7. In order to charge or stress the

washers

72 and 74 considered as spring members prior to the engagement of the break contact member 24 by the blades 26, the lock nut 64 is tightened down on the bolt 62 to a predetermined degree. It is important to note that the

contact portions

26A and 26B of each of the blades 26 engage the upright portion of the break contact member 24 along only a single line which is disposed generally transverse or perpendicular with respect to the longitudinal dimension of each of said blades as indicated in FIG. 8.

In the overall operation of the switch assembly 10, it has been found that during normal operating conditions the contact pressures between the blades 26 and the hinge contact member 22 established by the

spring washers

72 and 74 and the contact pressures between the

contact portions

26A and 26B of the blades 26 and the upright portion 24A of the break contact member 24 are sufficient to maintain the different contact portions in engagement without any special difficulty. When, however, the switch assembly 10 forms one pole unit of a three-phase switch structure having three pole units of a construction like that of the switch assembly 10 disposed in side-by-side relation and the pole units of such a three-phase switch structure are called upon to carry relatively high momentary currents such as 50,000 amperes or more, the blades of the respective pole units or switch assemblies 10 are subjected to severe cyclic magnetic forces. The forces exerted on the blades of each pole unit such as the switch assembly 10 due to the interaction between the respective pole units during such an operating condition, are in directions which are generally transverse or perpendicular with respect to the longitudinal dimensions of the blades 26 of the switch assembly 10. In other words, the blades 26 of the switch assembly 10 during such an operating condition will tend to either be attracted toward or repelled away from the adjacent pole units by the forces exerted on the blades 26 due to the interaction between the switch assembly 10 and the adjacent pole units of a three-phase switch structure. In addition, the pair of blades 26 of each switch assembly 10 will also be cyclically attracted toward each other by the magnetic forces which result from the relatively high momentary currents which flow through the pair of blades 26 of each switch assembly 10.

Due to the cyclic magnetic forces indicated above, it had been found that the blades 26 of a switch assembly 10 may oscillate with an amplitude of as high as onehalf inch at momentary currents in excess of 60,000 amperes flowing through the blades of the switch assembly 10 with the amplitude also depending on the natural frequency of the blades 26 and the relative rigidity of the blade mounting arrangements as previously described.

In the operation of the switch assembly 10, it has been found that the blades 26 of the switch assembly 10 may be considered as vibrating beams during the severe operating conditions described above and that considered as beams, the blades 26 have nodes of vibration at the break contact member 24 where the amplitude of vibration is zero. By disposing the

contact portions

26A and 26B of each of the blades 26 along only a single line of engagement with the break contact member 24 as previously described, only a single node of vibration is established between each of the blades 26 and the break contact member 24 at which the amplitude of vibration of the blades 26 is zero and therefore the

contact portions

26A and 26B remain in engagement with the break contact member 24 during those operating conditions when a switch assembly 10 is required to carry relatively high momentary currents as indicated previously. The curved or arcuate shapes of the

contact portions

26A and 26B of the blades 26 permit the blades 26 to vibrate or rock about said contact portions considered as fulcrums while said contact portions remain engaged with the upright portion 24A of the break contact member 24. In other words, the blades 26 of the switch assembly 10 during the abovedescribed operating condition function as beams which are effectively supported at two spaced fulcrums which are disposed at the hinge ends of said blades and at the break ends of said blades. It has been found that because of the more rigid support of the blades 26 at the hinge contact member 22, the blades 26 need only include substantially flat contact surfaces rather than curved or arcuate contact surfaces as are provided at the break ends of the blades 26.

At the hinge member 22, the contact forces may be considerably greater than at the break member without substantially increasing the operating forces required to move the blades since any forces acting at the hinge end of the switch 10 are effective only on a relatively small radius arm about the pin 42.

It has been found preferable to locate

thebiasing spring washers

72 and 74 between the

contact portions

26A and 26B of the blades 26 and the end of said blades away from hinge member 22 to avoid or eliminate the possibility that the portions of the blades 26 adjacent to the

contact portions

26A and 26B will either approach or touch the break contact member 24 during the oscillations of the intermediate portions of the blades 26 described above which would otherwise result in arcing between said blade portions and the break contact member 24. In other words, by squeezing or biasing the blades 26 toward one another on the sides of the

contact portions

26A and 26B away from the hinge member 22, the portions of the blades 26 on the other sides of said contact portions toward the hinge member 22 tend to pivot away from each other about the

contact portions

26A and 26B considered as fulcrum points.

It is important to note that since the

contact portions

26A and 26B are maintained in engagement with the associated break contact member 24 even during the relatively high momentary currents described, the forces of attraction between the pair of blades 26 of each switch assembly 10 tend to increase the contact pressure during such operating conditions and to assist in maintaining the desired engagement between the contact portions of the blade 26 and the break contact member 24.

Referring now to FIGS. 9 and 10 there is illustrated a modified blade 226 which may be employed in certain applications instead of the blades 26 where a relatively greater current carrying capacity is required between the blades and the break contact member of a disconnecting switch assembly; More, specifically, the blade 226 is similar to the blades 26 previously described except that the blade 226 as illustrated includes first and second longitudinally extending,'spaced

slots

232 and 234, respectively, which sub-divide the contact portions of the blade 226 into three

separate contact portions

226A, 2268 and 226C which are disposed generally along a line which is transverse or perpendicular with respect to the longitudinal dimension of the blade 226. Each of the contact portions 226A,

2263 and 226C are generally curved or arcuate in shape similarly to the contact portion of the blade 26 previously described. When the blade 226 is assembled with an associated blade of like construction in a switch assembly which is otherwise identical to the switch assembly 10 previously described, the spring washers provided adjacent to the break contact member will independently bias the different contact portions of the blades 226 into engagement with the associated break contact member such as the break contact member 24 previously described. The operation of a modified switch assembly including a pair of blades 226 would be the same as the operation of the switch assembly 10 as previously described except that a greater number of current transfer points will be provided between the blades 226 and the associated break contact member of such a modified switch assembly to provide greater current carrying capacity.

Referring now to FIGS. 11 and 12 there is illustrated an alternate construction of the invention in a switch assembly 10' in which the

spring washers

272 and 274 are disposed between the

contact portions

226A and 226B of the blades 226 and the associated hinge contact member 22 and are disposed adjacent to said contactportions. It is to be noted that the construction of the switch assembly 10' at the hinge end thereof may be the same as previously described in detail for the switch assembly 10. In order to prevent the possibility of arcing between the portions of the blades 226 and the break contact member 224 in such a modified construction, the clearances between the break contact member 224 and the adjacent portions of the blades 226 between the

contact portions

226A and 226B may be increased to avoid the possibility of arcing during the oscillations or vibrations of the blades 226 in such a modified construction. This alternate construction may require greater lateral spacing between the blades 226 of each pole unit, such as the switch assembly 10', and may also have the effect of reducing the magnetic forces of attraction between the blades 226 when the switch assembly 10' is carrying relatively high momentary currents as previously described. The corresponding contact pressure between the

contact portions

226A and 226B of the blades 226 and the associated break contact member 224 may therefore be decreased compared with the corresponding forces which would result in the operation of the switch assembly 10 previously described.

If, however, the distances between the adjacent edge of the break member 24 and the pivot points of the

contact portions

226A and 226B as indicated at X are relatively small, such as one-fourth inch or less, then the distances between the break member 224 and the main portions of the blades 226 as indicated at Y need not be increased to permit relatively large amplitudes of oscillations of said blades without arcing.

It is to be understood that the teachings of the invention may be applied to disconnecting switch structures in which the number of separate contact portions which are disposed along a single line which is generally transverse or perpendicular to the longitudinal dimensions of the blades as previously described may be varied as required in a particular application to provide the necessary current carrying capacity during the different operating conditions of the overall switch assembly.

The apparatus embodying the teachings of this invention has several advantages. For example, the contact portions of the blades actually remain in engagement with the associated hinge contact member and with the associated break contact member even when the disconnecting switch assembly of which the blades form a part is required to carry relatively high momentary currents such as 50,000 amperes or more. In addition, when a switch assembly as disclosed is carrying relatively high momentary currents, the contact pressures between the contact portions of the blades and the associated break contact member are actually increased due to the parallel current paths provided in the pair of blades which make up each pole unit of an overall three-phase switch. Since arcing between the switch current carrying parts is eliminated by the disclosed construction, the main contact portions on the switch blades may be formed from copper or silver plated copper instead of an are resistant contact material, such as tungsten alloy, and since the required contact pressure during normal operating conditions is considerably lower than known switch arrangements the mechanical forces required to operate the switch are reduced and the problem of galling certain contact portions is eliminated. A further advantage of the disclosed construction is that in at least one embodiment, the blades can be provided with slots which effectively divide the blade into a plurality of separate contact fingers with each finger being independently spring loaded or biased to apply the required contact pressure to each contact portion independently. It has also been found that contact bounce is also substantially eliminated during the closing of a switch assembly as disclosed during a fault condition.

What is claimed is:

1. An electrical switch comprising a hinge contact member, a break contact member spaced from the hinge contact member, a pair of spaced generally parallel elongated blades pivotally attached to the hinge contact member, each of said blades having one or more contact portions disposed to engage said break contact member when said switch is closed, said one or more contact portions of each of said blades projecting laterally toward the other blade and disposed to engage said break contact member along only a single line which is generally perpendicular to the length of each blade, and means extending between opposite portions of said blades adjacent to both said break contact member and to said contact portions of said blades at one side of said break contact member for biasing said blades toward one another and said contact portions into engagement with said break contact member.

2. The combination as claimed in claim 1 wherein the last-mentioned biasing means is disposed away from the hinge contact member beyond said contact portions of said blades.

3. The combination as claimed in claim 1 wherein each of said blades is formed from a generally flat electrical conductor, said contact portions of said blades being generally curved in shape.

4. The combination as claimed in claim 1 wherein the last-mentioned means is disposed between the hinge contact member and said contact portions of said blades.

5. The combination as claimed in claim 1 wherein each of said blades includes one or more slots which extend longitudinally and parallel to said elongated blades and which intersect said one or more contact portions of said blades to thereby provide a plurality of contact portions on each of said blades which engage said break contact member.

6. The combination as claimed in claim 2 wherein said pair of blades is formed from generally flat electrical conductors and is disposed on opposite sides of said break contact member, said contact portions of said blades being generally arcuate in shape.

7. The combination as claimed in claim 4 wherein said pair of blades is formed from generally flat electrical conductors and is disposed on opposite sides of said break contact member when said switch is closed, said contact portions of said blades being generally curved in shape.

8. The combination as claimed in claim 5 wherein the biasing means is disposed between the contact portions of said blades and the ends of said blades away from said hinge contact member.

9. The combination as claimed in claim 5 wherein said pair of blades is formed from generally flat electrical conductors and is disposed on opposite sides of said break contact member when said switch is closed, said contact portions of said blades being generally curved in shape.

10. The combination as claimed in claim 6 wherein an arc button is mounted on each of said blades adjacent to said contact portion and projects laterally toward the other blade a greater distance than the adjacent contact portion.