US3056009A

US3056009A - Electric-switch construction

Info

Publication number: US3056009A
Application number: US824114A
Authority: US
Inventors: Stephen A Mrenna
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1959-06-30
Filing date: 1959-06-30
Publication date: 1962-09-25
Anticipated expiration: 1979-09-25

Description

Sept. 25, 1962 s, MRENNA ELECTRIC-SWITCH CONSTRUCTION 4 Sheets-Sheet 1 Filed June 30, 1959 S. A. MRENNA ELECTRIC-SWITCH CONSTRUCTION Sept. 25, 1962 4 Sheets-Sheet 2 Filed June 30, 1959 Fig.6.

INVENTOR Stephen A. Mrennu ATTORNEY p 25, 1962 s. A. MRENNA 3,056,009

ELECTRIC-SWITCH CONSTRUCTION Filed June 50, 1959 4 Sheets-Sheet 3 54 EDI Sept. 25, 1962 s. A. MRENNA ELECTRIC-SWITCH CONSTRUCTION 4 Sheets-Sheet 4 Filed June 30, 1959 Fig.|O.

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m? a 4 m .m m F F VIC United States Patent 3,056,009 ELECTRIC-SWITCH CONSTRUCTION Stephen A. Mrenna, Brighton Township, Beaver County, 1a., assignor' to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed June 30, 1959, Ser. No. 824,114 15 Claims. (Cl. 200-144) This invention relates to electric switches in general, and more particularly to arc-extinguishing devices therefor.

A general object of the present invention is to provide an improved electric-switch construction, which shall be highly effective in interrupting all currents, for which the switch is rated.

Another object of the invention is to provide an im proved arc-suppressor device, which may quickly be assembled in position, and may also be applied to previously built switches, Without any necessity for effecting the dismantlement of such switches.

Still a further object of the invention is to provide a simple and highly effective arc-extinguishing device involving few parts which may be readily fabricated and quickly assembled into an operative position on the switch.

Still a further object of the invention is to considerably increase the ratings of standard switches by incorporating therewith a simple arc-extinguishing device which is readily assembled into position.

Yet a further object of the invention is to provide an improved arc-suppressor plate construction, which may be quickly inspected, and replaced, if necessary.

Still a further object of the invention is to provide an improved arc-suppressor plate arrangement, in which the several parts thereof may be quickly stamped into the desired configuration, and which may be readily assembled into the switch.

Still another object of the invention is to provide a combined arc-suppressor plate and operating member for an electric switch.

Further objects and. advantages will readily become apparentupon'reading the following specification, taken in conjunction with the drawings, in which:

FIGURE l'is a front elevational view of an electric switch incorporating the principles of the present invention, the cover of the enclosed switch being open, so that the interior of the switch may be viewed, the contact structure being shown in the closed-circuit position;

FIG. 2'is' a side elevational view, partially in vertical section, taken along the line IIII of the electric switch shown in FIG. 1, again'the contact structure being shown in the closed-circuit position;

FIG. 3 is a side elevational view of one of the arc-suppressor plates, which is employed in the switch construction illustrated in FIGS. 1 and'2;

FIG. 4 is a fragmentary, end view of the stationary contact structure, showing the operative position of the pair of arc-suppressor plates, withthe switch-knife-blade shown in the closed-circuit position;

FIG. 5 illustrates a side elevational view of a modified type arc-extinguishing device, which may be substituted for the pair of arc-suppressor plates, such as shown in FIG. 3;

FIG. 6 is a top in FIG. 5;

FIG. 7 is a front elevational view of a higher-rated switch,'.similar tothe view illustrated in FIG. 1, again looking into the interior of the switch casing, with the switch casing itself omitted for purposes of clarity. Again the contact structure is shown in the closed-circuit position;

FIG. 8 is a side elevational view of the modified type plan View of the modification shown of-arc-suppressing device for the higher-rated switch of FIG. 7, various parts being omitted for clarity, and the contact structure being illustrated in the closed-circuit position;

FIG. 9 is atop plan view of the relatively stationary stab contact, utilized as the stationary contact structure of the device of FIG. 8;

FiG. 10 is a fragmentary end view of the device shown in FIG. 8, taken along the line XX thereof, the contact structure being illustrated in the closed-circuit position, and only a fragmentary portion of the complete in terrupting device being illustrated;

FIG. 11 is .a side elevational view of one of the perforated arc-suppressor plates employed in the construction of FIGS. 7 and 8;

FIG. 12 is a top plan view of a relatively stationary hinge tab contact employed as the pivotal mounting for the switch arm of the" device illustrated in FIG. 8;

FIG. 13 is a side elevational View of the hinge stab contact of FIG. 12;

FIGS. 14 and 15 are side elevational and plan views, respectively, of one of the contact blades utilized in the bifurcated switch-arm construction illustrated in FIG. 8; and

FIGS. 16 and 17 respectively illustrate side elevational and plan views of a flat biasing spring employed in the switch-arm construction of FIG. 8.-

Referring to the drawings, and more particularly to FIGS. l-4 thereof, the reference numeral 1 generally designates an enclosed safety-switch construction, which may be employed for lighting circuits, or for relatively small motor applications.

The electric switch construction 1 generally includes an enclosing sheet metal switch boX, or case 2, for enclosing the several pole-units of the electric switch 1. There may be two, three, or more of the pole-units, depending upon the number of lines to be controlled from the line connections to the load connections. In addition, there will be a neutral terminal plate 4 to accommodate the neutral line.

As more clearly illustrated in FIG. 2, the switch box 2 has a front cover 5, which is hinged to curled tabs 6 provided at one side edge of the switch casing 2. Thus, the cover 5 and the switch box 2 provide a tot-ally enclosed construction for the switch elements.

The side walls 7 provide journals, or bearings 8, for.

the pivotal rotation of an'operating bail 9, one external end of which is configured to form a manually operable handle 10, shown in FIG. 1, which may be manually operated between a pair of stop lugs 11, '12 and may be locked in such positions, if desired.

The rear wall 49 of the switch box 2 has a plurality of mounting apertures 13, which may be employed to mount the switch casing 2 upon a wall, or other desired support.

As shown in FIG. 1, aninsulating molded panel, or base 14, formed from a suitable moldable material, may beemployed to mount the several switch parts.

Mounting. screws 14a thread into tapped holes provided in the rear wall 49 of the switch casing 2 and hold the molded base 14 securely into the proper position. Preferably, the insulating molded base has grooves and ridges molded thereon tofixedly secure the several parts into accurately aligned positions. Secured to the front of the insulating panel '14 are a plurality of bifurcated, contact break-jaws 15, having cooperating legs, or furcations 16, which converge toward each other, as more clearly shown. in FIG. 4 of the drawings.

The night portion 17 of the contact break-jaw 15 is secured to a terminal plate 18, and also the base 14 by a center mounting screw 19.

It will be noted that contacting intermediate portions of the legs 16 extend toward each other as indicated at 20 and serve to frictionally clamp into position the switch knife-blade 21, which is preferably pivotally mounted.

The terminal plate 18 is provided with a connector sleeve 22, shown in FIG. 1, which has a side portion tapped, to accommodate a clamping screw 23, which fixedly secures one end of a line connection fixedly into place.

The lower end of the switch knife-blade 21, as viewed in FIG. 1, is pivotally connected, as by a rivet 24, to an outwardly extending leg 25 of an L-shaped mounting bracket 26, which is fixedly secured by a screw 27 to the base 14. In addition, the mounting screw 27 fixedly secures into place a fuse clip 28, adapted to support a cartridge fuse 29 into position.

Disposed at the lower end of the panel 14, as viewed in FIG. 1, is a load terminal plate 30, which is secured by a mounting screw 31 to the panel 14. Also the mounting screw 31 fixedly secures into proper position the companion fuse clip 32 for the cartridge fuse 29. A second connector sleeve 33 is fixedly secured to the load terminal plate 30 by a mounting screw, which enters from the back of the panel 14. The connector sleeve 33 also has a clamping screw 34, which serves to fixedly clamp into position the end of a load connector wire, as well known by those skilled in the art.

The neutral terminal plate 4, previously referred to, has a pair of

connector sleeves

35, 36, together with mounting clamping screws 37, to fixedly secure into place the ends of the neutral Wire of the controlled circuit.

With reference to FIG. 2, it will be noted that an insulating operation arm 39 is riveted by rivets 40 to an intermediate portion of the switch-blade 21. The insulating operating arm 39 has a notch, or slot 41, to accommodate the operating bail 9. Thus, rotation of the handle 10, externally of the switch box 2, will effect pivotal rotation of the operating bail 9, and hence opening, or closing pivotal movement of the knife-blades 21, as effected by the insulating operating arms 39.

With reference to FIG. 3 of the drawings, it will be noted that a suitably configured fiber plate clip 42 is provided, and constitutes one of a pair of cooperable arc-suppressor plate clips 42, which are positioned as shown in FIG. 4 of the drawings. It will be noted that the outer edge of each arc-suppressor plate clip 42 is flared outwardly as at 43 to assist in guiding the switchblade 21 into proper position.

It will also be noted in connection with the arcsuppressor plate 42 that a rectangular slot, or perforation 44, is provided. The Width of the rectangular slot 44, as indicated by the distance X, is just the width of the leg, or furcation 16, of the contact break-jaw 15, so that the contacting portion 20 of the leg 16 may extend through the perforation, or hole 44, and make contact with the side of the switch-blade 21.

Additionally, the inner edges 45 of the arc-suppressor plates 42 straddle the center mounting screw 19, which biases the outer free ends of the arc-suppressor plates 42 toward each other, as illustrated in FIG. 4 of the drawings.

Preferably the arc-suppressor plates 42 are made of a suitable gas-evolving material, so that gas will be evolved during the establishment and drawing of an are, not shown, between the switch-blade 21 and the contacting portions 20 of the contact break-jaw 15. This will insure a rapid and efiicient extinction of the established arc.

As shown in the left-hand pole-unit of FIG. 1, it will be apparent that the arc-suppressor plates 42 are all of one type, and may simply be reversed, as shown in FIG. 1, and snapped into position. The rectangular slots 44, which accommodate the contacting portions 20 of the legs 16 of the break-jaw 15 assist in maintaining the arcsuppressor plates 42 in a proper position. Preferably the arc-suppressor plates 42 are formed of a gas-evolving material, such as fiber, so that during the establishment and drawing of the are, a considerable amount of gas will be evolved. The un-ionized evolved gas will quickly effect the extinction of the established arc, which will be drawn, of course, between the two cooperating arcsuppressor plates 42 in the region designated by the reference numeral 46 in FIG. 4 of the drawings.

FIGS. 5 and 6 illustrate a modification of the invention, in which, in place of employing a pair of cooperable arc-suppressing plates 42, instead, a single 'U-shaped fiber wrapper, generally designated by the reference numeral 47, is employed. Each side leg 48 of the U-shaped fiber wrapper 47 is provided with a hole, or perforation 44, which is of the same shape as the hole 44- in the fiber plate 42 of FIG. 3. As a result, the modified U-shaped fiber wrapper may be inserted into position between the legs 16 of the contact break-jaw 15, so that again the contacting portions 20 of the legs 16 extend, or protrude, through the holes 44 and make contact with the switchblade 21 in the closed-circuit position of the device. The right-hand pole unit of FIG. 1 shows the assembled construction. Preferably, the 'Ushaped fiber wrapper 47 is formed of a suitable gas-evolving material, such as fiber, which has considerable benefit during arc extinction by causing the evolution of considerable amount of un-ionized gas, as mentioned hereinbefore.

With reference to FIGS. 7-17 of the drawings, a modification of the invention is illustrated for a higherrated safety-switch. The enclosed box 2 for the higherrated safety-switch of FIG. 7 is not illustrated, but it may be of a type similar to that shown in FIGS. 1 and 2. The operating bail 9 of FIG. 7 is journalled in a manner similar to that illustrated in FIG. 1.

Supported to the rear wall 49 of the box 2 are three suitably-molded support blocks, generally designated by the reference numerals 50-52. These support blocks 5652 are fixedly secured to the rear wall 49 of the enclosing box 2 by machine screws 53. The ends of the mounting screws 53 extend into tapped holes provided in the rear wall 49 of the switch box 2. For the two-pole device shown in FIG. 7, it will be noted that there is mounted upon the upper support block 50 a pair of L- shaped, relatively stationary, stab contacts 54, having laterally extending mounting portions 55, as shown in FIG. 9. As illustrated in FIG. 8, mounting screws 55a extend through the mounting block 50 and thread into tapped holes 56 (FIG. 9) provided in the laterally extending leg portion 55. A sleeve connector 57 is secured by a screw 58 (FIG. 10) to the mounting plate portion 55 of the stab contact 54. Such screw also extends through the molded support block 50, as shown in FIG. 10 of the drawings. A clamping screw 59 is provided to fixedly secure the end of a line connector into place.

The rotatable switch-arm, generally designated by the reference numeral 60 in FIG. 8, comprises a pair of contact blades 61, each of which has a configuration more clearly shown in FIGS. 14 and 15 of the drawings. With reference to FIGS. 14 and 15, it will be noted that the contact blades 61 have an offset portion 62 provided intermediate the ends thereof. The contact blades 61 are placed back-to-back, as shown in FIG. 7, and there results thereby a pair of

bifurcated portions

63, 64 at the opposite ends of the switch-arm 60.

A pair of arc-suppressor plates 65, which is more clearly shown in FIG. 11, are mounted into position, with the legs, or furcations 66 extending through apertures or openings 67 provided in the sides of the arc-suppressor plates 65. The vertical width Y (FIG. 11) of the aperture 67 is slightly less than the vertical height of the leg 66, as indicated by the reference numeral Z indicated in FIG. 15, so that once the furcations, or legs 66 are inserted through the openings 67, the arc-suppressor plates 65 are not permitted to move laterally outwardly, and are maintained in the position illustrated in FIG. 7. In effect, the plates 65 are hence locked into their proper position. Bolts 68 and washers 69 (FIG. 8) are provided to clamp the offset the configuration of portions 62 of the switch-blades 61, together with the arc-suppressor plates 65 and additional flat springs 70, more clearly shown in FIGS. 16 and 17, into a proper clamped position. The holes 71 provided in the several elements accommodate the shank portions of the mounting bolts 68. Nuts 72, shown in FIG. 7, provide a fixedly clamped construction of the switch-arm 60. With reference to FIG. 7, it will be noted that the lower bifurcated portion 64 straddles a relatively stationary hinge stab contact 73, constituting one leg of a U-shaped mounting bracket, generally designated by the reference numeral 74, and fixedly secured to the mounting block 51 by a mounting screw 75.

FIGS. 12 and 13 more clearly show the construction of the U-shaped hinge mounting bracket 74. The mounting stab contact 73 has a hole 76 (FIG. 13) provided therein, through which a rivet 77 (FIG. 7) pivotally supports the switch-arm 60 into place. In addition, a contact finger 78 is provided, biased by a spring 79, encircling a mounting bolt 80. The contacting end 81 (FIG. 13) of the contact finger 78 cooperates with the side surface of the leg 82 of the U-shaped mounting bracket 74 to contactingly engage the knife-blade terminal 83 of a cartridge-type fuse 84. FIG. 7 more clearly shows this construction. The lower end of the cartridge fuse 84 is similarly clamped into position by a fuse receptacle, comprising an L-shaped mounting bracket, generally designated by the reference numeral 85, and including a spring finger 78 as described hereinbefore. The spring finger 78 is similarly biased toward the lower knife-blade terminal portion 86 of cartridge fuse 84 by a biasing spring 79, mounting nut and

bolt

80, 87 in a manner similar to that shown in FIG. 13 of the drawings. The L-shaped mounting bracket 85 has a laterally extending terminal-plate portion 88, which is mounted to the molded mounting block 52 by a mounting screw not shown. Finally, the L-shaped mounting bracket 85 has a connector sleeve 89 and a clamping screw 90, similar to the connector sleeve 57 and mounting screw 59 illustrated in FIG. 10.

A neutral plate 91 is provided, being mounted to the support block 52 by a machine screw 92, as shown in FIG. 7. The neutral terminal plate 91 has a pair of connector sleeves 89 and clamping screws 90, as heretofore described in connection with the mounting bracket 85. A ground connection 91a may also be provided.

The operation of this modification of the present invention will now be described. Upon operation of the manually operable handle (FIG. 1), the operating bail 9 (FIG. 7 accommodated in slots 93 of the arc-suppressor plates 65, eifects rotation of the several switch-arms 60, to cause thereby disengagement of the legs, or furcations 66 of the contact blades 61 from the stab contacts 54. The resulting arc is drawn between the lower side portions 94 (FIG. 10) of the arc-suppressor plates 65 and rapid extinction thereof is achieved in a manner similar to that heretofore described in connection with the extinguishing device of FIG. 1. The flat biasing springs 70 insure that the legs 66 are biased toward the relatively stationary stab contact 54 inthe closed-circuit position of the device, as illusrated in FIG. 10 of the drawings. With reference to FIG. 10, it will be noted that the inner, side-contacting portions 66a, extending through the openings. 67 of plates 65, maintain frictional contact with the sides of the relatively stationary stab contact 54 in the closed-circuit position. Also it will be noted that the side edges of the contact blades 61 are flared outwardly, as indicated at 6612, to insure a proper guiding action of the switch arm 60.

It will be seenthat upon removal of the bolts 68 and nuts 72 the rotatable switch arm 60 may be rapidly disassembled, and a new pair of arc-suppressor plates 65 inserted into proper position.

From the foregoing description, it will be apparent that there is provided an improved arc-extinguishing device associated with an electric safety-switch of the enclosed type. The fiber arc-

suppressor plates

42, 65 may be rapidly manufactured, by stamping out the desired configuration from fiber sheeting. The present invention results in an inexpensive arc-extinguisher particularly adaptable for use in light-duty safety-switches. Advan tageous features of the invention are excellent arc-extinguishing characteristics, simplicity, and low cost. Other advantageous features of the invention are the positive alignment of the blade and break-jaw, which are insured, which results in satisfactory operation of the switch mechanism. This results from the beveled surfaces provided on the arc suppressor plates 42, as provided by the beveled edges 43, and on the contact furcations 66 of FIGS. 14 and 15. By using a good gas-evolving material, such as fiber, and confining the established are, it is rapidly extinguished before it has a chance to expand, and are over to ground, or to an opposite phase. With the construction illustrated in FIG. 7, it will be noted that the arc-suppressor plates 65 may have an extended portion 95,. providing the operating slot 93 for accommodation of the actuating bar, or operating bail 9. This results in considerable simplicity.

With the device illustrated in FIG. 7, without the provision of the arc-suppressor plates 65, the devicev was good for less than 20 horsepower rating. By the addition of the arc-suppressor plates. 65,, the rating was. increased to 30 horsepower, and passed an endurance testof 10,000 operations.

Both of the constructions illustrated in FIGS. 1 and. 7 are simple to add to existing lines of switches without modification. No modification of the basic contact parts are necessary. There merely involves the addition of the arc-

suppressor plates

42, 47 or 65, depending upon the ratings. It has been discovered that the arc-suppressor plates of the present invention are considerably cheaper than molded arc-extinguishers, which are used on safety switches, and the arc-suppressor plates are more effective.

Although there have been shown and described particular embodiments of the invention, it is to be clearly understood that the same were merely, for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art, without departing from the spirit and scope of the invention.

I claim as my invention:

1. The combination in an electric switch of a relatively stationary break-jaw contact having a pair of leg portions, each leg portion having. an intermediate portion constituting a contact face and an outer free end clamping portion, a pivotally mounted cooperable movable switch blade which enters between said leg portions in the closed+ circuit position of the switch, a. pair of cooperable perforated arc-suppressor plate clips disposed between said leg portions with the contact faces of the leg portions pro.- tru ding through the perforations of the perforated arcsuppressor plate clips and with the outer free-end clamping portions of the leg portions assisting in clamping the plate clips in fixed position, and the are established during the opening operation of the switch extending'between said arc-suppressor plate clips and becoming extinguished;

2. The combination in an electric switch of a relatively stationary break-jaw contact'having a pair of leg portions, each leg portion having an intermediate portion constituting a contact face and a pair of clamping portions on opposite sides of said intermediate cont-act face portion, a pivotally mounted cooperable movable switch blade which enters between said leg portions in the closedcircuit positionof the switch, a pair of cooperable per,- forated arc-suppressor plate clips composed of a gasevolving material disposed between said leg portions-with the contact faces of the leg portions protruding through the perforations of the perforated arc-suppressor plate clamping portions on each leg into proper poclips and with the pair of portion clamping the respective plate clip sition, and the are established during the. opening-operation of the switch extending between said arc-suppressor plate clips and becoming extinguished.

3. The combination in an electric switch of a relatively stationary break-jaw contact having a pair of leg portions, each leg portion having an intermediate inwardly extending contact face portion and oppositely disposed strap-like clamping portions, a pivotally mounted cooperable movable switch blade which enters between said leg portions in the closed-circuit position of the switch and into engagement with the contact face portions, a pair of cooperable perforated fiber arc-suppressor plate clips disposed between said leg portions with the contact face portions of the leg portions protruding through the perforations of the perforated arc-suppressor plate clips and with the oppositely disposed strap-like clamping portions of each leg portion holding the respective plate clip into position, and the are established during the opening operation of the switch extending between said arc-suppressor plate clips and becoming extinguished.

4. The combination in an electric switch of a relatively stationary break-jaw contact having a pair of leg portions, each leg portion having an intermediate portion constituting a contact face and an outer free end clamping portion, a pivotally mounted cooperable movable switch blade which enters between said leg portions in the closedcircuit position of the switch, a U-shaped side perforated arc-suppressor wrapper disposed between said leg portions with the contact faces of the leg portions protruding through the side perforations of the U-shaped wrapper and with the outer free end clamping portions of the leg portions assisting in clamping the U-shaped wrapper into fixed position, and the established arc being drawn be tween the side legs of the U-shaped arc-suppressor wrapper during the opening operation of the switch to become extinguished.

5. The combination in an electric switch of a relatively stationary break-jaw contact having a pair of leg portions, each leg portion having an intermediate portion constituting a contact face and a pair of clamping portions on opposite sides of said intermediate contact face portion, a pivotally mounted cooperable movable switch blade which enters between said leg portions in the closedcircuit position of the switch, a U-shaped side perforated arc-suppressor wrapper composed of a gas-evolving material disposed between said leg portions with the contact faces of the leg portions protruding through the side perforations of the U-shaped wrapper and with the pair of clamping portions on each leg portion clamping the respective side Wall of the U-shaped wrapper into fixed position, and the established are being drawn between the side walls of the U-shaped arc-suppressor wrapper during the opening operation of the switch to become extinguished.

"6. The combination in an electric switch of a relatively stationary break-jaw contact having a pair of leg portions, each leg portion having an intermediate inwardly extending contact face portion and oppositely disposed strap-like clamping portions, a pivotally mounted cooperable movable switch blade which enters between said leg portions in the closed-circuit position of the switch, a U-shaped side perforated fiber arc-suppressor wrapper disposed between said leg portions with the contact faces of the leg portions protruding through the side perforations of the U-shaped wrapper and with the oppositely disposed strap-like clamping portions of each leg portion holding the respective side wall of the U- shaped wrapper into fixed position, and the established arc being drawn between the side walls of the U-shaped arc suppressor wrapper during the opening operation of the switch to become extinguished.

7. An electric switch including a spaced pair of relatively stationary stab contacts, a bifurcated switch blade pivotally mounted about one relatively stationary stab contact and making engagement and disengagement with the other relatively stationary stab contact, a pair of co- E3 operable arc-suppressor plates attached to and movable with the bifurcated switch blade independently of said other stab contact to extinguish the established arc, and said pair of arc-suppressor plates separating from said other relatively stationary stab contact in the fully open circuit position of the electric switch.

8. An electric switch including a spaced pair of relatively stationary stab contacts, a bifurcated switch blade pivotally mounted about one relatively stationary stab contact and making engagement and disengagement with the other relatively stationary stab contact, and a pair of cooperable arc-suppressor plates composed of a gas-evolving material attached to and movable with the bifurcated switch blade independently of said other stab contact to extinguish the established arc, and said pair of arc-suppressor plates separating from said other relatively stationary stab contact in the fully open circuit position of the electric switch.

9. An electric switch including a spaced pair of relatively stationary stab contacts, a bifurcated switch blade pivotally mounted about one relatively stationary stab contact and making engagement and disengagement with the other relatively stationary stab contact, a pair of cooperable fibre arc-suppressor plates attached to and movable with the bifurcated switch blade independently of said other stab contact to extinguish the established arc, and said pair of arc-suppressor plates separating from said other relatively stationary stab contact in the fully open circuit position of the electric switch.

10. An electric switch including a spaced pair of relatively stationary stab contacts, a bifurcated switch blade pivotally mounted about one relatively stationary stab contact and making engagement and disengagement with the other relatively stationary stab contact, a pair of cooperable arc-suppressor plates attached to and movable with the bifurcated switch blade independently of said other stab contact to extinguish the established are, an operating bar for effecting opening and closing motion of said bifurcated switch blade, and the arc-suppressor plates having slots therein to accommodate said operating bar.

11. An electric switch including a relatively stationary U-shaped contact jaw the outer free ends of the furcations of which are flared away from each other, intermediate portions of said furcations of the U-shaped contact jaw being more closely spaced together than other inner portions of the furcations of the U-shaped contact jaw, a movable switch blade adapted to enter between the outer flared-away portions of the contact jaw and make frictional clamping engagement with said closely spaced intermediate portions of the U-shaped contact jaw, a pair of arc-suppressor plate clips, each of said arcsuppressor plate clips having a rectangular hole therein, and the pair of arc-suppressor plate clips being positioned between said furcations with said intermediate contacting portions of the furcations extending through the rectangular slots.

12. An electric switch including a relatively stationary U-shaped contact jaw the outer free ends of the furcations of which are flared away from each other, intermediate portions of said furcations of the U-shaped contact jaw being more closely spaced together than other inner portions of the furcations of the U-shaped contact jaw, a movable switch blade adapted to enter between the outer flared-away portions of the contact jaw and make frictional clamping engagement with said closely spaced intermediate portions of the U-shaped contact jaw, a pair of arc-suppressor plate clips, each of said arc-suppressor plate clips having a rectangular hole therein, the pair of arcsuppressor plate clips being positioned between said furcations with said intermediate contacting portions of the furcations extending through the rectangular slots, a center mounting screw for holding said U-shaped contact jaw into position, and said center mounting screw having the extremity of the shank portion thereof extending between the inner ends of the suppressor plate clips to bias the outer blade-receiving ends thereof together- 13. An electric switch including a relatively stationary U-shaped contact jaw the outer free ends of the furcations of which are flared away from each other, intermediate portions of said furcations of the U-shaped contact jaw being more closely spaced together than other inner portions of the furcations of the U-shaped contact jaw, a movable switch blade adapted to enter between the outer flared-away portions of the contact jaw and make fric tional clamping engagement with said closely spaced intermediate portions of the U-shaped contact jaw, a pair of arc-suppressor plate clips, each of said arc-suppressor plate clips having a rectangular hole therein, the pair of arcsuppressor plate clips being positioned betwen said furcations with said intermediate contacting portions of the furcations extending through the rectangular slots, and the outer blade-receiving ends of the arc-suppressor plate clips being flared outwardly for proper guiding of the movable switch blade.

14. The combination in an electric switch of a relatively stationary contact stab, at pivotally mounted switch arm including a pair of generally rectangularly-shaped contact blades placed back-to-back forming an elongated generally rectangularly-shaped bifurcated portion at the free end of the pivotally mounted switch arm, said contact stab entering between the legs of said bifurcated portion in the closed position of the switch, a pair of arcsuppressor plates secured to and movable with said switch arm having substantially rectangular slots provided therein to accommodate the legs of the bifurcated portion of the pivotally mounted switch arm, contacting portions of said legs engaging said contact stab through the substantially rectangular slots of the arc-suppressor plates, and the lateral width of said substantially rectangular slots provided in the suppressor plates being less than the lateral Width of the elongated generally rectangularly-shaped contact blades so that the edge portions of the latter will exert clamping action upon the suppressor plates.

15. The combination in an enclosed electric switch having a switch box and an operating bail journalled in the side walls of the box of a relatively stationary contact stab, a pivotally mounted switch arm including a pair of generally rectangularly-shaped contact blades placed backto-back forming an elongated generally rectangularlyshaped bifurcated portion at the free end of the pivotally mounted switch arm, said contact stab entering between the legs of said bifurcated portion in the closed position of the switch, a pair of arc-suppressor plates secured to and movable with said switch arm having substantially rectangular slots provided therein to accommodate the legs of the bifurcated portion of the pivotally mounted switch arm, contacting portions of said legs engaging said contact stab through the substantially rectangular slots of the arc-suppressor plates, outer edge portions of the arc-suppressor plates having slots provided therein to accommodate said operating bail, and the lateral width of said substantially rectangular slots provided in the suppressor plates being less than the lateral Width of the elongated generally rectangularly-shaped contact blades so that the edge portions of the latter will exert clamping action upon the suppressor plates.

References Cited in the file of this patent UNITED STATES PATENTS 1,521,009 Colby et al. Dec. 30, 1924 1,898,128 Jackson et a1. Feb. 21, 1933 1,955,961 Jackson Apr. 24, 1934 1,993,273 Hammerly Mar. 5, 1935 2,116,673 Fisher et al. May 10, 1938 2,142,674 Jackson Jan. 3, 1939 2,325,697 Millermaster et a1. Aug. 3, 1943 2,588,195 Ballou Mar. 4, 1952 2,644,061 Dietrich June 30, 1953 2,654,011 Kingdon Sept. 29, 1953 2,840,671 Gietfers June 24, 1958 FOREIGN PATENTS 1,011,033 Germany June 27, 1957 1,053,615 Germany Mar. 6, 1959