US2027538A - Electric switch - Google Patents

Description

A. W. KRIEGER ELECTRIC SWITCH Jan. 14, 1936.

Filed May 14, 1934 INs ULFITION UNITED STATES PATENT OFFICE ELECTRIC SWITCH Alvin W. Krieger, Cutler-Hammer, poration oi Delaware Iltlililwaukee, Wis., assignor to Milwaukee, Wis., a cor- Application May 14, 1934, Serial No. 725,493

, 11 Claims.

This invention relates to improvements in electric switches of the toggle-type.

A primary object of the invention is to provide novel forms of switches for control of the landing lights or other signal lights of aeroplanes.

Another object of the invention is to improve the structural and operating characteristics of switches of the aforementioned character.

Another object is to provide an improved form of ball and socket bearing for the operating lever 01' the switch.

Another object is to provide novel forms of bridging contactors for switches of the aforementioned character.

Another object is to provide means enabling use of a minimum number of different parts for production of switches having substantially different electrical functions or characterics.

Another object is to provide a bridging contactor having a novel form of cam surface for cooperation with the actuator whereby the contactor is biased out of a given position.

Another and more specific object is to provide novel means for automatically returning the contactor to a given position thereof upon manual release of the operating lever.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates several embodiments of the invention which will now be described, it being understood that the embodiments illustrated are susceptible of modification as to certain details thereof without departing from the scope of the appended claims.

In the drawing, Figure 1 is a vertical sectional view (about one and one-half times actual size) of a single-throw toggle switch as constructed in accordance with my invention,the parts of the switch being arranged to insure biasing thereof to off position.

Fig. 2 is a perspective view, in separated relation, of certain of the parts illustrated in Fig. 1.

Fig. 3 is a perspective view of a modified form of contactor, which may be substituted for the contactor shown in Figs. 1 and 2 to provide a single-throw switch is normally biased to "on position.

Fig. 4 is a fragmentary elevation, looking at the right-hand end of the device in Fig. 1, for instance, and illustrating the manner in which the ends of'the sheet metal casing member are joined.

Fig. 5 is a top plan view of a three-position switch of the character illustrated in Fig. 6.

Fig. 6 is a vertical sectional view of a threeposition switch constructed in accordance with my invention,the bridging contactor being formed to insure biasing thereof to its interme diate or neutral position.

Fig. 'I is a perspective view of a modified form 5 of contactor, to be substituted for that shown in Fig. 6, to provide a three-position switch in which the contactor is biased out of only one of its extreme positions,-the support for said contactor being identical with that shown in Fig. 6. 10

Fig. 8 is a view, partly in elevation and partly in vertical section, illustrating a still further modified form of contactor adapted to provide a switch of the two-position, two-circuit controlling type,-the contactor being biased for movement 15 thereof to one or the other of its extreme posi tions.

Fig. 9 is a perspective view of the contactor shown in Fig. 8,the modified form of support for said contactor being shown in separated relation.

Fig. 10 is a bottom plan view of the switch shown in Fig. 12.

Fig. 11 is a perspective view of the bus member shown in Fig. 10, and 5 Fig. 12 is a fragmentary vertical sectional view of a three-position switch employing a contactor like that shown in Fig. 7 and a bus member like that shown in Fig. 11.

The switches herein illustrated are in general 30 of the character disclosed in the prior patents of George J. Meuer, Nos. 1,666,338 and 1,918,282, but differ therefrom in certain important particulars, as will hereinafter more clearly appear.

Referring first to Figs. 1 and 2, the numeral 5 designates a relatively thin but relatively rigid plate which is preferably punched from a sheet of insulating material of suitable character, as, for instance, canvas or other woven material impregnated with the phenol-formaldehyde condensation product sold commercially under the name of bakelite. Plate I5 is preferably of substantially elliptical contour (see, for instance, the correspondingly shaped plate 29 in Fig. 10), and the form of said plate is shown in detail in the aforementioned Meuer Patent No. 1,918,282. Also as shown in Patent No. 1,918,282 plate i5 is provided with four peripheral notches l6 located in pairs adjacent the respective ends thereof to receive lugs I! which are integral with the tubular 5 metal enclosing and spacing member I 8,-the lugs I1 being bent over the lower face of plate IE to secure the latter to said member Ill. The member I 8 may be formed in a well known manner from a single strip of metal having its abutting 5 of the contactor.

ends connected by a dove-tail connection or interlock, as shown at IB in Fig. 4. The interlocking portions of said ends are pressed together laterally, and thereafter the end of the casing embodying the interlock is dipped into a molten body of solder, for instance, which material flows into the seam or joint and adheres to the casing throughout a small area on either side of the joint, as indicated in dotted lines at m n-thus insuring against separation of said end portions under strains incident to assembly or use of the switch.

Base 15 is provided with openings I 5 l5, it, which are identical with the openings shown in Fig. 3 of Patent No. 1,918,282. A one-piece combined contact and wiring terminal member 89 of the identical form shown at 22 in said Patent No. 1,918,282 is inserted into opening l5 and attached to base i 5 in the manner disclosed in said patent. The one-piece combined contact or sup port and wiring terminal member 26 is in general quite similar to that shown at 36 in Patent No. 1,918,282,-the same being inserted through opening l5' and attached to base I 5 as by means of the rivet 2| which penetrates said opening l5. As best illustrated in Fig. 2, however, the upstanding portion 20 of member 20 is'so notched as to provide horizontal shoulders 20 and 20 against which the flat under surfaces of the intermediate portions of lugs 22 22 of a punched and stamped sheet metal contactor 22 are adapted to bear,- said lugs being notched as shown to loosely interlock with supporting portion 20 whereby substantial endwise displacement of said contactor is prevented. The contactor 22 is of substantially channel-shape in transverse cross section, and the bottom wall of the channel is sheared longitudinally along laterally spaced lines from a point (Fig. 1) at the left-hand side of the pivotal connection to a point adjacent to the right-hand end The sheared portion is then pressed upwardly as shown to provide a cam surface 22 which extends upwardly from the initial plane of the bottom wall of the channel at an angle of approximately forty-five degrees. As shown in Figs. 1 and 2 said cam surface 22 is of curved or concave form in both longitudinal and transverse cross section,the longitudinal curvature thereof being adapted to facilitate movement of the rounded lower end of an insulating actuating plunger 23 therealong, and the transverse curvature thereof assisting in limiting said plunger to movement in a single plane. The remainder 22 of said sheared portion acts as a strut or support for the upper end of the cam as thus formed.

Plunger 23 is slidable within a recess in the lower end of an actuating lever 24,- a coiled compression spring 24 being arranged to bias the plunger outwardly from the recess. Lever 24 and top plate 25 are preferably of the form shown in said Patent No. 1,918,282,said lever having a substantially spherical enlargement 24 which is adapted to bear upwardly against a socket 25 formed in said top plate. Top plate 25 is provided with an opening 25 of substantially elliptical contour to provide for upward insertion of the handle portion of lever 24,--the side walls of said opening acting to limit the degree of lateral displacement or movement of said lever and the end walls of said opening acting to limit the degree of oscillation of said lever from each extreme position thereof to the other.

In order to insure against substantial downward displacement of lever 24 with respect to its socket bearing, and to limit the same more definitely to oscillation in a single plane, I prefer to provide a punched and stamped sheet metal member 26 of the form shown in Figs. 1 and 2,the same having fiat end portions 26 and 2t to be engaged by the lower surface of top plate 25, and said end portions being reduced as shown at 26 and 26 to fit snugly within notches formed in the upper edge of tubular member l8 at opposite ends of the latter (see Figs. 1 and 4). Member 25 is bent as shown to provide an intermediate fiat portion 26 which is offset downwardly from the end portions 2E, 26, as by means of the angularly extending portions 26 26 Member 26 is provided with a slot 26 which is just sufliciently wide to provide clearance for the cylindrical lower end portion 24 of said lever. By the means aforedescribed the lever 24 is positively limited to oscillatory movement in a single plane, and substantial downward displacement thereof is prevented to insure against engagement thereof with the live parts of the switch. The tubular member 68 is provided with lugs H3 (see Fig. 5) which are bendable into suitable depressions or recesses formed in the upper surface of top plate 25. A suitable escutcheonor flush-plate (not shown) may be employed in the final-mounting or attachment of the switch to a suitable support.

As will be readily understood the movable switch parts will remain in the positions thereof shown in Fig. 1 only so long as a required degree of pressure is externally applied to lever 24 to retain the handle portion thereof in its extreme left-hand position. Upon manual release of the lever the spring-pressed plunger 23 carried thereby will automatically ride down the cam surface 22 to a point below and to the left-hand side of the point of pivotal support of contactor 22, whereby the latter is moved in a counterclockwise direction with a quick action out of engagement with the contact portion of member E9 to interrupt the controlled circuit (not shown). The aforementioned bias of plunger 23 in cooperation with cam surface 22 likewise results in automatic movement of the handle portion of lever 24 to its extreme right-hand position. By the means aforedescribed I have provided a simple form of single-pole, single-throw switch which is normallybiased to off position.

When it is desired to provide a single-pole, single-throw switch which is normally biased to on position, and momentarily movable to off position, all of the parts afore-described may be employed, with the exception of contactor 22, for which is substituted the contactor 21 shown in Fig. 3. Contactor 21 is preferably formed from a blank identical with that employed to provide the contactor 22. InFig. 3, however, the contactor 21 has the bottom wall of the channel sheared along parallel lines from a point adjacent to the left-hand end thereof to a point slightly to the right of the pivot portion,said sheared portion being bent upwardly as shown to provide the longitudinally and transversely curved cam surface 21 and the strut or support 21 therefor. Thus assuming use of the contactor 21 in a switch of the character shown in Fig. 1, it will be apparent that the spring-biased plunger 23 will normally bias contactor 2] in a clockwise direction to effect engagement thereof. with the contact portion of member l9, with a consequent bias of the handle portion of lever 24 to its extreme lefthand position. Upon manual operation of said handle portion toward the right the plunger 23 will ride upwardly on the cam surface 21 to mo- 2,027,538 mentarily eflect disengagement of contactor 21 from the contact portion of member l8.

In Figs. 5 and 6 I have illustrated a switch of the single-pole, double-throw type,said switch comprising a contactor 28 which is normally biased to an intermediate oif position, and which is movable or tiltable to either extreme position to momentarily engage one or another of a pair of stationary contacts. The parts I 8, 23, 24, 25 and 26 may be identical with those parts described in connection with the device of Fig. 1. The insulating base plate 29 is in general like that shown at I5 in Fig. 1, but plate 29 is provided with a pair of openings 29%, 29 to receive a pair of the combined contact and terminal members l9. Plate 29 is also provided with a central opening of rectangular contour to receive the shank portion 38" of a wiring terminal member 38, and said member 30 is provided with a pair of sharp lugs or projections 30', 38 which bite into the lower surface of said plate as a result of the riveting operation tobe described. Positioned centrally upon the upper surface of plate 29 is a center contact or supporting member 3| of U-shape in transverse cross section (see Fig. 7). The upstanding parallel arms of member 3| are notched as shown to provide horizontal shoulders 3|, 3| with which the laterally extending horizontal lugs (not shown) of contactor 28 are pivotally engaged. correspondingly shaped lugs 32*, 32 are shown on the contactor 32 of Fig. 7, which will be later described in detail. The bottom portion 3| of member 3| is provided with a rectangular opening to receive the aforementioned shank 38 of member 38,the end of said shank being thereafter riveted as shown to secure the parts in assembled relation.

The bottom wall of the channel of contactor 28 is provided with two pairs of parallel slits, which pairs of slits extend in opposite directions from points adjacent to the pivot portion of said contractor toward the opposite ends thereof, respectively. The sheared portions of said bottom wall are then bent upwardly as shown to provide a pair of cam surfaces 28 and 28 having struts or supports 28, 28 respectively associated therewith. As will be noted, the circuitcontrolling arms of contactor 28 extend upwardly in opposite directions at a slight angle to the horizontal. The cam surfaces 28, 29 preferably extend upwardly at angles of approximately forty-five degrees relatively to the respective arms of contactor 28,-said cam sur faces being of curved or concave form in both longitudinal and transverse cross section. The arrangement is therefore such that contactor 28 and actuating lever 24 are normally biased to the intermediate positions thereof illustrated. Upon manual operation of lever 24 to its extreme left-hand position, plunger 23 will'ride upwardly over cam surface 28 to effect tilting movement of contactor 28 into engagement with the contact portion of right-hand member l9 to complete an electrical connection between the latter and terminal member 30. Upon release of lever 24, however, the movable parts will automatically assume their biased positions as illustrated. In like manner lever 24 may be moved to its righthand extreme position, with consequent temporary engagement of contactor 28 with the contact portion of left-hand member l9; and upon release of said lever the contactor will move under the bias of plunger 23 to its intermediate or neutral position illustrated. By connecting the right-hand and left-hand members to suitable branch-circuit wires (not shown) and by utilizing the member 30 as a common circuit connection the switch shown in Fig. 6 may be employed for selectively eflecting energization of said branchcircuits.

The contactor 32 shown in Fig. 7 may be substituted for the contactor 28 shown in Fig. 6, to provide a switch of the character illustrated in Fig. 12. In Fig. 12 upon movement of lever 24 to its extreme left-hand position plunger 23 will ride onto the bottom wall 32 of the channel, and as a result the right-hand arm of contactor 32 will engage and remain in engagement with the contact portion of right-hand member l9 pending manual displacement of lever 24 from its left-hand extreme position. Upon intermediate positioning of lever 24 plunger 23 will engage the slight depression or pocket 32 in the bottom of thecontactor channel to retain the contactor in its intermediate or neutral position. contactor 32 is provided at the left-hand side of the pivot portion thereof with a cam surface 32 which is substantially like the cam surface 28 of contactor 28 and performs a corresponding function. A strut or support 32 for cam surface 32 is provided by the shearing and forming operation aforedescribed. Thus upon movement of lever 24 to its extreme right-hand position the plunger 23 cooperates with cam surface 32 of contactor 32 to effect tilting of the latter in a counterclockwise direction into engagement with the contact portion of left-hand member l9, and upon release of lever 24 the plunger 23 will automatically ride down the cam surface 32 to return contactor 32 to its intermediate or neutral position.

Thus with a switch like that shown in Fig. 12 I provide for completion of a given circuit so long as the actuating lever is held in one of its extreme positions, the switch parts acting automatically to interrupt said circuit upon release of the lever; whereas upon movement of the lever to its opposite extreme position an alternative circuit will be completed and maintained pending manual return of the lever to its intermediate position. The switch of Fig. 12 may have applied thereto a bus member 33 to permanently electrically connect the opposite members l9, l9. Thus with one wire of a circuit connected to terminal member 30 and with the other wire of the circuit connected to one of the members l9, it will be apparent that the circuit may be completed momentarily upon movement of lever 24 to one extreme position,- the switch parts acting automatically to interrupt circuit upon release of lever 24; whereas upon movement of said lever to its opposite extreme position the aforementioned circuit will be completed and maintained pending manual return of said lever to its intermediate position.

The switch shown in Fig. 8 utilizes most of the parts shown in Fig. 6, and to which like numerals of reference have been applied. In Fig. 8, how ever, I provide a still further modified form of contactor 34 and a modified form of center contact or pivotal support 35 therefon-the latter being secured to plate 29 by the shank of terminal member 38 as shown The contactor 34 is preferably formed from a blank identical with that employed for production of the contactors 28 and 32 aforedescribed. The lugs 34, 34 of contactor 34 are bent downwardly into parallelism with'each other to provide for bearing engagement of the curved lower ends thereof with contactor 34. The central or pivotal portion of the contactor 34 is pressed upwardly as shown to provide a convex cam surface 34. Plunger 23 therefore cooperates with cam surface 34 to insure quick movement of contactor 36 from each extreme position thereof to the other,-no intermediate off position being provided.

The actuating lever 24 in Fig. 8 has been shown as provided with a relatively shallow recess 2d in the upper end thereof, said recess being adapted to accommodate a hemispherical member 36 which is preferably formed of glass,the material of lever 24 around the recess 24 being spun inwardly as shown at RM to permanently retain member 36 in position. In practice the member 36 is provided at its inner end with a cavity or recess (indicated in dotted lines at 36) upon the surface of which cavity is applied a coating or layer of luminous paint of well known character. By this means location or position of lever 26 will be indicated in thedark. V Y

In all of the switches herein disclosed I prefer to employ stationary and movable contact and terminal elements composed of silver, whereby the same have a rating of 35 amperes, 26 volts. Where the required capacity of the switches is not so high, these parts may be composed of a relatively cheaper metal or alloy.

What I claim as new and desire to secure by Letters Patent is:

1. In an electric switch, in combination, an insulating base member, a plurality of contact members rigidly secured to said base member and having edge portions spaced upwardly from the latter, a bridging contactor having a loose pivotal connection with one of said contact members, said contactor being in general of channelform in transverse cross section, a portion of the bottom wall of the channel being sheared along parallel lines and deformed to provide an upwardly extending cam surface, a portion of said cam surface being located above the side walls of said contactor, an actuating lever pivotally supported in a predetermined spaced relationship to said base member, said lever having a recess in the lower end thereof, an insulating member slidably engaging the walls of said recess, a coiled compression spring located within said recess and adapted to bias said insulating member outwardly therefrom, the outer end of said insulating member being engageable with said cam surface whereby said contactor and said lever are normally biased to given positions thereof respectively, said lever being movable at will to a given extreme position against said bias to temporarily retain said contactor in one of its extreme positions, and'wiring terminal elements associated with the respective contact members and exposed below the lower surface of said base member.

2. In an electric switch, in combination, an insulating base member, a plurality of contact members rigidly secured to said base member and having edge portions spaced upwardly from the latter, a bridging contactor having a loose pivotal connection with one of said contact members, said contactor being in general of channelform in transverse cross section, a portion of the aoaasse bottom wall of the channel being sheared along parallel lines and bent upwardly relatively to the side walls thereof to provide a cam surface, said cam surface being located in a plane at an angle of approximately forty-five degrees with respect to the initial plane of said bottom wall and a portion thereof being located above the side walls of said contactor, a metal top plate,

a tubular casing member interposed between and attached to said base member and said top plate to retain the same in definitely spaced relation, said top plate having a socket formed in the lower surface thereof, an actuating lever extending upwardly through said top plate and having an enlargement adapted to bear within said sock-' said parts to provide a bearing surface for the enlargement of said lever to prevent downward displacement of the latter, said lever having a recess in the lower end thereof, an insulating member slidably engaging the walls of said recess, a coiled compression spring located within said recess and adapted to bias said insulating member outwardly therefrom, the outer end of said insulating member being engageable with said cam surface whereby said contactor and said lever are normally biased to given positions thereofrespectively, said lever being movable at will to a given extreme position against said bias to temporarily retain said contactor in one of its extreme positions, and wiring terminal elements associated with the respective contact members and exposed below the lower surface of said base member.

3. In an electric switch, in combination, an insulating base member, a plurality of combined contact and wiring terminal members rigidly secured to said base and having the wiring terminal portions thereof exposed upon the lower surface of said base, a metal top plate, a metal casing member of tubular form rigidly secured to said top plate and to said base to retain the same in predetermined spaced relationship to each other, said casing member having a pair of alined notches formed in the upper edge thereof, a punched and stamped sheet metal member having reduced end portions to fit within said notches in a substantially flush relationship to the upper edge of said casing member whereby said sheet metal member is retained in position by said top plate, said top plate and said sheet metal member having alined portions thereof ofiset from each other and adapted upon assembly thereof to provide a socket, an operating lever having a substantially spherical enlarge able within said recess and biased outwardly therefrom by said spring, and a bridging contactor having a loose pivotal connection with the contact portionof one of said combined contact and terminal members, said contactor being continuously engaged by said insulating member to provide for tilting of said contactor upon movement of said operating lever to opposite extreme positions respectively.

4. In an electric switch, in combination, a relatively thin but relatively rigid base of insulating material, a contact of substantially U- shape rigidly secured to the upper surface of said base substantially centrally of the latter, a pair of contacts arranged respectively on opposite sides of said center contact in equally spaced relationship thereto, the contacts of said pair each having a notch formed in the upper edge thereof, the walls of said notches extending downwardly in converging relationship to each other, a contactor having a loose pivotal connection with said center contact, said contactor being of substantially channel-form in transverse cross section and comprising a pair of integrally connected arms inclined upwardly from the pivot portion thereof, whereby said arms are respectively adapted to overlie the notched edges of said pair of contacts, an operating lever pivotally supported in vertical alinement with said contactor, said lever having an insulating plunger telescopically carried thereby and biased outwardly therefrom to continuously engage said contactor, said lever and said contactor being arranged to provide for positive retention thereof in an intermediate position wherein said contactor is disengaged from each of said pair of contacts, and said lever being movable at will to one of its extreme positions to temporarily effect opposite extreme positioning of said contactor, the bottom wall of the contactor with which said plunger engages being sheared along parallel lines and bent upwardly at an angle of approximately forty-five degrees to insure automatic return of said lever and said contactor to the intermediate positions thereof respectively upon manual release of said lever.

5. In an electric switch, in combination, a relatively thin but relatively rigid base of insulating material, a contact of substantially U- shape rigidly secured to the upper surface of said base substantially centrally of the latter, a pair of contacts arranged respectively on opposite sides of said center contact in equally spaced relationship thereto, the contacts of said pair each having a notch formed in the upper edge thereof, the walls of said notches extending downwardly in converging relationship to each other, a contactor having a loose pivotal connection with said center contact, said contactor being of substantially channel-form in transverse cross section and comprising a pair of integrally connected arms inclined upwardly from the pivot portion thereof, whereby said arms are respectively adapted to overlie the notched edges of said pair of contacts, an operating lever pivotally supported in vertical alinement with said contactor, said lever having an insulating plunger telescopically carried thereby and biased outwardly therefrom to continuously engage said contactor, said lever and said contactor being arranged to provide for positive retention thereof in an intermediate position wherein said contactor is disengaged from each of said pair of contacts, and said lever being movable at will to either of its extreme positions to temporarily effect a corresponding extreme positioning of said contactor, the bottom wall of said contactor being sheared and bent upwardly to provide cam surfaces on opposite sides of the intermediate portion thereof whereby automatic return of said contactor to the intermediate position thereof is insured upon manual release of said lever.

6. As an article of manufacture, a punched and stamped sheet metal bridging contactor for electric switches, said contactor being of substantially channel-form in transverse cross section, said contactor having lateral projections formed intermediate the ends thereof for pivotal engagement with a suitable support, an intermediate portion of the bottom wall of said channel being sheared along parallel lines and bent upwardly relatively to the side walls thereof to provide a cam surface extending above and to one side of the point of pivotal support, said cam surface being adapted for cooperation with a spring-pressed pivoted operating element of suitable form whereby said contactor and said operating element are normally biased out of given positions thereof respectively.

7. As an article of manufacture, a punched and stamped sheet metal bridging contactor for electric switches, said contactor being of substantially channel-form in transverse cross section, said contactor having lateral projections formed integrally with the side walls of the channel intermediate the ends thereof for pivotal engagement with a suitable support, at least one intermediate portion of the bottom wall of said channel being sheared and bent upwardly to provide a cam surface, said cam surface being inclined downwardly from a point above and to one side of the pivot portion of said contactor to a point below and to the opposite side of said pivot portion, said cam surface being adapted for cooperative engagement by a spring-pressed pivoted operating element of suitable form whereby said contactor and said operating element are biased to given positions thereof respectively.

8. As an article of manufacture, a bridging I contactor for electric switches, said contactor comprising a punched and stamped sheet metal member of substantially channel-form in transverse cross section, said member being provided intermediate the length thereof with integral lateral projections to provide for pivotal engagement thereof with a suitable support, and an intermediate portion of the, bottom wall of said channel being sheared longitudinally along laterally spaced lines and bent upwardly relatively to the side walls of said channel to provide a cam surface extending above the side walls of said channel, said cam surface being of concave form in both longitudinal and transverse cross section to facilitate engagement thereof by an oscillatabie actuating element of suitable form and to assist in limiting the latter to oscillatory movement in a single plane.

9. As an article of manufacture, a bridging contactor for electric switches of the three-position type, said contactor comprising a punched and stamped sheet metal member of substantially channel-form in transverse cross section, a pair of lateral pivot projections formed integrally with the side walls of said channel at the mid-point of the length thereof,'said metal member being formed to provide a pair of contactor arms extending upwardly in opposite directions from the point of pivotal support thereof at a slight angle to the horizontal, whereby said contactor may be positively held in an intermediate or neutral position upon engagement thereof by a yieldable actuating element of suitable form, and portions of the bottom wall of said channel on opposite sides of said pivot projections being sheared longitudinally along laterally spaced lines and bent upwardly relatively to the side walls of said channel to provide a pair of cam surfaces extending above the side walls of said channel and converging in a plane below the pivot point of said contactor, each of said cam surfaces being of concave form in both longitudinal and transverse cross section to facilitate cooperative engagement thereof by an oscillatable actuating element of suitable form and to assist in limiting the latter to movement in a single plane.

10. In an electric switch of the three-point type, in combination, a fiat punched plate of insulating material, a metal top plate having a centrally located slot, an operating lever having a portion thereof extending upwardly through said slot and engageable with the end walls of the latter to limit the throw of said lever, said lever having a substantially spherical enlargement and said top plate being deformed upwardly around said slot to provide a bearing socket for said enlargement, a tubular metal casing member interposed between and attached to said insulating plate and said top plate, said casing member having a pair of alined notches formed in the upper edge thereof, a punched and stamped sheet metal plate having reduced end portions to respectively fit within said notches in a flush relation to the upper edge of said casing member and to be retained therein by said top plate, said sheet metal plate having an intermediate portion thereof offset downwardly from' said top plate to provide an additional bearing surface, for said enlargement of the lever and to prevent substantial downward displacement of the latter, said ofiset portion having a slot formedtherein to accommodate a downwardly extending portion of said lever and to assist in limiting the latter to oscillatory movement in a single plane, said insulating plate having three combined contact and terminal members secured thereto, the contact portion of the center member being of substantially U- shape and the contact portions of the other members respectively having notches formed in the upper edges thereof, a bridging contactor having a loose pivotal connection with the contact portion first mentioned, said contactor being of substantially channel-form in transverse cross section and having arms extending upwardly at a slight angle to the horizontal and adapted to overlie the contact portions second mentioned, said contactorhaving an upwardly extending cam surface formed at one side of the mid-point of its length, said cam surface ex-- tending above the side walls of the channel at an angle of approximately forty-five degrees, said lever having a spring-pressed plunger en-' gageable with said contactor and cooperable with said cam surface to insure movement of said contactor from one extreme position thereof upon release of said, lever, the terminal portions of said combined contact and terminal members extending downwardly from the lower surface of said insulating plate and each having a wiring terminal screw associated therewith, and a, punched metal bus member having perfo- 5 rations at opposite ends thereof to provide for clamping engagement by the heads of screws associated with the end terminal members, the intermediate portion of said bus member being offset laterally and upwardly to clear the center 10 terminal member and the wiring terminal screw associated with the latter.

11. In an electric switch, in combination, a flat punched plate of insulating material, a punched and stamped sheet metal member of substantial- 15 ly U-shape in cross section positioned centrally upon the upper surface of said plate, the arms of said U-shaped member extending transverse-= ly of said plate in parallel relation to each other, said arms having'alined notches formed there- 20 in and extending downwardly to points closely adjacent to the lower ends thereof, a wiring terminal member exposed upon the lower surface of said plate and having a portion penetrating said plate and the bottom portion of said U- 25 shaped member and upset over the latter to secure said parts in position, a punched and stamped sheet metal contactor of channel form in transverse cross section, said contactor being of substantially V-shape in longitudinal 80 cross section and having alined lugs with rounded edge portions formed integrally with the upper edges of the side walls of said channel at the mid-point thereof, said lugs extending downwardly in parallel planes to provide for bearing 35 engagement thereof with the bottom portion of said U-shaped member, said lugs being also engageable with the arms of said U-shaped member to prevent longitudinal displacement of said contactor, the walls of said slots providing clearso ance for the arms of said contactor whereby the latter is freely oscillatable in opposite directions respectively, the bottom wall of said channel being sheared along parallel lines and bent upwardly at the mid-point of the contactor to provide a double cam the surfaces of which are inclined downwardly toward opposite ends of the latter, a spring-pressed actuating element pivotally supported above said contactor and operable to effect oscillatory movement of the latter 60 from each extreme position thereof to the other, said cam surfaces acting to insureagainst intermediate positioning of said contactor, and a pair of stationary contact members secured to said plate on opposite sides of said U-shaped mem- 55 ber, said contacts having notches formed in the upper edges thereof for cooperative engagement by the-respective arms of said contactor, said stationary contact members having wiring terminal elements formed integrally therewith 60 and exposed below the lower surface of said plate,

ALVIN W. mmGER.

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