US2295484A - Push-push operating mechanism for electric switches - Google Patents

Description

Sept. 8, 1942. A. w. KRIEGER 2,295,484 PUSHIPUSH OPERATING MECHANISM FOR ELECTRC SWITCHES I Filed June zo, 194,1v

INSULATION switches.

out departing from Patented Sept. 8, A1942- UNITED STATE PUSH-PUSH OPERATING HECHANI'SM liOB ELECTRIC SWITCHES Alvin w. miem. mi

Cutler-Hammer, Inc., poration of Delaware waukee, Wis., assignor to Milwaukee, Wis., a oor- Appnminn June so, 1941, serial No. 400,360

This invention relates to improvements in push-push operating mechanism for electric The operating mechanism is` particularly adapted for snap switch of the one-hole mounting type.

A primary object of the invention is to simplify Another object is to provide a simple push-push C operating mechanism of the one-hole mounting type adapted for use in conjunction with a snap `switch of well known form.

Another and more specic object is to minimize the required degree of accuracy in maintenance of tolerances normally specied for the various parts of the switch operating mechanism.

Another object is to increase the ruggedness and durability of switch operating mechanisms o the push-push type.

Another object is to provide a nevel form and arrangement of the anism, whereby all of the metal parts thereof may be readily assembled as a unit prior to rigid attachment thereof to the switch mechanism.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates an embodiment of the invention which will vnow be described, it being understood that the device illustrated is susceptible of modication in respect of certain structural details thereof withmy invention as defined by the appended claims.

In the drawing,

Figure 1 is a vertical sectional view, upon an use in the form of an electric` the structural details and improve the operative parts of the operating mech- 1s claims. (el: zoo-s1 2,171,368, dated August 29, 1939-to which reference may be had for a detailed description of the structural and operative characteristics thereof. It is to be understood. however, that the pushpush operating mechanism is likewise adapted for use with other forms of switches, particularly snap switches embodying over-the-center springs for eiecting snap movements of the contactors.

The switch illustrated comprises essentially a molded insulating base 6 having a recess `6 (Fig. 1) opening to the upper surface'thereof. Base 5 is provided with a pair of auxiliary recesses,

one of which is shown at 1 in Fig. 1, to vaccommodate intermediate portions of the combined contact and terminal members 8 and 9 in a substantially ush relationship to the upper surface of base 5. The resilient contact portions (see 9" Fig. 1) are located within recess 3 and the wiring terminal -portions 8b and 9b are located exteriorly of said base at one end of the latter.

- Base 5 is provided in its opposed side walls with a pair oi upwardly opening bearings, one of which is shown at I0 in Fig. l, to receive the outwardly extending integral lugs upon the arms of a punched sheet metal contactor II of substantially U-shape, The end wall of recess 6 adjacent to which the resilient contact portions are mounted is provided with an inward projection I2 forming a pair of vertical abutments to insure apredetermined normal spacing of the flared f portions of said contacts relatively to each other.

Contacter II is provided with an abutment I3 around which the lower end of the coiled com. pression spring I4 is adapted to t. A metal f Y member I5 is inserted downwardly into the upper end of spring I4, said member having a peripheral flange I6 to seat against the upper end of said spring-and said member having a circumirregular line, of a well known form of snap tion, .of certain elements ofthe operating mechanism. v

The switch parts, other than the operating mechanism, are of the character disclosed in my prior patents, No. 1,905,914, dated April 25, 1933; No. 1,998,962, dated April 23, 1935;- and No.

of the operating by the latter and member 2| when assembled are recess i'i with a concave bottom wall to accommodate and provide a cooperative abutment for the rounded lower end I8 of' a flat, punched insulating actuating element I9. Element I9 is provided at its upper edge with a substantially rectangular notch 20 of a width to accommodate the thickness of a lia-t, punched sheet metal member 2l, which is pivotally supported 'above base Y 5 in a predetermined spaced relationship thereto. Member 2l is provided in its lower edge with a substantially rectangular notch 22 of s'. width to accommodate the thickness of element I9,.where restrained against lateral movement .in any direction relatively to each other.

A nat punched insulating plate za n superimposed upon the upper surface of base 5 whereby the same overlies the intermediate portions of thek combined contact and terminal members 3 and 3 to clamp the latter in assembled relation to the base, and said plate overlies the bearings aforementioned to prevent accidental upward displacement of contactor vPlate 23 is provided with a longitudinally extending slot 24 which provides oscillatory clearancefor the tapered lower end portin-iof actuating element I9, and the side walls of which slot assist in limiting element |9 to oscillatory movement in a single plane-as best illustrated in Fig. The switch is provided with a punched and stamped sheet metal cover and support plate 25, a pair of headed rivets extending upwardly through alined openings in base 5, plate 23 and plate 25 adjacent to opposite ends thereof, the shank ends of said rivets being upset over the upper surface of plate 25 to rigidly and permanently secure the aforedescrlbed parts `in as'- sembled relation.l One of the pair of rivets is shown at 26 in Fig. 1, it being understood that the other rivet will be alined therewith longitudinally of base midway between the aforementioned combined contact and terminal members 6 and 9.

However, before riveting plate in assembled position, the push-push operating elements of the device are assembled with respect thereto.

'I'hus plate 25 is provided with a centrally located bulge or upward projection 21, which bulge is provided with a substantially circular opening 28 to accommodate the reduced lower end of an externally threaded hollow metal bushing 29, said reduced lower end being upset over the lower surface of plate 25 as shown at 30 to rigidly and permanently secure said parts to each other. Bushing 29 is provided with a vertical groove 3| (Fig. l) and plate 25 is provided with an integral upwardly projecting lug or tongue 32 which fits into said groove to positively prevent rotation of the bushing and plate relative to each other. Groove 3| is likewise adapted to accommodate a tongue formed integrally with the wall of an opening in a panel or other support (not shown) to restrain bushing 29 against rotation relatively thereto.

Bushing 29 is provided adjacent to its upper end with lan integralcylindrical portion 33 of reduced internal and external diameter, thus washer 46 of suitable material overlying the peripheral flange of the tip 45, and the upstanding ange of the button recess is spun or turned inwardly over washer 46. as indicated at 41, to

- secure tip in assembled relation.

4| or 4| pormember, a coiled After attachmentof button tion 31 of said hollow metal compression spring 43 of frusto-conical form is stud.

inserted into said member, with its large end abutting the upset end '42 or 42n of the button Thereafter a metal plunger member 49 has its reduced upper end 50 positioned within f the smaller lower end of spring 43, member 49 having a shoulder 5| formed thereon (see Fig. 3) to limit the amount of telescopic engagement thereof with said spring. The frusto-Qconical portion 52 oi' member 49 provides a relatively larger diameter lower shoulder 53 which is adapted to seat against .the upper edge 53 of an upstanding flange formed integrally with a cupwasher 54, which washer is adapted to telescopically lit into the enlarged lower end portion 36 of said metal member and to seat against the shoulder 55 formed therewithin. The inner pe- .riphery of the lower edge of portion 36 is then -upset or spun inwardly as shown at 56 (Figs. 1

and 2) to retain said washer 54 in position.

'Ihe central portion 54 of the lower surface of washer 54 is of frusto-conical shape to aiiord adequate oscillatory clearance for the downwardly tapered intermediate portion 51 of plunger 49-said plunger having a relatively smaller cylindrical lower portion 58 whose ex' tremity 59 is preferably of rounded or hemispheri -cal contour-for engagement with the pivoted toggle lever 2| aforementioned.l

Prior to assembly of lever 2|, a coiled compression spring 60 is inserted into bushing 29,

` the upper end of said spring being adapted to is adapted to cooperate with the annular shoulder 35 formed between the relatively large diameter lower portion 36 and the relatively smaller diameter upper portion 31 of a hollow metal member to limit the degree of upward movement of the latter. Portion 31 is provided with a at upper end 33 having a relatively small substantially circular opening 39 to'receive the stud 40 formed integrallywith the inverted cup-shaped pushbutton 4| (Fig. l), said stud having its lower end upset over the inner surface of the flat end 36, as shown at 42, to rigidly secure said parts to each other. The downwardly extending peripheral flange 45 of pushbutton 4| is adapted for slidable clearance with respect to the exterior of portion 33 of bushing 29. The pushbutton 4|n of Fig. 2 is lsubstantially like that of Fig. 1, and corresponding portions thereof lar notches engage the lower end of portion 36 of said metal member. Thereafter a pair of punched sheet metal members 6|, 6| of like form are inserted into said bushing jointly with lever 2|. Members 6|, 6| have reduced upper end portions 62, 62 which telescope into, and shoulders which engage, the lower end of spring 6U to effect compression of the latter to a degree to normally insure upper extreme positioning of Apushbutton 4| (or 4|) and its associated parts.

When members 6|, 6| and lever 2| are so inserted into the bushing, a pivot pin 64 is inserted latterally through alined openings 65 and 66 in bushing 29 and through substantially triangu- 61 in each of members 6| and the pivot opening 68 in lever 2|. The upper reduced ends 69, 69 of notches 61 are rounded to properly bear downwardly against pin 64. Pin 64 has at least one hollow end 19, which, after insertion thereof is spread or enlarged, as shown at 1|)B in Fig. 2, to' restrain the pin against displacement relatively to the bushing.

'I'he upper edge of lever 2| has a contour approximating the shape of the letter W, said contour including an apex 1| which is radial to the pivot opening 66, a pair of symmetrical, downwardly divergent camsurfaces 12 and 13, and

like upwardly angled edge portions 14 and 15 at 'K the respective extremities of said cam surfaces.

'a luminous tip memberf45 of known 101111 8f 75 pushbutton 4| the lower end 59 of plunger 4 When employed in conjunction with a toggle type snap switch the. lever 2| will normally be held in one or the other of its extreme positions, as best illustrated in Fig. 1, wherein the switch mechanism is shown in its circuit completing position. It follows that upon depression of the acca-s4 will engage the cam surface v12 to etrectcounterclockwise movement of lever 2| and the insulating actuating element I9 interlocked therewith pending movement of the upper end of spring I3 to the right beyond the pivotal, center of contactor whereupon said spring acts to snap the contactor to its circuit interrupting position.

. Under the conditions just mentioned lever. 2| will have been moved by plunger 29 to its extremeV counterclockwise position, such movement of the lever by the plunger 49 involving tilting of the er 49 to oneof the angular surfaces upon leverl 2|. On the other hand, it will be noted from the dotted line showing in Fig. 1 that oscillatory movement of insulating element I9 in each direction is positively limited by engagement of the -latter with the opposite walls respectively of the notches 61 in members 9|; and due to the interlocking connection between element I9 and lever 2| the oscillatory movements of the latter are -likewise positively limited. As a consequence the excess pressure applied to button 4| will be ab soibed in the spring 48 by compression of the latter, so that none of such excess pressure willbe transmitted to the switch contacts or contactor or to the spring |4 associated with the latter.

As will be understood, the bushing 29 is adapted to have one or more nuts threaded thereon to provide for one-hole mounting of the switch as a whole to a panel or the like.

Although I have herein illustrated a switch of the end wiring type, it is to be understood that the base 5 illustrated is adapted, by slight modifications thereof after molding, for use with either concealed terminals or bottom wiring terminals. Thus, as shown in Fig. 1, each auxiliary recess is provided with a bottom wall portion 16 of relatively thin cross section which may be readily tion 52 is adapted upon tilting of the-plunger to '-an extreme positionto engage said wall throughout the length of said portion, tofacilitate sliding movement thereof relatively to said wall. As

aforeindicated, the downwardly tapered form 'of spring permits such tilting of plunger '49 without interference with the inner wall of member 31, said lspring 48 acting not only to normally latter.toward'the left (Fig. 1) against the cenv tering eect thereon of spring 48, the shape of center plunger 49 but also to absorb any excess pressure applied to button 4|, or 4|. From the .ioregoing, it will be understood that spring 48.

is o! substantially greater strength than the overthe-center spring I3 .to insure snap operation of the switch mechanism by the latter prior to any substantial degree of downward movement of member 31 relatively to the plunger 49.

Iclaim: f 1. In a push-push operating mechanism for electric snap switches, in combination, a hollow metal bushing having Aan externally threaded cylindrical lower portion and an upper unthreaded' cylindrical portion of relatively smaller diameter with external and internal right-angle peripheral shoulders formed therebetween, a hollow metal member insertable upwardly into said bushing, .said member having an external periph-f eral shoulder formed thereon to limit the degree of upward movement thereof relatively to said bushing, said member being adapted in its upper extreme position to project a substantial distance upwardly beyond said bushing, an inverted cupvshaped metal pushbutton secured to the upper -end of said member, said pushbutton cooperating with said bushing to positively limit the extent .to which said membermay be depressed relative-A ly to said bushing, a coiled compression spring engaging the lower end of said memberto normally bias the same to its upper extreme position, and aspring and a plunger carried by said hollow metal member, said last mentioned spring acting to normallycenter said plunger while permitting bodily movement of the latter axially of said ,hollow metal member under certain conditions.

2. In a push-push operating mechanism for electric snap switches, vin combination, a hollow vmetal bushing having an externally threaded broached to provide a clearance opening for 1 and 2, the degree of compression of spring 48 as an incident to excess pressure upon button 4| or 4|'-i's positively limited by engagement of the lower edge of peripheral flange 43 or 43?l with the outer surface 11 of the shoulder formed between the lower threaded portion of bushing -29 and the upper unthreaded portion 33 thereof.

-hole mounting of the switch It should also be noted that the frusto-conical enlarged portion 52 of plunger 49 not only provides adequate clearance between the same and the inner cylindrical wall of member 31 upon tilt- -in/g of said plunger, but the surface oi said porcylindrical hollow portion and an upper unthreaded cylindrical portion of relatively smaller diameter with external and internal right-angle peripheral shoulders formed therebetween, a hollow metal member insertable upwardly into said bushing, said member having an external per-ipheral shoulder formed thereon to limit the degree of upward movement thereof relatively to said bushing, saidmember being-adapted in its upper extreme position t'oproject a substantial distance upwardly beyond said bushing, an inverted cup-` yshaped metal pushbutton rigidly and permanent- 1y secured to said member, said pushbutton beingl of smaller diameter than the root of the thread on said bushing to provide assembling clearance for a clamping nut or nuts to be threaded onto` said bushing, the downwardly extending peripheral flange of said pushbutton cooperating with the external right-angle peripheral shoulder on said bushing to positively limit the degree of downward depression of said member, a coiled spring engaged under a predetermined degree of compression with the lower end of said member to normally bias the same to itsupper extreme position, a plunger supported at the lower end of saidv member and tiltable and slidable 'with respect thereto,` and a coiled spring carried within said member and engaged under lcompression eral shoulders formed therebetween, a hollow metal member insertable upwardly into said bushing, said member having an external peripheral shoulder formed thereon to limit the degree of upward movement thereof relatively to said bushing, said member being adapted in its upper.

extreme position to project a substantial distance upwardly beyond said bushing, an inverted cupshaped pushbutton rigidly and permanently secured to said member, said pushbutton'being of smaller diameter than the root of the thread on said bushing to provide assembling clearance for a clamping nut or nuts to be threaded onto said bushing, thel downwardly extending peripheral flange of said pushbutton cooperating with the 'external right-angle peripheral shoulder on said bushing to positively limit the degree of downward depression of said member, a coiled spring engaged under a predetermined degree of compression with the lower end of said member to Vnormally bias the same to its upper extreme position, a coiled compression spring positioned attached to the'lower end of said member andv within said hollow metal member, a plunger engaged with the lower end of said spring, said plunger having an enlargement formed thereon, a washer attached to the lower end of said member and having an opening through which the lower end of said plunger extends, the periphery of said opening underlying said enlargement to retain said plunger while permitting tilting thereof against the centering bias of said last mentioned spring, and a `double inclined Ametal cam member with the cam surfaces of which said plunger is adapted to alternately engage.

4. In a push-push operating mechanismv forelectric switches, in combination, a hollow metal bushing having an externally threaded cylindrical lower portion and an upper unthreaded cylindrical portion of relatively smaller diameter with external and internal right-angle peripheral shoulders formed therebetween, a, hollow metal member insertable upwardly into said bushing, said member having an external peripheral shoulder formed thereon to limit-the degree of upward movement thereof relatively to said bushing, said member being adapted in its upper extreme position to project a substantial distance upwardly beyond said bushing, an inverted cupshaped pushbutton rigidly and permanently secured to said member, said pushbutton being of smaller diameter than the root of the thread on said bushing to provide assembling clearance for having an opening through which the lower end of said plunger extends, the periphery of said opening underlying said enlargement to retain saidl plunger while permitting tilting thereof against the centering bias of said last mentioned spring, a double inclined metal cam member with the cam surfaces of which said plunger is adapted to alternately engage, said cam member having a substantially rectangular notch formed in the lower edge thereof, and a flat, punched insulating member adapted to ilt within said notch, said last mentioned member having a notch formed in the upper edge thereof to accommodate thel thickness of said cam member, for the purpose set forth.

5. In a push-push operating mechanism for I electric switches in combination, a hollow metal bushing having an externally threaded cylindrical lower .portion and an upper unthreaded cylindrical portion of relatively smaller diameter with external and internal right-angle peripheral shoulders formed therebetween, ahollow' metal member insertable upwardly into said bushing, said member having an external peripheral shoulder formed thereon to limit the degree of upward movement thereof relatively to said bushing, said member being adapted in its upper extreme position to project a substantial distance -upwardly beyond said bushing, an inverted cupshaped pushbutton rigidly and permanently secured to said member, said pushbutton being of smaller diameter than the root of the thread on said bushing to provide assembling clearance for a clamping nut 'or nuts to be threaded onto said bushing, the downwardly extending peripheral flange of said pushbutton cooperating' with the external right-angle peripheral shoulder on said bushing. to positively limit the degree of downward depression of said member, a coiled spring engaged` undera predetermined degree of compression with the lower end of said member to normally bias the same to its upper extreme position, a coiled compression spring positioned within said hollow metal member, a plunger engaged with the lowerwend of said spring, said plunger having an enlargement formed thereon, a washer attached to the lower end of said member and having anv opening through which the lower end of said plunger extends, the periphery of said opening underlying said enlargement to retain said plunger while permitting tilting thereof against th centering bias of said last mentioned spring, a double inclined metal cam member with the cam surfaces of which said plunger is adapted to alternately engage, said cam member having a substantially rectangular notch formed in the lower edge thereof, a flat, punched insulating member adapted to fit within said notch, said last of said cam member, for lthe purpose set forth,

a clamping nut or nuts to be threaded onto said bushing, the downwardly extending peripheral flange of said pushbutton cooperating with the external right-angle peripheral shoulder on said bushing to positively limit the degree of downward depression of said member, a coiled spring pression with the lower end of said member to normally bias the same to its upper extreme position, a coiled compression spring positioned within said hollow metal member, a plunger engaged with the lower end of said spring, said plunger having an enlargement formed thereon, a washer `engaged under a predetermined degree of comsaid insulating member having an abutment 'formed at` thelowerend thereof, and a coiled over-the-center compression spring with the upper end of which said abutment is adapted to cooperate.I

' 6. In an electric vswitchadapted for one-hole mounting, 'in combination, a hollow metal bushing having an externally threaded cylindrical lower portion and 9, cylindrical upper portion of relatively smaller diameter formed integrally therewith, said bushing having-internal and external peripheral shoulders formed as an incident to the reduction in diameter of the upper portion thereof, a hollow metal member having integral lower and upper portions respectively slidable within the lower and upper portions of said bushpermit downward movement of a nut thereover for threaded engagement with said bushing. a

coiled compression spring positioned within said metal member, a plunger engaged with the lower end of said'sprlng under a predetermined degree of compression and centered by the latter, said plunger having an enlarged intermediate portion, and a washer underlying said last mentioned portion of the plunger to retain the same within said metal member while permitting lateral tilting and upward movement of said plunger against the bias of said compression spring. y

'1. In an electric switch adapted for one-hole mounting, in combination, a hollow metal bushing having an externally threaded cylindrical lower portion and a. cylindrical upper portion of relatively smaller diameter formed integrally therewith, said bushing having internal and external peripheral shou ders formed as-an incident to the reduction in diameter of the upper portion thereof, a hollow metal member having integral lower and upper portions respectively slidable within the lower and upper portions of said bushing,v

means to limit the degree of upward and downdownward movement of said member relatively to said bushing, said means for llimiting down- Y lward movement comprising a metal pushbutton,

. thereover for threaded engagement with said Y bushing, a coiled compression spring positioned i ing, means .to limit the degree of lupward and rigidly and permanently attached to the upper end of said member, said pushbutton being of `a size to' permit downward movement of a nut within said metal member, a plunger engaged with the lower end ofsaid spring under a 'prey determined degree of compression and centered by the latter, said plunger having an enlarged intermediate portion, a washerunderlying said last mentioned portion of the plunger to retain the same within said metal vmember while permitting lateral tilting and `upward movement of said plunger against the bias ofy said compression spring, a pivot pin extending diametrically through said' bushing adjacent to the lower end thereof, a metal cam member pivotally supported by' said pin, said cam member having a pair of downwardly diverging'l cam surfaces formed at theupper edge thereof for alternate engagement by said plunger, for the purpose set forth, a pair ward movement of said member relatively to said bushing, said means for limiting downward movement comprising a metal pushbutton rigidly and permanently attached to the upper end of said member, said pushbutton being of a size to permit downward movement of a nut thereover for threaded engagement with said bushing, a coiled compression spring positioned within said metal member, a plunger engaged with the lower end of said spring under a predetermined degree of compression and centered by the latter, said plunger having an enlarged intermediate portion, a washer underlying saidlast mentioned portion of the plunger to retain the same within said metal member while permitting lateral tilting and upward movement of said plunger against the bias of said compression spring, a pivot pin extending diametrically through said bushing adjacent to the lower end thereof, a metal cam member pivotally supported by said pin, said cam member having a pair of downwardly diverging cam surfaces formed at the upper edge thereof for alternate engagement by said plunger, for the purpose set forth, a pair of like fiat, punched sheet metal members also supported by said pin and arranged on opposite `sides of said cam member, each of ysaid pair of members having. two upwardly facing shoulders formed thereon, and

e a coiled compressionspring interposed between said shoulders and the lower end of said hollow metal member, to therebybias the latter to' its upper extreme position. i

8. In an electric switch adapted for one-hole mounting, in combination, a hollow metal bushing lower portion and a. cylindrical upper portion of relatively smaller diameterformed integrally therewitl, said bushing having internal and'external pe pheral shoulders formed as an incident to the reduction in diameter of the upper portion thereof, a hollow metal member having integral lower and upper portions respectively slidable having an externally threaded cylindrical of like at, punchedsheet metal membersalso supported by said pin and-arranged on opposite sidesof said cam member, each of said pair of members having two upwardly facing shoulders formed thereon, and a coiled compression spring interposed between said shoulders and the lower end of said hollow metal member, to thereby bias` the latter to its upper extreme position, said like metal members also cooperating with the lower end of said plunger to limit the same to tilting` movement in a single plane, whereby proper engagement thereof with said cam member is insured.

9. In an electric switch adapted for one-hole mounting, in combination, a hollow metal/bushing having an externally threaded cylindrical Vlower portion and a cylindrical upper portion of relatively smaller diameter formed integrally therewith, said bushing having internal and external peripheral shoulders formed as an incident to the reductiorrin diameter of the upper portion thereof, a hollow metal member having integral lower and upper portions respectively slidable within the lower and upper portions of said bushing, means to limit the degree of upward and downward movement of said member relatively to said bushing, said means for limiting downward movement comprising a metal pushbutton rigidly and permanently attached to the upper end of said member, said-pushbutton being of a size to permit downward movement of a nut thereovei` for threaded engagement with said bushing, a coiled compression spring positioned within said metal member, a plunger engaged with the lower endjof said spring under a predetermined degree of compression and centered by the latter, said plunger having an enlarged vintermediate portion, a washer underlying said last mentioned portion of the plunger to retain the same within said metal member while permitting lateral tilting and upward movement of said plunger against the bias of said compression spring, a pivot pin extending diametrically through said bushing adjacent to the lower end thereof, a metal cam member pivotally supported by said pin, said'cam member having a pair of downwardly diverging cam surfaces formed at the upper edge thereof for alternate engagement by said plunger, for the purpose set forth. a pair Y sl - within the lower and upper portions of said bu'shmetal members-also cooperating with the lower end of said plunger. to limit the same-to tilting movement in a single plane, whereby proper engagement thereof with said cam memberis insured, said like metal .members having downwardly opening substantially V shaped notches formed in the lower ends thereof. for cooperative engagement with said pivot pin, a fiat, punched insulating member arranged at a right angle to the plane of said cam member and interlocked with the lower edge thereof against lateral movement in anydirection, said insulating member having Opposite side portions jointly engageable with the lower portions of said notches to limit vthe degree of oscillatory movement of said insulating member in each direction.

10. In a push-push operating mechanism for v electric switches, in combination, a hollow metal member comprising a cylindrical upper portion having'an inwardly extending flange at the upper said member and seated against said upper endflange, a metal plunger having a reduced upper end telescoped into the lower end of said spring, said plunger having an enlarged intermediate portion of frusto-conical form, and a cup washer seated against said internal peripheral iiange and rigidly secured in position, said washer underlying said enlargement of the plunger to retain the latter in assembled position under a given degree of compression of the spring, said spring acting to normally center said plunger while providing for tilting and bodily movement thereof relatively to said member, for the purpose set forth.

1l. Ina push-push operating mechanism for electric switches, in combination, a hollow metal member comprising a cylindrical upper portion having an inwardly extending flange at the upper end thereof, a cylindrical lower portion of relatively larger diameter formed integrally ywith said upper portion and providing right-angled internal and external peripheral anges therebetween, a downwardly tapered coiled compression spring positioned within the upper portion of said member and seated against said upper end flange, a metal plunger having a reduced upper end telescoped into the lower end of said spring, said plunger having an enlarged intermediate portion of frusto-conical form, a cup washer seated against said internal peripheral flange and rigidly secured in position, said washer underlying said enlargement of the plunger to retainthe latter in assembled position under a given degree of compression of the spring, said spring acting to normally center said plunger while providing for'tilting and bodily movement thereof relatively to said member, for the purpose set forth, and a peripheral side portion of said frustoeconical enlargement being adapted to `en, lgage the inner wall of said cylindrical upper po-x\ v tion upon a given degree oi! tilting of said plunger, such engagement being adapted tofacilitate sliding movement of said member and said plunger relatively to each other in the event`of further compression and subsequent decompression'y of said spring.

12. In a push-push operating mechanism for electric snap switches, in combination, a hollow` an .externally threaded wardly into said bushing, said member having an external shoulder formed thereon to limit the degree of upward movement thereof relatively to said bushing, said member being adapted in its.

upper extreme position to project a substantial distance upwardly beyond said bushing, a me'tal pushbutton rigidly attached to the upper end of said member, said pushbutton cooperating with said bushing to positively limit the extent to' which said member may be depressed relatively to said bushing, a coiled compression spring en'- gaging the lower end of said member to normally bias the .same to its upper extreme' position, a

plunger carried by said member and tiltable and end thereof, a cylindrical lower portion of relaslidable relatively thereto, and a second coiled compression spring. providing a yieldable driving connection between said member and said plunger. l

13. In a push-push operating mechanism for electric switches, in combination, a hollow metal bushing having an externallyl threaded portion, a hollow metal member insertable upwardly intol said bushing, said member having an external shoulder formed thereon tov limit the degree of upward movement thereof relatively to said bushing, said member being adapted in its upper extreme position to project a substantial distance upwardly beyond said bushing, a pushbutton secured to the upper end of said member, said pushbutton cooperating with vsaid bushing to positively limit the extent to which said merli-'i'` ber may be depressed relatively to said bushing, a coiled compression spring engaging the lower end Vof said member to normally bias the samen, to its upper extreme position, a coiled compression spring positioned within said hollow metal member, a plunger engaged with the lower end of-said last mentioned spring, said plunger having an enlargement formed thereon, a washer attached to the lower end of said member and having an opening through which the lower'end of said plunger extends, the periphery of said opening underlying said enlargement to retain said plunger while4 permitting tilting thereof, a

double-inclined, pivoted, metal cam member with the cam surfaces of which said plunger is adapted to alternately engage, and an over-the-center spring associated with said cam member to bias" the latter -to one or the other of its extreme positions, said second mentioned spring being adapted to act as a centering means for said plunger and of suicient strength to hold the latter down during its operation of said cam member against the bias of said over-the-center spring, while providing for overtravel of said hollow metal member relativelyto said plunger in either extreme position of said cam member.

ALVIN w. KRIEGER. l

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