US2816195A - Snap action switch - Google Patents

Description

Dec. 10, 1957 G. HOLMES SNAP ACTION swncn Filed June 28, 1956 [ml 82717021 Robert 6. fvo/mes, b JZQMLL R. wt;

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United States Patent $816,195 SNAP ACTION SWITCH Robert G. Holmes, Asheboro, N. C.,'ass ign0r to General Electric Company, a corporation of NewYork Application June'28, 1956,Serial No. 594,508 8 :Claims. (Cl. lilo- 138) This invention relates to snap action switches, and particularly to that type of snap action switch having an over-center toggle spring.

Snap actionswitchescommonlyemployan actuator and a switch arm :carried by .acommon support and having their outer free ends interconnected by an over-center toggle spring. Whenthe actuator .isuon one side of the plane of the -switch;arm, .theswitch arm assumes one of its, extremezpositions;;and;as1the actuator moves through the plane of-said switch arm, .a snapzaction occurs to the other extreme rposition. The over-center toggle spring, -.in ;-a small sensitive-switch, is necessarily very light, and ,preferablyris in theformof atlooped .U' or V-shaped spring engaging respective knife edges .on the actuator and switch arm.

-While such snapzaction switches have been found generally reliable and effective, 'difliculties have been encountered by reason :of :accidental disengagement of the toggle spring'fromrone of the switch operating members. This difiiculty can be partially obviated :by the use of interrengaging tslots or apertures .and tongues to connect the toggle spring :to respective operating members. However, .the slot and tongue connection must be free and loose if binding :and inaccurateswitchroperation are to be vavoided. ;In-.practise, it has been found that accidental disengagement .of the toggle springstillroccursgeven with such aslotand tongue connection, especially at extremes of movement or where an unusual shock-is applied-to the switch assembly.

'One of the objects of this invention is to provide such a snap action switch of improved reliability by positively .locking the toggle spring in :position, but without in any way interfering with sensitivity or operation of the switch.

Another object aofthis invention is to provide a snap .action switch in which 'theactuator is a bimetallic element providing -wide deflection, and wherein positive locking means is provided between the bimetallic blade and the toggle spring.

in carrying out my invention in one form, the tension vand compression members of a snap action switch are secured together .at a common support and are interconnected at the outer free ends by an over-center toggle spring. Thetogglespring,having a looped configuration .and apertured-ends, engages knife edges on the respective opposed free ends of the tension and compressionmemhers-of the:switch,-and a tongue on each of these members projects outwardly from the knife edge through the corresponding ,apertured end of the toggle spring. To prevent any possible disengagement of the toggle-spring from one of the switch operating members, a locking plate is employed, which 'plate is apertured to receive freely an .end of the toggle spring. This plate further is provided with an enclosedouter end overlying the projecting end .of .the corresponding tongue, thereby preventing disen- .gagement of the .toggle spring from such member.

The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention itself,

2,816,195 Patented Dec. 10, 19,57

however, both as toorganization and method of operation, together with'further'objects and advantages thereof, may best be-understoodby reference to the following description taken in connection with the accompanying '4 provides a convenient mount 'and point for securement of the switch operating menibers. Asshown in this ;par ticular embodiment, asWitchtactuator "5 and a switch blade 6 are securedby rivets '7 -and'8 to support'4.

-Actuator 5 in the illustratedembodiment is in the form of a bimetallic blade, such a -blade being fabricated in a well-known manner by bondingtogethermetal strips having different coefiicients of expansion. 'To increase" the effective length of thebimetallicelement, and thus increase the temperature-responsivedeflection, it may be provided withone or more corrugationssuch as"9'and 10.

Switch -arm'-'6-'is in the form o'f-a *flex'ible metallic arm supported at oneendon support 4'and-extending in generally parallel relation'from the support with'the actuator or bimetallic *blade5. As shownclea'rlyby Figs. 2 and.3, the entire central portion of switch arm 6 'is cut out leaving-only side strips ll and IZ, a supported end13,-and a free-"or movable end-14. At *the-ex'tremityo'f this freeor :movable end is the contact button =15. As shown *by Fig.

'1 a fixed contact' button 16 is mounted on an appropriate support 17 which may be riveted to-base-l by'one or-more rivets 1-8 and 1 9'with an intermediate insulating-spacer '20. 'Thus,- when switch arm 6'is in an upper position (shown *by dotted lines in Fig. "1) acircuit may be comxpleted from support 4 through switch arm- -"6, contactslfi and 16, to support arm 17 for the fixed contact.

To provide snap 'action, -one'of the switch operating members is placed in tension while the other member .is in compression under the -influence-o'f1an over-center toggle spring 21. As 'shown clearly-by Fig. 2,-actuator 5 is somewhat shorter than switch arm -'6 so that the :free ends of *these'two members are spaced apart. The effective spacing between the free ends of'these 'memhers is lessthan'the normal distance betweenfree ends of toggle spring 21, -so that it is necessary to compress toggle spring 21 when 'it is engaged in position. Thus, as the :actuator moves 'downwardly thro'ugh the plane 'ofthe switch arm, the switch arm snaps to itsupper extreme position; and vice 'versa, as the actuator'moves upwardly, the switch-arm snaps'downwardly. Fixed contact 16 limits, of course, 'the'upward movement of'tlie .switch arm, and "preferably an adjustable stop screw 22 .is arranged to'limit the downward movement of 'th'e switch blade. Asshown by Fig. 1, stop screw 2'2 may be secured in :an adjusted position by lock nuts 23'and .24. .In this particular embodiment, it has been found therefore, preferred to employ a separate toggle spring engaging plate formed of a thin, hard material. Plate 25 provides a relatively sharp edge 26 for engagement with the toggle spring and includes a projecting tongue 27 adapted to engage an aperture 28 in one end of the toggle spring. Additionally, the toggle spring may be deformed along a line 29 to form a definite bearing surface for edge 26 of the switch actuator. The opposite end of toggle spring 21 is formed with a similar bearing surface 30 and aperture 31 cooperable respectively with the sharp edge 32 of switch arm 6 and projecting tongue 33 associated therewith.

From the foregoing description, it is seen that toggle spring 21 engages with line contact the free end of the switch actuator and similarly engages with line contact the free end of the switch blade, the toggle spring placing one of these switch members in compression and the other in tension. Additionally, the cooperative engagement of the respective projecting tongues 27 and 33 with apertures 28 and 31 in the toggle spring secures the toggle spring in position for normal conditions of operation. It may be noted, however, that for a sensitive switch, spring 21 is quite light and exerts only a small pressure against the switch operating members. Additionally, apertures 28 and 31 have a size substantially in excess of the size of their associated projecting tongues. Therefore, under conditions of severe shock, or possibly upon extreme deflection of one of the switch operating members, there is substantial risk that the toggle spring will become disconnected from one of the switch operating members, whereupon the switch ceases to be operative. In accordance with this invention, toggle spring 21 is effectively secured to the switch operating member, or more specifically to plate 25 thereof, with a positive locking means which, however, does not interfere with normal operation of the switch. This locking means in the illustrated embodiment includes a locking plate 34 having an elongated aperture 35 adjacent one end thereof.

Aperture 35 is dimensioned to receive freely an end of toggle spring 21, thus to provide freedom of movement of the toggle spring during switch operation. When the locking plate is assembled, however, the outer edge 36 thereof lies over projecting tongue 27, and thus it becomes substantially impossible to disengage toggle spring 21 from the switch actuator, without a rupture or destruction of one or more components of this switch. In other words, when tongue 27 is engaged in aperture 28, and locking plate 34 along with plate 25 are secured in position on actuator 5 by rivets 37 and 38, it is no longer possible, even under conditions of extreme switch movement or shock, to disengage the toggle spring from the actuator.

It would, of course, be feasible to incorporate a similar toggle spring locking plate in connection with the end of switch arm 6, thus to completely secure the toggle spring in its operative position. However, as a matter of practise wherein the movement of the switch arm between extreme positions is limited by stops, as shown by Fig. 1, disengagement of the toggle spring from an operative position does not occur.

In assembly of this switch, toggle spring bearing plate and locking plate 34 can be riveted to switch operating member 5. Furthermore, both switch operating members 5 and 6 may be riveted at 7 and 8 to support 4, an additional bearing plate 39 being employed as desired. Toggle spring 21 can then be inserted through aperture 35 in the locking plate, accompanied by a slight deformation of tongue 27, whereupon tongue 27 becomes engaged in aperture 28 of the toggle spring. As a final step in the assembly, the opposite end of the toggle spring is engaged on edge 32 with tongue 33 positioned in aperture 31.

It is found that with a switch in accordance with this construction that the sensitivity, reliability, or calibration of the switch is not affected by the, presence of the locking plate, since the locking plate in normal operation does not engage the toggle spring in any way. Nevertheless, the toggle spring, by means of this locking plate, is positively secured in position and accidental dislodgment is avoided. Furthermore, this construction lends itself to ease in assembly, since all of the permanently secured parts can be riveted or otherwise secured in position, and as a last step, the toggle spring may be engaged properly with the opposed edges and tongues of the switch operating members.

While the present invention has been described by reference to a particular embodiment thereof, it is to be understood that numerous modifications may be made by those skilled in the art without actually departing from the invention. It is, therefore, the aim of the appended claims to cover all such equivalent variations as come within the true spirit and scope of the foregoing disclosure.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a snap action switch having a tension member and a compression member secured together at a common support and interconnected by an over-center toggle spring at the respective free ends thereof, one of said members being an actuator and the other being an actuated switch blade, that improvement comprising means forming a knife edge on the respective opposed free end of each of said members, a tongue projecting outwardly from each of said knife edges, said toggle spring having a looped configuration with apertured end portions bearing against respective knife edges and engaging respective tongues, and a locking plate secured to at least one of said members, said locking plate being apertured to freely receive an end of said toggle spring and having an enclosed outer end overlying the projecting end of the corresponding tongue thereby to prevent disengagement of said toggle spring from said member.

2. In a snap action switch having a tension member and a compression member secured together at a common support and interconnected at the respective free ends thereof by an over-center toggle spring, one of said members being an actuator and the other being an actuated switch blade, that improvement comprising means forming a knife edge on the respective opposed free end of each of said members, a tongue projecting outwardly from each of said knife edges, said toggle spring having a looped configuration with apertured end portions bearing against a respective knife edge and engaging a respective tongue, a locking plate secured to one of said members, said locking plate being apertured to receive freely an end of said toggle spring and having an enclosed outer end overlying the projecting end of the corresponding tongue, thereby to prevent disengagement of said toggle spring from said member, and fixed stop means limiting movement of the other of said members.

3. The combination of claim 2 wherein said tension member is the actuated switch blade, said compression member is a bimetallic actuator, and said fixed stop means includes a fixed contact engaged by said switch blade.

4. A snap action switch comprising a fixed support, an actuator member, a spring contact member, said actuator and contact members being secured to said support and extending outwardly therefrom in the same direction, the free ends of said actuator and contact members being spaced apart, tongue means on the respective free ends of said actuator and contact members extending in opposite directions, a looped spring having apertured end portions engageable with respective tongue means to exert a tension on one of said members and compression on the other member, thereby to provide a snap action as said actuator member moves through the plane of said contact member, and a locking plate secured to said actuator member adjacent the tongue means thereon to prevent disengagement of said looped spring from said actuator.

5, A snap action switch comprising a fixed support, an actuator member, a spring contact member, said actuator and contact members being secured to said support and extending outwardly therefrom in the same direction, the free ends of said actuator and contact members being spaced apart, tongue means on the respective free ends of said actuator and contact members extending in opposite directions, a looped spring having apertured end portions engageable with respective tongue means to exert a tension on one of said members and compression on the other member, thereby to provide a snap action as said actuator member moves through the plane of said contact member, and a locking plate secured to at least one of said members adjacent the tongue means thereon to prevent disengagement of said looped spring from said one member.

6. A snap action switch comprising a support, a bimetallic actuator member, a spring contact member, said actuator and contact members being secured to said support and extending outwardly from said support in the same direction, the free ends of said actuator and contact members being spaced apart, tongue means on the respective free ends of said actuator and contact members extending in opposite directions, a looped toggle spring having apertured end portions engageable with respective tongue means and adapted to exert a tension on one of said members and compression on the other member, thereby to provide a snap action as said actuator member moves through the plane of said contact member, fixed stop means restraining the motion of said contact member, and a locking plate secured to said actuator member adjacent the tongue means thereon to prevent disengagement of said looped spring from said actuator.

7. In a snap action switch of the type having an actuator and a switch arm with one end of said actuator and a corresponding end of said switch arm secured to a support with opposite respective ends of said actuator and switch arm interconnected by a looped over-center toggle spring, that improvement comprising apertured end portions on said looped toggle spring, a projecting tongue on said actuator engageable with one end portion of said toggle spring and a corresponding tongue on said switch arm engageable with the opposite end of said toggle spring, and a toggle spring locking means for said actuator in the form of an apertured plate through which an end of said toggle spring may extend, said plate being secured to said actuator with the projecting actuator tongue extending outwardly beyond the aperture in said plate, thereby to prevent accidental disengagement of said toggle spring from said actuator.

8. The combination of claim 5 in which said actuator is a bimetallic blade.

References Cited in the file of this patent UNITED STATES PATENTS 2,429,784 Whitted et a1 Oct. 28, 1947 2,454,185 Kmiecik Nov. 16, 1948 2,581,705 Riche Jan. 8, 1952 2,603,727 Auer July 15, 1952

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