US2540421A

US2540421A - Electrical snap switch

Info

Publication number: US2540421A
Application number: US784676A
Authority: US
Inventors: Broch Frederick John
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-11-07
Filing date: 1947-11-07
Publication date: 1951-02-06
Anticipated expiration: 1968-02-06

Description

Feb. 6, 1951 F. J. BROCH 2,540,421

ELECTRICAL SNAP SWITCH Filed Nov. 7, 1947 2 Sheets-Sheet 1 [It vervtor fledera'c/Z J frock PM Feb. 6, 1951 UNITED STATES PATENT orrlcs Application November 7, 1947, Serb] No. 7,7'

16 Claims. (Cl. 2H7) This invention pertains to electrical switches. particularly to snap switches and more especially to a snap switch operative alternatively to close either of two electrical circuits, the present application being a continuation-in-part of my copending application for Letters Patent Serial No. 630,760, filed November 26, 1945, now abandoned. For many purposes snap acting switches are preferred to switches of'other types, particularly because they open with a minimum of arcing so that relatively heavy currents may be controlled by switches of small dimensions. However, switches of this type do not always provide the proper degree of pressure between the contacts when the switch is closed and in many cases are complicated and expensive to make and assemble, or are lacking in mechanical strength and durability. So far as is known to me switches'of this type have not heretofore been so designed as automatically to assume a neutral position with both circuits open when the actuating pressure is released.

A principal object of the present invention is to provide a snap action switch designed to provide good pressure between the contacts and in particular one wherein the pressure is substantially at a maximum just prior to the opening of the switch. A further object is to provide a snap acting switch of improved design which normally assumes a neutral position in which both circuits are automatically opened as soon as the switch closing force ceases to act. A further object is to provide a snap switch which is devoid of high precision parts or delicate members requiring pivotal bearings. A further object is to provide a snap action switch which is simple, inexpensive to manufacture, compact in design and of durable construction. Other'and further objects and advantages of the invention will be pointed out in the following more detailed description and by reference to the accompanying drawings wherein Fig. 1 is a side elevation, partly broken away and in section, illustrating one embodiment. of

the invention and showing the parts in the neutral position in which both circuits are open; Fig. 2 is a view similar to Fig.1 but to larger scale, showing the switch positioned to close one of the circuits; j I

Fig. 3 is a side elevation, to smaller scale, illustrating on'e'type of spring arm which may be used in the construction of a switch according to the present invention: I Fig.3 is a section on the line 9-3- of Fig. 3;

: Fig. .4 is a view generally similar to Fig. -1 but,

diagrammatic in character, showing a modified 2 construction in which the spring arms are-reversed inarrangement as compared with that of Fig. 1, the switch being shown in the neutral position with both circuits open;

Fig.5isaviewsimilarto1ig4butshowing tllie sgvitch parts arranged so that one circuit is c ose Fig. 6 is an elevation, with parts broken away,

illustrating a modification oi the arrangement of Fig. 1 wherein the actuating pressure is exerted by a cam so designed that the switch may be set to remain with either one or the other circuit closed;

Fig. 7 is a view similar to Fig. 6 but showing the parts arranged toclose one of the circuits; Fig. 8 is a view generally similar to Fig. 1 but showing the use of spring arms of a diflerent type, the parts being in the neutral position;

Fig. 9 is a view similar to Fig. 8 but showing one of the circuits closed; Fig. 10 is a plan view of one of the spring arms used in the switch of Figs. 8 and 9; Fig. 11- is a view generally similar to Fig.1 but showing a modification in which the movable contacts are mounted upon a part which is supported independently of the spring arms;

Fig. 12 is a view generally similar to 1 but showing a switch in which the spring arms are of another type; and

Fig. 13 is a perspective view' showing one of the spring arms of Fig. 12.

Briefly, the invention contemplates the provision of two normally equal opposed forces,.provided, for example, by two normally stressed resilient arms, acting against each other, and with provision for causing one or the other suddenly to exert a predominating efl'ective force thereby to close one or the other of two circuits.

For convenience in description, one of the spring arms may be termed the loaded arm and the other the loading a'r'mfalthough the spring arms arep'referably identical in construction; These arms may be of'various types customarily used in snap switches. For instance they may boot the kind illustrated inFig', 2 of the patent'to' Leupold 1,780,758, November (4. 1930. Considering such an arm, as theloading arm, it is fixed at one end and isjnormally bowed longitudinally, having its concave side toward the loaded arm,"its iree-jend-bearing with substantial resilient pressure against the free end of the loaded arm; The loading'a'nn is also normallyslightly curved transversely, at least near its fixed end, having a -"sensitive'spot at its convex side. Pressure exerted at the sensitive applies pressure to the arm 8, its first efiect isto decrease the section modulus ofthe a rm,8 at the.

region oi therseiisitive' spot" I9, atlthe same time" exertinga bending'stressjon the arm .8, tending to swing its free'end toward "the left. "I'hisjmowhich durihe thisactionis firstmoved slightly to the left untilit engages thestop,23, Except. for thestop 23, this 'moti onof the arm 9 would continue until the contact I engaged the fixed contact 5 which would thusfclosethe'wrong circuit for an instant: that the arm 9,

hhs b'een brought intoensa e e t with the stop 23,; the continued pressure of the inner endbi member 20 against the sensitivespot IQ of the arm l causes the latter-arm suddenly to try to reverse'its longitudinalfcurvatureg However,the

fixed contact 4 is so positionedthat thesprin armoannot reverse its curvature to a degreebe yond which it lo'ses'its tendency toreturn to its initial curvature-when the pressure is retarded, although its free end snaps suddenly'to'the right,

bringing movable contact l4 into engagement with fixed contact 4.; At this point it may be noted,

that-as described, the'spring arm has two 'different degrees of stillness, the first whenthe arm is of normal shape, before the actuating force has been applied, and the second, after reversal of curvature'has been initiated, the latterstifiness being much less than the first but still suiilcient to restore the arm to its original shape when the actuating force ceases. This movement of the arm 8 permits the arm ltomove further to the right (as it normally tries to do) so that its.

pressure is exerted on the actuating pin 20. As soon as the pressure exerted by the inner end oi the pin 201s released,the arm 8 automatically reassumes it original position. as shown in Fig. 1,

forcing the arm 9 bacl; until the'arnis again reach the neutral position. Obviously by actuating the pin 2|, the reverse action of the switch takes place, thereby closingthe circuit through-the fixed contacts. J

InFigs. 4 and 5 a: slight modification is illustrated wherein the base supports the't wo like ather of the arms may -'be caused to initiate a ha its ns tudin c tur The i s alts: action: isshowniinjfis here, the ova o ecflth r ilsht in o. 'e a m M lihih' -Pfifid bonn 6 L Fi 5, the actiiator 4.01 has, en aged the 'sexisltiv 'i no fv the g'a'rm l l. thus he} tt r i t straighten. i .In so doing it forces the I. 1 (bYJ means of thelinlg 3|!) into contact withthe fixed contact 36, the normal v tendency 6fjthearm Y I I to, d t the\ risht bein ac ntuated .b 'j the iorceg exerted by, the arm 32 in 'attempting'to move I ther to the right than is shown in l=lg.', 5.f. In Figs; 6 and7 a further modification is illuse trated wherein the, switch isdesigned to main tain one or the other of the circuits v closed until the circuit is properlyopened. In this arranger ment the base 7| has the'parallel arms 2' and 1'5] these arms carryin the spaced fixed contacts. 4 and 5 respectively. :The two likespring arms 8'! and 'Qamay be of the same general lgind as previ'ouslydescribed, but their lower ends are' bent to, U-sliape and"ar'e fixed at 8" and 8 respectively, to the switch base, these lowerends being con-1 nected to binding posts or other devices whereby they areconnected into the respective electrical circuits. In this instance, instead of the movable pins 20and 2| of Fig, 1 there are provided two fixed pressure-applying members 20" and, 2 l respectively carried by the arms 2* and 3* of the switch block and arranged with their inner ends opposed to the sensitive spots of the spring arms .40 closed through the fixedcontact ,4 so long as the longitudinallybowedspring arms 3| and 32" (like the arms 8 and!) which are secured at their lower ends to the base in any appropriate way, the lower ends of these arms being electrically connected to a binding post 33. in instance thelongitudi-v nal curvature of the arms is such that their free ends are widely separated, the convex faces of the arms being opposed to each-other. I'hetree ends of the-arms carry the v

movable contacts

34 and 35 which are designedj to'eng ge the fixed contacts 36 and31 respectivelyjfto close electrical circuits-.- The free ends of the arms are connected b3" a link 38- so thatwhen one" arm movesthe other must likewise move; Interposed between the'arms is'a motion-limiting element as, here shown of triangular shape, having opposite corners designed to limit movement of the respective 3i and 32 Between the arms there is arranged a single "actuator '40 mounted on a rotary shafts. I By swinging this actuator, whose lower comers, constituting the pressuregappiying ele-v ments, are arranged to engage thesensitive of the arms an respectly one or the raised to the remain indefinitely 8- and 9'. Motion-limiting elements22 and 23, like thoseshown in Fig. 1, are carried by thearms 2- and 3. interposed between the lower portions of the spring arms there is arranged a cam .24. mounted on avrockshaft 25. The cam 24 is of symmetrical shape, shown as segmental in contour, having the lower corners 21 and." ,which are normally disposedin a plane below the horizontal plane of the axis of the shaft 25. .A handle 26 is provided for swin ing the, actuating cam. Normallythe parts are as shown in Fig. 6 with the spring arms 8f and 9 longitudinally bowed anal with their free ends forcibly pressing, against each other with substantially equal pressure so that, the movable contacts l4 and ii are spaced from the

fixed contacts

4 and 5. when; for example. the cam 24 is rocked in a counterclockwise direction, as shown in Fig. 7, the comer 21 01 the cam engages the lower part of the spring 8 andiorces the latteroutwardly against the fixed pressure; applier 20?. Pressure exerted by the, spring against the @flxed pressure applier causes the spring suddenly to initiate reversal of its longitudinal curvature so that the movable contact I4 is forcibly; engaged with the fixed contact 4, the spring arm 9 following up the armll so as to increasethe contactpressure. If the cam 24b'e, turned fargenough, so that it' corner 2,], rises abovethe horizontal plane of theshaft'lithe parts will I inthis position with theHcir-Q, cuit'closed until the'camfis swung back tonormal] position. Obviously, the actuator cam need not be symmetrical, for example the.-jcorner ,28mayli be "so extended lat rally that it some never be horizontal plane of the cami axis and thuswou'ld'have no locking action. v In Figs. ,8, 9 and 1 0a furthermodification s illustrated wherein the switchfis ingeneral like.

a o "F g: bu i wh h a ld tr rn y e "or;

' springarm' is employedg 'lhus thefswitch com prises the base 4| with the'parallelarms Hand 43 carrying the fixed cohtac s 44 and, thearms 1 s i being spa d a a t mas ee w n able and available source. Merely by way of example it may come from the action of a bl-metalllc thermally responsive element. Such an element, for example a snap disk may take place of any of the above described actuating pins or parts, such as parts 20, or I20, or the part 40 of Fig. 4, so as to respond to ambient temperature changes, or it may be included in the circuit so as to respond to overload. Alternatively, the disk or other bi-metallic element may be incorporated in or form the switch arm itself, and in responding to temperature change will incline the arm in one or the other direction.

Furthermore, the opposed arms may be of different types, for example one may be like that of Fig. 3 and the other like that 01. Fig. 13. Again, for added contact pressure, each arm may consist of a plurality of individual members all of the snap acting type. and arranged so that all operate at the same time.

In order to provide for a wide gap between the terminals it may be desirable to hinge the spring arms at their lower ends so as to provide for a greater movement of the upper end of the arm.

While simple one-piece spring arms have here been illustrated as desirable, by reason of their simplicity and cheapness of construction, it is to be understood that spring arms of other types, for example arms comprising several parts and, in fact, arms in which the resilient element is a coil spring rather than than a leaf-spring, may be employed, providing the spring arms or elements be arranged so as to exert equal and opposite forces when in the mid-position. All such variations and modifications as fall with n the terms of the appended claims are thereby regarded as within the scope of the invention.

I claim:

1. A snap action switch comprising a pair ofspaced fixed contacts, a pair of elongate arms each fixed at one end, the fixed ends being spaced apart, an electric contact at the free end of each arm, said contacts being interposed between the fixed contacts and each being engageable at times with one of the respective fixed contacts, each arm comprising a thin longitudinally bowed spring, the material of each spring being internally strained and having a sensitive area at which a slight pressure will tend to cause a sudden reversal of the longitudinal curvature of the spring, the normal longitudinal curvatures of the arms being opposed to each other and the free ends of the arms normally pressing forcibly against each other, and actuators engageable with the sensitive areas Of the respective arms, and stop elements engageable by each arm respectively, at a point intermediate the free end of the arm and its sensitive area so as, when force is applied to one arm, motion of the other arm in response to the said force is limited.

2. A snap switch designed alternatively to close either of two independent electric circuits, said switch comprising an insulatin base which supports a pair of spaced, fixed contacts pertaining respectively to the two circuits, a pair of elongate arms having their lower ends rigidly fixed in spaced parallel relation in the base, means for electrically connecting the lower end signed that the metal is under a normal internal stress tending to how it longitudinally, but have ing a sensitive spot intermediate its ends at which pressure, applied perpendicular to the convex surface 01' the arm, causes a sudden reversal of curvature of the arm, the two arms being normally concave toward each other and I pressing against each other at their free ends with substantially equal pressure, the free ends of the arms being interposed between and normally spaced from the fixed contacts, motionlimiting stops designed to engage the outer surfaces of the respective arms at points intermediate the iree ends of the latter and their sensitive spots, and movable actuators independently operative to apply force to the sensitive spots of the respective arms with resultant sudden reversal of curvature of the arm to which such force is applied, whereby the free end of said arm is moved by the pressure of the other arm in a direction opposite to that of the applied force.

3. A snap switch comprising an insulating support, a pair of elongate, resilient current-conducting arms each fixed at one end to the support, the fixed end of each arm being electrically connected to a circuit terminal, each arm having an electrical contact element near its free end, a

erts stress tending to bow the other arm longi- I tudinally, the normal stiffness of the two arms and the normal bending stress exerted by each arm on the other being substantially equal whereby the free ends of the arms normally occupy a neutral position wherein each of the arm-supported contacts is spaced from the corresponding fixed contact, means selectively operative suddenly to reduce the effective stiffness of one or the other of said arms whereby the other 01' said arms becomes effective to swing the free ends of both arms from the normal position and thereby close one of the circuits, and normally-fixed, motion-limiting means engaging each arm at a point intermediate the free end of the arm and the support.

4. An actuating device for use in electrical snap switches or the like, said actuating device comprising a support, a pair of elongate, resilient, current-carrying arms each fixed at one end to the support, the fixed end of each arm being electrically connected to a circuit terminal, the arms being so constructed and arranged that each arm normally exerts stress tending to bow the other arm longitudinally, a pair of fixed, spaced stops arranged to be engaged at times by the free ends of the respective arms, said arms normally excrting substantially equal and opposite bending stress upon each other whereby their free ends are normally positioned substantially midway be tween the stops, a motion-limiting element operative by engagement with the convex side of each bowed arm, respectively, to prevent move= ment of the free end of said arm toward its proximate fixed contact, so long as said arm retains its normal direction of curvature, and independent means selectively operativ suddenly to decrease the bending stress which either arm exerts upon the other whereby the free ends of both arms selectively move toward one of the stops.

5. A snap switch comprising a support, a pair of like elongate, resilient current-conducting arms each. fixed at one end tothe support. the fixed end or each armsbeing electrically con- 13 arms consists of a length of thin, resilient sheet metal having one of the movable contacts secured to one of its ends, the other end portion of said length of material being longitudinally slitted to define three parallel legs, the middle leg being shorter than the other two, a support to which the ends of the longer legs are fixed, the free end of the shorter leg bein seated in a notch in the support, the position of the notch being such, relatively to the location of the ends of the longer legs that the length of resilient material is normally bowed longitudinally, the pressure applier contacting the longitudinally convex face of the shorter leg.

13. A snap switch as set forth in claim 8, further characterized in that the convex faces of the bowed arms are opposed. to each other with the free, contact-carrying ends of the arms normally spaced apart, and a link connecting the arms near their free ends so that when one arm moves the other must move likewise.

14. A snap switch as set forth in claim 8, further characterized in that the arms normally diverge toward their free ends and are united near their free ends by motion-transmitting means, the motion-limiting means being interposed between the arms, and the means for selectively reducing the effective stiffness of one or the other of the arms comprising a pivotally supported member which is interposed between the arms and which comprises parts engageable alternatively with the respective arms.

15. A snap action switch as set forth in claim 8, further characterized in that each pressure applier is a normally fixed part and that the means for causing relative movement of the pressure applier and the respective arm is a pivotally supported rocker interposed between the arms, and having parts which are alternatively engageable with the respective arms.

16. A snap action switch as set forth in claim 8, further characterized in that each pressure applier is a normally fixed part and that the means for causing relative movement of the pressure applier and the respective arm is a cam supported to rock about an axis midway between said arms. the cam having corners disposed in a plane below the pivotal axis of the cam and which are engageable alternatively with the respective arms at points between the fixed ends of the arms and the respective pressure appliers, and means for rocking the cam.

FREDERICK JOHN BROCH.

REFERENCES CITED The following references are of record in the