GB2131617A - Contact spring for snap switch - Google Patents

Abstract

A contact spring for a snap switch comprises a snap spring arm (1) and a setting spring arm (2) connected to one another at one end (3). A cut-out center tongue (9, 12) projects from each spring arm with the free ends of the two tongues bearing against one another so that in the final installed position, one tongue (12) is bent into an arched configuration (14) and is supported against a bent end (10) of the other tongue (9). The legs of snap spring arm (1), which flank the arched spring tongue (12) on both sides, are each provided with at least one reinforcement bead (20) extending in the longitudinal direction. A member (24) applies the actuating force to the contact spring and a member (32) adjusts the position of the tongue (9). <IMAGE>

Description

SPECIFICATION Contact spring for snap switch The present invention relates to a bistable contact spring fora snap switch. More particularly, the present invention relates two such a contact spring which comprises: a setting leaf spring whose free end forms the fastening end forthe contact spring and a snap leaf spring whose free end constitutes the moving contact of the snap switch, with both leaf springs being connected to one another attheiropposite stationary ends to form a vertex in the manner of the two sides of an angle; a cut-out centertongue projecting from the setting spring and from the snap spring, with each of the centertongues extending along the longitudinal axis ofthe respective setting and snap springs, and having its moving end facing the vertex; the center tongue which is connected with the setting spring serves as the adjustment tongue ofthecontactspring and is provided with a bent portion at its moving end, with the bent portion being oriented in the direction toward the other center tongue to provide a counterface; and the other, center tongue, which is connected with the snap spring, is bent in the form of an arch and has its moving end supported, againstthe counterface to form a tensioned arch spring.

The accuracy of operation of a snap switch equipped with such a contact spring depends essentially on the fact that the centertongue which, in the mounted position, is curved into an arched spring exhibits a constant spring behavior. This, however, is possible only if external influences on such spring behavior are avoided or substantially reduced so that the directional force exerted by the arched spring, i.e. the spring behavior ofthe arched spring, corresponds to the desired behavior within close tolerances.

It is the object of the present invention to provide a contact spring of the above-mentioned type which is constructed in such a mannerthat influences on the directional force of the arched spring, which influences may originate from the remaining parts ofthe contact spring, are avoided or limited.

This object is achieved according to the present invention by a contact spring for a snap switch which comprises: a setting leaf spring whose one end forms the fastening end forthe contact spring; a snap leaf spring whose one end constitutes the moving contact of the snap switch with the setting and snap springs being connected to one anotherattheir respective other ends to form a vertex in the manner ofthe two sides of an acute angle; first and second cut-out center tongues projecting from the setting leaf spring and from the snap leaf spring, respectively, with each of the first and second centertongues extending along the longitudinal axis of the respective setting and snap springs, and having its moving end facing the vertex; the first centertongue, which is connected with the setting spring, serves as the adjustmenttongue ofthe contactspringandisprovidedwitha bent portion at its moving end, with the bent portion being oriented in the direction toward the first center tongue to provide a counterface; the second centertongue, which is connected with the snap spring, is bent in the form of an arch and has its moving end supported against the counterface to form a tensioned arch spring; and, the legs ofthe snap spring which flank both sides of the arched second centertongue extend in the longitudinal direction ofthe snap spring and are each provided with at least one reinforcing bead.Preferably the contact spring is stamped from a single metal member and then bent to provide an acute angle with thetwo sidesthereof constituting the snap and setting springs.

With this solution,the bending line ofthe arched spring is substantially prevented from being able to continue along the snap spring in the region of the moving contact to there bend the snap spring, in addition to the normal spring curvature, over a small bending radius which curves with the peak region of the contact spring as the approximate center. Such additional curvature on a small bending radius, which results essentially from a continuation of the bending curvature ofthe arched spring, will produce an undesirably large angle between the surfaces ofthe moving contact and the oppositely disposed fixed contactwhen the contact switch is used in a snap switch. In the interest of the best possible contact, this angle should be as small as possible and, in the ideal case, approximate the parallel position of the contact surfaces.The present invention provides a resistance moment corresponding to the bending moment exerted by the arched spring on the moving end of the snap spring.The effect ofthe arched spring is thus concentrated entirely on its actual intended purpose, namely to initiate and perform the snapping and resetting ofthe moving contact into the contact position.

According to a preferred feature of the present invention, the effect intended by the present invention is enchanced by extending the reinforcing beads into the regions disposed to the side ofthe moving contact.

According to afurtherfeatureofthe invention, which feature relates to an alternative or cumulative solution of the above-mentioned problem, the central tongue which is curved into an arched spring is provided with a slight bent portion in the region thereofadjacentthe counterface on the other central tongue, and with the bent portion proceeding the direction of curvature of the bending line of the arched spring directed toward the counterface. This solution assuresthat, independently of manufacturing toler ances which are unavoidable when the contact spring is stamped,the edges of the moving end ofthe center tongue which is curved into the arched spring and of the counterface are in a uniform position which exists overthe entire operating range ofthe contact spring.

The centertongueforming the arched spring is stamped, in the conventional manner, out of one spring metal sheetjointlywith the snap spring and particularly also with the setting spring and with the adjustment tongue. The counterface ofthe moving end ofthe adjustment tongue is formed by a simple bend in the adjustment tongue against which, at least in theory, the arched spring rests conventionally underthe tension of its curvature not with the frontal face (end surface) of its moving end but with its delimiting edge-- hereinafter called the "cutting edg e" -- between the frontal face of the moving end and the convex side of the arched spring.Since, however, the bending radius ofthe arched spring, when in its position where it is inserted into the counterface, does not go below a certain dimension i.e., in any case, the arched spring is bent oniy slightly when in its operating position -this desired cutting edge contact cannot always be assured due to unavoidable manufacturing tolerances. If during operation this causes a surface contact between the moving end ofthe arched spring and the counterface formed bysimple bending oftheadjustmenttongue, this will result in just the annoying influences on the arched spring which are to be avoided by this feature of the invention.This feature intends to assure that the frontal face of the tongue forming the arched spring forms an average angle of 45" with the surface of the counterface.

According to a still further feature of the invention, the end surface ofthefree end of the central tongue which isformed into an arched spring is provided with a guide projection which extends through a guide opening provided in the bent member forming the counterface. This feature provides a secure position of the end of the tongue bent into an arched spring againstthe counterface even under strong vibratory stresses and the like, in the mannerofa hook-in support.

According to a still furtherfeature ofthe invention, the central tongue which is bent into an arched spring is penetrated by an elongated opening extending in the longitudinal direction of this tongue. This feature is a further alternative solution of the above-mentioned problem which can also be used cumulatively to the above-described solution features. This solution is based on the fact that to producetheone-piece contact springs according to the preferred embodi ment ofthe present invention, it is necessary to employ very complicated and thus expensive manufacturing and stamping molds. In practice, different contact spring materials are needed for different currents, for example steel for small currents and copper-nickel orcopper-berillium alloysforstrong currents.However, the spring behavior ofthe arched spring does not remain constant with these different materials. Also, depending on the intended purpose, different material thicknesses are required, which also influencethespring behavior of the arched spring.

Thisfeature ofthe invention now makes it possible to process different materials and different thicknesses of material in one and the same mold and nevertheless assure uniform mechanical spring behavior of the arched spring. Normally, this could be accomplished by varying the width ofthetongue forming the arched spring. However, making the stamping tool adjustable, possibly in very small steps, would be extremely expensive and would also result in susceptibility to breakage. By using this feature ofthe invention ali that is required in order to stamp tongues of different size is the replacement in the mold of a die having a different frontal shape but whose support region is of identical design.

The subject matter of the invention will now be explained in greater detail with the aid of an embodimentwhich is illustrated in the drawings.

Figure 1 is a longitudinal sectional view of the contact spring according to the present invention with the centertoungues in the initial installation position.

Figure 2 is a longitudinal sectional view correspond ing to Figure 1 with the center tongues in the final installation position.

Figure 3 is a top view ofthat portion of the snap spring according to arrow Ill in Figure 1 which surroundsthe centertongueforming the arched spring.

Figure 4 is an enlarged side view of the hook-in support between the arched spring and the adjustmenttongue.

Figure 5 is an enlarged basic illustration ofthe portion V of Figu re 4 used in the explanation of a specific feature of the invention.

Figure 6 is a side view of a snap switch equipped with the contact spring according to the present invention in the position where the contact is closed.

Figure 7 is a view corresponding to that of Figure 6 where the contacts are in the open position.

The contact spring shown in Figures 1 and 2 is essentially a leaf spring which is bent at an angle. The uppersideofthe angle hereforms the snap spring 1 and the lower side ofthe angle forms the setting spring 2, with both components being formed by stamping of a one-piece metal member. The vertex between snap spring 1 and setting spring 2 is marked 3. At its free end 4, the setting spring 2 is provided with a passage hole 5 which serves as a fastening opening for the passage of, for example, a fastening rivet four fastening the contactspring to a support. The free end of the snap spring 1 is provided, on its outer surface, with the moving contact 6 for the switch.

Projecting from the setting spring 2 isa cut-out center tongue 9 whose movable end 8 essentially faces vertex3 and forms the adjustable tongue of the contact spring. As shown, the tongue 12 extends in the longitudinal direction 7 ofthe contact spring, along the longitudinal axis of the setting spring 2 (see Figure 3). In the region of its moving end 8, the adjustable tongue 9 is provided with a bent portion 10which is oriented in the direction toward the snap spring 1 and whose planarsurfacefacing the free end 4 of the setting spring 2 forms a counterface 11 for a center tongue 12 projecting from snap spring 1.The center tongue 12 likewise extends in the longitudinal direction 7 ofthe spring and has its moving end 13 likewise facing vertex 3. lnthe installed position, asshown in Figure 2, the moving end 13 ofthe centertongue 12 is supported on counterface 11 and forms a tensioned arch 14. The bent portion 10 forming counterface 11 is provided with a guide opening 15through which extends a guide projection 16 which projects from the end surface of the.moving end 13 ofthe arched spring centertongue 12 and which is substantially narrower than the remainder ofthe centertongue 12 as shown in Figure3.

Asfurthershown in Figure 3, the legs 17,18 of snap spring 'which flank the arched spring center tongue 12 on both sides, likewise extend in the longitudinal direction 7. The surfaces of legs 17 and 18 are each provided with a respective reinforcement bead 20 and 19 with the beads 19 and 20 likewise being oriented in the longitudinal direction 7 ofthe spring. As shown, the beads 19 and 20 extend approximately over at leastthe contact-end one half ofthe length ofthe snap spring 1. In particular, the reinforcing beads 19,20 extend into the region of the snap spring disposed along the sides of the moving contact 6.Between the cut-outrecess21 and vertex3, snap spring 1 is provided with a passage hole 22so as to fix the position of conical end 23 (see Figures 6 and 7) of an insulating body 24, with this body 24 establishing the pressure connection with the bimetal actuator (not shown).

As shown in Figures4and 5, before reaching the counterface 11, the center tongue 12, which is curved into the spring arch 14, is provided with a portion 26 which is slightly bent so that it proceeds or is in advance ofthe theoretical bending direction 25 ofthe arch 14. The bending angle or angle of advance ofthe portion 26 is indicated in Figure 5 by the reference numeral 27 and the bend is indicated in Figures 4 and 5 bythe reference numeral 28.The provision of this slightly bent portion 26 causes the moving end 13 of the arched spring tongue 12 to rest againstcounter- face 11 of adjustment tongue 9, not with its frontal face or end surface 29 but always only with its cut edge 30, i.e., the edgeformed bythe end surface 29 and the outer (upper as shown) surface of the tongue 12. The angle 27 is selected so That the' angle between the frontal face 29 and the surface of counterface 11 is on the average about45", large enough so that, in every theoretical operational position of arched spring tongue 12, it is assured that the moving end 13 of the tongue 12 rests against counterface 11 exclusively via its cut edge 30.

Additionally, the centertongue 12 which is curved to form the spring arch 14 is penetrated by an elongated hole or opening 31 which extends in the longitudinal direction 7.

As shown in the figures, the moving end 13 of center tongue 12 projects farther in the direction toward vertex 3 than the bent portion 10 of adjustment tongue 9. This permits hanging the center tongue 12 with its guide projection 16 into the guide opening 15 ofthe bent portion 10, and thus producing the desired contact of the cutting edge 30 againstthe counterface 11 ofthe adjustment tongue 9 onlywith the center tongue 12 curved, undertension, to form a spring arch 14.

As shown in Figures 6 and 7, when the contact spring is in the installed position,the adjustment end of an adjustmentspindle32,which isstationarily mounted with respecttothefastened end 4 of the setting oradjustmentspring 2, rests againstthe exterior or outer surface of adjustment tongue 9. By rotating the adjustment spindle 32, the adjustment end 33 of the latter can be moved in the axial direction 34. This adjusts the snap spring 1 in that adjustment spindle 32 fixes the size of the angle between the setting spring 2 and the adjustment tongue 9.

Inthecontact-closed position shown in Figure 6, the snap spring 1 is disposed above the hook-in support between the arched spring tongue 12 and the adjust menttongue 9. The snap opening ofthe switch is produced in that the body 24 of insulating material is pressed downwardly in the direction of arrow 36, for example by means of a bimetal, while carrying along vertex 3. This causes snap spring 1 to pass the level of the hook-in support between the moving end 13 of the arched spring tongue 12 and the bent portion 10 of the adjustment tongue 9. As soon as snap spring 1 passes the height level ofthe contact of cut edge 30 with counterface 11, the switch snaps into its open position shown in Figure 7. The position of cut edge 30 with respect to counterface 11 to us constitutes the dead center position forthe switch, the passage of which snaps the switch either into its open or into its closed position.

It will be understood that the above description of the present invention is susceptible to various mod ifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

Claims (9)

1. A contact spring for a snap switch, comprising: a setting leaf spring whose one end forms the fastening end forth contact spring; a snap leaf spring whose one end constitutes the moving contact ofthe snap switch, said setting and snap springs being connected to one another at their respective other ends to form a vertex in the manner of the two sides of an angle; first and second cut-out'centertongues projecting from said setting leaf spring and from said snap leaf spring, respectively, with each of said first and second center tongues extending along the longitudinal axis ofthe respective said setting and snap springs and having its moving end facing said vertex;; said first center tongue, which is connected with said setting spring, serves asthe adjustment tongue of said contact spring and is provided with a bent portion at its said moving end, with said bent portion being oriented in the direction toward said first center tongue to provide a counterface; said second centertongue,which isconnectedwith said snap spring, is bent in the form of an arch and has its said moving end supported against said counter- face to form a tensioned arch spring; and, the legs of said snap spring which flank both sides of said arched second centre tongue extend in the longitudinal direction of said snap spring and are each provided with at least one reinforcing bead.

2. Acontact spring as defined in Claim 1 ,wherein said beads extend in the longitudinal direction along said legs ofsaid snap spring.

3. A contact spring as defined in Claim 1 or2, wherein said contact spring is stamped from a single piece of metal which is then bent to form said vertex.

4. A contact spring as defined in Claim 3, wherein said reinforcing beads extend approximately over at least the contact-end one-half ofthe length of said snap spring.

5. Acontactspring as defined in Claim 3 or4, wherein said reinforcing beads extend into the region of said snap spring disposed to the sides of the moving contact.

6. A contact spring as defined in any prececing claim, wherein said moving end of said second centre tongue is provided with a slightly bent portion, which, in the arched position of said tongue, extends toward said counterface at an angle to the arc of curvature of said arch.

7. A contact spring as defined in Claim 6, wherein, said bent portion of said first centre tongue forming said counterface is provided with a guide opening; and wherein said moving end of said second centre tongue is provided with a guide projection which extends through said guide opening.

8. A contact spring as defined in any preceding claim, wherein said second centre tongue is penetrated by an elongated opening which extends in the longitudinal direction of saidfirsttongue.

9. Acontact spring for a snap switch, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.