US3525833A - Snap action switch having low actuation force - Google Patents

Description

Aug.'25, 1970 P. w. SCHAFF ET AL 3,525,833

SNAP ACTION SWITCH HAVING LOW ACTUATION FORCE Filed Sept. 19, 1966 4 num y 1 NVENTOR. C5 C4 Pau/ W Saba/f law/"67766 4 Ka/ze BY w %w WTTORNEYS United States Patent 3,525,833 SNAP ACTION SWITCH HAVING LOW ACTUATION FORCE Paul W. Schatf, Arlington Heights, and Lawrence A. Kolze, Bensenville, lll., assignors to The Dole Valve Company, Morton Grove, 11]., a corporation of Illinois Filed Sept. 19, 1966, Ser. No. 580,369 Int. Cl. H01h 13/36 US. Cl. 200-67 3 Claims ABSTRACT OF THE DISCLOSURE A snap action switch having a snap lever fixedly mounted to a pivot and having a free outer end. A snap blade extends from the free outer end inwardly toward the mounting point of the snap lever and the free end of the snap blade is interconnected to the mounting point by means of an overcenter spring. An actuating member is located at the outer end of the snap lever and the contacts are mounted at the inner end of the snap blade between the mounting point of the snap lever and the actuation point thereof. In this way, low. actuating force is achieved and a correspondingly high contact force is attained. Also, a shearing action is generated at the surface of the contacts to break in a welds which may have occurred during the contacting action.

This invention relates to a snapaction switch and in particular relates to a snap-action switch having a novel structure which increases the ratio of contact force to actuating force, which develops a high shear force component at the switch contacts to break possible contact welds, and to control the arcing between contacts so as to increase the longevity of the switch.

Snap-action switches are not new in the art. However, snap-action switches heretofore used have not been entirely satisfactory. For instance, it is often desirable to actuate a snap-action switch with a small actuation force in comparison to the contact force needed to maintain proper electrical engagement of the switch contacts. However, reduction of the actuation force in comparison to contact force has not been possible prior to this invention due to the nature of the motion required to actuate the switch.

In particular, snap-action switches heretofore used have consisted of a snap lever and a snap blade, both extending in a common direction. The snap blade was actuated by moving an actuation member into contact with the snap lever. When the snap lever and snap blade were geometrically centered, an overcenter spring would snap the blade into electrical engagement with the required contact. In such a mechanism, the snap lever was usually mounted at a first end, and the overcenter spring was interconnected between the lever and the blade at the opposite end. The result was that a high degree of actuation force was required to initially move the snap lever into alignment with the snap blade.

In addition to the problem of acquiring a high ratio of contact force to actuation force, snap-action switches eretofore used have had the problem of overcoming the binding force of welds created by the arcing of the electrical contacts. When a snap blade snaps into position against an electrical contact, arcing tends to bind the contacts together and prevent the actuation of the snap blade. Since both the snap lever and the snap blade of earlier switches were generally mounted at a common point, the actuation of the snap blade was in a direction normal to the welds formed during engagement of the switch. This meant that the welds had to be broken by a tensile force, which required a high spring tension, which in turn required a higher actuation force.

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The arcing or welding of the contacts of a snap-action switch has been found to present the additional problem of excessively heating and eventually destroying the blade material and associated overcenter spring. Accordingly, it would be highly desirable to provide a means for controlling the arcing of the contacts of a snap-action switch and in particular to control the path of the arcing or to direct the arcing into a non-destructive area.

Accordingly it is a principal object of this invention to provide an improved snap-action switch.

It is also an object of this invention to provide a snapaction switch having a high ratio of contact to actuation force.

It is another object of this invention to provide a snap action switch which creates a high shear force on the contact members prior to snap actuation of the snap blade.

It is a further object of this invention to provide a snap-action switch having means for controlling the path of arcing of the contacts at the time of snap engagement thereof.

It is also an object of this invention to provide a snap-action switch wherein the snap lever is pivotally fixed to a switch housing and has its free end extended outwardly therefrom and wherein the associated snap blade is secured to the free end of the snap lever and extended in a reverse direction toward the rigidly mounted end of the snap lever and wherein the overcenter spring is connected between the free end of the snap blade and the fixed end of the snap lever.

It is a further object of this invention to provide a snapaction switch having a snap lever and a snap blade wherein the snap lever is rigidly mounted to a switch housing and wherein the snap blade is fixed to the snap lever in such a manner as to cause the entire snap blade to move through an arcuate path prior to snap disengagement of the snap blade thereby creating a rolling or high shearing force at the engaged contact.

It is another object of this invention to provide a snap-action switch having a large air gap formed adjacent to the contact surfaces of the snap blade such that the arcing of the contact members during snap-action of the snap blade through the snap lever is caused to follow a path away from the snap blade and away from the associated overcenter spring into the larger air gap.

These and other objects, features and advantages of the present invention will be understood in greater detail from the following description and the associated draw in gs wherein reference numerals are utilized in designating an illustrative embodiment and wherein:

FIG. 1 is a partially sectioned view of a snap-action switch according to this invention;

FIG. 2 is a view similar to FIG. 1 showing an alternate position of the snap blade of the snap-action switch;

FIG. 3 is a top view of the snap-action switch showing the orientation of the snap blade and the snap lever and showing the configuration of the large air gap formed adjacent to the contact member of the snap blade; and

FIG. 4 is a diagrammatic illustration of the functioning of the snap-action switch in accordance with this invention and in particular illustrating the manner in which a high shearing force is created between the snap blade contact and a contact of the switch housing.

This invention generally concerns a snap-action switch having a snap lever and a snap blade wherein the snap lever is rigidly mounted to a switch housing at one end and wherein the snap lever extends outwardly from the housing generally as a cantilever structure and wherein the snap blade is pivotally actuable from the free end of the snap lever.

A snap-action switch in accordance 'with the above specification is shown in FIG. 1 as comprising a snap lever and a snap blade 11. The snap lever 10 is fixedly mounted to a switch housing 12 only a portion of which is shown in these figures for illustrative purposes.

The snap lever 10 has a first end 13 which is fixedly secured to the housing 12 by means of a rivet 14 or other suitable connector. The rivet 14 may comprise a first lead of an external electrical circuit which is being controlled by the snap-action switch.

The switch housing 12 may have posts, studs or other members 15 and 16 which are rigidly secured thereto and which extend outwardly from a housing wall to the vicinity of the snap blade 11. The members 15 and 16 are provided with electrical contacts 17 and 18 which may comprise leads of second and third electrical circuits or may comprise further leads of the first electrical circuit associated with the electrical contact member 14.

The snap lever 10" extends outwardly from the electrical contact or rivet 14 as a cantilever structure and has a free end 19 extended a substantial distance from the point of support at 14. The snap blade 11 in this embodiment is formed integrally with the snap lever 10 and extends from the free end 19 thereof as at the point 20* in a reverse direction toward the point of mounting of the snap lever at the rivet 14. The snap blade 11 also has a free end 21 which is disposed adjacent the fixed end 13 of the snap lever 10.

Both the snap lever 10 and the snap blade 11 are provided with slots 22 and 23 for receiving an overcenter spring 24. The overcenter spring 24 has crimped ends 25 and 26 for engaging the slots 22 and 23 in a well understood manner.

The snap lever 10 and the snap blade 11 together act as an electrical conductor for making an electrical connection between the first lead 14 and one of the other switch contact leads 17 and 18. For this purpose a contact member 26 is fixedly secured to the free end 21 of the snap blade 11 and has arcuate faces 27 and 28 for contacting the faces 29 and 30 respectively of the contact members 17 and 18.

As is well understood, when the snap lever 10 is moved into substantial profile alignment with the snap blade 11, the overcenter spring 24 will cause the blade to snap from its given contact position to a contact position with the opposing contact member. For instance, if the snap lever 10 is moved from the position shown in FIG. 1 to a position into substantial alignment with the profile of the snap blade 11, the overcenter spring 24 will cause the snap blade 11 to move downwardly to a position shown in FIG. 2 thereby unseating the surface 28 from the surface 29 and seating the surface 27 at the surface 30. It is apparent therefore that snap-action switches of this type can be used to readily break and make contacts in an electrical circuit.

The means for actuating the snap-action switch of this invention comprises an actuation member 31 having an actuation slit 32 formed longitudinally therein. The actuation member 31 is mounted to be moved within the switch housing a plane substantially perpendicular to the normal position of the snap lever 10. In this way, movement of the actuation member 31 in a vertical upward direction in FIG. 1 will cause the surface 33 of the actuation slit 32 to contact the lower surface of the snap lever 10 and to carry that surface upward into substantial alignment with the snap blade 11. When this occurs, the overcenter spring 24 will carry the snap blade 11 from the position shown in FIG. 1 to the position shown in FIG. 2. Similarly, a vertical downward movement of the actuation member 31 as shown in FIG. 2 will cause the surface 34 of the actuation slit 32 to contact the upper surface of the snap lever 10 and to move that lever into substantial alignment with the plane of the snap blade 11. At that time, the overcenter spring 24 will snap the blade 11 into the position shown in FIG. 1.

Several aspects of the snap-action switch as described are to be noted. First, since the snap lever 10 is fixedly mounted at the point 14, and since the overcenter spring is also mounted at the point 14 and is connected to the snap blade 11 immediately adjacent the point of support 14, the actuation force required to move the actuation member 31 can be considerably reduced. This is because when mounted as described, the entire switch becomes a cantilever which may be pivoted about a point 35 to actuate the switch. The described orientation of the lever, blade, overcenter spring and contacts allows the actuation member 31 to be spaced outwardly from the point of support and point of resistance of movement of the switch. This allows the entire switch to act as a lever, and accordingly the spring 24 can have a high spring force, whille the contact member 31 can be moved comparatively eas1 y.

In addition to the ease of operation of the actuation member 31 due to the orientation of the spring 24 and the point of support 14 relative to the cantilever end 19 of the switch member, it can be seen from FIG. 4 that actuation of the contact switch causes a rolling or a high shear force between the engaged contacts to break contact welds. For instance, as the snap-action switch swings from the position A to the position B in FIG. 4, the contact member 26 rolls from C to C at the surface 27 against the surface 30 of the contact member 18 to break contact welds. This shearing action occurs prior to snapaction of the snap blade 11. This highly desirable rolling or shearing action is made possible due to the fact that the end 19 of the contact switch is caused to move through an arcuate path as indicated by reference numeral 36. This arcuate movement of the snap blade 11 is in turn made possible by the particular mounting of the snap lever and snap blade as described above.

FIG. 3 illustrates the technique employed in this invention to control the path of arcing of the electrical contacts whensnap-action of the snap blade 11 occurs. The snap lever 10 has first and second lever arms 37 and 38 and hasv a cross member 39 interconnecting the arms 37 and 38 and providing a means for supporting the snap blade 11. The snap blade 11 extends centrally of the arms 37 and 38 and connects to the overcenter spring 24 at the slots 22 and 23 as illustrated in FIGS. 1 and 3.

It is well known that arcing of the contact members such as the members 26 and 18 can cause excessive heating and destruction of the blade material and overcenter spring. Accordingly, it is highly desirable to keep the overcenter spring physically away from the path of the arc of the contact members. It has been found by empirical testing that the path can be controlled by having a large air gap, such as the gap 40 formed in the switch blade on one side of the contact 26. In this way it was discovered that the arc from the contact 26 is directed toward the air gap and away from the overcenter spring 24. Accordingly the snap-action switch of this invention has increased longevity.

Throughout the course of this specification and in the claims attached hereto, the designation snap lever and snap blade have been used. These terms are used widely in the art and are well understood by persons skilled in the art. However, for purposes of description, the following definition is intended to apply to the designation snap lever and snap blade as used in the claims:

A snap lever is the member of a snap action switch which is moved relatively slowly by an actuator prior to and for the purpose of aligning the snap lever with the snap blade. A snap blade is the other member of a snap action switch which after the snap lever has been moved into alignment therewith is caused to snap from one preset condition to an opposing predetermined position by virtue of the action of an overcenter spring.

It will be understood that various modifications and combinations of the features of this invention can be accomplished by those skilled in the art, but I desire to claim all such modifications and combinations as properly come within the scope and spirit of my invention.

What we claim is:

l. A snap-acting switch comprising:

a switch housing,

a snap lever rigidly mounted at a first end thereof to the switch housing,

said snap lever having first and second lever arms and a cross member connecting the two arms at said other end of the snap lever,

a snap blade pivotally secured to said cross member,

said snap blade extending from said cross member in a direction generally toward said first end and termimating in a free end,

said free end having a contact surface,

said housing having a contact member affixed thereto and extending to a point immediately adjacent said contact surface,

an overcenter spring interconnecting the free end of said snap blade and said snap lever,

actuator means engaging the same in an arcuate path, and said contact surface being located on said snap blade at a point intermediate said first end of the snap lever and the point of engagement of said actuator means therewith,

a large air gap formed in the snap blade immediately adjacent one side of the contact surfaces,

said air gap orientated on a side of said snap blade away from said overcenter spring.

.2. A snap-acting switch in accordance with claim 1 wherein said contact member has a contact face disposed substantially parallel to the normal position of the snap lever and wherein said contact surface of the snap blade has an arcuate profile for engaging the contact member and wherein the second end of the snap lever is pivotally movable about the first end thereof and wherein pivotal movement of said snap lever causes said contact surface to roll against the associated contact face of said contact member.

3. A snap-acting switch in accordance with claim 1 wherein said means for actuating the snap blade comprises an actuation member disposed for reciprocal movement in a path substantially perpendicular to the normal plane of the snap lever and having an actuation slit formed therein substantially parallel to the snap lever, and said snap lever and snap blade being received through said actuation slit adjacent said second end thereof wherein said snap blade is actuated by movement of said actuation member at said slit against said first and second lever arms.

References Cited UNITED STATES PATENTS 2,558,258 6/1951 Kohl. 2,788,409 4/ 1957 Grover. 2,892,050 6/ 1959 Fisher. 2,896,041 7/1959 Schwaneke. 2,977,436 3/1961 Haydon.

ROBERT K. SCHAEFER, Primary Examiner D. SMITH, 1a., Assistant Examiner

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