US3548132A - Miniature precision snap action switch with wiping contact action - Google Patents

Description

United States Patent [72] Inventor Alvin W. Krieger West Bend, Wis. [21] Appl. No. 811,314 [22] Filed March 28, 1969 [45] Patented Dec. 15. 1970 [73] Assignee Cutler-Hammer, Inc.

Milwaukee, Wis. a corporation of Delaware [54] MINIATURE PRECISION SNAP ACTION SWITCH WITH WIPING CONTACT. ACTION 7 Claims, 5 Drawing Figs.

[52] 11.8. CI 200/67 [SI] Int. Cl ..1I01h 13/36 [50] Field of Search 200/67, 67(D); 74/100(P) [56] References Cited UNITED STATES PATENTS 3,415,962 12/1968 Krieger 200/67D(UX) OTHER REFERENCES Lorsbach, GER. Appl. No. 1,226,387, pulb. 4-68, 2ppspec-1 sht dwg. (Copy ZOO-67D) Primary ExaminerRobert S. Macon Assistant Examiner-D. Smith, Jr. Att0rneyHugh R. Rather downward bow to another pivot point on the support for free a pivoting thereon, the bent end being movable by aplunger to cause switching action, and a shelf below the other compression strip causing the downward bow therein to flatten out when the bent end thereof is depressed by the plunger thereby to cause wiping contact action.

PATENTEU man 5 mm 33548132 SHEET 1 BF 2 PATENTED DEC] 51970 SHEET 2 BF 2 Inventor fl Wifl W Krieger By Attorney 1 MINIATURE PRECISION SNAI ACTION SWITCH WITH WLPING CONTACT ACTION BACKGROUND OF THEINVENTION This invention relates to improved miniature precision snap action switches havinga small size and'being capable of detecting a small amount of motion and responding thereto with a snap action. i

A. W. Krieger U.S. Pat. No. 3,4l5,962, dated Dec. 10, I968, discloses a miniature precision snap action switch of this type having a one-piece stressed blade construction including an upwardly bowed first pair of compression force spring strips and downwardly bowed second compression force spring strip. The present invention is an improvement thereon.

SUMMARY OF THIS INVENTION This invention relates to miniature precision snap action switches and more particularly to means providing improved wiping contact action therefor.

An object of the invention is to provide means affording wiping contact action in a switch having a bowed compression member as a part of its-movable contactblade.

A more specificobject of the invention is to provide a miniature precision ,snap action switch of the one-piece stressed blade construction type with means providing wiping BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of 'a miniature precision snap action switch constructed in accordance with the invention; FIG. 2 is an enlarged front elevationalviewof the switch of FIG. 1 with the cover removed'to show the switch mechanism within the base, this switch mechanism being shown in its normal off position;

- FIG. 3 is a front elevational view like plunger being shown depressed sufficiently to having actuated the switch to its operated or on position; f

FIG. 4 is a front elevational view like FIG. 3 with the plunger being shown depressed further to show the wiping action that is possible during the overtrav'el; and

and the base forms the other walls of this aperture whereby the plunger is slidably guided for longitudinal movement.

The base is provided with means forpivotaIly-supporting a so-called integral actuator for operating the plunger. This means comprises an external recess'2b in the upper wall of the base located slightly to the right of the midportion of the base and near rivet 8. The rear wall of thisrecess is provided with a depression 2c and the cover is provided with a similar depression 40 asshown in FIGS. 2 and 5 in alignment therewith for pivotally supporting a generally L-shaped actuator overlying the plunger. For this purpose, the toe of the actuator is provided with laterally oppositely'extending projections that are pivoted in these depressions while the horizontal width of the upper portion of the recess allows a limited amount of pivotal movement to depress the plunger. As will be apparent, such actuator extends up through recess 2b and then to the left to overlieplunger 6. Another similar recess may be provided to the left of rivet 8 as shown in the drawings alternatively. to receive a shorter actuator of similar type. As'actuators of this type have been known heretofore, it'has' not been illustrated herein but has been described briefly to show the purpose of the recesses in the base. As shown in FIG. 1, recess 2b extends from the forward edge of the upper wallof the base toward the rear a sufficient distance to center it on: the housing when the cover is riveted in place. A second rivet 10 extends through the cover and the right portion of the lower wall of the base to rigidly secure the cover.

FIG. 2 with the I FIG. 5 is an enlarged isometric view of the switch housing of FIG. I with the cover open to show the interior of the base and the inner surface ofthe cover.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I, there is shown the external appearance of a miniature precision snap action switch'constructed in ac cordance with the invention. As shown. therein, the switch is provided with an electrically insulating housing comprising a I base 2 and a cover 4. The base provides the rear wall and integrally molded therewith most of the upper and lower and left and right walls of the housing. The cover provides the front wall and a small part of the upper, lower, left and right walls of the housing.

The base is provided with means forsupporting a switch operating plunger 6. This means comprises'a rectangular aperture 2a shown in FIG. 2 extending down through the left-hand portion of the upper wall of the base. This aperture is in the form of a notch in that it communicates with the forward edge of such upper wall to enable the plunger to be dropped thereinto before the cover is riveted onto the base.'ln this manner, the cover is arranged'to form one wall of the aperture The base and cover are provided with complementary interfitting portions to register the cover to the base. For this purpose, the lower left and upper right corners of the cover are notched'away and the corresponding corners of the base have forward projections 2d and 2e, respectively, as shown in FIG.

1 and 5, fitting into the notches in the cover. These projections have horizontal mounting holes 2f and 2g 'therethrough with one of these holes such 2f being oblong to avoid close tolerance requirements in the location of the bolts or rivets that are used to secure the switch in place.

As shown in FIG. 2, theswitch is of the single pole double throw-type whereby a common external terminal may be connected to either one of two selected external terminals. For

- this purpose, the base is provided with a pair of spacedslots 2h in the right wall communicating with the forward edge thereof 4 for receiving a pair of flat terminals 12- and 14.- -These terminals are provided at their internal ends with'lateral ears 12a and 140 that fit into complementary recesses in the rear wall of the base and in the cover and a groove, 12b and 14b, that fit on complementary ribs in slots 2h rigidly to secure the terminals in place when the cover is assembled. Suitable contact elements 126 and Me of low electrical resistance metal are securely attached by riveting or other suitable means on the internal ends of the terminals on the surfaces facing one another. The external ends of these two terminals are provided with suitable terminal connectors such as screws 12d and 14d 'for connecting the switch to an external circuit.

A common terminal 16 is arranged to receive an improved snap action contactor 18. This common terminal is bent at a ing a suitable connectorthereon such as a screw 16b. The adjacent portion extends vertically through a slot2i in the lower wall of the base. Thenext portion 16d extends in the left direction within the base and the final portion 16e extends vertically from portion 16d. As shown in FIGS. 2-4, common terminal 16 is divided or has its center removed throughout portions 16c and 16d and into the upper partof portion 160 to provide space for contactor 18. Also, upper divided portion l6e has lateral extensions that continue into the left part of divided portion 16d, and vertical portion 16c has lateral extensions. These lateral extensions fit into complementary recesses in the walls of the base and cover rigidly to secure the common terminal in the housing.

I The switch is provided with a one-piece snap action contactor 18 for electrically connecting the common terminal to either one of the selected terminals 12 and 14. This contactor comprises a leaf spring having contact elements l8a'and 18b of low electrical resistance metal secured to the respective upper and lower surfaces at its relatively wide right end portion for engaging the contact elements of the selected terminals. For this purpose, this right end of the contactor extends between the internal ends of selected terminals 12 and 14. A pair of leaf spring compression elements 180 extend in the left direction at a small upward angle from the right end of the contactor and are separated by a center strip 18d. These compression elements and center strip are of substantially equal width and are spaced from one another by a pair of narrow gaps to allow freedom of relative movement. This center strip is longer than the compression elements and its left end portion is bent back parallel underneath to underlap the compression elements through a substantial portion of their length and to form a bent back or reentrant compression portion l8e and is otherwise shaped like that in the aforementioned patent. The extreme end of the reentrant portion is provided with a short central tongue 18f for retaining this end freely pivoted in the bottom of the U-shaped slot that divides the upper end of the common terminal andfor preventing side movement of the contactor blade, there being a downward angle in the bottom of this slot from the left to the right to provide a sharp pivot for the tongue. The operating force required to, actuate the contactor may be selected by'making this U- shaped slot the desired depth down into portion 160.

The switch is provided with simple and effective means for causing wiping action between contact elements 18b and 14c. This means comprises a shelf 2k integrally molded within the base so that it extends below downwardly bowed compression force portion l8e.

When the snap action contactor is assembled on the common terminal, elements 18c and bent back portion l8e become compression elements. The left ends of compression elements 18c are pivotally supported in the smaller than right angle corner pivot formed between portions 16d and 16s of the common terminal and are bowed upwardly. Also, the right end of bent back portion l8e is pivotally supported near the upper end of portion 160 with its tongue confined in the bottom of the U-shaped cutout in such upper end. This causes bent back portion l8e to be bowed downwardly whereby the bent end of center strip 18d is biased upwardly against the enlarged lower end 6a of the plunger. Center strip 18d of the contactor is in tension.

In its normal position as shown in FIG. 2, the compression elements bias the bent left end of the contactor upwardly against the plunger. With the plunger in its upper position, the line of action of the one one-piece contactor blade 18 from the point engaging the plunger to the point of connection of compression elements 180 thereto is above the pivot point P. Consequently, contact element 18a is biased against contact element 120 of the upper stationary contact with sufficient contact pressure to make a good electrical connection.

Now when the plunger is depressed to-move the bent left end of the contactor blade downward, the contactor will snap from the upper stationary contact element to the lower stationary contact element. To this end, a point will be read reached in the downward movement of the plunger wherein the line of action of the movable contactor passes from above pivot point P below such pivot. The line ofaction of the movable contactor may be defined as a straight line from the point where the left end thereof engages the plunder to the point where both of the compression elements 180 connect to the contactor blade near contact elements 180 and 18b. As this line of action passes just below pivot point P, the right end of the contactor will move with a snap action from the upper to the lower stationary contact as shown in FIG. 3.

A characteristic feature of the invention is that the im proved structure provides wiping contact action during the overtravel to keep the contacting surfaces clean and to insure good electrical connection. As will be apparent, after the switch has been operated as shown in FIG. 3', the plunger can be depressed farther all the way in to the position shown in' FIG. 4. This is overtravel. When the plunger is pressed all the way in, the enlarged lower end thereof stops against leg ledge 21. During this movement of the plunger, the downwardly bowed portion l8e flattens out against the upper surface of shelf 2k. This causes the contactor blade to move toward the left as shown in FIG. 4 to slide contact element- 18b on contact element 14cand increasing the bow on compression elements 180.

The large amount of overtravel avoids the necessity of close manufacturing or operating tolerancesin the operators that depress the plunger. This large overtravel is obtained by the one-piece construction of contactor blade wherein bent back portion l8e is also made as a compression element in addition to compression elements 180. When made as a compression element integral with and as a bent back continuation of the flat leaf spring, portion l8e will bow the proper amount when the plunger is depressed. Then by providing the shelf below this downwardly bowed portion at the proper height to cause it to flatten out the proper amount, suitable contact wiping action is economically and effectively obtained.

When the plunger is released, the switch will automatically return to its normal position. Referring to FIG. 4, it will be seen that the left end of the contactor blade applies an upward force on the plunger. Therefore, when the plunger is released, the contactor blade will push it upwardly. At the same time, the compression force on elements will cause contact element 18b to slide back toward the right as portion l8e rises from the shelf. This causes the line of action of the contactor blade to pass from below pivot P above this pivot, causing compression elements 18c to snap contact element 18b away from contact element 14c and to snap contact element 18a into engagement with contact element 120.

While the apparatus hereinbefore described is effectively adapted to fulfill the objects stated, his to be understood that the invention is not intended to be confined to the particular. preferred embodiment of miniature precision snap action switch with wiping contact action disclosed, inasmuch as it is susceptible of various modifications without departing from the scope of the appended claims.

lclaim: 1. In a miniature precision snap-action switch having: an insulating housing including an insulating actuatorplunger extending outof the housing and at least two conductive members within the housing and extending to the exterior thereof, one of said members including a stationary contact and the other of said members including supporting means for a movable contactor; a movable contactor mounted on said supporting means and including a contact element in overlying relation to but separated a short distance from the stationary contact comprising: an elongated member extending past said supporting means and having said contact element secured thereto at one end;

first compression force means extending from a point near said contact element to a pivot point on said supporting means for applying a force in one direction;

second compression force means extending with a downward bow from the other end of said elongated member to another pivot point on said supporting means for applying a force in the opposite direction and also upwardly against the actuator-plunger;

the other end portion of said elongated member being movable by the actuator-plunger to cause snap-action movement of said contact element into engagement with said stationary contact when said elongated member is moved past its dead center position at said first pivot point;

and the other end portion of said elongated member having substantial overtravel allowance following closure of the contacts;

the improvement comprising an abutment member below said second compression force means against which it bears during overtravel movement to straighten out said downward bow and thereby cause movement of said elongated member in the direction of its other end and wiping action of the contacts. 2. The invention defined in claim 1 wherein said abutment member comprises:

a shelf integrally molded within the housing below the downward bow of said second compression force means. 3. The invention defined in claim 2, wherein said shelf is horizontal.

4. In a miniature precision snap action'fswitch having: an insulating housing including an insulating actuatorplunger extending out of the housing and at least two conductive members within the housing and extending to the exterior thereof, one of said members including a stationary contact and the other of said members including supporting means for a movable contactor; a one-piece stressed blade movable contactor mounted on said supporting means and including a contact element in overlyingrelation to but separated a short distance from I the stationary contact comprising:

an elongated unitary member extending past said supporting means and having said contact element secured thereto at one end;

first compression force means integral with said unitary member and extending from a point near said contact element to a pivot point on said supporting means for applying a force in one direction:

the housing.

second compression force means that is an integral part of said unitary member and extending with a reentrant bend and a downward bow from the other end thereof to another pivot point on said supporting means for applying a force in the opposite direction and also upwardly against said actuator plunger;

the other end portion of said unitary member being movable by the actuator-plunger to cause snap-action movement of said contact element into engagement with said stationary contact when said unitary member is moved past its dead center position at said first pivot point;

and the other end portion of said unitary member having substantial overtravel allowance following closure of the contacts; I

the improvement comprising a member below said second compression force means against which it bears during overtravel movement to straighten out said downward bow and thereby cause wiping action of the movable contact element on the stationary contact.

5. The invention defined in claim 4, wherein said member below said second compression force means comprises a stationary member.

6. The invention defined in claim 5, wherein said stationary member comprises a horizontal shelf integrally molded within 7. The invention defined in claim 6, wherein said shelf extends almost throughout the horizontal length of said downwardly bowed second compression force means.

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