US3497648A - Snap action switch - Google Patents

Description

Feb. 24, 1970 Filed July 25, 1966 M. K. PARKHURST SNAP' ACTION SWITCH /2 /NU/N,

FIG I E] `i y" V///77 77/4/ VI 2 Sheets-Sheet l FIG 5 Feb. 24, 1970 M, K. PARKHURST & 4

SNAP ACTION SWITCH Filed July 25, 1966 2 Sheets-Sheet z FIG 6 w 50 34 D FIG 7 FIG 8 F!G 9 FIG IO FIG Io l 7 9 1 N.O. L 'T` S S SHUNTED Y 6 44 l I] FIG Ilb N.O. L UNSHUNTED FIG ||c U SNAPPING E FIG IId SHUNTED United States Parent O 3,497,648 SNAP ACTION SWITCH Malcolm Kingsley Parkhurst, New York, N.Y., assignor to Burch Parkhurst Associates Filed July 25, 1966, Ser. No. 567,495 Int. Cl. H01h 21/04 U.S. Cl. 200-67 11 Claims ABSTRACT OF THE DISCLOSURE A toggle member and overcenter spring assembly is mounted to cause a contact carried at the end of the toggle member to wipe a cooperating contact and at the same time transmitting force to the toggle member in the actuating direction. The toggle member is substantially rigid and is mounted in a direction perpendicular to the overcenter direction, the resistance in this latter direction being employed in forcing the contacts to wipe each other, so as to break incipient welds. The stops of the toggle member define the range of pivotal movement for the carrier and serves to shunt the toggle member so that the main current passes through the toggle pivot only during the actuation periods.

This invention relates to snap action electrical switches.

It is an object of this invention to provide improved snap action electrical switches from the points of view of reliability of contact action, fail-safe operation, ruggedness, Simplicity, small size, and ease of manufacture.

Particular objects are to provide snap action switches capable of being produced in the standard sub-miniature switch package (.500 in. X .200 in. X .390 in.) having the above features.

Another object is to provide a practical switch Construction which takes advantage of the wipe and shear principle disclosed in Patent 2,899,512, filed Dec. 13, 1956 and issued Aug. 11, 1959.

The invention features the mounting of a toggle member and overcenter spring assembly to cause a contact carried at the end of the toggle member to wipe a cooperating contact and at the same time transmitting force to the toggle member in the actuating direction. The toggle member is substantially rigid and is mounted in a direction perpendicular to the overcenter direction, the resistance in this latter direction being employed in forcing the contacts to wipe each other, so as to break incipient welds.

The invention features a toggle member, or other snap member coined or otherwise formed out of rigid noble metal, or stamped from a metal strip having such metal in the region defining the toggle pivot and the contact carried by the toggle member.

The invention features a toggle member mountcd on a pivotal carrier, the stops which define the range of pivotal movement for the carrier serving to shunt the toggle member so that the main current passes through the toggle pivot only during the actuation periods.

The invention features a stationary contact assembly defining both wipe-and-shear-type contacts and stops for movement of the snap member which are especially compact and suitable for use in subminiature switches and in other switches where it is advantageous to avoid the need for close assembly tolerances.

The invention features a stationary contact for wipe and shear switches in which the parts are so arranged that the critical contact surface is die-formed and in which an accurate relation between this surface and the movable contact is achieved by simple and uncritical assembly steps.

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The invention features in particular the combination of all the above features in an effective subminiature size switch.

These and numerous other objects and features will be understood from the following description of a preferred embodiment.

In the drawngs:

FIG. 1 is a vertical cross-sectional view taken on line 1-1 of FIG. 3 of the preferred embodiment;

FIG. 2 is a vertical cross-sectional view taken on line 2-2 of FIG. 1;

FIG. 3 is a horizontal cross-sectional View taken on line 3-3 of FIG. 1;

FIGS. 4 and 5 are perspective views of the toggle assembly of FIG. 1;

FIG. 6 is a view on an enlarged scale of a detail of the Construction of the toggle assembly;

FIG. 7 is a diagrammatic cross-sectional view of a starting material from which the toggle member is made;

FIGS. 8 and 9 are plan and cross-sectional views respectively of the toggle member partially formed;

FIG. 10 is a side View of the nearly completed toggle member;

FIGS. lla, b, c, and d are diagrams of the switch of FIG. 1 in various stages of operation; and

FIG. 12 is a perspective view showing the form and relation of the stationary contact assembly to the toggle member.

Referring to the drawings the housing 10 of this embodiment conforms to the standard subminiature switch dimensions, .500 x .350 x .200 in., and has three terminals, common terminal 12, normally open terminal 14 and normally closed terminal 16.

Common terminal 12 is connected to a U-shaped bracket 18 which supports a pivot pin 20 to which is pivoted a carrier`member 22. Upon the horizontal base of carrier member 22 is positioned a rigid toggle member 26 carrying at its upper end a contact surface 28.

Referring to FIGS. 4-6 the toggle member 26 has a rounded hearing surface 30 on axis A engaged upon the conductive plate 22a of carrier 22 and has a pair of lower extensions 32, one at each outer edge of the bearing, inserted in corresponding openings in the plate 22a. The upper end of the toggle member is confined between stationary contacts 34, 36, while pulled downwardly by an over-center spring 38 connected at midway up the toggle member and at 42 to a pin vertically aligned with, but spaced below axis A.

The carrier member 22 has an upwardly extending arm 44, engaged at moment arm M by actuator button 46 and arranged to engage at su'bstantially longer moment arm M the stops 48, 50.

Referring to FIGS. 1 and lla the actuator 46 is arranged to cause carrier 22 to rotate about axis 18 to carry both carrier arm 44 and the contact surface 28 of the toggle 26 in the direction of the arrow Z, FIGS. lla-c.

The contact 34 is sloped at a substantial angle Y to direction Z, hence movement of the carrier and its toggle member in direction Z causes contact 34 to deect toggle member 26 in the direction of arrow D until the overcenter position is reached, i.e. until the point of attachment 40 (FIGS. 4 and 5) of the toggle member 26 reaches the plane passing through axis A and point of attachment 42 of the spring. Suddenly the rigid toggle member snaps against contact 36.

According to the invention the stop is spaced so that at least a small amount of over-travel will occur, after the toggle snaps to contact 34, before the lever arm 44 engages the stop 50, FIG. lld.

Referring to FIG. 12 the contact 36 and the stop 50 comprise two edges die cut from a conductive plate of metal, e.g. silver. The plate also has a first bend 60 connecting to a mounting plate portion 62 and a second bend 64 connecting to a plate portion 66 to which terminal 14 is connected. 'From FIGS. 11 and 12 it can be seen that any variation in the degree of bend 60 has little affect on the relationship of the angle of the contact edge 36 to the direction of constrained moton of the carrier and toggle member.

Similarly contact 34 is die cut from a conductive plate, while the stop 48 is formed by a separate tab integral with the mounting plate portion.

By the integral relation of the stops 48, 50 to the respective stationary contacts 34, 36, it is seen that the toggle member 26 is shunted whenever sufficient over-travel occurs, e.g. under influence of actuator 46 or return spring 70. Accordingly the main electric current is required ,to pass through the toggle bearing at A only during switchng.

The difference in the moment arms M and M provide an amplification of the actuating movement so that it is easily possible within the tolerance of present manufacturing techniques to position the stops so that they will not be engaged until snap contact has been firmly made.

Referring to FIGS. 4 and 5 the toggle member 26 itself defines the contact surface 28.

In this embodiment it is merely necessary to start with a sheet of hard silver (e.g. GPx36 alloy of Texas lnstrument or Alloy 15065 of Englehard Industries H. A. Wilson Division) or a sheet of stiif metal such as stainless steel upon which stripes of noble metal are secured. Referring to FIG. 7 such a striped metal sheet is shown. Referring to FIGS. 8 and 9 from the sheet of metal a stamping is formed, with semi-cylindrical surfaces S at either end and bumped portions B in the center at the sides, then the stamping is folded about axis A, the noble metal forming the bearing surface 30, and the noble metal cylinders together forming the rounded contact surface 28.

The toggle member 26' of FIG. 5 is an example of a desirable alternative formation in which the entire rigid member is formed by a coinng process from a mass of hard noble metal alloy, the head 28' being solid, not hollow as in FIG. 4, while being integral with the legs of the toggle member.

An alternative construction of the toggle member may consist -of a strip of metal depending between the two legs 26a, integral with the member, and having a series of corrugations, forming the toggle spring.

Referring to FIG. 1 the return spring 70, shown in dotted lines, may be removed, converting the switch to push pull action, unique to such small size switches. In this instance the spring of the toggle mechanism holds the toggle member to 'whichever side it is forced by the actuator.

The cooperation of the rigid toggle member and wipe and shear with various of the relationship, described can produce a subminiature switch surprisingly free of critical relationship. Thus wear in the region of axis A Should have no detrimental elfect because the spring 38 can have ample power to accommodate the wear and still operate.

The integral nature of the toggle member avoids the necessity of critical positioning of a contact upon it.

The locating holes on the carrier precisely position the toggle member on the carrier while the side plates 62, 62a (not shown on drawing) and 62b of the U-shaped mernber 18 and the contact members 34 and 36 enable the carrier and toggle, mounted on the U member, to be accurately positioned relative to the contacts.

Numerous modifications may be made of the specific details within the spirit and scope of the invention as defined by the following claims.

What is claimed is:

1. A snap action switch comprisng a toggle member including a contact surface connected to a first electrical terminal,

a pivotal carrier member mounting said toggle member with said toggle member free to pivot through an unstable center position in a first direction upon the carrier, and constrained against relative movement in a second direction perpendicular to said first direction, said carrier member being pivotal in said second direction,

a pair of stop members spaced relative to said carrier member to confine said carrier member to pivot back and forth within a limited range,

a first stationary contact connected to a second electrical terminal, said stationary contact constructed and arranged to engage said contact surface, and having a portion sloped at a substantial angle to said second direction such that, upon pivotal movement of said carrier between said stops, said stationary contact both wipes against said contact surface and deflects said toggle member in said first direction toward and through said over-center position to break engagement of said contact surface and said first stationary contact, and

a second stationary contact connected to a third electrical terminal, and constructed and arranged to be engaged by said contact surface upon said deflection of said toggle member through said over-center position,

at least one of said stop members being electrically con nected to the stationary contact engaged by said contact surface when said carrier member is engaged by said stop member, the portion of said carrier member Contacting said stop being in electrical continuity with the contact surface of said toggle member, said stop member and said carrier thereby shunting said toggle member.

2. The snap action switch of claim 1 wherein the portion of said carrier member Contacting said stop comprises a lever arm, said snap action switch includes an actuating button arranged to contact said carrier member remote from said lever arm and apply an actuating force to said mem-ber at a first moment arm, and said stop member is arranged to be engaged by said lever arm at a moment arm distance substantially greater than said first moment arm.

3. The snap action switch of claim 1 wherein said stationary contact and said electrically connected stop member are formed integrally from a metal plate.

4. The snap action switch of claim 3 wherein said stationary contact and said stop member are formed by die-cut tab portions connected through a bend to a mounting plate portion.

5. The snap action switch of claim 3 wherein said stationary contact is dened by a die-cut edge of said plate.

6. A snap action switch adapted to be manufactured in a size approximating one half inch in its longest dinension, said switch comprisng the combination of a housing, including connecting terminals and means for mounting said housing, and a snap switch mechanism disposed within said housing, said housing defining an interior space that is substantially longer in one dimension than in the other two directions, said snap switch mechanism comprisng a pivot bearing secured to said housing and having a pivot aXis lying at a right angle to said longer dimension, said pivot bearing located adjacent a corner of said interior space of said housing, a pivotal carrier member pivotally mounted upon said pivot bearing to Swing in a pivotal plane extending in said longer dimension, a pair of stop members secured to said housing and spaced relative to the carrier member confining said carrier member to pivot back and forth within a limited range, means to apply an actuating force to said carrier member to cause it to pivot within said limited range, a snap member mounted upon said carrier member, said snap member being substantially rigid in the direction of said pivotal plane and constrained against movement relative to said carrier member in the direction of said plane whereby said snap member pivots with said carrier member in said plane, said snap member extending from said carrier member in the direction of said longer dimension to an electrical snap contact, said electrical snap contact snappable in a direction perpendicular to said pivotal plane, and connected to a first of said terminals, a stationary contact mounted in said housing and connected to a second said terminal, said statonary contact including an actuator surface disposed adjacent and at an acute angle to the path of pivotal travel of said snap contact, said snap contact and said statonary contact arranged so that as said snap contact wipes upon said statonary contact with pivotal movement of said carrier member in one direction, said actuator surface of said statonary contact urges said snap contact through its unstable center position whereby said snap contact snaps out of engagement with said statonary contact.

7. The snap action switch of claim 6 wherein one of said stop members and said statonary contact are formed integrally from a plate, said plate including a flat portion defining a flat mountng surface, said carrier member pivotally mounted on a second plate defining a flat mounting surface, a housing for said switch having preformed flat surfaces adapted to cooperate with said flat mounting surfaces to align said snap member and said contacts.

8. The snap action switch of claim 6 including a second statonary contact mounted in said housing and connected to a third said terminal, said statonary contact disposed on the side of said snap contact opposite to the side on which said first statonary contact is disposed, said second statonary contact including a surface which said snap contact engages as it snaps out of engagement with said first statonary contact, and said second statonary contact including an actuator surface disposed adjacent and at an acute angle to the path of pivotal travel of said snap contact, said snap contact and said secondary contact arranged so that as said snap contact wipes upon said second statonary contact with pivotal movement of said carrier member in the direction opposite to said one direction, said statonary contact urges said snap contact back through its unstable center positon whereby said snap contact snaps out of engagement With said second stationary contact and re-engages said first statonary contact.

9. The snap action switch of claim 8 wherein said carrier member includes two arms at substantially right angles to each other, a first of said arms extending in a direction substantially perpendicular to said longer dimension, said snap member mounted upon said arm, and said second arm extending substantially parallel to said longer dimension, said means to actuate said switch arranged to apply actuating force to said second arm at a first distance from said pivot aXis, and said pair of stops disposed across the path of pivotal travel of said second arm, to engage said arm at a second distance from said pivot axis greater than said first distance.

10. The snap action switch of claim 9 wherein said means to actuate said switch comprises a reciprocable plunger.

11. The snap action switch of claim 6 wherein said snap member comprises a toggle member having two leg portions spaced apart in the direction of said pivotal plane, said leg portions rotatably hearing upon said carrier member permitting pivotal movement of said toggle mernber at a right angle to said pivotal plane.

References Cited UNITED STATES PATENTS 1,838,983 12/1931 Angell 200-63 2,198,277 4/ 1940 Schellenger. 3,200-,213 8/ 1965 Murphy. 3,213,228 10/1965 Burch et al. 3,301,976 1/ 1967 OXley 200--63 ROBERT K. SCHAEFER, Primary Examiner D. SMITH, JR., Assistant Examner U.S. Cl. X.R. 200-164

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