US3541281A - Precision snap action switch with low differential between tripping positions - Google Patents

Description

V Nqv. 17, 1970 A. w. KRIEGER 3541,28!

7 PRECISION SNAP ACTION SWITCH WITH LOW DIFFERENTIAL BETWEEN TRIPPING POSITIONS Filed April '7, 1969 2 Sheets-Sheet 1 20d r 0 4 4G I] la a 8 ,-1K [8 0 & I

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I l 16c 18 '2 m I 186 ae 14 Nov. 17, 1970 A. w. KRIEGER 3,541,281

' PRECISION SNAP ACTION SWITCH WITH LOW DI RENTIAL BETWEEN TRIPPING POSITION Filed April 7., 1969 2 Sheets-Sheet z fil'vin W. Krieger United States Patent O PRECISION SNAP ACTION SWITCH WITH LOW DIFFERENTIAL BETWEEN TRIPPING POSITIONS Alvin W. Krieger, West Bend, Wis., assignor to Outler- Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Filed Apr. 7, 1969, Ser. No. 814,095

Int. Cl. H0111 13/36 US. Cl. 200-67 9 Claims ABSTRACT OF THE DISCLOSURE A precision snap action switch having a one-piece contactor blade removably mounted on a conductive support within an insulating housing and including a contact element at one end thereof, and a first pair of compression force spring strips extending from a point near the contact element with an upward bow to a pivot point on the support to apply a force in one direction, and a second compression force spring strip extending with a reentrantbend from the extreme other end thereof with a downward bow to another pivot point on the support for free pivoting thereon to apply a force in the other direction and also to bias the bent end upwardly against the support, an actuator engaging the contactor blade between the bent extreme other end thereof and the pivot points and including a plunger for depressing the actuator for snap action operation of the contact element between normally closed and normally open stationary contacts, and the bent extreme other end of the contactor blade being formed long enough and shaped to be biased against and to maintain engagement with a surface of the support until the line of action of the contactor blade passes overcenter at the firstmentioned pivot point for snap-action tripping of the contact element thereby to reduce the differential between the tripping positions and to disengage the surface of the support and move away therefrom in response to further depression of the plunger to afiord a large amount of overtravel without damaging the contactor blade.

BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION This invention relates to precision snap-action switches of the one-piece stressed contactor lblade type provided with a low diiferential between tripping positions, diiferential being the distance the actuator moves between the point where the contact closes and the point where the contact reopens.

An object of the invention is to provide means providing a low differential between tripping positions in a precision snap-action switch. A more specific object of the invention is to provide an improved construction for a precision snap-action switch of the one-piece stressed contactor blade type that affords a low differential between tripping positions combined with a large overtravel.

Another specific object of the invention is to provide a low differential switch of the aforementioned type with means aifording a predetermined low differential between tripping positions according to the construction "ice of the actuator with respect to its point of contact with the contactor blade.

Other objects and advantages of the invention will hereinafter appear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of a precision snap-action switch constructed in accordance with the invention;

FIG. 2 is an enlarged cross sectional view taken along the center line 22 of FIG. 1 showing the switch in its unactuated position,

FIG. 3 is a view like FIG. 2 showing the plunger depressed just beyond the tripping position and the switch in its actuated position;

FIG. 4 is a view like FIG. 3 showing the plunger depressed further to illustrate the overtravel allowance;

FIG. 5 is a bottom view of the cover with the actuator removed;

FIG. 6 is a top view of the base without the switch apparatus and including the inserts as they appear before the stationary contact plates and contactor blade support are riveted thereto; and

FIG. 7 is a fragmentary cross sectional view like a portion of FIG. 2 showing a modified actuator.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, there is shown the external appearance of a precision snap-action switch constructed in accordance with the invention. As shown therein, the switch is provided with an insulating housing comprising a base 2 and a cover 4 enclosing the switch mechanism therein. The cover is provided with a hole extending upwardly therethrough for slidably accommodating an actuator plunger 6. This hole is surrounded by a slightly raised portion 4a fixing the distance that the plunger extends above the cover. This plunger is located on the longitudinal center line of the cover and Offset toward the left end as shown in FIGS. 1 and 2. The base is provided with a pair of mounting holes 2a and 2b extending laterally therethrough transverse to the longitudinal center line of the switch and in widely spaced apart relation near the bottom, hole 2a being slightly oblong to avoid close tolerance positioning of mounting bolts. The bottom of the base is provided with suitable ribs 20 integrally molded thereon to protect the terminals and to increase the electrical clearance between the terminals of the stationary contacts.

As shown in FIG. 2, the housing encloses a precision snap action switch mechanism of the single-pole doublethrow type having normally closed and normally open contacts. That is, the switch is capable of opening one circuit and closing another circuit upon depression of the actuator plunger as shown in FIG. 3. When the actuator plunger is released, the switch returns to its original position shown in FIG. 2.

The switch is provided with a pair of stationary contact plates including an upper contact plate 8 and a lower contact plate 10. The upper contact plate is generally L-shaped when viewed from the top to provide a shank portion that is riveted to the upper end of a connector insert 12 and a foot portion that has secured thereto a contact element 8a in offset relation to the shank portion. The lower contact plate is similar to the upper one except that it is turned over to offset its contact element 10a directly :below contact element 8a, its shank portion being riveted to the upper end of a connector insert 14. This otfset or L-s'haped construction of the contact plates allows securing them to spaced apart inserts While their contact elements 8a and 10a are in vertical alinement. Insert 12 is longer than insert 14 to space the contact elements apart sufficiently to allow snap-action movement of the movable contact element therebetween. Inserts 12 and 14 are provided with suitable terminals 120 and 14a at their lower ends for connection to an external circuit. A ridge 2d shown in FIG. 6 is molded in the base between the upper ends of inserts 12 and 14 to increase the electrical clearance.

Movable contact 16 is a one-piece stressed blade member mounted on a support 18. This contactor blade 16 is generally similar to that shown in my aforementioned patent except for the length of the bent back left end. It is provided with a double contact element 16a for alternately engaging stationary contact elements 8a and 100. A pair of upwardly bowed compression strips 16b extend from points near contact element 16a on opposite sides of its main center strip 16 to pivot points 18a on support 18. Main strip 16 thereof extends through the space between divided parts of support 18 below and past actuator 20 into abutting engagement at its left end with a stop such as the lower surface of support 18. At this left end, strip 16 is bent back with a reentrant bend to form a downwardly bowed compression strip 160 extending back to a pivot point 18b on the support. As will be apparent, compression strips 16b tend to move the contact blade in the right hand direction whereas compression strip 160 tends to move it in the left-hand direction and up into engagement with the lower surface of the support at its left end.

Support 18 for the movable contact blade is a fiat metal ribbon riveted at its left end to the upper end of a conductive insert 22. The lower end of insert 22 has a terminal 22a connected thereto for connection to an external circuit. This support strip is provided with a round aperture 18c providing clearance for free movement of the lower cylindrical portion 20a of the actuator. Support 18 has its center portion cut out all the way from aperture 18c to its right hand end to provide a bifurcation having two spaced legs.

These two legs are provided with means affording pivot points for compression strips 1612. This means comprises a jog therein immediately to the right of aperture 18c constituted by a right angle bend downward in both legs followed immediately to the right thereof with a right angle bend to the right. The upper corner formed by the last mentioned bend is provided with a small notch providing an angle of less than 90 degrees in each such leg forming pivot point 18a for the compression strips of the movable contact blade.

These two legs are further provided with means affording a pivot point for compression strip 166. This means comprises a downward right angle bend of the right-hand end portions of the legs and notches in the vertical portions formed thereby to provide pivot point 18b for compression strip 160. The lower end of this vertical portion also serves to fix the support within the base by resting against side ledges 2e molded integrally on the inner walls of the base as shown in FIGS. 2 and 6.

Plunger 6 is provided with means securing it to actuator 20. This means comprises an enlarged head or flange 6a at its lower end that is secured into rigid engagement with the actuator as the latter is molded.

Actuator 20 is provided with means for operating the contactor blade when the plunger is depressed. This means comprises an elongated ridge 20b extending laterally all the way across the circular lower surface of cylindrical portion 20a. This ridge that has a rounded lowermost portion bears transversely on main strip 16 of the contactor blade and serves to bow this main strip downwardly when the plunger is depressed.

Actuator 20 is provided with means guiding it for vertical movement and for preventing rotary displacement thereof and for allowing only correct orientation thereof during assembly. This means comprises a generally square upper portion 20c formed by a square flange molded integrally at the top of cylindrical portion 20a. One corner of this flange is cut off to allow assembly thereof at only one rotary angle in the complementary recess 41) in the cover shown in FIG. 5. This recess is molded in a relatively thick portion 4c 0n the lower surface of the cover.

The upper portion of the actuator is provided with means for securing the enlarged coined end of plunger 6. This means comprises a recess extending down from the top into the cylindrical portion. This recess has a fiat round lower portion complementary to and for accommodating the enlarged coined end of plunger 6. A sawtooth shaped circular constricting 20d is integrally molded around the upper periphery of the flat round lower portion of the recess, and from this constriction the recess diverges to the top of the actuator. The enlarged end of the plunger is secured as in molding the actuator thereto and is securely held in the lower flat portion of the recess in final assembly.

The switch mechanism is constructed to provide a low differential between tripping positions. For this purpose, as shown in FIG. 2, actuator ridge 20b is arranged to engage the tension member (main strip 16) of the contactor blade at a distance A from pivot point 1811 rather than at the bent left end as in the aforementioned patent. Also, the bent left end is arranged to abut the lower surface of support 18 or other fixed point of housing or the like a distance B from pivot point 180. The distance from pivot point 18a to the movable contact element is indicated in FIG. 2 as distance C.

From the foregoing, it will be apparent that tension member 16 must move overcenter and cross pivot point 18a in order to cause snap action movement of the movable contact from one stationary contact to the other. That is, the part of the tension member where it crosses dead center at pivot point 18a must be actuated from above the pivot point to below the pivot point to cause snap action closure of contact elements 16a and 10a. This is done by depressing the plunger that causes actuator ridge 20b to move the tension member 16. During this movement, the bent left end of the contactor blade pivots on the remains in engagement with the lower surface of support 18.

Thus, it will be apparent that the movement of tension member 16 where it crosses dead center point 18a is greater than the actuator movement by the ratio of distances A over B. This ratio can be changed within limits by relocating ridge 20b as shown in FIG. 7. The greater this ratio is made within practical limits, the lower will be the differential at the plunger. On the other hand, in the aforementioned patent, the movement of the tension member where it crosses dead center is less than the actuator movement by the ratio of distances A over C. It will therefore be seen that reducing the actuator movement relative to the tension member reduces the differential between tripping positions, that is, the distance the actuator must be moved back from the point where contacts 16a and 10a snap closed as shown in FIG. 3 to the point where these contacts snap open.

After the contacts snap closed as shown in FIG. 3, the actuator plunger may be depressed further all the way affording substantial overtravel as shown in FIG. 4 without straining any of the parts since the bent left end of the contactor blade moves down from support 18.

When the plunger is released, the contactor blade returns the actuator up to its unactuated position causing contacts 16a and 10a to reopen and contacts 16a and 8a to reclose.

For minimum differential at dead center position 18a, the bent left end must be biased to touch the lower surface of support 18 as shown in FIGS. 2, 3 and 7 during the time that each tripping action occurs.

While the apparatus hereinbefore described is effectively adapted to fulfill the objects stated, it is to be understood that the invention is not intended to be confined to the particular preferred embodiments of precision snap-action switch with low differential between tripping positions disclosed, inasmuch as they are susceptible of various modifications without unduly departing from the scope of the appended claims.

an insulating housing including a plunger extending ito the housing and an actuator on the end of the plunger within the housing and at least two conductive memfirst compression force means integral with said elongated member and extending from a point near the movable contact to a first pivot point on said support for applying a force to said elongated member in one direction;

here within the housing and extending to the exterior second compression force means integral with said thereof for connection to an external circuit, one elongated member extending from the other end of said members including a stationary contact and thereof to another pivot point on said support for the other of said members including supporting applying a force to said elongated member in the means for a movable contactor; 10 opposlte direction and for biasing said other end upa stop in the housing; wardly against said stop so that the mtermedlate a otter-piece snap action o t t r r bl t d portion of said elongated member is above its dead on said supporting means and including a contact Center Position hy causing Said first p element in overlap in latio to b t separated a sion force means to bias the movable contact against short distance from the stationary contact comprist e normally closed upper stationary Co ta i means on said actuator operable when said plunger an elongated unitary member extending past a portion is depressed a first amount While Sald Other d of of said supporting means and the actuator to said said elorlsated member remains against said p stop and having said contact element secured theremoving the lhtelmedlate Pertiefl of said 61011- t t n d; gated member down past its dead center position first compression force means integral with said unitary eausihg p action PP 0f the movable member and extending from a point near said contact against the normally P lower Stationary tact element to a first pivot point on said supporting e I means f applying a force i one di i depression of said plunger beyond said first amount second compression force means which is an integral eallslhg Sald Othef end of Said elongated member to part of said unitary member and extending with a Sepal'ate from 531d p thereby Providing suhstah' reentraht b d fro h extreme other end th of tial overtravel allowance without excessive strain to another pivotpoint on said supporting means on Oh the P t which it is freely pivoted for applying a force in the release of sald plunger allowms said second p opposite direction and fo biasing the bent d s1on force means to restore said switch to its unwardly against the stop; actuated position by causing said other end of said means on said actuator effective when said plunger is elongated memher first to be biased against its Said depressed for deflecting the intermediate portion of stop an then eallslhg the intermediate Portion theresaid unitary member past its dead center position of move P R its dead eelltel Position thereby at the first pivot point while the bent end thereof eau1hg p aetleh pp 0f the mevable Co tact remains biased against said stop for causing snapagalhst the normally closed PP Stationary 6011- action tripping of the movable contact element into teeth engagement i h stationary Contact; and said biasing of said other end of said elongated said actuator upon release allowing the intermediate membel: agalhst Said p during both actuation and portion of said unitary member to return past its 40 l'estolatltfh t PP S Providing a 10W difiel'ential edead center position at said first pivot point while tweeh pph PesltiOhS 0f e p unger. the bent end thereof remains biased against said stop The lhvehtloh defined in c aim 4, wherein said movfor causing snap-action tripping of the contacts able P t PPQ p s! open; a div ded portion between the parallel branches of and said biasing of said bent end against said stop Whleh Said elongated member extends;

during both actuation and restoration of said switch and t @P at the Start of Said divided Portion providing low difi ti l between tripping Posi. providing clearance for movement of said actuator. tic 6. :lhe invention defined in claim 4, wherein said means 2. The invention defined in claim 1, wherein: on salfi aetuatof comprises! said unitary member is movable in response to further a Tldge beefing e ly 0n Said e gated ember depression of said actuator following tripping of the at a pledetel'hflhed P en Said other end contacts closed to cause the bent end thereof to theretff 531d first P P eparate from aid top thereby providing ubstan 7. The lHVentlOIl defined in claim wherein Said actuatial overtravel allowance without excessive strain on tor compflsesl th g a flat horizontal lower surface affording location of 3, Th i ti d fi d i l i 1, h i id stop the ridge thereon at the desired distance from said comprises; other end of said elongated member and from said a horizontal portion formed on said supporting means first pivot point that is the dead center point of said against which the bent end of said unitary member elongated member thereby to afford use of an actuabears. tor having its ridge at the proper location for opti- 5 a precislon ap action switch g: mum low difierential between tripping positions of an msulatms housing meludms a plunger extendm'g the plunger within limits consistent with proper down into the housing and an actuator on the end of operation thereof e Plunger Wlthlh the h 8. The invention defined in claim 7, wherein the actuaa pan of spaced apart stationary contacts and a suptor and plunger combination is adapted to be readily replaced by another having the ridge in a diiferent location to change the ratio of plunger movement to elongated member movement at dead center.

9. The invention defined in claim 4, wherein said support for the movable contactor comprises:

a flat metal stripformed to provide spaced apart parallel branches with a vertical bend section therein at the place where said elongated member extends past it between said branches;

port for a movable contactor within the housing and means connecting them to external terminals;

a stop in said housing;

a one-piece snap action contactor mounted on said support and including a movable contact at one end thereof extending between the stationary contacts comprising:

an elongated member extending from between the stationary contacts past a portion of said support and past the actuator to said stop;

and a horizontal portion iaroviding said stop for said OTHER RE FERENCES other end of Said elmgated member- Lorsbach: Ger. app. No. 1,226,387, publ. April 1968,

References Cited 2 spec" 1 UNITED STATES PATENTS 5 ROBERT S. MACON, Primary Examiner 3,415,962 12/1968 Krieger. D. SMITH, JR., Assistant Examiner

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