US3691331A

US3691331A - Switch mechanism with s-shaped snap acting spring member

Info

Publication number: US3691331A
Application number: US18413A
Authority: US
Inventors: John S Resh
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1970-03-11
Filing date: 1970-03-11
Publication date: 1972-09-12
Anticipated expiration: 1989-09-12
Also published as: CH518616A; FR2078496A5; DE2110696A1

Abstract

A snap acting switch arrangement having a normally flat elongated spring member supported in compression to either side of a pair of centrally located, spaced stop members to provide an S-shaped configuration whereby movement of one of the extremities thereof causes a change in the curvature, but not a reversal, of the S-shape and results in snap movement of the spring member from one stop member to the other.

Description

O United States Patent [151 3,691,331 Resh 1451 Sept. 12, 1972 [54] SWITCH MECHANISM WITH S- 2,113,227 4/1938 Bokeeno ..200/67 D UX SHAPED SNAP ACTING SPRING 2,515,324 7/1950 Thomson ..200/67 D UX MEMBER 2,789,172 4/1957 Happe ..200/67 D UX 2,993,102 7/1961 Anderson et al..200/67 D UX [72] Res", 3,176,109 3/1965 Wodtke ..200/166 H ux [73] Assignee: Honeywell Inc., Minneapolis,

Mi Primary Examiner-David Smith, Jr. Filed March 11 1970 Attorney-Lamont B. Koontz and Philip J. Zrimsek [21 Appl. No.: 18,413 ABSTRACT A snap acting switch arrangement having a normally [52] CL Wino/67 DB, 200/166 BA, 200/166 A flat elongated spring member supported in compres- 51 1111. c1. ..H0lh 13/48 either Side P 0f centrally mated [58] Field 61 Search ..200/67 D, 166 11, 166 BA Spaced members Provide ration whereby movement of one of the extremities [56] References Cited thereof causes a change in the curvature, but not a reversal, of the S-shape and results in snap movement UNITED STATES PATENTS of the spring member from one stop member to the th 1,593,726 7/1926 Sinner ..200/166 BA UX 0 er 2,074,132 3/1937 Rich ..200/67 D UX 4 Claims, 3 Drawing Figures PATENTEU 3.691.331

INVENTOR JOHN S. RESH SWITCH MECHANISM WITH S-SIIAPED SNAP ACTING SPRING MEMBER The present invention is directed to a snap acting switch arrangement wherein a normally flat elongated spring member which also functions as the movable contact is disposed lengthwise in compression between a pair of supports and is associated with a pair of stops, one of which functions as the fixed contact, the stops being centrally located with respect to the extremities of the spring member so as to place the spring member in an S-shape. Movement of one of the supports-causes variations in the effective length of the spring member and a change, but not areversal, in the curvature of the S-shape resulting in snap movement of the spring member from one stop member to the other.

While snap acting switch arrangements are in a welldeveloped art, some of the problems which they initially attempted to solve are still being attacked. Thus, long mechanical life, long electrical life and low cost in snap acting switch arrangements are attributes fervently sought. Long mechanical life dependsessentially on maintaining the stresses encountered in the arrangement within acceptable limits. Long electrical life depends upon, among other things, the ability to mechanically transfer contacts so as to provide engagements between clean surfaces and without excessive bounce so as to minimize frying, welding and/or erosion of the contacts. Low cost of course is that always desirable needed to successfully reach the market place.

The three attributes above set forth are inherent in my contribution to the art. Thus, my snap acting switch arrangement as initially set forth above includes a spring member which while it changes curvature to a slight degree during its snap movements between the stop members does not reverse curvature and hence the stresses set up in the spring member are not severe, thereby allowing for long mechanical life. Further, because of the S-shape form of the spring member and its free pivotal connections with the supports, where this is the case, snap movement of the spring member between the stop members results in an enhanced wiping action of the contact surfaces, thereby aiding in maintaining clean contact surfaces and also thereby absorbing and dissipating impact energy so as to minimize contact bounce. Finally, my snap acting switch arrangement lends itself to be manufactured from easily fabricated, non-precision parts which can be hand-assembled without any tools and which are associated together without the need of any conventional fasteners.

Therefore, it is an object of the present invention to provide a snap acting switch arrangement utilizing a spring member formed into an S-shape which in its excursions between a pair of stop members changes curvature but does not cause a reversal thereof, thereby providing for long mechanical life.

It is another object of the invention to provide a snap acting switch arrangement wherein the engaging contacts exhibit wipe to provide clean contact surfaces as well as to absorb energy and thereby reduce contact bounce so as to assure long electrical life.

Another object of the invention is to provide a snap acting switch arrangement which can be manufactured from easily fabricated parts that can be hand-assembled without conventional fasteners being required.

These and other objects of the'invention will become apparent from a reading of the following specification and claims taken together with the drawing in which:

FIG. 1 is an explosion view of the snap acting switch arrangement;

FIG. 2 is a view of the assembled snap acting switch arrangement when in the at rest" condition; and

FIG. 3 is a view of the snap acting switch arrangement when in the actuated condition.

Referring now to FIG. 1 of the drawing, attention is directed to a base member or housing 10 which supports the elements of the snap acting switch arrangement. Thus,- thehousing 10 includes a main cavity 11 and

openings

12, 13 and 14 at the lower extremity-as well as depressions 16, 17 and another, not shown, in the inside back wall of the cavity for association therewith of electrically

conductive terminal members

20, 22 and 24, respectively, in a conventionalfashion as will become apparent below.

Terminal members

20 and 22 include tab portions 20a and 22a, respectively, at the upper extremities thereof to slidably accommodate, engage and retain electrically

conductive coil springs

26 and 28, respectively, which serve as fixed contactportions. The coil springs 26and 28 are of a barrel shape, that is they are of greater outer diameter at the midpoint than at the extremities. The relative dimensions of the tabs 20a and 22a and the

coil springs

26 and 28 allow for deflection of the coils, especially those near the midpoint, toward and away from the tabs. While the preferred embodiment utilizes the

coil springs

26 and 28 for the fixed contact portions, other contact forms which are well known in the art could be utilized.

An electrically conductive lever or movable support member 30 includes a tab portion 30a which is arranged to be disposed in opening 24a of the terminal member 24 for pivotal association therewith as will become apparent below. The terminal member 24 and the movable support member 30 include

notch cutouts

24b and 30b, respectively, to accept

opposite extremities

32a and 32b of an electrically conductive, normally flat elongated spring member 32 to allow for free pivotal connections therebetween. Electrical contact material may be applied in any known manner to opposite sides of the spring member 32 at approximately its midpoint as at 32c.

The housing 10 also accommodates plunger 36 for inwardly and outwardly guided movement in opening 38 for engagement with the movable support member 30 as will be explained below. Additional guide means between the plunger 36 and the housing 10 is provided by oppositely located protrusions 36a of the plunger and slot 39 provided in the inside back wall of the cavi-' ty 11 and a comparable slot provided in the cover, not shown, which cover of course basically serves to close off the cavity.

Referring now also to FIG. 2, the

terminal members

20, 22 and 24 are slidable accepted, located and held in

openings

12, 13 and 14, respectively, of the housing 10 with the movable support member 30 pivotally associated with, referring specifically to FIG. 1, the opening 24a in terminal member 24 and engaged by plunger 36. Further, normally flat elongated spring member 32 is disposed in compression between the terminal member 24 and the movable support member 30 and,

referring specifically to FIG. 1, through opening 22b of terminal member 22 with the

extremities

32a and 32b in

notches

24b and 30b, respectively. The location of the

notches

24b and 30b and the lower coil spring 26 is such that the spring member 32 assumes an S-shape with its contact portion 320 in contact with the lower coil spring causing a deflection thereof whereby all of the coils are in engagement with the contact portion. Further, a counterclockwise force is placed on the movable support member 30 causing the plunger 36 to be located in the extreme outward position. The

terminal members

20 and 22 and the associated

coil springs

26 and 28, respectively, are so located that with the spring member 32 in place a contact gap is provided between the spring member and the upper coil spring 28.

It will be appreciated that the elements of the snap acting switch arrangement can be disposed in and with respect to the housing by hand assembly without conventional fasteners or special tools being required.

With the snap acting switch arrangement in the at rest condition shown in FIG. 2, a force is exerted by the spring member 32 and particularly by the contact portion 320 thereof substantially normal thereto and against the coil spring 26. Upon inward movement of the plunger 36, the movable support member 30 is moved clockwise causing a scrubbing or wiping relative movement between the coil spring 26 and the contact portion 32c, thereby aiding in maintaining clean contact surfaces. The contact wiping is caused by the change in the effective length of the spring member 32 brought about by the change in curvature thereof as the notch 30b of the movable support member 30 moves downwardly with respect to the fixed position of the notch 24b of the terminal member 24 and the relatively fixed position of the contact portion 32c engaging the coil spring 26. Further, the inward movement of the plunger 36 and the clockwise movement of the movable support member 30 causes the contact force between the coil spring 26 and the contact portion 320 to be reduced.

As the movement of the plunger 36 and the movable support member 30 continues, so does the contact wiping, while the contact force approaches zero. Upon the contact force passing through zero, a snap action arises causing the spring member 32 to move from the position shown in FIG. 2 to that where the contact portion 32c engages the coil spring 28 as shown in FIG. 3. In so doing, the coil spring 28 is deflected by the impact and force of the spring member 32. Further, because of the flexure of the spring member 32 which allows for the change in curvature, contact portion 32c wipes the coil spring 28. Thus, the energy of snap action is rapidly dissipated into deflection and wiping, thereby minimizing contact bounce and the resulting frying, welding and/or erosion of the engaging contacts. It will be noted from FIGS. 2 and 3 that merely a change in curvature of the spring member 32 arises upon actuation of the snap acting switch arrangement from one condition to the other and not a reversal of curvature. This of course minimizes the stress seen by the spring member 32, thereby enhancing mechanical life.

The snap acting switch arrangement can of course be made monostable or bistable. But in the preferred embodiment, it is of the former type. Thus, a stop surface 40 is provided in the cavity 11 of the housing 10 to limit the clockwise movement of the movable support member 30 and thereby prevent the overcenter condition of the snap acting arrangement from arising. Upon outward movement of the plunger 36 from the position shown in FIG. 3, ultimately a reverse snap action of the spring member 32 arises and the snap acting switch arrangement reverts to the condition of FIG. 2, the contact wiping and impact absorption again being encountered but this time by the opposite sets of contact surfaces.

In addition to the attributes above set forth with respect to my snap acting switch arrangement, it should be noted that it exhibits excellent shock and vibration characteristics due to inherent high contact and return forces. Further, high speed actuation is possible. Thus, devices incorporating my invention, in a package size approximately one half that shown in FIGS. 2 and 3, have been actuated at a rate in excess of 2,000 cycles per minute with the plunger and moving contact portion positions remaining in synchronization. Still further, my snap acting switch arrangement eliminates the possibility of deadbreak, since the contact force provided by the fixed contact and the direction of travel of the moving contact portion in the preactuation and pre-deactuation phases are in the same direction.

The snap acting switch arrangement I have disclosed may take other forms and my invention should be determined from the following claims:

I claim:

1. A snap acting switch arrangement comprising: a base member; a pair of spaced support members, one of which is movable, associated with said base member; a normally flat elongated spring member disposed lengthwise in compression between and the extremities thereof pivotally connected to said support members and including an electrical contact portion located approximately midway between the extremities thereof; and a pair of stop members associated with said base member at least one of which includes electrical conducting means, said stop members being disposed approximately midway between said support members and to either side of said spring member and spaced to allow for movement of the contact portion of said spring member from one to the other including engagement with the conducting means; said support members and said stop members located so that said spring member when in place assumes an S-shape engaging one of said stop members and so that opposite movements of said movable support member allows free pivotal movement of the extremities of said spring member and causes a change in the effective length of said spring member and a reversal in the direction of the force at the engagement between the spring member and the engaged stop member resulting in snap movements of the contact element thereof between said stop members and in a direction opposite to the movement of said movable support member, the free pivotal movement and the change in effective length of said spring member enhancing wiping movement between the contact portion of said spring member and the conducting means of said stop member, the change in the effective length of said spring member bringing about a change in curvature of the S-shape but not a reversal thereof.

minimize contact bounce, the longitudinal axis of said coil spring being substantially transverse to the direction of movement of the contact portion of said spring member and substantially transverse to the line extending between the support locations for the extremities of said spring member.

4. The arrangement of claim 3 wherein said coil springs are of barrel shape to enhance resilience and are supported at either extremity to provide stability.

Claims

2. The arrangement of claim 1 wherein the pivotal connections comprise the extremities of said spring member being disposed in notch cutouts provided in said support members.

3. The arrangement of claim 1 wherein the electrical conducting means is a coil spring to increase wiping movement between the electrical contact portions of said spring member and said stop members thereby absorbing and dissipating impact energy of said spring member caused by a snap movement thereof so as to minimize contact bounce, the longitudinal axis of said coil spring being substantially transverse to the direction of movement of the contact portion of said spring member and substantially transverse to the line extending between the support locations for the extremities of said spring member.