US 2616996 A
Description (OCR text may contain errors)
Nov. 4, 1952 L, BEEMAN 2,616,996
SNAP SWITCH Filed Dec. 6, 1947 N/4/1' fi 1w@ um i-5..-- rfa Lyle Beencm l ATTORNEY INVENTOR Patented Nov. 4, y.1952
` SNAP SWITCH Lyleeeman, AnnArbor, vMich.
Application December 6, 1947,-SerialiNofWIlJGl g "This inventionrelatestosnap--fswitchea I One obj ect of 'the v present invention `iis f to :sim-
yplify'and otherwiseimprovethe-constructionxand i 'operation I of snap `switches.
Amore vspecific object is to provide -a snap 'switch in which adequate pressures A:are maintain'ed between the switch contacts until the in- "stantfthat snapaction occurs. "This characteriisti'c is of importance-particularly in mechanically controlled switches'in that it avoidsarcingfand consequent pitting of the contacts which commonly result from lack of contact pressures during slow opening movement'of the jswitch actuator in :snap switches: heretofore designed. y,
Another object is to providefinasnap 'switch as n simple and reliable vmeans for modifying the switch action so as to regulate the point at which snapaction occurs.
'Another object is Vto provide La reliable-snap..v
switchv of :simple -inexpensivedesign. Y
Other 'objects andadvantages lwill appear, ex-
pressed orimplied, from the 'following description ofanillu-strativeembodiment of this invention.
.',In the 4accompanying drawing:
'Figure 1I is a ytopplan view cfa snap-switch `vvFig. 4 is a transverse -sectional'iview taken -su'b' stantially along the line 4-4 of Fig. 2.
Fig. 5 is a horizontal sectional view taken along the line 5--5 of Fig. 3, cover removed; and
Fig. 6 is a perspective View of the snap-action element shown in the other views.
The switch selected'for illustration is shown mounted on a block I of insulating material and contained within a suitable housing cover II in which the block I0 is fitted and to which it is;
A mm1 bar l2 extending lengthwise of thev block provides support for the several operating parts of the switch mechanism. This bar is shown bent to provide an elevated portion I3 seated upon a shoulder I4 at one end of the block and secured thereto by a screw I5 in such manner as to support a depressed portion I6 of the bar in a position immediately above the block.
lA metal strip I1, securely anchored at 0ne.` end I8 to the bar I2, overlies the depressed portion I6 of the bar, and provides support for a switch contact I9 mounted against the under face of the strip adjacent the anchored end thereof. The strip I1 also functions as an actuajfVI r1 yClaim. (Cl. :2110--67 :toriior'a` 'resilient snap-actiony element '20, rto'rbe later described'. `In thisv instance. one -send Uf fthe `element" 2U;is.shown.ranchored.to the .free 'endiZI fori-the strip I 1, while the other end of theelement :carries a .movable :switch contact `.22.'in r position to-cooperate with .contact I9. The freevend 2| ofthe stripV I11 is insulated Vfrom the .element 2II by, suitable material23. I
Although the 'snap action-element Ztl-may iassume :various forms, `that .shown particularly ."in
'Figs.r5rand.6` comprises a strip `of` resilient metal longitudinallyv lsl'ottedito form-a' pair of. sidestraps 24 and an :intermediate .strap 25, .zall Ainterconnectedateach end-oftherstrip. The .sidefstraps 2'4 are crimped", asat 261, ito 'foresh'ortenf :and thereby tension lthemand Arender them` lengthwise resilient, vand V'to thereby setfup` compression forces in the Aintermediate strap125`. 'Because :of
.Y th'esefforces the strap 125 normally :assumes-the `-s'l'ig'h-tly' bowed @or cambered shape' shown.
The snap-'action element 20' is rockably supported 'intermediate its ends .upon -a ysuitable fulerum-member 21,.preferablyverticallysadjustable.
A'Iheffulcrum lmember -showncomprises1a` resilient --metal stripbent intoinverted -V-shape and '-having spaced feet 2-8whic'h seat upon afsuitable pad *29- YofV insulating material xed onsthefdepressed portion I6 of the 'supportingban The-inter- Amediatestrap 25 of the snap-action-:element rests `upontheapex fof' 'this fulcrum and is retained thereon 'by fthe head of a vertical Ascrew 30. The screw extends through the strap 25, the fulcrum 21, and the bar portion I6 and is retained by a stationary nut 3| threaded on the lower end thereof. The fulcrum 21 is sufficiently stiff to sustain any normal load imposed thereon by the element 29, but is normally compressed by the screw 30, the height of the fulcrum apex is regulated and controlled by rotation of the screw in the nut 3|. A suitable aperture 32 in the strip I1 provides access to the screw 30 for purposes of adjustment. The screw 30 is insulated from the bar portion I6 by an insulating sleeve 33 and pad 34.
A suitable lead wire 35 is electrically connected to the movable switch contact 22 through the nut 3|, screw 30, and strap 25; while the other contact I9 is electrically connected to a second lead 36 through the strip I1, bar I2, and screw 31 carried by the bar.
An appropriate spring 38 seated on the block I0 reacts on the free end of the strip I1 to yieldably sustain the same in the upper position shown in Fig. 2, in which position the bowed strap 25 of the snap-action element 2D reacts on the ful- The free end of the strip I1 may be deabove the point where the intermediate strap 25 o rests on the fulcrum 21, and the strap 25 assumes a downward camber.
However, Whenever the free end 2| of the strip I1 is depressed by the switch-opening thrust of the pin 39, the connected end of the element 20 lowers correspondingly, carrying with it the side tension straps 24 until the latter pass through a dead center position, whereupon the intermediate compression strapy 25 snaps into a position of upward camber, causing the contact 22 to suddenly withdraw from contact I9 with a snap action. It will also be noted that, during the downward thrust of the pin 39, and until the snap action actually occurs, the element functions as a simple lever reacting on the fulcrum and converting this downward thrust into an upward thrust of the contact 22 against contact I9, thereby actually increasing the contact pressure between the contacts. This pressure continues until relieved by the ultimate snap-action movement of contact 22 away from contact I9.
It will be understood of course vthat upon release of the thrust pin 39, the strip II is returned by the spring 38 to the upper position of Fig. 2 causing the snap-action element 29 and the contact 22 to resume the positions therein shown.
It will be further understood that the action of the switch may be modied by adjusting the screw 30 so as to elevate or depress the fulcrum point of the element 20. By thus elevating the fulcrum point the switch opens at a point earlier in the down stroke of the pin 39 and the switch closing action is retarded, and when the fulcrum point is depressed the switch opens later and closes earlier.
Provision is also preferably made for adjusting the point at which closing of the switch occurs without aiecting the point at which opening of the switch occurs. In the device shown this is accomplished by the use of an adjustable stop by which the open position of the switch contact 22 may be regulated and determined, the stop shown comprising the end III of a screw in threaded engagement with the insulating plate 29. By elevating the stop 4I the open position of the contact 22 is correspondingly elevated toward the level of the fulcrum point of the element 20, causing the latter to snap into switch closing position at an earlier point in the down stroke of the pin 39; and by depressing'tlie stop 4I theswitch will close at a later point in the down stroke of the pin 39.
Various changes may be made in the embodiment of the invention hereinabove specifically described without departing from or sacricing the advantages of the invention as defined in the appended claim.
In a snap switch the combination of a yieldable fulcrum member, a resilient snap-action element rockably supported intermediate its ends on said fulcrum member, a switch contact, a second contact on one end of said element movable into and out of engagement with said first named contact in response to snap-action movements of the latter, means operable on the other end of said element to effect snap-action movements of the latter, and a screw extending through said element and said fulcrum for adjusting the latter and therebyv vary the switch action.
REFERENCES CITED The following references are of record in the le of this patent:
UNITED STATES PATENTS Richmond Aug. 9, 1949