US2639352A - Thermostatic switching device - Google Patents

Description

May 19, 1953 R. A. WATSON THERMOSTATIC swITcHING DEVICE Filed March 2, 1951 .Alrf/N M) 5 4 T ma r TW N Nam E MT 6 M m /M Vw 5 n w l i5 i\\ Z ....v4 .v 4 mv 4 j l L van.,

Patented May 19, 1953 Y UNIT @FFME THERMOSTATI'G SWITCHINGDEWCE Roberti A; Watson,` St. Louis-,-lVIo.,\.assig'norfv to' Missouri-*Automatic Control.4 Corporation, StirI Louis,-Mo., .a. corporation .of vMissouri Application 'March'y 2, 1951:,1SrialfNo. 21133507? 8 'Claims'. y- (Cl. .ZBO-#1409,

Thisazinvention':relates.totsnapeactionrthermos statically actua-ted switches, particularly tofthose employingf thermostati'e actuators'- of; themtype having' relatively.' small,.. though' relatively "posi-ftlve'movementin response to' temperature change, and 'I to f motion transmission means: for i 'suitably multiplying these-movements lfowopei:ation:of the switch;

Although. this typel of 2' temperature vresponsive actuator provides.l ammore positive fand'. therefore more'reliable? primary "movement .thisfimovem'ent 1s lrelatively' small and must=be :greatly 'multiplied forsnap-action'operatlon ofthe-switch contacts. It ."isalso'` necessaryslto adem-lately'.i multiply and transmit' these fsmall movement'si fwithout'iloss 'or variation'ldiierto 'reversal-Soffstressesf as .the actu? ator'L reverses; its a'ction',=. duefto :directional tem; perature-change' while.'l movement iisiresistedlby the snapaction'f means. While :iti isg". of; course; necessary vSto `provi'c'le r a 'L predetermined: degree.' 'of 'xing' at somev lpoint 2' in .'atztransmissionlmecha.- nismbetween the actuators and the= switch';con:: tacts'in' order to'.achieveatlieadesired/snaplaction; any other motionsses, hoWeven'vvhich maybe due to uncontrolldff 'exingiorf 'looseness `in i the mechanism-,- wouldf'resuiltf inlan funduly 'wideand unpredictable switch operating 'differentiali and arejtherefore; totb'ev avoide'd It fis' further-desire able Vthatf the -meansVL for multiplyingy andI trans-v mitting the-movements of fthe actuator'l bef'of ple"-' construction Awith" a'-'- minimum' number of members' and of "compact designs' It is;' therefore,'-an 'object-.of this' invention to provide 4a4 generally .'cievsr'fandl improved iswitoh'ig de'v'iceof 'the above-character, havingl 'a motion transmission mechanis'mwhich is simple-'and 'de pendable in operation,- and in' which the required relatively-[great vmultiplieation' 'of the' movements ofthe temperature actuator is= achieved-ima com'-Y pact arrangement.

AA furtherobject' is to provide 'in a4 switch as above', a `motionv transmission' mechanism'oomprlsing' a" simple lever' multiplicationv system in which 'the "great 'multiplying eifect of aI collapsing toggle joint is'employed to achieve; in a'compact design, the ,required multiplicationrof-'the move ments of the temperature responsive actuator:

Al'further. object is 4to' provide in'a switchas above, a" motion 'transmission system' comprising a simple lever multiplication' system" of" rugged and dependable constmction'in'whieh'tlie'slight movements of theotemperature responsive actuator are greatly multipled'and are transmitted in a substantially straight line.v Other objects l' and" advantages which" kbecome apparent.r upon-readings the following. complete desoription'in `"connection :with the accompanying drawing willbesetforth 'in theappended claims.

Fig.. luis? afplan View of a fthermostati'cfzsnapf action switching device constructed 'in accord'.- ence .-witnrthis :invention 1, portions :being-broken away to morefclearly. illustrate; v

Eig.;A 2 is a lon'gfitudinalsection oflfthezswitching devicershown. in Fig;..l.and is taken alonglineV 2-2 ofFig. V1;

Fig'.- 3-is astransverseesection i of: the switching deviceshown in Figs-.v -l 1and2 and'fisi taken' on :line

O'-Fg, .2.

The` switch is' mounted ina.. rectangular-boxe like casing I Iigzopenatthestopfandfhaving'a; cover I I -\vhioh completessthe closure and is removably attachedfto the casing I ill-byscrews -I 2. Fory sim. plicity, the casingds-y lshown :asfbeing constructed of a suitable f rig-id `.dielectric `Inaterialv` but may of; course, .be constructed: of any t suitable metal with suitableA provision forv r.electrical ''insulaftion Attached to the` left-end =wall I 3-ot ,the casing, and ori-,its exterior. surface, is .a vlcircular' expansible chamber'y element, generallyfindicated at' IlI-.-l Elements; IILv comprises'. an.. outercircL-ilar,l hea-vyi- Wa-lled, rigidacu-p ,memberi ltanrd an inner oircu lar, thin-iwalled;l flexible .cup-.member I which'is nested Within-f the-:outer-cup member and is 'at tached` thereto' :byzafoontinuous: Weldingtogether oixthe sidelwallsflofethe' cups-as= indicated atI1. A:fluid-tight;*.expansiblez chamber denedby;` the bottom. wallsfot.the` cup members is thusprovided/r.

The:.botten-1.V Wall. I5 -of y'the outer-.cupi isprovidedV with anexterior" projecting frogfeyeV eX-ztrusion- I8 Which-.is perforated and .receives .one endfofa'icapillaryftube I9; The tube I9'isrigid'- 1y. attached-...within vthe perforationasbyhard soldering-at; 20;V to *provide-Maf fluid-type-"connection. Tlieeother end-Tofoapillary tubef-ISfis connected tore. remote'rigid metal'bulb 2i (which is shown substantially. reduced' in-size), anclits con@ nection :therewith is.fluid-type.f The* bulb', z the capillary.tubej1and;r :ther expansible chamber denedfbythelwalls I5 and I'of the cups'iforma closedfluitight system?4 which is filled with'a thermally.' expansibl'ef liquid.. This liquid `has a relfativelyfhigh''boilingiipoint1 sufficiently high at least? so that'lthere` is nozfvaporia'ation'within the operating temperature'franefe "of the fcevi'ce'."

TheaamountV ofi 'liquid eplaeed iinr'the :system i is suclrrthat'the'nenilxle wally I6 is'norma-lly substanl tially contiguousiwitlt therigid'zwall 4I 5 'when the bulb'ftemperatureiisfb eloiv tnf'eoperating :temperature range, so that the full permissible deflection of the wall I9 may be utilized to extend the operating range of the device. The flexible wall i6 is stiffened against bulging by the provision of radially extending formed ribs 22, which provision, together with a practically incompressible, thermally expanding liquid, results in a relatively positive acting temperature responsive actuator. The amount of actuating movement in response to a unit temperature change in a `device of this character will, of course, vary with the design and proportions of the device. However, considerations such as desirable design proportions,

compactness, operating range, and the permissible deflection of the flexible metal wall I6 are limiting. In the contemplated construction, the effective actuating movement per degree of temperature change, Fahrenheit, is in the order of 1/{1000 of an inch for a minimum operating tem' perature range and may be as small as 2/10,000 or "710,000 of an inch-for a maximumoperating temper'ature range. The operating temperature range is increased and the movement per unit temperature change is decreased as the bulb is reduced with relation tothe size of the expansible chamber.

A great multiplication of these slight movements must, therefore, be accomplished if sufcient movement is to be obtained to store energy in a resilient member for imparting a snap-action to the switch contacts, and if the temperature differential within which the switch operates is to be closely held, say in the order of 1 Fahrenheit. To achieve this multiplication, a lever multiplication system is provided, comprising a pair of flat triangular- shaped links 23 and 24 lying end to end with one side of each adjacent the other and extending longitudinally in the casing I0. Link 23 is provided with a socket 25 at its `outer or left pointed end, which is adapted to receive the ball end 26 of a diaphragm follower member 21. The diaphragm follower 21 has a flat bearing surface 28 in engagement with the central portion of the flexible wall I6. A clearance aperture 29 is provided inthe casing wall I3 to permit the passing through and oscillation of the link 23. The link 24 is provided with a similar socket 3U at `its outer or right pointed end which is adapted to receive the ball end 3l of a threaded adjustment screw 32. The adjustment screw 32 is threadedly engaged in an internally threaded bushing 33, which is rigidly vsupported in the right-hand casing wall 34.

The adjustment screw 32 and the diaphragm follower 21 are `in alignment and concentric with the circular element I4. The links 23 and 24 are also provided with opposed notches or recesses and 35 in their adjacent ends which receive a pivot pin 31. The central portions of the adljacent flat ends of the links are out back as indicated at 33 in order to reduce the bearing area between the pin 31 and the links. Links 23 and 24 are further provided with opposed lugs 39 and 43 at each edge of their wide inner ends, over -each pair of which Iis placed a stressed springsteel restraining clip 4l. It will be seen that clip 4l will yield as the links 23 and 24 are'rotated and that they will exert a resilient holdingforce yto retain the pivot pin 31 Ain constant bearing engagement in the notches 35 and 35 as one link is caused to rotate by the rotation of the other. The links 23 and 24 are limited in their rotation toward alignment with each other by a stop member 4|a supported in a side wall casing. Link 23 is provided with a rigid extension 42 end, the contact arm carries a movable contact 43 which cooperates with a stationary contact 41 to control a circuit. The contact arm 45 is mounted on a pivot 48 which is, in turn, supported in a bracket 49. The contact carrying arm is of composite construction and comprises a stiff, non-flexing portion 59, extending from its pivoted end toward its free end, a flexible intermediate portion 5| near its outer free end, and a relatively stiff armature portion 52 at its outer end.

Directly above this outer armature portion 52, and supported-by the cover member Il, isa permanent magnet 53. The stationary contact 41 is attached to the lower end of a contact adjusting screw 54, which screw is threadedly engaged in Aa conductor plate 55. The permanent magnet 53 is also attached to the conductor plate 55 in a suitable manner. The conductor plate 55 is attached to the cover Il by means of a tubular :rivet 56. This tubular rivet is internally threaded to receive a screw 51 which, together with the rivet, forms a terminal binding post for the convenient attachment of a circuit lead. A second terminal binding post is provided by a screw 58 and a tubular rivet 59, which rivet attaches the pivot supporting bracket 49 to the cover Il. A thin, very flexible, electrical conductor strip G0 is provided to insure electrical conduction from the inner end of the contact arm to the binding post. A return spring 6l bearing against the cover Il at its upper end, and bearing at its lower end against the contact arm 45 at a point substantially in alignment with the button 43, urges the pivoted contact arm in a counterclockwise or switch opening direction. v

It Will'be seen from the foregoing that the small horizontal movements of the follower member 21, due to expansion or contraction of the liquid, will be greatly multiplied at the point 43 on extension 42 where these movements are imparted to the contact arm 50. This multiplication is due to the relatively great rotational movement imparted to link 23 and its extension 42 by relatively slight horizontal movement of the follower 21, when this link is near alignment with its companion link 24, as shown. By making the links 23 and 24 substantially the same length. and by provision of the extension 42 which carries the button 43 at a point in approximate vertical alignment with the pivot point 3| of link 24, the path of movement of button 43 is caused to follow a substantially straight line. As a result of this arrangement, lateral sliding movement between the button 43 and the contact arm 59 is reduced and the operative connection between extension 42 and arm 50 may, therefore, be made quite simple, as shown. From the point of engagement of button 43 with contact arm 50, the movements of follower 21 are further multiplied in the arm 50, which extends oppositely and overlies the link 23 and extension 42, resulting in a compact arrangement.

In operation The switching device is shown in Fig. 2 in a closed contact position. As the temperature to anaemia whlehith'ebulbi-21. ris scusitive'-decreases-fthefliqid therein contracts and".`- the; followers' 21 i" moves slightly-4 towardthe fle'rtif permittingsfthe return spring- 61! torotateftlie'link Zliclockwise and Vthe contactarm counterclockwise:l Thelmagnet: 53k; h'owevenzzresists :rotation :of fthe outerxend of .farm Sifand; asvarresult, the resilientfporticnifil is; therefore;'iieircciiI When the resilient portion .5l isv` flexed to r the point atll which it will transmit sufient force to44 overcome* theattractionl of magnet'f 5351 the 'armature-1 portion 52, together with themovable` Contact, will snapdownward; thus* breaking f the contacts #with f a snap eaction; Tl'ieat, iiexible'conductor 60 is foflsuchflexibility asfto'oii'erno more resistance-torotation of^arrnl ."Wfthan` does the usual" 'pig-tail connection.

If,'"with theswitch contacts now'-v infopen posi--v tion; the temperatureis increased, causing4 the follower 27"to-move-slig-htly toward the right, the link23 ,WilLbee rotatedi; ounterclockwise, ,opposing the turn spring 6( and rotating, contact arm 50 in a clockWise-or-"contact closing'direction. The expansion of the liquidgis, of coursepcharf acteristically slow, and thearm-Sl is, therefore, slowlyrotated until a point will.be.reached,.;orior totheemeeting of the contacts, lat wnicnthe magnetic attraction of magnet 53 will. attract the armature 52 with suiiicientiforcefto.(cause the portion i to flex, and the armature 52 and the movable contact llt to move rapidly ahead of 1 the inner portion of the arm in a switch closing direction, thus imparting a closing snap-action.

By constructing the motion transmission mechanism of adequately rigid members so as to eliminate iiexing at any point therein except the short portion 5 i, it will be seen that the required flexing to achieve the desired snap-action may be closely controlled or varied by simple calibration of the flexibility in one short portion or member.

It will also be seen that by locating this short flexing portion or member near the outer end of the contact arm as showns the mass which moves rapidly during the snap-action is greatly reduced over the arrangement in usual constructions. By this reduction in mass, the energy is also greatly reduced, resulting in a substantially non-bouncing contact. A further advantage in the shortened, iiexible portion or member 5l lies in the increased frequency and, therefore, the more rapid diminishing of its vabratory oscillations when stressed and released.

To adjust the device for operation at preselected temperatures within its operating range, the adjustment screw 32 is rotated. As the screw 32 is rotated outward, the temperature at which the device closes will be raised. The usual dial and indicator may be provided in connection with the adjusting screw 32. The stop member Ma limits the rotation of links 23 and 24 to a point just a few degrees from alignment,

The foregoing description is intended to be illustrative, not limiting, the scope of the invention being set forth in the appended claims.

I claim:

1. In a thermostatic switching device, a temperature responsive actuator having a. denite path of motion in response to temperature change, a pair of links lying end to end in general alignment with said path of motion and being pivotally connected to each other at their adjacent ends, one o said links being pivotally connected at its other end to said actuator, and the other of said links being pivoted at its other end on a xed pivot, a stationary switch contact 6 and1'aicooperatingqmovable switcirrcontacti ,are rangedto ube moved ibyc one of: saidllinks: as fitris rotated due-'Itolmovementfofsaid' actuator-.v

2'; In a= thermostati'cf switching device; altem# perature f responsive f actuators having a definite;t

patliof"motionl in responseto temperature changeg-acpairloi linkslying end 'to endin generar alignment with/said f pathof` lmotion and? beingl pivotally connected to'veachA other at their adjaeA cent ends, one of 'said `links-beingV pivotally-'cone' nected atrits other end tov said actuator-and the otherfof saidlinks v.being pivoted'atitsfother end on-a iixed pivot; cooperating stationary-'and movable switchvcontacts,` and-means carried `bye-'one of said links; for. moving.. said "movable Icontact/as saidrlink-.fisifrotated: `duel to.` movement: of." said actuators` 312.Inzazthermostaticf switching device',y azztem perature'lresponsive. actuator E having t a; iix'ediipatlr ofmotionrinresponse to temperature change; an adjustably iixed member spaced-from; saidiactu-f` ator and .substantially in .alignment with .theipath of lxnotiozrfof said .'.actuator,-'a` pair.- of linkszilying end to Vend rbetiveenzsaid' actuator 'and .saidiixed member and.' being..jzulvotaflly-y connected-sto: each other atitheir'adjacentiends, .theaother endof one linksbieing pivotallyjconnected to saidlactuator; andthe .otlie1".er1d'` of the otheilink Lbein'gzpivot's ally connected to said fixed member, cooperating stationary and movable switch contacts, and means carried by one of said links for moving said movable contact as said link is rotated due to movement of said actuator.

4. In a thermostatic switching device, a temperature responsive actuator having a definite path of movement, an adjustably xed member spaced from said actuator and substantially in line with the path of motion of said actuator, a pair of links lying end to end between said actuator and said fixed member and being pivotally connected to each other at their adjacent ends, one of said links being pivotally connected at its other end to said actuator and the other of said links being pivotally connected at its other end to said iixed member, stop means for limiting the rotation of said link members in a direction toward alignment and to a point slightly before alignment, a stationary switch contact, and a cooperating movable switch contact arranged to be moved by one of said links as it .is rotated due to movement of said actuator.

5. In a thermostatic switching device, a temperature responsive actuator having a definite path of movement in response to temperature change, a pair of link members lying end to end in general alignment with the path of motion of said actuator, said links being pivotally connected to each other at their adjacent ends, one of said links being pivotally connected at its other end to said actuator and the other of said links being pivoted at its other end on a fixed pivot, stationary and movable switch contacts, and means on one of said links extending beyond its pivoted connection with the other of said links for moving said movable contact as said link is rotated due to movement of said actuator.

G. In a thermostatic switching device, a temperature responsive actuator, a pair of spaced pivots, one of said pivots being movable by said actuator along a line substantially coinciding with a line passing through said spaced pivots, the other of said pivots being arranged to be adjustably fixed along said line, a pair of link members of substantially vequal length lying end to end between said pivots, said links being pivotally connected to each other at their adjacent ends and pivoted at their opposite ends on said spaced -pivots,lone of said'link members having al longitudinally projecting portion extending substantially to a perpendicular line intersecting the outer pivot of said other link, a stationary switch contact, anda cooperating movable switch contact arranged to be moved by the outer end of said projecting link portion as said link is rotated due to movement of said actuator.

-7. AIn a thermostatic switching device, a teinperature responsive actuator, a pair of spaced pivots, one of said pivots being movable by said actuator along a line substantially coinciding with a line` passing through said spaced pivots, the other of said pivots being arranged to be adjustably fixed along said line, a pair of link memberslyin'g end to end between said pivots, said links being pivotally connected to each other at their adjacent ends and pivoted at their outer A ends on said spaced pivots, one of said link meini bers having a rigid, longitudinally projecting portion extending substantially to the outer end 'of said other link, and a pivoted Contact carrying arm lying alongside'and substantially coexten sive with said link members, said arm being pivoted at one end and carrying a contact at its other end, and being operatively engaged by the end of said projecting link Vportion at-a point thereon near its pivoted end. f

' 8.`In va thermostatically operated control device," a pair of link members arranged end to end and being pivotally connected atvtheir adjacent ends, a llongitudinally adjustable pivot at the outer end of one of said links, a temperature responsive device having a pivotal connection with the outer end of the other of said links and arranged to act longitudinally thereon in response to temperature changes whereby said links are rotated thereby, a spring returned controlmember arranged to be actuated by the rotational movement of one of said links and arranged to normally urge said links in a direction toward alignment, and stop means for arresting the rotation of said links in a direction toward alignmentto a point slightly short of alignment.

/ ROBERT A. WATSON.

References Cited in the file of this patent UNITED STATES PATENTS Number

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