US2828373A - Condition responsive switch apparatus - Google Patents

Description

March 25, 1958 R. P. SWEGER 2,828,373

CONDITION RESPONSIVE swncn APPARATUS Filed Oct. 25, 1954' 2 Sheets-Sheet 1 INVENTOR.

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common RESPONSIVE swnca APPARATUS Filed Oct. 25, 1954 v 2 Sheets-Sheet 2 IN VEN TOR.

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ATTORA/EVj United States Patent CONDITION RESPONSIVE SWITCHEAPPARATIJS RusselL P. Sweger Rockford Illl, assignor to Barber Colman Compan'y, Rockford; llh, a corporation of Illinois Application October-1255 1954, Serial :No. 464,402

10'.Claims. (Cl; 200-18) This ,invention:relates-Iona condition responsive; switch apparatus, such as one; which responds .,to temperature changes, and has more particularq reference-to 1 an r oyer center switch: in which a-Cmoyable CQnIflGi iszsppported byea spring and-;moves between-- stationary/ contacts with a snap action=of the spring,; Such springs require a great or. force tOIbG shifted across center than to ,be held; in the over-center position. This difference; is utilized; to obtain .a =diiierential in the magnitudesv of ;thecondition at which the switchresponds upon an increase and-a (1Q! crease inathe condition,

One object of the. inventiontis to employ two switches ofithe ioregoing;characterlinta novel mannerto: obtain a two-stage control of thecondition.

A. more-detailed :object is ;to obtain. the: two -stagescon trol by: arranging; a movable.- member! between; the:v two switches .andiactuate the switches= through the mediumeof springs carried :by the member.

Another 1 object isto vary the: dilierential' by springs which are arranged" in: such a. manner that their spring rates may be adjusted wherebyditterent. amountsi oj movement of the movable member are-required to, actuate each switch.

Other objects and ad-vantagesof the invention will become' apparent from-thefollowing detailed' description taken in connection-with the accompanying drawings; inwhich:

Figure 1 is afront elevation view of acondition-re sponsive switch --apparatusconstructed in accordance with the-present invention, partszbeing broken away and shown in section Fig; 2 'is*- a sectional view=taken along the lined- 2 in-Fig; 1';

Fig. 3' is a perspective viewofthemovableswitch actuating member;

Fig; 4'is a view showing-theactuatingsprings-intwo positions of movement-with the parts arranged for a'- high spring rate.

Fig. 5*is a view similar to Fig. 4- but' shows the-parts arranged'for a low spring rate. v

While the invention is applicable to apparatus 'for sensing changes in various conditions, it' is shown in the drawings, for purposes of' illustration, as embodied in, a thermostat responsive to temperature changes. Such changes are sensedlbyta fluid filled'temperature bulb 'connected by a tube 11 to a resilientmetallic bellows 12. Tlie1lat= ter't'hus is expandedandfcontracted 'in response to changes in ternperature and this causes thfe actuation ofone or more1switches,13 andljl4wh'ich' may be utilized to control. heaters (not shown) for raising the temperature aboutthe bulb 1 0;.

Thevswitches 131 and 14 are enclosed within atcasing 15" composed of a fiangedmounting plate; 16 and; an L-shaped cover 17 (Big, 2), Preferably, the switches are -f het-snape et nlypezandompr setw paeedjstationary contacts, 18I,a '1d;19 mounted within. an insulated housing 20' with .a., thirdlcontact 21;,movab1e between gthe twostationary contacts. Thepmovablc contact: is carried on' the end 10f a-suitable leaf spring '22: which moves with an over-center action-so that thiscontact-is snapped'from one, otithe stationarycontacts to the other: Projecting through the'housings of the two. switches 13-and;1,4- are actuator? pins :23- and? 24 which: engage the springs of. the corresponding switches and; which when depressed; shift these springsacross center;

Disposed against the housing 20 -of=each2of the) switches 13;and=-14;is a terminal plate 25 whose three terminals 26 are-connected by rigid L-shapedtconductors 27 tot the terminals-2840f the switch, the latter terminalslbeing connected respectively to the contactse18,-,19 and '21-. Screws 29- proje ting through the-plate 25 are'threaded into: the housing-20aofa the switch l'ii andainto-the supporttplate 16 thereby securing-d this switch to thecasing 15:- Similar screws 29, andzZW-fasten the switch and theias'so ciated -terminal-plate to abar 30-which is pivoted'onthe snpp orttplate -16;-by means'of the screw 29 and clamped in selectedta-ngulm positions by a screw 32. The ban-isturned by -tur-ning the-head31 of'aneecentric 31 which'is jonrnaled on the barand receivedin-a slot 31 in" the mountingiplatetlfi; Mounting'the switch 14. on-.the plate 3oipermitsgthe p9sition ot this switch:to-be adjusted-to vary-the-spacing betweenrthe' two switches.

Inaorderto actuate-theiswitches'13v-and 14-in;response to temperaturerchanges, the; switches are arranged with their, actuators-23, and;24z'projectingtowardeach; other and .anelongateda-horizontal lever 33,- which isturned-by the bellows 12, projects in bet-weenthe-actuators: andrdes presses the lattervas itiswings upand down. Herein, the lever, 33. isasheet. metal stamping: formed with, down turnedeside flanges 34 through whicha pin 35: projects at theainneriend of t the lever to form the fulcrum:

Tha -bellows 12 r'istdisposed within anv'annular; boss-7.36 onthe lower-= flange-37 ofi the-plate A 16 and' is supported at itsrlower end by'a'cap-38-tbolted-tothe-boss. Con necting thei-upper end of the= bellows and :the lever; 33;is atvertical; pin-39 formed at its; lower end-;with: an ,en larged head; 40nwhich projects through -the boss 36? and restston top; of; the bellows: At=its=upper-end, the-pin abuts against the. pointed lower end of a: screw 41 threaded ethrough the-levera A- contractilewspring 42--an choredatwoneend to atlug 43 on the -fiange=-37l and at the other end; to, an; car: 44 struck down from I the: lever 33 biases; the latter to hold the 'screw- 41 ragainstrthe-pin 39 downwardly so that the lever movesup and down as the bellows: expands-and contracts; The bellowsiis loaded by; a compression spring 45 encircling the pin- 39 and acting between the head 40 and a stationary lug: 46 formed. integrally with theplateandhaving a-h ole through t which the pin projects.

Innthe-presentiinstance, one end of thefulcrum1pinc35 proie tsinto; a vertical recess 47(Fig-, 2) formed inothe plate- 16 whi1ethe, other end projects into 1 aslot '48 paralleling the recessand formed -in-abracket 49-which is-bolted to theplate. Thispermitsthe-pin 35- to slide up-and down and such sliding is limited in theqdownward direction-:by-aknobSfl (Fig. 1) threadedon the upper end: of a rod 51, which carries :the .'pin;. atitslower: end and projects through the ,uppervflange SZon-theplate .16; The. .knob, 50 l has a depending skirt ,5 3-=whichforms an internal shoulder ;54= and thisxshoulderabuts against an annular -bosst vupstanding from the flange 52' andencircling the rod 51., Thus, the. spring: 42; acting;.through thelever 33,,the pin 35 and the rod 51, urgcs'theshoulder 54 against the boss55 andnorma11y holds the fulcrum pin 35;in'a fixed position. By, threading therknob, 50 upand-d'own on the rod, the pin 51 is raised or, lowered and this adjusts the temperatures at. which; the switch actuators 23 and 24 are depressedb'y the lever 33.

3 The sliding arrangement of the fulcrum pin 35 also protects the entire apparatus from damage when the bulb is subjected to abnormally high temperatures. Under such conditions, the bellows 12 expands swinging the lever 33 against the actuator 24 of the switch 14. After this actuator has been depressed, the spring 42 yields and the fulcrum 35 is moved up so that the lever actually pivots about the actuator 24. In this manner, neither the switch 14, the lever 33 nor the bellows 12 are stressed to the point where they would be damaged. In snap action switches of the type used herein, a greater force is required to shift the spring 22 across center than is needed to hold the spring in the overcenter position. For example, an 11 ounce force may be required to shift the spring but a 7 ounce force will hold the spring. This difference may be utilized to obtain a differential between the temperatures at which the switch is actuated in each direction. For this pur ose, thelever 33 depresses the actuators 23 and 24 of the switches 13 and 14 through the medium of springs 56 and 57, so that, as the lever swings toward one actuator, the latter is engaged by the opposing spring which first is flexed a predetermined amount until it exerts a force great enough to shift the switch spring 22 across center. As the lever 33 swings away from the switch. the force of the actuating spring decreases but the switch spring remains over center due to the fact that a lesser force is required to hold it in this position. Eventually, the lever moves far enough that the force of the actuating spring decreases to a value below the minimum required to hold the switch spring and the latter moves back across center. In this manner, the switch is actuated at diflerent temperatures in each direction.

According to one aspect of the invention, advantage is taken of the difference in the temperatures at which each of the two switches 13 and 14 operate to obtain a two stage control of the ambient temperature at the bulb. In such a case, the heater used to raise the temperature about the bulb would, as is well known in the art, be capable of producing a low heat and a high heat such as by using one or both of two heating units. With this arrangement, each switch controls one of the heater units so that, when the temperature at the bulb is substantially below the desired value, both units are energized while only one is energized when the temperature is only slightly below the set value. At the same time, the arrangement provides an accurately controlled differential between the temperatures at which the two heater units are energized and the'temperatures at which the units are deenergized.

To achieve the foregoing ends, the switch 13 controls one unit of the heater and energizes this unit when the r actuator pin 23 is depressed, that is, when the movable contact 21 of this switch is against'the lower stationary contact 19. When the pin 23 is released to permit the movable contact to snap up against the contact 18, the heater unit is deenergized. The switch 14 operates in the opposite manner and functions to energize the second unit of the heater when the actuator pin 24 is released and deenergizes this unit when depressed. With this arrangement, a temperature at the bulb 10 substantially below the desired value causes the bellows 12 to contract to the extent that the lever 33 is swung down flexing the spring 56 sufficiently to overcome the force of the spring 22 of the switch 13. This depresses the 3C:- tuator pin 23 and snaps the contact 21 of the switch 13 down against the contact 19. At this time, therefore, both unitsof the heater are energized.

As the temperature at the bulb 10 rises, the bellows 12 expands and swings the lever 33 up reducing the force of the actuating spring 56. When the force of the spring is reduced below that required to hold the switch spring 22 down, below 7 ounces in, the example given above, the switch spring snaps back across center deenergizing the first heater unit and leaving only the second unit energized. With only one unit of the heater in operation, the temperature at the bulb rises more slowly and gradually approaches the desired value and, during this time, the spring 57 is flexed until the spring of the switch 14 is overcome so that the lever 33 depresses the actuator 24 and deenergizes the second heater unit.

At this time, the spring 57 is exerting a force sufiicient to move the switch spring across center, for example 11 ounces, and this is materially greater than the force re-' quired to hold the switch spring in the over-center position. Thus, as the temperature at the bulb It) begins to fall and the resulting contraction of the bellows 12 permits the lever 33 to turn down, the actuator pin 24 remains depressed so that both heater units are deenergized. Continued downward swinging of the lever reduces the force of the actuator spring 57 below that required to hold the pin depressed and, when this occurs, the spring of the switch 14 overcomes the spring 57 and moves back across center to energize the heater unit controlled by this switch. This may cause the temperature at the bulb to rise again or, under some circumstances, the temperature may continue to fall but more gradually.

Should the bulb temperature continue to drop, the resulting further downward swinging of the lever 33 will cause the actuating spring 56 to flex until the force it exerts is suflicient to snap the spring 22 of the switch 13 over center. This energizes the associated heater unit so that both units then are again in operation.

It will be observed that the foregoing arrangement provides a two-stage control such as may be used to control the operation of a multiple unit heater. At the same time, the system maintains a differential between the temperatures at which each unit is energized and deenergized. Thus, in the present instance, both units are deenergized at predetermined temperatures as the bulb temeprature rises but are energized at lower temperatures upon a drop in temperature at the bulb.

The present invention also contemplates the provision of a novel construction and arrangement of the lever 33 and the actuating springs 56 and 57 so that the temperatures atwhich each spring actuates the associated switch 13 or 14 may be set selectively. For this purpose, the springs actuate the switches directly and are arranged to flex when moved against the corresponding switch actuator pin. Such flexing continues increasing the force exerted by the spring until the force is sufiicient to overcome the force of the switch spring 22. In accordance with the invention, the actuating spring is constructed so that its effective spring rate may be varied. By' changing the spring rate, the amount of movement of the lever 33 required to flex the actuating spring enough to overcome the switch spring is varied. As a result the differential between temperatures at which the switch is actuated is adjusted selectively.

While the springs 56 and 57 may be constructed in various ways to efiect a change in spring rate, herein such change is achieved by employing leaf or cantilever springs which are shiftable longitudinally so that the actuating pins 23 and 24 of the switches 13 and 14 engage the springs at selected distances from the anchored ends of the latter. The springs 56 and 57 are disposed respectively above and below the lever 33 and extend along and beyond the free end portion of the latter. Washers 58 .(Fig. 4 are disposed between the inner ends of the springs and the lever'and the springs are clamped against the washers by a bolt 59 and a nut 60. The bolt projects through holes 61 in the springs, through the washers 58 and through an elongated slot 62 in the lever. The slot extends longitudinally of the lever and permits the bolt to be shifted back and forth along the lever.

With the foregoing arrangement, the nut 60 may be loosened and the bolt 59 slid along the lever 33 through the slot 62 to a selected position after which the nut is tightened clamping the bolt in this position. The springs magenta 5'6 a'nd' 57 a re shifted 'longitudinallyifofithe leverswitlrrthe *bolt 'and slime adjusted positionsgrelative to'the switch aetuaters zs and 24. Asaa resultg thesprings; areengageatbyithe actuators' at different selecteds distances from the spring ends Thus, with-the-bolt:disposed: near the- 'forwa'rd end'ofthe slot' 62 as shown .in Fig. 4; the aotnatofi 231 en'g'a'gesfthespring 56= at a point:- compara= tively farfrom' the end -ofithe spring. Inithi's position of the-parts, the spring has a.. relatively high springrrate so that th'e force of -the-spring: increases rapidly'up'on downward' swingingiof the lever. Because of this, only a small movement of theleven is required 'to overcome the force- 0f? the switch-spring. 22 and actuate the switch- 13;

By shifting; the bolt: 59: toward the inner. end :of: the slot 62* so thatsthe spring 56 is in the position shown inIFig.-5,l.the actuator'23 engages the' springsnear the outer endthereof; The effective rate of the spring is, therefore,v reduced: and: acorrespondingly" greater.- movement of .the lever is -required-to flex the=springsufhciently toc-actuate-the switch 13;: Thus, by;shifting;the springs 56 and 57 back and forth,- their springrates are adjusted and this varies the differential between the temperatures at which the switches 13{ and: 14. are actuated in each direction. If desired, a scale 63 (Fig. 1) may be marked on the flange 34 of-the lever 33'to indicate the variou'sipositionsof. the springsand hence the differentials' in theoperating.temperatures.

I claim as my. invention:

1; Conditionresponsive apparatus-having, in combination; 81 support,. a,1e.ver. fulcrumed on said support. to swingbacle and forth in response to changes in-thecondition being sensed, two snap action switches mounted on said support on opposite sides of said lever and each having a movable contact carried by an over-center spring, two actuators, one for each of said switches and each operable to shift the corresponding switch spring across center, said actuators being spaced apart and opposing each other, and two leaf springs anchored at one end to said lever with their free ends projecting in between said actuators, each of said leaf springs opposing one of said actuators to engage the latter, then flex a predetermined amount and finally overcome the force of the corresponding switch spring upon swinging of said lever.

2. Condition responsive mechanism comprising a first support, two actuating springs mounted on opposite sides of said support and each having a spring rate that varies according to the point at which it is engaged, a second support movable relative to the first upon changes in the condition to be sensed, two snap action switches mounted on said second support on opposite sides of said first support and each having a movable contact carried by an over-center spring, and two actuators, one for each of said switches and each engaging one of said actuating springs whereby the switches are actuated upon relative movement of said supports and after a predetermined flexing of the actuating springs.

3. Condition responsive mechanism comprising a first support, two snap action switches spaced apart and each having a movable contact carried by an over-center spring, said spring requiring a greater force to be shifted across center than to be held in the over-center position, an actuator for each of said switches movable to shift the corresponding spring across center, said switches being mounted on said support with their actuators opposing each other, a second support movable relative to the first in response to changes in the condition to be sensed, and two spring elements mounted on said second member between said actuators and each opposing and engaging one of the actuators to cause the latter to move and thereby shift the corresponding switch spring back and forth across center upon relative movement of said supports, said spring elements .yielding a predetermined amount when moved in each direction before effecting movement of said actuators.

4;. Condition; responsive apparatus. having. in combination, :a support, ,alever; fillcrurned on said support: to swing; baclc; and forth 1 in ,response toachangeszin the condition being; sensed; two; snap. action: switches: mounted on1saidsupport on: oppositesides of-isaid-glever, andieach having amovable contact carriedxby an overrcenterzspring; two: actuators,- one; for each of: said switches: and each operable to shiftthe corresponding switch spring; across center, said; actuators beingspaced: apart and: opposing each'other, two leaf springs. anchored atoneend-to. said lever with their free ends: projecting in between: said actuators, each of? said. leaf springs: opposing. one of said: actuators. to' engage the. latter, then flex and: finally overcomeathe; force: of" the; corresponding switch spring upon swingingofsaid'lever, and meansfor. shiftingsaid,

leaf springson said lever. to vary. the; points vofengage ment hetweentsaid actuators and leaf'springs therebyto change the: effective: spring;- rate of the; leaf springs, and adjustrthe. amount of flexingcofz the same.

5;: Condition, responsivemechanism comprising; a first support; two actuating springs mounted on. opposite sides of; said support. and each having a. spring rate: that-varies according to the point at which: it. is engaged, a: second support: movable: relativewto. the; first upon changes. in the condition, to be; sensed, two snap action. switches mounted on said second support. on opposite-sidesofsaid firstsupport and each havingamovablecontact carried by. an. over-center spring; two. actuators, onefor each of said switches and each engaging one of said-actuating springs; whereby the switches areactuated upon relative movementyofisaidgsupports: and afterfiexingof the actuating springs, and means for adjusting said actuating springs relative to said actuators to change the points of engagement thereby to change the effective rate of the actuating springs and vary the amount the latter flex be fore actuating said switches.

6. Condition responsive mechanism comprising a first support, two snap action switches spaced apart and each having a movable contact carried by an over-center spring, said spring requiring a greater force to be shifted across center than to be held in the over-center position, an actuator for each of said switches movable to shift the corresponding spring across center, said switches being mounted on said support with their actuators opposing each other, a second support movable relative to the first in response to changes in the condition to be sensed, two spring elements mounted on said second support between said actuators and each opposing and engaging one of the actuators to cause the latter to move and thereby shift the corresponding switch spring back and forth across center upon relative movement of said supports, said spring elements yielding when moved in each direction before effecting movement of said actuators, and means for varying the effective spring rates of said elements to change the amount the elements yield.

7. Condition responsive mechanism having, in combination, a first support, a leaf spring mounted on said support, a second support movable relative to said first support, a snap action switch mounted on said support and having a movable contact carried by a spring, said spring requiring a greater force to be moved across center than to be held in the over-center position, an actuator operable when moved to shift said switch spring over center and engaging said leaf spring, means to move said supports relatively together and apart in response to the condition being sensed whereby said leaf spring flexes upon initial movement of the supports together and then shifting said switch spring across center, said leaf spring flexing in the opposite direction upon separating movement of said supports and then permitting said switch spring to move back across center, and mechanism supporting said leaf spring on said first support for adjusting movement to change the point on the spring engaged by said actuator and thereby vary the effective rate of the spring.

8. Condition responsive mechanism having, in" combination, a first support, a leaf spring mounted on said support, a second support movable relative tosaid first support, a snap action switch mounted on said support and having a' movable contact carried by a spring, said spring requiring a greater force to be moved across center than to be held in the over-center position, an actuator operable when moved to shift said switch spring over center and engaging said leaf spring, means to move said supports relatively together and apart in response to the condition being sensed whereby said leaf spring upon initial movement of the supports together and then shifting said switch spring across center, said leaf spring flexing in the opposite direction upon separating movement of said supports and then permitting said switch spring to move back across center, and mechanism for changing the point on said leaf spring engaged by said actuator thereby to change the effective rate of the spring.

9. A condition responsive mechanism comprising a first supporting member, a snap action switch mounted on said member and having a movable contact carried by an over-center spring, said spring requiring a greater force to be shifted across center than to be held in the over-center position, an actuator movable to shift said spring across center, a second supporting member movable relative to the first, a second spring mounted on said second member to engage said actuator and overcome the switch spring as said members move together, said second spring having a spring rate varying according to the point engaged by said actuator, means for changing the point of engagement between said actuator and said second spring thereby to adjust the relative movement of saidmembers required to, shift said switch spring over center in each' direction, andmechanism responsive to changes in. the condition to be sensed and operable to move said members relatively together and apart.

10. A condition responsive apparatus having, in combination, first and second supporting members mounted to move together and apart relative to each other in response to changes in the condition to be sensed, a snap action switch mounted on said first member and having a movable contact supported by an over-center spring, said spring requiring a greater force to be moved across center than to be held in the over-center position, an actuator movable back and forth and operable to shift said spring over center, a second spring supported on said second member and yieldably engaging said actuator to oppose the spring of said switch, and means for varying the efiective spring rate of said second spring thereby to adjust the relative movement of said members in each direction before one of said springs overcomes the other and causes shifting of the switch spring.

References Cited in the file of this patent UNITED STATES PATENTS 2,181,829 Jeffrey Nov. 28, 1939 2,304,802 Crew d. Dec. 15, 1942 2,314,211 Hausler -4 Mar. 16, 1943 2,344,535 Clark Mar. 21, 1944 2,357,878 Crew Sept. 12, 1944 2,620,413' Johnson Dec. 2, 1952

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