I Dec. 24, 1946. G_ cRlSE Q 2313i“) THERKOSTATIC SWITCH Filed May 27, 1943 g5 // éwg M4444“ \ V 6 _ ' 3% gearyelZ/Cm %',&%W M Patented Dec. ‘24, 1946 ‘ 2,413,100 UNITED STATES PATENT ' ‘OFFICE ' George W. Crise, Columbus, Ohio, asslgnor to ‘Crise Electric Manufacturing Company, Columbus, Ohio, a corporation of Ohio Application May 27, 1943, Serial No. 488,706 7 Claims. (Cl, 200-138) 1 . This invention relates to thermostatic switches, having particular reference to switches of the type causing automatic opening and closing of electrical circuits in response to temperature vari - ations.‘ In the construction of such switches, it is'a common expedient to employ ?exible bimetallic strips as the temperature-responsive motivating element for moving the associated circuit closing 2 ture, magnetic attraction is created between the magnet and the armature to such a degree as to provide ?exing of the bimetallic element beyond that which said element normally assumes at the temperature when the attraction occurs, such at— , traction being utilized to accelerate the movement of the bimetallic element in effecting its circuit completing and breaking operations. Still, a further object of the invention resides in or opening contact devices into and out of phys~ iii providing a switch of the character aforesaid in ical engagement with each other. Due to the which the bimetallic element is formed with one relatively slow movement of such bimetallic ele of the contact devices of the switch and the mag ments, dii‘llculty has been encountered in provid net armature is provided with a second contact ing desired rapidity (snap action) in bringing the contact devices into and out of engagement, in order to avoid or minimize destructive arcing eiiects produced as a result of electric current device, the latter being adjustably carried by the armature for effecting desired spacing of said con tact device and regulate the temperature differen tial required toeflect the separation of said de discharges in the air space between the devices vices. By temperature di?erential, I refer to the when the same are but slightly spaced. Another decrease in temperature from that required to disadvantage present in conventional switches 29 bring the contact devices into relative engage employing bimetallic elements is the difficulty in ment with regard to that temperature at which varying or controlling de?nitely the duration of said devices are separated. ' the periods in which the contact devices associAnother object is to provide a thermostatic ated with such elements remain incircuit-com switch characterized by its simplicity and rugged pleting or interrupting relation. ness in construction, its high contact emciency, Accordingly, it is an object of the present in ease of adjustment and the fact that all the avail vention to provide a switch utilizing a bimetallic able differential is utilized to produce the maxi operating element for operating separable contact mum speed in causing the contact devices to make devices having embodied therein improved means and break an associated circuit. for effecting rapldlv executed relative movement For a further understanding of the invention, between said devices when the spacing of the lat reference is to be had to the following description ter is such as to be likely to produce damaging and the accompanying drawing,_wherein: electrical arcing therebetween. It is another object of the invention to provide a switch of the character set forth with improved Fig. l is a vertical sectional view taken through a thermostatic switch constructed in accordance ' with the present invention; adjustable means for controlling the duration of Fig. 2 is a top plan view thereof with the cover the periods in which the contact devices are plate or” the switch casing removed; caused to remain in circuit-closing engagement. Fig. 3 is a transverse cross sectional view taken For example, the period measured by the time re on the line II"—IIZ of Fig. 2. quired to effect separation between the contact 40 Referring more particularly to the drawing, devices when the switch responds to a decrease in the numeral i designates the casing of my im the temperature of the atmosphere surrounding proved switch, said casing embodying a base sec the bimetallic element with respect to that re tion 2 and a removable cover or lid section 3. In quired to effect closure of said devices, whereby to the particular form of the casing illustrated, the enable the switch to maintain an associated elec base section is formed with a depending bracket trical circuit in a complete condition for de?nite extension ii, to the lower portion of which is se intervals of time. cured, as by means of rivets 5, the fixed end of a A further object of the invention is to provide a ?exible bimetallic element 6. This element, as switch utilizing a bimetallic temperature-respon usual, is composed of a pair of metallic strips with sive element having the free or movable end there one strip having a higher coeiiicient of expansion of provided with a permanent magnet normally than the other, the strips being so mounted and spaced from a longitudinally adjustable armature, relatively united as to produce flexing movement the latter being so disposed that when the bi of the free end thereof in response to variations metallic element is ?exed to bring the magnet into in temperature of the surrounding atmosphere. relatively close proximity to the end of the arma 65 As shown, the element 8 is provided with a U-bend - . asiaioo . 3 - ‘l intermediately of its length in order to provide an upwardly extending arm 3 which terminates within the interior of the casing after passing through an opening 9 provided in the bottom of the base section 2. Adjacent to its free ?exible upper end, the arm 8 of the bimetallic element is apertured for the reception of a contact device 50. Said device, ‘ a the semicircular-1y headed end of the contact device I ii, and a complemental wire 32 extends from the strip 36 to the metallic bushing it of the bearing block Id. The conductors 2i and 28 lead to trunk conductors 33 and 36, a lead 35 may extend to an electric motor 36 employed for any suitable purpose, such as driving the fan or blower of the furnace of a forced air heating in this instance, partakes of the form of a rivet, having a shank which is semicircularly headed at one end and cylindrically- headed as at M at its opposite end. Desirably, the contact device I0 is formed from copper, silver or other good conducting material for electric current. The device ii] is carried by mica or other dielectric disks i2 disposed on opposite sides of the arm 8, in order that the contact it may be elec trically spaced or insulated from the bimetallic element. Also, supported on the shank of the contact device it is a permanent magnet i3, pref 20 erably of disk-like form and having north and system, a lead 31 extending from the return side of the motor, to the conductor 28, the circuit for the motor thus being opened or closed by the operation of the contact devices and their asso ciated parts. When the switch isused in con» nection with the forced air heating system, the switch casing i may be mounted on the bonnet or plenum housing of the furnace of such a sys tem, so that the bimetallic element will extend into the plenum chamber of the furnace, being thereby responsive to the temperature of the air south polarity regions. The magnet, the insu the armature i 5 is adjusted longitudinally toward . passing through said chamber. From the foregoing, it will be evident that when lating disk, and the contact device iii are uni the magnet and the bimetallic strip to reduce‘ tarily carried by and secured to the free end of the spacing between these parts, the switch will the bimetallic element by the heads formed at 25 respond to a lower environmental temperature to the opposite ends of said contact device. bring the contacts iii and it into circuit~complet~ Arranged within the casing i is a stationary ing engagement than when the armature is re; bearing block it, preferably of an insulating ma tracted to increase the spacing. When so re terial. This bloci; is bored to receive a station tracted, a higher environmental temperature is, ary metallic bushing it, which is internally of course, necessitated to cause the switch to com threaded for‘the reception of the external threads plete the associated circuit. In this manner, the provided on a tubular steel armature it. By the _ response of the switch to temperature is governed rotation’ of the armature, it‘will be seen that the solely by the spacing or relationship between the same may be advanced or retracted longitudinally armature and the magnet. ' with respect to the magnet it in order to control 35 The time period produced by a decrease in_ the spacing therebetween and render the switch temperature for breaking a completed circuit is responsive in a circuit opening or closing sense controlled by the positions of the differential to varying temperatures affecting the bimetallic screw iii and its associated contact 26. With the element 5. A manipulating wheel if? is thread armature in a given position of adjustment, it edly mounted on the outer end of the armature 4.0 will be seen that by retracting the screw it and and is held in secured engagement therewith by its contact 29 relative to the end of the armature a lock nut 58. The wheel i? may be formed from facingthe magnet 53, a longer period of time or . a molded plastic, if desired, ‘having dielectric a greater drop in temperature will be required properties. Preferably, the wheel has its outer to produce sumcient tension of the free end of I 45 surface suitably graduated to indicate temper the bimetallic strip to cause it to overcome the ature in degrees Fahrenheit and this surface may close attraction between the magnet and the be adjusted relatively to a suitable indexing point armature than when the screw it and its contact to provide exterior indication of the temperature is advanced to a more forward position. It will adjustment of the armature. be appreciated that the degree of attraction beThe armature is provided with an internally 50 tween the magnet '63 and the opposing end of threaded bore which is adapted to receive the external threads of a temperature di?’erential controlling screw 99. The inner end of this screw the armature increases or decreases with the dis tance therebetween. Since the contact 28 is non magnetic, it does not in?uence the magnet, this latter function being assigned to the armature. device 20 which, through the longitudinal adjust 55 ,Hence, the armature is used for temperature con ment of the screw i9, may be brought into desired trol and the screw is for differential regulation relationship with the first-named contact device By di?‘erential regulation, I refer to the duration it. To facilitate adjustment of the screw t9, of the operating cycle of ‘ the electrical apparatus the outer end of the latter is equipped with a in the circuit governed by the switch. The mag 60 knob 2| having its outer surface suitably cali net and armature are in all their operative posi brated, as at 22, for disclosing, exteriorly of the tions spaced from each other, and their positions casing, the adjustment of said screw. A coil of relative approach are limited by the engage spring 23 may be used to exert pressure on the ment of the contacts H and 20. knob 2! for the purpose of maintaining the screw The operation of the thermostatic switch when 65 l9 in set positions of adjustment. used in a furnace system may be explained as Many di?erent devices may be provided for follows: Assuming that the asociated furnace has conducting electrical current to the contact de been cold and is in process of warming up, the vices lU and 20. By way of illustration, the eas increased temperature in the plenum chamber ing, in this instance, has been shown as provided will cause the bimetallic element to ?ex in order 70 with a block 26 of an insulating material. This to advance the contact device it and the mag block carries a pair of, spaced upstanding threaded net iii gradually toward the inner end of the posts 25.carrying nuts 26. Conductors 2'? and 2d armature it. This movement is continued with are shown as electrically connected with these temperature increase until the attraction of the posts and with copper strips 29 and 30 carried magnet it‘ with respect to the armature is sum thereby. A wire 3i extends from the strip 29% i0 75 ciently great to overcome normal rigidity of the carries in ?xed engagement therewith a contact asiaioo ‘n w bimetallic element 8. at this time, the magnetic elated therewith, such as a furnace fan, fuel feeding atelier, incl control valve or the like. attraction is such that the contact devices will snap together and the circuit of ‘the switch will I claim: , be complete, causing the fan, motor or other 1. In thermostatic switch, a bimetallic strip apparatus in the circuit to be energized. 5 anchor at one end and adapated to have its When, in the course of time, the furnace has free end de?ected by temperature variations, a cooled so that the bimetallic element, which for magnet carried by the free end of said strip, a this application has its high expanding metal contact movable in unison with the deflectable strip on the inside of its bend, has generated su?i end of said strip and said magnet, atemperature cient tension to overcome the magnetic attraction 10 controlling armature adjustably mounted to vary between the magnet and the armature, thus pull~ the spacing between one end thereof and said ing the magnet away from the armature so that magnet, differential varying element movable engagement between the contact devices will be bodily with said armature and adjustable longi broken suddenly with spring action on the part ’ of the free end of the bimetallic element. tudinally and independently with respect to the Be sult as had the contacts separated at a much faster rate and to a greater distance than their actual mechanical movement. armature, and a second contact carried by said element adapted to be brought into and out of engagei'nent with said ?rst contact upon deflection of nail strip. ‘9 In thermostatic switch, a supporting base, bimetallic strip anchored at one end to said base and having its free end de?ectable in re adjusting screw is, which can be adjusted or r = naliy threaded bore provided longitudinally and cause of the strong magnetic ?eld across the path of the ensuing arc, the flame will be thrown laterally out of the natural shortest path and rapidly extinguished, with the same e?ect and re sa sponse to temperature variations, a contact mem Since appreciable power is required to separate ber carried by the free end of said strip, a perma the contact elements against the attraction of the magnet, a temperature differential results, de~ 25 nent magnet surrounding said member and mov able in unison therewith upon deflection of the pending upon the strength of the magnet and its free end of said strip, a temperature regulating proximity to the armature. As the strength of and armature-forming screw, mounting means the magnet is a fixed quantity, the only remain for said screw carried by said base, said means ing variable is the resistance between the magnet and the armature when the contact devices ill 30 admittinf7 oi’ adjustment of said screw toward and away from said magnet, a differential ad and 2c are in physical engagement. Thus, the justing screw having engagement with an inter contact device 20 is mounted on the differential axially in said temperature-regulating screw, tracted with respect to the inner end of the and a second contact member carried by the armature it by turning the knob 2!. Therefore, 35 differential regulating screw in registration with the closed contact position of the magnet 93 with said ?rst contact member. relation to the armature I6 is under complete 3. In a thermostatic switch, a supporting base, manual control. The difference between the cir== a bimetallic strip ?xed at one end to said base (‘nit-making and interrupting temperatures of ‘the and having its free end disposed for flexing move ment in response to temperature variations, a magnet and a contact member carried by and bodily movable with the free end of said strip, a thermostat switch are fully adjustable by the op~ eration of the knob 2i. Inasmuch as the armature, the ‘screw iii and the contact device to rotate as a unit by turning the wheel ii and thereby approach or recede from the bimetallic element, any working range of tem perature to which the switch is responsive may be obtained through the manual adjustment of temperature-regulating and armature-forming 45 screw, a threaded bearing carried by said base for the reception of said screw, a manually op erated control carried by one end of said screw 1 for effecting its rotation, whereby to govern the It is important to note that the temperature at spacing between the opposite end of said screw which the switch makes circuit-completing con and said magnet, and a manually adjustable dif tact is determined by the position of the armature ferential regulating screw mounted in a threaded i6 and not by the position of the contact 20. This bore formed longitudinally and axially in the is because of the fact that the attraction of the temperature-regulating screw, one end of said magnet it causes the contacts ill and 20 to snap differential regulating screw being formed to pro together whenever they come within a ?xed dis 55 vide a second contact member arranged for co tance of separation, which on a standard ‘as-i action with said iirst=named contact member. the wheel ll. sembly may be 33; of an inch. This is a very ' a. In a thermostatic switch, a supporting base, a bimetallic strip ?xed at one end to said base Code specifies certain limits at which fan switches and having its free end disposed for flexing move must contact, a condition with which the present (iii ment in response to temperature variations, a construction complies. Furthermore, the con magnet and a contact member carried by and struction permits accurate calibration of the bodily movable with the. free end of said strip, a thermostatic switch by means of the locking nut temperature-regulating and armature-forming is on the armature l6, and this calibration of the screw, a threaded bearing carried by said base armature is unaffected by the adjustment of the for the reception of said screw, a manually oper differential knob 2i. Another feature of impor ated control carried by one end of said screw for practical feature, since a standard Underwriters tance is that by increasing the magnetic action to absorb all the available power of the allowable differential, maximum advantage is obtained for the contact points and a greater current can be _ handled than would be possible with prior art designs. A further advantage is that the switch here disclosed admits of large variations in di?er , ential in order to regulate the operating cycle of the motor driven equipment which may be asso effecting its rotation, whereby to govern the spac ing between the opposite end 01' said screw and said magnet, a manually adjustable differential regulating screw mounted in a threaded bore formed longitudinally and axially in the tempera tum-regulating screw, one end of said differential regulating screw being formed to provide a sec ond contact member arranged for coaction with said first-named contact member, and circuit 2,418,100 7 forming conductors joined in current-transmit axially threaded therein for adjustment a: the ting union with said contact members. contact on the end thereof toward and away from ' , 5. In a thermostatic switch, a'supporting base, the contact element on said bimetallic strip, and a threaded bearing carried by said base,-a tem~ concentrically disposed calibrated manipulating perature-regulating armature screw supported by 5 devices accessible from the exterior of said casing: 'for e?ecting adjustment of said armature and said bearing for longitudinal movement, said screw having an internally threaded bore, a dif regulator. i'erentiai-adjusting screw adjustably mounted ‘in the threaded bore of said temperature-regulating screw, independently movable means, carried by ' " a _ I 7. A thermostatic switchcomprising acasing; , ‘ tension‘and body having strip having ofits said bottom onean stripadjacent end formed projecting ?xed with opening, to said upwardly a depending-ex; extension, a bimetallic through the the outer ends of said screws for manually ro tating and adjusting their operating positions, a contact member formed on the inner end vof the di?erential-regulating screw, a bimetallic strip said opening for unrestricted movement therein,v the upper de?ectable end of said strip being dis having a ?xed end and a free end de?ectable’in 15 posed within the con?nes of said casing, a contact ‘ response to temperature variations, and a second element and a permanent magnet carried by and contact member and a permanent magnet mount movable bodily in unison with the upper de?ect ed on, and bodily movable in unison with the able end of said strip, a bearing in said casing, de?ectable end of said strip. , 6. In a thermostatic switch, a casing, a bi a, temperature-regulating armature threadedly ' - 20 mounted in said bearing for adjusting 'r'novement - metallic strip ?xed at one end to said casing and having its'oppiosite end free for ?exing move ment in response to environmental temperature longitudinally toward and away from said arma ture, a di?erential regulator having a contact formed on one end thereof, said regulator being variations, a contact element and a surrounding coaxially threaded in said armature for adjusting permanent magnet carried by and movable bodily 25 movement of its contact toward and away fromv with the free de?ectable end of sai'dstrip, a tem the contact element of said bimetallic strip, and perature-regulating armature threadedly mount- I concentrically disposed calibrated manipulating ed in said casing for adjusting movement'toward ‘devices accessible exteriorly of said casing for and away from said magnet, a di?erential resu facilitating manual adjustment of said armature, lator having a contact at one end thereof, said‘ 30 and regulator. regulator being carried by‘ said armature and oo GEORGE W. CRISE.