7 Dec. 24, 1946. M. A. SCHWARTZ 2,413,079 'PHERMOSTAT Filed July 28, 194sv 4A a2 5 222 20 17 ~ .16 4723 Z@ _ 15 1.9 18 1'; 16 '. 32 55 2530 ' 294; 36 35 W04‘ . / . o 17 17 15 Z? 21 13 J1 ‘ IINVENTOR. Maze/s A . SCHWAQ 7'2, BY ivy/$141M ATTORNEY. UNlTED STATES PATENT 2,413,079 THERMOSTAT 1 I’Morris Schwartz, Los Angeles, Calif. Application July 28,'1943, Serial No. 496,446 4 Claims. (Cl. 200—139) This invention relates to improvements in ther mostats for electric irons, and is especially de signed for use in conjunction with electric steam 2 tures over which the strip is intended to function. Thus, if the bimetallic strip designed to function over a range of temperatures between 212° and. irons, or that type of iron embodying a steam 250° F., I prestress 0r pre?ex the strip to that generator for discharging steam on the ironing (71 position that it would assume when heated to surface of the iron. 212° F. In this manner the actual movement of Many materials, particular synthetic materials the strip under the in?uence of heat is merely that the iron is brought in contact with have that movement occasioned in its being heated critical temperature limits as ‘well as definite from 212” F. to 250° F. With the amount of‘ moisture requirements. In the case of electric 10 movement thus reduced the thermostat may be steam irons which embody a steam generator, made very compact so that it requires a mlni~ the thermostat must operate accurately so that mum amount of space in the body of the electric the iron will not be permitted to cool below 212° iron. otherwise the steam may condense to some Still another object of the invention is to pro extent and injuriously affect the fabric or ma vide a thermostat for electric irons wherein the terlal. At the same time the thermostat may be thermal responsive element having the above required to prevent the temperature exceeding mentioned characteristics, operates a lever car 250° F. in orderto avoid scorching or burning of the material that is being pressed. A primary object of the present invention is to 20 provide an improved thermostat for use in elec tric irons and analogous devices which will e?l-' ciently function to Open and close the electric circuit containing the heating element so as to rying a contact in its swinging end which multi plies the movernent of the thermal responsive ele ment, rendering the thermostat quite sensitive to variations in temperature. This contact is ar ranged to engage and bridge two opposed con tacts that are resiliently mounted and by this arrangement the connection of conductors to the accurately maintain the desired temperature. 25 lever itself is avoided which otherwise might in More particularly, an object of the invention terfere with or hamper its movement. is to provide a thermostat wherein the thermal With the foregoing and other objects in view, responsive means is heat insulated from the body which will be made manifest in the following de of the iron or heat conductors connected thcre= tailed description, and specifically pointed out in to, and which is influenced practically entirely the appended claims, reference is had to the ac by heat that is radiated from the body of the iron. companying drawing for an illustrative embodi= By utilizing-the radiated heat from the body of merit of the invention, wherein: the iron as distinguished from conducted heat, Figure l is a view in side elevation of the im the thermostat can ‘be made much more sensi~ proved thermostat embodying the present inver tive in operation and when operated will operate tion; ' in accordance with temperatures more truly rep resentative of the ironing surface. If the thermal responsive means is largely in?uenced by con ducted heat there is apt to be a considerable time lag between the ironing surface reaching a cer-: ‘ tain temperature. The utilization of radiated heat from the body of the iron itself eliminates v nearly all of this time lag. Another object of the invention is to provide a thermostat employing as its thermal responsive means a bimetallic strip, i. e. a strip formed of two metals rigidly connected together which Fig, 2 is atop plan view of the same; Fig. 3 is a longitudinal vertical section through the thermostat; and Figs. Li and 5 are horizontal sections taken sub stantially upon the lines 43-11‘ and 5-5 on Fig. 3, respectively, in the directions indicated. Referring to the accompanying drawing where in similar reference characters designate similar parts throughout, the improved thermostat com prises an outer housing; or framework which is receivable in a recess provided therefor in the body of an electric iron. This outer housing is preferably formed of sheet metal having a bot metals have different coefficients of expansion so that under the influence of temperature the strip tom iii, upstanding sides M, and a cover 112. The ' will alternately tend to curve and straighten and 50 cover is preferably provided with ears or lugs l3 in so doing to provide a means for holding the attached to the sides, such as by screws M. strip in a normal or cold position that is the In the bottom of the housing there is formed same as the position the strip would naturally an elongated opening it at the ends of which assume when the strip is subjected to the tem there are rivets it equipped with heat insulation perature at one end of the range of tempera 55 ii" and which serve to support a thermal respon aniaore 3 sive element it therebetween over the opening it». adapted to be bridged by the contact 25. The bars 3c are connected by ?exible conductors 3b and til to a binding post, generally indicated at of expansion. tacts be and 35 in circuit with a suitable source of electric current and with the heating element The thermal responsive element that I prefer to employ consists merely of an elongated strip formed of two metals having di?erent coe?iicients 38. Conductors as and at serve to place the con That metal having the greatest coemcient of expansion is disposed lowermost. of theiron. The upper lever 28 carries a pin 65 The strip being exposed over the opening I15 projecting through an aperture in the top of the receives heat from the body of the iron prin housing and which is engaged by a leaf spring £32 cipally by radiation, and when heated the dif which urges the lever into a clockwise direction ference in the coeiilcients of expansion produce 10 about its fulcrum 29, as viewed in Fig. 3. in. the a bending or curving of the strip to a somewhat top of the housing there is a nut :33 into which greater degree than is illustrated in Fig. 3. The is threaded a shank Liél carrying a cam 65 engage» ends of the strip are notched so as to partially receive the rivets whereby the strip is maintained in place. In the preferred 101m of construction a pin it extends transversely across the housing against the top of the strip and is so arranged as to main tain the strip in the pre?exed or pre-stressed condition. Thus, if the thermostat is intended 20 to open the circuit of the electric heating element of the iron at its minimum temperature of 212° F., pin i9 is so arranged as to flex the strip it into that position that the strip would assume under a temperature of 212° F, thereon as required. . It will be appreciated that as the bimetallic strip ‘is actuated by radiated heat,‘ as dis— tinguished from conducted heat, that it will promptly move in accordance with temperature variations of the body of the iron. When the bi metallic strip is heated to such an extent that it ‘will flex or curve beyond the curvature this al= lows the lower lever to descend causing contact 25 to disengage contacts 35 and 35, and thus open the circuit to aheating element. When the tem perature of the body of the iron falls and the i ' In other words, despite cooling of the strip it below a temperature of 212° F. the strip will not straighten to any greater degree than that degree _of straightness that it has at 212° F. In this man: ner provision need only be made for accommo dating movements of the strip it between 212° F. and the upper limit of the range of temperatures over which the thermostat must operate. Conse quently the thermostat can be made quite com pact in form. able with the upper lever 28. This shank can be rotated by means of a handle at. Leaf spring 652 serves to yieldably maintain the upper lever 28 in engagement with the cam and on rotation of the handle bit the upper lever '28 may be raised or lowered to raise and lower the contacts as and 85 _ - bimetallic strip returns to the position shown con tact Z5 reestablishes the electric circuit across contacts 3% and 35 and through the heating ele ment so as to bring the temperature of the iron back up to the desired degree. The desired degree can, of course, be varied by rotating handle lit and ., Above the bimetallic strip there is disposed a lever having a lower section 20 equipped with trunnions 2i that serve to pivotally mount the lever at one end between the sides of the housing. ‘ cam d5 so as to raise and lower the positions of the contacts 3d and 35. As these contacts are yielda This lever is also made up of an upper section 22 40 bly mounted by means of their‘leaf springs 32 and 33, they will not interfere with movements that is attached to the lever by means of rivets of the lower lever. It will be noted that as no conductors, such as conductors 86 and 37, are connected to the lower lever that these conduc= tors will in no way interfere with the proper or free movement of the lower lever which is 9.0-‘ 23. Electrical insulating material Ed is disposed between these sections‘ to electrically insulate the outer section 22 from the inner or lowersection 20. An electrical contact 25 is connected by the tuated by the thermal responsive means. outer or swinging end of the lever. 26 is a screw that is threaded into the inner or lower section 28 of the lever and which has its head bearing Ordinarily, as the iron cools, contraction of the'lower metal of the bimetallic strip is su?icient to actuate this strip with adequate force or power against the thermal responsive element 68. By to lift the lower lever. rotation of the screw the ‘adjustment of the lever with relation to the thermal responsive element is possible. I prefer to locate the screw 26 a dis However, in some in stances it may be desirable to place a steel spring d‘! between the rivets and which will bear against the under side of the bimetallic strip at all times, urging it to return to‘ its uppermost position ‘ tance from the fulcrum or axis of rotation of the lever a distance of approximately one-?fth of its entire length so that movements of the bimetallic strip it under the influence of heat are magni?ed against pin iii. The e?ect of this spring is, of course, overcome when the bimetallic strip is ?exed under the influence of heat, but when the strip is allowed to cool the spring may become . A U-shaped spring 21 has its ends extending 60 effective to urge the strip to return to its initial position and actuate the lower lever accordingly. outwardly through the sides ii of the housing ' From the above-described construction it will and extends over the top of the lower section 20. be appreciated that a simple compact sturdy This spring serves to gently but continually hold thermostat is provided which is highly sensitive the lever so that screw 26 is in engagement with and quickly responsive to temperature variations or multiplied approximately ?ve times at the lo cation of the contact 25. the bimetallic strip. '65 _ of the iron in which it may be installed, the Above the lever there is disposed an upper lever arrangement being such that the tendency to the body of which is indicated at 28 fulcrumed by _ wards arcing across the contacts 25, 34, and 35 -means of trunnions‘29 on the sides of the hous on the making or breaking of the electric circuit ing. Bars 30 are riveted or otherwise attached to‘ its underside and are electrically insulated there 70 is reduced to a minimum. The construction is highly advantageous over thermostats employ from such as by insulation 3L. Each of these bars ing snap-over discs which under the in?uence of adjacent its outer end has a leaf spring secured thereto,these springs being indicated at 32 and 33, see Fig. 4. At the outer ends of these springs. heat snap from a concave-convex condition irito a convexo-concave condition. Such snap-over discs require considerable force to actuate them there are contacts 34 and 35. These contacts are 75 ' 5 2,413,079 and are consequently slow in operation. When operated the snapping is apt to cause injury to the contacts which is entirely avoided in the smooth operation of the present thermostat. Various changes may be made in the details of construction without departing from the spirit and scope of the invention as de?ned by the appended claims, wherein I claim: range over which it is to operate and from which position upon a rise in temperature it will con tinue to bow in the same direction whereby until said end of the temperature range is reached said means and lever will remain undisturbed, and on a rise in temperature therefrom, said means and lever will be moved in accordance with tem 1. A thermostat for use in electric irons and 3. A thermostat for use in electric irons and perature variations. the like comprising a‘bimetallic element mounted 10 the like comprising a bimetallic element ar between spaced points and adapted to flex there ranged to ?ex under the in?uence of heat, means between under the in?uence of heat, a lever prestressing the bimetallic element in the direc carrying a contact engageable with and disen tion in which it ?exes under the in?uence of gageable from another contact to open and close heat to the position which it assumes at the lower an electric circuit, and means for causing the 15 end of the temperature range over which it is lever to be moved in response to ?exures of the intended to operate, and means operable by the bimetallic element but in such a manner that ?exing of the bimetallic element for controlling the movements of the contact will be at a multi an electric circuit whereby upon a rise in tem plied rate of the movements of the bimetallic perature the bimetallic element will not be dis element, said bimetallic element being bowed and 20 turbed nor caused to move until said lower end prestressed to a position that it would assume of the temperature range is reached, and there under the in?uence of heat at one end of the after it will continue to ?ex in the same direc temperature range over which itis to operate and tion beyond the position that it is caused to from which position upon a rise in temperature assume under the prestressing. it will continue to bow in the same direction 25 4. A thermostat for use in electric irons and whereby until said end of the temperature range the like comprising a, bimetallic element arranged is reached said means and lever will remain un to ?ex under the influence of heat, means pre- ' , disturbed, and on a rise in temperature there from, said means and lever will be movedpin ' accordance with’ temperature variations. ‘ 2. A thermostat for use in electric irons and the like comprising a bimetallic element mounted between spaced points and adapted to ?ex there between under the influence of heat, a pair of electrical contacts in an electric circuit one of' stressing the bimetallic element in the direction in which it?exes under the in?uence of heat to 30 the position which it assumes at the lower end of the temperature range over which it is intended to operate, and means operable by the ?exing of the bimetallic element for controlling an electric circuit whereby upon a rise in temperature the bimetallic element will not be disturbed nor caused to move until said lower end of the tem perature range is reached, and thereafter it will continue to ?ex in the same direction beyond the position that it is caused to assume under the which is movable into and out of engagement" with the other, and means for moving one of the contacts toward and away from the other by the bimetallic element at a multiplied rate of movement of the bimetallic element, said his 40 prestressing, the circuit control means being metallic element being bowed and prestressed to arranged to magnify movements of the bimetallic a position that it would assume under the in element. ?uence of heat at one end of the temperature MORRIS A. SCHWARTZ.