US2415795A - Sadiron - Google Patents

Description

Feb. 11, 1947.

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4 Sheets-Sheet 4 Patented Feb. 11, 1947 SADIRON Ludvik J. Kooi, Chicago, Ill., assignor to Sunbeam Corporation, Chicago, lll., a corporation of Illinois Application October 3. 1941, Serial No. 413,571

1s claims. 1

This is a continuation in part of my application Serial No..357,722, illed September 2l, 1940, for sadiron.

The invention relates to sadirons, and has special reference to an electric sadiron of the socalled automatic type.

During the past few years the electric sadiron has developed from a relatively low wattage device to a high wattage structure in which heat is generated in the iron at a very rapid rate. This has required considerable improvement in the temperature controls therefor, which improvement has, however, been inadequate to provide an iron with the nicety and accuracy of control required to prevent complications from arising in the use of the iron. These complications are in general undesirable variations in the temperature of the iron due to improper operation of the thermostat mechanism which in turn is due primarily to uneven heat distribution in the iron. The problem of proper heat distribution, it will be recognized, is a particularly difficult one in a sadlron due to the fact that the iron is essentially a heat transfer mechanism, heat being generated at one point and dissipated at another, that time is required to transfer heat through the mass, and that the object to be controlled is essentially a surface, that is, the ironing surface of the sole plate, rather than aV solid or fluid volume. the temperature of which must be controlled as a body. Y

One of the difficulties arising in high wattage irons and due to slow or uneven heat distribution is an overshoot in temperature occurring when the iron is rst heated up. that is, when the iron is cold and is connected to a source of electrical energy. Under these circumstances the sole plate heats up rapidly, in fact so rapidly that other portions of the iron, including the thermostat, lag behind so that the supply of electrical energy to the heating element continues to flow after the ironing surface has reached the temperature for which the thermostat would nominally be set. Thereafter, as the iron reaches uniformity in temperature, the make and break of the contacts will occur at a substantially lower sole plate temperature. The result is that if the operator uses the iron too soon after placing it in service, an excessive temperature may be present at the sole plate,.causlng burning or scorching of the fabric.

One well known type of sadiron has employed for control purpose a strip of thermostatic metal located in heat transfer relation to the sole plate and forming the main temperature control. to-

2 gether with a secondary thermostat element acting between the main thermostat and the electrical contacts furthe purpose of modifying the movement of the contacts by the main thermostat in response to temperature lag.

While this form of control structure can be made to eliminate the initial overshoot of the iron which is essentially due to the temperature lag of the thermostat upon increasing temperature, it tends to produce defective operation when the thermostat becomes highly heated and the lag occurs in decreasing temperature, aS, for example, when the iron is being used in heavy service and there is a great heat drain from the ironing surface. Under these circumstances, the secondary thermostat becomes highly heated and reaches a higher temperature than would be the case if used for light service, for the reason that the heating element is on for a greater period of time and the secondary thermostat is so located as to be appreciably ailected by the heating element temperature. If, under these circumstances, the iron is put aside. the temperature of the sole plate will overrun because the main thermostat must be heated to a much higher temperature to overcome this additional or over-compensation by the secondary thermostat. The result is that the sole plate will reach a higher temperature than that for which the control is set, and ii' used for ironing at this time may cause damage to the material.

In another well known iron a'. supplementary heating element is employed to act lon the thermostat element to effect partial compensation. This construction, however, results in what I have termed poor regulation in the iron. By regulation I mean that property of the sole plate to maintain uniform temperatures under varying amounts of heat withdrawal. Thus, by good regulation is meant that the temperature of the solo plate will vary but littleunder varying amounts of heat withdrawal; in other words, the thermostat control will tend to maintain the same average temperature of the sole plate under full load as under idling or partial load. An iron with poor regulation tends to maintain a sole plate temperature much lower than that for which the iron is set when operating under a condition of heavy heat withdrawal.

All of these prior art devices are, however, mere approximations for the reason that the compensating device is located away from the main thermostat and in different heat transfer relationship with the sole plate, and are therefore subjected to temperature changes which may be 3 and frequently are different in magnitude and in direction from those to which the main thermostat may be subjected.

I have found that this and other objectionable characteristics of prior art irons are due to two factors, one being due to lag or differences in temperature between the main and secondary thermostat structures due to their difference in location and mounting, and the second being temperature lag due to the mass of the thermostat itself, that is, due to the slower rate at which the heat is disseminated through the thermostat structure.

An important object of the invention is the provision of a sadiron so constructed as to substantially eliminate the initial temperature overshoot thereof.

I have also aimed to provide a sadiron having improved temperature control characteristics including a rapid rise to the temperature for which the iron is set and uniform control of the temperature within a dened range with variation in the ironing conditions.

Another object of the invention is the provision of a novel sadiron construction wherein the iron is constructed to have a minimum of capacity for storing heat consistent with satisfactory strength and rigidity of the parts to thereby reduce to a minimum the lag in temperature change throughout the iron, and wherein this lag becomes suiilciently small as to be capable of compensation by a novel form of thermostat mechanism without the use of secondary thermostats and similar mechanisms heretofore associated with such thermostatic devices and to combine therewith a thermostat structure inherently capable of compensating for such lag so as to maintain a uniform ironing temperature under varying conditions of use.

A further object of the invention is the provision of a sadiron structure in which the thermostat element is maintained in close or good heat conducting relation to the sole plate and maintained in said relationship under all possible conditions of use, as described hereinafter, and wherein the switch is actuated by relatively small thermostat movement.

A further object of the invention is the provision of a sadiron structure in which the compensating means is located in close proximity and substantially unvarying relation to the object to be controlled so as to be subjected to substantially the same temperature influences as the main thermostat. and thereby effectuate good regulation of the iron and elimination of temperature overshoot under all conditions of use.

A further object of the invention is the provision of a sadiron of the character above described in which the compensating thermostat means may be incorporated either in a snapacting or a. slow-acting (as hereinafter defined) thermostat structure and switch control.

A still further object of the invention is the provision, as one species, of a sadiron wherein the temperature is controlled by a snap-acting thermostat operating through a very small amplitude, and wherein the center line of the thermostatic strip is so located with respect to the surface of the sole plate that operation of the contacts occurs close to the center line with most of the movement of the strip occurring on the opposite side of the center line from the contacts, whereby to open the contacts with maximum acceleration.

A still further object of the invention is the provision, as another species, of a sadiron wherein the temperature is controlled by a so-called slow-acting thermostat and in which the construction and arrangement promotes greater simplicity and economy in cost of manufacture while still maintaining the desirable features of cornpensation.

More particularly, my invention aims to provide a new combination of elements in a sadiron having characteristics adapted for light-weight and high wattage construction, together with reduced scorching hazard without loss in ironing speed.' This is accomplished by a structure possessing inherent characteristics of perfect compensation along with good regulation. This structure enables the maintenance of the main thermal response element in close and substantially unvarying heat transfer relation to the ironing surface under all conditions of temperature of the latter, thus reducing to a minimum the need for compensating action. This is attained in my invention with minimum friction loss, and consequently with freedom from erratic characteristics.

I have also aimed to provide a sadiron having a thermostat structure wherein improved manually controlled means operate on the thermostat to vary the temperature of operation, and in which such means function in the compensation of the thermostat.

A still further object of the invention is the provision of a sadiron structure having a snapacting thermostat wherein the temperature differential between the make and Vbreak of the contacts can be adjusted from the exterior of the iron.

I have further' aimed to provide a sadiron construction in which novel means function for manually adjusting the temperature of operation thereof, and wherein novel spring means is provided for maintaining the adjusted position of said means.

Other objects and advantages will appear from the following description and the accompanying drawings, in which- Figure l is a longitudinal section through a sadiron embodying my invention having a snap action thermostat, showing the contacts and thermostat in closed position and the adjusting means set for operation of the thermostat at a high temperature;

Fig. 2 is a fragmentary section similar to Figure 1 showing the thermostat and contacts in open position and the control mechanism in the Oil position;

Fig. 3 is a top view of the sole plate and attached mechanism, the cover being removed;

Fig. 4 is a view on the line 4-4 of Fig. 2;

Fig. 5 is a section on the line 5 5 of Fig. 2; Fig. 6 is a longitudinal section through a sadiron embodying my invention, having what may be termed a slow-acting thermostat, showing the contacts and adjusting means set as in Fig. 1;

Fig. 7 is a top view of the sole plate and attached mechanism of the slow-acting embodiment, the cover being removed;

Fig. 8 is a view substantially on the line 8 8 of Fig. 6;

Fig. 9 is a top view of the thermostat strip of thesiow-acting embodiment, removed from the iron;

Fig. 10 is a side view of the thermostat strip of Fig. 9, showing the shape to which it is formed acting thermostat strip adapted for use in the Fig. 6 embodiment; and

Fig. 12 is a side View of a further modified form of slow-acting thermostat adapted for use in the Fig. 6 embodiment.

The invention is herein shown as embodied in asadiron ci' the general structure described and claimed in Bisley Patent No. 2,277,034, granted March 24, 1942, entitled Sadiron, and includes a handle designated generally by the numeral 1 of molded plastic material, a cover 3 and a sole plate 9 having the structure therein described. Interposed between the handle 1 and the cover 3 is plate Il serving to permit circulation of air between the handle and the cover. Positioned in the forward end of the handle is a wheel I2 adapted upon its rotation to move a bar I3 in an up and down direction, depending upon the direction of rotation of the wheel I2, the bar being moved by a pinion I4 connected to the wheel and a rack I5 formed on the bar I3, movement of the bar being effectual for the purpose o! determining the normal operating temperature of the iron and for the purpose oi' shifting the switch mechanism, presently to be described, to an "Gif" position. As described in said application, the sole plate has a bracket I3 carrying a pair of contact bars I1 and I3 (Fig. 3) connected through ilngers I3 and 2l to the ends of an appliance cord 22 (Figure 1) for the transfer of electrical'energy to the contact bars I1 and I8. These bars are connected through conductors 23 and 24 to a heating element 25 seated in the sole plate 9 and retained in position by a plate 28. Extending longitudinally of the sole plate is a thermostat well designated generally by the numeral 21. The manually operable wheel adjustment and the sole plate structure shown in the present embodiment, together with certain related features, are claimed in Jepson Patents 2,266,708 and 2,277,439, granted December 16, 1941, and March 24, 1942, respectively.

According to the present invention, a thermostat embodying the principles shown in my copending application Serial No. 327,255, filed April l, 1940, entitled 'I'hermostat, now Patent No. 2,332,518, is employed including a bimetallic strip 23 having the shape characteristics shown in Figs. 1 and 5 and comprising a portion 29 having its edges tapering inwardly toward the central portion thereof as 4shown at 3|, and a portion 32 of serpentine configuration is seated in the well 21, the end of the portion 29 being conned against the bottom of the well by a plate 33 and a screw 34 which presses the strip firmly into contact with the bottom surface of the well and prevents movement thereof. The top side of the strip is the high expansion side of the metal. The opposite end of the strip terminates in an end portion 35 which seats upon a shoulder 36 at the opposite end of the well, this end portion being coniined thereagainst to prevent angular movement by means of an arm 31, in this instance integral with the bracket I6. A screw 3B threaded into the sole plate and projecting into the well bears against the end of the strip 2B, stressing the same longitudinally in order to cause the strip to move with a snap action. In this instance the strip is given an arcuate curve at atmospheric temperature such that the strip would curve upwardly toward the end 35 if that end were released, and the strip is stressed by drawing the end 35 down to the position shown in the drawings. 'I'he strip is initially curved in this manner in order to increase the range of temperature within which 6 y. the strip may operate without set, a wide range o! temperature operation being necessary for sadiron purposes.

This drawing of the end 35 down acts to put maximumbcnding stress on the strip at atmospheric temperature. Under this condition increase in temperature of the strip would reduce said bending stress. 'Ihe thermostatic strip carries a Pin 38 riveted thereto adjacent its midpoint and projecting upwardly, the upper end thereof being riveted to the end of a spring designated generally by lthe numeral 4I. The end o! the spring also carries a yoke 42 xedly attached thereto and insulated therefrom by insulating disks 43, the yoke having spaced arms 44 and 45 to which a contact plate 4B ls pivotally attached by a pin 41. The contact plate 43 carries a pair of spaced contacts 43 adapted to cooperate with spaced contacts 43 carried on the contact bars I 7 and I3 for the purpose of controlling the flow of current through the heating element 25.

The spring 4|, face view of which is shown in Fig. 3, comprises a strip of spring metal having a central tongue 5I fixed to a post 52 (Figure l) forming one of the connections between the sole plate and the cover 8, and side members 53 and 54 to which the tongue connects substantially at their mid-point as shown at 55. The side members 53 and 54 each terminate in a relatively narrow band of metal in the form of a reverse bend as shown at 58 and 51, the ends of these strips being integrally connected and forming the rear end of the spring 4I and being iixedly attached to the pin 33. The forward ends of the side members 53 and 54 are connected by a transverse strip 53 which has a slot 53 in its forward edge adapted to receive the lower end of the bar I3 therein, the bar having spaced upper and lower shoulders 6I and 62 adapted to bear on opposite sides of the spring, whereby longitudinal movement of the bar will cause the end of the Spring to be moved up or down. thus, when the end 5B of the spring is moved upward the opposite end of the spring applies a downward pressure on the thermostat strip through the pin 33. This serves to reduce the contact pressure and thus provides a condition wherein a smaller temperature rise of the thermostat 23 is necessary to open the contact points. This then, serves as a means of lowering the temperature setting of the sadiron. Inversely, downward movement of the end 53 would result in the iron operating at a higher temperature. The serpentine configuration of the spring portions 56-51 reduces restraint to angular motion of this end at the point where the pin 39 is fastened and that serves to give the above mentioned action to a degree approaching that which would be had if there were s, pivotal connection between this end of the pin and the spring. One of the advantages of this spring construction as compared with a conventional pivotal lever construction is the elimination of friction and the uncertainties of operation which accompany such friction. Also, simplicity of this construction promotes economy in cost of manufacture.

The thermostat strip and its mounting inherently functions to compensate for lag due to the mass of the thermostat and due to the location of the thermostat with respect to the ironing surface ofthe sole plate. This compensation is incorporated in the thermostat through its thermov static strip, the manner of its mounting and its shape characteristics. The strip may be considered functionally to consist of the parts 29 and 32, though as will be obvious trom the drawings, the strip functions as a unit in producing snap action and the thermostatic action incidental to this snap action, the serpentine coniiguration of the portion 32 providing the necessary softness or resiliency necessary for good snap action. However, the portion 29 may be looked upon as being the main thermostat conilned at one end by the screw Il, the opposite end thereof being free to move but being restrained in its angular movement by the portion 22 and the pin 3l. It will be seen by reference to my Patent No. 2,332,518, that ii the end of the portion 2l connected to the portion 32 is restrained against angular movement, but is free to impart longitudinal movement to the pin I9, this end portion will act, thermostatically, in a direction opposite to that oi the main part of the portion 20. Therefore, upon rapid increase in temperature of the strip under conditions in which the junction between the portions 29 and 32 lags behind the end portions oi' the strip, it is necessary for the portion 29 to attain a higher temperature to cause the strip to snap than would be the case if the strip were of uniform temperature from end to end. For this reason. upon rapid rise of temperature in the sole plate, the movable end of the thermostat portion 29 will act to compensate for its own lag in temperature. Where the temperature of the movable end is higher than that of the fixed end. the opposite eil'ect will obtain and proper compensation result. The amount of this angular restraint can be varied by varying the iiexibility of the portion 32 at the side of the pin 39 adjacent to the portion 29, thereby varying the additional energy which must be generated by the main body of the portion 2B in order to snap through center. The pin I9 itself is restrained from angular movement, that ls, from motion other than longitudinal, by means of its iixed connection to spring ll. Because of this ilxed connection the spring Il has provided the bands-56 and 51 which are so shaped as to ilex freely upon movement of the pin.

It will be seen that when the wheel l2 is rotated to a position to elevate the bar i3 and materially distort the spring Il, the spring will exert a substantial downward pressure on the bar which may tend to rotate the wheel and change the adjustment of the iron in response to the vibration occasioned by handling of the iron in service. In order to remove this thrust I have provided a second spring designated generally by the numeral 64. The spring 6l has the form shown in Figs. I to 3. inclusive, one end oi the spring having a. tongue B5 arranged to project into an opening in the lower end of the lever i3 and the opposite end thereof having an arcuate conguration as shown at 6B receivable in a groove G1 of a pin 6B seated in the forward end of the sole plate. It will be seen that this arrangement is such that as the bar Il is moved upward, the vertical component of the pressure from the spring M increases, which increase is substantially equal in magnitude to the down-` ward pull of the spring 4I, whereby the position of the bar I3 and the wheel i2 is substantially stabilized, regardless of the elevation of the bar and of the downward pull exercised by the spring ll. This construction provides a toggle action in which. forces are applied to the bar I3 which are substantially equal and opposite except for a slight excess of force in one direction used to take up whatever play may exist ln the linkage.

Attention is directed to the novel sadiron and 8 thermostat structure and* to the novel structureot the strip 2l and the manner in which it is incorporated into the sole-plate. It will be seen that the structure is auch as to practically perfectly compensate for the temperature lag due to 4the mass of the thermostat itself, because of the fact that a large portionof greatest primary thermostatic eifectiveness, l. e., that portion 2l adjacent to the attached end of the strip. is maintained at all times in approximate contact with the top surface of the well or sole plate to which the strip is attached. The remaining portion of the strip (mainly the compensating portion) being slightly farther spaced from said top surface but maintained in substantially unvarying relationship thereto. will exhibit some lag in response to the temperature of said surface, although ultimately responsive to only the temperature of said surface. In Figs. 1 and 2, this spacing of the compensating thermostat portion above the top surface of the well or sole plate is somewhat exaggerated for the purpose of clarity, and in actual practice I have used such a spacing that the distance between the bottom of the compensating portion of the strip and said top surface of the .well directly below the pin 30 is approximately .025 to .030 of an inch when the strip is in the upper or contact making position. Furthermore. by properly controlling the forces on the strip, the lag in the temperature change of the thennostat with respect to the temperature change at the ironing surface of the sole plate can be compensated for in an ideal manner. By properly controlling the forces on the strip I mean control of the amount of restraint to angular motion at the lfree portion of the strip effected either by variation in width and shape and therefore resistance to bending along the length of the strip or by variation in resilience of the pin Il with respect to bending. As previously stated. .the greater the degree of this angular restraint the greater will be the degree of compensation. In addition to providing compensation for lag in temperature ot the thermostat with respect to the immediate portion oi the sole plate to which it is mounted, it is possible to also compensate for the lag in temperature which exists between that portion of the sole plate to which the thermostat is fastened and that portion of the sole plate whose temperature it is desired to control. 'Ihis is particularly advantageous in a sadiron because here it is not feasible to mount the thermostat directly on the ironing surface which temperature it is desired to control. This introduces a secondary lag existing between the point where the thermostat is mounted and a remote point on the ironing surface whose temperature is to be controlled. which lag is also compensated for by the structure here disclosed.

Furthermore, the strip is supported in such fashion as to obtain maximum heat transfer to the strip and yet allow the contacts to be opened and closed with an adequate range of movement. To obtain a desirable small temperature diierential between cut in" and out o of the snap-acting thermostat the screw 38 is ad- Justed so as to obtain only a very limited degree of snap-acting energy. To obtain maximum acceleration of contact break commensurate with this small degree of snap-acting energy the structure is designed so that the portion of the thermostat strip adjacent to the pin I9 is at or close to the center line connecting the opposite end portions when the thermostat is in its "contacts on position. This corresponds to a position wherein anni the thrnistat strip is under maximum compressive stress and is the position shown in Fig. l. With this structure I obtain to the fullest degree these advantages incident to snapaction operation, viz., reduced frequency of contact make and break resulting in reduced contact wear and radio interference, without the accompanying disadvantage oi' large temperature differential between "cut in" and "cut olf.

According to the present invention the thermostat strip is mounted insuch close and substantially unvaryins relationship to the sole plate that the main thermostat portion 29 and the compensating thermostat portion in the region of the pin 39 are primarily and ultimately responsive to the sole plate temperature but with the compensating thermostat portion laggingn behind the main thermostat portion. By reason of this new interrelationship between the novel thermostat structure and the sadiron I obtain in a high wattage iron the combined advantages of good regulation above defined and eiective elimination of temperature overshoot under all conditions of operation. This appreciably reduces the hazards of scorching without impairing speed of ironing under normal variations and particularly under heavy load ironing.

I also desire to direct particular attention to the novel structure of the spring Il and .the functions resulting therefrom, as previously described. Another advantage of the invention lies in the cooperative action between the spring 64, the spring 4| and the bar I3, whereby the setting of the iron is stabilized against accidental changes.

My improved structure is such as to give practically ideal regulation in the iron, and such that the initial overshoot in temperature common to thermostatically controlled irons as well as subsequent over-shoots caused by extreme variations in the operating conditions ot the iron are practically eliminated.

It will also be observed that in this snap action embodiment the .construction is such that both the operating temperature of the iron and the differential may be set from the exterior of the iron, the operating temperature being regulated by means of the wheel i2 and the difierential between the closed position of the contacts, and the open position thereof being determined by the stress applied to the strip through the screw 38.

In Figs. 6 to 10, inclusive, I have shown another embodiment of my invention characterized by what I have termed a slow-acting thermostat action as contrasted with snap action in the embodiment previously described. In these figures like reference numerals are used to designate generally similar parts in the description of the snap action embodiment. This slow-acting thermostat embodiment employs use of the same principle as in the snap action embodiment, of obtaining compensation within the main thermostat itself by imposing restraint -to angular motion of its free portion and of mounting the thermostat strip with its main and compensating portions in such close proximity to the sole plate as to be primarily and ultimately responsive thereto and practically independent of variations in load condition but with the compensating thermostat portion lagging behind the main thermostat portion. As shown in Fig. 6 this restraint to angular motion is accomplished through the pin connection 39 between the thermostat strip 2l' and the control spring Ii. 'l'his connection 10 lower endto thermostat 28' and by a threaded fastening between its upper end and the control spring 4i. In this case the thermostat strip is mounted in the same position in the well 21 in the sole plate and is rigidly fixed therein by a plate which is rmly pressed into position and retained therein by small staked projections BS. It will be noted from Fig. 9 that the sides of the thermostat strip are tapered towards decreasing width at the free end and merged into a serpentine conguration Il terminating in an enlarged flat end portion 12 to which the pin 39 is riveted. As in the snap acting embodiment the proper degree of restraint to angular motion of the free end is determined by trial to achieve proper degree of compensation. In the particular embodiment shown, a thinner thermostat strip is used than in the snap acting embodiment shown. A thinner thermostat gives more thermostatic lag, and this condition was found to require a greater degree of compensation than was necessary in the snap acting embodiment. For this purpose I have employed in actual practice a thermostat strip 28' of approximately .020" as compared with a thermostat strip of approximately .025" in the snap acting embodiment previously described. These dimensions are given for purpose of illustration in a sadiron structure of the kind shown in the drawings, and not for limitation. In the snap acting embodiment it is possible to obtain a desired long cycle of on and off operation by adjustment of the snap acting energy of the thermostat. In the slow acting case frequency of thermostat operation is controlled yby the intentional introduction of lagging thermostatic response by the use of thinner material and by including in the thermostat strip a step or oifset 13 shown in the modiied form, Figs. il and l2. This step serves to remove the major portion of the thermostat strip to a position slightly more remote from the sole plate and this results in a more lagging response of the thermostat with respect to the sole plate. As a consequence of this increased lag more compensation is necessary'to prevent initial overshoot of the iron temperature when heating from cold. This greater compemation is achieved by introducing more restraint to angular motion of the free end by using a thermostat construction shown in plan in Fig. 11. As is apparent from a comparison of Figs. 9 and 11, the portion i4 of Fig. l1 oiers greater resistance to bending than the portion 'Il of Fig. 9. That the step 13 is effective in producing the desired result is indicated by the fact that a cycle period of slightly less than 2 min- Utes is obtained with the thermostat of Fig. 9 and a cycle period of approximately 21/2 minutes is obtained with the thermostat shown in Fig. 11. From a consideration of all factors involved a cycle period of about 2% minutes has been regarded as most desirable. This cycle period is also obtained in the snap acting embodiment.

As previously mentioned, the frequency of thermostat action in the snap acting embodiment is controlled by adjusting the amount of snap acting energy by means of screw 38 which is accessible from the outside of the iron. In both manufacturing and servicing such an iron this is a distinct advantage. On the other hand, in the case oi' the slow-acting thermostat embodiment I have found it desirable to intentionally introduce a lagging response of the thermostat relative to the sole plate temperature as by means of the offset 'Il in the thermostat strip 1li preis accomplished by riveting the pin 39' at its viously described, to obtain the desirable long 11 cycle period of contact operation. More particularly| it is characteristic of a snap acting thermostat to out off at a given temperature and cut in at a given lower temperature, this dii'- ferential between the two being dependent on the degree of snap energy in the device. On the other hand, a simple slow-acting thermostat cuts in at the same temperature that it cuts ofi. It should be noted that we are referring here to temperature of the thermostat strip itself. By virtue oi the fact that the thermostat strip is never in perfect heat relationship with the sole plate surface its temperature will lag more or less behind the temperature of the sole plate surface, and as a consequence, the temperature of the sole plate surface itself will be lower at the instant of thermostat cut in as compared with its (the sole plate surface) temperature at the instant of thermostat out off, the difference in this case being proportional to the degree of lag of thermostat temperature behind sole plate temperature. As an obvious accompanying consequence oi this lag, the frequency of thermostat operation will be reduced as this lag is increased.

In this slow-acting embodiment I have employed a single set of Contact points 15 and 16 with the movable contact point 15 connected into` the circuit by means of a very thin and flexible strip of silver 11 approximately .0015" in thickness, this conductor connecting the movable point 15 with the line terminal bar I8. This flexibility is desirable to permit virtually unrestricted motion of the contact point 15. The contact points are located olf center relative to the pin 39', but there is no functional reason for this other than that it lends itself to more economical manufacture. The spring member 4|' is in principle the same as spring 4I above described. Also, the spring 64' functions in the same manner as the spring 64. The diierence in shape of the connection between the bar I3 and the springs 4I' and 64' as compared with that shown in the snap acting embodiment does not change the operation but permits economy in cost of manufacture.

As shown in Figs. l and 12, the thermostat strips in the slow-acting modications are preformed in a manner similar to and for the reason previously described in connection with the preforming of the strip 28 of the snap acting construction. r

Attention is now directed to an important iactor dealing with the novel relationship of the thermally responsive means and the sole plate. In this relationship the major length of the primary thermostat portion is always in close and consequently very goed thermal relation to the ironing surface. IFurthermore, this relationship is maintained substantially unvarying throughout all conditions of use of the iron as distinguished from prior art sadirons in which the main thermal element deflects to a position considerably removed from the influence of the ironing surface of the sole plate particularly at A the high temperature settings. According to the present invention various temperature settings are obtained by applying greater or less pressure acting against the tendency of the thermostat to move upon a rise in its temperature. Thus, instead of permitting the main thermostat to freely deflect through a distance corresponding with a high temperature setting. as in the prior art, I have in this invention provided 'a thermostat structure coacting with the sole plate in such manner as to be maintained in a close and substantially unvarying relation to the ironing surface throughout the entire rise in temperature from room temperature to the -selected temperature until when the lnal temperature is reached the thermostat by virtue of said tempelature change exhibits suiilcient force to overcome the previously applied pressure and only then exhibits movement to open the electrical circuit to the heating element. This condition applies in both the slow acting and snap acting embodiments of the invention herein illustrated. Thus, it is observed that the entire length of the main thermostat will remain in substantially the same close thermal relationship to the ironing surface when operating under all temperature settings as it does at room temperature. Under this relationship the main thermostat exhibits far less lag in response to change of temperature in the ironing surface and thusrequires considerably less compensating effect than if the thermostat were allowed to freely deflect as in the prior art sadirons. Furthermore, with this new relationship is combined the location of a secondary thermostat in a region where it is primarily and ultimately responsive to the temperature of the sole plate rather than to the varying and unpredictable temperatures associated with the space between the sole plate structure and the shell.

By providing an automatic sadiron which effectively eliminates overshoot and also embodies the characteristic of good regulation, I provide a sadiron which appreciably reduces thehazard of scorching without impairing its Speed of ironing when used under heavy load. In other words, a structure such as I have here disclosed can be set in practical ironing to maintain a temperature of value sufficiently low to effectively reduce scorching hazard. Because of the compensating feature disclosed, the sole plate temperature will not be permitted to rise above this value at any time, which factor becomes important when folding or pressing material previously freed of most of its moisture andthus in a. condition where it may be easily scorched. And because of the feature of good regulation, the sole plate temperature will not be permitted to drop appreciably below the above set value When ironing under a condition of heavy heat withdrawal (assuming that the available electrical input is adequate), which condition is met when beginning the operation of ironing of a fully dampened cloth.

Experience has shown that the scorching tendency of organic materials (particularly cloths) is critically related to temperature. Thus little or no scorching will occur at temperatures below 350 F. even when subjected to such temperature for an almost infinite period of time. As the temperature is raisechto 450 F., scorching is more likely to occur, but under a still abnormal period of exposure. However, at temperatures above 450 F. scorching occurs under an exposure period of but a few seconds, and at 600 F. it occurs practically instantaneously. These iigures are signicant when itis borne in mind that many present day automatic irons reach temperatures of 600 F. and sometimes higher under certain conditions of use, such high temperatures being invariably due to overshoot and poor reg- 0 ulation, which last circumstance compels the manufacturer to adjust the sadlron to maintain such a given high temperature under idling in order to obtain fast ironing under heavy load.

On the other hand, my experience has demon- 5 strated that an iron of conventional design, size and shape is capable oi' delivering a heat input into dampened material of over 1500 watts, with its sole plate surface maintained by this heavy withdrawal of heat atv a temperature of only 350 F. and in the hands of a fast operator. It follows, then, if such an iron were provided with a perfect thermostatic control which would maintain the sole plate surface at a. xed temperature of approximately 350 F. under all conditions of possible use (assuming an available electrical input greater than the maximum instantaneous demand); there would exist an iron of greater possible ironing speed than that achieved with the present 1000 watt irons, and yet possessing the very desirable characteristic of providing essential freedom from the possibility of scorching. I believe that my invention provides the closest approach to this ideal using a bimetallic thermostat strip in the thermostat control.

It is believed that the foregoing conveys a clear understanding of my invention and while I have shown several embodiments it will be understood thateI do not wish to be limited thereto since many modifications may be made, and I therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

I claim:

1. In an automatic sadron characterized by a sole plate structure provided with a heating erlement, a bottom ironing surface, and an upper surface the temperature of which is closely related to the temperature of the ironing surface, a shell structure enclosing a space above said sole plate structure, and a control for the heating element having means for selective temperature settings and including a ply metal responsive means adapted to maintain said ironing surface at a selected temperature irrespective of variations in rate of heat withdrawal from the bottom ironing surface and in consequence whereof said space is characterized by substantial increase in temperature in response to increase in load demand the combination described in which the thermally responsive means comprises a primary ply metal thermostat strip having one endr portion mounted in contact with said upper surface and having its remaining length in approximate contact with said upper surface to provide close thermal coupling thereto, means constraining said strip from movement to a position of less favorable thermal coupling with respect to said upper surface whereby to maintain said close thermal coupling under all conditions of operation and whereby said primary thermostat strip exhibits a minimum of lag in response to change in temperature of the ironing surface, and a secondary or compensating ply metal thermostat strip acting in the opposite direction from the primary thermostat strip to compensate for residual lag in response of the main thermostat strip, said secondary thermostat strip being located so as to exhibit a lagging response to temperature change of said upper surface but nevertheless ultimately responsive only to temperature of said upper surface rather than to temperature of said shell space.

2. In an automatic sadiron characterized by a sole plate structure provided with a heating element located intermediate its bottom ironing surface and its top surface, a shell struotureenclosing a space above said top surface, and a control for the heating element including a switch in the heating surface and means for selective temperature settings and including a ply metal thermally responsive means adapted to maintain said ironing surface at a selected temperature irrespective of variations in rate of heat withdrawal from the bottom ironing surface and in consequence whereof said space is characterized by large variations in temperature in relation to variations in rate of heat withdrawal from said ironing surface. the combination described in which the thermally responsive means comprises a primary ply metal thermostat strip maintained in close and substantially unvarying thermal relationship to said ironing surface and exhibiting a minimum of lag with respect to change in temperature thereof, and a secondary or compensating ply metal thermostat acting in the opposite direction from the primary thermostat to compensate for unavoidable lag in response of the main thermostat, said secondary thermostat being located so as to exhibit a lagging response to temperature change of said ironing surface but nevertheless ultimately responsive mainly to temperature 0f said ironing surface rather than to temperature of said space, said control means including a control member adapted to be set for said selected temperatures, means operative between said control member and said thermally responsive means to apply pressure which serves to restrain motion of said thermally responsive means tending to operate the switch, the value of said pressure being determined by the setting of said control member to thereby maintain said thermally responsive means in unvarying and close thermal relationship to said ironing surface irrespective of the temperature of the latter.

3. In an automatic sadiron characterized by a sole plate structure provided with an electric heating element, a bottom ironing surface, and an upper surface the temperature of which is closely related to the temperature of the ironing surface, a shell structure enclosing a space above said top surface, and a control for the heating element having means for selective temperature settings and including a ply metal thermally responsive means located in communication with said space and adapted to maintain said ironing surface at a selected temperature irrespective of variations in loadcondition incident to removal of heat from the bottom ironing surface when ironing and in consequence whereof said space is characterized by substantial increase in temperature in response to increase in load demand, the combination described in which the thermally responsive means comprises a strip of thermostatic metal having end portions, an intermediate portion of decreasing graduated rigidity extending from one end portion to th region of the other end portion, and a portion of high flexibility connecting the part of said intermediate portion of lowest flexibility to said other end portion, means for flxedly attaching said one end portion in face contact with said upper surface, the remaining length of thethermostat strip being in approximate contact with said upper surface to provide close thermal coupling thereto, means for preventing substantial angular movement of said other end portion with change in temperature of said strip to impart restraint to angular movement to said intermediate portion of lowest rigidity, said intermediate portion of lowest rigidity being located in such close thermal coupling to said upper surface as to be primarily and ultimately responsive to the sole plate temperature and practically independent of variations in load conditions but lagging behind said intermediate portion of decreasing graduated rigidity, stationl ary and movable contacts for controlling the flow o1' current through said heating element, and means disposed between said movable contact and said strip in the region of the part of said intermediate portion of lowest rigidity for moving said movable contact in response to movement of said strip, said selective temperature setting means being arranged to operate through the last described means to apply to the thermostat strip a degree of pressure according to the setting desired. said pressure acting to maintain the intermediate portion of graduating rigidity in said approximate contact with said upper surface oi' said well under all conditions of settings and sole plate temperatures.

4. In an automatic sadiron characterised by a sole plate structure provided with a heating element, a bottom ironing surface, and an upper surface the temperature of which is closely related to the temperature oi' the ironing surface, a shell structure enclosing a space above said upper surface. and a control for the heating element having means for selective temperature settings and including thermally responsive means adapted to maintain said ironing surface at a Selected temperature irrespective of variations in rate of heat withdrawal from the ironing surface and in consequence whereof said space is characterized by substantial increase in temperature in response to increase in load demand, the combination described in which the thermally responsive means comprises a thermostatic strip. said strip comprising a main thermostat portion of relatively low flexibility terminating in a cornpensating portion oi greater flexibility, said main thermostat portion beingiixedly mounted at one end to said upper surface and having its remaining length in approximate contact with said upper surface to provide close thermal coupling thereto, and means constraining said strip from movement to a position of less favorable thermal coupling with respect to said upper surface whereby to maintain said close thermal coupling under all conditions of operation and whereby said primary thermostat strip exhibits a minimum of lag in response to change in temperature of the ironing surface, said compensating portion of greater ilexibiiity being ultimately responsive only to the temperature of said upper surface rather than to temperature of said shell space and lagging in such response behind the main thermostat portion, and means acting against the end of said strip to stress the same longitudinally and cause said strip to move with a snap action.

5. In an automatic sadiron characterized by a sole plate structure provided with a heating element located intermediate its bottom ironing surface and its top surface, a shell structure enclosing a space above said top surface, and a control for the heating element having means for selective temperature settings and including a ply metal thermally responsive means adapted to maintain said ironing surface at a selected temperature irrespective of variations in raie of heat withdrawal from the bottom ironing surface and in consequence whereof said space is characterized by large variations in temperature in relation to variations in rate of heat withdrawal from said ironing surface. and in which said control means includes a switch having contacts one of which is movable for controlling the dow of current through the heating element, the combination described in which the thermally responsive means comprises a thermcstatic strip positioned to actuate said movable contact, said strip comasians i6 prising a main portion of relatively low exibiiity extending inward from one end of said strip and a portion of relatively high flexibility having a serpentine configuration extending inwardly from the opposite end of said strip and joining said n main portion, means for clamping the ends of said strip into good thermal contact with said plate and for retaining said ends against angular movement to cause said portion of high flexibility to yieldingly restrain the adjoining end of said main portion against angular movement with change in temperature and thereby compensate the action of said strip for lag of temperature in the thermostat and plate, the thermostat strip being mounted in such close substantially unvarying relationship to the soie plate that the main thermcstat portion and the compensating thermostat portion are primarily and ultimately responsive to the soie plate temperature and practically in.- dependent of variations in load conditions but said movable contact, and means acting against the end of said strip to stress the same longitudlxally and cause the strip to move with a snap ac on 8. In an automatic sadlron characterized by a sole plate structure provided with a heating element located in diate its bottom ironing surface and its top surface, a shell structure enclosing a space above said top surface. and a control for the heating element having means for selective temperature settings and including a ply metal thermally responsive means adapted to maintain said ironing surface at a selected temperature irrespective of variations in rate oi' heat withdrawal from the bottom ironing surface and in consequence whereof said space is characterised by large variations in temperature in relation to variations in rate of heat withdrawal from said ironing surface, and further characterized by the provision ofY a thermostat well in the top of said sole plate structure in which well said thermally responsive means is disposed, the combination described in which the thermally responsive means comprises a strip of thermostaticmetal of substantially uniform thickness, said strip having a main thermostat portion tapering inwardly from one end toward the other end thereof and terminating in a serpentine curve formed by cutting notches in opposite sides of said strip to give ilexibllity thereto through torsional movement of the components thereof, means for ilxedly supporting the mst-mentioned end of said strip in face conangles to the face of said strip, a strip of spring metal disposed in a position approaching parallelism with said thermostatic strip and risidly upright member to restrain of said upright member and tween said one end and the point of attachment of said uprisht member. the portion of the strip attachmen to the sole plate and the compensating thermostat portion are primarily and intimately responsive to the sole plate temperature and practically independent of variations in load conditions but' with the compensating thermostat portion lagging behind the main thermostat portion, and contacts actuated by movement of said strip to control the flow of current through said heating element.

7. In an automatic sadiron characterized by a sole plate structure provided with an electric heating element located intermediate its bottom ironing surface and its top surface, a shell structure enclosing a space'above said top surface, and a control for the heating element having means for selective temperature settings and including a ply metal thermally responsive means located in communication with said space and adapted to maintain said ironing surface at a selected temperature irrespective of variations in load condition incident to removal of heat from the bottom ironing surface when ironing and in consequence whereof said space is characterized by large variations in tempera/ture in relation to variations in heat demand from said ironing surface even though the ironing surface itself may not vary in temperature, and further characterized by the provision of a thermostat well in the top of said sole plate structure in which Well said thermally responsive means is disposed, the combination described in which the thermally responsive means comprises a stripof thermostatic metal of substantially uniform thickness throughout its length, one end thereof being a main thermostat portion attached in face contact with the bottom of said well, said strip tapering inwardly from said one end to a point adjacent the center of said strip, the remainder of said strip to a point adjacent the opposite end thereof having a serpentine configuration in the plane of the stripformed by cutting notches alternately in the side edges of said strip to provide longitudinal and lateral flexibility through torsional movement of the components thereof, means for holding said opposite end of said strip against lateral and angular movement and for supporting the thermally responsive portion of the strip in closely spaced substantially unvarying relation to the bottom of said well and for, stressing said strip longitudinally to cause the same to move with a temperature compensated snap action, an upright pin rigidly positioned on the serpentine portion of said strip for actuating said contacts, spring means for preventing angular movement of said pin and the portion of said strip to which said pin is attached, and said control means manually operable for applying lateral pressure to said strip through said pin and said spring to adjust the temperature range of said thermostat.

8. In an automatic sadiron characterized by sole plate structure provided with a heating element located intermediate its bottom ironing surface and its top surface, a shell structure enclosing a space above said top surface, and a control for the heating element having means for selective temperature settings and including a ply metal thermally responsive means adapted to maintain said ironing surface at a selected temperature irrespective of variations in rate of heat Withdrawal from the bottom ironing surface and in consequence whereof said space is characterized by large variations in temperature in relation to variation-s in rate of heat withdrawal from said ironing surface, the combination described in which the thermally responsive means comprises a bimetallic thermostat strip fixed at one end" in heat conducting relation to the sole plate and constructed and arranged to provide a main thermal response portion and a compensating thermal response portion acting in a direction opposite from that of the main thermal response portion, and motion transmitting means connected to the compensating thermal response portion of the strip for transmitting the resultant thermostat movements for control of the heating means, said motion transmitting means serving to restrain said thermostat strip from angular movement with respect to the attachment of said fixed end of the strip to effect compensation for lag in the thermostat temperature with respect to the ironing surface of the sole plate, the thermostat strip being mounted in such close substantially unvarying relationship to the sole plate that the main thermal response portion and the compensating thermal response portion are primarily and ultimately responsive to the sole plate temperature and practically in- Y dependent of variations in load conditions but with the compensating thermal response portion lagging behind the main thermal response portion, the thermostat strip being clamped at its fixed end flat against the sole plate and the remaining portion of the strip being offset from the plane of said clamped end.

9. In an automatic sadiron characterized by a sole plate structure provided with a heating element located intermediate its bottom ironing surface and its top surface, a shell structure enclosing a space above said top surface, and a control for the heating element having means for selective temperature settings and including a ply metal thermally responsive means adapted to maintain said ironing surface at a selected temperature irrespective of variations in rate of heat withdrawal from the bottom ironing'surface and in consequence whereof said space is characterized by large variations in temperature in relation to variations in rate of heat withdrawal from said ironing surface, the combination described in which the thermally responsive means comprises a bimetallic thermostat strip having end portions, an intermediate portion of decreasing graduated rigidity extending from one end portion to the region of the other end portion, and a portion of high flexibility connecting the part of said intermediate portion of lowest flexibility to said other end portion, means for fixedly attaching the rst named end portion in face contact with the sole plate, and means for preventing substantial angular movement of Said other end portion with change in temperature of said strip to impart restraint to angular movement to the part of said intermediate portion of lowest rigidity, whereby to effect compensation for temperature lag of the thermostat strip `with respect to the ironing surface of the sole plate, the thermostat strip being mounted in such close and substantially unvarying relationship to the sole plate that the iirst described intermediate portion and the second described intermediate portion are primarily and ultimately responsive to the sole plate temperature and practically independent of variations in load conditions but with the second described intermediate portion lagging behind the rst described intermediate portion.

10. In an automatic sadiron characterized by a sole plate structure provided with a heating element located intermediate its bottom ironing surface and its top surface, a shell structure enclosing a space above said top surface, and a 19 i control for the heating element having means for selective temperature settings and including a ply metal thermally responsive means adaptedthe sole plate and shaped to provide portions of greater and of lesser exibility, and motion transmitting means connected to said portion of greater flexibility to impart restraint to angular movement thereof with respect to said portion of lesser nexibility to eilect compensation for temperature lag or the thermostat strip with respect to the ironing surface of the sole plate,

the thermostat strip being mounted in such close and substantially unvarying relationship to the sole plate that said portions of greater and lesser exlbility are primarily and ultimately responsive to the sole plate temperature and practically independent of variations in load conditions but with the portion of greater flexibility lagging behind the portion of lesser flexibility, whereby to eiect substantially uniform temperature cycles without material overshoot `starting from cold or after any given load condition.

ll. In an automatic sadiron characterized by a sole plate structure provided with a heating element located intermediate its bottom ironing surface and its top surface, a shell structure enclosing a. space above said top surface, and a control for the heating element having means for selective temperature settings and including a ply metal thermally responsive means adapted to maintain said ironing surface at a selected temperature irrespective of variations in rate of heat withdrawal from the bottom ironing surface and in consequence whereof said space is characterized by large variations in temperature in relation to variations in rate of heat withdrawal from said ironing surface, and in which said control means includes a switch for controlling the ilow of current through the heating element,v the combination described in which the thermally responsive means comprises a bimetallic thermostat strip having a main thermostat portion ixed at one end to the sole plate diminishing in width therefrom and having a compensating thermostat portion, a. nat spring tlxed to the sole plate in substantially parallel relation with the thermostat strip having a iree end arranged for actuating the switch, and a nxed connection-between the free end oi' the spring and said compensating portion for imposing angular restraint thereto, the thermostat strip being mounted in'such close and substantially unvarying relationship to the sole plate that the main thermostat portion and the compensating thermostat portion are primarily and ultimately responsive to the sole plate temperature and practically independent of variations in load conditions but with the compensating thermostat portion lagging behind the main thermostat portion.

12. An automatic sadiron as set forth in claim ll, in which the compensating portion terminates the thermostat strip at the end thereof opposite from the fixed end of the main thermostat portion for slow action opening and closing .switch operations.

i3. In an automatic sadiron characterized by a sole plate structure provided with a heating element located intermediate its bottom ironing surface and its top surface, a shell structure enclosing a space above said top surface.V and a control for the heating element having means for selective temperature settings and including a ply metal thermally responsive means adapted to maintain said ironing surface at a selected temperature irrespective of variations inrate of heat withdrawal from the bottom ironing surface and in consequence whereof said space is characterized by large variations in temperature in relation to variations in rate of heat withdrawal from said ironing surface, and in which mid control means includes a switch for controlling the new oi current through the heating element. the combination described in which the thermally responsive means comprises a thermostat strip having a main thermostat portion iixed to the sole plate and a compensating thermostat portion, in

such close and substantially unvarying relationship to the sole plate as to be primarily and ultimately responsive to the sole plate temperature but lagging behind the main thermostat portion, a i'lat spring above the thermostat strip having a central longitudinal tongue xed with respect to the sole plate and longitudinal side portions joined by a front transverse portion and a rear transverse portion. a connection between the rear transverse spring portion and said temperature responsive portion oi the thermostat" strip serving to restrain angular movement of said portion but to permit said compensating switch control movement thereof, and said control means including manually operable means connected to the front transverse portion of the spring adjustable to impose variable tension against Vthe thermostat strip to change the temperature setting.

14. An automatic sadiron as set forth in claim 13, in which the manually operable means includes a member extending upwardly and connecting to a linger operable member for changing the temperature setting, and spring means acting against the front transverse portion of the flat spring to impose opposite pressure against the same.

l5. In an automatic sadiron characterized by a sole plate 'structure provided with a heating element located intermediate its bottom ironing surface and its top surface. a shell structure -enclosing a space above said top surface. and a control for the heating element having means for selective temperature settings and including a ply metal thermally responsive means adapted to maintain said ironing surface at a selected temperature irrespective of variations in rate oi heat withdrawal from the bottom ironing surface and in consequence whereof said space is characterized by large variations in temperature in relation to variations in rate of heat withdrawal from said ironing surface, and in which said control means includes a switch for controlling the now of current through the heating element, the combination described in which the thermally responsive means comprises a thermostat strip having a main thermostat portion fixed to the sole plate and a compensating thermostat portion in such close and substantially unvarying relationship to the sole plate as to be primarily and ultimately responsive to the sole plate temperature and practically independent oi variations in load conditions but lagging 4behind the main thermostat portion, a dat spring above the thermostat strip having a central longitudinal tongue fixed with respect to the sole plate and longi- 16. In combination with a heater, a body to be heated thereby, and means for controlling the application of heat from the heater to said body to maintain the body at a preselected temperature. of thermostatic means included in said control means constructedand arranged to provide a main thermostat portion and a compensating thermostat portion. the `main thermostat portion being in good he'at conducting relation to said body and exhibiting minimum `lag in respouse to temperature change thereof, the compensating portion being in such close and substantially unvarying relationship to said body as to be primarily and ultimately responsive to the temperaturethereof and so that the temperatureof said compensating portion at any instant is essentially a function of the temperature of said body and time alone and practically independent of the variation in average rate of heat output from said Vheater imposed by i iriation in load conditions, the compensating tigermostat portionhaving lag behind the main thermostat portion to compensate for the said minimum lag associated with the main thermostat portion, said thermostatic means being restrained from movement under all conditions of temperature of said body except at said preselected temperature whereby to maintain the described thermal relationship between said thermostatic means and said body under all conditions of use.

17. In ian automatic sadiron characterized by a sole' plate structure .provided with a heating element located intermediate its bottom ironing surface and its top surface, a shell structure enclosing a space above said top surface, and a control for the heating element having means for selective temperature settings and including a ply metal Vthermally responsive means adapted to maintain said `ironing surface at a selected temperature irrespective of variations in rate of heat withdrawal from the bottom ironing surface and in consequence whereof said space is characterized by large variations in temperature in relation to variations in rate of heat withdrawal from said ironing surface, the combination described in which the control includes thermostatic means constructed and arranged to provide a main thermostat portion and a compensating themostat portion, the main thermostat portion being in good heat conducting relation to the sole plate, the compensating portion being in such close and substantially unvarying relationship to the sole plate as to be primarily Aand ultimately responsive to thete'mperature thereof and so that the temperature of said compensating portion at any instant is essentially a 'function of the temperatureof the sole plate andV time alone and practically independent of the variation in average rate oi' heat output from said heater imposed by variation in load conditions, `the compensating thermostat portion having lag behind the main thermostat portion, thecombined action of the main and the secondary thermostat portions being by reason of said relationship so closely responsive to the temperature of the soie plate as to substantially eliminate temperature overshoot under succeeding cycles of operation whether starting from room temperature or after any given load condition.y

18. In an automatic sadiron characterized by a sole plate structure provided with la. heating element. a bottom ironing surface, and an upper surface the temperature of which is closely related to the temperature ofthe ironing surface,

and a control for the heating lelement having means for selective temperature settings and including thermostatic means adapted to maintain said ironing surface at a selected temperature irrespective of variations in rate of heat withdrawal from the ironing surface, the combina'- tion described in which the thermostatic means comprises a thermostat strip having one en'd portion mounted in contact with said upper surface and having its remaining length in close and substantially unvarying relation to said upper sur.- face to provide close thermal coupling thereto, means constraining said strip from movement to a position of less favorable thermal coupling with respect to said upper surface whereby to maintain said close thermal coupling under all conditions of operation, and in which said control includes means for varying the constraining pressure to obtain said selective temperature settin s.

g LUDVIK J. KOCI.

REFERENCES CITED The following references are of record in the file of'this patent:

UNITED STATES PATENTS Number Name Date 2,146,992 Saunders et al Feb. 14, 1939 2,233,615 Kuhn et al Mar. 4, 1941 2,277,439 Jepson Mar. 24, 1942 2,332,518 Koei Oct. 26, 1943 2,128,869 Winborne Aug. 30, 1938 2,266,708 Jepson Dec. 16, 1941 1,976,842 Eskin Oct, 16, 1934 1,743,073 Simmons Jan. 7, 1930 2,228,522 Johnson Jan. 14, 1941 Certcate of Correction Patent No. 2,415,795. February 11, 1947. LUDVIK J. KOCI It is hereby certified that errors appear in the xgnted specification of the above numbered patent requiring correction as follows: lumn 13 line 74, claim 2, for surface reed circuit; column 16, lines 71 end 72, claim 6, for constituing reed constituting; column 21, line 58, claim 17, for themostat 'read thermostat; und that the seid Letters Patent should be reed with these corrections therein that the same may conform to the record of the case in the Patent Ofce.

Signed and sealed this 5th dey of August, A. D; 1947.

LESLIE FRAZER,

First Assistant 'ommiaaoner of Patents.

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