US1975736A

US1975736A - Electric iron

Info

Publication number: US1975736A
Application number: US652754A
Authority: US
Inventors: Victor G Vaughan
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1933-01-20
Filing date: 1933-01-20
Publication date: 1934-10-02
Anticipated expiration: 1951-10-02

Description

Oct. 2, 1934. A. G. VAUGHAN ELECTRIC IRON Filed Jan. 20, 1935 2 Sheets-Sheet l lNvENToR l//c'or 6 Vaughan ATTORNEY Oct. 2, 1934. A G VAUGHAN 1,975,736

ELECTRIC IRON Filed Jan. 20, 1953 2 Sheets-Sheet 2 mWITNE ES INVENTOR l//cor 6. l/m/ han VWL/kid g Patented Oct. 2, 1934 PATENT OFFICE ELECTRIC IRON Victor G. County, tric & Manufacturin burgh, Pa.,

6 Claims.

This application is a continuation in part of my copending application Serial No. 354,242, filed April 11, 1929.

My invention relates to domestic portable-elec- 5 tric irons of the automatic type.

An object of my invention is to provide a novel combination of elements constituting an electric iron in which the direct supply of heat to the ironing surface shall be controlled substantially instantaneously by the temperature of the working surface.

Another object of my invention is to provide an electric iron of this type in which the'temperature of the ironing or working surface shall be l uniform at all times whether the iron is being used or is idling.

Another object of my invention is to provide an electric iron in which the amount of heat generated is greater than required by ironing operations and is transferred directly to the material being ironed without storage of any part thereof.

In practicing my invention I provide an electric iron having a relatively thin base plate which may be so designed as to combine relatively high mechanical strength with light weight and which will have high heat conductivity, which latter characteristic may be obtained by making the base plate of a metal or alloy that shall be highly heat conductive. The electric heating element is closely operatively associated with the base plate and translates such an amount of electric energy into heat that it is more than the amount which is required in ordinary ironing operations, irrespective of the weight of the materials being ironed or4 the degree of dampness thereof or of the speed of operation.

Athermally actuable switch for the heating element is provided and is preferably so associated with the base plate that it will follow the variations of the temperature of the ironing surfacethereof with substantially no lag. A clamping plate may be operatively associated with the heating element and the base plate in order to maintain these two latter elements in close operative engagement, whereby to provide for a quick transfer of heat from the heating element to the base plate as may be required by the ironing operations.

Other objects of my invention will become evident from the following description, taken in conjunction with the accompanying drawings, wherein Figure 1 is a view in vertical longitudinal sec- Vaughan, Miillin Township, Richland Ohio, assignor to Westinghouse Elecz Company, East Pittsa corporation of Pennsylvania Application January zo,

1933, Serial No. 652,754

tion through one form of electric iron embodying my invention;'

Fig. 2 is a time-temperature curve of an iron g1' this type when used in actual ironing operaions;

Fig. 3 is a view in vertical lateral section through a. modified form of device embodying my invention; and y Fig. 4 is a top plan view of a clamping plate which I may use in an electric iron embodying my invention.

Referring first to Fig. 1 of the drawings, I have there illustrated an electric iron which includes a base plate 11, which base plate may include an ironing surface of substantially the usual area in electric irons embodying such triangular shaped ironing surfaces and be provided with a thickened peripheral flange 12 which will cooperate with the relatively thin central portion thereof to provide sufficient mechanical strength to hold its initial shape during its operating life.

It is one of the elements of my invention to make this base plate of a metal or of an alloy which shall be highly heat conductive, 'such as aluminum, or an alloy thereof, or copper, or an alloy thereof, and it is further within the province of my invention to provide a hardened ironing surface which is indicated by the slightly different shading at the bottom of the base plate adjacent to the ironing surface thereof.

A heating element 14 is located in close operative engagement against the upper surface of the recessed portion of the base plate 11, and while I have shown this as including the usual resistor and a plurality of sheets of mica, I desire it to be understood that any suitable or desired heating element effective for the same purpose may be used. 'Ihis heating element 14 distinguishes more particularly from those which have been used heretofore in electric irons of this type in that the amount of energy which is translated into heat therein when energized is greater than that which has heretofore been translated into heat in such heating units and may reach an amount of 1000 or 1500 watts or over. Also the watts per square inch of ironing surface Will, in the preferred case, be over 32.

A clamping plate 16 is provided which operatively engages a part, at least, of the upper surface of the heating element 14 and which may 105 be clamped thereagainst by a plurality of clamping screws 17 which extend into the base plate. A cover member 18 is provided which may be of the usual construction and of dimensions and shape to cooperate with the upper surface of the 1,10

' flange 12 to provide an assembly of pleasing appearance. A handle 19 is'mounted on handle straps 21 and 22 of the usual kind and a terminal pin guard 23 may be located on the strap 22 to protect a pair of terminal pins 24 which are supported on a terminal support 26, which latter is of L-shape and may be secured to the top oi'A A thermostatic switch assembly includes a bimetal bar 28, one end of which is secured against the upper surface of a boss 29 on the base plate 11, the broad or iiat surface of the bar 28 initially extending substantially parallel to the inner surface of the base plate, the heating elelment 14 being, of course, cut away at the central portion of the iron, in order to provide a place for the thermostatic switch assembly. An adjustable contact arm 31 is supported by any suitable means above the inner surface of the base plate 11, as by a stirrup 32, it being understood, of course, thatsuitable electric insulating material is provided between the base plate and the stirrup or the arm 31. The bimetal strip 28 v4and the arm 31 have contact members secured thereto at the outer ends thereof, which contact members cooperate with each other in a wellknown manner to control the circuit of the heating element 14, which is connected in series circuit relation with the two members 28 and 31.

As it may be desirable for certain ironing operations to reduce the temperature at the ironing surface of. the base plate 11, I have provided a manually adjustable arm 33 at the top of the cover 18 and below the handle 19, which may turn a stud 34 whose upper end is interlocked with the arm 33, so that any turning movement of the arm will result in a turning movement of the stud 34, part of whose length is provided with external screw threads so intert with a bushing 36 of electric insulating material, whereby a turning movement of stud 34 will result in its axial movement relatively to the arm 31. The stud 34 has a projection 37 thereon, of electric insulating material, which may operatively engage the contact arm 31 in order to vary the position of the free end thereof, with regard to the bimetallic strip 28, so that the operating temperature of this thermostatic switch may be varied, as desired.

Referring now to Fig. 3 of the drawings, I have there illustrated a modified form of electric iron embodying my invention, which includes a base plate 41 which may be of substantially the same construction as the base plate 11. A heating element 42 is located in substantially the same position as the heating element 14, shown in Fig. 1, and a clamping plate 43 is provided which may be of substantially the same design as the clamping plate 16 of Fig. 1 of the drawings.

Inasmuch as the details as to the cover, the handle, the handle straps, the terminal pin guard, and the terminal pin construction, may be sub'- stantially the same as that already described in connection with Fig. 1 of the drawings, it has not been thought necessary to^describe or enumerate these in further detail.

The modification shown in Fig. 3 of the drawings distinguishes more particularly from that shown in Fig: 1 of the drawings by the use of a snap-acting type of thermostat which may he of the type which is disclosed and claimed in Patent No. 1,448,240, issued to J. A. Spencer. This includes, more particularly, a bimetal disc 51 having a plurality of contact members insulatedly mounted adjacent the periphery thereof, the disc being supported centrally thereof on a. suitable stud 52, which stud may be given a turning movement by means of a manually adjustable arm 53 cooperating with a stud 54,as was hereinbefore described in connection with similar elements in theA modification of Fig. 1 of the drawings. The thermostatic switch is provided also with a base 56 which has mounted thereon a plurality of contact members cooperating with the contact members on element 51, the thermostatic switch being connected in series circuit relation -with the entire heating element, substantially as was hereinbefore described in connection with Fig. 1 ofthe drawings.

Fig. 4 of the drawings shows a top plane view of the clamping plate 43, from which it will be noted that the clamping plate is made as light in weight as is consistent with mechanical strength necessary to hold the heating element against the base plate and to cooperate with the base plate to cause the latter to maintain its initial shape without 100 warping, irrespective of the large number of heating and cooling cycles to which it will be subjected during its life and operation.

Referring now to Fig. 2 of the drawings, I have there illustrated a curve of temperature values at the ironing surface of an electric iron embodying the construction hereinbefore set forth, and so designed and constructed as to weigh only 3 lbs., and having a heating element which can translate 1500 watts into heat. The thermal switch 110 was of the type shown in Fig. 1 of the drawings, that is, it was not a snap-acting device, and would, therefore, operate to interrupt and to close the circuit much more frequently than would be done by a snap-acting device. In other words, as is well known in the art, a bar or strip type of bimetal thermostat will open and close an electric circuit to be controlled thereby much more frequently and within a narrower range or differential of temperature than is the case with a snap-acting device of the general type shown in Fig. 3 of the drawings. While in some cases there have been some diiiiculties as to the operation of a slow acting strip thermostat, recent developments in such devices have made it possible to 125 secure the desired operation and long life thereof.

Referring to the temperature curve of Fig. 2 of the drawings, it will be noted that the part 57 of the curve is the idling temperature after the thermostatic' switch operates properly and 130 uniformly, and the idling temperature obtained is 358. Thereafter, cloths containing 75% by Ytemperatures are 355 and 356, respectively.

Portion 63 of the curve shows an average ironing temperature of 362 when the iron was used on cloths containing 54% moisture, other ironing 145 conditions being the same as for portion 53. Portion 64 shows an average ironing temperature of 362 whenl ironing cloths containing 20% by weight of moisture.

It will, therefore, be noted that the average ironing temperature has been maintained practically constant and that the maximum and minimum temperatures have also been maintained within relatively narrow limits considering the ironing operations in which the particular iron from which this temperature curve was obtained, was used. It is, of course, obvious that any electric iron will experience a sudden drop in temperature at the ironing surface when it is placed in engagement with a cold dampened cloth, and where a heating element is associated with this ironing surface of the character which can generate heat faster than is required by extreme ironing conditions, it is also obvious that this temperature will be quickly increased again until the circuit may be interrupted by disengagement of the contact members. It is further obvious from an inspection of the drawings of the curve of Fig. 3 and the substantially straight line variations of the temperature, particularly those obtained by suitable instruments during the respective ironing operation, that the control of the heating element is eiected substantially instantaneously by the thermostatic switch assembly of Fig. 1 of the drawings, and it is further evident that there is no appreciable lag of the temperature between the ironing surface and that of the bimetal strip shown Ain Fig. 1 of the drawings. One of the essential reasons for this is, of course, that the bimetal strip is clamped against the base plate closely adjacent to the ironing surface thereof, further, that the base plate is made of a material of a high heat conductivity and also that the bimetal strip has a broad surface receiving heat from the base plate itself.

I desire to point out again the very great difference between the temperature curve of Fig. 3 and those which have been heretofore obtained, in that the average temperature of the ironing surface is substantially the same irrespective of whether the iron is being used under ordinary ironing conditions or under extreme ironing conditions, as to thickness of cloth, moisture content and quickness of work of an operator, or whether it is idling so that the whole iron takes part in radiating the heat input as controlled by the thermal switch. It may be noted from Fig. 2 of the drawings that the momentary peak temperatures of the ironing surface do not exceed 400 and I consider this a very distinct advance in the art of design and control of domestic laundry irons which are to be utilized by different kinds of operators working under many different conditions. In other words, it is not necessary in an electric iron of the kind disclosed and claimed in this application and embodying my invention to permit a high peak temperature for the reason that the heating element is of such heat generating capacity as to be able to maintain a desired average operating temperature which will permit an operator to iron at top speed working on high moisture content, heavy cloths and still maintain the temperature of the ironing surface at minimum Values above that at which ironing is no longer possible.

It will be noted that the device embodying my invention provides an electric iron in which all of the heat generated is transferred substantially instantaneously to the surface of the material being ironed in such amount as is required by the ironing operation with no storage heat and any excess heat causes operation of a thermostatic switch which is actuated in accordance with the temperature of the ironing surface and therefore of the temperature of the surface of the material being ironed.

While I have illustrated and described several I specific devices embodying my invention, I do not desire to be limited to the details shown and described, and the present appended claims are, therefore, to be considered as being limited only by the prior art.

I claim as my invention:

1. An automatic electric iron having a base plate of low thermal capacity, an extended electric heating element in direct heat-transferring engagement with the base plate, the heating capacity of the element being greater than any possible working absorption of heat from the iron in use, a light weight skeleton clamping plate of low thermal capacity clamping the heating element against the base plate, a thermostatic switch for controlling the energization of the heating element in accordance with the temperature of the base plate, and means screening the control element of the switch from direct heating effect of the heating element whereby to make it directly and solely responsive to temperature of the base plate.

2. An automatic electric iron substantially free from heat storage elements having a base plate of low thermal capacity, an extended electric heating element in direct heat-transferring engagement with the base plate, the heating capacity of said element being greater than any possible working absorption of heat from the iron in use, a thermostatic switch for controlling the energization of the heating element in accordance with the temperature of the base plate, and means screening the control element of the switch from direct heating effect of the heating element whereby to make it directly and solely responsive to temperature of the base plate.

3. An automatic electric iron having a base plate of low thermal capacity, a heating element of a capacity of more than thirty watts per square inch of ironing surface and so positioned relative to the ironing surface of said plate as to be capable of supplying heat to the ironing surface as fast as its absorption by ironing operations regardless of the weight or degree of dampness of the material being ironed or the continuity or speed of ironing operation, and means responsive to and actuated by base plate temperature to vary the supply of heat to the base plate in proportion to its absorption therefrom, whereby to maintain the ironing surface of the plate constantly within a predetermined range of effective ironing temperature and to maintain the average temperature substantiallyvconstant under all conditions.

4. An automatic electric iron substantially independent of heat-storage elements in its operation, having a. base plate of low thermal capacity,

a heating element positioned near the ironing face of the base plate and capable of supplying heat substantially without time lag directly to the base plate and faster than it can be absorbed by material being ironed, and means directly actuated by and responsive to temperature in the base plate to interrupt the generation of heat when the plate reaches a fixed maximum temperature,l

and to restore it when the plate reaches a xed minimum temperature said maximum and minimum temperature values being substantially the same irrespective of whether the iron is idle or in operation. i

5. The method of automatically constantly maintaining the ironing surface of the base plate 6. The method of automatically supplying ironing heat to an electric iron, comprising intermittently applying directly to the base plate of the iron and near the ironing surface thereof heat at a rate in excess of the rate at which heat can be absorbed by any material being continuously ironed. and maintaining the base plate constantly within a predetermined range of ironing temperature during use by varying the time of said application of heat in proportion to the heat absorbed by the material being ironed.

VICTOR G. VAUGHAN.