Cordless iron with high-temperature, non-scorching sole plate surface

Cordless-iron apparatus in which the sole plate of the cordless iron is covered with a polyimide film synthesized by a polycondensation reaction between an aromatic tetrabasic acid and an aromatic amine. Such a film exhibits a broad range of temperature stabililty, thus permitting the heating of the sole plate to relatively high temperatures without wrinkling of the film and without causing scorching of the fabric to be ironed. Steam pressing without spotting is achieved by metering the water flowing to the heated recess in the non-exposed region of the sole plate, which sole plate has apertures for the passage of steam therethrough, the polyimide cover for the sole plate also being apertured.

BACKGROUND OF THE INVENTION 
1. Field of the Invention. 
This invention relates to cordless-iron apparatus and, more specifically, 
to such apparatus which permits effective use of the iron, itself, on any 
kind of fabric without damage to the fabric. 
2. Prior Art. 
Cordless irons and the bases therefor, together referred to herein as 
"cordless-iron apparatus", exist in various forms, all primarily including 
an iron having an electrically heated, heat-retention sole plate, the 
heating occurring while the iron, itself, is secured in its base, which 
base includes an electrical connector designed and positioned to 
co-operate with a corresponding connector carried on the heel of the iron. 
Consumer Reports in its March, 1987 issue reports that its biggest 
objection to cordless irons is the need to frequently replace the iron in 
its base. They also cite the need to set the temperature of the iron for a 
particular fabric in order to avoid melting the fabric being ironed. 
In my earlier U.S. Pat. Nos. 3,269,040 and 3,435,548 I attempted to solve 
this and other problems. However, I have found that the structure recited 
therein is unduly expensive and that the sole-plate-covering materials 
described therein tend to deform and sag, making ironing more difficult 
and the results of the ironing less satisfactory. Specifically, in my U.S. 
Pat. No. 3,435,548 at column 5, lines 43-51 I refer to the use of a sheet 
of aromatic polyamide laminated over the shoe. However, my experience has 
shown that such polyamides do not have the dimensional stability of the 
polyimide film used in this invention. 
Further, cordless irons are usually equipped with a steam generating 
mechanism which may cause wetting instead of steaming of the material 
being ironed as a result of an uncontrolled amount of water being injected 
into the steam-generating chamber. 
Therefore, it is an object of this invention to overcome the various 
problems described for prior art cordless-iron apparatus. 
It is a further object of this invention to provide cordless-iron apparatus 
including a cordless iron which may be heated to a high temperature and 
used without scorching the material being ironed. 
It is a further object of this invention to provide a cordless iron with 
effective and controlled steam generation. 
SUMMARY OF THE INVENTION 
By providing over the sole plate of a cordless iron a polyimide film 
synthesized by a polycondensation reaction between an aromatic tetrabasic 
acid and an aromatic amine (available from Du Pont Industrial Films 
Division as "KAPTON") the iron may be heated to nearly 400 degrees C. 
without warping or melting the film, thus permitting infrequent re-heating 
of the iron while assuring ironing without scorching or melting the fabric 
being ironed. 
The steaming of the fabric being ironed without merely wetting the fabric 
is achieved by metering the amount of water passing into the steam 
chamber, whereby all of the water entering the chamber is converted to 
steam.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIG. 1, iron 10 includes handle portion 12 which is attached to or 
integrally formed with foot portion 14 and body portion 16. Body portion 
16 includes main water reservoir 18 having a filling opening 20, not 
shown, on the reverse side of body 16. 
Spray outlet 22 is connected to main reservoir 18 by way of tube 24 through 
which water is pumped from reservoir 18 by the activation of spray pump 
button 26, which is connected to pump mechanism 28. The details of this 
kind of pump mechanism are well known and need not be described here. 
Foot portion 14 has attached thereto sole plate 30 which is made of die 
cast aluminum, for example, and contains openings 32 therein which can be 
seen more clearly in FIG. 3. Such openings are provided to permit the 
escape of steam from the iron. 
An electrically-insulated heating element 34 is carried in sole plate 30. 
It is connected to electrical terminal block 36 by means of connectors 38. 
Current to heater 34 is controlled by rheostat 40 operated by turning knob 
42. Rheostat 40 is connected to terminal block 36 by means of connectors 
44 Knob 42 contains thereon indicia from which the user can set the 
rheostat at the right resistance level (i.e. the right temperature level 
for sole plate 30) for any given fabric to be ironed. If the temperature 
of the sole plate 3 falls below the desired temperature light 46 is 
illuminated. Sole plate 30 is covered, on its lower surface 48, with a 
layer 50 of a polyimide film synthesized by a polycondensation reaction 
between an aromatic tetrabasic and an aromatic amine. It has dimensional 
stability from -269 degrees C. to 400 degrees C. It also has good heat 
conductivity and a low coefficient of friction. It is sold by the Du Pont 
Industrial Films Division of Wilmington, Del. under the name of 
"KAPTON"-Type H. Thus, this layer 50 does not wrinkle at ironing 
temperatures. At the same time, the material being ironed does not scorch, 
an ideal combination. 
Layer 50 has apertures 52 therein for the passage of steam therethrough. 
That steam is generated when a predetermined amount of water from secondary 
reservoir 54 is permitted to fall onto sole plate 30 in the region being 
heated by heating element 34. To produce the metered amount of steam, 
button 56 is depressed against the resistance of spring 58 until gasket 
60, carried in a fixed position on shaft 62, which shaft also carries 
button 56, engages upper wall 64 of secondary reservoir 54, which has an 
opening 66 therein. At the same time, the depression of steam button 56 
causes the poppet valve comprising seat 68 and poppet 70 to open, 
discharging the volume of water in secondary reservoir 54, and only that 
volume, onto heating element 34 and heated sole plate 30, producing the 
quantity of steam desired. It should be noted that water from the main 
reservoir 18 cannot, by reason of the closing of opening 66 by gasket 60, 
enter secondary reservoir 54 until button 56 is released, at which time 
the poppet valve comprising seat 68 and poppet 70 is closed. This control, 
or metering, of the water converted to steam is important because, in 
prior art devices, it did not exist and, if the operator pressed the 
"steam" button too long water, not steam, went onto the fabric and spotted 
it. Of course, the steam generated passes out of apertures 32 in sole 
plate 30 and through apertures 72 in sole plate covering layer 50, to the 
material being ironed. 
In FIG. 2, foot 14 of iron 10 carries connector 74 which has its contact 
elements enclosed to prevent sparking. Connector 74 is of the female type 
being adapted to cooperate with male connectors on base member 80 shown in 
FIGS. 4 thru 6. 
In FIG. 3, iron 10 has sole plate 30 with apertures 32 therein and 
scorch-preventing layer 50 with apertures 72 therein. 
Turning to FIGS. 4, 5 and 6, base 80 has platform portion 82 terminating in 
connector portion 84. Connector portion 84 has male connector 86, adapted 
to receive female connector 74 on iron 10. A light 88 is lighted when iron 
10 is drawing current. Light 88 is viewed through window 90 in housing 92 
which surrounds connector 86 and assures safety for the operator. 
Micro switch 94 is only closed (by pressure from iron 10 on actuator button 
96) when the iron 10 is placed in base 80 with connectors 74 and 86 
engaged. 
Base 80 includes a thermal cut-out switch 98 which receives heat from metal 
plate 100 in platform 82 and, after approximately 45 minutes of the iron 
sitting, unmoved, on platform 82, the electrical current flowing to iron 
10 is cut-off by switch 98. This alleviates the fear that the iron may be 
forgotten and, consequently cause a fire. To re-set thermal cut-out switch 
98, button 102 must be pushed. 
A layer 104 of KAPTON, or the like, may be carried on the upper surface of 
platform 82 to prevent abrasion of layer 50 on iron 10. Rubber feet 106, 
108 may be provided to preventing skidding of base 80 when iron 10 is 
placed on platform 82. 
While particular embodiments of this invention have been shown and 
described it will be apparent to those skilled in the art that alterations 
or modifications of such embodiments may be made without departing from 
the spirit and scope of this invention. It is the purpose of the appended 
claims to cover all such alterations and modifications.