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