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Патент USA US3069536

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Dec. 18, 1962
R. D. BREMER ETAL
3,069,526
ELECTRIC HOT PLATE
Filed July 20, 1959
3 Sheets-Sheet 1
INVENTORS.
Robert D. Breme'r
Géorge C. Pearce
Their i?orney
Dec. 18, 1962
R. D. BREMER ETAL
3,069,526
ELECTRIC HOT PLATE
Filed July 20. 1959
3 Sheets-Sheet- 2
52
I
.
.22
Fig.7
Robert
INVHVTORSZ
D. Bremer
zy/é‘eorge C. Pearce
Their Attorney
Dec. 18, 1962
R. D. BREMER ETAL
3,069,526
ELECTRIC HOT PLATE
Filed July 20. 1959
3 Sheets-Sheet 3
LI
INVENTORS,
George C. Pearce
Robert D. Bremer
MY
Their Attorney
United States Patent O?lice
B,l‘iii9,52?
Patented Dec. 18, 1952
2?
solid plate casting with a reinforcing grid in accordance
with a second embodiment of this invention.
FIGURE 5 is a fragmentary sectional view taken along
line 5—5 of FIGURE 4.
FIGURE 6 is a fragmentary top elevational View show
Mich, a corporation of Eeiaware
ing a solid plate casting with embedded metal particles in
Filled .in'iy 2h, lite/9, Ser. No. 328,356
accordance with a third embodiment of this invention.
(El. 219M397}
FIGURE 7 is a fragmentary sectional view taken along
This invention relates to a domestic appliance and more
line 7—7 of FIGURE 6.
particularly, to an improved surface cooking unit for an 10
FIGURE 8 is a schematic wiring diagram showing one
electric range.
means of rapidly heating a solid plate surface cooking
Robert D. Bremer and George E. Pearce, Dayton, @hio,
assignors to Generai Motors Gorpnration, Detroit,
In the development of surface cooking units for elec
unit, the control circuit being in ?ash condition.
tric ranges, the solid plate heater was the result of the
FIGURE 9 is a similar schematic wiring diagram where
earliest efforts in this ?eld. However, these prior art
in the solid plate surface cooking unit is energized for a
plate heaters lacked durable. insulation, heated slowly, and 15 high heat operation.
included fragile resistance wires for heating the plate. Due
In accordance with this invention and with reference
to these disadvantages, the electric range art concentrated
to FiGURES l, 2 and 3, a circular surface cooking unit
its efforts on sheathed tubular heaters which could be
It} is shown which may be adapted for a surface cooking
formed in spiral con?gurations and designed to Withstand
operation in an electric range. The cooking unit 10 is
the severe usage to which such structures are subjected. 20 comprised of a casting 12 having a top surface 14 and
The problems of durability and rapid heat~up were over
an irregular integrally cast protuberance 16 depending
come in the spirally formed tubular heaters. Still the
from a bottom 18 of the casting. Within the protuberance
spiral element does not have the advantage of cleanliness
16 is embedded a sheathed tubular heater 2d. The heater
and smooth appearance which attends the use of solid
29 is comprised of an outer sheath 22 of stainless steel
plate heaters. Thus, the electric range art has sought N) or other suitable material, an inner resistance element 24
solid plate heaters which heat as rapidly as their coiled
and a quantity of a compacted dielectric 26, such as mag
counterparts and which possess the rugged durability re
nesium oxide, to insulate the resistance element 24 from
quired in electric range operation. It is to this end that
the tubular sheath 22. The tubular heating element 20 is
the applicants’ invention is drawn.
embedded in the cast protuberance 16 and is merely dis
Accordingly, it is an object of this invention to provide
tributed along the bottom surface 18 of the casting in a
I
a solid plate heater having a metal casting with a sheathed
tubular heater embedded therein.
It is also an object of this invention to provide a solid
plate heater with means to heat the plate rapidly upon
initial energization thereof.
Another object of this invention is to provide a means
for ?ashing or rapid heating a solid plate cooking unit
wherein the amount of ?ashing is proportioned to the mass
of the solid plate.
Still another object of this invention is to provide a
casting for a solid plate cooking unit which has an integral
depending portion on the underside thereof to house in
close heat conducting relationship a sheathed tubular
heater provided with means for ?ashed heating, thereby
to offset the mass of the casting during heat-up.
A further advantage of this invention lies in the pro
vision of a casting of one material for a solid plate heater
which is reinforced with another abrasion resistant ma
manner to conduct the heat thereof in the most e?ioient
manner to the casting 12. Note that the tubular element
20 is encased and supported by the casting 12. This per~
mits the sheath 22 to be formed of a less expensive grade
of stainless steel, since oxidation is eliminated within the
casting and the sheath doesn’t require the high amount
of hot strength which an exposed spirally coiled heater
element would need. The cost savings in the sheath 22
is an important factor in offsetting the cost of the addi
tional material in the casting 12.
The tubular heatintI element 2i) includes terminal end
portions 28 and St} to which may be attached spades 32
and 34 respectively for engaging the electrical circuitry
in accordance with the teachings of this invention. The
heating element 20 is attached to a source of electricity
through a suitable flash heat switch means, to be de
scribed more fully hereinafter. As aforesaid, the sheathed
heater 2t? is adapted to be embedded in the casting pro
tuberance in. For this purpose the casting is formed in
terial.
Another object of this invention is embodied in the pro 50 a manner to terminate the protuberance l6 along a sur
vision for a solid cast plate heater wherein an aluminum
face 3-6, 38 from which the end portions 37, 39 of the
casting is reinforced with stainless steel.
heater 2t]? may project. When the heater 2d is clear of
A still further object of this invention is the provision
the casting 12, it should be understood that the end por
of a cast iron casting for a solid plate heater wherein the
tions 37, 3? may be formed to accommodate the particu
surface of the cast iron plate is metal ?ame sprayed with
lar range application ‘for which the solid plate heater if}
is to be used.
a stainless compound to guard against rust and corrosion
of the casting.
On the top surface 14 of the casting 12 a depression Iii}
Further objects and advantages of the present inven
is ‘formed. The depression will serve to eliminate the
spinning of the pans or utensils placed on the cooking
tion will be apparent from the following description, ref
erence being had to the accompanying drawings wherein 60 unit it}. Further, the depth of the depression (it) may
be designed to transfer a regulated amount of heat to any
preferred embodiments of the present invention are clear
ly shown.
suitable temperature sensing element 42. disposed there
In the drawings:
below. For instance, the thinner the section of the cast
ing is beneath the depression 40, the faster will be the
FIGURE 1 is a top elevational View of a solid plate
heater designed in accordance with one concept of this in 65 transfer of heat from the cooking load to the sensing
head 42, and the slower will be the transfer of heat from
vention.
the heating element 20 to the sensing head 42. This will
FIGURE 2 is a partial sectional view taken along line
prevent premature cycling of the ‘control circuit.
2-—2 of FIGURE 1.
As aforesaid, one major advantage of the solid plate
FIGURE 3 is a fragmentary side elevational view taken
heater
in is its durability. For this reason the casting 12
in the direction of line 3-3 of FIGURE 1.
FIGURE 4 is a fragmentary top elevational View of a
‘may be formed of any suitable metal such as cast iron,
aluminum or an aluminum alloy. Metals, such as these,
however, do have certain dis
come by the teachings of this i
novel appli ttion 0t
'
;o the casting
cation as follows.
FIGURE 8
stantially in a ?ash or
.E 9 illustrates the
conductor of heat
the tubular units
However, aluminum is not very 1
‘ ?ash heat and
Where tie rapid heat con-"in
minurn is desired, this inv- ion conic
volt do
the castiua, as shown in
4 and 5
steel grid
is embedded in an all
or
stantl lly similar in overall con'?gc
metal cast‘
“
t
' ed in co
wi
i i. try interrupt power to
9 may be desig
1, 2 and 3.
ing nctwor
' of the surface unit 16 in accord
l'l;e elements to extend over
The methods
to casting 52 e
entire top su F .
integrally with to
' source L1, L2, N for achieving
ca ‘
d neat outputs at the surface unit id
orth
they are believed conventional.
casting, as shown in FIGURE 5.
recognized that the resistance to abrasion ‘ ~
sils placed on the top surface 54 of ca
; ortion of eacn surface he ter energiza
ng 52 may ‘
‘ rapid or tlash heat is
accommodated with a grid which extends only slightly be
low the top surface
of the casting. It should be note .
also that the grid 56' will serve also to strengthen and re
inforce the casting as wel as to provide the abrasion wear
provided
mass of the pl“
characteristics desired for solid plate cool» ng units.
of this invention, t
Another means for strengthening a casting of aluminum
alloy or other non-abrasion resistant material is shown
in FIGURES 6 and 7.
this embodiment, metal par
ticles 60 ‘are embedded in the top surface 62 of a casting
6d. These particles, of stainless steel or other relatively
abrasion resistant material, are pressed into the top of
the casting all along with
n of a sufficient
amount of . eat to permit the pr _
1116i; des
latch bimetal ‘75
Ii‘:
srer conduction switch "m
which 7
‘i and normal operation con
between nash he '
atch bimetal '76 actuates switch
nuPM
o 013,
o/
respectively
for the solid plate
1.256 watt 118 volt unit which is
" swit h, shown in ELGURES 8
’
ll ieating. The
and 9, to
switch auton: itically connects the tubu or heating element
23 to 236 volt current (double vc- be) to develop four
bination these particles will provide t. e abrasion resist
ance required whereas the aluminum casting will provide
the rapid heat conducting characteristics so desirable in
e coo.
up to cooking
'-up function
temperature.
times the wattage (5986 watts) for
units for electric ranges.
' , above two methods of acquiring additional abrasion
limited time depend
me on the heat setting selected by the user. For instance,
resistance in a casting are merely by way of example and
may be Tigl " ?rm, Simmer, Low,
could take many other forms wi hin the purview of this
ium Low and Medium
.oi. \‘ . hc-ut the ?ash heat
stainless steel close-messed
principle, this is simply an ?nite heat switch of which
invention. For instance,
l
screen could be applied or embedded in the casting’s upper 40 there are many or 'able. The heating element 20 is
surface. Further, the stainless steel grid 56 could take
?ashed each time the switch 78 is turned from the Oil
position to the On. Switch '73 closes whenever the user
the plane
form of
of the
a spiral
top surface
element
of the
whose
casting.
convolutions lie
turns a switch to any dc
Where cast iron is utilized for a solid plate heater, there
is generally no problem with regard to abrasion resistance
to utensils placed on the heater. Ho ever, cast iron does
tend to discolor, corrode, or rust with extended usage.
For this reason the top surface of the casting should be
metal ‘flame sprayed with a stainless compound and may
be rubbed smooth or fused to enhance the appearance of
the cast iron casting. Thus, it should be seen that rein
forcement techniques have been taught
this invcr" on
in the switch auton"
‘
heat setting.
to 118 volt operation tor the n
CDClxlng period
after the it 1 heat operation.
Ti e circuit includes a user’s knob (not shown) appro
pria elv marked to pen. 1t selection of the desired average
wattage input to the tubular element 23 in accordance
with
of the s
Contact '7’
:
ting" recited above.
line
- to be closed each time the solid
'
The flash
whereby good conducting materials such as aluminum
trans
to change the volt
wice normal dur
be made abrasion resistant and whereby durable ma
terials such as cast iron may be made corrosion resistant.
"2 is included to
The primary difficulty with solid plate heaters for elec
' during normal
tric ranges has been their slowness to heat up upon initial
energization. The user of the modern electric ra
ob
‘he length
operation which
of time that the
jects to this delay and demands that
cooking op .tion
commence rapidly. it is, therefore, here proposed to
overcome this disadvantage of solid plate heaters throuoli
the application of a flash heat principle to a‘ solid pl te
heater. In
prior art the spiral type tubular elements
contact 'i’é in any given period deterr ' s
anount of
it
the surface heater ‘ . T he cycle-r 5'2 is
d of a iirnetallic actuator
’
'
have been frequently controlled through a 1 h heat
switch which connects t‘“
c113 spiral element for short pe
riods of time at maxnnum voltage to cause rapid heat
up. However, the mass of the tubul cooking unit is
considerably less than that of a solid p .te type cooking
unit and the prior art is is to consider this fact in over
etal o
and a ?at punched
moduh ng or modifying the action of the
The latch biinctal '75 is self~heated by the
passage of current theretlrough and cooperates with switch
blades ‘78, 84 an S6 to terminate t.e ?ash heat opera
tor‘. in accordance v' 1 user’s heat
Tl e switch of w
O
U
‘ration, also includes c.-n (not shown) v
the user’s heat selection to condition the internal con
‘
coming the slowness in heat response in plate heaters.
This invention adapts a ?ash heat switch which will supply
the desired amount of additional wattage for a predetei~~
mined period of time in accordance with
Contacts with
1v r ‘tore the heating element
and 87 or" the switch for the desired
M ore particularly, 1" * cams would
operate the "binietal contacts
mass of ‘
contact switch blade 7,, the latched
3-5 to overcome the action of the
latch bimetal and alter the setting of the cycler "£2 to pro»
1.‘ 9, c.
1. Y e comp‘
.: ital; e is duce the desired average wattage to the heating element
'1 mo
With reference to F’GURE 8 are
casting.
n
5
3,069,526
20. When the switch is turned to an Off position, the cams
may also serve to reset the latch bimetal '76 to the posi
tion shown in FIGURE 8 for switches 78, 8d and 86 to
ii)
the latch bimetal 76 to L2; and the parallel path through
cycler bimetal heater 9t}, cycler bimetal 88 and cycling
contact 74- to L2. With full current ?ow through the latch
ready the switch for the next ?ash heat operation.
bimetal 76, the heated latch bimetal will release a detent
As aforesaid, one major concept of this invention is the 01 for switches 78, 84 and 86 in about ?ve seconds. At this
application of a predetermined amount of ?ash heat to
point transfer switch blade 78 will be moved to contact 82
a surface cooking unit .10. This predetermined amount
thereby transferring the heating element 20 to a 118 volt,
depends upon the mass and the material of the casting and
1250 watt operation on the neutral line N. The total in—
thus must be adjustable for different castings. Some small
terval of the ?ash heat will be the sum of the time taken
?exibility is provided in the circuitry of FIGURE 8 by a 10 by the cycler bimetal88 to open contact 74, plus the time
resistance heater 92 which may be varied according to the
casting or plate. By changing the resistance of the ele
the latch bimetal 76 takes to move the switch blade 78
toward the neutral line \I. At the instant switch blade 78.
ment 92, a longer or shorter ?ash heat operation will
connects with contact 82. the circuitry is conditioned for
normal operation at the heat selected. Where High heat
be necessary to vary the latch bimetal 76 itself. A longer 15 has been selected, FIGURE 9 is representative of this cir
?ash time will require a slower acting latch bimetal.
cuitry. More particularly, a ?ow will be through the
For instance, the latch bimetal could have a lower re
tubular heater 26* from N, contact 82., transfer switch blade
continue. For greater flash time change, however, it will
sistance, a .greater mass or could be constructed of a
78, line 1%, line 162, heater 90, cycler bimetal 88, cycling
material of lower resistivity. The reverse of the fore
going will produce a shorter ?ash time. In other words,
the ?ash time depends on the proportions of bimetal
contact 74 to L2.
cross-section, length and resistivity. Still another method
of varying ?ash time is through the mechanism or linkage
which is responsive to the latch bimetal and interconnects
the latch ‘bimetal with the cams and switches of the ?asher
control, namely switches 78, 84 and 86. Thus, this in
vention, through current responsive elements, compen
sates for castings such as iron which require a different
?ash time than castings such as aluminum or copper.
The object of the invention is to provide a ?ash heat which
will cause a solid plate heater litl to heat up as quickly as
its counterpart, the conventional spiral tubular elements.
For particular ‘details with reference to the switches de
picted representatively in FEGURES 8 and 9 reference
may be had to the patent to Vogelsberg 2,666,124, issued
January 12, 1954. In this patent a suitable switch is set
forth which, when modi?ed in accordance with this inven
tion, will satisfactorily operate or energize the solid plate
heater it? in accordance with the teachings of this in
vention.
By Way of example only, reference may be had to FIG
At the same time a parallel path will
be connected through the series resistance strip 92, switch
86, line lib-t, cycler bimetal 88, cycling contact 74- and L2.
At other heat settings the cycler will operate in the manner
taught by the Vogelsberg patent. The contact 74 is
opened and closed to regulate power to the tubular heating _
element 28‘ and the solid plate cooking unit 18 in accord
ance with the settings of Medium, High, Medium Low,
Low, Simmer and Warm. When the user turns the con
trol to Off, a cam resets the latch switches '78, 84, 86
ready for the next ?ash heat operation as in FIGURE 8.
Tests have shown that the end result of obtaining rapid
heat-up of the plate heater it), may be accomplished in a
number of ways. On any given heater with any given
size heating element 28, the heating element may be ?ashed
at a greater wattage for a lesser time to achieve substan
tially the same results as a lesser wattage for a longer
tim . The important thing to know is that the amount of
?ash heat applied to a solid plate heater iii, in accordance
with the concepts of this invention, depends upon the ma
terial and the mass of the casting itself. Cast iron will,
of course, take a longer ?ash period than will an aluminum
alloy casting. These flash times are to be determined in
accordance with the mass and material by varying the
series resistance heater 92‘.
Operating temperatures for solid plate heaters are gen
45 erally limited to a temperature of approximately 1000° to
URES 8 and 9, wherein an explanation will be set forth
for an initial ?ash heating period with the heating element
29 connected for High heat operation. As soon as any
suitable user’s control knob (not shown) is rotated to the
High position, the main line contact switch 70 will be
prevent cracking or warping the casting. A temperature
closed. With reference to FIGURE 8, the ?ash heat op
range of from 850° to 950° F. has been believed most
eration will start immediately where a 1250 watt, 118 volt
desirable as a calibration range for ?ash heat switches.
heating element 20 is used at 236 volts, 21.2 amperes to
It will be recognized that even though exposed spiral tubu
give 5,000‘ watts load at the heating element 20. The 50 lar heatin0 elements operate at higher surface tempera
current will ?ow from L1 through main line switch 70,
tures, in the range of 1200° to 1400” F., the greater heated
?ash heat contact 80, transfer switch blade 78, line 100,
surface area of the solid plate heater or cooking unit Iitl,
the tubular heating element 20, line 102 and then through
while operating at lower temperatures, will provide the
parallel paths to the other side of the line L2. One par
same total Btu. output for the plate heater as with the
allel path will be through the bimetal heater 90 of the 55 tubular type.
cycler 72 and cycling contact 74 to L2. The other par
It should now be seen that an improved solid plate
heater has been designed wherein the slowness of the plate
allel path for current flow will be through the series resist
heater response is overcome by the application of a ?ash
ance strip 92, the latch bimetal actuated switch 86, line
heat principle tailored to the particular requirements of the
104, the cycler bimetal 88 and cycling contact 74 to L2.
Current ?ow through the closed latch bimetal contact 60 casting being used for the heater. Further, a plate has
been designed which will conduct heat rapidly and which
84 and latch bimetal 76 is insigni?cant at this point. After
is reinforced by abrasion resistant material to facilitate
a time interval, the cycler bimetal 88 moves to open cycling
long heater life.
contact 74 thereby ending the ?ash heat cycle. By Way
While the embodiments of the present invention as
of example, the timing interval is approximately 26 sec
onds for High or Medium High settings. At other set 65 herein disclosed, constitute preferred forms, it is to be
understood that other forms might be adopted.
tings, the timing is reduced proportionately to prevent
What is claimed is as follows:
overshooting temperatures at the surface unit It}. When
1.
A solid plate cooking unit comprising, a casting
the cycling contact 74 is open, all line current must then
of one material, said casting having a substantially flat
pass through the latched bimetal 76 which is heated by
70 plate portion forming a. top side thereof, a depression in
the current. At this time current will ?ow from L1, main
said top side, an irregular protuberance on the bottom
line switch 70, ?ash heat switch blade 78, line 103, tubular
of said casting, a sheathed tubular heating element em
heating element 20, line 102 and parallel paths as follows:
bedded in said protuberance, and means for reinforcing
through the series resistance heater 92, latch bimetal con
said casting, said reinforcing means including a ribbon
tact switch 86, latch bimetal contact switch 84, through
like grid member of another material embedded in said
(I)
O
7
flat plate portion, said grid member
thereof coplanar with said top side.
U
h C ling one edge
_
2. A solid plate cooking unit comprising, a casting
of one material, said casting having a substantially ?at
plate portion forming a top side thereof, an irregular
protuberance on the bottom of said casting, a sheathed
her is comprised of a network of intersecting elements
substantially coextensive With said top side.
Re?erences Cited in the ?le of this patent
UNITED STATES ‘PATENT S
Andrews
means inciuding a ribbon~like grid member of another 10
3. The combination of claim 2 wherein said grid mem
__ Dec.
14,
Jordan et al. _________ __ Apr. 23,
and means for reinforcing said casting, said reinforcing
material embedded in said ?at plate portion, said grid
member having one edge thereof coplanar with said top
side.
____ a-
Zublin _______________ __ Apr. 26,
tubular heating element embedded in said protuberance,
2,552,818
2,664,493
2,870,313
2,906,845
izard _______________ __ iune
Fry ________________ __ Oct.
Russell ______________ __ May
Fischer _____________ __ Dec.
McCormick __________ __ Jan.
Turner ______________ __ Sept.
13,
10,
15,
29,
20,
29,
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