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Патент USA US2412737

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Dec. 17, 1946.
Filed July 19, 1944
lsatented Dec. 17, 1946
Arthur J. Kerchcr, Berkeley, Calif.
Application July 19, 1944, Serial No. 545,673
2 Claims. (Cl. 219-38)
This invention relates to electrical heating units
and particularly to safety devices used in con
nection therewith and applies particularly where
it is desired to introduce a safety device to in
terrupt the flow of current in the event the heat
ing element exceeds a predetermined heat.
Those having had practical knowledge and ex
perience in the art are well acquainted with the
fact that at various times thermostatically con
trolled heaters are improperly connected so that
the thermostat cannot serve its purpose; or the
thermostat may be left out of the heater or dis
connected from it unintentionally; or it may be
tank and with the electrical contacts and control
unit being positioned outside of the tank. The
heating device illustrated in Figures 1 and 2 cor
responds generally to that heating device illus
trated and claimed in Kercher and Hicks Patent
No, 1,671,592, issued May 29, 1928, and consists
of a plurality of heating elements it which are
secured to a head 12 in such a manner that they
are entirely supported by the same so that the
entire device may be removed as a unit from the
The head i2 is suitably secured to tank
ill as by means of screws or bolts I3.
A suitable
gasket [4 is inserted between the opposed faces of
ill and head E2 to secure a water-tight ?t.
it may be broken in handling or shipping. In 15
The heating elements 9 l are preferably construct
any such event, electric current may continue to
ed of a single elongated casing and are then weld
be applied to the heating element and the water
brazed, or soldered to the head 52 as described
or other material being heated may be raised to
in said Kercher and Hicks Patent 1,671,592. A
an elevated temperature. Under such conditions
water may be converted to steam or the heating 20 suitable insulating block I5 is mounted on the
outer side of head l2 in a recess ll therein as
‘unit may be burned out.
by means of a plurality of bolts iii. Terminal
It is an object of the present invention to obvi
wires 26 of the heating elements H are brought
ate the di?iculties above referred to. It is a fur
out through apertures in the insulating block ES
ther object of the present invention to introduce
are connected to suitable terminals 22 and 23.
a thermally responsive safety unit in the electric
When terminals 22 and 23 are connected to a
supply line, which unit is responsive only to an
suitable source of electric current, the heating
excess of heat in the heating element.
device heretofore described is placed in opera
It is a further object of the invention to pro
vide a thermally responsive safety device which
will be responsive to the heating element and 30 The thermostatic means incorporated in the
structure illustrated in Figures 1 and 2 is gen
the tank or other container, and be independent
erally the same as shown in my Patent No.
of the conventional thermostatic control unit.
2,314,989, issued March 30, 1943, and consists gen
Additional objects of the invention will appear
erally of a switch element 30 which is adapted
from the following description in which the pre
secure a rapid opening and closing movement
ferred embodiment of the invention has been set 35 to
of its electrical contacts in response to ther
forth in detail in conjunction with the accom
mally responsive element 3i. As shown in Fig
panying drawing.
ure 1 thermally responsive element St is in the
Referring to the drawing:
form of a tube, the mode of operation of which
Figure 1 is a transverse sectional view showing
an electrical water heater embodying the safety 40 is disclosed in my Patent 2,314,989. Thermally
responsive tube 3| is mounted within a second
device of this invention.
tube 32 which is welded, brazed or soldered to
Figure 2 is a side elevational view showing an
head l2, and which extends into tank l8 and into
electrical water heater embodying my invention.
the medium to be heated. Thermally responsive
Figure 3 is a transverse sectional detail of the
tube 3! does not come in contact with either the
fusible element constituting the safety device of 45 heating
device or the heated medium. However
my invention.
it is in heat responsive relation to the water or
Figure 4 is a cross-sectional view showing a
other medium being heated and operates in re
modi?ed form of the enclosing casing adapted
sponse to the temperature of the same.
to cooperate with my safety device.
A plurality of insulated conductors 35 and 36
fhile the heating device of this invention may 50 serve to connect switch element 30 with a suit—
be employed to heat fluids of any kind, either
able supply of current, while a plurality of insu
gases or liquids, it is especially adapted for use
tampered with by inexperienced mechanics; or
as a hot water heater and as shown in Figure 1
lated conductors 31 and 38 serve to connect switch
element 30 to terminals 22 and 23 of heating ele
is mounted upon a suitable hot water tank H),
ments H. As is pointed out in my Patent No.
with the heating element ii extending into the 155 ‘2,314,989,
operation of switch element 36 is con~
trolled by thermally responsive element 3!,
whereby an increaseor decrease of the tempera
ture of the liquid within tank lb beyond the pre
determined range serves to open or close elec
trical contacts in switch 38 and either disconnect
or connect the heating element to a suitable
tank [0 reaches the predetermined maximum
temperature at which thermostatically operated
switch 36 is designed to open and halt the supply
of current to the heating element.
Let it further
be assumed that for some reason or other the
thermostatically operated switch does not open
and the circuit remains closed thereby causing
the temperature of the liquid within tank It to
interposed in conductors Bl and 38 between
be raised beyond the predetermined maximum.
thermostatically controlled switch 36 and termi
Current will continue to be supplied to the heat
nals 22 and 23 I have provided’ safety devices 10 ing
element so long as the circuit remains closed
generally illustrated at GE. As shown in Figure
thereby giving rise to the dangers and dif?culties
3, safety device fill consists generally of two simi
heretofore pointed out. Naturally, however, the
lar split housings 45 adapted to form a hollow
heat of the liquid within tank It will be trans
core 422. Portions of the insulated conductors 3'!
mitted to tank It and also to head if. This heat
source of electric current.
or 33 terminate within said hollow core 42, as
illustrated. A portion of the insulation of said
conductors is removed and the'ends of the con
ductors are spaced suiiiciently far apart that arc
ing will not occur. However termini $3 and 44
are suitably connected as by means of a link 45
of heat fusible material such as solder. Link 55
' is adapted to conduct electricity and when in un
fused condition permits a flow of current through
conductors ti’ or 38. However, body 135 is adapt
ed to fuse at a temperature of for example 220° F.,
and, upon fusion, to disconnect termini £33 and 4t
and interrupt the flow of current through ,the
conductors 3t and 38.
Safety devices it! are adapted to be in heat con
ductive relationship with and thermally respon- ,
sive to the metal head l2 and are mounted there
in either in ori?ces (i5 and 41 drilled therein as
shown in Figure l, or in recesses lit therein as
shown in Figure 4. Head i2 is in heat conduct
ing relation to tank in and its contents, and when
tank is and head i2 reach an elevated tempera
ture of for example 220° lit, this heat is transmit
ted to safety devicesdi] causing fusion of one or
both of the links 45 and interrupting the flow of
current to heating element H.
The device heretofore described operates as fol
lows: It will be presumed that the device is set
for a predetermined temperature level of opera
tion and that the terminals in thermostatic
switch elements 35 connect in a circuit'for sup- 4
plying current to the heating element, which in
turn heats the material within tank H) which is
is transmitted to one or both of the safety devices
42 and ultimately to one or both of the fusible
links 135. When the heat so transmitted ap
proaches the temperature of approximately 220°
F., or any'other ‘predetermined heat at which link
455 is designed to- fuse, one or both of said links
fuse thereby interrupting the flow of current
through the conductors 3'5 or 38, and thereby
opening the circuit and cutting o? the supply of
current to the heating element.
t will be evident that the apparatus described
above makes use of relatively simple means to
insure the opening of the circuit in the event the
conventional thermostatic switch fails to func
tion. rThe device cannot fail to operate and, once
having opened the circuit, prevents its being
closed until it has been replaced and the thermo
statically ‘controlled switch 39 made operative.
The device cannot get out of order and is not sub
I ject to the deterioration of time or element nor
to the imperfections of mechanical operation.
I claim:
1. In a device of the character described, a
tank, a heating device comprising an element
extending into said tank and a head outside of
said tank and in heat conducting relation there’
to, a source of electric current connected to said
heating element by suitable conductors, a ther
mostatically controlled switch adapted to permit
or interrupt the ?ow of current through said
conductors to said heating device depending up
on the temperature of the material being heated,
a safety device interposed in said conductors in
cluding said thermostatically controlled switch
in said heating device comprising an element hav
ing therein an enclosed space, conductors spaced
apart at the top and bottom of said space, a fusi
ble element adapted to be vertically mounted be
tween said conductors, said safety devices in
cluding a fusible link adapted to be mounted in
in thermal contact with the thermally responsive
element 3!. Assuming that the temperature of
the water or other material within tank if! is
below the predetermined temperature at which
thermostatically responsive switch 30 is set, as
heretofore described the circuit will remain closed
and current will be supplied to the heating ele
ment. However when the temperature of the
‘said head and to be thermostatically responsive
liquid within tank It! reaches the predetermined
thereto, whereby when said thermostatically con
maximum temperature, switch 38 is opened and
trolled swit-ch fails to interrupt the flow of cur
the circuit is disconnected whereby no further
rent through said conductors to said heating de
current is supplied to the heating element.
Switch 38 generally operates over a spread of 20°, 60 vice when the contents of said tank reach a pre
determined temperature, and the temperature
meaning that, for example, when the same is set
of said contents exceeds said temperature, the
for example for 180°, the circuit will be opened
heat of said contents will be transmitted to said
when the water reaches the temperature of 180°
. safety device and the link will fuse and interrupt
and will not be closed until the temperature de
the flow of current through said conductors to
creases to approximately 160°. When the tem
said heating device, said space being so designed
perature of the liquid being heated reaches the
that when said link fuses the fused portion will
minimum of 160° the thermally responsive switch
fall to the bottom of said space, said space being
so is closed thereby serving to close the circuit
sufficiently large that no arcing will occur be
and supply current to the heating element.
All of the foregoing assumes that the thermo 70 tween the upper conductor and the lower con
ductor and the fused material in the bottom of
statically controlled switch t? operates‘ properly.
said space.
However as is well known to those having had
practical experience with this type of device, such
2. In a device of the character described, an
electric heating device connected to a source of
is not always the case. Therefore let it be as
sinned that the liquid or other material within~~ 75 electric current by suitable conductors, a por
tion of said heating device being in thermally
responsive relationship to a material being
heated, a safety device interposed in said con
ductors and mounted
a portion of said heating
device, said safety device comprising a thermally
r sponsive element having a space therein, a
pair of spaced conductors in said space, a fusi
ble link between said conductors, said safety de
vice being thermally responsive to material be
ing heated whereby when the heat of said heating in
device exceeds a predetermined temperature said
link will fuse and ?ow to the bottom of the space
interrupting the flow of current through said
conductors to said heating device, said space be
ing suf?ciently 1arge that when said fusible link
has flowed to the bottom thereof, there will be
no arcing between said conductors and the fused
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