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July 22, 1947.
2,424,438
J. W. DOWNlE
PROTECTIVE SYSTEM FOR ELECTRIC BLANKETS
.F‘iled Nov. 1, 1944
'Invehbow
‘
John W. Downie ,
His Attorney.
Patented July 22, 1947
2,424,438
UNITED STATES PATENT OFFICE
2,424,438
PROTECTIVE SYSTEI“ FOR ELECTRIC
BLANKETS
John W. Downie, Schenectady, N. Y., assignor to
General Electric Company, a corporation of
New York
Application November 1, 1944, Serial No. 561,363
4 Claims.
(Cl. 219-20)
1
2
This invention relates to protective systems,
an electrically-heated blanket used upon a bed
heating circuit and operated responsively to the
?exing of the mattress support. When the bed
is unoccupied and the support un?exed the circuit
stead, and it has for its object the provision of
improved protective means of this character,
ever, when the support is ?exed due to the weight
more particularly to such a system for protecting
control device opens the blanket circuit.
Certain electric blankets now found upon the
market comprise a blanket having channels woven
or stitched therein through which is threaded an
electric heating conductor. The conductor is
energized from a suitable source of electrical sup
How
of a person in the bed the control device com
pletes the circuit through the control device and
conditions the blanket for energization, More~
over, once the control device has been operated
10 to energize the blanket it will keep it energized
ply and generates su?icient heat to keep the
blanket at some vdesired temperature under nor
for a predetermined period of time after the bed
is unloaded. This is for the purpose of giving
mal conditions of operation during which the
blanket is spread out over the bed. It occasion
the preliminary heating period referred to above.
ally happens that in the morning the occupant
gets up and folds the blanket up at the foot of
the bed without disconnecting the blanket from
For a more complete understanding of this in
vention, reference should be had to the accom
panying drawing in which Fig. 1 is a plan view of
a bed provided with an electric blanket embody
the supply source. As a result the heat lost from
ing the protective system of this invention, parts
a section of the heating conductor is greatly re
of the bed and blanket being broken away so as
duced and this tends to cause localized heating 20 to illustrate certain structural details; Fig. 2 is
with the attendant possibility of ?re. In order to
an enlarged fragmentary sectional view taken
preclude the possibility of such local overheat
through a portion of the bed shown in Fig. 1;
ing, there has been incorporated into the blanket
Fig. 3 is a view similar to Fig. 2 but illustrating
a number of ‘protective thermostats which are
certain elements in different operative positions
suitably placed in different areas and connect 25 than they occupy in Fig. 2; Fig. 4 is a fragmentary
ed so that overheating in any one of these areas
view showing certain of the elements of Figs. 2
causes the associated thermostat to operate to de
and 3 but in a different operative condition; Fig.
energize the blanket. At times the excessive over
5 is a perspective View of a controlling element
heating occurs in a part of the blanket which does
used in this protective system; and Fig. 6 is a
not have a protective thermostat. At other times _
some difficulty has arisen because the safety ther
mostats themselves have failed to function.
This invention contemplates an improved pro
tective system for blankets which, with the ex
ception of a relatively short preliminary heating
period, prevents the energization of the blanket
as long as the bed is unoccupied, regardless of
the fact that the blanket may be “plugged in” to
its supply source. However, whenever the bed is
occupied the system conditions the blanket for 40
energization.
Also, as intimated above, this invention con
templates such a system arranged so that it is
conditioned to effect the heating of the blanket
for a predetermined preliminary period merely by
momentarily “loading” the bed; that is, by press
ing down on the bed or by lying on it for a mo
ment and then unloading or releasing it, the
‘cbntrol will be conditioned to cause heating of
diagrammatic plan view of the electrically heat
ed blanket, and of certain temperature control~
ling mechanism therefor, and further, illustrating
the protective means provided therefor and ar
ranged in accordance with this invention.
Referring to the drawing, this invention has
been shown in connection with a bed I provided
with supporting end heads 2 and 3, and a bed
spring 4 having the usual wire mesh 5 anchored
to a supporting frame 6 by means of spiral springs
‘I. Mounted upon the bed spring 4 is a suitable
mattress 8, and positioned normally to cover the
mattress 8 is an electrically heated blanket 9.
The blanket 9 is provided with a resistance heat
ing Conductor H) which is formed into a series
of convolutions H extending throughout sub
stantially the full area of the blanket, as shown
in Figs. 1 and 6. It will be understood that the
conductor l0 preferably will be threaded through
suitable channels (not shown) provided for it in
the blanket for a selected period of time such as 50 the blanket, which channels may be formed by
30 or 40 minutes or so; this provides for a pre
stitching or weaving them into the blanket itself.
liminary heating period for the bed so that it may
Connected into the energizing circuit of the
be warmed up prior to retiring.
heating resistance ID are a plurality of suitable
More speci?cally, this system comprises a cir
protective thermostats l2 (not constituting a part
cuit controlling device connected in the blanket 55 ofv this invention), which thermostats are con
2,424,438
4
3
bed spring 4 unflexed the pool of mercury 26 will
nected in series with the conductor, as shown,
be in its position shown in Fig. 2 wherein the
and which are placed Within the blanket in heat
circuit between the contacts 23 is broken. Under
conducting relation therewith and set to operate
such conditions, the blanket cannot be energized,
in response to an abnormally high temperature
irrespective of the fact that the switch 14 and
to deenergize the resistance conductor. While six
the switch contacts 56 of the thermal control de
of these thermostats have been shown, it will be
vice I 5 be closed.
understood that any suitable number may be
However, when a person gets into the bed the
used.
bed spring ?exes downwardly, as is well under
The heating conductor 15 is energized from a
suitable source of electrical supply [3 through 10 stood, and when this happens the casing 19 tilts
from its position of Fig. 2 to its position of Fig, 3.
a manually operable control switch l4 and a suit
This tilts the envelope 22 and permits the pool
able temperature responsive controlling device
of mercury 25 freely to flow through pipe 29 and
l5 located in the bedroom to respond to its tem
attain a uniform level through both end portions
perature. This control device comprises a switch
it connected in series with the heating resist 15 of the envelope and thereby make contact with
both contacts 23, as shown in Fig. 3; this oper
ance ltl, which switch is operated by means of
ation closes the circuit to the resistance conduc
a bimetallic temperature responsive element IT.
tor ID through the control device [9. Therefore,
The bimetallic element i7 is heated by a local
the blanket may function in the normal manner
heater :8 as well as by the temperature of the
room in which the blanket is located. One end 20 to heat up under the control of the control de
vice l5, and as long as the bed is occupied the
of the resistance 58 is connected to one conduc
circuit will be completed through the control
tor of the supply source 53, while the other end
device l9.
is connected to the other conductor through the
When the bed occupant gets up, the mattress.
switch contacts 16 and the switch 14, as clearly
shown in Fig. 6. This system of control is de 25 of course is unloaded, and as a result the bed
spring 4 returns the envelope 22 to its position
scribed. and broadly claimed in the patent to
of Fig. 1. But because of the partition 2'! the
W. K. Kearsley No, 2,195,958, dated April 2, 1940,
mercury pool is divided, part thereof being
and reference is made thereto for a more com
dammed on the right side of the partition, as
plete description of the control system.
The protective system arranged in accordance 30 shown in Fig. 4. This maintains the blanket cir
cuit closed, and it will do so until enough of the
with this invention prevents undesired energiza
mercury in the right side leaks through the open
tion of the blanket 9 when the bed is not used,
ings 23 in the partition to the left side of the
but conditions the blanket for normal operation
partition to uncover the right-hand electrode
when the bed is occupied. This means com
23, as shown in Fig. 2. When this happens the
prises a switch iii connected in series with the
blanket circuit is interrupted. The openings 23
resistance conductor ill, as shown in Fig. 6.
have such a size that the blanket will remain
The switch l8 comprises a casing 25 which
energized for 30 to 40 minutes or for some other
is suspended from the mesh 5 by means of sup
suitable period of time which is sufficient to heat
porting arms 2!. Mounted within the casing
iii is an elongated envelope 22 within the end ~10 up the blanket and mattress initially. The ad
vantage of this is that by momentarily “loading”
portions of which are a pair of spaced ?xed con
the mattress 30 or 40 minutes prior to retiring,
tacts 23 which are connected into the circuit of
the blanket will be energized and remain ener
the resistance conductor it}, as clearly shown in
gized for that period so as to heat up the bed
Fig. 6. Preferably the lower half 24 (Fig. 5) of
the envelope will be formed of metal, while the 45 prior to retiring so that it is nice and warm when
the occupant gets into the bed. After that the
upper half 25 will be formed of glass; and pref
system will function as fully described above.
erably the contacts will enter the casing through
While I have shown and described a particu
the top wall of this glass upper half. Within the
lar embodiment of my invention, it will be obvi
envelope there is a pool 28 of electrically-con
ous to those skilled in the art that various
ducting liquid material such as mercury, this pool
constituting liquid contacting means for making
changes and modi?cations may be made without
and breaking contact between the two spaced
departing from my invention in its broader as
contacts 23. Also located Within the casing about
pects and I therefore aim in the appended claims
midway between its ends is a transverse partition
to cover all such changes and modi?cations as
2? located midway between the ends of the cas
fall within the true spirit and scope of my in
ing and dividing the lower half thereof into two
vention.
parts of substantially equal volume. This par
What I claim as new and desire to secure by
tition wall 2‘! has several relatively small aper
Letters Patent of the United States is:
tures 23 extending therethrough; and in addi
1. In combination, a bed, an electric heating
tion there is a tube 29 having one end passing
member for heating a person reclining on said
through the lower part of the partition and its
bed, said heating member having a heating cir
other end curved upwardly in the right-hand end
cuit, safety switch means connected in said cir
of the envelope, as shown.
cuit to control said heating member operated
The envelope 22 is mounted within a suitable
to close said circuit by the loading of said bed
ring support 39 which is pivotally mounted in the
due to the weight of a person reclining thereon,
casing l9 and the position of which with refer
and to open said circuit in response to the un
ence to the casing may be adjusted by means of
loading of said bed, and time~delay means con
a thumb screw 3!. As shown the support 39 is
trolling said switch to delay the opening of said
provided ~with an extension 32 which is biased
circuit so that said circuit can be closed to heat
against the thumb screw 3! by means of a tension
spring 33.
It will be observed that the casing i9 is posi
tioned crosswise of the bed so that the envelope
22 is also positioned crosswise thereof, as shown
in Fig. 2. When the bed is unoccupied and the 75
said bed for a predetermined time interval by
loading said bed momentarily and then unload
ing it.
2. In combination, a bed having a mattress, a
?exible bed spring supporting said mattress, an
electrically heated blanket covering said mattress
5
2,424,438
for heating a ‘person reclining on the mattress, said
blanket having a heating circuit,thermallyrespon
sive switchmeans responsive to the air temperature
of the room in which said bed and blanket are
located connected in said circuit for energizing
and deenergizing it responsively to variations in
said air temperature so as to hold a substan
tially constant temperature in said blanket, and
an auxiliary circuit controlling safety device elec
trically connected in said heating circuit to open
and close it comprising a closing casing mounted
bed for a predetermined time interval by momen
tarily loading said mattress and then unloading
it
4. In combination, a bed having a mattress, a
?exible bed spring supporting said mattress, an
electrically-heated blanket over said mattress
having a heating circuit, and a circuit controlling
device electrically connected in said heating cir
cuit to open and close it comprising a closed
casing mounted upon said bed spring, a pair
of spaced contacts in said casing, ?uid contact
means also within said casing normally out of
bridging contact with both of said contacts when
in said casing normally out of bridging contact
the bed spring is un?exed, but when said bed
with both of said contacts when the bed spring
spring is ?exed downwardly a predetermined
is un?exed, but when said bed spring is ?exed 15 degree due to the loading of the mattress said
downwardly a predetermined degree due to the
casing is tilted to cause said liquid contact
loading of the mattress by a person getting into
means to ?ow and bridge both of said contacts
said bed said casing is tilted to cause said liquid
to close the circuit through said control device,
contact means to bridge both of said contacts
and a partition within said casing between said
20
thereby to close the circuit through said safety
contacts provided with apertures to control the
device, and when said mattress is unloaded by the
rate of ?ow of said liquid contact means to break
person leaving said bed said casing is tilted to
contact with one of said contacts when said spring
cause the liquid contact means to break said con
is un?eXed and the casing tilted back so that said
tacts to reopen said circuit, irrespective of the
temperature of the air in said room and its effect 25 blanket circuit remains closed through said con
trolling device for a predetermined interval of
upon said thermally responsive switch.
time after said spring is unflexed.
3. In combination, a bed having a mattress, a
JOHN W. DOWNIE‘.
flexible bed spring for said mattress, an elec
upon said bed spring, a pair of spaced contacts
in said casing, and ?uid contact means also with
trically heated blanket covering said mattress
for heating a person reclining on the mattress, 30
said blanket having a heating circuit, and a
circuit controlling safety switch electrically con
nected in said heating circuit to open and close
it comprising a switch member connected in said
circuit and also connected to said bed spring so
as to be operated by its ?exing'and unflexing to
close said circuit through said safety device when
said bed spring is ?exed down a predetermined
degree by a person getting into said bed, and
to open said circuit through said safety device 40
when said spring unflexes responsively to the un
loading of said mattress when the person gets
out of said bed, and time-delay means controlling
said switch to delay the opening of said circuit
so that said circuit can be closed to heat said
REFERENCES CITED
The following references are of record in the
?le of this patent:
Number
UNITED STATES PATENTS
Name
Date
2,195,958
2,403,803
Kearsley __________ __ Apr. 2, 1940
Kearsley __________ __ July 9, 1946
2,185,051
2,260,715
2,206,436
2,359,254
Daigle ___________ __ Dec. 26,
Ketchem _________ __ Oct. 28,
Spencer ___________ __ July 2,
Silver ___________ __ Sept. 26,
1939
1941
1940
1944
1,758,546
1,661,354
2,114,152
Wartmann _______ __ May 13,
Ayre ______________ __ Mar. 6,
Shaw ____________ __ Apr, 12,
Shellhamer ______ __ Nov. 20,
Heiser et a1 _______ __ Apr. 20,
1930
1928
1938
1906
1943
836,282
2,317,189
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