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Патент USA US2116836

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May 10, 1938.
A. J. KERCHER
2,116,836
ELECTRI CAL THERMOSTAT
Filed July 19, 1955
2 Sheets-Sheet l
,6/
3
INVENTOR.
’ A/VI/IUI' J. ke/‘che/f
ATTORNEY.
Miry 10, 1938.
‘A. J. KERCHER
2,116,836 ‘
ELECTRICAL THERMOSTAT
Filed July 19, 1935
2 Sheets-Sheet 2
\<
INVENTOR.
,Jr/?ur J Kara/76W
_ 4347 J5 J9
BY p
MW
ATTORNEY.
Patented May 10, 1938
2,116,836
UNITED STATES PATENT OFFICE
2,116,836
EIECTBIOAL THERMOSTAT
Arthur J. Kerclier, Berkeley, Calif.
Application July 19, 1935, Serial No. 32,183
3 Claim. (01. 200-—137)
This invention relates generally to apparatus
for controlling ?ow of electric current in accord
ovens or electric water heaters, where it is desired
to interrupt current supply when the temperature
claimed in Patent No. 1,671,592, granted May
ance with the temperature of a ?uid or other
heated body. It has particular application to
5 electrically heated appliances, such as electric
of the heated air or water reaches a predeter
mined value, or where maintenance of a prede
16 termined temperature level is required.
It is an object of the invention to provide an
apparatus of the above character which will be
simple and reliable in operation, and which will
serve to control relatively heavy current loads.
Another object of the invention is to provide an
15
apparatus of the above character whichv will
make use of elements having diiferent tempera
ture coe?lcients of expansion, which will be so
coordinated as to afford ample relative move
20 ment for a given temperature change to operate
contacting mechanism, but which will not neces
sitate the use of thermostatic elements of undue
length.
’
Additional objects of the invention will appear
25 from the following description in which the pre
ferred embodiments of the invention have been
set forth in detail in conjunction with the ac
companying drawings.
Referring to the drawings:
30
Fig. 1 is a side elevational view, partly in cross
section, illustrating apparatus incorporating the
present invention, the particular form illustrated
being combined with elements of an electric
35
form shown, the apparatus is intended primarily
for use with electric -hot water heaters, the
mounting serves to carry a plurality of electrical
heating elements l3 of the immersion type, to
gether with a thermostatic operating unit It. 5
The elements l3 can be of the type disclosed and
water heater.
Fig. 2 is a side elevational detail of certain of
the operating parts as shown in Fig. 1, but show
ing different operating positions.
Fig. 3 is a sectional end view of the apparatus
.as shown in Fig. 1, the section being indicated
by the line 3-3 of Fig. 1.
Fig. 4 is a cross-sectional detail, taken along
the line 4-4 of Fig. 1.
Fig. 5 is a side elevational view, partly in cross
section and showing a modification of the inven
45 tion suitable for use in conjunction with an elec
tric oven.
Fig. 6 is a cross-sectional detail taken along
the line H oi.’ Fig. 5.
Fig. 'l is a diagrammatic view, illustrating typ
Brie?y, each element l3 consists of a
two passages for accommodating an electrical re
sistance conductor I8. The electrical resistance
conductor in this instance is coiled or convoluted,
and is disposed within beads or tubes IQ of suit
able refractory insulating material. One end of 15
each of the tubes l6. extends through a member
20, to which the plates I i and I2 are secured, and
which becomes a part of the general mounting.
The free ends of the tubes iii are sealed by clo
-.sure caps or plates 2|.
As disclosed in said Pat- '
ent No. 1,671,592 the creases ll terminate short
of the closure 2|, thus a?ording a lateral pas
sage-way through which the conductor‘ l8 and
its tubular insulation I! may extend.
The thermostatic operating unit It preferably 25
includes a tubular metal case 22, which is formed
similar to the sheath It for the heating elements
l3. One end of this casing likewise extends
through member 20 of the mounting, while the
free end is sealed by closure cap 23.
30
Extending longitudinally within the passages
2|, aiforded within the casing 22, are the rods 25
and 26. These rods are preferably made of a
metal or metal alloy having a negligible tem
perature coef?cient of expansion, as for example 35
invar. On the other hand casing 22 is made of
a metal or metal alloy having a substantial tem
perature coe?icient of expansion, as for exam
ple nichrome, copper or bronze. Within the
closed end of casing 22, there is a rocker 21, 40
havingv a pivotal mounting 28 to the supporting
bracket 29. The adjacent ends of rods 25 and
26 have spherical shaped end portions 3| which
are adapted to seat in spherical shaped sockets
32, provided in the arms of the rocker. The 45
other ends of rods 25 and 26 are shown project
ing from the casing 22. Where a terminal block
33 may be provided for making electrical con
nection to the heating elements I3. openings 34
can be provided through which the rods are ac
ical electrical circuit connections.
Referring ?rst to Figs. 1 to 4 inclusive, the
apparatus illustrated includes a mounting des
ignated generally at ll, which may vary as to
detail but which in this instance includes a pair
56 of spaced metal (plates II and I2.
29, 1928.
tubular metal sheath i6, having its opposite sides
provided with longitudinal creases H, to provide 10
Since in the
commodated.
One of the rods 25 and 26 and in this-instance
rod 26, is operativeiy connected to contacting
mechanism designated generally at 36. The other
rod 25 is engaged by abutment means carried by
60
2
52,116,836
the moimting ill, and which can be constructed
as follows:
A plunger 51] is aligned with rod 25, and is
slidably disposed within a sleeve 35. Sleeve 38 is
in turn threaded into a member 59, which ex
tends between the two plates ii and i2 and is
secured thereto. One end of the sleeve carries
ahand adjustment lever ill, by means of which
strip 18. Metal strip ‘ill is carried by an insulat
ing block ‘it, which is a part of lever 68.
In order to a?ord an interlock between lever
68 and armature 53, the lever carries an upward
extending spring tongue iii, the upper end of
tracted with respect to the mounting. Plunger
37 carries a head 53, which is provided with spher
ical shaped socket M to accommodate the spher
ical shaped end portion Mi of rod 25. A compres
which is shaped to form a latch 82. Swinging of
tongue M in one direction is limited by a rela
tively rigid portion 83 of the lever 68. Latch 82
is adapted to engage a dog 84, formed upon the
free end of armature 55.
Mounted on the lever 68, adjacentthe open
leg 85 of core 5!, there is a magnetic armature
55. The adjacent core leg 85 is slotted to accom
sion spring M has its one end seated upon the
modate a shading coil 81.
the sleeve can be turned and advanced or re
15 head 53, and its other end seated upon the ad
iacent end of sleeve 3&3. The outer end of plunger
3? is provided with some suitable form of limiting
shoulder, as for example, it can be threaded to
accommodate the lock nuts 45. It is apparent
20 that the abutment means described serves to ap
ply force to rod 25 against the rocker 2?, by virtue
of the compression spring M‘. The magnitude
of this force and the positioning of sleeve 38, can
be varied by changing the setting of lever M.
25
The contacting mechanism may be a simple
set oi‘ electrical contacts adapted to be opened and
closed by relative movement between the outer
end of rod 25 and the mounting ill. However,
for handling relatively heavy current loads, a
30 more elaborate type of contacting mechanism is
desirable, in order to avoid arcing. The mecha
nism illustrated is of the relay type, and includes
a magnetic core 5i, one leg of which is provided
with the winding 52. Near the poles of the core
35 5i there is a magnetic armature 53, carried by
pivot pin 55. Armature 53 carries a movable con
tact 55, adapted to cooperate with a stationary
contact 517. While various expedients can be uti
lized for attaching contact 55 to the armature 53,
the arrangement illustrated utilizes a block 55 of
.
The typical circuit connections shown in Fig. 15
7, can be brie?y explained as follows:—0ne side
of the current supply line i is shown connected
to terminal of the electrical heating unit Ma.
The other current supply line 2 is connected to
the stationary contacts 5? and 16. One terminal 20
of relay winding 52 is connected to contact ‘[4,
and the other to the other terminal of the heat
ing unit I311. The heating units also connect to
the movable contact 55, whereby when contacts
55 and 5'! are closed, the heating units are con 26
nected directly across the current supply.
Operation of the apparatus described above,
can now be explained as follows:—Assuming op
eration with a hot water heater, the heating
units 83, as well as the casing 22 of the thermo 80
stat operating means, extend into a water tank,
or into a chamber through which water to be
heated is being circulated. Lever 4| is set in
accordance with the temperature at which it is
desired to interrupt the ?ow of current, as for
example 180°. While the lever 68 is latched
with respect to armature 53, the main contacts
55 and 57 are closed, and current is supplied to
the electrical heating units. Likewise at such
time the relay winding 52 is short circuited, and 40
insulating material, mounted upon the armature no current flow occurs through the same. Lever
55. "Qverlylng the upper face of block 58, there 58 is held in closed position by virtue of the pres
is a metal strip 59, which carries the contact 56. sure of spring 4?, which is transmitted through
A. threaded pin 59 is mounted on block 58, and rod 25, rocker 2i, and rod 26. As the tempera~
45 extends loosely through the metal strip 59. A 'ture of water surrounding casing 22 increases, 45
light compression spring 52 presses down upon heating of this casing causes it to expand longi
strip 55, and has its upper end seated upon an
adjustable nut 85. Metal strip 59 also carries a
depending stud M, which extends loosely into a
recess 55 provided in block 58. Thus when arma
ture 55 is pulled downwardly by coil 52, a cer
tain amount of lost motion is provided between
the insulating block 58 and the metal strip 59,
so that contacts 55 and 571 are resiliently urged
r together by spring 52. A suitable spring Bl can
be provided for lifting the armature 55, and thus
causing the contacts 55 and 5? to open, when the
64)
65
core 5i is deenergized.
In addition to the armature 53 there is a lever
68, which is carried by a pivot pin 69. Immedi
ately below pivot pin 69 the lever is provided
with a spherical shaped socket ‘ii, in which the
adjacent end portion '52 oi rod 25 is seated. As
viewed in Fig. l, lever 58 is urged to turn in a
clockwise direction about the pivot pin. 69, by a
leaf spring is. Lever 55 carries a movable elec
trical contact TM, which is adapted to cooperate
with a stationary contact ‘175. Contacts 5?? and
70 15 are directly electrically connected with each
other, as illustrated.
As representative of suitable arrangement for
supporting the contacts M on lever 55, this con
tact is shown carried by a threaded stud ‘ill, which
75 in turn is adiustably carried by one end of a metal
tudinally, while the rods 25 and 26 do not ex»
pand. Thus if plunger 31 were ?xed, relative
movement would occur between the closed end
of the casing 22 and the corresponding end of 50
rod 25, to cause rotation of the rocker 2''! in a
counter-clockwise direction, as viewed in Fig. 1,
and such relative movement would be transmit
ted to rod 26. However since rod 26 would like
wise remain of fixed length, the relative move~ 55
merit between the end portion 12 of rod 26 and
the mounting iii, would amount to substantially
twice the change in length of casing 22, by vir
tue of thermal expansion. Since plunger 31 is
resiliently urged against rod 25 by compression
spring 41!, it may initially move somewhat rela
tive to the mounting as the temperature in
creases, until lock nuts 68 engage the outer end
of sleeve 38. Further expansion of casing 22
causes relative movement between the end por
05
tion ‘E2 of rod 26 and the pivot pin 69, thereby
causing lever 58 to swing towards open position,
to open contacts ‘M and ‘I6, and to displace the
latch 52 with respect to dog 84. Armature 53
now snaps to open position under the urge of 70
spring 5?, to open the main contacts 56 and 51,
and to interrupt supply of current to the heat
ing units. Full open positions of the levers 68
and 55, are shown in Fig. 2. When the casing
22 has cooled at sumcient amount, its contraction 75
3
2,116,836
causes lever 68 to swing in a counter-clockwise
direction, as shown in Fig. 2. Such movement
serves to close the contacts 14 and 16, which as
will be evident from the circuit diagram of Fig. 7’,
connects the relay winding 52 across the current
supply lines I and 2, in series with the heating
units i3a. Magnetization of core 5| immediately
causes armature 53 to snap to closed position,
which again causes the latch 82 to engage the
dog 84. For the short interval that core 5| is
energized, the magnetic pull of core leg 85 upon
armature 8G, prevents vibrating movements of
lever 58, and thus chattering of contacts 14 and
16 is prevented.
It is a simple matter to adjust the apparatus
for diiierent temperature level of operation, by
changing the setting of lever 4|. It will be noted
that the type of abutment means utilized in con
junction with this lever, for pressing upon rods
25, avoids displacement of parts or possible
breakage when the casing 22 is relatively cool.
The multiplied motion secured by utilizing two
rods 25 and 26 in a single expansible casing,
makes it possible 'to avoid the use of casings of
undue length, and at the same time makes pos
sible accurate regulation at a desired tempera
ture level. Likewise in the particular type of
apparatus illustrated, in which heating units are
I claim:
1. In an electrical thermostat, a mounting, an
elongated tubular casing having one end of the
same secured to said mounting, the other end
of said casing being closed, said casing being
formed 0‘ metal having a substantial tempera
ture coeilicient of expansion, a pair of metal rods
extending longitudinally through said casing in
parallel relationship, a rocker pivotally mounted
in a closed end of said casing and having its 10
arms ‘connected to corresponding ends of said
rod, both said rods being made of metal having
negligible temperature coemcient of expansion,
contacting means actuated by relative movement
between the other end of one of the rods and said 15
mounting, and means for adjusting the tempera
ture level of operation of said contacting means,
said last means including an adjustable abut
ment carried by the mounting and engaging that
end of the other rod removed from said rocker,
said last means including a movable abutment
engaging that end of the other rod remote from
the rocker, a spring serving to urge said abut
ment against its associated rod, and adjustable
means serving to limit movement of the abut
ment in one direction.
‘
2. In a thermostatic device, a mounting, an
elongated casing having one end of the same se
grouped in close proximity to the casing 22, the
cured to said mounting and being formed of ma
water is caused to thermally circulate about the
casing 22, and the casing 22 is heated to a tem
cient of expansion, that end of the casing re
perature somewhat higher than the temperature
of the main body of water being heated, so that
it will in e?ect anticipate a desired temperature
level, in interrupting the current supply. Fur
thermore, if for some reason water should be
drained from the heater, the casing 22 will be
heated by radiation from the units l3, and by
_hot currents of air, so that under such condi
tions it will interrupt the current supply before
the heating units are permanently injured by an
unduly high temperature.
The modi?cation illustrated in Figs. 5 and 6
is similar to that previously described with refer
ence to Figs. 1 to 4 inclusive, except that it is in
tended particularly for use with electrical ovens,
such
as
are
employed
on
domestic
cooking
ranges. In such applications the casing 22a is
arranged to extend into the oven compartment,
preferably in relatively close proximity with the
heating elements. The outer surface of easing
22a is shown provided with'scarf lines or grooves
Si, in order to afford a greater exposed area, and
.thercby increase heat transfer with respect to
the surrounding air. A modi?ed form of abut
ment means for engaging the rod 25, is also illus
trated, and is constructed as follows:—An L 92
is carried by pivot pin 93, and has its one arm
provided with a socket 94, in which the end por
tion 46 of rod 25 is seated. The other arm 96
()l lever 92 is forked and is connected to one end
of a tension spring 91. A rod 98 is threaded into
a member 99, which in turn is carried by the two
plates II and I2 of the mounting.‘ A collar llll
is formed on rod 98, and one face of this collar
bears upon the raised portions I02 of arm 96.
It is evident that the type of abutment means
described with respect to Figs. 5 and 6, operates
in substantially the same manner as the abut
ment means disclosed in Figs. 1 to 4 inclusive.
‘When the apparatus has been set for operation
at elevated temperatures, as for example, be
tween 205 and 500° F., collar l?l will be spaced
from the portions I02, when the casing 22a is
cold.
terial having a substantial temperature co-e?l- ‘
mote from'said mounting being closed, a rocker
pivotally connected to said casing within said
closed end, a pair of rods extending longitudi
nally within said casing, said rods being formed
of a material having a negligible temperature co
e?icient of expansion, connections between the
corresponding ends of said rods and the arms of
said rocker, adjustable abutment means for the
other end of one of the rods, said abutment 40
means normally serving to limit the longitudinal
movement of said‘one rod in a direction towards
said mounting, but permitting movement in an
opposite direction, a spring associated with the
abutment means and against which the abutment 45
means may yield when said one rod is moved
relative to the mounting beyond said limit, and
response means actuated by relative movement
between the mounting and the other end of the
second rod, said last means including _a movable 50
member engaging the second rod, and a second
spring for urging said last named member in a
direction to urge the second rod towards said
rocker, said second spring being incapable of sup
plying su?lcient force to e?ectively overcome the 55
force of the ?rst named spring.
3. In a thermostatic device, a mounting, an
elongated casing having one end of the same se
cured to said mounting and being formed of ma
terial having a substantial temperature co-e?i 60
cient of expansion, that end of the casing remote
from said mounting being closed, a rocker pivot
ally mounted within said casing at a point re
mote from said mounting, a pair of rods extend
ing longitudinally within said casing, said rods
being formed of a material having a negligible
temperature co-e?icient of expansion, connec
tions between the corresponding ends of said rods
and the arms of said rocker, adjustable abut
ment means for the other end of one of the rods,
said abutment means normally serving to limit
movement of the one rod in a direction toward
the mounting but permitting movement in an op
posite direction, a spring associated with the
abutment means and against which the abutment
4
emeeae
means may yield, and response means actuated
by relative movement between the mounting and
the other end of the second rod, said‘last means
including a lever pivotally carried by the meunt
mg and capable of limited oscillating movement,
one arm of said lever having abutting engage
ment with the adjacent end of the second met,
and a spring serving t0 urge said lever in a di
rectton to force said arm against said second rod,
the force thus exerted by said second named
spring being normally applied against the force
of the ?rst-named spring but being incapable of
overcoming the force exerted by the ?rst named
spring.
ARTHUR J. KERCHER.
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