close

Вход

Забыли?

вход по аккаунту

?

Патент USA US3091950

код для вставки
June 4, 1963
c. |_. FELDMAN ET AL
3,091,940
THERMOCOUPLE REFERENCE JUNCTION
Filed March 26, 1962
55 L53
INVENTORS
JOHN A. BERGIN
CHARLES L. FELDMAN
ARNOLD C_ FIELDS
WWgLW
ATTORNEYS
1C3
3,991,940
Patented June 4, 1963
2
3,091,940
TERMOCOUPLE REFERENCE JUNCTION
Charles L. Feldmau, Saxonville, Arnold C. Fields, Med
?eld, and John A. Bergin, Framingham, Mass, assign
ors to Joseph Kaye & Company, Inc., Cambridge,
Mass, a corporation of Massachusetts
Filed Mar. 26, 1962, Ser. No. 182,312
8 Claims. (Cl. 62-3)
unit whereupon heat is allowed to ?ow back into the con
tainer melting a portion of the ice until the volume of the
container and thus the length of the bellows decreases
sufficiently to deactnate the switch. The foregoing process
takes place at the constant equilibrium temperature of ice
and water thus maintaining the reference thermocouple at
a constant 0° C.
Means are provided for accurately
adjusting the position of the switch with respect to the
bellows so that the position of the water-ice interface in
This invention relates generally to devices for maintain 10 the container may be accurately controlled.
ing a constant temperature, and more speci?cally, to de
vices for maintaining a thermocouple junction at a known
reference temperature.
When a thermocouple is employed to make accurate
temperature measurements, it is imperative that one junc~
tion of the thermocouple be maintained at a constant,
known reference temperature. The reference temperature
customarily employed is 0° C., the melting point of ice.
Under the teachings of the prior art, it has been com
mon to provide an insulated container of the well-known
vacuum bottle or thermos type which is ?lled with crushed
ice and water and into which the reference junction of the
thermocouple is inserted. The thermos container is placed
at some convenient location, usually in the work area, and
a careful watch is maintained to replenish the ice in the
thermos as the ice melts. This replenishing operation
requires not only substantial attention by personnel in
volved, but also necessarily requires the transport of ice
These and other objects and the features of our inven
tion will appear as the description proceeds with the aid
of the accompanying drawings, in which:
FIG. 1 is a side view, partially in section, of a preferred
embodiment of our invention; and
FIG. 2 is a schematic diagram of the power supply for
our device.
Referring now to FIG. 1 of the drawings for a more
particular description of our invention in a preferred em
bodiment thereof, an open topped casing, indicated gen
orally at 10, is shown having a substantially ?at bottom 12.
The casing 16 is constructed of a suitable heat transfer
material in order that it may serve as a heat sink, as here
inafter described, and in the preferred embodiment is con
structed of aluminum. The bottom 12 ‘of the casing 10 is
provided with a plurality of feet 14 to prevent damage to
surfaces upon which the casing 10 may be placed and
also to elevate the bottom 12 thereof from such surfaces
to permit adequate how of air across the under surface
tainers thereby creating undesirable confusion and gen 30 of the device.
erally unfavorable working conditions.
Positioned within the casing 10‘ is a vertically movable
in and about the work area to the various thermos con—
It is, accordingly, an object of this invention to provide
a device for maintaining a thermocouple reference junc
carriage, indicated generally at 16. The carriage 16 is
mounted for vertical movement on a pair of adjustment
tion at a reference temperature, which device does not
screws 18 which extend upwardly through the bottom 12.
35
require frequent attention and which can operate for sub
A tubular sleeve 3'6 is positioned about the lower portion
stantial periods of time without consuming any of its oper
of each adjustment screw 18, and a horizontal plate 20 is
ative components.
slidably engaged on the screws 18 with its undersurface
It is a further object of this invention to provide means
resting on the sleeves 36‘. The plate 20 is provided to
for maintaining a thermocouple reference junction at 0° C.
position and securely hold a thermoelectric cooler and
in which the reference junction is maintained at a water 40 reference junction container, hereinafter described. A not
ice interface and in which the water~ice interface may be
22 is provided on each adjustment screw 18, in screw
adjusted, if necessary, to position it exactly at the reference
junction.
threaded engagement therewith; by changing the position
of the nuts 22 the holding force exerted on the plate 20
It is still another object of this invention to provide
means for maintaining a thermocouple reference junction
can be varied.
at 0° C. in which a water-ice reference environment is in
on each of the adjustment screws 113 resting at its bottom
end on the nut 22. A pair of L-shaped brackets, indicated
generally at 26, are also slidably engaged on the adjust
ment screws 18 respectively by providing a suitable aper
ture 28 in a horizontal leg 30 of each bracket 26. In
assembled condition, the horizontal legs 30 rest on the
upper ends of the compressible rubber sleeves 24, respec~
sulated from the effects of ambient temperature.
It is a still further object of this invention to provide
structure integrally incorporating a thermocouple ref
erence junction which structure will maintain the reference
junction at a desired reference temperature.
In the practice of our invention, in a preferred embodi
ment thereof, we provide a thermocouple reference junc
A compressible rubber sleeve 24 is slidably positioned
tively.
tion and reference environment producing device as a pre— 55 ' Vertical adjustment of the brackets 26 with respect to
assembled unit comprising a sealed cup-like container hav
ing an upstanding neck portion, the container and neck
portions being initially ?lled with water. A reference
junction for a thermocouple is positioned within the con
the bottom 12 of the casing 10 is accomplished by secur
ing an interiorly screw threaded nut 32 to the horizontal
legs 30 of the brackets 26, respectively. The nuts 32 are
secured to the brackets 26 in any suitable fashion, and in
tainer. The container is mounted upon a thermoelectric
the preferred embodiment a locking element 31 is pro
cooling unit which is operative to reduce the temperature
vided slidably engaged on the adjustment screw 18 and
within the container to convert a portion of the water
having a ?rst tab 33 which may be crimped over the nut
therein to ice. The upstanding neck portion of the con
32 and 1a second tab 35 which may ‘be crimped under the
tainer is constructed as a ?exible bellows, the upper ex
‘bracket 26. The nuts 32 are positioned in axial align
tremity of which is positioned adjacent a switch. As the 65
ment with the apertures 28 in the brackets 26, the com
thermoelectric cooling unit removes heat from the water,
pressible ‘sleeves 24 and the apertures in the horizontal
and as a percentage of the Water is converted to ice, the
bottom plate 20. The interior screw threads of the nuts
volume of the water-ice mixture within the container and
32 are in cooperating engagement with exterior screw
upstanding neck increases and the ?exible bellows portion
of the neck is extended, thereby actuating the switch. The 70 threads 34 provided along a substantial upper portion ‘of
the adjustment screws 18. It will thus be noted that by
switch is coupled to the thermoelectric cooling unit in such
rotation of the adjustment screws 18, the ibrackets 26
fashion that actuation {of the switch deactivates the cooling
3,091,940
3
may be caused to move vertically with respect to the bot
tom 12.
The brackets 26 are each provided with an upstanding
from escaping at the point at which the thermocouple
junction 64 passes through the side wall 52. In the pre
ferred embodiment of FIG. l, the thermocouple junction
vertical leg 38. The legs 33 are initially positioned in
64 is shown as permanently installed in the container St}.
opposed parallel relationship and are rigidly joined to 5 in this embodiment it is contemplated that a thermocou—
gether by a switch housing 49 as will be hereinafter de
scribed. The legs 38 and switch housing 40 are securely
joined together by means of a bolt 41. It will be noted
that the carriage 16 is dimensioned such that the switch
ple circuit having the same characteristics as the junction
64 will ‘be connected to the junction 64 in operation. It
should be noted, however, that the junction 64 may be
removable whereby the reference junction of ‘any desired
housing 40 will be movable vertically along the vertical 10 thermocouple circuit could be inserted in the container
centerline of the casing 10.
59. It should further be noted that in the preferred em
Positioned directly below the switch housing 49 at the
bodiment only one thermocouple junction 64 is shown in
vertical centerline of the casing 10 is ‘a thermoelectric
the container 50. It will, however, be appreciated that
cooling unit indicated generally vat 42, employing the
a plurality of such thermocouple junctions ss could be,
Well~known Peltier effect. The thermoelectric cooler 42, 15 positioned similarly in the container 563.
hereinafter referred to ‘as the Peltier cooler 42, is mounte
It will be noted that an aperture, indicated generally
directly on the upper surface of the horizontal bottom 12.
at 68, is formed in the horizontal plate 29 coaxial with
The Peltier cooler 42 in the preferred embodiment is
the bellows element 58 and the annular ?ange 56 on the
of semi-conductor construction having a p-type and an
container St} to permit the bellows 58 to extend upwardly
n-type element which, as usual, provide a hot junction 44 20 through the plate 26.
and a cold junction 46. A source of direct potential is
A switch 40 having an actuating button 72 is mounted
provided for the operation of the Peltier cooler 42, as
between the brackets 26, as above described, in depending
represented in the circuit diagram of FIG. 2. The power
relationship thereto. The actuating button 72 is initially
circuit of FIG. 2 comprises a step-down transformer 43,
positioned in vertical alignment with the end plate 60 on
a pair of silicon diodes 45 acting as recti?ers and a suit 25 the bellows element 53.
able choke ?lter 47 whereby a continuous DC. potential
In order to provide protection and thermal insulation
is provided for the Peltier cooler 42' at an output terminal
for the bellows 5% and further to prevent the accumula
indicated at 49. Line current is fed to the transformer
tion of any condensate on the vexterior surfaces thereof, a
43, through a switch hereinafter to be described ‘and here
rigid sleeve 76 is secured to the aperture 68 in the plate
indicated diagrammatically at 51. The power circuit 30 26 at its base. A protective rubber sleeve 78 is secured
‘ illustrated in FIG. 2 also shows fuse means 53, an ex
to the switch 40 and is mounted surrounding the rigid
ternal power switch 55 and a neon pilot'lamp sub-circuit
sleeve 76 in sliding engagement. An annular seal 80 of
indicated generally at 57.
compressible constructionis mounted co'axially with the
As stated above, the Peltier cooler 42 is mounted di
annular ?ange 56 on the top 54 of the container 54} and
rectly on the bottom 12 and its hot junction 44 is in direct 35 is of slightly larger radius than the aperture 68 provided
contact therewith. It will be noted that the casing to not
through the plate 20. It will thus be noted that when the
only serves the function of providing ‘a suitable container
under surface of plate 20 is in contact with the annular
within which the several components of the device may
seal 80 the exterior of the bellows element 53 is insulated
from conditions otherwise prevailing in the casing 10.
be assembled, but also serves the necessary function of
providing a suitable heat sinkfor the dissipation of the 40
The container 50 having been ?lled with a ?uid medi
heat produced at the hot junction 44 of the Peltier cooler
um, the interior of the casing 107 is partially ?lled with an
insulating material 82, as for example, a polyurethane
42. For this reason, and to provide electrical insulation,
anodized aluminum is used in'the fabrication of the cas
foam having a closed cellular structure. Prior to ?nal
adjustment the remaining portion of the casing 10 is
ing 10 in the preferred embodiment, however, it will be
understood that any other suitable heat transfer material 45 ?lled with ar?exible foam 84.
The preparation, adjustment and operation of the de
may be used.
'
.
vice is as follows:
The cold junction of the Peltier cooler 42 forms a hori
zontal plate 46. Mounted directly on the plate 46 is a
With the several components in assembled condition,
but prior to the addition of the foams 82 and 84, the
bottom plate 48 of a reference junction container, indi
cated generally at 50. The container 50 is provided with 50 carriage 16 is raised su?iciently to disengage the actu
ating button 72 of the switch 40 from the end plate 60
upstanding side walls 52 which are sealed to the bottom
on the bellows 58. The container 50 has been ?lled
plate 48 in a watertight fashion. The bottom plate 48
through the ?ll tube 62‘ at an earlier time with a ?uid
and container 50, in 'the preferred embodiment, are con
medium which will undergo a change of state accom~
structed of brass. A top plate 54 integrally formed with
the side walls 52 is provided having at its center an open 55 panied by a change in volume at the desired reference
temperature. In the preferred embodiment, the refer
ing de?ned by an upstanding annular ?ange 56. The
ence temperature is 0° C. and the ?uid used is distilled
transverse dimension of the annular ?ange .56 is substan
demineralized water. When the container 50 and the in
tially less than the transverse dimension of-the container’
terior of the bellows 58 are completely ?lled with water
50 as seeniin ‘FIG. 1 of the drawings.
A ?exible bellows element 58 is mounted at the upper 60 the ?ll tube 62 is pinched off to seal the water permanent
extremity of the annular ?ange 56 and is secured thereto
in watertight engagement. The upper extremity of the
bellows 58 is closed by a circular wear plate 60 which is
ly within the container.
The thermocouple reference junction 64 is connected
by suitable thermocouple wiring (not shown) to ter
minals 86 hereinafter described. The Peltier cooler 42
In order to ?ll the interior of the container 59 and the 65 is connected by wiring (not shown) to suitable. terminals
87. The switch 40, is Wired into the power circuit of
bellows 58 with a suitable ?uid medium, in the preferred
the Peltier cooler 42 in- such fashion that pressure ap
embodiment water, a ?ll tube 62 is provided which com
plied to the actuating button 72 will deactivate the power '
municates with the interior of the container 50 through
supply to the Peltier cooler~42 as shown in FIG. 2.
one of the side walls 52.
'
The nuts 32 are then rotated until the actuating button
A thermocouple junction 64 is inserted through a sec 70
72 of the switch 40 is in close proximity to the end plate
7 _ and side wall 52 of the container 50 and extends a sub
60 of the bellows 58. The insulating foam 82 is then
stantial distance into the ‘container Fl}.v It will be noted
secured thereto.
that the junction 64 is positioned parallel to the horizon
foamed in place Within the casing ‘10. The locking ele
tal bottom 48 of the container .59. A suitable seal 66
ments 31 are crimped to secure the nuts 32 to the legs
is provided to prevent the contents of the container 56 75 30 of the brackets 26 respectively and the flexible foam
3,091,940
5
.
6
.
.
obvious that a continuous control switch might be sub
84 is then foamed on top of the foam 82. A suitable
stituted therefor, whereby continuous operation of the
cover plate 88 carrying the terminals 86 for the thermo
Peltier cooler would be provided.
couple reference junction 64 is secured to the casing 10
Having thus described and illustrated a preferred em
to close it from the atmosphere.
bodiment of our invention, it is our intention to claim all
The thermocouple reference junction 64 is then con
changes and modi?cations of the example of the invention
nected through terminals 86 in a thermocouple circuit
within the spirit and scope of the appended claims.
to a known reference junction which is maintained at 0°
What we claim as new and desire to secure by Letters
C. and the Peltier cooler is actuated.
Patent of the United States is:
Because the container 50 and bellows 58 are substantial
1. Means for producing a thermocouple junction refer
ly insulated on all their external surfaces, except the 10
ence environment, said means comprising, in combination,
external surface of the bottom 48 of the container 50
a container, =a ?exible wall on said container; a ?uid me
which is in direct communication with the cold junction
dium within said container having a change of state tem
46 of the Peltier cooler 42, the cooling effect of the cooler
perature equal to the desired reference temperature; means
42 is directed almost entirely at the bottom of the con
15 on a wall of said container other than said ?exible wall
tainer 50.
for receiving a thermocouple junction to be disposed
The Peltier cooler 42 is permitted to operate until no
within said container; thermoelectric means positioned
current flows in the thermocouple circuit indicating that
at the exterior of said container and in thermal communi
the 0° C. water-ice interface within the container 50 has
cation with the interior thereof for removing heat from
reached the level of the thermocouple junction 64. The
adjustment screws 18 are then rotated to cause the 20 said ?uid medium contained within said container, and
means actuated by the movement of said ?exible wall for
brackets 26 to descend until the end plate 60 on the
controlling said thermoelectric means for removing heat
bellows 58 engages the actuating button 72 on the switch
from within said container when the desired reference
40 to deactivate the power supply to the Peltier cooler 42.
temperature has been established.
When the power to the cooler 42 has been turned off,
2. Means for producing a thermocouple junction refer
the ice contained within the container 50 will begin 25
ence environment, said means comprising, in combination,
to melt. This will cause a total volumetric reduction with
a container, ‘a top wall on said container, an upstanding
in the container 50 and the bellows 58 causing the bel
?ange on said top wall of said container de?ning an open
lows 58 to contract. When the bellows 58 has con
ing therethrough, said ?ange having a transverse dimen
tracted su?lciently, the end plate 60 thereon will exert
less pressure on the actuating button 72 whereupon the 30 sion substantially less than the transverse dimension of
said container, a ?exible Wall on said upstanding ?ange
power supply to the Peltier cooler 42 will again be actu
closing said opening into said container, a ?uid medium
ated. Through continuous cycling of the cooler 42, a
within said container having a change of state tempera
Water-ice interface may be maintained at the level of
ture equal to the desired reference temperature, means on
the thermocouple reference junction 64 for an extended
period of time. When the carriage 16 has been ?nally 35 a wall of said container other than said ?exible Wall for
adjusted such that the thermocouple reference junction
64 is properly calibrated at 0° C., the thermocouple
junction 64 may be disconnected from the known refer
ence junction and the thermocouple junction 64 itself used
receiving a thermocouple junction to be disposed within
said container, means positioned at the exterior of said
container for removing heat from said ?uid medium con
tained within said container, means including thermal in~
as a known reference junction by attaching a thermo 40 sulation whereby substantially only one path is provided
for heat transfer out of said container, and means actuated
by the movement of said ?exible wall for controlling
tion to the thermocouple terminals 86.
said means for removing heat from within said container.
It will be noted that providing a neck portion on the
3. Means for producing a reference environment for a
container 50 having a relatively small lateral dimension
into which the Water which is displaced by the ice can 45 thermocouple junction comprising, in combination, a con
tainer; a top wall on said container; an upstanding annular
move results in an hydraulic displacement multiplica
couple circuit containing a measuring thermocouple junc
?ange located on said top wall of said container de?ning
an opening through said top wall into said container; a
?exible wall secured to ‘and closing said annular ?ange at
also be noted that the situation of the thermoelectric cool
ing unit at the outside and at the bottom of the container 50 the upper periphery thereof; means ‘for introducing a ?uid
medium having a change of state temperature equal to
50 and the further insulation of the entire structure pro
the desired reference temperature into said container; a
vides substantially only one path for heat ?ow ‘out of the
thermoelectric cooling unit positioned at the exterior of
container, namely, through the bottom ‘48 thereof, there
said container and having its cold junction in direct con
by controlling the formation of ice in a manner suited for
maximum accuracy. The situation of the cooling unit 55 tact therewith; means for controlling the power supplied
to said thermoelectric cooling unit; adjustable carriage
at the exterior of the container is ‘further highly desirable
rmeans mounting said means for controlling said power in
to properly insulate the thermocouple junction from the
alignment with said ?exible wall, whereby de?ection of
electrical ?eld of the cooling junction. The use of a
said ?exible wall will operate said means for controlling
hermetically sealed structure employing a metal bellows
said
power to said thermoelectric cooling unit; means for
further eliminates problems of liquid leakage or contami
insulating said container to provide substantially only one
nation.
heat transfer path into and out of said container through
It will alSO be noted that the thermocouple junction
the portion of said container in direct contact with said
inside the container is oriented parallel to the water-ice
cold junction of said thermoelectric cooling unit; ‘and
interface and extends for some distance within the con
means including a seal for mounting at least one thermo
tainer thereby minimizing inaccuracies caused by heat 65 couple
junction Within said container.
tion, decreasing the amount of ice which must be formed
or melted to activate or deactivate the switch.
It will
conduction along the length of the thermocouple. By
providing a vertical adjustment for the switch, it is pos—
sible to control the water-ice interface, as described, to
4. Means for producing ‘a reference environment for a
thermocouple junction comprising, in combination, a con
tainer; ‘a top Wall on said container; an upstanding annular
position it at the thermocouple junction. In practice, it
has been discovered that the water-ice interface position 70 ?ange located on said top wall of said container de?ning
can be controlled to such a degree that it is possible to
produce a reference temperature which is consistently ac
curate in excess of 0.l° F.
an opening through said top wall into said container; a
bellows element secured to said annular ?ange at the upper
periphery thereof; ‘a ?ll tube in communication with said
container whereby a ?uid medium having a change of state
It should further be noted that whereas the switch 40
disclosed herein is of the on-off, snap switch type, it is 75 temperature equal to the desired reference temperature
1
y
7
3,091,940
may be introduced into said container and said bellows;
a thermoelectric cooling unit positioned at the exterior of
said container and having its coldjunction in direct con—
tact therewith; a switch; adjustable carriage means mount
ing said switch in alignment with an end portion of said
bellows; said switch being operatively connected in the
when said Pel-tier cooler is actuated, said ?uid medium
in said container will be cooled to its change of state
temperature and ‘the resulting volumetric change in the
contents of the said container and said bellows will cause
power circuit of said thermoelectric cooler to break the
said power circuit when said switch is actuated; and means
said bellows to change length to actuate said switch there
by deactuating said Peltier cooler; and means providing
including a seal for mounting a thermocouple junction
thermal insulation between said container and said ex
within said container; whereby when said thermoelectric
terior casing. ,
cooling unit is actuated said fluid medium in said con
tainer will be cooled to its change of state temperature and
the resulting volumetric change in the contents of the
said container and said bellows will cause said bellows
to change length to actuate said switch thereby deactuating
said thermoelectric cooling unit.
8
athermocouple junction; means including a seal mounting
said thermocouple junction within said ‘container, whereby
7. A thermocouple reference junction as de?ned in
claim 6 further characterized by said ?uid medium con
sisting of water.
'
8. A ‘thermocouple reference junction comprising, in
combination, an exterior casing; a ?at bottom on said
-
casing; a Peltier cooler mounted in said casing with its
hot junction in direct contact with said ?at bottom thereof;
a ?at plate formed by the cold junction of said Peltier
cooler; 'a container having its bottom mounted directly on
5. A thermocouple reference junction comprising, in
combination, a container; a top wall on said container; an
upstanding ?ange on said top ‘wall of said container de?n
ing an opening through said top wall into said container,
said ?ange having a transverse dimension substantially
said flat plate; a top on said container; a wall in the form
of an upstanding annular ?ange on said top of said con
tainer de?ning ‘a passage through said top into said con
less than said transverse dimension of said container; a
bellows element secured to said annular ?ange at the
upper periphery thereof; ‘a ?uid medium having a change
of state temperature equal to the desired reference tem
perature contained within said container and said bellows;
.tainer; a tubular bellows element of substantially less lat
eral dimension than said top of said container secured to
said upstanding annular ‘?ange; a wear plate closing said
tubular bellows element at its upper extremity; a ?ll tube
a Peltier cooling unit positioned ‘at the exterior of said
container and having its cold junction in direct contact
therewith; switch means for controlling said Peltier cooler;
adjustable carriage means mounting said switch means in
alignment with an end portion of said bellows; a thermo
couple junction; means including a seal for mounting said
positioned through a wall’ of said container whereby a ?uid
medium having a state change of state temperature equal
to the desired reference temperature may be admitted into
said container and said tubular bellows; at least one
6; A thermocouple reference junction comprising, in
thermocouple junction; means includirnr a seal mounting
said at least one thermocouple junction through a wall of
said container; ‘a pair of vadjustment screws positioned
through said ?at bcttomof said exterior casing substan
tially normal thereto; a carriage carried by said pair of
adjustment screws; a switch carried by said carriage and
combination, a container; a top wall on'said container;
an upstanding annular ?ange located on said top ‘wall and
wear plate closing said upper extremity of said bellows
thermocouple junction within said container; and thermal
insulating means to provide heat transfer out of said con:
tainer only at the portion thereof at which said cold
junction of said Peltier cooling unit is in direct contact.
initially positioned in spaced aligned relation with said
element; a ?exible insulating sleeve mounted to said
switch and coaxial therewith; a rigid sleeve mounted at its
de?ning an opening through said wall into said container;
at bellows element secured to said annular ?ange at the
lower end to said carriage, said insulating sleeve and said
rigid sleeve being each initially positioned coaxial with
said container whereby a ?uid medium having a change
and surrounding said bellows element; means for supply
of state temperature equal to the desired reference tem
‘ing a continuous D.'C. potential to said Peltier cooler,
perature may be introduced into said container and said
bellows; a Peltier cooler positioned beneath said container 45 said means being deactuated by [actuation of said switch;
and thermal insulating means including a foam having a
and having its cold junction in direct contact therewith;
closed cellular structure foamed and cured in place within
an exterior casing, said Peltier cooler having its hot junc
said exterior casing.
tion in direct contact with said exterior casing; a switch;
' upper periphery thereof; a ?ll tube in communication with
adjustable carriage means mounted on said exterior cas
ing to position said switch ‘in vertical alignment with an
end portion of said bellows, said switch being operatively
connected in the power circuit of said Peltier cooler to
break the said power circuit when said switch is actuated;
50
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,952,724
27,986,890
Fritts _______________ __ Sept. 13, 19160
Bevans _______________ __ June 6, 1961
Документ
Категория
Без категории
Просмотров
0
Размер файла
837 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа