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Патент USA US2406443

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Aug. 27, 1946.
2,406,443 ‘
‘Filed Jan. 1, 1944
' g.
Patented Aug. 27, 1946
THERMosTATIc swrror'f
Frederick W. Stein, Atchiso?; Kans'.
Application January 1, 1944, Serial No. 516,628
1 Claim‘. ( Cl. 200L140";
The invention relates to new and useful im
provements in thermostatic switches.
when the space is heated to the selected tempera
ture and cl'osesthe switch when the temperature
Speci?cally, the thermostatic switch is particu
larly adapted for use in grain germinators or in
other capacities where it is necessary to have a 5
readily adjustable temperature control means
capable or automatically and accurately vmain
drops below the selected temperature. The in
vention resides primarily in the structure for op
eratingrthenswitch from the wafer and in the
manner in which the wafer is mounted and ad
justed to operate the switch at a selected tempera
temperature range. For example, seed germina
’ _In the embodiment of the device shown in the
tors are most e?icient if maintained at a ‘lower 10 drawing’, the switch 7 is operated by the wafer
taining a selected temperature in a relatively wide
temperature during the nighttime than during
the daytime. Moreover, the different speci?c
through the medium“ of a slidable pin. The Wafer,
temperatures maintained, as well as the particu
manually movable to adjust the wafer relative
to the pin. The arrangement is essentially sim
lar range between the daytime and nighttime
temperatures, vary considerably according to the
particular type of seed being germinated.
An important object of the invention is to prom
Vide a thermostatic switch that is automatically
operative, to maintain different predetermined
temperatures and that can be readily adjusted to
provide a selected temperature,
Another object of the invention is to provide
a' device of the above mentioned character that
is operative over a wide temperature range.’
Still another object of the invention is the pro
vision of a device of the above mentioned char
actor that is simple in construction and eilicient
in operation.
Other objects and advantages of the invention
will be apparent during the course of the follow
ing description.
In the drawing forming a part of this speci?
cation and wherein like numerals are employed to
designate like parts throughout the same,
Fig. l is a top plan view of a thermostatic switch
embodying the invention,
Fig. 2 is a transverse sectional view taken on
the line 2—2 of Fig. 1,
Fig. 3 is a view similar to Fig. 1 but showing the
cover of the switch housing removed,
Fig. 4 is a fragmentary longitudinal sectional
view taken on the line 4-—4 of Fig. 3, ,
itself, is mountedin a shiftable carriage which‘ is
‘ ple, making the device economical to manufac
ture. At the same time, it permits precise ad
justment of the wafer so that the temperature
control is exceedingly accurate.
Referring now to‘ the drawing, wherein for the
. purpose of illustration is shown a preferred em
bodiment or the invention, the numeral IIJ desig
nates a‘ box or housing which consists of a base
plate ma ands cover'or case “lb. The housing
carries the various parts and adjuncts 0f the
switch‘ and is mounted on a wall ll of the struc
ture‘ to be" heated by means of end ?anges Illc.
When the device" is used on a grain germinator,
the housing is preferably mounted on the front
wall‘ above‘ the'seed trays. Within the housing II)
is a‘thermostatic'ally operated switch which com
prises a switch arm I2 and contacts I3‘ and I4.
The‘switch arm and contact I3 are insulated from
plate ma‘ by the dielectric member l5 while con
tact I4 is carried by‘ the switch arm. The switch
arm is ?exed when the contacts are separated and
normally urges the contacts together.
switch, together with the manually operated
switch‘ I6 on case‘ 101), controls the ?ow of cur
rent through an‘ electric heater‘ (not shown).
As shown in Figs. _5 and 6, a bank of contacts
I'Id, Ill) and He carried by a bracket I3 adjacent
oné'end of the housing isadapt'ed to register with
a bank of contacts I911, I91), and I90 on wall II.
Fig, 5 is a transverse sectional view taken on
the line 5-5 of Fig. 3 showing the manner in
The banks of contacts are electrically insulated
which electric current is supplied to the switch, 45 from the bracket I8 and wall I I by bars 2!! and 2 I.
When housing II) is mounted on wall I I, contacts
Fig. 6 is a fragmentary longitudinal sectional
I911, I91) and I90 extend through the opening I?d
view taken on the line 6-6 of Fig. 5,
in the base plate Illa and engage contacts I'la,
In brief, the device is adapted to automatically
11b and He.
control the ?ow of current through an electric 50 The manner in which electric current is sup“
heater so that the heater maintains the surround
plied to the switch and the manner in which the
ing space at a selected temperature. The ?ow of
current ?ows through the switch to control the
current to the heater is regulated by a switch
heater is now described. Current from a suitable
adapted to be opened and closed by a spirit wafer.
source passes through the heater, thence through
The wafer is adjustable so that it opens the switch 55 conductor 22 and contacts I9a and Na to a con
duotor 23 attached to the manually operated
switch it‘. From the switch 16 the current passes
through conductor 24 to contacts l3 and I4.
When these contacts are engaged, the current
?ows through switch arm I2 and conductor 25
to contacts lib and Nib and thence through con
ductor 26 back to the source. A small electro
lytic condenser 21 connected at opposite sides of
l3 and Hi, current can no longer flow to the
heater. The heater remains deenergized until
the thermostatic switch is again closed. This
cycle is repeated over and over again to maintain
a relatively constant temperature in the struc
ture being heated. The particular temperature
maintained depends upon the position of the
wafer with respect to the pin 39. As described,
the wafer may be selectively positioned by handle
the switch by conductors 28 and 29 prevents arc
ing between contacts l3 and iii when the switch 10 lit so that it operates the thermostatic switch
at a predetermined temperature. Temperature
is being opened or closed. The circuit also in
scale d8 is correlated with the movement and
cludes a pilot light 30 which is lighted when cur
position of wafer 38 so that indicator handle
rent ?ows through the heater. Current from
46 registers the temperature at which the wafer
conductor 28 passes to the bulb 20 through con
ductor 3i and thence through conductor 32, re 15 operates the switch. By providing the threaded
connection between crosshead lid and shaft 45
sistor ‘$3, conductor 315, contacts llc—l9c and
with a relatively long lead, ample adjustment of
conductor 35 to a suitable ground. Bulb 30 is
the wafer 38 is assured by rotation of the indi
supported by the horizontal arm 35 which projects
cator through 360° or less.
from an essentially U-shaped bracket 3'! bolted
By moving the wafer relative to a switch oper
to plate 18a. Bulb 3i] extends through cover 10b 20
ating member, a highly e?icient and accurate
as best shown in Fig, 1, and is clearly visible to
construction is achieved. Moreover, his unique
indicate whether the heater is operating.
arrangement is so mechanically simple that the
The thermostatic switch is automatically
device is economical to fabricate. This con
opened and closed by a spirit wafer 38 through
the medium of a pin
and a block of insulat 25 struction also permits ready and accurate ad
justment of the wafer relative to the switch
ing material Gil. The pin 3Q extends through and
operating means and the adjustment can be easily
is slidably supported by a hollow boss or hearaccomplished by a rotatable manual control in
ing M on the bottom of plate iiia. Block 48,
dicator. The switch is operative over a wide
secured to the inner end of pin 39 by nut 39a,
temperature range and can be accurately ad
extends under the movable end of the switch arm
justed by a relatively slight movement of the
E2. The wafer 33 is supported within the struc
manual indicator.
ture being heated by a carriage which is slid
It is to be understood that the form of the
ably mounted to selectively position the wafer
invention herewith shown and described is to
with respect to the distal end of pin .39. The
be taken as a preferred example of the same and
carriage comprises a rectangular frame 42, guide
rods 113 and a crosshead 44.
Frame 42 carries
the wafer and supports the outer end of pin
39, the guide rods are slidably supported by boss
Ill and crosshead 44 connects the inner ends of
the guide rods. The carriage is actuated by a
shaft lit which screw-threadedly engages cross
head M, as shown in Fig. 2. Shaft H5 is sup
that various changes are contemplated and can
be made Without departing from the spirit of
my invention or the scope of the appended claim.
Having thus described my invention, I claim:
A thermostatic switch comprising a housing, a
normally closed electrical switch within the
housing, a wafer sensitive to temperature vari—
ations, a pin slidably mounted between the switch
and the wafer adapted to coact with the wafer
through case i?b to receive the indicator knob
or handle 46. A latching plate ill carried by 45 to open said switch, a frame carrying said wafer,
guide rods slidably mounted in said housing sup
bracket 3? has a forked end which ?ts into the
porting said frame atone end, a crosshead within
annular groove the in the shaft holding the
the housing mounted on the other end of said
shaft against longitudinal movement but permit
guide rods, a dial calibrated with a temperature
ting free rotation thereof. As shown in Fig. 1,
indicator 6'5 moves across a temperature scale 50 scale mounted on the face of said housing, a
rotatable shaft screw-threadedly engaging said
48 when shaft 45 is rotated. Since it is held
ported by bracket 3i and its outer end, extends
against longitudinal movement, rotation of the
crosshead and extending through the center of
shaft causes the carriage to slide relative to the
said dial with an indicator mounted on its ex
switch operating pin 39. Wafer 38 contracts
when the media surrounding it cools. Pin 38
tending end, means for preventing longitudinal
movement of said shaft whereby rotation of
follows the Wafer and permits switch arm l2 to
bring contacts l3 and I4 together. When this
occurs current ?ows to the heater and the media
around the wafer becomes heated. As the tem
said indicator to any desired point on the cali
brated dial adjusts the position of said water
relative to the distal end of said pin causing
the switch to be opened when the temperature
perature rises, wafer 38 expands and pushes 60 of themedia surrounding said wafer corresponds
pin 38 against switch arm l2. When the wafer
has expanded sufficiently to separate contacts
' to that indicated on said dial.
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