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Патент USA US3025389

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March 1’3, 1962
Filed April 1e, 1957
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United States Patent
Patented Mar. 13, 1962
electric lheating element having terminal prongs 13, 14
engaged in terminal sockets 15, 16, FIG. 3 in the unit.
(Jackson, N.H.)
plemental top and bottom halves 17, 18 secured together
Frank Reingruber, Bartlett, N .H.
Filed Apr. 16, 1957, Ser. No. 653,082
1 Claim. (Cl. 200-137)
The invention herein disclosed relates to thermostats of
the probe type wherein the switch or other mechanism
to be controlled is actuated by a push rod of low thermal
expansion characteristics encased within a tube of higher
thermal expansion coeñicient.
Among materials used for the low expansion element
The case forming base of the unit is made up of co-m
by screws or other fastenings 19.
The probe 10 as shown in FIGS. 4 and 5, is made up
of a tube 20 of brass or other thermally expansive metal
and a rod of less expansive material connected with the
extended end of the tube but free `for the balance of its
length to actuate the switch or other mechanism.
In accordance with the present invention,the rod ele~
ment is made of ceramic and instead of being only one
continuous length, is in longitudinally extensive sections,
ceramics, because of low cost and availability, have been
two in number in this instance, designated 21 and 22.
found particularly suitable. There are disadvantages,
These ceramic sections are jointed at their meeting ends
however, in the use of ysuch materials. Because of their
by a coupling designed to hold them in alignment but to
brittle friable character, they are subject to fracture and
allow them limited freedom of movement so that under
breakage and being encased, the defect, rendering the
impact, they may rock or shift slightly enough to absorb
thermostat inaccurate or-inoperative, might not be known.
the shock and overcome the tendency of breakage or
Thus, a ceramic rod thermostat which may have been 20 fracture.
dropped or struck -in some way might very well appear
In a preferred form such as shown, the rod is of tubular
to be in perfect condition and yet be faulty to the extent
formation and the coup-ling is in the form of a double
of being inaccurate and unreliable or even entirely in
ended stud 23 to enter the opposite ends of the tubular
sections and having an intermediate annular flange 24 to
Objects of the present invention are to utilize the good 25 stand between the adjoining ends of the sections.
yfeatures of the ceramic operation but to overcome and
This tubular structure is desirable for lightness and
prevent the breakage and fracture heretofore usually ap
strength. In addition to the advantage of providing for
purtenant thereto.
an inserted double pin or stud form of coupling, it affords
Brieily, these objects have been accomplished ‘by mak
a convenient structure for centering and adjusting it in the
ing the ceramic rod element in longitudinal sections cou 30 expansion
tube 20.
pled together with freedom of movement such as to take
The centering and adjusting means is shown as a screw
up and accommodate any blow that might fracture a rod
25 entered in the free end of tube 20 and carrying a
in one continuous length.
central stud 26 at the inner end engageable in the end of
Other important objects of the invention are to provide
the ceramic tube.
suitable self-centering and adjusting means for the ceramic 35
After desired adjustment of the ceramic, the centering
thrust element, to provide proper operating connection
and adjusting screw 25 may be secured in the adjusted
between this rod and the switch mechanism, and to pro
position by a spot of solder 27.
vide Calibrating adjustment which will hold to a fixed
The inner end of the ceramic tube is shown as having
relation on the thermostat base regardless of angular ad
stud 28 entered therein, this stud having a rounded
justment for control purposes.
40 head 29 for centering engagement in the dimple socket
Other desirable objects attained by the invention and
30 in the contact spring abutment 31. The studs in the
the novel features of construction, combination and rela
ends of the tubular ceramic thus hold it properly
tion of parts through which the purposes of the invention
and preferably free of contact with the inner wa-ll
are accomplished are set forth or will appear in the course
of the containing tube 20.
of the following specification.
At the inner end, the probe tube 20 is rigidly secured
The drawing accompanying and forming part of the
by riveting and soldering at 32, FIG, 5, in the angular
specification is illustrative of a present commercial em
end abutment 33 of an inverted channel shaped frame 34.
bodiment of the invention. The structure, however, may
This frame forms the supporting base for the switch con
be modified and changedas regards the immediate illus
and has at the opposite end an angularly turned abut
tration all within the true intent and scope of the inven
35 which holds it seated in fixed relation in the
tion as hereinafter defined and claimed.
cavity 36 provided for it in the lower half 18 of the base.
FIG. 1 in the drawing is a plan view showing one of
The switch is shown as made up of relatively stationary
the thermostats attached in operative relation to an elec
moveable switch springs 37, 38 secured in insulated
tric cooking utensil, the latter shown broken away.
opposing relation in the top of the frame 34.
FIG. 2 is a side elevation of the thermostat unit in 55
The lower switch spring is of special construction hav
operative relation, the utensil broken away and shown in
ing an inclined intermediate portion 39 longitudinally
slotted at 40 to render it freely flexible and having the
FIG. 3 is an enlarged plan View showing the parts of
angular abutment 31 of similar shape and welded or
the unit as they lappear after removal of the top half of the
insulating case forming the base or body of the device, 60 otherwise secured over the lower part of the inclined slot
ted portion, FIGS. 6 and 7.
the fastenings securing the two parts of the case together
This construction renders the movable switch spring
shown in section.
quite sensitive and free to respond to the thrust and re
FIG. 4 is a broken longitudinal sectional View showing
traction of the ceramic element.
particularly the jointed `ceramic push rod.
As will be clear in FIG. 5, the thrust against the bracket
FIG. 5 is a »further enlarged broken longitudinal sec 65
31 extending angularly from the switch spring is applied
tional view of the switch mechanism and sectional rod
over the slotted, inclined portion of the spring where it
can ‘be most effective to accomplish switching movements
FIGS. 6 and 7 are detail views of the adjustable switch
of the spring.
In FIGS. 1 and 2, the temperature sensing probe of the 70 Calibration of the unit is effected in the illustration by
unit is indicated at 1€) entered in a thermometer well 11
ya rotary stem 41 having a screw mounting in the top of
provided in a cooking utensil 12, the latter containing an
the frame or housing 34 and carrying an insulating button
42 at the lower end engageable with the top contact spring
37 for positioning it in respect to the lower thermo~
statically controlled spring 38.
This Calibrating screw extends up through an opening
43 in the top of the base and to keep this opening always
closed against extraneous matter, the ‘knob
provided to
turn the screw is slidingly keyed over the stem of the
screw at 45 and is yieldingly pressed downward into close
fitting sliding engagement wit-h the top of the base by a
bowed spring 46 bearing down at opposite end on the
bottom of a cavity 47 in the top of the knob and secured
on the stem by a screw 4S.
The knob tensioning spring 46 is shown keyed at 49
on the splined portion of the stern so as to always turn
with the stern and the screw 4S is shown as having a de
pendent annular fllange 50 at the rim of the same bearing
on the spring to hold it always in keyed engagement on
the stem. With this construction, the knob will be yield
ingly held in sliding engagement with the top of the base
spring below the end of the stem and thus always engaged
with the splines in the side ofthe stem.
The ends of this bowed spring engaged with the knob
then act in the capacity of levers transmitting turning
effort of the knob to the stem and taking part of the
load of turning the stem off the splined or key connection
4S between the knob and the stern. The knob is usually
of molded plastic which may become brittle through
repeated heating and cooling, impairing the key connec
tion between the knob and the splines or serrations on
the stern. This possible loss of grip between the knob
and stem is overcome by the yielding connection between
the knob and the spring arms which have the sliding keyed
connection with the stem.
What is claimed is:
A thermostat of the probe type comprising a support~
ing tube of relatively high thermal expansibility, ceramic
tubes of lower thermal expansibility in longitudinally
aligned `relation in said supporting tube, a coupling stud
loosely engaged in opposing ends of said ceramic tubes,
while the stem moves up and down in its screw mounting 20 an ,adjusting screw engaged in one end of said supporting
in the supporting frame. Thus, the opening 43 in the top
of the base will be kept closed at all times and lche `fric
tional engagement of the knob with the base will serve to
hold the Calibrating screw in any position to which it may
be adjusted.
The top of the knob is shown closed over by an indicat
ing disc 51 carrying on and off, temperature indications
or the like.
This indicating cover is shown in FIG. 5 as seated in an
tube and having a projecting stud engaged in the end of
the ceramic tube adjoining the same, means for sealing
said screw inadjusted relation in the ~supporting tube, a
stud engaged in the end of the ceramic tube at the op
posite end of the supporting tube, said last mentioned stud
having a projecting rounded head, a switch spring having
a rigidly secured base portion and a projecting spring arm
oiiîset from said rigidly secured base portion by an inter
mediate angularly inclined portion, said angularly inclined
annular cavity 52 in the top of the dial and as having 30 portion having a bearing engaged by said projecting
tabs or prongs 53 struck downwardly in engagement with
rounded head of the stud in the end of the ceramic tube
positioning openings provided in the knob.
and whereby pressure exerted by said ceramic tube is ap
For quick convenient reading of the dial, the top mem
plied to said angularly inclined portion of said projecting
ber of the base is shown as having a triangular pilot-light
35 arm of said switch spring.
window 54 pointed toward the dial to serve as an index.
References Cited in the ñle of this patent
The pilot lamp is shown at 55 in FIGS. 3 and 4.
The construction is relatively simple `for what it ac
complishes and can be manufactured at reasonable cost.
Smallen ______________ _... Dec. 6, 1927
Making the lo-w expansion element in short sections con 40
nected by what may be considered universal joints of
limited lateral extent permits the ceramic rods to in
effect “bend” and thus yield rather than break. The con
necting studs have loose fitting engagement in the oppos
ing ends of the ceramic tube sections thus allowing slight
lateral movement or deflection in any direction and the
Spencer ______________ __ July 24, 1928
Leupold ______________ _.. Nov. 4, 1930
Satchwell ____________ __ .Tune 20, 1933
Foote _______________ __ Mar. 26, 1935
Beam _________________ __ Jan. 2, 1940
Burling _______________ __ Aug. 6, 1940
tube being held at opposite ends under compression will
be maintained at constant length and with no possibility
of the connecting stud coming loose or dropping out of
either tube section.
50 2,705,745
The Calibrating knob is held by the spring 46 in close,
fiat engagement against the top of the base in position
Where it can be instantly read in connection with the
pilot light window. The dependent flange or skirt 5G of
is inwardly over the end of the stem so as to hold the
Reingruber ___________ __ Dec. 24, 1957
Bletz ________________ _.. Oct. 14, 1958
Great Britain _________ __ June 25, 1940
the spring securing screw 48 is shown in `FlÍG. 5 as eX 55
tending down below the top of the screw stem 41, that
Dafforn et al __________ __ Nov. 11, 1941
Van Denberg et al ______ __ Sept. 6,
Smith ________________ __ Feb. 3,
Stephenson __________ __ Apr. 20,
Matthysse et al _________ __ Apr. 5,
Burling et al ___________ __ Oct. 15,
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