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Oct. 8, 1946.
2,408,873
c. M. OSTERHELD
SNAP ACTING THERMOST‘ATIC SWITCH
Filed March' 20, 1944
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2,408,873
Patented Oct. 8, 1946
UNITED STATES PATENT OFFICE
_,
-
2,408,873
_ smr some. THERMOSTATIC swrrcn
Clark M. Osterh'e'ld, Stoughton, Wis., assignor to
McGraw Electric Company, Elgin, Ill., a cor
poration of Delaware
Application March 20, 1944, Serial No. 528,549
9 Claims. (Cl. 200-138)
1
My invention relates to switches and particu
larly to snap acting thermostatic switches.
An object of my invention is to provide a
2
site‘ sides of the bar to form a socket of channel
shape, or secured thereto at its free end socket
members 28 and 29, which are of channel shape
relatively simple, compact and inexpensive snap
acting thermostatic switch assembly.
and are secured as by welding or brazing to op
shall increase the contact pressure until the in
may use a bimetal bar 3|, the thickness of which
posite sides of the bar 25. The shape of the
bottom wall of the socket members may be ?at
Another object of my invention is to provide
or have a special form, as will be referred to
a relatively simple snap acting thermostatic
hereinafter.
,
switch in which there shall be pressure between
I provide a second or auxiliary bimetal/bar 3|,
the contacts until theinstant of separation.
Another object of my invention is to provide 10 which is preferably, although not necessarily,
relatively thinner than the bimetal bar 25. I
means in a snap acting thermostatic switch that
is on the order of .015", although this particular
dimension is noted for illustrative purposes only.
Other objects of my invention will either be
apparent from a description of several different 15 The inner end of the second bimetal bar 3| is
provided with a knife edge, and the outer end
forms of devices embodying my invention or will
thereof has secured thereto a contact member
be pointed out during such description and set
stant of separation.
33. The knife edge end of bimeta1 bar 3| is
adapted to be located in the members of chan
Figure 1 is a view, in side elevation; of a snap 20 nel shape formed or provided at the free end of
the ?rst bimetal bar 25. I wish to point out that
acting thermostatic switch embodying my in
the high expansion element is on the same side
vention,
of the assembly in this form of device as well as
Fig. 2 is a View in front elevation thereof,
in all of the other forms using two bimetal
Fig. 3 is a top plan view thereof,
Fig. 4 is an enlarged view, in end elevation, 25 members.
The supporting block or base 2| has mounted
of the free end of one member of the switch,v
_
thereon
a contact member 35 adapted to engage
Fig. 5 is a top plan view of another form em
with and be disengaged from the contact mem
bodying my invention,
ber 33 on the second bimetal bar 3|. A stop
Fig. 6 is an exploded top plan view of the two
means for the free end of the second bimetal bar
toggle members embodied in the form shown in
3| comprises a bar 31, of substantially Z-shape,
Fig. 5,
having one end portion thereof secured against
Fig. 7 is a view, in side elevation, of the parts
the upper surface of base 2| as by a machine
shown in Fig. 6,
screw 39. The other end portion of the bracket
Fig. 8 is a view, in side elevation, of another
31 has secured therein an adjustable stop screw
form of device embodying my invention,
35 4| which may be held in any desired adjusted po
Fig. 9 is a fragmentary view, in side elevation,
sition by a lock nut 43.
of a modi?cation embodying my invention, and,
The bimetal bar 25 has a medial longitudinally
Fig. 10 is a view, in side 9 vation, of another
extending slot 45 therein starting at the free end
‘modi?cation embodying my invention.
Referring ?rst of all to Figs. 1 to 4 inclusive, ' 40 and extending thereinto over about one-half of
its length. The second bimetal bar 3| has a
I have there shown a base 2|, of electric-insulat—
similar elongated central slot 41 therein starting
ing material on which the parts of the switch
at the knife edge end thereof and an over-center
particularly constituting my invention are mount
spring 49 is located in the two slots and has the
ed. I provide a small block 23, of electric-insulat
ing material, secured to base 2| adjacent one of 45 ends thereof secured to the respective interme
diate portions of the two bimetal bars 25 and 3|.
the ends thereof. I provide a ?rst or main bi
The combination of the two bimeta1 bars 25 and
metal bar 25 having one of its ends secured to
3| and the over-center spring constitute a toggle
base 23 as by one or more machine screws 21.
and, upon change of temperature, the second bi
For illustrative purposes only I may here state
that the thickness of-the bimetal bar 25 may be 50 metal bar 3| will move from one limiting posi
tion to an opposite limiting position with a snap
on the order of .025” or .030", although I do
action.
not desire to be limited thereto. The free end
A brief description of the opera-tion of the de
of bar 25 has either formed therein a socket
vice shown in Figs. 1 to 4 is as follows: Fig. 1
member, which is of channel shape in lateral sec
tion, as by bending integral portions out on oppo 55 shows the general positions of the parts when
forth in the appended claims.
In the drawing,
.
3,408,878
3
the temperature of the air is at a relatively low
value so that the two contact members it and ll
are in circuit-closing position, that is if the
switch controls an electric heater, the said heater
/
ll. This results in greater pressure between the
contacts a and I! Just before disengagement
thereof.
Referring now to Figs." 5 to 'l inclusive of the
will be energized. The position of the knife edge
end of the second bar 3! will be substantially that
‘ drawing,
' I have there shown a modi?cation em
shown in Fig. 1 of the drawing, that is the knife
edge end will be in engagement with the upper
_ ,insulating material has mounted thereon adia
bodying my invention. A base II, of electric
corners of the socket members of channel shape.‘ ' , ‘ 1 cent toone end thereof a small block I: also of
electric-insulating material against which is se
The spring 40 is under tension and causes . the‘
knife edge end to be held tightLv in engagement ‘
. ‘with the inner wall of the socket member and
also causes a contact pressure to existbetween
the contact members it and SI.
‘
‘
V
ycured one end of a‘bimetal bar It as by machine
screws 51. The bimetal bar II is of
substantially
the shape shownin Fig. 6, having cut out side
, portions
I58 adjacent the free end thereof and
having ‘an extended slot 8| extending inwardly
Upon increase of the temperature of .the am-. 15 from
the free end, centrally of the bar 55.
bient air. the ?rst bimetal bar 25 will ?ex in a
A second bimetal bar BI, which is relatively
clockwise direction around its ?xed end, while
shorter than bimetal bar. iiphasside portions
the second bimetal bar II will tend to ?ex inia
ll removed. therefrom at thatv end adapted to
counter-clockwise direction around the ?xed con
engage
socket members “formed in or secured to
tact member 35. It may be here pointed out that 20
the free end of bar“. Bar 83 has slot 89 there
the lateral width of the socket member of chan
in extending substantially longitudinally central
nel shape is such that the bimetal bar 3| will not
ly thereof from itsinner end., An over-center
engage the outside ends of the lower siderpore
spring ‘II is adapted to be positioned in the alined
tions of the socket members when the parts are
in the positions shown in Fig. l of the drawing 25 slots 6i and ll and to have its ends connected
with the intermediate portions of the two bars
or in the opposite positions as shown by the bro
SI and 63. The inner ends ‘I! of the second bi
ken lines in Fig. 1. The tension of spring 49 will
metal
bars 83 are of rounded shape adapted to
cause a certain pressure between, the knife edge
fit into the socket members I‘! provided at the
end of bar SI and the socket member, the result
being that the parts comprising‘ particularly the 30 free end of bimetal bar II. In this form of the
device the second bimetal bar 63 may be thinner
adjacent engaged end portions of the two bimetal
than the ?rst bimetal bar 86.
bars will have a certain amount of frictional re
The second' bimetal bar 83 has a contact mem
sistance to any lateral movement of the knife
ber 15 provided at the outer, i’ree, movable end
edge end of bar II in the socket members. This
thereof which is adapted to engage with and be
has the result that there will be a predetermined 35 disengaged
from a ?xed contact member 11
amount of pressure between the two contact
mounted on the base II. I provide a stop mem
members 33 and SI. thereby reducing the voltage
ber for the free end of the second bimetal bar BI
comprising a bracket 19 01' L-shape, having one
end thereof secured to block 5| as by a machine
gagement of contact member 33 from the ?xed 40 screw
ii, an adjustable stop screw 83 being pro
contact member 3!, the knife edge end of bar ll
vided in the other end thereof adapted to be
will have moved laterally in the socket member
engaged by the movable end of bimetal bar 63.
to a position intermediate the side walls thereof
A pair of leaf springs 85 have one end thereof
in case the bottom wall is ?at, and immediately
secured against an intermediate portion
after, if not substantially coincident with the 45 ?xedly
of bimetal bar 55 at the sides thereof and extend
snap acting movement of bimetal bar ll to the
over the cut out portions 59, the length of these
opposite position, the knife edge end of bar ll
springs
being such as to extend to and slightly
will move into the ‘lower comer of the socket
overlap the side portions 81 on bimetal bar 63, the
member.
overlap of the leaf springs 85 over the portions
The longitudinal distance between the contact 50 81
being on the order of a few thousandths of an
member 33 and the holding screw 21 is less, in
inch
only. It is evident that the two springs
the positions of the parts shown in Fig. 1, than
85, having one end secured to the ?rst or main
it will be when the two bars 25 and ll are in sub
bimetal bar 55 and having the second end there
stantially longitudinally alined positions, which
of overlapping and engaging with an intermediate
latter positions they will occupy an instant be
portion of the second or auxiliary bar 63, will
fore the above described snap acting movement
cause a lateral pressure against bar 63, the result
of the second bar ii, with the attendant result
being that the contact member 15 will be sub
that during the change of positions from those
ject to an increased pressure against the ?xed
shown in Fig. 1 to when they are in substantial
contact member 11. This contact pressure is
alinement with each other, the contact member
II will have a sliding movement on contact mem 60 additive to that produced by the inner end of the
second bimetal bar moving in the socket members
ber II with the result that a self-cleaning pair
61 provided at the free ends of the ?rst bimetal
of contacts is obtained.
‘bar 55. It is evident that the springs 85, the
I may increase the frictional resistance to
movement of the inner end of bar 3| by making 65 ends of which engage one side of bimetal bar it,
will have those ends move past the ends of the
the bottom‘ wall of other than ?at shape. I
portions 81 of the second bimetal bar when snap
have shown a preferred shape in Figs. 1 and 4,
acting movement of the second bar occurs, so that
this shape including a raised central portion and
then the leaf springs 85 will exert a lateral pres
two lowered side portions. The longitudinal dis
tance between‘the contact member 33 and the 70 sure on the second bimetal bar 63, this pressure
now being in the opposite direction to that ex
holding screw 21 will be momentarily increased
erted by the'leaf springs 85 in the ?rst place.
during the time of snap-over action by the move
Referring now to Fig. 8 of the drawing, I have
ment of the knife edge end of bar 3| from one
there shown a modi?cation of the device shown
side portion to the other side portion with the
result of greater tension in the over-center spring 75 in Figs. 5 to 7 inclusive, comprising a base SI,
of electric-insulating material having a small
drop of the current ?owing through. and con
trolled by the switch. Just prior to the disen
3,408,878
-
.
5
6
block 99 also of electric-insulating material se
the ?xed contact member. This will be evident
cured thereagainst. A ?rst bimetal bar 95 has one
end thereof secured against block 93 as by one or
more machine screws 91. The free end of the bar
95 has mounted thereon a socket member com
prising a pair of leaf springs 99 which provide a
socket member of substantially channel shape in
from a consideration-of the'e?ect of the over
center tension spring provided ineach of the
various modi?cations, a component part of the
tension of the over-center spring being active to
cause the engaging contact pressure between the
engaged contact members. Further, it is evident
that the ?exing of the main bimetal bar, as in
lateral section, the main portions of the members
a clockwise direction toward the ?xed contact
99 being resilient and of arcuate shape, the length
of these portions being such as to extend over the 10 member (as seen in Fig. 1) causes inherently a
pressure of one contact member against the other.
knife edge end of a second bimetal bar Ilil, it
which contact pressure is absent in many other
being understood that the bottom face of the
forms of snap acting switches.
socket member provided by the spring members '
The provision of a knife edge end of the second
99 is ?at and even to receive the knife edge end
of the second bimetal bar llll. Here again I may 15 bar held in relatively tight frictional engagement
in a socket member further causes increased con
make the thickness of the second bimetal bar
tact pressure between the contact members. The
HH less than that of the ?rst or main bimetal
bar 95.
further provision of spring ‘means, of leaf shape,
‘
having one end thereof secured to the ?rst bimetal
I provide a contact member I03 on the outer
end of bimetal bar "H, which contact member is 20 bar and extending over the junction of the two
adapted to be engaged with and disengaged from
a ?xed contact member I05 secured to the other
end of base 9|. I provide further a stop for the
free end of bimetal bar I?l, this stop compris
ing a bracket ll", of Z-shape, having one end
thereof secured against base 9| and having an
adjustable stop screw I09 engaged with the other
end thereof.
It is evident that the same com
ments with regard to the wiping action of con
tact I93 on contact I05 made hereinbefore in
connection with the form shown in Figs. 1 to 4 in
clusive, will apply here also. Further, the effect
of the leaf springs 99 will be substantially the
bars to engage the second bar, laterally thereof,
intermediate its ends further provides additional
contact pressure between the engaged contacts.
The provision of two bimetal toggle arms also
ensures that the temperature differential of oper
ation of my improved thermostatic switch, that
is, the change of temperature necessary to cause
movement of the second arm from one to the
other of its positions, will be relatively small.
Making the thickness of the second bimetal bar
less than that of the ?rst bimetal bar also tends
to reduce the temperature differential of operation
and when combined with the leaf springs results
in a snap acting thermal switch, in which the en
same, as regards the increase of pressure be
tween the engaged contact members, as herein 35 gaged contacts are held with an appreciably
.large or heavy contact pressure up to the instant
before set forth in connection with the form
of disengagement.
shown in Figs. 5 to '7 inclusive, it being understood
Various modi?cations may be made without de
that the lateral distance between the outer ends
parting from the spirit and scope of my inven
of the arcuate portions of leaf springs 99 is such
that one such leaf will engage the second bimetal 40 tion, and all such modi?cations clearly covered
by the appended claims shall be considered as
bar IIH before substantial straight alinement of
part of my invention.
the two bars occurs, preparatory to snap-over
movement of the second bar.
.
I claim as my invention:
1. A snap acting thermostatic switch assembly
I have shown another modi?cation in Fig. 9
comprising a ?rst bimetal bar, a second bimetal
in which there is interposed, between the two
bar having one end pivotally engaging one end of
main arms HI and H3 of bimetal, a third short
the ?rst bar, the high expansion component of
arm H5 having ends of channel shape in lateral
the two bars being on the same side of the as
sections. The ends of the bimetal bars Ill and
sembly and an over—center spring having its ends
I I3 will be positioned in the upper corners of the
respective sockets when the bars are in the posi 60 connected to the intermediate portions of said
bars.
tions shown in Fig. 9 and will occupy the lower
2. A snap acting thermostatic switch assembly
corners of the sockets when the contact members
comprising a ?rst and a second bimetal bar hav
- ing ends pivotally connected with each other to
there shown a further modification comprising a 65 form a toggle, an elongated slot at the adjacent
- are out of engagement with each other.
Referring now to Fig. 10 of the drawing, I have
?rst bimetal bar H‘l having socket members
H9 at its free end. I provide a second arm IZI
made of a single metal and having a rounded
end portions of each of said bars, anover-center
spring positioned in said slot and having its ends
connected to intermediate portions of said bars
to cause snap acting movement of the other end
end adapted to be positioned in the socket mem
ber I I9, while a contact member I23 is secured 60 of said second bar between two opposite limiting
positions, a ?xed support for the other end of
to the other free end of the single metal bar l2l.
said ?rst bar, a contact member on the other end
It is to be understood that the device shown in
of said second bar, a ?xed contact member and a
Fig. 10 of the drawing is adapted to be mounted
stop
member de?ning said limiting positions, the
on a suitable base, and to be provided with an
over-center spring substantially as shown in Fig. 65 high expansion component of said two bars be
ing on the same side of the assembly to cause
1 of the drawing, but‘since the only di?erence be
?exing of both bars in the same direction around
tween the device shown in Figs. 1 to 4 inclusive
the fixed support and the ?xed vcontact member
and that shown in Fig. 10 is that the second bi
and stop upon change of ambient temperature.
metal‘ bar of Fig. 1 is replaced by a single metal
3. A snap acting thermostatic switch assembly
bar, it is thought unnecessary to show the addi 70
tional parts in Fig. 10 0f the drawing.
1’
The device particularly embodying my inven
' comprising a ?rst bimetal bar having one end
thereof ?xed and having a laterally enlarged re
cessed end portion at its other end, a second bi
tion and shown in various forms provides a struc
metal bar having one .end positioned in said en~
ture which inherently causes an appreciable con
tact pressure of the movable contact member on 75 larged recessed end portion of said ?rst bar and
2,408,873
7
.
movable laterally therein. an overcenter spring
having its ends connected to said ?rst and second
bar and bridging the engaged ends thereof, a
?xed contact member and ‘a contact member on
the other end oi'the second bar adapted to engage
with and be vdisengaaecl from said ?xed contact
member with a snap action by the coincident ?ex
ure in the same direction oi’ both bimetal bars
around the ?xed and contact members respec
tively.
.
4. A thermostatic switch assembly comprising
a ?rst bimetal bar having one end thereof ?xed,
a second bimetal bar having one end pivotally
engaging the other end of the ?rst bar, an over
center spring having its ends connected to inter
mediate portions or the respective‘ bars, a ?xed
contact member, a contact member on the other
end of the second bar adapted to be moved into
8
the side of the latter bar'intermediate its ends
as the two bars move into longitudinal alinement
with each other to cause a substantial pressure
01’ the contact on said auxiliary bar against the
?xed contact.
7. A thermostatic switch assembly comprising
a ?rst bimetal bar having one end thereof ?xed
and having laterally enlarged recessed portions
at its ‘other end, a second bimetal bar having a
10 knife edge end portion at one of its ends engag
ing said end portion or channel shape or the ?rst
bar and movable laterally therein, an over-center
spring bridging the engaging end portions of the
two bars and having its ends connected to the re
spective bars intermediate their ends, the high
expansion component 01' both bars being on the
same side of the assembly and cooperating with
engagement with and be disengaged from said , said over-center spring to cause the other end oi’
?xed contact member with a snap action and 20 the second bar to move from one limiting posi
tion to another with a snap action under‘rela
spring means on said ?rst bar at its other end
tively small changes or temperature.
and extending therebeyond over the second bar
to engage the latter at one side thereof as the
two bars move into alinement with each other to
cause a substantial pressure oi.’ the contact mem
ber on the second bar against the ?xed contact
member just prior to disengagement of said two
contact members.
5. A thermostatic switch assembly comprising
a ?rst bimetal bar having one end thereof ?xed.
a second bimetal bar having one end pivotally
engaging the other end of the ?rst bar, an over
center spring having its ends connected to inter
mediate portions 01' the respective bars and bridg
ing the engaged ends thereof, a ?xed contact
member, a, contact member on the other end oi’
the second bar adapted to be moved into engage
ment with and be disengaged from said ?xed con
tact member with a snap action and leaf spring .
means on said ?rst bar at its other end and ex
tending therebeyond over the second bar to en
sale the sides of the second bar intermediate its
ends to cause a substantial pressure of the con
8. A snap acting thermostatic switch mecha
nism comprising a pair of toggle arms. at least
one of which is a bimetal bar, one of said toggle
arms having one end ?xed and having socket
members of channel shape in lateral section at
its other end, the bottom wall of said socket mem
bers having a raised central portion and two low
er side portions, said second arm having one end
in said socket members and movable laterally
therein, an over-center spring having its ends
connected to the intermediate portions of said
toggle arms to cause snap acting movement of
the second arm upon change of ambient tempera
ture, the tension of said spring being increased
by said raised central portion to cause increased
contact pressure upon said lateral movement of
said second arm, a ?xed contact and a contact on
the other end of said second arm adapted to be
engaged with and disengaged from said ?xed con
tact with a snap action.
9. A snap acting thermostatic switch assembly
comprising a ?rst bimetal bar having one end
tact member on said second bar on said ?xed
?xed and having a socket member 01' channel
contact member just prior to disengagement or I ' shape
in lateral section at its other end, a sec
the two contact members.
6. A thermostatic switch‘assembly comprising
a main and an auxiliary bimetal bar pivotally
connected‘ with each other in end-to-end relation,
ond bimetal bar 01' lesser thickness than said ?rst
bar having an end positioned in said socket mem
her, the high expansion component of both bars
the high expansion component or both bars being 50 being on the same side 01' the assembly, said bars
having elongated slots in their adjacent end por
on the same side of the assembly, an over-center
tions,
an over-center spring in said slots having
spring connected with the two bars intermediate
its ends connected with the respective bars ad
their ends, a ?xed contact, a contact on the free
Jacent to the ends of the slots, at ?xed contact
end oi’ said auxiliary bar adapted to engage with
and be disengaged from the ?xed contact with -55 and a contact on the other end of said second bar
adapted to engage with and be disengaged from
a snap action and leaf spring means on that end
said ?xed contact with a snap action under rela
or the main bar pivotally engaged by the auxiliary
tively small changes of temperature.
bar extending over the auxiliary bar to engage
CLARK M. OSTERHELD.
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