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AP ' 1, 1947-
w. E. MENZIES
'
2,418,235
ELECTRIC uo'ron CONTROL
Filed July 10, 1945
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2,418,235
Patented Apr. 1, 1947 ’
UNITED STATES PATENT orrlca
2,418,235
ELECTRIC MOTOR CONTROL
William E. Menzies, Dayton, Ohio, assignor to
General Motors Corporation, Detroit, Mich., a
corporation of Delaware
Application July 10, 1943, Serial No. 494,196
5 Claims.
1
-
.
,
( Cl. 172-279)
2
rection. If on the other hand the frame is moved
This invention relates to improvements in elec
clockwise to a certain point, then the ?ngers 36
trical control devices for electric motors provid
and 31 will urge their respective blades 3| and
ing the motive power for refrigeration or air con
33 counter-clockwise or in a contact separating
ditioning apparatus.
direction.
It is among'the objects of the present inven
Between the free ends of the blades 3| and 33
tion to provide a device of simple structure and
there is provided a spacer bar 80 which has re
design adapted to control the starting of an elec
duced ends extending into openings in the re
tric motor, protect it against damage by over
spective blades. A stop 4|] is carried by the base
load or abnormal running conditions and also
to control operation of the motor in response 10 26, said stop limiting the counter-clockwise or
contact-separating movement of the blade 3|.
to and in accordance with variations in temper
The spacer bar 8!! acts as a limiting member for
ature remote from the motor.
the counter-clockwise or contact-separating
Further objects and advantages of the present
movement of the blade 33. Bar 80 also acts to
invention will be apparent from the following
move blade 33 clockwise under the in?uence of
description, reference being had to the acc'om
blade 3| which is the ?rst one to move clockwise
panying drawings wherein a preferred form of
‘in response to counter-clockwise movement of
the invention is clearly shown.
the frame 28. As soon as the frame 28 reaches
In the drawings:
,
,
.
the point in its travel where the ?nger 36 will
Fig. 1 is a diagrammatic view showing the pre
ferred arrangement of the various parts of the 20 urge the blade 3| clockwise into contact making
position, the blade 33 and its ?nger 31 will have
device and their electrical connections.
reached a point so near their flipping position
Fig. 2 is a similar view showing, however. a
as to enable‘the blade 3|, acting through bar
modified arrangement of the parts.
Referring to the drawings, ‘the electric motor
so, to throw blade 33 clockwise toward itssta
M is provided with a starting‘l winding 20 and a 25 tionary contact |2|. This assures substantially
simultaneous contact engagement. However,
running winding 2|. One end of ‘each of these‘
the separation of the two sets of contacts
windings is connected to a motor terminal 22 to
34—|20 and 35—|2l is successive, the. ?rst men
which one side 23 of the power‘ line is attached.
tioned set 34—|20 being separated ?rst, then, if
The other ends of these two motor windings 20
and 2| are connected respectively to the sta 30 conditions warrant, as will be explained, contacts
35 and |2| are separated.
tionary contacts I20 and I2! of the motor con
A thermo-elect-ric element or wire 50 has its
trol switch 25.
one end mechanically and electrically attached to '
The motor control switch 25 is identical to the
an extending ear 5| of the frame 28 adjacent its
switch illustrated, described. and claimed in the
pivot pin 21. The other end of said element 50
patent to C. J. Werner, 2,242,769, ?led February
is secured to a terminal 52 carried by the base 26.
17, 1938, and issued May 20, 1941. It comprises
An ear 55 on the frame 28, has one end of a
an insulating base 25 supporting a pivot pin 21
spring 56 attached thereto, the other end of the
upon which the frame 28 is pivotally mounted.
spring being secured to any suitable anchorage
The outer, free end of the frame has two V
notches 29 and 30. A resilient blade 3| is se 40 51 attached to the base 25. Spring 56 exerts a
yieldable force urging the frame to rotate c1ock-~
cured to one side of the frame 28 by rivet 32. In
, wise about its pivot post 21. The thermo-elec
a similar manner blade 33 is secured to the op
trio element 5!! opposes this spring action and
posite side of the frame. A contact 34 is car
holds the frame against movement. This ele
ried by blade 3| and a contact 35 by the blade 33.
Contact 34 is adapted to engage stationary con 45 ment is responsive to variations in temperature
due to the heating effects of an electric current
tact I20 carried by the insulating base 26 and
passing through it. As the element heats up due
contact 35 cooperates with stationary contact
to the current ?ow it will expand and thus per
|2| also carried by the base. Blades 33 and 34
mit the spring 56 to move the frame 28 clock
have integral, resilient ?ngers punched or struck
therefrom, the ?nger of blade 3| being designat 50 wise. As the element 50 cools, it contracts and
thus moves the frame 28 counter-clockwise
ed 36 and that of blade 33 being marked 31.
against the effect of the spring 56.
When the frame 28 rotates in one direction to a
An electromagnetic actuator 60 is provided to
certain point, say counter-clockwise, then the
actuate the switch 25 under certain circum
?ngers exert a push on their respective blades to
urge them clockwise or in a contact making di 55 stances. This actuator comprises a magnetic
2,418,285
;
3
core 6I provided with an actuating ?nger 62
adapted to engage and actuate the contact blade
33 out of circuit making position. An energiz
ing magnet winding 63 surrounds the core 6I.
one end of said winding being electrically con
nected'to one'end of the secondary winding 64
of a transformer 65. The primary winding 66
of, said transformer is connected across the power
lines 23 and I23. ' The other end of the secondary
winding 64 of the transformer is electrically
mitting the spring 6Ia to
4 move the magnet core
6I so that its ?nger 62 engages blade 33 and
moves it to open contacts 35--I2I. The tie bar
80 will, at the same time move blade 3| to open
contacts 34-I20. This breaks the motor wind
ing circuits and renders the motor _M inopera
tive to stop the refrigeration cycle. Gradually
the temperature at the evaporator v‘II-rises and '
the bimetal blade 6'! gradually, ?exes‘so that at
a given high temperature contacts 68—69 are
again engaged to cause energization of thelelec
connected to the'bimetallic blade 61 of a thermal
switch ‘I6. Blade 61 carries a contact 63 adapted
tromagnet 60 to release blade 33 of switch 25.
to engage a contact 69 on- the stationary blade
When the contacts 34-I20 and 35—I2Ifof
‘I0 of‘ the switch 15. Blade 10 is electrically con
switch 25 are engaged and the main power line
nected to an end of the winding 63 of the elec 15 switch ‘I1 is closed the motor windings 20 and
tromagnetic actuator 60. The thermal switch
2I are energized to cause the motor to start.
is placed in thermal relation with member .‘II
The heavy surge of starting current passing
which may be an evaporator when the device is
through the thermoelectric element 50 will cause
installed in an electric refrigeratoror. it may be.
it to be heated and heating thereof will result
a room cooled by an air conditioning apparatus
in its expansion. As the element 50 expands
in which the device is installed. The ambient
the spring 56 becomes effective to rotate the
temperature controls the action of switch ‘I5.
frame 28 clockwise about the pivot pin 21 thereby
When said temperature drops to a. predetermined
moving the point of engagement between the
level the bimetal blade 61 ?exes to cause its con
resilient finger 36 and bottom of notch 20 from
tact 68 to disengage contact 69 and-on the con
trary when the temperature rises to a predeter
mined point contacts 68 and 69 will be- again
25 the left of blade 3|, as shown in Fig. 1, toward
the right side thereof. As soon as this point of
engagement passes from the left to the right
side of blade 3I, the resilient ?nger 36 will ?ip
If, for instance, the element ‘II is an evaporator
the blade 3I away from the stationary contact
in an electric-refrigerator, and the temperature 30 I20 toward and against the stop 40 thereby
within the refrigerator and thus ambient to the
breaking the engagement of contact 34 with the
evaporator ‘II is predeterminately high, the con
stationary contact I20 and thus discontinuing
tacts 68 and 69 of the switch ‘I5 will be engaged
the motor starting circuit. At this time, how
engaged.
»
_
.
as shown in Fig. 1. By closing the main power
ever, resilient ?nger 3'! will, still be to the left
line switch 11 current from the power line is 35 of 'blade 33 and will thusystill hold contact 35
directed through the primary winding 66 of the
in engagement with stationary contact I2I to
transformer 65jenergizing the secondary wind
maintain the running circuit of the motor. Un
ing 64. > With contacts 68 and 69 in engagement
the following circuit is established: winding 64,
I contact blade 61, contacts 68 and 69, blade ‘I0,
magnet winding 63 back to the winding 64. This
causes theelectromagnet to be energized so that
its core is attracted and moved against the effect
of spring 6Ia to release the switch blade 33 so
that it may engage its stationary contact I2I.
At the same time contact 34 on blade 3I engages
the stationary contact I20. With these contacts
35—I2I and 36—I20 engaged the following mo
tor circuits are completed: power line I23 to
der normal running conditions the current flow
through the thermo-electric is not suf?ciently
high to cause said element to become heated and
expand so as to permit the spring 56 to shift the
frame 26 clockwise and move the ?nger 31 so
that it ?ips theblade 33 out of contact engage
ment.
This occurs only when an abnormal cur
rent flow through the element 50 is established
due to overload, short circuit or any other ab
normal condition.
In the modi?ed form of the invention as exem
pli?ed by Fig. 2 of the drawings, the electro
terminal 52, thermoelectric element 50, switch 50 magnetic switch I60 has a contact I62 which
frame 28, blade 3I, contacts 34-420, starting
normally provides a gap in the power line 23.
winding 20 of the motor to motor terminal 22
However. when the main power line switch 11
connected to power line 23. Also from switch
is closed and the transformer 65 energized, the
frame 20, blade 33, contacts 35-I2I, running
electromagnet I60 will be energized, provided
winding 2 I. motor terminal 22 and power line 23.
contacts 68 and 69 are engaged due- to a prede
Now the motor M will operate to drive the re
termined high ambient temperature at the evap
frigeration apparatus, not shown, and while the
orator, whereby contact I62 of said electromagnet
motor operates the temperature ambient to the
switch will close its power line gap and com
evaporator is gradually being reduced. The cur
plete the circuit to the motor winding. How
rent flow through the blades 61 and ‘I0 of switch 60 ever, as soon as contacts 66-66 are separated due
75 has a warming effect on the bimetal blade 61
to a predetermined low ambient temperature, the
causing it to ?ex and urge its contact 66 into
electromagnetic switch I60 15 deenergized and the '
engagement with contact 69 at an initially in- '
power line is ‘again broken by the shifting of
creased pressure whereby a temperature differen
contact I6I by spring I6Ia.
‘
'
tial is obtained which eliminates the fluttering 65 In the preferred form of Fig. 1, the electro
of blade 61 at slight temperature variations am
magnetic actuator carries only a light or' low
bient to the evaporator ‘II which would provide
current supplied by a suitable transformer 65,
control over a much too limited range of tem
while in the modi?ed form of Fig. 2, the contact
perature changes. With the present arrange
of the actuator is connected directly across the
ment the motor M operates until a predetermined 70 main power line of the motor.
v
'
p
low: temperature at the evaporator is reached.
The flow of current through the bimetal arm
at which time the bimetaliblade 61 ?exes to sep
61 of switch ‘I5 occurs only when said arm has
arate its contact .68 from contact; 63 thereby
been ?exed to cause contact engagement inre
breaking the circuit including the magnet wind
sponse to a predetermined high ambient temper
ing 63 and deenergizing the magnet, thus per 75 ature. This flow has a heating effect on said
I
2,418,235
bimetal arm which results in an initial increased
closing pressure and thus a temperature differ
ential is set up which will effect a belated open
ing or the switch 75. This eliminates what might
ment of the switch under the e?ect of the thermo
electric element; a solenoid energizable to actuate
the latch for releasing the movable contact en
gaged thereby; and a thermal switch, in circuit
with the solenoid and effecting its energization in
accordance with temperatures ambient to said
be termed a balanced operation of the bimetal
blade 61 under which conditions the blade would
thermal switch.
v
?utter between open and closed positions at slight
4. Control apparatus for an electric motor hav
temperature variations.
ing starting and running windings adapted to be
Being fed from a low voltage secondary of the
transformer, switch 15 does not require the de 10 connected to a source of electrical energy; a
switch having two sets of cooperating movable
gree of insulation needed in case said switch were
and stationary contacts each set being in circuit
directly connected to the power line of the motor.
with a respective motor winding; a thermo-elec
While the embodiment of the present'inven
tric element mechanically connected to the switch
tion as disclosed herein constitutes a preferred \\
form, it is to be understood that other forms 15 and electrically connected in circuit with said
sets of contacts, said element being effective to
might be adopted, all coming within the scope
control the operation of the switch in accordance
of the claims which follow.
with current flow therethrough; a spring loaded
What is claimed is as follows:
latch normally engaging the movable contact of
1. Control apparatus for an electric motor hav
ing starting and running windings adapted to 20 one set of contacts and holding it separated from
its cooperating, stationary contact and inopera
be connected to a source of electrical energy; a
tive by the thermo-electric element; means inter
switch having cooperating contacts in circuit with
posed between the latch engaged contact and the
said motor windings; a thermo-electric element
other movable contact to hold said other movable
for effecting operation of the switch to open or .
close said contacts in accordance with the current 25 contact separated from its cooperating contact
when the one movable contact is engaged by the
?ow through said element; electromagnetic
latch; a solenoid for actuating the latch to release
means yieldably urged to engage one of said con
the movable contacts and render them operative
tacts and hold it separated from its cooperating
under the effect of the thermo-electric element;
contact regardless of the effect of the thermo
electric element; and a thermal switch in circuit 30 and a thermal switch in circuit with the solenoid,
with the electromagnetic means and responsive
to a predetermined temperature ambient to said
for effecting energization of the solenoid to actu
ate the latch in accordance with predetermined
thermal switch for effecting energization of the
temperatures ambient to said thermal switch. '
electromagnetic means to release the contact nor
mally engaged by said means.
2. Control apparatus for an electric motor hav
5. Control apparatus for an electric motor hav
ing starting and running windings adapted to be
connected to a source of electrical energy; a
switch comprising a pivoted frame supporting two
?exible contacts each adapted to engage a sta
tionary contact in circuit with a respective motor
switch having two sets of cooperating movable
and stationary contacts each set being in circuit 40 winding; a thermo-electric element having one
end attached to the switch frame for effecting its
with a respective motor winding; a thermo
operation to open or close the contacts in accord
electric element mechanically connected to the
ance with the current ?ow through said element;
switch and electrically connected in circuit with
a spring loaded detent yieldably urged into en
said sets of contacts, said element being e?ective
gagement with one of said ?exible contacts to
to control the operation of the switch in accord
hold it disengaged from its stationary contact
ance with current ?ow therethrough; a magnetic
independently of the effect of the thermo-electric
latch normally, yieldably urged to engage the
element; a solenoid energizable to move the de
movable contact of one set of contacts and hold
ing starting and running windings adapted to be
connected to a source of electrical energy; a
it out of engagement with its cooperating sta
tionary contact regardless of the e?ect of the '
thermo~electric element; and a thermal switch
in circuit with the magnetic latch for effecting
energization of the latch to release the contact
normally engaged thereby, in response to a pre
determined temperature ambient to said thermal
switch.
3. Control apparatus for an electric motor hav-
tent for releasing the ?exible contact normally
engaged thereby; and a thermal switch, in circuit
with the solenoid, for effecting control of the
solenoid in accordance with the temperatures
ambient to said thermal switch.
WILLIAM E. MENZIES.
REFERENCES CITED
The following references are of record in the
‘ing starting and running windings adapted to be
?le of this patent:
connected to a source of electrical energy; a
UNITED STATES PATENTS
switch having two sets of cooperating movable 60
Name
Date
and stationary contacts each set being in circuit _ Number
with a respective motor winding; 8. thermo-elec
tric element mechanically connected to the switch
and electrically connected in circuit with said sets
of contacts, said element being effective to con
trol the operation of the switch in accordance
with current ?ow therethrough; a latch yieldably
urged into engagement with one of the movable
contacts for rendering it inoperative by the move
1,637,042
1,729,561
2,104,399
2,185,517
Hutt ____________ __ July 26,
Vaughn __________ __ Sept. 24,
Kuhn ____________ __ Jan. 4,
Pearce ____________ __ Jan. 2,
1927
1929
1938
1940
2,203,927
2,243,615
2,278,575
2.317.630
Rutherford _____ -___ June 11,
Werner et al ______ __ May 27,
Werner et a1 _______ __ Apr. 7,
Menzies et al ______ __ Anr. 27
1940
1941
1942
1943
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