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Патент USA US2404352

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G. C. ARMSTRONG
THERMOSTATIC OVERLOAD RELAY
Filed Jan. '7, 1944
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WITN ESSE‘SZ
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INVENTOR
George 6.’ ?rmsimzzg.
aha/(‘MAM
MK'BY .
ATTORNEY
Patented July 23, 1946
2,404,352
UNITED STATES PATENT OFFICE
2,404,352
THERMOSTATIC OVERLOAD RELAY
George G. Armstrong, Forest Hills, Pa., assignor to
Westinghouse Electric Corporation, East Pitts
burgh, Pa., a corporation of Pennsylvania
Application January 7, 1944, Serial No. 517,307
8 Claims.
(Cl. 200-122)
1
My invention relates to thermally operating
2
able member is normally prevented from fol
lowing its bias and is released electrically upon
mostatic metal winding on a pin or shaft member
so as to grip this member tightly when cold While
' loosening its grip when heated beyond a given
extent.
the occurrence of a given thermal condition.
More particularly, this invention concerns over
a helical bimetal winding or spring is provided
electric apparatus in which a spring biased mov
According to another feature of the invention,
load relays and the like protective ‘devices to be
or connected with a detent or latch member for
operated in response to the occurrence of a given
load condition.
retaining a spring biased switch member, and
It is known to provide devices of this type with
exert a clutching grip on the shaft when affected
by the spring bias and in cold condition, while
relaxing its grip when either heated or caused
to perform an unwinding motion, the latter way
a low melting solder joint which holds a spring
biased contact member in position as long as the
temperature remains below the fusing value and
becomes soft, thereby releasing the contact mem
ber, when this value is exceeded due to an undue
increase in heating current. These devices are
subject to change their operating characteristic
due to oxidation of the solder and other ageing
effects. More favorable in the latter respect
is seated on a stationary shaft structure so as to
of release operation being used for resetting the
relay.
A further feature of the invention consists in
providing a shaft structure of the above—men
tioned type which is composed of a slotted sleeve
and an inner conical post so as to permit varying
are overload relays in which a heat-deformable 20 the diameter of the sleeve in order to calibrate
thermostat is employed for actuating a ratchet
or latch mechanism so as to release the spring
biased contact member when heated beyond a
maximum temperature corresponding to a rated
overload current. However, the known devices '
of the latter type require considerably more space
and are more complicated, or less accurate and
usually more expensive to manufacture.
‘ It is an object of my invention to provide a
the release mechanism.
According to still another feature, my inven
tion provides a single insulating body for ac
commodating all individual parts, including the
above-mentioned mechanism as well as the con
tact and heater elements of the relay so as to
obtain a compact device of simple design and
small compass.
An embodiment in accordance with the above
device which combines the advantages of the 30 mentioned objects and features of the invention
thermostatic type with those of the alloy or solder
is illustrated in the drawing, in which:
type. That is, it is intended by this invention
Figure 1 is a top View; Fig. 2 a lateral view;
to devise a thermal or overload relay of Very small
and Fig. 3 a front View of a thermostatic over
load relay;
dimensions and great accuracy and reliability
that is free of the ageing effects of solder type 35 Fig. 4 is a cross-section taken along the plane
relays.
indicated in Fig. 2 by the dot-and-dash line
Another object of my invention is to provide
marked IV-IV;
improved thermoresponsive latching or clutching
Fig. 5 is an axial section along the plane de
means for relays or the like apparatus so as to
noted in Fig. 3 by the dot-and-dash line marked
obtain a release operation of high reliability and 10 V—V; and
sensitivity by mechanical means of extremely
Fig. '6 is an exploded View of a number of in
small dimensions.
‘ dividual parts which, when properly assembled,
It is also an object to design a device of the
form the thermostatic latching or clutching de
vice of the overload relay.
type above referred to in such a manner that the
releasable latching or clutching means act along
The illustrated device has an insulating body
the entire periphery of the movable member to
I with two raised portions 2 and 3. An axial
be latched so as to be capable of exerting a con
cavity 4 is provided in portion 3 of the insulating
siderable retaining force thereon, and it is fur
body, while the portion 2 has a bore extending
ther aimed at achieving this result while requir
substantially in a tangential direction to the
ing only a slight movement of the clutch or latch 50 cavity 4. The bore and the cavity are in com
means for elfecting the release of the movable
munication with each other (Figs. 4 and 5).
member.
Two openings 5 and 5 are provided in body I
In order to achieve these and other objects
for fastening it to a suitable support. A plunger
which will become apparent from the following
1 is arranged in the bore of body i. This plunger
description, my invention requires a helical ther- 88 carries a push button at its upper end and has a
2,404,352
3
4
radially restricted portion at 9. A helical com
pression spring [0 placed in the bore underneath
the plunger tends to move the plunger in the out
(Fig. 3). This has the e?ect of controlling a
contactor (not illustrated) to close the main cir
cuit to be controlled extending over the terminals
ward direction relative to the insulating body.
A contact bridge H is slidably mounted on the
plunger 1 underneath the push button 8, so as to
button 8, the end [6 of the bimetal winding [5 is
be axially displaceable relative to the plunger.
23 and 24 and the heater 29. When pushing the
moved downwardly (Fig. 4) in the unwinding di
rection. Hence the bimetal winding is capable of
rotation relative to the shaft structure. After the
lowermost position of the plunger 1 is reached and
the plunger 1 forms an abutment for the contact
bridge I I, and a spring I2 is provided for biasing 10 the spring l0 compressed, the bimetal winding l5
grips the sleeve I1 and retains the plunger 1 in
the bridge I I against the abutment 32.
the depressed position. As long as the load cur
Two contact terminals l3 and [4, each provided
A washer or projection 32 ?rmly connected with
rent remains below a Certain magnitude, the heat
developed by heater 29 is insufficient to loosen the
face of the raised base portion 2. These two ter
minals form stationary contacts which are 15 frictional grip of the bimetal winding. When an
overload occurs and persists for a su?icient time
bridged by the contact member I I when the push
with a binding screw, are mounted on the top sur
to overheat the bimetal, the loosening of the bi
metallic winding releases it for rotation, so that
now the spring I0 is capable of moving the
tended end portion IS in engagement with the
restricted portion 9 of the plunger, serves to latch 20 plunger 1 and the contact bridge into the illus
trated opening position. This causes an inter
the plunger in its depressed position. The wind
ruption of the main current through winding 29
ing [5 is relatively tightly seated on a slotted
button 8 is in depressed position.
A helical bimetal winding [5, which has an ex
so that the thermostatic mechanism is permitted
to cool. After expiration of the cooling period,
post [8. One end E9 of this post is riveted to the
angular poition 22 of a contact terminal 23. The 25 the mechanism is again in condition for returning
the plunger into contact closing position.
other end 20 of the post it! is threaded and carries
It will be apparent from the above-described
an adjusting nut 2 i. When the parts l5, IT, l8, 2!
embodiment in conjunction with the drawing that
and 22 are assembled as shown in Fig. 5, the nut
the releasable latching or clutching device of the
~2I rests against a washer which, in turn, rests
against the adjacent front surface of the slotted 30 relay is of extremely small dimensions, although
the holding force developed by the thermostatic
sleeve IT. The inner bore of the sleeve is tapered
winding is very large due to the fact that it acts
so that the diameter of the outer sleeve surface
along the entire periphery of the clutching de
engaged by the inner surface of the bimetal wind
vice and along any desired number of turns. It
ing l5, depends on the axial position of the sleeve
relative to the conical post i8. This position can 35 will also be apparent that the tripping value of
the load current can be readily adjusted with
be changed with the eifect of widening the sleeve
sleeve i‘! which, in turn, is mounted On a conical '
the aid of the nut 2|.
ll’ by screwing the nut 21 tighter against the
While I have illustrated an embodiment in
sleeve. Once properly adjusted, the nut 2i may
which a slotted and expansible sleeve is used in
be soldered to the threaded portion 28 of the post
in order to secure the adjusted setting. Due to 40 order to improve the adjustability of the thermo
static device, it is also possible to provide the
the frictional engagement between the sleeve H
helical thermostat winding with a slightly ta
and the bimetal winding, the winding is prevented
pered inner bore and to place it directly on a
from rotating relative to the sleeve in a direction
conical post, the operation and adjustability of
which would tend to wind the bimetal more
tightly about the sleeve. However, when the end 45 the device remaining substantially as described
in the foregoing.
It is moved in the opposite, i. e. unwinding, di
It should be understood that while I have illus
rection, the turns of the bimetal winding are
trated a single embodiment of my invention, the
loosened su?iciently to permit a rotation of the
essential elements of the releasable thermostatic
winding. The winding is surrounded by a helical
device may be associated with electric devices
heater 29.
different from the illustrated overload relay. In
The above-mentioned terminal 23 is mounted
view of such modi?cations which will be obvious
on the top face of the base portion 3 and has a
to those skilled in the art upon studying my pres
binding screw 25 for fastening one end 3| of the
ent disclosure, 1' wish this speci?cation to be un
heater winding 29 thereto. A second terminal 21%,
also mounted on the base portion 3, has a binding 55 derstood as illustrative and not in a limiting
sense.
screw 26 for fastening the other end 36 of the
I claim as my invention:
heater. The two terminals 23 and 24 have addi
1. A relay comprising a shaft member and a
tional binding screws 21 and 28, respectively, for
helical spring member revolvable relative to each
connecting thereto the leads of the electrical cir
other, said spring member being coaxially seated
cuit to be controlled by the relay. When in op
on said shaft to grip it normally in order to pre
eration, the current flowing from terminal 23
vent relative revolution in one direction, a mov
through the heater 2!} to the terminal 26 has the
able and spring biased relay structure connected
effect of heating the bimetal winding Hi. When
the temperature of winding i5 rises beyond a
with one of said members so as to be retained,
given value due to the occurrence and persistence v . when in proper position, in opposition to its spring
bias, and electric means for causing said spring
of an overload, the winding expands its turns and
member to expand radially in order to release
loosens from the sleeve l‘! to a su?icient extent
said shaft so as to permit said structure to move
to permit a rotation of the bimetal winding in
under its bias.
either direction,
2. A relay comprising a stationary shaft, a
The relay operates in the following manner.
helical clutch spring coaxially seated on said shaft
The illustration shows the control contacts 6 I, I3
so as to be revolvable in one direction while grip
and M in interrupted condition with the actuat
ping the shaft so as to be normally prevented
ing plunger 1 in its uppermost position. When
from revolving in the other direction, a movable
the push button 8 is depressed, the bridge H
and spring biased structure connected to said
closes the contact between terminals l3 and M
2,404,352‘
5
6
clutch spring so as to be retained, when in proper
against its bias so as to revolve said strip in its
position, against the action of its spring bias,
unwinding direction.
and electric means for causing said clutch spring
to expand radially in order to release said shaft
6. A relay mechanism comprising a conical
post, an expansible sleeve member disposed on
said post for adjusting the sleeve diameter in
accordance with the relative axial position of
sleeve and post, a helical clutch member coaxially
seated on said sleeve to grip it so as to be nor
so as to permit said structure to move under its
bias.
3. A relay comprising a shaft member and a
helical thermostatic member revolvable relative
to each other, said thermostatic member being
mally revolvable only in its unwinding direction
coaxially seated on said shaft so as to grip it 10 relative to said sleeve, a movable and spring
in order to prevent relative revolution in one
biased relay structure connected with one of said
direction, a movable and spring biased relay
members so as to be retained, when in proper
structure connected with one of said members
position, in opposition to its spring bias, and
so as to be retained, when in proper position, in
electric means for causing said helical clutch
opposition to its spring bias, and electric heating 15 member to expand radially in order to release
means associated with said thermostatic member
said shaft so as to permit said structure to move
for causing it to expand radially in order to loosen
under its bias.
its grip on said shaft member upon occurrence
7. A relay mechanism comprising a stationary
of given temperature conditions.
conical post, a slotted 'expansible sleeve having
4. A relay comprising a stationary shaft, a 20 a conical bore and being ?rmly seated on said
helical bimetal strip coaxially seated on said shaft
post in a position corresponding to a desired outer
so as to be revolvable in one direction while grip
sleeve diameter, a helical bimetal coaxially seated
ping the shaft so as to be normally prevented
on said sleeve to grip it so as to be normally
from revolving in the other direction, a movable
revolvable only in its unwinding direction rela
and spring biased structure connected to said 25 tive to said sleeve, a movable and spring biased
strip so as to be retained, when in proper position,
relay structure connected with one end of said
against the action of its spring bias, and electric
bimetal so as to be retained, when in proper posi
heating means associated with said strip for
tion, against the action of its spring bias, and
causing it to expand radially in order to loosen
electric heating means associated with said bi
its grip on said shaft member upon occurrence 30 metal for causing it to expand radially in order
of given temperature conditions.
to loosen its grip on said sleeve upon occurrence
5. A relay comprising a stationary shaft, a
helical bimetal strip coaxially seated on said shaft
of a predetermined electric condition.
8. A relay comprising a stationary shaft, a
helical bimetal strip coaxially seated on said shaft
ping the shaft so as to be normally prevented 35 so as to be revolvable in one direction while grip
ping the shaft so as to be normally prevented
from revolving in the other direction, a movable
and spring biased structure connected to said
from revolving in the other direction, a movable
strip so as to be retained, when in proper posi
and spring biased structure connected to said strip
tion, against the action of its spring bias, electric
so as to be retained, when in proper position,
heating means associated with said strip for caus 40 against the action of its spring bias, and an
ing it to expand radially in order to loosen its
electric heating winding surrounding said helical
grip on said shaft member upon occurrence of
strip in order to cause it to expand radially so
given temperature conditions, and reset means
as to loosen its grip on said shaft member upon
associated with said structure for moving it
occurrence of an electric overload.
GEORGE C. ARMSTRONG.
45
so as to be revolvable in one direction while grip
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