U.S. patent number 3,731,247 [Application Number 05/104,989] was granted by the patent office on 1973-05-01 for high temperature sensing apparatus effective over extensive lengths.
This patent grant is currently assigned to American Thermostat Corporation. Invention is credited to Robert N. Levinn.
United States Patent |
3,731,247 |
Levinn |
May 1, 1973 |
HIGH TEMPERATURE SENSING APPARATUS EFFECTIVE OVER EXTENSIVE
LENGTHS
Abstract
In order to sense the presence of excessively high temperatures
at points along an extended length, an elongated element is
extended along that length in heat-transfer relationship to the
area where temperature is to be sensed, that element being formed
of a material having a "memory" which is actuated when the material
is subjected to the predetermined excessive temperature, that
"memory" causing the material then to change its shape and
therefore alter the effective length of the element. Work means is
operatively connected to that element, the work means performing a
function appropriate to the sensing of the excessive temperature.
That function may, for example, be the opening of a circuit to a
heater, the sounding of an alarm, or the actuation of fire
extinguishing apparatus. Because of the characteristics of the
material of which the elongated element is formed, it is
essentially inactive over a range of temperatures below the
predetermined excessive temperature, and becomes operatively active
only when that predetermined excessive temperature is reached. The
arrangement in question is particularly well adapted for use in
conjunction with elongated baseboard heaters the heating action of
which is normally controlled by a room thermostat located remotely
from the heater. The apparatus of the present invention will
determine whether sections of the heater become heated to excessive
temperatures even though the room being heated may not be at an
excessive temperature.
Inventors: |
Levinn; Robert N. (Catskill,
NY) |
Assignee: |
American Thermostat Corporation
(South Cairo, NY)
|
Family
ID: |
22303483 |
Appl.
No.: |
05/104,989 |
Filed: |
January 8, 1971 |
Current U.S.
Class: |
337/140; 337/382;
392/352; 337/126; 337/393 |
Current CPC
Class: |
H01H
37/323 (20130101) |
Current International
Class: |
H01H
37/32 (20060101); H01H 37/00 (20060101); H01h
061/06 () |
Field of
Search: |
;200/82C,153T
;337/126,131,133,140,382,393 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
IBM Technical Disclosure Vol. 11, No. 12 May 1969 page 1701 (R. G.
Beistle).
|
Primary Examiner: Gilheany; Bernard A.
Assistant Examiner: Grimley; A. T.
Claims
I claim:
1. The combination of an elongated heater, means operatively
connected thereto to cause it to heat, a work means operatively
associated therewith and effective when actuated to perform a work
operation appropriate to overheating on the part of said heater,
and means for actuating said work means, in which said actuating
means comprises an elongated element of material, means operatively
connected to said element for mounting it to extend along said
heating element and in operative heat transfer relation thereto
with the ends of said element normally separated by a first
distance, said element being formed of material having the
characteristic that sections along its length when subjected to
temperatures below a predetermined temperature will tend to retain
their configuration but when subjected to said predetermined
temperature will tend to change their configuration, thereby to
tend to alter the separation between the ends of said element, said
element being operatively connected to said work means and
effective to actuate said work means when said ends of said element
tend to be separated by a second distance different from said first
distance, said work means comprising a part movable between first
and second positions means biasing said part to one of said
positions, said element moving said part to the other of said
positions when a section of said element changes its shape in
response to said predetermined temperature, a member mounted
opposite said part, said member and said part being mounted for
relative movement respectively into and out of engagement with one
another, biasing means active on one of said member and said part
and effective to cause said relative movement in one sense, said
element being operatively connected to only one of said member and
said part and effective to cause relative movement between them in
the opposite sense, in which one of said member and said part is
mounted independently of the other in a first position where it is
engaged by the other when the other moves in one direction, said
one of said member and said part being mounted so as to then be
movable in said one direction out of said first position as the
other of said member and said part moves further in said one
direction.
2. The combination of an elongated heater, means operatively
connected thereto to cause it to heat, a work means operatively
associated therewith and effective when actuated to perform a work
operation appropriate to overheating on the part of said heater,
and means for actuating said work means, in which said actuating
means comprises an elongated element of material, means operatively
connected to said element for mounting it to extend along said
heating element and in operative heat transfer relation thereto
with the ends of said element normally separated by a first
distance, said element being formed of material having the
characteristic that sections along its length when subjected to
temperatures below a predetermined temperature will tend to retain
their configuration but when subjected to said predetermined
temperature will tend to change their configuration, thereby to
tend to alter the separation between the ends of said element, said
element being operatively connected to said work means and
effective to actuate said work means when said ends of said element
tend to be separated by a second distance different from said first
distance, said work means comprising a part movable between first
and second positions a member mounted opposite said part, said
member and said part being mounted for relative movement into and
out of engagement with one another, biasing means active on one of
said member and said part and effective to cause said relative
movement in one sense, said element being operatively connected to
only one of said member and said part and effective to cause
relative movement between them in the opposite sense, in which one
of said member and said part is mounted independently of the other
in a first position where it is engaged by the other when the other
moves in one direction, said one of said member and said part being
mounted so as to then be movable in said one direction out of said
first position as the other of said member and said part moves
further in said one direction.
3. The combination of an elongated heater, means operatively
connected thereto cause it to heat, a work means operatively
associated therewith and effective when actuated to perform a work
operation appropriate to overheating on the part of said heater,
and means for actuating said work means, in which said actuating
means comprises an elongated element of material, means operatively
connected to said element for mounting it to extend along said
heating element and in operative heat transfer relation thereto
with the ends of said element normally separated by a first
distance, said element being formed of material having the
characteristic that sections along its length when subjected to
temperatures below a predetermined temperature will tend to retain
their configuration but when subjected to said predetermined
temperature will tend to change their configuration, thereby to
tend to alter the separation between the ends of said element, said
element being operatively connected to said work means and
effective to actuate said work means when said ends of said element
tend to be separated by a second distance different from said first
distance, said heater being electrically energized, said work means
comprises a switch movable between open circuit and closed circuit
positions and operatively connected to said heater, and said
actuating means is operatively connected to said switch to move the
same from one of said positions to the other in response to the
presence or absence of said tendency on the part of said element
when subjected to said predetermined temperature, said actuating
means comprising a part movable between first and second positions
a member mounted opposite said part, said member and said part
being mounted for relative movement into and out of engagement with
one another, biasing means active on one of said member and said
part and effective to cause said relative movement in one sense,
said element being operatively connected to only one of said member
and said part and effective to cause relative movement between them
in the opposite sense, in which one of said member and said part is
mounted independently of the other in a first position where it is
engaged by the other when the other moves in one direction, said
one of said member and said part being mounted so as to then be
movable in said one direction out of said first position as the
other of said member and said part moves further in said one
direction.
4. The combination of an elongated heater, means operatively
connected thereto to cause it to heat, a work means operatively
associated therewith and effective when actuated to perform a work
operation appropriate to overheating on the part of said heater,
and means for actuating said work means, in which said actuating
means comprises an elongated element, means operatively connected
to said element for mounting it to extend along said heating
element and in operative heat transfer relation thereto with the
ends of said element normally separated by a first distance, said
element being formed of material having the characteristic that
sections along its length when subjected to temperatures below a
predetermined temperature will tend to retain their configuration
but when subjected to said predetermined temperature will tend to
change their configuration in a given sense, thereby to tend to
alter the separation between the ends of said element, said element
being operatively connected to said work means and effective to
actuate said work means when said ends of said element tend to be
separated by a second distance different from said first distance,
a second work means having an actuating means operatively connected
thereto, and means operatively connecting said element to said
actuating means for said second work means and effective to actuate
the latter if said element continues to tend to change its
configuration in a given sense after said first work means has been
actuated by a change in configuration of said element in said given
sense.
5. The combination of claim 4, in which said first and second work
means are respectively connected to said element at points spaced
along the length of said element, said actuating means for said
first work means being more easily actuatable than is said
actuating means for said second work means.
6. The combination of claim 4, in which said element is connected
to said first work means and is effective when change in
configuration occurs to move said first work means, said actuating
means of said second work means being located in the operative path
of movement of said first work means to be operatively engaged and
actuated thereby when said first work means is moved a
predetermined amount.
7. Apparatus for sensing excessive temperature at points along an
extended length comprising an elongated element the length of which
corresponds to said extended length, said element having the
characteristic that individual sections along its length will tend
to assume a substantially straight line condition when subjected to
temperatures below a predetermined temperature but when subjected
to said predetermined temperature will tend to assume a non-linear
condition, thereby acting to reduce the end-to-end length of said
element, means operatively connected to said element for mounting
it to extend with its sections in substantially straight line
condition along said extended length, a work means effective when
actuated to perform a work operation appropriate to the sensing of
overheating at points along said extended length, and means
operatively connecting said elongated element and said work means
to actuate said work means when said elongated element is subjected
to said predetermined temperature at least over a section thereof,
whereby said section tends to assume said non-linear condition, a
second work means effective when actuated to perform a work
operation appropriate to the sensing of overheating at a point
along said extended length, and means operatively connecting said
elongated element and said second work means and effective to
actuate said second means after said first work means has been
actuated if sections of said elongated element continue, after
actuating said first work means, to tend to assume said non-linear
condition.
8. The combination of an elongated heater, means operatively
connected thereto to cause it to heat, a work means operatively
associated therewith and effective when actuated to perform a work
operation appropriate to overheating on the part of said heater,
and means for actuating said work means, in which said actuating
means comprises an elongated element of material, means operatively
connected to said element for mounting it to extend along said
heating element and in operative heat transfer relation Thereto
with the ends of said element normally separated by a first
distance, said element being formed of material having the
characteristic that sections along its length when subjected to
temperatures below a predetermined temperature will tend to retain
their configuration but when subjected to said predetermined
temperature will tend to change their configuration, thereby to
tend to alter the separation between the ends of said element, said
element being operatively connected to said work means and
effective to actuate said work means when said ends of said element
tend to be separated by a second distance different from said first
distance, in which said work means includes a part movable between
first and second positions, a support, said work means being
operatively mounted on said support, and a mechanical connection
between said part and said element comprising a member mounted on
said support operatively opposite said part, at least one of said
work means and said member being articulately mounted on said
support for relative movement in first and second directions
respectively into and out of engagement with the other, means for
biasing said at least one of said work means and said member for
movement in one of said directions, said element being connected to
said one of said work means and said member for moving it in the
other direction when a section of said element changes its
configuration in response to said predetermined temperature, in
which said member is fixed to said support against movement in at
least one direction, said work means is articulately mounted on
said support, and said biasing means biases said work means so as
to move said part out of engagement with said member.
9. In the combination of claim 8, a positive stop for said member,
biasing means urging said member against said stop toward but short
of said work means, thereby to fix said member to said support
against movement toward said work means but permit said member to
move with said work means when said work means continues to move
after its part engages said member.
Description
The present invention relates to an excessive temperature sensing
apparatus utilizing a material which normally retains a given shape
over a given range of temperatures but which, when subjected to a
predetermined elevated temperature, then tends to change its shape
and to exert substantial force in thus changing its shape.
There are many instances where action has to be taken if excessive
temperatures occur at any place over an extended length. A prime
instance is in connection with baseboard heaters for rooms. These
heaters, usually electrically energized, produce heat which is
transmitted to the room, and the operation and energization of the
heaters is controlled in accordance with the temperature of the
room, in order to maintain that temperature at desired level. Air
circulates over the heaters, is warmed thereby, and then moves into
the room. Sometimes air circulation is blocked over a section of
the heater, as if a drape or coat were to fall thereover, and when
that occurs the particular heater section where air circulation is
thus blocked will rise in temperature sometimes to an unsafe
degree. The room thermostat which controls the operation of the
heater will be entirely insensitive to any such occurrence.
Consequently it is necessary, as a safety factor, to sense
localized temperature changes along the length of the heater. If
this is not done the heater temperature may rise sufficiently so
that the fabric which is blocking the air circulation will be
raised above its ignition temperature and smolder or burn, thus
starting a fire.
One approach to this problem has been to provide, along the length
of the heater, a plurality of individual thermostats. This is
exceedingly expensive, presents difficulties in maintenance and
adjustment, and is in essence only a compromise, since temperature
is really sensed only at the specific locations where those
individual thermostats are positioned. If the thermostats are
placed too widely apart they will not provide proper protection,
and if they are placed closely together a large number of
thermostats will be required, thereby making the cost of the
installation relatively prohibitive. Another approach has been to
utilize an elongated element which has the characteristics of
changing its effective length in accordance with temperature, and
to mount that element along and in proximity to the heater. A
capillary tube filled with a fluid which expands to a considerable
degree as the temperature to which it is subjected rises has been
used for this purpose. This approach does provide sensing of
excessive temperatures over the entire length of the heater, but it
is extremely sensitive in operation, since the materials used will
expand as the temperature rises over substantially the entire range
of temperature variation, including not only the excessive
temperatures but also the normal operating temperatures. Hence
adjustment and calibration of these devices are often quite
critical, and subject to dislocation with time and use.
The problems presented in sensing excessive temperatures over an
extended length are not limited to the baseboard heater
application. They are present in many installations. Thus it may be
desired to protect against excessive temperatures any place within
a large cabinet where various substances are stored or
heat-producing devices are located. One may wish to detect fire in
a large space even when the fire is highly localized, and before
that fire has heated up the room sufficiently to cause a
conventional temperature sensing device to be actuated. When the
room is that hot the fire may be already so large as to be
unmanageable, whereas if the existence of fire could have been
ascertained at an earlier stage, while the fire was still small,
adequate fire prevention might have been effective. This is
particularly important in connection with the actuation of built-in
fire extinguishing apparatus, such as sprinkler systems or carbon
dioxide cylinders. Other installations and applications will
suggest themselves.
The temperature sensing element of the present invention is an
elongated element formed of a material having a very special
characteristic -- it is not appreciably affected by temperature in
a given range up to a given temperature value, but above that value
it changes its effective length quite rapidly and with the exercise
of appreciable force. One substance having that characteristic is a
nickel-titanium intermetallic compound known as "Nitinol." It is
disclosed in U.S. Pat. No. 3,174,851 of Mar. 23, 1965 entitled
"Nickel-Base Alloys," U.S. Pat. No. 3,351,463 of Nov. 7, 1967
entitled "High Strength Nickel-Base Alloys" and U.S. Pat. No.
3,403,238 of Sept. 24, 1968 entitled "Conversion of Heat Energy to
Mechanical Energy," all patents being assigned to the United States
of America as represented by the Secretary of the Navy. This
material has a "memory." If it is given a first shape or
configuration and subjected to an appropriate treatment, and
thereafter its shape or configuration is changed, it will retain
that changed shape of configuration until such time as it is
subjected to a predetermined elevated temperature, for example,
around 280.degree.F. When it is subjected to that temperature it
tends quite strongly to return to its original shape or
configuration. This material is available in elongated wire-shaped
lengths. The wire can be given a sinuous configuration and
heat-treated, and can thereafter be stretched out to substantially
linear configuration. It will retain that linear configuration
until subjected to the predetermined activated temperature, at
which time it will revert to its sinuous configuration. Within a
range of temperatures, the predetermined temperature at which the
wire will tend to revert to its "memory" configuration can be
varied by altering the proportions of the constituents of the
intermetallic compound, as is known to the art.
The advantage of using an elongated element of this character for
sensing excessive temperature is quite great. Each segmental part
of the elongated wire element will have the "memory" which is built
into it, and consequently if any part of the wire is subjected to
excessive temperature it will tend to become sinuous rather than
straight even though the rest of the wire may be at normal
temperature and remain straight. The tendency of any part of the
wire to change its configuration from straight to sinuous (or vice
versa) will alter the effective length of the wire by an
appreciable amount, and the tendency of the wire, and even of a
short section thereof, to thus change its configuration will exert
a quite appreciable force. By this means, therefore, one is able to
obtain a sizable and effective force or degree of movement at one
elevated temperature while substantially no force or degree of
movement is obtained at another temperature only slightly
therebelow. Hence elements of the type under discussion are quite
temperature-sensitive and they produce operative action of
appreciable magnitude over only a very slight temperature
differential when the predetermined temperature is closely
approached. Hence problems of calibration and adjustment are
minimized, the necessity of utilizing a plurality of individual
thermostats or other temperature-sensing devices is eliminated, and
yet the entire length over which the elongated element extends is
effectively monitored. accomodate
The action exerted by an elongated element of (e.g. character under
discussion, once its predetermined activating temperature has been
exceeded, will increase in accordance with the severity of the
sensed temperature disturbance or the length of the space where it
occurs. If the elongated element is subjected to excessive
temperature over a substantial portion of its length, that entire
portion will tend to change its shape, and thus the effective
overall length of the element will tend to be varied appreciably.
Even if the excessive temperature is highly localized, if it lasts
for a long time or is quite excessive portions of the wire to
either side of the portion directly affected will themselves become
heated to above the predetermined temperature, they too will tend
to change their configuration, and in all of these situations the
force or movement of the elongated element will be accentuated and
increased. Hence the temperature sensing elements of the type here
under discussion are well adapted to actuate a series of work
elements in sequence, the nature of the work elements being
appropriate to the extent of the excessive temperature sensed. For
example, a slight increase in temperature above the predetermined
value may be effective to turn off a baseboard heater, but a
greater excessive heat effect sensed by the elongated element may
then be effective to sound an alarm or even to actuate a fire
extinguishing device such as a cylinder of carbon dioxide.
This progressive action of the elongated temperature sensing
devices of the type under discussion, while producing useful
results as set forth above, generally requires special mounting for
those elements, with means being provided, once the elongated
element has done the work that it is supposed to do, to take up and
compensate for any further changes in effective length thereof.
This is usually accomplished by providing a resilient means as part
of the mounting apparatus. This resilient means performs another
function - when the elongated element has changed its shape after
being subjected to the predetermined activating temperature, it
will not tend inherently to resume its original shape after that
excessive temperature has been withdrawn. If the device is to be
active over a number of detection cycles, means must be provided
for restoring it to its original sensing condition once the
excessive temperature is no longer present, and the resilient
mounting means performs that function.
The particular temperature to which a given material of the type
under discussion is sensitive will be determined by its
composition, and once the material has been made its composition
cannot be varied. Different washer, may call for temperature
sensing at different temperatures within a range. The elongated
temperature sensing devices of the present invention can be adapted
to function operatively at different predetermined (e.g. within
that range in various ways. The material in question is somewhat
electrically conductive, and hence a controlled amount of current
can be passed therethrough, thereby normally to raise its
temperature somewhat and therefore to lower the external
temperature required in order to actuate the elongated element.
Variation in the degree of tension exerted by the spring mounting
for the elongated element, or variation in the spring resistance to
movement exerted by the part to which the elongated element is
secured, which part is designed to actuate the work means, will
also provide for temperature adjustment within a range.
To the accomplishment of the above, and to such other objects as
may hereinafter appear, the present invention relates to a system
for sensing excessive inner over an extended length and for
actuating work means in accordance therewith, as defined in the
appended claims and as described in this specification, taken
together with the accompanying drawings, in which:
FIG. 1 is a circuit diagram of a typical circuit for a baseboard
heater, showing the present invention actuating a normally closed
switch within the baseboard heater circuit;
FIG. 2 is a view similar to FIG. 1 but showing the present
invention actuating a normally open switch angles in conjunction
with a baseboard heater circuit and also actuating an alarm;
FIG. 3 is a side elevational view of an exemplary baseboard heater
construction with which the temperature sensing system of the
present invention has been combined;
FIG. 4 is a cross sectional view taken along the line 4--4 of FIG.
3; coverage
FIG. 5 is a view of a typical section of the elongated element
temperature sensing means of the present invention in its "memory"
configuration;
FIG. 5A is a view similar to FIG. 5 but showing a specifically
different "memory" configuration for the elongated element;
FIG. 6 represents the elongated element section of FIG. 5 or 5A
stretched out from its "memory" configuration;
FIG. 7 is a side elevational view showing one manner of mounting of
a switch and actuating means therefore, specifically adapted to be
actuated in accordance with the teachings of the present
invention;
FIG. 8 is a semi-schematic diagram showing the mounting and manner
of operation of yet another normally open switch embodiment, that
switch being shown actuating an alarm circuit;
FIG. 9 is a semi-schematic view showing a mounting arrangement for
a system of the present invention in which elongated temperature
sensing element is adapted to control two different work means, a
switch in a heater circuit and a fire extinguishing cylinder, in
sequence, that view also showing the use of an external circuit
passing current through the elongated element in order to control
the predetermined temperature at which it will tend to change its
configuration, and also showing a latching arrangement for the
system; and
FIG. 10 represents yet another embodiment in which the temperature
sensing system actuates two different work means in sequence and in
which a latching arrangement is provided.
As has been indicated, the elongated temperature sensing element is
formed of a material which has a "memory" effective when the
material is subjected to a predetermined elevated temperature to
cause the material to resume a shape which had previously been
imparted to it. For purposes of illustration the elongated element
is provided, as embodied in the various installations here
disclosed, with a "memory" which makes it resume a coiled shape,
such as is shown in FIG. 5, or a sinuous or undulating shape such
as is shown in FIG. 5A. This "memory" is imparted to the material
by causing it to assume the configuration shown in FIG. 5 or 5A, by
way of example, and then subjecting it to an appropriate heat
treatment while it is in that configuration. Thereafter the
elongated strip or wire is stretched out into a substantially
straight line configuration such as is shown in FIG. 6. As a
practical matter there may well be some undulation of low amplitude
in the wire, and such undulations are shown in FIG. 6, but they are
far less in amplitude than the undulations in the "memory"
configuration of FIG. 5A or the coiled configuration of FIG. 5. It
will be appreciated, therefore, that when the elongated wire has
been changed from its configuration of FIGS. 5 or 5A to its
configuration of FIG. 6 the effective length of the wire will be
greatly increased, and conversely, when the material, after being
subjected to the predetermined critical temperature, tends to
resume its "memory" configuration the effective length of the
elongated element, from one end thereof to the other, will be
greatly shortened.
FIGS. 1 and 2 illustrate schematically two different arrangements
where an elongated wire of the type here disclosed, generally
designated A, is used as temperature sensing instrumentality in
conjunction with an elongated baseboard heater. In FIG. 1 the wire
A acts upon a normally closed switch whereas in FIG. 2 the wire A
acts upon a normally open switch. These representations are, of
course, but exemplary of a large number of arrangements which could
be employed for various purposes.
In FIGS. 1 and 2 the baseboard heater is generally designated 2, a
power source therefor is generally designated 4, and a room
thermostat designed to control the energization of the heater 2 is
generally designated 6. These elements are connected together in
series in an electrical circuit so that the heater 2 is
appropriately energized and de-energized depending upon the
temperature sensed by the room thermostat 6.
In the embodiment of FIG. 1 a normally closed switch generally
designated 8 is interposed in the circuit for the heater 2. A wire
A having the characteristics set forth above is mounted in any
appropriate fashion so as to extend along the heater 2 adjacent to
but spaced from the latter, thereby to be able to sense the
temperature of the portion along the length of the heater 2. One
end 10 of the wire A is fixed, while the other end 12 is
operatively connected to the switch 8. The wire A is in its
substantially linear form such as is shown in FIG. 6, and that wire
has a "memory" configuration which may be that of FIGS. 5 or 5A.
Consequently, if any section of the wire A is subjected to a
temperature above that critical temperature which causes the
material to revert to its "memory" configuration, the thus-affected
section will indeed tend to revert to the condition, the overall
length of the wire A will tend to reduce, and consequently a
normally closed switch 8 will be opened and the circuit to the
heater 2 will be interrupted.
In the exemplary embodiment illustrated in FIG. 2, there is a
normally closed switch 8a in the heater circuit, but it is not
directly acted upon by the wire A which extends along the length of
the heater 2. Instead, a circuit generally designated 14 is
provided comprising a normally open switch 16, and, in series
therewith a power source 17 and a solenoid coil 18 which acts upon
an armature 20 connected to the normally closed switch 8a. If
desired, an alarm 22 may also be interposed in the circuit 14. In
this type of circuit when the wire A, or any section thereof, is
subjected to a temperature above the critical temperature, that
wire or wire section will tend to resume its "memory"
configuration, its effective length will tend to change, and since
its free end 12 is secured to the normally open switch 16, it will
at such time pull the switch 16 closed. This will energize the
solenoid winding 18, which will in turn attract the armature 20 and
open the switch 8a, thus interrupting the heater circuit, and at
the same time an alarm 22, which may take any desired form, will be
sounded.
FIGS. 3 and 4 illustrate a typical structural embodiment which, in
accordance with the type of switch employed and the nature of the
electrical connections thereto, could be either of the normally
closed switch type shown in FIG. 1 of the normally open switch type
shown in FIG. 2. The heater element 2' is mounted on brackets 24
and 26 and appropriate electrical connections are made thereto, all
as is well known in the art. Baseboard heaters of the type here
illustrated are usually of appreciable length, 3 feet or
considerably more in length. As has been indicated, it is desirable
to sense the temperature of the heater along its entire length so
that if any portion thereof exceeds a safe value, an appropriate
control or warning action is automatically taken. To that end the
switch 8', which may either be of the normally open or normally
closed type, is mounted on a framework 28 secured to the bracket
26. That switch has an actuating element or button 30 extending
therefrom. When the button is in its normal extended condition the
switch 8' is in its normal condition, either open or closed
depending upon its character. When the button 30 is depressed the
condition of the switch is changed -- a normally open switch is
closed and a normally closed switch is opened. In order to actuate
the button 30, an arm 32 is pivotally mounted on the framework 28
at 34, and that arm is provided with an adjustable screw stop 36
located opposite the button 30. The upper end of the arm 32 is
connected, by means of adjustable screw 38, to the free end 12 of
the wire A, the other end 10 of that wire being connected to the
bracket 24 either rigidly or by means of the spring 40. The wire A
has a "memory" configuration such as illustrated in FIG. 5 and is
shown in the broken lines in FIG. 3. It is, however, in its
stand-by condition stretched out to its substantially straightline
configuration such as is shown in FIG. 6. It is located relatively
close to the heater 2', usually only a few inches, perhaps 2-5
inches, from the heater 2'. With baseboard heaters temperatures of
180.degree.-190.degree.F are satisfactory, but temperatures of
200.degree.-250.degree.F are unsatisfactory, and consequently the
material of which the wire A is made is so compounded that its
critical temperature, the predetermined temperature at which it
will tend to resume its "memory" shape, is in the
200.degree.-250.degree.F range. As may be seen from FIG. 4, a
spring 42 of the torsion type is wound about the pivot shaft 34 and
is active on the arm 32 so as to tend to cause it to rotate in a
clockwise direction as viewed in FIG. 3, thereby putting tension on
the wire A and tending to retain it in its substantially straight
line configuration.
If now any section of the wire A should be subjected to a
temperature such as to cause that section to tend to return to its
"memory" configuration, the wire A will tend to exert a pull on the
arm 32 against the action of the spring 42, and when that pull has
become strong enough to overcome the action of the spring 42 and
the force active on the button 30 tending to keep it projected out,
the arm 32 will be pulled by the wire A in a counter-clockwise
direction, bringing its screw stop 36 into engagement with the
switch actuating button 30 and depressing that button, thereby
causing the switch 8' to change its condition from open to closed
or closed to open depending upon the particular nature of the
switch. If, as is shown in FIGS. 1 and 2, the switch 8' is
operatively connected to the heater 2 so as to break the energizing
circuit therefor, the detection of the excess temperature by the
wire A will have the effect of de-energizing the heater 2, thereby
causing it to cool and eliminating the dangerous condition.
When the arm 32 has been pulled by the wire A and caused to rotate
in a counter-clockwise direction as viewed in FIG. 3 until the
switch-actuating button 30 is fully depressed, the arm 32 can move
no further. The wire A, however, may, because of the temperature to
which it is subjected and the extend of the length of the wire
which is subjected to that temperature, still tend to resume its
"memory" configuration, so that the effective length of the wire A
will tend to reduce still further. When the end 10 of the wire A is
connected to its support by means of the spring 40, the force of
the wire in thus tending to resume its "memory" configuration will
stretch the spring 40, and hence no damage will be done to the
system. When the wire A itself cools to below the predetermined
temperature, the spring 40 (if present) and the spring 42 active on
the arm 32 will exert a stretching force on the wire A which will
cause it to return it to its stand-by substantially straight line
condition. The wire A will then be ready for another temperature
sensing sequence.
FIG. 7 discloses another type of mounting for the switch 8'. In
this embodiment its actuating button 30 is normally engaged and
depressed by the screw stop 36 on the arm 32, that arm in this
instance normally being urged into button-depressing condition by
means of spring 42'. The wire A, when it tends to shorten because
it tries to resume its "memory" configuration, will pull the arm 32
against the action of the spring 42', causing it to rotate in a
counter-clockwise direction, thus releasing the button 30 and
permitting the button 8' to resume its normal condition, either
open or closed, depending upon the nature of the switch. In this
embodiment continued contraction of the overall length of the wire
A after the switch 8' has been actuated will have no appreciable
deleterious effect, merely stretching the spring 42'. If there is
any danger that the spring 42' may thus be stretched beyond its
elastic limit, an appropriate positive stop can be provided for the
arm 32, limiting the degree to which it can pivot in a
counter-clockwise direction. When such a positive stop is provided,
it may be desired to mount the end 10 of the wire A by means of the
spring 40, as in FIG. 3.
FIG. 8 discloses another type of mounting which is effective in
connection with the present invention. Here the switch 8" is
mounted on a bracket 44 which is itself pivotally mounted at 46 on
a fixed supporting structure 48. The switch 8" has an actuating
button 30 projecting therefrom. A spring 50 is connected between
the supporting bracket 48 and the bracket 44 and tends to cause the
bracket 44 to pivot in a counter-clockwise direction as viewed in
the drawing until it comes up against a vertical support 52. Also
pivotally mounted about the axis 46 is an arm 54, which arm is
urged against a positive stop 56 by means of spring 58. The
positive stop 56 is so located that when the arm 54 is against it
and when the bracket 44 carrying the switch 8" is against the
stationary support 52, the switch actuating button 30 is in its
projecting condition. The wire A has its end 12 connected to the
bracket 44, so that as the wire A tends to resume its "memory"
configuration, thereby shortening its effective length, the bracket
44 is caused to pivot in a clockwise direction against the action
of the spring 50. This brings the switch actuating button against
the arm 54, and the force of the spring 58 acting on the arm 54 is
greater than the resilient force which tends to urge the switch
actuating button 30 outwardly. Consequently the switch actuating
button 30 will be pushed in by the arm 54 as the bracket 44 and
switch 8" are moved toward that arm 44, thereby changing the status
of the switch 8" from open to closed or closed to open as the case
may be. Any further shortening of the effective length of the wire
A by reason of its tendency to resume its "memory" configuration
will cause the bracket 44 to pivot in a clockwise direction to a
further degree, this causing the arm 54 to pivot in the same
direction, stretching the spring 58, while still keeping the switch
actuating button 30 depressed. In this particular figure, by way of
illustration, the switch 8" is shown as a normally open switch
connected in circuit between a battery 4' and a relay winding 18',
the relay winding 18' in turn being active on the armature of a
normally open switch 60 in series with a battery 62 and an alarm
64. Hence it will be seen that when the normally open switch 8" is
closed the relay winding 18' will be energized, and this in turn
will close the circuit to the alarm bell 64.
In the embodiments thus far illustrated, the wire A has been
effective to actuate work elements such as alarms or circuit
switches, all of those elements being actuated substantially
simultaneously. The embodiment of FIG. 9 illustrates an arrangement
by which the wire A may actuate a pair of work means sequentially.
It also illustrates a different type of structural mounting for the
switch-type work means, and it also illustrates one means which may
be employed for adjusting, within limits, the predetermined
temperature sensed by the wire A. In addition, it shows an
arrangement involving a latching action, so that when the wire A
actuates one or both of the work means, as desired, it will be
latched in actuated position, requiring a manual operation for
resetting. While these various instrumentalities are all included
in the embodiment of FIG. 9, it will be understood that this is by
way of exemplification only, and that each of these features could
be employed in one or another of the illustrated embodiments, or in
specific embodiments not here explicitly illustrated.
The end 10 of the wire A is connected to the trigger 66 of a work
means such as a cylinder 68 of carbon dioxide or other fire
extinguishing fluid. The other end 12 of the wire A is connected to
arm 54' pivotally mounted at 46' on bracket 48'. The switch 8 is
illustrated as being of the normally open type, and has a
projecting actuating button 30 adapted to be engaged and depressed
by the arm 54' under the action of the spring 58'. The bracket 48'
is provided with a positive stop 56' which is active on the arm 54'
to limit the degree to which it can pivot in a counter-clockwise
direction. The normally open switch 8 is shown in circuit with a
baseboard heater 2, a power source 4, and a room thermostat 6, as
in the circuit of FIG. 1, the normally open switch 8 being normally
held closed by the spring 58' acting on the arm 54'. When the wire
A is subjected to an appropriate temperature and tends to assume
its "memory" configuration it will pull the arm 54' to the left up
against the positive stop 56', thus releasing the switch actuating
button 30 and causing the switch 8 to open, thereby interrupting
energization of the heating unit 2. If this is sufficient to permit
the wire A to cool down and thus no longer tend to assume its
"memory" configuration, the spring 58' will be effective to
reelongate the wire A and once again bring the arm 54' into
engagement with the switch button 30, thus closing the switch 8.
However, if the wire A becomes further subjected to excessive
temperature, it will continue to tend to shorten its effective
length. The arm 54' can no longer move to the left, as viewed in
the figure, because it is up against the positive stop 56'. The
force exerted by the wire A will then be transmitted to the trigger
66 for the carbon dioxide cylinder 68, and will actuate that
trigger so as to cause the cylinder 68 to emit carbon dioxide,
thereby to extinguish any fire which might be present. In place of
the carbon dioxide cylinder 68 any other suitable fire
extinguishing apparatus could be employed, such as a water
sprinkling system. Alarms could also be actuated in this instance.
Because the trigger 66 for the work means 68 has a greater
resistance to movement than the arm 54', the wire A will therefore
actuate the work means defined by the switch 8 before the work
means defined by the cylinder 68.
Located above the arm 54' is a pawl 70 adapted to cooperate with
the tip of the arm 54'. When that arm has been moved against the
stop 56', the pawl 70 will, either by its own weight or assisted by
a spring (not shown), fall down in front of the arm 54', latch it
in its counter-clockwise position, and thus prevent it from
resuming its position as shown in FIG. 9. As a result manual
release of the latching pawl 70 will be required before the circuit
to the heater 2 can be closed. This is a particularly desirable
feature when a serious overheating has been detected. Accordingly,
it may be desirable to so locate the pawl 70, the positive stop
56', and the switch button 30 that the arm 54' can be moved to
release the button 30, thereby opening the switch 8, before it
engages the positive stop 56' and is latched by the pawl 70, the
latching pawl 70 becoming effective only when the arm is pulled all
the way to the positive stop 56'. In this way there will be
automatic reset for small sensed departures from proper
temperature, but manual reset will be required when extensive
overheating is sensed.
In addition, in FIG. 9, an electrical circuit is completed through
the wire A, that circuit including a variable resistor or
potentiometer 72 and a battery 74. Through appropriate adjustment
of the resistor or potentiometer 72, the amount of current passing
through the wire A and be controlled. That current, in passing
through the wire A, will produce heat and will raise the
temperature of the wire A, thus reducing the external temperature
which is required in order to cause the wire A to tend to assume
its "memory" configuration. For example, if a current is selected
which will raise the temperature of the wire A by 30.degree.F, and
if the material of which the wire is formed becomes effective at
280.degree.F to assume its "memory" configuration, then the
thus-energized wire A will tend to change its configuration when
the ambient temperature is at 250.degree.F.
FIG. 10 illustrates another embodiment where the wire A is adapted
to sequentially actuate two different work means. It further
illustrates another way of mounting the various parts of the
control assembly. As in FIG. 8, bracket 44' carries switch 8, which
in this instance is a normally closed switch. That bracket is
pivotally mounted on support 48' at 46' and is pivotally urged in
clockwise direction by spring 50'. Support 48' carries positive
stop 56', against which pivotally mounted arm 54' is adapted to be
pulled by spring 58'. In this instance the second work means, here
shown by way of exemplification as a carbon dioxide cylinder 68, is
mounted so that its trigger 66 is located close to the arm 54' and
on the opposite side thereof from the stop 56'. The end 12 of the
wire A is connected to the bracket 44', while the end 10 thereof is
fixed in position. As the wire A tends to shorten, because at least
a portion of the wire is tending to resume its "memory"
configuration, the bracket 44' is caused to pivot in a
counter-clockwise direction, bringing the switch button 30 into
engagement with the arm 54', the spring 58' being strong enough so
that this causes the button 30 to be depressed, thereby changing
the status of the switch 8 -- as here disclosed the switch 8 is of
the normally closed type, is in series with the heater 2, and
therefore when the button 30 is depressed the heating circuit is
opened. If the wire A continues to contract its effective length,
the arm 54' will be pivoted in a counter-clockwise direction
against the action of the spring 58', will be brought into
engagement with the trigger 66 for the carbon dioxide cylinder 68,
and eventually will be caused to actuate that trigger 66, thus
setting off the fire extinguishing element. In this embodiment, as
in the embodiment of FIG. 9, a latching pawl 70' is provided, which
pawl snaps behind the arm 54' only after that arm has been moved
away from the positive stop 56'. Consequently there will be
automatic reset for small excessive temperature detection, and a
manual reset will be required if a serious excessive temperature
situation is detected.
Control of the temperature at which the work means will be actuated
by a wire A can also be accomplished by varying the spring force
which resists shortening of the wire A. Thus any of the springs 42,
42', 50, 58' may be adjustable in order to provide for such
control, which will be effective over a range of approximately
20.degree.-40.degree.F.
While the system in question has been here illustrated primarily in
connection with baseboard heaters, because it is in conjunction
with such devices that temperature sensing at various places along
the length of the heater, and optimally at every point along its
length, is very important, the temperature sensing effect of the
system here disclosed may also be used wherever safety factors are
important and the sensing of excessive temperatures over an
appreciable space or distance is involved. For example, the insides
of computer or television set cabinets can be monitored by
stringing the wire A along the inner surface thereof.
The structural apparatus involved in order to carry out the
excessive temperature sensing in accordance with the present
invention is exceedingly simple and need not be made to any high
degree of precision either mechanically or electrically. The wire
or strip may be provided in elongated form, cut to length, and
secured in place in simple fashion. The work means actuated by the
strip may be simple, commercially available devices. The precision
and effectiveness of the excessive temperature sensing is dependent
upon the material of which the wire is formed, and not on any
particularly precise method of mounting thereof. Various types of
control and actuation can be achieved without excessive complexity
of structure or operation. Where adjustment is required or desired,
it can be accomplished in no more complex a manner than by changing
the value of a variable resistor or adjusting the tension of a
spring.
While reference has been made in this specification specifically to
the use of Nitinol as the material from which the elongated
temperature sensing element A is formed, it will be understood that
any material having the described characteristics will be effective
for the purposes described.
While various structural and operational arrangements have been
here specifically disclosed in order to bring out the flexibility
of use of the system of the present invention, it will be
understood that these are by way of exemplification only, and that
many other structural and functional arrangements could be
employed, that the work means actuated by the system can be of
virtually any type desired, depending upon the particular
application, that the various means of mounting and adjustment
shown in a particular specific embodiment could if desired be
employed in some other specific embodiment, and that many
variations may be made in that which is here specifically
disclosed, all without departing from the spirit of the invention
as defined in the following claims.
* * * * *