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Patented Oct. l5, 1946
Richard D., Kaul, Fairfield, Conn., assigner to Ther>
Sealand Corporation, Southport, Conn., a cor-_
poration of ComlcQticut
Application August> 17, 1943, Serial No. 499,000
5 Claims.
(Cl. 200-143)
This invention relates t0 improvements in ther
mo-responsive cable.
of the apertures b. Such alarm circuits, aswell
as auxiliary connectors and ñttings for use with
fire detecting cable, being well known and forme
ing no part of the present invention, will not; be
It is the general object of the invention to pro
vide an improved thermo-responsive cable for
indicating fire or other high temperature con`
A speciñc object of the invention is to pro
vide a cable in which the certainty of response
to the temperature condition to be indicated is
A second specific object of the invention is to
further referred to.
For indicating fires, a fusing temperature of
about 160° F. is generally suitable, and the core
A may be made of Wood’s metal or Lipperwitz’s
metal. The invention, however, is not conñned
provide a cable construction which reduces im- .
pairment of response or dielectric strength by
deterioration of the cable structure due to iiexure
or other mechanical abuse.
The cable of the present invention constitutes
an improvement upon that disclosed in Lindsey
Patent No. 2,048,271, granted July 2l, 1936, the
general purposes and functions of the cable be
ing similar.
With the foregoing objects, as well as others
to the indication of a speciñc temperature or
condition but may be applied to indicating any
desired temperature, an alloy Aor metal with a
suitable melting point being selected.
In manufacturing the cable in the preferred
form, an oversize tube B is drawn down onto the
core A so as to ñt the same closely or compres
sively and eliminate all voids, so far as possible,
with a View to compelling the alloy, when melted,
4to spurt through an aperture b. The apertures
20 b are spaced along the tube B as indicated in
Figure 2, so as to weaken the tube B as little as
which will appear in the following full descrip
possible, and in addition are preferably made in
tion in mind, the invention consists in the com
the form of narrow slots, which may conven
binations and arrangements of parts and details
iently be formed by slitting or punching the
of construction which will now first be fully de 25 metal of tube B after drawing the same down on
scribed Yin connection with the accompanying
the core A and then pressing the edges of the
drawing and then more particularly pointed, out
slit back together. While it will be understood
in the appended claims.
that the specific dimensions may be widely va
In the drawing:
ried, in the example selected for illustration, slits
Figure 1 is a perspective View of a section of 30 b approximately one-quarter inch long and
cable embodying the invention in a preferred form
spaced longitudinally of the cable at three inch
and with the elements progressively removed so
intervals have been found satisfactory in a cable
as to show the internal structure;
having an overall outside diameter of slightly
Figure 2 is a perspective View showing the cen
over one-eighth inch. Before applying the in
sulating layer C, a coat of insulating lacquer or
-ter conductor member of the cable of Figure 1;
varnish is preferably applied to the tube B. The
insulating layer C may be of any suitable in
Figures 3 and 4 are typical cross sections, upon
sulating material, and of any suitable form so
an enlarged scale, taken at different points along
the length of the cable of Figure l.
long as it will permit the molten alloy to pass
The cable elements, as shown in Figure l, in 40 through it; in the embodiment shown, a wrapping
of beeswax-impregnated cotton or paraffin-im
clude a fusible alloy core A, contained Within a
pregnated cotton has been found satisfactory.
seamless copper tube B, forming an inner con
ductor and having apertures b to permit the.
As indicated above, manufacture is completed by
alloy to fiow or spurt out upon melting. The
drawing down an oversize tube D so as to i'lt
tube B is covered by a winding C of insulating 45 tightly upon the insulating layer C. Figure 3
of the drawing shows the completed cable struc
material, and a second seamless copper tube D,
ture in typical cross section passing through an
which ~forms an outer conductor, is drawn onto
the insulating winding C. As in the Lindsey pat
aperture b, and Figure 4 is a typical cross section
at a point where there is no aperture b.
ent, above referred to, the cable will be located
The advantages of the present invention will
so as to indicate ñre or other conditions causing 50
be best understood by referring to significant
temperature rises, the inner and outer conductors
points of difference between the present con
B and D being included in an alarm circuit which
is completed upon fusing of the alloy core A
struction and that of the Lindsey patent, above
referred to.
which connects conductors B and D by means
of the fused alloy passing through one .or more 55
By employing separate apertures b, instead of a
continuous slot, in the inner conductor B, the ex
pansive force of the melting alloy core A is con
ñned and results in a more positive flow or spurt
of alloy through the apertures.
2. A thermo-responsive cable comprising inner
and outer tubular conductors, insulating material
between said conductors and a core of fusible
Secondly, the
conducting material Within the inner conductor,
use of a ductile and highly conductive metal,
such as copper, is. made possible, as it is unneces
the said inner conductor comprising a seamless
tube drawn onto said core and having longitudi
sary to use a steel or iron conductor B in order
nally spaced apertures.
to obtain the required strength, which is the case
when a continuously slotted conductor is used.
The ductility and continuity of the inner con
ductor B make it possible for the cable to with~
stand considerable bending or other mechanical
abuse without creating undue voids around the
core A or otherwise impairing the cable, While,
as is apparent, a continuously slotted conductor
cannot be bent Without gaping and creating
What is claimed is:
1. A thermo-responsive cable comprising inner
and outer tubular conductors, insulating ma
3. A thermo-responsive cable comprising inner
and outer seamless metal tubes, insulating ma
terial between said metal tubes and a core of
fusible conducting material within the inner
tube, the said inner tube having longitudinally
spaced apertures but having an otherwise con
tinuous wall.
4. A thermo-responsive cable according to
claim 3, in which the said inner tube is drawn
down onto said core in compressing relation
5. A thermo-responsive cable according to
claim 3, in which said inner and outer tubes
terial between said conductors and a core of fusi
are respectively drawn down onto said core and
ble conducting material within the inner con
said insulating material in compressing relation
ductor, the said inner conductor having longi
tudinally spaced apertures but having an other
wise continuous Wall.
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