U.S. patent number RE31,081 [Application Number 06/240,582] was granted by the patent office on 1982-11-16 for railroad switch heater.
Invention is credited to Henry Keep, Jr..
United States Patent |
RE31,081 |
Keep, Jr. |
November 16, 1982 |
Railroad switch heater
Abstract
An apparatus for heating railroad rails such as those forming a
railroad switch to prevent obstruction of the switch by ice and
snow includes an elongate, bendable, high temperature heating cable
disposed lengthwise against and along a side of the rail web. The
cable comprises an electrical resistance heating wire encased in a
high temperature resistant electrically insulating material
confined inside a thermally conductive deformable metal sheath. An
elongate, pliable heat insulating mat is disposed lengthwise
against and along a length of the cable and portions of the rail
web laterally adjacent thereto to prevent heat losses by convection
or radiation from the cable length. An elongate substantially rigid
casing member is fitted lengthwise over the mat and bears against
the web side to confine the mat in place, and is held tightly in
place against the rail web. Current is supplied at high
.[.wattage.]. .Iadd.watt density .Iaddend.through the resistance
wire of the cable, generating heat which flows into the rail and
through it and switch plates to a movable switch rail efficiently
by conduction.
Inventors: |
Keep, Jr.; Henry (Madison,
CT) |
Family
ID: |
26933516 |
Appl.
No.: |
06/240,582 |
Filed: |
March 4, 1981 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
890637 |
Mar 20, 1978 |
04195805 |
Apr 1, 1980 |
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Current U.S.
Class: |
246/428; 104/280;
126/271.2B; 174/109; 191/27; 219/213; 219/536 |
Current CPC
Class: |
E01B
7/24 (20130101) |
Current International
Class: |
E01B
7/00 (20060101); E01B 7/24 (20060101); E01B
007/24 () |
Field of
Search: |
;219/213,536 ;191/27
;246/428 ;104/279,280 ;126/271.1,271.2B ;174/109 ;338/214 ;138/33
;252/62 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Basinger; Sherman D.
Attorney, Agent or Firm: Johnston; Albert C.
Claims
I claim:
1. Apparatus for heating a railroad rail comprising:
an elongate, bendable, high temperature heating cable disposed
lengthwise against and along a side of the rail web, said cable
comprising an electrical resistance heating wire encased in high
temperature resistant electrically insulating material confined
inside a thermally conductive deformable metal sheath,
an elongate, .[.pliable,.]. heat insulating mat disposed lengthwise
against and along a length of said cable and portions of said web
laterally adjacent thereto to prevent heat losses by convection or
radiation from said cable length, said mat comprising an elongate
mass of high temperature resistant ceramic fiber insulation
confined .[.in a flexible sleeve.]. .Iadd.by means .Iaddend.that
prevents fiber of said mass from creeping between said cable and
the rail,
an elongate, substantially rigid casing member fitted lengthwise
over said mat and bearing against said web side to confine said mat
in place,
means holding said casing member .Iadd.and thereby said mat and
said cable .Iaddend.tightly in place against the rail web; and
means for supplying current at high .[.wattage to.]. .Iadd.watt
density through .Iaddend.said wire;
whereby the rail along said cable length is heated efficiently by
conduction, yet burn-out of said cable is prevented, during heating
of said cable by said current.
2. The apparatus of claim 1, said .Iadd.insulation confining means
comprising a flexible .Iaddend.sleeve .[.being.]. formed of a high
temperature resistant wire mesh.
3. The apparatus of claim 1, said cable being supported in proper
position by hooks .[.engaged on the inner side of.]. .Iadd.fastened
to and extending inward from .Iaddend.said casing member at
intervals therealong.
4. The apparatus of claim 1, said cable comprising as said wire a
single, central strand of chromium-nickel electrical resistance
alloy, as said insulating material a plurality of layers of ceramic
or silica fibers braided onto said strand, and as said sheath a
heat and oxidation resistant metal armor braided onto and about the
outermost of said layers.
5. The apparatus of claim 4, .Iadd.wherein .Iaddend.said strand,
said layers and said armor are constructed and assembled to
linearly expand at substantially the same rate.
6. The apparatus of claim 4, said armor being braided of
copper-nickel alloy wires.
7. The apparatus of claim 1, said casing member being of sheet
metal and of substantially U-shaped cross-section that encloses
said mat and the side walls of which bear along their edges against
said web side.
8. The apparatus of claim 7, said holding means comprising a spring
clip having a first section embracing the base flange of the rail
and a second section bearing resiliently against a front wall of
said casing member to hold the casing member against said rail
web.
9. Apparatus according to claim 1, for heating a railroad rail
supported laterally along a reach of said web side by a series of
rail braces spaced therealong, said cable .Iadd.being
.Iaddend.disposed against said web side along each region thereof
between adjacent braces, each said length of said cable having a
said insulating mat disposed against and along it as aforesaid with
a said casing member fitted over the mat and held against the rail
as aforesaid, said cable in the vicinity of each said brace being
bent upwardly and over the brace from ends of the casing members
adjacent to the brace.
10. Apparatus for heating a railroad rail switch that includes two
fixed rails and two switch rails movable laterally to and away from
the fixed rails on underlying switch plates and interconnected by
switch tie rods, said apparatus comprising:
an elongate, bendable, high temperature heating cable having a
first portion disposed along the outer side of one fixed rail,
second portions connected in series with said first portion,
extending from the outer side of said one fixed rail toward and
back from the other fixed rail under said rails in the region of
each of said tie rods, and a third portion connected in series with
said first and second portions disposed along the outer side of the
other of said fixed rails, each said cable portion comprising an
electrical resistance heating wire encased in high temperature
resistant electrically insulating material confined inside a
thermally conductive deformable metal sheath;
an elongate, .[.pliable.]. heat insulating mat disposed lengthwise
against and along a length of each of said first and third portions
of said cable disposed along the outer side of a fixed rail and
disposed against portions of the rail web laterally adjacent said
first and third cable portions to prevent heat losses by convection
or radiation from the cable length, each said mat comprising an
elongate mass of high temperature resistant ceramic fiber
insulation confined .[.in a flexible sleeve of high temperature
resistant wire mesh.]. .Iadd.by means .Iaddend.that prevents fiber
of said mass from creeping between the cable and said rail web;
an elongate, substantially rigid, sheet metal casing member fitted
lengthwise over and enclosing each said mat, and bearing along the
edges of its side walls against said wall rail web to confine the
mat in place;
means holding each said .[.channel.]. .Iadd.casing .Iaddend.member
.Iadd.and thereby said mat and said cable .Iaddend.tightly in place
against the related rail web; and means for supplying current at
high .[.wattage to.]. .Iadd.watt density through .Iaddend.said wire
of each said cable;
whereby said fixed rails along said cable lengths and consequently
said switch plates and said switch rails are heated efficiently by
conduction and said tie rods are heated by radiation and
convection, yet burn-out of said cables is prevented, during
heating of said cables by said current.
11. The apparatus of claim 10, said holding means comprising for
each said .[.channel.]. .Iadd.casing .Iaddend.member a spring clip
having a first section embracing the base flange of the related
track rail and a second section bearing resiliently against a base
portion of the .[.channel.]. .Iadd.casing .Iaddend.member to hold
the .[.channel.]. .Iadd.casing .Iaddend.member against the adjacent
rail web.
12. The apparatus of claim 10, each of said cables comprising as
its said wire a single, central strand of a chromium-nickel
electrical resistance alloy, as its said insulating material a
plurality of layers of ceramic or silica fibers braided onto said
strand, and as its said sheath a heat and oxidation resistant metal
armor braided onto and about the outermost of said layers.
13. The apparatus of claim 12, said armor being braided of
copper-nickel wires.
14. The apparatus of claim 12, .Iadd.wherein .Iaddend.said strand,
said layers and .Iadd.said .Iaddend.armor are constructed and
assembled to linearly expand at nearly the same rate.
15. The apparatus of claim 10, further comprising a trough
extending between said fixed rails in the region of each of said
tie rods and supporting a second portion of said cable.
16. Apparatus for heating a railroad rail switch that includes two
track rails and two switch rails movable laterally to and away from
the track rails on underlying switch plates, each of the track
rails being supported laterally at its outer side, along a reach
thereof beside a switch rail, by a series of rail braces spaced
apart therealong, said apparatus comprising:
an elongate, bendable, high temperature heating cable disposed
along the outer side of each track rail through said reach thereof,
each said cable comprising an electrical resistance heating wire
encased in high temperature resistant electrically insulating
material confined inside a thermally conductive deformable metal
sheath, each said cable having a length thereof disposed lengthwise
against the web of the related track rail along each region of such
rail between adjacent rail braces, and having in the vicinity of
each rail brace, between lengths of the cable so disposed, a
portion of the cable which is bent upwardly and over the brace;
an elongate, .[.pliable.]. heat insulating mat disposed lengthwise
against and along each said length of said cable and portions of
the rail web laterally adjacent thereto to prevent heat losses by
convection or radiation from the cable length, each said mat
comprising an elongate mass of high temperature resistant ceramic
fiber insulation confined .[.in a flexible sleeve of high
temperature resistant wire mesh.]. .Iadd.by means .Iaddend.that
prevents fiber of said mass from creeping between the cable and
said rail web;
an elongate, substantially rigid, sheet metal casing member of
substantially U-shaped cross-section fitted lengthwise over and
enclosing each said mat, and bearing along the edges of its side
walls against said rail web to confine the mat in place;
means holding each said .[.channel.]. .Iadd.casing .Iaddend.member
tightly in place against the related rail web; and
means for supplying current at high .[.wattage to.]. .Iadd.watt
density through .Iaddend.said wire of each said cable;
whereby said track rails along said cable lengths and consequently
said switch plates and said switch rails are heated efficiently by
conduction, yet burnout of said cables is prevented, during heating
of said cables by said current.
17. The apparatus of claim 16, said holding means comprising for
each said .[.channel.]. .Iadd.casing .Iaddend.member a spring clip
having a first section embracing the base flange of the related
track rail and a second section bearing resiliently against a base
portion of the .[.channel.]. .Iadd.casing .Iaddend.member to hold
the .[.channel.]. .Iadd.casing .Iaddend.member against the adjacent
rail web.
18. The apparatus of claim 16, each said cable comprising as its
said wire a single, central strand of a chromium-nickel electrical
resistance alloy, as its said insulating material a plurality of
layers of ceramic or silica fibers braided onto said strand, and as
its said sheath a heat and oxidation resistant metal armor bat
braided onto and about the outermost of said layers.
19. The apparatus of claim 18, said armor being braided of
copper-nickel wires.
20. The apparatus of claim 18, said strand, said layers and bat
having substantially the same linear coefficient of thermal
expansion.
21. A method of preventing obstruction of a railroad rail switch by
ice or snow, said switch including a fixed main track rail, a fixed
side track rail sloped away from said main rail to form a side
track, and main and side switch rails movable laterally to and away
from said fixed rails inside the latter on switch plates underlying
said rails, said method comprising at times of freezing weather
conditions flowing electrical current at high .[.wattage.].
.Iadd.watt density .Iaddend.through an electrical resistance wire
inside a thermally conductive electrically insulating cable fixed
along and next to the outer side of each of said fixed rails at the
location of said switch rails, said cable comprising said wire
encased in layers of electrically insulating ceramic fibers
confined in a heat-resistant metal sheath, obstructing heat flow by
radiation and convection from said cable with an elongate,
.[.pliable.]. heat insulating mat disposed lengthwise against and
along said cable and portions of the web of said fixed rails
laterally adjacent thereto, said mat comprising an elongate mass of
high temperature resistant ceramic fiber insulation confined .[.in
a flexible sleeve.]. .Iadd.by means .Iaddend.that prevents said
mass from creeping between said cable and said rails whereby the
heat generated in said cable by the current flow passes
predominantly into said fixed rails by conduction, and maintaining
said switch rails at above freezing temperature by conduction of
heat to them through said switch plates.
Description
This invention relates to an apparatus for heating a railroad rail
to melt ice and snow therefrom and is particularly useful for
heating the rails of a railroad switch that includes two fixed
rails and two switch rails movable laterally toward and away from
the fixed rails on underlying switch plates.
In climatic regions which frequently experience temperatures below
freezing, malfunction of railroad rail switch mechanisms is often a
problem. This difficulty is compounded in regions that experience
regular precipitation in the form of snow or freezing rain.
Temperatures below freezing and accumulation of snow and ice result
in malfunction of railroad switch mechanisms for two main reasons.
First, when snow falls heavily or drifts between the fixed rail and
the switch rail in large enough amounts it can pack and prevent
proper engagement of the two rails. Second, when water freezes and
forms ice around or on the pivot point of a movable switch rail, it
may also prevent proper switch rail movement and, therefore, proper
engagement of the two rails. Malfunction of the switch can cause
railroad stock moving over it to derail and thus result in
substantial property damage or personal injury.
The heating of a railroad rail switch involves needs for
reliability of the heating apparatus, safety and efficiency in its
operation and economy of production and installation of its
component parts, with assurance that failures of operation due to
burn-out or other cause will not occur over long periods of
service, during which the apparatus may be unattended by persons
familiar with its construction. It is also important that the
apparatus be susceptible to prompt repair at the switch location in
the event of being damaged by accident or otherwise.
So far as the applicant is aware, these needs have not been met
satisfactorily by the railroad switch heaters known and used
heretofore, although various methods and apparatus have been
proposed for heating railroad rail switches to prevent or to remedy
obstruction of the switches by ice or snow.
The principal object of the present invention is to provide a new
and improved apparatus for heating a railroad rail, and
particularly for heating rails that comprise a railroad switch, in
a reliable, safe, efficient and economical manner that will meet
satisfactorily the needs noted above.
It is another object of the invention to provide an apparatus and
method whereby the rails of a railroad rail switch are heated
predominantly by conduction, with relatively little loss of heat
from the regions of the heating elements by convection or
radiation, the heat being supplied to the fixed rails of the switch
from their outer sides and being conducted through these rails and
the underlying switch plates sufficiently to keep the movable
switch rails suitably heated.
According to the present invention, an elongate, bendable, high
temperature electrical heating cable is disposed lengthwise against
and along a side of the web of the rail to be heated. The cable
comprises an electrical resistance heating wire encased in high
temperature resistant electrically insulating material confined
inside a thermally conductive deformable metal sheath. The
confining sheath and the insulating material encasing the cable are
structures which will expand and contract to nearly the same extent
as the resistance wire over the wide ranges of temperature that
exist whenever the wire is heated or is allowed to cool from the
heating condition. An elongate, pliable heat insulating mat is
disposed lengthwise against and along a length of the cable and
portions of the rail web laterally adjacent the cable and is held
in place by an elongate, substantially rigid casing member which is
fitted lengthwise over the mat and bears against the rail web and
is secured tightly in place by suitable fastening means. The mat
prevents major losses of heat by convection or radiation from the
covered cable length. At times of freezing weather conditions,
current at high .[.wattage.].] watt density is supplied .[.to.].
.Iadd.through .Iaddend.the heating wire, causing the cable fixed
against the rail to be heated with conduction of most of the heat
directly into the rail at the heated rail length, and also
underlying switch plates and a switch rail displaceable on them,
will be heated sufficiently by conduction to prevent accumulation
of ice or snow.
The present invention also incorporates features which ease
installation of the rail heating apparatus, and a connector
construction is provided for connecting the heating cable safety to
a source of current.
Other objects, features and advantages of the invention will be
pointed out in or will be understood from the following detailed
description and the accompanying drawings of illustrative
embodiments.
IN THE DRAWINGS
FIG. 1 is a perspective view of a railroad switch on which a rail
heating apparatus constructed in accordance with the invention is
installed.
FIG. 2 is a side elevational view of the embodiment shown in FIG.
1.
FIG. 3 is a vertical cross-sectional view taken through plane 3--3
in FIG. 1, illustrating the two fixed rails, each having apparatus
of the invention installed on it, and the two switch rails.
FIG. 4 is a vertical cross-sectional view similar to that shown in
FIG. 3, taken through plane 4--4 in FIG. 2, illustrating
particularly a device for securing the apparatus to the web of the
rail.
FIG. 5 is a perspective view of a high temperature heating cable
used in the apparatus.
FIG. 6 is a perspective view of a heat insulating mat used in the
apparatus.
FIG. 7 is a vertical cross-sectional view through a connector
assembly for connecting the heating cable of the apparatus of the
invention to a current supply.
FIG. 8 is a schematic diagram of an electrical circuit for the
apparatus.
FIG. 1 illustrates a first embodiment of the apparatus of the
present invention, generally indicated at 10, installed on a
railroad rail switch, generally indicated at 12, to prevent
obstruction of the switch by ice and snow. The switch comprises two
fixed track rails 14a and 14b that are attached in a manner
described below to a plurality of rail ties 16 firmly supported on
a road bed 18, usually of concrete or crushed rock. The fixed rails
are further supported laterally at their outer sides along a reach
20 of the switch by a series of rail braces 22 which are spaced
apart and each of which is secured by suitable means such as spikes
to a tie 16.
The railroad rail switch further comprises two switch rails 24a and
24b, each of which is mounted to swing laterally toward and away
from the inner side of the fixed rail with which it is associated,
above a pivot point 26. Switch rail 24a leads into a rail 28a of
the side track, and switch rail 24b leads into a rail 28b of the
main track.
Portions of the switch rails near their ends are interconnected in
conventional manner by at least one tie rod 27, two of which are
indicated in FIGS. 1 and 2. Each tie rod 27 extends between and
substantially parallel to two adjacent ties 16. The tie rod is
axially reciprocable by a switch motor (not shown) to move the
switch rails simultaneously so that one of them engages its
associated fixed rail when the other is moved away from its
associated fixed rail. In FIG. 1, switch rail 24b is shown engaged
against the inner side of fixed rail 14b, while switch rail 24a is
shown moved away from the inner side of fixed rail 14a.
Accordingly, a train entering the switch from the right side of the
figure will be tracked along the main track.
As shown in FIGS. 2 through 4, each fixed rail 14 includes a rail
head 32, a base flange 34 and a vertically arranged web 36
interconnecting the head and base flange. The flange extends
laterally of both sides of the web giving each fixed rail an
I-shaped cross-section. Similarly each switch rail 24 also has a
head 31 and a vertically arranged web 33. However, the base flange
35 of each extends laterally to only one side of the web 33, giving
each switch rail an L-shaped cross-section.
The base flange of each fixed rail 14 is received in recesses 37
formed in a plurality of switch plates 39 each of which is secured
to a tie 16 by suitable means such as spikes. The base flange 35 of
each switch rail is supported by and slides on a portion of each
switch plate extending from the inner side of each fixed rail (FIG.
2).
As can be seen in FIGS. 2 through 4, the apparatus of the invention
includes an elongate, bendable, high temperature heating cable,
generally indicated at 38, which is disposed in discrete lengths 46
in the regions between adjacent braces 22 along and in intimate
contact with the outer side of the web 36 of fixed rail 14b through
the entire reach 20 of the switch. A stretch of such heating cable
extends similarly along the outer side of fixed rail 14a from
looped portions of this cable which are arranged to heat the switch
tie rods as described more particularly below. The heating cable,
as shown in greater detail in FIG. 5, comprises a core 40 of a high
temperature resistant heating wire that is a single solid strand of
an alloy of nickel and chromium. One such alloy which is commonly
used, known as Nichrome, comprises 80 percent nickel and 20 percent
chromium. A suitable size is No. 12 gauge having a diameter of
0.081 inch. This wire is encased within a highly heat resistant,
electrically insulating sleeve, generally indicated at 42, having
good heat conductance. In the preferred embodiment, this sleeve
comprises three layers of ceramic fibers braided onto the wire of
strand 40 of the heating cable. Commercially available ceramic
fiber made of an alumina-boria-silica composition, and identified
as "Fiber AB-312" is suitable since it exhibits excellent
dielectric properties and is resistant over long periods of time to
temperatures as high as about 2,600.degree. F., which exceed the
temperature of the heating wire when supplied with sufficient
current. Alternatively, the heat resistant electrically insulating
material may be a braided fiber of other ceramic substances
resistant to temperatures of the same order of magnitude, for
instance, of an amorphorous silica known as "REFISIL."
The heating wire and insulating material assembly is confined
inside a thermally conductive deformable heat and oxidation
resistant metal sheath 44. In the preferred embodiment this sheath
is an armor bat braided onto the outermost of the insulating layers
and is made of high temperature resistant copper-nickel alloy wires
such as those known as "INCONEL." Accordingly, the heating wire is
electrically insulated from the web of the track rail by the
insulating material 42 which is tightly confined in a
heat-resistant, pliable sheath that embraces the thermal
conductivity of the cable. It has also been found in the cable so
constructed, the wire 40, the insulating layers 42 and the metal
sheath expand and contract linearly nearly to the same extent in
response to changes in temperature. Consequently, the insulating
material experiences minimal wear due to abrasion between the wire
and metal sheath, and in this way deterioration and burn-out of the
heating cable is prevented.
Each of the heating cables 38 has lengths 46 thereof placed against
the web of a fixed rail 14 and suitably held in place beneath the
lengths by a pliable heat insulating mat generally indicated at 48.
The cable lengths 46 are disposed along regions of the rail between
adjacent rail braces 22 (FIGS. 1 and 2). Portions 51 of the cable
38 are bent upwardly and over the intervening braces. Therefore,
the integrity of each heating cable and heating from it are
maintained along the full reach 20 of the switch. The upbent cable
portions 51 desirably extend through sections 49 of metal tubing,
for instance copper tubing of about 5/8" internal diameter, which
are bent to a form suitable cable housing for straddling the
braces, and which prevent the cable from being displaced so as to
fall between a brace and a rail when trains move over a loosely
supported rail.
The elongate, pliable heat insulating mat, generally indicated at
48, and shown in detail in FIG. 6, is disposed lengthwise against
and along each length 46 of the cable between adjacent braces and
against and along portions 50 and 52 of the rail web adjacent the
cable 38, as can be seen in FIGS. 3 and 4. The heat insulating mat
48 comprises an elongate mass of high temperature resistant ceramic
fiber 54, preferably having a relatively high K factor as
represented by a density of about eight pounds per cubic foot. A
suitable material is known as "KAOWOOL." The mass of ceramic fiber
is confined in a knitted flexible sleeve of high temperature
resistant wire mesh 56, for instance a mesh of "INCONEL 600." This
mesh prevents the fiber from creeping between the cable and the
rail web. The assembled mat measures, for example, approximately 3
inches wide and 1 inch thick.
The heat insulating mat 48 placed over each length of heating cable
38 held against the rail web prevents major heat losses from the
cable by convection or radiation. Accordingly, the heat generated
in the cable is transferred predominantly by conduction directly
into the fixed rail 14.
An elongate, substantially rigid sheet metal casing member 58,
having a generally U-shaped cross-section, is fitted lengthwise
over and encloses the heat insulating mat 48. The casing is, for
example, about 3 inches wide and 3/4 inch deep, so that the mat is
compressed by it against the cable 38 and the web of the rail. The
side walls 60 of the casing member bear along their edges against
the rail web to confine the mat in place, as can be seen in FIGS. 3
and 4. It is preferred that the casing member 58 be made of
aluminum sheeting having, for instance, a thickness of
approximately 0.091 inch.
The heating cable, heat insulating mat and casing member assembly
may be held in firm engagement with the web of the fixed rail as
shown in FIG. 4, by a suitable number of spring clips 64. Each of
these clips has a first section 66 that embraces the base flange 34
of the rail and a second section 68 that bears resiliently against
the front wall 62 of the casing member. The casing member is
vertically confined between the rail head 32 and base flange 34. As
shown in FIG. 3, the cable 38 may be supported by hooks 53 which
are bolted to the inside of front wall 62 of the casing member 58
at intervals therealong. Assembly of the cable, mat, and casing
member is then done prior to securing the assembly to the rail
web.
As shown schematically in FIG. 8, each of the heating cables 38 is
connected to a source 70 of current.[.at high wattage.].. This
source should be capable of supplying the current .[.to.].
.Iadd.through .Iaddend.the cable at a watt density in the range
e.g. of approximately 32 Watts.Iadd., .Iaddend.per square inch of
resistance wire in the cable to be heated. In the case of
resistance wire of 0.081" diameter, the current supply at a watt
density of 32 Watts per square inch amounts to about 96 Watts per
linear foot of the cable.
In accordance with the invention, heat generated by the heating
cable acts to heat the rail to a temperature that effectively
prevents snow and ice from accumulating on the rail. In typical
operation of the apparatus, a resistance wire of 0.081" diameter in
the cable becomes heated to a temperature of, for instance,
1400.degree. F. at an ambient temperature of about 69.degree. F.,
and of about 1250.degree. F. at an ambient temperature of 0.degree.
F. The rail to which the cable is fixed becomes heated .[., for
instance, to a temperature of 0.degree. F..].. Further, the heat
which sinks into the directly heated rail has been found to pass
sufficiently, predominantly by conduction to the switch plates,
though also by radiation, to the adjacent switch rail so that
.[.objectional.]. .Iadd.objectionable .Iaddend.accumulation of ice
and snow is prevented both along the switch rail and between it and
the fixed rail.
The heating cable is made to serve effectively also at the location
of the tie rod and associated mechanism by an arrangement of the
cable, as illustrated in FIGS. 1, 2 and 8. Specifically, the space
between adjacent ties 16 which underlies a tie rod 27
interconnecting the switch rails 24, is provided with a trough 80.
The cable 38 extends in series from the outer side of one fixed
rail 14a, along one side of the trough, to the opposite fixed rail
14b, back along the other side of the trough to the same outer side
of one fixed rail 14a. This double length of cable extending in the
trough below each tie rod heats the rod by radiation and convection
to prevent accumulation of ice and snow thereon. Therefore, the
apparatus of the invention is effective to prevent the switch from
being obstructed by ice and snow, and ensures reliable
operation.
The power supply may be obtained from a conventional railroad
junction box 70 located at the rail switch and may be selectively
actuated by a controller 72 which receives signals from a
thermocouple 74. The controller may, for example, be set to turn
the power supply and hence the apparatus on at 35.degree. F. and
off at 36.degree. F. to ensure that ice and snow does not
accumulate on the switch.
FIG. 7 illustrates a connector 81 assembly suitable for
electrically connecting the heating cable 38 to a normal insulated
electrical conductor through which current is supplied to or from
the heating cable and at other points in the apparatus circuit as
shown in FIG. 8. The connector acts as a heat barrier joining the
hot resistance wire with the cold non-resisting conductor. The
connector comprises a copper sleeve 82 which is crimped at one end
84 onto the heating .[.strang.]. .Iadd.strand .Iaddend.40 . At its
opposite end 86 the copper sleeve is crimped to an insulated
conductor 88 connected to the power supply 70. The copper sleeve is
surrounded by a ceramic heat resistant sleeve 90 which is housed in
a larger diameter tube 92. The tube is crimped at one end 94
directly about the metal sheath 44 of the cable 38. At the opposite
end 96, the tube is crimped about a silicon sleeve that encircles
the insulation 98 of the power supply line. Accordingly, the
connector forms a unitary waterproof structure in co-operation with
the insulated conductor and the heating element. As noted, and as
illustrated in FIG. 8, this connector construction may be used at a
first location L.sub.1, where the apparatus is connected to a
non-resisting lead 100 from the power source 70, at second and
third locations L.sub.2 and L.sub.3 connecting an interconnecting
line 102 between the heating cables 38 attached to opposing fixed
.[.rail.]. .Iadd.rails .Iaddend.14a and 14b, and at a fourth
location L.sub.4 connecting the cable attached to rail 14b to a
lead 104 completing the circuit to the power source 70.
It will be appreciated from the above description that the
apparatus of the present invention provides a simple yet effective
means for heating railroad rails and particularly for heating and
keeping railroad rail switches clear of snow and ice. Moreover,
sufficient heat is generated to clear switch rails of accumulated
snow and ice in reasonable periods of time.
Accordingly, although specific embodiments of the present invention
have been described above in detail, it is to be understood that
this is for purposes of illustration. Modifications may be made to
the described railroad track heating apparatus in order to adapt it
to particular applications.
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