Railroad switch heater

A railroad switch heating system comprises lengths of a pliable insulated electrical resistance heating cable disposed against and along the outer sides of the fixed rails of the switch, with portions of these cable lengths between rail braces overlaid by thermally insulating mats and against the adjacent rail web surfaces, and supplemental heating to prevent ice formation in the crib space of, and excessive heat losses through, a rod interconnecting the displaceable rails near the switch points is provided by a crib heating unit having a sinuously bent length of the cable arranged over a pan-like support of sheet material that fits between and along the ties bordering the crib space beneath the rod therein. The pan-like support becomes heated by conduction and heats substantially the entire crib space by radiation and convection. Where the switch points move on a gauge plate extending between them on a track tie, the fixed rail heating is further supplemented by heating units that include rigid plate members which straddle and hold sinuously bent lengths of the cable against areas of the gauge plate near the switch points, with heat insulation. Each cable length has the ends of its heating wire fitted with connectors joining it with insulated conductors in a series heating circuit to be activated when weather conditions might cause freezing at the switch. Lengths of bendable metal tubing enclosing the cable lengths and special water-tight connectors render the heating system water-tight, thus enhancing its safety and reliability.

This invention relates to apparatus for heating a railroad switch so as to 
prevent obstruction of the switch operation by ice or snow in cold weather 
conditions. The invention relates more particularly to apparatus for 
heating not only the fixed rails at a switch but also structures extending 
between the moveable switch rails, such as one or more tie or throw rods 
and/or a track gauge plate, where needed to supplement the heat imparted 
to such structures by conduction from the heated fixed rails. 
In climatic regions which frequently experience temperatures below 
freezing, malfunction of railroad track switches is often a problem. This 
difficulty is compounded by frequent precipitation in the form of snow or 
freexing rain. Temperatures below freezing and accumulations of snow or 
ice result in malfunction of railroad switches for several reasons. Snow 
accumulated between a fixed rail and an adjacent movable rail of a switch 
can pack and prevent proper engagement of the two rails. Ice formed about 
or on the point of a movable rail or between it and a fixed rail may 
prevent proper engagement or separation of the two rails when required for 
switching a train or railroad car from one track to another. 
The crib spaces between adjacent ties of a railroad switch, which 
accommodate the rod or rods, such as one or more tie rods and/or a throw 
rod, interconnecting the movable rails are also susceptable to heat losses 
and to accumulations of snow or ice that can interfere with the proper 
operation of the switch. Further, even when the fixed rails in the region 
of a switch are heated suitably for keeping them clear of ice and snow, 
under extreme weather conditions a gauge plate joining the fixed rails on 
a track tie at the location of the switch rail points can become a source 
of switch malfunction by dissipating so much heat that ice will form on 
the gauge plate and obstruct or prevent displacement of the switch points. 
Malfunction of the switch of course can cause a train or cars moving over 
it to derail, with severe hazards of property damage and personal injury. 
The heating of a railroad rail switch to prevent failure or unreliability 
of the switch operation under cold weather conditions involves a variety 
of problems and needs. The heating apparatus to be employed must serve 
reliably to keep the switch clear of ice and snow, with safety and 
efficiency in its operation, economy in the production and installation of 
its component parts, and assurance that failures of operation due to 
burn-out or other cause will not occur over long periods of service. It is 
also important that the apparatus be susceptible to safe installation by 
railroad workmen, to prompt repair at the switch location in the event of 
damage by accident or otherwise, and to fast removal and replacement 
whenever needed to enable repair or replacement of the rails, ties, or 
other structures at the switch. 
These problems and needs in large part have been met satisfactorily by the 
railroad switch heater disclosed in applicant's above-mentioned U.S. Pat. 
No. 4,195,805. The apparatus disclosed therein, however, left some needs 
continuing in respect of the crib regions of switch rail connecting rods, 
and also, for some installations, in respect of the above-noted problem of 
ice formation on a track gauge plate. When lengths of heating cable are 
extended through crib spaces as disclosed in said patent, conditions can 
occur under which an accumulation of ice or snow immediately adjacent the 
heating cable will be melted without melting through the top of the 
accumulation, thus leaving about the heating cable a tunnel or "igloo" of 
ice or snow within which air insulates the cable so that the heat from it 
will not reach the tie or throw rod. 
The principal object of the present invention is to provide a new and 
improved apparatus or system for heating components of a railroad switch 
in a reliable, safe, efficient and economical manner. 
Another object of the invention is to provide for a heated railroad switch 
an apparatus by which the crib space of each tie or throw rod 
interconnecting the displaceable end portions of switch rails will be 
heated so that heat losses through the rod are compensated and the rod and 
the crib space are kept clear of ice and snow. 
A further object of the invention is to provide for a heated railroad 
switch an apparatus by which the hazard of a switch rail point becoming 
iced or obstructred at the location of a gauge plate can be overcome 
reliably. 
The heating system or apparatus of the present invention is applicable 
safely, efficiently, and reliably for preventing malfunctions of railroad 
switches of any of the various types and sizes existing in railroad 
operations. A railroad switch of any type or size typically includes fixed 
rails engaged by braces and fastened to track ties, switch rails having 
end portions terminating in points that are displaceable laterally 
relative to the fixed rails, and at least one rod interconnecting and 
displaceable with these rail end portions, with each rod extending along a 
crib space between adjacent track ties. 
According to the present invention, use is made of lengths of an electrical 
heating cable that comprises an electrical resistance heating wire encased 
in high temperature resistant electrically insulating material confined 
inside a thermally conductive, pliable metal sheath. The heating wire of 
each length of this cable is provided on each of its ends with means for 
connecting it in a circuit containing the wires of the other cable lengths 
of the system and a source of current for heating the several wires to 
high temperature. 
A length of such heating cable is disposed against and along the outer side 
of each fixed rail of the switch in heat conducting relation thereto 
through the region of the displaceable rail end portions, and elongate 
mats of high temperature resistant thermal insulation are confined, as by 
channel members formed of extruded or sheet metal, against the portions of 
these cable lengths that are not engaged with rail braces and against the 
rail surfaces adjacent to such cable portions, so as to prevent heat 
losses by convection and radiation. 
The heating of the fixed rails by conduction from the cable lengths 
disposed against them results in more or less effective conduction of heat 
through gauge or switch plates to the switch points and to structures such 
as one or more tie rods or a throw rod interconnecting the displaceable 
rail end portions. This resultant heating is supplemented according to the 
invention by a crib heating unit fitting into each crib space beneath and 
along the rod therein, each of which crib units comprises a unitary 
elongate, substantially flat pan-like support of thermally conductive, 
heat and weather resistant sheet material, such as stainless steel or 
aluminum sheeting, which is dimension to fit between and along the ties 
bordering the crib space, with a sinuously bent length of the electrical 
heating cable arranged over and held to a surface of the pan-like support 
so as to heat the support substantially uniformly by conduction and thus 
heat substantially the entire region of the crib space by convection and 
radiation. 
According to a further feature of the invention as it is applied to a 
switch having the fixed rails positioned by a gauge plate on which the 
switch rail points are slidable to and from the fixed rails, the gauge 
plate is provided with a supplemental heating unit fitted over a surface 
of this plate adjacent to each of the switch points. This heating unit 
comprises a rigid plate member having a substantially flat base wall 
overlying the gauge plate surface and having depending side walls fastened 
to opposite sides of the track tie under the gauge plate, with a layer of 
heat insulating material fixed beneath the base wall, and another 
sinuously bent length of the heating cable is arranged on and held to the 
insulating layer and is held by the plate member directly against the 
gauge plate surface for heat conduction into the gauge plate. Each end of 
the heating wire of this other cable length protrudes from beneath the 
base wall of the plate member into means for connecting the wire in a 
circuit as mentioned above. 
According to a further feature of the invention, each heating cable length 
of the switch heating system is enclosed inside a substantially 
coextensive length of water-impervious, bendable tubing, so that the 
switch heating system can be kept substantially waterproof. 
By still another feature of the invention, the means for connecting each 
end of the heating wire of each cable length in the heating circuit is 
provided in the form of a special substantially water-tight connector 
joining detachably an insulated electrical conductor forming part of a 
current supply circuit with the heating wire end and an end of a tubing 
length enclosing the cable length. The connector comprises a 
heat-absorbing electrically and thermally conductive tubular core member 
receiving and clamped onto the heating wire end and an end of the cold 
wire of the insulated conductor. This core member is enclosed in 
electrically insulating material confined inside a sleeve having a 
coupling ring fixed onto each of its ends. A threaded cap ring is fixed 
onto an end of the tubing length and joined with one of the coupling 
rings, as by compressing a pliable ring fitted inside the cap ring onto 
the tubing while being screwed onto the coupling ring. A protective 
flexible shield fitting over the insulated conductor carries a collar that 
is joined with and compresses an elastic gasket against the other coupling 
ring, as by being screwed onto it. Thus, a water-tight joint is provided 
that prevents the cold wire from becoming overheated and also excludes 
water so as to prevent current from leaking from the hot wire to the metal 
sheath of the cable; yet at any of the connectors, the coupling rings can 
be disconnected so as to enable movement of the sleeve and the insulating 
material away from the conductive core member clamped onto the wire ends, 
whereupon either or both of the wire ends can be released readily, or 
re-engaged readily, for removal or replacement of a component of the 
switch heating system.

A typical railroad switch to be equipped with heating apparatus according 
to the present invention, as illustrated in FIG. 1 of the drawings, 
comprises two fixed rails 1 and 2, called stock rails, with switch rails 3 
and 4 extending between them to displaceable end portions 3A and 4A, 
respectively, which terminate in switch points 3B and 4B. The fixed rails 
are fastened to track ties 8 and in the region of the switch are supported 
at intervals along their outer sides by track braces 9 fixed to ties. The 
switch points 3B and 4B are joined together by at least one rod, such as 
rod 6, that extends along a crib space, such as the space 10 between ties 
8A and 8B, and forms a part of or is connected with a switch throw rod so 
as to be displaceable by a switch operating mechanism or "machine" (not 
shown) located to one side of the track. 
When the switch mechanism holds switch point 3B engaged against fixed rail 
1, switch point 4B is spaced away from fixed rail 2 and a track for train 
or car transport is formed by rails 2 and 3. When switch point 4B is held 
engaged with rail 2, point 3B is spaced away from fixed rail 1 and the 
transport track is formed by rails 1 and 4. Depending upon the length of 
the displaceable rail end portions 3A and 4A, which in turn differs for 
different duties and sizes of railroad switch installations, these 
displaceable rail portions are connected together not only by at least one 
switching rod such as rod 6 but also by one or several additional tie rods 
such as the one shown at 12 in FIG. 1. Each such tie rod extends in and 
along a crib space between two track ties, such for instance as the space 
14 for rod 12 between the ties 8B and 8C. In some railroad switches, such 
as switches of narrow gauge tracks, mine car tracks, or the like, a single 
tie rod in a single crib space adjacent to the switch points suffices for 
both bracing and switching the displaceable end portions of the switch 
rails. 
At the location of the switch points 3B and 4B a track tie such as the tie 
8B often is provided with a gauge plate 16 that is fixed onto the tie and 
extends over it under and between the rails. The gauge plate is formed 
with recesses 17 in which the base flanges of the fixed rails are seated 
at the required distance apart, and it provides surface areas 18 which 
support the switch points for sliding movement to and from their 
respective track forming positions against the inner sides of the fixed 
rails. The gauge plate typically is composed of two heavy steel plate 
sections having connecting portions 19 bolted together near the center of 
the track, with electrical insulation sandwiched between these plate 
portions. At locations away from the switch points, relatively short 
switch plates 20 usually are fixed onto the ties, each beneath a fixed 
rail and the adjacent displaceable rail end portion, to keep these rails 
properly aligned. 
As shown in FIGS. 1, 2, 3 and 4, according to the present invention, the 
illustrative railroad switch is provided with a heating apparatus which 
comprises lengths 22 and 23 of a high temperature electrical heating cable 
30 disposed against and along the outer sides of the fixed rails 1 and 2 
in heat conducting relation thereto throughout the region of the 
displaceable rail end portions 3A and 4A, and also, for each crib space 
occupied by a rod interconnecting the displaceable rail end portions near 
the switch points 3B and 4B, such as the crib space 10 of rod 6 and the 
crib space 14 of rod 12, a sinuously bent length 25 or 25A of the heating 
cable forms part of a sheet-like radiant heating unit 27 or 27A. Further, 
for a switch as illustrated that has the fixed rails positioned by a gauge 
plate 16 on which the switch points are slidable to and from their working 
positions, supplementing heating is provided by gauge plate heating units 
28 and 28A each of which comprises another sinuously bent length 29 or 29A 
of the heating cable held as hereinafter described in heat conducting 
relation to the gauge plate surface at a location adjacent to a switch 
rail. 
The cable 30 of each of the heating cable lengths advantageously is of the 
kind disclosed in U.S. Pat. No. 3,774,013. As shown in FIG. 5, the cable 
comprises a core wire 32 that is a single solid strand of high temperature 
electrical resistance heating wire, with a sheath 34 of highly heat 
resistant electrically insulating material braided on the wire and 
confined inside a thermally conductive shielding layer 36, or outer 
sheath, of heat-resistant wire braided upon the insulating sheath. The 
core wire 32, for instance, is a No. 12 gauge wire of a nickel-chromium 
alloy, such as the alloy of 80% nickel and 20% chromium known as Nichrome, 
having a diameter of about 0.081 inch. The electrically insulating sheath 
34 in a preferred embodiment is formed of several layers of a ceramic 
fiber, typically three, braided one over another onto the wire core 32. A 
commercially available ceramic fiber made of an alumina-boria-silica 
composition and identified as "3M Fiber AB-312," if suitably pre-treated 
to burn off a sizing that may carbonize at high temperature, is 
advantageous for making the insulating sheath. This material when so 
pre-treated exhibits excellent dielectric properties and retains needed 
flexibility after long periods of heating to temperatures in excess of 
2,000.degree. F., which exceed the temperature reached by the heating wire 
32 in use in the switch heating apparatus. Alternatively, the insulating 
material may be composed of other ceramic substances that will resist 
temperatures of at least about 2,000.degree. F., over long periods of 
service, such for instance as an amorphorous silica fiber known as 
"REFISIL." The shielding layer 36 confining the insulating material 34 is 
a pliable sheath composed of a metal highly resistant to heat, abrasion 
and oxidation, and preferably is formed by braiding wires of a 
copper-nickel alloy such as "INCONEL" into a sleeve fitting tightly on the 
insulating sheath. 
It has been found that the components of the heating cable 30 expand and 
contract linearly to nearly the same extent in response to changes in 
temperature, so that little or no wear of the insulating material occurs 
in the use of the cable as a result of abrasion between the wire or the 
metal sheath and the insulating material. Consequently, the cable is 
highly resistant to deterioration and burn-out in the service required of 
it according to the present invention. 
As indicated further in FIG. 5, each length of the heating cable 30 is 
enclosed advantageously inside a length of water-impervious, bendable 
metal tubing 38, such for instance as extruded aluminum tubing having an 
inside diameter of about 0.5 inch and a wall thickness of about 0.05 inch. 
Each tubing length 38 is substantially coextensive with the cable length 
enclosed in it. By excluding water from access to the heating cable 30 the 
tubing 38 prevents current losses, short circuit or burn-out from being 
caused by water or other liquid that otherwise might be accessible to the 
cable at the switch location. The risk of water causing failure of the 
switch heating system is avoided further by the manner of connection 
provided for joining the wire 32 and the tubing 38 at each end of each 
heating cable length with an insulated electrical conductor of a current 
supply circuit, as described more particularly hereinafter with reference 
to FIGS. 7A and 7B of the drawings. 
As shown in FIGS. 1 and 2, the tubing-enclosed cable lengths 22 and 23 are 
disposed directly against and along the outer sides of the webs of fixed 
rails 1 and 2 at locations between the rail braces 9, and at the braces 
are bent over and against them so as to heat the rails by conduction 
through the braces. Portions of the cable lengths engaged over the braces 
preferably are enclosed in spiral spring guards 39 which protect the cable 
and tubing on the cable from being abraded by relative motions of the 
rails and braces. The portions of each cable length engaged directly 
against the rail web, i.e., those not engaged away from the web by rail 
braces, are embedded under elongate mats 40 of high temperature resistant 
thermal insulation, such as ceramic fiber insulation. The mats 40 are 
confined against these cable portions and against the rail web surfaces 
adjacent to them, as by being confined tightly inside channel members 42 
clamped against the rail web, so that the mats will prevent heat losses 
that otherwise would occur by convection and radition. The insulating mats 
40 may be formed advantageously of bonded insulating ceramic fiber, or 
fiber board, such for example as the commercial heat insulating material 
known as "K-FAX," which may be grooved longitudinally in one side to 
receive the cable. Another suitable form of insulating mats is made of 
loose ceramic fiber insulation, for instance the material known as KAOWOOL 
at a density of about eight pounds per cubic foot, confined in a flexible 
sleeve of high temperature resistant wire mesh, for example a knitted 
sleeve of wire known as "INCONEL 600." The wire mesh sleeve keeps the 
insulation pliable for fitting it over the cable up to the bordering rail 
web surfaces while confining the loose fiber so that it will not creep 
between the rail web and the heating cable or a tubing length on the 
cable. 
The channel members 42 confining the insulating mats 40 may be extruded or 
otherwise formed elongate sections of a suitable substantially rigid sheet 
material, such as an aluminium extrusion, having a generally U-shaped 
cross-section and a wall thickness, for instance, of about 0.09 inch. The 
channel members 42 typically are made with an inside width of about 3 
inches and an inside depth of about 0.75 inch, thus confining tightly 
against the cable and the rail surface an insulating mat 40 that in place 
has substantially corresponding outside dimensions. The channel members 42 
can be easily fitted over the mats and the cable portions encompassed by 
the mats and then clamped in place at intervals, for instance of 
approximately one to two feet, by suitable displaceable holding devices 
such as the rail clips 46 shown in FIGS. 2 and 4. Each of the clips 46 
comprises a flat bar of spring steel shaped to form an anchoring portion 
47 and an angled upright resilient leg 48. Portion 47 is snapped onto the 
base flange of the rail, causing leg 48 to bear firmly against the base 
wall 44 of the channel member 42 so as to hold the edges 45 and 45a of the 
channel member tightly against the rail web. 
As indicated in FIG. 1, each of the heating cable lengths 22 and 23 has its 
core wire 32 connected at each end through a connector 51 with an 
insulated cold conductor 52 in a circuit 50 for supplying heating current 
to the cable lengths. The source of the heating current should be capable 
of supplying it through the cable lengths at a watt density in the range 
of about 20 to 60 Watts per square inch of heating wire surface. In the 
case of resistance wire of 0.081" diameter in a system employing about 66 
to 74 feet of the cable, as for a railroad switch about 161/2 feet long 
from the heels to the points of the switch rails, a 220 V A.C. power 
source will supply current through the wire at a density, for example, of 
about 32 Watts per square inch, or about 93 Watts per linear foot of the 
heating cable. Such a switch heating system typically operates with an 
energy consumption of the order of about 6 to 7 kilowatts per hour. For a 
system containing about 33 to 37 feet of the cable, a 110 V A.C. source 
will supply about 93 Watts per foot. The current typically will generate 
enough heat to bring the wires in the cable lengths 22 and 23 to a 
temperature, for instance, of about 1,250.degree. F. at an ambient 
temperature of 0.degree. F. The fixed rails are thus heated, for instance, 
to a temperature about 90.degree. to 100.degree. F. above the ambient. 
Further, the heat that sinks directly into the fixed rails will pass 
sufficiently to the adjacent end portions 3A and 4A of the switch rails, 
predominantly by conduction through the switch plates and/or portions of a 
gauge plate when present, though also to some extent by radiation and 
convection, so that accumulation of ice or snow is prevented not only 
along the fixed rails but also, ordinarily, along the displaceable 
portions of the switch rails and between them and the fixed rails. 
The apparatus is made to serve effectively as well in the crib regions of 
rods interconnecting the displaceable rail end portions 3A and 4A near the 
switch points, such as the crib space 10 of throw rod 6 and the crib space 
14 of tie rod 12, by the crib heating units 27 and 27A, one of which is 
illustrated bottom-side-up in FIG. 8. 
Each crib heating unit 27 or 27A comprises essentially a unitary elongate, 
substantially flat pan-like support 60 of thermally conductive, heat and 
weather resistant sheet material, such as, for instance, a piece of 
stainless steel sheeting about 0.015 inch thick, about 10 inches wide and 
about 5 feet long, with a sinuously bent length 25 or 25A of the heating 
cable arranged over and held to a surface of the support 60 so as to heat 
the support substantially uniformly by conduction to a well elevated 
temperature, and a connector 51 fixed to each end of the cable length 
connects it with the "cold" wire of an insulated conductor 52 in the 
current supply circuit 50. The cable length is held to a surface of the 
support 60, preferably to its underside as shown in FIG. 8, by any 
suitable means such, for instance, as stainless steel bands 62 applied 
over the cable and welded to the support surface at intervals therealong. 
The support 60 with the cable length fixed to it is easily slid into a crib 
space 10 or 14 beneath the rod 6 or 12, between and along the track ties 
bordering the crib space. The thinness and pan-like form of the support 
and the bendability of the cable fixed to it enable the unit to be adapted 
readily to the dimensions and any restrictions of the crib space. The unit 
can be fastened in place advantageously by heat and weather resistant 
straps 64, such as strips of the stainless steel sheeting which are welded 
to the support 60 at spaced intervals therealong and extend from its 
opposite side edges so as to be nailed or screwed onto the bordering ties. 
The pan-like support of the crib heating unit in use distributes the heat 
from the cable length 25 substantially uniformly over the area of the 
support 60 and thence by radiation and convection from its upwardly facing 
surface throughout the crib region of the rod interconnecting the switch 
rails. Any snow or ice reaching its surface is melted. The heat 
distribution from its surface prevents snow and ice from accumulating in 
the crib space, with avoidance of the above mentioned "igloo"effect, and 
keeps heat from being drained excessively from the switch rails through 
the rod in the crib space. 
The crib heating unit 27 as shown in FIG. 8 has the cable length 25 
arranged over the under surface of the support 60 in three substantially 
parallel legs extending along the support and joined to one another by 
bends of the cable near opposite ends of the support, with the ends of the 
cable length disposed at opposite ends of the support and fitted with 
connectors 51 for joining them with conductors forming parts of the 
heating circuit 50 at opposite sides of the switch track. 
FIG. 8A shows another suitable form 70 of the crib heating unit. This unit 
differs from unit 27 principally in that the pan-like support is formed by 
two layers 71 and 72 of substantially flat weather-resistant sheet 
material, such as stainless steel sheeting about 0.015 inch thick, with a 
length 74 of the heating cable 30 arranged in two sinuously bent legs on 
one of the sheets and sandwiched between the two sheets. The lower sheet 
72 is provided with a layer 73 of heat insulating material to restrict 
heat losses downward into the track bed. Strips 75 hold the cable length 
to one of the support sheets. Straps 76 corresponding to the straps 64 of 
FIG. 8 are fastened to ties to hold the unit in place in a crib space. The 
sinuous cable legs are joined by a bend of the cable near one end of the 
support, and at its other end their ends 77 and 78 are fitted with 
connectors 79 for joining them with conductors forming parts of the 
heating circuit at one side of the switch track. The cable length 74 as 
shown in FIG. 8A is enclosed in a length of tubing 38. 
A switch heating system comprising the rail heating cable lengths 22 and 23 
and one or more crib heating units such as units 27 and 27A suffices to 
prevent malfunction of the switch under the winter weather conditions to 
be expected in many climatic regions. In regions that experience extremely 
cold weather, however, conditions may occur under which ice would still 
form so as to obstruct the operation of a switch having a gauge plate, 
such as plate 16, extending between the stock rails at the location of the 
switch rail points. Portions of the gauge plate extending between the 
switch points may dissipate heat so rapidly in extreme weather that ice or 
snow at the switch points may not be melted by the heat from the stock 
rails, or if melted may leave water that will freeze on the switch points 
or between them and the stock rails upon a further drop of the ambient 
temperature. 
This problem is overcome by the supplemental heating action of the gauge 
plate heating units 28 and 28A. As shown in FIGS. 1, 3, 4, 9 and 10, each 
of these units comprises a rigid plate member 80, such as an aluminum 
plate about 0.1 inch thick formed to a saddle shape. The plate member has 
a substantially flat base wall 82 that overlies the surface of the gauge 
plate 16 adjacent to a switch rail point 3B and 4B, with depending side 
walls 83 and 84 that straddle and are fastened to opposite sides of the 
tie 8B supporting the gauge plate. A layer 86 of heat insulating material, 
such for instance as a 1-inch thick layer of K-FAX insulation, is provided 
on the under side of the base wall 82, and a sinuously bent length 29 or 
29A of the heating cable is arranged on the insulating layer, preferably 
in a groove formed in it, so that the base wall 82 holds the cable length 
against the gauge plate surface with the insulating layer overlying the 
cable. The cable length may be fastened in place by metal straps 87, such 
as 0.015" thick by 1" wide stainless steel strapping, fixed about the 
plate member. Each cable length such as 29 or 29A comprises a length of 
the cable 30 enclosed in a coextensive length of tubing 38, with each end 
of the cable and tubing protruding from beneath wall 82 through a notch 85 
in side wall 83 and into a connector 51 joining the end with a conductor 
52 in the switch heating circuit 50. 
Thus, when the switch heating circuit is active the heat generated in the 
cable lengths 29 and 29A passes in major part by conduction directly into 
the gauge plate 16 over its surface areas adjacent to the switch points 3B 
and 4B, and passes through the gauge plate beneath and into the switch 
points so that ice formation obstructing movement of the switch points 
will not occur under even the most severe cold weather conditions. 
As indicated in FIGS. 1 and 11, the respective resistance wires 32 of the 
heating cable lengths 22, 23, 25, 25A, 29 and 29A are connected in series 
in the current supply circuit 50 by connectors 51 at the respective ends 
of these wires. Each connector 51 joins an end of the "hot" wire of a 
cable length with a "cold" wire of an insulated conductor 52, for instance 
a No. 6 gauge direct burial wire, forming part of the circuit. The circuit 
50 includes a power supply line 55 that may extend from a conventional 
railroad junction box 56. The circuit when desired may include a 
controller 58 that receives signals from a thermocouple 59 sensing the 
ambient temperature at the railroad switch location and acts in response 
to these signals to turn on the power supply circuit 50 when the ambient 
temperature falls below a preset limit of, for example, about 35.degree. 
F. and to turn off the power supply when the ambient temperature rises 
above the preset limit. 
The construction of a suitable connector 51 is shown in FIGS. 7A and 7B. 
Each connector 51 comprises a tubular core member 90 of electrically and 
thermally conductive metal, such as brass or copper, which serves as a 
heat sink. A bared end of wire 32 of a length of the heating cable 30 is 
inserted into and fastened in one end of member 90, and a bared end of the 
wire 92 of an insulated conductor 52 is inserted into and fastened in the 
other end of member 90. The core member 90 may be crimped so as to clamp 
the wire ends permanently in place. Preferably, however, member 90 is made 
of brass and is formed with screw-threaded radial bores 93 in which set 
screws 94 are fitted so that the wire ends will be clamped releasably in 
place by the screws, thus enabling quick disconnection and removal, or 
quick connection, of either of the wire ends whenever desired for 
disassembly or assembly of any of the components of the switch heating 
system. 
The tubular core member 90 with the wire ends attached is enclosed in a 
surrounding electrical insulator 96 of heat resistant insulation, such for 
instance as a tube of "Teflon" about 1/16 inch thick, and the insulation 
in turn is confined inside a rigid sleeve 97 which has coupling rings 98 
and 99 fixed onto its ends. The sleeve 97, for instance, is a 61/2 inch 
long piece of aluminum tubing having an inside diameter of about 9/16 
inch, and is externally screw-threaded at each of its ends. Each of the 
coupling rings 98 and 99 is internally threaded so as to screw onto one of 
the sleeve ends, and has an externally threaded shank 98A or 99A for 
connecting it with an internally threaded cap ring 100, or with a screw 
collar 101. The cap ring 100 receives a compressible ring 102 that fits 
onto an end 103 of a tubing length 38 enclosing the length of heating 
cable 30, and it is fastened to the tubing end by compressing the ring 102 
onto it when ring 100 is screwed onto the shank 98A. Collar 101 is coupled 
with the end of a spiral spring shield 104 that fits over and extends 
along a portion of the insulated conductor 52 near the connector 51 so as 
to protect the conductor 52 from injury by limiting access to it and 
limiting the angle to which it can be bent when assembled in the heating 
system. 
An insulating ceramic bead 105 that can be slid through the coupling ring 
98 is fitted over the bared end and up to the insulation 34 of the heating 
wire 32 at one end of core member 90, thus holding the end of cable sheath 
36 away and insulated from member 90. A length of the insulated conductor 
52 inside the sleeve 97 and coupling ring 99 is embedded in a mass 110 of 
a flexible silicone sealing compound to prevent moisture from entering the 
connector yet permit expansion and contraction of the core member 90 and 
the joined wires. An insulating heat resistant elastic bushing 106, made 
e.g. of a material such as Neoprene, and an adjacent washer 107, both of 
which fit inside the collar 101, are fitted over the end of the insulated 
conductor 52 so that the bushing 106 will be pressed and sealed against 
this conductor and against an inner surface of the shank 99A of coupling 
ring 99 when the collar 101 is screwed into engagement with ring 99. 
By virtue of the described construction, each of the connectors 51 in the 
switch heating circuit makes a secure yet readily separable electrical 
connection between adjacent ends of a "hot" wire and a "cold" wire of the 
circuit, and one which accommodates the thermal expansions and 
contractions of the wires and connector parts, while also serving 
effectively as a heat barrier to prevent injurious flow of heat from the 
hot wire to the insulated conductor and, in addition, rendering the 
electrical joint substantially water-tight so that it will not be affected 
by water or other liquid at the switch location. 
Whenever it is desired to remove a heating cable length or a conductor in 
the circuit, each related wire end at a connector 51 can be quickly 
disconnected, for instance, by detaching the coupling rings 98 and 99 and 
the collar 101 of the connector, sliding the collar 101 and spring shield 
104 away from the sleeve 97, sliding the sleeve 97 and the insulation 96 
off the core member 90, and turning set screws 94 to release the wire end 
for removal from the core member. Quick reconnection of a wire end of 
course can be effected by reversal of these steps. 
The switch heating system herein disclosed provides a unique combination of 
ruggedness and effectiveness with low power consumption in use. The stock 
rails are heated directly by conduction, with highly efficient utilization 
of the cable heat. They in turn serve as the principal agency for melting 
ice and snow, and at the region of the switch rail points, where the need 
for elimination of ice and snow is most critical, their heating action is 
reinforced and supplemented by the convective and radiant heating action 
of the crib heating unit or units, and also, where needed, by the 
conductive heating action of the gauge plate heating units. The system 
produces a safe, relatively low temperature in the heated components of 
the switch. The water-tight connectors and the tubing lengths enclosing 
the heating cable lengths assure long trouble-free operation of the 
system. Further, the components of the heating system can be installed 
properly at a railroad switch by railroad workmen, typically requiring 
only about two to four hours for installation, and can be disassembled if 
desired in about a half hour or less.