US3243573A

US3243573A - Railroad heater

Info

Publication number: US3243573A
Application number: US463707A
Authority: US
Inventors: Walter G Weisse; Philip F Famiglietti; Peter J Vozzola
Original assignee: United Aircraft Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1965-06-14
Filing date: 1965-06-14
Publication date: 1966-03-29
Anticipated expiration: 1983-03-29

Description

United gStates Patent O" 3,243,573 RAILRQAD HEATER I Walter G. Weisse, East Longmeadow, Mass., and Philip F. Famiglietti and Peter` J. Vozzola, Windsor Locks, Conn., assignors to United AircraftV Corporation, East Hartford, Conn., a corporation of Delaware Filed June 14, 1965, Ser. No. 463,707 3 Claims. (Cl. 219-213) `This invention relates to heaters and more particularly to electrical heaters mounted on the switching tracks of a railroad.

As is generally well known in the art, maintaining railroad switches free 'from snow and ice resulting from inclement weather has been an acute problem confronting the railroad industry for manyfyears. Methods for insuring the operability of the switches during freezing weather have been done principally by employing such devices as (l) oil pots or natural gas dire schemes, (Z) attaching electric heaters (generally of the Cal-rod type) by clamping the Cal-rod directly -to the transverse wall of the switching rail, and-(3) by manually chipping the ice away I.from the switches. All of these methods are not `only cumbersome but present, in varying degrees, installation, maintenance, operation and economy problems. Utilizing an electric heater of the Cal-rod type not only is ineflicient in this application because of poor heat transfer characteristics but also tends to lweaken the rail itself by virtue of its associated attachment mechanism.

Another serious problem attendant to railroad switch heaters is that the heating element in certain installations has to be mounted to the track under adverse weather conditions. That is to say, in some instances the heater must be applied to existing operational switches that are exposed to the open environment in whatever temperature extremes that environment may impose (particularly cold weather). Thus, it was desirable to provide a heater which` could be installed under ambient temperature conditions of as -low as -40 F., while still maintaining the` Y switch operational. Y

Under such conditions, itis important that the heater be capable of providing sufficient heat into the rail to raise the rail temperature from ambient temperature to at least 50 F., for operational effectiveness.

At the other extreme (high ambienttemperature) it is necessary that the materials utilized in the basic heater, bonding agent, and surface treatment agents be capable of withstanding relatively high operating temperatures (say.400 F.) d-uring those heater on periods when the ambient temperatures have risen above freezing conditions Ibut the heater has not been turned olf.

A system was found to satisfy these conditions by providing a conductive heating element limbedded in a plastic material and bondingrthe material directly to the switching portion of the rail. y

It is therefore an object of this invention to provide a railroad switch heater comprised of a heating element imbedded in a substantially rigid reinforced plastic material.

A still further object of this invention is to provide a railroad switch heater that is intimately bonded by adhesivesrto the track portion of the switch track.

Other features and advantages will be apparentfrom the specification and claims and from the accompanying drawings which illustrate an embodimentV of the invenillus- 3,243,573 Patented Mar. 29, 1966 icc 16. The heater is firmly bonded to the transverse wallk 16 in a manner to be Ifully described below.

The terminal lead wires are connected in any suitable manner to an electrical supply source lgenerally indicated by numeral 18. A contact switch 20 serves to open and close the circuit .when the heater is placed in the operative and inoperative condition.'

According to this invention, the heating element is suitafbly imbedded between woven .glass fabric reinforced plastic forming the heater bod-y 22. Preferably two layers of the woven glass fabric are placed under the heater element 23 and one layer is placed over the Iheater elementi 23. The woven glass fabric is then impregnated with suitable resins in any well-known manner to form a substantially rigid body. The method of molding a heater into the reinforced fabric may be `accomplished by any of the more common systems presently available in industry such as press molding, vacuum bag/wet lay-up, hand layJup, injection molding or vacuum injection molding. The particular systems that have been used in dervelopment of this invention are press molding and injection molding. In each case, the laminating resins employed were polyester fbase materials suitable for continuous operation at high temperatures.

IGlass fiber cloth in tape form (Style 181 or 2111) was used as the reinforcement agent. Epoxy and silicone base resins can be used in the application, as well as polyester resins.

Fixed to one end of the heater body z2 by any suitable means is the housing 24 lwhich contains therein the electrical connection terminal lug 30, which carries power from the source 1'8 through cable 40 to the heater element through the electrical terminal conductor 42 (via rivet attachment 26), to the heating element 23.

Disposed between terminals 28 and 32 is thermostat 34. Thermostat 34 may be of any well-known` type and for the purposes of illustration is shown to be comprised of a bimetal element 36 connected to terminal 32 andv contact member 38 connected to terminal 28, and serves Y to open Vthe circuit whenever the temperature of the heater reaches a predetermined (high) value for a sustained length of time and to reestablish circuit continuity complement the radius of the transverse wall 16. v It is essential that contiguous and intimate contact be made at this point to ensure -good and uniform heat conductance to the rail from the heater.

Woven graphite or carbon fabric commercially available from National Carbon Com-pany, Division Union Carbide, New York, N.Y. or Basic Carbon Company, Sanborn, N Y. may be used as the heater element 23, as well as wire element copper alloy resistance type Wire.

The method of atta-ching the heater to the rail will be described hereinbelow. While this method is the preferred one which has been tested and proven to be suitable for keeping the track free from ice and snow, it is to be understood that any suitable bonding techniques that give like characteristics are considered to be within the scope of this invention.

RAIL AND HEATER SURFACE PREPARATION (1) The inner web surface area of the rail to which the heater is to be bonded shall be sandblast-cleaned to remove alltraces of scale and surface contamination. It. may valso be advantageous to sandblast the outer web surface area in order that insulation foam can be bonded tothat' surface for the purpose of heat containment in the` rail. Degreasing by means of` a solvent and wiping with a dry lint-free cloth is desirable following the sandblasting and just prior to the bonding.

, (2) Once the surface is sandblasted, the bonding operation must be performed within two (2) hours unless a protective coating is applied to the rail. The coating is required because of the high corrosion sus- -ceptibility'of the rail metal alloy. A suitable coating is S-142F from B. F. Goodrich.

(3)'Prior to application of the actual heater, the coati'ng (if one exists) should be removed by peeling same 4free of the rail. At this time, use of a primer is recommended. The primer will :provide a bondable surface and will not require removal or any subsequent preparation except light sanding and cleaning. A suitable primer, commerciallyl available, is Silastic RTV 1'201 Primerfrom Dow Corning.

(4) Wipe the heater surface with a lint-free cloth and methyl-ethylketone (MEK) prior tothe adhesive application.

BONDING OF HEATER (1) Apply a uniform film of thermosetting adhesive, spread or brushed, 15-20l mils thick to the heater surface. A suitable adhesive is Silastic 732 which is thermosetting commercially available from Dow Corning.

Uniformity is essential to prevent the creation of voids starting at one end, Iand clamp each succeedingnclamp in sequence to avoid air entrapment.

(4)V Apply nominal positive pressure with the clamps to maintain contact and alignment of the assembly. Apply nal pressure when all clampsrare in place. A uniformlbead of adhesive should appear along the entire heater edge. y

(5) Repeat steps (1) through (4) for subsequent heaters.

(6) Attach leads between the heaters.

(7) `Attach the power lead from a suitable source to the extreme end of the rst heater and attach the ground lead to, the extreme end of the last heater.

(8) Apply lan insulating blanket over the entire assembly., v

(9) Cure the heater for 30 minutes at a bondline temperature ofapproximately 200 F. by energizing the heater,

(10) Check the bead of adhesive around the heater. The bead will'harden when the initial cure is obtained. Y

(11)Remove the clamps and allow the heater to be activated for an additional one-half hour.

It is apparent from the foregoing that the heater must contain certain characteristics which are critical to the method of preventing snow and/or ice from accreting on the rail yet will not interfere with the operation` of rail switching. The material between web 16 and heater element 23 Imust exhibit a dielectric strength between 1/2 and 20 megohms. The watt density of the heater must be between 8 to 18 watts per square inch. Additionally, the adhesive and material surrounding the heating element must be corrosion free, weather resistant and erosion resistant.

It should be understood that the invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made without departing from the spirit or scope of this novel concept as delined by the following claims:

We claim:

1. An electrical heater for a railroad switch track which track has a lrail head, a support ilange member and a vertical transverse web joining the rail head to the support flange member, said heater i'licluding a rigid elongated relatively thin body portion formed from a plurality of flat layers of glass fabric reinforced plastic consisting of at least one resin being selected from the group consisting of silicone, epoxy and polyester, an electrical resistive element having a watt density in the range of 8 to 18 watts per square inch mounted between said layers of said glass fabric reinforced plastic and spaced from said vertical transverse web, thermoset-ting adhesive means bonding` r said glass fabric reinforced plastic to said vertical transverse web, said adhesive means and said glass fabric reinforced plastic being characterized as being weather, cor-y rosion and erosion resistant, an electrical power sourceV and means for connecting said electrical resistive element to said electrical power source.

2. An electrical heater as claimed in claim 1 wherein said `thermosetting adhesive means is formed from a silicone base.

45 3. An electrical heater asclaimed in claim 1 wherein said glass fabric reinforced .plastic adjacent said vertical transverse web has a dielectric strength falling in the range of 1/2 to 20 megohms.r

References Cited by the Examiner RICHARD M. WCODyPrmary Examiner. IC. L.ALBRlTTON, Assistant Examiner.

Claims

1. AN ELECTRICAL HEATER FOR A RAILROAD SWITCH TRACK WHICH TRACK HAS A RAIL HEAD, A SUPPORT FLANGE MEMBER AND A VERTICAL TRANSVERSE WEB JOINING THE RAIL HEAD TO THE SUPPORT FLANGE MEMBER, SAID HEATER INCLUDING A RIGID ELONGATED RELATIVELY THIN BODY PORTION FORMED FROM A PLURALITY OF FLAT LAYERS OF GLASS FABRIC REINFORCED PLASTIC CONSISTING OF AT LEAST ONE RESIN BEING SELECTED FROM THE GROUP CONSISTING OF SILICONE, EPOXY AND POLYESTER, AN ELECTRICAL RESISTIVE ELEMENT HAVING A WATT DENSITY IN THE RANGE OF 8 TO 18 WATTS PER SQUARE INCH MOUNTED BETWEEN SAID LAYERS OF SAID GLASS FABRIC REINFORCED PLASTIC AND SPACED FROM SAID VERTICAL TRANSVERSE WEB, THERMOSETTING ADHESIVE MEANS BONDING SAID GLASS FABRIC REINFORCING PLAST TO SAID VERTICAL TRANSVERSE WEB, SAID ADHESIVE MEANS AND SAID GLASS FABRIC REINFORCED PLASTIC BEING CHARACTERIZED AS BEING WEATHER, CORROSION AND EROSION RESISTANT, AN ELECTRICAL POWER SOURCE AND MEANS FOR CONNECTING SAID ELECTRICAL RESISTIVE ELEMENT TO SAID ELECTRICAL POWER SOURCE.