US2930718A

US2930718A - Method and apparatus for coating an insulated conductor

Info

Publication number: US2930718A
Application number: US638507A
Authority: US
Inventors: Charles W Abbott
Original assignee: Whitney Blake Co
Current assignee: Whitney Blake Co
Priority date: 1957-02-06
Filing date: 1957-02-06
Publication date: 1960-03-29
Anticipated expiration: 1977-03-29

Description

March 29, 1960 c. w. ABBOTT METHOD AND APPARATUS FOR COATING AN INS ULATED CONDUCTOR 6, 1957 3 Sheets-Sheet 1 Filed, Feb.

' INVENTOR (240F155 I74 flzearr TMHHM E N March 29, 1960 w. ABBOTT 2,930,713

METHOD AND APPARATUS FOR comm:- AN INSULATED CONDUCTOR Filed Feb. 6, 1957 5 Sheets-Sheet 2 INVENTO (244,945: 14 )35607'7' March 29; 1960 c, w, ABBOTT 2,930,718

METHOD AND APPARATUS FOR COATING AN INSULATED CONDUCTOR I Filed Feb. 6, 1957 s Sheets-Sheet s 1 .E. T q 4 i j d ai //4 f INVENIIOR (399,915: 1/ 4515077- METHOD AND APPARATUS FOR COATING AN INSULATED CONDUCTOR Charles W. Abbott, Clearwater Beach, Fla., assignor to The Whitney Blake Company, New Haven, Conn, a corporation of Connecticut Application February 6, 1957, Serial No. 638,507

6 Claims. (Cl. 117-218) vThis invention relates to a process of coating and particularly color coating previously formed insulated conductors and the like and to the resulting product, and to apparatus for carrying out various steps of the process and to a system of apparatus and a combination of apparatus elements for carrying out the series of steps comprising the process.

While it has broader application, the process is particularly adapted for coating telephone cords-which are colored to match colored telephone sets and used to interconnect the receiver or receiver-mouthpiece combination with the main body of the telephone set and to intercon- Cords or" nect the set with the circuit connecting means. this type usually comprise three or four conductors, each comprising a conductive core of several small gauge tinsel wires twisted together contained within an outer jacket of neoprene, the periphery of which is not truly. circular. Telephone cord is often made retractile by forming it, or part of it, into a coil of spiral turns of the cord to insure its flexibility and to cause it to retract and be out of the way when not extended by the user. The insulation on the retractile cords is only partly vulcanized at the time the insulation is extruded on the cord, and vulcanization is completed after the coil portion of the cord has been givena set to cause it to retract to a coiled form after being extended.

It is especially contemplated to apply the coating process disclosed herein to insulated conductors which have been previously jacketed with rubber, neoprene or the like.

Coating may be applied for any of a variety of reasons, for example, for increasing the wear resistance of the insulation, or to give it a desired color, or for both reasons.

The term rubber is used herein broadly, to include rubber substitutes, such as neoprene and similar insulating materials.

The term jacketed conductor is used herein broadly to include a single insulated core or a plurality of such insulated cores enclosed in a jacket, and the term insulation is used herein broadly to include a single covering or a plural number of coverings, such for example as occur when a plurality of individually insulated cores are enclosed in a common jacket.

It is well-known that a conductor insulated with rubber and protected with a covering or coating adapted to resist abrasion has certain advantages over a conductor insulated with plastic. Plastic insulation, even when made according to standards approved by the Fire Underwriters Laboratories, is not truly satisfactory, for code wire and common forms of cords because of its cold flow qualities and lack of dependable elasticity. It is particularly unsatisfactory for cords which are to be coiled to make them retractile as their insulation needs to be particularly resilient and resistant to wear. However, plastic which came into use during World War II, due

'to the shortage of rubber, has largely replaced rubber as insulation for code wire and common forms of cords due to thecost ditferential between the single step operation 2,930,718 Patented Mar. 29, 196 0 ice tive colors having permanent, non-staining characteristics,

due largely to the ditficulties of coating cords of non-cir cular cross section. cords it has been, and still is, the practice to coat the insulated conductors by hand-dipping them in what is a time consuming, cumbersome operation. I

It has been suggested, in my Patent No. 2,175,099 to extrude a viscous rubber insulation onto-a conductor, vulcanize the insulation, and extrude a viscous, solvent containing wear resistant coating compound, such as a lacquer comprising cellulose, over the rubber insulation in a continuous operation, using the heat imparted to the conductor by the vulcanizing step to drive off solvents and suitably cure the coating material. This has not proven economically practical for price competition with plastic insulated conductors, because the vulcanizing step,

or a partial vulcanizing step, heats the conductor throughout to a high temperature in the order of 350 to 400 F. and the residual heat is sufficient to render the rubber insulation too hot to receive the coating even if the rubber insulated conductor is run through long troughs of cold water between the vulcanizing and coating steps. The

'core cools more slowly than the insulation and in order by the means employed, thus creating the same situation as when insulating and coating have been attempted in a single continuous operation. f

I have overcome these difficulties by performingrthe coating step on an insulated conductor which is at room temperature, and heating only thesurface of the insulation and not the ,core, using means and coating composi tion both novel in this art. I

The structure of my applicator pots also enables the coating material therein to be well mixed and to maintain even viscosity during a coating operation and prevents it from scaling over. Inorder to obtain agood bond between the insulation jacket and one or more coatings applied thereon in accordance with this invention, it is important to soften the outer surface of the insulation but the insulation covering on these thin conductors is so thin that substantial heating over an extended period, such for example as that ."to 'which the core is subjected during vulcanizing, maysoften the insulation too much and will cause substantial heating of the thinly insulated wires of the conductors and may permanently damage the cord by deformation and stressing of boththe thin insulation and the frail tinsel con- .a common jacket, and telephone cord which asstated I above, is usuallya multicondu'ctor cord, comprising three or four conductors eachcomprising a conductive core of In fact for manufacturing colored several small gauge tinsel wires individually insulated and twisted together with all of the conductors enclosed in a tight fitting insulating jacket, thus forming a non-circular core having larger and smaller diameters and a cross sectional shape which is very broadly similar to a three leaf or a four leaf clover depending on the number of conductors. V

In some jacketed cords comprising two, three or four conductors the conductors are intentionally twisted together at a fairly short lay to make the cords flexible. In other cords the conductors are usually twisted at irregular intervals, either because of the difference in feed tension during manufacture or carelessness of operators which permits twisting during the course of a reeling-up operation. When coating compound has been applied to the surface of such a cord and the cord is passed through rigid fixed wiping means of the prior art for the purpose 7 of leveling the coating and imparting an even coating of the thickness desired for the final product, coating is removed from the high portions or ridges of the structure where it is out of alignment with the orifice of fixed wiping means, causing the coating to be unevenly applied with little or no coating on the ridges and too much in the valleys and rotation of the cord within the wiper orifice and relative to the wiper will cause speedy wear of the wiper and undesired enlargement of the orifice therein.

Furthermore wipers of the prior art have been made of materials not able to withstand the corrosive action of solvents of the kind presented in the coating material which I prefer to use.

This invention overcomes this difficulty by providing a wiper, which is rotatable and slightly yielding and yet highly resistant to wear and the action of solvents. Provision of a wiper which is slightly yieldable enables the orifice in the wiper to expand and defo'rm as required to pass and satisfactorily coat a cord of non-circular cross section. Provision of a wiper which is rotatable as well as yieldable greatly reduces friction between the cord and the wiper as the latter is able to rotate with twists in the cord and is thus self-adapting to ridges and valleys o'r twists in the cord.

An object of my invention is to provide an improved process for the continuous coating of insulated conductors and the like and for color coating such objects which are non-circular in cross section.

Another object of my invention is to provide a coated conductor or the like comprising an improved coating.

Another object of my invention is to provide a novel combination or system of apparatus for the continuous coating of insulated conductors and the like.

Another object of my invention is to provide improved apparatus for carrying out individual steps of my process.

Another object of my invention is to overcome the deficiencies of the prior art and provide improved method and means for extruding coating on cords and particularly electrical conductors or cords of non-circular cross section including novel wiper and wiper nozzle means.

Another object of my invention is to provide improved apparatus for coating such co'res, insulated conductors and cords.

Another object of my invention is to provide an applicator pot of improved structure and composition.

The invention will best be understood if read in connectio'n with the drawings in which,

Figures 1 and It: show in side elevation at number of apparatus components for carrying out the process, disposed in sequence along the path of a traveling cord.

Fig. 1b is a cross-section of the applicator for antistick solution, taken along the line 1b--1b of Fig. 1a.

Figure 2 is a perspective view of an insulated conductor with its covering partly cut away to show a plurality of coatings applied over the insulation.

Figure 3 is a side view mo'stly in vertical cross section of apparatus for extruding a coating on a traveling co'rd.

Figure 4 is a plan view of.the applicator portion of the apparatus shown in Figure 3.

Figure 5 is a view taken on the line 5-5 of Figure 3 but showing the orifice deformed.

Figure 6 is a side elevation, partly in perspective of the preferred means for fiash heating the traveling cord, and

Figure 7 is a wiring diagram showing the electrical circuit by which automatic control is achieved for turning on the gas jets of the flash heating means shown in Figure 6, and lighting them when the cord is moving, and turning off the gas jets and applying cooling air to the portion of the cord within the flash heater when travel of the cord is stopped and simultaneously controlling other elements of the production line.

The drawings show a production line comprising in longitudinal alignment, a letofl reel 10, the flash heating unit 12, the

coating compound applicators

14 and 16, second or booster heating means 18a and 18b, a wax applicator 2i), the cooling unit 22, an anti-stick applicator 24, and a driven takeup reel 26.

Insulated cord C, which has been previously insulated with rubber, is drawn from reel 10 and advanced successively to the above mentioned units comprising the production line. Since the cord was insulated in a separate, previous operation, both the insulation covering and the conductive core or cores are at room temperature or substantially at room temperature upon leaving the letofi reel 10, and are at such temperature upon entering the flash heating unit 12. The flash heater is adjusted to cause the surface of the cord, when it issues from said flash heater, to have a temperature approximating the maximum temperature of the preferred temper ature range. Any given point along the insulated cord, when moving, remains within the heating means for so short a period of time that there is little or no increase in the temperature of the core by the time the insulated cord leaves the heating unit. The surface of the in sulation however has been heated to a temperature within the range of substantially ZOO-260 F. and preferably within a range having about 240 F. as its minimum and about 250 F. as its maximum. As the insulated cord passes through the

coating applicators

14 and 16, successive thin coatings 11a and 11b (Figure 2) of the coating compound are extruded on to the surface of the rubber insulation by means of specially moulded, yielding and long wearing wipers. With the first applicator 14 spaced approximately from two to three feet from the flash heater means 12 and a second applicator 16 spaced approximately two and one half feet from the first applicator, the surface heat of the rubber insulation is retained substantially within said preferred temperature range while passing through said co'ating applicators and is sufficient to effect slight expansion and desirable porosity of the outer jacket and to initiate both good bonding and evaporation of the solvents from the successive layers of coating material causing them to bo'nd tightly and securely to the surface of the rubber jacket. More exactly the first layer of coating material is deposited directly on, and bonds tightly to, the rubber jacket, and if a second layer of coating is used it is deposited over the first layer of coating material and bonds tightly to and around it.

Preferably each layer of coating material is not over one mil in thickness and desirably is about one-half mil in thickness. If a thicker application of coating is desired, one or more additional applicators may be employed.

Beyond the coating applicator means I provide blowers 18a and 18b for blowing air, preferably heated air, along the now-coated cord to drive off remaining solvents and substantially dry and set the coatings upon the insulation.

T temperature imparted to the cord surface by the speedy-1s means 18- shouldpreferably be substantially lessthan the temperature imparted within the flash heater 1-2. When coating rubber insulation of an insulated conductortraveb ingat the rate of 100 to 300 feet per minute depending upon the peripheral circumference, and with the flash heating means imparting to the surface of the insulation a surface temperature of from 240-250 F. as' it issues from the flash heater, and applying two coating layers, each of approximately /2 mil in thickness, of a coating composition comprising chlorosulfonated polyethylene, I have found that air at a temperature within the range 160-180 F. applied to the coated surface over a distance of approximately 8 to feet accomplishes drying of thecoating without transferring to the insulation-sufficient heat to render the surface tacky or to heat the conductive core or cores therein sufliciently to impart residual heat which will injure the core or cores or; in any way impair the rapid curing of the coating.

As a precaution, and to overcome any residual tackiness which might cause turns of the coated conductor to adhere together when reeled up on the takeup reel 26, or piled up in cut lengths, I may apply over the final coating a very thin deposit of wax, which desirably can be paraflin wax, and then pass the conductor through a cooling trough of running water, which may be of standard kind and of substantial length, for example on the order of six feet in length, or I may apply a coating of suitable anti-stick solution such for example as a known cellulose compound, in lieu of the wax before reeling up .the completed conductor on the takeup reel 26. his important that the deposit of either wax or cellulose compound be of only filmlike thickness, since a thicker layer has a tendency to pick up dust and dirt. In; the case of certain conductors as for example conductors the insulation of which has been only partially vulcanized, it may be desirable before the final vulcanizing step, and particularly when the conductor has been reeled up before the short final vulcanizing step and is placed in the vulcanizer on a reel, to apply either over the'thin wax or cellulose compound deposit. or, if they are not employed, directly over the coating, a thin application of fine screen soapstone or talc as added protection in preventing contacting turns from sticking together during final vulcanization.

I find that a deposit of wax, which is so thin that it is extremely difficult to measure its thickness, can be applied by passing the coated insulated conductor through a mist of liquid wax whichi provide within the wax applicator by means which will be described.

As best illustrated in Figures 1 and 3 the flash heating means 12 comprises a unit which is from 6 to 9' in length, and has therein at each side of the path of the insulated conductor, a number of jets 28 for directing air, alone or mixed with heating gas, against and around the surface of a portion of insulated conductor which is within said flash heating means 12. A more detailed description is given below of the flash heating means illustrated in Figure 6.

Each of the applicator pots comprises a receptacle 39 which may be of any suitable material, such for example as stainless steel or aluminum, to which the desired coating material is supplied from a supply reservoir 32.

From the supply reservoirs 32 the coating material is fed into the applicator pots through moulded flexible feed tubes 34 preferably of polysulphide elastomer, such as is commercially available under the trademark Thiokol, which is practically impervious to coating solvents. Tubes 34 are controlled by the flow control valves 38. The particular flow control valves illustrated in the drawing are of the squeeze type. Each coating "applicator comprises a tubular entrance portion '40 on which is screwed a bushing 42 having at its rear extremityv an annular disk 44,, the central opening of'which is preferab'ly' formed'by. a'copper eyelet 46' theorifice of: which is ofa diameter adapted to pass the insulated conduc tor without permitting: escape of coating material from the applicator. Member 44 and its central copper eyelet the narrowness of the container portion 30 in relation to the cord, conductor or other core traveling through it, taken together with the increased height of the front end of the container. Prior art applicators have been of greater width, usually three to four inches, and often circular, and are unsatisfactory because the rather large volume of compound contained therein is not thoroughly mixed and agitated by movement of the conductor traveling through it and the upper surface of the compound tends to thicken and form a crust; 7 I

The container portion 30 of the applicator pot -disclosed herein is sufiiciently narrow so that the conductor of other core traveling through it, setsthe whole body of compound therein into a rotary motion and the increased height of the front end portion of the container permits the rising of the level of the compound within the front portion of the container due to this whirling or rotary agitation of the compound, without spilling over. The travel of the core through this applicator pot keeps the compound therein well mixed and of even viscosity and prevents it fromscaling over.

The rolling action of the compound obtained in my narrow container not only keeps the components of the compound well blended but works out of the compound small air bubbles which may have become entrapped in it, due for example to airbeing drawn into the feed line or entrapped by even slightly blocked air vents in the supply reservoir 32* from which the compound is fed.

In order to feed the coating material evenly the lower end of each flexible feed tube 34 enters its applicator pot near its rear end, as' illustrated in Fig. 3, ata nonturbulent point behind the turbulence which is set .up near the elevated front end ofthe purposely narrow applicator by the action of the insulated conductor passing through this applicator at speeds within ranges set forth herein.

Assembled at the discharge end of the coating applicator is a threaded flange on which is screwed a bushing 52 having a threaded outside face to permit ready assembly of the wipe holder 54' and floating wipsy56. Holder 54 is a nozzle-like member supported only from its rear end, and for ordinary size conductors may be tapered from an internal diameter of about to one of about /1". At its discharge end holder 54 is partly closed by the end flange 58 which serves as a stop for the floating annular disk 56 which is the wiper means by which the thickness of the coating'applied is determined. The diameter of the opening in end 'fiange 58 is greater than the inside diameter of disk 56 but less than the outside diameter of disk 56. In assembling the parts the disk 56' is placed in the nozzle-like holder 54 before the holder is secured on bushing 52; at the start-of operation the insulated conductor or other core to'be coated is threaded through the orifice in disk 56 and the disk is heldloosely against the endflange 58 by the viscous coating composition and the movement of the cord. For applying a /2 mil coating on an insulated conductor of .210" in outside diameter for example, I have employed with very good results a wiper'disk-about .100"

in thickness with an orifice of from .212 to .213" in diameter. v i i I make both the wiper disk 56 and'the holder 54 of 3 material which is slightly flexible and yielding, so that the orifice in the wiper disk54can enlarge anddeform to pass enlarged and twisted portions of a. cord,- and-so. that theholder 54 em bend and it's orifice inend flange 5 8'be nioved to;conform to bends-or unevenness in afoqrd passingthrough it. I also-prefer to make the feed; tubes somewhat-flexible for convenience in cleaningithem.

I have found, that parts molded of polysulphide elastomer, such as is commercially available under the trademark Thiokol, are both tough and yielding and are remarkably impervious to solvents and in particular to the solvents employed in a coating composition comprising chlorosulphonated polyethylene which I prefer to employ for coating telephone cord. I have obtained very excellent results with the parts 34, S4, 58 and 56 molded of polysulphide elastomer type 500-A, type PR-l to which has been added ethylene diochloride to produce a formal reaction with sodium polysulphite of rank 2.0 cross linked through the use of trichloropane, which is the compound commercially available under the trademark Thiokol. Because of the resistance of this material to solvents, its inherent toughness and its ability to bend and to be deformed, the parts mentioned above have unusual life when made of it in addition to having the very important advantage which results from the unusual combination of toughness and deformability and great resistance to frictional wear by the cord being coated.

I have been able to compare the life of yielding wipes, of from 55 to 60 durometer hardness molded from a polysulphide elastomer, with rigid wipes molded from Butyl rubber, neoprene and the like and have found that the former give far longer wear than the latter and better and more accurate wiping.

Since disk 56 is of lesser diameter than the holder 54 it is free to move radially within the nozzle-like holder and since it is of yielding material and its orifice is able to adapt its size and shape to conform to a cord passing through it, it is able to compensate both for movement of the cord within the holder and the small irregularities and differences in diameter characteristic of the insulated cords being coated. Furthermore, floating disk 56 is arranged to rotate freely within holder 54 and thus when its orifice is deformed to conform for example, to the shape of a cord of slightly ribbed non-circular cross section, it will rotate with twists in the cord thus avoiding the frictional wear to which a fixed rigid wire is subject.

In Figure I have illustrated in an exaggerated manner an annular wipe 56 with its circular orifice deformed to pass a telephone cord having four ridges corresponding to four conductors enclosed in a common insulating jacket. This wipe tends to rotate with twists in the cord and is thus subject to much less friction and does a far better job than if it were rigid and unyielding.

The apparatus I have described herein makes it possible to extrude continuous coatings on cords of noncircular cross section including telephone cord, and P O cord, in an economical and satisfactory manner and without the unevenness of coating and the excessive wearing out of wipers which have characterized prior art attempts to coat such cords.

As shown herein the

coating applicators

14 and 16 are each supported on hubs 17 which are screwed into a clamp 60 adjustable along the horizontal support bar 62 extending between the upright supports 64 and 66 which between their upper ends also serve to support the ven tilating hood 68 which is vented by connection with the vent pipe 70 extending vertically from it. This serves to collect the solvents drawn out from the coating layers by the surface heat of the insulated conductor and to dispose of them through said vent pipes.

Two heated air blower units 18a and 18b are shown positioned directly after the coating extruders. Each comprises a horizontally extending heater tube portion 71 which is shown at floor level, a vertically extending pipe 72 interconnecting the heated portion 71 with the horizontally extending tubular portion 73 through which travels the insulated and now coated conductor. Air, such for example as shop air, by which is meant air under pressure of substantially 100 pounds per square inch such as is piped around many factories, is supplied into heater member 71 intermediate its ends as for example by the tap t. This air is heated within tube 71 as by electrical heating units it provided within member 71 and connected by

leads

132 and 134 to a 220 volt circuit. A fitting 75 is screwed tightly into the rear end of tubular member 73 and has a central bore to provide a passage for the insulated and coated cord into the rear end of tubular portion 73. Air supplied under pressure to heater portion 71 goes upwardly through pipe 72 into an air space surrounding the cone shaped center portion of member 75 and is thus discharged into the rear end of tubular member 73 around the coated cord and in the direction of travel of the coated conductor, and serves to dry said coating and release accumulated solvents at the open end of the tubular member.

The size of the

pipes

71, 72 and 73, the pressure under which air is supplied into this heater device and the extent to which it is heated may of course vary according to the nature of the operation. I have obtained very good results with a device in which portion 71 is a 2 /2" pipe from 48" to 50" long and has assembled in its ends respectively two 4,000 watt heaters approximately 15" in length to provide temperatures on the order of 200 F.

The temperature of the air issuing from the blowers 18a and 18b may be varied within a temperature range of say 150180 F. by adjustment of valves v which control the pressure of the air as it issues from heating units 71.

The means for causing a deposit of wax on the coated insulated conductor from a mist of liquid wax comprises a closed receptacle 20 having heated, fluid wax therein up to a level which is preferably maintained at such an elevation that substantial space is left above it in said receptacle through which the insulated conductor is passed and wherein a mist of the liquid wax is provided by means of one or more submerged pumps P driven by a motor M. The pump P has an inlet 74 for liquid wax below the liquid level within the wax container, and is connected to one or more nozzles 76 by one or more tubes 78 for directing a spray of liquid wax against a curved cone-like abutment member 80 and thereby creating a mist of liquid wax above the said liquid level. As illustrated herein, member 80 is a carefully designed, semi-cone-shaped metal member disposed at the conductors entrance into receptacle 20 which is apertured to pass the traveling coated cord and serves to direct a cone of wax spray over and around the cord in the form of an almost invisible film. Ports 80 and 82 are provided in the side walls of receptacle 22 through which the traveling insulated and coated conductor is passed.

Upon leaving the waxer 20 the insulated, coated and waxed cord passes through the trough 22 to the takeup reel 26. A stream of cooling water is continuously supplied to trough 22 through conduit 84 and exhausted through conduit 86. Trough 22 is long enough to cool the conductor throughout to room temperature and to harden the wax deposit.

Under certain circumstances, depending upon the materials with which a cord is insulated and coated, instead of applying wax to the coated cord I prefer to pass it directly from the air blower means 18 to trough 22 and, after the coating has been cooled and hardened in trough 22 but before reeling it up, to wet the cord surface with an anti-stick solution. Such solutions and means for applying them are known and it will suffice to say that such a solution, preferably of the cellulose type, may be dripped from container 23 onto the absorbtive, flexible sheets 24a and 24b, desirably of sponge or sponge like material superimposed Within the receptacle 25, the cord being passed between said sheets and wetted all around by contact with said sheets.

The flash heating means comprises the two

outlet manifolds

28a and 28b each having a multiplicity of orifices 29. Air at room temperature is supplied to manisuitable coupling connections;

t? folds-28:11am 285 respectively through thetubes; 86aiand 8615, the. outer ends of: which are interconnected, as. shown iniF ig. 6, by an intermediate curved tube 86c.

Air from a suitable pressure controlled source, such as:shop' air is supplied under predetermined pressure to tube 86c through tube 88, valves 87a and 87b and the pressure indicators 89a and 8% respectively. I.have had good results using air issuing from conduits 86a. and 86b under five' pound pressure.

Under normal operation these valves will be continu-' ously open so that whenever motor 92 is actuated air will be suppliedfrom compressor 90 through conduit 88 into conduiti86c and then in opposite directions tothe burners 29a and 29b through conduit portions 86a and 86b respectively.

Asv shown herein conduits 86a, 86b and 86c are supported: by the standard 94, having thebase 95, preferably telescopic so that its height may be adjusted, and by the standard branch arms 96a and 96b which are connected totstandard 94 as by the T-connector 98 andto the coridlllti portions 86a and 86b by the T connectors or conplings100. and 102 respectively. A valve 104 is shown n the air supply conduit 88 between compressor 90 and iltggunction with conduit portion 860 as by the coupling Also connected to the tubes 86a and 86b is a gas supply tube 108 from which branches 109a and communicafe with said tubes 86a and 86b respectively through The branch gas supply tubes. 109a and 109.: are controlled by solenoid valves 110a and 110;; respectively, positioned intermediate their ends, said branches 109a and 10% opening from said gassupply tube 108 beyond the gas supply governor 112 connected intermediate the ends of said gas supply tube 103; The'solenoids comprising said solenoid valves are connected in an electrically controlled circuit such as is shown. in Fig. 7 and whenever said circuit is opened, at

any one of the switches comprised in the circuit, the

solenoid portions of said'members 110a and 11% actuate the valve portions thereof to instantly close said branch supply tubes 109a and 1091: respectively, and conversely when the control circuit is closed the solenoid portions of said members 110a and 11% of said branch arms respectively cause thevalve portions thereof to open thus instantly opening the gas supply circuitiand causing gasto be supplied from gas supply tube 109 through said tubes 109a and 109k and tubes 86a and 86b respectively to the said'manifolds 29a and 2%, from the orifices-29 of which the gas is ejected by the pressure of the gas itself, supplemented by the pressure of the air continually suppliedto said manifolds, against, or in close proximity to, the surface of the insulated conductor being coated;

more spark plugs 114, the point or points of which are bent down close to the metallic surface of the manifold 28b", and these spark plugs are also connected to an. electrically controlled circuit in such a manner that the spark plugs are actuated when gas is issuing in jets frornorifices 29 thereby causing a multiplicity of jets to be ignited whenever. gas is flowing to said

manifolds

28a and 28b, said jets being immediately extinguished when only. air isbeing supplied to said manifolds 28a and 2815. It will be understood that, both while heating gas is being supplied to said manifolds and while heating gas flow to said manifold is cut off, compressed air at room temperature will be continually supplied to said manifolds and directed against the cord through the orifices 29. Aceordingly, if the. travel of the. cord is stopped for any reason, the flash. heatingzone and the portion of the cord therein will'be instantly cooled by air at room temper-attire is'sui-ng-alonefrom theeorificesi29, the'fs'uppl'y of gas having been cut otf by the operation of solenoid switch through which-electric power is supplied from any: suitable power source (not shown) to as many of the=pieces of. apparatus comprising the production line as.- it is desired by control simultaneously. Thus, in the single line diagram comprising Fig. 7, power from a main power source is supplied through the main switch 120 to lead 122 through the lead 124 having therein-the con? trol switch 126. Lead 122 is also connected in parallel with the motor, indicated at 116, which, through any suitable means, drives takeup reel 26 thereby controlling the-travel: of the cord C; and with the solenoid valves 110a and- 11% respectively, through branch leads 126 and 128 respectively; and to spark plug means 114 throughleador. leads 130 also branching from lead 122.

Thus,: the solenoid valves 110a and 110k will be instantly opened to supply gas to the manifolds and jet orifices of the flash heater and the spark plugs will be sparking to ignite gas issuing from said orifices whenever the conductor is traveling, and the supply of gas to said manifolds will be instantly cut off, and said spark plug means will bedeactuatedywhen travel of the conductor isstopped for any reason.

Otherelements of the apparatus comprised in the production linev illustrated in Figs. 1 and 7' may similarly be connected to lead 122 for actuation and deactuation simultaneously with said takeup reel 26, the solenoid valves 110a and 110!) and the spark plug means 114. As illustrated herein, the heaters in tubes 71 of blowers 18a and 18b areconnected to said lead 122 by branch leads-.132 and 134, respectively and the motor of the waxer 22 is shown connected to lead 122 by branch lead'136. a

If desired, other control switches similar to 126 may be suppliedwhereconvenient in the control circuit and such switches are shown in Fig. 7 included in the

branch circuits

132, 134 and 136.

While I do not wish to be limited only thereto, I have discovered that very excellent results are obtained by using, and I prefer to use, a coating composition com.- prising a chlorosulfonated polyethylene which is commercially available, with or without color as desired, under the trademarks Hypalon tnd Hypalon 20.

I have had very good results applying a chlorosulpho nated polyethylene coating in either two or three thin layers, each of less than one mil thickness, upon a rubber insulated conductor traveling at a speed of from 100 to 300 feet. per minute, the surface of which has been initially. and almostinstantaneously flash heated to a temperature in. the range of 240-250 F. by passing it through a short heating unit within which it is exposed to -a temperature suflicient to flash heat the cord surface to=a temperature within said range. The resulting coating' obtained iswear resistant and if pigmented is color fastiand free from staining.

I have found that neoprene and other similar coating 7 materials tend to discolor pigments and especially the brighter colors. Neoprene and like coating materials may be used when a' black coating is desired or when staining of other objects by the coated insulated conductor is not important, and maybe very readily and successfully applied by my process. a

The extrusion coating processeswhich have been attempted on partlyvulcanized telephone cord have ruined the cordfor coiling by. completing its vulcanization before it. has been set in the desired coiled. form. My processtmakes it possible to coat partly vulcanized cords without heating them to a. temperature which will increase their vulcanization, thusleaving them in. condition tobfe firstcoiled; and thereafter set in. a final vulcanizing step. lwhave: found that with the meansdisclo'sed. hereinfor initial flash heating the surface of an insulated conductor, and with the conductor being advanced at a speed on the order of from 100 to 300 feet per minute, a very short heating unit on the order of eight inches or less is desirable and a longer heating unit may be too long and impair the process by imparting a substantial amount of heat to the core of the insulated conductor. I prefer to use a heating unit which is approximately six to nine inches in length and, while the insulated conductor is advancing at approximately the said speed of 100 to 300 feet per minute, create a temperature within the heating zone sufiicient to heat the surface of the insulation to a temperature substantially within the range of 200-250 F. as it leaves the heating zone. With an insulated conductor of average size traveling through this flash heating unit at a speed within the range of speeds mentioned above a temperature on the order of 2000" F. within said flash heating unit will suffice to satisfactorily heat the surface of the conductor without heating the core sufficiently to damage it or prevent the satisfactory setting of the coating or coatings.

I have had very satisfactory results in coating rubber elements, such as a rubber insulated conductor, within my preferred coating composition using a production line along which the first coating applicator is spaced 24" to 30" from the flash heater; with substantially two to two and one half feet between the first and second coating applicators; and about three feet between the second and third coating applicators if a third applicator is employed.

If hot air reheater-blower means 18a is employed, the spacing of such means from the last applicator is not at all critical and will be determined in part by the space available. I have obtained good results with such means positioned approximately two feet beyond the last coating applicator.

There has thus beendisclosed a process and resulting product and apparatus elements and combination of apparatus elements by which the above stated objects are realized in a thoroughly practical manner.

What I claim is: v

1. In the process of coating a previously insulated conductor which is at room temperature the preliminary step of heating the surface of the conductor insulation to a temperature which is high enough to evaporate the solvent from a layer of coating material applied on the heated surface of the insulated conductor, the length of time the insulated conductor is subjected to heat and the heat employed being such as to heat only the surface of the insulated conductor without substantially heating the conductor core.

2. The process of coating an insulated conductor which comprises the successive steps of heating the surface of a previously insulated conductor, the temperature of which is initially at room temperature, to a temperature within the range of approximately 200 F.260 F. and

immediately passing the insulated conductor through a bath of coating material which includes a portion of solvent, and wiping the coating material to limit its depth to the desired thickness, the length of time the insulated conductor is subjected to heat and the heat employed being such as to heat only the surface of the insulated conductor to within the range specified above without substantially heating the conductor core.

3. The process of coating an insulated conductor which comprises the successive steps of heating the surface of a previously insulated conductor, the temperature of which is initially at room temperature, to a temperature within the range of approximately 200 F.-260 F. and immediately passing the insulated conductor through a bath of organic combustible coating material which includes a portion of solvent, and wiping the coating material to limit its depth to the desired thickness, the length of time the insulated conductor is subjected to heat and the heat employed being such as to heat only the surface of the insulated conductor to within the range specified above without substantially heating the conductor core.

4. The process of coating an insulated conductor, the insulation of which is selected from the group consisting of natural rubber and synthetic rubber, which comprises, heating the surface of the insulation to a temperature within the range of substantially 200 F.-260 F. without substantially heating the conductor core by exposing the surface of the conductor to a temperature of approximately 2000 F. along a distance of from 6 to 9 inches while moving the conductor at a speed of from feet to 300 feet per minute, and passing the portion of the conductor the surface of which has l'een so heated successively through a first bath of chlorosulfonated polyethylene and through a wiper having an orifice of a diameter such that the resultirg coating is approximately one half mil in thickness, and through a second bath of chlorosulfonated polyethylene and wiping the second coating thus obtained to limit the depth of the second coating also approximately to one-half mil in thickness, and passing the insulated conductor which is now coated with a plurality of coatings through a cooling medium to set the layers of coating composition.

5. Apparatus for applying coating on an insulated conductor which comprises, a let-off reel, a take-up reel, and means for driving the take-up reel, an air and gas manifold disposed along the path of the insulated conductor in travelling from the let-01f reel to the take-up reel, said manifold comprising a multiplicity of jets directed at the path of the insulated conductor, air and gas conduits connected to said manifold, and means for supplying gas and air to the manifold through said conduits including valve means for the gas conduit, means for igniting gas supplied to the jets of said manifold, and means responsive to the movement of the conductor for controlling said gas supply means and said gas igniting means, a container for a body of coating material having inlet and outlet orifices through the insulated conductor is led, wiper means for controlling the depth of the coating deposited on the insulated conductor, and cooling means for setting the coating.

6. The apparatus claimed in claim 5 in which the gas igniting means comprises, spark plug means positioned adjacent said manifold, solenoid means for controlling said valve means, and electric control circuit means .in which the spark plug means and the solenoid means are connected, said control circuit means including switch means responsive to movement of the conductor.

References Cited in the file of this patent UNITED STATES PATENTS 1,033,912 Lendi July 30, 1912 1,817,122 Black Aug. 4, 1931 1,956,401 Russ Apr. 24, 1934 2,072,557 Hinsky Mar. 2, 1937 2,175,099 Abbott Oct. 3, 1939 2,288,129 Feldhausen et a1 June 30, 1942 2,382,275 Van Lin et al Aug. 14, 1945 2,421,652 Robinson et a1. June .3, 1947 2,448,799 Happoldt et al Sept. 7, 1948 2,539,147 Loucks et a1. Jan. 23, 1951 2,600,567 Mol June 17, 1952 2,642,035 McDermott June 16, 1953 2,668,700 Zimmerman Feb. 9, 1954 2,684,050 Larsen et a1. July 20, 1954 2,734,478 Reynolds et a1 Feb. 14, 1956 2,789,922 Allen Apr. 23, 1957 2,811,746 Lerch Nov. 5, 1957 FOREIGN PATENTS 223,529 Great Britain Nov. 13, 1924

Claims

1.IN THE PROCESS OF COATING A PREVIOUSLY INSULATED CONDUCTOR WHICH IS AT ROOM TEMPERATUER THE PRELIMINARY STEP OF HEATING THE SURFACE OF THE CONDUCTOR INSULATION TO A TEMPERATURE WHICH IS HIGH ENOUGH TO EVAPORATE THE SOLVENT FROM A LAYER OF COATING MATERIAL APPLIED ON THE HEATED SURFACE OF THE INSULATED CONDUCTOR, THE LENGTH OF TIME THE INSULATED CONDUCTOR IS SUBJECT TO HEAT AND THE HEAT EMPLOYED BEING SUCH AS TO HEAT ONLY THE SURFACE OF THE INSULATED CONDUCTOR WITHOUT SUBSTANTIALLY HEATING THE CONDUCTOR CORE.