US2186788A - Electric conductor - Google Patents

Description

Jan. 9, 1940.

J. w. OLSON 2,186,788 ELECTRIC CONDUCTOR 2 Sheets-Sheet 1 Filed Sept. 18, 1937 FIG. 1

INVENTOR TTORNEY Patented Jan. 9, 1940 UNITED STATES PATENT OFFICE ELECTRIC CONDUCTOR Application September 18, 1937, Serial No. 164,474

2 Claims.

This invention relates to improvements in the marking and identification of insulated electric conductors and particularly those types of conductors which are provided with a finishing layer 6 of wax-like or bituminous compound.

Electric conductors as commonly made are frequently provided with exterior layers of wax-like finishing materials which tend to lubricate the surface of the conductors thus allowing them to be easily pulledinto conduits and also prevents sticking to other wires with which they may come in contact. Similarly the finish employed may be chosen for its resistance to burning and materials such as stearine pitch are commonly used to impart a degree of noninfiammability to the insulation. Quite frequently the same conduit will carry a considerable number of wires constituting difierent circuits and forease for instal-.

lation, it is essential that these be readily identified one from another. In the past various coloredlayers of lacquer or enamel have been placed over stearine pitch to provide a color coating and still retain a degree of flame resistance but the number of conductors which can be identified in this manner is limited by the number of available colors which are readily distinguishable from each other and it has generally been found that confusion results if more than five colors are used. It is the chief purpose of this invention to provide a method of printing on electric conductors which carry a finish of bituminous or waxlike material so that the individual strands may be readily identified.

'I'he various codes adopted by municipalities and bureaus of safety have for a long time advocated some method of marking whereby the characteristics and source of manufacture of electric conductors may be readily determined after installation. Heretofore no practical method of marking has been found for wires or cables which are finished with a bituminous material except by the use of colored marker threads within the insulation. Since these threads are saturated during manufacture with the bituminous material, it is necessary to extract the saturant with a solvent before the color of the threads can be determined. Even after this has been done the marking is meaningless unless the inspector has available data showing the markings adopted by various manufacturers.

The suggestion has been made that a layer of lacquer be applied over the fiameproofing compound, usually stearine pitch, and that printing be applied to the dried film of lacquer. When this is done it is necessary to apply a film of wax over the lacquer so that the wire may be readily drawn into conduit. Obviously the flame-resistance of the completed wire is much greater if no Wax or lacquer is necessary, but no satisfactory method has been known in the art for placing permanent marks on pitch-like or wax-like finishes. It will be understood that the various codes in force throughout the country require the presence of a layer of fiameproof material over the rubber insulation, and for this reason 10 the usual methods of molding identifying marks into the surface of rubber insulation would not provide a ready means of identifying conductors by visual inspection. Another purpose of this invention is to provide a means of marking on the surface of conductors which have been finished with a bituminous compound without the necessity of interposing a-layer of lacquer between the fiameproofing and lubricating coats.

A number of advantages are thus assured. The 20 markings may be applied to the finished wire after it has been completed in the usual manner without the necessity of further processing after printing. No other method of which I am aware permits of marking directly on the surface of a 25 conductor finished with bituminous compound, and the expense involved in applying a layer of material merely for the purpose of providing a base for the printing is avoided.

Obviously a wire which may be printed with- 30 out the necessity of interposing an extra layer of material merely to provide a base for printing may be marketed at a lower price than one which requires this extra step, thus reducing the premium on electric conductors which are so identified.

The present invention includes the marking method and the novel product of this process and will be further described in connection with the accompanying drawings which illustrate apparatus suitable for carrying out the invention as well as a conductor which has been marked in this manner. It will be understood that the general type of apparatus involved in' finishing the wire is well known and, for this reason and in the interest of clarity, only those details pertaining particularly to the invention will be described and illustrated, the drawings being diagrammatic in other respects.

In the accompanying drawings:

Figure 1 is an elevation, partially in section, of a finishing line adapted to practice the method of this invention in which suitable marking mechanism has been inserted.

Figure 2 is a detail elevation of marking mechanismsuitable for the practice of this invention.

Figure 3 is a detail cross-section taken along line AA of the mechanism illustrated in Figure 2.

Figure 4 is a conductor marked in accordance with this invention, certain parts having been broken away for ease of explanation.

Figure 5 is a cross-section of the wire illustrated in Figure 4.

Referring to the drawings, a supply of insulated electrical conductor H is carried upon a reel I2 which is free to rotate about the axle l3 mounted on the standard M. The conductor II preferably comprises a metallic strand which has received a jacket of rubber insulation, and which has been covered with a braid of fibrous material such as cotton. The successive steps of finishing to be described are for the purpose of placing layers of compound over the braid which will render the completed conductor flameproof, weather-resistant and free from stickiness. As used in this specification the term fiameproof implies that vthe conductor will not support a flame but will merely char when exposed to active combustion.

The conductor H is first passed about a wheel l5 which is partially immersed in a molten bath of flameproof material l6, such as stearine pitch kept at the proper temperature by an electric heater l'l. When dipped in the bath an excess amount of pitch is picked up on the wire and this is removed by drawing the conductor through a die I8, imparting a smooth finish to the surface. To minimize the effects of heating upon the rubber insulation due to passage through the molten pitch and also to expedite cooling, the strand is then pulled through a water bath l9 which is fitted with rollers 20 to keep the conductor beneath the surface of the water. Following this step the conductor is dried by passing it through a box 2| in which a strong jet of compressed air is directed against its surface from the supply pipe 22. The surface of the conductor at this point is sticky due to the inherent qualities of the stearine pitch and the strand is therefore pulled over the guide pulley 23 into a bath of molten wax 24 in which it is submerged by the wheel 25. This bath is similarly kept at the proper temperature by an electric heater ll. At this point the surface of the conductor is ready to receive marking in accordance with this invention.

It may be stated that marking may be applied after the pitch layer has been formed but before the coating of wax is applied. If this is done,

however, the external layer of wax must be transparent so that the markings will be clearly visible through this outer layer. If printing is applied as the final step in the manufacture of the wire a black wax may be used which imparts a finer finish to the conductor and is somewhat less expensive. The conductor is drawn through this finishing line by an appropriate capstan 26 with a suitable motor drive (not shown) and is finally coiled upon a shipping reel 21 as a completed product.

The details of the printing mechanism chosen for purposes of explanation are more readily apparent from Figure 2 of the drawings in which the strand II is first drawn between. a fixed grooved pulley 28'and a similar pulley 29 mounted on the arm 30 which is kept in constant bearing pressure with the wire by the spring 3|. The purpose of this treatment is to straighten the wire and. thus avoid the presence of any irregularities which might interfere with the marking operaaisavss tion. This invention contemplates the use of a pigment dispersed in a wax-like base as the marking medium and it has been found that this may be most conveniently handled when applied to a thin strip of paper, cloth or metal.

A satisfactory composition for producing markings of pleasing appearance may be made from the following ingredients:

Grams Paratfin wax (melting point F.) 50 Carnauba wax 15 Turpentine 112 Carbon tetrachloride 112 Light mineral oil 1 Extra fine copper powder 285 All the above materials are mixed together, slowly heated to approximately 200 F. and are maintained at this temperature until a homogeneous mass is obtained. When cool the mixture is quite viscous and is ready for application to paper or cloth strip in accordance with methods well known in the art. When applied in a thin layer the solvents evaporate leaving a film of pigment dispersed in a wax-like base which is is passed over pulley 35 mounted on the same bearing as the roll 32, and is provided with a weight 36 to prevent the roll from over-running when strip 31 is not being drawn from it. A guide 38 is provided to direct the strip between the marking wheel 39 and the conductor II and is pivoted about a bolt 40 so that it may accommodate itself to variations in diameter of the roll. The conductor II and the strip 31 are pressed between the marking wheel 39 and the grooved idler pulley 4| which is mounted on an arm 42 pivoted about the axle 43 and is maintained in pressure contact by the spring 44 whose tension may be regulated by tightening or loosening the wing nut 45. After marking the strip is coiled upon the roll 46 which is driven by the pulley 49, held in contact with the wire by the idler wheel 50 which serves to drive the belt 48. The belt should have sufiicient looseness to allow considerable slippage between it and the pulley 41 to compensate for variations in speed of rotation of the takeup depending upon the size of the roll or strip. The entire printing mechanism may be mounted upon a standard 5| secured to a suitable base or pedestal by the anchor bolt 52.

The degree of pressure on the ironing pulley 28 and the drive pulley 29 may be varied by appropriate adjustment of the turnbuckle 53 which will cause a corresponding variation in the tension spring 3|.

The details of the marking wheel 39 and the idler pulley 4| are clearly illustrated by the sectional elevation shown in Figure 3, the former being mounted so that it may be freely rotated about the stud bolt 54 which secures the inner raceway 55 of the bearing to the plate 5|. Washer 56 is provided to prevent the marking wheel from hearing against the back plate. Preferably the body of the markingwheel is formed from a recessed disc 51 which issecured to the contact with the marking type 60. The entire assembly of the marking wheel is secured together by appropriate bolts 62 so that the disc 59 may be readily removed and another carrying a different legend can be substituted. The

pulley 4| is similarly mounted on an anti-friction bearing 63 and is secured to the lever arm 42 by a bolt 64. As previously described the idler pulley 4| forces the type '60 against the pigmented strip 31 with sufl'icient force to produce marked indentations in the surface of the insulator canductor ll.

Referring to Figure 4 which illustrates a conductor marked in accordance with this invention, certain of the parts having been broken away for explanation, a metallic strand 65 is insulated with a jacket of rubber 66 which is in turn provided with a braided, served or woven jacket of fibrous material 61. As previously described a layer of flame-proofing material 68 such a.

as stearine pitch is then applied over the braid and the assembly is completed with an'outer coatingof wax-like material 69. The impressions 10 made in the finish of the insulated con ductor are partially filled with a pigment di persed in 'a base which is compatible with the wax or other finishing compound. Because the marking wheel 39 is rotated by the bearing be tween the marking type and the conductor H it is essential that contact be maintained be- .tween all points on the circumference of the wheel and the wire to insure steady rotation. For this purpose it has been found convenient to provide raised portions on the wheel suitable for marking dashes or line wherever other marking is not used. Such dashes. H are indicated in Figure 4 The markings placed on the wire would ordinarily comprise the name of the manufacturer and the maximum voltage for which the particular wire is intended. By varying the color of the imprint a coding may be obtained which is suflicient to identify the polarity of the various wires constituting a single circuit. If an extremely large number of wires are required in a single conduit, identifying marks or numerals may be stamped into the covering. Figure 5 illustrates a cross-section of the conductor shown in Figure 4 in which the layer of colored pigment 12 is clearly shown in the indentations 13 produced in the surface of the wire. Preferably the indentations are of sufllcient depth so that the upstanding portions of the finished layer 14 will protect the color in the recesses against abrasion.

So far as I am aware it is new in the art of finishing electric conductors to mark the surface of insulation coated with bituminous or wax like compound by means of indentations pressed beneath the surface of the wire and partially filled with a plastic material free from volatile solvents.

It will be understood that the advantages of using a marking medium which does not require a period for drying are of great importance in the commercial production of insulated wire and cable where any step which requires the-use of drying towers, heating ovens or extremely careful handling adds greatly to the complexity of the manufacturing process.

While this marking method has been described as applied to an asphaltic surface, since this has presented the greatest obstacles to satisfactory identification in the past it will of course be obvious that it is adaptable to marking on lacquer or painted surfaces since these present a smaller degree of diii'iculty.

While the method and product have been shown and the structure described in detail, it is obvious that this is not to be considered limited to the exact forms disclosed and that changes may be made therein within the scope of what is claimed without departing from the spirit of the invention.

Having thus set forth and disclosed the nature of this invention, what is claimed is:

1. An insulated electric conductor provided with a layer of bituminous compound capable of receiving and retaining impressions, said bituminous compound carrying marking indicia in the form of depressions denoting the characteristics of the conductor, said indicia being rendered clearly legible by a layer of pigmented waxpartially filling said depressions, said pigmented wax being protected by the surrounding upstanding walls of bituminous compound to prevent abrasion of the pigmented layer, said pigmented wax comprising finely divided coloring matter dispersed in a wax base which is free from volatile solvents at the time of application.

2. An insulated electric conductor provided.

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