US2976397A - Self-controlled strand annealer - Google Patents

Description

March 21, 1961 B. c. ELLIS, JR 2,976,397

SELF-CONTROLLED STRAND ANNEALER Filed Jan. 30, 1957 3 Sheets-Sheet 1 INVENTOR. B. C. ELL/S, JR.

BY Q.Q..

ATTORNEY March 21, 1961 B. c. ELLIS, JR 2,976,397

SELF-CONTROLLED STRAND ANNEALER Filed Jan. 30, 1957 5 Sheets-Sheet 2 INVENTOR. B. C. ELL/$.JR.

ATTORNEY March 21, 1961 B. c. ELLIS, JR 2,976,397 SELF-CONTROLLED STRAND ANNEALER Filed Jan. 50, 1957 5 Sheets-Sheet 5 FIG. 4

FIG. 3

INVENTOR.

a. c. ELL/S, JR.

BY QR.

ATTORNEY United States atcnt O 2,976,397 SELF-CONIRGLLED STRAND ANNEALER Benjamin C. 'Ellis, Jr., Baltimore, Md., assignor to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Filed Jan. 30, 1957, Ser. No. 637,285 1 Claim. (Cl. 219-455) This invention relates to an improvement in apparatus for electrically heating a continuously moving conductor, and more particularly, to a device for heating a rapidly and continuously moving conductor, by the utilization of electrical current, to a predetermined and different temperature at various points along the path of travel of the conductors to continuously anneal the conductor.

This invention is applicable to many operations in connection with many manufacturing processes but is here illustrated as particularly applicable to the electrical heating of a continuously moving conductor which is in motion between a supply source and prior to delivery of bright, annealed, unoxidized conductor at a predetermined temperature to an extruding apparatus for the purpose of raising the temperature of the conductor, which has previously been hardened as a result of cold Working of the conductor in a drawing operation, a sufiicient amount to partially or completely anneal the conductor, as

may be desired in any venting overheating of prevent discoloration given instance, and especially prethe surface of the conductor to thereof while it is exposed to the oxidizing influence of the atmosphere and subsequently drying the conducting, prior to extruding an insulating sheath thereon, to control adhesive qualities between the insulation and the conductor, to prevent blisters and bubbles from forming the quality of the plastic sheath applied thereto.

An object of the present invention is to provide apparatus for heating continuously moving conductor by direct passage of electrical current therethrough, in which the conductor passes over at least three sheaves arranged to form paths of unequal lengths to which currents of unequal amounts and the same voltage are applied to the paths between the sheaves so as to cause unequal heating of the conductor along different paths of the conductor while maintaining the conductor entering and leaving such apparatus at substantially the same potential, so that the possibility of electn'cal shock to the operator of the apparatus is minimized and potential differences from the conductor and other outside apparatus does not occur.

Yet another object of the invention is to provide an apparatus for annealing copper conductor in which the electrical heating current in the conductor causes uniform annealing to take place regardless of the speed of movement of the conductor therethrough without the need of controlling the voltage applied in accordance with a variation in speed of the conductor and which is stable even though the copper conductor is not fully annealed.

Still a further object of the present invention is to provide an open-ended insulating tube having an auxiliary source of cooling medium, such as steam, for surrounding the moving conductor while it is being annealed to prevent the outside surface of the conductor from attaining a temperature above which excessive oxidation will occur and so arranged that the lengths of the portion of the conductor heated by the current and the portion cooled'by steam be reduced to a minimum, thereby inin the'plastic sheath and improve- Patented Mar. 21, 1961 suring that the annealing apparatus will operate at maximum efliciency.

Another object of the invention is to sub ect the conductor to a steam blast to remove the water and foreign matter from the surface thereof, while the conductor 1s being heated so that upon exposure to the atmosphere, any remaining moisture is immediately evaporated to provide a dry conductor of a predetermined temperature at the entrance to the associated extruder.

A further object of the invention is to provide an apparatus for continuously annealing, insulating and reeling conductor which will be relatively simple in operation, inexpensive to build, compact, eflicient, and a durable device.

Other objects and features of the invention will be more readily understood from the following detailed description when read in conjunction with the accompanying drawings, in which:

Fig. 1 is a fragmental top plan view of the combined annealing apparatus, source of supply of the conductor, and extruder;

Fig. 2 is a side elevation view of the annealing apparatus, taken on line 2-2 of Fig. 1;

Fig. 3 is an end elevation view of the annealing apparatus, taken on line 3-3 of Fig. 1;

Fig. 4 is a rear elevation view of the annealing apparatus, taken on line 4-4 of Fig. 1;

Fig. 5 is a schematic diagram of the electrical circuitof the annealing apparatus of Fig. '1, and

Fig. 6 is a cross sectional view of a modified form of the annealing tube utilized in the annealing apparatus.

Referring now to the drawings, the strand annealer, designated generally by the numeral 10, is designed to be used in operations involving extruding apparatus, designated generally by the numeral 11, demanding continuous operation, and may be positioned between a supply, designated generally by the numeral 12, of bare copper conductor '13 and the plastic extruder 11 which will supply a sheath 14 of plastic insulation upon the conductor 13. The conductor 13 that is fed to the extruder 11 may be of any desirable cross section or configuration but must be annealed to the desired degree of softness, since, the conductor 11, when it is drawn through the die means (not shown) in the wire drawing operation, is subjected to a certain amount of working and therefore hardening. As the copper conductor 13 advances continuously through the strand annealer 10 it is cleaned, straightened, annealed, cooled and then reheated to a predetermined temperature at which time it enters the plastic extruder l1.

The strand annealer 10 includes a plurality of sheaves to guide the conductor :13 through a predetermined path, at least three of which are electrically conductive contact sheaves 21, 22 and 23, each of which are insulated electrically from the remainder of the annealing apparatus 10, and through which electrical current is supplied which causes the temperature of the conductor 13 to increase progressively from one contact sheave to the other as the bare copper conductor 13 is advancing continuously on its way to the plastic extruder 11. The contact sheaves 21, 22 and 23 are preferably spaced to provide a predetermined length of conductor 13 therebetween, so that the conductor 13 in passing progressively over the contact sheaves 21, 22 and 23 is divided electrically into two sections 24 and 26. The first section 24 is for heating to anneal the conductor 13 and the second section 26 for heating to dry the conductor 13. The path lengths situated between the contact sheaves 21 and 22 and contact sheaves 22 and 23 are the annealing leg 24 and reheat leg 26, respectively. The length of the paths in the annealing leg 24 and the reheat leg 26 are approximately 5 feet and 25 feet, respectively.

The conductor 13 which is supplied from a supply reel 27 or 28 into the annealing leg 24, wherein the conductor 13 first passes over a sheave 29 which serves to hold "more of the conductor 13 in contact with sheave 21, and then over the electrically conducting sheave .21, which serves as one terminal of the electrical circuit for heating the conductor 13 in the annealing operation. From the sheave 21, the conductor 13 passes through annealing leg 24 and partially around the second electric-ally conducting sheave 22, which may or may not be submerged partially in a quenching bath 31, which serves as a second electrical terminal on the annealing leg 24-, so that the portion 24 of the conductor 13 between-the contact sheaves 21 and 22 is a conductive part of the annealing leg 24 and, while it is in contact with the sheaves 21 and 22, the conductor 13 is conducting electricity and is being heated as a result thereof.

The current for producing the annealing heat in the conductor 13 may be either alternating or direct but is preferably in the form of alternating current produced in the secondary of a transformer 33. The heating of the conductor 13 is accomplished by the utilization of an electrical circuit in which the contact sheaves 21, 22 and 23 are energized to pass current through the sections 24 and 26 of the conductor 13 therebetween. The contact sheaves 21, 22 and 23 draw power from a suitable source such as the transformer, designated generally by the numeral 33. Preferably the two sections 24 and 26 of conductor 13 are supplied with electrical current from two parallel circuits energized by the secondary 37 of the power transformer 33. In the annealing leg 24, current is supplied to sheave 21 from one side of the secondary 37 of the transformer 33 and to sheave 22 from the other side of the secondary 37. In the reheat leg 26, current is supplied to sheave 22 from one side of the secondary 37 and to sheave 23 from the other side of the secondary 37.

It has been thought in the past that the speed at which the conductor 13 is passed through the annealing apparatus must bear a certain relationship to the voltage applied to a certain length of the conductor 13 in order to produce a desired amount of annealing in the conductor 13. Thus, it has been thought that if the voltage applied to a given portion of conductor 13 moving at a particular 7 7 speed is only suficient to produce'the desired amount of annealing of the conductor 13, that a higher speed and the same applied voltage would fail to produce the same desired amount of annealing, whereas a lower speed with the same voltage would produce an excessive amount of annealing. However, by utilizing the present invention it is possible to obtain a desired amount of annealing at a wide variation in speeds without varying the applied voltage in a given length of conductor 18.

In operation, the applied voltage is increased to a point where an additional increase in voltage does not produce a corresponding increase in current flowing in the conductor 13. This occurs because of the temperature coeificient of resistance of the conductor and the radiation of heat from the conductor. This provides a self-adjusting phenomena which with the construction described in the apparatus of the present invention will provide annealed copper conductors 13 over a range in speed from 2000 to 3000 feet per minute with'variation in elongation of only 26% to 29%.

The surface of the metal exposed to atmospheric conditions has a tendency to tarnish or oxidize which is greatly accelerated when the metal is heated to annealing temperatures. In the case of copper, oxidation is more pronounced than most other metals. While the conductor 13 is at an annealing temperature, it is important to protect it from oxidation by the atmosphere or keep the surface of the conductor 13 at a temperature below the point at which it discolors when in contact with the atmosphere.

It is thought that even if an inert atmosphere is furnished around the heated conductor 13 to prevent discoloring thereof that the conductor 13 may still discolor.

This may be explained by the fact that the free oxygen in the copper, which is in the neighborhood of 0.03%, is driven out by heating the copper in the conductor 13. The present theory is that if the surface of the conductor 13 is prevented from reaching the temperature at which the discoloration takes place (approximately 270 C.), there is no need to provide an inert atmosphere to protect the conductor 13 from oxidation as is indicated above.

Using this theory and the fact that with a given set of conditions for any particular strand annealing machine 10, the point along the annealing leg 24 where the conductor 13 reaches the temperature at which discoloration takes place can theoretically be pinpointed since the temperature of the conductor 13 in the annealing leg 24 will vary logarithmically from one sheave 21 to the other 22. The surface of the conductor 13 in the portion of the annealing leg 24 between that point and the sheave 22 must be cooled in some manner to prevent the temperature of the surface from increasing above the temperature at which the conductor 13 will discolor as the material in the interior regions of the conductor 13 is heated to a higher temperature to anneal the conductor 13, which is in excess of 400 C., depending on the time during which the conductor 13 is maintained at this temperature.

In the preferred practice of the invention, the portion of the conductor 13 in the annealing leg 24 which is heated to a temperature at which excessive oxidation will take place is surrounded by an open-ended annealing tube 38 which is positioned vertically with the lower end thereof secured to and projecting a short distance through the top cover 41 of a housing 42 which surrounds the contact sheave 22.

The conductor 13 is directed downwardly through the hollow tube 38 containing steam supplied from an auxiliary source (not shown). Steam under pressure is introduced into the annealing tube 38 through a steam inlet connection 43 near the lower end thereof. The steam operates as a cleaning medium and a cooling medium to maintain the temperature on the surface of the conductor 13 at a temperature low enough to prevent excessive oxidation while heat is continuously applied to the conductor 13 by the electrical current, to heat the interior of the conductor 13 to its annealing temperature. Some of the steam escapes into the housing 42 and partially fills the interior thereof and condenses and falls into the bottom of the housing.

A modified embodiment of the annealing tube 38 is illustrated in Fig. 6 and designated generally by the numeral 44. The annealing tube 38 may be shortened and provided with a small metal tube 46, filled with plastic material 47 except for a bore through which the conductor 13 passes, in one end thereof. The plastic material is used to electrically insulate the conductor 13 from the tube 46. The plastic filled metal tube 46 is utilized as a seal to prevent excessive steam from escaping upwardly from the annealing tube 44, and may be replaced or changed when it is desirable to anneal a different size of conductor. Ceramic guide bushing seals 49, 50 and 51 are secured in the ends of the tubes 44 and 46, are used to insulate the conductor 13 electrically from the grounded tube 44 and serve to prevent wearing of plastic material 47 and tubes 44 and 46. The modified annealing tube 44 may be relatively short since it is possible to determine the point in the annealing leg 24 at which the temperature of the conductor 13 will approach a point to which excessive oxidation would occur and the surface of the conductor 13 need only be cooled from that point on as discussed above.

After emerging from the annealing tube 38 the conductor advances partially around the contact sheave 22 to enter a vertically extending cooling tube 52 which is situated between contact sheave 22 and an idler sheave 53. Cool water is introduced into the cooling tube 52 at the top end thereof and the flow of the cooling water is controlled so that a substantially predetermined amount of cooling of the' conductor 13 takes place therein. The cooling water enters the top of the cooling tube 52, is supplied from an auxiliary source (not shown) at a relatively low temperature, emerges at the lower end thereof and spills into the bottom of the housing 42 wherein it collects and flows through an opening in anoverflow drain 54.

It will be understood that the contact sheave 22 may ormay not be submerged in the body of water 31 contained within the housing 42 since the overflow drain 54 has two openings 56 and 57, either of which may be closed depending on whether it is desired to submerge a contact sheave 22 partially in the water 31 to prevent the sheave 22 and the portion of the conductor 13 in contact therewith from becoming overheated. Additional heat will not be added to the portion of the conductor 13 in contact with the sheave 22 after the conductor 13 contacts the sheave 22 on the approach side and until the conductor 13 leaves the sheave 22 on the recess side and moves into the reheating leg 26, and, therefore, any cooling that would be necessary while the conductor 13 is in contact with the sheave 22 is only enough to dissipate the heat being conducted to the surface of the conductor 13 from the material inwardly of the surface thereof.

Immediately after emerging from the cooling tube 52 any remaining moisture on the advancing conductor 13 is removed by means of a conventional steam wiper 58 to remove any water or foreign material which remains on the conductor -13. The conductor 13 then makes several loops about an intermediate sheave assembly, designated generally by the numeral 59, and then advances partially around electric contact sheave 23 to form a path of a variable predetermined length which forms the reheat leg 26. The length of the conductor 13 in the reheat leg 26 may be varied by changing the relative positions of sheaves 55-55 and sheaves 60-60, in sheave assembly 59 by changing the position of sheaves 5555 in the slot 50 or by passing the conductor around a fewer or greater number of sheaves 55--55 and 60-60. The purpose of the reheat leg 26 is to accomplish the reheating of the conductor 13 to insure that the conductor 13 willexit from the anealer after passing through the cooling tube 52 in a dry state and at a predetermined temperature.

After advancing partially around the contact sheave 23, the conductor 13 travels around a jockey sheave assembly 61 which in turn is connected to a speed control rheost-at 62 forming a part of the drive system 63 to provide an accurate speed control for the conductor 13 as it travels through the annealer 10 to control the tension in the conductor 13 between the anealer 10 and extruder 11. The conductor 13 is guided through an extruder :11 to eXtrud-e a sheath 14 of an isulated material thereon and then to apropriate takeup means (not shown).

The temperature of the reheated conductor 13 may be accurately controlled by varying the length of the leg 26 to vary the current therein. Since the current in the two legs 24 and 26 will be different, the drop across the sheaves 21 and 23 will be different amounts. Therefore, in order to keep the potential of the portion of the conductors contacting sheaves 21 and 23 equal, a rheostat 64 is provided which forms a part of the circuit for energizing the contact sheave 23. Whenthe length of the conductor 13 in the reheat leg 26 is varied to vary the current therein, the value of the resistance in the rheostat 64 must also 'be varied to make the drop across the rheostat 64 and the sheave 23 equal to the drop across the sheave 21 to insure that the portions of the conductor 13 entering and recessing from the annealer 10 are both at the same potential to prevent externally grounded paths and possible arcing of the conductor to ground.

It will be understood that the cooling tube 52 and the reheat leg 26 are both situated between the electrical contact sheaves 22 and 23 and accordingly the conductor 13 is being heated as it passes through the cooling tube 52.

6 However, the cooling afiect of thewater flowing through the cooling tube 52 is by design suflicient so that the conductor 13 is cooled substantially to the temperature of the water before being reheated during the remainder of the travel through the reheat leg 26 from the cooling tube 52 to the contact sheave 23.

The apparatus of the present invention heats the condoctor 13 as it travels at a comparatively high rate of speed and the temperature required to anneal or soften the metal is generally so high that the tensile strength thereof is greatly reduced. Therefore it is preferable to prevent the conductor 13 from being stressed beyond its elastic limit by propelling the conductor 13 positively at both sides of the heating zones 24 and 26 to avoid stretching the soft portion of the conductor 13 therein.

by reducing the tension in the heated sections 24 and 26 of conductor 13 to a minimum. This may be accomplished by having all contact sheaves 21, 22 and 23 of the same diameter and driven at the same speed from the same source 63, through belt means 65, 66 and 67, the speed of which may be controlled by the jockey sheave 61.

It is to be understood that the above-described arrangements are simply illustrative of the invention. Numerous other arrangements may be readily devised by'those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

Annealing apparatus in which a moving conductor is heated by the passage of electrical current therethrough, which comprises at least three sheaves to guide the conductor in a predetermined path, at least three of said sheaves being electrically conductive contact sheaves individually insulated from the remainder of the annealing apparatus over which the conductor to be annealed is progressively passed at a variable speed, means for supplying electrical energy at a substantially constant voltage connected to the conductor through two of said sheaves to progressively heat successive portions of the conductor of a predetermined length to anneal the same, an annealing tube which is so positioned between said last two mentioned sheaves that the successive portions of the conductor passing at variable speeds therebetween are directed to said tube and which includes an elongated tube, a second elongated tube of comparatively small cross-sectional dimensions secured in one end of said rst-mentioned elongated tube for sealing the end thereof, a plastic composition lining the interior of said second elongated tube except for a bore of substantially the same cross-sectional dimensions as the conductor passing therethrough, and a plurality of ceramic guide bushings secured within said tubes for guiding the conductor and electrically insulating the conductor from said tubes, means to supply steam to said annealing tube for cooling and cleaning the surface of the conductor and preventing oxidation thereof, the means for supplying the electrical energy being connected to the annealed conductor through a third sheave and the last one of said last two mentioned sheaves over which successive portions of the conductor pass at variable speeds to progressively heat a section of said conductor of a predetermined length to a predetermined temperature, a cooling tube which is so positioned between said third sheave and said last one of the last two mentioned sheaves that the successive portions of the conductor passing therebetween are directed through said cooling tube, means to supply cooling fluid to said cooling tube, steam wiper means positioned adjacent to said cooling tube for wiping the conductor whereby the portions of the conductor leaving the cooling tube are cleared of moisture and foreign material, variable speed means for rotating said electrically conductive sheaves at equal peripheral speeds for propelling the conductor progressively at both sides of each of the heated sections of the conductor for preventing stretching of the conductor, and variable resistance means to com- References Cited in the file of this patent UNITED STATES PATENTS Procunier Apr. 25, Sheperdson July 27, Alexander et al. May 3, Cook Jan. 4, Hanson et a1. Mar. 22, OGrady Mar. 18, Rendel Nov. 10, OGrady Dec. 13,

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