US2932502A - Apparatus for continuous heat treating of wire - Google Patents

Description

w. c. RUDD ET AL pril 12, 1960 APPARATUS FOR CONTINUOUS HEAT TREATING OF WIRE Filed Dec. 26, 1957 3 Sheets-She t 1 INVENTORS. T l ALLA CE CEUDD HUGH JCAMEROM 5 Sheets-Sheet 2 INVENTORS.

April 1 1960 w. C. RUDD ET AL APPARATUS FOR CONTINUOUS HEAT TREATING OF WIRE Filed Dec. 26, 1957 mLACECEL/DD.

HUGH J. CA MEEO/V.

April 12, 1960 w. c. RUDD ET AL. 2, 32,

APPARATUS FOR CONTINUOUS HEAT TREATING OF WIRE Filed Dec. 26, 1957 3 Sheets-Sheet 3 7b HF? SOU/PCE Ill 3 ea /2/ I22 /29 12/ 13? 15a 14/ DIFFERENT/AL 132 GEA RING 757 INVENTORS.

I4 0 MLLA CECE/.100

HuGH J ChMEeoN.

A T TOR/V5751 APPARATUS FOR CONTINUOUS HEAT TREATING F WIRE Wallace C. Rudd, Larchmont, and Hugh J. Cameron, New Rochelle, N.Y., assignors to Magnetic Heating 501%., New Rochelle, N.Y., a corporation of New Application December 26, 1957, Serial No."705,38*5

15 Claims. (Cl. 266-3) This invention relates to the heat treating of wire and more particularly to the continuous annealing of wire by the use of high frequency electric current.

In making wire, a billet of metal is drawn through successively smaller dies until it finally reaches the required size for the finished wire. The drawing of the wire frequently proceeds at very high rates of speed. Speeds of from 200 to 1,000 ft. per minute are not uncommon and even faster speeds are frequently ob tained near the end of the process. In the absence of :additional heat treatment, the working of the wire by drawing causes it to harden and thus become embrittled .and subject to breaking on further drawing or in use. To prevent such embrittling of the wire, it is customarily annealed one or more times during its manufacture and may also be annealed after the final drawing in order to give a soft, pliable product. Previously, annealing of wire during manufacture has customarily been a batch operation in which the wire in coils is placed in furnaces and is brought up to high temperature. The temperature is then lowered slowly and the wire removed and drawn to finer sizes. This batch operation is, of course, a slow and cumbersome process and attempts have been made in the past to anneal or heat treat the wire continuously during the manufacturing process. These attempts unfortunately have not met with any substantial degree of success.

Previous attempts to continuously anneal wire have usually involved passing the wire around two spaced capstans and passing 60 cycle or other low frequency current through the wire between the capstans. This has resulted in a considerable tendency for the current to are and make small arc marks on the surface of the wire. In addition to these undesirable arc marks, the very heavy currents necessary to cause a sufiicient heating effect in brass wires or the like tended to make the arc marks even worse. It is an object of this invention to nited States Patent 0 provide an eflicient, continuous annealing process for i use in the heat treating of wire and in which the formation of arc marks on the wire is substantially eliminated.

According to one aspect of this invention wire is heat treated with apparatus which comprises a source of high frequency current and means for passing the current through succeeding lengths of the wire. The circuit for passing such current through the wire includes a hollow surrounding conductor which is coaxial with at least a portion of the length of wire through which the current is passed; and such surrounding coaxial conductor acts to minimize the reactance of the wire uniformly and entirely around on its surface thereby insuring uniform high frequency current distribution around on its surfaces and consequent uniform conductive resistance heating of the wire.

The use of high frequency current rather than low frequency or direct current in the heat treating of wire is highly advantageous because the eifective resistance of the wire at high frequencies is much greater than the resistance of the same wire when low frequency current is used and, therefore, for a given heating effect much less current need flow through the wire at high frequencies.

Also, the use of high frequency current is highly advantageous because the problem of arc marks on the Wire is thereby eliminated, possibly because of the capacitve effect through the very thin oxide film encompassing all metals, and the high frequency current may be transmitted to and from the wire by the use of simple sliding contacts. In practicing this invention currents having frequencies on the order of about kilocycles or higher are preferred.

The use of a conductor which is generally coaxial with the Wire through which the high frequency current is being passed is an important aspect of this invention since such a conductor avoids losses in efliciency which would otherwise be practically prohibitive, and at the same time it results in the distribution of current uniformly on the whole wire surface. If such conductor extended only along one side of the wire, for example, there would be a close concentration of the high frequency heating current on the side of the wire closest to the conductor.

Once the wire has been heated by the passage of the high frequency current therethrough, it is desirable to cool the wire prior to rewinding or further drawing. Such cooling may be accomplished conveniently by quenching the hot wire in a bath of water or other cooling medium either while the high frequency current is flowing through it or after the wire had passed the region Where the high frequency current is applied. This procedure is especially applicable to brass wire but is also applicable to all types of wire with the exception of such steel wire as may embody enough carbon to harden same to an undesirable degree when it is quenched or other wire which will so harden.

Various further and more specific objects, features and advantages of this invention will appear from the description taken in connection with the accompanying drawings Which form a part of this specification and illustrate by way of example certain embodiments of this invention. The invention consists in such novel features and combinations of parts as may be shown and described in connection with the method and apparatus herein disclosed.

In the drawings:

Fig. 1 is a perspective view showing an arrangement of apparatus embodying the invention;

Fig. 2 is a partial sectional view of the apparatus shown in Fig. 1;

Fig. 3 is a vertical sectional view taken along line 3-3 of Fig. 2;

Fig. 4 is a vertical sectional view taken along line 4-4 of Fig. 2;

Fig. 5 is a sectional view similar to Fig. 3 but showing a different conductor and cooling means;

Fig. 6 is a diagrammatic sectional View showing another arrangement of apparatus embodying the invention;

Fig. 7 is a diagrammatic sectional view showing still another arrangement of apparatus embodying the invention; and

Fig. 8 is a diagrammatic view showing a further arrangement of apparatus embodying the invention.

Referring to Figs. 1-4, a wire 11 which is to be heat treated is drawn from a storage reel 12 which is rotatable about an axle 13. The wire 11 is drawn oif of the storage reel 12 through the apparatus as described below and rewound on a wind up reel 14 by a motor or other suitable means connected with the wind up reel or the axle 16 on which same is mounted. As wire 11 is drawn oif of storage reel 12 it passes through a guide 17 and assent:

over a guide pulley 18, from which it passes across the top surface of a contact 19 which for example may be a silver-tungsten contact. The wire may be held against contact 19 as by nylon blocks 21 and 22 which are se cured to contact 19 by bolts, such as 23, which pass through the blocks and into the contact. Bolts 23 have adjustable nuts 24 on their threaded upper ends. Nuts '24 are used to adjust the tension in springs 26 which force blocks 21 against contact 19 thereby keeping the wire 11 in constant contact with the contact 19.

From contact 19 the wire 11 passes through a guide block 27 into a tube 28 which has an inner insulation liner 29 and an outer layer 31 of copper tubing. The

.insulation liner which supports the hot wire if it sags,

may be formed of a glass material having good heat shock resistant properties, such for example as a material commercially available under the trade name Vykor. The wire traverses the length of tube 28 and then emerges into a tank 32 containing water or other quenching medium. Tank 32 also contains a contact 33 similar to contact 19 over which the wire passes before leaving the tank and passing through a guide 34 to be taken up on wind up reel 14. During its passage over contact 33 the wire is kept pressed against the contact by blocks 36 and 37 which are similar to blocks 21 and 22.

Quench water is introduced into tank 32 through a conduit 38 and nozzles 39 and 41. Water is drained from the tank through a conduit 42. In order to prevent water from passing into tube 28 from tank 32, a. partition 43 is provided in tank 32. A hole is provided in partition 43 for the wire 11 to pass through, and water which overflows the partition 43 or leaks through this hole is drained from tank 32 through a conduit 44.

In order to heat treatthe wire as it passes through the apparatus between contact 19 and contact 33, high frequency current is provided through leads 46 and 47, from, for example a 450 kilocycle, 25 kilowatt generator or other sourcef The voltage at the output of such source may be of the order of 400 or 500 volts and hence the whole system may be of a relatively low potential. As can be seen from Fig. 3, lead 46 which is similar to lead 47, comprises a copper conduit 48 having a hollow center 49 filled with cooling water. It should be noted that tube 28 through which the wire 11 passes is severed, for example midway of its length, so that tube 46 is adjacent to one portion of tube 28 and tube 47 is adjacent to another portion of tube 28 while there is no electrical contact between the two portions of conduit 48 or between leads 46 and 47 near the point where the leads enter the apparatus.

From Fig. 3 it can be seen that lead 46 is maintained in both thermal and electrical contact with tube 28 by means of spot welds such as 51. It is necessary to provide cooling fluid for circulating through the conduit such as 48 because of the heating effects of the high frequency current used. By utilizing this arrangement it is unnecessary to provide separate cooling around tube 28 since tube 28 is in both thermal and electrical con.- tact with conduit 48. Since tube 28 is in electrical contact with conduit 48, the high frequency current travels through the copper tube portion 31 of tube 28 as well as through the conduit 48 of lead 46. The effect of this arrangement is that conduit 48 and tube portion 31 form a single electrical conduit, a portion of which (tube portion 31) is coaxial with wire 11 and another portion of which (conduit 48) is adapted to carry cooling water.

An insulation tube 52 is provided which is connected with leads 46 and 47 by means of connecting tubes such as 53 as shown in Fig. 1. Tube 52 serves'to circulate the cooling water between'lead 46 and lead 47 as shown in Fig. l. The end of tube 28 which is in proximity with contact 19 is caused to be in electrical contact with contact 19 by means of a metal plate 54 while the end of tube 28 which is closest to contact 33 is caused to be in electrical contact with contact 33 by means of the metal walls of the tank 32. It should be noted that the hole in partition 43 throughawhich the wire 11 passes is so insulated that the wire has no electrical contact with the tank or the partition at this point.

Fig. 5 illustrates another method of providing a coaxial conductor in accordance with this invention. Here a cross section of a tube 111 is shown through which a wire 112 passes during heat treatment. Tube 111 is similar in every respect to tube 28 shown in Fig. 1 except that tube 111, rather than being cooled by thermal contact with a water filled conductor as shown in Fig. 1 is surrounded by a cooling fluid tube 113 thus leaving a space 114 through which cooling water may be circulated. Water is introduced to tube 113 through a conduit 108 and withdrawn through a conduit 189. Tube 111, like tube 28, is internally insulated with a layer 116 and comprises an outer layer 117 of metal. The use of cooling tube 113 in connection with tube 111 as shown inFig. 5 eliminates the need for continuing the water filled power leads alongside and in contact with the tube 111. Instead, the high frequency current can simply be fed directly to the metal portions 117 of the tube 111 and cooling water may be circulated through outer tube 113 in order to provide any necessary degree of cooling.

In operation, the wire 11 is drawn through the apparatus as described while high frequency current is supplied to leads 46 and 47. The high frequency current passes through conduit 46 and the portion of tube 28 adjacent thereto to the wire 11 via contact 19 and from wire 11 through contact 33 back to the point of origin through lead 47 and the portion of tube 28 adjacent thereto. During its passage from contact 1'9 to contact 33 the wire is heated to the desired temperature for example in a typical case, 1250 F., by the high frequency current. Due to the use of coaxial conductors the current distribution on the wire'and hence the heating effect is uniform. As the heated wire passes through tank 32 it is quenched by the cooling fluid therein so that it is cool enough to be wound on wind up reel 14 for further drawing or use.

Fig. 6 illustrates an arrangement of apparatus for practicing an embodiment of the invention in'which a separate tank for quench water is not required. Here, wire 61 passes over a guide pulley 6 2 and across an electrical contact 63. The wire 61 then passes through a tube 64 having a construction similar to the tube 28 shown in Fig. land after passing over an electrical contact 66 is guided away from 'the apparatus by a guide pulley 67. The wire 61 is held in contact with electrical contacts 63 and 66 as blocks 68 and 69 in the same manner in which the Wire 11 "is held against the blocks 19 and 33 in the apparatus shown in Fig. 1. Contact 66 shown in Fig. 6 is electrically connected to the tube 64. High frequency current is supplied to contact 63 through a lead 71 and to the outer portion of tube 64 through a lead 72. The path of the high frequency current is thus, for instance, through contact 63 and wire 61 to contact 66 and then through tube .64 to lead 72. It can be seen readily that this arrangement has the same advantages of a conductor coaxial with the wire as the arrangement of apparatusishown in Fig. 1. The same arrangements of high frequency leads containing cooling fluid may be used as were used in the apparatus shown in 1, in which case the lead 72 would be in both thermal and electrical contact with the be 64 h 'ug'hbu e n h o tub 64- In ord'erto quench the hot wire being heat treated in tub 5, e tube is inclined slightly from the horizontal position as sh own in Fig. 6' and partitions 7 3 and 74 are provided to form a containing means for quenching liquid in tube 64. Cooling water or other liquid is admitted to this portion of tube 64 through a conduit 76 and is withdrawn through a conduit 77.

Referring now to Fig. 7 a diagrammatic arrangement of apparatus is Shown in which the wire to be heat treated masses is passed through chambers containing water coolant both before and after the heat treatment. Here a wire 78 passes over a guide pulley 79 and into a tube 81 through a seal 82. From seal 82 the wire passes through a section 83 of tube 81 which is filled with cooling liquid and then through an electrical contact 84 into the main portion of tube 81. Water or other coolant is supplied to section 83 through a conduit 86 and excess coolant is drained away through a hole 87 above seal 82. Any water which leaks through the contact 84 is drained from tube 81 through a hole 88 and such water is prevented from continuing further into tube 81 by a partial partition 89. Tube 81 is similar to the tube 28 shown in Fig. 1 and like tube 28 is interrupted near its mid-section. In the second portion of tube 81 the wire 78 passes through a seal 91 and through a section 92 of tube 81 which is filled with quench water or other coolant. The wire then passes from tube 81 through and in contact with an electrical contact 93 and passes over a guide pulley 94 from whence it may be wound on a take up reel or further processed. Quench liquid is supplied to section 92 through a conduit 96 and water leaves section 92 by overflowing contact 93 through a hole 97. Any water which leaks back through seal 91 is removed through a hole 98 in tube 81 and is prevented from entering further into the main part of tube 81 by a partial partition 99.

High frequency current is supplied to the outer conductive portion of tube 81 through leads 101 and 102. The current traverses a circuit comprising the leads 101, 102, the portions of tube 81 and contacts 82 and 93 to the wire.

An alternative arrangement of the apparatus is diagrammatically shown in Fig. 8, which makes possible the annealing of wire of types or sizes such that it cannot withstand much tension when subjected to the red hot annealing temperature without undue stretching, and the arrangement of this figure also is such as automatically to compensate for such changes in length of the wire as may occur during starting up, carrying on or shutting down of operations.

In Fig. 8, a wire 121 passes several times around a sheave 122 and then passes between a pair of tension rolls 123. From tension rolls 123 the wire 121 passes through a yoke 124 and then through an annealing tube 126 and a quench tank 127. After leaving the quench tank the wire passes between a pair of tension rolls 128 and is wrapped several times around a sheave 129 before passing on to a take up reel for further processing.

Sheave 122 is connected to sheave 129 by a diiferential 131. When the wire 121 is pulled out, as by a take up reel, the force is transmitted from sheave 129 through the differential to sheave 122 which draws in the wire. An electric motor 132 is connected to differential 131 in such a way that when the motor is not running it does not affect the operation of the differential as the differential transmits force from sheave 129 to sheave 122 and causes sheave 122 to run at the same speed as sheave 129. When the motor is operated, however, it modifies the operation of the diiferential so that sheave 122 runs faster or slower than sheave 129 depending on the direction in which the motor is run. Power to operate motor 132 is supplied through wires 139 and 140. Tension rolls 123 are driven from sheave 122 by a chain drive 133 and tension rolls 128 are driven from sheave 129 by a chain drive 134. The net result of this arrangement is that it is possible to maintain a very low tension in the section of wire being annealed in the annealing tube 126. Low tension in this section of wire is desirable because the wire is normally unable to withstand much tension when heated to annealing temperatures.

The annealing tube 126 may be similar to tube 28 shown in Fig. 1 and provided with similar contacts indicated by reference numerals 19' and 33, and it should be understood that the remainder of the apparatus necessary to heat treat the wire may. be of any suitable type which embodies the invention such as that shown in Figs. 17. The arrangement of apparatus shown in Fig. 8 is not restricted to a vertical arrangement as shown, but may be employed horizontally, as for instance similar to that shown in connection with the apparatus of Fig. 1, in which case the wire should pass through yoke such as at 124 prior to crossing the pulley 18 and would then pass through tension rolls such as at 134 and around a sheave such as at 129 after leaving the quench tank 32.

In Fig. 8 high frequency current is supplied to the two spaced portions of tube 126 through leads 142 and 143. Quenching liquid is supplied to quench tank 127 through conduit 144 and is withdrawn through a conduit 146.

Changes in the temperature of the wire as the system is put into use may be compensated for by the use of the yoke 124 which functions in cooperation with contacts 136 and 137 and wires 138, 139 and 14d to control the operation of the motor 132 which is connected with differential 131. If, for instance, the loop of wire passing through yoke 124 rises too high, it pushes the yoke upwards so that the yoke forms an electrical connection between wire 139 and wire 141 through contact 136. This will cause the motor 132 to start and rotate in a direction such that, through the differential 131, it will modify the normal drive connection through the differential between sheaves 122 and 129, whereby sheave 122 will run at a speed relatively slower than sheave 129. (Differential gearing which will operate in this way is available in various types well known per se.) Thus the input speed of the wire 21 as well as of the speed of rotation of sheave 122 and tension rollers 123 will become slower, thereby reducing the excessive height of the loop in the yoke 124 until such time as the loop falls out of contact with the upper arm of the yoke, thus opening the circuit at contact 136 and stopping the motor. On the other hand, if the loop of wire in the yoke 124- should at any time fall too low so as to contact with the lower arm of the yoke, this will cause closing of the circuit through contact 137, thereby starting the rotation of motor 132 in the opposite direction and this in turn will so modify the drive through the diiferential between sheaves 122 and 129 as to increase the speed of sheave 122 relative to that of sheave 129, until such time as the loop in the yoke is increased again in height sutficiently to rise out of contact with the lower yoke arm, thereby opening the circuit through contact 137 and stopping the motor again. The yoke 124, as mounted on a pivotal support as shown for example, may be yieldably held in its normal intermediate position as by a light weight spring at 124a and so that upon contact of the yoke arms with the wire loop, it will be easily actuated. Also the yoke arms as indicated may terminate in small insulation rollers for engaging the wire.

With the arrangement of Fig. 8, the wire 121 as it enters the apparatus, may be drawn for example from apparatus such as previous wire-drawing dies which have acted on the wire, and the wire as it leaves the apparatus may pass directly into subsequent wire-drawing equipment such as drawing dies, and thus the power for normally drawing the wire through this annealing apparatus may be supplied by such subsequent drawing equipment and so that the wire normally will be at the same tension as applied thereto by the subsequent drawing equipment. During the passage of the wire throughout the apparatus of Fig. 8, with the exception of the portions within the loop, the annealing tube and the quenching device, will normally be free of tension, or substantially so, and thus free of any liability of being stretched while heated. It will be apparent that the tensioning rollers 123 and 128 will serve to retain the wire wrapped under tension about the sheaves 122 and 129.

When operation of the apparatus of Fig. 8 is about to be started, the wire, both at the inlet and. outlehas-well as the wire within the apparatus Will normally be at room temperature. Then the system is brought up to speed with the wire being pulled through the apparatus by the subsequent drawing mechanism which applies tension to the wire. Then the high frequency current may be connected onto the annealing tubes 126. At this point, due to its increased temperature, the wire will increase in length and it is thus necessary to compensate for such difference in length, but this is readily accomplished in the manner above explained.

It is further noted that in the operation of the apparatus, the wire at the inlet may for example have a temperature of 70 "and at the outlet, after quenching, the temperature may for example be in the neighborhood of 120 with the wire running at a speed of say some 700 ft. per minute. Thus any given length of wire coming into the apparatus Will, upon being drawn from the apparatus, be slightly longer, the difference for example in a typical case amounting to A%. Accordingly, the loop at the yoke will tend to increase in height, but the yoke switch, differential and motor system, as above explained, will operate from time to time so as to maintain the loop of substantially normal size, but without varying the speed of the wire through the apparatus to a suflicient degree to interfere with uniform annealing operations.

While the invention has been described in detail with respect to certain preferred embodiments it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention and it is intended to cover all such changes and modifications in the appended claims.

What is claimed is:

.1. Apparatus for heat treating Wire comprising in combination: a pair of spaced-apart electrical contacts for engaging the wire; means for continuously advancing the wire longitudinally past said contacts and in engagement therewith; a source of electrical current of a frequency of the order of 100,000 cycles per second or higher; and a hollow conductor member mounted in a generally coaxial position surrounding a substantial length of the wire as it passes between said contacts, said member being connected in a series circuit extending therethrough from one of the terminals of said source to one of said contacts along the wire to the other contact and to the other terminal of said source, whereby said hollow member acts' substantially to reduce the reactance in that part of the circuit comprising the Wire and substantially uniformly around on the surface of the wire to cause substantially uniform resistance heating thereof.

2. Apparatus in accordance with the foregoing claim 1 in which said hollow member is provided interiorly with high temperature resistance insulating means capable of supporting the heated wire without substantial damage.

3. Apparatus for heat treating wire comprising in combination a source of high frequency current, a pair of spaced-apart electrical contacts, means for passing said wire in contact with said contacts successively, and conductor means for supplying high frequency current from said source to said contacts, said conductor means including a hollow conductor portion which is substantially coaxial with at least a substantial portion of the length of wire between said contacts and is in series with the circuit of such Wire portion and thereby acting to reduce the reactance thereof.

4. Apparatus for heat treating wire comprising in combination a source of high frequency current, means for continuously and longitudinally advancing the wire, and means for passing said current through a length of said advancing wire, said means including a pair of spaced apart contacts engaging the wire and a conductor, a first portion of which conductor is coaxial with a portion of said length of wire and, a second portion of which is adapted to carry cooling fluid in thermal contact with said first portion.

5. Apparatus for heat treating wire comprising in combination a source of high frequency current, a .pair of spaced apart electrical contacts, means for passing a length of wire between said contacts, conductor means for supplying high frequency current to said contacts whereby said current passes through said length of wire thereby heating the same, means for quenching said Wire as it passes from one contact to the other just prior to reaching the second contact, and means for cooling said conductor means, said conductor means including a conductor, a first portion of which is coaxial with at least a portion of said length of wire, and said cooling means including means for passing coolant through a second portion of said conductor in thermal contact with said first portion.

, 6. Apparatus for heat treating wire comprising in combination a source of high frequency current, means for passing said current through a length of said wire, said means including a pair of spaced apart contacts engaging the wire and a conductor coaxial with at least a portion of said length of wire, and cooling means for cooling said portion of said length of Wire, and cooling means for cooling the portion of the conductor coaxial with said wire, said cooling means comprising a tube coaxial with said wire and said portionof said conductor and means for circulating cooling medium within said tube in direct contact with said portion of said conductor.

7. Apparatus for heat treating wire comprising in combination first and second spaced electrical contacts, means for controlling passage of the wire in engagement with said contacts successively, and conductor means for supplying high frequency current to said contacts, said conductor means including a conductor at least a portion of which is coaxial with at least a portion of the length of Wire between said contacts and said control means including means for withdrawing wire at normally substantially constant speed from said second contact while varying the rate at which wire is contacted with said first contact in response to longitudinal expansion of the wire between the contacts.

8. Apparatus for heat treating wire and the like comprising a pair of spaced apart electrical contacts, means for advancing the wire past and in engagement with said contacts successively, the apparatus being characterized by the provision of conductor means which is generally coaxially arranged about and in spaced relation to at least a substantial portion of the length of the wire between said contacts, and which conductor means forms a part of a circuit for conducting current from a high frequency source to said contacts and along the wire between the contacts.

9. Apparatus for heat treating Wire and the like comprising a pair of spaced apart electrical contacts, means for advancing the Wire past and in engagement with said contacts successively, the apparatus being characterized by the provision of conductor means which extends along in closely spaced relation about and in spaced relation to a substantial portion of the length of the wire between said contacts, which conductor means forms a part of a circuit for conducting current from a high frequency source to said contacts and along the wire between the contacts, and means for quenching the advancing heated wire in advance of the second of the contacts which it successively engages.

10. Apparatus in accordance with the foregoing claim 8 and in which said conductor means is constituted of two tubular portions surrounding the advancing Wire and with a space therebetween, and the terminals of a source of high frequency current being connected respectively adjacent the ends of said conductor portions at opposite sides of said space.

1.1. Apparatus for heat treating wire and the like comprising a pair of spaced. apart electrical contacts,

means for advancing the wire past and in engagement with said contacts successively, the apparatus being characterized by the provision of conductor means which is generally coaxially arranged about at least a substantial portion of the length of the wire between said contacts, and which conductor means forms a part of a circuit for conducting current from a high frequency source to said contacts and along the wire between the contacts, said means for advancing the wire being associated with control means for withdrawing the wire past the second of the contacts normally at substantially a predetermined speed while automatically adjusting the rate at which the wire is advanced past the first of the contacts responsive to longitudinal expansion of the wire due to the heating of same between the contacts.

12. Apparatus in accordance with the foregoing claim 11 and in which the wire advancing and control means includes a sheave engaged by the wire as withdrawn from the apparatus, another sheave engaged by the wire entering the apparatus, difierential gearing interconnecting said sheaves whereby the latter sheave is driven by the first, means for engaging the wire at a location on its path of travel between said sheaves, said latter means being constructed and arranged to adjust said diiferential gearing in one direction when the length of the wire between the sheaves is excessively shortened and in the other direction when the length of the wire between the sheaves is excessively lengthened, the differential gearing thereby acting to adjust the speed of said second sheave to maintain said wire length within desired normal 13. Apparatus in accordance with the foregoing claim 12 and in which the wire is engaged by tension control means shortly in advance of the first sheave and by other tension control means subsequent to the second sheave and prior to the means which engages the wire for adjusting the difierential gearing.

14. Apparatus in accordance with the foregoing claim 13 and in which the differential gearing is driven by an electric motor and the means for engaging the wire to control the differential includes a two-way switch for controlling the motor alternatively to adjust the differential in one direction or the other depending upon whether the wire length is greater or less than the desired normal length.

15. Apparatus for heat treating wire and the like comprising a pair of spaced apart electrical contacts, means for advancing the wire past and in engagement with said contacts successively, the apparatus being characterized by the provision of conductor means positioned in spaced relation to at least a substantial portion of the length of the wire between said contacts, said conductor means being so shaped as to provide a field between same and the wire which will be substantially coaxial with the wire, and which conductor means forms a part of a circuit for conducting current from a high frequency source to said contacts and along the wire between the contacts.

Otis etal. Mar. 31, 1942 Wade May 25, 1954

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