US3398258A - Apparatus for improving the tensile properties of wire - Google Patents

Description

Aug. 20, 1968 Filed Sept. 21, 1965 J. M FA RLANE APPARATUS FOR IMPROVING THE TENSILE PROPERTIES OF WIRE Fig.

5 Sheets-Sheet 1 HUVEUT'OR.

TANES Nc. FAR LANE Agent Aug. 20, 1968 J. MCFARLANE 3,398,258

APPARATUS FOR IMPROVING THE TENSILE PROPERTIES OF WIRE Filed Sept. 21, 1965 5 Sheets-Sheet 2 INVENTOR.

.TA MES He. FARLANE 1nd 'K- Agent J. M FARLANE Aug. 20, 1968 APPARATUS FOR IMPROVING THE TENSILE PROPERTIES OF WIRE Filed Sept. 21, 1965 5 Sheets-Sheet 5 LIJIJI [IIIl/EN'T'OR. James m Fnnume and KM Aug. 20, 1968 J. MCFARLANE APPARATUS FOR IMPROVING THE TENSILE PROPERTIES OF WIRE Filed Sept. 21, 1965 5 Sheets-Sheet 4 Kw-KM Aug. 20, 1968 Y J. M FARLANE 3,398,25g

APPARATUS FOR IMPROVING THE TENSILE PROPERTIES OF WIRE Filed Sept. 21, 1965 5 Sheets-Sheet 5 luvs-T RI TANES MC FARLAME KJ-KLLM Agent United States Patent 3,398,258 APPARATUS FOR IMPROVING THE TENSILE PROPERTIES OF WIRE James McFarlane, Penn, Wolverhampton, England, assignor to G.K.N. Somerset Wire Limited, London, England, a British company Filed Sept. 21, 1965, Ser. No. 488,929 9 Claims. (Cl. 219-155) This invention relates to apparatus for effecting permanent elongation of wire made in martensitic forming steel, so as to improve the creep resistance of the wire under tensile loading, thereby enabling the wire to be especially eifective as prestressing element in concrete structures as well as a tensile element in other structures demanding a high tensile stress, e.g. suspension bridge cables. By the expression martensitic forming steel, as used herein, is meant steel that transforms into martensite when cooled rapidly from a martensitic forming temperature range. The wire, the creep resistance of which is improved by apparatus according to the present invention, may be in the form of a single length of wire or alternatively it may be in the form of a plurality of side by side lengths of wire, eg as wire in the form of helically wound strand or rope.

The invention is concerned with apparatus for effecting permanent elongation of martensitic forming steel wire and which apparatus is of the kind (herein called the kind specified), comprising one or more rotary members around which the wire is passed in such a manner as to apply tension to the wire, means for supplying a heating current to and along a predetermined length of the wire which is under tension, so as to heat such length to a temperature such that at the tension applied to the wire permanent elongation thereof is effected, said heating current supply means comprising at least one rotary member onto or off which the wire under tension passes, which rotary member is provided with a commutator segment and an associated current supply brush connected to a heating supply circuit.

For convenience in description the said length of wire will be herein referred to as the length of wire to be heated even though in respect of the length of wire passing onto a rotary member, at least some heating has already taken place.

Hitherto difliculty has been encountered in the operation of apparatus of the kind specified by reason of sparking and in some cases even arcing at the positions where the length of wire to be heated passes out of and into contactwith the periphery of the rotary members therein described.

This difiiculty arises from the fact that hitherto in apparatus of the kind specified, the heating current has been supplied to the rotary members referred to in such a manner as to be free to pass to the periphery of these members at the positions where the wire is passing off and onto the members, and by reason of the natural tendency for the heating current to take the shortest possible path, an appreciable portion of the entire current is supplied to the length of wire to be heated at the position where the wire is moving into or out of contact with the rotary member concerned as it passes onto or off such particular member.

The resultant sparking and arcing is liable to be of considerable magnitude, because to obtain the required heating temperature to ensure permanent elongation of the wire a relatively high heating current density must be employed, which hitherto has been of the order of 900 amperes, and for future developments, currents as high as 4000 to 5000 amperes are envisaged.

This parking or arcing is especially liable to happen where the wire is in the form of helically wound strand ice or rope so as to be of non-uniform configuration peripherally.

Such sparking or arcing can also occur as a result of shunt how of current between the wire and the adjacent periphery of the rotary member so as to flow circumferentially therein and then back from the rotary member to the wire even where the latter is in pressure engagement with the rotary member. This is because the crosssection of the wire engaging periphery of the rotary member is relatively large. This sh-unt flow is especially liable to produce sparking or arcing in the case of strand or rope, in that it occurs between circumferentially spaced positions at which the helical windings of the strand or rope engage the rotary members locally.

This sparking or arcing in addition to being liable to cause damage to the surface of the wire, which is undesirable irrespective of the intended use of the wire, is particularly serious in the case of high tensile wire formed of steel of the class specified, because the sparking or arcing, locally and momentarily, raises the temperature of the steel to such a high value as to produce martensite by subsequent immediate rapid conductive cooling to the neighbouring mass of steel which has not been so locally heated. As a result, the wire is locally brittle and its required tensile properties are seriously impaired.

The present invention has for its object the provision of an improved arrangement which enables the foregoing difiiculties to be avoided.

With the foregoing object in view, the present invention provides apparatus of the kind specified, which is characterised in that each rotary member which is provided with a commutator segment, has its wire engaging periphery formed as a set of commutator segments spaced around the circumference of the associated rotary member, with adjacent segments insulated from one another, and the associated current supply brush comprises at least one current carrying brush, each arranged to make contact with the commutator segments, at a circumferential position such that each segment which is in electrical contact with a current carrying brush, is out of electrical contact with that portion of the wire engaging periphery of the rotary member onto or off which the length of wire to be heated momentarily passes, the arrangement being such that the current flows between each brush and only that commutator segment or segments which is electrically connected to a part of the periphery of the rotary member with which the wire is momentarily in pressure engagement, and each commutator segment being of such a small circumferential length as to provide in parallel with the length of wire in engagement with its periphery a shunt resistance of value great enough as to preclude sparking or arcing by shunt current how of magnitude great enough to result in local formation of martensite.

In practice it is found that shunt current flow of magnitude great enough to result in martensite formation in the particular wire processed may be avoided by making the circumferential length of each segment at its Wire engaging periphery not greater than six times the diameter of the wire for which the apparatus is designed.

With the present invention, the heating current is prevented from flowing from the Wire to the periphery of the rotary member adjacent to the point of entry or exit of the wire from said rotary member, i.e. the position at which the wire passes onto or off the periphery of the member. This is because the commutator segments are connected only to that portion of the wire engaging periphery of the rotary member with which the wire is already momentarily in pressure contact. Thus the commutator segments which are momentarily adjacent the point of wire entry or exit are not in contact with the current supply brush or brushes, and are electrically insulated from the heating current circuit. The heating current apart from any shunt current of magnitude small enough to be tolerated is accordingly forced to flow along the wire beyond the point of wire entry or exit, so as to pass to or from the periphery of the rotary member concerned at a position where the wire as a result of the tension therein, is in pressure engagement with the rotary member, ie at a position where there is no likelihood of any arcing or sparking taking place.

The invention is illustrated in the accompanying drawings wherein:

FIGURE 1 is a side elevation of one form of apparatus embodying the invention.

FIGURE 2 is a plan view of the apparatus depicted in FIGURE 1.

FIGURE 3 is an end elevation looking in the direction of the arrow 3 in FIGURE 1.

FIGURE 4 is an interrupted sectional view to an enlarged scale on the line 44 of FIGURE 1.

FIGURE 5 is a side elevation to an enlarged scale of part of the construction shown in FIGURE 1, showing the arrangement of the current carrying brushes.

FIGURE 6 is a sectional view on theline 66 of FIGURE 5, showing to an enlarged scale certain details of one of the current carrying brushes.

FIGURE 7 is a diagrammatic side elevation of the construction shown in FIGURE 1, illustrating the arrangement of the electrical connections to the current carrying brushes.

FIGURE 8 is a detailed view of part of FIGURE 7, showing more clearly the arrangement of electric resistance in the current supply leads to the commutator segment brushes.

Referring firstly to FIGURES 1 to 3 of the drawings, the apparatus there illustrated comprises a frame 10 on which is supported for rotation about mutually parallel horizontal axes two rotary members 11, 12, each in the form of a pulley having a plurality of V section grooves 13. The two members are of the same peripheral diameter and are mechanically coupled together so as to rotate in the same direction and at the same peripheral velocity. For this purpose the two rotary members 11, 12 are provided at one side thereof with a sprocket wheel 14, the two sprocket wheels being connected by a sprocket chain 15.

The rotary member 11 which is disposed adjacent one end of the frame 10 is power rotated from an electric motor 16, which drives the main drive shaft 17 carrying sprocket wheel 18, which is connected through sprocket chain 19 not shown, to sprocket wheel 20 connected to the rotary member 11.

At the end of the frame 10 furthest from rotary member 11, so as to be on the side of rotary member 12 furthest from member 11, is a third rotary member 21 in the form of a pulley having a single peripheral V section groove 22 around which is passed the length of wire to be heated.

The wire 23 which is to be permanently elongated passes first of all around rotary member 12, then around member 11, then back to member 12 then back to member 11 and so on so as to pass successively between mem bers 12 and member 11 around one of the grooves 13 and each of these members in turn, in such a manner as to have an arc of contact with each groove of approximately 180". The grooves 13 are formed to ditferent diameters as shown, eg in FIGURE 4, so that the diameter of the several grooves of the members 11 and 12 around which the wire 23 passes increases progressively in the direction of wire advancement to apply progressive increase in tension to the wire. In the case, however, of the groove 13a of member 11, which is the last but one of the grooves of progressively increasing diameter, the wire passes directly from this groove 13a along wire path 23a to rotary pulley member 21, and from the latter along wire path 23b back to that groove 13b of member 11, which is the last of the succession of grooves which are of progressively increasing diameter in the direction of wire advancement. Thereafter the wire passes successively between members 11 and 12 around grooves 13, some of which are of progressively decreasing diameter in the direction of wire advancement, so as progressively to reduce the tension in the wire passing out of the apparatus, while the final grooves 13 in the direction of wire advancement are of the same diameter and act as a draw olf capstan for applying suflicient tension as to pull the wire through the apparatus. The wire initially passing onto member 12 is fed thereto from a supply reel not shown through pay off guide 24 and around pre-tensioning reel 25 mounted for free rotation about a vertical axis, and being provided with a brake 26, from which reel 25 the wire under a certain initial tension provided by the brake is fed to member 12.

Thus the length of wire to be heated, ie that designated 23a and 23b, passes from groove 13a of rotary member 11 around rotary pulley member 21 and back to groove 13b of member 11 without in so doing passing around member 12, and this is ensured by mounting member 21 for rotation about an axis which is inclined to the horizontal, as shown in FIG. 3, in such a manner that the portions of the periphery of member 21 onto and off which wire lengths 23a and 23b pass are situated in vertical planes, each lying beyond the corresponding end faces of member 12.

For supplying heating current to the length of wire 23a and 23b to be heated, members 11 and 21 are each provided with two sets of current carrying brushes; 27, 28 in the case of member 11; and 29, 30 in the case of member 21.

Each set of brushes 27, 28 are respectively adapted to supply current to the V section grooves 13a and 13b of rotary member 11, for which purpose each of these two grooves 13a and 13b is formed in a corresponding current conducting ring 31, 32 respectively, each ring being formed as a number of commutator segments 33, there being for example in one preferred arrangement as many as or even segments to each ring, where this has a diameter of about 2.3 metres.

In order to prevent undesirably large shunt flow of the heating current from the wire to the commutator segments along the periphery thereof parallel to the length of the wire with consequent risk of martensite being formed as above described, it has been found that the circumferential length of the wire engaging periphery of each commutator segment 33 should not exceed six times the diameter of the wire. If this length is exceeded the area of contact between the wire and the V groove of each segment 33 becomes so great as to encourage undesirably large shunt currents.

Where, as is the case with the preferred operation of the apparatus, the wire is in the form of helically wound strand or rope formed of steel of the class specified, the periphery of this will engage each of the two sides of V grooves 13a, 13b at circumferentially spaced positions corresponding to the axially adjacent crests of the wires or strands respectively forming the strand or rope to be elongated. Usually such axially adjacent crests are spaced by a distance which is just over twice the diameter of the strand or rope and by making the circumferential length of each segment 33 not more than four times the strand or rope diameter it is ensured that the strand or rope is in contact with each side of the V groove at two positions only, thereby making the shunt current of a mag nitude which in practice will be of about of the heating current which is a very small and quite acceptable figure. If the above ratio figure of circumferential length to strand or rope diameter is reduced to not more than two, each side of the V groove will be in contact with one crest only per segment, and the shunt current elfect is then eliminated or virtually eliminated, so that this latter ratio value of segment length to strand or rope diameter is the theoretical maximum value desired.

The two rings 31, 32 are mounted on adjacent corresponding ends of rotary member 11 by forming each end adjacent its periphery with a right angle section groove 34, the axially extending face of which is provided by an annular flange 35. Each of these flanges is formed with a circumferentially extending row of tapped holes 35, through which and the segments 33 pass bolts 37 to secure the segments in position.

Between each segment 33 and each of the two faces of the angle section recess 34 is a layer of electrical insulating material 38, while similar insulating material is provided between the bolts 37 and the segments 33, so that each of the two rings 32 providing the grooves 13a and 13b are electrically insulated from the main body of the rotary member 11.

The circumferential length of each segment constituting each ring 32 is such that a small air gap 39 is provided between circumferentially adjacent segments. Thus each segment is electrically insulated from adjacent segments in addition to being so insulated from the member 11.

Each segment 33 presents an outer axially directed fiat brush engaging face 40.

The wire receiving groove 22 of rotary pulley element 21 is provided in an annular ring 32 built up from a number of segments electrically insulated from one another and from the main body of the element 21 in like manner to the rings 32 of rotary member 11, and one of the two axially directed end faces 41 of this ring 32 of member 21 is of flat configuration, so as to be adapted to engage the associated current carrying brushes 29, 30.

The construction and arrangement of each set of current carrying brushes associated with the rotary members 11 and 21 will now be described. First of all referring to FIGURE 1, it will be seen that the length of wire 23a advances out of contact with groove 13a of member 11 substantially at the peripheral position A, and advances into contact with groove 22 of member 21 substantially at the peripheral position B.

Similarly, the length of wire 23b which is also heated, leaves groove 22 of rotary member 21 substantially at the peripheral position C, and passes to groove 13b of member 11 substantially at the peripheral position D. The two positions A and B are made slightly variable in a peripheral sense because the length of wire 23a passes over a tension measuring device consisting of a pulley 42, the wire engaging periphery of which is shown in FIGURE 1, so that the parts of the wire length 23a respectively approaching a leaving pulley 42 are at a slight inclination to one another, so that pulley 42 is subjected to a loading proportional to the tension in this length of wire 23a. The pulley 42 is supported against such loading by some form of measuring device such as an accurate spring balance, whereby the maximum tension to which the wire is subjected may be observed.

The brushes 27, 28, 29, 30 are circumferentially spaced from the above mentioned positions, A, D, B, C, respectively, by a distance in each case greater than the circumferential length of each commutator segment 33, so that the particular segment, the groove of which is momentarily in contact with the wire at positions A, B, C, D is at such time out of direct electrical connection with any of the adjacent current carrying brushes. This ensures that at each position A, B, C, D where the lengths of wire which are being heated pass into and out of pressure contact with the sides of the V shaped grooves 13a, 13b and 22 there is no sparking or arcing at all between the surface of the wire and the sides of the V shaped grooves apart from that resulting from any shunt current effect.

Each set of brushes comprises a number of separate brushes 43 each mounted in a brush holder 44 carried on but electrically insulated from an arcuate shaped mounting bar 45, the opposite ends of which are connected by brackets 46 to suitable supports on the machine frame 10. Each holder 44 carries an axially extending brush 43 which engages the adjacent end face of the corresponding segmental ring 32.

The ararngement is such that several individual brushes 43 are provided in each set, with circumferentially adjacent brushes spaced apart so as to be out of direct electrical contact with one another, with each brush being provided with its supply lead 47 to the current supply bus-bar 48, of which a pair are provided in the case of rotary member 11, one on each side thereof, and a single bus-bar in the case of rotary member 21.

Each brush 43 has a width measured in a circumferential direction which does not exceed and preferably is less than the circumferential length of each commutator segment. Thus each br-ush can never engage more than two commutator segments at any one time.

The several brush leads 47 of each set of brushes incorporate resistances 49 of differing electrical resistance such that the individual brush 46 of each set which is circumferentially nearest to point A, B, C, D as the case may be is associated with a brush lead 47 of greater electrical resistance, the electrical resistance of each brush lead 47 decreasing progressively in a circumferential direction from the point of wire engagement or disengagement A, B, C, D as the case may be.

By reason of the foregoing and the fact that each brush can never engage more than two commutator segments at the same time, the natural tendency of the heating current to take the shortest path between each set of brushes and the length of wire 23a or 23b is taken care of, and by suitably selecting the value of each brush lead resistance 49 having regard to the diameter of the wire to be heated and the heating current selected, it is readily possible to ensure that the current flow between the wire and the periphery of the rotary member is substantially uniform over a portion of the Wire of substantial length corresponding to the overall circumferential length of those circumferentially adjacent segments 33 which are simultaneously in contact with the various brushes constituting each set of brushes. Thus, an undesirably high local current flow between the wire receiving grooves and the adjacent surface of the wire with consequent overheating thereof is avoided.

This is of particular importance because the wire Will in practice he of circular or substantially circular form in cross-section, and the grooves 13a, 13b or 22 are made of V form in cross-section in order to minimise slip between the wire and the rotary members, and thus develop the required tension in the length of wire to be heated. Thus, the area of contact between the grooves and the wire is small. The provision of these differential resistances 49 also ensures that each individual brush will carry the maxim-um current that it is designed to carry, whereby the brushes are utilised in the most economical manner.

As shown in FIGURES 7 and 8, the several bus-bars 48 are connected to supply leads 50 themselves connected to a current supply transformer, not shown, which may be arranged to provide a heating current of the order of 50 volts and a magnitude which may be of the order of 4,000 to 5,000 am-peres or more, if desired. The particular voltage and current is dependent on the size, i.e. cross-sectional area of the wire, e.g. strand or rope to be processed.

If desired, for this latter reason, the number of individual brushes in the two brush sets 28, 30, may be less than those in the brush sets 27, 29. This is because the temperature of the advancing length of wire to be heated necessarily increases progressively in passing from position A to position D. Thus the mean electrical resistance of the steel Wire which increases with increase in temperature is greater for length 23b than for length 23a. Accordingly, the current passing along length 23b is less than for length 23a. Thus if all of the brushes are to be loaded to the same maximum current density and thus utilised in the most economical and efficient manner, less brushes are required for sets 28, 30 than for sets 27, 29. Thus, with twenty brushes at each of these latter sets there may be only fourteen brushes at sets 28, 30.

If desired, the rotary pulley member 21 need only be provided with a single set of brushes instead of two sets as shown, in which case the resistance of each lead must be adjusted from -a maximum at either end of the single set of brushes to a minimum at the mid-point.

Preferably, the length of heated wire 23b just before passing onto the rotary ember 11 is cooled in the known manner, so as to prevent undesirable heating of the rotary members 11, 12, as well as to prevent the wire from assuming a permanent curved configuration corresponding to the curvature of the members 11, 12, as the wire will tend so to do if it passed thereon while still hot.

The apparatus operates to effect a controlled permanent elongation of the wire, while completely avoiding any arcing or sparking of magnitude enough to form martensite at positions between the surface of the length of Wire which is being heated and the periphery of the associated rotary members, 11 and 21 through which the heating current passes.

If desired, the wire may pass in figure of eight fashion between the two rotary members 11, 12, so as thereby to increase the circumferential length of each member which is in engagement with the length of wire passing therearound, in which case it is necessary for the two members 11, 12 to be mechanically coupled together in such a manner as to rotate in opposite directions at the same peripheral velocity instead of rotating in the same direction.

The present invention is not limited to apparatus for improving the tensile properties of wire for structural purposes. Such wire with improved tensile properties may be used for other purposes where high tensile properties are of especial importance; for example, brake cables, control cables, overhead conductor wire supports.

What I claim then is:

1. Apparatus for effecting permanent elongation of martensitic forming steel wire, so as to improve the creep resistance thereof, said apparatus comprising rotary means adapted to apply tension to .a length of wire passing over said rotary means in engagement therewith, means for supplying a heating current to and along a predetermined length of the wire which is under tension, so as to heat such length to a temperature such that at the tension applied to the wire permanent elongation thereof is effected, said heating current supply means comprising a rotary member having a wire engaging periphery formed as a set of commutator segments spaced around the circumference of the associated rotary member, with circumferentially adjacent segments electrically insulated from one another, a current supply means associated with each set of commutator segments and comprising at least one current carrying brush, each arranged to make contact with the commutator segments at a circumferential position such that each segment which is in electrical contact with a current carrying brush, is out of electrical contact with that portion of the wire engaging periphery of the rotary member onto or off which the length of wire to be heated momentarily passes, and each commutator segment being of such a small circumferential length as to provide in parallel with the length of wire in engagement with its periphery a shunt resistance of value great enough as to preclude sparking or arcing by shunt current flow of magnitude great enough to result in local formation of martensite in the steel wire.

2. Apparatus according to claim 1, wherein in association with each set of commutator segments there is a plurality of brushes each having a circumferential width not exceeding the circumferential length of each of the commutator segments, and the current supply path to each of the several brushes from the current source is of different electrical resistance such that the maximum electrical resistance is provided in the current path to the brush which is circumferentially nearest to the point of initial engagement or disengagement of the wire from the rotary member and is least in respect of the brush furthest from such point of engagement or disengagement, so that the current flow between the commutator segments and the wire surface is substantially uniform along the length of the wire.

3. Apparatus for effecting permanent elongation of martensitic forming steel wire, so as to improve the creep resistance thereof, said apparatus comprising a pair of rotary members each provided with a plurality of peripheral wire engaging grooves around which the wire is adapted to pass from one rotary member to the other, said grooves in the direction of advancement of the wire being of progressively increasing diameter up to a predetermined maximum diameter, so as to apply a progressively increasing tension to the wire passing therearound, and being thereafter of progressively decreasing diameter in the direction of wire advancement, a third rotary member having a peripheral groove around which the length of wire is adapted to pass from the last but one groove of progressively increasing diameter to the groove of largest diameter, means for supplying heating current to the length of wire passing from between said two grooves last mentioned, said means comprising forming each of said two last mentioned grooves and the groove of the third rotary member as a set of commutator segments spaced around the circumference of the associated rotary member, with circumferentially adjacent segments electrically insulated from one another, a current supply means associated with each set of commutator segments and comprising at least one current carrying brush, each arranged to make contact with the commutator segments, at acircumferential position such that each segment which is in electrical contact with a current carrying brush, is out of electrical contact with that portion of the wire engaging periphery of the rotary member onto or off which the length of wire to be heated momentarily passes, and each commutator segment being of such a small circumferential length as to provide in parallel with the length of wire in engagement with its periphery a shunt resistance of value great enough as to preclude sparking or arcing by shunt current flow of magnitude great enough to result in local formation of martensite in the steel wire.

4. Apparatus according to claim 3, wherein in association with each set of commutator segments there is a plurality of brushes each having a circumferential width not exceeding the circumferential length of each of the commutator segments, and the current supply path to each of the several brushes from the current source is of different electrical resistance such that the maximum electrical resistance is provided in the current path to the brush which is circumferentially nearest to the point of initial engagement or disengagement of the wire from the rotary member and is least in respect of the brush furthest from such point of engagement or disengagement, so that the current flow between the commutator segments and the wire surface is substantially uniform along the length of the wire.

5. Apparatus according to claim 1, comprises two rotary members each provided with a plurality of wire engaging grooves around which the wire is adapted to pass from one rotary member to the other, with the grooves being of progressively increasing diameter up to a predetermined maximum diameter, so as to apply a progressively increasing tension to the wire passing therearound, and being thereafter of progressively decreasing diameter in the direction of wire advancement, a third rotary member having a peripheral groove around which the length of wire to be heated passes from the last but one groove of progressively increasing diameter to the groove of largest diameter, said last mentioned two grooves being provided adjacent opposite ends of one of the said two rotary members, and being each constituted by one of said sets of commutator segments, and having in association therewith one or more current carrying brushes, the third rotary member around which the length of wire to be heated passes being formed with a peripheral wire engaging groove constituted by a further set of commutator segments and having in association therewith one or more current carrying brushes, the arr angement being such that in the operation of the apparatus, the current passes between the third rotary member and each of the two commutator segments constituting the said two grooves of the one rotary member.

6. Apparatus according to claim 5, wherein the two rotary members providing the several wire engaging grooves of progressively increasing and progressively decreasing diameter are each mounted for rotation about spaced parallel axes, characterized in that the third rotary member around which passes the length of wire to be heated has its axis of rotation inclined to the mutually parallel axes of rotation of the other two rotary members, the arrangement being such that the plane of rotation of the two grooves of largest but one and largest diameter at opposite ends of the one rotary member are each respectively aligned in the position at which the length of wire respectively passes onto and oil? the third rotary member.

7. Apparatus according to claim 1, wherein the rotary members are provided with wire engaging grooves of V form in cross section with the circumferential length of the wireengaging part of each commutator segment being not more than six times the diameter of the wire to be elongated.

8. Apparatus according to claim 7, for use in improving the tensile properties of martensitic steel wire in the form of helically :wound strand or rope, wherein the circumferential length of the wire engaging part of each commutator segment is not more than four times the diameter of the wire to be elongated.

9. Apparatus according to claim 7, for use in improving the tensile properties of martensitic steel wire in the form of helically wound strand or rope, wherein the circumferential length of the wire engaging part of each commutator segment is not more than twice the diameter of the wire to be elongated.

References Cited UNITED STATES PATENTS 3,182,167 5/1965 McBrien 219-155 X RICHARD M, WOOD, Primary Examiner.

'B. A. STEIN, Assistant Examiner.

Claims (1)

1. APPARATUS FOR EFFECTIG PERMANENT ELONGATION OF MARTENSITIC FORMING STEEL WIRE, SO AS TO IMPROVE THE CREEP RESISTANCE THEREOF, SAID APPARATUS COMPRISING ROTARY MEANS ADAPTED TO APPLY TENSION TO A LENGTH OF WIRE PASSING OVER SAID ROTARY MEANS IN ENGAGEMENT THEREWITH, MEANS FOR SUPPLYING A HEATING CURRENT TO AND ALONG A PREDETERMINED LENGTH OF THE WIRE WHICH IS UNDER TENSION, SO AS TO HEAT SUCH LENGTH TO A TEMPERATURE SUCH THAT AT THE TENSION APPLIED TO THE WIRE PERMANENT ELONGATION THEREOF IS EFFECTED, SAID HEATING CURRENT SUPPLY MEANS COMPRISING A ROTARY MEMBER HAVING A WIRE ENGAGING PERIPHERY FORMED AS A SET OF COMMUTATOR SEGMENTS SPACED AROUND THE CIRCUMFERENCE OF THE ASSOCIATED ROTARY MEMBER, WITH CIRCUMFERENTIALLY ADJACENT SEGMENTS ELECTRICALLY INSULATED FROM ONE ANOTHER, A CURRENT SUPPLY MEANS ASSOCIATED WITH EACH SET OF COMMUTATOR SEGMENTS AND COMPRISING AT LEAST ONE CURRENT CARRYING BRUSH, EACH ARRANGED TO MAKE CONTACT WITH THE COMMUTATOR SEGMENTS AT A CIRCUMFERENTIAL POSITION SUCH THAT

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