US3102060A - Method for the mechanical twisting of cold-formed profile steels - Google Patents

Description

Aug. 27, 1963 scHocl-l ETAL 3,102,060

METHOD FOR THE MECHANICAL TWISTING OF COLD-FORMED PROFILE STEELS Filed Dec. 14, 1959 3 Sheets-Sheet 1 T que a lied y w? 77 Fig.4 83

Aug. 27, 1963 H. scHocH ETAL 3,102,060

METHOD FOR THE MECHANICAL TWISTING OF COLD-FORMED PROFILE STEELS Filed Dec. 14, 1959 3 Sheets-Sheet 2 Fig.8

Aug. 27, 1963 H. scHocH ETAL METHOD FOR THE MECHANICAL TWISTING 0F COLD-FORMED PROFILE STEELS 3 Sheets-Sheet 3 Filed Dec. 14, 1959 SE 295% NE \s 3.5% S St QEQE ME 3 5E 6 9E SEE QE Etzg v $525 us SE gait m EQEEM 35E (E m Us 5i 5% $5 QRQE m3 W M s E2 c United States Patent 3,102,060 METHOD FOR THE MECHANICAL TWISTING 0F COLD-FORMED PROFELE STEELS Hans Sehoeh, Zurich, and Eugen Wyss, Adliswii, near Zurich, Switzerland, assignors to Ernst Schoch Actiongeselischaft, Basel, Switzerland Filed Dec. 14, 1959, Ser. No. 859,530 Claims priority, application Austria Dec. 15, 1958 6 Claims. (Cl. 148-12) The present invention relates to a method for mechanically twisting cold-formed profile steels, particularly reinforcementwires ofless than millimetres diameter for concrete, in which the twisting is effected continuously or in sections between rchamping members, which are axially slidable or at a fixed distance from one another, preferably at a high rate of deforming, as well as to a machine for carrying'out this method.

Such methods and machines suitable for carrying them out have already become known. They are based on the following facts:

The tensile strength of concrete amounts to about of the compressive strength thereof. The transmission of outer forces applied to the concrete is possible only over the contact surface. In order to increase the transmission of forces one has endeavoured to increase the capacity of adhesion by profiles deviating from the round profile and by means of knots. However, since the cross section area of a rod increases by the square, while the surface increases linearly, the exploitation of the steel'in reinforced concrete is limited to this profile.

The highest tensile stresses occur in prestressed concrete, the reinforcements of which compress the concrete zone under the permissible loading and thereby reduce the width of cracks, if any. Since with all steels the modulus of elasticity remains constant, higher strains result in higher stresses, and accordingly in otherwise equal conditions larger Widths of cracks occur in the concrete with slack reinforcements without prestressing. At the present state of prcstressing technique the economy is limited to special structures of abnormal width of span (bridges etc). For by far the greatest part :of :applica: tions of reinforced concrete slack reinfoncements are used, the thinnest reinforcement carrying the theoretically highest permissible loads and being able to be executed at present only with high carbon steels or alloy steels. The less expensive sorts of iron lean in carbon are out of the question with the permissible steel stresses, which are at present still limited.

With an increasing cross section area of the steel its capacity of adhesion drops under otherwise equal conditions. Even with cross section areas of 3.14 square centimetres the tensile strength and elastic limit of high grade steels can no longer be exploited.

A measure for the possibility of exploiting the steel is given by the theory of the compound characteristic, which is based on the ratio of the cross section area to the circumference of the steel, and permits big and large the following allowable stresses, provided one succeeded in developing for the thin cross sections inexpensive steel sorts lean in carbon content, having suflicient tensile strength, and for the thicker sorts in developing steels having suflicient capacity of adhesion.

"ice

Compound characteristics for normal and high grade concrete qualities, wherein:

Fe=cross section area of steel in square centimetres U circumfer ence of steel in eenthnetres.

Fe/U, cm. U/Fe, cm.- Roundprofile, 4 mm. diameter above 0.5 below 2 above 20 0.2 to 0.35 5 to 2.86 8 to 14 0.075 to 0.2 13.3 to 5 3 to 8 are:

Tensile Permissible strength of stress leg/em. steel to be guaranteed,

kg./cm.

The tensile strength of ordinary iron can not be exploited since owing to insufiicient surface area the capacity for adhesion no longer suflices for transmitting the force to be taken by the concrete. Wastage of iron is unavoidable, since, even with 1700 kg./crn. widths of gaps are to be expected which by far exceed the permissible limit of A millimetre.

With stabilised Martin steels as Well as with the cheaper twisted steels brittleness failures have become known. The twisting of harder steels having initial strengths of 6000 lag/cm? has been unsatisfactory so far. Owing to the great tolerances and differences in hardness as unavoidable with unstabilised cheaper steels great differences in helical pitch resulted when twisting. Now the unexploited heavier cross sections on the onehand and the qualitative additions required by the steel works for descaled bar material or alloy additions on the other hand have the .efiect that by farthe most unhomogeneoussorts of iron are allotted to reinforcements for concrete, and

that examination of the cross section areas, which are statically loaded, becomes compulsory. l For purpose testing by torsion covering all bars is suitable. Even with the low rate of deforming as usual at present pipes become apparent. Elimination of material liable to brittleness failure becomes however possible only at a high rate of deformation.

Practice has taught that twisting at a high rate of deforming-gives alreadyvaluable information about'liability to brittleness failure of cold twisted steels. For example the critical cross section can be determined depending on the preceding cold deformation. While at the same degree of deformation a 3.7 mm. diameter material may be faultlessly twisted at a high rate of twisting already a thickness of material of 3.00 mm. fails owing to contraction and rupture due to poor elongation.

Hitherto one has been of opinion that a conversion of the structure of steels lean in carbon modifying their properties of strength occurs only at an annealing temperature of 520 C., and that lower temperatures have little effect in this respect. By tests it has however been established that on the behaviour of such steels when twisted previous annealing at considerably lower temperatures has an extremely beneficial effect. This applies in the first place to cheaper steels cold-deformed by rolling or drawing. Particularly with wires of less than millimetres diameter, such as those which have proved most favourable for concrete reinforcements according to the compound characteristics stated hereinabove and which have been produced by cold drawing and/ or cold rolling a considerable improvement as regards brittleness failure is attained by treatment according to the present invention.

According to the invention these previously cold-formed work pieces are brought to a temperature between 360 and 450 C. by annealing, and are only subsequently twisted at a maximum temperature of 300 C.

In this manner it is possible to faultlessly twist even cheaper and non-stabilised steels having a comparatively low carbon content (below 0.25%), and to use the same in the reinforced concrete technique at very much higher permissible stresses than hitherto usual, i.e. for tasks for which hitherto more expensive steels of higher carbon content had to be used. Considerable economic advantages result from this fact.

In many cases it may be advantageous to quench the work piece between the annealing and the twisting and/ or to anneal the same a second time after the twisting at temperatures not exceeding 450 C.

It has moreover been shown that with some steels optimum values are obtained only when the effective period of preliminary annealing at the aforesaid temperature is rather long, namely between minutes and 4 hours.

If it is intended to attain a particularly close helical pitch of twisting, it is convenient to carry this twisting out in several stages, an annealing period at a temperature between 360 and 450 being interposed at any one time.

Hereinafter some test results will be described in more detail for the explanation of the surprising effect of the method according to the invention. In the following table the symbols mean this:

D diameter of the wire test specimen in millimetres T-annealing temperature in centigrades t -period of annealing in minutes.

p -breaking load in kilograms s/ -specific breaking load in kilograms per square millimetre n-number of twists at which breakage occurred (in bracketszlength of twisting in centimetres) From the rise of n to double and three times the value (table of test results) it can be clearly seen that an optimum of torsion resistance with a minimum drop in tensile strength is attained, in contrast to the opinions hitherto held, already at preliminary annealing temperatures between 360 and 450 C., namely with an annealing period lasting generally between 10 minutes and 4 hours. Only in isolated cases already a preliminary annealing period of a few minutes has been found as effective. The great scatter is obviously to be explained by the fact that cold-drawn and cold-rolled wires of different origin and of irregular crystal lattice were investigated.

Test results Investigation of the twisting breakage strength of coldformed steel wires of different diameters after preliminary annealing to 360 440 C.:

Drum tmin Tadegmcs pkg film/mm n (1 682 90. s 3 (a) loo i {644 84.2 10 1 I 565 73.9 a (b) 2 s 360 534 69.8 4 00 52s as. 0 16 g 508 a 544 1. 5 12 G0 360 5 5 6 7 240 520 68. 0 11 1 400 685 89. a 5 (d) 3.12 8 665 86.9 9 630 82.4 10 1 553 72.3 4 (e) 3.12 s 400 517 07. 6 9 so 510 66.7 13 1 660 86.2 s 2 054 85.5 9 (f) 312 4 630 82.3 10 60 604 78.9 s

The 1nvent1on moreover relates to a machine for carrying out the method described. This machine is characterised in that ahead of the twisting device an annealing furnace is arranged through which runs the work piece to be twisted.

After the twisting machine likewise a device for annealing the work piece may be provided.

Even when using comparatively thick profiles it is moreover convenient to provide a release mechanism on the twisting machine for preventing an excessive deformation of the profile at the moment of passing the maximum strengthening possible of the work piece. 7

Profiles of say medium dimensions are produced economieally often in the form of rolled wire at maximum rate of passing through. The corresponding yield of ring material is to be expected which as regards being true to caliber (unilateral rolling, flat rolling, excessive rolling etc.) no longer satisfies the normal commercial sales requirements and can be used only as a stretched wire in the reinforced concrete technique. In this branch trueness to cross section area as a statically loaded structural element is important, while the trueness to profile or caliber is pronouncedly irrelevant. However in order to discover faulty spots such as pipes, twisting is advantageous here too. Weak cross sections are then characterised by abnormally close helical pitch when twisted. In spite of the possible tolerances in helical pitch, steels which are too soft and have an increased liability to brittleness failure are excessively twisted (close helical pitch), while the harder and larger cross section area sections are deformed too little, so that the elastic limit and tensile strength do not undergo the increase desired.

This disadvantage is conveniently overcome in that when twisting section-wire at a high rate of deformation the section of the rod following at any time the section actually being twisted is sensed as regards its dimensions. In accordance with the effective dimension the twisting members are automatically adjusted and allow a practically homogeneous twisting event of rod material not true to caliber. Thereby also the liability to brittleness failure is reduced, and sections particularly liable to failure are eliminated by breakage at a poor deformation. Exploitation of the cheaper non-stabilised steels, which shown considerably higher deformation values of the elastic limit and tensile strength as compared with Siemens-Martin and stabilised steels, is no longer to be found objectional. For this purpose a sensing device is provided on the machine for ascertaining the tolerance profiles of the work piece. to be twisted.

In order that the invention may be clearly understood and readily carried into effect, an embodiment thereof will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 shows the twisting device in side elevation and partly in longitudinal section.

FIG. 2 is a plan view to FIG. 1 from above,

FIG. 3 is an end view of a detail of FIG. 1.

'FIG. 4 is a graph plotting a torque applied by a spring of the embodiment according to FIGS. 1 to 3 against the twisting torque,

FIG. 5 shows a modification of a detail in side elevation on a larger scale.

FIG. 6 shows wire coils and an annealing furnace on a smaller scale.

FIGS. 7 and 8 show a twisting device and annealing device in series in a diagrammatic general arrangement in two consecutive parts, FIG. 8 being the continuation of the right hand side of 'FIG. 7.

FIG. 9 is a graph plotting values of strength against the ratio of the helical pitch of twisting to the diameter of the twisted rod.

in the drawings, 1 denotes the fixed head and 2 the torsion head. 3 denotes the driving disc which is driven by a driving motor (not shown) by means of a belt 4 and sets the twisting head 2 in rotation. 5 denotes a worm coupled to 3 and having a bore 6 for allowing the twisted iron 7 to pass through it. 8 denotes a worm Wheel which is coupled with two crank discs 9' and .10 which are connected to a forward cross beam, 13, by means of tension bars d4, so that cross beams 12, and 13 can perform a reciprocating movement in the axial direction of the machine, the amplitude of which corersponds approximately to the diameter of the pitch circle d5 of the crank pin. To this diameter corresponds also the magnitude of the champing stretch of the material to be twisted between the end of the tongues of the twisting head. The cross beams 12 and 13 are guided in slide tracks M and 117 or 18 and 19, respectively. The same length of stroke (diameter of the crank pitch circle) applies also to a rear and forward dog 2d and El, respectively, which are fixedly connected to one another by means of the pull rod-22, 2t and 21 being in turn guided in further tracks 23 and 24 or 25 and 2.6, respectively. At the forward cross beam .13 engages a pawl 27 into the forward dog 21 and carries the same with it on its stroke towards the left until a fork 2'8 abuts a release member 29, disengaging the pawl 27 from 21, so that the forward dog 21 and the rear one, 29, coupled to it move very quickly into their extreme right position owing to the dropping of a weight 31, and remain there until also the forward cross beam 13 has reached the right hand side extreme position, and the pawl 27 consequently engages again on the forward dog 21 .and at the subsequent stroke to the left pulls the forwardand the rear-dog into the extreme left hand side position, the weight 31, which is connected to the rear dog 2% by a cable or chain 32, being correspondingly raised. It is clear that the two cross beams 12 and 16, provided the number of revolutions per minute of the crank discs 9 is not excessively high, always move somewhat more slowly to the right, than the dogs 20 and 731, which are connected to the dropping weight 31. The maximum speed of the cross beam 13 (for thin wires) amounts to 30 cm. in /2 second, i.e. 60 centimetres per second; the 30 cm. drop of the weight Ed is covered (apart from friction) in t= 0 .45 /h=0.45 /3=0.24 sec.: i.e. 125 centimetres per second, which is about twice as fast. What importance applies to this circumstance willbe explained later.

At every stroke (of 30 centimetres) to the right, equal to the diameter of the crank pitch circle, rollers 33 mounted on the connecting rods 1!} move about 30 centimeters to the right and thereby impart a counterclockwise movement to two clamping levers 34. Accordingly also the pin 35 moves to the right. To the pin 35 webs 36. are connected on which two obliquely extending tenwith'a member 38. On this member 38 a spring casing 39 containing a comprsession spring 40 is attached. A

pull rod 41 has at its right hand side end a plate 42. and

passes through the spring 40 in-such-a manner that the plate 42 abuts the right hand side end ofthe spring 40.

Into this pull rod 41a nut (not shown) is built which.

abuts the spring casing 39 and serves for preloading the, compression spring 40. Finally the pull rod 41 ends in a cross beam 43 to which itis attached fixedly.

A movement of the'pin 35 to the, right involves also,- generally speaking, a movement to the right of the cross beam 43. This movement is transmitted; in the same sense to a cross beam 44, since the beams 43 and 44 are fixedly connected to one another by two pull rods 45 and 46'. These two pull rods pass through compression springs 47 and -48, which abut a cylinder 49. This cylinder is pivotally mounted in two presser levers 50 and 51, which are journalled on a support 52.

From this description it follows, that firstly a movement to the right of the pin 35 involves loading of the compression springs 47 and 48' provided the presser levers 50 and 51 are held stationary for one reason or other.

Secondly a movement to the right of the pin 35 closes a toggle lever 53, since the pin 54 partakes in this movement to the right and imparts through link 55 a clockwise turning movement to the toggle lever 53, so that its clockwise direction, their noses 59 abut the tongues 6.0;

of the fixed head 1. When previously the iron to be twisted had been pushed through the, tongues 61 of the fixed head as well as of the twisting head, the. tongues 60 as well as 61 bear on the iron when the nose 59. moves.

to the right since the tongues are articulated on thrust links 62. Accordingly'the tongues 60 and 61, respectively, meet a'natural resistance, i.e. the levers 50, 51 cannot perform any further rotary movement in the clockwise sense. When in the meantime the pin 35 nevertheless -continues its movement towards the right, the comparatively weak compression springs 47 and;48 are forcibly loaded, i.e. these springs are loaded because upon a movement to the right of the pin 35 the cross beam 44 likewise moves to the right.

On the cross beam 44 a stepped wedge member 63, is

mounted. An opposite wedge member 64 is mountedonthe cylinder 49. From FIG. 1 it can be seen that the two stepped wedges are at a certain distance from; one another, when the crank pin 11a, as shown in FIG, 1, has just moved out of its left hand side dead centre position in the clockwise sense- (This position of the crank pin film has been chosen in the drawing in order to show how the pawl 27 is just being disengaged from the dog 21.) A movement to the right of the pin 35 accordingly in volves also an approach of the wedge member 63 towards the wedge member 64. I

As will be clear'from FIGS. 1 and 2, the wedge member -64 is guided slidably in an opposite member. 66 by means of a dove-tailjoint 65. A displacement of member 64 upward or downward is effected by alink 67, which is articulated to the bell crank lever -68. One legof lever 68 is connected to a pull rod 69; and the, latter isguided in the angle piece 70 and biased by a compression spring- 5t), 51 move in theanticlockwise sense.

Accordingly, when the pin 35 moves to the right, the wedge member 64 will continue moving up until the levers (50, 51) come to a standstill in their clockwise movement, since, as explained hereinabove, the tongues (id and 61, respectively, bear on the inserted iron to be twisted.

However, when the pin 35 continues moving to the right, the vertical up-movement of the wedge member 64 is terminated, but then a horizontal movement of the wedge member 63 towards the right takes place, i.e. the latter approaches more and more the wedge member 64, until eventually the two toothed steps of 63 and 64 engage one another, whereby even this movement is blocked. When the pin 35 nevertheless continues its movement to the right, there is nothing left but the pull rod 41 consuming part of the path of the compression spring 46}, i.e. loading the latter.

It has now to be stated that the two compression springs 47 and 48 are chosen so weak that they could never twist an iron, but can merely overcome existing frictions and load the spring 72 for the opening of the head. For the twisting operation proper in any case the very strong compression spring 40 has to be used.

'If the tongues 60 and 61 were already in contact with the iron, when the crank pin coming from the left hand side has not yet reached its right hand side dead centre position, i.e. if the strong compression spring 4% were already effective, the inserted iron would be pretwisted an amount not controllable by adjustment of the machine, until the crank pin He had reached its right hand side dead centre position. (The twisting period proper extends from the right to the left dead centre position in the lower 180 semi-circle.) The upper 180 semi-circle is reserved for purely a followup movement.

Moreover it should be remarked that any application of the strong compression spring 40 before the right hand side dead centre position of the pin 11a, i.e. before the worm gearing 5, 8 had been preloaded by the clamping lever 34, could destroy this gearing.

The machine has accordingly to be adjusted in such a manner that the force of the spring 40 is applied only shortly before the right hand side dead centre position of the pin 11a.

This is done in such a manner that a standardised gauge bar is inserted from the front into the fixed head, and a similar one from behind into the twisting head. 'Ihen by turning the driving disc 3 the position of the crank pin 11a slightly before the right hand side dead centre position is adjusted. The tongues es and 61 have now to bear on these gauge bars. Then the driving disc 3 is turned further until the crank pin 11a is accurately in its right hand side dead centre position. It is clear that the compression spring 40 then must have covered a part, although a small one, of its expansion path. This, however, could be the case only when the stepped toothings of the wedge pieces 63 and 64 interengage with one another. When these toothings are spaced apart a certain distance from one another, the position of the crank pin 11a slightly before the right hand side dead centre position has to be restored, and by tightening the nuts 73, 74 the cross beam 44 and thereby the wedge member 63 to be moved to the right until firstly the stepped toothings interengage with one another in the dead centre position of the pin 11a, and secondly the spring 44 has covered a part, although only a little, of its spring path. Since the inserted gauge bars have a certain importance as will be shown later, care has to be taken that the wedge member 63 in this dead centre position is approximately in the middle of the stepped toothing of member 64-. This can be attained by loosening or tightening the nuts 75. The compression spring 71 effects a compensation, in case the wedge members 63 and 64 interengage with one another, while the levers 5t) ,51 yet continue moving in the clockwise sense. This would be the case with a wrong adjustment of the wedge members.

The gauge bars have been used for attaining an adjustment of the machine to irons true to tolerances. When however the iron to be twisted has diameters below and/ or above the permitted tolerances, the device of the stepped wedges must compensate these deviations from correct dimensions.

This is done as follows:

it has been explained hereinabove that the two compression springs 27 and 28 have the function of placing the tongues on to the iron, in order to sense as it were the quality of the diameter of the iron. Moreover it has been stated that the wedge member 6-? moves right up when the two levers 56, 51 perform a large angular turn to the right, while this Wedge member is in the lowest position when the levers 5'0, 51 are in the extreme left hand side angular position. In other words: the angle a is indirectly a measure for the overall amount the wedge member he can move from one extreme position to the other. it is clear that the heads 1 and 2 are completely opened, when the levers 56, 51 are in the extreme left hand side position as approximately illustrated in FIG. 1, and that the heads 1 and 2 are completely closed, when the levers 56', 5} have covered the angle or and have reached the extreme right hand side position.

This interval between tongues completely opened and tongues completely closed may approximately form a measure of the amount permitted for the underand/ or over-dimensioning of the iron to be twisted. This is only approximately so, since the full range between completely open and completely closed cannot be exploited, otherwise it would not be possible to push the iron on in the position heads opened.

Assuming the iron had once an excess dimension of +1 millimetre over the standard diameter of the gauge bar, and another time a deficiency of 1 millimetre, the Wedge member must move from the middle position shown in Flu. l in the first case into the extreme low position, in the second case into the extreme high position, i.e. the deviation of i1 millimetre are a criterion of how far the excess or deficiency in dimension may reach in order to be safely coped with by the machine.

When these deviations in dimensions are kept (the excess dimension can inherently not be surpassed) it can be ascertained that both with an iron thicker than the nominal dimension as with an iron which is too thin the strong compression spring 4% is reloaded to the same extent when closing the heads, i.e. no pre-twisting takes place with too thick an iron until the pin 11a has reached the right hand side dead centre position, and too thin an iron is twisted exactly like the normal iron or too thick an iron beginning from the same moment, mainly from the accurate right hand side dead centre position of the pin 11a onward. Of course the rods or wires to be twisted may assume any excessand deficiency-values between the limits -':1 millimetre. The variation of these diameters is simply catered for by a different adjustment of the stepped wedge members.

It has initially been stated that the speed of the two dogs 28' and 21 carrying along the iron when moving to the right, i.e. by the proper following up by the dropping weight, which is twice the speed of the cross beams 12 and 13, has a great importance. For, if the iron would be made to follow up only at the speed of the cross beams 12 and I3, which depends on the crank drive, the feed of irons having an excess dimension would be braked by the tongues contacting the iron too early namely by the action of the sensing springs 47 and 4-8. With irons having an excess dimension of +1 millimetre this may be equivalent to a loss of in feed. It is therefore necessary to increase the feed-velocity of the iron to such an extent at least that the iron following up has reached its end position already when the heads 1, 2 just begin to perform their closing operation.

Now the importance of the illustration in FIG. 3 will be considered, which makes the opening of the heads dependent on the iron to be twisted itself, instead of on the machine. rotatably about the iron 7 lying in the axis of the machine, so as to be capable of turning a few angular degrees to the'right or to the left. On the fixed head 1 a rocker arm 76 with tension spring 77 is attached, see FIGS. 1 and 3. A pull nod 78 has a screw thread at its upper end, while the tapping is provided in a hand wheel 79, whichrests on a cross beam 80. By means of the hand wheel 79 the tension spring 77 can accordingly be loaded or relaxed. To the rocker arm 76 there is attached also an electrical contact piece 81, the opposite contact piece 8-2 of which is mounted stationarily on the machine. Rotary movement of the fixed head 1 in the counterclockwise sense closes the contacts 81, 8-2, while a movement in the clockwise sense opens the same. By closing the contacts 81, 82 the magnet 58 is energized, i.e. the heads 1 and 2 are opened. The machine performs the twisting in the counterclockwise sense. When a certain degree of twisting is exceeded, which may overcome the force of the adjusted tension spring 74, the heads 1, 2 are accordingly opened automatically.

Another device may be provided, by which the conditions according to FIG. 4 are taken into account. In FIG. 4 the increase in force when twisting an iron is plotted, i.e. the torque, which the tension spring 77 has to oppose, the torque gradually increasing during the twisting operation; FIG. 4 shows the rise of this torque. At the point $3 this torque has reached its maximum. In order fully to exploit this maximum by the machine, it is not sufficient to keep the point 83, since the maxi- In this case the fixed head 1 is mounted mum itself can not be ascertained mechanically, only r the torque at which this maximum is just being given up,

i.e. when the torque applied to the arm 76 just drops a small amount. At this very moment the heads are opened. According to a conventional diagram, FIG. 9, wherein the strength values of ausual steel rod are plotted against the twist, this is the point A.

Thereby a device has been provided, by means of which a rod is subject to the same rise in force over its entire length; it could be said that the iron had been twisted in conformity with its material.

In FIG. 5 one of the dogs 20 or 21 is illustrated. As long as the iron does not exceed, or drop below, a normal diameter dimension, i.e. as long as its diameters deviate from the nominal dimension only by the usual tolerances, the feed does not constitute any problem. The difficulties start here, too, only at the moment when the iron diameter exceeds or drops below the ordinary tolerances i.e. when substantial excesses or deficiencies in diameter occur. With 20, 21 in FIG. 5 the dog (feeder-device) is denoted which is symbolically indicated in FIG. 1 as being movable to-and-fro in the guide tracks 23 and 24- or 25 and 26, respectively. Fixedly screwed to it there is a wedge piece '84, along which its opposite member 85 may slide to-and-fro along its oblique face. The angle of this oblique wedge face is so selected, that the wedges are self-locking, i.e. for steel at about 15". On the end face of the member 85 there is a guide plate 86 connected to the member '85. On the plate 25 21 a lever '89 is mounted pivotally about a screw 90*, a strong compression spring (not shown) between the lever 89 and plate 20, 21 assuring a certain friction for the lever. Depending on the diameter of the iron 7, a pin 91 is inserted into one of the holes 92. A tension spring 93 tends to force the guide plate 86 always to contact the iron 7 snugly. On the oblique wedge face of the wedge piece 85 there is a ratchet toothing 94 into which may engage a pawl 95. This pawl '95 is pivotally mounted at 96, the pivot axle 96 being fixedly connected to the wedge piece 84. The" lever 89' is shown in the closed position of the dog; when the latter is opened, the lever S9 is turned about 15 to the left from the position illustrated.

For adjustment, this dog-mechanism is brought into the position illustrated relative to the abutments 98, 99

and 100', 101, the lever '89 recording about 15 with the gauge bar 7 inserted. When the pawl is in the position illustrated, i.e. out of engagement with the toothing 94, the guide plate 6 will likewise hear at once on the gauge bar under the bias of the tension spring 93. In this condition a screw 102 has to be positioned approximately in the middle of a slot 16,3. When this is not the case, the pin 91 has to be withdrawn and to be inserted into that hole 92 for which this standard starting position in attained. v

When the dog 20, 21 moves to its left hand side starting position at the left hand stroke of the machine, the lever 89 is brought into the closing position illustrated in FIG. 5, owing to the abutment ltll. The iron 7 is then clamped between the guide plates 86 and 87. In this position the abutment 99 has also moved a fork 97 of the pawl 95 to the right, i.e. it has brought the pawl 95 out of engagement with the toothing 94, so that the wedge piece 95 can move to the left under the bias of the spring 93; only thereby the clamping of the iron 7 between the guide plates 86, 87 has been made possible. When the plate 20, 21 moves into its extreme right hand side position, the abutment opens likewise the lever 89. Slightly prior to this the abutment 98 has brought the pawl into the closing position, so that the opening position of the device established by the lever 89 is maintained at least until the device has reached the extreme left hand side position. Accordingly the iron 7 is left untouched by the guide plates 86, 87 during the twisting period.

It is clear that the wedge pieces 84 and 85 perform the same function as regards irons having excess or deficiency of dimensions as the wedge members 63, 64 according to FIG. 1. When the iron is too thick as compared with the standard dimension, the wedge piece 85 lies more to the right of its middle position; when it is on the other hand, too thin, more to the left. Thereby an automatic consideration of excess or deficiency in dimensions is assured.

FIG. 6 shows wire coils which are annealed in the annealing furnace 111 to a temperature below 520 C. before the wires get into the twisting machine 114 (FIG. 7). From the twisting machine 114 the twisted work piece 115 gets according to FIG. 8 into a high frequency furnace 116, in order to be annealed again. The high frequency furnace is supplied with current by a high frequency generator 118 driven by an electric motor 117. On the high frequency furnace a cooling line 119 is provided.

The device according to FIG. 8 may be dispensed with, when the work piece is not to be annealed again after being twisted.

While we have described herein and illustrated in the accompanying drawings what may be considered a typical and particularly useful embodiment of our said invention we wish it to be understood that we do not limit ourselves to the particular details and dimensions described and illustrated, for obvious modifications will occur to a person skilled in the art.

What we claim as our invention and desire to secure by Letters Patent, is:

1. In a method of mechanically twisting workpieces consisting of cold-drawn profile steel having a carbon content below 0.25%, such as concrete reinforcement wires of less than 5 millimeters diameter, the steps of first uniformly heating the cold-drawn workpiece to a temperature of between 360 C. and 450 C. while moving it lengthwise through said high temperature zone, cooling said workpiece to room temperature while continuing its lengthwise movement, and twisting said workpiece to a helical permanent pitch a plurality of times while at said room temperature.

2. In a method of mechanically twisting workpieces consisting of cold-drawn profile steel having a carbon content below 0.25% and a diameter of less than 5 millimeters, particularly concrete reinforcement wires, the steps of uniformly heating said workpiece to a tempera- 1 1 ture of between 360 C. and 450 C., cooling said workpiece to room temperature and then twisting said work piece to a close helical permanent pitch a plurality of times while at said room temperature.

3. In a method of mechanically twisting workpieces consisting of cold-drawn profile steel having a carbon content below 0.25% and a diameter less than 5 millimeters, particularly concrete reinforcement wires, the steps of uniformly heating said workpiece throughout to a temperature of between 360 C. and 450 C., cooling said workpiece to room temperature and then twisting said workpiece to a close helical permanent pitch a plurality of times while at said room temperature between two clamping members which are arranged at a fixed distance from each other.

4. In a method of mechanically twisting workpieces consisting of cold-drawn profile steel having a carbon content below 0.25% and of a diameter less than 5 millimeters, particularly concrete reinforcement wires, the steps of uniformly heating said workpiece throughout to a temperature of between 360 C. and 450 C., cooling said workpiece to room temperature, and twisting said workpiece to a close helical permanent pitch a plurality of times with a high deforming speed between two clamping members which are arranged at a fixed distance from each other.

5. In a method of mechanically twisting workpieces consisting of cold-drawn profile steel having a carbon content below 0.25 and having :a diameter of less than 5 millimeters, particularly concrete reinforcement wires, the steps of uniformly heating said workpiece to a temperature of between 360 C. and 450 C., maintaining said temperature for a period of time between 10 minutes and 4 hours, cooling said workpiece to room temperature, and then twisting said workpiece to a close helical permanent pitch a plurality of times while at said room temperature.

6. In a method of mechanically twisting workpieces consisting of cold-drawn profile steel having a carbon content below 0.25% and having a diameter of less than 5 millimeters, particularly concrete reinforcement wires, the steps of uniformly heating said workpiece to a temperature of between 360 C. and 450 C., cooling said workpiece to room temperature, twisting said workpiece to a close helical permanent pitch a plurality of times while at said room temperature, and then re-heating said twisted workpiece to a temperature not exceeding 450 C.

References Cited in the file of this patent UNITED STATES PATENTS 167,766 Hunt May 1, 1875 1,095,324 Hall May 5, 1914 1,692,505 Hoffman Nov. 20, 1928 2,260,779 Hoffman Oct. 28, 1941 2,723,702 Wyss Nov. 15, 1955 2,816,052 Hoff et al Dec. 10, 1957 2,881,108 Nachtman Apr. 7, 1959 2,881,822 Henry Apr. 14, 1959 OTHER REFERENCES Journal of the Iron and Steel Institute, vol. 108, No. II, 1923, pages 273-283, pages 275-277 particularly relied Metals Handbook, pages 2 and 18, 8th ed., 1961.

ASTM Standards, pages 91-94, Part I-A (Ferrous Metals), 1946.

The Making, Shaping and Treating of Steel, pages 558- 559, 7th ed., 1957.

Claims (1)

1. IN A METHOD OF MECHANICALLY TWISTING WORKPIECE CONSISTING OF COLD-DRAWN PROFILE STEEL HAVING A CARBON CONTENT BELOW 0.25%, SUCH AS CONCRETE REINFORCEMENT WIRES OF LESS THAN 5 MILLIMETERS DIAMETER, THE STEPS OF FIRST UNIFORMLY HEATING THE COLD-DRAWN WORKPIECE TO A TEMPERATURE OF BETWEEN 360*C, AND 450Z:C. WHILE MOVING IT LENGHT WISE THROUGH SAID HIGH TEMPERATURE ZONE, COOLING SAID WORKPIECE TO ROOM TEMPERATURE WHILE CONTINUING ITS LENGTHWISE MOVEMENT, AND TWISTING SAID WORKPIECE TO A HELICAL PERMANENT PITCH A PLURALITY OF TIMES WHILE AT SAID ROOM TEMPERATURE.

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