US1095324A - Method of making reinforcing-bars. - Google Patents

Description

N. L. HALL. METHOD OF MAKING RBINPORGING BARS.

APPLICATION FILED NOV. 23, 1910.

Patented May 5, 1914.

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UNITED STATES PATENT OFFICE.

NEWTON L. HALL, 0]? LOS ANGELES, CALIFORNIA.

METHOD OF MAKING BEINFORCING-BARS.

Specification 01 Letters Patent.

Patented May 5, 1914.

Application filed November 28. 1910. Serial No. 593,946.

To all whom it may concern:

Be it known that I, NEWTON L. HALL, citizen of the United States, residing at Los .-\ngeles, in the count-y of Los Angeles and Stateof California, have invented certain new and useful Improvements in Methods of Making Reinforcing-Bars, of which the following is a specification;

My invention relates to a novel method for forming reinforcing rods such as are used m concrete beams or hke structures.

The primary object of my invention is to provide a method whereby a reinforcing rod or bar may be produced having a very great tensile strength, a very great elastic limit and a very firm bond with the concrete in which it is embedded, the method producing a rod having a constant area of cross-section throughout its length and a uniform tensile strength throughout its length.

A further object of the invention is the provision of a simple and relatively cheap method whereby a reinforcing rod or bar will be given a varying twist or pitch while the bar is undergoing the twisting process.

The objects ofmy .invention are attained by varying the temperature of the reinforcing bar at a number of )oints along its length, preferably .while t e bar is being twisted, and these objects are specifically attained by applying relatively low heat at a number. ofpoints along the length of the bar at the time it is being twisted, thereby apparently changing the molecular constitution of the metal and slightly toughening it at these )ints, or for a distance on each side thereof, causing the rod or bar to twist less easily at these points and hence increasing the pitch of the twist, and by thus changingthe molecular consistency of the bar at these points or sections proportionately compensating for the reduced number of twists in'these portions of the bar.

My invention is shown in the accompanying drawing wherein:

Figure l is a plan view of atwisting ma.- chine whereby bars may be twisted in conformity to my method. Fig. 2 is a sectional perspective view of a concrete beam or like member showing a reinforcing rod or bar after being twisted according to my method Fig. 3 is an enlarged cross section through one of the electric heaters. Fig. 4 is a cross section on the line 4-4 of Fig. 2. Fig. 5 is a cross section on the line ;35 of Fig. 2.

Jorresponding and like parts are referred to m the following description and indicated in all the' views of the accompanying drawings by the same reference characters.

A reinforcing bar or rod 3, shown in full size in Fig. 2, according to my process, is formed of an ordinary stock rod or bar of cold-twisted steel. \Vhile I do not wish to limit myself to the specific variety of steel, it seems best to use for this purpose a steel having high degree of ductility with. a minimum of brittleness.

It is a well known fact in concrete engineering that a cold-twisted rod or bar is the best form. of reinforcement for the following reasons. It is a deformed rod or bar and therefore under stress will not slip relatively to the concrete as an undeformed rod is likely to do. While the rod is deformed yet it is made from ordinary stock and re- .quires therefore no special machinery for rolling it, as is the case with deformed rods which are formed with bonding, projections or indentations. Further than this, the rod has a uniform or constant area of cross section throughout its length, which is not the case with the last named reinforcing rod. A mechanical bond is formed between the cold twisted bar and the concrete, a mechanical bond which does not sacrifice the quality or economy of the bar since it requires no excess metal. Deforming the plain bar changes the fiat faces into concave spiral grooves into which the concrete readily flows. Such a bar therefore has a perfect mechanical bond continuous throughout the entire length of the bar and more than suflicient to develop the full strength of the steel.

Twisting the rod cold gives a test of the quality of the steel along the entife length of the rod and constitutes an automatic inspection. Inferior steel if cold-twisted reveals all its defects and any variation or imperfection of the steel is bound to show up in the process of twisting. If a hard or soft spot be anywhere in the steel, the bar cannot be twisted with perfect uniformity and therefore the irregularity is detected and the bar discarded. Furthermore, cold twisting tends to remove scale and oxids, thereby permitting a closer bond with the concrete. Cold twisting insures safety from brittleness and also increases the elastic limit of the rod and its ultimate strength. The uniformly twisted rod, though having the above named advantages over other deformed rods, is, however, lacking in a most important respect. :It tends to twist or unscrew within the concrete in which it is embedded when the concrete is placed under strain. The concrete tends to move along a spiral unobstructed channel and the twisted bar and concrete therefore tend to turn relatively to each other. This is be cause the pitch of the screw thread formed by the twisting of the bar is continuously uniform for all parts of the rod. If, however, this p-itch be varied at a. number of points along the bar or rod, the bar cannot turn relative to the concrete any more than could a screw having a varied pitch be turned in or out of the wood in which it was embedded.

It is obvious that the bond between the rod and the mass in which it is embedded will be still better if the twisted rod, instead of having its pitch varied at a number of points, has a pitch which is continuously and gradually changed, and better yet if the pitch of the twist is gradually changed through a plurality of successive sections.'

The preferable form of my invention consists therefore in the method of making a twisted rod in which the pitch is constantly and gradually changed or varied at successive portions along the length of the rod orbar.

In Fig. 2 the rod 3 at A to B has a uniform pitch which gradually increases from B to C. This pitch gradually decreases from C to D and then gradually increases again from I) to E. A reinforcing bar so constructed gives a union between the steel and concrete which is intimate and tenacious along its entire length and in which the bond is uniformly strong throughout the entire length. The reinforced beam is therefore uniformly strong. There is no weakest link in the chain which has to be allowed for. The reinforcing bar, as above described, has a uniform cross section; has uniform elongation and elasticity, and the strength and elastic limit of the bar is increased by twisting; the bar is tested by the twisting and scale is removed; the bar affords acontinuous bond not located or concentrated at any one point, and no material is displaced merely for the purpose of bonding. Furthermore, there is no violent distortion of the metal and no sharp corners are formed which extend across the line of tension. The pitch variation of a bar, as above described, throws stresses into the bar, which produce an internal shearing stress within the beam and this pitch variation also interrupts the course of any break of adherence between the concrete and the steel. sectional shape constantly changes. while the sectional area remains the same at any point on the bar, as seen in Figs. 4 and 5.

With a variably twisted bar the cross,

Furthermore, the deformity in the bar is distributed and no shoulders are formed on the bar to produce air voids when the concrete is placed around the bar.

It is to be noted that a defectively twisted bar, or a bar which shows defects under twisting, cannot be said to embody the features of my bar, for the reason that such a bar is not in condition for use and does not have a uniform strength along its entire length. The bar would have a uniform strength for a certain dist anre and the remainder of the bar which might have a constantly varying twist would not be twisted to a sufficient extent, nor would the remainder of the twist of the bar be varied for different sections.

It would be possible to form the bar above described by engaging it at a number of separated points along its length by independent twisting heads, clutches or other twisting devices and rotating said twisting devices at diflerent relative speeds. Such a process, however, would be open to a num ber of objections. It would be relatively expensive for one thing. and for another those parts of the bar having a. relatively high pitch would not be as strong as those portions of the bar having a relatively low pitch, and hence all portions of the bar would not have a uniform tensile strength or elongation. i

I have discovered that if the molecular constitution of different portions of the bar be changed so as to create a variable resistance to the turning action along different portions of the bar, I can produce a twisted bar having a variable pitch, while at the same time retaining the uniformity of tensile strength and elongation which is so much to be desired; and further I have discovered that if a portion or portions of the bar or rod be submitted to a relatively slight heat, so slight as not to soften the bar, preferably while the bar is being twisted, the portions so heated will become relatively tough and thus resist the torsional strength placed upon them. It may be objected that this toughening of a portion of the bar or rod will destroy the very uniformity of strength which is particularly desirable, but this is not the case for the reason that though the heated portion of the bar or rod takes less twist than the less heated portions, proportionately to the difference in temperature, yet the heated portions of the bar become toughened a proportionate degree. The two factors, therefore balance each other. In other words, while I reduce the twist at one or more portions of the bar. thereby apparently reducing its strength. I compensate for this by proportionately toughening the bar at these points by means of heat. It will be seen, therefore, that my improved reinforcing element consists of a bar having a uniform cross section in which the decrease in strength caused by the increase in pitch of the twist at points along the rod or bar is compensated for by an increased toughening at these points.

While I have described the effect of the heat as causing a molecular change in the constitution of the bar resulting in toughening or hardening the bar, I may say that this is-to some extent theoretical. however, been proved in actual practice that bars variably twisted in the manner above described, have a uniform tensile strength and uni'formelongation along their entire length, which goes to prove that the slightly heated portion orvportions of the bar are toughened, as,'if they were not so toughened or hardened they would undoubtedly be less strong than those portions of the bar having more twists to the foot.

he rationale of the action above set forth may be stated as follows: Assuming a bar heated in separate sections by the application of heat at separated points, the heat of the bar not being raised above the hardening point, then if the bar be subjected to a uni- .form twisting force, the amount of the resultant twist in the bar or rod will vary inversely as the tortional resistance of the separate sections, but the effect of the twist on the tensile strength of the rod will vary directly as the amount of twist. It follows, therefore, that the lessening of the twist at the slightly heated and hardened sections will be balanced by the increased strength of these sections due to the heating. In other words, a uniform twisting force applied along the whole length of the rod will have a permanentlyuniform effect on the tensile strength thereof, and the lesser twist at the heat hardened portions will have a proportionately greater permanent, effect.

It will also be plain to those'skilled in the art'of twisting rods or bars that when the bar is held at one end and a twisting force applied to the other that that portion of the bar at the twistin head of clutch will be the first to twist and that the twist will travel gradually along the rod or bar to the fixed end thereof. If heat should be applied simultaneously at a number of points along the bar while it is being twisted, it will be obvious that those portions of the rod which are twisted latest will receive more heat, priorto being twisted, than those portions which are first twisted, and thus the desired uniformity would'be destroyed. It will also be plain that were the heat continued after that portion of the rod to which the heat was applied had been twisted, this portion of the rod would be overheated with like effect. Furthermore, it is not advisable to subject the rod to a greater degree of heat than isabsolutely necessary to cause the proper variation in the pitch of the twist.

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This degree is comparatively slight, the temperature of the bar being raised to a degree only slightly above that bearable to the hand or roughly from 175 to 250 Fahr.

It is therefore necessary in the carrying out. of my process that successive portions of the bar shall be raised to the proper temperature as the said portions begin to become twisted and shall be lowered to the normal degree after they have become suflicientl y twisted. Therefore, my method contemplates primarily raisin the temperature of successive portions 0 proper degree at the time that each portion of the bar is being twisted, and lowering the tem erature at successive portions of the bar as t e twist proceeds along the bar.

. It'is plain that my method may be carried out in several ways, as by placing a heater adjacent to the bar, starting the twisting of the bar and successively shifting the heater to successive portions of the bar as the twisting proceeds, or I may use a plurality of heaters and successively increase the amount of heat given off thereby as the twisting proceeds and successively decrease said heat, or I may provide automatic means for energizing or denergizing the heatin element or elements so as to raise the bar to t e proper temperature at the time the twist reaches successive portions of the bar or successively decrease the temperature in the successive portions as the twist passes.

lVhile I do not wish to limit myself to any special mechanism for twisting the bar and causing the variation in the pitch of the twist, I have shown in Fig. 1 a very simple and efl'ective mechanism for accomplishing this object. For this purpose I use an ordinary twisting machine comprising a fixed gripping member 4 and a rotatable gripping member or clutch 5. There is no need of specifically describing these gripping members or-clutches inasmuchxas they are well known in the art and the, specific details thereof do not constitute any part of my invention.

Rota-table with the gripping member or clutch 5 is a screw threaded shaft 6 carrying upon it a coactingscrew threaded traveler 7 which as the member (3 is rotated in one direction or the other moves toward or from the clutch 5., The clutch 5 may be driven in any suitable manner as by a gear 8. In the illustration in Fig. 1 I have shown a pair of twisting devices located parallel to each other, the gears S of which are driven from a common power shaft 9. This is .purely, however. for illustrative purposes.

Disposed in the spacebetween the gripping member t and the clutch 5 are a plurality of heaters which may be either spaced equally or unequally as desired, and which may be either fixed in position or shiftable longitudinally. The rod to be twisted, desigthe bar to the nated 3, has one of its ends placed Within the gripping member 4: while the other end is engaged by the clutch The clutch 5 is then rotated through the power shaft 9 and as the bar becomes twisted heat is successively applied to successive portions of the bar. As a simple means for heating the bar and one that may be easily controlled, I have provided a plurality of electric heaters, designated 10, one of these heaters being shown in section in Fig. 3. The casing 11 of the heater is composed of nonconductive and'refractory material and is formed in two sections hinged to each other at 13. These sections are provided on their inner faces with mating electrical heating devices, which when the sections are closed entirely surround the bar 3. Preferably, these heating devices consist of heating coils let the coils of one section of the heater being so connected to the coils of the other section of the heater when the sections are closed, that current will pass into one of the binding posts and out of the other binding post 15. As shown, the completed heating coil is formed in two separate sections, the wires of one section of the coil contacting with the wires of the other section of the coil when the sections are closed. I do not wish to limit myself to any particular construction of this heater. The construction of heating coils being well known in electrical art, no extended description of these heating coils is necessary. It s suiiicient if coils are provided whereby the passage of electric current through the coils will slightly raise the temperature of the bar 3. Each of the heating coils is connected in circuit with a source of energy and with a switch carried by the traveler 7. As illustrated in Fig. 1, each coil is connected to a wire 16 which extends toward the clutch end of the twisting apparatus and is provided at the end with a terminal 17. The terminals of ,the wires are arranged in regular order. Thus the terminal of the wire extending from the heater (1 is disposed nearest to the clutch member 5, while the wire extending from the heater 6 is disposed next in succession and farther away from the clutch member and so on for all the heaters 11. (Z, c, f, {7, and 7t.

Mounted upon the traveler 7 is a contact finger 18 which is connected in circuit with p a source of energy. The heating coils are shown as connected by a return circuit to the source of power. The finger 18 may be of a length sufficient to contact with a plurality of the contacts 17.

As the clutch 5 is rotated the screw threaded member 6 will also be rotated and the traveler will begin to move in a direction away from the clutch member 5. The.

first terminal 17 to engage with the contact 18 will be the terminal from the heater a and this contact will be made only a sufli-- cient time before the twist in the rod 3 travat this portion of the bar for a suitable. length of time in consequence of the length ot' the finger 18. The finger meanwhile contacts with the next succeeding contact 1.7. and the heater 1; is energized at the time or sutliciently before the twist has reached the heater 1). Thus the contacts 17 are successively engaged by the contact 18 in correspondence with the travel of the twist along the bar and the circuit is completed through each of the heaters successively for a length of time depending upon the rate of movement of the traveler 7 and the length of the contact finger 18.

The time at which each heater shall be energized and the length of time during which it shall remain energized, of course, depends upon the circumstances of any particular case, the condition of the metal being twisted and the rate of twist. WVhile I have shown what I regard as a thoroughly eflective and simple device for making and breaking the circuit successively through successive heaters, I do not wish to be limited to these particular constructions inasmuch as other constructions might be used which would accomplish the same end.

In the practical operation of my device the heaters are all opened. The rod to be twisted is then inserted in the gripping devices 4 and The heaters are then closed and the clutch 5 rotated at a proper rate of speed until the twisting of the bar is completed. Under these circumstances, and with the heaters successively energized as before described, a bar will be produced having substantially the appearance of the bar shown in Fig. 2. It is to be noted that if those portions of the bar which are heated are insulated from the remaining portions of the bar, that is, provided with means to prevent the extension of the heat along the bar on either side of the heaters, the change in twist will be relatively sudden, but that if the heat is allowed to be distributed gradually along the bar on'either side of the heaters, the twists will gradually change and the ratio between the decreased ductility of the bar and the increased toughness will gradually and proportionately vary.

It will be obvious that the heaters may be made to cover longer or shorter sections along the bar so as to provide a bar in which -definite sections are variably twisted. By

providing a heater which has a maximum heating effect at one point in the bar and which gradually distributes this heat on either side of this point, I can form a twisted bar in which the twist increases in degree 01'' pitchalo'ng the length of the section, then diminishesin degree of twist along the next section, then again increases and again diminishes etc. throughout the length of the bar. In this form of bar the degree of twist constantly and gradually varies in definite sections of the bar.

While I have described the bar as being heated at separated points and simultaneously twisted, I wish it understood that I do not wish to limit myself to the order of these steps. It is obvious that the bar might be first heated at separated points to a requisite degree and then twisted. I do not regard this, however, as the best way of making the bar as the heating cannot be as easily regulated as it can where the heating is done simultaneously with the twisting. Furthermore, such a process requires two separated steps, whereas in the preferred method of applying my invention both steps take place at the same time.

What I claim is 1. The method of forming twisted members havin different portions thereof varying in pitch, consisting in raising the temperature of a portion of the member to a point sufficient to increase the resistance to torsional stress of said portion,,and twisting the heated and unheated portions of the member simultaneously.

2. The method of forming twisted members havingldifi'erent portions thereof varying in pitc consisting in raising the temperature of separated portions of the member to a degree sufiicient to increase the resistance to torsional stress of said portions, and simultaneously twisting the heated and unheated portions of the member.

3. The method of forming twisted members having different portions thereof varying in pitch, consisting in subjecting the member to a torsional strain to twist the same, and while the member is being twisted, subjecting the separated portions thereof to heat suflicient to increase resistance to tor- .sional stress at the points heated.

. 4. The method of forming twisted bars having different portions thereof varied in pitch, consisting in raisin the temperature of separated portions of the bar to a degree suflielent to increase the resistance to torsional stress of the heated portions, and simultaneously twisting the bar along its whole extent.

5. The method of forming twisted bars having different portions thereof varied'in pitch, consisting in twisting-the bar along its whole length, and simultaneousl hardening separated portions of the bar w ereby to cause the hardened portions of the bar to re sist the twisting action, thus rendering said portions of less pitch than the unhardened portions of the bar.

6. The method of forming twisted bars having different portions thereof varied in pitch, consisting in twisting the bar along its whole length, and simultaneously wit the twisting action heating the bar at separated points in progresslve order corresponding to the travel of the twist along the bar.

7. The method of forming twisted bars having different portions thereof varied in pitch, consisting in twisting said bar and as the twist travels'along the bar raising the temperature of the bar at separated points to a degree suflicient to increase the resistance to torsional stress at these points.

8. The method of forming twisted bars having different portibns thereof varied in consisting in relatively rotating the opposite ends of the bar in opposite directions to twist the bar along its entire length,

and simultaneously with said twisting action heating the bar at separated points in successive order corresponding to the travel of the twist along the bar.

9. The'method of forming a twisted bar of uniform strength having different portions thereof varied in pitch, which consists in twisting said bar so as to rovide separated portions along the bar having less twist than intervenin portions of the bar and compensating or the decrease in strength at the first named points by toughening the bar along the less twisted sections.

10. The method of forming twisted members having different portions thereof varying in pitch, consisting in changing the temperature of a portion of the member to a point suflicient to change the resistance to torsional stress of said portion, and twisting the changed and unchanged portions of the member simultaneously.

11. The method of forming twisted members having different portions thereof varying in pitch, consisting in subjecting the member to torsional strain to twist the same and while the member is being twisted changing the tem erature of separated portions thereof su ciently to change the resistance to torsional stress of said portions.

In testimon whereof, I afiix my signature in-presence 0 two witnesses.

NEWTON L. HALL. [1 s.]

Witnesses:

W. N. Woonson, FREDERIC B. WRIGHT.

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