US1899138A - Means for eliminating internal stresses in wire - Google Patents

Description

Feb. 28, 1933. A. v. DE FOREST MEANS FQR ELIMINATING INTERNAL STRESSES IN WIRE Original Filed Feb. 17., 1928 IN VEN TOR.

Alf/ ed l/deFonesz' A TTORNEY proved Patented Feb. 28, 19331- UNITED,

PATENT OFFICE ALFRED V. DE 'FOREST OF SOUTHPORT, CONNECTICUT, ASSIGNOR '10 AMERICAN CHAIN COMP-ANY, INC; A CORPORATION Oil? NEW YORK I I MEANS roe nijminnrinenvrmnnn :STBESSES nrwmn Original application filediebruary '17, 1928, SerialNo. 255,153, new Iatent No. 1,787,936, dated J'anuary 6,v

- 1931. Divided and-this application filed January 16, 1929. Serial No. 332,762. 1

The present invention relates ,to an immeans for eliminating internal stresses in wire, and is a division of a copending application Serra-1N0. 255,153, filed ,February 17,1928. t l x a A specific application of the present invention is to be found in the cables'of suspension bridges. It is customary to'yfofrm such cables of ..a number of strands, each strandhbeing, formed of a continuous wire which is carried. by a trolley back and forth from anchorage to anchorage "until the defsired number'o'f wire lengths for afis trand have been spun. Each wire length is subjected to tension as'soon as it is'spun and is then looped aboutan anchorage shoe. Q When the strand has been completed, the anchorage shoe is inserted between a pair of eye bars or other anchorage means and attached thereto, after which-it is drawn back by any suitable means such as an hydraulic j ackto adjust the strand as awhole to [a predetermined tension or sag. Y

However, internal stresses are introduced into the wire by bending it around an anchorage shoe, which stresses are by no means negligible even in cold drawn wire and which, in the ease of 'heat-treated'wire, are so serious as to preclude the use offbeattreated' metal for the tension members of suspension bridges.

elasticity and high yield point as compared with cold worked products. '-When such wire is bent around relatively small diameters such as the shoe at the anchorage of thesuspension bridge, a very high stress is introduced by this bendingin the outside fibres of the wire. If, as would usually be the case, this bend were beyond the elastic limit ofthe wire, the outside fibres would already be loaded with their-fullest capacitybeforeany reduce the load on" the wire at'tbis pointto The essential quality 'of heat-treated metal is its high modulus of the ,same'figure as that in the straight portions of the'wire. A more specific object ofthe invention is to provide means for forming an anchorage loop in a wire in which the outside fibres of the wire, are permanently stretched and the inside fibres are permanently'compressed, so that the forces across any section will be zero, as they arein the straight portionof the wire. In other words,

elastic limit will be temporarily lowered so that it may becsubjected' to a considerable amount of deformation, and after this deformation an aging effect will take place which will in time restore the full elastic properties of the wire. that heat-treated steel may have 'its'elastic' It is well known" l6 limits temporarily'lowered by subjecting the material to over-stressing and that the full elastic properties will be'restored' in time by an aging effect. 7

Another object of the invention is to provide means for applying a protective metallic coating on the loop end of the strand,this coating being applied in molten conditionat a temperature that will insure a certain amount of heat treatment to eliminate the in- I ternalstresses which may be presentqin the wire and tohasten the aging effect which will restore the wire to its full elastic properties.

With these and other objects in view which will appear hereinafter, the invention will now be described in connection with the accompanying drawing and thereafter the novelty andscope 'ofthe invention will bepoint ed outin the claims.

In the drawing: Figure l is a somewhat .diagrammatical plan View of a strand anchorage illustrating themeansused for preforming aloop ina wire before it is shoe.

, l' d t th ho app 1e 0 e anc rage vt Fig. 5 is a view in cross-section of a ortion of the anchorage shoe taken in the p ane 55 of Fig. 4% and v1ewed in the dlrection of the arrows.

The simplest method of preforming a loop in the wire before the wire is applied to the anchorage shoe, is to seize the wire length ad jacent theanchorage shoe in a suitable'clamp,

'after it has been subjected to the requisite preliminary tension, and then to form a loop in the wire by bending it around a stud or pulley of smaller diameter than that of the shoe. The wire is thus bent beyond its elastic limit, permanentlystretching the outside fibres and compressing the inside fibres, and the diameter ofthe stud is such that when the wire is released from the stud it will spring out to a diameter equal to that of the shoe, having taken a permanent set of such diameter. The internal stresses are thus overcome and, in time, the wire will resume its original elastic limit which was temporarily 1owered by bending it beyond its yield point. The preformed loop is then transferred to the anchorage shoe.

Another process of preforming a loop of requisite diameter is illustrated in Fig. 1. In this figure, which is a plan view, an anchorage shoe is shown which is formed with a peripheral channel or groove to receive Wires 11 of the strand. The shoe is rounded at the rear end about which the wires are to be bent, that is, the left-hand end as viewedin Fig. 1. The shoe 10 is temporarily secured in fixed position by a lug or other means introduced through an opening 12 therein, said means not being shown in the drawing.

As a wire length is spun across thebridge to the anchorage, it is subjected to tension by any well known means and then is clamped adjacent to the shoe 10 by means of a clamp 15. This clamp may be of any desired form, but is here shown as consisting of a pair of jaws 13 and 14:, the former being stationary and engaging one side of the wire while the j aw 14: slides in the frame of the clamp and may be adjusted against the opposite sid of the wire by means of a bolt 16.

Adjacent the shoe there is a fixed stud 17, which carries a pulley 18. Mounted on the stud 17 is an arm 19 formed with a handle 20 and on the arm 19 are three rollers 21. These rollers are relatively staggered so as to engage opposite sides of the wire 11 and pr0- duce reverse bends therein after the manner of a wire straightener. Thus, after thewire has been clamped between the jaws 13 and 14, it is threaded between the rollers 21, and the handle 20 is then operated to swing the arm 19 with the rollers about the stud 17 The rollers bend the wire beyond its elastic limit and as the handle 20 is swung around the stud 17, the wire 11 is formed into a loop which passes about the pulley 18. In this manner the wire 11 is bent into a loop which takes a permanent set, because of the over stressing produced by the rollers 21. Tl e preformed loop is then taken out of the rollers 21 and off the pulley 18 and transferred to the adjacent shoe 10. The wire length beyond the 100 may then be conveyed, by the trolley, to t e opposite anchorage of the bridge, where,by the same process a loop is preformed inthe wire before it is applied to the anchorage shoe at that end. Thus the strand is built up of a number of lengths of wire, each having a preformed loop therein in which'the internal stresses have been eliminated.

Another system is shown in Fig. 2 in which corresponding numerals are used. to indicate corresponding parts. In this instance, however, instead of preforming loop, the wire is subjected to treatment which temporarily re duces its elastic limit. Adjacentthe shoe 10 is asupport 25 on which is mounted number of rollers 26. These rollers are arranged in an upper and a lower series, somewhat like the rollers of a wire straightener, so as to produce bends in the wire. However, the rollers at the rear end of the support 25, that is the left hand end, as viewed in Fig. 2, are closer together, producing sharper bends in the wire than those near the right hand end. There is thus a tapering off of the bending operation so that the wire, after passing through the series of rollers, is left free of internal stresses. Preferably, the support 25 is made in two parts which are hinged together at one end as indicated at 27 and are clamped together at the opposite end by means of the clamp 28. The upper series of rollers 26 is supported on the upper section of the support 25 and lower series on the lower section. The wire is then laid on the lower rollers and the two sections are swung together and clamped, causing the upper rollers to bite into the wire and press it over and between the lower rollers. The support 25 is then crawn toward the left as Viewed in Fig. 2 so as to sub ject the wire to repeated bendings of such magnitude as to exceed the elastic limit of the wire and by. such working temporarily to reduce brittleness or hardness of the wire. This done, the wire is seized in the clamp 15, after which the support 25 is opened. Then the wire may be readily bent around the shoe 10 without introducing any serious internal stresses therein. An advantage of thus working the wire before forming the loop is that the exact radius over which the wire is bent an aging process takes place which restores is of no particular importance and there is no danger of weakness due to inexactness of the location of the tangent between the strain portion of the wire and the beginning of the curvature. After the loop has been formed,

thefull elastic properties to the wire.

Fig. 8 shows still another method of temporarily reducing the elasticlimit of that portion of the wire which is to be looped about the anchorage shoe. On the anchorage shoe 10 is mounted a form 30, such as a pulley,-

about which an incoming wire is bent. The wire, after passing about the form 30, is attached to a tension means 31, such as a block and tackle, by which the wire may be drawn up to the desired preliminary tension so that it will lie parallel to other wires in the strand. The diameter of the form is such that the wire on being drawn thereabout is bent beyond its elastic limit to such an extent as to take a fixed curvature corresponding to the curvature of the shoe 10. After the wire has been given this curvature, it is held in advance of the form 30 by the clamp 15 to 'maintain said preliminary tension in the main body of the wire while tensioningmeans 31 is released. The curved portion of the wire is then transferred to the shoe '10.

The length of wire subjected to the bending process by drawing it about the form 30 is considerably greater than the length of the curved portion of the shoe about which the wire loop is to be fitted. It is necessary, therefore, to eliminate the curvature in that part of the wire which extends beyond the curved part of the shoe. This is done by passing the wire, after it leaves the form 30, in a reverse bend about a second form 32, also mounted on the anchor shoe. The form 32 is so located with respect for form 30 that the length of wire from the point at which it begins to bend about the pulley 30 to the point at which it begins to bend about the form 32 equals the length of the curved part of the shoe.

The curve thus formed in the wire corresponds not only to the curvature of the shoe but also the length of said. curvature.

' Furthermore, the pulley 30 is so positioned that the wire will becur-ved in the proper location to coincidewith the curved part of the shoe.

Fig. 4 shows the shoe turned at right angles and secured between a pair of eye bolts 33 by which the shoe is seized and drawn backward to subject the strand as a whole tothe requisite tension. A stud 34 passes through the eye bolts and also through the opening 12 The shoe and strand, loop are'then heated and molten lead is poured into the peripheral recess around the wires 11. The lead is main-' tained at such temperature and introduced and said tensioning means.

After this, the strand may be subjected-to the necessarytension by drawing on the eye bolts 33 so as to raise the strand to the predetermined sag of the finished.cable.-

While particular reference has been made herein to the application of the present in vention to bridge strands and cables, and to high'tens'ile' heat-treated wire, obviously the invention is not limited to suchwire nor to such application, but can .be used in the loop- I ing of anytensi'on member in rod orwire form and in which it is desirable to eliminate I internal stresses. j Having thus described my invention, what. I claim and desire to protect by Letters Patentisr i 7 1. Means. for forming at one end of a run of wire whose other end is anchored,a stress free anchorage loop to fit a seat in an anchorage, which means comprises a form, means for drawing the wire topredetermined tensionabout the form to produce a loop, and means for temporarily clamping the wire in advance of the form afterthe-wire has been free anchorage loopto fita curved seat inan I anchorage, which means comprises ;aformadjacent said seat'and about which said wire may be bent, tension means for subjecting the wire to a predetermined tension by drawing it about the form, said formbeing ,of such shape and at such location with respect to the seat that the wire drawnabout the form will assume a fixed curvature substantially equal to that of the seat and corersponding in location to that of these'at when the wire is H under said tension, and a second form between the first mentioned form andsaid tensioning means about which the wire maybe reversely bent to straighten that portion of the wire which lies between said second form 3. Means for forming'at one end of a run of wire whose other end is anchored, a stress free anchorage loop to fit a curved seat in an anchorage shoe, which .meanscomprises a 5 form mounted. on the shoeandabout which the said wire maybe bent to form a loop, means for subjecting the wire to a predetermined tension by drawing the wire about the form, said i'orrn being of such shape that the wire drawn thereaboutwill assume a fixed curvature substantially equal tothat of the seat and at alocation corresponding to that of the seat when the Wire is under said tens sion, and a second form also mounted on the shoe between the first form and the tensioning means and about which the wire may be reversely bent to straighten that portion of the wire which lies between the second form and the tensioning means. J

4. Means for forming at one end of a run of wirewhose other end is anchored, astress free anchorage loop to fit a curved seat in an anchorage shoe, which means comprises a pair of rotary forms adjacentsaid seat about one of which the wire is bent in one direction and about the other of which the wire is bent in the opposite direction, and means for drawing the wire about said forms, the diameter of of wire whose other end is anchored, a stress free anchorage loop to fit acurved seat in an anchorage shoe, a pair of forms adjacent said seat about one of which the wire is bent in one direction and about the other of which the wire is bent in the opposite direction, means for drawing the wire under tension about said forms, and a clamp for holding the wire in advance of the forms after it has been tensioned, the diameter of the first of said forms being such as to give the wire a fixed curvaone of which the wire is bent in one direction and about the other of which the wire is bent in an opposite direction, the diameter of the first of the forms being such as to give the wire a fixed curvature corresponding to that of the seat, and the diameter and position of the specification.

ALFRED V. DE FOREST.

ture corresponding to, that of the seat and at a location also corresponding to that of the seat when the wire is under said tension and the diameter and relative position of the other form beingsuch as to straighten all the wire curved by the first form except such portion as is required to fit upon said seat.

6. Means for forming atone end of a run of wire whose other end is anchored, a stress free anchorage loop to engage a curved anchorage seat, which means comprises a plurality ofrollers adjacent said seat between which the wire may be drawn, the rollers being in such relative position as to reversely bend beyond its elastic limit that portion of the wire which is to form the loop prior to passing the Wire about the seat, and means for clamping the runof wire in advance of the anchorage after it has been drawnto predetermlned tension between said rollers.

7. Means for forming a stress free anchorage loop to fit an anchorage which comprises a pair of forms adjacent the anchorage about

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