US1787936A - Process of eliminating internal stresses in wire at anchorages thereof - Google Patents

Description

Jan. 6, 1931. A. v. DE FOREST PROCESS OF ELIMINATING INTERNAL STRESSES IN WIRE AT ANCHORAGES THEREOF Filed Feb. 17, 1928 INVENTOR Alfred Mde fbrest FUN/ ATTORNEY V Patented Jan. 6, 1931 im1-En {STAT-ES P ENT FF f {I I1 I AI REnv. ron'nsr, or s'rnn'rronco, ooNNEcr'IcUnAssIeNoR To AMERiGAN 01mm Y a COMPANY, 'mc;, CORPORATION OFVNEW YoRx' xraoonss or ELIMINATING INTERNAL STRESSES IN wInn'm ANorronAGEs 'rxmmior Application filed February 17, 1928. Serial No. 255,153.

The present invention relates to a process of eliminating lnternal stresses" in wire tension members which are looped around an anchorage or an attachment member. I I

5Aspecific applicationof the present invention is to be found in the cables of suspension bridges. ,It is customary to form such cables of a number of strands, each strand being formed of acontinuous wire which is carried by a trolley back and forth from, anchorage to anchorage until the desired number of wireleng ths for a strand have been spun. Each wire length is subjected to tens on as soon as it is spun and is thenlooped about an anchorage shoe. WVhen the strand-has been completed, the anchorage shoe is inserted between a pair of eye bars or other anchorage means and, attached there- J to, after which it is drawn backby anysuit able meanssuch asanhydraulic jack toadjust the strand as a whole tension or sag. I

However, internal stresses are introduced into the wire by bending it around an anchorage shoe, which stresses are by no means negligible even incold drawn wire and which,

in the case of heat-treated wire, are so'serious as to preclude the use of heat-treated metal .1

for the tension members of ;suspension bridges.

ticity and high yield point as compared with cold worked products. When such wire is bentaround relatively small diameters such as theshoe at the anchorage of the suspen-r sion bridge, avery high, stress is introduced v by thisrbending in the outside fibres of the I p I I amount of heat treatment to eliminate :the;

- wire, If, as would usually be the case, this It is an-object of the presentinvention to prevent any accumulation of a stress at the bend in the wire and. reduce the load on the wire atxthis point to the same figureas that inthe straight portions of the wire.

to a predetermined a ties of; the

The essential f-quality of heattreated. metal, is its high modulus of elasnow be described in connection with the ac- A more specific object of the invention is to subject the wire toatforming operation, which permanentlystretches the outside fibres and permanentlycoinpresses the inside fibres .so that the forces across any section will be zero, as they are in the straight portionofwire. In" other words, althou lithe wire is bent, the bending. The curved portion may then be loaded by any load which does notchange its radiusof curvature without introducin any other than the same tensile forces which operate, on the straight portions leading .to the curve. L f a 1' .Anotherobject of the invention is to subject the wire to over-stressing whereby its elasticlimit will be temporarily lowered so that, it'may be subjectedftoa considerable amount of deformation and after this deforination an aging effect will take place which will-intimerestore the full elasticproperwire; It iswell known that heatt-reat ed steel mayliave its elastic limits teme it is not under stress ueto;

porarily lowered byjsubjecting the material effect.

Anotherobj ect ofthe invention is to sub ject the-looped wires of the strand to heat 7 treatment afterthe strand, as a whole, has

beensubjectedto,finaltension, so as to elimi 1 nate any internal stresses which may still be present the members ofthestran'd.

S till another object is to apply a protective metallic coating on the loop: end of the strand, this'coating being applied inmolten condition; at a; temperature that will insure a certain internal stresseswhich may :be present in the wire and tofhasten the aging effect which will restore the wire to its full elastic prop; ertiesr ,g yq

With these andother objects in view. which will appear hereinafter, the inventionwill companying drawings 7 and thereafter the novelty and scope of the--invention will be, pointed outintheclaims f r c.

flInthedravvirigs,: t, l l Fig. 1 'sa somewhat'diagrammatical plan i takes place which restores the full elastic treat se over which the wire is bent 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 andthe beginning of the curvature. After" the loop has been formed, an aging process properties to the wire. 7

Fig. 3 shows still another. method oftem. porarily reducing the elastic limit 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 preliminarytension so that it will lie parallel to other wires in the strand. The diameter of the form 30 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 inv advance of the form 30 by the clamp to main- 'tain said preliminary tension in the main body of the wire While tensioning means 31 is released. The curved portion of the wire is then transferred to the shoe 10.

The length of wire sub'ected to the bending process by drawing it a out the form 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, therelbre, 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 re verse bend about a second form 32, also,

mounted on the anchor shoe. The form 32 is so located with respect to 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 1 butalso to the length of said curvature. Fur. thermore the pulley 30 is so positioned that the wire will becurved in the proper location to coincidewith the curved part of the shoe.

Fig. 4 shows the shoe turned at right. angles to the position shown in the plan views Figs. 1, 2 and 3 and secured between a pair of eye bolts 33 by which the shoe is seizedand drawn backwardjto subject the strand as a whole to the requisite tension. A stud 34: passes through the. eye bolts and also through the opening'12 in the shoe. After the shoe has been secured to the eye bolts, a metallic shield 35 is fitted around the shoe over the strand loop. The shoe'and strand loopfare then heated and molten'plead is poured intothe peripheral recess of theshoearound the wires ture andfintroduced in such quantit iasto raisethe;temperature'of the strand 00 to approximately 800 degrees Fahrenheit, w ich temperature is suflicient to draw the temper of the wires so that'if there be any internal stresses therein'they willbe dissipat'e'd. The lead filli-n thus serves not only "to coat the wires at Ens point andprotect them from; rust, but also to bind them all together and to heat-treat them, so as to eliminate objecti onal internal 1 "stresses. After this, the strand may'besubjected to the necessary tensionby drawing on the eye bolts 33 so as to raise the strand to the predetermined sag of the finishedcable. Y *VVhile' particular reference has been made herein tothe application of the present in ventionfto bridge strands and cables, and'to highte'nsile hqeat-treated wire, obviously the invention is not limited to such wire nor to such application, but can be used inthe loop-- i'n-g of'any tensioninember inrod or,wire. form and in which it is desirable to eliminate internal stresses. .7 i Having thus described my invention, what lclainr and'desire to protect by Letters Patentis:"* In the process-of forming a stress-free anchorage loop in high tensile wire,the steps which comprise progressively subjecting a portion'of the wire to reverse flexing beyond its elastic limit, and simultaneously bending suchporti'on ofth'e wire toform a loop having apermanent set of predetermined curvature' 2. Infthe process of forming a stress-free anchorage loop-in high tensile wire, the steps" v1n areverse bend about a secondform.

j "In the process of spinning bridge cables of high tensile wire, the steps which compriseprogressi-vely'subjecting a portion of the wire to reverse flexingbeyondits yield" point, sil multaneously bending- F'such portion of the wire into a loophaving a permanent set of Y predetermined curvature, and transferring the loop thus formed to an anchorage.

4. In the process of spinning bridge cables of high tensile wire, the steps which comprise drawing the .wire under tension in'one direction about. a form to progressively bend the wire beyond its elastic limit, drawing the wire in the opposite direction about another form to eliminate, from a portion of the wire, the I curvature produced by bending the wire around the first form, and fitting the remain-' ing curved portion of the wire about an. anchorage. i

5. In the process of spinning bridge cables of high tensile wire, the steps which comprise bending a portion of each length of Wire into a* loop;jaapplyin gmolten metal ab'out the loops thus-formed,smaintaining the metal at a predetermined temperaturesufiicient to; :relieve internal stress and artificially age the wires A and allowing the metal tosolidify about the wire-loops,

- i V I .-.6. ln tlieprocess ofispinning -bridge cables of'high-tensile;wire,-the steps-which'comprise bending-a portion of. each length of wire beyondits elasticlimitintofa loop of suchj dimensions thahwhen released the loop will assu'me a fixed form of predetermined curvature,transfer;ring each loopthus formed to an anchorage; applying molten metal about i the;loops 'n aintaining:the metalat aprede' terminedtemperature sufficienttozrelieve interna-l stress and. artificially age the: Wires,

' and allowing themetal to solidify about the wire loops. v 7 .7 d 1 .7 7. Inthe process of spinning bridge cables of high tensile-wire, the steps which comprise bending a portion of each length of wirebeyo'nd its elastic limit into a'loop of such dimansions thatgwhen released" the loop will a assume a fixed form of predetermined curvatnre, transferring each loop thus formed to an anchorage, vpreheating thewi re loops, applying molten metal about the loops and anchorage, maintaining the metal at a predetor-mined temperature suflicient to relieve internal-stress and artificially ageithe wires, and" allowingthe metalto solidify about the loops} and anchorage. v V 8 In the process of anchoring high tensile wire, the} steps which comprisesubjectingthe wire to a predetermined tension and simul tan'eou'sly drawing aportion of'the wire about a-form ofsucl diameter asto bend the-wire beyondits elastic limit and give the wire a prede'termined fixed curvature, drawing the wire-in a reverse bendabout a second form tostraightena portion of the wire curved by drawing it about the first form, and fittingf the remaining curved. portion or the wire 1 about ananohorage, 'c In-1testimony whereof, I have signed this o specification;

LALFREIj n F EST, I

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