US2321867A - Rail bond - Google Patents

Description

June 15, 1943. E; P. SMITH 2,321,867

RAIL BOND I Filed May 5, 1942 Evwazz: 5? SMITH Summon Patented June 15, 1943 UNITED STATE S PATENT, OFFICE RAIL BOND Edward P- Smith, Mansfield, Ohio, assignor to The Ohio Brass Company, corporation of New Jersey Mansfield, Ohio, a

Application May 5, 1942, Serial No. 441,774

9Claims. (class-14.12)

My invention relates to rail bonds and has particular application to rail bonds to connect the adjacent ends of rails forming a signal circuit.

In signal operation on railroads, while it is a serious matter if the signal circuit becomes broken, it is a far more serious matte if the 'bonds and many included pieces of apparatus.

Rail bonds may constitute a large number of elements making up the circuit, since there is a bond at each rail joint.

- A bond suitable for signal Systems may consist of a pair of terminals which are applied, one to each end of the adjacent ends of a pair of rails and the terminals connected by a short cable, the ends of which are positioned and held within the term nals. Such a bond is disclosed in Chandler U. S. Patents 2,162,655 and 2,232,999.

It is well known that rails will contractv and expand and should such contraction accumulate in one joint to such an extent that the. cable including its loop should be drawn out into a straight line and break within one of the terminals but the contraction be not suflicient to withdraw the broken end from the terminal, the bond might funct on successfully for a, considerable length of time. However, this bond in the course of time would permit moisture to enter 'the terminal and cause corrosion which would .destroy the electrical contact between the broken end of the cable and the terminal, thus producing a concealed open circuit which would not be visible to an inspector looking for thedefect in the circuit. This is particularly true if at the t me the defect manifested itself, the opening between the rail ends has closed.

If upon making a visual inspection of the entire c rcuit, no open circuit is found, then it will be necessary for the inspector to test out each joint in the circuit using what might be termed a bond tester}? the use of which involves considerable time and during which time the signal system will be out of commission.

The purpose of my invention is to provide a bond in which a concealed break is prevented and an open circuit or break is produced in lieu thereof at a po nt which is readily visible to an inspector passing along the track, thus eliminating the necessity of testing each rail bond, should the break in the circuit not be found in some other part of the circuit.

One object of my invention is to render visible a defect in a rail bond which otherwise might occur within the terminal and result in a concealed defect; as the result of an undue opening or spreading of the adjacent ends of a pair of rails.

Another object of my invention is to brin about an even a'nd'um'form stress upon the individual wires or strands of which the cable connecting the terminals is composed when they are held under compression within the terminal.

' Another object of my invention is to provide the cable connecting the terminals of a rail bond with a safety feature having a reduced tensile strength as compared with the balance of the cable.

Another object of my invention is to provide a cable connecting a pair of bond terminals'with a limited length having a tensile strength less than that portion of the cable held within the terminals whereby the cable will break at some point between the terminals before it will break within the terminals.

Another object of my invention is to provide a rail bond in which the conductor connectin the terminals'thereof is provided with means which will insure the cable being broken between its terminal due to excessive spreading of the adjacent rail ends.

My invention resides in the new, novel and useful construction,combination and relation of the parts described and shown in the following specification and in the drawing, respectively, in which Fig. 1 is a side view in elevation of a pair of rail ends of my invention applied thereto. Fig. 2 is an end view of Fig. 1 in partial section.

Fig. 3 is a side view in elevation of a pair of rails which have contracted sufficiently to rupture the cable connecting the bond terminals. ..One terminal is shown in section onthe line 33 of Fig. 2.

In the preferred embodiment of my invention, I providea bond I for electrically connecting the adjacent ends of conductor rails 2, having a pair of terminals provided with a portion 3 arranged terminal and the terminal then compressed on to the cable, thus securing the two parts together, or any other method may be used to secure the parts together which will produce a union at least somewhat in excess of the strength of the cable o equal to the original strength of the cable.

In Fig. 3 is shown one terminal sectioned to illustrate the cable end as associated with the terminal.

It has been found occasionally that the contraction of the connected rails of a track may accumulate largely at a single joint and that the opening between the rails may increase to such an extent as to exceed the developed length of. the loop 5 which has been incorporated in the bond to allow for reasonable contraction of the rails at the individual joints.

When there is an undue separation of the rail ends, the cable may be stretched out straight and if the contraction exceeds a predetermined amount a break is bound to occur somewhere in the cable or the cable pulled out of the terminal (a very rare occurrence). If the break occurs in the cable between the terminals, the defect is quickly and asily found by a rapid visual inspection, but if the break occurs within the terminal and the cable does not pull away from the terminal, corrosion will set in eventuallyand cause an open circuit in which case the only way to discover the bond in which such a defect exists is to test each bond until the defective one is found.

In order to produce a bond which will insure against the cable breaking within the terminal and which will visually show an open circuit when the cable has been stretched beyond a predetermined amount, I anneal the cable, preferably at the center of the loop 5, for a very short length thereof or for a greater length, so long as the anneal does not extend to the point 6 where the cable enters the terminal but stops a safe distance from the point 6 so as not to affect the original or normal strength of the cable or change the physical characteristics thereof at this point.

I find that a very short length, A" or of annealed cable, preferably at the center of the loop-5, is sufiicient.

The anneal may be accomplished in any suitable manner, as by apair of electrically heated carbons applied to the cable or by a heating flame and the cable may then be quenched, if desired. 7

I find that a bond having the cable thereof annealed, as described, will actually break through tension at some mint within the length of the annealed portion (represented by the letter A-) before it will break at any other point providing the rails=are spread asuflicient amount, as shown in Fig. 3.

I, also, find that by annealing a predetermined length of the bond cable adjacent its center, the tensile strength of the bond is actually improved by theannealing. In the un-annealed bond, only about 75% of the tensile strength of the strand is developed. This is because the strands or in dividual wires are not gripped equally and progressivev failure may take place under undue stretching of the cable. Annealing a portion of the cable allows it to stretch and load the individual strands or wires equally, thus the mechanical connection between the cable and the terminal has been strengthened by the annealmg.

The resistance to breakage of the cable from vibration causes is not reduced because th effect of vibration or fatigue is located principally at and adjacent the point 6 where the cable enters the terminal, and the physical properties of the cable have not been changed at this point by annealing the central portion of the cable.

The cable I employ is preferably of copper bronze, that is, copper with the addition of such other element as, phosphorus, tin, silicon, cadmiumor berrillium, in small quantities. One cable I have employed has a normal breaking strain of about 1800 pounds. The anneal or other treatment which I have employed reduces the tensile strength at a predetermined point of breakage below 1800 pounds or to about 1500 pounds. This cable is a 7X19 hard drawn rope laid cable about diameter.

The cable may be made to break exterior of the terminals and at a less value than the nor mal strength of the cable by reducing the cross sectional area of the cable but this is a questionable procedure as breakage due to vibration is quite sure to follow.

To manufacture my invention I produce the terminals, either by forging from a solid bar or by forming from sheet metal, depending upon the design of the terminal. The terminal may be of copper or of steel or of a combination thereof.

I then cut from an extended length of cable, lengths suitable for the bond. I then insert each end of the cut cable into an opening in the ter minal prepared for the cable end and then subject the terminal to pressure, preferably cold, to securely unite the parts.

The cable is then formed with a loop or expansible portion 5 and then heat treated.

The heat treatment is applied to a limited length of the cable at its center,'but is not extensive enough to effect the temper of the cable adjacent to and at the ends thereof when it enters the terminals. Other steps may be em ployed int-he manufacture of my invention, but the one described above is simple, economical and efiicient.

.Modifications of my invention will suggest themselves to those skilled in the art based upon my disclosure and, therefore, I wish to be limited only by my claims:

v.1. A rail bond. comprising a pair of terminals, each provided with a portion for attaching the terminal to a rail and a cable connecting the terminals and having its ends positioned within the terminals and securely held therein by compression, the exposed portion of said cable being of uniform cross-sectional area and formed with a-loop portion forming a part of the length of thecable between the terminals and means forming a part of the cable within the length of the loop whereby a break in the cable is assured within the length of the loop when the cable is stretched beyond the elastic limit of said means.

.2. In a rail bond comprising a pair of terminals, each provided with means to secure the same to a rail. the combination with said terminals of a cable having a visible portion of uniform cross-section and of the same metal throughout its length connecting the terminals, and means on each terminal to receive and securely hold thereto by compression an end of the cable which is provided with a portion so constructed and arranged as to have a lower tensile cable equals the breaking strength of a portion of the cable within either terminal.

3. A rail bond for attachment to a pair of rails adjacent the abutting ends thereof comprising a pair of terminals, each terminal provided with means to attach it to one of the rails, a cable having an exposed length of uniform cross-section and of the same metal throughout its length connecting the terminals and having its ends secured within the terminals, one end in each ter minal, the said cable having a continuous exposed length with three portions, two end portion of normal tensile strength and an inter mediate portion in which the tensile strength per square inch of said intermediate portion is less than that of the balance of the cable whereby the exposed length of said cable will break outside of the terminals within said intermediate portion located adjacent the longitudinal center of said exposed length when the rails spread sufficiently to efiect a tension in the cable equal to the breaking strength of the said intermediate portion but less than said end portions.

4. In combination, a pair of rails'having abutting ends, the ends of the rails separating under contraction of the rails, a rail bond electrically connecting the adjacent ends of said rails, the rail bond comprising a pair of terminals, one terminal attached to a rail, and connected by a cable having its ends secured within the termi- :i

nals and also having a loop portion allowing a limited amount of spread of the rail ends before the cable is subject to tension sufiicient to rupture the cable, the exposed or visible portion of the cable having adjacent its longitudinal center a heat treated or annealed portion of reduced tensile strength as compared with that of the balance of the cable whereupon the cable will break within said annealed portion when the rail ends have spread and effected a tension in the cable in excess of the tensile strength of the annealed portion.

5. A rail bond to connect the adjacent ends of a pair of rails comprising a pair of terminals, each terminal provided with a part arranged to be secured to a rail, a cable of non-ferrous meta1 and of uniform cross-section electrically and mechanically connecting the terminals and having its ends secured within the terminals, the cable provided with three portions, one portion being a heat-treated portion midway of the other two portions and having different physical properties from those of the other two portions whereby an easily, visible effect will be produced in the heat-treated portion of said cable terminals upon a sufficient separation of the rail ends producing a tensile stress in the cable less than the normal strength of the joint between the cable ends and the terminal.

6. A rail bond comprising, a pair of terminals for attachment to the adjacent ends of abutting rails subject to contraction and expansion, 21 noni'errous visible cable of uniform cross-section atheat-treated section whereby the tensile strength thereof is less than the tensile strength of the joints between the cable and terminal, whereby the cable will break at-or within said portion before the stress exceeds the strength of the i said points when the rails contract to produce an opening therebetween in excess of a predetermined separation.

7. In a rail bond comprising, a pair of terminals for attachment to the adjacent ends of abutting rails, a cable of uniform cross-section and predetermined normal tensile strength attached to the terminals and electrically and mechanically connecting the terminals, the combination with the exposed portion of the cable at its longitudinal center of a heat treated portion having a tensile strength below the normal tensile strength of said cable and joint between said cable and terminals, whereby the cable will rupture at said heat treated portion when the rail ends separate sufficiently to effect a tension in said cable in excess of the tensile strength of said heat treated portion.

8. The method of manufacturing rail bonds comprising the following steps, namely, forming terminals from suitable metal, preferably by forging in suitable dies and having a stud portion for insertion in an opening in a rail and an opening to receive the end of a cable, cutting a cable of uniform cross-section and of the same metal from end to end into predetermined lengths, inserting the ends of the cable pieces into the openings in the terminals, one end in an opening, forcing each terminal into intimate engagement with the end of the cable to hold it in place by compression and subjecting the cable pieces to a heat-treating process to reduce the tensile strength of a portion of the cable adjacent the longitudinal center without subjecting the cable adjacent the terminals to the heat-treat-' 2 ment and thereby not reducing the tensile strength of the cable adjacent the terminals be-- low that of the said predetermined strength.

9. In a rail bond comprising a pair of terminals for attachment to the adjacent ends of abut- I ting rails and a cable of uniform cross-section and predetermined normal tensile strength having the ends attached to the terminals, the combination with the exposed portion of the cable of a heat-treated portion having a tensile strength below the normal tensile strength of aid cable and of the joint between said cable and terminals, whereby the cable will rupture at said heat-treated portion when the rail ends sep arate sufiiciently to efiect a tension in said cable in excess of the tensile strength of said heattreated portion.

EDWARD P. SMITH.

Images