US2084212A - Rail bond - Google Patents

Description

June 5, 1937. s. MOREIRA 2,084,212

RAIL BOND Filed Dec. 29, 1933 2 Sheets-Sheet 1 @.%Q 5 TE 4 men/i02 5,44 1/4001? MORE/Ea,

June 15, 1937. s. MOREJRA I RAIL BOND 2 Sheets-Sheet 2 Filed Dec. 29, 1953 1910672307: 55 wagon? MORE/E147 y Patented June 15, 1937 UNITED STATES PATENT OFFICE RAIL BOND Application December 29, 1933, Serial No. 704,555

3 Claims.

My invention relates to rail bonds having flexible conductor strands provided with terminals for attaching them to the rails to be bonded, and is a continuation in part of my co-pending appli- 5 cation entitled Rail bonds, bearing Serial No. 450,676 and filed May 8, 1930; my object being to increase the service life of such bonds by diminishing strand breakages, especially those breakages which are so annoying in that they appear to be premature.

This particular problem has been the subject of much study. The generally accepted theory is that the relative vertical movements of the rail ends, resultin from the passage of trains, twist the bond strands in opposite directions and thus cause the trouble. Metallographers say that there is an actual change in the crystalline structures of broken bond strands, this being attributed to such twisting.

If this theory is true, the usual service test should accurately indicate the probable life of the bonds so far as strand breakages are concerned. The test mentioned is performed by a machine adapted to engage the terminals of rail bonds and rapidly move them in opposite vertical directions 2 so their conductor strands are twisted as they are in service. However, it is a rather well known fact that strand breakages actually occur much sooner than is indicated by this test.

In my endeavor to diminish or eliminate this trouble, I have constructed a machine for the purpose of testing rail bonds under conditions more accurately simulating those really encountered. This machine includes two railroad rails, providing the usual splice bar joint, and a very massive wheel carrying heavy rollers into dragging contact with these rails at this joint. The result is very similar if not exactly like that of a railroad train passing over the rails.

My method of testing bonds is to apply them to the rails at the joint and then start the wheel revolving. The fact that the strands break under my test much sooner than is indicated by the usual test previously mentioned, proves that I am able to simulate service conditions with great exactness.

Because of the discrepancy between the results obtained by the two tests, I have been led to believe that strand breakages are caused by something other than the mere twisting. To prove this, I attach rail bonds to the solid portion of one of the rails at a point rather remote from the joint and, consequently, rather remote from the point of contact of the rollers. The strands of these bonds break practically as soon as do those of bonds applied directly at the joint. This, I believe, conclusively shows that the strands do not break merely because they span the ends of the rails and are being twisted by the passage of trains.

The use of an oscillograph has convinced me that the real reason for strand breakages is highfrequency vibrations probably imparted to the rails by the pounding of passing trains and by the forces resulting from the driving wheels of locomotives. That is to say, vibrations having frequencies which are much faster than those of the rail ends as they are bent and released by the wheels of passing trains are the root of the evil.

Some patents have been granted which generally state that they are for the purpose of preventing strand breakages resulting from the effects of vibrations. In all cases, the vibrations referred to are simply those twisting effects which I have mentioned. It is apparent that such vibrations are of rather low frequency, since they depend, in each instance, on the spacing of the wheels of a train passing directly over the joints, to which the bonds are applied, multiplied by the speed of this train.

I do not believe that the high-frequency vibrations, which are the true cause of early strand breakages, necessarily result from the vertical or transverse rail movements caused by the weights of the trains being transferred to the rails at moving spaced points by the wheels. Instead, I believe that these high-frequency vibrations particularly result from the transmission of driving forces from locomotives to the ground by way of the rails. It is unreasonable to believe that such transmission can be one hundred per cent efficient, and any efilciency loss can only be accounted for by assuming that it is transferred into vibratory motion of the rails. Further, since the transmission of these forces are in lines approximately parallelin the rails, I believe that the vibrations causing the trouble travel longitudinally along the rails much in the manner and nature of sound waves.

The vibrations to which I refer are of rather small amplitudes and high frequencies. So far as I am aware, no one has ever appreciated the damaging'eifects of these high-frequency vibrations.

It is now possible to explain the reason that the structures of flexible rail bond strands change in service so that breakages occur prematurely, yet do not occur so soon during-the usual service test. The flexible strands are, as a general rule, made of a large number of individual copper wires, and the natural vibratory periods of these strands differ from the high-frequencies of the vibrations imparted to the rails by passing traffic. Since the terminals always rigidly connect these strands to the rails, the rail vibrations are transmitted directly to the same. However, because of these strands individual periods, they resist these high-frequencies. Consequently, there is probably a minute bending of each of the little individual copper wires at the points where the high-frequencies attempt or do change to the individual vibratory periods that naturally are inherent to the strands. It follows that the crystalline structures of the strands undergo a change so that they break prematurely or are easily broken by the twisting of the strands.

According to my invention, means are provided for retarding individual high-frequency vibrations of the strands, due to the latters individual vibratory periods, respecting the terminals. This may be done by providing means which synchronize the strands and terminals of the bonds to the high-frequency vibrations. The high-frequency vibrations may be transmitted from the terminals to the central portions of the strands so that the bonds respond in their entireties to the high-frequency vibrations of the rail.

When the terminals and strands vibrate at the same frequencies there is little or no tendency for these vibrations to have any ill eirects on the strands. Of course, the relative movements of the rail ends will still cause twisting of the strands which will ultimately result in breakages. Such breakages, however, do not occur nearly so soon as those I have been discussing, as is evidenced by the theoretical life of the strands as indicated by the usual service test.

I will now disclose several specific examples of rail bonds constructed according to the principles of my invention, the various figures in the accompanying drawings illustrating these bonds being as follows:

Figure 1 shows a portion of the sides of two joined rails to which a bond is applied.

Figure 2 is a cross-section from the line 11-11 in Figure l. '7

Figures 3 and 4 are suggestive modifications of the bond shown by Figure 1.

Figures 5 and 6 are cross-sections from the lines VV-VV and VI-VI in Figures 3 and 4, respectively.

In the first form shown, the bond includes a flexible conductor strand I having terminals 2 for connecting the strand to the abutting ends of rails 3 and 4. These rails are joined by a splice bar 5 in the usual manner, and the terminals 2 are welded to these rails, as is also usual. When a train passes over these rails there will be opposite vertical movements of the ends of the two rails 3 and 4, which will twist the strand in opposite directions.

As I have already explained, there will also be vibrations of high frequencies, that is, frequencies which are much higher than those of the relative displacements of the rail ends. These high-frequency vibrations, probably traveling longitudinally along the rails, will endeavor to vibrate the central portion of the strand l, the forces being transmitted through the rigid terminals 2. Since this strand has a definite natural vibratory period, it will offer resistance to these vibrations, of diiferent frequencies, at ealized points.

However, one of the terminals is provided with a relatively infiexible arm 6 rigidly extending from one of the terminals and rigidly fixed to the strand i adjacent or at the latters central portion. Therefore, the vibrations will be transmitted to the central portion of the strand so that the latter, the terminals and the rails will all vibrate at the same high frequencies. In other words, the vibratory motions of the strand and terminals are synchronized to these high-frequency vibrations. One arm is sufiicient for the reason that the splice bar 5 rigidly interconnects the rails 3 and 5, so that no matter in which rail the vibrations originate they will be present in both.

It should be understood that it is absolutely necessary that there be a rigid, practically inflexible connection between one of the terminals and some part of the central portion of the strand. The use of a clip fixed to one of the bolts of the splice bar 5 and loosely wrapped about the strand is not sufficient for this purpose.

Practically all heavy duty bonds are made with copper strands, consisting of a number of fine wires, which are provided with steel terminals that may be welded to the rails. Assuming the bond under discussion to be of this character, a particularly good example of the usefulness or the invention is provided. The strand will naturally have a high-frequency Vibratory period quite different from that of the long and heavy steel rails. The steel terminals, rigidly welded to these rails, will naturally tend to impart these high-frequency vibrations directly to this strand without any substantial loss. By constructing the arm 6 of steel so as to rigidly extend from one of these terminals and be rigidly connected to the center of this strand, a result will be obtained which is otherwise impossible. This re sult. which is freedom from premature strand breakages, is directly due to the fact that the strand i is forced to vibrate at the same high-frequencies as those of the vibrations which are in the rails 3 and i, the steel arm transmitting the vibrations with no more loss than is inherent in the steel terminals. I

More particularly referring to the arm 8, it may be constructed to follow the natural curvature of the strand l, and have a ferrule portion 1 which is in a rigid connection with the center of the strand. The portion 1 might be welded, or otherwise connected. Also, the arm may be straight, as is shown by the one numeraled 8, with its rigid strand connection 9 also at the center of the strand.

Various modifications of these specific struc tural details are, of course, possible, as is shown by the last illustrated form of the invention showing each of the terminals 2 provided with an arm l0 and ii each having a strand connection l2 and I3 adjacent, but not at, the strands center. This last form shows that it is generally sufficient if the high-frequency vibrations are transmitted to the central portion of the strand, since the very center strand portion will offer little or no resistance to the high-frequency vibrations. This results from the fact that the very short length of this central portion will prevent it from having a distinct vibratory period of its own, and also because the rail vibrations will be transmitted to two closely adjacent points so as to force the strand to the others frequencies.

For the purpose of emphasizing the features of my invention, I wish to repeat that the vibrations with which I am concerned have high frequencies iii and small amplitudes, this distinguishing them materially from the low frequency vibrations, of great amplitude, resulting in the strands from the relatively large displacements of the adjacent rail ends caused by the passage of wheels over the same. This latter effect I believe more aptly termed twisting, since this more clearly describes the action. In the case of a bond constructed according to my invention, this twisting will still be present, but it is not the effects of this motion which causes premature strand breakages.

In my invention, where I provide a means for forcing the strands to vibrate in synchronism with the high-frequency vibrations imparted to the terminals by the passage of traflic over the rails to which the bonds are applied, this being done regardless of the individual vibratory periods of the strands, there is no chance for premature crystallization of the strands. It is this premature crystallization which, when aided by the twisting of the strands, causes the premature breakages which it is my object to diminish or eliminate.

I claim:

1. A rail bond including the combination of a flexible conductor strand, terminals for rigidly fixing the ends of said strand to the rails to be bonded and a relatively rigid metal arm rigidly fixed to at least one of said terminals and arranged in rigid intermetallic connection with a part of said strand at least adjacent its central portion.

2. A rail bond including the combination of a flexible conductor strand, terminals for rigidly fixing the ends of said strand to the rails to be bonded and relatively rigid metal arms rigidly fixed to said terminals and arranged in rigid intermetallic connection with parts of said strand at least adjacent its central portion.

3. A rail bond including a flexible conductor strand, terminals for connecting said strand to railroad rails, said strand being of such construction as to have an individual high-frequency vibratory period and said rails carrying traflic creating high-frequency vibrations therein which are imparted to said terminals when the latter are connected thereto, and metallic vibration transmitting means interconnecting at least one of said terminals and a substantially central portion of said strand, said means being in such intermetallic contact with both said terminal and said strand and having such inherent physical characteristics as to be capable of transmitting said high-frequency vibrations from said terminal to said portion of said strand, whereby said strand is subjected to said high-frequency vibrations at both its terminal ends and said portion and is consequently forced to vibrate in synchronism therewith in its entirety regardless of its said individual vibratory period.

SALVADOR MOREIRA.

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