US2882489A - Method and means for magnetizing rails in rail flaw detection systems - Google Patents

Description

W. BRAZITIS ET AL 2,882,489 RAILS IN RAIL April 14, 1959 METHOD AND MEANS FOR MAGNETIZING FLAW DETECTION SYSTEMS 2 Sheets-Sheet 1 Filed May 7, 1956 J b-L mm l ll java/1250 2 5 M ZZlm fiidZiZ'Z-S 3y A n y Wffez/a'i April 14, 1959 'w. BRAZITIS ET AL 2,882,489

METHOD AND MEANS FOR MAGNETIZING RAILS IN RAIL. FLAW DETECTION SYSTEMS Filed May 7, 1956 2 Sheets-Sheet 2 J2me 72 5022s WL'ZZz'cun Brazz'izs United States Patent METHOD AND MEANS FOR MAGNETIZING RAILS IN RAIL FLAW DETECTION SYSTEMS Wflliam Brazitis, Homewood, and Henry W. Keevil, Evanston, Ill.

Application May 7, 1956, Serial No. 583,173

12 Claims. (Cl. 324-37) This invention relates to the so-called residual magnetism system of detecting flaws in rails.

In testing rails by 'the residual magnetism method, longitudinal magnetic flux is first introduced into the rail from a moving car and the residual magnetism left in the rail is then explored for flux patterns that are characteristic of transverse fissures or other internal defects.

The present invention is an improvement of the basic system shown in Barnes et al. Patent No. 2,317,720 wherein the magnetizing means comprises three longitudinally spaced electro magnets each having a separate function to perform in properly magnetizing the rail. The forward magnet, or as it is usually called the A magnet, is a relatively powerful magnet, as is also the second magnet, ordinarily called the B magnet. These magnets successively introduce high intensity magnetic flux into the rail, but are spaced apart far enough so that they act more or less independently. The final magnet, commonly referred to as the C magnet, is not as powerful as the A and B magnets and it introduces relatively low intensity magnetic flux into the rail. The C magnet is sometimes referred to as a clean-up magnet because it has the effect of erasing certain residual fields left by the A and B magnets in the vicinity of the superficial surface defects on the rail such as burns, gags, shell and the like.

The present invention seeks to strengthen the characteristic residual magnetic field created in the vicinity of fissures without establishing characteristic residual fields in the vicinity of superficial or inconsequential surface defects. New methods of rail magnetization are employed and special types of magnets enhance the effectiveness of these new methods.

Selective adjustment is provided in the system of the invention to adapt the magnetizing action of the apparatus to rail of different surface characteristics and thereby obtain optimum effectiveness. For example, accord- Fig. 4 is a front elevational view of the C magnet shown in Fig. 3.

Reference should now be had to the drawings and the following description for a more complete understanding of the present invention.

GENERAL ORGANIZATION In the present invention, the forward or A magnet 10 is located on the lead car 11 in advance of the front wheel 12. As will be explained later, the A magnet 10 is principally a shocking magnet as it loosens the rail molecules and facilitates their subsequent magnetic alignment. I

According to the invention, three B magnets are employed, the first of which 13 is located between thewheels of the lead car, the second of which 14 is located behind the rear wheel 12 of the lead car, and the last of which 15 is located forwardly of the front wheel 16 of the rear car 17. It will be noted that the front legs of magnets 13 and 14 are closer to the rail than the rear legs whereas in the case of magnet 15 the reverse is true.

The C magnet 18 is located between the wheels of the rear car 17 and immediately precedes the main detecting or pick-up device 19 which is suspended from a carriage 20 carried by the rear car.

The remaining apparatus shown in Fig. 1 plays no I part of the present invention but, for completeness, it

ing to a first method of magnetization, strong characteristic residual magnetic fields are set up in the vicinity of fissures and other serious internal defects without magnetizing burns, gags, shell, and the like, and strong, clean cut indications are produced on the tape. However, this first system is adversely affected by rail portions having corrugations. In such instances, the system may be adjusted appropriately to eliminate local fields due to corrugations and while such adjustment compromises, to some extent, the ability of the apparatus to In the accompanying drawings, forming a part of this may be described as consisting of a magnet 22 and pickup device 23 which are carried on their own sub-carriage and which are intended for the detection of vertical split heads. Finally, there is shown a D magnet 24 located behind the rear wheel of the rear car 17.

One of the important advantages of the present invention resides in the fact that the A magnet 10 and the B magnets 13, 14, and 15 set up powerful residual flux fields at the defects. This results from the fact that the individual magnets, due to their unique construction, are unusually powerful and also due to the fact that the arrangement of the magnets develops a magnetic cycling action in the rail and sets up what is herein termed a cyclic state of residual magnetism. A cyclic state of magnetism is said to exist when the residual magnetism developed approaches a maximum in relation to the value of exciting flux. In the prior art systems only two flux applications were employed and the system's fell far short of developing a cyclic magnetic condition in the rail. In the present instance, however, the rail is cycled four times by magnets 10, 13, 14, and 15 and this arrangement develops a substantially cyclic condition in the rail. Obviously a greater number of magnets will further enhance the residual magnetic condition but the economies of the situation militate against such an arrangement.

The present invention utilizes already existing space on the conventional type detector cars and provides a sufiicient number of flux cycles as to approach a cyclic magnetic condition in the rail. While the final B magnet 15 enters into the cycling action it is also selectively adjustable in its magnetic effect to develop certain an cillary magnetic effects which will be explained hereinafter. Similarly, the magnetic effect of C magnet 19 is Patented Apr. 14, 1959 CONSTRUCTION OF ELECTRO MAGNETS A magnet The A magnet is of large size and, generally is of an inverted U-shape, having a magnetic steel base portion provided with depending front and rear legs 31 and 32 which are also of magnetic material and define vertical front and rear poles. The front leg 31 is somewhat longer than the rear leg 32 and the magnet is suspended from the lead car 11 by suitable supporting arms 33 such that the front pole is carried closer to the rail surface 34 than is the rear pole. An energizing coil 35 is wrapped around the front leg 31 of the magnet 10. The coil 35, as are all of the coils described hereinafter, is energized from a suitable direct current source (not shown) that preferably may be 110 volts. This arrangement whereby a magnet of modified U-shape is provided with an energizing coil on its longer front leg minimizes the stray flux path existing above the magnet and directs the maximum flux into the rail.

While the magnet does not actually contact the rail, nevertheless, due to its novel arrangement, it passes approximately twice as much flux through the rail as was possible in the case of the old style A magnets. The magnet 10 is principally a shocking magnet in that it tends to break the molecules loose and more readily adapt them for longitudinal alignment by the subsequent magnets. However, the fact that the rear pole is slightly higher than the front pole does make magnet 10 act, to a certain degree, like a magnetizing magnet with the result that a certain amount of longitudinal flux remains in the rail after the A magnet passes.

B magnets Magnets 13 and 14 are generally similar to magnet 10 though they are considerably smaller in size. These magnets are generally of inverted U-shape and include a horizontal base leg 37 of magnetic steel and front and rear legs 38 and 39, also of magnetic steel, with separate direct current energizing coils 40 wrapped around the longer front legs 38. Suitable supports 41 suspend the magnets 13 and 14 from the lead car 11 and again the arrangement is such that these magnets do not contact the surface of rail 34.

While magnets 13 and 14 are appreciably smaller than the old type B magnets, their arrangement is such that they nevertheless pass a comparable quantity of flux through the rail.

Finally, the third B magnet 15 is of the same general form as magnets 13 and 14 withthe exception that the rear leg or pole is made longer than the'front pole. As best seen in Fig. 2, magnet 15 consists of a horizontal bar 43 and front and rear legs 44 and 45, respectively, with an energizing coil 46 wrapped around the shorter front leg 44. Suitable cap screws 47 secure the poles to the bar 43.

In the system of the present invention, the exact spacing of the rear pole of magnet 15 from the rail 34 is quite critical and in fact produces widely varying magnetizing actions. Accordingly, the front end of the magnet is pivotally connected to a forward support 48 by a pin 49 and the rear end of the magnet which is free to pivot about the pin 49, is provided with a non-magnetic spacing wheel 50 rotatably mounted between a pair of selectively adjustable positioning brackets 51 of brass or other suitable non-magnetic material that are slotted as at 52 for attachment to the rear end of the magnet by suitable fasteners 53. An eye bolt 54 is provided for raising the magnet 15 when not in use.

It will be apparent that the spacing wheel 50 maintains a predetermined spacing between the rear pole 45 and the rail 34. The exact amount of this spacing may be adjusted by means of the brackets 51.

4 C magnet The C magnet, as best shown in Figs. 3 and 4, is generally of an L-shape and consists of a horizontally extending bar 56 of magnetic steel, a downwardly projecting magnetic block 57 supported from the front end of the bar 56 by a suitable fastener such as cap screw 58, and a second magnetic block 59 underlying block 57 and magnetically connected thereto by support arms 60 that are pivotally suspended from a rod 61 carried by the upper block 57. Adjacent its bottom edge the lower block 59 is provided with a non-magnetic stainless steel wear plate 62 held by fasteners 63 and the arrangement is such that, the wear plate 62 is in continuous contact with the rail surface and maintans a non-magnetic gap of consent dimension between the front pole of magnet 18 and the rail surface. The arms 60 are free to pivot as the magnet progresses along the rail and thus tend to follow automatically the various changes in rail contour while maintaining the gap constant.

An energizing coil 65 is wrapped around the horizontal leg of the L-shaped magnet 18 and is confined by longitudinally spaced pairs of brass angles 66 attached to the opposite ends of the bar 56. As shown in Fig. l, the direct current supply circuit for coil 65 includes a selectively adjustable element 68, of any suitable type known to those skilled in this art, that controls the value of the energizing current passed through the coil 65. As is conventional, magnet 18 is weak in comparison to magnets 10, 13, 14, and 15. In addition, however, element 68 is adjustable to control the energizing current of magnet 18 from a relatively low strength current value to a relatively high strength current value though it should be recognized that even at the high strength current value, magnet 18 is weak in comparison with the other magnets.

The magnet 18 is carried by a main brass support 69 that is sandwiched between a pair of brass brackets 70 which in turn are pivotally supported from the car frame. The magnet is attached to the support 69 through a pair of intermediate brass plates 70 and 71 which preferably are arranged to provide a certain amount of vertical and transverse adjustment in order to properly position the magnet over the rail 34.

MAGNETIZING SYSTEM It has been found that at least to some extent, the effectiveness of any discriminating rail magnetizing system varies in accordance with the character of the surface of the rail being magnetized. For example, the general method of the present invention has proven remarkably effective in rail magnetization except in those instances involving corrugated rail. In these relatively infrequent instances, however, the effectiveness of the general method is adversely atfected by the presence of the corrugations. To handle magnetization of corrugated rail, a second or specific magnetizing method has been developed and the apparatus employed in this invention has been embodied in such a manner as to permit, by a simple adjustment, conversion from the general magnetizing method to the specific method. The only adjustment required in converting from the general method to the specific method, is to raise or lower the rear pole 45 of magnet 15 by means of the brackets 51 and to raise or lower the exciting current in the energizing coil 65 of C magnet 18 by appropriately adjusting element 68.

According to the general method, magnets 10, 13, 14, and 15 cyclically energize the rail with very strong flux and as a result of the high strength flux and the cycling action, a maximum of residual magnetism is set up at the defects in the rail.

In the general method, the magnet 15 is arranged as shown in Fig. 2 with its rear pole 45 closely adjacent the rail surface 34 and thus this magnet does not function purely as a longitudinally magnetizing magnet but rather leaves the top surface of the rail strongly magnetized in a vertical direction. It will be remembered, however, that even with its rear pole in its lowermost position, magnet 15 applied an additional round of cycling flux to further strengthen the residual magnetism in the rail. The pick-up 19, however, is conventional and therefore works on longitudinal flux and, of course, is not able to detect defects when the rail surface is magnetized vertically.

The C magnet 18 is located between the pick-up and magnet 15 and while this magnet is weak in relation to the other magnets, it develops a longitudinal flux in the rail that is sufiicient to overcome the vertical magnetization of the surface of the rail and thereby reestablish the longitudinal local field at the internal defects. Thus magnet 18 does not function like the conventional cleanup magnet of the prior art. In effect, therefore, the general method first cleans the surface of the rail by the vertical magnetizing action of magnet 15 and then, through magnet 18, remagnetizes the defects without remagnetizing the burns, gags, shell, etc. It should be noted that in this general method, the magnet 18 is set at a relatively high strength energizing current in order to effectively accomplish the remagnetizing action and while this method is highly advantageous, for the ordinary type surface defects, there is the disadvantage that magnet 18 brings out local fields at the top of rail corrugations and causes these corrugations to indicate strongly and interfere with the reliability of the apparatus. For this reason the general method is not practical on corrugated rail.

The specific method of this invention is primarily concerned with rail sections predominantly characterized by the presence of surface corrugations. As has been mentioned previously, the apparatus is converted to operation in accordance with the specific method by raising the rear pole of magnet 15 a sufficient distance above the rail surface 34 such that magnet 15 no longer develops any appreciable vertical magnetizing action and by adjusting element 68 to apply a low strength energizing current to C magnet 18. Thus, magnet 15 now merely functions to provide an additional cycle of flux through the rail and leaves it cyclically magnetized, and magnet 18 serves merely as a clean-up magnet that erases characteristic residual magnetic fields that exist in the region of the inconsequential surface defects. The cleaning action of magnet 18 affects only the surface portions of the rail, and in doing so, cleans up magnetic fields around the surface corrugations and prevents their producing any indications on the recording tape.

In the operation of the present arrangement, the only critical relationships involved relate to the spacing relative to the rail surface of magnets 15 and 18 such that each of these magnets develops the type of flux pattern that is best adapted for magnetizing fissures and other serious internal defects without setting up characteristic magnetic fields in the region of inconsequential surface defects.

Actually, the spacing of magnet 18 is considerably more critical than is the spacing of magnet 15, and the wear plate arrangement applied to the lower end of magnet 18 best maintains the desired spacing. It will be appreciated that the adjustments which are made on magnet 18 relate only to the strength of its energizing current and hence the strength of its flux pattern. In the case of the general method it is necessary that magnet 18 generate a sufiiciently strong flux as to enable it to remagnetize the rail, whereas, in the case of the special method, the flux of magnet 18 is necessarily weak since it alfects only the surface of the rail.

The adjustments which are made to magnet 15 actually alter the character of the flux pattern developed thereby, for, in the case of the general method, it is arranged with its rear pole close to the rail and in addition to performing a cycling action it leaves a vertically magnetized rail in its wake, while in the case of the specific method, its rear is raised and it develops only a cycling action and produces no vertical magnetization of the rail. While the precise spacing of the rear pole of magnet 15 is important, the spacing wheel has proven adequate though it is recognized that such wheels tend to pick up foreign particles from the surface of the rail and develop a slight bouncing action as they roll along the track. Should operating conditions require it, a wear plate could be substituted for the spacing wheel.

The invention described herein has proven its effectiveness in tests and has resulted in a substantial increase in the number of defects detected and a substantial decrease in the number of false indications. It has not been deemed necessary to analyze in detail all of the complex theoretical considerations which permeate the present method and apparatus and cause the invention to exhibit such remarkable improvements over prior methods. It is believed that the general considerations described herein adequately explain the mode of operation of the present invention and clearly define the advance which has been made in this art.

It should be understood that the description of the preferred form of the invention is for the purpose of complying with Section 112, Title 35 of the U8. Code and that the appended claims should be construed as broadly as the prior art will permit.

We claim:

1. The method of magnetizing rails and the like to establish characteristic residual magnetic fields in the vicinity of internal defects without establishing local magnetic fields in the vicinity of surface irregularities and comprising cyclically passing a relatively strong, unidirectional, flux in the same lengthwise direction through the rail to cyclically magnetize the same to a high value of residual flux; and then passing relatively weaker unidirectional fiux in said same lengthwise direction through the rail to eliminate local fields at surface irregularities and to leave characteristic fields at defects.

2. The method of magnetizing rails and the like to establish characteristic residual magnetic fields in the vicinity of internal defects without establishing local magnetic fields in the vicinity of surface defects such as burns, gags, shell, and the like, and comprising passing a relatively strong, unidirectional, flux in a lengthwise direction through the rail to strongly magnetize the same; then passing a unidirectional flux in the same lengthwise direction and vertically through the rail to magnetize it is a vertical direction; and then passing a unidirectional flux in the same lengthwise direction through the rail to remagnetize the surface longitudinally and restore the characteristic fields at the internal defects.

3. The method of magnetizing rails and the like to establish characteristic residual magnetic fields in the vicinity of internal defects without establishing local magnetic fields in the vicinity of surface defects such as burns, gags, shell, and the like, and comprising cyclically passing a relatively strong, unidirectional, flux in the same lengthwise direction through the rail to cyclically magnetize the same to a high value of residual flux; then passing a unidirectional flux in said same lengthwise direction and vertically through the rail to magnetize it in a vertical direction; and passing a unidirectional flux in said same lengthwise direction through the rail to remagnetize the surface longitudinally and restore the characteristic fields at the internal defects.

4. The method of magnetizing rails and the like to establish characteristic residual magnetic fields in the vicinity of internal defects without establishing local magnetic fields in the vicinity of surface corrugation and comprising cyclically passing a relatively strong unidirectional flux in the same lengthwise direction through the rail to cyclically magnetize the same to a high value of residual flux; and passing a relatively weak unidirectional flux in said same lengthwise direction through the rail to decrease residual surface flux and thereby clean the surface.

5. In apparatus for magnetizing rails and the like to establish characteristic residual magnetic fields in the vicinity of internal defects without establishing local magnetic fields in the vicinity of surface irregularities, said apparatus comprising at least four relatively strong lengthwise spaced, longitudinally magnetizing, unidirec tional magnets operatively located adjacent the rail, and a relatively weak longitudinally magnetizing unidirectional magnet operatively located adjacent the rail and disposed rearwardly of said strong magnets to eliminate local fields at surface irregularities and to leave characteristic fields at internal defects.

6. In apparatus for magnetizing rails and the like to establish characteristic residual magnetic fields in the vicinity of internal defects without establishing local magnetic fields in the vicinity of surface defects such as burns, gags, shell, and the like, said apparatus comprising first means for strongly magnetizing the rail in a longitudinal direction, second means acting on said strongly magnetizcd rail for magnetizing it in a Vertical direction, said second means being disposed rearwardly of said first means, and third means acting on said vertically magnetized rail and remagnetizing the surface longitudinally in the same longitudinal direction to restore the characteristic fields at the internal defects, said third means being disposed rearwardly of said second means.

7. In apparatus for magnetizing rails and the like to establish characteristic residual magnetic fields in the vicinity of internal defects without establishing local magnetic fields in the vicinity of surface corrugation, said apparatus comprising first means for cyclically magnetizing the rail in the same longitudinal direction, and second means for passing a relatively weak unidirectional flux lengthwise in said same longitudinally direction through the strongly magnetized rail to decrease residual surface flux and thereby clean the surface, said second means being disposed rearwardly of said first means.

8. In apparatus for magnetizing rails and the like to establish characteristic residual magnetic fields in the vicinity of internal defects without establishing local magnetic fields in the vicinity of surface defects such as burns, gags, shell, and the like, said apparatus comprising first unidirectional magnet means for strongly magnetizing the rail in a longitudinal direction, second unidirectional magnet means disposed rearwardly of said first magnet and having a vertical rear pole closely adjacent the rail for magnetizing the rail vertically, and third unidirectional magnet means disposed rearwardly of said second magnet means and remagnetizing the surface longitudinally in the same longitudinal direction to restore the characteristic fields at the internal defects.

9. In apparatus for magnetizing rails and the like to establish characteristic residual magnetic fields in the vicinity of internal defects without establishing local magnetic fields in the vicinity of surface defects such as burns, gags, shell, and the like, said apparatus comprising a plurality of lengthwise spaced unidirectional magnets having vertical front and rear poles with the front poles closer to the rail than the rear poles for strongly magnetizing the rails longitudinally, a unidirectional magnet spaced rearwardly of said plurality of magnets and having vertical front and rear poles with the rear pole closer to the rail than the front pole, and a relatively weak, unidirectional magnet spaced rearwardly of said last-mentioned magnet and longitudinally magnetizing the rail to eliminate fields at surface irregularities and to leave characteristic fields at internal defects.

10. In apparatus for magnetizing rails and the like to establish characteristic residual magnetic fields in the vicinity of internal defects without establishing local mag netic fields in the vicinity of surface defects such as burns, gags, shell, and the like, said apparatus comprising a plurality of lengthwise spaced unidirectional magnets having vertical front and rear poles with the front poles closer to the rail than the rear poles for strongly magnetizing the rails longitudinally, a unidirectional magnet spaced rearwardly of said plurality of magnets and having vertical front and rear poles with the rear pole closer to the rail than the front pole and close enough to vertically magnetize the rail, and a relatively weak unidirectional magnet spaced rearwardly of said last-mentioned magnet and remagnetizing the surface longitudinally to restore the characteristic fields at the internal defects.

11. In apparatus for magnetizing rails and the like to establish characteristic residual magnetic fields in the vicinity of internal defects without establishing local magnetic fields in the vicinity of surface corrugation, said apparatus comprising a plurality of lengthwise spaced unidirectional magnets having vertical front and rear poles with the front poles closer to the rail than the rear poles for strongly magnetizing the rails longitudinally, a unidirectional magnet spaced rearwardly of said plurality of magnets and having vertical front and rear poles with the rear pole closer to the rail than the front pole but spaced sutficiently therefrom such that said lastmentioned unidirectional magnet remagnetizes the rail longitudinally, and a relatively weak unidirectional magnet spaced rearwardly of said last-mentioned magnet and passing unidirectional flux lengthwise through the strongly magnetized rail to decrease residual surface flux and thereby clean the surface.

12. in apparatus for conditioning strongly longitudinally magnetized rails; a forward unidirectional magnet having a vertical rear pole, selectively adjustable nonmagnetic spacing means connected to said magnet and engaging the rail to maintain said rear pole spaced a fixed distance above said rail, a relatively weak rearward unidirectional magnet including means for selectively adjusting its energization from low strength to high strength, and non-magnetic spacing means reacting between said rail and said rearward magnet to maintain a non-magnetic gap of constant dimension therebetween, such that when conditioning rail having no corrugations said adjustable spacing means is adjusted to position the rear pole of said forward magnet relatively close to the rail and said rearward magnet is adjusted to high strength, said forward magnet magnetizes the rail vertically and said rearward magnet remagnetizes the surface longitudinally and restores characteristic fields at the internal defects without establishing characteristic magnetic fields in the vicinity of surface defects such as burns, gags, shell, and the like, and such that when conditioning rail having corrugations said adjustable spacing means is adjusted to position the rear pole of said forward magnet relatively farther from the rail and said rearward magnet is adjusted to low strength, whereby said forward magnet remagnetizes the rail longitudinally and sets up characteristic residual magnetic fields, and said rearward magnet decreases residual surface magnetism and eliminates characteristic residual magnetic fields in the vicinity of corrugation.

References Cited in the file of this patent UNITED STATES PATENTS 2,265,137 Barnes et al. Dec. 9, 1941 2,317,718 Barnes et al Apr. 27, 1943 2,317,720 Barnes et al Apr. 27, 1943 2,425,857 Barnes et al Aug. 19, 1947 2,461,253 Barnes et al. Feb. 8, 1949 2,497,855 Barnes et al. Feb. 21, 1950 2,688,725 McKee Sept. 7, 1954

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