CA1185904A - Magnetic brake shoe - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An electromagnetic track brake for braking a railway vehicle by utilizing the top of the running rail including a series of elementary contact shoes. An electromagnetic structure including a plurality of annular excitation coils and a plurality of U-shaped ferromagnetic cores which are in vertical alignment with the line of symmetry of the cen-ter of the running rail. The U-shaped ferromagnetic cores are inverted so that the ends of the two legs form a pair of pole faces adjacent the top of the rail. The pole faces are provided with wear-resistant friction material.
The U-shaped cores are attracted toward the rail and the wear-resistant friction material on the pole faces engages the top surface of the rail when the excitation coils are energized.

Description

MAGNET IC BRAKE S HOE

FIELD OF THE_INVENTION
The present invention relates to an eLectromagnetic brake shoe, especially for a braking system for railway ve-hicles by employing the steel running rail to brake thevehicle.
Norma'.ly, the type of brake shoe is composed of a series of elementary friction shoes constituted by a ferromagnetic core having a pair of pole faces~ namely, north and south poles, which are separated by a vertical clearance. During braking, the ferromagnetic core is magnetically excited by at least one electromagnetic coil which carries a D.C. electric current for causLng a ma~netic attraction between the polar aces and the running surface o the rail which closes the lS maCJnetic circuit.
The attractive force between the polar faces and the ~t:eel rail is relatively independent rom the rallway ve-hicles wheel's adherence on the running rail, with the excep-tion of the initiaL application effect force of the magnetic ~0 brake shoe on the rail which is generally greater than twice the action of gravity on the magnetic shoe, and ltS suspension and return system from an idle position remote from the rail.
The attractive force between the shce and the rail may reach very high values which could be more than 20 times the gravational force on the shoe and its suspension and lift-in~ system which may be in the vicinity of the application force upon the rail by the wheels of a railway truck frame.

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For example, it's possible to show that the two magnetic shoes of the railway truck weigh l/2 ton wlth their movable appli-cation and lifting equipment, but they can be applied on the rail by electromagnetic attraction with a maximum attractive force of approximately 14,000 decanewtons (daN). The re-tarding forces obtained with such shoes during braking tests do not usually exceed 1,000 to 1,200 daN values which may be interpreted as a low friction coefficient between the friction surface of the shoes and the rail as well as a decrease in the induction going through the surface of the rail as the shoe travels on the rall. In spite of these apparently mo-dest braking performances, the magnetic brake shoes are in-creasingly used on rapid railway vehicles which are destined for passenger transportation. The use of magnetic brakes, for ~x~mpLe, requires almost no adhesion between the wheels and th~ rail, and the stopping distance will not be decreased ~v~n itl the worst adhesive conditions. On the other hand, a magnetic brake might be considered as a safety device since the shoes may be automatically applied in the event of emer-gency braking by being supplied with D.C. current from thevehicle's batteries. The use of the magnetic brake shoes on the light railway vehicles for passenger transportation, such as streetcars, has always been preferred since it is possible to feed a great amount of electric power to the exciting coil ~5 by directly or almost directly deriving 600V D.C. current fxom an overhead contact wire, which is sufficient power to attain a 3m/sec deceleration rate for emergency braking of trucks.

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It will be appreciated ~hat numerous improvements have been proposed and/or applied in ordex to attempt to attain an improved braking performance of the magnetic shoes. The proposed increase in the electric excitation has been con-sidered, but has n ot been effective since the magnetic cir-cuit is almost totally saturated. Further, the suggested increase of dimensions, namely, the width and the length, which contact the limi~ed width of the head of the rail and also the limited available space between both wheels of the truck, would make it impossible to transmit to the vehicle the required friction forces applied by the rail to the shoe.
Another previous improvement consisted of adding, between the magnetlc poles of the shoe, specifically in the clear-ance between the two poles, some frictional lining posses-L~ ~ing a high coefficient of friction. Such a lining has beenEound to be practical]y ineffective, either because the appli cation force on the rail is low, or because the permeability between the magnetic shoe poles and the rail is seriously affected so that the gain on the friction coefficient is al-~O mo-qt cancelled by the decrease of the magnetic application force of the shoe on the rail.
OBJECTS AND SUMMARY OF THE INVENTION
One of the objects of this invention is to provide an improved magnetic brake shoe which is compatible with the actual weight, space, electric excitation power requirements, and in keeping with the price of the railway vehicle's truck meant for passenger transportation and, in turn, to provide a magnetic brake shoe which has effective braking performance on the track which is considerably improved.
Effectively, the electromagnetic shoe is utilized for the railway vehicle braking by employing the steel running rail. The brake includes at leas~ one elementary friction shoe formed by a ferromagnetic core having north and south polar faces which are separa-ted by a vertical clearance or air gap. The polar faces of the ferromagnetic core are cap-able of engaging the running surface of the rail. The corecooperates with at least one excitation coil which is cap-able of causing the magnetic attraction of the polar faces to the running surface of the rail which closes the magnetic circuit~ This is characterized by the fact that the ferro-lrj magnetic core and its poLar faces form a closed magnetic fluxpa~h with the rails which are made of a high rnagnetic per-meabLe material, such as soft steel. A plate made of a good magnetic permeability material, with a high friction coeffic-ient and good mechanical resistance, such as, a conglomerated and sintered powder with a smooth iron base or of ferrites, is added and rigidly fastened on each polar face. Thus, the plate becomes interposed between the rail surface and the polar face which i9 made of high magnetic permeable material when the shoe ls applied to the running rail. The friction ~5 material, the most generally used until now, to realize the polar faces, was a friction cast iron with good magnetic permeability but which did not have as high inductive characteristics as soft steel. In the invention, it is pos-sible to realize improved magnetic circuits comparable to soft steel with a high permeability and also to benefit from the high friction coefficient between the pole surfaces and the rail. There are sintered materials in existence which possess a high permeability and have a coefficient of friction between 0.3 and 0.5. The interposition of plates of such a material between the polar faces and the rail should enable the tripling of braking force attainable with the magn~tic shoes without increasing their weight, space raquirement and electric excitation.

~ ccording to another characteristic of the invention, the material with good magnetic permeability and high fric-tLon coeEfi.cient also possesses remanent magnetism proper-1~
t.i~s which is capable of intensifying the attraction force a~ t~d on the running rail without adversely affecting the re~u.rn of t.he magnetic shoe to idle position after cutting o~ the current to the excitating coil. A shoe having a slight amount of remanent magnetism may be applied to the ~0 rail without electric excitation of the coil during the ser-vice bra~ing of the vehicle in order to clean either a wet rail or one polluted by greasy substances. The application of such a shoe upon the rail may be controlled by the opera-tion of the brake pressure of the vehicle which causes the 25operation of one or several application pistons. Thus, the frictional materiaL of high coefficient of friction on -the poles causes an appreciable braking effect and an efficient cleaning of the rail surface results. When desired, the shoe may be returned to an idle positlon away from the rail by providing a return spring greater than that of returning force which is normally equal to twice the weight of the shoe and the movable portion of lts suspension and return system.
In another form, the material with good magnetic per-meability and high coefficient of friction may possess frag-mentation quality to abrasion due to a rubbing effect such as, that of cast iron in railroad brake shoes which permits the removal of a large portion of the frictional heat which is developed during the engagement of the shoe with the rail~
According to another important characteristic of the 1~ Lnvention, the material with good magnetic permeability and high coeEficient of friction also has a great abrasive re-~is~ance and is laid in thin layers on the polar faces by a m~ans of metallization spattering.
Another accomplishment of this invention consists of moLding the material with good magnetic permeability and high coefficient of friction into a massive block of friction shoe for attachment to each of the polar faces. Each of the shoe blocks is removably attached to the polar faces in such a-manner for insuring the magnetic circuit continuity through the ferromagnetic core. In practice, the two friction shoe blocks which correspond to the two poles, namely~ north and south poles, of an elementary friction shoe may be assembled as a unique monoblock, on one hand constituted by two shoe blocks separated by a continuous band of nonmagnetic mate-rial. The band may comprise a heat sensitive Material, such as, fusible wax, or the like. The wax block is a funnel-shaped section having a widened portion facing toward the excitation coil in order to create a minimum width clear-ance at the bottom end of both poles. The unitary monoblock is located between the two poles and the top side of the rail.
According to a particularly compact and innovating arrangement, the continuous band of nonmagnetic material is solidified by fritting to both friction shoe blocks which correspond to the respective poles. The unitary monoblock is clamped and assembled in a detachable way by any suitable L~ m~ans, such as, screws between ~he opposite lateraL polar f~c~ provided on each magnetic core pole. Further, it is ~upported by each o these side faces on another polar face par~lleL1y to the surface of the tail on each core pole. The opposite lateral polar ~aces provided on each magnetic core pole preferabLy offer a limited height which enables, in the idle position of the magnetic shoe mounted on the railroad vehicle, to become disengaged from the rail. Thus, the uni-que monoblock is disposed between the magnetic core poles.
In another application, the unique monoblock may be later-~5 ally pushed between both opposite lateral polar races pro-vided on each pole of the core until it reaches a lateral position to permit the seating and/or unseating of the monoblock in parallel to the rall. For the assembling on the nonmay~etic core, the two opposite lateral faces pro-vided on each of the poles of the core may be symmetrically slanted in relation to the longitudinal axis of the shoe and may form two retaining surfaces for the unique monoblock being assembled in dovetail between both polar faces of the ferromagnetic core.
The central continuous band of nonmagnetic material of the unique monoblock may be provided with teeth and/or flanges capable of working with teeth and/or flanges pro-vided on a rigid caslng of the exciting coil in order to transmit to this rigid casing the fric~ion forces being de-veloped on the rail to the part of the unique monoblock when lt ~i~ in contact with the rail.
1.5 BRIEF DFSCRIPTION OF THE DRAWINGS
Other ob~ects, advantages and characteristics of this inv~ntion will appear more readily evident by reading the dascription which follows, which is supplied as non-limitat-ive and opposite to the drawing where:
~O E'igs. 1 and 2 are cross-sectional views showing the invention, two types of different embodiments of the electro-magnetic shoe as applied to the running rail in a braking position for a railroad vehicle.
Fig. 3 is a partial elevational view of a railroad ve-hicle body equi~ped with electromagnetic shoes as disclosedin the present invention.

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DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, and in particular to Fig~ 3, there is shown a shoe in service on a vehicle. As shown, the reference numeral 1 indicates an electromagnetic shoe which is supported from the truck 2 of a railway vehicle by piston rods 4a and 4b of two suitable raising or lifting cylinders having a direction of motion as indicated by arrows 4. A plurality of annular excitation coils 6 are located in-side a rigid casing 5. The coils are set in line along the longitudinal axis of the running rail 30 These coils have a vertical line of symmetry 7 (see Fig. 1 and 2) extending along the entire height of the shoe which coincides with the ver-tical line of symmetry of the longitudinal rail 3. The shoe 1 comprises a series of rubbing contact elementary shoes mounted in line and positioned between two headpiece mem-b~r~ 9. The rlyid casing 5 forms the supporting frame so khat each elementary shoe may be connected with its respect-i.ve coil 6. The two elementary end shoes 9 are each pro-vLded with a beveled edge 18 for permitting them to gradually engage the rail 3 so as to clear and prevent a hangup when a sudden discontinuity occurs along the running surface, such as, at a rail joint or at switch points.
Referring now to Fig. 1, there is shown the details of one of the shoes 8 as applied on the running surface of the head 3a of the rail 3. Each of the shoes comprises an in-verted U-shaped ferromagnetic core. The core includes two depending legs or branches LO which form a central opening 6a g _ ~5~

facing toward the rail 3. The coil 6 surrounds the bight of the U-shaped core which has formed on the ends of the legs 10 a pair of poles or polar faces 11. The pole faces 11 are disposed opposite the upper surface of the rail 3 and are perpendicular to its longitudinal axis of the rail 3. As mentioned above, the upper end of the two branches of the U-shaped core pass through the cen~ral opening of -the coil 6 and are contiguous to one another as indicated by a surface line 12. The contiguous surfaces are flat without clearance to form a closed magnetic circuit of each elementary shoe 8.
Thus, the magnetic branches form t~o easily detachable parts 13 and 14 on each side of the vertical line of symmetry 7.
As shown, the parts 13 and 14 each include a lower base port.ion which comprises a friction tip 15. The tip portions 1~ .15 part.ially encompass the bottom side of the coil 6, and ar~ v~rti.cally directed toward the rail 3. The homologous ~i.p oE one part 13 is separated from the homologous tip of kh~ other part 14 by means of a separation band 16 made of st.rip or nonmagnetic material, such as, brass or sta nless steel. The two detachable parts 13 and 14 constitute the ferromagnetic core member of each elementary shoe 8 and are pressed against contiguous surface 12 and the separator 16 by a plurality of traverse bolts 170 The upper bolt which passes through apertures in the bight of the core and sur-~5 face 12 may be made of a highly magnetic permeable materialwhile the lower bolt, which passes through a space located at the base of the coil 6 and holes formed in the parts 15 ' ?~

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of the branches 10 and the dividing band 16 should be made of nonmagnetic material, such as, stainless steel, in order to prevent a magnetic short circuit from occurring across the clearance constituted by band 16.
In accordance with the invention, the pole faces 11 of the parts 13 and 14 are covered by a thin plate 19 which has a good magnetic permeability as well as a high coefflcient of friction, a good mechanic resictance and a good abrasive resistance. These plates are manufactured by powder metal-lurgy, specifically by sintering; however, the manner of fastening, which is usually achieved by screws, presents some dificulties when the plates are thin. In instances where the material used between the rail surface and the po-lar faces shows a high abrasive resistance, it is possible to consider attaching the material to the pole faces in thin layers by metal depositing or plating, i.e., by spattering the material at high impact speed when it is in the form of melted or micro-melted particles.
When the magnetic shoe assumes an active position as shown in Fig. 1 the shoes engage and slide on running sur-face of the rail 3. That is, when the piston cylinders allow the rods ~a and 4b to move downwardly the shoe will come to rest on top of the rail 3. At the same time, a D.~. current is caused to flow through the coil 6 which results in a high number of ampere-turns of excitation which is capable of al-most saturating the magnetic circuit. The magnetic flux flows through a closed magnetic circuit made up of parts 13 and 14 and head 3a of the rail 3. The magnetic flux enters -the rail head from one of the pole faces 11 and exits the rail head into the other pole face and causes concentric circles of flux to flow through rail head 3a as shown by fine lines 20. The separation band 16 and the nonmagnetic rod of the lower bolt 17 compels the rnagnetic flux to more readily flow through the rail head which has a relatively higher permeability to lines of force and causes the linking of the north and south poles of the polar faces 11. The high magnetic induction which passes through the head of the running surface 3a of the rail 3 causes a very large magnetic attractive force between plate 19 and the surface of the rail~ The application force which is created between ~he plate 1.9 and the rail by very long magnetic shoes may .LS rt-~ach statlc values of 7 to 10 thousand daN~ The fast dis-placement o the magnetic shoe on the rail induces Foucault ~r ed~y current into the rail Foucault or eddy currents which may tend to decrease the magnetic induction passing khrough the rail surface, but the higher coefficient of ~0 rictiorl exhibited by the plates 19 causes a higher braking force to be applied by the head 3a of the rail to the pLates 19 and to be transmitted to the parts 13 and 14 of the ferro-magnetic core which then supports the lateral faces of the opening 6a o the coil 6 located in the rigid casing 5 which is ixed to the frame of the truck of the vehicle.
In previously-known magnetic shoes, the ferromagnetic cores either are made of massi~e cast iron which has a rela-t:ively good magnetic permeability or are made of molded steel - ~2 -1 .1 8~i9~;4 which has a very good magnetic permeability with cast iron friction shoes which possess only averag~ magnetic permea-bility. The permeability of magnetic circuit of such cores is relativeLy lower than that attained with magnetic shoes as shown in Fig. 1. Such an advantage permits a considerable increase of the magnetic induction which passes through the surface of the rail and, accordingly, results in a consider-ably greater attraction between the shoe and rail since the attraction force is proportional to the square of the in-duction. In such a shoe arrangement, the bucking force pro-duced by the Foucault or eddy current is decreased as much as po~ssible in order to increase the friction action between the plates 19 which have high coefficient of friction (0.2 ~o 0.~) and the surface of rail 3. The roughness of the surface e the rail is augmented after the abrasive passing of the in.itiaL magnatic shoe of the first truck of the train so ~ha~ the shoe efficiency increases the following ones.
The magnetic brake shoe as shown in ~ig. 2 employs some of the same elements which are shown on Fig. 1. It will be ~0 observed that the same elements have identical references and deal with the excitation coil 6, the circuit branches 10 of the ferromagnetic core in two parts 13 and 14 and the common supporting surface 12, etc.
For the purpose of simplifying the disassembly of the ~S pole shoes from the outside of the truck frame 2~ the bolts and nuts are replaced by hexagonal cap screws 17 which have the heads exposed to the outer side of part L4 while part 13 ~5~ ~

is provided with threaded holes for receiving the threaded ends of screws 17. The lower tip portions 15 of parts 13 and 14 of the magnetic core are not completely extended -to the top of the rail, but includes two bearing surfaces 21 and 22, which are perpendicular one another. The surface 21 is parallel to the li~e of symmetry 7 while surface 22 is paral-lel to the upper surface of the running rail.
According to the invention, a massive friction block 23 is made up of two massive poles 24 and 25 of a good magnetic permeable material having a high coefficient of friction and good mechanical resistance. The pole pieces may be cast by a powder metalurgy and sintering process into a single or unitary monobLock 23 which includes a separation band 26.
The separation band establishes the clearance between both 15 pol~s 24 and 25. The monoblock is assembled on the magnetic co.r~ and is adapt0d to engage the lateral bearing faces of eac~s 2L and 22 of parts L3 and L4 of the magnetic core.
'rh~ monobLoclc is cLamped between both faces 21 by the Lower nonmagnetic screw 17 whc h passes through a clearance bore ~0 27 provided in the bLock. The separation band is made of a suitabLe nonma~netic material by any acceptable method, and specificaLly by powder metallurgy process. The nonmagnetic band includes a wide section near the top adjacent the coil 6, as shown in Fig. 2. This wide section, at the upper end o the band, provides a great distance in the vicinity of the coil 6 which is the most susceptlble to magnetic short cir-cuit due to induction leakage while a small width at the ~s~

lower end of the band provides little clearance between both poles around the fric-tion surface on the rail. This tapered configuration causes an increase in the contact surface be-tween the frictiorl shoes and the rail. It also lncreases the S induction field passing through contacting surfaces as well as increasing the attraction force between the magnetic shoe and the rail. The monoblock 23, which is mounted on the front contacting shoe 9, is provided with beveled edge 18 as previously described in reference to Fig. 3. As shown in Fig. 2, an exterior laterally extending fin 28 is provided on the monoblock to reposition it on the rail in the event that transversal lateral shock offsets the magnetic shoes a~sembly of a truck connected kogether by a frontal and late-ral thrust on the truck frame.
L5 L~t us suppose the magnetic shoe is applied on therrail and assumes its active position as shown in Fig. 2 so that it ~lides on the upper surface of the rail 3. Further, let u~ a~sume D.C. current passes through the coil 6 so that mag-n~tic 1ux readily passes through intimate contacting faces ~ 2L and 22, into the massive poles 24 and 25 which have good magnetic permeability. The magnPtic flux flows through one of the polar faces ll and enters the rail. The magnetic lines of force pass through the rail head 3a as shown by the concentric lines 20. The flux lines emerge from the rail and go back through the massive pole 24 into part 14 of the erromagnetic core without passing through the separation band 26 which exhibits a variable reluctance clearance. The , ~ ~

magnetic attraction developed between poles 24 and 25 and the rail produces a high rubbing force due to the high coefficient of friction of the sintered materlal of the poles and non-magnetic material of the separation band 26. In this vers-ion, it is possihle -to construct the massive block 23 of material which is less resistant to wear and abrasion than in the case of Fig. 1 since the block 23 may be more easily replaced on the shoe while still mounted on the truck 2. To accomplish this, it is only necessary to unscrew the lower stainless screws 17 and to drop the blocks 23 on the rail with the lever when the magnetic shoe is in idle position ag shown in Fig. 3. It is then possible to laterally remove thc blocks 23 since the clearance between the lower edge 22 and the rail is greater than the height of edge 21. In the L~ ~v~nt that the face 21 is higher than the available space b~twe~n the pole face 11 and the rail, it's possible to re-mov~ the blocks 23 by sliding them, longitudinally, between ~he faces 21 after releasing the lower screws 17 until reaching an open end of the end shoe 9. It is understood that the massive poles 24 and 25 may be separated from the band 26 if they are only held together by the lower screw 17.
The separation band 26 may have various cross-sectional con-figurations, specificallyt a rectangular cross~section of a known type which could facilitate the tightening of the mas-sive poles between two faces 21. Further, the nonmagneticband may be equipped with teeth and/or projections which ~35~

would cooperate with matching teeth and/or conjugated de-pressions, which are provided on the rigid casin~ 5 which is preferably made of stainless steel sheet metal in order to minimize magnetic leakage.
It is understood that the gap between the bore 27 and the intermediate portion of the screws 17 allows the massive poles 24 and 25 to be securely clamped between the faces 21 yet permits the free vertical expansion of these poles when the temperature rises during their frictional contact with the rail. In order to reduce the overheating of the rail and the pole pieces during the braking operation, it i5 highly advantageous to provide an additive to the pole piece such as the phosphorous in cast iron of brake shoes for railways, to di~ipate a part of the friction heat caused by the sliding .L5 abra~ion or to construct the separation band 26 o~ a heat accumulation b:Loclc of nonmagnetic material, such as, fusible w~
It is understood that this invention is not limited to only the specific types of embodiments shown and disclosed.
It is apparent that numerous changes and variations are avail-able to the state of the art, without deviating or departing from the invention. For example, in the event the magnetic brake shoe which includes the massive poles 24 and 25 might be heated excessively by the rubbing friction of the rail, 2S it is possible to make symmetrlcally inclined faces 21 in re-lat.ion to the axis 7 in order to form two retaining surfaces toward the bottom for the monoblock 23. Thus, a dovetail ~s~

will exist between both faces 21 ~ith a slight clearance for permitting it to rest on parts 13 and 14 of faces ~2 during braking. In such an arrangement, the magnetic circuit will have a slight clearance bet~een poles 24 and 25 and faces 22 but a good contact between those poles 24 and 25 and the sup-port surface 22. The block 23 and the poles 24 and 25 may freely expand in every direction with regard to the soft steel magnetic core. Such an arrangemant appears partlcularly ad-vantageous when the coefficient of expansion of the cores and block 23 are dramatically different, but it is evident that lower screws 17 must be extremely strong in order to meet the torsional forces and working forces applied to this core when the magnetic shoe i5 in service on the rail. The use o~ mono-block 23 having a dovetail requires a lateral sliding inter-L~ connection for these monoblocks at one of the ends of the magnetic 5hoe.
The use of magnetic shoes with friction parts, either th~ highly resistant to abrasion type, such as the thin plates 19 o Fig. 1, or the easily replaceable on the shoe ~0 in service type, such as monoblock 23 on Fig. 2, permits the use o such shoes in service braking. In an arrangement where the regulating braking is attempted without excitating current modulation is very difficult and expensive to attainn However, as previously described, controlled braking could ~5 be achieved by causing the shoe to be applied on the rail by a fluid pressure acting on at least one of the application pistons of the lifting mechanism~ The shoes are biased up-wardly by springs and other return means to lift the shoes to their nonbrake or idle position. The disadvantage of us-ing permanent magnets in railway environmen~ is that they have a tendency to pick up any ferromagnetic objects which they pass.
Another variation consists of employlng a material for the pole pieces 24 and 25 and also for the separation band 26 which has a relatively elastic characteristic in which the desired quality might be obtained by leaving voids between the grains of sintered material.
Sucn an elastic structure would permit the polar faces 11 to readily assume the shape of the running rail surface under the action of the magnetic attraction force which would increase the magnetic induction as well as the braking force of the shoe on the rail.

Claims (14)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An electromagnetic track brake for braking railway vehicles comprising, a plurality of U-shaped ferromagnetic cores disposed along the length of a running rail, the de-pending legs of said U-shaped cores disposed adjacent the top surface of the running rail and each forming a pole face situated on the respective sides of the vertical line of symmetry of the running rail, a plurality of excitation coils, a separate one of said plurality of excitation coils mounted on the bight portion of each of said plurality of U-shaped cores, a wear-resistant friction material coopera-tively associated with said pole faces to engage the top surface of the running rail when said excitation coils are energized to cause a magnetic attractive force between said U-shaped ferromagnetic cores and said running rail.

2. The electromagnetic track brake as defined in claim 1, wherein said wear-resistant friction material is deposited on the pole faces to form a thin plate.

3. The electromagnetic track brake as defined in claim 1, wherein each of said U-shaped ferromagnetic cores includes a pair of identical branch members.

4. The electromagnetic track brake as defined in claim 3, wherein said pair of branch members are joined together by upper and lower fasteners to form said U-shaped cores.

5. The electromagnetic track brake as defined in claim 1, wherein a nonmagnetic separator is inserted be-tween the depending legs of said U-shaped cores.

6. The electromagnetic track brake as defined in claim 1, wherein a rigid casing forms a supporting frame for said U-shaped cores and excitation coils.

7. The electromagnetic track brake as defined in claim 1, wherein said wear-resistant friction material takes the form of massive monoblock which is fixed to the ends of said depending legs of said U-shaped ferromagnetic cores.

8. The electromagnetic track brake as defined in claim 7, wherein an intermediate nonmagnetic separator is disposed in said massive monoblock.

9. The electromagnetic track brake as defined in claim 8, wherein said nonmagnetic separator is a wedge-shaped member in which the wide portion is facing said ex-citation coil and the narrow portion is facing the top surface of the running rail.

10. The electromagnetic track brake as defined in claim 8, wherein said monoblock includes a good magnetic permeable material having a high coefficient of friction and good mechanical resistance.

11. The electromagnetic track brake as defined in claim 4, wherein said upper fasteners are made of magnetic material and said lower fasteners are made of nonmangetic material.

12. The electromagnetic track brake as defined in claim 1, wherein said wear-resistant friction material is applied in thin layers by metallic depositing.

13. The electromagnetic track brake as defined in claim 12, wherein said deposited metal has good magnetic permeability, a high coefficient of friction, and good mechanical and abrasive resistance.

14. The electromagnetic track brake as defined in claim 2, said thin plate is deposited on the pole faces by spattering the material at high-impact speed when in the form of a melted particle.