FR2490760A1 - Wheel rim brake for railway vehicle - has sintered metal, glass and graphite bake lining on metal backing - Google Patents

Abstract

The brake has four separate brake blocks (11-13) brazed to a steel backing plate. The backing plate is welded along its two long sides to the brake shoe (1). Alternatively, the backing plate can be spot welded (3A) through holes drilled in the brake shoe. The brake lining material is a compound of bronze, copper, iron, molybdenum, glass and graphite powders sintered into a composite material. The brake shoe assembly is able to adapt immediately to the form of the wheel iron due to the flexibility of the brake shoe and the diamond relief on the wearing face of the brake blocks.

Description

-1 -

  RIM BRAKING DEVICE COMPRISING SKATES IN

WATERIAU COMPOSITE FRITE

  The braking device according to the invention is used for braking

  swims on wheel rim or other parts having an annular zone and capable of turning. It is particularly suitable for braking on the rim of the wheels of railway vehicles, such as locomotives,

  passenger cars and freight cars.

  The devices traditionally used for braking vehicles

  the railways are made up of cast iron shoes which are suitable for

  strongly bent on the steel rims of the wheels when braking.

  This braking mode has serious drawbacks: cast iron has a low coefficient of friction, of the order of 0.12 when dry. In addition, the friction of the cast iron shoes on the steel tires results in significant wear of these tires which is added to the natural wear caused

by friction on the rails.

  A final disadvantage of cast iron clogs is that it is rarely possible to

  ble, when replacing a worn hoof with a new one,

  ter the radius of curvature of the new shoe to that of the wheel rim.

  Indeed, the latter varies within fairly wide limits according to the degree

  of wear. This results in poor braking conditions during the

  period of adaptation of the new shoe to the rim and, in some cases,

  increased risk of locking the wheels or breaking the shoes.

  It has been proposed for a long time to adapt to new rim braking.

  calf friction materials such as those developed for braking motor vehicles and, more recently, for braking aircraft during high speed landing. Among these materials, those which appeared particularly promising are sintered composites based on

  metallic with a certain proportion of non-metallic additions

  ques. However, great difficulties have been encountered when attempts have been made to produce braking devices incorporating such friction materials. In fact, these materials have often proved to be ill-suited to the braking conditions of railway vehicles which require great robustness and a long service life, in often very severe conditions of exposure to the weather and to variations.

brutal temperature.

  Furthermore, these materials, which must have a relative density-

  high, to withstand the high unit pressures required

  rim braking, are often sensitive to main cracking

  Lement under the action of thermal or thermomechanical constraints. Cracking can cause more or more fragments to break

  less of the friction material and even in some cases the separation

  brutal tion of an entire block of this material which is torn from its sup-

  Harbor. In this extreme case, the braking capacity of the device may

  be canceled or at least reduced to very little. Finally, the risk

  that crack formation is increased by the differences in radius of curvature between the rim and the surface of the friction material that comes

  resting on it. These differences can lead to risks of blocking

  wheel cage when fragments of loose friction material

  get caught between the wheel rim and the brake device

swim.

  We therefore looked for the possibility of producing a braking device

  comprising friction materials with relative coefficient of friction

  high density, of sufficient density to withstand the braking forces on the rim, and having high resistance to cracking and

  disintegration. Such a device should, moreover, allow <repair-

  firing, as homogeneously as possible, the braking pressure over its entire length so that the friction material is put into action at

  rim contact in the most efficient way and without the constraints

  your thermomechanics do not involve risks of rupture.

  The braking device according to the invention comprises a curved sole made of sheet steel and at least two studs of composite friction material with a sintered metal base, each stud being brazed on a support plate.

  made of steel, the connection between this support plate and the sole being reali-

  welded. This welding is carried out by running, parallel to the two long sides of the sole, weld beads between the two

  opposite edges of each support plate and sole. Alternatively

  -3- ve or complementary, this welding can be carried out by at least one

  weld point between the back of the support plate and the sole.

  In addition, to improve the adaptation of the surface of each of the studs made of friction material with the surface of the rim with which it will come into contact, it is advantageous to provide the surface of these studs.

diamond point reliefs.

  The following nonlimiting examples and the attached figures will make it possible to better understand the characteristics of the new braking device according to the invention:

  Figure 1: elevation view of a brake shoe according to the invention.

  Figure 2: plan view along A of Figure 1.

  Figure 3: elevation view of a friction material pad.

  Figure 4: view along B of Figure 3.

  Figure 5: elevation view of a braking device according to the invention

tion.

  Figure 6: enlarged view of part of Figure 5.

  Figure 7: view of a sintered composite part in elevation.

  Figure 8: plan view of Figure 7.

  Figure 9: elevation view of an annular envelope.

  Figure 10: plan view of Figure 9.

  Figure 11: plan view of the composite part assembled with the annular casing.

  Figure 12: sectional view along C of Figure 11.

EXMPLBE 1:

  Figure 1 shows in elevation a sole for a braking device.

  ge according to the invention. This sole consists of a steel blade (1) whose curved shape is designed to adapt to a support piece in

  cast iron or steel not shown. Its width is generally equal or light-

  rement lower than that of the rim on which the studs of friction material will be applied. Its length is such that it allows the attachment of at least two studs of friction material. The ring (2), also made of steel, is welded to the sole (1) in the middle. It is

  intended to be crossed by a key which ensures the retention of the

  melle on the support piece. The curvature of the sole (1) and its

  thickness and mechanical characteristics of the steel which constitutes it

  kill are calculated in a well-known way of art fall to repair-

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  pull the clamping pressure against the rim of the wheel so as

regular as possible.

  The sole described in this example is equipped with four pads made of material

  friction line. FIG. 3 represents one of these studs which consists of a piece of sintered friction composite material (7) brazed on a support plate

  steel (8). The view along B, represented in FIG. 4, shows that the surface

  face (9) of the stud which will come to bear on the rim has reliefs

  such as diamond points which will facilitate the adaptation of the run

  bure of the stud to that of the rim at the time of commissioning

new studs.

  FIG. 5 shows the sole equipped with four studs (10), (11), (12) and

  (13) similar to that of Figures 3 and 4. Each of these. studs is so-

  secured with the sole (1) by lateral weld seams made

  killed on both sides of the support plate parallel to the length of the sole. We see in Figure 6 one of the two weld beads (14) which secure the plate (15) of the stud (10) with the sole (1). Furthermore,

  a weld point is made between the sole and each of the plates

  ques support in the center of these. These points are executed in the form of a "plug weld". For this, holes (3), (4), (5) and (6) pass through the sole. These plug welds are, for example, performed with an arc by adding metal to the holes (3), (4), (5) and (6) so as to fill them. This filling is made visible by the slight reliefs

  such as 3A which appear in FIGS. 5 and 6. It is possible, in certain

  in some cases, be content to ensure the connection between studs and sole either

  only by the lateral weld cords, or only by the weld

hard plug.

  This last mode of connection, carried out in the middle of the plates, makes it possible to avoid

  the development of excessive tension between plates and soles,

  evoked by mechanical forces at the time of braking, as well as by differential expansions> due to rapid overheating at the level

support plates.

  To reduce the stresses, due to differential expansions, it is also possible to limit the lateral weld beads to only a part -5 of the length of the side of each support plate, in the median zone thereof. For the same reasons, it is not desirable to weld

  the sole the other two sides of each support plate.

  Tests have shown that the braking device thus produced according to the invention gives excellent results because each of the pads is thus applied with a substantially equal pressure on the rim of the

  wheel when braking. In addition, the elastic deformation of the se-

  it allows the device to be adapted to the slight differences in diameter that can be observed in practice on the same type of wheel, depending on

rim wear.

  Finally, thanks to the method of connection by lateral welds and / or axial welds, a sufficiently solid connection of the studs with the sole is ensured without promoting the development of excessive preferential stresses liable to cause cracking of the studs or even the rupture of the connections between materials. composite and support plate or

between support plate and sole.

EXAMPLE 2

  A particularly effective embodiment of the brake device

  swimming according to the invention consists in using braking pads,

  such as those described in a parallel patent application, con-

  surrounding a brake shoe of sintered composite material, deposited the same

day.

  These studs consist of a piece of sintered composite friction material and of an annular envelope, of sintered metal of high ductility, which encloses and is linked to the side walls of the composite piece

metallurgically.

  Thus, four studs were made, each of these studs being obtained

  bare by compression and sintering from the following constituents, the contents of which are expressed by weight: - 90/10 bronze powder passing through a 35 Tyler sieve ......... 30% - Copper powder passing through a 60 Tyler sieve .

  ............ 30% - Sections of wire 0.15 mm, length 3 mm approximately 10% - Powder of 1b passing through a 150 Tyler sieve ......... ......... 10% - Glass powder passing through a 70 Tyler sieve ................ 10% .. DTD: 2490760 -

  -6- - Graphite powder fraction between sieve 16 and 32 Tyler .. 10% The mixture was compressed under a pressure of 400 lPa, then sintered under

  reducing atmosphere 1 hour at 830'C.

  A sintered part (16) represented in FIGS. 7 and 8 was thus obtained, having substantially the shape of a rectangular parallelepiped of approximately

  mm x 80 inn and about 54 mm thick.

  An annular envelope was also prepared by compression and sintering.

  re (17) which is represented in FIGS. 9 and 10.

  This envelope is made from a powder mixture containing: Weight% - 90/10 bronze powder passing through a 60 Tyler sieve ... 60% Cast iron powder at 4% C passing through a 60 Tyler sieve ... 40% Compression is carried out under a pressure of approximately 350 WPa and the

  sintering under a reducing atmosphere for 1 hour at 900 ° C.

  The dimensions after sintering are such that the sintered part (16) can be fitted inside the sintered annular casing (17) with

  a play of the order of a few tenths of a mm.

  The porosity of these two parts is approximately 35%.

  These parts were placed one inside the other in the die of a press, the punch of which has regularly distributed diamond point reliefs. After heating to 8200C, the parts were compressed with a press stroke to a pressure of 250 MPa. We have

  thus bonded the two parts metallurgically and lowered their porosity

  below 3% while forming diamond point reliefs on the face intended to come into rubbing contact. On the side opposite the

  rubbing face, a steel plate a few mm thick was brazed

  sister. This soldering was carried out by means of a solder containing by weight

  Ni 40 e%, Cu 54% and Sn 6% at a temperature of 820 ° C.

  Figures 11 and 12 show in plan and elevation the part ob-

  outfit. We recognize in Figure 11 after compression the composite part (18) linked to the annular casing (19). Figure 12 shows in section the support plate (20), the envelope (19) and the reliefs (21) in

  diamond point of the piece (18).

  The studs thus produced were then assembled with a sole of the

  same type as that of Example 1 and in the same way.

  The braking device produced according to the invention has shown, during

  long-term tests1 exceptional resistance to disintegration

  tion and cracking. Indeed, the ductile belt which surrounds each stud prevents tearing at the edges and, moreover, thanks to its composition, gradually wears out at the same speed as the composite material. Thus, this belt plays its protective role throughout the duration of

useful life of the stud.

  In addition, thanks to the assembly thus produced, which allows a distribution

  regular tightening efforts on the four studs, we do not observe

  increased wear of a stud compared to others, which could reduce

re the lifetime of the assembly.

  Many variations can be made to the realization of the new

  calf braking device according to the invention without departing from the claimed domain. In particular, the pads can be produced from a wide variety of friction material compositions, and the compression, sintering and assembly modes of these pads can also

  have many variations.

  In particular, in the case where the composite material is subjected to hot compression after sintering to reduce the porosity, an isostatic compression process can be used instead of using

a news.

  One can also carry out in a single operation the hot compression

  of the composite and its brazing on its support plate.

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Claims (2)

CLAIMS / - Braking device on a rim comprising a sole made of curved sheet steel and, at least, two studs in composite friction material with a sintered metal base, characterized in that each stud is secured to the sole via a steel support plate, one face of which is brazed with the composite stud and which is fixed to the soleplate by welding.   20 / - Device according to claim 1, characterized in that the support plate and the sole are linked together by two weld beads connecting to the sole, over at least part of their length, the two opposite sides of the support plate parallel to the large sides of the sole.   / - Device according to claim 1 or 2, characterized in that the connection between the support plate and the sole is achieved by means of at least one plug weld which fills an initially drilled hole in the sole.   4 / - Device according to one of claims 1 to 3, characterized   in that each stud comprises a piece of composite material of cash   sintered metal base, enclosed in an annular envelope   which is metallurgically linked to it.   / - Device according to one of claims 1 to 4, characterized   in that the sintered metal-based friction friction material, and optionally the annular envelope, have a porosity less than t.