Field of the invention

The invention relates to the field of railroad transport, namely to brake shoes of railroad vehicles.

Prior art

Brake shoes are replaceable working parts, which belong to the main part of the brake system. Quality of the brake shoes affects a length of braking path, increase in speeds and safety of operation. The brake shoes must have a given friction coefficient that is weakly dependent on the speed, a high resistance to actuation and must operate in different climatic conditions in a stable manner.

The known brake shoe that is intended to braking wheels of a railway car. The brake shoe comprises a support plate having a given configuration in the form of a curved stripe and a means for attaching of the support plate to a brake head, the means being arranged at each end of the support plate. The brake shoe further comprises brake shoe linings, which are attached to the support plate, and has a brake surface for engagement with a wheel pair of the railway car (patent US6581732 (B l)).

A drawback of the known brake shoe lies in insufficient thermal stability that is caused by a lack of a metal insert having a main purpose of a heat rejection from a friction surface. Furthermore, the brake shoe has a high number of attachment parts that does not enable to achieve the required heat rejection, as well as it is a source of generation of corrosion cells in joint locations between various surfaces.

Also, a brake shoe for use in a railway transport is known. The composite brake shoe includes a support plate that has a stirrup and a brake surface having a given configuration in the form of a curved stripe and a friction element that is made of a composite material of a first friction type that extends to the brake shoe surface. The composite brake shoe further comprises a second type friction material that is made in the form of at least one discrete insert and is mold into the first type friction composite material. The second type friction materials is fully embedded into the first type friction composite material. The first friction type composite material becomes eroded due to the friction interaction with the surface of the wheel pair during normal braking operations, wherein the second friction type material exhibits higher abrasion properties than the first friction type composite material. The at least one element of the friction material is associated with the support plate (patent US6241058 (B l)).

A drawback of the brake shoe lies in a lack of elements for the heat rejection from the contact zone between the shoe and the wheel. Furthermore, the shoe does not comprise additional means for attaching the friction element to the support plate that may lead to a possible detachment (break off) of the friction element

Also, a brake shoe is known, the shoe comprising a cast iron backing plate, wherein friction inserts made of a composite carbon-carbon material are arranged. The cast iron backing plate of the brake shoe is a base of the structure and a friction element on a working friction surface of the brake shoe (patent UA 88410).

A drawback of the brake shoe lies in that the friction surface has a high fraction of the cast iron that leads to a damage and a quick wear of steel wheel pairs when braking and formation of a so-called defect being a rolled iron thereon.

The known brake shoe comprises a steel backing plate, an arc-like body of a cast iron. The arc-like body consists of a main section of the shoe body provided with cylindrically shaped inserts that are arranged in groups and of a profile section of the shoe body having a cross-section provided with inserts. The shoe has an additional metal backing plate, on which the cylindrical inserts of the base section of the shoe body and ridged inserts of the profile section are arranged. The cylindrical inserts of the base section of the shoe body are made of a composite friction material having a friction coefficient greater than a friction coefficient of the base. The ridged inserts of the profile section are made in the form of profile elements and are placed in the cross-section of the shoe that is in contact with a ridged surface of the wheel thread and interacts with a side surface of a rail. The inserts are made of an anti-friction composite material having the friction coefficient lower than the friction coefficient of the base material and an abrasiveness lower than abrasiveness of the base material and the material of the inserts arranged in the base section of the shoe body (patent RU 2494901).

A drawback of the brake shoe lies in that use of metals being different in a chemical formulation (cast iron and steel) reduces a corrosion resistance, while the inserts made of the anti-friction composite material, which are wear-resistant, may lead to a non-uniform wear of the shoe along width and its skewness in the brake system.

A brake shoe of a railroad vehicle is known, the shoe comprising a composite friction element that is attached on a metal backing plate that is made in the form of a curved stripe having a surface with a central boss arrangement having an opening for arranging a peg located thereon and side boss arrangements, a means for mechanical attachment of the composite friction elements, a reinforcing plate and metal inserts. According to one embodiment, the inserts are attached to the metal backing plate by means of a threaded connection, while according to another embodiment, the inserts are attached on the metal backing plate by means of a mechanical attachment that is made in the form of clippings, which are cut in the metal backing plate, and curved edges of the reinforcing plate, which step into recesses, which are made on at least one side surface of the inserts. The friction element comprises transverse grooves, which are provided at both sides of each insert so as they are limited by the side surfaces of the inserts from one side (patent UA 115877).

A drawback of the known structure lies in that according to one embodiment, the attachment of the friction element to the metal backing plate is made by means of the threaded connection, while according to another embodiment, the friction element is attached on the metal backing plate by means of the mechanical attachment that is made in the form of clippings, which are cut in the metal backing plate, such method of attachment of the friction element is not reliable, particularly, in case of an emergency braking, and may cause the friction element to break off from the metal backing plate.

A composite braking shoe is known, the shoe is made of a metal, particularly, cast iron, for a composite braking block, particularly, for railway vehicles, wherein the composite braking shoe is equipped with a base housing in the form of a plate and has a support surface on an inner side for a plastic composition of the composite braking block. The base main housing is provided with at least one steel insert, wherein it is desirable that the inner side of the main housing is provided with retaining necks for the plastic composition. The steel insert has a non-rectangular cross-section along the entire length of the main housing, but it forms a circular cross-section (application WO2011006635 (Al)).

A drawback of the known brake shoe lies in that the established percent ratio between areas of the working surfaces of the insert and the friction elements is not sufficient to provide the required heat rejection from the friction zone. The shoe is also characterized by a lack of structural elements, which could contribute to reject the braking products.

The closest one is a braking block for railway vehicles that comprises a cast iron rear braking block and a friction material that is rigidly connected to the rear braking block. A rear part of the shoe has a curved laminated base having an inner support surface for the laminated material. A general braking surface of the braking block is preferably formed from at least one outer surface of the friction material and, to a lesser extent, from at least one outer surface of the rear part of the braking block. According to the invention, the base is formed without a backing plate on longitudinal sides and comprises a sidewall in the form of a cheek on each transverse side. The friction material is arranged between side plates. Each side plate has at least one discontinuation that extends from an upper surface of the sidewall towards the support surface and divides the sidewall into at least two sections. Edges of the side sections form a part of the general braking surface (application W02009036830 (A2)).

A drawback of the closest solution lies in the following: quick wear of the friction element during operation (plastic material), the friction inserts have a high wear-resistance, thereby reducing characteristics of the friction contact between the shoe and the wheel, a coefficient of mutual overlap, a friction coefficient , therefore, an overall braking efficiency. Also, the so-called side plates may be destroyed in the course of an emergency braking, since their coupling to the rear wall of the block is a console one and its rigidity may appear to be insufficient in view of a small thickness.

Summary of the invention

The invention is based on a task to increase the reliability of operation and wear-resistance of the shoe, to increase the heat rejection of the brake shoe and alignment of a temperature field along the working surface of the shoe due to a high value of a thermal capacity and thermal conductivity of the metal backing plate at a given level of the friction coefficient and a minimum wear of the wheel pair, to provide a reliable attachment of the friction element on the metal backing plate, as well as to provide more uniform wear along the length of the shoe during operation, to increase the corrosion resistance due to a cast-solid structure of the metal backing plate with thermally conductive elements. The improvement of the heat rejection from the friction zone will enable to reduce a number of defects of wheel pairs significantly, which occur in view of their overheating in the course of breaking.

The set task is resolved as follows.

A brake shoe of a railroad vehicle, the shoe comprising a metal backing plate having fabrication holes provided on an outer surface thereof, the backing plate is attached on the friction element that is made of a composite material. According to the invention, at least three thermally conductive elements in the form of elongated protrusions are provided along an inner surface of the metal backing plate, the protrusions having side recesses, wherein the boundary ones from them are arranged biased from edges of the metal backing plate in a longitudinal direction, and at least one intermediate thermally conductive element is arranged between the boundary thermally conductive elements, wherein the thermally conductive elements are made cast-solid with the metal backing plate, a proportion of the volume of the metal backing plate with the thermally conductive elements is 25-55% of the overall volume of the shoe, wherein a rubber-resin based asbestos- free material is used as the composite material of the friction element.

A technical effect is an increase of the overall thermal conductivity of the brake shoe and an alignment of the temperature field along the working surface of the shoe due to a high value of the thermal capacity and thermal conductivity of the metal backing plate at a given level of the friction coefficient and minimum wear of the wheel pair. Provision of a more uniform wear along the length of the shoe during operation and reliable attachment of the friction element. Increase of the corrosion resistance due to the structure of the thermally conductive elements that is cast-solid with the metal backing plate, lack of contact surfaces of metal materials of a different nature (chemical formulation) that may lead to a corrosive electro-chemical process that is enhanced by atmospheric phenomena (moisture, active gases in the air etc.).

Therewith, each of the boundary thermally conductive elements has at least one slot that divides the thermally conductive elements into parts, thereby forming thermally conductive sections, which are arranged at longitudinal edges of the working surface of the shoe, and the intermediate thermally conductive element forms at least one thermally conductive section in the central part of the working surface of the shoe. Provision of a uniform distribution of thermally conductive elements along the working surface of the shoe and an effective heat rejection during braking as well as an increase of wear-resistance of the brake shoe.

Therewith, at least two intermediate thermally conductive elements are arranged symmetrically relative to a center of the longitudinal axis. Therewith, the thermally conductive elements have a console connection with the rear part of the backing plate, thus, their thickness must be sufficient in order to avoid their destruction in the course of any braking modes.

Therewith, the brake shoe of a railroad vehicle comprises from 3 to 10 thermally conductive elements. When the number of the thermally conductive elements is reduced, namely to less than three, the heat rejection from the working surface is not sufficient that leads to overheat of the shoe, while the increase of the thermally conductive elements on the working surface to more than ten leads to damage or quick wear of the wheel pairs.

Therewith, the thermally conductive elements are made with casted slopes towards the backing plate, which constitute 0.2°...8.0°. Due to such solution, the heat from the working surface is uniformly distributed along the entire area of the shoe.

Therewith, the attachment of the friction material on the backing plate on the surfaces of the thermally conductive elements occurs due to its pressing in a disperse state and vulcanization under the action of the temperature and pressure. This provides a reliable attachment of the friction element on the backing plate and avoids its brake off during the emergency braking.

Therewith, the rubber-resin based asbestos-free material having a content of reinforcing fibers and impurities allows to achieve the Brinell hardness of the friction element surface within the range of 3...35 HB, the friction coefficient in the pair with wheel steel within the range of 0.06...0.30, the values are stated for the shoes having a low friction coefficient.

Therewith, the rubber-resin based asbestos-free material having a content of reinforcing fibers and impurities allows to achieve the Brinell hardness of the friction element surface within the range of 1.2...10 HB, the friction coefficient of the shoe in the pair with wheel steel within the range of 0.17...0.45, the values are stated for the shoes having a high friction coefficient. It has been experimentally found that due to use of the rubber-resin based asbestos-free material having a content of reinforcing fibers and impurities, the optimal values of the Brinell hardness for the shoes having a low friction coefficient must be within the range of 3...35 HB, while for the shoes having a high friction coefficient they must be within the range of 1.2...10 HB. These ranges enable to increase the wear-resistance of the shoe. Use of the materials having the hardness values of lower than the established ranges for each embodiment leads to a quick wear of the working surface, while use of the material having the hardness of more than the established ranges for each embodiment may lead to an accelerated wear of the wheel pair. Also, it has been experimentally found that the optimal ranges of the friction coefficient values for the rubber-resin based asbestos-free material having a content of reinforcing fibers are as follows: for the shoes having a low friction coefficient they are within the range of 0.06...0.30, while for the shoes having a high friction coefficient they are within the range of 0.17...0.45. These ranges are optimal ones, since within these ranges the friction coefficient remains the most stable for a long time operation, as well as it defines the most optimal values of a linear wear and facilitates improvement of the wear-resistance.

Therewith, the boundary thermally conductive elements are arranged at edges of the working surface or biased from the edge in the longitudinal direction for a value of up to 150 mm. It has been experimentally found that such arrangement provides the most effective distribution of the thermally conductive elements along the working surface with consideration of the thermally conductive elements, which are arranged between the boundary elements. In case of arrangement of the boundary thermally conductive elements from the edge for more than 150 mm towards the center of the working surface, the thermally conductive elements will accumulate and form sections, which lead to non-uniform wear or even to the damage of the wheel pair. Therewith, the metal backing plate comprises a reinforcing insert that is arranged in the central part under the fabrication hole. The metal inserts also act as elements, which compensate for a vibration and shock loads during breaking.

Fig.l depicts a temperature of the working surface of the wheel as a result of using the claimed shoe, which is indicated by the position 1 on the Fig.l, as compared to the one for the similar shoes from the known prior art, wherein the friction element is attached to the metal backing plate by means of a mechanical attachment, which is indicated by the position 2 on the Fig.l .

Results of studying the shoes on the cast-solid metal backing plates have shown that the final temperature of the working surface of the wheel using the shoes on the cast-solid metal backing plates during braking from starting speeds of from 50 to 140 km/h is averagely 30% lower than under the same conditions using the shoes from the known prior art. The final temperature of the working surface of the wheel during braking from 160 km/h is 4% lower than when using the shoes with the cast-solid metal backing plates. The ability to reject the heat from the working surface of the wheel is much more greater in the shoes on the cast-solid metal backing plates. Use of the claimed shoes significantly reduces a probability of occurrence of defects of the wheel pairs, as well as it reduces a frequency of occurrence of cases of ice accretion.

Brief description of the drawings

The invention disclosed herein will be more clearly understood from the following exemplary embodiment and the corresponding accompanying drawings in which:

Fig. 2 - a general view of the metal backing plate of the shoe with the friction element.

Fig. 3 - a general bottom view of the metal backing plate of the shoe.

Fig. 4 - a side view of the metal backing plate of the shoe.

Fig. 5 - the section A-A of the Fig. 4.

Fig. 6 - a top view of the metal backing plate of the shoe. Fig. 7 - a botom view of the metal backing plate of the shoe.

Figure drawings that illustrate the invention claimed as well as particular embodiments are merely exemplary in nature and are in no way intended to limit the claims appended hereto but to explain the essence of the invention.

Detailed description (information confirming the possibility of the invention implementation)

A brake shoe of a railroad vehicle comprises a metal backing plate 1 having fabrication holes 2 provided on an outer surface thereof and a composite friction element 3 that is made of a rubber-resin based asbestos-free material and attached to an inner base of the metal backing plate 1. Along the inner surface of the metal backing plate 1 , there are located boundary thermally elements 4, which are biased from edges of the metal backing plate 1 in the longitudinal direction, and intermediate thermally conductive 5, which are arranged between the boundary thermally conductive elements 4. The thermally conductive elements 4, 5 are made cast-solid with the metal backing plate 1. Therewith, the brake shoe comprises a reinforcing insert 6 that is arranged in the central part under the fabrication hole 7. The attachment of the friction element 3 on the metal backing plate 1 occurs due to its pressing in a disperse state and vulcanization under the action of the temperature and pressure.

The claimed invention may be used in a structure of brake shoes for certain types of railway vehicles, in particular, for passenger railway cars and multiple unit (electric trains). The shoes are made of the metal backing plate 1 that is made cast- solid with the thermally conductive elements 4, 5 to the working surface. During braking, the wheel pair contacts not only with the friction composite element 3 that is made of the rubber-resin based asbestos-free material, but also with the thermally conductive elements 4, 5. Presence of the thermally conductive elements 4, 5 with the surface of the wheel pair enables the shoe to perform a number of functions, wherein the main one lies in a significant increase of the heat rejection from the friction surface of the shoe and from the wheel pair, minimization of the wear of the wheel pair.

The invention provides stability of the friction characteristics of the working surface during the entire operation term of the shoe, reduction of the wear of the wheel pair and increase of the operation safety in modes of the emergency braking.