RU2499710C1 - Railway vehicle braking clamp - Google Patents

Abstract

FIELD: transport.

SUBSTANCE: invention relates to railway transport, namely, to railway vehicle braking clamps. Braking clamp comprises composite friction element, steel wire carcass, solid iron insert electrochemically coated with bronze alloy, arranged at clamp center and inserted into said composite friction element. Steel wire carcass represents two closed frames inserted in said composite friction element of clamp rear side, along clamp edges. Inner parts of two closed frames are overlapped and bent outward from clap rear side to make ear for cotter pin. Clamp rear side has steel gauze or perforated tin inserted in composite friction element. Iron insert with bronze alloy at its top idle part has the slot at its rear with inserted composite friction element with cotter pin ear and supports arranged in symmetry on insert both sides. Insert top idle part is inserted in steel carcass and clamped therein. All metal part of the clamp stay indirect contact.

EFFECT: higher reliability, longer life.

1 dwg

Description

The claimed invention relates to brake devices, namely to brake pads of railway vehicles.

From the prior art, cast-iron monolithic cast-iron brake pads, currently produced in series, are known, for example, those produced in accordance with GOST 1205-73 “Cast-iron brake shoes for railroad cars and tenders. Design and main dimensions ”and composite brake pads for railway cars. Composition brake pads for railway cars are made of two types:

- with a metal frame from a steel strip with a U-shaped protrusion and with a reinforcing plate welded to it;

- with a wire mesh frame.

(B.A. Shiryaev. Production of brake pads from composite materials for railway cars. M., Chemistry, 1982, pp. 8-14).

Known block railway vehicle copyright certificate of the USSR No. 518403 (IPC B61H 7/02, 1976), consisting of friction material and a metal frame. The metal frame is a back made in the form of two closed frames pressed into the friction material around the perimeter of the block, the internal parts of which are mutually overlapped and bent outward of the back of the block, forming an eyelet for passing checks. The back plate is equipped with a metal mesh or perforated plate pressed into the friction material. This frame has received the name of mesh-wire in serial production, as it consists of wire and mesh frames. Moreover, according to the technical conditions for these pads, it is allowed to expose on the back of the mesh-wire frame up to 50% of the area.

The main significant external and structural difference between composite blocks with a mesh wire frame and composite blocks with a steel metal frame is that the central boss of these blocks is made of composite material with internal reinforcement, which sharply increases the elastic properties of the block and, as a result, vibration resistance of the block and eliminates the separation of the composite material from the frame and the destruction of the frame in place of the U-shaped protrusion.

A metal frame made of a steel strip with a U-shaped protrusion and with a reinforcing plate welded to it and a wire mesh frame do not go out with their elements into the area of the block in contact with the wheel.

During the operation of composite brake pads, individual defects may occur, including: thermal cracks on the rolling surface of the wheels, wear of the surface of the wheels, decrease in the brake efficiency of pads when water enters the friction zone (rain, snow), as well as in the presence of coal or peat dust and leaves on the surface of the rail.

The known technical solution is used for the same purpose as the claimed one, and has common essential features with it: “composite friction material” and “wire frame”, made in the form of the back of the block pressed into the friction material, along the perimeter of the block, two closed frames , the internal parts of which are mutually overlapped and bent outward of the back of the block, forming an eyelet for skipping checks "," the central boss with a hole for the check and two side bosses are also made of friction composite of material "," Tylnik provided with a metal mesh or perforated sheet metal, press-fitted in the friction material. "

Composition pads are known in the art which contain one or more solid inserts and are intended to reduce the above disadvantages of composite pads.

The brake shoe is known (according to the author's certificate of the USSR No. 159186 (20f.1, IPC v61 h, 1963).

The brake shoe is designed primarily for railway rolling stock, with solid inserts on the friction part, characterized in that in order to increase the effectiveness of the interaction of the block with the wheel rim, a pair of solid inserts symmetrically located relative to the horizontal axis of the block cover its friction part over the entire width.

The inserts are held due to the friction forces arising between them and the friction material of the block.

The design of these pads does not provide the required reliability during operation, since during prolonged and emergency braking, intense heat transfer occurs from the friction zone to the surface of solid inserts, especially since the inserts have higher thermal conductivity, as a result of which the temperature of the composite material on surfaces in contact with solid inserts , increases sharply and there is a thermal destruction of organic materials that make up the composition of the composite pads, including a binder, due to Ie, the attachment of the inserts is weakened, and they cease to fulfill their purpose and may fall out of the block.

These pads do not reduce the uneven wear inherent to composite pads due to damage to the surface of the wheels due to the formation of thermal cracks, sliders and fat, increased wear on the surface of the wheel. These pads have an all-metal cage, as a result of which vibrations occurring in the brake assembly during operation can cause not only the solid inserts to fall out of the pads due to the weakening of their attachment with the friction composite material, but also the tear of the friction composite part of the pads from the all-metal frame cracks and fracture of the metal frame.

The solid inserts and the all-metal frame do not contact each other.

The essential features of the closest analogue: “solid inserts overlapping the block over its entire width” and the “friction part” are common with the essential features of the claimed block.

Known brake pad, mainly a railway vehicle according to the patent of the Russian Federation No. 2188347 from 08.27.2002. The brake pad contains a metal wire frame and a friction part consisting of three inserts fixed to it. The central part is made of cast iron and equipped with a pin hole, and the other two inserts are made of composite material and are located on both edges of the solid insert.

This brake pad allows you to increase the braking efficiency and increase the resource of the wheels, however, it has insufficient strength and service life. The thermal conductivity of cast iron is 25–30 times greater than the thermal conductivity of the composite material, and the thermal stability of the composite material is insufficient. At the joints of the cast iron insert with composite inserts, on the surface of their contact during operation, the composite material gradually burns out, as a result of which the brake shoe loses its required stiffness and can be divided into three parts, connected only by a wire frame, during long-term operation.

The separation of the block during operation into three inserts connected only by a wire frame especially determines the negative feature of this block design, namely, the contact of the inserts with each other in a vertical plane over the entire cross section of the block, which contributes to the rapid development of a single vertical crack and fracture of the block.

The steel wire frame is pressed into the friction material and is in direct contact with a cast-iron insert extending into the working area of the brake pad.

The well-known technical solution is used for the same purpose as the claimed one and has common essential features with it: “metal wire frame”, “friction part fixed to it”, “solid insert”, friction composite material ”.

The closest analogue is the brake shoe of a railway vehicle according to the patent of the Russian Federation No. 2340805 of 07.20.2007. The brake shoe comprises a composite friction element, a wire frame, a solid insert located in the central part of the shoe and pressed into the composite friction element. The wire frame is a block pressed into the composite friction element of the back side of the block, along the perimeter of the block, two closed frames. The internal parts of two closed frames are mutually overlapped and bent outward of the back of the block, forming an eyelet for passing checks. The block on its back contains a steel mesh or perforated sheet pressed into the composite friction element. The insert in the upper non-working part has a groove on its rear side, pressed with friction composite material with an opening for passing checks and cantilevers, symmetrically located along the length of the insert on each side of it. The upper non-working part of the insert is inserted into the wire frame and pinched in it. Achieved is an increase in the strength and reliability of the design of the pads, an increase in their resource during operation.

However, the considered composite brake pads with a combined frame have disadvantages. Since all the metal parts of the block are interconnected: a steel mesh or perforated sheet is in contact with the wire frame and solid insert, they form at least a bipolar electrode, one pole of which extends to the back surface of the block, and the other pole is in the friction zone contact. During storage, and especially during operation, the entire surface of the brake composite pads is under the influence of a corrosive environment. In the spring-summer period, the surface is irrigated by rains and moist condensate, and in autumn and winter it is covered with a continuous crust of ice and snow, that is, the entire surface of the block is in contact with the electrolyte. Moreover, if the back surface of the block is subject only to electrochemical corrosion due to the influence of natural precipitation, the working part is subjected to the combined effect of electrochemical corrosion and high-temperature gas corrosion.

High-temperature gas corrosion is caused by oxidation of the solid insert by atmospheric oxygen, hydrogen released during thermal degradation of the binder, and hydrogen sulfide due to the interaction of hydrogen and unbound sulfur, which is part of the friction material. In addition, hydrogen sulfide in contact with water forms sulfuric acid, which also has an adverse effect on the surface of the solid insert.

Some components of the friction element, in particular chrysotile asbestos, also contribute to the corrosion destruction of metals in contact with it.

As a result of corrosion, rust is formed on all metal elements of the block structure. In this case, the contact strength of the friction polymer material and metal structural elements of the pads coated with corrosion products decreases and may lead to a violation of the integrity of the pads.

The task to which the claimed brake shoe is directed is to minimize the harmful effects of corrosion of the metal parts of the shoe, increase the reliability of the shoe structures, and increase its service life.

It is proposed to solve the problem with the brake pads of a railway vehicle, shown in figure 1 and containing:

- composite friction element (item 1);

- wire frame (2), which is pressed into the composite friction material of the back of the block along the perimeter of the block, two closed frames, the inner parts of which are mutually overlapped and bent outward of the back of the block, forming an eyelet for passing checks;

- a metal mesh or perforated sheet (item 4), pressed into the composite friction element;

- a solid insert (pos. 3) with a protrusion (pos. 9) and a slope of the solid insert (pos. 10), electrochemical coated with a bronze alloy, located in the central part of the block and having a groove in the upper non-working part (pos. 7), a recess (pos. 8) and four consoles (pos. 11). The groove is located on the back of the insert and is pressed with a friction composite material with a hole drilled in it for passing checks. Four consoles are symmetrically located two on each side of the insert along its length. The length of the insert at the place of the consoles is greater than the length of the central boss (key 5), but less than the distance between the side bosses (key 6). The recess is located on one side on the length, on both sides in width and on one side in height so that the back surface of the insert is in the same plane with the surface of the mesh or perforated sheet in the back surface of the central boss, and the pinching force exceeds the weight of the insert.

The essential feature of the inventive pads "solid insert coated with a bronze alloy" is distinctive from the essential feature of the closest analogue.

The solid insert can be made of special cast iron, for example high-strength or malleable, by casting the desired shape with subsequent mechanical surface treatment.

After machining the surface, the solid insert is etched in concentrated hydrochloric acid, washed in water, pre-tinned from alkaline electrolytes, coating thickness 3 ÷ 5 μm, washed and directly electrochemically coated with a bronze alloy of sulfuric acid electrolytes with an antioxidant with tin content from 4 to 11% mass, coating thickness 15 ÷ 25 microns.

The electrochemical coating of the cast iron insert with bronze alloy allows 8 times to increase the adhesion of the friction material to cast iron after vulcanization of the blocks. During operation, the bronze coating is sintered in the presence of strong reducing agents, such as hydrogen and carbon monoxide (carbon monoxide), which are formed as a result of thermal degradation of the binder during braking. The resulting sintered material (cermet) has an intermediate indicator of the coefficient of thermal conductivity between cast iron and polymer composite material, and thereby prevents premature destruction of the surface of the block, on which high-temperature frictional contact with the wheel surface occurs. In addition, as a result of high temperature and pressure in the friction contact zone, an autoclave mode is created in which the formation of organotin compounds from fragments of a polymer binder and tin, which is part of bronze, is possible. Organotin compounds have a thermal conductivity coefficient 2–2.5 times higher than that for polymer brake pads. Finally, tin, falling on the working surface of the wheel, with its subsequent segregation at the grain boundaries of the iron matrix, will contribute to the hardening of the wheel material. The use of brass instead of bronze is not permissible, since zinc, which is part of brass, leads to embrittlement of the grain boundaries of the iron matrix and its destruction.

Thus, a bronze coating electrochemically applied to a cast iron insert:

- protects against atmospheric, high temperature gas and electrochemical corrosion;

- is a buffer on the path of heat flux distribution over the cast iron insert and polymer composite block;

- prevents the hydrogenation of metal surfaces in the area of frictional contact;

- significantly increases the adhesion of cast iron to the polymer composite mass of the block after vulcanization;

- prevents embrittlement of the grain boundaries of the iron matrix of the steel wheel and its premature destruction.

Claims (1)

A brake pad of a railway vehicle containing a composite friction element, a steel wire frame, a solid cast iron insert located in the central part of the block and pressed into the composite friction element, the steel wire frame is pressed into the friction element of the rear side of the block, along the perimeter of the block, two closed frames, the inner parts of two closed frames are mutually overlapped and bent outward of the back of the block, forming an eye To pass checks, the block on its back contains a steel mesh or perforated sheet pressed into the composite friction element, the cast-iron insert in the upper non-working part has a groove on its back, pressed into the friction composite material with a hole for passing checks and console, symmetrically located along the length of the insert on each side, the upper non-working part of the insert is inserted into the wire frame and pinched in it, all metal parts of the block are in direct contact e, characterized in that the entire cast iron insert is coated with a bronze layer deposited by an electrochemical method, and pressed into the friction composite material.