The subject of the invention is a brake block of a composite structure for railway vehicles, similar in shape to cast iron brake blocks, but with a different structure. Cast iron brake blocks are widely used for braking railway vehicle. The brake blocks are pressed by the brake system against the wheels of the vehicle during braking, generating a torque acting against the rotational motion of the wheels. In the braking process, the kinetic energy of the vehicle is converted to heat, and the heated brake blocks and wheels dissipate this thermal energy to the environment.

Cast iron is therefore a suitable material for brake blocks, due to its appropriate mechanical parameters and low production cost. A disadvantage of cast iron brake blocks is, however, their noisy operation, the dust pollution caused to the vehicle and the environment, as well as the frequent maintenance requirement due to the intensive wear of the brake blocks.

Plastic brake blocks are often used to eliminate these disadvantages of cast iron brake blocks. In these, the entire block structure is a mixture of resins and fillers, fastened to a steel back plate by pressing and heat treatment processes. Application of plastic brake blocks is more advantageous than cast iron brake blocks in terms of noise generation, dust formation and frequency of maintenance, but there are also disadvantages linked to the application of plastic brake blocks.

A disadvantage is that braking polishes the contact surface of the wheels, deteriorating the highly significant friction between the wheels and the rail surface, the safety of braking being sensitive to weather, extending the stopping distance in rainy and snowy conditions. A further disadvantage is that the thermal load on the couple of components involved in the braking, i.e. the wheel and the brake block is distorted, as the heat dissipation of the plastic is negligible, leaving the majority of the thermal load of the kinetic energy converted to heat to the wheel. An undesirable consequence of this is the potential overheating of the wheel as a function of the environmental and operating conditions, which may bring about the mechanical damage of the wheel. A further disadvantage is the waste generated by plastic layer remaining after the plastic brake blocks are worn away and the back plate carrying it, whose recycling is problematic, and whose deposition - being hazardous waste - is very costly.

A known solution of eliminating the disadvantages is the use of combinations of different compositions and arrangements of various types of brake pads on a single brake block; generally the combination of a plastic-bound and a hard material, usually cast iron. The document RU2309072 describes a composite insert arranged on a metal back plate, with a hard insert, a cast iron insert welded to the back plate at its middle section. The polymer material is die cast under pressure on the back plate welded together with the cast iron insert, and then it is vulcanised.

The subject of the document CN101900176 is a composite brake block, in which composite inserts are welded to the back plate, with the composite element cold pressed on the back plate, followed by heat treatment for curing and fixation.

The subject of the RU2298499 document is a composite brake block with a cast iron frame structure, and whose cavities are filled up by the composite friction insert, containing reinforcing metal wires.

Having reviewed the existing solutions and summarizing our experiences, we see that the problem of heat dissipation, the issues of recycling and waste management as well as those of simpler and more economical manufacturing call for further developments, and therefore we set the improvement of these as an objective.

The invention realising the objective is based on the recognition that the cast iron brake pad of the composite brake block is fixed separately to the back plate of the brake block, while the composite brake pad is mounted separately on its own back plate, and then this own back plate is affixed to the back plate of the brake block.

The main concept and preferred embodiments of the invention are described in the claim and the sub-claims respectively.

In the following, the invention is presented in greater detail based on drawings, where

Figure 1 . is the perspective exploded view of the components of the composite brake block, without the cast iron and composite brake pads,

Figure 2. is the back view of the composite brake block with the back plates, and

Figure 3. shows the perspective view of the composite brake block.

The cast iron brake pad 3 is directly fixed to the back plate 2 of the composite brake block 1 ; one known advantageous implementation of this is that the cast iron brake pad 3 is cast on the back plate 2. The projections 9 formed on the back plate 2 participate in opposing the lateral forces resulting from braking the wheel, and the fixed cast iron brake pad 3 stiffens the back plate 2.

On back plate 2 perforations 1 1 are arranged for connection of the key bridge 10, which element positions the brake block on the brake caliper (not shown). The connecting projections 12 of the key bridge 10 are practically clicked into the perforations 11 prior casting of the cast iron brake pad 3. Following casting, the projections 12 surrounded by cast iron fasten the key bridge 10 and the cast iron brake pad 3 to the back plate 2.

For clarity’s sake, Figure 2 shows cast iron brake pad 3 and composite brake pad 4 in dotted lines only, indicating the positions of these components.

There are projections on the back plate 5 of the composite brake pad 4, protruding from the back plate’s plane; at least one projection 8 facing towards composite brake pad 4 .

Projections 7 facing towards back plate 2 serve to guide a wedge, which wedge not shown in the drawing, as a known and necessary element for fixing a brake block in a brake system. Projections 7 serve also to fasten the back plate 5 to theback plate 2.

The composite brake pad 4 is fastened to the back plate 5, preferably by casting or pressing, depending on the material of the composite brake pad 4.

Inserting the projection 7 of the back plate 5 into the matching perforation 6 and fixing it there, the back plate 5 is fastened to back plate 2 along with the composite brake pad 4. Fixation is preferably implemented mechanically, by plastic deformation, bending the 7 projections.

By bending back or destroying projection 7 on the worn brake block, composite brake pad 4 is separated from back plate 2, and separated as waste from the part to be recycled.

In addition to ensuring the known advantages, such as more silent operation than the cast iron brake blocks and ensuring the appropriate roughness of the wheel’s contact surface, the smaller dimensions thanks to the separate production of the composite brake pad 4 and the simplified geometry means that it is simpler and cheaper to manufacture the composite brake block 1 . The majority of the worn brake blocks is recyclable, generating less waste, which is an environmental advantage.