PAD FOR DISC BRAKES FOR RAILWAY VEHICLES

Abstract

A pad for disc brakes for railway vehicles comprising a base plate and friction elements fixed to the plate arranged in at least two rows, which have an arcuate shape. Each row has friction elements with one same friction surface and a total friction surface ranging from 40% to 80% of the total friction surface of friction elements of an immediately following more external row. Each friction element of at least one more internal row has a friction surface, which is less than the friction surface of each friction element of an immediately following more external row. The friction elements of each row are arranged on the base plate to act on a surface portion of the disc, which partially overlaps surface portions of the disc on which friction elements of a possible immediately following more external row and friction elements of a possible immediately following more internal row act.

Claims

1. A pad for disc brakes for railway vehicles, the pad comprising: a base plate; and a plurality of friction elements fixed to said base plate; said plurality of friction elements being arranged in at least two rows that have an arcuate shape and, in use, substantially overlap respective concentric lines of a disc upon which the pad acts; each of the at least two rows having at least two friction elements of the plurality of friction elements with one same friction surface; wherein said at least two friction elements of each of the at least two rows having a total friction surface with a size in a range from 40% to 80% of a total friction surface of said at least two friction elements of an immediately following more external row of the at least two rows; wherein each of the at least two friction elements of at least one more internal row of the at least two rows has a friction surface, which is less than a friction surface of each of the at least two friction elements of an immediately following more external row of the at least two rows; wherein said at least two friction elements of each of the at least two rows being arranged on said base plate so as to act on one surface portion of the disc that partially overlaps surface portions of the disc on which friction elements of a possible immediately following more external row of the at least two rows and friction elements of a possible immediately following more internal row of the at least two rows act.

2. The pad according to claim 1, wherein each of said at least two friction elements of each of the at least two rows has a friction surface with a size in a range from 50% to 70% of the surface of each of the at least two friction elements of an immediately following more external row of the at least two rows.

3. The pad according to claim 1, wherein the at least two rows include three arcuate rows, of which a more external row of the three arcuate rows includes three of the plurality of friction elements equal to one another, an intermediate row of the three arcuate rows includes two of the plurality of friction elements equal to each other, and a more internal row of the three arcuate rows includes two of the plurality of friction elements equal to each other.

4. The pad according to claim 3, wherein the single friction elements of said more external row are a same size as the single friction elements of said intermediate row.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] For a better understanding of the invention, an embodiment is shown below, which is purely illustrative and non-limiting, with the aid of the figures of the accompanying drawing, wherein:

[0016] FIG. 1 is a perspective view from above of the pad that is the subject of the present invention;

[0017] FIG. 2 is a view from above, with parts that are transparent for clarity, of the pad in FIG. 1;

[0018] FIG. 3 is a view from below, with parts that are transparent for clarity, of the pad in FIG. 1 applied to a disc.

BEST MODE FOR CARRYING OUT THE INVENTION

[0019] In FIGS. 1 and 3, the reference number 1 denotes a pad for disc brakes according to this invention.

[0020] The pad 1 comprises a base plate 2, a dove-tail fixing element 3 fixed to a rear surface of the base plate 2 and designed to fix the pad 1 to a structure of the disc brake, a plurality of friction elements 4 fixed to the base plate 2 and arranged so as to exert the pressure on the brake disc to create the braking action, and a plurality of spacers 5 arranged in pairs between a friction element 4 and the base plate 2. The spacers are shown in dashed lines as they are transparently visible. Only two spacers in FIG. 2 are denoted with reference number 5.

[0021] For the purposes of this invention, it is irrelevant whether the friction elements 4 are reversibly or irreversibly fixed to the plate 2.

[0022] The friction elements 4 are arranged along the arcuate rows, shown in dashed lines, and denoted with 6, which, in use, substantially overlap the concentric lines C of the disc D upon which the pad acts 1. For simplicity, the disc D is shown only partially in FIG. 3 and the concentric lines C are shown in dashed lines in FIG. 3.

[0023] In particular, the friction elements 4 are arranged in three rows 6, which can be identified as an external row 6a, an intermediate row 6b, and an internal row 6c.

[0024] The external row 6a comprises three friction elements 4 equal to one another, while the intermediate row 6b comprises two friction elements 4 equal to each other and each of which has a friction surface equal to that of each of the elements of the external row 6a.

[0025] In contrast, the internal row 6c comprises two friction elements 4 equal to each other and each of which has a friction surface that is less than the surface of each of the elements of the external row 6a or of the intermediate row 6b.

[0026] In detail, the total surface of the friction elements 4 of the internal row 6c is equal to 58% of the total surface of the friction elements 4 of the internal row 6b, while the total surface of the friction elements 4 of the intermediate row 6b is equal to 66% of the total surface of the friction elements 4 of the external row 6a.

[0027] As shown in FIG. 3, the friction elements 4 of each row 6 act on a portion P of disc D, which overlaps the portions P of disc D upon which the friction elements 4 of the following more external and more internal rows 6 act. The portions are shown in dashed line surfaces in order to clearly show how the portions overlap. In FIG. 3, Q denotes the overlapping portions of two portions P.

[0028] It has been experimentally proven that if there are fewer than two rows 6 and/or if there are fewer than two friction elements 4 for each row 6, the pad is not capable of solving the technical problem described above. In fact, to prevent the circular depression from forming, the friction elements should be too big, thus losing the advantages in terms of braking and noise. In particular, the friction elements wouldn't be able to exert effective pressure on the disc and, above all, the friction elements themselves wouldn't be able to be cooled correctly.

[0029] It has been experimentally proven that if the friction surface of the various rows of friction elements were to be reduced by varying only the number of friction elements and not the size thereof, the results would not be those desired because a series of drawbacks would be encountered.

[0030] In fact, by using friction elements all of the same size in the pad and by reducing the number thereof per row in order to reduce the friction surface going from the more external row to the more internal row, too large a friction surface variation gradient would be created between the rows of the pad. Such a large difference in the friction surface between the rows of friction elements produces an imbalance of the pad portions, which inevitably results in abnormal disc wear.

[0031] Furthermore, having smaller friction elements in the more internal row guarantees a great reduction in vibrations in the same friction element, avoiding negative repercussions on the internal part of the disc, which is the most vulnerable part of the disc as it is closest to the hub.

[0032] Furthermore, having smaller friction elements in the more internal row guarantees a greater geometric adaptability of the same friction elements on the pad base plate. In this way, the present invention adapts to base plates, which are already in production, and without having to produce new ones.

[0033] It has been experimentally proven that a ratio between the friction surfaces, which is different from the one claimed, doesn't produce an effective braking action and would result in a detrimental imbalance between the pad portions.