TECHNICAL FIELD The invention relates to friction pads for disc brakes.

BACKGROUND ART

5 When braking, disc brake friction pads, which comprise a backing plate and a covering of friction material on one side of the backing plate, move into contact with the disc and then move away from the disc once the braking action has been completed. The sliding movement which the pads undertake

10 during use means that some freedom of movement must exist between the pad backing plates and the elements, usually known as callipers, into which the plates are fitted. Such freedom of movement has certain drawbacks inasmuch as It tends to make the pads squeal in use in addition to causing

15 vibration effects during braking.

Various solutions designed to overcome this problem are already known all of which start from one common design feature, namely the use of spring elements which assist in maintaining the positioning of the pad.

20 The solution of West German patent 1,475,372 of Jurid

Werke GmbH comprises helical wire springs which are coiled around pins which extend between the backing plates of an k opposed pair of pads. The ends of these springs flexibly t support the pads. This arrangement is illustrated in Fig. 7

25 of the drawings.

US Patents Nos. 3,616,878 and 3,712,423 of D.B.A. describe an arrangement in which the backing plate of each pad has lateral extensions which form tabs for receiving spring elements. This is shown in Figs. 8 and 9 of the drawings.

The D.B.A. arrangement has the advantageous feature that the springs are fitted in structures which are formed by the actual pad backing plate without the need to fix them to the plates by means of pins, cotters or screws, but the arrangement has the disadvantage of requiring springs at both ends of each pad, in other words, two springs for each pad.

US patent 3,958,667 of FERODO relates to an arrangement in which a spring is fitted to the exposed side of the backing plate on the opposite side to the friction covering by means of a threaded screw.

The FERODO arrangement, which can be seen in Fig. 10 of the drawings has the advantage of using only one spring for each pad but it has the disadvantage of needing a second element, a threaded screw, for its fitment.

Spanish Patent 443,780 of GIRLING LIMITED suggests a solution similar to the FERODO arrangement but has the spring coiled around the screw or pin and disposed in an upper part of the backing plate. This is shown in Fig. 11 of the drawings.

The GIRLING arrangement has the same advantage as the FERODO arrangement but also its disadvantage of requiring a second element for fitment of the spring, in this case, a rivetted rod. DISCLOSURE OF INVENTION

Advantageously an anti-squeal and anti-vibration brake pad would have a single one-piece spring element for each brake pad, which element, through its relationship with said pad, forms a unit with the pad without the need for any other element or additional means.

This basic premise is satisfied in the solution according to the present invention in which the friction lining backing plate is formed with accommodating means disposed in its upper area and in which are resiliently received the ends of an opposed pair of tabs formed by a leaf spring which embraces the backing plate.

In this way, with a single one-piece element such as the leaf spring, an anti-squeal and anti-vibration solution is achieved without this spring requiring the assistance of a screwed or rivetted rod for its fitment, thus avoiding the necessity of duplication of the components of the device and considerably simplifying its production and fitment. Obviously, the solution which is now being proposed simplifies the production of the brake pad enormously; moreover, this solution offers the following additional

advantages.

- Wire springs have inferior resistance to fatigue compared to leaf -springs.

- The production of a wire spring with all its bends and loops is considerably more complex than that of a leaf spring inasmuch as the latter is formed with a single press stroke.

- The fitment of the leaf spring enables the accommodating means in the backing plate to be formed by a simple drilled or punched through-hole through which the electric cable of the pad wear detector can pass.

- The fitment of the leaf spring ensures that the unit which is formed between it and the pad backing plate is held securely at all times without the possibility of unintentional loosening but with the possibility of selective or intentional removal of said leaf spring when this is necessary for its replacement or for other reasons, as required.

These improvements, together with other additional improvements will appear from the following description. BRIEF DESCRIPTION OF DRAWINGS

One preferred embodiment of the invention is diagrammatically illustrated, by way of example, in Figures 1 to 6 of the accompanying drawings, in which:-

Figure 1 is a perspective view of a friction pad, with the detail of Figure 1a showing a variant;

Figure 2 is a detail showing the attachment of the leaf spring;

Figures 3 and 4 are respectively an elevation and a plan view from above of the leaf spring; Figure 5 is a section on the line V-V of Figure 3, and

Figure 6 is the developed view of the spring leaf. Explanatory details

1-. - Spring leaf

2. - Backing plate 3. - Friction lining

4. - Through-hole (accommodating means)

5. - Electric cable

6. - Wings

7. - Tabs 8. - Central depression

9. - Engagement lugs

10. - Central projection

11. - Rods

12. - Springs 13. - Supports

14. - Side extensions

15. - Support structures

16. - Springs

17. - Springs 18. - Screw

19. - Spring

20. - Threaded drilling

21. - Spring

22. - Rivet

Turning first to the prior art Figure 7 of the attached drawings shows the solution of German patent 1,475,372. According to this solution a pair of rods (11), extend between the two pads onto which rods springs (12) are coiled, the ends (13) of which flexibly support the pads. Figure 8 shows the solution of US patent 3,616,878 in which the pad is provided with side extensions (14) in which support structures (15) are formed for the fitment of springs (16) which, in US patent 3,712,423, take the form of the filiform or wire spring (17), see Figure 9. On the other hand. Figure 10 shows the solution of US patent 3,958,667 in which a wire spring (19) is used which, in a central area, is formed as an open ring for receiving a threaded screw (18) which is fixed into an opening (20) in the pad backing plate (10).

Figure 11 shows the solution of Spanish patent 443,780 which is similar to that of Figure 10. In this case a spring (21) is fixed to the pad backing plate with a rivet (22) in the upper part of the backing plate.

The common denominator in all these solutions is the

need for at least two basic elements, namely springs (12) and rods (11 ) in the solution in Figure 7, the two spring elements (16 or 17) in Figures 8 and 9, the spring (19) and the screw (18) in Figure 10 and the spring (21 ) and rivet (22) in Figure 11.

BEST MODES FOR CARRYING OUT THIS INVENTION However, according to the solution which is now being proposed, all that is needed is a single one-piece element with the special feature that this improvement is supplemented by others which, albeit not so basic, are of great importance in order to simplify the manufacturing process and also improve the functional characteristics of the pad.

In fact, in accordance with the present invention, the pad formed as shown in Figure 1 by a backing plate (2) and by a friction lining (3) has a single one-piece element which is constituted by a leaf spring (1 ) as a means of avoiding squealing and vibration from said pad.

The leaf spring (1 ) is made from metal and its developed form is shown in Figure 6; this leaf is bent to the form shown in Figures 3, 4 and 5 by a single hammering or stamping operation, and has four extensions in substantially perpendicular directions. These extensions form equal pairs, with one pair forming wings (6) while the other pair form tabs (7) which extend vertically downwards. The tabs (7)

narrow progressively towards their free ends and terminate at their free ends in engagement lugs (9) .

The engagement lugs (9) are arranged to embrace and engage a central through-hole (4) in a central lug (10) extending from the upper surface of the backing plate (2) so that, through elastic deformation, the engagement lugs (9) can be accommodated in the hole (4), thereby forming a coupling which at all times prevents unintentional disengagement of the spring (1) from the backing plate (2) but, at the same time, allows its removal if this is needed for the purposes of replacement or the like, in an extremely simple operation which only entails prising the tabs (7)

•apart. According to one possible variant shown in Figure 1a, the coupling is formed by deformation of the tabs themselves (7) to form inwardly dished buttons (9a) which engage the holes (4) from opposite sides.

Moreover, the flexible support of the wings (6) ensures the action needed to prevent squealing and vibration since the spring element (1) is designed to describe a rocking movement in use for which purpose said element (1) has a central depression (8) with a rounded cross section; this depression (8) contacts the rounded upper edge of the central extension or lug (10) in which the hole (4) is located, thereby facilitating said rocking movement of the spring element (1).

INDUSTRIAL APPLICABILITY This solution not only requires just a single one-piece element (1) with the improvements which this entails per se; it also permits direct fitment of the spring element (1) without the need for any special tool in this connection; this also makes it easier to pack the brake pad with the spring element (1) next to but not fitted to it for presentation in "display" packs in which the spring element in the solutions known to dated posed a real problem. Similarly, it permits intentional removal while, on the other hand, it must be pointed out that the production of the element (1) in the form of a leaf spring not only makes manufacture (shaping) simpler but also ensures superior durability against fatigue resulting from repeated use. - It must also be pointed out that, as can be seen in

Figure 1, in this solution a large part of the hole (4) remains free, thereby allowing pas.sage of the cable (5) of the electrical lining wear detector (3), thereby providing guide and retention means for this cable (5) which had to run on the outside in the other solutions where the hole (4) was completely occupied.

Since the nature of the present invention and its industrial production have been described sufficiently, all that remains is to add that it is possible to make changes to the form, material and arrangement of the whole and its

component parts without going beyond the scope of the invention as defined in the following claims.