"IMPROVED METHOD OF MANUFACTURING CALLIPERS FOR DISC BRAKES"

The present invention relates to an innovative method of manufacturing callipers for disc brakes, in particular for motor cycles.

In the motor-cycle field, it is well known to make monobloc callipers that are intended to act on the brake disc during the braking step. These callipers comprise a monobloc body, obtained through casting, which body is provided with a slit that in use receives the periphery of the brake disc. In the body the chambers of two pairs of hydraulic cylinders are formed, which push the pads of the brake against opposite faces of the disc in such a way as to grip the periphery of the disc and achieve braking. Known methods for making this type of calliper do, nevertheless, have some disadvantages.

In fact, in order to form the channels inside the calliper for the hydraulic supply to the cylinders, it is necessary to perform complicated and costly machinings on the monobloc body. Also machining the internal surfaces of the cylinder chambers requires the use of sophisticated techniques, which raise the total cost of the process of manufacturing the product. The general object of the present invention is to overcome the aforesaid drawbacks by providing a method of manufacturing callipers for disc brakes that is simple and cheap.

In view of this object, it was decided to devise, according to the invention, a method of manufacturing callipers for

disc brakes of the type comprising at least a pair of facing piston and cylinder devices, intended to push a pair of pads against the disc for clamping the sides of the peripheral fascia of the disc during the braking step, comprising the steps of:

- cast-molding of a body intended to receive the chambers of the two cylinder and piston devices of a pair, the body being provided with a slit intended in use to receive the peripheral fascia of the disc and having a hole passing transversely to the slit, molding occurring with at least a pipe arranged in the mould before casting to form hydraulic supply channels to the cylinders,

- machining on the body by means of a tool passing through said hole for forming the side walls of the chambers and connecting openings between the pipe and the two chambers made in the body that are almost aligned on the through hole on opposite sides of the slit,

- closing the hole with a plug.

In order to clarify the explanation of the innovative principles of the present invention and the advantages thereof over the known art, a possible embodiment thereof applying these principles will be described with the help of the attached drawings. In the drawings:

- figure 1 is a plan view of a calliper obtained with the method according to the invention,

- figure 2 is a section view according to the plane II-II shown in figure 1, before machining,

- figure 3 is a section view similar to the one in figure 2, after machining and insertion of the closing plug,

-figure 4 is a perspective view of the counterpunch to be inserted into the casting mould to form the body of the calliper.

With reference to the figures, in figure 1 there is shown a calliper 11 for disc brakes obtained with the method according the present invention. The calliper 11 comprises a slit 13 intended in use for receiving the periphery of the brake disc (non shown in the figure) and two pairs of cylinder and piston devices, respectively 14-15 and 16-17, intended to push pads acting on opposite sides of the disc in such a way as to clamp the periphery thereof during the braking step.

The cylinder and piston devices of each pair are arranged aligned on opposite sides of the slit 13, according to known techniques. The chambers of the cylinders are formed in a monobloc body 12, obtained by casting and subsequently machined. In the body 12 a pipe 18 is included that is positioned inside the casting mould before casting and is intended to form the hydraulic supply channels to the cylinders of the calliper. The pipe 18 is connected to the hydraulic circuit of the brake at the inlets 21, that emerge from the body 12.

In figure 2 there is shown a section of the body 12 just after casting, with the pipe 18 included in the material of the body (for example aluminium).

By using the counterpunch 27 (fig. 4) inside the casting mould, in the body 12 obtained by casting the slit 13 is already formed that is intended to receive the brake disc. Further, in the body 12 there are formed two cylindrical

cavities 22, 23 intended for forming the part of the chambers 14a, 15a (shown in fig. 3) in which the pistons of the cylinder and piston devices slide. Cavities 22, 23 are formed by virtue of the presence of the cylindrical portions 30, 32 in the counterpunch 27.

The body 12 obtained by casting is also provided with a through hole 25, arranged at the slit 13 transversely thereto. The hole 25 leads into the slit 13 through the cavity 22 and, near the more external part of the body 12, has a transverse section that is less than the section of the cavity 22. The hole 25 is formed by virtue of the presence of the cylindrical portion 28 in the counterpunch 27, that is visible in figure 4. A similar hole will be formed for the other pair of cylinders 16-17, owing to the presence of the cylindrical portion 29 in the counterpunch.

The pipe 18 is inserted into the mould in such a way as to form a ring and passes adjacently to the bottom faces of the portions 30, 32 of the counterpunch intended to form cavities 22, 23 in the body 12 obtained by casting. Advantageously, the pipe 18 passes near the edge of the bottom surface of the cavities 22, 23. It will thus be necessary to machine away only a thin layer of material on the bottom of the cavities 22, 23 to connect the chambers to the hydraulic channels inside the body 12 of the calliper. Similarly, the pipe 18 passes near the cylindrical portions of the counterpunch (in figure 4 with reference 31) corresponding to the chambers of the cylinders 16, 17. In figure 3 there is shown a section similar to that of figure 2, with the body 12 already machined. This machining

occurs by using a tool 24 (shown schematically in figure 2) passing through the hole 25.

With machining the internal surfaces of the chambers 14a, 15a are formed and the pipe 18 is opened in such a way as to create a hydraulic connection between the supply channel and the chamber of the cylinders. The final internal surface of the chambers is marked by a dotted line also in figure 2. Through machining, the depth of the cylindrical cavity 23 is increased in such a way as to lead the pipe 18 into the chamber. Similarly, the bottom of the chamber 14a is machined in such a way as to make the pipe 18 lead into it. Machining also involves the side surface of the chambers 14a, 15a, where the piston of the cylinder slides (not shown in figure). After machining, the internal surface of the chambers 14a, 15a may have a step at the pipe 18, as shown in figure 3, having an end-of-stroke function of the piston of the cylinder. The presence of the hole 25 facilitates the aforementioned machining, inasmuch as complicated and costly undercut machinings are avoided, introducing, for example, the tool through the slit 13 to accede to the cavities 22 and 23 in the body obtained by casting. Once machining has terminated, the hole 25 is closed by means of a plug 20, which is welded to the body 12. The plug 20 is inserted from inside the calliper, through the slit 13, as indicated by the arrow in figure 3. Advantageously, the hole on the bottom of the chamber 14a, before being plugged with the plug 20, can be machined in

such a way as to form a light undercut 26 against which a corresponding flange in the plug 20 abuts to facilitate correct positioning of the plug 20 and the subsequent fixing thereof to the body 12. Advantageously, the undercut and the corresponding flange have an annular shape.

It is therefore possible to provide external surface machining for making the surface of the plug 20 and of the body 12 of the calliper uniform. It should be noted that the chambers of the other pair of cylinder and piston devices 16-17 are obtained in exactly the same way as disclosed for the cylinders 14-15, using a further plug 19 for closing one of the chambers of the cylinders of the pair, following machining. At this point, it is clear how the objects of the invention have been achieved.

In particular, a simple, rapid and cheap method has been provided for making monobloc callipers of the brake. Owing in fact to the solution of leaving the through hole in the body obtained by casting, it is possible to facilitate the machining necessary for forming the internal surfaces of the chambers of the cylinders and for creating the hydraulic connection between the chamber and the channel inside the calliper. Naturally, the above description of an embodiment applying the innovative principles of the present invention is provided by way of example of such innovative principles and must not therefore be taken to limit the protective scope claimed herein.