" SYSTEM FOR THE INTERNAL BROACHING OF A CYLINDRICAL BORE"

TECHNICAL FIELD

The present invention relates to an innovative system for the internal broaching of a cylindrical bore.

BACKGROUND ART

As is known, for the broached pieces the complete cycle generally provides a first preparation lathing operation, a second broaching operation and a third finish lathing operation of the outer cylindrical surface of the piece that has been broached.

The third finish lathing operation is aimed to ensure that the circumference which encompasses the outer surface is concentric with the circumference which encompasses the ends of the teeth that were obtained by broaching.

DISCLOSURE OF INVENTION

The present invention seeks to remove this third step which results in a considerable additional cost.

Obviously, the elimination of this operation must not be at the expense of a good concentricity between the pre-hole and the broached evolvent.

Therefore, in accordance with the present invention, a system as defined in claim 1 is provided, and preferably, in any claims depending directly or indirectly on the mentioned claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, a preferred embodiment will now be described, purely by way of non- limiting example and with reference to the accompanying drawings, wherein:

- Figure 1 illustrates an assembly of the system object of the present invention;

- Figure 2 shows an enlargement of a first detail of a broach; - - and

- Figure 3 shows an enlargement of a second detail of a piece bearing table.

BEST MODE FOR CARRYING OUT THE INVENTION

In Figure 1, with number 10 is indicated, as a whole, a system according to the present invention.

The system 10 is used to perform precision broaching of a cylindrical bore 20 which are previously obtained on a piece 30.

The system 10 comprises a broach 40 and a piece bearing table 50 which is suited to support the piece 30 to be machined. The system 10 is characterized in that a guiding and coupling device 60 is arranged between the broach 40 and the piece bearing table 50 so as to guide the broach 40 during the broaching operations.

In the embodiment shown in the attached figures the device 60 is given by the set of three slits 70 (Figure 2), which are obtained on the broach 40, and are able to be coupled with three wedges 80 arranged on the piece bearing table 50.

The three slits 70 (and therefore also the three wedges 80) are spaced apart by 120°.

According to a further embodiment of the present invention, not shown, the wedges are integral with the broach, while the three guide slits have been obtained on the piece bearing table.

It is obvious that any guiding and coupling system between a broach and a piece bearing table is within the teachings of the present invention.

The main advantages of the system object of the present invention are the following: - -

- simplicity of broaching execution ;

- low costs , and the

- possibility to use current broaches