FIELD OF THE INVENTION AND STATE OF THE ART

The present invention relates to a bellcrank for an aeronautical turbomachine.

In the aeronautical field, a bellcrank is an angle lever having three pivot points.

Particularly, one of the three pivot points is a fixed point of rotation of the bellcrank allowing to transmit a force, applied to one of the other two pivot points, to the last pivot point.

In the field of turbomachines, it is known to use a bellcrank1to connect, for example, a cylinder rod to a control ring301, by pivoting on a point of attachment303of a casing310on the outer side of the flowpath of a compressor of the turbomachine, as represented for example inFIG. 1.

Particular examples of bellcrank mounting for the control of a ring for actuating a variable-pitch stator of a compressor of the turbomachine are disclosed in document FR2936565.

Conventionally, the bellcrank is a part made of titanium obtained by conventional manufacturing means for example by forging then machining. Typically and in the general example of mounting represented inFIG. 1, the bellcrank serves as a connecting rod for transmitting a control force while being connected, on the one hand, to an actuator such as a cylinder and, on the other hand, to the control ring which is rotatable around the casing so as to actuate levers associated with a variable-pitch vane axis in a stator vane assembly of the compressor. Given that the variable-pitch vanes are numerous and undergo aerodynamic stresses affecting their pivot axes, significant forces are likely to be transmitted via the bellcrank. In addition, significant frictions are present and the actuator may be unique for example for a ring. The bellcrank has a substantially L-shaped geometry, as represented for example inFIG. 2.

In such a geometry, the angle of the “L” constitutes the fixed pivot point313serving in correspondence of the point of attachment303, the long end of the “L” has the pivot point312, here shaped as a clevis321, connected to the cylinder rod, and the short end of the “L” has the pivot point311connected to the control ring301.

With a view to reducing the consumption of an aeronautical turbomachine, and therefore decreasing the mass of the turbomachine (or even the aircraft to which it is fixed), it seems necessary to reduce the mass of the bellcrank because the density of the titanium makes it a heavy part in relation to its volume.

In order to reduce the mass of the bellcrank, the following paradox arises: it is difficult to change the material because the titanium has mechanical strength properties necessary for this part while having a density nevertheless lower than steel; but the geometry of the bellcrank must enable it to maintain its function of lever with three-pivot points and to withstand the forces applied thereto.

General Presentation of the Invention

In this context, the present invention aims at providing a bellcrank having a geometry adapted to have a function of lever with three-pivot points, while being adapted to mechanical stresses and having a reduced mass.

According to a first aspect, the invention relates to a bellcrank for a turbomachine having a first bore, a second bore and a third bore, the first bore being connected to the second bore by a first branch, the second bore being connected to the third bore by a second branch, the third bore being connected to the first bore by a third branch, a fourth branch connecting the first branch to the second branch.

The presence of four branches—instead of two in the prior art—allows having thinner branches while having a mechanical strength equivalent to or greater than that of the known bellcranks.

Thus, the present invention provides a bellcrank with a geometry adapted to have a function of lever with three-pivot points, while being adapted to mechanical stresses and having a reduced mass.

The first branch may have a first portion extending from the first bore to a point of junction of the first branch with the fourth branch, and a second portion extending from said point of junction of the first branch with the fourth branch to the second bore. the first portion being substantially rectilinear and the second portion being substantially curvilinear.

The second portion of the first branch may be strictly convex or strictly concave.

A length of the first portion of the first branch may be less than three times a length of the second portion of the first branch.

The second branch may have a first portion comprised between the second bore and a point of junction of the fourth branch with the second branch, and a second portion comprised between said junction point and the third bore, a length of said first portion being less than or equal to a length of said second portion.

The second bore may comprise two coaxial rings and the first branch and the second branch each have a forked end region to connect said two rings.

The second branch can be substantially curvilinear.

The second branch can be strictly convex or strictly concave.

The fourth branch can be substantially rectilinear.

The third branch can be substantially rectilinear.

A length of the third branch can be strictly less than: a length of the first branch, a length of the second branch and a length of the fourth branch.

According to one particular disposition, a first web of material can connect the second portion of the first branch, the first portion of the second branch and the fourth branch.

According to another particular disposition, a second web of material can connect the first portion of the first branch, the second portion of the second branch, the third branch and the fourth branch.

According to a second aspect, the invention relates to a turbomachine comprising at least one bellcrank according to the invention.

The turbomachine may comprise a compressor comprising at least one stator vane assembly of variable-pitch vanes, the bellcrank being adapted to the control of a ring for actuating said variable-pitch stator vanes of the compressor.

According to a third aspect, the invention relates to a method for manufacturing a bellcrank according to the invention, implemented by additive manufacturing of said bellcrank.

