FR3147320A1 - BLADE FLANGE SYSTEM OF A FAN EQUIPPED WITH A RATCHET WHEEL - Google Patents

Abstract

The invention relates to a fan (10) for an aircraft turbomachine test bench comprising a system (21) for clamping the blade (12) in position, comprising: - a ratchet wheel (22) rotatable relative to the annular hub (11) between: - at least one angular locking position in which a tooth (23) of the ratchet wheel (22) bears against a corresponding blade root (18) in order to apply a force for pressing the blade root (18) against the annular hub (11) to maintain the blades (12) in a desired angular position, and - an angular unlocking position in which a blade root (18) is positioned in a corresponding inter-tooth recess (24), such that said blade root (18) is released from the pressing force to allow a modification of an angular position of the blade (12).

Description

BLADE FLANGE SYSTEM OF A FAN EQUIPPED WITH A RATCHET WHEEL

The present invention relates to a fan blade clamping system provided with a ratchet wheel.

An aircraft turbomachine conventionally comprises, from upstream to downstream, with reference to the flow of gases in the turbomachine, a fan, one or more compressors, an annular combustion chamber, one or more turbines and a combustion gas exhaust nozzle.

Figures 1a and 1b show a fan 1 comprising a hub 2 having a longitudinal axis X. Blades 3 extend radially outwards from the hub 2 along their axis Y. The blades 3 are distributed angularly in a regular manner along a circumference of the hub 2. The blades 3 are of the variable pitch type, that is to say that they can be pitched in a predetermined angular position around their respective axis Y in order to adapt and optimize this position depending in particular on the speed of the turbomachine.

In practice, the blades 3 can be moved more than 90° around their Y axis, from a "flag" position in which a blade is substantially aligned with the X axis as illustrated by the , and a "reverse" position in which a blade is capable of generating an air flow reversed relative to the direction of flow of the air flow in the turbomachine, as illustrated by the .

It is known to use a system capable of locking different angular positions of the blades during fan tests. Document FR3111161 describes a clamping system that may include a flange screwed onto an annular portion of the hub so as to hold the blade root tight between the flange and the annular portion of the hub. It is also possible to use a piston device whose oil pressure makes it possible to modify an angular position of a blade.

However, these clamping systems are individual systems that require unlocking and then locking each blade one after the other in order to modify their angular position. This induces a long intervention time between two fan tests to modify the angular position of all the blades. There is therefore a need to be able to manage the locking of all the blades despite their geometric dispersions of manufacture or wear in one go to save handling and adjustment time.

The invention aims to effectively meet this need by proposing a fan for an aircraft turbomachine test bench comprising:
- an annular hub comprising at least one blade root housing,
- at least one blade provided with a blade root arranged in the blade root housing,
- said blower further comprises a system for restricting the position of the blade comprising:
- a ratchet wheel comprising alternating teeth and inter-tooth recesses, said ratchet wheel being rotatable relative to the annular hub between:
- at least one angular locking position in which a tooth of the ratchet wheel bears against a corresponding blade root in order to apply a force to press the blade root against the annular hub to maintain the blades in a desired angular position, and
- at least one angular unlocking position in which a blade root is positioned in a corresponding inter-tooth recess, such that said blade root is released from the plating force to allow a modification of an angular position of the blade.

The invention thus makes it possible, by a simple rotation of the ratchet wheel, to selectively loosen all the blade roots to allow a change in the angular position of the blades and then tighten all the blade roots to maintain the blades in a desired angular position.

According to one embodiment of the invention, an electric motor is integrated into the blade root.

According to one embodiment of the invention, the electric motor is autonomous.

According to one embodiment of the invention, the electric motor is connected to a remotely controllable electronic control box.

According to one embodiment of the invention, the ratchet wheel is mounted coaxially with the hub of the blower.

According to one embodiment of the invention, the ratchet wheel comprises a central annular portion screwed onto a shaft of the hub.

According to one embodiment of the invention, the teeth of the ratchet wheel come to bear against the blade roots along contact tracks.

According to one embodiment of the invention, a contact track is sliding relative to a blade root to allow a variation in movement between the blade root and the ratchet wheel.

According to one embodiment of the invention, the ratchet wheel comprises a flexible leg extending between the central annular portion and the contact tracks.

According to one embodiment of the invention, a projecting portion forming a mass is positioned radially under the contact tracks.

According to one embodiment of the invention, a lock nut is screwed onto a shaft of the hub to hold the ratchet wheel in position.

According to one embodiment of the invention, the blower comprises a means for controlling the rotation of the ratchet wheel allowing a change in the angular position of the blades.

The present invention will be better understood and other characteristics and advantages will become apparent upon reading the detailed description which follows, comprising embodiments given for illustrative purposes with reference to the appended figures, presented as non-limiting examples, which may serve to complete the understanding of the present invention and the description of its embodiment and, where appropriate, contribute to its definition, in which:

Figures 1a and 1b, already described, show a turbomachine fan equipped with variable-pitch blades in a "flag" position and a "reverser" position respectively;

There is a partial perspective view of a fan for an aircraft turbomachine test bench equipped with a ratchet wheel blade clamping system according to the invention;

There is a perspective view of a ratchet wheel of a blade clamping system according to the invention cooperating with blade roots arranged along a circumference of said ratchet wheel;

Figures 4a and 4b are schematic side views illustrating the operation of a blade clamping system according to the invention respectively in a locked position and in an unlocked position;

There is a schematic view of a blade root comprising an electric motor enabling a change in the angular setting of a blade to be carried out;

There is a longitudinal sectional view of a ratchet wheel of a blade clamping system according to the invention.

It should be noted that, in Figures 2 and following, the structural and/or functional elements common to the different embodiments may have the same references. Thus, unless otherwise stated, such elements have identical structural, dimensional and material properties.

There shows a fan 10 for an aircraft turbomachine test bench comprising an annular hub 11 having an axis X and a plurality of blades 12. An inlet cone 14 is mounted at the upstream end of the hub 11 to deflect a portion of the airflow entering the turbojet toward the blades 12 of the fan 10.

The annular hub 11 comprises a plurality of blade root receiving housings 13. The annular hub 11 may be a single-piece hub, i.e. it is made in a single part. Alternatively, the annular hub 11 is made in two coaxial annular parts assembled together.

Each blade root housing 13 comprises a retaining wall 15. The retaining wall 15 originates from an internal face of the housing 13 and extends radially, relative to the Y axis, from the internal face of the housing 13 towards the centre of the housing 13. The retaining wall 15 has a passage opening 16 for a blade root 18.

The blades 12 extend radially outward from the hub 11 along their axis Y. The blades 12 are distributed angularly in a regular manner along a circumference of the hub 11. Each blade 12 is provided with a blade root 18 arranged inside a corresponding blade root housing 13.

As can be seen in Figures 2 and 3, a clamping system 21 in position of the blade 12 makes it possible, in an unlocked state, to authorize a rotation of the blade root 18 inside a corresponding housing 13 around the Y axis so as to select a desired angular position of the blade 12 for a test and in a locked state to immobilize the blade 12 inside the housing 13 in the desired angular position.

The clamping system 21 in position of the blades 12 comprises a ratchet wheel 22 of axis X1 comprising an alternation of teeth 23 and inter-tooth recesses 24. An inter-tooth recess 24 is thus located between two consecutive teeth 23. The ratchet wheel 22 is mounted coaxially with the annular hub 11, such that the axes X and X1 coincide with each other. The ratchet wheel 22 is rotatable relative to the annular hub 11 about the axes X and X1. The ratchet wheel 22 is rotatable between at least one angular locking position and at least one angular unlocking position.

As illustrated in the , in the angular locking position, a tooth 23 of the ratchet wheel 22 comes to bear against a corresponding blade root 18 in order to apply a force to press the blade root 18 against the annular hub 11 to hold the blades 12 in a desired angular position. The clearance between the tooth head 23 and the blade root 18 is then tight, i.e. slightly negative. A radially projecting portion 19 of a blade root 18 relative to the Y axis comes to bear against a corresponding retaining wall 15. The projecting portion 19 is preferably composed of two half-rings assembled with screws, independent of the blade root 18 so that the blade 12 can be inserted from the outside of the hub 11.

As illustrated in the , in the angular unlocking position of the ratchet wheel 22, a blade root 18 is positioned in a corresponding inter-tooth recess 24, such that said blade root 18 is released from the plating force to allow a modification of an angular position of the blade 12. There is then a positive clearance J between the radially projecting portion 19 of a blade root 18 and the corresponding retaining wall 15. In another complementary mode, a more hollow inter-tooth 24 allows access to the screws of the half-rings of the projecting portion 19 to change a blade in situ without dismantling the wheel, its locking system and the other blades.

The locking angular position and the unlocking angular position may correspond respectively to a tight position of the ratchet wheel 22 on the shaft 31 of the hub 11 and to a loose position of the ratchet wheel 22 on the shaft 31 of the hub 11.

The change of angular setting of the blades 12 can be carried out manually during ground tests or mechanically via a piston according to the state of the art. Alternatively, as can be seen in the , the change of angular timing can be carried out by means of an electric motor 26 integrated in the blade root 18. The electric motor 26 can be arranged inside an internal volume delimited by the radially projecting portion 19 of the blade root 18. The locking of the blade root 18 is then ensured by the pressing of a lever 27 against the hub 11 after notching the ratchet wheel 22 in the locked position. respectively illustrates the locked position in which the lever 27 comes to bear against the hub 11 via the retaining wall 15 (half-view on the left in ) and the unlocked position in which the lever 27 is located at a distance from the retaining wall 15 (half-view on the right in ). The electric motor 26 can be autonomous or connected to a remotely controllable electronic control box. A means for controlling the rotation of the ratchet wheel 22 can allow a change in the angular position of the blades 12.

More precisely, the ratchet wheel 22 is mounted coaxially with the hub 11 of the fan 10. The ratchet wheel 22 is arranged radially under the blade roots 18.

As can be seen in Figures 2 and 6, the ratchet wheel 22 comprises a central annular portion 30 screwed onto a shaft 31 of the hub 11. The central annular portion 30 has an annular shape of axial orientation relative to the axis X1 of the ratchet wheel 22. The central annular portion 30 comprises a tapping intended to cooperate with a complementary threaded portion produced on the external periphery of the shaft 31 of the hub 11.

The teeth 23 of the ratchet wheel 22 come to bear against the blade roots 18 along contact tracks 33. A contact track 33 slides relative to a blade root 18 to allow a variation in movement between the blade root 18 and the ratchet wheel 22.

A flexible leg 34 extends between the screwed central annular portion 30 and the contact tracks 33. The flexible leg 34 is formed by an annular wall having a radial orientation relative to the axis X1 of the ratchet wheel 22. The flexible leg 34 provides a mechanical connection between the central annular portion 30 and an external annular portion 35 carrying the teeth 23. The flexible leg 34 allows the external annular portion 35 carrying the teeth 23 to adapt to the expansions of parts arranged between the shaft 31 and the blades 12. This flexible leg 34 also makes it possible to ensure deformation of the ratchet wheel 22 under the effect of centrifugal force to guarantee permanent support between the contact tracks 33 of the ratchet wheel 22 and the blade roots 18.

A projecting portion 38 forming a mass is positioned radially under the contact tracks 33. The projecting portion 38 thus extends circumferentially along a diameter smaller than the contact tracks 33. This makes it possible to optimize the centrifugal force applied by the ratchet wheel 22 on the blade roots 18.

A lock nut 40 is screwed onto the shaft 31 of the hub 11 to hold the ratchet wheel 22 in position, as shown in the . Such a configuration prevents the hub 11 from escaping in case its fixings break during overspeed.

Of course, the various features, variants and/or embodiments of the present invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive.

Furthermore, the invention is not limited to the embodiments described above and provided solely as examples. It encompasses various modifications, alternative forms and other variants that may be envisaged by those skilled in the art within the scope of the present invention and in particular any combinations of the different modes of operation described above, which may be taken separately or in association.

Claims (12)

Blower (10) for an aircraft turbomachine test bench comprising:
- an annular hub (11) comprising at least one blade root housing (13),
- at least one blade (12) provided with a blade root (18) arranged in the blade root housing (13),
characterized in that said blower (10) further comprises a clamping system (21) in position of the blade (12) comprising:
- a ratchet wheel (22) comprising an alternation of teeth (23) and inter-tooth recesses (24), said ratchet wheel (22) being rotatable relative to the annular hub (11) between:
- at least one angular locking position in which a tooth (23) of the ratchet wheel (22) comes to bear against a corresponding blade root (18) in order to apply a force for pressing the blade root (18) against the annular hub (11) to maintain the blades (12) in a desired angular position, and
- at least one angular unlocking position in which a blade root (18) is positioned in a corresponding inter-tooth recess (24), such that said blade root (18) is released from the plating force to allow a modification of an angular position of the blade (12). Blower according to claim 1, characterized in that an electric motor (26) is integrated in the blade root (18). Blower according to claim 2, characterized in that the electric motor (26) is autonomous. Blower according to claim 2 or 3, characterized in that the electric motor (26) is connected to a remotely controllable electronic control box. Blower according to any one of claims 1 to 4, characterized in that the ratchet wheel (22) is mounted coaxially with the hub (11) of the blower. Blower according to any one of claims 1 to 5, characterized in that the ratchet wheel (22) comprises a central annular portion (30) screwed onto a shaft of the hub (11). Blower according to any one of claims 1 to 6, characterized in that the teeth (23) of the ratchet wheel (22) come to bear against the blade roots (18) along contact tracks (33). Blower according to claim 7, characterized in that a contact track (33) is sliding relative to a blade root (18) to allow a variation in movement between the blade root (18) and the ratchet wheel (22). Blower according to claims 6 and 7, characterized in that the ratchet wheel (22) comprises a flexible leg (34) extending between the central annular portion (30) and the contact tracks (33). Blower according to any one of claims 7 to 9, characterized in that a projecting portion (38) forming a mass is positioned radially under the contact tracks (33). Blower according to any one of claims 1 to 10, characterized in that it comprises a lock nut (40) screwed onto a shaft of the hub (11) to hold the ratchet wheel (22) in position. Blower according to any one of claims 1 to 11, characterized in that it comprises a means for controlling the rotation of the ratchet wheel (22) allowing a change in the angular position of the blades (12).