TECHNICAL AREA
The present invention relates to an adjustable length connecting rod for an aircraft turbomachine such as a helicopter.
STATE OF THE ART
The prior art includes US-A-5,431, 540 and EP-A1 2499383.
A helicopter turbine engine is typically mounted in a cell and attached to the helicopter structure elements by connecting rods or the like. As is schematically shown in Figure 1 for example, the turbine engine 10 is fixed at its front end or upstream of the first longitudinal ends of connecting rods 12, 14 whose second opposing longitudinal ends are fixed to a structural element 16 of the helicopter. A tripod or set of three connecting rods 12 connects one side of the front end of the turbine engine 10 to the structural member 16, and a bipod or set of two connecting rods 14 connects a second opposite side of the front end of the turbomachine to the structural element 16.

The rear or downstream end of the turbine engine 10 is connected to the structural element 16 by a substantially vertical adjustable rod 18 in length. This connecting rod extends substantially at 6 o'clock in analogy to the face of a clock. Its upper longitudinal end fixed to an element of the turbomachine 10 and its lower longitudinal end is fastened to a hoop 20 inverted U whose free ends are fixed to the structural element 16 of the helicopter. This U-bracket 20 defines a space for passage of a drive shaft 22 of the helicopter tail rotor. Adjusting the length of the rear link 18 allows in particular to tilt more or less the turbomachine 10 vis-à-vis the front links 12, 14.

In the prior art shown in Figure 2, a first longitudinal end 24 of the rod 18 comprises a threaded hole screwing of an end portion 26 of a threaded shaft 28, and a second longitudinal end 30 of the connecting rod 18 comprises a tapped orifice of screwing of an end portion 32 opposite to the threaded shaft 28. the pin 28 comprises a hexagon 34 between the end portions 28, 32, which is configured to cooperate with a tool such that a key to move in rotation and screw or unscrew the shaft 28 vis-à-vis the ends 24, 30 of the connecting rod 18. rotation of the axis 28 makes it possible to translate the ends 24, 30 of the connecting rod , to bring them closer to or move them away from each other and thereby adjust the length of the connecting rod to a desired value.

However, in practice, this technology is not entirely satisfactory because, although it allows to extend a link to a desired maximum value, it does not shorten this same rod to a desired minimum value, for example, required for its integration in space (here vertical) extending between the turbomachine 10 and the headband 20 (Figure 3). The adjustment range can also be relatively narrow vis-à-vis the length of the rod. In a particular embodiment, the rod has a length of 126mm, adjustable between -12mm to + 12mm (+/- 10%).

The present invention provides a solution to this problem that is simple, effective and economical.

DISCLOSURE OF INVENTION

The invention provides for this purpose an adjustable length strut for an aircraft turbine engine, said connecting rod having a generally elongated shape and having two opposite longitudinal ends of fixing elements to be connected, characterized in that:

- a first of the longitudinal ends is connected to a first threaded pin screwed into a first tubular portion an adjusting sleeve, - a second of the longitudinal ends is connected to a second threaded shaft screwed into a second tubular portion of the sleeve setting, and further comprising a housing in which at least a portion of the first axis is configured to slide.

In the present application, the terms slide or slide must be understood as the movement of an element to another element (in this case the first axis in the housing of the second axis), without necessarily contact between these elements.

Advantageously, the first pin is slidable in the second axis. This increases the rod adjustment range and / or reduce its length to a relatively low value. In a particular embodiment of the invention, the rod has a length of 79mm, and adjustable between -12mm + 12mm (+/- 15%). The rod according to the invention further allows a significant weight gain compared to the prior art (about 35% in the aforementioned special case).

The rod according to the invention may comprise one or more of the following characteristics, taken in isolation from each other or in combination with each other:

- the first and second axes, the sleeve and the housing are coaxial,

- a first against nut is screwed onto the first axis and is adapted to rest on a free end of said first portion and a second against nut is screwed onto the second axis and is adapted to abut on one end free of said second portion; against these nuts are tightened onto the sleeve to secure the rod to a predetermined length,

- said longitudinal ends each comprise a housing in which is mounted a ball joint traversed by a fixing axis,

- the first axis is cylindrical and the second axis is tubular,

- the threads of the first and second axes are in opposite directions,

- the threads of the first and second axes are in the same direction but of different pitch,

- the connecting rod is configured such that the first and second axes are displaceable vis-à-vis each other, by rotation of the sleeve from a first position wherein the axes are at a distance each other, to a second position wherein the first pin is engaged in the second axis.

The present invention also relates to an aircraft turbomachine, such as a helicopter, equipped with at least one connecting rod as described above.

The present invention further relates to an aircraft such as a helicopter, comprising a cell in which is mounted a turbine engine as described above, said rod extending substantially vertically at 6 in analogy to the face of a clock, its top longitudinal end being secured to an element of the turbomachine and the bottom longitudinal end being secured to an inverted U-shaped bow whose free ends are fixed to a structural element of the helicopter and which is traversed by a tail rotor shaft of the last.

DESCRIPTION OF FIGURES

The invention will be better understood and other details, features and advantages of the invention will become apparent from reading the following description given by way of example and with reference to the accompanying drawings in which:

- Figure 1 is a partial schematic half perspective view of a helicopter equipped aircraft of type of a turbomachine,

- Figures 2 and 3 are schematic perspective views of an adjustable connecting rod of the prior art,

- Figure 4 is a schematic view in axial section of a connecting rod according to the invention,

- Figure 5 is a schematic exploded perspective sectional view of a connecting rod according to the invention,

- Figures 6 and 7 are schematic views in axial section and in perspective of the connecting rod of Figure 4, and respectively show two extreme positions of the adjustment rod, and

- Figure 8 is a schematic perspective view of the connecting rod of Figure 4 in an installation environment.

DETAILED DESCRIPTION

Figures 1 to 3 have been described in the foregoing and the prior art to illustrate the present invention.

Figures 4 and following illustrate one embodiment of the connecting rod 40 according to the invention, wherein:

- a first longitudinal end 42 of connecting rod 40 is connected to a first threaded shaft 44 screwed into a first tubular portion 46 of an adjustment sleeve 48, and

- a second longitudinal end 50 opposite of the connecting rod is connected to a second threaded shaft 52 screwed into a second tubular portion 54 of the sleeve 48, this axis 52 having a housing 56 wherein at least a portion of the first axis 44 is configured to slide when adjusting the rod.

The threaded shaft 44 is secured to the first end 42 and is preferably formed integrally therewith. The first axis 44 has an elongated axis A. The thread extends over a major portion of its length to its free end opposite to the end 42. This end 42 includes a housing in which is mounted a 58 through ball joint by a screw 60. the end 42 is engaged between the two ears of a yoke 62 which includes aligned mounting holes in the screw 60. bushings 64 are mounted in the holes of the yoke 62 and around the opinion. The screw 60 includes a head which bears on one of the sleeves by means of a washer 66, and receives at its opposite end a nut 68 which bears against the other bushing via a washer 70. the ball joint 58 associated to the fact that the thickness or axial dimension of the end 42 along the axis B of the screw 60 is less than the distance between the ears of the clevis 62 along the same axis B, permits tilting of the axis 44 vis-à-vis a plane perpendicular to the axis B.

Similarly, the threaded shaft 50 is secured to the second end 52 and is preferably formed integrally therewith. This axis 50 has an elongated shape along the axis A and is coaxial with the axis 44. The thread extends over a major portion of its length to its free end opposite to the end 52. this end 52 includes a housing in which is mounted a ball 72 traversed by a screw 74. the end 52 is engaged between the two ears of a yoke 76 which includes aligned mounting holes in the screw 74. at least one socket 78 is mounted in the orifices of the yoke 76 and around the screw. The screw 74 includes a head which bears on the socket through a washer 80, and receives at its opposite end a nut 82 which rests on a further sleeve and the corresponding lug of the cap 76 by the via a washer 84. the ball 72 associated with the fact that the thickness or axial dimension of the end 52 along the axis C of the screw 74 is less than the distance between the ears of the clevis 76 along the same axis C, authorizes tilting of the shaft 52 vis-à-vis a plane perpendicular to the axis C.

The axis 44 and in particular its thread has an outer diameter D1. The axis 52 and in particular its housing 56 has an inner diameter D2, which is greater than D1 so that the axis 44 can cooperate by sliding in the housing 56. The housing 56 of the shaft 52 is generally cylindrical in shape the example shown. Due to this housing, the axis 52 has a generally tubular shape.

The tubular portion 54 of the sleeve 48 surrounds the axis 52 and comprises a free end situated on the side of the end 50, which is intended to cooperate by abutment with a nut against 85 screwed on the axis 52. C ' here is the same thread of the spindle 52 which cooperates with the sleeve 48 and against the nut 85. the opposite end of this tubular portion 54 is connected to the tubular portion 46 of the sleeve which surrounds the axis 44. this tubular portion 46 has a free end situated on the side of the end 42, which is intended to cooperate by abutment with one another against nut 86 screwed onto the shaft 44. this is the same thread of the axis 44 which cooperates with the sleeve 48 and the nut 86 against.

In the example shown, housing 56 has a length along the axis A that is configured to receive at least a portion and for example up to 50% of the length of the axis 44. The tubular portion 54 of the sleeve 48 has a length along the axis a which is similar to the housing 56 or the thread of the spindle 52.

The threads of the first and second axes 44, 52 may be in opposite directions. Alternatively, they are in the same direction but different pitch. For a given rotation of the sleeve 48, the movement of the axes 44, 52 will be greater with opposite direction of threads with the same direction of threads and different pitch. The advantage of the first case is that a rotation by a small angle of the sleeve can be used to move the axes 44, 52 a significant distance, and the advantage of the latter lies in the fact that the adjusting the relative position of the axes can be more accurate.

Figures 6 and 7 show the connecting rod 40, respectively in a maximum extended position and a maximum retracted position. In other words, the connecting rod has a maximum length in Figure 6 and a minimum length in Figure 7.

In Figure 6, the tubular portion 54 of the sleeve 48 is screwed onto a first inlet portion of the thread of the axis 52 and, in the same way, the tubular portion 46 of the sleeve 48 is screwed onto a first portion input thread of the axis 44. the holder is then positioned at the greatest possible distance the axes 44, 52 from each other, the axis 44 is not engaged in the housing 56 of the axis 52.

In Figure 7, the tubular portion 54 of the sleeve 48 is screwed to an end portion of the thread of the shaft 52 and, in the same way, the tubular portion 46 of the sleeve 48 is screwed on a portion of end of the thread of the axis 44. the holder is then positioned so as to close as possible to the axes 44, 52 from each other, the axis 44 being engaged in the housing 56 of the shaft 52.

In both cases shown, against the nuts 85, 86 are screwed and take position in abutment on the respective free ends of the sleeve 48 to lock it in vis-à-vis rotation axes 44, 52. In the case of Figure 7, against nuts 85, 86 are adjacent the ends 42, 50 of the connecting rod.

8 shows the rod 40 in the environment corresponding to FIG 1. It connects a member such as a clevis 88 of a turbomachine 10 to the headband 20. It is therefore understandable that the yoke 88 forms the yoke 62 of Figure 4, and the yoke of the cradle 20 forms the yoke 76 of Figure 4.

It may also be noted in Figures 5-8 that against nuts 84, 85 comprise through-holes 90 for passage of at least one thread brake for their immobilization in rotation. One wire brake may for example traversed two orifices 90 against nuts 84, 85.

As mentioned in the foregoing, it is the rotation of the bushing 48 which adjusts the length of the connecting rod 40. The rotation of the bush can be achieved by means of a tool such as a wrench. In the example shown, the portion 54 of the sleeve 48 has in cross section a non-circular peripheral shape and for example hexagonal for cooperation with such key.

CLAIMS
1. Rod (40) of adjustable length for a turbomachine (10) of an aircraft, said connecting rod having a generally elongated shape and having two longitudinal ends (42, 50) opposite of fixing elements to be connected, characterized in that:

- a first (42) of these longitudinal ends is connected to a first threaded pin (44) screwed into a first tubular portion (46) of an adjusting sleeve (48),

- a second (50) of these longitudinal ends is connected to a second threaded shaft (52) screwed into a second tubular portion (54) of the adjusting sleeve, and further comprising a housing (56) wherein at least a portion the first axis is configured to slide.

2. A connecting rod (40) according to the main claim, wherein the first and second axes (44, 52), the sleeve (48) and the housing (56) are coaxial.

3. A connecting rod (40) according to one of the preceding claims, wherein a first against nut (86) is screwed onto the first axis (44) and is adapted to rest on a free end of said first portion (46 ), and against a second nut (85) is screwed onto the second axis and is adapted to rest on a free end of said second portion (54).

4. A connecting rod (40) according to one of the preceding claims, wherein said longitudinal ends (42, 50) each comprise a housing in which is mounted a ball (58, 72) through which a fixing screw (60, 74) .

5. A connecting rod (40) according to one of the preceding claims, wherein the first axis (44) is cylindrical and the second axis (52) is tubular.

6. A connecting rod (40) according to one of the preceding claims, wherein the threads of the first and second axes (44, 52) are in opposite directions.

7. A connecting rod (40) according to one of claims 1 to 5, wherein the threads of the first and second axes (44, 52) are in the same direction but of different pitch.

8. A connecting rod (40) according to one of the preceding claims, configured so that the first and second axes (44, 52) are displaceable vis-à-vis each other, by rotation of the bush (48) from a first position wherein the axes are at a distance from each other, to a second position wherein the first pin is engaged in the second axis.

9. The turbomachine (10) of aircraft such as a helicopter, equipped with at least one connecting rod (40) according to one of the preceding claims.

10. An aircraft such as a helicopter, comprising a cell in which is mounted a turbomachine (10) according to the preceding claim, said connecting rod (40) extending substantially vertically at 6 in analogy to the face of a clock, its top longitudinal end being secured to an element of the turbomachine and its lower longitudinal end being fixed to a structural element (1 6) of the helicopter.